Presentation type:
CR – Cryospheric Sciences

EGU24-6597 | Orals | MAL15-CR | Julia and Johannes Weertman Medal Lecture

Understanding glacier processes to decode the drivers of glacier change 

Gwenn Flowers

Detection, attribution and projection of glacier and ice-sheet change characterize much of our community’s work, motivated in part by the associated impacts ranging from local hazards to regional water supply to global sea-level rise. Toward improved attribution of glacier change on local to regional scales, I profile work aimed at discerning the internal versus external drivers of glacier behaviour through process-oriented studies. Using examples from northern Canada, combining observational and numerical approaches improves our understanding of fundamental processes that define the boundary conditions at the ice interface with bedrock, water and atmosphere. These studies have allowed us to revisit questions related to glacier surging, hydrology and ice-dammed lakes and the co-evolution of glacier geometry and thermal structure, with occasionally surprising and counter-intuitive results.

While the internal dynamics of glacier systems have the potential to confound the climate signal on societally relevant timescales, the direct effects of climate via surface mass balance remain as important as ever. Improved observational platforms, advances in modelling and the growing abundance and availability of remotely sensed data have amplified our capacity to study these systems, and more generously than ever reveal information archived by glacier processes. Using these tools, we are now beginning to disentangle the contributions of the geologic substrate, environmental setting, internal ice dynamics and climate forcing to observed glacier change in globally significant ice-rich parts of the world.

How to cite: Flowers, G.: Understanding glacier processes to decode the drivers of glacier change, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6597, https://doi.org/10.5194/egusphere-egu24-6597, 2024.

EGU24-11275 | ECS | Orals | MAL15-CR | Arne Richter Award for Outstanding ECS Lecture

Supraglacial Lake Drainage: from process puzzle to subglacial diagnostic 

Laura A. Stevens, Alison F. Banwell, Mark D. Behn, Danielle L. Chase, Sarah B. Das, Rebecca L. Dell, Emily Falconer, Ian R. Joughin, Ching-Yao Lai, Stacy Larochelle, George J. Lu, Jeffrey J. McGuire, Meredith Nettles, Marianne Okal, Joshua Rines, and Ian C. Willis

Supraglacial lake drainages are isolated events that deliver the largest observable fluxes of surface melt to the ice-sheet bed. This talk will present advances in the study of these lake drainages, through which we piece together an empirical understanding of glacier hydrology. We examine the ways in which lakes both respond to, and determine, the hydrologic and glaciologic conditions under which they exist. We begin with the process puzzle of what mechanisms drive the opening of fractures within the compressive regions where lakes form, allowing hydro-fracture-driven drainages to occur. Next, we follow drained lake water in time and space, using the natural experiments provided by the drainages to infer subglacial-drainage-system transmissivity and structure beneath kilometer-thick ice flowing at rates of tens to thousands of meters per year in Greenland. In widening our view to previous subglacial-flood events observed at other ice-sheet locations—as well as at alpine, valley, and tidewater glaciers—we observe surprising similarities across a wide range of ice thicknesses, flow speeds, and types of flood events. The similarities we observe are encouraging because they suggest that information on drainage-system structure and evolution gleaned from these episodic events can be used to understand the wider picture. Finally, we examine current challenges: how do we move from the observed mechanisms of individual lake drainages to an integrated understanding of the importance of hundreds of drainages for long-term ice-sheet response and ice-shelf collapse? Progress will require the combination of geodetic observations, hydrologic simulations, and geophysical models to deconvolve the differing mechanisms that result in clusters of drainages in the multiple settings in which lakes form.

How to cite: Stevens, L. A., Banwell, A. F., Behn, M. D., Chase, D. L., Das, S. B., Dell, R. L., Falconer, E., Joughin, I. R., Lai, C.-Y., Larochelle, S., Lu, G. J., McGuire, J. J., Nettles, M., Okal, M., Rines, J., and Willis, I. C.: Supraglacial Lake Drainage: from process puzzle to subglacial diagnostic, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11275, https://doi.org/10.5194/egusphere-egu24-11275, 2024.

CR1 – The State of the Cryosphere: Past, Present, Future

EGU24-920 | ECS | Orals | CR1.1

Increased up-glacier thinning in four major glaciers of High Mountain Asia revealed by geodetic mass balance estimates 

Arindan Mandal, Anshuman Bhardwaj, Mohd Farooq Azam, Bramha Dutt Vishwakarma, and Thupstan Angchuk

Given its profound implications for future water security, the response of High Mountain Asia (HMA) glaciers to climate change remains a topic of critical concern. While recent studies have primarily focused on small glaciers (with glacierised areas of less than 1 to ~20 km2) to understand the impact of climate change on HMA water resources, these studies assume that smaller glaciers are regionally representative. However, it has been shown that smaller glaciers respond differently due to their smaller accumulation area particularly during warm years and lesser hydrological contribution. On the other hand, large glaciers in a catchment often serve as major contributors to runoff, thus influencing long-term water availability. Hence, larger glaciers may offer a more representative understanding of regional changes and are essential for future water security.

In this study, we calculate the geodetic mass balance of four very large glaciers —Fedchenko (with a total area of 664 km2), Baltoro (809 km2), Bara Shigri (112 km2), and Gangotri (122 km2)— covering the period from 2009 to 2022. The analysis is conducted over two different time intervals, utilizing digital elevation models generated from ASTER stereo imagery. We examined distinct glacier surfaces — debris-covered, clean-ice, and accumulation areas — to discern mass loss patterns with elevations. Bias-corrected in-situ meteorological data along with surface ice velocity data (from ITS_LIVE and Sentinel-1) were used to elucidate recent mass balance patterns.

Results reveal an amplified mass loss rate during the recent period of ~2015-2022 compared to the preceding period of ~2009-2015. Bara Shigri is an exception, experiencing a slight reduction in mass loss during ~2015-2022. The increased mass loss is driven by rising local summer temperatures and declining winter precipitation. Thinning was prominent at higher elevations (> 5000 m a.s.l.) across all four glaciers, with its intensity increasing over time. This indicates warming in the accumulation areas of these glaciers. Furthermore, upper glacier areas near the equilibrium line altitude exhibited stable ice velocities in certain glaciers, and the lower ablation zones experienced gradual slowdown, likely due to persistent mass loss.

These findings highlight the propagation of up-glacier thinning in large HMA glaciers, indicating mass loss across higher elevations and underscoring the vulnerability of local river systems and water resources.

How to cite: Mandal, A., Bhardwaj, A., Azam, M. F., Vishwakarma, B. D., and Angchuk, T.: Increased up-glacier thinning in four major glaciers of High Mountain Asia revealed by geodetic mass balance estimates, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-920, https://doi.org/10.5194/egusphere-egu24-920, 2024.

EGU24-930 | ECS | Posters virtual | CR1.1

Projections of Elbrus glaciers, proglacial lakes and dead ice areas. 

Taisiya Postnikova, Oleg Rybak, Afanasy Gubanov, Harry Zekollari, and Matthias Huss

Mt Elbrus being the highest peak in Europe (5642 m a.s.l.) is an inactive volcano currently covered by nearly thirty glaciers. Glaciated area is 112.20 ± 0.58 km³ and 5.03 ± 0.85 km³ in volume as revealed by Kutuzov et al., (2019) for the year of 2017. Current and future deglaciation of the Caucasus in general and of the Elbrus glacial massif in particular can be the reason for various negative consequences for the local economy and environment. Therefore, relevant prognostic studies are of great value both for the academicians and for the policymakers.

In this research, we consider probable scenarios of Elbrus glacier change in the 21st century. We mostly focus at the phenomena accompanying degradation of glaciation, such as the formation of glacial lakes and areas of “dead” ice buried under the moraine, which is relevant for predicting Glacial Lake Outburst Floods (GLOFs). Future climate projections, based on SSP1-1.9, SSP1-2.6, SSP2-4.5, SSP3-7.0, SSP5-8.5 scenarios, were employed. Surface mass balance is calculated using temperature-index method (Huss and Hock, 2015). Glacier dynamics is emulated in 1-D global glacier model GloGEMflow (Zekollari et al., 2019) updated by incorporation of the module responsible for the description of debris cover evolution (Postnikova et al., 2023). Model adaptation for Elbrus involves the model transition from colluvial (e.g. slope erosion) to exarational (e.g. emergence of subglacial sediments) debris-cover sources, which aligns with the region's geological setting. These two modes of modelling the debris cover transformation in time are compared. While model validation reveals a slight underestimation of mass loss in the early 21st century, it accurately reproduces general mass loss patterns.

Under the warmest climate change scenarios, almost all of the remaining ice mass in the Central Caucasus will be concentrated on Elbrus. At the same time, Elbrus glaciers are anticipated to retreat above the 4000 m elevation by 2100. In case of moderate warming the position of glacier fronts may stabilize at an altitude of 3600-3700 m. According to our estimates, glacier retreat may lead to the formation of up to 17 new proglacial lakes. Under a moderate warming scenario (SSP1-2.6), up to 8 proglacial lakes may appear. The largest of them is expected to form at the terminus of the Djikaughenkioz ice plateau dammed by debris-covered dead ice in the 2030s-2040s assuming no sufficiently effective runoff channels are established.

This study was funded by the RSF grant number 23-27-00050.

How to cite: Postnikova, T., Rybak, O., Gubanov, A., Zekollari, H., and Huss, M.: Projections of Elbrus glaciers, proglacial lakes and dead ice areas., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-930, https://doi.org/10.5194/egusphere-egu24-930, 2024.

Glaciers of Baffin Island and nearby islands of Arctic Canada have experienced rapid mass losses over recent decades. However, projections of loss rates into the 21st century have so far been limited by the availability of model calibration and validation data. In this study we model the surface mass balance of the largest ice cap on Baffin Island, Penny Ice Cap, since 1959, using an enhanced temperature index model calibrated with in situ data from 2006–2014. Subsequently, we project changes to 2099 based on the RCP4.5 climate scenario. Since the mid-1990s, the surface mass balance over Penny Ice Cap has become increasingly negative, particularly after 2005. Using volume–area scaling to account for glacier retreat, peak net mass loss is projected to occur between ~2040–2080, and the ice cap is expected to lose 22% (377.4 Gt or 60 m w.e. a–1) of its 2014 ice mass by 2099, contributing 1.0 mm to sea level rise. Our 2015–2099 projections are approximately nine times more sensitive to changes in temperature than precipitation, with an absolute cumulative difference of 566 Gt a–1 (90 m w.e.) between +2°C and –2°C scenarios, and 63 Gt a–1 (10 m w.e.) between +20% and –20% precipitation scenarios.

How to cite: Schaffer, N.: Modeling the surface mass balance of Penny Ice Cap, Baffin Island, 1959–2099, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1173, https://doi.org/10.5194/egusphere-egu24-1173, 2024.

EGU24-1505 | ECS | Orals | CR1.1

Surge initiation at the terminus of Borebreen (Svalbard): Drivers and impact on calving 

William D. Harcourt, Wojciech Gajek, Danni Pearce, Richard Hann, Adrian Luckman, Brice R. Rea, Douglas I. Benn, Mike R. James, Matteo Spagnolo, and Ugo Nanni

Approximately 21% of Svalbard’s glaciers are classified as surge-type and undergo cyclical changes in ice velocity between quiescent (slow) and active (fast) phases. Whilst it is generally understood that processes at the glacier bed drive surge initiation, the physical mechanisms translating basal sliding to ice flow variability and cyclicity remain open questions. Recent mapping of glacier velocities across Svalbard has identified an acceleration in ice flow at the Borebreen tidewater glacier which terminates on the northwestern side of Isfjorden. Before 2018, average summer velocities at Borebreen were ~0.6 m/d but more than doubled to 2.4 m/d by 2023. Borebreen last surged ~100 years ago, hence the acceleration in ice velocity suggests it is the result of the glacier transitioning to an active surge. In this contribution, we will discuss results from a summer field campaign to Borebreen in August 2023. Using a multi-sensor network of seismic arrays, Terrestrial Laser Scanners (TLS), and drones, we characterise present day surge dynamics and use the data to understand the drivers. In addition, optical imagery from the PlanetScope constellation and Synthetic Aperture Radar (SAR) data from Sentinel-1 are used to determine surface conditions (e.g. surface melt patterns, crevasses, proglacial turbid plumes) and quantify ice velocities. Here, we will report on the following: 1) basal processes (e.g. stick-slip events, icequakes) under Borebreen; 2) calving processes at the over-steepened ice cliff of the surge front; 3) ice velocity extracted from drone photogrammetry, Planetscope imagery and Sentinel-1 SAR scenes; and 4) surface conditions (e.g. crevassing, surface melt) over the course of the ablation season and its relationship with ice dynamics. We find that the surge initiated at the glacier terminus and has been propagating upglacier. The glacier speed doubles each spring in response to elevated air temperatures which leads to surface melting and the delivery of meltwater to the glacier bed. Furthermore, we identify clusters of seismicity at the glacier bed, far from the terminus, which appear to indicate sliding. Our results push forward our understanding of the processes that initiate and sustain glacier surges and glacier instabilities in general.

How to cite: Harcourt, W. D., Gajek, W., Pearce, D., Hann, R., Luckman, A., Rea, B. R., Benn, D. I., James, M. R., Spagnolo, M., and Nanni, U.: Surge initiation at the terminus of Borebreen (Svalbard): Drivers and impact on calving, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1505, https://doi.org/10.5194/egusphere-egu24-1505, 2024.

EGU24-1728 | ECS | Posters virtual | CR1.1

6 Years in-situ mass balance study of Pensilungpa Glacier from 2016 to 2022 in Suru River Valley, Ladakh Himalaya, India.  

Pankaj Kunmar, Manish Mehta, Vinit Kumar, Ajay Rana, and HC Nainwal

Recent studies of Himalayan glacier recession indicate that there is wide variability in terminus retreat rate and mass balance in the different sectors of the mountain range, primarily linked to the topography and climate of the region. Variable retreat rates of glacier termini and inadequate supporting field data (e.g. mass balance, ice thickness, velocity, etc.) in the Himalayan glaciers make it difficult to develop a coherent picture of climate change impacts. The mass balance measurements of the Pensilungpa Glacier were conducted from 2016-2017 to 2021-2022 and the study was carried out by using the glaciological method, including fixed date measurement of net accumulation. The glaciological method includes measurements at stakes and in snow pits, which are interpolated to glacier-wide balance estimates. This six-year mass balance study shows a negative trend with an average rate of specific balance is -0.46 m water equivalent (w.e.) and annual mean mass balance was -4.1 x106 m3 w.e. The Glacier lost ~45 ±18 m lengths with an average rate of 6.4 ±3 ma-1, and 24.97 x106 m3 w.e. cumulative volume loss. Also, results show that Pensilungpa Glacier declined the ELAs 20 m from the year 2016.

How to cite: Kunmar, P., Mehta, M., Kumar, V., Rana, A., and Nainwal, H.: 6 Years in-situ mass balance study of Pensilungpa Glacier from 2016 to 2022 in Suru River Valley, Ladakh Himalaya, India. , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1728, https://doi.org/10.5194/egusphere-egu24-1728, 2024.

EGU24-1758 | ECS | Orals | CR1.1

Five years of change of two debris-covered glaciers monitored by unmanned aerial system 

Philip Kraaijenbrink and Walter Immerzeel

Glaciers in the Himalaya are often covered by debris, which affects melt rates and causes high spatial heterogeneity in surface elevation changes. In the past decade years, unmanned aerial system (UAS) data have been shown to be indispensable in mapping and monitoring this type of glacier and catalysed new research focusing on process understanding of ablation processes at unprecedented detail. In this study, we present the results of a five-year biannual UAS monitoring campaign in the Langtang Catchment in the Nepalese Himalaya in which we surveyed Lirung Glacier (9 surveys, 2013–2018) and Langtang Glacier (7 surveys, 2014–2018). Optical UAS imagery was processed into high-resolution image mosaics and elevation data, accurately positioned using ground control data and co-registered using tie points. Derived glacier surface velocities and modelled bed topography were used to perform fully distributed corrections for ice flow and emergence velocity. The resulting flow-corrected surface changes of the glacier were analysed and used to evaluate supraglacial ice cliff evolution, glacier retreat, and melt. Results show that on average the surveyed areas of Lirung Glacier and Langtang Glacier had comparable surface velocities ranging from about 1.0 to 3.5 m a-1 and a melt of −1.40 ± 0.05 m a-1 and -1.22 ± 0.08 m a-1, respectively, with both glaciers having strong spatial heterogeneity and temporal variability. Supraglacial ice cliffs on both glaciers exhibit variable (rates of) change in morphology, largely irrespective of aspect. The terminus of Lirung Glacier, which is characterized by a debris-free ice cliff, experienced very fast retreat of 41 m a-1. The five-year time series of UAS data presented in this study has provided unique insights in surface changes of debris-covered glaciers. UAS surveys are and continue to remain highly valuable tool to study such glaciers, with potential still to be unlocked.

How to cite: Kraaijenbrink, P. and Immerzeel, W.: Five years of change of two debris-covered glaciers monitored by unmanned aerial system, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1758, https://doi.org/10.5194/egusphere-egu24-1758, 2024.

EGU24-2575 | Orals | CR1.1 | Highlight

Projecting the evolution of the Northern Patagonian Ice Field until the year 2200 

Marius Schaefer, Ilaria Tabone, Ralf Greve, Johannes Fürst, and Matthias Braun

The Northern Patagonian Ice Field (NPI), Chile, is the second-largest ice body in the Southern Hemisphere outside Antarctica, and one of the two remnant parts of the Patagonian ice sheet that existed during the last glacial period. It is located in the Southern Andes, a region that was identified to have one of the most negative specific mass balances of the world’s glacierized regions. The NPI is a highly dynamic ice body, characterized by large accumulation/ablation rates and contains the equator nearest tidewater  calving glacier, Glaciar San Rafael. We used the ice-sheet model SICOPOLIS to reproduce the current state of NPI and realize projections under different climate change scenarios. Calving is treated by implementing an additional specific mass loss for grid cells which are in contact with the ocean (San Rafael Lagoon). Forcing the model with a constant present-day surface mass balance a steady state is achieved which shows much similarity with the current state of the NPI. When forcing the model with different climate change scenarios, a mostly constant mass loss during the 21st century and a stabilization of the NPI during the 22st century is observed. The representation of Glaciar San Rafaels' front position improves clearly when implementing a simple (constant) calving law, however, the effect on the projected overall ice volume is low. Our simulation suggest that even if climate stabilized during 21st century, glacier changes on NPI would continue during the 22nd century.

How to cite: Schaefer, M., Tabone, I., Greve, R., Fürst, J., and Braun, M.: Projecting the evolution of the Northern Patagonian Ice Field until the year 2200, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2575, https://doi.org/10.5194/egusphere-egu24-2575, 2024.

Greenland's snow and ice melting trends have increased since the conclusion of the Little Ice Age (LIA), leading to the emergence of new ice-free zones. Given its significant impacts on ecosystems and climate, a comprehensive understanding of the spatiotemporal patterns of Greenland meltwater, snow and ice cover is crucial. This study conducts a comparative analysis of recent snow and ice dynamics (1985-2022) within the Central-Western Greenland Ice-Sheet (GrIS) and Nuussuaq Peninsula Greenland peripheral glaciers (GICs). Specifically, we examine the extension of snow and ice cover, changes in mass balance, and the climatic evolution in these geographical areas. The regions of GICs and GrIS demonstrate a statistically significant (p-value <= 0.05) positive temperature trend, particularly during the accumulation season at GIC (R2 = 0.19) and GrIS (R2 = 0.13). However, precipitation trends reveal minimal and statistically non-significant changes. Despite their geographical proximity, the terminus positions of land-terminating glaciers in GrIS and GICs exhibit different spatial patterns and trend rates. Over the last two decades, Nuussuaq Peninsula GICs display an average negative mass loss of -0.3 GT/year, with the minimum mass loss recorded in 2007 (-0.2 GT/year), constituting an anomaly of -25% compared to the average mass loss for the temporal period analyzed. In contrast, peak mass loss values are observed in 2009, reaching anomalies of -0.4 GT/year. Further, the snow and ice cover area of GICs indicates a reduction of approximately 20% from the previous delineations of the LIA, with the most significant decreases observed in the southern-exposed Nuusuaq Peninsula GICs. Conversely, small differences in GrIS land-terminating terminus positions are detected from 1985 to 2022, despite substantial meltwater anomalies since the 1990s. These results highlight the different sensitivity of terminus positions between GICs and GrIS despite their proximity. Our findings contribute to a better understanding of the recent spatiotemporal evolution of glaciers in Western Greenland.

How to cite: Bonsoms, J., Oliva, M., and López-Moreno, J. I.: Contrasting glacier terminus position trend rates between Central-Western Greenland peripheral glaciers and ice sheet:  spatiotemporal patterns and trends (1985 to 2022), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3207, https://doi.org/10.5194/egusphere-egu24-3207, 2024.

High-resolution climate data is crucial for accurate glacier modeling in topographically complex regions. This study investigates the necessity of such data for accurate simulations of glacier and freshwater dynamics for the Flade Isblink Ice Cap (FIIC), Northeast (NE) Greenland. It also explores the potential of achieving comparable results using coarse-resolution global datasets with region-specific scaling.

The study employed an advanced subdivision of FIIC, consisting of 299 glaciers, including six active marine-terminating ones. Four climate datasets (ERA5, CRU, W5E5, and ERA-Interim dynamically downscaled using polar WRF for NE Greenland) with 5-50 km spatial resolutions were used to force the Open Global Glacier Model (OGGM) from 2014 to 2018. OGGM was calibrated glacier-by-glacier against high-resolution geodetic-altimetric mass balance, frontal ablation, and volume data. Sensitivity analyses were conducted with and without regional scaling for all selected climate datasets and calibration parameters.

The high-resolution WRF dataset provided an accurate initial regional volume estimate (with a minimal deviation of -0.6 % from the reference) without any local corrections, while other datasets underestimated volume, increasing with decreasing resolution from 8 % to 15 %. However, applying regional temperature bias and precipitation factor significantly improved the accuracy of these estimates, reducing the underestimation from just 2.1 % to 2.4 %. Sensitivity analysis revealed that the precipitation factor has a moderate influence, while temperature bias has a higher influence on the modeled volume. Without scaling, coarse datasets underestimated annual freshwater runoff by 25 % to 34 %, but with regional scaling, this discrepancy was markedly reduced to a near alignment with the WRF dataset at 0.5 % to 1.6 %, corresponding to 9.8 Gt/yr. Across datasets, summer months (June, July, August) runoff estimates showed no significant differences (p>0.05) after regional scaling.

The study concludes that high-resolution climate data enhances the accuracy of initial volume estimates, thereby increasing confidence in simulated results. However, appropriate local adjustments to coarser datasets can yield comparable glacier and freshwater runoff simulations. Initial volume estimates are crucial for future projections. Future modeling efforts will explore the sensitivities of regional scaling and parametrization on improving projections of freshwater contributions into the ocean and their feedback on glacier-ocean interactions.

How to cite: Shafeeque, M., Vlug, A., and Marzeion, B.: Assessing the Influence of Climate Forcing Data Resolution on Simulations of Glacier and Freshwater Dynamics for the Flade Isblink Ice Cap, Northeast Greenland, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5140, https://doi.org/10.5194/egusphere-egu24-5140, 2024.

EGU24-5815 | Posters on site | CR1.1

Temperature Decoupling on the World’s Mountain Glaciers 

Thomas Shaw, Evan Miles, Pascal Buri, Michael McCarthy, Nicolas Guyennon, Luca Carturan, Franco Salerno, and Francesca Pellicciotti

The development of a katabatic boundary layer can decouple near surface air temperature changes over glaciers from their surrounding environment during the ablation season, impacting the response of glaciers to ongoing climate change. Current glacier modelling efforts mostly neglect such processes and assume that glacier mass balance will evolve linearly with large-scale (ambient) air temperature changes into the future. Recent work has established that glacier evolution with climate will likely be non-linear, including in its sensitivity to ambient temperature. While past studies have explored this near-surface decoupling at a number of individual sites, the derived patterns have not been generalisable. We compile an extensive new inventory of on-glacier weather station data to explore this phenomena, with over 175 glacier-year sets, including more than 350 individual AWS locations and > 1.3 million hourly air temperature observations. Combining in situ on-glacier and near-glacier meteorological data with reanalysis and surface topography information we are able to explore how the climatic setting and local processes (e.g. wind interactions and local topography) may shape a glacier’s ability to become more or less coupled to the ambient climatic warming. Across all sites studied we find a mean (std.) cold bias of on-glacier vs. ambient temperatures of 1.22±1.35°C and a ratio of above-ice temperature changes compared to ambient, non-glacier conditions of 0.75±0.17 (i.e. a 1°C increase off-glacier equals ~0.75°C change on-glacier). We highlight the relevance of this to glacier modelling applications at select glacier sites and demonstrate hotspots around the world where above-glacier temperature changes during the recent decades are likely to have become decoupled from background warming. Preliminary results show how larger glaciers in maritime climates and those with minimal debris cover are most likely to decouple from ambient warming. However, as glaciers shrink and debris cover expands, the influence of the climatic setting in controlling this decoupling is diminished.

How to cite: Shaw, T., Miles, E., Buri, P., McCarthy, M., Guyennon, N., Carturan, L., Salerno, F., and Pellicciotti, F.: Temperature Decoupling on the World’s Mountain Glaciers, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5815, https://doi.org/10.5194/egusphere-egu24-5815, 2024.

EGU24-5843 | ECS | Orals | CR1.1 | Highlight

Irreversible glacier change and trough water for centuries after overshooting the Paris Agreement temperature goal 

Lilian Schuster, Fabien Maussion, Patrick Schmitt, David R. Rounce, Lizz Ultee, Fabrice Lacroix, and Thomas Frölicher

Mountain glaciers significantly impact sea level rise and water availability during droughts. Models project continued glacier mass loss in the 21st century due to past and future rising temperatures. Our study delves into the repercussions of overshooting the 1.5°C Paris Agreement target and returning to it afterwards. For the first time, we explore the effects of these peak-and-decline overshoot scenarios on glacier volume and runoff using the Open Global Glacier Model (OGGM) framework. We apply novel climate simulations from 2000 to 2500  conducted with a  comprehensive  Earth System Model. These simulations either stabilise at global warming levels of 1.2°C (current warming), 1.5°C and 3°C, or temporally overshoot 1.5°C peaking at 3°C before declining and stabilising at 1.5°C after 2300. Although some glacier regions regrow within a century after the overshoot, the slow global glacier response results in irreversible ice loss over centuries. In 2500, overshooting the 1.5°C scenario temporarily by a peak at 3°C results in 10% more global glacier loss than directly stabilising at 1.5°C. While glacier runoff may temporarily increase in some basins in the coming decades, all basins will see a reduced contribution of glacier runoff to streamflow by the end of the 22nd century under global stabilisation scenarios at 2°C or higher. In regions where glaciers regrow within the simulation period to reach a new equilibrium after a temporal temperature overshoot, glacier runoff contribution reduces temporally further than if temperature stabilises ("trough water"). The consequences of this newly documented "trough water" will depend on local conditions such as the local temperature overshoot magnitude, volume response time, future precipitation shifts, and melt versus precipitation seasonality. This study lays the first conceptual groundwork for overshoot scenarios on glaciers and introduces the potential of trough water risks. Additional Earth System Model realisations are needed for a detailed regional analysis and adaptation planning.

How to cite: Schuster, L., Maussion, F., Schmitt, P., Rounce, D. R., Ultee, L., Lacroix, F., and Frölicher, T.: Irreversible glacier change and trough water for centuries after overshooting the Paris Agreement temperature goal, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5843, https://doi.org/10.5194/egusphere-egu24-5843, 2024.

EGU24-6253 | Orals | CR1.1

Local cooling and drying induced by Himalayan glaciers under global warming 

Franco Salerno, Nicolas Guyennon, Kun Yang, Thomas E. Shaw, Changgui Lin, Nicola Colombo, Emanuele Romano, Stephan Gruber, Tobias Bolch, Andrea Alessandri, Paolo Cristofanelli, Davide Putero, Guglielmina Diolaiuti, Gianni Tartari, Sudeep Thakuri, Evan S. Miles, Sara Bonomelli, and Francesca Pellicciotti

Understanding the response of Himalayan glaciers to global warming is vital because of their role as a water source for the Asian subcontinent. However, great uncertainties still exist on the climate drivers of past and present glacier changes across scales. Here, we analyse continuous hourly climate station data from a glacierized elevation (Pyramid station, Mount Everest) since 1994 together with other ground observations and climate reanalysis. We show that a decrease in maximum air temperature and precipitation occurred during the last three decades at Pyramid in response to global warming. Reanalysis data suggest a broader occurrence of this effect in the glacierized areas of the Himalaya. We hypothesize that the counterintuitive cooling is caused by enhanced sensible heat exchange and the associated increase in glacier katabatic wind, which draws cool air downward from higher elevations. The stronger katabatic winds have also lowered the elevation of local wind convergence, thereby diminishing precipitation in glacial areas and negatively affecting glacier mass balance. This local cooling may have partially preserved glaciers from melting and could help protect the periglacial environment (Salerno, Guyennon, et al., 2023).

Salerno, F., Guyennon, N., et al. Local cooling and drying induced by Himalayan glaciers under global warming. Nat. Geosci. 16, 1120–1127 (2023). https://doi.org/10.1038/s41561-023-01331-y

How to cite: Salerno, F., Guyennon, N., Yang, K., E. Shaw, T., Lin, C., Colombo, N., Romano, E., Gruber, S., Bolch, T., Alessandri, A., Cristofanelli, P., Putero, D., Diolaiuti, G., Tartari, G., Thakuri, S., Miles, E. S., Bonomelli, S., and Pellicciotti, F.: Local cooling and drying induced by Himalayan glaciers under global warming, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6253, https://doi.org/10.5194/egusphere-egu24-6253, 2024.

EGU24-6780 | ECS | Posters on site | CR1.1

Effect of climate policies on the long-term equilibration of glaciers 

Harry Zekollari, Lilian Schuster, Regine Hock, Ben Marzeion, Fabien Maussion, and the GlacierMIP3 participants

Glaciers adapt to changing climatic conditions by losing or gaining mass, translating into a geometry change. Due to ice-dynamical processes within glaciers that gravitationally transport mass from high to low elevation, the adaptation of the glacier geometry to changing climatic conditions is not immediate but requires timescales ranging from decades up to millennia. As a consequence, today glaciers are in imbalance with current climatic conditions and will respond on timescales that extend beyond the 21st century time horizon that is typically considered in today’s glacier evolution studies.

As part of the Glacier Model Intercomparison Project – Phase 3 (GlacierMIP3), a global glacier modelling community effort, we quantify how glaciers will stabilize under a wide range of climatic conditions. Using 8 large-scale glacier models, we estimate the committed loss of all glaciers on Earth outside the ice sheets under current climate conditions (corresponding to +1.2°C above pre-industrial levels) and their long-term stabilization under various policy-relevant global warming scenarios, such as +1.5°C and +2°C (Paris agreement), and the projected warming following current policies (+2.7°C). The forcing is derived from historical and future simulations (3 SSP emission scenarios) from 5 GCMs, from which climatic conditions for given time periods are continuously repeated over millennial time scales, leading to an eventual glacier stabilization.

 

We find that the committed glacier loss is substantial, with about one third of global glacier volume to be lost under current climatic conditions. The final (steady state) global glacier volume strongly depends on future temperatures, with an increase in the order of 2-3% of global glacier loss per 0.1°C warming. We also evaluate regional differences and quantify the time scales involved in glacier stabilization. Here we find that the topographical features such as the elevation range and the surface slope of glaciers play an important role.

How to cite: Zekollari, H., Schuster, L., Hock, R., Marzeion, B., Maussion, F., and GlacierMIP3 participants, T.: Effect of climate policies on the long-term equilibration of glaciers, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6780, https://doi.org/10.5194/egusphere-egu24-6780, 2024.

EGU24-7118 | ECS | Posters on site | CR1.1

Quantifying runoff variability and Glacier thickness variations from 2011 to 2020 in Gangotri glaciated region, India 

Japjeet Singh, Vishal Singh, and Chandra Shekhar Prasad Ojha

Recent research indicates a substantial reduction in glacier mass within the Himalayas, primarily attributed to rising temperatures, leading to heightened uncertainties regarding downstream water availability. This study specifically investigates the impact of variations in thickness within the Gangotri glaciers, focusing on the Raktavaran and Chaturangi regions, during the period from 2011 to 2020. Employing a two-model coupling approach, the study integrates Glacier Bed Topology (GlabTop2) and Spatial Process in Hydrology (SPHY). Calibration is meticulously carried out through a two-step process, incorporating observed discharge data and Moderate Resolution Imaging Spectroradiometer (MODIS) snow cover information. The achieved R2 values for SPHY-modeled runoff (Q) and observed Q at Bhojwasa exhibit a commendable level of comparability, standing at approximately 0.73 on a daily scale. The analysis highlights that glacier-derived Q contributes to 22.11% of the total Q, with snow-derived Q accounting for 66.91%, underscoring their distinct roles in the hydrological system. A comparative assessment between Chaturangi and Raktavaran with the Gangotri glaciers reveals that the latter experienced a more substantial rate of thickness change, resulting in an estimated reduction of about 9.40% in mean glacier thickness over the period from 2011 to 2020. In consideration of these findings, the study emphasizes the urgent necessity for a comprehensive understanding of the intricate interplay between glacier dynamics and hydrological processes within the context of changing climatic conditions. This research contributes valuable insights that can serve to inform adaptive strategies and resource management practices aimed at addressing the evolving challenges posed by glacier melt and its downstream implications.

How to cite: Singh, J., Singh, V., and Ojha, C. S. P.: Quantifying runoff variability and Glacier thickness variations from 2011 to 2020 in Gangotri glaciated region, India, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7118, https://doi.org/10.5194/egusphere-egu24-7118, 2024.

EGU24-7454 | ECS | Posters on site | CR1.1

Ablation drivers over a cold-based ice cap in the Eastern Alps: a surface energy balance analysis 

Anna Baldo, Lindsey Nicholson, Lea Hartl, and Martin Stocker-Waldhuber

Glaciers are archives of past climatic conditions, reflected in the yearly amount of ice accumulation or depletion. Ice coring allows access to the information stored in glacial layers. However, discontinuities in an ice core create problems in reliably dating the core layers and questions regarding the origin of the discontinuity.

The analysis of an ice core from 2017 on Weißseespitze, a cold-based ice cap located at 3498 m a.s.l. in Tyrol (Austria), could be explained by the presence of a discontinuity around 400 CE. Since the glacier is nowadays experiencing potentially similar mass loss conditions, this study analyses present day surface energy balance to identify the potential climatic drivers behind the supposed discontinuity.

Energy balance at the core site is modelled with the COupled Snowpack and Ice surface energy and mass balance model in Python (COSIPY), forced with data collected between 2017 and 2022 by an automatic weather station on the glacier. COSIPY initialisation was optimised by comparing modelled and observed snowheight, the observed albedo was introduced as an input variable and the precipitation input was modified to better suit high altitude locations.

Comparison of the modelled and observed snowheight shows minor mismatches, connected in part to the absence of a wind erosion parameterization in the model and in part to the overestimation of surface temperature from the energy balance optimization algorithm. Nevertheless, COSIPY ice melt gradient agrees very well with observations and the simulation of the ablation season is not deeply affected by such problems.

Weißseespitze lost on average about 3 m of ice at the summit since 2018. The summer characterised by maximum ice melt in the observational period was 2022, where ablation stakes recorded on average 1.5 m of ice loss. On the contrary, summer 2020 was the only summer where most of the summit registered no ice loss. Comparison of energy balance components between the summer 2022 and 2020 showed that 2022 was characterised by positive and more intense sensible (9.8 W m-2 vs 5.8 W m-2) and latent (1.0 W m-2 vs -1.0 W m-2) heat fluxes and a lower outgoing shortwave energy flux (118.8 W m-2 vs 166.1 W m-2). The latter is caused by an abrupt albedo lowering at the beginning of July, which aligns with a period of uninterrupted positive air temperature of almost two weeks removing the snow from the previous winter. Therefore, air temperature and its impact on the glacier surface seems to be the main driver of ablation in 2022, which had about 20 positive temperature days more than 2020, resulting in an average air temperature 1.2 °C warmer.

These preliminary results will be shortly complemented by research in local archives of paleotemperature to verify whether the time of the hypothesised discontinuity was characterised by similar conditions.

How to cite: Baldo, A., Nicholson, L., Hartl, L., and Stocker-Waldhuber, M.: Ablation drivers over a cold-based ice cap in the Eastern Alps: a surface energy balance analysis, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7454, https://doi.org/10.5194/egusphere-egu24-7454, 2024.

EGU24-8079 | ECS | Posters on site | CR1.1

Global glacier climate disequilibrium from modelling steady state AAR 

Weilin Yang, Wenchao Chu, Yingkui Li, and Andrew Mackintosh

Most glaciers and ice caps (GIPs) are out of balance with the current climate, exhibiting continuous retreat and thinning. These changes impact regional runoff and contribute to sea level rise, causing glacier-related hazards. In this study, we estimate the area and volume losses for current GIPs to reach equilibrium through modelling the steady state accumulation area ratios (AAR0) and time-averaged AAR of each GIP. The modelled global average AAR0 is 0.541 ± 0.082, which is lower than most previous studies due to the inclusion of numerous unobserved GIPs. Ice caps exhibit a higher AAR0 (0.612 ± 0.11) compared to glaciers (0.538 ± 0.08). For regional distribution, the largest AAR0 appears in northern Arctic Canada (0.608 ± 0.114) and low latitude areas (0.570 ± 0.067), while the smallest AAR0 occurs in Central Europe (0.519 ± 0.066) and north Asia (0.522 ± 0.071). Accounting for debris-cover reveals a decrease in AAR0 due to reduced sub-debris melting, while considering the frontal ablation of marine-terminating glaciers leads to an increase in AAR0. Assessing the imbalance between global GIPs and the current (2000-2019) climate, we project an additional loss of 23 ± 6% in area and 29 ± 8% in volume. This corresponds to a sea level rise equivalent of 128 ± 34 mm. The Antarctic and subantarctic are the primary contributor to global mean sea level rise, accounting for 60 ± 20 mm. The GIPs in central and eastern Himalaya, as well as the Mt. Hengduan exhibit significant instability, characterized by an average imbalance ratio (AAR/AAR0) of 0.72 ± 0.25.

How to cite: Yang, W., Chu, W., Li, Y., and Mackintosh, A.: Global glacier climate disequilibrium from modelling steady state AAR, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8079, https://doi.org/10.5194/egusphere-egu24-8079, 2024.

EGU24-8481 | Orals | CR1.1

Observed weakening of glacier ice-bed interface caused by climatic and hydro-mechanical feedbacks: towards glacier-wide acceleration? 

Thomas Vikhamar Schuler, Ugo Nanni, Coline Bouchayer, Henning Åkesson, Pierre-Marie Lefeuvre, Erik Mannerfelt, Andreas Köhler, Louise Steffensen Schmidt, John Hulth, and Francois Renard
 
Stronger and more widespread surface melt may alter the flow of glaciers and ice sheets and trigger instability. However, observational deficiencies hamper our ability to better understand and thus predict such responses. We deployed surface and borehole seismometers along the centerline of a High Arctic glacier in Svalbard. The records span over six years and are analyzed in relation to the measured increase of surface velocity. We complement our seismic analysis (icequakes and seismic noise) with long-term measurements of glacier-surface velocity, surface-elevation changes, and runoff modeling. Since 2000, we observe glacier thinning and steepening, coinciding with acceleration of up to 1000%. In response, new crevasses have opened and provide access pathways for surface melt water to the base of the glacier, affecting the ice-bed coupling. This mechanism represents a positive hydro-mechanical feedback that fuels further acceleration and crevassing. This feedback may have wider implications for triggering of glacier-wide instabilities, increasing short-term sea-level rise and local hazards. Beyond the Arctic, we suggest that, under a warming atmosphere, glaciers may transition from stable to unstable flow through such a mechanism.
 

 

How to cite: Schuler, T. V., Nanni, U., Bouchayer, C., Åkesson, H., Lefeuvre, P.-M., Mannerfelt, E., Köhler, A., Schmidt, L. S., Hulth, J., and Renard, F.: Observed weakening of glacier ice-bed interface caused by climatic and hydro-mechanical feedbacks: towards glacier-wide acceleration?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8481, https://doi.org/10.5194/egusphere-egu24-8481, 2024.

EGU24-8865 | ECS | Posters on site | CR1.1

 Estimation of Snow Line Altitude Utilising Satellite Imagery of Alpine Glaciers 

Sobia Ayub, Carlo Camporeale, Luca Ridolfi, Erika Coppola, and Alberto Godio

Mountain glaciers form a critical component of the cryosphere and are sensitive to climate change. Snow
line altitude (SLA) at the end of the ablation season is an indicator of climate change and a proxy for
equilibrium line altitude (ELA). Here, we compute SLA by incorporating satellite imagery of 38 years
(1984-2022) through mapping snow and ice over the elevation. A digital elevation model is being utilized to
derive SLA over a period of time. This proxy database is quite useful in various glacier dynamics estimated
through numerical modelling such as mass balance reconstruction, thickness gradient, or glacier length
estimation. The study explores various techniques to estimate the snow and glacier cover area (Otsu, k-
means) apart from manual thresholding. Furthermore, the study also includes glacier surface shape changes
to reduce the occurrence of misclassification. We further evaluate the performance of these techniques,
however, each one has its own redundancies. In the case of Otsu image segmentation, the errors are quite eminent
as the technique does not take into account the variation in glacier dimensions. The results are better in
terms of classification in the case of manual thresholding but the whole process is quite cumbersome. In
the case of K-means, the clustering algorithm takes into account the glacier dynamics which improves the
classification but the technique does not work well in the case of large datasets. Furthermore, for validation,
Careser glacier is being considered as it has the longest monitored observational dataset in the Italian Alps.
The results are mostly in alignment with the observed dataset, particularly for years where the Sentinel
dataset is available. The SLA seems to depict a descending trend in the case of Careser in recent years.
However, this recent behavior further needs to be evaluated. The algorithm is then further applied to the
glaciers of Aosta Valley.

How to cite: Ayub, S., Camporeale, C., Ridolfi, L., Coppola, E., and Godio, A.:  Estimation of Snow Line Altitude Utilising Satellite Imagery of Alpine Glaciers, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8865, https://doi.org/10.5194/egusphere-egu24-8865, 2024.

EGU24-8944 | ECS | Orals | CR1.1 | Highlight

Global ice-thickness inversion using a deep-learning-aided 3D ice-flow model with data assimilation 

Samuel Cook, Guillaume Jouvet, Romain Millan, Antoine Rabatel, Fabien Maussion, Harry Zekollari, and Inès Dussaillant

Mountain glaciers are a major source of sea-level rise and also represent an important freshwater resource in many mountainous regions. Thus, accurate estimations of their thickness and, therefore, the total ice volume are important both in predicting and mitigating the global and local effects of climate change. However, to date, only 2% of the world’s glaciers outside the ice sheets have any thickness observations, due to the logistical difficulties of obtaining such measurements, creating a large and policy-relevant scientific gap.

The recent development of a global-scale ice-velocity dataset, however, provides an ideal opportunity to fill this gap and determine ice thickness across the 98% of glaciers for which no thickness data is available. This can be done by inverting an ice-dynamics model to solve for ice thickness. For accurate thickness results, this needs to be a higher-order model, but such a model is far too computationally cumbersome to apply on a global scale, and simpler, quicker methods usually based on the shallow ice approximation (SIA) are unsuitable, particularly where sliding dominates glacier motion. The only attempt that has been made to leverage the global velocity dataset to retrieve ice thickness has, though, used the SIA, simply because higher-order approaches are not computationally realistic at this scale. Consequently, most of the widely-used global glacier models have made no systematic attempt to invert global ice thickness, owing to these limitations. Allied to this is that, once an inversion is done, subsequent forward modelling is rarely physically consistent with the physics used in the inversion, leading to model inconsistencies that affect the accuracy of simulations.

As a solution to these problems, we extend our recent work on the European Alps using a deep-learning-driven inversion model, the Instructed Glacier Model (IGM), that emulates the performance of state-of-the-art higher-order models at a thousandth of the computational cost. This model, by solving a multi-variable optimisation problem, can fully use and assimilate all available input datasets (surface velocity and topography, ice thickness, etc.) as components of its cost function to invert ice thickness. This approach also gives us the possibility of using consistent ice-flow physics for inversion and forward modelling, reducing the magnitude of the shock inherent in traditional modelling approaches. We present here the first results of glacier-ice-thickness inference at a global scale obtained by the inversion of a higher-order three-dimensional ice-flow model.

How to cite: Cook, S., Jouvet, G., Millan, R., Rabatel, A., Maussion, F., Zekollari, H., and Dussaillant, I.: Global ice-thickness inversion using a deep-learning-aided 3D ice-flow model with data assimilation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8944, https://doi.org/10.5194/egusphere-egu24-8944, 2024.

EGU24-9185 | ECS | Posters on site | CR1.1

Seasonal speedup of glacier in the southeastern Tibetan Plateau 

Tianzhao zhang, Wei Yang, and Shaoting Ren

Most glaciers around the world are slowing down, but some marine-terminating outlet glaciers occur and trigger seasonal or shorter-term accelerations (up to 100% greater than the annual mean), and the speedup events of glaciers cause accelerated glacier loss. Although some speedup events have been observed in the Greenland and Antarctica, limited observed in the Tibetan Plateau and the trigger mechanism is also poorly understood. In this study, we used the high-frequency Global Navigation Satellite System (GNSS) observations collected on the Parlung No.4 Glacier in southeastern Tibetan Plateau in 2022 to characterize the seasonal dynamics of glacier velocity and analyze its mechanism. The results show that the velocity has a distinct seasonal variation, with highly fast in summer (1.42 times as fast as winter flow). A total of 9 speedup events were observed in spring and summer, with 3 GNSS stations simultaneously generating 5 acceleration events; the glacier accelerated frequently from 25 June to 3 July, with a total of 3 speedup events; with the maximum intensity occurred at the end of July, which was about 10 times as fast as others. In addition, we find that the speedup of the glacier is mainly consistent with precipitation and the glacial runoff, and we suggest that the speedup of the glacier is mainly due to enhanced meltwater leading to glacier basal motion.

How to cite: zhang, T., Yang, W., and Ren, S.: Seasonal speedup of glacier in the southeastern Tibetan Plateau, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9185, https://doi.org/10.5194/egusphere-egu24-9185, 2024.

EGU24-9831 | ECS | Orals | CR1.1

Unravelling the sources of uncertainty in glacier runoff in the Patagonian Andes (40–56° S)  

Rodrigo Aguayo, Fabien Maussion, Lilian Schuster, Marius Schaefer, Alexis Caro, Patrick Schmitt, Jonathan Mackay, Lizz Ultee, Jorge Leon-Muñoz, and Mauricio Aguayo

Glaciers are retreating globally and are projected to continue to lose mass in the coming decades, directly affecting downstream ecosystems through changes in glacier runoff. Estimating the future evolution of glacier runoff involves several sources of uncertainty in the modelling chain, which have not been comprehensively assessed on a regional scale. In this study, we used the Open Global Glacier Model (OGGM) to estimate the evolution of each glacier (area > 1 km2) in the Patagonian Andes (40–56° S), which together represent 82% of the glacier area of the Andes. We used different glacier inventories (n = 2), ice thickness datasets (n = 2), historical climate datasets (n = 4), general circulation models (GCMs; n = 10), emission scenarios (SSPs; n = 4), and bias correction methods (BCMs; n = 3) to generate 1,920 possible scenarios over the period 1980–2099. For each scenario and catchment, glacier runoff and melt time series were characterised by ten glacio-hydrological metrics. We used the permutation feature importance of random forest regression models to assess the relative importance of each source on the metrics of each catchment. Considering all scenarios, 30% ± 13% of the glacier area has already peaked in terms of glacier melt (year 2020), and 18% ± 7% of the glacier area will lose more than 80% of its volume this century. In terms of glacier melt metrics, future sources of uncertainty (GCMs, SSPs and BCMs) were the main source for only 18% ± 21% of the total glacier area. In contrast, the reference climate was the main source in 78% ± 21% of the glacier area, highlighting the importance of the choices we made in the calibration procedure. The results provide a basis for prioritising future efforts to reduce glacio-hydrological modelling gaps in poorly instrumented regions, such as the Patagonian Andes.

How to cite: Aguayo, R., Maussion, F., Schuster, L., Schaefer, M., Caro, A., Schmitt, P., Mackay, J., Ultee, L., Leon-Muñoz, J., and Aguayo, M.: Unravelling the sources of uncertainty in glacier runoff in the Patagonian Andes (40–56° S) , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9831, https://doi.org/10.5194/egusphere-egu24-9831, 2024.

EGU24-10112 | ECS | Orals | CR1.1

Poleward shift of the subtropical highs drives Patagonian ice fields mass loss 

Brice Noël, Michiel van den Broeke, Stef Lhermitte, Bert Wouters, and Xavier Fettweis

The Patagonian ice fields have been rapidly losing mass in the last decades, but little is known about the driving processes. Here we use state-of-the-art regional climate models to reconstruct the contemporary climate and glacier surface mass balance (SMB), i.e., the difference between snowfall accumulation and meltwater runoff, in the Southern Andes at 5 km spatial resolution for the period 1940-2022. Model outputs are further statistically downscaled to a 500 m grid that resolves SMB processes in high spatial detail. Our high-resolution SMB products show good agreement with both in-situ observations and GRACE/GRACE-FO satellite mass change measurements, when combined to solid ice discharge. We link recent glacier mass loss to an ongoing poleward shift of the subtropical highs that warms the ocean and atmosphere nearby Patagonian ice fields, in turn enhancing meltwater runoff.

How to cite: Noël, B., van den Broeke, M., Lhermitte, S., Wouters, B., and Fettweis, X.: Poleward shift of the subtropical highs drives Patagonian ice fields mass loss, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10112, https://doi.org/10.5194/egusphere-egu24-10112, 2024.

EGU24-11243 | ECS | Posters on site | CR1.1

Surface Mass Balance of the Cordillera Darwin Icefield, Tierra del Fuego, Chile 

Franziska Temme, Christian Sommer, and Johannes J. Fürst

The Cordillera Darwin Icefield (CDI) in Tierra del Fuego is the third-largest temperate icefield in the southern hemisphere, covering an area of 2606 km2 and storing at least twice the ice volume of the European Alps. More than half of the CDI glaciers are in direct contact with proglacial lakes or fjords, making them susceptible to both climatic surface mass change and ice-dynamic adjustments. Remote sensing studies have observed important mass losses in the region over the last decades. Despite the overall glacier retreat, individual glaciers show contrasting behavior, with some maintaining stable conditions or even thickening and advances, particularly in the central and southern part of the CDI. Associating the recent developments with atmospheric changes is challenging as in-situ observations of climatic conditions and glacier mass balance are scarce due to the harsh weather conditions and the difficult accessibility of the area.

We aim for generating a first, high-resolution simulation of surface mass balance for the entire CDI over the last two decades (2000-2022). Comprising all mass gain and loss terms at the surface, the surface mass balance is ultimately tied to robust high-resolution information on the atmospheric conditions. We will employ state-of-the-art statistical downscaling of atmospheric variables, paying special attention to downscaling of precipitation and the orographic effects over the high relief terrain. Moreover, climate conditions in Southern Patagonia are characterized by strong, year-round westerly winds, leading to efficient snow drift and increased spatially heterogeneity of snow deposition.

The results of our study will enable us to analyze variations in surface mass balance across space and time in the CDI. The key objective is to reliably disentangle the climatic imprint on glacier mass loss in the Cordillera Darwin for the last two decades. This climatic attribution is unprecedented and a unique opportunity to study the effects of climate variability and change in the higher mid latitudes of the southern hemisphere. Mass budgeting with remotely sensed mass balance observations will finally allow to derive a first estimate of frontal ablation and thus ice-dynamic controls on glacier changes in the CDI.

How to cite: Temme, F., Sommer, C., and Fürst, J. J.: Surface Mass Balance of the Cordillera Darwin Icefield, Tierra del Fuego, Chile, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11243, https://doi.org/10.5194/egusphere-egu24-11243, 2024.

EGU24-12014 | ECS | Orals | CR1.1 | Highlight

The dark zone of an alpine glacier - considering albedo impacts of firn loss 

Lea Hartl, Martin Stocker-Waldhuber, Federico Covi, Anna Baldo, and Kathrin Naegeli

As the decline of alpine glaciers continues and accelerates, many glaciers are losing their firn area. Former accumulation zones are increasingly seeing melt conditions and mass loss. The loss of brighter snow and firn surfaces lowers albedo locally and at the glacier scale, impacting surface energy balance and leading to an albedo-mass balance feedback effect.

We assess the recent progression of firn loss into the (former) accumulation zone of Gepatschferner, Austria, focusing particularly on ice surfaces that have newly become exposed. Broadband albedo in the visible and near-infrared generally shows an altitudinal gradient in early summer from the darker, bare-ice glacier tongue to the snow covered region at higher elevations. As the melt season progresses and ablation of multi-year firn at higher elevations begins, albedo decreases substantially in areas that lose their firn cover. We find that these areas can become darker than ice in the ablation zone where no firn was present in previous years. In the extreme summer of 2022, the glacier surface of Gepatschferner was darkest in parts of the former accumulation zone where the firn-line shifted upwards. Newly exposed ice surfaces formed a “dark zone” between the remaining firn and previously exposed bare-ice areas. This zone of minimal albedo at relatively high elevations of the glacier persisted until the first snow falls in autumn and reemerged during the 2023 ablation season. 

Time series of satellite imagery show melt patterns as well as trends and variability of homogenized broadband albedo in the study region. In addition to remote-sensing based observations, multiple in-situ datasets are available for the summit region of Gepatschferner (i.e. on-ice weather station, ablation stakes, automatic camera, ice thickness measurements). Combining these datasets provides a unique opportunity to explore the impact of firn loss and albedo decrease on energy and mass balance, generate calibration and validation data for point scale and distributed modeling, and generally improve understanding of processes related to firn loss at different spatial and temporal scales. However, each observational dataset comes with uncertainties related to the scale and method of observation and the parameter being observed. Leveraging the potential of the rich available data basis requires careful consideration of the characteristics of the different data types and, when combined with energy and mass balance modeling approaches, the forcing requirements of the model. We present preliminary results from a project addressing the above for Gepatschferner and hope to connect with the community regarding the observation, modeling, and impacts of darkening mountain glaciers.

How to cite: Hartl, L., Stocker-Waldhuber, M., Covi, F., Baldo, A., and Naegeli, K.: The dark zone of an alpine glacier - considering albedo impacts of firn loss, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12014, https://doi.org/10.5194/egusphere-egu24-12014, 2024.

EGU24-12396 | ECS | Posters on site | CR1.1

Reanalysis of the surface mass balance of Mittivakkat Gletsjer (Southeast Greenland): Synthesizing data sources 

Christoph Posch, Simon de Villiers, Niels Tvis Knudsen, Jacob Clement Yde, Anders Anker Bjørk, Wolfgang Schöner, Jakob Abermann, and Kamilla Hauknes Sjursen

The contribution of Arctic glaciers and ice caps (GICs) to sea level rise in the last decades was similar to that of the Greenland Ice Sheet, however, their mass loss per unit area was larger. Between 2006 and 2015, mass changes were largest for GICs in Greenland when compared to other regions in the Arctic. Mittivakkat Gletsjer (Southeast Greenland) has the longest surface mass balance (SMB) record from field-based observations (since 1995/1996) for peripheral Greenland and is significantly out of balance with the current climate. Synthesizing ablation stake records (glaciological SMB), 1 km-downscaled RACMO 2.3p2 SMB output (modelled SMB) and volume changes from photogrammetrically-derived digital elevation models (geodetic MB) indicate a change from an almost balanced state for 1959-1995 to a negative mass balance regime for 1996-2022. RACMO is a regional atmospheric climate model forced by meteorological (reanalysis) data and estimates SMB from multi-layer snow cover simulations and albedo scheme. The model output shows SMB to be between 0.10 ± 0.14 m w.e. yr-1 and -0.56 ± 0.14 m w.e. yr-1 for the periods 1959-1995 and 1996-2022, respectively. The modelled SMB for the latter period is contrasted by the glaciological SMB of -1.06 ± 0.16 m w.e. yr-1 for 1996-2022. The model output allows for assessing monthly and elevation-dependent changes in SMB between 1959-1995 and 1996-2022. Most months experienced a reduction in specific SMB with highest decreases in Jul (-0.19 m w.e.), Jun (-0.15 m w.e.) and Aug (-0.14 m w.e.), but Apr and Dec experienced no change (0.00 m w.e.) or an increase (0.10 m w.e.), respectively. The equilibrium line altitude increased from 600-650 to 800-850 m a.s.l., while there was a SMB decrease at each of the 11 altitude sections between 300-950 m a.s.l ranging from -0.59 to -0.70 m w.e yr-1. The modeled SMB correlates well with the glaciological SMB (R2 = 0.74; p < 0.01) but underestimates the glacier-wide mass loss by 47 % in the overlapping period.   The geodetic MB yields estimates of -0.73 ± 0.20 m w.e. yr-1 for 1981-2013 (modelled SMB: -0.33 ± 0.14 m w.e. yr-1) and -1.41 ± 0.76 m w.e. yr-1 for 2014-2021 (modelled SMB: -0.59 ± 0.14 m w.e. yr-1; glaciological SMB:  -1.15 ± 0.17 m w.e. yr-1).  These differences highlight the challenges of synthesizing results of different mass balance methods such as spatial coverage, density assumptions, data quality, scaling and spatial extrapolation. We ran different configurations for the geodetic and modelled SMB outputs with varying agreement. The change to a more negative regime in the mid-1990s is discussed in the context of climate indices and are in line with modelled and ablation stake SMBs being negative in 24 out of 27 years between 1996 and 2022. The three years with a slightly positive balance can be associated with unusually high winter precipitation.

How to cite: Posch, C., de Villiers, S., Knudsen, N. T., Yde, J. C., Bjørk, A. A., Schöner, W., Abermann, J., and Sjursen, K. H.: Reanalysis of the surface mass balance of Mittivakkat Gletsjer (Southeast Greenland): Synthesizing data sources, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12396, https://doi.org/10.5194/egusphere-egu24-12396, 2024.

EGU24-12488 | ECS | Orals | CR1.1

Distributed surface mass balance of the avalanche-fed Argentière glacier, French Alps 

Marin Kneib, Amaury Dehecq, Adrien Gilbert, Auguste Basset, Evan S. Miles, Etienne Ducasse, Luc Béraud, Jérémie Mouginot, Jérémie Mouginot, Guillaume Jouvet, Olivier Laarman, Bruno Jourdain, Fanny Brun, and Delphine Six

Avalanches are important contributors to the mass balance of glaciers located in mountain ranges with steep topographies. They result in localized mass inputs that are particularly difficult to quantify, due to the difficulty to access these avalanche cones in the field, and the need to account for ice dynamics when analyzing the elevation change signals from digital elevation models. Here, we aim to quantify the avalanche contribution to Argentière Glacier (Mont Blanc massif, French Alps) by inverting its distributed surface mass balance from remote sensing products and modeled ice thicknesses. Ultimately, we run the full-Stokes model Elmer-Ice with and without the additional contribution from avalanches to evaluate the importance of accounting for this process for future simulations of glacier evolution.

We used Pléiades satellite stereo acquisitions, captured at a high temporal resolution (more than 2 acquisitions per year), to generate detailed maps of elevation change and velocity spanning the years 2012 to 2021. We derived the distributed ice thickness of the glacier using three models of varying complexity, constrained by a dense array of ground penetrating radar measurements. To account for the uncertainty in ice thicknesses, we perturbed the modelled thicknesses using sequential gaussian simulations. We then combined ice thickness and velocity to derive the distributed flux divergence and surface mass balance at 20 m resolution across the whole glacier, carefully accounting for the uncertainties following a Monte Carlo approach. We evaluated our results against long-term mass balance measurements from stakes conducted as part of the French glacier monitoring service GLACIOCLIM, and in situ measurements of submergence on one of the main avalanche deposits.

There is a good agreement between our surface mass balance estimates and the stake observations (RMSE < 1.5 m.w.eq) for all ice thickness scenarios, even though ice thickness represents the most important source of uncertainty. Thus, the comparison of our distributed surface mass balance estimate with the mass balance gradient derived from the stake measurements allows us to 1) highlight the ability and potential of such an approach to provide robust estimates of distributed surface mass balance and 2) estimate the contribution of avalanches for Argentière Glacier with a relatively high accuracy. Notably, preliminary results show that the mass balance in avalanche-fed areas of the accumulation zone is approximately 2-10 times larger than in other areas at the same elevation.

How to cite: Kneib, M., Dehecq, A., Gilbert, A., Basset, A., Miles, E. S., Ducasse, E., Béraud, L., Mouginot, J., Mouginot, J., Jouvet, G., Laarman, O., Jourdain, B., Brun, F., and Six, D.: Distributed surface mass balance of the avalanche-fed Argentière glacier, French Alps, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12488, https://doi.org/10.5194/egusphere-egu24-12488, 2024.

EGU24-12617 | ECS | Posters on site | CR1.1

Do Grenzgletscher's Dynamics Shift? Insights from Terrestrial Radar Interferometry and Comparative Analyses 

Leah Sophie Muhle, Christian Thomas Wild, Reinhard Drews, and Elisa Mantelli

We present surface velocity maps of Grenzgletscher (Swiss Alps) obtained by terrestrial radar interferometry and compare them to velocity maps derived in earlier field campaigns to examine changes over time. To obtain recent velocity maps, we installed a Gamma Portable Radar Interferometer (GPRI) near Rotenboden Station facing the Grenzgletscher and collected data for five days in October 2023 with a three-minute sampling interval. From the resulting interferograms, the line-of-sight velocities can be calculated for various time intervals after averaging, which corrects for atmospheric noise. We find high line-of-sight velocities in the area of a steep ice fall, which suggests that the glacier is sliding in this area. We validate with concurrent GPS measurements and compare our velocity maps with those obtained in previous field campaigns, including a similar GPRI survey in 2008 and a survey utilizing unmanned aerial vehicles in 2017. This comparative analysis aims to identify temporal dynamic changes in areas where the various surveys overlap, ranging from sub-daily, to seasonal and yearly time intervals. This work will provide important observational boundary conditions to better understand mechanisms for the onset of basal sliding beneath glaciers in alpine and polar environments.

How to cite: Muhle, L. S., Wild, C. T., Drews, R., and Mantelli, E.: Do Grenzgletscher's Dynamics Shift? Insights from Terrestrial Radar Interferometry and Comparative Analyses, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12617, https://doi.org/10.5194/egusphere-egu24-12617, 2024.

EGU24-12833 | Orals | CR1.1

Western North American and Switzerland glaciers experience unprecedented mass loss over the last three years 

Brian Menounos, Matthias Huss, Shawn Marshall, Mark Ednie, and Caitlyn Florentine

Glaciers in western North America (WNA) and Switzerland represent important sources of freshwater, especially during times of drought. We employ extensive airborne laser altimetry campaigns in WNA coupled with in-situ surface mass balance measurements for both regions to quantify recent mass change. Over the last three years glaciers within these regions respectively lost mass at rates of -22.8±7.4 and -1.7±0.3 Gt yr-1 which, for both regions, represents an approximate twofold increase in mass loss compared to the period 2010-2020. Based on the estimated glacier volume in the year 2020, total volume change in these regions was depleted by 9% (WNA) and 10% (Switzerland) over the last three years. The year 2023 represents the year of greatest common mass loss for both regions where glaciers in both WNA and Switzerland respectively lost -37.1±10.4 and -1.8±0.3 Gt yr-1. Meteorological conditions that favored high rates of mass loss included low winter snow accumulation, early-season heat waves, and prolonged warm, dry conditions. Loss of firn, high transient snow lines, and potential impurity loading due to wildfires (WNA) or Saharan dust (Switzerland) darkened glaciers and thereby accelerated melt via an increase in absorbed shortwave radiation available for melt. This ice-albedo feedback will lead to continued accelerated loss unless recently exposed dark firn and ice at high elevation can be buried by subsequent snowfall. Rates of mass loss for the years 2021-2023 exceed even those projected for unabated global emissions though the twenty-first century, signaling the need to rapidly mitigate greenhouse gas emissions if glaciers in both regions are to survive.   

How to cite: Menounos, B., Huss, M., Marshall, S., Ednie, M., and Florentine, C.: Western North American and Switzerland glaciers experience unprecedented mass loss over the last three years, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12833, https://doi.org/10.5194/egusphere-egu24-12833, 2024.

EGU24-13473 | Orals | CR1.1

Monitoring the physical processes driving the mass loss of Tapado Glacier, Desert Andes of Chile 

Álvaro Ayala, Benjamin Robson, Shelley MacDonell, Gonzalo Navarro, Nicole Schaffer, Alexis Segovia, Michal Petlicki, Christophe Kinnard, Simone Schauwecker, Gino Casassa, Sebastián Vivero, and Augusto Lima

Tapado Glacier (30.15°S, 69.93°W) is a 1.6 km2 ice mass located at high-altitude in Chile’s Desert Andes. This region reaches up to 6000 m a.s.l. and is characterised by high solar radiation and scarce and episodic precipitation. Despite its relatively small size, the glacier extends from 4500 to 5500 m a.s.l and contains several types of surfaces and features, such as a debris-covered section populated by ice cliffs and supraglacial ponds, a field of large snow and ice penitentes, a steep section with crevasses and seracs, and wind-exposed upper areas with minimal snow accumulation. As the ablation and evolution of these elements depend on several physical processes occurring at different rates, monitoring and modelling changes on Tapado Glacier is challenging. Our study describes and quantifies the main glacier changes over the last five years amidst rising summer temperatures and below-average precipitation from a process perspective. Monitoring techniques include direct mass balance and surface geometry measurements, flights of uncrewed aerial vehicles (UAVs), geophysical methods, satellite products, terrestrial LiDAR and automatic cameras.

Enhanced melt at ice cliffs and supraglacial ponds primarily drives ablation in the debris-covered section. Ice cliffs and ponds have persisted on the glacier surface since at least 1955. Satellite products and photogrammetrically derived Digital Elevation Models (DEMs) from UAV flights in the period 2020-2023 show that the ablation over a selected cliff and pond was about 10 times higher than over the rest of the debris-covered section. Analysis of historical satellite imagery tracks the evolution of the selected cliff from its formation between 1978 and 2000 to its recent disappearance in 2023, which was corroborated by an automatic camera. Geophysical measurements suggest the presence of ancient supraglacial lakes within the debris cover. The debris-free section shows consistent patterns of thinning and increasing surface roughness. Terrestrial LiDAR indicates an annual surface lowering of about −0.4 m, while UAV flights and direct observations show that the end-of-summer height of penitentes has increased from 1-2 m to more than 2 m, reaching up to almost 6 m in spots. In the upper parts of the glacier, we have observed increasing instability from a serac that produces frequent ice and rock falls into the penitentes-covered area. Summer ablation at the top of the glacier, mainly by sublimation, varied from 0.15 to 1.15 m during 2021-2023. Using recent data from ablation stakes and UAVs, we estimate a summer glacier mass balance of about −0.8 m w.e., which is equivalent to 1.3 million m3 of water.

Tapado Glacier exemplifies how different physical processes can drive glacier mass loss and runoff contribution. Recent changes in the glacier have made the field monitoring difficult and pose interesting challenges for glacier modelling.

How to cite: Ayala, Á., Robson, B., MacDonell, S., Navarro, G., Schaffer, N., Segovia, A., Petlicki, M., Kinnard, C., Schauwecker, S., Casassa, G., Vivero, S., and Lima, A.: Monitoring the physical processes driving the mass loss of Tapado Glacier, Desert Andes of Chile, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13473, https://doi.org/10.5194/egusphere-egu24-13473, 2024.

Glaciers on Baffin Island present a mixture of abundant small to a few very large ice caps (Barnes, Penny) as well as thousands of valley glaciers, cirques and ice patches. Their large overall area (about 40,000 km2) combined with strong surface melting is responsible for their large contribution to sea-level rise over the past decades. However, area changes over the same time period are largely unknown, as a reliable glacier inventory for the year 2000 has only become available very recently. The previous version suffered from missing glaciers and missing debris cover on glaciers or outlines were outdated and had too large extents.

Here we present the results of a new glacier inventory for the entire region as obtained from Sentinel-2 and Landsat 8/9 satellite images acquired within a few days of August 2019. Although glacier mapping conditions were excellent in regard to seasonal snow, glacier boundaries were often polluted by dark material that was excluded from the applied automated mapping with a band ratio. Hence, all glacier boundaries were checked and manually adjusted when required. To obtain glacier specific area change rates, we used the same revised drainage divides as for the recent year 2000 inventory in RGI 7.0.

Overall, glacier area decreased by 10% from 2000 to 2019 i.e. at a rate of 0.54% per year. Thereby, glaciers <1 km2 contribute 3% to the total area but 13% to the loss, whereas glaciers >10 km2 contribute 70% to the total area and 40% to the loss. The area of Barnes Ice Cap decreased by 1.15%. As in other regions with glaciers, the shrinkage rate and scatter of values increases towards smaller glaciers and several glaciers melted away completely. Also some larger ice caps at low elevations suffered from substantial shrinkage and disintegration by down-wasting. The increasing extent of rock outcrops in the accumulation area of larger glaciers confirm the observed surface lowering over this period.

How to cite: Paul, F. and Rastner, P.: Glacier area changes on Baffin Island from 2000 to 2019 derived from Landsat and Sentinel-2 satellite images, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13526, https://doi.org/10.5194/egusphere-egu24-13526, 2024.

EGU24-14899 | ECS | Orals | CR1.1

Quantifying Basal Melt of Swiss Glaciers 

Leo Hösli, Matthias Huss, Mauro Werder, and Daniel Farinotti

Glaciers retreating due to climate change have significant impacts both locally and globally. An essential part of understanding their evolution are mass balance measurements. Although the surface mass balance of glaciers is well known, non-surface components, more specifically basal and internal melt, are not well understood as they are inherently difficult to observe. Local maxima in basal melt on alpine glaciers are believed to result in the formation of large subglacial cavities, potentially leading to so called “collapse features”. The ice loss caused by these collapse features is likely to impact the retreat dynamics of glaciers.

Using a parameterized model based on a complete consideration of factors of sub- and englacial energy exchange, basal melt for all 1400 Swiss glaciers was estimated. The model operates with data sets on surface mass balance and glacier geometry, as well as with simplified considerations of the relevant processes. Our model considers energy advection through ice-marginal streams and subglacial air flow, potential energy release from melt water, friction-induced heat release, geothermal heat flux and dissipation of heat uptake by surface melt water. Field observations were used to constrain some of the parameters. Additionally, high-resolution aerial imagery and digital elevation models (DEMs) were used to perform a geostatistical analysis to better understand glacio-hydrological relationships and processes. Besides modelling glacier-wide basal melt, we analyzed the spatial and temporal dynamics of individual collapse features on a selected group of glaciers in the Swiss Alps, using high resolution DEMs.

The model results indicate that the advection of energy through ice-marginal streams and potential-energy release from melt water are the primary contributors to basal melt for Swiss glaciers. The relevance of the modelled components importantly varies between glaciers and depends on glacier size and topography among other factors. At the Swiss-wide scale, total basal melt is modelled to be in the range of a few millimeters to several tens of centimeters water equivalent per year (total mass balance of Swiss glaciers is on average -1 meter water equivalent per year). These results suggest that for some glaciers, basal melt is both a relevant fraction of total mass balance, as well as large enough to be measured using high-resolution in situ GNSS observations.

The analysis of glacier collapse features yielded an average life span of 3.5 years and volumes of non-surface ice loss ranging from a few thousand to more than 175’000 m3. These findings, along with the model results, emphasize the substantial role of basal melt in both local retreat dynamics and total glacier-wide mass balance.

How to cite: Hösli, L., Huss, M., Werder, M., and Farinotti, D.: Quantifying Basal Melt of Swiss Glaciers, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14899, https://doi.org/10.5194/egusphere-egu24-14899, 2024.

EGU24-15836 | ECS | Posters on site | CR1.1

The rapid retreat of two lake-terminating outlet glaciers of the Northern Patagonian Ice Sheet and underestimation of mass loss due to subaqueous ice volume 

Pascal Emanuel Egli, Inés Dussaillant, Iñigo Irarrazaval, Marcelo Somos-Valenzuela, Benjamín Sotomayor González, Elizabet Lizama, Bastián Morales, and Joaquín Fernandez

The first-ever field measurements conducted at the outlet glaciers Gualas and Reichert at the Northern Patagonian Ice Sheet, Chile, provide the basis for this work. Both glaciers currently terminate in large (2 km resp. 9 km length) proglacial lakes. The glaciers have retreated rapidly over the past four decades, whereby Reichert glacier retreated by over 100 m per year. Our bathymetry measurements of these lakes make it possible to estimate the mass loss and make assumptions about floatation of these glaciers during retreat. The lakes have depths of up to 250 resp. 350 m and therefore the volume previously occupied by the glaciers is significant.
Recent UAV surveys of the final 3 km of the tongue of both glaciers and satellite data provide high-resolution elevation models and are employed to estimate mass loss since the 2000s. With this preliminary study we aim to investigate whether mass loss of these glaciers has been underestimated due to neglected subaqueous ice mass loss. Knowledge from this study will contribute to improving past, present and future mass change estimates of similar glaciers, with relevance for, e.g., sea level rise contribution from ice sheets and their outlet glaciers.

How to cite: Egli, P. E., Dussaillant, I., Irarrazaval, I., Somos-Valenzuela, M., Sotomayor González, B., Lizama, E., Morales, B., and Fernandez, J.: The rapid retreat of two lake-terminating outlet glaciers of the Northern Patagonian Ice Sheet and underestimation of mass loss due to subaqueous ice volume, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15836, https://doi.org/10.5194/egusphere-egu24-15836, 2024.

EGU24-16009 | ECS | Posters on site | CR1.1

Enhancing Flood Preparedness: Modeling the Shishper glacier's Glacial Lake Outburst Flooding in Pakistan using Satellite Data and 2D Hydraulic Modeling 

Aleš Urban, Falak Naz, Hossein Azadi, Babar Naeem, and Arjumand Zaidi

The Shishper Glacier in Pakistan has caused multiple incidents of glacier lake outburst flooding (GLOF), including recent events that occurred in consecutive years. The presence of an ice-dammed lake created by the Shishper Glacier poses significant risks to communities, infrastructure, and people's livelihoods downstream. To decrease the likelihood of GLOFs associated with the Shishper Glacier, it is important to implement an early warning system and effectively manage the water release from the glacial lake. This study used satellite imageries from Landsat and Sentinel 2, and ALOS 30 m DEM, to analyze the areal and volumetric expansion of glacial lake, formed by the blockade of Mochuwar Glacier by terminus of Shishper Glacier at the point of confluence. This terminus extends further downstream and has been the cause of several GLOF events in past. The Shishper Glacier has recently had many surges, the most recent of which occurred in 2022, 2020, 2019 and 2018. In this study, HEC-RAS 2D model was used to reproduce the Shishper glacier lake outburst flooding (GLOF2022) and assess its impacts on the areas located downstream. The findings of the study will contribute to proactive measures that can prevent future disasters and ensure the safety of the vulnerable population and critical infrastructure. 

How to cite: Urban, A., Naz, F., Azadi, H., Naeem, B., and Zaidi, A.: Enhancing Flood Preparedness: Modeling the Shishper glacier's Glacial Lake Outburst Flooding in Pakistan using Satellite Data and 2D Hydraulic Modeling, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16009, https://doi.org/10.5194/egusphere-egu24-16009, 2024.

EGU24-16092 | ECS | Posters on site | CR1.1

Satellite altimetry derived glacier mass changes over High Mountain Asia during 2003‒2022 

Fanyu Zhao, Di Long, Pengfei Han, Yiming Wang, Yifei Cui, and Xingwu Duan

High Mountain Asia (HMA) is a hotspot for research on global glacier change and its environmental impacts. Over the past few decades, HMA glaciers have undergone relatively slow but accelerating mass loss. However, our current understanding of the inter- and intra- annual variations in these glaciers remains insufficient. In this study, we derived glacier mass changes in HMA at different spatiotemporal scales through the integration of three altimetry products (i.e., ICESat, CryoSat-2, and ICESat-2). We constructed seasonal time series of glacier mass balance in HMA and its subregions and produced multiple elevation change maps for these glaciers over different periods. Our results showed that HMA glaciers experienced heterogeneous glacier ablation with a mean mass loss rate of 26.72 ± 3.30 Gt/yr during 2003 ‒ 2022. Among various subregions, the glaciers in Hengduan Shan experienced the most severe depletion and the most substantial mass loss (3.81 ± 0.47 Gt/yr). The glaciers in Western Himalaya and Eastern Himalaya suffered significant mass loss as well. The melting rate of HMA glaciers over the second decade has significantly accelerated compared to the preceding decade. Furthermore, in 2022, HMA glaciers experienced pronounced mass loss attributed to abnormally high temperatures, with the glacier ablation in the Qilian Mountains being the most severe on record. Our spatially explicit and high-temporal-resolution (monthly to seasonal) features of glaciers would improve understanding of HMA glacier changes and serve as a reference for future research in this field.

How to cite: Zhao, F., Long, D., Han, P., Wang, Y., Cui, Y., and Duan, X.: Satellite altimetry derived glacier mass changes over High Mountain Asia during 2003‒2022, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16092, https://doi.org/10.5194/egusphere-egu24-16092, 2024.

The Adamello Glacier, a rare example of a summit glacier in the Italian Alps, is undergoing profound transformations since the beginning of the century, with a substantial reduction in its surface area. Between 1995 and 2009, the net surface mass balance displayed an average decrease of -1439 mm w.e. per year. We analyze the retreat of the Adamello Glacier through diverse prospectives, discussing trends and variability in in-situ observations and remotely sensed images, and modelling its mass balance in the current and future climate. Firstly, we show the areal retreat of the glacierized area studied by means of satellite images (Landsat), obtaining an areal retreat of 11% every decade since 2007. Secondly, we present the timeseries of temperature and precipitation measured at nearby high elevation meteorological stations. Significant increasing trends are found in temperature, especially in the summer period (+0.8°C every decade since 1996). Accumulation variability and trends are also discussed, drawing insights from snow water equivalent measurements systematically collected since 1967, revealing concerning spring trends with a 5-6% decrease in water equivalent every decade on April 1, and no significant trends in winter. Thirdly, by means of the Physical based Distributed Snow Land and Ice Model (PDSLIM), validated by ablation measurements collected in August 2023, we compute the distributed surface mass balance of the Adamello glacier for the period 2010-2023, obtaining an average net mass balance of -2170 mm w.e., significantly larger than in the period 1995-2009. Finally, in order to assess the future evolution of the glacier, we make use of regional climate models (RCMs) simulations of the future climate conditions developed in the framework of the CORDEX experiment for different emission scenarios. Our results highlight the critical conditions the Adamello Glacier is experiencing nowadays, quantifying the surface mass balance in the current climate, and estimate its expected behavior by the end of the century considering different emission scenarios.

How to cite: Colosio, P., Liaqat, M. U., Grossi, G., and Ranzi, R.: The retreat of the Adamello Glacier (Italy) in a changing climate from snow and meteorological measurements, remote sensing observations and surface mass balance modelling, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16523, https://doi.org/10.5194/egusphere-egu24-16523, 2024.

EGU24-16774 | ECS | Orals | CR1.1

Combining ground-penetrating RaDAR, unmanned aerial vehicle photogrammetry and borehole thermal data to investigate the evolution of hanging glaciers in the western European Alps 

Ben Robson, Christophe Lambiel, Ludovic Ravanel, James Irving, Ludovic Baron, and Jérémie Gentizon

The evolution of hanging glaciers in a context of changing climate has significant implications because their stability is particularly sensitive to changes in their basal thermal regimes. Projections indicate that by the end of this century, all glaciers below 4000 m altitude in the European Alps will likely transition from a cold-based to a temperate-based state due to climate forcing. Unstable hanging glaciers already threaten villages, transport routes and ski infrastructure in the Alps. Given the high density of settlements, infrastructure and access for recreation, the evolution of hanging glaciers must be well understood. However, modelling the thermal regimes of hanging glaciers is often difficult because of their complex geometries, and the difficulties associated with data acquisition. Our study utilised ground-based ground-penetrating radar (GPR) techniques in a novel application to investigate the bedrock geometries of four hanging glaciers at two sites at the Pointes du Mourti (3563 m a.s.l.), Pennine Alps, Switzerland, and the Aiguille du Midi (3842 m a.s.l.), Mont-Blanc Massif, France.

By combining a GPR survey with two years of thermal data recorded in two boreholes, and two annually spaced UAV photogrammetric surveys, we investigated the geometry and the current evolution of the Pointes du Mourti hanging glacier. We were able to extract subglacial bedrock geometry and ice depths covering an area of 9791 m2, representing 16.2% of the glacier area in 2022. We demonstrated that this hanging glacier, with a mean inclination angle of 43°, resides in a concave feature on the mountain slope with a rugged subglacial surface. Basal temperatures in the upper part of the hanging glacier are below -2.5 °C, indicating cold-based conditions, whereas the central part may be in a more temperate-based condition. Furthermore, the surface topography of all the investigated glaciers underwent substantial changes during the unusually hot summer of 2022, which followed the very dry winter of 2021/2022, exceeding historical norms. The Pointes du Mourti hanging glacier lost 0.86 m of thickness on average and more than 7% of its surface area between October 2021 and September 2022. Similarly, the Jumeau Ouest hanging glacier, at the Aiguille du Midi, lost 0.92 m between June and September 2022.

Our study shows that ground-based GPR can be successfully employed in challenging topographical environments to determine sub-glacial geometries of hanging glaciers. This method can be a valuable tool in a multi-faceted approach to hanging glacier investigations, effectively providing necessary ice depths and bedrock configurations. This research contributes valuable insights for both scientific and administrative communities invested in comprehending the consequences associated with the evolution of hanging glaciers.

How to cite: Robson, B., Lambiel, C., Ravanel, L., Irving, J., Baron, L., and Gentizon, J.: Combining ground-penetrating RaDAR, unmanned aerial vehicle photogrammetry and borehole thermal data to investigate the evolution of hanging glaciers in the western European Alps, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16774, https://doi.org/10.5194/egusphere-egu24-16774, 2024.

EGU24-16984 | Posters virtual | CR1.1

How to balance the voids? Tackling rapid ice loss in western Austria 

Andrea Fischer, Martin Stocker-Waldhuber, Lea Hartl, Bernd Seiser, Kay Helfricht, Andreas Gschwentner, and Giulia Bertolotti

The extreme melt during the years 2022 and 2023 resulted not only in up to 3 m w.e. ice loss, but also to rapid shrinkage of glacier area. As a result of thinning in all altitudes, an increase in pace of area loss can be expected for the next years. The area loss for long term mass balance glaciers reached up to 10% in 2023 for Jamtalferner. This similar to the area loss of the last decade and rises the question, how significant the tracking of the area loss influences the accuracy of in situ mass balance, as we traditionally calculate mass balance based on the area of the previous year.

Another open question regarding mass balance methods are effects of the repositioning of stakes into flat areas with low debris cover which is forced by increasing rock fall activities. There also is evidence of wide spread melt at the base of the glacier which is so far unquantified.

With rapidly shrinking areas, specific mass balance curves and total balance show larger differences, i.e. although specific mass balance increases, the areas shrink so rapidly that the total melt water runoff decreases. Equilibrium line is above summits for most of the mass balance glaciers in western Austria in most years of the last decade.

So far, the Austrian glacier inventories did not split up glaciers in smaller entities, to allow to tackle the evolution of formerly larger glaciers without accounting for parent and child IDs. Now, for some glaciers the ice remnants are clearly not fulfilling the criteria for a glacier, as they consist only of a small part of the former glacier tongue, where the ice has been thicker and survived the former ablation area. Tackling glacier loss in a consistent way turns out to be tricky, as remote sensing data often does not allow to distinguish debris covered glaciers from cold rocky landforms as frozen base moraines. Aerial photography or LiDAR elevation models would be needed in shorter repeat periods as the decadal intervals used so far. During summer 2023, some smaller glaciers disappeared within weeks, and it is also the pace of this loss which is quite informative and relevant for local hydrology and hazard situation.

How to cite: Fischer, A., Stocker-Waldhuber, M., Hartl, L., Seiser, B., Helfricht, K., Gschwentner, A., and Bertolotti, G.: How to balance the voids? Tackling rapid ice loss in western Austria, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16984, https://doi.org/10.5194/egusphere-egu24-16984, 2024.

Research suggests that at least 40 % of mass loss from the Greenland ice sheet is related to calving at marine terminating glaciers and that the rate of calving is linked to glacier meltwater plume processes. Understanding plume extent and temporal and spatial variability is, therefore, important for estimating potential SLR.

This work presents satellite data observations of plume extents from multispectral sensors as well as the novel use of satellite synthetic aperture radar (SAR) sensors for this application. Ocean fronts, large-scale upwelling and estuarine plumes have been isolated in the past using SAR data but application of SAR to smaller-scale glacial meltwater plume extent has not so far been presented. With the advent of higher resolution SAR imagery in recent years there is an opportunity to apply the technique to study these glacial meltwater plumes as their presence modifies the wind, wave and current interactions on a water surface and so influence the backscatter signal presented in the SAR intensity image.

Plume observations from multispectral and SAR data are presented for the glacier-marine lagoon complex of Breiðamerkurjökull glacier and Jökulsárlón proglacial lake, Iceland. This system is a good analogue for a Greenlandic fjord-ocean systems and is where we will also conduct future fieldwork on the 3D structure of meltwater plumes.

How to cite: Edwards, L.: Glacial meltwater plume extent from multispectral and SAR satellite data, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19184, https://doi.org/10.5194/egusphere-egu24-19184, 2024.

EGU24-19339 | ECS | Posters on site | CR1.1

Monitoring high resolution variations in proglacial lake area using an Uncrewed Aerial Vehicle (UAV) at Fjallsjökull, Iceland 

Ameila Andrews, Nathaniel Baurley, Jadu Dash, and Jane Hart

The subglacial hydrological system is a key component in understanding the response of glaciers to climate change. However, due to its inaccessibility, the subglacial system is logistically difficult to investigate. Here we use an Uncrewed Aerial Vehicle (UAV) to monitor variations in the lake area of Fjallsárlón, a large proglacial lake in SE Iceland, at high spatial and temporal resolutions to better understand the hydrology of the adjacent soft-bedded outlet glacier Fjallsjökull. Surveys were undertaken over 10 days in July and 7 days in September 2023, with the acquired imagery used to generate high-resolution orthomosaics and DEMs (0.01 m and 0.03 m, respectively). We then developed and applied a novel method to the resultant 3D models to measure variations in proglacial lake area on a diurnal scale, bridging the gap between ground and satellite-based observations. We were able to measure a minimum diurnal variation of ~9,800 m2 and a maximum diurnal variation of ~56,000 m2 in lake area during the study period. As such, our results indicate the potential of UAVs to monitor changes in proglacial lake area at high resolutions. We suggest that the novel method applied here can successfully be used to measure variations in the lake area of Fjallsárlón, which can be used alone or alongside satellite records of lake area change. From these data, insights into the outputs of the hydrological system can be obtained, which can be used alongside meteorological data to better understand the subglacial system of Fjallsjökull.

How to cite: Andrews, A., Baurley, N., Dash, J., and Hart, J.: Monitoring high resolution variations in proglacial lake area using an Uncrewed Aerial Vehicle (UAV) at Fjallsjökull, Iceland, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19339, https://doi.org/10.5194/egusphere-egu24-19339, 2024.

EGU24-20265 | ECS | Posters on site | CR1.1

Deriving the Østrem curve to quantify supraglacial debris-related melt-altering effects on the Djankuat Glacier, Caucasus, Russian Federation 

Yoni Verhaegen, Philippe Huybrechts, Oleg Rybak, and Victor Popovnin

We have derived the glacier-specific Østrem curve to quantify the influence of a supraglacial debris cover on the mass and surface energy balance of the Djankuat Glacier, a northwest-facing and partly debris-covered temperate valley glacier in the Caucasus region (Russian Federation), which has been selected as a ‘reference glacier’ by the WGMS. A 2D energy balance model, in combination with meteorological data from automatic weather stations and ERA5-Land reanalysis data, is used to assess the melt-altering effect of supraglacial debris on the overall glacier runoff during 1 complete balance year. The main results show that both the surface energy balance and mass balance fluxes are modified significantly due to the presence of debris on the glacier surface, as the surface characteristics (albedo, emissivity, and roughness) and near-surface temperature, moisture and wind regimes are greatly altered when compare to bare ice surfaces.  As such, for very thin debris (< 3 cm), a slight relative melt-enhancement occurs due to a decreased surface albedo and/or the patchiness of the debris. If debris, however, further thickens (> 9 cm), the insulating effect becomes dominant and reduces the melt of the underlying ice significantly. Sensitivity experiments show that especially within-debris properties, such as the thermal conductivity and the vertical porosity gradient within the debris pack, highly impact the magnitude of the sub-debris melt rates. Moreover, the relative melt suppression of the debris cover is modelled to increase in a warming climate, regardless of debris thickness changes. The above-mentioned effects are found to be increasingly pronounced with an increasing thickness of the superimposed supraglacial debris cover and can be of great importance with respect to future glacio-hydrologic regimes and glacio-geomorphological processes. Quantifying such melt-modification effects is therefore also important to more accurately understand and assess the behavior of (partly) debris-covered glaciers under a future warming climate.

How to cite: Verhaegen, Y., Huybrechts, P., Rybak, O., and Popovnin, V.: Deriving the Østrem curve to quantify supraglacial debris-related melt-altering effects on the Djankuat Glacier, Caucasus, Russian Federation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20265, https://doi.org/10.5194/egusphere-egu24-20265, 2024.

 

Recent advancements in the numerical modelling of glaciers has enabled projections of glacier mass change at regional and global scales. However, this progress has been facilitated by the use of simple mass balance models that rely heavily on parameterisations, often with poorly constrained parameters. These models are typically calibrated by varying parameters in order to minimise the difference between modelled and observed mass balance. Though intuitive, this procedure risks an over-tuning of model parameters, ultimately resulting in an underestimation of uncertainty in projections of glacier change. In this study, we present a novel application of the calibration technique known as ‘history matching’. Rather than tuning parameters to obtain a single ‘best’ solution, this method is used to obtain an ensemble of plausible parameter sets; ultimately enabling an assessment of parameter uncertainty in projections. Here, we apply this approach to quantify parameter uncertainty in the GO model contribution to GlacierMIP3. We run the model for each experiment in GlacierMIP3 using a 250-member perturbed-parameter ensemble, generated using a Latin hypercube design. We then constrain this ensemble through history matching by filtering ensemble members that are inconsistent with geodetic mass balance observations outside defined limits of plausibility. The ensemble is used to assess the sensitivity of projections to total parameter uncertainty as well as individual model parameters. We find a high degree of equifinality in the ensemble, in which ensemble members that performed equally well in calibration produce contrasting responses to the same climate forcing. 

How to cite: James, M.: Quantifying parameter uncertainty in projections of glacier mass change in Iceland under GlacierMIP3 experiments , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20299, https://doi.org/10.5194/egusphere-egu24-20299, 2024.

EGU24-267 | Posters on site | CR1.3

Properties of the bed of Thwaites Glacier, West Antarctica, estimated from vibroseismic surveys (2022-23 and 2023-24) 

Olaf Eisen, Ole Zeising, Coen Hofstede, Hannes Laubach, Florian Koch, Sridhar Anandakrishnan, and Alex Brisbourne and the GHOST team

In the Antarctic field seasons 2022/23 and 2023/24 the GHOST team (Geophysical Habitat of Subglacial Thwaites: https://thwaitesglacier.org/projects/ghost) as part of the International Thwaites Glacier Collaboration (ITGC), collected several hundred kilometers of multi-fold seismic reflection profile of Thwaites Glacier. The data cover the center flow line (first season) and across flow profiles (second season), starting 60 km upstream from the grounding line. The seismic profiling set-up consisted of a seismic vibrator source and 60 geophones on a 1.5 km long cable, all towed by a tracked vehicle. The combination of surface seismic source and towed geophone array allows for rapid and high quality data acquisition. The seismic signal penetrates approximately 200 meters into the bed with deeper structures imaged in places. The along-flow profile revealed a repeating of bedforms alternating between relatively flat and smooth regions a few km long, and regions of more pronounced topography of 10s to 100s of meter high bumps. In addition we imaged what we interpret as sediment filled basins.  Comparison with high-resolution ground-based swath radar allows the identification of geomorphological bedforms, such as megascale glacial lineations, sediment-filled basins and troughs, which can then be directly identified in the seismograms. We present a first preliminary evaluation of the subglacial characteristics and discuss the potential relevance of the subglacial boundary condition for ice flow dynamics.

How to cite: Eisen, O., Zeising, O., Hofstede, C., Laubach, H., Koch, F., Anandakrishnan, S., and Brisbourne, A. and the GHOST team: Properties of the bed of Thwaites Glacier, West Antarctica, estimated from vibroseismic surveys (2022-23 and 2023-24), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-267, https://doi.org/10.5194/egusphere-egu24-267, 2024.

EGU24-1033 | Orals | CR1.3

Ice dynamics and structural evolution of Jutulstraumen, Queen Maud Land, East Antarctica (1963 – 2022) 

Anwesha Sharma, Chris R. Stokes, and Stewart S.R. Jamieson

Jutulstraumen, a major outlet glacier in East Antarctica, drains into the Fimbulisen (∼39,400 km2). Here, we produce the first long term (~ 60 years) record of its behaviour using optical satellite imagery to map changes in its frontal position between 1963 and 2022, together with more recent datasets of ice velocity, surface elevation changes and grounding line position. Our analysis reveals that the ice front has been steadily advancing since its last major calving event in 1967, with a consistent ice flow velocity of ~ 720 ± 20 m yr-1(2000-2022). This has been accompanied by spatially variable ice surface thickening at an average rate of +0.15 ± 0.02 m yr-1 (2003-2020) between 20 km and 120 km inland of the grounding line. We also find evidence to suggest a minor grounding line advance of ~ 200 m (~ 6 m yr- 1) between 1990 and 2022, albeit with large uncertainties. Mapping of the major rifts on Jutulstraumen’s ice tongue from 2003 to 2022 (MODIS) reveals an overall increase in their lengths on both sides of the floating ice tongue, accompanied by some minor calving events. Given present-day ice front advance rates (~ 755 m yr-1), it would take around 31 years for the ice tongue to reach its most recent maximum extent in the mid 1960s, but extrapolation of rift lengthening suggests the next major calving event could take place sooner, possibly as early as the 2040s. Overall, however, there is no evidence of any dynamic imbalance, with ice-tongue advance, inland thickening and grounding line advance mirroring other major glaciers in Dronning Maud Land.

How to cite: Sharma, A., Stokes, C. R., and Jamieson, S. S. R.: Ice dynamics and structural evolution of Jutulstraumen, Queen Maud Land, East Antarctica (1963 – 2022), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1033, https://doi.org/10.5194/egusphere-egu24-1033, 2024.

Fuelled by anthropogenic warming, the duration of sea ice and ocean circulation near the East Antarctic continent at present-day, is changing and contributing to further ice sheet melt. Studying the functioning of these parameters, atmosphere, ocean, and sea ice, during past climate transitions (such as warming stages, i.e., deglaciations, and cooling stages, i.e., glaciations) may give us more understanding to the stability of the East Antarctic ice sheet in the future. Fossil diatom records found in deep ocean sediment cores can provide indications of past sea ice and surface temperature variability and can therefore deepen our understanding of future outcomes of present-day anthropogenic warming, including ocean circulation changes. However, very few sea ice and sea surface temperature reconstructions exist from past warming stages (deglacials) near the Antarctic continent. This is partly due to the fact fossil records are lacking from sediment archives retrieved from the Antarctic continental margin, possibly as a result of extended ice sheets and prolonged periods or permanent sea ice cover. In this study we analysed diatom assemblages (based on relative abundances of identified species and statistical analysis), the Eucampia index, Thalassiothrix antarctica, ice rafted debris (IRD), and the geochemical productivity indicators (biogenic silica and XRF derived Si/Al and Ba/Ti) in core TAN1302-44, collected from the slope offshore Adélie Land. The results show a pattern of glacial (cool periods) to interglacial (warm periods) sedimentary facies changes and include last two deglacials and the last glaciation stage. Two diatom assemblages coincide well with changes in glacial (low IRD, low productivity) to interglacial (high IRD, high productivity) facies. The persisting presence of Thalassiosira lentiginosa, representative of Assemblage 1, suggests the last glacial (MIS 4-2) is characterised by an open ocean environment with respect to sea ice. However, due to the increasing presence of Fragilariopsis obliquecostata, representing Assemblage 2, we conclude the last glacial also comprised a gradual build-up of sea ice, reaching a maximum duration at the end of MIS 2, before rapidly vanishing. Following the decrease in sea ice, based on the increased of Thalassiothrix antarctica within the deglaciation facies, we conclude Circumpolar Deep Water (CDW) influx increased over the slope. This observation occurs in both deglacials, one leading to MIS 5e, and other to Holocene interglacial. Finally, based on IRD rich interglacial facies, we conclude the CDW increase occurred prior to regional ice sheet retreat, leading into the Holocene. Together, these datasets suggest major sea ice, and oceanographic changes occurred prior to the last major ice sheet retreat, suggesting a progression of events may influence the demise of the East Antarctic ice sheet in the future.

How to cite: Pesjak, L., McMinn, A., Chase, Z., and Bostock, H.: Sea ice and ocean circulation changes during the last 140 kyr, offshore Adélie Land, East Antarctic continental margin, with special emphasis on last two deglaciations, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1039, https://doi.org/10.5194/egusphere-egu24-1039, 2024.

EGU24-1488 | ECS | Orals | CR1.3

The impact of climate change on meteorite finds in East Antarctica 

Veronica Tollenaar, Harry Zekollari, Christophe Kittel, Daniel Farinotti, Stef Lhermitte, Vinciane Debaille, Steven Goderis, Philippe Claeys, Katherine Helen Joy, and Frank Pattyn

Antarctica is the most prolific place on Earth to find meteorites, which provide unique insights in the formation and evolution of our Solar System. Over 60% of all meteorite finds on Earth stem from so-called blue ice areas in the interior of the (East) Antarctic ice sheet. In these blue ice areas, a redirected ice flow and meteorological processes lead to the removal of surface layers. Meteorites once embedded in these layers of ice that are removed become exposed at the surface in high concentrations and are easy to spot in the field thanks to their contrasting dark color on blue ice. However, no meteorites have been found in areas where temperatures are relatively high. The absence of meteorites in these areas is explained by the fact that meteorites warm up under solar radiation, and as such these stones can melt the underlying ice, even when surface temperatures are well below zero. This very local melt causes the meteorite to move vertically downward into in the ice sheet, disappearing from the surface and hence impossible to see by eye and collect. Hence, in a warmer climate, meteorites are more prone to become unrecoverable.

 

Using a data-driven approach, we estimated that with the currently increasing surface temperatures, meteorite loss rates exceed recovery rates multiple times. To estimate this loss rate, we first performed regional climate model simulations, for a low and a high emission scenario, in which blue ice areas are prescribed. Next, we fed this data to a machine learning algorithm that identifies meteorite-rich sites using over 12,000 known meteorite finding locations and their corresponding properties such as ice flow velocity and surface temperature. Until mid-century, projected losses are identical for the emission scenarios, after which losses are reduced for the low emission scenario and nearly constant for the high emission scenario.

 

These meteorite losses demonstrate a (previously unnoticed) climate sensitivity of the interior of the Antarctic ice sheet. With temperatures remaining well below zero, even with several degrees of warming, meteorites are affected even by very minor (decimal) increases of surface temperatures during exceptionally warm events, which are expected to occur more frequently.

How to cite: Tollenaar, V., Zekollari, H., Kittel, C., Farinotti, D., Lhermitte, S., Debaille, V., Goderis, S., Claeys, P., Joy, K. H., and Pattyn, F.: The impact of climate change on meteorite finds in East Antarctica, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1488, https://doi.org/10.5194/egusphere-egu24-1488, 2024.

EGU24-2465 | ECS | Posters on site | CR1.3

Short-term Antarctic ice-sheet dynamics during the late Oligocene: Multi-proxy records from ODP Site 689 

Layla Creac'h, Swaantje Brzelinski, Oliver Friedrich, Martin Frank, Marcus Gutjahr, and Jörg Lippold

Paleoceanographic records spanning the Oligocene (33.9–23.03 Ma) provide insights into Antarctic ice-sheet (AIS) dynamics in a world warmer-than-today, allowing to improve future projections linked to current global warming. While the long-term evolution of Oligocene glaciations is relatively well-known, current knowledge about the short-term (i.e., orbital to suborbital scale) AIS dynamics is still limited. Here, we investigate short-term dynamics of the AIS during the late Oligocene (spanning ~26–25 Ma), using a high-resolution multi-proxy record from Ocean Drilling Program Site 689 (Maud Rise, Southern Ocean). Variations in ice volume were quantified using the stable oxygen isotope composition of seawater (δ18OSW) inferred from benthic foraminiferal δ18O and Mg/Ca-based bottom-water temperatures. Changes in sediment provenance and weathering inputs were characterised using detrital neodymium isotopic compositions (εNd) of the sediments. The δ18OSW record reflects a highly dynamic AIS during the late Oligocene, with glacial conditions characterised by an AIS volume larger than the modern one (up to +14%) and interglacial conditions characterised by a much smaller AIS volume (up to -29%) than today. Detrital εNd varies from -12 to -9, with less radiogenic εNd signatures generally matching higher δ18OSW values (i.e., glacials) and vice-versa. This co-variation between an ice-volume proxy and a tracer of sediment provenance characterises crustal sequences exposure to weathering as the ice-sheet retreated. The detrital εNd record thus supports recent interpretations of a highly dynamic AIS during the late Oligocene, which is mirrored by large changes in the provenance of weathering products induced by the waning and waxing of the AIS.

How to cite: Creac'h, L., Brzelinski, S., Friedrich, O., Frank, M., Gutjahr, M., and Lippold, J.: Short-term Antarctic ice-sheet dynamics during the late Oligocene: Multi-proxy records from ODP Site 689, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2465, https://doi.org/10.5194/egusphere-egu24-2465, 2024.

EGU24-3600 | ECS | Orals | CR1.3

Simulating 3D calving dynamics at Thwaites Glacier 

Iain Wheel, Douglas Benn, and Anna Crawford

Recent advances in the Elmer/Ice modelling suite have allowed 3D simulation of unrestricted calving geometries at tidewater glaciers such as Jakobshavn Isbrae. We present the first use of this model in an Antarctic setting. The more stochastic nature of calving at Antarctic ice sheets when compared to a Greenlandic setting has discouraged the development of calving laws and models. For shorter term calving simulations, it is sufficient to determine the local attractor or pinning point where the terminus stabilises following a transient period of retreat or advance. Importantly, this can only be achieved through a position-based law, as a positional attractor is independent of velocity.

Using a deterministic position-based crevasse depth calving law it is possible to simulate the observed calving behaviour at the western ice front of Thwaites Glacier. The calving law identifies the attractor point beyond which ice will calve following a variable but short delay. The geometric attractor is defined by local topography along with grounding zone dynamics. Beyond this point there are a lack of lateral or basal pinning points, so any downstream ice is effectively lost from the system. More generally, across the floating extensions of Thwaites Glacier, the model reliably predicts regions of crevasse formation. Accurately simulating crevasse formation on ice shelves along with determining the attractor within the glacier retreat and advance cycle is the first step towards a reliable Antarctic calving law. 

How to cite: Wheel, I., Benn, D., and Crawford, A.: Simulating 3D calving dynamics at Thwaites Glacier, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3600, https://doi.org/10.5194/egusphere-egu24-3600, 2024.

EGU24-3663 | Posters on site | CR1.3

Cook glacier-Ocean Antarctic Past Stability (COLLAPSE) project preliminary results from geophysical and oceanographic data analysis 

Laura De Santis, Flavio Accaino, Daniela Accettella, Manuel Bensi, Florence Colleoni, Andrea Cova, Federica Donda, Lorenzo Facchin, Vedrana Kovacevic, Riccardo Martellucci, Elena Mauri, Laura Ursella, and Fabrizio Zgur

The glaciers terminating in the Cook Ice Shelf and the Ninnis Glacier drain most of the Antarctic marine ice sheet covering the Wilkes Subglacial Basin (WSB), whose ice volume is equivalent to 3-4 m of global sea level rise. Long-term climate projections and multiproxies studies of ice records suggest that ice sheet retreat in this area, thought to be colder and more stable, may be triggered by warm ocean water intrusion.
During the 2022 campaign of the Italian Programma Nazionale delle Ricerche in Antartide (PNRA) with the icebreaker L. Bassi, the project COLLAPSE (Cook glacier-Ocean system, sea LeveL and Antarctic Past Stability) mapped two systems of canyons and hills located at the mouth of suspected glacial valleys off Cook and Ninnis glaciers. The combination of geomorphological, seismic, oceanographic, and sedimentary data (see abstract from Torricella et al.) allowed identification of a variety of processes active on the seafloor today and in the late Quaternary. The geophysical data show evidence of slope instability offshore of the presumed major glacial troughs. Sediment drifts controlled by bottom currents grow on channel-levees and slope terraces. This information will help, albeit indirectly, to reconstruct the dynamics of different glaciers in relation to paleoclimatic changes and ocean circulation, and to estimate their respective contributions to global sea-level rise.
In addition to the co-authors listed in this summary who are involved in the analysis of the geophysical and oceanographic data, the project PNRA COLLAPSE includes a large group of scientists for the analysis of the sediment cores, from the Universities of Trieste, Siena and Milan-Bicocca, CNR-ISP e ISMAR, INGV (I), Univ. Bordeaux, Grenoble and LOCEAN, Paris (F), CSIC (E), Colgate Univ. (USA), Australian National University and Univ. of Tasmania (AUS), Russian FSBI VNIIOkeangeologia, (RU), Alfred Wegener Institute (D), GNS (NZ).

How to cite: De Santis, L., Accaino, F., Accettella, D., Bensi, M., Colleoni, F., Cova, A., Donda, F., Facchin, L., Kovacevic, V., Martellucci, R., Mauri, E., Ursella, L., and Zgur, F.: Cook glacier-Ocean Antarctic Past Stability (COLLAPSE) project preliminary results from geophysical and oceanographic data analysis, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3663, https://doi.org/10.5194/egusphere-egu24-3663, 2024.

EGU24-4151 | Posters on site | CR1.3

The critical importance of Wilkes Land Subglacial Basin stability (East Antarctica) 

Florence Colleoni, Laura De Santis, Guilhem Barruol, and Pierre Dutrieux

While most of West Antarctic ice shelves are thinning due to ongoing oceanic warming, East Antarctic ice shelves, except a few ones, are apparently more stable. One sector in particular, the Wilkes Subglacial Basin, is not showing any or very little sign of weakness to ongoing climate change. This sector of Antarctica is drained by the Cook ice shelf, the Ninnis ice shelf and the Mertz ice tongue. Those ice shelves have experienced some observed calving events in the past decades, but actual ice flow does not indicate that this sector is retreating and contributing to global mean sea level rise. But can we really measure the sensitivity of a sector only accounting for two decades of observations? Geological archives and morphological evidence of the George V Land continental margin in front of those glaciers suggest, on the contrary, that the ice sheet over the WSB has been one of the most active of East Antarctic sectors through its glaciological history. A multi-year sea ice cover, reducing only under exceptional atmospheric conditions, does not allow the systematic exploration of the area.  Rare geophysical, glaciological, oceanographical, geological and geographical hampers a proper assessment of the instability potential of this area. International cooperation not only is needed to reach and operate in such difficult sector of Antarctica, both at land and on sea, but is also needed to perform multi-disciplinary measurements.

How to cite: Colleoni, F., De Santis, L., Barruol, G., and Dutrieux, P.: The critical importance of Wilkes Land Subglacial Basin stability (East Antarctica), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4151, https://doi.org/10.5194/egusphere-egu24-4151, 2024.

EGU24-4251 | ECS | Posters on site | CR1.3

Parameterization Solutions for Basal Melting at the Grounding Line in Ice Flow Models 

Yu Wang, Chen Zhao, Rupert Gladstone, Thomas Zwinger, Ben Galton-Fenzi, and Poul Christoffersen

Recent studies have indicated that the migration of grounding line is extremely sensitive to basal melt in the grounding zone. Different representations of melting at the grounding line introduce significant uncertainties in predictions of ice mass loss and global sea level rise. However, there remains an absence of targeted, systematic studies grounded in real-domain, and robustly representing melt in partially floating cells of ice sheet models remains a pressing technical challenge. This study delves into four distinct melt schemes at the grounding line within the Wilkes Subglacial Basin (WSB) model, focusing on their impact on ice loss predictions. Specifically, we analyse the No Melt Parameterization (NMP), Full Melt Parameterization (FMP), and two variants of the Sub-Element Melt parameterization (SEM1, SEM3) as applied to partially floating elements at the grounding line. We found that both the SEM and NMP schemes outperform FMP in terms of convergence with finer mesh resolution, with each exhibiting varying advantages over the other.  Notably, the discrepancies in results attributed to various melt schemes are significantly amplified when high melt rates are applied near the grounding line. Our results consistently suggest that the FMP should be avoided under all circumstances due to its poor convergence and substantial overestimation of ice mass loss. We recommend that future ice sheet models carefully evaluate the choice between NMP and SEM in their specific model contexts.

How to cite: Wang, Y., Zhao, C., Gladstone, R., Zwinger, T., Galton-Fenzi, B., and Christoffersen, P.: Parameterization Solutions for Basal Melting at the Grounding Line in Ice Flow Models, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4251, https://doi.org/10.5194/egusphere-egu24-4251, 2024.

EGU24-4785 | Orals | CR1.3

Large-scale climate modes dominate recent ice mass and elevation variations in much of East Antarctica 

Matt King, John Bright Ayabilah, Poul Christoffersen, Tessa Vance, and Danielle Udy

Large-scale climate modes have recently been shown to dominate the non-linear variability of Antarctic mass over the last 20 years. We explore these results in further detail in the context of East Antarctica and expand on this work to report on new analyses of Antarctic elevation change from satellite altimetry. Altimetric measurements provide insights into spatial variation of these signals at two orders of magnitude higher spatial resolution than mass-change measurements from GRACE, allowing for resolution of variability at sub-glacier scale. Exploring the same period as the GRACE data (2002-2021) we show that about 75% of the variance of the Totten Glacier elevation can be explained by a combination of Southern Annular Mode (SAM) and ENSO. Denman Glacier shows almost no non-linear variance over 2002-2021 but about 30% of the present signal is explainable by SAM with no evident ENSO response. Despite this, much of the signal is not focused on the outlet glaciers but diffusely spread across the interior, consistent with surface mass balance. We show that much of this signal can be explained by models of firn densification, although different models have different levels of agreement with the data at relevant decadal periods. We will show detailed results for Wilkes Subglacial Basin and Dronning Maud Land.

How to cite: King, M., Ayabilah, J. B., Christoffersen, P., Vance, T., and Udy, D.: Large-scale climate modes dominate recent ice mass and elevation variations in much of East Antarctica, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4785, https://doi.org/10.5194/egusphere-egu24-4785, 2024.

EGU24-4890 | Posters on site | CR1.3

60 Years of satellite record reveals high level velocity and mass discharge in Totten Glacier, East Antarctica 

Rongxing Li, Yuan Cheng, Tian Chang, David E. Gwyther, Martin Forbes, Lu An, Menglian Xia, Xiaohan Yuan, Gang Qiao, Xiaohua Tong, and Wenkai Ye

East Antarctic Ice Sheet (EAIS) has an overall balanced or slightly positive mass balance. However, Wilkes Land and Totten Glacier (TG) in EAIS have been losing ice mass significantly since 1989. There is a lack of knowledge of long-term mass balance in the region which hinders the estimation of its contribution to global sea level rise. We reconstruct ice flow velocity fields of 1963–1989 in TG from the first-generation satellite images of ARGON and Landsat-1&4, and build a five decade-long record of ice dynamics. Based on these velocity maps, we show that this acceleration trend in TG has occurred since the 1960s. Combined with recently published velocity maps, we find a persistent long-term ice discharge rate of 68 ± 1 Gt/y and an acceleration of 0.17 ± 0.02 Gt/y2 from 1963 to 2018, making TG the greatest contributor to global sea level rise in EA. We attribute the long-term acceleration near grounding line from 1963 to 2018 to basal melting likely induced by warm modified Circumpolar Deep Water. The speed up in shelf front during 1973–1989 was caused by a large calving front retreat. As the current trend continues, intensified monitoring in the TG region is recommended in the next decades.

How to cite: Li, R., Cheng, Y., Chang, T., Gwyther, D. E., Forbes, M., An, L., Xia, M., Yuan, X., Qiao, G., Tong, X., and Ye, W.: 60 Years of satellite record reveals high level velocity and mass discharge in Totten Glacier, East Antarctica, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4890, https://doi.org/10.5194/egusphere-egu24-4890, 2024.

EGU24-5419 | ECS | Orals | CR1.3 | Highlight

Widespread near-coastal bedrock erosion surfaces in East Antarctica and their implications for long-term ice-sheet behaviour 

Guy Paxman, Stewart Jamieson, Neil Ross, Charlotte Carter, Mike Bentley, Tom Jordan, Xiangbin Cui, Shinan Lang, and Martin Siegert

The sub-ice topography of East Antarctica provides a crucial record of the long-term geological, geomorphological, and glaciological evolution of the continent. In particular, the morphology of the East Antarctic Ice Sheet (EAIS) bed is a valuable and hitherto underexploited archive of past ice-sheet behaviour. Analysis of the subglacial landscape can therefore help improve our understanding of the response of the ice sheet to episodes of warming in the geological past that serve as analogues for current and projected future climate change.

Here, we conduct a systematic search of the extensive repositories of airborne ice-penetrating radar data acquired in the past two decades to map the distribution of low-relief subglacial bed surfaces close to the East Antarctic ice margin between Princess Elizabeth Land and George V Land (70°E to 160°E). Individual surfaces are characterised by consistent elevations over distances of 10s to 100s of kilometres and relatively low-amplitude, high-frequency roughness (i.e., valleys and inselbergs). We map 31 separate low-relief bed surfaces, which range from 500 to 50,000 km2 in area and comprise ~40% of the perimeter of this sector of the East Antarctic margin. The surfaces are typically overlain by cold-based, slow-moving ice and bounded by deep subglacial troughs that host fast-flowing ice streams and outlet glaciers.

Underneath the modern-day EAIS, these low-relief bed surfaces are situated at a broad range of elevations. However, when the elevations are isostatically adjusted for the removal of the EAIS, the distribution narrows substantially and, alongside cluster analysis of the morphology of the surfaces, indicates that they constitute a single, statistically consistent population around the entirety of this sector of the EAIS margin. Under ice-free conditions, the coastal surfaces would be situated above sea level and gently dipping in a seaward direction, and we suggest that they are remnants of a widespread fluvial planation surface formed following Gondwana break-up and preserved with only minor geomorphological modification since EAIS inception. The presence of these ancient surfaces has important implications for the past, present, and future behaviour of this sector of the EAIS.

How to cite: Paxman, G., Jamieson, S., Ross, N., Carter, C., Bentley, M., Jordan, T., Cui, X., Lang, S., and Siegert, M.: Widespread near-coastal bedrock erosion surfaces in East Antarctica and their implications for long-term ice-sheet behaviour, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5419, https://doi.org/10.5194/egusphere-egu24-5419, 2024.

EGU24-6760 | ECS | Orals | CR1.3

What's driving change at the Vanderford Glacier, East Antarctica? 

Lawrence Bird, Felicity McCormack, Johanna Beckmann, Andrew Mackintosh, and Richard Jones

The Aurora Subglacial Basin contains 7 m of global sea level equivalent (SLE). The Totten Glacier is currently the dominant outlet glacier of the Aurora Subglacial Basin; however, neighbouring the Totten Glacier, the smaller Vanderford Glacier drains a region containing 0.67 m of SLE. Vanderford Glacier is the fastest retreating glacier in East Antarctica, with over 18 km of grounding line retreat in the last two decades. The warmest modified circumpolar deep water in East Antarctica has been observed offshore the Vanderford Glacier, highlighting the potential vulnerability of this region to a warming climate. Here, we run transient simulations of the Ice-sheet and Sea-level System Model to examine the sensitivity of the Vanderford Glacier to key drivers of mass loss, namely sub-ice shelf basal melt and ice-front retreat. Simulations show that grounding line retreat is more sensitive to changes in basal melt than ice-front retreat, except for scenarios of extreme ice-front retreat. We show that the rate and extent of grounding line retreat comparable with observations only occurs under high magnitude basal melt conditions, while a similar extent of grounding line retreat occurs under the extreme ice-front retreat scenarios, but the temporal response of the grounding line is lagged. Given that grounding line retreat similar to observations is only achieved with basal melt magnitudes far exceeding those indicated by satellite remote sensing, our results highlight the need for methods to better estimate basal melt in this vulnerable region.

How to cite: Bird, L., McCormack, F., Beckmann, J., Mackintosh, A., and Jones, R.: What's driving change at the Vanderford Glacier, East Antarctica?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6760, https://doi.org/10.5194/egusphere-egu24-6760, 2024.

EGU24-7756 | Posters on site | CR1.3

Submarine landslides unravel the dynamics of the past East Antarctic Ice Sheet  

Xiaoxia Huang, Laura De Santis, German Leitchenkov, and Carlota Escutia

A giant submarine landslide in front of the Wilkes subglacial basin along the Cook continental margin—one of the least explored areas on Earth—has been documented for the first time. This area is critical to understanding the stability of one among the most vulnerable sectors of the Antarctic Ice sheet to climate and ocean warming. It is named as Cook mega-slide complex (CMSC), which occurred in the early Pliocene according to the seismic interpretation correlated to the IODP Exp 318 sites. The giant submarine landslide is well imaged on the seismic profiles and exhibits various kinematic indicators with the basal glide planes and original headwall scarps. It affected the area of c. 22, 686.5 km2, approximately 3399 km3 of sediments evacuated from the continental margin. With a scale similar to Storegga Slide on the Norway margin, the size of the CMSC is mostly likely the largest submarine landslide ever discovered around the Antarctic margin. We propose that glacial isostatic adjustment and glacial outburst floods caused by the East Antarctic Ice Sheet (EAIS) retreat lead to the formation of the large slides and create the condition for slope instability and erosion. The development and collapse of peripheral bulge has been firstly observed from Antarctic margin, associated with the glaciation and subsequent deglaciation of the EAIS, led to a distinct spatial variation in sea level changes and further affected the deposition on the slope. Our results yield intriguing insights into the relationship of stratigraphic evolution, submarine landslides, and past EAIS instabilities throughout the warm periods of the late Miocene-Pliocene, and thereby provide important constraints for ice sheet modeling and sea level prediction.

How to cite: Huang, X., De Santis, L., Leitchenkov, G., and Escutia, C.: Submarine landslides unravel the dynamics of the past East Antarctic Ice Sheet , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7756, https://doi.org/10.5194/egusphere-egu24-7756, 2024.

EGU24-8454 | Posters on site | CR1.3

New insights into the current dynamics of Thwaites and Pine Island Glaciers, West Antarctica. 

G. Hilmar Gudmundsson, Mathieu Morlighem, Daniel Goldberg, Jowan Barnes, Jan De Rydt, and Sebastian Rosier

We provide a summary of new insights into the contemporary dynamics of Thwaites and Pine Island Glacier, West Antarctica, obtained through series of recent modelling studies.  By conducting ice-flow modelling studies with three independent models (ISSM, StreamIce, Úa), all initialized to current day conditions, we show that all models provide very similar future estimates of future mass loss for a given forcing scenario. Importantly, while description of basal processes does impact our results to some degree, we nevertheless find that estimates of mass loss over time scale of 50 to 100 years, are insensitive to the choice of basal sliding law. This can be understood to be related to the compensating impact of the initialisation process that in each case produces correct initial state for the ice sheet (i.e. surface velocities and current rates of mass loss) irrespectively of the sliding law used. Furthermore, we find that inversion produces (e.g. estimates of basal slipperiness and englacial ice rate factors) can be exchanged between models, showing that these products are to large degree model independent. A common feature found in all our ice-flow studies, and coupled ice+ocean studies, is the existence of multiple tipping points within the Thwaites and Pine Island system. In all our ice-flow simulations, the grounding line of Thwaites always becomes unstable once it has retreated by about 75km upstream from its current position. We also conclude that the grounding line of Pine Island Glacier has recently undergone a phase of irreversible retreat, and that the glacier has at least 3 further tipping points that can be crossed in the near future (centennial time scale). Additionally, the western ice shelf of Thwaites has been dramatically weakening over the past decade and we used our three independent models to assess the effect of a potential complete collapse of Thwaites’ floating extension. First, we find that this ice shelf provides limited buttressing, and disintegrations of the ice shelf, in its current configuration, will not significantly impact upstream grounded. Second, it has been suggested that Thwaites would be subject to the Marine Ice Cliff Instability (MICI) if its ice shelf collapses, as it would expose a tall ice cliff. Using recently proposed cliff-height dependent calving laws, we find no indication that such calving laws give rise to an irreversible or unstable calving-front retreat.  Thus, those calving laws do not lead to a marine ice cliff instability despite prescribing calving rates as strongly increasing functions of cliff height.

How to cite: Gudmundsson, G. H., Morlighem, M., Goldberg, D., Barnes, J., De Rydt, J., and Rosier, S.: New insights into the current dynamics of Thwaites and Pine Island Glaciers, West Antarctica., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8454, https://doi.org/10.5194/egusphere-egu24-8454, 2024.

EGU24-8638 | Orals | CR1.3

The history of deep-water upwelling and heat delivery to the Amundsen Sea Embayment, West Antarctica: a palaeoceanographic perspective 

James A. Smith, Svetlana Radionovskaya, Elaine M. Mawbey, Claus-Dieter Hillenbrand, Julia S. Wellner, and Johann Klages and the THOR team

Thwaites and Pine Island glaciers serve as main outlets for ice draining the West Antarctic Ice Sheet into the Amundsen Sea Embayment (ASE). Observational records show that these ice streams exhibit continuous and substantial thinning and grounding-line retreat since the 1940s, particularly accelerating from the 1990s onwards . Furthermore, modeling studies suggest that ASE glaciers are susceptible to runaway retreat. Thus, the rate and magnitude of potential mass loss from these ice streams presents a major source of uncertainty for future sea level rise predictions.

Ocean-driven melting of the underside of ASE glacier ice-shelves, caused by the upwelling of warm Circumpolar Deep Water (CDW) at the shelf break and its advection across the continental shelf, is thought to be the main driver of mass loss. CDW upwelling onto the ASE shelf has varied due to natural decadal variability, longer centennial variability as well recent changes in anthropogenic forcing (Holland et al., 2022). However, regional observational records are limited to the last few decades, and the onset and evolution of the oceanic forcing, prior to the instrumental period, remains uncertain. Here, we present high-resolution foraminiferal geochemical data from marine sediment cores recovered from the ASE shelf, including material collected during the Thwaites Glacier Offshore Research (THOR) expeditions in 2019, 2020 and 2021. Preliminary Mg/Ca records of benthic foraminifera shells, a proxy for bottom-water temperature, accompanied by benthic foraminiferal δ13C records, used as a water mass tracer, reveal that CDW incursions onto the ASE shelf contributed to glacier retreat on centennial to millennial timescales. Future work will aim to further constrain changes in CDW advection to the inner ASE shelf, particularly in western Pine Island Bay and at the Dotson Ice Shelf front, for the 20th century and beyond.

How to cite: Smith, J. A., Radionovskaya, S., Mawbey, E. M., Hillenbrand, C.-D., Wellner, J. S., and Klages, J. and the THOR team: The history of deep-water upwelling and heat delivery to the Amundsen Sea Embayment, West Antarctica: a palaeoceanographic perspective, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8638, https://doi.org/10.5194/egusphere-egu24-8638, 2024.

EGU24-10149 | Posters on site | CR1.3

Lithosphere-cryosphere interactions at the Pacific coast of North Victoria Land: new evidence of past to recent geodynamic processes from offshore geophysical data (PNRA_BOOST Project) 

Laura Crispini, Dario Civile, Giulia Matilde Ferrante, Michele Locatelli, Danilo Morelli, Valentina Volpi, Daniela Accettella, Flavio Accaino, Martina Busetti, Andreas Läufer, Egidio Armadillo, Ester Colizza, Francesco Salvini, and Antonia Ruppel

As part of the PNRA_BOOST project (Bridging Onshore-Offshore STructures at the Pacific Coast of North Victoria Land, Antarctica: an integrated approach), new offshore geophysical data (multichannel high-resolution seismic lines, bathymetric and magnetic data) were acquired on board of OGS R/V Laura Bassi (Feb 2023, XXXVIII Italian Antarctic Expedition), along the Pacific side of North Victoria Land, an underexplored key area at the boundary between East and West Antarctica. A preliminary analysis of the seismic and bathymetric data allows the identification and interpretation of morphological and tectonic features representing key hints for the study of the influence of lithosphere dynamics on ice-sheet evolution.

In the study area, the northern sector of the shelf has an outer concave shape of its break and slope and is incised by several gullies; on the contrary the southern sector shows a stepped geometry with a WNW-ESE straight linear trend abruptly turning to a NW-SE trend. The continental shelf consists of a thin, horizontally layered succession lying on a crystalline basement dissected by two U-shaped glacial troughs several kilometers wide. The slope consists of seaward-prograding sedimentary strata that are truncated on the shelf by a regional unconformity (RSU 1). In the upper part of the slope of the NW sector, three distinct seaward prograding wedges were recognized, whereas they were not identified in the southern sector.

NW-trending basement highs, bounded by faults, are visible both on the shelf and on the continental rise (towards the abyssal plain). Growth strata associated with these faults allow a tentative dating of activation to Oligocene times. The unconformity at the top of the growth strata may be related to the U3 surface (36 Ma) of Sauermilch et al. (2019). In addition, a ca. 20 km-long ridge of basement, covered by drift deposits, revealed at a depth of about 2500 m, is bounded by faults with indications of recent tectonic activity. The observed faults could have reactivated inherited zones of weakness that bound rift blocks formed during the breakup between Australia and Antarctica. In particular, the U3 surface is associated with the beginning of the phase of fast seafloor-spreading between Australia and Antarctica.

In the SW part of the study area, two broad “linear” volcanic zones occur along a roughly NNW-SSE direction; i.e. the orientation of the main tectonic lineaments inland. These zones consist of individual volcanic edifices and small volcanic ridges composed of coalescing bodies. Several volcanoes are clearly active and fluid-related features are visible cutting through the surrounding sedimentary successions. This volcanism correlates well with airborne magnetic observations and may represent the NNW continuation of the Mid-Miocene to Quaternary Hallett Volcanic Province forming the Adare Peninsula, or may be related to the post-spreading Pliocene-Recent volcanism of the Adare Basin.

Sauermilch et al., 2019. JGR: Solid Earth, 124, 7699–7724 (doi.org/10.1029/2018JB016683).

 

 

 

 

How to cite: Crispini, L., Civile, D., Ferrante, G. M., Locatelli, M., Morelli, D., Volpi, V., Accettella, D., Accaino, F., Busetti, M., Läufer, A., Armadillo, E., Colizza, E., Salvini, F., and Ruppel, A.: Lithosphere-cryosphere interactions at the Pacific coast of North Victoria Land: new evidence of past to recent geodynamic processes from offshore geophysical data (PNRA_BOOST Project), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10149, https://doi.org/10.5194/egusphere-egu24-10149, 2024.

EGU24-10259 | ECS | Orals | CR1.3

The non-linear response of the AABW to the removal of the West Antarctic Ice Sheet and implications to future climate 

Katherine Power, Fernanda Matos, and Qiong Zhang

The West Antarctic Ice Sheet (WAIS) is considered one of the tipping points of the Earth System. Its retreat due to climate change progressively results in sea level rise, affecting large numbers of the world's population. We aim to understand the potential consequences of a future WAIS collapse by implementing a mid-Pliocene Warm Period (MP) Antarctic Ice Sheet configuration, based on reconstructions, where the WAIS is severely reduced.

We perform simulations with the EC-EARTH3.3 model at low resolution spanning 1400 years under 280, 400, and 560 ppmv of CO2 and derive the mean state of the last 200 years of simulation and the variability of climate patterns for the entire runtime.

With the near removal of the WAIS, we find a non-linear response in Antarctic Bottom Water (AABW) formation to increasing CO2 levels. The AABW formation is highly sensitive to increased stratification, which results from sea surface temperature increase driven by current climate change. With the presence of a modern WAIS, Antarctic surface air temperature and Southern Ocean sea surface temperature are positively correlated to atmospheric CO2, and we see a strengthening of the positive phase of the Southern Annular Mode (SAM). This affects mid-latitude westerlies and reinforces the negative feedback between surface warming and AABW formation.

However, with the near removal of WAIS, we observe a dampening in the otherwise doubling of atmospheric warming observed with increasing CO2 and the same pattern occurs for the SAM. This results in a non-linear behaviour of AABW formation, where the AABW is suppressed up to 4 Sv during a longer period compared to the control experiments (modern WAIS), followed by a recovery to pre-industrial strength levels that is not sustained under 560 ppmv. This response also induces a further weakening of the Atlantic Meridional Overturning Circulation (AMOC) and a reduced reach of the AABW transport into the Atlantic and Pacific Oceans, with potential cascading effects on the global climate.

Our longer simulations reveal that the AABW formation thresholds are highly dependent on atmospheric CO2concentrations and the freshwater input into the surrounding basins of the Antarctic region. These results suggest that WAIS retreat already deeply impacts societal development, but a collapse would induce a new climate regime that needs further investigation to allow for climate adaptation.

How to cite: Power, K., Matos, F., and Zhang, Q.: The non-linear response of the AABW to the removal of the West Antarctic Ice Sheet and implications to future climate, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10259, https://doi.org/10.5194/egusphere-egu24-10259, 2024.

EGU24-10321 | Posters on site | CR1.3 | Highlight

Ice-ocean-subglacial hydrology interactions, and recent evolution of the Thwaites glacier 

Noel Gourmelen, Livia Jakob, Paul Holland, Dan Goldberg, and Pierre Dutrieux

The retreat of the Antarctic Ice Sheet is conventionally attributed to ocean melting of fringing ice shelves, potentially enhanced by internal instability due to the proximity of its grounding lines to retrograde bed slopes. Ocean melting is enhanced by increased intrusion of modified Circumpolar Deep Water (mCDW) within ice shelf cavities. Several processes can enhance the ability of mCDW to melt ice shelves. Upwelling from the release of subglacial melt water at the grounding line is arguably one of the least well constrained and understood and is currently not accounted for in projections of ice sheet loss.

The Thwaites glacier in the Amundsen Sea sector of the west Antarctic ice sheet has been the focus of recent investigations given its current rapid retreat, potential instability, and its impact on rates of future sea level change. In 2013, a network of subglacial lakes under the Thwaites glacier drained, the combined outflow reached a peak discharge in excess of 500 m3 s-1 and likely reached the grounding line. During this period, several other processes took place at the grounding line and under the fringing floating ice. This event offers a natural experiment to examine the impact of subglacial outflow on ocean melting of ice shelves.

In this presentation we revisit the various events affecting the Thwaites system during this period and generate several new observations of lake discharge, rates of ice shelf basal melting, and grounding line thinning and retreat. We focus the discussion on the potential feedback between lake discharge, variation in ocean melting, and grounding line retreat, and on the contribution of subglacial discharge to the recent retreat of the Thwaites glacier.

How to cite: Gourmelen, N., Jakob, L., Holland, P., Goldberg, D., and Dutrieux, P.: Ice-ocean-subglacial hydrology interactions, and recent evolution of the Thwaites glacier, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10321, https://doi.org/10.5194/egusphere-egu24-10321, 2024.

EGU24-10527 | ECS | Orals | CR1.3 | Highlight

Does this moraine constrain a Late Holocene readvance in the Amundsen Sea sector of the West Antarctic Ice Sheet? 

Keir Nichols, Jonathan Adams, Katie Brown, Marion McKenzie, Ryan Venturelli, Brent Goehring, Joanne Johnson, Dylan Rood, Klaus Wilcken, John Woodward, and Stephen Roberts

Following rapid ice thinning in the mid-Holocene, Pope Glacier (adjacent to Thwaites Glacier in the Amundsen Sea sector) was at least 30-35 m thinner than present for at least 3 kyr in the mid- to Late Holocene. The timing of the end of this ice lowstand and subsequent rethickening of ice to near its present configuration is poorly constrained. We present five paired 10Be and 26Al cosmogenic nuclide exposure ages that provide constraints on the timing of this ice sheet readvance. The ages are sourced from samples collected from a moraine <1 km from the grounding line of Pope Glacier on a nunatak between Thwaites and Pope glaciers. To help interpret the new exposure ages, we measure the morphology of the moraine and assess modern ice flow directions to provide an insight into the processes that formed it. We conclude that the moraine is a type of medial moraine and hypothesise that it was formed by englacial thrusting during the advance of a small glacier on the flanks of Mount Murphy approximately 1.4 ± 0.5 ka. We infer that the timing of this glacier advance coincides with the Late Holocene thickening of the adjacent Pope Glacier and speculate that it also coincides with thickening of ice in the wider Amundsen Sea sector. We also note that it coincides with glacier readvances on the Antarctic Peninsula. Our results indicate an ice thickness change from 35 m beneath to 50 m above present levels occurred ~1.4 ka, a scale of ice thickness change that has implications for the interpretation of GPS measurements of ongoing surface uplift used to model the solid Earth’s response to surface mass loading and, in turn, on our ability to understand both past and future ice sheet dynamics.

How to cite: Nichols, K., Adams, J., Brown, K., McKenzie, M., Venturelli, R., Goehring, B., Johnson, J., Rood, D., Wilcken, K., Woodward, J., and Roberts, S.: Does this moraine constrain a Late Holocene readvance in the Amundsen Sea sector of the West Antarctic Ice Sheet?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10527, https://doi.org/10.5194/egusphere-egu24-10527, 2024.

EGU24-10545 | ECS | Orals | CR1.3

Direct observations of coupled ice-ocean interactions within a basal terrace beneath Thwaites Eastern Ice Shelf 

Peter Washam, Britney Schmidt, Keith Nicholls, Peter Davis, Clare Eayrs, Veronica Hegelein, Justin Lawrence, Matt Meister, Enrica Quartini, David Holland, and Frances Bryson

At present, considerable uncertainty surrounds the details of how Earth’s ice sheets interact with the surrounding ocean. This inhibits the reliability of future sea level rise projections from ice sheet models and highlights a need to better constrain ice-ocean interactions with in situ observations. Here, we present detailed ice and ocean data from beneath Thwaites Eastern Ice Shelf, Antarctica, collected with the underwater vehicle Icefin as part of the ITGC MELT project. The observations are a subset of the full data set that focus on the ice-ocean interactions within one 4-m-tall and 200-m-wide terrace formation in the ice base. We present ocean conditions in the terrace from 18 hydrographic profiles that reached within 1 cm of the ice along the feature’s flat roof and 13 cm from its steep sidewall. The ocean observations depict highly stable near-ice ocean stratification within 1 m of the terrace roof that break down near its sidewall, allowing warmer and more saline water to contact the ice there. The ocean observations are combined with ice base elevations and scaled morphological melt patterns in the ice to understand the dominant mechanisms driving ice-ocean interactions within this feature. We then input these data into the three-equation melt parameterization to estimate spatial variability in melt rates within these topographic features. We test various parameterizations for ocean heat flux into the flat and sloped ice surfaces, and compare the results to melt rates sampled along a nearby terrace sidewall and roof with a phase sensitive radar. This work in progress aims to better understand how ocean conditions interact with ice slope on small scales to drive variable melting in warm, highly stratified environments, with hopes of refining existing parameterizations of this process. We expect regions beneath much of the ice shelves occupying West Antarctica to interact similarly with the underlying ocean to what we observe beneath Thwaites. Hence, our observations hold relevance for how ice sheet models parameterize ocean-driven melting in this type of melt-driven regime.

How to cite: Washam, P., Schmidt, B., Nicholls, K., Davis, P., Eayrs, C., Hegelein, V., Lawrence, J., Meister, M., Quartini, E., Holland, D., and Bryson, F.: Direct observations of coupled ice-ocean interactions within a basal terrace beneath Thwaites Eastern Ice Shelf, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10545, https://doi.org/10.5194/egusphere-egu24-10545, 2024.

EGU24-12136 | Posters on site | CR1.3

New geological constraints on Holocene retreat-readvance of the West Antarctic Ice Sheet in the Weddell Sea Embayment 

David Small, Rachel Smedley, Tibor Dunai, Tom Lees, Stephan Trabucatti, and Grant Boeckmann

Predicting future change to the Antarctic Ice Sheets requires high quality data to constrain numerical ice sheet models. A major uncertainty stems from a lack of knowledge regarding the late Holocene trajectory of the West Antarctic Ice Sheet (WAIS). There are two hypotheses regarding the late Holocene behaviour of the WAIS. A) Steady retreat throughout the Holocene with stabilisation at or near the present-day position (ice relaxation hypothesis) or, B) retreat to a smaller-than-present configuration with subsequent readvance to the present-day position (the retreat-readvance hypothesis). The two hypotheses represent profoundly different ice sheet trajectories. These hypotheses have been discussed with particular reference to the Amundsen, Ross and Weddell Sea sectors of the WAIS.

Initial studies proposing the retreat-readvance model suggested that GIA related uplift caused re-grounding of ice rises in the Weddell Sea, increasing ice shelf buttressing and leading to grounding line re-advance. In the southern Weddell Sea major ice streams are currently at threshold positions on reverse bed slopes where they are vulnerable to Marine Ice Sheet/Cliff Instabilities. As this region drains ~22% of Antarctica the lack of geological constraint on the current ice sheet trajectory contributes significant uncertainty to future predictions. Any groundling line retreat beyond present day limits would be accompanied by up-stream ice sheet thinning thus retreat to a smaller-than-present configuration would be accompanied by thinning of the ice sheet surface below the present-day level. Consequently, determining whether sub-glacial rock samples from the Weddell Sea sector have been exposed in the recent past can robustly test for a smaller-than-present ice sheet configuration.

We present an update on two field seasons where, using a modified Winkie Drill, we recovered sub-glacial rock samples from the Ellsworth Mountains and Pensacola Mountains. These mountain ranges bracket the proposed zone of retreat and can thus provide limiting data points on the extent and duration of any retreat. The subglacial cores are to be analysed using in situ 14C and luminescence to test for any past exposure to cosmic rays and sunlight respectively. We will present a summary of the field season outcomes and preliminary analytical data along with initial interpretations.

How to cite: Small, D., Smedley, R., Dunai, T., Lees, T., Trabucatti, S., and Boeckmann, G.: New geological constraints on Holocene retreat-readvance of the West Antarctic Ice Sheet in the Weddell Sea Embayment, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12136, https://doi.org/10.5194/egusphere-egu24-12136, 2024.

EGU24-13054 | Orals | CR1.3

Aerogeophysical views of a major vulnerable marine-based sector of the East Antarctic Ice Sheet: the Wilkes Subglacial Basin 

Fausto Ferraccioli, Graeme Eagles, Jamin Greenbaum, Egidio Armadillo, Duncan Young, Donald Blankenship, Guy Paxman, and Martin Seigert

The Wilkes Subglacial Basin (WSB) continues to attract significant international attention as a potential area of substantial East Antarctic Ice Sheet (EAIS) retreat. Determining whether this sector of East Antarctica was indeed a major contributor to past global sea level rise and whether it will be again in the future beyond 2100, remains a key priority for new interdisciplinary research.

Aerogeophysical exploration has unveiled that the bedrock dips inland and is grounded up to 2.1 km below sea level (bsl) within its remarkably deep sub-basins and remains at a depth <500 m bsl along the length of this huge and geologically enigmatic basin. Its northern sector is particularly critical, as it hosts the catchments of the Cook and Ninnis glaciers that are fast flowing, dynamic and potentially unstable systems that penetrate >500 km inland of the present-day grounding zone.

Despite a growing body of knowledge, geological, geomorphological, and oceanographic evidence for the location, amount and rate of EAIS ice sheet retreat within the WSB remains incomplete and in parts controversial, and numerical model predictions for retreat during past warmer periods (e.g. the mid-Pliocene, mid-Miocene and even more recent Quaternary times) also differ significantly.

Here we review some of the results from different existing aerogeophysical campaigns and data compilations in the WSB to discuss the importance of also considering the heterogeneity in basal boundary conditions affecting and modulating EAIS behaviour, such as bed topography, geology, subglacial hydrology and geothermal heat flux, and also present several interpretations for past changes, including their associated uncertainties, unresolved issues and outstanding questions.

We conclude by presenting our case for major new international aerogephysical exploration efforts such as in our newly proposed ICEOLIA ERC initiative to:

1) provide key missing bathymetric and geological data coverage over the much less well surveyed continental shelf and ice shelf cavities, which is critical to study ice sheet-ocean interactions and to link marine geological/geophysical and drilling observations with the dynamics of the EAIS;

2) glean an improved understanding of past processes and tipping points and finally

3) help investigate 4D (i.e. both space and time dependent) Solid Earth influences on past, present and future ice sheet behaviour in this key sector of East Antarctica.

How to cite: Ferraccioli, F., Eagles, G., Greenbaum, J., Armadillo, E., Young, D., Blankenship, D., Paxman, G., and Seigert, M.: Aerogeophysical views of a major vulnerable marine-based sector of the East Antarctic Ice Sheet: the Wilkes Subglacial Basin, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13054, https://doi.org/10.5194/egusphere-egu24-13054, 2024.

EGU24-13090 | Posters on site | CR1.3

From the Surface Ocean to the Seafloor: Linking Modern and Paleo-Genetics at the Sabrina Coast, East Antarctica (IN2017_V01) 

Linda Armbrecht, Amaranta Focardi, Kelly-Anne Lawler, Phil O’Brien, Amy Leventer, Taryn Noble, Bradley Opdyke, Meghan Duffy, Dimitris Evangelinos, Simon C. George, Jan Lieser, Adrián López-Quirós, Alix Post, Martin Ostrowski, Ian Paulsen, and Leanne Armand

With ongoing climate change, research into the biological changes occurring in particularly vulnerable ecosystems, such as Antarctica, is critical. The Totten Glacier region, Sabrina Coast, is currently experiencing some of the highest rates of thinning across all East Antarctica. An assessment of the microscopic organisms supporting the ecosystem of the marginal sea-ice zone over the continental rise is important, yet there is a lack of knowledge about the diversity and distribution of these organisms throughout the water column, and their occurrence and/or preservation in the underlying sediments. Here, we provide a taxonomic overview of the modern and ancient marine bacterial and eukaryotic communities of the Totten Glacier region, using a combination of 16S and 18S rRNA gene amplicon sequencing (modern DNA) and shotgun metagenomics (sedimentary ancient DNA, sedaDNA). Our data show considerable differences between eukaryote and bacterial signals in the water column versus the sediments. Proteobacteria and diatoms dominate the bacterial and eukaryote composition in the upper water column, while diatoms, dinoflagellates, and haptophytes notably decrease in relative abundance with increasing water depth. Little diatom sedaDNA was recovered from the sediments. Instead, sedaDNA was dominated by Proteobacteria and Retaria. We compare the diatom microfossil and sedaDNA record and link the weak preservation of diatom sedaDNA to DNA degradation while sinking through the water column to the seafloor. This study provides the first assessment of DNA transfer from ocean waters to sediments and an overview of the microscopic communities occurring in the climatically important Totten Glacier region. Such knowledge is important when reconstructing past ecosystems using the emerging sedaDNA approach as a new paleo-proxy, and the interpretation of biological changes in response to Antarctic ice sheet advances and retreats.

How to cite: Armbrecht, L., Focardi, A., Lawler, K.-A., O’Brien, P., Leventer, A., Noble, T., Opdyke, B., Duffy, M., Evangelinos, D., George, S. C., Lieser, J., López-Quirós, A., Post, A., Ostrowski, M., Paulsen, I., and Armand, L.: From the Surface Ocean to the Seafloor: Linking Modern and Paleo-Genetics at the Sabrina Coast, East Antarctica (IN2017_V01), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13090, https://doi.org/10.5194/egusphere-egu24-13090, 2024.

EGU24-13155 | Orals | CR1.3 | Highlight

Grounding Zone Processes at Thwaites Glacier from ICESat-2 Data and Ice-Ocean Modelling 

Indrani Das, Daniel Goldberg, and Ted Scambos

It is now well accepted that ice shelves and grounding zones experience changes in elevation synchronous with ocean tides, atmospheric loading and other processes. Recent studies have demonstrated that tidal pumping at the grounding zone can cause a transient migration of the grounding line hundreds of meters upstream relative to the grounded zone at low tide. As the grounded edge shifts inland, ocean intrusion leads to enhanced basal melting and grounding zone retreat, as demonstrated by previous InSAR-based studies on Thwaites Glacier in the Amundsen Sea Embayment. In this work, we use ICESat 2 elevation profile data spanning the Thwaites Glacier grounding zone and demonstrate the uplift of grounding zone topography in high tides with ocean intrusion ranging from ~1–9 km inland. The uplift of surface topography in high tides and our inferred ocean intrusion underneath the ice is heterogenous both in the along-track direction and along the width of the grounding zone. This work using ICESat 2 provides evidence in support of similar InSAR-based observations of the dynamic grounding zone and permits an independent assessment of the scale and volume of ocean water intrusion underneath Thwaites Glacier.

 

How to cite: Das, I., Goldberg, D., and Scambos, T.: Grounding Zone Processes at Thwaites Glacier from ICESat-2 Data and Ice-Ocean Modelling, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13155, https://doi.org/10.5194/egusphere-egu24-13155, 2024.

EGU24-13668 | Posters on site | CR1.3 | Highlight

Climate, Ice, and Ocean Characteristics of the Thwaites Eastern Ice Shelf from two In-Situ Multi-Sensor Automated Stations 

Ted Scambos, Martin Truffer, Gabi Collao-Barrios, Tiago Dotto, Chris Kratt, Scott Tyler, and Erin Pettit

A pair of automated multi-sensor stations with satellite data downlinking were installed near the center of the Thwaites Eastern Ice Shelf (TEIS) in January, 2020 and continued operating (at least partially) until November, 2022. The stations, situated 4 km apart (initially near 75.05°S, 105.5°W) recorded and transmitted weather and snow accumulation data, position, images, firn and ice temperature, and ocean conditions through a suite of instruments managed with software and uplinked commands to conserve power and/or maximize observations of events. The stations, called Automated Meteorology-Ice-Geophysics Observing Systems, mark III (AMIGOS-III) are installed on a tower and adjacent ice borehole to measure air, ice, and ocean parameters. Weather and accumulation data from the stations spanning 22 months show a mean annual air temperature for TEIS of -14.6°C, with observed extremes of +1.7°C (08 Feb 2020) to -51.0°C (17 Aug 2021). Mean air pressure was 973.7 mbar (at ~25 m elevation). Winds are highly directional and dominated by dry katabatic flow from the southeast (from 115° to 130°); however, higher snowfall is correlated with winds from more easterly and northeasterly directions. Average annual snowfall in the observation period was 0.72 to 0.90 m water equivalent. Ice flow speed was observed to accelerate throughout the observation period, ranging from ~1.7 m/d in January 2020 to more than 2.2 m/d in late 2021. The rate of acceleration increased markedly after July 2020, coinciding with satellite observations of a more disrupted northern and western shear margin for TEIS. Maximum tidal amplitude is ~1.6 meters. Comparison with the CATS2008 tide model, after correction for IBE, showed a mean difference of ±17 cm. Ocean data was acquired from the two sub-shelf cavity moorings, each of which included paired SeaBird microCAT and Nortek Aquadopp sensors at mid-cavity depths (~520 m and ~317 m) and near-seabed depths (~746 m and ~785 m), in the modified Circumpolar Deep Water (mCDW) layer. These were augmented by a fiber optic thermal profiler system that measured both ice and ocean temperatures for 19 months. The fiber optic thermal data show a minimum temperature of -19.0°C in the interior, and lower temperature gradient suggesting truncation of the ice shelf base due to basal melting. Time-series of the profile data show very little basal melting of the ice at the two sites, but a thickening of the mCDW layer over the observation period. Overall, the AMIGOS-III data have supported six published studies to date, on ice shelf dynamics, ocean flow and layer properties, basal conditions, atmospheric river events, and weather. The units demonstrate the benefit of long-duration multi-sensor observing platforms in ice shelf or ice tongue areas.

How to cite: Scambos, T., Truffer, M., Collao-Barrios, G., Dotto, T., Kratt, C., Tyler, S., and Pettit, E.: Climate, Ice, and Ocean Characteristics of the Thwaites Eastern Ice Shelf from two In-Situ Multi-Sensor Automated Stations, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13668, https://doi.org/10.5194/egusphere-egu24-13668, 2024.

Increasing Antarctic snow accumulation can mitigate sea level rise, but considerable uncertainty surrounds both past snowfall trends and future sea level projections. Here, we present a reconstruction of 19th and 20th century Antarctic accumulation, and the 20th century cumulative impact on global mean sea level. Using the Last Millenium Reanalysis framework to integrate ice core accumulation and water isotope records with a multi-model ensemble of CMIP5 climate simulations, we produce annually resolved reconstructions from 1801-2000 CE. Reconstructions demonstrate significant skill through strong satellite-era correlation with instrumental reanalysis; we find a positive Antarctic accumulation trend over the 20th century, translating to a modest amount (~1 mm) of sea level mitigation. Mitigation is primarily driven by an accelerating trend since around 1970. These findings contrast with previous 20th century mitigation estimates of ~10-12 mm; we determine that this discrepancy is due to unconstrained baseline estimates of 19th century accumulation in East Antarctica. Our results suggest that uncertainties in East Antarctic accumulation history preclude a confident estimate of Antarctic sea level mitigation, thus highlighting the need for new, high-quality accumulation records from East Antarctica.

How to cite: Eswaran, A., Truax, O., and Fudge, T.: Antarctic 20th-Century Sea Level Mitigation Dominated By Uncertainty in 19th-Century East Antarctic Snow Accumulation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14163, https://doi.org/10.5194/egusphere-egu24-14163, 2024.

EGU24-15484 | Posters on site | CR1.3

Dating and interpreting a firn core from the East Antarctic Plateau 

Furkan Kaan Sagol, Georg Schwamborn, Johannes Freitag, Sepp Kipfstuhl, Frank Wilhelms, and Maria Hörhold

Detecting and understanding potential changes in annual mean temperature and accumulation rate at the East Antarctic Plateau is crucial to assess the sensitivity and future response of the Antarctic ice sheet to global warming. Due the very low accumulation rate and its spatial variability the interpretation of climate proxies from shallow firn cores with centennial to decadal time resolution is challenging. A major limitation is the available time resolution obtained by available dating approaches and a reliable assessment of its uncertainty.
In this study a 204 m long firn core, B56, drilled in 2016 on the East Antarctic Plateau, is analysed. The major goal of this study is dating of the firn core by combining different dating methods on the basis of available density data, dielectric properties, and ion chromatography (non-sea-salt sulphate) data. In order to utilize density, the Herron-Langway Model is used for determining the depth-age relation. In this model temperature and snow accumulation are assumed to be constant and the relationship between the snow density and the depth below the snow surface does not change over time. Depending on the used accumulation rate, the resulting age at 200 m depth varies between 6200 to 7200 years. Secondly, the dielectric profile and non-sea-salt sulphate's (nssSO4-2) concentration data are used for constructing another depth-age model, thereby matching prominent data peaks to known volcanic eruptions that have been recorded in the past. Here, the resulting age at 200 m depth is determined to about 4400 years, which compares well to published age models of firn cores from the East Antarctic Plateau. In comparison we find all age models to be consistent within the upper 40 of meters (approximately 1000years), but the Herron-Langway model to overestimate the age at greater depths. We propose that our findings indicate changes in accumulatıon rate in the past leading to the offset in the Herron-Langway model (using a constant accumulation rate).
However, by combining the dating methods we are able to not only provide a reasonable dating over the full firn core, but also to improve the time resolution of the derived age model. This will improve the interpretation of the climate proxies of this firn core and serve as a role model for other shallow firn cores from the East Antarctic Plateau.

How to cite: Sagol, F. K., Schwamborn, G., Freitag, J., Kipfstuhl, S., Wilhelms, F., and Hörhold, M.: Dating and interpreting a firn core from the East Antarctic Plateau, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15484, https://doi.org/10.5194/egusphere-egu24-15484, 2024.

EGU24-16595 | ECS | Posters on site | CR1.3

Change in melt pattern at Totten Ice Shelf in the 1950s 

Bertie Miles and Rob Bingham

Totten Glacier is the largest contributor to the global sea level rise from the East Antarctic Ice Sheet and has been losing mass since the earliest satellite observations in the 1970s. However, unlike other outlet glaciers that are losing mass in Antarctica (e.g. Pine Island and Thwaites), there has been no obvious long-term speed-up and subsequent increase in ice discharge over the satellite observational record, despite large interannual variability in ice flow. This indicates that the imbalance at Totten Glacier must have initiated prior to our earliest satellite observations.

Utilizing the complete record of satellite imagery, we track the pattern of surface undulations that form near the Totten grounding line and are preserved for decades as they are subsequently transported downstream. In our earliest satellite image from 1973, we observe surface undulations estimated to have formed near the grounding line in the 1920s. We suggest that changes in the size and formation of these surface undulations are caused by changes in the melt rate and ice thickness near the grounding line that alters the degree of contact between the ice shelf and a nearby pinning point. By monitoring the size of these surface undulations, we provide a qualitative record of ice thickness change near the grounding line from the 1920s to the present day. We reveal a clear shift in pattern in the mid-20th century, where, despite pronounced and consistent surface undulation formation between the 1920s and 1950s, no detectable surface undulations were formed between the late 1950s and 1980s.

Elsewhere on the glacier, we demonstrate the long-term opening of a previously identified channel connecting the eastern ice shelf to the open ocean and observe grounding line changes since the 1970s.

How to cite: Miles, B. and Bingham, R.: Change in melt pattern at Totten Ice Shelf in the 1950s, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16595, https://doi.org/10.5194/egusphere-egu24-16595, 2024.

EGU24-16837 | ECS | Orals | CR1.3

Assessing the Structural Stability of Thwaites Eastern Ice Shelf and Its Influence on the Future Evolution of Thwaites Glacier 

Christian Wild, Erin Pettit, Karen Alley, Martin Truffer, Ted Scambos, Karen Heywood, Atsuhiro Muto, Rob Hall, Meghan Sharp, Haylee Smith, Georgia Carroll, Lucy Wanzer, Celia Trunz, Anna Wahlin, Gabriela Collao-Barrios, Michelle Maclennan, Naomi Ochwat, Tiago Dotto, Adrian Luckman, and Samuel Kachuck and the TARSAN team

The Thwaites Eastern Ice Shelf stands as the last remaining floating extent of the consequential Thwaites Glacier in West Antarctica. In the past, it has provided buttressing of the grounded glacier ice, but in the last decade the ice shelf has undergone significant weakening that has reduced its ability to buttress the glacier. Important signs of weakening include: 1) the ice flow measured by ground-based GPS shows continuous acceleration, nearly doubling in speed from 1.65 m/d in 2019 to 2.85 m/d by early 2023; 2) a recent breakout of sea ice has accelerated retreat at the western calving front of the Eastern Ice Shelf; 3) increased damage in a confined shear zone along the north-western pinning point has effectively separated the ice shelf from this pinning point.; 4) five rifts formed since 2016 and have propagated episodically into the center of the most coherent section of the shelf; and 5) several full thickness “gashes” have opened and continue to open parallel to and just downstream of the grounding zone to accommodate the recent ice-shelf speed up through localized strain. Due to these full-depth rifts, the ice shelf has nearly entirely detached from the upstream grounded ice, and is now functioning as a relatively thin, floating ice plate that provides minimal support to the grounded sections of Thwaites Glacier. This accumulation of damage in the ice shelf is happening during a period in which we observe  suppressed basal melt rates and little measurable thinning, suggesting that melt is not the primary driver of ongoing changes. Here, we present the most up-to-date synthesis assessment of the structural integrity of this ice shelf, as well as its relation to ocean conditions underneath and the pinning point, and consider the stability of the ice shelf within the context of ice flow off the continent and projections for sea-level rise.

How to cite: Wild, C., Pettit, E., Alley, K., Truffer, M., Scambos, T., Heywood, K., Muto, A., Hall, R., Sharp, M., Smith, H., Carroll, G., Wanzer, L., Trunz, C., Wahlin, A., Collao-Barrios, G., Maclennan, M., Ochwat, N., Dotto, T., Luckman, A., and Kachuck, S. and the TARSAN team: Assessing the Structural Stability of Thwaites Eastern Ice Shelf and Its Influence on the Future Evolution of Thwaites Glacier, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16837, https://doi.org/10.5194/egusphere-egu24-16837, 2024.

EGU24-16990 | ECS | Orals | CR1.3

Ice Fabric on Thwaites Glacier from ApRES Polarimetric Measurements 

Elizabeth Case and Jonny Kingslake

Thwaites Glacier (TG) is a wide, fast moving ice stream that, along with Pine Island Glacier, drains much of the West Antarctic Ice Sheet (WAIS). This work presents preliminary results of ice fabric, bed topography, and englacial layering from a 200-km-long Autonomous phase-sensitive Radio Echo Sounder (ApRES) survey along the trunk of TG as part of the International Thwaites Glacier Consortium’s GHOST project in 2022-2023. From 235 point measurements and 47 polarimetric measurements, we find a variable, complex ice fabric that changes in strength and orientation along the transect and with depth. Fabric strength, measured as horizontal anisotropy, is on average stronger downstream than upstream, and the fast axis (also known as the symmetry axis) is more aligned along flow than across, as expected in an ice stream. Ice fabric is useful to both meaure and model because it both serves as a record of past stress and deformation, and affects viscosity, directionally softening the ice and impacting the glacier’s response to future stresses.

How to cite: Case, E. and Kingslake, J.: Ice Fabric on Thwaites Glacier from ApRES Polarimetric Measurements, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16990, https://doi.org/10.5194/egusphere-egu24-16990, 2024.

EGU24-18013 | ECS | Posters on site | CR1.3

East Antarctic Ice Sheet response to ocean forcing during the Middle Miocene Climate Transition: Insights from Prydz Bay 

Dimitris Evangelinos, Tina van de Flierdt, Eduardo Paredes, Leopoldo D. Pena, and Isabel Cacho

Understanding ocean-ice sheet interactions in the geological past is critical for evaluating the ice sheet sensitivity to ocean forcing in future climate warming. Geological evidence suggests major oceanographic changes across the Southern Ocean during the Middle Miocene Climate Transition (MMCT) (~15-12 Million years ago (Ma)). However, the response of the East Antarctic Ice Sheet to these changes remains poorly constrained. Here we explore ocean-ice interactions during the MMCT by presenting data from two marine sedimentary cores along a latitudinal transect offshore Prydz Bay (East Antarctica). Ocean Drilling Program (ODP) Site 1165 is located on the continental rise off Prydz Bay (64◦27.27o S, 67◦13.08o E, 3537.5 water depth) and ODP Site 744 is located on the Southern Kerguelen Plateau (61o 34.66´S, 80o 35.43´E, 2307 m water depth). Neodymium and strontium isotopic compositions of fine-grained (< 63μm) detrital sediments from ODP Site 1165 were generated to constrain potential changes in sediment provenance, revealing potential changes in ice sheet dynamics (expansion/retreat). Neodymium isotope ratios (εNd) from fossil fish teeth from ODP Site 744 were used to trace regional water masses and Southern Ocean circulation changes for the same period. Additionally, marine productivity records generated from both ODP sites were used to track changes on the position of the Southern Ocean frontal system. We report an equatorward migration of the Southern Ocean frontal system around 13 Ma, associated with global climate cooling, sea ice expansion and CO2 decline during the MMCT. Despite this major ocean-climate reorganization, our data suggest the presence of a rather stable and large ice sheet in the Prydz Bay throughout the MMCT, implying that the ice sheet was less sensitive to ocean forcing during the MMCT.

How to cite: Evangelinos, D., van de Flierdt, T., Paredes, E., D. Pena, L., and Cacho, I.: East Antarctic Ice Sheet response to ocean forcing during the Middle Miocene Climate Transition: Insights from Prydz Bay, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18013, https://doi.org/10.5194/egusphere-egu24-18013, 2024.

EGU24-18206 | ECS | Orals | CR1.3

Ice-rafted feldspar grains in recent shelf sediments of West Antarctica: provenance pathways via lead isotope compositions 

Thomas Arney, Claus-Dieter Hillenbrand, J. Andy Milton, Christine Siddoway, Gavin Foster, Paul Wilson, Julia S. Wellner, and Steven M. Bohaty

Knowledge of the past dynamics of the Antarctic ice sheets is essential for better understanding their present and future stability and, importantly, the resulting effects on global mean sea level rise in a warming world. The petrology and geochemistry of iceberg-rafted debris (IRD; >150 μm) produced by these ice sheets can provide vital information about past ice sheet extent, but the characteristics of geological sources are poorly constrained in ice-covered Antarctica. Lead isotope ratios (controlled by protolith age) in West Antarctic basement and derived sedimentary rocks (mostly <500 Ma) have previously been assumed to be largely homogenous, and therefore useful only for distinguishing West Antarctic IRD from older (0.5-3 Ga) East Antarctic IRD in Southern Ocean sediments. Laser ablation analysis of individual mineral grains, however, avoids the averaging effects of bulk mineral separate, sediment, or rock analyses and reveals the full variation of isotopic signatures in a sample of detrital grains. Here, we present a survey of lead isotope ratios determined in ~600 iceberg-rafted feldspar grains from 26 seafloor surface sediment samples from the West Antarctic continental shelf. Machine-learning clustering of the lead-isotope data reveals at least two major populations, including a previously unknown population of grains which are less radiogenic than the main cluster. These less radiogenic grains are only found in two areas: near the ice-shelf front of Thwaites Glacier and near the eastern edge of the Ross Ice Shelf. The Thwaites signal is not present at sites on the middle and outer continental shelf, suggesting an offshore dilution effect. Supervised clustering of the main group reveals additional subdivisions in Pb-isotope space that are geographically restricted to: (i) the wider Amundsen Sea, (ii) the Bellingshausen Sea, and (iii) Sulzberger Bay at the boundary between the Amundsen and Ross seas. These subdivisions will be further investigated using 87Rb-87Sr dating of a subset of the feldspar grains used for Pb-isotope analysis. Together, these new data provide a novel IRD provenance tool, allowing tracing of offshore IRD back to either Thwaites Glacier or the eastern Ross Ice Shelf source areas. Given the observed offshore dilution effect, detection of this signal in sediment cores from the outer shelf or deep-sea would indicate a significantly increased supply of detritus sourced from Thwaites Glacier or the Ross Ice Shelf, both important iceberg outlets of the West Antarctic Ice Sheet.

How to cite: Arney, T., Hillenbrand, C.-D., Milton, J. A., Siddoway, C., Foster, G., Wilson, P., Wellner, J. S., and Bohaty, S. M.: Ice-rafted feldspar grains in recent shelf sediments of West Antarctica: provenance pathways via lead isotope compositions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18206, https://doi.org/10.5194/egusphere-egu24-18206, 2024.

EGU24-19707 | Posters on site | CR1.3

How much, how deposited, how old – what can we learn from sediments in Pine Island Bay? 

Robert Larter, Kelly Hogan, Alastair Graham, Frank Nitsche, Julia Wellner, Claus-Dieter Hillenbrand, Rebecca Totten, James Smith, Lauren Miller, John Anderson, Elaine Mawbey, Rachel Clark, Rebecca Hopkins, Asmara Lehrmann, Allison Lepp, James Marschalek, Santiago Munevar Garcia, and Laura Taylor

A number of studies have defined a boundary in the Amundsen Sea embayment between an inner continental shelf, which contains areas where crystalline bedrock is at or near the seabed, and the shelf further offshore, which is underlain by sedimentary strata that increase in overall thickness oceanward. Other studies have shown that much of the inner shelf in Pine Island Bay is covered by a drape of sandy mud averaging about 1 m in thickness, interpreted as having been deposited from meltwater plumes during the mid-late Holocene. Much thicker sediments have been shown to be present in isolated deep basins based on acoustic sub-bottom profiles and sparse seismic reflection profiles, including an estimated maximum thickness of >400 m in one basin close to the front of Pine Island Glacier.  Thus, the widespread impression exists that, apart from the thin Holocene drape, sedimentary cover in Pine Island Bay is restricted to isolated basins.

Here we examine the distribution and thickness of sediments in Pine Island Bay using a network of high-resolution seismic reflection profiles collected in 2020 on RV Nathaniel B Palmer cruise NBP20-02. We show that more extensive thick sediments are present near the front of Pine Island Glacier than have been reported previously. In some places sediment units exhibit characteristics that suggest their deposition was influenced by bottom currents. We also show that sedimentary deposits are present over the tops and on the flanks of some bathymetric highs that must have been former ice shelf pinning points. Finally, we consider what the extent, thickness and character of the sedimentary units identified tell us about glacial/glacimarine processes and ice sheet history in the area, and what could be learned by further study and sampling.

How to cite: Larter, R., Hogan, K., Graham, A., Nitsche, F., Wellner, J., Hillenbrand, C.-D., Totten, R., Smith, J., Miller, L., Anderson, J., Mawbey, E., Clark, R., Hopkins, R., Lehrmann, A., Lepp, A., Marschalek, J., Munevar Garcia, S., and Taylor, L.: How much, how deposited, how old – what can we learn from sediments in Pine Island Bay?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19707, https://doi.org/10.5194/egusphere-egu24-19707, 2024.

EGU24-19800 | ECS | Posters on site | CR1.3

Sedimentological evidence for an early deglaciation in the Weddell Sector at ~19 ka 

Michael Bollen, Juliane Müller, Marcus Gutjahr, and Samuel Jaccard

Existing marine sedimentological constraints on the timing of deglaciation in the Weddell Sector are sparse, owing to the combination of inaccessibility due to thick sea ice, and chronological difficulties typical of Antarctic shelf sediments. Here, we present new results from near the calving line in the Hughes Trough, located in the central-southern Weddell Sea. Ramped pyrolysis 14C dating was used to determine a robust chronology from the 5.0 m long sediment core, PS111_53. The core preserves a full glaciomarine sequence from subglacial, sub-ice shelf, and open marine / polynya environments. The sedimentological transition interpreted to be formed at the grounding zone during ice shelf retreat was dated to 18.2 – 19.0 ka, indicating that grounded ice retreat was underway by this time. Further, the sedimentation rate was drastically reduced at ~6 ka, indicating that the oceanographic and glaciological regimes of the continental shelf may have changed at this time.

The proposed timing of glacial mass loss is well placed in the context of recent studies from the continental ice sheet and off-shelf marine sediments, which have suggested that a significant ice mass loss event from the Weddell Sector of the Antarctic Ice Sheet (AIS) may have occurred early in the deglaciation. A synchronous timing of deglaciation between the Weddell Sector of the AIS and Laurentide Ice Sheets during MWP-1A0 points towards bi-polar tele-connections.

How to cite: Bollen, M., Müller, J., Gutjahr, M., and Jaccard, S.: Sedimentological evidence for an early deglaciation in the Weddell Sector at ~19 ka, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19800, https://doi.org/10.5194/egusphere-egu24-19800, 2024.

EGU24-20880 | Orals | CR1.3

Modern-day mass gains over East Antarctica exceed the two decades prior 

Brooke Medley and Tyler Sutterley

The recent Ice sheet Mass Balance Inter-comparison Exercise (IMBIE) suggests that between 2012 and 2017 the East Antarctic Ice Sheet was approximately in balance, experiencing a rate of mass change of 23 ± 38 Gt yr-1.  While this study provided an important statistical reconciliation of various studies across several techniques, the root cause of the differences amongst the estimates remains unresolved.  Satellite gravimetry provides a direct measurement of mass change; however, it is sensitive to all mass changes, and the necessary corrections for solid earth changes are substantial and poorly constrained.  Satellite altimetry provides measurements of volume change, which includes changes in ice mass and non-ice mass.  The latter is largely driven by changes in the density of the snow and firn requiring poorly constrained models for conversion to mass.  Here, rather than deriving ice-sheet mass balance using a single technique, we use both satellite gravimetry and altimetry to better: (1) reconcile mass balance estimates between the two techniques, (2) improve constraint on firn dynamics, and (3) attempt to partition the driver of change.  Because these two measurements are sensitive to different processes, using them in conjunction provides additional constraint of the most unknown processes.

Our new technique solves for the change in total firn air content through time for the entire Antarctic Ice Sheet that provides a best-fit mass solution between altimetry and gravimetry.  In such a way, we produce ice-sheet mass change at the fine-scale resolution of ice elevation measurements (10 km) that best matches the coarsely resolved (>100km) mass change from gravimetry.  Our results indicate that during the ICESat-2 era (April 2019 through June 2023), the East Antarctic Ice Sheet gained mass at a rate of 160 Gt yr-1, three times the average mass gain over the two decades prior (52 Gt yr-1).  The sector that spans 60E to 130E received the largest anomalous gains in mass (precipitation).  These gains, in conjunction with minor gains from the Antarctic Peninsula (23 Gt yr-1), fully balance the continued mass losses from West Antarctica (-139 Gt yr-1).  Large precipitation events over both East Antarctica and the Antarctic Peninsula are driving the mass gains; however, more time is needed to determine whether these changes are long-term or only short-lived given the ICESat-2 time series is just over 4 years in length.  These results suggest that atmospheric dynamics play a key role in driving the mass balance of the East Antarctic Ice Sheet and have potential to rapidly change the overall mass balance of the ice sheet.

How to cite: Medley, B. and Sutterley, T.: Modern-day mass gains over East Antarctica exceed the two decades prior, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20880, https://doi.org/10.5194/egusphere-egu24-20880, 2024.

EGU24-21830 | ECS | Posters on site | CR1.3 | Highlight

A cross-disciplinary approach to understanding Antarctic Ice Sheet histories: combining cosmogenic nuclides with records of Antarctic springtails in Dronning Maud Land 

Emma-Louise Cooper, Mark I. Stevens, and Andrew N. Mackintosh

Our understanding of Antarctic Ice Sheet evolution has largely relied on geological evidence from a combination of onshore and offshore archives. In particular, terrestrial cosmogenic nuclides (e.g., 10Be, 26Al, 36Cl, 14C) have now been extensively employed to assess the timing and drivers of past ice sheet change. Yet, such chronologies are incomplete, can be compromised by complex burial-exposure histories, and are not ideally suited to reconstructing the long-term (hundreds of thousands to millions of years) evolution of the ice sheet.

To address this gap in understanding long-term Antarctic Ice Sheet evolution, we investigate the application of a cross-disciplinary approach that incorporates a combination of geological and biological evidence. Recent work has implied that certain biota, such as Antarctic springtails (Arthropoda: Collembola), survived consecutive glacial periods in ice-free refugia by shifting up and down nunataks or on moraines above the ice (see: Stevens and Mackintosh, 2023; https://doi.org/10.1098/rsbl.2022.0590). Due to these prolonged periods of isolation, springtails have now developed high levels of species endemism across Antarctica. These species are often short-range endemics, and now combined with extensive molecular data are the only terrestrial invertebrate group with unequivocal Antarctic provenance across successive glacial maxima on the continent. As a result, incorporating these growing records of Antarctic springtail distribution into chronological studies may yield a more complete understanding of ice sheet evolution through time. Here, we demonstrate the use of this combined approach across the whole of Dronning Maud Land, East Antarctica. 

How to cite: Cooper, E.-L., Stevens, M. I., and Mackintosh, A. N.: A cross-disciplinary approach to understanding Antarctic Ice Sheet histories: combining cosmogenic nuclides with records of Antarctic springtails in Dronning Maud Land, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21830, https://doi.org/10.5194/egusphere-egu24-21830, 2024.

EGU24-22344 | Posters on site | CR1.3

Pleistocene evolution of Ninnis and Cook glaciers (East Antarctica) from a micropaleontological and sedimentological study: Preliminary result 

Fiorenza Torricella, Sergio Andò, Francesca Battaglia, Andrea Caburlotto, Ester Colizza, Xavier Crosta, Laura De Santis, Johan Etorneau, Andrea Gallerani, Torben Gentz, Amy Leventer, Patrizia Macrì, Romana Melis, Matteo Perotti, Gianguido Salvi, Tommaso Tesi, and Luca Zurli

The Cook Ice Shelf and Ninnis Glacier drain a large part of the Wilkes Land Basin, which contains the equivalent of about 4 metres of sea level. The glaciers in this region are thought to have retreated during the warm climatic phases of the Pleistocene, but the extent of the retreat and the identification of the driving forces are still controversial. The aim of this study is to contribute to the understanding of regional depositional processes and environmental conditions that shed light on the dynamics of the ice sheet and the factors that determine its stability and instability (ocean and atmospheric temperature and precipitation), and ultimately to refine the projected evolution of these glaciers. We here present the preliminary results of a multidisciplinary study (textural analyses, geochemical, chemical and petrographic analyses, paleomagnetic and micropaleontological determinations) carried out on six sediment cores collected on the continental slope off the Cook Ice Shelf and Ninnis Glacier in the framework of the Programma Nazionale di Ricerca in Antartide - PNRA project COLLAPSE ("Cook glacier-Ocean system, sea LeveL and Antarctic Past Stability'). We are currently documenting sedimentological processes and oceanographic conditions in this region during the Late Pleistocene. We identified three main units: the first unit consists of laminated silt with low microfossil content and is interpreted as influenced by bottom current; the second unit is a massive silt with ice debris, and very low microfossil content and is interpreted as indicating a period with intense ice calving with iceberg production; the third unit is a bioturbated mud with high microfossil content.   The microfossil content, especially the diatoms, suggest that this unit is deposited during a period of open water.

How to cite: Torricella, F., Andò, S., Battaglia, F., Caburlotto, A., Colizza, E., Crosta, X., De Santis, L., Etorneau, J., Gallerani, A., Gentz, T., Leventer, A., Macrì, P., Melis, R., Perotti, M., Salvi, G., Tesi, T., and Zurli, L.: Pleistocene evolution of Ninnis and Cook glaciers (East Antarctica) from a micropaleontological and sedimentological study: Preliminary result, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-22344, https://doi.org/10.5194/egusphere-egu24-22344, 2024.

EGU24-728 | ECS | Orals | CR1.5

Characterization of snow mechanical properties using laser ultrasound: Role of snow crystal type 

James McCaslin, Thomas Mikesell, Hans-Peter Marshall, and Zoe Courville

Quantifying the mechanical properties of snow is crucial for various applications, including the assessment of slope stability, vehicle mobility on snow-covered terrain, and the understanding of snowpack evolution. To build our understanding of snowpack evolution, we utilize a novel non-contacting laser ultrasound system (LUS). This system collects ultrasonic wavefield data from tens to hundreds of kilohertz in a controlled cold lab environment, allowing us to interpret acoustic measurements and measure mechanical properties on a microscale and upscale this to the field scale.

 

 We investigated the relationship between P-wave velocity changes and snow properties such as density, snow crystal type, and metamorphism through sintering. We controlled the density of the snow samples by adjusting the volume while maintaining the same mass. We controlled the microstructure by manipulating the supersaturation and temperature (controlling air and water temperatures within an artificial snow maker) within a cold lab to make artificial snow of a specific crystal type (i.e., Dendritic, plate, column, and needle snow crystals). Homogeneous snow samples, each composed of their own single crystal type, were created and compacted to a density of 250 kilograms per cubic meter.

 

Over a period of 72 hours, we measured acoustic wave propagation through  these artificial snow samples to periodically observe changes in waves peed during metamorphism. This allowed us to monitor changes in mechanical properties as sintering occurred, for different snow crystal types. We also measured snow microstructure and micromechanical properties with destructive techniques, using the SnowMicroPen and MicroCT. Finally, we examined the relationship between velocity changes and snow crystal types, specifically in terms of sintering time. Our findings suggest that the crystal type, as influenced by time under isothermal temperature conditions, affects the observed bulk mechanical properties and their rate of change.  Observations of ultrasonic wavefields show that snow strengthened by a factor of 1 to 2 within 72 hours, depending on the snow crystal type. 

How to cite: McCaslin, J., Mikesell, T., Marshall, H.-P., and Courville, Z.: Characterization of snow mechanical properties using laser ultrasound: Role of snow crystal type, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-728, https://doi.org/10.5194/egusphere-egu24-728, 2024.

EGU24-1171 | ECS | Posters on site | CR1.5

Debris-covered area increased in the Central Andes of Argentina glaciers over the past four decades 

Juan Cruz Ghilardi Truffa and Lucas Ruiz

In the Central Andes of Argentina, glaciers are crucial components of the mountain hydrological system, as they can provide up to 60% of river flow in the driest season. This region concentrates 82% of the debris-covered glaciers in the country. Most of them are small valley glaciers (< 2 km2). Nevertheless, a few large debris-covered valley glaciers (>10 km2) concentrated the most significant ice volume. Despite their abundance and regional importance, the processes underlying mass exchange and response to climate change in debris-covered glaciers have been little studied.

We process over 60,000 images from Landsat and Sentinel satellites through Google Earth Engine to study changes in the extent of the debris-covered area and Debris Emergence Elevation (DEE) for 128 valley glaciers of the Central Andes of Argentina (42.6% of the debris-covered glacier area). Using an automated classification algorithm, we identified the different surface facies (snow, ice, debris, and water) at each glacier between 1985 and 2022. We validated our classification against the National Glacier Inventory of Argentina, obtaining coincidence in the classifications in more than 94% of the cases.

Assuming there were no changes in glacier extent, we found a 27 ± 15% increase in debris cover along the studied glaciers. Between 1985 and 2009, the debris-covered area had a significant interannual variation, and from 2009 to 2022, there was a substantial increase in the debris-covered area. Indeed, almost 68% of the increase in debris-covered areas occurred in the last decade. During the last four decades, DEE showed a mean increase of 127 ± 109 meters for simple basin valley glaciers. These changes follow a similar pattern but with greater interannual variability than changes in debris-covered area.

The increase of debris-covered area and DEE in the last decade coincides with an extensive drought period and an increase in the glacier mass loss in the Central Andes. Nevertheless, the automated classification algorithm cannot differentiate between debris-covered ice and internal outcrops. Thus, the increase in the debris-covered area includes the expansion of internal rock outcrop due to a loss of ice mass. Furthermore, we hypothesized that hypsometry and glacier morphology control the extent and elevation debris can reach. We found that low-slope glaciers are the ones that increase their debris cover the most. Meanwhile, glaciers with a very steep accumulation area or a strong slope change around the Equilibrium Line Altitude do not significantly change the debris-covered area. Also, due to the expansion of internal rock, the calculation of DEE at large compound or complex-basin glaciers shows more significant dispersion than at simple-basin glaciers. Improving the classification algorithm and assessing the influence of glacier morphology in the changes in debris-covered areas are crucial to better constrain the change in debris-covered glaciers.

How to cite: Ghilardi Truffa, J. C. and Ruiz, L.: Debris-covered area increased in the Central Andes of Argentina glaciers over the past four decades, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1171, https://doi.org/10.5194/egusphere-egu24-1171, 2024.

EGU24-4137 | ECS | Orals | CR1.5

Comparing multisensor optical-radar approaches for snow water equivalent retrievals 

Jack Tarricone, Ross Palomaki, Karl Rittger, Hans-Peter Marshall, Anne Nolin, and Carrie Vuyovich

No current remote sensing technique can accurately measure snow water equivalent (SWE) from space for mountain hydrologic applications. Optical sensors are robust for measuring the fractional snow-covered area (fSCA) at various spatial and temporal resolutions. Yet, these optical methods are limited by cloud cover and do not provide information on SWE. Synthetic aperture radar (SAR) can penetrate clouds, has a fine spatial resolution, and various algorithms allow us to quantify both SWE magnitude and changes. However, SAR cannot discriminate between snow-free and snow-covered areas when the snow is dry. To address this SWE monitoring challenge, we evaluate a multisensor approach that leverages the strengths of both optical and radar sensors. Our study aims to better understand the variability between common snow cover data products and how that uncertainty propagates into InSAR-based SWE retrieval techniques. We analyzed four UAVSAR InSAR pairs from one flight line over the Sierra Nevada, CA, during the SnowEx 2020 campaign and compared six satellite-based snow cover products. First, we computed InSAR-based SWE change estimates using in situ snowpack data. We then compared the summed SWE change values with a moving window analysis to quantify product variability. Lastly, we tested the volumetric SWE results for statistical differences. Results show that moderate-resolution (375–500 m) NDSI-based products provide broadly similar volumetric SWE change results to those using more complex spectral unmixing and machine learning retrieval methods. This suggests that the readily available moderate-resolution snow cover products from MODIS are adequate for an optical-radar SWE monitoring approach. Future work should focus on understanding how sub-canopy snow in forested regions affects snow cover product accuracy and variability. Furthermore, near-real-time, high-resolution cloud- and gap-filled optically-derived snow cover data will be important for supporting water resources decision-making.

How to cite: Tarricone, J., Palomaki, R., Rittger, K., Marshall, H.-P., Nolin, A., and Vuyovich, C.: Comparing multisensor optical-radar approaches for snow water equivalent retrievals, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4137, https://doi.org/10.5194/egusphere-egu24-4137, 2024.

EGU24-5825 | ECS | Orals | CR1.5

Tracking high-alpine snow mass evolution using signals of a superconducting gravimeter combined with snowpack modelling and stereo satellite imagery 

Franziska Koch, Simon Gascoin, Korbinian Achmüller, Paul Schattan, Karl-Friedrich Wetzel, Till Rehm, Karsten Schulz, and Christian Voigt

Monitoring the amount of snow, its spatiotemporal distribution as well as the onset and amount of snow-melt induced runoff generation are key challenges in alpine hydrology. Cryo-hydro-gravimetry is a non-invasive method of observing temporal gravity variations after the reduction of all other geophysical signals as the integral of all cryospheric and hydrological mass variations including snow accumulation and ablation. It has an accuracy of up to 9 decimals on a wide spectrum from high temporal resolution of up to 1 min to several years within footprints up to approx. 50 km². At the Zugspitze Geodynamic Observatory Germany (ZUGOG) with its worldwide unique installation of a superconducting gravimeter at a high-alpine summit (2.962 m a.s.l.), this method is applied for the first time on top of a well-instrumented, snow-dominated catchment. We use this instrumental setup in synthesis with in situ measured data, detailed physically-based snowpack modelling with Alpine3D as well as satellite-based snow depth maps derived by stereo photogrammetry. We will give an introduction into the novel sensor setup and will show first results, including the sensitivity of the integrative gravimetric signal regarding the spatially distributed snowpack and the cryo-hydro-gravimetric signal changes since 2019. The amount of the simulated snow water equivalent within the footprint of the gravimeter correlates well with the gravimetric signal (Pearson correlation coefficient r = 0.98). Based on the applied snowpack modelling approach including the snow depth maps for precipitation scaling, topography information as well as Newton’s Law of Gravitation, the gravimetric signal contribution and footprint can be described spatiotemporally over winter periods.

How to cite: Koch, F., Gascoin, S., Achmüller, K., Schattan, P., Wetzel, K.-F., Rehm, T., Schulz, K., and Voigt, C.: Tracking high-alpine snow mass evolution using signals of a superconducting gravimeter combined with snowpack modelling and stereo satellite imagery, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5825, https://doi.org/10.5194/egusphere-egu24-5825, 2024.

EGU24-6297 | ECS | Orals | CR1.5

Investigating the usage of physically modeled snow cover vs. webcam-based snow cover for driving plant species distribution models 

Andreas Kollert, Kryŝtof Chytrý, Andreas Mayr, Karl Hülber, and Martin Rutzinger

Snow is a crucial factor determining plant species distributions in alpine and arctic environments. Therefore, metrics like the duration of snow cover are important predictors to model plant distributions. Many studies employed snow cover metrics derived from optical satellite image time series. Such satellite-derived observations are easily accessible and highly consistent, making them a viable choice for current and past conditions. However, an inherent limitation is their applicability for future projections of snow cover, which is only possible by establishing statistical relationships to ancillary data sets. Snow cover simulated by a physically-based snow model could circumvent these constraints, but it was rarely employed for predicting alpine plant species distributions. Increasing availability of input data, computational power and data sets for validation nowadays allow for modeling at reasonably high resolutions.

To this end, we report first results of several modeling experiments, to quantify the differences of using snow cover metrics derived from webcam time series and modeled snow data for a study site of approximately 5 km² in the Stubaier Alps (Tyrol, Austria). Melt-out date is one of most commonly used snow metrics in species distribution models. Hence, we derive the melt-out dates from two seasons (2022 and 2023) of webcam-based and modeled snow cover. Subsequently, we modeled the distribution of 79 plant species with the melt-out dates as predictors along with several proxies for topographic heterogeneity at spatial resolutions of 1 m and 20 m in order to account for the small-scale variability of snow cover in alpine landscapes. The study demonstrates how the usage of modeled and observed snow data affects modeling of high-alpine vegetation distribution. These insights are important for appropriately designing species distribution modeling studies based on modeled rather than observed snow data.

Acknowledgements: This work has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (Grant agreement No. 883669).

How to cite: Kollert, A., Chytrý, K., Mayr, A., Hülber, K., and Rutzinger, M.: Investigating the usage of physically modeled snow cover vs. webcam-based snow cover for driving plant species distribution models, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6297, https://doi.org/10.5194/egusphere-egu24-6297, 2024.

Estimates of glacier accumulation are a vital part of determining annual glacier mass balance. Here, the annual accumulation of the Khumbu Glacier, Nepal, is estimated using data from a dense network of high-altitude weather stations in the Khumbu Valley, extending to the summit of Mount Everest. Observations of precipitation phase are used to refine methods of phase modelling using logistic regression in conjunction with weather station and precipitation gauge data. Seasonal temperature lapse rates and spatio-temporal patterns of precipitation are inferred from weather station data, and observed precipitation is adjusted for snow undercatch based on modelled precipitation phase and wind speed. These methods are then combined and distributed over the glacier surface to produce an overall estimate of seasonal and annual accumulation rates of the Khumbu Glacier. 

How to cite: Graves, B.: Estimating the annual accumulation of the Khumbu Glacier, Nepal, using weather station data, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6336, https://doi.org/10.5194/egusphere-egu24-6336, 2024.

EGU24-6979 | ECS | Posters on site | CR1.5

QFuego-Patagonia: a comprehensive glacier-related dataset for Patagonia and Tierra del Fuego, South America 

David Farías-Barahona, Marius Schaefer, Matthias Braun, Valentina Peña, and Jorge Hernández and the Team QFuego-Patagonia

Patagonia and Tierra del Fuego (Fuego-Patagonia 45°S to 56°S) comprise large ice fields known as Northern Patagonia Icefield (NPI) and Southern Patagonia Icefield (SPI), as well as other significant glacierized areas such as the Cordillera Darwin (CD), the Isla Santa Inés, Hoste, and hundreds of smaller glaciers. In total, this ice coverage adds up to an approximate area of 22,000 km2, accounting for about 80% of South America's total.

Throughout the 20th century, much of the knowledge about these glaciers was based on in-situ measurements and data extracted from emerging remote sensing techniques. These efforts were primarily undertaken by scientists from Argentina, Chile, Germany, the United States, France, Japan, and the United Kingdom, as well as the ongoing contributions of government institutions in Chile and Argentina.

Due to increased access to new and more precise satellites, optical and radar sensors, geophysical methods, meteorological instruments, and the sophistication of numerical models in the present century, knowledge about glaciers in Patagonia has significantly expanded. In recent decades, there have been regular updates on changes in area, elevation, surface speeds, determination of thickness in more locations, etc. In this work, we present a comprehensive dataset of the glaciers of Patagonia and Tierra del Fuego (QFuego-Patagonia) consolidated in a Geographic Information System (GIS), which will be made available to the community. This database includes elevation changes, GPR measurements, subglacial topography modeling, as well as time series of surface velocities, among others, which serve as the basis for modeling and projecting the future of Patagonian glaciers. We also announce the new QFuego-Patagonia web portal, where some of the data presented here will be available to the scientific community (https://qfuego-patagonia.org/).

How to cite: Farías-Barahona, D., Schaefer, M., Braun, M., Peña, V., and Hernández, J. and the Team QFuego-Patagonia: QFuego-Patagonia: a comprehensive glacier-related dataset for Patagonia and Tierra del Fuego, South America, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6979, https://doi.org/10.5194/egusphere-egu24-6979, 2024.

EGU24-7043 | ECS | Posters on site | CR1.5

Terrain effects on microwave emission transmission of snowpack and snow depth retrieval 

Tao Che and Liyun Dai

The existing snow depth products have mainly focused on influence of varying snow characteristics and forests, while neglecting the complicated mountainous terrain. Therefore, examining the influence of mountainous terrain on microwave radiation transmission of snowpack is beneficial for improvement of snow depth retrieval algorithms in mountainous areas. In this study, we established microwave emission transfer model of snowpack in Mountainous areas within the framework of MEMLS, thereafter, called MEMLS-T. MEMLS-T considers the influence of complicated terrain on the microwave radiation transmission of snowpack from three perspectives: 1) the varied hill slopes alter the local incidence angle; 2) the diverse hill slopes and aspects induce the polarization rotation; 3) The reduced sky visibility in mountainous regions results in an escalation of downward background radiation reaching the snow surface, as a consequence of the illumination from neighboring slopes. We simulate brightness temperatures at varying sky visibilities, slopes and aspects using MEMLS-T, and find that, in compared with flat terrain, brightness temperature gradient decreases in mountainous area, and the extent of reduction depends on complexity (Figure 1). The brightness temperatures are simulated based on various spatial resolutions of DEM and integrated into a grid of 6.25km×6.25km. The results reveal that coarser DEM results in greater sky visibility (Figure 2) and higher brightness temperature (Figure 3). Therefore, a fine DEM is necessary to simulate the brightness temperatures in mountainous areas. Additionally, the observation footprints vary with satellites and frequencies, resulting in discrepancies in snow depth retrieval and temporal consistency.

figure 1Brightness temperature difference between K and Ka bands varies with aspect, slope and sky radiation

figure 2 Comparison of sky visibility obtained from DEMs with different resolutions.

Figure 3 Comparison of brightness temperature simulated from DEMs with different resolutions

How to cite: Che, T. and Dai, L.: Terrain effects on microwave emission transmission of snowpack and snow depth retrieval, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7043, https://doi.org/10.5194/egusphere-egu24-7043, 2024.

EGU24-7703 | ECS | Posters on site | CR1.5 | Highlight

Centennial observed snowfall trends and variability in the European Alps 

Michele Bozzoli, Alice Crespi, Michael Matiu, Bruno Majone, Lorenzo Giovannini, Dino Zardi, Yuri Brugnara, Alessio Bozzo, Daniele Cat Berro, Luca Mercalli, and Giacomo Bertoldi

Climate change significantly affects snow, emphasizing the urgency to comprehend the temporal and spatial variations in snowfall trends. Analysing historical snowfall data across large areas is often impeded by the lack of continuous long-term time series. This study investigates snowfall trends (HN) by examining observed time series from 46 Alpine sites at various elevations spanning the period 1920-2020. In addition to HN, the analysis focuses on key parameters such as precipitation (P), mean temperature (TMEAN), and large-scale synoptic descriptors — the North Atlantic Oscillation (NAO), Arctic Oscillation (AO), and Atlantic Multidecadal Oscillation (AMO) indices — to discern patterns and variations in HN over the years.

The study reveals that over the past century, below 2000 m a.s.l., there has been a decline in HN across the Alps, particularly in southern and low-elevation sites, despite a slight increase in winter precipitation. The South-West and South-East regions experienced average losses of 4.9% and 3.8% per decade, respectively, while the Northern region showed a smaller relative loss of -2.3% per decade. The negative HN trends are primarily attributed to a TMEAN increase of 0.15 °C per decade. The majority of the HN decrease occurred between 1980 and 2020, as a result of a more pronounced increase in TMEAN. This is reinforced by changes in the running correlation between HN and TMEAN, NAO, AO over time; before 1980, there was no correlation, while in later years, the correlation increased. This suggests that in recent times, the right combination of temperature, precipitation, and atmospheric patterns has become crucial for snowfall. On the other hand, no correlation was found with the AMO index.

How to cite: Bozzoli, M., Crespi, A., Matiu, M., Majone, B., Giovannini, L., Zardi, D., Brugnara, Y., Bozzo, A., Cat Berro, D., Mercalli, L., and Bertoldi, G.: Centennial observed snowfall trends and variability in the European Alps, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7703, https://doi.org/10.5194/egusphere-egu24-7703, 2024.

Plant phenology is highly sensitive to climate change, and the Arctic region is experiencing rapid changes in vegetation and snowpack. However, the specific climatic drivers of these changes are poorly understood. This study aimed to investigate the effects of snowpack phenology and environmental variables on the onset of vegetation phenology in the Alaskan Arctic. The results showed that Snow cover end date (SCED) had a stronger correlation with the Start of the growing season (SOS) compared to other factors, with consistent spatial and temporal patterns. Forested vegetation exhibited strong positive feedback between SCED and SOS, while grassland, shrub, and tundra communities showed insignificant positive feedback. Temperature and Fractional photosynthetically active radiation (FPAR) also significantly affected SOS. Snow density and snow depth played a larger role in SOS variation during the short pre-season period. These findings highlight the need for further investigation into the role of snowpack in specific vegetation types, particularly after observing widespread greening. Future studies should consider factors such as changes in snowmelt timing and photoperiod and traditional climatic factors like temperature and precipitation.

How to cite: Mu, Y. and che, T.: Unraveling the Influence of Snow Phenology on Vegetation across Alaskan Plant Communities, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9574, https://doi.org/10.5194/egusphere-egu24-9574, 2024.

The Visible Infrared Imaging Radiometer Suite (VIIRS) sensor onboard Joint Polar Satellite System (JPSS) satellites will replace the Moderate-Resolution Imaging Spectroradiometer (MODIS) to prolong data recording in the future. 
Therefore, it is a fundamental task to analyze the consistency and assess the accuracy of the snow cover products retrieved from the two sensors. 
In this study, snow cover products from MODIS/Terra, MODIS/Aqua, VIIRS/SNPP and VIIRS/JPSS-1, were evaluated in terms of Normalized Difference Snow Index (NDSI) consistency and accuracy assessment using higher resolution images of Landsat and Sentinel-2 snow cover products. Paired comparisons were performed among the four products in five major snow distribution regions over the world: Northeast China (NE), Northwest China (NW), the Qinghai–Tibet Plateau (QT), Northern America (NA), and European Union (EU). The two categories of snow products are utilized: The L3 Daily Tiled products, referenced by their Earth Science Data Type (ESDT) names of VJ110A1, VNP10A1, MOD10A1, MYD10A1, and L3 Daily Cloud-Gap-Filled (CGF) products, VJ110A1F, VNP10A1F, MOD10A1F, MYD10A1F. The important conclusions demonstrated as follows.
(1) During the snow season, the four types of 10A1 snow products demonstrated good consistency, with higher R values and smaller BIAS under clear sky. VIIRS exhibited a higher snow cover percentage than MODIS. By combining the four 10A1snow products, it is effective and feasible to produce cloud-free snow products.
(2) The consistency of the four 10A1F snow products was lower than that of the 10A1 products under clear skies. SNPP showed good consistency with JPSS-1, and the same to TERRA with AQUA.
(3) In the 10A1F products based on the previous day's clear-sky cloud-filling algorithm, VJ1 and VNP products exhibited larger fluctuations compared to MOD and MYD products. Among the 10A1F products, the smaller fluctuations and higher snow cover percentage of MODIS, along with a cloud persistence duration higher than VIIRS, led to an overestimation in MODIS's 10A1F snow products.
(4) The snow-cloud confusion is existing both in products with the same sensor and with different sensors for the 10A1products, and the latter is much larger than the former, the percentage of which is approximately 10% in the five regions.
(5) High-resolution snow product validation indicates that VIIRS has higher accuracy in both snow products than MODIS. 
(6) The newest JPSS-1 snow cover products display good agreement with that of SNPP. The pixels with the flag of ‘no decision’ in VNP10A1, MOD10A1, MYD10A1 are labelled as land, waterbody, and mostly clouds in VJ110A1 product, respectively.               
Above all, in spite of existing sensor differences affecting consistency of snow cover products, the paired comparisons indicated that under clear skies, the four snow products exhibit good consistency, with higher consistency observed in snow products from the same sensor. The evaluations by higher resolution snow products assured the high accuracy. It is effective and feasible to produce cloud-free snow products considering the overestimation of 10A1F products.

How to cite: Liu, A. W. and Che, T.: Consistency and Accuracy Assessment of Snow Cover Products from Terra, Aqua, SNPP and JPSS-1 Satellites, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9925, https://doi.org/10.5194/egusphere-egu24-9925, 2024.

EGU24-11117 | Orals | CR1.5 | Highlight

Swiss snow cover in a changing climate: Evaluation of a long-term, high-resolution SWE climatology 

Sven Kotlarski, Sarina Danioth, Stefanie Gubler, Regula Muelchi, Adrien Michel, Tobias Jonas, Christian R. Steger, and Christoph Marty

Surface snow cover is an important and highly interactive component of global and regional climate systems and has already clearly responded to past warming trends in many regions of the world. Moreover, it is a key ingredient for tourism industry, water supply, irrigation, and hydro-power generation in many mountainous and high-latitude regions. Accurate information about the past, present and future evolution of snow cover is therefore of high importance.

In this context, we here present and evaluate a newly developed gridded SWE climatology for Switzerland, available at daily resolution since 1961 and at a 1 km grid spacing. The climatology is based on a variant of the snow cover model of the Operational Snow Hydrological Service (OSHD) of Switzerland, driven by gridded atmospheric input and bias-adjusted towards in-situ snow depth measurements. In accordance with previous works, the analysis shows that the Swiss snow cover has changed strongly over the last decades. The comparison of two climatological long-term periods, 1962-1990 and 1991-2020, in terms of mean September-May SWE and the number of snow days (SWE > 10 mm) within the snow season, reveals a decrease in both indicators over the majority of the country. Low elevations < 1000 m show relative decreases larger than 50% of the mean SWE and larger than 30% regarding the mean number of snow days (about -22 days). The largest absolute difference of mean SWE is found at medium elevations between 1500 and 2000 m with a decrease of about 45 mm (about -26%).

The validation of the new snow climatology indicates a high general agreement with in-situ observations and independent remote sensing products. Larger uncertainties and limitations are found at the highest elevations (> 3000 m). They originate from different sources, such as temporal inconsistencies in the gridded input data of the underlying OSHD snow model or the lack of stations at high elevations that are needed for the bias adjustment of the model. Nevertheless, the new snow climatology is able to provide adequate information on past snow cover for Switzerland as a whole and will, among others, serve as a reference for the development of future snow cover scenarios.

How to cite: Kotlarski, S., Danioth, S., Gubler, S., Muelchi, R., Michel, A., Jonas, T., Steger, C. R., and Marty, C.: Swiss snow cover in a changing climate: Evaluation of a long-term, high-resolution SWE climatology, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11117, https://doi.org/10.5194/egusphere-egu24-11117, 2024.

EGU24-11228 | ECS | Orals | CR1.5

Mapping snow depth in the Arctic with public satellite elevation datasets, a case study in Iceland with ICESat-2 and the ArcticDEM 

César Deschamps-Berger, Joaquin Belart, Andri Gunnarsson, Jesus Revuelto, Guðfinna Aðalgeirsdóttir, and Juan Ignacio Lopez-Moreno

Satellite datasets are especially useful to monitor the cryosphere in vast and remote environments, such as the Arctic, where seasonal snowpack controls permafrost distribution, surface runoff, plant growth and animal survival rate. The recent availability of free, high-precision and high-resolution elevation datasets show promises to map snow depth on a large scale, a key bulk variable of the snowpack. Here, we mapped the snow depth distribution across Iceland (65°N) using elevation data from ICESat-2, a photon-counting laser altimetry satellite, and the ArcticDEM, a large set of digital elevation models from satellite stereoimages. The snow depth was retrieved through comparison of acquisitions with snow-on conditions (ICESat-2, ArcticDEM) and snow-free (summer ArcticDEM). Despite the heterogeneous spatial coverage of the two datasets, negative impacts of clouds, polar night and a shallow snowpack often close to the limit of detection, we successfully retrieved snow depth from 2018 to 2023, at monthly resolution. By leveraging large publicly available datasets, this approach is promising to further monitor the snowpack in other regions of the Arctic.

How to cite: Deschamps-Berger, C., Belart, J., Gunnarsson, A., Revuelto, J., Aðalgeirsdóttir, G., and Lopez-Moreno, J. I.: Mapping snow depth in the Arctic with public satellite elevation datasets, a case study in Iceland with ICESat-2 and the ArcticDEM, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11228, https://doi.org/10.5194/egusphere-egu24-11228, 2024.

EGU24-11303 | ECS | Orals | CR1.5

Snow Distribution  Evaluation in High Mountain Asia: Observations and Modeling 

Guang Li, Hongxiang Yu, and Ning Huang

Snow in mountainous areas changes fast in space and time, resulting in strong spatial and temporal heterogeneity, which highly impacts the radiation balance and hydrological cycle. However, gaps still exist between observations and modeling due to serval issues. One issue is the absence of wind drifting and blowing snow (WDBS) processes in most mesoscale atmospheric models. A newly developed WDBS-coupled atmospheric model, CRYOWRF, was used to evaluate the snow distribution in the Tarim area and Namco area, to assess the impact of WDBS and its sublimation on the snow distribution. Field observations were also carried out to validate the modeling, which showed good agreement.  A highly temporal heterogeneity pattern is shown in High Mountain Asia due to the strong blowing snow sublimation. Our works prove that CRYOWRF has a good performance in High Mountain Asia.

How to cite: Li, G., Yu, H., and Huang, N.: Snow Distribution  Evaluation in High Mountain Asia: Observations and Modeling, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11303, https://doi.org/10.5194/egusphere-egu24-11303, 2024.

EGU24-11617 | ECS | Posters on site | CR1.5

Can we estimate snow accumulation and melt across climates using simple temperature-index modelling? 

Adrià Fontrodona-Bach, Josh Larsen, Bettina Schaefli, and Ross Woods

There are two main limitations to understanding large-scale impacts of environmental change on snow resources, 1) observational snow data at the point scale is highly limited, and 2) extrapolation using models can be challenging due to data availability and performance. This study seeks to address these limitations using widely available climate network data combined with a temperature-index snow model to derive large-scale estimates of mean snow water equivalent conditions across the Northern Hemisphere. Temperature-index modelling is a common approach for simulating snow accumulation and melt in hydrological models. Many studies use this method because of its simplicity, efficiency, and generally good performance if properly calibrated. The approach relies on three assumptions and parameters, namely the snowfall and snowmelt temperature thresholds and the degree-day factor. At scales beyond single gauged catchments, the estimation of these parameters was difficult to date due to a lack of observations on snowmelt. Using the new Northern Hemisphere snow water equivalent dataset (NH-SWE) and co-located climate network observations of temperature and precipitation, this work provides the first large-scale evaluation of temperature-index melt model assumptions and parameters across a diverse range of snow climates. Our study reveals the 0°C as snowfall air temperature threshold captures most snowfall events, especially in cold climates, but risks missing 13% of snowfall events, especially in climates hovering at near-freezing temperatures. Similarly, a snowmelt air temperature threshold of 0°C performs well for most daily snowmelt observations but may incorrectly identify the onset of the melt season too early. Estimated degree-day factors converge towards 3-5 mm/°C/day for deeper snowpack climates (> 300 mm), but their estimation may be more challenging for colder climates with shallower snowpacks (< 300 mm), conditions where the degree-day factors have much higher interannual variability. For estimating mean values of seasonal snow onset and snowmelt season onset and mean snow accumulation at a given location, the temperature-index melt model performs consistently well on average despite its simplicity, but challenges may arise due to warm biases in temperature records or solid precipitation undercatch, mainly over higher elevation areas. This study provides valuable insights into temperature-index melt modelling for large-scale applications, and the results should help refine modelling approaches to enhance our understanding of snowpack responses to global warming.

How to cite: Fontrodona-Bach, A., Larsen, J., Schaefli, B., and Woods, R.: Can we estimate snow accumulation and melt across climates using simple temperature-index modelling?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11617, https://doi.org/10.5194/egusphere-egu24-11617, 2024.

EGU24-12946 | ECS | Orals | CR1.5

Impact of Internal Structure on Water Routing in a Semiarid Andean Glacier 

Gonzalo Navarro, Shelley MacDonell, Rémi Valois, Giulia de Pasquale, and Benjamin Robson

In semiarid Andean regions, rock glaciers are more prevalent than debris-free glaciers and their relatively extensive areal coverage suggest the existence of significant frozen water reserves. Although there are some doubts whether permafrost landforms constitute a readily available water resource due to the effective thermal insulation provided by the active layer, there is some suggestion that permafrost can act as a primary factor controlling water flow and delivery to the catchment. The hydrogeomorphological connections and water system processes linking different hydrological units impacts the fate of the generated water, making it paramount to understand how water is transmitted from the headwater hydrological system to the wider catchment to better predict future impact of climate change in this important environment. However, unravelling their role is reasonably complicated since in semiarid regions glacial complexes (i.e. combination of glaciers and rock glaciers) are common and contain not only complicated structures but also complex hydrological connections.

In this study, the scientific understanding of the hydrological role of ice-debris glacial landforms is analysed to better understand how the transfer of water by glacier complexes relates to their internal structure. The research analyses the lower section of the Tapado glacier complex, in the Chilean semiarid Andes (30°S), which comprised the lower section of the debris-covered Tapado Glacier, that is in morphologic continuity to a rock glacier and a moraine at lower elevations. Geophysical measurements and elevation changes using uncrewed aerial vehicles (UAVs) were employed to inspect the internal structure of the selected ice-debris units in order to evaluate how it controls hydrological routing and storage, and in the delivery of cryospheric waters to the wider catchment.

Overall, internal structural arrangement and composition affect water routing and storage on the explored ice-debris landforms. Impermeable zones, characterised by massive glacial ice, ground ice or interstitial ice, not only represent a water storage capacity but are also a barrier to water flow. Therefore, at their interface with air-filled debris they also play a role in downstream water transmission, since sectors such as the debris layer (debris-covered glacier), active layer (rock glacier), intra-permafrost sectors (rock glacier), and main interstitial ice-free body of the moraine play important roles in the downglacier flow transfer. In addition, the potential subpermafrost hydrological connection between the rock glacier and the moraine area was recognised to occur as baseflow. Importantly, a potentially relevant hydrological role of the rock glacier is described based on its observed heterogenous internal structure associated with enhanced vertical infiltration compared to the debris-covered glacier. Lastly, in general, the moraine acts as a transmissive medium between generated glacial and snow meltwater and the proglacial area and river, buffering incoming flows due to the existence of interstitial ice within moraine structure, which also potentially enables deep groundwater circulation.

How to cite: Navarro, G., MacDonell, S., Valois, R., de Pasquale, G., and Robson, B.: Impact of Internal Structure on Water Routing in a Semiarid Andean Glacier, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12946, https://doi.org/10.5194/egusphere-egu24-12946, 2024.

EGU24-13564 | Orals | CR1.5 | Highlight

SWEET (Snow Water Equivalent Estimation Tool): A new tool to generate updated SWE estimates for poorly monitored regions 

Simone Schauwecker, Álvaro Ayala, Gonzalo Cortés, Eduardo Yáñez, Shelley MacDonell, Katerina Goubanova, and Cristian Orrego

In the dry Chilean North, the impact of the mountain snowpack on freshwater availability in the adjacent lowlands areas is crucial. The correlation between the snow water equivalent record and regionally averaged river discharges suggests that ~85% of the streamflow variance could be explained by the snowpack record alone. As seasonal snow cover depends on few winter events, there is a large year-to-year variability in the snow water equivalent (SWE). Typically, there are some dry years with very low annual precipitation which are compensated by wet years. However, since around 2010, the almost continuous extraordinarily dry conditions (so-called Central Chile “mega drought”) and increased water consumption in the region have led to significant stress on the water system. Hence, for an efficient water allocation and water management, it is crucial to know the actual SWE stored in the mountain snowpack. Until now, decisions have been based on scarce point measurements of the SWE or snow area estimates from MODIS. A drawback of these estimates is the large uncertainty that hampers efficient water allocation with important implications for water security of different sectors such as hydropower, agriculture and domestic use. 

To address this problem, we have developed a new operational SWE Estimation Tool for water resources decision making in the Coquimbo region (SWEET-Coquimbo), able to estimate current SWE in near real-time with a latency of ~10 days. SWE is estimated using a data assimilation framework that combines bias-corrected meteorological forcing ensembles from reanalysis data (ERA5, 5-day latency), hydrological modeling (Snowmodel) and satellite observations (Landsat) of the snow-covered area. SWEET-Coquimbo is placed in an open-access web platform, visualizing the current state of the SWE of five main catchments. The data can be downloaded and used for research and diagnostic purposes. 

The newly generated data show SWE for the period 2000-2023. We can now better understand the response of the regional snow cover to the Central Chile megadrought on snow cover and general trends in SWE over the last two decades. SWEET-Coquimbo has allowed, for the first time, a catchment-based estimation of the water available from the snowpack, which can now be used to improve seasonal runoff forecasts. Furthermore, our method has a great potential to be validated and applied to other mountainous regions with sparse in-situ data, as it does not rely directly on in-situ data.

How to cite: Schauwecker, S., Ayala, Á., Cortés, G., Yáñez, E., MacDonell, S., Goubanova, K., and Orrego, C.: SWEET (Snow Water Equivalent Estimation Tool): A new tool to generate updated SWE estimates for poorly monitored regions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13564, https://doi.org/10.5194/egusphere-egu24-13564, 2024.

EGU24-16383 | ECS | Posters on site | CR1.5

Decadal changes of the snow in the western Tian- shan derived from in-situ snow depth measurements  

Adkham Mamaraimov, Abror Gafurov, Andreas Güntner, and Bodo Bookhagen

Winter snow accumulation is important for summer water supply in Central Asia, and contributes more than 50 % to the annual runoff. The region’s water availability is highly dominated by snow reserves in the mountain, which will be affected by climate change. Volumetric snow data play a vital role for hydrologic forecast in mountainous river basins, where snow is considered as a dominating hydrological component. This study quantifies decadal snow depth changes in the Western Tian-Shan in the Chirchik River Basin in Uzbekistan. The snow depth measurements from Uzhydromet have been used in this research. The historical changes in snow depth has been statistically analyzed for the 1963-2020 hydrological years. Correspondingly, the impact of climatic factors (temperature and precipitation) on snow dynamics were assessed as well. The results of hydrometeorological parameters such as snow depth, air temperature at 2 meters and precipitation were plotted as the trend line on monthly, seasonal, and annual scales. To verify statistical significance of the trend dynamics, the slope method and the Mann-Kendall trend test were applied. Our results show that snow cover (duration) days were significantly decreased by 4 days per decade or 21 days for 57 years from 1963 to 2020. Particularly, the initial occurrence of a permanent snow onset day was significantly delayed by 3 days per decade or 16 days for 57 years. Likewise, annual peak snow depth day was significantly shifted earlier by 4 days per decade or 20 days for 57 years. Interestingly, the maximum snow depth did not change statistically significant, but we observe a decline of 3.33 cm per decade or 19 cm for 57 years. Overall, we conclude that the duration of snow cover (snow reserve) has significantly decreased in the Chirchik basin due to climate warming in the last 57 years.     

How to cite: Mamaraimov, A., Gafurov, A., Güntner, A., and Bookhagen, B.: Decadal changes of the snow in the western Tian- shan derived from in-situ snow depth measurements , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16383, https://doi.org/10.5194/egusphere-egu24-16383, 2024.

EGU24-17058 | Orals | CR1.5

Present and future evolution of the winter snow cover in the French Vosges massif with the help of the regional climate MAR model 

Xavier Fettweis, Bruno Ambroise, Pierre-Marie David, Nicolas Ghilain, and Patrice Paul

The current and future evolution of snow cover in the Vosges massif (N-E of France) was simulated at a resolution of 4 km with the regional climate model MAR (version 3.14) forced by the ERA5 reanalysis. Thanks to the adjustment of only few parameters, MAR (initially developed for the polar regions) was optimized and validated with respect to daily observations of temperature, precipitation and height of the snowpack. Over the 62 winters (DJF) 1960-2021, MAR suggests a statistically significant decrease of about a factor of two in the average snow depth due to the significant increase in temperatures (~+2°C/62 years). Although precipitation has slightly increased (+10-20%/62 years) due to a non-significant strengthening of the westerly circulation, it falls more and more in the form of rain, especially below 1000 m. Above 1000 m, it does not snow less than before but there is more melting reducing the snowpack between two snow events. By extrapolating current trends, an anomaly of +2.5°C (resp. +3.8°C) compared to the winters of 1960-90 would be sufficient to no longer have snowpack on average below 750m (resp. 1000m). This trend is fully confirmed by MAR forced by 5 global models (EC-EARTH3, IPSL-CM6A-LR, MIROC6, MPI-ESM1-HR, NorESM2) from the CMIP6 database using both SSP245 and SSP585 scenarios over 1980-2100. In 2050, the average winter snow cover at 1000m will be reduced by half and will become almost non-existent in 2100 following SSP585. While with SSP245, MAR suggests skiing conditions still possible until 2100 above 1000m.

How to cite: Fettweis, X., Ambroise, B., David, P.-M., Ghilain, N., and Paul, P.: Present and future evolution of the winter snow cover in the French Vosges massif with the help of the regional climate MAR model, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17058, https://doi.org/10.5194/egusphere-egu24-17058, 2024.

EGU24-17505 | ECS | Orals | CR1.5

Determining snow material properties from near-infrared photography 

Lars Mewes, Benjamin Walter, Jon Buchli, Valeria Büchel, Markus Suter, Martin Schneebeli, and Henning Löwe

It is well understood that snow is a complex, porous material, whose microstructural changes directly affect its physical properties. Therefore, – to gauge the snow's role within the climate system – it is of interest to accurately measure and characterize the spatio-temporal variability of snow surfaces and snowpacks.

On a local scale, for example inside a snowpit during a field campaign, snow measurements are often taken in a manual, point-like fashion resulting in single, one-dimensional profiles with a sampling resolution of a few centimeters. At this resolution thin layers are difficult to observe and spatial inhomogeneities of the snowpack are missed. State-of-the-art X-ray microtomography (μ‑CT) scans of snow provide excellent spatial resolution,1 however, the added experimental constraints prevent sampling extended spatio-temporal domains.

To address some of these limitations, we propose to use near-infrared (NIR) photography2 with 940 nm illumination to determine the snow's specific surface area (SSA) and density. Our device – called SnowImager – achieves millimeter resolution and covers a spatial extent of a few square meters, such as the surface area of a snowpit wall. While the SSA is determined directly from the measured NIR image using the well-established asymptotic radiation transfer theory,3–6 the density dependence is introduced by physically truncating the illuminating and back-scattered light. It results non-trivially from the lateral component of the sub-surface scattering process and enables us to recover density profiles that compare well to reference data from density cutter and μ‑CT measurements. As a demonstration, we present the spatial variability of an Antarctic snowpack at an unprecedented level of detail, revealing an extremely high spatial variability of the snow microstructure.

Using near-infrared photography enables accurate and fast determination of snow material properties, whenever millimeter spatial resolution and a spatial extent of several square meters are required. It is thus ideally suited to simultaneously capture thin layers within the snowpack and spatial inhomogeneities over a centimeter to meter scale, which is relevant as ground truth measurement for climate research, remote sensing and avalanche forecasting among others.

 

1. Kerbrat, M. et al., Atmos. Chem. Phys. 8, 1261–1275 (2008).

2. Matzl, M. & Schneebeli, M., J. Glaciol. 52, 558–564 (2006).

3. Bohren, C. F. & Barkstrom, B. R., J. Geophys. Res. 79, 4527–4535 (1974).

4. Warren, S. G., Rev. Geophys. 20, 67–89 (1982).

5. Kokhanovsky, A. A. & Zege, E. P., Appl. Opt. 43, 1589–1602 (2004).

6. Libois, Q. et al., The Cryosphere 7, 1803–1818 (2013).

How to cite: Mewes, L., Walter, B., Buchli, J., Büchel, V., Suter, M., Schneebeli, M., and Löwe, H.: Determining snow material properties from near-infrared photography, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17505, https://doi.org/10.5194/egusphere-egu24-17505, 2024.

Seasonal alpine snow is subject to fluctuating meteorological conditions with diurnal temperature cycles around the freezing point and a mix of snow and rain. Throughout the season, fresh snow accumulations repeatedly contribute to the snowpack whereas older layers beneath contain snow at various stages of the metamorphosis often including melting and refreezing periods. The increasing complexity of the snowpack throughout the snow season affects the interaction of radar signals with the snowpack and underlying ground.

Numerous radar/SAR missions, operating at different frequencies, aim to retrieve snow parameters such as snow mass, snow water equivalent, and snow cover extent. These include missions like CRISTAL, TSMM, ROSE-L, and NISAR, each utilizing specific frequency bands to study the temporal variations in snow properties. Understanding the vertical structure of seasonal snow and its interaction with radar signals at various microwave frequencies from L- to Ka-band is therefore essential.

In our study, we investigated tower-mounted rail-based tomographic SAR measurements obtained within the ESA SnowLab project in Davos Laret, Switzerland. The SAR tomography technique provides non-destructive measurements of the vertical structure of the snowpack by means of vertical profiles of radar backscatter, co-polar phase differences, and interferometric phase differences. The measurements were taken with the ESA SnowScat and the ESA Wide-Band Scatterometer, covering a wide range of frequency bands. Additional data on snow characteristics and meteorology complemented the radar measurements. We present time series of SAR tomographic profiles over entire snow seasons at different frequency bands (1-6 GHz, 12-18 GHz, and 28-40 GHz) with reference snow characterizations obtained from snow pits and SnowMicroPen measurements. Detailed analyses include depth-resolved co-polar phase differences, anisotropy, and differential interferometric phase, revealing insights into changes in snow properties over time.

The high-resolution SAR tomographic profiles offer valuable information on microwave interactions with seasonal alpine snow. Analysis of vertical radar backscatter profiles indicates relative changes in location and intensity within the snowpack, correlating with factors like melting and refreezing cycles, snow accumulation, and liquid water content.

We find that distinctive features of seasonal snow, such as melt-freeze crusts, varying penetration depths, and anisotropy can be tracked over time using a SAR tomography approach. To exploit this information for snow mass and structure retrieval, further research tailored to specific spaceborne SAR mission objectives is required. The ESA SnowLab time series of SAR tomographic profiles is a rich dataset covering a broad spectrum of frequencies and providing an opportunity to advance the understanding of scattering mechanisms in alpine snow for various spaceborne SAR missions. The comprehensive coverage includes frequency bands relevant to existing and future mission concepts.

How to cite: Frey, O., Wiesmann, A., Werner, C., Caduff, R., Löwe, H., and Jaggi, M.: High-resolution snow parameter/structure retrieval from tower-based radar time series of seasonal snow obtained with the ESA SnowScat and the ESA Wideband Scatterometer in SAR tomographic profiling mode, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17561, https://doi.org/10.5194/egusphere-egu24-17561, 2024.

EGU24-17624 | Orals | CR1.5

Snowfall variability, trends and their altitudinal dependence in the European Alps from ERA5, HISTALP and in-situ observations 

Silvia Terzago, Ludovica Martina Gatti, Enrico Arnone, and Michael Christian Matiu

Mountain precipitation is a key feature of the hydrological cycle since it feeds snowpack, glaciers, river runoff and supports ecosystems and human life both locally and downstream. However, available precipitation datasets are affected by large uncertainties in mountain regions, especially during the cold season when most of the precipitation falls as snow: on one hand, commonly used precipitation gauges can have systematic losses up to 80-100% in case of snow precipitation, mainly owing to wind undercatch; on the other hand, reanalysis datasets generally provide much larger precipitation amounts when compared to observations and observation-based datasets. So, an accurate quantification of the snowfall component is crucially needed to reduce the uncertainty on mountain total precipitation in the cold season.    

In this work we present an extensive analysis of snowfall precipitation over the Greater Alpine Region (GAR) considering snowfall data from different data sources, including long-term in-situ observations, reanalysis and gridded datasets. We analyze: i) the most comprehensive observational dataset of monthly fresh snow depth (commonly employed as a measure of snowfall precipitation), consisting of more than 2000 in-situ station time series, covering 6 alpine countries (Switzerland, Austria, Germany, Slovenia, Italy and France); ii) the snowfall dataset provided by the ECMWF ERA5 global reanalysis at 0.25° spatial resolution, and iii) the HISTALP gridded snowfall dataset at 0.08° spatial resolution, which is based on temperature and precipitation observations. We compare the three datasets over the last decades to investigate i) climatological features of seasonal and monthly snowfall over the GAR; ii) snowfall variability and trends in relation to elevation; iii) snowfall trends in relation to temperature and total precipitation, based on the best available observational datasets; iv) uncertainties in the snowfall climatology and trends, by comparing the different data sources. This study provides a first comprehensive evaluation of the quality of ERA5 and HISTALP snowfall datasets against ground observations. Moreover, by quantifying the snowfall component, it contributes to better characterize mountain precipitation in the cold season.  

How to cite: Terzago, S., Gatti, L. M., Arnone, E., and Matiu, M. C.: Snowfall variability, trends and their altitudinal dependence in the European Alps from ERA5, HISTALP and in-situ observations, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17624, https://doi.org/10.5194/egusphere-egu24-17624, 2024.

EGU24-17847 | ECS | Posters on site | CR1.5

Exploring potential nonlinear developments of snowline depletion in a changing climate in Austria 

Daniel Günther, Roland Koch, and Marc Olefs

The seasonal snow cover is of great interest in Austria due to its immense importance for numerous economic, ecological and social sectors. Meteorological conditions, expressed as the snowline altitude determine whether rain or snow falls on the ground. If the intensity of precipitation is sufficiently high and there is little atmospheric mixing, the melting of solid precipitation in valley areas can lead to a cooling of the atmosphere and to a further drop in the snowline altitude – the snowline depletion effect.  In the course of a changing climate, an increase in snowline altitude is predicted. However, these predictions do not consider the described effect of snowline depletion. From the theory, the increase of the snowline has nonlinear consequences for the frequency and intensity of the subsequent depletion effect. In this study, we investigate this effect for Austria during past precipitation events on the basis of station observations and gridded now-casting products, develop and test a simplified parametrization, and subsequently show its potential future evolution based on simulations.

How to cite: Günther, D., Koch, R., and Olefs, M.: Exploring potential nonlinear developments of snowline depletion in a changing climate in Austria, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17847, https://doi.org/10.5194/egusphere-egu24-17847, 2024.

EGU24-18184 | Posters on site | CR1.5

First results of an inventory of mountain snow information at global scale 

Wolfgang Schöner, Michael Matiu, and Carlos Wydra

Snow information from mountain regions worldwide is of high relevance but its spatial and temporal distribution inhomogeneous. The currently running IACS Joint Body on the Status of Mountain Snow Cover, a joint initiative of IACS together with MRI and WMO GCW aims at improving the snow information, data availability and the access to the data for mountain regions worldwide. As part of the initiative, an inventory was initiated which should provide a first and overall picture on the spatial and temporal availability of snow information in the various mountain regions of the world. As there is no strict delineation of mountain from non-mountain regions, it has been up to the contributing experts to decide on what is part/not part of a mountain region. For larger mountain regions with rather different snow climates, the spatial resolution of the inventory was split into several parts. The inventory was launched in May 2023 and was implemented as on online tool.

The paper presents initial analyses of the inventory, looking at the spatial and temporal patterns of snow information at a global scale. The picture derived from the feedback of the inventory shows fairly clear global differences, with regions where individual researchers (e.g. Central Asia) are driving access to snow information, while other regions have well established access routines/portals provided by the institutions operating the snow networks (e.g. the US). A preliminary analysis based on metadata from the inventory, a digital elevation model and the GMBA mountain delineation identifies the distribution of in-situ station and their snow information worldwide and how this varies by region and elevation. Information on already estimated spatial and temporal trends of key snow cover variables from mountain regions, such as for snow depth HS and depth of snowfall HN (from unpublished and published papers), are compiled together, although the different trend periods do not make comparison easy. Overall, a rather inhomogeneous picture emerges with regions such as the Alps or the Scandinavian mountains on the one hand, in which the snow information is spatially and temporally dense (with many published studies), and on the other hand regions (such as Greenland or Patagonia) in which the snow information from observations is extremely sparse.

How to cite: Schöner, W., Matiu, M., and Wydra, C.: First results of an inventory of mountain snow information at global scale, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18184, https://doi.org/10.5194/egusphere-egu24-18184, 2024.

EGU24-18472 | Orals | CR1.5

On the importance of the cryosphere in a tropical Andean basin: the past, present and future of the glaciers and runoff in the Rio Santa 

Catriona Fyffe, Emily Potter, Evan Miles, Thomas Shaw, Mike McCarthy, Andrew Orr, Edwin Loarte, Katy Medina, Simone Fatichi, and Francesca Pellicciotti

The Peruvian Andes contains the largest mass of glaciers in the tropics and these glaciers have shown considerable decay over the past 4 decades and into the present day. The historic and future runoff is tied to the cryospheric changes in the region and this could have important consequences for water resources, given the importance of snow and ice melt for dry season runoff. To disentangle the role of the cryosphere in the water cycle in the tropical Andes we run the fully distributed, hourly glacier-hydrological model TOPKAPI-ETH, both in the past (from 1987) and into the future over the upper Rio Santa catchment in the Cordillera Blanca. Meteorological forcing is provided by bias-corrected WRF simulations, which are also used for statistical downscaling of CMIP5 model projections to provide the future climatology. Calibration of model parameters is conducted using a step-wise approach using a wealth of ground-based data and model outputs are evaluated against gauged runoff data and remote sensing estimates of snow cover, glacier cover and glacier mass balance. 

We find that under present conditions (2008-2018) snowmelt is an important contributor to runoff, comprising 16% to 47% of inputs (the range in weekly average as a proportion of all snow melt (on and off-glacier), ice melt and rain contributions) into the catchment with its proportional contribution largest at the beginning of the dry season (early June). Off-glacier snowmelt is important in the wet season, but snow is confined to on-glacier areas by the mid-dry season. Snow cover <5000 m is ephemeral, lasting hours to days, with correspondingly thin average snow depths and rapid fluctuations in the wet season snowline. Meanwhile, ice melt is an important contributor to runoff in the dry season (up to 54% of the inputs in early August) in all glacierised catchments, even those with a small glacier cover, but the wet season contribution is small. We also explore the long term evolution of glaciers and snow cover in the catchment and its implications for catchment runoff. Through the long term modelling we investigate the timing of peak water in the catchment and the key drivers of runoff change in the past. Our future projections will allow us to examine the impact of future climate changes on the glaciers and snow dynamics. A key vulnerability is the impact of temperature increases on the ephemeral snowpack and the consequences for glacier mass balance. We will also investigate the potential implications for catchment runoff and dry season water availability.

How to cite: Fyffe, C., Potter, E., Miles, E., Shaw, T., McCarthy, M., Orr, A., Loarte, E., Medina, K., Fatichi, S., and Pellicciotti, F.: On the importance of the cryosphere in a tropical Andean basin: the past, present and future of the glaciers and runoff in the Rio Santa, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18472, https://doi.org/10.5194/egusphere-egu24-18472, 2024.

EGU24-19588 | Orals | CR1.5

Seasonal snow cover variations in Central Asia based on remote sensing data 

Akmal Gafurov, Adkham Mamaraimov, Busch Friedrich, and Abror Gafurov

Snow is an important hydrological component in Central Asia. The snowmelt contributes to about 50 % of total water formation in the region, depending on geographic conditions. Many hydro-meteorological phenomena such as floods or drought conditions can be triggered by snowmelt amounts in Central Asia. The amount of snow accumulation in the mountains of Tian-Shan and Pamir also defines the availability of water for summer months to be used for agricultural production or re-filling of reservoirs for energy production in the winter period. Thus, it is of high importance to better understand the seasonal variation of snow and if the over the global average climate warming in the region is affecting the processes related to snow accumulation and melt.

In this study, we analyze 22 years of daily Moderate Resolution Imaging Radiometer (MODIS) snow cover data that was processed using the MODSNOW-Tool, including cloud elimination. Additionally, observed snow depth data from meteorological stations were used to estimate trends related to snow cover change. We used several parameters such as snow cover duration, snow depth, snow cover extent, and snowline elevation to analyze changes.  We conducted this analysis in 18 river basins across the Central Asian domain with each river basin having different geographic conditions and the results show varying tendencies. In many river basins, a clear decrease of snow cover was found to be significant, whereas in some river basins also increase in the snow cover extent in particular months could be identified. We attributed the changes related to snow cover to available historical temperature and precipitation records from meteorological stations to better understand the driving forces. The results of this study indicate seasonal snow cover variations but also potential water shortages in particular months as well as water abundance in months where water demand is not high in Central Asia.

How to cite: Gafurov, A., Mamaraimov, A., Friedrich, B., and Gafurov, A.: Seasonal snow cover variations in Central Asia based on remote sensing data, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19588, https://doi.org/10.5194/egusphere-egu24-19588, 2024.

EGU24-21766 | ECS | Posters on site | CR1.5

Evaluating Sentinel-1 volume scattering based snow depth retrievals over NASA SnowEx sites 

Zachary Hoppinen, Ross Palomaki, Jack Tarricone, George Brencher, Devon Dunmire, Eric Gagliano, Adrian Marziliano, Naheem Adebisi, Randall Bonnell, and Hans-Peter Marshall

Synthetic aperture radar will be at the forefront of future advancements in global

remote sensing of snow depth and snow water equivalent. Recently, snow depth

retrievals using an empirical volume scattering approach with C-band Sentinel-1 (S1)

data have been demonstrated over the European Alps and Northern Hemisphere, with

the most accurate results obtained in regions with dry, deep (>1.5 m) snowpacks and

little vegetation influence. However, these S1-based snow depth retrievals have

previously been compared only to point-based measurements or modeled snow depth

products. In this study we develop an open-source version of the S1 snow depth

retrieval technique and compare the results to spatially-distributed lidar snow depth

measurements. The highly accurate and fine resolution lidar datasets were collected

during the NASA Snow SnowEx 2020 and 2021 field campaigns at six study sites

across the western United States. These regions represent different snow environments

and characteristics than the datasets used for comparison in previous investigations.

We compare the S1 and lidar snow depths at a range of spatial resolutions and interpret

the results within the context of snowpack, vegetation, and terrain characteristics. At 90

m resolution, comparisons between lidar and S1 snow depth retrievals show low to

moderate correlations (R = 0.38) and high RMSE (0.98 m) averaged across the study

sites, with improved performance at 500 m resolution (R = 0.59, RMSE = 0.69 m). The

distribution of S1 and lidar snow depths are more similar in regions of deeper snow,

lower forest coverage, higher incidence angles, dry snow, and at coarser spatial

resolutions. Our results highlight limitations of the current S1 snow depth algorithm and

present opportunities to improve the technique for future snow depth retrievals across

varied snow environments.

How to cite: Hoppinen, Z., Palomaki, R., Tarricone, J., Brencher, G., Dunmire, D., Gagliano, E., Marziliano, A., Adebisi, N., Bonnell, R., and Marshall, H.-P.: Evaluating Sentinel-1 volume scattering based snow depth retrievals over NASA SnowEx sites, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21766, https://doi.org/10.5194/egusphere-egu24-21766, 2024.

EGU24-22452 | Posters on site | CR1.5

Use of mobile L-Band interferometric synthetic aperture radar observations to inform snow property estimation 

Elias Deeb, Tate Meehan, Zach Hoppinen, Charles Werner, Othmar Frey, Richard Forster, and Adam LeWinter

With the dawn of future L-Band satellite interferometric missions (e.g., NISAR - NASA/ISRO SAR and ESA ROSE-L) upon us, there are unique opportunities to explore the use of radar methods and techniques across a variety of applications. Moreover, through the advancement of radar remote sensing hardare and software, additional opportunities exist to specifically target and explore the development of snow estimation, snowmelt impact, and resulting soil moisture detection applications. With the development of mobile interferometric synthetic aperture (InSAR) hardware and software solutions, we present findings from field campaigns using a multi-polarization L-band (1.6 GHz) InSAR system (Gamma Remote Sensing) deployed from mobile vehicle (car), unmanned aerial vehicle (UAV), and helicopter-based platforms. These platforms allow us to control the temporal repeat of InSAR acquisitions assessing the role of changing environmental conditions on InSAR coherence, bracketing synoptic weather events to identify change in the radar signal, as well as simulating the temporal repeat of future satellite missions to estimate what may be done with these data when available. Results from time-series of InSAR acquisitions exploring snow water equivalent estimation, soil moisture, and airborne deployments (e.g., helicopter and UAV) show sensitivity to L-Band coherence and phase for application development. Future work will also be discussed exploring interferometric tomography and bistatic radar applications.

How to cite: Deeb, E., Meehan, T., Hoppinen, Z., Werner, C., Frey, O., Forster, R., and LeWinter, A.: Use of mobile L-Band interferometric synthetic aperture radar observations to inform snow property estimation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-22452, https://doi.org/10.5194/egusphere-egu24-22452, 2024.

EGU24-22543 | Orals | CR1.5

Quantifying snow water storage from aerial LiDAR surveys in eight Pacific coastal watersheds, British Columbia, Canada 

Rosie Bisset, Bill Floyd, Brian Menounos, Alison Bishop, Sergey Marchenko, Peter Marshall, and Hakai Geospatial

While airborne Light Detection and Ranging (LiDAR) surveys are routinely used to measure snow volume in many types of mountain watersheds, those that are heavily forested and lie within maritime environments have been largely ignored to date. Here, we summarise our findings from a four-year study (2020-2023) of eight watersheds within the coastal rainforests of southwest British Columbia, which collectively represent an area of >330 km2. Aerial LiDAR surveys were conducted 3 to 5 times per year between March and June in order to measure snow depth across each watershed. Spatiotemporally-distributed snow density was estimated using a random forest model incorporating weather station data, LiDAR-derived metrics and in-situ snow density observations. At peak snow volume, we find typical mean catchment-wide snow water equivalent values of ~600-1200 mm, verified by a widespread field campaign consisting of > 25,000 in-situ measurements of snow depth and density. We show that, typically, ~60-90 % of the snow water volume is stored at mid-elevations of between 800 and 1500 m, where air temperatures are close to melting point and forest cover is prevalent, leaving the snowpack vulnerable to early seasonal melt onset and impacts due to forest management. We find that while peak measured snow volume typically represents ~20-40 % of surface runoff, providing an important buffer towards droughts within the region, snowmelt volumes can be insufficient to safeguard downstream water supply during extreme seasonal drought events. Overall, the results of this work provide valuable insights into the vulnerability of the snowpack in coastal maritime regions and the potential knock-on effects of a changing snowpack on regional water security.

How to cite: Bisset, R., Floyd, B., Menounos, B., Bishop, A., Marchenko, S., Marshall, P., and Geospatial, H.: Quantifying snow water storage from aerial LiDAR surveys in eight Pacific coastal watersheds, British Columbia, Canada, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-22543, https://doi.org/10.5194/egusphere-egu24-22543, 2024.

EGU24-9891 | ECS | PICO | CR1.9

Dynamic morphology of clathrate hydrates in porous media 

Zelin Xu and Yoshihiro Konno

Natural gas hydrates represent a significant and widely distributed potential energy source globally. Furthermore, hydrates are also considered a possible carbon capture and storage method in the permafrost and deep ocean sea areas. Hydrate morphology is critical in determining the sediments' flow properties and production/storage efficiency. However, the dynamic morphology remains unclear, especially in the microscale. This study was performed by MH21-S and funded by the Ministry of Economy, Trade and Industry, and we used our self-invented micromodels (micron level) for hydrate formation in an air bath of 1 °C for several months. Meanwhile, the state-of-the-art high-resolution microscope was used to detect the dynamic morphology of hydrate formation and dissociation. The result showed that the hydrate growth mechanism could be divided into four stages due to different driving forces: hydrate fingering formation, Ostwald ripening phenomenon, hydrate contraction, and heterogeneous hydrate dissociation processes. In the first stage, the hydrate fingering formation process consistently occurs from the inlet to the outlet area, and the fingering process stops after several days. In the second stage, the Ostwald ripening phenomenon was detected in the microscale for the first time. Smaller hydrate particles first dissolved and then redeposited onto larger hydrate particles, which is a spontaneous process. In the third stage, the surface area of hydrates tends to reduce to reach a more stable phase, resulting in the hydrate contraction. Finally, manual temperature increases induce heterogeneous hydrate dissociation. Our study aims to enhance the understanding of hydrate behaviors in sediments over an extended period.

How to cite: Xu, Z. and Konno, Y.: Dynamic morphology of clathrate hydrates in porous media, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9891, https://doi.org/10.5194/egusphere-egu24-9891, 2024.

EGU24-10226 | PICO | CR1.9

Widespread gas hydrate on Earth’s continental margins 

Ann Cook, Fawz Naim, Urmi Majumdar, Alexey Portnov, Benjamin Jones, and Ryan Heber

Over the last decade, our research team at Ohio State University has analyzed geophysical well logs in over 1000 petroleum industry wells for natural gas hydrate. This is the largest well log assessment for gas hydrate and includes a number of basins: the northern Gulf of Mexico, offshore Western Australia, the Norwegian Sea, the Barents Sea and the UK Atlantic Margin.

We find evidence for gas hydrate in nearly half of industry wells, indicating that hydrate is widespread in sediments on Earth’s continental margins. Hydrate typically occurs in discrete, cm to m-scale intervals with depth and is at relatively low concentration (~35% saturation or less in a hydrate bearing layer). In addition, we observe that most of these hydrate bearing layers are not near the base of hydrate stability.  

At most locations in our assessment, hydrate is not susceptible to current anthropogenic warming. However, our assessment lacks information about a crucial location on continental margins because this interval is not typical measured by industry well logs: the updip edge of hydrate stability. The updip edge of hydrate stability (~300-500 m water depth) is a critical, largely uncharacterized zone where ocean warming can affect hydrate stability. Scientific ocean drilling is required to characterize the global gas hydrate occurrence and modern seafloor carbon flux along this sensitive boundary.

 

How to cite: Cook, A., Naim, F., Majumdar, U., Portnov, A., Jones, B., and Heber, R.: Widespread gas hydrate on Earth’s continental margins, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10226, https://doi.org/10.5194/egusphere-egu24-10226, 2024.

EGU24-12146 | PICO | CR1.9

Small fractures in marine muds indicating nascent hydrate formation 

Saffron Martin, Morgane Brunet, and Ann Cook

On many marine continental slopes, gas hydrate has been observed filling fractures in marine muds.  Fracture filling hydrate likely forms because the pore size of clays is small, and therefore, hydrate can only form in secondary porosity; some scientists have suggested the process of hydrate formation causes these fractures to form. On borehole image logs, these fractures were found to have high angles and form in 3D planes. While the plane is filled with hydrate, the overall bulk concentration of hydrate can be quite low. In X-ray computed tomography (XCT) images, similar high angle planar fractures have been found that cut through whole round core. Typically, these fractures appear to have diffuse, wispy edges in comparison to other fractures that form due to core expansion or core collection. 

We have found new, smaller 3D planer fractures that are likely the initial stages of hydrate fracture formation. These hydrate-filled fractures range in lengths from around 10 – 400 mm with widths ranging from 0.5 - 15 mm. The fractures tend to be well oriented, having a high dip angles (>40°) and going through the whole core on a plane. The wispy, diffused edges suggest sediment displacement due to the hydrate formation process and are distinctly different than other fractures seen in the XCT data. The fractures must be unconnected to any other break in the sediment, existing solely as a fracture with a high dip angle, with diffused edges.

In New Zealand, IODP Site 1517, we found that these specific fractures appear near the sulfate-methane transition zone (SMTZ). We hypothesize that if more sediment cores and XCT data were collected through and close to the SMTZ, more similar small fractures would be imaged, potentially indicating nascent gas hydrate formation.

How to cite: Martin, S., Brunet, M., and Cook, A.: Small fractures in marine muds indicating nascent hydrate formation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12146, https://doi.org/10.5194/egusphere-egu24-12146, 2024.

EGU24-12671 | PICO | CR1.9

A diminishing stabilizer? Studies on the influence of ice and gas hydrates on the geo-mechanical properties of sediments. 

Erik Spangenberg, Ann Cook, Judith Schicks, and Fabian Heinig

Natural gas hydrates form at elevated pressure and low temperatures in the presence of sufficient quantities of gas and water and have therefore been discovered on all continental margins and in permafrost regions. In the marine hydrate-bearing sediments, gas hydrates, depending on their content, can transform a loose sediment into a consolidated rock with a strongly increased strength. In permafrost regions the hydrate stability zone can extent deep into the ice-bearing permafrost and, therefore, both, ice and hydrate can consolidate the sediment. However, the strength of methane hydrate is much higher than that of ice, which behaves much more ductile. Consequently, the resulting strength of a sediment, containing both components, strongly depends on the ice to hydrate ratio. Conversely, the decomposition of natural gas hydrates in marine or permafrost sediments leads to a reduction in the mechanical strength of the host sediment. In addition, the release of gas can create overpressure in the pore spaces, reducing the effective stress and leading to instabilities in the sediment structure.

Since both continental margins and permafrost regions are used by humans for various activities that largely depend on the mechanical stability of the sediments, knowledge of the main factors and processes that determine the stability of weakly consolidated sediments is crucial. Both the thawing of ice and the decomposition of gas hydrates in permafrost soils lead to a change in the geo-mechanical properties of the host sediment. The residual and peak shear strengths of ice- and hydrate-bearing sediments were investigated using a ring shear cell developed at the GFZ. Based on literature data and our results, we discuss the dependence of the geo-mechanical properties of sediments on ice and hydrate saturation and the possible consequences if their proportion diminishes.

How to cite: Spangenberg, E., Cook, A., Schicks, J., and Heinig, F.: A diminishing stabilizer? Studies on the influence of ice and gas hydrates on the geo-mechanical properties of sediments., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12671, https://doi.org/10.5194/egusphere-egu24-12671, 2024.

Natural gas hydrates are known to exist in vast quantities beneath the permafrost and deep-sea sediment layers worldwide, transcending national borders, making them a promising future energy resource. While test productions have been conducted by a few countries such as Japan, China, and the United States, a commercially viable production method has yet to be established. The technologies developed so far have limitations, as laboratory-scale experiments and computational models often fail to accurately predict production behavior in actual field conditions. To achieve reliable predictions of production patterns, it is crucial to understand the changes in phase distribution within hydrate-bearing sediment layers and the corresponding multiphase fluid behavior. This study utilizes low-field Nuclear Magnetic Resonance (NMR) to quantitatively analyze phase distribution, saturation, and pore occupancy changes within rock samples during hydrate formation and dissociation processes. Particularly, experiments on hydrate formation and dissociation, along with NMR signal analysis, were conducted under conditions where water is abundant to investigate the role and influence of excessive water. In cases of high initial water saturation (presence of movable water), it was observed that the phase saturation distribution during hydrate formation becomes heterogeneous due to water migration in an unexpected manner. During the depressurization-driven dissociation process, a quantifiable increase in water saturation due to dissociated water was observed, revealing the occurrence of hydrate reformation even during the dissociation process. This research provides a methodology and analytical data to understand phenomena that are challenging to predict during hydrate formation and dissociation processes.

How to cite: Ahn, T., Lee, J., and Park, C.: Quantitative Analysis of phase saturation distribution during hydrate formation and dissociation under high water saturation condition using low-field NMR, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14348, https://doi.org/10.5194/egusphere-egu24-14348, 2024.

EGU24-15668 | ECS | PICO | CR1.9

Modelling the base of submarine permafrost in the Canadian Beaufort Sea from seismic data and the depth of the gas hydrate stability zone  

Henrik Grob, Michael Riedel, Sebastian Krastel, Jonas Preine, Mathieu J. Duchesne, Young Keun Jin, and Jong Kuk Hong

During the last 1 Ma in the Canadian Arctic, permafrost and permafrost-associated gas hydrates formed extensively due to mean annual subaerial temperatures of approximately -20°C. Following the last glaciation, a marine transgression occurred and former terrestrially exposed shelves became inundated, resulting in present submarine bottom water temperatures around -1°C. Relict submarine permafrost and gas hydrates in the Canadian Beaufort Sea are still responding to this thermal change resulting in their ongoing degradation. Thawing of permafrost and destabilisation of permafrost-associated gas hydrates can release previously trapped greenhouse gases and can lead to even further gas hydrate dissociation with important implications for the global climate. However, both the extent of the submarine permafrost and the permafrost-associated gas hydrates are still not well known. In this study, we use marine multichannel seismic data to model the base of permafrost from the depth of the base of the gas hydrate stability zone. From this depth, we estimate the theoretical gas hydrate dissociation temperature, which allows us to model the depth of the thermal base of permafrost (0°C isotherm). The base of permafrost we modelled correlates with the lower boundary of a diffuse zone of high diffractivity in seismic data suggesting the presence of ice-bearing permafrost. These results combined show that the base of permafrost still extends close to the shelf edge indicating less permafrost retreat than previously suggested. Our study provides a different approach to accessing the current depth and extent of submarine permafrost on the outermost Canadian Beaufort Shelf.

How to cite: Grob, H., Riedel, M., Krastel, S., Preine, J., Duchesne, M. J., Jin, Y. K., and Hong, J. K.: Modelling the base of submarine permafrost in the Canadian Beaufort Sea from seismic data and the depth of the gas hydrate stability zone , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15668, https://doi.org/10.5194/egusphere-egu24-15668, 2024.

EGU24-16042 | PICO | CR1.9

Gas hydrate precipitation and microbial transformation affect the composition of gases migrating through sediments drilled off SW Taiwan 

Thomas Pape, Tzu-Hsuan Tu, Saulwood Lin, Christian Berndt, Klaus Wallmann, Yiting Tseng, Tim Freudenthal, and Gerhard Bohrmann

Molecular and stable isotopic compositions of light (C1–C3) hydrocarbons in sediments provide information on their formation pathways and postgenetic alterations. In 2018, gas hydrate-bearing sediment cores and borehole logging data were collected with R/V SONNE (cruise SO266) and the seafloor drill rig MARUM-MeBo200 at two sites off SW Taiwan (Bohrmann et al., 2023). The two sites are located on the passive continental margin and on the tectonically active convergent margin in the northern part of the South China Sea (SCS). Geophysical surveys have demonstrated the presence of hydrates at both sites as well as the base of the hydrate stability zone at ∼400 and 450 meters below seafloor (mbsf), respectively (Berndt et al., 2019; Bohrmann et al., 2023). At the passive margin, holes were drilled to a depth of ∼126 mbsf at the southern summit of Formosa Ridge (SSFR, ∼1,140 m water depth). A depth of ~144 mbsf was reached at Four-Way Closure Ridge (FWCR, ~1,320 water depth) on the active margin. Macroscopically, no hydrates were detected in recovered cores from either site, but hydrate-related proxies unequivocally demonstrated the in-situ presence of hydrates. For example, signals in sediment electrical resistivity detected during well logging correlated with anomalies in sediment temperature and pore water chloride concentrations detected in cores. Whereas two hydrate-bearing intervals were identified on SSFR (∼13–39 mbsf, ∼98–120 mbsf), a single interval was found on FWCR (∼65–120 mbsf).
Considerable variations in relative hydrocarbon concentrations expressed as C1/(C2–C3) values were observed in gas accumulated in voids in the cores from each site. C1/(C2–C3) values <10.000 in the hydrate-bearing sections, which contrast with values ranging between 10.000 and 25.000 in sections lacking hydrates, indicate that ethane (C2) and to a lesser extent propane (C3) are enriched during hydrate precipitation. Molecular fractionation is also observed for CO2, which is strongly depleted in the hydrate-bearing sections. The δ13C- (–79 to –69‰) and δ2H- (–197 to –187‰) values of methane (C1) indicate that microbial carbonate reduction is the major source of light hydrocarbons (Milkov & Etiope, 2018) at both sites. Based on pore water sulfate and methane concentrations, the zone of the microbially-mediated sulfate-dependent anaerobic oxidation of methane was identified at a depth of ~10–12 mbsf at both sites. Preferential consumption of C1 in this zone is indicated by low C1/(C2–C3) values. The process also resulted in depletions of C1 in 13C and 1H (δ13C-C1 as low as -100‰, δ2H-C1 as high as -179‰ at 18 mbsf at FWCR) as reported from other regions (e.g., Nankai Trough off Japan; Riedinger et al., 2015).
Our results show that physical fractionation and bio(chemical) transformation of individual light hydrocarbons can significantly change the molecular and isotopic composition of upward migrating gases. Therefore, the composition of shallow gas does not necessarily reflect that of the gas in the deeper subsurface, for example as bound in capacious hydrate reservoirs. The cores from the SCS are excellent for studying how hydrate occurrences and microbial transformation lead to alteration of gas composition.

How to cite: Pape, T., Tu, T.-H., Lin, S., Berndt, C., Wallmann, K., Tseng, Y., Freudenthal, T., and Bohrmann, G.: Gas hydrate precipitation and microbial transformation affect the composition of gases migrating through sediments drilled off SW Taiwan, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16042, https://doi.org/10.5194/egusphere-egu24-16042, 2024.

EGU24-16228 | PICO | CR1.9

Danube Fan gas hydrates: GEOHydrate project results 

Atanas Vasilev, Rositsa Pehlivanova, and Ivan Genov

This work outlines the theretical and field activities conducted under the Bulgarian Science Fund Project GEOHydrate: Geothermal evolution of marine gas hydrate deposits - Danube paleodelta, Black Sea. The purpose of this research is to enhance our understanding and perspectives of the study the connection between marine gas hydrate deposits formation and the measured in situ heat flow in seafloor sediments.

The aim of the GEOHydrate project is to prove the hypothesis about the existence on the seafloor of measurable temperature and heat flow (T&HF) anomalies above gas hydrates deposits (GHDs) and the possibility to restore the 4D-process of GHDs growth from these anomalies.

GEOHydrate data include 2D and 3D seismic and CSEM; in situ heat flow; hydro- and geo-physicochemical measurements; scientific drilling and logging. They are results from the projects BLASON, ASSEMBLAGE, GHASS and specially developed tools and methods for GHDs research from the German projects SUGAR I-III. The applied methods include seismic data interpretation; basin analysis; forward and inverse geothermal problems. The new heat flow approach continues to develop in the EU project DOORS with new cruise data and interpretation. Expected practical results are contribution to direct methods for GHDs search, resource estimation with a high signal-to-noise ratio, and a reduction in the future production costs from proper planning and reducing the number of production wells.

Results contribute to mitigating the effects of 3 modern global threats - climate change, clean air, and the cost of energy. European GHDs production is the most prospect and important for Bulgaria and Romania.

Acknowledgments: This work was supported by:

  • Bulgarian Science Fund project KP-06-OPR04/7 GEOHydrate “Geothermal evolution of marine gas hydrate deposits - Danube paleodelta, Black Sea” (2018-2023);
  • European Union project 101000518 DOORS: Developing Optimal and Open Research Support for the Black Sea (2021-2025).

How to cite: Vasilev, A., Pehlivanova, R., and Genov, I.: Danube Fan gas hydrates: GEOHydrate project results, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16228, https://doi.org/10.5194/egusphere-egu24-16228, 2024.

EGU24-16392 | ECS | PICO | CR1.9

Exploring the efficiency of anaerobic oxidation of methane as a sink to hydrate-sourced methane 

Maria De La Fuente Ruiz, Sandra Arndt, Héctor Marín-Moreno, Tim A. Minshull, and Jean Vaunat

Ocean warming threatens methane hydrate stability in continental margins, potentially leading to methane release into marine sediments, the water column, and ultimately the atmosphere. Over the decadal to millennial timescales during which hydrate-sourced methane release is anticipated, microbially mediated anaerobic oxidation of methane (AOM) in marine sediments may mitigate benthic methane efflux. While traditionally considered a highly efficient biofilter, recent studies reveal significant variability in the AOM sink efficiency. For instance, in cold seep settings, efficiency ranges from 80% to 20% with slow to high fluid flow, respectively, and this decreases to around 10% in pristine seepage environments. This variability is directly related to the balance between multiphase methane transport and the growth dynamics of microbial communities.

In this study, we use a novel 1D multiphase reaction-transport model to investigate the transient evolution of the AOM sink efficiency and its impact on seafloor methane emissions in response to a centennial-scale methane release caused by climate-driven hydrate destabilization. We examine the combined influence of gaseous methane transport, including induced tensile fracturing by pore fluid overpressure, and methanotrophic biomass dynamics on weakening the efficiency of the AOM sink. Preliminary findings suggest that the AOM sink is notably limited to mitigating benthic methane emissions in gassy sediments. Additionally, the slow growth rate of methane-oxidizing microorganisms may lead to significant temporal windows for methane to escape into the ocean. This integrated analysis provides insights into the intricate dynamics governing the efficiency of the benthic AOM sink subjected to hydrate-sourced methane. It contributes to a more comprehensive assessment of potential methane emissions in continental margins in the context of global warming.

How to cite: De La Fuente Ruiz, M., Arndt, S., Marín-Moreno, H., Minshull, T. A., and Vaunat, J.: Exploring the efficiency of anaerobic oxidation of methane as a sink to hydrate-sourced methane, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16392, https://doi.org/10.5194/egusphere-egu24-16392, 2024.

Given the scale and urgency of the climate crisis, the exploration of innovative approaches for greenhouse-gas CO2 capture and sequestration is imperative. This hinges on capturing of CO2 emissions from sources, and storing it into other long-lived, stable carbon “pools” or “sinks”, such as in the form of gas hydrates. Being crystalline solids, gas hydrates have the ability to store gas effectively therein –with gas molecules “imprisoned” in cavities within an otherwise ice-like lattice. To address the limitations of hydrate-based methods for carbon capture, such as stability, scalability, and environmental impacts, gas-nanobubble technology may be integrated into hydrate formation to enhance the efficiency and viability of gas-hydrate formation. Nanobubbles (NBs) have been confirmed to accelerate gas-hydrate crystallisation through the so-called memory effect. However, the mechanism of interactions between NBs and hydrate crystals has not been fully addressed. It is also vital to investigate the optimal conditions for hydrate formation in the presence of NBs for higher stability and scalability.

In this study, a novel method, combining NBs and gas hydrates to enhance the capturing of CO2, is reported. It aims to demonstrate the effects of NBs on hydrate-formation kinetics, and reveals the mechanism of their interactions during the hydrate-crystallisation process by an integration of laboratory experiments and molecular dynamics simulations. NBs were generated by external electric fields with CO2 gas in deionized water. By controlling the processing time and applied voltage, different size and concentration of NBs were expected. DLS measurements were applied to characterise the generated NBs. The kinetic properties of CO2 hydrate formed by NBs solution were analysed experimentally. Numerical dynamics simulations were also applied to simulate the hydrate-formation process in the presence of CO2 NBs with different concentrations. These modelling efforts help in predicting the behavior of the system under different conditions. The simulation results revealed that throughout the growth process, the size and shape of NBs changed, progressively reducing in size. It appears that the hydrate clusters absorbed gas molecules from the surrounding gas clusters, leading to the disappearance of the NB in some systems. These bubble remains in the vicinity of the hydrate interface and supplies CO2 for the hydrate growth. When these bubbles reached a critical size where stability was compromised, they collapsed, resulting in a localized increase in CO2 concentration in the aqueous phase, further promoting hydrate growth. The interaction between water and CO2 molecules increased as the hydrate surface absorbed the gas molecules from the solution and consumed them to form new hydrate cavities. Therefore, CO2 molecules have less preference to interact with each other and thus the gas clusters were shrinking during the simulation.

The outcome of this study deepens the understanding of nanobubble dynamics and addresses the critical role of nanobubbles in CO2 hydrate-crystallization processes - directly contributing to the mitigation of climate-change impacts. 

How to cite: English, N., Naeiji, P., and Pan, M.: Mitigating climate change: investigating the synergistic effects of nanobubbles and gas hydrates for enhanced carbon capture, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16492, https://doi.org/10.5194/egusphere-egu24-16492, 2024.

EGU24-17331 | PICO | CR1.9

Systematic Investigation of Natural Gas Hydrate Dissociation Processes with Regard to Global Warming 

Judith Schicks, Parisa Naeiji, and Mengdi Pan

Natural gas hydrates are crystalline compounds that are formed from hydrogen-bonded water molecules and gas molecules. They mainly contain climate-active CH4, but also other light hydrocarbons, CO2 or H2S They exhibit a high sensitivity to variations in temperature and pressure, mainly driven by environmental changes. The oceanic or atmospheric warming resulting from climate change may trigger the decompositions of hydrates, potentially releasing significant amounts of CH4. To assess the potential risks associated with CH4 release from destabilized hydrate deposits, a precise understanding of the dissociation behaviour of gas hydrates becomes crucial.

In this study, a systematic investigation on the dissociation process of sI CH4 hydrates, sII CH4+C3H8 hydrates, and sII multi-component CH4+C2H6+C3H8+CO2 mixed hydrates was reported. We employed a combination of experimental and molecular dynamics (MD) simulations to provide a more nuanced understanding of the hydrate dissociation behaviours, which primarily shed light on the molecular aspects. The dissociation was induced through thermal stimulation to mimic climate warming. Both in situ and ex situ Raman spectroscopic measurements were performed continuously to characterize the hydrate phase. Throughout the dissociation process, hydrate composition, surface morphology, and the large-to-small cavity ratios were determined.  MD simulations were carried out under similar conditions, providing advanced insights and perspectives that couldn't be readily extracted from experimental observations alone.

Both experimental and simulation outcomes indicate that intrinsic kinetics likely govern the early stage of hydrate dissociation. A significant development in the dissociation process is the hindrance caused by the formation of a quasi-liquid or amorphous phase at the surface of the hydrate particles after the breakup of the outer layer of hydrate cavities. The unstable (partial) hydrate cavities that form within this quasi-liquid phase are oversaturated with gas molecules. Consequently, gas hydrates undergo a cycle of decomposition-reformation-continuing decomposition until the crystal eventually disappears. With decomposition dominating the process, both experimental and numerical simulation results demonstrate that the breakup of large cavities (51262) is faster than that of small ones (512) in sI hydrates. Conversely, a faster breakdown of small 512 cavities in sII hydrates is observed. Additionally, during the dissociation process of sII CH4-C3H8 hydrate, the cavities occupied by CH4 preferentially collapse compared to those filled with C3H8. Similarly, over the dissociation of multi-component hydrate, cavities filled with CH4 exhibit a preferential collapse compared to those filled with C3H8, C2H6, and CO2.  These findings show the complexity and differences in the dissociation behavior of natural gas hydrates depending on their composition and structure and can therefore make an important contribution to an accurate assessment of CH4 release from destabilized hydrate deposits in response to climate change.

How to cite: Schicks, J., Naeiji, P., and Pan, M.: Systematic Investigation of Natural Gas Hydrate Dissociation Processes with Regard to Global Warming, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17331, https://doi.org/10.5194/egusphere-egu24-17331, 2024.

EGU24-18603 | ECS | PICO | CR1.9

The Pioneering Role of Natural-Occurring Peptides on Methane Hydrate Formation—Insights from Experiments and Numerical Simulations 

Mengdi Pan, Bastien Radola, Christopher C.R. Allen, and Niall J. English

Methane hydrates are the most abundant clathrates found in the environment, predominantly in the permafrost and marine continental margins. As such, they consitute an energy resource, a concern for climate change, as well as a potentially significant source of carbon for microorganisms. However, relatively little is known about the way that these microorganisms interact, if at all, with methane hydrate deposits in their environment. Recently, a porin produced by a marine methylotroph (Methylophaga aminisulfidivorans) was found to promote hydrate formation in conditions mimicking that of the seafloor. A specific peptide sequence (TAFDGGS) was shown to be at least partially responsible for this behaviour. However, the exact physico-chemical mechanisms underlying such effects are still unclear.

Our research employed a dual methodology, integrating experimental procedures with molecular dynamics simulations to answer the question of how naturally occurring peptides can influence methane hydrate formation. Initially, laboratory experiments were conducted to observe the kinetics of methane hydrate formation in the presence of the selected natural peptide (TAFDGGS) and the traditional hydrate promoter: sodium dodecyl sulfate (SDS). Methane hydrate formation from deionized water served as a reference. Parameters such as rate of formation, induction time and total gas consumption were meticulously recorded and analysed. In parallel, molecular dynamics simulations of the hydrate formation process with and without the peptide were carried out. The careful analysis of the interactions between water, methane and the peptide provided molecular-level insights on how peptides can influence the nucleation and growth of methane hydrate clusters. Our results indicate that the natural peptide exhibits a distinctive promoting effect on the formation kinetics of methane hydrates. However, the mechanistic hypothesis that the promotion effect is achieved by providing more nucleation sites was ruled out by comparison with the reference groups. Instead, the results suggest a more complex biocatalytic effect on hydrate kinetics.

These findings suggest a potential for peptides as eco-friendly alternatives to traditional chemical promoters in methane hydrate research and provide valuable insights into the design of more efficient and sustainable bio-based promoters. More fundamentally, this study lays a solid foundation for our understanding of the interactions between peptides and hydrates in nature and paves the way for further research on the role of proteins or microorganisms on hydrate deposits.

How to cite: Pan, M., Radola, B., Allen, C. C. R., and English, N. J.: The Pioneering Role of Natural-Occurring Peptides on Methane Hydrate Formation—Insights from Experiments and Numerical Simulations, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18603, https://doi.org/10.5194/egusphere-egu24-18603, 2024.

EGU24-18754 | PICO | CR1.9 | Highlight

The influence of gas hydrate cyclicity on global and regional gas hydrate inventories 

Ewa Burwicz-Galerne and Shubhangi Gupta

Gas hydrate (GH) formation and dissociation in natural systems is a complex, multi-process phenomenon controlled by local pressure-temperature-salinity (p-T-s) conditions and availability of methane gas. Our recent findings based on detailed analyses of GH systems using high fidelity multi-physics numerical model suggest that the long-term stability of the natural gas hydrate systems is not straightforward. On time scales ranging from hundreds to hundred of thousands of years, natural gas hydrate systems are able to develop, so-called, periodic steady-states characterized by a cyclic growth and dissolution of gas hydrate layers as well as a free gas migration through the gas hydrate stability zone (GHSZ). In this presentation, we show how these new results directly affect the estimates of global GH inventories and how they can be used to investigate the development of multiple bottom simulating reflectors (BSRs), slope failures, pockmarks, and gas migration pathways observed in the geological records that may have occurred spontaneously due to the internal system dynamics (i.e. gas hydrate cyclicity).

On a global scale, we have quantified the potential effect of the periodic states expressed as a new uncertainty measure that sets the hard limits on the predictability of present-day gas hydrate inventories through steady-state analysis. On a regional scale, focused on high-latitude locations, we present a combination of system parameters leading to periodic states and provide uncertainty quantifications on the gas hydrate system stability and faith. In that context, we discuss the relation between the time-periods of the cyclic states and the external triggers affecting gas hydrate systems in the Arctic (e.g. anthropogenic warming, sea level changes, glacial- interglacial cycles, etc.).

Keywords: methane cycle, global carbon budget, natural gas hydrate systems, periodic steady-states

How to cite: Burwicz-Galerne, E. and Gupta, S.: The influence of gas hydrate cyclicity on global and regional gas hydrate inventories, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18754, https://doi.org/10.5194/egusphere-egu24-18754, 2024.

By using X-ray computeted tomography(XCT), low-field nuclear magnetic resonance(NMR), N2 gas adsorption(N2GA) method, the microscopic pore system of hydrate-bearing sediments in  KG Basin was comprehensively characterized. Results shown that the pore types are complex, with diverse pore geometry, poor connectivity, foraminiferal shells provide certain pores, 4-20μm micropores contribute the most to permeability. For the lacking of measuring closed pores by N2GA leads to a significant difference in the total pore volume compared with NMR results.

Through monitoring the phase transition process in pores under temperature changes through NMR, the intensity value of the first peak signal of CPMG is collected, meanwhile the pure water signal is calibrated to calculate the unfrozen water content and pore size distribution. The results indicate that the water signal inside the macropores is constantly increasing, significantly weaker than in the micropores; the middle peak values corresponding to the mesopores are disorferly. Analysis shows that water migration occurs within the mesopores, the process of ice melting into water initial occurs in smaller pores.

How to cite: Guan, W.: Multi-scale characterization for pore systems of  hydrate-bearing reservoir, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20561, https://doi.org/10.5194/egusphere-egu24-20561, 2024.

EGU24-21623 | ECS | PICO | CR1.9

Temporal variability of the stability field of methane hydrates in the oceans 

Leonardo Riccucci, Angelo Camerlenghi, Stefano Salon, and Umberta Tinivella

Climate change is mainly monitored at the Earth's surface. However, it is well known that as part
of ongoing climate change, ocean circulation is also changing, and therefore the ocean floor is
also subject to temperature changes.
In this study, the depth of the global methane hydrate stability zone was assessed by analyzing its
changes over the period from 1993 to 2018 to investigate the effect of climate change on the
stability of methane hydrates.
Indeed, seafloor sediments are often permeated by a methane hydrate phase, the stability of
which depends on the pressure and temperature field, among other parameters, and any changes
in temperature conditions near the seafloor can bring the methane hydrate into unstable
conditions.
The data needed for the assessment of methane hydrate stability were obtained from The Global
Ocean Physics Reanalysis data set (GLORYS12V1), produced under the European Copernicus
Marine Environment Monitoring Service (CMEMS), and GEBCO- The General Bathymetric Chart
of the Oceans. The data were then processed with original data processing software developed in
Fortran and Python languages.
A quantitative estimate of the amount of methane released into ocean masses by the dissociation
of methane hydrate in shallow sediments over the period under consideration was also obtained.
The release of large amounts of methane could have an impact on submarine geological hazards,
such as submarine landslides, and the eventual reaching of the atmosphere by methane would
reinforce ongoing climate change.

How to cite: Riccucci, L., Camerlenghi, A., Salon, S., and Tinivella, U.: Temporal variability of the stability field of methane hydrates in the oceans, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21623, https://doi.org/10.5194/egusphere-egu24-21623, 2024.

EGU24-1026 | ECS | Orals | CL1.2.6

Input and output fluxes of surface CO2 over the Late Quaternary 

Luca Castrogiovanni, Pietro Sternai, Claudia Pasquero, and Nicola Piana Agostinetti

Ice core archives allow us to retrieve the atmospheric CO2 concentration of the past 800,000 years characterized by periodically lower and higher CO2 levels corresponding to ice ages and interglacials, respectively. However, there is no broadly accepted consensus regarding the leading drivers of such variability. To a large extent, what prevents us from identifying the mechanisms that underlie changes in atmospheric CO2 concentrations is our inability to split the overall atmospheric CO2 budget into its sources and sinks terms, thereby assessing the fluxes of carbon among different reservoirs. Here, we use a reversible-jump Markov chain Monte Carlo (rj-McMC) algorithm to invert the atmospheric CO2 concentration dataset provided by the EPICA ice core based on a general forward formulation of the geological carbon cycle. We can quantify the most likely temporal variability of atmospheric carbon fluxes in ppm/yr throughout the last 800,000 years. Results suggest that temperature changes have been driving the variations of atmospheric CO2 until the Mid-Brunhes Event (MBE), when the onset of a progressive cyclic increase of  the atmospheric carbon fluxes marks a distinct behavioral change of the climate system. We ascribe such change to mechanisms internal to the Earth system, possibly related to the deglacial triggering of global volcanism and associated feedbacks on climate or a combination of geological, biological, and physical processes. Regardless, our unprecedented quantification of past atmospheric input and output CO2 fluxes provide (1) new constraints for climate carbon cycle and paleoclimate models to assess dominant climate-driving mechanisms, and (2) the benchmark for climate models intercomparison projects and better assessing the anthropogenic perturbation to the geological carbon cycle an associated climatic effect.

 

How to cite: Castrogiovanni, L., Sternai, P., Pasquero, C., and Piana Agostinetti, N.: Input and output fluxes of surface CO2 over the Late Quaternary, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1026, https://doi.org/10.5194/egusphere-egu24-1026, 2024.

One of the critical features of deglaciations is the sudden increase in atmospheric CO2 levels. Regulating the Pleistocene atmospheric CO2 variations requires the involvement of oceanic carbon storage changes. However, the mechanisms and pathways for air-sea carbon exchanges remain elusive, partly resulting from the insufficiency of marine carbonate system proxy data with a robust age control beyond Termination I.

The deglacial CO2 rise toward Marine Isotope Stage (MIS) 9e (Termination IV) started from 197.1 ppm to 300.7 ppm[1], representing the highest natural atmospheric CO2 recorded in the Antarctic ice cores over the past 800 ka[2]. Our high-resolution carbonate system records from the Iberian Margin with a robust age control suggest an expansion of southern-sourced Glacial Antarctic Bottom Water at the onset of the deglaciation, followed by a net release of CO2 from the Atlantic sector of the Southern Ocean. However, our results indicate a different ocean circulation pattern during Termination III, when atmospheric CO2 increases by 85 ppm[2]. Unlike Termination III, the north-sourced water seems to take a large proportion of the deep Atlantic Ocean during this period.

References:

[1] Nehrbass-Ahles, C. et al. (2020), Science vol. 369 1000–1005.

[2] Bereiter, B. et al. (2015), Geophys. Res. Lett. 42, 542–549.

How to cite: Ji, X. and Yu, J.: The mechanism controlling air-sea CO2 exchange under different ocean circulation conditions, a case study from Iberian Margin, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1157, https://doi.org/10.5194/egusphere-egu24-1157, 2024.

EGU24-3128 | Orals | CL1.2.6

Bølling-Allerød warming as a part of orbitally induced climate oscillation  

Yuchen Sun, Xu Zhang, Gregor Knorr, Martin Werner, Lev Tarasov, and Gerrit Lohmann

Deglacial abrupt warming event is a ubiquitous feature of deglaciations during the Late Pleistocene. Nevertheless, during the last deglaciation an unusually early onset of abrupt Northern Hemisphere warming event, known as Bølling/Allerød (B/A) warming, complicates our understanding of their underlying dynamics, especially due to the large uncertainty in histories of ice sheet retreat and meltwater distributions. Here applying the latest reconstruction of ice sheet and meltwater flux, we conduct a set of transient climate experiments to investigate the triggering mechanism of the B/A warming. We find that the realistic spatial distribution of meltwater flux can stimulate the warming even under a persistent meltwater background. Our sensitivity experiments further show that its occurrence is associated with an orbitally induced climate self-oscillation under the very deglacial climate background related to atmospheric CO2 level and ice sheet configurations. Furthermore, the continuous atmospheric CO2 rising and ice sheet retreating appear to mute the oscillation by freshening the North Atlantic via modulating moisture transport by the Westerly. 

How to cite: Sun, Y., Zhang, X., Knorr, G., Werner, M., Tarasov, L., and Lohmann, G.: Bølling-Allerød warming as a part of orbitally induced climate oscillation , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3128, https://doi.org/10.5194/egusphere-egu24-3128, 2024.

EGU24-4269 | ECS | Posters on site | CL1.2.6

Impact of iron fertilisation on Southern Ocean ecosystems and global carbon cycle during the last glacial cycle 

Himadri Saini, Katrin Meissner, Laurie Menviel, and Karin Kvale

Rising atmospheric CO2 concentration is a major driver of climate change. One of the several processes proposed to explain the lower atmospheric CO2 concentration during the last glacial period is an increase in aeolian iron flux into the Southern Ocean. As the Southern Ocean is a high-nutrient-low-chlorophyll region, increased iron deposition can impact Southern Ocean marine ecosystems,  increase export production, and reduce surface Dissolved Inorganic Carbon (DIC) concentration. Here, we investigate the responses of Southern Ocean marine ecosystems to changes in iron flux and their impact on ocean biogeochemistry and atmospheric CO2 during the last glacial period. We use a recently developed complex ecosystem model that includes four different classes of phytoplankton functional types and fully incorporated iron, silica and calcium carbonate cycles. We show that the changes in atmospheric CO2 are more sensitive to the solubility of iron in the ocean than the regional distribution of the iron fluxes. If surface water iron solubility is considered constant through time, we find a CO2 drawdown of ∼4 to ∼8 ppm. However, there is evidence that iron solubility was higher during glacial times. A best estimate of solubility changing from 1 % during interglacials to 3 % to 5 % under glacial conditions yields a ∼9 to 11 ppm CO2 decrease at 70 ka, while a plausible range of CO2 drawdown between 4 to 16 ppm is obtained using the wider but possible range of 1 % to 10 %. We also show that the decrease in CO2 as a function of Southern Ocean iron input follows an exponential decay relationship, which arises due to the saturation of the biological pump efficiency and levels out at ∼21 ppm in our simulations.

We also investigate the role of iron flux changes on the abrupt atmospheric CO2 increase during Heinrich Stadials, which are associated with a near collapse of the Atlantic Meridional Overturning Circulation (AMOC), a sudden decrease in Greenland temperature and warming in the Southern Ocean. Previous modelling studies have investigated the role of the ocean circulation in driving changes in atmospheric CO2 concentration during these abrupt events, while the role of reduced aeolian iron input during Heinrich stadials remained poorly constrained. We show that a weakened iron fertilisation during Heinrich Stadials can lead to ~6 ppm rise in CO2 out of the total increase of 15 to 20ppm as observed. This is caused by a 5% reduction in nutrient utilisation in the Southern Ocean, leading to reduced export production and increased carbon outgassing from the Southern Ocean.

How to cite: Saini, H., Meissner, K., Menviel, L., and Kvale, K.: Impact of iron fertilisation on Southern Ocean ecosystems and global carbon cycle during the last glacial cycle, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4269, https://doi.org/10.5194/egusphere-egu24-4269, 2024.

EGU24-4451 | Posters on site | CL1.2.6

Simulating glacial-interglacial CO2 variations: What's right with CLIMBER? 

Malte Heinemann, Victor Brovkin, Matteo Willeit, Joachim Segschneider, and Birgit Schneider

Despite intense efforts, current generation comprehensive Earth system models have, to our knowledge, not been able to simulate the full extent of the atmospheric pCO2 drawdown (as recorded in ice cores) during the Last Glacial Maximum (LGM). Yet, the intermediate complexity model CLIMBER-2 has successfully been used to simulate not only the LGM drawdown but also the transient evolution of CO2 concentrations during entire glacial–interglacial cycles. To better understand why this is the case, we compare the CLIMBER-2 results to pre-industrial and LGM simulations using two related models with increasing complexity, namely, the recently developed intermediate complexity model CLIMBER-X and the state-of-the-art comprehensive Earth system model MPI-ESM as used in the PalMod project, focusing on ocean carbon cycle changes.

How to cite: Heinemann, M., Brovkin, V., Willeit, M., Segschneider, J., and Schneider, B.: Simulating glacial-interglacial CO2 variations: What's right with CLIMBER?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4451, https://doi.org/10.5194/egusphere-egu24-4451, 2024.

EGU24-4464 | ECS | Posters on site | CL1.2.6

Polar Twins: Glacial CO2 outgassing reduced in the Southern Ocean by upwelling of well-ventilated waters from the North Pacific  

Madison Shankle, Graeme MacGilchrist, William Gray, Casimir de Lavergne, Laurie Menviel, Andrea Burke, and James Rae

The Southern Ocean is widely thought to have played a driving role in the atmospheric CO2 fluctuations of the ice ages, ventilating carbon-rich deep waters to the atmosphere during interglacial periods and limiting this CO2 leakage during glacial periods. A more efficient Southern Ocean biological pump during glacial periods is one of the leading hypotheses for how this “leak” might have been stemmed, but the exact dynamics responsible are still debated. Previous hypotheses have invoked reduced upwelling and/or enhanced stratification in reducing the carbon and nutrient supply to the glacial Southern Ocean surface, thus enhancing the net efficiency of its biological pump. Here we consider an alternative, complementary scenario in which the nutrient and carbon content of the upwelled water itself is reduced. Noting the striking similarity between proxy records from the North Pacific and Southern Ocean over the Last Glacial Cycle and given that carbon-rich waters upwelling in the Southern Ocean today are largely fed by the North Pacific, we propose that low-carbon/nutrient glacial Southern Ocean surface waters could have been sourced from a well-ventilated, low-carbon/nutrient glacial North Pacific. We then show in intermediate-complexity Earth system model simulations how a well-ventilated North Pacific can directly reduce the outgassing potential of waters upwelled in the Southern Ocean. While not precluding the possibility of changes to upwelling or mixing, our results demonstrate the ability of changes in the upwelled waters’ carbon content – outside of any changes to Southern Ocean physical dynamics (e.g., upwelling rate) – to change Southern Ocean carbon content and outgassing. This provides a novel mechanism linking Northern Hemisphere climate to Southern Ocean carbon cycling and may thus help explain the cyclic CO2 variations of the ice ages.

How to cite: Shankle, M., MacGilchrist, G., Gray, W., de Lavergne, C., Menviel, L., Burke, A., and Rae, J.: Polar Twins: Glacial CO2 outgassing reduced in the Southern Ocean by upwelling of well-ventilated waters from the North Pacific , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4464, https://doi.org/10.5194/egusphere-egu24-4464, 2024.

EGU24-5280 | ECS | Orals | CL1.2.6

Sensitivity of millennial-scale climate oscillations to boundary conditions in HadCM3 glacial simulations 

Brooke Snoll, Ruza Ivanovic, Lauren Gregoire, Yvan Rome, and Sam Sherriff-Tadano

Romé et al. (2022) present a new set of long-run Last Glacial Maximum experiments with millennial-scale climate oscillations between cold and warm modes. These oscillations are triggered by different snapshots of ice-sheet meltwater derived from the early stages of the last deglaciation. The overall characteristics of the oscillating events share similarities with δ18O records of the last glacial period. We test the robustness of these oscillations under different climate conditions, i.e., changes in atmospheric carbon dioxide concentration and orbital configuration. These experiments were run with intentions to better understand the range of conditions the oscillations can be sustained within the model and provide additional insight into the triggering mechanisms that control abrupt climate changes. The results of our sensitivity analysis show that small changes in carbon dioxide concentrations can impact the periodicity and existence of oscillations. A decrease in carbon dioxide concentration decreases periodicity, and an increase in carbon dioxide concentration increases periodicity, leading to an end of the oscillations. Our results also show that for changes in orbital configuration, an increase in Northern Hemisphere summer insolation decreases periodicity and potentially also amplitude. The results show that small changes in climate conditions can impact the shape and existence of oscillations and how this could relate to the changing periodicity and amplitude of observed Dansgaard-Oeschger events as well as transitions from glacial to interglacial states.

How to cite: Snoll, B., Ivanovic, R., Gregoire, L., Rome, Y., and Sherriff-Tadano, S.: Sensitivity of millennial-scale climate oscillations to boundary conditions in HadCM3 glacial simulations, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5280, https://doi.org/10.5194/egusphere-egu24-5280, 2024.

Pleistocene temperatures correlate well with glacial-interglacial changes in global ice volume. While a discharge of ice-rafter debris (IRD) into the ocean directly reflects the rates of growth and decay (deglaciations) of glacial ice sheet margins at sea level, it is also the result of a rapidly changing global environment which affected both the meridional overturning in the ocean and the patterns in ocean-atmosphere circulation on a regional scale.  Circum-arctic land regions and adjacent ocean basins hold clues of varying ice sheet sizes through time. Understanding these records correctly is therefore an important asset to better appreciate Quaternary climate change also within a much broader global context. Marine sediment core data from the Nordic Seas show a stepwise trend of decreasing fluxes of IRD during major glaciations of the last 500 ka, i.e., marine isotope stages (MIS) 12, 6, and 2. Strongest IRD deposition occurred in MIS 12 (Elsterian), while it was lower in MIS 6 (Saalian) and 2 (Weichselian). These marine results of iceberg discharge rates from the western European margins, in particular, point to significant temporal changes in the ice-sheet coverage over northern Eurasia. Indeed, field data provide evidence for several major pre-Weichselian glaciations. Although their maximum limits were likely asynchronous in certain places, it seems evident that these ice sheets not only pre-date the Saalian time, they also extended much farther south (and east) than at any time later. The stepwise decreases in Eurasian ice-sheet extents during glacial maxima terminated in quite contrasting deglaciations and subsequent interglacial developments. It appears evident that such a systematic change in ice-sheet sizes were the result of specific ocean heat circulation, which influenced the pathways of atmospheric moisture transfer across northern Eurasia.

How to cite: Bauch, H.: Impact of waxing and waning of Northern Ice sheets on Pleistocene climate , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5426, https://doi.org/10.5194/egusphere-egu24-5426, 2024.

EGU24-5549 | Orals | CL1.2.6

Simulated radiocarbon cycle revisited by considering the bipolar seesaw and benthic 14C data 

Peter Köhler, Luke Skinner, and Florian Adolphi

Carbon cycle models used to interpret the IntCal20 compilation of atmospheric Δ14C have so far neglected a key aspect of the millennial-scale variability connected with the thermal bipolar seesaw: changes in the strength of the Atlantic meridional overturning circulation (AMOC) related to Dansgaard/Oeschger and Heinrich events. Here we implement such AMOC changes in the carbon cycle box model BICYCLE-SE to investigate how model performance over the last 55 kyr is affected, in particular with respect to available 14C and CO2 data. Constraints from deep ocean 14C suggest that the AMOC in the model during Heinrich stadial 1 needs to be highly reduced or even completely shutdown. Ocean circulation and sea ice coverage combined are the processes that almost completely explain modelled changes in deep ocean 14C age, and these are also responsible for a glacial drawdown of ~60 ppm of atmospheric CO2. A further CO2 drawdown of ~25 ppm is caused by the colder ocean surface at the last glacial maximum. We find that the implementation of AMOC changes in the model setup that was previously used for the calculation of the non-polar mean surface marine reservoir age, Marine20, leads to differences of less than ±100 14C years. The representation of AMOC changes therefore appears to be of minor importance for deriving mean ocean radiocarbon calibration products such as Marine20, where atmospheric carbon cycle variables are forced by reconstructions. However, simulated atmospheric CO2 exhibits minima during AMOC reductions in Heinrich stadials, in disagreement with ice core data. This mismatch supports previous suggestions that millennial-scale changes in CO2 were probably mainly driven by biological and physical processes in the Southern Ocean. By modifying the 14C production rate (Q), between one that varies so as to fit simulated atmospheric ∆14C to IntCal20 and an alternative constant Q, we can furthermore show that in our model setup the variability in deep ocean 14C age, especially during the Bølling/Allerød—Younger Dryas—Early Holocene climate transition, has its root cause in the carbon cycle, while a Q that achieves agreement with the IntCal20 atmospheric ∆14C record only enhances deep ocean age anomalies and thus optimizes agreement with the benthic 14C data.

How to cite: Köhler, P., Skinner, L., and Adolphi, F.: Simulated radiocarbon cycle revisited by considering the bipolar seesaw and benthic 14C data, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5549, https://doi.org/10.5194/egusphere-egu24-5549, 2024.

EGU24-6271 | ECS | Orals | CL1.2.6

High-resolution sedimentological and palaeoceanographic investigation of the Last Glacial Termination (T1) recorded on the western margin of the Svalbard (Arctic) 

Fernando Sergio Gois Smith, Renata Giulia Lucchi, Monica Bini, Caterina Morigi, Patrizia Ferretti, Laura Bronzo, and Nessim Douss

The Last Glacial Maximum (LGM) was defined based on the low stand sea-level records from the most recent period when global ice sheets reached their maximum volume, between 26,500 and 19,000 years before present. The end of this cold period was the last glacial termination (T1), occurred between 20 and 11.7 ka BP marking the transition to the current interglacial. During T1, the sea level rise responded to a variety of processes although the melting of the world widely distributed ice sheets was initially the main contributor and responsible for abrupt relative sea level rises known as meltwater pulses (MWPs) that deeply changed the Earth’s physiography. MWPs are short-lived global acceleration in sea-level rise resulting from intense glacial melting, surge of large ice streams into oceans and intense iceberg discharge during ice sheet disintegration. Nowadays, the main concerns related to the present fast global climate change is the possibility that sudden drastic ice loss from the Greenland and/or in the West Antarctic Ice Sheet would lead to a new abrupt acceleration of the relative sea level with consequent inundation of vast coastal areas and/or to cause an abrupt slowdown of the Atlantic Meridional Overturning Circulation (i.e. Golledge et al., 2019). To better understand the dynamics and risks associated with the onset of those events, their impact on thermohaline ocean circulation and climate it is pivotal the study of the well-preserved polar marine sediment records of the events occurred during the T1. Here, we present the results of a high-resolution sedimentological, micropaleontological and geochemical investigation of 3 sediment cores collected on the western margin of Svalbard and eastern side of the Fram Strait (Artic). The sediment cores were collected between 1322 m and 1725 m of water depth, in correspondence of the southern IODP sites that will be drilled during the IODP Exp-403 (June-August 2024).

How to cite: Gois Smith, F. S., Lucchi, R. G., Bini, M., Morigi, C., Ferretti, P., Bronzo, L., and Douss, N.: High-resolution sedimentological and palaeoceanographic investigation of the Last Glacial Termination (T1) recorded on the western margin of the Svalbard (Arctic), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6271, https://doi.org/10.5194/egusphere-egu24-6271, 2024.

EGU24-6599 | ECS | Posters virtual | CL1.2.6

A two-phased Heinrich Stadial 11 as revealed by alkenone-based temperature record from the western tropical North Atlantic  

Anastasia Zhuravleva, Kirsten Fahl, and Henning A. Bauch

Paleo-data and models show that reductions in the strength of the Atlantic meridional overturning circulation (AMOC) lead to significant subsurface warming in the western tropical North Atlantic. The thermal response at the sea surface is less constrained due to the competing nature of the atmospheric and oceanic processes that produce opposite signs of temperature change. Here, we used alkenone unsaturation in sediments to reconstruct sea surface temperature (SST) evolution in the southeastern Caribbean (core MD99-2198, 1330 m water depth) during the last glacial-interglacial cycle, including Heinrich Stadial 11, which was a period of intense AMOC weakening. Our data show a 1 °C SST warming associated with the onset of Heinrich Stadial 11, and a 1 °C cooling during the late Heinrich, followed by a gradual 1 °C warming during the early last interglacial. Although stadial events are generally associated with wind-induced surface cooling in the tropical North Atlantic, the positive Caribbean SST anomaly during Heinrich Stadial 11 is consistent with previous findings. It likely originates from the upwelling of subsurface water that warmed in response to the initial AMOC weakening. Reduction in the Caribbean SST during the late Heinrich, associated with a particularly weak AMOC strength as suggested by our benthic d13C values, can indicate that the subsurface warming has diminished in the tropical North Atlantic possibly due to a general cooling in the source region (i.e., the subtropical gyre). A two-phased Heinrich is supported by the planktic foraminifera assemblage data, indicating that cooling occurred in the late Heinrich. In addition, this late phase is characterized by coarser sediments, which can be due to a strongly reduced outflow of the Orinoco and a particularly southern position of the intertropical convergence zone. For the last interglacial, our alkenone-derived SST record suggests stable conditions. However, the obtained interglacial values are characterized by very high alkenone unsaturation indexes that can incorporate large measurement and calibration errors due to the lack of Caribbean sediment traps and core-top data. These results, therefore, emphasize the need to better quantify the effectiveness of alkenones in reconstructing interglacial SST history in the Caribbean.

How to cite: Zhuravleva, A., Fahl, K., and Bauch, H. A.: A two-phased Heinrich Stadial 11 as revealed by alkenone-based temperature record from the western tropical North Atlantic , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6599, https://doi.org/10.5194/egusphere-egu24-6599, 2024.

Understanding the impact of freshwater discharge from the late Pleistocene Laurentide Ice Sheet (LIS) to the North Atlantic has been considered pivotal due to its direct regulating influence on the climate of the surrounding continents. Numerous studies using indirect paleo-proxies for iceberg discharge and fine-grained sediment supply have reconstructed the instabilities of the LIS. This study employs direct proxies for iceberg discharge and fine-grained sediment supply using the ice-rafted detritus (IRD) and X-ray fluorescence (XRF) scan combined with published X-ray diffraction (XRD) data from the same samples of the Integrated Ocean Drilling Program (IODP) Site U1313 (41°N; 32.57°W). Prominent Heinrich IRD events (H-events) of the last glacial cycle were accompanied by Ti/Ca and Fe/Ca peaks, consistent with the dolomite and calcite peaks, suggesting their Ordovician and Silurian carbonate rocks source that floor the Hudson Bay and Hudson Strait. However, despite the lack of an IRD/g peak, Ti/Ca and Fe/Ca peaks in H-event 3 suggest the arrival of fine-grained sediments in the southern edge of the IRD belt, most likely by sediment plume. In contrast to the last glacial cycle, IRD/g and Ti/Ca and Fe/Ca peaks, often assigned as Heinrich-like events, were only identified during the cold marine isotope stage (MIS) 6, 8, 10, and 12. The IRD/g, Ti/Ca, and Fe/Ca peaks, in addition to the dolomite and calcite peaks during the MIS 7, suggest a fundamentally different configuration of the LIS compared to the other warm MISs of the last 500 ka. Our data suggest that the LIS-sourced icebergs impacted the northern edge of the subtropical gyre (STG) by directly injecting meltwater and modifying the upper water masses, which most likely resulted in the southward movements of the Polar and Arctic fronts. These frontal movements were accompanied by frequent encroachment of the subpolar to transitional water masses to the STG. The polar water-dwelling planktonic foraminifera Neogloboquadrina pachyderma coupled to the IRD/g or Fe/Ca and Ti/Ca peaks support this hypothesis. The new sedimentological and micropaleontological data suggest that the instability and configuration of the LIS were not uniform during all the warm MISs of the last 500 ka.

How to cite: Rashid, H., Zeng, M., and Menke, M.: Impact of the Laurentide Ice Sheet instabilities on the mid-latitude North Atlantic and subtropical gyre during the last five glacial cycles, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6815, https://doi.org/10.5194/egusphere-egu24-6815, 2024.

EGU24-7296 | Orals | CL1.2.6

The Southern Ocean’s role in the global carbon cycle over the last 800 kyr constrained using reconstructions of the CO2 system 

Chen Xu, Jessica Crumpton-Banks, Madison Shankle, Megan Pelly, Hana Jurikova, Jimin Yu, Bradley Opdyke, Claus-Dieter Hillenbrand, Andrea Burke, and James Rae

The critical role of the Southern Ocean in controlling the Pleistocene atmospheric CO2 oscillations is widely acknowledged. However, owing to sampling difficulties surrounding Antarctica, the underlying mechanism and associated pathway of ocean-atmosphere CO2 exchange in the Antarctic Zone (AZ) of the Southern Ocean remains mysterious. Here, we present a new planktonic δ11B record from sediment core PS1506 (68.73°S, 5.85°W) that tracks the pH and surface pCO2 of the AZ over the last 8 glacial cycles. These data are complemented by benthic B/Ca and carbonate preservation indices; due to the location of this core on the continental margin of the eastern Weddell Sea, these data allow us to track the source CO2 chemistry of the dense Antarctic waters that feed the ocean’s lower overturing cell. We find coherent CO2 change between surface and deep waters, indicating persistent formation of AABW that transfers Antarctic surface water signals to depth. Critically, we discover abrupt AZ CO2 decline during glacial onset conditions, coinciding with initial atmospheric CO2 drawdown, highlighting the AZ’s key control on glacial-interglacial CO2 change. After assessing proposed drivers, our findings implicate shifts in Southern Ocean circulation linked to changes in sea ice and/or the Southern Hemisphere westerlies in this glacial onset CO2 change, while productivity, solubility, and sea ice 'lid' effects appear insignificant or counterproductive in this region and time interval. Overall, these reconstructed CO2 system dynamics provide critical insights into Southern Ocean carbon cycling and the associated influence on the atmosphere.

How to cite: Xu, C., Crumpton-Banks, J., Shankle, M., Pelly, M., Jurikova, H., Yu, J., Opdyke, B., Hillenbrand, C.-D., Burke, A., and Rae, J.: The Southern Ocean’s role in the global carbon cycle over the last 800 kyr constrained using reconstructions of the CO2 system, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7296, https://doi.org/10.5194/egusphere-egu24-7296, 2024.

Global sea-level changes are significantly associated with variations in Northern Hemisphere ice sheets (NHISs) during the last glacial cycle. However, their responses to glacial millennial-scale climate variability (also known as Dansgaard - Oeschger (DO) cycles), especially during the Marine Isotope Stage 3 (MIS3, ~30-65ka), remains poorly studied, in addition to the contrast lines of geological evidence regarding paleo-sea level changes. Instead of applying Glacial Index Method which overlooks potential tempo-spatial heterogeneity of temperature and precipitation in the northern high latitudes, in this study, we conducted transient PISM ice sheet modeling by imposing full climate forcing derived from fully coupled climate model experiments which are characterized by spontaneous millennial variability. Our results show that control factors of ice volume changes in Laurentide and Eurasian ice sheets are different due to spatially heterogenous climate forcing. During stadial periods, North American Ice sheets is growing because of increased precipitation especially along the margins of the ice sheets, despite spatially heterogenous but trivial changes in the surface air temperature. Meanwhile, dramatic cooling on the southern regions of Eurasian Ice sheets effectively reduces ice loss and hence promote the overall ice growth. In brief, NHIS ice volume grows during stadials while declines during interstadials. We hence propose that stadial-to-interstadial duration ratio is the key to the net change in NHIS volume in a signal DO cycle, providing dynamic understanding of accelerated sea level drop during 40-30ka.

How to cite: Zhang, Y. and Zhang, X.: Millennial-scale Northern Hemisphere ice sheet growth controlled by stadial-versus-interstadial duration, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7339, https://doi.org/10.5194/egusphere-egu24-7339, 2024.

EGU24-8676 | Posters on site | CL1.2.6

Abrupt climate changes triggered with GLAC-1D ice sheet, but not with ICE-6G_C, in simulations of the Last Glacial Maximum/Deglaciation 

Ruza Ivanovic, Yvan Rome, Lauren Gregoire, Brooke Snoll, Oliver Pollard, and Jacob Perez

In the course of glacial terminations, the increases in greenhouse gas concentrations, summer insolation and the ice sheet demise can trigger episodes of millennial-scale variability. Such variability was observed during the last deglaciation, between 19 ka BP (thousand years ago) and 8 ka BP, in the form of  the abrupt North Atlantic temperature shifts of the Bølling–Allerød Warming (14.5 ka BP) and Younger Dryas (12.900 ka BP).

In some climate models, abrupt climate changes are generated by modifications to the boundary conditions and freshwater discharge. Despite much study, the sensitivity of climate simulations to ice sheet geometry and meltwater is complex and not fully understood, which is a caveat when considering the impact of the rapid demise of the Northern Hemisphere ice sheets during the last deglaciation. In a new set of last glacial maximum HadCM3 simulations that can produce millennial-scale variability, we studied the influence of two ice sheet reconstructions, ICE-6G_C and GLAC-1D, and their associated deglacial meltwater history, on the simulated chain of events of the last deglaciation.

In this experiment, our simulations using the GLAC-1D ice sheet reconstruction produced abrupt climate changes. Triggered by freshwater released close to the Nordic Seas and Iceland Basin deep water formation sites, these simulations display abrupt shifts in the Atlantic Meridional Overturning Circulation (AMOC) that are decoupled from the meltwater flux. In contrast, the reconstructed ICE-6_G ice sheet modifies the North Atlantic wind patterns in the model, preventing convection in the Nordic Seas and intensifying the Iceland Basin deep water formation. As a result, no abrupt climate changes are simulated with ICE-6G_C ice sheets and the AMOC decreases almost linearly with the introduction of freshwater.

The simulations do not capture the timing of the last deglaciation chain of events, but the modelled abrupt changes replicate the main Northern Hemisphere characteristics of the Bølling Warming/Younger Dryas transitions, and are very similar to Dansgaard-Oeschger events.

How to cite: Ivanovic, R., Rome, Y., Gregoire, L., Snoll, B., Pollard, O., and Perez, J.: Abrupt climate changes triggered with GLAC-1D ice sheet, but not with ICE-6G_C, in simulations of the Last Glacial Maximum/Deglaciation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8676, https://doi.org/10.5194/egusphere-egu24-8676, 2024.

EGU24-8715 | ECS | Orals | CL1.2.6

Tracking the fate of meltwater from different Northern ice sheet sectors over Heinrich Stadial 1 

Laura Endres, Ruza Ivanovic, Yvan Romé, Julia Tindall, and Heather Stoll

The addition of meltwater from continental ice sheets to the North Atlantic is thought to have played a pivotal role in the reorganization of climate and ocean circulation over the last deglaciation as well as during Heinrich events. This is supported by recent analysis of PMIP and CMIP results, which shows that meltwater addition into the North Atlantic can largely alter global climate, and remains a key uncertainty for both reconstruction and climate projections. 

To date, most model studies of freshwater “hosing” assume a relatively uniform distribution and apply meltwater to a large portion of the North Atlantic basin. However, AMOC weakening is sensitive to the actual input position of the typically cold and non-saline meltwater perturbation, and, on a centennial-millennial timescale, the resulting temperature and salt anomaly will only partially disperse over the entire North Atlantic surface ocean. In contrast, most proxy data sensitive to meltwater record the signal at a specific location. It is unclear if spatial heterogeneity of the ocean’s distribution of the meltwater anomaly may contribute to disagreements between freshwater proxy records and model simulations with freshwater additions tuned to reproduce the record of past AMOC weakenings.

To enhance understanding of the spatial distribution of meltwater anomalies during deglaciations, we present the results of a model sensitivity study using HadCM3 and artificial dye tracers to track the fate of meltwater originating from different Northern ice sheet sectors. We consider different meltwater scenarios consistent with Heinrich Stadial 1 ice sheet reconstructions and compare the results under different AMOC states. The results confirm that, on a centennial timescale, meltwater distribution is not uniform over the North Atlantic Ocean. The emerging patterns expose that the efficiency of a meltwater injection to produce a surface ocean anomaly (in, e.g., salinity or δ18Osw) at a given proxy location differs between different ice sheet sectors by orders of magnitudes. Further, besides the direct effect of meltwater, the sensitivity of climate indicators, such as temperature, to changes in AMOC strength also shows regional discrepancies. 

How to cite: Endres, L., Ivanovic, R., Romé, Y., Tindall, J., and Stoll, H.: Tracking the fate of meltwater from different Northern ice sheet sectors over Heinrich Stadial 1, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8715, https://doi.org/10.5194/egusphere-egu24-8715, 2024.

EGU24-9143 | Orals | CL1.2.6

Bipolar control on millennial atmospheric CO2 changes over the past glacial cycle 

Jimin Yu, Robert Anderson, Zhangdong Jin, Xuan Ji, David Thornalley, Lixin Wu, Nicolas Thouveny, Yanjun Cai, Liangcheng Tan, Fei Zhang, Laurie Menviel, Jun Tian, Xin Xie, Eelco Rohling, and Jerry McManus

Ice-core measurements show diverse atmospheric CO2 variations – increasing, decreasing or remaining stable – during millennial-scale North Atlantic cold periods called stadials. The reasons for these contrasting trends remain elusive. Ventilation of carbon-rich deep oceans can profoundly affect atmospheric CO2, but its millennial-scale history is poorly constrained. In this study, I will show a high-resolution deep-water acidity record from the Iberian Margin in the North Atlantic, a unique setting that allows us to construct a robust chronology for confident comparisons between marine and ice-core records. The new data combined with ice-core CO2 records reveal multiple ocean ventilation modes involving an interplay of the two polar regions, rather than by the Southern Ocean alone. These modes governed past deep-sea carbon storage and thereby atmospheric CO2 variations on millennial timescales. Overall, our record suggests a bipolar control on millennial atmospheric CO2 changes during the past glacial cycle.

How to cite: Yu, J., Anderson, R., Jin, Z., Ji, X., Thornalley, D., Wu, L., Thouveny, N., Cai, Y., Tan, L., Zhang, F., Menviel, L., Tian, J., Xie, X., Rohling, E., and McManus, J.: Bipolar control on millennial atmospheric CO2 changes over the past glacial cycle, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9143, https://doi.org/10.5194/egusphere-egu24-9143, 2024.

EGU24-9411 | ECS | Orals | CL1.2.6

An Early Warming Over the Southern Ocean During the Last Deglaciation 

Peisong Zheng, Matthew Osman, and Thomas Bauska

The last deglaciation, spanning approximately 23 to 6 thousand years before present (ky BP), represents the most recent period in which Earth’s climate underwent large-scale reorganizations comparable (albeit not strictly analogous) to those projected under future climate changes. However, the precise sequence of events – in particular, the timing and spatial manifestation of the initial warming – remains uncertain. Here we present a new method using Gaussian Mixture Model clustering to objectively decompose a model and proxy-based climate reconstruction (LGMR; Osman et al., 2021) into four patterns of temperature change across the last deglaciation. Broadly speaking, the patterns allow us to delineate the impact of retreating Northern Hemisphere ice sheets, the rise in greenhouse gases, and the influence of the bipolar seesaw. Crucially, our analysis reveals that the high latitudes of the Southern Hemisphere exhibited the earliest signs of warming onset around 21 kyr BP, coincident with a retreat of sea ice across the Southern Ocean. A similar pattern is observed when decomposing a solely model-based climate reconstruction (TraCE-21k; He et al., 2013).  Using a combination of both highly-simplified energy balance-type models and fully-coupled climate models forced with insolation alone, we show that the early warming and sea ice retreat was likely linked to an initial rise in high latitude summertime energy that is dominated by enhanced obliquity-driven forcing. Our findings collectively suggest that insolation dynamics in the Southern Hemisphere were a critical trigger of the Last Deglacial onset and, further, may represent one of the key prerequisites for glacial terminations during the late Pleistocene.

How to cite: Zheng, P., Osman, M., and Bauska, T.: An Early Warming Over the Southern Ocean During the Last Deglaciation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9411, https://doi.org/10.5194/egusphere-egu24-9411, 2024.

EGU24-9419 | ECS | Orals | CL1.2.6

Assessing transient changes in the ocean carbon cycle during the last deglaciation through carbon isotope modeling  

Hidetaka Kobayashi, Akira Oka, Takashi Obase, and Ayako Abe-Ouchi

Atmospheric carbon dioxide concentrations (pCO2) have increases by approximately  from the Last Glacial Maximum (LGM) to the late Holocene (last deglaciation). These changes in atmospheric greenhouse gases are recognized as climate system responses to gradual changes in insolation. Previous modeling studies have suggested that the deglacial increases in atmospheric pCO2 are primarily attributed to the release of CO2 from the ocean. In addition, it has been suggested that abrupt changes in the Atlantic Meridional Overturning Circulation (AMOC) and associated interhemispheric climate changes are involved in the release of CO2. However, there is still limited understanding in oceanic circulation changes, factors responsible for changes in chemical tracers in the ocean of the last deglaciation and its impact on atmospheric pCO2.

In this study, we investigate the evolution of the ocean carbon cycle during the last deglaciation (21 to 11 ka BP) using three-dimensional ocean fields from the transient simulation of the MIROC 4m climate model, which exhibits abrupt AMOC changes as in reconstructions. We validate the simulated ocean carbon cycle changes and discuss possible biases and missing or underestimated processes in the model by comparing simulated carbon isotope ratios with sediment core data.

The qualitative changes in atmospheric pCO2 are consistent with ice core records: during Heinrich Stadial 1 (HS1), atmospheric  increases by . This is followed by a decrease of  during the Bølling–Allerød (BA) and an increase of  during the Younger Dryas (YD). However, the model underestimates the changes in atmospheric  during these events compared to ice core data. Radiocarbon and stable isotope signatures ( and ) indicate that the model underestimates the activated deep ocean ventilation and reduced efficiency of biological carbon export in the Southern Ocean, and active ventilation in the North Pacific Intermediate Water during HS1. The relatively small changes in simulated atmospheric  changes during HS1 may be attributed to these underestimations of ocean circulation changes. The changes in  associated with strengthening and weakening in the AMOC during the BA and YD are generally consistent with the sediment core record. On the other hand, while the data show a continuous  increase in the deep ocean throughout the YD, the model shows the opposite trend. This suggests that the model simulates excessive weakening of the AMOC during the YD, or limited representations in geochemical processes in the model including marine ecosystem responses and terrestrial carbon storage.

Decomposing the factors behind changes in ocean  reveals that changes in temperature and alkalinity have the main effects on atmospheric  changes. The compensation of the effects of temperature and alkalinity suggests the AMOC changes and associated bipolar climate changes contribute to a slight decrease or increase in atmospheric  during the BA and YD periods, respectively.

How to cite: Kobayashi, H., Oka, A., Obase, T., and Abe-Ouchi, A.: Assessing transient changes in the ocean carbon cycle during the last deglaciation through carbon isotope modeling , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9419, https://doi.org/10.5194/egusphere-egu24-9419, 2024.

Be10 in ice cores provides a uniquely well resolved indication of past radionuclide production rates, with a direct bearing on past radiocarbon production.  In the absence of past carbon cycle perturbations (e.g. involving ocean-atmosphere carbon exchange), Be10-based radiocarbon production rate anomalies should correlate directly with atmospheric radiocarbon anomalies, as confirmed by models.  Over the past ~30ka, Be10-inferred radiocarbon production rates and atmospheric radiocarbon (i.e. Intcal20) both exhibit recurrent millennial anomalies, typically of ~5ka duration.  A correlation between these anomalies breaks down during the deglaciation.  This is intriguing and suggests a mix of millennial carbon cycle and radionuclide production influences. Here, global compilations of marine carbon isotope data (radiocarbon and 𝛿13C) are used to assess the potential contribution of ocean circulation and air-sea gas exchange to the apparent millennial component of variability in Intcal20, and atmospheric CO2. We find that existing marine 𝛿13C data provide strong support for a marine influence on atmospheric radiocarbon. Support from marine radiocarbon data is more complex, due to the influence of ‘attenuation biases’ (arising from radiocarbon production changes), and due to a distinct regionalism in the ocean’s impact on atmospheric radiocarbon, versus atmospheric CO2, with air-sea gas-exchange playing a significant role. Major differences in the long-term evolution of radiocarbon and 𝛿13C across the last deglaciation further point to distinct and independent controls on these isotopes systems, providing clues as to the nature and timing of different carbon cycle processes during deglaciation.

How to cite: Skinner, L.: Globally resolved marine carbon isotope data spanning the last 25ka: what do they tell us about the drivers of atmospheric radiocarbon and CO2 on millennial and deglacial timescales? , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9678, https://doi.org/10.5194/egusphere-egu24-9678, 2024.

EGU24-9708 | ECS | Orals | CL1.2.6

Glacial-interglacial variability using a low-complexity, physically based model 

Sergio Pérez-Montero, Jorge Alvarez-Solas, Marisa Montoya, and Alexander Robinson

Pleistocene glacial-interglacial variability is still under debate, as the many hypotheses proposed are subject to the models used and assumptions made. The longer time scales involved in glacial cycles make it difficult to use comprehensive climate models because of its large computational cost. In this context, conceptual models are built to mimic complex processes in a simpler and more computationally efficient way. Here we present a conceptual climate-ice sheet model that aims to represent the state-of-the-art physical processes affecting glacial-interglacial variability. Our model was constructed using linear equations that explicitly represent ice-sheet modeling approaches. Preliminary results are consistent with Late Pleistocene variability and point to the existence of nonlinearities related to both ice dynamics and ice aging that determine the timing and shape of deglaciations.

How to cite: Pérez-Montero, S., Alvarez-Solas, J., Montoya, M., and Robinson, A.: Glacial-interglacial variability using a low-complexity, physically based model, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9708, https://doi.org/10.5194/egusphere-egu24-9708, 2024.

EGU24-10190 | Orals | CL1.2.6

Perspective on ice age Terminations from absolute chronologies provided by global speleothem records 

Nikita Kaushal, Heather Stoll, and Carlos Pérez-Mejías

Glacial Terminations represent the largest amplitude climate changes of the last several million years.  Over ~ 10 ky timescale, large northern hemisphere ice sheets retreat and sea level rises, and atmospheric CO2 and global temperatures make a full transition from glacial to interglacial levels.  Several possible orbital-insolation triggers have been described to initiate and sustain glacial Terminations, and feedbacks between ice sheet retreat, ocean circulation and ocean carbon storage are invoked to explain the unstoppable progression. 

Because of the availability of radiocarbon dating, the most recent termination (TI) has been extensively characterized. Yet, it is widely discussed whether this sequence of feedbacks and millennial events, and rate of warming is recurrent over previous Terminations or is unique.  Beyond the limit of radiocarbon dating, the chronologies of climate records from ice and marine cores are often developed by tuning to orbital parameters which limits their use in understanding climate dynamics, particularly the response to orbital forcing.

Speleothems provide absolute age control and high-resolution proxy measurements. This archive therefore provides unique records of climate change across Terminations, and additionally may provide the opportunity to tune ice and marine core archives.  However, speleothem climate signals are encoded in a number of proxies. Unlike proxies in other archives like ice or marine cores, the climatic interpretation of a given proxy can vary quite significantly among different regions.

In this study, we

  • synthesize the available speleothem records providing climate information for Terminations: TII, TIII, TIV and TV.
  • present the records based on the aspect of climate encoded in the available records.
  • examine the effects of different ice volume corrections on the final climate proxy record.
  • evaluate whether there are leads and lags in the manifestation of Terminations across different aspects of the climate systems and different regions.
  • we speculate on suitable tuning targets among marine and ice core proxies, and discuss what model outputs maybe most suitable for comparison.

How to cite: Kaushal, N., Stoll, H., and Pérez-Mejías, C.: Perspective on ice age Terminations from absolute chronologies provided by global speleothem records, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10190, https://doi.org/10.5194/egusphere-egu24-10190, 2024.

EGU24-10579 | Orals | CL1.2.6

A mechanism for reconciling the synchronisation of Heinrich events and Dansgaard-Oeschger cycles 

Clemens Schannwell, Uwe Mikolajewicz, Marie-Luise Kapsch, and Florian Ziemen

The evolution of the northern hemispheric climate during the last glacial period was shaped by two prominent signals of glacial climate variability known as Dansgaard-Oeschger cycles and Heinrich events. Dansgaard- Oeschger cycles are characterised by a period of rapid, decadal warming of up to 14°C in the high northern latitudes, followed by a more gradual cooling spanning several centuries. Temperature reconstructions from ice cores indicate a dominant recurrence interval of ∼1,500 years for Dansgaard-Oeschger cycles. Heinrich events are quasi-episodic iceberg discharge events from the Laurentide ice sheet into the North Atlantic. The paleo record places most Heinrich events into the cold phase of the millennial-scale Dansgaard-Oeschger cycles. However, not every Dansgaard-Oeschger cycle is accompanied by a Heinrich event, revealing a complex interplay between the two prominent modes of glacial variability that remains poorly understood to this day. Here, we present simulations with a coupled ice sheet-solid earth model to introduce a new mechanism that explains the synchronicity between Heinrich events and the cooling phase of the Dansgaard-Oeschger cycles. Unlike earlier studies, our proposed mechanism does not require a trigger mechanism during the cooling phase. Instead, the atmospheric warming signal associated with the interstadial phase of the Dansgaard-Oeschger cycle causes enhanced ice stream thickening such that a critical ice thickenss and temperature threshold is reached faster, triggering the Heinrich event during the early cooling phase of the Dansgaard-Oeschger cycle. An advantage of our mechanism in comparison to previous theories is that it is not restricted to marine-terminating ice streams, but applies equally to land-terminating ice streams that only become marine-terminating during the actual Heinrich event. Our simulations demonstrate that this mechanism is able to reproduce the Heinrich event characteristics as known from the paleo record under a wide range of forcing scenarios and provides a simple explanation for the observational evidence of synchronous Heinrich events from different ice streams within the Laurentide ice sheet.

How to cite: Schannwell, C., Mikolajewicz, U., Kapsch, M.-L., and Ziemen, F.: A mechanism for reconciling the synchronisation of Heinrich events and Dansgaard-Oeschger cycles, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10579, https://doi.org/10.5194/egusphere-egu24-10579, 2024.

Despite decades of research, the cause of glacial-interglacial CO2 cycles is not fully understood, leaving a critical gap in our understanding of Earth’s climate system. One hypothesis is that shoaling of the boundary between Northern Source Water (NSW) and Southern Source Water (SSW) enhanced oceanic carbon sequestration during glacial intervals, resulting in lower atmospheric pCO2. To test this hypothesis, we generated vertical profiles of [CO32-], δ13C, and δ18O using a depth transect of cores from the Brazil Margin, focusing on the two major drops in atmospheric pCO2 during the last glacial cycle at ~115 ka and ~70 ka. Given that [CO32-] is inversely related to the concentration of dissolved inorganic carbon, [CO32-] should decrease if the Atlantic sequestered CO2. We observe no significant change in the [CO32-] across the first decrease in atmospheric pCO2 and no evidence for watermass boundary shoaling in the δ13C and δ18O profiles.  [CO32-] decreased only at ~3600 m, the core site most influenced by SSW.  During the second pCO2 decline at ~70 ka, [CO32-] decreased by ~30 µmol/kg below 2000 m water depth, coincident with marked shoaling in the δ13C and δ18O profiles. The lack of evidence for shoaling and deep Atlantic carbon sequestration at ~115 ka, a time of intermediate ice sheet extent and moderate global cooling, but the clear evidence for shoaling and carbon sequestration at ~70 ka, a time of near glacial maximum ice sheet extent, implies that the deep Atlantic’s capacity to store carbon depends on the Earth’s mean climate state. Our results highlight that distinct mechanisms are necessary to explain the two major drops in atmospheric pCO2 of the last glacial cycle. 

How to cite: Garity, M. and Lund, D.: Investigating oceanic carbon sequestration during glacial inception using vertical profiles of [CO32-], d13C, and d18O from the Southwest Atlantic, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12112, https://doi.org/10.5194/egusphere-egu24-12112, 2024.

EGU24-12199 | ECS | Orals | CL1.2.6

Reconstructing the global mean surface temperature of the last 130 thousand years 

Jean-Philippe Baudouin, Nils Weitzel, Lukas Jonkers, Andrew M. Dolman, and Kira Rehfeld

Global mean surface temperature (GMST) is a fundamental measure of climate evolution in both past and present and a key quantity to evaluate climate simulations. However, for paleoclimate periods, its reconstruction hinges on uncertain and indirect observations which are distributed sparsely and non-uniformly in both space and time. Large datasets of homogenised proxy records help to reduce the sparsity. Then, the records can be aggregated in an algorithm retrieving the GMST signal. Here, we build on the algorithm designed in Snyder 2016, and on a recent database of ocean temperature proxy records to reconstruct the GMST evolution over the last glacial cycle (the last 130 thousand years). First, we evaluate the algorithm and quantify the sources of uncertainty. This analysis draws on pseudo-proxy experiments using a range of simulations of the last glacial cycle. We find that the over-representation of some regions (e.g. coasts, the Atlantic), to the detriment of others (e.g. the central Pacific) significantly impacts the reconstructed temperature anomaly and its variations. Additionally, millennial and shorter timescale variability cannot be reconstructed by the algorithm, due to bioturbation and age uncertainty. However, these experiments also demonstrate the ability of our algorithm to reconstruct the amplitude and timing of GMST variations occurring at orbital timescale (>10.000 years). Second, we reconstruct the GMST evolution during the last glacial cycle. We compare our result to previous studies, and discuss the improvements coming from the use of the recent proxy database. The high number of proxy records allow us to additionally investigate smaller regions (e.g. hemisphere) and overall further our understanding of the driver of orbital-scale GMST variability.

How to cite: Baudouin, J.-P., Weitzel, N., Jonkers, L., Dolman, A. M., and Rehfeld, K.: Reconstructing the global mean surface temperature of the last 130 thousand years, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12199, https://doi.org/10.5194/egusphere-egu24-12199, 2024.

EGU24-13226 | Posters on site | CL1.2.6

Super-cooled glacial deep waters 

Miho Ishizu, Axel Timmermann, and Kyung-Sook Yun

Sea-ice formation in the Southern Ocean can generate supercooled waters, which can even remain below the in-situ freezing point at depths below 1,000 m. These water masses can play an important role in carbon transport to the abyssal ocean and may have therefore also played an important role in glacial-interglacial CO2 cycles.

To address this question, we examined model outputs from the transient 3 Ma simulation conducted with the CESM1.2 model (Community Earth System Model version 1.2, ~3.75 horizontal resolution. This simulation was driven by time-varying orbital forcing and estimates of atmospheric greenhouse gas concentrations and northern hemispheric ice-sheet orography and albedo. Our analysis shows the presence of large swaths of supercooled glacial deep waters mainly in the northern Pacific. This water is originally formed in the seasonal sea-ice formation regions in the subarctic North Pacific during periods of brine release and rapid mixed layer deepening. During interglacial periods, the volume of supercooled water decreases, which may hint towards a possible positive climate-carbon cycle feedback.

In climate models the freezing condition is usually only applied at the surface. Hence, they are incapable of simulating brinicles – vertical sea-ice structures that can extend from the surface to shallower depths, sometimes even reaching the ocean floor. In my presentation, I will address whether such structures may have played a more prominent role during glacial periods, and whether localized deep ocean freezing may have been a possibility.

How to cite: Ishizu, M., Timmermann, A., and Yun, K.-S.: Super-cooled glacial deep waters, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13226, https://doi.org/10.5194/egusphere-egu24-13226, 2024.

EGU24-14346 | Orals | CL1.2.6

Weathering of shelf sediments exposed during a glacial period: Evidence from geochemistry and Sr-Nd isotopes 

Gyana Ranjan Tripathy, Priyasha Negi, Rakesh Kumar Rout, and Ravi Bhushan

Erosion of continental rocks controls nutrient and sediment supply, soil formation and global climate. Intensity of this land-surface process is driven by both climatic (runoff, and temperature) and non-climatic (vegetation, lithology and basin slope) factors. Additionally, climatic-driven fluctuations in sea-level may also influence the exposed land-area, which is available for weathering. The coupling between exposed shelf sediments and weathering, however, has received limited attention. In this contribution, geochemical and Sr-Nd isotopic compositions of a sediment core (VM29-17PC) from the western Bay of Bengal have been investigated to reconstruct weathering and climate interaction during last glacial-interglacial cycle. Radiocarbon dating of foraminifera samples establishes that the core preserves a continuous erosional record for last 35 kyr.  Average Sr-Nd isotopic data for the decarbonated sediments confirm dominant sediment supply from the Higher Himalaya to the core site, with sub-ordinate input from the Deccan region. Temporal changes in the isotopic data hint at a sudden increase in the Himalayan source around 15 kyr BP, which is synchronous with the Bølling-Allerød (B/A) warm phase and the strengthening of the south-west (SW) monsoon. Downcore variation of Chemical Index of Alteration (CIA) and K/Al ratios indicates intensification of chemical weathering around 25 kyr BP. This change in weathering intensity is synchronous to dropping of sea level due to onset of glaciation. This sea-level regression and sudden rise in CaCO3 concentration during this period point to weathering of additional surface exposed in the shelf regions. This enhanced weathering of the shelf sediments may have contributed to the atmospheric CO2 level during the glacial period.

How to cite: Tripathy, G. R., Negi, P., Rout, R. K., and Bhushan, R.: Weathering of shelf sediments exposed during a glacial period: Evidence from geochemistry and Sr-Nd isotopes, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14346, https://doi.org/10.5194/egusphere-egu24-14346, 2024.

EGU24-14882 | ECS | Orals | CL1.2.6

Impact of marine productivity on atmospheric pCO2 during the Last Glacial Maximum: a model-data comparison 

Pauline Depuydt, Stéphanie Duchamp-Alphonse, Nathaelle Bouttes, Chiara Guarnieri, Alice Karsenti, Ji-Woong Yang, Jean-Yves Peterschmitt, and Amaëlle Landais

Measurements of the air trapped in Antarctic ice cores reveal that atmospheric CO2 concentration (pCO2) during the Last Glacial Maximum (LGM) was about 80 ppmv lower than that recorded during the current Holocene interglacial (Bereiter et al., 2015). Studies also show a strong link between pCO2, ice volume and Antarctic temperature, suggesting pCO2 as a forcing or amplifying factor behind glacial/interglacial cycles (Petit et al., 1999; Parrenin et al., 2013). Despite such importance in the global climate changes, mechanisms behind rapid variations in pre-anthropic pCO2 remain elusive. Numerical models emphasized the crucial role of exported marine productivity Pexp, (namely, the Soft Tissue Pump) in such changes. In particular, they feature marine productivity patterns from the Southern Ocean and show that a decrease in Pexp in the Sub-Antarctic zone, linked to a reduction in iron inputs from aeolian dusts, could have increased pCO2 by 20 to 50 ppmv (Köhler and Fischer, 2006; Martínez-Garcia et al., 2009; Lambert et al., 2012). However, these studies are usually compared to proxy data from the Atlantic sector of the Subantarctic Zone i.e., an area under the direct influence of wind fields that makes it possible to test the “Fe-hypothesis” (Martin et al., 1990) but that is not necessarily representative of the entire ocean (e.g. Lambert et al., 2015). Due to a lack of recent Pexp data compilation but also of direct comparisons with model outputs integrating marine biogeochemistry­­, it remains difficult to understand the role marine biological productivity exerted on the carbon cycle and more specifically on the low pCO2 during the LGM.

The aim of this study is to explore Pexp patterns during the LGM compared to the pre-industrial Holocene and understand the mechanisms driving their global changes, in order to try and estimate the contribution of marine productivity to the pCO2 signalbased on (i) a new compilation of Pexp proxy data using the strategy previously proposed by Kohfeld et al. (2005) after Bopp et al., (2003), and (ii) a comparison of these data to outputs from the iLOVECLIM intermediate complexity.

Proxy data show that Pexp is generally higher during the LGM compared to the pre-industrial Holocene. This is particularly the case in the sub-Antarctic and sub-Arctic areas, in the equatorial Atlantic Ocean and in coastal upwelling settings i.e., regions that usually witness higher nutrient content due to revigorated ocean circulation and/or intensified surface winds. Simulations generally confirm such features except from the coastal upwelling and the Southern Ocean, due to a lack of spatial resolution and of aeolian inputs in the model, respectively. However, preliminary results from sensitivity tests show (i) net marine productivity fronts around ~40°N and 45°S due to extended sea ice cover and reduced global temperature, (ii) a decreased Pexp in the Pacific Ocean due to an overall thermohaline circulation slow down and (iii) an increase of Pexp in areas where fertilization by iron-rich dusts is expected (Lambert et al., 2021).

How to cite: Depuydt, P., Duchamp-Alphonse, S., Bouttes, N., Guarnieri, C., Karsenti, A., Yang, J.-W., Peterschmitt, J.-Y., and Landais, A.: Impact of marine productivity on atmospheric pCO2 during the Last Glacial Maximum: a model-data comparison, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14882, https://doi.org/10.5194/egusphere-egu24-14882, 2024.

EGU24-14929 | ECS | Orals | CL1.2.6

Significant change in the flow regime in the deep Southern Ocean through the MPT 

Eva M. Rückert and Norbert Frank

The deep Southern Ocean (SO) circulation is of major significance for the understanding of the ocean´s impact on Earth’s climate as uptake and release of CO2 strongly depend on the redistribution of well and poorly ventilated water masses.

Neodymium isotopes (εNd) preserved in deep sea sediment have proven useful to study the Deep Ocean Circulation and water mass provenance and are of special interest over major climate changes as the Mid Pleistocene Transition (MPT). The MPT marks the change from a 41 ka to a 100 ka glacial-interglacial cyclicity and goes along with a significant intrusion of southern sourced waters (SSW) in the deep North Atlantic.

Here, we present the first millennial resolved authigenic εNd data in the Southern Atlantic spanning across  the MPT of a deep sea sediment core positioned at the polar front. The pre-MPT εNd values of ODP 1093 show a small variability of approx. 2 ε-units around the modern AABW signature of -8. In contrast, the post-MPT εNd variability increases to 6 ε-units with glacial extremes of around -3 – εNd values that can not be found in any Atlantic sourced water mass today!

This supports not only the exsiting hypotesis of stonger SSW export to the North, but rather advocates for a radiogenic  watermass influencing the flow regime in the Atlantic south of the polar front. Increasing ice volume during post-MPT glacials has been argued to lead to a reduced AABW production. Due to continuity of flow, this opens up the possiblity of glacial intrusion through the Drake passage of a water masses likely originating in the Pacific, which would generate  the strongly radiogenic glacial εNd values. At present Pacific deep waters are enriched with respired carbon. Assuming this to hold true in the past, the intrusion of such carbon rich water masses into the deep South Atlantic could further reinforce the strong glacials and the overall global cooling trend after the MPT as suggested previously.

Hence, the SO south of the polar front played a leading role in  reinjecting respired CO2 into the deep Atlantic Ocean and the Atmosphere during climate transitions. 

How to cite: Rückert, E. M. and Frank, N.: Significant change in the flow regime in the deep Southern Ocean through the MPT, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14929, https://doi.org/10.5194/egusphere-egu24-14929, 2024.

EGU24-15214 | Orals | CL1.2.6

Exploring the differing CO2 response to Dansgaard-Oeschger and Heinrich events 

Matteo Willeit, Daniela Dalmonech, Bo Liu, Tatiana Ilyina, and Andrey Ganopolski

Dansgaard-Oeschger (DO) and Heinrich (H) events are ubiquitous features of glacial climates involving abrupt and large changes in climate over the North Atlantic region, extending also to the Southern Hemisphere through the bipolar seesaw mechanism. Ice core data also indicate that the DO and H events are accompanied by pronounced changes in atmospheric CO2 concentration, but their origin remains uncertain. Here, we use simulations with the fast Earth system model CLIMBER-X, which produces self-sustained DO events as internal variability, to explore the processes involved in the atmospheric CO2 response. While the DO events are internally generated in the model, the Heinrich events are mimicked by adding a freshwater flux of 0.05 Sv over 1000 years in the latitudinal belt between 40°N and 60°N in the North Atlantic.
The simulated Greenland temperature varies by ~7-8°C between stadials and interstadials, with only small differences between H and DO stadials, while Antarctic temperature responds substantially stronger to H than to DO events, broadly in agreement with observations. In the CLIMBER-X simulations, atmospheric CO2 varies by ~5 ppm during DO events, but by ~15 ppm during H events, comparable with ice core data. The peak in CO2 concentrations is delayed by several centuries relative to both the stadial-interstadial transition and the peak in Antarctic temperature. The CO2 rise during the H stadial is driven by ocean outgassing. In contrast, the rapid CO2 increase after the transition to the interstadial results from soil carbon release from high NH latitudes originating from substantial warming.

How to cite: Willeit, M., Dalmonech, D., Liu, B., Ilyina, T., and Ganopolski, A.: Exploring the differing CO2 response to Dansgaard-Oeschger and Heinrich events, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15214, https://doi.org/10.5194/egusphere-egu24-15214, 2024.

EGU24-15672 | ECS | Orals | CL1.2.6

Carbon and nitrogen stable isotopes across the last deglaciation: perspectives from snow petrel stomach oil deposits 

Thale Damm-Johnsen, Michael J. Bentley, Darren R. Gröcke, Dominic Hodgson, and Erin L. McClymont

Evidence from both marine and ice cores strongly indicates that surface ocean processes influencing air-sea gas exchange of the Southern Ocean played a crucial role in the transition from a glacial to interglacial climate state. However, few archives have been able to reconstruct how high latitude surface ocean processes affected the biogeochemical changes occurring in nutrient utilization, primary productivity, and their effects on carbon sequestering in ecosystems. An opportunity to explore these processes is provided by accumulated snow petrel (Pagodroma nivea) stomach oil deposits, defensively regurgitated by snow petrels at their nest sites. These deposits provide a record of biogeochemical processes in the austral summer, at a high trophic level and integrated over a relatively wide area defined by snow petrel foraging range. Here, we present a joint carbon and nitrogen stable isotope record from stomach oil deposits from the Lake Untersee nunataks in Dronning Maud Land (DML) integrating data from a coastal area of 65-70°S. Our results show a 3‰ offset in δ13C and 4‰ offset in δ15N between LGM and Holocene, indicating that the coastal high latitudes underwent large changes over the deglaciation. The δ15N depletion into the Holocene shows strong similarity to changes occurring in nutrient utilization along the margin of the polar front, indicating that the Southern Ocean high latitudes were not an isolated oasis during the LGM but biogeochemically connected to the surface ocean beyond the summer sea-ice margin. In addition, the presence of stomach oil deposits indicates that open water was present in summer along the coast of DML over both the LGM and Holocene. Such highly productive, open water areas were potentially an important factor in the air-sea gas exchange contributing to the deglacial atmospheric CO2 -rise.

How to cite: Damm-Johnsen, T., Bentley, M. J., Gröcke, D. R., Hodgson, D., and McClymont, E. L.: Carbon and nitrogen stable isotopes across the last deglaciation: perspectives from snow petrel stomach oil deposits, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15672, https://doi.org/10.5194/egusphere-egu24-15672, 2024.

EGU24-16591 | Orals | CL1.2.6

Bridging Proxy Discrepancies: SST Reconstructions from the Alboran Sea During the Last Glacial Maximum and Deglaciation.  

Alvaro Fernandez, Laura Rodríguez-Sanz, Victoria Taylor, Nele Meckler, and Francisca Martínez-Ruiz

The last glacial maximum (LGM) is the most recent time period in Earth’s history with a climate that was much colder than the present. Robust temperature reconstructions from this period are needed to improve estimates of Earth's climate sensitivity and aid in future climate change projections. However, reconstructing sea surface temperatures (SSTs) during this period can be challenging due to the various limitations with the commonly used proxies. Here, we present new SST estimates from the Alboran Sea in the Western Mediterranean, an area where existing SST records for the LGM (derived from UK37, TEX86, planktic foraminiferal Mg/Ca) show large disagreements. Our new SST estimates are based on clumped isotope analyses of planktic foraminifera (G. bulloides), the same species as used for the Mg/Ca measurements in this area. Due to the insensitivity of the clumped isotope thermometer to changes in seawater chemistry, our results offer new independent constraints on the range of temperature shifts between glacial and interglacial periods in this area. Our findings are evaluated against existing SST estimates, highlighting the benefits and limitations of different proxy estimates. We find that while all proxies agree on the general millennial scale temperature trends during the period of deglaciation, they diverge in the magnitude of these temperature changes. Temperature reconstructions derived from clumped isotopes align more closely with those based on alkenone and Mg/Ca proxies than with those from TEX86, which show large differences. Our research demonstrates that clumped isotopes are a potentially effective tool to improve the accuracy of climate reconstructions from the LGM and the subsequent deglacial period.

 

 

How to cite: Fernandez, A., Rodríguez-Sanz, L., Taylor, V., Meckler, N., and Martínez-Ruiz, F.: Bridging Proxy Discrepancies: SST Reconstructions from the Alboran Sea During the Last Glacial Maximum and Deglaciation. , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16591, https://doi.org/10.5194/egusphere-egu24-16591, 2024.

EGU24-17501 | ECS | Posters on site | CL1.2.6

Constraining glacial ocean carbon cycle – A multi-model study 

Bo Liu, Tatiana Ilyina, Victor Brovkin, Matteo Willeit, Ying Ye, Christoph Völker, Peter Köhler, Malte Heinemann, Takasumi Kurahashi-Nakamura, André Paul, Michael Schulz, Ute Merkel, and Fanny Lhardy

The ocean contained a larger carbon content at the Last Glacial Maximum (LGM, ~21kyr before present) compared to the late Holocene, making a considerable contribution to the deglacial atmospheric CO2 rise of about 90 ppm. Yet, there’s no consensus on the mechanisms controlling the glacial-interglacial changes in oceanic carbon storage due to uncertainties and sparseness of proxy data. Numerical simulations have been widely used to quantify the impact of key factors, such as changes in sea surface temperatures, ocean circulation and biological production, on glacial ocean carbon sequestration. However, the robustness of these findings is subject to further testing due to the differences in process representation, parameterization, model architecture, or external forcing employed by models.

Towards further constraining the LGM ocean carbon cycle, we conducted a multi-model comparison with three comprehensive Earth System Models (Alfred Wegener Institute Earth System Model, AWI-ESM; Community Earth System Model, CESM; Max Planck Institute Earth System Model, MPI-ESM) and one Earth system Model of Intermediate Complexity (CLIMBER-X). We carried out three coordinated experiments with each model: 1) PI (the pre-industrial control simulation), 2) LGM-PMIP (following PMIP4 LGM protocol) and 3) LGM-LowCO2 (as LGM-PMIP, but with boosted alkalinity inventory to lower atmospheric CO2 to about 190 ppm. All experiments were conducted with the prognostic CO2 for the carbon cycle, considering only the atmosphere and ocean reservoirs, and prescribed CO2 for radiative forcing.

All models consistently show that applying the PMIP4 LGM boundary conditions alone leads to only a 5-40 ppm decrease in atmospheric CO2. Globally, the glacial CO2 drawdown in LGM-PMIP is mainly controlled by the enhanced solubility pump. The spatial distribution of the increased glacial DIC depends on the ocean circulation state in each model. In MPI-ESM and CLIMBER-X, the shallower and weaker AMOC facilitates carbon storage in the deep Atlantic. An LGM atmospheric CO2 of 190 ppm can be achieved by boosting alkalinity by 5-8% in scenario LGM-LowCO2. In all models, boosting LGM alkalinity inventory increases DIC in the bottom water. However, comparison to proxy data reveals that the models lack respired carbon, particularly in the deep Pacific. This suggests a need to enhance the glacial biological carbon pump in the models.

How to cite: Liu, B., Ilyina, T., Brovkin, V., Willeit, M., Ye, Y., Völker, C., Köhler, P., Heinemann, M., Kurahashi-Nakamura, T., Paul, A., Schulz, M., Merkel, U., and Lhardy, F.: Constraining glacial ocean carbon cycle – A multi-model study, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17501, https://doi.org/10.5194/egusphere-egu24-17501, 2024.

EGU24-17778 | ECS | Orals | CL1.2.6

Physical and biological controls on deep Pacific carbon storage over the last glacial cycle 

Megan Pelly, Madison Shankle, Molly Trudgill, Bruno Millet, Chen Xu, Gwyn Owens, Hermione Owen, Alan Foreman, Thomas Bauska, Andy Ridgwell, Elisabeth Michel, William Gray, Andrea Burke, and James Rae

The ability of the deep ocean to store and exchange large quantities of CO2 with the atmosphere on relatively short timescales means that it is thought to play a key role in dictating glacial-interglacial changes in atmospheric CO2, however records of deep ocean carbon storage and release remain sparse. The Pacific Ocean contains the largest store of carbon in the ocean-atmosphere system. As a result, changes in its circulation dynamics and biogeochemistry have the potential to significantly impact global climate. Despite this, changes in Pacific conditions and carbon storage over the last glacial cycle are poorly constrained.

Here we present new geochemical proxy records from abyssal, deep, and intermediate depths in the Southwestern Pacific to determine the changes in deep ocean carbon storage over the last glacial cycle and the mechanisms involved in driving these changes. Foraminiferal trace element and stable isotope data indicate that increased carbon storage occurred over the course of the last glaciation, promoting a drawdown in atmospheric CO2. The processes involved in driving glacial ocean carbon storage are debated, however proxy data from these sites indicate that changes in circulation dynamics promoting the isolation and expansion of deep Pacific waters was likely a key process involved. Comparison of δ13C data to box model and Earth system model output provides further insight into the physical as well as biogeochemical mechanisms involved and their relative contributions at different stages over the last glacial cycle. This includes the role of Southern Ocean sea-ice expansion, reduced ocean temperatures, and increased Southern Ocean stratification and biological productivity. We find that physical processes dominate the early in the glacial cycle, with biological processes promoting further drawdown as glacial conditions intensify. These results help to improve the understanding of deep ocean carbon cycling over the last glacial cycle and provide a new framework with which to interpret proxy δ13C data.

How to cite: Pelly, M., Shankle, M., Trudgill, M., Millet, B., Xu, C., Owens, G., Owen, H., Foreman, A., Bauska, T., Ridgwell, A., Michel, E., Gray, W., Burke, A., and Rae, J.: Physical and biological controls on deep Pacific carbon storage over the last glacial cycle, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17778, https://doi.org/10.5194/egusphere-egu24-17778, 2024.

EGU24-17827 | ECS | Orals | CL1.2.6

A million-year reconstruction of global volcanism intensity: How does it link to glaciation? 

Jack Longman, Thomas M. Gernon, Thea K. Hincks, Sina Panitz, and Martin R. Palmer

Reduced ice volume during interglacials is hypothesized to amplify volcanic activity because ice-mass removal reduces pressure on magma chambers (Huybers & Langmuir, 2009). There is some evidence for this process occurring on regional (Maclennan et al., 2002) and perhaps semi-global scales (Kutterolf et al., 2019), but there is a lack of globally representative tephra production records. Therefore, our understanding of the global relationship between glacial-interglacial cycles and volcanism uncertain. As a result, we do not know whether deglaciation directly drives enhanced volcanism, or if the feedbacks are more complex. In this work we use a database of visible tephra layers in marine sediments, and a weighted bootstrap resampling method to develop a record of global tephra (the products of explosive volcanism) production which covers the past million years.

Our results show an intensification of global tephra production around 420 to 400 thousand years ago (ka), which coincides with Marine Isotope Stage (MIS) 11 – the warmest interglacial of the past million years. MIS11 was a period of high sea level (up to 10 m above present) and low ice cover, with Greenland likely largely ice free. We suggest the low ice levels drove enhanced volcanism, and consequently enhanced volcanic carbon dioxide degassing, which in turn drove further ice sheet ablation. This positive feedback may the explain this warmth, and in turn, the Mid-Brunhes transition, which heralded the arrival of generally warmer interglacials after 400 ka. Further, after 400 ka we begin to see cyclicity in the tephra record, mirroring eccentricity forcing seen in ice volume records. More pronounced ice-volcano feedbacks may therefore explain the stronger interglacials of the past 400,000 years.

References

Huybers, P., & Langmuir, C. (2009). Feedback between deglaciation, volcanism, and atmospheric CO2. Earth and Planetary Science Letters, 286(3–4), 479–491.

Kutterolf, S., Schindlbeck, J. C., Jegen, M., Freundt, A., & Straub, S. M. (2019). Milankovitch frequencies in tephra records at volcanic arcs: The relation of kyr-scale cyclic variations in volcanism to global climate changes. Quaternary Science Reviews, 204, 1–16.

Maclennan, J., Jull, M., McKenzie, D., Slater, L., & Grönvold, K. (2002). The link between volcanism and deglaciation in Iceland. Geochemistry, Geophysics, Geosystems, 3(11), 1–25.

 

How to cite: Longman, J., Gernon, T. M., Hincks, T. K., Panitz, S., and Palmer, M. R.: A million-year reconstruction of global volcanism intensity: How does it link to glaciation?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17827, https://doi.org/10.5194/egusphere-egu24-17827, 2024.

The ocean plays an essential role in the rise of atmospheric CO2 by about 90 ppmv during the last deglaciation. The deglacial oceanic CO2 outgassing is jointly controlled by the physical, biological and geochemical processes, which affect the variations in ocean circulation, biological carbon pump and alkalinity inventory. Transient simulations of climate-carbon feedback, particularly using the comprehensive Earth System Models, are instrumental tools to quantify the contribution of different processes and their interactions. Nonetheless, knowledge gaps still exist in the deglacial variations of oceanic carbon and nutrient cycling because considerable model uncertainties arise from the choices of model processes and parameters, and the proxy data is too sparse to fully constrain the model outcome.

We conduct transient simulations for the last deglaciation with the Max Planck Institute Earth System Model (MPI-ESM) and examine the impact of different model tuning of the global ocean biogeochemistry component and a sediment module on the deglacial CO2 outgassing. The atmospheric CO2 is prognostically computed for the carbon cycle, considering only the atmosphere and ocean compartments, and it is prescribed for radiation computation. We force the model with reconstructions of atmospheric greenhouse gas concentrations, orbital parameters, ice sheet and dust deposition. In line with the physical ocean component, we account for the automatic adjustment of marine biogeochemical tracers in response to changing bathymetry and coastlines related to deglacial meltwater discharge and isostatic adjustment.

We find the deglacial CO2 outgassing is mainly driven by the sea surface warming in MPI-ESM, whereas variations in surface alkalinity and DIC have a relatively small contribution (~18%). Furthermore, the parameterisation of organic debris remineralisation considerably affects the deglacial increase in the global NPP due to different recycling rates of nutrients in the upper ocean. When a longer lifetime of dissolved organic matter is prescribed, the dissolved organic carbon pool in the glacial ocean increases, further facilitating the glacial ocean carbon sequestration. Including an interactive sediment module strongly impacts surface alkalinity due to input-sedimentation imbalance, affecting air-ocean CO2 flux. Thus, attention has to be given to tuning and adjustments regarding the input-sedimentation imbalance of alkalinity in ESMs to better represent proxy data and the deglacial oceanic CO2 outgassing.

How to cite: Liu, B. and Ilyina, T.: Quantifying the role of ocean biogeochemistry on the deglacial atmospheric CO2 rise using transient simulations with MPI-ESM, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18082, https://doi.org/10.5194/egusphere-egu24-18082, 2024.

EGU24-18786 | ECS | Posters on site | CL1.2.6

Mechanisms of atmospheric CO2 drawdown during Marine Isotope Stage 4 based on Atlantic deep-water temperature and bottom-water oxygenation reconstructions  

Svetlana Radionovskaya, Julia Gottschalk, David Thornalley, Mervyn Greaves, and Luke Skinner

Understanding the evolution of deep ocean circulation and chemistry over the last glacial cycle is key to elucidating the ocean’s role in modulating atmospheric CO2 changes on millennial and orbital timescales. MIS 4 is a key paleoclimatic interval of the last glacial inception for assessing the role of the deep-ocean carbon storage in driving atmospheric CO2 levels, because it is characterized by a large decrease of air temperature and a rapid atmospheric CO2 drop of ~40 ppmv, and includes several millennial climatic events, for example Heinrich Stadial 6. Although various paleo proxy records suggest a weakened Atlantic overturning during MIS 4, and particularly HS 6, changes in AMOC strength and the geometric extent of NADW shoaling remain poorly understood. Here, we present deep-water temperature reconstructions based on infaunal benthic foraminiferal Mg/Ca ratios and bottom water oxygen concentration reconstructions using redox-sensitive foraminiferal U/Ca, from the deep North (~2.65km) and South (~3.8km) Atlantic to assess the changes in deep water hydrography and by extension circulation.

Our reconstructed deep-water temperature changes from the Iberian Margin (~2.65 km water depth) suggest a stronger influence of colder southern sourced waters during MIS 4 and particularly during HS 6; and a clear subsurface warming during MIS 5a stadials. Meanwhile, changes in deep-water temperatures in the Atlantic Sector of the Southern Ocean (SO) closely follow variations in Antarctic temperature, atmospheric CO2 and the mean ocean temperature, likely mediated by buoyancy forcing in the SO, which is in turn likely linked to sea-ice expansion at the MIS 5a/4 transition. Together with (arguably smaller) contributions from reduced air-sea gas exchange efficiency in the SO, these combined changes would have lowered atmospheric CO2through more efficient carbon sequestration in an expanded deep Atlantic reservoir during MIS 4, through their impact on the solubility- and soft tissue “pumps” (i.e. the ocean’s disequilibrium and respired carbon budgets). Indeed, bottom water oxygenation reconstructions from the South Atlantic support the conclusion that the Southern Ocean appears to have represented a significant reservoir for sequestering CO2 away from the atmosphere during MIS 4.

How to cite: Radionovskaya, S., Gottschalk, J., Thornalley, D., Greaves, M., and Skinner, L.: Mechanisms of atmospheric CO2 drawdown during Marine Isotope Stage 4 based on Atlantic deep-water temperature and bottom-water oxygenation reconstructions , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18786, https://doi.org/10.5194/egusphere-egu24-18786, 2024.

EGU24-19515 | Posters on site | CL1.2.6

Sea surface temperature variations in the Eastern Equatorial Pacific (ODP Site 1240) over the last 160 kyr from three lipid paleothermometers (UK'37, TEXH86 and LDI) 

Eva Calvo, Lucía Quirós-Collazos, Marta Rodrigo, Stefan Schouten, Jaap Sinninghe-Damsté, Leopoldo Pena, Isabel Cacho, and Carles Pelejero

The Pacific Ocean equatorial upwelling region is of great interest to understand climate dynamics within the context of current global change. It plays a key role in global biogeochemical cycles, especially in the carbon cycle, as it stands for being one of the areas with largest CO2 fluxes from the ocean to the atmosphere. Moreover, tropical regions play a key role in regulating global climate, since they control the transfer of thermal energy from low to high latitudes. In this context, and with the aim of reconstructing paleoclimate conditions at glacial-interglacial time scales in this region, we analysed selected molecular biomarkers in the marine sediment core ODP 1240, at the easternmost region of the Eastern Equatorial Pacific (EEP), covering the last 160 kyr. We focused on long-chain alkenones, glycerol dialkyl glycerol tetraethers (GDGTs) and long-chain alkyl diols (LCDs). Upon quantification of these lipids, we calculated the UK'37, TEXH86 and LDI indices, and discussed their suitability as paleotemperature proxies to reconstruct sea surface conditions in the study region. We found that UK'37 and TEXH86 derived-temperatures track the warming and cooling trends typical of glacial-interglacial variations. However, while they provide similar temperatures during the last two interglacial maxima, they disagree during glacial periods, when the TEXH86-based estimations display significantly cooler temperatures. The LDI-derived record also shows similar temperatures to those from the UK'37 and TEXH86during the more recent interglacial but, for the last glacial-interglacial period, LDI-derived temperatures remain colder than those of the UK’37 and even colder than those of the TEXH86 at some periods. Multiple factors could be behind this variability and disagreement between the three paleothermometers: depth dwelling, production or exportation of the different biological producers of each lipid, seasonality, diagenetic processes and changes in biogeochemistry conditions of the studied marine region, amongst others. In this presentation, the factors that we believe are most important in the study region will be presented and discussed, to improve our understanding of the biological dynamics of the precursors of each proxy and of their reconstructed marine temperatures in the EEP.

How to cite: Calvo, E., Quirós-Collazos, L., Rodrigo, M., Schouten, S., Sinninghe-Damsté, J., Pena, L., Cacho, I., and Pelejero, C.: Sea surface temperature variations in the Eastern Equatorial Pacific (ODP Site 1240) over the last 160 kyr from three lipid paleothermometers (UK'37, TEXH86 and LDI), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19515, https://doi.org/10.5194/egusphere-egu24-19515, 2024.

EGU24-19780 | Orals | CL1.2.6

The influence of proglacial lakes on climate and surface mass balance of retreating ice sheets: A study of the Laurentide and Fennoscandian ice sheets at 13 ka BP 

Uta Krebs-Kanzow, Lianne Sijbrandij, Gregor Knorr, Lars Ackermann, Lu Niu, and Gerrit Lohmann

During the last deglaciation large proglacial lakes formed at the base of the retreating northern hemisphere ice sheets. We assess the effect of these ice-contact lakes on regional climate and on the ice sheet surface mass balance components of the adjacent  Laurentide (LIS) and Fennoscandian (FIS) ice sheets,  using an atmosphere general circulation model with a novel extension for proglacial lakes in combination with a surface mass balance scheme for ice sheets, which, for the first time, allows to estimate the effect of the cold surface of these extensive lakes on the surface mass balance of the adjacent ice sheets. In a set of simulations inspired by the  Allerød interstadial around 13000 years before present, we demonstrate that the presence of proglacial lakes significantly reduces summer air temperatures in a larger area around the proglacial lakes and leads to reduced precipitation with increased snow/rain ratio. In consequence surface ablation reduces by 39% over the FIS and 28% over the LIS while accumulation only changes slightly by 1% and -3%  respectively. About one quarter of the response in surface ablation is related to the perennially cold surface of the proglacial lakes.

How to cite: Krebs-Kanzow, U., Sijbrandij, L., Knorr, G., Ackermann, L., Niu, L., and Lohmann, G.: The influence of proglacial lakes on climate and surface mass balance of retreating ice sheets: A study of the Laurentide and Fennoscandian ice sheets at 13 ka BP, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19780, https://doi.org/10.5194/egusphere-egu24-19780, 2024.

CR2 – lce sheets, ice shelves and glaciers

EGU24-2403 | Posters on site | CR2.1

Using specularity content to evaluate eight geothermal heat flow maps of Totten Glacier 

Liyun Zhao, Yan Huang, Michael Wolovick, Liliang Ma, and John Moore

Geothermal heat flow (GHF) is the dominant factor affecting the basal thermal regime of ice sheet dynamics. But it is poorly defined for the Antarctic ice sheet. We compare basal thermal state of the Totten Glacier catchment as simulated by eight different GHF datasets. We use a basal energy and water flow model coupled with a 3D full-Stokes ice dynamics model to estimate the basal temperature, basal friction heat and basal melting rate. In addition to the location of subglacial lakes, we use specularity content of the airborne radar returns as a two-sided constraint to discriminate between local wet or dry basal conditions and compare them with the basal state simulations with different GHF. Two medium magnitude GHF distribution maps derived from seismic modelling rank well at simulating both cold and warm bed regions, the GHFs from Shen et al. (2020) and Shapiro and Ritzwoller (2004). The best-fit simulated result shows that most of the inland bed area is frozen. Only the central inland subglacial canyon, co-located with high specularity content, reaches pressure-melting point consistently in all the eight GHFs. Modelled basal melting rates in the slow-flowing region are generally 0-5 mm yr-1 but with local maxima of 10 mm yr-1 at the central inland subglacial canyon. The fast-flowing grounded glaciers close to Totten ice shelf are lubricating their bases with melt water at rates of 10-400 mm yr-1.

How to cite: Zhao, L., Huang, Y., Wolovick, M., Ma, L., and Moore, J.: Using specularity content to evaluate eight geothermal heat flow maps of Totten Glacier, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2403, https://doi.org/10.5194/egusphere-egu24-2403, 2024.

The influence of supraglacial debris cover on glacier dynamics in the Karakoram is noteworthy. However, the investigation of how debris cover affects the seasonal and long-term variations in glacier mass balance through alterations in the glacier's energy budget is scarce. The present study applied an energy-mass balance model coupling heat conduction within debris layers on Batura Glacier in Hunza valley, renowned as the most representative debris-covered glacier in the Karakoram, to demonstrate the influence of debris cover on glacial surface energy and mass exchanges. The mass balance of Batura Glacier is estimated to be -0.262 ± 0.561 m w.e. yr-1, with debris cover accounting for 45% of the mass balance variation. Due to the presence of debris cover, a significant portion of the energy income is utilized for heat conduction within the debris layer, reducing the melt latent heat at the glacier surface. We found that the mass balance reveals a pronounced arch-shaped structure along the elevation gradient, which primarily attributes to the distribution of debris thickness and the impact of debris cover on the energy structure within various elevation zones. Through a comprehensive analysis of the energy transfer within each debris layer, we have demonstrated that the primary impact of debris cover lies in its ability to modify the energy reaching the surface of the glacier. Thicker debris cover results in a smaller decrease in temperature between debris layers and the ice-contact zone, consequently reducing heat conduction. Over the past two decades, Batura Glacier has maintained a relatively small negative mass balance, owing to the protective effect of debris cover. The glacier exhibits a tendency towards a smaller negative mass balance, with diminishing dominance of ablation at the glacier terminus on glacier mass changes. 

How to cite: Zhu, Y., Liu, S., Brock, B. W., Xie, F., and Yi, Y.: Controls on the relatively slow thinning rate of a debris-covered glacier in the Karakoram over the past 20 years: evidence from mass and energy budget modelling of Batura Glacier, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2585, https://doi.org/10.5194/egusphere-egu24-2585, 2024.

EGU24-3996 | ECS | Orals | CR2.1

Retreat of Thwaites Glacier, West Antarctica, triggered by its neighbours. 

Matt Trevers, Anthony Payne, Stephen Cornford, and Ed Gasson

The drainage catchments of the neighbouring Thwaites and Pine Island Glaciers, situated in the Amundson Sea Embayment, West Antarctica, contain sufficient ice to raise global mean sea level by a meter. In recent years, significant scientific attention has been given to the potential for sustained retreat of these glaciers as a possible pathway towards widespread deglaciation of the marine-based West Antarctic Ice Sheet. Some recent studies have demonstrated that the Thwaites Ice Shelf provides only limited buttressing to the upstream grounded ice, suggesting limited sensitivity to the melt-driven loss of the ice shelf.

We use the BISICLES ice sheet model to perform a series of 1000-year model experiments on the Amundson Sea domain. A synthetic sub-shelf melt rate is selectively applied to the Pine Island, Thwaites and Crosson/Dotson basins or combinations of those basins. We find that over millennial timescales, Thwaites is relatively insensitive to melt-driven thinning of its ice shelf, with its grounding line rapidly restabilising ~60km upstream of its current location. The same melt forcing applied to Pine Island Glacier leads to widespread deglaciation of the Pine Island catchment and significant retreat in the neighbouring Thwaites catchment despite the lack of melting there. Applying melting simultaneously in the Thwaites and Crosson/Dotson basins leads to widespread deglaciation that is much greater than the sum of its parts. This retreat is driven by a feedback between the ice fluxes crossing the basin boundary.

We also conduct further experiments to determine the melt rates or additional processes required to trigger retreat of Thwaites Glacier in isolation. The results of our experiments support the suggestion that the Thwaites ice shelf provides limited buttressing, while also demonstrating that Thwaites is still vulnerable to retreat via other pathways.

How to cite: Trevers, M., Payne, A., Cornford, S., and Gasson, E.: Retreat of Thwaites Glacier, West Antarctica, triggered by its neighbours., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3996, https://doi.org/10.5194/egusphere-egu24-3996, 2024.

EGU24-4001 | ECS | Orals | CR2.1

Melt sensitivity of irreversible retreat of Pine Island Glacier 

Brad Reed, Mattias Green, Adrian Jenkins, and Hilmar Gudmundsson

In recent decades glaciers in the Amundsen Sea Embayment in West Antarctica have undergone substantial changes, including widespread retreat and acceleration. The subsequent mass loss caused the largest contribution to sea level rise from the entire Antarctic Ice Sheet. These changes have led to concerns about the stability of the region and the implications of future climate change. Recent modelling results show that one of the largest and fastest flowing of these glaciers, Pine Island Glacier (PIG), has already undergone an unstable and irreversible retreat in its recent history, when it detached from a subglacial ridge between the 1940s and 1970s.

Here we use the ice-flow model Úa to study the sensitivity of this retreat to changes in basal melting. We show that an intermittent increase in basal melting would have been sufficient to force PIG into a retreat from its stable position on the ridge. Once high melting begins upstream of the ridge, only near-zero melt rates can stop the retreat. Our results suggest that unstable and irreversible responses to warm anomalies are possible, and this can lead to substantial changes in ice flux over relatively short periods of only a few decades.

How to cite: Reed, B., Green, M., Jenkins, A., and Gudmundsson, H.: Melt sensitivity of irreversible retreat of Pine Island Glacier, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4001, https://doi.org/10.5194/egusphere-egu24-4001, 2024.

EGU24-4155 | ECS | Orals | CR2.1

Improving modeled ice dynamics in Northwest Greenland with transient calibration: From multi-decadal trends to seasonal cycles 

Jessica Badgeley, Helene Seroussi, and Mathieu Morlighem

State-of-the-art ice sheet model simulations used in the Ice Sheet Model Intercomparison Project (ISMIP) show a mismatch with recent observations of dynamic ice sheet change. In particular, the difference between the modeled and observed cumulative mass balance trend over the last several decades calls into question the accuracy of current projections of ice sheet contribution to sea level rise. Here, we use one of these models, the Ice-sheet and Sea-level System Model, to investigate how transient calibration may improve model hindcasts of ice dynamics and impact projections. Transient calibration is a relatively new capability in ice flow models; it uses a time series of observations to invert for uncertain model parameters, such as basal friction and ice rheology. With more observational constraints than the common snapshot inversion method, transient calibration has been shown to better capture trends and to have the ability to estimate how parameters evolve through time. We apply this method to Northwest Greenland, a region undergoing rapid changes that also has high-resolution, high-accuracy data for bed topography, ice surface velocity, and ice front positions. We find that transient calibration brings hindcast simulations of cumulative mass balance to within observational error. We also find that, when the basal friction parameter is allowed to vary, transient calibration can help mimic the impacts of subglacial hydrology and reproduce observations of seasonal velocity variability. Future simulations to 2100 using the ISMIP6 protocols show that the use of transient calibration leads to greater mass loss and, in the near term out to 2050, has a greater impact on mass balance than the choice of climate forcing scenario.

How to cite: Badgeley, J., Seroussi, H., and Morlighem, M.: Improving modeled ice dynamics in Northwest Greenland with transient calibration: From multi-decadal trends to seasonal cycles, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4155, https://doi.org/10.5194/egusphere-egu24-4155, 2024.

EGU24-4943 | ECS | Posters on site | CR2.1

Modelling the complex response of debris covered glaciers on variations in climate and debris input  

Florian Hardmeier, James C. Ferguson, and Andreas Vieli

Debris-covered glaciers are found in most glaciated areas in the world and often represent an important water resource for downstream areas. The dynamics of coupled debris and glacier interactions are not fully understood, which is why there has been an increasing effort in recent years to use numerical modelling to gain a better understanding thereof.

As process understanding is quite limited, implementations of the debris-glacier system vary widely. Here we model the glacier in the along-flow dimension and set the focus on debris transport and tracking debris within and on the ice. We examine feasible implementations of involved processes and their coupled effects on glacier dynamics in a transient climate and that allows to vary the location and rate of debris input into the system.

We perform a sensitivity analysis on this model and conduct experiments of increasing complexity, varying both climate forcing and debris deposition and on both simple synthetic and realistic bedrock topographies. Our modelling corroborates the earlier finding from earlier simpler models (without internal debris tracking) of strongly delayed retreat that only sets in after stagnation of the tongue. Our results show beyond that after retreat following warming, debris covered glaciers show a long-term re-advance effect, even when the absolute debris entrainment rate stays the same. We explain this by the increase of the debris-ice ratio in the debris deposition zone. Interestingly, results also show that – when accompanied with a permanent, regular supply of debris input– single large deposition events can have a sustainable growth effect on the glacier, even after the debris from that event has exited the system. In experiments with below century scale fluctuations in climate and/or debris input the glacier length does not really respond. We conclude that this insensitivity and the response of debris covered glacier in general is not only influenced by debris insulation on the tongue, but is also affected by the long time-scale (centuries) involved in transporting the debris through the glacier system.

How to cite: Hardmeier, F., Ferguson, J. C., and Vieli, A.: Modelling the complex response of debris covered glaciers on variations in climate and debris input , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4943, https://doi.org/10.5194/egusphere-egu24-4943, 2024.

The representation of ice shelf calving in numerical ice models is a new and emerging field in cryospheric modelling. As yet, there has been no systematic, in-depth study of how this process is implemented and whether the results can be trusted. Calving MIP is an ongoing model intercomparison project that seeks to address this issue by providing a common framework for model simulations of ice shelf calving, so that results between different models and approaches can be compared. We find it helpful to distinguish between a calving algorithm, the numerical implementation in a model of how ice is removed due to calving, and a calving law, a law with some physical basis that determines how much ice needs to be removed due to calving. The first phase of Calving MIP experiments are primarily interested in comparing different calving algorithms, whilst future experiments are planned to investigate different calving laws as well as compare simulated results with real world observations.

We present here results from across the cryospheric modelling community from the first phase of Calving MIP experiments investigating calving algorithms as well as future plans for further experiments.

How to cite: Jordan, J.: Calving MIP: Results and conclusions from the first phase of a model intercomparison project into ice shelf calving, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5370, https://doi.org/10.5194/egusphere-egu24-5370, 2024.

EGU24-8114 | Orals | CR2.1

Calculating exposure to extreme sea level risk will require high resolution ice sheet models 

C. Rosie Williams, Pierre Thodoroff, Robert J. Arthern, James Byrne, J. Scott Hosking, Markus Kaiser, Neil D. Lawrence, and Ieva Kazlauskaite

The West Antarctic Ice Sheet (WAIS) is losing ice and its annual contribution to sea level is increasing. The future behaviour of WAIS will impact societies worldwide, yet deep uncertainty remains in the expected rate of ice loss. High impact low likelihood scenarios of sea level rise are needed by risk-averse stakeholders but are particularly difficult to constrain. Here we combine traditional model simulations of the Amundsen Sea sector of WAIS with Gaussian process emulation to show that ice-sheet models capable of resolving kilometre-scale basal topography will be needed to assess the probability of extreme scenarios of sea level rise. This resolution exceeds many state-of-the-art continent-scale simulations. Our model simulations show that lower resolutions tend to overestimate future sea level contribution and inflate the tails of the distribution. We therefore caution against relying purely upon low resolution simulations when assessing the potential for societally important high impact sea level rise.

How to cite: Williams, C. R., Thodoroff, P., Arthern, R. J., Byrne, J., Hosking, J. S., Kaiser, M., Lawrence, N. D., and Kazlauskaite, I.: Calculating exposure to extreme sea level risk will require high resolution ice sheet models, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8114, https://doi.org/10.5194/egusphere-egu24-8114, 2024.

EGU24-8524 | Posters on site | CR2.1

Simulated influence of ice-shelf calving on the evolution of a potential West Antarctic Ice Sheet instability 

Johannes Feldmann, Ronja Reese, and Ricarda Winkelmann

The observed rapid thinning, speed-up and retreat of the ice in West Antarctica’s Amundsen Sea Embayment might indicate an early stage of a marine ice sheet instability (MISI), potentially leading to the disintegration of the West Antarctic Ice Sheet (WAIS). In general, the stability of a marine ice sheet is strongly linked to the dynamics of its buttressing ice shelves which act as a regulator of the ice discharge into the ocean. Existing numerical modeling studies usually simulated MISI-type WAIS retreat either under prescribed fixed present-day calving front positions (associated with very strong ice-shelf buttressing) or in the absence of ice shelves (neglecting ice-shelf buttressing). These approaches represent extreme cases of realizing ice-shelf buttressing in simulations of a WAIS retreat and comparison between the study results are difficult due to the use of different numerical models and experimental designs. Here we aim to investigate the influence of time-evolving calving fronts and associated buttressing changes in the course of an unfolding WAIS disintegration, based on simulations with the Parallel Ice Sheet Model (PISM). One focus will be on how ice-shelf calving affects MISI retreat rates and the extent of a potential WAIS collapse, i.e., the time evolution and magnitude of the associated sea-level contribution.

How to cite: Feldmann, J., Reese, R., and Winkelmann, R.: Simulated influence of ice-shelf calving on the evolution of a potential West Antarctic Ice Sheet instability, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8524, https://doi.org/10.5194/egusphere-egu24-8524, 2024.

EGU24-8997 | Orals | CR2.1

Capabilities of IGM, a thermo-mechanical glacier evolution model accelerated by deep-learning and GPU 

Guillaume Jouvet, Guillaume Cordonnier, Fabien Maussion, Samuel Cook, Brandon Finley, Andreas Henz, Oskar Herrmann, Sarah Kamleitner, Tancrede Leger, Kejdi Lleshi, Jürgen Mey, Dirk Scherler, and Ethan Welty

We present the concepts and capabilities of IGM (https://github.com/jouvetg/igm), a fast and accessible Python model that simulates the evolution of glaciers at any scale by coupling ice thermomechanics, surface mass balance, and mass conservation. IGM models the ice flow by physics-informed deep learning. Specifically, we use a convolutional neural network, which is trained to minimise the energy associated with high-order ice flow physics. Based on the Tensorflow library, IGM performs a suite of fast, vectorised, and differentiable operations, which can be accelerated with a graphics processing unit (GPU). In turn, this allows fully-parallelised implementations of key model components in glacier modelling applications such as the positive degree day surface mass balance scheme, the enthalpy scheme for modelling the thermal regime of ice, or the integration of a large amount of particle trajectories for modelling debris transportation. As a result, IGM combines coding simplicity and modularity, high computational efficiency, state-of-the-art thermomechanical modelling, and efficient data assimilation thanks to underlying automatic differentiation tools. We demonstrate the capability of IGM for two different applications. First, we present a complete workflow (including OGGM-based data preprocessing, inverse and forward modelling, rendering of results) that allows us to model any mountain glacier in the world within a few minutes requiring only its Randolph Glacier Inventory (RGI) ID. Second, we present an application in paleo glacier modelling by simulating the entire European Alpine ice field (about 800 km long) in high resolution (200 m) during the Last Glacial Maximum.

How to cite: Jouvet, G., Cordonnier, G., Maussion, F., Cook, S., Finley, B., Henz, A., Herrmann, O., Kamleitner, S., Leger, T., Lleshi, K., Mey, J., Scherler, D., and Welty, E.: Capabilities of IGM, a thermo-mechanical glacier evolution model accelerated by deep-learning and GPU, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8997, https://doi.org/10.5194/egusphere-egu24-8997, 2024.

EGU24-9861 | Posters on site | CR2.1

Using observations of surface fracture to address ill-posed ice softness estimation over Pine Island Glacier 

Trystan Surawy-Stepney, Stephen L. Cornford, and Anna E. Hogg

Many numerical models used to simulate ice streams require the specification of control fields representing the slipperiness of the ice/bed interface and local deviations in the assumed rheological properties of the ice. These poorly constrained components of the system are often found by solving an inverse problem given observations of model state variables - typically ice flow speed. However, these inverse problems are generally ill-posed, resulting in degenerate or error-dominated solutions. The clearest way to improve this is to take advantage of additional prior information regarding the control fields. 

In this study, we investigate two ways of using maps of surface fracture, derived from Sentinel-1 satellite imagery, to provide prior information to the inverse problem. We first consider a prior that assumes values of effective viscosity significantly different from Glen's flow law are, for the most part, due to observable fractures. Using Pine Island Glacier as a case study, we investigate the solutions and conditioning of this data-informed inverse problem and compare with a typical heuristic regularisation technique. We find that the inclusion of fracture data results in softness fields that resemble fracture features on floating ice. On grounded ice, despite the prevalence of surface crevassing, the softness fields look no more plausible when fracture data is included - suggesting that the presence of surface fracture is not the largest contribution to our uncertainty in the ice rheology. We go on to investigate the use of timeseries of fracture maps to constrain the evolution of the softness field on ice shelves through time, making the assumption that changes to ice rheology occurring on annual timescales are dominated by the fracturing of ice. We show that this method can result in softness fields that visually mimic fracture patterns on floating ice without significantly affecting the quality of the misfit. Such softness fields could be used to constrain evolution equations in isotropic damage models.

How to cite: Surawy-Stepney, T., Cornford, S. L., and Hogg, A. E.: Using observations of surface fracture to address ill-posed ice softness estimation over Pine Island Glacier, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9861, https://doi.org/10.5194/egusphere-egu24-9861, 2024.

EGU24-10305 | Orals | CR2.1

Transient calibration of the Amundsen Sea Embayment: a model and methodology comparison 

Daniel Goldberg and Morlighem Mathieu

It is important that modellers be able to make reasonable projections of ice-sheet loss over the next 50-100 years so that costal planners can make informed decisions. Despite many innovations in modelling and satellite observing, several recent studies show that the agreement between models and the observational record remains poor -- raising concerns about their ability to predict responses to changes in climate on decadal to centennial time scales. A common means to address model-data misfit is via assimilation of satellite data, in which poorly constrained parameters are chosen in a way to minimize this misfit. Data assimilation has been employed extensively, including by many of the models participating in the ISMIP6 intercomparison. However, they are limited to observations at a single point in time (a "snapshot"). Such inversions do not take advantage of the time series of velocity and altimetry observations currently available -- largely due to the complexity and computational expense. The use of Automatic Differentiation makes such approaches possible. The method -- termed "transient assimilation" or "transient calibration" -- provides a physically consistent, time-dependent model which agrees with time-resolved observations.

But with such a development, questions arise: how does transient calibration impact future modelled behaviour? Which types of observations most strongly constrain models? Are results consistent across different models? Here we apply transient calibration to the Amundsen Sea Embayment using two independent models, the Ice-sheet and Sea-level System Model (ISSM) and the MITgcm STREAMICE model, using time-resolved velocities and surface altimetry from 2004 to 2017. We assess the performance of transient compared to snapshot calibrations in terms of capturing past and current trends in speed change, thinning, and grounded ice loss; and we additionally run 50-year projections using the calibrated models. While overall 50-year mass loss is not strongly dependent on assimilation strategy, the rates of mass loss vary greatly, suggesting greater differences on the century time scale or longer. Moreover, we see that the runs calibrated with altimetry: (i) agree best with recent mass loss rates; (ii) show the greatest conformity between models; and (iii) show the largest mass loss rates at the end of the 50-year runs. The results likely have implications for optimal data needs and assimilation strategies in the next generation of ice-sheet models.

How to cite: Goldberg, D. and Mathieu, M.: Transient calibration of the Amundsen Sea Embayment: a model and methodology comparison, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10305, https://doi.org/10.5194/egusphere-egu24-10305, 2024.

EGU24-10817 | Posters on site | CR2.1

Constraining the basal sliding of alpine glaciers using adjoint-based inversions and automatic differentiation on GPUs 

Yilu Chen, Ivan Utkin, Ludovic Räss, and Mauro Werder

There are many uncertainties associated with natural processes governing the evolution of glaciers and ice sheets. Unknown parameters, such as basal drag or surface mass balance, can be estimated through data assimilation workflows coupled with physics-based models of ice flow. The multi-scale nature of ice dynamics and significant spatial and temporal variations in physical properties challenges accurate estimations of distributed fields of unknown parameters. High-performance computing and modern computational architectures such as graphics processing units (GPUs) enable efficient and scalable solvers for the ice flow.

In this work, we introduce a novel GPU-accelerated inversion framework to enable a point-wise reconstruction of unknown parameter fields at high resolution. The inversion framework is based on the adjoint sensitivity method combined to a gradient-based optimisation. The derivation of the adjoint problem often represents a tedious task which limits the applicability of adjoint-based inversions to simplified ice flow models and hinders fast development. To address these limitations we use differentiable programming and the Julia language which permit automatic differentiation (AD) of arbitrary GPU code. Our GPU-based inversion procedure combines an automatically generated adjoint solver by the Enzyme.jl package using AD and a forward solver to retrieve the point-wise gradient we further use to minimise a cost-function.

We demonstrate the capabilities of our inversion framework by developing a forward solver, based on shallow ice approximation (SIA), and several inverse models, utilising different assumptions about the ice flow. One inversion model assumes that the glacier is in a steady-state, which requires iterative solution of SIA equations. The inversion procedure estimates distributions of sliding coefficient, matching the observed ice thickness, glacier outline, and surface velocities. Another inversion model is based on a "snapshot" approach, in which the surface elevation is fixed from observations, and the sliding coefficient is solved to only match observed surface velocities. These two models represent two end members of the spectrum of data assimilation approaches, which will serve as building blocks for more complex workflows, such as transient evolution of glaciers.

The feasibility of our inversion algorithms is validated through extensive testing on synthetic glaciers. Then we consider the application of our inversion approach to glaciers in the European Alps using remote sensing data. A map of sliding coefficients is reconstructed by matching the observed ice surface velocity and elevation. The successful application to real glaciers confirms that our inversion models are well suited for large scale and high-resolution simulations. We also present the performance testing results demonstrating close-to-optimal performance of forward and inverse models on NVIDIA GPUs.

How to cite: Chen, Y., Utkin, I., Räss, L., and Werder, M.: Constraining the basal sliding of alpine glaciers using adjoint-based inversions and automatic differentiation on GPUs, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10817, https://doi.org/10.5194/egusphere-egu24-10817, 2024.

EGU24-10845 | Posters on site | CR2.1

Revisiting the implications of cliff-height dependent calving law on West Antarctic glaciers 

Sainan Sun and G. Hilmar Gudmundsson

High-end estimates of sea-level change from Antarctica have been derived from simulations using upper-end forcing scenarios and ice-cliff height dependent calving laws. Those have been hypothesised to cause collapse of glaciers in West Antarctica through marine ice cliff instability (MICI). However, some previously published high-end estimate are based on results from a limited number of ice-sheet models, or even only a single ice-flow modelling study. There is, furthermore, low agreement on the implications of some of those calving laws for the West Antarctic Ice Sheet, and limited evidence of MICI having occurred in the past. Here we investigate the dynamic response of West Antarctic glaciers to high-end calving laws using the Úa ice-sheet model. Specifically, we conduct ice-shelf collapse experiments as defined in ABUMIP (Sun et al., 2020) with and without cliff failure mechanism in transient simulations conduced over centennial time scales. We find that the ice-cliff height dependent calving laws can cause glaciers to retreat and collapse from both fast and slow flowing regions. Furthermore, we find that the results are sensitive to numerical resolution near the grounding line. We suggest therefore that ice-sheet modellers always conduct convergence studies when implementing high-end calving laws.

How to cite: Sun, S. and Gudmundsson, G. H.: Revisiting the implications of cliff-height dependent calving law on West Antarctic glaciers, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10845, https://doi.org/10.5194/egusphere-egu24-10845, 2024.

EGU24-10934 | Orals | CR2.1

Evolution of marine ice sheets with bed sedimentation 

Ian Hewitt and Emilie Herpain

Marine ice sheets terminate in the ocean where they form floating ice shelves or calve icebergs.  They can significantly influence sea level because of the potential for rapid transfer of grounded ice (with thickness greater than floatation) to floating ice shelves or icebergs.  Most models of marine ice sheet evolution assume that the bed elevation stays constant, or responds isostatically to the weight of the ice sheet.  However, it is known that there is sediment deformation beneath the ice sheet (which is in part what enables the ice to move), and that deposition of this sediment in the vicinity of the grounding line can result in the formation of a grounding-zone wedge.  Although it is widely recognised that such a wedge can influence the evolution of the grounding line (where the ice becomes afloat), there is incomplete knowledge about the interaction of the ice and sediment/bed dynamics.

In this study, we build on idealised two-dimensional (flow-line) models of a marine ice sheet to investigate the influence of a deforming sediment layer at the bed.  We examine how different conditions lead to the development of a grounding zone wedge, and how this impacts the possible steady states of the model under given climate forcing, and under different assumptions about the sediment dynamics.  We then examine how the sediment dynamics, and the presence of the grounding-zone wedge, influence the stability of the system.

How to cite: Hewitt, I. and Herpain, E.: Evolution of marine ice sheets with bed sedimentation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10934, https://doi.org/10.5194/egusphere-egu24-10934, 2024.

EGU24-11040 | ECS | Orals | CR2.1

Insights into the LGM-to-present evolution of the Greenland Ice Sheet from a data evaluated ensemble of numerical model simulations 

Tancrède Leger, Jeremy Ely, Christopher Clark, Sarah Bradley, Rose Archer, and Jiang Zhu

Ice sheets have a memory that is stored within both the geometry and thermal properties of the ice. The current Greenland Ice Sheet is thus not in equilibrium with present-day climate, but is in fact affected by a complex product of past changes that occurred over millennial timescales. Therefore, simulating the late-Pleistocene evolution of the Greenland Ice Sheet accurately is important when running future projections using paleo model initialization procedures. Using a novel model-data comparison procedure, we ran an experiment that aimed to produce numerical model simulations that fit available empirical data on the extent and timing of the grounded margin evolution of the Greenland Ice Sheet from the global LGM (24 kyr BP) to 1850 AD. Given the numerous uncertain parameters and boundary conditions required by numerical ice sheet models, finding simulations which adequately replicate empirical data on past grounded ice extent is a challenging task. In an attempt to address this challenge, we ran a perturbed parameter ensemble of 100 ice-sheet-wide simulations at 5 km spatial resolution using the Parallel Ice Sheet Model. Our simulations are forced by the latest transient paleo-climate and ocean simulations of the isotope-enabled Community Earth System Model (iCESM 1.2 and 1.3). Using quantitative model-data comparison tools and the newly developed, Greenland-wide PaleoGrIS 1.0 isochrone reconstruction of former ice extent, each ensemble simulation’s fit with empirical data was assessed quantitatively across both space and time. Using our best-scoring simulations, we here present new insights into the former Greenland Ice Sheet’s likely response to transitional climatic phases throughout the last deglaciation. Secondly, our results suggest ice temperature, geometry, and glacial isostatic adjustment-induced mechanisms of centennial to millennial-scale inertia in ice-extent response to past climatic forcing, with potential implications for the future evolution of the ice sheet. Thirdly, our results show that different parameter combinations produce a better model-data fit during different time periods and for different regions of the ice sheet – i.e. parameter values that work well at one place or time, produce worse fit at others. We hypothesise that better paleo model initializations may be achieved using time- and space-dependent parameter configurations. Finally, after extending several past ensemble simulations to the end of the 21st century under CMIP6-derived forcing, we find that accounting for the past modifies projections of the future. Using a steady-state contemporary ice sheet as an initial state leads to vastly different projected sea level contributions when compared to simulations that perform well at recreating past glacial history.

How to cite: Leger, T., Ely, J., Clark, C., Bradley, S., Archer, R., and Zhu, J.: Insights into the LGM-to-present evolution of the Greenland Ice Sheet from a data evaluated ensemble of numerical model simulations, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11040, https://doi.org/10.5194/egusphere-egu24-11040, 2024.

The force balance of an ice steam determines its velocity, and along with cross sectional area, influences total flux of glacial ice to the ocean. Satellite datasets provide us strong time series velocity data, while radar, seismics, and geophysical inversion methods yield width and depth estimates within an ice column. However, should an ice stream widen or narrow, the flux of ice to the ocean could change perceptibly. 
Thwaites Glacier’s eastern shear margin is not topographically bounded, but rather arcs across a shallow subglacial rise of intermittent hills and valleys. To determine the stability of the margin it is imperative to understand the force balance and total energy of the glacier system along the shear zone. Driving forces are balanced by normal and shear stresses along the bed, and longitudinal shearing in the margin. The resistance (or lack thereof) creates deformational (frictional-sliding) heating which add energy to the system altering rate factor and meltwater generation, which in turn alter the viscosity and slip factors, making a complex feedback system.
To analyze this system, we develop a 3D full-Stokes flow model in the Elmer/ICE finite element software. The model resolves at 500 m horizontally over realistic surface and bed topography from BedMachinev3. Model domains cover key data acquisition sites from the International Thwaites Glacier Collaboration, Thwaites Interdisciplinary shear Margin Evolution (ITGC TIME) seismic and radar field studies. To determine energy balance, we employ the enthalpy field equations which efficiently solve the thermal field, solve for water content generation, and couple nicely with variable rate factors. Models are initialized by a suite of 1D thermal profiles, converted to enthalpy values, derived from quartile statistics of RACMO2.3p1 surface specific mass balance data, and then advected to steady state flow. 
These models are then run with a flow-coupled glacier drainage system (GlaDS) and enthalpy relation to determine temperate ice distribution, and basal water production. Non-linear Coulomb and Weertman sliding laws are tested between scenarios of natural melt generation, through full drainage piracy of the upper Pine Island catchment, which will determine the effect of spatiotemporal variation in effective pressure (N) on shear margin stability.
Through the suite of spin up models and scenarios, we aim to determine the stability of Thwaites Glacier’s eastern shear margin from perturbations in enthalpy from both sliding friction, and viscous heating from temperate ice generation over non-idealized bed topography and within the shear margin itself. Results will help inform catchment scale transient flow models which aid in determining sea level contribution and West Antarctic Ice Sheet stability.  

How to cite: Martin, C. and Hehlen, M.: An Enthalpy-Hydrology Coupled 3D full-Stokes Flow Model of Thwaites’ Eastern Shear Margin, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11319, https://doi.org/10.5194/egusphere-egu24-11319, 2024.

EGU24-11836 | Orals | CR2.1

Observing and modeling short-term changes in basal friction during rain-induced speed-ups on an Alpine glacier 

Anuar Togaibekov, Florent Gimbert, Adrien Gilbert, and Andrea Walpersdorf

Basal shear stress on hard-bedded glaciers results from normal stress against bed roughness, which depends on basal water pressure and cavity size. These quantities are related in a steady state but are expected to behave differently under rapid changes in water input, which may lead to a transient frictional response not captured by existing friction laws. Here, we investigate transient friction using GPS vertical displacement and horizontal velocity observations, basal water pressure measurements, and cavitation model predictions during rain-induced speed-up events at Glacier d'Argentière, French Alps. We observe up to a threefold increase in horizontal surface velocity, spatially migrating at rates consistent with subglacial flow drainage, and associated with surface uplift and increased water pressure. We show that frictional changes are mainly driven by changes in water pressure at nearly constant cavity size. We propose a generalized friction law capable of capturing observations in both the transient and steady-state regimes.

How to cite: Togaibekov, A., Gimbert, F., Gilbert, A., and Walpersdorf, A.: Observing and modeling short-term changes in basal friction during rain-induced speed-ups on an Alpine glacier, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11836, https://doi.org/10.5194/egusphere-egu24-11836, 2024.

EGU24-12564 | Posters on site | CR2.1

Exploring physics-informed neural networks for glacier flow. 

Mamta K C, Harald Köstler, and Johannes Fürst

Deep learning-based surrogate models have emerged as computationally inexpensive tools for simulating glacier dynamic systems defined by complex, nonlinear partial differential equations. Despite the potential, the application of physics-informed neural networks  (PINNS) in glacier modelling is sparse. Thus, this study explores the potential of  NVIDIA Modulus-Sym, a PyTorch-based framework, in simulating glacier velocities. The framework NVIDIA Modulus-Sym provides ground for building, training and fine-tuning physics-based surrogate models targeting computational fluid problems. This study presents the pipeline to generate glacier velocities using the physics-constraint approach that incorporates the physics regularisation term within the loss function to enhance generalisation performance. The study further emphasises the challenges and limitations of tools in glaciological research. 

Keywords: Deep learning, Surrogate Models, Glacier Dynamics,  Glaciology

How to cite: K C, M., Köstler, H., and Fürst, J.: Exploring physics-informed neural networks for glacier flow., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12564, https://doi.org/10.5194/egusphere-egu24-12564, 2024.

EGU24-12685 | ECS | Orals | CR2.1

The importance of calving in ice sheet models: A sensitivity study of ice front retreat in the Amundsen Sea Embayment 

Jowan Barnes, G. Hilmar Gudmundsson, Daniel Goldberg, and Sainan Sun

Calving is a key process in the dynamics of marine-terminating glaciers with large ice shelves, such as those in West Antarctica. However, this process is currently not included in most predictive models, due to its difficulty to implement in a general form which can reliably reproduce rates of calving over a range of scenarios. We set out to investigate how important it is to develop such representation of calving for future modelling.

In this study, we quantify the sensitivity of modelled future mass loss to ice front retreat in the Amundsen Sea Embayment, including Pine Island and Thwaites Glaciers. We find that prescribing constant frontal retreat rates from 0.1 to 1 km a­­-1 progressively increases the contribution to sea level rise when compared to experiments with a fixed ice front. The result is up to 80% more loss of ice by 2100, and more than triple the ice loss in projections beyond 2200 with the higher rates of retreat. The spatial pattern of ice loss is non-uniformly distributed, with some regions thinning and others thickening as an initial response to the calving front retreat. We identify specific thresholds in the geometry of the system, which have clear effects on the ice flow and are reached at different times depending on the retreat rate.

We compare variability in the range of our results using different retreat rates to that in the range of ISMIP6 ocean forcing products, as ocean-induced melt is known to be a major factor in determining the future evolution of the Antarctic ice sheet. We find that the variability due to these two factors is initially similar, and that variability due to ice front retreat becomes comparatively greater over time. Our results demonstrate the high importance of accurately representing calving processes in models, showing that they are at least as important as ocean forcing and deserve a similar amount of attention in future model development work.

How to cite: Barnes, J., Gudmundsson, G. H., Goldberg, D., and Sun, S.: The importance of calving in ice sheet models: A sensitivity study of ice front retreat in the Amundsen Sea Embayment, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12685, https://doi.org/10.5194/egusphere-egu24-12685, 2024.

EGU24-12813 | ECS | Orals | CR2.1

Quantifying the Buttressing Contribution of Sea Ice to Crane Glacier 

Richard Parsons, Sainan Sun, and Hilmar Gudmundsson

Antarctic sea ice extent reached a record minimum in 2023. Whilst the buttressing resistance provided by ice shelves has been quantified through past numerical studies, the degree to which sea ice can buttress and regulate upstream ice flow is not known. If significant, a future decline in sea ice extent would lead to increased ice discharge rates and a higher global mean sea level.

The January 2022 disintegration of landfast sea ice in the Larsen B embayment was closely followed by a significant increase in ice flow velocities and retreat rates of numerous outlet glaciers in the region. Notably, Crane glacier saw an initial ~8km retreat over six weeks, during which time a 5% increase in velocity was observed. Afterwards, the full evacuation of ambient sea ice between October and November was accompanied by the most significant monthly increase in velocities.

We use the numerical ice flow model, Ua, to investigate the buttressing effect of sea ice to Crane glacier. The ice-sheet model was initialised with sea ice included and constrained with observational velocity and geometry data sets. We conducted perturbation experiments on sea ice properties to explore its impact on the glacier. The results suggest that sea ice provided significant buttressing to the glacier before its collapse.

How to cite: Parsons, R., Sun, S., and Gudmundsson, H.: Quantifying the Buttressing Contribution of Sea Ice to Crane Glacier, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12813, https://doi.org/10.5194/egusphere-egu24-12813, 2024.

EGU24-13210 | ECS | Orals | CR2.1

Unifying and comparing different models of viscous anisotropy to be included in ice sheet models. 

Daniel Richards, Elisa Mantelli, Samuel Pegler, and Sandra Piazolo

Ice fabrics – the alignment of crystal orientations - can cause the ice viscosity to vary by an order of magnitude, consequently having a strong impact on the large-scale flow of ice sheets and glaciers. Because of this, there is a need for fabric models which are computationally efficient enough to be included in large-scale ice sheet models. We examine a range of existing models in this class and show they can be combined into a common equation which is a function of 2-3 parameters. By comparing with observations from the Greenland ice sheet, we get the best model predictions by assuming the ice deforms close to the Sachs hypothesis – that all grains experience the same stress. As these fabric predictions also depend on the flow law used, we provide a test of competing anisotropic flow laws for the first time, making a step towards reliably incorporating the effect of fabric and viscous anisotropy in ice sheet flow models.

How to cite: Richards, D., Mantelli, E., Pegler, S., and Piazolo, S.: Unifying and comparing different models of viscous anisotropy to be included in ice sheet models., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13210, https://doi.org/10.5194/egusphere-egu24-13210, 2024.

EGU24-13290 | ECS | Orals | CR2.1

Description and validation of the ice sheet model Nix v1.0 

Daniel Moreno-Parada, Alexander Robinson, Marisa Montoya, and Jorge Alvarez-Solas

We present a physical description of the ice-sheet model Nix v1.0, an open-source project intended for collaborative development. Nix is a 2D thermomechanical model written in C/C++ that simultaneously solves for the momentum balance equations, mass conservation and temperature evolution. Nix's velocity solver includes a hierarchy of Stokes approximations: Blatter-Pattyn, depth-integrated higher order, shallow-shelf and shallow-ice. The grounding-line position is explicitly solved by a moving coordinate system that avoids further interpolations. The model can be easily forced with any external boundary conditions, including those of stochastic nature. Nix has been verified for standard test problems. Here we show results for a number of benchmark tests from standard intercomparison projects and assess grounding-line migration with an overdeepened bed geometry. Lastly, we further exploit the thermomechanical coupling by designing a suite of experiments where the forcing is a physical variable, unlike previously idealised forcing scenarios where ice temperatures are implicitly fixed via an ice rate factor. Namely, we use atmospheric temperatures and oceanic temperature anomalies to assess model hysteresis behaviour with active thermodynamics. Our results show that hysteresis in an overdeepened bed geometry is similar for atmospheric and oceanic forcings. We find that not only the particular sub-shelf melting parametrisation determines the temperature anomaly at which the ice sheet retreats, but also the particular value of calibrated heat exchange velocities. Notably, the classical hysteresis loop is narrowed for both forcing scenarios (i.e., atmospheric and oceanic) if the ice sheet is thermomechanically active as a results of the internal feedback among ice temperature, stress balance and viscosity. In summary, Nix combines rapid computational capabilities with a Blatter-Pattyn stress balance fully coupled to a thermomechanical solver, not only validating against established benchmarks but also offering a powerful tool for advancing our insight on ice dynamics and grounding line stability.

How to cite: Moreno-Parada, D., Robinson, A., Montoya, M., and Alvarez-Solas, J.: Description and validation of the ice sheet model Nix v1.0, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13290, https://doi.org/10.5194/egusphere-egu24-13290, 2024.

EGU24-13830 | Posters on site | CR2.1

Simulating glacier evolution with a 3D ice sheet model 

Gunter Leguy, William Lipscomb, and Samar Minallah

We have implemented a new framework for simulating the dynamic evolution of mountain glaciers in the Community Ice Sheet Model (CISM), a 3D, higher-order ice sheet model that serves as the ice dynamics component of the Community Earth System Model. We have used CISM to simulate all the glaciers of the European Alps at a resolution of 100 m. We describe the modeling framework and present results for the third phase of the GlacierMIP project (GlacierMIP3), which aims to determine the equilibrium area and volume of all glaciers outside the ice sheets, if global mean temperatures were to stabilize at present-day or various warmer levels. Compared to other glacier models, CISM is relatively sensitive to warming. We project that Alpine glaciers will lose a majority of their area and volume under present-day temperatures, with nearly complete ice loss under warmer scenarios. We are extending this framework to other glacier regions and will show preliminary result.

How to cite: Leguy, G., Lipscomb, W., and Minallah, S.: Simulating glacier evolution with a 3D ice sheet model, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13830, https://doi.org/10.5194/egusphere-egu24-13830, 2024.

EGU24-14128 | ECS | Orals | CR2.1

Simulating Mass Balance and Dynamics of Mountain Glaciers within an Earth System Modeling Framework 

Samar Minallah, William Lipscomb, Sean Swenson, and Gunter Leguy

Simulating mass changes and ice dynamics for mountain glaciers using Earth System Models (ESMs) is challenging due to their small size, sheer number, and spatial discontinuities in the ground ice coverage. This has resulted in a knowledge and representational gap in ESMs. However, there is a need for scaling ESMs from global to regional domains for comprehensive glacio-hydrological and hydroclimatic assessments.

We introduce new developments for simulating the mass balance and dynamic evolution of mountain glaciers within the Community Earth System Model (CESM). We provide an overview of this work across two spatiotemporal scales related to: (1) the dynamic evolution of the Central European glaciers under the GlacierMIP3 protocol using the Community Ice Sheet Model (CISM) and (2) the energy and water balance of the Upper Indus glaciated basins at daily-monthly timescales using the Hillslope Hydrology configuration of the Community Land Model (CLM).

How to cite: Minallah, S., Lipscomb, W., Swenson, S., and Leguy, G.: Simulating Mass Balance and Dynamics of Mountain Glaciers within an Earth System Modeling Framework, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14128, https://doi.org/10.5194/egusphere-egu24-14128, 2024.

EGU24-14499 | ECS | Orals | CR2.1

Subglacial Water Pressure Reshapes projected Antarctic Sea-Level Rise 

Chen Zhao, Rupert Gladstone, Thomas Zwinger, Fabien Gillet-Chaulet, Yu Wang, Justine Caillet, Pierre Mathiot, Leopekka Saraste, Ben Galton-Fenzi, Poul Christoffersen, and Matt King

Subglaical hydrology significantly influences the basal sliding that controls how fast ice sheets transport ice from land to oceans. The absence of hydrologic systems in ice sheet models is therefore a notable source of uncertainty in projected ice-mass loss and its subsequent impact on sea-level rise. Specifically, the uncertainty associated with the representation of effective pressure (the difference between subglacial water pressure and ice overburden pressure) in basal sliding lacks comprehensive investigation in Antarctic sea-level rise projections. Here we use Elmer/Ice ice-sheet model setups to examine how different approaches to determining effective pressure in the regularised Coulomb sliding law impact the projected ice mass loss pre-2300 under both continental and basin scales. Our results reveal basin-specific responses to the representation of effective pressure in basal sliding, significantly influencing projected ice-mass loss and the timing of the passing of tipping points. We find that the ongoing interactions between ice dynamics and the hydrologic system render the grounding line much more mobile than in models with no such interaction. Notably, for the entire Antarctic Ice Sheet, grounding line flux is more than doubled by 2300 when employing a smoothly decreasing effective pressure near the grounding line, compared to constant pressure. Remarkably, Thwaites Glacier shows a tenfold increase in its grounding line flux by 2300. These findings underscore the critical need to better understand the interactions between ice dynamic evolution and the subglacial hydrologic system. Explicitly modelling the hydrologic system in a coupled ice sheet-subglacial hydrology models is crucial to make more robust predictions of Antarctica's future ice-mass loss, thereby reducing uncertainty in sea-level rise projections. 

How to cite: Zhao, C., Gladstone, R., Zwinger, T., Gillet-Chaulet, F., Wang, Y., Caillet, J., Mathiot, P., Saraste, L., Galton-Fenzi, B., Christoffersen, P., and King, M.: Subglacial Water Pressure Reshapes projected Antarctic Sea-Level Rise, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14499, https://doi.org/10.5194/egusphere-egu24-14499, 2024.

EGU24-15275 | ECS | Orals | CR2.1

Modelled ice sheet sensitivity to basal friction parameterizations is controlled by the amount of buttressing 

Tim van den Akker, William H. Lipscomb, Gunter R. Leguy, Willem Jan van de Berg, and Roderik S.W. van de Wal

The basal friction parameterization is often mentioned as key source of uncertainty when using ice sheet models to project future evolution of the ice sheet. Previous work suggests that parameterizations with an exponential relationship between friction and basal velocity (power laws) predict lower sea level rise than ‘Coulomb-style’ friction laws. For Coulomb laws, the basal friction asymptotes for high velocities and is effectively independent of velocity for fast-flowing ice. We use the Community Ice Sheet Model (CISM) for two kinds of simulations: one with present-day climate forcing, including sub-shelf ocean temperatures kept constant and one with 1-degree ocean warming in the Ross Sea, both matching the current rate of ice thickness changes. In the constant scenario, Thwaites Glacier and Pine Island Glacier collapse, creating a huge, laterally bounded ice shelf. In the scenario with Ross Sea warming, a large part of the Ross Ice Shelf disappears, allowing Siple Coast glaciers to flow freely into the ocean. For Thwaites and Pine Island Glaciers, there are competing processes causing increases or decreases in ice flux across the grounding line, ice shelf thickness, buttressing, and ice velocities, once the glaciers are collapsing. These processes work in the opposite direction of the differences caused by choosing different basal friction parameterizations. Therefore, in our model runs, the choice of basal friction parameterization has little effect on the collapse of Thwaites and Pine Island glacier. In the unbuttressed Siple Coast case, we confirm earlier results: Coulomb friction leads to more ice mass loss and sea level rise. We conclude that unbuttressed glaciers are more sensitive to the choice of basal friction parameterizations than are heavily buttressed glaciers, and that the presence of a large buttressing ice shelf decreases the sensitivity of glacier dynamics to different basal friction parameterizations. 

How to cite: van den Akker, T., Lipscomb, W. H., Leguy, G. R., van de Berg, W. J., and van de Wal, R. S. W.: Modelled ice sheet sensitivity to basal friction parameterizations is controlled by the amount of buttressing, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15275, https://doi.org/10.5194/egusphere-egu24-15275, 2024.

EGU24-15478 | ECS | Orals | CR2.1

The effect of ice damage on future Antarctic projections 

Javier Blasco, Yanjun Li, Violaine Coulon, and Frank Pattyn

The Antarctic Ice Sheet (AIS) is the largest ice sheet and hence the potentially largest contributor to future sea-level rise. However, the AIS represents also the largest source of uncertainty regarding future projections. One of the main sources for this uncertainty are the floating ice shelves. While these ice shelves do not directly contribute to sea-level rise, they play a major role in the dynamics of the AIS. By transmitting resistive stress to the grounding line, they are capable of slowing down inland ice. If ice shelves disintegrate, this buttressing effect disappears, promoting the flow of inland ice into the ocean. Thus, the assessment of ice shelf stability in future scenarios becomes crucial for accurate predictions.

One key element which is often overlooked is the formation of ice fractures. Satellite images display increased crevasse formation on Antarctic ice shelves and grounded ice near the grounding line over the past decade. These fractures, referred to as damage, impact the ice flow by reducing its viscosity. Reduced viscosity enhances ice flow, leading to higher strain rates which further promotes more damage formation. However, despite its known effect, its application has been only done on idealized domains so far.

Here we will assess the damage sensitivity of a three-dimensional ice-sheet-shelf model in a simplified, symmetric case (MISMIP+ domain) and a complex real-world scenario such as the Amundsen-Sea Embayment (ASE). For this we will test three different damage formulations from literature which account for explicit crevasse formation. In addition, we will also test a new regularization approximation in our viscosity formulation. This approximation ensures that if no damage is applied, then the effective yield strength of our model cannot exceed the failure strength of ice.

Our findings reveal that incorporating damage or viscosity regularization into future projections of the ASE results in higher sea-level contribution and faster grounding-line migration. This underscores the critical need to enhance our understanding of damage and its implications for future sea-level rise, since current projections do not account for this process.

How to cite: Blasco, J., Li, Y., Coulon, V., and Pattyn, F.: The effect of ice damage on future Antarctic projections, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15478, https://doi.org/10.5194/egusphere-egu24-15478, 2024.

EGU24-16256 | ECS | Posters on site | CR2.1

Modelling subglacial drainage with GlaDS on GPUs 

Annegret Pohle, Ivan Utkin, Ludovic Räss, and Mauro Werder

The Subglacial Drainage System model (GlaDS) is one of the most widely used advanced glacier drainage models, with implementations in several ice sheet models. Here we present a new version of this model capable of execution on graphics processing units (GPUs) programmed in Julia. The aim is for the model to run on meshes larger than 10,000² grid points, which would allow, for instance, to simulate Antarctica at 500m resolution. Unlike the original GlaDS implementation, this is based on a finite difference scheme on a structured grid. Together with a matrix-free solver, this allows us to leverage the full performance capabilities of GPUs. We present model runs of the SHMIP test cases, show the model's scalability and provide an outlook towards higher-resolution continental-scale applications and inversion schemes.

How to cite: Pohle, A., Utkin, I., Räss, L., and Werder, M.: Modelling subglacial drainage with GlaDS on GPUs, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16256, https://doi.org/10.5194/egusphere-egu24-16256, 2024.

EGU24-16675 | ECS | Posters on site | CR2.1

Benchmarking FastIce, a new massively parallel thermomechanical ice flow solver 

Ivan Utkin, Ludovic Räss, Filippo Quarenghi, and Mauro Werder

Efficient modeling of ice sheets involves considering multiple coupled physical processes, including thermomechanical interactions. While using a Full-Stokes model for ice flow in Greenland and Antarctica provides most accurate results, it is can be extremely costly on a large scale with existing software, justifying the use of various reduced models.

Some important features of ice sheets, such as ice streams, are inherently three-dimensional. Accurate stress distribution, particularly around topography features comparable to ice thickness and near a grounding line, can only be achieved with a full stress tensor. In addition, a reference Full-Stokes solver for regional to ice sheet scale simulations can be a valuable tool for calibrating reduced models.

We introduce FastIce, a novel ice flow model for massively parallel architectures, written in Julia. Leveraging GPUs (Nvidia, AMD) and supporting distributed computing, FastIce includes a thermo-mechanically coupled Full-Stokes ice flow model and a novel conservative energy formulation for describing thermal effects. FastIce is written to be easily extensible, and its core is fully differentiable, enabling data assimilation pipelines using adjoint sensitivities and automatic differentiation (AD).

We validate FastIce through ISMIP-HOM benchmark tests and assess the coupled thermomechanical solver using the method of manufactured solutions. Our results showcase the thermo-mechanical instability arising from the non-linear interaction between temperature-dependent viscosity of ice and shear heating, reproducing existing analytical results. We present the performance testing of FastIce in single-node and distributed scaling benchmarks on LUMI, the largest European supercomputer.

How to cite: Utkin, I., Räss, L., Quarenghi, F., and Werder, M.: Benchmarking FastIce, a new massively parallel thermomechanical ice flow solver, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16675, https://doi.org/10.5194/egusphere-egu24-16675, 2024.

EGU24-17095 | Posters on site | CR2.1

Assessing Antarctic Ice Sheet Dynamics and Sea Level Rise: Insights from PROTECT Model Intercomparison 

Cyrille Mosbeux, Gael Durand, Nicolas Jourdain, Fabien Gillet-Chaulet, Justine Caillet, Violaine Coulon, Frank Pattyn, Simon Schoell, Ann Kristin Klose, Ricarda Winkelman, Stephen Cornford, Suzanne Bevan, Tijn Berends, Roderik van de Wal, Heiko Goelzer, Tamsin Edwards, Fiona Turner, Charles Amory, Christoph Kittel, and Michiel van den Broeke and the PROTECT

Mass loss from the Antarctic Ice Sheet is increasing, accelerating its contribution to global sea level rise. Projecting the future evolution of the Antarctic Ice Sheet but also better understanding the processes at play is therefore of major importance for the mitigation/adaptation of/to sea level rise.  

Despite considerable advancements in the initialization of ice sheet models over the last decade, challenges persist in reproducing the observed trend in global Antarctic mass loss. This discrepancy between models and reality reflects in the large range of sea level projections in the recent Ice Sheet Model Intercomparison Project (ISMIP6). As part of the European H2020 project, PROTECT, we conducted Antarctic Ice Sheet simulations with six European ice-sheet models until 2150, focusing on the ability of the model to reproduce observations. These simulations were driven by a range of ocean and atmospheric forcings derived from Earth System models or downscaled by regional climate models under various Shared Socioeconomic Pathways (SSPs). Our experimental design enables us  to sample climate forcing as well as model and parametric uncertainties, ensuring a comprehensive exploration of the future evolution of the Antarctic System and its contribution to sea level rise

Our simulations confirm that, regardless of the model used, the Amundsen sector is the region that will most likely dominate mass loss in the decades to come. In high emission scenarios (SSP5-8.5), a large increase in surface mass balance is also expected to temporarily overshadow acceleration in mass loss caused by ice-shelf basal melting. All the models show an acceleration in mass loss from the middle of the 22th century, following the significant increase in surface melting from the end of the 21st century for the SSP5-8.5 scenario. This emphasizes the pivotal role of surface melt in the long-term evolution of the Antarctic ice sheet and its contribution to sea level rise.

 

How to cite: Mosbeux, C., Durand, G., Jourdain, N., Gillet-Chaulet, F., Caillet, J., Coulon, V., Pattyn, F., Schoell, S., Klose, A. K., Winkelman, R., Cornford, S., Bevan, S., Berends, T., van de Wal, R., Goelzer, H., Edwards, T., Turner, F., Amory, C., Kittel, C., and van den Broeke, M. and the PROTECT: Assessing Antarctic Ice Sheet Dynamics and Sea Level Rise: Insights from PROTECT Model Intercomparison, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17095, https://doi.org/10.5194/egusphere-egu24-17095, 2024.

EGU24-17427 | ECS | Posters on site | CR2.1

Determining the englacial temperature evolution of very small glaciers in the Swiss Alps: An enthalpy-based modelling approach 

Janosch Beer, Mylène Jacquemart, Ivan Utkin, Matthias Huss, Andreas Vieli, and Daniel Farinotti

Despite constituting 80% of the total number of glaciers in mid- to low-mountain range catchments, the attention paid to very small glaciers (< 0.5 km2) in glacier research remains relatively low. However, glaciers of this size category are expected to undergo dramatic changes. Within Switzerland, more than half are predicted to disappear within the next two decades. As these glaciers shrink, they lose their firn cover, a crucial latent heat source through refreezing meltwater. Simultaneously, reduced glacier dynamics result in less ice deformation and decreased frictional heating at the base. Various studies suggest that such conditions can promote cooling, possibly enabling a transition from temperate to polythermal or cold states. Polythermal glaciers, especially those with partly frozen glacier beds, have been found to accumulate excessive meltwater, significantly increasing their hazard potential. In this study we present a new enthalpy-based englacial temperature model (IceT) to investigate the potential transition of very small Swiss glaciers from temperate to polythermal or cold conditions. The study focuses on identifying key parameters influencing glacier thermal transitions through a sensitivity analysis. Furthermore, we apply the model on a subset of 20 very small Swiss glaciers and compare our findings against previously generated model results of the Glacier Evolution Runoff Model (GERM). Our results indicate that mass balance and the liquid water content are the most significant factors for predicting glacier thermal states. The influence of mass balance works in two ways: (1) Highly negative mass balances hinder the development of a polythermal structure by allowing surface melt to surpass the propagation of the cold-temperate transition surface (CTS). (2) Less negative mass balances combined with limited snowfall, induce a transition to polythermal conditions by enabling the CTS propagation to outpace surface melt. Ultimately, the liquid water content (φ) appears as the most critical parameter in predicting ice temperatures. A mere increase of φ by 1% could reduce the maximum CTS depth by 165.07 m and lower the annual CTS propagation rate by 13.85 m a-1. Significant differences emerge between GERM and IceT findings. GERM suggests that the majority of all very small Swiss glaciers exhibit polythermal conditions, while in the subset of 20 glaciers modeled with IceT, only 15% show indications of a polythermal regime. However, the considerable impact of liquid water on predicting ice temperatures, coupled with the incomplete knowledge regarding its distribution within glaciers, leads to substantial uncertainties in the presented model outcomes.

How to cite: Beer, J., Jacquemart, M., Utkin, I., Huss, M., Vieli, A., and Farinotti, D.: Determining the englacial temperature evolution of very small glaciers in the Swiss Alps: An enthalpy-based modelling approach, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17427, https://doi.org/10.5194/egusphere-egu24-17427, 2024.

EGU24-17606 | ECS | Posters on site | CR2.1

Effect of initial states on the uncertainty in sea-level rise projections until 2100 and beyond 

Simon Schöll, Ann Kristin Klose, Ronja Reese, Nicolas Jourdain, and Ricarda Winkelmann

Projections for Antarctica's contribution to global sea-level rise until 2100 range from a positive contribution due to increased ice loss, caused by an increase in surface melt and in dynamic loss of grounded ice, to a negative contribution due to increased snowfall. The high uncertainties in projections can be attributed to different sources, including emission trajectories, climate forcings from Global Circulation Models (GCMs) and Regional Climate Models (RCMs), as well as inter- and intra-ice-model differences.
Here, we present an ensemble of future projections based on simulations with the Parallel Ice Sheet Model (PISM), driven by multiple climate forcings. These are based on several initial states and ice-sheet trajectories over the historical period, consistent with observations.
We assess the influence of the initial states on the spread in projected sea-level change and compare these to the uncertainties arising from climatic forcings, to compare the sources of uncertainty in future sea-level projections until 2100 and beyond.

How to cite: Schöll, S., Klose, A. K., Reese, R., Jourdain, N., and Winkelmann, R.: Effect of initial states on the uncertainty in sea-level rise projections until 2100 and beyond, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17606, https://doi.org/10.5194/egusphere-egu24-17606, 2024.

EGU24-19141 | ECS | Orals | CR2.1

FastIsostasy - An accelerated regional GIA model for coupled ice-sheet/solid-Earth simulations with laterally-variable solid-Earth structures 

Jan Swierczek-Jereczek, Marisa Montoya, Konstantin Latychev, Alexander Robinson, Jorge Alvarez-Solas, and Jerry Mitrovica

The vast majority of ice-sheet modelling studies rely on simplified representations of the Glacial Isostatic Adjustment (GIA), which, among other limitations, do not account for lateral variations of the lithospheric thickness and upper-mantle viscosity. In studies using 3D GIA models, this has however been shown to have major impacts on the dynamics of marine-based sectors of Antarctica, which are likely to be the greatest contributors to sea-level rise in the coming centuries. This gap in comprehensiveness is explained by the fact that 3D GIA models are computationally expensive, seldomly open-source and require the implementation of an iterative coupling scheme to converge with the history of the ice-sheet model. To close this gap between "best" and "tractable" GIA models, we here propose FastIsostasy, a regional GIA model capturing lateral variations of the lithospheric thickness and mantle viscosity. By means of Fast-Fourier transforms and a hybrid collocation scheme to solve its underlying partial differential equation, FastIsostasy can simulate 100,000 years of high-resolution bedrock displacement in only minutes of single-CPU computation, including the changes in sea-surface height due to mass redistribution. Despite its 2D grid, FastIsostasy parametrises the depth-dependent viscosity in a physically meaningful way and therefore represents the depth dimension to a certain extent. FastIsostasy is here benchmarked against analytical, 1D and 3D GIA solutions and shows very good agreement with them. It is fully open-source, documented with many examples and provides a straight-forward interface for coupling to an ice-sheet model. The model is benchmarked here based on its implementation in Julia, while a Fortran version is also provided to allow for compatibility with most existing ice-sheet models. The Julia version provides additional features, including a vast library of time-stepping methods and GPU support.

How to cite: Swierczek-Jereczek, J., Montoya, M., Latychev, K., Robinson, A., Alvarez-Solas, J., and Mitrovica, J.: FastIsostasy - An accelerated regional GIA model for coupled ice-sheet/solid-Earth simulations with laterally-variable solid-Earth structures, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19141, https://doi.org/10.5194/egusphere-egu24-19141, 2024.

EGU24-19220 | Posters on site | CR2.1

The importance of bed roughness on ice sheet flow investigated using a full-Stokes ice flow model 

Darrel Swift, Carlos Martin, and Jeremy Ely

We present detailed modelling of ice flow over a synthetic topography using the full-Stokes ice flow model ELMER-ICE. Our results indicate that landforms/obstacles under 1000 m wavelength contribute importantly to basal drag, implying that predictive ice sheet models that are initialised using static parameterisations of basal drag will greatly underestimate the possible mediating effects of bedrock topography. We conducted numerous simulations using a 10 m resolution, 40 x 22 km model domain with a uniform ice thickness of 1000 m and with sliding restricted to a 20 km-wide central corridor to negate ice leaving the lateral margins. Basal slipperiness (i.e. skin drag) in all simulations used the value obtained during an initial simulation using an entirely flat bed and an imposed surface velocity of 150 m a-1. Subsequent simulations used a synthetic bed with wavelength 5 km, amplitude 200 m, and randomised superimposed smaller-scale roughness. Because ice sheet beds are bumpy at a range of scales - from landforms reflective of km-scale patterns of glacial bedrock erosion down to m-scale obstacles characteristic of bedrock structure – roughness was introduced gradually into the simulations by stepwise reduction of the degree of smoothing applied to the synthetic topography using a band-pass filter. Our results demonstrated that around two-thirds of observed surface velocity was by sliding, and that mean sliding velocity (and thus surface velocity) declined rapidly when introducing roughness with length scale smaller than 1000 m. Further, the observed decline appeared broadly exponential in relation to obstacle size as smaller roughness length scales were added, down to the smallest length scale (10 m) permitted by present model resolution. The results therefore highlight the potential importance of form drag provided by sub-km scale bed roughness in stabilising ice flow, including flow in grounding line locations that are critical to marine ice sheet stability. The results also have implications for predictive ice sheet models, which typically use static fields of basal drag derived from inversions of present-day surface observations, and do not distinguish between form and skin drag. As such, current models could imprecisely predict ice discharge and grounding line behaviour in regions of evolving bedrock or sedimentary landforms, which are ubiquitous to ice sheet beds.

How to cite: Swift, D., Martin, C., and Ely, J.: The importance of bed roughness on ice sheet flow investigated using a full-Stokes ice flow model, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19220, https://doi.org/10.5194/egusphere-egu24-19220, 2024.

EGU24-926 | ECS | Posters on site | CR2.2

Simulating the impact of an AMOC weakening on the Antarctic Ice Sheet using a coupled climate and ice sheet model 

Anna Höse, Moritz Kreuzer, Willem Huiskamp, Torsten Albrecht, Stefan Petri, Ricarda Winkelmann, and Georg Feulner

Many model studies show that a shutdown of the Atlantic meridional overturning circulation (AMOC) causes reduced northward heat transport into the North Atlantic and a warming Southern Ocean in addition to shifts in large-scale atmospheric circulations. How these changing climate conditions could influence the present-day state of the Antarctic Ice Sheet is little studied even though observational data of AMOC strength show a slowdown trend over the last decades. The ocean current as well as the Antarctic Ice Sheet might reach climate tipping points triggering irreversible processes with consequences already on human time-scales. It's unclear whether increasing Southern Ocean temperatures due to a AMOC shutdown could accelerate basal melting rates, the critical parameter which in turn may induce tipping of the West Antarctic Ice Sheet.

Here, a freshwater hosing that forces the shutdown of the AMOC is applied to the North Atlantic in a global climate model with an interactive ice sheet model for Antarctica. This model framework consists of the Parallel Ice Sheet Model (PISM) that is coupled to the CM2Mc global Earth system model via the ice shelf cavity model PICO (Potsdam Ice-shelf Cavity mOdel). PISM is interactively coupled to the ocean module in order to investigate feedbacks at the ice-ocean boundary, while the atmospheric forcing is prescribed. Preliminary results show that an AMOC shutdown results in warming sea surface temperatures in the southern hemisphere along with a small shift in the mid-latitude westerlies due to reduced northward heat transport, which is in line with previous studies. Antarctic marginal temperatures decrease, however, resulting in a reduction of Antarctic mass through increased calving and decreased basal melting.

How to cite: Höse, A., Kreuzer, M., Huiskamp, W., Albrecht, T., Petri, S., Winkelmann, R., and Feulner, G.: Simulating the impact of an AMOC weakening on the Antarctic Ice Sheet using a coupled climate and ice sheet model, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-926, https://doi.org/10.5194/egusphere-egu24-926, 2024.

EGU24-966 | ECS | Orals | CR2.2

Greenland Ice Sheet evolution during the Last Interglacial with an improved surface mass balance modeling approach  

Thi Khanh Dieu Hoang, Aurélien Quiquet, Christophe Dumas, Andreas Born, and Didier M. Roche

The Last Interglacial period (LIG) (130 - 116 kaBP), characterized by higher global mean temperature and sea levels compared to the present-day due to the Earth’s orbit configuration, has been well-studied as a recent example of a climate period warmer than today. There is particular interest in studying the ice sheet-climate interactions in view of our current climate change. However, the extent of the ice sheet and its contribution to the rise of sea levels during the LIG remain debatable as different approaches suggest a wide range of estimations. In order to cover such a long period, some processes are simplified in the modeling approach by using prescribed forcings, simple surface mass balance (SMB) schemes, or equilibrium simulations, which all affect the numerical estimation of ice sheet evolution. 

In our work, to perform transient simulations, we use an Earth system model of intermediate complexity (iLOVECLIM), which has been widely used to study various long-timescale periods. Additionally, we use a physically-based energy and mass balance model with 15 vertical snow layers BESSI (BErgen Snow Simulator) to account for the effect of insolation changes as well as snow-albedo feedback. The climate forcings of the snow model are obtained by running iLOVECLIM transiently from 135 to 115 kaBP, downscaled over the Northern Polar region. Using the SMB computed by BESSI, we then simulate the ice sheet evolution during the LIG with GRISLI - the ice sheet model in the iLOVECLIM framework. 

To assess the benefits of using a physically-based SMB model in the ice sheets simulation, the outputs of GRISLI-BESSI are compared to the current SMB scheme of iLOVECLIM, a simple parametrization called ITM (Insolation Temperature Melt). The Greenland ice sheet volume simulated by the two SMB models reaches the minimum value at 127.5 kaBP, around 500 years after the peak of global mean temperature. The magnitude of ice sheet retreat and its contribution to the sea level in ITM simulations are significantly higher than in BESSI due to an overestimation of the zones of ablation. 

The findings suggest that, compared to a parameterization, we have more confidence in the ice sheet estimation with a physically-based SMB model. Further works with fully interactive ice sheet modeling that takes into account the melt-elevation feedback can improve the simulation of the ice sheet-climate interactions of long-time scales. 

How to cite: Hoang, T. K. D., Quiquet, A., Dumas, C., Born, A., and Roche, D. M.: Greenland Ice Sheet evolution during the Last Interglacial with an improved surface mass balance modeling approach , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-966, https://doi.org/10.5194/egusphere-egu24-966, 2024.

EGU24-1991 | ECS | Orals | CR2.2 | Highlight

When will the Antarctic ice shelves not be viable anymore? 

Clara Burgard, Nicolas C. Jourdain, Christoph Kittel, Cyrille Mosbeux, Justine Caillet, and Pierre Mathiot

The Antarctic contribution to sea-level rise in the coming centuries remains very uncertain, due to the possible triggering of instabilities such as the Marine Ice Sheet Instability (MISI) and Marine Ice Cliff Instability (MICI). These instabilities are mainly linked to the evolution of the floating ice shelves, which usually buttress the ice flow from the ice-sheet to the ocean. However, these are currently thinning. Better understanding the evolution of ice shelves in the next decades to centuries is therefore important and crucial to better anticipate the evolution of sea-level rise.

In this study, we investigate the viability of ice shelves for a number of climate models and scenarios. This is estimated from the emulation of the surface and basal mass balance of MAR and NEMO respectively, and from high-end dynamical ice flows obtained through Elmer/Ice. We then use a Bayesian calibration to give weight to members closer to observations. We find that large uncertainties remain, mainly because of the uncertainty in basal melt, and that viability limits vary largely depending on the ice-shelf location.

How to cite: Burgard, C., Jourdain, N. C., Kittel, C., Mosbeux, C., Caillet, J., and Mathiot, P.: When will the Antarctic ice shelves not be viable anymore?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1991, https://doi.org/10.5194/egusphere-egu24-1991, 2024.

EGU24-3666 | Orals | CR2.2

Deciphering Antarctic Ice Sheet Mass Loss: A Modeling Approach to Distinguish Climate Change from Natural Variability 

Johanna Beckmann, Hélène Seroussi, Lawrence Bird, Justine Caillet, Nicolas Jourdain, Felcity McCormack, and Andrew Mackintosh

The Antarctic Ice Sheet (AIS) is currently undergoing accelerated mass loss, significantly contributing to rising sea levels (SLR). Despite numerous observations, uncertainties persist in understanding the drivers and dynamic responses of AIS mass loss. Climate variability strongly influences AIS dynamics, but limited observational data hinders precise attribution to climate change or natural variability. This study addresses this gap by employing advanced modeling techniques to assess the extent to which observed and future AIS mass loss can be attributed to climate change versus variability. Utilizing a unique "initialization method" with the ISSM model, we approximate the AIS state circa 1850, a period minimally affected by anthropogenic forces. From this baseline, we project AIS development using UKESM1 forcing, comparing scenarios with and without anthropogenic influence. This investigation aims to enhance our understanding of the impact of climate change on the AIS and its implications for future SLR.

How to cite: Beckmann, J., Seroussi, H., Bird, L., Caillet, J., Jourdain, N., McCormack, F., and Mackintosh, A.: Deciphering Antarctic Ice Sheet Mass Loss: A Modeling Approach to Distinguish Climate Change from Natural Variability, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3666, https://doi.org/10.5194/egusphere-egu24-3666, 2024.

EGU24-4093 | ECS | Posters on site | CR2.2

Interactions between ocean circulation and the Northern Hemisphere ice sheets at 40 ky B.P. in an Earth System Model (iLOVECLIM-GRISLI) 

Louise Abot, Claire Waelbroeck, Aurélien Quiquet, Casimir Delavergne, and Nathaelle Bouttes

During the last glacial period, the climate went through rapid fluctuations together with changes in ocean circulation and ice sheets volume accompanied by iceberg discharges. These rapid climate variations, namely Dansgaard-Oeschger events, are still not fully explained. This study’s aim is to contribute to their better understanding, focusing on interactions between ice sheets and ocean circulation. To this end, we use the iLOVECLIM-GRISLI coupled climate-ice sheet model and run two different perturbation experiments related to the ice sheet and ocean components. Starting from a quasi equilibrium corresponding to 40 ky B.P. greenhouse gas concentration, incoming solar radiation and ice sheet volume, the first experiment consists in imposing either constant or amplified sub-shelf melt rates in comparison with the control simulation. In the second experiment, we focus on the interface between the ice sheets and the bedrock. The basal friction coefficient values are imposed following the same procedure. These two experiments are similar to freshwater hosing experiments but here the water comes directly from the interactively computed ice sheets change. For each experiment, the perturbation is imposed for 500 years before returning to the unperturbed conditions for one thousand years and its impacts on the climate system are investigated. Our results highlight feedbacks that may help to explain the abrupt nature of the climate transitions observed during the last glacial period. 

How to cite: Abot, L., Waelbroeck, C., Quiquet, A., Delavergne, C., and Bouttes, N.: Interactions between ocean circulation and the Northern Hemisphere ice sheets at 40 ky B.P. in an Earth System Model (iLOVECLIM-GRISLI), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4093, https://doi.org/10.5194/egusphere-egu24-4093, 2024.

EGU24-4802 | Orals | CR2.2

A synchronously coupled global model iOM4: a new modeling tool for simulations of the ocean-cryosphere interactions  

Olga Sergienko, Matthew Harrison, Alexander Huth, and Nicole Schlegel

How to cite: Sergienko, O., Harrison, M., Huth, A., and Schlegel, N.: A synchronously coupled global model iOM4: a new modeling tool for simulations of the ocean-cryosphere interactions , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4802, https://doi.org/10.5194/egusphere-egu24-4802, 2024.

EGU24-5104 | ECS | Posters on site | CR2.2

Simulating Antarctic Ice Sheet evolution through the mid-Pleistocene transition 

Christian Wirths, Antoine Hermant, Christian Stepanek, Johannes Sutter, and Thomas Stocker

Unravelling the main drivers of the mid-Pleistocene transition (MPT; around 1.2–0.8 million years ago) remains a significant challenge in paleoclimate research. Noteworthy changes that occurred in the climate system during that time include a pronounced shift from 41-kyr to 100-kyr periodicity of glacial cycles and the emergence of much larger ice sheets. While a number of studies have focused on the interplay between the climate system and northern hemispheric ice sheets during the MPT, the role of Antarctica in driving and responding to climate change at that time remains largely unknown. This is particularly relevant as, consequently, the response of Antarctica’s vast ice sheets to a major transition in Quaternary climate, and their potential role in shaping the transition, remain uncertain. 

Here, we use the Parallel Ice Sheet Model (PISM) to simulate the transient evolution of the Antarctic Ice Sheet through the MPT. Computation of the evolution of ice sheets in PISM is enabled by means of a climate index approach that is based on snapshots of climatic conditions at key periods. The climate index approach interpolates between individual climate snapshots based on various paleo-proxy records. Further, we test Antarctica's response to different pre-MPT GCM snapshots of different CO2, orbital, and land-sea mask configurations. Climate snapshots are derived from the Community Earth System Models (COSMOS), a general circulation model that simulates atmosphere, ocean, sea ice and land vegetation in dependence of reconstructions of paleogeography, orbital configuration, and greenhouse gas concentrations.  

Our study aims to better understand the evolution of the Antarctic Ice Sheets during the MPT and to constrain potential dynamical transitions in the climate-cryosphere system. Furthermore, we seek to clarify the influence of different pre-MPT ice sheet configurations on simulated characteristics of this transition.  

The findings from this study will contribute to an improved understanding of cryospheric changes that occurred during the Quaternary. Furthermore, we aim to provide insights into potential future Antarctic trajectories under anthropogenic climate change. 

How to cite: Wirths, C., Hermant, A., Stepanek, C., Sutter, J., and Stocker, T.: Simulating Antarctic Ice Sheet evolution through the mid-Pleistocene transition, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5104, https://doi.org/10.5194/egusphere-egu24-5104, 2024.

EGU24-5525 | Orals | CR2.2

Modeling the Antarctic Surface Mass Balance with a coarse temporal resolution 

Enrico Maiero, Florence Colleoni, Cécile Agosta, Carlo Barbante, and Barbara Stenni

Sublimation is the most important ablation term in the Antarctic Surface Mass Balance (SMB) (Agosta et al., 2019), while it is currently negligible for both Greenland and mountain glaciers (prevailing surface melt). Since simple parameterized SMB models are usually developed for Greenland and Alpine glaciers, they mostly misrepresent sublimation. To face this problem, we developed EBAL, a new parameterized Energy SMB model for Antarctica based on SEMIC (Krapp et al., 2017), which is an Energy SMB model developed for Greenland whose main innovations are a sinusoidal parameterization for the diurnal cycle to assess melt and refreezing and an albedo dependence on snow depth. EBAL was calibrated with both MAR (Kittel et al., 2022) and RACMO (Wessem et al., 2018) outputs for the period 1979-2000 and for the period 2075-2099 under the SSP5-8.5. EBAL can reproduce the statistical properties of MAR and RACMO sublimation time series and spatial distribution even if it uses a coarse time step (1 day). However, our final aim is to use EBAL for paleoclimate simulations, for which the temporal resolution of the inputs is even coarser, as often only monthly data is available. Thus, we have tested the idea of superimposing the present day-to-day variability on the MAR monthly atmospheric forcing of SSP5-8.5. Simulated SMB with EBAL forced with MAR original daily SSP5-8.5 inputs leads to a 210 Gt/yr sublimation, and to a 1425 Gt/yr melt. When forcing EBAL with monthly means only (linearly interpolated), we obtain a 113 Gt/yr sublimation and a 620 Gt/yr melt. When adding present-day variability to linearly interpolated monthly inputs, EBAL computes a 175 Gt/yr sublimation and a 1386 Gt/yr melt. Those latter numbers are very similar to those obtained when forcing with daily inputs. We propose to use this method to test EBAL for paleoclimate applications.

References

  • Agosta, C. et al., (2019). “Estimation of the Antarctic surface mass balance using the regional climate model MAR (1979–2015) and identification of dominant processes”. The Cryosphere. 13,  pp. 281-296. 10.5194/tc-13-281-2019. 
  • Kittel, C. et al., (2022). “Clouds drive differences in future surface melt over the Antarctic ice shelves”. The Cryosphere. 16, pp. 2655-2669. 10.5194/tc-16-2655-2022.
  • Krapp, M et al., (July 2017). “SEMIC: an efficient surface energy and mass balance model applied to the Greenland ice sheet”. The Cryosphere 11.4, pp. 1519–1535. 10.5194/tc-11-1519-2017
  • Wessem, J. M. et al., (Apr. 2018). “Modelling the climate and surface mass balance of polar ice sheets using RACMO2 – Part 2: Antarctica (1979–2016)”. The Cryosphere 12, pp. 1479–1498. 10.5194/tc-12-1479-2018

How to cite: Maiero, E., Colleoni, F., Agosta, C., Barbante, C., and Stenni, B.: Modeling the Antarctic Surface Mass Balance with a coarse temporal resolution, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5525, https://doi.org/10.5194/egusphere-egu24-5525, 2024.

EGU24-5584 | Orals | CR2.2

Future Greenland melt in coupled ice sheet-climate CESM simulations: feedbacks, thresholds, reversibility 

Miren Vizcaino, Thirza Feenstra, Michele Petrini, Raymond Sellevold, Georgiou Sotiria, Katherine Thayer-Calder, William Lipscomb, and Julia Rudlang

Estimates of future Greenland ice sheet (GrIS) melt are mostly based on regional climate modelling for a fixed GrIS topography or on ice sheet modelling with forcing from climate models. This prevents the modelling of climate and GrIS feedbacks and other types of interaction. Here we examine a set of multi-century simulations with the Community Earth System Model featuring an interactive GrIS to explore future relationship between global climate change and ice sheet change. To this end, we compare a set of coupled CESM-CISM 1% CO2 increase simulations until stabilization at two, two and a half, three and four times pre-industrial CO2 levels to examine the sensitivity of the GrIS to emission mitigation. Here we find a large role of ocean circulation weakening and associated regional climate changes on GrIS melt for moderate emission scenarios and large melt differences between the three times and four times CO2 stabilization scenarios. In addition, we examine the role of feedbacks on ice sheet evolution by comparing a 1% to 4xCO2 coupled simulation with a simulation where the GrIS topography and meltwater fluxes to the ocean are prescribed as pre-industrial. Finally, we explore the effects on GrIS melt rates of a fast 5% CO2 reduction from four times to pre-industrial levels, with a focus on restoration of high latitude climate, GrIS albedo, surface energy fluxes and refreezing capacity.  

How to cite: Vizcaino, M., Feenstra, T., Petrini, M., Sellevold, R., Sotiria, G., Thayer-Calder, K., Lipscomb, W., and Rudlang, J.: Future Greenland melt in coupled ice sheet-climate CESM simulations: feedbacks, thresholds, reversibility, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5584, https://doi.org/10.5194/egusphere-egu24-5584, 2024.

EGU24-5698 | ECS | Posters on site | CR2.2

Geoengineering's role in reducing future Antarctic mass loss is unclear 

Mira Adhikari, Daniel Martin, Tamsin Edwards, Antony Payne, James O'Neill, and Peter Irvine

Using the BISICLES ice sheet model, we compare the Antarctic ice sheet’s response over the 22nd century in a scenario where idealised large scale, instantaneous geoengineering is implemented in 2100 or 2050 (geoengineering), with scenarios where the climate forcing is held constant in the same year (stabilisation). Results are highly climate model dependent, with larger differences between models than between geoengineering and stabilisation scenarios, but show that geoengineering cannot prevent significant losses from Antarctica over the next two centuries. If implemented in 2050, sea level contributions under geoengineering are lower than under stabilisation scenarios. If implemented in 2100, under high emissions, geoengineering produces higher sea level than stabilisation scenarios, as increased surface mass balance in the warmer stabilisation scenarios offsets some of the dynamic losses. Despite this, dynamic losses appear to accelerate and may eventually negate this initial offset, indicating that beyond 2200, geoengineering could eventually be more effective.

How to cite: Adhikari, M., Martin, D., Edwards, T., Payne, A., O'Neill, J., and Irvine, P.: Geoengineering's role in reducing future Antarctic mass loss is unclear, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5698, https://doi.org/10.5194/egusphere-egu24-5698, 2024.

EGU24-6140 | ECS | Orals | CR2.2

Long term ice-sheet albedo feedback constrained by most recent deglaciation 

Alice Booth, Philip Goodwin, and Bb Cael

Slow climate feedbacks that operate on timescales of more than a century are currently underrepresented in model assessments of climate sensitivity, and this continues to hinder efforts to accurately predict future climate change beyond the end of the 21st Century. As such, the magnitude of multi-centennial and millennial climate feedbacks are still poorly constrained. We utilise recent reconstructions of Earth’s Energy Imbalance (EEI) to estimate both the total climate feedback parameter and the ice-sheet albedo feedback since the Last Glacial Maximum. This new proxy-based record of EEI facilitates the first opportunity to simultaneously calculate both the magnitude and timescale of Earth’s climate feedback over the most recent deglaciation using a purely proxy data-driven approach, and without the need for simulated reconstructions. We find the ice-sheet albedo feedback to have been an amplifying feedback reaching an equilibrium magnitude of 0.55 Wm-2K-1, with a 66% confidence interval of 0.45 Wm-2K-1 to 0.63 Wm-2K-1. The timescale for the ice-sheet albedo feedback to reach equilibrium is estimated as 3.61Kyrs, with a 66% confidence interval of 1.88Kyrs to 5.48Kyrs. These results provide new evidence for the timescale and magnitude of the amplifying ice-sheet albedo feedback that will continue to drive anthropogenic warming for millennia to come, further increasing the urgency for an effective climate change mitigation strategy to avoid serious long-term consequences for our planet and its ecosystems.

How to cite: Booth, A., Goodwin, P., and Cael, B.: Long term ice-sheet albedo feedback constrained by most recent deglaciation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6140, https://doi.org/10.5194/egusphere-egu24-6140, 2024.

EGU24-7415 | ECS | Orals | CR2.2 | Highlight

Stability regimes and safe overshoots in West and East Antarctica 

Ann Kristin Klose and Ricarda Winkelmann

Earth's climate will likely exceed a warming of 1.5°C in the coming decades. Maintaining such warming levels for a longer period of time may pose a considerable risk of crossing critical thresholds in Antarctica and, thereby, triggering self-sustained, potentially irreversible ice loss, even if the forcing is reduced in a temperature overshoot. Due to the complex interplay of several amplifying and dampening feedbacks at play in Antarctica, the duration and amplitude of such warming overshoots as well as their eventual 'landing' climate will determine the long-term evolution of the ice sheet.

Using the Parallel Ice Sheet Model, we systematically test for the reversibility of committed large-scale ice-sheet changes triggered by warming projected over the next centuries, and thereby explore (1) the stability regimes of the Antarctic Ice Sheet and (2) the potential for safe overshoots of critical thresholds in Antarctica.

We demonstrate crucial features of the Antarctic Ice Sheet's stability landscape for its long-term trajectory in response to future human actions: Given ice-sheet inertia, an early reversal of climate may allow for avoiding self-sustained ice loss that would otherwise be irreversible (for the same reduction in warming) due to multistability of the ice sheet at the basin- and continental scale. While we show that such safe overshoots of critical thresholds in Antarctica may be possible, it is also clear that limiting global warming is the only viable option to evade the risk of widespread ice loss in the long term.

How to cite: Klose, A. K. and Winkelmann, R.: Stability regimes and safe overshoots in West and East Antarctica, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7415, https://doi.org/10.5194/egusphere-egu24-7415, 2024.

EGU24-8333 | ECS | Orals | CR2.2

Coupled ensemble simulations of the Northern Hemisphere ice sheets at last two glacial maxima  

Violet Patterson, Lauren Gregoire, Ruza Ivanovic, Niall Gandy, Stephen Cornford, and Sam Sherriff-Tadano

Coupled climate-ice sheet models can capture important interactions between the ice sheets and the climate that can help us better understand an ice sheet's response to changes in forcings. In this respect, they are a useful tool for simulating future ice sheet and sea level changes as a result of climate change. However, such models have large uncertainties related to the choice of climate and ice sheet parameters used. The same processes that operate today, also occurred in glacial times, and previous work has shown that simulating the North American ice sheet at the Last Glacial Maximum (LGM; ~21 ka BP) provides a strong benchmark for testing coupled climate-ice sheet models and recalibrating uncertain parameters that control surface mass balance and ice flow (Gandy et al., 2023).

Here, we build on this work by performing the first coupled FAMOUS-BISICLES simulations of the last two glacial maxima, including all Northern Hemisphere ice sheets interactively. The ice sheet component of this model is capable of efficiently simulating marine ice sheets, such as the Eurasian ice sheet, despite the high computational cost of higher order physics. We simulate and compare both the LGM and the Penultimate Glacial Maximum (PGM; ~140 ka BP), since both periods displayed major differences in the distribution of ice between Eurasia and North America. Uncertainty is explored by running ensembles of 120 simulations, randomly varying the uncertain parameters controlling ice sheet dynamics and climate through Latin Hypercube Sampling. We also work on improving the representation of ice streams in the model through performing internal ice temperature spin ups and sensitivity tests varying till water drainage properties. The ensemble members are evaluated against empirical data on ice sheet extent and ice stream location to find combinations of parameters that produce reasonable simulations of the North American and Eurasian ice sheets for both periods. We determine the impact of the uncertainty in these parameters on the result and whether both ice sheets show similar sensitivities to the model parameters. These simulations will provide a starting point for analysing some of the interactions between the climate and the ice sheets during glacial periods and how they may have led to different ice sheet evolutions.

How to cite: Patterson, V., Gregoire, L., Ivanovic, R., Gandy, N., Cornford, S., and Sherriff-Tadano, S.: Coupled ensemble simulations of the Northern Hemisphere ice sheets at last two glacial maxima , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8333, https://doi.org/10.5194/egusphere-egu24-8333, 2024.

The dynamics of the ice sheets on glacial-interglacial time scales are highly controlled by interactions with the solid Earth, i.e., glacial isostatic adjustment (GIA). Particularly at marine ice sheets, competing feedback mechanisms govern the migration of the ice sheet’s grounding line and hence the ice sheet stability.

In this study, we run coupled ice sheet–solid Earth simulations over the last two glacial cycles. For the ice sheet dynamics we apply the Parallel Ice Sheet Model PISM and for the load response of the solid Earth we use the three-dimensional viscoelastic Earth in view of sea-level and vertical displacement changes we apply the Viscoelastic Lithosphere and Mantle Model VILMA.

With our coupling setup we evaluate the relevance of feedback mechanisms for the glaciation anddeglaciation phases in Antarctica considering different 3D Earth structures resulting in a range of load-response time scales. For rather long time scales, in a glacial climate associated with far-field sea level low stand, we find grounding line advance up to the edge of the continental shelf mainly in West Antarctica, dominated by a self-amplifying GIA feedback, which we call the ‘forebulge feedback’. For the much shorter time scale of deglaciation, dominated by the Marine Ice Sheet Instability, our simulations suggest that the stabilizing GIA feedback can significantly slow-down grounding line retreat in the Ross sector, which is dominated by a very weak Earth structure (i.e. low mantle viscosity and thin lithosphere).

The described coupled framework, PISM-VILMA, allows for defining restart states to which to run multiple sensitivity simulations. It can be easily implemented in Earth System Models (ESMs) and provides the tools to gain a better understanding of ice sheet stability on glacial time scales as wellas in a warmer future climate.

How to cite: Albrecht, T., Bagge, M., and Klemann, V.: Feedback mechanisms controlling Antarctic glacial cycle dynamics simulated with a coupled ice sheet–solid Earth model, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9032, https://doi.org/10.5194/egusphere-egu24-9032, 2024.

EGU24-10162 | ECS | Orals | CR2.2

A new climate and surface mass balance product for the Antarctic and Greenland ice sheet using RACMO2.4.1 

Christiaan van Dalum, Willem Jan van de Berg, Srinidhi Nagarada Gadde, and Michiel van den Broeke

Recent progress in parameterizations of surface and atmospheric processes have led to the development of a major update of the polar version of the Regional Atmospheric Climate Model (RACMO2.4.1). Here, we present a new high-resolution climate and surface mass balance product by applying RACMO2.4.1 to the Antarctic and Greenland ice sheet for the historical period (starting in 1960 and 1945, respectively). In addition, RACMO output is now available for the first time on a pan-Arctic domain, starting in 1980. We assess these products by comparing model output of the surface mass balance and its components and the near-surface climate with in-situ and remote sensing observations, and study differences with the previously operational RACMO iteration, RACMO2.3p2. 

Among other changes, RACMO2.4.1 includes new and updated parameterizations related to surface and atmospheric processes. Most major updates are part of the physics package of cycle 47r1 of the Integrated Forecast System (IFS) of the European Center for Medium-Range Weather Forecasts (ECMWF), which is embedded in RACMO2.4.1. This includes updates to the cloud, radiation, convection, turbulence, aerosol and lake scheme. Other major changes are directly related to the cryosphere, such as the introduction of a new spectral albedo and radiative transfer scheme for glaciated snow, fixes to the snow drift scheme, a new multilayer snow scheme for seasonal snow and an updated ice mask. These updates lead to changes in the near-surface climate. For example, the horizontal transport of snow that is present in the atmosphere leads to a redistribution of snowfall. Furthermore, the spatial resolution for the Antarctic domain is increased to 11 km, which is also used for the pan-Arctic domain, while 5.5 km is used for Greenland. Here, we also discuss the impact that aforementioned changes have on the climate of the polar regions and the surface mass balance and its components of the ice sheets.

How to cite: van Dalum, C., van de Berg, W. J., Nagarada Gadde, S., and van den Broeke, M.: A new climate and surface mass balance product for the Antarctic and Greenland ice sheet using RACMO2.4.1, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10162, https://doi.org/10.5194/egusphere-egu24-10162, 2024.

EGU24-10256 | ECS | Orals | CR2.2

Reconstructing the Greenland ice Sheet during the last two deglaciations 

Majbritt Kristin Eckert, Mikkel Lauritzen, Nicholas Rathmann, Anne Solgaard, and Christine Hvidberg

The Parallel Ice Sheet Model (PISM) is used to build up a glacial Greenland ice sheet, simulate the evolution of the Greenland ice sheet through glacial terminations I and II and investigate the evolution during previous warmer climates, the Eemian and the Holocene thermal maximum. During the Holocene, surface elevation changes derived from ice cores suggest a large thinning in the North, suggesting that the Greenland ice sheet was connected to the North American ice sheet in Canada during the last glacial. By including Canada in the modelling domain this thinning in the early Holocene as the connecting ice bridge broke up will be investigated. 

How to cite: Eckert, M. K., Lauritzen, M., Rathmann, N., Solgaard, A., and Hvidberg, C.: Reconstructing the Greenland ice Sheet during the last two deglaciations, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10256, https://doi.org/10.5194/egusphere-egu24-10256, 2024.

EGU24-12773 | ECS | Orals | CR2.2

Improved treatment of snow over ice sheets in the NASA GISS climate model: towards ice sheet–climate coupling 

Damien Ringeisen, Patrick Alexander, Lettie Roach, Ken Mankoff, and Igor Aleinov

Representing the interactions between ice sheets and climate is essential for more accurate prediction of climate change and sea level rise. Ice sheets interact with the overlying atmosphere via the accumulation of snow and its compaction into firn, then ice, as well as the melting of surface snow and ice and the creation of runoff water. Getting an adequate representation of heat transfer, compaction, and melting processes is essential for an accurate representation of snow on land ice in global climate models. We are implementing an improved snow model on top of land ice as part of an effort to couple the NASA GISS climate model with the PISM ice sheet model. The new snow model includes additional layers and processes that are not currently incorporated (e.g., liquid water retention, percolation and refreezing, and snow densification), and mass and energy transfer methods that are consistent with both static ice sheets (with implicit iceberg fluxes) and interactive ice sheets (with explicit dynamics). We are tuning the densification scheme of this snow model with temperature and density data from common FirnCover and SumUp observations at locations in the accumulation zone of Greenland, and we compare the resulting density profiles to other SumUp density profiles in Greenland and Antarctica. We will assess the impact of this new snow model in climate model simulations with a static ice sheet compared with the previous (simpler) 2-layer snow model. Finally, we aim to use the non-coupled simulations as a baseline to assess the impact of dynamic coupling with an interactive ice sheet model.

How to cite: Ringeisen, D., Alexander, P., Roach, L., Mankoff, K., and Aleinov, I.: Improved treatment of snow over ice sheets in the NASA GISS climate model: towards ice sheet–climate coupling, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12773, https://doi.org/10.5194/egusphere-egu24-12773, 2024.

EGU24-13618 | ECS | Orals | CR2.2

Reconstructing the coupled Greenland Ice Sheet–climate evolution during the Last Interglacial warm period 

Matt Osman, Jessica Tierney, and Marcus Lofverstrom

During the Last Interglacial (LIG), approximately 130-118 thousand years ago (ka), the Arctic experienced relative warmth and global sea levels considerably higher than modern.  While this interval is thus considered key for understanding long-term ice–climate feedbacks under warm-state climate conditions, large uncertainties remain surrounding i. the magnitude and spatial expression of LIG global temperature change, ii. the relative contributions of the Antarctic vs. Greenlandic Ice Sheets (GrIS) to LIG sea level rise, and iii. the sensitivity of the GrIS to centennial- to millennial-scale ocean-atmospheric forcing.  Here, we present, to our knowledge, a first attempt at reconstructing the coupled GrIS–climate evolution during the LIG using an internally consistent offline “paleoclimate data assimilation” approach.  Our methodology combines a newly compiled database of nearly 400 chronologically consistent marine geochemical and ice sheet-derived climate-proxy records (spanning 250 sites globally) with recently developed, state-of-the-art transient simulations of the LIG using the coupled Community Earth System Model v2 featuring an interactive Community Ice Sheet Model v2 (CESM2-CISM2).  Our preliminary assimilations suggest LIG peak global mean surface warming of +0.1-0.5˚C (±2 range) above the pre-industrial state, arising from enhanced and widespread (>2-5˚C) high Arctic warming.  Leveraging our CESM2-coupled CISM2 results, we further identify a max GrIS contribution of 2.0 (±0.6) meters of sea level rise equivalent at around 125 ka, nearly ~two millennia after peak LIG climate forcing.  These initial results provide a new proxy-model integration framework for reconciling past GrIS contributions to global sea level rise and benchmark the potential long-term sensitivity of the GrIS to ongoing Arctic warming.

How to cite: Osman, M., Tierney, J., and Lofverstrom, M.: Reconstructing the coupled Greenland Ice Sheet–climate evolution during the Last Interglacial warm period, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13618, https://doi.org/10.5194/egusphere-egu24-13618, 2024.

Mass loss from ice sheets under the ongoing anthropogenic warming episode is a major source for sea-level rise. Due to the slow responses of ice sheets to changes in atmospheric and oceanic boundary conditions, ice sheets are projected to undergo further retreat as the climate reaches a new equilibrium, producing a long-term commitment to future sea-level rise that is fulfilled on multi-millennial scale. Future projections of ice sheets beyond 2100 have routinely employed end-of-the-century atmosphere-ocean conditions from climate model output under specified emission scenarios. This approach, however, does not account for long-term responses of the climate system to external forcings. Here we analyze the long-term atmospheric and oceanic responses to a variety of emission scenarios in several climate models and show that polar climates may see substantial changes after the atmospheric CO2 level stabilizes. With a 3-D ice sheet model, we demonstrate that the long-term climate responses are crucial for evaluating ice sheets' commitment to future sea-level rise.

How to cite: Li, D.: Effects of long-term climate responses on ice sheets' commitment to future sea-level rise, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15160, https://doi.org/10.5194/egusphere-egu24-15160, 2024.

EGU24-15323 | ECS | Posters on site | CR2.2

Investigating the evolution and stability of the Greenland ice sheet using remapped surface mass balance forcing 

Charlotte Rahlves, Heiko Goelzer, and Michele Petrini

Surface mass balance (SMB) forcing for projections of the future evolution of the Greenland ice sheet with stand-alone modeling approaches is commonly produced on a fixed ice sheet geometry. As changes of ice sheet geometry become significant over longer time scales, conducting projections for the long-term evolution and stability of the Greenland ice sheet usually requires a coupled climate-ice sheet modeling setup. In this study we use an SMB remapping procedure to capture the first order feedbacks of a coupled climate-ice sheet system with a stand-alone modeling approach. Following a remapping procedure originally developed to apply SMB forcing to a range of initial ice sheet geometries (Goelzer et al., 2020), we produce SMB forcing that adapts to the changing ice sheet geometry as it evolves over time. SMB forcing from a regional climate model is translated from a function of absolute location to a function of surface elevation depending on 25 regional drainage basins, thereby reducing biases that would arise by applying the SMB derived from a fixed ice sheet geometry. We use forcing for different emission scenarios from the CMIP6 archive to compare results from the remapping approach with results from commonly used methods of parameterizing the SMB-height feedback, as well as with results from a semi-coupled climate-ice sheet simulation.

How to cite: Rahlves, C., Goelzer, H., and Petrini, M.: Investigating the evolution and stability of the Greenland ice sheet using remapped surface mass balance forcing, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15323, https://doi.org/10.5194/egusphere-egu24-15323, 2024.

EGU24-15401 | Posters on site | CR2.2

Development and implementation of a refined climate index forcing for paleo ice-sheet modeling applications  

Antoine Hermant, Christian Wirths, and Johannes Sutter

The contribution of the Antarctic Ice Sheet (AIS) to sea-level rise under future scenarios remains uncertain. Simulations of the AIS covering past-climate periods provide valuable insights into its response to a range of climatological background states and transitions, as well as its past contributions to sea-level change. However, data to constrain the modelled ice-flow and the paleo-climate forcing is often lacking, leading to considerable uncertainties with respect to paleo ice sheet evolution. Here, we implement and test a framework to provide paleo-climate scenarios for continental scale ice sheet models. Our approach involves the use of an improved climate index based on ice-core records to translate paleo forcing snapshots from Earth System Models and regional models into transient paleo-climate scenarios, specifically to simulate the dynamics of the AIS throughout the last glaciation and deglaciation. Additionally, we refine paleo-accumulation scenarios by introducing a regionally-specific and temperature-dependant scaling of accumulation. Our study aims to enhance our understanding of AIS dynamics on glacial-interglacial time-scales and provide improved paleo-informed initializations for AIS projections. 

How to cite: Hermant, A., Wirths, C., and Sutter, J.: Development and implementation of a refined climate index forcing for paleo ice-sheet modeling applications , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15401, https://doi.org/10.5194/egusphere-egu24-15401, 2024.

EGU24-15987 | ECS | Posters on site | CR2.2

Assessing Antarctic Ice Sheet dynamics under temporary overshoot and long-term temperature stabilization scenarios   

Emma Spezia, Fabrice Kenneth Michel Lacroix, Vjeran Visnjevic, Christian Wirths, Antoine Hermant, Thomas Frölicher, and Johannes Sutter

Current projections of Antarctic Ice Sheet dynamics during the next centuries are subject to large uncertainties both reflecting the ice sheet model setup as well as the climate pathways taken into consideration. Assessing both we present model projections of the Antarctic Ice Sheet’s response to a range of temporary temperature overshoot and stabilization scenarios until the year 2500 accounting for various ice sheet sensitivities. We employ the ice sheet model PISM at continental scale forced by Earth system model data tailored to specific global temperature scenarios via an adaptive greenhouse gas emissions approach. These scenarios reflect both emission pathways which result in a transient temperature overshoot during the 21st and 22nd century as well as stabilization of global temperatures without overshoot. We contrast these simulations with the well- known CMIP6 scenarios to illustrate the diverse potential pathways of Antarctic Ice Sheet dynamics under uncertain future climate trajectories. 

How to cite: Spezia, E., Lacroix, F. K. M., Visnjevic, V., Wirths, C., Hermant, A., Frölicher, T., and Sutter, J.: Assessing Antarctic Ice Sheet dynamics under temporary overshoot and long-term temperature stabilization scenarios  , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15987, https://doi.org/10.5194/egusphere-egu24-15987, 2024.

EGU24-16455 | ECS | Posters on site | CR2.2

Ice-dammed lake-glacier interactions: Modelling the impact on Fennoscandian Ice Sheet retreat 

Ankit Pramanik, Sarah Greenwood, Carl Carl Regnéll, and Richard Gyllencreutz

Ice-dammed lakes expedite glacier retreat, leading to the expansion of lakes and an elevated risk of Glacial Lake Outburst Floods (GLOFs), and delay the freshwater inflow to the ocean. The escalating number of ice-dammed lakes in Greenland, High Mountain Asia, and Patagonia, driven by the swift retreat of glaciers amid rapid warming, poses a significant threat of natural disasters. In the geological record, evidence indicates the rapid retreat of the Fennoscandian ice sheet, marked by the formation, expansion, and drainage of large (10s-1000s km2 surface area and up to 100s m deep) ice-dammed proglacial lakes along the entire length of the late-deglacial ice margin. The deglaciation and ice-lake interactions of the Fennoscandian Ice Sheet (FIS) provide a valuable analogue for projecting the future retreat of the Greenland ice sheet, where a manifold increase in the number and volume of ice-dammed lakes is anticipated.

Despite extensive research on marine-terminating glaciers, the dynamics of lacustrine-terminating glaciers remain poorly understood. While there are some notable differences in thermo-mechanical processes between marine and lacustrine glaciers, a significant contrast lies in the fact that the calving of lake-terminating glaciers is governed by the stress balance induced by rapidly fluctuating lake levels and thermodynamics inherent of lakes. Our study delves into accessing the impact of critical factors, such as lake size and bathymetry, on the retreat of the Fennoscandian Ice Sheet, using the Ice-sheet and Sea-level System Model (ISSM). Furthermore, we aim to evaluate the influence of calving, subaqueous melt, and rapidly fluctuating lake levels on the FIS retreat. The model's accuracy will be ensured through calibration and validation against geologically reconstructed ice sheet boundaries and lake levels.

How to cite: Pramanik, A., Greenwood, S., Carl Regnéll, C., and Gyllencreutz, R.: Ice-dammed lake-glacier interactions: Modelling the impact on Fennoscandian Ice Sheet retreat, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16455, https://doi.org/10.5194/egusphere-egu24-16455, 2024.

EGU24-16702 | ECS | Posters on site | CR2.2

Isochronally constrained ice flow evolution of Dronning Maud Land, Antarctica during the Last Glacial Period 

Vjeran Visnjevic, Julien Bodart, Antoine Hermant, Christian Wirths, Emma Spezia, and Johannes Sutter

To improve the robustness of future simulations of ice flow across the Antarctic continent as well as the projections of sea-level rise accompanying it, it is necessary to improve our understanding of the past evolution of ice dynamics. This is specially the case considering the lack of constraints on climate and basal conditions on the regional scale. To address this, we use high resolution regional ice flow modeling combined with radar obtained repositories of internal reflection horizons and ice core data, to constrain the ice flow evolution of both grounded and floating ice across the Dronning Maud Land during the Last Glacial Period. Combining the modeling results obtained using the ice sheet model PISM with radar and ice core data will enable us to improve our knowledge of conditions at the ice base, but also provide an opportunity to test and compare a range of potential climate reconstructions. The presented workflow will further be expanded to other basins in Antarctica as well as to the interglacial-glacial transition, and the results will be used to improve future simulations of ice flow across Antarctica.

How to cite: Visnjevic, V., Bodart, J., Hermant, A., Wirths, C., Spezia, E., and Sutter, J.: Isochronally constrained ice flow evolution of Dronning Maud Land, Antarctica during the Last Glacial Period, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16702, https://doi.org/10.5194/egusphere-egu24-16702, 2024.

EGU24-17391 | ECS | Orals | CR2.2

Critical thresholds of the Greenland Ice Sheet from the LGM to the future 

Lucía Gutiérrez-González, Jorge Alvarez-Solas, Marisa Montoya, Ilaria Tabone, and Alexander Robinson

In recent decades the Greenland Ice Sheet (GrIS) has undergone accelerating ice-mass loss. The GrIS is thought to be a tipping element of the Earth system due to the existence of positive feedbacks with the climate. Previous work has shown threshold behavior in the system, and its stability has been studied in a range of temperatures of the present to a global warming of +4K. However, there is still no consensus on the values of its critical thresholds for the future. Furthermore,  its stability at  lower temperatures hasn’t been studied yet. Here we use the ice-sheet model Yelmo coupled with the regional climate model REMBO and a parametrization of the ice-ocean interactions to obtain the bifurcation diagram of the GrIS from temperatures representative of the LGM (-12K) to a warmer scenario (+4K). The preindustrial simulated equilibrium volume is larger than the observations, a feature common to many other ice-sheet models. This could indicate model biases, but also that the GrIS could currently not be fully in equilibrium with the preindustrial forcing, with implications for future projections. To investigate this issue, we simulated the transient evolution of the GrIS since the LGM to the present day in the context of the bifurcation diagram, with equilibrium states acting as attractors. 

How to cite: Gutiérrez-González, L., Alvarez-Solas, J., Montoya, M., Tabone, I., and Robinson, A.: Critical thresholds of the Greenland Ice Sheet from the LGM to the future, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17391, https://doi.org/10.5194/egusphere-egu24-17391, 2024.

EGU24-18501 | Posters on site | CR2.2

Protocol for a Last Interglacial Antarctic ice-sheet model inter-comparison 

Lauren Gregoire, Maxence Menthon, Edward Gasson, and Louise Sime

During the last interglacial, geological records show evidence that the sea level peaked between 6 and 9 m above pre-industrial sea level, with a major contribution from the Antarctic ice sheet. However, ice-sheet models give a very large range of values due to a lack of understanding of the mechanisms leading to the Antarctic ice sheet retreat during the Last Interglacial

Here, we propose a protocol to apply systematically to multiple ice-sheet models to better understand the climate and ice-sheet model uncertainties as well as mechanisms leading to a smaller Antarctic ice sheet. We present the climate forcing choices and methodology, ice-sheet model requirements and the group of simulations suggested. The protocol includes transient penultimate deglaciation and last interglacial equilibrium simulations to make it accessible to all types of ice-sheet models. The protocol includes also sensitivity experiments such as hosing.

Inputs from the community are welcome to improve the protocol under development and make it relevant to all ice-sheet modelling groups interested in participating!

How to cite: Gregoire, L., Menthon, M., Gasson, E., and Sime, L.: Protocol for a Last Interglacial Antarctic ice-sheet model inter-comparison, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18501, https://doi.org/10.5194/egusphere-egu24-18501, 2024.

EGU24-19165 | Posters on site | CR2.2

Oceanic gateways in Antarctica - Impact of relative sea-level change on sub-shelf melt 

Moritz Kreuzer, Torsten Albrecht, Lena Nicola, Ronja Reese, and Ricarda Winkelmann

Relative sea level (local water depth) on the Antarctic continental shelf is changing by the complex interplay of processes associated with Glacial Isostatic Adjustment (GIA). This involves near-field visco-elastic bedrock displacement and gravitational effects in response to changes in Antarctic ice load, but also far-field interhemispheric effects on the sea-level pattern. On glacial time scales, these changes can be in the order of several hundred meters, potentially affecting the access of ocean water masses at different depths to Antarctic grounding lines and ice sheet margins. Due to strong vertical gradients in ocean temperature and salinity at the continental shelf margin, basal melt rates of ice shelves could change significantly just by variations in relative sea level alone.
Based on a coupled ice sheet – GIA model setup and the analysis of bathymetric features such as troughs and sills that regulate the access of open ocean water masses onto the continental shelf (oceanic gateways), we conduct sensitivity experiments to derive maximum estimates of Antarctic basal melt
rate changes, solely driven by relative sea-level variations.
Under Last Glacial Maximum sea-level conditions, this effect would lead to a substantial decrease of present-day sub-shelf melt rates in East Antarctica, while the strong subsidence of bedrock in West Antarctica can lead up to a doubling of basal melt rates. For a hypothetical globally ice-free sea-level
scenario, which would lead to a global mean (barystatic) sea-level rise of around +70 m, sub-shelf melt rates for a present-day ice sheet geometry can more than double in East Antarctica, but can also decrease substantially, where bedrock uplift dominates. Also for projected sea-level changes at the
year 2300 we find maximum possible changes of ±20 % in sub-shelf melt rates, as a consequence of relative sea-level changes only.

How to cite: Kreuzer, M., Albrecht, T., Nicola, L., Reese, R., and Winkelmann, R.: Oceanic gateways in Antarctica - Impact of relative sea-level change on sub-shelf melt, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19165, https://doi.org/10.5194/egusphere-egu24-19165, 2024.

EGU24-20197 | ECS | Posters on site | CR2.2

Constraining projections of future freshwater fluxes from Antarctica  

Violaine Coulon, Javier Blasco, Qing Qin, Jan De Rydt, and Frank Pattyn

As global temperatures rise, Antarctica's grounded ice sheet and floating ice shelves are experiencing accelerated mass loss, releasing meltwater into the Southern Ocean. This increasing freshwater discharge poses significant implications for global climate change. Despite these consequences, interactive ice sheets and ice shelves have generally not been included in coupled climate model simulations, such as those in CMIP6. Consequently, CMIP6 projections lack a detailed representation of spatiotemporal trends in ice-sheet freshwater fluxes and their impact on the global climate system, introducing major uncertainties in future climate and sea-level projections. To address this, we provide future Antarctic freshwater forcing data and uncertainty estimates for climate models. These are derived from an ensemble of historically calibrated standalone ice sheet model projections, produced with the Kori-ULB ice flow model, under different climate scenarios up to 2300. Here, we analyse spatiotemporal trends in calving rates, ice shelf basal melt and surface mass balance for all Antarctic ice shelves. 

How to cite: Coulon, V., Blasco, J., Qin, Q., De Rydt, J., and Pattyn, F.: Constraining projections of future freshwater fluxes from Antarctica , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20197, https://doi.org/10.5194/egusphere-egu24-20197, 2024.

EGU24-20332 | ECS | Orals | CR2.2

The effect of Pacific climatology on the North American Ice Sheet at the Last Glacial Maximum 

William J. Dow, Sam Sherriff-Tadano, Lauren J. Gregoire, and Ruza Ivanovic

Surface ocean conditions and atmospheric dynamics can affect the surface mass balance (SMB) of remote ice sheets via their influence on heat and moisture transport. Here, we use the FAMOUS-ice coupled climate-ice sheet model, coupled to a slab ocean, to simulate the Last Glacial Maximum (LGM). The model was run hundreds of times to produce a large ensemble that captures a range of uncertain model inputs (parameter values). We investigate the range of simulated atmospheric circulation patterns in the 16 ‘best’ ensemble members based on constraints, such as global temperature, their relationship to sea surface conditions in the North Pacific and the interactions with the North American ice sheet. We present evidence of upper tropospheric planetary waves that facilitate communication between the tropical Pacific and extratropical Laurentide ice sheet region, yet there are clear differences in upper tropopsheric dynamics when compared to recent historical period. There is limited evidence for this tropical-extra-tropical relationship being directly responsible for regional differences in Laurentide SMB evolution.

How to cite: Dow, W. J., Sherriff-Tadano, S., Gregoire, L. J., and Ivanovic, R.: The effect of Pacific climatology on the North American Ice Sheet at the Last Glacial Maximum, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20332, https://doi.org/10.5194/egusphere-egu24-20332, 2024.

EGU24-21079 | Orals | CR2.2

Understanding conditions leading to WAIS collapse, from the Last Interglacial to the modern 

Mira Berdahl, Gunter Leguy, Eric Steig, William Lipscomb, Bette Otto-Bliesner, Nathan Urban, Ian Miller, and Harriet Morgan

It is virtually certain that the West Antarctic Ice Sheet (WAIS) collapsed during past warm periods in Earth’s history, prompting concerns about the potential recurrence under anthropogenic climate change. Despite observed ice shelf thinning in the region, the combination of climate forcing and ice sheet sensitivity driving these changes remains unclear. Here, we investigate the joint effects of climate forcing and ice sheet sensitivity to evaluate conditions leading to WAIS collapse. We run ensembles of the Community Ice Sheet Model (CISM), spun up to a pre-industrial state, and apply climate anomalies from the Last Interglacial (LIG, 129 to 116 yr ago), and the future (SSP2-4.5).  Forcing is derived from Community Earth System Model (CESM2) global simulations. We find that only modest ocean warming is required to cause significant WAIS mass loss, though such loss takes multiple centuries to millennia to manifest.

How to cite: Berdahl, M., Leguy, G., Steig, E., Lipscomb, W., Otto-Bliesner, B., Urban, N., Miller, I., and Morgan, H.: Understanding conditions leading to WAIS collapse, from the Last Interglacial to the modern, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21079, https://doi.org/10.5194/egusphere-egu24-21079, 2024.

EGU24-789 | ECS | Orals | CR2.3

Spatio-temporal variable drag for the sub-ice-shelf melt parameterisation in NEMO, ocean model 

Dorothée Vallot, Nicolas Jourdain, and Pierre Mathiot
Ice-shelf basal melting in NEMO, as in most ocean models, is parameterised based on a friction velocity calculated from a drag coefficient that is constant in space and time, usually tuned to approach observed melt. But the drag between the ice and the ocean should depend on the roughness at different scale. This means that roughness evolution in space and time is not taken into account in today's model. In recent decades, some ice shelves, particularly in the Amundsen Sea Embayement (ASE), have experienced an increase of their damage, associated with more surface and basal crevasses so their sub-shelf environment is rougher. There is good chances that this phenomenon is to happen more in the future and in an extended number of ice shelves. Here we present a study using a spatially variable coefficient of drag, which depends on the topography and is applied on the first wet cell height. We use the ice shelf parameterisation of NEMO4.2 on a configuration of ASE at 12th of a degree.

How to cite: Vallot, D., Jourdain, N., and Mathiot, P.: Spatio-temporal variable drag for the sub-ice-shelf melt parameterisation in NEMO, ocean model, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-789, https://doi.org/10.5194/egusphere-egu24-789, 2024.

EGU24-797 | ECS | Orals | CR2.3

Annual Terminus Prediction Errors for Greenland Glaciers from Calving Laws and Melt Parameterizations 

Benjamin Reynolds, Sophie Nowicki, Kristin Poinar, and Sophie Goliber

Many calving laws have been proposed leading to a need to characterize the ability of these laws to predict terminus movement across years. The influence of terminus change on glacier discharge makes this an important source of uncertainty for multi-decadal sea level rise prediction from ice sheet models. Here, we develop a workflow to tune calving laws and then calculate error in predicted terminus positions based on Greenland Ice Sheet Mapping Project (GrIMP) surface velocity data sets compiled from Sentinel, Landsat, TerraSAR-X, TanDEM-X, and COSMO-SkyMed satellites as well as digital elevation models (DEMs) from ASTER mission and ArcticDEM data.  Greenland glaciers with available data are used to test the height above flotation, fraction above flotation, crevasse depth criterion, von Mises criterion, and surface stress maximum calving laws over a multi-year period. Several versions of the crevasse depth law based on stress input are tested providing insight into the law’s dependence on stress calculation. This dependence is important as the crevasse depth law has been recommended by calving law comparison but has been implemented with various stress calculations to work with three-dimensional stress fields. The terminus melt parameterization used in the Ice Sheet Model Intercomparison Project for CMIP6 standard experiments is included as reference to show the degree to which calving laws are needed to accurately model retreat for future model intercomparison efforts. While testing calving laws independent of an ice sheet model will not provide insight into all the challenges of calving implementation for ice-sheet-wide studies, this remote-sensing based workflow can rapidly test calving laws’ terminus prediction errors. With the availability of monthly-averaged velocity data sets and frequent instantaneous DEMs, this method will allow for analysis of calving law success on many regimes of multi-year glacier movement.  

How to cite: Reynolds, B., Nowicki, S., Poinar, K., and Goliber, S.: Annual Terminus Prediction Errors for Greenland Glaciers from Calving Laws and Melt Parameterizations, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-797, https://doi.org/10.5194/egusphere-egu24-797, 2024.

EGU24-1569 | ECS | Posters on site | CR2.3

A framework for observing and modelling ice-ocean interactions building on a community workshop organised by the Joint Commission on Ice-Ocean Interactions 

Isabel Nias, Felicity McCormack, Sue Cook, Susheel Adusumilli, Lu An, Daniel Goldberg, Tore Hattermann, Yoshihiro Nakayama, Hélène Seroussi, and Donald Slater

Mass loss from the Antarctic and Greenland Ice Sheets could lead to a rise in global mean sea level of 0.25 m by 2100 and several metres by 2300 if greenhouse gas emissions remain unmitigated. Uncertainties in these estimates are strongly related to ocean-driven ice melt, which can lead to grounding line retreat, thinning and acceleration of the fast-flowing regions of both Antarctica and Greenland. The processes of ocean-driven ice melt on large spatial and temporal scales are imperfectly known, and measurements are sparse, impacting the accuracy of ice sheet and ocean model projection studies. The Joint Commission on Ice-Ocean Interactions (JCIOI) hosted the first community workshop in October 2022 with the aims to: (1) identify critical knowledge gaps surrounding processes that govern ocean-driven melt of ice sheets across a range of spatio-temporal scales; and (2) identify options to address the knowledge gaps through observing, parameterising, and modelling ice-ocean interactions, and their impacts on ice mass loss and ocean dynamics. Community discussions from the workshop highlighted the need for concurrent and sustained measurements of ice, ocean and atmosphere properties at the ice sheet-ocean interface, and making best use of existing observations to improve models, capture observed changes, better understand physical mechanisms and improve future projections. Building on the workshop outputs, we propose to develop a framework for ice-ocean observations that details the essential measurements that need to be collected, and the temporal and spatial scales on which to measure. This framework will require widespread community engagement on key scientific questions, agreement and coordination, including protocols for data collection, processing, and sharing.

How to cite: Nias, I., McCormack, F., Cook, S., Adusumilli, S., An, L., Goldberg, D., Hattermann, T., Nakayama, Y., Seroussi, H., and Slater, D.: A framework for observing and modelling ice-ocean interactions building on a community workshop organised by the Joint Commission on Ice-Ocean Interactions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1569, https://doi.org/10.5194/egusphere-egu24-1569, 2024.

EGU24-3027 | Orals | CR2.3

Strong ice-ocean interaction drives and enhances calving of Antarctic ice shelves 

Yan Liu, Xiao Cheng, Jiping Liu, John Moore, Xichen Li, and Sue Cook

Since 2015, there has been a significant increase in iceberg calving rates from Antarctic ice shelves. It is crucial to comprehend the climate-related reasons for this enhanced iceberg calving to improve coupled simulations with the ice sheet and predict their future effects on sea-level rise. Based on continuous observations of iceberg calving around Antarctica over 15 years, we demonstrate that sea ice extent is the primary control on iceberg calving rates in Antarctica, regardless of ice shelf size, location, or ocean regime. The recent increase in calving rates coincides precisely with a significant reduction in sea ice area in most sectors around the continent. We propose a calving model, where iceberg calving is dominated by ocean-wave induced flexure and basal shear and enhanced by ice-shelf basal melt. We also find links between iceberg calving rate and El Niño/Southern Oscillation (ENSO), which are particularly strong in East Antarctica. Given that further decreases in sea ice extent and increases in extreme ENSO events are predicted in future, we raise concern that previously stable East Antarctic ice shelves may soon begin to retreat, with potential to trigger significant mass loss from this massive ice sheet.

How to cite: Liu, Y., Cheng, X., Liu, J., Moore, J., Li, X., and Cook, S.: Strong ice-ocean interaction drives and enhances calving of Antarctic ice shelves, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3027, https://doi.org/10.5194/egusphere-egu24-3027, 2024.

EGU24-3138 | ECS | Posters on site | CR2.3

Variability of calving and ice flow during a two-week period using terrestrial radar interferometry 

Armin Dachauer, Andrea Kneib-Walter, and Andreas Vieli

Frontal ablation at tidewater outlet glaciers is responsible for a major part of mass loss of the Greenland Ice Sheet. This underscores the need to understand the underlying processes, such as calving and ice flow, with regard to global sea level rise. In this study we explore the temporal and spatial variability of calving activity and ice flow at the major tidewater outlet glacier Eqalorutsit Kangilliit Sermiat (also referred to as Qajuuttap Sermia) in South Greenland and thereby try to get insights into the forcing and relationships between these two processes. This requires high-resolution data which we achieve by using a terrestrial radar interferometer. The instrument provides a temporal resolution of 1 minute and a spatial resolution of a few meters and was running continuously for a two-week field period in August 2023. The data shows considerable spatial and temporal variability of both calving activity and ice flow. Parts of the flow variability can be attributed to a diurnal cycle that is forced by surface melt, whereas enhanced calving activity seems to be tightly linked to locations of major subglacial discharge plumes.

How to cite: Dachauer, A., Kneib-Walter, A., and Vieli, A.: Variability of calving and ice flow during a two-week period using terrestrial radar interferometry, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3138, https://doi.org/10.5194/egusphere-egu24-3138, 2024.

EGU24-3442 | Orals | CR2.3

Tidewater Glaciers and Ice Shelves as Self-Organising Systems 

Douglas Benn, Jan Åström, Iain Wheel, Adrian Luckman, and Faezeh Nick

Marine-terminating glaciers and ice shelves are notoriously complex, with a wide range of ice-dynamic and calving processes occuring in response to oceanographic, atmospheric and glaciological influences. Within this complexity, however, we can recognise order on at least two scales. First, marine ice fronts typically form vertical cliffs, reflecting competition between oversteepening (ice flow and melt-undercutting) and failure. Calving magnitude-frequency distributions have power-law form with an exponent of -1.2, characteristic of self-organising criticality (SOC). Such systems have a critical point as an attractor, such that the system converges on the failure threshold.

The second scale is that of the whole ice tongue. Tidewater glaciers and ice shelves typically oscillate around stable positions for multiple years, punctuated by transitions to new quasi-stable positions. Stability is encouraged by pinning points which function as attractors at thresholds between stable and metastable states. Ice tongues may exist in metastable states for variable amounts of time, from days to decades. Factors encouraging rapid relaxation to the threshold include large stress gradients and rapid basal melt, and factors encouraging long relaxation times include low stress gradients, low melt rates, and buttressing from mélange or sea ice. Calving magnitude-frequency distributions have exponential form, reflecting the stochastic nature of calving in the metastable zone.

Both scales of self-organisation emerge spontaneously from physically-based calving models such as the Helsinki Discrete Element Model (HiDEM) and the crevasse-depth (CD) calving law implemented in Elmer/Ice. Purely deterministic models, however, are not optimal for long-term simulations, especially in Antarctic contexts. We present results of preliminary simulations using a stochastic CD calving law, which opens up the possibility of a universal calving model applicable to both the Greenland and Antarctic ice sheets.

How to cite: Benn, D., Åström, J., Wheel, I., Luckman, A., and Nick, F.: Tidewater Glaciers and Ice Shelves as Self-Organising Systems, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3442, https://doi.org/10.5194/egusphere-egu24-3442, 2024.

EGU24-3542 | ECS | Orals | CR2.3

Ice base slope effects on the turbulent ice shelf-ocean boundary current 

Josephine Anselin, Paul Holland, John Taylor, and Adrian Jenkins

The majority of Antarctica’s contribution to sea level rise can be attributed to changes in ocean-driven melting at the base of ice shelves. Turbulent ocean currents and melting are strongest where the ice base is steeply sloped, but few studies have systematically examined this effect. Here we use 3-D, turbulence-permitting large-eddy simulations (LES) of an idealised ice shelf-ocean boundary current to examine how variations in ice base slope influence ocean mixing and ice melting. The range of simulated slope angles is appropriate to the grounding zone of small Antarctic ice shelves and to the flanks of relatively wide ice base channels, with far-field ocean conditions representative of warm-water ice shelf cavities. Within this parameter space, we derive formulations for the friction velocity, thermal forcing, and melt rate in terms of total melt-induced buoyancy input and ice base slope. This theory predicts that melt rate varies like the square root of slope, which is consistent with the LES results and differs from a previously proposed linear trend. With the caveat that further simulations with an expanded range of basal slope angles and ocean conditions would be necessary to evaluate the validity of our conclusions across the full Antarctic ice base slope parameter space, the derived scalings provide a potential framework for incorporating slope-dependence into parameterisations of mixing and melting at the base of ice shelves.

How to cite: Anselin, J., Holland, P., Taylor, J., and Jenkins, A.: Ice base slope effects on the turbulent ice shelf-ocean boundary current, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3542, https://doi.org/10.5194/egusphere-egu24-3542, 2024.

EGU24-5087 | ECS | Orals | CR2.3

The integrated ice sheet response to stochastic iceberg calving 

Aminat Ambelorun and Alexander Robel

Iceberg calving is one of the dominant sources of ice loss from the Antarctic and Greenland Ice sheets. Iceberg calving is still one of the most poorly understood aspects of ice sheet dynamics due to its variability at a wide range of spatial and temporal scales. Despite this variability, current large-scale ice sheet models assume that calving can be represented as a deterministic flux. Failure to parameterize calving accurately in predictive models could lead to large errors in warming-induced sea-level rise. In this study, we introduce stochastic calving within a one-dimensional depth-integrated tidewater glacier and ice shelf models to determine how changes in the calving style and size distribution of calving events cause changes in glacier state. We apply stochastic variability in the calving rate by drawing the calving rate from two different probability distributions.e also quantify the time scale on which individual calving events need to be resolved within a stochastic calving model to accurately simulate the probabilistic distribution of glacier state. We find that incorporating stochastic calving with a glacier model with or without buttressing ice shelves changes the simulated mean glacier state, due to nonlinearities in glacier terminus dynamics. This has important implications for the intrinsic biases in current ice sheet models, none of which include stochastic processes. Additionally, changes in calving frequency, without changes in total calving flux, lead to substantial changes in the distribution of glacier state. This new approach to modeling calving provides a framework for ongoing work to implement stochastic calving capabilities in large-scale ice sheet models, which should improve our capability to make well-constrained predictions of future ice sheet change.

How to cite: Ambelorun, A. and Robel, A.: The integrated ice sheet response to stochastic iceberg calving, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5087, https://doi.org/10.5194/egusphere-egu24-5087, 2024.

EGU24-5666 | ECS | Orals | CR2.3

Circulation, mixing and heat transport in a Greenland fjord 

Anneke Vries, Lorenz Meire, John Mortensen, Kirstin Schulz, Willem Jan van de Berg, and Michiel van den Broeke

Greenland's glacial fjords transport heat and freshwater between the shelf and the outlet glaciers of the Greenland Ice Sheet. Therefore they are crucial to understand ice-ocean interaction in the Norhern Hemisphere. Despite increasing attention from the research community, much of the seasonal variability of fjord circulation remains unknown, especially in the non-summer months. This study presents current velocity and water mass data for a full year in Nuup Kangerlua. We provide insights into the dynamics of this South West Greenland fjord, focusing on winter and the upper layer currents. We show that in winter fjord circulation remains active, including a large cross fjord component that has not been observed before. There is a disconnect between the mouth and the inner part of the fjord, causing heat to be stored in the inner fjord. The stored heat could potentially act as reservoir of melt energy for glaciers in winter.

How to cite: Vries, A., Meire, L., Mortensen, J., Schulz, K., van de Berg, W. J., and van den Broeke, M.: Circulation, mixing and heat transport in a Greenland fjord, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5666, https://doi.org/10.5194/egusphere-egu24-5666, 2024.

EGU24-5804 | ECS | Orals | CR2.3

Sub-shelf melt patterns… does detail matter? 

Franka Jesse, Erwin Lambert, and Roderik van de Wal

Observations show that some of the ice shelves surrounding Antarctica are thinning, driven by warming of the underlying ocean. These ice shelves play an important role in moderating the rate of mass loss from the ice sheet by buttressing the ice flow from the grounded parts of the ice sheet. The increased ocean-induced sub-shelf melt is therefore an important process for the stability of the ice sheet and representing it in ice sheet models is essential to study the evolution of the Antarctic Ice Sheet. Here, we present a coupled ice-ocean setup, applied to an idealised ice shelf.

The sub-shelf melting occurs in highly heterogeneous patterns, typically exhibiting higher melt rates near the grounding line. Currently, most ice sheet models rely on parameterisations which derive sub-shelf melt rates from far-field ocean hydrography. Despite their computational advantage and ease in handling grounding line migration, these parameterisations fall short of accurately representing the right details in the melt patterns. To capture more physically consistent melt patterns, we implemented an online coupling between the ice sheet model IMAU-ICE and the sub-shelf melt model LADDIE. The latter resolves the necessary physics governing the melt, including the Coriolis deflection and topographic steering of meltwater, and provides sub-shelf melt fields at sub-kilometre spatial resolution.

We will show the impact of detailed sub-shelf melt fields in an idealised set-up. We compare IMAU-ICE simulations using existing sub-shelf melt parameterisations with simulations in the coupled set-up with IMAU-ICE and LADDIE. Three parameterisations are considered for this comparison: the quadratic scaling with temperature, the box model PICO, and the plume model. All simulations are performed in the idealised MISMIP+ domain. We consider a range of oceanic temperature forcings similar to present-day temperatures in warmer and colder basins surrounding Antarctica. We present and discuss the results, primarily focusing on the evolution of three key indicators for ice sheet stability: grounding line position, ice shelf extent, and grounding zone shape. These results demonstrate the importance of accounting for realistic melt patterns in ice sheet models.

How to cite: Jesse, F., Lambert, E., and van de Wal, R.: Sub-shelf melt patterns… does detail matter?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5804, https://doi.org/10.5194/egusphere-egu24-5804, 2024.

EGU24-6423 | ECS | Orals | CR2.3

Re-evaluating Rapid Glacier Retreats: Hektoria Glacier’s Unprecedented Tidewater Collapse 

Naomi E. Ochwat, Ted A. Scambos, Robert S. Anderson, Catherine C. Walker, and Bailey L. Fluegel

Hektoria Glacier on the Eastern Antarctic Peninsula underwent a heretofore unseen rate of tidewater-style glacier retreat from 2022 to 2023 after the loss of decade-old fast ice in the Larsen B embayment. The glacier has retreated 25 km between February 2022 and January 2024, of which at least 8-13 km was grounded ice. Remote sensing data in the months following the fast ice break-out reveals an ice flow speed increase of up to 4-fold, and rapid elevation loss up to 20-30 m, representing an 8-fold increase in the glacier thinning rate. Hektoria and Green Glaciers underwent three phases of retreat displaying differing calving styles. During the first two months after the loss of the fast ice in January 2022 the Hektoria-Green ice tongue calved large tabular bergs. In March 2022, an abrupt change in Hektoria’s calving style was observed, changing from large tabular icebergs to buoyantly rotated smaller bergs. Following this transition, Hektoria underwent several short periods of rapid retreat. In December 2022, 2.5 km of grounded ice were lost over 2.5 days. These retreat rates for grounded tidewater ice are greater than any reported in the modern glaciological record. Here we examine the evidence for locating the pre-fast ice break-out grounding zone as well as the drivers that could cause such a rapid retreat. We link these observations to known causes of glacier instability, such as Marine Ice Sheet Instability and Marine Ice Cliff Instability, as well as the classical tidewater glacier retreat cycle.

How to cite: Ochwat, N. E., Scambos, T. A., Anderson, R. S., Walker, C. C., and Fluegel, B. L.: Re-evaluating Rapid Glacier Retreats: Hektoria Glacier’s Unprecedented Tidewater Collapse, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6423, https://doi.org/10.5194/egusphere-egu24-6423, 2024.

EGU24-6639 | ECS | Orals | CR2.3

Multi-decadal evolution of Crary Ice Rise region, West Antarctica, amidst modern ice stream deceleration 

Hannah Verboncoeur, Matthew Siegfried, J. Paul Winberry, Nicholas Holschuh, Duncan Byrne, Wilson Sauthoff, Tyler Sutterley, and Brooke Medley

The ongoing deceleration of Whillans Ice Stream, West Antarctica, provides an opportunity to investigate the role of grounded ice flux in downstream pinning point evolution on decadal time scales. Here, we construct and analyze a 20-year, multi-mission satellite altimetry record of dynamic ice surface-elevation change (dh/dt) in the grounded region between lower Whillans Ice Stream and Crary Ice Rise, a major Ross Ice Shelf pinning point. We developed a new method for generating multi-mission time series that reduces spatial bias and implemented this method with altimetry data from the Ice, Cloud, and land Elevation Satellite (ICESat; 2003–09), CryoSat-2 (2010–present), and ICESat-2 (2018–present) altimetry missions. We then used the 20-year dh/dt time series to identify persistent patterns of surface elevation change and to evaluate regional mass balance. Our results suggest that changes in ice flux associated with Whillans Ice Stream stagnation drive non-linear mass change responses isolated to the Crary Ice Rise region, producing persistent, spatially heterogeneous thickness changes. The resulting mass redistribution modifies the grounding zone and mass balance of the Crary Ice Rise region, in turn adjusting the buttressing regime of the southern Ross Ice Shelf embayment.

How to cite: Verboncoeur, H., Siegfried, M., Winberry, J. P., Holschuh, N., Byrne, D., Sauthoff, W., Sutterley, T., and Medley, B.: Multi-decadal evolution of Crary Ice Rise region, West Antarctica, amidst modern ice stream deceleration, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6639, https://doi.org/10.5194/egusphere-egu24-6639, 2024.

EGU24-6749 | ECS | Orals | CR2.3

Two Decades of Satellite Observations: Sensible-Heat Polynya Variability at Pine Island Glacier, West Antarctica 

Elena Savidge, Tasha Snow, and Matthew R. Siegfried

Thermodynamically maintained open ocean areas surrounded by sea ice, or sensible-heat polynyas, are linked to key ice-sheet processes, such as ice-shelf basal melt and ice-shelf fracture, when they occur near ice-shelf fronts. However, the lack of detailed multi-year records of polynya variability pose a barrier to assessing the potential interconnectivity between polynya and frontal dynamics. Here, we present the first multi-decadal record (2000–2022) of polynya area at Pine Island Glacier (PIG) from thermal and optical satellite imagery. We found that although polynya area was highly variable, there were consistencies in the timing of polynya maximal extent, and opening and closing. Furthermore, we found that the largest polynya (269 km2) in our record occurred at PIG’s western margin just 68 days before iceberg B-27 calved, suggesting that polynya size and position may influence rifting dynamics. We suspect that large sensible-heat polynyas have the potential to reduce both ice-shelf buttressing (via reduced landfast ice) and shear margin dynamics (via reduced contact with slower marginal ice), which may lead to structural instability and eventually contribute to calving. Our new dataset provides a pathway to assess coevolving polynya and frontal dynamics, demonstrating the importance of building long-term records of polynya variability across the continent.

How to cite: Savidge, E., Snow, T., and Siegfried, M. R.: Two Decades of Satellite Observations: Sensible-Heat Polynya Variability at Pine Island Glacier, West Antarctica, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6749, https://doi.org/10.5194/egusphere-egu24-6749, 2024.

EGU24-7829 | ECS | Orals | CR2.3

High fidelity modelling of iceberg capsize 

Nicolas De Pinho Dias, Alban Leroyer, Anne Mangeney, Olivier Castelnau, and Jean-Baptiste Thiebot

One of the major questions in climate science is to improve the accuracy of sea-level rise prediction, for which mass loss of the polar ice caps has a significant contribution. In this work, the focus is on buoyancy-dominated capsize of large icebergs. The capsizes generate specific seismic signals, which in turn can be analysed and used as a unique tool to study the long term evolution of such large icebergs capsize and the glacier response.

To better quantify ice mass loss due to iceberg calving at marine terminating glaciers, coupling iceberg calving simulation and inversion of the seismic waves generated by these events and recorded at teleseismic distances is necessary. To achieve our task, a complex fluid/structure model of the iceberg capsize is required to obtain accurate forces history acting on the glacier terminus. The simulated forces can then be compared to the force inverted from the seismic signal. Therefore, based on our recent work, we implement a Computation Fluid Dynamics (CFD) approach to reach a high fidelity modelling of the iceberg capsize. First work using the experimental data of an iceberg capsize showed the need and ability of CFD computations to precisely reproduce the iceberg kinematics for different cases. We will present more advanced CFD configurations, including the contact between the capsizing iceberg and a rigid glacier front. Computation results are compared and validated against lab scale experiments, where we outline that some 3D effects cannot be neglected. We will also present full scale capsize simulations, in which the mixing of ocean layers occurs. In particular, we will quantify the transport of particles within the ocean to illustrate the potential change of nutriments distribution or of pressure experienced by local fauna due to iceberg calving.

How to cite: De Pinho Dias, N., Leroyer, A., Mangeney, A., Castelnau, O., and Thiebot, J.-B.: High fidelity modelling of iceberg capsize, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7829, https://doi.org/10.5194/egusphere-egu24-7829, 2024.

EGU24-8352 | ECS | Orals | CR2.3

A reassessment of the role of atmospheric and oceanic forcing on ice dynamics at Jakobshavn Isbræ, Ilulissat Icefjord 

Hannah Picton, Peter Nienow, Donald Slater, and Thomas Chudley

Jakobshavn Isbræ (Sermeq Kujalleq) has been the largest single contributor to mass loss from the Greenland Ice Sheet over recent decades. Previous work has emphasised the dominant role of oceanic forcing on ice dynamics, with the short-lived (2016-2018) advance, deceleration and thickening of Jakobshavn attributed to decreased ocean temperatures within Disko Bay. Here, we use satellite imagery to extend observations of ice dynamics at Jakobshavn Isbræ between 2018 and 2023. We then employ hydrographic measurements, weather station data, and modelled estimates of surface runoff, to explore the role of climatic forcing on ice dynamics over this most recent five-year period. 

Between 2018 and 2022, Jakobshavn Isbræ accelerated significantly, with peak summer terminus velocity increasing by 79%, from 9.4 to 16.8 km/yr. Despite sustained surface lowering, peak solid ice discharge also increased, rising from 39.4 Gt/yr in 2018 to 54.7 Gt/yr in 2021. Whilst the initial onset of re-acceleration occurred in 2019, a dramatic speedup occurred between May and August 2020, with ice velocity increasing from 7.6 to 13.8 km/yr. In contrast to previous years, ice velocity remained high throughout the subsequent winter, thereby facilitating a peak velocity of 16.8 km/yr in July 2021.

Jakobshavn Isbræ exhibited a typical seasonal calving cycle of winter advance and summer retreat throughout 2018 and 2019. However, a clear switch in dynamics was observed in 2020, with the terminus undergoing minimal readvance over the winter months. This shift coincided with a clear reduction in the extent of rigid mélange within Ilulissat Icefjord, in contrast to preceding years. Although sparse, hydrographic measurements indicate that the mean water temperature within Disko Bay was ~ 0.75⁰C higher in 2020, relative to 2019.

We argue that the initial onset of reacceleration and thinning at Jakobshavn Isbræ was driven primarily by atmospheric forcing, with annual runoff in 2019 approximately double that observed in the other years. Furthermore, we emphasise that at glaciers close to floatation, such as Jakobshavn, surface thinning can significantly impact buoyant flexure, and hence rates of calving. However, we also provide evidence of oceanic forcing, postulating that increased water temperatures reduced the formation of rigid mélange in 2020, thereby facilitating sustained calving and elevated ice velocities throughout the winter months. Our study therefore highlights the critical importance of considering both atmospheric and oceanic forcing when investigating and predicting the future behaviour of ice dynamics at marine-terminating outlet glaciers.

How to cite: Picton, H., Nienow, P., Slater, D., and Chudley, T.: A reassessment of the role of atmospheric and oceanic forcing on ice dynamics at Jakobshavn Isbræ, Ilulissat Icefjord, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8352, https://doi.org/10.5194/egusphere-egu24-8352, 2024.

EGU24-8616 | ECS | Orals | CR2.3

Calving dynamics and mélange buttressing conditions at the Thwaites Glacier calving face 

Anna Crawford, Jan Åström, Doug Benn, Adrian Luckman, Rupert Gladstone, Thomas Zwinger, Fredrik Robertsén, and Suzanne Bevan

Thwaites Glacier, a large outlet glacier of the West Antarctic Ice Sheet, holds over a half meter of sea level rise equivalent. The large potential contribution to sea level is concerning given that the glacier may be vulnerable to self-sustaining processes of rapid retreat due to the retrograde bed slope that characterises much of the glacier’s bed. Such a reverse-sloping bed exists behind the relatively high ridge on which the western calving front (WCF) of the Thwaites Glacier terminus currently rests. Our study focuses on the factors that control the calving dynamics of the WCF and the ability of mélange to influence these dynamics. Employing the 3D Helsinki Discrete Element Model (HiDEM), we find that calving at this location currently occurs as rifts form and widen due to longitudinal tensile stresses associated with ice flow across the grounding line. Calving is restricted in HiDEM simulations that include a constricted mélange field that is confined within the bounds of the model domain. A thicker, constricted mélange field fully suppresses calving. These simulations show the development of robust force chains that transmit resistive forces to the Thwaites WCF. In the future, the ability for mélange to influence the calving dynamics at the WCF will depend on the degree to which it is constrained in the wide Amundsen Sea Embayment, either through binding in land-fast sea ice or jamming behind large, grounded icebergs. As such, sea-ice conditions and iceberg characteristics will need to be considered along with the presence of mélange in investigations of the future retreat of the prominently recognised Thwaites Glacier.

How to cite: Crawford, A., Åström, J., Benn, D., Luckman, A., Gladstone, R., Zwinger, T., Robertsén, F., and Bevan, S.: Calving dynamics and mélange buttressing conditions at the Thwaites Glacier calving face, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8616, https://doi.org/10.5194/egusphere-egu24-8616, 2024.

EGU24-9102 | ECS | Posters on site | CR2.3

Calving of floating ice shelves and icebergs in Antarctica triggered by internal ocean waves driven by marine ice-cliff 

Zhenfu Guan, Yan Liu, Teng Li, and Xiao Cheng

Ice calving around Antarctica has a significant impact on glacier dynamics, sea ice, and marine productivity, which in turn affect global sea level and climate.  However, there is limited documented knowledge of the causes of ice calving triggered by internal ocean processes throughout Antarctica, especially during the austral winter.  A total of 3708 iceberg calving events were observed along the circum-Antarctic coastline over a three-month winter period.  These events included the calving of ice cliffs, ice shelves, and icebergs, spanning seven orders of magnitude in spatial scale.  The results suggest that ice cliff calving is primarily driven by internal glacier stresses and is widespread along the Antarctic coast.  The frequency of calving is primarily controlled by glacier ice velocity.  About 70% of the calving in Antarctica occurs on the Antarctic Peninsula.  Internal waves generated by ice cliff calving cascade to small enough scales to induce shear that leads to near-field (~40 km) calving of floating ice shelves and icebergs in regions of high topographic relief.  This study presents a newly discovered mechanism for ice shelf and iceberg calving driven by oceanic forces.  The mechanism has broad applicability and can serve as a catalyst for calving modeling and the study of oceanic internal waves.

How to cite: Guan, Z., Liu, Y., Li, T., and Cheng, X.: Calving of floating ice shelves and icebergs in Antarctica triggered by internal ocean waves driven by marine ice-cliff, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9102, https://doi.org/10.5194/egusphere-egu24-9102, 2024.

EGU24-9429 | Posters on site | CR2.3

Distributed and time-series estimates of basal melt from Kamb Ice Stream’s grounding zone ocean cavity 

Huw Horgan, Natalie Robinson, Craig Stevens, Craig Stewart, Christina Hulbe, Justin Lawrence, Britney Schmidt, and Peter Washam

Melt beneath Antarctica’s large cold-cavity ice shelves remains a major source of uncertainty in ice sheet projections. Beneath these ice shelves melt is typically greatest both at the ice shelf front and at the grounding zone where ice first goes afloat. Grounding zone melt is thought to have a significant influence on ice flow across the grounding line, but can be difficult to estimate using remote sensing methods due to flexure of the overriding ice shelf. Added complexity in the grounding zone is caused by the thin water column, abundant basal crevassing, and the possible addition of subglacial fresh water draining from beneath the ice sheets. Here we present two independent estimates of basal melt from the ocean cavity of Kamb Ice Stream’s grounding zone, Ross Ice Shelf, West Antarctica. The first method uses repeat phase-sensitive radar observations to estimate melt in profiles from approximately 5 km seaward of the grounding line to approximately 3 km upstream of the grounding line. The second method uses an approximately 10-month long time series of oceanographic observations from a site 3.5 km seaward of the grounding line. Both methods are complemented by the high resolution observations provided by the Remotely Operated Vehicle (ROV) Icefin. The spatially distributed estimates show a more than tripling of melt rate within 5 km of the grounding line. The mooring derived melt rates demonstrate a melt-rate dependence on diurnal and spring-neap tidal currents. The average mooring melt rate more closely matches the radar-based estimates when a drag coefficient previously estimated using Icefin observations is used. Lastly we demonstrate an interesting correlation between mooring derived melt rates and ice shelf surface velocities obtained from Global Navigation Satellite System (GNSS) observations.

How to cite: Horgan, H., Robinson, N., Stevens, C., Stewart, C., Hulbe, C., Lawrence, J., Schmidt, B., and Washam, P.: Distributed and time-series estimates of basal melt from Kamb Ice Stream’s grounding zone ocean cavity, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9429, https://doi.org/10.5194/egusphere-egu24-9429, 2024.

EGU24-9500 | Posters on site | CR2.3

A viscoelastic phase-field model for iceberg calving 

Robert Arthern, Jakub Stocek, and Oliver Marsh

Iceberg calving accounts for around half of the ice lost annually from Antarctica, but realistic representation of fracture and calving in large-scale ice sheet models remains a major unsolved problem in glaciology. We present a new phase-field viscoelastic model for fracture that simulates the slow deformation of ice and the distribution and evolution of cracks. Cracks nucleate and propagate in response to the evolving stress field, and are influenced by water pressure below sea level. The model incorporates nonlinear-viscous rheology, linear-elastic rheology, and a phase-field variational formulation, which allows simulation of complex fracture phenomena. We show that this approach is capable of simulating the physical process of calving. Numerical experiments supported by a simplified model suggest that calving rate will scale with the fourth power of ice thickness for a floating ice front that has no variation across flow. The equations make no assumptions about the style of calving, so they would also simulate numerous more realistic settings in Antarctica for which material parameters and three-dimensional effects can be expected to influence the calving rate.

How to cite: Arthern, R., Stocek, J., and Marsh, O.: A viscoelastic phase-field model for iceberg calving, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9500, https://doi.org/10.5194/egusphere-egu24-9500, 2024.

EGU24-9876 | ECS | Posters on site | CR2.3

Is climate change responsible for recent retreat of the Pine Island Glacier in West Antarctica? 

Alex Bradley, David Bett, Paul Holland, C. Rosie Williams, and Robert Arthern

Pine Island Glacier is a fast flowing ice stream in West Antarctica. At present, it is rapidly thinning and retreating, and has been since at least the 1970s, when satellite records began. Sediment records indicate that this retreat was initiated in the 1940s, but the influence of climate change on key forcing components only became significant in the 1960s, i.e. the trigger for retreat occurred naturally. However, current ice loss remains responsive to fluctuations in forcing, indicating that Pine Island Glacier is not undergoing a purely unstable retreat after this trigger. This begs the question: to what extent is climate change responsible for the recent retreat of the Pine Island Glacier?

Adopting a recently published framework, we assess this question. One major challenge is the computational expense associated with the large ensemble of simulations required to account for significant uncertainties in ice sheet model parameters; to overcome this, we use a two stage Ensemble Kalman Inversion and Model Emulation approach. Ultimately, this procedure yields posterior distributions of parameters, including the trend in forcing resulting from climate change; essentially, this allows us to address the question: given the observed Pine Island Glacier retreat, how large does the trend in forcing have to have been?

How to cite: Bradley, A., Bett, D., Holland, P., Williams, C. R., and Arthern, R.: Is climate change responsible for recent retreat of the Pine Island Glacier in West Antarctica?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9876, https://doi.org/10.5194/egusphere-egu24-9876, 2024.

EGU24-10186 | ECS | Orals | CR2.3

Exposing Underestimated Channelized Basal Melt Rates in Antarctic Ice Shelves 

Ann-Sofie Priergaard Zinck, Stef Lhermitte, and Bert Wouters

Ice shelves play a pivotal role in stabilizing the Antarctic ice sheet by providing crucial buttressing support. However, their vulnerability to basal melting poses significant concerns for ice sheet and shelf stability. Our study focuses on assessing basal melt rates at a 50 m posting of 12 ice shelves where earlier studies have identified high melt rates. We make use of the Reference Elevation Model of Antarctica (REMA) strips to generate surface elevation- and melt rates using the Basal melt rates Using Rema and Google Earth Engine (BURGEE) methodology.

BURGEE reveals higher melt rates in areas with thinner ice than existing remote sensing basal melt products. This is for instance the case for basal channels on both Dotson, Totten and Pine Island ice shelves. Modelling studies have already shown that remote sensing inferred basal melt rates are underestimated at the thinnest part of basal channels, and that this underestimation scales with resolution coarsening. Since the thinner parts of an ice shelf also represent its weakest part, it is crucial that we capture its melting well to fully grasp the vulnerability of the ice shelf.

Our work, therefore, represents a crucial step in uncovering the vulnerability of Antarctic ice shelves. By exposing detailed melting patterns, particularly in areas like basal channels, we highlight not just extensive melting but also potential weak points, significantly contributing to our understanding of ice shelf stability. These findings bear substantial importance in comprehending the broader implications of ongoing climate changes on Antarctica's ice sheet integrity and, consequently, global sea levels.

How to cite: Zinck, A.-S. P., Lhermitte, S., and Wouters, B.: Exposing Underestimated Channelized Basal Melt Rates in Antarctic Ice Shelves, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10186, https://doi.org/10.5194/egusphere-egu24-10186, 2024.

EGU24-10287 | ECS | Posters on site | CR2.3

Ocean-induced glacier retreat drives mass loss in Svalbard  

Tian Li, Konrad Heidler, Adam Igneczi, Stefan Hofer, Xiao Xiang Zhu, and Jonathan Bamber

Arctic Amplification is making Svalbard one of the most climatically sensitive regions in the world and it has been undergoing accelerated mass loss over the past several decades. A major uncertainty in predicting the future sea-level rise contribution from marine-terminating glaciers is ice dynamics, which can be driven by non-linear calving processes. However, the relationship between calving and ice dynamics is not well understood in Svalbard, in part due to the lack of high-resolution calving front observations. To improve our understanding of the glacier calving dynamics and its relation to dynamic mass loss, here we use a novel fully automated deep learning framework to produce a new calving front dataset of 149 marine-terminating glaciers in Svalbard. This dataset, which includes 124919 glacier calving front positions from 1985 to 2023, has high spatial and temporal resolutions and is derived from multiple optical and SAR satellite images. We then use this new calving front dataset to systematically quantify the calving front change variabilities at different temporal scales, and identify the key climate drivers controlling the calving dynamics. We show that ocean forcing plays a central role in controlling the glacier calving front changes and mass imbalance. Our study highlights the importance of including ice-ocean interaction in projecting future glacier mass loss from Svalbard.  

How to cite: Li, T., Heidler, K., Igneczi, A., Hofer, S., Zhu, X. X., and Bamber, J.: Ocean-induced glacier retreat drives mass loss in Svalbard , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10287, https://doi.org/10.5194/egusphere-egu24-10287, 2024.

EGU24-10402 | ECS | Posters on site | CR2.3

Idealized, High Resolution, 3D Modelling of Ice-Sheet Ocean interactions in long and narrow fjords 

Jonathan Wiskandt, Inga Monika Koszalka, and Johan Nilsson

Ocean forcing of basal melt at the Greenland and Antarctic ice sheets remains a major source of uncertainty in climate ice sheet modelling. Previous efforts to represent these effects focused mainly on the properties of the ocean waters reaching the marine terminating glaciers as well as the near-ice boundary layer flows and processes at the ice-ocean interface. We use high resolution, three dimensional modelling to show the influence that rotational effects have on the fjords circulation and the melt rate distribution and compare the total melt to earlier estimates from two dimensional simulations. Furthermore we investigate the influence that the along and across fjord bathymetry of Greenlandic glacial fjords has on the exchange flow of the warm ocean waters towards the ice sheets and the glacially modified water toward the open ocean. We find that the circulation pattern produced by rotational effects has a profound effect on the distribution of the melt rate at the ice base, producing a concentrated outflow and a melt maximum at the eastern side of a fjord that opens to the open ocean in the north even in narrow fjords (width of the order of the local Rossby Radius). The bathymetry in the fjord has a restricting effect on the inflow of warm Atlantic water and hence on the temperature forcing at the ice base. We compare the inflow strengths for different fjord bathymetries to theoretical estimateion using hydraulic theory (Whitehead, 1998).

How to cite: Wiskandt, J., Koszalka, I. M., and Nilsson, J.: Idealized, High Resolution, 3D Modelling of Ice-Sheet Ocean interactions in long and narrow fjords, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10402, https://doi.org/10.5194/egusphere-egu24-10402, 2024.

EGU24-10590 | ECS | Orals | CR2.3

Weathering crust and cryoconite holes on the Hells Gate and Nansen Ice Shelves (East Antarctica) 

Giacomo Traversa and Biagio Di Mauro

The penetration of shortwave radiation at the surface of an ice shelf has the potential to induce internal melting, resulting in the formation of a porous layer close to the surface commonly known as the weathering crust. This dynamic hydrological system is known to host light-absorbing impurities and microbes, forming a highly porous layer at the ice sheet's surface. The presence of the weathering crust significantly impacts the overall volume of generated meltwater by modulating the extent to which shortwave radiation is absorbed or reflected by the ice. Beyond external meteorological forcing, local conditions leading to weathering crust formation can be influenced by biological impurities on ice surfaces. This interplay between surface ice structures, cryoconite holes (CHs) and weathering crust contributes to the spatial and temporal variability of albedo and surface melt. In this study, we analysed uncrewed aerial vehicle (UAV) data and ground-based field spectroscopy data collected during the 2022/23 austral summer in Antarctica. The aim is to map CHs spatial distribution and to evaluate their radiative impact on blue ice fields at the Hells Gate Ice Shelf in Northern Victoria Land (East Antarctica). Furthermore, we documented the formation of the weathering crust and supraglacial ponds at Hells Gate and Nansen Ice Shelves across the summer solstice. By analysing Sentinel-2 satellite data, we were able to determine the spatial variability in surface albedo before and after the formation of the weathering crust. In detail, at the Hells Gate Ice Shelf, we estimated < 1% of area covered by CHs. Over frozen ponds and ice bands the area covered in CHs reached almost 10%. The corresponding spatially integrated-radiative forcing resulted to be about 1 Wm-2 in average, but locally it reached values of over 200 Wm-2, thus sustaining liquid water inside the CHs. As for the weathering crust, the delta albedo (Δα) was found to be about +0.10 and +0.40 respectively where weathering crust covered blue and marine ice. On the other hand, the supraglacial pond and stream formation provided an opposite Δα of about -0.30 over blue ice and -0.50 over areas previously characterised by snow cover. However, the fractional area interested by positive Δα resulted to be significantly higher than positive Δα areas over the two ice shelves.

How to cite: Traversa, G. and Di Mauro, B.: Weathering crust and cryoconite holes on the Hells Gate and Nansen Ice Shelves (East Antarctica), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10590, https://doi.org/10.5194/egusphere-egu24-10590, 2024.

EGU24-10983 | ECS | Posters on site | CR2.3

Ice-ocean coupled modelling for Nioghalvfjerdsbræ (79NG), Greenland 

Joanna Zanker and Jan De Rydt

The Northeast Greenland Ice Stream (NEGIS) drains approximately 12 % of the Greenland Ice Sheet’s surface area, containing an ice volume of 1.1 m sea-level equivalent. Nioghalvfjerdsbræ (79NG) is one of two main outlet glaciers of NEGIS, extending into a large floating ice tongue, one of few remaining in Greenland. It is currently not well understood how 79NG will respond to the changing atmosphere and warming oceans, with possible implications for the catchment’s surface mass balance (SMB) and ocean-induced ablation. This research aims to assess the importance of feedbacks between ice-sheet geometry, SMB and ocean-driven melt by having a mutually evolving dynamical ice sheet with evolving SMB parameterization and a 3D ocean circulation model utilising the ice-ocean coupled model Úa-MITgcm. The potential feedbacks between changes in ice-sheet surface geometry, ice-tongue cavity geometry and the atmosphere/ocean mass balance are as-of-yet poorly understood, especially in the context of Greenland. Of particular interest for NEGIS is the potential for geometry induced changes in melting of the ice tongue, as found for some Antarctic ice shelves. Development of the Úa ice-flow model will begin with a Greenland-wide setup and experiments based on the ISMIP6 protocol, before focussing on a regional setup of the NEGIS catchment and coupling to a regional configuration of the MITgcm ocean model of the adjacent fjord and continental shelf. The coupled approach of this project aims to improve the representation of the feedbacks between different climate components at a regional scale and draw conclusions about the fidelity of projections of ice sheet-wide mass loss and sea-level rise from ISMIP. 

How to cite: Zanker, J. and De Rydt, J.: Ice-ocean coupled modelling for Nioghalvfjerdsbræ (79NG), Greenland, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10983, https://doi.org/10.5194/egusphere-egu24-10983, 2024.

EGU24-11023 | ECS | Posters on site | CR2.3

Spatiotemporal evolution of subaerial ice cliff heights at marine-terminating outlet glaciers in Northwestern Greenland 

Emma Carr, Rachel Carr, Chris Stokes, Emily Hill, Hilmar Gudmundsson, and Neil Ross

Many tidewater glaciers in Greenland terminate in near-vertical ice cliffs from which icebergs calve. Marine Ice Cliff Instability (MICI) is the hypothesis that above a subaerial ice cliff height limit, the tensile or shear stresses at the glacier terminus surpass the ice yield strength, causing catastrophic cliff failure and self-sustaining ice frontal retreat as sequentially taller subaerial cliffs are exposed. Previous modelling studies have proposed this threshold subaerial cliff height is at least 100 m, with estimated thresholds including 100 m and 110 m for damaged ice, and up to 540 m when ice is treated as undamaged. However, modern-day observations to test MICI are limited because few marine-terminating outlet glaciers without a buttressing ice shelf are known to terminate in subaerial ice cliffs greater than 100 m high. Here, we expand the observations of subaerial ice cliff heights at ten marine-terminating outlet glaciers in northwest Greenland using 2 m spatial resolution Arctic DEM strips. Our results identify three marine-terminating outlet glaciers that currently terminate in exposed subaerial ice cliffs approaching or exceeding the stability thresholds estimated for MICI. During at least two years between 2016 and 2021, subaerial ice cliffs at Nuussuup Sermia (NuS), Nunnatakassaap Sermia (NkS) and Sermeq North (SqN) exceeded heights of 100 m and 110 m. Despite being above these postulated thresholds thought conducive for cliff failure, SqN underwent relatively limited net retreat (0.25 km), and NuS and NkS exhibited distinct seasonal cycles of terminus advance (up to 0.92 km) from March to June/July each year prior to the disintegration and removal of proglacial ice mélange. Consequently, none of the glaciers identified as potentially susceptible to MICI underwent rapid, unforced retreat. We hypothesise that MICI processes were mitigated by dynamic thinning lowering the ice surface elevation immediately up-glacier of the ice cliff so that progressively taller subaerial cliffs were not exposed after retreat. Further research is required to monitor and model the evolution of subaerial ice cliffs to better understand the potential for unstable retreat in West Antarctica due to MICI.

How to cite: Carr, E., Carr, R., Stokes, C., Hill, E., Gudmundsson, H., and Ross, N.: Spatiotemporal evolution of subaerial ice cliff heights at marine-terminating outlet glaciers in Northwestern Greenland, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11023, https://doi.org/10.5194/egusphere-egu24-11023, 2024.

EGU24-11297 | Posters on site | CR2.3

Temporal evolution of basal terraces at Ekström Ice Shelf, East Antarctica  

Reinhard Drews, Falk Oraschewski, M. Reza Ershadi, Jonathan Hawkins, Christian Wild, Rebecca Schlegel, Inka Koch, Ole Zeising, and Olaf Eisen

Ekström Ice Shelf is a representative ice shelf for the ice-shelf belt of the Dronning Maud Land Coast in East Antarctica. It has cold ocean-cavity with moderate basal melt rates averaging a few meters per year across the ice shelf. In spite of the comparatively small average basal melt rates, we find basal terraces in a ground-penetrating radar dataset revealing near-vertical walls of more than 30 meters height. Such features have also been observed  elsewhere and linked to large localized basal melt rates which is in parts oriented in the horizontal direction. Here we use a ground-penetrating radar dataset with a profile spacing of <100 m which was revisited in an Eulerian sense in two consecutive field seasons 2021 and 2022. This dataset images the 3D extent of basal terracing and shows that these are remarkably stable and can be clearly identified in both seasons. They are  laterally offset  by along-flow advection and possibly also horizontal basal melting oriented perpendicular to the vertical walls. There is very little vertical difference between both datasets which is consistent with the small sub-daily melt rates derived from a continuously measuring ApRES located above a horizontal plateau linking two basal terraces at the ice base. These two 3D time slices are a unique dataset to better understand how such basal terraces initially form, how they are maintained over time and whether or not ocean-induced melting in the horizontal direction (which is typically not picked up by the ApRES data) is relevant on larger spatial scales.

How to cite: Drews, R., Oraschewski, F., Ershadi, M. R., Hawkins, J., Wild, C., Schlegel, R., Koch, I., Zeising, O., and Eisen, O.: Temporal evolution of basal terraces at Ekström Ice Shelf, East Antarctica , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11297, https://doi.org/10.5194/egusphere-egu24-11297, 2024.

EGU24-11490 | ECS | Orals | CR2.3

The buttressing capacity of Antarctic ice shelves 

Tom Mitcham, G. Hilmar Gudmundsson, and Jonathan L. Bamber

Ice shelves can control the flux of ice across the grounding line of the Antarctic Ice Sheet (AIS), and hence the rate of mass loss, through the process of ice-shelf buttressing. Recent, increased mass loss from the AIS, particularly in the Amundsen Sea Embayment and the Antarctic Peninsula, has been attributed to a reduction in buttressing due to ice-shelf thinning, calving or ice-shelf collapse events. To determine how further changes in ice-shelf geometry might affect the contribution of the AIS to global sea levels, it is therefore important to quantify the total amount of buttressing that the ice shelves currently provide and to determine where within the ice shelves that buttressing is generated.

Previous work has sought to characterise the buttressing of Antarctic ice shelves by, for example, calculating the sensitivity of grounding line flux (GLF) to small perturbations in ice-shelf thickness, or defining regions of passive shelf ice. In this work, we calculate the total buttressing capacity of all Antarctic ice shelves for the first time and then explore the spatial distribution of that total buttressing capacity within each ice shelf.

We use the ice-flow model Úa to conduct a series of diagnostic, idealised calving experiments on a present-day, Antarctic-wide model domain, with high spatial resolution over ice shelves and grounding lines. We calculate the total buttressing capacity of each ice shelf as the relative change in GLF in response to the complete removal of the shelf and find that the total buttressing capacity varies by over two orders of magnitude around the ice sheet.

We then conduct a series of idealised calving perturbations, using a range of procedures for generating new calving front locations, and explore the spatial distribution of the total buttressing capacity within each ice shelf. We find that the vast majority of the buttressing is typically generated in ice shelf regions within a few kilometres of the grounding line. Thus, we suggest that a greater area of Antarctica’s ice shelves could be considered passive than previously proposed.

 
 
 

How to cite: Mitcham, T., Gudmundsson, G. H., and Bamber, J. L.: The buttressing capacity of Antarctic ice shelves, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11490, https://doi.org/10.5194/egusphere-egu24-11490, 2024.

EGU24-11541 | ECS | Posters on site | CR2.3

Regime-shifts in ice-shelf melt could trigger irreversible ice loss from the Antarctic Ice Sheet 

Emily Hill, G. Hilmar Gudmundsson, and David Chandler

Changes in ocean conditions surrounding the Antarctic ice sheet, and the impact on melt rates beneath buttressing ice shelves, is one of the largest sources of uncertainty in future ice loss projections. If conditions were to suddenly undergo a regime-shift from cold to warm, melt rates could increase drastically and trigger large and potentially irreversible changes in the interior of the ice sheet. Here, we take an ensemble of ocean-circulation model melt rates as input to an ice-sheet model, to quantify ice loss and the potential for irreversible retreat under such warm conditions. We find that the currently cold-cavity basins of the Filchner-Ronne and Ross ice shelves, in contrast to present-day, could become large contributors to future sea level relevant ice loss. In major basins in West Antarctica, we find high-melt rates can trigger instances of irreversible grounding line retreat, which could only be recovered if arguably unattainable melt rate conditions prevailed over timescales of 100s of years.

How to cite: Hill, E., Gudmundsson, G. H., and Chandler, D.: Regime-shifts in ice-shelf melt could trigger irreversible ice loss from the Antarctic Ice Sheet, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11541, https://doi.org/10.5194/egusphere-egu24-11541, 2024.

EGU24-12071 | ECS | Orals | CR2.3

Monitoring Shear-Zone Weakening in East Antarctic Outlet Glaciers through Differential InSAR Measurements 

Christian Wild, Reinhard Drews, Niklas Neckel, Joohan Lee, Kim Sihyung, Hyangsun Han, Won Sang Lee, Veit Helm, Oliver Marsh, and Wolfgang Rack

The stability of polar ice sheets is governed by the seaward movement of ice streams which is decelerated by resistance originating from lateral shear zones. We explore the impact of crystal-scale anisotropy on effective ice stiffness, with regional-scale consequences on ice dynamics. Using the flexural response of Priestley Glacier to tidal forcing as an experimental framework, we constrain isotropic and anisotropic elastic models of vertical tidal ice-shelf flexure. We find that a five-fold reduction of local ice stiffness within narrow lateral shear-zone best fits DInSAR measurements from Sentinel-1. Our modeling not only reproduces 31 double-differential interferograms but also resolves them into 56 individual maps of vertical displacement during SAR image acquisition. Validated with GPS measurements, the inclusion of effective shear-zone weakening significantly reduces the root-mean-square-error of predicted and observed vertical displacement by 84%, from 0.182 m to 0.03 m. These results highlight the untapped potential of DInSAR imagery for mapping ice anisotropy along the feature-rich Antarctic grounding zone, an essential parameter for advancing current ice-sheet flow models.

How to cite: Wild, C., Drews, R., Neckel, N., Lee, J., Sihyung, K., Han, H., Lee, W. S., Helm, V., Marsh, O., and Rack, W.: Monitoring Shear-Zone Weakening in East Antarctic Outlet Glaciers through Differential InSAR Measurements, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12071, https://doi.org/10.5194/egusphere-egu24-12071, 2024.

EGU24-12332 | Posters on site | CR2.3

Summer speedup at Zachariæ Isstrøm, northeast Greenland 

Shfaqat Abbas Khan, Mathieu Morlighem, Youngmin Choi, Shivani Ehrenfeucht, Eric Rignot, Angelika Humbert, and Javed Hassan

The dynamics of The North East Greenland Ice Stream (NEGIS) are influenced by various factors such as ice thickness, topography, basal conditions, and surface meltwater inputs. The presence of basal lubrication significantly affects NEGIS ice flow by reducing friction at the ice-bed interface. Consequently, alterations in subglacial hydrology and the prevalence of meltwater can result in significant variations in ice stream velocity and mass discharge. In this study, we utilize GPS data from six stations along the main trunk to identify the inland propagation of summer speed-ups, peaking between June and August. Complementing the GPS data, we incorporate ice speed information from mosaics based on ESA Sentinel-1 SAR offset tracking, covering the entire NEGIS. These velocity maps, derived from intensity-tracking of ESA Sentinel-1 data with a 12-day repeat and utilizing the operational interferometric post-processing chain IPP for analysis, reveal substantial acceleration in surface speed from June onwards, followed by a deceleration in August. To simulate the observed summer speed-up, we employ the Ice-sheet and Sea-level System Model (ISSM). Our model results indicate that hydrology is the primary driver of the summer speed-up, leading to changes in speed that extend deep into the interior, reaching over 150 km inland. Understanding the dynamics of NEGIS is essential for predicting its future behavior and potential contributions to sea level rise in a warmer climate with increased meltwater.

How to cite: Khan, S. A., Morlighem, M., Choi, Y., Ehrenfeucht, S., Rignot, E., Humbert, A., and Hassan, J.: Summer speedup at Zachariæ Isstrøm, northeast Greenland, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12332, https://doi.org/10.5194/egusphere-egu24-12332, 2024.

EGU24-12334 | Orals | CR2.3

Observed and modelled meltwater-induced flexure and fracture at a doline on north George VI Ice Shelf, Antarctica 

Alison Banwell, Ian Willis, Laura Stevens, Rebecca Dell, and Douglas MacAyeal

Hundreds of surface lakes are known to form each summer on north George VI Ice Shelf, Antarctic Peninsula. To investigate surface-meltwater induced ice-shelf flexure and fracture, we obtained Global Navigation Satellite System (GNSS) observations and ground-based timelapse photography over north George VI for three melt seasons from November 2019 to November 2022.

In particular, we used these field observations to characterize the flexure and fracture behaviour of a mature doline (i.e. drained lake basin formed in a prior melt season) on north George VI Ice Shelf. The GNSS displacement timeseries shows a downward vertical displacement of the doline centre with respect to the doline rim of ~60 cm in response to loading from the development of a central meltwater lake. Viscous flexure modelling indicates that this vertical displacement generates flexure tensile surface stresses of ~>75 kPa. The GNSS data also show a tens-of-days episode of rapid-onset, exponentially decaying horizontal displacement, where the horizontal distance from the rim of the doline with respect to its centre increases by ~70 cm. We interpret this event as the initiation and/or widening of a single fracture, possibly aided by stress perturbations associated with meltwater loading in the doline basin. This observation, together with our observations of circular fractures around the doline basin in timelapse imagery, suggests the first such documentation of “ring fracture” formation on an ice shelf, equivalent to the type of fracture proposed to be part of the chain reaction lake drainage process involved in the 2002 breakup of Larsen B Ice Shelf.

How to cite: Banwell, A., Willis, I., Stevens, L., Dell, R., and MacAyeal, D.: Observed and modelled meltwater-induced flexure and fracture at a doline on north George VI Ice Shelf, Antarctica, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12334, https://doi.org/10.5194/egusphere-egu24-12334, 2024.

EGU24-12347 | ECS | Posters on site | CR2.3

The effects of including Antarctic subglacial meltwater flux to the ocean in the Energy Exascale Earth System Model 

Carolyn Branecky Begeman, Irena Vaňková, Xylar Asay-Davis, Darin Comeau, Alex Hager, Matthew Hoffman, Matthew Maltrud, Courtney Shafer, and Jonathan Wolfe

Subglacial runoff beneath ice shelves is a source of freshwater, and therefore buoyancy, at the grounding line. Being released at depth, it accelerates an ascending plume along the ice-shelf base, enhancing entrainment of ambient waters, and increasing melt rates. By now it is understood that subglacial runoff is a key control on melt rate variability at the majority of Greenland's glaciers. However, its importance in present-day and future Antarctic melt rates is less clear.

To address this point, we use the Energy Exascale Earth System Model (E3SM) and investigate the effects of Antarctic freshwater volume flux addition in both idealized setups and realistic, global, sea-ice ocean coupled configurations. For realistic Antarctic configurations, we use the subglacial hydrology model from the MALI ice-sheet model with both distributed and channelized drainage run at 4-20 km resolution to calculate steady state subglacial discharge across the grounding line under historical ice-sheet conditions.  This meltwater discharge is implemented as a freshwater flux in MPAS-Ocean, the ocean component of E3SM.

How to cite: Branecky Begeman, C., Vaňková, I., Asay-Davis, X., Comeau, D., Hager, A., Hoffman, M., Maltrud, M., Shafer, C., and Wolfe, J.: The effects of including Antarctic subglacial meltwater flux to the ocean in the Energy Exascale Earth System Model, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12347, https://doi.org/10.5194/egusphere-egu24-12347, 2024.

EGU24-12499 | ECS | Posters on site | CR2.3

Role of buttressing in the dynamic response to Western Antarctic Peninsula ice shelf collapse 

Luisa Wagner, Martin Rückamp, and Johannes Fürst

Ice shelves on the western Antarctic Peninsula have partially or completely disappeared due to widespread thinning and retreat. The loss of floating ice results in a reduction of the buttressing on the upstream grounded ice body. As a consequence, tributary glaciers are accelerating and retreating further, leading to increased ice discharge and, in turn, an increased contribution to sea-level rise. Improving projections of the rate of sea-level rise from the area demands an in-depth understanding of the current mechanisms at play.

In order to gain this, we aim to quantify and characterise the buttressing effect of the ice shelves. To achieve this, we model hypothetical upper-end scenarios by either an immediate complete collapse of all floating ice or a sustained extreme melting. The main focus here is on the stability of the tributary glaciers and the ability of the ice shelf to rebuild itself.

To run the scenarios, we operate ISSM based on surface and basal topography from BedMachine and MEaSURE velocities. A Shallow-Shelf-Approximation with Budd and Weertman sliding laws, Beckmann and Goosse basal forcing parameterisation and von Mises calving is used. To initialise the retreat scenarios, we determine the basal friction coefficient of the grounded area and the ice shelf rheology using a joint inversion technique with regularisation.

How to cite: Wagner, L., Rückamp, M., and Fürst, J.: Role of buttressing in the dynamic response to Western Antarctic Peninsula ice shelf collapse, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12499, https://doi.org/10.5194/egusphere-egu24-12499, 2024.

EGU24-12886 | Posters on site | CR2.3

The Crevasse Depth Calving Law Applied to Ice Shelves: Insights from a 1D Flowline Model  

Faezeh M. Nick and Doug Benn
The crevasse depth (CD) calving law predicts the position of glacier termini from the penetration of surface and basal crevasses computed from stresses in the ice. When applied to Greenland tidewater glaciers, it has high skill when implemented in a full-Stokes 3D model, although its performance in 2D and 1D models is still subject to debate, especially its ability to induce ice shelf calving without the addition of unrealistic amounts of  water in surface crevasses.  This study re-evaluates the CD law within a 1D flowline model of an ice shelf.
 
We show that the model predicts deep crevasse penetration at locations where drag at the shelf boundaries diminishes,such as the grounding line or embayment mouths. Crevasse depth depends on the rate at which these resistance sources decrease along-flow, influencing the longitudinal stress gradient. While full-depth penetration may occur in thinned shelves (due to extensive basal melt), full-depth calving is generally not predicted for unconfined ice shelves. Observations of Antarctic ice shelves and floating ice tongues well beyond embayments or basal pinning points suggest that additional triggers, like slow rift growth, basal melting, or oceanographic stresses, are essential for calving.
 
The addition of water to surface crevasses can greatly facilitate calving. In some cases, reflecting real-world conditions, such as the hydrofracturing-induced collapse of vulnerable ice shelves. However, the need for water-depth tuning in other situations has raised concerns about the physical fidelity of the model. We propose a modified stochastic CD calving criterion in which the probability of calving ramps from zero for a threshold crevasse depth to one for full-depth penetration. This non-deterministic approach captures the statistical structure of calving events, and allows a range of observed behaviours to emerge, such as long Antarctic ice shelf calving cycles (ice-tongue advance punctuated by rare calving events), and short-term fluctuations of tidewater glaciers (frequent calving retreat back to pinning points). We argue that a probabilistic approach represents an important step towards a universal calving law.  

How to cite: M. Nick, F. and Benn, D.: The Crevasse Depth Calving Law Applied to Ice Shelves: Insights from a 1D Flowline Model , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12886, https://doi.org/10.5194/egusphere-egu24-12886, 2024.

EGU24-13188 | ECS | Orals | CR2.3

Circum-Antarctic seasonality in grounded ice flow 

Karla Boxall, Ian Willis, Jan Wuite, Thomas Nagler, Stefan Scheiblauer, and Frazer Christie

Recent advances in high-temporal-resolution satellite imaging has revealed the occurrence of seasonal ice-flow variability in the Antarctic Peninsula for the first time. This newly documented phenomenon provides motivation for identifying the as-yet-unknown ice, ocean and climate interactions responsible for driving the seasonal signals observed across the Antarctic Peninsula, and raises important questions about the possible presence and drivers of seasonality elsewhere in Antarctica. Knowledge of such mechanisms and the extent of seasonality around Antarctica will be important for refining discharge-based ice-sheet mass balance estimations, and for improving predictions of Antarctica’s future response to climate change.

Here, we identify the likely drivers of the recently observed ice-flow seasonality in the western Antarctic Peninsula by carrying out statistical time series analysis using our published Sentinel-1-derived velocity observations (Boxall et al., 2022; doi:10.5194/tc-16-3907-2022) and an array of environmental variables. Our results reveal that both surface and oceanic forcing are statistically significant controls upon ice-flow seasonality in the western Antarctic Peninsula, although each mechanism elicits a unique lag between forcing and the ice-velocity response.

By upscaling our Sentinel-1-derived velocity observations, we also report upon the nature of ice-flow seasonality along Antarctica’s entire coastal margin for the first time and, through additional time series analysis, assess the glacier- to regional-scale importance of surface and ocean forcing upon circum-Antarctic rates of flow.

How to cite: Boxall, K., Willis, I., Wuite, J., Nagler, T., Scheiblauer, S., and Christie, F.: Circum-Antarctic seasonality in grounded ice flow, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13188, https://doi.org/10.5194/egusphere-egu24-13188, 2024.

EGU24-14126 | ECS | Orals | CR2.3

Improved Parameterizations of Ice-Ocean Boundary Layers 

Ken Zhao, Tomas Chor, Eric Skyllingstad, and Jonathan Nash

Glacial melt rates at ice-ocean interfaces are critical to understanding ice-ocean interactions in polar regions and are commonly parameterized as a turbulent shear boundary with a time-invariant drag coefficient. This assumes the exchange of heat and freshwater across the mm-scale diffusive thermal and salinity boundary layers varies proportionally with the strength of external momentum. However, this is only appropriate when melt/buoyancy-driven turbulence and the suppression of turbulence by stratification is weak.

Guided by GPU-accelerated Direct Numerical Simulations (10 micron resolution) of the ice-ocean boundary layer for varying geometric and ocean forcing parameters, I will present an updated understanding of the basic principles of ice-ocean boundary layers as a complex interplay between diffusive freshwater/thermal and viscous shear layers nested within different types of turbulent boundary layers. I will present numerical simulation results that seek to merge the different turbulent ice-ocean boundary layer regimes: (1) meltwater-driven buoyancy, (2) meltwater-driven shear, and (3) externally-driven shear from both horizontal and vertical sources of momentum.

This updated understanding allows us to develop more accurate predictions for the turbulently-constrained momentum, thermal, and freshwater boundary layer thicknesses, which is required to predict the ocean-driven melt rate of ice in polar regions.

How to cite: Zhao, K., Chor, T., Skyllingstad, E., and Nash, J.: Improved Parameterizations of Ice-Ocean Boundary Layers, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14126, https://doi.org/10.5194/egusphere-egu24-14126, 2024.

EGU24-14713 | Posters on site | CR2.3

Multi-sensor approach of monitoring ice-ocean interaction at high resolution at a major ocean-terminating glacier in South Greenland 

Andreas Vieli, Armin Dachauer, Dominik Gräff, Andrea Walter, Brad Lipovsky, Fabian Walter, and Ethan Welty

About half of the current rapid mass loss of the Greenland ice sheet (GIS) is through dynamic processes driven by calving and frontal ablation. However, related insitu observations in such dynamic environments are challenging and our process understanding is therefore still limited. Within the wider context of the GreenFjord-project on Greenland Fjord ecosystem we introduce here a multi-sensor approach for observing process interactions at high spatial and temporal resolution at the ice-ocean boundary of the major ocean-terminating outlet glacier Eqalorutsit Kangillit Sermiat (EKaS) in South Greenland.

Besides multiple all year-round time lapse cameras, broadband seismometers and tidegauges distributed around the glacier terminus and running since summer 2022, we deployed for the first time in summer 2023 a fibre optic cable at the fjord-bed along the calving front and performed continuous distributed acoustic and temperature sensing measurements (DAS and DTS) during more than two weeks. In parallel, we run a terrestrial radar interferometer (TRI) at 1min repeat intervals that recorded high resolution flow-fields as well as calving events (time, size and location). Our comprehensive observational approach is further complemented by local meteo-station data and more than 20 CTD profiles in the fjord near the calving front. In addition, two ocean bottom seismometers together with a simple CTD mooring have been deployed in summer 2023 and are planned to be recovered in the coming summer.

Besides our observational approach, we present here a broad overview and preliminary analysis of this unique observational dataset. We are not only able to record and cross-validate the same processes or events (e. g. calving and ice flow) from multiple sensors, but also clearly extend our observational ability (e. g. detection sensitivity, calving type and size, fjord circulation, spatial and temporal resolution).  We further get more insights into related subglacial and submarine processes such as fjord temperature variations, plume discharge and internal waves in the fjord. Our results thereby contribute to improve our understanding of ice-ocean interaction at a calving front and helps to develop sustainable observational systems of related processes.

How to cite: Vieli, A., Dachauer, A., Gräff, D., Walter, A., Lipovsky, B., Walter, F., and Welty, E.: Multi-sensor approach of monitoring ice-ocean interaction at high resolution at a major ocean-terminating glacier in South Greenland, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14713, https://doi.org/10.5194/egusphere-egu24-14713, 2024.

EGU24-15935 | ECS | Posters on site | CR2.3

Modelling Ryder Glacier in Northern Greenland until 2100 under various emissions scenarios; Under which circumstances is the ice tongue lost? 

Felicity Holmes, Jamie Barnett, Henning Åkesson, Johan Nilsson, Nina Kirchner, and Martin Jakobsson

The Greenland Ice Sheet is currently the largest single contributor to global sea level rise, with recent decades having been characterised by an acceleration of mass loss. The Northern sector of the Greenland Ice Sheet has been relatively understudied, but is also the sector containing several of the last remaining ice tongues in Greenland. If these floating ice tongues are lost, the associated reduction in buttressing has the potential to lead to large increases in velocities and mass loss. One such glacier is Ryder glacier which, in contrast to the nearby Petermann glacier, has been reasonably stable in recent decades. As such, this glacier was targeted during the Ryder 2019 expedition with Swedish Icebreaker Oden, leading to a wealth of data on its present-day setting and Holocene history. In conjunction with this observational data, the numerical Ice Sheet and Sea Level System Model (ISSM) is used to investigate both the controls on glacier behaviour since 1900 and the likely trajectory of Ryder glacier towards 2100 under different emissions scenarios. The key focus is on understanding under which circumstances Ryder glacier may lose its ice tongue and what the impacts of this are likely to be in terms of glacier dynamics and sea level rise contribution.

How to cite: Holmes, F., Barnett, J., Åkesson, H., Nilsson, J., Kirchner, N., and Jakobsson, M.: Modelling Ryder Glacier in Northern Greenland until 2100 under various emissions scenarios; Under which circumstances is the ice tongue lost?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15935, https://doi.org/10.5194/egusphere-egu24-15935, 2024.

EGU24-15939 | ECS | Posters on site | CR2.3

Modelling the evolution of Ryder Glacier, Greenland, through the Holocene to investigate its responses to marine and atmospheric forcings. 

Jamie Barnett, Felicity Holmes, Henning Åkesson, Johan Nilsson, Nina Kirchner, and Martin Jakobsson

Coupling paleo numerical simulations of the Greenland Ice Sheet with physical geological evidence of past ice sheet extent can greatly improve our understanding of the factors driving ice loss. Geological observations can be used to reconstruct the state of the Greenland Ice Sheet at snap shots in time, thus acting as constraints to test the fidelity of ice sheet models that can tell a continuous story of retreat over the same geologic timescales. Swedish Ice Breaker Oden’s visit to Sherard Osborn Fjord and Ryder Glacier in 2019 collected a plethora of marine-geological data that describes the glacier’s behaviour and retreat during the Holocene. Here we use a 3D thermo-coupled Higher-Order ice flow module incorporated in the Ice-sheet and Sea-level System Model (ISSM) to simulate the dynamics of Ryder Glacier from 12500 ka to present day. By focusing on a specific individual glacier, we can run the model at resolutions <1km near the grounding line to shed light on the marine (calving and submarine melt) and atmospheric factors that potentially drove Ryder’s retreat from its Younger Dryas position. Of particular interest is understanding whether the glacier withdrew from its marine setting during the Holocene Thermal Maximum and what conditions were required for Ryder to regrow its modern-day ice tongue during the neoglacial cooling at the end of the Holocene.

How to cite: Barnett, J., Holmes, F., Åkesson, H., Nilsson, J., Kirchner, N., and Jakobsson, M.: Modelling the evolution of Ryder Glacier, Greenland, through the Holocene to investigate its responses to marine and atmospheric forcings., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15939, https://doi.org/10.5194/egusphere-egu24-15939, 2024.

EGU24-16868 | ECS | Posters on site | CR2.3

Large-scale and High-resolution Frontal Ablation Estimates in the Arctic through a Machine Learning Approach 

Dakota Pyles, Nora Gourmelon, Vincent Christlein, and Thorsten Seehaus

Frontal ablation is an important component of tidewater glacier mass loss, however, high temporal resolution estimates have remained elusive due to difficulty in reliably capturing terminus position changes with satellite imagery. Recent developments in machine learning-based radar image segmentation to automatically delineate glacier fronts has opened an opportunity to calculate frontal ablation over fine timescales. Through segmentation of Sentinel-1 synthetic aperture radar image sequences, we aim to quantify seasonal and annual frontal ablation across several Arctic regions, using a deep learning-based terminus segmentation algorithm. Svalbard, an Arctic region characterized by variable and complex glacier and fjord geometries, will serve as a methodological test site before expanding the scope to the Canadian Arctic, Greenland periphery, and Russian Arctic, or ~1400-1500 marine-terminating glaciers in the Northern Hemisphere. The derived frontal ablation information is valuable to climate and glacier models, which could benefit from high-resolution reference data, resulting in improved calibrations and parameterizations. Future project efforts will include quantifying total mass budget for all glaciers in the study by integrating frontal changes, ice discharge calculations from ice thickness and surface velocity products, and climatic mass balance data. To identify and evaluate external drivers of glacier change, the frontal ablation and mass balance products will be combined with modeled and observational atmospheric, oceanic, and sea ice data. Through multivariate statistical analyses between these Earth system datasets and mass balance components, we look to provide an improved understanding of dynamic tidewater glacier processes, their spatio-temporal variability, and the influence of glacier geometry on observed changes throughout the Arctic.

How to cite: Pyles, D., Gourmelon, N., Christlein, V., and Seehaus, T.: Large-scale and High-resolution Frontal Ablation Estimates in the Arctic through a Machine Learning Approach, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16868, https://doi.org/10.5194/egusphere-egu24-16868, 2024.

EGU24-17109 | ECS | Posters on site | CR2.3

Ice- Ocean- Atmosphere Interactions in the Arctic: Glaciers and Ice Caps 

Morag Fotheringham, Noel Gourmelen, Michel Tsamados, and Donald Slater

Arctic glaciers and ice caps are currently major contributors to global sea level rise, with future projections showing a sustained input. The monitoring of these smaller land-ice masses is challenging due to the high temporal and spatial resolution required.

These glaciers and ice caps are losing mass in response to climate forcings, both atmospheric and oceanic. The relative significance of these forcings is currently unknown with most recent catagorisation focusing on separating loss caused by internal dynamics vs surface mass balance changes.

This leaves the specific roles of the atmosphere and the ocean unconstrained; this understanding is key to improving the accuracy of future loss of ice from these smaller land-ice masses and future sea level rise projections.

This study uses CryoSAT-2 swath interferometric radar altimetry to provide high spatial and temporal observations to produce elevation timeseries in order to evaluate the trends of mass loss. It also utilises an ocean thermal model, previously used to study Greenland's outlet glaciers, to gain a better understanding of the relative contributions of atmospheric and ocean forcings to this mass loss.

How to cite: Fotheringham, M., Gourmelen, N., Tsamados, M., and Slater, D.: Ice- Ocean- Atmosphere Interactions in the Arctic: Glaciers and Ice Caps, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17109, https://doi.org/10.5194/egusphere-egu24-17109, 2024.

EGU24-17177 | ECS | Posters on site | CR2.3

Testing a PICO quadratic sub-shelf basal melt module in the GRISLI ice sheet model 

Maxence Menthon, Pepijn Bakker, Aurélien Quiquet, and Didier Roche

The Antarctic ice sheet dynamics is primarily driven by basal melting under the ice shelves. The limitation of computational resources forces the usage of simplified parametrizations in ice-sheet models. Multiple parametrizations have been developed and implemented over the last years (Reese et al. 2018, Lazeroms et al. 2018, Pelle et al. 2019, Jourdain et al. 2020, etc.). The PICO module (Reese et al. 2018) demonstrates to be a good trade-off between complexity and computational resources for paleo ice-sheet reconstructions. Lately, Burgard et al. 2022 suggested that the implementation of a quadratic version of the PICO module could improve it significantly.

Here we test the implementation of the PICO module with a quadratic relationship between the thermal forcing and the melt in the GRISLI ice sheet model. We test a wide range of parameter values to calibrate the module, we compare the quadratic version of the module with the original version, under 2 different resolutions. Eventually, we show the results of simulations on paleo and future applications.

How to cite: Menthon, M., Bakker, P., Quiquet, A., and Roche, D.: Testing a PICO quadratic sub-shelf basal melt module in the GRISLI ice sheet model, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17177, https://doi.org/10.5194/egusphere-egu24-17177, 2024.

EGU24-17297 | Orals | CR2.3

Geometric amplification and suppression of ice-shelf basal melt in West Antarctica 

Jan De Rydt and Kaitlin Naughten

Ice shelves along the Amundsen Sea coastline in West Antarctica are continuing to thin, albeit at a decelerating rate, whilst ice discharge across the grounding lines has been observed to increase by up to 100% since the early 1990s. Here, the ongoing and future evolution of ice-shelf mass balance components (basal melt, grounding line flux, calving flux) is assessed in a high-resolution coupled ice-ocean model that includes the Pine Island, Thwaites, Crosson and Dotson ice shelves. For a range of idealized ocean-forcing scenarios, the combined evolution of ice-shelf geometry and basal melt rates is simulated over a 200-year period. For all ice-shelf cavities, a reconfiguration of the 3D ocean circulation in response to changes in cavity geometry is found to cause significant and sustained changes in basal melt rate, ranging from a 75% decrease up to a 75% increase near the grounding lines, irrespective of the far-field ocean conditions. These poorly explored feedbacks between changes in ice-shelf geometry, ocean circulation and basal melting have a demonstrable impact on the net ice-shelf mass balance, including grounding line discharge, at multidecadal timescales. They should be considered in future projections of Antarctic mass loss, alongside changes in ice-shelf melt due to anthropogenic trends in the ocean temperature and salinity.

How to cite: De Rydt, J. and Naughten, K.: Geometric amplification and suppression of ice-shelf basal melt in West Antarctica, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17297, https://doi.org/10.5194/egusphere-egu24-17297, 2024.

EGU24-17302 | ECS | Posters on site | CR2.3

Modelling ocean melt of ice mélange at Greenland's marine-terminating glaciers 

Lokesh Jain, Donald Slater, and Peter Nienow

Greenland’s marine-terminating glaciers have retreated and accelerated in recent decades, contributing significantly to sea level rise. An increase in ocean temperatures, and in particular the increased submarine melting of calving fronts, is often cited as the dominant driver of this retreat. However, the presence of ice mélange and its associated buttressing force on a glacier terminus also has a substantial impact on glacier advance and retreat. The buttressing force theoretically depends on the mélange thickness, and thickness will be modulated by ocean melt rate, but our understanding of mélange melting remains limited, and it is not yet known how melt rates vary across a range of glacial and environmental conditions.

Here, we perform high-resolution numerical simulations using MITgcm to model the melting of ice mélange. In order to map out the parameter space for mélange melting at Greenland’s marine-terminating glaciers, we vary each of the ocean temperature, ocean stratification, the flux of freshwater emerging from beneath the glacier (subglacial discharge) and the mélange geometry. We study how each factor affects the magnitude and distribution of ocean melt of the ice mélange and seek a parameterisation that would allow us to simply predict mélange melt rate. Furthermore, this work is also a step towards including iceberg melting in larger climate and ice sheet models which is important because of the need to improve the characterisation of freshwater fluxes into fjord systems.

How to cite: Jain, L., Slater, D., and Nienow, P.: Modelling ocean melt of ice mélange at Greenland's marine-terminating glaciers, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17302, https://doi.org/10.5194/egusphere-egu24-17302, 2024.

EGU24-17430 | Posters on site | CR2.3

The changes of basal conditions on Fleming Glacier, Antarctic Peninsula, between 2008 and 2021 

Yuting Dong, Huimin Liu, Angelika Humbert, Ji Zhao, Dana Floricioiu, Lukas Krieger, Michael Wolovick, Thomas Kleiner, and Lea-Sophie Höyns

The Wordie Ice Shelf (WIS) in the Antarctic Peninsula (AP) has continued to retreat since 1966, and it almost completely disintegrated in the late 1990s. Although the main supply glacier of the WIS, the Fleming Glacier (FG), did not respond immediately, increases in the glacier velocity and dynamic thinning have been observed over the past two decades, especially after 2008 when only a small ice shelf remained at the Fleming Glacier front. As FG is now the fastest flowing outlet glaciers in the west Antarctic Peninsula, ice dynamics is the primary cause of mass loss. Basal sliding is the key mechanism for glacier acceleration and as it responds to thinning and changes in basal conditions. Furthermore, changes in ice-ocean interaction, such as changes in buttressing of ice streams and outlet glaciers like Fleming Glacier, are also leading to acceleration.

Here, we use the Shallow Shelf Approximation (SSA) implementation of the Ice-sheet and Sea-level System Model (ISSM) simulating the basal shear stress distribution of FG in the years 2008, 2011, 2014, 2017, 2019 and 2021 using inverse modelling. To better regularize the glaciological inverse problem, we adopt the latest published L-curve analysis to select the optimal regularization level. Considering Fleming Glacier has a relatively small drainage basin, high resolution geometric data is necessary to obtain better constrained information of the basal conditions. We use TanDEM-X DEMs acquired in austral winter of 2011, 2014, 2017, 2019, and 2021 to provide accurate glacier surface elevations. These DEMs were generated from bi-static InSAR data acquired by the TanDEM-X mission and are with the most complete time series and the best quality that can be obtained in this area at present.  We evaluate the existing ice velocity products and performed a spatio-temporal interpolation to obtain the average velocity of the year corresponding to the elevation data. We use the higher Antarctic ice sheet surface mass balance data RACM2.3p2 at 2 km resolution as a boundary condition. Regarding the bedrock topography, one of the main factors restricting the inversion accuracy, we evaluated all the existing subglacial topography data products within our inversions. To more accurately represent friction at the bed, we also tested Budd’s, Weertman’s and Schoof’s sliding laws, with different friction exponents and variable geometric data.

Comparison of simulated basal shear stresses for 2008 and 2021 suggests the migration of the grounding line 8~9 km upstream by 2021 from the 2008 ice front/grounding line positions. This migration is consistent with the change in floating areas deduced from the calculated height above buoyancy. Our results indicate that the reducing basal shear stress may be directly related to the subglacial hydrologic system and lead to rapid increases in basal sliding and ongoing ungrounding. It will further promote the dynamic loss of glaciers when coupled with ocean forcing and retrograde bedrock. 

How to cite: Dong, Y., Liu, H., Humbert, A., Zhao, J., Floricioiu, D., Krieger, L., Wolovick, M., Kleiner, T., and Höyns, L.-S.: The changes of basal conditions on Fleming Glacier, Antarctic Peninsula, between 2008 and 2021, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17430, https://doi.org/10.5194/egusphere-egu24-17430, 2024.

EGU24-17929 | ECS | Orals | CR2.3

The relative importance of subglacial discharge and iceberg melt forcing in Greenlandic glacial fjord circulation 

Eleanor Johnstone, Donald Slater, Tom Cowton, Neil Fraser, Mark Inall, and Martim Mas e Braga

Glacial fjords form a crucial coupling between the Greenland ice sheet and the surrounding ocean, but observational data is scarce and their complex multi-scale physics can be difficult to model. Thus, glacial fjord processes are often excluded from large-scale ice sheet models that project  sea level contribution and ocean models that are forced by ice sheet freshwater. A key driver of fjord dynamics is the input of ice sheet freshwater, primarily from subglacial discharge rising in a buoyant plume and from iceberg melt. These freshwater sources set up a density gradient between the fjord and shelf, driving fjord circulation and exporting freshwater to the ocean. Observational evidence from a few fjords suggests that fjords can store this freshwater, leading to an export to the shelf that is modified in properties and lagged in time compared to the input of the freshwater to the fjord. Yet little is known about how this freshwater modification varies across Greenland’s diverse fjords, and the relative importance of the sources of freshwater in this process has not been quantified.  

Here, we use a two-layer box model to simulate fjord dynamics in a simple yet realistic way. We isolate the circulation driven by freshwater input from each of subglacial discharge and iceberg melting to assess the relative impact of each process on (i) strength of circulation and (ii) modification and export of freshwater. The model suggests that fjord geometry and the strength of the fjord-shelf exchange are the key controllers of the lag time for freshwater export, with strong fjord-shelf exchange and smaller fjords promoting nearly instant freshwater export, and weak fjord-shelf exchange and large fjords giving long lags in freshwater export. The wider aims of the project are to quantify freshwater export and heat import at glacial fjords on a Greenland-wide scale.

How to cite: Johnstone, E., Slater, D., Cowton, T., Fraser, N., Inall, M., and Mas e Braga, M.: The relative importance of subglacial discharge and iceberg melt forcing in Greenlandic glacial fjord circulation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17929, https://doi.org/10.5194/egusphere-egu24-17929, 2024.

EGU24-18382 | ECS | Posters on site | CR2.3

An attempt to capture diverse tidewater glacier calving styles within a single framework 

Donald Slater, Doug Benn, and Till Wagner

The complexity of the processes and the difficulty of collecting observations mean that the treatment of the ice-ocean boundary remains one of the most challenging aspects of running models of the Greenland ice sheet. With geometry, climate forcing, ice properties and feedbacks between these factors all playing a role, tidewater glaciers display a range of calving styles that are hard to capture within the simple parameterisations that are necessary for large-scale ice sheet modeling.

Here we attempt to place some dominant calving styles within a single framework. We study submarine melt undercut-driven calving using linear elastic fracture mechanics within 2D elastic simulations, together with analytical approaches to calving driven by the intersection of basal and surface crevasses and to ice cliff failure. Taken together, these approaches give a prediction of calving style as a function of the calving front ice thickness, ocean depth and submarine melt undercut length, or equivalently as a function of the frontal tension, bending moment and shear. We discuss possible implementations in ice sheet models.

How to cite: Slater, D., Benn, D., and Wagner, T.: An attempt to capture diverse tidewater glacier calving styles within a single framework, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18382, https://doi.org/10.5194/egusphere-egu24-18382, 2024.

The marine-terminating glaciers in Svalbard are retreating and losing mass at an alarming rate due to the rapidly warming climate. And glacier calving is one of the most important process contributing to the glacier mass loss. Hence, it is very important to observe the glacier termini to understand calving variability and the influence of local environmental conditions on them.

Here, high frequency time-lapse images have been used to observe the calving front of Hansbreen (a tidewater glacier in the Honrsund fjord, Svalbard) at a 15-minute interval. The time-lapse images have been visually analyzed from April 2016 to October 2016, to observe the calving variability. The calving events are identified and then classified based on several parameters. The environmental parameters like air temperature, sea surface temperature, tidal cycle, water salinity, etc, for the same region have been understood to see if they have any influence spatial and temporal distribution of the observed calving events. [This research has been supported by the National Science Centre, Poland (grant no. 2021/43/D/ST10/00616) and the Ministry of Education and Science, Poland (subsidy for the Institute of Geophysics, Polish Academy of Sciences).]

How to cite: Maniktala, D. and Glowacki, O.: Studying the influence of environmental parameters on calving variability at Hansbreen, in Svalbard, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18558, https://doi.org/10.5194/egusphere-egu24-18558, 2024.

EGU24-18561 | ECS | Orals | CR2.3

Simulating cracks in glacier ice by means of the phase field method 

Rabea Sondershaus, Angelika Humbert, and Ralf Müller

Calving is still a poorly understood process, hence a physically based calving law has not yet been found. Large ice sheet models are using simplified parameterisations to describe calving, which are tuned by observational data. Therefore the demands for the development of physically based models for calving are large.

Calving is facilitated by fracture formation and propagation, which description is the objective of fracture mechanics. Based on the fundamental theory for fracture proposed by Griffith a numerical approach has been developed to describe cracks: the so-called phase field method. This method represents the state of a material, whether it is intact or broken, by means of an additional continuous scalar field. The advantage of the phase field method is its simple numerical implementation and the avoidance of explicit representation of crack faces as well as costly remeshing.

This work adjust the phase field method for fracture to simulate fracture in glacier ice. Thereby the ice rheology is considered by using a viscoelastic material description where a nonlinear viscosity, based on Glen’s flow law, is taken into account. Furthermore finite strain theory is used to capture the large deformations occurring in ice shelves and floating glacier tongues.

The developed theoretical framework is utilized to simulate crack initiation and propagation at ice rises. Here the calving front geometry of the 79N Glacier in Greenland is used to validate the proposed model by comparing the simulated crack paths to satellite imagery.

How to cite: Sondershaus, R., Humbert, A., and Müller, R.: Simulating cracks in glacier ice by means of the phase field method, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18561, https://doi.org/10.5194/egusphere-egu24-18561, 2024.

EGU24-19514 | ECS | Orals | CR2.3

Stability of radially spreading extensional flows and ice shelves 

Lielle Stern and Roiy Sayag

Ice shelves that spread into the ocean can develop rifts, which can trigger ice-berg calving and enhance ocean-induced melting. Fluid mechanically, this system is analogous to the radial propagation of a non-Newtonian, strain-rate-softening fluid representing ice that displaces a relatively inviscid and denser fluid that represents an ocean. Laboratory experiments showed that rift patterns can emerge in such systems and that the number of rifts declines in time. Such a dynamics was confirmed theoretically, but only for the earlier stage of the flow and for a fluid layer of uniform thickness. We investigate numerically the stability and late-time evolution of radially spreading, axisymmetric fluid layer of non-uniform thickness. We validate the two dimensional finite-element Úa model using similarity solutions of radially spreading layers of Newtonian fluid that were found consistent with laboratory experiments. We then explore the stability of the flow by introducing geometric perturbations to the initial front and tracing their evolution. Our simulations show that the front of Newtonian fluids is stable, though memory of the perturbation spectral form persists.

How to cite: Stern, L. and Sayag, R.: Stability of radially spreading extensional flows and ice shelves, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19514, https://doi.org/10.5194/egusphere-egu24-19514, 2024.

EGU24-22433 | Orals | CR2.3

Grounding line migration at Orville Coast, Ronne Ice Shelf, West Antarctica, based on long interferometric Sentinel-1 time series 

Michał Tympalski, Marek Sompolski, Anna Kopeć, and Wojciech Milczarek

Determining the grounding lines of ice shelf glaciers (the border at which the ice begins to float in the ocean) is obligatory in precise measuring and understanding of ice sheet mass balance and glacier dynamics. Awareness of its migration range (grounding zone) is also crucial when estimating the impact of glacier/ice sheet waters on the ocean water level. Currently, the most precise large-scale method is based on the viscoelastic tidal movement of the ice shelf identified on a 4-pass DInSAR results. In some places, however, the measurements are impossible or significantly difficult due to the decorrelation between scenes. According to our preliminary results, it may be possible to use unwrapped phase interferograms as a new/supportive method for detecting ground lines. Combined with algorithms for automatic delineation, it can become a powerful solution for obtaining results with unprecedented frequency.


The latest results revealed that for many glaciers the grounding zone width is two orders of magnitude larger than expected. This contradicts existing physical models, which are based on zero ice melt and fixed grounding line position. Irregular interactions between ice and seawater might have a strong impact on glacier evolution and projections if implemented in physical models. We employed a long-time series of Sentinel-1 differential radar interferometry from 2017 to 2021 to detect the variability in grounding line position on Orville Coast, the region of the western Ronne Ice Shelf. The research carried out over a long period and with high frequency allowed a more detailed study of changes occurring in the grounding zone. Observation from a broader perspective gave us the opportunity to detect seasonality and a persistent trend. We compared changes in grounding line migration with external factors e.g. ocean tides. This might provide a better understanding of the behavior of the ice sheet and glaciers, which are currently undergoing such rapid changes.

How to cite: Tympalski, M., Sompolski, M., Kopeć, A., and Milczarek, W.: Grounding line migration at Orville Coast, Ronne Ice Shelf, West Antarctica, based on long interferometric Sentinel-1 time series, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-22433, https://doi.org/10.5194/egusphere-egu24-22433, 2024.

EGU24-1052 | ECS | Orals | CR2.4

Modelling the evolution of the weathering crust 

Tilly Woods and Ian Hewitt

The weathering crust is a porous layer of ice found at an ice sheet surface, formed by shortwave radiation penetrating below the surface and causing internal melting. It is a dynamic hydrological system that acts to transport meltwater, impurities, and microbes across the ice sheet surface into larger-scale hydrological features such as surface streams. The weathering crust is very variable, growing and decaying on the order of hours and days in response to changing weather conditions, with consequences for the surface albedo as well as meltwater storage and transport. The albedo is impacted both by the weathering crust structure and the presence of microbes and impurities (for example in the south-western Greenland ‘dark zone’). We have developed two mathematical models to investigate the evolution of the weathering crust and microbes over space and time: a one-dimensional model for the vertical structure, and a depth-integrated model to explore the lateral extent of the weathering crust and transport of meltwater. We present solutions generated by idealised forcings as well as observations from the field. This explains the observed response of the weathering crust to short-term changes in weather, and provides insight into the longer-term response of the weathering crust and algal blooms to climate change.

How to cite: Woods, T. and Hewitt, I.: Modelling the evolution of the weathering crust, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1052, https://doi.org/10.5194/egusphere-egu24-1052, 2024.

EGU24-1076 | ECS | Posters on site | CR2.4

Distribution and Morphometry of Large Supraglacial Channels on Five Antarctic Ice Shelves 

Jiao Chen, Rebecca Hodge, Stewart Jamieson, and Chris Stokes

Supraglacial channels play a crucial role in glacial hydrology by transporting meltwater across ice sheets and ice shelves. Despite their importance, recent research has tended to focus on the storage of supraglacial meltwater (e.g., in lakes), and our understanding of the distribution and connectivity of channels is more limited, particularly in Antarctica. Here we investigate large supraglacial channels (i.e., width > 20 m) on five contrasting ice shelves in Antarctica during the melt seasons of 2020 and 2022. Supraglacial channels are mapped by applying an automated delineation method to Landsat-8 satellite imagery, and various metrics are calculated to comprehensively describe their fluvial morphometry. Results show that supraglacial channels are extensive on all five ice shelves, forming a total of 119 channel networks with significantly different drainage patterns. Channel networks exhibit relatively simple structures but large in extent and occur on low ice surface slopes (<0.001) and low elevations (< 70 m) where ice is slow-flowing (<150 m a-1). The orientation of channels broadly coincides with the ice flow direction, and they are clearly influenced by surface flow structures (e.g., longitudinal flow-stripes), which appear to exert a clear control on both channel formation and their morphological properties. Future research will focus on temporal (i.e., seasonal and interannual) analysis of channels on each ice shelf by using Sentinel-2 imagery.

How to cite: Chen, J., Hodge, R., Jamieson, S., and Stokes, C.: Distribution and Morphometry of Large Supraglacial Channels on Five Antarctic Ice Shelves, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1076, https://doi.org/10.5194/egusphere-egu24-1076, 2024.

EGU24-1570 | ECS | Orals | CR2.4

Subglacial lake detection in Dronning Maud Land, East Antarctica using ICESat-2 

Jennifer Arthur, Jelte van Oostveen, Calvin Shackleton, Geir Moholdt, and Kenichi Matsuoka

Subglacial lakes beneath the Antarctic Ice Sheet are known to influence ice-sheet dynamics and form part of an extensive active hydrological network. Ice surface elevation anomalies from repeat-track altimetry can be useful for detecting subglacial lakes and the evolution of subglacial water transport towards sub-ice-shelf cavities. Here, we analyse a 5-year time series of laser altimetry data from the ICESat-2 satellite to investigate potential subglacial lake activity in the coastal Dronning Maud Land region of East Antarctica. Our results reveal ice surface uplift and subsidence events which we interpret to reflect the active draining and filling of subglacial lakes over annual timescales. We find lake locations to be topographically-controlled and coincide spatially with predicted subglacial water routing pathways. Our results highlight subglacial lake activity as close as 10 km from the grounding line in a region of East Antarctica where no subglacial water has been observed in the coastal zone previously. These findings bring knowledge of the dynamics and evolution of subglacial meltwater in this region and provide new observational data to refine subglacial hydrological model estimates of water flux towards ice-shelf grounding zones.

How to cite: Arthur, J., van Oostveen, J., Shackleton, C., Moholdt, G., and Matsuoka, K.: Subglacial lake detection in Dronning Maud Land, East Antarctica using ICESat-2, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1570, https://doi.org/10.5194/egusphere-egu24-1570, 2024.

EGU24-1655 | ECS | Posters on site | CR2.4

Assessing the distribution and characteristics of supraglacial channels in an Alpine setting 

Holly Wytiahlowsky, Chris Stokes, Rebecca Hodge, Caroline Clason, and Stewart Jamieson

Supraglacial channels are an increasingly common glaciological feature due to intensifying surface melt and form a key component of glacier hydrology and mass balance, transporting meltwater to englacial, subglacial, and peripheral positions. Whilst their occurrence is becoming increasingly well-documented on ice sheets, little is known about the distribution of channels on mountain glaciers, which often fall below the resolution of commercial satellites. Using high-resolution orthophoto imagery (~10 cm) and digital elevation models (~0.5 m), we provide the first inventory of supraglacial channels in an alpine environment, focusing on Valais Canton, Switzerland. We manually delineated 1890 channel segments on 85 glaciers, recording glacier characteristics across all 207 snow-free glaciers >0.1 km2 in Valais Canton, encompassing glaciers of differing debris-cover, altitude, and slope. We find that channel segments have a mean length of 212 m and a slope of 8°, with most channels exhibiting low sinuosity (mean: 1.1) and those with higher sinuosity (max: 3.8) only existing on very low surface slopes (<5°). Glaciers containing supraglacial streams have a mean area of 5.0 km2, with a mean drainage density of 1.0 km/km2 (max: 11.0 km/km2) and are likely to extend to lower elevations (mean: 2797 m.a.s.l). Conversely, glaciers without streams are smaller, with a mean area of 0.6 km2, and have a higher minimum elevation (mean: 2945 m.a.s.l). Our observations suggest that the highest drainage densities are found on glaciers characterised by low surface slopes, large ablation areas, low crevasse densities, and limited debris cover. Additionally, stream sinuosity and length appear to be controlled by glacier structure (i.e., crevasses and moulins), slope, and debris content. Our future work will expand on these results using field-based investigations to directly measure channel characteristics and improve estimates of the proportion of meltwater transported as supraglacial run-off versus that entering en- and sub-glacial pathways.

How to cite: Wytiahlowsky, H., Stokes, C., Hodge, R., Clason, C., and Jamieson, S.: Assessing the distribution and characteristics of supraglacial channels in an Alpine setting, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1655, https://doi.org/10.5194/egusphere-egu24-1655, 2024.

EGU24-2035 | ECS | Orals | CR2.4

A parameterization for the closure rate of canals incised in subglacial till 

Simon Jung, Mauro A. Werder, Anders Damsgaard, and Daniel Farinotti

Many of Antarctica’s ice streams reside on deformable beds. The description of their basal
conditions is a major source of uncertainty in modeling studies attempting to predict their
response to a changing climate. The mechanics at the glacier bed, often divided into glacier
sliding and deformation of the subglacial sediments (so-called till), depend on the subglacial
water pressure and thus on the subglacial drainage. To understand the drainage system at
the ice-till interface, past works modeled the stability of channels incised in the till (so-called
canals). Such canals open due to erosion by water flow and close due to till creep and fluvial
deposition. Till rheology is a central point of discussion in these models.
The original description by Walder and Fowler (1994) of canals assumed a viscous rheology of
the subglacial till. Lab and field experiments show the subglacial till to be better described by
a plastic rheology. A recent study by one of the co-authors of this contribution implemented a
plastic rheology and showed that this leads to plastic behaviour of the canals’ closure, such as
rapid canal collapse when their size is too large for prevailing effective pressure.
In this contribution, we extend this latter model to parameterize the effect of till deformation
induced by glacier sliding on canal dynamics. Our results show the glacier sliding to drive
canal closure at all effective pressures. We describe this process with a closure rate that scales
linearly with the basal sliding velocity and is increasing non-linearly with both the effective
pressure and the canals size.
By controlling the canals’ closure, basal sliding thus impacts the drainage capacity, and in
turn, the subglacial water pressure. Thus the positive relation between the basal sliding speed
and canal closure could potentially be a mechanism leading to high sliding speeds, such as
found in ice streams.

How to cite: Jung, S., Werder, M. A., Damsgaard, A., and Farinotti, D.: A parameterization for the closure rate of canals incised in subglacial till, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2035, https://doi.org/10.5194/egusphere-egu24-2035, 2024.

Supraglacial lakes are dynamic hydrological features that play a significant role in surface mass balance estimations. These lakes act as conduits for surface and subglacial runoff, the amount of which varies quite strongly based on the local surface temperature, rainfall, and snowpack thickness. Additionally, supraglacial lakes tend to undergo impactful events called rapid drainages, during which a crack opens at the lake bed, draining the meltwater to the glacier bed within hours or days. Not only does this contribute to glacier mass loss and freshwater influx into the ocean, but it can also cause temporary glacier speed-ups due to the reduction of friction on the glacier bed. Currently, the influencing factors involved in triggering these rapid drainages are minimally understood. This research firstly focuses on the comparison of several lake depth estimation methods in order to be able to accurately monitor seasonal lake development and quantify meltwater volumes. Secondly, the temporal and spatial variances in rapid drainages in Northeast Greenland, specifically over Zachariae Isstrom and Nioghalvfjerdsfjorden (79N Glacier), are evaluated in order to understand underlying causes and to quantify the amount of meltwater lost through them. 

Several established and novel supraglacial lake depth estimation methods are evaluated in this research, comprising of (1) a radiative transfer model based on Sentinel-2 data, (2) an empirical equation derived from ICESat-2 lake crossings and Sentinel-2 data, (3) an empirical equation derived from in situ sonar data gathered in Northeast Greenland and Sentinel-2 data, and (4) TanDEM-X elevation data. These four methods are directly compared on five supraglacial lakes in Northeast Greenland, highlighting the advantages and limitations of each method. Furthermore, the three methods based on Sentinel-2 imagery are applied to the peak melt dates in Northeast Greenland over the 2016 to 2022 melt seasons to understand seasonal variations. Finally, individual lakes are tracked throughout the seven melt seasons to allow for a detailed assessment of rapid drainage occurrences in the region. Overall, insight into the behavioral patterns and influencing factors involved with the rapid drainages of supraglacial lakes and the amount of meltwater lost from them has been gained. 

How to cite: Lutz, K., Sommer, C., Humbert, A., and Braun, M.: Evaluation of supraglacial lake depth estimation techniques using Sentinel-2, ICESat-2, TanDEM-X, and in situ data, along with an analysis of rapid drainage events over Northeast Greenland, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2115, https://doi.org/10.5194/egusphere-egu24-2115, 2024.

EGU24-6372 | ECS | Orals | CR2.4

Intercomparison of melt observed by ASCAT and modeled by Greenland Regional Climate Models 

Anna Puggaard, Nicolaj Hansen, Ruth Mottram, Thomas Nagler, Stefan Scheiblauer, Sebastian B. Simonsen, Louise S. Sørensen, and Anne M. Solgaard

Since the early 1990s, a decrease in the surface mass balance has contributed to about half of the observed Greenland Ice Sheet mass loss. Since surface melt is the primary driver of surface mass loss, an accurate representation of surface melt is crucial for understanding the surface mass balance and, ultimately, the total contribution to rising sea levels. Although Regional Climate Models (RCMs) can simulate ice-sheet-wide melt volume, significant variability exists among state-of-the-art RCMs, underpinning the need for validation of the melt. Here, we explore a novel processing of Advanced SCATterometer (ASCAT) data, which provides estimates of the spatiotemporal variability of melt extent across the Greenland Ice Sheet. We apply these new maps to pinpoint differences in the melt products from three RCMs. Using Programme for Monitoring of the Greenland Ice Sheet & Greenland Climate Network (PROMICE GC-net) air temperature observations, we evaluate how well RCM-modeled melt volume aligns with temperature measurements. With this evaluation, we establish thresholds for the RCMs to identify the amount of meltwater before it is observed at the AWS stations, thus allowing us to infer melt extent in RCMs. Results show that applying thresholds, informed by in-situ measurement, reduces the differences between ASCAT and RCMs and minimizes the discrepancies among RCMs. We leverage the differences between modeled melt extent and ASCAT-observed melt extent to further pinpoint (i) limitations in ASCAT's melt detection, including misclassification in the ablation zone as well as a temporal melt onset bias, and (ii) biases inherent in RCMs, including variability in albedo schemes, snow layer thickness, and temperature and radiation biases in the boundary forcing.

How to cite: Puggaard, A., Hansen, N., Mottram, R., Nagler, T., Scheiblauer, S., Simonsen, S. B., Sørensen, L. S., and Solgaard, A. M.: Intercomparison of melt observed by ASCAT and modeled by Greenland Regional Climate Models, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6372, https://doi.org/10.5194/egusphere-egu24-6372, 2024.

EGU24-6396 | Orals | CR2.4

Combining seismic tremor and GPS observations to characterize the seasonal evolution of the Greenland basal hydrologic system and its relationship to ice dynamics 

Mark Behn, Wenyuan Fan, Nicholas Lau, Sarah Das, Jeffrey McGuire, Kirsten Arnell, Joshua Rines, and Erin Towns

The mass-loss rate of the Greenland Ice Sheet is accelerating due to increased surface melt and changes in ice-sheet dynamics; however, our understanding of how and when increased melt may lead to increased ice velocity is limited in part by the difficulty in characterizing the evolution of the basal meltwater system and its effects on ice sheet-bedrock coupling.  To monitor the evolution of the basal hydrologic system and its relationship to surface ice velocities, we conducted a field experiment from May to September 2022 near North Lake on the western margin of Greenland. We deployed seismic and geodetic instruments that captured the seasonal evolution of the basal hydrologic system, as well as the drainage of two nearby supraglacial lakes.  Our seismic network included three small-aperture dense arrays, which recorded continuous data generated by the evolving hydrologic systems. The seismic arrays are used to detect and locate seismic tremor sources at the ice-sheet bed, likely correlated with basal meltwater flow.  We locate tremor sources every 5 seconds and use their spatiotemporal distributions to monitor the evolution of the basal flow system over the melt season.  Our observations show tremor activity increases starting around day 175, preceding the increase in ice surface velocities relative to the winter velocity.  Tremor activity peaks in the days before the two rapid lake drainage events (day 195), likely associated with precursory surface-to-bed drainage through a moulin west of North Lake.  Immediately after lake drainage, tremor activity shuts down, though ice velocities remain elevated over winter velocities.  Finally, around day 213 tremor activity increases, becoming more episodic, while ice velocities decrease toward winter velocities.  These observations provide new constraints on the interconnected feedback processes between supraglacial and subglacial hydrologic systems and suggest that ice surface velocities may not be directly correlated to the activity of basal meltwater flow over the melt season. 

How to cite: Behn, M., Fan, W., Lau, N., Das, S., McGuire, J., Arnell, K., Rines, J., and Towns, E.: Combining seismic tremor and GPS observations to characterize the seasonal evolution of the Greenland basal hydrologic system and its relationship to ice dynamics, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6396, https://doi.org/10.5194/egusphere-egu24-6396, 2024.

EGU24-6661 | ECS | Posters on site | CR2.4

Mapping the hydrology of Greenland’s crevasses with deep learning  

Thomas Chudley, Thomas Winterbottom, Chris Stokes, and James Lea

Greenland’s crevasse fields transfer nearly half of the seasonal runoff to the bed of the ice sheet, with implications for ice rheology, subglacial hydrology, and subsequent feedbacks in ice dynamics. The hydrological behaviour of crevasses has been shown to be complex and spatially heterogenous, but the drainage mechanics are poorly understood, particularly in comparison to other water pathways (lake drainage, moulins, and finer-scale fractures). To better understand crevasse drainage processes at scale, we develop a convolutional neural network (CNN) to map water-filled crevasses from 10 metre resolution Sentinel-2 MSI imagery. Training and validation datasets are produced using NDWI-based approaches that are accurate but require time-consuming and scene-specific manual tuning. In contrast, our scaleable CNN approach allows for the seasonal and multiannual evolution of ponded crevasse fields to be efficiently monitored. After constructing a comprehensive, time-evolving dataset of crevasse field hydrology, we aim to quantify controls (strain rate, melt rate, etc.) on the time-evolving filling and drainage of crevasses. Our ultimate objective is to use these derived relationships to improve the parameterisation of spatially heterogenous crevasse hydrological behaviour into coupled models of Greenland Ice Sheet hydrology-dynamics. 

How to cite: Chudley, T., Winterbottom, T., Stokes, C., and Lea, J.: Mapping the hydrology of Greenland’s crevasses with deep learning , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6661, https://doi.org/10.5194/egusphere-egu24-6661, 2024.

Active subglacial and proglacial lakes drain and fill constantly, contributing to glacier and ice sheet mass balance in a way that is not always easy to quantify. Active subglacial lakes account for about 20% of the first worldwide subglacial lake inventory (published by Livingstone et al., 2022); however, none have been previously identified in the Canadian Arctic. Here, we report at least 28 drainage and fill events identified by analyzing time-stamped ArcticDEM elevation data. We stack all the available 2-m DEM strips (23,691 in total) from the latest ArcticDEM release (October 2022) and calculate the elevation change rate at every 15-m sized pixel in a reference grid. Glacier areas with the following signals are interpreted to be associated with the lake drainage or refill beneath the ice: (1) a significantly higher elevation change rate than the neighboring regions within the same glacier catchment, and (2) no adjacent zones showing reversed elevation change (to avoid surge event being misclassified). If such an area touches the glacier terminus, we interpret the elevation change to be governed by a proglacial lake where the floating ice terminus rises and falls when the lake level changes. These drainage and refill events are scattered throughout the region, from the North Ellesmere Icefields to Penny Ice Cap (South Baffin Island). Almost none of the lake locations have been previously reported, probably due to their small size (a few kilometers wide on average), but some of them caused significant ice elevation drops of up to 100 meters during a drainage event. It is not clear whether these significant drainage events produced outburst floods due to temporal sampling gaps in the data. Nevertheless, the water mass lost or gained during the events should be independently calculated from the land ice budget, and we should keep monitoring these newly discovered lakes for their potential impact on the ice flow dynamics and localized mass balances, especially in the context of rapid Arctic warming.

How to cite: Zheng, W. and Van Wychen, W.: Significant subglacial and proglacial lake drainages in the Canadian Arctic identified by time-stamped ArcticDEM strips, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6955, https://doi.org/10.5194/egusphere-egu24-6955, 2024.

EGU24-7605 | ECS | Posters on site | CR2.4

Melt detection from SMOS enhanced resolution brightness temperatures on the Antarctic and Greenland ice sheets 

Pierre Zeiger, Ghislain Picard, Philippe Richaume, Nemesio Rodriguez Fernandez, and Arnaud Mialon

The Soil Moisture and Ocean Salinity (SMOS) mission has been providing surface brightness temperatures (TB) at L-band since 2010. These measurements feed geophysical applications over the ice sheets including melt detection. The synergy between SMOS and other sensors operating at higher frequencies such as AMSR2 is furthermore promising to give insights on the percolation of meltwater in the snowpack and the presence of firn aquifers. However, most of the algorithms currently use the SMOS Level 3 (L3) gridded data which suffer from a coarse spatial resolution. To overcome this issue, we developed a new SMOS enhanced resolution TB dataset over Antarctica and Greenland which is further used to detect melt. The resolution enhancement process is based on the radiometer version of the Scatterometer Image Reconstruction (rSIR) algorithm which was previously successfully applied to SSM/I, SSMIS, AMSR and SMAP. Our methodology also takes advantage of the multi-incidence nature of SMOS measurements to use information with the best native resolution, i.e. low-incidence measurements (15-40°). We evaluated the effective spatial resolution to be ~30 km for the new SMOS enhanced TB maps. It is twice finer than the spatial resolution of the conventional SMOS L3 dataset (~60 km). Finally, a state-of-the-art melt detection algorithm was applied to both the enhanced resolution and the conventional L3 datasets. The new product unravels many localized melt patterns that were not detected using the SMOS L3, especially near the grounding lines of Antarctic ice shelves, due to smoothing of the TB between melting and non melting area. We also identify a clear aquifer signature over the ~25 km wide northern George 6 ice shelf in the Antarctic Peninsula thanks to the gain in resolution. The new SMOS enhanced resolution TB and melt products are posted on the same 12.5 km polar stereographic grid and are comparable to AMSR-E and 2 in terms of spatial resolution to facilitate further synergetic use of multi-frequency passive microwave datasets.

How to cite: Zeiger, P., Picard, G., Richaume, P., Rodriguez Fernandez, N., and Mialon, A.: Melt detection from SMOS enhanced resolution brightness temperatures on the Antarctic and Greenland ice sheets, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7605, https://doi.org/10.5194/egusphere-egu24-7605, 2024.

EGU24-7667 | Orals | CR2.4 | Highlight

Superimposed ice formation reduces meltwater runoff from ice slab areas of the Greenland Ice Sheet  

Andrew Tedstone, Horst Machguth, Nicole Clerx, Nicolas Jullien, Hannah Picton, Julien Ducrey, Dirk van As, Paolo Colosio, Marco Tedesco, and Stef Lhermitte

Refreezing is an important component of the Greenland Ice Sheet's surface mass balance. At higher elevations of the ice sheet which are underlain by porous firn, meltwater percolates into the firn pore space where it refreezes in-situ, and therefore does not run off. However, in the last three decades, surface melting has increased at a faster rate than accumulation. In the percolation zone, this has caused anomalous densification of the firn pore space by meltwater percolation and refreezing, leading to metres-thick near-impermeable ice 'slabs' forming and causing the runoff limit to rise.

In-situ hydrological observations on ice slabs show that surface meltwater percolates through the seasonal snowpack to flow laterally at metres an hour through a slush matrix atop the ice slab. A saturated slush matrix on top of a cold ice slab therefore has the potential to accrete superimposed ice onto the slab surface.

We present the first measurements of superimposed ice formation (SIF) on top of ice slabs in the vicinity of the runoff limit on the K-Transect, south-west Greenland and quantify the impact of SIF on local surface mass balance and runoff. Next, we use vertical heat flow modelling to calculate the ability of an ice slab to refreeze surface melt during a melt season. With synthetic aperture radar observations, we estimate the contribution of residual stored meltwater to autumn-time refreezing. Finally, we assess the importance of SIF across all regions of the ice sheet underlain by ice slabs.

Our findings reveal widespread and substantial refreezing in areas that, at a first glance of recent satellite imagery, can appear to be dominated by runoff. Ice slabs undoubtedly enable surface runoff from higher elevations of the ice sheet. However, their cold content and their shallow surface slopes, promoting water retention, can also enable substantial refreezing. In our field area at the 2022-2023 runoff limit, net refreezing corresponded to roughly 50 % of melt. Ice-sheet-wide, ice slabs enable runoff but are also hotspots of refreezing, retaining around 27 Gt of melt as superimposed ice between 2017 and 2022.

How to cite: Tedstone, A., Machguth, H., Clerx, N., Jullien, N., Picton, H., Ducrey, J., van As, D., Colosio, P., Tedesco, M., and Lhermitte, S.: Superimposed ice formation reduces meltwater runoff from ice slab areas of the Greenland Ice Sheet , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7667, https://doi.org/10.5194/egusphere-egu24-7667, 2024.

EGU24-8038 | ECS | Orals | CR2.4

Modeling the evolution of hummocky topography on debris-covered glaciers 

Ryan Strickland and Matthew Covington

Debris-covered glaciers develop complex, hummocky topography in their ablation zones. The development of hummocky topography coincides with the formation of supraglacial ponds and ice cliffs. Because the ponds and ice cliffs significantly increase melt rates, there is a need to understand how the hummocky topography evolves to better predict melt from debris-covered glaciers. Supraglacial ponds, and the ice cliffs that form along pond shorelines, develop within topographic depressions in the hummocky topography. Recent work (Strickland et al., 2023) showed that topographic depressions on the debris-covered Ngozumpa Glacier, Nepal, undergo positive feedback growth. The development of depressions is often attributed to contrasts in melt rates caused by contrasts in debris thickness. However, this hypothesis cannot explain positive feedback growth because it ignores the negative feedback caused by hillslope debris transport into the depression. Although not included in current models of surface evolution, meltwater drainage provides a potential mechanism for positive feedback depression growth. To better understand depression growth and the evolution of hummocky topography, we develop a two-dimensional topographic evolution model for debris-covered glaciers. Here, we explore how the emergence of englacial debris, hillslope transport of supraglacial debris, and meltwater drainage influence the development of topographic depressions. We first examine the topography that develops from a heterogeneous debris layer. Then, we add the influence of channel incision on topographic evolution. With these mechanisms included, the model only produces small, transient depressions. However, if we include englacial drainage points—locations where supraglacial meltwater and debris enters the subsurface drainage network— this spurs the growth of large, lasting depressions. These results suggest that englacial drainage is necessary to produce persistent depressions in hummocky topography.

How to cite: Strickland, R. and Covington, M.: Modeling the evolution of hummocky topography on debris-covered glaciers, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8038, https://doi.org/10.5194/egusphere-egu24-8038, 2024.

EGU24-8364 | Orals | CR2.4

Observed multi-scale variations of subglacial hydro-mechanical conditions at Kongsvegen, Svalbard. 

Coline Bouchayer, Ugo Nanni, Pierre-marie Lefeuvre, John Hulth, Louise steffensen Schmidt, Jack Kohler, Francois Renard, and Thomas vikhamar Schuler

Glacier flow variations are predominantly due to changes at the ice-bed interface, where basal slip and sediment deformation drive basal glacier motion. Determining subglacial conditions and their responses to hydraulic forcing remains challenging due to the difficulty of accessing the glacier bed. In this study, we analyze data series from instruments placed at the base of Kongsvegen glacier (Svalbard) thanks to a 350 m borehole.The borehole was instrumented witha pressure sensor, seismometers, and a ploughmeter to monitor the interplay between surface runoff and hydro-mechanical conditions. Covering the two ablation seasons of 2021 and 2022, , we measured point-scale subglacial water pressure and till strength, and we derived at a kilometre scale the subglacial hydraulic gradient and radius from seismic observations.. Across seasonal, multi-day, and diurnal time scales, we compared these measurements to characterize the variations in subglacial conditions caused by changes in surface runoff. We discuss our results in light of existing theories of subglacial hydrology and till mechanics. We find that during the short, low intensity melt season of 2021, the subglacial drainage system evolves to accommodate runoff variations, increasing its capacity as the melt season progressed. In contrast, during the long and high intensity melt season of 2022, the subglacial drainage system evolved transiently to respond to the abrupt and large water supply. We suggest that in this configuration, the drainage capacity of the hydraulically active part of the subglacial drainage system is exceeded, promoting the expansion of hydraulically connected regions and local weakening of ice-bed coupling, thus enhancing sliding. Our in-situ, multi-method approach provides a unique insight into conditions at the ice-bed interface.

How to cite: Bouchayer, C., Nanni, U., Lefeuvre, P., Hulth, J., Schmidt, L. S., Kohler, J., Renard, F., and Schuler, T. V.: Observed multi-scale variations of subglacial hydro-mechanical conditions at Kongsvegen, Svalbard., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8364, https://doi.org/10.5194/egusphere-egu24-8364, 2024.

EGU24-8534 | ECS | Posters on site | CR2.4

Firn aquifer properties of Wilkins ice shelf from multi-source spaceborne microwave observations 

Xinyi Shang, Xiao Cheng, Lei Zheng, Qi Liang, and Teng Li

The potential impact of increased snowmelt and related hydrological processes on ice sheet stability has become a focus of academic attention. Hydro-fracture caused by liquid water is one of the main triggers of ice shelf disintegration. Recent discoveries of firn aquifer (FA) in the Wilkins Ice Shelf (WIS) have updated our understanding of surface hydrological processes, mass and energy balance. However, the limited field and airborne radar observations of FA cannot provide a complete picture of their distribution and characteristics. Microwave remote sensing is highly sensitive to the dielectric constant change caused by the dynamics in buried liquid water. However, it is challenging to obtain the buried depth of FA from space. In this study, the extent and depth to the water table (DWT) of FA are investigated with the combination of active and passive microwave observations, as well as airborne radar measurements. First, with the verification points from airborne radar, the extent of FA is mapped from satellite-derived snowmelt and accumulation conditions based on a K-Nearest Neighbors classification model (OA=97.2%, Kappa=0.94). Next, we use a Gaussian Process Regression model to estimate the DWT of FA (R=0.8, RMSE=2.17 m). The results show that FA occurred in most areas of WIS in 2014, with a DWT of 12.8±2.9 m. The DWT increased from north to south. Further study will examine the dynamics in FA and their hydro-fracture effect on ice shelf calving and the stability of the Antarctic ice sheet.

How to cite: Shang, X., Cheng, X., Zheng, L., Liang, Q., and Li, T.: Firn aquifer properties of Wilkins ice shelf from multi-source spaceborne microwave observations, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8534, https://doi.org/10.5194/egusphere-egu24-8534, 2024.

EGU24-8950 | ECS | Orals | CR2.4

New Active Antarctic Subglacial Lakes using 10 years of CryoSat-2 Altimetry 

Sally Wilson, Anna Hogg, Richard Rigby, Thomas Slater, and Isabel Nias

Subglacial lakes beneath the Antarctic Ice Sheet were first identified using airborne radio-echo sounding (RES) surveys from the 1960s. In Antarctica, 20% of 675 currently identified subglacial lakes are “active,” exhibiting draining and filling behaviour as water flows through them. Clusters of active subglacial lakes often form in networks, connected by subglacial hydrological pathways which enable transfer of water between lakes themselves. Signals of this hydrological activity at the ice base can be detected in height changes at the ice sheet surface. Despite efforts to observe and understand this component of ice sheet mechanics, triggers of lake drainage events, in addition to drainage mechanisms and their variability are currently unresolved. An ongoing challenge lies in accurately identifying the location and extent of subglacial lakes.

We present a new dataset of locations and boundaries for over 100 newly identified subglacial lakes in Antarctica. Using 10 years of CryoSat-2 swath-processed altimetry data, from 2011-2021, we identify localised regions of ice surface uplift and subsidence associated with subglacial lake filling and draining cycles. We use a new method to manually delineate subglacial lake maximum extent boundaries for individual filling and drainage periods. These results provide insights into new areas of subglacial hydrological activity in Antarctica and their evolution over time, which are vital to resolve in order to understand their impacts on Antarctic Ice Sheet stability.

How to cite: Wilson, S., Hogg, A., Rigby, R., Slater, T., and Nias, I.: New Active Antarctic Subglacial Lakes using 10 years of CryoSat-2 Altimetry, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8950, https://doi.org/10.5194/egusphere-egu24-8950, 2024.

EGU24-9037 | Orals | CR2.4

A coupled model of glacier-ice dynamics, bed-hydrology and bedrock groundwater flow including heat-transfer 

Thomas Zwinger, Peter Råback, and Rupert Gladstone

Within the modelling framework of Elmer/Ice we have existing model components to compute the thermo-mechanical ice flow problem, using a full-stress approach as well as several model approaches for the bedrock hydrology, for instance the Glacier Drainage System model (GlaDS - Werder et al., 2013). Further, a thermodynamically consistent groundwater model including freezing (permafrost) and thawing of the pore-water  and the stress-induced deformation of the rock skeleton is implemented in Elmer. The real challenge lies within coupling those three components with mutual feedback, both, in mechanical and thermal aspects that mutually depend on each other, e.g. through a temperature and water-pressure dependent sliding law. The fact that all equations are implemented in the same Finite Element framework enables a consistent coupling of the equations solved on different domains (ice, water-sheet and sediment), in case of weakly coupling being able to use the residual to transfer loads. Along the lines of a synthetic glacier setup, we highlight the workflow of such a coupled simulation and point out the challenges of such a highly complex process model.

How to cite: Zwinger, T., Råback, P., and Gladstone, R.: A coupled model of glacier-ice dynamics, bed-hydrology and bedrock groundwater flow including heat-transfer, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9037, https://doi.org/10.5194/egusphere-egu24-9037, 2024.

EGU24-9707 | ECS | Orals | CR2.4

Minimal Impact of Late-Season Melt Events on Greenland Ice Sheet Annual Motion 

Ryan Ing, Peter Nienow, Andrew Sole, Andrew Tedstone, and Kenneth Mankoff

Extreme melt and rainfall events can induce temporary acceleration of Greenland Ice Sheet motion, leading to increased advection of ice to lower elevations where melt rates are higher. In a warmer climate, these events are likely to become more frequent. In September 2022, unprecedented air temperatures caused multiple melt events over the Greenland Ice Sheet, generating the highest melt rates of the year. In this study we investigate the impact of these large late-season melt events on the ice dynamics of five land- and two marine-terminating outlet glaciers of the west Greenland Ice Sheet. The scale and timing of the largest event overwhelmed the subglacial drainage system, enhancing basal sliding and increasing ice velocities by up to ~240% relative to pre-event velocities. However, ice velocity returned rapidly to pre-event levels, and the speed-ups caused a regional increase in annual ice discharge of only ~2% compared to when the effects of the speed-ups on ice discharge were excluded. In contrast, the total annual runoff from the studied glaciers increased by 24%. Therefore, although late-season melt events are forecast to become more frequent and drive large amounts of runoff, their impact on net mass loss via ice discharge is minimal.

How to cite: Ing, R., Nienow, P., Sole, A., Tedstone, A., and Mankoff, K.: Minimal Impact of Late-Season Melt Events on Greenland Ice Sheet Annual Motion, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9707, https://doi.org/10.5194/egusphere-egu24-9707, 2024.

EGU24-10739 | Posters on site | CR2.4

Changes in soft bed subglacial hydrology associated with Climate Change 

Jane Hart, Nathaniel Baurley, and Kirk Martinez

Recent research on the subglacial hydrology beneath the soft bedded West Antarctic Ice streams has shown the presence of a braided subglacial hydrology. We have been able to investigate the seasonal changes associated with a soft-bedded braided system from a series of instrumented temperate glaciers, and show there is a continuum between a subglacial channelized and braided system.

In particular, a braided subglacial river system can store summer meltwater, which is released during winter during positive degree days during winter (winter events) resulting in speed-ups. Here we show how recent increases in air temperature (and associated feedbacks such as proglacial lake growth), from a series of temperate soft-bedded glaciers, lead to potential changes in the subglacial hydrology and resultant glacier dynamics.

How to cite: Hart, J., Baurley, N., and Martinez, K.: Changes in soft bed subglacial hydrology associated with Climate Change, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10739, https://doi.org/10.5194/egusphere-egu24-10739, 2024.

EGU24-11819 | ECS | Posters on site | CR2.4

Simulating Subglacial Hydrology: Insights into the Triggers of Surges and GLOFs 

Neosha Narayanan, Aleah Sommers, Jakob Steiner, Winnie Chu, Muhammad Adnan Siddique, Colin Meyer, and Brent Minchew

The snowpack and glaciers of the Himalaya-Karakoram range feed several major river systems in Asia which provide water to over one billion people. Glacial retreat, glacial lake outburst flooding (GLOFs), and glacial ice mass balance are all likely strongly affected by subglacial hydrology. Unfortunately, little is known about Himalayan glaciers due to their remoteness and the danger of doing field work there. Recent advances in subglacial hydrological modeling may allow us to shed more light on subglacial processes that lead to changes in ice mass balance and glacial lake flooding. We present the first application of the SHAKTI subglacial hydrology model to a Himalayan glacier. We model the subglacial drainage network of Shishper Glacier, located in Gilgit-Baltistan, Pakistan, to understand its seasonal evolution and history of surges and GLOFs. We find that the modeled seasonal evolution of Shishper's subglacial system follows a similar seasonal pattern to past observed and modeled subglacial systems. Additionally, a central Röthlisberger channel persists through the winter and serves as the basis for the subglacial drainage system throughout the melt season. We also investigate the 2017-2019 surge of Shishper glacier and find that subglacial hydrology, while likely an important component of surging, cannot provide a standalone explanation for surges. This work serves as a nucleus for future modeling work in the Himalayas and provides a new framework for studying the effects of climate change on glacier dynamics, water availability, and glacier-related hazards in the Himalaya-Karakoram (H-K) region.

How to cite: Narayanan, N., Sommers, A., Steiner, J., Chu, W., Siddique, M. A., Meyer, C., and Minchew, B.: Simulating Subglacial Hydrology: Insights into the Triggers of Surges and GLOFs, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11819, https://doi.org/10.5194/egusphere-egu24-11819, 2024.

EGU24-11852 | Posters on site | CR2.4

GNSS-based Observation of seasonal acceleration at 79°N Glacier (Greenland)  

Benjamin Männel, Angelika Humbert, Markus Ramatschi, and Daniel Steinhage

The 79° North Glacier (Nioghalvfjerdsbrae, 79NG) is one of three glaciers with a floating tongue in Greenland. Recent investigations indicate an increased subglacial discharge due to a considerably enlarged area of summer surface melt due to the warming of the atmosphere, resulting in increased water input to the base of glaciers. Consequently, ice velocities measured at the surface respond directly to changes in water pressure, revealing detailed insights about the ice dynamics. Global Navigation Satellite System, like GPS and Galileo, can observe ice velocities with high temporal resolution in horizontal and vertical directions.

We will present results from the 2022-2023 GNSS measurement campaign where two tinyBlack GNSS receivers were installed at 79NG. Firstly, data quality regarding common indicators like the number of tracked satellites, signal strength, and multipath will be discussed. Secondly, variations in the ice reflection characteristics will be presented based on the GNSS-reflectometry technique. The final processing was carried out as kinematic precise point processing (sampling rate 30s) using GFZ’s processing software EPOS.P8 and GFZ’s operational GNSS products. Thus, thirdly, the derived time series will be discussed with a focus on short-term variations in the surface velocity. We can link speed-up events in July 2022 to rapid lake drainage using optical satellite imagery and interferometrically derived digital elevation models.

How to cite: Männel, B., Humbert, A., Ramatschi, M., and Steinhage, D.: GNSS-based Observation of seasonal acceleration at 79°N Glacier (Greenland) , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11852, https://doi.org/10.5194/egusphere-egu24-11852, 2024.

EGU24-11855 | ECS | Orals | CR2.4

Exploring the future expansion of perennial firn aquifers in Antarctica using a random forest emulator 

Sanne Veldhuijsen, Willem Jan van de Berg, Peter Kuipers Munneke, Nicolaj Hansen, Fredrik Boberg, and Michiel van den Broeke

Perennial firn aquifers (PFAs) are year-round bodies of liquid water within firn. In Antarctica, they can cause hydrofracturing of ice shelves, leading to accelerated ice-sheet mass loss. PFAs were only recently discovered in the Antarctic Peninsula, at locations with high melt and snow accumulation rates. Likely, PFAs will expand in the future as both snowfall and melt increase. So far, this has not been considered when assessing the future vulnerability of Antarctic ice shelves. One could use a firn model to predict future Antarctic PFA evolution, but to do so for a wide range of climatic forcings is computationally expensive. Therefore, we set up a random forest emulator. The emulator represents both firn and surface climate processes, so that only 2 metre temperature and precipitation are required as input. To train the emulator, we use simulations of three scenarios (SSP1-2.6, SSP2-4.5 and SSP5-8.5) from firn densification model IMAU-FDM forced by the regional climate model RACMO2, which was driven by CESM2 in turn. The emulator successfully explains 98% of the PFAs variation, therefore we use its versatility and speed to predict Antarctic PFA evolution for 15 additional RCM/GCM model forcings. We find a range of solutions, highlighting the usefulness of the emulator. Until 2100, PFA occurrence remains restricted to ice shelves in the Antarctic Peninsula for SSP1-2.6 and SSP2-4.5. For SSP5-8.5, PFAs expand to the Bellingshausen Sea region in West-Antarctica, and to Enderby Land in East-Antarctica. The meteorological conditions in Enderby Land exhibit similarities to those observed in the Antarctic Peninsula. In contrast, Getz ice shelf, which experiences high snow accumulation rates, remains insensitive to PFA formation, because it is rather cold. Our results highlight the sensitivity of relatively warm, high-accumulation ice shelves to future PFA formation and subsequent hydrofracturing.

How to cite: Veldhuijsen, S., van de Berg, W. J., Kuipers Munneke, P., Hansen, N., Boberg, F., and van den Broeke, M.: Exploring the future expansion of perennial firn aquifers in Antarctica using a random forest emulator, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11855, https://doi.org/10.5194/egusphere-egu24-11855, 2024.

EGU24-12186 | Posters on site | CR2.4

Ice Velocity Response to Surface Melt and Lake Drainages at a Land-Terminating Margin of the Greenland Ice Sheet 

Ian Willis, Luke Donaldson, and Becky Dell

Approximately 50% of current mass loss from the Greenland Ice Sheet is from ice dynamics. It is important to understand the processes controlling ice dynamics to better calculate current rates of mass loss and predict rates into the future. Previous work has shown that both surface runoff and surface lake drainages control subglacial drainage development and therefore seasonal and annual velocities of the ice sheet, although few studies have considered these together. Here we analyse monthly patterns of runoff, lake drainages and ice velocities across a 6 753 km2 land terminating part of the ice sheet between 2016 and 2021. We find that annual runoff is inversely correlated with annual velocity across the study area, supporting previous work showing the importance of subglacial drainage development in driving down water pressures and therefore basal sliding speeds. We also show that rapid surface lake drainages (a surrogate for moulin formation by hydrofracture) have an impact superimposed on the runoff control. 2016 and 2019 have comparably high annual runoff totals but the former experiences three times more rapid lake drainages than the latter, resulting in greater depressurisation of the subglacial drainage system, greater net summer slowdown and lower annual velocities. We also demonstrate ‘interannual subglacial memory’ with years succeeding high runoff years showing net summer speedup, higher winter velocities and higher annual velocities than might otherwise be expected. We identify, therefore, high runoff ‘depressurisation’ years and subsequent ’recharge’ years, with effects on seasonal and annual glacier velocities. Finally, we see localised impacts of lake drainages on spatial patterns of net summer speed up or slowdown, with lake drainages acting to depressurise cavities causing local slowdown in some instances, or recharge cavities causing local speedup in others. These processes should be considered for modelling of the future impacts of climate-controlled runoff on ice sheet dynamics and mass balance.

How to cite: Willis, I., Donaldson, L., and Dell, B.: Ice Velocity Response to Surface Melt and Lake Drainages at a Land-Terminating Margin of the Greenland Ice Sheet, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12186, https://doi.org/10.5194/egusphere-egu24-12186, 2024.

EGU24-12569 | ECS | Orals | CR2.4

A new, fast and unified subglacial hydrological model applied to Thwaites Glacier, Antarctica 

Thomas Gregov, Elise Kazmierczak, Violaine Coulon, and Frank Pattyn

Subglacial hydrology is a crucial element for understanding the dynamics of marine ice sheets. Indeed, the presence of subglacial water modulates the ice basal motion, resulting in a modified ice flow across the entire ice sheet. Nonetheless, the subglacial environment is difficult to reach, which makes it necessary to develop models. Many efforts have recently been made in the glaciological and hydrological communities to improve their accuracy and efficiency. Even so, the models currently being developed are typically fairly costly in terms of computing time. As a consequence, conducting numerical simulations over long time scales or running ensemble simulations remains particularly challenging.

Here, we propose a simplified approach for coupling subglacial hydrology with the motion of ice. First, we introduce a computationally efficient subglacial hydrology model that is suited for hard and soft bed types as well as efficient and inefficient drainage systems. Then, we show some numerical results based on our implementation of this model within the Kori-ULB ice-sheet code. We first study the impact of subglacial hydrology in the idealized MISMIP configuration. Subsequently, we show results of simulations conducted over Thwaites Glacier which suggest that the coupling of subglacial hydrology with ice flow could significantly increase the contribution of marine ice sheets to future sea-level rise.

How to cite: Gregov, T., Kazmierczak, E., Coulon, V., and Pattyn, F.: A new, fast and unified subglacial hydrological model applied to Thwaites Glacier, Antarctica, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12569, https://doi.org/10.5194/egusphere-egu24-12569, 2024.

EGU24-12692 | Posters on site | CR2.4

Improved Monitoring of Subglacial Lake Activity in Greenland using CryoSat-2 swath processed data and TanDEM-X DEMs.  

Louise Sandberg Sørensen, Sebastian Simonsen, Natalia Havelund Andersen, Rasmus Bahbah, Nanna Karlsson, Anne Solgaard, Amber Leeson, Jennifer Maddalena, Malcolm McMillan, Jade Bowling, Noel Gourmelen, Alex Horton, and Birgit Wessel

Subglacial lakes form beneath ice sheets and ice caps if water is available, and if bedrock and surface topography are able to retain the water. On a regional scale, the lakes modulate the timing and rate of freshwater flow through the subglacial system to the ocean by acting as reservoirs. More than one hundred hydrologically active subglacial lakes, that drain and recharge periodically, have been documented under the Antarctic Ice Sheet, while only approximately 20 active lakes have been identified in Greenland. Active lakes may be identified by local changes in ice topography caused by drainage or recharge of the lake beneath the ice. The small size of the Greenlandic subglacial lakes puts additional demands on mapping capabilities to resolve the evolving surface topography in sufficient detail to record their temporal behavior. Here, we explore the potential for using CryoSat-2 swath-processed data together with TanDEM-X digital elevation models to improve the monitoring capabilities of active subglacial lakes in Greenland. We focus on four subglacial lakes previously described in the literature, and combine the new data with ArcticDEMs to obtain improved measurements of the evolution of these four lakes.

We find that with careful tuning of the swath-processor and filtering of the output data, the inclusion of these new data together with the TanDEM-X data provides important information on lake activity, documenting, for example, that the ice surface collapse basin on Flade Isblink Ice Cap was 30 meters deeper than previously recorded. 

How to cite: Sandberg Sørensen, L., Simonsen, S., Havelund Andersen, N., Bahbah, R., Karlsson, N., Solgaard, A., Leeson, A., Maddalena, J., McMillan, M., Bowling, J., Gourmelen, N., Horton, A., and Wessel, B.: Improved Monitoring of Subglacial Lake Activity in Greenland using CryoSat-2 swath processed data and TanDEM-X DEMs. , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12692, https://doi.org/10.5194/egusphere-egu24-12692, 2024.

EGU24-12711 | Orals | CR2.4

Geophysical investigation of active subglacial lake dynamics in West Greenland 

Samuel Doyle, Stephen Livingstone, Andrew Sole, Robert Storrar, Tun Jan Young, Ryan Ing, Neil Ross, Liz Bagshaw, Caroline Clason, Laura Edwards, Mike Prior-Jones, Gianluca Bianchi, Sammie Buzzard, Tifenn Le Bris, Guilhem Barruol, Florent Gimbert, Adrien Gilbert, Matthew Peacey, and Adam Booth

Hydrologically active subglacial lakes modulate subglacial hydrology, ice motion, microbial habitats, biogeochemical fluxes, and subglacial and proglacial geomorphic activity. The recent potential identification of active subglacial lakes beneath the ablation area of the Greenland Ice Sheet from repeat satellite altimetry data suggests that they are a significant yet poorly constrained component of the ice sheet hydrological system. These subglacial lakes, which are presumably fed by both supraglacial and subglacial water inputs, appear to be highly dynamic features that fill gradually (i.e. over years) but drain rapidly (i.e. hours to days), causing high discharge flood events observed in the proglacial area. While remote sensing observations constrain lake dynamics to a coarse temporal and spatial resolution the precise timing of lake filling and drainage and the detailed effect on ice dynamics can only be determined from field-based measurements. Here we present initial results from a comprehensive geophysical investigation of subglacial lake dynamics beginning in April 2023. We report measurements of horizontal and vertical ice surface motion together with horizontal strain rates from an array of 11 GNSS receivers installed across three juxtaposed subglacial lakes on Isunnguata Sermia — an ~6 km wide land-terminating outlet glacier in West Greenland. We combine these GNSS data with autonomous phase-sensitive radio echo sounding measurements of ice thickness and vertical strain to construct a time series of lake filling and drainage spanning the 2023 melt season. To investigate inter-relationships between subglacial lake hydrology and ice dynamics at both short (hourly) and seasonal timescales, we supplement these time series with data from an array of seismometers installed in between two of the lakes and at the glacier terminus, together with several kilometres of radio echo sounding measurements of ice thickness. 

How to cite: Doyle, S., Livingstone, S., Sole, A., Storrar, R., Young, T. J., Ing, R., Ross, N., Bagshaw, L., Clason, C., Edwards, L., Prior-Jones, M., Bianchi, G., Buzzard, S., Le Bris, T., Barruol, G., Gimbert, F., Gilbert, A., Peacey, M., and Booth, A.: Geophysical investigation of active subglacial lake dynamics in West Greenland, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12711, https://doi.org/10.5194/egusphere-egu24-12711, 2024.

EGU24-12972 | Posters on site | CR2.4

Towards Ice Sheet and Ice Shelf Meltwater Profile Retrieval from Copernicus Imaging Microwave Radiometer (CIMR) 

Andreas Colliander, Alamgir Hossan, Joel Harper, Baptiste Vandecrux, Julie Miller, Nicole Schlegel, Shawn Marshall, and Craig Donlon

Successful adaptation and mitigation of rising sea level demands improved constraints on emerging ice sheet processes controlling the magnitude and rate of sea level change in a warming climate. Therefore, it is vital to enhance the confidence in quantitative assessments of present-day ice sheet mass balance arising from meltwater generation and refine the explicit treatment of meltwater refreezing in firn densification models to evaluate the time evolution of runoff/retention and surface elevation change. The European Space Agency's Copernicus Imaging Microwave Radiometer (CIMR), scheduled for launch in 2028, responds to this need by measuring the brightness temperature (TB) at 1.4, 6.9, 10.7, 18.7, and 36.5 GHz frequencies multiple times a day over polar regions without gaps at the poles. These measurements can resolve the stratification of the seasonal meltwater from the immediate surface to the deeper firn layers. Furthermore, the 1.4 GHz TB is sensitive to the amount of meltwater.

We are developing retrieval algorithms using 1.4 GHz measurements from NASA Soil Moisture Active Passive (SMAP) and ESA Soil Moisture Ocean Salinity (SMOS) satellites and 6.9, 10.7, 18.7, and 36.5 GHz measurements from JAXA Advanced Microwave Scanning Radiometer – EOS (AMSR-E) and AMSR2 instruments on NASA Aqua and JAXA (Global Change Observation Mission – Water) GCOM-W satellites. In the algorithm development, we use ground measurements and coupled energy and mass balance models to test, calibrate, and validate the algorithm. The ground measurements include surface and subsurface measurements from PROMICE/GC-Net (Greenland) and other station and campaign data sets. The model suite includes locally calibrated and forced energy balance models and regionally forced models, such as the Ice Sheet System Model's Glacier Energy and Mass Balance module. The retrieved data product will provide twice-daily parameters such as meltwater amount, melt layer depth, and near-surface snow status (wet/dry) profile. It will also include seasonal parameters such as firn aquifer extent and evolution.

The meltwater algorithm for the CIMR mission will eventually encompass two satellites capable of monitoring diurnal melt-freeze cycles and perennial firn aquifers for at least a 15-year mission period. CIMR will measure all frequencies simultaneously, which will eliminate the uncertainties related to different observation times of the current instrument combinations, increase the revisit time of the L-band observations, and improve the spatial resolution of the 6.9, 10.7, 18.9, and 36.5 GHz channels compared to what is currently available.

How to cite: Colliander, A., Hossan, A., Harper, J., Vandecrux, B., Miller, J., Schlegel, N., Marshall, S., and Donlon, C.: Towards Ice Sheet and Ice Shelf Meltwater Profile Retrieval from Copernicus Imaging Microwave Radiometer (CIMR), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12972, https://doi.org/10.5194/egusphere-egu24-12972, 2024.

EGU24-13358 | ECS | Posters on site | CR2.4

Melt Pond Pattern Formation In Greenland 

Alessandro Cotronei and Ulrike Feudel

The Greenland Ice Sheet is a massive glacier that covers most of Greenland's surface and contains enough ice to raise the sea level by up to seven meters, if it melts due to climate change. Moreover, this melting could potentially lead to the disruption of the Atlantic Meridional Overturning Circulation (AMOC). For this reason, it is crucial to understand the processes that influence its melting. Meltponds, which form on its surface during the warmest months, are believed to potentially accelerate the melting process and its evolution significantly. Their variety of characteristics, can be seen as a result of a pattern-forming process that involves the interplay of multiple components, such as temperature, albedo, and mechanical processes. We employ a conceptual model of the Greenland ice sheet to unravel the possible role of such pattern formation related to meltponds in the context of global warming and climate change. This analysis is meant to contribute to a further understanding of possible essential processes influencing the future of the Greenland Ice Sheet.

How to cite: Cotronei, A. and Feudel, U.: Melt Pond Pattern Formation In Greenland, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13358, https://doi.org/10.5194/egusphere-egu24-13358, 2024.

EGU24-13766 | ECS | Orals | CR2.4

Measurement of the Total Meltwater Amount in the Greenland Ice Sheet Using SMAP L-band Radiometry  

Alamgir Hossan, Andreas Colliander, Julie Miller, Shawn Marshall, Joel Harper, and Baptiste Vandecrux

With the growing concern of climate change, an accurate estimation of the total meltwater amounts (MWA) in the Greenland ice sheet (GIS) becomes crucial for understanding the physical processes of the GrIS and its mass balance, thereby enabling accurate prediction of its contribution to the global sea-level rise. Satellite microwave radiometers have been widely used for monitoring ice sheet melting for the last four decades; nevertheless, quantification of total MWA, especially the sub-surface MWA, remains a challenge.

Here, we used the enhanced resolution L-band brightness temperature (TB) observations from the NASA Soil Moisture Active Passive (SMAP) mission to quantify the magnitude of the total MWA in GrIS for 2015-2023. Because of the larger penetration depth, L-band signals can track liquid water in deeper layers and provide a reliable estimate of surface-to-subsurface MWA, contrary to the higher frequency signals (18 or 37 GHz bands), which are limited to the top few centimeters of the surface snow. The algorithm uses vertically polarized (V-pol) TBs and an empirically derived adaptive thresholding technique to detect melt events. A simple microwave emission model, based on ice sheet radiative transfer, was used to simulate L-band TBs. The simulated TBs were then used in an inversion algorithm for MWA retrieval.

Finally, the retrieval was compared with the corresponding MWA derived from an ice sheet energy and mass balance (EMB) model which was forced by hourly in situ observations from the Programme for Monitoring of the Greenland Ice Sheet (PROMICE) automatic weather station (AWS) network. The model was initialized and constrained by the relevant ice core density and sub-surface temperature profiles. The retrievals generally demonstrate a stronger agreement with the in situ observations in the percolation zone than in the ablation and upper elevation regions. The radiometric sensitivity, meltwater process, and their spatiotemporal variability were analyzed. The results demonstrate the potential for advancing our understanding of ice sheet physical processes to better project Greenland’s contribution to global sea level rise in response to the warming climate.

How to cite: Hossan, A., Colliander, A., Miller, J., Marshall, S., Harper, J., and Vandecrux, B.: Measurement of the Total Meltwater Amount in the Greenland Ice Sheet Using SMAP L-band Radiometry , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13766, https://doi.org/10.5194/egusphere-egu24-13766, 2024.

EGU24-14576 | Posters on site | CR2.4

Firn aquifers in Antarctica: High-resolution mapping highlights predominance in the Antarctic Peninsula 

Valeria Di Biase, Peter Kuipers Munneke, Sophie de Roda Husman, Sanne Veldhuijsen, Michiel van den Broeke, Bert Wouters, and Brice Noël

Perennial firn aquifers in Greenland are crucial for meltwater storage, significantly influencing ice-sheet hydrology. In Antarctica, although firn aquifers have been identified in situ, a comprehensive continent-wide overview is currently lacking. Using an advanced methodology that integrates multiple datasets, our pioneering study presents a 2 x 2 km resolution assessment of firn aquifer distribution in Antarctica.
The focal point of our analysis is the creation of a heat map of firn aquifer locations across Antarctica. In contrast to prior studies, reliant on traditional binary evaluations of aquifer presence or absence, our method addresses the inherent uncertainty associated with firn aquifer extent and overcoming challenges posed by the vast and remote Antarctic environment.
We use a Monte Carlo method that exploits multiple datasets as input, spanning from 2017 to 2021. Data includes Sentinel-1, Advanced SCATterometer (ASCAT), and statistically downscaled output from the RACMO2.3p2 climate model. Each of these datasets highlights a particular property of firn aquifers.
Our high-resolution heat map reveals a concentration of firn aquifers across the Antarctic Peninsula (AP). Elevated probabilities are observed along its northern, northwest, and western coastlines, as well as on the Wilkins, Müller, and part of George VI ice shelves. Beyond the AP, aquifer evidence is sparse, with only a few locations exhibiting slightly elevated probabilities, such as on the Abbot, Shackleton, and Holmes ice shelves.
Validation of the methodology applied in Greenland using Operation IceBridge (OIB) data demonstrates a 91% correspondence with observed aquifers, firmly establishing the robustness of our approach.
Leveraging the sustained accessibility of freely available C-band and scatterometer observations, complemented by modeling data, our approach allows for ongoing long-term monitoring of aquifer conditions, proving crucial to explore the response of the Antarctic ice sheet to climate change.

How to cite: Di Biase, V., Kuipers Munneke, P., de Roda Husman, S., Veldhuijsen, S., van den Broeke, M., Wouters, B., and Noël, B.: Firn aquifers in Antarctica: High-resolution mapping highlights predominance in the Antarctic Peninsula, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14576, https://doi.org/10.5194/egusphere-egu24-14576, 2024.

EGU24-16236 | ECS | Posters on site | CR2.4

Distribution and morphology of moulins at Isunnguata Sermia, West Greenland  

Matthew Peacey, Stephen Livingstone, Samuel Doyle, Andrew Sole, Robert Storrar, Laura Edwards, Elizabeth Bagshaw, Thomas Chudley, Neil Ross, Sammie Buzzard, Adam Booth, Gianluca Bianchi, Ryan Ing, Caroline Clason, Tun Jan Young, Sian Thorpe, Florent Gimbert, Tifenn Le Bris, Guilhem Barruol, and Adrien Gilbert and the Cryoegg

This study presents high resolution mapping of moulins located above three subglacial lakes at Isunguata Sermia. Moulins are the primary pathway for transferring supraglacial melt to englacial and subglacial environments. The formation of moulins has been explained by the flow of water into a notch, associated with glacier structures and incision of supraglacial streams, which are directly related to glacier morphology and dynamics. Meltwater input to subglacial systems, along with glacier dynamics, will in turn affect the development of subglacial meltwater networks, which control glacier morphology and dynamics. This study focusses on Isunguata Sermia, West Greenland, which has an active subglacial drainage system that includes distinct subglacial lakes. Hydrologically connected or active subglacial lakes may be directly influenced by water input from supraglacial to englacial systems via moulins during the ablation season.

Moulins were mapped using a combination of high resolution orthomosaics and digital elevation models derived from uncrewed aerial vehicle flights. Moulin locations and morphologies were compared with glacier structures, ice flow velocities, and bed topography. We reveal a distinct pattern of moulin locations relative to each subglacial lake and the locations of primary and secondary glacier structures an supraglacial hydrology. Furthermore, we also outline a clear morphological pattern, wherein morphology of moulins varies distinctly at with the location of each subglacial lake between vertical shafts, crevasse associated and keyhole morphology. These observations will be used to consider the efficiency of meltwater routing from the surface to the bed, and the potential for inputs to subglacial lakes, and the wider implications for varying ice flow velocity and evolution of the subglacial drainage system.

How to cite: Peacey, M., Livingstone, S., Doyle, S., Sole, A., Storrar, R., Edwards, L., Bagshaw, E., Chudley, T., Ross, N., Buzzard, S., Booth, A., Bianchi, G., Ing, R., Clason, C., Young, T. J., Thorpe, S., Gimbert, F., Le Bris, T., Barruol, G., and Gilbert, A. and the Cryoegg: Distribution and morphology of moulins at Isunnguata Sermia, West Greenland , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16236, https://doi.org/10.5194/egusphere-egu24-16236, 2024.

EGU24-16416 | Orals | CR2.4

Supraglacial lake drainage through gullies and fractures 

Angelika Humbert, Veit Helm, Ole Zeising, Niklas Neckel, Robert Salzano, Giulio Esposito, Matthias Braun, Holger Steeb, Julia Sohn, Matthias Bohnen, Ralf Müller, and Martin Rückamp

The mechanisms of drainage of supraglacial lakes are not yet fully understood. Here we present an indepth study of drainage characteristics of a 21km^2 large supraglacial lake in Northeast Greenland from its genesis in mid 1990s to 2023. We discuss the fracture modes involved in drainage and compare this to simulated principal stress fields. A particular focus of the presentation is the formation of gullies. Using high resolution optical satellite imagery (WV2 and Planet), we detect fracture networks at the surface. We find evidence for reactivation of former gullies in subsequent lake drainage events. In addition we present viscoelastic modelling of gullies at the surface that support the continued existence of open gullies at the surface. In vertical direction, we surveyed the glacier using airborne radio echo sounding in 2016, 2018 and 2021. This data reveals englacial channels and their remnants over the entire live span of the lake. 

How to cite: Humbert, A., Helm, V., Zeising, O., Neckel, N., Salzano, R., Esposito, G., Braun, M., Steeb, H., Sohn, J., Bohnen, M., Müller, R., and Rückamp, M.: Supraglacial lake drainage through gullies and fractures, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16416, https://doi.org/10.5194/egusphere-egu24-16416, 2024.

EGU24-16642 | ECS | Posters on site | CR2.4

Modelling the Hydro-fracture driven collapse of the Larsen B ice shelf 

James ONeill and Ed Gasson

Ice shelves play a key role in buttressing upstream ice - modulating the flow of grounded ice into the ocean and in turn affecting ice sheet contribution to sea level. Iceberg calving, which has approximately equalled thinning in terms of mass loss from Antarctic ice shelves since 2007, is an important ablation process for balancing accumulation. However, rapid ice shelf disintegration, driven by surface melting, can dramatically impact grounded ice dynamics on relatively short time scales. In 2002, the Larsen B ice shelf lost ~60% of its area, following extensive surface melt ponding, observed over months.  This event has been associated with a ‘hydro-fracture’ mode of ice shelf collapse, where surface melt ponds enhance surface crevasse penetration, causing the ice shelf to disintegrate. Following the collapse of Larsen B, retreat of its largest tributary glacier increased by >50% over two years. Whilst surface melting on the scale that preceded Larsen B collapse has historically been limited to the North of the Antarctic Peninsula, under future anthropogenic warming, more of Antarctica’s ice shelf area could become vulnerable to hydro-fracture.

To quantify the role of ice shelf hydro-fracture in ice sheet response to warming, the PSU ice sheet model (PSUISM) incorporates a simple parameterisation of this process, as well as ice cliff failure following loss of buttressing. With its computationally tractable hydro-fracture parameterisation, PSUISM has been used to reproduce large long term Antarctic mass loss under periods of past warmth. It has also simulated high Antarctic contribution to future sea level. However, the break-up of Larsen B, which provides the observational basis for its hydro-fracture scheme, has been less well explored in PSUISM.

We present a suite of high-resolution simulations of the Larsen B ice shelf and its tributary glaciers. We explore the role of hydro-fracture parameters and a range of climate boundary conditions in driving ice shelf collapse. We also compare modelled ice shelf retreat, and grounded ice response, to available observational data. Finally, we explore modifications to the simple hydro-fracture scheme that can better capture Larsen B shelf collapse.

Ice shelf processes remain a key challenge in predicting future Antarctic ice sheet retreat. Despite advances in ice sheet modelling, capturing hydro-fracture in models capable of long integration times, at high resolution, remains a challenge. Our work explores how well the current approach in PSUISM captures the best observed ‘hydro-fracture’ driven ice shelf collapse, and how that impacts our understanding of existing projections.  

How to cite: ONeill, J. and Gasson, E.: Modelling the Hydro-fracture driven collapse of the Larsen B ice shelf, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16642, https://doi.org/10.5194/egusphere-egu24-16642, 2024.

EGU24-18204 | Orals | CR2.4

New insights into the development of slowly rising jökulhlaups from the Grímsvötn subglacial lake, Iceland, deduced from ICEYE SAR images and in-situ observations 

Eyjólfur Magnússon, Vincent Drouin, Finnur Pálsson, Krista Hannesdóttir, Joaquín M. C. Belart, Jan Wuite, Gunnar Sigurðsson, Bergur Einarsson, Tómas Jóhannesson, Benedikt G. Ófeigsson, Thomas Nagler, Magnús T. Gudmundsson, Thórdís Högnadóttir, and Etienne Berthier

We present a study on two jökulhlaups from the subglacial lake Grímsvötn, beneath Vatnajökull ice cap, SE-Iceland, giving new insights into the development of slowly rising jökulhlaups. In the first, spanning the period 14 November – 10 December, 2021, ~0.92 km3 of water was released, reaching peak discharge from the lake of ~3500 m3 s–1 from the lake on 4 December. In the latter, taking place 4­–22 October, 2022, the corresponding numbers were ~0.16 km3 and ~500 m3 s–1. Both jökulhlaups were captured by ICEYE X-band radar satellites, with daily repeated SAR images, allowing construction of 3D ice motion above the ~50-km long subglacial flood route, using InSAR and amplitude offset-tracking results. During both jökulhlaups, the outflow from the lake, derived from the lake level (with GNSS), was monitored, as well as the development of the flood near the glacier margin in the river Gígjukvísl. During the 2021 jökulhlaup, the ice motion above the flood path, deduced from the satellite data, was validated with data from a GNSS station operated ~30 km from the glacier margin. Surface elevation changes above the lake before, during and in between the jökulhaups were derived from Pléiades optical stereo images. Our data show that during the early phase of these jökulhaups, a flood wave propagates down glacier at pace of ~7 km d–1. The flood waves were most likely initiated at a bottleneck formed in a tunnel flow somewhere along the first 10 km of the flood path, while the discharge from the lake was still only few tens of m3 s–1. Five to seven days passed from the likely initiation of the flood wave until floodwater was detected in the river Gígjukvísl. The maximum observed horizontal ice motion above the flood path in 2021 was around 3 m d-–1 or ~5 times the maximum during normal winter conditions. At many locations, the horizontal velocity is increased by an order of magnitude. After the peak discharge from Grímsvötn was reached, the glacier almost immediately started slowing down, first rapidly or by ~50% over 1–2 days, but then gradually down to normal velocities in 4–5 days. In 2021, the observed rate of uplift was up to 0.5 m d1 during the rise of the jökulhlaup and the subsequent subsidence reached up 1.0 m d–1 during its decline. The study shows that ~0.3 km3 was stored beneath the glacier during the peak of the jökulhlaup, and it is therefore expected that the magnitude of the uplift/subsidence reached 2–3 m in some areas. The width of the flooded areas, observed from the subsidence during the early decline of the jökulhlaups, was typically 0.5–1 km the first 20 km of the flood path, while for the remaining 30 km, it was typically 2­–4 km. The effect of the floods on horizontal ice motion, presumably due to a disturbance in the subglacial water pressure, are, however, observed over a much larger area.

How to cite: Magnússon, E., Drouin, V., Pálsson, F., Hannesdóttir, K., Belart, J. M. C., Wuite, J., Sigurðsson, G., Einarsson, B., Jóhannesson, T., Ófeigsson, B. G., Nagler, T., Gudmundsson, M. T., Högnadóttir, T., and Berthier, E.: New insights into the development of slowly rising jökulhlaups from the Grímsvötn subglacial lake, Iceland, deduced from ICEYE SAR images and in-situ observations, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18204, https://doi.org/10.5194/egusphere-egu24-18204, 2024.

EGU24-18932 | ECS | Posters on site | CR2.4

Impact of supraglacial lakes on the Greenland Ice Sheet Surface Mass Balance into the regional climate model MAR 

Guillaume Timmermans and Xavier Fettweis

The Greenland Ice Sheet is currently one of the primary contributors to the rise of sea levels . The Total Mass Balance (TMB) of the Greenland Ice Sheet can be decomposed into Surface Mass Balance (SMB) and ice discharge (D). At present, both terms contribute approximately equally to mass loss. However, it has been anticipated that surface losses will become more significant in the future (because coastal glaciers will retreat if the ice sheet continues to melt). Our understanding of SMB is currently notably based on polar regional climate models (RCMs) like MAR ("Modèle Atmosphérique Régional"), that simulates most of the different surface processes involved in SMB. However, one potential important process is currently missing in all model based estimates: the role of supraglacial lakes. The excess of meltwater is directly removed from the pixels by assuming that this mass fully runoffes towards the ocean in models until now. These lakes notably impact on the surface albedo of bare ice and could retain a part of produced surface meltwater that can refreeze at the beginning of winter or evaporate during summer (impacting them clouds and precipitation afterwards).

To evaluate the importance of supraglacial lakes as a potential SMB component needed to take into account, we have run MARv3.14 at very high resolution over the South-West of Greenland during the 2018-2019 hydrological year by allowing the produced surface meltwater in the ablation zone to remain liquid or solid above the surface in the bare ice areas where supraglacial lakes have been detected by MODIS.

How to cite: Timmermans, G. and Fettweis, X.: Impact of supraglacial lakes on the Greenland Ice Sheet Surface Mass Balance into the regional climate model MAR, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18932, https://doi.org/10.5194/egusphere-egu24-18932, 2024.

EGU24-19042 | Posters on site | CR2.4

Simulating the impact of Antarctic subglacial hydrology on ice sheet evolution 

Rupert Gladstone, Chen Zhao, Thomas Zwinger, Samuel Cook, Yu Wang, David Gwyther, Mauro Werder, and John Moore
While the slow moving interior of the Antarctic Ice Sheet is not prone to rapid change, the fast flowing outlet glaciers may exhibit accelerations and unstable retreat in response to ocean induced melting of the ice shelves. This rapid motion is only possible due to sliding of ice over the bed, motion which is dependent on the presence, and pressure, of liquid water under the ice sheet.  This subglacial hydrologic system is fed by in-situ melting caused mainly by friction heat as ice slides over the bed, and its outflow feeds into ice shelf cavities across deep grounding lines.  Two-way interactions between ice dynamics and the hydrologic system may occur due to changing sliding speeds, subsequent meltwater generation, and the responding changes in basal water pressure, which in turn impact on sliding resistance.  The subglacial water system may also impact on ice shelf cavity circulation due to its very low density relative to ocean water, and this may also impact indirectly on ice dynamics due to the changing cavity circulation driving changing ice shelf melt rates, which affect ice shelf thickness and therefore backstress.
 
The current generation of ice sheet models used in sea level prediction do not represent the evolution of the subglacial hydrologic system.  A typical approach is to spatially tune a sliding parameter in which all aspects of basal physics relating to sliding and hydrology are implicitly hidden.  We will outline a modelling approach to incorporate the GLAcier Drainage System (GlaDS) model into a coupled system in which the hydrologic system can interact with both ice dynamics and cavity circulation. Ice dynamic model Elmer/Ice and the Regional Ocean Modelling System (ROMS) will be used, coupled through the Framework for Ice Sheet - Ocean Coupling (FISOC).  GlaDS represents the subglacial hydrologic system as two interacting components: a distributed network of linked cavities and a network of channels.  We will show preliminary simulations of these linked cavities and channels from Antarctic simulations. We will outline a plan for moving towards fully coupling GlaDS to the ice dynamics and ice shelf cavities, along with an "accelerated forcing" approach to handle asynchronicities.

How to cite: Gladstone, R., Zhao, C., Zwinger, T., Cook, S., Wang, Y., Gwyther, D., Werder, M., and Moore, J.: Simulating the impact of Antarctic subglacial hydrology on ice sheet evolution, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19042, https://doi.org/10.5194/egusphere-egu24-19042, 2024.

EGU24-19875 | ECS | Posters on site | CR2.4

Validation of effective subglacial hydrology models 

Jeremie Schmiedel, Angelika Humbert, Thomas Kleiner, and Roiy Sayag

The presence of subglacial lubrication networks at the ice-bed interface is a key component for ice sheet dynamics. A subglacial network has the potential to facilitate rapid ice flow through reduction in basal friction, possibly resulting in the formation of surges and ice streams. A wide range of numerical models are designed to simulate the impact such networks on ice flow. Validating these models is crucial to ensure that the important subglacial physical processes are accurately resolved.

One class of subglacial network models is based on an effective porous medium (EPM) approach. A major component of such models involves a nonlinear diffusion equation for the subglacial water pressure, which include variable transmissivity that represent a range of subglacial and groundwater processes.

We present solutions to a generalized nonlinear diffusion equation that can model a wide range of flows of this kind. We use scaling analysis to find general similarity solutions and other solutions with explicit time-dependent transmissivity. We use this method to validate the parallel implementation of the Confined–Unconfined Aquifer System model (CUAS-MPI) for subglacial hydrology. The model is based on an effective porous media (EPM) approach. Our results show, that CUAS-MPI is able to accurately solve highly non linear flows, equivalent to cavity opening and creep closure terms in subglacial hydrology. Because of their generality, our solutions are readily applicable to other subglacial hydrology models that are based on the EPM approach. We anticipate that a validated hydrology model with our solutions can achieve more credible results in subglacial network simulations, and consequently in predicting ice sheet evolution.

How to cite: Schmiedel, J., Humbert, A., Kleiner, T., and Sayag, R.: Validation of effective subglacial hydrology models, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19875, https://doi.org/10.5194/egusphere-egu24-19875, 2024.

EGU24-20925 | Orals | CR2.4

The fate of Greenland Ice Sheet supraglacial lakes in a warm and cool year 

Aneesh Subramanian, Devon Dunmire, Emam Hossain, Md Osman Gani, Alison Banwell, and Brendan Myers

Supraglacial lakes form on the surface of the Greenland Ice Sheet during the summer months and can directly impact ice sheet mass balance by removing mass via drainage and runoff or indirectly impact mass balance by influencing ice sheet dynamics. Here, we utilize the growing inventory of optical and microwave satellite imagery to automatically determine the fate of Greenland-wide supraglacial lakes during 2018 and 2019, a cool and warm melt season respectively. We use a machine learning time series classification approach to categorize lakes into four different categories: lakes that 1) refreeze, 2) rapidly drain, 3) slowly drain, and 4) become buried lakes at the end of the melt season. We find that during the warmer 2019, not only was the number of lake drainage events higher than in 2018, but also the proportion of lakes that drained was greater. By investigating mean lake depths for these four categories, we show that drained lakes were, on average, 22% deeper than lakes that refroze or became buried lakes. Interestingly, drained lakes had approximately the same maximum depth in 2018 and 2019; however, lakes that did not drain were 29% deeper in 2018, a cooler year. Our unique two-year dataset describing the fate of every Greenland supraglacial lake provides novel insight into lake drainage and refreeze in a relatively warm and cool year, which may be increasingly relevant in a warming climate.

How to cite: Subramanian, A., Dunmire, D., Hossain, E., Gani, M. O., Banwell, A., and Myers, B.: The fate of Greenland Ice Sheet supraglacial lakes in a warm and cool year, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20925, https://doi.org/10.5194/egusphere-egu24-20925, 2024.

EGU24-291 | ECS | Orals | OS1.6 | Highlight

Oceanic gateways to Antarctic grounding lines - Impact of critical access depths on sub-shelf melt 

Lena Nicola, Ronja Reese, Moritz Kreuzer, Torsten Albrecht, and Ricarda Winkelmann

Melting underneath the floating ice shelves surrounding the Antarctic continent is a key process for the stability of the Antarctic Ice Sheet and therefore its current and future mass loss. Troughs and sills on the continental shelf play a crucial role in modulating sub-shelf melt rates, as they can allow or block the access of relatively warm, modified Circumpolar Deep Water to ice-shelf cavities.

In our study (Nicola et al., subm.), we identify potential oceanic gateways that could allow the access of warm water masses to Antarctic grounding lines based on critical access depths inferred from high-resolution bathymetry data. We analyse the properties of water masses that are currently present in front of the ice shelf and that might intrude into the respective ice-shelf cavities in the future. We use the ice-shelf cavity model PICO to estimate an upper limit of melt rate changes in case all warm water masses up to a certain depth level gain access to the cavities. The identification of oceanic gateways is thus valuable for assessing the potential of ice-shelf cavities to switch from a 'cold' to a 'warm' state, which could result in widespread ice loss from Antarctica.

How to cite: Nicola, L., Reese, R., Kreuzer, M., Albrecht, T., and Winkelmann, R.: Oceanic gateways to Antarctic grounding lines - Impact of critical access depths on sub-shelf melt, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-291, https://doi.org/10.5194/egusphere-egu24-291, 2024.

EGU24-609 | ECS | Orals | OS1.6

High resolution pH measurements at the edge of the Dotson Ice shelf using state-of-the-art autonomous technologies. 

Daisy Pickup, Karen Heywood, Dorothee Bakker, Emily Hammermeister, Socratis Loucaides, Yixi Zheng, Gareth Lee, Patricia Yager, and Rob Hall

The global ocean takes up about a quarter of anthropogenic carbon dioxide emissions, with the Southern Ocean playing a disproportionately large role. This uptake has led to changes in the Southern Ocean's carbonate chemistry, reducing pH through ocean acidification. The Amundsen Sea, West Antarctica, is surrounded by rapidly melting ice shelves, that may be impacting the carbonate balance of this coastal region. Near the Dotson Ice Shelf, we collected the first high-resolution, full-depth pH dataset using a Lab-on-Chip spectrophotometric sensor attached to an autonomous profiling ocean glider. The sensor collected data within 10 km of the Dotson Ice Shelf over a 19-day period in January/February 2022 and captured the variability that results from summertime biogeochemical and physical processes. In the upper 150 m, net primary production dominates variation in pH, producing a maximum pH of 8.34 (on the total hydrogen scale) in front of Dotson Ice Shelf, where chlorophyll fluorescence also peaks. Below 150 m, pH is generally lower, likely as a result of net respiration. The inflow of modified Circumpolar Deep Water near the east side of Dotson Ice Shelf exhibits a slightly elevated pH (0.05 units) compared to surrounding deep waters. The meltwater-laden outflow that exits on the west side of the ice shelf at depths between 300 - 500 m displays a lower pH (0.1 units) relative to the surrounding waters, which shoals and mixes, reducing pH in the overlying surface waters. In the coastal current along Dotson Ice Shelf, an unusual subsurface maximum in pH (0.1 units at 150 m, compared to surrounding waters) is observed and is also associated with increased chlorophyll fluorescence. Possible explanations for the observed features are discussed. These high-resolution findings reveal the potential of pH measurements on an autonomous vehicle for investigating difficult to access regions with glacial melt.

How to cite: Pickup, D., Heywood, K., Bakker, D., Hammermeister, E., Loucaides, S., Zheng, Y., Lee, G., Yager, P., and Hall, R.: High resolution pH measurements at the edge of the Dotson Ice shelf using state-of-the-art autonomous technologies., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-609, https://doi.org/10.5194/egusphere-egu24-609, 2024.

The ice sheets flowing into the Amundsen Sea, West Antarctica, are losing mass faster than most others about the continent due to rapid basal melting of their floating ice shelf extensions. A key oceanographic control of the rate of ice-shelf basal melting is a warm eastward undercurrent that flows along the continental shelf break and eventually towards the ice shelves. On monthly timescales surface winds drive fast barotropic variability in the undercurrent. On decadal timescales, however, undercurrent variability is not well understood. We present model results that show that on decadal timescales undercurrent variability opposes wind variability, with this being a consequence of sea-ice and ice-shelf freshwater flux variability. Specifically, periods of fast (more eastward) undercurrent are a result of enhanced brine rejection north of the continental shelf break, which enhances the cross-slope pressure gradient at depth and accelerates the undercurrent baroclinically. Opposite anomalies in the sea-ice freshwater flux decelerate the undercurrent. A positive feedback mechanism between the undercurrent and ice-shelf basal melt strengthens the undercurrent anomalies. Lastly, we show that variability in sea-ice freshwater fluxes, and by extension the Amundsen Sea undercurrent and ice-shelf basal melt, can be attributed to tropical Pacific variability impacting atmospheric conditions over the Amundsen Sea.

How to cite: Haigh, M. and Holland, P.: Freshwater fluxes drive decadal variability of the Amundsen Sea undercurrent and ice-shelf basal melt, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1302, https://doi.org/10.5194/egusphere-egu24-1302, 2024.

EGU24-1729 | ECS | Posters on site | OS1.6

Revisiting the iceberg thickness distribution in Southern Ocean simulations. 

Anna Olivé Abelló, Pierre Mathiot, Nicolas Jourdain, Yavor Kostov, and Paul Holland

The acceleration of glaciers in the Antarctic ice sheet amplifies the flow of icebergs into the Southern Ocean. The presence of these icebergs has a significant impact on the penetration of warm water toward ice shelves and can also induce the formation of large polynyas when grounded, thereby promoting dense water formation. The existing implementation of the Lagrangian iceberg module in NEMO does not consider the Antarctic ice-shelf thicknesses from which the icebergs are originated, so the model cannot represent whether icebergs are thin enough to cross the shallow bathymetric ridges. In the present model, the iceberg masses, thicknesses, and size distribution are prescribed a priori as input parameters irrespective of the source ice-shelf characteristics. In addition, the categorization of iceberg classes and the scaling of smaller icebergs are not optimized, which is a strong limitation for climate modelling. Hence, the main aim of this study is to improve the thickness distribution of the calved icebergs based on ice shelf characteristics, decrease the computational cost of the model, and assess how these improvements alter the lifespan of the icebergs and their freshwater flux distribution across Antarctica.

The new approach has been implemented in a 0.25° Southern Ocean configuration of the NEMO ocean–sea-ice model. We used a power-law probability distribution function of iceberg occurrence as a function of iceberg area and a tabular iceberg definition to establish the thickness distribution for the small iceberg categories, imposing that each class exhibits the same total mass. In order to reduce computational costs, we constrained the frequency of icebergs released per class so that the smaller classes of multiple icebergs are gathered into one particle. Our preliminary results show that the iceberg thickness distribution, implemented as a function of areas, is supported by in-situ observations measured from high-resolution SAR-1 satellite images. The released icebergs display a typical thickness per class depending on the ice shelf's source, with a broader distribution when more calving classes are established. Ultimately, the findings reveal that accounting for realistic Antarctic ice-shelf thicknesses leads to thicker icebergs, particularly in larger classes, consequently increasing the mass that each transports westward around Antarctica. Future iceberg simulations, carried out for 25 years, will assess the iceberg's sensitivity to the maximum iceberg area, the number of different sizes and the area bounds used to define each size, among others. It is also expected that these simulations will also unveil high-melting regions and high iceberg densities in regions where icebergs ground, and will determine if fragmentation processes are needed to achieve realistic iceberg lifespans.

How to cite: Olivé Abelló, A., Mathiot, P., Jourdain, N., Kostov, Y., and Holland, P.: Revisiting the iceberg thickness distribution in Southern Ocean simulations., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1729, https://doi.org/10.5194/egusphere-egu24-1729, 2024.

EGU24-2153 | ECS | Orals | OS1.6

Ocean Circulation and Ice Shelf Melting in the Bellingshausen Sea 

Emma White, Adrian Jenkins, Paul Holland, Jan de Rydt, and Miguel Morales-Maqueda

A modified version of warm Circumpolar Deep Water (CDW) is able to flow onto the continental shelf in the Bellingshausen Sea, leading to high melt rates beneath the floating ice shelves. Data are presented from a 2007 research cruise to the Bellingshausen Sea, during which temperature, salinity and dissolved oxygen measurements were made at 253 stations. These observations provide detailed insights into the physical oceanographic regime of the region and its impact on the ice shelves, particularly in the western Bellingshausen Sea where few other ship-based observations exist. The transport of CDW across the shelf break at Marguerite Trough and Belgica Trough is assessed, as well as the modification of CDW properties as it flows onto the continental shelf. The spatial variability seen in water masses across the Bellingshausen Sea and regional circulation patterns are also evaluated. Finally, we present an assessment of the meltwater production and circulation within the ice shelf cavities.

How to cite: White, E., Jenkins, A., Holland, P., de Rydt, J., and Morales-Maqueda, M.: Ocean Circulation and Ice Shelf Melting in the Bellingshausen Sea, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2153, https://doi.org/10.5194/egusphere-egu24-2153, 2024.

EGU24-3500 | Orals | OS1.6

How much can we get from Gade's mixing line? 

Louis-Alexandre Couston

Gade’s meltwater mixing line theory is consistent with numerous under-ice ocean observations. However, it is built on an assumption that is difficult to test with field measurements, especially near the ice boundary, which is that the effective salt and temperature diffusivities are equal. In this presentation, I will discuss the validity of Gade’s mixing line theory and show how it can be used to predict melt rates, using results from direct numerical simulations of a canonical model for externally forced ice-ocean boundary layers. I will first demonstrate that the effective salt and temperature diffusivities are approximately equal across most of the boundary layer in the well mixed regime. Then, I will show how knowledge of one turbulent diffusivity (salt, temperature, or thermal driving) can be combined with knowledge of one vertical profile in the bulk (salt, temperature, or thermal driving) to predict the heat and salt fluxes at the ice-ocean boundary.

How to cite: Couston, L.-A.: How much can we get from Gade's mixing line?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3500, https://doi.org/10.5194/egusphere-egu24-3500, 2024.

EGU24-3579 | ECS | Orals | OS1.6

Turbulent heat exchange between Circumpolar Deep Water and Winter Water on the Amundsen Sea Continental Shelf, Antarctica  

Xingchi Wang, Yvonne Firing, Alberto Naveira Garabato, Bieito Fernández Castro, and Carl Spingys

The intrusion of Circumpolar Deep Water (CDW) onto the Amundsen Sea continental shelf is a primary driver of basal melting and thinning of the West Antarctic ice shelves. The interaction between CDW and the overlying, near-freezing Winter Water (WW) on the continental shelf is thought to limit the heat that ultimately reaches the ice shelves. However, such interaction, and the processes underpinning it, remain little understood. In this study, we analyze over one hundred microstructure and finestructure profiles across the Amundsen Sea continental shelf. Our analysis indicates a strong correlation between microstructure turbulent kinetic energy dissipation and the finescale horizontal kinetic energy (HKE) associated with internal waves, suggesting that wave breaking is key to turbulence production in the region. Exploiting this relationship, we construct a 2-year time series of finescale HKE and turbulent dissipation from a mooring dataset acquired at the Pine Island-Thwaites West (PITW) trough. The time series reveals a distinct seasonal signal, with a range spanning one order of magnitude and diverse drivers. By combining a regional numerical model with the mooring diagnostics, we then estimate the turbulent diapycnal diffusivity and associated vertical heat flux between CDW and WW at the PITW trough. This provides insight into the heat loss experienced by CDW on its pathway toward the ice shelves.

How to cite: Wang, X., Firing, Y., Naveira Garabato, A., Fernández Castro, B., and Spingys, C.: Turbulent heat exchange between Circumpolar Deep Water and Winter Water on the Amundsen Sea Continental Shelf, Antarctica , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3579, https://doi.org/10.5194/egusphere-egu24-3579, 2024.

EGU24-4097 | ECS | Posters on site | OS1.6

A regime change within Amery Ice Shelf cavity by a reversed current in the twenty-first century 

Jing Jin, Antony Payne, and Christopher Bull

The Amery Ice Shelf (AmIS), the third largest ice shelf in Antarctica, has experienced a relatively low basal melting during the past decades. However, it is unclear how AmIS melting will respond to a future warming climate. Here, we use a regional ocean model forced by a low-emission scenario and a high-emission scenario to investigate AIS melting by 2100. The melt rate is projected to increase multiple times in 2100. An abrupt increase in melt rate happens in the 2060s in both scenarios. A mechanism that drives the jump of melting is investigated. A redistribution of local salinity (and then density) in front of AmIS forms a new geostrophic balance, leading to the reversal of local currents. This transforms AmIS from a cold cavity to a warm cavity, and results in a jump of ice shelf melting. This regime change draws our attention to the role of oceanic processes in the basal mass loss of Antarctic ice shelves in climate change.

How to cite: Jin, J., Payne, A., and Bull, C.: A regime change within Amery Ice Shelf cavity by a reversed current in the twenty-first century, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4097, https://doi.org/10.5194/egusphere-egu24-4097, 2024.

EGU24-5201 | ECS | Posters on site | OS1.6

Evolution processes of Ross sea polyny aassociated with modified Circumpolar Deep Water intrusion 

Qing Qin, Zhaomin Wang, Liangjun Yan, Chengyan Liu, and Jan De Rydt

In the central Ross Sea continental shelf, the modified Circumpolar Deep Water could intrude the continental shelf between March and July, and reach about 76 °S. According to seal-CTD data, in March and April, the potential temperature of the modified Circumpolar Deep Water was up to - 0.55 °C, and was widely distributed within the depths of 100 - 300 m. In May and June, the potential temperature of the modified Circumpolar Deep Water was up to - 0.65 °C, and was found to the north of 76 °S above the depth of 350 m, but discontinuous above the depth of 200 m. In July, the modified Circumpolar Deep Water sharply cooled, with the maximum potential temperature being -1.45 °C.

By analysing the seal-CTD observations and the numerical model results, this study found strong mixing in the central part of the shelf, owing to topography-induced upwelling. The resulted mixed layer warming is also attributed to the intrusion of the modified Circumpolar Deep Water. This oceanic process, along with the katabatic wind forcing, contributed to forming unique sea ice distribution characteristics in the Ross Sea Polynya, featured by ‘’less ice, more ice, less ice” from the front of the Ross Ice Shelf to the upwelling zone. This kind of sea ice distribution characteristics can also promote the northward expansion of the Ross Sea Polynya.

How to cite: Qin, Q., Wang, Z., Yan, L., Liu, C., and De Rydt, J.: Evolution processes of Ross sea polyny aassociated with modified Circumpolar Deep Water intrusion, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5201, https://doi.org/10.5194/egusphere-egu24-5201, 2024.

EGU24-5406 | ECS | Posters on site | OS1.6

Reconstructing historical ocean changes around the West Antarctic Ice Sheet over the past centuries 

Quentin Dalaiden, Paul Holland, Kaitlin Naughten, Pierre Mathiot, Noé Pirlet, Antoine Barthelemy, and Nicolas Jourdain

Over recent decades, the West Antarctic Ice Sheet (WAIS) has witnessed a large increase in ice shelf melting. This ice loss is recognized to be associated with a response to changes in the ocean state, in particular of the Circumpolar Deep Water (CDW) on the Amundsen Sea continental shelf. It has been shown that the variability of the CDW inflow is strongly related to wind changes. While instrumental-based atmospheric reanalysis products are available since 1979, given the strong natural variability of the West Antarctic climate, this period of a few decades might be too short to identify the mechanisms driving the long-term changes in ice shelf melting, and to distinguish the relative contribution of natural and forced variability to the total changes. Therefore, there is a need to provide long-term historical changes in oceanic conditions to put the recently observed ice shelf melting into a longer context and to ultimately better constrain the future contribution of the WAIS to the global sea-level rise. Over the past few years, atmospheric reanalysis based on paleoclimate records spanning the last centuries have been released. This offers us the opportunity to assess historical changes in oceanic conditions in response to changes in the atmosphere. In this study, we propose a framework to reconstruct past ocean conditions around the WAIS over the last few centuries by using an ocean–sea-ice model (NEMO-SI3) forced by a paleo-based atmospheric reanalysis. Specifically, we use a paleo-reanalysis based on data assimilation that aims at dynamically combining information from paleoclimate records from the Southern Hemisphere (especially ice-core records) and the physics of Earth System Models. This has the advantage of guaranteeing a dynamical consistency between the reconstructed variables. Along with the methodology, we present the first reconstructed oceanic conditions from the NEMO-SI3 simulations.

How to cite: Dalaiden, Q., Holland, P., Naughten, K., Mathiot, P., Pirlet, N., Barthelemy, A., and Jourdain, N.: Reconstructing historical ocean changes around the West Antarctic Ice Sheet over the past centuries, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5406, https://doi.org/10.5194/egusphere-egu24-5406, 2024.

EGU24-6270 | ECS | Orals | OS1.6

Assessing the degree of impact from iceberg activities on penguin colonies of Clarence Island 

Hong Lin, Xiao Cheng, Teng Li, Qian Shi, Qi Liang, Xinyu Meng, Shaoyin Wang, and Lei Zheng

During August and September 2023, three giant icebergs, each bigger than Paris, successively grazed Clarence Island in the northeast of the Antarctic Peninsula, a home to a population of over 100,000 penguins. This incident may serve as a clarion call for the increasing iceberg calving due to global warming and its subsequent impact on the Antarctic ecosystem. Here we investigated this unexpected event using satellite imagery, employing wind speed, ocean currents, and seabed topography data to understand the behavior of the icebergs. During the study period, eastward winds and northward currents favored the drift of icebergs away from the island, and the deeper waters off the east coast reduced the probability of iceberg grounding. Nevertheless, iceberg D30A still left a significant amount of floating ice during its grazing passage. Moreover, we integrated historical records and probabilistic analyses of iceberg grounding to assess the degree of impact on penguin colonies of Clarence Island. Among the eleven colonies, only one in the northern region exhibits low impact, whereas two colonies in the southeastern region experience high impact. In a warming future, with an increase in iceberg calving events, penguin colonies located in iceberg drift hotspots are likely to experience greater impacts from iceberg activities. Therefore, we call upon the public to pay heed to climate warming and implement measures to mitigate anthropogenic greenhouse gas emissions, thereby alleviating the threat to penguin ecosystems.

How to cite: Lin, H., Cheng, X., Li, T., Shi, Q., Liang, Q., Meng, X., Wang, S., and Zheng, L.: Assessing the degree of impact from iceberg activities on penguin colonies of Clarence Island, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6270, https://doi.org/10.5194/egusphere-egu24-6270, 2024.

EGU24-7961 | ECS | Orals | OS1.6

Exploring drivers of change in the Ross Sea with a regional ocean model 

Alethea S. Mountford, Christopher Y. S. Bull, Adrian Jenkins, Nicolas C. Jourdain, and Pierre Mathiot

The Ross Sea and Ross Ice Shelf have remained relatively unchanged over recent decades, despite increasing global anthropogenic influences, and ocean temperatures and ice shelf melt rates increasing nearby. Future atmospheric warming, for example, could lead to a transition of the sub-ice shelf cavity from its current cold state to a warm state, which could in turn result in a dramatic increase to the currently low basal melt rates in the Ross Ice Shelf. We present a regional ocean model configuration (NEMO) at 1/4° resolution, which encompasses the whole of the Ross Sea, Ross Gyre and Ross Ice Shelf, as well as eastwards to include the Amundsen Sea, with a series of perturbation experiments to near-surface air temperature (an increase of 10°C) and precipitation (an increase by a factor of two) and a combination of the two. The model includes static ice shelves, extending from Merz to Venable, and their thermodynamic interaction with the ocean. Perturbations to the air temperature and precipitation alone are not sufficient to significantly alter the circulation or oceanographic conditions within the Ross Sea or within the cavity of the Ross Ice Shelf. However, when both perturbations are applied simultaneously, waters within the Ross Ice Shelf cavity warm to over 1°C, inducing an increase in basal melt of around 1000 Gt/yr within the cavity over the course of the simulated period 2017-2100. We see an increase in the strength of the Ross Gyre, with an eastward extension of the gyre into the Amundsen Sea. Circulation within the cavity is also affected, with a visible reduction in the outflow of waters from the cavity. Oceanographic changes within the cavity and the Ross Sea could have an effect on deep water formation and wider reaching impacts on global circulation.

How to cite: Mountford, A. S., Bull, C. Y. S., Jenkins, A., Jourdain, N. C., and Mathiot, P.: Exploring drivers of change in the Ross Sea with a regional ocean model, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7961, https://doi.org/10.5194/egusphere-egu24-7961, 2024.

EGU24-8239 | ECS | Orals | OS1.6

Mid-Holocene ecosystem reorganisation in the Weddell Sea: dynamic sea ice and climate inferred from novel Antarctic snow petrel deposits (Heimefrontfjella Range) 

Mark Stevenson, Dominic Hodgson, Michael Bentley, Darren Gröcke, and Erin McClymont

Sea ice in Antarctica is closely coupled to the climate system, influencing water mass upwelling, albedo and the exchange of heat and gas between the ocean and atmosphere. Sea ice also supports a diverse ecosystem which is sensitive to changes in climate and biogeochemistry. The Heimefrontfjella mountain range in East Antarctica features the nesting sites of the snow petrel (Pagodroma nivea) where finely laminated stomach-oil deposits (regurgitated dietary contents) are deposited. Such deposits can provide valuable information on Holocene dietary changes of the snow petrel that may relate to palaeoclimatic variations. Snow petrel feeding grounds in the Weddell Sea range from neritic (coastal) zones rich in fish, to the productive open ocean where Antarctic krill (Euphausia superba) become increasingly important. Distinct dietary signatures are recorded in the biomarkers of these deposits, providing new evidence of changing sea-ice and climate in the Weddell Sea.

Here we focus on stomach-oil deposits from Heimefrontfjella. A highly resolved radiocarbon-dated (14C-AMS) sequence spanning ~6,500 to 2,000 cal. yr BP has been investigated for organic biomarkers (fatty acids, sterols), stable isotopes of carbon and nitrogen (δ13C, δ15N) and inorganic composition by X-ray fluorescence (XRF).  From ~6,500 to 6,000 cal. yr BP fatty acid markers were generally high in concentration, with particularly high levels of C14:0 mirrored by high δ15N suggesting food sources rich in Antarctic krill and periods of enhanced feeding in the open ocean. Subsequently between 6,000 and 4,500 cal. yr BP there was a marked reduction in C14:0, C18:0 and δ15N, although phytol concentration remained high. This trophic shift suggests a transitional Weddell Sea still rich in productivity with snow petrels feeding in both the open ocean and close to the shore on a mixture of fish, krill and squid. This is consistent with regional mid-Holocene warmth, and also suggests dynamic variable meteorological and oceanographic conditions during this period. Subsequently, between ~4,500 and 2,000 cal. yr BP organic marker concentrations were markedly lower, suggesting a relatively low productivity period, which we anticipate required more coastal feeding by snow petrels. This change is consistent with evidence from regional reconstructions suggesting movement into neoglacial conditions.

Together these findings highlight that the Weddell Sea experienced relatively short-term decadal and centennial-scale changes in sea ice and climate during the Holocene. Our results support existing regional proxies (e.g. offshore sediment records, lake records, ice-core records and palaeo-glacial thinning history) and highlight the importance of snow petrel deposits in recording palaeo-dietary and ecosystem changes in Antarctic marine systems.

How to cite: Stevenson, M., Hodgson, D., Bentley, M., Gröcke, D., and McClymont, E.: Mid-Holocene ecosystem reorganisation in the Weddell Sea: dynamic sea ice and climate inferred from novel Antarctic snow petrel deposits (Heimefrontfjella Range), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8239, https://doi.org/10.5194/egusphere-egu24-8239, 2024.

EGU24-8904 | ECS | Orals | OS1.6

Towards Parameterizing Eddy-Mediated Transport of Circumpolar Deep Water across Antarctic Continental Slopes 

Nicolas Dettling, Martin Losch, Friederike Pollmann, and Torsten Kanzow

The onshore transport of warm Circumpolar Deep Water (CDW) is associated with a heat flux onto the Antarctic continental shelves and strongly contributes to Antarctic ice shelf decline. On the continental shelf of the Weddell Sea, dense water forms through interactions with sea and shelf ice and subsequently propagates down the continental slope. The descent of dense water simultaneously produces an onshore transport of CDW. Here, mesoscale eddies drive a vertical momentum flux that is necessary to overcome the potential vorticity gradient imposed by the continental slope. The resolution of current climate models, however, is too coarse to resolve the Rossby Radius of deformation at high latitudes so that eddies need to be parameterized.

In an idealized model setup (MITgcm) representing the continental slope and shelf of the Weddell Sea, we show that eddy-driven shoreward CDW transport can be parameterized using the classical Gent-McWilliams and Redi (GM/Redi) parameterization for mesoscale eddies. In particular, the coarse resolution model with the GM/Redi parameterization simulates an onshore heat flux that is comparable to a high-resolution reference simulation. In contrast, no shoreward heat flux is observed without the eddy parameterization. When parameterizing eddies, the isopycnal slopes and the hydrographic mean fields also strongly improve compared to the runs without the parameterization. 

We further show that the parameterization works best when the GM transfer coefficient strongly decreases over the continental slope, representing the eddy-suppressive effect of steeply sloped topography. Motivated by this observation, we propose a simple modification to the GM/Redi scheme that reduces the coefficients in the presence of sloping topography. Only this „slope-aware“ version of the GM/Redi parameterization yields coefficients suitable for the continental shelf and slope and the open ocean and produces the best fit to the high-resolution model fields. We expect this addition to also be beneficial for modelling other parts of the ocean where eddy effects are moderated by topographic slopes. We therefore discuss the application of the modified parameterization to a regional model of the Cape Darnley region, East Antarctica, where dense water flows down realistic topography and drives an onshore flow of CDW at high resolution.

How to cite: Dettling, N., Losch, M., Pollmann, F., and Kanzow, T.: Towards Parameterizing Eddy-Mediated Transport of Circumpolar Deep Water across Antarctic Continental Slopes, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8904, https://doi.org/10.5194/egusphere-egu24-8904, 2024.

EGU24-10184 | ECS | Orals | OS1.6 | Highlight | OS Division Outstanding ECS Award Lecture

The global influence of ice-ocean interactions in Antarctica 

Alessandro Silvano

In this seminar, I will explore the oceanic processes that drive melting of the Antarctic Ice Sheet, and consequent global sea level rise. Different processes lead certain areas of the Antarctic Ice Sheet to be more susceptible to rapid ocean-driven melting, while other areas to be more resilient. I will also show the emergence of a feedback between the ice sheet and Southern Ocean: increased melting leads to warming of the oceanic waters surrounding Antarctica, with consequences for future sea level rise. I will conclude by describing how increased melting of the Antarctic Ice Sheet as well as changes in sea ice affect the global ocean abyss and its ability to store anthropogenic heat and carbon.

How to cite: Silvano, A.: The global influence of ice-ocean interactions in Antarctica, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10184, https://doi.org/10.5194/egusphere-egu24-10184, 2024.

EGU24-11152 | Posters on site | OS1.6

The effect of grid resolution on sub-ice shelf circulation in the Energy Exascale Earth System Model 

Irena Vaňková, Xylar Asay-Davis, Darin Comeau, Stephen Price, and Jonathan Wolfe

Global ocean models are typically too coarse to explicitly resolve physical processes, such as mesoscale eddies, that transport heat into ice-shelf cavities and contribute to melting. As a result, mesoscale processes around Antarctica in such models need to be parameterized. Here we investigate the performance of these parameterizations in the Energy Exascale Earth System Model (E3SM), specifically focusing on the heat transport into an ice shelf cavity, the strength and direction of sub ice shelf circulation, and the rate of basal melting. Taking advantage of E3SM’s variable-resolution capabilities we set up a sequence of configurations with nominal grid sizes of 12, 8, 4, 2, and 1 km in the southern Weddell Sea, such that with increasing resolution, less eddies are parameterized and more resolved explicitly. The analysis is focused on the Filchner-Ronne Ice Shelf, because it is oceanographically interesting, it is important for sea level projections, and there are relatively abundant datasets from this region available for model validation.

How to cite: Vaňková, I., Asay-Davis, X., Comeau, D., Price, S., and Wolfe, J.: The effect of grid resolution on sub-ice shelf circulation in the Energy Exascale Earth System Model, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11152, https://doi.org/10.5194/egusphere-egu24-11152, 2024.

Laminated diatomaceous deposits have been documented in some regions of Antarctica, including the Antarctic Peninsula and the Ross Sea. In general, very high sedimentation rates can overwhelm limited bioturbation, thus favoring the varve preservation, for example, in certain glacio-marine environments. The laminated sediments collected in the Edisto Inlet, western Ross Sea, exhibited well-defined dark and light laminae on a mm- to cm-scale. Dark laminae contained relatively high concentrations of a biomarker for fast ice, IPSO25, while low IPSO25 concentrations characterized the light laminae, and the diatom Corethron pennatum became the dominant species. Based on these assumptions, the dynamics of fast ice was reconstructed over the last 2.6 ka for the western Ross Sea. However, the absence of direct observations leaves the paleoclimatic and paleoceanographic interpretation of these laminated sediments with a certain degree of uncertainty.

The project LASAGNE (Laminated Sediments in the Magnificent Edisto Inlet, Victoria Land: What processes control their deposition and preservation?), funded by the Italian Program of Antarctic Research (PNRA), proposes a multidisciplinary study that integrates the characteristics of fast ice, water column, and surface sediment, aiming to obtain information on the factors influencing both formation and preservation of laminated sediment in Edisto Inlet. The project integrates also biological data (phytoplankton, microzooplankton and foraminifera) collected in situ, and time series of satellite images of sea ice. The main goal is to provide new insights into the sub-seasonal formation of laminated sediments, offering a backbone for the interpretation of paleoclimatic sedimentary archives.

Here, we present the results obtained from a comprehensive dataset collected in Edisto Inlet during the XXXVIII Italian PNRA expedition conducted on board the I/B Laura Bassi in February 2023. Collected data include CTD (Conductivity-Temperature-Depth) profiles with additional parameters (Dissolved Oxygen, fluorescence, turbidity) spatially distributed within and at the entrance of the bay, which was still partially covered by seasonal sea ice at the time of the cruise. Additionally, vessel-mounted and lowered ADCPs (Acoustic Doppler Current Profilers) were collected along transects and at each CTD station, respectively.  The synoptic survey conducted during the austral Antarctic summer is used to describe the distribution of water masses and current dynamics in the bay, primarily driven by sea ice formation and melting, as well as atmospheric and tidal forcing. Time series obtained from a mooring deployed 1-year before the cruise (data covers the period February 2022 - February 2024) provide thermohaline variability of the water column even during the winter season, and fluxes and composition of organic debris sinking in the water column through time-series sediment trap samples. Sea ice cores, short sediment cores, and water samples are used to gain insight into the phytoplankton and microzooplankton living in platelet ice in spring and in open water in summer, respectively. Early diagenesis has also been taken into account to define how the original signal is preserved in the sedimentary record.

How to cite: Langone, L. and the LASAGNE team: Environmental factors influencing deposition and preservation of laminated sediments in Edisto Inlet, western Ross Sea (Antarctica), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11258, https://doi.org/10.5194/egusphere-egu24-11258, 2024.

EGU24-11749 | ECS | Orals | OS1.6

Heat and meltwater fluxes across the front of Dotson ice shelf cavity, Amundsen Sea 

Yixi Zheng, Rob Hall, Karen Heywood, Bastien Queste, Peter Sheehan, and Gillian Damerell

Ice shelves terminating in the Amundsen Sea are losing mass rapidly, exporting an increasing amount of meltwater into the ocean. Investigation into the melt rates of ice shelves near in the Amundsen Sea is therefore crucial for predicting the impact of ice shelf processes on future climate. However, observations near ice shelves often lack continuity in either time or space, limiting our knowledge of their melt rates. During a research cruise in austral summer 2022, we undertook a high resolution (horizontal sampling interval: ~ 2 km) CTD/LADCP transect spanning the front of the Dotson ice shelf encompassing the inflow and outflow to the ice shelf cavity.  In addition, we deployed three ocean gliders yielding five fine-resolution (horizontal sampling interval: ~ 650 m) hydrographic transects along the front of the Dotson Ice Shelf over three weeks. With an average of just 4.5 days between occupations, these new observations allow us to comprehensively investigate short-term variability along the ice front. The glider transects revealed considerable temporal variability in the across-ice shelf current speed.

The CTD section reveals that the meltwater content is higher (around 20 g/kg) in the west (outflow) and lower (around 10 g/kg) in the east (inflow), with a meltwater-poor layer centred at about 350 m sandwiched between two meltwater-rich layers along the ice shelf transect (one above about 250 m and the second centred at about 450 m). We reference geostrophic shear to the LADCP velocity profiles and demonstrate that the net volume flux across the ice shelf front is close to zero. We then calculate the net ocean heat flux across the ice shelf front to be  2.9×1011 W. Assuming that this net heat loss all results from basal melting, we estimate the glacial melt rate from this heat flux to be 28.1 Gt yr-1. The net transport of meltwater out of the cavity is 9.8×105 kg s-1, which is equivalent to 31 Gt yr-1, remarkably similar to the heat-flux-derived value. The small difference between the meltwater-flux-derived and heat-flux-derived melt rates might be attributed to subglacial rivers or other uncertainties in the estimates. Finally, we discuss the heat and meltwater fluxes using the glider transects and determine their temporal variability.

How to cite: Zheng, Y., Hall, R., Heywood, K., Queste, B., Sheehan, P., and Damerell, G.: Heat and meltwater fluxes across the front of Dotson ice shelf cavity, Amundsen Sea, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11749, https://doi.org/10.5194/egusphere-egu24-11749, 2024.

EGU24-12570 | Posters on site | OS1.6 | Highlight

Spatial distribution of Antarctic meltwater governs Southern Ocean deep convection and shelf warming feedback 

Torge Martin, Janika Rhein, Malin Ödalen, and Mathias Zeller

Increasing Antarctic ice sheet mass loss is anticipated to become a major player in Southern Ocean and global climate change. Since most climate models are lacking an interactive ice sheet, numerous freshwater-release scenarios have been conducted recently, in which the effect of melting of ice shelves and calving of icebergs on the ocean and climate system is studied by prescribing a freshwater flux to the high latitude Southern Ocean. The Southern Ocean Freshwater Input from Antarctica (SOFIA, https://sofiamip.github.io) initiative is designed to reconcile these studies and quantify model uncertainty.

In the framework of SOFIA we conduct experiments with the Flexible Ocean and Climate Infrastructure (FOCI) model, which consists of NEMO3.6-LIM 0.5˚ ocean-sea ice and ECHAM6.3-JSBACH 1.8˚ atmosphere-land components. We study the effect of freshwater input (0.1 Sv) along the Antarctic coast (antwater) versus a wide-spread, iceberg melt-like input field south of 60˚S (60Swater) under pre-industrial climate control conditions. A small ensemble of eight members each also serves to demonstrate a significant effect by centennial-scale internal variability on the magnitude of the Southern Ocean’s response to the freshwater.

Besides responses like surface cooling, sea ice expansion, deep ocean warming, weakening of the Antarctic Circumpolar Current, which are robust across models and experiments, we find two intriguing differences between antwater and 60Swater experiments: In three of the eight ensemble members of antwater, large-scale open ocean deep convection emerges in the central Weddell Gyre, which is absent from the reference run without freshwater perturbation and the eight ensemble runs of 60Swater. This can be linked to the spin-up of the Weddell Gyre in the experiments, increasing the doming of isotherms, but being counterbalanced by surface freshening in the gyre center in 60Swater. Further, the zonal mean warming of >1˚C at mid depth in the Weddell Sea sector present in all experiments spills onto the continental shelf in antwater whereas it resides below the shelf break in 60Swater. This gives rise to the assumption that the spatial distribution of the freshwater has the potential to drive or limit a positive melt feedback loop associated with warming on the shelf.

How to cite: Martin, T., Rhein, J., Ödalen, M., and Zeller, M.: Spatial distribution of Antarctic meltwater governs Southern Ocean deep convection and shelf warming feedback, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12570, https://doi.org/10.5194/egusphere-egu24-12570, 2024.

EGU24-12592 | ECS | Orals | OS1.6 | Highlight

Sea ice and climate impacts from Antarctic ice-mass loss in the SOFIA multi-model ensemble 

Andrew Pauling, Neil Swart, Torge Martin, Rebecca Beadling, Jia-Jia Chen, Matthew England, Riccardo Farneti, Stephen Griffies, Tore Hattermann, F. Alexander Haumann, Qian Li, John Marshall, Morven Muilwijk, Ariaan Purich, Jeff Ridley, Inga Smith, and Max Thomas

We assess the response of Antarctic sea ice, the Southern Ocean, and global climate to mass loss from the Antarctic continent in a new multi-model ensemble. Antarctic ice-mass loss from ice sheets and ice shelves is increasing and is projected to increase further as the climate warms. The fresh water entering the Southern Ocean due to this ice-mass loss has been proposed as a mechanism responsible for the lack of decline in Antarctic sea ice area between 1979 and 2015, in contrast to the sea-ice loss seen in the Arctic. The fresh water impacts sea ice by increasing the density gradient between the near-surface waters and deeper waters around the Antarctic continent, which inhibits vertical transport of warmer, deeper water to the surface. This results in surface cooling and increased sea ice growth, as has been shown in previous studies. Though this increased Antarctic ice-mass loss is expected to impact climate it is absent from almost all models in the current Coupled Model Intercomparison Project (CMIP6), which typically enforce that the continent remain in perpetual mass balance, with no gain or loss of mass over time. Further, previous non-CMIP6 model experiments that include changing Antarctic ice-mass loss suggest that the climate response depends on the model used, and that the reasons for this model dependence are not clear.

We present results from the Southern Ocean Freshwater Input from Antarctica (SOFIA) Initiative, an international model intercomparison, in which freshwater is added to the ocean surrounding Antarctica to simulate the otherwise missing ice-sheet mass loss. This unique suite of models allows us compare the response to Antarctic mass loss across climate models, identify reasons for model discrepancies, and quantify the potential impact of the absence of increasing Antarctic ice-mass loss on Antarctic sea ice and climate. We will give an overview of the SOFIA initiative including the experiment design and participating models. We will present results from the “antwater” experiment outlined in the SOFIA protocol in which a constant freshwater input of 0.1 Sv is distributed evenly around the Antarctic continent at the ocean surface in an experiment with pre-industrial control forcing. We show that there is a spread of up to a factor of 3 across models in the Antarctic sea ice area response to identical freshwater forcing. There are also substantial differences in the spatial pattern of the sea ice response depending on the model used. We explore the dependence of the response on the mean state of Antarctic sea ice and the Southern Ocean in the pre-industrial control runs, as well as the response of the ocean stratification and oceanic deep convection in the models. We also explore the seasonality of the sea ice and oceanic response.

How to cite: Pauling, A., Swart, N., Martin, T., Beadling, R., Chen, J.-J., England, M., Farneti, R., Griffies, S., Hattermann, T., Haumann, F. A., Li, Q., Marshall, J., Muilwijk, M., Purich, A., Ridley, J., Smith, I., and Thomas, M.: Sea ice and climate impacts from Antarctic ice-mass loss in the SOFIA multi-model ensemble, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12592, https://doi.org/10.5194/egusphere-egu24-12592, 2024.

Antarctica's solar-warmed surface waters subduct beneath the region's ice shelves as a result of Ekman forcing. In December 2022, an ocean glider collected unprecedented observations of such waters beneath the Ross Ice Shelf, during a serendipitous four-day foray into the sub-glacial cavity; the glider surveyed the cavity in high resolution between the ice base and a depth of 200 m. During most of this period, a 50 m-thick layer of water with a high chlorophyll concentration, which must have come from the Ross Sea polynya and which has the same properties as waters immediately beneath adjacent sea ice, was in contact with the ice base. Super-cooled water was also sometimes observed to be in contact with the ice base. When warm water was present, temperature in the uppermost 5 m decreased towards the ice base in near-perfect agreement with an exponential fit. When super-cooled water was present, no such decrease was observed. From these observations, we estimate the heat loss from the ocean to overlying ice sheet. From re-analysis output, we demonstrate that Ekman forcing drives a heat into the sub-glacial cavity sufficient to contribute significantly to near-front melting of the Ross Ice Sheet. We further show that there has been an increase in the Ekman heat flux into the cavity over the last four decades (i.e. since 1979); this is driven by an increase in the heat content of the seasonally ice-free waters of the Ross Sea polynya, immediately in front of the ice shelf. Interannual variability of the Ekman heat flux, however, is driven not by ocean heat content, or indeed by sea ice cover, but by interannual variability of the along-front zonal wind stress.

How to cite: Sheehan, P. and Heywood, K.: Observations and year-on-year increase of warm surface waters entering the Ross Ice Shelf cavity, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12628, https://doi.org/10.5194/egusphere-egu24-12628, 2024.

EGU24-13601 | ECS | Posters virtual | OS1.6

Seasonal circulation and volume transport in the Gerlache Strait 

Laia Puyal-Astals, Borja Aguiar-González, Marta Veny, and Francisco Machín

We present the first observational-based assessment of the year-round circulation and volume transport in the Gerlache Strait, a key location for the water mass exchanges occurring along the west Antarctic Peninsula (wAP) between the relatively warm Bellingshausen Sea, flowing northeastward, and the colder Weddell Sea, flowing southwestward. These relatively warm/cold ocean water pathways have been documented to play a major role in the glacier retreat/stabilization of glaciers along the wAP (Cook et al., 2016). Bearing this in mind, we investigate a dataset of direct velocity measurements which were routinely collected along ship tracks from 379 cruises performed by R/V Nathaniel B. Palmer and R/V Laurence M. Gould between 1999 and 2018. A first set of analyses of an earlier version of this dataset was presented in Savidge & Amft (2009), who focused on the summer and winter views of the shelf circulation along the entire wAP. More recently, an updated version of such a dataset addressed the year-round circulation and volume transport of the Bransfield Current in the Bransfield Strait between 1999 and 2014 (Veny et al., 2022).

Preliminary results of this work focus on the ocean current variability displayed between 2008 and 2009, two years known in the literature as featuring remarkably opposite Weddell Sea influences along the central wAP (Wang et al., 2022); the former year with a weaker influence than the later one. Ongoing steps include the construction of a high-resolution (~5km) seasonal climatology of the ocean currents flowing through the Gerlache Strait, where the dataset of study ensures a multi-year spatial coverage of volume transport.

Key words: Gerlache Strait, Direct Velocity Measurements, Dynamic Structure, Volume Transport, Seasonal and Interannual Variability.

References: 

Cook, A. J., Holland, P. R., Meredith, M. P., Murray, T., Luckman, A., & Vaughan, D. G. (2016). Ocean forcing of glacier retreat in the western Antarctic Peninsula. Science, 353(6296), 283–286. https://doi.org/10.1126/science.aae0017

Savidge, D. K., & Amft, J. A. (2009). Circulation on the West Antarctic Peninsula derived from 6 years of shipboard ADCP transects. Deep Sea Research Part I: Oceanographic Research Papers, 56(10), 1633–1655. https://doi.org/10.1016/j.dsr.2009.05.011

Veny, M., Aguiar-González, B., Marrero-Díaz, Á., & Rodríguez-Santana, Á. (2022). Seasonal circulation and volume transport of the Bransfield Current. Progress in Oceanography, 204, 102795. https://doi.org/10.1016/j.pocean.2022.102795

Wang, X., Moffat, C., Dinniman, M. S., Klinck, J. M., Sutherland, D. A., & Aguiar‐González, B. (2022). Variability and Dynamics of Along‐Shore Exchange on the West Antarctic Peninsula (WAP) Continental Shelf. Journal of Geophysical Research: Oceans, 127(2). https://doi.org/10.1029/2021JC017645

How to cite: Puyal-Astals, L., Aguiar-González, B., Veny, M., and Machín, F.: Seasonal circulation and volume transport in the Gerlache Strait, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13601, https://doi.org/10.5194/egusphere-egu24-13601, 2024.

EGU24-15178 | Orals | OS1.6

Water mass formation and export from the Filchner-Ronne Ice Shelf 

Markus Janout, Mathias van Caspel, Elin Darelius, Peter Davis, Tore Hattermann, Mario Hoppmann, Torsten Kanzow, Svein Østerhus, Jean-Baptiste Sallée, and Nadine Steiger

The Filchner-Ronne-Ice Shelf (FRIS) is the earth’s largest ice shelf by volume and its cavity a crucial part of the southern Weddell Sea ocean circulation. In mid-2017, the Filchner Ice Shelf (FIS) cavity experienced a shift towards a stronger circulation and increased outflow of Ice Shelf Water (ISW) into Filchner Trough. The increase was attributed to enhanced sea ice formation and the associated production of High Salinity Shelf Water (HSSW) in the source region north of Ronne Ice Shelf. The corresponding circulation pattern was termed “Ronne-mode”, which contrasts the “Berkner-mode”, characterized by a more locally-enhanced circulation at the northern FIS edge. Here we employ new time series from two drill hole mooring sites underneath FIS, as well as moorings from the Filchner Trough and Filchner Sill, to highlight the spatial and temporal extent of this recent ISW outflow event. Underneath FIS, the “Ronne-mode” overruled the normally-observed seasonality in currents and hydrography, and resulted in northward ISW transport for about two years. The export led to the subsequent filling of Filchner Trough with ISW from 2018 until mid-2020, which then overflowed across the Sill between late 2018 for nearly one year. Our observations provide new insights into the variability of the southern Weddell Sea shelf and FRIS cavity circulation, which is important for the abyssal water mass export and thus for global ocean circulation.

How to cite: Janout, M., van Caspel, M., Darelius, E., Davis, P., Hattermann, T., Hoppmann, M., Kanzow, T., Østerhus, S., Sallée, J.-B., and Steiger, N.: Water mass formation and export from the Filchner-Ronne Ice Shelf, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15178, https://doi.org/10.5194/egusphere-egu24-15178, 2024.

EGU24-16331 | ECS | Orals | OS1.6

Deciphering the impact of future individual Antarctic freshwater sources on the Southern Ocean properties and ice shelf basal melting 

Christoph Kittel, Nicolas Jourdain, Pierre Mathiot, Violaine Coulon, Clara Burgard, Justine Caillet, Damien Maure, and Clara Lambin

The Antarctic ice sheet is losing mass. This mass loss is primarily due to ice shelf basal melting and the subsequent acceleration of glaciers. The substantial freshwater fluxes resulting from ice shelf and iceberg melting affect the Southern Ocean and beyond. As emphasized by some studies, they slow down the decline of Antarctic sea ice and hinder mixing between surface water and Circumpolar Deep Waters, further intensifying ice shelf basal melting. In this context, most studies so far have neglected the impact of surface meltwater runoff , but recent CMIP6 projections using the SSP5-8.5 scenario challenge this view, suggesting runoff values in 2100 similar to current basal melt rates. This prompts a reassessment of surface meltwater future impact on the ocean.  We use the ocean and sea-ice model NEMO-SI3 resolving the sub-shelf cavities of Antarctica and including an interactive iceberg module. We perform thorough sensitivity experiments to disentangle the effect of changes in the atmospheric forcing, increased ice shelf basal melting, surface freshwater runoff and iceberg calving flux by 2100 in a high-end scenario. Contrary to expectations, the atmosphere alone does not substantially warm ice shelf cavities compared to present temperatures. However, the introduction of additional freshwater sources amplifies warming, leading to escalated melt rates and establishing a positive feedback. The magnitude of this effect correlates with the quantity of released freshwater, with the most substantial impact originating from ice shelf basal melting. Moreover, larger surface freshwater runoff and iceberg calving flux contribute to further cavity warming, resulting in a noteworthy 10% increase in ice shelf basal melt rates. We also describe a potential tipping point for cold ice shelves, such as Filchner-Ronne, before the year 2100.

How to cite: Kittel, C., Jourdain, N., Mathiot, P., Coulon, V., Burgard, C., Caillet, J., Maure, D., and Lambin, C.: Deciphering the impact of future individual Antarctic freshwater sources on the Southern Ocean properties and ice shelf basal melting, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16331, https://doi.org/10.5194/egusphere-egu24-16331, 2024.

EGU24-16511 | Orals | OS1.6

Cryospheric Change as a Driver of Antarctic Seep Emergence  

Sarah Seabrook, Andrew Thurber, Yoann Ladroit, Vonda Cummings, Leigh Tait, Alicia Maurice, and Cliff Law

While the climate sensitivity and significance of subsurface fluid and greenhouse gas reservoirs have received attention in the Arctic, the presence of these features in Antarctica and their contribution to global methane and the carbon cycle remains unknown. Here, we report the discovery of extensive and emergent seafloor seeps, some initiated within the last decade, that are releasing climate-reactive fluids and gases in the coastal Ross Sea. Emission of methane in these shallow waters would expedite transfer to the atmosphere, as reported at other shallow global seep systems. While the origin, driving mechanisms, and environmental consequence of these emerging Antarctic seep systems remains unknown, we postulate that the emergent seepage results from cryospheric cap degradation, which initiates new fluid flow pathways and liberates subsurface fluids and gases. This mechanism is inherently climate sensitive with potential for positive feedback, and may be widespread around the Antarctic Continent, yet the magnitude and scale is currently undetermined. 

How to cite: Seabrook, S., Thurber, A., Ladroit, Y., Cummings, V., Tait, L., Maurice, A., and Law, C.: Cryospheric Change as a Driver of Antarctic Seep Emergence , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16511, https://doi.org/10.5194/egusphere-egu24-16511, 2024.

The Southern Ocean (SO) plays a key role in global carbon and nutrient cycles, as the SO overturning circulation feeds into both deep-water formation (lower branch) and Subantarctic intermediate and mode water formation (upper branch). While the air-sea CO2 balance is influenced mainly by deep-water formation, global export production is more sensitive to intermediate and mode water formation, giving rise to the concept of a SO biogeochemical divide [1]. Sea ice formation, transport and melting plays a prominent role in the transformation of buoyancy for both the upper and lower branches of the overturning circulation [2]. Hence, changes in sea ice parameterisation have potential for substantially altering carbon uptake and export production in global Earth System Models (ESMs).

Global ESMs seek to simulate physical, chemical and biological processes that are relevant for the evolution of global climate, including fluxes of greenhouse gasses and aerosols between the atmosphere and ocean. The air-sea gas exchange is determined by the difference in concentration across the air-sea interface, and a gas transfer velocity that is specific for the gas in question. However, the air-sea gas exchange is inhibited by the presence of sea ice. A modified formula proposed by Steiner et al. [3], accounting for cracks and leads in the sea ice, has recently been  implemented in the Norwegian Earth System Model NorESM2 [4]. In this study we investigate how the change in this sea ice parameterisation influences the carbon uptake and export production associated with the Southern Ocean overturning circulation.

REFERENCES

[1] I. Marinov, A. Gnanadesikan, J. R. Toggweiler and J. L. Sarmiento, "The Southern Ocean biogeochemical divide", Nature, Vol. 441, 964-967, 2006. DOI: 10.1038/nature04883

[2] R. P. Abernathey, I. Cerovecki, P. R. Holland, E. Newsom, M. Mazlo and L. D. Talley, "Water-mass transformation by sea ice in the upper branches of
the Southern Ocean overturning", Nature Geoscience, Vol. 9, 596-601, 2016. DOI: 10.1038/ngeo2749

[3] N. S. Steiner, W. G. Lee and J. R. Christian, "Enhanced gas uxes in small sea ice leads and cracks: Efects on CO2 exchange and ocean acidiccation", JGR Oceans, Vol. 118(3), 1195-1205, 2013. DOI: 10.1002/jgrc.20100

[4] Ø. Seland, M. Bentsen, D. Olivié, T. Toniazzo, A. Gjermundsen, L. S. Graff, J. B. Debernard, A. K. Gupta, Y.-C. He, A. Kirkevåg, J. Schwinger, J. Tjiputra, K. S. Aas, I. Bethke, Y. Fan, J. Griesfeller, A. Grini, C. Guo, M. Ilicak, I. H. H. Karset, O. Landgren, J. Liakka, K. O. Moseid, A. Nummelin, C. Spensberger, H. Tang, Z. Zhang, C. Heinze, T. Iversen and M. Schulz, "Overview of the Norwegian Earth System Model (NorESM2) and key climate response of CMIP6 DECK, historical, and scenario simulations", Geoscientifc Model Development, Vol. 13(12), 6165-6200, 2020. DOI: 10.5194/gmd-13-6165-2020

How to cite: Torsvik, T.: Influence of changing sea ice parameterisation on Southern Ocean  carbon uptake and export production, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16957, https://doi.org/10.5194/egusphere-egu24-16957, 2024.

EGU24-17376 | ECS | Posters on site | OS1.6

Present-day ocean simulations of the circumpolar Antarctic 

Birgit Rogalla, Kaitlin Naughten, Paul Holland, Pierre Mathiot, Nicolas Jourdain, and Christoph Kittel

The West Antarctic Ice Sheet (WAIS) is rapidly losing mass due to ocean-driven melt of its ice shelves, contributing to sea level rise. This melt is associated with the intrusion of circumpolar deep water onto the continental shelf which is impacted by winds, the Amundsen undercurrent, thermodynamic processes, and buoyancy forcing. To study the sensitivity of melt to changes in these components, model configurations need to represent key processes while reducing computational cost to allow for large ensemble simulations. Regional ocean simulations have proven useful in this context, however, configurations that allow interactions between Antarctic regions would be beneficial. We will present results from present-day ocean simulations with a  ¼° circumpolar Antarctic NEMO configuration including sea ice, icebergs, and ice shelf cavities, and up-to-date forcing and bathymetry datasets. We will also discuss challenges associated with open boundary conditions and sensitivity to different forcing datasets. This configuration will provide a platform for attribution studies of ocean-driven melt of the WAIS, ocean projections, and form the starting point for coupled ocean-ice sheet simulations. 

How to cite: Rogalla, B., Naughten, K., Holland, P., Mathiot, P., Jourdain, N., and Kittel, C.: Present-day ocean simulations of the circumpolar Antarctic, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17376, https://doi.org/10.5194/egusphere-egu24-17376, 2024.

EGU24-17676 | ECS | Orals | OS1.6

Benefits of the Brinkman Volume Penalisation Method for the Ice-Shelf Melt Rates Produced by Z-coordinate Ocean Models 

Antoine-Alexis Nasser, Nicolas C. Jourdain, Pierre Mathiot, and Gurvan Madec

Antarctic ice-shelf basal melting is a major source of uncertainty in sea level rise projections. A persistent challenge in simulating the ice-shelf-ocean interactions in z-coordinate ocean models is the introduction of artificial steps, leading to the generation of noise that impacts both melting and ocean currents. This study explores the potential of the Brinkman Volume Penalisation (BVP) method (Debreu et al. 2020, 2022) to address the recurrent issue of steps in ice-shelf-ocean models. While penalisation methods are typically applied to land topography, here, the method is generalised to ice-shelf interactions with oceans. This approach introduces porous cells that are half-ice, half-ocean, combined with a permeability parameter (friction within porous cells) to model the blocking effect of the ice draft. A unique aspect of this method is its ability to spread the penalisation region, thereby reducing model sensitivity to numerical level changes. We assess the potential benefits of the BVP approach within the idealised ice-shelf configuration ISOMIP+ as presented by Asay-Davis et al. (2016). First, a new calculation of the horizontal pressure gradient is formulated using the BVP approach, which eliminates residual biases in ocean currents down to zero machine precision. Second, the spreading of the penalised interface significantly reduces noise in the melt rates, enabling a smooth response of the ocean beneath the ice-shelf without the need for further mesh refinement. Other simulations are used to investigate the sensitivity of basal melting and freezing in the penalised configuration to changes in numerical parameters (e.g. spatial resolution). These results pave the way for a better numerical treatment of ice-shelves in earth system models.

How to cite: Nasser, A.-A., Jourdain, N. C., Mathiot, P., and Madec, G.: Benefits of the Brinkman Volume Penalisation Method for the Ice-Shelf Melt Rates Produced by Z-coordinate Ocean Models, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17676, https://doi.org/10.5194/egusphere-egu24-17676, 2024.

EGU24-20002 | ECS | Orals | OS1.6

Weddell Sea subsurface warming revealed by an updated Southern Ocean climatology 

Shenjie Zhou, Pierre Dutrieux, and Andrew Meijers

A new monthly climatology of Southern Ocean hydrography is constructed with updated observational dataset. CTD casts from World Ocean Database, Pangaea Database, CLIVAR and Carbon Hydrographic Data Office, Southern Ocean Database and Korean Polar Data Centre were assembled. All ‘Delayed Mode’ Argo floats profiles and ‘Real-time Mode’ or ‘Real-time Adjusted Mode’ over the within 2000 m isobath near the continental shelves are included. All flagged-good Seal-tag profiles are included. The interpolation scheme employs an elliptical detecting area to select profiles to be averaged into gridded product. The ellipse is designed to align with the dynamic height contour to consider the effect of large-scale circulation. The detecting radius confined by ellipse size varies with the bathymetry and facilitate to resolve local gradient in temperature and salinity field over the continental shelves. A timeseries is constructed by removing the temperature and salinity climatology from the individual profiles in Weddell Sea, and a clear subsurface warming is revealed. An entrainment of warm and saline anomalies from subsurface into the surface layer is captured around 2016 corresponding to the recent sea ice extent decline. A further regional analysis on the temperature and salinity anomaly signal will shed light on the heat delivery pathway and the cause of the subsurface heat entrainment.

How to cite: Zhou, S., Dutrieux, P., and Meijers, A.: Weddell Sea subsurface warming revealed by an updated Southern Ocean climatology, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20002, https://doi.org/10.5194/egusphere-egu24-20002, 2024.

EGU24-804 | ECS | Orals | HS2.1.9

The role of proglacial rock glaciers in redistributing glacial meltwater 

Bastien Charonnat, Michel Baraer, Janie Masse-Dufresne, Eole Valence, Jeffrey McKenzie, Chloé Monty, Kaiyuan Wang, and Elise Devoie

The deglaciation of high mountain ranges is leading to the expansion of proglacial areas, which encompasses diverse permafrost and ground ice landforms. These features exert an increased influence on the hydrology and hydrogeology of alpine catchments as glaciers retreat. Despite the heightened attention received by rock glaciers for the last decades, their role within the broader hydrological and hydrogeological valley system remains understudied. Previous studies have highlighted rock glaciers’ ability to act as hydrological storage and to buffer water release from alpine catchments. However, there is a lack of studies about their ability to modify the groundwater flow paths in a proglacial valley system and to redistribute glacial meltwater. This study addresses this knowledge gap by investigating how the rock glacier redistributes glacial meltwater in a study catchment.

Shar Shäw Tágà (Grizzly Creek) is a subarctic glaciated catchment located in the St. Elias Mountains, Yukon (Canada) that experiences significant glacial retreat. A non-relict rock glacier at the outlet of a glacial sub-catchment obstructs the valley thalweg, with only a few springs exhibiting minimal discharge from its front. These minor springs contrast remarkably with the substantial discharge observed at higher elevations above the rock glacier.

Water level, water temperature and electrical conductivity variables were monitored in identified springs throughout the summer 2022. Results were compared to meteorological data with wavelet coherence analysis to determine the springs’ origins and drivers. Additionally, multiple sampling campaigns were conducted in the summers of 2022 and 2023 to analyze major ions concentrations and water stable isotopes signatures in the catchment’s streams.

The results reveal that the rock glacier serves as a critical obstacle and deflector to subsurface meltwater, either forcing upstream meltwater to penetrate deeper into the subsurface, or redirecting lateral subsurface flow to resurge at its front, forcing part of the alluvial floodplain shallow aquifer to reach the surface.

While rock glaciers are often considered potential water reservoirs, this study illuminates their dual role as critical deflectors for shallow subsurface flow in proglacial valley systems. They can impede glacial meltwater flow, originating alternative pathways toward deep aquifers or lowlands’ surface waters. Such findings nuance the ability of rock glaciers to store and release glacial meltwater, as they can deflect shallow subsurface flow. Additionally, it shows that rock glaciers can force infiltration and resurgence of water at specific locations, affecting the broader mountain hydrogeological system. Furthermore, it enforces their critical role in the future of water resources supplied by high mountain ranges in a deglaciation context.

How to cite: Charonnat, B., Baraer, M., Masse-Dufresne, J., Valence, E., McKenzie, J., Monty, C., Wang, K., and Devoie, E.: The role of proglacial rock glaciers in redistributing glacial meltwater, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-804, https://doi.org/10.5194/egusphere-egu24-804, 2024.

Spaceborne gravimetry is the only satellite method that can observe terrestrial water storage at a continental scale. The time variable gravity field, observed by GRACE and GRACE-FO, is a measure of mass transport primarily in the global water cycle. In this contribution we analyse the runoff-storage relationship in the GRACE time frame for the pan-Arctic drainage basins. Over these boreal catchments, the conventional hysteresis-type formulation requires algorithmic adaptations in order to accommodate snowload and base-flow during winter periods. We show that the parameters involved in the pan-Arctic runoff-storage relationships are transferable, albeit with a few exceptions, between the various catchments. This remarkable fact allows us access to determining runoff from ungauged drainage areas across the pan-Arctic. As a result we can quantify the total freshwater flux from pan-Arctic basins into the Arctic Ocean.

How to cite: Sneeuw, N., Yi, S., Saemian, P., and Tourian, M. J.: Estimating runoff from pan-Arctic basins through an improved runoff-storage relationship using satellite gravimetry in the GRACE period 2002-2019, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2098, https://doi.org/10.5194/egusphere-egu24-2098, 2024.

EGU24-2191 | ECS | Orals | HS2.1.9

Process-based modeling of the streamflow generation in a highly glaciated Alpine headwater catchment since the last little Ice Age (i.e., 1850). 

Florentin Hofmeister, Xinyang Fan, Madlene Pfeiffer, Inga Labuhn, Ben Marzeion, Bettina Schaefli, and Gabriele Chiogna

The streamflow generation related to snow and glacier melt is particularly sensitive to temperature fluctuations and, hence, highly affected by global warming. However, the non-linear and complex interaction between streamflow contributions originating from snow melt versus glacier melt and being transferred to stream via the subsurface complicates the investigation of climate-induced changes in high-elevation catchments. We used the physically-based hydrological model WaSiM to simulate the climate-induced changes in the streamflow generation in the Kaunertal (Austria), a highly glaciated Alpine headwater catchment. The simulations extend from the last little Ice Age (i.e., 1850) to 2015. Large-scale climate processes of a general circulation model (GCM) were dynamically downscaled with the Weather Research & Forecasting Model (WRF) to the central Alpine region at a 2 km spatial resolution from 1850 to 2015. The WaSiM model parameters were transferred from a WaSiM configuration driven by station data and partly optimized by a manual calibration on observed streamflow. For model evaluation, a multi-objective approach was chosen considering streamflow, SWE, snow cover duration, and glacier mass balances. The hydrological model results showed a good representation of the individual components and seasonal streamflow generation. However, difficulties exist in the spatial representation of the heterogeneous and small-scale differences in the snowpack. In addition, there are limitations in the simulation of glacier evolution using WaSiM over long periods (> 30 years) in highly glaciated catchments, as WaSiM does not contain an ice flow routine that can simulate the glacier dynamics during advance or retreat. Despite the cascade of uncertainties in this complex model chain (i.e., GCM, WRF, WaSiM), the results of the long-term simulation show interesting dynamics and enable an analysis of streamflow generation for periods where no observational data is available. For instance, glacier melt indicates a high dependence on the development of summer temperatures (i.e., JJA). The rising temperatures led to an earlier onset of snow and glacier melt, which shifted the streamflow regime and increased the daily streamflow magnitude, especially from 1995 onwards. The next step will be the comparison of the hydrological model results with those from other headwater catchments in the eastern Central Alps with a different degree of glaciation. The novelty lies in comparing 165 years of simulated streamflow and the contributions from snow and glacier melt. This comparison will validate the transferability and generalizability of the complex model chain and the simulation results.

How to cite: Hofmeister, F., Fan, X., Pfeiffer, M., Labuhn, I., Marzeion, B., Schaefli, B., and Chiogna, G.: Process-based modeling of the streamflow generation in a highly glaciated Alpine headwater catchment since the last little Ice Age (i.e., 1850)., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2191, https://doi.org/10.5194/egusphere-egu24-2191, 2024.

EGU24-2310 | ECS | Posters on site | HS2.1.9

Spring floods and their major influential factors in the source region of the Yangtze River during 2001–2020 

Ying Yi, Shiyin Liu, Yu Zhu, Kunpeng Wu, and Fuming Xie

    Many reservoirs have been constructed in the Yangtze River basin, however, spring floods in its source region pose increasingly severe challenges to reservoirs operation and water resources management due to increased climatic variability under global warming. Understanding spring flood variability and their major influential factors under changing climates is crucial to improving water management, agricultural irrigation, reservoir operation, and flood prevention. In this study, we have examined the spring flood characteristics and their influential factors in the source region of the Yangtze River based on station data and multisource remote sensing products during 2001–2020. Late Mays have seen most of the highest spring flood discharge, while some springs have experienced multiple peaks. Extreme spring floods were identified in the years 2012, 2013, 2019, and 2020, with the highest peak discharge (1365.83 m3/s) and longest flood duration (47 days) in 2019. Spring snowmelt played a key role in 2019 spring flood and others were also driven by snowmelt in the UJSB. We defined Snow Water Volume (SWV) as an indicator of the precondition for high spring flood. In 2019, large winter SWV along with spring snowfall melted into meltwater under the rising temperature, resulting in extreme spring flood event in late April. Whereas, in 2012 and 2020, snowmelt and rainfall combined to contribute to the extreme spring flood events in late Mays. In 2013, although snowmelt made a contribution to the first spring flood peak, the flood event at the end of May was primarily contributed by rainfall. Based on spatiotemporal variations in spring SWV and the isotherm of critical temperature for snow melting, the key regions dominating spring floods were identified as the regions with large amount of SWV. Weather pattern analysis showed that the enhanced Westerly jets in winters brought about large snowfall and extended snow cover in the region which can be released as floods triggered by rapid increase in air temperature in the coming spring.

How to cite: Yi, Y., Liu, S., Zhu, Y., Wu, K., and Xie, F.: Spring floods and their major influential factors in the source region of the Yangtze River during 2001–2020, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2310, https://doi.org/10.5194/egusphere-egu24-2310, 2024.

EGU24-5329 | ECS | Orals | HS2.1.9

Contribution of glacier melt to runoff under climate change using a conceptual hydrological model in selected high alpine regions in Austria 

Caroline Ehrendorfer, Franziska Koch, Sophie Lücking, Thomas Pulka, Hubert Holzmann, Philipp Maier, Fabian Lehner, Herbert Formayer, and Mathew Herrnegger

The timing and quantity of snow and ice melt in high-alpine regions is of great importance, especially for time-sensitive processes such as hydropower production. In most conceptual hydrological models, the simulations of these components are frequently only based on simple temperature index methods, and the question arises whether these are sufficient to derive useful information on changing runoff seasonality and quantities for hydropower producers.

This study examines the quantitative and seasonal changes in glacier melt contribution to total runoff under climate change in several Austrian high-alpine catchments with hydropower production (Stubaital, Stubachtal, Kölnbrein/Maltatal, Schlegeis/Zillertal). As the estimation of precipitation model inputs for areas with complex terrain is characterised by a high degree of uncertainty, an undercatch-correction adapted for high-alpine areas was applied, integrating information from local weather stations, topography and iterative feedback from the modelled water balance. The conceptual, semi-distributed rainfall-runoff model COSERO was set up for the case study regions.  To cover long-term changes, the model was run for Stubai- and Stubachtal for the reference period (1990-2020) and future scenarios (2021-2100) with daily timesteps. In addition to the daily timesteps, COSERO was also coupled with the physically-based snowpack model Alpine3D for simulations in the Kölnbrein and Schlegeis catchments for recent decades to implement the simulation of relevant components of the water balance including snow and ice processes at an hourly timestep based on more complex energy-balance modelling. Besides air temperature and precipitation, the coupling requires additional hourly meteorological input such as radiation, relative humidity and wind information.

The combination of COSERO with Alpine3D improves results at the hourly timestep, but the conceptual model delivers satisfying results on its own as well. Moreover, the results are in line with literature and show the expected decrease of ice volume and ice melt in coming years. By 2050, the ice melt contribution to total runoff is significantly reduced in all case study areas and seasonality shifts due to less ice melt and earlier snowmelt in the form of more winter and spring runoff and less flow in summer are prevalent. In addition, we show that the modelling of the water balance components in the past can be greatly improved by using the undercatch-corrected precipitation data.

 

Acknowledgements: We thank the VERBUND Energy4Business GmbH, the Austrian Climate Research Programme (ACRP), the Austrian Research Promotion Agency (FFG), and the ÖBB for funding, fruitful discussions and providing us with data.

How to cite: Ehrendorfer, C., Koch, F., Lücking, S., Pulka, T., Holzmann, H., Maier, P., Lehner, F., Formayer, H., and Herrnegger, M.: Contribution of glacier melt to runoff under climate change using a conceptual hydrological model in selected high alpine regions in Austria, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5329, https://doi.org/10.5194/egusphere-egu24-5329, 2024.

EGU24-5531 | ECS | Posters on site | HS2.1.9

Enhancing Snow Ablation Modeling in the Generation of Gridded Snow Water Equivalent Data 

Michelle Yu, Christopher Paciorek, Alan Rhoades, Mark Risser, and Fernando Perez

Snow Water Equivalent (SWE) is a critical parameter for understanding water availability in regions with seasonal snow cover. Ensuring an accurate representation of SWE across regular spatial and temporal intervals is essential and plays a pivotal role in hydrological and climatological studies. This work critically examines the ablation modeling strategy employed by the University of Arizona daily 4km SWE dataset (UA SWE), a widely adopted SWE gridded product in the United States, highlighting limitations inherent in methodologies that rely solely on temperature data.

Recognizing the utility of a more nuanced perspective to capture the complexities of snowmelt dynamics, we propose a novel method that incorporates a diverse set of meteorological and terrain characteristics as input variables in the predictive modeling of snow ablation. Our approach is further extended to directly model SWE, eliminating the need for intermediate ablation estimation and providing a more intuitive solution for empirical SWE prediction.

Our versatile methodology can be easily applied to produce high-resolution gridded SWE data. By addressing deficiencies in a leading empirical approach, our technique aims to enhance the accuracy of SWE representation at both the point and grid levels.

How to cite: Yu, M., Paciorek, C., Rhoades, A., Risser, M., and Perez, F.: Enhancing Snow Ablation Modeling in the Generation of Gridded Snow Water Equivalent Data, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5531, https://doi.org/10.5194/egusphere-egu24-5531, 2024.

EGU24-7278 | ECS | Orals | HS2.1.9

Cold-laboratory experiments to observe meltwater and ice layer interactions in snowpacks 

Connor Shiggins, Douglas Mair, James Lea, and Isabel Nias

The fate of percolating surface meltwater encountering ‘impermeable’ ice layers is uncertain in the accumulation zone of the Greenland Ice Sheet (GrIS). Often, ice layers are considered to retard meltwater and cause lateral runoff. However, modelled and field-based observations in the percolation zone of the GrIS have suggested ice layers are not necessarily impermeable and meltwater can breakthrough, percolating to deeper depths of snow/firn and consequently inferring a greater refreezing capacity within the accumulation zone. The physical and thermal conditions which control the permeability of ice layers remain unclear and effective parameterisation of these processes is lacking for snow/firn modelling of melt, refreezing and runoff. Here we present repeat cold-laboratory experiments which seek to understand how meltwater interacts with thin ice layers (5 to 20 mm) for two differing thermal regime contexts whereby the surrounding snow/firn thermal regime is either (i) below or (ii) at the melting point.

We find that under extreme melt regimes, ice layers continually retard wetted fronts of percolating meltwater when the thermal regime of the snowpack is below the melting point. This barrier results in the snowpack at depth remaining at least ~1oC cooler than snow above the ice layer which is saturated with meltwater. We also find that the ice layer forces ~35% of the percolating meltwater to runoff, cooling the overlying snow and increasing the refreezing capacity of the snow closer to the snowpack surface. The remaining ~65% of meltwater ponds and later refreezes on the ice layer, thickening the impenetrable surface.

When the thermal regime of the surrounding snow/firn is at the melting point, we find that meltwater is able to pond without refreezing, resulting in the ice layer failing and allowing deeper percolation into the snowpack. These findings suggest that the thermal regime of a snowpack is crucial for the structural integrity of an ice layer and thus the permeability of a snowpack.

Consequently, these findings have implications for parameterising meltwater runoff and ice layer integrity in snow and firn models which incorporate ‘impermeable’ barriers in their domains. Future work will continue to explore similar experiments with thicker ice layers (~60 mm) to determine whether ice layer breakthrough is primarily a function of snow/firn thermal regime and/or ice layer thickness. 

How to cite: Shiggins, C., Mair, D., Lea, J., and Nias, I.: Cold-laboratory experiments to observe meltwater and ice layer interactions in snowpacks, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7278, https://doi.org/10.5194/egusphere-egu24-7278, 2024.

EGU24-9702 | ECS | Posters on site | HS2.1.9

Inferring Debris Properties on Debris-Covered Glaciers: Implications for Glacier Modelling 

Vicente Melo Velasco, Evan Miles, Michael McCarthy, Thomas E. Shaw, Catirona Fyffe, and Francesca Pellicciotti

Debris, ranging from thin surface dust to medial moraines and thick, continuous layers in ablation zones, partially covers glaciers all around the world. By modifying energy transfer from the atmosphere to the ice, the supraglacial debris layer fundamentally controls sub-debris melt rates. Debris physical properties such as surface roughness (z0) and thermal conductivity (k) have only been derived from local measurements at a few sites, and modelling studies of debris-covered glaciers have often relied on literature values. The correct representation of these properties in energy-balance models is crucial for understanding the climate-glacier dynamics and how debris-covered glaciers will behave in the future. There are several established methods to derive these properties from field measurements, yet relatively few studies undertake to measure properties for their sites, or to evaluate the resulting property values.

We undertook an observational campaign to investigate supraglacial debris properties at Pirámide Glacier, in the central Chilean Andes. First, we used established approaches, as well as some variations on those approaches, to derive z0 from wind-temperature tower data and k from thermistor strings in the debris at three glacier locations. Second, we determined locally-optimal k and z0 values to reproduce observed ice melt: we optimised k by simulating energy conduction through the debris with the surface temperature as an input, then optimised z0 by running a complete energy-balance model using the observed surface meteorology. We then conducted point-scale energy-balance modelling using the z0 and k values obtained i) with the derivations from field measurements; ii) through optimisation, or; iii) from the typical values found in literature. This allowed us to evaluate how the different methods perform by comparing the modelled and measured ice melt. 

Our results show that deriving local debris properties from measurements is challenging and that measured values can differ significantly from common literature values. The values derived from measured data can vary significantly depending on the method employed. It is important to note that these values can also differ significantly from the values required by an energy-balance model to accurately represent sub-debris ice melt. Furthermore, energy-balance models typically assume a representation of heat transfer within the supraglacial debris layer based solely on conduction and require a bulk thermal conductivity value. This highlights the necessity of efforts to reevaluate measurements in the field and reconsider our definition of debris properties in melt modelling.

How to cite: Melo Velasco, V., Miles, E., McCarthy, M., Shaw, T. E., Fyffe, C., and Pellicciotti, F.: Inferring Debris Properties on Debris-Covered Glaciers: Implications for Glacier Modelling, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9702, https://doi.org/10.5194/egusphere-egu24-9702, 2024.

EGU24-12337 | ECS | Orals | HS2.1.9

Current and future glacier melt contribution to groundwater dynamics in a high-altitude, Himalaya basin 

Caroline Aubry-Wake and Walter Immerzeel

While mountain groundwater in glacierized regions has gained increasing attention, comprehensive insights of glacier melt contributions to groundwater and their resurfacing patterns remain limited. Our study employs a cryosphere-surface hydrology model in combination with numerical groundwater simulations to estimate the water table variations across the high-altitude Langshisha basin in the Langtang Himalaya (4094-6049 m). We evaluate surface water-groundwater interactions amidst current and projected climatic conditions. Utilizing in-situ weather forcings and evaluated with field measurements, our findings indicate that glacier melt contributes up to 70% of groundwater recharge in the Langshisha basin during the 2012-2020 period. This substantial contribution is attributed to the basin's considerable glacier cover (40%) and its high elevation, where cold temperatures in areas above 5300 m limit melt and are underlain by permafrost, restricting recharge. Groundwater simulations based on these recharge rates reveal a high sensitivity to hydraulic conductivity parameters but are constrained by field measurements of creek exfiltration indicating a water table near the surface along the main streams. The combination of groundwater simulations and field measurements suggests that groundwater exfiltration along the proglacial stream is a predominant surface-water-groundwater exchange mechanism within the basin. Considering the important role of glacier melt in groundwater recharge, our study applies future climate scenarios to gauge the impact of warming trends and glacier retreat on surface water-groundwater dynamics within the basin.

How to cite: Aubry-Wake, C. and Immerzeel, W.: Current and future glacier melt contribution to groundwater dynamics in a high-altitude, Himalaya basin, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12337, https://doi.org/10.5194/egusphere-egu24-12337, 2024.

EGU24-13919 | Orals | HS2.1.9 | Highlight

Accounting for interannual variability in dust accelerated snowmelt in process-based hydrologic prediction, Rocky Mountains, USA 

S. McKenzie Skiles, Patrick Naple, Otto Lang, and Joachim Meyer

Seasonal mountain snowmelt is an important contributor to surface water resources and groundwater recharge in the midlatitudes, making forecasting of snowmelt timing and duration critical for accurate hydrologic prediction. Net solar radiation, controlled primarily by snow albedo, is the main driver of snowmelt in most snow covered environments. Lowering of snow albedo from episodic dust deposition has been shown to be an important control on snowmelt patterns in the Rocky Mountains of the Western United States. Here, we compare and contrast trends in dust impacted albedo over the previous two decades with a focus on two regions: 1) the Colorado Rockies, headwaters of the Colorado River, which recieves dust from the southern Colorado Plateau and 2) the Wasatch Mountains (UT), headwaters of the Great Salt Lake, which recieves dust from the Great Basin. Results show that while snow darkening occurs every year, the magnitude of impact is spatially and temporally variable, and there are no emerging relationships that indicate when 'high-impact' dust years will occur. To account for spatial and interannual variability in dust impacted net solar radiation in hydrologic prediction we developed a spatially distributed process-based snowmelt model that incorporates near-real time snow albedo from remote sensing and incoming solar radiation from numerical weather prediction. The model improves simulated timing of snowmelt initiation and duration in all years, even those with lower dust impacts, demonstrating the importance of accurate snow albedo in snowmelt modeling. 

How to cite: Skiles, S. M., Naple, P., Lang, O., and Meyer, J.: Accounting for interannual variability in dust accelerated snowmelt in process-based hydrologic prediction, Rocky Mountains, USA, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13919, https://doi.org/10.5194/egusphere-egu24-13919, 2024.

EGU24-14158 | Posters on site | HS2.1.9

Enhancing NESDIS Global Automated Snow and Ice Cover Mapping System 

Peter Romanov

A new version of the Global Multisensor Automated Snow and Ice Mapping System (GMASI) has been implemented into operations at NESDIS is summer 2023. The new system is an upgrade of the previous version of the GMASI which was operated since 2006. The system provides information on the snow and ice distribution for NOAA numerical weather prediction and climate models as well as for a number of other atmosphere and land remote sensing products. The retrieval algorithm uses satellite observations in the visible/infrared and in the microwave spectral bands and delivers daily spatially continuous (gap-free) maps of the snow and ice cover.  

Compared to previous version, the new system incorporates data from a larger set of microwave sensors and features an enhanced retrieval algorithm. The spatial resolution of the output maps has been improved from es improved from 4km to 2km.  In the presentation we provide details of the data processing algorithm and of the output product focusing on the improvements and upgrades. We demonstrate that the output of the new GMASI system closely matches the accuracy of snow maps produced within NOAA Interactive Multisensor Snow and Ice Mapping System (IMS) and agrees well to in situ station snow depth report. Improvements to the retrieval algorithm mostly affected reproduction of small-scale features in the snow and ice cover distribution, particularly in alpine areas.  In the same time, large-scale climatologically-important cryosphere features as the continental and hemisphere snow and ice extent estimated with the new snow and ice maps remain consistent with the previous version of the product. 

How to cite: Romanov, P.: Enhancing NESDIS Global Automated Snow and Ice Cover Mapping System, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14158, https://doi.org/10.5194/egusphere-egu24-14158, 2024.

EGU24-15373 | ECS | Posters on site | HS2.1.9 | Highlight

The importance of small glaciers for accurate projection of future runoff in High Mountain Asia 

Alexandra von der Esch, Matthias Huss, Marit Van Tiel, Justine Berg, Tarang Patadiya, Pascal Horton, Saurabh Vijay, and Daniel Farinotti

High Mountain Asia is characterized by a substantial glacier coverage with glaciers of varying sizes. These glaciers are crucial in the area's hydrological cycle since they feed large rivers such as the Indus, Ganges, and Brahmaputra rivers. However, ongoing climate change is having a significant negative impact on glacier mass and projections show strong further declines of glacier mass in the future. This is raising concerns about future water security. How big the impact of the evolution of small glaciers (< 2 km2) is towards changing water availability remains to be investigated.

Most studies focus on the regional evolution of glaciers as a whole, which means that small-scale glaciers are often overlooked due to larger glaciers dominating the signal in area and volume changes, despite the fact that small glaciers make up about 30% of the glacierized area in High Mountain Asia. To address this issue, we applied the Global Glacier Evolution Model (GloGEM) to simulate all ca. 100’000 glaciers of High Mountain Asia (Regions 13-15 of the Randolph Glacier Inventory v6.0) under various climate scenarios in the period of 1980-2100. We compared the spatio-temporal variability of the timing of peak water, as well as glacier volume change, between small and large glaciers for a set of approximately 30 catchments in the headwater of Indus, Ganges and Brahmaputra rivers.

We find that there is a larger difference between future scenarios for the timing of peak water for smaller glacier, with it ranging from 2030-2060 and then runoff declining rapidly. Meanwhile, peak water for larger glaciers is likely to occur between 2070-2080 according to an intermediate emission scenario, with glacier runoff decreasing gradually thereafter. As for the ice volume change, smaller glaciers are expected to reach volumes close to zero near the year 2080, while larger glaciers are expected to reach this point only after 2100. The quicker response of small glaciers compared to large glaciers emphasize the need for a particular focus on small glaciers to better understand their responses to climate change and make accurate projections about local and regional scale near future water availability.

How to cite: von der Esch, A., Huss, M., Van Tiel, M., Berg, J., Patadiya, T., Horton, P., Vijay, S., and Farinotti, D.: The importance of small glaciers for accurate projection of future runoff in High Mountain Asia, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15373, https://doi.org/10.5194/egusphere-egu24-15373, 2024.

EGU24-15646 | Posters on site | HS2.1.9

Combined use of evolutionary algorithms and hydrological models to simulate snow cover and flow in alpine basins 

Jose David Hidalgo Hidalgo, Antonio Juan Collados Lara, David Pulido Velazquez, Eulogio Pardo Iguzquiza, Juan de Dios Gomez Gomez, and Francisco Jose Rueda Valdivia

Snow cover area, which can be obtained from satellite, is a valuable information to simulate streamflow in snow-dominated mountain basins where snowmelt is a major runoff factor. However, usually satellite do not provide long completed snow cover area spatiotemporal series, which are required to calibrate and validate hydrological models. It is due to difference limitations, as presence of clouds, sensor failure, low revisit time or spatial resolution, or recent launch.

Cellular automata models, which use precipitation and temperature as driving variables and some transition rules between cells through calibrated parameters, are capable of capturing the dynamics of snow cover area. Therefore, they can be used to complete and extend the information provided by satellite.

In this work, we simulate long series of daily streamflow in the Canales basin (Sierra Nevada, south Spain) by combining a cellular automata model and the Snowmelt Runoff Model. The Snowmelt Runoff Model is a degree-day model that requires data of temperature, precipitation, and snow cover area and has been widely used in simulation of streamflow in snow-dominated mountainous basins around the world.

The water resources in the Canales basin are regulated by a reservoir, which contributes to supply the Granada city water demand. The main resources stored in reservoir come from Sierra Nevada Mountains during the melting season. Therefore, the dynamics of snow is essential to simulate streamflow in the Canales basin.

It has been also used to simulate future local climate scenarios generated for specific level of warming in peninsular Spain.

Aknowledments: This research has been partially supported by the projects: STAGES-IPCC (TED2021-130744B-C21), SIGLO-PRO project (PID2021-128021OB-I00), SIERRA-CC project (PID2022-137623OA-I00) from the Spanish Ministry of Science, Innovation and Universities, and SER-PM (2908/22) from the National Park Research Program.

How to cite: Hidalgo Hidalgo, J. D., Collados Lara, A. J., Pulido Velazquez, D., Pardo Iguzquiza, E., Gomez Gomez, J. D. D., and Rueda Valdivia, F. J.: Combined use of evolutionary algorithms and hydrological models to simulate snow cover and flow in alpine basins, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15646, https://doi.org/10.5194/egusphere-egu24-15646, 2024.

EGU24-16055 | Posters on site | HS2.1.9

A Central Asian pro-glacial discharge database for improving hydrological models 

Eric Pohl, Mukhammed uulu Esenaman, Ardamehr Halimov, Dominik Amschwand, Tomas Saks, and Jingheng Huang

Central Asia’s mountain rivers are to a large degree fed by snow and ice melt and are a crucial contributor of fresh water downstream for millions of people. The attribution of how these meltwater sources will change their contribution to stream flow in a warmer future are, however, very uncertain. A major reason for this is an extremely sparse hydrometeorological monitoring network. This affects the calibration and validation of large-scale cryo-hydrological models that could be used for the task, or the validation and bias correction of reanalysis and remote sensing data needed to run such models. In combination with uncertainties about the glacier mass balances in the region, hydrological models are facing a pronounced equifinality problem. In order to improve this, and to understand better the glacier response to the current meteorological forcing in different climate zones of Central Asia, we instrumented 8 pro-glacial streams in Kyrgyzstan and Tajikistan with automated runoff gauges running at hourly resolution to also capture diurnal variability. These measurements complement the already (re-)established glaciological monitoring network at most of these sites and allow tackling the equifinality problem by constraining many variables. Here, we present first results from this database that shall serve to improve hydrological model calibration and parameterization, and understand relationships between meteorological forcing, annual glacier mass balance and meltwater generation. We also discuss instrumenting strategies and problems, and uncertainties related to gauge calibration.

How to cite: Pohl, E., uulu Esenaman, M., Halimov, A., Amschwand, D., Saks, T., and Huang, J.: A Central Asian pro-glacial discharge database for improving hydrological models, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16055, https://doi.org/10.5194/egusphere-egu24-16055, 2024.

EGU24-18059 | ECS | Posters on site | HS2.1.9

On the Importance of groundwater constraining in hydrological modeling of the Pamir region 

Jingheng Huang, Eric Pohl, and Juan Carlos Richard-Cerda

Central Asia is a climate change hot spot, facing an unprecedented juxtaposition of regional climate- and water-related issues. Meltwater from the Pamir Mountains plays a crucial role in Central Asia's hydrological cycle, and its response to climate change has been widely investigated using glacial-hydrological models. However, the hydrological simulation in Pamirs is highly uncertain, primarily driven by data scarcity and the complex interplay between climatic factors and glacier dynamics. Ongoing efforts concentrate on including more calibration data and constraining the uncertainty about the exact internal process representation of hydrological models. However, the quality of the groundwater simulation is often neglected. Groundwater reservoirs, buffering meltwaters and providing river flow when little to no surface runoff occurs, are extremely important in the Pamir region. Although physically based groundwater models provide a more detailed picture of the possible evolution of the system, empirical groundwater models are often used in hydrological modeling due to their minimal input data requirements and low computational cost compared to physically based models. However, the traditional empirical groundwater model with single linear storage is not suitable for the Pamir region. The region is characterized by a variety of sedimentary deposits in different landscape morphologies, resulting in varying delays in water recharge, release, and storage capacities. We improved the baseflow representation by coupling two linear groundwater reservoirs (one fast and one slow) into a widely-used hydrological model in the region. A representative catchment in the central Pamir, the Gunt River basin, is used as a case study to demonstrate the importance of groundwater in constraining the hydrological calibration process. Groundwater is the only contribution to winter river discharge in the Gunt basin and can thus be used as an indicator of groundwater parameter constraint. Here we show that the hydrological model can achieve good performance (in terms of daily discharge, seasonal snow cover fraction, and annual glacier mass balance) even when calibrated with only total daily discharge and winter baseflow. Especially the baseflow calibration helps constraining snowmelt onset in spring and improving adjustments of precipitation and temperature, which are the most uncertain sources in hydrological modeling in the region. Despite improvements, degree day factors still show a large variability. The resulting model equifinality problem still leads to predictive uncertainty, indicating that more glacier observations are needed for a sound process understanding. Based on the simulated results, the hydrological cycle in Gunt was analyzed and compared with previous studies.

How to cite: Huang, J., Pohl, E., and Richard-Cerda, J. C.: On the Importance of groundwater constraining in hydrological modeling of the Pamir region, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18059, https://doi.org/10.5194/egusphere-egu24-18059, 2024.

EGU24-18338 | ECS | Posters on site | HS2.1.9

Assessing the use of GPR and drone snow data for model development and runoff predictions in Northern Sweden 

Ilaria Clemenzi, David Gustafsson, Viktor Fagerström, Daniel Wennerberg, Björn Norell, Jie Zhang, Rickard Pettersson, and Veijo Pohjola

In cold regions, snow is a crucial component of the cryosphere, experiencing changes such as decreasing snowpack and snow cover. These changes impact the seasonal amount of snow and cause a shift in the timing of spring floods, particularly in mountainous areas. The complex and diverse snow processes and interactions in mountainous environments challenge making accurate predictions on snow and runoff. Moreover, snow is not uniformly distributed in space and time, which emphasizes the importance of monitoring mountain snowpack to enhance the understanding of hydrological processes and improve forecasting in the face of changing conditions. In the past few years, ground penetrating radar and drone acquisitions have emerged as a state-of-the-art methodology for obtaining snow data at high spatial resolution with a significant area coverage compared to traditional point observations. This study used data from ground penetrating radar and drone acquisitions to develop and evaluate a new snowfall distribution function based on wind speed, direction and topography to model wind redistribution in the semi-distributed hydrological model HYPE. We assessed the effect of the new snowfall distribution function compared to the one based on wind direction and topography on the snow distribution close to the accumulation peak in the Överuman catchment, Northern Sweden. We further assessed the impact of the two snowfall distribution functions on the catchment runoff predictions. Results show that the snowfall distribution function based on wind speed and direction better simulated the snow spatial distribution in the catchment than the snowfall function based on wind direction. Ground penetrating radar and drone acquisitions provided complementary model development and evaluation information.

How to cite: Clemenzi, I., Gustafsson, D., Fagerström, V., Wennerberg, D., Norell, B., Zhang, J., Pettersson, R., and Pohjola, V.: Assessing the use of GPR and drone snow data for model development and runoff predictions in Northern Sweden, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18338, https://doi.org/10.5194/egusphere-egu24-18338, 2024.

EGU24-18443 | ECS | Orals | HS2.1.9

Snow accumulation dynamics and its contribution to the hydrology of a glacierized catchment in the Northern Pamirs 

Achille Jouberton, Stefan Fugger, Thomas Shaw, Evan Miles, Marin Kneib, Abdulhamid Kayumov, Ardamehr Halimov, Hofiz Navruzshoev, Husraf Kabutov, Firdavs Vosidov, and Francesca Pellicciotti

Mountain glaciers are shrinking at accelerating rates due to enhanced ablation and reduced accumulation. In High Mountain Asia (HMA), recent glacier and snow changes have been highly heterogeneous, due to differences in accumulation regimes and sensitivity of glacier mass balances to temperature increases. The Pamir-Karakoram region is well known for hosting some of the only glaciers featuring neutral or even positive mass balance since the 2000, yet the causes for this anomaly are not fully understood, neither how long it will persist in the future nor its hydrological implications. In the semi-arid basins of Central Asia, snow- and glacier melt sustains most of the annual streamflow, with glacier melt being especially important towards the end of the dry summers. However, very few direct observations exist at high elevation, hindering the quantification of glacier mass inputs which is essential to estimate the long-term sensitivity of glaciers to warming. 

In this study, we combine in-situ hydro-meteorological observations with remote sensing observations to constrain a land-surface model and understand snow accumulation dynamics at a glacierized catchment in the Pamir mountains of Tajikistan. In-situ snow height and mass changes have been collected since 2021 from automatic weather stations, time-lapse cameras and pressure loggers in seasonally frozen lakes, providing a uniquely rich dataset for this region. We use MODIS, Landsat-8 and Sentinel-2 satellite images to derive snow cover dynamics at high spatial and temporal resolutions, and very high-resolution (2m) optical stereo imagery (Pleiades) to derive spatially resolved snow depths. These in-situ and remote-sensing observations are then used to inform a land-surface model that we force with statistically downscaled and bias-corrected reanalysis data (ERA5-Land) at 100m spatial and hourly temporal resolution, from 2015 to 2023.

We use our model to dissect the glacier mass balance seasonal dynamics, to quantify how much mass is gained through snowfall and avalanches, and how much mass is lost through melting and sublimation. We find that glaciers in our catchment receive a large part (58 %) of their annual mass input (1081 mm w.e.) from March to July, suggesting that spring and early summer precipitation events are key to control accumulation and therefore dictate glacier mass balances. Importantly, 11% of the annual snowfall is returned to the atmosphere via sublimation. At the catchment scale, snowmelt contributes to 67% of the annual runoff (625 mm), followed by glacier melt (24%) and rain (9%). When most of the seasonal snowpack has melted out (usually in August), glacier melt becomes the dominant contribution (with 55% in September). In most of the study period years, the glacier mass balance is close to neutral, but it turned negative in the last three years, where warmer conditions have led to more rapid seasonal snowpack melt-out and higher glacier ELAs, deteriorating the health of these previously spared glaciers and casting doubts on their ability to provide fresh water during the dry summers in the longer term.

How to cite: Jouberton, A., Fugger, S., Shaw, T., Miles, E., Kneib, M., Kayumov, A., Halimov, A., Navruzshoev, H., Kabutov, H., Vosidov, F., and Pellicciotti, F.: Snow accumulation dynamics and its contribution to the hydrology of a glacierized catchment in the Northern Pamirs, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18443, https://doi.org/10.5194/egusphere-egu24-18443, 2024.

EGU24-19899 | Posters on site | HS2.1.9

Flood modelling of a partly glacierized catchment in the Himalayas in a context of climate change 

Domenico De Santis, Christian Massari, Silvia Barbetta, Farhad Bahmanpouri, Viviana Maggioni, Sagar Gupta, Ashutosh Sharma, Ankit Agarwal, and Sumit Sen

The Himalayan region is severely exposed to the flood risk due to the heavy rainfall during the summer monsoon. The dynamics of the hydrological response during extreme events is relatively less understood, because of several complex and interactive processes. In this scenario, the use of rainfall-runoff models capable of adequately taking these processes into account could be crucial for reliable flood forecasting. However, in areas with such complex topography, accurately characterizing meteorological forcing and streamflow dynamics remains a challenging task due to the lack of ground measurements. Furthermore, in highly glacierized Himalayan basins, the significant contribution to streamflow by snow and ice melting has been shown to be progressively increasing due to its sensitivity to climate change, in parallel with the loss in glacier mass.

In this study, a conceptual and parsimonious hydrological model was implemented in semi-distributed mode and calibrated against streamflow and glacier loss volume data simultaneously. The MISDc-2L model was modified to simulate not only the snow accumulation and melt, but also the glacier melting in the ice-covered fraction of sub-basin area, assumed to occur once the seasonal snowpack is locally depleted. The Alaknanda River (one of the two headstreams of the Ganges) was chosen as a case study because it experiences several disastrous flood events in recent years. The basin upstream the Rudraprayag gauge was considered (≈8600 km2), for the period 2000-2020. The Randolph Glacier Inventory v7.0 was employed to locate glacierized areas, while glacier storage change data were extracted from available literature studies. Elevation data from NASADEM and hourly variables from ERA5-Land reanalysis dataset were used. A joint objective function was considered for calibration, including the Kling-Gupta efficiency, a high-flows hydrological signature and the error in glacier stored water loss. The model, constrained with glacier storage change data, was found to be able to provide good hydrological performances, both in calibration and validation, also with specific reference to annual flood peaks.

Despite the simplicity and the flood-oriented approach, the proposed modelling procedure simulated the dominant hydrological processes in a physically plausible way, in a basin with high-altitude glacierized areas in a context of climate change. The goal of adequately characterizing the contribution of glacier melt to total streamflow was pursued by aiming for consistency with additional data sources.

 

This work was funded by:

-          the Next Generation EU - Italian NRRP, Mission 4, Component 2, Investment 1.5, call for the creation and strengthening of 'Innovation Ecosystems', building 'Territorial R&D Leaders' (Directorial Decree n. 2021/3277) - project Tech4You - Technologies for climate change adaptation and quality of life improvement, n. ECS0000009. This work reflects only the authors’ views and opinions, neither the Ministry for University and Research nor the European Commission can be considered responsible for them.

-          the FLOSET Project 'Probabilistic floods and sediment transport forecasting in the Himalayas during the extreme events’, funded in the context of the 'ITALY-INDIA JOINT SCIENCE AND TECHNOLOGY COOPERATION CALL FOR JOINT PROJECT PROPOSALS FOR THE YEARS 2021 2023'.

How to cite: De Santis, D., Massari, C., Barbetta, S., Bahmanpouri, F., Maggioni, V., Gupta, S., Sharma, A., Agarwal, A., and Sen, S.: Flood modelling of a partly glacierized catchment in the Himalayas in a context of climate change, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19899, https://doi.org/10.5194/egusphere-egu24-19899, 2024.

EGU24-19969 | Orals | HS2.1.9

Correction of raingages' snow undercatch at meteorological stations using data from snow surveys: an Armenian case study 

Vazken Andréassian, Amalya Misakyan, and Artur Gevorgyan

The hydrological analysis of high elevation catchments is particularly difficult for two reasons:

. first, precipitation measurements are scarce at higher elevations,

. second, even when there are precipitation measurements, the collected amounts are strongly biased due to the well-known effect of wind on snowflakes.

Several formulations have been proposed to correct this wind-dependent underestimation of solid precipitation amounts. They all depend on at least one parameter, which must be calibrated for the specific location. At a few locations in the world, a double-fenced shielded raingage can be used to provide a reference precipitation amount, and the parameter of the correction can be determined experimentally. But at most locations, we have no real way to parameterize the adjustment relationship.

We use here a newly released dataset comprising 30 years of data for 11 stations located at high elevation in Armenia, where the precipitation gage network is strongly impacted by snow undercatch. Using ground snow surveys jointly with a degree-day based snow accumulation and melt model, we show that we can propose an adapted parameterization of the correction formula.

How to cite: Andréassian, V., Misakyan, A., and Gevorgyan, A.: Correction of raingages' snow undercatch at meteorological stations using data from snow surveys: an Armenian case study, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19969, https://doi.org/10.5194/egusphere-egu24-19969, 2024.

CR3 – Sea, Lake and River Ice

EGU24-875 | Orals | CR3.2

Origin of the trends in Antarctic sea ice extent over the period 1958-2023  

Hugues Goosse, Quentin Dalaiden, Feba Francis, and Ryan Fogt

The Antarctic sea ice extent has displayed several regime shifts over the past 65 years. Consistent lines of evidence indicate a decline in Antarctic sea ice extent from 1958 to 1978, which precedes the availability of continuous satellite observations. Subsequently, there was a significant sea ice expansion over 1979–2015 before the large drop observed in the past few years that led to record lows. The origin of those shifts and contrasting trends are analyzed here using a new reconstruction of atmospheric temperature, sea level pressure and sea ice extent spanning the period 1958-2023. We employ a data assimilation method that combines long simulations as well as large ensembles performed with climate models with long-term station-based records of temperature and sea level pressure at mid and high latitudes of the Southern Hemisphere. The reconstruction is thus totally independent from sea ice extent observations that are used as validation, showing the good performance of the method. In contrast to previous reconstructions and estimates, reconstructing simultaneously the atmospheric circulation, temperature, and sea ice extent ensures compatibility among the variables and thus a more straightforward dynamical interpretation. Our reconstruction indicates that no change in the reconstructed atmospheric circulation could be directly related to the regime shifts in sea ice extent trends but the covariance structure of the temperature strongly varies across periods, with more homogenous temperature anomalies for the early and recent periods and a more complex spatial pattern for the years 1979–2015. This might suggest a time-dependent contribution of the ocean, which will be further analyzed in a simulation performed with the NEMO model driven by the ERA5 reanalysis.

How to cite: Goosse, H., Dalaiden, Q., Francis, F., and Fogt, R.: Origin of the trends in Antarctic sea ice extent over the period 1958-2023 , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-875, https://doi.org/10.5194/egusphere-egu24-875, 2024.

EGU24-1737 | ECS | Orals | CR3.2 | Highlight

The 2023 record low Antarctic sea ice traced to synergistic influences of preconditioning, wind-induced transport and the ice albedo feedback 

Jinfei Wang, François Massonnet, Hugues Goosse, Hao Luo, Qinghua Yang, and Antoine Barthélemy

Antarctic sea ice extent (SIE) reached a new record low of 1.79 million km2 on 21 February 2023, 38% lower than the climatological average. In this study, we trace this record back to its possible origins by providing a detailed view on the evolution of the coupled ocean-atmosphere-sea ice system during the 12 months that preceded the event (March 2022 to February 2023). The impact of preceding winter and spring conditions on the summer minimum is assessed with the help of observations, reanalyses, and output from a regional ocean-sea ice coupled model NEMO3.6-LIM3. We find that the 2022-2023 annual cycle was characterized by consistently low SIE values throughout the year preceding the record, by anomalously high SIE melting rates in December 2022, and by circumpolar negative SIE anomalies in almost all basins of the Southern Ocean in February 2023. Through autumn and winter (March to August 2022), advection-induced positive air temperature anomalies inhibited the development of sea ice in the Weddell and Bellingshausen Seas, which preconditioned an ice-free state in the Bellingshausen Sea as early as October 2022. Concurrently, strong southerly winds in the Eastern Ross Sea caused by an anomalously deep Amundsen Sea Low in spring (September to November) transported significant volumes of sea ice northward, contributing to severe melting offshore in December and, through increased divergence near the coast, triggered the ice-albedo feedback onshore. As a consequence, a coastal polynya appeared in the western part of the Amundsen Sea due to stronger surface sea ice melting. This ice-albedo feedback was unusually active in late 2022 and favored accelerated melt towards the minimum in February 2023. This study highlights the impacts of multifactorial processes during the preceding seasons to explain the recent summer sea ice minima.

How to cite: Wang, J., Massonnet, F., Goosse, H., Luo, H., Yang, Q., and Barthélemy, A.: The 2023 record low Antarctic sea ice traced to synergistic influences of preconditioning, wind-induced transport and the ice albedo feedback, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1737, https://doi.org/10.5194/egusphere-egu24-1737, 2024.

EGU24-1943 | ECS | Posters on site | CR3.2

Annual evolution of the ice–ocean interaction beneath landfast ice in Prydz Bay, East Antarctica 

Haihan Hu, Jiechen Zhao, Petra Heil, Zhiliang Qin, Jingkai Ma, Fengming Hui, and Xiao Cheng

High-frequency observations of the ice–ocean interaction and high-precision estimation of the ice–ocean heat exchange are critical to understanding the thermodynamics of the landfast ice mass balance in Antarctica. To investigate the oceanic contribution to the evolution of the landfast ice, an integrated ocean observation system, including an acoustic Doppler velocimeter (ADV), conductivity–temperature–depth (CTD) sensors, and a sea ice mass balance array (SIMBA), was deployed on the landfast ice near Chinese Zhongshan Station in Prydz Bay, East Antarctica from April to November 2021. The CTD sensors recorded the ocean temperature and salinity. The ocean temperature experienced a rapid increase in late April, from −1.62°C to the maximum of −1.30°C, and then, it gradually decreased to −1.75°C in May and remained at this temperature until November. The seawater salinity and density exhibited similar increasing trends during April and May, with mean rates of 0.04 psu day1 and 0.03 kg m3 day1, respectively, which was related to the strong salt rejection caused by freezing of the landfast ice. The ocean current observed by the ADV had mean horizontal and vertical velocities of 9.5±3.9 cm s1 and 0.2±0.8 cm s1, respectively. The domain current direction was ESE (120°)–WSW (240°), and the domain velocity (79%) was 5–15 cm s1. The oceanic heat flux (Fw) estimated using the residual method reached a peak of 41.3±9.8 W m2 in April, and then, it gradually decreased to a stable level of 7.8±2.9 W m2 from June to October. The Fw values calculated using three different bulk parameterizations exhibited similar trends with different magnitudes due to the uncertainties of the empirical friction velocity. The spectral analysis results suggest that all of the observed ocean variables exhibited a typical half-day period, indicating the strong diurnal influence of the local tidal oscillations. The large-scale sea ice distribution and ocean circulation contributed to the seasonal variations in the ocean variables, revealing the important relationship between the large-scale and local phenomena. The high frequency and cross-seasonal observations of oceanic variables obtained in this study allow us to deeply investigate their diurnal and seasonal variations and to evaluate their influences on the landfast ice evolution.

How to cite: Hu, H., Zhao, J., Heil, P., Qin, Z., Ma, J., Hui, F., and Cheng, X.: Annual evolution of the ice–ocean interaction beneath landfast ice in Prydz Bay, East Antarctica, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1943, https://doi.org/10.5194/egusphere-egu24-1943, 2024.

EGU24-3173 | Posters on site | CR3.2

Ocean heat transport modulates Arctic sea ice loss 

Daniel Feltham, Jake Aylmer, and David Ferreira

Decades of literature propose ocean heat transport (OHT) as a potential cause for uncertainty in the rates of Arctic sea ice loss based on strong correlations across different climate models. This study presents a simple underlying physical theory, derived from the large-scale energy budget of the polar region, that explains the impact of OHT on Arctic sea ice. Expressed in an intuitive linear equation, we show that this captures the relationship between historical and future Arctic sea ice loss, OHT, and polar warming, across 20 of the latest-generation climate models. Furthermore, using a lagged-correlation analysis, we find that changes in OHT lead the losses in sea ice, implying that OHT exerts a systematic modulation of historical and future Arctic sea ice loss. Our simple equation applies equally in the Southern hemisphere, for which Antarctic sea ice loss is also strongly correlated with the change in poleward OHT. However, here sea ice loss leads changes in the OHT, with further scrutiny of the other terms in our equation identifying changes to the atmospheric circulation as the primary driver. On the basis of these findings, we strongly advocate further research into the causes of different ocean (atmospheric) circulation changes in the Arctic (Antarctic) and better validation in climate models to ultimately reduce uncertainty in future projections

How to cite: Feltham, D., Aylmer, J., and Ferreira, D.: Ocean heat transport modulates Arctic sea ice loss, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3173, https://doi.org/10.5194/egusphere-egu24-3173, 2024.

Arctic sea ice outflow to the Atlantic Ocean is essential to the Arctic sea ice mass budget and the marine environments in the Barents and Greenland seas (BGS). With the extremely positive Arctic Oscillation (AO) in winter (JFM) 2020, the feedback mechanisms of anomalies in Arctic sea ice outflow and their impacts on winter–spring sea ice and other marine environmental conditions in the subsequent months until early summer in the BGS were investigated. The results reveal that the total sea ice area flux (SIAF) through the Fram Strait, the Svalbard–Franz Josef Land passageway, and the Franz Josef Land–Novaya Zemlya passageway in winter and June 2020 was higher than the 1988–2020 climatology. The relatively large total SIAF, which was dominated by that through the Fram Strait (77.6 %), can be significantly related to atmospheric circulation anomalies, especially with the positive phases of the winter AO and the winter–spring relatively high air pressure gradient across the western and eastern Arctic Ocean. Such abnormal winter
atmospheric circulation patterns have induced wind speeds anomalies that accelerate sea ice motion (SIM) in the Atlantic sector of Transpolar Drift, subsequently contributing to the variability in the SIAF (R=+0.86, P<0.001). The abnormally large Arctic sea ice outflow led to increased sea
ice area (SIA) and thickness in the BGS, which has been observed since March 2020, especially in May–June. The increased SIA impeded the warming of the sea surface temperature (SST), with a significant negative correlation between April SIA and synchronous SST as well as the lagging SST of 1–3 months based on the historic data from 1982–2020. Therefore, this study suggests that winter–spring Arctic sea ice outflow can be considered a predictor of changes in sea ice and other marine environmental conditions in the BGS in the subsequent months, at least until early summer. The results promote our understanding of the physical connection between the central Arctic Ocean and the BGS.

How to cite: Zhang, F., Lei, R., Zhai, M., Pang, X., and Li, N.: The impacts of anomalies in atmospheric circulations on Arctic sea ice outflow and sea ice conditions in the Barents and Greenland seas: case study in 2020, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3299, https://doi.org/10.5194/egusphere-egu24-3299, 2024.

EGU24-4173 | Posters on site | CR3.2

Multi-year and first-year ice from RCM for assimilation in ECCC ice type analysis system 

Alexander Komarov, Alain Caya, and Mark Buehner

Arctic sea ice type information is essential for various operational and scientific applications including the support of marine users and guiding ice thickness retrieval algorithms operating with SMOS and CryoSat-2 data for improved sea ice prediction. A sea ice type analysis system developed at Environment and Climate Change Canada’s (ECCC) generates pan-Arctic ice type analyses at 5 km resolution every 6 hours. The ice type analysis system assimilates ice type information provided by passive microwave (AMSR2, SSMIS) and scatterometer (ASCAT) data, but assimilation of these observations is not reliable in the areas near land and in the narrow channels of the Canadian Arctic Archipelago due to their low spatial resolution of ~20-50 km. Therefore, assimilation of high-resolution ice type observations from synthetic aperture radar (SAR) is highly desired.

In this study, we extended our approach for automated detection of winter multi-year ice (MYI) and first-year ice (FYI) at 1.6 km scale from RADARSAT-2 to RCM data. To this end, we collected more than 2,000 RCM images and corresponding image analyses products that were manually generated by the Canadian Ice Service (CIS) ice experts for the period of time between July 1, 2020 and July 31, 2023. From these RCM images we extracted SAR information for more than 30,000 pure MYI and more than 619,000 pure FYI data samples under no melt conditions as identified by the CIS image analyses.

We demonstrated that separability measures for MYI and FYI classes in the spaces of the two predictor parameters (HV/HH polarization ratio and standard deviation of HV signal) are consistent with those we previously observed for RADARSAT-2. Furthermore, we found that our RCM-based MYI/FYI detection approach allows us to classify 60% of the winter CIS ice data samples with the accuracy of 99.6%. Preliminary results of assimilating RCM-based MYI/FYI high-resolution retrievals in combination with passive microwave and scatterometer data in the ECCC ice type analysis system will be also presented.

How to cite: Komarov, A., Caya, A., and Buehner, M.: Multi-year and first-year ice from RCM for assimilation in ECCC ice type analysis system, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4173, https://doi.org/10.5194/egusphere-egu24-4173, 2024.

The efficiency of air-sea momentum exchange depends on top and bottom sea ice surface roughness which varies with ice types and conditions, but constants are applied in most climate models. Future sea ice reduction is expected to lead to an increase in efficiency of air-sea momentum transfer. Accurate representation of momentum transfer processes will be a requirement for realistic model predictions. Within the CANARI project (Climate change in the Arctic-North Atlantic Region and Impacts on the UK) we have implemented the CICE form drag scheme into the sea ice model SI3. Based on parameters of the ice cover such as ice concentration, size, and frequency of the sails and keels, freeboard and floe draft, and size of floes and melt pond fraction, the total form drag can be computed as a sum of form drag from sails and keels, form drag from floe edges, form drag from melt pond edges, and a reduced skin drag due to a sheltering effect. Ocean – sea ice simulations reveal that the inclusion of form drag has a significant impact by reducing sea ice drift and near surface ocean currents by more than 20% in the marginal sea ice regions. However, results depend on the poorly know input variables which are parameterised from the volume of ridged ice. We apply a new surface topography data set which has been derived from the ICESat-2 ATL03 global geolocated photon height data product. We use the continuous data sets of surface roughness, sail heights and frequency of pressure ridges across the Arctic to calibrate the form drag parameterization and present new simulation results.

How to cite: Schroeder, D., Feltham, D., Duncan, K., and Farrell, S.: Implementation of form drag into the ocean – sea ice model NEMO-SI3, calibration of input parameters with ICESat-2 surface heights and its impact on sea ice and ocean circulation , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5940, https://doi.org/10.5194/egusphere-egu24-5940, 2024.

EGU24-6230 | ECS | Orals | CR3.2

The Significance of the Melt-Pond Scheme in a CMIP6 Global Climate Model 

Rachel Diamond, David Schroeder, Louise Sime, Jeff Ridley, and Danny Feltham

The impact of melt ponds on sea ice albedo has been observed and documented. In general circulation models, ponds are now accounted for through indirect diagnostic treatments (“implicit” schemes) or prognostic melt-pond parameterizations (“explicit” schemes). However, there has been a lack of studies showing the impacts of these schemes on simulated Arctic climate. We focus here on rectifying this using the general circulation model HadGEM3, one of the few models with a detailed explicit pond scheme. We identify the impact of melt ponds on the sea ice and climate, and associated ice–ocean–atmosphere interactions. We run a set of constant forcing simulations for three different periods and show, for the first time, that using mechanistically different pond schemes can lead to very significantly different sea ice and climate states. Under near-future conditions, an implicit scheme never yields an ice-free summer Arctic, while an explicit scheme yields an ice-free Arctic in 35% of years and raises autumn Arctic air temperatures by 5° to 8°C. We find that impacts on climate and sea ice depend on the ice state: under near-future and last-interglacial conditions, the thin sea ice is very sensitive to pond formation and parameterization, whereas during the preindustrial period the thicker sea ice is less sensitive to the pond scheme choice. Both of these two commonly used parameterizations of sea ice albedo yield similar results under preindustrial conditions but in warmer climates lead to very different Arctic sea ice and ocean and atmospheric temperatures. Thus, changes to physical parameterizations in the sea ice model can have large impacts on simulated sea ice, ocean, and atmosphere.

How to cite: Diamond, R., Schroeder, D., Sime, L., Ridley, J., and Feltham, D.: The Significance of the Melt-Pond Scheme in a CMIP6 Global Climate Model, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6230, https://doi.org/10.5194/egusphere-egu24-6230, 2024.

EGU24-9532 | ECS | Posters on site | CR3.2

The variability and predictability of regional Antarctic sea ice on seasonal timescale 

Yongwu Xiu, Yiguo Wang, Hao Luo, Lilian Garcia-Oliva, and Qinghua Yang

Antarctic sea ice is an important part of the Earth's system and provides key habitats for wild animals. This study assesses the variability and predictability of regional Antarctic sea ice, particularly focusing on the impact of the initialization of different components on its seasonal predictions. We run three hindcasts (retrospective forecast) experiments within the Norwegian Climate Prediction Model (NorCPM), whose atmosphere, ocean, or sea ice is initialized, respectively. These hindcasts are conducted four times per year over 1985-2010 and last for 13 months. We first evaluate three reanalyses that provide initial conditions for the hindcasts. It shows that solely constraining the ocean or atmosphere cannot reproduce the overall observed sea ice concentration (SIC) trend, but has some skill in capturing the variability of the SIC and Antarctic sea ice extent (SIE). Sea ice assimilation further improves the estimate of the SIC/SIE trend and variability, but the performance in the Pacific section is degraded. According to the hindcast experiments, the predictive skill varies with region and season. For example, winter SIE in the Weddell Sea and Amundsen-Bellingshausen Sea can be skillfully predicted 12 months in advance and the predictive skill in the Pacific Section is lower. Among the three hindcast experiments, atmosphere initialization generally yields comparable or even more prolonged prediction skills when compared to ocean or ocean/sea-ice initialization. Compared to ocean initialization, additional sea ice initialization improves prediction in the Indian Section, Pacific Section, and the Ross Sea, but degrades in the Amundsen-Bellingshausen Sea. Further analysis demonstrates that a large part of regional SIE predictability can be explained by high SST predictability on seasonal timescale. In addition, sea ice thickness plays a key role in prolonging the prediction skill in the Ross Sea until the summer season due to the memory of thick ice.

How to cite: Xiu, Y., Wang, Y., Luo, H., Garcia-Oliva, L., and Yang, Q.: The variability and predictability of regional Antarctic sea ice on seasonal timescale, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9532, https://doi.org/10.5194/egusphere-egu24-9532, 2024.

EGU24-9852 | ECS | Orals | CR3.2

Comprehensive assessment of sea-ice thickness datasets: The ESA SIN’XS project 

Valentin Ludwig, Carole Belot, Elodie Da Silva, Sara Fleury, Christian Haas, Stefan Hendricks, Eric Munesa, Javier Pastor, Stephan Paul, Michel Tsamados, Jérôme Bouffard, Alessandro Di Bella, and Michele Scagliola

Sea-ice thickness is a crucial parameter for a variety of scientific disciplines, including climate science, oceanography, and ecology. It plays a vital role in regulating exchanges of heat, moisture and momentum between the polar oceans and the atmosphere, influencing ocean currents, and affecting local cloud cover and precipitation.

The ESA-funded project SIN’XS, led by NOVELTIS, AWI, LEGOS, and UCL, aims to comprehensively assess available sea-ice thickness and snow thickness products and their uncertainties. We are building up a database of large-scale datasets (satellite-based and models) as well as reference datasets (in-situ, airborne, moorings, etc.) to better understand the variability and change in observed ice thickness in both hemispheres. A web portal enables users to interactively explore and analyse data. In the talk, we will introduce the project and database and present the first results. We will also encourage potential collaborators to contribute to the project by submitting data to our website. We look forward to collaborating with the scientific community to better understand the complexities of sea-ice thickness and its impact on our planet. The ultimate goal of SIN’XS is to provide a reconciled and comprehensive sea-ice thickness estimate.

How to cite: Ludwig, V., Belot, C., Da Silva, E., Fleury, S., Haas, C., Hendricks, S., Munesa, E., Pastor, J., Paul, S., Tsamados, M., Bouffard, J., Di Bella, A., and Scagliola, M.: Comprehensive assessment of sea-ice thickness datasets: The ESA SIN’XS project, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9852, https://doi.org/10.5194/egusphere-egu24-9852, 2024.

EGU24-10094 | ECS | Posters on site | CR3.2

Satellite-based detection of snow wetness and wave-induced surface wetting of Antarctic sea ice 

Marta Stentella, Ghislain Picard, Petra Heil, Stuart Corney, Jonathan Wille, and Vincent Favier
Sea ice is a fundamental, highly variable element of the polar environments. Its variability deeply affects, not only the local climate- and ecosystem but also the global Earth system. Until recently Arctic sea ice experienced a general retreat as expected under global warming whilst Antarctic sea ice extent increased up to 2014. However, Antarctic sea-ice extent at maximum annual cover shifted from a record high (2014) to a record minimum extent (2023), begging to explore the relationship between sea ice and ocean/atmospheric forcing. In this work, we pinpoint some extreme atmospheric events, specifically, atmospheric rivers (ARs) to analyse their influence on sea ice and snow properties. ARs can have a direct impact on the nature of oceanic surface gravity waves. Increasing wind speed causes an increase in wave height and energy, leading to greater repercussions on snow and sea ice. The sea ice area most affected by this forcing is the one that separates the pack ice from the open oceans, known as the marginal ice zone (MIZ). Our analysis aims to understand wave-sea ice interaction and its effect on accelerating snow melt or changing sea ice morphology. To accomplish this we focus on the influence of wave overwash on sea ice surfaces during the spring season in the Weddell Sea. The MIZ is identified by posing the limits of sea ice concentration (SIC) ranging from 15% to 80%. ARs events are identified using ERA5 reanalysis data, estimating their integrated water vapour transport (IWV) and vertically integrated vapour transport (vIVT) values, which are considered extreme if they exceed 95% of historical norms for the same location and time of year over a time interval that spreads from 1980 to 2022. Data obtained from AMSRE, AMSR2 & SMOS passive microwave sensors are used to generate time series and local maps of brightness temperature. These microwave signatures serve in the analysis of the possible spatial and temporal correlation between ARs events and sea ice and snow characteristics. Initial findings suggest that ARs and their subsequent gravity waves may significantly affect the wetting of sea ice and of the snow on it leading to increased melting of the MIZ. This study will improve the methods to inform models used to forecast the impact that extreme atmospheric events can have on sea ice and snow, offering new directions to investigate the coupled ocean-sea ice-atmosphere system in a changing climate.

How to cite: Stentella, M., Picard, G., Heil, P., Corney, S., Wille, J., and Favier, V.: Satellite-based detection of snow wetness and wave-induced surface wetting of Antarctic sea ice, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10094, https://doi.org/10.5194/egusphere-egu24-10094, 2024.

EGU24-10502 | Orals | CR3.2

Annual Cycle of Antarctic Sea Ice Deformation from ICESat-2 

Kyle Duncan and Sinead Farrell

Since 2015, Antarctic sea ice extent has declined by ~53%, and reached consecutive record lows in the austral summers of 2022 and 2023. These events have raised major concern as to whether a regime shift towards more extreme and frequent low sea ice extents has begun. Potential impacts on the climate system are far-reaching and continent-wide studies are urgently needed. Due to Antarctica's remote and harsh environment, in situ observations are however sparse. NASA's ICESat-2, a laser altimeter launched in 2018, provides precise sea ice surface elevation data at high-resolution, with along-track sampling every ~0.7 m. This sampling allows us to resolve meter-scale features in the sea ice pack, such as pressure ridges, which modify the shape of the ice thickness distribution and play an important role in ocean-atmosphere momentum flux through form drag. We apply a bespoke processing technique, called the University of Maryland-Ridge Detection Algorithm (UMD-RDA), to derive the surface topography of sea ice in the Southern Ocean over a 5-year period, spanning 2018-2023. Using the UMD-RDA we can capture seasonal and interannual variability in surface roughness, pressure ridge sail height, and ridge sail spacing. We find that during the 2018-2023 period, on average, across the full Southern Ocean ice pack, sea ice surface roughness reaches a maximum in January/February followed by a minimum in April. Sail height is at its maximum in January and minimum in June, while sail spacing is at its minimum in January and maximum in June. Interannual variability shows that the 2023 season is an outlier with respect to the 5-year 2018-2023 average. In 2023 there was a decrease of ~20% in surface roughness during the April minimum, a decrease of ~8% in sail height during the June minimum, and an increase of ~31% in sail spacing during the June maximum. This suggests that, in 2023, the sea ice pack was less deformed overall than in preceding years. We also assess seasonal and interannual variability in surface roughness and ridge morphology in five distinct regions including the Amundsen-Bellingshausen (A-B), Ross, Pacific, Indian, and Weddell Seas. The A-B, Ross, and Pacific sectors showed the greatest change in 2023, with respect to the 2018-2023 average, with a decrease in surface roughness of ~34%, ~26%, and ~14%, respectively. Sail spacing within the A-B, Ross, and Pacific sectors, with respect to the 2018-2023 average, increased by ~83%, ~61%, and ~35%, respectively. Furthermore, the ICESat-2 ATL10 sea ice freeboard dataset shows a ~50% decrease in freeboard within the A-B sector in 2023. These results provide evidence that a substantial amount of thicker, older, and rougher ice was likely exported out of the A-B region. Our results can provide insight into the mechanisms responsible for the recent record low sea ice extents and could uncover new relationships between deformation, roughness, and ice extent.

How to cite: Duncan, K. and Farrell, S.: Annual Cycle of Antarctic Sea Ice Deformation from ICESat-2, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10502, https://doi.org/10.5194/egusphere-egu24-10502, 2024.

EGU24-10681 | Orals | CR3.2

Improving sea ice projections with the modern-era satellite altimetry record of freeboard and thickness 

Alek Petty, Christopher Cardinale, and Madison Smith

Future projections of Arctic sea ice remain poorly constrained, due in large part to the significant inter-model spread across the CMIP6 archive. Various recent studies have explored novel calibration methods to better constrain future sea ice conditions, especially the timing of an ice-free Arctic, but can come to different conclusions based on the calibration approach taken. Some approaches exclude outlier models, while others seek to exploit sensitivities of sea ice area/extent to global warming (e.g., Northern Hemisphere temperatures) to better constrain the multi-model ensemble. As long-term and reliable observations of sea ice thickness are lacking, calibration efforts have primarily relied on sea ice concentration/area data from the passive microwave satellite record. 

We are leading a new NASA-funded effort to utilize the multi-year record of observed sea ice freeboard and derived sea ice thickness from ICESat-2, together with similar data from the original ICESat and ESA’s CryoSat-2 missions, to reduce inter-model uncertainty in future sea ice projections. Although the sea ice altimetry data record is more limited in space and time than the longer-term passive microwave concentration record, it can offer significant advantages; for example, freeboard is measured very accurately by modern laser altimetry satellites, providing more information within the consolidated ice pack, and is now output by some of the CMIP6 models, enabling direct comparisons between the model and the satellite measurements. Only a small fraction of CMIP6 models provide the direct output of derived freeboard so assumptions (mainly related to the bulk ice and snow density) need to be made when estimating freeboard with the core model output. Initial results suggest this can have an important impact on the comparisons. Converting the observations of freeboard to sea ice thickness introduces significantly more uncertainty to the observed data but can radically simplify the model comparison effort. 

In this presentation we will showcase our initial efforts to better utilize the satellite altimetry record for calibrating CMIP6 simulations of future sea ice conditions across both poles, but with a primary focus on projections of the timing of an ice-free Arctic. We discuss some of the nuances of using freeboard as a more direct observational constraint compared to thickness, providing motivation for more modeling groups to provide the direct ice density and freeboard outputs in the lead-up to CMIP7. 

Finally, our analysis has all been carried out within the NASA-supported CryoCloud compute environment using the cloud-based (AWS) CMIP6 data archive, so we include additional insight into the benefits of this analysis approach and the small but important impact from differences in model output availability (compared to the recent IPCC analysis). 

How to cite: Petty, A., Cardinale, C., and Smith, M.: Improving sea ice projections with the modern-era satellite altimetry record of freeboard and thickness, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10681, https://doi.org/10.5194/egusphere-egu24-10681, 2024.

EGU24-12970 | Posters on site | CR3.2

A Mushy Model of Gas Bubble Nucleation and Transport in Sea Ice 

Andrew Wells, Joseph Fishlock, and Christopher MacMinn

Gas bubble nucleation and transport within porous sea ice is an important factor in the biogeochemistry of sea ice. Freezing concentrates dissolved gas species present in ocean water, which can subsequently exceed saturation and nucleate as bubbles. Buoyant gas bubbles can escape to the atmosphere or redissolve into the liquid inclusions. The resulting transport is a key physical uncertainty for the flux of climatically important gases between the ice and the atmosphere, as well as the chemical and optical properties of the ice. 

We develop a phenomenological model for the motion of a bubble rising in porous sea ice which includes viscous drag and bubble trapping. We apply this description of bubble transport to a thermodynamic model of sea ice growth. Our model extends the traditional mushy-layer theory describing the solidification of saltwater solutions to include a gas phase. The resulting model is solved numerically to investigate idealized gas dynamics during a seasonal cycle of ice growth and melt. We find that the total gas flux to the atmosphere during a season is highly sensitive to the ratio of the bubble size to the characteristic scale of the ice pore geometry. We also extend the description of bubble transport to include a distribution of bubble sizes. We evaluate the output of different versions of the model by comparing to field observations of argon content in sea ice from a study in Barrow, Alaska.

How to cite: Wells, A., Fishlock, J., and MacMinn, C.: A Mushy Model of Gas Bubble Nucleation and Transport in Sea Ice, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12970, https://doi.org/10.5194/egusphere-egu24-12970, 2024.

EGU24-13674 | Posters on site | CR3.2

Seasonal and interannual variations in landfast ice mass balance between 2009–2018 in Prydz Bay, East Antarctica 

Na Li, Ruibo Lei, Petra Heil, Bin Cheng, Minghu Ding, Zhongxiang Tian, and Bingrui Li

Landfast ice (LFI) is an indispensable component in the Antarctic coastal system, which is very important for coastal climate and ecological processes. However, the regional differences of LFI mass balance with respect to the seasonal and inter-annual variations and the impact factors responsible to those differences have not been investigated systematically in the Prydz Bay, i.e., the third largest bay along the Antarctic coast. 

We analyzed the data measured by 11 ice mass balance buoys (IMBs) obtained in the coastal areas off the Chinese Zhongshan station (ZS) and Australian Davis station (DS), and covered 2009–2010, 2013–2016 and 2018 ice seasons. We identified the local spatial changes in LFI based on the data.  The observed annual maximum ice thickness for LFI off ZS (DS) was 1.59±0.17 m (1.64±0.08 m), with the dominant influencing factors of air temperature anomaly, snow depth atop, local topography and wind regime, and oceanic heat flux. Larger interannual and local spatial variabilities for the seasonality of LFI mass balance were observed at ZS than at DS because of the differences in local topography and katabatic wind regime. LFI at DS (0.6±0.2 cm d-1) grew faster in winter due to the relatively low air temperature and small oceanic heat flux compared to that at ZS (0.5±0.2 cm d-1). Snow ice contributes up to 26% of the observed LFI maximum ice thickness at the offshore site close to ground icebergs off ZS because of substantial snow accumulation. Oceanic heat flux would promote the LFI growth during winter at the sites nearby Dålk Glacier off ZS because of the supercooled meltwater. At interannual timescale, we find that variability of LFI properties across the study domain prevailed, over any trend during the recent decades. Our results suggests that increased understanding of local atmospheric and oceanic conditions, as well as surface morphology and coastal bathymetry, are required to improve Antarctic LFI modelling at local and regional scale.

How to cite: Li, N., Lei, R., Heil, P., Cheng, B., Ding, M., Tian, Z., and Li, B.: Seasonal and interannual variations in landfast ice mass balance between 2009–2018 in Prydz Bay, East Antarctica, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13674, https://doi.org/10.5194/egusphere-egu24-13674, 2024.

EGU24-14415 | ECS | Orals | CR3.2

Significant contribution of internal variability to recent Barents-Kara sea ice loss in winter 

Peter Yu Feng Siew, Yutian Wu, Mingfang Ting, Cheng Zheng, Qinghua Ding, and Richard Seager

The Arctic has experienced a rapid sea ice loss in the Barents and Kara Seas in winter during the last few decades. Such sea ice loss has been attributed to anthropogenic warming and internal variability, but their relative contribution remains unclear. Using machine-learning methods and large ensemble simulations, we successfully reproduce Barents-Kara sea ice trends as the joint impact of anthropogenic and internal atmospheric variability components. Results show that the loss of Barents-Kara sea ice extent over the recent 20 years (1997-2017) is significantly enhanced by atmospheric internal variability (>50%) acting on top of anthropogenic warming. Overall, this study highlights that internal variability plays a more important role in recent winter Arctic sea ice loss than previously thought, and promotes similar machine-learning methods for attributing sea ice trends in other polar regions and seasons.

How to cite: Siew, P. Y. F., Wu, Y., Ting, M., Zheng, C., Ding, Q., and Seager, R.: Significant contribution of internal variability to recent Barents-Kara sea ice loss in winter, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14415, https://doi.org/10.5194/egusphere-egu24-14415, 2024.

EGU24-14705 | Posters on site | CR3.2

How Has the Ferrel Cell Contributed to the Maintenance of Antarctic Sea Ice at Low Levels Since 2016? 

Shaoyin Wang, Jiping Liu, Zixin Wei, Hua Li, Dongxia Yang, and Xiao Cheng

This study investigates the specific circulation anomalies that have sustained the low Antarctic sea ice state since 2016. Firstly, we find a significant strengthening and southward shift in the Ferrel Cell during 2016–2022, resulting in a marked increase in zonally southward transport of heat and moisture. Secondly, this enhanced Ferrel Cell is closely associated with a stronger circumpolar wave pattern (CWP) over the same period. This pattern is zonally asymmetric and greatly amplifies the poleward advections of heat and moisture, leading to the increased downward longwave radiation, more liquid precipitation and sea ice retreat in specific regions, including the western Pacific and Indian Ocean sectors, eastern Ross and northern Weddell Seas. The strong correlation between the Ferrel Cell and CWP was reproduced by the Community Earth System Model - Large Ensemble. As global warming continues, the potential southward shift of the Ferrel Cell poses a major threat to sea ice retreat.

How to cite: Wang, S., Liu, J., Wei, Z., Li, H., Yang, D., and Cheng, X.: How Has the Ferrel Cell Contributed to the Maintenance of Antarctic Sea Ice at Low Levels Since 2016?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14705, https://doi.org/10.5194/egusphere-egu24-14705, 2024.

EGU24-14727 | ECS | Posters on site | CR3.2

Intensifying circumpolar winds contributes to reducing winter Antarctic sea ice growth 

Daniel Topal, Thierry Fichefet, François Massonnet, Antoine Barthélemy, Hugues Goosse, Quentin Dalaiden, and Pierre-Yves Barriat

During the austral autumn/winter of 2023 Antarctic sea ice exhibited a pan-Antarctic wide delay in refreezing of roughly a month (peaked in July 2023, hereafter referred to as W23 event). As such it is unprecedented over the satellite era and may point to a start of a transitioning to a new state of Antarctic sea ice. However, the relatively short observational record obscures our understanding how natural variability in Antarctic sea ice can act together with anthropogenic climate change in creating favorable conditions for extreme Antarctic sea ice changes. Here we show that an anomalous atmospheric circulation pattern prior to W23 (May-to-July 2023) is part of a longer-term (1979-2022) trend in observed mid-to-upper tropospheric winds around the Antarctic continent towards a wavier manner that favors anomalous moisture transport to the Weddell Sea. We further show that this circulation pattern is associated with winter sea ice anomalies on both year-to-year and interdecadal timescales in preindustrial control simulations of CMIP6 climate models as well as in future projections of large ensemble simulations under greenhouse gas emission scenarios. By conducting standalone simulations with the global ocean-sea ice model NEMO4-SI3 (forced by the atmospheric reanalysis ERA5) at two horizontal resolutions (1º & 0.25º), we also study the influence of the recently observed acceleration of ocean warming around the Antarctic continent and the effect of model horizontal resolution on the simulation of sea ice extremes. Our results overall suggest that internal atmospheric-sea ice coupling could be an important contributor to future winter Antarctic sea ice changes, enhancing the forced Antarctic sea ice changes that are primarily driven by ocean warming.

How to cite: Topal, D., Fichefet, T., Massonnet, F., Barthélemy, A., Goosse, H., Dalaiden, Q., and Barriat, P.-Y.: Intensifying circumpolar winds contributes to reducing winter Antarctic sea ice growth, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14727, https://doi.org/10.5194/egusphere-egu24-14727, 2024.

EGU24-16719 | ECS | Posters on site | CR3.2

Arctic sea ice freeboard during summer – a new Cryo-TEMPO product 

Anne Braakmann-Folgmann, Jack Landy, Geoffrey Dawson, Robert Ricker, Stefan Hendricks, Lin Gilbert, David Brockley, and Eero Rinne

Arctic sea ice thickness impacts various physical and biogeochemical processes at the air-ice-ocean interface. For example, it determines how much sunlight reaches the base of the ice – a key parameter for primary production. It is also an essential variable for sea ice forecasts, shipping and other marine activities. During the summer months (May-September) melt ponds complicate the retrieval of sea ice thickness compared to winter. On the other hand, summer sea ice thickness observations are particularly important as this is when most shipping and biological production happen. Summer sea ice thickness estimates are also crucial to extend predictions by many months.

In this study, we present the novel summer sea ice Cryo-TEMPO product. Cryo-TEMPO is a set of easily accessible thematic products derived from CryoSat data targeted at both expert and non-expert users. The summer sea ice product contains freeboard measurements and smoothed freeboard, which are calculated at each lead position along the altimetry tracks. The product covers the whole Arctic and the full CryoSat lifetime since 2010. It will be updated operationally from summer 2024 onwards. Comparisons against various airborne and mooring data were conducted for validation and will be presented, too.

How to cite: Braakmann-Folgmann, A., Landy, J., Dawson, G., Ricker, R., Hendricks, S., Gilbert, L., Brockley, D., and Rinne, E.: Arctic sea ice freeboard during summer – a new Cryo-TEMPO product, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16719, https://doi.org/10.5194/egusphere-egu24-16719, 2024.

EGU24-19034 | ECS | Orals | CR3.2

Local-scale analysis on sea-ice deformation based on radar imagery and deep learning 

Matias Uusinoka, Arttu Polojärvi, and Jari Haapala

Sea-ice deformation is commonly estimated from satellite imagery in low spatial and temporal resolutions. This coincides with the fact that the lower bound of scale invariance in ice deformation is analytically estimated at the scale of ice thickness. Estimating deformation patterns from more accurate buoy records can in turn be problematic due to their sparse spatial coverage while the previous analysis of radar imagery has been disturbed noisy data. In response to the gap in high resolution empirical data, we deploy a novel deep neural network-based motion tracking method with ice-radar imagery gathered continuously during MOSAiC expedition for statistical analysis of sea ice deformation. The proposed method enables estimating ice dynamics at length scales down to 10 meters at a 10-minute temporal scale in a 10 km ×10 km domain. Overcoming issues with high-frequency noise in radar data, we output ~10^8 daily deformation-rate estimates with accuracy comparable or higher than those gained by using ice buoys. The method allows quantification of the highly intermittent and localized deformation and, thus, the analysis of established scaling laws at resolutions never analyzed before. In light of the changing ice conditions in the Arctic, we emphasize seasonal variability and separation between ice zones.

How to cite: Uusinoka, M., Polojärvi, A., and Haapala, J.: Local-scale analysis on sea-ice deformation based on radar imagery and deep learning, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19034, https://doi.org/10.5194/egusphere-egu24-19034, 2024.

EGU24-348 | ECS | Orals | CR3.3

Ridge-formation simulations in three dimensions using discrete element methods 

Marek Muchow and Arttu Polojärvi

Sea-ice ridges form as a part of sea-ice deformation, while the ice is moved by winds and ocean currents. While ridging is a localized process, it is assumed to limit the compressive strength of sea ice in large scale. However, formulations of large-scale ice strength, as used in Earth System Models, do not consider individual ridge formation processes in detail. Thus, it is necessary to understand the energy spend in ridge formation and various processes related to generating ice rubble and redistributing it. To investigate ridge formation in detail, we use the Aalto University in-house discrete-element-method (DEM) model. This three-dimensional DEM model features deformable, multi-fracturing, ice floes, which can fail and form ridges when coming into contact, while recording the ridging forces. With this, we discuss why three-dimensional simulations are important to investigate ridge formation process.

How to cite: Muchow, M. and Polojärvi, A.: Ridge-formation simulations in three dimensions using discrete element methods, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-348, https://doi.org/10.5194/egusphere-egu24-348, 2024.

EGU24-1671 | ECS | Posters on site | CR3.3

Monthly Arctic sea ice prediction based on a data-driven deep learning model  

Xiaohe Huan, Jielong Wang, and Zhongfang Liu

There is growing interest in sub-seasonal to seasonal predictions of Arctic sea ice due to its potential effects on midlatitude weather and climate extremes. Current prediction systems are largely dependent on physics-based climate models. While climate models can provide good forecasts for Arctic sea ice at different timescales, they are susceptible to initial states and high computational costs. Here we present a purely data-driven deep learning model, UNet-F/M, to predict monthly sea ice concentration (SIC) one month ahead. We train the model using monthly satellite-observed SIC for the melting and freezing seasons, respectively. Results show that UNet-F/M has a good predictive skill of Arctic SIC at monthly time scales, generally outperforming several recently proposed deep learning models, particularly for September sea-ice minimum. Our study offers a perspective on sub-seasonal prediction of future Arctic sea ice and may have implications for forecasting weather and climate in northern midlatitudes.

How to cite: Huan, X., Wang, J., and Liu, Z.: Monthly Arctic sea ice prediction based on a data-driven deep learning model , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1671, https://doi.org/10.5194/egusphere-egu24-1671, 2024.

EGU24-2377 | ECS | Posters on site | CR3.3

Multivariate state and parameter estimation using data assimilation in a Maxwell-Elasto-Brittle sea ice model 

Yumeng Chen, Polly Smith, Alberto Carrassi, Ivo Pasmans, Laurent Bertino, Marc Bocquet, Tobias Sebastian Finn, Pierre Rampal, and Véronique Dansereau

In an idealised setup, a dynamics-only sea ice model is used to investigate the fully multivariate state and parameter estimations that uses a novel Maxwell-Elasto-Brittle (MEB) sea ice rheology. In the fully multivariate state estimation, the level of damage, internal stress and cohesion are estimated along with the observed sea ice concentration, thickness and velocity. In the case of parameter estimation, we estimate the air drag coefficient and the damage parameter of the MEB model. The air drag coefficients adjust the strength of the forcing on the sea ice dynamics while the damage parameter controls the mechanical behaviour of the internal property of sea ice. We show that, with the current observation network, it is possible to improve all model state forecast and the parameter accuracy using data assimilation approaches even though problems could arise in such an idealised setup where the external forcing dominates the model forecast error growth.

How to cite: Chen, Y., Smith, P., Carrassi, A., Pasmans, I., Bertino, L., Bocquet, M., Finn, T. S., Rampal, P., and Dansereau, V.: Multivariate state and parameter estimation using data assimilation in a Maxwell-Elasto-Brittle sea ice model, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2377, https://doi.org/10.5194/egusphere-egu24-2377, 2024.

EGU24-3367 | ECS | Orals | CR3.3

Perscribing Antarctic landfast sea ice in a sea ice-ocean model. 

Noé Pirlet, Thierry Fichefet, Martin Vancoppenolle, Clément Rousset, Pierre Mathiot, Alexander Fraser, Antoine Barthélemy, and Christoph Kittel

The coastal polynyas of the Southern Ocean play a crucial role in the formation of dense water and have an impact on the stability of ice shelves. Therefore, it is important to accurately simulate them in climate models. To achieve this goal, the relationship between grounded icebergs, landfast ice and polynyas appears to be central. Indeed, grounded icebergs and landfast ice are believed to be key drivers of coastal polynyas. However, ESMs do not simulate Antarctic landfast ice. Moreover, at a circumpolar scale, there are no observations of grounded icebergs available. Hence, we must seek model representations that can overcome these issues. To address these gaps, we conducted a study using an antarctic circumpolar configuration of the ocean–sea ice model NEMO4.2-SI–3 at the 1/4° resolution. We ran two simulations for the period 2001–17, with the only difference being the inclusion or exclusion of landfast ice information based on observations. All other factors, including initial conditions, resolution and atmospheric forcings, were kept the same. We then compared the results of these simulations with observations from the advanced microwave scanning radiometer to evaluate the performance of the new simulation. Our analysis allowed us to determine the extent to which prescribing the distribution of landfast ice and setting the sea ice velocity to zero on landfast ice regions influenced various aspects of the sea ice, such as polynyas, landfast ice and sea ice distribution in the model. In the future, we plan to look at the impact on the ocean and to develop a physical parameterization in order to model landfast ice and consequently polynyas on a permanent basis.

How to cite: Pirlet, N., Fichefet, T., Vancoppenolle, M., Rousset, C., Mathiot, P., Fraser, A., Barthélemy, A., and Kittel, C.: Perscribing Antarctic landfast sea ice in a sea ice-ocean model., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3367, https://doi.org/10.5194/egusphere-egu24-3367, 2024.

EGU24-4144 | ECS | Orals | CR3.3

A model for ice-mélange based on particle and continuums mechanics 

Saskia Kahl and Carolin Mehlmann

Ice mélange (a mixture of sea ice, bergy bits and icebergs) can have a strong influence on the sea-ice-ocean interaction. So far, ice mélange is not represented in climate models as numerically efficient realizations are missing. This motivates the development of an ice-mélange model based on the viscous-plastic sea-ice rheology, which is currently the most commonly used material law for sea ice in climate models. Starting from the continuum mechanical formulation, we modify the rheology so that icebergs are represented by thick, highly compact pieces of sea ice. These compact pieces of sea ice are held together by a modified tensile strength in the material law. In this framework, the ice mélange is considered as one single fluid, where the icebergs are realised by particles.
Using idealized test cases, we demonstrate that the proposed changes in the material law are crucial to represent icebergs with the viscous-plastic rheology. Similar to the viscous-plastic sea-ice model, the ice-mélange model is highly nonlinear. Solving the model at the resolution needed to represent the typical size of icebergs in ice mélange (< 300m) is therefore challenging. We show that the ice-mélange formulation can be approximated efficiently with a modified Newton's method. Overall, the simple extension of the viscous-plastic sea-ice model is a promising path towards the integration of ice mélange into climate models.

How to cite: Kahl, S. and Mehlmann, C.: A model for ice-mélange based on particle and continuums mechanics, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4144, https://doi.org/10.5194/egusphere-egu24-4144, 2024.

Rapid decline of Arctic sea ice has created more open water for ocean wave development and highlighted the importance of wave-ice interactions in the Arctic. Some studies have made contributions to our understanding of the potential role of the prognostic floe size distribution (FSD) on sea ice changes. However, these efforts do not capture the full interactions between atmosphere, ocean, wave, and sea-ice. In this study, a modified joint floe size and thickness distribution (FSTD) is implemented in a newly-developed regional atmosphere-ocean-wave-sea ice coupled model and a series of pan-Arctic simulation is conducted with different physical configurations related to FSD changes, including FSD-fixed, FSD-varied, lateral melting rate, wave-fracturing formulation, and wave attenuation rate. Firstly, atmosphere-ocean-wave-sea ice coupled simulations show that the prognostic FSD leads to reduced ice area due to enhanced ice-ocean heat fluxes, but the feedbacks from the atmosphere and the ocean partially offset the reduced ice area induced by the prognostic FSD. Secondly, lateral melting rate formulations do not change the simulated FSD significantly, but they influence the flux exchanges across atmosphere, ocean, and sea-ice and thus sea ice responses. Thirdly, the changes of FSD are sensitive to the simulated wave parameters associated with different wave-fracturing formulations and wave attenuation rates, and the limited oceanic energy imposes a strong constraint on the response of sea ice to FSD changes. Finally, the results also show that wave-related physical processes can have impacts on sea ice changes with the constant FSD, indicating the indirect influences of ocean waves on sea-ice through the atmosphere and the ocean.

How to cite: Yang, C.-Y. and Liu, J.: Understanding influence of ocean waves on Arctic sea ice simulation: A modeling study with an atmosphere-ocean-wave-sea ice coupled model, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4502, https://doi.org/10.5194/egusphere-egu24-4502, 2024.

EGU24-5177 | ECS | Posters on site | CR3.3

Improving the representation of snow over sea-ice in the SI3 model 

Theo Brivoal, Virginie Guemas, Clement Rousset, and Martin Vancoppenolle

Snow plays a crucial role in the formation and sustainability of sea ice. Due to its thermal properties, snow acts as an insulating layer, shielding the ice from the air above. This insulation reduces the heat transfer between the sea-ice and the atmosphere. Due to its reflective properties, the snow cover also strongly contributes to albedo over ice-covered region, which gives it a significant role in the Earth's climate system.

Current state-of-art climate models use over-simple representations of the snow cover. The snow cover is often represented with a one-layer scheme, assuming a constant density, no wet or dry metamorphism or assuming that no liquid water is stored in the snow. Here, we present the integration of a more advanced snow scheme (ISBA-ES) into the sea-ice model SI3, which serves as the sea-ice component for upcoming versions of the CNRM climate model (CNRM-CM). We compare 1D simulations over the Arctic using this new scheme with observational data and simulations utilizing the previous SI3 snow scheme. Overall, the snow simulated by the ISBA-ES scheme is realistic. We also present a sensitivity analysis of the snow and sea-ice in the SI3 model, exploring various options in the ISBA-ES scheme. Our findings reveal a strong sensitivity of both the snow and the sea-ice to the representation of liquid water in snow and the parameterization employed for calculating snowfall density.

How to cite: Brivoal, T., Guemas, V., Rousset, C., and Vancoppenolle, M.: Improving the representation of snow over sea-ice in the SI3 model, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5177, https://doi.org/10.5194/egusphere-egu24-5177, 2024.

EGU24-5374 | ECS | Orals | CR3.3

Floe-scale ocean / sea ice energy transfers in the marginal ice zone 

Mukund Gupta, Andrew Thompson, and Patrice Klein

Marginal ice zones are regions where individual sea ice floes interact mechanically and thermodynamically with turbulent ocean currents at the (sub-)mesoscale. Fine scale exchanges of momentum, heat and salinity at the interface between the ocean and the sea ice floes have important effects on upper-ocean energetics, under-ice tracer mixing, and the ice-pack melt rates. The dynamics of these moving floes remain poorly constrained, notably due to the challenge of numerically resolving sub-mesoscale processes and modelling the discrete behavior of sea ice in traditional climate models. 

Here, we use oceanic Large Eddy Simulations (LES), two-way coupled to a Discrete Element Model (DEM) of disk-shaped sea ice floes, to quantify the kinetic energy transfers between ocean and sea ice during summer-like conditions, varying sea ice concentration and floe size distribution. The damping of oceanic currents by floes is found to be important for a sea ice concentration as low as 40%, when the sizes of floes are comparable to the characteristic eddy size. This damping is largely compensated by the generation of kinetic energy due to melt-induced baroclinic instability at the edge of sea ice floes, leading to a net energy sink of approximately 15%, relative to a simulation with no floes. At higher sea ice concentrations, the oceanic kinetic energy production weakens, while energy loss due to ice/ocean damping and floe-floe collisions both increase. These energy fluxes are mediated by the spatial aggregation of sea ice floes that occurs within the high-strain regions surrounding ocean mesoscale eddies. Eddy-driven aggregation can also reduce the melt rate of small floes as they become shielded from warm waters by neighboring larger floes. These results highlight the need for scale-aware, and specifically floe-scale parameterizations of sea ice and its coupling to ocean turbulence, within global climate models.

How to cite: Gupta, M., Thompson, A., and Klein, P.: Floe-scale ocean / sea ice energy transfers in the marginal ice zone, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5374, https://doi.org/10.5194/egusphere-egu24-5374, 2024.

EGU24-6441 | ECS | Posters on site | CR3.3

Application of mixed least-squares FEM to study sea ice dynamics 

Sonja Hellebrand, Carina Schwarz, and Jörg Schröder

The behavior of sea ice has been studied for many decades. In order to model its viscous-plastic behavior at scales spanning several thousand kilometers, different numerical models have been proposed. Based on the established approach in [1], this contribution presents a simulation model for sea ice dynamics to describe the sea ice circulation and its evolution over one seasonal cycle. In course of that, the sea ice concentration and the sea ice thickness are considered, of which the physical behavior is governed by transient advection equations. Here, the sea ice velocity serves as coupling field.

Recently developed approaches base on a finite element implementation choosing a (mixed) Galerkin variational approach, see e.g. [2] and [3]. But therein, challenges may occur regarding the stability of the numerically complex scheme, especially when dealing with the first-order advection equations. Thus, we propose the application of the mixed least-squares finite element method, which has the advantage to be also applicable to first-order systems, i.e., it provides stable and robust formulations even for non-self-adjoint operators, such as the tracer equations (for sea ice thickness and sea ice concentration).

For solving the instationary sea ice equation the presented least-squares finite element formulation takes into account the balance of momentum and a constitutive law for the viscous-plastic flow. The considered primary fields are the stresses σ, the velocity v, the concentration Aice and the thickness Hice. In relation, four residuals are defined for the derivation of a first-order least-squares formulation based on the balance of momentum, the constitutive relation for the stresses, and two tracer-equations. Different approaches can be made with respect to the approximation functions of the primary fields, i.e., choosing e.g. conforming (H(div) interpolation functions) or non-conforming (Lagrangian interpolation functions) stress approximations, while Lagrangian interpolation functions are chosen for the remaining fields. In order to compare such approaches, the box test case is utilized, cf. [3], which is well described in literature.

References:

[1] W.D. Hibler III. A dynamic thermodynamic sea ice model. Journal of Physical Oceanography, 9(4):815-846, 1979.

[2] S. Danilov, Q. Wang, R. Timmermann, M. Iakovlev, D. Sidorenko, M. Kimmritz, T. Jung. Finite-Element Sea Ice Model (FESIM), Version 2. Geoscientific Model Development, 8:1747-1761, 2015.

[3] C. Mehlmann and T. Richter. A modified global Newton solver for viscous-plastic sea ice models. Ocean Modelling, 116:96-107, 2017.

How to cite: Hellebrand, S., Schwarz, C., and Schröder, J.: Application of mixed least-squares FEM to study sea ice dynamics, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6441, https://doi.org/10.5194/egusphere-egu24-6441, 2024.

EGU24-6569 | ECS | Posters on site | CR3.3

Using discrete element methods to understand in-plane fragmentation of sea ice floes 

Adam Bateson, Daniel Feltham, David Schröder, Scott Durski, Jennifer Hutchings, Rajlaxmi Basu, and Byongjun Hwang

Sea ice floe size can impact several processes that determine the evolution of the Arctic sea ice, including lateral melt volume, momentum exchange, and rheology. Floe size distribution (FSD) models are applied within continuum sea ice models to capture the evolution of the FSD through parameterisations of the processes that modify floe size such as lateral melting and wave break-up of floes. FSD models do not yet adequately resolve in-plane fragmentation processes of floes such as the breakup of floes under wind forcing, through interactions between neighbouring floes, or through thermal weakening. It is challenging to characterise and therefore parameterise these in-plane floe breakup processes due to limited availability of in-situ observations. Discrete element models (DEMs) offer an alternative way to understand the different mechanisms of floe fragmentation. By resolving relevant properties such as shear and normal stress and sea ice strength at the sub-floe scale, it is possible to use DEMs as a virtual laboratory and directly simulate the break-up of floes into smaller fragments.

In this study, we describe how in-situ observations of sea ice can be combined with output from sea ice DEMs to develop parameterisations of in-plane breakup of floes that can then be applied in continuum models. We then discuss the necessary model developments in order to apply a sea ice DEM to floe fragmentation at smaller scales. We will also present results from a series of DEM simulations used to model the fracture of sea ice under different forcing conditions and with varying sea ice states to identify the important sea ice parameters and processes in determining the size of the floes that form from in-plane breakup events.

How to cite: Bateson, A., Feltham, D., Schröder, D., Durski, S., Hutchings, J., Basu, R., and Hwang, B.: Using discrete element methods to understand in-plane fragmentation of sea ice floes, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6569, https://doi.org/10.5194/egusphere-egu24-6569, 2024.

Arctic sea ice has experienced a differential decline in speed due to the same anthropogenic greenhouse gas forcing, as evidenced by rapid decline after the end of the last century. Our convergent observations, last-millennium reanalysis, and model analyses have revealed that large tropical volcanic eruptions can lead to a decadal increase in Arctic sea ice, and the 1982 and 1991 large volcanic eruptions slowed down the decline of Arctic sea ice during the last century. The models, selected based on the observed sensitivity of Arctic sea ice to volcanic eruptions, suggest that the earliest ice-free summer year in the Arctic will be around 2040 in high-emission sceneria of SSP585. These findings emphasized the crucial need to incorporate volcanic influences when projecting future Arctic changes amid global warming.

How to cite: Wang, X.: Historical volcanic eruptions slowed down rapid decline in Arctic sea ice linked to global warming, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9554, https://doi.org/10.5194/egusphere-egu24-9554, 2024.

EGU24-9802 | ECS | Posters virtual | CR3.3

The sea ice component of MUSE, the unstructured-mesh global ocean model of CMCC 

Francesco Cocetta, Lorenzo Zampieri, and Doroteaciro Iovino

The rapidly evolving sea ice cover requires novel modeling approaches and mathematical techniques to accurately simulate the sea ice dynamics, thermodynamics, and its interactions with the atmosphere and ocean at varying spatiotemporal resolutions. In this context, the CMCC is developing the Multiscale Unstructured model for Simulating the Earth’s water environment (MUSE), a novel global ocean-sea ice model on unstructured meshes.

MUSE employs a finite-element numerical discretization on unstructured meshes, aiming at offering flexibility in simulating the global ocean for various applications, ranging from physical process understanding to operational sea ice predictions. The ongoing implementation of the sea ice component utilizes the traditional continuous sea ice formulation and the 2+1 split assumption, meaning that the sea ice dynamics and advection are solved for horizontal motions while the thermodynamics and radiative processes are parameterized at the subgrid scale.   

MUSE employs a modified elastic-viscous-plastic (mEVP) solver for the sea ice dynamics and a Flux Corrected Transport (FCT) advection scheme, alongside the state-of-the-art column physics package "Icepack" maintained by the CICE consortium.

Here, we describe the global implementation of the sea ice component in MUSE and its coupling with the ocean. We present the resulting representation of vertical thermodynamic processes and horizontal dynamics of sea ice.

How to cite: Cocetta, F., Zampieri, L., and Iovino, D.: The sea ice component of MUSE, the unstructured-mesh global ocean model of CMCC, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9802, https://doi.org/10.5194/egusphere-egu24-9802, 2024.

EGU24-10098 | Posters on site | CR3.3

Best of SIDFEx: Highlights and lessons learned from six years of sea-ice drift forecasting 

Simon F. Reifenberg, Valentin Ludwig, and Helge F. Goessling and the SIDFEx Team

We showcase the Sea Ice Drift Forecast Experiment (SIDFEx) database. SIDFEx is a collection of close to 225,000 lagrangian drift forecasts for the trajectories of assets (mostly buoys) on the Arctic and Antarctic sea ice, at lead times from daily to seasonal with mostly daily resolution. The forecasts are based on systems with varying degrees of complexity, ranging from free-drift forecasts to forecasts by fully coupled dynamical general circulation models. Combining several independent forecasts allows us to construct a best-guess consensus forecast, with a seamless transition from systems with lead times of up to 10 days to systems with seasonal lead times. The forecasts are generated by 13 research groups using 23 distinct forecasting systems and sent regularly to the Alfred-Wegener-Institute, where they are archived and evaluated. Many groups send forecasts operationally in near-real time.

In our presentation, we will introduce the motivation behind and setup of SIDFEx, as well as an overview on the general forecast skill. We will focus on selected highlights, comprising the operational support of research cruises, short-term predictions of sea-ice deformation and regular contributions to the Sea Ice Outlook competition.

How to cite: Reifenberg, S. F., Ludwig, V., and Goessling, H. F. and the SIDFEx Team: Best of SIDFEx: Highlights and lessons learned from six years of sea-ice drift forecasting, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10098, https://doi.org/10.5194/egusphere-egu24-10098, 2024.

EGU24-11288 | Orals | CR3.3

Towards improving numerical sea ice predictions with data assimilation and machine learning 

William Gregory, Mitchell Bushuk, Yongfei Zhang, Alistair Adcroft, and Laure Zanna

In this presentation we highlight recent developments in the implementation of Machine Learning (ML) algorithms into the large-scale sea ice model, SIS2. Specifically, we show how a Convolutional Neural Network (CNN) can be used to systematically reduce global sea ice biases during a 5-year ice-ocean simulation. The CNN has been trained to learn a functional mapping from model state variables to sea ice concentration Data Assimilation (DA) increments. Therefore, during model integration, the CNN ingests information about the numerical model's atmosphere, ocean, and sea ice conditions, and predicts the appropriate correction to the sub-grid category sea ice concentration terms (without seeing any actual sea ice observations). We also show how this combined DA+ML approach leads to a natural framework for augmenting training data for neural networks; one which can lead to significant improvements in online performance, without the need for direct online learning. The bias reductions over the 5-year simulation period for this CNN correction scheme are even competitive with the bias reductions achieved from DA. These findings therefore suggest that our approach could be used to reduce systematic sea ice biases in fully coupled climate model predictions on seasonal-to-climate timescales.

How to cite: Gregory, W., Bushuk, M., Zhang, Y., Adcroft, A., and Zanna, L.: Towards improving numerical sea ice predictions with data assimilation and machine learning, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11288, https://doi.org/10.5194/egusphere-egu24-11288, 2024.

EGU24-11413 | Posters virtual | CR3.3

Sea ice strength in SI3 

Emma Fiedler, Ed Blockley, Clement Rousset, and Martin Vancoppenolle

The NEMO sea ice model, SI3, includes the simple formulation of Hibler (1979; H79) to parameterise the compressive strength of sea ice. This assumes that thick and compact sea ice has more strength than thin and low concentration sea ice. However, the H79 strength scheme does not consider physical assumptions around energy conservation. The strength scheme of Rothrock (1975; R75) is based on the amount of potential energy gained and frictional energy dissipated during ridging, and has been introduced to SI3. Additionally, the option for a negative exponential redistribution of ridged ice among thickness categories, to better approximate observations and improve stability compared to the existing uniform redistribution when using R75, has been included. The R75 strength formulation is stable and works well in SI3 at version 4.2 with an EVP rheology, under a Met Office forced NEMO/SI3 model configuration. Sea ice strength is generally reduced for the R75 scheme compared to H79. The most notable effect on the model output is a greater number of, and sharper, features in the resulting modelled ice field when using the R75 scheme compared to the H79 scheme, which are particularly apparent in the ice thickness field. An increase in the model effective resolution is therefore demonstrated.

How to cite: Fiedler, E., Blockley, E., Rousset, C., and Vancoppenolle, M.: Sea ice strength in SI3, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11413, https://doi.org/10.5194/egusphere-egu24-11413, 2024.

EGU24-11908 | ECS | Orals | CR3.3

A data-driven sea-ice model with generative deep learning 

Tobias Sebastian Finn, Charlotte Durand, Flavia Porro, Alban Farchi, Marc Bocquet, Yumeng Chen, and Alberto Carrassi

The current generation of sea-ice models with Brittle rheologies can represent the observed temporal and spatial scaling of the sea-ice dynamics at resolutions of around 10 km. However, running those models is expensive, which can prohibit their use in coupled Earth system models. The promising results of neural networks for the fast prediction of the sea-ice extent or sea-ice thickness offer an opportunity to remedy this shortcoming. Here, we present the development of a data-driven sea-ice model based on generative deep learning that predicts together the sea-ice velocities, concentration, thickness, and damage. Trained with more than twenty years of simulation data from neXtSIM, the model can extrapolate to previously unseen conditions, thereby exceeding the performance of baseline models.

Relying on deterministic data-driven models can lead to overly smoothed predictions, caused by a loss of small-scale information. This is why the ability to perform stochastic predictions can be instrumental to the success of data-driven sea-ice models. To generate stochastic predictions with neural networks, we employ denoising diffusion models. We show that they can predict the uncertainty that remains unexplained by deterministic models. Furthermore, diffusion models can recover the information at all scales. This resolves the issues with the smoothing effects and results in sharp predictions even for longer horizons. Therefore, we see a huge potential of generative deep learning for sea-ice modelling, which can pave the way towards the use of data-driven models within coupled Earth system models.

How to cite: Finn, T. S., Durand, C., Porro, F., Farchi, A., Bocquet, M., Chen, Y., and Carrassi, A.: A data-driven sea-ice model with generative deep learning, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11908, https://doi.org/10.5194/egusphere-egu24-11908, 2024.

EGU24-12451 | ECS | Posters on site | CR3.3

Development of ship navigation risk indicator in sea ice-infested water 

Xinfang Zhang

There's increasing transpolar shipping in both the Arctic and Antarctic as a result of the reduction of sea ice and the desire from social economics.  Sea ice is a hazard for shipping in ice-infested water, Ship navigability in ice-covered sea depends on sea ice concentration, ice thickness, fraction of pressure ridges, and multi-year ice as well as ice speed and compression, it also depends on the vessel ice class. IMO introduced Risk Index Outcome(RIO) to provide guidelines for safe navigation, calculation of RIO requires accurate sea ice information including sea ice concentration and thickness. We developed a method similar to RIO to calculate navigation risk indicators using forecasting models including ECMWF S2S data, Copernicus data, and DMI data. Other than conventional sea ice parameters sea ice concentration and sea ice thickness, ice salinity, and ice age are also taken into account in risk indicator calculation. We select the time March 2019 -Oct 2020 and adopt the initial condition of the model forecast for sea ice to demonstrate the capabilities of seasonal forecasting of this navigation risk indicator in different models. In future, the calculation method will be implemented within the ClimateDT environment.

How to cite: Zhang, X.: Development of ship navigation risk indicator in sea ice-infested water, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12451, https://doi.org/10.5194/egusphere-egu24-12451, 2024.

EGU24-12804 | Posters on site | CR3.3

 A laboratory model of fragmentation of a 2D membrane by waves. Analogies and differences with sea ice. 

Michael Berhanu, Louis Saddier, Mathéo Aksil, Palotai Ambre, and Michel Tsamados

The marginal ice zone is the transition region between the dense floating ice pack and the open ocean. In this zone, the interaction of surface waves with sea ice is highly complex. The sea ice is broken up into fragments, the floes, which can split into smaller parts and drift under the action of waves and underwater current. Although the downscaling is challenging, laboratory model experiments can contribute to a better understanding of this process coupling fluid and solid mechanics on a large range of time and space scales. We propose to study the fragmentation of a floating membrane, made up of 10 µm graphite particles arranged in a monolayer, by gravity surface waves with a wavelength of around 15 cm [1]. For a sufficiently strong wave amplitude, the raft progressively breaks up, developing cracks and producing fragments whose sizes decrease over a time scale that is long relative to the wave period. We then study the distribution of the fragments produced during the fragmentation process. The visual appearance of the size-distributed fragments surrounded by open water bears a striking resemblance to the floes produced by the fracturing of sea ice by waves. The fragmentation concepts and morphological tools developed for sea ice floes can be applied to our macroscopic analog. Although the mechanics of the two systems differ in their physical properties and in the fracture process, our experiment provides a model laboratory system for studying the fragmentation of floating 2D materials

 

[1] Saddier, L., Palotai, A., Aksil, M., Tsamados, M., & Berhanu, M. (2023). Breaking of a floating particle raft by water waves. In arXiv preprint arXiv:2310.16188.

How to cite: Berhanu, M., Saddier, L., Aksil, M., Ambre, P., and Tsamados, M.:  A laboratory model of fragmentation of a 2D membrane by waves. Analogies and differences with sea ice., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12804, https://doi.org/10.5194/egusphere-egu24-12804, 2024.

EGU24-12912 | Orals | CR3.3

Improvements in September Arctic sea ice predictions via assimilation of summer CryoSat-2 sea ice thickness observations 

Yong-Fei Zhang, Mitch Bushuk, Michael Winton, Bill Hurlin, William Gregory, Jack Landy, and Liwei Jia

Because of a spring predictability barrier, the seasonal forecast skill of Arctic summer sea ice is limited by the availability of melt-season sea ice thickness (SIT) observations. The first year-round SIT observations, retrieved from CryoSat-2 from 2011 to 2020, are assimilated into the GFDL ocean–sea ice model. The model's SIT anomaly field is brought into significantly better agreement with the observations, particularly in the Central Arctic. Although the short observational period makes forecast assessment challenging, we find that the addition of May–August SIT assimilation improves September local sea ice concentration (SIC) and extent forecasts similarly to SIC-only assimilation. Although most regional forecasts are improved by SIT assimilation, the Chukchi Sea forecasts are degraded. This degradation is likely due to the introduction of negative correlations between September SIC and earlier SIT introduced by SIT assimilation, contrary to the increased correlations found in other regions.

How to cite: Zhang, Y.-F., Bushuk, M., Winton, M., Hurlin, B., Gregory, W., Landy, J., and Jia, L.: Improvements in September Arctic sea ice predictions via assimilation of summer CryoSat-2 sea ice thickness observations, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12912, https://doi.org/10.5194/egusphere-egu24-12912, 2024.

EGU24-13528 | ECS | Orals | CR3.3

A MAGICC Arctic Sea Ice Emulator 

Sian Chilcott, Malte Meinshausen, and Dirk Notz

CMIP6 models present our best understanding of the Earth system, yet they currently fail to simulate a plausible evolution of sea ice area to changes in the global-mean temperature. We aim to assess whether correcting the temperature and Arctic Amplification biases between CMIP6 models and observations can simulate a sensitivity of sea ice loss to global warming that is within the plausible range. To do this, we develop an emulator that is calibrated to physically-based CMIP6 models and then constrained to observations. Such a tool efficiently translates the global-mean temperature of a specific year into a physically-based and observationally constrained probabilistic ensemble of SIA in each month. This setup allows our emulator to capture the core physical processes of CMIP6 projections, while capturing the observed sensitivity of sea ice loss to global warming through the observational constraint of Arctic Amplification. While there are many application possibilities of our emulator, we use our model here to probabilistically diagnose the timing of an ice-free Arctic Ocean. We find that under a high (SSP5-8.5), medium (SSP2-4.5) and low (SSP1-2.6) emission scenario, an ice-free September Ocean is ‘likely’ at 1.73 of global warming above the pre-industrial level, however we note that the probability in the lower emission scenario reduces to ‘unlikely’ in the late 21st century as the global temperature partially recovers. Our projections suggest that the probability of an ice-free summer ocean rises rapidly from ‘unlikely’ at 1.5 of global warming to ‘likely’ at 2 of global warming, stressing the importance of preventing global temperatures rising above 1.5, as the probability of losing sea ice coverage in September rises sharply thereafter. For March, we also find that the observational constraints increase the probability of an ice-free ocean under SSP5-8.5, becoming ‘likely’ in early 2200, while the probability remains very low under SSP2-4.5 and SSP1-2.6 as less than 5% of models reach ice-free conditions. Our projections suggest an ice-free summer ocean could occur at 0.5 cooler levels than the CMIP6 multi-model ensemble mean implies. Likewise, our approach suggests the probability of an ice-free Arctic Ocean year-round is increased when constraining the Arctic Amplification to observations.

How to cite: Chilcott, S., Meinshausen, M., and Notz, D.: A MAGICC Arctic Sea Ice Emulator, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13528, https://doi.org/10.5194/egusphere-egu24-13528, 2024.

EGU24-15156 | Posters on site | CR3.3

Calibration of a  hybrid sea-ice model based on particle and continuums mechanics 

Carolin Mehlmann and Thomas Richter

Presently, climate models employ a continuum approach to describe sea ice. This approach assumes that statistical averages can be derived from a large number of ice floes. However, employing continuum rheological models at or below the scale of individual floes is only valid if the failure mode of a single floe aligns with that of an aggregate of floes. Initially, continuum models were designed for a grid resolution of 100 km. With recent advancements in computing power, sea-ice models are frequently operated at higher mesh resolutions, potentially leading to grid cells that no longer contains a representative sample of sea-ice floes.

We are addressing these shortcomings of current continuum sea-ice models by developing a hybrid model. The idea of the hybrid approach is to nest a particle model into a continuum sea-ice model in order to predict sea ice on fine spatial scales in a region of interest. An important component of particle models is a drag law to describe the influence of ocean and atmospheric currents on the floes. Measurements obtained onboard the Polarstern expedition PS 138 have shown that the correlation cannot be described fully locally, in regions with strongly heterogenous ice cover. Instead, larger surrounding flows have a substantial effect on the motion of small ones. Detailed numerical simulations of idealised test cases do confirm these findings.   

How to cite: Mehlmann, C. and Richter, T.: Calibration of a  hybrid sea-ice model based on particle and continuums mechanics, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15156, https://doi.org/10.5194/egusphere-egu24-15156, 2024.

EGU24-15487 | Posters on site | CR3.3

Extended seasonal forecast of Antarctic Sea Ice using ANTSIC-UNet 

Ziying Yang, Jiping Liu, and Rune Grand Graversen

Antarctic sea-ice variability affects the ocean and atmosphere both locally through thermodynamic processes and beyond the Antarctic regions remotely through dynamic processes, which may all change due to global warming. In this study, we develop the ANTSIC-UNet, a deep-learning model trained on physically enriched climate variables, to predict the extended seasonal Antarctic sea ice concentration of up to 6 months in advance. We assess the predictive skill of ANTSIC-UNet as regards linear trend prediction and anomaly persistence prediction in the Pan- and regional Antarctic areas using comparative analyses with two baseline models. Our results exhibit superior performance of ANTSIC-UNet for the extended seasonal Antarctic forecast. The predictive skill of ANTSIC-UNet is notably season-dependent, showing distinct variations across regions. Optimal prediction accuracy is found in winter, while diminished skill found during the summer can be largely attributed to the ice-edge error. High predictive skills are found in the Weddell Sea throughout the year, which suggests that regional Antarctic sea-ice predictions beyond 6 months are possible. We further quantify variable importance through a post-hoc interpretation method which indicates that ANTSIC-UNet has learned the relationships between SIC and other climate variables and the method therefore provides information on the physics of the model. At short lead times, on timescales of up to two months, ANTSIC-UNet predictions exhibit heightened sensitivity to sea surface temperature, radiation conditions and vertical atmospheric circulation conditions in addition to the sea-ice itself. At longer lead times, predictions are dependent on stratospheric circulation patterns at 7-8 months lead in addition to sea-ice. Furthermore, we discuss the potential of implementing physical constraints to enhance sea-ice-edge predictability.

How to cite: Yang, Z., Liu, J., and Grand Graversen, R.: Extended seasonal forecast of Antarctic Sea Ice using ANTSIC-UNet, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15487, https://doi.org/10.5194/egusphere-egu24-15487, 2024.

EGU24-18506 | ECS | Orals | CR3.3

Direct Numerical Simulation of shear turbulence interacting with a melting-freezing ice layer 

Diego Perissutti, Francesco Zonta, Alessio Roccon, Cristian Marchioli, and Alfredo Soldati

When a turbulent flow of water interacts with an ice boundary at near-freezing temperature, the fluid can undergo freezing or melting, depending on the local temperature. The turbulence structures that develop in proximity to the ice layer can affect the convective heat transport patterns, leading to the formation of complex phase-boundary morphologies. The ice layer evolves as part of the solution and modifies the near-boundary fluid structures, resulting in heat transfer perturbations. We investigate these ice-water interactions at small scales by performing Direct Numerical Simulations of an open channel flow at shear Reynolds number in the range between 10^2 and 10^3. The upper section of the channel is occupied by ice, while free shear conditions are applied at the bottom. Temperature is imposed on both walls. The ice melting/freezing is simulated using a phase field method [1] combined with a volume penalization immersed boundary method. A pseudo-spectral scheme [2] is used to solve the equations for momentum and energy transport and for phase evolution. We investigated how the behavior of the system changes with the flow conditions (i.e. Reynolds number), with a specific focus on characterizing the features of the ice morphology. In particular, we observed a remarkable influence of turbulence intensity on the ice morphology: at low shear Reynolds, the typical streamwise-oriented canyons already reported in similar studies [3] are present. However, at higher shear Reynolds, spanwise instabilities are triggered, making the final ice morphology more complex.

FIgure1: Render view from below of the open channel flow at a low Reynolds number. On the top section of the channel, the corrugated ice layer is shown. On the ice boundary, the normalized heat flux passing through it is displayed (high heat flux is shown in red, low heat flux in blue). The local temperature field is reported on the side domain boundaries. The typical streamwise-oriented canyons at the ice interface are visible and the heat flux correlates well with those patterns (the heat flux is higher inside the canyons).

[1]R. Yang et al., Morphology evolution of a melting solid layer above its melt heated from below, Journal of Fluid Mechanics, 956, A23, 2023.

[2]F Zonta et al., Nusselt number and friction factor in thermally stratified turbulent channel flow under non-Oberbeck–Boussinesq conditions, International journal of heat and fluid flow, 44:489–494, 2013.

[3]L. A. Couston et al., Topography generation by melting and freezing in a turbulent shear flow, Journal of Fluid Mechanics, 911, A44, 2021.

How to cite: Perissutti, D., Zonta, F., Roccon, A., Marchioli, C., and Soldati, A.: Direct Numerical Simulation of shear turbulence interacting with a melting-freezing ice layer, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18506, https://doi.org/10.5194/egusphere-egu24-18506, 2024.

EGU24-19333 | Orals | CR3.3

Recent progress in nesting a DEM- based regional sea ice model within a continuum model 

Wenjun Lu, Andrei Tsarau, Yuan Zhang, Raed Lubbad, and Sveinung Løset

Understanding sea-ice dynamics at the floe scale is crucial to improve regional ice forecast and comprehend the polar climate systems. Continuum models are commonly used to simulate large-scale sea-ice dynamics. However, they have both theoretical and computational limitations in accurately representing sea-ice behaviour at small scales. Discrete Element Models (DEMs), on the other hand, are well-suited for modelling the behaviour of individual ice floes but face limitations due to computational constraints. To address the limitations of both approaches while combining their strengths, we explored the feasibility of nesting a DEM within a continuum model. This paper reports recent progresses in addressing two challenges associated with this method: 1) how to couple a discrete element method (DEM) – based model (a Lagrangian model explicitly tracking each element in space) into a continuum model (a Eulerian model with fixed spatial mesh transferring state variables within); 2) how to explicitly model fracture of sea ice at large scales. Based on our assessment, integrating DEM and continuum model simulations showed potential for offering accurate, high-resolution predictions of sea ice, particularly in coastal areas and near islands. Simulating fracture of sea ice still poses great computational challenges. However, we see a potential in a data-driven approach to accelerate the computational efficiency in resolving floe-scale ice fractures.  

How to cite: Lu, W., Tsarau, A., Zhang, Y., Lubbad, R., and Løset, S.: Recent progress in nesting a DEM- based regional sea ice model within a continuum model, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19333, https://doi.org/10.5194/egusphere-egu24-19333, 2024.

EGU24-22361 | Posters on site | CR3.3

neXtSIM-DG – A next-generation discontinuous Galerkin sea ice model 

Einar Ólason, Timothy Spain, and Thomas Richter and the The neXtSIM team

We present neXtSIM-DG, the novel sea ice model created as part of the Scale Aware Sea Ice Project (SASIP). NeXtSIM-DG is a continuum sea ice model that combines several new model paradigms at once: besides established rheologies, we use the newly developed Brittle Bingham–Maxwell rheology. The discretization is based on higher-order continuous and discontinuous finite elements. We take advantage of the object orientation of the C++ implementation of the model to create a flexible, maintainable, and easily modifiable code base ready for adaptation and adaptation by the user. Finally, the C++ implementation uses modern data structures that allow for efficient shared-memory parallelization and are ready for GPU acceleration. These aspects reflect better the different scales of sea ice dynamics in space and time. In this poster, we review the basic modelling features and present some details of numerical realization. In particular, we study the effect of high-order discretization and the role of different rheologies. 

How to cite: Ólason, E., Spain, T., and Richter, T. and the The neXtSIM team: neXtSIM-DG – A next-generation discontinuous Galerkin sea ice model, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-22361, https://doi.org/10.5194/egusphere-egu24-22361, 2024.

EGU24-775 | ECS | Posters on site | OS1.1

The rapid life of Arctic sea-ice ridge consolidation and melt 

Evgenii Salganik, Benjamin Lange, Christian Katlein, Ilkka Matero, Dmitry Divine, Polona Itkin, Knut Høyland, and Mats Granskog

In this study, we cover observations of the rapid consolidation and enhanced melt of Arctic sea-ice ridges. During the freezing period, the consolidated part of sea ice ridges is usually up to 1.6–1.8 times thicker than surrounding level ice. Meanwhile, during the melt season, ridges are often observed to be fully consolidated, but this process is not fully understood. We present the evolution of the morphology and temperature of a first-year ice ridge studied during MOSAiC from its formation to advanced melt. From October to May, the draft of first-year ice at the MOSAiC coring site increased from 0.3 m to 1.5 m, while from January to July, the consolidated layer thickness in the ridge reached 3.9 m. We observed several types of ridge consolidation. From the beginning of January until mid-April, the ridge consolidated slowly through heat loss to the atmosphere, with a total consolidated layer growth of 0.7 m. From mid-April to mid-June, there was a rapid increase in ridge consolidation rates, despite conductive heat fluxes not increasing. In this period, the mean thickness of the consolidated layer increased by 2.2 m. We also estimated a substantial snow mass fraction (6%–11%) of ridges using analysis of oxygen isotope composition. Our observations suggest that this sudden change was related to the transport of snow-slush inside the ridge keel via adjacent open leads that decreased ridge macroporosity, which could result in more rapid consolidation.

During the summer season, sea ice melts from the surface and bottom. The melt rates substantially vary for sea ice ridges and undeformed first- and second-year ice. Ridges generally melt faster than undeformed ice, while the melt of ridge keels is often accompanied by further summer growth of their consolidated layer, which increases their survivability. We examined the spatial variability of ice melt for different types of ice from in situ drilling, coring, and multibeam sonar scans of the remotely operated underwater vehicle. Six sonar scans performed from 24 June to 21 July were analyzed and validated using seven ice drilling transects. The area investigated by the sonar (0.4 km by 0.2 km) consisted of several ice ridges, surrounded by first- and second-year ice. We show a substantial difference in melt rates for sea ice with a different draft. We also show how ridge keels decay depending on the keel draft, width, steepness, and location relative to the surrounding ridge keel edges. We also use temperature buoy data to distinguish snow, ice surface, and bottom melt rates for both ridges and level ice. These results are important for quantifying ocean heat fluxes for different types of ice during the advanced melt and for estimating the ridge contribution to the total ice mass and summer meltwater balances of the Arctic Ocean.

How to cite: Salganik, E., Lange, B., Katlein, C., Matero, I., Divine, D., Itkin, P., Høyland, K., and Granskog, M.: The rapid life of Arctic sea-ice ridge consolidation and melt, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-775, https://doi.org/10.5194/egusphere-egu24-775, 2024.

EGU24-929 | ECS | Posters on site | OS1.1 | Highlight

Potential effects of summer Cryosat-2 sea ice thickness observations on sea ice forecast 

Ruizhe Song, Longjiang Mu, Xianyao Chen, Frank Kauker, Svetlana Loza, and Martin Losch

Skillful Arctic sea ice forecast for the melting season remains a great challenge because there is no reliable pan-Arctic sea ice thickness (SIT) data set for the summertime. A new summer Cryosat-2 SIT observation data set based on an artificial intelligence algorithm may mitigate the situation. We assess the impact of this new data set on the initialization of both short-term and long-term sea ice forecasts in the melting seasons of 2015 and 2016 in a sea-ice couple model with data assimilation. We find that the assimilation of the new summer CryoSat-2 SIT observations can reduce the summer ice edge prediction error. Further, adding SIT observations to an established forecast system with sea ice concentration assimilation leads to a more realistic short-term summer ice edge forecast in the Arctic Pacific sector. The long-term Arctic-wide SIT prediction is also improved especially before the onset of freezing. In spite of remaining uncertainties,  summer CryoSat-2 SIT observations have the potential to enhance Arctic sea ice forecast on multiple time scales.

How to cite: Song, R., Mu, L., Chen, X., Kauker, F., Loza, S., and Losch, M.: Potential effects of summer Cryosat-2 sea ice thickness observations on sea ice forecast, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-929, https://doi.org/10.5194/egusphere-egu24-929, 2024.

The Arctic region is experiencing a notable increase in precipitation, known as Arctic wetting, amidst the backdrop of Arctic warming. This phenomenon has implications for the Arctic hydrological cycle and numerous socio-ecological systems. However, the ability of climate models to accurately simulate changes in Arctic wetting has not been thoroughly assessed. In this study, we analyze total precipitation in the Arctic using station data, multiple reanalyses, and 35 models participating in the Coupled Model Intercomparison Project Phase 6 (CMIP6). By employing the moisture budget equation and an evaluation method for model performance with ERA5 reanalysis as a reference, we evaluated the models’ capability to reproduce past Arctic wetting patterns. Our findings indicate that most reanalyses and models are able to replicate Arctic wetting. However, the CMIP6 models generally exhibit an overestimation of Arctic wetting during the warm season and an underestimation during the cold season from 1979 to 2014 when compared to the ERA5 reanalysis. Further investigation reveals that the overestimation of wetting during the warm season is largest over the Arctic Ocean’s northern part, specifically the Canadian Arctic Archipelago, and is associated with an overestimation of atmospheric moisture transport. Conversely, the models significantly underestimate wetting over the Barents-Kara Sea during the cold season, which can be attributed to an underestimation of evaporation resulting from the models’ inadequate representation of sea ice reduction in that region. The models with the best performance in simulating historical Arctic wetting indicate a projected intensification of Arctic wetting, and optimal models significantly reduce uncertainties in future projections compared to the original models, particularly in the cold season and oceanic regions. Our study highlights significant biases in the CMIP6 models’ simulation of Arctic precipitation, and improving the model’s ability to simulate historical Arctic precipitation could reduce uncertainties in future projections.

How to cite: Cai, Z. and You, Q.: Arctic wetting: Performances of CMIP6 models and projections of precipitation changes, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1673, https://doi.org/10.5194/egusphere-egu24-1673, 2024.

EGU24-1892 | ECS | Orals | OS1.1

Observations of deep near-inertial internal waves in the Eurasian Basin. 

Joel Bracamontes Ramírez and Maren Walter

The Arctic Ocean has a less energetic internal wave climate than other oceans, mainly due to the thick sea ice cover which inhibits wind interaction with the surface. With the continued decrease in summer sea ice extent and the increase in seasonal ice-free areas, wind-driven internal waves, especially in the near-inertial range, are becoming more energetic. Coupled with the fact that most of the Arctic Ocean lies north of the critical latitude for semi-diurnal tides, the shift in ice dynamics implies an increase in the importance of near-inertial waves (NIW) for the internal wave climate. In particular, increased NIW amplitude and kinetic energy in the Canadian Basin and enhanced wind-driven vertical heat fluxes and dissipation rates in the Eurasian Basin have already been observed in the upper column. In the deep ocean beyond the critical latitude, NIWs are expected to drive mixing in the interior, but it is unclear to what extent. Here, we present innovative and unprecedented deep current observations from a mooring in the Gakkel Ridge in the Eurasian Basin at 82.53°N. The presence of barotropic diurnal and semi-diurnal tides and semi-diurnal harmonics enriches the complex interplay of internal waves. By comparing the observed downward and upward NIW kinetic energy with wind speed, sea ice properties and numerical simulations, we discuss the likely surface origin of the NIW. In particular, there is a lagged correlation of <26 days between ice drift speed and downward NIW energy, and of ~15 days between wind factor and downward NIW energy. In addition, the buoyancy frequency is weaker than the local Coriolis frequency, effectively limiting NIW propagation. Evidence for wave reflection is found and also discussed, with a focus on the implications for NIW coming from the surface.

How to cite: Bracamontes Ramírez, J. and Walter, M.: Observations of deep near-inertial internal waves in the Eurasian Basin., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1892, https://doi.org/10.5194/egusphere-egu24-1892, 2024.

The Arctic is one of Earth’s regions most susceptible to climate change. Climate models show that in a warming climate, the Arctic Ocean warms much faster than the global ocean mean, mainly due to the rapid warming of the Atlantic layer, which is called 'Arctic Ocean Amplification.' However, climate models still encounter challenges with large biases and considerable inter-model spread in the Arctic Ocean. For example, the Atlantic layer in the Arctic Ocean, simulated by the climate models, is too thick and too deep. This leads to the warming trend, and inter-annual variability of the simulated Atlantic Water that are too small compared to the observations. Here, we present Arctic Ocean dynamical downscaling simulations and projections based on a high-resolution ice-ocean coupled model, FESOM, and a climate model, FIO-ESM. The historical results demonstrate that the root mean square errors of temperature and salinity in the downscaling simulations are much smaller than those from CMIP6 climate models. The common biases, such as the overly deep and thick Atlantic layer in climate models, are significantly reduced by dynamical downscaling. Dynamical downscaling projections show that the Arctic Ocean may warm faster than the projections made by CMIP6 fully-coupled climate models.

How to cite: Shu, Q. and Wang, Q.: Dynamical downscaling simulations and future projections of the Arctic Ocean based on FESOM and FIO-ESM., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1921, https://doi.org/10.5194/egusphere-egu24-1921, 2024.

EGU24-1922 | Posters on site | OS1.1

Estimation of Sea Ice Production in the North Water Polynya Based on Ice Arch Duration in Winter During 2006–2019 

Fengming Hui, Haiyi Ren, Mohammed Shokr, Xiao Cheng, Xinqing Li, and Zhilun Zhang

The North Water Polynya (NOW) is the largest recurrent Arctic coastal polynya. The formation of the NOW is critically dependent on the development of an ice arch that defines its northern boundary. In this study, high-resolution ENVISAT Advanced Synthetic Aperture Radar data, Sentinel-1A data, and Moderate Resolution Imaging Spectroradiometer data were employed to identify the spatio-temporal characteristics of the ice arch during 2006–2019. Polynya pixels were identified based on the thin ice thickness (TIT), using a threshold of TIT <0.2 m, from which the polynya extent, heat flux, and ice production (IP) were estimated. The results show the different locations of the ice arch in different years, with a mean duration of 132 ± 69 days. The average annual polynya extent over the 14 years is ∼38.8 ± 8 × 103 km2, and we found that it is more closely correlated with wind speed during the winter and air temperature during early spring. The average heat flux drops from about 248 W/m2 in the winter months to about 34 W/m2 in May. The average accumulated IP varies significantly every year, with an average of 144 ± 103 km3, and peak values in March in most years. No apparent interannual trends are shown for the polynya area, heat flux, and IP during 2006–2019. The results also show that IP calculated based on the ice arch data is approximately 25% lower than that obtained by assuming a fixed time, location, and duration for the polynya.

How to cite: Hui, F., Ren, H., Shokr, M., Cheng, X., Li, X., and Zhang, Z.: Estimation of Sea Ice Production in the North Water Polynya Based on Ice Arch Duration in Winter During 2006–2019, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1922, https://doi.org/10.5194/egusphere-egu24-1922, 2024.

Sea ice in the high latitude is an indicator of climate change and has undergone dramatic changes because of recent global warming. Synthetic aperture radar (SAR) is a relatively practical tool for sea ice monitoring because of its low sensitivity to clouds, rain, and fog, as well as its capability for high-resolution earth observation in daylight or darkness. With the progression in SAR systems from single-pol to dual-pol, quad-pol and hybrid-pol, large numbers of parameters have been proposed for sea ice classification. Even though a large number of SAR characteristics have been used to classify sea ice, it remains unclear which parameters are the most effective for different regions and seasonal or environmental conditions. Meanwhile, classification studies for fine sea ice with high spatial resolution and many sub-types of sea ice, particularly in the case of rapidly changing first-year ice (FYI), which includes new ice (NI), young ice (YI), and FYI, are rather few. NI and YI have comparatively thinner thickness, and are often classified as FYI in these studies[1].

A new method of sea ice classification based on feature selection from Gaofen-3 polarimetric SAR observations is proposed. The new approach classifies sea ice into four categories: open water, NI, YI, and FYI. Seventy parameters that have previously been applied to sea ice studies are re-examined for sea ice classification in the Okhotsk Sea near the melting point on 28 February 2020. The ‘separability index’ is used for the selection of optimal features for sea ice classification. Full polarization (σohh, SEi, Ks) and hybrid polarization parameters (σorl, CPSEirh-rv, αs) are determined as optimal. The selected parameters are used to classify NI, YI, and FYI using a SVM machine learning classifier; and classification results are validated by manually interpreted ice maps derived from Landsat-8 data.

 


[1]Sea ice: types and forms - Canada.ca

How to cite: Li, H. and Yang, K.: Fine resolution classification of new ice, young ice, and first-year ice based on feature selection from Gaofen-3 quad-polarization SAR, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2666, https://doi.org/10.5194/egusphere-egu24-2666, 2024.

EGU24-2699 | Posters on site | OS1.1

Changes in ocean circulation and dissolved oxygen/nutrient distributions in the Canadian Basin 

Shigeto Nishino, Jinyoung Jung, Kyoung-Ho Cho, William Williams, Amane Fujiwara, Akihiko Murata, Motoyo Itoh, Eiji Watanabe, Mariko Hatta, Michiyo Yamamoto-Kawai, Takashi Kikuchi, Eun Jin Yang, and Sung-Ho Kang

The Arctic Ocean is facing dramatic environmental and ecosystem changes. To obtain the current baseline data, a coordinated multiship and multination pan-Arctic ship-based sampling campaign was implemented for the period between 2020 and 2022 under the project of Synoptic Arctic Survey (SAS). During the 2020 survey, unusually low dissolved oxygen and acidified water (salinity = 34.5) were found in a high-seas fishable area of the western (Pacific-side) Arctic Ocean. The data showed that the Beaufort Gyre (BG) shrunk to the east of the Chukchi Plateau (CP) and formed a front between the water within the gyre and the water from the eastern (Atlantic-side) Arctic. That phenomenon triggered a frontal northward flow along the CP. This flow likely transported the low oxygen and acidified water toward the high-seas fishable area; similar biogeochemical properties had previously been observed only on the shelf-slope north of the East Siberian Sea (ESS). Northward flows were also predominant west of the CP associated with the penetration of the water from the eastern Arctic. The northward flows would transport nutrient-rich shelf water (salinity = 32.5) from the ESS to the southwestern Canadian Basin (CB). Furthermore, the northeastward flow of the shrunk BG during the SAS period (2020-2022) could spread the nutrient-rich ESS shelf water to the northeastern CB. As a result, the nutrient concentration there during the SAS period was higher than the period when the BG enlarged to the west of CP, because the westward flow of the BG that overshot the CP inhibited the northward transport of the nutrient-rich ESS shelf water toward the southwestern CB. As a future study, we would like to combine the data from the Atlantic gateway because the ocean circulation and dissolved oxygen/nutrient distributions in the CB are largely influenced by the penetration of the water from the eastern Arctic. This is a reason why we have applied to present in this session.

How to cite: Nishino, S., Jung, J., Cho, K.-H., Williams, W., Fujiwara, A., Murata, A., Itoh, M., Watanabe, E., Hatta, M., Yamamoto-Kawai, M., Kikuchi, T., Yang, E. J., and Kang, S.-H.: Changes in ocean circulation and dissolved oxygen/nutrient distributions in the Canadian Basin, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2699, https://doi.org/10.5194/egusphere-egu24-2699, 2024.

EGU24-3080 | Posters on site | OS1.1

No emergence of deep convection in the Arctic Ocean across CMIP6 models 

Céline Heuzé and Hailong Liu

As sea ice disappears, the emergence of open ocean deep convection in the Arctic, which would enhance ice loss, has been suggested. Here, using 36 state-of-the-art climate models and up to 50 ensemble members per model, we show that Arctic deep convection is rare under the strongest warming scenario. Only 5 models have convection by 2100, while 11 have had convection by the middle of the run. For all, the deepest mixed layers are in the eastern Eurasian basin. When the models convect, that region undergoes a salinification and increasing wind speeds; it is freshening otherwise. The models that do not convect have the strongest halocline and most stable sea ice, but those that lose their ice earliest -because of their strongly warming Atlantic Water- do not have a persistent deep convection: it shuts down mid-century. Halocline and Atlantic Water changes urgently need to be better constrained in models.  

How to cite: Heuzé, C. and Liu, H.: No emergence of deep convection in the Arctic Ocean across CMIP6 models, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3080, https://doi.org/10.5194/egusphere-egu24-3080, 2024.

EGU24-3635 | Orals | OS1.1

Drivers of interannual salinity variability in the Arctic Ocean 

Antoine Hochet, Camille Lique, Florian Sévellec, and William Llovel

Accurate projections and attributions of Arctic ocean changes in climate models require a good understanding of the mechanisms underlying interannual salinity variability in the region. Although some mechanisms have been extensively studied in idealized settings, in particular for the dynamics of the Beaufort Gyre (BG), their applicability to the more complex system remains unclear. This study introduces a new diagnostic based on the salinity variance budget to robustly assess the mechanisms of salinity variations. The diagnostic is then applied to the Estimating the Circulation and Climate of the Ocean state estimate. 
The results indicate that the advection of salinity anomalies in the direction of the mean salinity gradient, produced by velocity anomalies is the primary source of interannual salinity variability. These velocities are primarily caused by fluctuating winds via Ekman transports.
Fluctuating surface freshwater fluxes from the atmosphere and sea ice are the second most important source of variability and cannot be neglected. The two sinks of interannual salinity variance are associated with the erosion of large-scale  mean circulation gradients by eddies and to a lesser extent to the diffusive terms. Over continental shelves, particularly over the East Siberian Shelf (ESS), ocean surface freshwater fluxes and diffusion play a more important role than in the deep basins.
We also report a strong intensification of all sources and sinks of interannual salinity variability in the BG and an opposite weakening in the ESS in the second decade of the analysis (2004-2014) with respect to the first (1993-2003). 

How to cite: Hochet, A., Lique, C., Sévellec, F., and Llovel, W.: Drivers of interannual salinity variability in the Arctic Ocean, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3635, https://doi.org/10.5194/egusphere-egu24-3635, 2024.

EGU24-3752 | ECS | Posters on site | OS1.1

Latitudinal distribution of biomarkers across the western Arctic Ocean and the Bering Sea: an approach to assess sympagic and pelagic algal production 

Youcheng Bai, Marie-Alexandrine Sicre, Jian Ren, Vincent Klein, Haiyan Jin, and Jianfang Chen

The drastic decline of Arctic sea ice due to global warming and polar amplification of environmental changes in the Arctic basin profoundly alter primary production with consequences for polar ecosystems and the carbon cycle. In this study, we use highly branched isoprenoids (HBIs), brassicasterol, dinosterol and terrestrial biomarkers (n-alkanes and campesterol) in surface sediments to assess sympagic and pelagic algal production with changing sea-ice conditions along a latitudinal transect from the Bering Sea to the high latitudes of the western Arctic Ocean. Suspended particulate matter (SPM) was also collected in surface waters at several stations of the Chukchi Sea to provide snapshots of phytoplankton communities under various sea-ice conditions for comparison with underlying surface sediments. Our results show that sympagic production (IP25 and HBI-II) increased northward between 62°N and 73°N, with maximum values at the sea-ice edge in the Marginal Ice Zone (MIZ) between 70°N and 73°N in southeastern Chukchi Sea and along the coast of Alaska. They were consistently low at northern high latitudes (>73°N) under extensive summer sea-ice cover and in the Ice-Free Zone (IFZ) of the Bering Sea. Enhanced pelagic sterols and HBI-III occurred in the IFZ across the Bering Sea and in southeastern Chukchi Sea up to 70°N-73°N in the MIZ conditions that marks a shift of sympagic over pelagic production. In surface water SPM, pelagic sterols display similar patterns as Chl a, increasing southwards with higher amounts found in the Chukchi shelf pointing out the dominance of diatom production. Higher cholesterol values were found in the mid-Chukchi Sea shelf where phytosterols were also abundant. This compound prevailed over phytosterols in sediments, compared to SPM, reflecting efficient consumption of algal material in the water column by herbivorous zooplankton.

How to cite: Bai, Y., Sicre, M.-A., Ren, J., Klein, V., Jin, H., and Chen, J.: Latitudinal distribution of biomarkers across the western Arctic Ocean and the Bering Sea: an approach to assess sympagic and pelagic algal production, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3752, https://doi.org/10.5194/egusphere-egu24-3752, 2024.

EGU24-3959 | ECS | Posters on site | OS1.1

Arctic Wintertime Sea Ice Lead Detection from Sentinel-1 SAR Images 

Shiyi Chen, Mohammed Shokr, Lu Zhang, Zhilun Zhang, Fengming Hui, Xiao Cheng, and Peng Qin

Leads in sea ice cover are almost linear fractures within the pack ice, and are commonly observed in the polar regions. In winter, leads promote energy flux from the underlying ocean to the atmosphere. Synthetic aperture radar (SAR) can monitor leads with a fine spatial resolution, regardless of solar illumination and atmospheric conditions. In this paper, we present an approach for automatic sea ice lead detection (SILDET) in the Arctic wintertime using Sentinel-1 SAR images. SILDET is made up of four modules: 1) a segmentation module; 2) a balance module; 3) an optimization module; and 4) a mask module. The validation results presented in this paper show that SILDET has the capability of detecting open and frozen leads at different stages of freezing. The lead map obtained from SILDET was compared to a lead dataset based on Moderate Resolution Imaging Spectroradiometer (MODIS) data and validated by the use of Sentinel-2 images. This shows that SILDET can provide a more detailed distribution of leads and better estimation of lead width and area. Compared with visual interpretation of Sentinel-1 images, the overall detection accuracy is 97.80% and the Kappa coefficient is 0.88 (for all types). The pyramid scene parsing network (PSPNet) in the segmentation module shows a better performance in detecting frozen leads, compared with the deep learning methods of UNet and DeepLabv3+. The optimization module utilizing shape features also improves the precision in detecting frozen leads. SILDET was applied to present the Arctic lead distribution in January and April 2023 with a spatial resolution of 40 m. The Arctic-wide lead width distribution follows a power law with an exponent of 1.64 ± 0.07. SILDET can be expected to provide long-term high-resolution lead distribution records.

How to cite: Chen, S., Shokr, M., Zhang, L., Zhang, Z., Hui, F., Cheng, X., and Qin, P.: Arctic Wintertime Sea Ice Lead Detection from Sentinel-1 SAR Images, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3959, https://doi.org/10.5194/egusphere-egu24-3959, 2024.

EGU24-4291 | ECS | Orals | OS1.1

Arctic sea ice drift fields extraction based on feature tracking to MODIS imagery 

Yan Fang, Xue Wang, Gang Li, Zhuoqi Chen, Fengming Hui, and Xiao Cheng

Moderate-resolution optical imagery holds great potential in deriving Arctic sea ice drift fields because of its higher resolution than microwave radiometers and scatterometers, as well as its larger swath widths than most other optical and synthetic aperture radar (SAR) images. However, the application of such imagery is hindered by cloud influences and a lack of texture. In this study, we propose a method of deriving Arctic sea ice drift fields based on applying feature tracking to Moderate Resolution Imaging Spectroradiometer (MODIS) imagery. To enhance the quality of the feature tracking step, a bundle of digital image processing techniques is first introduced, including histogram equalization which is based on the Cumulative Distribution Function (CDF) of the sea ice area, and Laplacian filtering which enhances image texture. Various MODIS bands and A-KAZE parameter settings are subsequently compared to balance the quality of sea ice drifting fields and calculation efficiency. Three pairs of MODIS images observed in different zones of the Arctic Ocean are selected to evaluate the performance of the proposed method. International Arctic Buoy Programme (IABP) buoy data are employed for validating the derived drift vectors with MODIS imagery. The results show that our proposed method effectively increases the number of vectors and their coverage rates of the sea ice drift fields extracted with MODIS images. The coverage rates of sea ice drift fields in three regions increase from 4.8%, 2.3%, and 2.5% to 56.5%, 23.5%, and 53.0% compared to using the A-KAZE algorithm directly, respectively. The MAEs of the derived sea ice motion vectors are 707 m/d in speed and 6.4° in direction, superior to the sea ice drift products based on the Advanced Very High Resolution Radiometer (AVHRR) imagery. The proposed method enables MODIS and other medium-resolution optical data to be utilized in deriving Arctic sea ice drift fields, which is of great significance to the long-term and large-scale Arctic environment, climate, and oceanography research in the future. 

How to cite: Fang, Y., Wang, X., Li, G., Chen, Z., Hui, F., and Cheng, X.: Arctic sea ice drift fields extraction based on feature tracking to MODIS imagery, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4291, https://doi.org/10.5194/egusphere-egu24-4291, 2024.

EGU24-6019 | ECS | Orals | OS1.1

Variability in the Arctic Ocean currents during 1990-2100 

Xiaoyan Wei, Chris Wilson, Sheldon Bacon, and Benjamin Barton

The Arctic Ocean is changing rapidly due to climate change, with significant impacts on subpolar ocean dynamics and mid-latitude regional weather. By utilizing a global, 1/12 degree, ocean sea-ice model (NEMO-SI3), which is forced at its surface by an Earth System Model, UKESM1.1, and simulates from 1981 to 2100 under scenario SSP3-7.0, we will demonstrate significant differences in the spatial structure and energy spectrum of Arctic Ocean currents among the past, the present, and the future. We will then explore the implications of changes in Arctic Ocean currents on mass transport pathways within the Arctic and transport across its boundaries. Subsequently, our study will identify the dominant physical drivers of these changes, such as sea ice melting, freshwater discharge, wind stresses, surface heat fluxes, and tides.

How to cite: Wei, X., Wilson, C., Bacon, S., and Barton, B.: Variability in the Arctic Ocean currents during 1990-2100, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6019, https://doi.org/10.5194/egusphere-egu24-6019, 2024.

EGU24-6330 | Orals | OS1.1

Recent estimates of the sea ice volume and solid freshwater flux across the Arctic’s major export passageways 

Stephen Howell, David Babb, Jack Landy, and Mike Brady

Sea ice export from the Arctic Ocean is important to the ice mass balance and freshwater budget of the Arctic Ocean and the delivery of freshwater to the North Atlantic. Historically, estimates of the sea ice volume and solid freshwater flux across the Arctic’s major export passageways were temporally limited in terms of available ice thickness data together with low spatial resolution satellite derived sea ice motion data. However, observational advances now provide year-round estimates of ice thickness from CryoSat-2 and high spatiotemporal estimates of sea ice motion can be derived from Senitnel-1 and the RADARSAT Constellation Mission (RCM) synthetic aperture radar (SAR) satellites. In this presentation, we present the results of merging these datasets that provide new high-quality annual and monthly estimates of the sea ice volume flux across the Arctic’s major export passageways of Fram Strait, Nares Strait, Davis Strait and the Canadian Arctic Archipelago from 2016-2022. Over our study period, the annual average volume export at Fram Strait was 1586 km3 that agrees with its longer-term decline. The annual average volume export at Nares Strait and the Canadian Arctic Archipelago was 160 km3, and 43 km3, respectively that is in agreement with longer-term increases and indicates a divergent trajectory compared to Fram Strait. The annual average sea ice volume flux through Davis Strait was 816 km3, nearly double previous estimates. Annually, a total of 1912 km3 of solid freshwater was delivered to the North Atlantic from the passageways of Fram Strait and Davis Strait. Overall, our new high-quality estimates of these sea ice variables provide updated quantities for understanding recent changes in ice mass balance and freshwater budget of the Arctic Ocean and the freshwater balance of the North Atlantic, where overturning is critical to the global climate.

How to cite: Howell, S., Babb, D., Landy, J., and Brady, M.: Recent estimates of the sea ice volume and solid freshwater flux across the Arctic’s major export passageways, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6330, https://doi.org/10.5194/egusphere-egu24-6330, 2024.

The surface Arctic Ocean is subject to rapidly changing freshwater inputs, from increasing ice melt and riverine inputs. Close monitoring of inflow waters from the Pacific and Atlantic is also needed for understanding the balance of geochemical cycles and making future predictions in the Arctic.  However, our knowledge of ocean biogeochemical data is very limited, necessitating an expansion of spatial and temporal coverage. However, the acquisition of ocean samples is hindered by the intricate sampling and analytical procedures employed both at sea and on land.

In our recent work [Hatta et al, 2021; 2023], a miniaturized, automated, microfluidic analyzer for nutrient analysis was developed using the programmable flow injection (pFI) technique.  This innovative system achieves accurate measurements with minimal reagent use, computer-controlled manipulations, and auto-calibration techniques, thus it is a promising oceanographic tool for increasing sample acquisition and determination, as well as minimizing human error.  For the pFI technique, the traditional silicate (Si) molybdenum blue method was modified by combining oxalate and ascorbic acid into a single reagent. This new method obtained a limit of detection of 514 nM Si, r.s.d. 2.1%, sampling frequency rate of 40 samples per hour, reagent consumption of 700 microliters per sample, and use of deionized (DI) water as a carrier solution. Phosphate (P) does not interfere significantly in this technique if the Si:P ratio is 4:1 or larger. Additionally, since there is no salinity influence, samples collected from the open ocean, coastal areas, or rivers can all be determined accurately using a DI water-based standard calibration covering a single small range by diluting samples to fall within this limited range.

In this contribution, this new shipboard method using programmable Flow Injection will be presented along with high-resolution Si data from the Chukchi shelf.  These data were obtained every 10-20 minutes by directly connecting the pFI platform to the underway water sampling system during the RV Mirai summer cruises. This new analytical platform will allow us to significantly expand our database and thus help to constrain and quantify geochemical processes and budgets in the Arctic Ocean.

How to cite: Hatta, M., Davis, M., and Measures, C.: Surface silicate distribution in the Chukchi-shelf region during the Arctic summer cruises using programmable flow injection technique, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6998, https://doi.org/10.5194/egusphere-egu24-6998, 2024.

EGU24-7486 | Orals | OS1.1

Sea-ice lead dynamics in the Arctic Ocean and associated drivers 

Sascha Willmes, Günther Heinemann, and Michelle Rasic

Based on a novel sea-ice lead climatology derived from thermal-infrared satellite imagery we identify drivers of wintertime sea-ice dynamics in the Arctic Ocean. ERA-5 atmospheric reanalyses and large-scale sea-ice drift data are used to investigate the causes for prominent spatial patterns and for the inter-annual variability in the occurrence of sea-ice leads. We can show that large-scale atmospheric circulation patterns and the Arctic Oscillation determine where and to which extent leads form on weekly to monthly timescales. Events with strong lead openings can directly be associated with pronounced anomalies in wind divergence and sea-ice drift. We also show the dominant modes in the Arctic sea-ice lead variability and their relation to atmospheric circulation. Moreover, the role of ocean processes in shaping long-term spatial lead patterns in the Arctic Ocean is presented. Implications for sea-ice modelling, forecasts and future trends are discussed.

How to cite: Willmes, S., Heinemann, G., and Rasic, M.: Sea-ice lead dynamics in the Arctic Ocean and associated drivers, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7486, https://doi.org/10.5194/egusphere-egu24-7486, 2024.

EGU24-8264 * | Orals | OS1.1 | Highlight

Still Arctic? - The changing Barents Sea 

Sebastian Gerland, Randi B. Ingvaldsen, Marit Reigstad, Arild Sundfjord, Bjarte Bogstad, Melissa Chierici, Tor Eldevik, Haakon Hop, Paul E. Renaud, Lars H. Smedsrud, Leif Christian Stige, and Marius Årthun

The Barents Sea is one of the Polar regions where current climate and ecosystem change is most pronounced. In a recent review (DOI: 10.1525/elementa.2022.00088) as a part of the cross-disciplinary Norwegian research project “The Nansen Legacy”, the current state of knowledge of the physical, chemical and biological systems in the Barents Sea is described. Here, we present some of the key findings from this review. Physical conditions in this area are characterized by large seasonal contrasts between partial sea-ice cover in winter and spring versus predominantly open water in summer and autumn. Observations over recent decades show that surface air and ocean temperatures have increased, sea-ice extent has decreased, ocean stratification has weakened, and water chemistry and ecosystem components have changed. In general changes can be described as “Atlantification” and “borealisation,” with a less “Arctic” appearance. In consequence, only the northern part of the Barents Sea can be still called “Arctic”. The temporal and spatial changes have a wider relevance reaching beyond the Barents Sea, such as in the context of large-scale climatic (air, water mass and sea-ice) transport processes. The observed changes also have socioeconomic consequences, such as for fisheries and other human activities. Recent Barents Sea mooring data shows stronger inflow of warm water from the north during winter, affecting the sea ice locally. “The Nansen Legacy” has significantly reduced Barents Sea observation- and knowledge gaps, especially for winter months when field observations and sample collections have been sparse until recent.

How to cite: Gerland, S., Ingvaldsen, R. B., Reigstad, M., Sundfjord, A., Bogstad, B., Chierici, M., Eldevik, T., Hop, H., Renaud, P. E., Smedsrud, L. H., Stige, L. C., and Årthun, M.: Still Arctic? - The changing Barents Sea, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8264, https://doi.org/10.5194/egusphere-egu24-8264, 2024.

EGU24-8828 | Posters on site | OS1.1

Changes of mesoscale eddy activity in the Eurasian Basin from 1-km simulations 

Vasco Müller, Qiang Wang, Nikolay Koldunov, Sergey Danilov, Xinyue Li, Caili Liu, and Thomas Jung

Mesoscale eddies play a crucial role in shaping the dynamics of the Arctic Ocean, making them essential for understanding future Arctic changes and the ongoing 'Atlantification' of the region. In this study, we use simulations generated by the unstructured-mesh Finite volumE Sea ice-Ocean Model (FESOM2) with a 1-km horizontal resolution in the Arctic Ocean.

Our investigation includes multiple simulations, namely a seven-year run representing the present-day climate and a slice simulation for the end of the 21st century, representative for a 4°C warmer world. Through these simulations, we evaluate changes in Eddy Kinetic Energy (EKE) within the Eurasian Basin and analyze their correlation with factors like sea-ice cover, baroclinic conversion rate, and stratification. To deepen our understanding, we combine Eulerian properties like EKE and baroclinic conversion rate with Lagrangian properties obtained from an algorithm that automatically identifies and tracks eddies using vector geometry.

Our findings from the end-of-century slice simulation indicate a significant increase in Arctic eddy activity in the future, accompanied by retreating sea ice. The present-day simulation reveals that the seasonality of EKE is mainly influenced by changes in sea ice, with distinct drivers at different depth levels for monthly anomalies. The mixed layer shows a robust connection to sea ice variability, while deeper levels, protected by stratification, are more significantly influenced by baroclinic conversion.

How to cite: Müller, V., Wang, Q., Koldunov, N., Danilov, S., Li, X., Liu, C., and Jung, T.: Changes of mesoscale eddy activity in the Eurasian Basin from 1-km simulations, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8828, https://doi.org/10.5194/egusphere-egu24-8828, 2024.

EGU24-9183 | ECS | Orals | OS1.1 | Highlight

Thin Ice, Large Impact: Temporal and spatial trends of Arctic thermodynamic and dynamic sea ice thickness change 

Luisa von Albedyll and Robert Ricker

The Arctic Ocean's transition from perennial sea ice to more ice-free summers has halved sea ice thickness in the last six decades, significantly impacting the Arctic climate and ecosystem. Recent trends show a slowing in ice thickness and volume decline, prompting a need to investigate the underlying seasonal and long-term feedback mechanisms of sea ice thickness change. To do so, we use a Lagrangian drift-aware sea ice thickness product (DA-SIT), combined with extensive data on thermodynamic growth conditions and sea ice deformation, to quantify thermodynamic and dynamic thickness change in selected Arctic regions. A key focus is the Multidisciplinary Drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition, which provided regional-scale analysis of seasonal sea ice thickness change using airborne ice thickness measurements, sea ice deformation, and in-situ snow and thermodynamic growth data. Our study extends these findings to larger temporal and spatial scales, evaluating their pan-Arctic applicability using long-term satellite datasets. We compare the MOSAiC trajectory with different dynamic regimes and ask how representative the conditions were for the “old” and the “new” Arctic. This analysis is key to understanding future sea ice thickness change, which is of great relevance for many climate and ecosystem processes.

How to cite: von Albedyll, L. and Ricker, R.: Thin Ice, Large Impact: Temporal and spatial trends of Arctic thermodynamic and dynamic sea ice thickness change, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9183, https://doi.org/10.5194/egusphere-egu24-9183, 2024.

EGU24-9293 | Posters on site | OS1.1

Analyzing Mesoscale Eddy Impact on the West Spitsbergen Current in the Fram Strait 

Hwa Chien, Yen-Chen Chen, Huang-Meng Chang, Ke-Hsien Fu, and Bo-Shian Wang

Accelerated melting of Arctic sea ice, a consequence of global warming, is being exacerbated by increased freshwater inputs. This has led to a significant reduction in the halocline layer within the Fram Strait, enhancing ocean stratification and creating a feedback loop that further accelerates sea ice loss. This process is critical for the formation of North Atlantic Deep Water (NADW), where the West Spitsbergen Current (WSC) plays an essential role in recirculation.

Our study delves into the characteristics and influences of mesoscale eddies in the Fram Strait, particularly focusing on their impact on the WSC recirculation and NADW formation. Conducted over three years (2021-2023) during the months of minimal sea ice cover (August to October), the research involved deploying 36 specialized surface mini buoys across the strait. Analytical methods such as horizontal dispersion coefficients, finite-size Lyapunov exponents (FSLE), Lagrangian eddy identification, and sea surface temperature (SST) e-folding time were employed to assess WSC surface dynamics, eddy activities, and air-sea heat exchange.

Notably, we observed WSC bifurcation and intense mesoscale seawater mixing in the southwest Yermak Plateau and east of Molloy Deep (MD), areas marked by a rise in SST e-folding scale time gradient and considerable heat loss to the atmosphere (approximately 120 W/m²). Surface water convergence and sinking were detected near the western side of Molloy Deep and the Hovgaard (HG) regions, coinciding with high vorticity zones. Analysis of the buoy trajectories identified 682 eddy samples, forming the basis for a statistical examination of their size, period, intensity, and cyclonic features. This analysis was complemented by correlating eddy trajectories with sea surface height anomaly (SSHA) data, showing notable alignment.

Our results reveal a predominance of anticyclonic eddies in the Fram Strait, accounting for nearly 65% of the total eddies. Further, a consistency analysis between these eddies and wind stress curl indicated that about 66% of the anticyclonic eddies in the Molloy Deep region correlate with wind stress curl patterns, suggesting wind influence in their formation

How to cite: Chien, H., Chen, Y.-C., Chang, H.-M., Fu, K.-H., and Wang, B.-S.: Analyzing Mesoscale Eddy Impact on the West Spitsbergen Current in the Fram Strait, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9293, https://doi.org/10.5194/egusphere-egu24-9293, 2024.

EGU24-9304 | ECS | Orals | OS1.1

Distribution and characteristics of subsurface eddies in the Aleutian Basin, Bering Sea 

Kun Zhang, Haibin Song, and Linghan Meng

The subarctic Bering Sea, situated between the Pacific Ocean and Arctic Ocean, stands as one of the world's most productive oceanic regions. While the role of oceanic eddies in material transport and energy transfer has been extensively studied, surface eddies have dominated these investigations owing to advancements in remote sensing technology. Recently, attention has shifted to subsurface eddies for their influence on enhancing oceanic mixing. However, challenges persist in delineating the distribution and characteristics of subsurface eddies in the Bering Sea due to the limited effectiveness of satellite methods and the scarcity of field observation.

Multichannel seismic (MCS) data can provide high-resolution acoustic images of subsurface thermohaline fine structures, known as seismic oceanography. In this study, we integrate MCS with concurrent vessel-mounted Acoustic Doppler Current Profiles (vmADCP), expendable bathythermograph (XBT), and expendable Conductivity Temperature Depth (XCTD) data collected during cruise MGL1111, along with Argo and Copernicus Marine Service Global Ocean Physics Reanalysis data to investigate the distribution and characteristics of subsurface eddies in the Aleutian Basin.

The results underscore the presence of 44 subsurface eddies in the Aleutian Basin, primarily submesoscale with diameters averaging around 20 km. Eddy thickness spans 71.14 - 416.57 m, with eddy core depths ranging from 69.96 - 657.24 m, predominantly concentrated in the 100 - 200 m depth range; only 5 eddies exhibit core depths below 300 m. The cumulative volume of these eddies reaches approximately 434.38 × 109 m3, with the majority exhibiting anticyclonic characteristics, as corroborated by concurrent ADCP data. Analysis of historical CTD data, along with concurrent XBT and XCTD data from cruise MGL1111, delineates distinct water masses—Bering Sea Upper Water (BUW), Bering Sea Intermediate Water (BIW), and Bering Sea Deep Water (BDW)—in the study area. Most identified eddies are characterized as cold core, facilitating the transport of BIW. Trajectory assessments, incorporating concurrent Argo and Copernicus Marine Service Global Ocean Physics Reanalysis data, suggest an eastern and southern origin for these eddies, predominantly propagating westward. Assuming a propagating velocity of 1 cm/s, the estimated total transport of these eddies is approximately 1.76 Sv.

We believe that these findings will contribute essential insights to the fields of marine ecology, and climate studies, enhancing our knowledge of ocean dynamics in this critical region.

How to cite: Zhang, K., Song, H., and Meng, L.: Distribution and characteristics of subsurface eddies in the Aleutian Basin, Bering Sea, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9304, https://doi.org/10.5194/egusphere-egu24-9304, 2024.

EGU24-9400 | ECS | Posters on site | OS1.1

Spatial and temporal distribution of all Arctic Polynyas since 1979 

Hau Man Wong, Céline Heuzé, Luisa Ickes, and Lu Zhou

Polynyas, open water regions within the sea ice cover, have been observed by satellites intermittently in the Arctic region over the past few decades. Their formation is complex, requiring various drivers to precondition and trigger the opening, which then influences local and regional weather significantly. Therefore, understanding Arctic polynyas’ spatial and temporal distribution is crucial to studying the polynyas’ impacts on climate. To date, most research is local and short-term, focusing on the major active Arctic polynyas or specific events; there is a need for pan-Arctic, long-term studies of all polynyas. Here, we use all available sea ice satellite data products to investigate all Arctic polynya events since 1979, in particular their locations for each day. The location preciseness and robustness are examined by sensitivity tests, varying the sea ice concentration (20 – 40%) and thickness (10 – 30 cm) thresholds. In the meantime, polynyas’ daily area extent, event duration, and recurrence are also obtained. The results indicate that the Franz-Josef Land, Eastern Kara Sea, and Nares Strait are the most active polynya formation-prone regions during wintertime. In addition, there is an increasing trend of polynya formation across the observation period. In future work, we plan to use the retrieved locations to determine whether thermodynamics or dynamic forcings contribute most to the Arctic polynyas’ opening.

How to cite: Wong, H. M., Heuzé, C., Ickes, L., and Zhou, L.: Spatial and temporal distribution of all Arctic Polynyas since 1979, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9400, https://doi.org/10.5194/egusphere-egu24-9400, 2024.

EGU24-10445 | ECS | Posters on site | OS1.1

Temporal and spatial variability of the oceanic front between the Atlantic Water and adjacent water masses north of Svalbard 

Stian Vikanes, Frank Nilsen, and Ragnheid Skogseth

The inflow of warm Atlantic Water (AW) into the Arctic Ocean is controlled by
oceanic fronts and air-ocean interactions north of Svalbard. The warm AW has
a significant impact on the sea ice extent and marine ecosystems in the region.
Therefore, it is crucial to understand the variability of the oceanic fronts offshore and
onshore of the AW, including their temporal and spatial characteristics, as well as
the mechanisms that govern them, such as atmospheric forcing, frontal instabilities,
and advection. However, our current understanding of the variability of these fronts
and AW north of Svalbard is limited due to lack of observational data. In this study,
we will use historical and more recent hydrographic data to analyze and describe
surface and subsurface fronts, both offshore and onshore of the AW core, in terms of
their dominant water masses along the continental slope north of Svalbard. We will
also determine the strength and position of these fronts by examining the horizontal
gradients in temperature, salinity, and density, and connect it to known changes in
the wind forcing.

How to cite: Vikanes, S., Nilsen, F., and Skogseth, R.: Temporal and spatial variability of the oceanic front between the Atlantic Water and adjacent water masses north of Svalbard, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10445, https://doi.org/10.5194/egusphere-egu24-10445, 2024.

The polar sea ice cover exhibits narrow bands of increased deformation, resulting in the formation of leads and pressure ridges. They are referred to as linear kinematic features (LKFs). They are important features of the sea ice field as they directly influence the heat and momentum exchange between ocean and atmosphere. By doing so, they influence the development of not only the sea ice cover but also the ocean and the local climate. Conversely, LKFs are also influenced by climate changes as the sea ice cover will be affected by changes in atmospheric and ocean temperature. In this work, the LKFs in the Arctic sea ice cover in current climate are compared to those in a warmer world. An LKF detection and tracking algorithm will be used to create a climate change signal. For this, the number of LKFs as well as their lifetimes are taken into account. The data analyzed in this work is created by the ocean-sea ice model FESOM. As LKFs are highly localized features, using a high spatial resolution is crucial. The resolution used in the analyzed runs is 1km. They span over five years starting at 2010, 2050, and 2090.

How to cite: Gärtner, J.: Detecting Linear Kinematic Features in Arctic Sea Ice in a Warmer World Using High Resolution Model Output, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10598, https://doi.org/10.5194/egusphere-egu24-10598, 2024.

EGU24-11226 | Posters on site | OS1.1

Weak signals of dense shelf water cascading in 2020 during a persisting phase of sporadic Atlantic water intrusions into the deep layer of the SW-Svalbard slope 

Patrizia Giordano, Manuel Bensi, Vedrana Kovacevic, Aniello Russo, and Leonardo Langone

The intensifying influence of warmer Atlantic Ocean waters in the Arctic, known as Arctic Atlantification, amplifies climate change effects by accelerating sea ice melting and altering ecosystems. Long-term data series are indispensable for discerning nuances in climate changes, especially when occurring in the deep ocean. They also provide a crucial temporal foundation for accurate modeling, useful to predict future scenarios and formulate effective strategies to address the challenges of climate change.

Here, we present oceanographic data collected from June 2014 to June 2023 at mooring site S1 (76°N, 14°E, 1040 m water depth), above the continental slope on the southwestern margin of Svalbard Archipelago (Fram Strait). There, the main branch of the West Spitsbergen Current transports Atlantic Water (in the upper layer) and Norwegian Sea Deep Water (below 900 m depth) poleward into the Arctic Ocean. Site S1 strategically lies at the convergence of Atlantic waters, the Arctic Ocean heat source, with waters from Storfjorden (Spitsbergen largest fjord) and shelf waters from the West Spitsbergen continental shelf. The oceanographic mooring S1 is part of the SIOS marine infrastructure network (Svalbard Integrated Arctic Earth Observing System, https://sios-svalbard.org/), and has undergone progressive instrument improvement over time, adding data collection at the intermediate layer since the summer 2022.

We focus on exploring short-term and seasonal variations in thermohaline properties, ocean currents, and particulate fluxes recorded in the deep layer over the last nine years. This analysis is undertaken in conjunction with meteorological conditions and trends in sea ice concentration. Oceanographic mooring data together with repeated Conductivity-Temperature-Depth (CTD) casts during summer surveys, show that the period 2014-2021 was characterized by the absence of dense shelf water exported at the near bottom on the slope, probably due to a limited production of dense water in the fjords, while the wind-induced vertical mixing and the resulting internal oscillations were probably favoured. During this period, a gradual decline in sea ice cover in winter is observed in the S1 area and adjacent fjords. The only exception is the winter 2020, when the sea ice extent returned apparently to pre-2013 levels, and at 1000m depth there were weak signals of cascading of dense shelf water, probably originated in the Storfjorden polynya.

Contrary to what is clearly evident in the literature regarding the increasing propagation of Atlantic waters northwards, temperature and salinity at mooring S1 showed no, or very little, positive trends over the investigated period. However, sporadic intrusions of relatively warm and saline water into the deep layer were observed. These occur most frequently in winter and are associated with the passage of internal waves that promote turbulent mixing of intermediate Atlantic waters with deep waters, facilitating the heat diffusion into the ocean depths.

How to cite: Giordano, P., Bensi, M., Kovacevic, V., Russo, A., and Langone, L.: Weak signals of dense shelf water cascading in 2020 during a persisting phase of sporadic Atlantic water intrusions into the deep layer of the SW-Svalbard slope, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11226, https://doi.org/10.5194/egusphere-egu24-11226, 2024.

EGU24-11917 | Orals | OS1.1 | Highlight

Atlantic Water warming increases melt below Northeast Greenland's last floating ice tongue 

Claudia Wekerle, Rebecca McPherson, Wilken-Jon von Appen, Qiang Wang, Ralph Timmermann, Patrick Scholz, Sergey Danilov, and Torsten Kanzow

Rising sea level poses a significant challenge and threat to our societies, given that coastal regions are densely populated. The Greenland ice sheet has been a major contributor to global sea level rise in the last decades, particularly its marine-terminating glaciers and their extensions into the ocean. The 79 North Glacier (79NG) features Greenland's largest floating ice tongue, stretching over 80 km in length in a 20 km wide fjord. The 79NG and its neighboring glacier, the Zachariæ Isstrøm, drain the Northeast Greenland Ice Stream which covers 12% of the Greenland Ice Sheet area. Its complete melt would lead to a 1.1-m global sea level rise. Though the extent of the 79NG has not changed significantly in recent years, observations have indicated a major thinning of its ice tongue from below.  Both ocean warming and an increase in subglacial discharge from the ice sheet induced by atmospheric warming could increase the basal melt; however, available observations alone cannot tell which of these is the main driver.

In this study, we present a setup of the Finite-volumE Sea ice-Ocean Model (FESOM2.1) which explicitly resolves the ocean circulation in the cavity of the 79NG with 700 m resolution. With this novel methodology, we seamlessly connect the global and regional ocean circulation to the circulation in the cavity. Our simulation with realistic bathymetry and ice shelf geometry covers the period 1970-2021, allowing us to disentangle the drivers of the upward trend and interannual variability of basal melt. We find that ocean warming in the subsurface Atlantic Intermediate Water layer that enters the cavity below the 79NG has played a dominant role in the basal melt rate over the past 50 years. The temperature variability can be traced back across the continental shelf of Northeast Greenland to the eastern Fram Strait with a lag of 3 years, implying a predictability of the basal melt of the 79NG. In contrast, subglacial discharge has a relatively small contribution to the interannual variation of the basal melt.

How to cite: Wekerle, C., McPherson, R., von Appen, W.-J., Wang, Q., Timmermann, R., Scholz, P., Danilov, S., and Kanzow, T.: Atlantic Water warming increases melt below Northeast Greenland's last floating ice tongue, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11917, https://doi.org/10.5194/egusphere-egu24-11917, 2024.

EGU24-12163 | ECS | Orals | OS1.1

Atlantification at the gateway of the Arctic Ocean over the last thousand years 

Francesco De Rovere, Angelo Rubino, and Davide Zanchettin

Atlantification is a major process driving rapid changes in the Arctic Ocean, e.g., sea-ice loss, warming and
salinification of the near-surface, enhanced mixing and changes in the ecosystem structure. The recent
scientific literature highlights the importance of the transport of Atlantic water as a cause of Atlantification,
but fundamental climatic processes driving this phenomenon are far from being fully understood.
Moreover, most studies focused on the analysis of recent observational data covering the last decades,
while recent studies showed that Atlantification had started in the 19th century.


In this contribution, we illustrate scope and progress of the Italian funded project “ATTRACTION: Atlantification dRiven by polAr-subpolar ConnecTIONs in a changing climate”. The project aims to provide a historical perspective on Atlantification by integrating observational evidence over the last decades, paleo-reconstructions and numerical paleoclimate simulations covering the past several centuries. We assess the capability of available tools to robustly describe coupled dynamics at the gateway of the Arctic Ocean (Fram Strait and Barents Sea), and their variations over multi-centennial periods. Furthermore, we provide a solid past reference for attribution of the ongoing Atlantification and discuss how paleoclimate simulations could support the identification of key locations for proxy-based reconstruction of the Atlantification. Toward a mechanistic understanding of Atlantification-like events over the last millennium, our assessment focus on the role of heat and salt redistribution by sub-polar dynamics by its major controls, including the Atlantic Multidecadal Overturning Circulation, the Sub-Polar Gyre and the Greenland Sea Gyre.

How to cite: De Rovere, F., Rubino, A., and Zanchettin, D.: Atlantification at the gateway of the Arctic Ocean over the last thousand years, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12163, https://doi.org/10.5194/egusphere-egu24-12163, 2024.

EGU24-12174 | ECS | Posters on site | OS1.1

Feasibility of using C-band Synthetic Aperture Radar datasets for long term (1991-present) sea ice monitoring: towards multi-decadal analysis of sea ice type changes in the Atlantic sector of the Arctic Ocean 

Wenkai Guo, Anthony Paul Doulgeris, Johannes Lohse, Malin Johansson, Polona Itkin, Torbjorn Eltoft, Jack Landy, and Shiming Xu

We present a feasibility assessment of using several publicly available C-band wide-swath SAR datasets to derive sea ice type maps in the Atlantic sector of the Arctic Ocean from 1991 to present. This region is characterized by highly variable and dynamic sea ice conditions, and temporally consistent, large-scale monitoring of sea ice parameters is only possible through satellite remote sensing. We use data from C-band sensors including Sentinel-1, RADARSAT-2, Envisat ASAR and ERS-1/2, which have similar central frequencies and spatial resolution, to cover the study period. We evaluate comparative image classification performances and classification consistency using these datasets with common training datasets in geographically and temporally overlapping scenes and a sea ice classifier correcting for per-class incidence angle (IA) effects. Through this evaluation, we demonstrate the differences in these datasets affecting sea ice classification and the feasibility of using legacy sensors including Envisat ASAR and ERS-1/2 to extend the time series of sea ice type maps back to 1991 in our study area. This study provides theoretical support for the establishment of a multi-decadal SAR-based sea ice type product, which will contribute to the assessment of seasonal and inter-annual sea ice variations, especially the variability in new ice formation, which strongly influences physical and biogeochemical processes across the ocean-ice-atmosphere interface. This study is part of the collaborative project INTERAAC (air-snow-ice-ocean INTERactions transforming Atlantic Arctic Climate) between Norway and China, which aims at generating a reconciled multi-mission Climate Data Record (CDR) for Atlantic Arctic sea ice.

How to cite: Guo, W., Doulgeris, A. P., Lohse, J., Johansson, M., Itkin, P., Eltoft, T., Landy, J., and Xu, S.: Feasibility of using C-band Synthetic Aperture Radar datasets for long term (1991-present) sea ice monitoring: towards multi-decadal analysis of sea ice type changes in the Atlantic sector of the Arctic Ocean, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12174, https://doi.org/10.5194/egusphere-egu24-12174, 2024.

In this study, we investigate the interannual variability of the sea ice area (SIA) in the Barents-Kara Sea (BKS) region. We explore the contributing factors to this variability, primarily focusing on oceanic influences evident in the Barents Sea Opening (BSO). The BSO, characterized by eastward warm Atlantic Water (AW) inflow, plays a crucial role in shaping the BKS SIA. While the inflow has been extensively studied, the westward-directed outflow known as Bear Island Slope Current (BISC), remains insufficiently observed. Being fed by relatively warm recirculating modified AW (mAW), the BISCs impact on the overall ocean heat transport (OHT) variability is uncertain.

 

Utilizing the global Finite Volume Sea Ice and Ocean Model (FESOM2.1), we derive estimates of the interannual volume transport and temperature variability of the BISC, filling the observational gap. We find that whereas the variability of BSO inflow/BISC volume transport is similar in magnitude, the temperature variability of the BISC exceeds the BSO inflow temperature variability. By linking the simulated BISC variability to BKS SIA, our findings reveal a yet unknown, strong co-variation between the volume transport of the BISC and the BKS SIA at the end of the freezing season, with a short lead time of zero to three months. We thus further examine the role of the BISC in generating interannual anomalies in the BKS SIA. Our model simulations illustrate that the volume transport of the BISC can be modified by the emergence of a secondary mAW recirculation downstream the northern AW path through the BS in the months preceding anomalously large BKS SIA. This secondary mAW recirculation is thereby increasing the volume transport of mAW leaving the BS via the BISC, reducing the amount of AW reaching the northern Barents Sea ice edge downstream. Additionally, we identify a connection between the atmospheric forcing pattern associated with the volume transport variability of the BISC and anomalous sea ice advection into the BKS as a second cause for the BISC volume transport/BKS SIA co-variability.

In general, our study emphasizes the co-variability between BKS SIA and the BISC. We highlight the role of the mAW recirculations in altering the amount of AW, and consequently ocean heat, reaching the ice edge in the northwestern Barents Sea.

How to cite: Heukamp, F. and Wekerle, C.: Variability of the Barents-Kara Sea Sea Ice Area and its Correlation with Atlantic Water Recirculation through the Barents Sea Opening, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12688, https://doi.org/10.5194/egusphere-egu24-12688, 2024.

EGU24-13067 | Orals | OS1.1 | Highlight

Intra- and interannual variability in the Atlantic Water inflow region north of Svalbard: sea ice, hydrography, nutrients and the potential for primary production 

Angelika Renner, Arild Sundfjord, Marit Reigstad, Allison Bailey, Øyvind Lundesgaard, Randi Ingvaldsen, Melissa Chierici, Elizabeth Jones, and Agnieszka Beszczynska-Möller

Atlantic Water (AW) is the major source of heat and nutrients to the Arctic Ocean. Changing AW inflow promotes sea ice decline and borealisation of marine ecosystems and affects primary production in the Eurasian Arctic. North of Svalbard, the AW inflow dominates oceanographic conditions along the shelf break and hence the distribution of heat and nutrients in the region. However, interaction with sea ice and Polar Surface Water determines nutrient supply to the euphotic layer. Using a combination of multidisciplinary approaches such as ship-based measurements and sampling, moored sensors, remote sensing and numerical modelling, we have been monitoring and studying the AW boundary current north of Svalbard since 2012. In this presentation, I will show some of our findings with particular focus on repeated measurements from a transect across the AW inflow at 31°E, 81.5°N. Large interannual variability in hydrography, nutrients and chl a indicates varying levels of nutrient drawdown by primary producers over summer. Sea ice conditions impact surface stratification, light availability, and wind-driven mixing, with a strong potential for steering chl a concentration over the productive season. In early winter, nutrient re-supply through vertical mixing varied in efficiency, again related to sea ice conditions. The autumn re-supply elevated nutrient concentrations sufficiently for primary production but likely happened too late as high-latitude light levels limited potential autumn blooms. Multidisciplinary observations are key to gain insight into the interplay between physical, chemical, and biological drivers and to understand ongoing and future changes. They are particularly important in regions like north of Svalbard that can indicate what we can expect in the central Arctic Ocean in the future.

How to cite: Renner, A., Sundfjord, A., Reigstad, M., Bailey, A., Lundesgaard, Ø., Ingvaldsen, R., Chierici, M., Jones, E., and Beszczynska-Möller, A.: Intra- and interannual variability in the Atlantic Water inflow region north of Svalbard: sea ice, hydrography, nutrients and the potential for primary production, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13067, https://doi.org/10.5194/egusphere-egu24-13067, 2024.

EGU24-13914 | ECS | Orals | OS1.1

Sea Ice Drift Retrieval based on Fengyun-3D Multi-Sensor Data 

Xue Wang, Zhuoqi Chen, Zhizhuo Xu, Ruirui Wang, Ran Lu, Fengming Hui, and Xiao Cheng

Under the background of global warming, sea ice changes rapidly. Sea ice drift is an important indicator for sea ice flux, atmospheric and ocean circulation, and ship navigation. Currently, the large-scale observed sea ice drift datasets are mainly obtained based on single-sensor remotely sensed data, which suffer low spatial resolution or poor spatial continuity. Considering that passive microwave radiometer and medium-resolution optical sensor complement each other in terms of spatial resolution and continuity, this study proposed a novel sea ice drift retrieval method based on Fengyun-3D (FY-3D) multi-sensor data. The proposed method is summarized as follows. First, low resolution sea ice drift fields were obtained from FY-3D Microwave Radiation Imager (MWRI) data based on the normalized cross-correlation pattern-matching method. Then, fine resolution vectors were extracted from FY-3D Medium-Resolution Spectral Imager (MERSI) data based on A-KAZE feature-tracking method. Finally, the low resolution pattern-matching vectors and fine resolution feature-tracking vectors were merged together based on Co-Kriging algorithm to obtain the final sea ice drift result. The proposed method was evaluated by comparing the buoy displacements obtained from the International Arctic Buoy Program (IABP) with the retrieved merged vectors from FY-3D remotely sensed images collected in the Beaufort Sea, the East Siberian Sea, and the Fram Strait on 2020. The results showed that the proposed method can retrieve accurate, fine resolution and spatial continuous sea ice motion fields.

How to cite: Wang, X., Chen, Z., Xu, Z., Wang, R., Lu, R., Hui, F., and Cheng, X.: Sea Ice Drift Retrieval based on Fengyun-3D Multi-Sensor Data, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13914, https://doi.org/10.5194/egusphere-egu24-13914, 2024.

EGU24-14215 | ECS | Posters on site | OS1.1

Potential of diatoms in sediments as seeds for autumn blooms in the Pacific Arctic shelf 

Yuri Fukai, Amane Fujiwara, Shigeto Nishino, Kohei Matsuno, and Koji Suzuki

The Pacific gateway to the Arctic has a vast continental shelf spanning the northern Bering and the Chukchi Seas. Within this shelf region, diatoms are crucial in sustaining high primary production and facilitating the sinking particulate organic carbon flux from spring to summer. Consequently, the bottom sediments have abundant viable diatoms, including resting stages. Despite the importance of diatoms, our understanding of the dynamics of this organism in sediments and their capacity to initiate primary production in the Pacific Arctic shelf remains limited.

In this study, we delved into the photophysiological capabilities of diatoms in the surface sediments collected from the Chukchi Sea in autumn through a laboratory incubation experiment at 3°C under the light conditions of 300 or 30 µmol photons m-2 s-1 for seven days. This experiment revealed that diatoms, mainly Chaetoceros, quickly resumed photosynthesis after light exposure and reached the maximum photosynthetic carbon fixation rates within only several days. These results suggest that diatoms in sediments have a significant potential to function as “seeds” for bloom formation in the sunlit water column. We further examined diatom communities, including resting spores, in the water column of the Chukchi Sea during autumn using scanning electron microscopy (SEM) and DNA metabarcoding techniques, as well as environmental parameters. Consequently, intense winds and subsequent water turbulence in the shallow Chukchi caused the predominance of Chaetoceros resting spores, probably derived from the sediments, in the diatom assemblages. As speculated from the incubation experiment mentioned above, diatom resting spores from the sediments can germinate immediately in the water column. Thus, settled diatoms could work as seeds for subsequent autumn blooms by being supplied from the seafloor along with nutrient-rich water.

The recent delayed sea ice formation in the autumn Arctic leads to increased storm occurrence over open water and enhanced vertical mixing, resulting in more frequent autumn blooms. Therefore, diatoms in sediments could be one of the critical contributors to autumn blooms in the shallow Pacific Arctic.

How to cite: Fukai, Y., Fujiwara, A., Nishino, S., Matsuno, K., and Suzuki, K.: Potential of diatoms in sediments as seeds for autumn blooms in the Pacific Arctic shelf, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14215, https://doi.org/10.5194/egusphere-egu24-14215, 2024.

EGU24-14505 | ECS | Posters on site | OS1.1

Winter to summer evolution of pCO2 in surface water of northern Greenland fjords  

Camille Akhoudas, Christian Stranne, Karl Adam Ulfsbo, Brett Thornton, and Martin Jakobsson

Ocean acidification induced by the absorption of anthropogenic CO2 and its consequences pose a potential threat to marine ecosystems around the globe. The Arctic Ocean, particularly vulnerable to acidification, provides an ideal region to investigate the progression and impacts of acidification before they manifest globally. Recent documentation of undersaturated surface waters in carbonate minerals in the Sherard Osborn fjord in northwest Greenland, a region visited for the first time in summer 2019, reveals inherent variability in biogeochemical processes. Associated with highly acidic surface waters, the partial pressure of CO2 (pCO2) was undersaturated relative to the atmosphere, indicating this study area as a CO2 sink. To comprehend variations in pCO2 in the northwest Greenland fjords and identify its drivers, we conducted a comparative study between two fjords in the region (Petermann and Sherard Osborn fjords) and used carbonate system data from the temperature minimum layer to examine the winter-to-summer evolution of pCO2 and influencing factors. Additionally, we evaluated pCO2 variations (δpCO2) concerning temperature, freshwater inputs, biological activity, and air-sea CO2 uptake to quantitatively assess the seasonal influencing factors on surface ocean pCO2. In the Sherard Osborn fjord, despite a substantial increase in surface temperature from winter to summer potentially increasing pCO2 and causing CO2 supersaturation relative to the atmosphere, freshwater inflow and biological activity reduced pCO2, resulting in CO2 undersaturation relative to the atmosphere. In the Petermann fjord, pCO2 remained lower than atmospheric levels due to a slight seasonal variation in surface temperature and significant biological activity, reducing pCO2 in surface water.

How to cite: Akhoudas, C., Stranne, C., Ulfsbo, K. A., Thornton, B., and Jakobsson, M.: Winter to summer evolution of pCO2 in surface water of northern Greenland fjords , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14505, https://doi.org/10.5194/egusphere-egu24-14505, 2024.

EGU24-15778 | Orals | OS1.1

Genesis and Decay of Baroclinic Eddies in the Seasonally Ice-Covered Arctic Ocean 

Gianluca Meneghello, John Marshall, Camille Lique, Pål Erik Isachsen, Edward Doddridge, Jean-Michel Campin, Heather Regan, and Claude Talandier

We explore the origin and evolution of mesoscale eddies in the seasonally ice-covered interior Arctic Ocean. Observations of ocean currents show a curious, and hitherto unexplained, vertical and temporal distribution of mesoscale activity. A marked seasonal cycle is found close to the surface: strong eddy activity during summer, observed from both satellites and moorings, is followed by very quiet winters. In contrast, subsurface eddies persist all year long within the deeper halocline and below.

We find that the surface seasonal cycle is controlled by friction with sea ice, dissipating existing eddies and preventing the growth of new ones. In contrast, subsurface eddies, enabled by interior potential vorticity gradients and shielded by a strong stratification at a depth of approximately 50 m, can grow independently of the presence of sea ice. 

We address possible implications for the transport of water masses between the margins and the interior of the Arctic basin, and for climate models’ ability to capture the fundamental difference in mesoscale activity between ice-covered and ice-free regions.

How to cite: Meneghello, G., Marshall, J., Lique, C., Isachsen, P. E., Doddridge, E., Campin, J.-M., Regan, H., and Talandier, C.: Genesis and Decay of Baroclinic Eddies in the Seasonally Ice-Covered Arctic Ocean, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15778, https://doi.org/10.5194/egusphere-egu24-15778, 2024.

EGU24-16897 | Orals | OS1.1

Assessing changes in winter sea ice deformation – from MOSAiC to the Fram Strait 

Polona Itkin and Dmitry Divine

During winter, sea ice is moving in cohesive clusters of ice plates. These clusters – hereafter named ‘Coherent Dynamic Elements’ (CDE) are composed of several areas of deformed and level ice, that slide coherently along active sea ice fractures. The largest sea ice fractures detectable from medium resolution Synthetic Aperture Radar (SAR) satellites (about 50 m spatial resolution) are the Linear Kinematic Features (LKFs). Sea ice deformation information can be estimated from the strain rates in the LKFs and as well from the geometrical characteristics of the CDEs. However, there is a sudden seasonal transition, at the point where the sea ice warms and loses its internal strength. After this transition the delineation of LKFs and CDEs from SAR becomes challenging. In this contribution we will analyze sea ice deformation during the drift of the MOSAiC expedition from October 2019 to July 2020. During this time, the expedition drifted the entire length of the Transpolar drift from the northern Laptev Sea into the Fram Strait and the sea ice surrounding it underwent numerous deformation events. The MOSAiC sea ice deformation data and the onset of the melt period is compared to the data over the Fram Strait, where the sea ice deformation can was estimated from SAR and upward looking sonar devices on fixed moorings for the period of 2010-2023. We will present the data on the changes in the onset of the melt period and show that MOSAiC year was a typical year representative for the sea ice deformation of the recent decade.

How to cite: Itkin, P. and Divine, D.: Assessing changes in winter sea ice deformation – from MOSAiC to the Fram Strait, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16897, https://doi.org/10.5194/egusphere-egu24-16897, 2024.

EGU24-17166 | ECS | Orals | OS1.1

The Northeast Water Polynya, Greenland; Climatology, Atmospheric Forcing and Ocean Response 

Miriam Bennett, Ian Renfrew, David Stevens, and Kent Moore

The Northeast Water Polynya is a significant annually recurring summertime Arctic polynya, located off the coast of Northeast Greenland. It is important for marine wildlife and affects local atmospheric and oceanic processes. In this study, over 40 years of observational and reanalysis products (ERA5 and ORAS5) are analysed to characterise the polynya's climatology and ascertain forcing mechanisms. The Northeast Water Polynya has high spatiotemporal variability; its location, size and structure vary interannually, and the period for which it is open is changing. We show this variability is largely driven by atmospheric forcing. The polynya extent is determined by the direction of the near-surface flow regime, and the relative locations of high and low sea-level pressure centers over the region. The surface conditions also impact the oceanic water column, which has a strong seasonal cycle in potential temperature and salinity, the amplitude of which decreases with depth. The ocean reanalyses also show a significant warming trend at all depths and a freshening near the surface consistent with greater ice melt, but salinification at lower depths (~ 200 m). As the Arctic region changes due to anthropogenic forcing, the sea-ice edge is migrating northwards and the Northeast Water Polynya is generally opening earlier and closing later in the year. This could have significant implications for both the atmosphere and ocean in this complex and rapidly changing environment.

How to cite: Bennett, M., Renfrew, I., Stevens, D., and Moore, K.: The Northeast Water Polynya, Greenland; Climatology, Atmospheric Forcing and Ocean Response, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17166, https://doi.org/10.5194/egusphere-egu24-17166, 2024.

EGU24-18118 | Posters on site | OS1.1

Arctic Ocean simulations in two high-resolution coupled climate models 

Chuncheng Guo, Mats Bentsen, Aleksi Nummelin, Mehmet Ilicak, Alok Gupta, and Andreas Klocker

Large model spread and biases exist in simulating the Arctic Ocean water mass and circulations from the latest CMIP6 coupled and ocean-sea ice-only simulations. This can be at least partly attributed to large uncertainties due to unresolved key processes in this region, and it is hoped that high resolution can - to a certain extent - come to the rescue.

In this work, we first examined two high-resolution simulations by two CMIP6-class models: 1) a multi-centennial integration of CESM (CESM-HR; ocean resolution 1/10-deg), and 2) a 50-year integration of NorESM (NorESM-MX; ocean resolution 1/8-deg). The two models show clear signs of improvements in simulating the Arctic Ocean compared to their standard 1-deg resolution counterparts, but certain biases remain, such as the incorrect pathway of the Atlantic Water and the too-deep mixed layer depth in NorESM-MX.

We then performed and analysed a similar NorESM-MX simulation, but this time with a newly developed hybrid vertical coordinate (z-density) in the ocean model (the default is isopycnal/density coordinate). ​​Experience from hybrid coordinate testing runs in standard 1-deg resolution shows e.g. much-improved water masses and sea ice extent in the Southern Ocean, mixed layer depths, and importantly more rapid equilibration to energy balance in coupled simulations. When applied in the high-resolution NorESM-MX configuration, the results with the new coordinate show a much-improved representation of the pathway of Atlantic water and the distribution of mixed layer depth in the Arctic Ocean. 

How to cite: Guo, C., Bentsen, M., Nummelin, A., Ilicak, M., Gupta, A., and Klocker, A.: Arctic Ocean simulations in two high-resolution coupled climate models, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18118, https://doi.org/10.5194/egusphere-egu24-18118, 2024.

EGU24-18702 | ECS | Posters on site | OS1.1

Observation of temporal and spatial variability of deep near-inertial waves in the western Arctic Ocean 

Chanhyung Jeon, Samuel Boury, Kyoung-Ho Cho, Eun-Joo Lee, Jae-Hun Park, and Thomas Peacock

Near‐inertial waves are waves propagating in the interior of the ocean. Created by surface storms, they have the potential to influence the ocean environment by inducing vertical mixing. Compared to other oceans, the Arctic Ocean has low near-inertial wave activity, but might be changing. It is a challenge, however, to predict near-inertial wave activity in the Arctic Ocean due to its intricate vertical salinity and temperature stratification. Our in-situ campaign has obtained the first direct deep current measurements revealing notable temporal and spatial variability of deep near-inertial waves in the western Arctic Ocean. These observations are an important step towards a clearer depiction of the evolving energy budget, and concomitant mixing, associated with potentially high impact near-inertial wave activity in an increasingly ice-free Arctic Ocean.

How to cite: Jeon, C., Boury, S., Cho, K.-H., Lee, E.-J., Park, J.-H., and Peacock, T.: Observation of temporal and spatial variability of deep near-inertial waves in the western Arctic Ocean, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18702, https://doi.org/10.5194/egusphere-egu24-18702, 2024.

EGU24-18990 | Posters on site | OS1.1

Extreme sea ice motion -- analysis of ice drifter buoy data in the Gulf of Bothnia  

Henri Vuollekoski, Mikko Lensu, and Jari Haapala

Sea ice and particularly its motion are problematic for vessels and structures in water areas that experience sea ice. For example, several offshore wind farms are planned to be installed in the Gulf of Bothnia, but uncertainty related to extreme sea ice motion is likely to worry potential investors. Winter navigation, particularly in the coastal boundary zone, can be difficult. While climate change is likely to decrease the average ice concentration, extrema may become more severe. 

The motion of sea ice is affected by wind, currents and internal dynamics of the ice field, which are highly complex and inadequately understood. In this study we analyze time-series of data from ice drifter buoys deployed in the Gulf of Bothnia, Baltic Sea, during 2012 - 2023. The combination of data from multiple buoys, ice charts as well as other observations and model forecasts on the atmosphere-sea-ice interaction allows for estimating various parameters for the respective ice fields, such as shear, divergence and deformation, as well as temporal and spatial variability.

How to cite: Vuollekoski, H., Lensu, M., and Haapala, J.: Extreme sea ice motion -- analysis of ice drifter buoy data in the Gulf of Bothnia , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18990, https://doi.org/10.5194/egusphere-egu24-18990, 2024.

Currently freshwater anomaly is building up in the Beaufort gyre of the Arctic Ocean. There is a risk that this freshwater may discharge into the North Atlantic, disrupting the Atlantic Meridional Overturing Circulation (AMOC). Recent changes in Beaufort gyre size and circulation suggest this may occur soon or has already started: the North Atlantic has recently experienced its largest freshening for the last 120 years. In contrast, so far there is only limited evidence of Arctic fresh water impacting freshwater accumulation in the Labrador Sea. The North Atlantic is a region of high variability on interannual to decadal timescales, potentially affecting European and global climates.

The study focuses on changes in oceanic transports through the Arctic gateways under the Carbon Dioxide Removal (CDR) es-SSP5-3.4-ov CMIP6 emission–driven scenario 2015-2100 and analyses UKESM1 simulations. We examine historical and projected periods and compare the model results to the long-term observations in the key Arctic straits. The difference between the present-day and future model transports is in their partitioning between Fram Strait: in the future most of the Atlantic model inflow occurs via the Barents Sea (5.2 Sv northwards); model 2000-2020s and 2040-2090s Fram Strait transports are 2.4 Sv and 4.6 Sv southwards. It is worth noting that the observed Fram Strait volume transport estimates bear a large uncertainty, from 2.0±2.7 Sv southwards from moorings to 1.1±1.2 Sv from inverse modelling and 0.8 ±1.5 Sv from geostrophic analysis.

The model results show that during the increase of CO2 in the 2040s–2060s, the Beaufort Gyre is getting stronger, whereas the North Atlantic Subpolar Gyre (SPG) weakens. At the carbon dioxide removal phase (2060s–2090s) the Beaufort Gyre is strengthened while SPG weakened further. However, the cyclonic gyres in the Nordic Seas (Greenland, Iceland and Norwegian) become stronger. This points to a potential future change in the oceanic pathways between the Arctic and the North Atlantic. The corresponding heat transports due to overturning and gyres present different trends in the North Atlantic and the Arctic Ocean and different reversibility at latitudes between 26°N and 80°N, suggesting loss of immediate oceanic connectivity between the Atlantic and the Arctic via Nordic Seas. The simulations show a hysteresis in the AMOC: AMOC does not recover to the same level as before the mitigation even if the atmospheric CO2 concentration does.

Acknowledgement: We acknowledge funding from the EC Horizon Europe project OptimESM “Optimal High Resolution Earth System Models for Exploring Future Climate Changes”, grant 101081193 and UKRI grant 10039429, from the project EPOC “Explaining and Predicting the Ocean Conveyer”, EU grant 101059547 and UKRI grant 10038003, as well as from NERC highlight topics 2023 project “Interacting ice Sheet and Ocean Tipping - Indicators, Processes, Impacts and Challenges (ISOTIPIC)”. For the EU projects the work reflects only the authors’ view; the European Commission and their executive agency are not responsible for any use that may be made of the information the work contains.

How to cite: Aksenov, Y. and Rynders, S.: Transports through the Arctic gateways linked to the ocean gyres in the Carbon Dioxide removal (CDR) CMIP6 simulations, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19583, https://doi.org/10.5194/egusphere-egu24-19583, 2024.

EGU24-19973 | ECS | Posters on site | OS1.1

Exploring links between Mixed-Layer depth and Sea Ice concentration variability in the Greenland Sea. 

Sonia Domingo, Joan Mateu Horrach, Alfredo Izquierdo, and Ángel Rodriguez

The Greenland Sea is a key player in the Atlantic Meridional Overturning Circulation (AMOC), crucial for forming dense waters through open-water convection and influencing global climate dynamics. Recent changes, such as decreasing sea ice concentration (SIC) and the shoaling of the mixed layer depth (MLD), have spurred detailed research into their impact on the AMOC. Our study, using the latest TOPAZ reanalysis, explores these changes from 1991 to 2021.

To strengthen our findings, we meticulously compare a 10-year observational dataset, validating TOPAZ's ability to reproduce processes like dense water formation and MLD evolution in the Greenland Sea. We find notable agreement, with the MLD reaching intermediate depths, and TOPAZ's overflow water density aligning with observations. Results show a decrease in SIC and a shallowing of the MLD, linked to rising surface water temperatures.

While our results indicate a similar trend, we're not ready to draw final conclusions. Further analysis is needed to understand how observational data compares to TOPAZ findings. Although reanalysis data provides valuable insights, it's crucial to validate everything with observational data. The comprehensive dataset and almost daily temporal resolution of our observational platforms significantly bolster the reliability of our conclusions.

Understanding Greenland Sea variability is vital not only for decoding its role in the AMOC but also for grasping broader implications for the global climate system. By highlighting the intricate relationship between SIC, MLD, temperature, and salinity, our research contributes to the ongoing dialogue on climate change dynamics.

 

How to cite: Domingo, S., Horrach, J. M., Izquierdo, A., and Rodriguez, Á.: Exploring links between Mixed-Layer depth and Sea Ice concentration variability in the Greenland Sea., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19973, https://doi.org/10.5194/egusphere-egu24-19973, 2024.

EGU24-20222 | ECS | Orals | OS1.1

Surface Controls of Freshwater Export through Denmark Strait  

Emma Boland, Yavor Kostov, and Dani Jones

Denmark Strait is a key route for the export of freshwater from the Arctic. Understanding the controls on the amount of freshwater entering the Subpolar North Atlantic is key for understanding the implications of rapid changes in the region, such as recent observed freshening of the Arctic Ocean. We present the results of an adjoint modelling study, which uses the ECCOv4 ocean state estimate to produce a reconstruction of the freshwater transport at Denmark Strait from 1992 to 2017. The reconstruction is formed of contributions from surface fluxes of buoyancy and momentum. We investigate the relative importance of these different contributions on different spatial and temporal scales. We find that surface wind stress at up to 2 years lag dominates variability. We also find a seasonally varying pattern in the dominant lags, with winter fluxes showing peak correlations with contributions from lags of up to 4 years, whereas spring fluxes showing a peak correlations on the scale of weeks.

How to cite: Boland, E., Kostov, Y., and Jones, D.: Surface Controls of Freshwater Export through Denmark Strait , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20222, https://doi.org/10.5194/egusphere-egu24-20222, 2024.

EGU24-20285 | Orals | OS1.1

Export of Greenland Sea Water across the Mohn Ridge as Measured by a Mooring during 2016–2018 

Jinping Zhao, Xusiyang Shen, and Tore Hattermann

Cold and dense water from the Greenland Sea, which has been found in the Lofoten Basin in the Norwegian Sea, is an important contributor to the Greenland–Scotland Ridge overflow, which feeds the deep and bottom waters in the North Atlantic. These two basins are divided by the Mohn Ridge, but there is no clear current connecting them. The aim of this study is to investigate how the Greenland Sea water enters the Lofoten Basin. We deployed a mooring on the western flank of the Mohn Ridge to measure the potential transport across the ridge during two periods: 2016/17 and 2017/18. The observation results indicate that the water above 1500 m in the Greenland Sea can be intermittently transported to the Lofoten Basin. In addition, we observed periods of flow reversal, which indicate bidirectional exchange between the two basins across the ridge. Our data from three consecutive seasons indicate that such inflows in August–September are a typical feature of the exchange across the Mohn Ridge. Net exports during these two periods into the Lofoten Basin were eltimated to be 5.86 Sv and 3.00 Sv, exhibiting noticeable interannual variations. We propose two possible mechanisms that could be driving the export. One is due to passing cyclones, which lower the sea level height along the Mohn Ridge and drive outflow. The second is due to the sudden weakening of the wind in summer, which results in outflow from the Greenland Sea through temporary geostrophic deviation.

How to cite: Zhao, J., Shen, X., and Hattermann, T.: Export of Greenland Sea Water across the Mohn Ridge as Measured by a Mooring during 2016–2018, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20285, https://doi.org/10.5194/egusphere-egu24-20285, 2024.

EGU24-20571 | Posters on site | OS1.1

A New Sea Ice Type Concentration Retrieval Algorithm from Microwave Remote Sensing Data 

Yufang Ye, Yanbing Luo, Mohammed Shokr, Zhuoqi Chen, and Xiao Cheng

Sea ice types, e.g., first-year ice (FYI) and multi-year ice (MYI), can be discriminated based on their radiometric and scattering signatures. However, changes in ice surfaces caused by factors such as ice deformation and melt-refreeze events can lead to extensive ice type misclassification. To solve this problem, a new sea ice type concentration (SITC) algorithm from microwave observations (SITCAM) is proposed in this study. It builds upon a previous algorithm, namely ECICE, but improves from two perspectives. Firstly, a new cost function is employed, with weights indicating the separation efficiencies of microwave parameters. Secondly, a pre-classification scheme is incorporated to account for the bimodal distributions in microwave characteristics. With SITCAM, daily Arctic SITCs are retrieved for the winters of 2002–2011 using passive (AMSR-E) and active (QuikSCAT and ASCAT) microwave data. The results are compared with a sea ice age product (SIA) and evaluated with ice type samples and SAR images. Overall, SITCAM performs well on mitigating the misclassifications induced by the aforementioned factors. The Arctic MYI area agrees well with that from SIA. Compared to ECICE, the retrieval accuracy for MYI and FYI samples increases to 96% and 90%, respectively (increasing by 5% and 15%, respectively), in SITCAM. The bias in MYI concentration between the SITC retrievals and SAR-based results has reduced from 15% to 4%. Furthermore, instead of being limited to specific observations (e.g., Ku-band scatterometer data), SITCAM performs well with various combinations of microwave data, even solely passive microwave data. This universality allows for a long-term record of SITC, which enables the potential of dating SITC back to late 1970s.

How to cite: Ye, Y., Luo, Y., Shokr, M., Chen, Z., and Cheng, X.: A New Sea Ice Type Concentration Retrieval Algorithm from Microwave Remote Sensing Data, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20571, https://doi.org/10.5194/egusphere-egu24-20571, 2024.

EGU24-3232 | Posters on site | AS4.2

A climatological satellite view of marine cold air outbreaks in the northeast Atlantic 

Abhay Devasthale and Michael Tjernström

Given the high rate of sea ice loss and the Arctic amplification, the dynamical processes responsible for airmass transport into or out of the Arctic, thus affecting the seasonal melt and recovery of sea ice, need to be understood and scrutinized from different observational perspectives. In a classical, rather binary view of transport “into or out of the Arctic”, a lot of attention in the recent years has rightfully been given on understanding the role of heat and moisture transport into the Arctic in regulating the sea ice melt. However, the cold and dry Arctic airmasses with long residence times are more than occasionally transported out of the Arctic over the open ocean waters, creating one of the most spectacular air mass transformations: the marine cold air outbreaks (MCAOs). The most tangible manifestation of MCAOs are the convectively rolled, narrow cloud streets formed over open water off the edges of the Arctic sea ice in the Nordic and Barents Seas, seen vividly in visible satellite imageries. MCAOs can also locally influence the onset of sea ice melt as they often happen in spring.  

By combining nearly 20 years of remotely sensed data from the hyperspectral Atmospheric Infrared Sounder (AIRS), the Moderate Resolution Imaging Spectroradiometer (MODIS) and the Clouds and the Earth’s Radiant Energy System (CERES) instruments onboard NASA’s Aqua satellite, this study presents a climatological view of the vertical structure of atmosphere and the cloud radiative effects during MCAOs in the northeast Atlantic.

How to cite: Devasthale, A. and Tjernström, M.: A climatological satellite view of marine cold air outbreaks in the northeast Atlantic, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3232, https://doi.org/10.5194/egusphere-egu24-3232, 2024.

EGU24-3662 | ECS | Orals | AS4.2

Non-conservative nature of Boron in low salinity Arctic ice and ice melt zones 

Samantha Rush, Chang-Ho Lee, Kitack Lee, Penny Vlahos, and Lauren Barrett

The Arctic Ocean is one of the most rapidly changing environments on the planet as sea ice extent and thickness have declined extensively over the last 40 years. It is predicted that by 2050, Arctic summers will become mostly ice-free, and the Arctic Ocean will be dominated by seasonally annual, rather than multiyear, sea ice. Arctic sea ice serves as a mediator of biogeochemical processes globally, though the impacts of increased ice melt and water column freshening on Arctic biogeochemistry are uncertain. Specifically, declining sea ice raises significant concerns regarding the future carbon uptake potential of the Arctic and the buffering capacity, or alkalinity, of seawater. Boron (B) is a major element in seawater, and in the form of the borate ion, it serves as the third largest contributor to alkalinity. Boron concentrations in the open ocean are typically conservative and accounted for through relationships with other water components, such as with salinity (S) in the boron to salinity ratio (B/S). Well established B/S ratios have been defined for the open ocean; however, salinity variability can create discrepancies in the open ocean boron corrections for alkalinity. In 2021, work in the marginal ice zone of the Bering and Chukchi Seas revealed non-conservative boron behavior and significant alkalinity system inaccuracies based on the deviation in computed B/S ratios in ice cores and brine. In this study, we investigate the B/S ratio in ice melt zone waters, snow, brine, annual, and multiyear sea ice from the eastern Arctic basin. A total of 169 samples were collected during the onset on melt (May-June 2023) on the ARTofMELT expedition across a range of salinities (2 - 63). High salinity samples (S>29) included 1 lead, 7 brine, 16 under-ice, and 28 open ocean water samples. Low salinity samples (S<29) included 1 brine, 10 snow, and 106 ice core samples. Excluding snow, results indicate deviations from the accepted open ocean B/S ratio (0.1336 mg/kg). For both the entire high salinity sample set and the open ocean subset within it, the B/S average value (0.1304 ± 0.001 mg/kg) was lower. For low salinity samples, the average B/S value (0.1328 ± 0.003) was higher than the high salinity sample value but still lower than the accepted field value. The range of B/S ratios was much larger in low salinity samples (0.1260-0.1425 mg/kg) than high salinity samples (0.1275-0.1350 mg/kg); however, both ranges were significantly smaller than the 2021 B/S ratio range (0.0900-0.1850 mg/kg). The smaller deviation from the accepted B/S ratio in this study resulted in carbon system analysis inaccuracies less than 2 µmol/kg across the entire salinity range. We present the computed B/S ratios and the differences in these datasets using the δ18O isotopic ratios to understand the heterogeneity of western, annual ice in the marginal ice zone and eastern, multiyear ice in pack ice regions. The marked distinction in the datasets allows potential insight into boron concentrations and the conversion of total alkalinity to carbonate alkalinity across current and future systemic climate-change shifts in the Arctic.

How to cite: Rush, S., Lee, C.-H., Lee, K., Vlahos, P., and Barrett, L.: Non-conservative nature of Boron in low salinity Arctic ice and ice melt zones, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3662, https://doi.org/10.5194/egusphere-egu24-3662, 2024.

EGU24-4403 | ECS | Posters on site | AS4.2

Near-surface particle concentration profiles above the Arctic sea ice 

Theresa Mathes and Andreas Held

The Arctic region is warming rapidly, and aerosol-cloud-sea-ice interactions are considered to be one of the key features of the Arctic climate system. It is therefore crucial to identify Arctic particle sources and sinks in order to study their impact on cloud formation and properties. Scott and Levin (1972) were the first to describe open leads as potential sources of atmospheric particles and thus a local source of particle emissions in the central Arctic. Held et al. (2011) found that open leads and ice ridges in particular emit high levels of particles. Particle concentrations have also been shown to be altered by the intrusion of warm and moist air masses and can be strongly enhanced in turbulence-dominated cases (You et al., 2022). Despite significant progress in Arctic research in recent years, there is still a lack of information on near-surface particle concentrations over different surface types, especially before and during the ice-melting period.

Here, we present measurements of near-surface particle concentration profiles to help to quantify the vertical aerosol exchange between Arctic sea ice and the atmosphere. In spring 2023, during the research cruise ARTofMELT on board the icebreaker Oden, we successfully carried out vertical particle measurements. From 17 May to 9 June 2023, near-surface particle concentration profiles were measured during 16 individual measurement periods. Due to the early season, measurements could be taken both before and during the melting process.

For the profile measurements, an aersol inlet was automatically moved up and down by a 1.50 m linear actuator. A plate was attached to the lift to hold sensors for the distance, wind and temperature as well as the aerosol inlet. An  box containing the condensation particle counter (CPC 3007, TSI, St. Paul, MN, USA) was connected to the inlet. Total particle number concentrations with a lower cut-off diameter of 10 nm were then determined at six different heights from 6 cm above the surface to 1.30 m. These measurements were carried out on the ice close to an open lead or surrounded by a closed ice surface.

Figure 1 shows an example for two days of fluxes at 79.8 ° N and 1.9° W. Due to the proximity to the open lead, an emission (red) of aerosols predominates, which is partially alternated by a deposition (blue). The flow calculations are based on 26 height profiles measured on 17 May and 24 on 18 May.

We thank our colleagues from Leibniz Institute for Tropospheric Research, Stockholm University, Swedish polar research secretariat as well as all expedition participants who provided insight and expertise that greatly assisted the research.

Held, A., Brooks, I.M., Leck, C., and Tjernström, M. (2011) On the potential contribution of open lead particle emissions to the central Arctic aerosol concentration. Atmos.Chem.Phys. 11, 3093-3105.
Scott, W. D. and Z. Levin (1972) Open channels in sea ice as ion sources. Science 177, 425-426.
You, C., Tjernström, M., Devasthale, A. (2022) Warm and moist air intrusions into the winter Arctic: a Lagrangian view on the near-surface energy budgets. Atmos.Chem.Phys. 22, 8037–8057.

How to cite: Mathes, T. and Held, A.: Near-surface particle concentration profiles above the Arctic sea ice, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4403, https://doi.org/10.5194/egusphere-egu24-4403, 2024.

EGU24-5124 | ECS | Orals | AS4.2 | Highlight

Is spring melting in the Arctic detectable by under-ice radiation? 

Philipp Anhaus, Christian Katlein, Marcel Nicolaus, Noémie Planat, and Martin Schiller

A trend towards earlier sea-ice melt is detected in many ice-covered regions in the Arctic. The timing of the melt onset has a strong impact on the sea-ice energy budget. Melt onset changes the radiative properties of the ice due to increasing snow wetness and meltwater. So far, satellite passive microwave data are used to detect the melt onset. We analyzed transmitted radiation spectra as collected underneath drifting sea-ice using a remotely operated vehicle during the ARTofMELT expedition in the Fram Strait in spring 2023. We colocated those spectra with measurements of snow depth, sea ice and surface topography, chlorophyll-a concentration in the water column, and with aerial images. This combined dataset enables us to track down possible subsurface pathways and accumulation pools of meltwater. Areas of low snow load and depressed surface topography are characterized by higher transmitted radiation compared to areas with a thick snow cover. Those areas overlapped with areas that showed the first signs of surface melt. Chlorophyll-a concentrations varied only slightly in magnitude and did not match with the heterogeneous pattern of snow depth and ice topography. Here we discuss how to disentangle the influences of chlorophyll a and the subsurface meltwater on the spectral shape of transmitted radiation. We propose that upon successful disentanglement, the spectra can be used as an indicator for subsurface melting. Our study suggests that sea-ice melting starts subsurface and that measurements of transmitted solar radiation spectra could be used to identify the melt onset prior to surface melting. This can provide an interesting complementary information on melt occurrence and on the location of the water in the snowpack in addition to satellite passive microwave data.

How to cite: Anhaus, P., Katlein, C., Nicolaus, M., Planat, N., and Schiller, M.: Is spring melting in the Arctic detectable by under-ice radiation?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5124, https://doi.org/10.5194/egusphere-egu24-5124, 2024.

EGU24-5372 | Orals | AS4.2

Impact of warm and moist intrusions on black carbon deposition and summer snow melt in the central Arctic 

Hélène Angot, Marion Réveillet, and Julia Schmale and the MOSAiC team

Warm and moist intrusions (WAMIs) into the central Arctic, predominantly observed in winter and early spring, are becoming more frequent, significantly affecting the region’s near-surface energy budget. This study focuses on the deposition pulses of black carbon (BC) triggered by WAMIs and their subsequent impact on snow properties and melting during the summer, using a modeling approach and comprehensive datasets from the 2019–2020 Multidisciplinary drifting Observatory for the Study of the Arctic Climate (MOSAiC) expedition. Our findings reveal that WAMIs induce episodes of intense BC wet deposition in the central Arctic shoulder season (Nov–Apr) due to transported pollution and moisture. We demonstrate that WAMIs result in exceptionally high BC deposition (> 4 orders of magnitude compared to typical winter/spring conditions) across an area of nearly 1 million km2, approximately 20% of the central Arctic Ocean. Furthermore, we establish a direct connection between these winter/spring BC deposition pulses and subsequent summer increases in absorbed solar energy (> 4 W/m2) and snowpack melt rate (+15%). Despite their sporadic occurrence (only 8% of the time), WAMIs play a significant role in the central Arctic surface energy budget through the BC snow albedo effect.

How to cite: Angot, H., Réveillet, M., and Schmale, J. and the MOSAiC team: Impact of warm and moist intrusions on black carbon deposition and summer snow melt in the central Arctic, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5372, https://doi.org/10.5194/egusphere-egu24-5372, 2024.

EGU24-5901 | ECS | Posters on site | AS4.2

Aerosol-Cloud-Precipitation Interactions in the Arctic: Insights from the ARTofMELT Campaign 

Lea Haberstock, Julia Asplund, Almuth Neuberger, Luisa Ickes, Gabriel Freitas, Fredrik Mattsson, Darrel Baumgardner, Ilona Riipinen, and Paul Zieger

Aerosol-cloud interactions play a crucial role in the Arctic’s radiative budget. During the campaign ‘Atmospheric rivers and the onset of sea ice melt’ (ARTofMELT 2023) we aimed to improve our understanding of aerosol-cloud interactions by conducting in-situ measurements of microphysical and chemical properties of aerosols, cloud droplets, and precipitation in the Arctic during the onset of sea ice melt. A ground-based fog and aerosol spectrometer (GFAS) and a fog monitor (FM-120) from Droplet Measurement Technologies (DMT) were used to measure among other things droplet size, number concentration, and liquid water content. Precipitation was measured with a meteorological particle spectrometer (MPS, DMT). Throughout the campaign, we observed several fog and blowing snow events, along with occasional precipitation. These events provided an opportunity to investigate and compare the distinctive microphysical properties associated with each event. Our findings reveal significant variations in the size distribution and particle phase of blowing snow, precipitation, and fog.

How to cite: Haberstock, L., Asplund, J., Neuberger, A., Ickes, L., Freitas, G., Mattsson, F., Baumgardner, D., Riipinen, I., and Zieger, P.: Aerosol-Cloud-Precipitation Interactions in the Arctic: Insights from the ARTofMELT Campaign, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5901, https://doi.org/10.5194/egusphere-egu24-5901, 2024.

EGU24-5950 | ECS | Posters on site | AS4.2

What we can learn from aerosol size distribution measurements over the spring Arctic pack ice 

Julia Asplund, Lea Haberstock, Jessica Matthew, Fredrik Mattson, Lovisa Nilsson, Erik Swietlicki, Megan Willis, Cort Zang, and Paul Zieger

Aerosol- cloud interactions remain among the most uncertain key parameters in the fast-changing Arctic climate system, in large part due to a lack of observational data from this hardly accessible region. The spring-summer transition is a particularly under sampled time period, due to harsh ice conditions. Here, we present five weeks of aerosol size distribution measurements over the spring Arctic pack ice, including more than 30 hours of in-cloud data, obtained during the ARTofMELT 2023 expedition. A setup of three inlets, including a whole-air, an interstitial, and a counterflow virtual impactor inlet, were used to cover the full aerosol population as well as both the activated and interstitial aerosol when in cloud. We will show an overview of the collected observations and the link between the size distribution properties and parallel measured aerosol parameters such as chemical tracers, as well as an air mass source analysis. Fog events were recorded during a range of aerosol conditions, allowing us to study the activated fraction when concentrations span from under 20 particles per cc, to over 150. The dataset also features several distinct regimes where different processes such as blowing snow, new particle formation, and secondary ice production dominate or influence the aerosol population, and we will demonstrate how the regimes are characterized by the dominant mode of the size distribution.

How to cite: Asplund, J., Haberstock, L., Matthew, J., Mattson, F., Nilsson, L., Swietlicki, E., Willis, M., Zang, C., and Zieger, P.: What we can learn from aerosol size distribution measurements over the spring Arctic pack ice, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5950, https://doi.org/10.5194/egusphere-egu24-5950, 2024.

EGU24-6663 | Orals | AS4.2

Perspectives on limitations and mechanisms for atmospheric initiation of onset of the summer melt season over sea ice 

Christopher Cox, Amy Solomon, Ola Persson, Matthew Shupe, Michael Gallagher, Von Walden, Michael Town, Donald Perovich, Sarah Webster, and Jacob Anderson

Onset of surface melt over sea ice is a factor in the duration of the melt season. Onset is often triggered by advection of warm, moist air from lower latitudes. This is especially characteristic of early dates of onset, but such events have also been hypothesized to precondition the ice for an earlier onset even when they don’t act as the trigger. The importance of atmospheric advection to the melt season is well-recognized by the community. Less attention has been given to the potential limitations of these events and to what alternate mechanisms may also be important for initiation, which is the subject of this presentation. We discuss two case studies.

In the first case, atmospheric advection from the North Atlantic in late May 2020 caused onset to occur over a wide area of the sea ice north of Greenland, including the floe being measured by the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition. Approximately 6 weeks prior, in April, an anomalously warm advection event also impacted the MOSAiC floe and was responsible for ~40% of the total warming the ice underwent that spring. Using a diffusion model for the ice forced by surface temperatures that both include (observationally) and exclude (synthetically) the April event, we show that its influence relative to its absence was reduced by ~80% within 10 days. The result is explained by a negative feedback that suppresses conduction within the ice when warming events occur. Consequently, despite the apparent influential nature of the April event suggested by the observations, the ice temperatures would likely have been similar several weeks before onset if the April event had not occurred. This implies there are limitations to such events in preconditioning the sea ice for early onset.

Our second case examines data collected from a buoy in the Beaufort Sea during a regional onset event observed in June 2022. In this case, the air that caused melt at the buoy came from the north during a period of generally zonal flow of the polar jet (and lack of poleward moisture transport). Analysis of back trajectories indicates that the air had a residence time in the Arctic of 7-10 days prior to causing melt. The air began at mid-tropospheric levels near the pole then circulated around persistent, large-scale high pressure over the East Siberian Sea, descending along its track. Reanalysis data suggests the adiabatic contribution to the subsidence was sufficient to warm the air to the freezing point when it reached the surface, moving southward across the Beaufort Sea. This case indicates that subsidence is a mechanism internal to the Arctic that is capable of causing melt onset, though its climatological significance remains an open question.

How to cite: Cox, C., Solomon, A., Persson, O., Shupe, M., Gallagher, M., Walden, V., Town, M., Perovich, D., Webster, S., and Anderson, J.: Perspectives on limitations and mechanisms for atmospheric initiation of onset of the summer melt season over sea ice, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6663, https://doi.org/10.5194/egusphere-egu24-6663, 2024.

EGU24-11158 | ECS | Orals | AS4.2

Synoptic situation during the ARTofMELT 2023 spring expedition 

Sonja Murto and Michael Tjernström

A 6-week long expedition ARTofMELT (Atmospheric rivers and the onset of Arctic sea-ice melt) with the Swedish Icebreaker Oden took place in the Arctic Ocean during late winter and spring of 2023. The aim was to collect observations and study processes leading up to the sea-ice melt onset. One of the targets was to assess the role of atmospheric rivers (ARs), i.e., southerly warm and moist-air injections, in advancing the melt-timing. This paper presents the synoptic situation during the expedition, based on observations measured onboard Oden and reanalysis data (ERA5). Additionally, the origin and paths of airmasses reaching Oden are determined using 7-day backward trajectories computed with the Lagrangian analysis tool LAGRANTO. The meteorological conditions were quite dynamic during these 35 days, strongly influenced by several (at least 6) surface cyclones passing Oden and only two warming events accompanied by rather weak ARs were observed, the latter one leading to the melt onset at the end of the expedition.

 

Based on meteorological conditions from 6-hourly launched radiosoundings, the expedition can be divided into six periods. The first short period encompasses the first days of the expedition, when Oden was located at the marginal ice zone. The winds were variable, mainly southerly, and it was moist with slightly below-freezing temperatures. As Oden was moving northwestwards, a one-week cold (~-15 - -10) and dry period followed. This period was mainly governed by northerly winds, guided by a persistent family of surface cyclones located over the Laptev and Kara Seas. The first major storm, that coincided with an atmospheric blocking over Scandinavia, was related to a cyclone forming to the southwest of Greenland and moving northeast, bringing winds over 25 m/s as it hit Oden on 13 May.  Northerly winds followed after the stormed had passed, guided by a surface pressure dipole between a high over Greenland and a low over the Arctic Ocean.

 

The first one-week long ice camp was built at the end of the second period, extending into the third period. A low-pressure over Greenland and high-pressure and an upper-level blocking over Scandinavia resulted in a pathway for a transient warm-air mass from the south, and melting was observed for the first-time. However, this warming was only temporary, as temperatures dropped below freezing after the AR had passed. Several weaker storms governed this third milder period, ending with the second major storm associated with a cyclone on 25 May. Again, winds turned northerly after the storm passed, which made the entry to the fourth longer, colder and drier period. The second 2-week long ice camp was established at the beginning of this period and expanded over the two last periods. These captured the forecasted (6 June) and the real melt onset (10 June). A surface pressure dipole with a high over Greenland and a low over the Arctic Ocean dominated at the beginning of the fifth period, and warm but dry air aloft was observed. As the winds turned southerly, the melt-onset period was characterized as warm and moist.

How to cite: Murto, S. and Tjernström, M.: Synoptic situation during the ARTofMELT 2023 spring expedition, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11158, https://doi.org/10.5194/egusphere-egu24-11158, 2024.

EGU24-11515 | ECS | Posters on site | AS4.2

Overview of SMÄLTA: Secondary Marine Aerosol precursors and Links to aerosol growth at ice-melT onset in the Arctic 

Cort Zang, Megan Willis, Julia Asplund, Fredrik Mattsson, Paul Zieger, and Michael Tjernström

The sources, composition, and reactive transformation of reactive organic carbon (ROC, non-methane organic carbon) as well as the processing, abundances, and distribution of organosulfur compounds in the Arctic marine atmosphere are unconstrained partially due to a lack of targeted measurements.  Understanding the emission, transport and processing of ROC and organosulfur compounds is important for improving our understanding of the impacts of gaseous precursors on aerosol nucleation and growth, and atmospheric oxidation capacity. There is a shift in aerosol size distribution that occurs with the Arctic spring-to-summer transition period and there are very few Arctic marine measurements of trace gases during this same period. Constraining the composition of organosulfur compounds and ROC is important for understanding the drivers in the shift of aerosol size distribution.

We present shipborne gas-phase measurements of ROC and organosulfur compounds in the Arctic marine atmosphere as part of the Atmospheric Rivers and the onseT of sea ice MELT (ARTofMELT) campaign. ARTofMELT took place from May 7th to June 15th of 2023 over pack ice and within the marginal ice zone between 78 and 81°N in the Fram Strait. We deployed a reagent ion switching chemical ionization mass spectrometer to target ROC and organosulfur compounds using H­3O+ ionization for the detection of reduced compounds and NH4+ ionization for the detection oxidized species. The measurements encompass a variety of different conditions including ozone depleted air masses (<10ppbv), cloud influenced air masses, a range of aerosol concentrations, and air masses with southern and northern airmass history with influences from biologically rich marine regions as well as transport from over pack ice. Additionally, measurements of ROC show the presence of ≥C5 organics in the environment with implications for aerosol size and growth. Here, we show an overview of our measurements and some initial observations of the ROC present during the campaign.

How to cite: Zang, C., Willis, M., Asplund, J., Mattsson, F., Zieger, P., and Tjernström, M.: Overview of SMÄLTA: Secondary Marine Aerosol precursors and Links to aerosol growth at ice-melT onset in the Arctic, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11515, https://doi.org/10.5194/egusphere-egu24-11515, 2024.

EGU24-12340 | ECS | Orals | AS4.2

Sea ice drift and wave pattern analysis of the early melt onset during the ARTofMELT cruise 2023 

Thibault Desjonquères, Leif E. B. Eriksson, Malin Johansson, Denis Demchev, Truls Karlsen, Timo Vihma, and Bing Cheng

In May-June 2023 the ARTofMELT 2023 expedition took place, with the aim to capture the melt onset in the Arctic Ocean. For the sea ice dynamics part of the cruise, in-situ observations were collected to co-inside with satellite observations, enabling studies of changes in drift patterns, capture the breakup of ice floes and studies of changes in backscatter signatures in satellite images as a consequence of melt onset. 

Seven OpenMETbuoys-v2021 and three SIMBA buoys, were placed on four first-year ice floes, away from the Marginal Ice Zone (MIZ). The OpenMETbuoys, equipped with GNSS (Global Navigation Satellite Systems), gyro, and accelerometer, facilitated horizontal motion, rotation, potential deformation, and wave action analysis. SIMBA buoys, with GNSS and thermistor strings, focused on temperature effects connected to melt onset. Three OpenMETbuoys and one SIMBA buoy were deployed on two larger floes. The two remaining drifters were deployed on individual floes. Deploying multiple buoys on each floe allowed detailed examination of small-scale drift changes, convergence, divergence, rotational patterns, frequencies, and connections to satellite Synthetic Aperture Radar (SAR) images. This deployment provides insights into the remaining wave energy in the pack ice. 

Low noise Radarsat Constellation Missions (RCM) SAR images in dual polarization (HH+VV or HH+HV) were acquired to overlap with the campaign in space and time. The temperature sensors onboard the SIMBA buoys enables us to connect changes in  backscatter values in the SAR images from the winter conditions into the early melt season and help define limitations for the SAR sea ice drift retrieval algorithm. 

Initial findings from wave and GNSS data offer insights into the condition of ice floes, including dislocation, disintegration, melting, and interactions with neighboring floes. The dislocation of the floes is indicated by the physical dissociation of the buoys present on the same floe. The OpenMETbuoys' recorded wave height and wave period indicate the drifter's location: on ice, in a transition phase on a small piece of ice or floating in the water between pieces of brash ice, or in open water.

Regarding the two bigger floes, on the first one, the drifters were launched 2023-05-22. An OpenMET drifter was dislocated from the rest of the floe on the 26th of May, and was in the transition phase on the 1st of July. The two remaining drifters were separated on the 29th of May. The last OpenMET drifter reached the transition phase on the 25th of May. The drifters on the second floe were launched 2023-05-28. The first dislocation occurred on the 8th of June, the second one on the 18th of June. The two remaining OpenMET drifters on this floe reached the transition phase on the 13th of June and 15th of June. The third floe contained a SIMBA drifter launched 2023-06-06 and the fourth one an OpenMETbuoy launched 2023-05-28. The latter reached the transition phase on the 10th of June.

How to cite: Desjonquères, T., Eriksson, L. E. B., Johansson, M., Demchev, D., Karlsen, T., Vihma, T., and Cheng, B.: Sea ice drift and wave pattern analysis of the early melt onset during the ARTofMELT cruise 2023, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12340, https://doi.org/10.5194/egusphere-egu24-12340, 2024.

EGU24-15627 | Orals | AS4.2 | Highlight

Arctic spring and the onset of sea-ice melt: Early impressions from the ARTofMELT expedition 

Michael Tjernström, Paul Zieger, and Sonja Murto and the ARTofMELT Science Team

The spring season in the Arctic Ocean has gained relatively little attention with detailed observations from expeditions, due to difficulties to navigate in the ice at this time of the year. This paper reviews experiences from the ARTofMELT (Atmospheric rivers and the onset of sea-ice melt) expedition in spring of 2023.

ARTofMELT had two objectives: To study processes leading up to the onset of the sea-ice melt and to explore links to so-called atmospheric rivers (ARs). ARs are spatially and temporally distinct inflows of warm and moist air from farther south. To fulfill these goals, we instrumented the Swedish research icebreaker Oden and planned to locate her in the Atlantic sector of the Arctic Ocean north of Svalbard from early May to mid-June. Oden was equipped with advanced meteorological instrumentation including standard meteorology and 6-horly radiosoundings, radar and lidars for cloud and wind measurements, and a surface flux tower with eddy-covariance. An advanced suite of atmospheric chemistry and aerosol observations were also deployed along with water isotope measurements, and also sampled and profiled the upper ocean structure. To identify upcoming ARs, we used ensemble forecasts from the European Centre for Medium-Range Weather Forecasts (ECMWF) at lead time up to seven days, to allow time to navigate the icebreaker to optimal positions and establish ice camps. While carrying out most of the observations on board, in-situ observations on the ice provide valuable details on the impact of ARs on the ice. On ice camps we therefore deployed a surface energy budget station and an ROV surveying the ice from below and also flew a tethered balloon HELIKITE system from the aft of the ship. Additionally, we also used the helicopter to deploy scientists on the ice (sampling snow, ice and water) and deploying buoys, and for flying the HELIPOD instrument package.

ARTofMELT left Svalbard on 8 May and returned on 15 June. Starting with quite cold later winter conditions there was a brief warming period around mid-May, with an AR that brought air temperatures above the melting point twice (19 and 20 May). This was interrupted by a major storm, followed by a cooler period. From the end of May the surface started to gain heat, culminating in the onset of the melt at a second AR on 10 June. Both ARs were documented from ice stations.

A major uncertainty was the navigation in the ice during late winter and this also tuned out to be the most difficult part of the deployment. The ice was thick and hard to break, the size of the largest ice floes was much larger than expected and short-term variations of the ice pressure made navigation very difficult. The maximum latitude obtained was ~80.5 °N, hence, we stayed in the Fram Strait ice pack. Also, only two brief ARs were encountered, less than expected. In spite of this we were able to gain a large amount of unique observations, both from the icebreaker when in transit and from two ice camps.

How to cite: Tjernström, M., Zieger, P., and Murto, S. and the ARTofMELT Science Team: Arctic spring and the onset of sea-ice melt: Early impressions from the ARTofMELT expedition, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15627, https://doi.org/10.5194/egusphere-egu24-15627, 2024.

EGU24-17193 | ECS | Orals | AS4.2

The composition and sources of airborne bacteria and proteinaceous Ice Nucleating Particles in the High Arctic marine region during Spring 

Jennie Spicker Schmidt, Marianne Glasius, Camille Mavis, Jessie Creamean, Gabriel Freitas, Paul Zieger, Kai Finster, and Tina Šantl-Temkiv

The Arctic is a particularly vulnerable region on Earth, where climate change takes place at an intense pace. Clouds represent an essential element within the Arctic atmosphere and play a crucial role in the regional radiative balance. The physical properties of clouds are tightly interlinked with the presence of aerosols that can serve as cloud condensation nuclei (CCN) and as ice nucleating particles (INPs), which facilitate the formation of cloud droplets and ice crystals, respectively. Consequently, they affect cloud thickness, lifetime, and albedo.

More studies propose that various biological aerosols e.g., aerosolized microbial cells, proteinaceous compounds and fragments actively contribute to cloud processes serving as INPs active at high subzero temperatures (>-15°C). However, our understanding of microorganisms responsible for producing compounds serving as INPs, their source environments, and their level of activity, remains highly uncertain.

Given the profound impact of climate change in the Arctic region, understanding the role of biological INPs in the atmosphere becomes particularly critical during Arctic melt season. Here, we present an overview of bioaerosol observations and sources tracking from the recent Arctic expedition ”Atmospheric rivers and the onset of Arctic melt” (ARTofMELT 2023).

Biological INPs are thought to originate from the ocean and meltwater sources during the Arctic Spring and Summer. To assess the potential contribution of these sources to INP active aerosols, aerosols were generated from bulk seawater and sea ice melt water with a temperature-controlled sea spray simulation chamber. The presence of microorganisms in the bulk water and aerosol was quantified using flow cytometry and qPCR while the composition of the microbial communities was determined by amplicon sequencing. Additionally, fluorescent bioaerosols generated by the chamber were  analyzed using a Multiparameter Bioaerosol Spectrometer (MBS). Simultaneously, ambient air samples were analyzed for the presence of microbial cells, bioaerosols, and the composition of the collected microbial community. The ice nucleating properties of water, sea ice melt, and aerosols from the chamber and ambient aerosol were also measured to determine their relevance for Arctic cloud formation.

Preliminary results from the ambient measurements revealed low concentrations of airborne bacterial cells and highly active INPs. From the sea spray simulations, we found that ice melt, snow melt and seawater samples generated a high flux of bacterial cells which were accompanied by INPs active predominantly at low freezing temperatures (<-15°C). Therefore, it seems that the local sea spray is not a likely source of proteinaceous INPs detected in the Arctic spring atmosphere, which will be further explored through bacterial community analysis. Our results will thus provide comprehensive insights into the contribution of local and long-range transported sources of bioaerosols to the Arctic.

How to cite: Schmidt, J. S., Glasius, M., Mavis, C., Creamean, J., Freitas, G., Zieger, P., Finster, K., and Šantl-Temkiv, T.: The composition and sources of airborne bacteria and proteinaceous Ice Nucleating Particles in the High Arctic marine region during Spring, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17193, https://doi.org/10.5194/egusphere-egu24-17193, 2024.

EGU24-17589 | Posters on site | AS4.2

Intense formation of low liquid clouds over the Arctic sea-ice during May.   

Jean Lac and Hélène Chepfer

Low-liquid stratiform clouds are ubiquitous in the Arctic. Their high surface longwave warming induces change in the surface radiative budget that might have effects on the sea-ice melt especially during transitioning seasons. In particular, low liquid clouds formed in Spring may trigger early melt onset that might have an impact on the following evolution of the sea-ice during summer. 

However, relatively little is known about the existence and the drivers of such clouds in the early melt season. Here we used 13 years of space based lidar cloud profile observations with complementary data to show that the predominance of low clouds happens in May. First, we showed that the low cloud fraction reaches 75% of the Arctic Ocean in May over the sea-ice only with a low interannual variability. This cover increase in May seems to be homogeneous over the whole Arctic Ocean. Second, we investigated potential early summer drivers forming those low liquid clouds. One feature is the moisture sources that could explain the availability of such liquid droplets to form liquid clouds. While the other feature is the boundary layer structure, that might affect the stability and the ocean/atmosphere interaction over sea-ice leads.  

Overall, this study suggests a peak of Arctic low liquid clouds occurring in May that might impact the sea-ice summer melt by triggering early Spring melt. 

How to cite: Lac, J. and Chepfer, H.: Intense formation of low liquid clouds over the Arctic sea-ice during May.  , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17589, https://doi.org/10.5194/egusphere-egu24-17589, 2024.

EGU24-17977 | ECS | Posters on site | AS4.2

Springtime observations of black carbon aerosols in and outside of low-level Arctic clouds 

Lovisa Nilsson, August Thomasson, Paul Zieger, Julia Asplund, Pontus Roldin, Fredrik Mattson, Erik Ahlberg, and Erik Swietlicki

Few expeditions have ventured into the Arctic to observe the processes that take place in the transition from winter to summer. Particularly, direct observations of aerosol-cloud interactions are scarce, and comprise a large source of uncertainty in radiative forcing estimations in the Arctic.

Light absorbing aerosol particles, such as black carbon (BC) from incomplete combustion, exert a positive forcing upon direct absorption of sunlight, and affect clouds by serving as cloud condensation nuclei (CCN). During the icebreaker expedition ARTofMELT in spring 2023, we measured BC with a multi-angle absorption photometer (MAAP) and a single particle soot photometer (SP2) for five weeks. The two instruments differ by principle and can be used to inform on complementary aspects of the light absorbing aerosol. For example, the MAAP provides the total mass concentrations of so-called equivalent BC (eBC), whereas the single particle instrument SP2 determines the mass of individual refractory BC (rBC) aggregates. Most of the time, the MAAP and SP2 sampled the total BC concentration on the same inlet (whole-air). However, during cloud-events, the SP2 measured downstream of a counterflow virtual impactor (CVI) inlet that samples just cloud droplets or ice crystals without the interstitial or non-activated aerosol.

Our first results indicate overall low out-of-cloud BC mass concentrations for both instruments (median and interquartile range, IQR: 4.4 (1.6-8.5) ngm-3 for the MAAP and 2.5 (1.2-4.7) ngm-3 for the SP2). The variation in mass concentration was small, although the tendency of a gradual decrease was observed towards the onset of the melt.

The SP2 instrument enables studies of the BC mass size distribution. For example, during a cloud event we observed that the geometric mean diameter (GMD, mass equivalent diameter) shifted from smaller (171 nm, whole-air inlet) to larger sizes (175-192 nm), as the SP2 switched to sampling the cloud-residual BC (CVI inlet). Further investigation is needed to examine the underlying causes for this observation (e.g. variation in airmass origin). 

The total aerosol concentration is influenced by local natural sources and production from gaseous precursors, as opposed to the BC concentration which is mainly affected by anthropogenic activities. BC source footprints from the Lagrangian dispersion model FLEXPART, indicate little influence from industrialized regions during the whole campaign. This may explain the comparably low median concentration of rBC-particles (1.1 cm-3, IQR: 0.5-2.1) to the total aerosol number concentration (in the range ~20-150 cm-3).

How to cite: Nilsson, L., Thomasson, A., Zieger, P., Asplund, J., Roldin, P., Mattson, F., Ahlberg, E., and Swietlicki, E.: Springtime observations of black carbon aerosols in and outside of low-level Arctic clouds, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17977, https://doi.org/10.5194/egusphere-egu24-17977, 2024.

EGU24-19851 | ECS | Orals | AS4.2

Characteristics of natural Arctic aerosols emitted from a wide range of local sources during ARTofMELT2023 

Gabriel Freitas, Kouji Adachi, Julia Asplund, Jessie Creamean, Fredrik Mattsson, Camille Mavis, Lovisa Nilsson, Matthew Salter, Jennie Spiecker Schmidt, Tina Šantl-Temkiv, and Paul Zieger

The Arctic has been experiencing a rise in ambient temperature several times higher than the global average. This warming trend has led to a continuous decline in sea ice coverage and snowpack prevalence. Aerosol sources, such as those from the open ocean and tundra, have become more prevalent throughout the year. These sources emit primary biological aerosol particles (bioaerosols) some of which exhibit ice nucleating properties at high temperatures (>-15C). Ice nucleating particles (INPs) play a crucial role in cloud ice formation, affecting cloud physical and optical properties, as well as their lifetime. Consequently, this has a substantial impact on the Arctic climate. 

During the ARTofMELT2023 expedition (“Atmospheric Rivers and the Onset of Sea Ice Melt 2023”) conducted aboard the Swedish icebreaker Oden in the Atlantic sector of the Arctic Ocean, we assessed the relative importance of several natural bioaerosol sources, such as sea ice, snow melt (to simulate melt ponds) and bulk ocean water. This involved several sea spray simulation chamber and nebulizer experiments, referred to as “source experiments”. The aerosol particles generated in the 61 source experiments conducted were analyzed using single-particle ultraviolet fluorescence spectroscopy along with other complementary aerosol measurements. These included particle size, black carbon content, particle chemical composition, as well as the microbial community and INP concentration of emitted particles. Additionally, filter samples were obtained for transmission electron microscopy (TEM) analysis. 

Our findings indicate that sea ice and snow melt are more significant sources of bioaerosols compared to the bulk ocean water, including the sea surface microlayer, indicating the potential importance of melt ponds as a local Arctic bioaerosol source. Furthermore, we found significant differences in the chemical composition, black carbon content and size distribution of the various analyzed aerosol sources.

How to cite: Freitas, G., Adachi, K., Asplund, J., Creamean, J., Mattsson, F., Mavis, C., Nilsson, L., Salter, M., Spiecker Schmidt, J., Šantl-Temkiv, T., and Zieger, P.: Characteristics of natural Arctic aerosols emitted from a wide range of local sources during ARTofMELT2023, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19851, https://doi.org/10.5194/egusphere-egu24-19851, 2024.

EGU24-19946 | Orals | AS4.2 | Highlight

Helicopter borne measurements during melt onset in the Fram strait as part of ARTofMELT23 

Falk Pätzold, Lutz Bretschneider, Magnus Asmussen, Barbara Altstädter, Evelyn Jäkel, Hendrik Stapel, Tim Sperzel, Manfred Wendisch, Birgit Wehner, Ralf Käthner, and Astrid Lampert

In the Arctic climate system, the onset of melting is a crucial point, and timing is still difficult to predict. Therefore, the expedition ARTofMELT was dedicated to exploring atmospheric conditions and processes that are involved in triggering the onset of melting.

The helicopter borne sensor system HELIPOD was deployed in this expedition to measure the spatial variability of atmospheric dynamics, radiation, aerosols, trace gases and surface properties on a horizontal scale up to 40 km around the icebreaker ODEN. During the ARTofMELT23 expedition, the HELIPOD conducted 12 measurement flights in the FRAM strait around 80° North and the prime meridian between 9 May and 9 June 2023 with 26.5 hours in the air. The flights covered an area of about 20 NM around the location of the icebreaker ODEN and a vertical range from 50 m to 2700 m above sea level. The flight patterns were aligned parallel and perpendicular to dominating directions as the sea ice edge and the wind direction. In one case a cloud layer edge apparently structured the atmospheric situation. The flights covered pre-melt onset conditions, refreezing situations and the melt onset. Synoptic air mass changes were probed as well.    

The presentation gives an overview of the temporal changes of the ambient conditions during the research flights, and a first assessment of the flights during transient weather situations.

How to cite: Pätzold, F., Bretschneider, L., Asmussen, M., Altstädter, B., Jäkel, E., Stapel, H., Sperzel, T., Wendisch, M., Wehner, B., Käthner, R., and Lampert, A.: Helicopter borne measurements during melt onset in the Fram strait as part of ARTofMELT23, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19946, https://doi.org/10.5194/egusphere-egu24-19946, 2024.

EGU24-20594 | Posters on site | AS4.2

Sea ice, snow caps, and freshwater lenses: The hurdles local Arctic aerosols must overcome to become airborne 

Jessie Creamean and the MOSAiC and ARTofMELT field teams

Aerosol particles and clouds play a critical role in regulating radiation reaching the Arctic, which is warming faster than anywhere else globally. However, the magnitude of their effects is not adequately quantified, especially in the Arctic Ocean over sea ice. Specifically, particles generated from open leads, melt ponds, and the snow-covered sea ice surfaces remain poorly understood, yet could have significant impacts on cloud condensation nuclei (CCN) and ice nucleating particle (INP) concentrations, and thus, central Arctic cloud formation. While marine biological processes have been demonstrated to be potentially key primary aerosol sources in the Arctic summer, exact sources and emission processes of these particles remain highly uncertain. 

For this presentation, we provide an overview of aerosol observations from two recent Arctic field campaigns: the 2019–2020 Multidisciplinary drifting Observatory for Study of Arctic Climate (MOSAiC) and the 2023 Atmospheric rivers and the onset of Arctic melt (ARTofMELT) expeditions. We highlight preliminary findings focused on aerosols that have the potential to impact cloud phase and lifetime over the Arctic Ocean, specifically those from local sources in the early spring and summer melt periods. The evolution of open water within the pack ice in late spring and the Arctic melt season coincides with an increase in aerosol particle concentration, which may be attributed to biological activity within seawater and sea ice. However, the emission of aerosol particles is contingent on features like open leads and melt ponds, and whether they are covered by snow, freshwater melt layers, or ice lids. This integrative study involves the use of detailed aerosol, meteorological, oceanographic, and sea ice observations from MOSAiC and ARTofMELT. Overall, this work will enable us to assess local aerosol processes associated with cloud formation to better understand the Arctic system through a holistic approach.

How to cite: Creamean, J. and the MOSAiC and ARTofMELT field teams: Sea ice, snow caps, and freshwater lenses: The hurdles local Arctic aerosols must overcome to become airborne, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20594, https://doi.org/10.5194/egusphere-egu24-20594, 2024.

EGU24-21926 | Posters on site | AS4.2

Water Isotope measurements contribute to the understanding of atmospheric, sea ice, ocean interactions during the ArtofMelt expedition, Fram Strait, spring 2023 

Jeff Welker, Ben Kopec, Eric Klein, Julia Muchowski, Timo Vihma, Paul Zieger, Falk Paetzold, Astrid Lampert, Penny Vlahos, John Prytherch, Valtteri Hyöky, and Truls Karlsen

Transitions periods between seasons in the Arctic are phases when the atmosphere-sea ice-ocean interactions are heightened, especially during these periods of exceptional warming.  These transition periods may be accompanied by shifts in atmospheric transport patterns, the distribution of sea ice and extreme events, such as atmospheric rivers.  Atmospheric Rivers may act as accelerants of sea ice melt and its redistribution, leading to spatial complexity in ice-ocean-atmosphere exchanges of mass and energy.

As part of an interdisciplinary team aboard the I/B Oden from early May to mid-June, four main water isotope measurement packages were collected to maximize collaborations and to resolve nuisances of the Arctic System throughout the cruise track between Svalbard and NE Greenland (Figure 1).  First, in order to delineate longitudinal distribution of the warm and salty W Svalbard current compared to the cold and fresh E Greenland current, we continuously measured the near surface water δ18O, δ2H and d-excess values. Second, in order to source water vapor and moisture sources from the warm, moist, and isotopically enriched subpolar & N Atlantic, compared to cold, dry and isotopically depleted Arctic air, we also continuously measured the δ18O, δ2H and d-excess values of water vapor collected from the ship’s, bow-mounted, eddy covariance tower. Third, in order to understand the horizontal and altitudinal patterns of water vapor parcels that surround the ship; in-situ water vapor isotopes were measured during fHeliPod flight lines that extended up to 30 km N-S-E-W of the Oden and from ~ 50 m above the sea ice and open water to over 2k in altitude.  Fourth, in order to delineate the source of moisture (sea water vs. meteoric water) throughout the sea ice core profiles and the patterns and sources of moisture in the snow pack profiles; ice cores and snow pits were collected (drilled) and dug at ~10 different locations and water isotope samples were analyzed for δ18O, δ2H and d-excess values back in the laboratory.

Four major discoveries will be presented: A) mixing of the surface W Svalbard and NE Greenland current is found to be farther east than previously reported and the surface water masses may differ by up to 5 ‰ δ18O during spring; B) water vapor isotopes responded at hourly time scales as moisture sources during Atmospheric River events begin with northward fluxes of warm, moist air masses but passing cyclones deliver N-S cold-dry, isotopically depleted water vapor in extreme Arctic-sourced storm events lasting a day or more; C) Horizontal and vertical transects during Heliopod flights captured horizontal and altitudinal variation in water vapor isotopes during periods when the weather of the ship was dominated by cold-dry Arctic air, interrupted by periods when the ship was experiencing pulses of warm, moist, and high humidity conditions; D) ice cores and snow packs exhibit vertical isotopic variation indicative of different moisture sources and morphogenesis processes.

How to cite: Welker, J., Kopec, B., Klein, E., Muchowski, J., Vihma, T., Zieger, P., Paetzold, F., Lampert, A., Vlahos, P., Prytherch, J., Hyöky, V., and Karlsen, T.: Water Isotope measurements contribute to the understanding of atmospheric, sea ice, ocean interactions during the ArtofMelt expedition, Fram Strait, spring 2023, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21926, https://doi.org/10.5194/egusphere-egu24-21926, 2024.

CR4 – Frozen ground, debris-covered glaciers and geomorphology

EGU24-1475 | ECS | Orals | CR4.1

The impact of climate change on mercury in permafrost: insights from the ORCHIDEE-MICT-PEAT-LEAK model  

Laura Sereni, Bertrand Guenet, and Hélène Angot

Arctic permafrost, with inherent low microbial activity, has historically immobilized soil organic matter (OM) and other substances such as mercury (Hg). Derived from both natural sources (e.g., forest fires, volcanism) and human activities, Hg is a highly toxic contaminant.

As permafrost thaws, microbial activity reactivates, leading to the degradation of soil OM. Simultaneously, Hg, once sequestered with OM, is released into the environment. However, the extent of Hg remobilization and its subsequent fate remain uncertain. To address this knowledge gap, we are developing a continental model that focuses on the fate of Hg, particularly from permafrost, within the context of Arctic climate change.

Given the strong affinity of Hg to OM, their cycles within the terrestrial biosphere are intricately interconnected. Leveraging the foundational framework of the ORCHIDEE land surface model, which mechanistically represents the production, transport, and transformation of organic carbon in soils and permafrost, we are integrating the Hg cycle.

This model will be evaluated using available observational data, including soil cores with vertical and latitudinal gradients, as well as measurements of Hg riverine exports on a pan-Arctic scale. Then, the model will be used to estimate the quantities of Hg emitted into the atmosphere and rivers during permafrost thawing, along with the associated timing. Different climate change scenarios from CMIP6 will be used to assess the sensitivity of permafrost thaw and Hg emissions to varying climatic conditions.

How to cite: Sereni, L., Guenet, B., and Angot, H.: The impact of climate change on mercury in permafrost: insights from the ORCHIDEE-MICT-PEAT-LEAK model , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1475, https://doi.org/10.5194/egusphere-egu24-1475, 2024.

EGU24-2100 | ECS | Posters on site | CR4.1

The start of frozen dates over northern permafrost regions with the changing climate 

Jialing Li, Chaoyang Wu, Josep Peñuelas, Youhua Ran, and Yongguang Zhang

Climate warming exerts important impacts on the freeze-thaw cycle in permafrost regions. Although increasing attention has been paid on understanding the responses of spring thawing to climate change, the mechanisms controlling the global interannual variability of the start date of permafrost frozen (SOF) remain unclear. Using long term SOF derived from the freeze–thaw Earth system data record (FT-ESDR) over 1979-2020, and analytical techniques, including partial correlation, ridge regression, path analysis, the Random Forest (RF) and SHapley Additive exPlanations (SHAP), we explored the responses of SOF to multiple climate factors, including warming (surface and air temperature), start date of permafrost thawing (SOT), soil properties (soil temperature and volume of water), and the snow depth water equivalent (SDWE). In summary, while climate warming exerted predominant influence on SOF, SOT in spring also played a significant role in shaping SOF variability. Among the observed 65.9% significant correlations between SOT and SOF, 79.3% were positive, indicating that an earlier thawing would contribute to an earlier frozen in winter. Machine learning analysis reinforced the significance of SOT as the second most crucial determinant of SOF. To elucidate the mechanism behind the SOT-SOF relationship, path analysis was employed, revealing that changes in soil temperature had the maximum impact on this relationship, irrespective of the permafrost type. Finally, we analyzed the temporal changes in these responses using the moving window approach and found an increasing influence of soil warming on SOF. In conclusion, these findings offer valuable insights for understanding and predicting variations in SOF in the context of future climate change.

How to cite: Li, J., Wu, C., Peñuelas, J., Ran, Y., and Zhang, Y.: The start of frozen dates over northern permafrost regions with the changing climate, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2100, https://doi.org/10.5194/egusphere-egu24-2100, 2024.

Qinghai-Tibet Plateau (QTP) is the largest permafrost region among middle- and low-latitude regions in the world. Permafrost in QTP is dominated by unstable and climate-driven. It is especially vulnerable to climate change and ecosystem disturbances (both natural and human). Currently, more than 9389 km of roads, 580 km of railways, 2631 km of power lines, and 1064590 m2 of buildings are located in the QTP permafrost area. Depending on altitude, the warming rate of the QTP has been twice the global average in recent decades and in the foreseeable future. Climate change-induced permafrost degradation can seriously threaten the stability of infrastructure and thus increase the infrastructure repair and replacement frequency. The consequence can be expressed as the shortening of useful life and increases maintenance costs, leading to diverse financial risks. The damage to infrastructure caused by near-surface permafrost degradation is directly related to the well-being of 10 million people and the sustainable development on the Qinghai-Tibet Plateau, the Third Pole of the Earth. Here we identify the economic damage caused by permafrost degradation to infrastructure on the Qinghai-Tibet Plateau by integrating data-driven projection, multihazard index, and lifespan replacement model. We found that additional cost of approximately $6.31 billion will be needed to maintain the service function of current infrastructure under the historical scenario (SSP245) by 2090. While 20.9% of these potential costs can be saved with strategic adaptations. Controlling global warming to below 1.5 °C will reduce the costs by $1.32 billion relative to the 2 °C target of Paris Agreement. These findings highlight the importance of mitigating global warming and of investment in the adaptation and maintenance of infrastructure on the Qinghai-Tibet Plateau, which has a sparse population but is a climate hotspot.

How to cite: Ran, Y., Li, X., and Cheng, G.: Permafrost degradation increases risk and large future costs of infrastructure on the Qinghai-Tibet Plateau, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2508, https://doi.org/10.5194/egusphere-egu24-2508, 2024.

EGU24-4217 | Orals | CR4.1

Permafrost stability in and around three North Slope Borough communities in Alaska 

Vladimir Romanovsky, Dmitry Nicolsky, Louise Farquharson, Sergei Rybakov, and Thomas Wright

The impact of climate warming on permafrost and the potential of climate feedback resulting from permafrost thawing have recently received remarkable attention. Climate warming promotes an increase in permafrost temperature and active layer thickness, which, in turn, affect the stability of northern ecosystems, threaten infrastructure, and cause the release of carbon dioxide and methane into the atmosphere. The timing and the rate of permafrost degradation are two of the major factors in determining the anticipated negative impacts of climate warming on the Arctic ecosystems and infrastructure. The results of permafrost and active layer temperature observations (from the ground surface down to 1.5 m) at the three North Slope Borough communities of Point Lay, Wainwright, and Utqiagvik will be presented in this paper. Ground temperatures were measured both in natural conditions around the villages and under residential and commercial buildings to estimate the impact of infrastructure on permafrost stability. Generally, for all three villages, permafrost is still thermally stable. The mean annual ground temperature at 1.5-m depth is typically below -4°C for both natural conditions and under the elevated above ground engineering structures. One of the exceptions is thermokarst depressions such as deep troughs or ponds filled with water within and outside of the village of Point Lay. The mean annual water temperature at the bottom of some of these ponds with the water depth more than 0.5 m approaches the 0°C threshold, and in some cases even exceeds it, which can trigger development of a talik under these depressions. This may accelerate permafrost degradation at these locations with certain negative consequences for the stability of the village infrastructure and may manifest in numerous hazards for the residents. The methods of stabilization of permafrost and mitigation of adverse impacts of permafrost degradation will be discussed in this presentation. To enhance our understanding of possible future rates and pathways of permafrost degradation and to predict the consequences to residents, accurate high spatial resolution permafrost models are needed. Establishment of these models is possible only by integrating available high-resolution environmental data and by the assimilation of existing field and remote sensing data and observations into these models. The use of high-resolution (30x30 m) stand-alone permafrost dynamics GIPL2 model will be discussed to illustrate how changes in climate and further development of infrastructure will affect permafrost and people in this area.

How to cite: Romanovsky, V., Nicolsky, D., Farquharson, L., Rybakov, S., and Wright, T.: Permafrost stability in and around three North Slope Borough communities in Alaska, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4217, https://doi.org/10.5194/egusphere-egu24-4217, 2024.

EGU24-4225 | ECS | Posters on site | CR4.1

Tracking permafrost thaw using iron as a geochemical tracer for climate change 

Amanda Barker, William Baxter, Robyn Barbato, Taylor Sullivan, and Thomas Douglas

Arctic ecosystems are changing as a result of climate warming, altering soil thermal and moisture regimes and contributing to permafrost thaw, which impacts the biogeochemistry of terrestrial and aquatic environments. This occurs across broad scales of space and time. Assessing how and to what extent thawing permafrost impacts soils, sediments, and aquatic environments is integral to constraining greenhouse gas emission estimates, microbial diversity, vegetation succession, and water quality, but quantifications remain difficult to assess on a landscape-scale. When top-down thaw of near-surface permafrost occurs porewaters infiltrate deeper and expose fresh, previously frozen material. This input of oxygenated water greatly alters the oxidation/reduction (redox) conditions, which are intricately tied to soil moisture/temperature, ionic strength, and play a critical role in carbon release. Using optical sensors, satellite and unmanned aerial surveys, and bulk- and micro-scale analytical techniques, we present a comprehensive approach for tracking iron concentrations and redox conditions in permafrost regimes in the Arctic. Overall, we found evidence that iron (Fe) and to a lesser extent manganese (Mn) could be useful as geochemical indicators of permafrost thaw and release of Fe(II) from thawing permafrost and further oxidation to Fe(III) could translate to a higher degree of seasonal rusting coinciding with the warming and thawing of near surface-permafrost.

How to cite: Barker, A., Baxter, W., Barbato, R., Sullivan, T., and Douglas, T.: Tracking permafrost thaw using iron as a geochemical tracer for climate change, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4225, https://doi.org/10.5194/egusphere-egu24-4225, 2024.

EGU24-4466 | Orals | CR4.1

Mercury, carbon, and nitrogen characteristics of Permafrost From 40,000 years old to modern age in Interior Alaska 

Thomas Douglas, Amanda Barker, Arthur Gelvin, David Brodylo, and Jens Strauss

Permafrost soils contain twice as much carbon as earth’s atmosphere and almost twice as much mercury as is stored in the total of all other soils, the ocean, and the atmosphere (Schuster et al., 2018). Significant nitrogen stocks have also been identified in permafrost (Strauss et al., 2022). The CRREL Permafrost Tunnel near Fairbanks, Alaska provides access to 500 meters of 40,000 year syngenetic permafrost. This is predominantly ice and carbon rich loess with ice wedges, segregated ice, and some large thermokarst cave ice features that are attributed to sudden permafrost thaw. The walls and ceiling of the Tunnel provide ready access to these varied permafrost soil and ice types. Above the Tunnel modern syngenetic permafrost is accessible via trenching and coring.

We surveyed the entire surface area of the walls and ceiling of the Tunnel with light distance and ranging (LiDAR). Return intensity values from different laser wavelengths allowed us to quantify exposed ice features versus ice cemented silt. Full LiDAR coverage of the entire tunnel interior after all artificial, floor, and extreme values were removed totaled 10,753,495 individual points. From this, we calculate 90.5 % of the surface area of the Tunnel walls and ceiling are represented by ice cemented silt and gravel and the remaining 9.5 % are ice features. Of the ice, 89.9 % are ice wedges and 10.1 % is thermokarst cave ice.

Based on these measurements, we collected roughly 80 SIPRE cores of frozen silt and ice features in the Tunnel and from modern permafrost above the Tunnel. Thawed soil and water ice were analyzed for major ions, trace metals, stable water isotopes, and carbon and nitrogen.

Major ion and trace metal concentrations are higher in ice wedges than replacement thermokarst cave ice. Mercury concentrations in ice cemented silt (n=28; 42.9 ng/g +/- 11.0), ice wedges (n=32; 54.0 ng/g +/- 16.3), thermokarst cave ice (n=17; 32.5 ng/g +/- 20.0), and the active layer above the Tunnel (n=5; 47.4 ng/g +/- 10.8) are similar to the 43 ng/g soil reported by Schuster et al. (2018). Carbon and nitrogen concentrations are greater in replacement thermokarst cave ice than in ice wedges and this is indicative of their formation during high intensity summer erosion events. Ice wedge total dissolved nitrogen (n= 30; 5.4 +/- 4.0 mg/L) and dissolved organic carbon (n= 30; 22.7 +/- 6.6 mg/L) values are greater than total dissolved nitrogen (n= 12; 2.9 +/- 4.3 mg/L) and dissolved organic carbon (n= 12; 17.4 +/- 21.0 mg/L) in thermokarst cave ice. Our values for yedoma permafrost inside the Permafrost Tunnel (n=28; 1.9 +/-0.6 kgN/cubic meter) and active layer above the Tunnel (n=5; 1.4 +/-0.5 kgN/cubic meter) are similar to the values of 0.9 kgN/cubic meter for yedoma and 1.6 kgN/cubic meter for active layer soils presented in Strauss et al. (2022).

Schuster PF, et a. Permafrost stores a globally significant amount of mercury. Geophysical Research Letters. 2018 Feb 16;45(3):1463-71.

Strauss J, et al. A globally relevant stock of soil nitrogen in the Yedoma permafrost domain. Nature Communications. 2022 Oct 14;13(1).

How to cite: Douglas, T., Barker, A., Gelvin, A., Brodylo, D., and Strauss, J.: Mercury, carbon, and nitrogen characteristics of Permafrost From 40,000 years old to modern age in Interior Alaska, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4466, https://doi.org/10.5194/egusphere-egu24-4466, 2024.

EGU24-6537 | ECS | Posters on site | CR4.1

Climate Change Impacts on Active Zone Groundwater Dynamics in the High Arctic, Canada 

Selsey Stribling, Jeffrey McKenzie, Pierrick Lamontagne-Hallé, Nathaniel Novosad, Dylan Hemmings, and Tom MacNeil

With Arctic amplification, the rate of Arctic warming is estimated to be between two to four times greater than at lower latitudes. Northern warming is leading to environmental change, including permafrost thaw and changes in groundwater flow due to alterations in the timing and the depth of the active zone. Research suggests that, due to permafrost degradation and concomitant increased groundwater mobility, exfiltration to northern groundwater-fed lakes may increase with continued warming. Many parts of the terrestrial Arctic are experiencing warming and increased precipitation, both of which affect both the annual timing of formation and depth of the active zone, thereby controlling the amount of water that may be transmitted through the shallow subsurface. The objective of our research is to use a numerical modeling approach to disentangle the effects of changes in precipitation and warming for a site in the Canadian High Arctic (63°30′N).

Through an archetypal modeling approach for a site with limited field data, we use SUTRA 4.0 to simulate groundwater flow and energy transport with dynamic freeze-thaw processes. To assess active layer zone changes, we simulate a two-dimensional 280 m long hill underlain by continuous permafrost that terminates in a lake. The site has thin unconsolidated overburden on bedrock, with current depth to permafrost between 1.3 m and 2.2 m. We simulate four cases using downscaled CMIP5 projections: modern conditions, near climate (2020s), mid-climate (2050s), and far-climate projection (2080s). The climate projects show increasing annual mean temperatures, decreasing annual temperature amplitude, and increasing precipitation. The groundwater model results primarily focus on the groundwater flux to the lake, as it integrates the flows across the entire system. The results show that there will be increasing flows of groundwater to the lake due to climate change. Further, the increase in mean annual temperature (as opposed to increased precipitation) and associated annual development of the active zone is the primary control on groundwater flow through the system. With warming, the active zone deepens and opens for a longer period each year, allowing for more groundwater flow, particularly during snowmelt.

Understanding active zone changes and groundwater in the Arctic allows us to better assess potential future hydrologic changes and discharge into northern lakes. The results from this study have implications for the potential transport and fate of anthropogenic and geogenic contaminants in Northern environments.

How to cite: Stribling, S., McKenzie, J., Lamontagne-Hallé, P., Novosad, N., Hemmings, D., and MacNeil, T.: Climate Change Impacts on Active Zone Groundwater Dynamics in the High Arctic, Canada, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6537, https://doi.org/10.5194/egusphere-egu24-6537, 2024.

EGU24-6884 | ECS | Orals | CR4.1

Quantifying cross-shelf degradation of terrigenous organic carbon in Eurasian Arctic Shelf Seas 

Junjie Wu, Felipe Matsubara, Birgit Wild, Gesine Mollenhauer, Ruediger Stein, Kirsten Fahl, Xiaotong Xiao, and Örjan Gustafsson

The permafrost in the Northern Hemisphere holds approximately 50% of the global soil organic carbon, constituting a reservoir that is twice the size of atmospheric carbon storage. Permafrost carbon plays a vital role in governing the global carbon cycle through its reactivity and accessibility to microbial respiration to release greenhouse gases. Existing studies have revealed spatial variability of degradation of coastally-exported organic matter across regimes in the East Siberian Arctic Shelf Seas. While the degradation patterns and ambient rates are reasonably constrained for the Laptev Sea, these aspects are less well understood for the Kara Sea. Here, we quantified carbon isotopes (13C and 14C), TOC, specific surface area, lipid biomarkers, and lignin phenols along a Kara Sea cross-shelf transect to assess terrigenous organic matter degradation, and compare patterns with three East Siberian cross-shelf transects (Kara Sea, Laptev Sea, Western East Siberian Sea, and Eastern East Siberian Sea). The data demonstrate the highest degradation rate constant of 2.5 kyr-1 in the Eastern East Siberian Sea, a moderate value of 2.0 kyr-1 in the Laptev Sea, and the lowest value of 1.2 kyr-1 in the Western East Siberian Sea. Intriguingly, no statistical trend in degradation was observed across the Kara Sea. The recalcitrant fractions of terrestrial organic carbon are determined to be largest (50%) in the Western East Siberian Sea, moderate (31%) in the Eastern East Siberian Sea, and smallest (11%) in the Laptev Sea. The spatial variabilities in degradation rate constants and recalcitrant fractions are likely attributed to different organic carbon speciation across regimes on land, e.g., from fibrous plant residues to mineral-associated organic carbon, and potential biological controls (e.g., priming effect) during transport.

How to cite: Wu, J., Matsubara, F., Wild, B., Mollenhauer, G., Stein, R., Fahl, K., Xiao, X., and Gustafsson, Ö.: Quantifying cross-shelf degradation of terrigenous organic carbon in Eurasian Arctic Shelf Seas, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6884, https://doi.org/10.5194/egusphere-egu24-6884, 2024.

EGU24-6903 | ECS | Orals | CR4.1

Forecasting Permafrost Carbon Dynamics in Alaska with GeoCryoAI 

Bradley Gay, Neal Pastick, Jennifer Watts, Amanda Armstrong, Kimberley Miner, and Charles Miller

Complex non-linear relationships exist between the permafrost thermal state, active layer thickness, and terrestrial carbon cycle dynamics In Arctic and boreal Alaska. The rate, magnitude, and extent of permafrost degradation remain uncertain, with an increasing recognition of the importance of abrupt thaw mechanisms. Similarly, large uncertainties in the rate, magnitude, timing, location, and composition of the permafrost carbon feedback complicate this issue. The challenge of monitoring sub-surface phenomena, such as the soil temperature and soil moisture profiles, with remote sensing technology further complicates the situation. There is an urgent need to understand how and to what extent permafrost degradation is destabilizing the Alaskan carbon balance and to characterize the feedbacks involved. We employ our artificial intelligence (AI)-driven model GeoCryoAI to quantify permafrost thaw dynamics and greenhouse gas emissions in Alaska. GeoCryoAI uses a hybridized multimodal deep learning architecture of stacked convolutionally layered memory-encoded bidirectional recurrent neural networks and 12.4 million parameters to simultaneously ingest and analyze 13.1 million in situ measurements (i.e., CALM, GTNP, ABoVE ReSALT, FLUXNET, NEON), 8.06 billion remote sensing airborne observations (i.e., UAVSAR, AVIRIS-NG), and 7.48 billion process-based modeling outputs (i.e., SIBBORK-TTE, TCFM-Arctic) with disparate spatiotemporal sampling and data densities. This framework introduces ecological memory components and effectively learns subtle spatiotemporal covariate complexities in high-latitude ecosystems by emulating permafrost degradation and carbon flux dynamics across Alaska with high precision and minimal loss (RMSE: 1.007cm, 0.694nmolCH4m-2s-1, 0.213µmolCO2m-2s-1). GeoCryoAI captures abrupt and persistent changes while providing a novel methodology for assimilating contemporaneous information on scales from individual sites to the pan-Arctic. Our approach overcomes traditional model inefficiencies and seamlessly resolves spatiotemporal disparities.

How to cite: Gay, B., Pastick, N., Watts, J., Armstrong, A., Miner, K., and Miller, C.: Forecasting Permafrost Carbon Dynamics in Alaska with GeoCryoAI, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6903, https://doi.org/10.5194/egusphere-egu24-6903, 2024.

EGU24-7116 | Posters on site | CR4.1

Analysis of seismic characteristics for permafrost according to porosity ratio using 3D printing technology 

Daechul Kim, Sungryul Shin, and Wookeen Chung

Permafrost means soil that remains below 0 ℃ for at least two continuous years. Due to climate change, permafrost is thawing, releasing greenhouse gases(Schuur et al., 2015; Colett et al., 1988). Greenhouse gas emissions from permafrost could accelerate climate change. Therefore, it is necessary to detect and predict changes by estimating the distribution and thickness of permafrost. One of the methods to detect permafrost and detect changes is seismic exploration. Permafrost has various geological characteristics depending on the region, and the porosity of permafrost affects the acoustic wave characteristics(Brothers et al., 2016). Therefore, in order to detect permafrost and detect changes in seismic exploration data, a study is needed to analyze seismic characteristics according to the porosity of permafrost.

In order to create a model according to the porosity of the permafrost and analyze the characteristics of seismic, the porosity was controlled using 3D printing technology and seismic data was acquired through an seismic physical modeling. In this study, an FDM(fused deposition modeling) 3D printer was used to control the porosity of permafrost. Since the porosity of permafrost is about 20-50 % depending on the region, the pore size was set to 3, 4, and 5 mm to create a model similar to the porosity of permafrost. Permafrost was simulated by saturating and freezing water in the pores of the porosity model according to porosity.

A seismic physical modeling was performed to acquire seismic data in permafrost according to porosity. The seismic physical modeling is an experiment that reduces field exploration to a laboratory scale and has excellent field reproducibility. A 1 MHz transducer was used as the source and receiver, and signals were generated using a pulser/receiver. Signals were received and stored using a digital oscilloscope. In order to analyze the characteristics of permafrost according to porosity, the velocity and maximum amplitude were analyzed in the time domain from the acquired seismic data. In addition, the maximum frequency and magnitude according to the porosity of the permafrost were analyzed in the frequency domain.

In this study, 3D printing technology was used to control the porosity of permafrost. Additionally, seismic characteristics were analyzed according to the porosity of the permafrost using a seismic physical modeling. The results of this study are expected to be used as basic data to understand the characteristics of permafrost according to its porosity and to detect and detect changes in permafrost.

 

Acknowledgement

This research was supported by Korea Institute of Marine Science & Technology Promotion (KIMST) funded by the Ministry of Oceans and Fisheries, Korea (RS-2023-00259633).

How to cite: Kim, D., Shin, S., and Chung, W.: Analysis of seismic characteristics for permafrost according to porosity ratio using 3D printing technology, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7116, https://doi.org/10.5194/egusphere-egu24-7116, 2024.

EGU24-7431 | ECS | Posters on site | CR4.1

Effects of permafrost thaw on vegetation productivity 

Ting Li, Xing Wu, and BoJie Fu

When the permafrost thaws, it brings changes in soil hydrothermal conditions and nutrient levels, which can influence vegetation dynamics. The impact of permafrost degradation on vegetation growth with a warming climate and rising carbon dioxide levels remains unclear. This presentation synthesizes various ground observation records, satellite data, and multi-model multi-scenario data from Phase 6 of the Coupled Model Comparison Project to drive the machine learning models to investigate the contribution of deepening active layers to vegetation productivity at different growth stages and how these changes may vary under different shared socioeconomic pathways in the Northern Hemisphere. The results show that the machine learning model effectively simulates changes in permafrost active layer in the northern hemisphere. Currently, most permafrost in the northern Hemisphere show a positive correlation between active layer thickness (ALT) and vegetation gross primary productivity (GPP), with ALT explaining 8.5%-21.5% of the variation in permafrost GPP across the region. Tundra, temperate coniferous forests, and alpine grasslands are the most impacted vegetation types as the active layer thickens due to tundra degradation. However, in the future, ALT's contribution to GPP is expected to weaken further, especially under the high emission scenario SSP585. These findings help to improve our understanding of permafrost-vegetation feedbacks under the influence of climate change and human activities, and can be leveraged for optimizing simulations of carbon cycle processes in terrestrial ecosystems.

How to cite: Li, T., Wu, X., and Fu, B.: Effects of permafrost thaw on vegetation productivity, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7431, https://doi.org/10.5194/egusphere-egu24-7431, 2024.

EGU24-7507 | ECS | Orals | CR4.1

The hypothesis of the bottom of the permafrost in Spitsbergen and its overall "shape" - a case study from Hornsund 

Artur Marciniak, Mariusz Majdański, Wojciech Dobiński, and Justyna Cader

The permafrost-covered areas in polar regions face rapid changes in the current climate. While the active layer and permafrost zone near the surface are well-studied, the precise boundaries of the bottom permafrost remain unclear. Consequently, there is insufficient accuracy in understanding the overall shape of permafrost between the upper and lower boundaries. The evolution of deep cryotic structures, influenced by subsurface factors, is also relatively unknown.

In this study, based on the results of seismic reflection imaging we propose a hypothesis regarding the permafrost shape in the coastal area of Svalbard, Southern Spitsbergen. Additional Ground penetrating radar survey using a low-frequency antenna, as well as results of previous researches based on multiple geophysical methods, allowed for correlation of the obtained seismic results with surface observations. The entire methods were complemented by synthetic modeling, in order to better understand the obtained data. The work emphasizes the importance of recognizing not only the upper active layer but also the bottom permafrost boundary and its transition zone due to the underestimated potential role in observing climatic changes. The estimated bottom permafrost border ranges from 70 m below the surface near the shore to 180 m deep further inland, with a continuous frozen matrix layer identified between 40 m and 100 m depth. We also present a hypothesis about the possible presence of subsea permafrost in the Hornsund.

Factors such as seawater intrusions, isostatic uplift of deglaciated areas, and surface-related processes influencing permafrost evolution may lead to extensive changes in the hydrology and geology of polar regions in the future. Therefore, global attention and scientific efforts are essential for monitoring, geophysical imaging, and understanding the characteristics and evolution of deep permafrost structures. The research presented here forms the basis for a full understanding of permafrost evolution and degradation, and should be repeated across the globe to monitor climate change on a worldwide scale.

How to cite: Marciniak, A., Majdański, M., Dobiński, W., and Cader, J.: The hypothesis of the bottom of the permafrost in Spitsbergen and its overall "shape" - a case study from Hornsund, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7507, https://doi.org/10.5194/egusphere-egu24-7507, 2024.

EGU24-7885 | ECS | Posters virtual | CR4.1

Advancing Permafrost Monitoring: the EO-PERSIST Project  

Katerina Dermosinoglou, Spyridon E. Detsikas, Loukia-Maria Fratsea, Apostolos G. Papadopoulos, Giuseppe DiCaprio, and George P. Petropoulos

Permafrost, a pivotal component of the Arctic ecosystem, remains particularly vulnerable to the effects of global warming, exerting profound impacts on both environmental and socioeconomic facets. In the light of increasing challenges posed by climate change, understanding and monitoring the dynamics of permafrost regions in the Arctic have gained paramount importance. In response to this critical need, the EO-PERSIST project [https://eo-persist.eu/], a 4 years MSCA staff exchanges project funded by EU, aims to leverage existing services, datasets, and innovative technologies to establish a consistently updated ecosystem with Earth Observation (EO)-based datasets suitable for permafrost applications.

By harnessing advanced EO technologies, including innovative tools and datasets such as cloud platforms, and tapping into an extensive array of remote sensing datasets, EO-PERSIST aspires to revolutionize the monitoring and assessment of permafrost dynamics. The project aims to advance methodological approaches in the field of permafrost by leveraging the huge volume of remote sensing (RS) datasets and providing indicators directly linked to socioeconomic effects from permafrost dynamics.

The aim of this study is twofold: (i) to provide an overview of the EO-PERSIST project and its objectives, and (ii) to present the results of a case study in which EO was utilized to map urban sprawl through monitoring Impervious Surface Areas (ISA), in an Arctic setting characterized by high structural density over the past decade. A pixel-based machine learning classifier in conjunction with Landsat imagery in Google Earth Engine (GEE) cloud platform has been employed to map with high accuracy ISA changes in Tromso area, Norway, from 1993 to 2023. The results of this study not only precisely map the urban changes in the study area but also hold promise of enhancing our comprehension of the dynamics behind urban expansion, the primary factors associated with urban sprawl and their interaction with the challenges posed by climate change in Arctic environments. All in all, results of this case study showcase the overall potential of EO datasets to be used for socioeconomic studies along with the recent advancements in cloud-based platforms paving the way for new opportunities and challenges.

EO-PERSIST project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No. 101086386

How to cite: Dermosinoglou, K., Detsikas, S. E., Fratsea, L.-M., Papadopoulos, A. G., DiCaprio, G., and Petropoulos, G. P.: Advancing Permafrost Monitoring: the EO-PERSIST Project , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7885, https://doi.org/10.5194/egusphere-egu24-7885, 2024.

EGU24-7976 | ECS | Posters on site | CR4.1

Hydraulic characterization of the variably saturated zone in peatland permafrost mires 

Radhakrishna Bangalore Lakshmiprasad, Thomas Graf, Stephan Peth, Susanne Woche, and Martin Volkmann

Peatlands acquire only 3% of the terrestrial earth's surface; however, they store up to 30% of the global soil carbon. These peatlands also dominate the northern Hemisphere, which is covered by more than 25% of permafrost. An accelerating trend in the rate of permafrost degradation due to climate warming has been observed in most regions of the Northern Hemisphere. An indicator of permafrost degradation is the active layer depth, which is situated in the variably saturated zone. The hydraulic properties of the peatland top soil layer are influenced by its unstructured porous media, high organic matter, and high porosity. The water content in the variably saturated zone in cold regions is influenced by both drying-wetting and freezing-thawing cycles. The soil water characteristic curves (SWCC) define the relationship between unfrozen water content and matric potential. The soil freezing characteristic curves (SFCC) define the relationship between unfrozen water content and temperature around 0°C. The SWCC, SFCC, and the similarities between them have been intensively investigated for mineral soils in comparison to organic soils.  

The three main goals of the study for peatland permafrost mires are as follows: (i) Determine the SWCC using inverse modeling of transient evaporation experiments. (ii) Estimate the SFCC using field-based volumetric water content measurements using a simple empirical function. (iii) Compare and develop a relationship between the SWCC and SFCC. 

The lowland permafrost mires in the Abisko region, located in the northern part of Sweden, were investigated. For the SWCC evaporation experiments, 12 soil samples at six locations and two depths (10 and 25 cm) were taken. Inverse numerical modeling was used to fit and compare the three pressure-saturation functions: (i) Van Genuchten model. (ii) Peter Durner Iden (PDI)-variant of the Van Genuchten model (iii) PDI-variant of the bimodal van Genuchten model. The goodness of fit was checked by Root Mean Square Error and Akaike Information Criterion. It was observed that the PDI-variant of the bimodal van Genuchten model was most suitable for all the soil samples. 12 soil moisture sensors were also installed at the six locations and five depths (10 to 50 cm). An exponential logarithmic function with two parameters (transition temperature and temperature dispersion) was fitted to individual freezing and thawing curves from the soil moisture sensor data. The function showed a very good fit, and it was observed that the two fitting parameters were higher for thawing curves compared to freezing curves. A new SFCC function was developed based on the PDI variant of the bimodal van Genuchten model. This function was compared with the fitted SFCC logarithmic function. Reasonable differences were identified, which could be attributed to the field-installed soil moisture sensors and laboratory-conducted evaporation experiments. It is one of the few hydrological studies that has investigated the effects of bimodal behavior in organic soils on soil freezing and thawing. The measured parameters and datasets provide the necessary functions for developing cryohydrogeological models. The cryohydrogeological models can be used to assess the impacts of climate change on permafrost. 

How to cite: Bangalore Lakshmiprasad, R., Graf, T., Peth, S., Woche, S., and Volkmann, M.: Hydraulic characterization of the variably saturated zone in peatland permafrost mires, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7976, https://doi.org/10.5194/egusphere-egu24-7976, 2024.

EGU24-8439 | ECS | Orals | CR4.1

Labile components as geochemical tracers at the soil column-scale in permafrost peatlands 

Lucia Perez-Serrano, Sergey Loiko, Lim Artem, Oleg Pokrovsky, and Jean-Luc Rols

Permafrost peatlands constitute a reservoir of highly labile components such as dissolved organic carbon (DOC), macro- and micro-nutrients, and toxic elements. Fast thawing of permafrost peatlands in most of climate warming scenarios will lead to the mobilisation of dissolved components from soils to rivers and lakes. Permafrost peatlands situated in western Siberia are especially vulnerable to thawing, as they contain the largest soil water and ice resources in the northern hemisphere.  Half of the volume of ice resources is in form of dispersed ice on the soil top layer (0-3 m) [1]. Dispersed ice is enriched in dissolved components, which may be highly reactive and even provide sizable contributions to the hydrological system via suprapermafrost flow [2]. However, contributions from local soil column-scale in the context of micro-environments potential deepening of the active layer remain to be assessed.

To characterize the dissolved fraction of dispersed peat ice, a study was performed in Tazovsky, a representative site located in a continuous permafrost zone in Siberia. Four peat cores (0-180 cm depth) were collected along a gradient from the bog to mineral-fen. DOC, nutrients and trace elements were analysed for both the porewater (active layer) and dispersed ice (frozen layer). Lateral and in-depth approaches were employed to quantify the pools of dissolved components. Preliminary results show an enrichment of highly labile components in the frozen layer, consistent with previous findings in the discontinuous permafrost zone [3]. We hypothesize that the highest concentrations of DOC and certain macro/micro-nutrients in the frozen layer are mostly driven by downwards colloidal migration during the freezing phase. These organic and inorganic nutrients may be released due to progressive thawing, and eventually become bioavailable for microbial uptake. Consequently, the production of CO2 may increase, contributing to the ongoing climate change.

[1] W. H. Pollard and H. M. French, « A first approximation of the volume of ground ice, Richards Island, Pleistocene Mackenzie delta, Northwest Territories, Canada », Can. Geotech. J., vol. 17, no 4, p. 509-516, november 1980, doi: 10.1139/t80-059.

[2] A. G. Lim et al., « Dispersed ground ice of permafrost peatlands: Potential unaccounted carbon, nutrient and metal sources », Chemosphere, vol. 266, p. 128953, march 2021, doi: 10.1016/j.chemosphere.2020.128953.

[3] D. M. Kuzmina et al., « Dispersed ice of permafrost peatlands represents an important source of labile carboxylic acids, nutrients and metals », Geoderma, vol. 429, p. 116256, january 2023, doi: 10.1016/j.geoderma.2022.116256.

How to cite: Perez-Serrano, L., Loiko, S., Artem, L., Pokrovsky, O., and Rols, J.-L.: Labile components as geochemical tracers at the soil column-scale in permafrost peatlands, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8439, https://doi.org/10.5194/egusphere-egu24-8439, 2024.

EGU24-8513 | Orals | CR4.1 | Highlight

Land-derived organic matter drives benthic carbon and nutrient cycling on the Siberian Arctic Ocean shelves 

Birgit Wild, Lewis Sauerland, Nicholas E. Ray, Ivan Gangnus, Evgeniy Yakushev, Örjan Gustafsson, Oleg Dudarev, and Igor Semiletov

The Arctic Ocean is currently changing at a high rate, and projections over the next decades include an increase in water temperature and retreat of sea ice, as well as increased input of freshwater and land-derived material released by permafrost thaw. These changes might substantially alter marine biogeochemical cycles and primary production, with repercussions for the Arctic Ocean greenhouse gas balance as well as ocean acidification. The large and shallow continental shelf seas north of Siberia are particularly affected by these changes as they receive land-derived material from strong coastal erosion and large rivers such as Ob, Yenisey and Lena. In recent studies, we have shown a transition from predominantly land- to marine-derived organic matter in sediments from the coast to the shelf break based on isotopes and biomarkers, an increased decomposition state of land-derived organic matter, as well as a decrease in sediment and water column nitrogen concentrations. We here combine this understanding with incubation experiments to assess the impact of these gradients on benthic CO2 production and nutrient remineralization. We found that fresh, land-derived organic matter typical for near-shore environments showed highest decomposability to CO2 in controlled, aerobic laboratory incubations, as indicated by correlations of CO2 production with concentrations of terrigenous biomarkers (lignin, high molecular weight n-alkanes), and biomarker proxies indicating the decomposition state of these compounds. Fresh, land-derived organic matter was also associated with highest ammonium and nitrite release to the water column, measured during on-board incubation of intact sediment cores. The opposite pattern was observed for phosphate and silicate fluxes that were highest in more marine-influenced settings. Our data suggest that increased input of land-derived organic matter to the Siberian Arctic Ocean shelves could promote benthic decomposition processes near the coast, including CO2 release that might contribute to the strong ocean acidification already observed in the region. Furthermore, the different controls on nutrient fluxes indicate a de-coupling of nitrogen, phosphorus and silicon remineralization, with implications for nutrient limitation and primary production in the Arctic Ocean.

How to cite: Wild, B., Sauerland, L., Ray, N. E., Gangnus, I., Yakushev, E., Gustafsson, Ö., Dudarev, O., and Semiletov, I.: Land-derived organic matter drives benthic carbon and nutrient cycling on the Siberian Arctic Ocean shelves, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8513, https://doi.org/10.5194/egusphere-egu24-8513, 2024.

EGU24-8707 | Orals | CR4.1 | Highlight

Ice content estimation in the frozen subsurface with an innovative geophysical method: high-frequency induced polarization 

Andreas Hördt, Madhuri Sugand, and Raphael Schulz

The degradation of permafrost due to global warming has pronounced adverse effects, including damage to the infrastructure and climate feedback mechanisms through the release of CO2. Numerical simulations are often used to predict the speed at which frozen ground is thawing. One essential parameter for these simulations is the ice content, due to its increased heat conductivity and nonlinear behavior during phase changes. Despite its importance, ice content is normally only recorded sporadically as it is difficult to collect measurements at high spatial resolution.

Geophysical methods, which investigate the physical properties of the subsurface, have the potential to estimate the spatial distribution of ice content. Geoelectric measurements are sensitive to the existence of ice since the electrical resistivity of ice is orders of magnitudes greater than that of unfrozen water. However, a quantitative estimate of ice content from resistivity alone is difficult because large resistivities may also be caused by low porosities. Therefore, DC resistivity is sometimes combined with seismic methods to reduce ambiguity.

The high-frequency induced polarization (HFIP) method is capable of measuring ice content as a stand-alone technique. HFIP measures the complex electrical resistivity over a broad frequency range, typically up to 200 kHz. In this frequency range the data is sensitive to an additional property, that is, the dielectric permittivity which represents the material’s capability to be polarized by an electric field. The permittivity of ice exhibits a unique behavior in this frequency range, and therefore HFIP may be used to estimate ice content at the field scale. In order to convert this concept into to a practical method, several challenges must be considered. These include the removal of undesired electromagnetic coupling, efficient data acquisition, the inversion of the raw data to obtain useful images of the subsurface, and the conversion of the frequency dependent resistivity into ice content.

Here, we discuss the progress that has been made in recent years to overcome some of these challenges. Data acquisition relies on the Chameleon II equipment that was designed specifically for HFIP measurements. The Chameleon II is one of the few measuring devices that can perform HFIP measurements on field scale and is able to minimize the undesired coupling between electrical components. Subsurface images are obtained through a 2-D inversion of all frequencies separately, followed by the calculation of ice content using a 2-component model where the electrical properties of the ice fraction and the non-ice fraction are considered. We demonstrate the feasibility of the method using recent case histories from alpine and subarctic permafrost areas. We also show by comparison with independent estimates obtained from drill cores that the obtained estimates are sufficiently accurate. We suggest that this method is ready for practical application and may contribute to the understanding of permafrost degradation processes and to the prediction of the future development of permafrost regions under global warming conditions.

How to cite: Hördt, A., Sugand, M., and Schulz, R.: Ice content estimation in the frozen subsurface with an innovative geophysical method: high-frequency induced polarization, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8707, https://doi.org/10.5194/egusphere-egu24-8707, 2024.

EGU24-8919 | ECS | Orals | CR4.1

Stochastic modelling of thermokarst lake distributions 

Constanze Reinken, Victor Brovkin, Philipp de Vrese, Ingmar Nitze, and Helena Bergstedt

Thermokarst lakes are among the most common and dynamic landscape features in ice-rich permafrost regions. They form due to melting of ground ice and subsequent ground subsidence. Their presence and dynamic behavior do not only influence the carbon exchange with the atmosphere by accelerating permafrost thaw and facilitating the production of methane, but also have an impact on soil hydrology as well as biophysical fluxes between atmosphere and land surface, such as energy and water transfer. These feedbacks have implications for both the regional and global climate and are therefore highly relevant when investigating the climate response to changes in permafrost systems under different future carbon emission and warming scenarios. Despite their significant role in the climate system, thermokarst lakes are only rudimentarily or not at all represented in Earth system models. Because the involved hydrological processes are complex and depend on small-scale sub-surface heterogeneities that are difficult to measure, we treat them as probabilistic and use a stochastic approach to create a model of thermokarst lake dynamics (formation, expansion and drainage). More specifically, we utilize common stochastic approaches, such as the Poisson process and Brownian motion, as tools to simulate changes in lake density, size distributions and fractions of water and drained area. Recent advancements in remote sensing offer an opportunity to use high-resolution satellite data products for model calibration and the parameterization of inherent and/or climate-induced thermokarst lake dynamics. We expect our approach and the results of our simulations to contribute to a more accurate representation of permafrost dynamics in Earth system models.

How to cite: Reinken, C., Brovkin, V., de Vrese, P., Nitze, I., and Bergstedt, H.: Stochastic modelling of thermokarst lake distributions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8919, https://doi.org/10.5194/egusphere-egu24-8919, 2024.

EGU24-9490 | ECS | Orals | CR4.1

Impact of plant community composition and soil characteristics on Mo and V cycling in subarctic habitats at Abisko, Northern Sweden. 

Hugo M. G. Potier, Xavier Raynaud, Marie A. Alexis, Yannick Agnan, Alienor Allain, and Maryse Castrec-Rouelle

Arctic ecosystems are changing rapidly due to climate warming. Increased air temperature increases shrub proportions in plant communities at large scales, and increased soil moisture associated with permafrost thawing favours herbaceous cover at local scales. Changes in vegetation community composition or soil moisture could particularly affect the biogeochemical cycling of elements in arctic environments through the variation in the proportion of slow-cycling woody biomass and in the mineralisation rates of organic matter with soil water saturation. Nitrogen (N), often considered to limit primary production in these ecosystems, could be particularly affected by these changes. Biological fixation of atmospheric dinitrogen represents a major input of N in these systems and is catalysed by nitrogenase enzymes that contain either Molybdenum (Mo) or Vanadium (V). Thus, the concentrations, stocks and bioavailability of these two lithogenic trace elements (TE) may be key factors in alleviating the N constraint on primary productivity and vegetation change. Understanding their biogeochemical cycles is therefore crucial for our comprehension of changes in arctic environments.

Our study evaluated the concentrations and stocks of Mo and V   in vegetation and soils of different subarctic habitats with different soil characteristics and vegetation communities in a mire and a tundra ecosystem at Abisko, northern Sweden. Mo was more concentrated in the biomass of herbaceous species than in shrubs, resulting in higher stocks in the biomass of herbaceous-dominated habitats than in shrub-dominated habitats. Conversely, V concentrations and stocks were not different between the two vegetation types. In soils, Mo concentrations were globally the same between deep and surface horizons (0.38 mg kg-1), whereas V concentrations were globally higher in deep horizons than at the surface (61.0 to 22.9 mg kg-1, respectively). Accordingly, enrichment factors of the surface horizons compared to deep horizons showed that Mo was highly enriched at the surface (EF > 1 and up to > 8), highlighting the importance of surface processes on Mo cycling. V was not enriched in the tundra but presented EF values similar to Mo in the mire, indicating a locally higher influence of surface processes in this ecosystem. Exploring the possible reasons behind these behaviours, we found that 1) atmospheric deposition seems to play little role in their concentrations in surface soils, 2) soil pH and redox conditions could partially explain the surface enrichment of these two elements through their sorption on organic matter and metallic oxides.

We conclude that global and local changes in plant communities in arctic ecosystems could decrease Mo and V litter fluxes with increased shrub cover, with a greater impact on the Mo cycle than on V due to the stronger influence of surface processes on the Mo cycle. We also highlight the importance of local factors for TE speciation that would control the bioavailability of these elements for organisms. Altogether, these results underline the need to consider the changes in TE cycling in regard to their importance for underlying processes controlling major elements (C, N) dynamics in the changing Arctic.

How to cite: Potier, H. M. G., Raynaud, X., Alexis, M. A., Agnan, Y., Allain, A., and Castrec-Rouelle, M.: Impact of plant community composition and soil characteristics on Mo and V cycling in subarctic habitats at Abisko, Northern Sweden., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9490, https://doi.org/10.5194/egusphere-egu24-9490, 2024.

EGU24-10257 | Posters on site | CR4.1 | Highlight

Using radiogenic Sr isotopes to trace nutrient uplift from permafrost thaw: a field-based soil warming experiment 

Philippe Roux, Edward Schuur, and Sophie Opfergelt

The amplified warming at the poles have largely impacted arctic and subarctic ecosystem by accelerating permafrost degradation. The resulting topographical and hydrological consequences have induced significant shifts in vegetation development and composition with a clear trend of increased productivity since the early 1980’s. This trend, referred to as Arctic greening, causes significant feedback to climate dynamics by altering ground albedo, solar radiation, and shading, as well as the ecosystem net C balance through respiration, photosynthesis and litter degradation.

Firstly, Arctic greening is characterized by increased productivity, resulting from warmer temperatures, longer growing seasons, increased precipitation, atmospheric CO2 concentrations, and access to newly thawed nutrients from deeper soil horizons. Secondly, over the past decades, a notable shift in vegetation has been occuring with an overall increase in shrub dominance accompanied by local increase in graminoid expansion in subsided and poorly drained areas. Given that changing nutrient sources for tundra vegetation has major implications for vegetation changes in the Arctic, and thereby on vegetation-climate feedback, there is a need to identify the processes controlling changes in nutrient sources and mobility for Arctic tundra vegetation upon permafrost thaw. We hypothesize the release and uplift of essential nutrients at depth to result from vegetation cycling and/or water table rise.

To test this hypothesis, we compared radiogenic Sr isotopes composition of three typical tundra plants with different rooting depth subjected to an eight-year soil warming experiment at the Eight-Mile Lake study site in Alaska. We show that plants subjected to soil warming exhibit access to a different nutrient source than that of the control plants, representative of a deeper, recently thawed soil layer. This shift is observed regardless of rooting depth, indicating uplift of thawed nutrients. Therefore, to identify the dominant process governing nutrient mobility upon permafrost thaw, we used vegetation composition survey and mass balance equation to model the magnitude of nutrient transfer from vegetation cycling and water table rise.

How to cite: Roux, P., Schuur, E., and Opfergelt, S.: Using radiogenic Sr isotopes to trace nutrient uplift from permafrost thaw: a field-based soil warming experiment, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10257, https://doi.org/10.5194/egusphere-egu24-10257, 2024.

EGU24-10315 | ECS | Orals | CR4.1

Time-lapse GPR Measurements for Observing Shallow Cryo-Hydrogeological Borders in Spitsbergen's Fuglebekken Catchment 

Marjan Izadi Yazdanabadi, Artur Marciniak, Szymon Oryński, Tomasz Wawrzyniak, and Marzena Osuch

This study investigates the changes in shallow cryo-hydrogeological layers over time using Ground Penetrating Radar (GPR) in the unique Arctic environment of the Fuglebekken catchment on Spitsbergen Island. Accurate identification of permafrost changes is essential for understanding geotechnical and environmental processes, making precise monitoring imperative. GPR has proven to be a valuable non-destructive method, providing high-resolution spatially distributed data in permafrost regions and overcoming environmental limitations inherent in Arctic areas.

Utilizing a 250 MHz shielded antenna, GPR measurements facilitated the identification of the groundwater layer and changes in the top border of permafrost at different seasons in the Fuglebekken catchment. A distinctive aspect of this research involved the repetition of GPR profiles at the same location during three different seasons, enabling the observation of temporal variations in subsurface conditions across different seasons. These profiles were complemented by strategically placed boreholes and piezometers recording ground temperature at various depths and groundwater levels, providing key data for the validation and correlation of GPR results. Additionally, drone-based digital elevation models (DEM) were employed during GPR data processing to enhance the accuracy of results.

In the majority of recorded profiles, GPR measurements captured well-defined reflections of subsurface features. The emphasis is on revealing changes over time in the study area by distinguishing geological structures from the groundwater and upper permafrost boundaries. The study convincingly demonstrated the efficacy of GPR in capturing underground time-lapse changes throughout the studied area. The comprehensive insights gained through GPR offered distinct advantages over traditional methods reliant on limited borehole data, especially in terms of demonstrating spatial changes. Integration of GPR data with ground temperature measurements from boreholes and the use of Drone-based DEM during data processing provided a holistic perspective on the evolving nature of permafrost borders, significantly enhancing the accuracy and reliability of the findings.

Comprehending spatial and temporal variations in permafrost borders is critical for predicting the impacts of climate change and guiding geotechnical and environmental management strategies. This research serves as a valuable reference for future studies aiming to explore permafrost conditions in polar regions, offering a comprehensive framework for more effective monitoring and management practices.

How to cite: Izadi Yazdanabadi, M., Marciniak, A., Oryński, S., Wawrzyniak, T., and Osuch, M.: Time-lapse GPR Measurements for Observing Shallow Cryo-Hydrogeological Borders in Spitsbergen's Fuglebekken Catchment, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10315, https://doi.org/10.5194/egusphere-egu24-10315, 2024.

EGU24-11100 | Posters on site | CR4.1

To what extent do iron organic carbon interactions attenuate C release from permafrost thaw? 

Sophie Opfergelt, Philippe Roux, Eléonore du Bois d'Aische, Maëlle Villani, Maxime Thomas, and Cécile Osy

Enhanced thawing of the permafrost in a warming Arctic exposes previously frozen soil organic carbon (OC) to microbial decomposition, leading to the release of soil C as greenhouse gases. Depending on temperature and moisture environmental variables, a centennial to millennial-year-old C pool can be reached, thus accelerating the feedback to climate change. Iron-OC interactions in soils and sediments contribute to stabilize OC (by adsorption onto Fe oxides or forming Fe-OC complexes), thus mitigating permafrost C emissions. However, their formation and stability are dependent on soil pH and redox conditions. The heterogeneous soil moisture conditions and drastic changes in soil water pathways upon permafrost thaw make the significance of Fe-OC interactions in attenuating permafrost C emissions uncertain. Using radiogenic Sr isotopes, we show that, in saturated layers, Fe-OC interactions can remain undissociated and preserved since their formation. In contrast, we highlight that at the redox interface, processes of dissolution and precipitation of the Fe-OC interactions occur, changing the OC stabilization potential. Given the implications for overall long-term ecosystem C storage, we will discuss an approach to estimate at the landscape scale in the Arctic: (i) the proportion of permafrost soils Fe with potential for interactions with OC (reactive Fe), and (ii) the locations which are the most sensitive to changes in Fe-OC interactions.

How to cite: Opfergelt, S., Roux, P., du Bois d'Aische, E., Villani, M., Thomas, M., and Osy, C.: To what extent do iron organic carbon interactions attenuate C release from permafrost thaw?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11100, https://doi.org/10.5194/egusphere-egu24-11100, 2024.

EGU24-11455 | ECS | Orals | CR4.1 | Highlight

Fluvial versus coastal input of permafrost organic carbon - insights from the Canadian Beaufort Sea 

Lina Madaj, Fleur van Crimpen, Dustin Whalen, Lisa Bröder, Thomas Langens, Thomas Bosse-Demers, and Jorien Vonk

Around 65% of the Arctic coastline consists of permafrost. Rising global air temperatures cause these permafrost grounds to thaw which leads to the release of organic matter and sediments into the coastal ocean. This influences coastal ecosystem functioning and may further enhance atmospheric warming due to greenhouse gas emissions when the released carbon decomposes. Permafrost organic carbon enters the coastal ocean either through coastal erosion or through fluvial discharge and both fluxes are expected to increase in the future. The Canadian Beaufort Sea receives material from both sources, the region has some of the highest erosion rates in the Arctic and receives additional input through the Mackenzie River, the largest sediment supplier to the Arctic Ocean. To reliably estimate the current and future impacts of permafrost carbon on the coastal ocean and its potential climate feedback, we need to distinguish between these two sources whose fluxes may respond differently to ongoing Arctic change. However, we still lack reliable methods to do so.

Here we propose a multiproxy approach to distinguish between sources of permafrost organic carbon by combining organic with inorganic geochemical tracers, grain size and grain shape data on a land-coast-ocean transect in the Mackenzie River Delta. The combined data pinpoints to differences in sediment source, composition, degradation, and transport pathways of both fluvially-discharged and coastally-eroded carbon. Degradation processes of organic and inorganic matter are tightly coupled, but do change within different environments (salinity, energy regimes). By combining degradation state (stable isotopes) and transport indicators (such as grain roundness) with source region tracers (XRF, radiogenic isotopes) we aim to gain insights into the interaction, transition, and origin of this different kind of matter. If successful, this approach can be applied and compared to other Arctic delta environments to fully understand the impacts of increased permafrost thaw and changing river discharge patterns on the coastal Arctic Ocean.

How to cite: Madaj, L., van Crimpen, F., Whalen, D., Bröder, L., Langens, T., Bosse-Demers, T., and Vonk, J.: Fluvial versus coastal input of permafrost organic carbon - insights from the Canadian Beaufort Sea, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11455, https://doi.org/10.5194/egusphere-egu24-11455, 2024.

EGU24-12030 | ECS | Orals | CR4.1 | Highlight

Plant-specific rhizosphere influences on soil redox and soil biogeochemistry affect methane release from thawing permafrost soils 

Marie Mollenkopf, Katja Lenge, Prachi Joshi, Birgit Wild, Ellen Dorrepaal, Sylvain Monteux, Andreas Kappler, and Marie Muehe

Thawing of permafrost soils results in drastic changes in soil biogeochemistry and plant community composition. Specifically, the thawing process in subarctic regions can transform previously stable permafrost soils, home to slow growing, shallow-rooted shrubs into water-saturated, oxygen-depleted soils with fast-growing, deep-rooted graminoids. This change in soil biogeochemistry, along with the distinct characteristics and requirements of these contrasting plant types, leads to the hypothesis that the way these plants interact with the soil may impact biogeochemical cycles. Consequently, this could result in changes in the amounts and ratios of released greenhouse gases, influencing climate-relevant processes. On the one hand, tall graminoids may increase CO2 fixation. On the other hand, root exudation might prime the formation of CH4 and the root internal CH4 transport protecting it from oxidation outweighing increased CO2 fixation in thawed permafrost soils as compared to intact permafrost soil.

To explore this idea, we conducted a study in Stordalen, Abisko, Sweden, at a permafrost site with three different thawing stages. Sampling locations in intact, intermediately, and fully thawed permafrost soil were selected, each with varying densities of shrubs and graminoids. Representative plants were sampled to analyze the quantity and composition of root exudates. Data on soil redox potential at different depths were combined with porewater geochemical parameters like the amount and speciation of dissolved iron, dissolved organic carbon, inorganic nitrogen species, dissolved porewater gases, and soil microbial functional genes. Net emissions of CO2, CH4, and N2O were tracked using static gas flux chambers. 

Most reducing redox conditions were observed in fully thawed soils compared to intact and intermediately thawed permafrost soils. Additionally, redox potentials decreased at greater depth in the soil and with higher graminoid density. At the same time graminoid roots exuded larger amounts of organic carbon than shrub roots with a high fraction of easily available organic molecules. We relate the decreasing redox potentials with increasing graminoid density to the rapid depletion of available electron acceptors such as iron(III) caused by an increased supply of easily available organic molecules through root exudation. This, in turn, might prime CH4 production, indicated by increased porewater CH4 at depth. Given the net CH4 flux increase at an increased porewater CH4 at depth, we suggest that this is partly from CH4-priming and partly from aerenchyma transport of CH4 from the soil to the atmosphere (Ström et al. 2005). Since thawing permafrost areas are rapidly expanding and contribute to climate change, the plant-specific alterations of these contrasting rhizosphere biogeochemical systems are important to consider altering greenhouse gas fluxes and warming potentials.

Ström, L. et al. Species-specific Effects of Vascular Plants on Carbon Turnover and Methane Emissions from Wetlands. Biogeochemistry 75, 65–82 (2005).

 

How to cite: Mollenkopf, M., Lenge, K., Joshi, P., Wild, B., Dorrepaal, E., Monteux, S., Kappler, A., and Muehe, M.: Plant-specific rhizosphere influences on soil redox and soil biogeochemistry affect methane release from thawing permafrost soils, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12030, https://doi.org/10.5194/egusphere-egu24-12030, 2024.

EGU24-12327 | ECS | Posters on site | CR4.1

Combining in situ flux measurements and multi-temporal UAV LiDAR on a degrading palsa. 

Siri Holm Hjelmerud, Cas Renette, Mats Björkman, and Heather Reese

Palsa mires are elevated mounds of peat with a permanently frozen core found in areas of discontinuous permafrost. Peatlands in the subarctic, which is where these landforms are located, hold more than 30% of the stored global soil carbon, which is a disproportionate amount considering their extent. As permafrost thaws, as a result of the subarctic region warming approximately twice as fast as the global average, this carbon is released to the atmosphere in the form of CH4 or CO2.

The aim of this study is to measure methane emissions on a degrading palsa in the Vissátvuopmi palsa mire complex located in the northernmost part of Sweden, using carbon flux measurements. The 4 m tall palsa under study has been mapped with repeat UAV LiDAR data (five campaigns during one year) to characterize the intra-annual subsidence of the palsa in high spatial detail. Using the flux measurements and UAV LiDAR data, correlations will be investigated between methane fluxes and other factors such as topographic position, soil moisture and soil temperature, active layer depth and vegetation.  

The findings show some expected results with high emission of methane in areas where the palsa has fully collapsed, and low uptake in areas which have undergone the least amount of degradation. Surprisingly, there is low uptake to low emission in areas of the palsa which have recently degraded significantly. There is no significant correlation between fluxes and the other factors measured in connection to this study (soil moisture, soil temperature, active layer depth and type of vegetation). However, it is possible to detect in the data that, in general, the measurements with low or negative flux have a lower soil moisture percentage (>40-50%) while the measurements with higher fluxes have a soil moisture content above 50%. Using available geospatial data and field observations, an estimation of the current methane emissions from the palsa was made. From these calculations, in addition to the decay rate of the palsa (established in Olvmo et al. (2020)), future emissions will be estimated.

How to cite: Hjelmerud, S. H., Renette, C., Björkman, M., and Reese, H.: Combining in situ flux measurements and multi-temporal UAV LiDAR on a degrading palsa., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12327, https://doi.org/10.5194/egusphere-egu24-12327, 2024.

EGU24-12771 | ECS | Posters on site | CR4.1

Hybrid AI permafrost modelling 

Diego Martinez Barberi, Hugo Beltrami, Iker Gondra, Agnes Richards, Felix Ouellet, Fidel González Rouco, and Elena García-Bustamante

Deep learning is an approach capable of extracting spatio-temporal features automatically while processing large amounts of data through complex structures. Structures that, for example, are able to learn from past patterns and share with the future if strong correlation is found. It could be assumed AI models only need to be built and gather enough data to find links between input and outputs. However, this approach cannot ensure that predictions would respect the laws of physics, e.g. due to extrapolation or observational biases. Restricting models by introducing physics can add strong theoretical guidelines alongside observations.
In the context of permafrost models, data observations are lacking (e.g. wind speed or humidity) and models lose the possibility of spatial extrapolation. In this case, simplification of the physics is an usual procedure. Such that the problem is solved by an approximate solution that still captures broad spatio-temporal features while responding to more accessible predictors (e.g. surface air temperature or air pressure). More specifically, permafrost present-day thermal state is the consequence of past climate conditions that induced long-term variations of deep reservoirs of organic carbon and ground ice. Reproducing permafrost evolution at century to millennia scale requires models to operate with limited and highly uncertain information about thermal and hydrological ground properties.
In need of both data and physical constraints, climate models themselves could be used as data generators. Here, CryoGrid Lite, a simplified version of the permafrost model CryoGrid 3, is used to simulate ground thermal regime and ice balance. Daily data of air temperature, pressure and geothermal flux run CryoGrid Lite to simulate the evolution of the thermal state of permafrost and active layer thickness over many centuries for the Canadian Arctic permafrost region. This dataset, generated by CryoGrid Lite, trains a neural network model to emulate its behavior. Physics equations governing the original model are also introduced into the objective function to penalize the network training when outputs exceed a tolerance range. This approach restricts outputs to the knowledge provided by CryoGrid Lite, enhancing physical reliability of forecasts. This is in contrast to the traditional 'black-box' structure of neural networks, which usually rely on minimizing errors with respect to observations. An assessment of the impact of including such additional constraints is provided. 

This study explores an hybrid approach between coupling physical process models with the flexibility of data-driven machine learning. The inclusion of physics within AI structures could improve their performance in permafrost modeling, while overcoming the reliability challenge that hampers its adoption in geoscience.

How to cite: Martinez Barberi, D., Beltrami, H., Gondra, I., Richards, A., Ouellet, F., González Rouco, F., and García-Bustamante, E.: Hybrid AI permafrost modelling, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12771, https://doi.org/10.5194/egusphere-egu24-12771, 2024.

EGU24-13106 | ECS | Posters on site | CR4.1

Spring water characteristics in the marginal permafrost region of the Southern Carpathians 

Oana Berzescu, Alexandru Onaca, Aurel Perșoiu, Constantin Marin, Petru Urdea, and Florina Ardelean

Permafrost is defined as the ground (including soil or rock) that remains at or below 0°C for a minimum of two consecutive years (Harris et al., 1988). Due to permafrost`s sensitivity to climate change, it is essential to study the hydrology of rock glaciers to predict and mitigate the impacts of climate-induced changes, including permafrost thaw.

Physico-chemical analyses along with temperature monitoring of springs seeping from the base of the rock glacier fronts were conducted over two consecutive years (2022 and 2023) in various glacial valleys in the central part of the Retezat Mountains.

The measurement of spring water temperature during late summer (SWTS) is employed to discern permafrost distribution in alpine regions. According to previous studies (Frauenfelder et al., 1998; Scapozza, 2009), a water temperature above 2°C indicates the absence of permafrost, while a temperature between 1 and 2°C indicates the possible presence of permafrost, and a temperature below 1°C indicates that permafrost is likely.

In this study physico-chemical and isotopic analyses along with temperature measurements were conducted on springs not originating from rock glaciers, serving as a comparative approach.

The springs associated to rock glaciers draw water from four sources: groundwater, rain, snow and permafrost (Krainer et al., 2007). Among these, snow and permafrost are the primary sources that regulate the low spring temperatures. The cooling effect of a persistent snow layer in mountainous regions such as the Retezat Mountains can have significant influence on spring water temperatures even in the summer months. After snow melts, the presence of permafrost mainly governs the low temperatures of the springs. Only four springs exhibited temperatures below 2°C during the warm season, while many others showed temperatures close to 2-3°C. Given the patchy occurrence of permafrost in the Southern Carpathians and the fact that the frozen materials are located a few hundred meters away from the rock glacier front we hypothesize that permafrost may also be present in rock glaciers characterized by spring temperatures above 2°C. Based solely on the results of physico-chemical analysis, it is impossible to differentiate whether the spring water originates from ice or snow.

KEYWORDS: permafrost, spring water, rock glaciers, SWTS

REFERENCES

Frauenfelder, R., Allgöwer, B., Haeberli, W. & Hoelzle, M. (1998). Permafrost investigations with GIS – a case study in the Fletschhorn area, Wallis, Swiss Alps. In Permafrost, Proceedings of the Seventh International Conference, 23–27June 1998, Yellowknife, Canada, Lewkowicz AG, Allard M (eds) eds, Collection Nordicana 57. Centre d’études Nordiques, Université Laval: Québec; 291–295.

Harris, S.A., French, H.M., Heginbottom, J.A., Johnston, G.H., Ladanyi, B., Sego, D.C., van Everdingen, R.O., 1988, Glossary of Permafrost and Related Ground-Ice Terms, National Research Council of Canada, Ottawa, 156 p.

Krainer, K., Mostler, W. & Spötl, C. (2007). Discharge from active rock glaciers, Austrian Alps: a stable isotope approach. Austrian Journal of Earth Sciences 100: 102–112.

Scapozza, C. (2009). Contributo dei metodi termici alla prospezione del permafrost montano: esempi dal massiccio della Cima di Gana Bianca (Val Blenio, Svizzera). Bollettino della Società Ticinese di Scienze Naturali 97: 55–66.

How to cite: Berzescu, O., Onaca, A., Perșoiu, A., Marin, C., Urdea, P., and Ardelean, F.: Spring water characteristics in the marginal permafrost region of the Southern Carpathians, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13106, https://doi.org/10.5194/egusphere-egu24-13106, 2024.

EGU24-13110 | ECS | Posters on site | CR4.1

Carbon Cycling and Nutrient Storage in Supraglacial Environments on the western margin of the Greenland Ice sheet 

Quincy Faber, Madison Flint, Katelyn Palmer, Tatiana Salinas, Yuseung Shin, Matthew Cohen, Ellen Martin, Jonathan Martin, Andrea Pain, and Brent Christner

During summer, exposed ice on the surface of glaciers becomes weathered by solar radiation, creating a ~1 m water-saturated layer of porous ice referred to as the weathering crust aquifer. Here we present results from a hydrological, biogeochemical, and microbiological study of supraglacial waters from the Greenland Ice Sheet margin in proximity to Kangerlussuaq. Through comparisons with supraglacial streams with relatively shorter water residence times, we demonstrate the weathering crust aquifer contains a distinct geochemical composition and unique community of microorganisms that is actively cycling carbon and nutrients. This evidence includes changes in the abundance of organic nutrients and compositional changes in the fluorescent dissolved organic matter properties over the melt season. Sources of organic matter production include photosynthesis, which was indicated by changes in the natural abundance of δ13C in inorganic carbon as well as in experiments where added 13CO2 was incorporated into biomass. Our results show there were relatively high dissolved concentrations of solute in the weathering crust aquifer in relation to supraglacial streams, implying water-sediment interactions occurring in the weathering crust affected the meltwater chemistry. Solutes enriched in the meltwater included trace elements (e.g., Zn, Ni, and Cu) and phosphorus, the latter of which could be due to the presence of apatite, an easily weatherable phosphorus-bearing mineral. Processes affecting the availability of phosphorus in supraglacial waters are significant considering results from nutrient addition experiments that demonstrated the supraglacial phototrophic communities were phosphorus limited. Cell and Chlorophyll a concentrations initially increased with progression of the melt season but decreased the late season, suggesting that much of the new biomass accumulating in the weathering crust aquifer during the summer months was subsequently transported downstream with meltwater. The study site is a component of a ~3000 km2  supraglacial catchment estimated to store ~0.5 km3 of meltwater per season that is discharged to the Akuliarusiarsuup Kuua, highlighting the scale of hydrological and biogeochemical processes influencing ecosystems near the ice sheet margin. Consequently, a better understanding of microbial processes cycling carbon and contributing to nutrient availability in the weathering crust aquifer is needed to decipher the biogeochemical effects on Arctic supraglacial and proglacial systems that are undergoing rapid changes.  

How to cite: Faber, Q., Flint, M., Palmer, K., Salinas, T., Shin, Y., Cohen, M., Martin, E., Martin, J., Pain, A., and Christner, B.: Carbon Cycling and Nutrient Storage in Supraglacial Environments on the western margin of the Greenland Ice sheet, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13110, https://doi.org/10.5194/egusphere-egu24-13110, 2024.

EGU24-13170 | ECS | Orals | CR4.1

Railways on Permafrost: Unique Challenges Observed at Bridge Crossings along the Hudson Bay Railway 

Natalie Arpin, Andy Take, and Ryley Beddoe

The Hudson Bay Railway (HBR) serves as the singular land pathway connecting the Pas to Churchill, Manitoba, Canada. Hence, it is an essential means of transportation for northern communities, enabling the transport of both goods and individuals. However, it has faced many operational challenges because of its remote geographical location and the permafrost conditions it passes over. Over its 1000-kilometre length, the permafrost conditions transition. The railway starts in the isolated permafrost zone in its most southern portions before passing over discontinuous permafrost and then reaching continuous permafrost in its northern section. One of the unique operational challenges present at bridge crossings is the phenomena of “frost jacking”.

Frost jacking refers to the upward displacement of pile bridge foundations caused by forces generated from frost heave in the surrounding ground. If the driving force from frost heave exceeds the frictional resisting forces anchoring a pile into the ground, uplift occurs. When designing pile foundations in cold regions, the potential effects of frost jacking must be considered, as any significant differential heave between piers or the abutments can lead to track geometry issues that affect operations and, in extreme cases, require bridge maintenance. However, research on frost jacking experienced by operational infrastructure has been very limited, which hinders the ability to account for its impacts.

The Horn Creek Crossing on the Hudson Bay Railway is a 30-metre-long, steel ballast deck bridge supported by H-piles. Over a 10-year period, the foundations of the bridge underwent hundreds of millimetres of differential heave before repairs were completed to level the structure in July 2022. Because of the bridge’s remote location, there is limited information on the rate and timing of when frost jacking occurred. Therefore, in 2022, a multi-sensor monitoring program was designed and subsequently installed on the bridge with the purpose of collecting data to explore the mechanism of frost jacking at this site.

Preliminary results from the first monitored winter season resulted in an average upward movement of 33 mm of the spans surrounding the northern pier. This upward movement occurred throughout the winter and ended when daily average temperatures became above 0°C. Afterwards, limited recovery was present in the spring when temperatures rose and was measured to be 11 mm, less than the upward movement measured. The monitoring process is still ongoing, with the aim of identifying longer-term trends and analyzing the outcomes of the repair work. Furthermore, using this site as the location of known differential heave at a railway bridge, methods are being developed to explore whether a parallel data source (track geometry data) can capture patterns and rates of seasonal differential heave at this and other bridges along the HBR.

How to cite: Arpin, N., Take, A., and Beddoe, R.: Railways on Permafrost: Unique Challenges Observed at Bridge Crossings along the Hudson Bay Railway, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13170, https://doi.org/10.5194/egusphere-egu24-13170, 2024.

EGU24-13291 | ECS | Orals | CR4.1

Developing, Testing, and Modeling of an Innovative Thermal Stabilization Method for Alpine Permafrost Protection 

Elizaveta Sharaborova, Hendrik Huwald, and Michael Lehning

Permafrost thawing in the Alps and elsewhere is leading to infrastructure failure. Implementation of protective measures is therefore necessary to avoid incidents and damage to both infrastructure and the environment. Existing methods for thermal stabilization of permafrost are not directly applicable to the particular conditions of the Alps. For instance, traditional passive thermal stabilization techniques do not provide rapid and substantial soil stabilization. Meanwhile, active methods present financial constraints and have not yet achieved complete efficiency. Here we present a novel solar-powered thermal stabilization system to effectively protect Alpine permafrost and the most vulnerable infrastructure built on it from the impacts of global warming. To understand how these thermal stabilization methods affect the permafrost, numerical simulations using the SNOWPACK model are performed for the Schilthorn Alpine permafrost site (Switzerland, 2900 m a.s.l.). First, the natural permafrost conditions in the soil are simulated as reference state. Then, thermal stabilization components are included and their effect is quantified and evaluated.

To demonstrate the working principle of the thermal stabilization system and to gauge its performance and requirements, a laboratory-scale prototype demonstrator of the system was built and experimental data of the prototype are compared to numerical simulations of a digital twin. The setup includes the components of the thermal stabilization system, which are a cooling pipe for generating a cold barrier layer, as well as temperature, soil moisture, and heat flux sensors for measuring the conditions and processes occurring in the permafrost sample. This data is used to assess the performance and efficiency of the thermal stabilization system. Measurement results indicate that a frozen barrier layer at the level of the pipes can be created and maintained, avoiding heat penetration deeper into the soil and keeping the permafrost sample frozen during the time of the experiment.

Findings from the prototype experiment combined with numerical modeling and optimized engineering will enable advanced engineering design and physical process understanding of effective thermal stabilization systems even considering further impact of climate change.

How to cite: Sharaborova, E., Huwald, H., and Lehning, M.: Developing, Testing, and Modeling of an Innovative Thermal Stabilization Method for Alpine Permafrost Protection, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13291, https://doi.org/10.5194/egusphere-egu24-13291, 2024.

EGU24-13630 | ECS | Posters on site | CR4.1

Time-series InSAR monitoring and analysis of permafrost thaw-subsidence dynamics based on the ARIMA Method 

Wenyan Yu, Mi Jiang, and Xiao Cheng

The freezing and thawing processes of the active permafrost layer, driven by temperature variations between summer and winter, lead to surface seasonal uplift and subsidence, which can be captured by time-series InSAR techniques and associated permafrost modeling. As climate change introduces variations in factors like soil moisture and temperature, the seasonal surface deformation experiences interannual and fluctuating variations. However, these variations have often eluded capture due to either the spatiotemporal filtering processes to mitigate atmospheric delay of temporal InSAR and the approximate assumptions in permafrost deformation models. To better capture the dynamic changes in surface deformation caused by permafrost freeze-thaw processes, we develop a seasonally varying deformation method based on Autoregressive Integrated Moving Average Model (ARIMA) time series analysis. Through both synthetic data and real data experiments, we validate that the proposed method can provide more accurate deformation results while capturing the interannual variations in permafrost deformation. The real-data experiment, utilizing Sentinel-1 data, reveals that the maximum seasonal deformations in the continuous permafrost region of northern Alaska exhibit an increasing-decreasing trend from 2017 to 2021, with 2019 showing a relative maximum, correlating with the number of thawing days and air temperature in that year. This study contributes to a deeper understanding of freeze-thaw processes in permafrost regions, providing robust support for analyzing the impact of climate change on surface deformations in permafrost areas.

How to cite: Yu, W., Jiang, M., and Cheng, X.: Time-series InSAR monitoring and analysis of permafrost thaw-subsidence dynamics based on the ARIMA Method, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13630, https://doi.org/10.5194/egusphere-egu24-13630, 2024.

EGU24-13876 | Posters on site | CR4.1

Permafrost hydrology in an Arctic tundra ecosystem: quantifying water sources using stable water isotopes 

Hyejung Jung, Jinho Ahn, Go Iwahana, and Jeonghoon Lee

Global warming in the Arctic can lead to the alteration of the hydrological cycle and the thawing of permafrost. In this study, we utilized stable water isotope techniques (δ2H and δ18O) to infer the sources mixing of stream water at two sites (HV and PS) along the Sag River on the North Slope, Alaska (USA) during August 2022. The isotopes of snow and rain samples were plotted above the LMWL and reflected the isotopic characteristics of seasonal precipitation in Alaska. The porewater collected within the active layer showed enriched isotope values than other samples, indicating summer precipitation. Using δ18O and deuterium excess in a Bayesian mixing model, we estimated the contribution rates of summer precipitation, seasonal ice, and ice wedge. The results indicated a substantial contribution from melted seasonal ice (HV: 96.8% and PS: 74.1%), formed by frozen precipitation from the previous year, to surface water in August. Additionally, it was observed that the contribution of ice wedge was relatively greater in the downstream (PS: 21.8%) compared to the upstream (HV: 2.1%). Furthermore, we observed that the isotopic compositions of surface water in the PS site revealed evidence of evaporation, as indicated by a characteristic isotopic fractionation slope. Summer precipitation (HV: 1.1% and PS:4.1%) did not contribute substantially to surface waters. This research provides insight into fundamental processes related to sources and mixing of waters in permafrost hydrology.

How to cite: Jung, H., Ahn, J., Iwahana, G., and Lee, J.: Permafrost hydrology in an Arctic tundra ecosystem: quantifying water sources using stable water isotopes, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13876, https://doi.org/10.5194/egusphere-egu24-13876, 2024.

EGU24-14509 | Posters on site | CR4.1

Carbon dioxide flux of various surface conditions for tundra ecosystem in High Arctic and Antarctic Peninsula 

Namyi Chae, Hyewon Hwang, Taejin Choi, Soon Gyu Hong, Hyoungseok Lee, and Bang Yong Lee

Carbon dioxide fluxes were measured in the tundra ecosystem in order to evaluate the potential future sensitivity of the carbon cycle to climate change using chamber methods during summer in the Antarctic and high Arctic. The study sites are located on tundra in Baton Peninsula of King George Island, Antarctic Peninsula (62°13’ 28.87"S, 58°47’18.37"W) and high-arctic near Cambridge Bay, Nunavut, Canada (69°7'47.7"N, 105°3'35.3"W). The site of Baton Peninsula is mainly covered with various lichens and mosses and the site of Cambridge Bay is mainly covered with dwarf-shrubs, graminoids, mosses and lichens. CO2 flux was examined to understand change of the carbon cycle over the tundra ecosystems with various conditions for vegetation and soil. The emission CO2 flux and net CO2 exchange showed distinguished differences on type of vegetation and surface soil organic content. The variability of carbon flux depends on soil temperature and soil water content. Net CO2 exchange, soil respiration, and gross primary production were measured or calculated to investigate the influence of the ecosystem in the tundra carbon cycle in the Polar region. This study was supported by a National Research Foundation of Korea grant from the Korean government (MSIP) (NRF-2021M1A5A1065679 and NRF-2021R1I1A1A01053870) and PE 24130.  

 

How to cite: Chae, N., Hwang, H., Choi, T., Hong, S. G., Lee, H., and Lee, B. Y.: Carbon dioxide flux of various surface conditions for tundra ecosystem in High Arctic and Antarctic Peninsula, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14509, https://doi.org/10.5194/egusphere-egu24-14509, 2024.

EGU24-14950 | Posters on site | CR4.1

Simulating ground temperatures in mountainous terrain with remote sensing observations and modeling 

Dirk Scherler, Moritz Langer, Hendrik Wulf, Deniz Gök, and Marcia Phillips

The warming of high mountain regions caused by climate change leads to decreasing snow cover and thawing permafrost, which has far-reaching effects on ecosystems and societies. In this study, we used historical observations of land surface temperature (LST) derived from Landsat satellite data in conjunction with 1-D thermal modeling to simulate the annual evolution of ground temperatures. Our model includes precipitation and the evolution of snow cover, which exerts important control on ground temperatures. We tested this approach in the European Alps, where snow depth observations from high-elevation sites in Switzerland allowed us to evaluate the performance of different precipitation data sets and a simple scheme for snow removal by avalanches. We assessed our model results by comparing them with existing temperature measurements at boreholes and with Landsat-derived snow cover frequencies. All our analysis is based on daily conditions, but averaged over multiple years, hence neglecting interannual variability. Preliminary results indicate generally good agreement between modelled and observed values at weather stations, depending on the used precipitation data set and the sensitivity of the simple snow avalanche scheme. Typical root-mean-square errors (RMSE) are (1) ~2.7 K for daily ground surface temperature, (2) ~50 cm for daily snow depth, and (3) ~25% for monthly snow cover frequency. Typical RMSE for borehole temperatures are ~2 K at depths >1 m, and somewhat higher, at ~4 K for shallow depths (<1 m). It is worth noting that the global statistics is unevenly distributed, with some sites showing much larger errors than others. Besides deficiencies in the modeling, this could also be related to steep spatial gradients in LST, not well captured by the coarser resolution of the Landsat series (60-120 m) in comparison with the ground observations. Unless the used precipitation data sets exhibit regional bias or the snow avalanche model requires regional tuning, the presented approach is independent from ground-truth measurements and can in principle be applied anywhere on Earth. The model can be used to infer ground temperatures and its likely changes as a function of changes in LST and snow cover.

How to cite: Scherler, D., Langer, M., Wulf, H., Gök, D., and Phillips, M.: Simulating ground temperatures in mountainous terrain with remote sensing observations and modeling, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14950, https://doi.org/10.5194/egusphere-egu24-14950, 2024.

EGU24-16607 | ECS | Orals | CR4.1

Long-term soil redox dynamics of intact and degraded permafrost in Interior Alaska 

Patrick Liebmann, Cordula Vogel, Jiri Barta, Tim Urich, Alexander Kholodov, Milan Varsadiya, Muhammad Waqas, Haitao Wang, Oliver Donnerhack, Olga Shibistova, Stefan Wessel-Bothe, Tim Mansfeldt, and Georg Guggenberger

Permafrost degradation, freezing and thawing processes, and poor drainage due to underlain frozen ground have far-reaching consequences on soil hydrology and biology and, thus, on the redox dynamic in soils of the Arctic. Assessing the redox status of these soils is essential for understanding soil organic matter decomposition processes and can be done by temporal measurements in the field, analyses of redox-sensitive elements, or identification of microbial species or enzymes in redox process chains. While such approaches provide snippets of the complex redox dynamic, publications reporting long-term in-situ redox potential (EH) measurements in arctic permafrost soils are scarce. Limited accessibility to study sites and technical limitations in measuring the redox potential in a frozen environment may be two reasons for this research gap.

But how does the redox potential develop in permafrost soils at different depths in the active layer during the summer? What happens during freezing and thawing? Finally, do thawing/degrading permafrost soils show different patterns compared to intact permafrost?

We approached these research questions by installation of a unique soil monitoring setup at 3 sites near Fairbanks, Alaska, in August 2021. An intact permafrost soil (active layer depth about 50 cm) was equipped with 3 redox electrodes (for EH) and 3 hydra probes (for water content and soil temperature) in the topsoil and subsoil, respectively, and connected to a logger unit allowing continuous measurement of these parameters in both depths every 15 minutes. In addition, two sites with advanced permafrost degradation (permafrost level below 100 cm) were equipped in the same way. One degraded site featured large water contents, representing a wet thaw scenario, while the other site was well-drained, representing a dry thaw scenario, thus representing different endmembers of the ongoing climate-change induced permafrost thaw.

Here, we present the first 2 years of soil monitoring in a discontinuous permafrost area in Interior Alaska from 09/2021 to 09/2023. Overall, pH values of all soils varied between 4.5-6.3. The dry thaw scenario showed oxic conditions (i.e., EH >600 mV) in top- and subsoil, while water contents were low. The wet thaw scenario exhibited high topsoil redox potentials (i.e., EH >500 mV), while subsoil redox potential was lower (i.e., EH <500 mV). High water contents in both intact permafrost and wet thaw scenario demonstrated a pronounced zero curtain effect over several months during the long winter season due to the release of latent heat during freezing. We further detected a strong 200-600 mV decrease in EH in the topsoil of the intact permafrost active layer during the summer season, reaching reducing conditions 1-3 months after seasonal thaw. Redox measurements in the subsoil of the intact permafrost active layer, which was about 25 cm below the topsoil measuring depth and about 5 cm above the frozen ground, revealed EH of >400 mV in the summer period (August to October), suggesting less oxygen consumption in this recently thawed permafrost subsoil.

How to cite: Liebmann, P., Vogel, C., Barta, J., Urich, T., Kholodov, A., Varsadiya, M., Waqas, M., Wang, H., Donnerhack, O., Shibistova, O., Wessel-Bothe, S., Mansfeldt, T., and Guggenberger, G.: Long-term soil redox dynamics of intact and degraded permafrost in Interior Alaska, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16607, https://doi.org/10.5194/egusphere-egu24-16607, 2024.

Knowing the Freeze-Thaw (FT) state/ice content/freezing front depth of the land surface is essential for many aspects of weather forecasting, climate, hydrology, and agriculture. Microwave L-band emission contains rather direct information about the FT-state because of its impact on the soil dielectric constant, which determines microwave emissivity and the optical depth profile. However, current L band-based FT algorithms need reference values to distinguish between frozen and thawed soil, which are often not well known. 

We present a series of new frozen soil detection algorithms based on the daily variation of the H-polarized brightness temperature. Exploiting the daily variation signal allows for a more reliable state detection, particularly during the transition periods, when the near-surface soil layer may freeze and thaw on sub-daily time scales. The new algorithms explore and prove that we can get the Freeze-Thaw (FT) state/ice content/freezing front depth of the land surface with a delicate analysis of the L-band passive brightness temperature signals. These studies are expected to extend L-band microwave remote sensing data for improved FT detection.

How to cite: Lv, S.: Validation of the Diurnal Amplitude Variations for Freeze-Thaw (DAV-FT) algorithm with the National Ecological Observatory Network (NEON) soil temperature data, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20202, https://doi.org/10.5194/egusphere-egu24-20202, 2024.

EGU24-22269 | Orals | CR4.1 | Highlight

The Virtual Alpine Observatory (VAO) acting to better observe, understand, forecast and react to climate change in a combined Network of European High-Altitude Research Stations 

Michael Krautblatter, Verena Stammberger, Birgit Einhellinger, Helmut Theiler, Reinhard Zeitler, Marc Zebisch, Elke Ludewig, Peter Marton, Nathalie Cotte, Griša Močnik, Markus Leuenberger, Silvio Decurtins, and Sabine Kraushaar

The Alpine region undergoes a faster and more pronounced climate change than surrounding lowlands and, therefore, is a time machine showing the things to come in a changing climate and environment. Under the influence of a robust warming trend, witnessing an ascent of >1°C since the 1980s significant effects are visible and measurable in atmosphere, biosphere, hydrosphere, and most apparently the cryosphere.

The Virtual Alpine Observatory is an assemblage comprising European Alpine Observatories, high alpine research facilities, data archives, and supercomputing centers, seamlessly interwoven through shared infrastructure and collaborative research pursuits. It is the answer to how the complex Alpine environmental system can be addressed by an interdisciplinary, cross-border collaborating research paradigm. At its core, the primary objective is to orchestrate collective endeavors aimed at observing, comprehending, and prognosticating the ramifications of climate change on the Alpine expanse. This extends to the multifaceted facets of the environment in multiple aspects.

This alliance of researchers and data-gathering institutions spanning the Alpine landscape and analogous mountainous terrains in Europe propels the exploration of data patterns transcending national boundaries. In doing so, it creates a reservoir of data, knowledge and scientific approaches that surpasses the cumulative understanding derived from its individual constituents.

In the upcoming discourse, we illuminate the network's future goals, composition, unveil forthcoming research initiatives, expound upon data availabilities, and deliberate on the trajectories that lie ahead for collaborative efforts.

The VAO network is substantially funded by the Bavarian State Ministry of the Environment and Consumer Protection.

How to cite: Krautblatter, M., Stammberger, V., Einhellinger, B., Theiler, H., Zeitler, R., Zebisch, M., Ludewig, E., Marton, P., Cotte, N., Močnik, G., Leuenberger, M., Decurtins, S., and Kraushaar, S.: The Virtual Alpine Observatory (VAO) acting to better observe, understand, forecast and react to climate change in a combined Network of European High-Altitude Research Stations, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-22269, https://doi.org/10.5194/egusphere-egu24-22269, 2024.

EGU24-149 | ECS | Orals | CR4.2

Quantifying permafrost organic carbon remineralization after redeposition on the ocean floor, using  δ13C and F14C. 

Manuel Ruben, Jens Hefter, Torben Gentz, Florence Schubotz, Bingbing Wei, Bo Liu, Michael Fritz, Anna Maria Irrgang, Anabel von Jackowski, Walter Geibert, and Gesine Mollenhauer

Arctic permafrost is a critical global tipping element in a warming climate. Annually, the erosion of coastal permafrost discharges an estimated 5 to 14 Tg of organic carbon (OC) into the Arctic Ocean. Although this previously stored OC has the potential to be reintroduced into the atmosphere, thus accelerating human-induced climate change, little is known about the benthic remineralization processes of permafrost OC after erosion and redeposition on the ocean floor. Our research quantified fluxes of dissolved inorganic carbon (DIC) and analyzed its isotopic composition of nearshore sediments in the Canadian Beaufort Sea, specifically off Herschel Island. Our findings showed a DIC release of 0.217 mmo/m²/d, with an average signature of δ13C = -22.44 ± 72 ‰ and F14C = 0.548 ± 0.007. Utilizing a model that combines two carbon isotopes, we estimate that approximately 38 ± 10% of the released DIC is a result of subsurface degradation of redeposited permafrost OC, with an additional 15 ± 12% originating from redeposited active layer OC. Additionally, isotopic endmember analysis was utilized on bacterial membrane lipids from live sedimentary bacteria to determine the relative utilization of OC sources in bacterial communities within shallow subsurface sediment (<25 cm). Our results indicate that, on average, these communities obtain 73 ± 10% of their OC from recent marine primary production, 11 ± 6% from permafrost OC, and 16 ± 11% from active layer OC. This study is the first direct quantitative assessment of the release of permafrost OC into the active carbon cycle after it has been redeposited on the ocean floor, as far as we know. The data suggest that the redeposited permafrost OC is easily accessible and utilized by subsurface bacteria. Considering the immense size and vulnerability of the eroding coastal permafrost OC pool, 27 to 53% of it contributing to benthic DIC fluxes could have a prolonged effect on the world's climate, worsening the climate emergency.

How to cite: Ruben, M., Hefter, J., Gentz, T., Schubotz, F., Wei, B., Liu, B., Fritz, M., Irrgang, A. M., von Jackowski, A., Geibert, W., and Mollenhauer, G.: Quantifying permafrost organic carbon remineralization after redeposition on the ocean floor, using  δ13C and F14C., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-149, https://doi.org/10.5194/egusphere-egu24-149, 2024.

EGU24-559 | ECS | Orals | CR4.2

Detecting lowland thermokarst development by UAV remote sensing in the Stordalen mire, Abisko, Sweden  

Maxime Thomas, Thomas Moenaert, Éléonore du Bois d’Aische, Maëlle Villani, Catherine Hirst, Erik Lundin, François Jonard, Sébastien Lambot, Kristof Van Oost, Veerle Vanacker, Reiner Giesler, Carl-Magnus Mörth, and Sophie Opfergelt

In situ field studies in thawing permafrost regions have shown that C emissions resulting from organic carbon (OC) decomposition depend among others on the variability in soil water content, which can be directly related to microtopography. A more precise assessment of the evolution of permafrost C emissions as a function of thermokarst development requires high-resolution quantification of thermokarst-affected areas, as lowland thermokarst development induces fine-scale spatial variability (~ 50 – 100 cm). Here, we investigate a gradient of lowland thermokarst development at Stordalen mire, Abisko, Sweden, from well-drained undisturbed palsas to inundated fens, which have undergone ground subsidence. We produced orthomosaics and digital elevation models from very-high resolution (10 cm) UAV photogrammetry as well as a spatially continuous map of soil electrical conductivity (EC) based on Electromagnetic Induction (EMI) measurements performed in September 2021. In conjunction, we measured in situ the soil water content from the different stages of thermokarst development at the same period. The soil EC values are contrasted along the gradient in line with contrasts observed in the landscape classification derived from the orthomosaics and digital elevation models: palsas are flat areas with low soil EC (drier), whereas fens are subsided areas with higher EC (water-saturated). Areas in the course of degradation (transition zones) are well identified based on their higher slope, and broad range of EC. Importantly, these transition zones are only detected using a very fine spatial scale (i.e., 10 cm) coupled to information on the microtopography. Compared to a set of previously collected orthomosaics and digital elevation models, our results show an acceleration of thermokarst development in this area with a rate of palsa decline 4 to 10 times greater in 2019-2021 than in 2000-2014.

How to cite: Thomas, M., Moenaert, T., du Bois d’Aische, É., Villani, M., Hirst, C., Lundin, E., Jonard, F., Lambot, S., Van Oost, K., Vanacker, V., Giesler, R., Mörth, C.-M., and Opfergelt, S.: Detecting lowland thermokarst development by UAV remote sensing in the Stordalen mire, Abisko, Sweden , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-559, https://doi.org/10.5194/egusphere-egu24-559, 2024.

EGU24-630 | ECS | Posters on site | CR4.2

Multitemporal UAV LiDAR detects seasonal heave and subsidence on palsas 

Cas Renette, Sofia Thorson, Mats Olvmo, Björn Holmer, and Heather Reese

In the context of the accelerating impacts of climate change on permafrost landscapes, this study employs UAV (Unmanned Aerial Vehicle) LiDAR technology to investigate seasonal terrain changes in palsas – mounds of frozen peat – since traditional remote sensing methods have struggled to capture the full dynamics of these landforms. We investigated two tall (4–5 m tall) palsas in Sweden's largest palsa mire complex, where we performed five field campaigns between September 2022 and September 2023 to track intra-annual frost heave and thaw subsidence. Our approach allowed us to create digital terrain models (DTMs) from high density point clouds (>1,000 points/m²) and analyze elevation changes over time. We found that both palsas heaved 0.15 m from September to April and subsided back to their height from the previous year, or slightly below, over the course of the following summer. At one of the palsas, we observed notable lateral degradation over the study period in a 300 m2 area, with 0.5–2.0 m height loss, likely initiated during the preceding warm and wet summer months. Part of this degradation occurred between September 2022 and April 2023, suggesting that the degradation of these palsas is not limited to the summer months. Our study shows the value of using UAV LiDAR for understanding how permafrost areas are changing. It helps in tracking the ongoing effects of climate change and highlights palsa dynamics that would not be captured by annual measurements only.

How to cite: Renette, C., Thorson, S., Olvmo, M., Holmer, B., and Reese, H.: Multitemporal UAV LiDAR detects seasonal heave and subsidence on palsas, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-630, https://doi.org/10.5194/egusphere-egu24-630, 2024.

EGU24-2165 | ECS | Orals | CR4.2

Modern spatial distribution of diverse retrogressive thaw slumps in West Siberia 

Nina Nesterova, Ilya Tarasevich, Marina Leibman, Aleksander Kizyakov, Ingmar Nitze, and Guido Grosse

Regressive thaw slumps (RTSs) are permafrost landforms formed by the thawing of ice-rich permafrost or the melting of massive ground ice. The West Siberian Arctic (Yamal and Gydan peninsulas) is an area with widespread distribution of RTSs due to continuous permafrost and massive tabular ground ice close to the surface. The initiation of RTS in the region strongly affects the environment by altering vegetation and topography and releasing carbon. Roads and railways are also affected by RTS occurrence.  

There is still no complete understanding of the true RTS distribution and its environmental controls in the West Siberian Arctic because of the remote location of the region. A remote sensing technique can be used to enhance our understanding of the characteristics of RTS over a large area. However, automated mapping of RTSs has certain limitations, including the lack of ground truth data, the large number of false-positive detections, and the ambiguity in interpretation. Moreover, the polycyclic nature of RTS development leads to a very complex spatial aggradation with numerous overlapping or nested RTSs. This poses additional challenges for mapping.

Based on theoretical and field studies, we developed a classification to capture the main morphological and environmental parameters of RTS nature visible on satellite imagery. To minimize false-positive detections we performed in-detail manual mapping of the RTSs in West Siberia using multiple sources including the ESRI satellite base map, Google Earth satellite base map, and Yandex Maps satellite base map. Each point was classified by several parameters: morphology, spatial aggradation, concurrent cryogenic processes, terrain position, and attachment to the base level. Field experience and data at the key sites, as well as a helicopter-based inventory, helped to perform verification and estimate accuracy.

We identified more than 4000 RTSs. The spatial distribution of identified RTSs demonstrates clusters over the western Yamal Peninsula and central-northern Gydan Peninsula. This research aims at a comprehensive analysis of the spatial distribution of classified RTS concerning regional geological, climate, and other available environmental data. Our results are valuable for understanding the nature of this widespread phenomenon in the Arctic.

How to cite: Nesterova, N., Tarasevich, I., Leibman, M., Kizyakov, A., Nitze, I., and Grosse, G.: Modern spatial distribution of diverse retrogressive thaw slumps in West Siberia, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2165, https://doi.org/10.5194/egusphere-egu24-2165, 2024.

EGU24-2291 | ECS | Orals | CR4.2

Expansion of wildfires and their impact on carbon emissions over pan-Arctic permafrost 

Xingru Zhu, Gensuo Jia, and Xiyan Xu

Wildfires over permafrost put perennially frozen carbon at risk. However, burned area and wildfire carbon emissions from biomass burning over the diverse range of permafrost regions have not been revealed. Here, we show that continuous permafrost was a major contribution to wildfire expansion and carbon emission in the pan-Arctic over the last two decades. Burned area and wildfire carbon emissions dramatically increased over continuous permafrost during the last two decades, but decreased in other permafrost regions. Accelerating wildfire emission from continuous permafrost region is the single largest contribution to the increased emissions in northern permafrost regions. The share of permafrost in global wildfire CO2 emissions grew from 2.42% in 1997 to 20.86% in 2021. Wildfire expansion is closely linked to an increased soil moisture deficit, considering wildfires there combust more than 90% of belowground fuel. Continuous permafrost experiences more severe fire-induced degradation. Active layer thickening following wildfires over continuous permafrost lasts more than three decades to reach a maximum of more than triple the pre-fire thickness. These findings highlight expansion of wildfires and acceleration of fire-induced carbon emission from continuous permafrost region, which disturbs organic carbon stock, accelerates the positive feedback between permafrost degradation and climate warming.

 

How to cite: Zhu, X., Jia, G., and Xu, X.: Expansion of wildfires and their impact on carbon emissions over pan-Arctic permafrost, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2291, https://doi.org/10.5194/egusphere-egu24-2291, 2024.

Thawing of permafrost due to climate change is known to release gases such as the climate drivers carbon dioxide and methane, as well as the carcinogen radon. Radon is a natural radioactive gas responsible for about 10% of lung cancer deaths globally, and substantially greater rates in sub-Arctic communities. Gas transport is significantly reduced in permafrost, but now that permafrost is thawing due to climate change, the effect on the release of CO2 and CH4, and on domestic radon exposure is unknown.

Measurement: Few experimental measurements have shown the gas permeability of permafrost to be very small (order of 10-16 m2). Here we present the initial measurements of the changes in porosity and gas permeability during the thawing of synthetic permafrost using a pyknopermeameter that we are developing. The results show increases in gas permeability by many orders of magnitude, that remain during freeze-thaw cycles providing the thawed water does not drain from the sample. Draining the thawed water leads to compaction which decreases the effects of subsequent thawing on the matrix gas permeability, but can cause fracturing which provide high permeability pathways for gas flow.

Modelling: Results from radon transport modelling through soil, permafrost, and model buildings either with basements or built on piles show that permafrost acts as an effective radon barrier, reducing radiation exposure to a tenth of the background level in dwellings while producing a ten-fold increase in the radon activity below the permafrost. When we model thawing of the permafrost barrier, we find no increase in radon to the background level for buildings on piles.  However, for buildings with basements, the level of radioactivity due to the radon increases to over one hundred times its initial value and can remain above the 200 Bq/m3 threshold for up to 7 years depending on the depth of the permafrost and the speed of thawing. When thawing speed is taken into account, radiations remain higher than the threshold for all scenarios where 40% thawing occurs within 15 years. This new information suggests that the sub-Arctic population could be exposed to dangerous radon levels as a result of climate change.

How to cite: Glover, P.: Modelling and Measurement of Radon and CO2 Release from Thawing Permafrost Caused by Climate Change, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2682, https://doi.org/10.5194/egusphere-egu24-2682, 2024.

EGU24-2979 | Orals | CR4.2

Intensified warming effects on soil respiration upon thermokarst formation 

Yuanhe Yang, Guanqing Wang, and Yunfeng Peng

As global temperatures continue to rise, a key uncertainty of terrestrial carbon (C) climate feedback is the rates of C loss upon abrupt permafrost thaw. This type of thawing - termed thermokarst - may in turn accelerate or dampen the response of microbial degradation of soil organic matter and carbon dioxide (CO2) release to climate warming. However, such impacts have not yet been explored in experimental studies. Here, by experimentally warming three thermo-erosion gullies in an upland thermokarst site combined with incubating soils from another five thermokarst-impacted sites on the Tibetan Plateau, we investigate whether and how abrupt permafrost thaw would influence the responses of soil CO2 release to climate warming. Our results show that warming-induced increase in soil CO2 release is higher in thermokarst features than the adjacent non-thermokarst landforms. This larger warming response is mainly attributed to the lower substrate quality and higher abundance of microbial functional genes for recalcitrant C degradation in thermokarst-affected soils. Taken together, our study provides experimental evidence that abrupt permafrost thaw aggravates the warming-associated soil CO2 loss, which will exacerbate the positive soil C-climate feedback in permafrost-affected regions under future warming scenarios.

How to cite: Yang, Y., Wang, G., and Peng, Y.: Intensified warming effects on soil respiration upon thermokarst formation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2979, https://doi.org/10.5194/egusphere-egu24-2979, 2024.

EGU24-3674 | Posters on site | CR4.2

Rapidly forming submarine craters and massive ice outcrops along the Arctic shelf edge: by-products of subsea permafrost degradation 

Charles K. Paull, Jong Kuk Hong, David W. Caress, Roberto Gwiazda, Ji-Hoon Kim, Mathieu J. Duchesne, Eve Lundsten, Jennifer B. Paduan, Tae Siek Rhee, Young Keun Jin, Virginia Brake, Jeffrey Obelcz, and Maureen Walton

Substantial morphological changes are rapidly occurring along the Canadian Arctic shelf edge (Paull et al., 2022, PNAS). During a 2022 IBRV Araon cruise, autonomous underwater vehicle mapping surveys identified several new craters that formed between 2019 and 2022. Five multibeam bathymetric mapping surveys, each partially covering a 15 km2 study area between 120 and 200 mwd have now been conducted over a 12-year time period. These repeat surveys reveal 65 new depressions developed averaging 6.5 m deep and reaching up to 30 m deep. Remotely operated vehicle investigations also discovered outcrops of massive ice exposed on the flanks of the newest craters. This ice is not believed to be relic permafrost formed during Pleistocene sea-level low-stands because the host sediments were deposited in a submarine setting. The low porewater salinity and light isotopic compositions in the meltwater of ice samples from sediment cores indicate brackish waters reflecting a meteoric source are discharging and freezing in this area. The ascending brackish groundwater is likely derived from melting relict permafrost under the shelf. The ~ -1.4°C bottom water temperatures provide conditions appropriate for freezing brackish porewaters within the near seafloor sediments. Conditions appropriate for the melting of ice also exist nearby where ice is in contact with seawater or warmed by ascending groundwater. Small variations in either temperature or salinity, over time, can shift equilibrium conditions of ice formation and degradation, which leads to repetitive freezing and thawing of ascending brackish groundwater and the development of wide-spread ice layers in the near seafloor sediments. These conditions have produced a dramatic submarine thermokarst morphology riddled with multi-aged depressions captured in the repeat mapping surveys. These findings suggest that the distribution of submarine permafrost ice should be reassessed as it may include extensive areas where ice formed during the Holocene where groundwaters discharge at sub-zero temperatures, in addition to relict Pleistocene permafrost.

How to cite: Paull, C. K., Hong, J. K., Caress, D. W., Gwiazda, R., Kim, J.-H., Duchesne, M. J., Lundsten, E., Paduan, J. B., Rhee, T. S., Jin, Y. K., Brake, V., Obelcz, J., and Walton, M.: Rapidly forming submarine craters and massive ice outcrops along the Arctic shelf edge: by-products of subsea permafrost degradation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3674, https://doi.org/10.5194/egusphere-egu24-3674, 2024.

EGU24-4091 | ECS | Orals | CR4.2

Artificial light at night reveals hotspots and rapid development of industrial activity in the Arctic 

Cengiz Akandil, Elena Plekhanova, Nils Rietze, Jacqueline Oehri, Miguel O. Roman, Zhuosen Wang, Volker Radeloff, and Gabriela Schaepman-Strub

Climate warming enables easier access and operation in the Arctic, fostering industrial and urban development. However, there is no comprehensive pan-Arctic overview of industrial and urban development, which is crucial for the planning of sustainable development of the region. In this study, we utilize satellite derived artificial light at night (ALAN) data to quantify the hotspots and the development of human activity across the Arctic from 1992 – 2013. We find that out of 16.4 million km2 analyzed a total area of 839,710 km2 (5.14%) is lit by human activity with an annual increase of 4.8%. The European Arctic and the oil and gas extraction regions in Russia and Alaska are hotspots of ALAN with up to a third of the land area lit, while the Canadian Arctic remains dark to a large extent. On average, only 15% of lit area in the Arctic contains human settlement, indicating that artificial light is largely attributable to industrial human activity. With this study, we provide a new, standardized approach to spatially assess human industrial activity across the Arctic, independent from economic data. Our results provide a crucial baseline for sustainable development and conservation planning across the highly vulnerable Arctic region.

 

How to cite: Akandil, C., Plekhanova, E., Rietze, N., Oehri, J., Roman, M. O., Wang, Z., Radeloff, V., and Schaepman-Strub, G.: Artificial light at night reveals hotspots and rapid development of industrial activity in the Arctic, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4091, https://doi.org/10.5194/egusphere-egu24-4091, 2024.

EGU24-4769 | ECS | Posters on site | CR4.2

Permafrost thermal response to improved soil hydro-thermodynamics in historical and scenario simulations with a modified version of the MPI-ESM  

Félix García-Pereira, Jesús Fidel González-Rouco, Nagore Meabe-Yanguas, Norman Julius Steinert, Johann Jungclaus, Philip de Vrese, and Stephan Lorenz

Soil warming is particularly sensitive in Arctic regions, underlain by permafrost. Permafrost degradation with warming enhances the release of substantial amounts of carbon into the atmosphere, which acts as a positive radiative feedback. However, the increasing temperature is not the only factor affecting permafrost degradation. Water availability changes affecting the Arctic, induced by changes in the atmospheric general circulation considerably affect the soil moisture and ice presence and subsequently thermal structure in permafrost regions. The interaction between soil hydrology and thermodynamics is still poorly represented by most of the CMIP6 land surface models (LSMs), mainly in terms of the soil depth, vertical resolution, and coupling between hydrology and thermodynamics.

This work explores the response of the Max Planck Institute Earth System Model (MPI-ESM) in historical and scenario simulations to changes in the hydrological and thermodynamic features of its LSM, JSBACH, in permafrost-affected regions. An ensemble of experiments was performed with varying soil depth and vertical resolution under two configurations of the hydro-thermodynamical coupling, which generate comparatively drier or wetter conditions over permafrost areas. Results show that deepening JSBACH reduces the intensity of near-surface warming, reducing the deep permafrost degradation area by ca. 2 million km2 and constraining the active layer thickness deepening by the end of the 21st century in high radiative forcing scenarios. Nevertheless, the largest impacts on permafrost extent and active layer thickness are produced by the dry and wet settings, which yield diverging soil moisture and warming conditions during the 21st century. These two configurations show differences in near-surface and deep permafrost extent of up to 5 million km2 by the end of the 21st century.

How to cite: García-Pereira, F., González-Rouco, J. F., Meabe-Yanguas, N., Steinert, N. J., Jungclaus, J., de Vrese, P., and Lorenz, S.: Permafrost thermal response to improved soil hydro-thermodynamics in historical and scenario simulations with a modified version of the MPI-ESM , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4769, https://doi.org/10.5194/egusphere-egu24-4769, 2024.

EGU24-5063 | Posters on site | CR4.2

Geological features of methane vents in the East Siberian Sea, the Arctic Ocean 

Jong Kuk Hong, Seung-Goo Kang, Yeonjin Choi, Tae Siek Rhee, Sookwan Kim, Younggyun Kim, and Young Keun Jin

The Eastern Siberian Sea is known for the presence of subsurface permafrost and for emitting significant amounts of methane close to the coastline. The thawing of permafrost accelerates the release of methane and carbon dioxide, contributing to increased greenhouse gas concentrations in the atmosphere. In 2021 and 2023, a multidisciplinary survey aboard the Korean icebreaker Araon was conducted on the continental shelf of the East Siberian Sea. The survey area lies more than 500 km away from the nearest coastline and falls within international waters. During the survey, areas with high methane concentration were identified on the shallow continental shelf, at depths ranging from 50 to 70 meters, utilizing underway CH4 measurements. These zones extend in a northwest-southeast direction. Multiple surveys were conducted to pinpoint gas seepage zones and delineate subsurface structures. The EK80 scientific echosounder proved instrumental in locating the gas vents, as it displayed methane gas eruptions clearly, resembling pillars in the imaging. The shallow sedimentrary structure of the lower part of the gas vent, observed  by the SBP survey, revealed high-amplitude reflections at a shallow depth (~5 m) below the seafloor. At the gas expulsion sites, seismic profiles show numerous vertical faults within the shallow sedimentary layers and scatterings in the water column caused by the methane emission from the seafloor. Backscattered images from the side-scan sonar clearly depict gases emitting from the vents and moving upward in the water column. These gas vents were found to have about 10 meters in diameter.

How to cite: Hong, J. K., Kang, S.-G., Choi, Y., Rhee, T. S., Kim, S., Kim, Y., and Jin, Y. K.: Geological features of methane vents in the East Siberian Sea, the Arctic Ocean, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5063, https://doi.org/10.5194/egusphere-egu24-5063, 2024.

The stability and spatial distribution of subsea permafrost across the Arctic continental shelves play a pivotal role in our understanding of global warming. Serving as a significant carbon store, this permafrost has the potential to release greenhouse gases when it thaws, significantly influencing the global climate. This study is dedicated to a comprehensive investigation of the extent and state of submarine permafrost within the Arctic, with a particular focus on the comparative analysis of subsea permafrost development along the continental shelves of the Beaufort and East Siberian Seas. This research enhances our grasp of Arctic subsea permafrost's current variability and its role in global warming processes. To map the extent of subsea permafrost, we utilized multichannel seismic data from the Beaufort Sea (2014) and East Siberian Sea (2016, 2019), collected by the IBRV Araon. Employing a full waveform inversion approach, we precisely determined the seafloor permafrost's velocity structure, offering insights into its depth and state. The research reveals pronounced regional variations in the development of subsea permafrost on Arctic continental shelves. In particular, the continental shelf of the Beaufort Sea is characterized by a densely concentrated distribution of subsea permafrost extending to depths of up to 600 meters. In contrast, the continental shelf of the East Siberian Sea is dominated by permafrost that has thawed significantly, reaching depths of around 400 meters. These different regional patterns may be influenced by a number of factors, including the proximity of the shelf to the coast, the influence of ocean currents, the geological composition of the seabed and the prevailing thermal conditions. These findings suggest that the highly variable nature of submarine permafrost across the Arctic shelf is crucial to understanding warming induced changes in Arctic submarine permafrost and the potential for greenhouse gas release through permafrost dissociation.

How to cite: Jin, Y. K., Kang, S.-G., Choi, Y., Kim, S., and Hong, J. K.: Regional Variations of Subsea Permafrost Development on the Arctic Continental Shelves: A comparative analysis of the Beaufort and East Siberian Seas, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5198, https://doi.org/10.5194/egusphere-egu24-5198, 2024.

EGU24-5562 | ECS | Posters on site | CR4.2

Dynamics of permafrost thaw in Western Siberia - a 200 years multi-proxy and high-resolution reconstruction from Khanymei peatlands 

Agnieszka Halaś, Mariusz Lamentowicz, Milena Obremska, Dominika Łuców, and Michał Słowiński

Western Siberian peatlands are one of the biggest peatland complexes in the world. Despite playing an essential role in regulating global climate, these ecosystems still remain understudied. A lack of long-term multi-proxy studies comprehensively examining the dynamics between permafrost thaw and peatland ecosystems in Siberia makes it difficult to determine how these areas will be affected by future climate change. Our research covers the history of the Khanymei peatlands (63°43’N, 75°57’E), located in the discontinuous permafrost zone in the last 200 years (from the end of the Little Ice Age to modern times). In this study, we applied multi-proxy analysis (testate amoebae, plant macrofossil, pollen, micro and macro charcoal, LOI and XRF) on two cores from a transect between a peat mound and a thermokarst lake. A newly developed by Halaś et al. (2023) testate amoebae calibration data set based on samples from the Khanymei peatlands complex was used to reconstruct past changes in peatland hydrology. In the last 200 years, we observed constant drying of studied peatlands with events of wetting caused by thawing permafrost. Reconstructed changes in peatland vegetation indicate that lichens (genus Cladonia) dominate during stable permafrost phases. We discovered that peatland drying in recent decades caused the expansion of shrubs onto Khanymei peatlands, which is also widely observed in other parts of Arctic tundra. The increase in peatland moisture after thawing is noted only in the initial period and in a limited area. Thawing led to high Sphagnum growth and change in the structure of testate amoebae communities, with an increase of mixotrophic species like Placocista spinosa. Species with organic and idiosomic tests started to dominate in the community replacing species with agglutinated shells. We discovered that permafrost thawing resulted in a short-term increase of peat accumulation and carbon sequestration, increased abundance of fungal communities, and promotion of oxic conditions. Initially, positive effects of thawing (like carbon accumulation) quickly weakened as favorable moisture conditions disappeared.
As permafrost continues to thaw, these processes will occur on an increasingly larger scale. According to climate change predictions, this region in Western Siberia may become unsuitable for the functioning of permafrost peatlands in their current form.

References:

Halaś, A., Lamentowicz, M., Łuców, D., & Słowiński, M. (2023). Developing a new testate amoeba hydrological transfer function for permafrost peatlands of NW Siberia. Quaternary Science Reviews, 308, 108067. https://doi.org/10.1016/j.quascirev.2023.108067

The study was supported by the National Science Center (Grant no. 2019/35/O/ST10/0290 and 2021/41/B/ST10/00060) and INTERACT No. 730938.

How to cite: Halaś, A., Lamentowicz, M., Obremska, M., Łuców, D., and Słowiński, M.: Dynamics of permafrost thaw in Western Siberia - a 200 years multi-proxy and high-resolution reconstruction from Khanymei peatlands, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5562, https://doi.org/10.5194/egusphere-egu24-5562, 2024.

EGU24-7215 | ECS | Posters on site | CR4.2

Abrupt increase in Arctic-Subarctic wildfires following permafrost thawing in a warmer climate 

In-Won Kim, Axel Timmermann, Ji-Eun Kim, Keith Rodgers, Sun-Seon Lee, Hanna Lee, and William Wieder

Greenhouse warming is accelerating permafrost thaw and the risk of wildfires in the northern high latitudes. However, the impact of permafrost thaw on Arctic-Subarctic wildfires and the associated release of greenhouse gases and aerosols is less well understood. Here we investigate the effect of future permafrost thaw on Arctic-Subarctic wildfires using the CESM2 large ensemble simulations forced by the SSP3-7.0 greenhouse gas emission scenario. We find that an increase in soil permeability induced by rapid permafrost thawing leads to an abrupt increase in sub-surface runoff and a decrease in soil moisture over the Arctic-Subarctic region. This sudden soil drying causes a significant increase in surface air temperature and a decrease in relative humidity during summer. The resulting soil drying and atmospheric dryness lead to a rapid intensification of wildfires in western Siberia and Canada in the mid-to-late 21st century.

How to cite: Kim, I.-W., Timmermann, A., Kim, J.-E., Rodgers, K., Lee, S.-S., Lee, H., and Wieder, W.: Abrupt increase in Arctic-Subarctic wildfires following permafrost thawing in a warmer climate, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7215, https://doi.org/10.5194/egusphere-egu24-7215, 2024.

EGU24-8248 | Posters on site | CR4.2

To tile or not to tile? 

Melanie A. Thurner, Xavier Rodriguez-Lloveras, and Christian Beer

Soils and landscapes vary within centimeters to decameters, which is not captured by state-of-the-art land-surface models that operate on kilometer scale. This leads to potential mismatches when simulating the exchange of energy, water and gasses between land and atmosphere, which are summarized under the term “aggregation error”, and is a major source of uncertainty. To overcome this issue and account for subgrid-scale heterogeneity so-called tiling approaches are used, which separate grid cells internally into different tiles that interact with each other. Although this is a valid approach, it remains unclear, if and to what extend tiling reduces the aggregation error and consequently, if tiling is sufficient to account for subgrid-scale heterogeneity.

Permafrost soils are especially heterogeneous and the aggregation error when simulating permafrost landscapes is especially problematic, because it can make the differences between frozen and unfrozen, as well as waterlogged and unsaturated areas. This affects the presence of permafrost itself, the build of soil ice and resulting frost heave, and determines pond locations as well as the duration and thickness of the seasonal snow cover, which all together influence vegetation and thus ecosystem dynamics.

To address the sufficiency of tiling at permafrost landscapes, we apply the two-dimensional pedon-scale soil model DynSoM at a non-sorted circle site. We run DynSoM with four different horizontal resolutions: (i) with an explicit resolution of 10cm, (ii) with three tiles, representing center, rim, and interface area, (iii) with two tiles, representing center and rim, and (iv) without tiling, representing a typical state-of-the-art land surface model. By comparing mean simulations, we assess the benefits, but also the shortcomings and limitations of the different tiling set-ups, and discuss implications for tiling within kilometer-scale land-surface models.

How to cite: Thurner, M. A., Rodriguez-Lloveras, X., and Beer, C.: To tile or not to tile?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8248, https://doi.org/10.5194/egusphere-egu24-8248, 2024.

EGU24-8527 | ECS | Orals | CR4.2

Geospatial modelling of soil organic carbon density in 3D across the northern circumpolar permafrost region 

Friedrich Röseler, Claire Treat, and Gerard Heuvelink

The northern circumpolar permafrost region contains up to half of the global soil carbon pool and twice as much carbon as currently is in the atmosphere. At the same time, the Arctic is rapidly warming due to climate change, causing the permafrost to thaw. There is a risk that substantial amounts of soil organic carbon (SOC) may be released into the atmosphere as greenhouse gases during this process. This makes permafrost carbon a potentially strong climate feedback that could further amplify global warming.

Currently, only a few studies attempted to quantify this permafrost carbon on a global scale. Despite the advances in estimating how much SOC is stored in the northern circumpolar permafrost region, there are still large uncertainties. Modelling permafrost carbon is particularly challenging due to the scarce availability of reference datasets on SOC content and great subsurface variability in the Arctic environment caused by cryoturbation. The high lateral (i.e. horizontal) and vertical (i.e. along the soil profile) variability results in several obstacles when mapping SOC in permafrost regions.

While previous studies on modelling permafrost carbon focused on quantifying its spatial heterogeneity, they lacked in capturing the complex (vertical) distribution of SOC as a function of depth. Furthermore, they often rely on discrete models to estimate the spatial variation. In this work, we focus on providing more accurate high-resolution, continuous global maps of permafrost SOC density using a 3D digital soil mapping approach. Digital soil mapping has shown to be a valuable tool in mapping SOC, as it can better capture the continuous variation of soil properties. Here, we used a random forest machine learning model to predict SOC based on a number of spatial variables representing soil forming factors (such as topographic attributes, climate, carbon age and land cover). The reference dataset that we used to train the model consists of soil profile observations from the permafrost region of the Northern Hemisphere, excluding alpine permafrost. We harmonised this dataset from existing databases and recent studies that provide information on carbon content from soil core measurements. Information on the bulk density was needed to calculate the SOC density and estimated for missing observations using pedotransfer functions. Results indicate that 3D modelling of permafrost carbon produces substantially different results than conventional 2D approaches. Furthermore, accounting for the vertical variation in SOC improves the prediction accuracy.

How to cite: Röseler, F., Treat, C., and Heuvelink, G.: Geospatial modelling of soil organic carbon density in 3D across the northern circumpolar permafrost region, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8527, https://doi.org/10.5194/egusphere-egu24-8527, 2024.

The vulnerability of Arctic permafrost to climate change is evident, with anticipated widespread enhanced thawing under climate warming. This process may release substantial amounts of organic carbon. The positive feedback mechanism resulting from accelerated thaw and increased carbon emission is suspected to be a potential tipping element, possibly occurring within the 1.5 °C global warming range of the Paris Agreement. The consequences of Arctic permafrost thaw extend beyond carbon release, with the capability to drastically alter Earth's surface in Northern high latitudes.

This study employs high-resolution Large Eddy Simulations to investigate the impact of changing surfaces in the Arctic region on the neutrally stratified Atmospheric Boundary Layer. Utilizing a stochastic land cover model based on Gaussian Random Fields, representative permafrost landscapes are classified by distinct surface features. Experiments varying the areal fraction and surface correlation length of these surface features reveal significant insights into the sensitivity of the boundary layer to surface heterogeneity.

Key findings include a substantial impact of areal fraction of open water bodies on aggregated sensible heat flux at the blending height, suggesting a potential feedback mechanism: The smaller the areal fraction of open water bodies, the greater the sensible heat flux, the warmer the surface. Additionally, the blending height is significantly influenced by the correlation length of surface features. A longer surface correlation length leads to an increased blending height, highlighting the relevance of this metric for land surface models focused on Arctic permafrost.

How to cite: Schlutow, M. and Göckede, M.: Interaction of the Atmospheric Boundary Layer with degrading Arctic permafrost: A numerical study, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9594, https://doi.org/10.5194/egusphere-egu24-9594, 2024.

EGU24-13717 | ECS | Posters on site | CR4.2

Evaluation of Standalone In-situ Simulations of Frozen Soil 

Zhicheng Luo, Bodo Ahrens, Danny Risto, and Mittal Parmar

The performance of a climate model to reproduce frozen soil depends on the modeled atmospheric forcing and the parameterizations in the land surface. Due to the complex land-air interactions caused by snow and soil freezing and thawing, biased simulations of climate models may be compensated or amplified by errors in land surface models. This may lead to a misjudgment of the simulation capabilities of the land surface model itself, especially when we are trying to improve the overall performance of the climate model without being able to balance the results in frozen soil. In order to separately investigate the simulation performance of the land surface model in the frozen soil region, we conduct simulations using the stand-alone land surface models CLM5, TERRA, and JSBACH at representative sites in Siberia, Alaska, and the Tibetan Plateau and explore the performance of the models from daily to interannual scales using the same atmospheric forcing and initial conditions.

The main evaluation objects will be the insulating effect of snow, soil energy balance, and soil moisture transportation to a depth of 3 meters below the ground surface. We look forward to the offline simulation experiments to evaluate the accuracy of different land surface model simulations, the optimal soil hydrothermal parameterization scheme, and important physical processes that may be neglected by the models’ prediction of frozen soil in daily and monthly time scales.

How to cite: Luo, Z., Ahrens, B., Risto, D., and Parmar, M.: Evaluation of Standalone In-situ Simulations of Frozen Soil, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13717, https://doi.org/10.5194/egusphere-egu24-13717, 2024.

EGU24-14659 | Orals | CR4.2

Q-Arctic: A synergetic approach to observe and model pan-Arctic interactions between hydrology and carbon 

Mathias Göckede, Victor Brovkin, Annett Bartsch, and Martin Heimann and the Q-Arctic Team

Arctic permafrost has been identified as a critical element in the global climate system, since it stores a vast amount of carbon that is at high risk of being released under climate change. The feedbacks between permafrost carbon and climate change are moderated by complex interactions between physical, hydrological, biogeochemical, and ecological processes. Many of these are not well understood to date, and therefore also only rudimentarily represented in current Earth System Models (ESMs). A particular problem in this context is a scaling gap between processes and model grid.

The Q-ARCTIC project funded by the European Research Council (ERC) follows a synergetic approach by combining remote sensing and local-scale observations with modeling on scales from a few meters to hundreds of kilometers. The primary objective of Q-ARCTIC is to close the gap between process scales and the much coarser grid resolution of Earth System Models (ESMs), with a particular focus on the net effect of disturbance processes and associated changes in hydrology on the pan-Arctic scale. To close this gap, we developed new ESM modules representing subgrid through stochastic parameterizations, trained and evaluated with high-resolution remote sensing data and site-level observations.

We will present novel results based on in-situ observations that characterize prominent Arctic disturbance features, and satellite remote sensing products investigating fine scale (few meters) patterns in Arctic landscapes that are undergoing modifications linked to climate change. Targets investigated include for example sinking surfaces, wetness gradients in heterogeneous landscapes, or drained lake basins. Assimilation of these new datasets supported the development of new ESM model components that successfully capture the statistics of small-scale features, e.g. depressions linked to sinking surfaces, or surface water bodies that form when soil ice melts. Our results demonstrate that the ability to project the response of the high-latitude water, energy and carbon cycles to rising global temperatures may strongly depend on the ability to adequately represent the soil hydrology in permafrost affected regions.

How to cite: Göckede, M., Brovkin, V., Bartsch, A., and Heimann, M. and the Q-Arctic Team: Q-Arctic: A synergetic approach to observe and model pan-Arctic interactions between hydrology and carbon, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14659, https://doi.org/10.5194/egusphere-egu24-14659, 2024.

EGU24-15078 | ECS | Posters on site | CR4.2

Characterizing drained lake basins across the Arctic  

Helena Bergstedt, Annett Bartsch, Clemens von Baeckmann, Benjamin Jones, Amy Breen, Juliane Wolter, Louise Farquharson, Guido Grosse, and Mikhail Kanevskiy

Lakes and drained lake basins (DLB) are common landforms in permafrost lowland regions in the Arctic and widely cover 50% to 75% of the landscape in parts of Alaska, Siberia, and Canada. Lakes and DLBs create a heterogeneous and dynamic mosaic of terrain units, providing unique habitats for flora and fauna. Lakes and drained lake basins in permafrost regions play a crucial role in the regions landscape and ecosystem processes, influencing permafrost dynamics, biogeochemical processes, the hydrologic regime, as well as carbon cycling and greenhouse gas emissions. Depending on time passed since drainage of a given DLB, characteristics like surface roughness, vegetation, moisture, and abundance of ponds may vary between basins. Spatial heterogeneity within a single basin also varies between basins of different age. The mosaic of vegetative and geomorphic succession within DLBs and the distinct differences between DLBs and surrounding areas can be discriminated with remote sensing and used to derive a landscape-scale classification. In situ observations of these surface characteristics of DLBs are crucial for a better understanding of these features but can only describe a small percentage of existing DLBs.

In this study, we use a novel pan-Arctic assessment on DLB occurrence and the ESA Permafrost_cci circumpolar landcover unit data set based on Sentinel-1 and Sentinel-2 satellite imagery to assess the inter and intra-DLB spatial heterogeneity of surface characteristics. Building on existing research, we sort DLBs into distinct groups corresponding to previously published DLB age classification schemes (young, medium, old and ancient DLBs). DLB groupings show different landcover distribution within the basins, allowing for assumptions about the relative time passed since a drainage event occurred. To compliment and verify our remote sensing-based approach, a wide array of field data was collected at multiple sites across the Arctic, including on the Alaska North Slope. First results show distinct differences between DLBs within the study area, based on the landcover occurring within basins and other surface properties. Comprehensive mapping and characterizing of DLBs on a circumpolar scale will allow for improved parametrization of regional to pan-Arctic modeling efforts and improve our understanding of DLBs as a crucial landform in Arctic permafrost landscapes.  

How to cite: Bergstedt, H., Bartsch, A., von Baeckmann, C., Jones, B., Breen, A., Wolter, J., Farquharson, L., Grosse, G., and Kanevskiy, M.: Characterizing drained lake basins across the Arctic , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15078, https://doi.org/10.5194/egusphere-egu24-15078, 2024.

EGU24-15688 | Posters on site | CR4.2

Assessment of the Topographic Wetness Index in Permafrost landscapes  

Barbara Widhalm, Annett Bartsch, Helena Bergstedt, Clemens von Baeckmann, and Tazio Strozzi

Arctic permafrost regions are subject to rapid changes due to climate warming affecting hydrology, topography and ecology. Soil wetness is of great importance in these regions facilitating for example upscaling of carbon fluxes. In this study we therefore investigate the Topographic Wetness Index (TWI) as often used in land surface modelling, focusing on study regions in the Siberian and Canadian Arctic. We analyse the influence of the used Digital Elevation Model (DEM) by comparing results of the openly available ArcticDEM (2m resolution) and Copernicus DEM (30m resolution). Results are being validated against near-surface soil moisture in-situ measurements. Further comparisons are being made to other wetness indices such as the Tasselled Cap Wetness index or the Normalized Differential Moisture Index derived from Landsat 8. The relationship to InSAR derived surface displacements as an indicator of soil wetness is explored, as well as additional parameters such as the Topographic Position Index and correlations to other moisture indicators including land cover products.

How to cite: Widhalm, B., Bartsch, A., Bergstedt, H., von Baeckmann, C., and Strozzi, T.: Assessment of the Topographic Wetness Index in Permafrost landscapes , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15688, https://doi.org/10.5194/egusphere-egu24-15688, 2024.

EGU24-15989 | ECS | Orals | CR4.2

Vulnerability assessment of Arctic coastal communities to the effects of coastal erosion and permafrost warming. 

Rodrigue Tanguy, Annett Bartsch, Ingmar Nitze, Anna Irrgang, Pia Petzold, Barbara Widhalm, Clemens von Baeckmann, Julia Boike, Julia Martin, Aleksandra Efimova, Gonçalo Vieira, Birgit Heim, Mareike Wieczorek, Guido Grosse, and Dorothee Ehrich

This study assesses the escalating vulnerability of Arctic coastal communities due to the combined impacts of coastal erosion and permafrost warming. With the Arctic experiencing heightened temperatures, coastal permafrost areas face increased instability, endangering vital infrastructures. The study focuses on a pan-Arctic evaluation of settlements and infrastructures at risk, enhancing the existing Arctic coastal infrastructure dataset (SACHI) to include road types, airstrips, and artificial water reservoirs.

By analyzing coastline change rates from 2000 to 2020, alongside permafrost ground temperature and active layer thickness trends from the ESA Permafrost Climate Change Initiative datasets, the research identifies settlements at risk for the years 2030, 2050, and 2100. The accuracy of the dataset is rigorously evaluated. Results indicate that by 2100, 23% of coastal settlements will face the impacts of coastal erosion. Projections based on linear trends suggest an 8°C increase in coastal permafrost ground temperature and a 0.9-meter growth in active layer thickness by the same year.

Crucially, the study reveals that 65% of all infrastructures and settlements will be affected by permafrost warming within the range of 5-15°C, with 35% experiencing active layer thickening between 1-5 meters. This research marks the first regional-scale identification of settlements at risk from coastal erosion along Arctic and permafrost-dominated coasts in the northern hemisphere. The findings emphasize the urgency of adapting to current and future environmental changes to mitigate the deterioration of living conditions in permafrost coastal settlements. Immediate action is imperative to counteract these challenges and ensure the resilience of these vulnerable communities.

How to cite: Tanguy, R., Bartsch, A., Nitze, I., Irrgang, A., Petzold, P., Widhalm, B., von Baeckmann, C., Boike, J., Martin, J., Efimova, A., Vieira, G., Heim, B., Wieczorek, M., Grosse, G., and Ehrich, D.: Vulnerability assessment of Arctic coastal communities to the effects of coastal erosion and permafrost warming., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15989, https://doi.org/10.5194/egusphere-egu24-15989, 2024.

EGU24-16738 | Posters on site | CR4.2

Modelling heterogeneity of land surface waters in the permafrost region 

Thomas Kleinen, Philipp de Vrese, Tobias Stacke, and Victor Brovkin

When considering high latitude regions, one of the striking characteristics is the abundance of surface water in comparison to lower latitudes. This difference is not just limited to the total area covered by surface water, but it also extends to the size distribution of water bodies: While surface water in lower latitudes most often occurs in the form of larger lakes or rivers, high latitude regions often display a wide variety of surface water features, ranging from small puddles to huge lakes. Considering the climatic and carbon cycle consequences of lower latitude large water bodies in land models is relatively straightforward – they can be considered static, be prescribed from observations, and described using dedicated submodels. However, considering surface water in the high latitudes comprehensively is substantially more challenging, as a much larger range of sizes needs to be considered, parts of which will not be available from observations. Furthermore, due to the dynamics of permafrost, these cannot be considered static any more and need to be treated dynamically.

To better represent high latitude regions in the ICON-Land land surface model, part of the ICON-ESM Earth System Modelling framework, we are developing a representation of multiple scales of water bodies, ranging from large lakes to small puddles, as well as areas of water-saturated soil. The smaller-scale features are of particular interest, as they do not just affect the exchange of water and energy between surface and atmosphere, but also have large impacts on the carbon cycle and methane emissions. To do this, we employ a statistical distribution function of water body sizes, allowing us to obtain energy, water, carbon and methane fluxes for water features of all sizes.

We will present our novel modelling framework and show first results covering selected Arctic locations.

How to cite: Kleinen, T., de Vrese, P., Stacke, T., and Brovkin, V.: Modelling heterogeneity of land surface waters in the permafrost region, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16738, https://doi.org/10.5194/egusphere-egu24-16738, 2024.

EGU24-16785 | ECS | Posters on site | CR4.2

Status of the Circumpolar Landcover Unit database 

Rustam Khairullin, Clemens von Baeckmann, Annett Bartsch, Helena Bergstedt, Barbara Widhalm, Aleksandra Efimova, Xaver Muri, Ksenia Ermokhina, and Birgit Heim

The Circumpolar Landcover unit database provides landcover information in high detail, spatially (10m) and thematically (23 units). Such detail is needed for a wide range of applications targeting climate change impacts and ecological research questions. The landcover unit retrieval scheme used provides unprecedented detail. The landcover units have been derived by fusion of satellite data using Sentinel-1 (synthetic aperture radar) and Sentinel-2 (multispectral). The units reflect gradients of moisture as well as vegetation physiognomy.

 

The original database covered the Arctic north of the tree line. It has been extended towards south, providing additional detail within the tundra-taiga transition zone in permafrost regions. The available spatial detail provides the means to assess the complexity of this zone in addition to information on recent disturbance related to for example wildfire and thermokarst lake change.

 

Bartsch, A., Efimova, A., Widhalm, B., Muri, X., von Baeckmann, C., Bergstedt, H., Ermokhina, K., Hugelius, G., Heim, B., & Leibmann, M. (2023). Circumpolar Landcover Units (1.0) [Data set]. Zenodo. https://doi.org/10.5281/zenodo.8399018

How to cite: Khairullin, R., von Baeckmann, C., Bartsch, A., Bergstedt, H., Widhalm, B., Efimova, A., Muri, X., Ermokhina, K., and Heim, B.: Status of the Circumpolar Landcover Unit database, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16785, https://doi.org/10.5194/egusphere-egu24-16785, 2024.

EGU24-17224 | ECS | Orals | CR4.2

Statistical Modelling of Permafrost Subsidence Based on High-resolution InSAR Data 

Zhijun Liu, Barbara Widhalm, Annett Bartsch, Thomas Kleinen, and Victor Brovkin

The northern high latitudes are warming much faster than the rest of the planet. While gradual thaw of permafrost is accounted for in the recent generation of the Earth System Models (ESMs), consequences of the abrupt thaw of permafrost and the subsequent greenhouse gas release are not yet taken into consideration. However, an abrupt thaw of very small fraction of the northern permafrost region can lead to significant carbon release and subsequent global warming (Turetsky et al. 2020).

An in-depth analysis of fine-scale permafrost subsidence processes is crucial for improved representation of abrupt thawing in simulations. Currently, permafrost subsidence is only taken into consideration in a few models, where subsidence is described in a deterministic process-based approach. This approach overlooks the high spatial heterogeneity in fine-scale permafrost processes.

Recent advancements in satellite technology allow the acquisition of Interferometric Synthetic Aperture Radar (InSAR) data on permafrost vertical displacement at meter-scale resolution. We conducted a case study on the Yamal Peninsula, Russia, where we compare permafrost subsidence data from Sentinel-1 with various potential driving factors, including climate forcing data from ERA5-Land and geomorphology data from MERIT Hydro. A statistical approach is taken to analyse the relationships between different factors and their contributions to permafrost subsidence. The results demonstrate the high heterogeneity of permafrost subsidence in the form of probability distribution functions at ESM-scale resolution. Eventually, our study aims to obtain a parameterization for pan-Arctic permafrost subsidence that can be implemented into the ICON-ESM in order to close the gap in permafrost modelling between process- and ESM-scale.

 

Reference: Turetsky, M.R., Abbott, B.W., Jones, M.C. et al. Carbon release through abrupt permafrost thaw. Nat. Geosci. 13, 138–143 (2020). https://doi.org/10.1038/s41561-019-0526-0

How to cite: Liu, Z., Widhalm, B., Bartsch, A., Kleinen, T., and Brovkin, V.: Statistical Modelling of Permafrost Subsidence Based on High-resolution InSAR Data, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17224, https://doi.org/10.5194/egusphere-egu24-17224, 2024.

EGU24-17398 | ECS | Orals | CR4.2

Cryogrid modelling of permafrost temperature in the Maritime Antarctic (Barton Peninsula, King George Island) 

Joana Baptista, Gonçalo Vieira, Sebastian Westermann, and Hyoungseok Lee

The temperature dynamics of permafrost is crucial for ecosystem processes in the ice-free areas of the Antarctic Peninsula, where a strong long-term warming trend with an increase of 3.4 ºC in the mean annual air temperature since 1950 has been recorded (Turner et al., 2020). The consequences of this warming on past and future permafrost degradation are still not fully understood, mainly due to the sparse spatial coverage and short time span of borehole data, only available after the mid to late 2000’s (Vieira et al., 2010; Bockheim et al., 2013). The Cryogrid Community Model is an adaptable toolbox for simulating the ground thermal regime and the ice/water balance for permafrost (Westermann et al., 2017, 2022). The modular structure allows combinations of classes that represent the snow conditions and the subsurface materials. Here, permafrost temperatures from the 13 m depth King Sejong Station borehole (KSS), from Barton Peninsula, King George Island were used to assess the performance of Cryogrid and the quality of ERA5 forcing. For evaluating model performance, the setup was firstly used in its basic version with the GROUND_freeW_ubtf class, which considers a temperature boundary condition, for which air temperatures from KSS were used. Modifications to the stratigraphy and parameters were performed to achieve the strongest correlations and lower Mean Absolute Errors (MAE) between the simulated and observed ground temperature at nine depth levels. This approach allowed for the definition of the stratigraphy and parameters later used with the GROUND_freeW_seb_snow class, in which the surface energy balance scheme is included. The results show that ERA5 air temperature underestimates the records from KSS, especially during the summer, impacting the representation of surface warming. This deviation was corrected using linear regression corrected temperatures. The Cryogrid modelling results indicate an overestimation of the ground temperature during the thawing season and an underestimation during the freezing season, being the difference more pronounced at the surface. A strong correlation was shown between the simulated and measured ground temperatures in KSS down to 6 m depth (r>0.9) with MAE ranging from 0.4 to 0.9 ºC. Below 6 m the correlation weakens to 0.45 (13 m depth) due to differences in heat propagation and lack of temperature oscillation on the records when compared with the simulation. However, MAE values are residual, ranging from 0.1 to 0.2 ºC. The active layer thickness was overestimated in about 1 m. This research was funded by the project THAWIMPACT (FCT2022.06628.PTDC) and by CEG/IGOT (UIDP/00295/2020). Joana Baptista is funded by the FCT with a doctoral grant (2021.05119.BD).

How to cite: Baptista, J., Vieira, G., Westermann, S., and Lee, H.: Cryogrid modelling of permafrost temperature in the Maritime Antarctic (Barton Peninsula, King George Island), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17398, https://doi.org/10.5194/egusphere-egu24-17398, 2024.

EGU24-17812 | ECS | Orals | CR4.2

Improving the simulation of permafrost extent by representing the multi-tiling energy budgets in ORCHIDEE-MICT model 

Yi Xi, Chunjing Qiu, Yuan Zhang, Dan Zhu, Shushi Peng, Gustaf Hugelius, Jinfeng Chang, Elodie Salmon, and Philippe Ciais

The surface energy budget plays a critical role in terrestrial hydrologic and biogeochemical cycles. Nevertheless, its highly spatial heterogeneity across different vegetation types is still missing in the land surface model, ORCHIDEE-MICT (ORganizing Carbon and Hydrology in Dynamic EcosystEms–aMeliorated Interactions between Carbon and Temperature). In this study, we describe the representation of a multi-tiling energy budget in ORCHIDEE-MICT and assess its short and long-term impacts on energy, hydrology, and carbon processes. We found that: 1) With the specific values of surface properties for each vegetation type, the new version presents warmer surface and soil temperatures, wetter soil moisture, and increased soil organic carbon storage across the Northern Hemisphere. 2) Despite reproducing the absolute values and spatial gradients of surface and soil temperatures from satellite and in-situ observations, the considerable uncertainties in simulated soil organic carbon and hydrologic processes prevent an obvious improvement of temperature bias existing in the original ORCHIDEE-MICT. 3) The simulated continuous permafrost area (15.2 Mkm2) and non-continuous permafrost area (3.1 Mkm2) are comparative to observation-based datasets from Brown et al. (2002) (10.8 Mkm2 for continuous and 4.6 Mkm2 for non-continuous) and Obu et al. (2019) (11.5 Mkm2 for continuous and 5.3 Mkm2 for non-continuous). Consequently, the new version will facilitate various model-based permafrost studies in the future. 

How to cite: Xi, Y., Qiu, C., Zhang, Y., Zhu, D., Peng, S., Hugelius, G., Chang, J., Salmon, E., and Ciais, P.: Improving the simulation of permafrost extent by representing the multi-tiling energy budgets in ORCHIDEE-MICT model, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17812, https://doi.org/10.5194/egusphere-egu24-17812, 2024.

EGU24-19404 | ECS | Orals | CR4.2

Degradation and composition of organic carbon in the flocculation layer on the Laptev, East Siberian, and Kara seas 

Kirsi Keskitalo, Paul Mann, Tommaso Tesi, Bart van Dongen, Jannik Martens, Igor Semiletov, Oleg Dudarev, Örjan Gustafsson, and Jorien Vonk

Rapidly rising temperatures in the Arctic cause thaw of permafrost and increase coastal erosion that mobilizes permafrost-derived organic carbon (OC) into coastal waters. In the water column, permafrost-OC may either degrade and thus, enhance climate warming by adding greenhouse gases to the atmosphere or settle on the seabed and be buried in the sediments. In this study, we focused on the composition and degradation of particulate OC (POC) within the flocculation (nepheloid) layer - a turbulent layer close to seabed that holds a high amount of suspended sediments/particles and transports them across the vast Siberian Arctic shelves. More importantly, previous studies have shown that permafrost-OC, exported to the Arctic Ocean via coastal erosion, is largely carried in the POC fraction of the flocculation layer.

To study flocculation layer dynamics, sediment cores were collected using a multicorer device from the East Siberian Sea, Laptev Sea, and Kara Sea onboard R/V Akademik Mstistlav Keldysh in 2020. The overlying water of the sediment cores was stirred under controlled conditions to mimic sediment resuspension. The entrained suspended sediments were collected and incubated for two weeks (in the dark) to assess their susceptibility to degradation. During the incubation, dissolved O2, POC, dissolved OC (DOC), dissolved inorganic carbon and δ13C of each carbon pool were measured at set time points. Additionally, to better understand sediment entrainment and degradation, sediment physical properties, including grain size and mineral-specific surface area, and macromolecular composition were determined.

Our preliminary results show that stirring largely entrains the smallest sediment particles, while it seems not to influence sediment macromolecular composition suggesting that none of the compound classes such as polysaccharides or aromatic compounds are preferentially entrained. Our incubation data show losses in dissolved O2 suggesting microbial degradation, however, instead of decreases in the OC pools, especially POC shows increases combined with increases or decreases in DOC. These carbon dynamics likely result from interactions between different carbon pools such as adsorption of DOC to particles and/or leaching of POC to the DOC pool. With accelerated coastal erosion and increase in storminess in the Arctic Ocean due to sea ice loss, understanding dynamics of the flocculation layer and degradation of permafrost-OC on the Arctic sea shelves is becoming even more important to better constrain their potential climate impact.  

How to cite: Keskitalo, K., Mann, P., Tesi, T., van Dongen, B., Martens, J., Semiletov, I., Dudarev, O., Gustafsson, Ö., and Vonk, J.: Degradation and composition of organic carbon in the flocculation layer on the Laptev, East Siberian, and Kara seas, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19404, https://doi.org/10.5194/egusphere-egu24-19404, 2024.

EGU24-19799 | ECS | Posters on site | CR4.2

Simulating Saline Permafrost and Cryopeg Evolution Using a Coupled Heat and Salt Diffusion Model 

Michael Angelopoulos, Pier Paul Overduin, Frederieke Miesner, Julia Boike, Michael Krautblatter, and Sebastian Westermann

Saline permafrost is primarily found in marine deposits beneath shallow shelf seas and can often extend several kilometres inland from present Arctic coastlines. On land, saline permafrost forms when previously submerged marine sediments are exposed to the atmosphere, either through a sea level regression or post-glacial rebound. Cryopegs are perennially cryotic layers or pockets within permafrost that remain unfrozen due to their high salt content. While heat and salt flow models have been applied to study subsea permafrost degradation, adapting these models to terrestrial saline permafrost remains a significant gap in model development. We utilize a version of the CryoGrid modelling suite that couples heat and salt diffusion. This enables us to simulate the formation of saline permafrost and the development of cryopegs during transitions from sub-aquatic to sub-aerial conditions. As the freezing front descends, ice forms in the sediment matrix, expulsing salts into the remaining unfrozen liquid water at sub-zero temperatures. The increased unfrozen porewater salt concentration gradient increases the rate at which salt diffuses downwards into the sediment column. Over time the thermal gradient weakens, potentially allowing a more effective salt build-up ahead of the freezing front.

How to cite: Angelopoulos, M., Overduin, P. P., Miesner, F., Boike, J., Krautblatter, M., and Westermann, S.: Simulating Saline Permafrost and Cryopeg Evolution Using a Coupled Heat and Salt Diffusion Model, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19799, https://doi.org/10.5194/egusphere-egu24-19799, 2024.

EGU24-20159 | Orals | CR4.2

MethaneCAMP project – overview of results 

Johanna Tamminen and the MethaneCAMP project team

The ESA funded MethaneCAMP project has focused on assessing, improving, and analysing satellite observations of methane (CH4) in the Arctic in support of the collaborative ESA-NASA Arctic Methane and Permafrost Challenge (AMPAC) initiative. 

Traditionally, the high latitude conditions have received minor attention when the satellite retrievals for methane have been optimised for global purposes as there has been known challenges caused by high solar zenith angles, low reflectivity over snow and ice, frequent cloudiness, varying polar vortex conditions and limited number of validation data sets. Now when the two-year MethaneCAMP project is finishing, we will demonstrate the recent improvements in the observation capacity over the polar regions by assessing and optimising methane SWIR and TIR retrievals at high northern latitudes. Moreover, the importance of AirCore reference observations of methane profiles in the varying polar vortex conditions will be highlighted.

We will analyse the long-term methane trends in the northern high latitudes and permafrost regions by using satellite observations and inverse modelling. We aim to demonstrate the potential of using satellite observations of methane together with modelling and surface observations in analysing spatial and temporal changes of the Arctic methane. Detection of methane hot spots will also be mentioned.

In MethaneCAMP project our focus has been on Sentinel 5P/TROPMI, GOSAT, GOSAT-2 and IASI XCH4 observations and GHGSat emission estimates. In this presentation we summarise the results of the project and discuss how the outcomes can be utilised in the AMPAC working group activities.

How to cite: Tamminen, J. and the MethaneCAMP project team: MethaneCAMP project – overview of results, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20159, https://doi.org/10.5194/egusphere-egu24-20159, 2024.

EGU24-20267 | Posters on site | CR4.2

Projecting future permafrost thaw and subsidence driven infrastructure damage in the discontinuous permafrost zone 

Louise Farquharson, Dmitry Nicolsky, Monika Calif, Jennifer Schmidt, Vladimir Romanovsky, and Thomas Douglas

Permafrost thaw, ground-ice melt, and associated ground settlement pose significant hazards to northern communities and industry. Thaw of permafrost affected soils can decrease bearing capacity while settlement due to ground ice melt can cause ground collapse (thermokarst) and localized flooding. Here, explore ground ice distribution and potential for thaw induced settlement in the Fairbanks North Star Borough (FNSB), located in an area of discontinuous permafrost in Interior Alaska, USA. Pleistocene-Holocene sediment deposition, ice wedge development, and subsequent reworking due to thaw and hillslope processes have left a complex mosaic of cryolithological conditions that make thaw-related hazards a challenge to predict. The Borough is home to critical infrastructure including two military bases, a university, several gold mines, and the Trans Alaska Pipeline.

 

We created a permafrost hazard map by combining modelled ground ice distribution with projections of ground temperature through to 2090 using the GIPL 2.0 model for key ecotypes in the area. From this we were able to infer temperature dynamics, active layer deepening, talik development, and the potential for thermokarst degradation for IPCC Representative Concentration Pathway scenarios 4.5 and 8.5 through to 2090. We established ground ice distribution through a combination of existing geologic maps, numerical modeling, lidar derived thaw feature maps, and industry bore holes.  To extrapolate ground ice values from the representative sub-sample of ~ 2000km2 to the entire Borough we utilized a gradient-boosted decision tree aggregate model.

 

 Across the FNSB 23 % of the terrain is underlain by the high ground ice class, 10% medium, 4% low, 44% negligible, and 17% of the region is unaffected. High ground ice content underlines 23 % powerlines, 21% of roads and 4% of critical infrastructure (schools, hospitals, power plants etc.). Future projections of subsidence in areas of black spruce forest under RCP4.5 and 8.5 for areas respectively show that areas of high ice content could see subsidence of up to 5 and 10 meters respectively by 2090. Subsidence values for a range of topographic locations were calculated. Results from this study may help the FNSB, land managers, and homeowners best prepare and plan for the impacts of climate change in the Fairbanks region and potentially provide a hazard mitigation and climate change adaptation guides for other sub-Arctic communities.

How to cite: Farquharson, L., Nicolsky, D., Calif, M., Schmidt, J., Romanovsky, V., and Douglas, T.: Projecting future permafrost thaw and subsidence driven infrastructure damage in the discontinuous permafrost zone, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20267, https://doi.org/10.5194/egusphere-egu24-20267, 2024.

Estimates of the future methane (CH4) budget of northern permafrost landscapes remain highly uncertain with projections ranging from negligible to major CH4 releases to the atmosphere.

The German collaborative MOMENT project aims to address important gaps in process understanding of the high-latitude methane cycle using multi-scale methane flux observations in western Greenland linked to microbiological and biogeochemical laboratory studies. Through an innovative model-data integration framework, these novel datasets will be used to develop and evaluate land surface schemes of German Earth System Models (ESM) across terrestrial systems and multiple scales with the overarching goal to reduce uncertainties in future greenhouse gas projections.

We will introduce the overall project along with the innovations in experimental and observational techniques that facilitate observations at remote Arctic locations as well as in the lab. New remote sensing products allow for wall-to-wall mapping of structures on the finest scale across the Arctic, while novel computational infrastructure and modelling frameworks help with integration of all this information into next generation ESMs.

Selected preliminary results of the first field season and lab experiments will be highlighted.

How to cite: Sachs, T. and the the MOMENT project team: The MOMENT Project - Permafrost Research Towards Integrated Observation and Modelling of the Methane Budget of Ecosystems, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21829, https://doi.org/10.5194/egusphere-egu24-21829, 2024.

EGU24-8396 | PICO | CR4.3

Predisposition and triggering conditions at a permafrost-affected rock avalanche site in the French Alps (Étache, June 2020) 

Maëva Cathala, Josué Bock, Florence Magnin, Ludovic Ravanel, Matan Ben-Asher, Laurent Astrade, Xavier Bodin, Guillaume Chambon, Philip Deline, Thierry Faug, Kim Genuite, Stephane Jaillet, Jean Yves Josnin, André Revil, and Jessy Richard

Permafrost-affected rockwalls are highly sensitive to rapid climate change, sometimes leading to rock slope failures threatening human lives and activities. Many studies have demonstrated a link between permafrost degradation and rockwall instability, but there is still a need to document destabilization events to improve the understanding of triggering mechanisms to ultimately develop relevant approaches for hazard assessment.

 

Our study investigates the little rock-avalanche (c. 229,000 m3) that occurred in the Vallon d'Étache (Savoy, France) on June 18, 2020, after several days of heavy precipitation. We try to decipher the preconditioning and triggering factors of the rock avalanche by combining ground surface temperature monitoring, numerical modelling of permafrost evolution, energy balance modelling and geoelectrical survey interpreted with a petrophysical model to bring a detailed description of the hydrological and thermal mechanisms. The results show an intense permafrost warming especially since 2012 (annual trend: +0.06 °C a-1 at 30 m depth), with permafrost transitioning from cold to warm permafrost along the scar plan at a depth of c. 45 m when the event occurred. This warming may have preconditioned the rock avalanche. The geoelectrical soundings (240 to 640m long profiles) confirm that the crest around the scarp is still largely frozen with possible ice-rich layers (high resistivity values; 360 kΩ m). Furthermore, the energy balance model shows that the event occurred during the highest water input from rain and snowmelt, since at least 1985 which may have played as a triggering factor.  It also shows that the ground surface temperature experienced its highest winter and spring values before the event.

 

This multi-method approach shows that this rock avalanche occurred in still largely frozen bedrock but subject to recent and very intense warming, and that water infiltration may have played a key-role in its triggering, either due to the development of high hydrostatic pressure or to accelerated permafrost thawing along fractures.

How to cite: Cathala, M., Bock, J., Magnin, F., Ravanel, L., Ben-Asher, M., Astrade, L., Bodin, X., Chambon, G., Deline, P., Faug, T., Genuite, K., Jaillet, S., Josnin, J. Y., Revil, A., and Richard, J.: Predisposition and triggering conditions at a permafrost-affected rock avalanche site in the French Alps (Étache, June 2020), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8396, https://doi.org/10.5194/egusphere-egu24-8396, 2024.

EGU24-9220 | ECS | PICO | CR4.3

Integration of DInSAR, climatic, and morphometric data through data-driven models for regional-scale activity classification of rock glaciers in South Tyrol (Italy) 

Chiara Crippa, Stefan Steger, Giovanni Cuozzo, Francesca Bearzot, and Claudia Notarnicola

High-altitude regions serve as crucial indicators of climate change, with the Alps acting as a natural laboratory for studying glacial and periglacial processes. In situ and remote sensing techniques reveal permafrost degradation, coinciding with accelerated rates of rock glacier creep, potentially leading to destabilization.

Our study, focused on South Tyrol (North-East Italy), aims to screen and classify rock glaciers, thus pinpointing hotspots and unraveling the factors influencing their activity through the integration of remote sensing approaches and data-driven models. Our analyses are based on an existing inventory of periglacial landforms (1779 in total) across South Tyrol, mapped using LIDAR DTMs (2.5 m GSD) and orthophotos. The dataset already includes a descriptive attribute of activity from independent morphological observations and a DInSAR coherence-based estimation (Bertone et al., 2019). However, it lacks a comprehensive definition of activity based on climatic drivers, displacement rate, and morphometric parameters.

To quantify the velocity for each feature, we adopted a replicable workflow utilizing Sentinel 1A/B C-band images (2020-2022). This workflow involves three main steps: i) SAR pairs selection, filtering and processing using the Alaska Satellite Facility's Hybrid Pluggable Processing Pipeline (ASF HyP3); ii) atmospheric correction through a CNN (convolutional neural network) approach (Brencher et al., 2023); iii) time series inversion to produce mean LOS (Line-of-Sight) displacement rate maps through the MintPy algorithm (Yunjun et al., 2019).

We processed geomorphological (slope, aspect, insolation, curvature, etc.) and climatic maps (precipitation, temperature, snow cover duration) from both in situ (weather stations) and remote sensing products (MODIS, Landsat) to extract 19 descriptive parameters potentially influencing the development and state of activity of rock glaciers. These parameters served as predictor variables in a multiclass GAM classifier (Generalized Additive Mixing Models) to categorize all mapped landforms in active, relict, or transitional classes (RGIK, 2022).

After training the model on a subset of confidently classified features, we applied it to the entire rock glacier dataset, including features without an activity definition. Quantitative assessment of the model's performance, using the area under the ROC curve, consistently yielded results exceeding 0.86 across various k-fold cross-validation approaches.

Our analysis not only enhanced classification accuracy but also provided insights into the factors influencing activity classes. A final classification using the Bulk Creep Factor (BCF) indicator (Cicioira et al., 2021), describing the dynamic state and rheology of large-scale rock glacier datasets, facilitated the selection of key case studies for a detailed local-scale investigation.

This comprehensive approach refines the categorization of mapped features and contributes to a more detailed understanding of the factors controlling rock glacier activity in the alpine environment, particularly in South Tyrol.

How to cite: Crippa, C., Steger, S., Cuozzo, G., Bearzot, F., and Notarnicola, C.: Integration of DInSAR, climatic, and morphometric data through data-driven models for regional-scale activity classification of rock glaciers in South Tyrol (Italy), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9220, https://doi.org/10.5194/egusphere-egu24-9220, 2024.

Permafrost is warming and thawing globally because of climate change, which has consequences for slope stability. Despite numerous studies focusing on permafrost evolution, knowledge of the physical properties of frozen ground is based on a few in-situ measurements and laboratory experiments. There are few observations on water fluxes in permafrost, which are rapidly changing due to active layer thickening, ground ice melt, talik formation, and modified permeability. Particular attention should be given to changes in the thermal regime, an indicator of permafrost degradation and deep water infiltration, which are currently inducing deep-seated slope instabilities.

In this study, we use data from the 29 temperature boreholes of the Swiss Permafrost Monitoring Network PERMOS to quantify the thermal diffusivity in different permafrost rock slopes characterized by the three landforms: rock glacier, talus slope, or bedrock. We apply statistical and numerical modeling approaches and calculate the thermal diffusivity for each instrumented depth in a two-month window that iterates by one day. The thermal diffusivity at each instrumented depth is additionally inverted for each calendar year using analytical modeling to validate the results.

This systematic analysis of the PERMOS borehole temperature data, with three independent methods, allows us to derive a well-constrained range for the thermal properties of different substrates in mountain permafrost. Isolating spatial and temporal anomalies in thermal diffusivity, we can further investigate non-conductive processes governed by thawing and/or water advection. Given the one-dimensional heat conservation equation, the non-conductive heat flux can be quantified using the difference between the observed and modeled temperature change. Once concluded, this analysis will represent the basis for many other studies investigating the thermal and mechanical behavior of mountain permafrost rock slopes.

How to cite: Weber, S. and Cicoira, A.: Modeling thermal diffusivity in permafrost rock slopes to identify non-conductive heat fluxes, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9757, https://doi.org/10.5194/egusphere-egu24-9757, 2024.

EGU24-9989 | ECS | PICO | CR4.3

Strong regulation of permafrost coverage on runoff recession in the high-altitude permafrost basin 

Huiru Jiang, Yonghong Yi, and Rongxing Li

Permafrost plays a crucial role in influencing regional water resources by impeding surface water infiltration and regulating surface runoff discharge. Great efforts have been made to investigate the hydrological effects of permafrost degradation, but the underlying mechanisms behind the impacts of permafrost change on runoff production remain unclear, especially in the high-altitudinal permafrost basins with high spatial heterogeneity and limited soil observations. Therefore, this study combines long-term discharge records, process-based model simulations and remote sensing measurements to investigate the characteristics of runoff recession processes, which directly reflect the variation of soil storages affected by permafrost changes. With 60-year daily discharge records from eight high-altitude permafrost basins and subbasins of the Tibetan Plateau, we first analyzed the long-term temporal evolution of runoff recession rates. Then taking the source region of the Yangtze River (SRYR) in the central Tibetan Plateau as an example, we further investigated the specific soil freeze/thaw (F/T) factors that impact the runoff recession rates, by modifying a process-based permafrost hydrology model and simulating the soil F/T dynamics and related hydrological responses.

The preliminary results show that permafrost coverage strongly impacts the storage-discharge relationships indicated by runoff recession rates. In basins with high permafrost coverage (>80%), the long-term runoff recession rates exhibit a significant decreasing trend across all recession events, and a discontinuous runoff recession process is generally observed during the autumn and early winter recession periods. With a reduction in the permafrost coverage, we did not observe a significant trend in the long-term recession rate except for the recession events during early freezing periods (around autumn). In basins with much lower permafrost coverage (<50%), no distinct long-term trend in the seasonal runoff recession rates is observed. The process-based model simulation results in the SRYR (~80% of permafrost coverage) further reveal strong regulation of permafrost on the runoff production. A slower autumn recession rate is often related to a delayed soil freeze onset, especially in the deep soils of the active layer, which facilitates a larger soil water reservoir. In addition, the observed discontinuous recession during fall and early winter runoff recession period may result from a delayed soil freeze onset and longer unfrozen state (e.g., a longer duration of zero-curtain), influencing the connectivity of groundwater flow channels. In the next phase, we plan to include more remote sensing observations, such as InSAR deformation, to further investigate how active-layer soil water dynamics and its F/T state affect regional runoff production and water balance. This study shall enhance our understanding of the fundamental influence of permafrost changes on river runoff and support predictions of permafrost hydrological responses to future climate changes.

How to cite: Jiang, H., Yi, Y., and Li, R.: Strong regulation of permafrost coverage on runoff recession in the high-altitude permafrost basin, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9989, https://doi.org/10.5194/egusphere-egu24-9989, 2024.

EGU24-11060 | ECS | PICO | CR4.3

Modelling the thermal regime of a recently destabilised talus: the Eyjafirdi landslide (October 6th 2020, Iceland) 

Meven Philippe, Florence Magnin, Costanza Morino, Philip Deline, and Susan J. Conway

In mountainous periglacial environments, permafrost degradation can be comprised among the triggering factors of landslides. Such hazards represent a threat for human lives and infrastructures (Geertsema et al., 2009). The extent of permafrost, and hence location of areas at risk of landslides, is estimated at the global scale using models based on air temperatures (e.g. Gruber, 2012). However, at the local scale, specific geological settings can allow the persistence of permafrost beyond its climate boundaries. In talus slopes specifically, peculiar air circulation named “chimney effect” can exist and favour permafrost formation and persistence at their foot, at location where it is not always predicted by models (Wicky and Hauck, 2017).

In Iceland, talus slopes can be destabilised and generate landslides (Morino et al., 2019). However, due to the complexity of their geological setting, the thermal regime of talus slopes is difficult to model. Hence, only few numerical studies were conducted (e.g. Wicky and Hauck, 2017; Tanaka et al., 2006). This makes challenging to understand the destabilisation mechanisms of talus slopes, when determining the triggering mechanisms associated with permafrost degradation remains a crucial challenge.

 

In that scope, we installed 16 temperature sensors within the talus (and close rockwall) where the Eyjafirdi landslide originated from (October 6th 2020, Iceland). They recorded temperature hourly from August 2021 to July 2022. The primary analysis of the dataset reveals that a chimney effect indeed occurs within the talus; therefore, we suspect that an ice lens could have persisted at the bottom of the talus – outside of the predicted extent of permafrost. This hypothesis is supported by the observation of molards within the landslide deposits – i.e. cones of loose debris formed by the degradation of ice-cemented blocks of sediment, transported by the landslide (Morino et al., 2019).

In order to better characterise the thermal regime of the Eyjafirdi talus slope, we first reconstruct the temperature back to 1881 at the level of our sensors. We base that reconstruction on the correlation between our measured temperatures and air temperature datasets from meteorological stations – that go back to 1881. The reconstructed temperatures will then be used as forcing data, to constrain a thermal numerical model of the Eyjafirdi talus slope.

Model runs will be performed using the commercial software FEFLOW. It uses the finite element method (i.e. a discretisation of the studied object as a mesh) to solve equations of heat transfer, taking into account freezing and thawing processes. These numerical models will allow us to determine whether the chimney effect indeed maintained an ice lens within the Eyjafirdi talus slope. Moreover, thanks to our unique temperature dataset, our study will represent the most accurate effort to model talus slopes so far.

How to cite: Philippe, M., Magnin, F., Morino, C., Deline, P., and J. Conway, S.: Modelling the thermal regime of a recently destabilised talus: the Eyjafirdi landslide (October 6th 2020, Iceland), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11060, https://doi.org/10.5194/egusphere-egu24-11060, 2024.

In mountain permafrost areas, frozen rocks are thawing due to the rise in air temperatures and, thus, ground ice content decreases, which in turn does not only lead to changes in subsurface water storage but also affects slope stability in solid rock walls. Monitoring changes of the electrical conductivity in the subsurface has emerged as a suitable technique to differentiate between non-frozen and frozen areas because of the much lower conductivity of frozen than of unfrozen media. However, the direct estimation of ice content directly from conductivity measurements is challenging because this property is also dependent on the temperature and the geological media, i.e., porosity, saturation, and fluid conductivity of the pore-water and the surface conductivity taking place at the interface between water and grains or ice. For a proper discrimination between frozen and unfrozen areas, the induced polarization (IP) has emerged as a suitable method, as it measures not only the conductivity but also the electrical capacitive properties (polarization) in the low-frequency range (mHz - kHz). Previous studies have revealed an increase in the IP effect with decreasing temperature, arguing that such response is due to the polarization either from charges in the ice (at the kHz range) or at the interface between ice and water (around 100 Hz). In this study, we investigated the IP response from small rocks in an imaging framework under well-controlled freezing conditions in the laboratory. First, we aimed to understand the role of surface conductivity in frozen rocks by a multi-salinity analysis (in the range between 0.1 and 10 S/m), which also permits to estimate the porosity of the rocks. Second, we investigate the polarization response of rocks in presence of features with high ice content in multi-electrode imaging configurations. The rocks have been collected at different sites in the European Alps to evaluate the effect in the data due to changing lithology. IP imaging measurements were conducted over a broad range of frequencies (0.1 Hz - 30 kHz) using to-date approaches to reduce capacitive coupling arising from changes in galvanic contact of the electrodes with the rocks at frequencies above 100 Hz. The data were inverted in ResIPy, which solves for the conductivity magnitude and phase angle by using complex calculus. The salinity experiments result in porosities around 2-4% and a linear relation between the surface conductivity and the polarization (quadrature conductivity) with a slope around 0.01, which reveals the importance of surface conductivity, even at low frequencies and positive temperatures. For measurements on rocks with ice features, inversion results show that the IP imaging method is able to delineate ice-saturated holes due to a contrast in polarization. Based on our results, we evaluate existing petrophysical relationships linking the frequency-dependence of the IP results with porosity, ice content and temperature.

How to cite: Moser, C., Funk, B., and Flores Orozco, A.: Investigating IP imaging measurements in frozen rocks for a better understanding of electrical signatures in alpine permafrost investigations, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12384, https://doi.org/10.5194/egusphere-egu24-12384, 2024.

EGU24-12821 | PICO | CR4.3

Permafrost in talus slopes: what are the main drivers of low temperatures and ice content ? 

Christian Hauck, Dominik Amschwand, Tomasz Gluzinski, Christin Hilbich, Martin Hoelzle, Tamara Mathys, Coline Mollaret, and Sarah Morard

Coarse-blocky landforms are assumed to be the most resilient permafrost occurrences due to low thermal conductivity and their seasonal asymmetric internal convection processes and have been addressed in many field and modelling studies. In this contribution we will put a specific focus on the most general of these landforms, the ubiquitous talus slopes, which are understudied compared to other mountain permafrost landforms such as rock glaciers. Talus slopes exist in all mountain ranges and at different elevations, including middle mountains where they give rise to specific undercooled micro-climatic conditions. In many cases, internal convection processes are the main reason that the cool micro-climatic conditions could be preserved over long time scales. The ice content can be variable, ranging from zero at low elevations to the presence of ice cores at elevations where permafrost is widespread. However, the ice content in most talus slopes is generally unknown, as boreholes are extremely scarce and standard geophysical techniques (such as Electrical Resistivity Tomography and Seismic Refraction techniques) exhibit problems in detecting medium to small ice contents in coarse blocky substrates. In this contribution we use a compilation of data from a large number of different talus slopes in Europe, the Central Andes and Central Asia to attempt to (1) quantify the influence of slope angle, substrate and thickness of the talus on the internal air circulation and its cooling effect and (2) address the application of emerging geophysical techniques to improve the quantification of ice content in these substrates.

How to cite: Hauck, C., Amschwand, D., Gluzinski, T., Hilbich, C., Hoelzle, M., Mathys, T., Mollaret, C., and Morard, S.: Permafrost in talus slopes: what are the main drivers of low temperatures and ice content ?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12821, https://doi.org/10.5194/egusphere-egu24-12821, 2024.

EGU24-13408 | PICO | CR4.3

Permafrost is disappearing at the Mount Zugspitze (D/A): challenges and results after 10 years of monthly geoelectrical measurements. 

Riccardo Scandroglio, Jonas K. Limbrock, and Michael Krautblatter

Alpine permafrost degradation boosted by climate change is recorded worldwide, posing a significant threat to slope stability. A comprehensive assessment of this risk necessitates continuous monitoring of the rate of permafrost changes, for example, with electrical resistivity tomography (ERT). Although ERT has been employed in more than 1000 studies worldwide to detect permafrost, only a few sites are monitored with high temporal resolution and present more than a decade of uninterrupted observations.

Whitin the Kammstollen tunnel (2750 m asl, Mount Zugspitze, DE/AT), geoelectrical tomographies of the north face have been conducted since 2007. In the last ten years, an extensive dataset has been collected monthly employing consistent procedures and permanent electrodes. Recently, we updated the inversion methods to the most recent standards, and after reprocessing old data, we precisely quantified the evolution of permafrost in the last decade. In line with the observed increase in air temperature, the permanently frozen area shows a gradual but consistent reduction during the summer months, with the record minimum value recorded at the end of summer 2023. This study highlights the limits of laboratory calibrations, especially in the presence of different degrees of rock fragmentation (fault zone). Further, we show the influence of error models on inversion results and on the quantification of resistivity changes, confirming the need for repeated estimation of measurement errors. 

The unique geoelectrical dataset here presented, bolstered by many simultaneous supplementary information, contributes to better defining the role of geoelectrical monitoring for understanding the thermal responses of alpine permafrost environments to present and future climate-change-induced stresses.

How to cite: Scandroglio, R., Limbrock, J. K., and Krautblatter, M.: Permafrost is disappearing at the Mount Zugspitze (D/A): challenges and results after 10 years of monthly geoelectrical measurements., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13408, https://doi.org/10.5194/egusphere-egu24-13408, 2024.

EGU24-15002 | ECS | PICO | CR4.3

The influence of sub-seasonal to seasonal atmospheric temperature variability on alpine permafrost 

Dominik Büeler, Elizaveta Sharaborova, Maria Pyrina, Michael Lehning, and Daniela I. V. Domeisen

Alpine permafrost thawing due to climate warming has been rapidly intensifying in the past decades. Since permafrost stabilizes the rock, its thawing has and will become a growing risk for mountainous countries like Switzerland, with potential implications for rockfall magnitude and frequency, mountain infrastructure, mountain ecosystems, and tourism. The long-term trend in the thickening of the active layer and thus the subsidence of the permafrost table in the Swiss Alps due to climate warming is well observed and documented. However, less is known about how sub-seasonal to seasonal variability of atmospheric temperature, in particular individual multi-weekly heatwaves in summer, influence below-ground temperature from year to year. In this interdisciplinary study, we thus explore how atmospheric temperature variability on timescales of days to seasons affects the variability of below-ground temperature and the depth of the permafrost table, measured at various rock borehole stations of the Swiss Permafrost Monitoring Network PERMOS. In addition, we evaluate how well the snowpack and ground surface model SNOWPACK is able to reproduce this relationship. The insights from this analysis will pave the way to couple the SNOWPACK model to sub-seasonal to seasonal weather prediction models, which are increasingly being used to predict the probability of heatwave occurrence several weeks ahead. Such a coupling could allow for a prediction of the evolution of below-ground temperature and of significant permafrost anomalies on an operational basis, and thereby support early warning systems for alpine hazards.

How to cite: Büeler, D., Sharaborova, E., Pyrina, M., Lehning, M., and Domeisen, D. I. V.: The influence of sub-seasonal to seasonal atmospheric temperature variability on alpine permafrost, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15002, https://doi.org/10.5194/egusphere-egu24-15002, 2024.

EGU24-15928 | ECS | PICO | CR4.3

Field study of permafrost molards from diverse origins of landslides in Matanuska Valley, Alaska 

Calvin Beck, Susan Conway, Costanza Morino, Bretwood Higman, Bill Billmeier, and Marianne Font

Permafrost is receding and warming globally due to current climate change trends. Mountain regions with areas of discontinuous to isolated permafrost are especially sensitive to these changes. In high relief mountainsides, ground ice can be essential in stabilising mountain slopes and can result in slope failures if this ice degrades. To determine the state of degrading permafrost and related slope failures, we studied the Matanuska Valley in Alaska (USA), an area characterised by a high density of landslides with permafrost molards .

Permafrost molards are cones of loose debris that can be found in landslide deposits in periglacial terrains, originating from ice-cemented blocks of debris that are transported down-slope within the landslide. These ice-cemented blocks are fragmented parts of the frozen material initially located in the landslide source area. Therefore, they can indicate the presence of degrading permafrost at the level of the detachment zone. Landslides containing permafrost molards have been detected in geographically and geologically diverse regions such as Argentina, Canada, Colorado, the European Alps, Greenland, Iceland, and Norway.

Our Alaskan field site contains 9 molard landslides within only a 15 km radius. These densely clustered landslides have a unique variety of geological, geomorphological and dynamic characteristics. This allows us to study a large parameter space of permafrost slope instabilities within a small region. Therefore, we studied the following five molard landslides in detail: Amulet, East and West Index Lake, Yellowjacket, and Matanuska River 2021 landslide.

These landslides are diverse in terms of landslide type, transported volume, run-out length, source materials, expositions, and altitudes. For instance, the Matanuska River 2021 landslide is a rotational slide of initially forested terrain with the head scarp at 780 m.a.s.l., and with a length of ~400 m plunging into the Matanuska River. In contrast, the Amulet landslide is a channelized debris slide with the head scarp at 1500 m.a.s.l., a run out length of ~2100 m, and with hundreds of molards with diameters ranging up to 44 m in the landslide deposits.

To document the variability between these landslides, we performed traditional geomorphological and geological field measurements, dug transects in the molards, took samples, and we obtained digital terrain models of the landslides by drone-based photogrammetry. We acquired drone-based photogrammetry data of Yellowjacket landslide only two weeks after the failure, before the initial ice-cemented blocks fully degraded, as well as four years after the slope failure. For the first time, this allows us to compare spatial data of permafrost molards before and after the degradation of the initial ice-cemented blocks and to perform statistical analysis on this data.

We investigated molard shape, size, and size-distribution parameters to compare these to variables such as source material and expected permafrost conditions. This allows us to confine the composition of the initially ice-cemented blocks of debris, which will help us to understand under what conditions molards can form. In the future, this will allow us to quantify the currently often uncertain state of mountain permafrost more precisely.

How to cite: Beck, C., Conway, S., Morino, C., Higman, B., Billmeier, B., and Font, M.: Field study of permafrost molards from diverse origins of landslides in Matanuska Valley, Alaska, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15928, https://doi.org/10.5194/egusphere-egu24-15928, 2024.

EGU24-17962 | ECS | PICO | CR4.3

The impact of thermokarst development on flow and transport processes in alpine rock glaciers 

Simon Seelig, Magdalena Seelig, Karl Krainer, and Gerfried Winkler

Active rock glaciers represent permafrost-affected aquifers that govern the response of many alpine headwater catchments. Their heterogeneous internal structure tends to channelize groundwater flowing along the permafrost table or within the frozen rock glacier core. This study derives the hydraulic properties of such thermokarst channel systems at three active rock glaciers in the Austrian Alps. Their basic configuration is assessed through spring flow analysis and dye tracer tests. Breakthrough curves are characterized by multiple peaks and strong tailing, implying flow path separation and partial retardation of the tracer cloud travelling through the rock glaciers. Individual channels can reach diameters up to several decimeters and are characterized by a convoluted, irregular geometry. Flow along the channels is fast, highly turbulent, and characterized by high frictional resistance. Heat transfer is predominantly advective, inducing a positive feedback loop that allows larger channels to grow at the expense of smaller ones, effectively increasing the hydraulic conductivity at the rock glacier scale. The preferential flow paths provided by the thermokarst channel networks dominate flow and transport through the rock glaciers in particular during the summer months, and thus govern spring flow dynamics, solute transport, permafrost degradation, thermokarst lake outburst hazard, and rock glacier front stability.

How to cite: Seelig, S., Seelig, M., Krainer, K., and Winkler, G.: The impact of thermokarst development on flow and transport processes in alpine rock glaciers, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17962, https://doi.org/10.5194/egusphere-egu24-17962, 2024.

EGU24-18050 * | ECS | PICO | CR4.3 | Highlight

State of permafrost in the Swiss Alps in 2023 

Cécile Pellet and Jeannette Noetzli and the PERMOS Scientific Committee

Permafrost is classified as an essential climatic variable (ECV) by the Global Climate Observing System (GCOS) because of its sensitivity to changes in climatic conditions. The Swiss Permafrost Monitoring Network PERMOS documents the state and changes of permafrost conditions in the Swiss Alps since 2000 based on long-term field measurements. To account for the heterogeneous distribution and characteristics of mountain permafrost, PERMOS developed and implemented a comprehensive monitoring strategy, which relies on three complementary observation elements: (1) ground temperatures near the surface and at depth, (2) permafrost electrical resistivity to determine changes in ground ice content, and (3) rock glacier velocities, which can be used as a proxy to assess the permafrost thermal regime.

In this contribution, we discuss permafrost conditions in the Swiss Alps during the hydrological year 2023 with respect to the observations of the past two decades. Combining results from the three observation elements, we analyse the short and long-term responses of permafrost to climate evolution. The hydrological years 2022 and 2023 were characterized by two consecutive winters with below average snow heights and two summers ranked second and fifth warmest on record since 1864. These weather and climate conditions lead to different permafrost evolutions at different depth levels and at different sites. While ground surface temperatures and active layer thicknesses at or close to record values were registered, a slight decrease of the permafrost temperatures was observed at 10 and 20 m depth, which is consistent with the decreasing rock glacier velocity and increasing permafrost resistivity observations. The permafrost conditions observed in 2023 constitute short term variations likely not affecting the long-term trend of warming and degrading permafrost consistently observed in the Swiss Alps for the past two decades.

How to cite: Pellet, C. and Noetzli, J. and the PERMOS Scientific Committee: State of permafrost in the Swiss Alps in 2023, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18050, https://doi.org/10.5194/egusphere-egu24-18050, 2024.

Rock glacier monitoring has revealed a long-term increase in rock glacier surface velocity in the European Alps, often associated with increased air and ground temperatures as well as water content. The long-term acceleration of rock glaciers is superimposed by high interannual variability of their velocity, and there is still a gap in the quantitative assessment of the role of water in rock glaciers and the factors leading to the short-term deceleration of rock glaciers.

To address this research gap, we drilled and documented the stratigraphy of three vertical boreholes in the Schafberg Ursina III rock glacier, Swiss Alps (46°29'50.391" N, 9°55'34.779" E; 2’750m asl), in August 2020. One of the boreholes was instrumented with ten Keller PAA-36XiW piezometers, which measure pore water pressure (www.keller-druck.ch) at depths ranging from 2 m to 8.5 m depth. In addition, each piezometer is equipped with a PT 1000 temperature sensor. The other two boreholes were equipped with a permanently installed cross-borehole electrical resistivity tomography (ERT) setup consisting of 24 electrodes in each borehole, spaced at 0.5 m, to a depth of 11.5 m, reaching the top of the shear horizon of the rock glacier. We used a Syscal Pro Switch 48 resistivity meter and a Syscal monitoring unit to automatically collect, record and transmit the acquired data (www.iris-intruments.com). ERT monitoring provides information on relative changes in ice water content. Rock glacier velocities were determined from terrestrial laser scans taken in July each year using a Riegel VZ6000 long-range scanner (www.riegl.com). Using data from nearby weather stations of the Intercantonal Measurement and Information System (IMIS network) and ground surface temperature sensors, we analysed the interplay between meteorological and subsurface conditions during a rock glacier deceleration period from January 2021 to June 2023, which included two snow-poor winters (2021-2022, 2022-2023) and a summer heat wave in 2022.

Our results show that a reduction of the water content of rock glaciers is crucial for intermittent, interannual rock glacier deceleration. The influence of snow cover on rock glacier kinematics is significant, both as an insulator and as a water source. Winters with little snow and relatively dry summers are ideal for cooling and drying rock glaciers, leading to deceleration. Summer heat waves have a limited effect if preceded by dry winters. The importance of rainfall and snow melt water infiltration from the entire catchment remains to be determined. High-resolution GNSS data and information on water contents in rock glacier shear horizons is needed to improve our understanding of the role of water on rock glacier kinematics.

Our contribution highlights an innovative combination of borehole data to gain insight into an alpine rock glacier's ground temperature and water content, allowing us to detect relative changes in ice/water content in ice-rich permafrost.

How to cite: Bast, A., Kenner, R., and Phillips, M.: Unveiling cooling, drying and deceleration of a rock glacier during a warm period through ground temperature, piezometer and cross-borehole ERT data, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18614, https://doi.org/10.5194/egusphere-egu24-18614, 2024.

EGU24-19057 | PICO | CR4.3

Insights from steep-bedrock, high-altitude mountain permafrost laboratory at the Matterhorn 

Jan Beutel, Alessandro Cicoira, Umberto Morra di Cella, Paolo Pogliotti, and Samuel Weber

High-altitude mountain areas are very susceptible to the climate evolution at all scales. However little is known about this extreme end member characterized by steep topographies and remoteness. Therefore in-situ observations are scarce and often limited in their temporal and spatial coverage as well as their fidelity. Over the past two decades teams from Italy as well as Switzerland have concentrated multiple interdisciplinary research efforts at and on the slopes of the Matterhorn. This cross-border laboratory today covers a full altitude transect from the valley floor to the summit at 4478 m asl as well as from south to north with a dense network of permanent in-situ observation locations. In addition, several research campaigns have been historically undertaken and add to this unique footprint of observation data as well as insight. Primary data observed are ground-surface temperature as well as permafrost active layer depth, meteorological parameters, surface kinematics using crackmeters as well as GNSS, resistivity, optical imaging, seismic signals as well as personal observations through a regional observer network. In this presentation, we will summarize the activities over the past two decades and discuss insights, key findings as well as data availability.

How to cite: Beutel, J., Cicoira, A., Morra di Cella, U., Pogliotti, P., and Weber, S.: Insights from steep-bedrock, high-altitude mountain permafrost laboratory at the Matterhorn, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19057, https://doi.org/10.5194/egusphere-egu24-19057, 2024.

EGU24-19517 | ECS | PICO | CR4.3

A database integrating the electrical resistivity data of Switzerland for mountain permafrost spatio-temporal characterisation 

Coline Mollaret, Christin Hilbich, Cecile Pellet, Christian Hauck, Tomasz Gluzinski, Eva De Mits, Theresa Maierhofer, Christophe Lambiel, Alex Bast, Jacopo Boaga, Adrian Flores Orozco, Hanne Hendricks, Christof Kneisel, Julius Kunz, Sarah Morard, Mirko Pavoni, Sebastian Pfaehler, Marcia Philips, Riccardo Scandroglio, and Cristian Scapozza and the Swiss Electrical Database on Permafrost Team

In permafrost research, geoelectrical surveys are increasingly used to detect the presence and extent of permafrost and to characterise the stratigraphy and material composition of permanently frozen terrain. When repeated, the resulting temporal changes in electrical resistivity can be related to changes in ground temperature and ice content, and therefore also to ground ice loss over time. However, for financial and logistical reasons, only a few continuous electrical resistivity tomography (ERT) monitoring installations on permafrost exist worldwide. An alternative approach is manual but regularly repeated ERT measurements, such as - besides other examples - in the context of the Swiss Permafrost Monitoring Network (PERMOS, 2023). In contrast, there are many permafrost sites (estimated to be over 500 in Switzerland) where single ERT measurements have been performed in the past. In the context of atmospheric warming, these historical datasets can serve as a baseline for analysing current changes in ground ice content in permafrost regions and the associated challenges to mountain slope stability.

In this contribution, we present the analysis of the Swiss datasets, which are integrated in the International Database of Geoelectrical Surveys on Permafrost (IDGSP), led by the International Permafrost Association (IPA) Action Group of the same name. Before this initiative, geoelectrical datasets (mainly ERT) were not included in a common and dedicated database. Since the launch of the IPA Action Group in 2021, a database has been designed and set up (using PostgreSQL), numerous metadata and data have been collected and homogenised, and public access via a searchable web map is available (https://resibase.unifr.ch). We present the strategy developed for consistent filtering, processing, and inversion for this extensive dataset. In this contribution, we analyse both spatial and temporal variations in surveys conducted at various Swiss mountain sites.

The overall goal is to establish a complete database of electrical measurements on permafrost in Switzerland, including all historical measurements. The data are re-processed with the newly developed filtering and inversion routines and made available to the public to facilitate the repetition of measurements in the context of permafrost degradation, geotechnical studies of permafrost stability, hydrological studies in the context of natural hazards and water availability from thawing permafrost environments, and to serve as a baseline dataset for permafrost distribution and modelling.

PERMOS 2023. Swiss Permafrost Bulletin 2022. Noetzli, J. and Pellet, C. (eds.) 22 pp, https://doi.org/doi:10.13093/permos-bull-2023

How to cite: Mollaret, C., Hilbich, C., Pellet, C., Hauck, C., Gluzinski, T., De Mits, E., Maierhofer, T., Lambiel, C., Bast, A., Boaga, J., Flores Orozco, A., Hendricks, H., Kneisel, C., Kunz, J., Morard, S., Pavoni, M., Pfaehler, S., Philips, M., Scandroglio, R., and Scapozza, C. and the Swiss Electrical Database on Permafrost Team: A database integrating the electrical resistivity data of Switzerland for mountain permafrost spatio-temporal characterisation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19517, https://doi.org/10.5194/egusphere-egu24-19517, 2024.

EGU24-20989 | PICO | CR4.3

The 2023 Fluchthorn massive permafrost rock slope failure analysed 

Michael Krautblatter, Samuel Weber, Michael Dietze, Markus Keuschnig, Georg Stockinger, Lisa Brückner, Jan Beutel, Thomas Figl, Claudia Trepmann, Robert Hofmann, Maximilian Rau, Felix Pfluger, Laura Barbosa Mejia, and Florian Siegert

Warming in the last two decades has caused massive rockfall activity with limited mobility in the range of 101-6 m³. However, only a few highly destructive and mobile rock avalanches above 1 Mio. m³ have been documented. Rock-ice mechanical models explaining high-magnitude rock slope failure in permafrost have been postulated but not validated on real failures.

This study combines complementary expert knowledge to decipher the 1 Mio. m³ Fluchthorn rock slope failure that detached on June 12, 2023, from the before 3399 m high summit causing a rock avalanche that additionally eroded ca. 120.000 m³ of ice. InSAR data shows deformation rates in the range 4.1 – 7.1 ± 0.13 cm/a from April 2021 to March 2023, but these are surprisingly linked to a westward deformation of the entire Silvretta nappe (in the range of 3 cm/a) oversteepening the Fluchthorn. Mountain guides have observed singular failures before the event. IR drone flights immediately after the event indicate rock temperatures at the failure planes in the range of 0°C - -2°C and ice-filled fractures. Solid, scarcely fractured pseudotachilitic sequences in the summit regions may have contributed to the massive oversteepening of the Fluchthorn Westface without significant pre-failures. The grain size compositions shows massive material take up of fine-grained material and fragmentation (Pudasaini & Krautblatter 2021).

In a seismic analysis we can for the first time exactly reconstruct the temporal and spatial trajectory of a rock-ice avalanche, velocities and energy release during the 120-second rock-ice-avalanche propagation consistent with fragmentation and deposits. High-resolution photogrammetry highlights massive ice erosion and accumulation patterns during the rock avalanche propagation. In addition, we analyse all precursors in the last two years before the failure in detail (Leinauer et al. 2023): These include small prefailure volumes, seismic precursors, kinematic precursors and kinematic precursors detected in UltraCam & LiDAR surveys.

In an IRAZU model, capable of nucleation and growth of fractures based on nonlinear fracture mechanics applied stresses act to produce a progressive fracturing path that closely resembles the real failure and we can show the impact of the solid pseudotachilitic roof on the oversteepening. In a discontinuum model (UDEC), we can show the stabilizing effect of permafrost on developing fracturing patterns in a combined rock-ice mechanical approach, including temperature-dependent rock mechanical (Krautblatter et al. 2013, Draebing & Krautblatter 2019, Jia et al. 2017, 2019) and destabilization processes in ice-filled fractures and along rock-ice interfaces (Mamot et al. 2018, 2020, 2021).

In summary, we show a unique combination of datasets deciphering pre-failure tectonic and geological controls and forcing, syn-failure permafrost-related mechanics, and second-resolution data on rock avalanche evolution in a cryospheric terrain with massive ice uptake.

How to cite: Krautblatter, M., Weber, S., Dietze, M., Keuschnig, M., Stockinger, G., Brückner, L., Beutel, J., Figl, T., Trepmann, C., Hofmann, R., Rau, M., Pfluger, F., Barbosa Mejia, L., and Siegert, F.: The 2023 Fluchthorn massive permafrost rock slope failure analysed, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20989, https://doi.org/10.5194/egusphere-egu24-20989, 2024.

EGU24-367 | ECS | Posters on site | GM10.5

Controls on glacial divide migration in Southern Canadian Rocky Mountain fold and thrust belt 

Himani Yadav and Lindsay Schoenbohm

The present-day landscape of Southern Canadian Rocky Mountains is a product of the interaction among tectonics, lithologic resistance, and surface processes including erosion by rivers and glaciers. Rivers have adjusted to the orogeny-associated structures, regional tectonic uplift and growing terrain slope, and post-orogenic, extensive glaciation by modifying their channel profile and planform geometry. Understanding the relationship between fluvial and glacial erosion is crucial, as not only does it reflect the landscape’s sensitivity to the climate change, but also because it can indicate whether glacier-driven stream piracy (and basin reorganization) can cause significant downstream discharge alterations. The mechanisms of glacial headwall erosion, drainage divide migration, and resulting stream capture, still form a considerable research gap in landscape evolution studies. The Canadian Rockies provide an excellent opportunity for understanding the progression of subglacial channel network geometry and related basin reorganization. This study aims to evaluate glacial headwall erosion processes in glaciated headwaters through progressive divide lowering, lateral migration, and stream capture. We remotely analyze topographic features, corroborating them in the field. We completed the morphometric investigation using the MATLAB based TopoToolbox, Topographic Analysis Kit, and a customized DivideMigration function. We observe two unique signatures of glacial divide migration in the Canadian Rockies: (1) breached drainage divides that suggest lateral erosion by glaciated headwaters directed along weak lithologies and (2) the presence of low relief, high elevation divides without headwall preservation, possibly indicating periods of paleo-drainage capture during glaciation. Our preliminary results have implications for the role of glacial erosion in reshaping the landscape with respect to the structure, lithology, and climate.  

How to cite: Yadav, H. and Schoenbohm, L.: Controls on glacial divide migration in Southern Canadian Rocky Mountain fold and thrust belt, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-367, https://doi.org/10.5194/egusphere-egu24-367, 2024.

The mid-Pleistocene Transition (MPT) from 41 kyr to 100 kyr glacial cycles occurred in the absence of a change in orbital forcing. This presents a challenge for the Milankovitch theory of glacial cycles. A change from a low to high friction bed under the North American Ice Complex through the removal of pre-glacial regolith is hypothesized to play a critical role in crossing the threshold to longer and stronger glaciations. However, testing this Regolith Hypothesis requires constraint on currently unknown pre-glacial regolith cover as well as assessing whether glacial sediment processes remove the appropriate amount of regolith to enable glacial system change consistent with the MPT. Pleistocene regolith removal has not yet been simulated for a realistic, 3D North American ice sheet fully considering basal processes. Constraints on pre-glacial bed elevation and sediment thickness are sparse and the bounds are wide.

What limits on pre-glacial regolith thickness in North America can be inferred from our current understanding of glacial processes and the present-day distribution of unconsolidated sediment? How does pre-glacial sediment thickness influence the evolution of Pleistocene glacial cycles? We answer these questions with an ensemble of whole-Pleistocene simulations with high-variance parametrizations and range of pre-glacial regolith thicknesses.

We use the 3D Glacial Systems Model which incorporates the relevant glacial processes: 3D thermomechanically coupled hybrid SIA/SSA ice physics, fully coupled sediment production and transport, subglacial linked-cavity and tunnel hydrology, isostatic adjustment from dynamic loading and erosion, and climate from a 2D non-linear energy balance model and glacial index. This fully coupled system is driven only by atmospheric CO2 and insolation. The model captures the Pleistocene evolution of North American glaciation: 41 to 100 kyr glacial cycles shift, similar latitudinal extent in the early and late Pleistocene, LGM ice volume, deglacial ice margin chronology, and the broad present-day sediment distribution within the parametric and observational uncertainty. Constrained by large scale reconstructions of present-day surface sediment distribution, regional sediment distribution estimates, and regional bedrock erosion estimates, these results bound the mean pre-glacial sediment thickness.

Our results suggest thin (<40 m) regolith and its removal occurring in advance of the MPT -- a challenge to the regolith hypothesis. In the case of very thin regolith cover, sufficient physical weathering via glacial processes occurs to increase the soft bed distribution during the course of the Pleistocene.

How to cite: Drew, M., Gosse, J., and Tarasov, L.: A challenge to the Regolith Hypothesis for the MPT from present day sediment distribution and coupled climate-ice-sediment physics, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-809, https://doi.org/10.5194/egusphere-egu24-809, 2024.

EGU24-1381 | Orals | GM10.5

Regime shifts in sediment transport driven by warming-intensified cryosphere degradation and hydrological fluctuation 

Ting Zhang, dongfeng Li, Amy East, Albert Kettner, Jim Best, Jinren Ni, and Xixi Lu

Climate change and cryosphere degradation have remarkably impacted riverine water and sediment fluxes from polar and high-mountain regions. Shifts in the timing and magnitude of fluvial fluxes have crucial implications as they fundamentally alter the seasonal allocation of sediment, organic matter, nutrients and pollutants, thus affecting the year-round provision of water, food, and energy to populated and vulnerable mountain communities. However, the responses of seasonal dynamics of sediment transport remain largely understudied due to the lack of long-term and fine-scale hydrological records and the complexity of the underlying hydrogeomorphic processes. In our recent paper published in Science Advances, we identified the climate-driven regime shifts in suspended sediment transport in four distinct basins in the Third Pole, characterized as glacial, nival, pluvial, and mixed hydrological regimes and developed a monthly scale sediment-availability-transport model (SAT-M) to simulate climate-driven sediment dynamics and reproduce such regime shifts. SAT-M can help facilitate sustainable reservoir operation and river management in wide cryospheric regions under future climate and hydrological change.

By leveraging decadal monthly hydro-climatic observations in studied basins from the 1960s to 2000s, this research finds that spring sediment fluxes are shifting from a nival- towards a pluvial-dominated regime due to less snowmelt and more erosive rainfall. Meanwhile, summer sediment fluxes have substantially increased due to disproportionately higher sediment transport yielded by greater glacier meltwater pulses and pluvial pulses. Such shifted sediment-transport regimes and amplified hydrological variability in cryosphere-fed rivers add additional stresses to downstream hydropower and irrigation infrastructure and ecosystems, and exacerbate the damage caused by floods. Specifically, increases in river turbidity in the melt season can threaten river biotic conditions by blocking sunlight from reaching the streambed, limiting respiration and deteriorating feeding conditions of benthic macroinvertebrates and fishes, causing severe ecological consequences. Besides, the substantially increased proportion of sediment flux transported in summer can jeopardize downstream hydropower and irrigation infrastructure by causing rapid reservoir sedimentation and thus reducing effective storage capacity.

SAT-M presented herein effectively reproduces the shifted sediment-transport regime by constraining runoff surges and climate-driven changes in sediment supply, e.g., thermally activated sediment sources from thawing permafrost and the retreat of glaciers. More importantly, SAT-M offers a flexible methodology framework to simulate sediment transport in response to rapid hydroclimatic changes and thus can be freely applied in wide cryospheric regions by selecting basin-specific drivers. Given anticipated increases in flooding risks and increased variability in precipitation and runoff in cold mountain regions, SAT-M presented herein provides a promising simulation tool to assist in predicting sediment fluxes and peaks, optimizing sediment management of dams and reservoirs, and mitigating their downstream impacts under future climate change scenarios.

How to cite: Zhang, T., Li, D., East, A., Kettner, A., Best, J., Ni, J., and Lu, X.: Regime shifts in sediment transport driven by warming-intensified cryosphere degradation and hydrological fluctuation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1381, https://doi.org/10.5194/egusphere-egu24-1381, 2024.

EGU24-3349 | ECS | Orals | GM10.5

Assessing rock glacier velocities on the Tibetan Plateau using satellite SAR interferometry 

Zhangyu Sun, Lin Liu, Yan Hu, and Chengyan Fan

The information pertaining to rock glacier kinematics plays a crucial role in addressing various scientific inquiries related to permafrost distribution, mountain hydrology, climate change, and geohazards in alpine regions. However, our understanding of rock glacier kinematics on the Tibetan Plateau remains incomplete, with limited observations only made in a few local regions. To fill in this knowledge gap, our study employed the Interferometric Synthetic Aperture Radar (InSAR) technique to comprehensively assess the moving velocities of rock glaciers across the entire Tibetan Plateau. The velocities were assessed using two different methods: the processing of single interferometric pair data and the time series analysis. By utilizing the single interferometric pair data from Sentinel-1 and incorporating time series analysis results using LiCSAR products, we derived the downslope velocities of 41,441 rock glaciers as included in the plateau-wide inventory, i.e., TPRoGI [v1.0]. Our results revealed that a significant proportion of rock glaciers exhibit downslope velocities of 3-10 cm/yr (39.5%) and 10-30 cm/yr (32.7%). Around half of the rock glaciers on the plateau fall into the transitional category (53%), active rock glaciers also occupy a substantial portion (45.6%). Both active and transitional rock glaciers exhibit widespread distribution in the northwestern and southeastern plateaus. The average downslope velocity of the rock glaciers is 15 cm/yr. Rock glaciers on the western and northern plateaus tend to move faster (mean velocity = 26 cm/yr) than those on the eastern and southern plateaus (mean velocity = 12 cm/yr). Our assessment is valuable for the future monitoring of rock glacier kinematics on the Tibetan Plateau in the context of Rock Glacier Velocity (RGV) as an associated parameter of Essential Climate Variable (ECV) Permafrost.

How to cite: Sun, Z., Liu, L., Hu, Y., and Fan, C.: Assessing rock glacier velocities on the Tibetan Plateau using satellite SAR interferometry, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3349, https://doi.org/10.5194/egusphere-egu24-3349, 2024.

EGU24-4107 | ECS | Posters virtual | GM10.5

Assessing the Role of Outburst Floods in the Formation of the Lower St. Croix River Valley, MN/WI, USA 

Hunter Delikowski, Grace Uchytil, Jayda Rowen, Abigail Fischer, Phillip Larson, Mark Johnson, Douglas Faulkner, Garry Running, Tammy Rittenour, Andrew Wickert, Andy Brown, Zachary Hilgendorf, and Ronald Schirmer

A burgeoning theme of research has focused on overflow and outburst flood events in reorganizing drainage basins, creating new fluvial landscapes and transverse drainages. Generalized conceptual ideas may not fully grasp the complexity of real proglacial and deglacial landscapes, making these landscapes important to examine. The St. Croix River valley (SCRV), MN/WI, USA, and its drainage basin contain well understood glacial geology, and the complex evolution of SCRV is largely the result of dyssynchronous advance and retreat of the Superior Lobe and Grantsburg Sublobe through the SCRV basin. Several proglacial lakes formed in and surrounding the SCRV, including Glacial Lake Duluth (GLD) in the Superior basin and Glacial Lake Grantsburg (GLG) at the margin of the Grantsburg Sublobe. Prior research identified multiple high-magnitude meltwater flood spillways that drain into the SCRV that formed between ~22–10.6 ka. However, these floods are not well constrained in terms of process, magnitude, and timing. Thus, the landscape evolution of the SCRV fluvial system remains poorly understood.
We focus on a specific reach of SCRV through which all high-magnitude meltwater discharge was routed. This reach contains numerous terraces, abandoned paleovalleys, a transverse reach and bedrock canyon, and an anomalously high and extensive terrace-like surface called the Osceola Bench (OB). We compile pre-existing data and add ground penetrating radar (GPR) data, describe sediments extracted with hand augers and a Geoprobe, date sediments with optically stimulated luminescence (OSL), and interpret sediment geochemistry using X-ray fluorescence (XRF). In addition, we map landforms using LiDAR DEMs and aerial imagery. We identify alluvial terraces and paleovalleys that step down from the OB towards the modern river. GPR results from OB and adjacent terraces reveal a horizontally continuous and shallow (<2.5 m) reflection. We interpret this to be a strath beneath alluvial sediments. Hyperbolic and inclined reflections within the alluvial sediments capping these landforms are interpreted as large clasts embedded within cross-bedded sands and gravels – supported by augering/coring that encountered large boulders within deposits of sand and gravel. These landforms were capped by a silt to sandy loam that commonly fines upward. We interpret these sediments as being deposited during waning stages of high-magnitude flows.
We hypothesize OB was formed by catastrophic outflows from GLG (sometime between 16.3-13.6 ka), released as the Grantsburg Sublobe retreated westward. Sculpted bars on OB indicate a northeastern source and likely outlet of GLG. Strath terraces and incised paleovalleys inset into the western margin of OB step down towards the river, providing evidence for a progressive westward shift in meltwater flow and valley incision that mirrored retreat of the Grantsburg Sublobe. Incision does not appear to have reached the modern river level, suggesting later flows from GLD punctuated GLG incision. GLD flows are likely the primary cause of bedrock incision across the transverse reach at St. Croix Dells (between 13.6-10.6 ka). This superimposed sequence of top-down drainage events demonstrates the complexity of drainage-basin evolution in deglacial settings and emphasizes the need for field-based investigations to develop more comprehensive models of drainage basin evolution and integration.

How to cite: Delikowski, H., Uchytil, G., Rowen, J., Fischer, A., Larson, P., Johnson, M., Faulkner, D., Running, G., Rittenour, T., Wickert, A., Brown, A., Hilgendorf, Z., and Schirmer, R.: Assessing the Role of Outburst Floods in the Formation of the Lower St. Croix River Valley, MN/WI, USA, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4107, https://doi.org/10.5194/egusphere-egu24-4107, 2024.

EGU24-4108 | Posters virtual | GM10.5

A Sedimentologic, Morphometric, and Geochronologic Investigation of Ambiguous Dune-like Landforms: An Indicator of Proglacial Lake Drainage in the Lake Superior Basin, USA 

Abigail Fischer, Chris Susnik, Nathan Stafford, Hunter Delikowski, Jayda Rowen, Andy Breckenridge, Phillip Larson, Yeong Bae Seong, Douglas Faulkner, David Ullman, Andy Wickert, Eric Barefoot, and Andy Brown

Preliminary observations of three trains of dune-like landforms, just south of the shore of Lake Superior, near Christmas, MI, USA, reveal the presence of large and imbricated boulder clasts on their surface and 20–33 m deep bedrock canyons in close proximity. These characteristics suggest an ambiguous episode of high-magnitude discharge across this landscape before the modern physical geography of the Lake Superior basin was established. Understanding the formation of these landforms is important in reconstructing regional deglacial chronology, meltwater routing history, and proglacial lake-level fluctuations within the Lake Superior basin. In addition, because these landforms are similar to other landscapes where catastrophic drainage occurred, like the Camas Prairie (Missoula Floods, Montana, USA), such comparisons further our understanding of the processes that occur during these high-magnitude events. Unfortunately, little data exists from this site that can elucidate the depositional chronology and genesis of these landforms, herein named the Christmas Dunes (CD). 

We collected 20 ground penetrating radar (GPR) lines and measured 814 boulders (dimensions, strike and dip). Additionally, we collected 7 cosmogenic nuclide (CN) samples for 10Be exposure ages, 6 from imbricated sandstone boulders and 1 from a granitic boulder. Morphologic analysis was conducted using newly available LiDAR DEMs. The GPR data from a landform most proximal to a spillway contained inclined reflections that dip up-flow. It is possible dipping reflections are imbricated boulders buried within the dune because the ~23° reflection angle is similar to imbrication angles of surface boulders (21° - 59°), but no down-flow reflection indicating a potential buried boulder could be positively identified. Thus, we hypothesize these are antidune-like forms. The presence of antidunes suggests that the flows stopped abruptly because antidunes are commonly obliterated once a flow transitions from supercritical to subcritical. We hypothesize rapid lake draw-down caused abrupt spillway abandonment allowing the antidune forms to be preserved. 

Dune-like landforms further from the spillways contain inclined GPR reflections interpreted as down-flow dipping sedimentary structures and suggest a transition in flow regime beyond the most spillway-proximal landforms. Boulder B-axis diameters (0.2 - 10.7 m) decrease with distance from the spillways, supporting the interpretation of a flow and transport-regime shift. Preliminary estimates of paleodischarge suggest flows may have been 0.22 Sv (0.106 – 0.33 Sv; Breckenridge and Fisher, 2021). Given similarities between CD and sites like Camas Prairie, we hypothesize that CD formed during rapid proglacial lake draw-down across the sandstone bedrock ridge into which the spillways are incised. CD also represents a well-preserved location indicative of internal basin evolution dynamics during the rapid draining of a proglacial lake basin – inadequately understood in overflow and outburst flood literature. This event likely occurred when the easternmost outlet of the Lake Superior basin opened, abruptly rerouting southward-flowing meltwater from the Au-Train/Whitefish spillway across the CD site prior to 10.5 ka.

How to cite: Fischer, A., Susnik, C., Stafford, N., Delikowski, H., Rowen, J., Breckenridge, A., Larson, P., Seong, Y. B., Faulkner, D., Ullman, D., Wickert, A., Barefoot, E., and Brown, A.: A Sedimentologic, Morphometric, and Geochronologic Investigation of Ambiguous Dune-like Landforms: An Indicator of Proglacial Lake Drainage in the Lake Superior Basin, USA, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4108, https://doi.org/10.5194/egusphere-egu24-4108, 2024.

EGU24-5833 | ECS | Posters on site | GM10.5

Advancing understanding of Holocene rock glacier dynamics 

Benjamin Lehmann, Robert S. Anderson, Diego Cusicanqui, and Pierre G. Valla

Rock glaciers, major cryospheric features in alpine landscapes, pose formidable challenges in extracting climatic information over recent to Holocene timescales. This presentation delves into an integrative multi-method approach, striving to replicate modern motion through feature tracking, exposure ages from 10Be concentrations, and observations of rock glacier morphology. Applying a novel numerical model for rock-glacier dynamics, our study focuses on the Holocene to modern activity of a prominent rock glacier flowing northeast from a 300-m tall headwall on the Mt. Sopris (West Elk Mountains, Colorado USA).

The Mt. Sopris rock glacier spans 2 km from its headwall avalanche source cone to a 25 m tall terminus, adorned with metric size granitic blocks exhibiting systematic variations in lichen cover and weathering. Fine-grained material fills voids between blocks in the lowermost reaches, supporting tree clusters. The 10Be-based exposure ages of block surfaces range from 1.5 to 12 kyr, with ages older than 6 kyr being compressed into the bottom quarter of the rock glacier. Modern rock-glacier surface velocities, ranging from 0.6 to 2 m/yr, can be explained by the internal deformation of a 25-m thick ice core beneath the rocky surface. However, interpreting the 10Be exposure age profile proves challenging, leading to the development of a new numerical model for rock-glacier dynamics.

Our model simplifies the mass balance to an avalanche cone accumulation zone, and the rock cover is assumed to damp melting of underlying ice over the remaining areas of the rock glacier. Climate forcing is achieved through a proposed history of the snow avalanche activity. The rock glacier velocity is calculated assuming Glen’s flow law in the interior ice and acknowledges the role of debris cover in augmenting the stress profile throughout. Preliminary modeling suggests that an avalanche cone history with two independent pulses, one in the early Holocene and the other simulating the Neoglacial, captures dominant features of the 10Be exposure age structure. The first manifestation of the rock glacier extends to approximately 1.5 km in lengths, then extends, thins, and slows over the mid-Holocene lull in input, before being overtaken and re-accelerated by the Neoglacial pulse.

This study contributes new insights into rock glacier dynamics, bridging multiple timescales and quantitatively assessing physical processes in action. Rock glaciers, key players in alpine landscape evolution, exhibit a response to climate that differs from typical glacier systems in that they never retreat, and can survive long periods of low snow input. Our numerical simulations allow investigation of dynamic responses to variations in both climate and headwall backwearing erosion. Success of our approach on the Mt. Sopris rock-glacier system suggests its utility in developing a deeper understanding of how different high mountain landscapes respond to climatic fluctuations over Holocene timescales.

How to cite: Lehmann, B., Anderson, R. S., Cusicanqui, D., and Valla, P. G.: Advancing understanding of Holocene rock glacier dynamics, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5833, https://doi.org/10.5194/egusphere-egu24-5833, 2024.

EGU24-6056 | ECS | Posters on site | GM10.5

Morphodynamics of three active rock glaciers and its influence on spring hydrochemistry in the Swiss Alps 

Chantal Del Siro, Giona Crivelli, Isabelle Gärtner-Roer, Christophe Lambiel, Reynald Delaloye, and Cristian Scapozza

In the current context of climate change, intact rock glaciers represent potentially important water resources in high mountain regions, regarding the storage of both liquid and solid water. In particular, water stored in ground ice could become a valuable resource in the long term, due to slower ice melt rates occurring in rock glaciers than in surface glaciers. However, the amounts of ground ice are difficult to detect, and the related processes (i.e melting and refreezing) are complicated to monitor and therefore poorly understood. In this regard, geochemistry of water emerging from rock glaciers can help gaining more insight. In this study, morphodynamic analyses of three active rock glaciers located in the Swiss Alps were therefore combined with the physico-chemical monitoring of water emerging from these periglacial landforms. The three studied rock glaciers (Monte Prosa A, Ganoni di Schenadüi and Piancabella) are located in the Lepontine Alps (Canton of Ticino) and their ground surface temperatures and kinematics are monitored since 2009. Two of them (Monte Prosa A and Piancabella) belong to the Swiss Permafrost Monitoring Network PERMOS.

Changes in morphodynamics of the rock glaciers were investigated through repeated Unmanned Aerial Vehicle (UAV) and differential Global Navigation Satellite System (dGNSS) surveys during the warm season (i.e in early summer, late summer and early autumn). Intra-seasonal comparison between dense point clouds obtained through Structure from Motion (SfM) photogrammetry shows significant seasonal changes in elevation, especially a negative volumetric change in the rooting zone of two rock glaciers (Monte Prosa A and Ganoni di Schenadüi), with thickness losses ranging from about 0.15 to 0.55 m. Rooting zone also shows the largest seasonal horizontal displacements (up to 0.3 m) for these rock glaciers, obtained through image correlation. Furthermore, isotopic analysis (δ18O) were performed on water samples arising from rock glacier springs, precipitation, snowpack and seasonal ground ice, the latter sampled between blocks within the active layer. A seasonal increase in δ18O was observed in rock glacier springs, indicating a change in the water origin, from a supply fed mainly by snowmelt to a supply fed by a mixture of more 18O-enriched water. In addition, ion content of water samples collected from rock glacier springs and seasonal ground ice was also measured. Rock glacier springs show a seasonal increase in the solute export (e.g. SO42-, Ca2+ and Na+), while high concentrations of Na+, K+ and Cl- were found in seasonal ground ice samples. These first results show a clear seasonal pattern and indicate a probable influence of ground ice melting on both morphodynamics and chemistry of water emerging from the studied active rock glaciers.

How to cite: Del Siro, C., Crivelli, G., Gärtner-Roer, I., Lambiel, C., Delaloye, R., and Scapozza, C.: Morphodynamics of three active rock glaciers and its influence on spring hydrochemistry in the Swiss Alps, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6056, https://doi.org/10.5194/egusphere-egu24-6056, 2024.

EGU24-7422 | ECS | Orals | GM10.5

Formation and preservation of low-relief surfaces by Pliocene-Quaternary glaciations  

Maxime Bernard, Peter van der Beek, Vivi Pedersen, and Cody Colleps

The Plio-Quaternary period is characterized by a cold and variable climate with the periodic advance and retreat of glaciers and ice sheets in many mountain areas. As such, mountainous topographies have undergone episodic changes from fluvial to glacially dominated erosion processes in both space and time. How these continuous changes in the dominant surface processes impacted erosion rates and topographic relief remains unclear, and in particular the role of glacial erosion. Indeed, while previous work has shown that Plio-Quaternary glaciations increased topographic relief in many mountain areas, others have argued that glaciations are capable of efficiently removing area above the mean position of the equilibrium line of glaciers limiting the topographic relief (i.e., the glacial buzzsaw mechanism). In some high latitude glaciated passive margins, it has also been suggested that glaciations could have reduced topographic relief and formed extensive low-relief surfaces, mostly during the early stages of glaciation. This view challenged previous ideas of extrapolating cold-based, non-erosive ice conditions observed during the most recent glacial cycle on these elevated plateaus to the entire Plio-Quaternary period. If true, this means that glaciations have a larger impact on topography, erosion, and the sediment budget than previously thought. However, the glacial origin of these low-relief surfaces (LRS) remains debated.

Here, we present a new modelling study designed to explore the impact of Plio-Quaternary glaciations on topography. Specifically, we investigate how climatic parameters such as temperature, precipitation, and the nature of climatic cycles control the development of topographic relief. We use iSOSIA, a glacial landscape evolution model, to simulate periodic advance and retreat of glaciers to mimick Plio-Quaternary glaciations at the mountain range scale. We define our climatic scenario into two stages. The first stage is represented by symmetrical 41 kyrs glacial cycles, whereas the second stage imposes asymmetrical 100 kyrs cycles. Our model framework considers fluvial, glacial, and hillslope erosion processes. From the models we assess the production of LRS facilitated by the combination of 1) protective non-erosive ice at intermediate elevations and 2) focused erosion on ice-free summits and in main valleys, mostly during the first climatic stage. The extent of LRS depends on the efficiency of glacial erosion and climatic parameters, with simulations suggesting that the most extensive LRS are found in colder/wetter settings. However, the final preservation and extent of these LRS is significantly influenced by erosion during the second climatic stage. Indeed, former LRS can be dissected by headward propagation of erosion promoted by the higher amplitude of the asymmetric 100 kyrs cycles. This reworking of LRS thus leads to a preservation bias that is expected to occur in most alpine settings. Our model results provide new insights into the impact of glaciations on topography and bring a plausible new comprehensive framework that explains both the presence of LRS and their absence in glaciated areas.

How to cite: Bernard, M., van der Beek, P., Pedersen, V., and Colleps, C.: Formation and preservation of low-relief surfaces by Pliocene-Quaternary glaciations , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7422, https://doi.org/10.5194/egusphere-egu24-7422, 2024.

In steep alpine environments, the succession of glacial-interglacial cycles during the Quaternary led to multiple transient geomorphological phases. These periods are induced by an imbalance between the inherited shape of the topography and the dominant geomorphological processes. In particular, post-glacial periods are key transition phases experiencing rapid geomorphic changes, characterized by intense hillslope processes where ice and permafrost have shrunk. As landslides are the main factors controlling sediment production in steep mountain environments, we approach numerically their late-glacial to interglacial dynamics and explore the associated evolution of catchment topography across a wide range of morphological signatures (i.e. from fluvial to glacial initial topographies). Using the landscape evolution model ‘Hyland’, we quantitatively assess the response of each type of catchment to landsliding. We focus on the cumulative impact of landslides, during the post-glacial phase, on catchment slope distribution, hypsometry and produced sediment volume.  Moreover, glacial topographic inheritance seems strongly sensitive to hillslope processes with a non-homogeneous spreading of landslides over the catchments, both spatially and temporarily. Our results reveal a temporal change in slope-elevation distribution associated to a general lowering in maximum catchment elevations. On the contrary, fluvial catchments show more stable topography and less intense landslide activity. Landscape evolution models appear as a suitable tool to quantitatively explore (1) the role of different internal or external parameters (e.g., bedrock cohesion, return time of landslides), and (2) the non-linear interactions between landsliding and catchment topographic evolution, which are strongly influenced by external forcing such as climatic fluctuations in mountainous settings.

How to cite: Ariagno, C., Steer, P., and Valla, P.: Investigating post-glacial transient phases as hot-moments of landscape dynamics - combining numerical modelling and topographic analysis, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7434, https://doi.org/10.5194/egusphere-egu24-7434, 2024.

EGU24-7461 | ECS | Posters on site | GM10.5

How glacial landscape evolution has impacted Scandinavian Ice Sheet dynamics and dimensions 

Gustav Jungdal-Olesen, Jane Lund Andersen, Andreas Born, and Vivi Kathrine Pedersen

The topography and bathymetry of Scandinavia have been molded by ice across numerous glacial cycles during the Quaternary. In this study, we explore the interplay between this changing morphology and the Scandinavian Ice Sheet (SIS). Using a higher-order ice-sheet model, we simulate the SIS over a glacial cycle on three different topographies, representing different stages of Quaternary glacial landscape evolution. By subjecting these simulations to identical climate conditions, we isolate the effects of landscape morphology on the evolution and dynamics of the ice sheet. Our findings indicate that early Quaternary glaciations in Scandinavia were restricted in both extent and volume by the pre-glacial bathymetry. It was only as glacial deposits filled a depression in the North Sea and expanded the Norwegian shelf that the ice sheet could expand further. This is illustrated by our middle to late Quaternary simulation (around 0.5 million years ago), where a filled bathymetry facilitated both a faster and further southward expansion, resulting in a relative increase in both ice-sheet volume and extent. Additionally, our study highlights that the formation of The Norwegian Channel acted as a barrier to southward ice-sheet expansion. This limitation only allowed the ice sheet to advance into the southern North Sea close to glacial maxima. Notably, our experiments suggest that distinct segments of The Norwegian Channel may have formed in different stages during glacial periods after the bathymetry was sufficiently filled with glacial sediments. These results underscore the importance of considering changes in landscape morphology over time when interpreting ice-sheet history based on ice-volume proxies and when interpreting climate variability from past ice-sheet extents.

How to cite: Jungdal-Olesen, G., Andersen, J. L., Born, A., and Pedersen, V. K.: How glacial landscape evolution has impacted Scandinavian Ice Sheet dynamics and dimensions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7461, https://doi.org/10.5194/egusphere-egu24-7461, 2024.

EGU24-7706 | ECS | Posters on site | GM10.5

The current and future state of mountain permafrost in the Eastern Italian Alps: the RETURN project 

Costanza Morino, Luca Carturan, Mirko Pavoni, Jacopo Boaga, Roberto Seppi, and Matteo Zumiani

The present climate change is affecting geomorphic processes and landforms related to mountain permafrost in alpine areas. Impressive expressions of permafrost degradation include significant ground surface warming of rock glaciers, a general acceleration of rock-glacier surface-flow velocity, and rapid gravitational mass movements in steep terrains. In this context, the interest in mountain permafrost conditions in the Eastern Italian Alps is growing, in view of the possible consequences in terms of natural hazard assessment and mitigation, and of management of water resources. Therefore, there is a great need to assess the current and future changes of geomorphological processes and landform evolution related to degrading permafrost in this region.

Here, we present the study approach and preliminary results of the ongoing project RETURN, which is an Extended Partnership funded by the European Union Next-GenerationEU (National Recovery and Resilience Plan – NRRP, Mission 4, Component 2, Investment 1.3 – D.D. 1243 2/8/2022, PE0000005). Our research group is working on the current and projected impacts of climate change on the alpine cryosphere of the Eastern Italian Alps. The activities of this project, which is focussing on the area of the Province of Trento, are aimed at: i) understanding the current local and regional permafrost state and distribution, ii) modelling the distribution and state of permafrost in future warming scenarios, and iii) determining whether the ongoing permafrost degradation is causing an increase of slope instability in terms of frequency and magnitude. These aims are accomplished by using a multidisciplinary approach that comprises a) photogrammetric analyses aimed at reconstructing interannual variations and possible acceleration of rock glacier kinematics, b) geophysics aimed at estimating the volume of permafrost in active and pseudo-relict rock glaciers, c) ground-surface temperature monitoring aimed at modelling the  conditions of permafrost at local and regional scale, and d) geomorphological analyses of areas affected by landslides induced by permafrost degradation.

The results of the RETURN project are expected to contribute to a better understanding of ongoing processes and similar issues in other mountain areas affected by warming and degrading permafrost.

How to cite: Morino, C., Carturan, L., Pavoni, M., Boaga, J., Seppi, R., and Zumiani, M.: The current and future state of mountain permafrost in the Eastern Italian Alps: the RETURN project, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7706, https://doi.org/10.5194/egusphere-egu24-7706, 2024.

EGU24-8327 | ECS | Orals | GM10.5

Multi-annual Rock Glacier Velocity (RGV) products based on InSAR  

Lea Schmid, Line Rouyet, Reynald Delaloye, Cécile Pellet, Nina Jones, and Tazio Strozzi

Rock glaciers are debris landforms resulting from the creep of mountain permafrost. Whereas motion rates are related to multiple structural, topographic and climatic factors, and range from a few cm/a to multiple m/a, their interannual variations are primarily linked to those of the thermal state of the permafrost. With the objective to provide a novel climate change indicator suitable for mountain permafrost environments, the established parameters of the Essential Climate Variable (ECV) Permafrost Active Layer Thickness (ALT) and Permafrost Temperature (PT) have been complemented in 2021 by Rock Glacier Velocity (RGV). RGV is an annualized rock glacier velocity time series documenting the creep rate of mountain permafrost. Relative velocity changes extracted from multiple sites are needed to robustly represent the climate signal. However, RGV production on the basis of in-situ measurements is costly and therefore restricted to some specific sites. We propose a new approach to extract RGV using spaceborne Synthetic Aperture Radar Interferometry (InSAR). We used Sentinel-1 SAR images (wavelength: approx. 5.55 cm) between 2015 and 2022 to compute and average (stack) interferograms with short temporal baselines of 6 to 12 days, extract multiple spatially distributed velocity time series and identify dominant trends through clustering. Pilot results on selected rock glaciers in Switzerland show good agreement between InSAR-based RGV and in-situ measured RGV from the Swiss Permafrost Monitoring Network PERMOS, especially regarding the relative change of velocities. Despite some limitations, the method makes it possible to systematically extract time series for a large amount of rock glaciers, thereby contributing to further use RGV as climate change indicator. Future research will focus on testing the method on additional rock glaciers, with an emphasis on rock glaciers suitable for analysis with 12-day interferograms (current Sentinel-1 repeat-pass). We aim to produce time series in multiple mountain ranges worldwide, providing a comprehensive dataset of InSAR-based-RGV products.

How to cite: Schmid, L., Rouyet, L., Delaloye, R., Pellet, C., Jones, N., and Strozzi, T.: Multi-annual Rock Glacier Velocity (RGV) products based on InSAR , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8327, https://doi.org/10.5194/egusphere-egu24-8327, 2024.

EGU24-9551 | ECS | Orals | GM10.5

Quantifying water and ice content variability in ice-rich permafrost using piezometer measurements 

Matthias Lichtenegger, Marcia Phillips, Reynald Delaloye, and Alexander Bast

Mountain permafrost ground that consists of rock debris supersaturated with ice can deform under its own weight and form rock glaciers, a creeping periglacial landform. Over the past decades, much research has been dedicated to examining the dynamics of rock glaciers and identifying their main drivers across different spatiotemporal scales and their coupling to climate. Creep causes deformation within the rock glacier body and, dominantly, shearing in a discrete horizon commonly at about 15-30m depth. However, current understanding of the driving forces of these processes is limited. Rock glacier surface velocity time series highlight the effect of temperature on creep rates at inter-annual to multi-decennial timescales. Seasonal velocity variations also point out a thermally driven effect, even if there is no temperature change at the depth of the shear horizon. A temperature change within the rock glacier body potentially alters the water content. Increasing water pore pressure in the shear horizon of rock glaciers could have an accelerating effect. We aim to investigate (i) how changes in water content taking place at shallow depths within the permafrost could affect the shear process occurring lower down (ii) how and where water infiltration is occurring within the permafrost. Direct insights into the internal hydrology of rock glaciers have yet to be quantitatively described using field data.

In this study, we measured relative changes in pore water pressure in different layers of a rock glacier using piezometers, which allowed us to describe the water-to-ice ratio variability and investigate its effect on kinematics. Seasonal pore water pressure variations can be attributed to phase change, as indicated by parallel ground temperature measurements and cross-borehole electrical resistivity tomography (ERT) data. To improve the understanding of piezometer measurements in permafrost field environments, we carried out laboratory tests to validate piezometers in ice-rich ground undergoing phase change. To do this, we created an experimental setup in which we froze and thawed a mixture of sand, gravel and water containing Keller PAA-36XiW piezometers under controlled laboratory conditions. The results of the laboratory experiments, their implications on the interpretation of field data, and the advantages and limitations of piezometer measurements in ice-rich permafrost with variable water contents will be presented.

How to cite: Lichtenegger, M., Phillips, M., Delaloye, R., and Bast, A.: Quantifying water and ice content variability in ice-rich permafrost using piezometer measurements, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9551, https://doi.org/10.5194/egusphere-egu24-9551, 2024.

EGU24-10577 | ECS | Orals | GM10.5

Kinematic Insights from Optical Feature Tracking on Rock Glaciers in the Kazakh Tien Shan: Understanding Sub-Landform Scale Patterns of Rock Glacier Flow 

Ella Wood, Tobias Bolch, Richard Streeter, Lothar Schrott, and Richard Bates

Rock glaciers exhibit complex and heterogenous dynamics, which are expressed in their pattern of surface flow; these surface kinematics provide insights into the processes taking place within the rock glacier system. Remote sensing methods using optical and radar imagery to detect movement are well established and have been widely applied at different spatial and temporal scales. However, the sub-landform scale is often overlooked despite considerable flow heterogeneity observed within individual rock glaciers. Feature tracking methods are suited to investigating kinematic detail as they are able to measure vector direction as well as magnitude, allowing them to identify complex and non-linear patterns of flow. This compliments widely used SAR interferometric methods which accurately detect slow displacements but don’t account for flow direction.

Here we show how optical imagery can be used to investigate rock glacier kinematics at the sub-landform scale. The study focuses on 18 rock glaciers in the Kazakh Tien Shan. This region hosts numerous large, complex rock glacier landforms, many of which are part of larger systems composed of small, retreating normal glaciers, moraines and downwasting debris zones. These rock glaciers are an important and interconnected component of the deglaciating environment and are likely to be hydrologically significant stores of ice in the Tien Shan region.

Rock glacier velocities have been measured using an intensity based cross correlation algorithm implemented in Python, with adaptable pre and post processing steps that enable the best results to be achieved on different types of optical imagery. The results from Pleiades, Planet and Sentinel image pairs taken from 2016 onwards are compared to investigate how source image resolution and sensor type impact the spatial patterns detected. High resolution Pleiades imagery provides the most detailed results, however, lower resolution Sentinel and Planet imagery is also able to detect sub-landform scale variations in flow. Over a 7-year time interval Sentinel imagery identifies flow velocities comparable to those derived from high-resolution imagery across the 18 rock glaciers investigated. Planet imagery performed the worst of the three data sources, highlighting the importance of image quality as well as resolution for intensity-based image matching methods. There is considerable variability in the mean, maximum and range of velocities detected between the landforms investigated. Rock glacier flow is heterogenous at both intra and inter landform scales, this is related to local topography but is also likely to be dependent on rock glacier internal structure and the distribution of material input. 

How to cite: Wood, E., Bolch, T., Streeter, R., Schrott, L., and Bates, R.: Kinematic Insights from Optical Feature Tracking on Rock Glaciers in the Kazakh Tien Shan: Understanding Sub-Landform Scale Patterns of Rock Glacier Flow, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10577, https://doi.org/10.5194/egusphere-egu24-10577, 2024.

Glacial retreat quickly and dramatically changes erosion dynamics across catchments. As ice retreats, newly exposed valley walls and sediment can become the target of hillslope and fluvial erosion that in turn can significantly increase sediment fluxes downstream. These increasing fluxes have important implications for hydropower generation and water quality, presenting risks to biodiversity, ecosystem stability, and human inhabitants. Determining where this new influx of sediment is derived from, and hence what parts of catchments are experiencing the greatest erosion, requires the ability to trace exactly where is sediment derived from in the catchment.

Recent analytical advances in the dating of apatite have improved its utility as a provenance tool. The advent of LA-ICP-MS techniques now allow thermochronometric, geochronometric, and chemical data to be collected from each individual grains of a detrital sample. As such, we are able to trace sediment sources across a partially glaciated catchment based on lithology, and source-rock elevation. In this work, we collected samples across the Bugaboo Glacier catchment in western Canada, where ice has retreated >2 km in the last century. Detrital samples were collected from the outwash river and two moraine samples, coupled with a bedrock elevation profile. Bedrock samples encompass the catchment’s two principal lithologies, a Cretaceous granitic intrusion, and Neoproterozoic metasediments. Thermochronometric dates range from 41.4 Ma at the highest elevation to 23.9 Ma at the lowest, while geochronometric dates range 68.7–151.3 Ma in granites to 90.5–1952 Ma in metasediments. Supplementary chemical data also help to highlight key differences between the lithologies.

Dates and chemistry from moraine samples show they are likely derived primarily from upstream granitic sources, while sample from the modern outwash river suggests a greater mixture of sources. Detrital mixture models and multi-dimensional scaling suggest moraine samples are composed of sediment derived from a wide range of elevations within the catchment, while the sediments of the modern outwash river appear to be derived entirely from erosion of these moraines, left exposed by retreating ice. This suggests the widely documented increase in sediment flux during glacial retreat is primarily driven by the erosion of newly exposed unconsolidated moraines in catchments. Moreover, this work helps to highlight how the analysis of detrital apatite can be harnessed to produce a highly accurate provenance tool in glacial catchments.

How to cite: Jess, S., Schoenbohm, L., and Enkelmann, E.:  Changes in erosion and sediment dynamics in a retreating world: high resolution provenance analysis from detrital apatite, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12572, https://doi.org/10.5194/egusphere-egu24-12572, 2024.

EGU24-13150 | Posters on site | GM10.5

Assessing rock glacier activity in the Austrian Alps using radar interferometry and image correlation techniques 

Jan-Christoph Otto, Timon Ruben Schroeckh, and Markus Keuschnig

Rock glaciers serve as crucial indicators of climate change impacts, offering valuable insights into environmental consequences. Assessing the activity rate of these landforms is essential for understanding their vitality, yet recent activity remains largely undocumented, particularly across extensive regions. In this study, we present an innovative methodology for categorizing rock glacier activity, leveraging state-of-the-art remote sensing technologies and adhering to the latest guidelines established by the IPA Action Group on rock glaciers.

In this work, we use SqueeSAR© processed Sentinel-1 data over two years (2020-2022) and digital image correlation (DIC) of repeated airborne imagery and digital elevation models using SAGA IMCORR tool to classify rock glaciers in Austria. DIC techniques were used in several local test sites to calibrate a model of SqueeSAR classification for rock glacier activity based on a threshold approach. The approach was verified using existing local rock glacier kinematic data from across the country.

Our results show that around 10% of the almost 5800 rock glaciers in Austria can be considered active, showing motion rates above a 10 cm/yr threshold within more than 40% of their total area.  Another 350 rock glaciers (6%) have been categorised a transient status characterised by low movement rates at limited parts of the landforms. Furthermore, we identified about 1100 rock glaciers relict that have been classified intact in the original inventory. This increases the number of relict rock glaciers in Austria from 60% to 77%.  Active rock glaciers are located mainly in the Ötztal, Zillertal and Hohe Tauern ranges.

This new categorisation enables to identify rock glaciers in motion that may react sensitive to increasing ground temperatures and may contribute to a local hazard potential.

How to cite: Otto, J.-C., Schroeckh, T. R., and Keuschnig, M.: Assessing rock glacier activity in the Austrian Alps using radar interferometry and image correlation techniques, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13150, https://doi.org/10.5194/egusphere-egu24-13150, 2024.

EGU24-15821 | ECS | Posters on site | GM10.5

Towards a comprehensive rock glacier inventory in the Swiss Alps 

Thibaut Duvanel, Christophe Lambiel, and Reynald Delaloye

Rock glaciers are debris landforms typical of high mountain environments. They can be identified in the landscape by their steep frontal and lateral margins, as well as their lobed surface and the frequent occurrence of ridges and furrows (RGIK, 2023). Their morphology is related to the downslope creeping movement. Over the recent years, the scientific community has highlighted the importance of studying these landforms to improve our understanding of the impacts of climate change on high mountain regions. 

The RoDynAlps research project, funded by the Swiss National Foundation and led by the Universities of Fribourg, Lausanne, Zurich and the WSL Institute for Snow and Avalanche Research, aims to better understand the dynamics of rock glaciers in the Swiss Alps. One of the main objectives of the project is to assess the current state of the rock glaciers in the Swiss Alps, in the continuity of an initiative launched by Delaloye et al. (2019), with the result being a comprehensive inventory of rock glaciers in the Swiss Alps, including kinematic characterization. To this aim, we are applying a standard methodology developed by a consortium of experts (RGIK, 2023).  

This poster presents preliminary results obtained in the Valais Alps.  More than 1300 rock glaciers were identified, based on aerial ortho-images and on the new 0.5 m SwissSURFACE3D Lidar DEM analyses. In a next step, kinematic data will be computed from a wide range of interferograms derived from Sentinel 1 images 2020–2022. Then, statistical and spatial analysis will be performed in order to improve our knowledge on the factor governing the spatial distribution and the kinematics of the rock glaciers in the investigated region.  

REFERENCES  

Delaloye R., Barboux C., Gärtner-Roer I., Lambiel C., Pellet, C., Phillips, M. and Scapozza, C. (2019). Toward the first national rock glacier inventory in the Swiss Alps (SwissRG2020). Abstract, 17th Swiss Geoscience Meeting, Fribourg 2019 

RGIK 2023. Guidelines for inventorying rock glaciers: baseline and practical concepts (version 1.0). IPA Action Group Rock glacier inventories and kinematics, 26 pp. 

How to cite: Duvanel, T., Lambiel, C., and Delaloye, R.: Towards a comprehensive rock glacier inventory in the Swiss Alps, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15821, https://doi.org/10.5194/egusphere-egu24-15821, 2024.

EGU24-16141 | Posters on site | GM10.5

Rock glacier inventorying and validation across the Hindu Kush Himalaya from deep learning and high-resolution images 

Adina Racoviteanu, Zhangyu Sun, Yan Hu, Lin Liu, and Stephan Harrison

Rock glaciers are important to monitor due to their importance (i) as indicators of permafrost distribution, (ii) as integral components of the mountain hydrological systems, (iii) as indicators of permafrost temperature and pore-water pressure reflected in their kinematic behaviour under climate change and (iv) as potential triggers for geohazards such as rockfalls, debris flows, and lake outbursts related to their destabilization. Understanding these aspects requires accurate, systematic and updated rock glacier inventories. Currently, these remain patchy over extensive areas of High Mountain Asia. In a recent study, we presented a deep-learning-based approach for mapping rock glaciers across the Tibetan Plateau based on Deeplabv3+ deep learning network, trained using visually consistent and cloud-free Planet Basemaps and multi-source rock glacier inventories from multiple regions. This resulted in 44,273 rock glaciers covering a total area of ~6,038 km2, including both intact and relict types. In this work, we used the well-trained model to extend the mapping of rock glaciers over the entire Hindu-Kush Himalaya (HKH) range, resulting in an additional 46,425 rock glaciers candidates covering an area of ~5,700 km2. The raw number of rock glaciers mapped is significantly higher than previous estimates based on upscaled samples. We first screened the deep learning output based on AW3D30 elevation data to remove outliers and then validated the remaining candidates over several key regions in HKH (Manaslu, Khumbu and Ladakh regions) using independent satellite data from Pléiades, SPOT etc.

The now complete inventory over the Tibetan Plateau-KHK constitutes a significant contribution to the IPA RGIK action group and serves as a benchmark dataset for modeling and monitoring the state of permafrost in a changing climate. Furthermore, this provides an important dataset for training deep learning models for global application.

How to cite: Racoviteanu, A., Sun, Z., Hu, Y., Liu, L., and Harrison, S.: Rock glacier inventorying and validation across the Hindu Kush Himalaya from deep learning and high-resolution images, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16141, https://doi.org/10.5194/egusphere-egu24-16141, 2024.

EGU24-17330 | ECS | Posters on site | GM10.5

Inventory and kinematics of rock glaciers in Goikarla Rigyu, Tibetan Plateau 

Mengzhen Li, Gengnian Liu, Xie Hu, and Sayyed Mohammad Javad Mirzadeh

Rock glaciers are periglacial landforms often observed above the timberline in alpine mountains. Their activity states can indicate the existence of permafrost. To help further explore the development and motion mechanisms of rock glaciers in semi-arid and humid transition regions, we used a manual visual interpretation of Google Earth Pro remote sensing imagery and a 7-year (2017-2023) InSAR time series analysis to provide a detailed rock glacier inventory of the Goikarla Rigyu area of the Tibetan Plateau (TP). Approximately 5057 rock glaciers were identified, covering a total area of ∼ 404.69 km2. Rock glaciers are unevenly distributed in the study area from west to east, with 80 % of them concentrated in the central region, where climatic and topographic conditions are most favorable. Under the same ground temperature conditions, increases in precipitation are conducive to rock glaciers forming at lower altitudes. Indeed, the lower limit of rock glaciers’ mean altitude decreased eastward with increasing precipitation. The LOS deformation velocities results showed that 71.3% (n=3608) of the rock glaciers were in the transitional state, including 58.4% (n=2954) of the rock glaciers with deformation rates in the range of 10-30 mm/year and 12.9% (n=654) of the rock glaciers with deformation rates in the range of 30-100 mm/year. And 28.7% (n=1449) of the rock glaciers were in the relict state. Analysis of mean annual air temperature and annual precipitation data for the period 2000-2022 in the region where the rock glaciers are located shows that the faster-moving rock glaciers are distributed in locations where the mean annual air temperature is warming significantly faster and the rate of decrease in annual precipitation is relatively low. By comparing the results of rock glacier activity discrimination based on different indicators, it is found that the method based on kinematic data is more applicable to the discrimination of transitional state rock glaciers in the region, especially for those rock glaciers whose surfaces have been covered by vegetation but are still in motion. This study contributes to the understanding of the complex response of rock glaciers to environmental and climate change in semi-arid and semi-humid climatic zones.

How to cite: Li, M., Liu, G., Hu, X., and Mohammad Javad Mirzadeh, S.: Inventory and kinematics of rock glaciers in Goikarla Rigyu, Tibetan Plateau, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17330, https://doi.org/10.5194/egusphere-egu24-17330, 2024.

EGU24-17419 | ECS | Posters on site | GM10.5

Increased erosion rates on high-Alpine rockwalls evidenced by comparison of short-term (terrestrial LiDAR) and long-term (cosmogenic nuclides) approaches 

Léa Courtial-Manent, Jean-Louis Mugnier, Ludovic Ravanel, Julien Carcaillet, Riccardo Vassallo, Alexandre Lhosmot, and Arthur Schwing

Rockwall erosion due to rockfalls is one of the most efficient erosion processes at high elevations. It is, therefore, important to quantify this erosion to understand the long-term evolution of mountain topography. This is especially crucial since rockfall frequency is increasing in high-Alpine areas, such as in the Mont-Blanc massif (MBM), due to regional scale permafrost degradation (which occurs through thickening of the active layer, the subsurface layer freezing and thawing throughout the year), a consequence of climate warming and the multiplication of heat waves.

To better understand rockfalls as a permafrost-related process, we quantify the erosion rates at different time scales by i) a short-term (  ̴ ten-year scale) quantification of the dynamics of the rock walls based on the diachronic comparison of topographic measurements carried out by terrestrial laser scanning (LiDAR) and ii) a long-term quantification (102-104 year scale) based on the 10Be concentration of sediment sampled downglacier on medial moraines. Our analysis considered that once the rockfalls have occurred, clasts are transported within the ice stream and amalgamated by ice melt in the ablation zone, forming medial moraines. The 10Be concentration is linked to the rockwall erosion rate and the time needed to transport from the glacier equilibrium line to the sampling location.

Scanned rockwalls and rockwall sources vary in elevation, aspect, slope, and area, allowing us to assess whether these factors influence the measured 10Be concentration and erosion rates. We studied rockwalls located on the French side between 2800 m and 4200 m a.s.l. and between 2500 m and 4600 m a.s.l. on the Italian side. We collected 8 (Géant basin and Vallée Blanche, France) and 10 supraglacial samples (Brouillard and Frêney glaciers, Italy), respectively.  

Our results reveal substantial variations in 10Be concentrations. On the French side of the MBM, 10Be concentrations vary from 1.2 ± 0.2 to 6.7 ± 0.4 x 104 atoms g-1, while they range from 3.0 ± 0.2 to 92.0 ± 3.2 x 104 atoms g-1 on the Italian side. These results suggest that the long-term erosion rates vary between 0.8-1.7 and 0.1-0.3 mm.yr-1, respectively. The short-term erosion rates for the French side are 4.3 mm.yr-1 for 2005-2014 and 39.3 for the period of 2015-2022. On the Italian side, they are 0.8 mm.yr-1 for 2005-2011 and 6.1 for 2011-2017.

Our results show spatial differences in erosion rates on both sides of the MBM. Short-term erosion rate is lower on the Italian side, and 10Be concentrations are higher, meaning that the rock walls are more stable in this area. However, on both sides of the MBM, erosion rates have increased significantly recently, with a further acceleration during the last decade. This suggests that high-altitude rockwalls, previously unaffected by global warming, are progressively entering a state of permafrost degradation.

How to cite: Courtial-Manent, L., Mugnier, J.-L., Ravanel, L., Carcaillet, J., Vassallo, R., Lhosmot, A., and Schwing, A.: Increased erosion rates on high-Alpine rockwalls evidenced by comparison of short-term (terrestrial LiDAR) and long-term (cosmogenic nuclides) approaches, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17419, https://doi.org/10.5194/egusphere-egu24-17419, 2024.

EGU24-18492 | ECS | Orals | GM10.5

How does rock glaciers deactivate? Geomorphic and activity states of French Alpine rock glaciers in transition 

Julia Agziou, Diego Cusicanqui, Benjamin Lehmann, Xavier Bodin, Thibaut Duvanel, and Philippe Schoeneich

Rock glaciers are the visible expression of mountain permafrost. The deformation of internal ice and basal horizon make them creeping downward, which allows their detection. Their geomorphological characteristics tend to evolve as a response to degrading permafrost conditions. If the internal ice is melting, the surface creeping gradually decreases until the landform stabilizes. This gradual deactivation has led to the definition of “rock glaciers in transition”. Recent studies highlighted a general trend of active rock glaciers’ increasing surface velocity in the last decades. In this context, we are asking if remaining ice in rock glaciers in transition could allow an increase of surface velocity trend similar to active rock glaciers? This study aims to describe rock glaciers in transition geomorphic settings and their present-day kinematics, and explore how their intrinsic and extrinsic characteristics can explain their activity.

To answer this question, we applied remote sensing techniques from a French inventory of rock glaciers such as i) High resolution differential radar interferometry images to describe present days surface velocities for all “inactive” inventoried rock glaciers and reveal global trends at a large scale. ii) Geomorphic mapping of the rock glaciers characteristics such as their geometry, geomorphological and geological settings (rock glacier system, slope, latitude/longitude, altitude, concavities, vegetation cover, exposition, aspect and lithology of the blocks…). iii) By combining a dataset with i) and ii), we analyze correlations and dominant parameters using an MCA factorial analysis and a multimodal linear regression.

Over 521 rock glaciers, 305 present displacements detectable from 30 InSAR images during summer period between 2016 and 2018. Most of them have velocities rates lower than 10 cm. yrˉ¹ (N=184), and for 1/3 (N=120) it ranges from 10 to 50 cm. yrˉ¹. Higher rates only concern 11 rock glaciers. For 80% of them (N=247), the mean surface area of displacements is lower than a half of the rock glacier surface area. The most represented geomorphic criteria are related to sagging landforms. Indeed, more than 50% of rock glaciers have a concave transversal profile matching with subsidence, whereas the others face with a high asymmetric topography. We support the hypothesis that lithology, exposition and the slope could be external factors that explains the most the heterogeneity of rock glaciers responses to a global climatic impact. The concavity/convexity index of transversal profiles, the surface slope and the vegetation cover should be the best parameters to describe the state of a transitional rock glacier in accordance with its activity. However, for many of rock glaciers with velocities ranging between 10 and 50cm. yrˉ¹ these criteria are met.

Morphodynamical approaches are essential to better understand the link between external parameters and morphological settings of rock glaciers in transition, in responses to their activity. Nonetheless, the ice content and amount of water input can be essential drivers of rock glaciers activity. It is therefore important to complement such morphodynamical studies with an analysis of the subsurface in order to correlate these characteristics with the actual internal properties of rock glaciers.

How to cite: Agziou, J., Cusicanqui, D., Lehmann, B., Bodin, X., Duvanel, T., and Schoeneich, P.: How does rock glaciers deactivate? Geomorphic and activity states of French Alpine rock glaciers in transition, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18492, https://doi.org/10.5194/egusphere-egu24-18492, 2024.

EGU24-19785 | ECS | Posters on site | GM10.5

Characterizing ground ice content and origin to better understand the seasonal surface dynamics of the Gruben rock glacier (western Swiss Alps) 

Julie Wee, Sebastián Vivero, Coline Mollaret, Christian Hauck, Christophe Lambiel, and Jan Beutel

Over the recent years, there has been focused international efforts to coordinate the development and compilation of rock glacier inventories. Nevertheless, in some contexts, identifying and characterizing rock glaciers can be challenging as complex conditions and interactions, such as glacier-rock glacier interactions, can yield landforms or landform assemblages that are beyond a straightforward interpretation and classification.

To gain a better understanding of the spatial and temporal complexity of the ongoing processes where glacier-permafrost interactions have occurred, the characterization of the subsurface is quantitively assessed using a petrophysical joint inversion (PJI) scheme (Mollaret et al., 2020), based on electrical resistivity (ERT) and refraction seismic (RST) data. Surface dynamics are assessed using both in-situ and close-range remote sensing techniques. These techniques include stationary GNSS stations to monitor daily and seasonal displacements, and biannual GNSS and UAV surveys to monitor landform-wide surface changes at high spatial resolution.

Both the geophysical data and geodetic data allowed to delineate two zones of the rock glacier: the intact permafrost zone and the complex contact zone where both permafrost and embedded surface ice are present. In the complex contact zone, resistivity values ranging up to MΩm are discernible, indicating very high ice contents (estimated up to 85%). However, in the uppermost zone, the liquid water-to-ice content ratio is greater, which probably indicates an ongoing thermal degradation (melt) of the embedded surface ice. This ongoing thermal degradation is reflected by important ice-melt induced subsidence, which ranges between -0.5 m to -0.7 m over the summer season (03.07.2023 – 07.10.2023). Yet, in winter when ground surface temperatures are below 0°C, the ice melt stops. In the intact permafrost zone of the Gruben rock glacier, the uppermost part of the section shows a distinct 5 m thick layer with low resistivity values and low velocity, which corresponds to the active layer. Right below this layer, a 30 m thick layer with high kΩm resistivity values dominates the lower section of the profile, suggesting widespread ice-saturated sediments. Surface displacement rates in this zone are typical of permafrost creep behaviour, with a gradual acceleration in late spring and a gradual deceleration in winter. Moreover, the coherent nature of the intact zone surface deformation contrasts with the back-creeping and slightly chaotic surface deformation of the complex contact zone.

Favouring a multi-method approach allowed a detailed representation of the spatial distribution of ground ice content and origin, which enabled to discriminate glacial from periglacial processes as their spatio-temporal patterns of surface change and geophysical signatures are (mostly) different.  

 

References

Mollaret, C., Wagner, F., Hilbich, C., Scapozza, C. and Hauck, C. 2020. Petrophysical Joint Inversion Applied to Alpine Permafrost Field Sites to Image Subsurface Ice, Water, Air, and Rock Contents, Frontiers in Earth Sciences, 8(85): 1-23. doi: 10.3389/feart.2020.00085

How to cite: Wee, J., Vivero, S., Mollaret, C., Hauck, C., Lambiel, C., and Beutel, J.: Characterizing ground ice content and origin to better understand the seasonal surface dynamics of the Gruben rock glacier (western Swiss Alps), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19785, https://doi.org/10.5194/egusphere-egu24-19785, 2024.

EGU24-20171 | Orals | GM10.5

Quantifying cut-and-fill terrace cycles since the Middle Pleistocene in the Patagonian Steppe, Argentina 

Victoria Milanez Fernandes, Andreas Ruby, Fergus McNab, Samuel Niedermann, Hella Wittmann, and Taylor Schildgen

The rapid response of Patagonian topography to ice-mass changes, facilitated by the presence of a slab-window, offers an ideal setting for investigating the interplay between surface processes, climate dynamics, and solid Earth rheology. This study focuses on glacio-fluvial terrace sequences of the Río Santa Cruz and Río Shehuen (50ºS), which are fed by glacial meltwater from the Southern Patagonian Icefield and extend for over 200 km along the entire length of the river. Recent research in Patagonia demonstrates that glacio-fluvial gravels from terraces formed in the vicinity of glacier outlets can be reliably correlated to glacial terminations. Thus, these cut-and-fill terrace sequences provide a geomorphic archive uniquely positioned to directly correlate landscape responses with periodic climate forcing. Yet, the spatially extensive preservation of these terraces over 100s of kilometers likely reflects the influence of geodynamic processes active over continental length-scales. Radiometric dating of basalts overlying the oldest terrace generations documents eastward-draining paleo-valleys by 3.2 Ma. New surface exposure-dating of terraces using in situ cosmogenic 10Be and 21Ne reveal onset of net incision at ~1 Ma, with individual terrace ages well-correlated to Patagonian glaciations and global cold periods. We attribute terrace abandonment and incision following glacial cycles to a drop in sediment supply relative to water discharge, likely influenced by the formation of a proglacial lake (Lago Argentino). While the onset of net incision aligns with the decline of the greatest ice extent in Patagonia and the Mid-Pleistocene Transition (MPT), terrace ages and geometry underscore the need to link net incision to regional geodynamic processes. Sub-parallel, vertically offset terrace profiles require a regional base-level fall of 100 m since 1 Ma, while terrace age-elevation relationships show a temporally non-uniform regional incision history. These observations cannot be explained by climatically-forced sediment supply variation, but likely relate to the evolution of the mantle underlying the slab window. Our study highlights the complex interplay between climate-driven factors and regional geodynamics in shaping the fluvial landscape of southern Patagonia.

How to cite: Milanez Fernandes, V., Ruby, A., McNab, F., Niedermann, S., Wittmann, H., and Schildgen, T.: Quantifying cut-and-fill terrace cycles since the Middle Pleistocene in the Patagonian Steppe, Argentina, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20171, https://doi.org/10.5194/egusphere-egu24-20171, 2024.

The aim of this study was to quantify the seasonal to daily freeze-thaw cycles of a rock glacier (RG) located in the Val d'Ursé catchment (Bernina Range, Switzerland) and their role in controlling the dynamic of the connected groundwater system. We combined digital image correlation techniques (Bickel et al., 2018) and time series analysis of discharge rates and physicochemical properties of springs and streams influenced by the RG, as well as changes in hydraulic head in nearby deep boreholes. The results indicate an acceleration of creep since 1990 due to rising temperatures, with the most active regions exhibiting horizontal velocities of ~1 m/yr. Distinct geochemical signatures of springs affected by RG discharge reflect different mixing rates with groundwater. Observed variations in discharge and dilution/enrichment cycles (based on the electrical conductivity signal) reveal an afternoon onset linked to the diurnal freeze/thaw cycle of the RG ice. This daily signal is superimposed on a seasonal trend that combines the effect of the changes in temperature and recharge/discharge dynamics of the deep groundwater system. Based on the results of a FFT-based analysis performed on the electrical conductivities and temperature signals of springs, we discuss the evolution of flow and transport mechanisms involved at the seasonal timescale. Specifically, the analysis of the phase lag between the signal of electrical conductivity with respect to the air temperature reveal key information on transport properties and timescales. Further investigations using a cryo-hydrogeological model (HEATFLOW-SMOKER code, Molson and Frind, 2019) allowed us to investigate the coupled processes governing groundwater-meltwater mixing on daily to seasonal time scales, supporting the interpretations of our field observations.

How to cite: Halloran, L., Louis, C., Molson, J., and Roques, C.: Seasonal and daily freeze-thaw dynamics of a rock glacier and their impacts on mixing and solute transport: a case study from the Val d’Ursé, Bernina Range, Switzerland, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20330, https://doi.org/10.5194/egusphere-egu24-20330, 2024.

Investigating the regional distribution of ice-wedge polygons allows for the estimation of permafrost conditions in periglacial environments, assess its vulnerability to degradation and anticipate how ice-wedge polygons will respond to climate change. Here we investigate the spatial distribution, substrate, and geometric properties of ice-wedge polygons as well as their relationship with other periglacial landforms in Western Greenland near the settlement of Kangerlussuaq. Ice-wedge polygons are networks of interconnected ice-filled fractures that develop in periglacial environments during cyclical drops of temperatures. To investigate the current state of ice-wedge polygons near Kangerlussuaq we conducted a field campaign in July 2023 as part of the Europlanet Transnational Access program. We mapped and characterized ice-wedge polygons using a series of 2004 aerial photographs and our field observations. Polygons in our research area are decameter scale and are found on hillslopes in a sandy loess material that is overlain by a layer of peat and vegetation. We have observed polygons on hillslopes as steep as 36° which suggests that the slope material in our study area is stable and resistant to solifluction. While the polygons themselves did not display any substantial morphological modification between the 2004 aerial photographs and our study, we observed signs of rapid slope modification in the form of active layer detachment slides (ALDS). These relatively small slides (1.2-1.5 × 102 m3) overprinted ice-wedge polygons morphologies downslope, effectively obscuring the polygons without removing them. The frequency of ALDS in permafrost area could increase under the current context of warming temperatures in the Arctic, which would locally affect the ability of any satellite or aerial based studies to detect ice-wedge polygons on the affected hillslopes. We find that polygons are anti correlated with earth hummocks, another type of periglacial landform that develops in poorly drained sites. This suggests that the presence of polygons on a slope modifies the local hydrology by increasing the drainage efficiency, which inhibits the formation of earth hummocks. Our field observations indeed indicate that polygon troughs modify the local drainage and act as water tracks. We observed soil piping and mobilization of small volumes (~1m3) of subsurface material along these troughs. This removal of material is probably facilitated by the absence of coarse material in the sandy loess that composes these slopes. While the extensive vegetation cover in our study area most probably increases the ground resistance to surface erosion via root consolidation and absorption of ground moisture, we suggest that subsurface erosion along polygon troughs will increase if the magnitude of water flow on these hillslopes increases, which should be expected under the current context of wetter-than-normal conditions in the Arctic due to climate change. Finally, we find that 64 % of all polygonised areas we mapped are found on north-west facing hillslopes and 76% are found on slopes steeper than five degrees, which indicate that topography and insolation have been the most likely controls for the development of ice-wedge polygons in this region.

How to cite: Noblet, A., Grau Galofre, A., and Osinski, G. R.: Distribution of ice-wedge polygons in Kangerlussuaq, Western Greenland, and association with other periglacial landforms , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-792, https://doi.org/10.5194/egusphere-egu24-792, 2024.

Rock glaciers as typical periglacial landforms in alpine environments constitute valuable palaeoclimatic indicators due to their connection to the climate-driven permafrost conditions responsible for both their initial formation and continuing activity. In particular for the Late Glacial/Early Holocene transition in cases local morphological evidence for glacial activity is sparse, targeting rock glaciers may successfully complement investigations on contemporaneous landform evolution or climatic variability in mountain regions. The Ben Ohau Range southeast of the Main Divide of the Southern Alps in New Zealand is an example where such conditions prevail. Only few studies focusing on chronological aspects, mostly older ones applying weathering-ring thickness as main dating technique, have been conducted on the rock glaciers occurring in considerable numbers in this selected mountain range to date. Consequently, the chronological data available remain limited.  

Following successful application during a previous pilot study, Schmidt-hammer exposure-age dating (SHD) regarded as suitable calibrated-age dating technique has recently been extensively applied in the Ben Ohau Range. Overarching aim of the related research project is to spatially expand and simultaneously improve the chronological data set for both initial formation and periods of morphodynamic activity of rock glaciers. The obtained chronological data are, furthermore, intended to eventually support the analysis of regional Holocene glacier activity in the Southern Alps.

Additional to SHD-sampling on various rock glaciers, published numerical TCND 10Be-ages from glacial landforms at two independent sites in the Ben Ohau Range have been utilised to establish a new regional SHD age-calibration equation. Including the abovementioned pilot study SHD age-estimates are now available for eight individual rock glaciers placed in three separate cirques/valley heads located in the middle and southern part of the range. These improved chronological constraints are based on no less than 16,500 sampled boulders on individual transversal rock glacier ridges and SHD age-calibration equation's control points. 

With SHD age-estimates for their initial formation of 11.4 ± 0.4 ka (Duncan Stream), between 9.4 ± 0.9 and 8.6 ± 0.8 ka (Double Basin), and between 11.8 ± 1.6 and 7.3 ± 0.8 ka (Irishman Stream) the studied rock glaciers appear to be significantly older than anticipated and previously reported. Some rock glaciers must have commenced their morphodynamic activity directly around the onset of the Early Holocene, what concurrently indicates that deglaciation of these cirques must have been completed at this point. Because the age difference between the innermost Late Glacial/Early Holocene moraines and the outermost rock glacier ridges sometimes averages only several hundred years, transition from glacial to periglacial processes must have been relatively rapid. With the palaeoclimatic interpretation of this development the significant precipitation gradient east of the Main Divide causing comparatively dry conditions in the middle and southern Ben Ohau Range needs to be taken into account.

Some of the studied rock glaciers are currently active, whereas others need to be classified as inactive. All seem, however, have experienced longer periods of activity during the Holocene.  

How to cite: Winkler, S.: Improved chronological constraints on rock glacier activity in the Ben Ohau Range, Southern Alps/New Zealand, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2308, https://doi.org/10.5194/egusphere-egu24-2308, 2024.

In recent years, increased theoretical and modelling-based research has explored the persistence of mountain topography and the processes and timescales over which landscapes achieve a stable or ‘steady state’ form. Across various sub-disciplines of geomorphology, amphitheatre or arm-chair-shaped topography has been recognised as a more persistent landscape form, attainable through glacial, periglacial and/or fluvial processes. Once achieved, rates of landscape change may be subdued, or a higher magnitude forcing or event is needed to significantly alter the form. This has yet to be empirically tested in the headwaters of mountain catchments.

This study evaluates the extent to which the morphometrics of catchment headwaters can provide insight into the persistence of mountain landscapes. This is achieved by exploring the dynamic relationships between topographic form and erosion in the Swiss Alps and Blue Ridge Mountains, USA.  We focus on two distinct mountain regions to capture a range of tectonic, climatic, and glacial settings. We use the novel ACME 2.0 GIS tool and high-resolution LiDAR data to characterise the morphometrics (inc. circularity, relief, hilltop curvature, hillslope length) of more than 50 catchments. We introduce a new Headwaters Topographic Form Index (HTFI) derived from these data, which allows us to compare topographic form between diverse mountain environments. To explore the links between form and rates of landscape change, we compare the HTFI and morphometric data with published catchment-averaged erosion rates.

This study aims to explore some of the factors influencing landscape persistence in mountain catchment headwaters, providing new insights into how vulnerable mountain landscapes may respond to ongoing and future climate change. This work has implications for research focused on hillslope stability, mountain hazards (e.g., landsliding), and landscape evolution modelling.

How to cite: Orr, E. and Oien, R.: Exploring landscape persistence and erosion dynamics in mountain catchments: A morphometric approach in the Swiss Alps and Blue Ridge Mountains, USA, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3918, https://doi.org/10.5194/egusphere-egu24-3918, 2024.

EGU24-4926 | ECS | Orals | GM10.2

Inventory and topographic analysis of glacial and high-altitude lakes in Kargil district, Union Territory of Ladakh 

Mohit Prajapati, Purushottam Kumar Garg, Sandipan Mukherjee, and Ajay Kumar Gupta

A glacial lake, characterized by its significant water volume, exists in association with a glacier (under, besides, and in front). They form due to glacial activities influenced by climatic variations. Glacial lakes generally impounded behind weak materials and can rupture suddenly due to various triggers, resulting to catastrophic floods known as Glacial Lake Outburst Floods (GLOFs). Lake’s topography particularity plays a crucial role in its formation and sustenance. Glacial lake related hazards are increasingly gaining attention due to their potential for causing significant damage and loss of life and property in high mountain regions worldwide. Therefore, it is imperative to regularly map and analyze various lake characteristics to understand any potential hazards originating from them.  Considering this, current study aims to present a comprehensive and updated inventory of glacial and high-altitude lakes in the Kargil district of Ladakh and systematically analyzes their types and topographic attributes. With the analysis of recent Sentinel-2 MSI imagery (2022), we identified a total of 355 glacier and high-altitude lakes in the Kargil district, encompassing an area of 4.8 ± 1.2 km2. These lakes are divided into four classes mainly based on their relationship with the glaciers: proglacial lakes away from the glacier (PGLA), proglacial lake in contact with glacier (PGLC), supraglacial lakes (SGL) and other lakes (OL). Results reveal that though PGLCs are comparatively low in number (85) but they occupy the largest area share of 60% in total glacial lakes covering an area of 2.88 ± 0.7 km2. PGLAs are 138 in number and occupy the second largest area of 0.9 ± 0.2 km2. There are large number (103) of SGLs with an area coverage of 0.32 ± 0.07 km2. OLs are limited in number (29) and cover 0.6 ± 0.1 km2 of area.  The lake sizes range from 0.001 km2 to 0.579 km2 with an average lake area of 0.013 km2 indicating that the lakes in the region are small in size and are in their initial phase of development. The mean elevation for the lakes is 4605 m and notably, ~21% of them predominantly oriented in a southward direction. The majority of lakes are situated on slopes with a gradient ranging 2-8° which reflects their potential to grow in size. It can be deduced from the analysis that the glaciated areas in Kargil region is dominated by large number of PGLC and PGLAs which are likely expand in future posing serious threat to the communities living in immediate proximities to the glaciers. Overall, this research contributes to our understanding of glacier lakes in the Kargil district of the Ladakh region, providing essential data for informed decision-making in order to minimize the glacial lake related hazards.

Keywords: Glacial lake inventory; High altitude lakes; Ladakh Himalaya; Remote sensing; Glacier Lake hazards.

How to cite: Prajapati, M., Garg, P. K., Mukherjee, S., and Gupta, A. K.: Inventory and topographic analysis of glacial and high-altitude lakes in Kargil district, Union Territory of Ladakh, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4926, https://doi.org/10.5194/egusphere-egu24-4926, 2024.

EGU24-5293 | Posters on site | GM10.2

Thermal characteristics of springs fed by mountain permafrost in Val di Sole (Eastern Italian Alps) 

Luca Carturan, Giulia Zuecco, Jacopo Boaga, Costanza Morino, Mirko Pavoni, Roberto Seppi, Monica Tolotti, Thomas Zanoner, and Matteo Zumiani

In alpine areas, spring-water temperature is affected by the presence of permafrost and by changes in the periglacial domain caused by the current atmospheric warming. Our interest in spring-water temperature is related to the possibility of investigating the spatial distribution of alpine permafrost and its changes. In particular, spring-water temperature might be helpful as indicator of permafrost occurrence in areas where it is discontinuous or sporadic, and in general where its distribution is poorly known.

The spring-water temperature in late summer is a useful evidence of permafrost, and various authors employed such method as auxiliary permafrost evidence, or as a stand-alone method that can be used for mapping permafrost distribution at the catchment scale. However, little is known on the spatial and temporal variability of water temperature at springs with different permafrost contribution and characteristics.

Here we present an analysis of the spatial and temporal variability of spring-water temperature in a 795 km2 catchment located in the Eastern Italian Alps, aimed at investigating the spatial distribution of permafrost and its effect on spring-water temperature. From 2018 to 2021, we measured the late-summer spring-water temperature at 220 springs, 133 of which are located downslope of rock glaciers, 81 downslope of other deposits, and 8 in bedrock. In addition, we installed dataloggers for continuous temperature measurements at 31 springs.

Results show that the cold springs are mainly associated with intact rock glaciers but also with rock glaciers classified as relict, especially if they have blocky and sparsely vegetated surface. Accordingly, the latter should be reclassified as pseudo-relict, i.e. they appear to be visually relict but host patchy permafrost, as confirmed by geophysics carried out at selected case studies. These results have important implications for the study and modelling of the hydrological, hydrochemical and ecological response of periglacial environments under ongoing climate change.

How to cite: Carturan, L., Zuecco, G., Boaga, J., Morino, C., Pavoni, M., Seppi, R., Tolotti, M., Zanoner, T., and Zumiani, M.: Thermal characteristics of springs fed by mountain permafrost in Val di Sole (Eastern Italian Alps), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5293, https://doi.org/10.5194/egusphere-egu24-5293, 2024.

EGU24-7745 | Posters on site | GM10.2

Investigating the signature of a tidewater glacier surge behaviour using geomorphological, sedimentological and geotechnical data: Borebreen, Svalbard.  

Danni Pearce, William Harcourt, Wojciech Gajek, Richard Hann, Brice Rea, Douglas Benn, Sven Lukas, Harold Lovell, and Matteo Spagnolo

The sedimentary processes taking place beneath contemporary surging glaciers are difficult to observe directly, yet they are crucial for building a holistic understanding of glacier surge processes and mechanisms. Settings where the sediment-landform assemblages characterising the ice-bed interface are preserved without significant modification are therefore an important archive of the subglacial processes that are active during a surge. At tidewater surging glaciers, landforms are often excellently preserved in a submarine setting, but analysis of these beyond mapping from high-resolution bathymetry data (where available) can be limited. However, in most cases, there are also subaerially exposed sediments and landforms at the terrestrial fjord margins, providing an accessible and rich source of data of the subglacial environment of a surging glacier.

Borebreen is a tidewater glacier on the northwestern side of Isfjorden in Svalbard. Previously published detailed bathymetric data has identified a suit of submarine glacial landforms formed during the last surge of Borebreen ~100 years ago. The subsequent quiescent phase has exposed a wide spread of crevasse-squeeze ridges (CSRs) both in the fjord and on the terrestrial margins. These are important landforms that are unique to surging glaciers and can therefore provide information concerning surge dynamics and subglacial processes. We present initial geomorphological and geotechnical data from the CSRs through mapping and direct measurements using a hand-held shear vane test, pocket penetrometer and particle size analysis. High-resolution orthmosaics and Digital Elevation Models (DEMs) from drone surveys of the proglacial foreland were collected in order to assess the spatial pattern of CSRs and a Python-based ArcGIS toolbox was used to automatically extract 3D morphometric data from the DEMs. These data provide an opportunity to investigate the links between the sediment geotechnical properties, CSR geometries and surge processes and mechanisms; such as the identification of spatial patterns in the state of sediment consolidation within CSRs and CSR morphometrics.

How to cite: Pearce, D., Harcourt, W., Gajek, W., Hann, R., Rea, B., Benn, D., Lukas, S., Lovell, H., and Spagnolo, M.: Investigating the signature of a tidewater glacier surge behaviour using geomorphological, sedimentological and geotechnical data: Borebreen, Svalbard. , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7745, https://doi.org/10.5194/egusphere-egu24-7745, 2024.

EGU24-7901 | ECS | Orals | GM10.2

Quantifying thaw subsidence in a permafrost landscape (Bayelva basin, Svalbard) 

Marie Rolf, Inge Grünberg, Jennika Hammar, and Julia Boike

Rising temperatures have led to permafrost degradation throughout the Arctic. The melting of excess ground ice leads to a loss of structural support and consolidation of soils. As a consequence, the surface subsides, which, in turn, can accelerate further ground ice loss. Therefore, thaw subsidence is an important metric for monitoring permafrost degradation. With temperature rise reaching twice the Arctic and seven times the global average rate, warming trends in Svalbard are particularly high, leading to severe impacts on permafrost conditions. However, knowledge on subsurface permafrost changes in Svalbard is mostly limited to a few in situ observations. In this study, we aimed to spatially expand research on permafrost degradation by applying a multimethod approach to quantify thaw subsidence in the Bayelva basin (near Ny-Ålesund, Svalbard). First, during a field campaign in summer 2023, we measured Global Navigation Satellite System (GNSS) points and calculated elevation changes since an earlier GNSS survey in 2019. Second, we coregistered and differenced high-resolution digital elevation models (DEMs) for a period of more than 80 years (from 1936, 1995, 2008, 2010, 2019, and 2020) to identify spatial patterns of thaw subsidence over a larger area. Third, we analysed how thaw subsidence relates to various terrain attributes and land cover. By employing these methods, we clearly detected thaw subsidence in the Bayelva basin. The GNSS measurements showed a spatially averaged subsidence of 2.7 cm between 2019 and 2023. With DEM differencing, we observed annual surface subsidence in the order of metres for areas of glacial retreat, in the order of decimetres for moraines, and up to a few centimetres for tundra areas in the glacier foreland. We furthermore detected spatial variations in thaw subsidence throughout the tundra. We conclude that surface subsidence is an ongoing, widespread, and important process in Svalbard’s permafrost landscapes. In this study, we demonstrate the challenges of DEM coregistration in areas with a lack of stable terrain. Nevertheless, our results highlight the potential of GNSS measurements and DEM differencing for quantifying thaw subsidence in the Arctic.

How to cite: Rolf, M., Grünberg, I., Hammar, J., and Boike, J.: Quantifying thaw subsidence in a permafrost landscape (Bayelva basin, Svalbard), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7901, https://doi.org/10.5194/egusphere-egu24-7901, 2024.

EGU24-8710 | ECS | Posters on site | GM10.2

Exploring the modern-day sedimentary record of glacial margins in central Chilean Patagonia  

Paulina Mejías Osorio, Daniel Le Heron, Ricarda Wohlschlägl, Bethan Davies, and Bernhard Grasemann

Glacial forefields host a wide array of processes and landforms, which can vary significantly, even within today’s overarching context of rapid melting and recession correlated to anthropogenic climate forcing. Detailed studies of the geomorphology and sedimentology of glacial forefields provide insight regarding sediment transport, meltwater pathways, and the behavior of the ice itself. Patagonia’s glaciers have been inventoried, there is vast knowledge of paleoglacier extent, and remote sensing has focused mainly on calculating geometrical changes and velocities. By comparison, detailed sedimentological analyses are long overdue and landsystems models for the present-day state of these environments require updating. This work focuses on the sedimentary processes that are occurring at modern glacial margins, specifically at selected sites in the Northern Patagonian Icefield and the neighboring Monte San Lorenzo massif to the east. High resolution geomorphological maps generated with photogrammetric data from an uncrewed aerial vehicle are presented. These maps, complimented with sedimentological facies descriptions and stratigraphic logging seek to characterize landsystems for the margins of glaciers in and near the Northern Patagonian Icefield, thus working towards an accurate reading of the sedimentary record and a better understanding of current glacial processes.

How to cite: Mejías Osorio, P., Le Heron, D., Wohlschlägl, R., Davies, B., and Grasemann, B.: Exploring the modern-day sedimentary record of glacial margins in central Chilean Patagonia , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8710, https://doi.org/10.5194/egusphere-egu24-8710, 2024.

EGU24-9425 | ECS | Posters on site | GM10.2

Feasible task? The application of the Schmidt-hammer method for dating rock glaciers made of conglomerate rock 

Eva Gautsch and Andreas Kellerer-Pirklbauer

The Schmidt-hammer (SH) is a well-established method in studying glacial and periglacial landforms in alpine regions. Schmidt-hammer rebound values (or R-values) allow the relative-age dating of landforms by quantifying the degree of weathering and therefore length of surface exposure. R-values are controlled by lithological variations impacting weathering rates. SH sampling in a specific study should therefore focus on one lithology. Earlier studies found out that some rock types are less suitable than others because of their specific weathering rind development over time. Some rock types are even unsuitable for the application of the SH. In the past, conglomerates for instance were rarely used for SH measurements, which may be related to problems in SH discrimination between the matrix and the clasts of conglomerates. In this study, we applied the SH method at several relict rock glacier systems and lateral moraine ridges which consist of conglomerate and sandstone material of Upper Carboniferous age. The landforms studied are in two cirques (Rosaninalm, Hinteralm; 46.9°N, 13.8°E) in the Gurktal Alps, Austria. We accomplished SH sampling at altogether 21 sites with 100 individual SH measurements per site. The 21 SH measurement sites are located along five longitudinal profiles that were placed over the different landscape forms, the longest one over a horizontal distance of 1.3 km. Measurements focussed on the matrix material of the conglomerates. Mean R-values vary between 29.6 and 39.0. Using these results and assuming a reasonable mean decrease in R-value of 1.5 per ka (based on nearby data from gneiss material), one can assume that the landforms studied were formed over a total period of approximately 6000 years. Individual landform units, in our case mostly rock glaciers, seem to have formed over periods of between 1.1 and 4.9 ka. By using these age estimates and present permafrost conditions, the onset of moraine and rock glacier formation was presumably during the Oldest Dryas and landform stabilisation occurred during the early Holocene. Several uncertainties remain, however, which will be addressed at the poster.

How to cite: Gautsch, E. and Kellerer-Pirklbauer, A.: Feasible task? The application of the Schmidt-hammer method for dating rock glaciers made of conglomerate rock, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9425, https://doi.org/10.5194/egusphere-egu24-9425, 2024.

EGU24-9888 | Posters on site | GM10.2

Periglacial processes and landforms in the European Alps: From the Last Glacial Maximum via Leonardo da Vinci to the present 

Andreas Kellerer-Pirklbauer, Isabelle Gärtner-Roer, Xavier Bodin, and Luca Paro

Periglacial landforms are widespread features in the European Alps, which cover an area of 190,900 km². The mountain range is arcuated in the western part, extend over a length of 1200 km, are up to 280 km wide, and reach their highest elevation at Mont Blanc (4807.8 m a.s.l.) at the French/Italian border. About 19% of the Alps exceed 2000 m and some 52% of the area consists of carbonate rocks at the surface, which is relevant for karstification processes. During the Last Glacial Maximum some 20 ka ago, 55% of the Alps were covered by glaciers whereas the remaining area was impacted by moderate to severe periglacial conditions causing the formation of widespread periglacial landforms still visible today, particularly at the Alpine margin. During the following Late Glacial period terminating with the Younger Dryas period about 11.7 ka ago, previously glaciated areas were reshaped by periglacial processes forming for instance complex rock glacier systems and solifluction landforms which characterize many high-elevated regions in the Alps until today. Nowadays, active periglacial processes are restricted to elevations above 2000 m in the marginal areas and above 2400 m at the central parts of the Alps. Around 11% of the European Alps are in this active periglacial belt, constrained by the potential treeline as the lower limit and the currently glaciated areas (1% of the Alps) as the upper limit. The widespread existence of relict and active periglacial landforms in the Alps inspired research by many scholars and scientists since centuries. Even Leonardo da Vinci made some periglacial-related observations in the late 15th century. Despite this long traditions and comprehensive experiences in periglacial landform research, future periglacial research is still needed and will help to better understand the impact of ongoing climate change on the periglacial reshaping of this remarkable mountain chain. In this contribution we will present a summary of a recently published book chapter dedicated to the European Alps (Kellerer-Pirklbauer et al. 2022), which is part of a book dealing with the periglacial landscapes of Europe (Oliva et al. 2022).

References:

Kellerer-Pirklbauer A, Gärtner-Roer I, Bodin X, Paro L (2022) European Alps. In: Oliva M, Nyvlt D, Fernández-Fernández JM (eds), Periglacial landscapes of Europe. Springer, Cham. 147-224. https://doi.org/10.1007/978-3-031-14895-8_9

Oliva M, Nyvlt D, Fernández-Fernández JM (eds) (2022) Periglacial landscapes of Europe. Springer, Cham. 523 pp. https://doi.org/10.1007/978-3-031-14895-8

How to cite: Kellerer-Pirklbauer, A., Gärtner-Roer, I., Bodin, X., and Paro, L.: Periglacial processes and landforms in the European Alps: From the Last Glacial Maximum via Leonardo da Vinci to the present, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9888, https://doi.org/10.5194/egusphere-egu24-9888, 2024.

EGU24-11592 | ECS | Orals | GM10.2

InSAR monitoring of solifluction and permafrost evolution in the Northeastern Tibetan Plateau 

Hugo Watine, Simon Daout, Jérôme Lavé, and Marie-Pierre Doin

The Tibetan Plateau is characterized by a high periglacial landscape. The average annual surface temperature is below 0°C over most of the Plateau, so permafrost (permanently frozen ground) is present over most of its extent. Excess ice in the frost-sensitive materials of the active layer, above the permafrost, thaws during the summer and autumn months and freezes during the winter and spring months. These freezing and thawing phenomena lead to cyclic vertical movements of the surface. On the slopes, solifluction phenomena also related to freeze-thaw activity take place, associated to permanent horizontal displacements. Both movements can be measured by spatial geodesy techniques such as Synthetic Aperture Radar Interferometry (InSAR).

The high-altitude Tibetan Plateau, like the Arctic regions, is particularly sensitive to global warming, and recent studies  have documented an apparent acceleration of solifluction processes as well as permanent ground subsidence likely due to ice loss in permafrost. Here, we developed a methodology to analyse hillslope processes from multi-temporal InSAR data to further document this worrying trend, and confirm or not its relation with global and regional temperature increase or with glacier ice loss in Tibet. 

InSAR time series of surface deformation from 16 yr of Envisat (2003-2011) and Sentinel-1 (2014-2020) ESA satellite radar measurements have been built over an 80,000km2 area to study the permafrost evolution of the northeastern Tibetan Plateau. Time series exhibit three trends, (1) a linear trend of continuous deformation, (2) an annual cyclical deformation whose amplitude appears to (3) increase over time. We conducted an analysis of the annual cyclic and cumulative deformation from the InSAR time series and projected those three trends parallel and normal to the line of the greatest slope. Areas with poor constraints were masked based on hillslope aspect from synthetic tests. The measurements (seasonal cycles and cumulative deformation in the slope and normal) were correlated to the lithology, the nature of the surface formations (moraines, alluvial fans, etc.), the altitude, the slope, the curvature, and the orientation of the slopes, in order to characterize the distribution of these processes.

Our change of reference frame strategy proved effective in automatically extracting hillslope processes and quantifying their dynamics. Downward movements affect nearly all terrains, with velocities increasing in line with slope angles. Steeper displacements are observes in unconsolidated, frost-susceptible, and fine-grained sediments, exhibiting higher seasonal amplitude perpendicular to the slope. In contrast, for sedimentary and magmatic rocks that display lower seasonal amplitude, continuous creeping appears to be the primary downward displacement process. Permafrost degradation (long-term subsidence) appears more pronounced at higher altitudes (above 3800m) where one would expect to find the coldest annual average temperatures. We also illustrate significant increases in seasonal amplitude, potentially doubling within 5 years in intermontain basin. These findings suggest a recent degradation of the permafrost and a deepening of the active layer in the northeastern Tibetan Plateau, likely induced by global warming.

How to cite: Watine, H., Daout, S., Lavé, J., and Doin, M.-P.: InSAR monitoring of solifluction and permafrost evolution in the Northeastern Tibetan Plateau, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11592, https://doi.org/10.5194/egusphere-egu24-11592, 2024.

EGU24-11992 | Posters on site | GM10.2 | Highlight

Geomorphological record of a former ice stream to ice shelf lateral transition zone in Northeast Greenland 

Timothy Lane, Christopher Darvill, Brice Rea, Mike Bentley, James Smith, Stewart Jamieson, Colm Ó Cofaigh, and David Roberts

Understanding ice stream dynamics over decadal to millennial timescales is crucial for improving numerical model projections of ice sheet behaviour and future ice loss. Here, we document the terrestrial deglacial landsystem of Nioghalvfjerdsfjorden Glacier (79N) in Northeast Greenland following the Last Glacial Maximum, and the lateral transition of that margin to a floating ice shelf. High-elevation areas are influenced by local ice caps and display autochthonous to allochthonous blockfields that mark the interaction of local ice caps with the ice stream below. Below ~600 m a.s.l. glacially abraded bedrock surfaces and assemblages of lateral moraines, ‘hummocky’ moraine, fluted terrain, and ice-contact deltas record the former presence of warm-based ice and thinning of the grounded ice stream margin through time. In the outer fjord a range of landforms such as ice shelf moraines, dead-ice topography, and weakly developed ice marginal glaciofluvial outwash was produced by an ice shelf during deglaciation. Along the mid- and inner-fjord areas this ice shelf signal is absent, suggesting ice shelf disintegration prior to grounding line retreat under tidewater conditions. However, below the marine limit, the geomorphological record along the fjord indicates the expansion of the 79N ice shelf during the Neoglacial, which culminated in the Little Ice Age. This has been followed by 20th Century recession, with the development of a suite of compressional ice shelf moraines, ice-marginal fluvioglacial corridors, kame terraces, dead-ice terrain, and crevasse infill ridges. These mark rapid ice shelf thinning and typify the present-day ice shelf landsystem in a warming climate.

How to cite: Lane, T., Darvill, C., Rea, B., Bentley, M., Smith, J., Jamieson, S., Ó Cofaigh, C., and Roberts, D.: Geomorphological record of a former ice stream to ice shelf lateral transition zone in Northeast Greenland, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11992, https://doi.org/10.5194/egusphere-egu24-11992, 2024.

EGU24-12056 | ECS | Orals | GM10.2

The lifecycle of a relict periglacial boulder landscape, southern Appalachians, USA 

Michelle Fame, Kristin Chilton, James Spotila, Meredith Kelly, and Summer Caton

The deposition of large, resistant boulders on hillslopes and in channels can have an armouring effect on the landscape leading to a decrease in erosion rates, a decrease in the efficiency of downslope sediment transport, and a coeval mismatched increase in slope angle. Such boulder accumulations are a significant component of hillslopes and channels in the southern Appalachian Mountains and influence the landscape's morphology. It has long been speculated that these boulder deposits originated during Quaternary glacial advances under the influence of periglacial processes operating in cold regions south of the maximum extent of the Laurentide Ice Sheet. However, no prior work has tied these features to a specific time or climatically modulated mechanism. By testing and refining the hypothesis of the periglacial origin of these relict boulders and the mechanisms driving their initial deposition and subsequent reworking we hope to contribute to our understanding of the climatically correlated timescales over which contemporary warming can be expected to be a dominating influence on modern boulder armoured periglacial alpine and arctic landscapes.

In this study, we investigated the lifecycle of such boulder deposits by determining cosmogenic 10Be exposure ages from large boulders on hillslopes and in channels in the Virginia Appalachians, United States. The correlation between the resulting boulder exposure ages (101.7 ± 6.9 ka to 10.8 ± 0.8 ka; n = 23) and the most recent Wisconsin Glacial Stage and subsequent deglaciation (~115 – 11.7 ka) supports their periglacial origin. The lack of exposure ages corresponding to the Last Interglacial Stage or following Wisconsin ice retreat suggests interglacial non-deposition and stability. The absence of exposure ages from the penultimate Illinoian or older Quaternary Glacial Stages suggests that periglacial hillslope processes allow the landscape to be resurfaced with large boulders during each return to cold climate conditions. This cyclic resurfacing of hillslopes and channels is an example of how climatic oscillations insert disequilibrium into the landscape cycle and contributes to our appreciation of the timescales over which climate change may impact boulder landscapes in modern periglacial environments.

How to cite: Fame, M., Chilton, K., Spotila, J., Kelly, M., and Caton, S.: The lifecycle of a relict periglacial boulder landscape, southern Appalachians, USA, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12056, https://doi.org/10.5194/egusphere-egu24-12056, 2024.

EGU24-12138 | ECS | Posters on site | GM10.2 | Highlight

Morphological comparison of polygonal patterned ground across the Arctic and Antarctic: Implications for polygon formation on Earth and Mars 

Jonas Eschenfelder, Cansu Culha, Shawn Chartrand, and Mark Jellinek

Polygonal patterned ground (polygons) is ubiquitous in polar periglacial regions. It is thought to form due to repeated fracturing of the ground during freeze-thaw as a result of fluctuations in air temperature and soil conditions. Polygons can channelise overland flow in their troughs and guide groundwater flow during permafrost thaw, providing pathways for channel network development. Given the importance of polygons on local hydrology and geomorphology in cold regions, a key knowledge gap exists: We do not yet understand the evolution of existing polygons or the formation of new polygons under a changing climate. This is especially important as climate change is causing cold region water budgets to change, driving landscape change.

We investigate the morphologic characteristics that are associated with polygons to indirectly examine their formation mechanism. We extensively map polygon morphologies across the McMurdo Dry Valleys in Antarctica, Prudhoe Bay in Alaska, as well as on Devon Island and Axel-Heiberg Island in the Canadian High Arctic using high-resolution DEMs derived from LiDAR data. We use a semi-automatic mapping tool based on adaptive thresholding to accelerate and scale our efforts while also improving reproducibility. We calculate surface slope and roughness for baseline lengths of 3m to 300m to investigate how and whether polygon morphology varies with local and regional topography.

Overall, we quantify how polygon shape and form varies by proximity to important hydrological features. For example, in the McMurdo Dry Valleys, polygons are more often orthogonal and low-centred when they are closer to streams and glacier termini, but are characteristically hexagonal and high-centred  elsewhere. Orthogonal polygons are characterised by a smoother surface compared to hexagonal polygons across all baseline lengths, bounded by a rough `ridge’ on one side and a stream on the other. Further, on Axel-Heiberg, polygons that formed within the last 60 years are more orthogonal the closer they are to a lake. These observations suggest that polygon shape is controlled by soil moisture. 

It is commonly accepted that polygons form as a result of thermal contraction cracking followed by ice- or sand-wedge formation, and field studies suggest that the formation of ice-wedges over sand-wedges can be explained by elevated soil or air moisture. Sand-wedges potentially are more deformable than ice-wedges, allowing for the fracture network to evolve and relax into a hexagonal pattern, whereas ice-wedges would preserve the initial, orthogonal, pattern. Consequently, we hypothesise that the number and size of ice-wedges decreases along soil moisture gradients, and hence polygons farther away from water sources evolve into hexagonal shapes over repeated fracture cycles. This would mean that existing streams and other water sources set up gradients in the amount of ice stored throughout a polygon field, which in turn will influence both surface and groundwater flow during permafrost thaw, pointing towards complex interactions between polygons and landscape evolution in a changing climate.

How to cite: Eschenfelder, J., Culha, C., Chartrand, S., and Jellinek, M.: Morphological comparison of polygonal patterned ground across the Arctic and Antarctic: Implications for polygon formation on Earth and Mars, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12138, https://doi.org/10.5194/egusphere-egu24-12138, 2024.

EGU24-12797 | ECS | Orals | GM10.2

Future proglacial lake evolution and outburst flood hazards in south Iceland 

Greta Wells, Þorsteinn Sæmundsson, Finnur Pálsson, Eyjólfur Magnússon, Guðfinna Aðalgeirsdóttir, and Snævarr Guðmundsson

Arctic regions are warming at more than double the global average rate, causing significant changes in cryospheric and hydrologic patterns. As glaciers retreat, meltwater can accumulate in expanding proglacial lakes, which often form in overdeepened basins with large storage capacities and steep valley walls that are prone to paraglacial slope failures. If a mass movement event such as a rockfall or landslide enters the lake, the water can drain in a glacial outburst flood, significantly modifying the landscape. Moreover, many lakes are upstream of infrastructure, communities, and tourism sites, resulting in a high potential societal impact in the event of a flood. This process is a well-documented trigger of floods in glacial regions across the world, but it remains an emerging and understudied hazard in Iceland.

This study investigates past and future proglacial lake evolution and evaluates mass movement-triggered outburst flood risk at two sites in south Iceland. We present: 1) updated maps of lake bathymetry and subglacial topography derived from multibeam sonar and radio-echo sounding surveys, respectively; 2) past lake volume changes and projected future lake extent and volume; and 3) potential slope failure source areas and scenarios of mass movement-triggered outburst floods. These results lay the foundation for future work on flood modeling and hazard planning to mitigate impacts on communities and infrastructure. This project also serves as an excellent pilot study for this emerging hazard in Iceland and has significant potential for application to proglacial lakes in other Arctic and alpine regions.  

How to cite: Wells, G., Sæmundsson, Þ., Pálsson, F., Magnússon, E., Aðalgeirsdóttir, G., and Guðmundsson, S.: Future proglacial lake evolution and outburst flood hazards in south Iceland, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12797, https://doi.org/10.5194/egusphere-egu24-12797, 2024.

EGU24-12880 | Orals | GM10.2

Wind erosion rates in the Arctic as recorded the roots of tundra shrubs  – a new dendrochronological approach 

Piotr Owczarek, Magdalena Opała-Owczarek, Pavla Dagsson-Waldhauserova, Randall J. Schaetzl, and Krzysztof Migała

Arctic and sub-Arctic terrestrial environments often have bare surfaces, thin and poorly developed soils, large amounts of loose sediment, and low and sparse vegetation. The sensitivity of these sites to modern climate change is reflected, among other things, in an increase in the activity of erosion processes mainly via deflation. Despite the development of modern research tools and monitoring methods, the temporal and spatial changes in the intensity of soil degradation by aeolian processes in high latitude environments is still poorly understood. In this study, we sought to determine soil erosion rates, using anatomical features of Arctic shrubs and dwarf shrubs in northeastern Iceland, central Spitsbergen, and southern Greenland. The main research question we posed was: can the dendrochronological information contained in the anatomy of shrub roots be used to reconstruct soil degradation and erosion histories? We applied dendrochronological techniques to the exposed roots of dwarf willow (Salix herbacea L.), net-leaved willow (Salix reticulata L.), and common juniper (Juniperus communis L.), and estimated surficial erosion based on abrupt changes in cell size and width of annual growth increments in the roots. The accuracy of the dating of erosion processes was checked by comparison with dendrochronological reference scales from specimens collected from undisturbed site. We observed, that after exposure of shrub roots, cell size decreases by at least 50%, with the maximum changes in individual plants exceeding 150-200%. Based on this relationship, we estimated surficial erosion rates for Iceland (1970’s-present), as well as for Spitsbergen and Greenland (1980’s-present). We observed a rapid increase in erosion rates in the latter half of the 1990’s, approaching 5.4 – 6.1 cm/year. Our results confirmed the efficiency of the dendrochronological method we employed, for determining soil erosion rates, even in unforested areas. The method is particularly applicable to low-growing, Arctic dwarf shrubs, which develop measurable growth rings and cells, making them a reliable proxy in soil degradation studies.

The research was founded by a Polish National Science Centre project no. UMO-2021/41/B/ST10/03381 and project no. UMO-2019/35/D/ST10/03137.

How to cite: Owczarek, P., Opała-Owczarek, M., Dagsson-Waldhauserova, P., Schaetzl, R. J., and Migała, K.: Wind erosion rates in the Arctic as recorded the roots of tundra shrubs  – a new dendrochronological approach, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12880, https://doi.org/10.5194/egusphere-egu24-12880, 2024.

EGU24-14648 | Posters on site | GM10.2

Depositional environments in the fjord head delta of deglaciated Dicksonfjorden, Svalbard: The impact of global warming after the post-little ice age 

Joohee Jo, Dohyeong Kim, Seungyeon Sohn, Seolhui Bang, Maria Ansine Jensen, Seung-il Nam, and Kyungsik Choi

Global warming after the Little Ice Age (LIA) has triggered rapid glacier retreat in an arctic coastal region, instigating substantial environmental changes in the fluvial-marine transition zone (FMTZ). A comprehensive understanding of the sedimentary environments affected by glaciofluvial, tidal, and wave processes is imperative for predicting the ongoing impacts of global warming. Despite logistical challenges and limited accessibility, we investigate the influence of glacier melting on the evolution of depositional environments in the Arctic FMTZ, focusing on the deglaciated Dicksonfjorden in Svalbard. Our study involves the collection of undisturbed cores from glaciofluvial rivers, tidal channels, and spits to elucidate the spatial distribution of sedimentary facies. Hydrodynamic observations in tidal channels enable to comprehend sediment transport dynamics. The glaciofluvial river which is nourished by high-turbid snowmelt waters forms braided channels that intricately dissect extensive tidal flats in the downfjord. Sedimentary facies reflect an increasing tidal influence, transitioning from downstream-directed climbing-rippled sands to interlaminated sands and muds towards the sea. Tidal point bars exhibit inclined heterolithic stratification, comprising bidirectional rippled silts and interlaminated silts. Gravelly beds on the spits incline towards the shore, primarily attributed to wave-induced cliff erosion. The microtidal regime, characterized by ebb tidal asymmetry, experiences peaks in suspended sediment concentration during ebb tides. Estimated sedimentation rates calculated from 210-Pb activities averaged 0.14 cm/year from the 1920s to 2020. Notably, the rate has increased from 0.07 cm/year (1980s-2000) to 0.23 cm/year (2000-2020). This study underscores the profound impact of accelerated climate warming on increased meltwater and sediment discharges post-LIA, driving active delta progradation and instigating morphological changes in deglaciated arctic coastal environments.

How to cite: Jo, J., Kim, D., Sohn, S., Bang, S., Jensen, M. A., Nam, S., and Choi, K.: Depositional environments in the fjord head delta of deglaciated Dicksonfjorden, Svalbard: The impact of global warming after the post-little ice age, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14648, https://doi.org/10.5194/egusphere-egu24-14648, 2024.

EGU24-14909 | ECS | Posters on site | GM10.2

Identifying Moraine-Dammed Glacial Lakes Using Moraine Accumulation Characteristics and Vision Transformer  

Jinhao Xu, Min Feng, and Yijie Sui

Moraine-dammed glacial lakes are naturally formed by the accumulation of moraine debris in high mountain glacier environments. Due to their remote locations and the challenges in identification, these lakes often elude systematic and comprehensive surveys. However, under the influences of glacier melting and climate change, they can potentially cause catastrophic outburst floods, threatening the safety of downstream communities and the stability of ecosystems. Therefore, precise identification and monitoring of these lakes are crucial for disaster early warning and risk management.

The aim of this study is to develop a novel method based on multi-source remote sensing data and Vision Transformer technology for effectively identifying moraine-dammed glacial lakes. Traditional remote sensing methods face numerous challenges in these high mountain environments, such as confusion with similar water bodies and the impact of complex terrain. Our proposed method focuses on utilizing moraine accumulation characteristics, a key factor in the formation of moraine-dammed lakes. By analyzing the relationship between glacier movement and lake formation, we aim to more accurately identify potential dammed lakes, thereby reducing misidentifications.

We are using high-resolution satellite imagery and terrain data, combined with the Vision Transformer model for feature extraction. This model is capable of efficiently processing a large amount of complex spatial data and identifying specific geographical and geomorphological features. We are focusing on changes at the glacier front and terrain changes related to lake formation. Through this approach, we aim to extract key features directly related to the formation of moraine-dammed glacial lakes, thus improving the accuracy of identification.

Additionally, we are establishing a database containing samples of known moraine-dammed glacial lakes to train and validate our model. By comparing it with existing databases of moraine-dammed glacial lakes, we aim to further test the effectiveness and reliability of our method. We are anticipating that this research will provide a new technological approach for monitoring moraine-dammed glacial lakes, with significant scientific importance and practical value in understanding the mechanisms of lake formation, assessing potential risks, and developing effective disaster prevention measures.

How to cite: Xu, J., Feng, M., and Sui, Y.: Identifying Moraine-Dammed Glacial Lakes Using Moraine Accumulation Characteristics and Vision Transformer , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14909, https://doi.org/10.5194/egusphere-egu24-14909, 2024.

EGU24-16439 | ECS | Orals | GM10.2

Contrasting regional ice margin dynamics of the Scandinavian Ice Sheet revealed by the landform record 

Helen Dulfer, Benjamin Boyes, Nico Dewald, Frances Butcher, Chris Clark, Jeremy Ely, and Anna Hughes

Under current climate conditions the Greenland and Antarctic sheets are rapidly losing mass and these losses are projected to accelerate into the future. Consequently, potential changes in the ice marginal environment across these ice sheets are a future concern. Palaeo-ice sheets, such as the Scandinavian Ice Sheet, provide an opportunity to investigate ice-marginal changes over longer timescales that span a variety of physiographic and geological settings and climate conditions. Landform signatures across Fennoscandia reveal a range of palaeo-ice marginal settings, including lake-terminating, marine-terminating, and higher-altitude environments. This makes the landform record of the Scandinavian Ice Sheet a rich and diverse archive for studying ice margin behaviour. Furthermore, high-resolution digital elevation models (DEMs) that exist for the former bed of this ice sheet allow us to examine ice marginal settings and dynamics in unprecedented and consistent detail across Norway, Sweden and Finland.

We present a geomorphological ice margin dataset of ~56,000 mapped features that categorises each ice margin by its dominant landform type of moraine, hummocky moraine, lateral meltwater channel or glaciofluvial sediment. We then use the morphology of the landforms and overprinting relationships to determine which landforms were likely formed prior to the last deglaciation. The distribution of landform-types in our dataset provides interesting insights into the behaviour of different sectors of the ice sheet. For example, we find ice margins characterised by lateral meltwater channels are almost exclusively found in locations of Quaternary sediment cover, which may indicate that surficial sediment thickness influences their formation, rather than the thermal regime of the ice. We also find ice margins defined by hummocky moraines are more prevalent at higher latitudes. We hypotheses this pattern may be controlled by lower ablation rates at higher latitudes. Additionally, we find contrasts in the density and size of the ice margins between the aquatic and land terminating environments, which results from differences in sedimentation processes within each environment.

How to cite: Dulfer, H., Boyes, B., Dewald, N., Butcher, F., Clark, C., Ely, J., and Hughes, A.: Contrasting regional ice margin dynamics of the Scandinavian Ice Sheet revealed by the landform record, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16439, https://doi.org/10.5194/egusphere-egu24-16439, 2024.

EGU24-17083 | Orals | GM10.2

Inherited glacier structures influence glacial lake dam morphology 

Neil Glasser, Matt Peacey, John Reynolds, Tom Holt, and Adam Hepburn

We investigate the influence of inherited glacier structures on the development of moraine dam morphology over 61 years on four glacial lake dams in the Eastern Himalaya. We compare glacier structures from 1962 Corona imagery with current dam features from 2023 Maxar imagery at Imja, West Barun, Melung and Dang Pu glaciers. From the Corona imagery, maximum glacier extents were identified, along with discrete flow units, ice cliffs, transverse structures, and supraglacial ponds at a 2.5 m resolution. In the Maxar imagery, key dam components were identified including extent of dead ice, hummocky moraines, thermokarst, and surface drainage features and surface structures, mapped at 1 m resolution. Our analysis revealed that former glacier flow unit boundary locations coincide with the development of hydrological features on the dam surface. This was augmented with further analysis of surface elevation change, thermokarst, and surface drainage development using historical aerial imagery, satellite imagery, and DEMs for Imja from 1962 to 2023. We propose that hydrological features exploit relict flow unit boundaries and conclude that inherited glacier structures are key in understanding the development of lake dams that contain dead ice. The glaciological influences on dam features should be included in integrated hazard assessments in glacial settings.

How to cite: Glasser, N., Peacey, M., Reynolds, J., Holt, T., and Hepburn, A.: Inherited glacier structures influence glacial lake dam morphology, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17083, https://doi.org/10.5194/egusphere-egu24-17083, 2024.

EGU24-17442 | Posters on site | GM10.2

December 2021 Jökulhlaup impact on landform and sedimentary assemblages on the decoupled Skeiðarársandur system, SE Iceland: implications for the Quaternary record. 

Louise Callard, Sebastian Pitman, Devin Harrison, Neil McDonald, Matthew Perks, Rupert Bainbridge, Matthew Roberts, Jenny Snell, and Andrew Russell

Since the turn of the 21st century the appearance and expansion of the most recent proglacial lakes fronting Skeiðarárjökull in SE Iceland, has led to the sandur being disconnected or decoupled from the glacier. Consequently, the sediment that would otherwise be deposited on the sandur is instead trapped within these lakes, leading to sediment deprivation of the distal sandar which in-turn impacts the fluvial and coastal systems. The recent formation of proglacial lakes also provides new challenges for jökulhlaup hazard assessment. Despite their importance, there have been no detailed studies of this large-scale proglacial sedimentary systems undergoing active decoupling, and the role of this process for sediment flux and landscape development remains unclear. In December 2021, Grimsvötn subglacial lake drained 0.9 km3 of water as a jökulhlaup from Skeiðarárjökull. A comprehensive survey of the proglacial lakes (sub-bottom profiling and single beam echosounder) and proximal sandur system (ground penetrating radar (GPR) and UAS survey), along with the collection of sediment cores, was conducted after the event. This provides a rare opportunity to capture the geomorphological and sedimentary signature of a jökulhlaup within a subaqueous setting and the downstream fluvial system. We present a model of the controls on jökulhlaup impact on landform and sedimentary assemblages within the proglacial lakes and connected glacifluvial system of Skeiðarársandur. This provides a modern analogue for Quaternary glacier and ice sheet margins.

How to cite: Callard, L., Pitman, S., Harrison, D., McDonald, N., Perks, M., Bainbridge, R., Roberts, M., Snell, J., and Russell, A.: December 2021 Jökulhlaup impact on landform and sedimentary assemblages on the decoupled Skeiðarársandur system, SE Iceland: implications for the Quaternary record., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17442, https://doi.org/10.5194/egusphere-egu24-17442, 2024.

EGU24-20546 | Posters on site | GM10.2

Is the asymmetry of dolines in the Central Styrian Karst determined by periglacial processes?  

Christian Bauer, Andreas Kellerer-Pirklbauer, and Thomas Wagner

The formation of dolines (or sinkholes) lasts commonly for long periods of time exceeding 10 ka or even 100 ka. Climatic conditions over such long timescales might vary substantially and thus dolines in nowadays temperate climatic conditions were substantially shaped during markedly different climates, namely the colder conditions which dominated during the Pleistocene. In this contribution we focus on a specific form of dolines which are located at the eastern boundary of the European Alps in the so-called Central Styrian Karst (CSK) where periglacial conditions dominated during the colder periods of the Pleistocene. The CSK comprises the occurrence of karst formations in carbonate rocks near Graz, Austria. Unlike in alpine regions further west, this area remained unaffected by Pleistocene glacial erosion and was never glaciated. Given the absence of glacial erosion and the dominance of subaerial processes, (karst-) morphological features are assumed to exist since a long period of time. Consequently, the CSK is a prominent area to investigate landscape evolution in a non-glaciated Alpine area where karstifiable rock were also affected by periglacial processes during the colder periods of the Pleistocene. In addition, the landscape comprises numerous planation surfaces grouped into several levels dating to several Mio. yrs BP. Previously unknown for the CSK are the asymmetries of many dolines detected recently due to airborne laser scanning data. These dolines exhibit a NW-SE elongation, with steeper slopes facing S-to-SE, and flatter ones facing N-to-NW. Some authors have attributed asymmetric dolines in other regions to tectonic influences. However, dolines in close proximity to main fault systems in the CSK do not display these peculiar asymmetries. In addition, dolines further away from the main fault systems show obvious asymmetries. The detected asymmetries of dolines occur at various levels ranging from 540 to 780 m a.s.l. indicating possibly different ages of formation. This contradicts a syngenetic origin of elongation and suggests subsequent re-shaping after primary formation of dolines. Similar asymmetries observed in the Northern Calcareous Alps further to the north have been interpreted as the result of snow-patches, where prevailing wind directions cause snow accumulation in the lee side of doline rims. This type of karst is known as nival karst, which requires the absence of glacial erosion and permafrost to impede subsurface drainage. The CSK satisfies the climatic conditions for the development of nival karst during colder periods of the Pleistocene as judged from past periglacial climate estimations for this area. We hypothesize that the morphometry and formation of asymmetric dolines in the CSK must be seen in relation to a severe periglacial influence and are thus a legacy of (severe/long-term?) periglacial conditions of the past.

How to cite: Bauer, C., Kellerer-Pirklbauer, A., and Wagner, T.: Is the asymmetry of dolines in the Central Styrian Karst determined by periglacial processes? , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20546, https://doi.org/10.5194/egusphere-egu24-20546, 2024.

EGU24-574 | ECS | Orals | GM10.4

Using sediment facies & ground penetrating radar profiles to investigate the internal architecture and genesis of De Geer moraines 

Gwyneth Rivers, Robert Storrar, Joni Mäkinen, Antti Ojala, Naomi Holmes, and Camilla Holmroos

De Geer moraines (DGMs) have the potential to generate very high-resolution spatial and temporal ice margin reconstructions (~annual in contrast to 100-500 years, the current state-of-the-art). Existing studies suggest that DGMs likely form annually in a sub-aqueous, ice-marginal environment whereby basal sediments are advected and deposited at the grounding-line during seasonal advances. However, there have also been suggestions of a crevasse-fill origin that challenges this temporal regularity. Whilst the spatiotemporal properties of DGMs are disputed, the balance of evidence suggests an ice-marginal depositional environment with annual/seasonal regularities. Understanding the processes related to DGM formation is therefore critical, as it underpins the ability to use DGM to delineate ice-marginal retreat at unprecedented (potentially annual) resolutions.

A recent large-scale 3D morphometry study of DGMs and Crevasse-Squeeze Ridges (CSRs) was undertaken to constrain landform metrics and explore their formation processes. The results revealed statistically significant differences across all morphometrics between the sampled DGMs and CSRs. DGMs were found to be lower-relief, narrower, slightly more asymmetrical, and more sinuous than the studied CSRs. The morphometrics of DGMs support an ice marginal depositional environment. Furthermore, tendencies for cross-sectional asymmetry suggest a unidirectional push movement involved during formation. These inferences, however, must be supported with geophysical and/or sedimentological investigations.

Here we present the results of a field study using sedimentological and geophysical (Ground Penetrating Radar) techniques to investigate the internal architecture of DGMs in southwest Finland. Sedimentological data was acquired from two excavated exposures and 55 GPR profiles were obtained from four different locations across SW Finland. Radar facies were identified and corroborated with the lithofacies units as observed in the ca. 30 m long trench excavations. Typically, these facies comprise of stacked thrusted planes of laminated clay and diamicton on proximal slopes, sheared diamicton on surfaces indicative of proglacial pushing/overriding, and gravity-driven flow deposits on distal slopes. At places, glaciotectonic structures such as dipping, faults and folds were also identified.

The results may be used to complement the existing morphometry study, constraining the main processes involved in DGM formation and validating the use of DGMs as ice marginal indicators. This can ultimately be used as a foundation to explore the climatic significance of DGM ridges, thus meriting further work to constrain the spatial and temporal properties of DGMs during deglaciation.

How to cite: Rivers, G., Storrar, R., Mäkinen, J., Ojala, A., Holmes, N., and Holmroos, C.: Using sediment facies & ground penetrating radar profiles to investigate the internal architecture and genesis of De Geer moraines, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-574, https://doi.org/10.5194/egusphere-egu24-574, 2024.

EGU24-1010 | ECS | Orals | GM10.4 | Highlight

  A glacier-based reconstruction of the Last Glacial Maximum climate in the southern European Alps     

Lukas Rettig, Giovanni Monegato, Sarah Kamleitner, Matteo Spagnolo, Adriano Ribolini, Susan Ivy-Ochs, Brice R. Rea, Franco Gianotti, and Paolo Mozzi

Improved records of precipitation and temperature are crucial to understand the evolution of Alpine glaciers during the Last Glacial Maximum (LGM). Palaeoclimate models and proxy data have suggested an increased moisture supply to the southern face of the Alps during the LGM, following a south-ward shift of the North-Atlantic jet stream. Ground control for such models, however, has been lacking for many sectors of the Alps, and regional climatic gradients have therefore remained poorly constrained. Here, we present new insights into the LGM palaeoclimate in the southern Alps, using the Equilibrium Line Altitudes (ELAs) of marginal glaciers as proxy. Marginal glaciers include ice caps, cirque, and valley glaciers that throughout the LGM remained isolated from larger outlet lobes connected to the Alpine ice network. Several sites of marginal glaciation were investigated through a combination of geomorphological mapping, surface exposure dating (both 10Be and 36Cl dating), and numerical reconstructions of palaeoglacier geometries and ELAs.

The chronological data indicate that marginal glaciers across the southern Alps reached their maximum extent by ca. 24 ka and that an important readvance occurred at 19 ka, at the end of the LGM. Reconstructed palaeoglacier ELAs show considerable variations, from ca. 1100 m a.s.l. in the Julian and Carnic Prealps (SE-Alps) up to almost 2000 m a.s.l. in the Maritime Alps (SW-Alps). Minor differences between the sites can be attributed to topoclimatic factors (i.e., received solar radiation related to catchment aspect). Spatial trends in ELA, however, primarily reflect regional climatic gradients. More specifically, we recognised: (1) a N-S gradient related to increasing summer temperatures with lower latitudes, and (2) a strong E-W gradient driven by precipitation. For all sites, our data indicate little to no reduction in LGM precipitation compared to the present day, highlighting the importance of substantial precipitation for the build-up of marginal LGM glaciers in the southern Alps.

How to cite: Rettig, L., Monegato, G., Kamleitner, S., Spagnolo, M., Ribolini, A., Ivy-Ochs, S., Rea, B. R., Gianotti, F., and Mozzi, P.:   A glacier-based reconstruction of the Last Glacial Maximum climate in the southern European Alps    , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1010, https://doi.org/10.5194/egusphere-egu24-1010, 2024.

EGU24-2307 | Orals | GM10.4

Schmidt hammer exposure dating (SHD) the Last Glacial-Interglacial Transition in Wester Ross, Scotland  

Alastair Curry, Olly Bartlett, and Jonathan Newitt

Understanding the extent, retreat dynamics and climate-glacier coupling of the Scottish Ice Sheet during the Last Glacial-Interglacial Transition (LGIT) is hampered by a highly fragmentary geomorphological record, and is dependent on a precise and accurate dating framework to constrain deglaciation. On land, readvance of the retreating ice margin is recorded in part of NW Scotland by moraines of the Wester Ross Readvance at ~15.4-15.8 ka, preceding the Lateglacial Interstade and the Loch Lomond Stade ~12.9-11.7 ka. While the number of dated landforms has increased in recent years, the LGIT chronology in NW Scotland is primarily based on a limited number of samples per site, using Terrestrial Cosmogenic Nuclide Dating (TCND) methods that can yield conflicting or uncertain results. This highlights the value of developing complementary dating methods.

Previous studies have questioned the reliability of the Schmidt hammer exposure dating (SHD) technique on lithologies other than granite. This research (i) evaluates the use of SHD on sandstone in the NW Scottish Highlands; (ii) develops a local, lithology-specific calibration curve; (iii) applies this to estimate the age of undated surfaces and tests existing interpretations of landscape change during the LGIT. Field results from a 1,500 km2 area of NW Scotland conclude that SHD can detect significant differences (p <0.001) between Torridonian sandstone surfaces of Wester Ross Readvance and Loch Lomond Stadial age. Based on 31 existing, re-calibrated 10Be ages, a calibration curve was generated (R2 = 0.58, p <0.001) for the period ~18-11 ka BP, and applied to 17 undated Torridonian sandstone surfaces. Our findings support the view that on selected lithologies and with rigorous adherence to careful field procedures, SHD can represent a valuable, cost-effective and reliable tool for obtaining large numerical dating samples for landforms in formerly glaciated terrain.

How to cite: Curry, A., Bartlett, O., and Newitt, J.: Schmidt hammer exposure dating (SHD) the Last Glacial-Interglacial Transition in Wester Ross, Scotland , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2307, https://doi.org/10.5194/egusphere-egu24-2307, 2024.

EGU24-3491 | ECS | Posters on site | GM10.4

Quantification of landslide-induced changes in glacier dynamics – project outline 

Arunabh Bhattacharyya, Marek Ewertowski, Jakub Małecki, and Gisela Domej

The response of glacial masses to climate change is well documented. However, the impact of landslides on glacier dynamics and stability requires greater research. Landslides in glacierized mountains can be caused by climate change (e.g. permafrost thawing), intense precipitation, paraglacial response of slopes or earthquakes and can, in turn, limit ablation, increase meltwater production and alter glacier velocities. Besides, landslides can be hazardous to life and infrastructure. Permafrost degradation, de-buttressing of slopes, extreme precipitation and freezing and thawing cycles make mountain glaciers susceptible to instability and cascading hazards. Our project thus focuses on identifying the research gaps associated with landslide-glacier dynamics and related hazards. The two components of our project are 1) Remote sensing and GIS and 2) Modelling. Different spatial scales (landform, catchment, global) will be considered for our research.

This presentation aims to outline PhD project and discuss proposed approaches with the glaciological, geomorphological, and remote sensing community. A literature review aimed at generating an inventory of landslide-affected glaciers globally is the first step. This will be complemented by detailed analyses and quantification of landslide-induced changes in glaciers’ behaviour by selecting benchmark case studies across different glacial systems representing different environmental conditions. Acquiring UAV data (0.05-0.10 m), high resolution (0.3-1.0 m) (Pleiades, WorldView, etc.), and medium resolution (10-50 m) satellite imagery (Landsat, Sentinel, Aster) will be essential for the quantification of changes in glaciers velocity and mass balance. We also plan field visits to benchmark glaciers to ground-truth remote sensing data and collect information about sedimentological and geomorphological characteristics of landslide deposits.

This research was funded by the National Science Centre, Poland, project number 2021/42/E/ST10/00186

How to cite: Bhattacharyya, A., Ewertowski, M., Małecki, J., and Domej, G.: Quantification of landslide-induced changes in glacier dynamics – project outline, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3491, https://doi.org/10.5194/egusphere-egu24-3491, 2024.

EGU24-3632 | ECS | Posters on site | GM10.4

Insights from Cirque Floor Altitudes in the Western Putorana Nature Reserve, Russian Federation 

Ethan Lee and Rachel Oien

This study presents the first palaeoglacial assessment of the mountainous terrain in the western region of the Putorana Nature Reserve, Russian Federation. This exploration, the first of its kind in this region, focuses on approximately 200 cirques, utilising cirque floor altitudes as a proxy for Equilibrium Line Altitudes (ELAs) as a pivotal palaeoclimate indicator. The primary objective is to gain unprecedented insights into the last glacial advancement in the area and to contribute to our understanding of the palaeoclimate during the potential Last Glacial Maximum (LGM) in Russia.

Employing the Ohmura equation, this research aims to construct a comprehensive palaeo climate profile, with ELAs estimated from cirque floor altitudes. These cirques are systematically mapped using the 10 m Arctic DEM and reconstructed using the GlaRe tool. Additionally, the physical parameters of the cirques will be rigorously evaluated using the newly developed ACME2.0 tool. By concentrating on the last glacial advancement, this study seeks to provide valuable information about the palaeoclimatic conditions and glacial dynamics within the Western Putorana Nature Reserve. This offers the first insights into the understanding of the mountain glacial history of the region.

How to cite: Lee, E. and Oien, R.: Insights from Cirque Floor Altitudes in the Western Putorana Nature Reserve, Russian Federation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3632, https://doi.org/10.5194/egusphere-egu24-3632, 2024.

Knowledge of subglacial conditions is of great relevance in understanding glacier dynamics. A combination of micro- and macrosedimentological analysis of diamictons and deformation structures can form the basis for the reconstruction of past subglacial conditions. We present the results of such a study on subglacial tills, within an Alpine environment, at Einödgraben in the Kitzbühel Alps (Tyrol/Austria). The Late Pleistocene succession there (MIS 5d-MIS 2) shows great diversity in facies from wood-bearing alluvial to glaciolacustrine to subglacial deposits. Two glaciogenic diamictons (tills) within the sequence were analysed at the microscale and are correlated to the Last Glacial Maximum (LGM; Würmian Pleniglacial) and the early Lateglacial phase of ice decay. The first deformation phase of pre-LGM deposits occurred most likely in a subglacial setting close to the advancing glacier margin and resulted in diapir-like glaciotectonic macro-structures, which are unique for an inneralpine area. Subglacial erosion over these structures occurred and later pre-LGM emplaced deposits underwent deformation and partial homogenisation immediately beneath the glacier base leading to diamictons, indicative of subglacial deformable bed conditions. The tills of the LGM and the Würmian Lateglacial show a range of microfacies and deformation structures evidence of close and rapid changes in till rheology and stress field dynamic in the subglacial environment. Our study demonstrates the need for a reinvestigation of deposits occurring in the proximity of past active ice interfaces. The paleoglaciological evidence assembled from the detailed and spatially close research on the microsedimentology of till at Einödgraben reflects our increasing comprehension and understanding of till microsedimentology in Alpine environments. An awareness is also shown of the need for much further research on the glacial depositional mechanics in mountainous terrains that are different from those in the immense lowland plains of the extensive paleo-ice sheets of North America and Northern Europe.

How to cite: Reitner, J. M. and Menzies, J.: Till formation and subglacial deformation in a stratigraphic complex Late Pleistocene sequence (Einödgraben / Aurach, Kitzbühel Alps, Austria), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4566, https://doi.org/10.5194/egusphere-egu24-4566, 2024.

Subglacial hydrology has been shown to significantly influence ice sheet dynamics in both Greenland and Antarctica.  Though direct observation and study of the subglacial hydrological network is limited by the presence of thick overlying ice, insights into subglacial hydraulics can be gained by studying landforms derived from meltwater in deglaciated landscapes.  Murtoos and meltwater corridors are examples of meltwater derived landforms, the former being triangular-shaped hills flanked by shallow troughs, and the latter being broad, shallow landforms with clear erosional boundaries and distinct internal morphologies.  While meltwater corridors have been previously identified in British Columbia, this study represents the first identification and study of murtoos associated with the Cordilleran Ice Sheet.  We identified a large network of murtoos and meltwater corridors in south-central British Columbia and studied both the morphology and internal composition of both landform groups using high resolution elevation data and near surface geophysical surveys. Electrical resistivity tomography (ERT) and ground-penetrating radar (GPR) surveys on different murtoos reveal a homogeneous internal composition of sandy diamicton, while the troughs lateral to murtoos contain sorted sediment.  We interpret the murtoos as subglacial meltwater erosional remnants, their morphology determined by meltwater erosion of the lateral troughs.  The meltwater corridors studied contain two distinct morpho-stratigraphic relationships: channelized reaches exhibiting shallow intersecting and/or parallel troughs floored by sandy diamicton, the residuals resembling glacial curvilineations; and flat bed reaches with narrow eskers composed of fine sand and gravel.  We interpret the channelized and flat bed reaches as being formed by subglacial meltwater erosion and deposition, respectively, with the switch in process and form being determined by bed topography.  Together, these landforms suggest extremely wet-bed conditions during deglaciation of the Cordilleran Ice Sheet, with widespread subglacial meltwater erosion and deposition.  These observations provide insight into the likely conditions beneath portions of the Greenland and/or Antarctic ice sheets where widespread meltwater production has been reported, such as the western land terminating portion of the Greenland Ice Sheet.

How to cite: Sodeman, A. and Brennand, T.: Morphology and Composition of Murtoos and Meltwater Corridors Associated with the Cordilleran Ice Sheet in South-Central British Columbia, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4704, https://doi.org/10.5194/egusphere-egu24-4704, 2024.

EGU24-6044 | Orals | GM10.4 | Highlight

A landform-driven simulation of deglaciation of the Scandinavian Ice Sheet and the PalGlac project’s progress on data-modelling integration 

Chris Clark, Jeremy Ely, Anna Hughes, Rosie Archer, Ben Boyes, Frances Butcher, Nico Dewald, Chris Diemont, Helen Dulfer, and Sarah Bradley

The field of palaeo-glaciology has evolved from inquisitiveness about glaciated landscapes - how they came into being - into the wider role of improving glaciological understanding and more recently, into testing or improving the fidelity of ice sheet modelling approaches. Such endeavors are crucial for improving forecasts of today’s diminishing polar ice sheets and for predicting sea-level rise. The PalGlac project (2018 to 2024) is using glacial landform mapping and analysis to advance our understanding of ice sheets, and in this talk, we will focus on the demise of the Scandinavian Ice Sheet and how landform data is used to either test or calibrate (nudge) ice sheet modelling simulations.

Glacial landforms such as drumlins, moraines, meltwater channels and eskers record spatially extensive components of ice sheet activity, namely 1) ice flow geometry and thermal regime, 2) the pattern of ice-marginal recession, and 3) the subglacial flow of meltwater that likely modulated the first two. High-resolution (metres) digital elevation models (DEMs) are revolutionising the mapping and understanding of glacial landforms (Johnson et al. 2015). They permit detailed investigation across areas so large as to have been unimaginable decades ago. We here report on a multi-person mapping investigation of glacial landforms across the land areas of Fennoscandia, northern Europe, and parts of Russia, and which have yielded over 350,000  individual features recording ice flow (250,000), ice margins (70,000), and meltwater routing (30,000). All data, held in a GIS, are used to build a first-order reconstruction of the pattern of ice flow changes and ice margin retreat. Much of these data reveal a useful confirmation and replication of prior studies, which we now know with improved robustness, and with many new aspects being revealed, notably in ice divide positions.

Our ultimate aim is to build a simulation of whole ice sheet growth and decay incorporating changes in ice thickness and flow geometry and tracking successive ice-marginal positions. This is being achieved using the mapped landform data along with chronological data (Hughes et al. 2016), glacio-isostatic constraints and other constraints from the literature and comparing them with ice sheet modelling simulations using PISM (Winkelmann et al. 2011). We focus on using identified empirical changes in ice flow geometry (from the landforms) to choose between dozens of alternate ensemble ice sheet model simulations. The challenge is to build a three-dimensional simulation of ice sheet evolution that is physically well-founded that satisfies most of the flow geometry changes, and fits within empirically defined ice marginal positions.

 

References

Johnson, M.D., Fredin, O., Ojala, A.E.K., Peterson, G., 2015: Unraveling Scandinavian geomorphology: the LiDAR revolution. GFF 137, 245-251.

Hughes, A.L.C., Gyllencreutz, R., Lohne, Ø.S., Mangerud, J., Svendsen, J.I., 2016: The last Eurasian ice sheets--a chronological database and time-slice reconstruction, DATED-1. Boreas 45, 1–45.

Winkelmann, R., Martin, M.A., Haseloff, M., Albrecht, T., Bueler, E., Khroulev, C., Levermann, A., 2011: The Potsdam parallel ice sheet model (PISM-PIK)--Part 1: Model description. The Cryosphere 5, 715–726.

How to cite: Clark, C., Ely, J., Hughes, A., Archer, R., Boyes, B., Butcher, F., Dewald, N., Diemont, C., Dulfer, H., and Bradley, S.: A landform-driven simulation of deglaciation of the Scandinavian Ice Sheet and the PalGlac project’s progress on data-modelling integration, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6044, https://doi.org/10.5194/egusphere-egu24-6044, 2024.

EGU24-6551 | Posters on site | GM10.4

Geomorphological and sedimentological records of Greenland Ice Sheet advance and retreat on the continental shelf offshore of NE Greenland during the last glaciation 

Colm O'Cofaigh, Dave Roberts, S. Louise Callard, Jerry Lloyd, Georgia Ware, Katharina Streuff, Stewart Jamieson, Boris Dorschel, and Torsten Kanzow

Marine geophysical data combined with radiocarbon dated sediment cores provide a record of the advance and retreat of the ancestral Northeast Greenland Ice Stream (NEGIS) across the continental shelf offshore of NE Greenland during the last glaciation. Today, NEGIS is the largest ice stream to drain the Greenland Ice Sheet (GrIS), holding a sea-level equivalent of 1.1-1.4 m. However, the longer-term history of the ice stream, especially on the adjoining outer continental shelf has, to date, been poorly constrained. Streamlined subglacial landforms record grounded ice flow in the outer shelf section in cross shelf bathymetric troughs, with mega-scale glacial lineations recording former streaming flow towards the shelf edge. Flow transverse landforms in the form of downlow-tapering, sediment wedges occur at the shelf edge and on the outer-mid shelf of the bathymetric troughs. These landforms differ in their morphology from the classic ‘ramp-step’ form of typical grounding wedges but are similarly interpreted as a form of grounding-zone wedge in which sediment prograded and thinned away from the grounding-zone. The wedges record a shelf-edge terminating, grounded ancestral NEGIS, as well as the subsequent episodic retreat of the ice stream inshore during deglaciation. Beyond the shelf edge, glacigenic debris flows imaged on acoustic stratigraphic profiles and recovered in sediment cores document sediment delivery onto the slope; such deposits are typical of submarine slopes offshore of shelf-edge terminating palaeo-ice streams. On the outer shelf subglacial tills and grounding-zone proximal sediments overlain by deglacial stratified glacimarine sediments record ice stream advance and retreat in the troughs. Radiocarbon dates from glacimarine sediments in these cores indicate early deglaciation from the shelf edge but with relatively slow rates of subsequent ice-stream retreat across the outer shelf.

How to cite: O'Cofaigh, C., Roberts, D., Callard, S. L., Lloyd, J., Ware, G., Streuff, K., Jamieson, S., Dorschel, B., and Kanzow, T.: Geomorphological and sedimentological records of Greenland Ice Sheet advance and retreat on the continental shelf offshore of NE Greenland during the last glaciation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6551, https://doi.org/10.5194/egusphere-egu24-6551, 2024.

EGU24-7690 | ECS | Orals | GM10.4

Glacial history of the King Haakon Trough System, sub-Antarctic South Georgia 

Katharina Streuff, Nina-Marie Lešić, Gerhard Kuhn, Miriam Römer, Sabine Kasten, and Gerhard Bohrmann

In an effort to elucidate an important part of the Quaternary evolution of sub-Antarctic South Georgia, hydroacoustic data from its southern continental shelf are presented. The island with its surrounding shelf is of key interest for climate reconstructions, because it is located within the core belt of the Southern Westerlies and between the main fronts of the Antarctic Circumpolar Current in the Southern Ocean. This makes it particularly susceptible to changes in climate conditions on a local, regional, but also Southern Hemisphere-wide scale.

The data provide new insights into the glacial evolution of the King Haakon Trough, one of several cross-shelf trough systems around the island. Numerous landforms, identified from high-resolution bathymetry data, document phases of ice advance and retreat. They are interpreted to be related to the confluence of two major trunk glaciers fed by an extended, possibly warm-based, South Georgia Ice Cap. Linear bedforms become progressively elongated towards the shelf and imply accelerated ice flow and/or softer sediment substrate towards the shelf edge. In contrast, recessional moraines and large morainal banks not only evidence shelf-wide ice extent during a peak glaciation, but also attest to staggered retreat, at least during the initial phase of deglaciation. The establishment of a complex bottom-current system around the onset of the last deglaciation is implied by the presence of moats and contourite drifts, which are mainly recorded in sub-bottom profiler data from the trough system. These data also show an acoustically semi-transparent facies of variable thickness present on the mid- and outer shelf as basal trough fill, which, on the basis of its acoustic appearance and the presence of several strong internal reflectors, is interpreted as a sequence of stacked glacial tills. These are similar to stacked tills previously documented from the Antarctic Peninsula and probably document a minimum of three extensive ice advances around South Georgia. Because the tills in the King Haakon Trough occur over a distance of ~26 km across the shelf, it is postulated that they derive from a minimum of three separate glaciations, rather than from re-advances within one glaciation period. Accordingly, the new findings from the combined bathymetry and sub-bottom profiler data show that the marine-geological archives around South Georgia offer unique potential to constrain how ice masses in the Southern Ocean responded to Quaternary climate change.

How to cite: Streuff, K., Lešić, N.-M., Kuhn, G., Römer, M., Kasten, S., and Bohrmann, G.: Glacial history of the King Haakon Trough System, sub-Antarctic South Georgia, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7690, https://doi.org/10.5194/egusphere-egu24-7690, 2024.

EGU24-9282 | ECS | Posters on site | GM10.4

AlpIce - Towards an Alps-wide database of empirical geo(morpho)logical and geochronological data constraining Last Glacial Maximum to Holocene glacier fluctuations 

Sarah Kamleitner, Tancrède P. M. Leger, Susan Ivy-Ochs, Samuel U. Nussbaumer, Andreas Vieli, and Guillaume Jouvet

Latest advances in numerical modelling using machine learning sped-up glacier models by several orders of magnitude, thus facilitating glacier evolution models to run at high resolutions (hundreds of metres) over timescales of several tens of millennia and over mountain range scales. The RECONCILE project seeks to use the Instructed Glacier Model (IGM) to simulate the maximum state and deglaciation of the last glaciation of the European Alps and to test model output against the geological record. A robust framework against which to test Alps-wide and transient paleoglacier model simulations is however missing. Despite the long history of Quaternary research in the Alps and abundant publications on the topic, the integration of field evidence for model validation has thus far largely been restricted to the Last Glacial Maximum (LGM) ice extent. Inspired by work on the (former) British, Fennoscandian, Patagonian and Greenland ice sheets, we aim to build a comprehensive and standardized dataset on paleoglacier variations for the European Alps. Coupling geo(morpho)logical data and geochronological markers, the AlpIce database will act as an empirical basis for future quantitative model-data comparisons. Published empirical evidence that restrains the build-up, culmination, and disintegration of the Alpine LGM glaciers as well as subsequent Alpine Lateglacial and Holocene glacier advances are considered. Relevant surface exposure and radiocarbon datings are currently gathered and fed into the database. Data reliability assessments and paleoglaciological context classifications are undertaken concurrently. The database structure also allows the inclusion of additional chronological methods (e.g. luminescence dating, dendrochronology, archeological and historical sources) into AlpIce. Where applicable, the chronological constraints will be linked to related geo(morpho)logical features (e.g. former ice margins, trimlines) using GIS software. AlpIce is designed as an open-access resource hoping to prove useful for both empirical and modelling communities and beyond the scope of model validation.

How to cite: Kamleitner, S., Leger, T. P. M., Ivy-Ochs, S., Nussbaumer, S. U., Vieli, A., and Jouvet, G.: AlpIce - Towards an Alps-wide database of empirical geo(morpho)logical and geochronological data constraining Last Glacial Maximum to Holocene glacier fluctuations, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9282, https://doi.org/10.5194/egusphere-egu24-9282, 2024.

EGU24-9498 | ECS | Orals | GM10.4

Reconstructing the Enns valley in the course of the ice ages based on findings on Gröbminger Mitterberg (Austria) 

Gerit E.U. Griesmeier, Jürgen M. Reitner, Daniel P. Le Heron, Christopher Lüthgens, and Gustav Firla

Within the Alps, the erosive effects of glaciers during the Last Glacial Maximum (LGM) means that evidence for earlier glaciations is rare. At Gröbminger Mitterberg (GM), traces of the history prior to the LGM are conserved below a layer of basal till of the LGM. The GM itself is a flat-topped hill located in the Enns valley in Styria (Austria), rising to an elevation of ca. 200 m above the Enns valley floor. It is situated between Mesozoic carbonates in the north and crystalline basement units in the south. The GM comprises crystalline basement covered by fluvial and deltaic sediments, overlain by a subglacial till. Based on the distribution of the sediments, borehole data and geoelectric data, an ancient river channel across GM can be reconstructed. 
The lithological spectrum of the fluvial and deltaic sediments at GM shows that the distribution of material from the south and the north is around 70 : 30 % throughout the GM, which is the same as that of the modern Enns river. This suggests that all sediments at GM and the channel across it were greatly impacted by the Enns river. The Enns valley in the area of GM can now be reconstructed as follows:
Some time before the Riss Glaciation (MIS 6), the Enns river meandered in a valley, situated at an elevation ca. 100 m higher than the present-day river. Large alluvial fans flowing northward into the Enns valley forced the Enns river to flow across Mitterberg in a channel, which was probably already partly created during earlier glaciations. The first crystalline pebbles reached the north of GM. During the phase of ice decay of the Riss Glaciation, ice marginal lakes developed at the margin of GM, where deltaic sediments developed. After the Riss Glaciation, the Enns river found itself in a similar situation like today and the Enns valley aggraded until it reached the top of GM shortly before the last glaciation. Large alluvial fans further east dammed a lake, which covered GM and was quickly filled with sediments. This part of the chronology is also supported by optically stimulated luminescence data using single grains of potassium-rich feldspar. They will be presented at the conference. The braided Enns valley was not only much wider than today, but also transported crystalline pebbles to the northern part of GM. In the course of the LGM, most of the previously deposited sediments were preserved and covered by basal till. 
The evolution of the Enns valley emphasises the close coupling between climate, erosion and sedimentation processes. Today, the Enns river incises again and sediments at GM are going to be eroded, but parts remain in their position. These current changes have probably repeatedly occurred through time and we can never be sure, how much time is really preserved on GM. Nevertheless, the proposed reconstruction in the Enns valley can also give hints on the history of other alpine valleys and may be helpful for future models of alpine wide glaciation and greenhouse phases.

How to cite: Griesmeier, G. E. U., Reitner, J. M., Le Heron, D. P., Lüthgens, C., and Firla, G.: Reconstructing the Enns valley in the course of the ice ages based on findings on Gröbminger Mitterberg (Austria), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9498, https://doi.org/10.5194/egusphere-egu24-9498, 2024.

EGU24-10169 | ECS | Posters on site | GM10.4

Field observations of interlinked subglacial cavities in Kangerlussuaq - Greenland ice sheet western margin. 

Anna Grau Galofre and Axel Noblet

The glacial hydrology and stability to sliding episodes of the Greenland Ice Sheet (GIS) are closely linked to the subglacial drainage capacity of its bed, which depends on its structure and connectivity. The central-western portion of the GIS, specifically in the region around Kangerlussuaq, is characterized by subglacial drainage systems consisting on meltwater-filled cavities on a hard bed (Harper et al., 2017), which may become interconnected following episodes of increased discharge. Episodes of connectivity following high pressure subglacial meltwater events may lead to enhanced sliding followed by channelization, and emplacement of subglacial floods (Harper et al., 2017).

We present preliminary field and remote sensing observations describing the morphology, topology, organization, and other field characteristics of recently exposed elements of the glacial hydrology system, which were emplaced by the western margin of the GIS. Our field site is located by the Europlanet Transnational Access TA1 Facility 4: Greenland-Kangerlussaq, which offers a unique opportunity to study the subglacial drainage patterns in this region (Carrivick et al., 2016). Few regions in the world offer the opportunity to study recently emplaced, well exposed subglacial morphologies at the level of accessibility of this site. Field data includes in situ-imagery, observations of glacial sliding directions, description of sedimentary deposits, morphology, scale and characteristics of subglacial cavities, and nature of the connection passages. Data acquired in the field is complimented with remote sensing data from the ArcticDEM and Maxar imagery.

We conclude with a discussion of the implications of our observations for the geometry and volumetric capabilities of currently active subglacial hydrology pathways under the western portion of the GIS, including addressing the possible modes of meltwater drainage from the observed morphologies and subglacial geological reconstructions (e.g., White et al., 2016), as well as a comparison of the morphology and geometry of observed interconnected subglacial cavities to morphologically and topologically similar systems located at the east of Hellas Basin on Mars. 

How to cite: Grau Galofre, A. and Noblet, A.: Field observations of interlinked subglacial cavities in Kangerlussuaq - Greenland ice sheet western margin., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10169, https://doi.org/10.5194/egusphere-egu24-10169, 2024.

EGU24-11008 | ECS | Posters on site | GM10.4

Application of a new statistically rigorous comparison tool of observed and modelled flow directions of the last British-Irish ice sheet over time 

Rosie Archer, Jeremy Ely, Timothy Heaton, Frances Butcher, Anna Hughes, and Chris Clark

Past ice flow direction can be inferred through mapping of subglacial lineations (e.g. drumlins and mega-scale glacial lineations). A numerical ice sheet model can also be used to reconstruct possible ice flow directions according to ice physics. These two methods are rarely integrated to see if the model can explain the observational data. Previous model-data comparison workflows made a large step forward. However, they lack statistical rigour and certain capabilities, such as comparing an ensemble of model simulations. To overcome these challenges, we created the Likelihood of Accordant Lineations Analysis (LALA) tool.  LALA is a tool to compare numerical model ice sheet simulations to observational data of past flow direction. LALA was created to take a step forward in improving model-data comparisons; making comparisons statistically rigorous and adding the ability to directly grade multiple simulations against each other, a feature that was missing from previous tools. For this poster, we show an example of the tool in action and use LALA to compare model simulations of the British-Irish ice sheet and observations of flow direction from subglacial lineations taken from the BRITICE-CHRONO project. We present the best and the worst fitting simulations according to LALA. We also dissect the score produced to give an indication of the flow directions which are most (and least) regularly matched by the numerical modelling. These results highlight opportunities for model development and the potential to reevaluate observations.

How to cite: Archer, R., Ely, J., Heaton, T., Butcher, F., Hughes, A., and Clark, C.: Application of a new statistically rigorous comparison tool of observed and modelled flow directions of the last British-Irish ice sheet over time, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11008, https://doi.org/10.5194/egusphere-egu24-11008, 2024.

EGU24-11208 | Orals | GM10.4

Tracking sediment transport through the Miage Glacier, Italy, combining a Lagrangian approach with luminescence burial dating of englacial clasts 

Audrey Margirier, Ann Rowan, Julien Brondex, Georgina E. King, Christoph Schmidt, David L. Egholm, Vivi K. Pedersen, C. Scott Watson, Remy Veness, Leif Anderson, and Benjamin Lehmann

 

Constraining the pathways and time scales of englacial sediment transport is of primary importance for both understanding the processes that move sediment through glacierised catchments and quantifying the response of mountain glaciers to climate change. However, sediment transport through glaciers is a more complex process than ice flow and difficult to observe; clasts can be transported englacially and at the ice margins, but also deposited into moraines before being re-entrained into englacial transport.

We developed a novel method taking a Lagrangian approach that combines luminescence rock surface burial dating of the time for englacial transport of individual rock debris with ice-dynamical glacier evolution modelling of glacial sediment transport to quantify rates of sediment transport through the Miage Glacier catchment in the Italian Alps. Luminescence rock surface burial dating allows determining the burial duration of rocks after they have been exposed to sunlight, but this method has not previously been applied to englacial clasts.

We obtained luminescence ages for seven samples embedded in the ice in the ablation zone of Miage Glacier, with burial ages ranging from 0.2 ± 0.1 ka to 5.0 ± 1.4 ka. Samples collected in the upper part of the ablation zone yield younger ages than samples collected near the terminus. The younger luminescence ages (0.2 ± 0.1 ka and 0.3 ± 0.1 ka) are consistent with expected burial duration based on the present-day glacier velocity. In contrast, older luminescence ages obtained for samples located in the lower part of the ablation zone (1.2 ± 0.1 ka to 5.0 ± 1.4 ka) show that these samples record a longer and more complex burial history, suggesting that these samples were either stored in the headwall area or within moraines for several thousand years before being entrained in the ice. In the Miage catchment, debris could have been stored in a moraine at the junction between the Bionnassay Glacier and the Dome Glacier before being entrained in the Miage glacier. We compare the burial ages of the englacial clasts with simulations of glacial sediment transport using a Lagrangian particle tracking scheme in the glacier model iSOSIA. The model results illustrate the range of englacial and subglacial sediment flow paths through the Miage Glacier and simulate similar durations of englacial transport to those obtained for our luminescence samples.

How to cite: Margirier, A., Rowan, A., Brondex, J., King, G. E., Schmidt, C., Egholm, D. L., Pedersen, V. K., Watson, C. S., Veness, R., Anderson, L., and Lehmann, B.: Tracking sediment transport through the Miage Glacier, Italy, combining a Lagrangian approach with luminescence burial dating of englacial clasts, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11208, https://doi.org/10.5194/egusphere-egu24-11208, 2024.

EGU24-11358 | ECS | Orals | GM10.4

Quantitative CT scan analysis: an innovative tool for interpreting ice-contact sediments from overdeepened basins of the northern Alpine foreland 

Bennet Schuster, Sebastian Schaller, Lukas Gegg, Marius W. Buechi, Flavio S. Anselmetti, and Frank Preusser

Overdeepened basins are shaped and filled by the interplay of erosion and deposition during one or more glacial-interglacial cycles. Understanding and correlating the sedimentary infill of overdeepened systems is a key to understanding glacial dynamics in terms of the timing, extent, and character of Quaternary glaciations. Therefore, numerous overdeepened structures in the northern Alpine foreland have been explored by research drilling in recent years, resulting in a large collection of sediment cores of excellent quality, providing a unique opportunity to gain insight into these structures. Exploration of these basins shows that a depositional sequence in the sedimentary record of a glacial overdeepening typically begins with the subglacial deposition of coarse-grained units (diamicts and gravels), reflecting complex ice-bed-interactions during the transition from erosion to deposition. The identification and interpretation of these potential ice-contact sediments is crucial for understanding the glacial sedimentary sequences.

In this study, we use X-ray computed tomography (CT) scanning to identify and quantify sedimentological features and systematically characterise a wide range of potential ice-contact sediments from different levels within the sedimentary record of several overdeepened basins in the northern Alpine foreland. CT scanning provides a powerful tool for the detailed analysis of sedimentary drill cores, particularly in these glacial sediments, where such examinations have never been carried out on a large scale. This study aims to establish a CT analysis workflow and a database of characteristics of ice-contact sediments. This will contribute to the controversial discussion of the relevant processes that form ice-contact sediments and improve our ability to identify ice-contact sediments and their genesis in overdeepened basins.

How to cite: Schuster, B., Schaller, S., Gegg, L., Buechi, M. W., Anselmetti, F. S., and Preusser, F.: Quantitative CT scan analysis: an innovative tool for interpreting ice-contact sediments from overdeepened basins of the northern Alpine foreland, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11358, https://doi.org/10.5194/egusphere-egu24-11358, 2024.

EGU24-11858 | ECS | Posters on site | GM10.4

Geomorphological Analysis of Cirques in the Western Islands of Greenland 

Rachel Oien and Bartosz Kurjanski

This study employs Arctic DEM data and GIS tools, ACME 2.0 (Li et al., 2024), and GlaRe (Pellietero et al., 2016), to systematically investigate cirques in the western islands off central Greenland. The primary objective is to reconstruct past Equilibrium Line Altitude (ELA) variations at the end of the Younger Dryas period and derive insights into palaeoclimate conditions in this region.

By leveraging high-resolution Arctic DEM datasets and advanced GIS methodologies, we analyse cirque morphologies and elevations to reconstruct ELAs, a key indicator of glacial development and climate conditions. The Younger Dryas, a well-documented, abrupt and relatively short climatic event, represents a critical period for understanding past climate dynamics and their impact on glacial landscapes on a timescale relevant to the contemporary human population.

Our approach combines the semi-automated extraction of cirque parameters from the Arctic DEM with GIS-based modelling to reconstruct palaeo-ELA variations. Through spatial and temporal analysis, we aim to discern patterns of glacial response to climatic shifts between 13-9.5ka (Leger et al., 2024), shedding light on the sensitivity of Arctic cirques to rapid environmental changes.

Preliminary results indicate distinct patterns in cirque morphology and ELAs consistent with variations in the ELA during the Younger Dryas. These findings contribute to a more comprehensive understanding of the regional impact of past climatic events on the Greenlandic glacial landscape. This research enhances our knowledge of the Younger Dryas climate dynamics in the western islands off Greenland, providing valuable insights into the region's palaeoclimate history and contributing to broader discussions on Arctic environmental change.

How to cite: Oien, R. and Kurjanski, B.: Geomorphological Analysis of Cirques in the Western Islands of Greenland, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11858, https://doi.org/10.5194/egusphere-egu24-11858, 2024.

EGU24-11985 | ECS | Posters on site | GM10.4 | Highlight

Luminescence rock surface dating of englacial transported debris from Mer de Glace glacier, French Alps 

Léa Rodari, Audrey Margirier, Georgina King, Ann Rowan, Christoph Schmidt, and Guillaume Jouvet

Significant mass loss and increased rock debris cover have been observed across many mountain glaciers due to climate change. However, the dynamics of sediment transport through alpine glaciers are not fully understood and should be investigated to better constrain the future evolution of mountain glaciers under a changing climate. Englacial sediment transport is difficult to observe and to that end, we quantify the englacial transport time of debris within a glacier using a novel method combining luminescence rock surface burial dating and ice-flow modelling. Our study focuses on Mer de Glace, Mont Blanc Massif, French Alps, where supraglacial debris has expanded over the past 20 years.

We collected near-surface rock debris (4–22 cm in diameter) of granite from the ablation area of Mer de Glace that we expect to have experienced different englacial transport durations. Under subdued red light, we cored the samples perpendicular to their surfaces and sliced the cores into ~1 mm discs for luminescence dating. We first evaluated whether the luminescence signals had been well bleached prior to deposition by measuring the evolution of luminescence signals with depth throughout the core (i.e. measurement of the bleaching plateau). We used a protocol comprising infra-red stimulation at 50 °C and 225 °C, followed by blue stimulation at 125 °C to explore the signals of different minerals with different luminescence properties. Of the 29 samples investigated, 20 were well bleached, exhibiting a clear plateau in luminescence signals with depth (following the approach of Rades et al., 2018). We are currently using a single-aliquot regenerative dose protocol to date the rock surfaces of these samples to obtain englacial transport durations. In the next step, we will contrast the englacial transport durations measured using luminescence with those predicted using the ice-flow model IGM (Jouvet et al., 2022), allowing us to better understand the dynamics of mountain glaciers over centennial to millennial time scales.

 

References

Jouvet, G., Cordonnier, G., Kim, B., Lüthi, M., Vieli, A., & Aschwanden, A. (2022). Deep learning speeds up ice flow modelling by several orders of magnitude. Journal of Glaciology68(270), 651-664.

Rades, E. F., Sohbati, R., Lüthgens, C., Jain, M., & Murray, A. S. (2018). First luminescence-depth profiles from boulders from moraine deposits: Insights into glaciation chronology and transport dynamics in Malta valley, Austria. Radiation Measurements120, 281-289.

How to cite: Rodari, L., Margirier, A., King, G., Rowan, A., Schmidt, C., and Jouvet, G.: Luminescence rock surface dating of englacial transported debris from Mer de Glace glacier, French Alps, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11985, https://doi.org/10.5194/egusphere-egu24-11985, 2024.

EGU24-12152 | ECS | Orals | GM10.4

Geomorphic evidence for along-margin ice flow from Melville Bugt slope, west Greenland 

Shannon Klotsko, Rob Hatfield, Brendan Reilly, Alan Mix, Anne Jennings, Erin Gregory, Joe Stoner, Maureen Walczak, Jonas Donnenfield, Cara Fritz, Alice Hough, Robert Kelleher, Lindsay Monito, Paloma Olarte, Megan Siragusa, Katherine Stelling, and Tobias Vonahme

In summer 2023, the Baffin Bay Deglacial Experiment (BADEX) completed a 33-day cruise focused on the west Greenland margin; the overarching goal of this project is to investigate the evolving ocean and ice conditions along the west Greenland ice sheet from the last glacial maximum through the deglaciation. The cruise collected seafloor and sub-seafloor data, as well as water and plankton samples, with the aim of establishing 1) the timing and extent of warm Atlantic water incursion along the north-western Greenland margin; 2) the phasing of the initial ice margin retreat relative to oceanic and atmospheric changes; 3) the role of local or regional ice shelves in buttressing trough-bound outlet glaciers; and 4) the influence of regional geology, geomorphology, and ice dynamics on ice-margin retreat. Here, we present results from the ~600 km of new multibeam sonar data collected on the slope just north of the Melville Bugt trough mouth fan (TMF). The margin in this area curves landward, forming a crescent-shaped, submarine amphitheater that contains a range of bathymetric features, which vary in form with water depth and their proximity to the TMF. This includes a series of contour-following ridges that occur in depths from ~1000 to ~450 meters below modern water level. These ridges are more prominent farther away from the TMF but are more numerous closer to the trough. They are interpreted to be of glaciogenic origin, potentially formed by an ice shelf, fed by the trough, that flowed to the north and grounded on the slope. These ridges and other bathymetric features, extending up to 2000 meters water depth will be discussed. These results add to our understanding of the ice margin configuration in northern Baffin Bay during and after the last glacial period.  

How to cite: Klotsko, S., Hatfield, R., Reilly, B., Mix, A., Jennings, A., Gregory, E., Stoner, J., Walczak, M., Donnenfield, J., Fritz, C., Hough, A., Kelleher, R., Monito, L., Olarte, P., Siragusa, M., Stelling, K., and Vonahme, T.: Geomorphic evidence for along-margin ice flow from Melville Bugt slope, west Greenland, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12152, https://doi.org/10.5194/egusphere-egu24-12152, 2024.

EGU24-12758 | Posters on site | GM10.4

New surface exposure age data using cosmogenic radionuclides 10Be and 14C to constrain the age of the last deglaciation in the Retezat Mts, Southern Carpathians, Romania 

Zsófia Ruszkiczay-Rüdiger, Zoltán Kern, Balázs Madarász, Petru Urdea, Régis Braucher, Mihály Molnár, Botond Búró, and Aster Team

The presence of cosmogenic radionuclide concentrations inherited from previous exposure(s) of glacially transported boulders and moulded bedrock surfaces may hinder the determination of the surface exposure age (SED) of the last phase of (de)glaciation.

A previous study revealed that glacial landforms of the cirque area in the southern side of the Retezat Mountains (Southern Carpathians, Romania) hold significant amount inherited 10Be (t1/2=1.4 My), which was used for a tentative estimation of the amount of glacial erosion, assuming that the lowest 10Be concentration was representative of the true age of deglaciation (Ruszkiczay-Rüdiger et al., 2021, Geomorphology 384, 107719).

In this study, a western valley, the Zlătuia-Dobrunu valley of the Retezat Mts was sampled for 10Be SED. The novel data are in agreement with the previous datasets suggesting that the most extended glaciers belonged to the Last Glacial Maximum. However, the old apparent exposure durations based on 10Be analysis of samples from the cirque area provided firm evidence for the presence of excessive abundances of cosmogenic 10Be in this valley as well.

The use of the short-lived in situ produced 14C (t1/2= 5.7 ky) provides an independent age constraint for the timing of the last deglaciation, because all 14C inventories that might be inherited from a previous exposure would have already been decayed. As a consequence, the 14C concentrations are not biased by inheritance, thus i) enable the age determination of the landforms belonging to the last phases of deglaciation and ii) the 14C exposure ages compared to the 10Be data will allow an assessment of the inherited amount of 10Be and thus a more precise determination of the amount of glacial erosion.

In this study the new 10Be and 14C SED ages will be presented together with the mapped glacial landforms, reconstructed paleoglaciers and their Equilibrium Line Altitudes.

Funding: NKFIH FK124807, INSU/CNRS, ANR - “EQUIPEX Investissement d’Avenir”, IRD and CEA, the PNRR-III-C9-2022 - I8, no. 760055/23.05.2023, CF 253/29.11.2022. and Horizon 2020 grant 871149 ”EUROPLANET”.

How to cite: Ruszkiczay-Rüdiger, Z., Kern, Z., Madarász, B., Urdea, P., Braucher, R., Molnár, M., Búró, B., and Team, A.: New surface exposure age data using cosmogenic radionuclides 10Be and 14C to constrain the age of the last deglaciation in the Retezat Mts, Southern Carpathians, Romania, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12758, https://doi.org/10.5194/egusphere-egu24-12758, 2024.

EGU24-13494 | ECS | Orals | GM10.4

First evidence and dating of Glacial Lake Yukon using paleomagnetic dating and cosmogenic nuclides 

Raphael Gromig, Brent Ward, Jeff Bond, Rene Barendregt, and Tibor Dunai

Yukon Territory has been repeatedly affected by the northern Cordilleran Ice Sheet during the last 2.6 million years, which has significantly affected the landscape. Yukon is unique in Canada in that it has three broad mappable chrono-geomorphic regions representing regionally coherent advances of the northern Cordilleran Ice Sheet and, unlike all other parts of Canada, a large unglaciated area. The oldest surface is a composite of several glaciations that are so old individual limits cannot be resolved. The oldest of these glaciations has occurred 2.6 million years ago and is believed to be responsible for shifting the route of the Yukon River.

Geological evidence suggests that the Yukon River, which now flows in northern/western direction into the Bering Sea, was initially flowing south into southwest Yukon and west into the Tanana River basin. Reversal of the Yukon River is believed to be a consequence of the onset of Northern Cordillera glaciations at the beginning of the Quaternary period. Glaciation of the St. Elias Mountains blocked the passage of the paleo-Yukon River and formed a glacially dammed lake. This lake covered an extensive area in central Yukon and then catastrophically drained after overtopping a threshold north of Dawson City. This formed the present route of the Yukon River flowing to the Bering Sea. The presence and timing of the formation of Glacial Lake Yukon has been subject of debate for several decades. However, this hypothesis was widely accepted despite the absence of physical evidence for the glacial lake.

The first physical evidence of Glacial Lake Yukon was discovered in 2022 when a succession of lake sediments was exposed in a placer mining operation in the Bonanza Creek Valley (tributary of the Klondike River) at the Lovett Hill site. The sampled section comprises more than 8 m of clays, silts and sands. This section is underlain by the Pliocene ‘White Channel gravel’, and the Quaternary Klondike outwash, with the latter representing first evidence of Quaternary glaciation in the Yukon. The lake sediment succession is overtopped by an erosive gravel unit, which likely marks the drainage of the lake.

In order to refine the regional glacial stratigraphy, we utilize a multidisciplinary approach to provide chronological control on the formation of Glacial Lake Yukon. This allows us to test the hypothesis that the reversal of the Yukon River and the formation of Glacial Lake Yukon are associated with the first large Cordilleran Ice Sheet. We combine paleomagnetic measurements and cosmogenic 26Al–10Be isochron dating. In addition, we test the utility of cosmogenic krypton on zircon grains in this setting. Initial paleomagnetic data indicate the lake sequence is reversely magnetized; this combined with a previous burial age of ca. 2.6 Ma for the initiation of Klondike outwash deposition, suggests deposition of the lake sediments during the Matuyama Chron (0.78 to 2.6 Ma). Cosmogenic nuclide data will further refine this age.

How to cite: Gromig, R., Ward, B., Bond, J., Barendregt, R., and Dunai, T.: First evidence and dating of Glacial Lake Yukon using paleomagnetic dating and cosmogenic nuclides, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13494, https://doi.org/10.5194/egusphere-egu24-13494, 2024.

EGU24-13860 | Posters on site | GM10.4

Late Quaternary glacier-climate reconstruction in the Ahuriri River valley, Southern Alps of New Zealand 

Levan Tielidze, Shaun Eaves, Kevin Norton, Andrew Mackintosh, and Alan Hidy

I present the first dataset of Late Quaternary glacial maximum extent and deglaciation along with quantitative paleoclimate reconstructions from the Ahuriri River valley, Southern Alps, New Zealand. The new constraints based on geomorphological mapping and sixty-six cosmogenic 10Be surface exposure ages offer the opportunity to test hypotheses about the climate system, to better understand the processes that drove ice retreat and readvance during the Last Glacial Maximum and the subsequent glacial termination.

Reconstructions of past glacier geometries indicate that the local ELA was depressed by ~880 m and climate was 5±1 °C colder than present (1981–2010) at 19.8±0.3 ka, while ELA was depressed by ~770 m and climate was 4.4±0.9 °C colder at 16.7±0.3 ka. Subsequent estimations suggest ELA elevations at 14.5±0.3 ka, 13.6±0.3 ka, and 12.6±0.2 ka were ≤700 m, ≤630 m, and ~360 m lower than today. This equates to air temperatures of ≤3.9 °C, ≤3.5 °C, and 2.3±0.7 °C colder than today, assuming no changes in past precipitation.

The small amount of warming estimated in this study between 19.8±0.3 and 16.7±0.3 ka differs somewhat from glacial reconstructions in other major valleys in the Southern Alps, specifically from Rakaia River valley. Robust constraints of glacier changes in the Ahuriri valley between 14.5±0.3 and 12.6±0.2 ka confirm that an early glacier readvance occurred in New Zealand at this time, which has been previously recognised with only limited evidence. The reconstructed ELA suggests that the coldest part of the Late Glacial reversal occurred at 14.5±0.3 ka. 

How to cite: Tielidze, L., Eaves, S., Norton, K., Mackintosh, A., and Hidy, A.: Late Quaternary glacier-climate reconstruction in the Ahuriri River valley, Southern Alps of New Zealand, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13860, https://doi.org/10.5194/egusphere-egu24-13860, 2024.

EGU24-14426 | Orals | GM10.4 | Highlight

Reconstructing the deglacial dynamics of the northwestern Laurentide Ice Sheet  

Martin Margold, Benjamin J. Stoker, Helen E. Dulfer, Chris R. Stokes, Victoria H. Brown, Christopher D. Clark, Colm Ó Cofaigh, David J.A. Evans, Duane Froese, and Sophie L. Norris

The northwestern sector of the Laurentide Ice Sheet drained ice from the Cordilleran-Laurentide ice saddle and the Keewatin ice dome towards the ice margin on the arctic continental shelf during its late local Last Glacial Maximum. The glacial geomorphological and geological record of the region documents several massive palaeo-ice streams. However, the deglacial dynamics of this sector has not yet been reconstructed in detail and questions remain about the nature of deglaciation in this region: Did ice streams operate far up-ice or were they limited to a rather narrow ice-margin zone? Was ice stagnation widespread?

We reconstruct the deglaciation of the northwestern sector of the Laurentide Ice Sheet by glacial geomorphological inversion methods, based on our recent regional-scale mapping of the glacial geomorphological record. We find that the ice stream network evolved from large, marine-terminating ice streams to shorter, terrestrial ice streams. The ice drainage network experienced a reorganisation following the disappearance of the Cordilleran-Laurentide ice saddle, which previously feed ice in a northerly direction along the modern-day Mackenzie River, to more westerly ice flow sourced from the Keewatin ice dome. Deglaciation was dominated by dynamic ice retreat but we also find traces of localized ice stagnation in areas of higher ground fringing the major fast ice flow corridors. The ice flow pattern changed markedly once the ice front stepped back onto the Canadian Shield, where ice streaming largely ceased. This empirical reconstruction, fitted to the latest version of ice margin chronology, can serve as validation for numerical modelling efforts and provides information on broad-scale ice sheet dynamics during the last deglaciation. 

How to cite: Margold, M., Stoker, B. J., Dulfer, H. E., Stokes, C. R., Brown, V. H., Clark, C. D., Ó Cofaigh, C., Evans, D. J. A., Froese, D., and Norris, S. L.: Reconstructing the deglacial dynamics of the northwestern Laurentide Ice Sheet , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14426, https://doi.org/10.5194/egusphere-egu24-14426, 2024.

EGU24-15483 | Posters on site | GM10.4

The valley glacier network of the Valsugana (south-eastern Alps) during the LGM: Chronology and Equilibrium Line Altitudes  

Giovanni Monegato, Lukas Rettig, Sandro Rossato, Sarah Kamleitner, Susan Ivy-Ochs, Alessia Modesti, Francesco Gosio, Mirko Demozzi, Matteo Rinaldo, Enrico Marcato, Tommaso Trentini, Silvana Martin, and Paolo Mozzi

During the Last Glacial Maximum the Valsugana sector in the south-eastern European Alps was characterized by an extensive glacier network that included the large valley glacier belonging to the Adige glacier, through the transfluence in the Fersina area, and major tributaries from the Calamento and Cavè valleys. The glacier surface reached up to 1400 m a.s.l. in the western sector of the study area with a downstream gentle slope to the east. At Borgo Valsugana, the trunk glacier merged with several tributaries and flowed also towards the Tesino plateau to the east, where it merged with the tributary valley glacier. In the Tesino area, the glaciers flowed mainly to the south towards the major trunk glacier. This flowed downstream until Primolano, where the narrow reach of Canal del Brenta dammed its flow. The gorge promoted the bulging of the glacier front and its split into two lobes: the first to the south formed the lateral moraines of Enego and Col del Gallo ending with a seracs cascade; the second lobe to the east merged with the Cismon-Piave glacier. This latter was a major ice-field originated in the central Dolomites and reached its western frontal position above the Corlo gorge (Rossato et al., 2018).

 In this articulate network several nunataks remained ice-free; here, lateral moraines with erratic boulders mark the elevation of the trimline. At Mt. Lefre, three boulders were dated to the LGM with exposure dating method (10Be). These are the first exposure ages for an LGM glacier in the south-eastern Alps and can be compared to radiocarbon chronologies from other glaciated valleys

In the study area also independent glaciers (Mt. Agaro, Mt. Coppolo, Mt. Cavallara) developed. In the Prealps the large Altopiano dei Sette Comuni plateau glacier had a calculated Equilibrium Line Altitude (ELA) of 1680 m a.s.l. (Rettig et al., 2023), while the Monte Grappa ice cap had a calculated ELA of 1450 m a.s.l. (Baratto et al., 2003; Rettig et al., 2023). The ELA estimates allow insights into the climatic conditions under which the LGM glaciers in the Valsugana evolved.

 

References

Baratto A., Ferrarese F., Meneghel M., Sauro U. 2003. La ricostruzione della glaciazione Wurmiana nel Gruppo del Monte Grappa (Prealpi Venete). In: Biancotti, A., Motta, M. (Eds.), Risposta dei processi geomorfologici alle variazioni ambientali. Brigati G., Genova, pp. 67–77.

Rettig L., Monegato G., Spagnolo M., Hajdas I., Mozzi P. 2023. The Equilibrium Line Altitude of isolated glaciers during the Last Glacial Maximum – New insights from the geomorphological record of the Monte Cavallo Group (south-eastern European Alps). CATENA, 107187.

Rossato S., Carraro A., Monegato G., Mozzi P., Tateo F. 2018. Glacial dynamics in pre-Alpine narrow valleys during the Last Glacial Maximum inferred by lowland fluvial records (northeast Italy). Earth Surface Dynamics, 6, 809-828.

How to cite: Monegato, G., Rettig, L., Rossato, S., Kamleitner, S., Ivy-Ochs, S., Modesti, A., Gosio, F., Demozzi, M., Rinaldo, M., Marcato, E., Trentini, T., Martin, S., and Mozzi, P.: The valley glacier network of the Valsugana (south-eastern Alps) during the LGM: Chronology and Equilibrium Line Altitudes , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15483, https://doi.org/10.5194/egusphere-egu24-15483, 2024.

EGU24-15554 | ECS | Orals | GM10.4

Early Pleistocene onset of glacial incision in the Baltic Basin revealed by 10Be-26Al burial dating of the Hattem Beds 

Kaleb Wagner, Lotta Ylä-Mella, Martin Margold, Mads Faurschou Knudsen, Freek Busschers, Marcel Bakker, Birte Lindahl Eriksen, Jesper Olsen, Jane Lund Andersen, and John Jansen

In Northwest Europe, the earliest presence of the Fennoscandian Ice Sheet (FIS) is registered in the Dutch-German border region, where fluvio-deltaic sediments of the ancient Eridanos river system contain weathered Nordic erratics within the so-called “Hattem Beds” (Upper Pieze Fm. [f.k.a. Lower member of the Enschede Fm.]). The Eridanos operated from the Early Miocene, integrating drainage across the east Fennoscandian Shield and Baltic Platform, until its headwaters were overridden by the FIS for the first time. The Hattem Beds, conventionally attributed to the Dutch Menapian Stage (~MIS 34; 1.1 Ma), mark the onset of glacial erosion within the Baltic Basin and termination of the Eridanos system.

Here we provide new sediment burial ages for this key stratum by exploiting the cosmogenic 10Be-26Al pair in quartz. We measure nuclide concentrations in archived drill-core samples obtained from the type locality at the Wapenveld quarry near Molenweg (NL), including those of the overlying Urk and underlying Lower Pieze Fms. (f.k.a. Harderwijk Fm).

Results with our Particle Pathway Inversion of Nuclide Inventories (P-PINI) burial dating model suggest a significantly older age for the Upper Pieze Fm. than has been previously inferred, underscoring glacial incision of the Baltic Basin and collapse of the Eridanos river system beginning in the Early Pleistocene (~2 Ma). This initial advance of the FIS into the Baltic Basin tracks the overall intensification of Northern Hemisphere glaciation indicated by marine records and alludes to the expansion of European ice masses prior to the Middle Pleistocene Transition (MPT; ~1.2–0.8 Ma). These findings add to a growing sense of mismatch between large empirically-derived pre-MPT ice sheet extents and low coeval glacial-interglacial ice volumes implicit in the global δ18O record.

How to cite: Wagner, K., Ylä-Mella, L., Margold, M., Faurschou Knudsen, M., Busschers, F., Bakker, M., Lindahl Eriksen, B., Olsen, J., Lund Andersen, J., and Jansen, J.: Early Pleistocene onset of glacial incision in the Baltic Basin revealed by 10Be-26Al burial dating of the Hattem Beds, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15554, https://doi.org/10.5194/egusphere-egu24-15554, 2024.

EGU24-16431 | Orals | GM10.4

New data from Făgăraș and Retezat Massifs set the timeframe of the last glacial activity in Southern Carpathins during Younger Dryas and Early Holocene 

Daniela Pascal, Alfred Vespremeanu-Stroe, Regis Braucher, Razvan Popescu, Mihaela Enachescu, Alexandru Berbecariu, and Adrian Vasile

Past glaciations extent and chronology in the Romanian Carpathians have been disputed along most of the 20th century. Despite the recent studies presenting numerical age datings of the glacial deposits and erosion surfaces, the view on the latest glacial activity remained in debate due to results from Retezat Massif (one of the high and best studied massifs from Southern Carpathians), where authors found no evidences of Younger Dryas glaciers. In this context, we bring in the discussion new data from Retezat but even more from the Făgăraș Massif, which is the highest and largest massif from Southern Carpathians but less studied in relation to the Pleistocene glaciations with only a handful of numerical ages obtained so far. The new 10Be exposure ages collected from the highest morraines, fit the Younger Dryas - Early Holocene interval, in good agreement with European records, suggesting the glaciers reformation and advance during the Younger Dryas. It appears that some of the Younger Dryas glaciers survived in the first two millenia of the Early Holocene or reformed during Pre-Boreal Oscillation when cool and humid conditions have been present over Europe. Finally, we modeled the presence of Younger Dryas glaciers for the whole Făgăraș massif using the topographic and microclimatic characteristics of the glacial cirques which hosted new glaciers (proven by numerical ages) and found that ca 90 glaciers restricted to cirques formed during Younger Dryas in the Făgăraș massif. Samples were chemically processed at LN2C at CEREGE, France and at RoAMS Laboratory - IFIN HH, Romania. Targets of purified BeO were prepared for AMS measurements and measured at ASTER, the French National AMS Facility (CEREGE, Aix en Provence).

How to cite: Pascal, D., Vespremeanu-Stroe, A., Braucher, R., Popescu, R., Enachescu, M., Berbecariu, A., and Vasile, A.: New data from Făgăraș and Retezat Massifs set the timeframe of the last glacial activity in Southern Carpathins during Younger Dryas and Early Holocene, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16431, https://doi.org/10.5194/egusphere-egu24-16431, 2024.

EGU24-16440 | ECS | Posters on site | GM10.4 | Highlight

Deglaciation pattern of the last Scandinavian Ice Sheet across Fennoscandia 

Benjamin Boyes, Helen Dulfer, Nico Dewald, Frances Butcher, Chris Clark, Jeremy Ely, and Anna Hughes

Palaeo-ice sheets leave behind a landform record that we can decipher to understand glaciological processes and the responses of ice sheets to warming climates. Reconstructions of past ice sheet behaviour can inform numerical ice sheet models and are important for understanding ongoing glacio-isostatic uplift. The Scandinavian Ice Sheet, which was the largest component of the Eurasian Ice Sheet Complex during the last glaciation, glaciated Fennoscandia and northern Europe. Since the 19th Century, there has been considerable research into the deglaciation pattern of Scandinavian Ice Sheet during the last Glacial-Interglacial Transition. However, many reconstructions of retreat have been conducted at local-regional scales, which can be difficult to reconcile across ice sheet-scales, and ice-sheet scale reconstructions based on consistent approaches to mapping and data sources are rare. These inconsistencies lead to difficulties in creating ice-sheet wide reconstructions of deglaciation.

Using the glacial inversion approach, we combine our independently mapped ice marginal landforms, subglacial meltwater routes, and subglacial bedforms to produce a consistent ice sheet-scale assessment of deglaciation patterns across Norway, Sweden, and Finland. Here we present our latest version of the deglaciation pattern for the last Scandinavian Ice Sheet. This reconstruction has many similarities to previous efforts but adds significant detail. For example, in addition to overall retreat patterns, we capture instances of ice margin readvance. We also reconstruct a complex retreat pattern with the ice sheet breaking into small ice masses located within and adjacent to the Scandinavian Mountains.

How to cite: Boyes, B., Dulfer, H., Dewald, N., Butcher, F., Clark, C., Ely, J., and Hughes, A.: Deglaciation pattern of the last Scandinavian Ice Sheet across Fennoscandia, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16440, https://doi.org/10.5194/egusphere-egu24-16440, 2024.

EGU24-16566 | ECS | Posters on site | GM10.4

Early stage Quaternary overdeepening in Upper Swabia - Germany 

Johannes Pomper, Clare Bamford, Frank Preusser, Ulrike Wielandt-Schuster, and Lukas Gegg

Overdeepenings are glacially shaped basins, incised into the bedrock deeper than the fluvial base level by subglacial erosion. Their sedimentary fillings are important archives for understanding glacial and postglacial history and the glacial impact on environmental transformation. Investigation of overdeepened features and their sedimentary contents is essential for understanding the processes and drivers of subglacial erosion, the timing and sequence of past glaciations, and accordingly their cumulated impact on landscape and topography.

This study is centred around an already acquired high quality drill core plus a correlating outcrop on the highest summit of Upper Swabia (The Hoechsten) in the North of the Lake Constance area (southwestern Germany). We investigate an overdeepening in an exceptional stratigraphic position: The sediment succession at Hoechsten is one of only a few examples of glacial basin fills that are correlated with the Early Pleistocene, and a key profile for this otherwise merely poorly constrained period. Situated in an elevated position, it is considered a component of an old highland-ramp topography that has since been largely reshaped over the course of repeated glaciations (Ellwanger et al. 2011).

Besides sedimentological analysis we apply standard geotechnical methods to reconstruct the deglaciation and potential phases of readvancement. Geotechnical data has proven valuable for the identification of a glacial sediment component, of previous mechanical loading by ice, or of the modification of a deposit by non-glacial processes. Furthermore, we compare micromorphological structures on the basis of microscale computed tomography analysis with results of a previously conducted thin-section study (Menzies & Ellwanger 2011). In the future, these analyses will be complemented by a multi-method dating approach (integrating e.g. luminescence and paleomagnetic properties and cosmogenic nuclides).

References:
Ellwanger, D., Wielandt-Schuster, U., Franz, M., & Simon, T. (2011). The Quaternary of the southwest German Alpine Foreland (Bodensee-Oberschwaben, Baden-Wuerttemberg, southwest Germany). E&G Quaternary Science Journal, 60(2/3), 306-328, DOI 10.3285/eg.60.2-3.07
Menzies, J. & Ellwanger, D. (2011). Insights into subglacial processes inferred from the micromorphological analyses of complex diamicton stratigraphy near Illmensee-Lichtenegg, Hoechsten, Germany. Boreas, 40(2), 271-288, DOI 10.1111/j.1502-3885.2010.00194.x

How to cite: Pomper, J., Bamford, C., Preusser, F., Wielandt-Schuster, U., and Gegg, L.: Early stage Quaternary overdeepening in Upper Swabia - Germany, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16566, https://doi.org/10.5194/egusphere-egu24-16566, 2024.

EGU24-17599 | ECS | Posters on site | GM10.4

Unravelling the Patagonian Local Last Glacial Maximum and its Deglaciation History from a Modelling Perspective 

Andrés Castillo-Llarena, Franco Retamal-Ramirez, Jorge Bernales, Martin Jacques-Coper, Matthias Prange, and Irina Rogozhina

During the Marine Isotope Stages (MIS) 2-3, the Patagonian ice sheet (PIS) stretched along the southern Andes from 55°S to 38°S. Based on Glacial geomorphological and geochronological evidence, its western margin reached the Pacific Ocean, while its easternmost sectors were characterised by terrestrial lobes that fed large paleo-glacial lakes. Previous studies suggest that the maximum extension of PIS was reached towards the end of the MIS 3. However, uncertainty remains regarding the glacial and climate evolution that led to its maximum extension in asynchrony with the Northern Hemisphere ice masses and Antarctica.

We present an ensemble of transient numerical simulations of the PIS that were carried out through the MIS 3 and MIS 2, aiming to determine the range of climate conditions that match the field-derived ice sheet geometries and climate history of the Patagonian ice sheet prior the global LGM, which corresponds to the timing of the local glacial maximum and its subsequent deglaciation. Furthermore, we bracketed the spread in possible ice volumes and sea level contributions originating from uncertainties in the internal parameters and external forcings. The model ensemble is built using the ice sheet model SICOPOLIS forced by phases 3 and 4 of the Paleoclimate Modeling Intercomparison Project (PMIP). The transient simulations are based on a glacial index method by using a combination of Patagonian offshore records and Antarctic cores. Our results indicate that the regional climate conditions required to reproduce a realistic growth and demise of the PIS through the Late Quaternary are not captured by coarse-resolution global climate models, implying the need of climate models with high spatial resolution and a well-constrained ice mask, which could reproduce the necessary cooling to promote the adequate growth. Our results also suggest that the MIS3 should have witnessed colder conditions than those modeled at the LGM by global climate models to realistically simulate the evolution of the PIS in agreement with geological archives.

How to cite: Castillo-Llarena, A., Retamal-Ramirez, F., Bernales, J., Jacques-Coper, M., Prange, M., and Rogozhina, I.: Unravelling the Patagonian Local Last Glacial Maximum and its Deglaciation History from a Modelling Perspective, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17599, https://doi.org/10.5194/egusphere-egu24-17599, 2024.

EGU24-19781 | ECS | Posters on site | GM10.4

The first glaciers at Ivrea, southern Alpine Foreland  

Shantamoy Guha, Pierre Valla, Lotta Yla-Mella, Mads Faurschou Knudsen, Franco Gianotti, Giovanni Monegato, Elena Serra, Konstanze Stübner, Johannes Lachner, Georg Rugel, and John D. Jansen

Pleistocene Glaciations and their effects on Alpine topography have drawn scientific attention since well before the days of Penck and Brückner (1909), although this indomitable pair left a strong legacy to build upon. The onset of large-scale glaciations in the Alps relative to the growth of the other great Northern Hemisphere ice sheets remains a first-order question in the Quaternary sciences. Previous chronologies from the southern Alpine Foreland based on magnetostratigraphy (Muttoni et al. 2003) and from the northern Alpine Foreland based on 10Be-26Al burial dating (Knudsen et al. 2020) converge around 1.0–0.9 Ma, during the Middle Pleistocene Transition (~1.2–0.8 Ma).

Extensive moraine complexes in the southern Alpine Foreland, such as those at Ivrea, offer a valuable opportunity to determine when glaciers advanced beyond the Alpine rangefront for the first time. The Ivrea Morainic Amphitheatre comprises interbedded glacial tills at the outlet of the Aosta Valley in NW Italy (Gianotti et al. 2015). The oldest tills have been attributed by previous workers to a stage before the Matuyama-Brunhes magnetic polarity reversal (~ 0.8 Ma).

We apply 10Be-26Al burial dating to the oldest glacigenic deposits at Ivrea, utilizing the Monte Carlo-based inversion model, P-PINI (Particle-Pathway Inversion of Nuclide Inventories). Our preliminary results indicate that the first major glacial advance occurred ~ 1.3–1.1 Ma. We combine these analyses with detrital thermochronology measurements on pebbles collected from preglacial sediments at Ivrea. These pebbles indicate provenance from the Austroalpine Massifs and an absence of the External Massifs (Mont Blanc granites)-in contrast to the present-day Aosta Valley sediments, which show the cooling signature of the Mont Blanc granites. 

We reflect on the coincident timing of the exhumation of the External Massifs and the earliest large-scale Alpine glaciations at the onset of the Middle Pleistocene Transition.

How to cite: Guha, S., Valla, P., Yla-Mella, L., Knudsen, M. F., Gianotti, F., Monegato, G., Serra, E., Stübner, K., Lachner, J., Rugel, G., and Jansen, J. D.: The first glaciers at Ivrea, southern Alpine Foreland , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19781, https://doi.org/10.5194/egusphere-egu24-19781, 2024.

EGU24-20311 | Posters on site | GM10.4

Glacial cirque morphometry of Rila and Pirin Mountains (Bulgaria) 

Tamás Telbisz, Márton Krasznai, Emil Gachev, Alexander Gikov, and Zsófia Ruszkiczay-Rüdiger

Cirque valleys are typical landforms of formerly glaciated high mountains, which also play an important role in paleoclimate reconstruction. In Bulgaria, the Rila (highest peak, Musala 2925 m) and Pirin (highest peak, Vihren 2915 m) mountains were the only terrains, where significant glacial cover developed during the Pleistocene glaciations, although some minor glacial landforms also exist elsewhere in Bulgaria. During the glacial periods, valleys of the Rila and Pirin Mts were re-shaped by glacial erosion and currently are characterized by glacial cirques and U-shaped valleys reaching lengths of 22 km (in Rila) and 13.5 km (in Pirin).

In these two mountain ranges, a comprehensive, quantitative geomorphometric analysis of glacial cirques valleys has not yet been carried out, thus we try to fill this gap with the present work. Primarily, digital terrain models and GIS tools were used to delineate the cirques. Based on the delineations, the main morphometric parameters of the cirques (elevation, relative depth, width, length, area, aspect, slope conditions, etc.) were calculated and a careful statistical analysis of these parameters was performed. Both the topographic orientation and the lithological structure of the two neighbouring mountains are different, that gives us an opportunity for a comparison of topo-climatic and lithological factors of cirque development. For instance, based on elevation, size and orientation of the cirques, the possible correlations with the paleoclimate factors, like exposure or moisture transport directions can be examined. Finally, our results were compared with available cirque valley morphometric data of other high mountains rising on the Balkan Peninsula.

How to cite: Telbisz, T., Krasznai, M., Gachev, E., Gikov, A., and Ruszkiczay-Rüdiger, Z.: Glacial cirque morphometry of Rila and Pirin Mountains (Bulgaria), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20311, https://doi.org/10.5194/egusphere-egu24-20311, 2024.

  • Reconstructing the extent and timing of palaeoglaciers and their associated climate is of great importance for understanding the responses of glaciers to climate change. Glacial landforms are well-preserved in Zheduo Shan, one of the high mountain ranges on the eastern Tibetan Plateau (TP). However, few studies have constrained glacial chronologies and estimated palaeoclimate in this area. We investigated the glacial advance during the Last Glacial Maximum (LGM) in Zheduo Shan using 10Be surface exposure dating. We then reconstructed the extent and thickness of LGM glaciers based on geomorphological mapping and a flowline-based glacial modelPalaeoIce. Eleven 10Be exposure ages confirmed a major LGM glacial advance between 20.0 ± 3.2 ka and 19.3 ± 2.8 ka. The reconstructed LGM glaciers in this mountain range covered an area of 499.16 km2 with an average ice thickness of 54.4 m and a total ice volume of 52.82 km3. The regional average equilibrium-line altitude (ELA) was estimated as 4524 ± 140 m, 535 ± 140 m lower than the present value. Based on the empirical relationship between precipitation and temperature (P-T model) at the ELAs on the TP, the temperature and precipitation were estimated as 3.10–5.27 ◦C and 10–16% lower during the LGM than the present values, respectively. These results suggest that the LGM glacial advance was more sensitive to temperature than precipitation in Zheduo Shan.

How to cite: Yang, Y.: Reconstruction of palaeoglaciers and palaeoclimate in Zheduo Shan, Eastern Tibetan Plateau, during the Last Glacial Maximum, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21174, https://doi.org/10.5194/egusphere-egu24-21174, 2024.

CR5 – Instrumental and paleo-archive observations, analyses and data methodologies in the cryospheric sciences

EGU24-1383 | ECS | PICO | CR5.1

Basal debris at an Antarctic ice rise revealed by seismic amplitude-vs-angle analysis.  

Ronan Agnew, Alex Brisbourne, Adam Booth, and Roger Clark

Reconstructing past ice sheets is important for understanding the response of modern ice sheets to changes in climate. The evolution of the Weddell Sea Sector’s grounding line since the last glacial maximum (LGM) to its present position remains ambiguous; previous authors have proposed hypotheses both of monotonic grounding line retreat and of rapid grounding line retreat followed by readvance. However, distinguishing these scenarios with current observations remains difficult. To explore these scenarios, we report seismic measurements of basal properties at KIR, an ice rise in the Weddell Sea Sector, West Antarctica. A three-component seismic survey enabled detection of the compressional (P) wave reflection and the converted (PS) wave reflection (an incident P wave converted to a shear wave at the base-ice reflector) from the base of KIR. Amplitude-vs-angle (AVA) analysis aims to constrain the physical properties (namely density, seismic velocity, by measuring the variation of reflectivity with incidence angle at the reflector. By jointly inverting the AVA responses of the PP wave reflection and the PS reflection, we increase the confidence in the interpretation of the base-ice properties. 

Analysis of PP and PS AVA responses at KIR indicates that the reflection arises from a material with a P wave velocity of 4.03 ± 0.05 km/s, an S wave velocity of 2.16 ± 0.06 km/s and a density of 1.44 ± 0.06 g/cm3; these properties are consistent with a reflection from a layer of entrained basal debris, with 20-30% debris by volume. The observed properties are not indicative of interference at a thin layer, as observed beneath glaciers elsewhere. The absence of deeper subglacial reflections indicates a poorly-defined boundary between this basal debris layer and the underlying subglacial material, which we therefore propose consists of frozen sediments . If this interpretation is correct, the presence of a debris layer overlying basal frozen sediment indicates a potential retreat/readvance scenario for KIR. A possible scenario is a previous episode of flow during which KIR may have been weakly grounded as an ice rumple, followed by grounding on the lee side of the bathymetric high and subsequent freezing of subglacial sediments. However, the origin of such a homogeneous and debris-rich layer remains unclear. The indication of a reflection from a basal debris layer raises questions about whether conventionally interpreted basal reflections can truly be considered as such, and whether these interpretations may mask the true nature of the underlying subglacial material. This ambiguity may be most effectively reconciled by borehole sampling.

How to cite: Agnew, R., Brisbourne, A., Booth, A., and Clark, R.: Basal debris at an Antarctic ice rise revealed by seismic amplitude-vs-angle analysis. , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1383, https://doi.org/10.5194/egusphere-egu24-1383, 2024.

EGU24-4532 | ECS | PICO | CR5.1

Conductive textile electrodes for time-efficient ERT surveys performed in coarse-blocky mountain environments 

Mirko Pavoni, Jacopo Boaga, Alexander Bast, Matthias Lichtenegger, and Johannes Buckel

Electrical resistivity tomography (ERT) is one of the most accurate geophysical techniques to distinguish between frozen and unfrozen ground in permafrost areas. Performing the measurements, however, requires considerable logistics and time efforts. This is mainly due to the fact that optimal galvanic contact between the electrodes and the ground surface is necessary to collect reliable ERT datasets. Therefore, the traditional steel-spike electrodes must be steadily coupled between the boulders and wet with salt water on coarse blocky surfaces. To further decrease the contact resistances, sponges soaked in salt water can be inserted between the spike and the surface of rocks. Nevertheless, this traditional coupling system is particularly time-consuming, making it challenging to collect several ERT survey lines in a single workday in mountain environments. Recently developed conductive textile electrodes were applied to facilitate the deployment of ERT arrays in rock glacier environments. Instead of hammering the steel spikes, the conductive textile electrodes can be easily pushed between the boulders and wet with less water (compared to the sponges). Consequently, this new electrode approach decreases the time needed to prepare an ERT array. In this work, we evaluate the performance of the textile electrodes by comparing these with the traditional electrode approach, considering common investigation lines. This comparative test has been carried out in three test sites, which present different lithologies, surface characteristics and using different electrode spacing. The collected datasets were statistically analysed with robust regression analysis and Wilcoxon rank-sum test to examine the accuracy and significant differences between the two electrode systems regarding contact resistances, injected electrical current, measured apparent resistivities, reciprocal error, and inverted resistivity values. The obtained results demonstrate that conductive textile electrodes are suitable to collect reliable ERT datasets and, consequently, applying this approach in future ERT measurements performed in high mountain environments with coarse blocky surfaces (e.g. rockfall deposits, blocky slopes, or rock glaciers) would allow to acquire more survey lines (e.g. realisation of pseudo-3D geometries) extending the characterisation of the subsurface.

How to cite: Pavoni, M., Boaga, J., Bast, A., Lichtenegger, M., and Buckel, J.: Conductive textile electrodes for time-efficient ERT surveys performed in coarse-blocky mountain environments, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4532, https://doi.org/10.5194/egusphere-egu24-4532, 2024.

EGU24-5435 | PICO | CR5.1

Demonstrating a large UAV for Antarctic environmental science 

Tom Jordan and Carl Robinson

Airborne survey is one of the most important observational techniques in environmental science. This is especially true in polar settings where access is challenging and observational requirements, such as ice sounding radar, in situ study of turbulent atmospheric processes, cloud cover, or requirements for high resolution potential field data, limit use of satellite data. Although critical, airborne survey using traditional platforms, such as the versatile twin otter aircraft operated by the British Antarctic Survey (BAS), come with a relatively high logistical, financial, and environmental (CO2) footprint. Larger UAV’s offer an alternative, but as yet un-realised, lower impact platform to deliver the same, if not more scientific data.

Through the Innovate UK SWARM project BAS is collaborating with Windracers to trial their large (10 m wing span) Ultra UAV as a platform for environmental science. Making use of the large (700 L/max 100 kg), easily accessible payload bay and a series of interchangeable payload floors this trial will be carried out in February/March 2023. The science payloads will include: Atmospheric (turbulence probe), environmental (hyperspectral and visual cameras), cryosphere (600-900 MHz accumulation radar), and potential field geophysics (gravity/magnetic sensors). The missions, between 10 and 330 km long, will be flown beyond visual line of sight (BVLOS) of the operator using the Distributed Avionics autopilot, including take-off and landing, which will be overseen by an in-field safety pilot.

Here we present the first results of this trial, including our experience integrating BVLOS UAV operations with traditional aircraft in an Antarctic context and initial results and lessons learned from the four trailed instrument suites. Our demonstration will be an important milestone in the transition to widespread use of larger UAVs for environmental science. We will discuss how the reduced environmental and logistical impact can open up new opportunities in Antarctic and beyond.

How to cite: Jordan, T. and Robinson, C.: Demonstrating a large UAV for Antarctic environmental science, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5435, https://doi.org/10.5194/egusphere-egu24-5435, 2024.

EGU24-5751 | ECS | PICO | CR5.1

Firn Density Distribution and Annual Snow Water Equivalent Estimates from Ground Penetrating Radar 

Akash Patil, Christoph Mayer, and Matthias Braun

Abstract: Accurate estimation of glacier volume-to-mass conversion relies on a thorough understanding of firn density, both in-depth and over time. Ground-penetrating radar (GPR) serves as a suitable geophysical tool to trace internal reflection horizons (IRHs) and estimate the physical properties of different layers. Our goal is to characterize the IRHs as annual layers and ascertain the spatial firn density-depth profile in the accumulation zone of the Aletsch glacier.

The process involves identifying IRHs from radargrams and iteratively selecting the annual layers by excluding unreasonable layer structures. For an accurate estimation of firn density distribution, it is necessary to derive the velocity-depth profile of electromagnetic waves within the firn zone. The common mid-point (CMP) method was applied to track the velocity distribution within the firn body. Additionally, a method was introduced to estimate the velocity-depth profile for longer GPR profiles by backtracking the calculated velocity from the CMP gather.

To validate IRHs as annual firn layers, we utilized annual accumulation measurements at a nearby stake for Snow Water Equivalent (SWE) estimation. The resulting firn density-depth profile was compared to different firn densification models, considering regional meteorological information. This approach enables us to determine a reliable density-depth function for bulk SWE computations. The study also addresses uncertainties associated with selecting IRHs as annual layers and enhances the application of local volume-to-mass estimates.

How to cite: Patil, A., Mayer, C., and Braun, M.: Firn Density Distribution and Annual Snow Water Equivalent Estimates from Ground Penetrating Radar, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5751, https://doi.org/10.5194/egusphere-egu24-5751, 2024.

EGU24-7654 | ECS | PICO | CR5.1

Coupling Solid Earth and ice temperature models to estimate geothermal heat flow 

Judith Freienstein, Wolfgang Szwillus, Marion Leduc-Leballeur, Giovanni Macelloni, and Joerg Ebbing

Geothermal heat flow (GHF) is a key element of Solid Earth-cryosphere interactions. However, polar regions as Antarctica are only sparsely covered with heat flow determinations from boreholes, so one must rely on interpolation or regression models of GHF (e.g. machine learning) from other sources to derive a regional map. Interpolation/regression of GHF in this manner depends strongly on the available sparse boreholes, which can distort the resulting regional map.

Additional information can be gained from the SMOS (Soil Moisture and Ocean Salinity) satellite by inferring ice temperature profiles with a Bayesian inversion from remote sensing microwave radiometer data. This retrieval uses geothermal heat flow as a free parameter so that it provides a posterior distribution of the GHF needed to explain the ice temperature profiles.

We aim to reconcile geophysical geothermal heat flow models with the ice temperature profiles and improve the estimates of GHF with this coupling.

We use stationary thermal modelling where we force the ice temperature and lithospheric temperature model to converge at the base of the ice. Using stochastic inversion, we estimate the thermal parameters in the lithosphere. The posterior distribution of the retrieval as constraint for the GHF is included as prior distribution to the inversion to the stationary thermal modelling so that the GHF with the highest likelihood can be estimated.

With our approach, we can evaluate a GHF distribution that both explains the ice temperature and lithospheric temperature models and covers large parts of Antarctica.

How to cite: Freienstein, J., Szwillus, W., Leduc-Leballeur, M., Macelloni, G., and Ebbing, J.: Coupling Solid Earth and ice temperature models to estimate geothermal heat flow, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7654, https://doi.org/10.5194/egusphere-egu24-7654, 2024.

EGU24-8245 | ECS | PICO | CR5.1

Sensitivity Study for Seismic Waves Guided in an Ice Pack: Influence of the Frequency Content and Snow Layer Thickness Covering the Ice 

Hooshmand Zandi, Ludovic Moreau, Ludovic Métivier, and Romain Brossier

Studying Arctic sea ice is essential as it plays an important role in climate regulation, influencing weather
patterns, as well as impacting the local ecosystems and living conditions of people. Among different
methods for collecting data and studying sea ice, seismology has proved to be an efficient way to extract
the ice properties, from which the mechanical behavior of sea ice can be explored. Seismic data recorded on
sea ice, using 3-component geophones, are used as a starting point to derive useful information regarding
the ice. To devise an efficient inversion method for deriving ice properties, an effective tool would be
necessary to generate synthetic data in a way that encompasses the physics of sea ice. While there are
approximate solutions to wave propagation problem in a floating ice layer based on plate theory, which is
based on the assumptions of homogeneity of the ice layer and valid at low values of frequency×wavelength,
numerical counterparts such as wavenumber integration method and finite element method have been
also used to to create synthetic waveforms. The numerical methods have shown the limitations of these
approximate solutions in modeling wave propagation; nonetheless, the effects of these limitations on the
estimations of the location of icequakes and thickness of ice need to be investigated.

In this study, these limitations are explored. To do this, two possible scenarios that can happen in
practice are taken into account: (1) when there is high-frequency content in the source generating the
seismic data, and (2) when the physical model includes a snow layer overlying the ice layer. First, we
will show the limitations of the approximate solutions for these two cases by comparing the waveforms,
derived from these approximate solutions, with those of a numerical method at a given distance from
the source. The numerical used here is spectral element method. Then, the effects of these limitations
on the estimations of icequake location and ice thickness are explored in an inversion process, in which
synthetic data are created using the approximate solutions. Results indicate that when there are high-
frequency content in the data and a snow layer on top of the ice, the use of the approximate solutions
to generate synthetic data introduces bias in the estimation of ice thickness and source-receiver distance
in the inversion process. This bias is in the form of underestimations, smaller ice thicknesses and smaller
source-receiver distances. Furthermore, to tackle the biases associated with the inversion method based on
the approximate solutions, a novel strategy is adopted, where a database of simulations using the proposed
numerical method is built for various models of ice and snow. Here the inversion comprises of searching
in the database to find the best ice thickness and source-receiver distance for each icequake. In addition,
the database-based inversion reduces the computational cost. Thanks to this inversion strategy, and
using real data recorded on sea ice, the ice thicknesses along different source-receiver paths are estimated
efficiently, from which a 3D map of ice thickness is constructed.

How to cite: Zandi, H., Moreau, L., Métivier, L., and Brossier, R.: Sensitivity Study for Seismic Waves Guided in an Ice Pack: Influence of the Frequency Content and Snow Layer Thickness Covering the Ice, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8245, https://doi.org/10.5194/egusphere-egu24-8245, 2024.

EGU24-9857 | ECS | PICO | CR5.1

Broadband Spectral Induced Polarization in Permafrost Peatlands of Northern Sweden  

Madhuri Sugand and Andreas Hördt

Permafrost peatlands, located in the Arctic and high mountain regions, are typically known to be ice-rich. This is primarily linked to significant water content and often oversaturation, a characteristic property of peat soil. The current understanding of the effects of human-induced climate warming suggests that these regions are approaching a climatic tipping point with substantial permafrost thaw expected in the coming decades. Ice content is an important parameter for modelling permafrost evolution and at present limited studies exist that determine its in-situ spatial distribution in such areas.

The geophysical method known as high-frequency induced polarisation (HFIP) is advantageous for cryohydrological research in these environments. This method can capture the frequency-dependent polarisation of ice (also termed dielectric relaxation peak), which occurs within the range of 100 Hz to 100 kHz and is expressed by complex resistivity. Therefore, by analysing the spectral behaviour of this complex resistivity within the target frequency range the distribution and quantity of ice can be estimated.

The results from the latest field campaign conducted at Storflaket mire and Stordalen mire in Abisko, Sweden, are presented. Two-dimensional HFIP profiles were measured to resolve the near-surface unfrozen layer (no-ice) and the underlying frozen layer (ice-bearing). The measurements were performed in late summer when the depth of the unfrozen layer was at its maximum. Field data are inverted as independent frequencies to obtain the spectral variation of complex resistivity. No-ice and ice-bearing regions are classified by the presence of the relaxation peak. Subsequently, a two-component mixture model, with one component as ice and the second as the surrounding matrix, is applied to determine ice content distribution. Boundary constraints and starting parameters are chosen using the spectral analysis of the inverted complex resistivity. The model accuracy is evaluated using unfrozen layer probing and a permafrost core extracted along the HFIP profile. The HFIP-derived ice content distribution is consistent with unfrozen layer probing, i.e., the classification of no-ice and ice-bearing regions is successful. The model tends to underestimate ice content percentages compared to permafrost core laboratory measurements. This discrepancy can be explained since laboratory measurements are based on gravimetric water content and assumes all pore-water is frozen. However, it is known that residual pore-water is present in these soils even below 0°C. Additionally, it is observed that the model performs well when the ice content percentage is 10% or greater and its applicability might be limited in scenarios where the ice content is less than 10%.

The latest results are discussed in comparison with previous findings from Heliport, a permafrost mire also located in Abisko. In the Heliport study, HFIP successfully resolved the complex resistivity and ice content distribution on a larger scale. Building on the field knowledge gained at Heliport, this study incorporates improvements in electrode configuration setup, data acquisition speed, and minimising cable-earth coupling effects. The findings contribute to the understanding of the induced polarisation of permafrost peatlands, which is an underexplored area from a geophysical perspective.

How to cite: Sugand, M. and Hördt, A.: Broadband Spectral Induced Polarization in Permafrost Peatlands of Northern Sweden , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9857, https://doi.org/10.5194/egusphere-egu24-9857, 2024.

EGU24-10814 | ECS | PICO | CR5.1

Analysis of H/V spectral ratio curves from passive seismic data acquired on glaciers worldwide 

Julien Govoorts, Koen Van Noten, Corentin Caudron, Bergur Einarsson, Thomas Lecocq, Sylvain Nowé, Finnur Pálsson, Jonas Pätzel, and Harry Zekollari

Estimations of bedrock topography below glaciers and ice thickness are vital for quantifying freshwater availability for surrounding populations and understanding the contribution of melting glaciers to sea-level rise in the context of global warming. While active seismology is commonly used for ice thickness estimation, the utilization of passive methods remains relatively rare. Passive seismology solutions offer cost-effectiveness, non-invasiveness and continuous monitoring capabilities that present valuable benefits in glaciological research.

Over the past two decades, numerous seismic stations have been deployed on glaciers worldwide for various purposes. Through passive seismology approaches, these seismic stations could show their potential as new sources of ice thickness measurements and feed the related database. For this purpose, we analyzed data of 3-components seismic sensors from different deployments as well as data from open access databases, such as IRIS, employing the Horizontal-to-Vertical Spectral Ratio (HVSR) technique. HVSR has been predominantly used in microzonation studies to determine site effects and the thickness of sediments in sedimentary basins.  Even though the use of this technique in glacial seismology is quite new, HVSR has been already utilized to estimate in-situ ice thickness, to retrieve the basal properties or to detect cavities under the ice.

Our primary objective is to demonstrate the potential of the HVSR technique to retrieve in-situ ice thickness on different glaciers. Subsequently, we will compare the HVSR results with different data sources including models, ground-penetrating radar or active seismology. By performing this comparison we evaluate the limitations of the HVSR method in an icy environment. We investigate these limitations by studying the effect of other natural agents such as wind on the H/V amplitude and fundamental frequency retrieved from the HVSR curves. Having a global understanding of these influences will eventually help deciphering variations in continuous H/V monitoring.

How to cite: Govoorts, J., Van Noten, K., Caudron, C., Einarsson, B., Lecocq, T., Nowé, S., Pálsson, F., Pätzel, J., and Zekollari, H.: Analysis of H/V spectral ratio curves from passive seismic data acquired on glaciers worldwide, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10814, https://doi.org/10.5194/egusphere-egu24-10814, 2024.

EGU24-11300 | PICO | CR5.1

Icequakes beneath Thwaites Glacier eastern shear margin  

Emma C. Smith, Ronan Agnew, Adam D. Booth, Poul Christoffersen, Eliza J. Dawson, Lucia Gonzalez, Marianne Karplus, Daniel F. May, Nori Nakata, Andrew Pretorius, Paul Summers, Slawek Tulaczyk, Stephen Vietch, Jake Walter, and Tun Jan Young

The stability of Thwaites Glacier, the second largest marine ice stream in West Antarctica, is a major source of uncertainty in future predictions of global sea level rise. Critical to understanding the stability of Thwaites Glacier, is understanding the dynamics of the shear margins, which provide important lateral resistance that counters basal weakening associated with ice flow acceleration and forcing at the grounding line. The eastern shear margin of Thwaites Glacier is of interest as it is poorly topographically constrained, meaning it could migrate rapidly, causing further ice flow acceleration and drawing a larger volume of ice into the fast-flowing ice stream.  

In this study, we present an analysis of ~4000 icequakes, recorded over a two-year-period on a broadband seismic array deployed across the eastern shear margin of Thwaites Glacier. The array consisted of seven three-component seismometers, deployed around a central station in a circle, roughly 10 km in diameter.  We use an automated approach to detect and locate “high-frequency” seismic events (10-90 Hz), the majority of which are concentrated in clusters around the ice-bed interface on the slow-moving side of the shear margin, as opposed to within the ice-stream itself. The event waveforms exhibit clear shear-wave splitting, indicative of the presence of an anisotropic ice fabric, likely formed within the shear margin, which is consistent with published radar studies from the field site. Initial analysis of the split shear-waves suggests that they can be used to better constrain the region's ice fabric, and likely used to infer past shear margin location and assess the future stability of this ice rheology.

How to cite: Smith, E. C., Agnew, R., Booth, A. D., Christoffersen, P., Dawson, E. J., Gonzalez, L., Karplus, M., May, D. F., Nakata, N., Pretorius, A., Summers, P., Tulaczyk, S., Vietch, S., Walter, J., and Young, T. J.: Icequakes beneath Thwaites Glacier eastern shear margin , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11300, https://doi.org/10.5194/egusphere-egu24-11300, 2024.

EGU24-11386 | PICO | CR5.1

Towards a unified description of the count rate – snow water equivalent relationship in cosmic-ray neutron sensing 

Benjamin Fersch, Markéta Součková, Paul Schattan, Nora Krebs, Jannis Weimar, Carsten Jahn, Peter Martin Grosse, and Martin Schrön

The observation of near-ground cosmogenic neutrons enables the monitoring of various water storage variations at the land surface at the field scale including soil moisture and the water content of snow layers. The parabolic neutron-count versus soil moisture function is quite uniform among different locations, and soil types and requires typically a one-time-only in situ reference observation. For the detection of snowpack water equivalent (SWE) variations by cosmic-ray neutron sensing such a uniform approach has so far not been developed. Therefore, the establishment of new cosmic-ray snow monitoring sites requires substantial in situ measurements for obtaining the local relationship of SWE amounts and neutron count rates. Observations suggest that the relationship is quite uniform for grass-vegetated locations which is different to what is found for stony ground.

Within the framework of the research unit Cosmic Sense, we generated extensive in situ measurements of snow water equivalent and cosmogenic neutron count rates at various sites with differing elevations in the German and Austrian Alps. From these data, we investigate commonalities among the site conditions and if the varying patterns of the relationships can be reasonably explained by physical reasons and therefore be modeled with a unified approach.

How to cite: Fersch, B., Součková, M., Schattan, P., Krebs, N., Weimar, J., Jahn, C., Grosse, P. M., and Schrön, M.: Towards a unified description of the count rate – snow water equivalent relationship in cosmic-ray neutron sensing, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11386, https://doi.org/10.5194/egusphere-egu24-11386, 2024.

EGU24-11729 | ECS | PICO | CR5.1

A physically-based fractal model for predicting the electrical conductivity in partially saturated frozen porous media 

Haoliang Luo, Damien Jougnot, Anne Jost, Aida Mendieta, and Luong Duy Thanh

Macro-scale transport properties (e.g., electrical conductivity, effective excess charge density and hydraulic conductivity) can be conceptualized as capillary bundle models, in which the pore structure of porous medium is viewed as a bundle of capillary tubes of varying sizes. This approach can be used to understand and address the relationship between the petrophysical properties and the geometry of soil phases. When the temperature of porous medium decreases below the freezing temperature, the soil physical properties (transport properties) change drastically. This is attributed to the complexity of the heterogeneous formation of ice in the porous medium. Therefore, understanding better pore ice formation from microscale insights is crucial to describe the evolution of electrical conductivity with temperature in frozen porous medium. In this study, we consider that capillary radius and tortuous length follow fractal distributions, and that total conductance at the microscale scale is determined by the Gibbs-Thomson and Young-Laplace effects as well as by the surface complexation model. A new capillary bundle model is then proposed using an upscaling procedure, which considers the effects of both bulk and surface conductions. Based primarily on an electrical resistance apparatus and the NMR method, a series of laboratory experiments are carried out to study the influence of initial water saturation and salinity on electrical conductivity under unfrozen and frozen conditions. Additionally, the rationality and validity of the proposed model were successfully verified with published data in the literature and experimental data of this study. Our new physically-based model for electrical conductivity opens up new possibilities to interpret electrical and electromagnetic monitoring to easily infer changes in key variables such as liquid water content and moisture gradients.

How to cite: Luo, H., Jougnot, D., Jost, A., Mendieta, A., and Thanh, L. D.: A physically-based fractal model for predicting the electrical conductivity in partially saturated frozen porous media, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11729, https://doi.org/10.5194/egusphere-egu24-11729, 2024.

EGU24-12583 | PICO | CR5.1

Locating subglacial cavities and investigating basal conditions on glaciers with ambient seismic noise: toward acquisition optimization. 

Eric Larose, Noelie Bontemps, Antoine Guillemot, and Laurent Baillet

Subglacial cavities may trap a considerable quantity of liquid water, causing devastating outburst floods in densely populated mountain areas. Both active and passive geophysical methods are employed for the glacier-bedrock interface and intra-glacial characterization, including Ground Penetrating Radar (GPR), refraction seismic, borehole measurements, and surface nuclear magnetic resonance (SNMR). 

Ambient seismic noise can be collected by light and dense arrays at a relatively moderate cost, and allows to access some mechanical properties of the glacier, including the detection and localization of ice cavities and, possibly, basal detachment, taking advantage of spectral anomalies in the horizontal-to-vertical-spectral ratio (HVSR) and in the Vertical-to-Horizontal spectral ratio (VHSR). Specifically, a peak in the VHSR indicates a low impedance volume beneath the surface [1,2]. As a simple picture, we can refer to the “bridge” vibrating mode, where the vertical displacement in the middle of the bridge largely dominates other components of the movement.  Antunes et al. [2] furthermore noticed that the VHSR gives information about seismic energy anomalies generated by fluids in reservoirs since the wavefield is polarized mainly in the vertical direction.
In this work, we apply the HVSR and VHSR techniques to locate a subglacial water-filled cavity in the Tête Rousse glacier (Mont Blanc area, French Alps), using 15 days of data collected in may, 2022 [3]. The results also confirm the general basal conditions of the glacier suggested by other methods, locating temperate areas of the glacier where basal detachments are possible.

We evaluate the optimal seismic noise record duration to obtain a reliable and stable mapping of the VHSR over the glacier to properly locate the main cavity (or secondary cavities). In our case, results suggest that 6 days of record are enough to detect and locate a cavity

 

[1] Saenger, E-H. et al: A passive seismic survey over a gas field: Analysis of low-frequency anomalies, Geophysics, 74 (2), O29–O40 (2009).

[2] Antunes V. et al: Insights into the dynamics of the Nirano Mud Volcano through seismic characterization of drumbeat signals and V/H analysis. Journal of Volcanology and Geothermal Research, 431 (2022).

[3] A. Guillemot, N. Bontemps, E. Larose, D. Teodor, S. Faller, L. Baillet, S. Garambois, E. Thibert, O. Gagliardini, C. Vincent: Investigating Subglacial Water-filled Cavities by Spectral Analysis of Ambient Seismic Noise : Results on the Polythermal Tête-Rousse Glacier (Mont Blanc, France), Geophys. Res. Lett. accepted (2024). DOI:10.1029/2023GL105038

How to cite: Larose, E., Bontemps, N., Guillemot, A., and Baillet, L.: Locating subglacial cavities and investigating basal conditions on glaciers with ambient seismic noise: toward acquisition optimization., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12583, https://doi.org/10.5194/egusphere-egu24-12583, 2024.

The Totten Glacier is a fast moving glacier that serves as a major outlet of the East Antarctic Ice Sheet. During December 2018 and January 2019, we deployed a 12 station broadband seismic array near the grounding zone of the Totten Glacier. We observed a significant number ( > 10,000) of repeating basal stick-slip icequakes across the region. Much of this seismic activity was dominated by higher frequency events (20-75 Hz) similar in size and temporal character (“bursty”) to those found in previous studies, such as those on the Rutford Ice Stream and Greenland Ice Sheet. Additionally, we observe a large number of repeating events dominated by lower frequencies (< 10 Hz) that have larger magnitudes and longer inter-event time than the high-frequency seismic activity. We will provide an overview into both the temporal and spatial variability of this seismic activity and discuss implications for fast flow in the region.

How to cite: Winberry, P.: Repeating Glacier Seismicity Near the Totten Glacier Grounding Zone., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12865, https://doi.org/10.5194/egusphere-egu24-12865, 2024.

EGU24-13124 | ECS | PICO | CR5.1

Exploring englacial hydrology with surface nuclear magnetic resonance 

Laura Gabriel, Marian Hertrich, Raphael Moser, Christophe Ogier, Hansruedi Maurer, and Daniel Farinotti

The amount and distribution of liquid water inside a glacier are relevant for its dynamics, related natural hazards or for sediment transport. Experimentally investigating the glacier's hydrology is challenging because of restricted accessibility, investigation depth, material properties, and environmental factors. In addition, the subglacial drainage network is highly dynamic and undergoes diurnal and seasonal changes.

This contribution investigates the application of surface nuclear magnetic resonance (SNMR) to characterize the liquid water distribution within Swiss Alpine glaciers. Analogous to magnetic resonance imaging (MRI) in medicine, SNMR utilizes an oscillating magnetic field to excite nuclear spins of hydrogen atoms within water molecules. The subsequent spin relaxation is then analyzed, providing insights into the probed material. In simpler terms, this process allows us to directly detect liquid water in ice and gain information on its spatial distribution.

We conducted a first SNMR field survey on Rhonegletscher in the summer of 2023. During this survey, we tested various measurement configurations, including separate-loop measurements and the application of noise-compensation loops. The latter proved crucial for subsequent data processing. After carefully optimizing the processing scheme, we extracted SNMR signals in several recordings despite the poor signal-to-noise ratio. The results were compared to 1D forward-modelled data, suggesting that the average water content in the survey area lay between 0.7 and 1.2 %. In addition, we could show that a homogenous water distribution over the entire ice column cannot explain the observed data and that we need to consider more complex subsurface models including at least one additional water layer. Specifically, our ongoing research aims to identify which configurations of the subglacial water distribution (e.g., homogenous water distribution vs layered water-ice structure resulting from an englacial water channel) are distinguishable experimentally. Moreover, the study seeks to optimize measurement design and data processing methodologies to acquire information more efficiently, and effectively handle the expected low signal-to-noise ratios.

In future field campaigns, we intend to deploy SNMR for selected glaciological case studies within the Swiss Alps. A primary focus will be on efficiently detecting water pockets that may pose a potential risk of downstream flooding upon rupture. Similarly, we want to investigate the extent to which we can distinguish cold from temperate ice.

How to cite: Gabriel, L., Hertrich, M., Moser, R., Ogier, C., Maurer, H., and Farinotti, D.: Exploring englacial hydrology with surface nuclear magnetic resonance, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13124, https://doi.org/10.5194/egusphere-egu24-13124, 2024.

EGU24-13663 | ECS | PICO | CR5.1

 Assessing the rate of ice fracture using co-located geophysical surveys on the Brunt Ice Shelf, Antarctica 

Emma Pearce, Oliver Marsh, Alex Brisbourne, and Thomas Hudson

The rate of fracture-induced ice instability is an important factor contributing to uncertainties in sea level projections used for global flood mitigation planning. While the occurrence of ice fracturing at critical stress thresholds is well-documented, the detailed mechanisms controlling fracture timing, rate, and orientation are not fully understood. This gap is particularly evident in differences in fracture behaviour across varying ice types, such as meteoric ice and ice mélange. Observations on the Brunt Ice Shelf reveal a unique behaviour, where rifts deviate from the pathway predicted by the principal stresses to avoid thick blocks of meteoric ice. Their growth rate is significantly reduced when required to cross through these blocks. This stands in contrast to observations on other ice shelves, such as Larsen C, where rift propagation is slower in marine ice bands.

Here we use co-located geophysical methods, seismic and ground-penetrating radar (GPR), to assess the fracture pattern and dynamics and the relationship to ice properties at the leading edge of two active rifts, Halloween Crack and Chasm 2, on the Brunt Ice Shelf.

By determining the depth of seismic events using P to Rayleigh wave amplitude ratios, we estimate a theoretical maximum dry crevasse depth—the depth at which fracturing can occur without the presence of englacial water. Additionally, GPR data are used to precisely locate rift terminations and identify refrozen layers associated with seawater intrusion into the firn layer. Combining these data, we provide new insight into the mechanisms controlling fracture propagation within the Brunt Ice shelf. The synthesis of observations from Chasm 2 and Halloween Crack contributes to a comprehensive understanding of fracture mechanics, enhancing our knowledge of regional-scale ice dynamics.

How to cite: Pearce, E., Marsh, O., Brisbourne, A., and Hudson, T.:  Assessing the rate of ice fracture using co-located geophysical surveys on the Brunt Ice Shelf, Antarctica, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13663, https://doi.org/10.5194/egusphere-egu24-13663, 2024.

EGU24-13683 | ECS | PICO | CR5.1

Testing four Sentinel (1 and 2) and MODIS Fractional Snow Cover products for the evaluation of five Alpine Cosmic Ray Neutron Sensing sites 

Nora Krebs, Paul Schattan, Valentina Premier, Abraham Mejia-Aguilar, and Martin Rutzinger

Above-ground cosmic ray neutron sensing (CRNS) is an emerging technique for the investigation of dynamics in soil moisture, snow water equivalent (SWE), and vegetation at a spatial scale of several hectares. The measurement principle is based on the moderation of natural secondary cosmogenic neutrons by hydrogen atoms. On the earth surface hydrogen atoms are mainly bound in water molecules. However, at complex research sites the signal distinction between various water sources remains challenging. Especially in alpine terrain and at elevated topography, hydrological features are linked in an intricate patchwork, hampering signal discrimination. Satellite observations offer valuable complementary surface information and are commonly provided at a spatial resolution that meets the integrated footprint area of the CRNS detector. In this study we investigate if the interpretation of the CRNS signal can be enhanced by the use of remote sensing products. We compare three readily available fractional snow cover (FSC) products based on Sentinel (1 and 2) and MODIS and one reference FSC Sentinel-2 scene-based machine learning product at the approximate footprint resolution of CRNS, comprising a circular area of 250 m radius. The performance of all four products is assessed at five CRNS sites in the Austrian and Italian Alps that represent a variety of environmental properties, ranging from flat to steep topography, from low to high elevation and from sparse to abundant vegetation cover. At three sites, the presence and absence of snow can be validated by local snow height measurements. The analysis shows that remote sensing snow cover information can be extracted on around 80% of the analyzed days, demonstrating the use of FSC products for the estimation of snow cover duration and timing. Comparing the four products shows overall agreements and allows to deduce product-specific thresholds for the distinction of snow-covered and snow-free situations. Further, pairing remote FSC observations with neutron count measurements provides a first indication on the complexity of local hydrogen pool dynamics and consequent requirements on the calibration routine for ambient water monitoring with CRNS. We conclude that satellite-based FSC products can be used to fortify the choice of CRNS observation location and period prior to the detector installation and for a robust and viable first-order assessment of expected CRNS site conditions. Remote sensing FSC products and CRNS measurements hold complementary data that can mutually benefit snow observations and should be explored further in the future.

How to cite: Krebs, N., Schattan, P., Premier, V., Mejia-Aguilar, A., and Rutzinger, M.: Testing four Sentinel (1 and 2) and MODIS Fractional Snow Cover products for the evaluation of five Alpine Cosmic Ray Neutron Sensing sites, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13683, https://doi.org/10.5194/egusphere-egu24-13683, 2024.

EGU24-14420 | PICO | CR5.1

Using seismic and gravity data to constrain subglacial seafloor stratigraphy in the vicinity of the Kamb Ice Stream grounding line, Ross Ice Shelf, Antarctica 

Andrew Gorman, Gary Wilson, Huw Horgan, Gavin Dunbar, Caitlin Hall, Jenny Black, Bob Dagg, Matthew Tankersley, and Laurine van Haastrecht

The sedimentary units beneath the Ross Ice Shelf in the vicinity of the Kamb Ice Stream grounding line on the Siple Coast of the eastern Ross Ice Shelf play an important role in evaluating past advances and retreats of grounded ice in West Antarctica through the Quaternary. This region is an ongoing focus for drilling efforts that involve melting through the ice shelf and recovering sediments from beneath the seafloor. Seismic (and to a lesser extent gravity) methods have played a critical role in establishing a stratigraphic framework for these sediment sampling endeavours. Approximately 73 km of seismic data have been collected in this region during three seasons since early 2015, complemented by finely sampled gravity transects and a coarser regional gravity grid. Data acquisition provides localised coverage of the sub-ice-shelf ocean and sediments in a region where ROSETTA-Ice airborne-gravity data identified a gravity low. Seismic acquisition parameters have varied from survey to survey, but all involve explosive charges frozen into a hot-water-drilled holes that are recorded by conventional geophones buried in the firn. Such an acquisition configuration provides imaging of the ice shelf and underlying geological units. Processed seismic data show a mostly flat layered seafloor lying beneath the ocean cavity with at least 200 m of sub-horizontally layered sedimentary strata containing several mappable unconformities that are identified as distinct reflective horizons in the seismic data as well as reflection terminations and pinchouts in overlying and underlying units. These unconformities could correspond to past glacial erosion episodes as the position of the grounding line in this region has migrated landward and oceanward. Gravity modelling suggests that the thickness of the sedimentary basins in the region are variable beyond what we see in the shallow (few hundred metre) penetration of the seafloor.

How to cite: Gorman, A., Wilson, G., Horgan, H., Dunbar, G., Hall, C., Black, J., Dagg, B., Tankersley, M., and van Haastrecht, L.: Using seismic and gravity data to constrain subglacial seafloor stratigraphy in the vicinity of the Kamb Ice Stream grounding line, Ross Ice Shelf, Antarctica, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14420, https://doi.org/10.5194/egusphere-egu24-14420, 2024.

EGU24-15907 | PICO | CR5.1

Long-term refraction seismic monitoring: a reliable method to detect ground ice loss at mountain permafrost sites 

Christin Hilbich, Bernd Etzelmüller, Ketil Isaksen, Coline Mollaret, Sarah Morard, Cécile Pellet, and Christian Hauck

Geophysical monitoring becomes more and more popular in permafrost environments due to its remarkable success to detect permafrost thawing and spatio-temporal changes in the ground ice content. Mostly geoelectric methods such as Electrical Resistivity Tomography (ERT) are applied due to the strong differences in the electrical properties between frozen and unfrozen state. However, seismic properties also change markedly upon freezing/thawing and time-lapse refraction seismic tomography (RST) has been shown to be applicable to permafrost over smaller time scales (e.g., Hilbich 2010). The reason why only few studies employ long-term seismic monitoring in permafrost is probably due to the higher logistical effort required.

At two Swiss permafrost monitoring sites (Schilthorn and Stockhorn) yearly RST surveys are conducted using the same setup for more than 15 years, in addition to standard borehole temperature, climatic and ERT measurements (www.permos.ch). The monitoring aim is to image the interannual changes of the thickness of the active layer as well as differences in ice content within the permafrost layer below.

Additional long-term observations are available from RST (and contemporary ERT) surveys from several mountain permafrost sites in Norway that were initially conducted to characterise permafrost conditions around boreholes drilled in 1999/2008 (Juvvasshoe/Jotunheimen), and 2007/2008 (Iskoras/Finnmark, Guolasjavri/Troms, and Tronfjell, cf. Isaksen et al. 2011, Farbrot et al. 2013). These surveys were repeated with the same geometry in 2019 after 11 years in northern Norway, and after 8 and 20 years in southern Norway. As for the Swiss sites, temperatures from all these boreholes show a clear warming trend over the last 1-2 decades (Etzelmüller et al, 2020, 2023).

We here present the observed long-term changes in electrical resistivity and seismic P-wave velocity based on a) annually repeated measurements in the Swiss Alps, and b) on long-term repetition in northern and southern Norway. The geophysical changes are related to the observed borehole temperature increase during the same period (Etzelmüller et al. 2023) and analysed with respect to climate-induced thawing. We evaluate the advantages and disadvantages of seismic monitoring compared to the more standard ERT monitoring. Finally, the results are also analysed with respect to their suitability for future ERT-seismic joint inversion approaches in a monitoring context.

 

References

Etzelmüller B, Guglielmin M, Hauck C, Hilbich C, Hoelzle M, Isaksen K, Noetzli J, Oliva M and Ramos M 2020. Twenty years of European mountain permafrost dynamics—the PACE legacy. Environ. Res. Lett. 15 104070 DOI 10.1088/1748-9326/abae9d

Etzelmüller B, Isaksen K, Czekirda J, Westermann S, Hilbich C, Hauck C 2023. Rapid warming and degradation of mountain permafrost in Norway and Iceland. The Cryosphere. 17.5477-5497.10.5194/tc-17-5477-2023.

Farbrot H, Isaksen K, Etzelmüller B, Gisnås K 2013. Ground Thermal Regime and Permafrost Distribution under a Changing Climate in Northern Norway. Permafrost Periglac.,24(1):20-38. https://doi.org/10.1002/ppp.1763

Isaksen K, Ødegård RS, Etzelmüller B, Hilbich C, Hauck C, Farbrot H, Eiken T, Hygen HO, Hipp T 2011. Degrading mountain permafrost in southern Norway - spatial and temporal variability of mean ground temperatures 1999-2009. Permafrost Periglac.,22(4):361-377, https://doi 10.1002/ppp.728.

Hilbich C 2010. Time-lapse refraction seismic tomography for the detection of ground ice degradation, The Cryosphere, 4, 243–259, https://doi.org/10.5194/tc-4-243-2010, 2010.

How to cite: Hilbich, C., Etzelmüller, B., Isaksen, K., Mollaret, C., Morard, S., Pellet, C., and Hauck, C.: Long-term refraction seismic monitoring: a reliable method to detect ground ice loss at mountain permafrost sites, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15907, https://doi.org/10.5194/egusphere-egu24-15907, 2024.

EGU24-16320 | PICO | CR5.1

Quieting of hydraulic tremor: sudden changes in frictional conditions in subglacial channels 

Małgorzata Chmiel, Nicoletta Caldera, Fabian Walter, Gerrit Olivier, Daniel Farinotti, Alberto Guadagnini, Dominik Gräff, Manuela Köpfli, and Florent Gimbert

The state and evolution of subglacial channels strongly impact glacier motion and as a result the mass balance of flowing ice bodies. Yet, the subglacial environment is difficult to access and thus often poorly constrained over significant temporal and spatial scales. This limits our understanding of complex subglacial hydraulic processes and consequently ice dynamics.

Seismology can help overcome these observational constraints, providing new insights into fundamental processes in the cryosphere, such as frictional sliding and subglacial water flow. However, different seismogenic processes of the cryosphere often overlap in both time and space. Differentiating between them and interpreting associated seismic signals require appropriate methodological and instrumental approaches.

Here, we investigate subglacial channel dynamics at the Rhone glacier (Switzerland) over one month in the summer of 2020, focusing on periods coinciding with glacier sliding episodes. To this end, we leverage the sensitivity of near-bed borehole geophones combined with seismic interferometry and beamforming techniques.

We show that the hydraulic tremor, generated by turbulent water flow and resulting pressure variations acting against the subglacial channel bed and walls, acts as a dominant, stable, and coherent noise source. Beamforming analysis reveals the directional stability of the hydraulic tremor and points toward the junction of two subglacial hydraulic channels from which stick-slip asperities originate. The analysis also reveals instances of sudden hydraulic tremor quieting, in agreement with previous observations before and after seismogenic sliding episodes. We explain this quieting as sudden changes in frictional conditions within the subglacial channel corresponding to a rapid transition between a fully and partially filled channel. We discuss channel properties (geometry and bed conditions) that are needed to satisfy the physical conditions for the frictional quieting mechanism. Our analysis offers new insights into the complex mechanical interactions between ice, water, and bed properties and the hydraulic control of glacier sliding.

How to cite: Chmiel, M., Caldera, N., Walter, F., Olivier, G., Farinotti, D., Guadagnini, A., Gräff, D., Köpfli, M., and Gimbert, F.: Quieting of hydraulic tremor: sudden changes in frictional conditions in subglacial channels, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16320, https://doi.org/10.5194/egusphere-egu24-16320, 2024.

EGU24-17134 | ECS | PICO | CR5.1

Lightweight In-Situ Analysis of snow density and accumulation 

Johanna von Drachenfels, Helle Astrid Kjær, and Josephine Lindsey-Clark

A critical factor in accurate Surface Mass Balance predictions of the Greenland Ice Sheet is the availability of spatially and temporally extensive snow accumulation data (Montgomery et al., 2018). Currently, this data remains deficient due to incomplete geographical coverage and poor temporal resolution (Sheperd et al., 2012).

An innovative approach to expanding the existing dataset is the utilization of the LISA box: a portable Lightweight In-Situ Analysis system designed for fast and straightforward snow and ice core measurements (Kjær et al., 2021), which speeds up the delivery of the results. With the LISA box, the sample cores are melted, and continuous flow analysis of chemical impurities and conductivity in the meltwater reveals annual peaks and climatic horizons. This information allows for dating of the single ice and snow layers. The registration of the melt speed furthermore permits the determination of the layer thickness, while the layer density can be inferred with an additional measurement of the meltwater flowrate. By combining these insights, past accumulation rates, as indicated by the volume of annually deposited snow, can be reconstructed.

Here we present updates to the existing LISA box enhancing its abilities to further analyse for density variations in snow and firn cores.

How to cite: von Drachenfels, J., Kjær, H. A., and Lindsey-Clark, J.: Lightweight In-Situ Analysis of snow density and accumulation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17134, https://doi.org/10.5194/egusphere-egu24-17134, 2024.

EGU24-17421 | PICO | CR5.1

Lake ice seismicity: seismic and acoustic observations 

Cedric Schmelzbach, Christoph Wetter, Simon Stähler, John Clinton, Zinan Lyu, Maria Mesimeri, and Frédérick Massin

Seismic events (icequakes) associated with floating ice sheets on lakes are a frequently observed phenomenon. We find at our study site on the frozen Lake St. Moritz in the Swiss Alps typically a clear diurnal pattern with hundreds to thousands of icequake signals per hour during night time, while the rate of observed events during daytime is about two orders of magnitude smaller. The seismicity rate shows a significant correlation with temperature changes. It is therefore assumed that the generation of the ice quakes is related to melting and freezing processes as well as the extension and contraction of the ice. Potentially the seismicity rate is also moderated by loading and unloading due to human activities on the ice and/or lake level changes.

These ice quakes generate seismic waves that propagate through the thin ice sheet as plate waves modulated by the air and water half-spaces above and below the ice (quasi-guided waves). One member of this wave-type family, the quasi-Scholte waves, are characterised by distinct dispersion that can be observed with seismic sensors on the ice. Furthermore, the seismic waves traveling through the ice couple into the air leading to audible seismo-acoustic signals. One particularity of the ice-air coupling is a so-called coincidence phenomenon. The particular velocity-frequency combination where the seismic wavelength in the ice matches the apparent acoustic wavelength in the air leads to a resonance phenomenon. Observation of the related coincidence frequency allows us, for example, to infer on the ice thickness from the acoustic observations with a low cost microphone above the ice only. Recording the acoustic signals with small microphone arrays enables additionally, for example, locating the source of the seismo-acoustic signal.

Combined observations of the seismic and acoustic signals provide new insights into the seismicity of lake ice which has rarely been studied in the past. The seismo-acoustic signals have the potential to provide information about the ice properties such as thickness and ice quality as well as waxing and waning processes of ice sheets. These observations are relevant for safe operations on the ice but also to complement other remote-sensing observations with autonomous in situ seismo-acoustic measurements for climate studies.

How to cite: Schmelzbach, C., Wetter, C., Stähler, S., Clinton, J., Lyu, Z., Mesimeri, M., and Massin, F.: Lake ice seismicity: seismic and acoustic observations, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17421, https://doi.org/10.5194/egusphere-egu24-17421, 2024.

EGU24-17767 | PICO | CR5.1

Glaciological characterization of Little Dome C: Influence of ice flow on the future Beyond Epica – Oldest Ice Core drilling project 

Robert Mulvaney, Carlos Martín, Catherine Ritz, Luca Vittuari, Massimo Frezzotti, and Olaf Eisen

An ice core is being drilled near Little Dome C, a small promontory about 30km downstream from the summit of Dome C, to extract a continuous record of climate over the last 1.5 million years. Present and past ice flow conditions are important to interpret the ice core because the surface velocity at the drilling site is about 40 mm/yr and the oldest ice in the record was deposited in the surface about 10km upstream of the drilling site. Here we explore newly acquired and existing geophysical data to describe present ice flow and investigate signs of past changes. We present new GNSS data that describes the subtle but complex local surface velocity, and ApRES radar data that provides englacial strain-rates along the flow path from the summit of Dome C and bulk englacial crystal orientation fabric. Ice currently flows from Dome C summit along the ridge to Little Dome C, even though a subtle uphill slope, but basal conditions are variable along the path due to the strong basal topography. Of special interest is an ice unit in contact with the bedrock with variable thickness up to about 300m that is vertically stagnant and produce a strong radar reflection.  This basal unit is not present in an area of strong melting about 5km upstream from the drilling site. The crystal orientation fabric reflects the ice flow horizontal extension along the path and changes with depth on ice flow properties following climatic transitions and, more intriguing, indicate a possible change in ice flow extension at the beginning of the Holocene. We aim to facilitate detailed ice flow models to better interpret the ice core data.  

How to cite: Mulvaney, R., Martín, C., Ritz, C., Vittuari, L., Frezzotti, M., and Eisen, O.: Glaciological characterization of Little Dome C: Influence of ice flow on the future Beyond Epica – Oldest Ice Core drilling project, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17767, https://doi.org/10.5194/egusphere-egu24-17767, 2024.

EGU24-17917 | PICO | CR5.1

Using received laser signal intensity to measure snow and ice surface properties automatically  

Alexander Prokop, Florian Tolle, Jean-Michelle Friedt, and Eric Bernard

In the context of climate warming it is a common scientific goal to study and monitor surface and volume changes of glaciers and melting dynamics of its snow and ice. Therefore several measurement techniques exist to track permanently ice melting e.g. DGPS stations on glaciers, Smart stake, and snow and ice depth measurements via e.g. ultrasonic depth sensors to create time series of snow and ice loss or gain. None of the existing methods measure if actually liquid water is present and melting occurs, this is later concluded by interpretation of the geometric data. The capability of the laser sensor to do so via the reflectance value, in fact the received signal intensity, we consider as a big advantage and worth investigating further as a direct measure of snow or ice melt that helps not only to analyze glacier dynamics but is also important e.g. for providing reliable ground truth data for satellite remote sensing. When melting of snow and ice occurs, water changes the reflectance properties as due to absorption of the laser in water, only a portion of the laser is reflected. This allows determining if liquid water is present at the surface measured. We present the data collected in the last 2 melting seasons of the Austre Lovénbreen glacier near Ny Alesund, Svalbard. We show how we classify wet snow and wet ice hours with confidence and are able to compute melting rates. The single point measurement is put into context to area wide LiDAR measurements and melting dynamics of the glacier are analyzed. The data was verified against visual inspections from automatic cameras, data from an automatic weather station both located in the glacier catchment and ice melt was measured in close proximity with a SmartStake station.

How to cite: Prokop, A., Tolle, F., Friedt, J.-M., and Bernard, E.: Using received laser signal intensity to measure snow and ice surface properties automatically , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17917, https://doi.org/10.5194/egusphere-egu24-17917, 2024.

EGU24-18177 | ECS | PICO | CR5.1

Applying Cosmic-Ray Neutron Sensing in Highly Heterogeneous Conditions: Monitoring Snow Water Equivalent in Periods with Partial Snow Coverage 

Paul Schattan, Jan Schmieder, Markus Köhli, Christine Fey, and Martin Schrön

Cosmic-Ray Neutron Sensing (CRNS) constitutes an emerging method for monitoring soil moisture and snow dynamics at intermediate spatial scales of several hectares. In complex environments such as mountain regions, however, the presence of areas with a high contrast of hydrogen content was found to cause a hysteresis in the relationship between neutron counts and water equivalent. A simulation study using the newly developed hierarchical scenario tool YULIA (Your URANOS Layer Integration Assistant) for the Monte-Carlo neutron simulation model URANOS was conducted to quantify the effect of snow-free areas on above-ground neutron sensing of the snow water equivalent (SWE). It was found that the size and distance of the snow free patches have the largest impact on the neutron flux. The simulations also showed a sensitivity of the signal towards soil moisture and SWE. Correction functions were developed and validated with observed CRNS measurements and LiDAR based distributed SWE maps. The main aim of the correction procedure is to estimate SWE under partly snow-covered conditions. Furthermore, also the soil moisture of the snow-free areas can be inferred if the SWE distribution is known. The latter can be used for other high-contrast CRNS applications like monitoring soil moisture in the presence of ponding water.

How to cite: Schattan, P., Schmieder, J., Köhli, M., Fey, C., and Schrön, M.: Applying Cosmic-Ray Neutron Sensing in Highly Heterogeneous Conditions: Monitoring Snow Water Equivalent in Periods with Partial Snow Coverage, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18177, https://doi.org/10.5194/egusphere-egu24-18177, 2024.

EGU24-18639 | PICO | CR5.1

Stick-slip imaging through the GPR phase: Turning  temperate ice 'noise' into signal 

Johannes Aichele, Christophe Ogier, and Barthélémy Anhorn


Ground Penetrating Radar (GPR) is a major tool to investigate, map and monitor polar ice sheets and alpine glaciers. Alpine glaciers are often composed of temperate ice, which has significantly different backscatter properties from cold ice. Radar attenuation is much stronger in temperate ice than in cold ice, because the radar signal encounters strong scattering in temperate ice. 
A major candidate for this scattering is the presence of liquid water inclusions, which are much smaller than the radar wavelength. The large contrast between water and ice dielectric permittivity would explain the diffuse radar scattering in temperate ice. Indeed, recent numerical modelling of the radar signal in temperate ice confirmed the contribution of liquid water inclusions on the scattering of the radar signal (Ogier, 2023). 
Here, we investigate if the strong scattering caused by liquid water inclusions, which is usually treated as noise, can be in fact exploited to unravel dynamic processes inside the glacier. This strong scattering results in large radar phase variations in space, which remain constant over short timescales (hours - days), during which the glacial water content remains constant. During that timescale, however, the mountain glacier might experience sudden internal deformation due to intermittent sliding at the glacier base, also called glacier stick-slip.  This deformation might be resolved using difference imaging and the spatio-temporal properties of the radar phase.
We numerically model radar wave propagation throughout temperate ice (i.e. with the presence of liquid water inclusions) before and after an idealized glacier deformation and show, that through phase difference imaging the internal movement of the sub-wavelength scatterers can be mapped. 
Finally, we discuss how this novel type of monitoring could be applied in the field, which is planned for spring 2024.

 

Ogier, Christophe, Dirk-Jan van Manen, Hansruedi Maurer, Ludovic Räss, Marian Hertrich, Andreas Bauder, and Daniel Farinotti. 2023. “Ground Penetrating Radar in Temperate Ice: Englacial Water Inclusions as Limiting Factor for Data Interpretation.” Journal of Glaciology, September, 1–12. https://doi.org/10.1017/jog.2023.68.

How to cite: Aichele, J., Ogier, C., and Anhorn, B.: Stick-slip imaging through the GPR phase: Turning  temperate ice 'noise' into signal, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18639, https://doi.org/10.5194/egusphere-egu24-18639, 2024.

EGU24-19098 | PICO | CR5.1

Observing glacier bed topography: the H/V spectral method applied on a dense seismic array as a simple alternative to radar 

Florent Gimbert, Neil Ross, Tifenn Le Bris, Guilhem Barruol, Tun Jan Young, Samuel Doyle, Stephen Livingstone, Andrew Sole, Adrien Gilbert, Ryan Ing, Liz Bagshaw, Mike Prior-Jones, and Laura Edwards

Accurate knowledge of glacier bed topography is critical for quantifying ice volumes and modelling ice and subglacial hydrology dynamics. Bed topography observations are traditionally obtained from airborne and ice penetrating radar, which offers the crucial advantage of recovering the detailed glacier structure over a range of scales. A main difficulty with radar, however, is that waves can be strongly scattered and attenuated by englacial heterogeneities, in particular by water inclusions, which can potentially limit the applicability of the technique under certain conditions.

Here we present a case study on Isunguata Sermia, West Greenland, where we conducted an ice penetrating radar survey together with dense seismic array acquisitions from 87 nodes spread over a 1 km2 area. We show that, in the area of investigation, radar observations were only partially successful in identifying the ice-bed interface, likely due to the thick warm ice, presence of some surface water and near-surfacing crevassing and other englacial structures. The H/V analysis performed over the seismic array yielded surprisingly coherent estimates of ice thickness, along with its spatial variation along and across the glacier. These findings raise questions about the interpretation of traditional radar measurements under certain glacier conditions, and how dense seismic arrays could retrieve bed topography more systematically. 

How to cite: Gimbert, F., Ross, N., Le Bris, T., Barruol, G., Young, T. J., Doyle, S., Livingstone, S., Sole, A., Gilbert, A., Ing, R., Bagshaw, L., Prior-Jones, M., and Edwards, L.: Observing glacier bed topography: the H/V spectral method applied on a dense seismic array as a simple alternative to radar, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19098, https://doi.org/10.5194/egusphere-egu24-19098, 2024.

EGU24-20308 | ECS | PICO | CR5.1

“Determination of Hydric Potencial through Geoelectric and Piezometric methods in the Ichickcollcococha Wetland, Pachacoto Hydrographic Unit, Cordillera Blanca, Perú.”  

Leila Maribel Mamani, W. Harrinson Jara, Velnia Chacca Luna, Juan C. Torres, Helder Mallqui, Manuel Cosi, Cristian Quispe, and Milagros Aquino

Abstracts

High-Andean bofedales are vegetated wetlands that play a crucial role in the context of climate change by facilitating the capture of carbon dioxide and regulating water. However, global warming has led to the glacial retreat of major snow-capped peaks, such as the Pastoruri Glacier, resulting in water scarcity that directly impacts these ecosystems. Hence, there is a pressing need to study them. This research aims to characterize the physical structure of the Ichickcollcococha bofedal, located in the Pachacoto Hydrographic Unit in the southern sector of the Cordillera Blanca, Peru. The objective is to determine its water storage potential during periods of high precipitation and drought. The study employs the Vertical Electrical Sounding (VES) geophysical prospecting method, corroborated by vibrating wire piezometers installed in the Ichickcollcococha bofedal. This method allows for a detailed analysis of the subsurface resistive properties, generating geo-electric profiles that detail the internal structure of the bofedal.

Three horizons have been identified: the upper layer is loosely composed of organic material (vegetation, cushioned bofedales) with high moisture content, reaching a depth of approximately 1.5 meters and average resistivity values around 431 Ohm.m. The second layer extends to a depth of 11 meters with resistivities of 67 Ohm.m, corresponding to organic materials such as peat and saturated sands. The third horizon, with estimated depths of 80 meters and resistivities around 1301 Ohm.m, corresponds to underlying limestone rock. The data obtained from the Ichickcollcococha bofedal align with characteristic values of glacial-origin peat bogs.

The findings of this study provide a comprehensive understanding of the internal characteristics of the Ichickcollcococha bofedal, highlighting its contribution to the knowledge of its internal dynamics and its implications for the water potential of high-Andean bofedales. Furthermore, the results offer valuable information for modeling and water resource management.

Keywords: Bofedal, Hydric potential, geoelectric method, VES.

How to cite: Mamani, L. M., Jara, W. H., Chacca Luna, V., Torres, J. C., Mallqui, H., Cosi, M., Quispe, C., and Aquino, M.: “Determination of Hydric Potencial through Geoelectric and Piezometric methods in the Ichickcollcococha Wetland, Pachacoto Hydrographic Unit, Cordillera Blanca, Perú.” , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20308, https://doi.org/10.5194/egusphere-egu24-20308, 2024.

EGU24-21232 | ECS | PICO | CR5.1

Quantifying Ground Ice in Tien Shan and Pamir Permafrost: A Comprehensive Petrophysical Joint Inversion Study Applying the electrical Geometric Mean Model  

Tamara Mathys, Christin Hilbich, Coline Mollaret, Christian Hauck, Tomas Saks, Ryksul Usubaliev, Bolot Moldobekov, Zhoodarbeshim Bektursunov, Muslim Azimshoev, Hofiz Navruzshoev, and Martin Hoelzle

Central Asian Mountain regions (Tien Shan and Pamir) are expected to be significantly impacted by climate change, affecting water availability and natural hazards. The cryosphere plays a crucial role in many watersheds of the region by providing water for hydropower station, irrigation, and domestic use downstream. At the same time, retreating glaciers and thawing permafrost increase the risk of natural hazards. Therefore, cryosphere monitoring systems are necessary to provide baseline data for estimating future water availability and detecting dangerous hazard zones. Despite the large areas underlain by permafrost in the Tien Shan and Pamir Mountain ranges, data on permafrost distribution, characteristics and evolution are scarce. However, quantitative estimations of permafrost subsurface components, especially water and ice contents, are needed to evaluate the consequences of current climate change on mountain permafrost environments.

Recent field-based investigations have emphasised the coupled use of geophysical techniques, e.g., by employing the Petrophysical Joint Inversion scheme (PJI, Wagner et al., 2019) that combines electrical resistivity and seismic refraction p-wave velocity data to estimate the four phases present in the subsurface (volumetric contents of air, water, ice, and rock). The traditional PJI implementation relies on Archie’s law (Archie, 1942) as one of the primary petrophysical equation to link resistivity to porosity and water content. Archie's law is generally considered valid when electrolytic conduction dominates, a condition that is not universally justified for dry and coarse blocky substrates and landforms in mountainous terrain. Recognizing this limitation, Mollaret et al. (2020) introduced the electrical Geometric Mean Model as an alternative implementation in the PJI. The Geometric Mean Model  assumes random distributions of the four phases and offers the advantage of including the fractions of ice and air in the petrophysical equation for resistivity, which are not present in Archie’s law. In this study, we assess the feasibility and effectiveness of using the Geometric Mean Model within the PJI framework across an extensive geophysical dataset comprising 22 profiles in Central Asia (Kyrgyzstan and Tajikistan). Our research encompasses diverse landforms, including moraines, rock glaciers, talus slopes, and fine-grained sediments. Our goals are to (i) evaluate the performance of the Geometric Mean Model in comparison to Archies law across different landforms and (ii) address the existing data gap concerning mountain permafrost and ground ice contents in the Central Asian region.

References

Archie, G. E. (1942). The Electrical Resistivity Log as an Aid in Determining Some Reservoir Characteristics. Transactions of the AIME, 146(01), 54–62. https://doi.org/10.2118/942054-G

Mollaret, C., Wagner, F. M., Hilbich, C., Scapozza, C., & Hauck, C. (2020). Petrophysical Joint Inversion Applied to Alpine Permafrost Field Sites to Image Subsurface Ice, Water, Air, and Rock Contents. Frontiers in Earth Science, 8, 85. https://doi.org/10.3389/feart.2020.00085

Wagner, F. M., Mollaret, C., Günther, T., Kemna, A., & Hauck, C. (2019). Quantitative imaging of water, ice and air in permafrost systems through petrophysical joint inversion of seismic refraction and electrical resistivity data. Geophysical Journal International, 219(3), 1866–1875. https://doi.org/10.1093/gji/ggz402

How to cite: Mathys, T., Hilbich, C., Mollaret, C., Hauck, C., Saks, T., Usubaliev, R., Moldobekov, B., Bektursunov, Z., Azimshoev, M., Navruzshoev, H., and Hoelzle, M.: Quantifying Ground Ice in Tien Shan and Pamir Permafrost: A Comprehensive Petrophysical Joint Inversion Study Applying the electrical Geometric Mean Model , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21232, https://doi.org/10.5194/egusphere-egu24-21232, 2024.

Glacier surges are prevalent in the Karakoram and often threaten local residents by submerging land and initiating secondary disasters. The Kyagar Glacier is well known for its surge history as it frequently blocked the downstream valley, leading to a series of high-magnitude glacial lake outburst floods. Although the surge dynamics of the Kyagar Glacier have been broadly described in the literature, there remains an extensive archive of remote sensing observations that have great potential for revealing specific surge characteristics and their relationship with historic lake outburst floods. We propose a new perspective on quantifying the surging process using successive digital elevation models (DEMs), which could be applied to other sites where glacier surges are known to occur. Advanced Spaceborne Thermal Emission and Reflection Radiometer DEMs, High Mountain Asia 8-meter DEMs, and the Shuttle Radar Topography Mission DEM were used to characterize surface elevation changes throughout the period from 2000 to 2021.We also used Landsat time series imagery to quantify glacier surface velocities and associated lake changes over the course of two surge events between 1989 and 2021. Using these datasets, we reconstruct the surging process of the Kyagar Glacier in unprecedented detail and find a clear signal of surface uplift over the lower glacier tongue, along with uniformly increasing velocities, associated with the period of surge initiation. Seasonal variations in surface flow are still evident throughout the surge phase, indicating the presence of water at the glacier bed. Surge activity of the Kyagar Glacier is strongly related to the development and drainage of the terminal ice-dammed lake, which is controlled by the drainage system beneath the glacier terminus.

How to cite: Lv, M.: Quantifying the surging process of the Kyagar Glacier in the Karakoram using successive digital elevation models and optical satellite images, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2778, https://doi.org/10.5194/egusphere-egu24-2778, 2024.

EGU24-3498 | ECS | Orals | CR5.2 | Highlight

Reconstructed global glacier mass change since LIA strongly influenced by the sample of observed glaciers 

Anouk Vlug, Fabien Maussion, Paul Leclercq, Larissa van der Laan, Jonathan Carrivick, and Ben Marzeion

An accurate global reconstruction of glacier mass change since the Little Ice Age (LIA) is of importance for, e.g., glacier mass change attribution studies and constraining the past sea-level budget. However, there are significant inconsistencies between reconstructions of the global LIA volume derived from (i) glacier length change records and (ii) glacier models that include the build-up to the LIA. The inconsistencies are present in both the magnitude and timing of the LIA maximum. Model reconstructions have shown a smaller peak of glacier volume, occurring many decades later than glacier length records indicate. Furthermore, as the maximum LIA volume did not occur synchronously between glaciers, the sampling choice of glaciers from the global population will have an impact on the total reconstructed LIA volume. Here, we tested the effect of different sampling strategies on reconstructed LIA volume, using a model based reconstruction from the Open Global Glacier Model, forced with the Last Millennium Reanalysis, as a surrogate world. Our analysis shows that glaciers for which length change observations prior to 1945 are available (the “real-world sample”) are not representative of the global signal. This shortcoming has the potential to explain large inconsistencies between the model-based reconstructions of glacier mass and reconstructions from observations. While the real-world sample is skewed, it is still a better representation of the global signal than would be expected from a random sample of the same size.

How to cite: Vlug, A., Maussion, F., Leclercq, P., van der Laan, L., Carrivick, J., and Marzeion, B.: Reconstructed global glacier mass change since LIA strongly influenced by the sample of observed glaciers, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3498, https://doi.org/10.5194/egusphere-egu24-3498, 2024.

EGU24-4066 | Orals | CR5.2 | Highlight

Reconciled regional & global glacier mass changes 2000−2022 

Michael Zemp, Livia Jakob, Inés Dussaillant, Samuel, U. Nussbaumer, Sophie Dubber, and Noel Gourmelen and the GlaMBIE Team

Glacier changes are a sign of climate change and have an impact on the local hazard situation, region runoff, and global sea level. In previous reports of the Intergovernmental Panel on Climate Change (IPCC), the assessment of glacier mass changes was hampered by spatial and temporal limitations as well as by the restricted comparability of different observing methods. The Glacier Mass Balance Intercomparison Exercise (GlaMBIE; https://glambie.org) aims to overcome these challenges in a community effort to reconcile in-situ and remotely sensed observations of glacier mass changes at regional to global scales.

In this contribution, we will present the approach and results of the new data-driven consensus estimation of regional and global mass changes from glaciological, DEM-differencing, altimetric, and gravimetric methods. Our reconciled estimate suggests a global glacier mass loss of about 5,500 Gt from 2000 to 2022, with an acceleration of about 25% when comparing the second with the first half period. Since 2000, glaciers regionally have lost between 1 and 30% of their total ice volume, and about 4.5% globally. We will discuss these results in view of differences between observation methods and in comparison to previous IPCC reports, the implications for regional glacier mass loss and global sea-level rise, and remaining opportunities for further research.

How to cite: Zemp, M., Jakob, L., Dussaillant, I., Nussbaumer, S. U., Dubber, S., and Gourmelen, N. and the GlaMBIE Team: Reconciled regional & global glacier mass changes 2000−2022, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4066, https://doi.org/10.5194/egusphere-egu24-4066, 2024.

EGU24-4111 | ECS | Orals | CR5.2

Alpine-wide LIA glacier reconstruction and ELA patterns using glacier modelling 

Andreas Henz, Andreas Vieli, Samuel Nussbaumer, and Guillaume Jouvet

The maximum extent of the glaciers in the European Alps during the Little Ice Age (LIA) is relatively well known. However, the ice surface geometry and related ice volume are still poorly constrained. We provide an Alpine-wide reconstruction of glacier thickness using the novel Instructed Glacier Model (IGM). The IGM uses the innovative approach based on deep-learning and GPU to accelerate the solving of computationally expensive 3D physics of glacier flow, which is key to work in high-resolution at the Alpine scale. The mass-balance model is tuned to fit each glacier of the Alps to its known maximum LIA extent resulting in ice-surface geometries and volumes that are consistent with glacier physics and the principles of mass conservation. In addition, our approach provides the corresponding equilibrium-line altitudes (ELAs) for individual glaciers and thereby reveals regional ELA patterns. Comparing these patterns with pre-industrial climate model data permits to analyse the relationship between ELA and climate factors such as temperature, precipitation, aspect, and solar radiation. In conclusion, our approach not only contributes to the estimates of LIA glacier shapes and geometries, but also permits to infer first-order relationships between glacier dynamics and climate conditions.

How to cite: Henz, A., Vieli, A., Nussbaumer, S., and Jouvet, G.: Alpine-wide LIA glacier reconstruction and ELA patterns using glacier modelling, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4111, https://doi.org/10.5194/egusphere-egu24-4111, 2024.

The Little Ice Age (LIA) was originally understood as a period of increased glaciation in the late Holocene. Today, the term is used to describe the multi-centennial glacier advance and maximum level period in the last millennium, but it is also used to refer to the contemporaneous cooler climatic conditions beyond glaciated areas.

Glacier dynamics in the Alps during the last centuries of the LIA are especially known from historical documents, i.e., written and pictorial sources, which essentially date from around 1600 CE and cover some well-known glaciers. Today, these data are enhanced in particular by tree-ring analyses on remnants of trees buried during glacial advances, which can provide calendar dates for advances and glacier maxima, also for the early centuries of the LIA. Moreover, our knowledge of the LIA period is increasingly enhanced by regional climate reconstructions and analyses on climate forcings.

The LIA in the Alps can be defined as the period between the onset of climate cooling, which led to a first LIA-type maximum of glaciers, and the last LIA maximum level generally observed around the middle of the 1800s, i.e., between 1260 and 1860 CE. The first LIA-type maxima are demonstrable for the 1300s, around 1320 and 1380 CE, and then further, often seven maxima for the period ca. 1600-1860 CE. Accordingly, and taking into account the climatic variability, the LIA can be divided into an early (ca. 1260-1380), intermediate (ca. 1380-1575) and main phase (ca. 1575-1860 CE).

Compared to the preceding period of the Medieval Climate Anomaly, reconstructions demonstrate increased climatic variability for the LIA, marked by repeated and pronounced cooling phases that finally triggered the glacier advances. These climatic disturbances correlate remarkably directly with significant volcanic eruptions or phases of increased volcanic activity and, albeit less clearly, with periods of reduced solar insolation, which can be derived from reduced solar activity. Distinctive and historically documented glacier advance phases are often correlated with climatic disturbances following major volcanic eruptions, e.g., the advance period around 1820 CE is following the preceding volcanic events of 1809 and 1815 CE.

Today, the LIA is not only the coolest multi-centennial period of the last 10,000 years but also the reference period for assessing the changes from a system of climate and glacier variability largely determined by natural factors to an environmental system clearly shaped by human activities.

How to cite: Nicolussi, K.: Glacier variability in the Alps during the Little Ice Age - overview on course, evidences and causes, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4392, https://doi.org/10.5194/egusphere-egu24-4392, 2024.

Interdisciplinary approaches are needed to reconstruct the behaviour of glaciers beyond the beginning of systematic, direct measurements. Particularly for the period of the Little Ice Age (LIA), historical documents have been very valuable to successfully reconstruct former glacier extents at different sites. An analysis of historical documents on the well-documented Mont Blanc region, for example, provides unique insights into the LIA glacier development.

The Mont Blanc area became popular with artists, scientists, and travellers in the mid-18th century, including Jean-Antoine Linck from Geneva, who is probably the artist to whom we owe the greatest number of unique glacier views. Jean-Antoine Linck was particularly interested in the icy regions, which he discovered and drew with alpinistic daring and naturalistic accuracy, preferably in gouache, although many pencil sketches have also been preserved. From a glacier history perspective, Linck's work is indispensable, even if many of his artworks are not precisely dated by the author: It represents the whole development of the Mont Blanc glaciers, specifically the Mer de Glace and Glacier des Bossons, but also other glaciers during the period from the end of the 18th century until the 19th century glacier maximum around 1820. As an amazing novelty, Linck was probably the first observer to show a glacier advance with the help of two realistic and accurate views from the same position; one as the Glacier des Bossons retreats and the other as it advances. In addition, various views by Linck make it possible to quantify smaller glacier extents, e.g. around 1800 at the Glacier des Bois (Mer de Glace), which were depicted much more rarely.

To distribute his work, Linck subtly used the etching technique to create easily reproducible plates in large format, which are then hand-coloured with gouache and watercolour. This technique allowed him to create numerous reproductions of the same view, while still giving them a unique and original aspect, views that are remarkable for their serenity and silence, while offering luminous atmospheres. These illustrations introduced the realistic representation of the high mountains into the iconography of Genevese painting and thus led to a new kind of landscape painting with a permanent character.

In terms of glacier history, the work of Jean-Antoine Linck has the same significance for the Mont Blanc area as that of Caspar Wolf and Samuel Birmann for the central Swiss Alps or that of Thomas Ender for the Austrian Alps in terms of glacier iconography. Linck was therefore both an artist and a glacier historian.

How to cite: Nussbaumer, S. U. and Zumbühl, H. J.: The glacier views of Jean-Antoine Linck - a milestone for the Mont Blanc glacier history from the 18th to the 19th century, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5311, https://doi.org/10.5194/egusphere-egu24-5311, 2024.

High Mountain Asia (HMA) contains the largest glacier inventory outside the polar regions and the melting of these glaciers provides an important freshwater supply for over 250 million people in south, central, and east Asia. Recent studies have quantified glacier changes over the past decades in this area mainly based on the interpretation of satellite imagery, while few studies have investigated the longer-term (centennial-scale) glacier changes due to the lack of mapped outlines and reliable methods to reconstruct the three-dimensional surfaces and volumes of past glaciers. We compiled a dataset of >15,000 mapped glacier outlines during the Little Ice Age (LIA) in the Himalayas, Gangdise, Tanggula, and Tian Shan and reconstructed the ice thickness and volumes of LIA glaciers and their corresponding contemporary glaciers based on a flowline-based GIS model, PalaeoIce. Initial results of 640 LIA glaciers and their corresponding 1466 contemporary glaciers from Tian Shan indicate a total of 47.6% loss of ice volumes since the LIA and the ice volume loss are negatively correlated with glacier area and equilibrium line altitude. This presentation reports the reconstruction of >15,000 LIA glaciers and their corresponding >20,000 contemporary glaciers in the four mountain ranges (Himalayas, Gangdise, Tanggula, and Tian Shan) to examine the spatial pattern of LIA glacier changes and their influencing factors (climate, topography, and debris cover). This work provides important insights into the impacts of glacier changes on water resources in High Mountain Asia in the past 300-500 years.

How to cite: Li, Y.: Patterns and influencing factors of glacier changes in High Mountain Asia since the Little Ice Age, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6015, https://doi.org/10.5194/egusphere-egu24-6015, 2024.

Extensive databases of satellite imagery are now available and can be used to undertake assessments of the mass balance of glaciers. Previous studies have mapped the end-of-season snowlines (ESS) on glaciers from satellite imagery to find their snowline altitudes (SLA) and used these as proxies for the glacier equilibrium-line altitudes (ELA). This approach is advantageous because it can be implemented at scale and may employ automated methods. The veracity of using remotely measured SLAs as a proxy for in-situ measured ELAs however, has not yet been robustly demonstrated.

This project is undertaking a systematic mapping of ESSs on glaciers with existing measured mass balance records to determine the errors associated with remotely measured SLAs. Glaciers are selected from the World Glacier Monitoring Service (WGMS) Fluctuations of Glacier (FoG) database. For each ELA record, we identify the Landsat image closest in date to the original ELA measurement (where cloud cover is minimal) and the image with the highest altitude snowline for the year. For each image, the snowline is mapped, and its corresponding SLA is extracted from the ASTER Global Digital Elevation Map (ASTERGDEM). The SLAs vs. ELAs of glaciers covering time series greater than 20 years are presented.

How to cite: Hallford, M.: Testing the veracity of satellite-derived end-of-season snowline altitudes as a proxy for the glacier ELA., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6439, https://doi.org/10.5194/egusphere-egu24-6439, 2024.

EGU24-7010 | Orals | CR5.2

Progress on third glacier inventory of Xinjiang Uygur Autonomous Region (XUAR), northwestern China 

Zhongqin Li, Feiteng Wang, Puyu Wang, and Zexin Zhan

There are nearly half of the glaciers in China distributed in the Xinjiang Uygur Autonomous Region (XUAR) in northwestern China, where the largest glacierized centers outside polar region are nourished by the highest mountain ranges on earth such as Karakoram, western Kunlun mountains, eastern Pamir and Tianshan etc. Glaciers are water tower in this vast arid land in northwestern China. Up-to-date glacier inventory is highly demanded. Based on the latest glacier inventory compilation techniques including those for the first and second Chinese glacier inventories, we currently compiled the third glacier inventory of XUAR, named as Chinese Glacier Inventory of Xinjiang 2020 (CGI-X2020). Comparing to the second Chinese glacier inventory (CGI-2), three improvement has been made in the CGI-X2020. Firstly, CGI-X2020 is based on a total of 235 scenes Chinese satellite imageries were selected out of 30,000 :ZY1 (5); ZY3 (59);  GF1 (135); GF2 (1) ; GF7 (2) and GF6 (33) during the period 2018-2021, mainly during 2020 summer, having a resolution better the 2 m, whereas CGI-2 was based on Landsat TM/ETM+ imageries acquired during 2006–09 with a resolution of 30 m. Secondly, the glacier volume (an important parameter of the glacier inventory) was computed by scaling method which was validated by 22 in-suit glacier thickness measurements through GPR cross glacierized region in XUAR by our research team. Thirdly, the debris coverage of the glaciers were better identified on the basis of high-resolution imageries.

According to GIX2020, by 2020, there are 24,448 glaciers in XUAR, covering an area of 23,531.65 km2 with a total volume about 1548.80 km; There are 20,586 glaciers with an area smaller than 1km2, but the area and volume occupy only 19.16% and 7.95%. Glacier volume in Tarim basin accounts for 64.72% of that in total river systems; The glacier volume is distributed in Kunlun Mountains, followed by Tien Shan and Karakoram Mountains, respectively; 30.68% and 23.92% of the total glacier volume are distributed in Kashgar and Hotian region, respectively.

How to cite: Li, Z., Wang, F., Wang, P., and Zhan, Z.: Progress on third glacier inventory of Xinjiang Uygur Autonomous Region (XUAR), northwestern China, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7010, https://doi.org/10.5194/egusphere-egu24-7010, 2024.

EGU24-8967 | ECS | Posters on site | CR5.2

Quantifying the morphological evolution and interaction of ice cliffs and supraglacial stream incision on debris-covered glaciers using high-resolution terrestrial lidar and UAV methods 

Boris Ouvry, Céline Walker, Marin Kneib, Johannes Reinthaler, Francesca Pellicciotti, and Andreas Vieli

Ice cliffs are known to enhance ablation on debris-covered glaciers and surface ablation. The upstream part of debris-covered glacier tongues is often characterised by downstream-widening supraglacial valleys with hummocky topography, arch-shaped ice cliffs alongside incised and meandering supraglacial channels. The incision of supraglacial channels has been suggested as a potentially important process for the formation of ice cliffs; however, the interactions between channel undercutting and ice-cliff formation are poorly understood and remain to be quantified. In particular, the stream undercutting cannot be observed from nadir-based satellite or UAV methods.

In this study, we therefore use a more local approach to investigate these interactions by applying high-resolution terrestrial remote-sensing methods at the example of two debris-covered glaciers: Satopanth Glacier, located in the Indian Himalayas, and Zmutt Glacier in the European Alps. We combined (i) high-density point cloud data from a terrestrial laser scanner, (ii) drone imagery, (iii) time-lapse imagery, and in situ stake measurements of the channel overhangs and the debris and ice-cliff surfaces at daily and fortnightly intervals during the melting season. By differencing the point clouds and DEMs using a Lagragian reference system, we are able to calculate channel incision and melt rates alongside ice-cliff backwasting rates. We further constrain the evolution of these surfaces with the stake measurements and continuous time-lapse imagery of 30 (Zmutt) and 5 (Satopanth) minute intervals.

Our results show that our approach, particularly the acquisition of point cloud data using terrestrial laser-scanning, offers promising perspectives for analysing channel incision and related ice-cliff backwasting. The dominating processes observed for the evolution of the surface morphology are the backwasting of the exposed ice cliff, the erosion of the stream in the undercut below, and the ablation of the debris-covered surface, which are exposed to a range of external factors (e.g., meltwater flow, air temperature, solar radiation, deposition, and debris thickness). We find that the sideway component of the channel incision usually exceeds the downward component and creates, depending on the size of the stream, undercuts of several 10s of cm (Zmutt) to several meters (Satopanth) in width. The related horizontal undercutting rates are generally comparable or more significant than ice-cliff backwasting and sub-debris ablation. However, we note that the incision and ice cliff morphology varies according to their location and orientation along the meandering meltwater stream. For deeply undercut ice overhangs, we are able to detect downward deformation that occasionally leads to a collapse of the ice cliff above and may thereby indirectly further enhance ice cliff backwasting. 

Our results imply that stream incision is the driving process of undercutting and maintaining the ice cliffs, hence a crucial process for their formation and evolution. The integrated use of high-resolution field-based remote-sensing methods thereby contributed successfully towards a better understanding of the morphological evolution of surfaces with relatively thin debris and the related characteristic supraglacial valleys.

How to cite: Ouvry, B., Walker, C., Kneib, M., Reinthaler, J., Pellicciotti, F., and Vieli, A.: Quantifying the morphological evolution and interaction of ice cliffs and supraglacial stream incision on debris-covered glaciers using high-resolution terrestrial lidar and UAV methods, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8967, https://doi.org/10.5194/egusphere-egu24-8967, 2024.

EGU24-9700 | ECS | Posters on site | CR5.2

Tapping the potential of multi-temporal thermal infrared UAV over a debris-covered glacier  

Gabriele Bramati, Florian Hardmeier, Jennifer Susan Adams, Andreas Vieli, and Kathrin Naegeli

Understanding the role and dynamics of debris covering alpine glaciers is complex and multi-faceted. A thin or non-continuous layer (smaller than 2cm) promotes melting, whereas a thicker layer insulates the underlying ice. The response of debris-covered glaciers to climate change is not uniform worldwide. These glaciers not only react to the changing climate, but they are also sensitive to debris-cover evolution. To date, studies analysed limited spatio-temporal data and thus do not describe multi-temporal changes in debris cover thickness. However, these strongly impact long-term glacier evolution as topography changes can lead to ice cliff formation, which is known to considerably speed up glacier melt. Multi-temporal high-resolution remote sensing offers the possibility to fill this gap and monitor changes at a small scale. In this contribution, we apply multi-temporal close-range remote sensing to a debris-covered glacier in the Swiss Alps (Zmuttgletscher, Valais, CH). We make use of Unmanned Aerial Vehicle (UAV) surveys equipped with a dual optical-thermal camera together with manual debris excavations and in-situ meteorological data in different years (2020 and 2023). The thermal surveys are calibrated using supraglacial and proglacial lake water temperatures, combined with debris surface temperature measurements. We explore the debris thickness, morphology, and topography evolution of a portion of the glacier, and discuss it in relation to glacier dynamics and debris transport. The work contributes to the understanding of glacier debris evolution, which is often neglected in debris-covered glacier models and global projections.

How to cite: Bramati, G., Hardmeier, F., Adams, J. S., Vieli, A., and Naegeli, K.: Tapping the potential of multi-temporal thermal infrared UAV over a debris-covered glacier , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9700, https://doi.org/10.5194/egusphere-egu24-9700, 2024.

Direct glaciological measurements are an important dataset of glacier mass balances but remain concentrated on a small number of glaciers. On hydrological years 2019/20 and 2020/21, 318 annual mass-balance observations were compiled based on 169 glaciers worldwide (Zemp et al., 2023). On the other hand, the current climate crisis now requires a description of cryosphere evolution at a larger scale by quantifying annual snow and ice losses on a larger number of glaciers.

A relevant attempt to fill this gap has been provided by Huggonet et al. (2021) where a global dataset of mass balances at a glacier scale have been generated from 2000 to 2020. While being an extremely valuable glacier mass balance dataset, it is limited to provide mass balance estimation with a time scale longer than 5 years, i.e. annual mass balances cannot be considered reliable.

On the other side, the equilibrium line altitude (ELA) method (Rabatel et al., 2016) have been proven to be an effective approach to reconstruct annual glacier mass balance time series as soon as annual estimation of ELA from satellite multispectral images (e.g. Landsat, Sentinel-2) and at least two digital terrain models (DTMs) acquired at different years are available. Typically, highly accurate DTMs (e.g. airborne LiDAR or photogrammetric DTMs), which are only available on a regional scale base, have been employed within the ELA method.

The main objective of this work is to test the ELA method using as input: 1) Landsat and Sentinel-2 estimation of ELA and 2) ASTER DTMs (Hugonnet et al., 2021). In this way, annual mass balances can be retrieved using satellite data only.

We initially tested this approach over the glaciers in Trentino and South Tyrol where seven glaciers have been monitored through glaciological measurements and different airborne DTMs have been acquired during the last 20 years. Our results show that the use of the ELA method with high resolution airborne DTMs can produce mass balance estimations characterized by an error around 0.3 m w.e. with respect to ground measurements. This error value is in line with estimations conducted with the same method in other regions (e.g. Rabatel et al., 2016) and it is in the error range of ground based measurements. The use of ASTER-based 5 years DTM differences as input of the ELA method can produce estimations with a similar error range. Therefore, the combination of ASTER DTM and ELA extracted from Landsat or Sentinel-2 images may be an interesting approach to produce accurate annual mass balance estimations for many glaciers in the world.

 

References :

Hugonnet, R. et al. (2021). Accelerated global glacier mass loss in the early twenty-first century. Nature 592, 726–731

Rabatel, A. et al. (2016). Spatio-temporal changes in glacier-wide mass balance quantified by optical remote sensing on 30 glaciers in the French Alps for the period 1983–2014. Journal of Glaciology62(236), 1153-1166.

Zemp, M. et al. (2023). Global Glacier Change Bulletin No. 5 (2020-2021). WGMS.

How to cite: Casarotto, C. and Callegari, M.: Annual glacier mass balance estimation through ASTER DTMs and snowlines extracted from Landsat and Sentinel-2 images, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9745, https://doi.org/10.5194/egusphere-egu24-9745, 2024.

EGU24-10176 | ECS | Orals | CR5.2

Glacier Monitoring Using GEDI Data in Google Earth Engine: Outlier Removal and Accuracy Assessment 

Alireza Hamoudzadeh, Roberta Ravanelli, and Mattia Crespi

Climate change has notably altered the elevation of mountain glaciers, particularly in alpine regions. Alpine glaciers play a pivotal role not only as indicators of climate change but also as crucial elements for human and wildlife well-being, regulating freshwater supply and providing vital habitats in Europe. Consequently, continuous monitoring of these glaciers offers valuable insights into their changing structure and surface dynamics [1].

 

While Unmanned Aerial Vehicles (UAV) offer the most precise method for tracking glacier surface changes, their practicality is often hindered by cost limitations and challenging in-situ measurements in extreme weather or remote areas. Therefore, remote sensing and satellite altimetry emerge as a feasible alternative in such scenarios.

 

Numerous LiDAR and RADAR altimetry sensors, such as Jason-2 and 3, CryoSat, and ICESat-1 and 2, have been employed. However, the Global Ecosystem Dynamics Investigation (GEDI), a reliable source of altimetry data, has been overlooked due to its restricted latitude range of 51.6 and -51.6 [2]. GEDI has proven its efficacy in measuring forest and canopy top height, monitoring lakes and water resources and generating Digital Surface Models (DSM).

 

Google Earth Engine (GEE), a cloud-based platform renowned for its ability to integrate diverse datasets and potent analytical tools, has recently incorporated GEDI into its extensive repository [3].

Our initial analysis aims to assess the accuracy of GEDI data for glacier monitoring. Firstly, we focus on detecting and eliminating outliers. Secondly, we compare the glacier levels obtained from GEDI with reference ground truth. Thus, we've chosen the Rutor and Belvedere glaciers in Northern Italy, where we have access to reference-level measurements from UAV DEMs.

 

The proposed outlier detection consists of two steps for each GEDI passage over the glacier surface.
The first step relies on quality surface flags available within GEDI bands, In the subsequent phase, the outlier removal process was refined by employing the x-means algorithm, an unsupervised classifier available within GEE. This approach facilitated the identification and elimination of outliers within the GEDI data set, contributing to refining the dataset's accuracy for comparative analysis with the reference ground truth.

After the above-mentioned outlier removals, we obtained a median difference of -0.27m and NMAD of 4.9 m for Rutor Glacier in 2021 from more than 500 footprints, whereas for Belvedere a median difference of -0.43 and NMAD of 3.7m were obtained. These underestimated values might be due to the nearly 2-month difference between the DEM and the GEDI acquisitions.

 

[1] Belloni, V., et al. (2023). High-resolution high-accuracy orthophoto map and digital surface model of Forni Glacier tongue (Central Italian Alps) from UAV photogrammetry. Journal of Maps, 19(1), 2217508.

[2] Hamoudzadeh, A., et al.: Gedi Data Within Google Earth Engine: Potentials And Analysis For Inland Surface Water Monitoring, EGU General Assembly 2023, Vienna, Austria, EGU23-15083

 

[3] Hamoudzadeh, A., et al. (2023). GEDI data within google earth engine: preliminary analysis of a resource for inland surface water monitoring. In The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences.

How to cite: Hamoudzadeh, A., Ravanelli, R., and Crespi, M.: Glacier Monitoring Using GEDI Data in Google Earth Engine: Outlier Removal and Accuracy Assessment, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10176, https://doi.org/10.5194/egusphere-egu24-10176, 2024.

EGU24-10439 | Posters on site | CR5.2

The Laki Eruption – studying Weather and Climate during the Little Ice Age with Paleo-Reanalysis 

Jörg Franke, Andrew Friedman, Noemi Imfeld, and Stefan Brönnimann

The assimilation of early instrumental, documentary, and proxy data into model simulations allows the study of multivariate climate variability from monthly to centennial time scales. The strength of our paleo-reanalysis ModE-RA (Modern Era Reanalysis) lies specifically in the period of the Little Ice Age because the number of assimilated values per year increases from hundreds in the 17th century to thousands in the 18th century to tens of thousands in the 19th century. In addition, recent efforts of weather reconstruction based on early instrumental data even allow for European reconstructions at daily time scales back into the 18th century.

Here, we present a case study of the global climate and European weather anomalies following the Laki eruption in 1783. Most reports have been limited to the European domain and described an unexpectedly warm summer of 1783 and extremely cold winters in the three following years. Our weather reconstruction and ModE-RA support recent model simulations which suggested atmospheric blocking to be the cause of the unexpected warm anomalies in Europe. However, the entire summer of 1783 was not hot, but only a relatively short period in June and July. On the northern hemisphere scale, we find an aerosol-induced cooling. African and Indian Monsoon rainfall is reduced due to a weaker land-sea temperature gradient in line with the response to strong tropical eruptions and an interhemispheric temperature contrast in line with the response to strong extratropical eruptions. In contrast to recent simulations of the Laki eruption, ModE-RA shows a clear boreal winter warming at high latitudes, slightly dampening the hemispheric-scale cooling signal. In the future, monthly paleo-reanalysis or even daily weather reconstructions could be used to drive models of Little Ice Age glacier dynamics.

How to cite: Franke, J., Friedman, A., Imfeld, N., and Brönnimann, S.: The Laki Eruption – studying Weather and Climate during the Little Ice Age with Paleo-Reanalysis, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10439, https://doi.org/10.5194/egusphere-egu24-10439, 2024.

EGU24-11248 | ECS | Orals | CR5.2

A new inventory of High Mountain Asia surging glaciers derived from multiple elevation datasets since the 1970s 

Lei Guo, Jia Li, Amaury Dehecq, Zhiwei Li, Xin Li, and Jianjun Zhu

Glacier surging is an unusual instability of ice flow, and inventories of surging glaciers are important for regional glacier mass balance studies and glacier dynamic studies. Glacier surges in High Mountain Asia (HMA) have been widely reported. However, the completeness of available inventories of HMA surging glaciers is hampered by the insufficient spatial and temporal coverage of glacier change observations or by the limitations of the identification methods. In this project, we established a new inventory of HMA surging glaciers based on glacier surface elevation changes and morphological changes over four decades. Three elevation change observations based on four elevation sources (the KH-9 DEM, NASA DEM, COP30 DEM, and HMA DEM), three publicly released datasets, and long-term Landsat satellite image series were utilized to assess the presence of typical surging features over two time periods (1970s–2000 and 2000–2020). Through a multi-criteria and cross-validation workflow, all surging glaciers within HMA were identified and indicated with different possibility of surging. Particular efforts were taken to exclude advancing glaciers and separate surging tributaries from glacier complexes. In total, 890 surging and 336 probably or possibly surging glaciers were identified in HMA. Compared to the most recent inventory of surging glaciers in HMA, our inventory incorporated 253 previously unidentified surging glaciers, and most of them are quite small glaciers due to the more complete coverage. The number and area of surging glaciers accounted for ∼ 2.49 % (excluding glaciers smaller than 0.4 km2) and ∼ 16.59 % of the total glacier number and glacier area in HMA, respectively. Glacier surges were found in 21 of the 22 subregions of HMA (except for the Dzhungarsky Alatau); however, the density of surging glaciers is highly uneven. Glacier surges occur frequently in the northwestern subregions (e.g., Pamir and Karakoram) but less often in the peripheral subregions. The inventory further shows that surge activity is more likely to occur for glaciers with a larger area, longer length, and wider elevation range. Among glaciers with similar areas, the surging ones usually have steeper slopes than non-surging ones. Finally, we leverage 50 years of multi-temporal glacier mass balance observations to investigate the relationship between glacier surges and mass balance.

How to cite: Guo, L., Li, J., Dehecq, A., Li, Z., Li, X., and Zhu, J.: A new inventory of High Mountain Asia surging glaciers derived from multiple elevation datasets since the 1970s, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11248, https://doi.org/10.5194/egusphere-egu24-11248, 2024.

EGU24-12440 | Posters on site | CR5.2

Integration of historical glacier images into the Euro-Climhist database 

Christian Rohr, Samuel U. Nussbaumer, Céline Walker, Corina Haller, Tamara T. Widmer, Matthias Fries, Lukas Würsch, and Heinz Zumbühl

Glaciers are excellent climate indicators, and the worldwide glacier retreat serves as a warning signal for the current climate change with its dramatic effects on humans and the environment. Visualizing glacier change by means of images can reach a broad public. Historical glacier images, especially from the so-called Little Ice Age (LIA, approx. AD 1300 to 1850 in the European Alps), show the earlier glacier fluctuations in a particularly impressive way and give us a unique insight into the climatic events of that time. These findings are in turn the key to understand current and possible future climate changes.

The long-term research project "Euro-Climhist" is one of the first projects of its kind worldwide to extract historical documentary data on climate and weather from a wide variety of source types, evaluate the data accordingly, and make it generally accessible in an online database (https://www.euroclimhist.unibe.ch). Until now, the Euro-Climhist database consisted mainly of written sources and measurement data. Within this project, the Euro-Climhist database was conceptually extended to include and secure glacier images in the long term, and to make them accessible to researchers and to the public. Around 500 glacier images were specially prepared for the database and provided with the corresponding metadata, i.e., the name of the artist, the original descriptions as well as supplementary descriptions from the literature, the dating of the images, and the image type. In particular, the assignment to one of five image types - drawing, oil painting, print, photograph, or map - allows conclusions to be drawn about the accuracy of the glacier extents depicted.

Besides written evidence, historical pictorial representations of glaciers allow us to reconstruct glacier extents in the Alps from the early 17th century onwards. Satisfactory quantities of historical material are only available for those glaciers that achieved the necessary degree of fame early on to attract travellers, scientists, and artists. Pictorial representations in painting and graphic arts date back to the early 17th century, but only appear in large numbers with the emerging popularity of Alpine travel during the 18th century. Photographs are available from the end of the 1840s.

How to cite: Rohr, C., Nussbaumer, S. U., Walker, C., Haller, C., Widmer, T. T., Fries, M., Würsch, L., and Zumbühl, H.: Integration of historical glacier images into the Euro-Climhist database, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12440, https://doi.org/10.5194/egusphere-egu24-12440, 2024.

Glaciers play a fundamental role in the Earth’s water cycles. They are one of the most important freshwater resources for societies and ecosystems and the recent increase in ice melt contributes directly to the rise of ocean levels. For this reasons, they have been declared as an Essential Climate Variable (ECV) by the Global Climate Observing System (GCOS). Within the Copernicus Climate Change Services (C3S), the global gridded annual glacier mass change dataset provides information on changing glacier resources for the last five decades by combining the glacier outlines from the globally complete Randolph Glacier Inventory with the mass balance and elevation change observations from the Fluctuation of Glaciers database of the World Glacier Monitoring Service (WGMS).

The glacier change product provides a global assessment of annual glacier mass change and related uncertainties (in m w.e. and Gt) and gridded area changes (km2)  since the hydrological year 1975/76 to present, provided in a 0.5°x0.5° (latitude-longitude) global regular grid and in netcdf file format. The new product bridges the gap on spatio-temporal coverage of glacier change observations, providing for the first time in the CDS an annually resolved glacier mass change product using the glacier elevation change sample as calibration. This goal has become feasible at the global scale only recently and thanks to a new globally near-complete (96% of the world’s glaciers) dataset of glacier elevation changes between 2000 and 2020.

The global gridded annual glacier mass change product integrates nicely into the family of the gridded ECV products provided by the C3S CDS. It provides new insights into regional to global glacier mass changes and, hence, has a great potential for contributing to the various state of the climate reports as well as to assessments of the global sea-level budget, the global energy cycle or the global water cycle. Continuation and expansion of the glaciological in-situ observation network is essential for providing the temporal variability of the glacier mass change product. Ensuring the continuation of open source spaceborne datasets with extensive acquisitions tasking planned over glaciated regions is crucial for ensuring the good quality of future glacier products, and one of the greatest gaps in the quality and continuation of the glacier services delivered to C3S.

How to cite: Dussaillant, I., Bannwart, J., Paul, F., and Zemp, M.: Glacier mass change gridded data from 1976 to present derived from the Fluctuations of Glaciers Database - A new product in the Copernicus Service Climate Data Store, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13856, https://doi.org/10.5194/egusphere-egu24-13856, 2024.

EGU24-14469 | ECS | Posters virtual | CR5.2

Evolution of the covered glaciers in the Cordillera Blanca during the period 1962 - 2020 

Yadira Curo, Juan de Dios Fernandez, Gladis Celmi, Danny Robles, and Mayra Mejia

Glacier dynamics and the effects of climate change accelerate bedrock erosion and instability of the surrounding topography, causing clean glaciers to be gradually covered by debris, particularly in the ablation zones. While the area of glaciers covered worldwide is increasing, there are few studies on this phenomenon in tropical glaciers and its possible significant effects on glacier melt. In this context, this study analyzes the spatio-temporal evolution of the area of glaciers covered by debris in the Cordillera Blanca from 1962 to 2020. 

To achieve this aim, we used data from the Peruvian National Glacier Inventory for 1962 and 2020. We also identify the covered glaciers through the photo-interpretation of geomorphological features, such as the color and texture of the ground surface, the presence of thermokarst zones, and the formation of small lakes/lagoons observed in the satellite images. In addition, we got the topographic features from the ALOS PALSAR digital elevation model.

The outcomes of this investigation reveal an increase in the number and surface area of glaciers covered, from 33 units (15.41 km2) in 1962 to 173 units (23.06 km2) in 2020. This shows an increase of 49.64% from the glacier area covered by debris. The increase in covered glaciers in the Cordillera Blanca could be because many glaciers identified as debris-free in 1962 were partially or totally covered in 2020; 17.13 km2 of the glacier debris-free area was covered by debris during this period. It has been observed that 93% of the area covered by debris is on slopes greater than 8°. Of these, 25% were in the 24° - 33° range, and 23% were on steeper slopes than 33°. The orientation analysis indicates a predominance of surface covered towards the southwest and south.

Likewise, the areas of glacier retreat covered between 1962 and 2020 were analyzed, identifying 9.45 km2 of glacier surface loss. 18% of the loss areas are on slopes steeper than 8º, mainly from 8º to 17º slope, where 28% of the loss area is located. Meanwhile, a clear retreat trend is observed in those areas with a north orientation of 95% and a northeast orientation of 5%.

These findings suggest a possible association between the higher magnitude slope conditions and the formation of covered glaciers, while the orientation influences the retreat of these glaciers.

How to cite: Curo, Y., Fernandez, J. D. D., Celmi, G., Robles, D., and Mejia, M.: Evolution of the covered glaciers in the Cordillera Blanca during the period 1962 - 2020, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14469, https://doi.org/10.5194/egusphere-egu24-14469, 2024.

This paper presents a dendroglaciological study of Hailuogou Glacier, a maritime glacier in Hengduan Mountains, southwest China. We used tree-ring data collected from the glacier forefield, including buried wood and oldest living trees on moraine ridges, to reconstruct the glacier fluctuations during the past six centuries. The tree-ring data were combined with radiocarbon dating and remote sensing interpretation to determine the ages of moraine ridges and glacial deposits. The results show that Hailuogou Glacier experienced five equilibrium stages since the Little Ice Age, with the most extensive advance around 1760s AD and the most rapid retreat since the 20th century. The glacier fluctuations were compared with temperature and precipitation reconstructions from nearby regions, and the response relationship between the glacier and climate change was discussed. The paper demonstrates the potential of dendroglaciology to provide high-resolution records of maritime glacier history and its link to climate change in the Tibetan Plateau. The paper also contributes to the better understanding of the long-term relationship between the fluctuation of maritime glaciers and climate change, and provides a scientific basis and basic data for the prediction of glacier change under the future climate change scenario.

How to cite: Zhu, H., Xu, P., and Zhu, X.:  Hailuogou Glacier activities during the past six centuries inferred from tree rings and 14C dating, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15154, https://doi.org/10.5194/egusphere-egu24-15154, 2024.

EGU24-15640 | Posters on site | CR5.2

Establishing glacier proximal meteorological and glacier ablation stations in different climatic zones along the South American Andes. 

Owen King, Tom Matthews, Marcos Andrade, Juan-Luis Garcia, Claudio Bravo, Wouter Buytaert, Juan Marcos Calle, Alejandro Dussaillant, Tamsin Edwards, Iñigo Irarrazaval, Baker Perry, Emily Potter, Laura Ticona, Bethan Davies, and Jeremy Ely

Climate change has had a significant impact on the behaviour of the high mountain cryosphere, with widespread glacier retreat and mass loss now occurring in most of the planet’s glacierised mountain ranges over multi-decadal timescales. If we are to accurately understand the impacts of deglaciation on freshwater availability to communities downstream, robust modelling of future glacier meltwater yield is paramount. Meteorological observations at glacierised elevations are essential to drive simulations of the energy balance at glacier surfaces, and therefore glacier melt, although such records are sparse in most high mountain regions due to the logistical challenges associated with making even short-term measurements. The scarcity of high-altitude meteorological observations has resulted in only limited understanding of factors such as the spatial and temporal variability of temperature lapse rates, precipitation amounts and phase, and the prevalence of conditions suited to sublimation, all of which have an important influence on glacier mass loss rates at high elevation.

Here we summarise the installation of meteorological and glacier ablation stations in different climatic zones of the South American Andes - the Tropical Andes of Peru (Nevado Ausangate basecamp, 4800 m, (13°48'45.96"S, 71°12'53.18"W) and Bolivia (Laguna Glaciar, 5300 m, 15°50'10.59"S, 68°33'11.30"W), the Subtropical Andes (Glaciar Universidad, Chile, 2540 m, 34°43'10.07"S, 70°20'44.98"W) and Patagonian Andes (Lago Tranquillo, Chile, 280 m, 46°35'47.00"S, 72°47'38.91"W) – as part of the NERC-funded Deplete and Retreat Project. Meteorological station records include time series of air temperature and pressure, relative humidity, wind speed and direction, incoming and outgoing short- and longwave radiation, precipitation amount and phase. Coincident glacier ablation is monitored at each site using ‘Smart Stakes’, recording surface elevation change on-glacier. We describe station situation, installation and preliminary measurements, along with aims and objectives of analyses using the meteorological time series.

How to cite: King, O., Matthews, T., Andrade, M., Garcia, J.-L., Bravo, C., Buytaert, W., Calle, J. M., Dussaillant, A., Edwards, T., Irarrazaval, I., Perry, B., Potter, E., Ticona, L., Davies, B., and Ely, J.: Establishing glacier proximal meteorological and glacier ablation stations in different climatic zones along the South American Andes., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15640, https://doi.org/10.5194/egusphere-egu24-15640, 2024.

EGU24-15934 | Orals | CR5.2 | Highlight

The pulse of the Pamirs: using remote sensing and in situ data to investigate accelerating glacier mass loss in the Pamirs 

Evan Miles, Thomas Shaw, Shaoting Ren, Martina Barandun, Dilara Kim, Haruki Hagiwara, Sultan Belekov, Marlene Kronenberg, Eric Pohl, Joel Fiddes, Achille Jouberton, Stefan Fugger, Tomas Saks, Abdulhamid Kayumov, Martin Hoelzle, and Francesca Pellicciotti

In situ and satellite observations have unambiguously indicated the hastening rate of global glacier decay over the past two decades. In the region affected by the Karakoram Anomaly, however, the near-zero mass change and relatively high uncertainty from satellite observations combine with complex glacier dynamics to make glacier mass balances difficult to interpret, yet very few direct observations are available to confirm glacier mass changes. A pressing question for this region is therefore whether this glacier mass stability has already ended, or how long it will persist. Our observations over the past several years in the Pamir mountains, located on the periphery of this anomalous zone, have highlighted glaciers suffering from small accumulation areas at the end of the balance year, due to a combination of reduced winter snowfall and increased summer melt. In this study, we draw together a variety of field and remote sensing observations to assess the severity of Pamir glacier changes in recent years as compared to the historical baseline.

We first examine historic climatic records and reanalyses from the region to examine the degree to which recent years fit within the observed historic seasonal and annual ranges. We compare the recent period to historic in situ and remote sensing glacier mass balance measurements recorded at Abramov Glacier, the single long-term monitoring reference glacier for the region, and to the historic network of Soviet meteorological measurements. We then consider regional changes to glacier surface albedo and surface temperature over the past 23 years based on satellite measurements. Taken together, these data sources enable us to link direct meteorological and glaciological conditions to broad spatial and temporal patterns of change across the Pamir mountains.

Our results highlight progressively worsening conditions for glaciers since 2000, as indicated by warming air temperatures, decreasing precipitation, and decreasing albedo. 2021 and 2022 were likely the worst two years for glaciers at the regional scale, experiencing the hottest air temperatures and land surface temperatures in the 21st century, but poor conditions also occurred in 2006-2008. Our results highlight that Pamir surface albedos in these years were the lowest of the 21st century, excepting in the East Pamir, which also shows the least negative mass balances and the most moderated climatic changes. 

Satellite albedo and thinning measurements agree with both reanalysis data and in situ measurements at Abramov Glacier that mass losses have accelerated. However, historic glaciological measurements at Abramov and regional meteorological stations both highlight that similar periods in terms of hot air temperatures, low precipitation and rapid glacier mass loss occurred in the 1970s, and likely the 1940s, across much of the Pamirs.  Consequently, although observations and projections suggest trends towards hotter and drier conditions with increased mass loss, it may be too soon to draw the curtains on the 40-year mass stability of the Karakoram Anomaly.

How to cite: Miles, E., Shaw, T., Ren, S., Barandun, M., Kim, D., Hagiwara, H., Belekov, S., Kronenberg, M., Pohl, E., Fiddes, J., Jouberton, A., Fugger, S., Saks, T., Kayumov, A., Hoelzle, M., and Pellicciotti, F.: The pulse of the Pamirs: using remote sensing and in situ data to investigate accelerating glacier mass loss in the Pamirs, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15934, https://doi.org/10.5194/egusphere-egu24-15934, 2024.

EGU24-19324 | ECS | Posters on site | CR5.2

An improved dataset of ASTER elevation time series in High Mountain Asia to study surge dynamics 

Luc Béraud, Fanny Brun, Amaury Dehecq, Laurane Charrier, and Romain Hugonnet

Some glaciers display flow instabilities, among which surge events particularly stand out. Surges are quasi-periodic flow perturbations with an abnormally fast flow over a few months to years. It can result in surface elevation changes of more than 100 m in a few months.

The estimation of the mass transfer and the flow variation can be inferred from the glacier surface elevation and velocities. It is critical data to better understand the dynamics of a surge. While satellite-based DEMs provide useful information for studying surges, their use in previous studies was generally limited to a few DEM differences extending over periods of several years. To date, very few studies have leveraged the full time series of elevation data available since ~2000 which could help quantify the variations of mass transfer during the very short surge phases.

Here, we exploited the high temporal and spatial coverage of the ASTER optical satellite sensor to compute a dense time series of elevation suited for the study of surges. Our case study area is the Karakoram range, in High Mountain Asia. We used non-filtered ASTER digital elevation models (DEMs) of 100 m resolution from Hugonnet et al. (2021). The time series range from about 2001 to 2019, with a median of 56 observations per on-glacier pixel over the whole period. We developed a specific method for filtering the elevation time series that preserves surge signals, as opposed to the original method that tends to reject this behaviour as outliers. A LOWESS method – locally weighted polynomial regression (Derkacheva et al., 2020; Cleveland, 1979) is at the core of this workflow. Then, we predicted the elevation over a regular temporal and spatial grid from filtered data, with the B-spline method ALPS-REML (Shekhar et al., 2021).

In this presentation, we will present the results of this method applied to more than 1000 DEMs covering the Karakoram region to derive elevation time series at 100 m resolution. The filter and the prediction performances will be discussed. The results will be compared with those of other studies, in terms of surge onset and end dates, location or volume transported. Finally, the  elevation data set will be analysed with regard to velocities extracted from ITS_LIVE (Gardner et al., 2024) to validate the approach and highlight the complementarity of both types of observations.

How to cite: Béraud, L., Brun, F., Dehecq, A., Charrier, L., and Hugonnet, R.: An improved dataset of ASTER elevation time series in High Mountain Asia to study surge dynamics, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19324, https://doi.org/10.5194/egusphere-egu24-19324, 2024.

EGU24-154 | ECS | Orals | CR5.3

High-Resolution UAV Hyperspectral Imagery for Antarctic Research 

Alejandro Roman, Antonio Tovar-Sánchez, Beatriz Fernández-Marín, Gabriel Navarro, and Luis Barbero

Unmanned Aerial Vehicles (UAVs) have emerged as a promising tool, providing exciting opportunities for Antarctic research. They constitute a non-invasive, repeatable, affordable, and time-efficient alternative to address the observational gap between satellite imagery and ground-based techniques. Additionally, they provide an unparalleled advantage for collecting data in remote and difficult-to-access regions, as is the case of a significant portion of the cryosphere. In the last few years, a rising number of studies have used a wide variety of multispectral sensors mounted on UAVs to describe vegetated areas, monitor penguin colonies, or detect changes on Antarctic terrestrial ecosystems. The recent development of new hyperspectral (HS) sensors adapted to UAV platforms has enhanced the characterization of such heterogeneous ecosystems, combining an unprecedented scale in spectral and spatial resolutions for better discrimination in smaller and sparser areas within the Antarctic ecosystem. In this work, we demonstrate the potential of the synergy between HS technology and UAV imagery to address important and diverse ecological issues on Antarctic environments, including the spectral characterization of penguin colony ecosystems and the detection of massive snow algae blooms on glacial formations. Furthermore, this methodology has been validated using in-situ spectroradiometry and has been applied in conjunction with other remote sensing techniques, such as UAV-based multispectral technology and satellite imagery, to cover broader regions in a climate change context.

How to cite: Roman, A., Tovar-Sánchez, A., Fernández-Marín, B., Navarro, G., and Barbero, L.: High-Resolution UAV Hyperspectral Imagery for Antarctic Research, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-154, https://doi.org/10.5194/egusphere-egu24-154, 2024.

EGU24-831 | ECS | Posters on site | CR5.3

Processing Pipeline for Computing Time Series of 3D Glacier Surface Flow and Mass Balance 

Ayush Gupta, Balaji Devaraju, and Ashutosh Tiwari

To comprehend glacier dynamics for a region, a time-series study of glacier change is essential. Existing research often relies exclusively on glacier mass balance or surface displacements to understand how glaciers adapt to a warming climate. Moreover, the generation of large time series data often requires a substantial amount of computation and time. We address these limitations by building an efficient open-source pipeline for the mass processing of satellite images, generating extensive time series data for tracking glacier changes. This pipeline employs Sentinel-1 (S-1) interferometric wide swath SAR data to produce seasonal time series of glacier surface displacements and annual time series of glacier mass balance over prolonged durations. Our processing chain utilizes the ISCE framework for SAR data processing and autoRIFT software for performing offset tracking. It combines both ascending and descending S-1 images and utilizes offset tracking to compute displacements in both azimuthal and range directions. These estimates are then fine-tuned through the use of OT-SBAS. Our pipeline computes northward, eastward, and vertical flow velocities through weighted least squares, with weights designed to make the model more robust. Furthermore, it employs a machine-learning algorithm for pixel-wise segmentation of glaciers using optical data, facilitating the computation of areal changes in glaciers. The derived vertical and areal changes are then leveraged to compute glacier mass balance. Three valley-type glaciers (Bara Shigri, Chota Shigri, and Samudra Tapu) located in the Chandra basin, Himachal Himalaya, were selected to test out the proposed pipeline. The 3D surface displacement and mass balance time series were retrieved from 2017 to 2022. This software can be employed to monitor glaciers through the analysis of frequent revisit SAR data obtained from satellites like Sentinel-1 and the upcoming NISAR. 

How to cite: Gupta, A., Devaraju, B., and Tiwari, A.: Processing Pipeline for Computing Time Series of 3D Glacier Surface Flow and Mass Balance, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-831, https://doi.org/10.5194/egusphere-egu24-831, 2024.

EGU24-1365 | ECS | Orals | CR5.3

ARTS: a scalable data set for Arctic Retrogressive Thaw Slumps 

Yili Yang, Heidi Rodenhizer, Brendan M. Rogers, Jacqueline Dean, Ridhima Singh, Tiffany Windholz, Amanda Poston, Stefano Potter, Scott Zolkos, Greg Fiske, Jennifer Watts, Lingcao Huang, Chandi Witharana, Ingmar Nitze, Nina Nesterova, Sophia Barth, Guido Grosse, Trevor Lantz, Alexandra Runge, and Luigi Lombardo and the coauthors

Retrogressive thaw slumps (RTS) are one of the most rapid abrupt thaw events that have a positive feedback on climate warming. RTS are not yet well understood because of the lack of geospatial products describing abrupt thaw distribution and changes over time in the Arctic. Although many standalone RTS digitisation data sets have been archived, it is challenging to find, access and pool the existing data sets into a comprehensive and unified one due to the lack of common data curation standards. Therefore we collected the existing RTS digitisation data sets known to date and compiled them into a scalable and uniform data set - Arctic Retrogressive Thaw Slumps (ARTS). Besides, we developed an RTS data curation framework, which provides guidelines for RTS remote sensing data digitisation, metadata formatting, RTS indexing, storage format, contribution guidelines and more. So far the ARTS data set contains around 24,000 RTS digitisations and 3,300 non-RTS background labels. This data set will empower a wide range of Arctic studies, especially beneficial for deep learning studies that are highly data-intensive.

How to cite: Yang, Y., Rodenhizer, H., Rogers, B. M., Dean, J., Singh, R., Windholz, T., Poston, A., Potter, S., Zolkos, S., Fiske, G., Watts, J., Huang, L., Witharana, C., Nitze, I., Nesterova, N., Barth, S., Grosse, G., Lantz, T., Runge, A., and Lombardo, L. and the coauthors: ARTS: a scalable data set for Arctic Retrogressive Thaw Slumps, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1365, https://doi.org/10.5194/egusphere-egu24-1365, 2024.

EGU24-1563 | ECS | Posters on site | CR5.3

Investigating short-term glacial velocity variations in High Mountain Asia using remote sensing  

Francesca Baldacchino and Tobias Bolch

Glacier flow is a sensitive indicator of mass balance and dynamics. Monitoring changes in glacier flow at high temporal resolutions enables understanding of the glacier’s sensitivity to short-term climate variability. We focus on different regions across High Mountain Asia (HMA) where glaciers have different average velocities (slow, median, and fast). HMA has the largest glacier coverage outside the polar regions and is considered the water tower of Asia. Previous studies have found that the glaciers in HMA are in tendency slowing down concomitant to losing mass at an accelerating rate. We use both optical and SAR remote sensing data including Sentinel-1 and -2, Planet and Pléiades images to present multiple remotely sensed calculated glacial velocities for the different regions of HMA over the last decade. We calculate the velocity variations using different tracking methods. By analysing the accuracy of the velocity variations through validation with the higher spatial resolution Pleiades velocity dataset and field data as well as using statistical techniques such as the GLAcier Feature Tracking testkit (Zheng et al., 2023), we provide insights into the accuracy of the different remote sensing data and tracking methods. Finally, we explore possible internal and external drivers of the observed glacial velocity variations, with a focus on mass balance and short-term climate variability.

Zheng, W., Bhushan, S., Van Wyk De Vries, M., Kochtitzky, W., Shean, D., Copland, L., Dow, C., Jones-Ivey, R., and Pérez, F.: GLAcier Feature Tracking testkit (GLAFT): a statistically and physically based framework for evaluating glacier velocity products derived from optical satellite image feature tracking, The Cryosphere, 17, 4063–4078, https://doi.org/10.5194/tc-17-4063-2023, 2023.

How to cite: Baldacchino, F. and Bolch, T.: Investigating short-term glacial velocity variations in High Mountain Asia using remote sensing , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1563, https://doi.org/10.5194/egusphere-egu24-1563, 2024.

EGU24-2200 | ECS | Orals | CR5.3

A Temporal Study of the Proglacial Lakes Surrounding Múlajökull Outlet Glacier, Iceland Between 1987 and 2021. 

Natasha Lee, Andrew Shepherd, Emily Hill, and Rachel Carr

Proglacial lakes often form due to the availability of meltwater at a glacier margin. The greatest increase in proglacial lake area and volume is currently occurring in the Arctic. This research quantified the annual change and seasonal variations in proglacial lake area and colour of Múlajökull outlet glacier southeast Hofsjökull. The Normalised Difference Water Index is used to calculate the annual and seasonal area of proglacial lakes between 1987 and 2021 in Google Earth Engine. As the terminus of Múlajökull has retreated, the number and area of proglacial lakes has increased. This has been most noticeable after the year 2000 following which, the glacier terminus retreated up to 400m. Results from this study have shown a retreat of Múlajökull terminus caused increase in area of proglacial lakes. Between 1987 and 2021 an increase in proglacial lake area from 0.16 km2 to 1.27 km2 was observed and the glacier terminus retreated by 700m. In addition to this, spatial and temporal variation of proglacial colour was observed between 1987 and 2021. The results of this study will provide greater insight into the annual and seasonal changes in the proglacial lake area and colour of Múlajökull outlet glacier.

How to cite: Lee, N., Shepherd, A., Hill, E., and Carr, R.: A Temporal Study of the Proglacial Lakes Surrounding Múlajökull Outlet Glacier, Iceland Between 1987 and 2021., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2200, https://doi.org/10.5194/egusphere-egu24-2200, 2024.

EGU24-2353 | ECS | Orals | CR5.3

Automated glacier extraction using a Transformer based deep learning approach from multi-sensor remote sensing imagery 

Yanfei Peng, Jiang He, Qiangqiang Yuan, Shouxing Wang, Xinde Chu, and Liangpei Zhang

Glaciers serve as sensitive indicators of climate change, making accurate glacier boundary delineation crucial for understanding their response to environmental and local factors. However, traditional semi-automatic remote sensing methods for glacier extraction lack precision and fail to fully leverage multi-source data. In this study, we propose a Transformer-based deep learning approach to address these limitations. Our method employs a U-Net architecture with a Local-Global Transformer (LGT) encoder and multiple Local-Global CNN Blocks (LGCB) in the decoder. The model design aims to integrate both global and local information. Training data for the model were generated using Sentinel-1 Synthetic Aperture Radar (SAR) data, Sentinel-2 multispectral data, High Mountain Asia (HMA) Digital Elevation Model (DEM), and Shuttle Radar Topography Mission(SRTM) DEM. The ground truth was obtained for a glaciated area of 1498.06 km2 in the Qilian mountains using classic band ratio and manual delineation based on 2 m resolution GaoFen (GF) imagery. A series of experiments including the comparison between different models, model modules and data combinations were conducted to evaluate the model accuracy. The best overall accuracy achieved was 0.972. Additionally, our findings highlight the significant contribution of Sentinel-2 data to glacier extraction.

How to cite: Peng, Y., He, J., Yuan, Q., Wang, S., Chu, X., and Zhang, L.: Automated glacier extraction using a Transformer based deep learning approach from multi-sensor remote sensing imagery, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2353, https://doi.org/10.5194/egusphere-egu24-2353, 2024.

EGU24-5136 | Orals | CR5.3

PRODEM: An annual series of summer DEMs (2019-2023) for the marginal areas of the Greenland Ice Sheet 

Mai Winstrup, Heidi Ranndal, Signe H. Larsen, Sebastian B. Simonsen, Kenneth D. Mankoff, Robert S. Fausto, and Louise S. Sørensen

Surface topography within the marginal zone of the Greenland Ice Sheet continually evolves in response to varying weather, season, climate and ice dynamics. However, existing ice sheet Digital Elevation Models (DEMs) usually rely on multi-year data, obscuring these changes over time. We have here developed an annual series (2019-2023) of summer DEMs in 500m resolution for the Greenland ice sheet marginal zone, referred to as PRODEMs. Encompassing all outlet glaciers from the Greenland ice sheet, these PRODEMs result from fusing CryoSat-2 radar altimetry and ICESat-2 laser altimetry using a regionally-varying Kriging method. Validated through leave-one-out cross-validation, they demonstrate accurate representation of surface elevations within the spatially varying prediction uncertainties with a median value of 1.4m.

The PRODEMs capture the recent annual evolution in summer surface topography of all outlet glaciers from the Greenland ice sheet. We observe a general lowering of surface elevations compared to ArcticDEM, but the spatial pattern of change is highly complex and with annual changes superimposed. The PRODEMs offer detailed insights into marginal ice sheet elevation changes, temporally as well as spatially, making them valuable for researchers and users studying ice sheet dynamics under changing environmental conditions.

How to cite: Winstrup, M., Ranndal, H., Larsen, S. H., Simonsen, S. B., Mankoff, K. D., Fausto, R. S., and Sørensen, L. S.: PRODEM: An annual series of summer DEMs (2019-2023) for the marginal areas of the Greenland Ice Sheet, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5136, https://doi.org/10.5194/egusphere-egu24-5136, 2024.

EGU24-6243 | ECS | Orals | CR5.3

Detection of Supraglacial Lakes using Gaofen-3 data and Advanced Attention U-Net 

Di Jiang, Shiyi Li, and Irena Hajnsek

Detecting supraglacial lakes is becoming increasingly crucial in the rising of global warming. Serving as vital indicators of glacier surface runoff storage and loss, these lakes provide significant insights to the understanding of glacier mass balance and global sea-level changes. Synthetic Aperture Radar (SAR) images have been used in numerous automatic detection algorithms due to their unique advantages of being independent from weather and illumination conditions. However, most SAR-based algorithms primarily use SAR backscattering intensities, which limits detection accuracy due to the high sensitivity of backscattering intensities to varying surface dielectric and geometric properties. To address this problem, it becomes essential to incorporate the polarization information to better distinguish different surface properties.

In this work, we introduced an innovative automated lake detection method that integrated a dual-polarization decomposition approach in a deep learning scheme. We enhanced the traditional decomposition method for HH and HV polarizations by segmenting the Stokes vector into fully and partially polarized sections to isolate volume and surface scattering components. The alpha angle, derived through eigenvalue decomposition of the covariance matrix, was further determined to quantify the degree of polarization. Subsequently, the decomposed SAR images were used to train an Attention U-Net deep learning model for lake segmentation. The Atrous Spatial Pyramid Pooling (ASPP) technique was introduced to the Attention U-Net to facilitate end-to-end training with limited datasets. 

The proposed method was applied to the Gaofen-3 dual-polarization SAR imagery over expansive study regions in Greenland. Results indicated that the proposed decomposition approach was effective in detecting lakes in areas of complex surface conditions and discriminating frozen lakes in winter months. The method significantly reduced misidentification and inaccuracy in distinguishing various surface features such as dark ice, blue ice, wet snow, and actual lakes. Compared to existing methods, the proposed method provided improved attention to the finer details, exhibiting higher accuracy in identifying small lakes. More importantly, comprehensive physical interpretations of the data were also provided based on the polarization decomposition, offered valuable insights into the future development of lake detection algorithms.

In summary, this work introduces an effective and innovative methodology combining SAR dual-polarization decomposition and deep learning for accurate supraglacial lake detection. The proposed method shows promising potential for an operational supraglacial lake mapping on a large scale and is expected to provide valuable insights into the understanding of ice sheet and glacier runoff dynamics.

How to cite: Jiang, D., Li, S., and Hajnsek, I.: Detection of Supraglacial Lakes using Gaofen-3 data and Advanced Attention U-Net, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6243, https://doi.org/10.5194/egusphere-egu24-6243, 2024.

EGU24-6327 | ECS | Posters on site | CR5.3

Draining or Refreezing? Investigating Meltwater Lake Evolution through Deep Learning 

Sophie de Roda Husman, Stef Lhermitte, Theofani Psomouli, Meike van Noord, Jonathan Bambler, Xiao Xiang Zhu, and Bert Wouters

Antarctic ice shelves are becoming more vulnerable as a warming atmosphere leads to surface melting and the formation of meltwater lakes. Some meltwater lakes in Antarctica refreeze, but others drain into ice fractures, potentially destabilizing ice shelves and thereby contributing to rising sea levels. Conventional monitoring, using optical satellites, tracks lake changes during a melt season if data is accessible. However, cloud cover in Antarctica limits the use of optical imagery, creating a shortage of useful images and making it challenging to track lake progression. Unlike optical imagery, radar data from sources like Sentinel-1 offers frequent coverage of Antarctic ice shelves, because Sentinel-1 works independently from sun illumination and weather conditions. However, interpreting it is complex due to factors such as looking geometry, polarization, and speckle noise. By training our model on optical imagery from both refreezing and draining lakes—serving as ground truth—we applied a spatiotemporal deep learning technique to extract meaningful information from the Sentinel-1 images. Our results show that the majority of Antarctic meltwater lakes underwent refreezing from 2017 to 2023. However, a significant number of draining lakes were also identified, many of which had not been previously discovered through optical imagery. As the vulnerability of Antarctica's ice shelves intensifies, Sentinel-1's ability to provide insights into surface lake dynamics presents a promising avenue for research, enhancing our understanding of these crucial systems in the context of climate change and sea level rise.

How to cite: de Roda Husman, S., Lhermitte, S., Psomouli, T., van Noord, M., Bambler, J., Zhu, X. X., and Wouters, B.: Draining or Refreezing? Investigating Meltwater Lake Evolution through Deep Learning, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6327, https://doi.org/10.5194/egusphere-egu24-6327, 2024.

EGU24-7048 | Orals | CR5.3

Satellite thermal mapping of the lowest surface temperatures in Greenland 

George Campbell and Theodore Scambos

Inspired by a recent paper on the lowest observed air temperature in the
northern hemisphere (AWS observation near Summit Station; Weidner et al., 2021),
we will composite Aqua MODIS Land Surface Temperatures (LST, data set
MYD11_I2 ver061) over the Greenland Ice Sheet spanning 2003-2023. Our preliminary
analysis shows LST below 200°K with just part of the data processed. or colder
than -100°F. Using the record-setting AWS station data, we estimate the
temperature inversion between the ~2 meter air temperature and the snow surface
to adjust the LST satellite measurements.  Greenland shows a similar gradient in
temperature between LST ‘skin’ temperature and air temperatures as seen in
Antarctica from our earlier research (Scambos et al., 2018).  Lowest
temperatures occur on clear-sky polar nights under calm or nearly calm winds,
in general just to the west and northwest of the ice divide. Maps of LST show
small scale geographic variations that are closely associated with local lows in
topography. We infer that this is a result of cold air pooling and further
chilling of the surface under conditions that maximize radiative heat loss.

How to cite: Campbell, G. and Scambos, T.: Satellite thermal mapping of the lowest surface temperatures in Greenland, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7048, https://doi.org/10.5194/egusphere-egu24-7048, 2024.

EGU24-7973 | Posters on site | CR5.3

Snow Water Equivalent monitoring at the regional level by a Finapp Cosmic Rays Neutron Sensors network 

Barbara Biasuzzi, Enrico Gazzola, Stefano Gianessi, Mauro Valt, Luca Stevanato, Luca Morselli, Federica Lorenzi, and Marcello Lunardon

Cosmic Rays Neutron Sensing (CRNS) is a technology of increasing importance in a variety of fields that can benefit from the ability of directly measure the amount of water in the environment, within a large footprint and in depth. This indeed includes snow, which opened to the possibility to directly quantify the Snow Water Equivalent (mm SWE) within the sensor footprint, using a specialized and properly calibrated CRNS setup.

CRNS is based on the detection of neutrons, particles naturally flowing from space and capable to travel across matter while strongly interacting with water molecules. They therefore carry information about the presence of water in any form, naturally averaging the amount within a footprint up to hectares. When applied to SWE measurement, the approach overcomes crucial hurdles faced by traditional techniques, where additional modelling is needed to derive SWE data from point measurements of the snow height provided by nivometers, or from the remote sensing of snow coverage over large areas by satellites.

Finapp developed a compact and easy to install CRNS probe, suitable for large-scale deployment. Requiring low power supply and minimal maintenance, it can operates autonomously also in remote areas while transmitting the data for a real-time monitoring. As the knowledge of the water content in the snowpack is paramount for a rational management of the resource and also for wider climatological considerations, we aim to the deployment of Finapp networks on mountain ranges to support the critical task of hydrological balance at the basin or regional scale.

The first full nivological network of Finapp probes has been acquired and deployed by the Regional Environmental Protection Agency of Veneto (ARPAV), including them into the ARPAV nivological stations in view of the 2023/2024 winter season. We will present the outcome of the first operational season of the new network, its expected impact and potential developments.

How to cite: Biasuzzi, B., Gazzola, E., Gianessi, S., Valt, M., Stevanato, L., Morselli, L., Lorenzi, F., and Lunardon, M.: Snow Water Equivalent monitoring at the regional level by a Finapp Cosmic Rays Neutron Sensors network, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7973, https://doi.org/10.5194/egusphere-egu24-7973, 2024.

EGU24-8846 | Posters on site | CR5.3

Advancing Alpine Landform Monitoring: AI-Driven Tracking on Hourly Monoscopic Time-Lapse Imagery 

Hanne Hendrickx, Xabier Blanch, Melanie Elias, Reynald Delaloye, and Anette Eltner

Monoscopic webcams or time-lapse cameras in the European Alps capture geomorphic processes with high resolution, proving invaluable for studying periglacial landforms like rock glaciers and permafrost-affected landslides over long time series, spanning decades. This capability becomes more significant when considering the temporal acquisition frequency; often hourly or daily. Despite their utility, managing the vast volume of hourly photographs requires efficient automatic image processing using Artificial Intelligence (AI) techniques.

This research aims to acquire high-quality landform velocities from monoscopic time-lapse cameras, verified by GNSS surveys, using an AI-enhanced particle tracker PIPs++ (Zheng et al., 2023). This model performs well without additional training, swiftly processing consecutive images. The algorithm tracks points without assuming movement direction and in multiple timesteps instead of frame-by-frame. Moreover, the model incorporates a template-update mechanism, allowing for changes in feature appearance, making it more robust in real-world applications. This flexibility accommodates occlusions (e.g., fog), self-occlusion (e.g., deforming boulders), or challenging lighting conditions. Real-world velocities will be derived by scaling images using high-resolution 3D models from UAV or ALS data through an image-to-geometry approach, matching 2D images with synthesized 2.5D images (Elias et al., 2023). While a fully automatic scaling is under development, initial results indicate the need for adjustments to the algorithm by Elias et al. (2023), leading to a semi-automatic workflow.

The approach is tested on a fast-moving landslide (up to 2 m per year) and rock glacier (70 to 100 m per year) at the Grabengufer site (Swiss Alps). The site is extensively monitored, with bi-annual dGNSS surveys, a permanent GNSS installation, and three time-lapse cameras since 2010/2013, covering a landslide, a rock glacier, and a torrent below. A temporal selection of the time-lapse data was made to test our approach, resulting in velocity vectors validated by GNSS measurements. Initial results are promising, demonstrating the model's rapid performance (two min for 400 images, tracking features through a temporal window of 19 frames, on a NVIDIA RTX A6000, with a GPU of 48GB) and tracking through occlusion when encountering fog. Validated by discrete GNSS measurements, our approach enables a spatially more continuous understanding of landform movement, allowing data acquisition where in-situ measurements are not possible due to logistical and safety constraints.

The overall goal of this research is to derive reliable velocity values at high temporal resolution from low-cost monoscopic time-lapse cameras. To achieve this, an open-source workflow will be developed, applicable to research sites where validation data is limited or where other remote sensing monitoring techniques fail due to high landform displacements.

 

Elias, M., Weitkamp, A., & Eltner, A. (2023). Multi-modal image matching to colorize a SLAM based point cloud with arbitrary data from a thermal camera. ISPRS Open Journal of Photogrammetry and Remote Sensing, 9, 100041.

Zheng, Y., Harley, A. W., Shen, B., Wetzstein, G., & Guibas, L. J. (2023). Pointodyssey: A large-scale synthetic dataset for long-term point tracking. In Proceedings of the IEEE/CVF International Conference on Computer Vision (pp. 19855-19865).

How to cite: Hendrickx, H., Blanch, X., Elias, M., Delaloye, R., and Eltner, A.: Advancing Alpine Landform Monitoring: AI-Driven Tracking on Hourly Monoscopic Time-Lapse Imagery, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8846, https://doi.org/10.5194/egusphere-egu24-8846, 2024.

EGU24-9710 | ECS | Orals | CR5.3

Sentinel-1 reveals large variability of dominant scattering in a drifting snow-dominated environment of East Antarctica 

Shashwat Shukla, Bert Wouters, Ghislain Picard, Nander Wever, Maaike Izeboud, Sophie de Roda Husman, Thore Kausch, Sanne Veldhuijsen, Christian Matzler, and Stef Lhermitte

Assessing the Surface Mass Balance (SMB) of the Antarctic Ice Sheet is crucial for understanding its response to climate change. Synthetic Aperture Radar (SAR) observations from Sentinel-1 provide a potential to monitor the variability of SMB processes through changes in the scattering response of near-surface layers and internal snow layers. However, the interplay between accumulation, wind erosion, deposition and melt is complex, thereby complicating the interpretation of the changes in scattering of the microwave signal. Additionally, the lack of reliable ground truth measurements of snow surface limits our capability to relate the SMB processes to the dominant scattering processes. In this study, we focus on understanding how the surface processes relate to the changes in the dominant scattering mechanism from Sentinel-1 in a drifting snow-dominated region of East Antarctica. We introduce a new parameter, alpha_scat, derived from scattering-type and scattering entropy descriptors from Sentinel-1 SAR observations. This parameter quantifies the continuous scattering response from near-surface layers (i.e., pure scattering) and from internal snow layers (i.e., volume scattering). The changes in alpha_scat are evaluated from the repeated in-situ surface measurements acquired during Mass2Ant field campaigns. These measurements include roughness and accumulation derived from a terrestrial laser scanner, and surface densities from SnowMicroPen. At the field-scale, our analysis shows a strong correlation between surface roughness and alpha_scat (R-squared value of 0.99), thereby indicating the role of roughness on the dominant scattering mechanism. During periods associated with erosion, the vertical component of roughness (Root Mean Squared Height) is found to be more important than the horizontal component (Autocorrelation length) in changing the scattering response. This is also marked by an increase in alpha_scat value, indicating a tendency towards pure scattering. In contrast, accumulation events lead to surface smoothening with dominant scattering from internal snow layers. Looking at the long-term changes in alpha_scat (i.e., period 2017 - 2023), high surface densities are found to be associated with an increase in pure scattering. However, increasing (decreasing) accumulation rates contribute to suppressing (enhancing) the effect of surface density on dominant scattering. The analyses provide new insights into the connection between SMB processes and dominant scattering in Sentinel-1 observations, but more field data is needed from multiple locations to quantify the combined effect of roughness, surface density, and accumulation rates on dominant scattering mechanisms. Such a framework could lead into a better separation between pure scattering and volume scattering, thereby furthering our knowledge on observing the variability of SMB processes from Sentinel-1. 

How to cite: Shukla, S., Wouters, B., Picard, G., Wever, N., Izeboud, M., de Roda Husman, S., Kausch, T., Veldhuijsen, S., Matzler, C., and Lhermitte, S.: Sentinel-1 reveals large variability of dominant scattering in a drifting snow-dominated environment of East Antarctica, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9710, https://doi.org/10.5194/egusphere-egu24-9710, 2024.

EGU24-9873 | ECS | Orals | CR5.3

Close-range thermal remote sensing over a cryospheric landform in complex topography – challenges and lessons learnt 

Kathrin Naegeli, Jennifer Susan Adams, Gabriele Bramati, Isabelle Gärtner-Roer, and Nils Rietze

Close-range remote sensing often fills the gap between in situ measurements and space-based observations. While most platforms are equipped with RGB cameras, there is a growing availability of thermal infrared (TIR) cameras. Both Uncrewed Aerial Vehicles (UAV) surveys in general and TIR remote sensing pose their individual challenges, especially in complex topography. In particular, TIR datasets are far from being ready-to-use upon acquisition, and thorough post-processing is required. However, they offer a great potential to monitor cryospheric landforms and assess their surface energy budget and related dynamics.

In this contribution, we present two years of TIR and RGB UAV data in combination with multiple in situ measurements, both for calibration and validation, obtained for a creeping permafrost landform, rock glacier Murtèl in the Engadine, Switzerland. We highlight the challenges evoked by the complex topography in the alpine environment (e.g. irradiance distribution, wind) and shed light on varying correction possibilities (e.g. laboratory-, field-, camera-based) that allow for a more accurate retrieval of land surface temperature over middle-sized landforms, such as a rock glacier.

In light of future thermal infrared satellite missions, an appropriate use of close-range remote sensing techniques, including survey protocols for calibration and validation, is urgently needed. This application study contributes to a better across-scale methodological understanding of sensors and methods, as well as the role of close-range remote sensing in complementing in situ and space-based observations, but also illustrates the potential of TIR datasets for cryospheric process understanding and long-term monitoring.

How to cite: Naegeli, K., Adams, J. S., Bramati, G., Gärtner-Roer, I., and Rietze, N.: Close-range thermal remote sensing over a cryospheric landform in complex topography – challenges and lessons learnt, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9873, https://doi.org/10.5194/egusphere-egu24-9873, 2024.

EGU24-10069 | Orals | CR5.3

Monitoring an ice-dammed lake outburst using topographic data at Kongsvegen, Svalbard  

Livia Piermattei, Andreas Alexander, Simon Filhol, Ugo Nanni, Pierre-Marie Lefeuvre, Jack Kohler, Désirée Treichler, Claire S. Earlie, Louise S. Schmidt, and Thomas V. Schuler

Glacial lake outburst floods (GLOFs) from ice-dammed lakes are frequent in Svalbard, impacting local ice dynamics, and subglacial hydrological systems, causing geomorphological changes, and posing flooding hazards. Additionally, GLOFs can influence nutrient dynamics in the fjord of tidewater glaciers, affecting the local ecosystem.

In this study, we use high-resolution topographic data to monitor the formation of an ice-dammed lake and identify the drainage mechanisms of a GLOF that occurred in the summer of 2021 on the Kongsvegen glacier, a surge-type tidewater glacier located in Kongsfjorden (Svalbard). Additionally, seismometers were deployed to monitor the subglacial dynamics at the kilometre scale.

Over the 2.5-month-long process starting in early June, terrestrial laser scanning (TLS) data and drone images were acquired at nearly daily intervals to monitor the ice-dammed lake formation and drainage. A time-lapse camera and pressure logger installed at the border of the ice-dammed lake allowed us to estimate the drainage timing, occurring from July 23 to July 26, resulting in a total drainage duration of 77 hours. To reconstruct the lake volume, the lake extension was manually digitized from the TLS data and drone orthophotos. Elevation information of the corresponding lake outlines was extracted from a 1 m resolution Digital Elevation Model (DEM) generated from Pléiades stereo satellite images acquired on 20 September 2020, at the end of the thaw season. This DEM serves as bathymetric data, representing the lake bottom. The extracted water level was used to calculate the stage-volume curve. The lake's maximum volume reached approximately 7.17 million m3 with an average discharge rate of 26 m3/s. Analyzing seismic data allowed for monitoring of the development of the subglacial drainage, assessing the transition from an inefficient to an efficient system.

This study highlights the importance of very high spatial and temporal resolution data for accurate lake volume quantification and a better understanding of the link between GLOF and subglacial system.

How to cite: Piermattei, L., Alexander, A., Filhol, S., Nanni, U., Lefeuvre, P.-M., Kohler, J., Treichler, D., Earlie, C. S., Schmidt, L. S., and Schuler, T. V.: Monitoring an ice-dammed lake outburst using topographic data at Kongsvegen, Svalbard , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10069, https://doi.org/10.5194/egusphere-egu24-10069, 2024.

EGU24-10497 | Posters on site | CR5.3

UAV placement of GNSS trackers on glaciers 

Kirk Martinez, Jane Hart, Graeme Bragg, Sherif Attia, Nathaniel Baurley, and Amelia Andrews

Commercially available UAVs can carry different types of payload such as cameras, Lidars and GPR. They also feature safety sensors such as collision awareness as well as mission planning with high accuracy RTK GPS. This makes them valuable tools to deploy sensors onto glaciers as long as the payload is within the maximum the UAV can carry.

We have been installing sensor networks inside and under glaciers since 2003 (https://glacsweb.org). Our most recent projects designed an RTK GNSS system to measure ice movement on two glaciers in Iceland. They send the location fixes back to a server every day and have been made smaller as well as lighter in our most recent version. The units use a custom aluminium “quadpod” to stay securely on the glacier. This enabled us to investigate methods to deploy and collect them using a DJI Matrice 300. This quadcopter has a maximum payload of 2kg so we designed the system to meet that requirement. This involved testing a lighter frame structure and smaller GPS antenna than the original versions. However they maintained the same high capacity battery, electronics and 5W solar panel. By using a commercially available release and camera module (PTS4) we were able to use a roughly 2m chord to attach the unit underneath the UAV. Once the tracker was positioned and set down onto the ice, with constant monitoring of the downwards facing camera included in the PTS4, the release mechanism was triggered. This was first carried out first at Breiðamerkurjökull then at Fjallsjokull. The first flight of around 1300m was to an easily accessible area in case of placement issues. The second flight was to a central part of Fjallsjokull which is inaccessible due to crevasses.

To test pick-up techniques, we investigated a range of hooks and grabbers as the combination of flight controls and logistics make it an interesting problem to solve. Our initial tests point to a hooking technique rather than a grabber and this aspect will be ongoing for tests of units on the glacier, which sink in a few centimetres when first placed in the summer.

Tracker22 being lifted to Fjallsjokull

How to cite: Martinez, K., Hart, J., Bragg, G., Attia, S., Baurley, N., and Andrews, A.: UAV placement of GNSS trackers on glaciers, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10497, https://doi.org/10.5194/egusphere-egu24-10497, 2024.

EGU24-11133 | ECS | Orals | CR5.3

GlacierGan: Visualizing the Alps during the Last Ice Age 

Brandon Finley and Guillaume Jouvet

In this work, we develop a deep-learning generative model to offer a new visualization for the Alps and its glaciation over the last 120’000 years as if a satellite had passed over and taken high resolution images from above. This visualization utilizes a recently coupled climate-glacier evolution model, which uses the latest paleo-climate and ice thickness field reconstructions (Jouvet et al., 2023). The ultimate goal of this project is to use it in the “IceAgeCam”, a joint SNSF (Swiss National Science Foundaton) project developed by ZHDK, UZH and UNIL that aims to better inform the public about the cause of climate change in a long-term climatic context.

To obtain such a visualization, we use an image-2-image translation model called Pix2PixHD (Wang et al., 2018). Similar to how one can use an image-2-image translation model to map images of winter to summer, or zebras to horses, we will map relevant fields of multi-band climatic images into artificial satellite images. Each multi-band image is composed of physical predictors such as ice thickness, ice velocity, precipitation, surface temperature, etc. In the end, the model produces semantically meaningful results that allow one to visualize the last glacial cycle. Moreover, although the motivation is rooted in the aforementioned ''IceAgeCam'' and seeks to visualize the last 120'000 years, it is a well-generalizable model, and as such, can be applied to visualize future simulations as well as terrain outside the Alps, given that the user has access to the same predictors. Finally, we aim to include this into IGM (the Instructed Glacial Model), a community-led glacier modeling software, such that it is user-friendly and easily accessible. Overall, we hope to advance efforts in the domain of remote sensing in relation to the cryosphere by providing a new way to visualize scientific results and foster community outreach.

How to cite: Finley, B. and Jouvet, G.: GlacierGan: Visualizing the Alps during the Last Ice Age, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11133, https://doi.org/10.5194/egusphere-egu24-11133, 2024.

EGU24-11685 | ECS | Orals | CR5.3

Feature tracking of sub-metre resolution Capella SAR imagery to measure mountain glacier ice flow 

Jamie Izzard, Duncan J. Quincey, John R. Elliott, and Anna Wendleder

In recent years, the number and capability of Synthetic Aperture Radar (SAR) sensors in low earth orbit has grown considerably, with multiple satellites now capable of capturing sub-metre resolution imagery. We present the first application of such very fine resolution SAR imagery to measure ice velocity of a high mountain glacier. To achieve this, we apply feature tracking to a pair of Capella images in spotlight mode (0.35 m resolution) acquired in July 2021 over Baltoro Glacier in the Karakoram, Pakistan, and compare the results to ice velocities derived from feature tracking using more commonly employed TerraSAR-X Stripmap (3 m) and Sentinel-1 Interferometric Wide (IW) (5 x 20 m) imagery. We show that Capella-derived velocities reveal subtle features that are not evident in velocities derived using coarser resolution imagery. In particular, slower moving ice at the glacier margin, variations in velocity between different flow units, and lateral fluctuations reflecting the local topography are all more clearly resolved. However, the small footprint of the imagery and lack of stable ground within the frame poses a challenge for co-registration which could affect the feasibility of broad-scale applications. Despite this, we show that sub-metre resolution SAR imagery enables us to observe and analyse glacier dynamics at temporal and spatial resolutions that were previously impossible using satellite-based methods. We suggest that such imagery may be used alongside in-situ methods to improve our understanding of fine-scale glaciological processes which may have a significant impact on broader scale glaciological systems. 

How to cite: Izzard, J., Quincey, D. J., Elliott, J. R., and Wendleder, A.: Feature tracking of sub-metre resolution Capella SAR imagery to measure mountain glacier ice flow, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11685, https://doi.org/10.5194/egusphere-egu24-11685, 2024.

EGU24-11722 | ECS | Posters on site | CR5.3

The EOLIS dataset: Monitoring Land Ice from CryoSat-2 Swath Processing 

Livia Jakob, Noel Gourmelen, Carolyn Michael, Sophie Dubber, Martin Ewart, Julia Bizon, Alex Horton, Tristan Goss, Andrea Incatasciato, Alessandro Di Bella, Jerome Bouffard, and Tommaso Parrinello

Satellite radar altimetry has been routinely used to monitor land ice heights since the 1990s. However, the launch of CryoSat-2 – the first altimetry mission to carry a synthetic aperture radar interferometer on board – has allowed several technical breakthroughs and led to many new applications that were previously unforeseen. One such breakthrough is Swath processing of CryoSat’s SARIn mode, making full exploitation of the information contained in CryoSat’s waveforms and leading to one to two orders of magnitude more measurements than the conventional so-called Point-Of-Closest-Approach (POCA) technique.

Following on from the early demonstration of the technique and of its potential impact, the CryoTEMPO EOLIS (Elevation Over Land Ice From Swath) dataset now routinely provides information of elevation over land ice at high resolution on a monthly basis. The dataset allows the use of radar altimetry in new environments such as the more complex terrain over glaciers and ice caps, as well as new applications thanks to the superior spatial and temporal resolution, such as the more precise quantification of subglacial lake drainage events. Currently, the EOLIS dataset is provided at monthly intervals over both ice sheets as well as all larger glacier regions, with future developments such as the expansion of the dataset to the ice shelves and new gapless annual DEMs over the two ice sheets coming soon.

With the aim of making CryoSat-2 altimetry data available to non-altimetry experts and encouraging its use more broadly by the community, the platform CS2EO (cs2eo.org) provides advanced data access to the EOLIS suite datasets. In CS2EO, users can query coincident data with other altimetry sensors, as well as explore and download custom elevation change time series over desired areas on ice sheets and glaciers, without having to download the EOLIS data first.

How to cite: Jakob, L., Gourmelen, N., Michael, C., Dubber, S., Ewart, M., Bizon, J., Horton, A., Goss, T., Incatasciato, A., Di Bella, A., Bouffard, J., and Parrinello, T.: The EOLIS dataset: Monitoring Land Ice from CryoSat-2 Swath Processing, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11722, https://doi.org/10.5194/egusphere-egu24-11722, 2024.

EGU24-15497 | ECS | Orals | CR5.3

Trends in Antarctic Ice Speed 2014-2023 From Big Data Processing of Satellite Observations 

Ross A. W. Slater, Anna E. Hogg, Pierre Dutrieux, Benjamin J. Davison, and Richard Rigby

The speed at which the Antarctic Ice Sheet (AIS) flows from the continental interior to the ocean is a key indicator of its stability, and satellite-derived ice velocity measurements play a major role in our assessment of changes in ice dynamics. The Sentinel-1 constellation of synthetic aperture radar (SAR) satellites, part of the European Commission’s Copernicus program, has acquired repeat images of the AIS margins at a combination of 6 and 12-day intervals since 2014, leading to a dramatic improvement in the spatio-temporal resolution and coverage of key velocity measurements at the edge of the AIS.

Such modern Earth observation satellites provide ever increasing volumes of data which can be used to study changes over time; however, this growing archive poses two key issues when performing timeseries analysis at continental scale. Firstly, generation of dense, pixelwise time series from thousands of successive observations, each stored in separate files corresponding to observation date, can require extremely large numbers of file reads, limiting computation speeds and increasing the memory required for data handling. Secondly, with ever increasing volumes of data, analysis must be able to scale effectively and easily handle out-of-core computation where datasets are larger than the available memory.

In this study, we present results from an analysis pipeline built on the Xarray and Dask python packages, and deployed on a HPC service, which allows both large scale interactive analysis in Jupyter notebooks as well as traditional batch processing. We first use an ice velocity processing chain to generate Antarctic-wide mosaics of ice speed on a 100 m grid for each combination of 6 and 12-day Sentinel-1 repeat observation dates, using the GAMMA Remote Sensing software to derive ice displacements from offset tracking of the SAR image pairs. The resulting stack of 2-dimensional mosaics is then restructured into a 3-dimensional data cube with dimensions x, y, time to facilitate time series analysis, overcoming the issue of excessive file reads and memory requirements by storing chunks of time series data together using the Zarr storage format.

Using this pipeline we investigate trends in ice speed across the AIS, performing time series outlier removal on 11 billion time series and subsequently calculating linear rates of change across both grounded and floating ice during the study period. We present the resulting map of ice speed trends and highlight time series of notable individual outlet glaciers and ice shelves.

How to cite: Slater, R. A. W., Hogg, A. E., Dutrieux, P., Davison, B. J., and Rigby, R.: Trends in Antarctic Ice Speed 2014-2023 From Big Data Processing of Satellite Observations, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15497, https://doi.org/10.5194/egusphere-egu24-15497, 2024.

EGU24-16162 | ECS | Posters on site | CR5.3

A new method for weekly sub-kilometer mapping of deep snow in mountainous regions using ICESat-2 and Sentinel-1 

Rasmus Meyer, Mathias Schødt, Mikkel Lydholm Rasmussen, Jonas Kvist Andersen, and Anders Anker Bjørk

The following abstract is based on a master thesis project in Geography from University of Copenhagen. It relies on freely available satellite data and uses Google Earth Engine and python for large scale analysis of deep snow in the Southern Scandinavian Mountains of Norway.

Knowledge about seasonal snow accumulation is key for managing water resources, especially in mountainous regions. However, accurate measurements of snow depth or SWE at a high spatiotemporal resolution are sparse. In this study, we investigate the effectiveness of a multi-satellite approach to mapping the depth of large-scale deep snow in the Southern Scandinavian Mountains of Norway. First, snow depths are measured using geolocated photons from the ICESat-2 satellite. These snow depths are matched spatio-temporally with the nearest Sentinel-1 scene, where an index based on the ratio between VV and VH polarization has been proven to be correlating partially with snow depth. Using a simple regression analysis, we model this relationship using a new sampling method, to further investigate the relationship between Sentinel-1 index and snow depths. The model is used to predict snow depths at 500m resolution every 6/12 days. When compared to in situ measurements from weather stations within the study area, our model has an RMSE of 36 cm.

How to cite: Meyer, R., Schødt, M., Rasmussen, M. L., Andersen, J. K., and Bjørk, A. A.: A new method for weekly sub-kilometer mapping of deep snow in mountainous regions using ICESat-2 and Sentinel-1, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16162, https://doi.org/10.5194/egusphere-egu24-16162, 2024.

Glacial lakes are growing rapidly, driven by climatic change and glacial retreat. The growth of glacial lakes may increase the magnitude and frequency of glacial lake outburst floods (GLOFs), posing a hazard to downstream populated regions. Satellite remote sensing provides a way to improve monitoring efforts, though automatic methods are needed to accurately and rapidly monitor changes in these lakes. In this study, we develop and apply an Object-Based Image Analysis (OBIA) approach to 71 multispectral Landsat 5-9 Top-Of-Atmosphere (TOA) satellite imagery in Google Earth Engine (GEE) to monitor the changes of 14 lake-terminating glacial lakes across the Southern Alps of New Zealand outside of the winter season (June-September) between 2000-2023. The Southern Alps of New Zealand are experiencing increasing glacial mass loss and despite previous glacial lake monitoring it remains necessary to continue monitoring these glacial lakes to understand the magnitude of their contribution to past regional ice mass loss. Our results show that the collective area of these 14 glacial lakes increased by 69% between 2000-2023, from 12.84 ± 0.06 km2 to 21.71 ± 0.1 km2. We evaluate the accuracy of this method by comparing automatically generated classification to manually classified points, using a stratified random sampling approach. Preliminary results derived for the accuracy of Landsat 9 satellite imagery resulted in an overall accuracy of 89%, with a producer’s accuracy and user’s accuracy of 98% and 96% respectively, for water. These preliminary results suggest that the method has the potential to map glacial lakes accurately and rapidly and can be applied to other glaciated regions.

How to cite: Morgan, T., McNabb, R., and Dunlop, P.: Monitoring the changes in glacial lakes in the Southern Alps, New Zealand from 2000-2023 using an Object-Based Image Analysis (OBIA) approach in Google Earth Engine (GEE), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16723, https://doi.org/10.5194/egusphere-egu24-16723, 2024.

EGU24-17452 | ECS | Posters on site | CR5.3

MOSEP: A Multi-Sensor Platform for Environmental Monitoring: Bridging the Scale Gap in Precipitation Measurement 

Christoph Gaisberger, Stefan Muckenhuber, Wolfgang Schöner, Birgit Schlager, Thomas Gölles, and Benjamin Schrei

The cryosphere's dynamic processes, from snow accumulation and avalanche activity to glacier calving, demand innovative monitoring solutions that offer both high spatial and temporal resolution. Current advancements in sensor technology are revolutionizing environmental monitoring. Our research introduces MOSEP (Modular Multi-Sensor System for Environment Perception), a novel, adaptable multi-sensor platform employing sensors traditionally used in autonomous vehicles, repurposed for environmental monitoring. This system integrates lidar, camera, radar, and a weather station powered by a Raspberry Pi 4 and equipped with open-source software for detailed environmental analysis. Previously utilized for mapping applications with automotive lidar, GPS, and an IMU, our platform has been enhanced with additional sensors to complement the lidar, notably radar and camera. The automotive sensors' high temporal resolution enables the observation of rapid environmental changes, offering an affordable and effective alternative to traditional geophysical sensors like TLS, particularly with the additional benefits of sensor fusion.

In cryospheric applications, the camera, radar, and lidar can work together to monitor surface changes, snow depth, accumulation rates, and potentially detect avalanches or other mass movements. The platform's flexibility and mobility are particularly advantageous for studying small-scale features and processes that are otherwise difficult to capture with satellite methods due to their coarse resolution and infrequent revisit times. While we have shown that lidar-based mapping using SLAM algorithms is effective, current research focuses on sensor performance in adverse weather conditions and the capability to detect and quantify weather effects. Traditional precipitation measurements face a 'scale gap,' with satellite and weather radar observations offering extensive spatial coverage at low resolution and rain gauges providing high accuracy at specific locations. Automotive sensor and specifically lidar could help bridge this gap especially in complex terrain. The inclusion of a camera assists in differentiating meteorological phenomena, such as rain from snowfall. However, the 'black box' nature of automotive sensors also present challenges. A measurement campaign was conducted last fall, and this contribution will present preliminary results alongside an overview of the latest hardware and software enhancements.

By introducing the novel use of easily accessible automotive sensors for environmental monitoring, our work contributes to the evolving field of cryospheric research, emphasizing the potential for cross-disciplinary innovation and the development of scalable, cost-effective environmental sensing networks.

How to cite: Gaisberger, C., Muckenhuber, S., Schöner, W., Schlager, B., Gölles, T., and Schrei, B.: MOSEP: A Multi-Sensor Platform for Environmental Monitoring: Bridging the Scale Gap in Precipitation Measurement, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17452, https://doi.org/10.5194/egusphere-egu24-17452, 2024.

EGU24-18311 | Posters on site | CR5.3

Crevasse field response to glacier dynamic change in Greenland 

James Lea, Thomas Chudley, Bethan Davies, and Maximillian Van Wyk De Vries

Crevassing provides visual information regarding gradients in ice flow velocity (i.e. strain rates), with relevance for multiple processes occurring at Greenland marine terminating margins, in the ice sheet interior, and for its peripheral glaciers and ice caps. Mapping crevasse distribution and relating them to ice dynamics can provide critical understanding for iceberg calving, ice damage enhanced glacier flow and glacier detachment in valley glacier and ice cap settings. Substantial effort has previously been exerted in structural glaciology to both map crevasses and relate their sizes and distribution to the dynamics of individual glaciers, though this has frequently involved time consuming manual mapping making large temporal/spatial scale investigations impractical. Building on recent work towards the automation of crevasse mapping, we present a new, highly flexible, methodologically simple automated approach for crevasse identification from top-of-atmosphere (TOA) Sentinel-2 optical satellite imagery. This has been developed to be computationally light, and unlike other thresholding based methods does not require standardisation of reflectance values through surface reflectance correction of imagery. The approach is implemented within the Google Earth Engine platform, meaning that the method has the potential to be applied rapidly and at scale for near-real time monitoring.

Our new approach allows rapid characterisation of the response of crevasse fields (and therefore glacier stress/strain environments) to glacier dynamic change. In this presentation we evaluate the efficacy of this approach against previously developed automated methods of crevasse mapping (namely Gabor filtering and digital elevation model based approaches). We conduct initial exploration into: whether analysis of crevasse fields allow identification of precursor signs of marine terminating glacier destabilisation; how crevasse fields evolve in response to observed terminus retreat; and if key summary statistics that result from the analysis can be related glacier calving styles. Through comparisons results generated by different methods we also highlight the strengths and weaknesses of each in characterising these signals.

How to cite: Lea, J., Chudley, T., Davies, B., and Van Wyk De Vries, M.: Crevasse field response to glacier dynamic change in Greenland, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18311, https://doi.org/10.5194/egusphere-egu24-18311, 2024.

EGU24-18388 | ECS | Posters on site | CR5.3

Intra-annual velocity variability extracted from multi-sensor and multi-temporal datasets produced by different processing chains 

Laurane Charrier, Amaury Dehecq, Fanny Brun, Romain Millan, Luc Beraud, Etienne Ducasse, Antoine Rabatel, Luc Copland, and Christine Dow

Ice velocity products with a sub-annual resolution are needed to better understand subglacial hydrology, glacier instabilities and glacier response to short-term events, such as calving or increased melt. Different processing chains are now releasing scene-pair velocities worldwide (ITS_LIVE, GOLIVE, RETREAT, PROMICE, MEaSUREs, Millan et al., 2019). Their temporal resolution is up to 2 days and their spatial sampling up to 50 m. However, analysing the sub-annual variability of glacier dynamics on a global scale remains challenging. Indeed, the amplitude of the velocity at high temporal resolution is frequently smaller than the uncertainty in many areas. In addition, the available datasets are complex to use because the velocities span different temporal baselines, are derived from images from different sensors, and are computed using different correlation and post-processing parameters. The methods developed to post-process ice velocities usually select only a subset of the datasets, require strong a priori knowledge of glacier velocities, remain sensitive to systematic errors and/or have not been validated for different glacier dynamics. Therefore, there is a need to develop and validate an operational method able to fully exploit the available ice velocity datasets in order to provide homogeneous and robust sub-annual velocity time series.

Here, we propose a method based on the temporal closure of the displacement measurement network. To be robust to both systematic and random errors (e.g., temporal decorrelation and random noise), we invert the system using an iterative reweighted least square with a robust downweighting function. We propose a regularisation strategy that can account for different glacier dynamics (e.g., normal vs. surge flow). The performance of the method is evaluated using GNSS stations in the Yukon (Canada) and the European Alps. The resulting velocity time series have a homogeneous temporal sampling and reduced uncertainty (up to 60%). Annual velocity peaks are retrieved with a Mean Absolute Error in the order of 10 to 30 days, and 1 to 40 m/y. The results reveal the spatio-temporal propagation of annual velocity peaks and glacier surges along glacier centerlines. This method can be applied to any available dataset. The code will be published in a github repository.

How to cite: Charrier, L., Dehecq, A., Brun, F., Millan, R., Beraud, L., Ducasse, E., Rabatel, A., Copland, L., and Dow, C.: Intra-annual velocity variability extracted from multi-sensor and multi-temporal datasets produced by different processing chains, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18388, https://doi.org/10.5194/egusphere-egu24-18388, 2024.

EGU24-18646 | ECS | Orals | CR5.3

How to obtain a highly accurate dataset of the snow surface temperature with a thermal infrared camera? 

Sara Arioli, Ghislain Picard, Laurent Arnaud, Simon Gascoin, Esteban Alonso-González, Marine Poizat, and Mark Irvine

Snow plays a critical role in alpine areas, influencing the local climate and serving as a crucial water reservoir for downstream ecosystems and human activities. The surface temperature of snow provides many insights about the current state of the snowpack and helps water storage estimations. While satellites are regularly used to measure surface temperature of snow over alpine areas, accurate measurements are still difficult to retrieve from space, and calibration-validation initiatives over snow-covered areas are scarce. In this context, we produced a two-winter timeseries of approximately 130,000 maps of the radiative surface temperature of snow acquired with an uncooled Thermal Infrared camera. TIR images were acquired November 2021 to May 2022 and February to May 2023 at the Col du Lautaret, 2057 m a.sl. in the French Alps. During the first season, the camera operated in the off-the-shelf configuration, with a rough thermal regulation (7°C - 39°C) resulted in timeseries of snow surface temperature maps with an absolute accuracy <1.25 K. The large variations of the camera’s internal temperature were identified as the main source of error. An improved setup using a thermoelectric cooler to stabilize the internal temperature was therefore developed for the second campaign, while comprehensive laboratory experiments led to a thorough characterization of the physical properties of the TIR camera and its calibration. A meticulous processing includes radiometric processing, orthorectification and a filter for foggy and snowy images. The validation against precision TIR radiometers deployed in the camera’s field of view results in an estimated absolute accuracy <0.7 K for spring 2023. The efforts to stabilize the internal temperature of the TIR camera therefore led to a notable improvement of the accuracy. This methodology represents a significant advance in the capacity to map the snow surface temperature over complex terrain, overcoming the issues found to get accurate thermal infrared images of absolute temperature discussed in previous studies. The methodology, as well as the resulting timeseries, will be useful for the investigation of the surface energy budget of snow and for the calibration/validation of satellite thermal infrared products such as Landsat, ECOSTRESS and, starting in 2025, TRISHNA over snow.

How to cite: Arioli, S., Picard, G., Arnaud, L., Gascoin, S., Alonso-González, E., Poizat, M., and Irvine, M.: How to obtain a highly accurate dataset of the snow surface temperature with a thermal infrared camera?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18646, https://doi.org/10.5194/egusphere-egu24-18646, 2024.

EGU24-18928 | Posters on site | CR5.3

Novel developments in automated ice sheet mass balance measurements 

Andreas P. Ahlstrøm, Robert S. Fausto, Jason E. Box, Nanna B. Karlsson, Penelope R. How, Baptiste Vandecrux, Anja Rutishauser, Mads C. Lund, William T. Colgan, Alexandra Messerli, Anne M. Solgaard, Kirsty Langley, Rasmus B. Nielsen, Signe B. Andersen, Synne H. Svendsen, Jakob Jakobsen, Allan Ø. Petersen, and Christopher L. Shields and the GC-Net team

The rapid demise of ice sheets and glaciers worldwide has increased the need for mass balance observations at a temporal and spatial resolution, where they can both help us understand the physical processes and also serve as validation or calibration for remote sensing data products or regional climate model output. Here we present the latest developments in measuring crucial components of the surface mass balance at automatic weather stations, including snow water equivalent, snow height in the vicinity of the station, sufficiently accurate transmitted position and elevation of the station, snow compaction and non-stake ice sheet ablation.

Immediate access to the observations is key to certain applications, such as numerical weather forecasts. Hence, we also present the complications of providing near real-time data transmission and quality-checking as well as obstacles to a wider distribution on the WMO Global Telecommunication System (GTS).

How to cite: Ahlstrøm, A. P., Fausto, R. S., Box, J. E., Karlsson, N. B., How, P. R., Vandecrux, B., Rutishauser, A., Lund, M. C., Colgan, W. T., Messerli, A., Solgaard, A. M., Langley, K., Nielsen, R. B., Andersen, S. B., Svendsen, S. H., Jakobsen, J., Petersen, A. Ø., and Shields, C. L. and the GC-Net team: Novel developments in automated ice sheet mass balance measurements, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18928, https://doi.org/10.5194/egusphere-egu24-18928, 2024.

EGU24-19059 | Posters on site | CR5.3

Potential of Employing a Machine Learning Model for Glacier Motion Monitoring 

Magdalena Łucka, Ryszard Hejmanowski, and Wojciech Witkowski

Monitoring marine-terminating glaciers and their dynamics in the light of advancing climate change is a critical concern for many scientists. Observing marine-terminating glaciers in Greenland is especially significant because glacier calving and melting influence sea level. One component of glacier monitoring is velocity estimation, which can also be used as an indicator of climatic change and may reveal the existence of other underlying processes that cause speed changes on the surface. Using SAR images, this type of monitoring can be done permanently and at a minimal cost. However, present approaches that focus on offset-tracking algorithms have some disadvantages. Despite the rapid development of artificial intelligence, there is still some immense potential in the synergy of SAR datasets and machine learning models to determine rapid displacement, such as in the case of glaciers. This study demonstrates the feasibility of determining glacier displacement using Sentinel-1 satellite SAR information and convolutional neural networks (CNN).

The method proposed in this study uses pairs of SAR data to find the matching patterns on both images. The CNN with the AlexNET architecture is utilized to discover the corresponding areas, and data augmentation techniques such as rotation, filtering, or resizing of the SAR image are employed to extend the training dataset. Finding the appropriate areas on both images allows for the calculation of the displacement in radar coordinates, as well as the mean velocity and direction of the movements over the investigated period. This study examines the proposed method's results for two Greenland glaciers with varying speeds: Jakobshavn and Petterman. Furthermore, two different input datasets are evaluated and compared. The first strategy simply employs the amplitude obtained in HH polarization, while the second uses amplitude information from HH and HV polarizations, as well as the backscatter coefficient. Displacement values obtained for both glaciers and using various input datasets are compared to the velocities collected using the offset-tracking approach, which is extensively used for glacier monitoring.

The potential of using machine learning models to determine glacier displacement values utilizing SAR datasets is presented in this study. The results' reliability is further validated by comparison with well-known processing procedures. In addition, different input datasets are examined for two glaciers with different dynamics to determine the utility of the proposed approach for monitoring glacier motion. The proposed method's adoption could benefit glaciological society by providing an alternate method for detecting ice motion.

How to cite: Łucka, M., Hejmanowski, R., and Witkowski, W.: Potential of Employing a Machine Learning Model for Glacier Motion Monitoring, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19059, https://doi.org/10.5194/egusphere-egu24-19059, 2024.

EGU24-22404 | ECS | Posters on site | CR5.3

Monthly Monitoring of Greenland Glacier Dynamics Using Swath processed CryoSat-2 SARIn Data 

Natalia Havelund Andersen, Louise Sandberg Sørensen, Sebastian Bjerregaard Simonsen, and Mai Winstrup

This study presents a novel methodology for developing monthly surface elevation change maps from over a decade of CryoSat-2 Synthetic Aperture Radar Interferometry (SARIn) data. This offers a detailed spatial and temporal understanding of sub-annual mass loss from Greenland Ice Sheet glaciers. Leveraging the satellite's swath processing capabilities, we derive precise surface elevations to capture seasonal variations. The resulting maps enable us to identify and analyze dynamic glacier changes, and responses to climatic conditions. This research enhances our comprehension of glacier dynamics and aids in validating the mass loss from the Greenland ice sheet. It contributes data for predicting future sea-level rise in the context of climate change.

How to cite: Havelund Andersen, N., Sandberg Sørensen, L., Bjerregaard Simonsen, S., and Winstrup, M.: Monthly Monitoring of Greenland Glacier Dynamics Using Swath processed CryoSat-2 SARIn Data, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-22404, https://doi.org/10.5194/egusphere-egu24-22404, 2024.

EGU24-61 | ECS | Orals | CR5.4

Multi-Offset Radio-Echo Sounding for Estimation of Englacial and Subglacial Thermal Conditions and Material Properties 

Daniel May, Dustin Schroeder, Paul Summers, Thomas Teisberg, Anna Broome, and Nicole Bienert

Radio-echo sounding (RES) is a widely used tool in the field of glaciology with which critical information about englacial and subglacial conditions can be derived. However, RES observations have historically been limited to zero-offset or small-offset surveys, typically employing one transmitting and one receiving antenna. The poor spatial and azimuthal coverage of the subsurface associated with these sparse geometries limits the ability to robustly constrain key englacial and subglacial properties including ice temperature, bed material composition, water content, ice fabric, and firn density. Furthermore, using radar only in zero- or small-offset configurations limits its potential to provide high resolution imaging of bed geometry. The maximum achievable offset in ground-based radar surveys is typically limited by the relatively high-loss coaxial cable which connects the radar transmitter and receiver. To overcome this limitation, two multi-offset ground-based radar systems, both built around an autonomous phase-sensitive radio-echo sounder (ApRES) as a transmitter, have been developed and deployed by the Radio Glaciology Group at Stanford. The first system forgoes cabled connection between a transmitting ApRES unit and a software-defined radio (SDR) based receiver, instead relying on a post-acquisition processing flow to ensure coherent summation of repeated measurements to achieve sufficient signal-to-noise ratios. The second system replaces the standard high-loss coaxial cable with low-loss fiber optic cable in order to extend the maximum achievable offset between transmitter and receiver. This requires outfitting the ApRES radar system with hardware to convert radio-frequency signals into optical signals that can be transmitted over fiber optic cable (RFoF). Both systems were deployed during the 2023-24 Antarctic field season as part of the Thwaites Interdisciplinary Margin Evolution project in order to collect multi-offset RES data on both floating and grounded ice. These surveys are aimed at detecting englacial temperature anomalies and the estimation of dielectric properties of englacial and subglacial materials through amplitude-versus-offset analysis of radar data. The dense multi-offset coverage in surveys described here was built up by frequent repositioning of only four SDR-based and one ApRES-based receiver; however, future surveys with these systems could have 10s or 100s of radar receivers simultaneously recording, allowing for survey geometries commonly employed in active source seismic imaging to be applied to radar imaging. 

How to cite: May, D., Schroeder, D., Summers, P., Teisberg, T., Broome, A., and Bienert, N.: Multi-Offset Radio-Echo Sounding for Estimation of Englacial and Subglacial Thermal Conditions and Material Properties, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-61, https://doi.org/10.5194/egusphere-egu24-61, 2024.

EGU24-266 | ECS | Orals | CR5.4

High resolution subglacial topography from airborne swath radar beneath the Northeast Greenland Ice Stream (NEGIS) 

Charlotte Carter, Steven Franke, Veit Helm, Daniela Jansen, Coen Hofstede, John Paden, and Olaf Eisen

Here we present an extensive swath radar dataset collected in the onset region of the Northeast Greenland Ice Stream, surrounding the East Greenland Ice Core Project site (EGRIP). We produce a new digital elevation model (DEM) of the subglacial topography at a resolution of 25 m, covering a study area of 40 km by 60 km. The data was collected using the AWI airborne ultra-wideband radar system, in profiles mainly perpendicular to the ice flow direction with a spacing of 2 km so that the swaths overlapped.

The high-resolution subglacial topography DEM shows subglacial landforms beneath an active ice stream, located approximately 600 km into the interior of the ice sheet. These landforms indicate spatially variable bed conditions which are partly reflected in the surface velocity field. Some features appear to be crag and tail formations up to 4 km in length, with steep stoss-side slopes and tapering lee-side tails which are oriented in the direction of ice flow. Megascale glacial lineations up to 7 km in length are evident, but appear restricted to the inner ice stream within the modern shear margins, where the ice flow velocity increases from approximately 11 m/a to 58 m/a. Meltwater channels curve around a high point in the topography, which are on the scale of tunnel valleys formed from subglacial meltwater incision. Seismic data located in a channel at the eastern shear margin indicates soft sedimentation inflow. In summary, differences in landform morphology can be seen within and outside of the ice stream shear margins, indicating that NEGIS ice flow may have been transitory in this region.

This survey provides a new insight into the active subglacial environment of a Greenlandic ice stream, matching in quality surveys from ice-free land surface or marine areas. Further analysis will contribute to the understanding of how glacially sculpted landscapes are formed, as well as the effects of small-scale topography on the dynamics and the surface of the overlying ice sheet, in particular ice streams. Moreover, the dataset emphasises the usage of swath radar mapping of bedforms and thus a more widespread application of this method in all radar surveys.

How to cite: Carter, C., Franke, S., Helm, V., Jansen, D., Hofstede, C., Paden, J., and Eisen, O.: High resolution subglacial topography from airborne swath radar beneath the Northeast Greenland Ice Stream (NEGIS), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-266, https://doi.org/10.5194/egusphere-egu24-266, 2024.

EGU24-1096 | ECS | Orals | CR5.4

Automatic detection of cold-temperate transition surface in polythermal glaciers using GPR and machine learning 

Unai Letamendia, Iván Ramírez, Francisco Navarro, Beatriz Benjumea, and Emanuel Schiavi

Ground-penetrating radar (GPR) has been shown to be an effective tool to infer the hydrothermal structure of polythermal glaciers. Knowledge of this structure is fundamental to the study of their dynamics. The cold-temperate transition surface (CTS) is the englacial boundary between cold and temperate ice. It can be identified by GPR because of the contrast in permittivity between dry cold ice and water-rich temperate ice. However, the interpretation of the CTS using GPR has traditionally been a very time-consuming and manual process. Here we show a procedure based on machine learning for detecting CTS automatically. The data used for training a convolutional neural network were collected in both Svalbard, in the Arctic (radar with central frequency of 25 MHz), and the South Shetland Islands in the Antarctic Peninsula region (200 MHz central frequency). Various metrics revealed success rates in the classification in the order of 90%. The size of the training dataset is limited, so current work is focused on enlarging its size by using random variations of synthetic radargrams generated by forward modelling with gprMax.

How to cite: Letamendia, U., Ramírez, I., Navarro, F., Benjumea, B., and Schiavi, E.: Automatic detection of cold-temperate transition surface in polythermal glaciers using GPR and machine learning, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1096, https://doi.org/10.5194/egusphere-egu24-1096, 2024.

EGU24-1398 | ECS | Posters on site | CR5.4

Spatial and temporal changes in surface mass balance derived from airborne radio sounding for the plateau area in Dronning Maud Land 

Alexandra Zuhr, Steven Franke, Daniel Steinhage, Daniela Jansen, Olaf Eisen, and Reinhard Drews

Contrary to the rest of the Antarctic ice sheet, East Antarctica currently gains mass due to an increase in snow accumulation over the last decades. How or if this increase is linked to anthropogenic warming is not yet clear and requires better understanding of the surface mass balance history over the last centuries, and also the dependency of snow accumulation with the local surface slopes across different spatial scales.

Here, we present a novel airborne dataset using the multichannel ultra-wideband radar system from the Alfred Wegener Institute in Germany with a decadal vertical resolution for the plateau area in Dronning Maud Land. We assess the spatial and temporal variability of surface mass balance and snow accumulation for the past centuries for an area of ~200,000 km2. With this contribution, we aim to (1) show the potential to use ultra-wideband radar systems to reconstruct the recent surface mass balance and accumulation rates in low-accumulation regions, (2) present information on large spatial scales, and (3) discuss potential overlap of interests and/or data in this and/or other areas on the plateau of East Antarctica.

How to cite: Zuhr, A., Franke, S., Steinhage, D., Jansen, D., Eisen, O., and Drews, R.: Spatial and temporal changes in surface mass balance derived from airborne radio sounding for the plateau area in Dronning Maud Land, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1398, https://doi.org/10.5194/egusphere-egu24-1398, 2024.

EGU24-1721 | Posters on site | CR5.4

AIRETH 2.0 – a revamped helicopter-borne GPR for glaciological applications 

Daniel Farinotti, Raphael Moser, Barthelemy Anhorn, Christophe Ogier, Andreas Bauder, Benedikt Pohl, Benedikt Soja, and Hansruedi Maurer

The Airborne Ice Radar of ETH Zurich (AIRETH) is a dual-polarization, helicopter-borne GPR system that was developed for glaciological applications. At the core of AIRETH are two pairs of commercial, orthogonally oriented, bistatic dipole antennas operating at a center frequency of 25 HMz or higher. The system has extensively been operated in the past, e.g. for collecting close to 2,500 km of GPR data for estimating the ice thickness of glaciers across the Swiss Alps.

Here, we present a series of amendments that have recently performed to the AIRETH system in order to increase its versatility and operability. The corresponding work notably included:
1. a re-design of AIRETH’s air-frame, aiming at decreasing the system’s overall weight, as well as at increasing the system’s stability and ease of operation;
2. a newly developed positioning system, which is now based on the integration of information obtained from a set of four low-cost Global Navigation Satellite System (GNSS) sensors placed at the corners of the main air-frame in combination with an Inertial measurement unit (IMU); and
3. an experimental antenna shielding based on low-cost materials, aiming at minimizing the ringing noise caused by the proximity of the GPR system to the carrying helicopter.

The contribution will focus on the advances that were achieved compared to the previous AIRETH setup, and will point out the challenges faced during system re-design. The capabilities of the new system will, moreover, be illustrated by presenting some recent datasets acquired over Alpine glaciers.

How to cite: Farinotti, D., Moser, R., Anhorn, B., Ogier, C., Bauder, A., Pohl, B., Soja, B., and Maurer, H.: AIRETH 2.0 – a revamped helicopter-borne GPR for glaciological applications, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1721, https://doi.org/10.5194/egusphere-egu24-1721, 2024.

EGU24-5342 | ECS | Posters on site | CR5.4

Sediment-laden basal ice units near the onset of a fast-flowing glacier in East Antarctica 

Steven Franke, Michael Wolovick, Reinhard Drews, Daniela Jansen, Kenichi Matsuoka, and Paul Bons

Understanding the material properties and physical conditions of basal ice is crucial for a comprehensive understanding of Antarctic ice-sheet dynamics. Yet, direct data are sparse and difficult to acquire, necessitating geophysical data for analysis. We employed high-resolution ultra-wideband radar to map high-backscatter zones near the glacier bed within East Antarctica's Jutulstraumen drainage basin. In addition, we used radar forward modelling to constrain their material composition. Our results reveal along-flow oriented sediment-laden basal ice units connected to the basal substrate, extending to several hundred meters thick. Three-dimensional thermomechanical modelling suggests these units initially form via basal freeze-on of subglacial water originating upstream. We suggest that basal freeze-on and the entrainment and transport of subglacial material play a significant role in an accurate representation of the material, physical, and rheological properties of the Antarctic ice sheet's basal ice, ultimately enhancing the accuracy and reliability of ice-sheet modelling.

How to cite: Franke, S., Wolovick, M., Drews, R., Jansen, D., Matsuoka, K., and Bons, P.: Sediment-laden basal ice units near the onset of a fast-flowing glacier in East Antarctica, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5342, https://doi.org/10.5194/egusphere-egu24-5342, 2024.

EGU24-6717 | ECS | Posters on site | CR5.4

Satellite-derived sea ice motion data: daily-maps (DM) and swath-to-swath (S2S) 

Tian Tian, Alexander Fraser, Petra Heil, Thomas Lavergne, Xuanji Wang, Yinghui Liu, and Jay Hoffman

Remotely sensed ice motion is a crucial component in sea, lake, or river ice research. Over the past few decades, the ice movement has been detected and retrieved predominantly through the application of the Maximum Cross-Correlation (MCC) technique by analyzing the overlapped consecutive satellite images.

Traditionally, ice motion products have been derived from daily averaged satellite imagery, commonly referred to as 'daily-map' (DM) ice motion. This DM ice motion product has gained widespread usage in sea ice studies due to its inherent timescale and extensive coverage.

Recently, a new approach known as the swath-to-swath (S2S) method has emerged, deriving ice motion from individual satellite swath pairs. The S2S ice motion product has proven valuable in sea ice kinematics research, revealing a robust relationship between ice kinematics and thickness, characterized by its diverse timescale. Consequently, these two types of satellite-derived ice motion products contribute distinct perspectives to ice kinematics research.

The latest generation of NOAA's Geostationary Operational Environmental Satellites (GOES), specifically the GOES-R Series, offers sea/lake/river ice observations at a relatively high resolution. A recent development involves the MCC approach generating a new DM ice motion product with a 2 km resolution using GOES-R reflectance imagery (0.5 km resolution). This ice motion dataset holds potential for final users engaged in analyzing small-scale sea/lake/river ice status and its changes.

How to cite: Tian, T., Fraser, A., Heil, P., Lavergne, T., Wang, X., Liu, Y., and Hoffman, J.: Satellite-derived sea ice motion data: daily-maps (DM) and swath-to-swath (S2S), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6717, https://doi.org/10.5194/egusphere-egu24-6717, 2024.

Satellite remote sensing is one of the few ways to comprehensively monitor changes in the Greenland Ice Sheet ‘s surface conditions through both time and space. From orbit, satellites can efficiently collect repeated measurements covering the entire ice sheet surface and elucidate the processes controlling how Greenland responds to a changing climate. Active radar and passive microwave measurements are especially valuable datasets, as cloud cover or illumination conditions are not limiting factors.

In this vein, recent research has shown how near-surface properties (i.e., density and roughness) across Greenland can be derived through the Radar Statistical Reconnaissance analysis of Ku-band ESA CryoSat-2 and Ka-band CNES/ISRO SARAL surface echo powers. While this approach yields densities at individual depths in the near-surface, a fuller result would include constraining a continuous density profile as a function of depth. At the same time, L-band ESA SMOS passive microwave brightness temperatures are sensitive to the entire snow-firn-ice column. However, the inversion of brightness temperatures for a property of interest in a specific layer (e.g., snow wetness, density, etc.) requires numerous assumptions regarding the subsurface conditions.

The EO4GRHO project seeks to merge these two approaches to investigate whether the inversion of SMOS brightness temperatures using a subsurface structure pre-conditioned with results derived from the analysis of radar altimetry surface echoes (i.e., density at known depth(s)) can provide a more complete picture of how Greenland Ice Sheet near-surface densities vary with depth, time, and space. Here, EO4GRHO leverages a decade (2013-2023) of contemporaneous CryoSat-2, SARAL, and SMOS measurements, makes use of modelled brightness temperatures from the Snow Microwave Radiative Transfer model software and, finally, hundreds of in-situ measurements. The ultimate aim of EO4GRHO is to operationally produce observation-based maps and time series for the near-surface density structure of the Greenland Ice Sheet that can be incorporated in future mass balance calculations.

How to cite: Scanlan, K. M. and Simonsen, S. B.: EO4GRHO: A multi-satellite synthesis constraining the near-surface density profile of the Greenland Ice Sheet through time and space, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8824, https://doi.org/10.5194/egusphere-egu24-8824, 2024.

EGU24-10754 | Orals | CR5.4 | Highlight

International Mars Ice Mapper Mission: Detection, mapping and characterization of subsurface water ice and overburden on Mars with Synthetic Aperture Radar combined with VHF Sounding and High-Resolution Imaging 

Marilena Amoroso, Enrico Flamini, Eleonora Ammanito, Michele Viotti, Raffaele Mugnuolo, Timothy Haltigin, Etienne Boulais, Tomohiro Usui, David M. Hollibaugh Baker, Richard M. Davis, Michael S. Kelley, Bob Collom, Sébastien Lafrance, and Patrick Plourde

The primary goal of the International Mars Ice Mapper (I-MIM) mission concept is to identify and characterize accessible water-ice and its overburden in the upper 0-10 m of the Martian subsurface in preparation for future human-robotic exploration. The I-MIM concept mission has been developed by the Italian, Canadian, Japanese, and US space Agency Partners (ASI, CSA, JAXA, and NASA).

In 2021, the Agency Partners competitively selected a Measurement Definition Team (MDT) to define the core measurements for the mission’s primary payload, to suggest possible augmentations, and to develop a concept of operations. In August 2022, the MDT released a Final Report [1], concluding that the mission’s primary instrument, a Synthetic Aperture Radar (SAR) centred at 930 MHz, would satisfy all of the Reconnaissance Objectives (ROs) and would provide the opportunity to accomplish unique new science covering a broad range of international science priorities. In order to expand the capabilities of I-MIM to undertake high-priority science investigations, the MDT also recommended that the concept team consider the inclusion of complementary payloads identified as highest priority: a very high frequency (VHF) radar sounder, a high-resolution optical imager, and a sub-millimetre sounder for atmospheric profiling.

Based on the MDT inputs, the Agency Partners have updated the I-MIM mission architecture to consist of three spacecraft elements with complementary science payloads:

Element 1 – Ice-Mapping Orbiter: Provided by JAXA, with two radar instruments and an atmospheric sensor: a CSA-provided polarimetric L-band (930 MHz) SAR, an ASI-provided Very High Frequency (VHF) Shallow Radar Sounder (100-200 MHz), and a JAXA-provided sub-millimetre sounder. Moreover, an ASI-provided Large Deployable Reflector (LDR) would support the SAR and act as part of the ASI-provided telecommunications subsystem.

Element 2– Demonstration Lander: A JAXA-provided demonstration lander would piggyback on the main orbiter to provide ground-truthing capabilities with a potential complementary small instrument package.

Element 3 – Free-flying Smallsat: A NASA-provided, free-flying smallsat with a high-resolution imager would provide high-resolution imaging for context and continuity under a small low-cost mission profile and to meet the requirements for multiple scientific investigations and future mission site selection.

Mapping the unstudied near surface of Mars thanks to the synergic observations L-band SAR and the VHF Sounder, augmented by the High-resolution Imager, has the potential to fill a major data gap unmet by prior instruments sent to Mars and provide a broad evaluation of the abundance of water ice reservoirs at medium latitudes.

In order to characterize variability in the ionosphere both the SAR and the sub-millimeter sounder further addresses key questions about the connections in Mars’s dynamic climate regions and seasonal interactions of shallow subsurface volatiles with the atmospheric structure, of critical importance to both science and human-robotic mission planning.

In the International Moon to Mars objectives context, I-MIM would provide core information about the role of water ice and other volatiles in prior and active changes globally on Mars, identifying landed locations in ice-rich areas that represent potential habitable environments, for future robotic and human missions.

References: [1] I-MIM MDT Final Report (2022) 239 pp., online: https://science.nasa.gov/researchers/ice-mapper-measurement-definition-team

How to cite: Amoroso, M., Flamini, E., Ammanito, E., Viotti, M., Mugnuolo, R., Haltigin, T., Boulais, E., Usui, T., Hollibaugh Baker, D. M., Davis, R. M., Kelley, M. S., Collom, B., Lafrance, S., and Plourde, P.: International Mars Ice Mapper Mission: Detection, mapping and characterization of subsurface water ice and overburden on Mars with Synthetic Aperture Radar combined with VHF Sounding and High-Resolution Imaging, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10754, https://doi.org/10.5194/egusphere-egu24-10754, 2024.

EGU24-11581 | ECS | Orals | CR5.4

Evidence of Ice Flow Switching from Carlson Inlet to Rutford Ice Stream Based on Polarimetric Radar 

Álvaro Arenas-Pingarrón, Alex M. Brisbourne, Carlos Martín, Hugh F.J. Corr, Carl Robinson, and Tom A. Jordan

The flow of polar ice is controlled by its viscosity that is spatially variable and depends, among other factors, on the orientations of the anisotropic crystals of ice, often referred as crystal orientation fabric. Ice crystalizes in planes represented by the c-axis, a direction perpendicular to the main plane of the crystals, and it is highly anisotropic: the viscosity along the c-axis is two orders of magnitude greater than across, and hence it can be a key factor for ice flow modelling. Interestingly, the ice crystals rotate to accommodate ice flow, similarly to how dominoes tend to align under strain, and ice c-axis orientation evolves to be perpendicular to the direction of the maximum strain rate. Thus, ice flow and crystal orientation fabric are related. However, critically for our work, c-axis evolution is not instantaneous and, particularly in currently slow deforming ice, crystal orientation fabric contains traces or past ice flow conditions. Here, we use data from the British Antarctic Survey (BAS) airborne radar PASIN2 for deep ice sounding in Rutford Ice Stream, collected during the 2019-2020 season, to derive crystal orientation fabric. Because electromagnetic waves propagate at different speeds depending on the wave polarisation being parallel or perpendicular to the c-axis, an optical phenomenon called birefringence, we compare signals from different antenna orientations in our array to derive englacial crystal orientation fabric. We then compare our radar-derived crystal orientation fabric with strain rate derived from satellite ice flow observations. To aid the interpretation, we use a numerical model that bounds the prediction of ice fabric from ice flow under different assumptions. We find that Carlson Inlet, now stagnant, show traces of past fast flow on its crystal orientation fabric. This agrees with previous studies that suggest flow-switching and water-piracy between neighbouring Carlson Inlet and Rutford Ice Stream (Vaughan et al., 2008). Our method provides a framework to investigate the timing and the causes of the flow-switching event. More in general, we demonstrate the use of existing and future airborne polarimetric data to investigate recent changes in the cryosphere.

How to cite: Arenas-Pingarrón, Á., M. Brisbourne, A., Martín, C., F.J. Corr, H., Robinson, C., and A. Jordan, T.: Evidence of Ice Flow Switching from Carlson Inlet to Rutford Ice Stream Based on Polarimetric Radar, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11581, https://doi.org/10.5194/egusphere-egu24-11581, 2024.

EGU24-11645 | ECS | Posters on site | CR5.4

A Seamless Ice Sheet Digital Elevation Model using CryoSat 

Carolyn Michael, Livia Jakob, Noel Gourmelen, Sophie Dubber, Karla Boxall, Andrea Incatasciato, Martin Ewart, Jerome Bouffard, and Alessandro Di Bella

The Greenland and Antarctic ice sheets are contributing to a quarter of current sea level change and have the potential to raise sea level by several metres in the future. The surface elevation of ice sheets, and its temporal evolution, is one of the essential climate variables, it forms the basis observation for mass balance monitoring and the projection of sea level contribution under future climate scenarios. This work explores the creation of a seamless and gapless annual digital elevation model (DEM) derived from CryoSat radar altimetry measurements to aid in the ongoing study of their ever-changing topography.

 

CryoSat-2 waveforms can be processed using two distinct techniques; (1) the conventional Point-Of-Closest-Approach (POCA), sampling a single elevation beneath the satellite, and (2) Swath processing which produces a swath of elevation measurements across the satellite ground track beyond the POCA, increasing spatial and temporal resolution. CryoSat operates in its Synthetic Aperture Radar Interferometric (SARIn) mode over the margins of the ice sheets allowing both processing techniques, however, within the ice sheet interior, CryoSat switches to its Low Resolution Mode (LRM), allowing solely the POCA technique for data processing. To achieve a comprehensive DEM encompassing the entirety of the ice sheet, whilst optimising data coverage, it is imperative to integrate and reconcile the outputs obtained from these distinct processing methodologies. This investigation uses two data sets provided by ESA’s CryoSat thematic product range: the CryoSat-2 ThEMatic PrOducts (CryoTEMPO) land ice data set that applies the POCA processing technique and covers the entirety of the ice sheets and the CryoTEMPO-EOLIS (Elevation Over Land Ice from Swath) data set that provides a comprehensive point cloud data set specific to the ice sheet margins.

 

In this investigation, the EOLIS and CryoTEMPO land ice datasets are aggregated into a spatial grid, utilising a Gaussian Radial Basis Function kernel to consider both, the spatial and temporal distribution of data points. To integrate EOLIS measurements from the margins of the ice sheet with CryoTEMPO land ice measurements from its interior, adjustments for variations in penetration are necessary to facilitate a seamless transition and mitigate the impact of anomalies. The combined and adjusted dataset is then post-processed to remove outliers while missing data is interpolated to generate a continuous DEM. Various spatio-temporal interpolation methods - such as External Drift Kriging, radial basis function, and DINCAE (Data Interpolating Convolutional Auto-Encoder) - have been explored and compared for their effectiveness.

 

This poster will provide and summarise an overview of the gridding, merging, and interpolation methodologies. Additionally, an assessment of the performance of different interpolation methods and their accuracies will be presented with comparisons to existing DEMs.

How to cite: Michael, C., Jakob, L., Gourmelen, N., Dubber, S., Boxall, K., Incatasciato, A., Ewart, M., Bouffard, J., and Di Bella, A.: A Seamless Ice Sheet Digital Elevation Model using CryoSat, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11645, https://doi.org/10.5194/egusphere-egu24-11645, 2024.

EGU24-11801 | Posters on site | CR5.4

Radar tomography of asteroid deep interior. JuRa / HERA to DIDYMOS and Ra proposed to APOPHIS  

Alain Herique, Dirk Plettemeier, and Wlodek Kofman

Our knowledge of the internal structure of asteroids relies entirely on inferences from remote sensing observations of the surface and theoretical modeling. Is the body a monolithic piece of rock or a rubble-pile, and how high is the porosity? What is the typical size distribution of the constituent blocks? Are these blocks homogeneous or heterogeneous? Direct measurements of an asteroid’s deep interior structure are needed to better understand asteroid accretion and their dynamic evolution. The characterization of the asteroids’ internal structure is crucial for science, planetary defense and exploration. In orbit Radar sounding is the most mature instruments capable of achieving the objective of characterizing the internal structure and heterogeneity, for the benefit of science as well as for planetary defense or exploration.

This is the goal of JuRa, the Juventas radar, onboard the ESA HERA mission. JuRa is a monostatic radar, BPSK coded at 60MHz carrier frequency and 20MHz bandwidth, inherited from CONSERT/Rosetta. The instrument design is under integration on Juventas cubesat for the ESA HERA mission. HERA will be launched this autumn to deeply investigate the Didymos binary system and especially its moonlet Dimorphos, five years after the DART/NASA impact. The main objective of JuRA is to characterize the asteroid interior, to identify internal geological structure such as layers, voids and sub-aggregates, to bring out the aggregate structure and to characterize its constituent blocks in terms of size distribution from submetric to global scale. The second objective is to estimate the average permittivity and to monitor its spatial variation in order to retrieve information on its composition and porosity.

This radar is also proposed to probe Asteroid 99942 Apophis in 2029, a potentially dangerous asteroid which will then approach Earth as close as 32000 kilometers on the DROID JPL/CNES and the RAMSES ESA proposed missions. This radar, which is a modified version of JuRa, will be able to operate in both monostatic and bistatic modes between orbiting or landed CubeSats. The knowledge of Apophis’ internal structure is crucial to improve our ability to study its stability conditions and to model its response to the gravitational constraints induced by Earth close approach. The Multipass processing will allow us to build a 3D tomographic image of the interior at different scales from submeter to global.

In this talk will present the instrument, its status, performances and goals as well as the science objectives in the context of the different targets.

How to cite: Herique, A., Plettemeier, D., and Kofman, W.: Radar tomography of asteroid deep interior. JuRa / HERA to DIDYMOS and Ra proposed to APOPHIS , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11801, https://doi.org/10.5194/egusphere-egu24-11801, 2024.

EGU24-12324 | ECS | Posters on site | CR5.4

Exploring Canyons Beneath Devon Ice Cap for Sub-Glacial Drainage Using Radar and Thermodynamic Modeling 

Chris Pierce, Mark Skidmore, Lucas Beem, Don Blankenship, Ed Adams, and Christopher Gerekos

Sub-glacial canyon features up to 580m deep between broad, flat mesas were identified beneath Devon Ice Cap, Devon Island, Nunavut, Canada during a recent Radar Echo Sounding (RES) survey. The largest canyon connects a hypothesized area of distributed sub-glacial water near the ice cap's summit with the marine-terminating Sverdrup outlet glacier. This canyon represents a probable drainage route for the hypothesized sub-glacial water system. Radar bed reflectivity is consistently 30 dB lower along the canyon floor than on the mesas, contradicting the signature expected in the presence of sub-glacial water. We compare these data with radar backscattering simulations to demonstrate that the reflectivity pattern may be topographically induced. Our simulated results indicated a 10m wide canal-like water feature is unlikely along the canyon floor averaging ~300m wide, however, smaller features may be difficult to detect via RES.

We calculated basal temperature profiles along the canyon using a 2-D finite difference method, and found basal conditions at the canyon floor may be significantly warmer than at the mesas. Despite elevated temperatures, there is limited evidence that the basal environment along the canyon floor could support a connected drainage system between the Devon Ice Cap summit and Sverdrup Glacier.

The complex terrain beneath Devon Ice Cap demonstrates some limitations for RES. Future studies should carefully consider attenuation correction methods near steep or complex terrain, and seek validation of RES analyses with multiple methods, as we have demonstrated here.  

How to cite: Pierce, C., Skidmore, M., Beem, L., Blankenship, D., Adams, E., and Gerekos, C.: Exploring Canyons Beneath Devon Ice Cap for Sub-Glacial Drainage Using Radar and Thermodynamic Modeling, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12324, https://doi.org/10.5194/egusphere-egu24-12324, 2024.

EGU24-12330 | Orals | CR5.4

Retracker-dependent radar freeboard correction methods for satellite radar altimetry-based sea ice thickness estimation 

Hoyeon Shi, Gorm Dybkjær, Suman Singha, Sang-Moo Lee, Rasmus Tonboe, and Fabrizio Baordo

Sea ice thickness is derived from its freeboard measured by satellite radar altimeters. However, the radar freeboard, which is initially estimated freeboard by interpreting the observed waveform, needs correction before sea ice thickness estimation so that it coincides with the height of the snow-ice interface from the sea surface. The so-called radar freeboard correction is thus an essential procedure for sea ice thickness estimation from satellite radar altimeter data, such as those from the CryoSat-2 mission. Today, most studies do the correction taking into account a slower wave propagation speed in the snow layer on sea ice under the assumption that the main scattering horizon is the snow-ice interface. However, while several recent studies have raised questions on that assumption, there is also a possibility that a retracker, which is an algorithm that estimates radar freeboard from waveform, has systematic bias. Accordingly, this study revisits the conventional way of doing the radar freeboard correction. First, we directly compare the CryoSat-2-derived radar freeboards from different retrackers with reference airborne freeboard measurements to introduce alternative correction methods for each retracker. Then, those correction methods are combined with a recently developed methodology where snow depth, sea ice thickness, freeboard, and ice draft are retrieved simultaneously. In order to compare the performance of different correction methods, including the conventional light speed correction, retrievals are done using the updated methodology, and those results are assessed using various reference datasets. Those are snow depth and freeboard from airborne observation, ice draft from mooring observation, and freeboard from satellite laser altimeter observation. In addition, the correction methods are combined with another independent retrieval method that estimates snow depth and sea ice thickness by combining satellite laser and radar altimeter measurements. Lastly, the consistency between the results from the two retrieval methods is examined for each radar freeboard correction method.

How to cite: Shi, H., Dybkjær, G., Singha, S., Lee, S.-M., Tonboe, R., and Baordo, F.: Retracker-dependent radar freeboard correction methods for satellite radar altimetry-based sea ice thickness estimation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12330, https://doi.org/10.5194/egusphere-egu24-12330, 2024.

EGU24-12995 | Posters on site | CR5.4 | Highlight

Comprehensive multi frequency airborne mapping of the southern flank of Dome A: results of the COLDEX airborne program. 

Duncan Young, John Paden, Megan Kerr, Shivangini Singh, Shravan Kaundinya, Shuai Yan, Alejandra Vega González, Jamin Greenbaum, Dillon Buhl, Gregory Ng, Kristian Chan, Bradley Schroeder, Gonzalo Echeverry, Thomas Richter, Scott Kempf, Fernando Rodriguez-Morales, Richard Hale, Donald Blankenship, and Edward Brook

The Center for Oldest Ice Exploration (COLDEX) is a US initiative funded to search for climate records over the last 5 million years, including locating sites for an accessible continuous ice core going back 1.5 million years.  As part of this effort, COLDEX has mapped the southern flank of Dome A, East Antarctica using an instrumented Basler, including dual frequency radar observations of the ice sheet and ice bed, as well as potential fields measurements (see presentation by Kerr in EGU session G4.3) across two field seasons from Amundsen-Scott South Pole Station.  The aerogeophysical system included both the UTIG VHF MARFA radar system operating at 52.5-67.5 MHz, as well as a new large high resolution UHF array from CReSIS operating at 670-750 MHz operating simultanously.  A goal of this project was to obtain airborne repeat interferometry for segments of the survey, as well as directly feed ice sheet models using englacial isochrons (see Singh presentation in EGU session CR5.6).  These goals lead to a survey explicitly designed around ice sheet flow lines.  

While prior work had sampled the region at lithospheric scales, the COLDEX survey had two components - the first was to map the region at crustal scales (line spacing of 15 km), and the second was to map subareas at ice sheet scales (line spacing of 3 km).  Immediate observations include an extensive basal unit and strong discontinuity in englacial stratigraphy that runs across the survey area and appears correlated with changes in bed interface properties.  The airborne campaign will be used to inform follow up ground campaigns to understand processes relevant for old ice preservation.

How to cite: Young, D., Paden, J., Kerr, M., Singh, S., Kaundinya, S., Yan, S., Vega González, A., Greenbaum, J., Buhl, D., Ng, G., Chan, K., Schroeder, B., Echeverry, G., Richter, T., Kempf, S., Rodriguez-Morales, F., Hale, R., Blankenship, D., and Brook, E.: Comprehensive multi frequency airborne mapping of the southern flank of Dome A: results of the COLDEX airborne program., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12995, https://doi.org/10.5194/egusphere-egu24-12995, 2024.

EGU24-13404 | ECS | Orals | CR5.4

Characterizing the altitude dependence of radar reflectometry for the (near-)surface of icy worlds 

Kristian Chan, Cyril Grima, Christopher Gerekos, and Donald Blankenship

Knowledge of (near-)surface properties and their spatial heterogeneity can reveal much about the processes that dominate the evolution of the top few-to-tens of meters of icy worlds. Radar reflectometry has been demonstrated to be a valuable technique for characterizing near-surface ice on Earth and Mars with mature plans for it to be applied to future observations of the Jovian icy moons, collected by the Europa Clipper and Juice missions. Both missions host nadir-pointing ice-penetrating radar instruments: the Radar for Europa Assessment and Sounding: Ocean to Near-surface (REASON) on Europa Clipper operating at center frequencies of 60 MHz and 9 MHz, with bandwidths of 10 MHz and 1 MHz, respectively, and the Radar for Icy Moons Exploration (RIME) on Juice at a single 9 MHz center frequency but bandwidths of 1 and 2.8 MHz.

Previous applications of reflectometry rested on the assumptions implicit in the Radar Statistical Reconnaissance (RSR) technique, which has been regularly used to characterize bulk near-surface properties (e.g., porosity) and surface roughness, each predominantly dependent on the coherent and incoherent components of the total surface return, respectively. However, these previous applications of RSR utilized observations collected at near constant altitude. Europa Clipper and Juice will both perform flybys of their targets of interest with altitude that rapidly changes across the observation window. Thus, an understanding of how altitude (convolved with changes in the surface geology) can affect the balance between observed coherent and incoherent backscattered energy is necessary to confidently apply RSR on Europa and Ganymede.

Here, we simulate the radar surface echo from synthetic Europa-like terrains, using a version of the multilayer Stratton-Chu coherent simulator that computes the scattering contributions from every frequency component within the bandwidth of the emitted chirp. We then apply RSR to deconvolve the total simulated surface power into its coherent and incoherent components. We assess the coherent content of the total power to changes in altitude, by comparing the coherent power derived from simulated surface echoes at the REASON/RIME shared center frequency (9 MHz) but different bandwidths (1 vs. 2.8 MHz). Coherent and incoherent geometric power falls off at different rates with altitude. Thus, the coherent content of the total return at a particular altitude over the target of interest could affect our ability to invert for near-surface properties. Note in particular that different terrain types (e.g., chaos terrain versus ridged plains on Europa) may be better observed at different altitudes from the perspective of reflectometry. In addition, our results provide valuable insight into targets and altitudes suitable for cross calibrating RIME and REASON [9/1 MHz] for comparative radar studies across the Jovian icy moons.

How to cite: Chan, K., Grima, C., Gerekos, C., and Blankenship, D.: Characterizing the altitude dependence of radar reflectometry for the (near-)surface of icy worlds, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13404, https://doi.org/10.5194/egusphere-egu24-13404, 2024.

EGU24-14072 | Posters on site | CR5.4

The Potential Role of Anomalous Geothermal Flux for Enhanced Basal Melting and Suppressed Ice Velocity at Haynes Glacier, West Antarctica 

Jason Bott, Don Blankenship, Shuai Yan, Lucas Beem, and Duncan Young

In NASA’s MEaSUREs Ice Velocity Data, a distinctive 8.5km diameter patch of slow-moving to stationary ice (0-15m/year) can be observed near the grounding line of Haynes Glacier, amidst much faster-flowing ice (300-1300 m/year). Additionally, a number of anomalously drawn-down englacial radar reflections are observed in multiple aerogeophysical surveys with the McCORDs (Multichannel Coherent Radar Depth Sounder) Instrument upstream of this ice velocity anomaly. 

The potential source of this velocity anomaly is hypothesized to be either anomalous geothermal flux or high frictional heat upstream, coupled to a thinning of the ice column as it nears the grounding line. These factors, taken together, imply a scenario where the warmer ice at the base of the ice column melts away while colder ice enters from above at the accumulation rate along the flowline. Upstream, with the ice column's relatively high thickness (~1000m), the basal ice experiences sufficient pressure to induce significant down draw of layers from substantial melting that is consistent with basal friction and/or a source of anomalous geothermal flux; the result is significant thermal advection of the much colder surface accumulation deep into the ice column. Downstream, where the ice thins, the  reduced pressure results in freezing of the anomalously cold ice to the bed, leading to the observed velocity anomaly.The testing of this hypothesis requires reconciling of the vertical velocity profile necessary to produce the down draw with either expected frictional melt or anomalous geothermal flux along the flowline (given the accumulation gradient). We present here this coupled thermal and kinematic modeling of Haynes Glacier from the site of the down draw to the sticky spot near the grounding line. With our models of temperature variations and ice flow characteristics within the Haynes Glacier system, we can further refine our understanding of the importance of heterogeneous geothermal flux for cryosphere evolution  - which may prove to be vitally important to fully understand fast-flowing and vulnerable ice streams in the Amundsen Embayment of West Antarctica. This, in turn, may have further implications for the study of heterogeneous heat flux and volcanic activity within the broader context of West Antarctica.

How to cite: Bott, J., Blankenship, D., Yan, S., Beem, L., and Young, D.: The Potential Role of Anomalous Geothermal Flux for Enhanced Basal Melting and Suppressed Ice Velocity at Haynes Glacier, West Antarctica, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14072, https://doi.org/10.5194/egusphere-egu24-14072, 2024.

EGU24-14822 | Posters on site | CR5.4

Big Data Analysis of Antarctic Ice Structures and Subglacial Lakes: Utilizing Moving IQR for Radar Intensity Processing 

Yong-Gil Park, Chol-Young Lee, Joo-Han Lee, and Dong-Chan Joo

The structure of Antarctic ice preserves the sequence of ice deposition, offering insights into ancient environmental conditions. Organisms discovered beneath the ice sheets, spanning from hundreds to thousands of meters in thickness, hold information on survival in extreme environments. Antarctic ice investigations are conducted using radar systems mounted on helicopters or vehicles, generating vast datasets covering hundreds of kilometers. Analyzing this large-scale data is essential to reduce time and cost for detecting ice structures and subglacial lakes. In this study, we developed algorithms for ice structure analysis and subglacial lake detection using big data analysis techniques, specifically outlier detection methods applied to radar signal values. Utilizing radar signal values represented in an 800x83,344 matrix, we employed the Spark platform with specifications of 400 cores and 1.6TB of memory for data analysis. To facilitate data processing in Spark, the data was transformed into a 3x66,675,200 dataframe after uploading to HDFS. Outlier detection, using the Moving Interquartile Range (IQR), identified abrupt changes in signal values based on columns, adjusting the IQR's range and scale to optimize the results. Detected outlier values were normalized within a 0-255 range and visualized based on intensity. Results revealed that using the Moving IQR for radar imagery processing effectively detected localized changes as the range increased; however, detection rates decreased with larger scales. Analyzing radar exploration results in a big data environment is anticipated to significantly reduce time and costs compared to traditional methods, contributing to Antarctic exploration and climate change response efforts.

 

How to cite: Park, Y.-G., Lee, C.-Y., Lee, J.-H., and Joo, D.-C.: Big Data Analysis of Antarctic Ice Structures and Subglacial Lakes: Utilizing Moving IQR for Radar Intensity Processing, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14822, https://doi.org/10.5194/egusphere-egu24-14822, 2024.

EGU24-16685 | ECS | Posters on site | CR5.4

Mapping Glacier Hydrology in 3D: Novel GPR Acquisition and Processing Techniques 

Johanna Klahold, Benjamin Schwarz, Alexander Bauer, Gabriela Clara Racz, Bastien Ruols, and James Irving

Ground-penetrating radar (GPR) has become a well-established tool in the field of glaciology thanks to its capacity for high-resolution imaging and the excellent propagation characteristics of radar waves in snow and ice. In this context, 3D surveying and processing techniques hold significant promise for examining the internal structure and dynamics of glaciers, yet 3D studies are rarely done due to time and cost constraints. In particular, the field of glacier hydrology could immensely benefit from the acquisition and dedicated processing of high-density 3D GPR data sets, as observations of hydrological conditions inside the glacier and at its base are of critical importance for model calibration and validation.

In this contribution, we attempt to exploit the full potential of high-resolution 3D GPR data to study glacier hydrology. A novel drone-based GPR acquisition system enables us to collect high-density 3D data with unprecedented spatial coverage. Our corresponding processing scheme considers two complementary components: the prominent reflected arrivals, and the faint (often neglected) diffracted wavefield. Reflection amplitudes at the ice-bedrock interface are used to delineate subglacial channels, whereas diffraction imaging methods borrowed from exploration seismology facilitate the localization of englacial conduits.

We present results from two case studies in the Swiss Alps: the Haut Glacier d’Arolla and the Glacier d’Otemma. Our workflow provides complementary maps of the subglacial drainage system and of well-developed englacial channels. For the Glacier d’Otemma, we combine these results with supplementary methods (photogrammetry, dye tracing, time lapse cameras, steam drilling, and hydrological modeling) to obtain a more comprehensive characterization of the drainage system.

How to cite: Klahold, J., Schwarz, B., Bauer, A., Racz, G. C., Ruols, B., and Irving, J.: Mapping Glacier Hydrology in 3D: Novel GPR Acquisition and Processing Techniques, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16685, https://doi.org/10.5194/egusphere-egu24-16685, 2024.

EGU24-17445 | ECS | Posters on site | CR5.4

ApRES observations of ice fabric in Greenland: From a climatic transition in the North to a potential historical ice stream remnant in the South 

Anja Rutishauser, Reinhard Drews, Reza M. Ershadi, Falk M. Oraschewski, Kirk M. Scanlan, Nanna B. Karlsson, Carlos Martin, Anne M. Solgaard, Camilla S. Andresen, and Andreas P. Ahlstrøm

The crystal orientation fabric (COF) of ice sheets, characterized as the net alignment of ice crystals, can contain a record of past ice sheet dynamics and potentially climatic conditions. In turn, the COF significantly influences ice viscosity, thus impacting present-day ice deformation and flow velocities. Due to its dielectric properties, anisotropic COF can be detected with polarimetric radar measurements, including Autonomous phase-sensitive Radio-Echo Sounders (ApRES).

Here, we present findings from polarimetric ApRES measurements conducted at Camp Century North-West Greenland, and two sites in Southwest Greenland: Dye-2 and KAN-U. At Camp Century, the ApRES measurements indicate some COF anisotropy throughout the ice column, with a distinct boundary at the depth of the Holocene-Wisconsin ice transition, previously identified in a nearby ice core. We investigate the origin of this boundary in the ApRES data, and whether such signatures can be used to identify glacial-interglacial transitions from polarimetric radar data.

At both sites in Southwest Greenland, the signal is strongly attenuated and falls below the noise level beyond 500 m depth, likely due to significant scattering within a heterogeneous firn column. However, Dye-2 exhibits strong COF anisotropy in the uppermost 100-500 m of the ice column, despite the region’s slow ice flow. Conversely, KAN-U displays no evidence of  COF anisotropy. We investigate causes of the peculiar localized anisotropy at Dye-2, hypothesizing it as a residual imprint of a historic fast flowing, far inland-reaching ice stream.

How to cite: Rutishauser, A., Drews, R., Ershadi, R. M., Oraschewski, F. M., Scanlan, K. M., Karlsson, N. B., Martin, C., Solgaard, A. M., Andresen, C. S., and Ahlstrøm, A. P.: ApRES observations of ice fabric in Greenland: From a climatic transition in the North to a potential historical ice stream remnant in the South, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17445, https://doi.org/10.5194/egusphere-egu24-17445, 2024.

EGU24-18028 | Posters on site | CR5.4

Folded ice in the upper North East Greenland Ice Stream reveal timing of the onset of streaming 

Daniela Jansen, Steven Franke, Catherine Bauer, Tobias Binder, Dorthe Dahl-Jensen, Jan Eichler, Olaf Eisen, Yuanbang Hu, Johanna Kerch, Maria Gema Llorens, Heinrich Miller, Niklas Neckel, John Paden, Tamara de Riese, Till Sachau, Nicolas Stoll, Ilka Weikusat, Frank Wilhelms, Yu Zhang, and Paul Dirk Bons

Only a few localised ice streams drain most ice from the Greenland Ice Sheet. Thus, understanding ice stream behaviour and their temporal variability is crucially important to predict future sea-level change. The interior trunk of the 700 km-long North-East Greenland Ice Stream (NEGIS) is remarkable for the lack of any clear bedrock channel to explain its presence. Here we use isochronous radar reflections from an airborne radar survey as passive tracers of ice deformation. We present the first-ever 3-dimensional analysis of folding and advection of stratigraphic horizons within an ice stream, which shows that the localised flow and shear margins in the upstream part were fully developed only ca. 2000 years ago. This indicates that this type of streaming in the interior of an ice sheet can be triggered on short time scales.

How to cite: Jansen, D., Franke, S., Bauer, C., Binder, T., Dahl-Jensen, D., Eichler, J., Eisen, O., Hu, Y., Kerch, J., Llorens, M. G., Miller, H., Neckel, N., Paden, J., de Riese, T., Sachau, T., Stoll, N., Weikusat, I., Wilhelms, F., Zhang, Y., and Bons, P. D.: Folded ice in the upper North East Greenland Ice Stream reveal timing of the onset of streaming, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18028, https://doi.org/10.5194/egusphere-egu24-18028, 2024.

EGU24-18077 | ECS | Orals | CR5.4

Can polarimetric wide-angle radar surveys teach us more about ice fabric anisotropy? 

Falk M. Oraschewski, M. Reza Ershadi, Clara Henry, and Reinhard Drews

The fabric anisotropy of ice and its flow dynamics are co-dependent. Parameters used in models that solve the evolution of ice fabric are currently unconstrained, for which comparisons with observations are needed. In observations and models, the ice fabric can be represented by a crystal orientation tensor, describing the spatial distribution of ice crystal orientations. Because ice crystals are not only mechanically, but also dielectrically anisotropic, the fabric anisotropy causes birefringence and anisotropic scattering and can be inferred by polarimetric radar surveys. In recent years, the advancement of polarimetric radar methods has resulted in a surge of available observational data. However, all existing methods are performed with a nadir-looking radar geometry. As a consequence, these approaches are only sensitive to horizontal fabric anisotropy, making the assumption necessary that one eigenvector of the crystal orientation tensor is aligned in vertical (nadir) direction. We aim to develop an approach to measure the actual orientation of this eigenvector. 

Here, we present the results of a polarimetric wide-angle common midpoint (CMP) survey conducted on Ekström Ice Shelf, Dronning Maud Land, Antarctica, using the Autonomous phase-sensitive Radio Echo Sounder (ApRES). Our CMP survey had a maximum antenna offset of 200 m, with an ice shelf thickness of 250 m. For several englacial reflectors, we observe offset-dependent phase shifts between orthogonal antenna orientations. We explore these phase variations by modelling the off-nadir radio wave propagation in the birefringent ice. These wide-angle radar surveys have the potential to infer the full crystal orientation tensor, required for a constitutive paramerization of glacial flow.

How to cite: Oraschewski, F. M., Ershadi, M. R., Henry, C., and Drews, R.: Can polarimetric wide-angle radar surveys teach us more about ice fabric anisotropy?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18077, https://doi.org/10.5194/egusphere-egu24-18077, 2024.

EGU24-18237 | ECS | Posters on site | CR5.4

Mapping of deep internal reflection horizons, method modifications and applications. 

Hameed Moqadam, Claudius Zelenka, and Olaf Eisen

The task of mapping of deep internal reflection horizons (IRH) of ice sheets has been a crucial step for a variety of glaciological studies, for instance relating ice core age-depth relationships, tuning ice sheet models, and extend dated layers beyond ice core sites. However, mapping a sufficient number of IRHs is a time-consuming and error-proned task. Thus, there have been ongoing endeavors for automatized pipelines to perform this.

In this work, a complete pipeline for automatic mapping of deep IRH, which determine ice layer boundaries, is presented. This pipeline is tested on radargrams from Dronning Maud Land Antarctica and shows good performance in mapping a number of deep IRHs. The model shows great promise to be used on snow radargrams and obtaining recent accumulation rates as well.

We have applied convolutional neural networks (CNN) to achieve this. The training data is composed of a small set of complete hand-labeled radargrams as well as radargrams that are labeled using conventional feature extraction methods. This task requires dense pixel-level predictions, and ground-truth collection is time-consuming and prone to errors, therefore a group of modifications have been implemented on the model. The role of post-processing is discussed, since the output of the model is a raw image and much work is done on the model output. The potential of such a deep mapped stratigraphy is discussed and various applications are pointed out.

How to cite: Moqadam, H., Zelenka, C., and Eisen, O.: Mapping of deep internal reflection horizons, method modifications and applications., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18237, https://doi.org/10.5194/egusphere-egu24-18237, 2024.

Radar sounder (or Ice-penetrating radar) is one of the most suitable geophysical instruments to explore planets and moons given the very dry and/or cold conditions of their crusts, which favor the penetration of the radio waves at great depth. The first ever planetary subsurface radar was tested on the Moon, during the Apollo 17 mission: the ALSE (Apollo Lunar Sounder Experiment) multifrequency radar sounder operating onboard the Apollo Service Module (ASM) (Porcello et al., 1974). After this successful experiment more than twenty years passed before another radar sounder was included in the payload of a planetary mission. MARSIS was launched in 2003, on board Mars Express, and SHARAD in 2007 onboard Mars Reconnaissance Orbiter. Since the successful deployed on Mars, such radars collected data for more than 15 years, mapping the structures of the Martian poles and discovering the first extraterrestrial stable body of subglacial liquid water below the South pole cap. Six orbiting radar sounders have been employed so far to explore the Moon, Mars and the 67P/GC comet, and some of them are still in full operation today. The Jupiter icy moons will be the next destination of a new generations of radars: RIME, already on his way to Ganymede onboard JUICE and REASON that will be launch this year onboard Europa Clipper. These radars will explore the icy shells of Europa, Ganymede and Callisto to establish their habitability conditions and in search for evidence of liquid water. Finally, also Venus will be investigated in the next decade by a similar radar to help understand the geological and climatic evolution of the Earth twin.

In this talk I will discuss the new opportunities and challenges for the radar sounder community in the years to come.

How to cite: Pettinelli, E.: In search for liquid water using radio waves: from Earth to the icy moons of Jupiter, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18640, https://doi.org/10.5194/egusphere-egu24-18640, 2024.

EGU24-3826 | PICO | CR5.6 | Highlight

Super-resolution of satellite observations of sea ice thickness using diffusion models and physical modeling. 

Julien Brajard, Anton Korosov, Richard Davy, and Yiguo Wang

This work introduces a simulator of high-resolution sea ice thickness in the Arctic based on diffusion models, which is a type of artificial intelligence (AI) generative model. Diffusion models have already shown impressive skill in generating realistic high-resolution images (e.g., DALL-E, Midjourney, Stable Diffusion).

Current satellite-based observations or climate model simulations of sea ice thickness provide valuable data but are limited by their coarse spatial resolution. High-resolution information is crucial for useful predictions and understanding small-scale features such as leads and thin ice, which significantly impact seasonal forecasting and heat flux calculations.

To increase the resolution of sea ice thickness products, we propose the following. First, a physically-based sea ice model, neXtSIM, is employed to generate a synthetic but realistic high-resolution sea ice thickness dataset. This synthetic dataset is then filtered to mimic the resolution of present satellite products or climate model outputs. An AI-based diffusion model is then trained to enhance the low-resolution SIT data. 

By comparing the field produced by the simulator and a high-resolution test image, we will demonstrate that the simulator is able to produce accurate and realistic high-resolution sea ice thickness fields. Accuracy is demonstrated by assessing the error of the reconstruction, while realism is assessed by visual inspection and by computing the power density spectra. For both criteria, accuracy, and realism, our simulator outperforms a linear interpolation of the low-resolution field, which is used as a baseline.

This work is held in the framework of the project SuperIce, funded by ESA.

How to cite: Brajard, J., Korosov, A., Davy, R., and Wang, Y.: Super-resolution of satellite observations of sea ice thickness using diffusion models and physical modeling., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3826, https://doi.org/10.5194/egusphere-egu24-3826, 2024.

EGU24-5964 | ECS | PICO | CR5.6

Introducing ELSA: An isochronal model for ice sheet layer-age tracing 

Therese Rieckh, Andreas Born, Alexander Robinson, Robert Law, and Gerrit Gülle

We are presenting the ice-sheet layer-age tracer ELSA (Englacial Layer Simulation Architecture) — a model that uses a straightforward method to simulate the englacial stratification of large ice sheets — as an alternative to Eulerian or Lagrangian tracer schemes. ELSA’s vertical axis is time; individual layers of accumulation are modeled explicitly and are isochronal. 

ELSA is not a stand-alone ice-sheet model, but requires uni-directional coupling to another model providing ice physics and dynamics (the “host model”). Via ELSA’s layer tracing, the host model’s output can be evaluated throughout the ice sheet interior using ice core or radiostratigraphy data. 

We show results regarding the stability and resolution-dependence of this coupled modeling system using simulations of the last glacial cycle of the Greenland ice sheet with Yelmo as the host model. We present options for making ELSA computationally efficient enough for ensemble runs, as well as requirements for offline forcing of ELSA with output from a range of existing ice-sheet models. 

ELSA is an open source project and available on git (https://git.app.uib.no/melt-team-bergen/elsa) for the ice sheet modeling community.

How to cite: Rieckh, T., Born, A., Robinson, A., Law, R., and Gülle, G.: Introducing ELSA: An isochronal model for ice sheet layer-age tracing, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5964, https://doi.org/10.5194/egusphere-egu24-5964, 2024.

EGU24-6433 | ECS | PICO | CR5.6

Assessing the Impact of Ice Velocity Observations on Ice Sheet Mass Loss Projections from the Amundsen Sector 

Beatriz Recinos, Daniel Goldberg, and James R. Maddison

Ice streams in the Amundsen Sea Embayment (ASE) are some of most rapidly thinning in Antarctica, experiencing ocean-driven grounding-line retreat and increased mass loss. Ice streams in this sector are crucial for maintaining the stability of the West Antarctic ice sheet, which contains enough ice to raise global mean sea-level by 5.3 m. Ice sheet models are our main tool to make projections of ice sheet mass loss or volume above floatation (which is equivalent to sea level rise). Standard methodologies consist of constraining model parameter fields using satellite observations, and then simulating model response to climate forcing. However, to date there is no comprehensive assessment of how sensitive these projections are to different satellite products or to spatial variations in ice velocity observations, or changes in the spatial distribution of unknown model parameters.  

Mapping the sensitivity of ice streams to a given set of model inputs can be done using an ensemble of simulations and running the model workflow tens (or hundreds) of thousands of times. Automatic Differentiation (AD) and data assimilation, however, provides an efficient method to perform this analysis and get these sensitivity maps at the scale of the model’s mesh. Here we use the ice sheet model Fenics_ice and its AD capabilities to construct maps of the sensitivity of volume above floatation to changes in the calibrated unknown model parameters, as well as changes in ice velocity observations. Our preliminary results show that the sea level rise forecast is more sensitive to ice velocity changes at the grounding line and to changes to the basal drag coefficient at those same locations.  

How to cite: Recinos, B., Goldberg, D., and Maddison, J. R.: Assessing the Impact of Ice Velocity Observations on Ice Sheet Mass Loss Projections from the Amundsen Sector, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6433, https://doi.org/10.5194/egusphere-egu24-6433, 2024.

EGU24-6532 | ECS | PICO | CR5.6

Stochastic Simulation of Mass-Conserving Subglacial Topography with Monte Carlo Markov Chain 

Niya Shao, Michael Field, Emma MacKie, and Felicity McCormack

While subglacial topography serves a crucial role in ice sheet models, it remains generally sparsely sampled across Antarctica. Subglacial topography is primarily measured by airborne ice-penetrating radar with data gaps exceeding 100s of kilometers. Traditional kriging methods used to interpolate the sparse radar data cause spurious effects on ice flow divergence. Numerically solving for mass conservation equations addresses this issue but may smooth out the roughness of topography observed in the covariance structure of radar data. In this study, we propose a novel approach to generate an ensemble of realistically rough and mass-conserving subglacial topography. We utilize the Monte Carlo Markov Chain algorithm, where in each iteration of the Markov Chain, the topography is perturbed by Sequential Gaussian Simulation to reproduce the covariance structure in the radar data. The perturbed topography is then accepted with a probability constrained by both prior probability based on the radar measurement uncertainty and likelihood indicated by the topography’s deviation from mass conservation law. After the Markov Chain converges to a stable state, an ensemble of topography is sampled from the chain. We tested the method on Denman Glacier and produced posterior distribution of topography constrained by radar measurements and mass conservation. Moreover, the covariance structure of radar data is preserved in every generated topography realization. The method we developed provides a possibility to incorporate realistically rough topography into ice sheet models while avoiding artifacts caused by the violation of mass conservation. Furthermore, multiple subglacial topography realizations allow the propagation of inherent uncertainties in the sparsity of radar measurement to the result of downstream models.

How to cite: Shao, N., Field, M., MacKie, E., and McCormack, F.: Stochastic Simulation of Mass-Conserving Subglacial Topography with Monte Carlo Markov Chain, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6532, https://doi.org/10.5194/egusphere-egu24-6532, 2024.

EGU24-8113 | ECS | PICO | CR5.6

Increasing the information flow into glacier system models using an Ensemble Kalman Filter 

Oskar Herrmann and Johannes Fürst

We are introducing a novel technique for calibrating the unknown parameters of a glacier model by integrating remote sensing data. Our approach involves the fusion of the Instructed Glacier Model (IGM) with an Ensemble Kalman Filter designed explicitly for transient data assimilation. Our primary objective is to assimilate remotely sensed observations at the respective time of acquisition during forward simulations. During the presentation, we explore the Ensemble Kalman Filter's core concept and showcase our approach's effectiveness through twin experiments, fine-tuning model parameters related to ice dynamics and surface mass balance. Utilizing observations from prominent glaciers in the European Alps, our methodology concurrently minimizes uncertainty estimates of crucial parameters such as equilibrium line altitude and ablation/accumulation gradients. The resulting uncertainty estimate is then integrated into future projections.

How to cite: Herrmann, O. and Fürst, J.: Increasing the information flow into glacier system models using an Ensemble Kalman Filter, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8113, https://doi.org/10.5194/egusphere-egu24-8113, 2024.

State-of-the-art sea ice models struggle to accurately simulate historical sea ice thickness changes, which could be partially due to inadequate representation of dynamics and thermodynamic processes. High-resolution observations are fundamental tools for improving our understanding of the sea ice physical processes, validating numerical models, and ultimately formulating better sea ice parameterization. Winter observations collected during the Multidisciplinary Drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition in winter 2019-2020 are unique tools for evaluating our models during the freezing season. However, a shortcoming of these observations is that they cannot be easily combined due to differences in measurement techniques and processing chain, impeding a comprehensive characterization of the sea ice system and limiting their diagnostic employment with models. Here, we present an advanced spatiotemporal colocation algorithm designed to integrate airborne measurements collected during multiple helicopter surveys, which provide a two-dimensional characterization of the sea ice surface temperature through infrared camera images and of the surface elevation through an airborne laser scanner at a resolution of approximately one meter over areas spanning several kilometers. The co-located temperature and elevation fields can be combined with boundary layer observations and ground-based transect surveys via drift correction approaches. These observations put in relation for the first time snow freeboard with the equilibrium skin temperature resulting from the surface energy balance while resolving small-scale thickness features (e.g., snow dunes, ridges, and refrozen leads). We will showcase how this innovative observational dataset enables multi-category sea ice model evaluation and the development of new parameterizations. 

How to cite: Zampieri, L., Hutter, N., and Cocetta, F.: Colocated airborne observations from MOSAiC enable sea ice process understanding and new model parameterization development, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9945, https://doi.org/10.5194/egusphere-egu24-9945, 2024.

EGU24-11310 | PICO | CR5.6

A Benchmark Dataset for Radio Echo Sounding Data 

Marcel Dreier, Nora Gourmelon, Moritz Koch, Thorsten Seehaus, Matthias Braun, Andreas Maier, and Vincent Christlein

Melting glaciers and ice sheets contribute significantly to the global sea level rise, posing an existential threat to coastal regions. For that reason, many expeditions collect radio echo sounding data to track, model, and predict the changes in ice mass and thickness. However, manually analyzing the data collected to determine the thickness of the ice sheet and mountain glaciers is a time-consuming task, as the collected data often extends over tens to hundreds of kilometers. Hence, the development and utilization of automated and semi-automated tools have risen in popularity to alleviate the problem. Especially machine learning-based approaches show promising results as they can capture complex relationships in the data. However, such methods require large labeled datasets to achieve their full potential. Thus, we are currently gathering and cleaning data that will be released as a benchmark dataset for radio echo sounding data to train, test, and compare different approaches. 

In detail, the dataset will consist of 2D radar data with georeferenced labels for the position of the air-ice and ice-bedrock interface. We plan to incorporate radar data from multiple sources since the underlying radar system and expedition area play a significant role in depicting the data and the general difficulty of the task. That way, the performance of a system can be fairly assessed with the benchmark dataset without the evaluation results being skewed by external factors. We will further ensure a fair comparison by dividing the data of every source in an independent training, validation, and test set. This division will also allow us to use the benchmark dataset to train and compare systems specialized on only a single data source. Thus, future work can also utilize our benchmark dataset to develop systems specialized on only a single data source. 
Lastly, we will release a baseline model alongside the benchmark dataset to demonstrate its practicality. Thereby giving an initial point of reference that future work can compare to. 

How to cite: Dreier, M., Gourmelon, N., Koch, M., Seehaus, T., Braun, M., Maier, A., and Christlein, V.: A Benchmark Dataset for Radio Echo Sounding Data, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11310, https://doi.org/10.5194/egusphere-egu24-11310, 2024.

Sea ice poses a significant threat to high-latitude navigation and offshore operations. Accurate and timely classification of sea ice is crucial for ensuring the safety of maritime activities in polar regions. Synthetic aperture radar (SAR) is widely used for sea ice classification due to its high resolution and all-weather observation capability. However, the Sentinel-1 extra-wide (EW) swath mode images, which are commonly used to monitor sea ice in the polar region, exhibit thermal noise in the cross-polarization images, and it is thought to affect the accuracy of sea ice classification models. In this study, we used Sentinel-1 EW mode images and a deep learning (DL) model, U-Net, to investigate the impact of thermal noise on sea ice classification. Sensitivity experiments were conducted for the U-Net and the comparison models, such as support vector machine (SVM), random forest (RF), and convolutional neural network (CNN), with or without using a denoising method for cross-polarization images. Both co-polarization and cross-polarization images were used to train these models. The experimental results indicate that SVM, RF, CNN, and U-Net achieved classification accuracies of 67.98%, 77.96%, 86.49%, and 90.00% respectively, using undenoised images. The classification accuracies improved to 71.69%, 80.75%, 86.65%, and 90.73% respectively after the denoising method was used. The SVM and RF models show an increase in accuracy of about 3%, while the CNN and U-Net models show an improvement of less than 1%, suggesting that CNN and U-Net are more tolerant to noise when used for sea ice classification.

How to cite: Huang, Y. and Yang, X.: Assessment of thermal noise impact on sea ice classification using Sentinel-1 images and U-Net, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13621, https://doi.org/10.5194/egusphere-egu24-13621, 2024.

EGU24-13789 | ECS | PICO | CR5.6

Optimizing rapid access englacial sampling location to date deep radiostratigraphy for old ice 

Shivangini Singh, Duncan Young, Shuai Yan, Gregory Ng, Dillon Buhl, Alejandra Vega Gonzalez, Megan Kerr, Jamin Greenbaum, Scott Kempf, and Donald Blankenship

The Center for Oldest Ice Exploration (COLDEX) aims to unearth a stratigraphically intact ice core record going back to 1.5 million years. The target area is the corridor between South Pole and the southern flank of Dome A. While our current survey has yielded dated stratigraphy extending to 93.9 thousand years ago across the region, a significant portion of the stratigraphy remains undated. Our approach has involved leveraging englacial connections with existing ice cores and dust loggers, yet much of the stratigraphy awaits dating. Rapid ice access tools are capable of sampling the ice sheet using far fewer resources as compared to conventional drilling. By optimizing the site for such sampling, we can preemptively maximize the information that can be extracted eventually.

Our study’s objective in selecting a rapid ice access site is twofold: firstly, to maximize the age-depth scale extraction by dating the hitherto undateable deeper isochrones, and secondly, to strategically sample the pervasive basal layer in the survey region to understand its role in preserving old ice. To achieve an optimal age-depth scale extraction, we aim to target sites containing a larger portion of undated stratigraphy while maintaining the optimum resolution to understand ice age dust cycles. For instance, Ice Diver, a melt probe by COLDEX, houses an optical dust logger capable of counting ice age dust cycles.

Previous research (e.g., Chung et al., 2023) indicates that a basal layer identified through radar sounding may exhibit a distinct flow regime compared to the stratigraphic portion of the ice sheet column. Accessing this layer in advance could provide insights into the interface between the echo-free zone and stratigraphic ice, thereby refining our understanding of current ice sheet models and how to exploit them in the pursuit of old ice. An ideal access site would facilitate quick sampling without requiring deep drilling to reach the basal layer. Our aim is to reconcile these methodologies by identifying the most suitable site(s) for deploying such probes or drills.

How to cite: Singh, S., Young, D., Yan, S., Ng, G., Buhl, D., Vega Gonzalez, A., Kerr, M., Greenbaum, J., Kempf, S., and Blankenship, D.: Optimizing rapid access englacial sampling location to date deep radiostratigraphy for old ice, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13789, https://doi.org/10.5194/egusphere-egu24-13789, 2024.

The Arctic is one of the important drivers of global climate and environmental change. Its atmosphere, oceans, and sea ice movements have direct or indirect impacts on global atmosphere and ocean circulation as well as climate variability. Sea ice plays a crucial role in maintaining climate balance in the Arctic region, preventing more solar radiation from entering the sea through its high reflectivity and limiting air sea heat exchange, reducing sea surface temperature and sea ice melting rate. Sea ice thickness is an important parameter that describes the properties of sea ice. Obtaining the freeboard of sea ice through satellite altimetry measurements is of critical importance for sea ice thickness retrieval and understanding changes in Arctic sea ice. So far, research on satellite observations of pan-Arctic sea ice thickness has been limited to winter months. The key to measuring the freeboard using altimetry lies in distinguishing sea surface types and correctly identifying adjacent inter ice waterways. However, there are a large number of melting pools on the surface of summer floating ice, which make traditional waveform classification schemes unable to accurately distinguish sea surface types and become the main obstacle to retrieval freeboard of summer sea ice. In this study, a one-dimensional convolutional neural network classification model is built using CryoSat-2 summer sea ice classification training and testing dataset to improve summer sea ice freeboard retrieval. The model uses three parameters as input sources, i.e., elevation, pulse peakness, and backscatter coefficient. It achieves an overall accuracy of 84.3%. The sea ice freeboard is calculated from the elevation difference between the ice-covered waterways and its surrounding floating ice, resulting in distributions of 15-day individual sea ice freeboard and sea ice freeboard on an 80-km resolution grid. The results show that although there are many missing data due to noise and other issues, effective sea ice freeboard can be obtained in all months in summer. It demonstrates the feasibility of this method.

How to cite: Yang, X.: Research on Sea Ice Freeboard Retrieval from CryoSat-2 Based on Artificial Intelligence, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13988, https://doi.org/10.5194/egusphere-egu24-13988, 2024.

EGU24-14303 | ECS | PICO | CR5.6

Subseasonal prediction of regional Antarctic sea ice by a deep learning model 

Yunhe Wang, Xiaojun Yuan, Yibin Ren, Mitchell Bushuk, Qi Shu, Cuihua Li, and Xiaofeng Li

Antarctic sea ice concentration (SIC) prediction at seasonal scale has been documented, but a gap remains at subseasonal scale (1-8 weeks) due to limited understanding of ice-related physical mechanisms. To overcome this limitation, we developed a deep learning model named SIPNet that can predict SIC without the need to account for complex physical processes. Compared to mainstream dynamical models like ECMWF, NCEP, and GFDL-SPEAR, as well as a relatively advanced statistical model like the linear Markov model, SIPNet outperforms them all, effectively filling the gap in subseasonal Antarctic SIC prediction capability. SIPNet results indicate that autumn SIC variability contributes the most to sea ice predictability, whereas spring contributes the least. In addition, the Weddell Sea displays the highest sea ice predictability, while predictability is low in the West Pacific. SIPNet can also capture the signal of ENSO and SAM on sea ice.

How to cite: Wang, Y., Yuan, X., Ren, Y., Bushuk, M., Shu, Q., Li, C., and Li, X.: Subseasonal prediction of regional Antarctic sea ice by a deep learning model, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14303, https://doi.org/10.5194/egusphere-egu24-14303, 2024.

EGU24-16023 | ECS | PICO | CR5.6

A global englacial temperature database (glenglat) 

Mylène Jacquemart and Ethan Welty

Ice temperature is an important characteristic of any glacier. It influences glacier dynamics, subglacial hydrology, glacier retreat behavior, and potential glacier hazards. Additionally, ice temperature can serve as an archive of past air temperature changes and be used for climate reconstructions and validation of thermo-mechanical glacier models. Measuring (deep) ice temperatures, however, is very laborious and costly, and most  ice temperature measurements are hidden away in publications that span almost a century.

To overcome the gap between data availability and data need, we have compiled ice temperature data from 132 glaciers in an open-source, version-controlled database available to the scientific community. This global englacial temperature database (glenglat; https://github.com/mjacqu/glenglat) contains temperatures measured in 410 different boreholes in the Americas, Greenland, Eurasia, Africa, and Antarctica between 1938 and 2023. Roughly 20% of all boreholes are known to have reached the glacier bed; the deepest borehole is 743 meters deep; and most measurements are from cold or polythermal glaciers. Data for 369 boreholes were extracted from published literature while data for the remaining 41 boreholes were directly submitted to the authors.

The database is structured following the Frictionless Data Tabular Data Package specification. The data are stored as comma-separated-value (CSV) files and the metadata are provided in a single YAML file – text formats which are both human and machine readable. Following a standard structure provides two key advantages: First, upon any change to the data or metadata, the structure and content of the database can automatically be validated using existing software. Second, documentation and data submission templates can be rendered automatically from the machine-readable metadata, which lowers the bar for data maintainers and future contributors. We hope that glenglat can serve many glaciological applications and become the  repository of choice for future ice temperature measurements.

How to cite: Jacquemart, M. and Welty, E.: A global englacial temperature database (glenglat), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16023, https://doi.org/10.5194/egusphere-egu24-16023, 2024.

EGU24-16508 | PICO | CR5.6 | Highlight

Improving dynamical seasonal sea ice prediction in the Arctic with machine learning 

Zikang He, Yiguo Wang, Julien Brajard, and Xidong Wang

 

Dynamical sea ice predictions have significant biases or systematic errors that are difficult to effectively remove. In this work, we introduce machine learning into the Norwegian Climate Prediction Model (NorCPM, a state-of-the-art dynamical prediction system) to improve Arctic sea ice predictions.

We build a statistics bias-correction methodology employing machine learning techniques. An artificial neural network is trained with NorCPM data. It is then used to predict sea ice concentration biases or systematic errors and correct them either in post-processing of the predictions (offline manner) or during the production of the prediction (online manner). We evaluate the outcomes by assessing sea ice extent (SIE) and comparing them against observational data. Our findings reveal that offline correction markedly reduces the prediction biases in summer (more than 30%), while online correction enhances the variability in sea ice predictions up to four months. These results underscore the potential of machine learning as a potent tool for refining the accuracy of Arctic sea ice seasonal predictions.

How to cite: He, Z., Wang, Y., Brajard, J., and Wang, X.: Improving dynamical seasonal sea ice prediction in the Arctic with machine learning, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16508, https://doi.org/10.5194/egusphere-egu24-16508, 2024.

EGU24-17119 | ECS | PICO | CR5.6

Simulation-Based Inference of Surface Mass Balance of Antarctic Ice Sheets 

Anne Hermann, Clara Henry, Guy Moss, and Reinhard Drews

Uncertainties in surface mass balance (SMB) have the potential to significantly impact modelled ice thickness and ice-flow dynamics. A common approach is to reconstruct the surface mass balance history from the internal ice stratigraphy as imaged by radar. Particularly for intermediate and deeper layers, this requires accounting for deformation by ice flow using ice-dynamic forward models in an inverse framework. Numerous approaches to do so exist, but many of them are tailored to specific stratigraphy datasets and do not include uncertainties.

Previous work used simulation-based inference (SBI) to infer the SMB rates of steady state ice shelves, solving velocities using the shallow shelf approximation [1]. The approach not only estimates the spatially varying SMB field but also their uncertainties. We adapt this framework to infer SMB on grounded ice, where flow is dominated by internal deformation rather than longitudinal stretching. The forward model used in this study calculates velocities by solving the shallow ice approximation. The resulting velocities are used as input to an isochronal tracer scheme which calculates the stratigraphy of the ice [2]. Initial testing of our method is conducted on an idealized ice sheet, namely the Vialov profile. In future work, we aim to infer for the SMB history along a radar transact of Derwael Ice Rise in East Antarctica, where internal stratigraphy data is available. Our method provides a new uncertainty aware approach to estimate the SMB field on grounded ice.

 

[1] Moss et al.: Simulation-Based Inference of Surface Accumulation and Basal Melt Rates of an Antarctic Ice Shelf from Isochronal Layers (2023).

[2] Born: Tracer transport in an isochronal ice-sheet model (2017).

How to cite: Hermann, A., Henry, C., Moss, G., and Drews, R.: Simulation-Based Inference of Surface Mass Balance of Antarctic Ice Sheets, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17119, https://doi.org/10.5194/egusphere-egu24-17119, 2024.

Sea ice plays a significant role in Arctic research and operations. However, the lack of high spatiotemporal resolution observations on sea ice makes it challenging to accurately depict short-term sea ice changes. This limitation hampers the development of small-scale sea ice change studies and increases uncertainties in Arctic research and operational safety. With advancements in deep learning techniques and the abundance of multi-source remote sensing data such as optical, radar, and passive microwave, reconstructing high spatiotemporal resolution sea ice concentration in the Arctic becomes feasible. Based on multi-source remote sensing data and the integration of sea ice dynamics and thermodynamics, this study proposes a novel deep learning model for high spatiotemporal resolution sea ice concentration reconstruction. Based on this model, we achieved sub-kilometer scale and hourly-level reconstructions of Arctic sea ice concentration from 2021 to 2022, with a mean absolute error of less than 5%, thereby providing data support for Arctic research and operations.

How to cite: Qiu, Y., Li, Y., Yu, S., and Jin, Z.: High spatiotemporal reconstruction of Arctic sea ice concentration based on multi-source remote sensing data, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19134, https://doi.org/10.5194/egusphere-egu24-19134, 2024.

EGU24-19721 | PICO | CR5.6

Quantifying of the ten-year variation in surface velocity of the Svalbard Archipelago glaciers using SAR data 

Wojciech Milczarek, Anna Kopeć, Michał Tymplaski, and Marek Sompolski


Dynamic climate changes are especially noticeable in polar regions, where glaciers are retreating landward at an increased rate. This study emphasizes the application of the feature tracking method for analyzing the ice flow velocity across the entire Svalbard archipelago from 2015 to 2024. We conducted our analysis using the Geogrid and autoRIFT platforms, complemented by Sentinel-1 imagery. To validate our ice velocity products, we employed the Glacier Feature Tracking (GLAFT) aproach. Our analysis culminated in the development of an extensive glacier repository for the archipelago, which includes velocity data spanning the study period. These results facilitated the identification of glaciers demonstrating surging behavior. Additionally, the study introduces a novel approach to analyzing glacier flow velocities, focusing on their acceleration characteristics.

How to cite: Milczarek, W., Kopeć, A., Tymplaski, M., and Sompolski, M.: Quantifying of the ten-year variation in surface velocity of the Svalbard Archipelago glaciers using SAR data, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19721, https://doi.org/10.5194/egusphere-egu24-19721, 2024.

EGU24-20355 | ECS | PICO | CR5.6

Detection of Melt Ponds on Arctic Sea Ice from Infrared Images using AutoSAM 

Marlena Reil, Gunnar Spreen, Marcus Huntemann, Lena Buth, and Dennis Wilson

The Arctic is significantly affected by climate change, as evidenced by the constant decline of sea ice since the beginning of satellite observations. One driver of this transformation are melt ponds - pools of water that form as a result of melting sea ice during summer. Due to their darker color, they increase the absorption of incoming sunlight and accelerate ice melt. Accurate determination of melt pond extent and characteristics is considered a main factor in reducing uncertainty in Arctic climate models and sea ice concentration retrievals, but precise large scale observations are not available. Most knowledge to date is based on in-situ measurements, which are restricted to small areas. Satellite retrievals offer Arctic-wide coverage on a regular basis but lack resolution. To validate satellite measurements and allow observation at a moderate scale, helicopter-borne images are used. This ongoing work exploits a new dataset of helicopter-borne thermal infrared (TIR) imagery for melt pond retrieval. The derivation of geophysical parameters requires effective segmentation of different surface classes, which is challenged by temporally and spatially varying surface temperatures. We adapt and fine-tune AutoSAM, a prompt-free Segment Anything (SAM)-based segmentation tool that was introduced by Xinrong Hu et al. for medical imagery (Hu, X., Xu, X., & Shi, Y. (2023). How to Efficiently Adapt Large Segmentation Model (SAM) to Medical Images. arXiv preprint arXiv:2306.13731). Initial results with a limited number of annotated images indicate promising outcomes in the generalization of AutoSAM to cases that are rare in the training set, compared to U-Net and PSP-Net approaches. Beyond the scope of this project, this could serve as an example of how to use SAM as a segmentation tool for the remote sensing domain, which is typically hampered by the lack of labeled training data. Code and first results are provided at https://github.com/marlens123/autoSAM_pond_segmentation.

How to cite: Reil, M., Spreen, G., Huntemann, M., Buth, L., and Wilson, D.: Detection of Melt Ponds on Arctic Sea Ice from Infrared Images using AutoSAM, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20355, https://doi.org/10.5194/egusphere-egu24-20355, 2024.

EGU24-21693 | PICO | CR5.6 | Highlight

Extracting Dated Isochrones on Airborne Radar Data Across EastAntarctica for Input into 3-D Regional Ice Sheet Models 

Julien Bodart, Vjeran Višnjević, Antoine Hermant, and Johannes Sutter

Modelling the past evolution of the East Antarctic Ice Sheet (EAIS) in response to climate
and ocean forcing is challenged by the scarcity of observed palaeo boundary conditions. One
of the most spatially extensive records of past ice-sheet conditions comes from radar-detected
isochrones which, if dated precisely at ice cores, can provide a highly accurate temporal and
spatial history of ice-sheet evolution over time. Previous work has highlighted the benefit of
using such isochrones for testing and benchmarking 3-D ice sheet models; however,

uncertainty remains as to which model parameters fare better and how different bed and ice-
flow conditions affect the ability of ice-sheet models to reproduce the observed isochrones.

Here, we make use of previously acquired airborne radar data over the Wilkes Subglacial
Basin (East Antarctica) to connect existing stratigraphies and extract a temporal record of
isochrones at regular time intervals spanning the Holocene to the last interglacial and beyond.
The radar flight lines were carefully selected to provide a record of isochrones crossing
boundaries of different bed and ice-flow conditions situated between the ice divide and the
ice-sheet margins to represent as diverse a set of conditions as possible. The aim of this work
is to ultimately be able to test the ability of dated isochrones to tune ice-sheet model
parameters that will reproduce isochrone elevations in different parts of the catchment and
under different bed and ice-flow conditions.

How to cite: Bodart, J., Višnjević, V., Hermant, A., and Sutter, J.: Extracting Dated Isochrones on Airborne Radar Data Across EastAntarctica for Input into 3-D Regional Ice Sheet Models, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21693, https://doi.org/10.5194/egusphere-egu24-21693, 2024.

EGU24-701 | ECS | Orals | CR5.8

Investigating the drivers of global glacier volume changes over the last two decades using machine learning 

Codrut-Andrei Diaconu, Jonathan L. Bamber, Fabien Maussion, and Harry Zekollari

Machine learning plays an increasingly important role in modelling and better quantifying observed changes in various subcomponents of the Earth system. For instance, in the field of glaciology, machine learning methods have the potential to help unravel the ever-growing datasets on observed glacier changes, allowing for a better understanding of these changes and their driving factors.

In this study, we investigate the benefit of using a non-linear machine learning framework to model the observed recent glacier changes (individual glaciers’ geodetic mass balance over the 2000-2019 period) for nearly all the land-terminating glaciers larger than 2 km^2. To this end, we build a Random Forest model driven by a set of predictors, composed of both topographic (e.g. area, slope, debris coverage) and climatic features (e.g. temperature and precipitation anomalies), which explain up to 70% of the global variance in the observational dataset. Generally, we find that the climatic features are more important, explaining alone approx. 55% of the variance, as compared to the approx. 40% obtained with the topographical ones alone. We further investigate the importance of the topographical predictors within subregions that are assumed to be climatically homogeneous, showing different behaviours across them.

Our study illustrates the benefit of using non-linear models when statistically modelling multi-decadal geodetic mass balances, providing further insights into the drivers of current glacier changes. The proposed framework also has the potential to be used as a gap-filling tool to estimate the geodetic mass balance of unmeasured glaciers or those with uncertain geodetic mass balance observations and to predict future mass balance when forced with CMIP6 climate data or similar Earth System Model output.

How to cite: Diaconu, C.-A., Bamber, J. L., Maussion, F., and Zekollari, H.: Investigating the drivers of global glacier volume changes over the last two decades using machine learning, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-701, https://doi.org/10.5194/egusphere-egu24-701, 2024.

EGU24-2110 | ECS | Posters on site | CR5.8

Glacier point mass balance modeling using machine learning 

Marijn van der Meer, Harry Zekollari, Matthias Huss, Jordi Bolibar, Kamilla Hauknes Sjursen, and Daniel Farinotti

Estimations of glacier mass balance are commonly made using field techniques, empirical or physically based models, and remote sensing. More recently, data-driven tools like machine learning have become powerful complements to these conventional techniques. This study explores the potential of using machine learning to simulate the individual point mass balance of 30 sites from 13 glaciers in Switzerland spanning over 60 years, sourced from the Glacier Monitoring Switzerland (GLAMOS) network. To this end, we use two machine-learning models: LASSO regression, a linear regression model with L1-regularisation, and eXtreme Gradient Boosting (XGBoost), a gradient-boosted ensemble of decision trees. The models are driven by temperature and precipitation data at 1 km grid resolution from the Federal Office of Meteorology and Climatology (MeteoSwiss). The seasonal point mass balance data are used to train and test the models for each site individually. A comparative analysis is performed in which the performance of the LASSO regression and XGBoost are compared to a standard approach of calculating mass balance from a temperature-index model. In this analysis, we also explore how different temporal frequencies of climate variables, ranging from annual to monthly, affect the performance of the machine learning methods. Beyond their computational efficiency, these machine learning models are particularly suited to provide valuable insights into feature importance. Harnessing this, we study which months’ temperature and precipitation most significantly contribute to explaining individual stake mass balances and compare these findings with commonly assumed drivers of mass balance.

How to cite: van der Meer, M., Zekollari, H., Huss, M., Bolibar, J., Hauknes Sjursen, K., and Farinotti, D.: Glacier point mass balance modeling using machine learning, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2110, https://doi.org/10.5194/egusphere-egu24-2110, 2024.

EGU24-2444 | ECS | Orals | CR5.8 | Highlight

Retrieving climatic and temporal information from the last glacial maximum using an invert glacier model 

Kejdi Lleshi, Guillaume Jouvet, Frédéric Herman, and Samuel Cook

Understanding past natural climate variations during the Quaternary period is crucial for understanding the ongoing climate change. Glaciation events during the Quaternary have left visible footprints in today's landscape, such as moraines and trimlines, that could be used to reconstruct paleo glacier extent. 

Reconstructed glacier extent offers great potential to retrieve paleo-climate information during the coldest episodes of the Quaternary by inverting a glacier evolution model. However, current inversion methods are computationally expensive and their forward model relies on simplified physics. Fundamentally, they all assume glaciers are in a stationary state, which is simplistic and fails to capture essential transient features linking climate to glacier response.

Here, we develop a new Machine-Learning (ML)-based inversion technique that overcomes the previously-mentioned limitations to reconstruct the glacier equilibrium line altitude (ELA), a proxy for temperature and precipitation, during a glacial maximum from reconstructed glacier extent. Our forward model consists of  a deep-learning emulator that learns the physical processes of a glacier from climate forcing to the glacier response. This approach has the advantage of being computationally highly-efficient, as well as allowing for automatic (thanks to the automatic differentiation) inversion of reconstructed glacier extent to retrieve a realistic ELA field that informs us about paleoclimates.

When applying our method to the Last Glacial Maximum in the European Alps, our reconstructed ELA fields show  a clear separation between the northern and southern Alps, with northern ELAs being considerably lower as shown in Fig 1. Our results are supported by the glacier footprints reconstructed from geomorphological observations in the northern Alps, which suggest the presence of large glacier lobes. In contrast, the glacial lobes in the southern Alps were noticeably smaller.

Our method is applicable in any formerly glaciated areas, and therefore has a high potential for paleoclimate reconstruction of the Earth’s coldest episodes.

Figure1. The resulting ELA field from inverting the ‘observed’ glacier footprint. There is a visible difference in the climate between the north and the south.

How to cite: Lleshi, K., Jouvet, G., Herman, F., and Cook, S.: Retrieving climatic and temporal information from the last glacial maximum using an invert glacier model, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2444, https://doi.org/10.5194/egusphere-egu24-2444, 2024.

EGU24-2495 | ECS | Posters on site | CR5.8 | Highlight

A Unified Framework for Forward and Inverse Modeling of Ice Sheet Flow using Physics Informed Neural Networks 

Gong Cheng, Mathieu Morlighem, and Sade Francis

Predicting the future contribution of the ice sheets to sea level presents several challenges due to the lack of observations of critical boundary conditions, such as basal sliding. Traditional numerical models often rely on data assimilation methods to determine spatially variable friction coefficients by solving an inverse problem, given an empirical friction law. However, these approaches are not versatile, as they demand sometimes extensive code development efforts when integrating new physics into the model. Furthermore, the requirement for comprehensive data alignment on the computational grid hampers their adaptability, especially in handling sparse data effectively. To tackle these challenges, we propose a transformative approach utilizing Physics-Informed Neural Networks (PINNs) to seamlessly integrate observational data and underlying physical laws into a unified loss function, facilitating the solution of both forward and inverse problems within the same framework. We illustrate the versatility of PINNs by applying the framework to two-dimensional problems on Helheim Glacier in southeast Greenland. By systematically concealing one component within the system, we showcase the ability of PINNs to accurately predict and reconstruct hidden information, emphasizing their adaptability to handle scenarios marked by missing or incomplete datasets. Furthermore, we extend the application to address a challenging mixed inversion problem. We show how PINNs are capable of inferring the basal friction coefficient while simultaneously filling gaps in sparsely observed ice thickness. This mixed inversion problem represents a class of scenarios beyond the reach of conventional numerical methods. Our unified framework offers a promising avenue to enhance the predictive capabilities of ice sheet models, reducing uncertainties and advancing our understanding of intricate ice dynamics.

How to cite: Cheng, G., Morlighem, M., and Francis, S.: A Unified Framework for Forward and Inverse Modeling of Ice Sheet Flow using Physics Informed Neural Networks, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2495, https://doi.org/10.5194/egusphere-egu24-2495, 2024.

EGU24-4036 | ECS | Posters on site | CR5.8

Mapping glacial sediment plumes in the Antarctic Peninsula using deep learning 

Benjamin Wallis, Anna Hogg, and David Hogg

The subglacial discharge of sediment-rich meltwater plumes can be detected in satellite imagery where plumes reach the ocean surface at the terminus of tidewater glaciers. These meltwater plumes can influence glacier melting and ocean properties in important ways. Studying them provides insights into meltwater pathways in glacial hydrological systems.

Sediment-rich meltwater plumes are observed extensively in Greenland, Svalbard and other regions, however in Antarctica observations have been more limited. Recent detections of seasonal speed variations on tidewater glaciers of the Antarctic Peninsula suggest that surface meltwater reaching the glacier bed may be an important factor influencing ice dynamic behaviour on the Antarctic Peninsula Ice Sheet (APIS), however surface-bed hydrological connections have not been directly observed through fieldwork on the mainland APIS. Therefore, studying the presence and distribution of sediment plumes around the Peninsula can provide insights to understand the factors influencing newly observed seasonal ice speed fluctuations.

Here we develop a remote-sensing approach to map the locations and frequency of sediment plumes on the Antarctic Peninsula coastline using high-resolution multi-spectral imaging from Sentinel-2 satellites and a U-Net based convolutional neural network. This methodology allows us to detect small sediment plumes in images with high cloud and sea-ice densities. We apply our approach to the Antarctic Peninsula north of 65°S, including the South Shetland Islands, to produce a time-series of sediment plumes from 2016 to 2023 covering 150,000 km2.

We use these results combined with outputs from regional climate models and reanalysis to assess the link between surface-visible sediment plumes and surface melt and runoff from the Antarctic Peninsula’s glaciers. We find that the timings and locations of sediment plumes correspond to modelled runoff, providing evidence for widespread surface-bed hydrological connections in the Antarctic Peninsula.

How to cite: Wallis, B., Hogg, A., and Hogg, D.: Mapping glacial sediment plumes in the Antarctic Peninsula using deep learning, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4036, https://doi.org/10.5194/egusphere-egu24-4036, 2024.

EGU24-7804 | ECS | Posters on site | CR5.8

Evaluation of a tool to simulate high resolution mountain SWE from global datasets 

Laura Sourp, Simon Gascoin, Vanessa Pedinotti, Lionel Jarlan, and Esteban Alonso-González

Despite its significance, the snow water equivalent (SWE) is poorly characterized in many mountain regions due to i) a lack of in situ measurements and ii) the difficulty to measure the SWE directly from satellite observations. 

We developed a tool to simulate the spatial distribution of SWE at high resolution (typically 100 m) in any region of interest using SnowModel (Liston and Elder, 2006a, 2006b), global meteorological data (ERA5) and satellite observations of the snow cover fraction (SCF). Satellite observations are used to mitigate errors in the model parameterization and the meteorological forcings using the particle batch smoother  (Margulis et al., 2015). This method consists in computing N perturbed simulations on the whole hydrological season and transforming the simulated SWE in a simulated SCF. In this study, we used the formula linking the SWE and the SCF of the Noah Land Surface Model as the measurement operator. After that, the simulations are compared to remotely sensed SCF data and weighted according to their agreements with the observations. 

We implemented this data assimilation method with both MODIS and Sentinel-2 SCF data. We are testing it on the Bassies catchment in the French Pyrenees, and on the Tuolumne River Catchment in the Sierra Nevada, USA. In the Bassies catchment, we compare the results with snow depth maps from Pléiade satellites. We perturbed the precipitations with a log-normal law and found a very good agreement between the posterior simulated SCF and the observed one in Bassies as expected. However, the simulated snow depths in this catchment do not match the Pléiades snow depths observations. We added the perturbation of the air temperature with a normal law and found similar results. We also found a very small sensitivity of the posterior snow depth on the empirical parameters of the measurement operator. These results suggest that the SWE-SCF relationship may not be sufficiently informative in the study site of Bassiès.  We will present the extension of this work to the Tuolumne river basin where the Airborne Observatory provides SWE maps over a larger region.

How to cite: Sourp, L., Gascoin, S., Pedinotti, V., Jarlan, L., and Alonso-González, E.: Evaluation of a tool to simulate high resolution mountain SWE from global datasets, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7804, https://doi.org/10.5194/egusphere-egu24-7804, 2024.

EGU24-9175 | ECS | Posters on site | CR5.8

Co-located OLCI optical imagery and SAR altimetry from Sentinel-3 for enhanced surface classification in sea ice 

Weibin Chen, Michel Tsamados, Rosemary Willatt, David Brockley, Marc Deisenroth, Claude De Rijke-Thomas, Alistair Francis, Len Hirata, Thomas Johnson, Isobel Lawrence, Jack Landy, Sanggyun Lee, Wenxuan Liu, Dorsa Nasrollahi Shirazi, Connor Nelson, Julienne Stroeve, and So Takao

In our research, we leverage the capabilities of the Sentinel-3A and Sentinel-3B satellites, launched in February 2016 and April 2018, respectively, to deepen our understanding of the polar regions. These satellites offer a unique blend of high-resolution Ku-band radar altimetry data, synthetic aperture radar (SAR) mode altimetry, and the Ocean and Land Colour Instrument (OLCI) imaging spectrometer. This combination enables the acquisition of both optical imagery and SAR radar altimetry data, extending up to 81 degrees North. Central to our study is the application of deep learning techniques, specifically the Vision Transformers (ViT), which adapt the Transformer algorithm for surface classification in polar environments. This approach is instrumental in distinguishing between sea ice and leads, demonstrating robust performance across various metrics, including accuracy and model roll-out on comprehensive OLCI image datasets. We produce our first lead classification maps at the original OLCI swath level resolution of 300m and a lead fraction prototype mosaic spring pan-Arctic product at gridded level of 1km, 5km and 10km resolution and on daily, weekly and monthly timescales. The use of binned statistics in conjunction with our deep learning classifications provides valuable insights into the spatial distribution and changes of leads within the polar ice. We compare our prototype product with other existing lead products and with auxiliary datasets on thin ice (roughness, thickness). Our work combining different satellite products at pan-Arctic intermediate resolution enhances our capacity to estimate sea ice thickness and aids in forecasting future changes in the Arctic and Antarctic regions, thereby contributing to the field of polar remote sensing with direct applications to the future polar missions CRISTAL and CMIR.

How to cite: Chen, W., Tsamados, M., Willatt, R., Brockley, D., Deisenroth, M., De Rijke-Thomas, C., Francis, A., Hirata, L., Johnson, T., Lawrence, I., Landy, J., Lee, S., Liu, W., Nasrollahi Shirazi, D., Nelson, C., Stroeve, J., and Takao, S.: Co-located OLCI optical imagery and SAR altimetry from Sentinel-3 for enhanced surface classification in sea ice, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9175, https://doi.org/10.5194/egusphere-egu24-9175, 2024.

EGU24-9687 | Posters on site | CR5.8

Assimilating the Greenland ice sheet stratigraphy for reconstructing accumulation rates 

Philipp Immanuel Voigt and Andreas Born

The thickness of englacial isochrones is the combined product of accumulation and dynamical thinning by the flow of ice.Dated ice stratigraphy data provides access to this archive , which in principle holds the potential for improving simulations and reconstructions  of the Greenland ice sheet. However, the combined effects of accumulation and dynamical thinning are convoluted and spatially heterogeneous, making it difficult to separate their respective contributions to the observed thickness of isochrones.

Here we simulate isochrones explicitly using the Englacial Layer Simulation Architecture (ELSA) coupled with a fully transient thermomechanical ice sheet model. This enables us to link accumulation rates to the ice stratigraphy, including a physically consistent representation of dynamical thinning. By ensemble data assimilation techniques, the linear model response to changes in past local accumulation are estimated, enabling the inversion of the model and reconstruction of accumulation rates from stratigraphy. An iterative approach is chosen to account for the nonlinear response of ice flow to anomalous accumulation. The result is an optimized simulation of the Greenland ice sheet with an englacial stratigraphy matching the observations, forced by the reconstructed accumulation. Because the model is fully transient including ice dynamics, our approach also constrains ice sheet stability and sea level contribution.

Here we present preliminary findings from inversions of idealized ice sheet stratigraphy, including some encouraging insights, physical and methodological limitations and challenges yet to be overcome.

How to cite: Voigt, P. I. and Born, A.: Assimilating the Greenland ice sheet stratigraphy for reconstructing accumulation rates, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9687, https://doi.org/10.5194/egusphere-egu24-9687, 2024.

EGU24-10231 | ECS | Posters on site | CR5.8

Advancing Physical Interpretability of Arctic Sea Ice Dynamics through Automatic Feature Selection 

Luca Bianchi, Matteo Sangiorgio, Stefano Materia, Doroteaciro Iovino, and Andrea Castelletti

Modelling Arctic sea ice dynamics has proven to be a successful application for machine learning, leveraging its ability to generate accurate and computationally efficient forecasts. Nevertheless, prevailing limitations lie in the need for physical interpretability and the inability to unveil the dynamics and interdependencies between relevant ice-related variables and their drivers. In this study, we provide a two-step framework designed to combine the high accuracy and computational efficiency characteristics of machine learning while ensuring high interpretability.

The first step of our framework entails time series clustering to identify subregions that are homogeneous with respect to the spatiotemporal variability in the considered variable and obtain the barycentric time series of each cluster. We then use an advanced feature selection algorithm, the Wrapper for Quasi Equally Informative Subset Selection, that identifies neural predictors, specifically Extreme Learning Machines, to forecast the future evolution of sea ice. It then provides the most relevant set of inputs necessary for accurately describing the evolution for each cluster.

Our investigation focuses on the monthly evolution of sea ice thickness and uses data from the Pan-Arctic Ice-Ocean Modeling and Assimilation System (PIOMAS). Other PIOMAS variables (i.e., sea ice concentration, snow depth, sea surface temperature, and sea surface salinity) as well as observed discharge from five major Arctic rivers (i.e., Ob, Yenisey, and Lena in Asia, Mackenzie and Yukon in North America, provided by the Arctic Great Rivers Observatory discharge dataset) are considered as potential driving factors. 

Our results indicate the pivotal role of past sea ice thickness values, since the forthcoming state of sea ice seems to be influenced by both the current situation and historical trends and periodicity. Sea surface salinity in the open Arctic Ocean is highly persistent, and therefore is not used by the algorithm to explain the sea ice evolution. On the other hand, the Arctic rivers’ flows are more representative of the processes occurring in the clusters along the coast. Finally, the interaction between sea surface temperature and snow depth controls the interplay between ice formation and melting, and therefore plays a significant role in shaping the sea ice evolution in the short term.

Our framework aims to advance our comprehension of the complex physical processes governing sea ice thickness evolution in the Arctic region. Moreover, its effectiveness in uncovering sea ice related processes is expected to further improve with the inclusion of additional input variables and, possibly, of a longer data record.

How to cite: Bianchi, L., Sangiorgio, M., Materia, S., Iovino, D., and Castelletti, A.: Advancing Physical Interpretability of Arctic Sea Ice Dynamics through Automatic Feature Selection, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10231, https://doi.org/10.5194/egusphere-egu24-10231, 2024.

EGU24-12922 | ECS | Orals | CR5.8

Automated Crevasse Mapping Using Deep Learning Foundation Models to Analyse Climate Change and Glaciology  

Steven Wallace, Aiden Durrant, William D. Harcourt, and Georgios Leontidis

Climate change poses a significant global challenge, with its effects manifesting prominently through melting and retreating glaciers in the Arctic and Antarctic. Understanding the dynamics of glacier flow is imperative for predicting the future evolution of the Polar ice sheets. Crevasses play an important role in regulating ice flow by acting as a conduit for surface meltwater to reach the bed and speed up ice flow, as well as providing the line of weakness through which icebergs detach from tidewater glacier termini. Furthermore, this study delves into the potential of computer vision techniques that use deep learning, leveraging foundation models trained using self-supervised learning like the Segment Anything Model (SAM) and DINOv2 from Meta AI, to automate crevasse mapping on glacial surfaces. Manual mapping crevasses on any glacier is currently labour-intensive and time-consuming without automation. Therefore, automating the process will allow scientists to map crevasses automatically over time in the exact location and over larger areas. Notably, this research addresses the scarcity of image segmentation datasets specifically tailored for mapping crevasses in polar regions and explores alternative deep learning methodologies, such as domain adaptation and few-shot learning, to overcome data limitations. The evaluation of foundation models harnesses high-resolution satellite imagery sourced from open-source remote sensing satellites such as Sentinel-1 and Sentinel-2 provided by the European Space Agency (ESA). Using multiple high-resolution image data modalities (e.g. Synthetic Aperture Radar (SAR) and optical satellite images) will provide insights into how different image data types help deep learning models generalise to crevasse mapping segmentation applications. The study seeks to develop advanced technological solutions to automate the mapping of crevasses tens of metres in width in order to address the knowledge gap of the role that crevasses play in modulating ice flow, particularly in response to climate warming.

How to cite: Wallace, S., Durrant, A., Harcourt, W. D., and Leontidis, G.: Automated Crevasse Mapping Using Deep Learning Foundation Models to Analyse Climate Change and Glaciology , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12922, https://doi.org/10.5194/egusphere-egu24-12922, 2024.

EGU24-13035 | ECS | Orals | CR5.8

Probabilistic Estimates of Fractional Snow Cover Area in Mountainous Terrain 

David R. Casson, Andrew W. Wood, Guoqiang Tang, Karl Rittger, and Martyn Clark

This study investigates probabilistic estimates of fractional Snow Cover Area (fSCA) in mountainous terrain, aiming to bridge the gap between mechanistic hydrological models and operational remote sensing measurements. To capture the spatial variability of snow cover, we generate high-resolution ensemble meteorological forcing datasets from in-situ measurements, employing locally weighted regression and random forest methods. We then discretize a physically-based hydrological model tailored for mountainous terrain, incorporating the dominant factors influencing snow cover. Subsequently, fluxes from an intermediate complexity snowpack model are utilized to simulate fSCA, which we evaluate against an operational data source. This research is a progressive step toward integrating ensemble data assimilation techniques, with the goal of improving hydrological forecast performance.

How to cite: Casson, D. R., Wood, A. W., Tang, G., Rittger, K., and Clark, M.: Probabilistic Estimates of Fractional Snow Cover Area in Mountainous Terrain, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13035, https://doi.org/10.5194/egusphere-egu24-13035, 2024.

EGU24-13310 | ECS | Orals | CR5.8

A data fusion approach to produce daily, high resolution snow albedo using multispectral and hyperspectral imagery 

Ross T. Palomaki, Karl Rittger, Sebastien J. P. Lenard, Jeff Dozier, and S. McKenzie Skiles

Snow albedo data are required for various research and applications at a wide range of spatial and temporal scales. Typically, spatially-distributed snow albedo measurements are generated using multispectral satellite data, including MODIS, Sentinel-2, and Landsat imagery. While a number of algorithms can be employed to create snow albedo products from multispectral satellite imagery, a recent MODIS-focused analysis shows that spectrally-based approaches result in the most accurate snow albedo. These approaches use spectral libraries of snow, vegetation, and rock reflectance to solve for snow fraction, grain size, and the impact of light absorbing particles (LAP) on snow albedo; snow albedo is estimated by combining the grain size with darkening due to LAP.

Spectral unmixing algorithms produce more accurate snow albedo measurements when applied to hyperspectral data because the additional spectral information removes ambiguities associated with sparser multispectral imagery. Various airborne sensors and satellite missions EnMAP, EMIT, and PRISMA provide hyperspectral data with spatial resolutions on the order of tens of meters, but depending on the platform have repeat periods between 8-29 days, and may miss important albedo changes related to early season snow accumulation and late season dust events.

In this presentation, we show initial results from a data fusion approach to produce daily snow albedo data at high spatial resolutions using multispectral and hyperspectral imagery. Our model fuses snow albedo measurements directly instead of reflectance data to take advantage of the improved ability of the spectral unmixing algorithm to address mixed pixels and better discern clouds from snow. To demonstrate our approach, we train a random forest model on snow albedo measurements generated from airborne hyperspectral data at 50 m resolution. Predictor variables include daily, 463 m MODIS snow albedo generated using a spectral unmixing algorithm, as well as terrain characteristics and solar illumination. The fused snow albedo data take advantage of the more accurate and finer resolution hyperspectral data will maintaining the daily temporal resolution of multispectral MODIS imagery. Additionally, our fusion approach is flexible and can incorporate snow albedo measurements from additional airborne or satellite sensors, including multispectral VIIRS data and hyperspectral data from the upcoming SBG and CHIME satellite missions.

How to cite: Palomaki, R. T., Rittger, K., Lenard, S. J. P., Dozier, J., and Skiles, S. M.: A data fusion approach to produce daily, high resolution snow albedo using multispectral and hyperspectral imagery, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13310, https://doi.org/10.5194/egusphere-egu24-13310, 2024.

EGU24-13556 | Posters on site | CR5.8

Multi-task predictions of the Arctic sea ice by a transformer-based deep learning model 

Yibin Ren and Xiaofeng Li

The Arctic sea ice has been retreating dramatically in recent years in summer and fall. The navigation season for open water vessels along the Northeast Passage has lengthened to sub-seasonal scales. Accurate perditions of Arctic sea ice in sub-seasonal scales are essential for planning shipping activities. The numerical model cannot achieve a high accuracy of daily sea ice predictions on a sub-seasonal scale. The advanced deep learning brings new solutions for the data-driven-based sea ice prediction.

This study proposed a transformer-based deep learning model to predict multiple sea ice parameters, including sea ice concentration (SIC), sea ice thickness (SIT), and sea ice drift (SID), in the Pan-Arctic in a sub-seasonal scale, 90 days’ lead. An encoder and decoder are constructed based on transformer modules to extract spatio-temporal dependencies from daily SIC, SIT, and SID sequences. The spatio-temporal dependencies at different scales are fused to form the final feature maps. Three SIC, SIT, and SID output modules are designed based on the final feature maps to output different parameters for the next 90 days. The satellite-observed sea ice data from the National Sea Ice Data Center (NSIDC) are employed to train the proposed model. We compared our model with anomaly persistence and the European Centre for Medium-Range Weather Forecasts (ECMWF) ensemble predictions to demonstrate the model’s prediction skill.

Further, based on the proposed model, we discuss the effects of typical thermal and dynamic factors on sub-seasonal scale daily sea ice prediction. The selected factors include surface air temperature (SAT), sea surface temperature (SST), surface solar radiation downwards (SSRD), and geopotential height. Finally, we conclude with some scientific guidelines for the sub-seasonal sea ice predictability of the Arctic. 

How to cite: Ren, Y. and Li, X.: Multi-task predictions of the Arctic sea ice by a transformer-based deep learning model, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13556, https://doi.org/10.5194/egusphere-egu24-13556, 2024.

EGU24-13710 | Orals | CR5.8

A glacier ice volume modeling framework based on generative adversarial networks and graph neural networks 

Niccolò Maffezzoli, Gianluca Lagnese, Sebastiano Vascon, Troels Petersen, Carlo Barbante, and Eric Rignot

Estimating the ice volume of Earth's glaciers is a key challenge in Earth System science, crucial for understanding their evolution, quantifying future global sea level rise and freshwater resources in climate-sensitive regions. Given current global warming that causes glaciers mass loss, precise ice volume estimates become a top priority in face of future climate scenarios. 

Here we present the SKYNET project, which aims to develop a general modeling framework for estimating ice volumes of Earth’s glaciers using generative deep learning. 

The modeling framework comprises two main networks. The first network, a generative adversarial network, reconstructs glacier bedrocks using elevation maps of surrounding ice-denuded regions. Trained on over 1 million Digital Elevation Maps, the model learns key geometrical features and patterns of Earth’s mountain regions. The challenge is addressed as an image inpainting problem, in which the objective is to reconstruct the bedrock altitude in a missing portion of the image, using surrounding information. 

The second network leverages existing ice thickness measurements. Such a network is trained on local features such as ice velocity, slope, distance from glacier boundaries, and other glacier statistics to predict local ice thickness. We use the Glacier Ice Thickness Dataset (GlaThiDa) and other input products as training dataset. We employ a graph neural network (GNN) with an architecture that explicitly accounts for the connectivity of the data. The GNN’s local ice thickness estimates serve as a prior to refine the inpainting network’s generated ice thickness maps. 

We introduce the model, discuss its concept, advantages, limitations, current challenges and present preliminary results and tests on diverse continental glaciers across the globe. 

How to cite: Maffezzoli, N., Lagnese, G., Vascon, S., Petersen, T., Barbante, C., and Rignot, E.: A glacier ice volume modeling framework based on generative adversarial networks and graph neural networks, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13710, https://doi.org/10.5194/egusphere-egu24-13710, 2024.

EGU24-14894 | ECS | Posters on site | CR5.8

Towards monitoring supraglacial lake dynamics in Antarctica with convolutional neural networks 

Celia A. Baumhoer, Jonas Koehler, Stef Lhermitte, Bert Wouters, and Andreas J. Dietz

Monitoring the dynamics of Antarctic supraglacial lakes is of particular interest in the context of global warming. Supraglacial meltwater accumulation on ice sheets and ice shelves can be a major driver of accelerated ice discharge. This is caused through processes such as surface runoff leading to ice thinning, basal meltwater injection causing basal sliding, and hydrofracture triggering ice shelf collapse and subsequent glacier acceleration. In addition, an increased presence of supraglacial lakes around the Antarctic margin can trigger enhanced melting due to the low albedo of surface lakes, which leads to increased absorption of solar radiation. Hence, continuous monitoring of supraglacial lakes is crucial for improving our understanding of their seasonal variations in extent and their impacts on ice shelf stability and ice sheet surface mass balance. Initially, an automated supraglacial lake mapping approach was developed to create bi-weekly lake extent maps for six Antarctic ice shelves based on fused results from convolutional neural network predictions and a Random Forest (RF) classification trained on Sentinel-1/-2 data. However, regular large-scale monitoring beyond these six selected areas requires a model with higher spatio-temporal transferability and an efficient fully automated data processing workflow. We tested for a potential improvement by replacing the RF-based mapping with an attention-based U-Net, expanding the training and test sites on a total of 23 regions and switching the processing to a more powerful high-performance computing infrastructure. We will discuss how remote sensing-based mapping accuracies can be improved by extending the training/test dataset, selecting the right machine learning model and the choice of processing infrastructure. In the future, the automated processing workflow will provide a regularly updated dataset on supraglacial lake dynamics of 23 Antarctic ice shelves via a web service by exploiting the full archive of available Sentinel-1/-2 satellite imagery.

How to cite: Baumhoer, C. A., Koehler, J., Lhermitte, S., Wouters, B., and Dietz, A. J.: Towards monitoring supraglacial lake dynamics in Antarctica with convolutional neural networks, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14894, https://doi.org/10.5194/egusphere-egu24-14894, 2024.

EGU24-15332 | ECS | Posters on site | CR5.8

Data assimilation in glacier mass balance modeling 

Wenxue Cao, Louise Steffensen Schmidt, Kristoffer Aalstad, Sebastian Westermann, and Thomas V Schuler

The accurate quantification of glacier mass balance is of vital importance for the evaluation of climate change impact and the management of hydrological resources. However, traditional modeling methodologies on a regional scale are frequently plagued by uncertainties in forcing data, model structure, and parameters. Data assimilation emerges as an effective technique to incorporate observations into modeling, thereby reducing the uncertainty of results. In this study, we evaluate the performance of different ensemble-based schemes, including the Ensemble Smoother (ES) and the Ensemble Smoother-Multiple Data Assimilation (ES-MDA), to incorporate albedo derived from MODIS satellite observations and in-situ mass-balance measurements vis stakes into the full energy balance model CryoGrid applied to Svalbard glaciers. Our primary aim is to enhance the accuracy of both the reconstruction and prediction of glacier mass balance in the Svalbard region through the synergistic use of observational data and model. In a range of experiments, we analyze the performance of different assimilation methods and different observation products. The implementation of ES-MDA has demonstrated marked improvements, while the variations in parameter dynamics have varied effects on the results. We compare the prior and posterior states to help disentangle which process or forcing has the most impact on the uncertainty of the model’s results.

How to cite: Cao, W., Schmidt, L. S., Aalstad, K., Westermann, S., and Schuler, T. V.: Data assimilation in glacier mass balance modeling, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15332, https://doi.org/10.5194/egusphere-egu24-15332, 2024.

EGU24-16672 | Posters on site | CR5.8

Arctic Meltponds: Automated Detection Algorithm Using Enhanced Machine Learning 

Anja Rösel, Niklas Neckel, and Vytautas Jancauscas

Melt ponds are pools of water that form during summer on the surface of the arctic ice. Due to the lower albedo, melt ponds absorb more solar radiation than surrounding ice and hence have higher temperature. This causes more water to melt, creating a feedback loop. This means that melt pond fraction in ice sheets is an important factor to consider in global climate and sea ice models. In situ measurements are difficult and expensive in terms of time and labor. Furthermore, these measurements can only cover limited areas. This makes using Earth Observation methods for this task particularly attractive.

Until today, there is no sophisticated global melt pond data set available:

Accurate methods may exist for determining melt ponds from Sentinel-2 data. The downside of using Sentinel-2 is that parts of the High Arctic are not covered by this mission.

MODIS data covers the whole globe at least once every three days, but the downside of it is that MODIS resolution is much coarser (250m  vs. 10m). Since melt ponds are in general much smaller than 250m, it means that accurately capturing melt pond fraction from these data is difficult.

We propose to address these issues by employing Deep Learning techniques. Namely, we use Sentinel-2 data to train a model to super-resolve MODIS images to higher resolution and to use all available MODIS bands and their surrounding pixels for information context when predicting melt pond and open water fractions.

In addition, a thorough uncertainty quantification (UQ) will be applied by using the UQ Toolbox.

How to cite: Rösel, A., Neckel, N., and Jancauscas, V.: Arctic Meltponds: Automated Detection Algorithm Using Enhanced Machine Learning, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16672, https://doi.org/10.5194/egusphere-egu24-16672, 2024.

EGU24-16820 | ECS | Orals | CR5.8

Building probabilistic projections of the Antarctic contribution to global sea level rise using a random forests emulato 

Fiona Turner, Jonathan Rougier, Tamsin Edwards, Violaine Coulon, and Ann Kristin Klose

In order to predict future global sea level rise, it is key for us to have better understanding of the changes in the cryosphere, as is being done in the PROTECT project (https://protect-slr.eu). Large uncertainties exist around how these changes will present over the coming centuries, with the Antarctic ice sheet being the most uncertain component with regards to predicted mass changes. It is therefore necessary to turn to statistical techniques to create more robust predictions.

Here, we present results from a random forests emulator simultaneously trained on two ice sheet models, Kori and PISM, forced by four global climate models. We emulate the relationship between inputs, namely climate change and ice sheet model settings, and an output, sea level contribution. The use of random forests allows us to improve on previous Gaussian Process emulators (Edwards et al., 2021) in speed and the treatment of factor inputs. We also transform the multi-centennial output in order to allow us to model the whole time series, rather than each year individually. The emulator allows us to interpolate (and extrapolate slightly) in order to build probabilistic projections of sea level contribution to 2300 that include climate and ice sheet modelling uncertainties under all five Shared Socioeconomic Pathways (SSPs), despite only two being used in the ensemble of simulations.

References

Edwards, T. L., Nowicki, S., Marzeion, B., Hock, R., Goelzer, H., Seroussi, H., Jourdain, N. C., Slater, D. A., Turner, F. E., Smith, C. J., et al. (2021). Projected land ice contributions to twenty-first-century sea level rise. Nature, 593(7857):74–82.

How to cite: Turner, F., Rougier, J., Edwards, T., Coulon, V., and Klose, A. K.: Building probabilistic projections of the Antarctic contribution to global sea level rise using a random forests emulato, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16820, https://doi.org/10.5194/egusphere-egu24-16820, 2024.

EGU24-18641 | ECS | Orals | CR5.8

Forecasting Permafrost Carbon Dynamics in Alaska with GeoCryoAI 

Bradley Gay, Neal Pastick, Jennifer Watts, Amanda Armstrong, Kimberley Miner, and Charles Miller

Complex non-linear relationships exist between the permafrost thermal state, active layer thickness, and terrestrial carbon cycle dynamics In Arctic and boreal Alaska. The rate, magnitude, and extent of permafrost degradation remain uncertain, with an increasing recognition of the importance of abrupt thaw mechanisms. Similarly, large uncertainties in the rate, magnitude, timing, location, and composition of the permafrost carbon feedback complicate this issue. The challenge of monitoring sub-surface phenomena, such as the soil temperature and soil moisture profiles, with remote sensing technology further complicates the situation. There is an urgent need to understand how and to what extent permafrost degradation is destabilizing the Alaskan carbon balance and to characterize the feedbacks involved. We employ our artificial intelligence (AI)-driven model GeoCryoAI to quantify permafrost thaw dynamics and greenhouse gas emissions in Alaska. GeoCryoAI uses a hybridized multimodal deep learning architecture of stacked convolutionally layered memory-encoded bidirectional recurrent neural networks and 12.4 million parameters to simultaneously ingest and analyze 13.1 million in situ measurements (i.e., CALM, GTNP, ABoVE ReSALT, FLUXNET, NEON), 8.06 billion remote sensing airborne observations (i.e., UAVSAR, AVIRIS-NG), and 7.48 billion process-based modeling outputs (i.e., SIBBORK-TTE, TCFM-Arctic) with disparate spatiotemporal sampling and data densities. This framework introduces ecological memory components and effectively learns subtle spatiotemporal covariate complexities in high-latitude ecosystems by emulating permafrost degradation and carbon flux dynamics across Alaska with high precision and minimal loss (RMSE: 1.007cm, 0.694nmolCH4m-2s-1, 0.213µmolCO2m-2s-1). GeoCryoAI captures abrupt and persistent changes while providing a novel methodology for assimilating contemporaneous information on scales from individual sites to the pan-Arctic. Our approach overcomes traditional model inefficiencies and seamlessly resolves spatiotemporal disparities.

How to cite: Gay, B., Pastick, N., Watts, J., Armstrong, A., Miner, K., and Miller, C.: Forecasting Permafrost Carbon Dynamics in Alaska with GeoCryoAI, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18641, https://doi.org/10.5194/egusphere-egu24-18641, 2024.

Remote sensing imagery offers a unique tool to monitor the snow cover evolution both at global and regional scales. However, the availability of the time series of normally 3-4 decades limits the applicability of the data to understand the dynamics of snow processes at longer time scale (Pulliainen et al., 2020). In this perspective the possibility to generate hybrid dataset merging satellite records with model simulations is offering the chance to both cross-validate the model simulations and to extent the time series (Lenton et al 2024).

In this work, an approach proposed by Notarnicola 2022, with the aim to merge earth observation imagery and modelled data was adapted to generate longer time series. The method is a machine learning approach based on Artificial Neural Network (ANN), where the uncertainties on the ANN trained model were obtained through a bootstrap procedure with a resampling technique. As modelled data, the NOAA-CIRES-DOE 20th Century Reanalysis V3 contains land surface and meteorological maps and their uncertainty available in the period 1806-2015 was addressed (Slivinski et al., 2019). For satellite data, the longest time series on snow parameters were used derived from ESA Climate Change Initiative (CCI) Snow project, namely Snow Water Equivalent (SWE) data available from 1979 to 2020 (https://climate.esa.int/en/odp/#/project/snow). As predictors for the ANN training and test, dynamics variables such as air temperature and precipitation were considered as they regulate the snow dynamics and rainfall events. As static parameters, the location in terms of latitude and longitude, mean elevation, the land cover type, and percentage of vegetation cover were inserted. The target variable to be improved is the snow water equivalent value at pixel level. 

Before the application of the ANN approach, a comparison between the SWE values in two data sets for the overlapping period (1979-2015) indicated an averaged correlation coefficient of around 0.52, a bias in the range 35-42 mm, the latter one being strongly depending on the different months. After the application of the model derived by the trained ANN applied to the test dataset, the correlation coefficients raised on average to 0.87, and the RMSE is reduced to around 20 mm. The merged data set will be further compared with ground data where available and then used to derive long-term trends for the SWE variable.

 

References

Lenton, T.M., Abrams, J.F., Bartsch, A. et al. Remotely sensing potential climate change tipping points across scales. Nat Commun 15, 343 (2024). https://doi.org/10.1038/s41467-023-44609-w

Notarnicola, C. Overall negative trends for snow cover extent and duration in global mountain regions over 1982–2020. Sci Rep 12, 13731 (2022). https://doi.org/10.1038/s41598-022-16743-w

Pulliainen, J. et al. Patterns and trends of Northern Hemisphere snow mass from 1980 to 2018. Nature, 582, E18, doi:10.1038/s41586-020-2416-4 (2020).

Slivinski L.C., Compo G.P., Whitaker J.S., et al. Towards a more reliable historical reanalysis: Improvements for version 3 of the Twentieth Century Reanalysis system. Q J R Meteorol Soc. 2019; 145: 2876–2908.https://doi.org/10.1002/qj.3598

How to cite: Notarnicola, C.: Merging Earth Observation imagery and model simulations to monitor long-term global snow cover dynamics, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20329, https://doi.org/10.5194/egusphere-egu24-20329, 2024.

EGU24-20649 | ECS | Posters on site | CR5.8

Inverse hydrological modeling to infer historical snow mass based on streamflow records 

Pau Wiersma and Grégoire Mariéthoz

Mapping the dynamics of snow water equivalent (SWE) is critical for understanding the hydrology of mountain regions. While methods to reconstruct SWE exist, they usually rely on either remote sensing data or the presence of in-situ observations. Streamflow observations can be considered an indirect and delayed observation of catchment-wide SWE, but despite their broad spatial and temporal availability, their potential for SWE reconstructions has not been explored so far.

In this study, we investigate how much SWE information can be extracted from the streamflow record, both in terms of its total mass as well as its spatial distribution. To this end, we set up an inverse streamflow-based SWE reconstruction framework that can operate without remote sensing data or in-situ snow observations. As a basis, we use a distributed hydrological model with a temperature-index snow model at 1km resolution, which generates SWE reconstructions from a set of prior snow and climate parameters and translates them into streamflow. By using the streamflow observations to optimize these parameters, we obtain SWE reconstructions that better match the streamflow.

However, there is likely a multitude of SWE reconstructions that all lead to the same streamflow, which is defined as an ill-posed inverse problem. In order to find out by how much the streamflow can constrain the prior SWE reconstructions, we perform an experiment with synthetic observations. Using synthetic observations instead of real observations eliminates both model and observation errors, allowing us to focus solely on the nature of this ill-posed problem.

Firstly, we select a set of soil, snow and climate parameters to generate synthetic SWE observations and their corresponding streamflow. All parameters are kept constant over the entire period except the parameter controlling the snowfall bias correction, which is set to fluctuate on a yearly basis and consequently also needs to be optimized for each year separately. Then, we run a single calibration to attempt to rederive these parameters and reconstruct the synthetic observations. Finally, we analyze our posterior ensemble of parameter sets and SWE reconstructions and quantify the resemblance to the synthetic streamflow and SWE observations. We expect to find a near-perfect match with the synthetic streamflow observations, a strong constraint of the total catchment-wide SWE but a weak constraint of the spatial distribution of this SWE.

How to cite: Wiersma, P. and Mariéthoz, G.: Inverse hydrological modeling to infer historical snow mass based on streamflow records, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20649, https://doi.org/10.5194/egusphere-egu24-20649, 2024.

EGU24-21497 | ECS | Orals | CR5.8 | Highlight

Transfer learning for Antarctic bed topography super-resolution 

Kim Bente, Roman Marchant, and Fabio Ramos

High-fidelity maps of Antarctica's subglacial bed topography constitute a critical input into a range of cryospheric models. For instance, ice flow models, which inform high-stakes sea level rise projections, rely on truthful and sufficiently detailed Digital Elevation Models (DEMs) of the ice-bedrock interface. Adversely, data collection of bed elevation profiles is extremely challenging, requiring airborne geophysical surveys of the vast landscape. Subsequent processing, as well as interpolation of the limited measurements onto a regular grid, introduce additional layers of uncertainty.

While the prevalent continent-wide gridded data products for Antarctica's bed topography, like BedMachine or upcoming Bedmap3, which arise from laborious ongoing international collaborations, are limited to a spatial resolution of 500 meters, machine learning methods present new opportunities to go beyond existing resolutions. Super-resolution, a class of computer vision techniques, aims to increase the resolution of a given low-resolution image and thereby generate a high-resolution version of that image. With a grid of elevation values interpreted as a special case of a grid of pixel values (i.e. an image), super-resolution approaches can hence be applied to topography grids. 

While existing bed topography super-resolution approaches for Antarctica have been challenged by the lack of available gridded data at dense target resolutions, which are needed to train deep learning architectures, we propose a probabilistic approach based on Gaussian Processes (GPs), that generates more robust and uncertainty-aware high-resolution topographies without the need for gridded target resolution training data. In addition, our proposed method leverages abundant high-resolution ice surface data from satellites by transferring covariance patterns from the ice surface to the bed via a purpose-designed covariance function.

We evaluate our multimodal Bayesian fusion model in a controlled topography reconstruction experiment over mountainous regions of East Antarctica, where we assess various models' skills to reconstruct original 500 m BedMachine topography, given the respective artificially degraded 1000 m, 1500 m, 2000 m, 2500 m, and 3000 m low-resolution input grids. As metrics we use root mean square error (RMSE), peak signal-to-noise ratio (PSNR), and the structural similarity index measure (SSIM) between reconstructions and withheld ground truth topographies. We compare our model against bilinear and bicubic interpolation baselines, DeepBedMap DEM and its multi-branch extension, MB_DeepBedMap DEM, as well as the Hybrid Attention Transformer (HAT), a pretrained state-of-the-art single image super-resolution model, for which we explore various fine-tuning strategies. Our results highlight the utility of our proposed uncertainty-aware and interpretable fusion model for the data-constrained endeavour of mapping Antarctica's subglacial bed topography at high resolutions.

How to cite: Bente, K., Marchant, R., and Ramos, F.: Transfer learning for Antarctic bed topography super-resolution, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21497, https://doi.org/10.5194/egusphere-egu24-21497, 2024.

EGU24-480 | ECS | Posters on site | GM2.1

Probabilistic optimal transport-driven inversion of the 2012 Palisades rockfall seismic source 

Rebeca Ursu, Mark Naylor, Hui Tang, and Jens M. Turowski

During rockfall events, the seismic waves are generated in response to the time-varying normal and tangential forces between the Earth and colliding and sliding mass. These forces carry information about the nature of the generative seismic source; hence, the source dynamics can be estimated. Several studies have used forward modeling to determine the amplitude and duration of these forces and, implicitly, the source process that could generate the observed seismic waves. Through running multiple forward models, the force history inversion involves adjusting the force amplitude and duration to minimize the misfit between the proposed source model, convoluted with the force-impulse Green’s functions, and the observations. In the Bayesian framework, the normal likelihood function is traditionally used to measure the misfit between the observed and predicted waveforms with respect to amplitude. However, the normal likelihood function is insensitive to the potential misalignment of the waveforms in time. Moreover, the relevant parameter space often exhibits multiple local minima, which may lead to a convergence to a minimum that does not present the global optimum. Optimal transport distances-driven exponential likelihoods were recently proposed as alternatives thanks to their ability to capture the time structure of the signals. We employed a Metropolis-Hastings sampling strategy in the probabilistic framework to reconstruct the 2012 Palisades rockfall seismic source using two implementations of the Wasserstein distance-based exponential likelihood function. The first implementation transforms between density functions, which are always positive and integrate to one. Therefore, it requires the transformation of the signals into probability density functions, which is done here via a modified graph-space transform scheme. The second method is applied directly to the signals. We evaluated the robustness of the two implementations of the Wasserstein distance-based exponential likelihood function in simulating the source characteristics with respect to the normal likelihood. Preliminary results show that contrary to the expectations, using optimal transport distances-driven exponential likelihoods leads to negligible improvement in the fit to the observed waveform.

How to cite: Ursu, R., Naylor, M., Tang, H., and Turowski, J. M.: Probabilistic optimal transport-driven inversion of the 2012 Palisades rockfall seismic source, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-480, https://doi.org/10.5194/egusphere-egu24-480, 2024.

EGU24-1972 | ECS | Orals | GM2.1 | Highlight

Do earthquakes cause more damage in the summer? 

Eldert Fokker, Elmer Ruigrok, and Jeannot Trampert

Shallow soft sedimentary layers overlaying harder bedrock are known to amplify ground motion generated by earthquakes. Such an amplification occurs when seismic waves travel from high impedance (density times wave speed) to low impedance layers. Large impedance contrasts can lead to substantially larger earthquake damages. As the impedance contrast determines the amplification factor, variations in shallow shear-wave speed contribute directly to changes in site amplification.

Seasonal temperature fluctuations have been shown to induce shear-wave speed variations and, hence, affect site amplification factors. This naturally leads to the question: is the strength of earthquake damage season dependent? In this study we model by how much seasonal temperature variations affect site amplification. The site-specific physical properties determine whether site amplification is more pronounced during summer or winter. For parameters from the Groningen region of the Netherlands, affected by the gas extraction induced seismicity, we expect in the summer a relative increase in amplification of 8% with respect to the amplification factor in the winter.

How to cite: Fokker, E., Ruigrok, E., and Trampert, J.: Do earthquakes cause more damage in the summer?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1972, https://doi.org/10.5194/egusphere-egu24-1972, 2024.

EGU24-3399 | ECS | Orals | GM2.1

Enhancing debris flow warning through seismic feature selection and machine learning model comparison 

Qi Zhou, Jens turowski, Hui Tang, Clément Hibert, Małgorzata Chmiel, Fabian Walter, and Michael Dietze

Machine learning can improve the accuracy of detecting mass movements in seismic signals and extend early warning times. However, we lack a profound understanding of the limitations of different machine learning methods and the most effective seismic features especially for the identifcation of debris flows. This contribution explores the importance of seismic features with Random Forest and XGBoost models. We find that a widely used approach based on more than seventy seismic features, including waveform, spectrum, spectrogram, and network metrics features, suffers from redundant input information. Our results show that six seismic features are sufficient to perform binary debris flow classification with equivalent or even better results., e.g., the Random Forest and XGBoost models achieve improvements over the benchmark of 0.09% and 1.10%, respectively, when validated on the ILL12 station. Considering models that aim to capture patterns in sequential data rather than information in the current time window, using the Long Short-Term Memory algorithm does not improve the binary classification performance over Random Forest and XGBoost models. However, in the early warning context, the Long Short-Term Memory model performs better and more consistently detects the initiation of debris flows. Our proposed framework simplifies seismic signal-driven early warning for debris flows and provides a proper workflow that can be used for detecting also other mass movements.

How to cite: Zhou, Q., turowski, J., Tang, H., Hibert, C., Chmiel, M., Walter, F., and Dietze, M.: Enhancing debris flow warning through seismic feature selection and machine learning model comparison, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3399, https://doi.org/10.5194/egusphere-egu24-3399, 2024.

EGU24-3861 | ECS | Posters on site | GM2.1

Capturing the short-term dynamics of outlet glaciers:  insights from seismic monitoring on Sermeq Kujalleq in Kangia, Greenland 

Janneke van Ginkel, Ana Nap, Adrien Wehrlé, Fabian Walter, and Martin Lüthi

Sermeq Kujalleq in Kangia, also known as Jakobshavn Isbræ, a major outlet glacier of the Greenland Ice Sheet, exhibits a flow speed higher than 30 m/day near the terminus. Basal sliding, iceberg calving, and subglacial hydraulics play pivotal roles in ice flow dynamics of this outlet glacier, and understanding these processes is crucial for predicting the impact of outlet glaciers on the Earth system in a changing climate.

 Seismic and geophysical field campaigns were conducted in 2021, 2022 and 2023 in the region of Sermeq Kujalleq in Kangia. The project has the aim to monitor the dynamic behavior of such a fast-flowing outlet glacier and its interaction with the surrounding shear margins. Shallow borehole seismic sensors and self-sufficient seismic boxes were deployed in multiple arrays on the fast-moving ice stream and its margin. The sensors capture seismic sources and monitor subglacial conditions and spatiotemporal variabilities throughout the ice mass. An on-rock broadband seismometer near the terminus records iceberg calving activity ideally complementing observations of a Terrestrial Radar Interferometer operating simultaneously.

 Here we report on first results of a seismic analysis that provides insights into details of ice dynamic variations of Sermeq Kujalleq. Power spectrograms of the 2023 upstream arrays feature a 4-day tremor-like signal between 2.5 and 6 Hz. This phenomenon was not observed for other calving events and was missing in the 2022 record. Beamforming techniques are employed to constrain the source location of this tremor as well as other seismic events. Potentially this multi-day tremor signal corresponds to the ice stream response to a major calving event. Additionally, beamforming and spectral analysis provide insights into hydraulic cycles of the glacier, such as widespread diurnal water drainage and the activity of moulins. By comparing these seismic observations with ice flow speed and satellite images we aim at understanding the details of short-term perturbations to ice flow, which may influence larger-scale ice stream dynamics.

How to cite: van Ginkel, J., Nap, A., Wehrlé, A., Walter, F., and Lüthi, M.: Capturing the short-term dynamics of outlet glaciers:  insights from seismic monitoring on Sermeq Kujalleq in Kangia, Greenland, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3861, https://doi.org/10.5194/egusphere-egu24-3861, 2024.

EGU24-5306 | ECS | Posters on site | GM2.1

Quantifying snout marginal bedload export from alpine glaciers 

Eva Wolf, Michael Dietze, and Stuart Lane

Bedload export from Alpine glaciers by rivers is a geomorphological process of increasing interest given the high retreat rates of temperate ice masses in the context of global warming. Access and measurement difficulties make it very poorly known and contradictory hypotheses exist about how it might respond to receding glaciers. In subglacial channels, bedload transport is a key mechanism for evacuating one of the products of glacial erosion. It likely constrains glacial erosion rates as removal of the products of erosion is needed so as to yield fresh bedrock for further erosion. Environmental seismology may be a valuable tool in understanding rates of subglacial bedload export.
Previous studies have considered subglacial bedload export in glacial forefields using seismic sensors and tracked particles moving underneath the ice sheet. We are taking former studies forward and extend the monitoring of bedload export detecting coarse grain impacts using seismometers right at the glacial terminus. The project aims to determine diurnal as well as seasonal sediment export quantities and compare results among different field sites.
We studied subglacial bedload export for the Otemma and Arolla glacier in Valais, Switzerland in the summer of 2023 by installing two seismic stations (PE-6/B geophones) close to each glacier terminus throughout the melt season. These four-month records of seismic signals were processed using fluvial inversion algorithms of the eseis package implemented in R. The algorithm is refined with wave propagation- and ground properties determined through active seismic experiments as well as measured grain size distributions from field sampling. We are able to separate turbulent water noise and bedload noise in the seismic signal and estimate water stage as well as bedload transport rates. Results are validated by comparing the water stage estimates to measurements from a discharge gauging station. Over a full season, we compare the behaviour of the two different glaciers regarding sediment export taking into account their size, orientation, elevation and other factors. We relate the detected bedload export events to meteorological conditions and shifts in seasonal melt processes from snow melt to ice melt.
The results of this study help to get a clearer picture of diurnal as well as seasonal patterns of bedload export from glaciers, impacting downstream riverbed erosion and deposition in the light of increasingly rapid glacier melt. These geomorphological processes are of interest for different infrastructural facilities such as hydropower plants.

How to cite: Wolf, E., Dietze, M., and Lane, S.: Quantifying snout marginal bedload export from alpine glaciers, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5306, https://doi.org/10.5194/egusphere-egu24-5306, 2024.

EGU24-5821 | Orals | GM2.1

Global observations of an up to 9 day long, recurring, monochromatic seismic source near 10.9 mHz associated with tsunamigenic landslides in a Northeast Greenland fjord 

Paula Koelemeijer, Rudolf Widmer-Schnidrig, Kristian Svennevig, Stephen Hicks, Thomas Forbriger, Thomas Lecocq, Anne Mangeney, Clément Hibert, Niels Korsgaard, Antoine Lucas, Claudio Satriano, Robert Anthony, Aurélien Mordret, Sven Schippkus, Søren Rysgaard, Wieter Boone, Steven Gibbons, Kristen Cook, Sylfest Glimsdal, and Finn Løvholt and the VLPGreenland team

We report the discovery of an unprecedented, monochromatic low-frequency seismic source arising from the fjords of North-East Greenland. Following a landslide and tsunami event in Dickson fjord on 16 September 2023, the seismic waves were detected by broad-band seismometers worldwide. Here we focus on a detailed analysis of the long-period seismic signal, while a reconstruction of the dynamics of the landslide is presented by Svennevig et al. in session NH3.5. 

Both frequency and phase velocity of the waves are consistent with fundamental mode Rayleigh- and Love-waves. However, the decay rate of these waves is much slower than predicted for freely propagating surface waves so that we infer a long-lasting and slowly decaying source process. Although the 16 September 2023 event was by far the largest, analysis of historical seismic data has revealed five other previously undetected events, all with a fundamental frequency between 10.85 and 11.02 mHz. The signal of the largest two events initially decayed with a quality factor, Q close to Q=500, which increased to Q=3000 within the first 10 hours and could thus be detected for up to nine days. The smaller four events had a slow decay-rate (Q>1000) for their entire duration. In comparison, the global average attenuation of Rayleigh waves at these frequencies is Q=117 for PREM, thus precluding a single, impulsive source for these signals.

Gleaning archives of optical and SAR satellite images reveals that at least four out of six events could be associated with landslides in Dickson fjord, the two others remain unresolved. However, such rapid transient events cannot explain the long duration of the radiated seismic waves. Our modelling of the largest event shows that a transversal seiche in Dickson fjord, excited by a landslide induced tsunami, can account for both the monochromatic low frequency signal as well as its seismic signal amplitude and radiation pattern. However, the seiche modelling results in Q values lower than 250 and hence the seiche needs to be continuously driven for the entire duration of the observed seismic signal. Thus, a full understanding of the source process that produces the monochromatic signal remains enigmatic.

How to cite: Koelemeijer, P., Widmer-Schnidrig, R., Svennevig, K., Hicks, S., Forbriger, T., Lecocq, T., Mangeney, A., Hibert, C., Korsgaard, N., Lucas, A., Satriano, C., Anthony, R., Mordret, A., Schippkus, S., Rysgaard, S., Boone, W., Gibbons, S., Cook, K., Glimsdal, S., and Løvholt, F. and the VLPGreenland team: Global observations of an up to 9 day long, recurring, monochromatic seismic source near 10.9 mHz associated with tsunamigenic landslides in a Northeast Greenland fjord, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5821, https://doi.org/10.5194/egusphere-egu24-5821, 2024.

EGU24-5947 | ECS | Posters on site | GM2.1

Low-cost raindrop sizing with piezoelectric sensor: A mechanical approach 

Chi-Ling Wei and Li-Pen Wang

Raindrop size distribution (DSD) is a key factor to derive reliable rainfall estimates. It is highly related to a number of integral rainfall variables, such as rain intensity (R), rain water content (W) and radar echo (Z) and thus can contribute to a range of hydrological and meteorological applications, such as rainfall-induced landslide warnings and radar rainfall calibration. Disdrometers are commonly used to measure DSDc. Well-known disdrometer sensors include JWD, Parsivel and 2DVD . These sensors may have their own strengths and weaknesses, but their costs are all much higher than that of widely-deployed catching gauges (e.g. tipping bucket and weighing gauges). This makes it infeasible to have a widespread, or dense, DSD monitoring network. To address this issue, our ultimate goal is to develop a lightweight and low-cost disdrometer with descent accuracy.

In this work, we have prototyped a disdrometer with a piezoelectric cantilever. It is not new to use piezoelectric materials as rain sensors because of its low cost and low maintenance. It is however not trivial to ‘calibrate’ this type of sensors, and various calibration methods have been proposed in the literature. However, whereas most of these sensors associate received signal with rainfall properties directly (via statistical or machine learning approaches), we propose to formulate the drop sensing process as a ‘mechanical’ problem. More specifically, we first form a physical model that can well simulate the signal response of continuous excitation force on a piezoelectric cantilever based on an existing theoretical model. We then analytically derive the inverse function of the model which can obtain the excitation force directly from the measured signals. The derived force-time signal is found to linearly associate with DSD and can also be used for other purposes including kinetic energy analysis.

In spite of the sound underlying theory, the real-world signal is far from perfect, containing a considerable amount of noise. Additionally, as our physical model requires conducting differentiation and second-order differentiation, to which the impact of noise is even destructive. Although we have made efforts to improve the quality of signal from the source, it does not fully solve the problem because the physical model is highly sensitive to signal gradients. To effectively deduce the impact of noise, we then introduced various signal ‘noise’ models, which were reported to well resemble the behavior of real-world signal noises, to train a machine learning (ML) model, such that the actual excitation force function can be derived from various weather conditions.

To verify the proposed sensor and signal processing model, we have set up lab experiments using an in-house device with micropumps and high-voltage raindrop detachment devices to control the required size, drop location, and timing of the drops. Preliminary results from a given range of drop sizes have shown the potential of the proposed sensor and ML-based signal processing model to well derive drop sizes from our experimental device. We plan on further testing our sensor outdoor and compare the measurements with those collected from a co-located Parseval2 disdrometer.

How to cite: Wei, C.-L. and Wang, L.-P.: Low-cost raindrop sizing with piezoelectric sensor: A mechanical approach, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5947, https://doi.org/10.5194/egusphere-egu24-5947, 2024.

EGU24-6218 | ECS | Orals | GM2.1

High resolution observations of tide induced icequake activity at the Astrolabe glacier grounding zone 

Tifenn Le Bris, Guilhem Barruol, Florent Gimbert, Emmanuel Le Meur, and Dimitri Zigone

Cryoseismology, which records ice-induced seismic activity, is emerging as a powerful tool for studying the grounding zone - a critical spatio-temporal area where outlet glaciers grounded on the continent starts floating and interacting with the ocean underneath. The SEIS-ADELICE project supported by the French Polar Institute (IPEV) aims to characterise the dynamics of the Astrolabe glacier in Terre Adélie (East Antarctica), from its grounded part to its terminus in the ocean. Over the past 3 years, we deployed broad-band seismometers both at the grounding zone and on stable ice around the glacier, along with ocean bottom seismometers (OBS) close to the glacier terminus. In January 2023, the recording system was complemented by a dense array of 50 seismic nodes over the grounding zone. This allowed us to cover spatial scales from metres to several kilometres, providing a high-resolution observation of tidal forcing on the floating tongue and its repercussions on the glacier behaviour. The seismic records contain a wide range of signals, including icequakes, accepted to result from the brittle deformation of the ice. Although the seismic patterns at the different stations show clear modulation of icequakes by tidal cycles, their phasing with the tide depends on the location of the sensors, whether they are grounded or floating and on their distance from the active part of the glacier. This highlights the importance of the network typology and its proximity to the grounding line when characterising icequake occurrence patterns. Local icequakes detected at the grounding line exhibit a consistent occurrence during both rising and falling tides, with the peak activity observed during high tide. Source location analysis reveals that events are distributed across both the grounding line and the lateral shear zones of the glacier which are under strong stress from the ice-ocean interactions during tides.

How to cite: Le Bris, T., Barruol, G., Gimbert, F., Le Meur, E., and Zigone, D.: High resolution observations of tide induced icequake activity at the Astrolabe glacier grounding zone, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6218, https://doi.org/10.5194/egusphere-egu24-6218, 2024.

EGU24-6613 | Orals | GM2.1

Tracking baleen whale calls in the Lower St. Lawrence Seaway, Canada, using land seismometers   

Yajing Liu, Eva Goblot, and Alexandre Plourde

The Lower St. Lawrence Seaway (LSLS) is part of a major marine shipping corridor in eastern Canada, and also an essential feeding ground for fin whales and blue whales. Understanding the whale migration and habitat usage in the LSLS is critical for informing conservation policies that minimize noise pollution and risk of collision to the whale populations. In this study we utilize continuous recordings of six broadband seismometers located on the north and south shores of the St. Lawrence River to characterize the frequency range, recurrence interval and duration of fin and blue whale calls. We further use the whale call detections to quantify their spatial and temporal variations along the LSLS between February 2020 and January 2022, with the caveat that the detection range at these land stations is probably limited to a few kilometers due to energy loss along the seismic wave travel paths through multiple interfaces. We identified higher whale call detection rates at stations near the northwest of St. Lawrence Gulf than the upstream Estuary, suggesting possible influences of ocean currents and ice conditions. Whale calls are detected year around, with majority in the fall/winter months (September to February), implying seasonal and annual variations that may be influenced by climate change. We are currently analyzing recordings from a temporary deployment of 48 nodal seismometers, at 10-km average spacing, along the shorelines of the LSLS between September-October 2023, to further quantify the spatial patterns of whale calls and identify possible linkages to coastal bathymetry, ocean currents and preferential diets for the baleen whales.

How to cite: Liu, Y., Goblot, E., and Plourde, A.: Tracking baleen whale calls in the Lower St. Lawrence Seaway, Canada, using land seismometers  , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6613, https://doi.org/10.5194/egusphere-egu24-6613, 2024.

The EarthScope Transportable Array (TA) in Alaska has been a unique seismic network since about 2014 because most stations are equipped with environmental sensors to record pressure, temperature, and wind (speed and direction). We will summarize some physical insights of near-surface properties in Alaska that can be gained from the combined analysis of seismic and environmental sensors. We also point out a possible effect of the thick sea ice on the climate in the North Slope region that faces the polar ocean.

First, the combined analysis of seismic data and pressure data allows us to separate two distinct types of seismic noise; one is the ordinary seismic noise, consisting of propagating body and surface waves, and the other is the deformation caused by the local pressure loading. This loading effect is observed at many stations when surface pressure becomes high. It can be confirmed based on two pieces of evidence; one from high coherence between seismic and pressure data and the other from the phase difference between pressure and vertical seismic displacement. By selecting data from a high-pressure range, we can apply the compliance method, similar to the compliance method applied to ocean bottom observations (e.g., Webb and Crawford, 1998). We will show a map of shallow rigidity variations for the depth range of 50-100m.

Second, the combined analysis of temperature and seismic noise allows us to identify the major effects caused by near-surface melting, primarily in the permafrost area. Some stations show a thousand-fold increase of horizontal noise in summer at 0.01-0.03 Hz in comparison to the frozen state. This anomalous horizontal noise can be seen at low frequency (< 0.1 Hz) and is undoubtedly related to tilt effects as its amplitude increases towards lower frequency.

Third, seasonal variation in horizontal noise shows a rapid increase in summer due to melting but the way the noise level returns to the frozen (low-noise) state varies from station to station. For most stations, this return occurs well after the surface temperature becomes negative in September or October. But some stations require time until March of next year to return to the low noise level. These data suggest that the melt layer remains at depth for a long time even after temperature drops below freezing, perhaps developing a sandwiched molten layer between the developing ice from the surface and the underlying permafrost ice.

How to cite: Tanimoto, T.: New Perspectives on the Shallow Environment in Alaska from co-located seismic, pressure, temperature, and wind sensors, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6637, https://doi.org/10.5194/egusphere-egu24-6637, 2024.

EGU24-7490 | Posters on site | GM2.1 | Highlight

August 2023 Slovenian flood anatomy from national seismometer network data analysis 

Michael Dietze, Mateja Jemec Auflič, Sašo Petan, and Nejc Bezak

Excessive and sustained rainfall can trigger regional floods with a large propagation range. Their non-linear onset, rapid evolution and massive impact make prediction, mitigation and posteriour anatomy efforts difficult.

The atmospheric low “Petar” that struck Europe in early August 2023 was one drastic example of such flood triggering rain events. It was able to gain abundant moisture and heat over an exceptionally warm Mediterranean Sea, before it moved to continental Europe, crossing Slovenia, Austria, and Germany. It caused severe flooding as a result of locally more than 350 mm rain within less than two days. We focus on Slovenian examples, where the event was perceived the most devastating natural hazard in the last decades.

Here, we follow a seismic approach to study the spatially contrasting effects of the rain signal from available FDSN data (SL network). We study the time variant spectral signatures of reaches in steep mountain, graded upland and wide basin landscapes across northern Slovenia and exemplarily invert the seismic data for key flood parameters: water level and debris flux, and propagation velocity. We discuss the detection range of existing earthquake seismometer networks and the potential to improve those with respect to flood quantification. Our analysis highlights the compound effects of channel geometry, event magnitude and network density for flood detection and signature consistency.

How to cite: Dietze, M., Jemec Auflič, M., Petan, S., and Bezak, N.: August 2023 Slovenian flood anatomy from national seismometer network data analysis, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7490, https://doi.org/10.5194/egusphere-egu24-7490, 2024.

EGU24-7576 | ECS | Orals | GM2.1

Constructing a New Catalogue of Greenland's Iceberg Calving Events through Seismic Data Analysis and Machine Learning 

Selina Wetter, Clément Hibert, Anne Mangeney, and Eléonore Stutzmann

The Greenland ice sheet, a critical component of the global climate system, has played a substantial role in rising sea level, marked by a fourfold increase in mass loss due to iceberg calving between 1992-2000 and 2000-2011. Through the quantification of the spatio-temporal changes in Greenland’s ice mass loss resulting from iceberg calving, we gain a deeper understanding of the impacts of climate change.

The mass loss related to calving icebergs can be estimated by combining mechanical simulation of iceberg calving and inversion of seismic data. Seismic signals are generated by the time-varying force produced during iceberg calving on marine-terminating glacier termini. These events, known as glacial earthquakes, are recorded by the Greenland Ice Sheet Monitoring Network at tens of kilometres from the source.

However, differentiating these signals from tectonic events, anthropogenic noise, and other natural noise is challenging due to their complex frequency content (1-100s), multi-phase waveforms and low amplitude. To overcome this difficulty, we use a detection algorithm based on the Short-Time Average over Long-Time Average (STA/LTA) method and combine it with machine learning (Random Forests). By training the machine learning algorithm on seismic event catalogues containing more than 400 earthquakes and glacial earthquakes each, our approach is apt for identifying glacial earthquakes. Applying this methodology to continuous data offers the possibility to uncover smaller and previously undetected events. As a result, we present a comprehensive catalogue spanning several years and discuss its relevance and reliability. The generated catalogue allows us to develop new methods to better understand the spatio-temporal evolution of the ice-calving activity in the region. Among these, we will initially focus on locating and inverting the force of the largest events, providing a basis for testing new machine learning approaches for the characterisation of the source. This includes extracting properties like the iceberg volume and shape from both large and smaller events, ultimately advancing our understanding of Greenland's ice mass loss dynamics.

How to cite: Wetter, S., Hibert, C., Mangeney, A., and Stutzmann, E.: Constructing a New Catalogue of Greenland's Iceberg Calving Events through Seismic Data Analysis and Machine Learning, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7576, https://doi.org/10.5194/egusphere-egu24-7576, 2024.

EGU24-8208 | ECS | Orals | GM2.1

Icequake source location using seismic data in Dålk Glacier, East Antarctica 

Shun Zhao, Zheyi Cao, Yuanyuan Gu, Chen Lv, Zhitu Ma, Tong Hao, Gang Qiao, Benfeng Wang, and Rongxing Li

Icequakes are closely associated with glacier movement and rupture, and their temporal and spatial distribution patterns can portray the dynamics of glaciers. In this study, we used the seismic data recorded by 34 short-period Smartsolo seismometers deployed in Dålk Glacier, East Antarctica for about 60 days to detect and locate icequakes. The array was deployed at the edge of the Dålk Glacier and across the grounding line previously generated by satellite observations. The recorded data were strongly affected by Antarctica storms and we selected two days with little wind noise for preliminary analysis. Using time-frequency analysis and particle motion, we found that the seismic events are either dominated by body waves or surface waves, which likely correspond to deep icequakes or near-surface crevasse icequakes. Since the propagation of surface waves is easier to analyze and possible detections of crevasse icequakes are more likely to be verified from satellite images, we chose to focus on surface wave signals in this preliminary analysis. We first filtered records to 5-20 Hz and manually examined records with clear surface wave arrivals. We then produced templates using these events to scan through our records. We successfully identified 89 events within the two-day period. Lastly, these signals were located using a grid-search approach for their latitudes and longitudes, together with an average group velocity for each event. Nearly half of the incidents were concentrated on the edges of rock outcrops, which suggests they were generated by the relative movement between the glacier and outcrops. The other half of the events was found in the eastern region, where a large number of surface crevasses were observed on satellite imagery. In addition, the optimal velocity from the grid search is ~2.8 km/s for events from the North and West, while the optimal velocity for events from the East is ~1.8 km/s. The difference in wave velocity suggests the existence of a boundary between rock and ice at a depth of about 100-150m within or near our seismometer array. By analyzing the amplitude variations of incidents in different directions recorded at various stations, we observed that this boundary is within our array and its location and geometry can be estimated. Compared to the grounding line predicted from satellite observations, our result shows that the boundary is offset to the East by ~100 m. The reason for this discrepancy will be further discussed in the meeting.

How to cite: Zhao, S., Cao, Z., Gu, Y., Lv, C., Ma, Z., Hao, T., Qiao, G., Wang, B., and Li, R.: Icequake source location using seismic data in Dålk Glacier, East Antarctica, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8208, https://doi.org/10.5194/egusphere-egu24-8208, 2024.

EGU24-8304 | Posters on site | GM2.1

Water table height maps prediction from passive surface-wave dispersion using deep learning 

José Cunha Teixeira, Ludovic Bodet, Agnès Rivière, Marine Dangeard, Amélie Hallier, Alexandrine Gesret, Amine Dhemaied, and Joséphine Boisson Gaboriau

Monitoring underground water reservoirs is challenging due to limited spatial and temporal observations. This study presents an innovative approach utilizing supervised deep learning (DL), specifically a multilayer perceptron (MLP), and continuous passive-Multichannel Analysis of Surface Waves (passive-MASW) for constructing 2D water table height maps. The study site, geologically well-constrained, features two 20-meter-deep piezometers and a permanent 2D geophone array capturing train-induced surface waves. For each point of the 2D array, dispersion curves (DCs), displaying Rayleigh-wave phase velocities (VR) across a frequency range of 5 to 50 Hz, have been computed each day between December 2022 and September 2023. In the present study, these DCs are sampled in wavelengths ranging from 4.5 to 10.5 m in order to focus the monitoring on the expected water table depths. All VR data around one of the two piezometers is used to train the MLP model. Water table heights are then predicted across the entire geophone array, generating daily 2D piezometric maps. Model's performance is tested through cross-validation and comparisons with water table data at the second piezometer. Model’s efficiency is quantified with the root-mean-square error (RMSE) and the coefficient of determination (R²). A R² is estimated above 80 % for data surrounding the training piezometer and above 55 % for data surrounding the test piezometer. Additionally, the RMSE is impressively low at 0.03 m at both piezometers. Results showcase the effectiveness of DL in generating predictions of water table heights from passive-MASW data. This research contributes to advancing our understanding of subsurface hydrological dynamics, providing a valuable tool for water resource management and environmental monitoring. The ability to predict 2D piezometric maps from a single piezometer is particularly noteworthy, offering a practical and efficient solution for monitoring water table variations across broader spatial extents.

How to cite: Cunha Teixeira, J., Bodet, L., Rivière, A., Dangeard, M., Hallier, A., Gesret, A., Dhemaied, A., and Boisson Gaboriau, J.: Water table height maps prediction from passive surface-wave dispersion using deep learning, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8304, https://doi.org/10.5194/egusphere-egu24-8304, 2024.

EGU24-9067 | ECS | Posters on site | GM2.1

Seasonal variations in sediment transport from ice sheet terminus through a proglacial forefield. A case study from Leverett glacier, Western Kalaallit Nunaat (Greenland).  

Marjolein Gevers, Stuart N. Lane, Floreana Miesen, Davide Mancini, Matthew Jenkin, Chloé Bouscary, Faye Perchanok, and Ian Delaney

Current climatic warming is causing accelerated melt of the Greenland Ice Sheet. Whilst the changing hydrological response is well known, the sediment export as well as the geomorphic changes in the proglacial area remain uncertain.  

Here we present records of sediment transport from melt seasons 2022 and 2023 in the proglacial area of Leverett glacier, a land terminating glacier outlet on the Western part of the Greenland Ice Sheet. The proglacial area here is very well denifed by a waterfall cutting through bedrock functioning as terminal gauge, which allows for the installation of hydrological stations. These hydrological gauging stations, containing turbidity and pressure sensors, allow for estimation of discharge and suspended sediment concentrations over the melt season. Variations in bedload transport can be analysed using the sesimic data obtained from the geophones placed on the river bank close to the hydrological gauging stations. To convert the recorded seismic data into bedload flux, a Fluvial Inversion Model is used, which is calibrated using active seismics surveys and the water stage data from the hydrological gauging stations.

The dataset allows us to investigate the relationships between bedload, suspended sediment, and water discharge from the Leverett glacier as well as sediment transport and deposition in the proglacial area. We observe several spring events in the first half of July, where suspended sediment concentration and water discharge increase simultaneously at the start of the melt season. During the first half of August, we observe a clear dilution signal, where increase in water discharge coincides with a decrease in suspended sediment concentration From insights about the relationship between water and sediment discharge from the ice sheet, we can speculate about the sediment export response to increased water discharge from the Ice Sheet.

How to cite: Gevers, M., Lane, S. N., Miesen, F., Mancini, D., Jenkin, M., Bouscary, C., Perchanok, F., and Delaney, I.: Seasonal variations in sediment transport from ice sheet terminus through a proglacial forefield. A case study from Leverett glacier, Western Kalaallit Nunaat (Greenland). , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9067, https://doi.org/10.5194/egusphere-egu24-9067, 2024.

Groundwater storage monitoring is now one of the most promising application of seismic interferometry techniques. In steep mountain environments, where drilling wells is particularly challenging, the use of seismic stations to retrieve relative seismic velocity changes could fundamentally advance our understanding of groundwater dynamics. However, very few studies have looked at seismic velocity variations at the scale of a single steep topography unit. Here, we estimate velocity variations from six stations covering a distance of 3.5 km on a single mountain ridge in the county of Hualien, Taiwan. One station was placed at the top of a ridge (900m elevation), two at the mid-slope of the topography and two others at the bottom (200m elevation), near the river banks. The aim is twofold: Determining how homogenous these velocity changes are and understanding the possible impact of topography on groundwater variations in a mountainous setting. Results from auto-correlations and cross-correlations are compared with meteorological data and other geophysical analysis. We identify the average hydrological dynamics of the ridge unit and connect the residual velocity changes to local site characteristics and upstream weather conditions.

How to cite: Illien, L., Kuehn, J., Andermann, C., and Hovius, N.: Monitoring groundwater dynamics in a mountain ridge using seismic interferometry: Influence of topography, local subsurface structure and meteorological conditions., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9608, https://doi.org/10.5194/egusphere-egu24-9608, 2024.

EGU24-9822 | ECS | Posters on site | GM2.1

Intermediate-depth icequakes at Greenland’s fastest outlet glacier: evidence for englacial thrust faulting? 

Ana Nap, Fabian Walter, Martin P. Lüthi, Adrien Wehrlé, Janneke van Ginkel, Andrea Kneib-Walter, and Hugo Rousseau

In traditional glacier flow laws and consequently glacier models, a widely used assumption is that the ice behaves as a non-Newtonian viscous fluid that slides either across hard bedrock or via deforming subglacial till. Elastic effects and brittle deformation within the ice are often neglected for simplicity, as even ubiquitous surface crevasses are difficult to capture in numerical schemes. While there is ample seismological evidence that stick-slip motion plays a significant role in basal sliding of both alpine and polar glaciers, similar evidence is lacking for brittle deformation within the ice mass itself. Instead, it is commonly assumed that the ice moves and deforms in a purely viscous or ductile manner, which may not be an accurate representation of reality.

Here, we present observations of high-frequency (>50Hz) signals of intermediate-depth seismic sources occurring along the fast ice-stream of Sermeq Kujalleq in Kangia (Jakobshavn Isbræ), Greenland’s fastest flowing outlet glacier. The waveform characteristics of these events closely resemble the known characteristics of waveforms associated with basal stick-slip events, making them easily distinguishable from the more prevalent icequake signals generated by surface crevasse opening and propagation. However, differences in P and S wave arrival times as well as probabilistic source locations show that these events occur at ~170-400 m depth, whereas at those locations the glacier has a total depth of approximately 2000 m. Hence, these events cannot be caused by stick-slip motion at the base of the glacier, but must originate from englacial dislocations such as e.g., thrust faulting. Hundreds of these englacial icequakes are observed at several seismic arrays that were temporarily deployed in 2022 and 2023 along the fast ice-stream of Sermeq Kujalleq. Using waveform clustering and source mechanism analysis, we discuss the role of these events in ice dynamics and in particular englacial deformation.

 

How to cite: Nap, A., Walter, F., Lüthi, M. P., Wehrlé, A., van Ginkel, J., Kneib-Walter, A., and Rousseau, H.: Intermediate-depth icequakes at Greenland’s fastest outlet glacier: evidence for englacial thrust faulting?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9822, https://doi.org/10.5194/egusphere-egu24-9822, 2024.

EGU24-10147 | ECS | Posters on site | GM2.1

Uncovering Stick-Slip Events: Denoising Cryoseismological Distributed Acoustic Sensing Data with an Autoencoder 

Johanna Zitt, Patrick Paitz, Fabian Walter, and Josefine Umlauft

One major challenge in cryoseismology is that signals of interest are often buried within the high noise level emitted by a multitude of environmental processes. Specifically, basal sources such as stick-slip events often stay unnoticed due to long travel paths to surface sensors and accompanied wave attenuation. Yet, stick-slip events play a crucial role in understanding glacier sliding and therefore, it is of great interest to investigate their spatio-temporal evolution, across the entire glacier from its ablation to its accumulation zone.
Distributed Acoustic Sensing (DAS) is a technology for measuring strain rate by using common fiber-optic cables in combination with an interrogation unit. This technology enables us to acquire seismic data over an entire glacier with great spatial and temporal resolution. To unmask stick-slip events, new techniques are required that effectively and efficiently denoise large cryoseismological DAS data sets. 
Here, we propose an autoencoder, a type of deep neural network, which is able to separate the incoherent environmental noise from the temporally and spatially coherent signals of interest (e.g., stick-slip events or crevasse formations). We trained the autoencoder in order to denoise a DAS data set acquired on Rhonegletscher, Switzerland, in July 2020. Due to the highly active and dynamic cryospheric environment as well as non-ideal cable-ground coupling the collected DAS data are characterized by a low signal to noise ratio compared to classical point sensors.
Several models were trained on a variety of data subsets, differing in recording positions (ablation or accumulation zone), event types (stick-slip event or surface event) and the quantity of training events. We compare and discuss the denoising capabilities of these models with several metrics, such as inter-channel coherence, similarity between seismometer and DAS recordings, and visual assessment. This evaluation is conducted while considering different data types in a qualitative and quantitative manner. All models show an increase in inter-channel coherence of the seismic records after denoising. Further, all models uncover previously undetected stick-slip events, whereby models trained on manually picked training data perform better than models trained on randomly picked training data. We believe that the application of our models can improve the understanding of basal stick-slip information in cryoseismological DAS datasets, potentially uncovering previously hidden information.

How to cite: Zitt, J., Paitz, P., Walter, F., and Umlauft, J.: Uncovering Stick-Slip Events: Denoising Cryoseismological Distributed Acoustic Sensing Data with an Autoencoder, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10147, https://doi.org/10.5194/egusphere-egu24-10147, 2024.

EGU24-10347 | Orals | GM2.1 | Highlight

The seismic signature of skiing 

Heiner Igel, Sophie Brass, Fabian Lindner, Koen Van Noten, Raphael de Plaen, Joachim Wassermann, Felix Bernauer, and Thomas Lecocq

In March 2023 the annual winter school SKIENCE (www.skience.de) was held in the Bavaria alps, south-east of Munich. The topic was environmental seismology with a focus on seismic monitoring using ambient seismic noise. The winter school had strong practical training aspects. Prior to the meeting 12 5Hz nodes (SmartSolo) were deployed in the valley near Bayrischzell with the goal to explore local structure and site effects using interferometric methods. During the midweek free afternoon the 12 SmartSolo nodes were installed on both sides of a slalom run with several gates through which participants of the winterschool skied one after each other. First inspection of the data showed that clear signals of the skiers could be identified. Here, we report on attempts to use the seismic data records to recover the tracks of the skiers as moving seismic sources. Questions associated with this experiment are at which points in the tracks seismic energy is generated, where exactly the incoming signals propagate and with what velocities, and how well the source locations can be backprojected. A simple theoretical model is used to develop the inversion tools to recover the moving sources.   

How to cite: Igel, H., Brass, S., Lindner, F., Van Noten, K., de Plaen, R., Wassermann, J., Bernauer, F., and Lecocq, T.: The seismic signature of skiing, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10347, https://doi.org/10.5194/egusphere-egu24-10347, 2024.

EGU24-10380 | Orals | GM2.1

Observing ice-bed weakening on a fast flowing glacier with seismic noise interferometry and unsupevised clustering. 

Léonard Seydoux, Ugo Nanni, Lucien Goulet, Thomas Pauze, and Andreas Köhler
Glacier flow instability often results from changes at the ice-bed interface. However, understanding these processes is challenging due to limited access to the glacier bed. Our study focuses on Kongsvegen glacier in Svalbard, which shows signs of an upcoming rapid flow event. To investigate the potential causes of such acceleration, we installed 20 seismometers along the glacier flowline, from the surface down to 350 m near the ice-bed interface. We combined our seismic monitoring with measurements of surface velocity, basal water pressure, and basal sediment deformation.
First, we performed seismic noise interferometry between stations located along the glacier flowline with inter-station distances ranging from 1 to 12 km. We observed a multi-year decrease in seismic velocity, with a seasonal signal superimposed, showing a melt-season decrease in seismic velocity of 2 to 4%. We compared our observations with 1D models and concluded on the presence of damaged basal ice and/or a weakening of the subglacial sediments. This indicates a mechanical weakening of the ice-bed interface, promoting further glacier acceleration.
Second, we conducted unsupervised clustering of seismic waveforms using a novel approach based on a deep scattering network. Doing so, we observed a yearly increase in surface crevasses concomitant with an increase in basal events, likely indicating stick-slip and/or basal crevasses. This increase is particularly visible during winter, where the number of events steadily increases from year to year. We suggest that, in response to an initial glacier acceleration, new crevasses have opened, providing access pathways for surface meltwater to the base of the glacier, affecting the ice-bed coupling. This mechanism represents a positive hydro-mechanical feedback that fuels further acceleration and crevassing, potentially having wider implications for triggering glacier-wide instabilities, increasing short-term sea-level rise, and local hazards.

 

How to cite: Seydoux, L., Nanni, U., Goulet, L., Pauze, T., and Köhler, A.: Observing ice-bed weakening on a fast flowing glacier with seismic noise interferometry and unsupevised clustering., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10380, https://doi.org/10.5194/egusphere-egu24-10380, 2024.

EGU24-10525 | ECS | Posters on site | GM2.1

Deep Embedded Clustering of a Cryo-Data-Cube 

Julia Peters, Felix Roth, and Josefine Umaluft

Cryoseismological records consist of numerous signals generated by various sources within or surrounding glacial ice, including icequakes, water flow, avalanches, rockfalls, wind, or precipitation. This results in a notably high noise level within the data, posing a significant challenge in detecting and distinguishing individual seismic events and sources.

Our research employs Deep Embedded Clustering (DEC) to address this challenge, focusing on the analysis of a Distributed Acoustic Sensing (DAS) dataset acquired on Rhonegletscher (Switzerland) in 2020.

To visualize and efficiently streamline the DEC processing of this substantial volume of data, we reorganize the numerous continuous DAS channels as a 3D data cube featuring the three dimensions: time, space, and frequency. The DEC approach involves first transforming high-dimensional seismic data into a more manageable lower-dimensional latent space using an autoencoder. This transformation is vital in emphasizing the essential characteristics of the data, thereby enabling more effective clustering. Subsequently, the DEC algorithm autonomously categorizes these seismic signals into distinct clusters based on their unique spatio-temporal characteristics, without the prerequisite of manual annotation.

The primary aim of this approach is to utilize DEC for the effective mapping of clearly defined spatio-temporal clusters within cryoseismological records. This approach is geared towards achieving a more nuanced understanding of the various sources contributing to these records and their complex dynamics. By successfully segregating these clusters, the aim is to reveal new insights into the complex processes and interactions in glacial environments.

Both the DAS data and the clustering results can be explored interactively using the data cube viewer Lexcube. Come find us at the poster stand!

How to cite: Peters, J., Roth, F., and Umaluft, J.: Deep Embedded Clustering of a Cryo-Data-Cube, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10525, https://doi.org/10.5194/egusphere-egu24-10525, 2024.

EGU24-11086 | ECS | Posters on site | GM2.1

Support vector regression-based model for the prediction of surface displacement and vibration using meteorological data 

Chi En Hi, Kate Huihsuan Chen, Wei Peng, Wan-Ru Huang, Hsiang Han Chen, Ko Chih Wang, and Kuo En Ching

Can we use environmental data to predict changes in surface displacement fields? Do severe weather events alter the near-surface geomechanical properties? The seasonal variations in GPS time series and crustal seismic velocities have been frequently observed at different study areas. Such variation has been tied closely to the cyclic hydrological loads [e.g., Costain et al., 1987; Heki, 2003; Roth et al., 1992], which its association with tectonic deformation remains debated. Using the 15 years meteorological, geodetic, and seismic data recorded in southern Taiwan (near Chaozhou fault where the background seismicity level is low), we aim to explore the possibility of predicting surface displacement and vibration using climatic variables (time series of temperature, precipitation, and wind velocity) and groundwater levels. Here the Support Vector Regression (SVR) model is developed for the prediction of the GNSS and seismic signals, while 15-yr datasets are divided into groups of 75%  and 25% datasets for model calibration and testing. When the predicted surface displacement is compared with the real data, the R-square values reach 95%, indicating the applicability of SVR model on long-term surface deformation prediction. In the future, long-term prediction model will be conducted to target several extreme weather events in Taiwan.

How to cite: Hi, C. E., Chen, K. H., Peng, W., Huang, W.-R., Chen, H. H., Wang, K. C., and Ching, K. E.: Support vector regression-based model for the prediction of surface displacement and vibration using meteorological data, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11086, https://doi.org/10.5194/egusphere-egu24-11086, 2024.

EGU24-11562 | ECS | Posters on site | GM2.1 | Highlight

How trees sway and what it tells us about their overall vitality 

Jana Roth, Karin Mora, Djamil Al-Halbouni, Ronny Richter, Teja Kattenborn, Sebastian Johannes Wieneke, Ana Bastos, Alexandra Weigelt, Christian Wirth, and Josefine Umlauft

Changing climate, especially the increase in frequency and intensity of extreme events such as heat waves and droughts, poses a significant challenge to the biosphere, threatening biodiversity overall and specifically exacerbating tree mortality. Countermeasures and management actions often prove insufficient due to delayed visual indicators of tree stress. 

Real-time monitoring of physiological and structural changes in tree characteristics and related abiotic parameters, such as sap flow, leaf angle, or soil moisture, plays a crucial role in tracking the trees’ overall vitality. However, conventional monitoring approaches are often expensive, require high maintenance and are therefore not feasible on a larger spatio-temporal scale.     

In a groundbreaking approach, we propose to measure the seismic oscillation generated by tree sway under specific weather conditions, potentially reflecting tree vitality. Specifically, oscillations are related to material properties of leaves, branches, and trunks, which change when they become dry. Seismic measurements offer scalability and low maintenance, making them viable for extensive spatio-temporal coverage. Through integrated observations from dense seismic arrays, direct tree trait measurements, and meteorological parameters collected at the research arboretum (ARBOfun) during autumn 2023, we successfully isolated the seismic fingerprint of tree sway.

However, the unique nature of this novel data introduces challenges, for example noise from human and animal activities, allowing for only time series snapshots. To overcome these challenges, we explored various time series and frequency related analysis methods to separate the tree signal from other influences.

How to cite: Roth, J., Mora, K., Al-Halbouni, D., Richter, R., Kattenborn, T., Wieneke, S. J., Bastos, A., Weigelt, A., Wirth, C., and Umlauft, J.: How trees sway and what it tells us about their overall vitality, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11562, https://doi.org/10.5194/egusphere-egu24-11562, 2024.

EGU24-13007 | Orals | GM2.1 | Highlight

Assessing the seismic signature of turbulent flow and intense bedload transport from designed laboratory experiments 

Florent Gimbert, Maarten Bakker, Marco Piantini, Alain Recking, and Michael Lamb

The field of fluvial seismology has undergone significant advances over the past decade. The development of dedicated physical theories and their applications in various contexts have allowed separating the respective contributions of turbulent flow and bedload transport, such that physical parameters like flow depth and sediment flux may be inferred from seismic observations. However, the quantitative link between signal characteristics (amplitude, frequency) and the underlying physics yet involves simplified considerations that do not necessarily apply to more complex situations, such as for example under rough flow conditions or during extreme floods.

In this talk I will present results from laboratory experiments that we designed specifically in order to quantify the seismic signature of flow turbulence and intense bedload transport under a range of conditions using force sensors coupled to the river bed. On one hand, I will show that existing theory regarding turbulent flow properly captures the main characteristics of the seismic source, but that additional dependencies on flow conditions and particle-wake development need to be included for more accurate predictions. On the other hand, I will show that existing theory regarding bedload transport fails at capturing the main characteristics of the seismic source under intense bedload transport conditions associated with complex changes in internal flow dynamics. In this case the seismic source appears to be a decreased function of solid concentration, as opposed to an increased function such as considered in current theories, which we suggest is due to grain impacts being agitation-controlled rather than bed-roughness controlled. Finally, I will discuss possible ways towards building more generic theories of ground motion induced by sediment transport.  

How to cite: Gimbert, F., Bakker, M., Piantini, M., Recking, A., and Lamb, M.: Assessing the seismic signature of turbulent flow and intense bedload transport from designed laboratory experiments, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13007, https://doi.org/10.5194/egusphere-egu24-13007, 2024.

EGU24-13208 | Posters on site | GM2.1 | Highlight

Analysis of Precursors and Collapse of June 15, 2023, Brienz/Brinzauls Rockslide in Switzerland: Integrating Seismic and Remote Sensing Observations 

Sibashish Dash, Michael Dietze, Fabian Walter, Marcel Fulde, Wandi Wang, Mahdi Motagh, and Niels Hovius

The early detection of slope instability and the monitoring of frequent hazard processes in mountainous regions is of paramount importance due to their sudden occurrence, and the risk of causing numerous fatalities and significant economic damage. The recent collapse of the Brienz/Brinzauls rockslide on June 15, 2023, in an active, deep-seated mountain slope deformation complex in Switzerland, provides a unique opportunity to investigate the evolution of precursors leading up to the collapse. Early identification of accelerating rockmass enabled us to set up a network of five broadband seismometers, strategically deployed to systematically record seismic signals in close proximity, reducing information loss due to attenuation of seismic waves. 

The internal rock damage dynamics in the displacing rock mass were interacting with external seasonal forcings, such as snow melt and rainfall, for years preceding the collapse at approximately 21:38:00 UTC on June 15, 2023. Seismic events of various types have been detected in the entire landslide complex, characterised by the recurrence of identical seismic events that aggregate prominently within the most rapid compartment, referred to as the "Insel," positioned directly above the village of Brienz. This study aims to investigate the influence of seasonal forcings on accelerating the rate of displacements and to understand how the nature of detected precursors changes over time. We systematically examine the feedback loop between seasonal triggers and gravity-driven internal rock damage under changing stress conditions during fluctuations in compartment velocity. Initially, events exhibit accelerations following periods of precipitation, but subsequently, a runaway acceleration in seismic events was noted even during dry periods. The locations detected reveal communication between the upper and lower parts of the “Insel” mass in the build-up to the main collapse. From June 1 onward, there is a consistent and gradual increase in the mean spectral power of the recurring seismic events, with a rapid escalation observed in the three days leading up to the collapse. Interestingly, on the final day preceding the main collapse, a significant decrease in the mean spectral power was identified. To complement seismic observations, the spatial and temporal changes in pre-failure slope instability for the period 05.2014-06.2023 were also analyzed using Sentinel-1 synthetic aperture radar (SAR) data using a multi-temporal interferometric (MTI) approach. MTI analysis indicates several patches of instability and surface deformation on the slope, along with signs of significant surface displacement of a few centimetres per year, also manifesting in the village of Brienz. To facilitate automatic detection and classification, we apply data science methods to various statistical seismic attributes of the identified precursors. This study contributes to advancing our understanding of the mechanisms leading to rockslide collapses, with the potential to significantly enhance warning system effectiveness.

How to cite: Dash, S., Dietze, M., Walter, F., Fulde, M., Wang, W., Motagh, M., and Hovius, N.: Analysis of Precursors and Collapse of June 15, 2023, Brienz/Brinzauls Rockslide in Switzerland: Integrating Seismic and Remote Sensing Observations, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13208, https://doi.org/10.5194/egusphere-egu24-13208, 2024.

EGU24-13569 | Orals | GM2.1

Validation of seismic bedload saltation model: From laboratory flume to field-scale experiments 

Wei-An Chao, Chi-Yao Hung, and Yu-Shiu Chen

Reliable bedload flux estimations are necessary for a variety of applications such as sedimentation engineering, flood risk mitigation and river restoration. Several seismic physical models with considering different bedload transport mechanisms have been proposed, which provided an opportunity to have quantitative observation in practical. However, a lack of direct measurements of bedload fluxes in field application cause a challenge for the validation of seismic models. In the practical application, the bedload impact kinematics (elasticity and velocity) and particle dynamics assumed in models are crucial for achieving high accuracy in bedload inversion. In-situ seismic parameters such as shear-wave velocity and seismic quality factor are also required to reduce the uncertainty in model prediction. Thus, this study first conducts bedload transport experiments in a flume laboratory to understand the kinematics and mechanics of particle transport by using the smart rock embedded with accelerometer and gyroscope, geophone and hydrophone. For the field-scale experiments, we further studied distributed acoustic sensing (DAS) measurement during the experiments, which can record the dynamic strain in fiber optic cable under riverbed. Both case of laboratory flume and field-scale experiments, we will evaluate the performance of the different physical models by comparing in-situ measurements of bedload mass and impact forces recorded by the smart rock. In the case of field experiment, we adopted the active and passive seismic surface wave exploration to investigate the properties of wave propagation and attenuation. The effect of the process of rolling and/or sliding particles, as opposed to saltating particles, contributing in seismic signal generation, was also explored.   

How to cite: Chao, W.-A., Hung, C.-Y., and Chen, Y.-S.: Validation of seismic bedload saltation model: From laboratory flume to field-scale experiments, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13569, https://doi.org/10.5194/egusphere-egu24-13569, 2024.

EGU24-13722 | ECS | Posters on site | GM2.1

Investigating bedload transport in mountain rivers through seismic methods: the new monitoring station in the Solda River (South Tyrol, Italy) 

Marco Piantini, Matthias Bonfrisco, Rudi Nadalet, Roberto Dinale, Gianluca Vignoli, Gianluca Antonacci, Silvia Simoni, Fabrizio Zanotti, Stefano Crema, Marco Cavalli, Alessandro Sarretta, Velio Coviello, and Francesco Comiti

Bedload transport plays a key role in the morphodynamics of mountain rivers by regulating erosion and aggradation processes. However, it is still challenging to estimate and predict bedload transport rates with reliability because of a complex interplay between different types of sediment supply, hydrological forcing, and fluvial morphologies. In the last two decades, passive sensors recording the seismic signals generated by coarse particles impacting the riverbed have been proposed to provide a continuous indirect measure of bedload transport. Among them, geophone plates and seismometers have been demonstrated to be valid tools.

Here, we present the preliminary results from the new monitoring station of Stilfserbrücke/Ponte Stelvio designed and built to monitor both water and sediment fluxes in the Solda River (Italian Alps). The station, mainly financed through two ERDF 2014-2020 projects of the Autonomous Province of Bolzano South-Tyrol, is part of the operational gauging network of the Civil Protection Agency of Bolzano (Italy). Bedload transport is indirectly monitored by sixteen geophone plates covering the downstream side of a consolidation check dam. The signal associated with the vibrations generated by particle impacts on the steel plates is recorded continuously with a sampling frequency of 5 kHz. In order to calibrate the instruments, direct bedload measurements have been carried out through an innovative bridge-like structure (BLS) consisting of an electronically controlled mobile trap. The collected samples have been sieved by hand to characterize their grain size distribution. At the end of summer 2023 we have also explored the possibility to additionally monitor the river with seismometers installed on the left bank at the monitoring station. We have analyzed the signal from the geophone plates by counting the number of times its amplitude exceeds a preselected threshold expressed in volts (i.e. the impulses, Rickenmann et al., 2014), and by computing its power (Coviello et al., 2022). The best correlation is found between impulses (threshold of 0.04 V) and the bedload transport rates of particles larger than 22 mm, with a power law regression characterized by a coefficient of determination (R2) of 0.85 and a low root mean square error (RMSE) of 3.3 kg/min against peak bedload transport rates reaching 41 kg/min.

These findings pave the way towards ensuring the continuous quantification of coarse sediment transport in the Solda River, allowing for the evaluation of the impact of glacier retreat and slope instabilities associated with global warming on river dynamics. Finally, the simultaneous use of seismometers may provide a unique opportunity to test existing theoretical models on bedload-induced ground vibrations through the indirect measurements provided by the geophone plates.

References

Coviello, V., Vignoli, G., Simoni, S., Bertoldi, W., Engel, M., Buter, A., et al. (2022). Bedload fluxes in a glacier-fed river at multiple temporal scales. Water Resources Research, 58, e2021WR031873.

Rickenmann, D., Turowski, J.M., Fritschi, B., Wyss, C., Laronne, J., Barzilai, R., Reid, I., Kreisler, A., Aigner, J., Seitz, H. and Habersack, H. (2014), Bedload transport measurements with impact plate geophones: comparison of sensor calibration in different gravel-bed streams. Earth Surf. Process. Landforms, 39: 928-942.

How to cite: Piantini, M., Bonfrisco, M., Nadalet, R., Dinale, R., Vignoli, G., Antonacci, G., Simoni, S., Zanotti, F., Crema, S., Cavalli, M., Sarretta, A., Coviello, V., and Comiti, F.: Investigating bedload transport in mountain rivers through seismic methods: the new monitoring station in the Solda River (South Tyrol, Italy), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13722, https://doi.org/10.5194/egusphere-egu24-13722, 2024.

Solid Earth Sciences:SE07 Faults and Earthquakes: Networks, Precursors, Monitoring Systems and Numerical Modelling Techniques

Research on new methods and equipment for seismological monitoring of glaciers on the Qinghai-Tibet Plateau

Lei Zou1, Richard Games2, ……

1 SmartSolo Inc., China

2 SmartSolo Inc., Huston, USA

Abstract: Glacier seismology combines the advantages of glaciology and seismology to form a young interdisciplinary subject. Icequakes are vibrations produced during the movement and breakup of glaciers, ranging from small squeaks to sudden ruptures or slides equivalent to earthquakes (MW7). According to the location and mechanism of icequake occurrence, icequakes can be divided into five types: surface fissures, stick-slip movement, iceberg calving, subglacial flow, and hydraulic fracturing. In addition to traditional seismological methods, icequake research can also be conducted using multidisciplinary methods such as GPS, numerical simulation, and glacier physical properties. Icequake research can further explore the occurrence process and risk assessment of ice avalanches. We review advances in glacier seismology.

Our users use SmartSolo scientific instruments to successfully analyze ice avalanche events through vibration signals by observing multi-parameter glacier environment and climate changes, combined with seismological observation instruments. Provide a new and effective monitoring method for glacier seismic monitoring. It enriches the process observation and risk assessment methods of ice avalanche occurrence, and the combination of multiple parameters further improves the accuracy and effectiveness of ice avalanche event monitoring.

How to cite: Gamez, R. and Zou, L.: Research on new methods and equipment for seismological monitoring of glaciers on the Qinghai-Tibet Plateau, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13798, https://doi.org/10.5194/egusphere-egu24-13798, 2024.

EGU24-13859 | ECS | Orals | GM2.1 | Highlight

An overview of environmental seismology used to study the internal structure of the North East Greenland Ice Stream  

Emma Pearce, Dimitri Zigone, Andreas Fitchner, Coen Hofstead, Joachim Rimpot, Johannas Brehmer-Moltmann, and Olaf Eisen

In 2022 a network of 23 seismometers and Distributed Acoustic Sensing (DAS) fibre optic cable were deployed on the North East Greenland Ice Stream (NEGIS). Using a combination of environmental seismology methods, we were able to gain a comprehensive understanding of the ice streams internal structure, giving insight into its past and present dynamics.  

From ambient noise recording, we utilise the 9-component correlation tensors associated with all station pairs.  We derived dispersion curves for Rayleigh and Love wave group velocities with usable data in the frequencies from 1 to 25 Hz. These data are then inverted to obtain shear wave velocity measurements for the top 150 m of the ice stream using an MCMC approach. We reveal variations in the radial anisotropy for both the along and across-flow components.

Alternative methods of passive seismology were explored, such as using the seismic signal from an airplane landing. The recorded signals by the surface DAS cable displayed exceptional clarity, revealing at least 15 visible wave propagation modes, including various Rayleigh and pseudo-acoustic waves within the frequency range of 8 to 55 Hz.

Seismic While Drilling (SWD) methods utilising the noise from ice core drilling and cutting at NEGIS were investigated as an unconventional signal at the borehole camp. While not successful in this instance, recommendations for future deployments were provided to optimize the utilisation of these techniques.

These methods collectively offer insight into the layering of snow, firn, and ice within the ice stream, indicating the presence of seismic anisotropy. Demonstrating the effectiveness of short-duration (2-3 weeks) seismic deployments in glaciology.  

How to cite: Pearce, E., Zigone, D., Fitchner, A., Hofstead, C., Rimpot, J., Brehmer-Moltmann, J., and Eisen, O.: An overview of environmental seismology used to study the internal structure of the North East Greenland Ice Stream , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13859, https://doi.org/10.5194/egusphere-egu24-13859, 2024.

EGU24-14117 | ECS | Posters on site | GM2.1

Probing relation between rainfall pattern and seismic detected water-and-sediment events 

Guan-Syun Huang and Wei-An Chao

Southern Taiwan often experienced abundant monsoon seasons during seasonal transitions, and monsoons and typhoons controlled the rainfall patterns to be complex and varied, resulting the high intensity, prolonged duration, and high concentration. The aforementioned rainfall characteristics can increase the risk of water-and-sediment-related disasters.  To explore the correlation between rainfall patterns and water-and-sediment events, this study employs micro-seismic monitoring network, and the selected Putanpunuas River in southern Taiwan as a case study site. Frequent landslides in the middle and upper watershed supply the river with stable source of sediment materials. Consequently, during the periods with strong precipitation, our study site the shows high susceptibility of water-and-sediment events.  The seismic network comprises one station (BNAR) on the right bank and two stations (BNAL, BNAS) on the left bank downstream of the Putanpunuas River, and an additional station (BNAF) at the confluence of the Putanpunuas River and the Laonong River.  By conducting a series of spectrogram analysis, the average power spectral density (PSD) time series of each station can be computed. Then, we further quantified the seismic signal characteristic parameters for each water-and-sediment events.  This study initially employs various machine learning algorithms (Decision Tree, KNN, K-means, Auto-sklearn) to develop an optimized model for identifying water-and-sediment events, classifying different types of events, such as flooding (FD), debris flooding (DFD) and debris flow (DF), then providing a 4-year-length (2019~2023) catalog of water-and-sediment events.  Rainfall data including hourly precipitation and LiDAR estimated rainfall are collected from the rain gauge stations nearby study area. Using a certain definition (e.g., 4 mm/hr threshold for picking start time) of rain episodes, we calculated total number of episodes and established a rain episodes catalog.  The aforementioned datasets allow us to probe the relationship between rainfall patterns and water-and-sediment events, aiding in inferring the main rain episodes characteristics associated with water-and-sediment events . The  results of this study can be applied to predict potential water-and-sediment event types in Putanpunuas River using rainfall information as input. This can facilitate relevant early warning operations, reducing the societal impact of water-and-sediment disasters.

Key words : Rainfall Patterns, Rain Episode, Micro-seismic monitoring network, Putanpunuas River, Water-and-Sediment Events, Machine Learning

How to cite: Huang, G.-S. and Chao, W.-A.: Probing relation between rainfall pattern and seismic detected water-and-sediment events, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14117, https://doi.org/10.5194/egusphere-egu24-14117, 2024.

EGU24-14125 | ECS | Posters on site | GM2.1

Studying field-scale dam breach due to overtopping by using seismic signals 

You-Lin Hou, Wei-An Chao, Chi-Yao Hung, Su-Chin Chen, and Tzu-Yao Chang

A dam is the natural damming of a river by the geohazards, such as landslides and debris flows. When the dam materials are eroded or washed away due to scour, erosion, and/or an increasing in water level of dam lake, leading dam breach and catastrophic outburst of flooding, which affect the downstream area. Therefore, real-time monitoring of dam failure would facilitate relevant early warning message for the impending floods. The conventional approach using image-based analysis and hydrological measurements is for providing timely warnings of breach; however, landslide dams often occur in mountainous areas, where the methods may face limitations of in-situ measurement. Additionally, the observations of landslide dam breach process are rare and cause the large uncertainties in scientific research. Hence, this study utilizes seismic signals to study the overtopping breach process of field-scale dams. Seismic signals serve as a monitoring tool while simultaneously monitoring the seismic characteristics of overtopping failure in the field-scale dams. In fact, there is a scarcity of observed seismic signal records related to dam breach process in field. Even if some observational data is available, there is a lack of corresponding image analysis or hydrological information for comprehensive discussions. Thus, this study aims to observe and understand overtopping failure through a series of field-scale dam breach experiments. In this study, we first investigate the time-frequency characteristics of seismic power spectral density (PSD) corresponding to the dam breaches primarily involves retrogression erosion, longitudinal and lateral erosion, and the stabilization period. Then, the results of photographic analysis (surface flow velocity, breach geometry), discharge measurements and the time-frequency characteristics of PSD are integrated to discuss the phenomena associated with dam breach. Finally, a series of comparison between compacted and non-compacted dams for PSD spectrogram patterns. The time-series of mean PSD and flow discharge data for the compacted dam exhibit a single-peak and short-term signal duration. Notably, the mean PSD time-series recorded by the seismic station located at the left bank showed a similar trend with flow discharge. Furthermore, during the retrogression erosion period, significant high-frequency PSD energy can be observed only in a case of the compacted dam. In contrast, the PSD energy for the non-compacted dam is concentrated in a relatively lower frequency range (between 10 to 30 Hz). The PSD and flow time series data for the non-compacted dam present a bimodal shape with longer time duration. Based on the flow velocity of breach notch, both in the compacted and non-compacted dams, the maximum velocity occurred during the transition from longitudinal to lateral erosion. In practical application, the results of seismic characteristics for the non-compacted dam case can be applied to the monitoring of dams formed by natural landslides in the field. Our results not only advance in understanding of the field-scale dam breach process but also can be directly applied to breach flooding warnings.
Key words : field-scale dam breach experiments, overtopping breach, power spectral density, time-frequency characteristic

How to cite: Hou, Y.-L., Chao, W.-A., Hung, C.-Y., Chen, S.-C., and Chang, T.-Y.: Studying field-scale dam breach due to overtopping by using seismic signals, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14125, https://doi.org/10.5194/egusphere-egu24-14125, 2024.

EGU24-15165 | Orals | GM2.1

Investigating Rainfall-Driven Resonance Frequency Changes in a Natural Rock Formation 

Juliane Starke, Laurent Baillet, Eric Larose, Antoine Guillemot, and Laurence Audin

Rainfall, temperature variations, and chemical processes are well-known drivers of rock erosion. The impact of rainfall on rocks is not well-understood yet but may impact the mechanical properties (including damage, rigidity, deformation) of the rock. In this study, we exhibit the effect of rainfall events on the resonance frequency of a rock column.

Resonance frequencies of structures have been utilized to monitor rock columns due to their sensitivity to changes in the rock apparent rigidity (1). For instance, daily temperature changes induce stress variations in the rock column, resulting in a daily cycle of resonance frequency changes (thermal-acousto-elasticity, 2).

This research involves long-term monitoring of the first resonance frequency of a 50 m high limestone cliff covering the Chauvet cave in the Ardèche plateau, SW France, exposed to climatic solicitations including daily solar radiation, air temperature fluctuations, and rain events. The rock column was equipped with seismic and meteorologic stations and monitored continuously during three years.

To demonstrate the effect of rainfall events on the mechanical properties of the rock, we calculated the resonance frequency depending only on air temperature and solar radiation, using a simple bivariate linear regression. The regression provides well-fitting results for dry periods but shows larger deviations during most rainy periods. This indicates that rain has an effect on the changes in rock resonance frequency. Identifying and quantifying these changes would be a key factor in understanding the evolution of damage.

 

1) Bottelin, P., Baillet, L., Larose, E., Jongmans, D., Hantz, D., Brenguier, O., ... & Helmstetter, A. (2017). Monitoring rock reinforcement works with ambient vibrations: La Bourne case study (Vercors, France). Engineering Geology, 226, 136-145.

2) Guillemot, A., Baillet, L., Larose, E., & Bottelin, P. (2022). Changes in resonance frequency of rock columns due to thermoelastic effects on a daily scale: observations, modelling and insights to improve monitoring systems. Geophysical Journal International, 231(2), 894-906.

How to cite: Starke, J., Baillet, L., Larose, E., Guillemot, A., and Audin, L.: Investigating Rainfall-Driven Resonance Frequency Changes in a Natural Rock Formation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15165, https://doi.org/10.5194/egusphere-egu24-15165, 2024.

EGU24-15365 | Posters on site | GM2.1

Automatic Monitoring of Seismogenic Slope Failure Activity at Brienz (Switzerland) Using Distributed Acoustic Sensing and Semi-Supervised Learning 

Jiahui Kang, Fabian Walter, Patrick Paitz, Johannes Aichele, Pascal Edme, Andreas Fichtner, and Lorenz Meier

Distributed Acoustic Sensing (DAS) represents a leap in seismic monitoring capabilities. Compared to traditional single-seismometer stations, DAS measures seismic strain at meter to sub-meter intervals along fiber-optic cables thus offering unprecedented temporal and spatial resolution. Leveraging the resolution of DAS enables us to monitor and detect seismogenic processes in the domain of hazardous mass-movements, including catastrophic rock avalanches.

Here, we present a semi-supervised neural network algorithm for screening DAS data related to mass movements at the Brienz landslide in Eastern Switzerland, which partially failed on 15 June 2023. A DAS interrogator connected to a 10 km-long dark fiber provided by Swisscom Broadcast AG near the landslide recorded seismic data from 16 May to 30 June 2023, with a sampling frequency of 200 Hz and a channel spacing of 4m. During a test period from June 1 to June 19, 2023, a total of 634 characteristic waveforms potentially related to slope failures, including the 15 June 2023 event, were detected, along with vehicle and other anthropogenic noise sources with characteristic diurnal and weekday/weekend variations.

For information extraction, we selected a subset of adjacent DAS channels, which include cable sections that were parallel to the failure event trajectory and thus particularly sensitive to mass movement activity. To facilitate efficient processing, we downsampled the data to 20 Hz, considering that slope failure events predominantly excite seismicity at below 10 Hz. We conceptualize the DAS data as a series of images representing consecutive strain rate data in the two dimensions of time and space. To bring out signal coherence between DAS channels, we transform the waveforms into cross-spectral density matrices (CSDM’s) which serve as the input image for unsupervised feature learning using an autoencoder (AE). Leveraging the features learned from the AE, we focus on activity classification using approximately 1500 samples. As ground truth for the slope failure class, we utilize concurrent Doppler radar data. The radar provides an event magnitude, which scales with failure volume and the number of individual rockfalls. Furthermore, the radar provides a measure of the moving mass’s trajectory length and front speed. The radar detected 516 slope failures during the test period.

Our algorithm captures 41.09 % of the slope failures recorded by the Doppler radar. The undetected events mainly have low radar magnitudes suggesting that they are associated with mass movements generating reduced seismic activity. Among the slope failure-type signals detected by DAS, 87.85% are also present in the radar catalogue. Interference from vehicle or human-triggered seismic waves, deteriorating the signal-to-noise ratio significantly, poses a challenge for our algorithm to differentiate between slope failures and those activities. Our study thus provides a benchmark for future natural hazard monitoring and suggests that using existing fiber optic infrastructure has a high potential for early warning purposes.

How to cite: Kang, J., Walter, F., Paitz, P., Aichele, J., Edme, P., Fichtner, A., and Meier, L.: Automatic Monitoring of Seismogenic Slope Failure Activity at Brienz (Switzerland) Using Distributed Acoustic Sensing and Semi-Supervised Learning, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15365, https://doi.org/10.5194/egusphere-egu24-15365, 2024.

EGU24-15794 | ECS | Orals | GM2.1 | Highlight

Monitoring subsurface changes in a quick clay area during extreme weather 

Charlotte Bruland, Andreas Köhler, Anna Maria Dichiarante, Volker Oye, and Ivan Van Bever

Some of the more densely populated areas in Norway are in potential quick clay zones. When disturbed, the structure of quick clay can suddenly collapse, and behave and flow as a liquid, potentially having disastrous impact over large areas One of the triggering factors for quick clay slides is heavy rainfall. Here, we focus on passive seismic data from two Raspberry shake sensors located in an urban area in Oslo, Norway with quick clay in the subsurface. Using coda wave interferometry, near-surface velocity variations are estimated during the extreme weather ”Hans” (August 2023).

We compute auto-correlations and single station cross-correlations of anthropogenic seismic noise (> 1 Hz) over a two-year period leading up to ”Hans”. We observe environmental velocity fluctuations well correlated with air temperature, precipitation and the water level in a nearby river. In particular, freezing and thawing produces strong changes in seismic velocity (up to 4 %). Disregarding freezing, we see the largest change in seismic velocity following the heavy rainfall associated with ”Hans”. This extreme event is associated with a sharp velocity drop anti-correlated with pore pressure. The surface wave-coda is sensitive to changes in shear wave velocity, which in turn can be used to detect changes of the subsurface properties. Therefore, observed velocity variations at the site could have potential for monitoring and early warning of quick clay instabilities.

How to cite: Bruland, C., Köhler, A., Dichiarante, A. M., Oye, V., and Van Bever, I.: Monitoring subsurface changes in a quick clay area during extreme weather, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15794, https://doi.org/10.5194/egusphere-egu24-15794, 2024.

EGU24-16742 | ECS | Posters on site | GM2.1

Detection and localisation of wadi flow events utilizing seismic sensors 

Robert Krüger, Michael Dietze, Xabier Blanch, Jens Grundmann, Issa El-Hussain, Ghazi Al-Rawas, and Anette Eltner

In Oman, the frequency of flash floods has significantly increased in recent years. This phenomenon is correlated with climate change, resulting in an intensification of the atmospheric water cycle. Consequently, a further escalation of flash floods can be anticipated in the future. In Oman, the issue of flash floods is exacerbated by the frequent occurrence of tropical cyclones. Furthermore, the rapid expansion of urban areas, in some cases extending directly into wadis, coupled with the advancing sealing of the ground and insufficient drainage systems, leads to an increased risk of flooding. This is accompanied by substantial property damage and recurring loss of life.

Despite the growing danger posed by flash floods, there is currently no early warning system for precise prediction of these events in Oman. To establish such a system, densely distributed networks for rainfall and water level measurements would be required. However, due to the challenging topography and vastness of the country, implementing such networks is currently not feasible.

Recent studies have shown that seismic sensors could be used for measuring flow conditions. Further, seismic networks could be utilized to detect and track extreme flow events. The increasing availability of low-cost seismic sensors opens up the possibility of instrumenting previously ungauged wadi systems. However, the question remains if seismic networks can pick up smaller flow events and flow events happening in multiple smaller catchments at the same time.

In this study we used flow data from wadi gauge stations in the Al-Batinah Region (NW Oman) and data from broadband seismometers of the Earthquake Monitoring Center to research how flow events of various sizes can be detected by seismic networks. Initial results suggest that flow regimes in wadi systems offer favourable conditions for detection, as they mainly change between flow and no flow conditions. As the amplitude of seismic signals decreases with distance from the source, detection range is limited by background noise. To overcome this, low-cost seismic sensors have recently been installed in a wadi system together with camera based river gauges. Further work utilizing this data is currently ongoing.

How to cite: Krüger, R., Dietze, M., Blanch, X., Grundmann, J., El-Hussain, I., Al-Rawas, G., and Eltner, A.: Detection and localisation of wadi flow events utilizing seismic sensors, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16742, https://doi.org/10.5194/egusphere-egu24-16742, 2024.

EGU24-17219 | ECS | Posters on site | GM2.1

Towards seismic monitoring of terrestial ecosystems: an exploratory data analysis of the SeisSavanna dataset 

Rene Steinmann, Tarje Nissen-Meyer, Fabrice Cotton, Frederik Tilmann, and Beth Mortimer

Our planet experiences ongoing unrest across various scales, from human footsteps to the powerful forces of volcanic eruptions and megathrust earthquakes. Seismic sensors, typically employed for geophysical studies, record diverse phenomena, including ground vibrations caused by the movement of terrestrial animals, known as footfall signals. The recently released SeisSavanna dataset comprises approximately 70,637 footfall signals from 11 different species in the African savanna. Consequently, ground-based vibrations might represent an underexplored sensory mode for continuously monitoring habitat usage and undisturbed animal behavior. To gain a deeper understanding of footfall signals, we conduct exploratory data analysis on the SeisSavanna dataset. Utilizing a scattering transform, we capture the distinctive features of footfall signals, creating a high-level and interpretable data representation for subsequent analyses. Seismogram atlases and clustering enable us to group similar types of footfall signals and investigate the signal-altering path and site effects, providing a comprehensive overview of the entire dataset. Moreover, this data-driven approach serves as a quality check for the species labels retrieved from co-located camera traps with a limited angle of view.

How to cite: Steinmann, R., Nissen-Meyer, T., Cotton, F., Tilmann, F., and Mortimer, B.: Towards seismic monitoring of terrestial ecosystems: an exploratory data analysis of the SeisSavanna dataset, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17219, https://doi.org/10.5194/egusphere-egu24-17219, 2024.

EGU24-17786 | Orals | GM2.1

Monitoring the mechanics of mountain permafrost using ambient noise seismology 

Antoine Guillemot, Eric Larose, Laurent Baillet, Agnès Helmstetter, Xavier Bodin, and Reynald Delaloye

Since last decades, coda wave interferometry (CWI) from ambient seismic noise has become an efficient method to probe continuous temporal changes of mechanical properties of the subsurface and crust. This method has successfully been used for environmental seismology issues, in a view of investigating the response of subsurface to environmental changes, in particular hydrological and thermal forcings (2). More, it has contributed to monitoring instabilities such rock slopes or landslides (3). Applying these methods to permafrost is then relevant to assess and monitor its mechanical response to environmental forcings.

As lobate or tongue-shaped superficial landforms composed of frozen rock debris, active rock glaciers are widespread features of mountain permafrost (4), potentially causing emerging hazards linked to permafrost thawing and debris flows.

Passive seismic instrumentation has been deployed for several years at Gugla, Tsarmine (Valais, Switzerland) and Laurichard (Hautes-Alpes, France) rock glaciers.

CWI has been applied to compute daily averaged dV/V (or relative change in velocity of the surface waves). For the three sites studied, seasonal variations of shear stiffness have been measured, associated with freeze-thawing cycles (5) (6). We located these daily fluctuations in depth by using a 1D coda wave inversion scheme. We also tracked water-induced power spectral density (PSD) and we detected microseismic events, highlighting the role of water inputs in changing the mechanical state, thus accelerating the whole rock glacier body. Also, we developed a viscoelastic model to explain the seasonal variability of the kinematics of rock glaciers. Combined with other geophysical methods, environmental seismology paves hence the way to deeply understand the mechanical response of mountain permafrost landforms to thermo-hydrological forcings.

 References

  • Richter, T., Sens‐Schönfelder, C., Kind, R., & Asch, G. (2014). Comprehensive observation and modeling of earthquake and temperature‐related seismic velocity changes in northern Chile with passive image interferometry. Journal of Geophysical Research: Solid Earth, 119(6), 4747-4765
  • Le Breton, M., Bontemps, N., Guillemot, A., Baillet, L., & Larose, É. (2021). Landslide monitoring using seismic ambient noise correlation: challenges and applications. Earth-Science Reviews, 216, 103518.
  • Haeberli, W., Hallet, B., Arenson, L., Elconin, R., Humlum, O., Kääb, A., ... & Mühll, D. V. (2006). Permafrost creep and rock glacier dynamics.Permafrost and periglacial processes, 17(3), 189-214.
  • Guillemot, A., Helmstetter, A., Larose, É., Baillet, L., Garambois, S., Mayoraz, R., & Delaloye, R. (2020). Seismic monitoring in the Gugla rock glacier (Switzerland): ambient noise correlation, microseismicity and modelling.Geophysical Journal International, 221(3), 1719-1735. https://doi.org/10.1093/gji/ggaa097
  • Guillemot, A., Baillet, L., Garambois, S., Bodin, X., Helmstetter, A., Mayoraz, R., and Larose, E.: Modal sensitivity of rock glaciers to elastic changes from spectral seismic noise monitoring and modeling, The Cryosphere, 15, 501–529, https://doi.org/10.5194/tc-15-501-2021, 2021.

How to cite: Guillemot, A., Larose, E., Baillet, L., Helmstetter, A., Bodin, X., and Delaloye, R.: Monitoring the mechanics of mountain permafrost using ambient noise seismology, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17786, https://doi.org/10.5194/egusphere-egu24-17786, 2024.

EGU24-17787 | Posters on site | GM2.1

(Multi)annual variations in the microseism of the Northern Atlantic 

Lars Wiesenberg, Sunke Schmidtko, and Thomas Meier

Microseism is one of the biggest parts of ambient seismic noise and has a huge effect on seismic measurements on almost every regular broad band seismometer, but especially in coastal areas. Generally, microseism describes the interaction of water waves and the seafloor. Its variation over time is from huge interest. It is often used on short-period scales to investigate local weather effects, like storm events or seasonal variations. In this work, we are investigating variations in the microseism of the Northern Atlantic on multiannual scales. For that reason, we utilize up to 50 years of seismic data from several onshore stations across Central and Northern Europe. The focus is on secondary microseism of the Northern Atlantic which is normally sensitive at periods of ≈10 to 5 s. It is estimated over two-hour segments of seismic data, separately. Secondary microseism is post processed to eliminate effects of data gaps or outliers before lowpass filtering for the periods of interest. Besides of a dominant peak at one year period, secondary microseism shows also distinct variations at several year of periods. These variations clearly correlate with the North-Atlantic-Oscillation Index (NAO), not only visually, but also quantitatively and might therefore be relatable to climate variations affecting the North Atlantic.

How to cite: Wiesenberg, L., Schmidtko, S., and Meier, T.: (Multi)annual variations in the microseism of the Northern Atlantic, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17787, https://doi.org/10.5194/egusphere-egu24-17787, 2024.

Predicting bedload transport is a key element of water-related hazard assessment and hydraulic engineering applications. However, knowledge of bedload transport processes remains limited, particularly in steep mountain streams. Previous studies have revealed that bedload transport rates in mountain streams exhibits a large spatio-temporal variability for given flow conditions. This results from the direct influence of streambed structure on bedload transport, where sediment movement, in turn, interacts with streambed evolution. Furthermore, variations in sediment availability contribute to the spatio-temporal bedload variability. The complex interactions between water flow, bedload transport, and bed structure are not yet fully understood. In this work, systematic flume experiments were conducted to investigate the acoustic signal responses of impact plate geophone systems generated by bedload particles impacting on the flume bed during experimental flows in the transitional regime. The experiments varied in the grain size distribution of the transported particles and the bed material, and the compactness and the water content of the flume bed. Geophones were installed on the underside of steel plates flush with the flume bed both upstream and downstream to effectively capture the changes in vibration signals generated by the moving bedload mass impacting on the bed. Triaxial force sensors were utilized to measure the impact forces of the bedload particles on the bed material layer. Pore-water pressure sensors were embedded at different depths in the bed material to measure the change in pore-water pressure in the bed under the influence of the bedload mass. Flow velocities and depths of the moving bedload mass were recorded using a binocular high-speed camera and were analyzed with an image processing method. The observed vibration signals and fluctuating forces were used to calculate the characteristic parameters of bedload transport using calibrated relationships and seismic theory. In addition, a high-precision Digital Elevation Model (DEM) of the bed was constructed using the photography and 3D modeling techniques. The results of this work show that geotechnical material parameters of the bed such as compactness, compression modulus, and grain size distribution may affect the changes of bed structure caused by bedload transport This in turn influences the spatio-temporal variability of the transport rate. The findings of this work may help to explain the variability of the bedload transport process in mountain streams.

How to cite: Chen, Z., Badoux, A., and Rickenmann, D.: Quantitative measurement of bedload transport variability with acoustic monitoring systems: Insight from controlled laboratory flume experiments, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18262, https://doi.org/10.5194/egusphere-egu24-18262, 2024.

EGU24-18668 | Posters on site | GM2.1

Bedload sediment dynamics in two contrasting alpine glacier headwater catchments 

Simon Cook, Darrel Swift, Kristen Cook, Christoff Andermann, Michael Dietze, William Wenban, and Rory White

Glaciated landscapes are showing an amplified reaction to global climate change. Glacial streams are the primary conveyor belts of the incipient sediment cascade, implementing the export of glacially scoured sediment to lower reaches, where the exported sediment controls fluvial geometry, valley floor evolution and ecosystem functioning, water reservoir lifetime and energy production in several alpine countries. Despite that importance, especially of the coarse bedload fraction, there is a striking lack of knowledge about the timing, magnitude and control factors of bedload flux in glacial streams. This is predominantly due to the difficulties to obtain such flux data by classic empirical approaches that require direct in-stream sampling. Here, we pursue a seismic approach to bedload transport quantification, where geophysical sensors are installed along the banks of glacial streams that continuously record ground motion caused by both the turbulent flow of the stream and coarse particle impact on the river bed. We installed small geophone networks along straight reaches of streams draining the glacierised catchments of Oberaargletscher and Steingletscher in Switzerland and recorded the target signals for several days in August 2022, when the melt driven, diurnal river stage fluctuated significantly. River level, turbidity and stream geometry were also observed. Ground parameters for the inverse seismic-model approach were determined using an active seismic survey. We present results of the instrumentation concepts, parameter estimation and data inversion. This allows a discussion of the temporal variability, non-linearity and site-specific nature of hydraulic and sediment transport patterns in catchments where sediment export is dominated by glacial processes.

How to cite: Cook, S., Swift, D., Cook, K., Andermann, C., Dietze, M., Wenban, W., and White, R.: Bedload sediment dynamics in two contrasting alpine glacier headwater catchments, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18668, https://doi.org/10.5194/egusphere-egu24-18668, 2024.

EGU24-20192 | ECS | Orals | GM2.1

Boulder-induced Turbulence Drives Shift in Seismic Frequency 

Ron Nativ, Jonathan Laronne, Jens Turowski, Jui-Ming Chang, Ci-Jian Yang, Niels Hovius, Wen-Sheng Chen, and Wen-Yen Chang

Turbulent flows capable of mobilizing sediments, despite being studied over the past 100 years, continue to constitute an elusive process. In environmental seismology, seismic waves generated by the interplay of surface processes and the Earth offer a key to unraveling the dynamics of river processes. We studied the seismic signals emitted during floods in two tributaries with large boulders. Early findings indicated an unusually high dominant seismic frequency, reaching 2-4 times the frequency observed in nearby channels with smoother beds. Consistent anomalous high-frequency content during times without sediment transport prompts our hypothesis that turbulence is the key process driving the frequency shift. We hypothesized that the most energetic turbulent eddies, dominating the signal, decrease in size in response to the boulder-influenced constrained flow geometry, and we argue that this effect possesses a first-order control on the frequency shift. A frequency scaling law with boulder spacing, approximating boulder-induced eddy size, shows good agreement with our field data. The dynamics of the eddies under changing flow velocity are well predicted by a power law function of seismic frequency with water depth. The trend breaks at the onset of bedload transport, indicating that energy is dissipated through the partitioning between turbulence and sediment transport. Our study emphasizes that seismic frequency effectively records the dominant morphology and fluvial processes, revealing the intricate interaction between roughness and seismic energy.

How to cite: Nativ, R., Laronne, J., Turowski, J., Chang, J.-M., Yang, C.-J., Hovius, N., Chen, W.-S., and Chang, W.-Y.: Boulder-induced Turbulence Drives Shift in Seismic Frequency, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20192, https://doi.org/10.5194/egusphere-egu24-20192, 2024.

EGU24-1261 | Orals | GM3.1

Machine-learning based 3D point cloud classification and multitemporal change analysis with simulated laser scanning data using open source scientific software 

Bernhard Höfle, Ronald Tabernig, Vivien Zahs, Alberto M. Esmorís Pena, Lukas Winiwarter, and Hannah Weiser

AIM: We will present how virtual laser scanning (VLS), i.e., simulation of realistic LiDAR campaigns, can be key for applying machine/deep learning (ML/DL) approaches to geographic point clouds. Recent results will be shown for semantic classification and change analysis in multitemporal point clouds using exclusively open source scientific software.

MOTIVATION: Laser scanning is able to deliver precise 3D point clouds which have made huge progress in research in geosciences over the last decade. Capturing multitemporal (4D: 3D + time) point clouds enables to observe and quantify Earth surface process activities, their complex interactions and triggers. Due to the large size of 3D/4D datasets that can be captured by modern systems, automatic methods are required for point cloud analysis. Machine learning approaches applied to geographic point clouds, in particular DL, have shown very promising results for many different geoscientific applications [1,2].

METHODS & RESULTS: While new approaches for deep neural networks are rapidly developing [1], the bottleneck of sufficient and appropriate training data (typically annotated point clouds) remains the major obstacle for many applications in geosciences. Those data hungry learning methods depend on proper domain representation by training data, which is challenging for natural surfaces and dynamics, where there is high intra-class variability. Synthetic LiDAR point clouds generated by means of VLS, e.g., with the open-source simulator HELIOS++ [3], can be a possible solution to overcome the lack of training data for a given task. In a virtual 3D/4D scene representing the target surface classes, different LiDAR campaigns can be simulated, with all generated point clouds being automatically annotated. VLS software like HELIOS++ allows to simulate any LiDAR platform and settings for a given scene, which offers high potential for data augmentation and the creation of training samples tailored to specific applications. In recent experiments [1], purely synthetic training data could achieve similar performances to costly labeled training data from real-world acquisitions for semantic scene classification.

Furthermore, surface changes can be introduced to create dynamic VLS scenes (e.g., erosion, accumulation, movement/transport). Combining LiDAR simulation with automatic change analysis, such as offered by the open-source scientific software py4dgeo [5], enables to perform ML for change analysis in multitemporal point clouds [6]. Recent results show that rockfall activity mapping and classification for permanent laser scanning data can be successfully implemented by combining HELIOS++, py4dgeo and the open-source framework VL3D, which can be used for investigating various ML/DL approaches in parallel.

CONCLUSION: Expert domain knowledge (i.e., definition of proper 3D/4D scenes) and the power of AI can be closely coupled in VLS-driven ML/DL approaches to analyze 3D/4D point clouds in the geosciences. Open-source scientific software already offers all required components (HELIOS++, VL3D, py4dgeo). 

REFERENCES:

[1] Esmorís Pena, A. M., et al. (2024): Deep learning with simulated laser scanning data for 3D point cloud classification. ISPRS Journal of Photogrammetry and Remote Sensing. under revision.

[2] Winiwarter, L., et al. (2022): DOI: https://doi.org/10.1016/j.rse.2021.112772 

[3] HELIOS++: https://github.com/3dgeo-heidelberg/helios

[4] VL3D framework: https://github.com/3dgeo-heidelberg/virtualearn3d

[5] py4dgeo: https://github.com/3dgeo-heidelberg/py4dgeo

[6] Zahs, V. et al. (2023): DOI: https://doi.org/10.1016/j.jag.2023.103406

How to cite: Höfle, B., Tabernig, R., Zahs, V., Esmorís Pena, A. M., Winiwarter, L., and Weiser, H.: Machine-learning based 3D point cloud classification and multitemporal change analysis with simulated laser scanning data using open source scientific software, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1261, https://doi.org/10.5194/egusphere-egu24-1261, 2024.

EGU24-1640 | ECS | Posters on site | GM3.1

Automatic Classification of Surface Activity Types from Geographic 4D Monitoring Combining Virtual Laser Scanning, Change Analysis and Machine Learning 

Vivien Zahs, Bernhard Höfle, Maria Federer, Hannah Weiser, Ronald Tabernig, and Katharina Anders

We advance the characterization of landscape dynamics through analysis of point cloud time series by integrating virtual laser scanning, machine learning and innovative open source methods for 4D change analysis. We present a novel approach for automatic identification of different surface activity types in real-world 4D geospatial data using a machine learning model trained exclusively on simulated data.

Our method focuses on classifying surface activity types based on spatiotemporal features. We generate training data using virtual laser scanning of a dynamic coastal scene with artificially induced surface changes. Scenes with surface change are generated using geographic knowledge and the concept of 4D objects-by-change (4D-OBCs) [1, 2], which represent spatiotemporal subsets of the scene that exhibit change with similar properties. A realistic 3D scene modelling is essential for accurately replicating the dynamic nature of coastal landscapes, where morphological changes are driven by both natural processes and anthropogenic activities.

The Earth's landscapes exhibit complex dynamics, spanning large spatiotemporal scales, from high-mountain glaciers to sandy coastlines. The challenge lies in effectively detecting and classifying diverse surface activities with varying magnitudes, spatial extents, velocities, and return frequencies. Effective characterization of these dynamics is crucial for understanding the underlying environmental processes and their interplay with human activities. Supervised machine learning classification of surface activities from point cloud time series is challenging due to the limited availability of comprehensive and diverse real-world datasets for training and validation. Our approach combines virtual laser scanning with machine learning-based classification, enabling the generation of comprehensive training datasets covering the full spectrum of expected change patterns [3].

In our approach, the simulation of LiDAR point clouds is performed in the open-source framework HELIOS++ [4, 5]. HELIOS++ allows the flexible simulation of custom LiDAR campaigns with diverse acquisition modes and settings together with automatic annotations of artificially induced surface changes. We train a supervised machine learning model to classify synthetic 4D-OBCs into typical surface activity types of a sandy beach (e.g. dune erosion/accretion, sediment transport, etc.). Moreover, we investigate descriptors for 4D-OBCs, assessing their suitability for representing general types of surface activity (transferable between use cases) and types specific to particular surface processes.

We evaluate our model for 4D-OBC classification in terms of its capacity to discriminate surface activity types in a real-world dataset of a sandy beach in the Netherlands [6]. 4D-OBCs are extracted, classified into our target classes and validated with manually labelled reference data based on expert evaluation.

Our study showcases the efficacy of coupling virtual laser scanning, innovative open-source 4D change analysis methods, and machine learning for classifying natural surface changes [7]. Our findings not only contribute to advancing the understanding of landscape dynamics but also provide a promising approach to mitigating environmental challenges.

REFERENCES

[1] Anders et al. (2022): DOI: https://doi.org/10.5194/egusphere-egu22-4225

[2] py4dgeo: https://github.com/3dgeo-heidelberg/py4dgeo 

[3] Zahs et al. (2022): DOI: https://doi.org/10.1016/j.jag.2023.103406

[4] HELIOS++: https://github.com/3dgeo-heidelberg/helios

[5] Winiwarter et al. (2022): DOI: https://doi.org/10.1016/j.rse.2021.112772 

[6] Vos et al. (2022): DOI: https://doi.org/10.1038/s41597-022-01291-9

[7] CharAct4D: www.uni-heidelberg.de/charact4d

How to cite: Zahs, V., Höfle, B., Federer, M., Weiser, H., Tabernig, R., and Anders, K.: Automatic Classification of Surface Activity Types from Geographic 4D Monitoring Combining Virtual Laser Scanning, Change Analysis and Machine Learning, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1640, https://doi.org/10.5194/egusphere-egu24-1640, 2024.

The acquisition of aerial photographs for cartographic applications started in the 1930s, and more intensively after World War II. Such old, often panchromatic, imagery offers metre to sub-metre scale spatial resolution over landscapes that have significantly evolved over the decades. Before the appearance of the first digital aerial camera systems at the end of the 20th Century, surveys were performed with analogue metric cameras, with images acquired on films or glass plates and, next, developed on photo papers. In Europe and North America, several institutions hold unique collections of historical aerial photographs having local, national and, in some cases, colonial coverages. They represent invaluable opportunities for environmental studies, allowing the comparison with today’s land use land cover, and the analysis of long-term surface displacements.

Initially, the photogrammetric processing of analogue aerial photographs would require expensive equipment, specialised operators, and significant processing time. Thanks to the digital revolution of the past two decades and the development of modern digital photogrammetric approaches, the processing of this type of image datasets has become less cumbersome, time consuming and expensive, at least in theory. In practice, this is more complex, with digitising and processing issues related to the ageing and quality of conservation of the aerial photographs, the potential distortions created during the digitising process, and the lack of ancillary data, such as, flight plans, and camera calibration reports. The limited overlap between photographs, typically 60 % and 10-20 %, along-track and across-track, respectively, make their processing with Structure-from-Motion Multi-View Stereo (SfM-MVS) photogrammetry poorly reliable to accurately reconstruct the topography and orthorectify the images. Given the fact that some collections reach up to millions of historical aerial photographs, the digitising, pre-processing, and photogrammetric processing of these images remain a challenge that must be properly tackle if we would like to ensure their preservation and large-scale valorisation.

In the present work, we describe the mass-digitising, digital image pre-processing and photogrammetric processing approaches implemented at the Royal Museum for Central Africa (RMCA, Belgium) to preserve and valorise the collection of >320,000 historical aerial photographs conserved in this federal institution. This imagery was acquired between the 1940’s and the 1980’s, over Central Africa, and mostly D.R. Congo, Rwanda and Burundi. For the digitising, a system of parallelized flatbed scanners controlled by a Linux computer and a self-developed software allows speeding-up the scanning of the entire collection in only few years. A series of Python scripts were developed and combined to allow a swift pre-processing that prepare and optimise the digitised images for photogrammetric processing. Finally, a SfM-MVS photogrammetric approach adapted to historical aerial photos is used. Examples of application for geo-hydrological hazards studies in the western branch of the East African Rift are shown.

How to cite: Smets, B., Dille, A., Dewitte, O., and Kervyn, F.: Digitising, pre-processing and photogrammetric processing of historical aerial photographs for the production of high resolution orthomosaics and the study of geohazards, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2356, https://doi.org/10.5194/egusphere-egu24-2356, 2024.

EGU24-4399 | ECS | Posters on site | GM3.1

Evaluating the efficacy of multitemporal TLS and UAS surveys for quantifying wind erosion magnitudes of sand dune topography 

László Bertalan, Gábor Négyesi, Gergely Szabó, Zoltán Túri, and Szilárd Szabó

Wind erosion constitutes a prominent land degradation process in regions of Hungary characterized by low annual precipitation. In these areas, it poses significant challenges to agricultural productivity and adversely impacts soil and environmental quality. Presently, human activities exert a more pronounced influence on the endangered areas of Hungary in comparison to climate-related factors. It is noteworthy that the wind erodibility of Hungarian soils not only poses a soil conservation challenge but also gives rise to economic ramifications, such as nutrient loss, as well as environmental and human health concerns. Within agricultural landscapes, wind erosion contributes to the removal and transportation of the finest and biologically active soil fractions, rich in organic matter and nutrients.

High-resolution topographic surveys have become integral for assessing volumetric changes in sand dune mobility and mapping wind erosion. While Unmanned Aerial Systems (UAS) surveys have been extensively employed for erosion rates exceeding the decimeter scale, Terrestrial Laser Scanning (TLS) surveys have demonstrated efficiency in capturing more extensive negative erosional forms, even in a vertical orientation. To enhance the field of view, a mounting framework can be implemented to elevate the TLS. However, determining centimeter-scale material displacement in flat terrain conditions remains challenging and requires an increased number of scanning positions.

To identify optimal settings for surveying centimeter-scale wind erosion magnitudes, we conducted combined multi-temporal TLS and UAS surveys at the Westsik experimental site near Nyíregyháza during the spring of 2023. This site features dune topography with a height of 6 meters. Our investigations encompassed various UAS image acquisition modes, involving different flight altitudes and camera settings, utilizing a DJI Matrice M210 RTK v2 drone and a Zenmuse X7 24 mm lens. Additionally, we generated diverse point clouds through various scanning scenarios using a Trimble X7 TLS device. In the data processing phase, we explored multiple co-registration algorithms to address the challenge of larger Root Mean Square Error (RMSE) in Digital Terrain Models (DTMs) from UAS Structure from Motion (SfM) compared to the actual wind erosion rates.

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The research is supported by the NKFI K138079 project.

How to cite: Bertalan, L., Négyesi, G., Szabó, G., Túri, Z., and Szabó, S.: Evaluating the efficacy of multitemporal TLS and UAS surveys for quantifying wind erosion magnitudes of sand dune topography, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4399, https://doi.org/10.5194/egusphere-egu24-4399, 2024.

EGU24-5142 | Posters on site | GM3.1 | Highlight

Four nationwide Digital Surface Models from airborne historical stereo-images 

Christian Ginzler, Livia Piermattei, Mauro Marty, and Lars T. Waser

Historical aerial images, captured by film cameras in the previous century, have emerged as valuable resources for quantifying Earth's surface and landscape changes over time. In the post-war period, historical aerial images were often acquired to create topographic maps, resulting in the acquisition of large-scale aerial photographs with stereo coverage. Using photogrammetric techniques on stereo-images enables extracting 3D information to reconstruct Digital Surface Models (DSMs), and orthoimages.

This study presents a highly automated photogrammetric approach for generating nationwide DSMs for Switzerland at 1 m resolution using aerial stereo-images acquired between 1979 and 2006. The 8-bit scanned images, with known exterior and interior orientation, were processed using BAE Systems' SocetSet (v5.6.0) with the "Next-Generation Automatic Terrain Extraction" (NGATE) package for DSM generation. The primary objective of the study is to derive four nationwide DSMs for the epochs 1979-1985, 1985-1991, 1991-1998, and 1998-2006. The study assesses DSM quality in terms of vertical accuracy and completeness of image matching across different land cover types, with a focus on forest dynamics and management research.

The elevation accuracy of the generated DSMs was assessed using two reference datasets. Firstly, the elevation differences between a nationwide reference Digital Terrain Model (DTM - swissAlti3d 2017 by Swisstopo) and the generated DSMs were calculated on points classified as "sealed surface". Secondly, elevation values of the DSMs were compared to approximately 500 independent geodetic points distributed across the country. Six study areas were chosen to assess completeness, and it was calculated as the percentage of successfully matched points to the potential total number of matched points within a predefined area. This assessment was conducted for six land cover classes based on the land cover/land-use statistics dataset from the Federal Office of Statistics.

Across the entire country, the median elevation accuracy of the DSMs on sealed points ranges between 0.28 to 0.53 m, with a Normalized Median Absolute Deviation (NMAD) of around 1 m (maximum 1.41 m) and an RMSE of a maximum of 3.90 m. The elevation differences between geodetic points and DSMs show higher accuracy, with a median value of a maximum of 0.05 m and an NMAD smaller than 1 m. Completeness results reveal mean completeness between 64 % to 98 % for the classes "glacial and perpetual snow" and "sealed surfaces," respectively and 93 % specifically for the “closed forest” class.

This work demonstrates the feasibility of generating accurate DSM time series (spanning four epochs) from historical scanned images for the entire Switzerland in a highly automated manner. The resulting DSMs will be available upon publication, providing an excellent opportunity to detect major surface changes, such as forest dynamics.

How to cite: Ginzler, C., Piermattei, L., Marty, M., and Waser, L. T.: Four nationwide Digital Surface Models from airborne historical stereo-images, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5142, https://doi.org/10.5194/egusphere-egu24-5142, 2024.

EGU24-5670 | ECS | Posters on site | GM3.1

Enhancing 3D Feature-based Landslide Monitoring Efficiency by Integrating Contour Lines in Laser Scanner Point Clouds 

Kourosh Hosseini, Jakob Hummelsberger, Daniel Czerwonka-Schröder, and Christoph Holst

Landslides are a pervasive natural hazard with significant societal and environmental impacts. In addressing the critical need for accurate landslide detection and monitoring, our previous research introduced a feature-based monitoring method enhanced by histogram analyses, straddling a middle ground between point-based and point cloud-based methods. This paper expands upon that foundation, introducing an innovative contour line extraction technique from various epochs to precisely identify areas prone to deformation. This refined focus diverges from conventional methodologies that analyze entire point clouds. By applying on regions where contour lines do not match, indicating potential ground movement, we significantly elevate the efficiency and precision of our feature-based monitoring system.

 

One of the principal challenges of feature-based monitoring is managing a substantial number of outliers. Our prior research tackled this issue effectively by integrating feature tracking with histogram analysis, thereby filtering these outliers from the final results. However, the process of extracting features from each patch and matching them with corresponding patches from different epochs was time-intensive.

 

The incorporation of contour line extraction into our workflow, using high-resolution laser scanner data, allows for a more focused and efficient analysis. We can now identify and analyze areas of landscape alteration with greater accuracy. This approach limits the application of feature tracking and histogram analysis to these critical areas, thus streamlining the process and significantly reducing computational demands. This focused methodology not only accelerates data processing but also enhances the accuracy of landslide predictions.

 

Our findings indicate a substantial improvement in the efficiency of landslide monitoring methods. This methodology represents a promising advancement in geospatial analysis, particularly for environmental monitoring and risk management in regions susceptible to landslides. This research contributes to the ongoing efforts to develop more effective, efficient, and accurate approaches to landslide monitoring, ultimately aiding in better informed and timely decision-making processes for hazard mitigation and risk management.

How to cite: Hosseini, K., Hummelsberger, J., Czerwonka-Schröder, D., and Holst, C.: Enhancing 3D Feature-based Landslide Monitoring Efficiency by Integrating Contour Lines in Laser Scanner Point Clouds, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5670, https://doi.org/10.5194/egusphere-egu24-5670, 2024.

EGU24-5674 | ECS | Orals | GM3.1

Piecewise-ICP: Efficient Registration of 4D Point Clouds for Geodetic Monitoring 

Yihui Yang, Daniel Czerwonka-Schröder, and Christoph Holst

The permanent terrestrial laser scanning (PLS) system has opened the possibilities for efficient data acquisition with high-temporal and spatial resolution, thus allowing for improved capture and analyses of complex geomorphological changes on the Earth's surface. Accurate georeferencing of generated four-dimensional point clouds (4DPC) from PLS is the prerequisite of the following change analysis. Due to the massive data volume and potential changes between scans, however, efficient, robust, and automatic georeferencing of 4DPC remains challenging, especially in scenarios lacking signalized and reliable targets. This georeferencing procedure can be typically realized by designating a reference epoch and registering all other scans to this epoch. Addressing the challenges in targetless registration of topographic 4DPC, we propose a simple and efficient registration method called Piecewise-ICP, which first segments point clouds into piecewise patches and aligns them in a piecewise manner.

Assuming the stable areas on monitored surfaces are locally planar, supervoxel-based segmentation is employed to generate small planes from adjacent point clouds. These planes are then refined and classified by comparing defined correspondence distances to a monotonically decreasing distance threshold, thus progressively eliminating unstable planes in an efficient iterative process as well as preventing local minimization in the ICP process. Finally, point-to-plane ICP is performed on the centroids of the remaining stable planes. We introduce the level of detection in change analysis to determine the minimum distance threshold, which mitigates the influence of outliers and deformed areas on registration accuracy. Besides, the spatial distribution of empirical registration uncertainties on registered point clouds is derived based on the variance-covariance propagation law.

Our registration method is demonstrated on two datasets: (1) Synthetic point cloud time series with defined changes and transformation parameters, and (2) a 4DPC dataset from a PLS system installed in the Vals Valley (Tyrol, Austria) for monitoring a rockfall. The experimental results show that the proposed algorithm exhibits higher registration accuracy compared to the existing robust ICP variants. The real-time capability of Piecewise-ICP is significantly improved owing to the centroid-based point-to-plane ICP and the efficient iteration process.

How to cite: Yang, Y., Czerwonka-Schröder, D., and Holst, C.: Piecewise-ICP: Efficient Registration of 4D Point Clouds for Geodetic Monitoring, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5674, https://doi.org/10.5194/egusphere-egu24-5674, 2024.

EGU24-5757 | Posters on site | GM3.1

Arctic puzzle: pioneering a shrimp habitat model in topographically complex Disko Bay (West Greenland) 

Diana Krawczyk, Tobias Vonnahme, Ann-Dorte Burmeister, Sandra Maier, Martin Blicher, Lorenz Meire, and Rasmus Nygaard

Our study focuses on the geologically, topographically, and oceanographically complex region of Disko Bay in West Greenland. Disko Bay is also considered a marine biodiversity hotspot in Greenland. Given the impact of commercial fishing on seafloor integrity in the area, seafloor habitats studies are crucial for sustainable use of marine resources. One of the key fishery resources in Greenland, as well as in the North Atlantic Ocean, is northern shrimp.

In this study we analyzed multiple (1) monitoring datasets from 2010 to 2019, including data from shrimp and fish surveys, commercial shrimp fishery catches, satellite chlorophyll data, and (2) seafloor models, encompassing high-resolution (25 x 25 m) multibeam data with a low-resolution (200 x 200 m) IBCAO grid. Using multivariate regression analysis and spatial linear mixed-effect model we assessed the impact of physical (water depth, bottom water temperature, sediment type), biological (chlorophyll a, Greenland halibut predation), and anthropogenic factors (shrimp fishery catch and effort) on shrimp density in the area. The resulting high-resolution predictive model of northern shrimp distribution in Disko Bay is the first model of this kind developed for an Arctic area.

Our findings reveal that shrimp density is significantly associated with static habitat factors, namely sediment type and water depth, explaining 34% of the variation. The optimal shrimp habitat is characterized by medium-deep water (approximately 150-350 m) and mixed sediments, primarily in the north-eastern, south-eastern, and north-western Disko Bay. This pioneering study highlights the importance of seafloor habitat mapping and modeling, providing fundamental geophysical knowledge necessary for long-term sustainable use of marine resources in Greenland.

The developed high-resolution model contributes to a better understanding of detailed patterns in northern shrimp distribution in the Arctic, offering valuable insights for stock assessments and sustainable fishery management. This novel approach to seafloor habitat mapping supports the broader goal of ensuring the responsible utilization of marine resources, aligning with principles of environmental conservation and fisheries management. Our work serves as a foundation for ongoing efforts to balance economic interests with the preservation of marine ecosystems, fostering a harmonious coexistence between human activities and the fragile Arctic environment.

How to cite: Krawczyk, D., Vonnahme, T., Burmeister, A.-D., Maier, S., Blicher, M., Meire, L., and Nygaard, R.: Arctic puzzle: pioneering a shrimp habitat model in topographically complex Disko Bay (West Greenland), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5757, https://doi.org/10.5194/egusphere-egu24-5757, 2024.

EGU24-10361 | ECS | Orals | GM3.1

A Time-Series Analysis of Rockfall Evolution in a Coastal Region Using Remote Sensing Data 

Aliki Konsolaki, Emmanuel Vassilakis, Evelina Kotsi, Michalis Diakakis, Spyridon Mavroulis, Stelios Petrakis, Christos Filis, and Efthymios Lekkas

The evolution of technology, particularly the integration of Unmanned Aerial Systems (UAS), earth observation datasets, and historical data such as aerial photographs, stand as fundamental tools for comprehending and reconstructing surface evolution and potential environmental changes. In addition, the active geodynamic phenomena in conjunction with climate crisis and the increasing frequency of extreme weather phenomena can cause abrupt events such as rockfalls and landslides, altering completely the morphology on both small and large scales.

This study deals generally with the temporal evolution of landscapes and specifically focuses on the detection and quantification of a significant rockfall event that occurred at Kalamaki Beach on Zakynthos Island, Greece – a very popular summer destination. Utilizing UAS surveys conducted in July 2020 and July 2023, this research revealed a rockfall that has significantly altered the coastal morphology. During this period, two severe natural phenomena occurred, one of which could potentially be the cause of this rockfall event. Initially, the Mediterranean hurricane (‘medicane’) ‘Ianos’ made landfall in September 2020, affecting a large part of the country including the Ionian Islands. The result was severe damage to property and infrastructures, along with human casualties, induced by intense precipitation, flash flooding, strong winds, and wave action. Second, in September of 2022, an ML=5.4 earthquake struck between Cephalonia and Zakynthos Islands in the Ionian Sea, triggering considerable impact in both islands. The study employs satellite images postdating these natural disasters, to detect the source of the rockfall in Kalamaki Beach. Additionally, historical analog aerial images from 1996 and 2010 were used as assets for understanding the surface’s evolution. For the quantitative analysis, we applied 3D semi-automated change detection techniques such as the M3C2 algorithm, to estimate the volume of the rockfall.

The results provide insights into the complex interplay between natural disasters and geological processes, shedding light on the dynamic nature of landscapes and the potential implications for visitor-preferred areas.

This research not only contributes to our understanding of landscape evolution but also underscores the importance of integrating modern and historical datasets to decipher the dynamic processes shaping the Earth's surface. The methodology proposed, serves as a valuable approach for assessing and managing geological hazards in coastal regions affected by both climatic events and geodynamic activities.

How to cite: Konsolaki, A., Vassilakis, E., Kotsi, E., Diakakis, M., Mavroulis, S., Petrakis, S., Filis, C., and Lekkas, E.: A Time-Series Analysis of Rockfall Evolution in a Coastal Region Using Remote Sensing Data, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10361, https://doi.org/10.5194/egusphere-egu24-10361, 2024.

EGU24-10373 | Orals | GM3.1

A database for ancillary information of three-dimensional soil surface microtopography measurements. 

Kossi Nouwakpo, Anette Eltner, Bernardo Candido, Yingkui Li, Kenneth Wacha, Mary Nichols, and Robert Washington-Allen

Understanding the complex processes occurring at the soil surface is challenging due to the intricate spatial variability and dynamic nature of these processes. An effective tool for elucidating these phenomena is three-dimensional (3D) reconstruction, which employs advanced imaging technologies to create a comprehensive representation of the soil surface at high spatial resolution, often at the mm-scale. Three-dimensional reconstruction techniques are increasingly available to scientists in the fields of soil science, geomorphology, hydrology, and ecology and many studies have employed these novel tools to advance understanding of surface processes. Much of the data being collected in these studies are however not interoperable, i.e., 3D data from one study may not be directly combined with 3D data from other studies thus limiting the ability of researchers to advance process understanding at a broader scope. The limited interoperability of existing data is due in part to the fact that 3D surface reconstruction data are influenced by many factors including experimental conditions, intrinsic soil properties and accuracy and precision limits of the 3D reconstruction technique used. These ancillary data are crucial to any broad-scope efforts that leverage the increasing number of 3D datasets collected by scientists across disciplines, geographic regions, and experimental conditions. We have developed a relational database that archives and serves ancillary data associated with published high-resolution 3D data representing soil surface processes. This presentation introduces the structure of the database with its required and optional variables. We also provide analytics on the currently available records in the database and discuss potential applications of the database and future developments.

How to cite: Nouwakpo, K., Eltner, A., Candido, B., Li, Y., Wacha, K., Nichols, M., and Washington-Allen, R.: A database for ancillary information of three-dimensional soil surface microtopography measurements., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10373, https://doi.org/10.5194/egusphere-egu24-10373, 2024.

EGU24-11949 | ECS | Posters on site | GM3.1

Employng satellite immagery interpretation tools to detect land-use land-change dynamics in Italian historical rural landscapes 

Virginia Chiara Cuccaro, Claudio Di Giovannantonio, Giovanni Pica, Luca Malatesta, and Fabio Attorre

Rural landscapes inherited from the past are marked by a strong interaction between man and nature, a relationship rooted in a long history that testifies to the importance of the landscape as one of the most historically representative expressions of a country's cultural identity.

In this broad context, olive groves markedly characterize the agricultural landscape of many European rural areas, particularly in the Mediterranean region. Along with other rural landscapes, they form a semi-natural environment that can contribute to biodiversity conservation, soil protection and ecosystem resilience.

In addition to the global increase in temperatures, the main threats affecting these agrarian landscapes include the abandonment of traditional practices and the intensification of cultivation through the installation of irregular, intensive and overly dense planting beds.

The Land Cover classification and change-detection can provide useful indications for the restoration, conservation, and enhancement of olive groves

The objective of this work was to identify , rural landscapes in the Lazio region with characteristics of historical interest and determine their level of conservation. In particular, it was investigated the olive landscape of Cures (historic province of Sabina) trough a multi-temporal analysis of literature and cartographic information (e.g. orthophotos from the Italian Aeronautical Group flight of 1954)

The technique concerns the VASA (Historical Environmental Assessment) methodology, which allows the temporal evaluation of a given landscape and can inform on how agricultural practices and land use have changed over time.

Softwares  Collect Earth and Google Earth were employed to manipulate the historical series of high-resolution satellite images and implement photointerpretation. The coverage of identitied land units  was then estimated to address the configuration of the target landscape.

Landscape evolution over time was achieved by overlaying the 1954 and 2022 land use polygons, resulting in a merging database, in which an evolutionary dynamic was associated with each land use change.

The approach generated in-depth insights on the significant elements of the CURES olive landscape and informed on the dynamics of the area in relation to the risk of their disappearance, making it possible to identify what are the "landscape emergencies," i.e., the land uses that have seen the most̀ reduction in their area.

The methodologies employed have proven reliability in improving the knowledge ng target landscapes.  It might be useful to promote  sustainable agricultural practices for better preservation and management of rural environments so that cultural traditions can be preserved as well, and the environmental balance of the agrarian land can be maintained.

How to cite: Cuccaro, V. C., Di Giovannantonio, C., Pica, G., Malatesta, L., and Attorre, F.: Employng satellite immagery interpretation tools to detect land-use land-change dynamics in Italian historical rural landscapes, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11949, https://doi.org/10.5194/egusphere-egu24-11949, 2024.

EGU24-12105 | ECS | Orals | GM3.1 | Highlight

Unleashing the archive of aerial photographs of Iceland, 1945-2000. Applications in geosciences  

Joaquín M. C. Belart, Sydney Gunnarson, Etienne Berthier, Amaury Dehecq, Tómas Jóhannesson, Hrafnhildur Hannesdóttir, and Kieran Baxter

The archive of historical aerial photographs of Iceland consists of ~140,000 vertical aerial photographs acquired between the years 1945 and 2000. It contains an invaluable amount of information about human and natural changes in the landscape of Iceland. We have developed a series of automated processing workflows for producing accurate orthomosaics and Digital Elevation Models (DEMs) from these aerial photographs, which we’re making openly available in a data repository and a web map visualization service. The workflow requires two primary inputs: a modern orthomosaic to automatically extract Ground Control Points (GCPs) and an accurate DEM for a fine-scale (sub-meter) alignment of the historical datasets. We evaluated the accuracy of the DEMs by comparing them in unchanged terrain against accurate recent lidar and Pléiades-based DEMs, and we evaluated the accuracy of the orthomosaics by comparing them against Pléiades-based orthomosaics. The data are becoming available at https://loftmyndasja.lmi.is/. To show the potential applications of this repository, we present the following showcases where these data reveal significant changes the landscape in Iceland in the past 80 years: (1) volcanic eruptions (Askja 1961, Heimaey 1973 and the Krafla eruptions, 1975-1984), (2) decadal changes of Múlajökull glacier from 1960-2023, (3) Landslides (Steinsholtsjökull 1967, Tungnakvíslarjökull 1945-present) and (4) coastal erosion (Surtsey island).

How to cite: Belart, J. M. C., Gunnarson, S., Berthier, E., Dehecq, A., Jóhannesson, T., Hannesdóttir, H., and Baxter, K.: Unleashing the archive of aerial photographs of Iceland, 1945-2000. Applications in geosciences , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12105, https://doi.org/10.5194/egusphere-egu24-12105, 2024.

EGU24-14087 | ECS | Posters on site | GM3.1

A point-cloud deep learning model based on RGB-D images: Application of riverbed grain size survey 

Bo Rui Chen and Wei An Chao

The water level and discharge of river are crucial parameters to understand the variance in riverbed scour. The detail behavior of scouring can be studied by the hydraulic simulation. The grain-size distribution of riverbed is also one of crucial parameter for modeling. Thus, how to investigate the grain-size of riverbed efficiently and swiftly is the urgent issue. However, the conventional measurement methods including Wolman counts (particles sampled at a fixed interval) which are a long and laborious task cannot survey the grain-size efficiently in the large area. In recent years, with an advantage of image segmentation and recognition has been applied to the investigation of grain-size, for example, capturing images through UAV and generating orthoimage is one of commonly used image technique. Although above the method can investigate the grain-size in the large area, it does not provide the information in the field immediately. Hence, a recent study developed the low-cost portable scanner to obtain the information of grain-size distribution in the field. However, the calibrating parameters of camera (e.g., height camera capture) are necessary before survey, and the uncertainties in calculation of image resolution will significantly affect the accuracy of grain-size analysis. Therefore, this study provides the additional algorithm to analyze the grain-size by using RGB-D image as inputs. The application of RGB-D can be categorized into two-dimensional (2D) and three-dimensional (3D) spaces. In a case of 2D, it integrates depth information with traditional RGB image processing to separate the grain-size of riverbed from the background (e.g., bottomland). Furthermore, depth information is also applied for grain-size edge detection. In a case of 3D, the collected RGB-D image information is transformed into point cloud data, then extract 3D features of grain particle by Deep learning, specifically PointNet. Our study demonstrates that clustering of 3D features can achieve the automatic identification of particle. The grain-size of particle can also be estimated by fitting 3D ellipsoid geometry. In the end, results show the grain-size distribution curves with the RGB、RGB-D、PointNet recognition, and compare with the true observations. 3D image information provides the cloud points of grain object, leading the possibility of estimating the 3D geometric morphology of the object. Our study successfully overcomes the limitations of conventional RGB-based process, which could only capture size and shape information in 2D planar. RGB-D-based image recognition, is an innovative technique for the hydraulic problem, not only advances survey efficiency but also addresses the intricate steps required for field investigations.

 

Key words: Riverbed grain size, RGB-D image, Point cloud, Deep Learning

How to cite: Chen, B. R. and Chao, W. A.: A point-cloud deep learning model based on RGB-D images: Application of riverbed grain size survey, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14087, https://doi.org/10.5194/egusphere-egu24-14087, 2024.

EGU24-14680 | Orals | GM3.1

Using current 3D point clouds as a tool to infer on past geomorphological processes 

Reuma Arav, Sagi Filin, and Yoav Avni

Examining deposition and erosion dynamics during the late Pleistocene and Holocene is crucial for gaining insights into soil development, erosion, and climate fluctuations. This urgency intensifies as arable lands face escalating degradation rates, particularly in arid and semi-arid environments. Nevertheless, as the destructive nature of erosional processes allows only for short-term studies, long-term processes in these regions are insufficiently investigated. In that respect, the ancient agricultural installations in the arid Southern Levant offer distinctive and undisturbed evidence of long-term land dynamics. Constructed on a late Pleistocene fluvial-loess section during the 3rd-4th CE and abandoned after 600-700 years, these installations record sediment deposition, soil formation, and erosion processes. The challenge is to trace and quantify these processes based on their current state. In this presentation, we demonstrate how the use of 3D point cloud data enables us to follow past geomorphological processes and reconstruct trends and rates. Utilizing data gathered in the immediate vicinity of the UNESCO World Heritage Site of Avdat (Israel), we illustrate how these point clouds comprehensively document the history of soil dynamics in the region. This encompasses the initial erosion phase, subsequent soil aggradation processes resulting from anthropogenic interruption, and the ongoing reinstated erosion. The unique setting, which uncovers the different fluvial sections, together with the detailed 3D documentation of the site, allows us to develop means for the reconstruction of the natural environment in each of the erosion/siltation stages. Therefore, by utilizing the obtained data, we can recreate the site during its developmental stages till the present day. Furthermore, we utilize terrestrial laser scan data sequence acquired in the past decade (2012-2022) to compute current erosion rates. These are then used to determine past rates, enabling inferences about the climatic conditions prevalent in the region over the last millennium. The in-depth examination of these installations provides valuable insights into approaches for soil conservation, sustainable desert living, and strategies to safeguard world-heritage sites subjected to soil erosion. As the global imperative to address soil erosion intensifies, this case study gains heightened relevance.

How to cite: Arav, R., Filin, S., and Avni, Y.: Using current 3D point clouds as a tool to infer on past geomorphological processes, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14680, https://doi.org/10.5194/egusphere-egu24-14680, 2024.

EGU24-15439 | ECS | Orals | GM3.1 | Highlight

Utilizing historical aerial imagery for change detection in Antarctica 

Felix Dahle, Roderik Lindenbergh, and Bert Wouters

Our research explores the potential of historical images of Antarctica for change detection in 2D and 3D. We
make use of the TMA Archive, a vast collection of over 330,000 black and white photographs of Antarctica taken
between 1940 to 1990. These photographs, available in both nadir and oblique, are systematically captured
from airplanes along flight paths and offer an unprecedented historical snapshot of the Antarctic landscape.
Detecting changes between past and present observations provides a unique insight into the long-term impact
of changing climate conditions on Antarctica’s glaciers, and their dynamical response to ice shelf weakening and
disintegration. Furthermore, it provides essential validation data for ice modelling efforts, thereby contributing
to reducing the uncertainties in future sea level rise scenarios.

In previous work, we applied semantic segmentation to these images [1]. By employing classes derived from this
segmentation, we can focus on features of interest and exclude images with extensive cloud coverage, enhancing
the accuracy of change analyses. In the next step, we geo-referenced the images: We assigned the images to
their actual position, scaled them to their true size, and aligned them with their genuine orientation. This
presents novel opportunities for detecting environmental changes in Antarctica, particularly in the retreat of
glaciers and sea ice.

Furthermore, the combination of these two steps allows for the first time a large scale reconstruction of these
images in 3D through Structure from Motion (SfM) techniques, which enables further multidimensional change
detection by comparing historical 3D models with contemporary ones. Due to the high number of images,
manual processing is impractical. Therefore, we are investigating the possibility of automatizing this process.
We utilize MicMac, an open-source software developed by the French National Geographic Institute for the
creation of the 3D models. Its high modularity allows for necessary customizations to automate the SfM
process effectively. Further adaptions are required due to the poor image quality and monotonous scenery. By
comparing historical 3D models with contemporary ones, we can assess alterations in elevation due to factors
such as glacial isostatic adjustments and glacier retreat.

We have already employed geo-referenced images for detecting changes on the Antarctic peninsula and are in the
process of creating initial 3D models. Our presentation will outline the workflow we developed for this process
and showcase the initial results of the change detection, both in 2D and 3D formats. This approach marks a
significant step in understanding and visualizing the impacts of climate change on the Antarctic landscape.

Acknowledgements
This work was funded by NWO-grant ALWGO.2019.044.

References
[1] F. Dahle, R. Lindenbergh, and B. Wouters. Revisiting the past: A comparative study for semantic segmen-
tation of historical images of Adelaide Island using U-nets. ISPRS Open Journal of Photogrammetry and
Remote Sensing, 11:100056, 2024.

How to cite: Dahle, F., Lindenbergh, R., and Wouters, B.: Utilizing historical aerial imagery for change detection in Antarctica, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15439, https://doi.org/10.5194/egusphere-egu24-15439, 2024.

EGU24-15896 | Orals | GM3.1

Classification and segmentation of 3D point clouds to survey river dynamics and evolution  

Laure Guerit, Philippe Steer, Paul Leroy, Dimitri Lague, Dobromir Filipov, Jiri Jakubinsky, Ana Petrovic, and Valentina Nikolova

3D data for natural environments are now widely available via open data at large scales (e.g., OpenTopography) and can be easily acquired on the field by terrestrial LiDAR scan (TLS) or by structure-from-motion (SFM) from camera or drone imagery. The 3D description of landscapes gives access to an unprecedented level of details that can significantly change the way we look at, understand, and study natural systems. Point clouds with millimetric resolution even allow to go further and to investigate the properties of riverbed sediments: dedicated algorithms are now able to extract the sediment size distribution or their spatial orientation directly from the point cloud. 

Such data can be real game changers to study for example torrential streams prone to flash floods or debris flows. Such events are usually associated with heavy rainfall events, while conditioned by the geomorphological state of a stream (e.g., channel geometry, vegetation cover). The size and the shape of the grains available in the river also strongly influence river erosion and sediment transport during a flood. 3D data can thus help to design prevention and mitigation measures in streams prone to torrential events. 

However, it is not straightforward to go from data acquisition to river erosion or to grain-size distributions. Indeed, isolating and classifying the areas of interest can be complex and time-consuming. This can be done manually, at the cost of time and absence of reproducibility. We rather take advantage of state-of-the-art classification method (3DMASC) to develop a general classifier for point clouds in fluvial environments designed to identify five classes usually found in such settings: coarse sediments, sand, bedrock, vegetation and human-made structures. We also improved the G3Point sediment segmentation algorithm, developed by our team, to make it more efficient and straightforward to use in the CloudCompare software, which is dedicated to point cloud visualization and analysis. We apply it to the coarse sediments class identified by 3DMASC to provide a more accurate description of grain size and orientation. We also make a profit of the sand class to estimate its relative areal distribution that can then be compared to the coarse sediment class. This provides valuable information about the type of flows which are also important for planning torrential events mitigation measures.

We illustrate this combined approach with two field examples. The first one is based on SFM data acquired along streams prone to torrential events in Bulgaria and in Serbia where we documented sediment size and orientation. The second one is based on TLS data acquired along a bedrock river in France that experienced a major flood which induced dramatic changes in the river morphology. 

This work has been partially funded by PHC Danube n° 49921ZG/ n° KP-06-Danube/5, 14.08.2023 (National Science Fund, Bulgaria) and the H2020 European Research Council (grant no. 803721). 

How to cite: Guerit, L., Steer, P., Leroy, P., Lague, D., Filipov, D., Jakubinsky, J., Petrovic, A., and Nikolova, V.: Classification and segmentation of 3D point clouds to survey river dynamics and evolution , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15896, https://doi.org/10.5194/egusphere-egu24-15896, 2024.

EGU24-16939 | ECS | Posters on site | GM3.1 | Highlight

Integrating structure-from-motion photogrammetry with 3D webGIS for risk assessment, mapping and monitoring of coastal area changes in the Maltese archipelago 

Emanuele Colica, Daniel Fenech, Christopher Gauci, and George Buhagiar

The Maltese coasts extend for approximately 273km, representing a notable resource for the country and of one of its pillar economies, the tourism sector. Natural processes and anthropic interventions continue to threaten Malta's coastal morphology, shaping its landscape and triggering soil erosion phenomena. Therefore, many research projects (Colica et al., 2021, 2022 and 2023) have concentrated their work on the investigation and monitoring of the instability of cliffs and the erosion of pocket beaches. The results of such activities can be widely disseminated and shared with expert and non-expert users through web mapping, which has only been used in a very limited way in collaborative coastal management and monitoring by different entities in Malta. This study describes the performance of a WebGIS designed to disseminate the results of innovative geomatic investigations for monitoring and analyzing erosion risk, performed by the Research and Planning Unit within the Public Works Department of Malta. While aiming to include the entire national coastline, three study areas along the NE and NW regional coasts of the island of Malta have already been implemented as pilot cases. This WebGIS was generated using ArcGIS pro software by ESRI and a user-friendly interactive interface has been programmed to help users view in 2D and 3D, satisfying both multi-temporal and multi-scale perspectives. It is envisaged that through further development and wider dissemination there will be a stronger uptake across different agencies involved in coastal risk assessment, monitoring and management.

References

Colica, E., D’Amico, S., Iannucci, R., Martino, S., Gauci, A., Galone, L., ... & Paciello, A. (2021). Using unmanned aerial vehicle photogrammetry for digital geological surveys: Case study of Selmun promontory, northern of Malta. Environmental Earth Sciences, 80, 1-14.

Colica, E. (2022). Geophysics and geomatics methods for coastal monitoring and hazard evaluation.

Colica, E., Galone, L., D’Amico, S., Gauci, A., Iannucci, R., Martino, S., ... & Valentino, G. (2023). Evaluating Characteristics of an Active Coastal Spreading Area Combining Geophysical Data with Satellite, Aerial, and Unmanned Aerial Vehicles Images. Remote Sensing, 15(5), 1465.

How to cite: Colica, E., Fenech, D., Gauci, C., and Buhagiar, G.: Integrating structure-from-motion photogrammetry with 3D webGIS for risk assessment, mapping and monitoring of coastal area changes in the Maltese archipelago, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16939, https://doi.org/10.5194/egusphere-egu24-16939, 2024.

EGU24-17822 | ECS | Posters on site | GM3.1

Evaluating Ordnance Survey sheets (1890s – 1957) for shoreline change analysis in the Maltese Islands  

Daniel Fenech, Jeremie Tranchant, Christopher Gauci, Daniela Ghirxi, Ines Felix-Martins, Emanuele Colica, and George Buhagiar

 

Jeremie' Tranchant1, Daniel Fenech1, Christopher Gauci1, Daniela Ghirxi1, Ines Felix Martins1, Emanuele Colica1, George Buhagiar1

1  Research and Planning Unit, Ministry for Transport, Infrastructure and Public Works, Project House, Triq Francesco    Buonamici, Floriana, FRN1700, Malta

The assessment of coastal erosion through shoreline change analysis, is an exercise of national utility undertaken in many countries. The Maltese Islands are particularly vulnerable to coastal erosion given the economic value of coastal activities and their high ratio of coast-to-land surface. The integration of historical cartographic material is often used to hindcast shoreline change across long periods of time, as well as to model future erosion rates. The Public Works Department have produced detailed 1:2500 maps of Malta in collaboration with the British Ordnance Survey from the end of the 19th century to 1957, however these maps have never been scientifically assessed. The initial research carried out evaluated the usefulness of the two oldest 25-inches Maltese maps series (early 20th century and 1957) for shoreline change analysis.  The two series were digitised, georeferenced, and compared in a GIS environment to assess their differences. The inaccuracies of the original drawings, absent shoreline indicators, and the absence of a geographic coordinate system (datum and projection) were identified as limitations for their use in evaluating small gradual changes, but were ideal for the identification of stochastic, large-scale historic erosion events using difference maps. This assessment showed that the two series are highly congruous and any changes between the two series are largely attributed to changes in infrastructure. There were, however, minor exceptions and these need to be explored on a case-by-case basis. These methods and the insights garnered from their production will function as scientific steppingstones towards developing a holistic coastal erosion national monitoring program.  

How to cite: Fenech, D., Tranchant, J., Gauci, C., Ghirxi, D., Felix-Martins, I., Colica, E., and Buhagiar, G.: Evaluating Ordnance Survey sheets (1890s – 1957) for shoreline change analysis in the Maltese Islands , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17822, https://doi.org/10.5194/egusphere-egu24-17822, 2024.

EGU24-21396 | ECS | Orals | GM3.1

Automatic detection of river bankfull parameters from high density lidar data 

Alexandre Rétat, Nathalie Thommeret, Frédéric Gob, Thomas Depret, Jean-Stéphane Bailly, Laurent Lespez, and Karl Kreutzenberger

The European Water Framework Directive (WFD), adopted in 2000, set out requirements for a
better understanding of aquatic environments and ecosystems. In 2006, following the transposition of
the WFD into French law (LEMA), France began work on a field protocol for the geomorphological
characterization of watercourses, as part of a partnership between the Centre National de la Recherche
Scientifique (CNRS) and the Office Français de la Biodiversité (OFB). This protocol, known as "Carhyce"
(For « River Hydromorphological Caracterisation »), has been tested, strengthened and approved over
the last 15 years at more than 2500 reaches. It consists of collecting standardised qualitative and
quantitative data in the field, essential for the caracterisation of a watercourse: channel geometry,
substrate, riparian vegetation... However, certain rivers that are difficult to survey (too deep or too
wide) pose problems for data collection.
To address these issues, and to extend the analysis to a wider scale (full river section), using
remote sensing, and in particular LiDAR data, was considered. The major advantages of LiDAR over
passive optical sensors are better geometric accuracy and especially under vegetation. For a long time,
LiDAR data rarely exists at national scale with data density similar to passive imagery. Today, the French
LiDAR HD dataset (10 pulses per meter square) program run by the French mapping agency offers an
unprecedented amount of data at this scale. Thanks to them, a national 3D coverage of the ground can
be used, and numerous geomorphological measurements can be carried out on a more or less large
scale. This is the case for hydromorphological parameters such as water level and width.
The aim of this study is therefore to use this high-density lidar to automatically determine the
hydromorphological parameters sought in the Carhyce protocol. In particular, we have developed a
lidar-based algorithm to reconstruct the topography from point cloud and automatically identify the
bankfull level at reach scale. Designed to be applicable to every French river, the method must be
robust to all river features such as longitudinal slope, width, sinuosity, multi-channel etc... For
validation purposes, the bankfull geometry calculated by the algorithm has been compared with field
measurements at some twenty Carhyce stations across France. To determine the test stations, we
looked for the diversity of situations in terms of river characteristics describe above to observed the
influence of this features on the results.

How to cite: Rétat, A., Thommeret, N., Gob, F., Depret, T., Bailly, J.-S., Lespez, L., and Kreutzenberger, K.: Automatic detection of river bankfull parameters from high density lidar data, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21396, https://doi.org/10.5194/egusphere-egu24-21396, 2024.

EGU24-22358 | ECS | Orals | GM3.1 | Highlight

UAV’s to monitor the mass balance of glaciers 

Lander Van Tricht, Harry Zekollari, Matthias Huss, Philippe Huybrechts, and Daniel Farinotti

Uncrewed Aerial Vehicles (UAVs) are increasingly employed for glacier monitoring, particularly for small to medium-sized glaciers. The UAVs are mainly used to generate high-resolution Digital Elevation Models (DEMs), delineate glacier areas, determine surface velocities, and map supraglacial features. In this study, we utilise UAVs across various sites in the Alps and the Tien Shan (Central Asia) to monitor the mass balance of glaciers. We present a workflow for calculating the annual geodetic mass balance and obtaining the surface mass balance using the continuity-equation method. Our results demonstrate generally a close alignment between the determined mass balances and those obtained through traditional glaciological methods involving intensive fieldwork. We show that utilising UAV data reveals significantly more spatial details, such as the influence of debris and collapsing ice caves, which are challenging to capture using conventional methods that strongly rely on interpolation and extrapolation. This underscores the UAV's significance as a valuable add-on tool for quantifying annual glacier mass balance and validating glaciological assessments. Drawing on our experience in on-site UAV glacier surveys, we discuss the methodology's advantages, disadvantages, and potential pitfalls. 

How to cite: Van Tricht, L., Zekollari, H., Huss, M., Huybrechts, P., and Farinotti, D.: UAV’s to monitor the mass balance of glaciers, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-22358, https://doi.org/10.5194/egusphere-egu24-22358, 2024.

EGU24-64 | ECS | Orals | CL1.2.5

The Largely Linear Response of Earth’s Ice Volume to Orbital Forcing 

Liam Wheen, Thomas Gernon, Cameron Hall, Jerry Wright, and Oscar Benjamin

 

We investigate the effect of Earth’s orbitally governed incoming solar radiation on global ice volume over the past 800,000 years. It is well established that the orbital parameters play some role in the pacing of the glacial-interglacial cycles. However, due to limited data and enigmatic dynamics, the mechanics that could facilitate this relationship remain unresolved. We therefore consider a simple linear model of ice volume that imposes minimal assumptions about its dynamics. This model adequately reproduces the ice volume data for most of the 800,000 year period, with the exception of Marine Isotope Stage 11. This suggests that, aside from a few extrema, the ice volume dynamics primarily result from an approximately linear response to orbital forcing. We substantiate this finding by addressing some of the key criticisms of the orbitally forced hypothesis. In particular, we show that eccentricity can significantly vary the ocean temperature without the need for amplification on Earth. We also present a feasible mechanism to explain the absence of eccentricity’s 400,000 year period in the ice volume data. This requires part of the forcing from eccentricity to be lagged via a slow-reacting mechanism, resulting in a signal that closer approximates the change in eccentricity. A physical interpretation of our model is proposed, using bulk ocean and surface temperatures as intermediate mechanisms through which the orbital parameters affect ice volume. These show reasonable alignment with their relevant proxy data, though we acknowledge that these variables likely represent a combination of mechanisms.

How to cite: Wheen, L., Gernon, T., Hall, C., Wright, J., and Benjamin, O.: The Largely Linear Response of Earth’s Ice Volume to Orbital Forcing, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-64, https://doi.org/10.5194/egusphere-egu24-64, 2024.

EGU24-113 | ECS | Posters on site | CL1.2.5

Development of a Continuous Flow Analysis system for studying Allan Hills, Antarctica ice cores 

Abigail Hudak, Asmita Banerjee, Edward Brook, Christo Buizert, Maciej Sliwinski, Lindsey Davidge, Eric Steig, Andy Schauer, Noah Brown, Miranda Miranda, and Eric Saltzman

Extending ice core records beyond 800 thousand years (kyr) is a pivotal goal in paleoclimate research. Allan Hills, East Antarctica, provides a unique opportunity to evaluate old ice and reconstruct climate well beyond 800 kyr with preliminary research uncovering ice ages up to 4.5 million years. Although old ice has been found and proven to be valuable, the ice in this area demonstrates several peculiarities—such as strong layer thinning, folding, and non-atmospheric CO2 – that warrant an in-depth investigation of the ice at this site and the climate record it holds. To address these challenges, we aim to initially conduct a high-resolution continuous flow analysis (CFA) of dust, water stable isotopes, water chemistry, and methane on the upper 70m of an ice core drilled in the 2022-2023 field season at the Allan Hills. A new CFA system has been developed at Oregon State University to analyze old ice, consisting of separate laser spectrometers for water stable isotopes and methane, an Abakus particle sensor for dust, and a fraction collector for sample analysis of melt-water chemistry.

Here, we aim to present preliminary data on dust and methane and demonstrate the newly developed CFA system. Preliminary analyses on this ice have revealed the surface ice to be ~400 kyr old, with the majority of the upper 70m likely in stratigraphic order. This enables meaningful comparisons to other Antarctic ice cores and strengthens our comprehension of the climate-recording behavior of the ice. A high-resolution investigation of this ice is a critical step in understanding the discrete records from the Allan Hills that extend beyond the Mid-Pleistocene Transition and into the Pliocene, pushing our ice core records into unique and enigmatic parts of Earth’s climate history.

How to cite: Hudak, A., Banerjee, A., Brook, E., Buizert, C., Sliwinski, M., Davidge, L., Steig, E., Schauer, A., Brown, N., Miranda, M., and Saltzman, E.: Development of a Continuous Flow Analysis system for studying Allan Hills, Antarctica ice cores, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-113, https://doi.org/10.5194/egusphere-egu24-113, 2024.

During the early Pleistocene (prior to 1.25 Ma), obliquity dominated the cyclicity of climatic variations, resulting in glacial and interglacial cycles. A significant change occurred between 1.25 Ma and 0.7 Ma, which altered the dominant frequency from 41 kyr to 100 kyr. This transition period is known as the Mid-Pleistocene Transition (MPT). Although several climate models and records have focused on the MPT, our understanding of how climatic variations in the 41 kyr-world affected the planktonic foraminiferal fauna, and their response to the millennial-scale sea surface temperature (SST) oscillations remains limited. Here, we present a sub-millennial scale planktonic foraminiferal assemblage and G. bulloides stable isotope data from southern Iberian margin IODP Site U1387 (36°48.321´N 7°43.1321´W, 559 water depth), influenced by subtropical surface waters from the Azores current. The main goal is to reconstruct temporal trends in SST and to infer ecological changes during the interval from Marine Isotope Stage (MIS) 50 to MIS 40 (1.5-1.28 Ma).

Planktonic foraminifera assemblages show a distinct pattern between glacial and interglacial periods, correlating with changes in the mid-latitudinal North Atlantic's surface circulation. Interglacial periods (MIS 49, MIS 47, MIS 43) exhibit a strong influence of warm, oligotrophic waters. The abundances of subtropical species vary between 40% and 65%, whereas tropical species reach up to 10%. The SSTs were around 23.7°C during summer and 18.5°C during winter. In these periods, insolation appears to influence interglacial intensity, peaking at the onset of MIS 47 and MIS 43. In contrast, during cooler MIS 45, the subtropical species only reached values up to 20% and tropical species up to 2%, with temperatures about 21°C in summer and 16°C in winter. The expansion of the subtropical gyre during the interglacials, but also interstadial periods, could have played a significant role in those species’ assemblages and the SST fluctuations.

In contrast, during glacial periods (MIS 50, MIS 48, MIS 46, MIS 44), extreme cold events of short duration were documented, with MIS 50 and MIS 48 recording distinct terminal stadial events. Those short-term episodes were marked by abrupt abundance increases of polar species N. pachyderma up to 40% to 65%, respectively, and SSTs dropping down to 8°C in summer and 5°C in winter. The coldest temperatures were documented during the MIS 48 stadial terminal event and is consistent with alkenone-derived SST data, indicating colder deglacial conditions compared to MIS 46 and MIS 40. The SSTs, and the faunal data, including the increase in cold water calcareous nannofossil taxa, are consistent with evidence of the southward displacement of subpolar waters and the contraction of the subtropical gyre. In addition to the faunal data, changes in the G. bulloides δ18O record reveal a gradual increase of values during MIS 48 and abrupt oscillations during MIS 46, MIS 44, MIS 42, and MIS 40. Overall, we confirm the presence of millennial-scale climate variability during the 41 kyr-world with strong impacts on the planktonic foraminifera fauna and implications for the dimension of the subtropical gyre in the North Atlantic.

How to cite: Duque Castaño, M., Voelker, A. H. L., Rodrigues, T., and Trotta, S.: Millennial-scale climate variability in the 41 kyr world of MIS 50 to MIS 40 (1.5-1.28 Ma): Insights from planktonic foraminifera and sea surface temperature data from the southern Iberian margin, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-439, https://doi.org/10.5194/egusphere-egu24-439, 2024.

EGU24-511 | ECS | Orals | CL1.2.5

Precisely dated climate records challenge the Southern Hemisphere glacial aridity paradigm 

Rieneke Weij, Kale Sniderman, Jon Woodhead, John Hellstrom, Josephine Brown, Russell Drysdale, Liz Reed, Steven Bourne, and Jay Gordon

While global changes in temperature during the last 1.5 Ma are well constrained, the terrestrial response to these changes is less understood, particularly in the Southern Hemisphere. Late Pleistocene ice-age climates are routinely characterised as having imposed moisture-stress on low/mid-latitude ecosystems. This idea is largely based on fossil pollen evidence for widespread, low-biomass glacial vegetation, interpreted as indicating climatic dryness. However, woody plant growth is inhibited under low atmospheric CO2, so understanding glacial environments requires the development of new palaeoclimate indicators that are independent of vegetation. Here, we present two new, well-dated speleothem records from subtropical, southern Australia, both spanning the last three glacial-interglacial cycles. We show that, contrary to expectations, over the past ~350 ka, peaks in southern Australian climatic moisture availability were largely confined to glacial periods, including the last glacial maximum, while warm interglacials were relatively dry. By measuring the timing of speleothem growth in the Southern Hemisphere subtropics, which today has a predominantly negative annual moisture balance, we developed a record of climatic moisture availability that is independent of vegetation and extends through multiple glacial-interglacial cycles. Our results demonstrate that a cool-moist response is consistent across the austral subtropics, and in part may result from reduced evaporation under cool glacial temperatures. Insofar as cold glacial environments in the Southern Hemisphere subtropics have been portrayed as uniformly arid, our findings suggest that their characterisation as evolutionary or physiological obstacles to movement and expansion of animal, plant and, potentially, human populations should be reconsidered.

How to cite: Weij, R., Sniderman, K., Woodhead, J., Hellstrom, J., Brown, J., Drysdale, R., Reed, L., Bourne, S., and Gordon, J.: Precisely dated climate records challenge the Southern Hemisphere glacial aridity paradigm, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-511, https://doi.org/10.5194/egusphere-egu24-511, 2024.

EGU24-1845 | ECS | Orals | CL1.2.5

Variability of the North Atlantic westerlies during MIS 31-16 (1.1- 0.65 Ma) from SW Iberian margin records 

Xiaowen Quan, Maria Fernanda Sanchez Goñi, Paul Moal-Darrigade, Qiuzhen Yin, and Josue Polanco-Martinez

The driving mechanisms of the middle Pleistocene Transition (MPT) are still unclear but the most likely hypotheses are related to ice-sheet dynamic feedbacks, such as ice albedo, precipitation at the ice margins, elevation-temperature and the regoliths. Here we focus on the “precipitation at the ice margins” hypothesis. To test this hypothesis, we have analysed the pollen content of SW Iberian margin sedimentary sequences that document changes in the direction and intensity of the westerlies during the MPT. In my presentation I will show the pollen-based vegetation and winter rainfall changes in the adjacent landmasses of the southwestern Iberian margin during the MPT. Changes in the reconstructed vegetation from IODP Site U1386 (1.2-0.8 Ma), combined with IODP Site U1385 (0.8-0.67 Ma), and their comparison with changes in the North Atlantic Ocean thermal gradient reveal the variability in the intensity and position of the westerlies and in the position of the moisture source, respectively. Preliminary pollen results reveal a long-term decreasing trend in the Mediterranean forest cover during MIS 31-20 (1.1-0.8 Ma), associated with long-term southward migration of the thermocline water source. This trend abruptly shifted northward at 0.8 Ma, and probably was related to progressive northward shift of the westerlies that bring moisture to the margin of the ice sheets feeding the ice caps, and leading to the shift of the dominant ice sheet cyclicity from 41 kyrs to 100 kyrs.

How to cite: Quan, X., Sanchez Goñi, M. F., Moal-Darrigade, P., Yin, Q., and Polanco-Martinez, J.: Variability of the North Atlantic westerlies during MIS 31-16 (1.1- 0.65 Ma) from SW Iberian margin records, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1845, https://doi.org/10.5194/egusphere-egu24-1845, 2024.

EGU24-2423 | ECS | Orals | CL1.2.5

The association of AMOC and Atlantic sea ice in a transient CGCM simulation for the past 2.6 million years. 

Gagan Mandal, Soon-Il An, Axel Timmermann, Kyung-Sook Yun, and Jae-Heung Park

The Quaternary period (0–2.58 million years) is an important time in the early evolution of our human ancestors. This period is featured by distinctive glacial-interglacial cycles, primarily caused by variations in orbital parameters (i.e., eccentricity (100 thousand years (kyr)), obliquity (41 kyr), and precession (23/19 kyr)), atmospheric CO2 concentration (GHG), and their feedbacks. Therefore, it is essential to understand the climate system, mainly focusing on the variability of the Atlantic Meridional Overturning Circulation (AMOC) due to its huge impact.

In this study, we have employed a quasi-continuous simulation to understand the AMOC variability in response to changes in orbital, GHG, and continental ice sheet forcings over the past 2.6 million years. It is found that the AMOC variability is associated with the sea ice coverage and mixed layer depths over the Labrador Sea and Irminger and Iceland basins. The overall mixed layer depth over the Labrador Sea, Irminger, and Iceland basins and the corresponding AMOC variability vary in precession and obliquity periodicity. Meanwhile, the mixed layer depth in the Labrador Sea exhibits a dominant precession, and the Irminger and Iceland basins exhibit a dominant obliquity periodicity. Further, we have divided the entire Quaternary period into three subsets based on the dominant periodicity of the climate state: 0ka–700ka (post-MPT; 100kyr dominant), 700ka–1200ka (MPT; 100–80kyr and 41kyr dominant), and 1200ka–2600ka (pre-MPT; 41kyr dominant). We have found that sea ice coverage and mixed layer depth in the Labrador Sea (Irminger and Iceland basins) are out of (in) phase with a Pearson correlation coefficient of −0.70 (0.42) during post-MPT, −0.78 (0.32) during MPT, and −0.85 (0.38) during pre-MPT periods. These results indicate that during glacial periods, the southward expansion of Labrador sea ice covered the deep convection sites, which impeded deep convection and weakened the AMOC strength. Therefore, the expansion and contraction of Labrador sea ice and its feedback contributed to AMOC variability over glacial‐interglacial cycles for the past 2.6 million years.

How to cite: Mandal, G., An, S.-I., Timmermann, A., Yun, K.-S., and Park, J.-H.: The association of AMOC and Atlantic sea ice in a transient CGCM simulation for the past 2.6 million years., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2423, https://doi.org/10.5194/egusphere-egu24-2423, 2024.

EGU24-3211 | Posters on site | CL1.2.5

The intensity of interglacials during the last 800 kyr 

Eric Wolff, Emilie Capron, Polychronis Tzedakis, Etienne Legrain, Takahito Mitsui, and Qiuzhen Yin

An ultimate target of Quaternary climate studies is to predict the strength and timing of glacial cycles using only the Milankovic forcing as input.  Here we consider just one aspect of this challenge, the intensity of interglacials. Previous work (PIGS Working Group, 2015) has identified 11 interglacials in the last 800 kyr. Are some of them globally strong or weak? Is there a step change at the mid-Brunhes (between MIS 13 and MIS11)? And what controls the observed intensity?

We first discuss what we mean by intensity.  Some datasets (such as mean global temperature or sea level) have a more global character and might be considered more robust indicators of interglacial strength, but are more difficult to estimate compared to simpler parameters such as CO2 concentration and Antarctic temperature.  Many records show “overshoots”, temporary maxima that are followed by longer plateaus of interglacial character.  Despite these complications, some patterns do emerge. In global scale records, MIS 5e, 11, 9, 1 stand out as particularly warm, with 13 and 17 particularly cold. Some terrestrial records show a different pattern with MIS 13 unusually strong in many Asian records.  There is a tendency to more intense interglacials after 450 ka, but MIS 7e and 7c would sit quite happily in the pre-mid-Brunhes pattern.

A first look at the astronomical/orbital context is not encouraging. We see the obvious MIS11 paradox, that weak precessional forcing leads to a strong interglacial (or the opposite, most clearly seen in MIS 15e and 7c). However two different approaches have been quite successful, and may point the way to a more satisfying conclusion. Yin and Berger (2010, 2012) predicted the strength of interglacials using Milankovic forcing plus CO2 concentration as inputs.  This approach suggests that the main cause of stronger interglacials after the mid-Brunhes is higher CO2 and pushes the problem into understanding the controls on the intensity of CO2 maxima. Mitsui et al (2022) used Milankovic forcing plus the strength of the previous glacial. In this model, the tendency to stronger interglacials after the mid-Brunhes arises essentially from a tendency to higher obliquity, as part of a 1.2 Myr cycle. Neither approach views the change across the mid-Brunhes as an ”event” and we propose it should rather be termed a mid-Brunhes “Shift” (MBS).

Here we discuss how we might approach a unified explanation that draws on both models, with periods of highest CO2 perhaps being related to the pattern and timing of AMOC strength during the termination. This is influenced by the size of glacial ice sheets and by orbital intensity through their influence on the amount of freshwater available and the rate at which it is delivered into the ocean.  Finally we consider whether the pattern of obliquity is enough to understand the MBS, i.e. is it part of a longer term oscillation.

How to cite: Wolff, E., Capron, E., Tzedakis, P., Legrain, E., Mitsui, T., and Yin, Q.: The intensity of interglacials during the last 800 kyr, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3211, https://doi.org/10.5194/egusphere-egu24-3211, 2024.

EGU24-3722 | Orals | CL1.2.5 | Milutin Milankovic Medal Lecture by Peter U. Clark

A Revisionist View of the Mid-Pleistocene Transition 

Peter U. Clark, Jeremy Shakun, Yair Rosenthal, David Pollard, Peter Köhler, Steven Hostetler, Patrick Bartlein, Zhengyu Liu, Chenyu Zhu, Daniel Schrag, and Nicklas Pisias

The Mid-Pleistocene Transition (MPT) is commonly characterized as a change in both temperature and ice volume from smaller amplitude, 41-kyr variability to higher amplitude, ~100-kyr variability in the absence of any significant change in orbital forcing. Here we reassess these characteristics based on our new reconstructions of changes in global mean surface temperature (DGMST) and global mean sea level over the last 2.5 Myr. Our reconstruction of DGMST includes an initial phase of long-term cooling through the early Pleistocene followed by a second phase of accelerated cooling during the MPT (1.5-0.9 Ma) that was accompanied by a transition from dominant 41-kyr low-amplitude periodicity to dominant ~100-kyr high-amplitude periodicity. Changes in rates of long-term cooling and variability are consistent with changes in the carbon cycle driven initially by geologic processes followed by additional changes during the MPT in the Southern Ocean carbon cycle. The spectrum of our sea-level reconstruction is dominated by 41-kyr variance until ~1.2 Ma with subsequent emergence of a ~100-kyr signal that, unlike global temperature, has nearly the same concentration of variance as the 41-kyr signal during this time. Moreover, our sea-level reconstruction is significantly different than all other reconstructions in showing fluctuations of large ice sheets throughout the Pleistocene as compared to a change from fluctuations in smaller to larger ice sheets during the MPT. We attribute their longer period variations after the MPT to modulation of obliquity forcing by the newly established low-frequency CO2 variability. Specifically, prior to reaching their maximum size at the end of each ~100-kyr interval, ice-sheet response to periods of lower CO2 was modulated by higher obliquity, and vice versa, with the times of maximum ice-sheet growth only occurring when low CO2 combined with the next obliquity low. Ice sheets then began to melt in response to the next increase in obliquity, with the subsequent sequence of events and feedbacks leading to a termination. High-resolution ice-core CO2 records that extend beyond 0.8 Ma are needed to test this hypothesis. Otherwise, large ice sheets shared a common size threshold throughout the Pleistocene equivalent to sea level below -80 m that, when exceeded, resulted in a termination that was paced by the next increase in obliquity.

How to cite: Clark, P. U., Shakun, J., Rosenthal, Y., Pollard, D., Köhler, P., Hostetler, S., Bartlein, P., Liu, Z., Zhu, C., Schrag, D., and Pisias, N.: A Revisionist View of the Mid-Pleistocene Transition, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3722, https://doi.org/10.5194/egusphere-egu24-3722, 2024.

EGU24-3753 | Orals | CL1.2.5

Simulating Antarctic ice-sheet variability of the past 3 million years 

Kyung-Sook Yun and Axel Timmermann

Little is known about the evolution of the Antarctic ice-sheet (AIS) during the Pleistocene and its response to external drivers, such as CO2, orbital and sea-level forcing. Here, we apply realistic transient climate forcings generated by the 3Ma Community Earth System model (CESM, version 1.2) simulation [1],[2] to the bi-hemispheric Pen State University ice-sheet shelf model (PSUIM). The CESM-simulated surface air temperature, surface solar insolation, precipitation, and sub-surface ocean temperature serve as inputs for PSUIM. This application enables us to simulate a more reliable variability of the AIS over the past 3 million years ago (Ma). Our simulation reveals a more pronounced precessional modulation of early to mid-Pleistocene AIS variability than previously suggested. The results further show the mid-Pleistocene transition (MPT, ~ 1Ma) of AIS, with dominant frequencies changing  from 20-40 kyrs to 80-120 kyrs and a clear regime shift in its surface mass balance. We also find that the pre-MPT precessional variability is significant only in the marine (floating) ice-sheet, not in terrestrial (grounded) ice. This suggests the influence of competing ocean and atmospheric processes in controlling the AIS variability over the past 3Ma. We will further discuss the mechanisms of simulated AIS variability and its climate interactions on orbital timescales and compare our results with paleo reconstructions.

 

[1] 3Ma-Data: Transient CESM1.2 model simulation data over the 3 million years ago (Ma),   https://climatedata.ibs.re.kr/data/3ma-transient-climate-simulation, doi:10.22741/iccp.20230001.

[2] Yun, K.-S., Timmermann, A., et al. (2023), A transient coupled general circulation model (CGCM) simulation of the past 3 million years, Clim. Past, 19, 1951–1974, https://doi.org/10.5194/cp-19-1951-2023.

 

How to cite: Yun, K.-S. and Timmermann, A.: Simulating Antarctic ice-sheet variability of the past 3 million years, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3753, https://doi.org/10.5194/egusphere-egu24-3753, 2024.

EGU24-4211 | ECS | Orals | CL1.2.5

CO2-forced change in glacial response to precession likely causes the Middle-Pleistocene Transition and ~100-kyr glacial cycles 

Zhifeng Zhang, Yongjian Huang, Chao Ma, Qiuzhen Yin, Hanfei Yang, Eun Young Lee, Hai Cheng, Benjamin Sames, Michael Wagreich, Qingping Liu, Tiantian Wang, and Chengshan Wang

Around ~800-1200 ka, the transition of glacial-interglacial cycles from earlier ~40-kyr into later ~100-kyr cyclicities without obvious changes in orbital parameters, known as the Middle-Pleistocene Transition (MPT), suggests that Earth’s internal factors, in addition to external astronomical forcing, are also essential for the glacial cycles. However, it is still unclear how internal and external factors interact to lead to the MPT and the ~100-kyr cycle. Here, we statistically analyzed the power spectral relationship between the ~21-kyr, ~41-kyr, and ~100-kyr components within 57 paleoclimate archives and reconstructed the astronomical phase relative to the maximal changing rate of benthic foraminifer oxygen isotopes (δ18O) over the past 2700 ka to explore the role of astronomical forcings in driving glacial cycles and their relationship with internal factors. The statistical results show that the ~21-kyr power ratio complements the ~100-kyr power ratio. The precession phase covaries with pCO2-modulated glacial dynamics and exhibits a contrasting correlation with the precession power ratio of benthic δ18O before and after ~1500 ka. These findings suggest that pCO2-modulated latitudinal extension of the icesheets determined the glacial response to precession. Around 1500 ka, the response apparently shifted into a nonlinear mode, enabling the gradual extension of glacial cycles into ~100-kyr periodicities at the expense of precession power, which signified the onset of the ~100-kyr glacial cycles. Our study confirms the nonlinear precession origin of ~100-kyr glacial cycles, featuring the possible low- and high-latitude interplay at the precession band.

How to cite: Zhang, Z., Huang, Y., Ma, C., Yin, Q., Yang, H., Lee, E. Y., Cheng, H., Sames, B., Wagreich, M., Liu, Q., Wang, T., and Wang, C.: CO2-forced change in glacial response to precession likely causes the Middle-Pleistocene Transition and ~100-kyr glacial cycles, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4211, https://doi.org/10.5194/egusphere-egu24-4211, 2024.

EGU24-5365 | ECS | Orals | CL1.2.5

Temperature and salinity changes in the abyssal Atlantic and Pacific Oceans over the Middle Pleistocene Transition 

Nicola Thomas, David Hodell, Heather Ford, and Mervyn Greaves

Ocean thermohaline circulation (THC) is driven by temperature and salinity in source areas of deep-water formation. THC underwent a fundamental change ~950 to 860 thousand years ago (ka) during the Middle Pleistocene Transition (Pena and Goldstein, 2014). However, the relative contributions of temperature (‘thermo-’) versus salinity ('haline’) change to this fundamental THC reorganization remain unclear. Here we compiled North Atlantic and Pacific Ocean stacks of deep-water temperature (estimated using foraminiferal Mg/Ca) and salinity (estimated from δ18Oseawater) for the past 1.5-million-years (Myr). The deep North Atlantic became colder and the deep Pacific saltier during glacial periods younger than ~900 ka. Cooling of northern sourced water likely led to increased salinity of southern sourced water by decreasing the melting of land-based ice around Antarctica (Adkins, 2013) and increasing sea ice formation and associated brine rejection. With increased stratification the abyssal ocean became a more effective carbon trap lowering the concentration of atmospheric pCO2, thereby permitting ice sheets to grow larger and lengthening the glacial cycle. Expansion of Antarctic ice sheets would have also contributed to increasing the salinity of southern source areas as Antarctica shifted from dominantly terrestrial melting to marine-based calving margins (Raymo et al., 2006). Our temperature and salinity reconstructions support a fundamental reorganization of the density structure and stratification of the abyssal glacial ocean across the Middle Pleistocene Transition.

 

References:

Adkins, J.F. (2013) ‘The role of deep ocean circulation in setting glacial climates’, Paleoceanography, 28(3), pp. 539–561. Available at: https://doi.org/10.1002/palo.20046.

Pena, L.D. and Goldstein, S.L. (2014) ‘Thermohaline circulation crisis and impacts during the mid-Pleistocene transition’, Science, 345(6194), pp. 318–322. Available at: https://doi.org/10.1126/science.1249770.

Raymo, M.E. et al. (2006) ‘Plio-Pleistocene Ice Volume, Antarctic Climate, and the Global’, Nature, 313(July), pp. 492–495. Available at: https://doi.org/10.1126/science.1123296.

 

How to cite: Thomas, N., Hodell, D., Ford, H., and Greaves, M.: Temperature and salinity changes in the abyssal Atlantic and Pacific Oceans over the Middle Pleistocene Transition, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5365, https://doi.org/10.5194/egusphere-egu24-5365, 2024.

EGU24-5630 | ECS | Orals | CL1.2.5

Inferring past temperature from δ15N measurements in air bubbles trapped in Antarctic ice 

Marie Bouchet, Amaëlle Landais, Frédéric Parrenin, Etienne Legrain, Emilie Capron, Antoine Grisart, Frédéric Prié, Thomas Extier, Roxanne Jacob, Aurélien Quiquet, Christophe Dumas, and Anna Klüssendorf

Ice cores are unique archives capturing records of past temperature (through the ice isotopic composition, e.g. δD) and past atmosphere composition over the last 800 kyr. In particular, their analysis revealed that glacial-interglacial transitions, altering the Earth's climate since the beginning of the Quaternary, are associated with significant variations in the atmospheric levels of CO2 and CH4. However, comparison of past temperatures imprinted in ice-phase and atmospheric composition records imprinted in the air-phase is difficult. Indeed, the air is trapped at a depth of 50-100 m, at the bottom of the firn, where snow transforms into ice. Therefore, at a given depth, the air is always younger than the ice and firn densification modeling is needed to estimate the age difference between the air and the ice at each level. Firn densification modeling is associated with large uncertainties when it is applied to low accumulation and low temperature drilling sites of the East Antarctic plateau.

An alternative approach to reconstruct air temperature directly in the air bubbles involves analyzing the isotopic composition of N2 (δ15N). Indeed, local temperature and accumulation rate evolutions affect firn thickness and hence modulated the δ15N in air bubbles trapped at the bottom of the firn via gravitational enrichment of δ15N over large glacial-interglacial transition on the East Antarctic plateau. The observation of a robust correlation between ice core records of δ15N and δD (Dreyfus et al., 2010) confirms the strong influence of local climate on the δ15N. δ15N measurements have already been applied to determine the phasing between CO2 and temperature increases over Antarctic temperature increase associated with glacial terminations. However, this strong relationship between δ15N and δD is not necessarily valid outside of glacial terminations. Here, we address the question to what extent the δ15N can be used to infer past temperatures and to study the CO2-temperature relationship, hence circumventing age uncertainties that arise when comparing ice and gas phase measurements.

We first examine the δ15N record from EPICA Dome C with respect to East Antarctic climate over the last eight glacial-interglacial cycles. We use the good agreement between δD and δ15N over Termination II as a satisfactory criterion to discern when the δ15N is a reliable proxy of past temperature. Using this criterion, we assert that the correlation between δ15N and δD is robust over the past eight terminations. Focusing on the 100-300 ka BP period, we note also three intervals characterized by a weak correlation: the glacial inceptions from MIS 7e to 7d and 7a to 6e, and the MIS 6 glacial period. To explain why δ15N and δD evolutions contrast over these periods, we connect water stable isotopes with new δ15N measurements from EDC ice core and explore various snow densification scenarios yielded by a firn model under different climate conditions at the ice sheet surface. Our study permits to identify a criterion to safely use δ15N as an indicator of the past temperature in the air bubbles of the EDC ice core to study the CO2-local temperature relationship.

How to cite: Bouchet, M., Landais, A., Parrenin, F., Legrain, E., Capron, E., Grisart, A., Prié, F., Extier, T., Jacob, R., Quiquet, A., Dumas, C., and Klüssendorf, A.: Inferring past temperature from δ15N measurements in air bubbles trapped in Antarctic ice, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5630, https://doi.org/10.5194/egusphere-egu24-5630, 2024.

EGU24-5995 | Orals | CL1.2.5

Little glacial/interglacial net change in Southern Ocean bioproductivity over termination II - an integrated sulfate isotope ice core perspective 

Hubertus Fischer, Andrea Burke, James Ray, Patrick Sugden, Eric Wolff, Helena Pryer, Emily Doyle, Mirko Severi, Bradley Markle, Maria Hörhold, Johannes Freitag, Birthe Twarloh, and Tobias Erhardt

Glacial export productivity in the glacial Southern Ocean may have been enhanced due to iron fertilization from aeolian dust input. Marine sediments indicate such a glacial increase north of the modern Antarctic Polar Front but reduced biogenic activity and reduced nitrogen supply by upwelled deep waters south of it. Due to the sparsity of Southern Ocean sediment data, deriving an overall estimate of marine productivity changes is, however, difficult to achieve. Due to their larger spatial footprint, additional information on basin-wide productivity changes can be obtained from marine biogenic aerosol tracers in Antarctic ice cores.

We use SO42- concentrations and its sulfur isotopic composition as well as other geochemical tracers in the EPICA Dronning Maud Land (EDML) ice core in the Atlantic Sector of the Southern Ocean (AS-SO) to provide the first complete glacial/interglacial source decomposition of total SO42- from the penultimate glacial to the last glacial inception. Our isotopic source decomposition shows that despite other (e.g. terrestrial) sources being significant contributors to total SO42- during glacial times, biogenic SO42- production is always the dominant source at EDML. Using information on recent dimethylsulfide emissions and aerosol forward modeling, we can show that biogenic sulfate recorded in the EDML ice core is derived from the AS-SO south of 35°S but the major source lies south of 50°S, i.e., mainly the seasonal sea ice zone. During the penultimate glacial these sources shifted about 4° northward in parallel to sea ice expansion.

Taking reduced wet deposition of biogenic sulfate aerosol during glacial times into account, we can show that the biogenic sulfate production during the Penultimate Glacial Maximum and the Last Interglacial integrated over the AS-SO may have been only slightly higher in the penultimate glacial and differed by less than 15%. We see millennial biogenic sulfur changes of the same order during the Last Interglacial, which we attribute to temporal changes in the seasonal sea ice zone. An early interglacial productivity minimum in our biogenic sulfate record parallels within age uncertainties features previously reported in the literature, i.e., a minimum in winter, thus seasonal, sea ice extent, a stagnation event in Antarctic Bottom Water and a maximum in summer surface temperature encountered during the early LIG.

How to cite: Fischer, H., Burke, A., Ray, J., Sugden, P., Wolff, E., Pryer, H., Doyle, E., Severi, M., Markle, B., Hörhold, M., Freitag, J., Twarloh, B., and Erhardt, T.: Little glacial/interglacial net change in Southern Ocean bioproductivity over termination II - an integrated sulfate isotope ice core perspective, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5995, https://doi.org/10.5194/egusphere-egu24-5995, 2024.

EGU24-6781 | ECS | Orals | CL1.2.5

Late Pliocene and Early Pleistocene CO2 and CH4 from ice cores from the Allan Hills, Antarctica 

Julia Marks Peterson, Sarah Shackleton, Jeffrey Severinghaus, Edward Brook, John Higgins, Andrei Kurbatov, Yuzhen Yan, Christo Buizert, Michael Kalk, Ross Beaudette, Austin Carter, Jenna Epifanio, and Jacob Morgan

Currently, chronologically discontinuous ice cores from the Allan Hills Blue Ice Area (BIA), Antarctica, are our only direct insight into the atmospheric composition of periods beyond the continuous ice core record (800 ka BP). An accurate and precise greenhouse gas history beyond 800 ka would aid understanding of the mechanisms involved in the climatic transitions across the late Pliocene and early Pleistocene. Here we present carbon dioxide (CO2) and methane (CH4) results from a new core from the Allan Hills BIA (ALHIC1901). The bottom 25 m of ALHIC1901 contain 52 sampled depths with co-registered 40Aratm dates (Shackleton et al. in prep), measurements of δD of ice, δ18Oatm, and concentrations of CO2 and CH4 in trapped air. Of these samples, 25 are older than the continuous ice core record, with ages from 821 ± 80 ka to 2700 ± 270 ka. The bottom meter contains ice from the Pliocene with ages from 2700 ± 270 ka to 4000 ± 400 ka. The carbon isotope ratio of CO213C-CO2) was measured on 18 samples to examine the possibility of input of non-atmospheric CO2 from oxidation of organic matter. Our results indicate that CO2 and CH4 levels were similar in the early Pleistocene to those found for the last 800 ka. A small decline of approximately 20 ppm is seen in CO2 across the Pleistocene, and no secular trend is observed in CH4. Pliocene-aged samples appear to contain a mixture of atmospheric CO2 and CO2 derived from respiration of organic matter at the glacier bed. Using an isotope mixing model we estimate that atmospheric CO2 was lower than 350 ppm at ~3.1 Ma,

How to cite: Marks Peterson, J., Shackleton, S., Severinghaus, J., Brook, E., Higgins, J., Kurbatov, A., Yan, Y., Buizert, C., Kalk, M., Beaudette, R., Carter, A., Epifanio, J., and Morgan, J.: Late Pliocene and Early Pleistocene CO2 and CH4 from ice cores from the Allan Hills, Antarctica, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6781, https://doi.org/10.5194/egusphere-egu24-6781, 2024.

EGU24-8041 | Orals | CL1.2.5

Progress report on Beyond EPICA – oldest ice (BE-OI) Little Dome C (LDC) activity 

Frank Wilhelms and the LDC field parties 2022/2023 & 2023/2024, drill & science workpackage, stable isotope field measurements group

The European Project for Ice Coring in Antarctica (EPICA) Beyond EPICA – oldest ice aims at retrieving a continuous ice core record of climate feedback and forcing spanning about 1.5 Ma back in time. After determining a suitable drill-site LDC during an extensive pre-site survey 35 km southwest of Concordia station, we are in the second deep drilling season. At the time of submission of this abstract, we penetrated beyond 1604.92 m, roughly spanning one glacial-interglacial cycle. We will report on the drilling and core processing activities and verify the prognostic age scale by comparison with dielectric profiling (DEP) and stable isotope saw dust measurements in the field.

How to cite: Wilhelms, F. and the LDC field parties 2022/2023 & 2023/2024, drill & science workpackage, stable isotope field measurements group: Progress report on Beyond EPICA – oldest ice (BE-OI) Little Dome C (LDC) activity, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8041, https://doi.org/10.5194/egusphere-egu24-8041, 2024.

The Arctic Ocean is one of Earth's most dynamically evolving regions, especially for orbital timescale during the Quaternary marked by the waxing and waning of continental ice sheets in the circum-Arctic. The consequential environmental shifts have been imprinted in marine sedimentary deposits in the Arctic Ocean, rendering them invaluable for paleoclimatic and paleoceanographic subjects. Despite their potential significance, the accurate chronology of these sediment records remains debatable due to numerous uncertainties from different dating methods, resulting in difficulties in paleoenvironmental reconstruction. Even widely used absolute age measurement techniques, for example, such as radiocarbon dating using calcareous microfossils, have exhibited limitations in certain cases. To address these challenges and enhance the precision of age determination for Arctic Ocean marine sediments, this study aims to assess and compare various dating methods comprehensively. By critically examining their strengths and weaknesses, it can be sought to establish a more robust framework for constraining the ages of marine sedimentary sequences in the Arctic Ocean. Additionally, this research endeavors to explore the implications of improved chronological accuracy for reconstructing paleoenvironmental conditions in the Arctic Ocean. By refining the timeline of past events, it can be anticipated that a clearer picture of the interplay between ice sheet dynamics, oceanic circulation, and climatic variations will emerge.

How to cite: Park, K.: Stratigraphic correlation across the western to central Arctic Ocean for Quaternary Paleoenvironmental reconstruction, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8220, https://doi.org/10.5194/egusphere-egu24-8220, 2024.

EGU24-8444 | Orals | CL1.2.5

A 1.4 Myr record of export production at the Pacific entrance of the Drake Passage considering syndepositional redistribution of sediments 

Maria H. Toyos Simon, Frank Lamy, Carina B. Lange, Jordan T. Abell, Lester Lembke-Jene, Helge W. Arz, and Gisela Winckler

Increased export production in the Subantarctic Zone of the Southern Ocean has been proposed as a key mechanism for explaining carbon drawdown during glacial times. Therefore, reconstructions of oceanic particle fluxes from the sedimentary record in this sector are vital. Traditionally, fluxes of various materials to the seafloor have been estimated from stratigraphy-based mass accumulation rates (MARs), which are calculated using a combination of sediment dry bulk density and linear sedimentation rates between dated sediment horizons. We refer to these MARs here as age model-derived bulk MAR (BMARs). However, BMARs and any resulting paleoceanographic interpretations may suffer from substantial errors if lateral redistribution of sediments is not considered. In fact, this is expected to be a common phenomenon in the Southern Ocean due to the strong bottom water circulation of the Antarctic Circumpolar Current. Here, using material from a marine sediment core recovered at the Pacific entrance of the Drake Passage, we evaluate export production and its drivers over the past 1.4 million years by applying several paleoproductivity indicators (biogenic barium, organic carbon, biogenic opal, calcium carbonate, and iron). Crucially, we determine MARs of these various sediment components that are corrected for the lateral movement of sediments that occurred simultaneously to or soon after initial deposition. The results show that the export production indicators varied according to some of the characteristic features of the main climatic events of Earth over the past 1.4 Ma. (The Mid-Pleistocene Transition and Mid-Brunhes Event). Additionally, the productivity response in the area was enhanced (weakened) during globally strong (faint) glacials or interglacials (e.g., MIS 16, MIS 11, MIS 5, and the Holocene for strong and MIS 15-12 for weak responses, respectively).

How to cite: Toyos Simon, M. H., Lamy, F., Lange, C. B., Abell, J. T., Lembke-Jene, L., Arz, H. W., and Winckler, G.: A 1.4 Myr record of export production at the Pacific entrance of the Drake Passage considering syndepositional redistribution of sediments, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8444, https://doi.org/10.5194/egusphere-egu24-8444, 2024.

EGU24-9245 | ECS | Posters on site | CL1.2.5

Simulating ice sheets during Pleistocene glacial cycles: A dance of CO2, ice and orbital cycles 

Meike D.W. Scherrenberg, Roderik S.W. van de Wal, and Constantijn J. Berends

During the Mid Pleistocene Transition (MPT; 1.2-0.7 Ma) glacial cycle periodicity shifted from 40 thousand years (ka) to an average 100 ka. While orbital cycles have a large influence on glacial cycle periodicity, the MPT took place without any clear change in the power spectrum of the orbital forcing. This suggests that the MPT must have resulted from Earth system processes rather than a change in external forcing.

In this study, we use an ice-sheet model to simulate the evolution throughout the past 1.5 million years of the Laurentide, Eurasian, Greenland and Antarctic ice sheets. We force the model with last glacial maximum and pre-industrial climate time-slices from the PMIP4, which are interpolated according to prescribed CO2 and insolation reconstructions, as well as modelled ice-sheet geometry, thereby implicitly including the temperature-albedo and precipitation-topography feedbacks.

We show that forcing the model with the combination of CO2 and insolation can capture the 40 ka cycles before the MPT and the 100 ka cycles after the MPT, without requiring a change in the ice-sheet model set-up. Deglaciations are initiated when the combination of CO2 and insolation creates a warm enough climate. Before the MPT, these conditions are met in almost all 40 ka cycles, as interglacial CO2 levels are high enough to cause deglaciations. After the MPT, interstadial CO2 levels tend to be low enough not to trigger a deglaciation during orbital maxima, resulting in longer glacial cycles. Results are most sensitive to the parameterization of the basal friction. Increased basal friction leads to more merged cycles before the MPT. Decreased basal friction will result in an increased likelihood for interstadial CO2 and insolation levels to result in complete melt of the North American ice sheet.

How to cite: Scherrenberg, M. D. W., van de Wal, R. S. W., and Berends, C. J.: Simulating ice sheets during Pleistocene glacial cycles: A dance of CO2, ice and orbital cycles, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9245, https://doi.org/10.5194/egusphere-egu24-9245, 2024.

EGU24-9485 | ECS | Orals | CL1.2.5

Late Pleistocene hydroclimatic and vegetation changes in Northeast Brazil: which role played the western tropical Atlantic? 

Louis Rouyer-Denimal, Aline Govin, Ioanna Bouloubassi, Ana Luiza Albuquerque, Thanh Thuy Nguyen Tu, Magloire Mandeng-Yogo, Christelle Anquetil, and Arnaud Huguet

   Nowadays, the hydroclimate of the semi-arid Northeast Brazil is tightly linked with, inter alia, temperature of the adjacent Atlantic Ocean and its interactions with the Atmosphere. The short humid season peaks in April while (i) the intertropical convergence zone (ITCZ) is at its southernmost position, (ii) the southern tropical Atlantic is warm and (iii) the southeast trade winds are weak. Uncertainties remain on past long-term hydroclimate changes and on the drivers controlling these variations in the NE Brazil region. One of the reasons is the lack of available long-term paleoclimate records.

   Very recently, we reconstructed ocean temperature changes in the western tropical Atlantic on glacial-interglacial time scales and highlighted relatively cold (warm) upper ocean waters during glacial (deglacial and interglacial) intervals over the last 300 000 kyr1. It remains unknown how these changes impacted the NE Brazilian hydroclimate on orbital time scales. This work aims at examining the response of continental vegetation to variations in the western tropical Atlantic heat content over the last two climatic cycles. We used the same sedimentary core (GL-1180) collected off the NE Brazilian margin on which temperature reconstructions were conducted.

   We developed a multi-proxy approach at a 2 kyr temporal resolution to reconstruct the sources and the composition of the sedimentary organic matter (OM) produced on-land and within the water column at both bulk and molecular scales. We first investigated the organic signature of present-day dry (caatinga) and humid (Atlantic tropical forest) vegetation in our study area using modern litter samples. After statistical investigations, we developed new local vegetation proxies based on the relative abundance of long-chain n-alkanes (n-C33/[n-C29+n-C31+n-C33]), n-alkenes (n-C27/[n-C27+n-C28]) and n-alkan-1-ols (n-C28/[n-C28+n-C30]). Secondly, we reconstructed vegetation dynamics and hydroclimate changes using these new proxies together with the bulk elemental (%Corg, %Ntot) and isotopic (δ13Corg, δ15Ntot) composition and the molecular isotopic composition (δ13C) of specific C29 and C31 n-alkanes. We found that a caatinga-like dry vegetation expanded during arid glacial periods while humid conditions prevailed over interglacial intervals in agreement with previous regional studies. Comparing our vegetation and upper ocean temperature records, we highlighted that continental humid (arid) conditions occured during intervals of warm (cold) western tropical Atlantic and weak (strong) southeast trade winds.

   In conclusion, our work highlights glacial-interglacial vegetation and hydroclimate changes in NE Brazil. It further shows that the heat content of the tropical Atlantic was a major driver of these changes over the last 300 000 kyr. In addition, we suggest that the three major features (Atlantic heat content – ITCZ – SE trades) were likely controlling together hydroclimate changes and vegetation dynamics over, at least, the last two climatic cycles.

1Rouyer-Denimal et al., 2023. QSR 321, DOI: 108370. 10.1016/j.quascirev.2023.108370

How to cite: Rouyer-Denimal, L., Govin, A., Bouloubassi, I., Albuquerque, A. L., Nguyen Tu, T. T., Mandeng-Yogo, M., Anquetil, C., and Huguet, A.: Late Pleistocene hydroclimatic and vegetation changes in Northeast Brazil: which role played the western tropical Atlantic?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9485, https://doi.org/10.5194/egusphere-egu24-9485, 2024.

EGU24-10240 | ECS | Posters on site | CL1.2.5

Signal Preservation in the Deepest Part of the EPICA Dome C Ice Core and Application to Palaeoclimate Reconstruction from 600,000 to 800,000 years ago 

Anna Klüssendorf, Amaëlle Landais, Mathieu Casado, Grégory Teste, Frédéric Prié, Marie Bouchet, and Romilly Harris Stuart

In the framework of the new ice core project Beyond EPICA an ice core is currently being drilled to provide a climate record extending over the past 1.5 million years. This ice core will cover the Mid-Pleistocene Transition (~1.2 − 0.8 million years before present) where the glacial-interglacial cycles shifted from following the obliquity to the eccentricity periodicity, as well as the Marine Isotope Stage 19 interglaciation which is considerably the best analogue for a natural Holocene climate regarding the orbital configuration. However, dating the old ice and the interpretation of the climate signal is hampered by extensive annual layer thinning at that depth, high basal temperatures close to melting point, and long residence time favouring diffusive exchanges leading to muted signals even if high-resolution data can be obtained. We are particularly concerned by the possible diffusion of the δ(O2/N2) and δ18O of O2 signals in the deepest part since these two parameters, measured in the air bubbles, are essential tools to provide dating of the deep part of the ice core. To investigate how these signals will be preserved in the bottom part of the ice core after diffusion, we present new high-resolution records of the elemental and isotopic composition of O2 and N2 from the deepest 200 m of the EPICA Dome C ice core spanning over the period from 600,000 to 800,000 years before present. We address the effect of diffusion by comparing the amplitude of the orbital scale variability of the δ(O2/N2) and δ18O of O2 signals in the deepest part of the EPICA Dome C ice core to the expected amplitude of these signals without diffusion and propose some perspectives for the analysis of the Beyond EPICA ice core.

How to cite: Klüssendorf, A., Landais, A., Casado, M., Teste, G., Prié, F., Bouchet, M., and Harris Stuart, R.: Signal Preservation in the Deepest Part of the EPICA Dome C Ice Core and Application to Palaeoclimate Reconstruction from 600,000 to 800,000 years ago, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10240, https://doi.org/10.5194/egusphere-egu24-10240, 2024.

EGU24-11250 | Orals | CL1.2.5

Reinforced precipitation in Eurasia as an important feedback mechanism contributing to the Middle Pleistocene Transition ice-sheet expansion 

Maria Fernanda Sanchez Goñi, Thomas Extier, Josué M. Polanco-Martinez, Coralie Zorzi, Teresa Rodrigues, and André Bahr

The late Middle Pleistocene Transition (MPT, ~ 800-670 thousand years before present, ka) was characterised by the emergence of large glacial ice-sheets associated with anomalously warm  mid North Atlantic sea surface temperatures (SST) enhancing moisture production. Still, the moisture transport across Eurasia towards high northern latitudes is poorly constrained despite its potential role as feedback mechanisms feeding the ice caps. To reconstruct late MPT moisture production and spreading, we combine records of upper ocean temperature and pollen-based Mediterranean forest cover, a tracer of westerlies and precipitation, from a subtropical drill-core collected off SW Iberia Margin, with records of East Asia summer monsoon (EASM) strength and West Pacific surface temperatures, and compare them with the iLOVECLIM model simulations. We observe that the strongest Mediterranean forest development occurred during Marine Isotope Stage (MIS) 17, centered at 700 ka, reflecting a high amount of regional winter precipitation. In contrast, MIS 19 (~785 ka), under the influence of both similar ice volume and higher atmospheric CO2 concentration, is marked by limited forest expansion indicating lower winter precipitation in SW Europe compared to MIS 17. More interestingly, the MIS 18 glacial was more forested, reflecting stronger winter rainfall, compared to the preceding MIS 19, despite that the latter interglacial was characterised by higher insolation, sea level, atmospheric CO2 concentrations and similar warm SST. The long-term increasing trend in winter precipitation in SW Europe parallels the trend of the EASM strength that reached high levels during MIS 18. The model results show high amount of winter rainfall in SW Europe and enhanced EASM (based on the modelled East Asian δ18Ocalcite and summer precipitation) for the three MISs. Similar SW European tree fraction percentages are also modelled during MIS 18 and MIS 19, as inferred from the pollen data. In contrast to the proxy data, the simulated tree fraction is the weakest during MIS 17. The simulated winter rainfall is the highest during MIS 17, but the simulated EASM is the lowest during MIS 18. This mismatch between model and proxy reconstructions could be explained by the difficulty in quantitatively estimating the forest cover from pollen data and/or the result of a feedback process that is not well reproduced in the model such as the poor prediction of the intensity and position of the oceanic moisture source despite a robust SST simulation. Here the data show that SW European winter precipitation and EASM strength reached high levels during the MIS 18 glacial. We explained that this anomalous situation was caused by nearly-continuous moisture supply from both Pacific and Atlantic oceans and its transport to higher latitudes through the westerlies, likely fueling the accelerated expansion of northern hemisphere ice-sheets during the late MPT.

How to cite: Sanchez Goñi, M. F., Extier, T., Polanco-Martinez, J. M., Zorzi, C., Rodrigues, T., and Bahr, A.: Reinforced precipitation in Eurasia as an important feedback mechanism contributing to the Middle Pleistocene Transition ice-sheet expansion, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11250, https://doi.org/10.5194/egusphere-egu24-11250, 2024.

The Mid-Pleistocene Transition (MPT) is a period marked by significant changes in the LR04 benthic δ18O record. During this interval (ca. 1.25-0.65 Ma), glacial cycles shifted from symmetrical 41-thousand-year (kyr) cyclicity to asymmetrical 100-kyr cycles. This transition was characterized by a number of large-scale ice sheets, including terrestrial-based ice sheets in the northern hemisphere (e.g.,  the Laurentide and Greenland ice sheets) and a marine-based ice sheet in the southern hemisphere (e.g., the West Antarctic Ice Sheet). Since these different ice sheets respond to climate variability in unique ways, the LR04  stack may fail to capture certain aspects of regional cryospheric behavior across the MPT. Specifically, a potential lag in ice-rafted debris (IRD) fluxes, hinting at possible bipolarity in glacial terminations. This study aims to investigate glacial weathering fluxes from West Antarctica across the MPT by constructing an osmium isotope chemostratigraphic record in conjunction with published IRD records from IODP site U1536 in Iceberg Alley, in the Scotia Sea. This record will be compared to a previously published record from the IRD Belt in the North Atlantic. By examining glacial weathering products in regions with high accumulation of glacially-derived debris, these two records will provide a comprehensive comparison of cryospheric behavior in the North and South Atlantic across the MPT. This new dataset will offer a more detailed perspective of global cryospheric behavior during the MPT and may reveal synchronicity between the two hemispheres.

How to cite: Goss, G. and Rooney, A.: Investigating glacial weathering fluxes from West Antarctica across the Mid-Pleistocene: Insights from  Os isotopes, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11738, https://doi.org/10.5194/egusphere-egu24-11738, 2024.

EGU24-11973 | ECS | Posters on site | CL1.2.5

Sea-ice variability along the Antarctic continental margin since the Last Penultimate Glacial  

Wee Wei Khoo, Juliane Müller, Oliver Esper, Wenshen Xiao, Christian Stepanek, Paul Gierz, Gerrit Lohmann, Walter Geibert, and Gesine Mollenhauer

Antarctic sea ice plays a crucial role in buttressing ice shelves, enhancing their stability, and protecting them from potential catastrophic collapse – a significance underscored by recent calving events along the Antarctic Peninsula. Presence or absence of sea ice in the Southern Ocean, and details of its distribution patterns, therefore have relevance far beyond the realm of high latitudes of the Southern Hemisphere. Investigating past sea-ice conditions in proximity to ice shelves, and changes in sea ice distribution over time, particularly across glacial-interglacial cycles, is therefore essential. We may gain insights into the sea-ice’s response to a changing climate, and address gaps in our understanding of ocean-sea ice-ice shelf interactions and dynamics. In our study, we adopt a multiproxy approach to explore glacial-interglacial environmental variability since the Last Penultimate Glacial close to the Antarctic continental margin in the Weddell Sea. We analyze the novel sea-ice biomarker IPSO25 (a di-unsaturated highly branched isoprenoid (HBI)), open-water biomarkers z-/e-trienes (tri-unsaturated HBI), diatom assemblages and primary productivity proxies in a marine sediment core (PS118_63-1) retrieved from Powell Basin in the northwestern Weddell Sea. These biomarkers are reliable proxies for reconstructing near-coastal sea-ice conditions in the Southern Ocean, where the use of sea ice-related diatoms may be subject to bias due to silica dissolution. We present the first continuous record of ice-proximal Antarctic sea ice since the Last Penultimate Glacial. Our results unveil a highly dynamic environment, characterized by significant shifts from a climate with perennial (sea) ice cover to more seasonal sea-ice cover and open ocean conditions, over the last approximately 145 kyrs. Furthermore, to gain a better understanding of the spatial heterogeneity of sea-ice distribution and sea ice-ice shelf system dynamics in the Southern Ocean, we use numerical climate modeling to expand our view across the Southern Ocean, while comparing data from marine cores PS67/219-1 (southern Scotia Sea) and PS128_14 (eastern Weddell Sea) helps track latitudinal sea-ice changes and identify common forces driving sea ice-ice shelf system dynamics along continental margin, respectively.

How to cite: Khoo, W. W., Müller, J., Esper, O., Xiao, W., Stepanek, C., Gierz, P., Lohmann, G., Geibert, W., and Mollenhauer, G.: Sea-ice variability along the Antarctic continental margin since the Last Penultimate Glacial , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11973, https://doi.org/10.5194/egusphere-egu24-11973, 2024.

EGU24-13589 | ECS | Posters on site | CL1.2.5

Early Pleistocene Sediment Record from the Antarctic Zone of the Southern Ocean Dominated by Obliquity 

Bastian Muench, Bella Garrioch, Louisa Bradtmiller, and Katharina Billups

We present an orbital-scale record of percent biogenic silica (opal) at Ocean Drilling Program Site 745B situated in the Antarctic Zone of the Indian Ocean sector of the Southern Ocean spanning a majority of the early Pleistocene (1.1-2.6 Ma). By investigating the relative importance of obliquity versus precession-paced variability in our record, we seek to contextualize the apparent dominance of obliquity pacing in early Pleistocene d18O records. Notably, between 1.1 and 1.8 Ma, both the site’s shipboard magnetic susceptibility record and our biogenic silica record principally exhibit obliquity-related spectral peaks at a periodicity of 41 kyr, with relatively minor spectral power at precessional periodicities (23-19 kyr). During the older part of the record (1.8-2.6 Ma), only d18O and magnetic susceptibility vary at the 41 kyr obliquity periodicity, while the biogenic silica record does not show prominent orbital pacing at any of the major periodicities. We suggest that the surprising dominance of obliquity-paced variability in all records between 1.1 and 1.8 Ma indicate a lack of response of the proxies to precessional forcing during this period. The notable lack of orbital forcing in the opal record before 1.8 Ma may reflect both a more southerly location of the polar frontal zone with respect to the site and thus outside the region of wind-driven upwelling and waters undersaturated with respect to silica prior to the establishment of the opal belt at about 2 Ma.

How to cite: Muench, B., Garrioch, B., Bradtmiller, L., and Billups, K.: Early Pleistocene Sediment Record from the Antarctic Zone of the Southern Ocean Dominated by Obliquity, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13589, https://doi.org/10.5194/egusphere-egu24-13589, 2024.

EGU24-14100 | Orals | CL1.2.5

Stability of interior East Antarctic wind scour and ice flow on glacial-interglacial timescales 

Tyler Fudge, Michelle Koutnik, Duncan Young, Shivangini Singh, Nicholas Holschuh, Shuai Yan, Don Blankenship, and Megan Kerr

The region between Dome A and South Pole has likely preserved ice older than the current 800-thousand-year limit of continuous ice core records; however, until now this region has been largely unexplored. The Center for Oldest Ice Exploration (COLDEX) is currently performing the second of two planned years of airborne geophysical surveys on the Southern flank of Dome A. These surveys are providing new geological and glaciological constraints that we combine with ice-flow models to help target suitable deep ice core sites with the goal of recovering a continuous ice-core record going back at least 1.5 million years.

 

Using the new airborne ice penetrating radar data from COLDEX, as well as existing data from the AGAP project, we investigate how local variations in surface conditions may affect the ice record over time. First, we trace englacial layers and date them at the intersection with the South Pole ice core to infer the rate and pattern of past accumulation averaged over different time intervals. Second, we assess the impact of local zones of wind scour that occur on the Southern flank of Dome A (Das et al, 2013), which is at the upstream edge of the COLDEX airborne survey. Local zones of wind scour that lead to ablation or no accumulation, create time-transgressive unconformities that can be mapped from ice penetrating radar data. While the unconformity is initiated due to a relatively local change in surface conditions, the unconformity trace is imaged for many tens of kilometers downstream as it is advected by ice flow. Because the airborne survey flight lines are oriented along flowlines, the unconformities act as particle trajectories.

 

We use an ice-flow model set up along a flowline to evaluate the surface and flow conditions that develop an unconformity similar to a well-imaged unconformity that is observed in the COLDEX data. The unconformity can be well matched with the simple ice-flow model using a fixed position of the scour zone, indicating that the scour zone has been a persistent feature for the past glacial-interglacial cycle (~100 ka). Consistent with previous work (Das et al, 2013), the scour zones are co-located with subglacial ridges that create steeper surface topography. Thus, the positions of the scour zones are likely independent of the climate state and permanent features on long timescales.

 

By modeling this unconformity trace we can constrain the modern horizontal velocity to ~1.5 m/yr near the scour zone that is located ~400 km from Dome A. The unconformity disrupts the continuity of all of the dated internal layers, which extend to 94 ka. Running the model back 1.5 Ma, we can evaluate where the climate record is disrupted at different positions along the flowline. The farther downstream a potential drill site is, the more problematic the unconformities become for obtaining a continuous climate record because the unconformity disrupts the continuity at deeper depths and older ages.

How to cite: Fudge, T., Koutnik, M., Young, D., Singh, S., Holschuh, N., Yan, S., Blankenship, D., and Kerr, M.: Stability of interior East Antarctic wind scour and ice flow on glacial-interglacial timescales, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14100, https://doi.org/10.5194/egusphere-egu24-14100, 2024.

EGU24-14335 | ECS | Orals | CL1.2.5

Early-Mid Pleistocene ice core records of Antarctic and global cooling  

Sarah Shackleton and the Allan Hills Blue Ice Coring Team

Here we present water isotope and noble gas data from the Allan Hills, Antarctica, which provide insight into the local and global climate extending through the Mid Pleistocene Transition and beyond. The Allan Hills blue ice archive provides snapshots of climate that extend well beyond continuous ice core records, but their interpretation has challenges, including complex stratigraphy, potential preservation bias, and highly thinned records.  The water isotope and noble gas data (which come from the same ice samples) suggest a statistically significant correlation between Antarctic temperature and mean ocean temperature, consistent with previous studies. However, we observe subtle differences between these climate reconstructions, including within the mid-Pleistocene transition. We discuss these datasets in the context of broader global changes, and the nuances of the Allan Hills archives.

How to cite: Shackleton, S. and the Allan Hills Blue Ice Coring Team: Early-Mid Pleistocene ice core records of Antarctic and global cooling , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14335, https://doi.org/10.5194/egusphere-egu24-14335, 2024.

The weakening or shutdown of Atlantic Meridional Overturning Circulation (AMOC) likely played a significant role in the glacial inception during the past million years. Previous modeling studies have shown that orbital forcing could have been triggered multiple AMOC weakening or shutdown, but it is still unclear which orbital parameter is the most essential trigger. In this study, we performed multiple long simulations with a fully coupled atmosphere-ocean general circulation model, CESM1.2.2, to investigate the influence precession on AMOC. It is found that precession is able to trigger a shutdown of AMOC. However, this happens only when the eccentricity is high and the atmospheric CO2 concentration is relatively low. The growth and expansion of Arctic sea ice is responsible for the shutdown. Therefore, the results may advance our understanding of the mechanisms driving the glacial-interglacial cycles of the Quaternary Period, and may be related to the mid-Pleistocene transition.

How to cite: Liu, Y. and Liu, H.: Shutdown of Atlantic Meridional Overturning Circulation Induced by Precession, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14755, https://doi.org/10.5194/egusphere-egu24-14755, 2024.

EGU24-15013 | Orals | CL1.2.5

A one-dimensional temperature and age modeling study for selecting the drill site of the oldest ice core near Dome Fuji, Antarctica 

Ayako Abe-Ouchi, Takashi Obase, Fuyuki Saito, Shun Tsutaki, Shuji Fujita, Kenji Kawamura, and Hideaki Motoyama

The recovery of a new Antarctic ice core spanning the past  1.5 million years will advance our understanding of climate system dynamics during the Quaternary. Recently, glaciological field surveys have been conducted to select the most suitable core location near Dome Fuji (DF), Antarctica. Specifically, ground-based radar-echo soundings have been used to acquire highly detailed images of bedrock topography and internal ice layers. In this study, we use a one-dimensional (1-D) ice-flow model to compute the temporal evolutions of age and temperature, in which the ice flow is linked with not only transient climate forcing associated with past glacial–interglacial cycles but also transient basal melting diagnosed along the evolving temperature profile. We investigated the influence of ice thickness, accumulation rate, and geothermal heat flux on the age and temperature profiles. The model was constrained by the observed temperature and age profiles reconstructed from the DF ice-core analysis. The results of sensitivity experiments indicate that ice thickness is the most crucial parameter influencing the computed age of the ice because it is critical to the history of basal temperature and basal melting, which can eliminate old ice. The 1-D model was applied to a 54 km long transect in the vicinity of DF and compared with radargram data. We found that the basal age of the ice is mostly controlled by the local ice thickness, demonstrating the importance of high-spatial-resolution surveys of bedrock topography for selecting ice-core drilling sites.

How to cite: Abe-Ouchi, A., Obase, T., Saito, F., Tsutaki, S., Fujita, S., Kawamura, K., and Motoyama, H.: A one-dimensional temperature and age modeling study for selecting the drill site of the oldest ice core near Dome Fuji, Antarctica, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15013, https://doi.org/10.5194/egusphere-egu24-15013, 2024.

EGU24-16061 | Posters on site | CL1.2.5

Insolation triggered abrupt cooling at the end of interglacials and implication for the future  

Qiuzhen Yin, Zhipeng Wu, Ming-Qiang Liang, Andre Berger, Hugues Goosse, and David Hodell

Paleoclimate records show that the end of interglacials of the late Pleistocene was marked by abrupt cooling events. Strong abrupt cooling occurring when climate was still in a warm interglacial condition is puzzling. Our transient climate simulations for the eleven interglacial (sub)stages of the past 800,000 years show that, when summer insolation in the Northern Hemisphere (NH) high latitudes decreases to a critical value (a threshold), it triggers a strong, abrupt weakening of the Atlantic meridional overturning circulation and consequently an abrupt cooling in the NH. The mechanism involves sea ice-ocean feedbacks in the northern Nordic Sea and the Labrador Sea (Yin et al., 2021, doi: 10.1126/science.abg1737). The insolation-induced abrupt cooling is accompanied by abrupt changes in precipitation, vegetation from low to high latitudes and by abrupt snow accumulation in northern polar regions. The timing of the simulated abrupt events is highly consistent with those observed in marine and terrestrial records, especially with those observed in high-resolution, absolutely-dated speleothem records in Asia and Europe, which validates the model results and reveals that the astronomically-induced slow variations of insolation could trigger abrupt climate events.  Our results show that the insolation threshold occurred at the end of each interglacial of the past 800,000 years, suggesting its fundamental role in terminating the warm climate conditions of the interglacials. The next insolation threshold will occur in 50,000 years, implying an exceptionally long interglacial ahead naturally speaking, confirming earlier studies using other models. 

How to cite: Yin, Q., Wu, Z., Liang, M.-Q., Berger, A., Goosse, H., and Hodell, D.: Insolation triggered abrupt cooling at the end of interglacials and implication for the future , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16061, https://doi.org/10.5194/egusphere-egu24-16061, 2024.

EGU24-16073 | Posters on site | CL1.2.5

Ice sheet related glacial/interglacial cyclicity of granitic tetrafluoromethane (CF4) emissions before and after the Mid Brunhes 

Jochen Schmitt, Barbara Seth, Peter Köhler, Jane Willenbring, and Hubertus Fischer

CF4 is a long-lived atmospheric trace gas that was thought to be emitted only by anthropogenic processes. However, small quantities of CF4 are released from a natural source – chemical weathering of granitic rocks generate an atmospheric background concentration that is archived in polar ice. We measured CF4 concentrations over the last 800 kyr and used an inversion to calculate CF4 emission fluxes. We consistently found higher CF4 fluxes for each interglacial, resulting in an increase of atmospheric CF4 concentrations, while glacials show lower CF4 fluxes and declining CF4 concentrations. Different processes might be responsible for this pattern. First, higher CF4 fluxes during warm conditions are expected as chemical weathering rates are known to increase with temperature and precipitation. Second, granitic rocks are not randomly distributed but preferentially located in high northern latitudes which are largely covered by continental ice sheets and permafrost during glacials inhibiting CF4 release as weathering requires liquid water and a connection to the atmosphere. Thus, the waxing and waning of the northern hemispheric ice sheets has a larger leverage on CF4 fluxes than expected from the area alone. Interestingly, the peaks of the CF4 emission fluxes occurred at the starts of the interglacials. Our interpretation is that moraines left behind at the southern fringes of the retreating ice sheets provide easily weatherable material under already warm conditions. Conversely, from the late interglacials throughout the glacials we observe drops in CF4 concentration. The minima of both CF4 concentrations and CF4 fluxes are located at the end of the glacials, i.e. before the deglaciations started. This observation helps to assess the activity of glaciers via their erosional grinding of bedrock which produces suspended fine materials, so-called “glacier flour”.  Because the mineral fluorite, which is typically enclosing CF4 within the granite rock, is highly soluble in water, CF4 would be quickly released after grinding since it should occur in wet conditions. Our data suggest that this process is small compared to the suppression of granite weathering via ice coverage, otherwise the maxima in CF4 fluxes should have been found during glacial maxima.   

On the long-term, our record reveals a marked rise in CF4 fluxes after the Mid Brunhes event (MBE). Beginning with MIS 11, the first strong interglacial after a series of weak interglacials, the glacial/interglacial amplitudes in CF4 emissions but also for CO2 and ice volume increased. For the 430 kyr after the MBE the reconstructed CF4 fluxes increased by ca. 8%, predominantly due to increasing interglacial emissions, especially for MIS 5, 9, 11. We discuss three possible scenarios for this post-MBE rise in granite weathering: First, higher temperatures in northern high latitudes. Second, the exposure of granitic rocks that was ice covered during previous weak interglacials. Third, a remaining fraction of the former regolith covering large parts of North America was eroded during MIS 12 initiating the climatic changes associated with of MBE.        

How to cite: Schmitt, J., Seth, B., Köhler, P., Willenbring, J., and Fischer, H.: Ice sheet related glacial/interglacial cyclicity of granitic tetrafluoromethane (CF4) emissions before and after the Mid Brunhes, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16073, https://doi.org/10.5194/egusphere-egu24-16073, 2024.

EGU24-16932 | Orals | CL1.2.5

Increase in strength and orbital variability of the South Pacific Antarctic Circumpolar Current across the Mid-Pleistocene Transition 

Frank Lamy, Gisela Winckler, Helge Arz, Jesse R. Farmer, Lester Lembke-Jene, Julia Gottschalk, and Maria Toyos

The Antarctic Circumpolar Current (ACC) represents the world’s largest ocean current system and impacts global ocean circulation, climate, and Antarctic ice sheet stability. Today, ACC dynamics are controlled by atmospheric forcing, Southern Ocean density gradients, and mesoscale eddy activity in the southern high latitudes. Yet, its role in driving the lengthening and intensification of glacial cycles is insufficiently studied. Here, we present a 1.5 Ma-record of changes in ACC strength based on bottom water flow reconstructions and sedimentary opal contents at IODP Sites U1540 and U1541 drilled in the Subantarctic Zone (SAZ) of the Pacific Southern Ocean. Our new data indicate that glacial and interglacial ACC strength gradually increased between ~1.3 and ~ 1 Ma coinciding with the early part of the MPT. This interval culminates in a pronounced ACC maximum during Marine Isotope Stage (MIS) 31 at ~1 Ma reaching ~160 % of the mean Holocene values. The increase in subantarctic ACC strength during the initial part of the MPT is paralleled by the emergence of stronger orbital-scale fluctuations in opal contents at both Sites U1540 and U1541 after MIS 31, suggesting a link between the onset of consistently higher amplitude glacial-interglacial fluctuations of ACC changes and latitudinal shifts of the ‘opal belt’ in the Southern Ocean. Specifically, higher opal contents correlate to decreased ACC strength, suggesting that the opal belt extended northward into the SAZ during glacials. We argue that the early change in ACC dynamics at the beginning of the MPT might be linked with sea surface temperature changes in the eastern subtropical and tropical Pacific, because surface cooling by ~2-3 °C at ODP Site 1237 off Peru between ~1.05 Ma and ~0.8 Ma parallels the reconstructed ACC strengthening at IODP Sites U1540 and U1541. This may result from enhanced advection of subantarctic water masses northward along the Humboldt Current system as a response to the intensification of the ACC starting during MIS 31. Our findings emphasize a contribution of Southern Ocean processes to the climate events causing intensification of glacial-interglacial climate variability during the MPT.

How to cite: Lamy, F., Winckler, G., Arz, H., Farmer, J. R., Lembke-Jene, L., Gottschalk, J., and Toyos, M.: Increase in strength and orbital variability of the South Pacific Antarctic Circumpolar Current across the Mid-Pleistocene Transition, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16932, https://doi.org/10.5194/egusphere-egu24-16932, 2024.

The evolution of Earth’s climate during the Quaternary is characterized by glacial cycles with the periodic waxing and waning of large ice sheets most notably in the Northern Hemisphere. A fundamental transition in Earth climate occurred between 1250 and 650 kyr ago (ka) as the dominant glacial-interglacial variability shifted from ~40 to ~100-kyr cycles with more intense glacial climate. This is known as the Mid-Pleistocene Transition (MPT). The absence of appreciable change in the Milankovitch astronomical climate forcings during the MPT indicates that its occurrence might be a result of self-perpetuating climate feedback processes which would have been stimulated at ~900ka (i.e. Marine Isotope Stage 25-22) when global ice volume (e.g. Elderfield et al., 2012, Ford & Raymo, 2020), glacial ocean circulation (e.g. Pena &Goldstein 2014; Kim et al., 2021), deep ocean carbon reservoir (e.g. Lear et al., 2016; Farmer et al., 2019) and atmospheric CO2 levels (e.g. Hoenish et al., 2009; Chalk et al., 2017; Yamamoto et al., 2022) coherently experienced stepwise changes to post-MPT like glacial states from MIS22 onwards. Nevertheless, the triggering mechanism remains enigmatic because of the intertwined nature of these internal processes which precludes the disentanglement into their individual roles in the onset of post-MPT glacial ice volume and the pCO2 level at MIS22.

In this study, applying a combined climate – ice sheet – marine biogeochemical modeling approach, we investigate unidirectional impacts of changes in either atmospheric CO2 levels or northern hemisphere ice sheet (NHIS) volume on the other in transient simulations spanning two successive obliquity cycles. Our results show that the emergence of a 100-kyr glacial cycle is controlled by the interglacial rather than glacial CO2 levels. A lower glacial CO2 levels does increase NHIS volume and hence intensify the glacial climate. But only when the interglacial CO2 levels are below a threshold (~250ppm in our model) at the first obliquity peak, the developed glacial NHISs can skip the summer insolation maximum and reach a larger volume in the following glaciation, heralding the onset of 100-kyr glacial cycles. Meanwhile, the increased glacial NHISs, as a positive climate feedback process, promote atmospheric CO2 absorption in the subpolar North Atlantic via the strengthened upper cell of Atlantic Meridional Overturning Circulation. This, coupled with the enhanced formation of Antarctic Bottom Water, eventually sequesters the absorbed carbon in the North Pacific, further lowering glacial CO2 levels. Consistent with available proxy records, our results thus reconcile previously competing hypotheses for the occurrence of the MPT, providing a new and coherent dynamic framework accounting for the emergence of 100-kyr glacial cycles.

How to cite: Zhang, X., Stap, L. B., Du, J., and Nuber, S.: Control of subpar interglacial CO2 levels on the emergence of 100-kyr glacial cycles during the Mid-Pleistocene Transition, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17220, https://doi.org/10.5194/egusphere-egu24-17220, 2024.

Qualitative faunal analyses of the Recent Antarctic glacjal fjordic cold-water bryozoans from the Admiralty Bay show the dominant ascophoran umbonulomorphs, mostly represented by the endemic species and accompanied by lepraliomorphs, schizoporellids, phidoloporoids, flustrinids, hippothoomorphs and cellaroids. The majority of the studied fauna form large-sized erect robust zoaria either bilamellar folded sheets or erect rigid cylindrical branches (Hara et al., 2010).

Four bryozoan assemblages (37 species) of cheilostomes dominated by ascophoran umbunulomorphs and lepraliomorphs, 4 cyclostomes and 1 ctenostome were analysed from a depth range of 15 to 280 m. The species richness (27 species), biomass and diversity were the greatest is the third assemblage from 120-200 m, where the fauna settled on the muddy substrate in the central part of the fjord. Dominant colony form was the adeoniform represented by erect, bilamellar plates, frondose or folded sheets, branched or lobate zoaria accompanied by numerous erect bugulids attached by chitinous rhizoids covered by epibionts.

The spatial variability in the bryozoan community structure, species richness and biomass are strongly associated with the number of environmental factors such as substrate type, water depth, location within the basin, hydrodynamic regime, influence of the suspended matter inflow or glacial disturbance (Pabis et al. 2014).

Mineralogically, the bryozoan skeletons from the Admiralty Bay are cheilostomes composed of intermediate magnesian calcite (IMC) where the Mg content ranges from ca. 4.3 to 6.5 wt% MgCO3. The bryozoans skeletons exhibit ẟ18O and ẟ13C values typical of cool marine waters (according to the aquition given by Friedman, O’Neil, 1977), see Hara, 2022. Their ẟ18O ranges from ca. 2.25 to 4.3% PBD, with most data clustering between 3 and 4 % PBD. The ẟ13C varies from ca. – 1 to + 1.5% PBD with most data plotted between + 0.5 and +1.5% PBD (Hara et al. 2010).

To add the Cenozoic evolution of the modern community structure occurred more recently, due to the factors such as further cooling and isolation of the continent leading to widespread glaciation, which resulted in a loss of shallow shelf habitats (see also Whittle et al., 2014).

Hara U. Jasinowski M. & Presler P. 2010. Geochemistry and mineralogy of bryozoan skeletons from Admiralty Bay (South Sheltland Islands, Antarctica: a preliminary account, p. 56. Terra Nostra, 15th International Conference IBA.

Hara U., 2022 – Geochemistry of the fossil and Recent bryozoan faunas in the natural diagenetic environments and their significance for the reconstruction of the biota and climatic regimes in Cenozoic. Archive of the Polish Geological Institute-National Research Institute, nr. 5210/2022.

Pabis K, Hara U. Presler P. & Siciński J. 2014. Structure of the bryozoans communities in an Antarctic glacjal fjord (Admiralty Bay), Polar Biology 37: 737-751.

Whittle R.J, Quaglio F., Griffiths H.J., Linse K., Crame J.A., 2014 – The Early Miocene Cape Melville Formation fossil assemblage and the evolution of modern Antarctic marine communities. Naturwissenschaften DOI 10.1007/s00114-013-1128-0.

How to cite: Hara, U.: Fjordic bryozoan community: (Admiralty Bay, King George Island, South Shetlands, West Antarctic) – biodiversity, distribution and geochemistry, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18478, https://doi.org/10.5194/egusphere-egu24-18478, 2024.

EGU24-18691 | ECS | Orals | CL1.2.5

Environmental parameters affect palaeothermometry of Alkenones and GDGTs: A case study at the Southern Chilean Margin (46° S) 

Julia Rieke Hagemann, Alfredo Martínez-Garcia, Frank Lamy, Jérôme Kaiser, Lester Lembke-Jene, Helge W. Arz, Carina B. Lange, and Ralf Tiedemann

Isoprenoid glycerol dialkyl glycerol tetraethers (isoGDGT) and alkenones are widely used tools for reconstructing past sea surface and subsurface temperatures. IsoGDGTs are membrane lipids synthesized by ammonia-oxidizing Nitrososphaerota and contain up to four cyclopentane moieties. Alkenones are unsaturated carbon chains, whose origin is mainly the coccolithophorid algae Emiliania huxleyi. The number of moieties of the isoGDGTs, as well as the degree of unsaturation of the alkenones depends on the ambient water temperature. Both biomarker-synthesizing organisms (Nitrososphaerota and E. huxleyi) are subject to several environmental influences, like nutrient availability, light conditions, salinity changes, changes in the biomarker-producing community, or terrigenous input, that can bias the temperature signal. In this study, we focus on the influence of terrigenous input and changes in salinity on both biomarkers. We use the 17 m-long piston core MR16-069 PC03, which is located at 46° S and ~150 km offshore the Chilean margin. This core covers a full glacial-interglacial cycle (140 ka) and shows recurring high inputs of terrigenous material and freshwater during the glacial period. This extreme contrast between interglacial and glacial is suitable for examining the influence of high terrigenous input on the temperature signal. Due to changes in the depositional setting, our results show a significant change in the expected temperature signal in both proxies during phases of high terrigenous input. We further discuss which temperature calibration is most appropriate for both biomarkers and conclude that for GDGT-based temperatures at this site, a calibration based on the TEXL86 index is more suitable, while for alkenone-based temperatures the UK37 index appears to be most accuracy.

How to cite: Hagemann, J. R., Martínez-Garcia, A., Lamy, F., Kaiser, J., Lembke-Jene, L., Arz, H. W., Lange, C. B., and Tiedemann, R.: Environmental parameters affect palaeothermometry of Alkenones and GDGTs: A case study at the Southern Chilean Margin (46° S), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18691, https://doi.org/10.5194/egusphere-egu24-18691, 2024.

EGU24-18813 | Orals | CL1.2.5

Continuous atmospheric CO2 across the Mid Pleistocene Transition from boron isotopes: decoupling of CO2 from insolation and temperature 

Thomas Chalk, Sophie Nuber, Lennert Stap, Meike Scherrenberg, Xu Zhang, Mathis Hain, Rachel Brown, Jimin Yu, Morten Anderson, Stephen Barker, James Rae, and Gavin Foster

Changes in atmospheric CO2 and global ice volume as a response to changes in insolation are one of the Earth’s most important feedback mechanisms during glacial-interglacial cycles. During the obliquity paced glacial-interglacial cycles of the 41kyr world prior to 1.2 million years ago (Ma), the response between insolation and the CO2-ice volume feedback is relatively linear. However, during the Mid-Pleistocene transition (0.6Ma – 1.2Ma), this linear response breaks down leading to a large increase in ice volume with a relatively modest decrease in CO2 during glacials in late Pleistocene. Here, we present atmospheric CO2 records derived from boron isotopes measured in the planktic foraminifera G. ruber sensu stricto from 3 ocean sediment cores, each well validated against ice records of CO2. We find two notable CO2 features during the MPT, an early de-coupling of CO2 and ice volume from insolation during MIS 36 (~1.05 Ma), where CO2 stays relatively constant despite multiple (but muted) orbital cycles. Secondly, during MIS 22 (0.9Ma), CO2 decreases step-wise, in combination with rising global ice volume, and recovers to “luke-warm style” interglacial levels in the following interglacial MIS 21. The periods of low CO2 and high ice volume occur in line with saltier Atlantic deep waters enriched in δ13C which we interpret as southern origin water masses, and increased ocean carbon storage. We therefore conclude that changes in ocean circulation may have caused an increased uptake of atmospheric carbon during these periods. In contrast, global sea surface temperatures during MIS36 follow insolation and not CO2 suggesting a de-coupling of the CO2/ice volume feedback from insolation and temperature. This may have prepositioned the climate system for the significant CO2 reduction and ice sheet expansion during and after 0.9Ma.

How to cite: Chalk, T., Nuber, S., Stap, L., Scherrenberg, M., Zhang, X., Hain, M., Brown, R., Yu, J., Anderson, M., Barker, S., Rae, J., and Foster, G.: Continuous atmospheric CO2 across the Mid Pleistocene Transition from boron isotopes: decoupling of CO2 from insolation and temperature, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18813, https://doi.org/10.5194/egusphere-egu24-18813, 2024.

EGU24-18855 | ECS | Posters on site | CL1.2.5

Conceptual Model of Global Ice Volume during the Quaternary for the Mid-Pleistocene Transition 

Felix Pollak, Emilie Capron, Zanna Chase, Lenneke Jong, and Frédéric Parrenin

During the Quaternary, the dominant periodicity and amplitude of glacial-interglacial cycles underwent a transition from low-amplitude cycles of 41 kyr to high-amplitude 100 kyr cycles around 1.2-0.8 Myr ago. This transition is known as the Mid-Pleistocene Transition (MPT). The cause of the MPT is still unclear, as there was no change in the external orbital forcing during this time. Various hypotheses have been proposed to explain this phenomenon. Proposed hypotheses include scenarios of gradual and abrupt changes in the climate system over the Pleistocene, with ongoing debate about whether the MPT was triggered by an abrupt or gradual change.

Here, we utilize a conceptual model, which is a zero-dimensional representation of the climate system that simulates the global ice volume over the past 2 Myr. While the standard model is solely driven by orbital forcing namely obliquity and precession, it can be extended to take internal forcing into account, either caused by an abrupt or gradual change during the Pleistocene. Since the gradual setup has been shown to yield the best results, we focus on improving this model configuration by investigating different parameterizations and their influence on the model output. The model is fitted onto reconstructed global sea levels of the past 2 Myr, using a Monte Carlo random walk for tuning the parameters. Once properly tuned, the model can be used to simulate future glacial-interglacial cycles. The objective is to gain further insights into the underlying mechanisms that initiated the MPT and which mathematical features in this model are the most relevant. In future work, this conceptual model could be extended to include other paleoclimatic records like atmospheric CO2 or methane.

How to cite: Pollak, F., Capron, E., Chase, Z., Jong, L., and Parrenin, F.: Conceptual Model of Global Ice Volume during the Quaternary for the Mid-Pleistocene Transition, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18855, https://doi.org/10.5194/egusphere-egu24-18855, 2024.

EGU24-20306 | Orals | CL1.2.5

A first step towards a complete Southern Ocean proxy compilation for the Last Glacial Cycle: glacial-interglacial changes in Sea Surface Temperature 

Lena Thöle, Karen Kohfeld, Zanna Chase, Xavier Crosta, Peter Bijl, and Nicholas McKay

Previous research has suggested that different processes in the Southern Ocean contributed to the drawdown and release of atmospheric carbon dioxide (CO2) during the last glacial cycle (0–130 ka), yet their dynamics and interplay are not fully understood. To unravel the interactions between different processes and to allow for more comprehensive analyses, we aim to compile all previously published proxy data and convert them into the Linked open Paleo Data (LiPD) format, overall increasing interoperability, reusability and impact.

The PAGES C-SIDE working group recently highlighted substantial open-ocean sea-ice extent changes during the mid-glacial period (Marine Isotope Stage 4, ~72 to 60 ka), coinciding with a significant drop in atmospheric CO2. However, sea-ice changes are notably absent during the early glaciation (Marine Isotope Stage 5d, ~115 to 105 ka), suggesting they cannot account for the early CO2 decrease (Chadwick et al., 2022).

As an initial step, we present our compilation of sea surface temperature (SST) reconstructions from marine sediment records across the Southern Ocean (Latitude > 30°S) for the last glacial cycle. This compilation assesses SST changes in different zones and basins, evaluates SST gradients, and explores the interplay between SST and sea ice.

Our findings reveal a consistent glacial-interglacial amplitude of 5-10°C across all basins and zones, with uniform timing. SST gradients from the Antarctic to Subantarctic Zone remain unchanged over time, eliminating them as a mechanism for early CO2 decrease. Additionally, we observe that 50% of the total MIS 5e-to-LGM cooling in Southern Ocean SST occurred from MIS 5e to MIS 5d, with a second drop from MIS 5a to MIS 4, essentially reaching LGM cooling. A distinct decoupling of SST cooling and sea ice expansion over MIS 5 suggests that circulation and/or subsurface temperatures may exert a stronger influence than SST on sea ice extent. This emphasizes the necessity for additional proxy compilations to further disentangle these complex relationships.

How to cite: Thöle, L., Kohfeld, K., Chase, Z., Crosta, X., Bijl, P., and McKay, N.: A first step towards a complete Southern Ocean proxy compilation for the Last Glacial Cycle: glacial-interglacial changes in Sea Surface Temperature, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20306, https://doi.org/10.5194/egusphere-egu24-20306, 2024.

EGU24-25 | Orals | G3.4

Enabling Subglacial Geodesy Through High-Precision Radar Sounding and GNSS Time Series Observations 

Dustin Schroeder, Jasmin Falconer, and Matthew Siegfried

Our capacity to estimate vertical motion of the solid Earth with high precision has transformed our understanding of a variety of Earth processes, including mantle dynamics, plate tectonics, volcanic hazards, earthquake rupture, and surface-water balance. Geodetic observations of solid Earth deformation were first achieved on land with conventional surveying techniques, global navigation satellite system (GNSS) deployment, and satellite remote sensing, then expanded to the global ocean with seafloor geodesy techniques like GNSS-Acoustic (GNSS-A) experiments and fiber-optic sensing. Although we can now assess solid Earth deformation nearly everywhere on Earth, we still have not achieved subglacial geodesy: directly observing uplift or subsidence beneath glaciers and ice sheets. Due to decreasing ice mass, we expect high rates of uplift beneath Earth’s ice masses (i.e., glacial isostatic adjustment, or GIA), but available GNSS observations from exposed rock on the periphery of the Greenland and Antarctic ice sheets suggest uplift rates can be highly variable on 10s of km length scales. Recent observational and modeling studies have suggested that GIA could provide a critical stabilizing feedback for ice-sheet mass loss on decadal and centennial timescales, therefore developing and deploying the technology needed for subglacial geodesy is critical for accurate projections of sea level change, particularly in Antarctica where areas of exposed bedrock are rare. To address this challenge, we present a suite of combined radar sounding / GNSS experiments and systems under development to constrain uplift rates beneath both slow-flowing (< 10 m/yr) and fast-flowing ( > 10 m/yr) ice. We also discuss a range of related systems and experiments under development to constrain and correct for potentially confounding firn compaction signals.

How to cite: Schroeder, D., Falconer, J., and Siegfried, M.: Enabling Subglacial Geodesy Through High-Precision Radar Sounding and GNSS Time Series Observations, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-25, https://doi.org/10.5194/egusphere-egu24-25, 2024.

EGU24-2515 | ECS | Posters on site | G3.4

Towards exact free oscillation spectra through generalised normal mode coupling 

Alex Myhill and David Al-Attar

Long period free oscillation spectra provide one of the main constraints on large-scale lateral structures within the Earth’s mantle. These observations are particularly noteworthy for their direct sensitivity to density variations, which gives them the potential to resolve long-standing questions relating to the nature of the two Large Low Shear Velocity Provinces. However, due to both computational expediency and incomplete theory, there are inaccuracies within existing codes for forward modelling of free oscillation spectra. This has limited the ability of previous studies to reliably infer Earth structure using such observations.

This poster outlines work on a new open-source code for modelling free oscillation spectra within laterally heterogeneous Earth models. We apply a generalised normal mode coupling method that overcomes various limitations with the traditional mode coupling approach. We account fully for the non-linear dependence of the matrix elements on density and boundary topography, and exactly solve the equations of motion. Computational costs have been minimised by using high-performance libraries, and efficient numerical linear algebra, in addition to parallelisation. Our code is also suitable for calculation of sensitivity kernels using the adjoint method. Benchmarks against current codes as well as performance benchmarks are shown to demonstrate the accuracy and efficiency of our new method.

How to cite: Myhill, A. and Al-Attar, D.: Towards exact free oscillation spectra through generalised normal mode coupling, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2515, https://doi.org/10.5194/egusphere-egu24-2515, 2024.

EGU24-3467 | ECS | Posters on site | G3.4

A comparison of linear and non-linear theories for modelling solid Earth dynamics 

Ziheng Yu, Matthew Maitra, and David Al-Attar

To date, most computational work in solid Earth geophysics has been based on linearised continuum mechanics. This is justified so long as deformation from the reference state remains sufficiently small. The dependence on linearisation also reflects computational limitations of the past: most tractable problems relied on geometric symmetries along with linearity to reduce the calculation to the solution of decoupled systems of ordinary differential equations.

Increases in computational power have allowed for increasingly routine applications of fully numerical techniques such as finite-difference, finite-element, and finite-volume methods. This has allowed geophysical problems to be solved in increasingly realistic Earth models. Although for the most part, the equations being solved are the same as linearised ones used previously, keeping nonlinear terms significantly increases the complexity of solution schemes. Within the context of fully numerical methods, non-linear problems are solved using iterative schemes that involve repeated solution of the corresponding linearised equations. This implies that solving non-linear equations should only be appreciably more expensive if non-linear effects are physically important.

Within this presentation, we compare the use of linearised and non-linear equations of motion, focusing on quasi-static elastic and viscoelastic loading problems of relevance to studies of glacial isostatic adjustment. This is achieved using the open-source finite-element package FeniCSx which facilitates rapid development and testing. Starting from simple representative examples, we quantify the errors associated with linearisation along with the added cost of solving non-linear problems.

How to cite: Yu, Z., Maitra, M., and Al-Attar, D.: A comparison of linear and non-linear theories for modelling solid Earth dynamics, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3467, https://doi.org/10.5194/egusphere-egu24-3467, 2024.

EGU24-4786 | Posters on site | G3.4

Towards closing the Australian vertical land movement budget 

Matt King, Carsten Ankjær Ludwigsen, and Christopher Watson

GPS analysis of Australian vertical land motion (VLM) consistently suggests widespread subsidence of Australia of about 1-1.5mm/yr since ~2000, in contrast to most models of Glacial Isostatic Adjustment which predict motion closer to zero or slightly positive. These GPS findings have been corroborated by estimates from altimeter-minus-tide gauge measurements, suggesting they are robust within their terrestrial reference frame. Here we revisit the potential causes for this misfit, exploring a new reconstruction of global ice-loading changes and its impact on vertical land motion. We show this likely produces a subsidence of Australia of about 0.5mm/yr. We explore this in combination with estimates of hydrological, atmospheric and non-tidal ocean loading displacements. The residual signal is discussed within the context of different GIA model predictions, reference frame errors, and the possible impact of far-field postseismic signal.

How to cite: King, M., Ludwigsen, C. A., and Watson, C.: Towards closing the Australian vertical land movement budget, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4786, https://doi.org/10.5194/egusphere-egu24-4786, 2024.

EGU24-5259 | ECS | Orals | G3.4

The lateral heterogeneity of Glacial Isostatic Adjustment modelling across the Arctic 

Tanghua Li, Timothy Shaw, Nicole Khan, F. Chantel Nixon, W. Richard Peltier, and Benjamin Horton

The Arctic has been key area for glacial isostatic adjustment (GIA) studies because it was covered by large ice sheets at the Last Glacial Maximum. Previous GIA studies applied mainly 1D Earth models. The few studies that did include 3D Earth structures have not considered the lateral heterogeneity differences across different regions of the Arctic. Here, using the latest standardized deglacial relative sea-level (RSL) databases from Norway and Russian Arctic, we investigate the effects of 3D structure on GIA predictions and explore the magnitudes of the lateral heterogeneity in both regions.

The 3D Earth structure consists of 1D background viscosity model (ηo) and lateral viscosity variation, the latter is derived from the shear velocity anomaly from seismic tomography model and controlled by scaling factor (ß) denoting the magnitude of lateral heterogeneity.

The Norway RSL database includes 413 sea-level index points (SLIPs), 175 marine limiting data and 433 terrestrial limiting data, while the Russian Arctic database includes 353 SLIPs, 78 marine limiting data and 92 terrestrial limiting data.

We find 3D Earth structures have significant influences on RSL predictions and the optimal 3D model notably improves the fit with RSL data. However, we realize RSL data from Norway and Russian Arctic prefer different 3D structures to provide the best fits. The Russian Arctic database prefers a softer background viscosity model (ηo), but larger scaling factors (ß) than those preferred by Norway database. We further test the extent to which the 3D structure can be eliminated by refinement of ice model.

How to cite: Li, T., Shaw, T., Khan, N., Nixon, F. C., Peltier, W. R., and Horton, B.: The lateral heterogeneity of Glacial Isostatic Adjustment modelling across the Arctic, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5259, https://doi.org/10.5194/egusphere-egu24-5259, 2024.

EGU24-5642 | Orals | G3.4

Polar motion of a 3D viscoelastic earth model: Consequences for GIA signals in GRACE-FO 

Volker Klemann, Meike Bagge, Robert Dill, Jan M. Hagedoorn, Zdeněk Martinec, and Henryk Dobslaw

Surface deformations due to changes in the rotation of the Earth are significantly impacted by glacial isostatic adjustment (GIA). The long-term trend of polar motion contributes to global observations like that of the current satellite gravity mission GRACE-FO. The theory and how to apply this contribution to correct GRACE observational data is well understood and goes back to the concise studies of Mitrovica et al. (2005) and Wahr et al. (2015), respectively. According to the International Earth Rotation Service (IERS), a standard correction method is suggested, where the observed long-term trend of the polar motion is considered to originate from GIA. Recent studies show that the modelled GIA contribution to polar motion strongly depends on structural features of the Earth's interior as well as on the glacial history. Other processes like mantle convection or more recent climatic processes are attributed to contribute as well (Adhikari et al. 2018).

In this presentation we focus on the impact of the Earth's viscosity structure on the modelled polar motion. In addition to its radial stratification, we discuss the influence of lateral variability. We apply the numerical 3D viscoelastic lithosphere and mantle model VILMA, which solves the gravitationally self-consistent field equations in a spherical geometry, and which considers the rotational feedback and the sea-level equation. The theory of Martinec and Hagedoorn (2014) applied here is not based on the normal mode theory, but solves the field equations in the time domain. We show the consistency of the chosen approach and rate the influence of lateral changes in viscosity against the impact of radial viscosity stratification. The study was motivated by the ESA Third Party Mission 'GRACE-FO' and contributes to the German Climate Modelling Initiative 'PalMod'.

Lit:
Adhikari, S, Caron L, Steinberger, B, ..., Ivins, ER (2018). What drives 20th century polar motion? Earth Planet. Sci. Lett. doi:10.1016/j.epsl.2018.08.059
Martinec, Z, Hagedoorn, JM (2014). The rotational feedback on linear-momentum balance in glacial isostatic adjustment. Geophys. J. Int. doi:10.1093/gji/ggu369
Mitrovica, JX, Wahr, J, Matsuyama, I, Paulson, A (2005). The rotational stability of an ice-age earth. Geophys. J. Int. doi:10.1111/j.1365-246X.2005.02609.x
Wahr, J, Nerem, RS, Bettadpur, SV (2015). The pole tide and its effect on GRACE time-variable gravity measurements: Implications for estimates of surface mass variations. J. Geophys. Res. Solid Earth. doi:10.1002/2015JB011986

How to cite: Klemann, V., Bagge, M., Dill, R., Hagedoorn, J. M., Martinec, Z., and Dobslaw, H.: Polar motion of a 3D viscoelastic earth model: Consequences for GIA signals in GRACE-FO, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5642, https://doi.org/10.5194/egusphere-egu24-5642, 2024.

EGU24-5655 | Posters on site | G3.4 | Highlight

Causes of Global Elastic Vertical Land Movement from 1900 to 2022 

Per Knudsen, Carsten Bjerre Ludwigsen, Ole Baltazar Andersen, Matt King, and Christopher Watson

Elastic vertical land movement (eVLM) is the lithosphere's immediate elastic response to the loading and unloading of the Earth's surface mass. Understanding eVLM is crucial for interpreting relative sea level changes, particularly in coastal regions where subsidence or uplift can significantly alter the impacts of sea level changes recorded by tide gauges. Here we present a comprehensive global eVLM model, offering valuable insights for geodesy and related fields, especially in assessing observations from tide gauges and GNSS.

Our eVLM model spans from 1900 to 2022, featuring a 0.5-degree spatial resolution. It provides annual data from 1900 to 1990 and monthly data from 1991 to 2022, enabling both long-term and seasonal assessment. The dataset is available in three different reference frames: Centre of Mass (CM), Centre of Figure (CF), and ITRF2020, and thus suitable for many geodetic applications.

This study incorporates mass change estimations from Greenland, Antarctica, global glaciers, and land water storage (LWS), divided into natural LWS variations and anthropogenic water management like groundwater depletion and dam retention. Thus, we can explain regional VLM patterns that cannot be solely attributed to Glacial Isostatic Adjustment (GIA) models, for example, subsidence across Australia or uplift in Scandinavia that is larger than modeled GIA.

Methodology: We employed a composite loading model, integrating ice models from Greenland (Mankoff et al., 2021) and Antarctica (Otosaka et al, 2022; Nilsson et al, 2022) and glacier models (Hugonnet et al., 2022), GRACE observations, and a land water storage model (Müller-Schmied et al, 2023). Each of the aforementioned five causes of eVLM was perturbed with its uncertainty a thousand times, and the sea level equation was resolved for each variant using the ISSM-SEESAW framework (Adhikari et al., 2016). To align the results with observations in the ITRF2020 reference frame, which mirrors CM on secular timescales and CF on non-secular timescales (Dong et al, 2003). To accommodate this, we applied CM and CF Love loading numbers (Blewitt, 2003) in our calculations, enabling analysis in all three reference frames.

How to cite: Knudsen, P., Ludwigsen, C. B., Andersen, O. B., King, M., and Watson, C.: Causes of Global Elastic Vertical Land Movement from 1900 to 2022, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5655, https://doi.org/10.5194/egusphere-egu24-5655, 2024.

EGU24-5748 | ECS | Orals | G3.4

Rapid Earth uplift in southeast Greenland driven by recent ice melt above low-viscosity upper mantle 

Maaike F. M. Weerdesteijn and Clinton P. Conrad

Along the periphery of the Greenland ice sheet, Global Navigation Satellite System (GNSS) stations observe uplift of a few mm/yr, reflecting Earth’s response to past and contemporary changes in Greenland’s ice mass. On the coast of southeast Greenland, near the Kangerlussuaq glacier, GNSS stations show abnormally rapid ground uplift, faster than 10 mm/yr. Current earth deformation models, which employ a layered Earth structure, cannot explain such rapid uplift. Here we develop 3D regional models of uplift in response to deglaciation occurring over timescales corresponding to the last glacial cycle (past 1000s of years), the last millennium (past 100s of years), and recent rapid deglaciation (past 10s of years). These 3D models incorporate a track of low-viscosity upper mantle and thin lithosphere, consistent with the passage of Greenland over the Iceland plume during the past ~50 Myr. We find that the fastest ground uplift occurs where rapid deglaciation occurs above the low-viscosity plume track of the Iceland plume. This uplift reflects viscous deformation of the upper mantle, and is much larger than the (instantaneous) elastic deformation that also results from this deglaciation. Above the low-viscosity plume track, the uplift contribution is greatest for the most recent deglaciation (past decades), followed by the contribution from deglaciation during the last millennium. The combination of these viscous contributions can explain uplift observations of more than 10 mm/yr near the rapidly deglaciating Kangerlussuaq glacier, which lies above the Iceland plume track, and slower uplift in the surrounding areas. Rapid uplift observed to the south of the Kangerlussuaq glacier can be explained if the low-viscosity plume track extends farther southward beneath the Helheim glacier, which is also rapidly deglaciating. Such rapid viscous uplift from recent and local ice melt is not usually considered in glacial isostatic adjustment (GIA) models, but likely happened in the past in response to previous deglaciation. It will also become increasingly important in the future as deglaciation accelerates.

How to cite: Weerdesteijn, M. F. M. and Conrad, C. P.: Rapid Earth uplift in southeast Greenland driven by recent ice melt above low-viscosity upper mantle, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5748, https://doi.org/10.5194/egusphere-egu24-5748, 2024.

EGU24-6043 | ECS | Posters virtual | G3.4

A parametric study of sea level and grounding line projections in the Amundsen Sea sector for coupled solid Earth - ice sheet models. 

Luc Houriez, Eric Larour, Lambert Caron, Nicole-Jeanne Schlegel, Tyler Pelle, and Hélène Seroussi

The evolution of the Antarctic Ice Sheet (AIS) represents one of the most important and uncertain contributions to sea level rise in the upcoming centuries. Thwaites glacier and the Amundsen Sea sector of the West Antarctic Ice Sheet (WAIS) have been identified as the continent's most critical areas. The retreat of Thwaites' glacier grounding line - the transition area where ice is no longer grounded and becomes afloat - is the subject of considerable study for modelers as it governs the collapse of the glacier.

 

Recent advances towards coupling of dynamical ice models with Glacial Isostatic Adjustment (GIA) models has provided the means to improve grounding line projections by considering solid-Earth processes and their interactions with the cryosphere and hydrosphere. However, the spatial and temporal model resolution necessary to fully capture these interactions, and its sensitivity to model parametrization, remains elusive.

 

We investigate the grounding line retreat of Thwaites Glacier through 2350 using the parallelized coupled physics capabilities of the Ice-sheet and Sea-level System Model (ISSM) which capture the complex interactions between solid-Earth, ice-sheets, and ocean. We incorporate realistic climatology, ocean melt rates, and GIA models and we discuss the impact of spatial and temporal model resolution, and solid-Earth parametrization, on the grounding line retreat and sea level change.

 

© 2024 California Institute of Technology. Government sponsorship acknowledged.

How to cite: Houriez, L., Larour, E., Caron, L., Schlegel, N.-J., Pelle, T., and Seroussi, H.: A parametric study of sea level and grounding line projections in the Amundsen Sea sector for coupled solid Earth - ice sheet models., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6043, https://doi.org/10.5194/egusphere-egu24-6043, 2024.

EGU24-6485 | Posters on site | G3.4

Body tides and elastic stresses in the Earth’s crust 

Marianne Greff-Lefftz and Laurent Métivier

Solid tides, predominantly diurnal and semi-diurnal, are commonly observed on Earth's surface through horizontal and vertical movements (a few tens of centimeters), along with gravity measurements (~100 microgal). This study focuses specifically on tidal effects within the elastic stress field at the surface, which is approximately 1000 Pascals.

We initially established a correlation between tidal elastic pressure and natural hydrogen emission. Hydrogen, in its gaseous form, escaping from Proterozoic basins, represents a potential source of carbon-free energy, leading to extensive research on vents. A notable characteristic of these emissions is the consistent daily cycle observed in specific regions. While atmospheric pressure effects have been shown to account for this cycle, solid tides could serve as an alternative explanation. Considering that tidal waves do not have a uniform spatial distribution on the Earth's surface, we computed time series of elastic pressure at two locations where natural hydrogen emissions are observed: one near the equator in the Sao Francisco basin (Brazil) and another near the North Pole in the Lovozero deposits (Kola Peninsula).

We then explored the maximum shear stress generated by tidal potential in areas experiencing tectonic stresses. We demonstrated that in expansive regions, the maximum shear stress correlates with the peak of the tidal potential, while in compressive regions, it is associated with the minimum tidal peak.

How to cite: Greff-Lefftz, M. and Métivier, L.: Body tides and elastic stresses in the Earth’s crust, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6485, https://doi.org/10.5194/egusphere-egu24-6485, 2024.

EGU24-6863 | ECS | Orals | G3.4

Modelling Glacial Isostatic Adjustment in Firedrake  

William Scott, Mark Hoggard, Sia Ghelichkhan, Angus Gibson, Stephan Kramer, and Rhodri Davies

Melting ice sheets transfer water from land into ocean basins. The resulting sea-level rise is, however, highly spatially non uniform and time dependent due to complex feedbacks between viscoelastic deformation of the solid Earth in response to these evolving surface loads and coupled perturbations in the gravitational field and rotation axis. Together, these processes are referred to as Glacial Isostatic Adjustment (GIA) and accurate models of GIA are crucial for robust interpretation of both modern and paleo measurements of sea-level change and ice-mass balance. 

A limitation with many existing GIA modelling codes is their inability to incorporate lateral variations in Earth structure. Nevertheless, there is mounting evidence for the presence of significant lateral changes in mantle viscosity, for example beneath West Antarctica, that give rise to complex interactions between rates of surface rebound, sea-level change and ice retreat. Understanding these processes requires development of a new generation of GIA codes capable of handling such variations in rheology at increasingly fine spatial and temporal evolution. 

In this presentation, we will introduce a new project to model GIA using the Firedrake finite element framework and present results for several community benchmarks. Firedrake leverages automatic code generation to create a separation of concerns between employing the finite-element method and implementing it. This approach maximises the potential for collaboration between computer scientists, mathematicians, scientists and engineers and enables sophisticated high performance simulations. A key advantage of Firedrake is the automatic availability of sensitivity information through the adjoint method, allowing us to investigate inverse problems. We are developing an open-source tool highly suited to the challenge of modelling complex Earth structure in GIA, building on the Firedrake-based G-ADOPT project for mantle convection. We envision that future applications might include, but are not limited to, investigating non-linear and transient rheologies, feedbacks between sea-level and glacier dynamics, and reducing uncertainty on sea-level projections into the future. 

How to cite: Scott, W., Hoggard, M., Ghelichkhan, S., Gibson, A., Kramer, S., and Davies, R.: Modelling Glacial Isostatic Adjustment in Firedrake , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6863, https://doi.org/10.5194/egusphere-egu24-6863, 2024.

EGU24-6898 | Posters on site | G3.4

Mid-Holocene ice history inferred from GIA-induced crustal motion around Lützow-Holm Bay, East Antarctica 

Jun'ichi Okuno, Akihisa Hattori, Koichiro Doi, Yoshiya Irie, and Yuichi Aoyama

The history of ice melting and the viscoelastic properties of the mantle heavily influence Antarctic crustal deformation caused by Glacial Isostatic Adjustment (GIA). The interaction between ice history and mantle viscosity further complicates the complex Antarctic GIA. Nonetheless, geodetic observations, such as GNSS, are crucial for constraints on the GIA model parameters.

For over two decades, the Japanese Antarctic Research Expedition (JARE) has been using GNSS and absolute gravity measurements to obtain data along the coast of Lützow-Holm Bay, primarily at Syowa Station. This study examines the geodetic signals associated with GIA from observations along the Lützow-Holm Bay coastline in East Antarctica, and we also conduct GIA simulations based on the recent report of rapid ice thinning in the target region during the mid-Holocene.

Based on geomorphological surveys and surface exposure ages, Kawamata et al. (2020: QSR) showed that the region experienced rapid ice thinning of over 400 m from about 9 to 6 ka. Representative deglaciation models, such as ICE-6G, do not account for this rapid thinning process. Therefore, we investigate the variability of the geodetic signals using the ice history, including this rapid thinning. Our predictions demonstrate that incorporating the modified ice history results in consistent outcomes with the observations. This finding supports the notion that rapid ice melting occurred in the Holocene and suggests that geodetic observations can help constrain this region's ice sheet melting process. Additionally, we will present a possibility of the readvance following the rapid retreat based on the precise GIA modelling.

How to cite: Okuno, J., Hattori, A., Doi, K., Irie, Y., and Aoyama, Y.: Mid-Holocene ice history inferred from GIA-induced crustal motion around Lützow-Holm Bay, East Antarctica, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6898, https://doi.org/10.5194/egusphere-egu24-6898, 2024.

EGU24-7839 | ECS | Posters on site | G3.4

Holocene water-level indicator database for the Dutch coastal plain 

Kim de Wit, Roderik S.W. van de Wal, and Kim M. Cohen

The evolution of the Holocene coastal plain in the Netherlands is strongly influenced by global sea-level rise and regional subsidence patterns. Added up these components are known as relative sea-level rise (RSLR), and explain the coastal plain build-up and accommodation space. Due to RSLR, geological indicators of gradual-drowning formed, such as basal peat layers. These indicators have been sampled and dated from different depths and locations across the coastal plain and are used to document rising coastal sea levels and inland groundwater levels. Databasing and spatial-temporal analysis of the large set of indicators (N=~720) serves to assess local and regional variabilities in RSLR.

Collection of geological water level indicators in the Netherlands started as early as the 1950ies. It was carried out for various purposes: RSLR reconstruction, geological mapping of the coastal-deltaic plain, wetland paleoenvironmental reconstructions. Full formal overview of this data did not exist, as past reviews and data compilations (N=50-300) were subregion restricted and usage specific. Regional differences within the Netherlands, e.g. greater RSLR in the north than in the SW, are also long noticed, and mostly attributed to  differential subsidence as caused by glacial isostatic adjustment (GIA: Scandinavian forebulge collapse, at non-linear rate) and longer-term North Sea Basin tectono-sedimentary subsidence (at a linear rate).

Here, we present a uniform database of Holocene coastal plain water level indicators for the Netherlands, using the HOLSEA workbook format. By compiling a database of geological water level indicators, with an explicit and consistent  standardized treatment of dealing with vertical uncertainties, age uncertainties, and indicative meaning of each indicator (e.g. does it resemble former inland  groundwater level, or former sea-level), we enable more accurate break down of differential subsidence and its source components.

Database compilation included documentation of all vertical corrections applied, such as for water depth, (paleo-)tides, long-term background land motion and for compaction, as well as the propagation of uncertainties associated with these corrections.  The ~720 indicators are further categorized into sea level index points (SLIPs), sea-level upper limiting data (ULD) and sea-level lower limiting data (LLD). ULD data is further categorized to separate tidally, river gradient and local-hydrology influenced indicators. Vertically corrected relative sea-level positions and relative groundwater-level positions are reported separately.

Spatial-temporal analysis of the Holocene water level data allowed for an interpolated reconstruction of Holocene RSLR, resulting in map-output that has continuous coverage of the Dutch coastal plain. Furthermore, this data-driven RSLR reconstruction is used to further disentangle components of RSLR: the Holocene water level rise part versus the two main land subsidence parts, independently from global sea-level analysis, basin-geological subsidence reconstructions and geophysical GIA-modelling  output.  We  compare our reconstructed sea level plains to the RSLR output of glacio-isostatic adjustment modelling, which incorporate ice sheet deglaciation history and Earth-rheological models. This enhances our ability to quantify the contributions of GIA and basin subsidence to past and ongoing RSLR and subsidence in the Netherlands.

How to cite: de Wit, K., van de Wal, R. S. W., and Cohen, K. M.: Holocene water-level indicator database for the Dutch coastal plain, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7839, https://doi.org/10.5194/egusphere-egu24-7839, 2024.

EGU24-8753 | ECS | Posters on site | G3.4

Internal Mass-Induced Elastic Deformation: A Semi-Analytic Approach     

He Tang, Wenke Sun, and Yuting Ji

This research presents an innovative semi-analytical method to study the deformation of a viscoelastic, spherical, layered Earth model under periodic loading. We explore the effects of surface mass changes on deformation over various timescales, including annual and interannual, using a linear rheology profile. Our approach leverages a novel set of formulas in the spectral domain, linking mass, geoid, and displacement through complex Love numbers and Stokes coefficients. This technique bypasses the traditional reliance on viscoelastic Green’s functions.

In our analysis, we particularly focus on the impact of annual cyclic mass loading on viscoelastic loading deformation. We consider both steady-state creep and additional transient creep across a broad spectrum of viscosities. Our findings reveal that while steady-state viscosity values, constrained by Glacial Isostatic Adjustment (GIA) data, show minimal viscoelastic impact on annual load deformation, the inclusion of transient creep, primarily informed by post-seismic data and modeled through the Burgers model, significantly alters the deformation's amplitude and phase. This underscores the importance of rheological properties in understanding Earth's deformation.

Furthermore, our results demonstrate a notable difference in how the horizontal displacement, as opposed to geoid and vertical displacement, responds to viscosity changes. This disparity is observed regardless of the rheological model applied, indicating a greater sensitivity of horizontal displacement to viscosity variations in periodic load deformation. Our study provides new insights into the complexities of Earth's viscoelastic response to cyclic loading, contributing to a deeper understanding of geophysical processes.

How to cite: Tang, H., Sun, W., and Ji, Y.: Internal Mass-Induced Elastic Deformation: A Semi-Analytic Approach    , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8753, https://doi.org/10.5194/egusphere-egu24-8753, 2024.

EGU24-10534 | ECS | Posters on site | G3.4

Reduction of temporal variations in tidal parameters by application of the local response models at globally distributed SG stations 

Adam Ciesielski, Thomas Forbriger, Walter Zürn, Andreas Rietbrock, and Przemysław Dykowski

The already 100 years old harmonic analysis of tides is based on the assumption of separable and non-separable contributions depending on the time series length (Rayleigh criterion in tidal analysis). A priori wave groups had to be composed of different harmonics, which leads to an inaccurate (biased) estimate of tidal parameters. An alternative Regularization Approach to Tidal Analysis, RATA, constrains the solution to be close to a reference model what stabilises the linear regression, making wave grouping obsolete. In this way, the resolution power of the harmonic analysis is exploited to a much larger extent, since the risk of over-fitting is strongly reduced.

We used RATA method to analyse data from globally distributed superconducting gravimeters (SGs) and we are able to achieve super resolution that even highly violates the Rayleigh criterion. The results from double-sphere SG instruments give an indication of the minimum error for the accuracy. We estimated local response models for over 10 stations in Europe, which confirms the consistency of the method. The small differences in phases and amplitudes are most likely caused by ocean loading with varying distance to the ocean. The investigation of stations on other continents reveals significant disparities between the observed tidal response (which accounts for the loading signals as well) and the Earth body model assumptions (like Wahr-Dehant-Zschau elastic analysis model).

Temporal variations of tidal parameters, seen in the moving window analysis (MWA), are known for all tidal wave groups at different SG stations around the globe. The amplitude of variations usually is greater than the standard deviation by a factor of 2 (minimum) to 32 (maximum). In our investigation, we approximated the effect of the time-invariant ocean loading and radiation tides in the data by application of the local response models, already estimated with RATA. We repeated the MWA of 12 wave groups composed from summed harmonics. We found that the periodic variations of groups M2, K1, µ2, N2, L2, and S2 are reduced by up to a factor of 9 compared to earlier studies. Some long-period variations previously seen in the M1, O1, Q1, and J1 groups are captured as well. The previously neglected influence of radiation tides, degree 3 tides, and significant satellite constituents were the main causes of apparent modulations in previous studies. Hence, with the local model correction, a proper investigation of the remaining temporal variations to study instrument stability or time-varying contributions of ocean loading is more applicable.

How to cite: Ciesielski, A., Forbriger, T., Zürn, W., Rietbrock, A., and Dykowski, P.: Reduction of temporal variations in tidal parameters by application of the local response models at globally distributed SG stations, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10534, https://doi.org/10.5194/egusphere-egu24-10534, 2024.

EGU24-10834 | ECS | Orals | G3.4

Towards imaging 3D crust and mantle structure by means of ocean tidal loading tomography 

Andrei Dmitrovskii, Federico Munch, Christian Boehm, Hilary Martens, and Amir Khan

Ocean tide loading (OTL) brings about recurring deformation of the Earth’s surface. Some of the OTL harmonics, e.g. M2, O1, Mf, cause sufficiently large surface displacement to be registered by the Global Navigation Satellite Systems (GNSS). These displacements are sensitive to the interior structure of the planet in a broad range of temporal and spatial scales making them a potentially unique source of information about the planet’s response at low frequencies. Comparison between observations and predictions for 1D elastic Earth models result in discrepancies of up to 3 mm (Bos et al., 2015, Martens et al., 2016). Spatial coherency of these discrepancies hints to 3D interior structure as one of the main sources of such residuals.
In this context, we present a framework to invert OTL observations for 3D crustal and mantle structure based on a trust-region Newton-type iterative algorithm. Furthermore, we resort to the adjoint approach as an efficient means of computing the gradient for the high-dimensional model space. Focusing on the design of the inverse algorithm, we constrain ourselves to deformations of an isotropic elastic planet, which are governed by a self-adjoint forward operator. In order to assess the robustness of the method, we perform a suite of 3D synthetic inversions that mimic the distribution of the GNSS stations in South America. Preliminary results indicate enhanced sensitivities to the crustal and upper mantle density and elastic properties in the vicinity of the coastlines.

How to cite: Dmitrovskii, A., Munch, F., Boehm, C., Martens, H., and Khan, A.: Towards imaging 3D crust and mantle structure by means of ocean tidal loading tomography, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10834, https://doi.org/10.5194/egusphere-egu24-10834, 2024.

We compute daily GPS solutions for about 200 permanent stations in Greenland, Scandinavia and Canada for the 2000 – 2023 period, using the CNES/GINS software in precise point positioning with integer ambiguity resolution (IPPP) mode. The observed vertical displacements are caused by both past- and present-day ice mass (PDIM) changes. The glacial isostatic adjustement (GIA) is the visco-elastic Earth’s response to the Pleistocene glaciation and deglaciation, whereas the PDIM is often estimated assuming an elastic Earth’s response.

We revisit the problem of the separation of GIA and PDIM using state-of-the-art ice models (for example, ICE-6G and ICE-7G) and observations from space gravimetry (GRACE and GRACE Follow On) and altimetry (CryoSat-2 and ICESat-2).

In particular, we investigate different rheology models, including the classical Maxwell model used in GIA modeling, but also the Burgers model allowing transient anelastic deformation at timescales of 10 to 20 years.

We found that the Burgers model with a transient viscosity of about 1018 Pa.s in the upper mantle, combined with the VM5a or VM7 viscosity profiles (Maxwell component) is in better agreement with the observed GPS vertical displacements.

 

How to cite: Boy, J.-P. and Taghiyev, V.: Vertical deformation in Greenland: separation of past and present-day ice mass loss contributions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12953, https://doi.org/10.5194/egusphere-egu24-12953, 2024.

EGU24-13658 | Orals | G3.4

GIA constraints for Greenland from combined GRACE and GNSS observations 

Valentina R. Barletta, Andrea Bordoni, and Shfaqat Abbas Khan

Currently, many different glacial isostatic adjustment (GIA) models have been proposed for Greenland, as a consequence of a still largely unknown deglaciation there. GNSS trends are often used to constrain GIA models regionally. However, the GNSS uplift rates contain a large contribution from present-day mass changes (mostly due to ice melting) that must be removed to extract the GIA uplift rates. The elastic uplift rates estimates are potentially affected by uncertainties. They depend on the Earth model chosen (usually PREM-based models) and on high-resolution mass changes estimates, usually obtained from volume changes measured with altimetry. The volume changes need to be converted into mass variations, mostly using models (surface mass balance and firn compaction models) that can introduce biases. Since the elastic uplift rates are proportional to the mass changes, any uncertainty in the mass variations directly affects the elastic uplift rates eventually, as well as the GIA GNSS residuals uplift rates obtained from them. And in turn, these biases reflect directly in the GIA models constrained with those GNSS.

Here we propose a novel additional GIA constraint based on both GRACE and GNSS observations. We start from a very simple model, based on three basic and general assumptions: 1) Elastic uplift rates at a given distance from a mass distribution (e.g. a disk changing height) are proportional to the mass variation. 2) The GIA induced uplift rates can be considered proportional to the apparent mass changes produced by GIA gravity changes (e.g. Wahr et al 2000 and Riva et al. 2009). 3) The total uplift rate measured by a GNSS is the sum of the elastic uplift rate caused by any surface mass changes and the GIA induced uplift rate (assuming that uplifts rates due to plate tectonics are negligible in Greenland). We then show that this simple model can be applied to Greenland, and still retain most of its validity. The three points above become three equations in four unknowns, namely the surface mass changes and the related elastic uplift rate, the GIA uplift rate and its related apparent mass change.  Using the average uplift rate measured by the whole GNET (Greenland GNSS Network) and the total GMB (Greenland Mass Balance) measured with GRACE, from the three equations we derive a global consistency relation between the average GIA uplift rate and its related apparent mass change for the whole Greenland.

In this way, the combined analysis of the GMB from GRACE and GNET provides a very solid constraint for Greenland-wide GIA models. GIA models constrained only regionally might provide estimates that are not consistent in other Greenland regions. The four GIA models that we tested do not respect the consistency relation we found. This relation does not allow to determine the GIA uplift rate uniquely, but we show that together with some basic considerations about the plausible deglaciation scenarios, it allows to identify a reasonable range for the GIA component in the average GNSS uplift rate.

How to cite: Barletta, V. R., Bordoni, A., and Khan, S. A.: GIA constraints for Greenland from combined GRACE and GNSS observations, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13658, https://doi.org/10.5194/egusphere-egu24-13658, 2024.

EGU24-13928 | ECS | Orals | G3.4

The impact of regional-scale variability in upper mantle viscosity on GIA in West Antarctica 

Erica Lucas, Natalya Gomez, Konstantin Latychev, and Maryam Yousefi

West Antarctica is underlain by a laterally heterogenous upper mantle, with localized regions of mantle viscosity reaching several orders of magnitude below the global average. Accounting for 3-D variability in upper mantle structure in glacial isostatic adjustment (GIA) simulations has been shown to significantly impact the predicted spatial rates and patterns of crustal deformation, geoid and sea-level changes. Uncertainty in constraining the viscoelastic structure of the solid Earth remains a major limitation in GIA modeling. To date, investigations of the impact of 3-D Earth structure on GIA have adopted solid Earth viscoelastic models based on global- and continental-scale seismic imaging with variability at spatial scales >150 km. However, regional body-wave tomography shows mantle structure variability at smaller spatial scales (~50-100 km) in central West Antarctica (Lucas et al., 2020). Here, we investigate the effects of incorporating this smaller-scale lateral variability in upper mantle viscosity into 3-D GIA simulations. Lateral variability in upper mantle structure at the glacial basin scale is found to have a significant impact on GIA model predictions, especially in coastal regions undergoing rapid ice mass loss. For example, incorporating a transition from lower viscosity at the mouth of Thwaites Glacier to higher viscosity further upstream impacts the predicted rate and pattern of solid Earth deformation and sea-level change in response to ongoing and projected ice mass loss, with possible implications for the evolution of the overlying ice and the interpretation of geophysical observables.

How to cite: Lucas, E., Gomez, N., Latychev, K., and Yousefi, M.: The impact of regional-scale variability in upper mantle viscosity on GIA in West Antarctica, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13928, https://doi.org/10.5194/egusphere-egu24-13928, 2024.

EGU24-15498 | Posters on site | G3.4 | Highlight

Earth’s hypsometry and what it tells us about global sea level 

Vivi Kathrine Pedersen, Natalya Gomez, Jerry X. Mitrovica, Gustav Jungdal-Olesen, Jane Lund Andersen, Julius Garbe, Andy Aschwanden, and Ricarda Winkelmann

Over geological time scales, the combination of solid-Earth deformation and climate-dependent surface processes have resulted in a distinct hypsometry (distribution of surface area with elevation), with the highest concentration of surface area focused near the present-day sea surface. However, this distinctive signature of Earth’s hypsometry does not constitute a single well-defined maximum at the present-day sea surface (0 m). Earth’s hypsometry also shows a prominent maximum ~5 m above the present-day sea surface. Here we explore the nature of this 5-m maximum and examine how it evolved over the last glacial cycle and may evolve moving towards a near-ice-free future. We find that the current elevation of this 5-m hypsometric maximum cannot be explained by ongoing sea-level adjustments following the last glacial cycle. Instead, we suggest that global sea level must have been higher for a significant portion of Earth’s recent multi-million-year history. Indeed, global sea level must have been higher by as much as ~9.5 m to bring this hypsometric maximum in accordance with the sea surface, to account for glacial isostatic adjustments such as ocean syphoning. This signifies that our current polar ice-sheet and sea-level state (and our global reference level) should be considered an anomaly in a geological perspective.

How to cite: Pedersen, V. K., Gomez, N., Mitrovica, J. X., Jungdal-Olesen, G., Andersen, J. L., Garbe, J., Aschwanden, A., and Winkelmann, R.: Earth’s hypsometry and what it tells us about global sea level, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15498, https://doi.org/10.5194/egusphere-egu24-15498, 2024.

EGU24-15975 | ECS | Posters on site | G3.4

A rapid numerical routine for viscoelastic earthquake cycle simulations.  

Sharadha Sathiakumar and Rishav Mallick

Earth’s largest quakes and trans-oceanic tsunamis emanate from subduction zones around the world. Following such large earthquakes, viscoelastic processes and on-fault aseismic fault slip play a crucial role in dissipating the stresses induced by the earthquake, facilitating the solid Earth's return to equilibrium.  The rheological properties of lithospheric rocks govern these postseismic processes and influence time-dependent deformation during the earthquake cycle. Geodetic observations offer an opportunity to constrain these rheological properties, providing valuable insights into the regional lithospheric structure, and potentially improving our understanding of earthquake-related hazards.   

To build intuition for geodetically recorded postseismic deformation, we develop a robust and efficient two-dimensional quasi-static periodic earthquake cycle simulator exploiting the boundary element method and semi-analytical solutions to systems of coupled ordinary differential equations. We investigate the impact of lateral and depth-dependent variations in the viscosity structure of the mantle wedge and the oceanic mantle, to discern their respective contributions and roles in surface deformation observations. We account for the long-term viscous flow rate in the mantle and show that neglecting this term in the earthquake cycle introduces biases in the effective viscosity structure of the lithosphere-asthenosphere system, particularly in the context of power-law rheologies. The low computational cost of our numerical routine makes it ideal for incorporating into future inverse modelling frameworks to estimate regional rheological structure from geodetic observations of subduction zone earthquake cycles.  

How to cite: Sathiakumar, S. and Mallick, R.: A rapid numerical routine for viscoelastic earthquake cycle simulations. , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15975, https://doi.org/10.5194/egusphere-egu24-15975, 2024.

EGU24-16655 | ECS | Orals | G3.4

Does thicker ice cover cause stronger glacially triggered earthquakes? - A case study from the southwestern Baltic Sea 

Elisabeth Seidel, Holger Steffen, Rebekka Steffen, Niklas Ahlrichs, and Christian Hübscher

Increasing and decreasing ice masses cause an isostatic adjustment of the crust, which can trigger fault reactivation. It could be assumed that the higher the ice load, the stronger the glacially induced fault reactivation, leading to stronger earthquakes. Here we focus on glacially triggered fault reactivation in the southern Baltic Sea over the past 200,000 years (since the Upper Saalian). Our study area comprises the Caledonian Suture Zone between the East European Craton and the West European Platform as well as the trans-regional Tornquist Zone. Consequently, it reflects a polyphase tectonic history. The fault zones and systems in this geoarchive have been mapped and studied through several reflection seismic investigations. They display variations in their characters, strike and dip directions, age, and depths, documenting the complex evolution.

We focus on faults indicating reactivation during the Quaternary, determined by the seismic sections. After documenting their fault properties, we calculated the glacially induced Coulomb Failure Stress changes (∆CFS) at the faults over the past 200,000 years using finite-element simulations of various glacial isostatic adjustment models. The results show significant local and temporal differences in fault reactivation. We observe that shorter ice advances and lower ice loads correlate with higher ∆CFS, suggesting a higher potential for fault reactivation, which could potentially lead to stronger earthquakes if released in one event. Moreover, we will discuss if the lateral ice thickness gradient or the steepness of the flanks of the ice sheet might play a major role.

How to cite: Seidel, E., Steffen, H., Steffen, R., Ahlrichs, N., and Hübscher, C.: Does thicker ice cover cause stronger glacially triggered earthquakes? - A case study from the southwestern Baltic Sea, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16655, https://doi.org/10.5194/egusphere-egu24-16655, 2024.

EGU24-18171 | ECS | Posters on site | G3.4

Impact of the Earth's mantle transient rheology on surface deformation induced by decades of hydrological mass redistribution 

Maxime Rousselet, Alexandre Couhert, Kristel Chanard, and Pierre Exertier

Over the past decades, modern geodetic observations have provided crucial constraints on the Earth's rheological properties over a wide range of time scales. Whole mantle steady-state viscosity has been inferred from geodetic observations related to glacial isostatic adjustment. More recently, geodesy has helped probing Earth’s upper mantle transient response to stresses induced by rapid regional changes in hydrology, including recent ice melting, during which viscosity rapidly increases from an elastic to a viscous regime. Here we investigate the potential of using decades of global hydrological mass redistributions, mainly driven by recent ice melting, to constrain the Earth's mantle transient rheology. We quantify the sensitivity of the Earth surface deformation and gravity field to mass redistribution at very large spatial scales to variations in the Earth’s mantle rheology using a spherically layered model and considering Maxwell and Burgers behaviors. Mass redistribution is estimated using low-degree spherical harmonics of the Earth’s gravity field inferred from over 30 years of Satellite Laser Ranging (SLR) observations. We discuss the importance of accounting for the Earth's lower mantle transient rheology at timescales of a few decades and evaluate to what extent it can be constrained by combining long geodetic time series of the Earth’s gravity field and surface deformation.

How to cite: Rousselet, M., Couhert, A., Chanard, K., and Exertier, P.: Impact of the Earth's mantle transient rheology on surface deformation induced by decades of hydrological mass redistribution, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18171, https://doi.org/10.5194/egusphere-egu24-18171, 2024.

EGU24-18865 | ECS | Posters on site | G3.4

Towards constraining Venus structure by means of atmospheric loading displacement response  

Federico Daniel Munch, Amir Khan, Hilary Martens, and Christian Boehm

Surface mass loads produce a wide spectrum of deformation responses in planetary bodies that can be exploited to probe material properties in planetary interiors. In particular, the redistribution of fluid mass associated with Venus’s atmospheric dynamics leads to periodic changes in the Venusian surface displacements and thus gravitational field. These periodic variations could potentially be detected by upcoming Venus missions, e.g., VERITAS (Venus Emissivity, Radio Science, InSAR, Topography, and Spectroscopy) and EnVision, which are expected to greatly  improve our knowledge of Venus’s gravity field. 

By combining a state-of-the-art general circulation model of Venus’s atmosphere with a novel approach to the solution of the quasi-static momentum equations in the coupled gravito-elastic problem, we explore the sensitivity of the atmospheric loading response to mantle structure. In addition, we investigate the effect of 3-D crustal and lithospheric variations on Venus’s gravity field and the tidal and load Love numbers. Preliminary results suggest that an accurate estimation of the time-varying gravity field and surface displacements can provide important constraints on the interior structure of Venus through the measurement of the load Love numbers.

How to cite: Munch, F. D., Khan, A., Martens, H., and Boehm, C.: Towards constraining Venus structure by means of atmospheric loading displacement response , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18865, https://doi.org/10.5194/egusphere-egu24-18865, 2024.

CR6 – Snow and ice: properties, processes, hazards

Mass loss of snow packs due to recrystallization processes and subsequent vapor fluxes are inherently difficult to measure experimentally. Present numerical advances enable new simulation tools to explore the otherwise invisible mass fluxes due to diffusive and convective water vapor transport. In this study we calculate the effective vapor fluxes as a function of the local mass transfer coefficient, snow depth, and a range of microstructure parameters given by porosity and specific surface area. A set of flow, heat transport and vapor transport equations re developed. Heat transport is characterized by the Rayleigh number while vapor transport depends on the Péclet and Damkhöler numbers. The latter measures the relative importance of vapor transfer to advective fluxes. For low Rayleigh numbers, the system behaves in a purely diffusive manner. however, convective transport mechanisms dominate for high Rayleigh values. Convection is found to enhance vapor transport. This is in agreement with previously unexplained mass losses in field observations. The effect of vapor mass transfer between the solid and gas phase is also analyzed. The results can be used for macroscale snow pack models to predict large scale mass loss due to sublimation for snow covered areas such as Antarctica, Greenland and seasonally covered Tundra.

How to cite: Hidalgo, J. J. and Krol, Q.: Effective vapor transport in snow: The role of convection and the local mass transfer coefficient, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3827, https://doi.org/10.5194/egusphere-egu24-3827, 2024.

EGU24-6861 | ECS | PICO | CR6.2

Aeolian snow transport induces airborne snow metamorphism with implications for snowpack physical properties 

Sonja Wahl, Benjamin Walter, Franziska Aemisegger, Luca Bianchi, and Michael Lehning

Aeolian transport of snow is a cryospheric process prevalent in all snow-covered areas. It influences the energy and mass balance of these cold regions. Apart from the direct effects during the process, aeolian transport alters the snow’s microstructure, leaving behind a wind-blown snow layer with different snowpack characteristics than before the wind event. For high-resolution climate modeling in snow-covered regions, it is thus important to incorporate the immediate and lasting effects of wind-induced aeolian snow transport for an accurate representation of the energy and mass balances of a snowpack. Apart from mechanical mechanisms such as fragmentation and aggregation of snow crystals, the metamorphic mechanism (sublimation and deposition of water molecules on the suspended snow particles) can alter the microstructure of snow during aeolian transport. It is difficult to predict the relative importance of the two mechanisms for the evolution of the microstructure of wind-blown snow, not least because the process is happening on the micro-scale but is unfolding on large spatial scales on the respective particle trajectories. Thus, it is difficult to observe.
However, metamorphic processes leave a fingerprint on the snow’s composition of stable water isotopes whereas the mechanical mechanisms do not. Hence, monitoring the evolution of the stable water isotope signal of the snow can act as a macro-scale tracer for the metamorphic micro-scale processes. The stable water isotope signal can thus help to differentiate the processes at play during aeolian snow transport.
Here we show through observations of cold laboratory ring-wind tunnel experiments that aeolian transport of snow involves airborne snow metamorphism. We monitored the evolution of the microstructure and the isotopic composition of airborne snow through repeated sampling of snow from the air stream. In a total of 19 experiments we varied the temperature in a range of -20°C to -3°C and the transport times varied between 50 - 180 minutes. We find a rapid exponential decay in specific surface area (SSA) with transport time which reduces the SSA value to 35-70% of its starting value by the end of the experiments. Further, we observe a shift in the particle size distribution towards larger snow particles, both for the most abundant and maximum particle sizes with aeolian transport time. Simultaneously, the water isotope signature shows mainly an enrichment in δ18O and a decrease in d-excess which is a strong indicator for isotopic fractionation and thus evidence for the presence of metamorphic processes. Combining the results, we attribute the change in snow microstructure to airborne snow metamorphism. The unique combination of information on the isotopic composition and microstructure of airborne snow under well-constrained laboratory conditions can be used to develop parameterizations for the incorporation of airborne snow metamorphism in snow-process models.

How to cite: Wahl, S., Walter, B., Aemisegger, F., Bianchi, L., and Lehning, M.: Aeolian snow transport induces airborne snow metamorphism with implications for snowpack physical properties, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6861, https://doi.org/10.5194/egusphere-egu24-6861, 2024.

EGU24-8976 | ECS | PICO | CR6.2

Spatiotemporal variability of turbulent fluxes over snow in mountain regions  

Rainette Engbers, Sergi González-Herrero, Nander Wever, Franziska Gerber, and Michael Lehning

Turbulent exchange of heat and moisture plays an important role in snow cover dynamics in mountain regions and governs the boundary layer dynamics. While these processes are subject to great spatiotemporal variability, particularly in complex terrain, virtually all measurements of heat, moisture and momentum fluxes are point observations. To quantify the spatial variability, and assess the representativeness of the observations, numerical modelling of the atmosphere and surface is a useful tool. Still, there is substantial uncertainty in the accuracy of how surface models capture this spatial variability, particularly in complex terrain with large spatial variability on small scales. These uncertainties can be partially attributed to (1) the use of Monin-Obukhov similarity theory (MOST) which has limitations in complex terrain due to the role of advection and (2) the errors in representing near-surface atmospheric gradients in the simulations. In this study, we analyse sources of errors in representing energy exchange over snow in mountain regions and look specifically at the spatiotemporal variability during different meteorological events in the region of Davos, Switzerland. To verify common modelling approaches with observations, we use model predictions of turbulent fluxes from CRYOWRF, the atmospheric model WRF coupled to the surface model SNOWPACK. The fluxes at different resolutions are compared to turbulent fluxes measured using the Eddy Covariance method (EC) and calculated with MOST. This model validation is done for different meteorological events representative of the local climate. Preliminary results indicate that the fluxes are highly spatially variable, being an order of magnitude higher on the leeside than on the windward side of a mountain ridge. This indicates that local heat fluxes are not representative of the whole mountain area, which has implications for the calculation of snow melt, sublimation and accumulation across mountainous terrain. The resolution of the model also plays a large role in representing the fluxes as the modelled fluxes differ greatly depending on the resolution. Our results quantify to what extent snow-atmosphere interactions and their spatial variability are correctly represented in state-of-the-art numerical weather and snow models. 

 

How to cite: Engbers, R., González-Herrero, S., Wever, N., Gerber, F., and Lehning, M.: Spatiotemporal variability of turbulent fluxes over snow in mountain regions , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8976, https://doi.org/10.5194/egusphere-egu24-8976, 2024.

EGU24-12325 | PICO | CR6.2

A comparison of snow depth scaling patterns from TLS, UAV and Pleiades observations  

Jesús Revuelto, Pablo Mendoza, Cesar Deschamps-Berger, Esteban Alonso-González, Francisco Rojas-Heredia, and Juan Ignacio López-Moreno

Understanding the evolution of snowpack in heterogeneous mountain areas is a highly demanding task and requires the application of suitable observation techniques to retrieve snow properties at distinct spatial scales. In turn, once the reliability of these techniques is established, the comprehension of snowpack scaling properties helps to determine which processes are more relevant on the control of snow distribution and its temporal evolution. Previous studies have reported detailed observational datasets and insights on the main drivers of snowpack distribution through variogram analysis up to 500-800 m, identifying scale break lengths and their anisotropies. Here, we examine scale breaks derived from variogram analysis applied to snow depth observations at the Izas Experimental Catchment (located in Central Spanish Pyrenees) and the surrounding area for the period 2019-2023. To this end, we use data retrieved with three observation techniques: Terrestrial Laser Scanning (TLS-LiDAR, 12 acquisitions), Unmanned Aerial Vehicles (UAV-SfM, 20 acquisitions), and satellite stereo images (4 Pléiades acquisitions), covering different domains around the experimental site. First, we analyze the consistency among the observational techniques, and then we explore possible drivers explaining detected scale breaks through variogram analysis up to 4000 m. Overall, similar results were obtained with the three observational techniques, with a very high temporal consistency for the first detected scale break length and little variations with direction. We also found good agreement between the search distance used to compute the topographic position index (TPI), the first scale break length, and the mean distance between peak snow accumulations, which vary between 15 and 25 m, not only for the entire study domain, but also in manually delineated Hydrological Response Units.

How to cite: Revuelto, J., Mendoza, P., Deschamps-Berger, C., Alonso-González, E., Rojas-Heredia, F., and López-Moreno, J. I.: A comparison of snow depth scaling patterns from TLS, UAV and Pleiades observations , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12325, https://doi.org/10.5194/egusphere-egu24-12325, 2024.

EGU24-12854 | ECS | PICO | CR6.2

Quantifying the Impact of Dynamic Lapse Regimes on Spatially-Distributed Snow Simulations 

Kristen Whitney, Sujay Kumar, John Bolten, Justin Pflug, Fadji Maina, Christopher Hain, David Mocko, and Melissa Wrzesien

Accurate characterization of surface meteorological distributions over coastal areas and complex terrain, especially the relationship between temperature and altitude, is essential for the accurate simulation of snowpack dynamics. This becomes increasingly difficult at spatial resolutions smaller than common gridded meteorological forcing datasets due to the sparsity of long-term temperature measurements and the influence of local factors like cool air pooling and inversions. Near-surface air temperatures (Ta) are often assumed to decrease with elevation at a constant rate of 6.5oC km-1, which could lead to large model errors in snow evolution and other processes key to snow hydrology, water resource management, and other applications. This study evaluates the impact of local dynamical adjustments to downscaled Ta on snow simulations over two coastal mountainous terrains using the Noah-MultiParameterization (NoahMP) land surface model. Forcings are derived from remote sensing and reanalysis precipitation products and the (Modern-Era Retrospective Analysis for Research and Applications, version 2) MERRA-2 atmospheric products (including Ta) at the downscaled 1-km resolution. Hourly lapse rates at each grid cell are calculated by applying linear regression to Ta and elevation from surrounding grid cells (within one grid lengths in the x or y direction) at the Ta native MERRA-2 resolution and applied to the downscaled 1-km Ta product. We will present the impact on simulated snow water equivalent, snow cover, and snow depth across simulations forced with the downscaled Ta (1) without lapse rate correction, (2) corrected with a constant lapse rate (6.5oC km-1), and (3) corrected with the dynamic hourly lapse rate. Results will be compared against remote sensing-based products.

How to cite: Whitney, K., Kumar, S., Bolten, J., Pflug, J., Maina, F., Hain, C., Mocko, D., and Wrzesien, M.: Quantifying the Impact of Dynamic Lapse Regimes on Spatially-Distributed Snow Simulations, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12854, https://doi.org/10.5194/egusphere-egu24-12854, 2024.

To maintain computational efficiency and avoid adding too many uncertainties into Land Surface Models (LSMs) with fine-scale parameterization, many efforts have been made to improve sub-grid representations of heterogeneous landscapes. HydroBlocks LSM stands out as a model that employs advanced hierarchical clustering methods, utilizing field-scale satellite-derived data to construct sub-grid tiles or clusters. The Noah-MP land surface model is applied within each tile. Unlike conventional tiling approaches, knowing the spatial location of the clusters provides the opportunity to incorporate the interactions across the distinct clusters. Presently, they interact through the subsurface flow processes. Despite the comprehensiveness of these models, both Noah-MP and HydroBlocks lack consideration for the wind-induced snow transport which plays a pivotal role in snow-related hazards. Other than that, the sublimation and redistribution of wind-blown snow in exposed environments contributes significantly to variations in snow depth. It not only exerts local influence on surface water and energy balance, but also can have expansive impact since the snowmelt is critical for the water availability of downstream basins. To address this limitation, we propose the integration of a blowing snow module into HydroBlocks. This module, inspired by the Prairie Blowing Snow Model, consists of physical-based wind transport and sublimation algorithms. Clusters will be categorized into source and sink regions considering their topography and vegetation. The redistribution of snow mass at every timestep will be calculated based on the wind condition and the adjacent borders between clusters. This research seeks to pave the way for modeling other mass transport processes between tiles which considers the complex interactions within heterogeneous landscapes.

How to cite: Cai, J. and Chaney, N.: Integrating a Blowing Snow Module for Enhanced Representation of Snow Dynamics and Surface in the HydroBlocks modeling framework, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13274, https://doi.org/10.5194/egusphere-egu24-13274, 2024.

EGU24-15202 | PICO | CR6.2

Wind tunnel experiments to characterize snow densification and SSA reduction caused by aeolian snow transport 

Benjamin Walter, Sonja Wahl, Hagen Weigel, and Henning Löwe

Snow precipitation frequently occurs under moderate to strong wind conditions, resulting in drifting and blowing snow. Processes like particle fragmentation and airborne metamorphism during snow transport result in microstructural modifications of the ultimately deposited snow. Despite the relevance (optically and mechanically) of surface snow for alpine and polar environments, this effect of wind on the snow microstructure remains poorly understood and quantified. Available descriptions of snow densification due to wind are exclusively derived from field measurements where conditions are difficult to control. Information on the effect of wind on the specific surface area (SSA) is basically nonexistent. The goal of this experimental study was to systematically quantify the influence of wind on the surface snow density and SSA for various atmospheric conditions (temperature, wind speed, precipitation intensity), and to identify the relevant processes. 

We conducted experiments in a cold laboratory using a closed-circuit ring wind tunnel with an infinite fetch to investigate wind-induced microstructure modifications under controlled atmospheric, flow and snow conditions. Artificially produced dendritic nature-identical snow was manually poured into the ring wind tunnel for simulating precipitation during the experiments. Airborne snow particles are characterized by high-speed imaging, and deposited snow is characterized by density and SSA measurements resulting in a comprehensive dataset.

            The high-speed images support a snow particle transport scheme in the saltation layer similar to natural conditions. We measured an increase of the densification rate with increasing wind speed which differs from available model parameterizations. The SSA was found to decrease under the influence of wind, while increasing wind velocities intensified the SSA decrease. For higher air temperatures (Ta > -5°C), both the densification and SSA rates significantly differ from the rather constant rates at lower temperatures. We attribute this to the effects of enhanced cohesion or sintering (density) and intensified airborne snow metamorphism (SSA) at higher air temperatures. A sensitivity experiment revealed a strong influence of airborne snow metamorphism on the SSA decrease. Our results provide a first step towards an improved understanding and modeling of the effect of aeolian snow transport on optically and mechanically relevant microstructural properties of surface snow.

How to cite: Walter, B., Wahl, S., Weigel, H., and Löwe, H.: Wind tunnel experiments to characterize snow densification and SSA reduction caused by aeolian snow transport, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15202, https://doi.org/10.5194/egusphere-egu24-15202, 2024.

The snowpack plays a fundamental role in regulating the global climate thanks to its high albedo and thermal insulation properties, and for many regions of the world it also has very local and important impacts. Indeed, the snow is an important water reservoir, storing the water in solid state during cold months, and releasing it in liquid state during warmer months. But the snow is also the necessary condition for the development of rural places which base their economy on winter sports. However, a certain risk is always associated with snow when it deposits on the ground, since the snow can slide down, creating avalanches which may cause several damages to the local flora, fauna, buildings and infrastructures. Typically, the conditions that allow the occurrence of snow avalanches span from the point scale to the slope scale, and depend on the snowpack properties. Kilometer-resolution numerical models are not able to reproduce the slope-scale variability of the snowpack properties because of the complex interaction between the atmospheric flows and the topography at finer scale. To address this limitation, we apply several algorithms to downscale 1 km horizontal resolution WRF atmospheric simulations to 500 m horizontal resolution in order to force the snow cover model Alpine3D with more representative weather data. Additionally, we train a fully convolutional neural network to downscale 10 km resolution IMERG precipitation data to 1 km horizontal resolution, further downscaled to 500 m. Furthermore, 2m temperature point observations are interpolated at 500 m resolution using geostatistical techniques. Finally, we force Alpine3D with a combination of forecasted and observed data, obtaining improved simulation results compared to using only forecasted weather data. This implies that the use of a combination of simulated and observed weather data is particularly promising for the estimation of the snowpack properties at slope-scale resolution in regions characterized by complex topography, providing more reliable information for risk mitigation, and sustainable development of snow-prone areas.

How to cite: Raparelli, E. and Tuccella, P.: Improving snowpack simulation at slope-scale resolution with machine learning and geostatistical downscaling of observed and forecasted weather data., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15809, https://doi.org/10.5194/egusphere-egu24-15809, 2024.

Mountain snowpack serves as a vital water source for both high-altitude regions and adjacent lowlands, significantly impacting local economies through its influence on tourism, communication, logistics, and recreational risks. However, mid-elevation snow cover is diminishing due to climate change (IPCC-2021), emerging as a critical concern in water management. Despite its importance, a lack of comprehensive understanding stems from a scarcity of well-distributed mountain snowpack observations and specific simulation tools. This knowledge gap is more pronounced in Mediterranean mountainous regions, where intricate processes of growth and ablation, high spatial variability, and a high inter-annual variability pose obstacles for models. To address these challenges, hyper-high resolution models (<1 km) have been developed, but they often come with significant computational expenses. As an alternative, SnowCast has been introduced, which nests ERA5 atmospheric reanalysis (ECMWF), the Intermediate Atmospheric Research model (ICAR, NCAR), and the Flexible Snow Model (FSM2, University of Edinburgh), incorporating custom parametrizations and high-resolution topographic forcing models. This approach enables highly parallelized computations, enhancing the efficiency of simulating multiple years. This capability allows the application of such resolution for climate studies while managing computational costs effectively. Validation through extensive fieldwork, automated snowpack monitoring, and satellite imagery shows that the model provides a realistic temporal and spatial representation of snow cover. In-depth analysis of model performance will be presented, along with discussions on potential new processes for implementation, exploration of additional validation techniques, and future prospects for coupling with a hydrological model.

How to cite: González Cervera, Á. and Durán, L.: SnowCast: Hyper-high resolution downscaling model. Snowpack simulation in a mountainous region in Central Spain (Peñalara Massif), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15828, https://doi.org/10.5194/egusphere-egu24-15828, 2024.

EGU24-17057 | PICO | CR6.2

Snow on permafrost: the effect of spatial snow variability on soil temperature in Trail Valley Creek, NWT, Canada 

Inge Grünberg, Daniela Hollenbach Borges, Jennika Hammar, Nick Rutter, Philip Marsh, and Julia Boike

Snow is a potent insulator, influencing the temperature of the active layer and the permafrost in the Arctic region. However, our understanding of spatial patterns of snow properties and their interplay with vegetation remains limited due to scarcity of local and regional snow data. Furthermore, the duration, depth, and physical properties of the Arctic snow cover are changing with rising air temperature and new precipitation patterns. We study the spatial snow distribution and its drivers and consequences around the Trail Valley Creek research catchment in the Northwest Territories, Canada. Our dataset includes a 143 km² snow depth raster captured on April 2, 2023, at a 1-meter spatial resolution, as well as data from 13 spatially distributed loggers measuring air/snow temperature, soil surface temperature, and soil temperature at 8 cm depth from August 27, 2022, to August 9, 2023. Detailed information on vegetation types, structure, and soil properties at all locations is included. Our analysis covers the timing of soil freeze and thaw, snow and soil temperatures, and their correlation with vegetation characteristics, particularly focusing on April snow depth. Our findings underscore the pivotal role of snow in regulating soil temperature, making it a key driver for permafrost protection or thaw. The results reveal significant variability in April snow depth across the 13 study locations, ranging from no snow to 1.7 meters, resulting in winter minimum soil temperatures between -31°C and -4°C. The study confirms that thicker snow cover contributes to warmer soil temperatures. While the soil at 8 cm freezes uniformly in mid-October across all sites, snow patterns lead to high variability in soil thawing dates, which span one month between May 10 and June 08, 2023. Understanding the spatial patterns of snow depth, thermal properties, and timing is crucial for assessing the snow effect on soil temperature. The large range of winter soil temperatures, which we observed, may lead to differences in thaw depth development in the following summer and potentially to talik formation affecting permafrost stability.

How to cite: Grünberg, I., Hollenbach Borges, D., Hammar, J., Rutter, N., Marsh, P., and Boike, J.: Snow on permafrost: the effect of spatial snow variability on soil temperature in Trail Valley Creek, NWT, Canada, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17057, https://doi.org/10.5194/egusphere-egu24-17057, 2024.

EGU24-19751 | ECS | PICO | CR6.2

A continuum mechanics perspective on the rheology of firn in the context of firn densification 

Timm Schultz, Angelika Humbert, and Ralf Müller

While the complex nonlinear rheology of ice is well known and often discussed, for example in the context of large-scale ice sheet modeling, calving, and isotropy occurring at shear margins, the rheology of firn is often considered to be rather simple. According to Truesdell’s first metaphysical principle, which states that ”all properties of a mixture must be mathematical consequences of properties of the constituents” (Truesdell, C. (1984), Rational Thermodynamics, Springer-Verlag, p. 221), the material behavior of firn should be related to that of ice, since firn is primarily a mixture of ice and air. What distinguishes firn from ice is its microstructure. The field of continuum mechanics provides methods to relate the microstructural properties of a material to its macroscopic material behavior.

Here we review a homogenization method developed for the densification of nonlinear creeping metallic powders and first applied to the simulation of firn densification by Gagliardini and Meyssonnier (1997, Annals of Glaciology, 24, pp. 242–248). The method links the rheology of ice to that of firn by describing firn as a porous medium with an ice matrix. The advantage of this approach is that it is formulated in all three spatial dimensions, allowing the inclusion of horizontal divergence due to ice flow without additional parameterization. A large database of dated firn cores allows the determination of the governing model parameters using an optimization approach. We discuss the results, advantages, and limitations of this approach, as well as validation strategies.

How to cite: Schultz, T., Humbert, A., and Müller, R.: A continuum mechanics perspective on the rheology of firn in the context of firn densification, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19751, https://doi.org/10.5194/egusphere-egu24-19751, 2024.

EGU24-20320 | PICO | CR6.2

Monitoring snow depth by Integrating in an optimal way citizen science and other techniques 

David Pulido-Velazquez, Antonio Collados_Lara, Pedro Sánchez, Leticia Baena-Ruiz, Eulogio Pardo-Iguzquiza, Carlos Lorenzo-Carnicero, Juan Carlos García-Davalillo, Luis Carcavilla, Steven Fassnatch, Javier Herrero, Jose David Hidalgo, Victor Cruz Gallegos, Juan de Dios Gomez Gomez, Mónica Leonor Meléndez, Nemesio Heredia, Ignacio Lopez-Moreno, Jesús Revuelto, Helen Flynn, Amalia Romero, África de la Hera Portillo, Jorge Jódar, and Elisabeth Diaz-Losada

The snow depth (SD) is an excellent indicator of climate, yet a poorly monitored variable in many mountain ranges. A novel integrated approach is proposed for optimal monitoring of SD dynamics in the 5 National Parks located in Alpine (NPA) zones of Spain (i.e., Sierra Nevada, Guadarrama, Picos de Europa, Ordesa y Monte Perdido, and Aigüestortes i Estany de Sant Maurici). It will leverage the existing infrastructure of snow poles installed by the Snow Monitoring National Program in Spain (ERHIN). This program obtains SD measurements by direct observation from helicopter flights (1-3 per year). This monitoring activity has been drastically reduced in some mountain ranges during the economic crisis. The objective of this current work is to avoiding potential gaps in the valuable long-term SD timeseries of the pole measurements. An innovative Citizen Science Activity (CSA) methodology is being implemented to engage volunteers to collect the maximum number of photos of the snow poles. It is designed as a sports challenge, in which ranking and awards will be given to the most active participants. It aims to enhance the project with a minimum economic cost, and has the additional objective of raising awareness and encouraging responsible visits to these NPA. It has been tested in Sierra Nevada National Park, where we have identified the necessity to combine the information obtained from this CSA with other approaches to maximize the amount of useful information collected, and in order to reduce the uncertainty in snow distribution.

A number of automatic point sensors have been installed to collect additional snow depth data at snow poles with a high number of days with snow, as identified from a historical analyses of snow cover area (SCA). These locations also have higher uncertainty SD measurements, and thus far, there have been less opportunity for the citizen science collection of photos. In order to identify the most relevant snow poles, we have used a regression model that estimates the spatial distribution of snow depth and its uncertainty from snow cover area and snow depth data. since the high cost of this complementary monitoring actions needs to be considered. a multi-sensors experiment is being performed to identify the best cost-benefit automatic sensors (ultrasound sensors, time-lapse cameras, etc). Drone field campaigns will be also performed, together with distributed information from airborne LIDAR and high resolution Pléiades satellite imagery. Such field campaigns there are costly, and thus the CSA has been also extended to the other 4 NPA. We are using a variety of media (e.g., social networks, TV, radio, and newspapers) to disseminate and communicate the CSA activity in order to maximize participation.

Acknowledgements:
This research has been partially supported by the projects: STAGES-IPCC (TED2021-130744B-C21), SIGLO-PRO (PID2021-128021OB-I00), from the Spanish Ministry of Science, Innovation and Universities, SER-PM (2908/22) from the National Park Research Program, RISKYEARTH (Recovery funds), and SIERRA-CC (PID2022-137623OA-I00) funded by MICIU/AEI/10.13039/501100011033 and by FEDER, UE.

How to cite: Pulido-Velazquez, D., Collados_Lara, A., Sánchez, P., Baena-Ruiz, L., Pardo-Iguzquiza, E., Lorenzo-Carnicero, C., García-Davalillo, J. C., Carcavilla, L., Fassnatch, S., Herrero, J., Hidalgo, J. D., Cruz Gallegos, V., Gomez Gomez, J. D. D., Meléndez, M. L., Heredia, N., Lopez-Moreno, I., Revuelto, J., Flynn, H., Romero, A., de la Hera Portillo, Á., Jódar, J., and Diaz-Losada, E.: Monitoring snow depth by Integrating in an optimal way citizen science and other techniques, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20320, https://doi.org/10.5194/egusphere-egu24-20320, 2024.

EGU24-7008 | PICO | CR6.3

Research on avalanches caused by stability of snow cornices developed by blowing snow 

Satoru Yamaguchi, Yoichi Ito, Takahiro Tanabe, Koichi Nishimura, Satoru Adachi, Sojiro Sunako, Yoshihiko Saito, Tsubasa Okaze, Hirofumi Niiya, Kae Tsunematsu, and Hiraku Nishimori

Our research is aimed at improving the prediction accuracy of avalanches caused by the stability of snow cornices developed by blowing snow in the Niseko region, one of Japan's international ski resorts. For this purpose, several studies were conducted in cooperation with local authorities and ski resorts in the Niseko region. Specifically, a network of anemometers was installed and a system was developed to estimate areal wind conditions and snow redistribution over the entire mountain area from wind observation data. To validate the developed system, the snow cover distribution over the entire mountain area for two winters was obtained by laser survey using an aircraft. In addition, several portable ultrasonic anemometers were installed on the slopes where snow cornices develop to observe detailed wind conditions, and small LiDAR was used to continuously survey snow cornice development. We sampled snow in the developing snow cornice and analyzed its microstructure using X-ray computed tomography imaging. The presentation presents a first analysis.

 

 

How to cite: Yamaguchi, S., Ito, Y., Tanabe, T., Nishimura, K., Adachi, S., Sunako, S., Saito, Y., Okaze, T., Niiya, H., Tsunematsu, K., and Nishimori, H.: Research on avalanches caused by stability of snow cornices developed by blowing snow, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7008, https://doi.org/10.5194/egusphere-egu24-7008, 2024.

EGU24-9222 | ECS | PICO | CR6.3 | Highlight

Climate change impacts on large scale avalanche risk in alpine regions 

Gregor Ortner, Adrien Michel, Chahan M. Kropf, Yves Bühler, Marc Christen, Michael Bründl, and David N. Bresch

Observations in various regions worldwide document a decline in mean snow depth, spatial extent, and duration of snow cover, indicating a connection to climate change, especially at low elevations. Climate scenarios project further changes, but the exact consequences on future snow cover and avalanche patterns remain unknown. Our work investigates the influence of climate change on the snow cover, specifically focusing on its impact on avalanches and the associated risk to buildings. To compare the consequences of these potential changes on snow avalanche hazard and risk with the current situation, we have developed a framework to model avalanche risk on a large scale. We applied an algorithm to generate a protection forest layer, potential release areas, and conduct snow analysis for current climatic conditions. The RAMMS::LSHIM algorithm within the RAMMS avalanche model produces avalanche hazard indication maps. They are combined with the CLIMADA risk assessment platform, incorporating exposure and vulnerability data, to create spatially explicit risk maps under different avalanche return period scenarios.
To address climate change impacts, we have integrated the CH2018 climate scenario data including various model chains into avalanche hazard mapping, using the SNOWPACK snow cover model. Snow cover simulations cover the years from 1997 to 2100 and deliver three day snow accumulation data and layer temperatures for potential future avalanches. We used this data to run the RAMMS::EXTENDED avalanche model with modified snow and temperature parameters. This enabled us to create hazard indication maps considering climate change.
Results indicate a potential decrease in the spatial extent of avalanches, especially at lower altitudes, due to rising snowline, particularly in model chains with reduced snowfall. However, within CH2018, other climate model chains suggest increased snow accumulation, resulting in larger avalanches and increased pressure in high-altitude areas.
Applying the CLIMADA risk tool to climate change hazard analysis using an enhanced vulnerability curve and uncertainty analysis results in various risk outcomes. An average approach over all model chains suggests a decrease in risk, particularly in low-altitude side valleys. Single model chains with increased snowfall project higher risks despite a reduced affected area. The study underlines the need to incorporate climate change into practical avalanche hazard assessment and subsequently risk analysis.
Overall, this research, for the first time, quantifies the impact of climate change on the potential future spatial distribution of avalanches and associated changes in potential risk. The practical applicability of climate change avalanche hazard assessment was demonstrated, offering insights for stakeholders to assess future risks and consider climate change risk appraisal options. 

How to cite: Ortner, G., Michel, A., Kropf, C. M., Bühler, Y., Christen, M., Bründl, M., and Bresch, D. N.: Climate change impacts on large scale avalanche risk in alpine regions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9222, https://doi.org/10.5194/egusphere-egu24-9222, 2024.

EGU24-10420 | PICO | CR6.3

Follow-up at the small scale during snow deformation. Microstructure evolution and local heterogeneities at various strain-rates. 

David Georges, Louis Védrine, Antoine Bernard, Mathilde Bonnetier, Maurine Montagnat, Pascal Hagenmuller, and Guillaume Chambon

Snow deforms naturally in a large range of strain rates covering ductile to brittle regimes. In all situations, snow deformation is characterized by complex mechanisms taking place at the microstructure scale, with interplay between metamorphism, sintering and grain rearrangements. Current modeling efforts require better understanding and formulation of the microstructure-scale complexity.
We performed compression experiments on snow samples in order to follow the microstructure evolution at various imposed displacement velocities. The resulting strain-rates varied between 10-2 s-1 and 10-7 s-1. Samples (15 mm height, 15 mm diameter) were made out of rounded grains with an initial density of about 250 kg m-3. Samples evolution was followed by means of micro-computed X-Ray tomography (microCT) with full 3D scans performed during the slower tests and simple radiographies at a high frequency for faster tests.
In this presentation we will focus on the various metrics used to analyse the microstructure evolution on one side, in particular specific surface area (SSA) and the minimum cut area. On the other side, we will present recent developments based on digital image and volume correlations (DIC and DVC) performed on the radiographies and the 3D microCT images with the open access SPAM software (https://hal.univ-grenoble-alpes.fr/hal-03020460), in order to follow the local strain field.
We will provide analyses of the interplay between metamorphism and strain in the microstructure evolution and of the impact of mechanisms at bonds in the various strain-rate regimes explored (ductile to brittle). Snow deformation localisations revealed by DIC and DVC observations will be presented. They can be inherited from initial sample heterogeneities or take the shape of compaction bands, depending on the strain rate.
All these data and analyses will be further interpreted regarding the understanding of the small scale mechanisms of metamorphism and deformation of snow and their modeling frame.

How to cite: Georges, D., Védrine, L., Bernard, A., Bonnetier, M., Montagnat, M., Hagenmuller, P., and Chambon, G.: Follow-up at the small scale during snow deformation. Microstructure evolution and local heterogeneities at various strain-rates., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10420, https://doi.org/10.5194/egusphere-egu24-10420, 2024.

EGU24-11202 | PICO | CR6.3

Toward automatic avalanche detection with Distributed-Acoustic-Sensing leveraging telecommunication infrastructure 

Pascal Edme, Patrick Paitz, Andreas Fichtner, Alec van Herwijnen, and Fabian Walter

Snow avalanches pose significant threats in alpine regions, leading to considerable human and economic losses. The ability to promptly identify the locations and timing of avalanche events is essential for effective prediction and risk mitigation. Conventional automatic avalanche detection systems typically rely on radars and/or seismo-acoustic sensors. While these systems operate successfully regardless of weather conditions, their coverage is often confined to a single slope or a small catchment (distances < 3 km).

In our study, we demonstrate the feasibility of detecting snow avalanches using Distributed Acoustic Sensing (DAS) through existing fiber-optic telecommunication cables. Our pilot experiment, conducted over the 2021/2022 winter, involved a 10km long fiber-optic dark cable running parallel to the Flüelapass road in the eastern Swiss Alps close to Davos. The DAS data reveal distinct evidence of numerous dry- and wet-snow avalanches, even when they do not reach the cable, as confirmed photographically. We show that avalanches can be distinguished from other signals (e.g., vehicle traffic) using a frequency-dependent STA/LTA attribute, enabling their detection with high spatiotemporal resolution. These findings pave the way for cost-effective and near-real-time avalanche monitoring over extensive distances, leveraging existing fiber-optic infrastructure.

How to cite: Edme, P., Paitz, P., Fichtner, A., van Herwijnen, A., and Walter, F.: Toward automatic avalanche detection with Distributed-Acoustic-Sensing leveraging telecommunication infrastructure, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11202, https://doi.org/10.5194/egusphere-egu24-11202, 2024.

EGU24-12238 | ECS | PICO | CR6.3

Influence of snow microstructure on the compressive strength of weak layers 

Jakob Schöttner, Melin Walet, Valentin Adam, Florian Rheinschmidt, Philipp Rosendahl, Philipp Weißgraeber, Jürg Schweizer, and Alec van Herwijnen

Slab avalanches result from the failure of a weak snowpack layer buried underneath a cohesive slab. Determining the material properties of different weak layer morphologies is therefore necessary to better understand and model slab avalanche formation. Natural weak layers exhibit a variety of different microstructures and densities, and thus show different mechanical behavior. Up to now, mechanical properties of snow have been mainly evaluated based on bulk proxies such as snow density, while relevant microstructural characteristics have not been accounted for.

To establish a link between the microstructure of weak layers and their mechanical properties, we performed displacement-controlled laboratory experiments using a uniaxial testing machine. The compression experiments were recorded using a high-speed camera, allowing us to derive the strain within the weak layer. The microstructure of each batch of specimens was analyzed using micro-tomography to obtain density, specific surface area, anisotropy and correlation lengths. As testing a wide range of microstructural morphologies is difficult due to seasonal availability and the need to transport the fragile samples to the laboratory, we used both natural and artificially grown weak layers. We tested weak layers composed of facetted grains, depth hoar, surface hoar, precipitation particles and rounded grains.  

The compressive strength of more than 200 tested samples covered two orders of magnitude (0.5 kPa to 150 kPa) for weak layer densities ranging from 110 kg/m3 to 380 kg/m3. As expected, our results show a strong correlation between weak layer density and compressive strength, but also a dependence on other microstructural quantities. These results will help us improve our understanding of the mechanical properties of weak snowpack layers and will ultimately allow us to better forecast avalanche release probability.

How to cite: Schöttner, J., Walet, M., Adam, V., Rheinschmidt, F., Rosendahl, P., Weißgraeber, P., Schweizer, J., and van Herwijnen, A.: Influence of snow microstructure on the compressive strength of weak layers, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12238, https://doi.org/10.5194/egusphere-egu24-12238, 2024.

EGU24-15088 | ECS | PICO | CR6.3

Snow depth distribution measurements using low cost LiDAR sensors 

Pia Ruttner-Jansen, Julia Glaus, Annelies Voordendag, Andreas Wieser, and Yves Bühler

Redistribution of snow by wind is an important factor influencing the avalanche danger. However, it is challenging to get detailed information on variations of snow depth in avalanche release areas with sufficiently high spatiotemporal resolution. We have developed a distributed measurement system containing two low cost LiDAR sensors, cameras and meteorological sensors. In autumn 2023 we have deployed this system at a first test site, in the area of a frequently released avalanche. Two stations equipped with the sensors cover an area of around 20'000 m² and provide the snow depth distribution once per hour with a spatial resolution on the cm to m-level. The (near) real time data transmission to a local server allows for an up-to-date assessment of the conditions in the slope. First analyses show the small temporal changes of average snow depth from epoch to epoch for small areas (1m²), including some local avalanche events. We will present first results obtained from the unique dataset resulting from acquisition at high spatio-temporal resolution over the entire winter season 2023/2024, focusing particularly on the snow depth variations before and after avalanche events. In the future, the newly built up snow depth database and the additionally recorded meteorological parameters will be used to model, predict and evaluate the snow depth redistribution on a slope scale level. The data collected directly within the release areas will improve the process understanding of avalanche formation and forecasting, and will thus contribute to better protection of people and infrastructure.

How to cite: Ruttner-Jansen, P., Glaus, J., Voordendag, A., Wieser, A., and Bühler, Y.: Snow depth distribution measurements using low cost LiDAR sensors, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15088, https://doi.org/10.5194/egusphere-egu24-15088, 2024.

EGU24-16056 | PICO | CR6.3

Decennial infrasonic array analysis of snow-avalanche activity and its weather forcing in Pennine Alps: implications for forecasting 

Giacomo Belli, Duccio Gheri, Emanuele Marchetti, Paola Dellavedova, Nathalie Durand, and Eloise Bovet

Snow avalanches rank among the deadliest natural hazards in mountain environments worldwide. To date, forecasting is mostly based on measuring meteorological forcing, aiming at assessing the probability of event triggering in a certain area. To validate forecast models, information on avalanche occurrence is critical. However, real-time avalanche detection is still challenging and generally limited to radar or visual surveillance of one or a few known channels; here the need for novel monitoring solutions. In the last decades, infrasound has proven to be one of the most promising tools for real-time detection of avalanches. Indeed, snow avalanches, moving downhill, generate acoustic pressure waves in the air, which can be recorded with an array of infrasonic sensors that allows to detect and characterize the source. However, many difficulties still exist, mostly connected to the discrimination of the avalanche infrasound among the signals radiated by other natural or anthropic infrasonic sources active at the Earth's surface or in the atmosphere.

Here we present an analysis of >10 years of data recorded by a small-aperture infrasonic array deployed at an altitude of ~2000 m in Valle d'Aosta (Itay). To detect snow-avalanche events, we develop an algorithm aimed at identifying avalanche signals in the recorded infrasound dataset and calibrated on two avalanche crises occurred in the site. The identified avalanche-type infrasonic signals are then compared to local meteorological data and avalanche bulletins, to test the accuracy of our algorithm. Several clusters of avalanche-type infrasonic signals are identified on days with favourable weather conditions for the triggering of snow avalanches. Our study also allows us to investigate the meteorological forcing of snow avalanches in the Pennine Alps, showing that avalanche storms are induced preferentially as a result of the destabilisation of thick snow accumulations, but also highlighting the importance of weather patterns at seasonal scale.

This study was financially supported by the National Recovery and Resilience Plan, Mission 4 Component 2 - Investment 1.4 - NATIONAL CENTER FOR HPC, BIG DATA AND QUANTUM COMPUTING - funded by the European Union - NextGenerationEU - CUPB83C22002830001.

How to cite: Belli, G., Gheri, D., Marchetti, E., Dellavedova, P., Durand, N., and Bovet, E.: Decennial infrasonic array analysis of snow-avalanche activity and its weather forcing in Pennine Alps: implications for forecasting, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16056, https://doi.org/10.5194/egusphere-egu24-16056, 2024.

EGU24-16637 | ECS | PICO | CR6.3

The role of capillary forces in the formation of interfacial water layers in “cold” glide-snow avalanches 

Michael Lombardo, Amelie Fees, Peter Lehmann, Alec van Herwijnen, and Jürg Schweizer

Glide-snow avalanches are generally thought to come in two flavors: “cold” and “warm”. The main difference between them is the mechanism by which liquid water is generated and reaches the basal snowpack. For warm avalanches, the water comes from the snow surface via rain or surface melt. For cold avalanches, the water is thought to be generated by capillary suction or geothermal melting. Here, we focus on cold avalanches and address the role of capillary forces at the soil-snow interface. To do so, we combine theoretical considerations, snowpack simulations, and field data. Calculations based on basic principles show that the conditions necessary for capillary suction are unlikely for the representative soil types, because high soil saturation is required. Field data from the “Dorfberg” field site above Davos (eastern Swiss Alps) confirms that these saturated conditions rarely occur. Simulations of two “cold” glide-snow avalanches at the field site further confirm (i) the absence of capillary suction and (ii) the presence of geothermal melting. Thus, we suggest that in the absence of a distinct water source (e.g. spring), geothermal melting is likely responsible for the formation of liquid water in cold avalanches, while the capillary forces are responsible for the retention of this water within the basal snowpack layers.

How to cite: Lombardo, M., Fees, A., Lehmann, P., van Herwijnen, A., and Schweizer, J.: The role of capillary forces in the formation of interfacial water layers in “cold” glide-snow avalanches, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16637, https://doi.org/10.5194/egusphere-egu24-16637, 2024.

EGU24-16711 | ECS | PICO | CR6.3

Assessing avalanche activity in seismic data with modern machine learning methods. 

Andri Simeon, Cristina Pérez-Guillén, Michele Volpi, Christine Seupel, and Alec van Herwijnen

Monitoring snow avalanche activity is essential for operational avalanche forecasting and the successful implementation of mitigation measures to ensure safety in mountain regions. To facilitate and automate the monitoring process, avalanche detection systems equipped with seismic sensors provide a cost-effective solution. Still, automatically differentiating avalanche signals from other sources in seismic data remains rather challenging. This is mainly due to the complexity of the seismic signals generated by avalanches, the relatively rare occurrence of avalanches and the presence of multiple sources in the continuous recordings.

To discriminate avalanches from other sources in the continuous seismic recordings, we test three random forest classifiers using two feature sets extracted with two autoencoders and a set of 57 statistical features. We extract these features from 10s windows of the seismograms recorded with an array of five seismometers installed in Davos, Switzerland. The statistical feature set includes waveform, spectral and spectrogram attributes. The first autoencoder is composed of convolutional layers and a long short-term memory unit. This neuronal network automatically extracts 64 features from the raw waveform signal. The second autoencoder applies a sequence of fully connected layers to extract the same number of features from the spectrum of the signals. We assess the performance of each classifier and compare the results. To improve the predictive performance of the seismic system, we employ different post-processing, e.g. adaption of classification thresholds and ensembling the predictions from the three classifiers. The final model is tested with the continuous seismic data of the last winter season to potentially be used as an operational, near-real-time detection system.

How to cite: Simeon, A., Pérez-Guillén, C., Volpi, M., Seupel, C., and van Herwijnen, A.: Assessing avalanche activity in seismic data with modern machine learning methods., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16711, https://doi.org/10.5194/egusphere-egu24-16711, 2024.

EGU24-17750 | PICO | CR6.3

ISeeSnow - initiating an avalanche simulation tool intercomparison 

Anna Wirbel, Felix Oesterle, Jan-Thomas Fischer, Guillaume Chambon, Thierry Faug, Johan Gaume, Julia Glaus, Stefan Hergarten, Dieter Issler, Alexander Jarosch, Tómas Jóhannesson, Marco Martini, Martin Mergili, Matthias Rauter, Joerg Robl, Giorgio Rosatti, Paula Spannring, Christian Tollinger, Hervé Vicari, and Daniel Zugliani

The ISeeSnow pilot-study aims at bringing together and starting a conversation among the different groups in the field of gravitational mass flow simulations, with a focus on snow avalanches. These simulation tools are an integral part of engineering practice, scientific development and academic education.

At its core, an objective comparison of simulation results is performed for three different test cases, based on a generic, idealized topography as well as a real-world simulation scenario. In this initial effort, we focus on thickness-integrated shallow water models using a simple Coulomb- or classical Voellmy rheology. In this manner, comparing simulation results for the test cases, prescribing the friction parameters, topography, release area and release thickness, allows us to analyze common features and differences stemming from the various implementations, i.e. formulation of model equations, choice of numerical methods and their implementation into computer code as well as geo-data handling (input/output). We also include simulation tools that rely on a different mathematical formulation and basic assumptions (e.g. 3D models or conceptual approaches) and perform a qualitative comparison for a specially designed test case. Furthermore, performing this pilot-study helps to identify common data needs, come up with standard result formats and discuss helpful visualization options. As a third outcome, we summarize ideas on what is needed to perform a more comprehensive model intercomparison study which also tackles model verification and validation tests, with respect to test designs, required input data as well as model configuration options. In this community-based contribution, we present the concept of the ISeeSnow pilot-study, show preliminary results of the simulation comparison and give an outlook on potential avenues for a future comprehensive model intercomparison project.

How to cite: Wirbel, A., Oesterle, F., Fischer, J.-T., Chambon, G., Faug, T., Gaume, J., Glaus, J., Hergarten, S., Issler, D., Jarosch, A., Jóhannesson, T., Martini, M., Mergili, M., Rauter, M., Robl, J., Rosatti, G., Spannring, P., Tollinger, C., Vicari, H., and Zugliani, D.: ISeeSnow - initiating an avalanche simulation tool intercomparison, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17750, https://doi.org/10.5194/egusphere-egu24-17750, 2024.

EGU24-18590 | ECS | PICO | CR6.3

Elastic snow properties for the optimization of weak layer fracture toughness estimates 

Melin Walet, Jakob Schöttner, Valentin Adam, Florian Rheinschmidt, Jürg Schweizer, Philipp Rosendahl, Philipp Weissgraeber, and Alec van Herwijnen

Dry-snow slab avalanches release due to crack propagation in a weak layer inside the snowpack. Understanding the fracture characteristics of the weak layer is essential for describing the onset of crack propagation and hence for predicting avalanche release. Avalanches release on steep slopes, thus crack propagation is a mixed mode fracture problem. Yet, thus far little is known about the mixed-mode fracture toughness of weak layers, a material property describing the resistance to crack growth under different loading conditions, from mode I normal to the crack faces to mode II parallel to the crack face.

Here, we present experiments that were conducted to derive a full range interaction between mode I and mode II fracture toughness of natural weak layers. Using a mechanical model, we derived fracture toughness values under different mixed-mode loading conditions. Crucial model variables are the elastic properties of the slab and the weak layer, which we retrieved from high-speed video recordings of the experiments and digital image correlation. These elastic properties allow for optimization of the estimates for weak layer fracture toughness values. Our results show that the specific fracture energy is larger in mode II than in mode II. This agrees with the behavior observed in other materials.

In future we will investigate the fracture properties of numerous weak layer microstructures. Since the snow microstructure most likely controls the mechanical properties, a characterization of the microstructure is essential. The connection between weak layer fracture and the microstructure of weak snowpack layers can be used to ultimately improve slab avalanche forecasting.

How to cite: Walet, M., Schöttner, J., Adam, V., Rheinschmidt, F., Schweizer, J., Rosendahl, P., Weissgraeber, P., and van Herwijnen, A.: Elastic snow properties for the optimization of weak layer fracture toughness estimates, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18590, https://doi.org/10.5194/egusphere-egu24-18590, 2024.

Snow avalanches are one of the principal glacial threats, which are limited to high snow-covered alpine terrain. Mapping of Avalanche hazard and its modeling are useful in minimizing the fall risk. The current study assesses the utility of satellite imagery and GIS-based analytical hierarchical process (AHP) for mapping of possible avalanche locations for Draupadi ka Danda peak in Garhwal Himalaya, Uttarakhand. Various protruding terrain factors such as elevation, aspect, slope, curvature and land use land cover are used in this model and are derived from ALOS PALSAR DEM and Sentinel-2 images. Sensitivity analysis was performed on the chosen parameters and maximum weightage was set to slope, trailed by elevation, aspect, curvature and land use land cover. Using weighted overlay in ArcGIS avalanche susceptibility maps are formulated and distributed into five zones i.e. very low, low, moderate, high and very high zones and their validation was done by the listed avalanche occasions. Consecutively, Rapid Mass Movement Simulation (RAMMS) which is a three dimensional numerical model is used which generates parameters such as flow distance, height, velocity, pressure and momentum. The model requires a DEM of high resolution, release area of avalanche, friction parameter and was executed on the very high and high zones of avalanche susceptibility map.

How to cite: Mishra, N., Keshari, A. K., and Chahar, B. R.: Remote Sensing based mapping and modelling of potential avalanche zones in Draupadi ka Danda, Garhwal Himalayas, Uttarakhand, India, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19817, https://doi.org/10.5194/egusphere-egu24-19817, 2024.

EGU24-21128 | PICO | CR6.3

Quantification of reliability of roofs subjected to snow loadsdetermined by hydrological models 

Thomas Thiis, Iver Frimannslund, Hevi Nori, and Zhen Mustafa

Snow loads exert a significant influence on the structural integrity of buildings in the northern hemisphere, necessitating precise assessment methodologies to ensure the reliability of roofs under this environmental stressor. The determination of roof snow load is intricately linked to evaluating the weight of accumulated snow on the roof surface, a critical consideration in the design and construction of buildings. The reliability of a roof structure is conventionally gauged through the computation of the reliability index, denoted as beta. This index integrates the characteristic ground snow load and an estimation of the associated accuracy, forming a crucial metric for structural engineers. Traditionally, the characteristic ground snow load is determined by fitting a series of yearly maximum ground snow load data to a Gumbel distribution, enabling the extraction of the 50-year return period value. This process traditionally relies on data obtained from weather stations, where meticulous measurements of snow depth are conducted alongside either direct measurements or modeling of snow density. However, the landscape of snow load determination is evolving with the advent of more sophisticated hydrological models. In this context, the paper investigates the impact of transitioning from traditional station data to utilizing gridded simulation data for estimating the characteristic snow load on the ground. The hydrological model "SeNorge" serves as a pivotal tool in this investigation, offering simulated ground snow load data at a 1 km grid. The objective is to scrutinize whether this shift in methodology affects the reliability of buildings and infrastructure subjected to snow loads. The study extends its reach across various climatic zones in Norway, comparing results obtained from the hydrological model with measured data from diverse sources. The fundamental question is whether the adoption of simulated ground snow load data, as generated by advanced hydrological models, translates into a corresponding level of reliability when compared to the established paradigm of utilizing standardized ground snow load data. The results demonstrate a variable uncertainty in the quantification of the snow load depending on the climate region and elevation. When this uncertainty is applied to a reliability calculation a straightforward application of hydrological model may not maintain the same level of reliability as the traditional approach employing standardized ground snow load data. The shift in the structural reliability implies that the partial factors should be adjusted achieve the target reliability criteria when moving from measured to simulated snow load maps. This revelation holds substantial implications for the engineering community, urging a cautious approach to the adoption of newer methodologies in snow load assessments.

How to cite: Thiis, T., Frimannslund, I., Nori, H., and Mustafa, Z.: Quantification of reliability of roofs subjected to snow loadsdetermined by hydrological models, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21128, https://doi.org/10.5194/egusphere-egu24-21128, 2024.

EGU24-1603 | PICO | HS6.4

Spatial extent of rain-on-snow (ROS) events in the Arctic (Svalbard) : combining wet snow maps from TerraSAR-X and Radarsat Constellation Mission with ERA5 reanalysis, glaciological measurements, and optical Planet images 

Jean-Pierre Dedieu, Marion Momber, Olivier Champagne, Anna Wendleder, Benoit Montpetit, Eric Bernard, Jean-Michel Friedt, Olga Zolina, and Hans-Werner Jacobi

In the Arctic, extreme weather conditions such as rain-on-snow events (ROS) make the monitoring of the snowpack with remote sensing techniques increasingly relevant and necessary. In recent years, remote sensing methods based on active radar images (SAR) are well described for mapping the spatial extent of ROS events in the terrestrial Arctic (Vickers, 2022; Bartsch, 2023). However, few methods are proposed to validate the relationship between ROS and elevation for such events over glaciers likely due to the lack of in-situ measurement networks in these high latitude areas. Svalbard provides several meteorological and snow monitoring sites, which is a great value for detecting the occurrence of these ROS events and validation of the remote sensing methods.

The purpose of this study is to investigate the spatial and temporal effects of recent ROS events over the Brøgger peninsula (210 km2) in Svalbard (N 78°55’ / E 11° 55’), using remote sensing methods, local meteorological measurements and reanalyses. For each ROS event of the 2017-2023 time period, remote sensing SAR maps of wet snow (Nagler and Rott, 2000) are produced from images obtained with the TerraSAR-X (DLR) and RCM (CSA) high resolution sensors (5-m), respectively at X- and C-band frequency.

The validation of the affected areas is based (i) on ERA5 reanalysis data used to estimate the altitude of the 0°C isoline and (ii) on a network of temperature sensors installed on the Austre Lovén glacier. SAR maps, ERA5 isoline, and in-situ data are in good agreement, resulting in altitude differences between 10 and 25 m for the transition of wet and dry snow, depending on the event.

Although optical images availability is limited due to polar night and cloud cover during precipitation, it was further possible to use optical Planet images at high temporal and spatial resolution (3-m) to determine the ROS impact after the events on the properties of the snow cover. The decreasing signal of the red-edge and near-infrared bands indicate higher snow densities and a stronger wetness of the snowpack, which closely aligns with in-situ observations through snow stratigraphy.

How to cite: Dedieu, J.-P., Momber, M., Champagne, O., Wendleder, A., Montpetit, B., Bernard, E., Friedt, J.-M., Zolina, O., and Jacobi, H.-W.: Spatial extent of rain-on-snow (ROS) events in the Arctic (Svalbard) : combining wet snow maps from TerraSAR-X and Radarsat Constellation Mission with ERA5 reanalysis, glaciological measurements, and optical Planet images, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1603, https://doi.org/10.5194/egusphere-egu24-1603, 2024.

EGU24-1915 | ECS | PICO | HS6.4

Evaluating MODIS snow products using an extensive wildlife camera network 

Catherine Breen, Carrie Vuyovich, John Odden, Dorothy Hall, and Laura Prugh

Snow covers a maximum of 47 million km2 of Earth ’s northern hemisphere each winter and is an important component of the planet ’s energy balance, hydrology cycles, and ecosystems. Monitoring regional and global snow cover has increased in urgency in recent years due to warming temperatures and declines in snow cover extent. Optical satellite instruments provide large-scale observations of snow cover, but cloud cover and dense forest canopy can reduce accuracy in mapping snow cover. Remote camera networks deployed for wildlife monitoring operate below cloud cover and in forests, representing a virtually untapped source of snow cover observations to supplement satellite observations. Using images from 1181 wildlife cameras deployed by the Norwegian Institute for Nature Research (NINA), we compared snow cover extracted from camera images to Moderate Resolution Imaging Spectroradiometer (MODIS) snow cover products during winter months of 2018–2020. Ordinal snow classifications (scale = 0–4) from cameras were closely related to normalized difference snow index (NDSI) values from the MODIS Terra Snow Cover Daily L3 Global 500 m (MOD10A1) Collection 6 product (R2 = 0.70). Tree canopy cover, the normalized difference vegetation index (NDVI), and image color mode influenced agreement between camera images and MOD10A1 NDSI values. For MOD10A1F, MOD10A1’s corresponding cloud-gap filled product, agreement with cloud-gap filled values decreased from 78.5% to 56.4% in the first three days of cloudy periods and stabilized thereafter. Using our camera data as validation, we derived a threshold to create daily binary maps of snow cover from the MOD10A1 product. The threshold corresponding to snow presence was an NDSI value of 40.50, which closely matched a previously defined global binary threshold of 40 using the MOD10A2 8-day product. These analyses demonstrate the utility of camera trap networks for validation of snow cover products from satellite remote sensing, as well as their potential to identify sources of inaccuracy.

How to cite: Breen, C., Vuyovich, C., Odden, J., Hall, D., and Prugh, L.: Evaluating MODIS snow products using an extensive wildlife camera network, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1915, https://doi.org/10.5194/egusphere-egu24-1915, 2024.

EGU24-10881 | PICO | HS6.4

SNOWTRAN: a software package for the solution of direct and inverse problems of snow optics 

Alexander Kokhanovsky, Maximillian Brell, Karl Segl, and Sabine Chabrillat

We present a software suite SNOWTRAN aimed at the solution of forward and inverse problems of snow optics. The numerical procedure is based on the approximate solutions of the radiative transfer equation and the geometrical optics approximation for local optical parameters of snow such as the probability of photon absorption and the average cosine of the single light scattering angle. The model is validated using EnMAP and PRISMA spaceborne imaging spectroscopy data close to the Concordia research station in Antarctica. The SNOWTRAN is applied for the determination of the total ozone, the precipitable water vapor, the snow grain size and the assessment of the snowpack vertical inhomogeneity using EnMAP imagery over the Aviator Glacier and in the vicinity of the Concordia research station in Antarctica. The remote sensing results based on EnMAP measurements revealed a large increase in precipitable water vapor at the Concordia research station in February 2023 linked to warming event, and a 4 times larger grain size at Aviator Glacier compared to the Concordia station.

How to cite: Kokhanovsky, A., Brell, M., Segl, K., and Chabrillat, S.: SNOWTRAN: a software package for the solution of direct and inverse problems of snow optics, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10881, https://doi.org/10.5194/egusphere-egu24-10881, 2024.

EGU24-11034 | ECS | PICO | HS6.4

Using Multitemporal Sentinel-1 imagery for wet snow dynamics characterization in Mediterranean mountain catchments: a case study in Sierra Nevada, Spain 

Pedro Torralbo Muñoz, Rafael Pimentel Leiva, María José Polo Gómez, and Claudia Notarnicola

Monitoring snowmelt dynamics in mountainous catchments  is essential for comprehending downstream water release, streamflow response and consequently, for a better management of water resources at the catchment scale.  In a consolidated snowpack when external inputs become positive, the snow turns into wet snow and the melting phase begins. This change modifies the dielectric constant of the snowpack which can be detected remotely using information in the microwave region of the electromagnetic spectrum. Sentinel-1 (S-1) synthetic-aperture radar (SAR) has emerged as a widely utilized technique for this purpose due to its frequent acquisitions and all-weather capability. 

This study seeks to, first, explore the capabilities of C-band S-1 SAR imagery, which has been demonstrated in previous studies in other regions such as the Alps, in capturing multi-seasonal snowmelt dynamics and, second to linked these wet-dynamics to changes in streamflow response over Mediterranean mountain areas . The study was carried out at two scales: plot and catchment: At the plot scale, the Refugio Poqueira experimental site, which is located at 2500 m a.s.l. was chosen. At the catchment scale, the headwaters of the Poqueria River, which is a  snow-driven catchment  located in the southern face of Sierra Nevada, was selected. Four hydrological years with high hydroclimatic variability, from 2016-2017 to 2019-2020, were used in the study to capture the heterogeneity of the area. 

The general change detection approach for identifying wet snow was adapted for these regions, utilizing the average S-1 SAR image from the preceding summer as  reference imagery and employing a threshold of −3.00 dB for discriminating wet snow. This adaptation was validated using Landsat images as a reference dataset, yielding a general accuracy of 0.79. The local scale analysis demonstrates that S-1 SAR imagery was  able to capture four types of melting cycles including the well-known main melting event during the spring season. The other three melting cycles are linked to the Mediterranean mountains climate and can occur throughout the hydrological year. When applied at the catchment scale, distributed melting-runoff onset maps were developed to enhance understanding of the spatiotemporal evolution of melting dynamics. Finally, a linear correlation between melting dynamics and streamflow was established for prolonged melting cycles, with a determination coefficient (R2) ranging from 0.62 to 0.83 and an average delay of approximately 21 days between melting onset and streamflow peak.

Acknowledgments: This work has been funded by the project PID2021-12323SNB-I00, HYPOMED—“Incorporating hydrological uncertainty and risk analysis to the operation of hydropower facilities in Mediterranean mountain watersheds”.

How to cite: Torralbo Muñoz, P., Pimentel Leiva, R., Polo Gómez, M. J., and Notarnicola, C.: Using Multitemporal Sentinel-1 imagery for wet snow dynamics characterization in Mediterranean mountain catchments: a case study in Sierra Nevada, Spain, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11034, https://doi.org/10.5194/egusphere-egu24-11034, 2024.

EGU24-11542 | ECS | PICO | HS6.4

Trends in snow persistence at the Central Pyrenees derived from 40 years of Landsat satellite images 

Martí Navarro Planes, Cristina Cea López, Xavier Pons, Lluís Pesquer Mayos, and Lluís Gómez Gener

An accurate quantification of the spatiotemporal dynamics of seasonal snow is essential for understanding and predicting the impacts of climate change on mountain regions and their feedback on global climate. This is especially critical in southernmost Mediterranean mountains such as the Pyrenees, where the extent of seasonally snow-covered zones (or persistent snow areas) are expected to decrease more abruptly than other mountain regions of the world. Here we use 40 years of Landsat satellite images (from 1984 to 2023) to study the trend in snow surface area and snow persistence (the fraction of time that the snow remains on the ground) across different spatial scales (from catchment to region) within the Central Pyrenees, Spain. In addition, snow surface data has been correlated with altitude and incident solar radiation to understand the role of topography on driving snow persistence distribution patterns.

How to cite: Navarro Planes, M., Cea López, C., Pons, X., Pesquer Mayos, L., and Gómez Gener, L.: Trends in snow persistence at the Central Pyrenees derived from 40 years of Landsat satellite images, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11542, https://doi.org/10.5194/egusphere-egu24-11542, 2024.

EGU24-11557 | ECS | PICO | HS6.4 | Highlight

Correlation of Land Surface Temperature and air temperature with albedo in Maritime Antarctica using MODIS and in situ data. 

Alejandro Corbea-Pérez, Carmen Recondo, and Javier F. Calleja

In this work, we analyze the relationship between albedo and temperature using albedo and Land Surface Temperature (LST) MODIS collection 6 (C6) and in situ data at Livingston Island, Maritime Antarctica. It is known that the relationship between temperature and albedo could have an important impact on global climate models, especially in places where permafrost distribution is complex, as in the South Shetland Islands (SSI) archipelago. Our results show that LST is not well correlated with albedo, which is consistent with the fact that air temperature (Ta) and surface temperature (Ts) do not separately explain the albedo drop, as previous work in the study area has shown. The best agreement was obtained between Aqua and Terra LST and in situ albedo, while the comparison between albedo MODIS and LST yields the worst results, which could be due to the difference in pixel size of MODIS albedo and LST products (500 m and 1000 m, respectively). However, for Ta versus albedo for all data, the decreasing slope of the fit suggests that higher temperatures are associated with lower snow albedo values. This reaffirms the idea that in polar areas, due to their characteristics, the decrease in snow albedo depends not only or mainly on temperature, but also on multiple factors such as the evolution of snow grain size and precipitation rates, among others. 

How to cite: Corbea-Pérez, A., Recondo, C., and Calleja, J. F.: Correlation of Land Surface Temperature and air temperature with albedo in Maritime Antarctica using MODIS and in situ data., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11557, https://doi.org/10.5194/egusphere-egu24-11557, 2024.

EGU24-11620 | ECS | PICO | HS6.4

Towards operational mapping and estimation of snow cover phenology parameters in the Atlas Mountains, Morocco, using multi-sensor satellite data and Google Earth Engine.  

youssra El jabiri, Abdelghani Boudhar, Abdelaziz Htitiou, Eric Sproles, Mostafa Bousbaa, Hafsa Bouamri, and Abdelghani Chehbouni

The lack of knowledge about the temporal variability, or snow cover phenology and its spatial variation poses enormous challenges to water resource managers who mostly rely on a few weather stations with limited spatial coverage which prevents them from having a complete understanding of snow changes as a whole. Meanwhile, the free availability, wide-coverage, frequent updating, and long-term time horizon make data from programs such as Landsat and Sentinel-2 a valuable data source for reliable snow data information at an unprecedented spatial scale.

In this context, this research aims to derive the snow phenology parameters (first day of snowfall, last day of snow melt; and snow duration) over Morocco’s Atlas Mountains by combining over 10,000 images from Landsat-8 and Sentinel-2 satellites for four hydrological years (2016-2021) to create a harmonized product with a time interval of about 3 days using Google Earth Engine platform. The time series produced allowed us to create detailed maps of snow cover and extract a homogeneous normalized difference snow index (NDSI) profile over the four years whereby we were able to determine the optimal threshold to separate the presence of snow from its absence.

  The results showed that derived seasonality snow metrics provide considerable variation in both time and space, where an increase in snowpack measurement values at higher elevations can be observed. The experimental results demonstrate that the proposed workflow can accurately derive snow seasonality timing with almost a day and a half delay than the in-situ observed dates and with an overall accuracy equal to 0.96.

  We expect these results to benefit various applications such as hydrological modeling, natural hazards, and regional climate change studies.

How to cite: El jabiri, Y., Boudhar, A., Htitiou, A., Sproles, E., Bousbaa, M., Bouamri, H., and Chehbouni, A.: Towards operational mapping and estimation of snow cover phenology parameters in the Atlas Mountains, Morocco, using multi-sensor satellite data and Google Earth Engine. , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11620, https://doi.org/10.5194/egusphere-egu24-11620, 2024.

EGU24-11677 | ECS | PICO | HS6.4

A novel machine learning approach for estimating snow depth in the European Alps from Sentinel-1 imagery 

Devon Dunmire, Hans Lievens, Isis Brangers, Lucas Boeykens, and Gabriëlle De Lannoy

Despite the critical importance of understanding trends in snow depth and mass for making informed decisions about water resources and adaptation to climate change, these properties are challenging to quantify, especially in remote, mountainous areas with complex topography.  The increasing availability of frequent, high resolution synthetic aperture radar (SAR) observations from active microwave satellites has provided the opportunity to provide high-resolution estimates of mountain snow depth at large spatial and frequent temporal scales. As a result, novel approaches have been developed for SAR-based snow depth retrievals utilizing C-band microwave imagery. These SAR-based methods are not without their own set of limitations and are challenged by shallow snowpacks, high vegetation cover, and wet snow conditions. Here, we seek to overcome these existing challenges by developing a machine learning approach to estimate snow depth over the European Alps using Sentinel-1 imagery, an optical satellite-based snow cover product, and static information such as elevation, slope, aspect, topographical position index and forest cover fraction. We demonstrate that our machine learning approach can more accurately estimate snow depth than existing methods at independent in-situ test sites throughout the Alps and has especially improved performance in deep snow and wet snow conditions. Using feature importance scores, we also investigate when and where the Sentinel-1 data provides the most benefit for snow depth estimation. Our approach optimizes the use of Sentinel-1 imagery by learning when these observations are effective for retrieving snow depth, while relying on other topographical information when Sentinel-1 observations are not suitable.

How to cite: Dunmire, D., Lievens, H., Brangers, I., Boeykens, L., and De Lannoy, G.: A novel machine learning approach for estimating snow depth in the European Alps from Sentinel-1 imagery, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11677, https://doi.org/10.5194/egusphere-egu24-11677, 2024.

EGU24-13030 | ECS | PICO | HS6.4

Towards a Deep Learning-based Spatio-temporal Fusion Approach for Accurately Improving Snow Cover Mapping: A Case Study in the Moroccan Atlas Mountains with Performance Evaluation 

Mostafa Bousbaa, Abdelghani Boudhar, Christoph Kinnard, Haytam Elyoussfi, Nadir Elbouanani, Abdelaziz Htitiou, Bouchra Bargam, Karima Nifa, and Abdelghani Chehbouni

Remote sensing technologies provide continuous and detailed observations of various land surface parameters, including snow cover, vegetation, land surface temperature, soil moisture, and evapotranspiration, offering invaluable information at various scales and contexts. One of the major uses is the precise mapping and monitoring of seasonal snow cover dynamics, which are essential for water management and global water balance modeling. Since an intelligent ecosystem based on accurate snow cover estimation requires a collection of high-resolution satellite images, both temporally and spatially, to capture snow dynamics, particularly in semi-arid areas where snowfall is extremely variable. These requirements can be difficult to achieve based on a single sensor, mainly due to the trade-offs between the temporal, spectral, and spatial resolutions of the available satellites. In addition, atmospheric conditions and cloud contamination can increase the number of missing satellite observations. However, there is a promising solution to these limitations. Exploiting the complementary capabilities of the new-generation multispectral sensors aboard Landsat-8 (L8) and Sentinel-2 (S2), with spatial resolutions ranging from 10 to 30 meters, offers an unprecedented opportunity to significantly advance the accuracy of snow cover mapping. Hence, this study aims to investigate the effectiveness of the combined use of optical sensors through deep learning-based spatiotemporal image fusion to capture snow dynamics and produce detailed and dense Normalized Snow Difference Index (NDSI) time series in a semi-arid context. Three distinct deep learning models, namely Very Deep Super Resolution (VDSR), Super Resolution Unet (SR-Unet), and Residual Convolutional Neural Network (RCNN), were evaluated and compared to fuse L8 and S2 data. The findings indicate that all three approaches can provide accurate estimates for a coarse-resolution image at a given fusion date, although there are notable disparities in prediction quality between the different approaches. Specifically, R-squared values were measured at 0.94, 0.92, and 0.96 for RCNN, SR-Unet, and VDSR, respectively, with corresponding root mean square error (RMSE) values of 0.09, 0.11, and 0.08. Our results suggest that the VDSR model is particularly effective in producing high-resolution merged snow time series and can compensate for the absence of ground snow cover data.

How to cite: Bousbaa, M., Boudhar, A., Kinnard, C., Elyoussfi, H., Elbouanani, N., Htitiou, A., Bargam, B., Nifa, K., and Chehbouni, A.: Towards a Deep Learning-based Spatio-temporal Fusion Approach for Accurately Improving Snow Cover Mapping: A Case Study in the Moroccan Atlas Mountains with Performance Evaluation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13030, https://doi.org/10.5194/egusphere-egu24-13030, 2024.

EGU24-14040 | PICO | HS6.4

Snow-depth Spatial Distribution Analysis Technology linked to Ground Observation Network 

Narae Kang, Jungsoo Yoon, and Seokhwan Hwang

In this study, we attempted to classify snowfall patterns using multiple dual-polarization radars and quantitatively review the amount of snowfall observed from radar using a ground observation network (snow depth). In order to more quantitatively compare the difference between radar reflectivity and precipitation (snow) intensity compared to ground observed snow depth, comparison was made on an hourly basis, taking into account the Korea Meteorological Administration's snow observation data provision period (1 hour). Radar observation data were compared with precipitation intensity based on cumulative reflectivity, differential reflectivity, and specific differential phase difference. Compared to radar reflectivity, there were various delays ranging from 2 to 7 hours from the time the precipitation intensity accumulated with the snow depth. In addition, the difference between the time of increase in snow cover is judged to be an error generated by the wind, and it is necessary to expand the range of radar pixels as well as the blinding factor to take into account the influence of wind.

 

Acknowledgments

This research was supported by a grant(2022-MOIS61-003(RS-2022-ND634022)) of Development Risk Prediction Technology of Storm and Flood for Climate Change based on Artificial Intelligence funded by Ministry of Interior and Safety(MOIS, Korea).

How to cite: Kang, N., Yoon, J., and Hwang, S.: Snow-depth Spatial Distribution Analysis Technology linked to Ground Observation Network, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14040, https://doi.org/10.5194/egusphere-egu24-14040, 2024.

EGU24-15736 | PICO | HS6.4

A new snow depth forecast data using cumulative distribution function matching in South Korea 

Hyunho Jeon, Seulchan Lee, and Minha Choi

Over the past decade, heavy snow has caused the third-largest amount of disaster damage in South Korea, following typhoons and heavy rain. To prevent damage from heavy snow effectively, it is necessary to forecast weather conditions. The Korea Meteorological Administration uses the Local Data Assimilation and Prediction System (LDAPS) to forecast hydrometeorological factors. However, the performance of LDAPS snow depth data is inferior to that of other models and requires correction. In this study, a cumulative distribution function (CDF) matching was used to correct LDAPS snow depth data. The CDF matching was carried out by utilizing ERA5-Land snow depth data to generate snow depth forecasting data for 12, 24, and 36-hour intervals. The forecasting data for snow depth is expected to generate snow disaster risk prediction data that can help reduce disaster losses on the Korean Peninsula.

How to cite: Jeon, H., Lee, S., and Choi, M.: A new snow depth forecast data using cumulative distribution function matching in South Korea, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15736, https://doi.org/10.5194/egusphere-egu24-15736, 2024.

EGU24-16806 | ECS | PICO | HS6.4

Snow accumulation patterns from 2023 Airborne Laser Scanning data in Trail Valley Creek, Western Canadian Arctic 

Daniela Hollenbach Borges, Inge Grünberg, Jennika Hammar, Nick Rutter, Thomas Krumpen, and Julia Boike

Snow cover plays a pivotal role in the Arctic's climate, hydrology, and ecology, making the understanding of its deposition and accumulation dynamics crucial. Snow depth and its duration can directly influence soil temperature: the insulating properties of snow increase with greater snow depth, which prevents soil temperatures from declining in winter.  Trail Valley Creek, NWT, Canada, is located at the northern boundary of the tundra-taiga transition zone, approximately 45 km north of Inuvik, and is underlain by continuous permafrost. The region’s rapid warming points to a trend of vegetation changes such as shrub expansion northwards into the tundra.

Topography and vegetation cover are the main drivers of spatial variation of snow depth across different landscapes, while wind significantly influences snow redistribution. This reallocation causes snow to accumulate preferably in terrain features such as valleys and leeward sides of ridges, and taller vegetation, as their height and intricate structure can favour snow trapping. Understanding the relationships among snow distribution, topography features, and vegetation types is vital, though it is often limited by the scarcity of high-resolution data with broad spatial cover.

To investigate the spatial snow distribution in Trail Valley Creek, we analyzed how snow depth varies according to different topography classes and slope aspects, as well as the region’s different vegetation classes and heights. 

For this purpose, we explored records from Aerial Laser Scanning (ALS) collected during both winter and summer of 2023, covering an area of over 170 km2. We generated a high-resolution Digital Elevation Model (DEM) from the winter snow-covered surface (2023-04-02), a Digital Terrain Model (DTM) from the summer snow-free terrain (2023-07-10), and by combining both, created a 1-m resolution snow depth map of the area. Additionally, we used 3129 Magnaprobe ground-based snow depth measurements for validation (2023-03-26 to 2023-03-29). 

For the topography analysis, we classified the slope aspects, and subdivided the terrain into 10 geomorphological classes using the geomorphons approach. This method calculates terrain forms, such as plateaus, slopes, ridges and valleys, and their associated geometry using a machine vision approach. To analyze the role of vegetation cover, we used a 13-class map that categorizes land-cover features and vegetation types, such as graminoids, shrubs and trees, and vegetation height rasters, derived from the ALS summer data.

Snow is the main driver of the hydrological system in Trail Valley Creek, and the outcomes of this study will provide insights in the important interplay between vegetation, snow depth and terrain characteristics in a permafrost landscape.

How to cite: Hollenbach Borges, D., Grünberg, I., Hammar, J., Rutter, N., Krumpen, T., and Boike, J.: Snow accumulation patterns from 2023 Airborne Laser Scanning data in Trail Valley Creek, Western Canadian Arctic, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16806, https://doi.org/10.5194/egusphere-egu24-16806, 2024.

EGU24-425 | ECS | Posters on site | ITS5.14/GD7.3

Dynamic recrystallization of olivine during simple shear: evolution of microstructure and crystallographic preferred orientation from full-field numerical simulations 

Yuanchao Yu, Maria-Gema Llorens, Albert Griera, Enrique Gomez-Rivas, Paul D. Bons, Daniel Garcia-Castellanos, Baoqin Hao, and Ricardo A. Lebensohn

The deformation of the upper mantle is predominantly governed by the mechanical behavior of olivine (Karato et al., 1989). During mantle flow, olivine undergoes crystal-plastic deformation, leading to the development of crystallographic preferred orientations (CPOs). In this process, the a-axes of olivine polycrystalline aggregates align with the flow direction (Hansen et al., 2012). Consequently, the observed CPOs in olivine-rich rocks serves as an indicator of the mantle flow direction. While the influence of plastic deformation is well understood, the role of dynamic recrystallization during deformation remains not fully comprehended, hindering our ability to interpret the deformation history of naturally-deformed rocks.

This contribution employs microdynamic numerical simulations of olivine polycrystalline aggregates with varying iron content (fayalite content) to explore the CPO and grain size response to dynamic recrystallization. Utilizing a full-field approach with explicit simulation of viscoplastic deformation (http://www.elle.ws; Bons et al., 2008; Piazolo et al., 2019) and dynamic recrystallization processes under simple shear boundary conditions up to high strain, this study indicates that simulations with only dislocation glide and also those including recrystallization successfully reproduce such steady state conditions, without requiring other potential mechanisms. The model establishes a framework for understanding the development of olivine CPOs in mantle rocks, highlighting the interplay between plastic deformation and dynamic recrystallization processes, including grain boundary migration, intracrystalline recovery, and new grain nucleation.

Acknowledgements: Yuanchao Yu acknowledges funding by the China Scholarship Council for a PhD scholarship (CSC-202008130104). This work has been developed using the facilities of the Laboratory of Geodynamic Modelling of GEO3BCN-CSIC.

How to cite: Yu, Y., Llorens, M.-G., Griera, A., Gomez-Rivas, E., Bons, P. D., Garcia-Castellanos, D., Hao, B., and Lebensohn, R. A.: Dynamic recrystallization of olivine during simple shear: evolution of microstructure and crystallographic preferred orientation from full-field numerical simulations, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-425, https://doi.org/10.5194/egusphere-egu24-425, 2024.

EGU24-2189 | ECS | Orals | ITS5.14/GD7.3

Modeling ice and olivine CPO evolution and its affect on large-scale flow in two-way coupled simulations 

Nicholas Rathmann, David Lilien, Christine Hvidberg, Aslak Grinsted, Dorthe Dahl-Jensen, Klaus Mosegaard, Ivanka Bekkevold, and David Prior

We present a spectral-space CPO model that allows for efficient and seamless simulation of anisotropic polycrystalline flows at large scale, relevant for ice sheets and Earth’s upper mantle. The CPO model is two-way coupled with a bulk orthotropic power-law rheology using a linear grain homogenization scheme, making analytical and frame-independent calculations of CPO-induced viscous anisotropy possible and computationally cheap. The effect of two-way coupling flow and CPO evolution is explored in idealized finite element simulations of ice stream flow and mantle thermal convection. In both cases, we find that strain-rate fields are non-trivially affected, and we briefly discuss the consequences for ice-stream self-reinforcement and the coupling between plate motions and the sublithospheric mantle.

This contribution is mainly focused on introducing our modeling framework “specfab” to the wider community.

How to cite: Rathmann, N., Lilien, D., Hvidberg, C., Grinsted, A., Dahl-Jensen, D., Mosegaard, K., Bekkevold, I., and Prior, D.: Modeling ice and olivine CPO evolution and its affect on large-scale flow in two-way coupled simulations, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2189, https://doi.org/10.5194/egusphere-egu24-2189, 2024.

EGU24-4569 | Orals | ITS5.14/GD7.3 | Highlight

A structural geologist's view on the Northeast Greenland Ice Stream 

Paul D. Bons, Steven Franke, Daniela Jansen, Yu Zhang, and Ilka Weikusat

The Northeast Greenland Ice Stream (NEGIS) is a fascinating, over 500 km long structure in the Greenland Ice Sheet. The ice stream shows many features, such as folds and shear zones, that are also common in other ductile rocks. Geological methods and expertise may contribute to a better understanding of NEGIS and similar deformation structures in ice sheets. It is standard practice in oil and gas exploration to create 3D-structural models from parallel seismic lines. This approach, applied to radar profiles, is relatively new in glaciology (Bons et al., Nat. Comm. 2016, DOI: 10.1038/ncomms11427) but provides far more insight into the structural architecture and evolution of ice sheets than single radar sections. A 3D-structural model of upstream NEGIS reveals how pre-existing folds are offset within the ice stream. With that, classical strain analysis methods can be applied to quantify the deformation of these folds in the shear margins. This reveals that the total offset at the level of the EGRIP drilling project is in the order of up to 75 km and that the finite shear strain in the shear margins is around 18. With present-day shear-strain rates in the shear margins, such a finite offset and shear strain are achieved in ≤2000 yrs. This strain analysis also proves that ice does not flow through shear margins, but that the shear margins instead advect with the ice. This means that 'flow lines' (which should better be called 'streamlines') are not the same as 'path lines', as is now often assumed. The two are only the same in a time-invariant velocity field, which does not apply to NEGIS. Shear zones in other ductile rocks show that rocks never flow through shear zones, but shear zones can shift or 'jump' to new locations, as is actually observed in NEGIS. Geological principles to analyse and date the formation and activity of salt diapirs and syn-sedimentary faults can also be applied to folds observed in and around NEGIS. This reveals that fold amplification inside the shear margins ceased about 2000 yrs ago, which can be explained by the formation of the shear margins and concomitant reorientation of the CPO. A combination of several structural geological methods thus enables constraining the age of NEGIS as we now know it to about 2000 yrs, which is much less than previously assumed. The surprisingly late appearance of NEGIS, as well as the demise of ice streams in the Holocene (based on 3D-analyses of folded stratigraphy; Franke et al., Nature Geosci. 2022, Doi: 10.1038/s41561-022-01082-2) indicates that ice sheets are very dynamic, mostly due to the highly non-linear (n=4) and anisotropic rheology of ice.

How to cite: Bons, P. D., Franke, S., Jansen, D., Zhang, Y., and Weikusat, I.: A structural geologist's view on the Northeast Greenland Ice Stream, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4569, https://doi.org/10.5194/egusphere-egu24-4569, 2024.

EGU24-5872 | ECS | Orals | ITS5.14/GD7.3

How ice anisotropy contributes to fold and ice stream in large-scale ice-sheet models 

Yu Zhang, Paul D. Bons, Till Sachau, and Steven Franke

Satellite and airborne sensors have provided detailed data on ice surface flow velocities, englacial structures of ice sheets and bedrock elevations. These data give insight into the flow behaviour of ice sheets and glaciers. One significant phenomenon observed is large-scale folds (over 100 m in amplitude) in the englacial stratigraphy in the Greenland ice sheet. A large population of folds is located at ice streams, where the flow is distinctly faster than in the surroundings, such as the North-East Greenland Ice Stream (NEGIS). While there is no consensus regarding the formation of large-scale folds, unraveling the underlying mechanisms presents significant potential for enhancing our understanding of the formation and dynamics of ice streams.

Ice in ice sheets is a ductile material, i.e., it can flow as a thick viscous fluid with a power-law rheology. Furthermore, ice is significantly anisotropic in its flow properties due to its crystallographic preferred orientation (CPO). Here, we use the Full-Stokes code Underworld2 (Mansour et al.,2022) for 3D modelling of the power-law and transversely isotropic ice flow, also in comparison with the isotropic ice models.

Our simulated folds with anisotropic ice show complex patterns on a bumpy bedrock, and are classified into three types: large-scale folds (fold amplitudes >100 m), small-scale folds (fold amplitudes <<100 m, wavelength <<km) and recumbent basal-shear folds. Our results indicate that bedrock topography contributes to perturbations in ice layers, and that ice anisotropy due to the CPO amplifies these into large-scale folds in convergent flow by horizontal shortening. As for our ice stream model, we simulate convergent flow as initial condition, which subsequently initiates the development of shear margins due to the rotation of the ice crystal basal planes. As soon as the shear margins develop, the ice stream starts to propagate upstream in a short time and narrows in the upstream part. Our modeling shows that the anisotropic rheology of ice and CPO change play a significant role for large-scale folding and for the initiation of ice streams with distinct shear margins. Hence, we promote the implementation of ice anisotropy in large-scale ice-sheet evolution models as it holds the potential to introduce novel perspectives to the glaciological community on the dynamics of ice flow.

 

References

John Mansour, Julian Giordani, Louis Moresi, Romain Beucher, Owen Kaluza, Mirko Velic, Rebecca Farrington, Steve Quenette, & Adam Beall. (2022). Underworld2: Python Geodynamics Modelling for Desktop, HPC and Cloud (v2.12.0b). Zenodo. https://doi.org/10.5281/zenodo.5935717

How to cite: Zhang, Y., Bons, P. D., Sachau, T., and Franke, S.: How ice anisotropy contributes to fold and ice stream in large-scale ice-sheet models, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5872, https://doi.org/10.5194/egusphere-egu24-5872, 2024.

EGU24-7333 | Orals | ITS5.14/GD7.3

A physically-based formulation for texture evolution during dynamic recrystallization. A case study for ice 

Maurine Montagnat, Thomas Chauve, Véronique Dansereau, Pierre Saramito, Kevin Fourteau, and Andréa Tommasi

Dynamic recrystallization can have a strong impact on texture development during the deformation of polycrystalline materials at high temperature, in particular for those with strong viscoplastic anisotropy such as ice. Owing to this anisotropy, recrystallization is essential for ensuring strain compatibility. The development of recrystallization textures leads to significant mechanical softening, both in laboratory or natural conditions (glaciers, ice sheets). Accurately predicting ice texture evolution due to recrystallization during tertiary creep remains a challenge, yet is crucial to account adequately for texture-induced anisotropy in large-scale models of glacial ice flow. We propose a new formulation for texture evolution due to dynamic recrystallization. This formulation is physically-based on an orientation attractor which maximizes the Resolved Shear Stress (RSS) on the easiest slip system in the crystal (basal slip for ice). The attractor is implemented in an equation of evolution of the crystal orientation with deformation, which is coupled to an anisotropic viscoplastic law (Continuous Transverse Isotropic - CTI) that provides the mechanical response of the ice crystal. The set of equations, which is the core of the R3iCe open source model is solved using finite elements method with a semi implicit scheme coded using the Rheolef library. R3iCe is validated by comparison with laboratory creep data for ice polycrystals under simple shear, uniaxial compression and tension. It correctly reproduces the texture evolution and the mechanical softening observed during tertiary creep. R3iCe therefore allows predicting enhancement factors that may be implemented in large-scale flow models. Although the validation was performed for ice, the R3iCe implementation is generic and applies for any material adequately described using a CTI law.

How to cite: Montagnat, M., Chauve, T., Dansereau, V., Saramito, P., Fourteau, K., and Tommasi, A.: A physically-based formulation for texture evolution during dynamic recrystallization. A case study for ice, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7333, https://doi.org/10.5194/egusphere-egu24-7333, 2024.

EGU24-8169 | ECS | Posters on site | ITS5.14/GD7.3

The coupled evolution of crystal orientation fabric and ice flow in ice streams 

Laura Rysager, Nicholas Rathmann, Christine Hvidberg, and Aslak Grinsted

The evolution of grain orientations as a function of flow in polycrystalline glacier ice can greatly affect the bulk viscous anisotropy of ice, and hence mass loss from Earth’s large ice sheets through fast-flowing ice streams where such effects are thought to be important. In this study, we model the strain-induced evolution of grain orientation (fabric) of Lagrangian parcels of ice propagating into, and through, the North-East Greenland Ice Stream (NEGIS) given the local deformation as observed from satellite-derived surface strain rate fields. This allows us to estimate the local flow enhancement factors to be better at understanding the relevance of viscous anisotropy of ice in the ice streams. As the parcels move into and through the ice stream, very different strain-rate regimes are encountered (outside, in the shear margin, and inside the ice stream) which change the fabric over short spatial/temporal scales. To test the model predictions, we compare the modeled fabric eigenvalues with horizontal eigenvalue differences inferred from radar measurements made near the EGRIP drill site.

How to cite: Rysager, L., Rathmann, N., Hvidberg, C., and Grinsted, A.: The coupled evolution of crystal orientation fabric and ice flow in ice streams, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8169, https://doi.org/10.5194/egusphere-egu24-8169, 2024.

Rocks from the Earth mantle and polar ices have in common a nonlinear rheology and low crystal symmetries leading often to a limited number of independent slip systems for the glide or climb of dislocations. Both deform at elevated homologous temperatures, mostly under creep. Very large plastic deformation occurs during large scale geophysical flows, leading to pronounced crystallographic texture and an associated anisotropic rheology. Polar ice is a pure material, whereas several mineral phases are present simultaneously the mantle. The mantle deforms at extremely slow strain-rates, 10 orders of magnitude smaller than standard laboratory strain-rates, and thus the estimation of the mantle behaviour requires a drastic extrapolation from lab data. A consequence of the features outlined above is that deformation of mantle rocks or polar ices leads to a strong heterogeneity of the stress and strain-rate fields inside the polycrystalline aggregates, at the intragranular (micron) scale. This field heterogeneity has strong implication in terms of texture evolution, recrystallization, but also on the effective flow stress. Another consequence is that simple or ad-hoc micromechanical models are often inaccurate when the goal is to estimate the in situ nonlinear and anisotropic rheology, and the microstructure evolution at large strain, as the activation of slip systems is highly sensitive to stress fluctuations. In this presentation, we will review existing mean-field models for polycrystalline aggregates, show their capabilities / limitations with respect to reference full-field solutions, and show the benefit of the fully-optimized second order self-consistent scheme recently proposed by Song and Ponte Castañeda [2018]. Examples for ice and few mantle minerals will be given for illustrative purpose.

 

D. Song and P. Ponte Castañeda, Fully optimized second-order homogenization estimates for the macroscopic response and texture evolution of low-symmetry viscoplastic polycrystals, Int. J. plasticity 110 (2018), 272–293

How to cite: Castelnau, O. and Ponte Castañeda, P.: Accurate mean-field micromechanical modelling of the nonlinear anisotropic response of polycrystalline aggregates, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8435, https://doi.org/10.5194/egusphere-egu24-8435, 2024.

EGU24-10371 | ECS | Posters on site | ITS5.14/GD7.3

Eggs and sausages: wireless instrumentation for measuring ice anisotropy and kinematics 

Lisa Craw, Michael Prior-Jones, Nicolas Rathmann, Jonathan Hawkins, Christine Dow, and Elizabeth Bagshaw

Field observations of ice flow properties on large temporal and spatial scales are vital to improve our understanding of ice sheet and glacier dynamics. However, we are currently limited in what we can observe, and on what timescales, with wired instrumentation and remote sensing. We present preliminary tests of wireless instrumentation to measure the kinematics and anisotropy of flowing ice.

We used a spherical probe ("cryoegg") emitting VHF radio waves to measure birefringence in 19 azimuthal directions around a borehole in the Northeast Greenland Ice Stream (NEGIS). From these data we are able to infer information about crystal anisotropy in the ice in three dimensions, and compare with a transfer matrix radio propagation model. This is a significant improvement on previous monostatic radar methods, which are limited to observations of crystal orientations in the horizontal plane.

Additionally, we present initial observations of borehole tilt, temperature, pressure and conductivity from Donjek Glacier, Canada, collected using wireless borehole instruments ("cryowursts''). These data were transmitted through up to 170m of ice, and received at a solar-powered and satellite-enabled receiving station on the glacier surface. There is potential for these instruments to transmit data continuously from surging glaciers over multiple years.

These preliminary studies demonstrate new possibilities for collecting exciting long-term datasets for glaciology.

How to cite: Craw, L., Prior-Jones, M., Rathmann, N., Hawkins, J., Dow, C., and Bagshaw, E.: Eggs and sausages: wireless instrumentation for measuring ice anisotropy and kinematics, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10371, https://doi.org/10.5194/egusphere-egu24-10371, 2024.

EGU24-11119 | ECS | Posters on site | ITS5.14/GD7.3

Direct estimation of anisotropic viscosity parameters using texture scores of olivine polycrystals 

Ágnes Király, Clinton P. Conrad, Lars N. Hansen, Yijun Wang, and Ben Mather

Earth’s various layers – from the inner core to the cryosphere – exhibit mechanical anisotropy, meaning their properties depend on the direction in which forces are applied. In the upper mantle, the primary source of anisotropy is the crystallographic preferred orientation (CPO) of olivine that is a result of sub-grain rotation during plastic deformation. The alignment of olivine grains allows the anisotropic behavior of single olivine crystals to add up leading to a macroscopic scale anisotropic viscosity (AV) linked to the CPO.

The role of anisotropic viscosity has been examined in various geodynamic scenarios. However, due to the computational complexity of the problem, there has not been a comprehensive integration of olivine CPO development with the linked anisotropic viscous behavior into geodynamic models. Here, we present an approach that directly derives anisotropic viscosity parameters from the orientation distribution (texture) of olivine grains.

Olivine polycrystals exhibit an orthotropic symmetry within the CPO’s reference frame, i.e., when the models' reference frame is aligned with the mean orientation of the olivine symmetry axes. In this case, AV can be characterized by six independent parameters, which are related to the Hill plastic yield criteria (Hill, 1948; Signorelli et al., 2021).  To determine these independent parameters, existing micromechanical models are employed, enabling the calculation of the stress required to achieve a specific strain rate on an aggregate. By applying the micromechanical model to a given texture, we can evaluate different strain rates and use the anisotropic constitutive equation (e.g. Signorelli et al., 2021) to fit the calculated strain rates with those employed in the micromechanical model, thereby identifying the best-fitting anisotropic parameters. However, simply applying this method inside a geodynamic model is too computationally costly. Thus, we built a large database (>10 000 entries) of textures occurring in geodynamic simulations, describing each texture with a set of scores derived from the orientation matrices of the three olivine symmetry axes. For each texture we applied the micromechanical model by Hansen et al., (2016), and used a minimum search function to find the best fitting AV parameters. Finally, linear regression models were utilized to establish a straightforward mapping of anisotropic parameters directly from a combination of textures scores. To determine which combination of texture scores provides the best outcome, we tested the results against both laboratory data and on a simple shear (numerical) experiment.

The approach presented here is advantageous for integrating anisotropic viscosity into 4D geodynamic models because it allows for a direct determination of the viscosity tensor from the evolving rock texture, saving a large amount of computational time.

 

Hansen, L.N., Conrad, C.P., Boneh, Y., Skemer, P., Warren, J.M., and Kohlstedt, D.L., 2016a, Viscous anisotropy of textured olivine aggregates: 2. Micromechanical model: Journal of Geophysical Research: Solid Earth

Hill, R., 1948, A theory of the yielding and plastic flow of anisotropic metals: Proceedings of the Royal Society of London. Series A. Mathematical and Physical Sciences

Signorelli, J., Hassani, R., Tommasi, A., and Mameri, L., 2021, An effective parameterization of texture-induced viscous anisotropy in orthotropic materials with application for modeling geodynamical flows

How to cite: Király, Á., Conrad, C. P., Hansen, L. N., Wang, Y., and Mather, B.: Direct estimation of anisotropic viscosity parameters using texture scores of olivine polycrystals, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11119, https://doi.org/10.5194/egusphere-egu24-11119, 2024.

EGU24-11580 | ECS | Orals | ITS5.14/GD7.3

Deformation and recrystallization inside the Northeast Greenland Ice Stream – findings from microstructural analysis of the EastGRIP ice core 

Kyra Streng, Johanna Kerch, Paul Bons, Nicolas Stoll, Daniela Jansen, and Ilka Weikusat

Solid ice discharge from land-based ice masses into the ocean raises the global sea level and accelerates due to anthropogenic climate change. Modelling ice flow dynamics aims to provide better projections of future sea level rise. The Antarctic and Greenland ice sheets are predominantly drained through ice streams, which are regions of higher ice flow velocity than their surroundings, and thus play an important role in ice sheet dynamics. However, little is known about their rheology. Therefore, they may introduce large uncertainties in ice sheet models.

In order to study the main deformation and recrystallization mechanisms dominant in an ice stream, we conducted microstructural analyses on samples from the EastGRIP ice core that was drilled in the largest Greenlandic ice stream, the Northeast Greenland Ice Stream (NEGIS).

The data set contains 1064 samples, oriented vertically and horizontally to the ice core axis, from depths between 111 and 2121 m. Analyses of the deepest 550 m of the ice core are pending. All samples were scanned with 5 µm resolution under bright-field illumination with a Large Area Scanning Macroscope (LASM). The obtained microstructure, i.e. grain shape, size, and elongation, was extracted using digitalised grain boundary networks by means of a machine-learning based image analysis software. We determined six different rheological regimes through the ice column. Most microstructural changes were interpreted as changes in recrystallization mechanisms, whereas the dominant deformation mode, horizontal extension, appears to remain fairly constant below 500 m of depth. Previous numerical high-strain ice deformation simulations showed strain localisation with the development of visible shear bands. A similar setting was expected inside ice streams, but at the investigated depths of the EastGRIP ice core, no clear shear bands could be discerned so far for the applied sampling resolution.

These results indicate that NEGIS has no strong high-strain localisation down to 2121 m depth but probably deforms as a block with extension along flow. The high ice flow velocities, therefore, might have to be compensated either in the lowest 500 m or below the ice.

How to cite: Streng, K., Kerch, J., Bons, P., Stoll, N., Jansen, D., and Weikusat, I.: Deformation and recrystallization inside the Northeast Greenland Ice Stream – findings from microstructural analysis of the EastGRIP ice core, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11580, https://doi.org/10.5194/egusphere-egu24-11580, 2024.

EGU24-12319 | ECS | Posters on site | ITS5.14/GD7.3

Refractive Index Matched (RIM) PIV in Free Surface Flows of Particle-Laden Yield Stress Fluids 

Kasra Amini, Yanan Chen, Christophe Ancey, Outi Tammisola, and Fredrik Lundell

Flow of lava, avalanches, mudslides, and many geophysical and planetary flow systems are examples of free-surface flows of Yield Stress Fluids (YSFs). This category of fluids is known for its dual behavior below- and above a yielding threshold for the applied shear stress on each fluid element. The material behaves as an amorphous elastic solid below the yielding threshold and fluidizes above it. This will lead to the presence of unyielded plug regions translating and rotating as solid-like segments within the yielded surrounding fluids. The existence of macroscopic particles in the fluid adds to the complexity of the flow setting. Transport of debris in the riverbeds and avalanches, dispersion of the cooled-down agglomerates of lava in the molten medium, and migration of solid material such as icy rocks in high pressure YSF-like, sub-terranean oceans of Europa (Jupiter’s moon) are among numerous natural examples of particle-laden flows of YSFs. To replicate the conditions experimentally, aqueous solutions of Carbopol with yield stress  are used in combination with hydrogel particles. The elastic hydrogel particles have been used in volume fractions φ = 0, 10, 20, and 30 % as mono- and duodispersed suspensions. The excellent refractive index matching of these elastic particles with Carbopol permits accurate recording of the illuminated flow field seeded with tracer particles for PIV measurements, without optical blockage of the macro particles in the optical path. Measurements are performed with channel inclinations ranging from zero to 18°, with controlled deployment of gate opening ranging from 3 cm (i.e. 50 % of the channel width) to a full open dam-break situation. Stream-wise PIV recordings of the transient and semi-steady field are complemented with span-wise recordings targeting statistical results on the particle migration and sedimentation. The results are put in context with the experiments on Newtonian and YSFs in free surface flumes containing rigid particles [1,2], as well as duct flow experiments on Carbopol with the same elastic particles [3].      

References

 [1] Christophe Ancey, Nicolas Andreini, Gaël Epely-Chauvin, The dam-break problem for concentrated suspensions of neutrally buoyant particles, J. Fluid Mech. (2013), vol. 724, pp. 95–122.

[2] G Rousseau, C Ancey, An experimental investigation of turbulent free-surface flows over a steep permeable bed, J. Fluid Mech. (2022), vol. 941, A51.

[3] Sagar Zade, Tafadzwa John Shamu, Fredrik Lundell, Luca Brandt, Finite-size spherical particles in a square duct flow of an elastoviscoplastic fluid: an experimental study, J. Fluid Mech. (2020), vol. 883, A6

How to cite: Amini, K., Chen, Y., Ancey, C., Tammisola, O., and Lundell, F.: Refractive Index Matched (RIM) PIV in Free Surface Flows of Particle-Laden Yield Stress Fluids, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12319, https://doi.org/10.5194/egusphere-egu24-12319, 2024.

EGU24-14098 | ECS | Orals | ITS5.14/GD7.3

Nonlinear Viscoelastic Model for Ice and Olivine, Constrained by Experimental Data using MCMC 

Ron Maor, Lars Hansen, and David Goldsby

Mechanisms of energy dissipation in ice and olivine have been studied experimentally in the past, with an observed strain-amplitude dependence that indicates nonlinear viscoelastic behavior resulting from the presence and motion of dislocations. In a range of low to moderate stress amplitudes, dislocations can ”bow out” between pinning points. If the resolved shear stress is sufficiently large, dislocations may escape their pinning points and elastically interact with each other. The transition from pinned to unpinned motion, along with the subsequent interactions and recovery processes, are associated with the shift from anelastic to steady-state viscous behavior. This transition forms the basis of a viscoelastic model. Despite the experimental evidence of nonlinear mechanisms, the availability of comprehensive nonlinear viscoelastic models for geological materials is limited. In this work, we propose a nonlinear viscoelastic model that captures the effect of dislocation dynamics on energy dissipation. The model is based on the well-known linear Burgers model, modified to incorporate non-linear steady-state viscous flow, and enhanced by the integration of fabric and grain-size evolution dynamics. The proposed model is tested against data from constant strain-rate and forced oscillation experiments, and the parameters are constrained using Markov Chain Monte Carlo (MCMC) methods. The model successfully reproduces data from deformation experiments in the dislocation creep regime and can be extended to experiments involving other deformation mechanisms as well.

How to cite: Maor, R., Hansen, L., and Goldsby, D.: Nonlinear Viscoelastic Model for Ice and Olivine, Constrained by Experimental Data using MCMC, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14098, https://doi.org/10.5194/egusphere-egu24-14098, 2024.

The rheology and deformation mechanisms of mafic blueschists play a key role in the mechanical behavior of subducting oceanic crust in subduction zones. While mafic blueschists are often ubiquitous along the plate interface from the base of the seismogenic zone (~35 km) to the sub-arc depths (~100 km), the strength of this lithology still remains poorly constrained. Observations of blueschists from exhumed subduction terranes suggests that blueschist can accommodate significant strain, largely partitioned into the sodic amphibole glaucophane. However, it remains an open question whether the observed deformation is accommodated by dislocation or diffusion deformation processes.

We present microstructural and textural analyses to investigate the glaucophane fabric and deformation mechanisms in three naturally deformed blueschists exhumed from variable P-T conditions: (1) a lawsonite blueschist from the Catalina Schist (Santa Catalina Island, CA, USA), (2) higher-grade epidote blueschist from the Bandon blueschist (Bandon, OR, USA) and (3) an epidote-blueschist from the Cycladic Blueschist Unit (Tinos, GR). We used electron backscatter diffraction (EBSD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS) to interpret the textural and geochemical record of deformation mechanisms that were active during the subduction history of these exhumed blueschists. All three blueschists display well-developed foliations and lineations which are defined by interconnected layers of glaucophane. EBSD microstructural analysis of glaucophane in the samples reveals evidence of dislocation accommodated deformation including: (1) strong crystallographic preferred orientation (CPO) development, (2) intragranular orientation gradients, (3) activity of dislocation motion on multiple slip systems, and (4) subgrain boundary formation. Core-mantle structures in which the daughter grains display evidence of a weakened CPO inherited from the mother (core) grains imply the activity of subgrain boundary recrystallization in the samples. Taken together, this microstructural evidence implies that dislocation creep accommodated deformation was active in all three blueschists during their deformation history. SEM images and EDS maps of glaucophane reveal evidence of chemical zoning in grains with higher Ca and Al concentrations in the rims and along the walls of  (micro)fractures within the grains (Bandon, OR Sample). The Catalina lawsonite blueschist displays interspersed evidence of microfractures with higher concentrations of Fe and lower Al and Mg concentrations. This chemical zoning and microfractures suggest micro-boudinage and/or coupled dissolution-precipitation occurred in these samples, and that potential fluid-mediated diffusion accommodated deformation processes may be preserved in these two mafic blueschists. We leverage the relationships between the textural and chemical evidence in concert with P-T estimates for their host terranes to interpret the deformation histories of these samples during subduction and exhumation. Crosscutting relationships between the chemical zoning and intragranular orientation gradients in the samples suggests that dislocation-related deformation was prograde and predates diffusion-related processes which became active in the Catalina and Bandon samples at or near peak conditions and during retrogression. Together, these results suggest that glaucophane can readily deform by dislocation creep, and also record fluid-mediated processes during deformation.

How to cite: Ott, J., Condit, C., Pec, M., and Journaux, B.: Microstructural evidence of dislocation creep and diffusion accommodated deformation of glaucophane in naturally deformed lawsonite and epidote blueschists, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14104, https://doi.org/10.5194/egusphere-egu24-14104, 2024.

EGU24-19147 | ECS | Orals | ITS5.14/GD7.3

Multi-scale anisotropy development in viscous flow due to fabric evolution: Numerical modelling, upscaling, and application for strain localization 

William R. Halter, Roman Kulakov, Thibault Duretz, and Stefan M. Schmalholz

Viscous flow controls large parts of tectonic deformation. Viscous strain localization and associated softening mechanisms are important for subduction initiation and the generation of tectonic nappes. However, viscous flow of geologic materials can have a complex behaviour due to their evolving microstructure, such as an evolving anisotropy due to fabric development or a crystallographic preferred orientation, or due to other evolving microstructure, like, e.g., grain size or dynamic recrystallization.

In this contribution, we focus on strain localization in viscous rock due to the generation of anisotropy resulting from fabric evolution. Particularly, we focus on multi-scale anisotropy evolution in shear zones with many strong or weak inclusions, representing for example porphyroclasts. The shape change and relative alignment of the inclusions during shearing generates an anisotropy on the scale of the inclusions, termed here macroscale. We spatially resolve this macroscale anisotropy in the numerical simulations. Additionally, we consider the evolution of a microscale anisotropy in the shear zone matrix, representing the formation of a mylonitic foliation. We do not spatially resolve this microscale anisotropy but model it with an anisotropic flow law that involves different normal and tangential viscosities. We calculate the finite strain ellipse during shearing and use its aspect ratio as proxy for the anisotropy that governs the ratio of normal to tangential viscosity. To track the orientation of the anisotropy during deformation we apply a director method.

We perform numerical simulations with the two-dimensional state-of-the-art thermo-mechanical code MDoodz (Duretz et al. 2021). We evaluate the impact of micro- and macroscale anisotropy on strain softening and localization in shear zone up to shear strains in the order of ten. We further discuss the quantification of effective anisotropies that can be used for upscaling, for example for lithospheric scale numerical models. Moreover, we compare the numerical results to the analytical solution and the numerical results of Dabrowski et al. (2012). A particular feature of some simulations is the formation of buckle folds in regions with highly stretched weak inclusions.

 

Bibliography

Duretz T., R. de Borst and P. Yamato (2021), Modeling Lithospheric Deformation Using a Compressible Visco-Elasto-Viscoplastic Rheology and the Effective Viscosity Approach, Geochemistry, Geophysics, Geosystems, Vol. 22 (8), e2021GC009675

Dabrowski, M., D. W. Schmid, and Y. Y. Podladchikov (2012), A two-phase composite in simple shear: Effective mechanical anisotropy development and localization potential, J. Geophys. Res., 117, B08406, doi:10.1029/2012JB009183

How to cite: Halter, W. R., Kulakov, R., Duretz, T., and Schmalholz, S. M.: Multi-scale anisotropy development in viscous flow due to fabric evolution: Numerical modelling, upscaling, and application for strain localization, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19147, https://doi.org/10.5194/egusphere-egu24-19147, 2024.

CR7 – The Cryosphere in the Earth system: interdisciplinary topics

EGU24-965 | ECS | Orals | CR7.5

Resilience and adaptation of First Nations communities in Canada to disappearing winter road infrastructure in a changing climate 

Annette Salles, Donal Mullan, Matteo Spagnolo, and Gemma Catney

In Canada’s North, winter roads serve as vital lifelines for remote First Nations communities, connecting them to essential resources and services. Constructed over seasonally frozen lakes, rivers, and land, these temporary roads are the only means to transport food, fuel and building materials in large volumes. Winter temperature increases of > 3° C in several provinces have already led to shorter operating seasons and less lake ice thickness, compromising safety, supply, and well-being.

Limited meteorological data, a lack of economic or political relevance and the provincial jurisdiction over winter roads have so far discouraged broader research. The few localised studies leave a large knowledge gap with respect to the historical correlation of climate data with winter road seasons and the ability to predict their future. In addition, scientific studies rarely include the existing traditional environmental knowledge without which the adaptive capacity and resilience potential of Indigenous communities cannot be fully understood and realised.

Using GIS tools to create a map of all Canadian winter road systems, ERA5 data to analyse location-specific temperature trends, and observations of lake ice thickness to validate a one-dimensional lake model as proxy for freezing trends all aim to explore the natural science base. Surveys and extended interviews in a Manitoba First Nations community complement the study in a decolonising approach, following the concept of Two-Eyed Seeing.

Comprehensive mapping shows that most winter road tracks have recently been rerouted to avoid lake surfaces despite the difficult terrestrial underground. Temperature trends are highest in January and vary from +0.4° C in Ontario to +1° C per decade in the Northwest Territories, while modelled ice thickness has decreased between 9% and 14% from 1950 until 2022. Shorter winter road seasons have resulted in food insecurity, educational deprivation, and a housing crisis in many remote First Nations communities, worsened by the intergenerational trauma of residential schools and legislative hurdles to self-determination as defined by the UN Declaration on the Rights of Indigenous Peoples.

For Indigenous communities in Canada, cryosphere services are not limited to winter road infrastructure, they include traditional food harvesting, cultural connectivity and identity. Without a profound connection to the land, change observations remain inconsequential, adaptive measures and resilience unobtainable.

How to cite: Salles, A., Mullan, D., Spagnolo, M., and Catney, G.: Resilience and adaptation of First Nations communities in Canada to disappearing winter road infrastructure in a changing climate, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-965, https://doi.org/10.5194/egusphere-egu24-965, 2024.

EGU24-3302 | Orals | CR7.5

Changes in coastal environments and their impact on society in northwestern Greenland 

Shin Sugiyama and the ArCS II Coastal Environments Project

Coastal environments around Greenland are rapidly changing under the influence of a warming climate. Glaciers are melting and glacial meltwater discharge is affecting ocean environments, resulting in a wide range of impacts on marine ecosystems. Steep terrains along the coast are destabilized by thawing permafrost and more frequent heavy rain events. These changes in natural environments are serious concerns of Greenlandic societies. An increasing amount of glacial melt causes flooding of streams. Settlements at the foot of steep slopes are threatened by landslide hazards. Accordingly, an increasing number of damages to buildings and infrastructures are reported. To investigate changing coastal environments and their impact on society in Greenland, we have been running a research project in Qaanaaq, a small village in northwestern Greenland, under the framework of Japanese Arctic research projects GRENE (Green Network of Excellence), ArCS (Arctic Challenge for Sustainability) and ArCS II. In this presentation, we introduce the overview of our multidisciplinary research activities performed in the Qaanaaq region since 2012.

On Qaanaaq Ice Cap, annual mass balance and ice speed have been measured since 2012 to investigate glacier changes and processes driving rapid ice loss. Discharge of a glacial stream is measured to study the mechanism of foods, which frequently destroy a road connecting the village with Oaanaaq Airport. In a nearby smaller settlement Siorapaluk, a slope affected by a landslide was surveyed to study the triggering mechanism of the failure. During the late summer season, research activities were performed in the largest glacial fjord in the region, Inglefield Bredening. Using boats operated by local collaborators, seawater properties are measured, moorings are installed for year-round measurements, and habitats of fish, seabirds and marine mammals are surveyed. Biologger tagging is performed in collaboration with hunters as well as a researcher from the Greenland Institute of Natural Resources in Nuuk. Recently, a dump site in the village was surveyed by waste management engineers to investigate possible soil and water pollution. Measurements were also carried out in houses to evaluate the performance of the buildings for energy efficiency and a healthy living environment.

Project activities and study results are reported to the community in a workshop organized in Qaanaaq since 2016. About 50 people attend presentations by researchers. The focus of discussion after the presentations is health and safety. Questions are raised about possible pollution around the dump site and concentrations of toxic substances in animals. The involvement of local society in scientific research is a matter of importance in the Arctic. To contribute sustainable future of Arctic societies, we continue collaboration, conversation and designing research together with the local community.

How to cite: Sugiyama, S. and the ArCS II Coastal Environments Project: Changes in coastal environments and their impact on society in northwestern Greenland, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3302, https://doi.org/10.5194/egusphere-egu24-3302, 2024.

EGU24-4300 | ECS | Orals | CR7.5

A theoretical framework for evaluating cryosphere services 

Bo Su, Cunde Xiao, and Deliang Chen

The cryosphere makes significant contributions to human well-being directly or indirectly and materially or spiritually, providing a wide array of benefits, i.e., cryosphere services. However, with the global warming, the diminishing cryosphere would profoundly impact, not only on climate systems, but also its functions and services to support our societies. Although there is a wealth of studies on cryospheric processes and mechanisms, the interaction between the cryosphere and other spheres, and the cryospheric disaster risk, the systematic research on cryosphere services is still in its early stage. There needs to be a more systematic theoretical framework and methodology to enable the valuation and management of cryosphere services. Here, we will systematically present our recent work about the development of theoretical framework and methodology system, as well as related case studies. we first present a classification system based on the current process-based understanding of their nature and sustainability. Then, three different methods (i.e., empirical-based, monetary-based, and emergy-based approaches) for evaluating cryosphere services, are systematically introduced, and illustrated by three case studies. Finally, to adapt to the changing cryosphere services and mitigate risks, we further propose the approach to enhance society’s resilience in the cryosphere. The theoretical framework and methodology system is conducive for conceptualizing, monitoring, assessing and managing cryosphere services, and can help enhance socio-ecological sustainability and human well-being over cryosphere-affected areas.

How to cite: Su, B., Xiao, C., and Chen, D.: A theoretical framework for evaluating cryosphere services, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4300, https://doi.org/10.5194/egusphere-egu24-4300, 2024.

EGU24-6496 | Orals | CR7.5

What Proglacial Aufeis Formations Tell Us about the Evolution of Hydrological Processes in a Glacier Decline Context 

Michel Baraer, Bastien Charonnat, Eole Valence, Jeffrey McKenzie, and Janie Masse-Dufresne

Alpine environments in cold regions are undergoing rapid transformations due to shifting climates, raising concerns about the future of ecosystems and downstream water supplies. Traditionally, hydrological studies have focused on visible cryospheric elements, often overlooking buried features like permafrost, ice-cored moraines, and rock glaciers, as well as the significance of groundwater in alpine valleys. Recent investigations, however, highlight the pivotal role of groundwater in shaping local watershed dynamics and regional water resources in these cold regions.

 

Understanding hydrogeology in cold region alpine environments presents challenges due to remote and inaccessible study sites and harsh winter conditions. Recent studies suggest that the winter hydrogeological dynamics of proglacial areas are captured within proglacial aufeis, ice formations persisting during winter despite extended sub-zero temperatures.

 

This study focuses on aufeis formation within a tributary of the Duke Valley, a glacierized catchment in the green belt of Mount St-Elias on the Kluane First Nation territory in Yukon. Employing a field-based approach at the Shar Shäw Tágà study site and remote sensing analysis using satellite imagery, our research aims to delineate key aufeis growth stages and identify contributing water sources.

 

The field study, conducted from 2018 to 2023, utilizes time-lapse imagery, hydrochemical tracers, and meteorological records to reveal aufeis growth variability. Observations in Shar Shäw Tágà show aufeis forming consistently across most years, spanning from the canyon exit to the meander of the Grizzly Creek River. However, results indicate a three-year absence of aufeis formation and variability in formation dates when present. Notably, aufeis growth deceleration or cessation in March, despite sustained sub-zero temperatures, suggests groundwater's role.

 

Remote sensing analysis dating back to 1974 indicates a declining trend in aufeis occurrences. Statistical analysis on relative frequencies suggests a potential link between non-formation and meteorological conditions from the preceding summer, supporting the hypothesis that aufeis occurrence is influenced by factors impacting groundwater behavior.

 

The correlation between aufeis formation and longer-term factors implies aufeis as a valuable indicator of groundwater evolution in alpine cold regions, sensitive to processes beyond immediate seasonal variations. These findings contribute to our understanding of broader changes in groundwater behavior over extended periods in these dynamic environments.

How to cite: Baraer, M., Charonnat, B., Valence, E., McKenzie, J., and Masse-Dufresne, J.: What Proglacial Aufeis Formations Tell Us about the Evolution of Hydrological Processes in a Glacier Decline Context, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6496, https://doi.org/10.5194/egusphere-egu24-6496, 2024.

EGU24-7565 | Orals | CR7.5

Radionuclides and heavy metal concentrations in glacier mice on Austerdalsbreen, an outlet glacier from Jostedalsbreen ice cap, Norway 

Katarzyna Kołtonik, Krzysztof Zawierucha, Kamil Wojciechowski, Tomasz Mróz, Przemysław Niedzielski, Juliana Souza-Kasprzyk, Mariusz Wierzgoń, Kayode Olabode, Anna Cwanek, Dariusz Sala, Jacob Clement Yde, Przemysław Wachniew, and Edyta Łokas

Glacier mice are ovoid-shaped conglomerations of bryophytes and mineral particles that are rarely found on glacier surfaces. They form colonies, host diverse organism communities and possess the ability to roll around on the glacier surface. Their movement on the glacier appears non-random, assuming a herd-like behaviour. This study is the first survey of the occurrence of radionuclides (137Cs, 210Pb, 238,239,240Pu) and heavy metals (Pb, As, Hg, Cd) in glacier mice, cryoconite debris, and proglacial bryophytes at Austerdalsbreen, an outlet glacier from Jostedalsbreen ice cap, western Norway. Ongoing research on cryoconite shows that glacier surfaces host dynamic ecosystems capable of capturing and processing airborne contaminants. However, nothing is known about the role of glacier mice in the cycling of contaminants, particularly in relation to cryoconite.

The following objectives are pursued in this study:

  • Determining and comparing radionuclide and heavy metal concentrations across glacier ecosystems in bryophytes (glacier surface vs. terminal moraine vs. proglacial forefield) and cryoconite.
  • Identifying nuclear contamination sources in the investigated samples using the mass and activity ratios (240Pu/239Pu and 239+240Pu/137Cs).

The analysis of radionuclides was performed by alpha and gamma spectrometry, while mass ratio and heavy metals quantification using ICP MS. We found that glacier mice are characterized by activity concentrations of radionuclides several times lower than those in cryoconite. There is no clear statistically significant difference between the activity of studied isotopes and bryophytes on a spatial scale. When concentrations of radionuclides in cryoconite from Austerdalsbreen are compared with data from other Scandinavian glaciers, plutonium and cesium signatures in the Austerdalsbreen samples show compatible levels for global fallout and Chernobyl accident, respectively. Regarding heavy metals, the highest concentrations were found in bryophytes from the glacier surface compared to samples from the forefield. Levels of Hg and Pb are elevated in bryophytes especially from the glacier surface (0.7 ppm and 30 ppm, respectively), whereas Cd and As (0.06 ppm and 0.49 ppm, respectively) are relatively similar to values reported for mosses in Norway. The concentrations of Hg and Pb in bryophytes from the glacier surface are similar to values found in cryoconite from Austerdalsbreen and Blåisen, an outlet glacier from Hardangerjøkulen ice cap located 120 km south of Austerdalsbreen.

The results show that concentrations of radionuclides and heavy metals are mainly influenced by atmospheric deposition from long-range transport, although potential local sources must also be considered. Increased concentrations of some heavy metals in bryophytes from glacier surfaces may suggest that the rolling of bryophytes (glacier mice) on glacier surfaces may absorb heavy metals from cryoconite. Additionally, glacier mice rolling from the melting glacier may serve as a secondary source of inorganic pollutants to newly developed proglacial ecosystems.

How to cite: Kołtonik, K., Zawierucha, K., Wojciechowski, K., Mróz, T., Niedzielski, P., Souza-Kasprzyk, J., Wierzgoń, M., Olabode, K., Cwanek, A., Sala, D., Yde, J. C., Wachniew, P., and Łokas, E.: Radionuclides and heavy metal concentrations in glacier mice on Austerdalsbreen, an outlet glacier from Jostedalsbreen ice cap, Norway, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7565, https://doi.org/10.5194/egusphere-egu24-7565, 2024.

EGU24-7783 | ECS | Posters on site | CR7.5

Accumulation of natural and artificial radionuclides in cryoconite holes on Alpine glacial environment 

Dariusz Sala, Jakub Buda, Giovanni Baccolo, Anna Cwanek, Sylwia Błażej, Roberto Ambrosini, Biagio Di Mauro, and Edyta Łokas

Over the last century, alpine glaciers have melted rapidly. According to current climate models, it is predicted that 80% of these glaciers will likely disappear between the 2060s and the 2080s. The storage of natural and anthropogenic contaminants in these ice masses, which might be released with water, creates a potential threat for communities, especially those closely related to glacierised regions, and the surrounding glacier habitats.

In recent years, cryoconite – a mineral-organic debris that accumulates on the glacier surface - has been the subject of interest due to its ability to accumulate specific substances, surpassing levels found in other terrestrial ecosystems (e.g., proglacial, sediments, soil, lichens, mosses). This phenomenon is attributed to a combination of natural and anthropogenic factors, yet still not well-studied. The majority of artificial radionuclides released into the environment can be attributed to nuclear reactor accidents like Chernobyl (1986) and the stratospheric global fallout.

Our main objective is to comprehensively understand the accumulation of natural (210Pb) and artificial (137Cs, 238,239,240Pu) radioisotopes in cryoconite and identify the different sources of contamination based on isotopic and mass ratios of subject radionuclides. To achieve these objectives, we analysed activity concentrations, their relation with the global and local signals, and their variability between glaciers. Samples were collected from eight glaciers in the European Alps, including the glaciers Blanc, Gries, Mandrone, Pastrze, Preda Rossa, Tsanteleina, Ventina, and Zebrù.

The highest values of 210Pb were found in cryoconite from the Ventina and the Zebrù Glaciers (more than 11,000 Bq kg−1). The lowest values of 210Pb in individual samples (<100 Bq kg−1) were found in the Gries and Mandrone Glaciers. Sediment from the Ventina Glacier had the highest 137Cs activity concentration (up to 12,000 Bq kg−1), while the one from Gries Glacier exhibited the lowest values (4.00 Bq kg−1). The highest activity concentrations of 238Pu (up to 5.0 Bq kg−1) and 239+240Pu (up to 103.0 Bq kg−1) were observed also on the Ventina Glacier. The atomic ratio 240Pu/239Pu and activity ratio 238Pu/239+240Pu showed that the plutonium-related radioactivity from different Alpine glaciers is mostly compatible with global radioactive fallout. On average, more than 88.0% to 97.7% of the Pu found in cryoconite samples are from global fallout. In contrast, the major contribution of 137Cs is identified as the Chernobyl accident. Our observations found a positive correlation between the activity concentrations of studied isotopes and organic matter content.

These results confirm the ability of cryoconite to accumulate radioactivity and show that multiple regional and global sources influence the radioactive signature of Alpine cryoconite. Also, activities in cryoconite are significantly higher than those in the published matrices usually used for the environmental monitoring of radioactivity. Moreover, due to its organic matter content (and the positive correlation of the latter to the amount of the studied radionuclides), cryoconite effectively captures (mostly from atmospheric deposition) and collects the impurities present in meltwater.

How to cite: Sala, D., Buda, J., Baccolo, G., Cwanek, A., Błażej, S., Ambrosini, R., Di Mauro, B., and Łokas, E.: Accumulation of natural and artificial radionuclides in cryoconite holes on Alpine glacial environment, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7783, https://doi.org/10.5194/egusphere-egu24-7783, 2024.

EGU24-7857 | ECS | Posters on site | CR7.5

Radioactive contamination of a peripheral glacier in Southeast Greenland 

Kamil Wojciechowski, Jacob Clement Yde, Simon de Villiers, Krzysztof Samolej, Michał Bonczyk, and Edyta Łokas

Glaciers host complex and dynamic microbial ecosystems that are influenced by anthropogenic contaminants and can be regarded, not only as a considerable pollutant repositories, but also as secondary sources of pollutants. Contaminants such as heavy metals and fallout radionuclides are being brought to glaciers by long-range atmospheric transport and then deposited with wet and dry precipitation. Special attention has been given to cryoconite, debris found on glacier surfaces forming granule-shaped aggregates of minerals and organic matter. Cryoconite is known for its potential for exceptionally high accumulation of radioactive isotopes. Accumulated anthropogenic radionuclides, originating from atmospheric nuclear weapon tests and incidents, can be released back into the environment with sediment and meltwater fluxes and as a melt-out during glacier recession, posing a risk to downstream and proglacial ecosystem health. Many factors contribute to the secondary pollutant release, with climate change and glacier recession playing an increasingly important role in recent decades. Mittivakkat Gletsjer, a peripheral glacier located on Ammassalik Island in Southeast Greenland, shows significant volume and area losses, and although being one of Greenland’s most extensively explored glaciers, little is known about the radioactive pollution presence and its possible sources. This is true not only for Mittivakkat Gletsjer but for glaciers in Greenland in general. Cryoconite samples were collected from the glacier surface of Mittivakkat Gletsjer in August 2022 and activity concentrations of 238Pu, 239+240Pu, 241Am, 137Cs and 210Pb were measured (up to 1.44Bq/kg, 28.5Bq/kg, 14.4Bq/kg, 1100Bq/kg, 2900Bq/kg, respectively). Obtained values are higher than other environmental matrices (soils, mosses, lichens) indicating high radionuclide accumulation in cryoconite. Radioactive contamination sources were identified by determining the isotope ratios 238Pu/239+240Pu, 239+240Pu/137Cs and 241Am/239+240Pu (0.0514±0.0071, 0.0251±0.0044, 0.54±0.12). The results suggest that global fallout, an aftermath of atmospheric nuclear weapon tests, is likely the main source of radioactive pollution at Mittivakkat Gletsjer. A two-sources model (global fallout and Chernobyl incident) shows that global fallout is responsible for 92% of plutonium and 62% of cesium in the measured samples. High correlations (r2>0.75) between sample altitude and 238Pu, 239+240Pu, 241Am, 137Cs activity concentrations have been found. Samples collected from higher elevation accumulated more radionuclides, a relationship also observed at other glaciers. The same is not true for 210Pb for which a very weak correlation (r2<0.3) might be explained by constant influx of the nuclide from the atmosphere as it varies depending on rainfall and geographical location. Relationship between organic matter content and radioisotope activity concentrations has been examined, showing stronger correlations for plutonium isotopes (r2>0.7) and weaker for 137Cs and 210Pb (r2<0.65). Higher concentrations in samples with more organic content indicate cryoconite’s capability of binding radionuclides in extracellular polymeric substances. Our study documents radioactive pollution in Southeast Greenland and shows that further research regarding possible risks of environmental contamination through glacier recession and climate change is necessary.

This study was supported by the National Science Centre, Poland under research project No. 2021/43/O/ST10/02428.

How to cite: Wojciechowski, K., Yde, J. C., de Villiers, S., Samolej, K., Bonczyk, M., and Łokas, E.: Radioactive contamination of a peripheral glacier in Southeast Greenland, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7857, https://doi.org/10.5194/egusphere-egu24-7857, 2024.

EGU24-8179 | ECS | Orals | CR7.5

Worldwide Accumulation of Atmospheric Mercury in Glacier Cryoconite 

Agnieszka Pasieka, Kamil Brudecki, Przemysław Niedzielski, Aleksandra Proch, Nozomu Takeuchi, Roberto Ambrosini, Phil Owens, Krzysztof Zawierucha, Giovanni Baccolo, Caroline Clason, Dylan Beard, Jacob Clement Yde, and Edyta Łokas

Mercury (Hg) is a chemical element recognized as one of the most toxic among all naturally occurring elements, with health risks depending on its form, concentration, route and time of exposure. Mercury appears in the environment as a result of human activities, which include burning coal or lignite, improper waste disposal, oil refining, use of mercury-containing pesticides and fertilizers, and industrial development such as mining, chemical, pharmaceutical and paper industries. The element also appears in the environment as a consequence of natural phenomena, among which are volcanic emissions, rock erosion, biomass burning and geothermal processes, but also as a result of re-emissions. Mercury can persist in the atmosphere for up to several months, which promotes the transfer of the element to areas far from the emitting source.

Cryoconite, a sediment accumulating on the surface of glaciers, is known to accumulate atmospheric contaminants such as Hg likely due to biofilm producing extracellular polymeric substances. Mercury is a contaminant of primary concern in the global environment, including cryosphere environments such as glaciers, due to its high toxicity to biota. This study, for the first time, presents a comprehensive global analysis of the variation in Hg concentrations, observed in cryoconite holes and deposits from the surface of 27 glaciers in both hemispheres, comprising 105 samples in total. Concentrations of Hg were determined through ICP-MS/MS.  

The results indicate a higher Hg content in cryoconite from glaciers located in the Northern Hemisphere, which can be linked to the proximity of highly industrialized areas, which contrasts to glaciers located in the Southern Hemisphere. The highest Hg content was measured in cryoconite located in Norway and Alaska (up to 0.7 ppm), and the Alps (close to 0.5 ppm), correlated with the levels of industrialization in these regions. Our results reveal a broad pattern of reduction in Hg concentrations in cryoconite with altitude, which may be related to the topographical relief affecting the transport of contaminants from higher altitudes to lower.

As a result of global warming, the majority of glaciers are retreating. The accumulated Hg in the cryoconite can be released during melting of glaciers and thus may also contribute to contamination of the downstream ecosystems and local communities through consumption of contaminated food and water in polar and alpine regions. Therefore, studies like this are needed to monitor the levels and fate of Hg in glaciers and ice caps.

How to cite: Pasieka, A., Brudecki, K., Niedzielski, P., Proch, A., Takeuchi, N., Ambrosini, R., Owens, P., Zawierucha, K., Baccolo, G., Clason, C., Beard, D., Yde, J. C., and Łokas, E.: Worldwide Accumulation of Atmospheric Mercury in Glacier Cryoconite, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8179, https://doi.org/10.5194/egusphere-egu24-8179, 2024.

EGU24-9850 | Posters on site | CR7.5

Emergy-based accounting method for glacier ecosystem services valuation (ESV): A case of Tibetan Plateau 

Can Zhang, Bo Su, Shiming Fang, Michael Beckmann, and Martin Volk

Glacier ecosystems play a vital role in providing freshwater resources to humans, in regulating and stabilizing climate, runoff and offering potential for hydropower generation, and in providing unique cultural services for humans. However, few studies have systematically assessed the socio-economic contribution of glaciers, especially from a contributor perspective. To fill this knowledge gap, the aim of this study is to develop an assessment method applied to glacier ESV based on emergy theory. Emergy analysis is a measure that converts all forms of energy into the same unit of comparison, providing a common scale for measuring and comparing all forms of energy. This includes: (1) to develop an emergy-based accounting system and methods for glacier ESV from a donor-side perspective; (2) to evaluate the spatiotemporal characteristics of glacier ecosystem services (ESs) on Tibetan Plateau (TP) during the early 21st century. The results show that: (1) glacier ESs on TP increased from 1.25E+25 sej/yr in the 2000s to 1.28E+25 sej/yr in the 2010s, which is mainly due to the fast growth of provisioning services, although a slow decrease of regulating services is observed during the study period; (2) among the various services, the descending order of value is climate regulation (7.34E+24 sej/yr, 55.65%), hydropower generation (2.73E+24 sej/yr, 20.67%), and freshwater resources (2.68E+24 sej/yr, 20.31%); (3) the spatial characteristics of glacier ESs, where the glacier ESs values in the marginal TP are larger than in endorheic TP; (4) glacier ecosystems are divided in stock and flow, with stock referring to glaciers in the solid state and flow referring to glaciers in the so-called meltwater state. The glacier stock service still dominates in the early 21st century with a small downward trend in the last decade, while the glacier flow service has increased significantly from 2000s to 2010s due to the glacier recession. (5) Except climate regulation and carbon sequestration, all other services values are increasing, especially for tourism and recreation, and knowledge and education, which have shown a rapid growth with the social development. The theory and methodology used here are conducive to enhancing the understanding of material and energy flows within the cryosphere-society system and providing common scales for measuring and comparing different material, energy and monetary flows. Furthermore, this study will help to improve the glacier service assessment system, lay the theoretical and methodological foundation for the development of regional and global glacier service accounting, and provide a scientific basis for glacier resource development and management.

How to cite: Zhang, C., Su, B., Fang, S., Beckmann, M., and Volk, M.: Emergy-based accounting method for glacier ecosystem services valuation (ESV): A case of Tibetan Plateau, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9850, https://doi.org/10.5194/egusphere-egu24-9850, 2024.

EGU24-13397 | Posters on site | CR7.5

The Political Ecology of the Cryosphere: Theory and Praxis 

Amy Lauren Lovecraft and Nicholas Parlato

Globalization is not just a process of technological and economic interconnection but of the symbolic transformation of the geophysical world into social objects. As the planet warms, it has become a thinly-veiled doctrine among the world’s nations and industries that state and market control over and access to the polar regions, and their high mountain counterparts, is a geopolitical and economic imperative. Whether in the Arctic, Antarctic, or the “Third Pole”, human conceptions of the cold are understood as increasingly driven by anthropogenic state changes in the cryosphere itself and by contradictions of the market economy. An approach to accurately grasp the breadth and diversity of human perspectives, uses, and valuations of the cold thus requires deep contextualization and a theoretical approach. In this paper, we propose to synthesize core social findings about the nature of the cryosphere and its changes, centering the knowledge of Indigenous residents, and working outward through other layers of stakeholder groupings and positions.  Broadly, we identify sites of conflict and alignment among stakeholder positions related to permafrost, sea ice, snow, and land ice (e.g. direct users, “downstream” users, state administrators, corporate interests, scientists) to create a comprehensive framework of current services and hazards with flexibility for ongoing changes. We build on the development of the IPBES framework initiative (Diaz et al., 2015), it’s recent future-oriented adaptation (Pereira et al., 2020), and contributions by diverse scholars focused on cryosphere functions and services (Wang et al., 2019). Our effort is conducted to produce a formal space for discussion of the political ecology of coldness and “storying multipolar climes” (Yü and Wouters 2023) with the objective of matching the pace of social environmental change through the development of a multi-epistemic dialectical method of cryosphere inquiry that can inform multiple stakeholders.

How to cite: Lovecraft, A. L. and Parlato, N.: The Political Ecology of the Cryosphere: Theory and Praxis, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13397, https://doi.org/10.5194/egusphere-egu24-13397, 2024.

EGU24-15591 | ECS | Orals | CR7.5

Reframing the Arctic: An interdisciplinary and multi-scalar perspective on the divergence of boundaries and risk change in the Anthropocene 

Aapo Lundén, Patricia DeRepentigny, Ugo Nanni, Virginija Popovaitė, Yiyi Shen, Ilker K Basaran, Natalia Duarte Neubern, Llucia Mascorda-Cabre, Alec Bennett, Tiril Vold Hansen, Felicity A Holmes, Eleni Kavvatha, Alexandra Meyer, Abhay Prakash, and Aleksandra Wołoszyn

The Arctic is experiencing rapid transformations driven by global warming and increased human activities. These changes have significant implications for the region's established boundaries and the risks tied to its transformation. Here, we investigate the complex dynamics and consequences of contemporary pressure on these boundaries through a socio-environmental perspective. By employing an interdisciplinary and multi-scalar approach, we examine the intricate interconnections between global, regional, and local changes within the Arctic. Our analysis revolves around three spheres: the boundaries historically used to define the Arctic and how recent changes in climate and political interest challenge our perception of the Arctic as a region; the complexity of bio-physical boundaries and jurisdictional disputes surrounding the Svalbard Archipelago; and the relationship between changing natural hazards and societal perception of risk in the town of Longyearbyen. Altogether, we underscore the interplay between policy-based science, science-based policy, and performative behavior in shaping borders and boundaries. In order to avoid crossing tipping points and irreversible limits of human adaptation, we argue for the adoption of a holistic approach that integrates diverse perspectives and scales to effectively manage resources, preserve the environment, mitigate risks, and uphold international relations within and beyond the Arctic. By considering ecological and social factors, our study emphasizes the need for integrated approaches to address time-sensitive challenges surpassing the resilience capacities of local communities and encompassing vast spatial scales extending beyond their usual spheres of influence.

How to cite: Lundén, A., DeRepentigny, P., Nanni, U., Popovaitė, V., Shen, Y., Basaran, I. K., Neubern, N. D., Mascorda-Cabre, L., Bennett, A., Vold Hansen, T., Holmes, F. A., Kavvatha, E., Meyer, A., Prakash, A., and Wołoszyn, A.: Reframing the Arctic: An interdisciplinary and multi-scalar perspective on the divergence of boundaries and risk change in the Anthropocene, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15591, https://doi.org/10.5194/egusphere-egu24-15591, 2024.

EGU24-17538 | ECS | Orals | CR7.5

Political and physical limits to using formerly glaciated regions for hydropower production 

Rebekka Frøystad, Andreas Born, and Yvette Peters

Glacier retreat changes hydropower production, both by changing melt patterns and seasonality and by revealing new possible reservoirs. This holds potential for expanding the production of hydroelectric power. However, these glaciers are typically situated in valuable nature and protected areas, making the construction of new infrastructure difficult. Mitigating climate change by producing renewable energy therefore comes in conflict with protecting nature.

In this study, we present survey results from the Norwegian Panel of Elected Representatives to investigate how democratically elected politicians approach such trade-offs, the conflict between protecting global climate or local nature. Which arguments drive support or opposition to building a hypothetical hydropower dam? How do they relate to the politicians' personal and political background? Interestingly, we find that politicians that are more concerned about climate change also are more opposed to building new hydropower infrastructure.

In addition, we assess how the physical potential of hydropower will change in Norway under climate change. As a case study, we simulate the surface mass balance of Folgefonna ice cap to the end of the century under a range of climate scenarios. This enables us to quantify how uncertain such future projections are and to what degree we can provide policy makers with reliable information on hydropower potential. Thus, by a multidisciplinary approach, we assess both the physical and political potential for new hydropower due to glacier melt.

How to cite: Frøystad, R., Born, A., and Peters, Y.: Political and physical limits to using formerly glaciated regions for hydropower production, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17538, https://doi.org/10.5194/egusphere-egu24-17538, 2024.

EGU24-20294 | ECS | Posters on site | CR7.5

Limnological assessment of 51 climate-sensitive permafrost-thaw lakes in Central Yakutia, Siberia 

Izabella Baisheva, Birgit Heim, Ramesh Glückler, Amelie Stieg, Kathleen R. Stoof-Leichsenring, Antje Eulenburg, Pier Paul Overduin, Hanno Meyer, Evgenii S. Zakharov, Lena A. Ushnitskaya, Paraskovya V. Davydova, Boris K. Biskaborn, Sardana N. Levina, Ruslan M. Gorodnichev, Jorge García Molinos, Luidmila A. Pestryakova, and Ulrike Herzschuh

Climate is rapidly changing in northern regions, including Central Yakutia, a densely populated area in Siberia. Here, permafrost-thaw lakes in topographical depressions, named “alaas”, are widely distributed. Alaases and the residual lakes within became the traditional home to the indigenous Sakha people, providing critical ecosystem services like fresh water supply, meadows for cattle breeding, or fishing and hunting grounds. Alaas formation is closely related to the Late Glacial and Early Holocene warming, as it was caused by the degradation of permafrost. This makes alaases, and permafrost-thaw lakes in general, highly sensitive to both climatic changes and land use impacts. Global warming is predicted to cause permafrost loss, potentially resulting in new alaas formations and irreversibly changing water quality and biodiversity within the existing alaas lakes. The exact consequences of anthropogenic climate change and land use on these unique landforms are still poorly understood, which may also be a result of lacking data availability.

Here, we present a comprehensive new dataset of limnological characteristics of 66 lakes across Central Yakutia Lowland and the Oymyakon Highlands, with a focus on 51 alaas lakes in Central Yakutia. During field work in summer of 2021, we measured lake physical properties (lake depth, pH, specific conductivity) and afterwards we analyzed lake water hydrochemistry including ions, dissolved organic carbon (DOC), isotopic composition (δ18O H20, δD H20), and aquatic and terrestrial plant composition via surface sediment environmental DNA metabarcoding. The majority of alaas lakes are classified as magnesium-bicarbonate types. Isotope concentrations indicate that lakes in the Central Yakutian Lowlands are controlled mainly by evaporation, underlining their sensitivity to future warming. Aquatic vegetation is dominated by submerged macrophytes, whereas terrestrial vegetation mainly consists of graminoids and forbs. Settlements are mostly situated in connected alaas systems, where flowing water results in lower DOC concentration. This “snapshot” of limnological characteristics can be helpful to assess the most critical factors which may be impacted by land use or respond to future warming.

How to cite: Baisheva, I., Heim, B., Glückler, R., Stieg, A., Stoof-Leichsenring, K. R., Eulenburg, A., Overduin, P. P., Meyer, H., Zakharov, E. S., Ushnitskaya, L. A., Davydova, P. V., Biskaborn, B. K., Levina, S. N., Gorodnichev, R. M., Molinos, J. G., Pestryakova, L. A., and Herzschuh, U.: Limnological assessment of 51 climate-sensitive permafrost-thaw lakes in Central Yakutia, Siberia, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20294, https://doi.org/10.5194/egusphere-egu24-20294, 2024.

EGU24-20388 | Posters on site | CR7.5

Distinct anoxygenic phototrophic lifestyles on the Greenland Ice Sheet expand the light harvesting community during microbial summer blooms on ice surfaces 

Christoph Keuschnig, Christopher B. Trivedi, Helen K. Feord, Rey Mourot, Athanasios Zervas, Marie Bolander Jensen, Katie Sipes, Laura Perini, Martyn Tranter, Alexandre M. Anesio, and Liane G. Benning

Aerobic anoxygenic photosystems, identified within specific bacterial clades, have been described recently as pivotal components influencing the carbon cycle in ocean surface waters. These pigmented bacteria exhibit diverse life strategies, transitioning from anaerobic habitats, such as the sulfur cycle in purple sulfur bacteria, to harnessing sunlight for enhanced carbon assimilation efficiency through aerobic anoxygenic photosynthesis. Remarkably, these microbial entities have been found across varied environments, including soil, rivers, hypersaline waters, and thermal springs.

In cryospheric habitats like snow and ice, phototrophic organisms are predominantly represented by eukaryotic green algae, with Cyanobacteria confined to cryoconite habitats. However, bacterial phototrophy in these environments remains poorly understood. While recent studies have described anoxygenic phototrophy in ice samples, the ecological roles of these organisms remain elusive. In this study, we hypothesize that the ice surface and cryoconites provide suitable habitats for widespread  aerobic and anaerobic anoxygenic photosynthesis.

Metagenomic analysis was performed on 21 samples collected from three distinct locations in east and south Greenland, representing sub-habitats of surface ice, snow, and cryoconites. Anoxygenic photosystem II genes were identified in 9 metagenome-assembled genomes (MAGs), primarily associated with surface ice and cryoconites, with no detection in the summer snowpack. Interestingly, three of these MAGs lacked genes for carbon fixation, a characteristic feature observed in aerobic anoxygenic phototrophs. Detection of the SOX complex in specific MAGs suggested a potential role in anaerobic photosynthetic reactions. The diverse phototrophic lifestyles did not exhibit clear associations with specific sub-habitats, although the majority of MAGs exhibited higher coverage in cryoconite samples, where anoxic microlayers are known to exist. A comprehensive meta-analysis utilizing 2000  metagenomes from various environments across the globe revealed that the identified MAGs from the GrIS are unique to cryospheric habitats.

Our findings indicate the development of distinct bacterial photosynthetic lifestyles in glacial habitats within Arctic regions. This raises intriguing questions about the ecological roles of these microorganisms in cryoconites, where they coexist with cyanobacteria, and on glacial surface ice, where they may play a crucial role in the carbon cycle akin to their contributions surface water blooms in the ocean. Our findings suggest that the observed global biological darkening of ice surfaces may be influenced by a complex microbial community comprising pigmented bacteria alongside cryospheric algae. This interaction ultimately contributes to increased runoff from glacier surfaces, driven by the resulting increase in albedo.

How to cite: Keuschnig, C., Trivedi, C. B., Feord, H. K., Mourot, R., Zervas, A., Bolander Jensen, M., Sipes, K., Perini, L., Tranter, M., Anesio, A. M., and Benning, L. G.: Distinct anoxygenic phototrophic lifestyles on the Greenland Ice Sheet expand the light harvesting community during microbial summer blooms on ice surfaces, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20388, https://doi.org/10.5194/egusphere-egu24-20388, 2024.

EGU24-20637 | Orals | CR7.5

Tweedsmuir Glacier, Alsek River, and the salmon migration that wasn’t 

Dan Shugar, Gwenn Flowers, Derek Cronmiller, Laurent Mingo, Al von Finster, and Meghan Sharp

Sockeye salmon are an important species both ecologically as well as culturally. At some point in the recent geological past, as substantiated by Indigenous oral history and ecological data, sockeye would migrate up Alsek River through the St Elias Mountains into southwest Yukon. But they no longer do so, and river-blocking surges of Nàłùdäy (Lowell Glacier), which translates to ‘Fish Stop’, have been blamed. During multiple surges over the past few thousand years, Nàłùdäy impounded massive glacial lakes, which drained catastrophically and transported vast quantities of gravel and boulders downstream. Although Nàłùdäy has not blocked Alsek River since the late 1800s, sockeye have yet to recolonize this stretch of the river. In this study, we suggest a recent advance of Tweedsmuir Glacier, about 65 km downstream of Nàłùdäy, caused Alsek River to carve the narrow Turnback Canyon into bedrock. This canyon, which stretches for ~10 km along the glacier’s terminus and in places is only a few metres wide, produces a functionally insurmountable velocity barrier to upstream fish migration. The ultimate goal of the study is to determine whether Alsek River was rerouted in the recent geological past, cutting off the sockeye salmon migration. Our specific objectives are to (1) determine whether an ancestral paleochannel of Alsek River exists beneath Tweedsmuir Glacier; (2) establish the chronology of canyon incision and determine whether it was related to rapid drainage of ice-dammed lakes at Nàłùdäy; and (3) evaluate whether the subglacial topography may be conducive to Alsek River abandoning Turnback Canyon as the glacier retreats, creating a gentler stretch of river allowing fish to reach upstream habitat.

 

Between 2019 and 2022, we collected more than 450 line-km of airborne and ground-based ice-penetrating radar data over the lower glacier to map the subglacial topography with the intent of determining whether a paleochannel might exist up which sockeye may have traveled prior to Neoglacial advances. Results suggest that the terminal lobe of Tweedsmuir Glacier is up to ~500 m thick and in some places the bed is up to ~100 m below sea level. Based on preliminary analyses of the radar data, it is conceivable that Alsek River could abandon Turnback Canyon for the lower elevation terrain, as the glacier retreats in the coming decades and centuries. Terrestrial cosmogenic nuclide dating of the canyon walls using 36Cl suggests that the canyon was cut within the last thousand years, and very quickly, possibly in a single episode of downcutting.

How to cite: Shugar, D., Flowers, G., Cronmiller, D., Mingo, L., von Finster, A., and Sharp, M.: Tweedsmuir Glacier, Alsek River, and the salmon migration that wasn’t, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20637, https://doi.org/10.5194/egusphere-egu24-20637, 2024.

EGU24-381 | ECS | Posters on site | CR7.7

Effects of Arctic sea-ice concentration on turbulent surface fluxes in four atmospheric reanalyses 

Tereza Uhlíková, Timo Vihma, Alexey Karpechko, and Petteri Uotila

A prerequisite for understanding the local, regional, and hemispherical impacts of Arctic sea-ice decline on the atmosphere is to quantify the effects of sea-ice concentration (SIC) on the turbulent surface fluxes of sensible and latent heat in the Arctic.

The best available information in data-sparse regions such as the Arctic is provided by global atmospheric reanalyses. Because each reanalysis uses its own forecast model, data-assimilation system, and often also different atmospheric and surface observations to create the data sets, their atmospheric and surface variables, and boundary conditions often differ. While the differences between reanalyses in variables SIC, latent and sensible heat flux have been demonstrated via comparisons against observations and inter-comparisons between reanalyses, how much these data sets scatter in the effects of SIC on surface turbulent fluxes is not known.

To fill these knowledge gaps, we analyse these effects utilising four global atmospheric reanalyses: ERA5, JRA-55, MERRA-2, and NCEP/CFSR (CFSR and CFSv2), and evaluate their uncertainties arising from inter-reanalysis differences in SIC and in the sensitivity of the turbulent surface fluxes to SIC.

Using daily field means in nine Arctic basins, the magnitude of the differences in SIC is up to 0.15, but typically around 0.05 during all four seasons. Bilateral orthogonal-distance regression analyses indicate that the greatest sensitivity of both the latent and the sensible heat flux to SIC occurs in the cold season, November to April. For these months, using daily means of data, the average sensitivity is 400 W m-2 for the latent heat flux and over 800 W m‑2 for the sensible heat flux per unit of SIC (change of SIC from 0 to 1, positive sign referring to the downward flux). The differences between reanalyses are as large as 300 W m-2 for the latent heat flux and 600 W m-2 for the sensible heat flux per unit of SIC. The sensitivity is highest for the NCEP/CFSR reanalysis. Comparing two study periods 1980–2000 and 2001–2021, we find that the effect of SIC on turbulent surface fluxes has weakened, due to the increasing surface temperature of sea ice and the sea-ice decline.

Multilateral ordinary-least-square regression analyses show that the effect of SIC on turbulent surface fluxes arises mostly via its effect on atmosphere-surface differences in temperature and specific humidity, whereas the effect of SIC on wind speed (via surface roughness and atmospheric-boundary-layer stratification) partly cancels out in the turbulent surface fluxes, as the wind speed increases the magnitude of both upward and downward fluxes.

How to cite: Uhlíková, T., Vihma, T., Karpechko, A., and Uotila, P.: Effects of Arctic sea-ice concentration on turbulent surface fluxes in four atmospheric reanalyses, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-381, https://doi.org/10.5194/egusphere-egu24-381, 2024.

EGU24-450 | ECS | Posters on site | CR7.7

Impact of stratospheric polar vortex variability on Antarctic surface climate and sea ice 

Bianca Mezzina, Froila M. Palmeiro, and Hugues Goosse

The interannual variability of Antarctic sea ice is considered to be mainly driven by tropospheric and oceanic processes. However, the stratosphere also constitutes a possible source of sea ice variability. The stratospheric variability in the southern high latitudes is dominated by the stratospheric polar vortex (SPV), an extremely cold air mass confined to the pole by strong westerly winds. The SPV is characterized by a large seasonal cycle, peaking in austral winter and breaking down in late spring (with the so-called stratospheric final warming, SFW), but also by interannual variations. While there is robust evidence of a downward impact of the polar stratospheric variability on the Northern Hemisphere surface climate, including sea ice, whether a similar link is present in the Southern Hemisphere is still unsettled.

Here, we perform a multi-model assessment of the impact of the dynamical state of the SPV on Antarctic surface climate and sea ice by applying the same experimental protocol to three state-of-the-art general circulation models (GCMs): EC-EARTH, CMCC-ESM and CanESM. The three GCMs have similar ocean and sea ice components but different atmosphere.

First, we examine 200-year control experiments and compare them to observations. To assess the impact of the SPV state on the surface and sea ice, we build composites of “strong” and “weak” SPV years based on the late-winter stratospheric conditions. We then compare the anomalous patterns of sea ice concentration during the following spring, as well as anomalies of atmospheric fields such as sea-level pressure and surface temperature. To detect the possible downward stratosphere-troposphere coupling, we also compute the temporal evolution of vertical profiles of zonal-mean zonal wind and temperature. A similar analysis is also carried out using composites based on the timing of the SFW (“early” versus “late”).

To further isolate the potential role of the polar stratosphere in driving Antarctic surface climate, we run an additional set of sensitivity experiments with suppressed stratospheric variability. For each model, we build 200-member ensembles of 1-year long runs initialized from the control experiment, with the polar stratosphere nudged to the models' climatology, while the troposphere and the extra-polar stratosphere evolve freely. We then compare the variability of Antarctic sea ice and surface climate in these sensitivity experiments to that of the control run and investigate changes in the suggested mechanisms for the stratospheric downward influence.

How to cite: Mezzina, B., Palmeiro, F. M., and Goosse, H.: Impact of stratospheric polar vortex variability on Antarctic surface climate and sea ice, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-450, https://doi.org/10.5194/egusphere-egu24-450, 2024.

EGU24-2610 | Posters on site | CR7.7

Similarities and differences in circulation beneath the Filchner-Ronne and Ross Ice Shelves: Lagrangian point of view 

Vladimir Maderich, Roman Bezhenar, Igor Brovchenko, Dias Fabio Boeira, Cecilia Äijälä, and Petteri Uotila

The two world’s largest ice shelves, the Filchner-Ronne Ice Shelf (FRIS) and the Ross Ice Shelf (RIS) account for half the area of Antarctic ice shelves. They play a key role in transforming water masses on the shelf and forming Antarctic Bottom Water.

The objective of the work was to study the similarities and differences of circulation under the FRIS and RIS using the data of numerical simulation of currents, temperature, and salinity in the Weddell and Ross Seas from the Whole Antarctica Ocean Model (WAOM). The modelling results were used to run the particle-tracking model Parcels for computing Lagrangian particle trajectories. Three Lagrangian characteristics were calculated for FRIS and RIS: (i) Visitation frequency is defined as the percentage of the particles P visited each 2x2 km grid column at least once in a period of modelling (20 y); (2) Representative particle trajectory is the particle trajectory which deviates least from rest of trajectories; (iii) The mean age is the age of particles visited each 2x2 km grid column at least once.

The representative particle trajectories show that anticyclonic circulation beneath the FRIS and RIS is caused by the inflow of High Salinity Shelf Water (HSSW) through troughs off the western coast of the Weddell and Ross Seas. Transformed into ISW water, it flows out through the troughs in these seas. Part of the transformed water under the FRIS flows out through the Filchner Trough between Berkner Island, while water under RIS flows into the Ross Sea in the strait between Roosevelt Island and the shore. The eastern part of RIS is not ventilated by water inflowing from Ross Island. It is slowly ventilated by water entering a trough between Roosevelt Island and the eastern coast of the Ross Sea. Visitation frequency and representative trajectories suggest similar paths for water mass entering RIS in all seasons. Except December-February particles in anticyclonic gyre can return under RIS. Meanwhile, for particles released in January-August, outflows from FRIS took place through both the Ronne and Filchner ice fronts. In the October-December release the outflow through the Ronne ice front essentially exceeds flow through the Filchner depression.

How to cite: Maderich, V., Bezhenar, R., Brovchenko, I., Fabio Boeira, D., Äijälä, C., and Uotila, P.: Similarities and differences in circulation beneath the Filchner-Ronne and Ross Ice Shelves: Lagrangian point of view, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2610, https://doi.org/10.5194/egusphere-egu24-2610, 2024.

This study investigates the Arctic sea ice concentration trend during 1979-2021 and explores why the autumn Arctic sea ice loss is accelerated after 2002 and its trend declining center shifts from the Chukchi Sea to the Barents-Kara-Laptev Seas. Attribution analysis reveals that the enhanced summer sea ice concentration negative trend in large part explains the autumn sea ice concentration accelerating reduction, whereas it is the trend center shift of increased downward longwave radiation that accounts for mostly of the autumn sea ice concentration decline center shift. Further analysis suggests the downward longwave radiation trend is closely related to large-scale atmospheric circulation changes. A tendency towards a dipole structure with an anticyclonic circulation over Greenland and the Arctic Ocean and a cyclonic circulation over Barents-Kara Seas enhances (suppresses) the downward longwave radiation over Western (Eastern) Arctic by warming and moistening (cooling and drying) the lower troposphere during 1979-2001. In comparison, a tendency towards a stronger Ural anticyclone combined with positive phase of the North Atlantic Oscillation pattern significantly promotes the increase of downward longwave radiation over Barents-Kara-Laptev Seas during 2002-2021. Our results set new insights into the Arctic sea ice variability and deepen our understanding of the climate change.

How to cite: Jiang, Z.: Two distinct declining trend of autumn Arctic sea ice concentration before and after 2002, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2781, https://doi.org/10.5194/egusphere-egu24-2781, 2024.

EGU24-5533 | ECS | Posters on site | CR7.7

Updated sea ice code and atmospheric forcing improve the Antarctic summer sea ice of an ocean model 

Cecilia Äijälä, Yafei Nie, Lucia Gutierrez-Loza, Chiara De Falco, Siv Kari Lauvset, Bin Cheng, and Petteri Uotila

The ocean and sea ice play an important role in the Antarctic climate system, and the atmosphere plays an important role in forcing the sea ice and the ocean. A better understanding of these interactions is needed to understand recent changes and anticipate future changes in the Antarctic. ​

We present a regional ocean model MetROMS-UHel for a quarter-degree resolution domain of the Antarctic Ocean. MetROMS-UHel is based on the MetROMS-Iceshelf model that uses ROMS (Regional Ocean Modeling System), with ocean-ice shelf thermodynamics. For the sea ice, MetROMS-Iceshelf uses CICE (Community Ice CodE) 5.1.2., while MetROMS-UHel has been updated to CICE 6.3.1. We run both models with two different atmospheric forcings, ERA-Interim (ECMWF Re-Analysis ERA-Interim from 1992 to 2018) and ERA5 (ECMWF Reanalysis v5 from 1992 to 2023). The atmospheric reanalysis plays an important role in the results, and this way we see which changes are due to the updated sea-ice model and which are from the updated atmospheric forcing.

The models simulate the interannual variability of the Antarctic sea ice extent reasonably well. The sea ice extent is similar for all model runs and close to observed in all seasons except JFM. In JFM the extent varies between the models especially in the Ross and Weddell Seas, with the largest, and closest to observed extent produced by the MetROMS-UHel CICE 6, ERA5 run. Important watermasses are well represented by the models, with cold waters being slightly fresher in the MetROMS-UHel runs.

How to cite: Äijälä, C., Nie, Y., Gutierrez-Loza, L., De Falco, C., Lauvset, S. K., Cheng, B., and Uotila, P.: Updated sea ice code and atmospheric forcing improve the Antarctic summer sea ice of an ocean model, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5533, https://doi.org/10.5194/egusphere-egu24-5533, 2024.

EGU24-5813 | ECS | Orals | CR7.7

Antarctic sea ice sensitivity to the orographic gravity wave drag in a fully coupled climate model  

Maria Vittoria Guarino, Jeff Ridley, Riccardo Farneti, Fred Kucharski, and Adrian Tompkins

Low-level winds over Antarctica are overwhelmingly controlled by the local orography. They, in turn, exert a large control on sea ice formation and transport.

In Global Circulation Models, the influence of orography on the climate system is modelled via orographic gravity wave drag (OGWD) parameterizations. Models usually partition the drag exerted on the atmosphere by the sub-grid scale orography into two components due to flow blocking and gravity waves.

In this work, we investigate the relationship between Antarctic sea ice and the parameterized OGWD in the UK Earth System Model (UKESM). We present results from sensitivity tests performed using the UKESM-CMIP6 historical runs.
In these simulations, the partition between the “flow-blocking” component and the “gravity wave” component of the OGWD parameterization was altered to simulate “flow-over” and “flow-blocking” regimes. These experiments show that sea ice strongly responds to changes in the orographic gravity wave drag. The strong sea ice decline simulated by the control run from 1980 to 2015, not matched by the observational record, is halted and is delayed by 15-20 years (across the ensemble members) in our flow-blocking regime simulation. Conversely, in the flow-over regime simulation, sea ice begins declining about 10 years earlier than in the control run. The systematic response of the coupled system suggests the existence of a dynamical relationship between sea ice and OGWD.

The pan-Antarctic signal for sea ice decline derives from the Weddell Sea sector. The pathway through which OGWD influences sea ice is via modifications of the flow regime across the Antarctic Peninsula, and thus the surface wind stress across the Weddell Sea sector, which in turn alters the occurrence of oceanic deep convection. This happens because the flow regime across the Antarctic Peninsula is critical in determining the strength and pattern of the surface winds on both the windward side (Bellingshausen and Amundsen Seas sector) and the lee side (Weddell Sea sector) of the mountain ridge.

How to cite: Guarino, M. V., Ridley, J., Farneti, R., Kucharski, F., and Tompkins, A.: Antarctic sea ice sensitivity to the orographic gravity wave drag in a fully coupled climate model , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5813, https://doi.org/10.5194/egusphere-egu24-5813, 2024.

EGU24-7523 | ECS | Posters on site | CR7.7

Amplified Interannual Variation of the Summer Sea Ice in the Weddell Sea, Antarctic After the Late 1990s 

Yuanyuan Guo, Xiaodan Chen, Sihua Huang, and Zhiping Wen

The sea-ice extent (SIE) in the Weddell Sea plays a crucial role in the Antarctic climate system. Many studies have examined its long-term trend, however whether its year-to-year variation has changed remains unclear. We found an amplified year-to-year variance of the Weddell Sea SIE in austral summer since 1998/1999 in observational datasets. Analyses of sea-ice concentration budget and surface fluxes indicate that it is the thermodynamic process that drives the amplification of SIE variations, rather than the sea-ice-drift- related dynamic process. Compared to 1979–1998, the Southern Annular Mode in the preceding spring shows a closer linkage with the Weddell Sea SIE in 1999–2021 through a stronger and more prolonged impact on sea surface temperature, which thermodynamically modulates local sea ice via changing surface heat and radiation fluxes. Our study helps advance the understanding of extreme low Antarctic-SIE records occurring in recent decades and improve future projections of the Antarctic sea-ice variability.

How to cite: Guo, Y., Chen, X., Huang, S., and Wen, Z.: Amplified Interannual Variation of the Summer Sea Ice in the Weddell Sea, Antarctic After the Late 1990s, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7523, https://doi.org/10.5194/egusphere-egu24-7523, 2024.

EGU24-8422 | ECS | Posters on site | CR7.7

The impact of atmospheric forcing on wintertime sea-ice lead patterns in the Southern Ocean 

Umesh Dubey, Sascha Willmes, Alexander Frost, and Gunther Heinemann

Sea-ice leads are narrow, linear fractures in sea ice, and are an important basis for understanding the mechanism of the atmosphere-sea ice-ocean system in the Southern Ocean. We use monthly sea-ice lead frequencies based on satellite thermal imagery with 1 km2 grid resolution to investigate potential causes for the observed spatial and temporal variabilities of sea-ice leads during wintertime (April-September), 2003-2023, using ERA5 winds and sea level pressure, as well as climate indices El Niño–Southern Oscillation (ENSO) and Southern Annular Mode (SAM). The presented investigation provides evidence for correlations between mean monthly lead frequency and monthly wind divergence, as well as monthly sea level pressure across the majority of the circum-Antarctic regions (significantly in the Weddell Sea, Ross Sea and Amundsen & Bellingshausen Sea). Furthermore, our investigation evaluates the influence of wintertime ENSO and SAM on sea-ice lead patterns in the Southern Ocean. Results reveal a positive correlation between sea-ice leads and SAM, in the Weddell Sea and specific regions of the Ross Sea. Moreover, a positive correlation is found between sea-ice leads and ENSO, particularly in the Ross Sea, Western Pacific Ocean, and certain portions of the Indian Ocean. While the driving mechanisms for these observations are not yet understood in detail, the presented results can contribute to opening new hypotheses on atmospheric forcing and sea-ice interactions. The contribution of atmospheric forcing to regional lead dynamics is complex, and a more profound understanding requires detailed investigations in combination with considerations of ocean processes. This study provides a starting point for further research into the detailed relationships between sea-ice leads and atmosphere, ocean, combined effect of ENSO-SAM, respectively in the Southern Ocean.

How to cite: Dubey, U., Willmes, S., Frost, A., and Heinemann, G.: The impact of atmospheric forcing on wintertime sea-ice lead patterns in the Southern Ocean, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8422, https://doi.org/10.5194/egusphere-egu24-8422, 2024.

EGU24-8652 | Posters on site | CR7.7

SSP3-7.0 projections of Antarctic sub-ice-shelf melting with the Energy Exascale Earth System Model 

Xylar Asay-Davis, Darin Comeau, Alice Barthel, Carolyn Begeman, Wuyin Lin, Mark Petersen, Stephen Price, Andrew Roberts, Irena Vankova, Milena Veneziani, Jonathan Wolfe, and Shixuan Zhang

To date, few Earth System Models (ESMs) have the ability to simulate the flow in the ocean cavities below Antarctic ice shelves and its influence on basal melting.  Yet capturing both this flow and the resulting melt patterns is critical for representing local, regional, and global feedbacks between the climate and sub-ice-shelf melting.  Here, we present a small ensemble of historical simulations and SSP3-7.0 projections in an ESM that includes Antarctic ice-shelf cavities, the Energy Exascale Earth System Model (E3SM) v2.1.  The simulations have active ocean, sea-ice, atmosphere, land and river components.  The model domain has 12 km horizontal resolution around Antarctica, which is adequate for capturing dynamics in the larger ice-shelf cavities, melt fluxes aggregated across Antarctic regions, and water masses across most of the Antarctic continental shelf. The projections show significant warming and freshening of water masses on the Antarctic continental shelf, a deepening and poleward shift of the Amundsen Sea Low (ASL), and a significant increase in Antarctic melting through the 20th and 21st centuries.  We also see a significantly more modest drift in water-mass properties and melt rates in our control simulation with constant 1950 conditions from which the historical runs were branched.  In addition to providing an estimate of future melting and other changes in regional and global climate under SSP3-7.0, these simulations are also a steppingstone to coupled ice sheet-ocean simulations planned for the near future.  We briefly discuss these plans and the coupling strategy that we are developing.

How to cite: Asay-Davis, X., Comeau, D., Barthel, A., Begeman, C., Lin, W., Petersen, M., Price, S., Roberts, A., Vankova, I., Veneziani, M., Wolfe, J., and Zhang, S.: SSP3-7.0 projections of Antarctic sub-ice-shelf melting with the Energy Exascale Earth System Model, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8652, https://doi.org/10.5194/egusphere-egu24-8652, 2024.

EGU24-9796 | ECS | Posters on site | CR7.7

Development of Polar Lows in Future Climate Scenarios over the Barents Sea 

Ting Lin, Anna Rutgersson, and Lichuan Wu

Polar lows (PLs) are intense mesoscale cyclones that form over polar oceans during colder months. Characterized by high wind speeds and heavy precipitation, they profoundly impact coastal communities, shipping, and offshore activities. Amid the substantial environmental changes in polar regions due to global warming, PLs are expected to undergo noteworthy transformations. In this study, we investigate the response of PL development in the Barents Sea to climate warming based on two representative PLs. Sensitivity experiments were conducted including the PLs in the present climate and the PLs in a pseudo-global warming scenario projected by the late 21st century for SSP 2-4.5 and SSP 3-7.0 scenarios from CMIP6. In both warming climate scenarios, there is an anticipated decrease in PL intensity, in terms of the maximum surface wind speed and minimum sea level pressure. Despite the foreseen increase in latent heat release in the future climate, contributing to the enhancement of PL intensity, other primary factors such as decreased baroclinic instability, heightened atmospheric static stability, and reduced overall surface heat fluxes play pivotal roles in the overall decrease in PL intensity in the Barents Sea under warming conditions. The augmentation of surface latent heat flux, however, results in increased precipitation associated with PLs by enhancing the latent heat release. Furthermore, the regional steering flow shifts in the warming climate can influence the trajectory of PLs during their development.

How to cite: Lin, T., Rutgersson, A., and Wu, L.: Development of Polar Lows in Future Climate Scenarios over the Barents Sea, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9796, https://doi.org/10.5194/egusphere-egu24-9796, 2024.

EGU24-10555 | ECS | Posters on site | CR7.7

Towards an improved Antarctic sea-ice representation in HadGEM3-GC5 

Tarkan Bilge, Kaitlin Naughten, Paul Holland, Edward Blockley, David Storkey, and Jeff Ridley

The historical runs of CMIP6-era coupled climate models generally exhibit negative biases in Antarctic sea ice, as identified across a range of models during the CMIP6 simulations (Roach et al. 2020). The UK's national coupled climate model, HadGEM3, has been no exception to this. The CMIP6 version, HadGEM3-GC3, underestimated Antarctic sea ice in historical simulations owing to a Southern Ocean warm bias (Andrews et al. 2020). As part of the DEFIANT (Drivers and Effects of Fluctuations in sea Ice in the ANTarctic) project, in this research we perform an analysis of the representation of sea ice in HadGEM3-GC5, a more recent version of the coupled model. Analysis of existing HadGEM3-GC5 simulations has identified unrealistic convection events associated with open water polynyas. We have started to perform a suite of sensitivity experiments to investigate the importance of the freshwater budget and ocean mixing parameterisation scheme on these convection events, and subsequently on pan-Antarctic sea ice. These initial experiments take the form of short simulations with constant year-2000 forcings, incorporating various parameter perturbations and modifications to freshwater input. We present evidence of the improved characterisation of pan-Antarctic sea ice in HadGEM3-GC5 compared to HadGEM3-GC3, and the preliminary analysis of perturbation simulations aimed at understanding and addressing the remaining challenges in the model coupled climate system.

How to cite: Bilge, T., Naughten, K., Holland, P., Blockley, E., Storkey, D., and Ridley, J.: Towards an improved Antarctic sea-ice representation in HadGEM3-GC5, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10555, https://doi.org/10.5194/egusphere-egu24-10555, 2024.

EGU24-11497 | Orals | CR7.7

How well do the regional atmospheric, oceanic and coupled models describe the Antarctic sea ice albedo? 

Kristiina Verro, Cecilia Äijälä, Roberta Pirazzini, Damien Maure, Willem Jan van de Berg, Petteri Uotila, and Xavier Fettweis

A realistic representation of the Antarctic sea ice surface albedo, especially during the melting period, is essential to obtain reliable atmospheric and oceanic model predictions. Antarctic sea ice cover influences the atmosphere by reflecting solar radiation and acting as a barrier between the atmosphere and the ocean, for example. The Antarctic sea ice consists of ice floes of varying thickness, usually covered by snow, and broken up by cracks, leads and polynyas. Therefore, the optical properties of sea ice can vary greatly.

We use regional atmospheric (HCLIM-AROME), oceanic (MetROMS-UHel) and coupled (MAR-NEMO) models to compare the representation of the basic sea ice characteristics: sea ice albedo, snow and ice thickness, and meteorological data during the melt periods of two Antarctic domains with very different sea ice conditions, using data of the ISPOL and Marsden field campaigns. During the ISPOL campaign (Dec 2004; Hellmer et al. 2008) RV Polarstern was moored to an ice floe in the Weddell Sea, where snow-covered multi-year ice persists. The Marsden field campaign (Nov. 2022; Dadic et al. 2023) was established over 2.4m thick land-fast ice of McMurdo Sound, where snow thickness ranged from 0 to 40 cm in patches over the roughest ice. We aim to bridge the models to observations, by comparing model output to various levels of observations, from in-situ measurements of the ISPOL and Marsden campaigns to smaller/larger scale satellite observations over Weddell and Ross Seas. 

The first comparisons revealed that HCLIM, with a simplistic 1D thermodynamic sea ice scheme (SICE, Bartrak et al. 2018), was underestimating snow albedo up to 30%, and needed retuning for Antarctic conditions. Overall, preliminary results indicate that the models do well reproducing the snow-covered sea ice during the ISPOL campaign, when the weather was warm, with the air temperature mostly above −5◦C. MetROMS-UHel, which uses the Delta-Eddington multiple scattering radiative transfer model to calculate the sea ice albedo, even reproduced similar diurnal variability than observed. The Marsden field campaign took place in an area of complex topography, cold weather conditions, and greatly varying sea ice. The models tend to overestimate the albedo of the land-fast ice of the Marsden field campaign, as a uniform, instead of patchy, snow layer is modelled. Models also cannot reproduce the variety of sea ice, such as freshly formed ice, in the McMurdo Sound area apparent on the satellite images.

How to cite: Verro, K., Äijälä, C., Pirazzini, R., Maure, D., van de Berg, W. J., Uotila, P., and Fettweis, X.: How well do the regional atmospheric, oceanic and coupled models describe the Antarctic sea ice albedo?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11497, https://doi.org/10.5194/egusphere-egu24-11497, 2024.

EGU24-12637 | ECS | Orals | CR7.7

Does Strength Matter? An Exploration into Cyclone Strength and the Impact on Arctic Sea Ice 

Elina Valkonen, Chelsea Parker, and Linette Boisvert

Arctic cyclones are an integral part of the polar climate system. They import moisture and energy from the midlatitude and impact the underlying surface through dynamic adn thermodynamic interactions. The rapid warming and sea ice decline in the Arctic makes it more important than ever to understand the tightly coupled interactions between the Arctic sea ice and episodic weather events, such as cyclones.

In this presentation, we use a Lagrangian ice parcel database to study the impact different strength cyclones have on the Arctic Sea ice. The database includes daily 25km Arctic ice parcel tracks and associated atmospheric and sea ice conditions, including passing cyclone track data from 2002-2021. We divide these cyclone tracks into three distinctive groups based on their central pressure and average wind speed. After this, we split the ice parcel tracks and associated atmospheric data based on these cyclone groups: ice affected by weak cyclones, ice affected by normal cyclones, and ice affected by extreme cyclones.

We will then utilize these parcel groups to study the atmospheric conditions (precipitation, temperature, radiative balance) and sea ice changes for three days before, during, and three days after the cyclone passes. We will average the ice parcel and associated atmospheric variable data over the ice parcel life cycle and across the before, during, and after cyclone pass timescales. We will then apply statistical pattern recognition on these averaged sea ice and atmospheric variable fields. This analysis will allow us to better understand the role cyclone strength has in cyclone-sea ice interactions. We will present these results separately for individual seasons, locations, and surrounding SIC.

How to cite: Valkonen, E., Parker, C., and Boisvert, L.: Does Strength Matter? An Exploration into Cyclone Strength and the Impact on Arctic Sea Ice, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12637, https://doi.org/10.5194/egusphere-egu24-12637, 2024.

EGU24-12913 | Orals | CR7.7

Do clouds care about aerosol from sea ice sources (blowing snow, open leads) during Arctic winter/ spring? – a case study from MOSAiC 2019-20 

Markus Frey, Floor van den Heuvel, Amélie Kirchgäßner, Simran Chopra, Thomas Lachlan-Cope, Ronny Engelmann, Albert Ansmann, Heike Wex, Ananth Ranjihkumar, Xin Yang, Jessica Mirrielees, Kerri Pratt, Ivo Beck, Julia Schmale, and Xianda Gong

Aerosols play a key role in Arctic warming via radiative direct and indirect effects. It is well-known that increased aerosol concentration due to Arctic haze raises cloud longwave emissivity, resulting in surface warming. Recently, a MOSAiC study demonstrated that blowing snow above sea ice generates fine sea salt aerosol, which results in up to tenfold enhancement of cloud condensation nuclei leading to potentially significant surface warming rivalling that due to Arctic haze. Yet, radiative properties of aerosol emitted by sea ice sources, vertical coupling and interaction with clouds remain major uncertainties in quantifying the aerosol impact on Arctic climate change.

We use MOSAiC observations to analyse the coupled ocean-ice/snow-atmosphere system and assess contributions of sea ice sources (blowing snow, open leads) to atmospheric cloud-forming particles in particular ice-nucleating particles (INP). Choosing the 2020 winter/spring transition with profound seasonal changes in sea ice and air mass origin, we discuss the importance of sea ice aerosol to low-level clouds in comparison to advected aerosol. We consider measurements of snow particles, physico-chemical properties and INP content of aerosol and snow on sea ice, vertical profiles linking ground observations to the level of cloud formation, and assess climate sensitivity using the UKESM model.

How to cite: Frey, M., van den Heuvel, F., Kirchgäßner, A., Chopra, S., Lachlan-Cope, T., Engelmann, R., Ansmann, A., Wex, H., Ranjihkumar, A., Yang, X., Mirrielees, J., Pratt, K., Beck, I., Schmale, J., and Gong, X.: Do clouds care about aerosol from sea ice sources (blowing snow, open leads) during Arctic winter/ spring? – a case study from MOSAiC 2019-20, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12913, https://doi.org/10.5194/egusphere-egu24-12913, 2024.

EGU24-14392 | ECS | Orals | CR7.7

Impact of Weakened Antarctic Circumpolar Current on the Northern Hemisphere Climate 

Peixi Wang, Yuhui Han, Song Yang, Jun Ying, Zhenning Li, Xichen Li, and Xiaoming Hu

Recent findings show a remarkable linkage between the Northern Hemisphere and Southern Hemisphere climates. Previous studies have focused on the impact of the climate change in the northern high-latitudes on that in the Southern Hemisphere, but few studies concerned the impact of Southern Ocean circulation on the Northern Hemisphere, especially the Arctic climate. In this study, we close the Drake Passage (DP) to slow down the Antarctic Circumpolar Circulation (ACC) in the fully coupled Community Earth System Model, to investigate the impact of weakened ACC on the Northern Hemisphere.

Two model experiments, DP opened and DP closed experiments, are performed. Relative to the DP opened case, a warmer Antarctic with less sea ice cover but a colder Arctic with more sea ice cover appear in the DP closed case resulting from weaker ACC and Atlantic Meridional Overturning Circulation (AMOC). Especially, the changes in surface air temperature in the two poles are largest in winter.

Compared to the DP opened case, the anomalous southward heat transport by weakened ACC is largest in winter, contributing to the winter amplification in the Antarctic. However, the seasonal difference in AMOC change is insignificant. To understand the winter amplification in the Arctic, we further analyze local surface heat flux changes in the Arctic. The anomalous downward longwave radiation and sensible and latent heat fluxes are stored in the ocean in summer and released to the atmosphere in the following winter. Although the ocean heat content warms the surface, the upward sensible and latent heat fluxes cool the surface more significantly in winter. This local atmosphere-ocean-ice interaction contributes to the winter amplification in the Arctic. 

When DP is closed, the westerlies become stronger and move poleward in the Northern Hemisphere because of the increased meridional temperature gradients, especially in winter. The change in surface temperature also contribute to the weakening of Aleutian Low in winter. The warming in the Antarctic and the cooling in the Arctic leads to the notable weakening of Hadley circulation in the Southern Hemisphere. Additionally, compared to the DP opened case, the Intertropical Convergence Zone shifts southward and the Walker circulation and trade winds over the Pacific strengthen. These results shed light on understanding the interhemispheric interaction and the pole-to-pole connection.

How to cite: Wang, P., Han, Y., Yang, S., Ying, J., Li, Z., Li, X., and Hu, X.: Impact of Weakened Antarctic Circumpolar Current on the Northern Hemisphere Climate, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14392, https://doi.org/10.5194/egusphere-egu24-14392, 2024.

During space reentry, satellites undergo ablation in the Mesosphere, leading to the dispersion of ablated material across the globe. The Mesospheric circulation efficiently concentrates this material into the polar winter stratosphere, from where its fate is not well known. Historically, the mass of satellite debris has been significantly smaller than that of naturally occurring meteoroids. The meteoric material also undergoes ablation and deposit similar material, which is transported to the poles and can be observed in Greenland ice cores. With the current exponential increase in the number of launched satellites, the mass of the satellite debris will go from negligible to surpassing the mass of natural meteoric material within the next few years. Here, the quantity and composition of material to be expected in the polar stratosphere the coming years are presented. The question is raised: What potential impacts will the drastic increase of satellite debris have on the polar atmosphere/cryosphere?

How to cite: Megner, L.: Should we worry about the massive increase of satellite reentry debris in the polar regions?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14537, https://doi.org/10.5194/egusphere-egu24-14537, 2024.

Cyclones are an important driver of heat and moisture transport into the Arctic and additionally cause high wind speeds and abrupt wind direction changes during their passage. The subsequent impacts on the Arctic sea ice cover consist of i) a thermodynamic stalling/enhancement of the seasonal sea-ice growth/melt, and ii) enhanced drift and deformation of sea ice. The statistical quantification of these cyclone impacts on the Arctic sea-ice cover is a very recent research topic.

By conducting a climatological monthly analysis based on the ERA5 reanalysis and a cyclone tracking algorithm, we reveal a distinct seasonal cycle of cyclone impacts on sea-ice concentration in the Atlantic Arctic Ocean (strong impacts from autumn to spring, but weak impacts in summer). We further demonstrate that the cyclone impacts have changed significantly throughout the last four decades in a warming Arctic, magnitude-wise strongest in the Barents Sea in autumn.

Still, open questions remain with respect to the impacts of cyclones on the Arctic sea ice in the present climate and regarding their possible changes in a warming Arctic. Specifically, the influence of cyclone passages on the formation of leads in the sea-ice cover has not been statistically analyzed so far. Thus, we extend our analysis to cyclone related changes in sea-ice lead fraction derived from horizontally high-resolved (down to 1km²) MODIS sea-ice observations.

Our results indicate that cyclone passages significantly increase sea-ice lead fraction in large parts of the central Arctic Ocean. Mixed results are found for the Arctic marginal seas. The analysis of particular cyclone cases further suggests that groups of consecutive cyclones traversing the sea ice within short time are particularly effective in driving changes in sea-ice concentration and lead fraction. The statistical quantification of the importance of such a temporal clustering of cyclones for their sea-ice impacts is topic of ongoing research.

How to cite: Aue, L. and Rinke, A.: Advancing the understanding of cyclone impacts on Arctic sea-ice concentration and sea-ice lead formation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15589, https://doi.org/10.5194/egusphere-egu24-15589, 2024.

EGU24-15744 | ECS | Orals | CR7.7

Topographically constrained tipping point for complete Greenland Ice Sheet melt 

Michele Petrini, Meike D. W. Scherrenberg, Laura Muntjewerf, Miren Vizcaino, Raymond Sellevold, Gunter Leguy, William H. Lipscomb, and Heiko Goelzer

A major impact of anthropogenic climate change is the potential triggering of tipping points, such as the complete loss of the Greenland Ice Sheet (GrIS). Currently, the GrIS is losing mass at an accelerated pace, mainly due to a steep decrease in its Surface Mass Balance (SMB, snow accumulation minus surface ablation from melt and associated runoff). Here, we investigate a potential SMB threshold for complete GrIS melt, the processes that control this threshold, and whether it exhibits characteristics commonly associated with tipping points, such as a non-linear response to external forcings. To do this, we adopt a semi-coupled approach, forcing the Community Ice Sheet Model v.2 (CISM2) with different SMB levels previously calculated at multiple elevation classes with the Community Earth System Model v.2 (CESM2). The SMB calculation in CESM2 and the elevation class method allow us to account for the SMB-elevation feedback based on snow/firn processes and energy fluxes at the ice sheet surface. We find a positive SMB threshold for complete GrIS melt of 230±84 Gt/yr, corresponding to a 60% decrease from the GrIS simulated pre-industrial SMB. The ice sheet shows a highly non-linear response to sustained melt, and its final state is determined by the effect of the SMB-height feedback in response to surface melt and Glacial Isostatic Adjustment (GIA). The GrIS is tipping from nearly 50% equilibrium volume towards complete melt when the ice margin in the central west unpins from a coastal region with high bedrock elevation and SMB. We find that this relatively small coastal region is important to determine the ice sheet stability in response to sustained warming. Based on the ice sheet geometry in previous modelling studies of the GrIS during the last interglacial, we suggest that a stabilizing effect of the bedrock topography in the central West might have occurred in the past.

How to cite: Petrini, M., Scherrenberg, M. D. W., Muntjewerf, L., Vizcaino, M., Sellevold, R., Leguy, G., Lipscomb, W. H., and Goelzer, H.: Topographically constrained tipping point for complete Greenland Ice Sheet melt, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15744, https://doi.org/10.5194/egusphere-egu24-15744, 2024.

EGU24-15858 | ECS | Orals | CR7.7

Contrasting trends of marine bromoform emissions in a future climate 

Dennis Booge, Jerry Tjiputra, Dirk Olivié, Birgit Quack, and Kirstin Krüger

Bromoform (CHBr3) from the ocean is the most important organic compound for atmospheric bromine with an atmospheric lifetime of ~2-4 weeks. Natural production, being the main source of oceanic CHBr3, is high at the coasts and in open ocean upwelling regions due to production by macroalgae and phytoplankton. Although highly relevant for the future halogen burden and ozone layer in the stratosphere, the global bromoform production in the ocean and its emissions are still poorly constrained in observations and are mostly neglected in Earth System Model (ESM) climate projections. Anthropogenically forced climate change may lead to considerable changes in ocean temperature and ocean acidification, and will also influence primary productivity. Especially biogeochemical processes in the Arctic will be strongly influenced by climate change in the near future.  However, the future trend of the marine emissions of bromoform and other very short-lived substances (VSLS) remains unclear. Two studies projected an increase of the relative importance of brominated VSLS for stratospheric ozone loss in contrast to other ozone depleting substances, due to increasing oceanic emissions of the brominated VSLS. Both studies applied constant (observation based) oceanic concentrations for the emission calculations in a future warming ocean, which assumes a production increase. Thus, a consistent way of addressing the bromoform production and concentration in the global ocean, its air-sea gas exchange and concentration in the atmosphere with high spatial and temporal resolution is ultimately needed to further progress with our understanding of potential future climate trends.

Here, we show first model results of fully coupled ocean-atmosphere bromoform interactions in the Norwegian ESM (NorESM) with the ocean model BLOM and the ocean biogeochemistry component iHAMOCC for the period from 2015 to 2100 (SSP585 scenario). Model data for the historical period until 2014 is validated with oceanic and atmospheric observations listed in the HalOcAt (Halocarbons in the Ocean and Atmosphere) data base.

On global average, our model results indicate decreasing oceanic CHBr3 concentrations and emissions until the end of this century. In contrast, atmospheric CHBr3 mixing ratios are projected to increase during the same period. The results indicate that the lifetime of atmospheric CHBr3 increases until 2100 compared to current days as atmospheric loss due to photolysis and reaction with hydroxyl radicals is projected to decrease.

In contrast, bromoform in the Arctic shows an increasing trend of marine CHBr3 concentrations, their emissions and atmospheric mixing ratios. Moreover, annual mean Arctic marine bromoform concentrations in 2100 (5.2 pmol L-1) are projected to exceed global values (4.5 pmol L-1). Increasing sea surface temperature and sea ice retreat in the Arctic drives the higher CHBr3 productivity. The resulting emissions in the Arctic are projected to increase by 67% until 2100 indicating this region to be a significant source of brominated VSLS in a future climate. The relevance and uncertainties of the model results are discussed.

How to cite: Booge, D., Tjiputra, J., Olivié, D., Quack, B., and Krüger, K.: Contrasting trends of marine bromoform emissions in a future climate, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15858, https://doi.org/10.5194/egusphere-egu24-15858, 2024.

EGU24-16385 | ECS | Posters on site | CR7.7

Simulating Arctic aerosol-cloud interactions in a warm air intrusion event during the MOSAiC campaign 

Ruth Price, Paul R. Field, Bjørg Jenny Kokkvoll Engdahl, Oskar Landgren, Annette Rinke, and Andrew Orr

Aerosols play a crucial role in determining the characteristics and radiative impacts of Arctic clouds. Parameterisations of aerosols and clouds in climate models remain uncertain, confounding efforts to improve our understanding of their behaviour both now and in the future. Moreover, model biases in cloud microphysics are compounded by interlinked biases in Arctic boundary layer structure, surface properties and large-scale meteorology. This interdependence among variables poses significant hurdles for modelers attempting to accurately simulate Arctic atmospheric processes.

In this study, we have used a regional atmospheric model, the UK Met Office Unified Model, coupled to a cloud microphysical model (Cloud Aerosol Interacting Microphysics, CASIM) and an aerosol-chemistry-climate model (UK Chemistry and Aerosols, UKCA). This integrated approach has been employed to investigate warm air intrusion events during April 2020 of the MOSAiC campaign. Our results provide vital information on the behaviour of model processes that have been tuned for mid-latitude regimes, such as cloud droplet activation, in the Arctic environment during warm air intrusion events that had clear impacts on the surface energy budget. 

How to cite: Price, R., Field, P. R., Engdahl, B. J. K., Landgren, O., Rinke, A., and Orr, A.: Simulating Arctic aerosol-cloud interactions in a warm air intrusion event during the MOSAiC campaign, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16385, https://doi.org/10.5194/egusphere-egu24-16385, 2024.

EGU24-16632 | Posters on site | CR7.7

Bounding the contribution of open leads to sea spray aerosol emissions in the high Arctic 

Rémy Lapere, Jennie L. Thomas, Louis Marelle, and Pierre Rampal

In the Arctic ocean, open leads have the ability to release sea spray into the atmosphere. However, the magnitude and seasonality of this flux are relatively unknown, which is a limitation to our understanding of the polar climate. Most atmospheric models do not include sea spray from leads, because of the lack of existing parameterization. In this work we propose a parameterization for sea spray fluxes from open leads in the Arctic, which leverages aerosol flux measurements from a past campaign combined with the latest generation of sea ice modeling.

Based on our parameterization, the annual total emitted mass of sea salt from open leads, [0.1–1.5] Tg/yr, is comparable to emissions from blowing snow and to the transported mass of sea salt from open ocean coming from the lower latitudes. Furthermore, the seasonality of open lead and blowing snow sea salt emissions have opposite phases, and their spatial distribution across the Arctic is also different. Therefore, we find that including both open lead and blowing snow sea salt fluxes can improve the reproduction of the annual cycle of sea salt aerosol atmospheric concentration at high latitude stations.

Using sea ice concentration fields from the neXtSimv2 sea ice model and implementing our parameterization in the WRF-Chem chemistry-transport model, we evaluate the impacts of open lead emissions on sea salt concentrations and clouds in the high Arctic.

How to cite: Lapere, R., Thomas, J. L., Marelle, L., and Rampal, P.: Bounding the contribution of open leads to sea spray aerosol emissions in the high Arctic, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16632, https://doi.org/10.5194/egusphere-egu24-16632, 2024.

EGU24-16827 | Orals | CR7.7

Ocean-driven basal channel growth at Fimbulisen 

Qin Zhou, Tore Hattermann, Chen Zhao, Rupert Gladstone, Ashely Morris, and Petteri Uotila

Small-scale basal features, such as channels and crevasses, are abundant on many ice shelves.  These features may, either directly or via modulating basal melting, impact ice shelf stability and, therefore, also global sea level. However, simulating the effect of these features on ice shelves at a hundred-meter scale or smaller is still challenging even for dedicated regional simulations, which typically ignore the small-scale features and smooth the ice draft. Fine-resolution (8 m) basal topography retrieved from the Reference Elevation Model of Antarctica (REMA) data reveals that channelized basal features of several tens of kilometers traverse the ice base both along and across the Jutulstraum ice stream on the Fimbulisen Ice Shelf (FIS). The FIS cavity is currently filled with fresh and cold Eastern Shelf Water (ESW), and recent observations have shown a sustained inflow of Warm Deep Water (WDW) since 2016. In this study, we first assess the effect of the basal channels on the cavity circulation and basal melting of the FIS with a fine-scale unstructured grid Finite-Volume Community Ocean Model (FVCOM) model of the FIS ice cavity. The grid resolution varies from 50 m in the focused region along the ice stream to 1500 m in the open ocean. Sensitivity studies are carried out using the high-resolution ice draft from REMA and a smoothed version of it, combined with varying proportions of WDW in the cavity. Our results show that the basal channels lead to (i) a redistribution of basal melting, (ii) a net melt increase at the deep ice area, and (iii) the entrapment of melt-modified WDW in the channels where WDW reaches the deep ice area. Using an idealized ice sheet model, we demonstrate that this entrapment of warm water in the channel results in a net melt increase with a preferential melt that promotes channel growth and migration, forming a positive feedback loop. We further investigate the positive feedback mechanism using an Elmer/Ice–FVCOM model setup with the same fine-scale mesh as the ocean model. This ocean-driven coupled evolution of the channelized system may occur on other shelves in East Antarctica where ESW and WDW coexist. Considering this coupled process in generating sea level projections could constrain East Antarctica's contribution to future sea level rise.

 

How to cite: Zhou, Q., Hattermann, T., Zhao, C., Gladstone, R., Morris, A., and Uotila, P.: Ocean-driven basal channel growth at Fimbulisen, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16827, https://doi.org/10.5194/egusphere-egu24-16827, 2024.

EGU24-17682 | ECS | Posters on site | CR7.7

Changes of clouds and sea ice in EC-Earth- and ERA5-driven retrospective ensemble hindcasts with the fully coupled ice-sheet–ocean–sea ice–atmosphere–land circum-Antarctic model PARASO 

Florian Sauerland, Pierre-Vincent Huot, Sylvain Marchi, Hugues Goosse, and Nicole van Lipzig

We created 4 retrospective hindcasts using PARASO, a five-component (ice sheet, ocean, sea ice, atmosphere, and land) fully coupled regional climate model over an Antarctic circumpolar domain: a control run forced with reanalysis data from ERA5 and ORAS5, and an ensemble of 3 members forced by 3 different EC-Earth global hindcasts. We compare the ocean and sea ice properties of the ERA5-driven simulation to the ensemble mean of the EC-Earth-driven ones, to separate the impact of the different source of boundary conditions from internal variability generated by the different ensemble members. Moreover, we analyse if and how the different ocean temperatures and sea ice extents influence the formation of clouds. We compare the moisture and heat fluxes at the ocean surface between the EC-Earth-driven ensemble and the ERA5-driven hindcast, as well as the moisture and cloud water contents in the atmosphere. This not only provides information on the contribution of external and internal variability inside the PARASO domain for those variables, but by comparing the variability in fluxes to the variability of clouds, we can also estimate the importance of ocean-cloud-interactions. Our results also show that the increasing trend observed in Antarctic sea ice extent observed prior to 2015 is well represented in the ERA5-driven run, but not in the EC-Earth-driven ensemble, indicating a stronger influence of mid-latitude forcings compared to local processes. 

How to cite: Sauerland, F., Huot, P.-V., Marchi, S., Goosse, H., and van Lipzig, N.: Changes of clouds and sea ice in EC-Earth- and ERA5-driven retrospective ensemble hindcasts with the fully coupled ice-sheet–ocean–sea ice–atmosphere–land circum-Antarctic model PARASO, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17682, https://doi.org/10.5194/egusphere-egu24-17682, 2024.

EGU24-17841 | ECS | Orals | CR7.7

Response of EC-Earth3 to Antarctic meltwater 

André Jüling, Erwin Lambert, Philippe Le Sager, and Sybren Drijfhout

Ice-sheet meltwater affects ocean stratification and circulation, sea ice, and ultimately the global climate through various feedback mechanisms. Most current generation global climate models do not include interactive ice sheets and as such do not capture the projected increases in additional meltwater under future emission scenarios. We use the EC-Earth3 coupled climate model to investigate the climate response to various scenarios of Antarctic meltwater input. With the idealized experiments of the Southern Ocean Freshwater Input from Antarctica Model Intercomparison Project (SOFIAMIP), as well as a plausible future meltwater release experiment, we investigate the sensitivity to both amount and location of the freshwater forcing in both the eddy-permitting (0.25°) and the standard, non-eddying (1°) resolution model versions. We find that the amount of freshwater strongly controls the sea ice with associated atmospheric adjustments and feedbacks. We also see that while inserting additional meltwater at the surface enhances stratification increasing sea ice cover, inserting it at depth decreases stratification and enables more ocean heat to be released at the surface. Our results represent improved model physics and support calls for using prescribed Antarctic meltwater input as forcing in the Coupled Model Intercomparison Project to, for example, improve modelled sea ice evolution and sea level trends.

How to cite: Jüling, A., Lambert, E., Le Sager, P., and Drijfhout, S.: Response of EC-Earth3 to Antarctic meltwater, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17841, https://doi.org/10.5194/egusphere-egu24-17841, 2024.

The Filchner-Ronne Ice Shelf currently has a “cold” cavity with comparably low melt rates or refreezing at the ice-ocean interface. However, it has been shown that a switch to “warm” conditions under a very strong climate warming scenario is possible within this century (Hellmer et al., 2012). In this case, modified Circumpolar Deep Water that resides at intermediate levels offshore enters the cavity and fuels a 21-fold increase in aggregated melt rates (Naughten et al., 2021), with implications for ice-shelf buttressing and thereby the dynamics of tributary ice streams and glaciers. Interactions of resulting cavity changes with the ocean could furthermore amplify or weaken the increase in ice shelf melting. Here we investigate the influence of ice-ocean feedbacks on sub-shelf melt rates and the regime shift from a “cold” to a “warm” ice-shelf cavity using standalone and coupled configurations of the ice sheet model Úa and the ocean model MITgcm (De Rydt and Gudmundsson, 2016; Naughten et al., 2021). Furthermore, we test their influence on reversibility back to “cold” conditions, and the impact of a regime shift on grounded ice dynamics.

How to cite: Reese, R. and De Rydt, J.: Do ice-ocean feedbacks influence a regime shift of the Filchner-Ronne ice shelf cavity?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18887, https://doi.org/10.5194/egusphere-egu24-18887, 2024.

EGU24-1458 | Orals | PS2.5 | Highlight

Constraining the Thickness of the Conductive Portion Europa's Ice Shell using Sparse Radar Echoes 

Dustin Schroeder, Natalie Wolfenbarger, and Gregor Steinbrügge

Ice penetrating radars are intuitively appealing for probing ice shells because it is perceived as a way to directly imaging the ice/ocean interface or as a way to "picture" and interpret visually the structural  cross-section of the ice. While this approach is significant and can lead to substantial discoveries, it's also likely that many radar sounding measurements will not exhibit these obvious, intuitive features.

Here, we address the potential of more subtle radar echoes (or the absence thereof) in providing valuable information. These echoes can impose constraints on ice temperature and thickness, offering insights similar to those obtained from other planetary geophysical methods like gravity science or magnetic induction measurements.

In our study, we examine four potential radar signatures: pore-closure, eutectic melt, isolated echo detection, and attenuation horizons. We demonstrate that each of these signatures, by providing observational constraints on either the temperature or the integrated two-way attenuation at a given depth, can help determine the thickness of the conductive portion of Europa's ice shell.

By integrating these findings with other geophysical approaches (e.g., gravity, magnetics), radar sounding data can significantly enhance studies and models of the ice-shell interior, even without the direct detection of the ice/ocean interface.

 

How to cite: Schroeder, D., Wolfenbarger, N., and Steinbrügge, G.: Constraining the Thickness of the Conductive Portion Europa's Ice Shell using Sparse Radar Echoes, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1458, https://doi.org/10.5194/egusphere-egu24-1458, 2024.

EGU24-2392 | Posters on site | PS2.5

Titan in Late Northern Summer from JWST and Keck Observations 

Conor Nixon, Bruno Bézard, Thomas Cornet, Brandon Coy, Imke de Pater, Maël Es-Sayeh, Heidi Hammel, Emmanuel Lellouch, Juan Lora, Nicholas Lombardo, Manuel López-Puertas, Pascal Rannou, Sébastien Rodriguez, Nicholas Teanby, and Elizabeth Turtle and the Titan JWST and Keck Observation Team

Titan is an object of fascination for scientists researching the solar system, as a ‘terrestrial-like’ world with active meteorology and fluvial and lacustrine formations based on methane chemistry and condensation. The Cassini-Huygens mission explored Titan extensively from 2004 to 2017, but since that time further observation of its slow seasonal cycle has been possible only via telescopes positioned on or close to the Earth. Titan’s unique characteristics led to a concerted post-Cassini observational campaign, with many of the most powerful telescopes available to astronomy. In this work we report on observations from 2022 & 2023 with three instruments on the James Webb Space Telescope (JWST), NIRCam, NIRSpec and MIRI, also in coordination with imaging from Keck II. In November 2022 and July 2023, Titan was the subject of multi-spectral filter imaging with JWST NIRCam and Keck II NIRC2, revealing tropospheric clouds at mid-northern latitudes, in line with climate modeling predictions for this season (late northern summer). In filters sensitive to the upper troposphere, we observed clouds growing and apparently ascending in altitude during a Titan day. JWST NIRSpec spectroscopy yielded for the first time a high resolution (R=2700) spectrum of Titan across the entire near-infrared (1-5 microns) unobscured by telluric absorption. This, among other things, enabled measuring the detailed structure of the CO 4.7 micron non-LTE emission, including the fundamental, the first two overtone bands and two isotopic bands. It is also the first time that CO2 emission has been resolved in the NIR and the first time it has been seen on Titan’s dayside.  Finally, very sensitive spectroscopy with JWST MIRI in the mid infrared (5-28 microns) confirmed the many stratospheric gases seen by Cassini CIRS, but also added a new detection of methyl (CH3) in the middle atmosphere, a product of methane photochemistry that was expected but not previously seen. We modeled parts of the spectra to find a global mean temperature profile and profiles of minor gases. Soon we hope to extract yet more results from the NIRSpec and MIRI spectra as our understanding of the calibration and modeling progresses. In this presentation we summarize our results to date and describe planned future observations of Titan with JWST and Keck cycles.

How to cite: Nixon, C., Bézard, B., Cornet, T., Coy, B., de Pater, I., Es-Sayeh, M., Hammel, H., Lellouch, E., Lora, J., Lombardo, N., López-Puertas, M., Rannou, P., Rodriguez, S., Teanby, N., and Turtle, E. and the Titan JWST and Keck Observation Team: Titan in Late Northern Summer from JWST and Keck Observations, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2392, https://doi.org/10.5194/egusphere-egu24-2392, 2024.

EGU24-5965 | Posters on site | PS2.5

Ground-based monitoring of atmospheric species on Titan and a search for new nitriles with IRTF/TEXES 

Athena Coustenis, Therese Encrenaz, Thomas K. Greathouse, David Jacquemart, Rohini Giles, Conor A. Nixon, Panayotis Lavvas, Nicholas Lombardo, Sandrine Vinatier, Bruno Bezard, Krim Lahouari, Pascale Soulard, Benoit Tremblay, Antoine Jolly, and Brendan Steffens

The atmosphere of Titan is known to be a laboratory of complex organic chemistry. (Coustenis, 2021) From the Voyager missions, and later the Cassini-Huygens mission, several hydrocarbons and nitriles have been detected and their seasonal variations have been monitored during a period of one Titan season (30 years). Other minor species have been detected from the ground mainly in the millimeter range or using space-borne observatories like ISO. These results have been included in photochemical models that have also predicted the presence of other minor species, among which some have infrared transitions in the 5-25-µm spectral range where propane (C3H8) and allene (CH2CCH2) have already been detected. We have started an observing program using the TEXES thermal infrared imaging spectrometer at the Infrared Telescope Facility (Mauna Kea Observatory) to monitor the infrared signatures of hydrogen cyanide (HCN) and cyanoacetylene (HC3N), along with acetylene (C2H2 and C2HD). In addition, we have been searching for cyanopropyne (C4H3N) and isobutyronitrile (C4H7N) in the 20-micron region. High-resolution spectra of Titan with TEXES were recorded before where Lombardo et al. (2019) measured HNC (hydrogen isocyanide) in Titan’s lower stratosphere (1 ppb around 100 km), which is the first time HNC has been measured at these altitudes.  In September 2022 we obtained spectra of Titan in the following spectral ranges: (1) 498-500 cm-1 (C2HD, HC3N, search for C4H3N); (2) 537-540 cm-1 (C2HD, search for C4H7N); (3) 744-749 cm-1 (C2H2, HCN); (4) 1244-1250 cm-1 (CH4). Observations are presently being processed. In 2023, laboratory spectra of cyanopropyne and isobutyronitrile have been recorded at Sorbonne Université in the 495-505 cm-1 and 510-570 cm-1 spectral ranges, respectively, with a spectral resolution of 0.01 cm-1 and 0.056 cm-1 (Coustenis et al., 2023). Cross sections have been derived for these two molecules and upper limits will be derived for these two molecules in the atmosphere of Titan. TEXES data will also be used for a study of the variations of HCN and HC3N since the end of the Cassini mission, and for a retrieval of D/H from C2HD/C2H2.

References

  • Coustenis, A., 2021. “The Atmosphere of Titan”. In Read, P. (Ed.), Oxford Research Encyclopedia of Planetary Science. Oxford University Press. doi:https://doi.org/10.1093/acrefore/9780190647926.013.120
  • Lombardo, N.A., Nixon, C.A., Greathouse, T.K., Bézard, B., Jolly, A., Vinatier, S., Teanby, N.A.A, Richter, M.J., Irwin, P.J.G., Coustenis, A., Flasar, F.M., 2019. Detection of propadiene on Titan. Astroph. J. Lett. 881, Issue 2, article id. L33, 6 pp.
  • Coustenis, A., Nixon, C. A., Encrenaz, Th., Lavvas, P., 2023. Titan’s chemical composition from Cassini and ground-based measurements. IUGG 2023, Berlin, Germany, 11-20 July.

How to cite: Coustenis, A., Encrenaz, T., Greathouse, T. K., Jacquemart, D., Giles, R., Nixon, C. A., Lavvas, P., Lombardo, N., Vinatier, S., Bezard, B., Lahouari, K., Soulard, P., Tremblay, B., Jolly, A., and Steffens, B.: Ground-based monitoring of atmospheric species on Titan and a search for new nitriles with IRTF/TEXES, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5965, https://doi.org/10.5194/egusphere-egu24-5965, 2024.

EGU24-6159 | ECS | Posters on site | PS2.5

The effects of an icy porous layer on the two-way radar attenuation on Enceladus 

William Byrne, Ana-Catalina Plesa, Tina Rückriemen-Bez, Andreas Benedikter, and Hauke Hussmann

Saturn's moon, Enceladus is considered a priority target for future planetary missions due to its high astrobiological potential [1]. Water jets presumably originating from a subsurface ocean have been observed at the south pole of Enceladus by NASA’s Cassini mission [2], and their analysis provides a direct window into the ocean composition [3] that, in turn, can help to understand the nature and amount of impurities that may exist within the ice shell.

Enceladus’ jet activity generates a highly porous material that affects the thermal state of the ice shell. The thickness of that layer and its distribution are poorly constrained, but local thicknesses of up to 700m have been reported from the analysis of pit chains on the surface of Enceladus [4]. Such a thick porous layer can strongly attenuate the signal of radar sounders that have been proposed to investigate the Enceladus’ subsurface [5].

Here, we use numerical simulations to determine the effects of a porous layer on the two-way radar attenuation. We generate a variety of steady-state one-dimensional thermal models based on proposed parameters for Enceladus’ ice shell thickness (5 - 35 km, [6]), porous layer thickness (0 - 700 m [4]) and its thermal conductivity (0.1 - 0.001 W/mK [7,8]). In addition to systematically testing parameter combinations, we use two ice shell thickness maps [6] together with local thermal profiles to provide a global spatial distribution of potential penetration depths that could be achieved by radar measurements. We use two material models ("high" and "low" loss) to identify the impact of chemical impurities on attenuation [9]. While the “low” loss scenario considers an ice shell composed of pure water ice, the “high” loss case is characterized by a homogeneous mixture of water ice and chlorides in concentrations extrapolated from the particle composition of Enceladus’ plume [5].

Our results show that the presence of a porous layer has a first-order effect on the two-way radar attenuation. For regions covered by porous layers with thicknesses larger than 250 m and a thermal conductivity lower than 0.025 W/(mK) the two-way radar attenuation reaches a threshold value of 100 dB before reaching the ice-ocean interface in the low loss scenarios. In the high loss cases, for similar porous layer thicknesses and thermal conductivity, the two-way attenuation remains below 100 dB for at most 48% of the ice shell. Depending on the local ice shell thickness and properties of the snow deposits, as little as a few percent of the ice shell can be penetrated before the 100 dB limit is reached. We note, however, that the presence of a porous layer leads to high subsurface temperatures and promotes the formation of brines at shallow depth that can be detected by future radar measurements.

 

References:

[1] Choblet et al., 2021. [2] Hansen et al., 2006. [3] Postberg et al., 2008. [4] Martin et al., 2023. [5] Soucek et al., 2023. [6] Hemingway & Mittal, 2019. [7] Seiferlin et al., 1996. [8] Ferrari et al., 2021. [9] Kalousova et al., 2017.

How to cite: Byrne, W., Plesa, A.-C., Rückriemen-Bez, T., Benedikter, A., and Hussmann, H.: The effects of an icy porous layer on the two-way radar attenuation on Enceladus, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6159, https://doi.org/10.5194/egusphere-egu24-6159, 2024.

EGU24-7948 | ECS | Orals | PS2.5

The role of ammonia in the primordial distribution of volatiles in the hydrosphere of Europa 

Alizée Amsler Moulanier, Olivier Mousis, and Alexis Bouquet

The presence of hydrospheres within the Galilean moons raises the question of whether or not they could provide habitable environments. The study of nowadays’ volatiles inventory on those moons is indicative of their formation processes and their effects on this inventory. However, for the ability to disentangle between the possible scenarios, it is necessary to examine the post-accretion processes that could impact the volatile inventory of the hydrospheres. Especially, an “open-ocean” phase which took place shortly after accretion, before the icy crust formation, must be considered, in view of its influence on the volatile inventory. More specifically, the abundance of ammonia in Europa’s building blocks is a key constrain, both on the habitability conditions of the ocean and the volatile distribution in the primordial thick atmosphere of the moon.

Our work focuses on modelling the ocean-atmosphere equilibrium which took place over this period, based on different formation scenarios of Europa. To do so, we compute the vapor-liquid equilibrium between water and volatiles, as well as the chemical equilibria happening within the ocean to investigate the primitive hydrosphere of Europa. Our model allows for an assessment of the impact of the initial distribution of volatiles resulting from the thermodynamic equilibrium between Europa’s primordial atmosphere and ocean. In particular, we show the correlation between the ratio of dissolved CO2 and NH3 and the distribution of partial pressures in the primordial atmosphere of Europa.

Navigating between two endmembers for the composition of the building blocks (nitrogen delivered by hydrated rocks or cometary ices), and varying the proportion of ammonia incorporated into the ocean after accretion, we obtain a range of primordial volatile distributions, to be linked to nowadays inventory. We also find ammonia abundance thresholds above which CO2 content is significantly depleted by NH2COO-  formation.

How to cite: Amsler Moulanier, A., Mousis, O., and Bouquet, A.: The role of ammonia in the primordial distribution of volatiles in the hydrosphere of Europa, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7948, https://doi.org/10.5194/egusphere-egu24-7948, 2024.

EGU24-9751 | ECS | Posters on site | PS2.5

Icy Moon Surfaces Microstructure through Multiphysics Simulations 

Cyril Mergny and Frédéric Schmidt

Water ice has a microstructure shaped by a complex interplay of coupled multi-physics processes. Among them, ice sintering—also referred to as metamorphism or annealing—transports material from ice grains into their neck region, resulting in changes in the mechanical and thermal properties of the ice. Understanding sintering is essential to investigate the properties and microstructure of ice. While the sintering process of snow on Earth has been extensively studied, there is a scarce amount of information regarding the alteration of ice in planetary surface environments characterized by low temperatures and pressures.

Here we present a multiphysics simulation model designed to study the evolution of planetary ice microstructure.  Coupled to a heat transfer solver, we have built a new model for the sintering of ice grain  with mathematical refinement to the diffusion process. As changes in ice microstructure affect the thermal properties we have expressed the heat conductivity with a formulation that consider microstructure and porosity which enables a two coupling between sintering and heat transfers.

Our simulations of Europa's icy surface spanned a million years, allowing us to thoroughly explore the evolution of ice microstructure. Results show that the hottest regions experience significant sintering, even if high temperatures are only reached during a brief portion of the day. This process takes place on timescales shorter than Europa's ice crust age, suggests that these regions should currently have surface ice composed of interconnected grains. Accurately simulating these highly coupled processes, plays a crucial role in accurately determining the microstructure and quantitative composition of Europa's surface, a key objective for upcoming missions such as JUICE and Europa Clipper.

How to cite: Mergny, C. and Schmidt, F.: Icy Moon Surfaces Microstructure through Multiphysics Simulations, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9751, https://doi.org/10.5194/egusphere-egu24-9751, 2024.

EGU24-13407 | ECS | Posters on site | PS2.5

From Sea Ice to Icy Shells: Modeling the Dielectric Properties of Ice-Brine Mixtures 

Natalie Wolfenbarger, Dustin Schroeder, and Donald Blankenship

The search for habitable worlds within our solar system is guided by liquid water. Evidence for global, salty oceans hidden beneath the icy shells of moons in the Jovian system has motivated two upcoming missions: ESA’s Jupiter Icy Moons Explorer (Juice), launched April 2023, and NASA’s Europa Clipper, launching October 2024. Both spacecraft are equipped with ice-penetrating radar instruments, the Radar for Icy Moon Exploration (RIME) and the Radar for Europa Assessment and Sounding: Ocean to Near-surface (REASON), that will transmit radio waves into the subsurface and record energy reflected from interfaces defined by contrasts in dielectric properties, such as the ice-ocean interface.

The ocean is presumed to be the most extensive liquid water reservoir beneath the surface. However, various ice-water interfaces could exist throughout the ice shell. Dynamic processes such as impacts, convection, tidal heating, strike-slip faulting, and basal fracturing have been hypothesized to influence melt generation or inject ocean water in the ice shell interior. Even in the absence of these dynamic processes, impurities within the ice allow liquid water to be thermodynamically stable as brine at temperatures below the freezing point. In ice shells with non-zero bulk salinity, transitions from solid ice to ice-brine mixtures, or eutectic interfaces, invariably precede the ice-ocean interface. Understanding the detectability and radiometric character of eutectic interfaces is therefore a critical step towards interpreting the data collected by these ice-penetrating radar instruments.

In this work, we review measurements and models of the dielectric properties of sea ice and marine ice on Earth. We use these measurements and models as a foundation to propose a path forward for modeling the dielectric properties of eutectic interfaces within an ice shell. We assess how the ice shell's bulk salinity and the thickness of the thermally conductive layer impact the detectability and radiometric characteristics of eutectic interfaces. Our discussion includes how future laboratory measurements of existing terrestrial ice samples coupled to measurements of proxy samples consistent with off-world ocean sources can inform and refine our proposed framework.

How to cite: Wolfenbarger, N., Schroeder, D., and Blankenship, D.: From Sea Ice to Icy Shells: Modeling the Dielectric Properties of Ice-Brine Mixtures, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13407, https://doi.org/10.5194/egusphere-egu24-13407, 2024.

EGU24-13575 | ECS | Orals | PS2.5

Supercooling and Glass Formation upon Freezing of Enceladus-relevant Salt Solutions 

Fabian Klenner, Lucas M. Fifer, Ardith D. Bravenec, Baptiste Journaux, and David C. Catling

Analysis of ice grains emitted from Saturn’s moon Enceladus revealed that the moon’s subsurface ocean represents a potentially habitable place in the Solar System [1-4].

The emitted ice grains could be crystalline, glassy, or a mixture of both [5,6]. These phase states of the grains are ultimately linked to their formation, i.e. liquid-solid phase transitions. Recent work indicates that emitted plume material does not directly reflect ocean composition [7]. However, even a small fraction of glass within the grains may be favorable for the preservation of organics or even cells [8,9], potentially present in Enceladus’s ocean.

Supercooling, vitrification (glass formation) and heat capacities of aqueous solutions can be measured with or derived from Differential Scanning Calorimetry (DSC). This technique was recently used to study Mars-relevant brines [10]. For Enceladus-relevant salt systems (described below), liquid-solid phase transitions remain an open area of research with limited thermodynamic data.

Here, we present results from DSC experiments with aliquots of aqueous solutions of NaCl, KCl, Na2CO3, NaHCO3, NH4OH, Na2HPO4, K2HPO4, as well as mixtures thereof. Measured salt concentrations covered the range of estimated concentrations of these compounds in Enceladus’s ocean [3,7,11]. We analyzed samples (volumes from 4 to 40 μL) over a wide range of cooling rates, from as low as 10 K/min up to ~1000 K/min via drop-quenching into liquid nitrogen (flash freezing). We then modeled the freezing process of these solutions and associated mineral formation using the aqueous chemistry package PHREEQC and compared the modeling results with our DSC experiments.

Our preliminary results show that at least 60 K supercooling is possible to occur during freezing of salty ice grains from Enceladus. Between 0.5 – 15 percent of the grain’s total volume form a glassy state, with salt-rich grains containing more glass than salt-poor grains. Flash freezing leads to a significantly higher degree of vitrification and lower glass transition temperatures (Tg) than other cooling rates.

Our work is an important step toward understanding the formation and structure of ice grains from Enceladus as well as their capability for cryopreservation of organics and cells. Thermodynamic and kinetic data derived from our experimental results, such as heat capacities and Tg, help inform future models. Our results are also relevant to Jupiter’s moon Europa where a potential plume might also be sourced from the moon’s underlying water ocean.

 

References

[1] Postberg et al. (2018) Nature 558, 564–568.

[2] Khawaja et al. (2019) Mon. Not. R. Astron. Soc. 489, 5231–5243.

[3] Postberg et al. (2023) Nature 618, 489–493.

[4] Hsu et al. (2015) Nature 519, 1098–1101.

[5] Newman et al. (2008) Icarus 193, 397–406.

[6] Fox-Powell & Cousins (2021) J. Geophys. Res.: Planets 126, e2020JE006628.

[7] Fifer et al. (2022) Planet Sci. J. 3, 191.

[8] Fahy & Wowk (2015) in Cryopreservation and freeze-drying protocols, pp.21–82.

[9] Berejnov et al. (2006) J. Appl. Cryst. 39, 7848–7939.

[10] Bravenec & Catling (2023) ACS Earth Space Chem. 7, 1433–1445.

[11] Postberg et al. (2009) Nature 459, 1098–1101.

How to cite: Klenner, F., Fifer, L. M., Bravenec, A. D., Journaux, B., and Catling, D. C.: Supercooling and Glass Formation upon Freezing of Enceladus-relevant Salt Solutions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13575, https://doi.org/10.5194/egusphere-egu24-13575, 2024.

EGU24-15222 | Orals | PS2.5

Titan’s surface chemical composition: what we learnt after 13 years of Cassini exploration 

Anezina Solomonidou, Alice Le Gall, Paul Hayne, and Athena Coustenis

The Cassini spacecraft spent 13 years in the Saturnian system and performed observations of Titan through 127 flybys, along with the in situ observations of the surface by Huygens. This led to the detailed investigation of Titan’s surface composition at both local and global scale. However, due to the complexity of Titan’s atmosphere and surface, the surface composition is only partially unveiled and is still considered to be one of Titan’s largest mysteries. Titan is resembling Earth like no other body in our solar system even though its mean surface temperature in -180 ºC (~93 K), and instead of silicate rocks like on Earth, water ice is abundant in the crust. Sedimentary deposits in the form of hydrocarbon grains cover the top layer of the surface, while liquid hydrocarbons are found in the polar lakes. Titan’s active geology with its resurfacing processes creates a surficial topography where exposed materials from the underlying ‘old’ crust along with new atmospheric sediments are present. After Cassini and Huygens with their several instruments investigated Titan for more than a decade one of the prevailing questions that still remains unanswered is whether and where water ice is exposed on the surface. Additionally, advanced knowledge with regards to the mixtures and the materials that create and cover the surface is yet to be gained from future missions and ground/space telescopes that would carry advanced technology. Here, we present an overview of what we have learnt so far about the composition as well as its correlation and constraints with regards to Titan’s astrobiology.

How to cite: Solomonidou, A., Le Gall, A., Hayne, P., and Coustenis, A.: Titan’s surface chemical composition: what we learnt after 13 years of Cassini exploration, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15222, https://doi.org/10.5194/egusphere-egu24-15222, 2024.

EGU24-16084 | ECS | Posters on site | PS2.5

Towards biosignature detection on Icy Moons with ORIGIN 

Nikita Jennifer Boeren, Peter Keresztes Schmidt, Marek Tulej, Peter Wurz, and Andreas Riedo

In the search for life beyond Earth, the icy moons Europa and Enceladus have been brought forward as the most promising targets within our Solar System. Recently, the Enceladus Orbilander mission has gained significant interest as it has been selected as a NASA flagship mission1. This emphasises the need for reliable in-situ instrumentation capable of biosignature detection and identification.

In-situ instrumentation must not only meet flight-capability requirements, but the detection capabilities should extend beyond single molecules or compound groups. Various groups of compounds are listed to be of astrobiological interest, such as amino acids, lipids, and nucleobases1–3. Ideally, instruments should be capable of simultaneously detecting several different compound groups, in varying abundances from major components down to trace level. Therefore, to successfully detect both trace abundances and highly abundant compounds, a high sensitivity and wide dynamic range coverage are essential as well.

This contribution will provide a comprehensive overview of the ORIGIN (ORganics Information Gathering INstrument) space-prototype, a Laser Desorption Ionisation Mass Spectrometer (LDI-MS), designed for the in-situ detection of molecular biosignatures. ORIGIN's light-weight and robust design, includes a nanosecond pulsed laser system (λ=266 nm, 20 Hz, τ=3 ns) and a miniature reflectron-type Time-Of-Flight mass analyser (RTOF) (160 mm x Ø 60 mm)4. The instrument is designed to address the challenges of flight-capability, sensitivity, and dynamic range coverage, which are all essential for reliable biosignature detection on exploration missions.

ORIGIN's analytical capabilities have been demonstrated for amino acids and lipids, and have recently been extended to nucleobases4-6. We will discuss results of the recent experiments to give an overview of ORIGIN’s detection capabilities including sensitivity and dynamic range, which are crucial for future space exploration missions. The determined limit of detection for three lipids (∼7×10−13 mol μL−1) aligns with the specified requirements in the Enceladus Orbilander mission concept (1×10−12 mol μL−1)3,6. The application of ORIGIN towards the detection of biosignatures on icy moons and the envisioned concept of ice sample handling will also be discussed.

1. National Academies of Sciences, Engineering, and Medicine. Origins, Worlds, Life: A Decadal Strategy for Planetary Science and Astrobiology 2023-2032. 26522 (The National Academies Press, 2022). doi:10.17226/26522.
2. Hand, K. P. et al. Report of the Europa Lander Science Definition Team. (Jet Propulsion Laboratory, 2017).
3. MacKenzie, S. et al. Enceladus Orbilander: A Flagship Mission Concept for the Planetary Decadal Survey. vol. 2020 (John Hopkins Applied Physics Laboratory, 2020).
4. Ligterink, N. F. W. et al. ORIGIN: a novel and compact Laser Desorption – Mass Spectrometry system for sensitive in situ detection of amino acids on extraterrestrial surfaces. Sci. Rep. 10, 9641 (2020).
5. Boeren, N. J. et al. Detecting Lipids on Planetary Surfaces with Laser Desorption Ionization Mass Spectrometry. Planet. Sci. J. 3, 241 (2022).
6. Boeren N.J. et al. Laser Desorption Ionization Mass Spectrometry of Nucleobases for Future Space Exploration Missions, Planet. Sci. J., to be submitted.

How to cite: Boeren, N. J., Keresztes Schmidt, P., Tulej, M., Wurz, P., and Riedo, A.: Towards biosignature detection on Icy Moons with ORIGIN, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16084, https://doi.org/10.5194/egusphere-egu24-16084, 2024.

EGU24-17310 | ECS | Orals | PS2.5

Reflectance properties of analogues for the surfaces of icy moons 

Rafael Ottersberg, Antoine Pommerol, Linus Leo Stöckli, and Nicolas Thomas

Spectrometers and colour imagers on past and future space missions, as well as ground-based telescopes, help us to improve our understanding of the composition of icy surfaces in the outer solar system. To help interpret these datasets, we study the VIS-NIR (0.4-2.5 µm) reflectance properties of granular (salty) ice particles exposed to simulated space environments.

We further developed an original experimental chamber (SCITEAS-2) to study the evolution of samples at temperatures representative of icy planetary surfaces in the outer solar system. We built a new cooling/heating stage to precisely control the sample’s temperature, allowing us to decouple the effects of temperature and time on the sublimation process. The surface temperature of the ice is monitored by measuring IR-emission using Thermopile sensors. To study the reflectance of the sample, we use a hyperspectral imaging system consisting of a Halogen light source, a monochromator, and two cameras (CCD and MCT). We produce granular ice particles with a broad size distribution (d≈1-400µm) by flash-freezing dispersed droplets in LN2. These particles can be made from pure water or salty solutions.

We observe that the VIS-spectrum of pure water ice is flatter than the one of the ice produced from a 10wt% NaCl solution, which has a blue slope. The most prominent feature of granular 10wt% NaCl-ice is a narrow absorption feature at 1.98 µm, attributed to hydrohalite (NaCl · 2H2O), which is not present in the pure ice sample. However, it only appears after some sublimation of the sample. While the spectra of pure water ice and 10wt% NaCl ice match well for the pristine samples, sublimation strongly increases the albedo of salty ice. Sublimation forms a crust atop the sample, affecting the reflectance and strongly influencing other thermo-physical properties. Therefore, we propose that sublimation is an important ingredient in interpreting spectral data of the Jovian Moon Europa because the timescales of the effects of sublimation are smaller than surface renewal by micrometeorite gardening or sputtering.

These datasets will help to interpret high-resolution colour images and spectra acquired by the EIS and MISE instruments on Europa Clipper as well as similar instruments on JUICE.

How to cite: Ottersberg, R., Pommerol, A., Stöckli, L. L., and Thomas, N.: Reflectance properties of analogues for the surfaces of icy moons, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17310, https://doi.org/10.5194/egusphere-egu24-17310, 2024.

EGU24-17359 | ECS | Orals | PS2.5

Microwave scattering in the Antarctic megadunes region: reconciling radar and radiometry 

Lea Bonnefoy, Catherine Prigent, Ghislain Picard, Clément Soriot, Lise Kilic, and Carlos Jimenez

Icy surfaces across the solar system display unusual microwave radar and radiometry properties, including very high backscattering cross-sections and polarization ratios. At low temperature, snow and ice are very transparent to microwaves, leading to long path lengths and multiple scattering. Yet despite the large volume of available passive and active microwave satellite observations over the Earth cryosphere, physical interpretation of the co-variability of the multi-frequency observations is still challenging, especially when trying to reconcile radiometry and radar observations. To shed light on microwave scattering in icy regoliths, we focus on the Antarctic megadunes region, the coldest and driest area on Earth, which we propose as a new analog for icy satellites due to its very low precipitation (net zero snow accumulation) and temperature (averaging -50°C), combined with the highest microwave backscatter in Antarctica. We assemble a dataset consisting of 5.2 GHz ASCAT and 13.4 GHz QuikSCAT and OSCAT scatterometry, as well as AMSR2 radiometry at 6.9 to 89 GHz. Using the Snow Microwave Radiative Transfer (SMRT) model with a simplified snowpack with constant temperature and continuously increasing grain size and density with depth, we simulate simultaneously radar and radiometry. For the first time, we show that scatterometry and 6.9 to 37 GHz radiometry at V polarization can be successfully simulated with a unique simple snowpack model, indicating that incoherent volume scattering on subsurface heterogeneities dominates both the active and passive signal. The success of our approach encourages further work to analyze and simulate jointly active and passive microwave observations, both in the Earth cryosphere and on icy moons.

How to cite: Bonnefoy, L., Prigent, C., Picard, G., Soriot, C., Kilic, L., and Jimenez, C.: Microwave scattering in the Antarctic megadunes region: reconciling radar and radiometry, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17359, https://doi.org/10.5194/egusphere-egu24-17359, 2024.

EGU24-17668 | ECS | Posters on site | PS2.5

Numerical analysis of polar orbits for future Enceladus missions 

Taruna Parihar, Hauke Hussmann, Kai Wickhusen, Gabriel Caritá, Alexander Stark, Jürgen Oberst, Andreas Benedikter, Eduardo Rodrigues Silva Filho, Jalal Matar, and Roman Galas

Saturn's moon Enceladus gained limelight with the discovery by the Cassini spacecraft of plumes of ejected gas and ice particles from pronounced linear structures in its South Pole region called “Tiger Stripes". The small (500 km) satellite is believed to have a porous rocky core and an ice shell, separated by a global subsurface saltwater ocean. The tidal heating potentially aids in driving chemical reactions in the moon’s interior which makes it a very promising candidate where the right conditions for life formation may exist. This makes Enceladus a prime target for a future spacecraft remote sensing mission. Due to the strong gravitational perturbations caused by Saturn, the higher gravitational moments of Enceladus and additional perturbations by the other moons of Saturn, the dynamic environment for artificial satellites around Enceladus is extremely complex. As a consequence, the search for natural stable orbits is far from trivial. We carried out comprehensive numerical integrations of spacecraft orbits, with the aim to find suitable candidate orbits for a remote sensing mission. A polar orbit is desirable to further investigate the tiger stripes region, and for mapping of the global subsurface ocean. Also, the orbit should provide repeated coverage for various instruments on board the satellite. All the relevant perturbations caused by the Sun, Jupiter, Saturn and its other moons, the higher degrees and order of Enceladus’ gravity field and solar radiation pressure are taken into account. We searched for suitable orbits in inertial space by varying orbital parameters such as semi-major axis (350 to 450 km), inclination (40° to 120°) and longitude of ascending node. Moderately inclined orbits (inclination between 45° and 60°) covering the equatorial and mid-latitude regions of Enceladus were found to be stable from several months up to years. In contrast, the more useful polar mapping orbits were found to be extremely unstable due to the so-called “Kozai mechanism”, due to which a spacecraft would impact the moon’s surface within a few days. However, an example of a highly inclined orbit was found with inclination of approximately 79°, which had an orbital life time of 13 days. A longer mission in this orbit would require correction maneuvers every approximately 10 days. This would provide coverage of the tiger stripes region and allow for a global characterization of the ocean. We also determined the delta-v that would be necessary to maintain such an orbit over a mission of several months. Also, special attention was paid to satellite formation flying in this orbit to maintain a stable baseline for a distributed radar sounder system (across-track formation of multiple satellites).

How to cite: Parihar, T., Hussmann, H., Wickhusen, K., Caritá, G., Stark, A., Oberst, J., Benedikter, A., Rodrigues Silva Filho, E., Matar, J., and Galas, R.: Numerical analysis of polar orbits for future Enceladus missions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17668, https://doi.org/10.5194/egusphere-egu24-17668, 2024.

EGU24-18102 * | Orals | PS2.5 | Highlight

JUICE flybys at Europa: context for MAJIS observations 

Emiliano D'Aversa, Nicolas Ligier, François Poulet, Yves Langevin, John Carter, and Giuseppe Piccioni

We report here about the currently foreseen scientific activity of the MAJIS instrument during the two planned JUICE flybys of Europa in 2032. MAJIS [1] (Moon and Jupiter Imaging Spectrometer) is a two-channel imaging spectrometer onboard JUICE, covering the spectral range 0.5-5.55 μm, splitted in a VISNIR channel (0.5-2.36 μm, <4.6 nm sampling) and a IR channel (2.27-5.55 μm, <7 nm sampling). This work has been developed in the framework of an inter-instrumental planning exercise carried on by ESA in 2022/23 to establish the best scientific and technical strategy to be adopted by the JUICE spacecraft during its low-altitude encounters with the Jovian satellite. Although the final JUICE trajectory is still subject to change (version Crema 5.0 [2] has been used), and several details of the actual observations are pending, the overall framework of the operations is well established and able to give an idea of the possible scientific constraints and outcomes for MAJIS.

The two Europa flybys are expected to be rather similar in terms of overall geometry, but almost specular about equator, enabling a good complementary coverage of both northern and southern hemispheres. Only the first one has been studied in detail and discussed here.

Due to favorable illumination conditions, the flyby inbound leg is mainly devoted to surface studies. A first almost full coverage of the trailing hemisphere for all latitudes below 45°N, including some slant view of the southern polar cap, can be obtained at lower resolutions (3-10 km/px), during the initial flyby phase.A wider surface coverage can then be achieved at medium spatial resolution (1-2 km/px), encompassing a wide portion of Europa’s darker trailing hemisphere. The 150 μrad IFOV will also enable MAJIS to acquire multispectral images of the Europa surface at high resolution (110-300 m/px) in small postage stamps distributed along narrow tracks (about 80 x 1800 km), near the closest approach. While current evaluations make them cover mid latitudes linear features (a region around Cadmus and Minos Lineae, ~160°E,45°N), the precise location of these high-res tracks might change significantly as a consequence of trajectory adjustments. 

A search for thermal anomalies can be performed during the outbound flyby leg, when the spacecraft mostly flies over the night (leading) hemisphere. The rest of the outbound is devoted to limb observations at different latitudes, with vertical resolution changing from 1.1 to 10 km/px. The high solar phase angle encountered in this section (~140°) is optimal for searching eventual active plumes thanks to the high forward scattering efficiency of small ice particles in the MAJIS spectral range. The region covered by such limb observations should also be compatible with the location of plumes reported in literature [3,4,5].

 

References

[1] Poulet et al., 2023, Submitted to Space Science Review.

[2] ESA SPICE Service, JUICE Operational SPICE Kernel Dataset, DOI: 10.5270/esa-ybmj68p.

[3] Roth et al.,2014, Science, 343, 171, DOI: 10.1126/science.1247051.

[4] Sparks et al.,2016, ApJ,829,121, DOI: 10.3847/0004-637X/829/2/121.

[5] Jia et al.,2018, Nature Astronomy, 2, 459, DOI: 10.1038/s41550-018-0450-z.

 

Acknowledgments

This work has been developed under the ASI-INAF agreement n. 2023-6-HH.0.

How to cite: D'Aversa, E., Ligier, N., Poulet, F., Langevin, Y., Carter, J., and Piccioni, G.: JUICE flybys at Europa: context for MAJIS observations, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18102, https://doi.org/10.5194/egusphere-egu24-18102, 2024.

EGU24-18178 | ECS | Posters on site | PS2.5

Microphysics of Europa’s surface with Galileo/NIMS data 

Guillaume Cruz Mermy, Frederic Schmidt, François Andrieu, Thomas Cornet, and Ines Belgacem

Europa’s surface is one of the youngest in the solar system. The Jovian moon is believed to hide a global liquid water ocean under its icy crust [1] and is exposed to intense space weathering due to the continuous bombardment by electrons and ions from Jupiter’s magnetosphere [2]. To understand the processes governing the evolution of the surface it is necessary to finely characterize the microphysics of the ice (composition via endmember volume abundance, grain size and surface roughness). However, the majority of the previous studies [3,4] do not allow to constrain precisely these parameters.

 

Here we report the use of a radiative transfer model [5] in a Bayesian MCMC inference framework [6,7] to retrieve microphysical properties of Europa's surface using the Galileo Near-Infrared Mapping Spectrometer (NIMS) hyperspectral data [8]. We present the analysis of a calibrated spectrum of a dark lineament from the trailing Anti-jovian hemisphere. The estimated signal-to-noise ratio (SNR) is between 5 and 50, we mainly focus on the 1.0-2.5 µm region for which the SNR is higher with an uncertainty on the absolute calibration up to 10% [8].

 

A first work has allowed us to test all combinations of 3, 4 and 5 endmembers from a list of 15 relevant compounds [9]. We were able to test over 5,000 combinations and show that some compounds appear necessary to reproduce the observation, such as water ice and sulfuric acid octahydrate, in agreement with previous studies [3,4,10]. However, adding either hydrated sulfates or chlorine salts produces results substantially similar [9]. Here we present a follow-up study in which we focus on the few acceptable combinations identified by our Bayesian inversions and we analyze the results in terms of grain size and surface roughness. We show that the grain size of the mandatory endmembers is well constrained and similar from one combination to another [11]. The macroscopic roughness is however poorly constrained [11], as expected. Thanks to numerical optimizations we are able to invert independently every spectel of a NIMS hyperspectral cube with the bayesian MCMC algorithm. From this result, we present maps of microphysical properties on an entire hyperspectral image of a dark lineament. 


References: [1] Pappalardo, R. et al. (1999) JGR. [2] Carlson, R. W. et al. (2005) Icar. [3] Ligier, N. Et al. (2016) The Astr. Jour. [4] King, O. Et al. (2022) PSS. [5] Hapke, B. (2012). Cambridge Univ. Press. [6] Cubillos, P. et al. (2016), The Astr. Jour. [7] Braak, C. J. F. (2008), Stat & Comp. [8] Carlson, R. et al. (1992) ed. C. T. Russell. [9] Cruz-Mermy, G. (2022) Icarus. [10] Mishra, I. et al. (2021) Planet. Sci. [11] Cruz-Mermy, G. (2024) In prep.

How to cite: Cruz Mermy, G., Schmidt, F., Andrieu, F., Cornet, T., and Belgacem, I.: Microphysics of Europa’s surface with Galileo/NIMS data, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18178, https://doi.org/10.5194/egusphere-egu24-18178, 2024.

EGU24-18532 | ECS | Posters on site | PS2.5

The thermal and dynamic state of Europa’s ice shell: Revealed by global-scale convection models 

Tina Rückriemen-Bez, Ana-Catalina Plesa, William Byrne, Hauke Hussmann, and Andreas Benedikter

Europa’s hydro- and cryosphere is of primary interest in the quest for habitable environments in the solar system (e.g., [1]). The ice shell, which connects the potential subsurface ocean to the surface, may itself provide niches for life if liquid brine pockets can form and exist for extended periods of time. It is thus crucial to understand the thermal and dynamic state of the ice shell in order to characterize the existence and transport of liquid brines within the ice shell.

Recent work by [2] and [3] investigated the effects of temperature dependent thermal conductivity (k) as well as heat capacity (cp) and a complex composite rheology on convection in the ice shell. In this work, we build upon these previous efforts by combining the influence of both - varying thermodynamic parameters and complex rheology - in geodynamic simulations performed with the convection code GAIA [4]. Instead of a temperature-dependent heat capacity, we investigate the effect of a temperature- and depth-dependent thermal expansivity (α), which is a crucial term in determining the buoyancy induced by temperature differences.

 

We study the dynamic state (Nu-Ra scaling), the mechanical state (elastic thickness, brittle-to-ductile transition, deformation maps), and the thermal state (bottom and top boundary heat flux, occurrence of brines) of the ice shell for various setups (using both constant and variable α and k) and input parameters (ice shell thickness and grain size). For selected models, i.e. distinct thermal and dynamic states, we calculate the local two-way attenuation based on [5], [6]. The resulting two-way attenuation patterns will offer initial insights into the radar's ability to penetrate to the ice-ocean interface. If attenuation proves excessive due to the presence of hot thermal plumes, making the sampling of the ice-ocean interface unlikely, the patterns can still provide valuable insights into the dynamic state of Europa's ice shell. This includes parameters such as the thickness of the conductive layer (the so-called stagnant lid) that forms in the top part of the ice shell or the wavelength of convective structures deeper in the ice shell.

References:

[1] Coustenis & Encrenaz et al., 2013. [2] Carnahan et al. 2021. [3] Harel et al. 2020. [4] Hüttig et al., 2013. [5] Kalousova et al., 2017. [6] Soucek et al., 2023.

How to cite: Rückriemen-Bez, T., Plesa, A.-C., Byrne, W., Hussmann, H., and Benedikter, A.: The thermal and dynamic state of Europa’s ice shell: Revealed by global-scale convection models, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18532, https://doi.org/10.5194/egusphere-egu24-18532, 2024.

EGU24-20219 | ECS | Posters on site | PS2.5

The Leaky Cauldron; an experimental study of the icy plumes of Enceladus 

Yael Bourgeois, Fabrizio Giordano, Stephanie Cazaux, and Ferry Schrijer

The discovery of vast subsurface oceans hidden under kilometers of ices on icy moons in our Solar System has sparked worldwide interests in ascertaining their potential habitability. In the case of Saturn’s moon Enceladus, supersonic plumes of water vapour and icy grains have been observed by the Cassini mission spewing from the surface, giving us indirect knowledge of the composition of this subsurface ocean. The exact mechanisms of the plumes however, and their effect on the composition of the ejected matter has yet to be clearly understood. The focus of this study is to experimentally investigate physical characteristics of the plumes located at the South Polar Terrain (SPT) of Enceladus. Using facilities at TU Delft faculty, we simulate experimentally the topology of the ice crevasses and the subsurface ocean with a narrow channel mounted atop a liquid water reservoir placed inside a vacuum chamber. We inquire upon the dependence of the channel walls temperature on the plume’s exhaust velocity. Using a straight channel, our results show that colder wall temperatures enable a saturated water vapour flow with a minima 1.5-3 % solid fraction and vent velocities reaching around 400-500 m/s. The data ranges for velocities and solid fraction extrapolated from the Cassini data (550-2000 m/s and 7-70 %) thus cannot be explained by straight channel models. Using a channel with an expansion ratio of 1.73 however, the measured supersonic plume velocity becomes comparable to some of the in situ Mach number determined at Enceladus. Using a method based on the energy conservation law, it is possible to extrapolate from our experimental data some plausible geometries of the ice crevasses of Enceladus. This work lays the ground work for a coming comprehensive parametric study of the channel geometry and its effect on exhaust Mach number, temperature and solid fraction.

How to cite: Bourgeois, Y., Giordano, F., Cazaux, S., and Schrijer, F.: The Leaky Cauldron; an experimental study of the icy plumes of Enceladus, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20219, https://doi.org/10.5194/egusphere-egu24-20219, 2024.

EGU24-20872 | ECS | Orals | PS2.5

Optimising Thermal Mapping Instrument Filters to Unveil Enceladus' Subsurface Secrets 

Duncan Lyster, Carly Howett, Neil Bowles, Rory Evans, Tristram Warren, and Keith Nowicki

Introduction: Enceladus is a key target for astrobiological study, with its subsurface ocean and cryovolcanism focused at the South Pole’s 'tiger stripe' fractures; understanding temperature variations is essential to decipher the moon's geological activity and potential for life. Blending heritage from TechDemoSat-1, Mars Climate Sounder, and Lunar Trailblazer, the University of Oxford’s Enceladus Thermal Mapper (ETM) faces new opportunities and challenges in observing this active icy moon of Saturn. This high heritage thermal instrument will characterise Enceladus’ activity and surface properties by measuring its day, night, and polar-night temperatures, with particular focus on the tiger stripes. The winter temperatures are the most challenging, as they plunge as low as 45 K. This cold temperature regime is driving adaptations to sensor design and operations, for example requiring long exposure times and meticulous noise control.

High-Resolution Multi-Band Radiometric Thermal Mapping vs Spectroscopy: Cassini's Composite Infrared Spectrometer (CIRS) achieved high spectral and spatial resolution, with its highest spatial-resolution detectors (focal planes 3 and 4) having 10 pixels, each with an instantaneous field of view (iFOV) of 0.273 mrad [1]. However, due to the limited flyby nature of Cassini much of Enceladus was left without high-resolution thermal mapping. In contrast, the University of Oxford's multi-band radiometric instrument operates 384 cross-track line scanning pixels, each with an iFOV of 0.540 mrad. The instrument has space for 15 wavelength bands and operates as a 384 x 288 pixel push-broom sensor. Preliminary mission concepts anticipate flying this instrument in orbit around Enceladus at an altitude of 150 km. This would mean ETM could globally map Enceladus at 80 m/pixel resolution, with a track 31 km wide (Fig. 1).

Digital Twin Instrument for Optimised Filter Selection: We will discuss the newly developed digital model of the instrument, which creates a framework for comparing and selecting various bandpass filters and sensor geometries. Strategically chosen filter profiles will facilitate the determination of black body emission curves, allowing for precise temperature measurements with a goal of improving constraints on global thermal emission due to tidal heating. The suitability of different filter profiles for NASA’s science goals will be discussed.

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Figure 1: Fractures at Enceladus’ South Pole – Cassini’s CIRS compared to Enceladus Thermal Mapper Warm fractures at Enceladus’ South Pole vary in temperature along their length. (Left) One of the highest resolution thermal maps captured by Cassini. [2] (Right) Artistic impression: Orbiting at 150 km, ETM’s ground track would be 31 km, and it would be capable of resolving 80 m features at nadir.

References: [1] Howett, C. J. A., Spencer, J. R., Pearl, J., and Segura, M. (2011) J. Geophys. Res., 116, E03003. [2] NASA/JPL/GSFC/SWRI/SSI (2010) "Zooming in on heat at Baghdad Sulcus", Cassini-Huygens, https://saturn.jpl.nasa.gov/

How to cite: Lyster, D., Howett, C., Bowles, N., Evans, R., Warren, T., and Nowicki, K.: Optimising Thermal Mapping Instrument Filters to Unveil Enceladus' Subsurface Secrets, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20872, https://doi.org/10.5194/egusphere-egu24-20872, 2024.

EGU24-21117 | Posters on site | PS2.5 | Highlight

 Compiling analysis-ready ice data across cryosphere disciplines  

Julia Kowalski, Ana-Catalina Plesa, Marc Boxberg, Jacob Buffo, Klara Kalousova, Johanna Kerch, Maria Gema Llorens, Maurine Montagnat, Tina Rückriemen-Bez, Dustin Schroeder, Anna L. Simson, Christophe Sotin, Katrin Stephan, Benjamin Terschanski, Gabriel Tobie, and Natalie S. Wolfenbarger

Ice is omnipresent in our Solar System: on Earth, on different planetary bodies, and on moons in the outer Solar System. In the past, terrestrial and extraterrestrial cryosphere science mostly developed as independent research fields whereas synergies may shed light on both fields. In fact, close cooperation across different cryosphere research communities is a necessary prerequisite for designing future planetary exploration missions. An in-depth knowledge of similarities and differences between ice regimes on Earth and beyond paves the way for a mission preparation that optimally orchestrates terrestrial analogue field test, lab experiments, and simulation-based extrapolation to hypothesized ice regimes at the target body.


The authors of this contribution constitute the International Space Science Institute (ISSI) team Bridging the gap: from terrestrial to icy moons cryospheres, which started in 2023 and brings together scientists of different focus in terrestrial and extra-terrestrial cryosphere research. The overall goal of our project is to make knowledge hidden in the vast amounts of existing data from different research groups accessible by consolidating it into a comprehensive meta-data enriched compilation of ice properties including uncertainty margins if available. This extends to relevant physical regimes and different scales on both Earth, and icy moons including data from field campaign measurements, laboratory experiments, and planetary missions. A particular focus of our work will be to increase the analysis readiness of the data for subsequent data-driven or simulation-based analysis. This approach will provide us with the unique opportunity to transfer and extrapolate the information from the Earth to the outer Solar System bodies.


Here, we will introduce the project and its rationale, describe our approach to selecting and compiling the data, as well as how we will make them accessible, and present first results.

How to cite: Kowalski, J., Plesa, A.-C., Boxberg, M., Buffo, J., Kalousova, K., Kerch, J., Llorens, M. G., Montagnat, M., Rückriemen-Bez, T., Schroeder, D., Simson, A. L., Sotin, C., Stephan, K., Terschanski, B., Tobie, G., and Wolfenbarger, N. S.:  Compiling analysis-ready ice data across cryosphere disciplines , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21117, https://doi.org/10.5194/egusphere-egu24-21117, 2024.

EGU24-4948 | Orals | PS1.5

A New Global Color Image Dataset and Reference Frame for Mars by Tianwen-1 

Wei Yan, Jianjun Liu, Xin Ren, Wangli Chen, Xingguo Zeng, Weibin Wen, Chunlai Li, Yan Geng, and Jiawei Li

Global-scale Mars remote-sensing image datasets with accurate and consistent spatial positions contain a wealth of information on its surface morphology, topography, and geological structure. These data are fundamental for scientific research and exploration missions of Mars. Prior to China's first Mars exploration mission (Tianwen-1), none of the available global color-image maps of Mars with a spatial resolution of hundreds of meters were true-color products. On the other hand, there is currently a lack of global optical image datasets on a scale of several tens of meters with high-precision positioning and consistency that can be served as a reference frame for Mars.

Global remote sensing of Mars is one of the primary scientific goals of Tianwen-1. As of July 25, 2022, The Moderate Resolution Imaging Camera (MoRIC) onboard the orbiter has obtained 14,757 images, which have allowed acquiring global stereo images of the entire Martian surface. Additionally, the Mars Mineralogical Spectrometer (MMS) has returned 325 strips of visible and near-infrared spectral measurement data. These measurement data have laid the foundation for the development of a high-resolution global color-image map of Mars with high positioning accuracy and internal consistency. After processing of radiometric calibration (atmospheric correction, photometric correction and color correction), geometric correction (global adjustments and orthorectification) and global image cartography (global color uniformity, mosaicking and subdivision), the development of the Tianwen-1 Mars Global Color Orthomosaic and datasets based on these data was completed, with a spatial resolution of 76m and a planar position accuracy of 68m (a root mean square (RMS) residual of 0.9 pixels for tie points). This is currently the highest resolution global true color image map of Mars in the world, which can be served as a new Mars geodetic control network and reference frame. It can provide crucial foundational data for Mars scientific research and engineering implementation.

How to cite: Yan, W., Liu, J., Ren, X., Chen, W., Zeng, X., Wen, W., Li, C., Geng, Y., and Li, J.: A New Global Color Image Dataset and Reference Frame for Mars by Tianwen-1, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4948, https://doi.org/10.5194/egusphere-egu24-4948, 2024.

EGU24-6424 | Orals | PS1.5

Lateral variations of density and composition in the Martian south polar layered deposits 

Antonio Genova, Flavio Petricca, Simone Andolfo, Anna Maria Gargiulo, Davide Sulcanese, Giuseppe Mitri, and Gianluca Chiarolanza

A joint analysis of subsurface sounding, topography and gravity data is presented in this study to provide constraints on the lateral density variations of the south polar layered deposits (SPLD). The enhanced resolution of the gravity field enables a thorough characterization of the signal associated with the polar deposits that highly correlates to the surface global topography. A novel iterative method is used to determine the radial gravity disturbances that depend on the density contrast and topography of the surface deposits across the polar cap. By using a constrained least-squares approach on localized three-dimensional mass concentrations (mascons), we locally inverted the bulk density from the gravity disturbances, leading to a new map of its lateral variations.

We thus leverage our retrieved map of the lateral density variations to provide bounds on the volumes of the main constituents of the SPLD. By assuming that the polar cap is composed of water ice, carbon dioxide ice and dust, a preliminary analysis of the compositional distribution is carried out. Our results show with unprecedented resolution extensive regions with bulk density consistent with pure water ice. The resulting map of the SPLD composition is fully consistent with complementary data, including the mass fraction of water-equivalent hydrogen measured through epithermal neutron and fast neutron counting rates acquired by the Mars Odyssey Neutron Spectrometer (MONS).

How to cite: Genova, A., Petricca, F., Andolfo, S., Gargiulo, A. M., Sulcanese, D., Mitri, G., and Chiarolanza, G.: Lateral variations of density and composition in the Martian south polar layered deposits, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6424, https://doi.org/10.5194/egusphere-egu24-6424, 2024.

EGU24-7059 | ECS | Posters on site | PS1.5

Effects of regolith properties on the Martian subsurface water distribution using a global climate model 

Mirai Kobayashi, Arihiro Kamada, Takeshi Kuroda, Hiroyuki Kurokawa, Shohei Aoki, Hiromu Nakagawa, and Naoki Terada

In today’s extremely dry Mars, water vapor “adsorption” on regolith grains is thought to play crucial roles in subsurface water retention and water vapor exchange with the atmosphere (Fanale & Cannon, 1971; Zent et al., 1993, 1995, 2001; Böttger et al., 2005; Savijärvi et al., 2016, 2020). Global models that explicitly account for water diffusion in the shallow subsurface and calculate subsurface water distribution have assumed globally uniform regolith properties to simplify assumptions (Böttger et al., 2005; Schorghofer & Aharonson, 2005; Steele et al., 2017). However, Pommerol et al. (2009) examined the adsorption efficiency of six samples similar to the Martian regolith and found that the samples with smaller grain sizes store more adsorbed water due to their larger specific surface areas. Therefore, we have newly implemented a regolith scheme in a Mars Global Climate Model (MGCM), considering regolith properties like grain size, porosity, and the specific surface area. The grain size distribution was obtained from the empirical equation as a function of thermal conductivity (Presley & Christensen, 1997). The distributions of porosity and the specific surface area are also determined, referring to the laboratory experiments of Sizemore & Mellon (2008). Our results clarify that regolith grains with large specific surface areas in the northern low and mid-latitudes and the southern high latitudes, which have high adsorption coefficients, affect water storage. Subsurface water in the northern low and mid-latitudes exists up to 0.5–1wt% as adsorbed water. Regolith with high adsorption properties makes the depth of subsurface ice shallower in the southern high latitudes. Pore ice accumulates in regions poleward of 50°N and 50°S and the west of Elysium Mons and Olympus Mons, which is consistent with previous simulations. Also, with a homogeneous specific surface area, seasonal increases in pore ice were calculated at a depth of about 60 cm in mid-latitudes with low thermal inertia and high atmospheric water vapor content, but with the specific surface area map, the seasonal increases were not demonstrated. This study suggests that adsorption properties influence subsurface water dynamics, emphasizing the importance of considering inhomogeneous regolith properties in models of subsurface water distributions and the atmospheric water cycle including the regolith.

How to cite: Kobayashi, M., Kamada, A., Kuroda, T., Kurokawa, H., Aoki, S., Nakagawa, H., and Terada, N.: Effects of regolith properties on the Martian subsurface water distribution using a global climate model, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7059, https://doi.org/10.5194/egusphere-egu24-7059, 2024.

EGU24-7065 | ECS | Orals | PS1.5 | Highlight

Long-term evolution of the subsurface water environment on Mars over the past million years 

Arihiro Kamada, Takeshi Kuroda, Yasuto Watanabe, Mirai Kobayashi, Takanori Kodama, Ralf Greve, Hiromu Nakagawa, Yasumasa Kasaba, and Naoki Terada

Mars is an extremely cold and dry planet today, but it is thought to have been a water-rich planet in the past. Most of the water reservoir could represent hydrated crust and/or ground ice interbedded within sediments. Unlike Earth, Mars does not have a large satellite, so its obliquity varies greatly, and atmospheric circulation, water circulation, and subsurface water distribution are expected to change significantly over time. Currently, water ice is unstable at the pressure-temperature conditions found at the surface or subsurface of low/mid-latitude Mars, but recent observations by SHARAD revealed that large amounts of water remain beneath Utopia Planitia, which is thought to have formed during periods of high obliquity.

Here, we have newly developed a fully coupled global water circulation model for the atmosphere, hydrosphere, and cryosphere down to a depth of 1 km in the subsurface, and we used an iterative time integration scheme. We performed a series of simulations with changing Martian obliquity and eccentricity over the last few million years, and north polar layer deposit as an initial water reservoir. Our model implemented a water exchange scheme between the atmosphere and the regolith/crust for different porosities and grain sizes. We found that in the recent Milankovitch cycle, during the smaller obliquity periods, subsurface ice was mainly distributed around higher latitudes, but during the larger obliquity periods, the distribution of subsurface ice extended to lower latitudes of around 40° N. It is possible that water ice with a volume content of more than 10% may remain at high latitudes above 60° N. The abundance of water at such high latitudes could be an important indicator in the search for possible life on Mars, or a valuable water resource in future manned Mars missions.

How to cite: Kamada, A., Kuroda, T., Watanabe, Y., Kobayashi, M., Kodama, T., Greve, R., Nakagawa, H., Kasaba, Y., and Terada, N.: Long-term evolution of the subsurface water environment on Mars over the past million years, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7065, https://doi.org/10.5194/egusphere-egu24-7065, 2024.

EGU24-7073 | Orals | PS1.5

Progress and achievement of Tianwen-1 mission 

Yan Geng, Jianjun Liu, Lihua Zhang, and Xiao Zhang

Tianwen-1 mission is the first in the world to achieve Mars orbiting, landing and roving exploration through a single launch, and has developed technologies for planetary exploration launch and flight, planetary capture control, Mars entry and descent landing, Mars surface roving for Zhurong, scientific payload design and operation, long-distance deep space TT&C communication, etc. The mission has obtained a large number of scientific exploration data, formed a series of basic information such as true color image maps covering Mars surface, and a series of new discoveries such as new evidence of water and wind and sand activities in the Martian Utopia Plain. It enriches mankind's scientific understanding of Mars.

The report will introduce the progress and achievements of the Tianwen-1 mission in terms of technological development and scientific discovery.

How to cite: Geng, Y., Liu, J., Zhang, L., and Zhang, X.: Progress and achievement of Tianwen-1 mission, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7073, https://doi.org/10.5194/egusphere-egu24-7073, 2024.

EGU24-9136 | ECS | Posters on site | PS1.5

Simulation of a satellite gravimetry mission at Mars 

Marvin Bredlau, Stefanie Bremer, Manuel Schilling, and Noa Katharina Wassermann

Improving the data on the gravitational field of Mars can yield enhanced knowledge about Martian planetary dynamics and subsurface water reservoirs. In this study, we augment the VENQS software tool to perform simulations for a future dedicated satellite gravimetry mission at Mars following the archetype of GRACE-FO and as a result to study the challenges of such a mission.

The VENQS software tool consists of two parts: the VENQS App and the VENQS library. The VENQS App provides users with an easy access to a variety of simulation models, that can be combined to an individual VENQS library setup. These simulation models include amongst others orbit propagation of single satellites with embedded test masses, simulations of satellite constellations, and detailed disturbance analysis for satellites due to the space environment. Interaction with versioning systems allows the VENQS App to effectively track the software of the simulation models. In addition, a dedicated release management system enables the provision of different versions of the VENQS library.

Initially designed for satellites orbiting Earth, we are working on an augmentation of the VENQS library for interplanetary spacecraft or to be more precise for satellites orbiting arbitrary celestial bodies. In this context we want to propose the adaptation of VENQS for precise orbit propagation at Mars, which can assist the assessment of different mission influences on gravity field recovery (via dedicated software tools such as GRAVFIRE). We present the general simulation procedure including the modelling of perturbating forces along with gravitational acceleration for the orbit integration. Furthermore, we explain the differences to simulations of terrestrial spacecraft and outline occurring challenges with Martian atmosphere, time and reference frames, solid Mars tides as well as more complex satellite geometries inducing micro-vibrations and the non-availability of GNSS, that may deteriorate gravity field solutions.

How to cite: Bredlau, M., Bremer, S., Schilling, M., and Wassermann, N. K.: Simulation of a satellite gravimetry mission at Mars, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9136, https://doi.org/10.5194/egusphere-egu24-9136, 2024.

EGU24-10083 | ECS | Posters on site | PS1.5

Unraveling the climate evolution on Mars and Earth with AI-driven surface mapping and explainable AI 

Lida Fanara, Shu Su, Oleksii Martynchuk, Ernst Hauber, Anastasia Schlegel, Jakob Ludwig, David Melching, Ronny Hänsch, and Klaus Gwinner

Our research leverages state-of-the-art deep learning techniques to automate surface mapping and continuous monitoring on planetary bodies. We are also developing tools to analyze the model uncertainty and decision-making in AI models with evaluation in our surface mapping projects and beyond.

We focus on one of the solar system's most dynamic Earth-analog environment on terrestrial planets - Mars' northern polar region, a repository of the planet's climatic history within its extensive ice-layered dome. We detect small blocks [1] and their sources yielding a reliable method for monitoring mass wasting activity with valuable present-day erosion rate results [2].

In parallel, we investigate and map polygonal patterns on both Earth and Mars to assess the global distribution of polygons and their potential as indicator for climate conditions and changes. On Earth, polygons are indicators of the volume of ground ice and provide insights into permafrost vulnerability to climate change. On Mars, similar young landforms could be linked to geologically recent freeze-thaw cycles. This would be conflicting with the current environment and would have implications for the recent hydrologic past of the planet. The distribution of polygonal ground on Mars can provide valuable information on the role of liquid water in the recent past by shedding light on the formation mechanism.

We use AI models for automated surface mapping because they achieve highly complex decision-making. However, they are usually treated as Black-Box systems. To tackle this problem, we are developing software tools for analyzing model uncertainty and decision-making within an application-independent framework. Typical questions are why did the model produce exactly this response and how certain is it about the correctness of its results?

References: [1] Martynchuk O. et al., 2024. EGU 2024. [2] Su S. et al., AGU 2023.

How to cite: Fanara, L., Su, S., Martynchuk, O., Hauber, E., Schlegel, A., Ludwig, J., Melching, D., Hänsch, R., and Gwinner, K.: Unraveling the climate evolution on Mars and Earth with AI-driven surface mapping and explainable AI, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10083, https://doi.org/10.5194/egusphere-egu24-10083, 2024.

EGU24-10784 | ECS | Orals | PS1.5

Recent ice ages on Mars by destabilization of the Northern Polar Cap at 35° obliquity 

Joseph Naar, François Forget, Ehouarn Millour, Eran Vos, Charlotte Segonne, Lucas Lange, Jean-Baptiste Clément, and Franck Montmessin

Surface water ice is unstable on present-day Mars outside of the polar regions. However, prominent geological features show that during its recent past the surface of Mars was covered, on multiple occasions, by a « latitude-dependent mantle » (LDM) of water ice, from the polar regions to the tropics [1].

Different studies conducted with Global Climate Models, in particular the Mars PCM (previously Mars LMD-GCM) led to the formulation of a climate scenario for the emplacement of ice ages : during high obliquity phases (>45°, as opposed to present-day ~25°), strong destabilization of the Northern Cap allowed for the aerial deposition of ice on the flank of tropical volcanoes, forming glaciers. When returning at lower obliquity, these glaciers were in turn destabilized but ice accumulated in the mid and high latitudes, and thus formed the observed surface ice deposits (LDM) [2]. However, the 45° obliquity excursions occurred before the last 5 million years, while the last ice age occurrence is dated of 400 000 years at most.

Previous numerical experiments did not account for the radiative effect of water-ice clouds. Previous studies show that, even though somewhat negligible in the present-day Martian climate, this effect is overriding at higher obliquity with the intensification of the water cycle [3]. We have conducted new experiments at 35° obliquity with the Mars PCM using an improved physical package for the radiatively active clouds (RACs) and surface ice. Here, we present the resulting climate regime in our simulations. At 35° obliquity, the atmosphere is almost two orders of magnitude wetter than present-day, due to the greenhouse effect of RACs over the polar regions. In the high to mid latitudes, the seasonal winter ice accumulation is increased dramatically, while the summer sublimation is dampened by the latent heat cooling. Surface water ice thus accumulates at rates corresponding to tens of meters at each high obliquity excursion, reconciling the climatic scenario with the inferred age of emplacements of the LDM.

References:

[1] Head et al. (2003), Recent ice ages on Mars, Nature, 426, 797.

[2] Madeleine et al. (2009), Amazonian northern mid-latitude glaciation on Mars: A proposed climate scenario, Icarus, 203, 390

[3] Madeleine et al. (2014), Recent Ice Ages on Mars: The role of radiatively active clouds and cloud microphysics, Geophysical Research Letters, 41, 4873

Acknowledgements:

This project has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation program (grant agreement No 835275).

How to cite: Naar, J., Forget, F., Millour, E., Vos, E., Segonne, C., Lange, L., Clément, J.-B., and Montmessin, F.: Recent ice ages on Mars by destabilization of the Northern Polar Cap at 35° obliquity, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10784, https://doi.org/10.5194/egusphere-egu24-10784, 2024.

EGU24-12473 | Posters on site | PS1.5

Thermal state of the Martian interior at present day as constrained by elastic lithosphere thickness estimates and recent volcanic activity 

Ana-Catalina Plesa, Adrien Broquet, Joana R. C. Voigt, Mark A. Wieczorek, Ernst Hauber, and Doris Breuer

Previous studies have constrained the lithosphere at the north and south poles of Mars to be thick and cold, with elastic thicknesses of 330 to 450km [1], and >150km [2], respectively. The elastic thickness characterizes the stiffness of the lithosphere in response to loading and is directly linked to the thermal state of the lithosphere and the surface heat flow. Thus, elastic thickness estimates at the north and south poles provide crucial constraints on the present-day surface heat flow on Mars. Additional information on the present-day planetary thermal state comes from evidence of ongoing melting in the mantle, as indicated by the presence of both young lava flows in Tharsis and Elysium provinces and an active mantle plume beneath Elysium Planitia [3,4,5]. 

In this study we explore the thermal evolution of Mars using global 3D geodynamic models. These models improve upon our previous work [6] by including updated interior structure information from the InSight (Interior Exploration using Seismic Investigations, Geodesy and Heat Transport) mission [7,8] and by considering constraints on the present-day thermal state of the planet as noted above. Thermal evolution models using the most recent crustal thickness estimates [8,9], require that the crust contains more than half of the total amount of heat producing elements (HPEs) to explain localized recent volcanic activity on Mars [8]. 

We find that the crustal thickness variations control the surface heat flow and the elastic thickness pattern, as well as the location of melting zones in the present-day Martian mantle. The strongest constraint for the thermal history and present-day state of the interior is given by the elastic thickness at the north pole. While at the south pole, all models show values >150km, compatible with the latest estimate [2], only a few models present an elastic thickness >300km at the north pole, with values still lower than the recent estimate of [1].  A larger elastic thickness at the north pole could indicate: 1) a northern crust less enriched in HPEs, 2) a colder lithosphere due to a weaker blanketing effect caused by a thinner or higher-conductivity crust on the northern hemisphere, 3) ongoing viscoelastic relaxation, suggesting that the observed surface deflection beneath the north polar cap is not the final one [1], or a combination thereof. 

In contrast to the cold lithosphere inferred for the Martian polar regions, recent volcanic activity suggests a warmer interior beneath Tharsis and Elysium provinces [3,4]. This reveals an important spatial variability in the thermal state and thickness of the Martian lithosphere. Our work shows that only a narrow range of models can match elastic thickness estimates at the polar caps and explain Mars’ recent volcanic activity, thereby providing important insights into the structure and thermal evolution of the interior.

References:

[1] Broquet et al., 2020. [2] Broquet et al., 2021. [3] Voigt et al., 2023. [4] Hauber et al., 2011. [5] Broquet & Andrews-Hanna, 2023. [6] Plesa et al., 2018. [7] Stähler et al., 2021. [8] Knapmeyer-Endrun et al., 2021. [9] Wieczorek et al., 2023.

How to cite: Plesa, A.-C., Broquet, A., Voigt, J. R. C., Wieczorek, M. A., Hauber, E., and Breuer, D.: Thermal state of the Martian interior at present day as constrained by elastic lithosphere thickness estimates and recent volcanic activity, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12473, https://doi.org/10.5194/egusphere-egu24-12473, 2024.

EGU24-12497 | Posters on site | PS1.5

Lander Induced Thermo-Elastic Noise at InSight Location on Mars 

Sreejaya Kizhaekke Pakkathillam, Philippe Lognonne, Sébastien De Raucourt, and Taichi Kawamura

Understanding the intricate thermal dynamics on Mars is crucial for accurate scientific measurements, particularly for seismological studies. The InSight Mission to study the interior structure and composition of Mars has recorded the Mars seismograms and in-situ data for the initial assessment of Mars' geothermal heat flow. Given that these measurements are obtained in close proximity to the lander at the surface, a primary concern is the presence of thermo-elastic noise, originating from fluctuations in solar radiation, within the collected data. Experiments such as those conducted by SEIS on Mars have specifically identified this phenomenon, detecting noise during the eclipse of Phobos (Stähler et al, 2020). While managing periodic temperature variations of instruments is feasible, challenges arise with other factors, such as those associated with moving shadows on the ground and solar radiation fluctuations. This implies that the presence of the lander will introduce thermal perturbations, causing alterations in both local surface and subsurface temperature measurements. These challenges necessitate numerical quantification due to difficulties in filtering them from the data. Hence, this study investigates first how the shadowing effect from the lander's structure and solar radiation variations impacts subsurface soil temperatures and consideration of this effect on the tilt recorded on the seismometers. We develop a 3D numerical model within Comsol Multiphysics 6.1 finite element package. The key element in adapting this model for use on Mars is accurately replicating the illumination conditions on the surface. Based on sub solar latitude and longitude derived using the JPL Horizons Ephemeris output, an illumination model is set at the instrument site for a desired duration. Unlike the Moon, where no atmospheric contribution affects temperature variations, Mars possesses a thin atmosphere that contributes to convective heat transfer. First, an analytical model is employed to find the transient solution of temperature at any given depth and time instances. The solution to the energy balance analysis determines the boundary conditions at the ground surface, which are then applied in the heat conduction equations governing subsurface temperature distribution.  The numerical temperature distribution output at an unperturbed location, far away from the lander is then compared with the analytical solution.  Once the 3D model is calibrated, the resulting temperature profiles can be utilized to assess the tilt of the seismometer feet and the sensitivity to additional solar radiation fluctuations. The findings suggest that the presence of a lander can exert substantial effects on the surrounding temperature environment under Martian conditions. This can introduce noise into the data collected by the seismometer, emphasizing the importance of accounting for and mitigating such influences in both the design and data analysis.

How to cite: Kizhaekke Pakkathillam, S., Lognonne, P., De Raucourt, S., and Kawamura, T.: Lander Induced Thermo-Elastic Noise at InSight Location on Mars, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12497, https://doi.org/10.5194/egusphere-egu24-12497, 2024.

EGU24-12635 | Posters on site | PS1.5

A quantum gradiometry mission concept for the improvement of Mars gravity field models 

Mirko Reguzzoni, Lorenzo Rossi, and Federica Migliaccio

The excellent performances of quantum accelerometers, due to their very good behaviour in the low frequency measurement bandwidth and to their intrinsic stability, which does not call for periodic calibration of the sensors, foster their application to extra-terrestrial investigations. In particular, the study of Mars and of its planetary composition, evolution, density and surface properties is going to be of great importance in the next decades for many reasons, both for the enhancement of the scientific knowledge and for applications in future missions.

So far, the gravity models of Mars have been derived from tracking data of different missions. Preliminary simulations performed at POLIMI considering a one-arm gradiometer pointing in the radial direction, flying on a polar orbit and acquiring data for a time span of two months show that a significant improvement in the knowledge of the gravity field of Mars could be achieved by launching a dedicated mission collecting gravity gradiometry observations by means of a quantum sensor. Even taking into account a degradation of the solution due to more realistic conditions, allowing for a possible mission lifetime of a few years (which is feasible under Mars conditions) would mean that the already available CAI technology could lead to very high benefits in terms of the scientific knowledge of the Martian gravity field.

How to cite: Reguzzoni, M., Rossi, L., and Migliaccio, F.: A quantum gradiometry mission concept for the improvement of Mars gravity field models, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12635, https://doi.org/10.5194/egusphere-egu24-12635, 2024.

EGU24-13493 | Orals | PS1.5

Study of Martian Polar Caps with GISS ROCKE-3D GCM 

Igor Aleinov, Donald Glaser, Scott Guzewich, Jan Perlwitz, Kostas Tsigaridis, Michael Way, and Eric Wolf

Martian polar caps consist of both H2O and CO2 ice. While H2O ice is mainly passive on modern Mars, it may have not been the case in recent Martian history, when its obliquity was higher, or when it was changing rapidly. The distribution of ice species in the snowpack affects its physical and thermodynamic properties. In the upper layers, it determines its albedo and thermal emissivity. Thus understanding the mutual effect between these ices and their interaction with the atmosphere is crucial for understanding the evolution of Martian polar regions. In this study, we employ a newly-developed Exotic Ices snow model coupled to the NASA Goddard Institute for Space Studies (GISS) ROCKE-3D planetary General Circulation Model (GCM) [1]  to study the behavior of Martian polar caps. ROCKE-3D is a planetary GCM developed at NASA GISS as an extension of its Earth climate model, modelE [2]. It has been extensively used to simulate climate of various planets, including Mars (e.g. [3,4]).

The Exotic Ices snow model was specially developed for planetary applications which involve more than one condensable in the atmosphere, in which case snow can contain multiple species of ice (CO2 and H2O in the Mars case). For each species of ice, the model uses their proper physical properties and phase diagram, but otherwise it treats all species of ice on an equal footing.  The combined effects on albedo, thermal inertia and mutual insulation are treated accordingly. The snowpack interacts with the atmospheric dust cycle, and can accumulate a prognostic amount of dust, though the effect of dust on snow properties is not currently treated explicitly, and is prescribed. 

In this study, we first validate our model against the modern Martial climate, for which we use mission results from Mars Climate Sounder (atmospheric temperature and dust optical depth), SPICAM on Mars Express (atmospheric water), and Viking 2 (surface pressure). We investigate the effect of snow radiative properties on CO2 and water cycles and the ability of our model to accurately reproduce those with minimal model tuning. We then perform simulations for several obliquities from a recent Martian past, and investigate the behavior of the Martian polar caps in such conditions.

References: [1] Way, M. J. et al. (2017) ApJS, 231, 12. [2] Kelley, M. et al. (2020) J. Adv. Model. Earth Syst., 12, no. 8, e2019MS002025. [3] Schmidt, F. et al. (2022) Proc. Natl. Acad. Sci., 119, no. 4, e2112930118. [4] Guzewich, S.D. et al. (2021) J. Geophys. Res. Planets, 126, no. 7, e2021JE006825.

How to cite: Aleinov, I., Glaser, D., Guzewich, S., Perlwitz, J., Tsigaridis, K., Way, M., and Wolf, E.: Study of Martian Polar Caps with GISS ROCKE-3D GCM, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13493, https://doi.org/10.5194/egusphere-egu24-13493, 2024.

EGU24-14925 | ECS | Posters virtual | PS1.5

Thickness of the seasonal deposits by examining the shadow variations of the fallen ice blocks at Martian North Pole 

Haifeng Xiao, Yuchi Xiao, Shu Su, Frédéric Schmidt, Luisa M. Lara, and Pedro J. Gutierrez

Due to its axial tilt of ~25°, Mars has seasons. During its fall and winter, when temperature drops, there exist two depositional mechanisms of atmospheric CO2, that is, precipitation as snowfall and direct surface condensation in the form of frost (Hayne et al., 2012). Up to one third of the atmospheric CO2 exchanges with the polar surface through the seasonal deposition/sublimation process. Therefore, accurate measurements of the evolution of the seasonal polar caps can place crucial constraints on the Martian climate and volatile cycles. 

Recently, by reprocessing and co-registering the MOLA profiles, Xiao et al. (2022a, 2022b) derived both spatial and temporal thickness variations of the seasonal polar caps at grid elements of 0.5° in latitude and 10° in longitude. However, the MOLA-derived results can suffer from biases related to various processes, for example, pulse saturation due to high albedo of the seasonal deposits, non-Gaussian return pulses due to rough terrain and dynamic seasonal features, incomplete correction for the global temporal bias, and penetration of the laser pulses into the translucent slab ice. Furthermore, MOLA altimetric observations are limited to Mars Year 24 and 25 which prevents the detection of possible interannual variations in the CO2 seasonal transport. 

In this contribution, we will show how the shadow variations of fallen ice blocks at the bottom of steep scarps of the North Polar Layered Deposits (NPLDs) allow us to infer the thickness evolution of the seasonal deposits (Xiao et al., 2024). For this, we utilize the High Resolution Imaging Science Experiment (HiRISE/MRO) images with a spatial resolution of up to 0.25 m/pixel (McEwen et al., 2007). We successfully conduct an experiment at a steep scarp centered at (85.0°N, 151.5°E). We assume that no, or negligible, snowfall remains on top of the selected ice blocks, the frost ice layer is homogeneous around the ice blocks and their surroundings, and no significant moating is present. These assumptions enable us to separately determine the thickness of the snowfall and frost. We find that maximum thickness of the seasonal deposits at the study scarp in MY31 is 1.63±0.22 m to which snowfall contributes 0.97±0.13 m. Interestingly, our thickness values in the northern spring are up to 0.8 m lower than the existing MOLA results (Smith et al., 2001; Aharonson et al., 2004; Xiao et al., 2022a, 2022b). We attribute these differences mainly to the remaining biases in the MOLA heights. Furthermore, we demonstrate how the long time span of the HiRISE images (2008—2021; Mars Year 29—36) allows us to measure the interannual variations of the deposited CO2. Specifically, we observe that snowfall in the very early spring of Mars Year 36 is 0.36±0.13 m thicker than that in Mars Year 31. 

 

Hayne et al. (2012). JGR: Planets, 117(E8).

Xiao et al. (2022a). JGR: Planets, 127(7), e2022JE007196.

Xiao et al. (2022b). JGR: Planets, 127(10), e2021JE007158.

Xiao et al. (2024). JGR: Planets (In Revision).

McEwen et al. (2007). JGR: Planets, 112(E5).

Smith et al. (2001). Science, 294(5549), 2141-2146.

Aharonson et al. (2004). JGR: Planets, 109(E5).

How to cite: Xiao, H., Xiao, Y., Su, S., Schmidt, F., Lara, L. M., and Gutierrez, P. J.: Thickness of the seasonal deposits by examining the shadow variations of the fallen ice blocks at Martian North Pole, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14925, https://doi.org/10.5194/egusphere-egu24-14925, 2024.

Mars harbors two geologically young (<100 Ma) and large (~1000 km across) polar ice caps, which represent the only million-year-old surface features that induce measurable surface deformations. In the absence of in situ heat flow measurements, analyses of these deformations is one of the few methods that give access to the present-day planetary thermal state. The latter is indicative of the concentration of radiogenic elements in the interior, which is an important metric to determine the planet’s bulk composition, structure, and geologic evolution (Plesa et al., 2022). In previous work, we have imaged the deformed basements beneath the two polar caps and have determined the present-day thermal state of Mars (Broquet et al., 2020; 2021). The results of these studies are currently widely used as firm constraints on Martian thermal evolution models (e.g., Plesa et al., 2022). However, these models struggle to explain both the thick lithospheres inferred at the poles and the planet’s young volcanism and ongoing plume activity (e.g., Broquet & Andrews-Hanna, 2023). Importantly, Broquet et al. have assumed the polar deformations to be at equilibrium, which is only valid if the time elapsed since the polar caps’ formation is greater than the time required for viscous adjustments. This assumption is central to these models and depends upon the poorly known age of the polar caps and the internal viscosity structure of Mars. In this work, we couple a novel viscoelastic modelling approach of the polar deformations to thermal evolution models that account for InSight seismic measurements and observational constraints on recent volcanic activity. Our preliminary investigations reveal that viscosity structures, outlined in the thermal models presented in Plesa et al. (2022), lead to polar deformations reaching equilibrium in a few Myr and up to hundreds of Myr. These findings demonstrate that viscoelastic relaxation can surpass the polar caps’ ages, emphasizing the necessity for a comprehensive exploration of polar viscoelastic relaxation. This approach will yield critical insights into the internal viscosity structure of Mars together with the polar caps' age and formation history, ultimately leading to a better understanding of the planet’s geologic and climatic evolution.

 

Broquet A., et al., (2021). The composition of the south polar cap of Mars derived from orbital data. JGR:Planets 126, e2020JE006730. 10.1029/2020JE006730.

Broquet A. et al., (2020). Flexure of the lithosphere beneath the north polar cap of Mars: Implications for ice composition and heat flow. GRL 47, e2019GL086746. 10.1029/2019GL086746.

Broquet A., & Andrews-Hanna J. C., (2023). Geophysical evidence for an active mantle plume underneath Elysium Planitia on Mars. Nat. Astro. 7, 160–169. 10.1038/s41550-022-01836-3.

Plesa A.-C., et al., (2022). Interior Dynamics and Thermal Evolution of Mars – a Geodynamic Perspective. Adv. Geophys. 63, 179–230. 10.1016/bs.agph.2022.07.005.

How to cite: Broquet, A., Wieczorek, M. A., and Breuer, D.: Viscoelastic relaxation of the lithosphere beneath the Martian polar caps: Implications for the polar caps’ formation history and planetary thermal evolution, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15270, https://doi.org/10.5194/egusphere-egu24-15270, 2024.

EGU24-19019 | Orals | PS1.5

Evolution Strategy-Based Approach for Joint Analysis of Laser Altimeter Tracks and Photogrammetric Stereo DTMs: MOLA and HRSC 

Konrad Willner, Klaus Gwinner, Alexander Stark, Stephan Elgner, and Hauke Hussmann

Introduction: Data by the MGS MOLA [1] instrument provide a dense global network of laser shots with unprecedented height precision for Mars. The extraction of planetary radii from laser pulses requires precise knowledge of spacecraft trajectory and the instrument’s orientation in space. Limited knowledge of these extrinsic parameters causes deviating height information at cross-over points of the laser tracks and occasionally substantially offset outlier profiles. Applying adjustment techniques, the final mission data products [2] minimized the cross-over residuals while still showing considerable variability in height differences when compared to HRSC Mars quadrangle DTMs [3].

We accurately co-register MOLA profiles to existing HRSC DTMs allowing to increase the accuracy of the co-registration of the single laser tracks while providing similar internal a-posteriori cross-over accuracies as in [2]. The method applies Evolution Strategy (ES) [4] to directly solve for extrinsic observation parameters. Combined HRSC / MOLA DTMs will provide a most comprehensive, best resolved global data product currently available for Mars.

Method: Starting with a seed vector the ES repeatedly creates sets of random parameter vectors that are evaluated by the quality function. The latter is defined by the RMS of the height difference between DTM and corrected laser shots. The lowest RMS vector of each generation will be the seed for the next generation random vectors.

The optimization of the parameter vector for each laser data segment is performed on an equatorial HRSC half-quadrangle and parameters are applied to all data of a laser data segment reaching from North to South pole.

Results: ES-based adjustment of MOLA tracks was applied using two existing equatorial HRSC DTM half-quadrangles (MC-13E and MC-21E) and the laser track segments intersecting these quadrangles. The quality of the adjustment was evaluated by visual inspection of gridded DTM data products generated from the adjusted tracks and by analyzing the consistency of the results in terms of height residuals at cross-overs. Inspection of DTM products is sensitive to outlier track detection, that commonly occur in the uncorrected MOLA data but also appear in the ES adjusted DTMs. The average absolute residual height differences at cross-overs amount to 4.44 m for the nominal profile solutions, 4.58 m in the crossover-adjusted version [2], and to only 2.78 m with ES-adjusted profiles. The same values are also derived eliminating globally the 3s-blunder height differences. The corresponding values are then 3.48 m (nominal case), 2.93 m [2], and 2.09 m (ES-adjusted). The method establishes a high-quality co-registration between MOLA and HRSC DTMs considered very promising for future joint HRSC/MOLA DTMs. We discuss the potential to re-assess temporal variation in the MOLA data record not uniquely resolved in the past, such as estimates of the seasonal deposition  and sublimation in the polar areas.

References:
[1] Smith, D. E. et al. JGR 106, 23689-23722 (2001). Doi:10.1029/2000JE001364
[2] Smith, D. E. et al. NASA PDS (2003). MGS-M-MOLA-5-MEGDR-L3-V1.0.
[3] Gwinner, K. et al. PSS 126, 93-138 (2016). Doi: 10.1016/j.pss.2016.02.014
[4] Rechenberg, I. Evolutionsstrategie 94. Vol. 1 (Frommann-Holzboog, 1994).

How to cite: Willner, K., Gwinner, K., Stark, A., Elgner, S., and Hussmann, H.: Evolution Strategy-Based Approach for Joint Analysis of Laser Altimeter Tracks and Photogrammetric Stereo DTMs: MOLA and HRSC, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19019, https://doi.org/10.5194/egusphere-egu24-19019, 2024.

EGU24-19493 | ECS | Posters on site | PS1.5

Erosion rate of the north polar steep scarps on Mars 

Shu Su, Lida Fanara, Haifeng Xiao, Ernst Hauber, and Jürgen Oberst

Mass wasting activity, in the form of ice block falls, has been observed as the main erosion process at steep scarps of the North Polar Layered Deposits (NPLD) [1,2]. Our study focuses on leveraging a state-of-the-art deep learning technique to map the sources of such events throughout the entire NPLD region. By quantifying water ice loss, we derive the current erosion and retreat rate for each active NPLD scarp. We notice that these scarps have varying degrees of erosion, from less than 0.01 up to 0.88 m3 per Mars Year per meter along the scarp. The current most active scarp shows a retreat rate of ~6 mm per Mars Year. We want to compare our results to the detected ice block falls at the underlying Basal Unit (BU) region [3], to understand the difference between the two units’ geological processes, and help to constitute important constraints to the present-day mass flux of the north polar region.

 

References

[1] Herkenhof et al., 2007. Science, 317(5845), pp.1711-1715.

[2] Dundas et al., 2021. J. Geophys. Res. Planets, 126(8), p.e2021JE006876.

[3] Martynchuk, et al., 2023. AGU23, 11-15 Dec.

How to cite: Su, S., Fanara, L., Xiao, H., Hauber, E., and Oberst, J.: Erosion rate of the north polar steep scarps on Mars, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19493, https://doi.org/10.5194/egusphere-egu24-19493, 2024.

EGU24-19665 | Posters on site | PS1.5

Spectral Albedo of Dusty Martian CO2  Snow and Ice 

Sehajpal Singh, Deepak Singh, and Chloe A. Whicker

There is ample evidence to conclude that the ice deposits on solar system bodies—aside from Earth—have complex chemical constitutions. Carbon dioxide ice is prevalent at the poles of Mars and owing to its substantial reflectivity and seasonal variability, it significantly influences the planet's energy budget. Recent evidence of the existence of CO2 ice glaciers on Mars explains the volumetric distribution and accumulation of CO2 ice into the curvilinear basins at the south pole of Mars. While spectral measurements of martian ice have been made, no model of the dusty martian firn or CO2 glacier ice exists at present. Due to their significant effects on snow and ice's albedo reduction, dust and snow metamorphism must be taken into consideration. Here, we adapt the terrestrial Snow, Ice, and Aerosol Radiation (SNICAR) model and apply it to martian glaciers by incorporating CO2 ice capabilities in the model and validating with the observed remote sensing data. Compared with CO2 snow, we find that CO2 glacier ice albedo is much lower in visible and near-infrared (NIR) spectra. CO2 ice albedo is more sensitive to layer thickness than CO2 snow. We observe a noticeable transition between snow albedos and firn/glacier ice albedos. In particular, the absorption features at 1.435 µm and 2.0 µm caused by asymmetric stretching overtones and combinations of fundamental vibrational modes become damped. At these two wavelengths, the albedo is very small; the glacier ice has a higher albedo than coarse-grained snow because of specular reflection. We observe that small amounts (<1%) of Martian dust can lower the albedo of CO2 ice by at least 50%. Once validated, our model can be used to characterize orbital measurements of martian CO2 ice and refine climate-model predictions of ice stability. In the future, we plan to study the spectral albedo of other exotic ices in the solar system (N2 and methane ice in case of Pluto, CO ice on Umbriel).

How to cite: Singh, S., Singh, D., and Whicker, C. A.: Spectral Albedo of Dusty Martian CO2  Snow and Ice, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19665, https://doi.org/10.5194/egusphere-egu24-19665, 2024.

EGU24-20145 | ECS | Orals | PS1.5

Next Generation Intersatellite Laser Ranging Interferometry for Mars Gravity Research 

Alexander Koch, Gerald Bergmann, Moritz Fock, Kévin Grossel, and Julia van den Toren

The Laser Ranging Interferometer (LRI) technology demonstrator on-board the Gravity Recovery and Climate Experiment Follow-On (GRACE-FO) mission has proved an unmatched sub-nanometer per square root of Hertz ranging performance above 100 mHz surpassing the noise floor of the until then state-of-the-art K/Ka-band ranging instrument by orders of magnitude. The LRI’s reliability and its outstanding performance have led to the decision of implementing LRI-like systems as primary instruments for the measurement of the intersatellite range in all currently planned NASA, DLR and ESA Earth gravity missions.

Interferometric laser ranging has proven to be an indispensable technique for the long-term monitoring of Earth’s gravitational field and its spatial and temporal variations, enabling in-depth analyses of many Essential Climate Variables (ECVs). We propose to bring this proven technology to an application in a constellation of satellites dedicated to Mars gravity research as outlined in the paper titled “MaQuIs—Concept for a Mars Quantum Gravity Mission”.

In this talk we will give an overview of the architecture of the LRI as it is currently flying on GRACE-FO as well as the measurement principle and its consequences for the overall mission design. Additionally, we are going to highlight a few of the following development activities, which could be applied for a mission around Mars: enhancement of the long-term stability of the laser frequency, improved redundancy schemes as well as a novel sensor type for the acquisition and maintenance of the constellation. Progress with respect to these aspects will yield a next generation of intersatellite laser interferometers with improved performance and enhanced reliability.

How to cite: Koch, A., Bergmann, G., Fock, M., Grossel, K., and van den Toren, J.: Next Generation Intersatellite Laser Ranging Interferometry for Mars Gravity Research, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20145, https://doi.org/10.5194/egusphere-egu24-20145, 2024.

EGU24-22233 | ECS | Posters on site | PS1.5

Computer vision model for monitoring block falls in the Martian north polar region 

Oleksii Martynchuk, Lida Fanara, Klaus Gwinner, and Jürgen Oberst

The north polar region of Mars is one of the most active places of the planet with avalanches and ice block falls being observed every year on High Resolution Imaging Science Experiment (HiRISE) data. Both phenomena originate at the steep icy scarps, which exist on the interface between two adjacent geological units, the older and darker Planum Boreum Cavi unit, also called Basal Unit (BU) and the younger and brighter Planum Boreum 1 unit, which is a part of the so called North Polar Layered Deposits (NPLD). These exposed layers of ice and dust contain important information about the climate cycles of the planet. We are primarily interested in monitoring the current scarp erosion rate (quantified through analyzing ice debris) at the same time differentiating between the activity originating in the NPLD [1] from that originating in the BU

The large scale of the region of interest, combined with a growing amount of available satellite data makes automation key for this project. To achieve the latter we propose a computational pipeline consisting of three consecutive steps, namely: scarp segmentation, single image super-resolution and ice-block detection. For the final analysis Mean Average Precision (mAP.95) was used as a benchmark metric. The performance value of 93.6% was obtained on a test dataset, leading us to conclude that the network is able to perform even on small ice fragments (which comprise the majority of the debris). On a system running 4 RTX3090 GPUs the finished pipeline processes a single HiRISE product in just under 20 minutes, returning the scarp outline and precise ice boulder coordinates. Using this pipeline, we next plan to robustly monitor the mass wasting activity in the whole north polar region and throughout the entire Mars Reconnaissance Orbiter (MRO) mission.

[1] Su, S. et al., 2024. EGU 2024.

How to cite: Martynchuk, O., Fanara, L., Gwinner, K., and Oberst, J.: Computer vision model for monitoring block falls in the Martian north polar region, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-22233, https://doi.org/10.5194/egusphere-egu24-22233, 2024.

Extratropical cyclone (EC) is a main source of precipitation at midlatitudes, but its contribution to the Antarctic surface mass balance (SMB) still remains uncertain. Based on five global climate model simulations, we propose that it probably exists a tipping point of the SMB during the evolution of the Antarctic Ice Sheet (AIS), and EC greatly contributes to the tipping point. Before the tipping point, decreasing elevation of the AIS and warming sea surface temperature promote southward movement of ECs, leading to increased precipitation and inhibiting the AIS melting. However, EC becomes a negative contribution to SMB due to increased AIS surface temperature, runoff and rainfall. This study highlights that EC contributes to the tipping point of the AIS evolution.

How to cite: Xu, D. and Lin, Y.: A tipping point in the contribution of extratropical cyclones to Antarctic surface mass balance, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-234, https://doi.org/10.5194/egusphere-egu24-234, 2024.

EGU24-788 | ECS | Posters on site | AS1.13

Characterization of cirrus clouds in the arctic depending on ambient conditions 

Georgios Dekoutsidis, Silke Groß, Martin Wirth, Christian Rolf, Andreas Schäfler, and Florian Ewald

The increase of the average global temperature of the Earth’s atmosphere has been measured with various methods dating back to the 19th century. In the past few decades scientists have shown that the arctic regions are warming even faster than the global average. This phenomenon has been labeled Arctic Amplification. Cirrus clouds are a potential contributor to this phenomenon. They reflect only a small part of the incoming solar radiation and can absorb and reemit earth’s long-wave radiation, thus potentially having a warming effect. Warm Air Intrusion (WAI) events transport warm, water-vapor- and aerosol-rich airmasses from the mid-latitudes into the arctic and can also contribute to arctic amplification. On the one hand the transported airmasses are already warm and contain significant amounts of water vapor which is a strong greenhouse gas. On the other hand, the cirrus clouds that form during such an event might have different and potentially stronger effects on the radiation budget of the atmosphere. Since it has also been shown that WAI events in the arctic are becoming more frequent or long-lasting, it is important to study the effects these events have on the macrophysical and optical properties of cirrus clouds in the arctic.

The HALO-(AC)3 field campaign took place in March and April of 2022. One of the central goals of the campaign was to study WAI events in the arctic regions of the Northern Hemisphere. Among others, the German research aircraft HALO was used to perform remote sensing measurements. In this study we use data collected during this campaign by the combined water vapor differential absorption and high spectral resolution lidar system WALES and the HAMP cloud radar. We selected two research flights: RF03, performed during an active warm air intrusion event (WAI case) and RF17, performed during undisturbed arctic conditions (AC case). For these flights we calculated the relative humidity over ice (RHi) and the backwards trajectories using the Lagrangian analysis tool LAGRANTO and the CLaMS-Ice model, which combines the Chemical Lagrangian Model of the Stratosphere (CLaMS) with two-moment ice microphysics. Our aim is to provide an in-depth analysis of the two types of cirrus clouds and find potential differences between them.

The clouds of the WAI case had a greater mean geometrical and optical depth as well as a slightly higher linear depolarization ratio, as measured by WALES. The distributions of RHi for the WAI case had its maximum slightly over saturation and a small negative skewness, while the AC case had its maximum at saturation with a bigger negative skewness. The supersaturations within and at close proximity to the WAI clouds reached high values over 127% more frequently than for the AC case. Surprisingly, the backwards trajectories revealed that the AC case had a significant part being of liquid origin and formed via heterogeneous nucleation, whilst the WAI case was predominantly of in-situ origin with homogeneous nucleation being the dominant process.

How to cite: Dekoutsidis, G., Groß, S., Wirth, M., Rolf, C., Schäfler, A., and Ewald, F.: Characterization of cirrus clouds in the arctic depending on ambient conditions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-788, https://doi.org/10.5194/egusphere-egu24-788, 2024.

EGU24-914 | ECS | Posters on site | AS1.13

Intense precipitation events during polar winter over the Academic Vernadsky station: clouds, precipitation and temperature extremes 

Anastasiia Chyhareva, Svitlana Krakovska, Irina Gorodetskaya, and Liudmyla Palamarchuk

West Antarctica and the Antarctic Peninsula are considered to be climate tipping point regions where climate change processes can cause irreversible impacts. The Antarctic Peninsula region has a unique ecosystem, which can be harmfully affected by these changes. In the past decades have from Pacific mid-latitudes and specifically atmospheric rivers, accompanied by mixed-phase clouds and precipitation, can lead to surface melt on both sides of the Antarctic Peninsula.

This study focused on intense precipitation events during the winter in the Southern Hemisphere in 2022 in the Antarctic Peninsula observed during the Year of Polar Prediction targeted observing periods. Polar WRF (v. 4.5) simulation data with grid step 1km and temporal resolution 10 minutes were analysed for the region of Academic Vernadsky station, Antarctic Peninsula mountains and former glacier Larsen B bay.

Distributions of clouds and precipitation were analysed, as well as their concentrations and phases in the cross-section of the mountains. Also, temperature profiles were examined in the cross-sections, specifically for the 2km profile.

According to the simulations data, based on Thompson’s microphysical scheme found that mixed phased and liquid clouds and precipitation could occur up to 3km even in August, which is climatically the coldest month over the coastal areas and mountains. Maximum concentrations of ice crystals and liquid droplets could exceed 1g/kg. After the intense precipitation that occur on the western Antarctic Peninsula slopes, strong warming up to 6°C in a 2km layer is simulated for the eastern slopes of AP (Larsen B ice shelf embayment).

Simulation results were compared with radiosounding data and instrumental measurements at the Akademic Vernadsky station. According to the radiosounding that were held during all events, Polar WRF underestimated the temperature in the lower troposphere (up to around 950hPa), which can impact the surface precipitation phase and temperature simulations. However, as far as Polar WRF simulations for wind speed, direction, temperature, and vertical movements are correlated with radiosounding data, we can assume that the distribution of considered microphysical and thermodynamical characteristics gained from Polar WRF simulations are trustable.  

How to cite: Chyhareva, A., Krakovska, S., Gorodetskaya, I., and Palamarchuk, L.: Intense precipitation events during polar winter over the Academic Vernadsky station: clouds, precipitation and temperature extremes, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-914, https://doi.org/10.5194/egusphere-egu24-914, 2024.

EGU24-1678 | ECS | Posters on site | AS1.13

Shortwave cloud warming effect observed over Greenland 

Haotian Zhang, Chuanfeng Zhao, Annan Chen, Xin Zhao, and Yue Zhou

Clouds play a pivotal role in regulating the Earth's energy budget, primarily by exerting a global net cooling effect through the competing effects of shortwave radiation shading and longwave radiation trapping. However, here we report a shortwave warming effect by clouds over Greenland, contrary to the conventional belief of a cooling effect. Utilizing satellite observations from the Greenland region during the summers from 2013 to 2022, we identify a positive shortwave cloud radiative forcing when the ratio of surface albedo to top-of-atmosphere (TOA) reflectivity surpasses 1.42, implying that cloud induced warming can occur in any place when the surface is bright enough compared with TOA. Moreover, we find that the shortwave cloud warming effect on the Earth-atmosphere system is particularly prominent for optically thin clouds. These findings are crucial for understanding the radiation budget over polar regions and improving the prediction of polar ice melting.

How to cite: Zhang, H., Zhao, C., Chen, A., Zhao, X., and Zhou, Y.: Shortwave cloud warming effect observed over Greenland, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1678, https://doi.org/10.5194/egusphere-egu24-1678, 2024.

EGU24-1691 | ECS | Posters on site | AS1.13

The vertical structure of atmospheric rivers in Antarctica in the present-day and future 

Marlen Kolbe, Richard Bintanja, Eveline C. van der Linden, and Raul R. Cordero

Recent extremes in Antarctic temperature, surface melt and sea ice loss have been robustly linked to the occurrence of atmospheric rivers (ARs). However, the precise mechanisms that generate variations in the surface impacts of ARs are poorly understood, especially in the Antarctic region. Based on Arctic evidence that the vertical and horizontal advancement of ARs over sea ice strongly depends on the sea ice-preceding surface type, the season, as well as meteorological conditions, we investigate the vertical structure and propagation of extreme ARs reaching sea ice and the Antarctic ice sheet, and further quantify the associated surface impacts. We further link the wind speed and surface vertical structure and proximity of ARs to variations in turbulent mixing and radiative fluxes, which ultimately determine the impact on the surface and subsequent AR pathway. While previous studies have mostly detected ARs based on  observations and reanalyses, we additionally assess AR characteristics based on 6 CMIP6 models under present-day and future conditions (SSP5-8.5) to robustly study their propagation and impacts when reaching Antarctic sea ice and the ice sheet. 

How to cite: Kolbe, M., Bintanja, R., van der Linden, E. C., and Cordero, R. R.: The vertical structure of atmospheric rivers in Antarctica in the present-day and future, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1691, https://doi.org/10.5194/egusphere-egu24-1691, 2024.

EGU24-3671 | ECS | Orals | AS1.13 | Highlight

Antarctic Atmospheric Rivers in Present and Future Climates 

Michelle Maclennan, Andrew Winters, Christine Shields, Léonard Barthelemy, Rudradutt Thaker, and Jonathan Wille

Atmospheric rivers (ARs) are long, narrow bands of moisture that propagate poleward from the midlatitudes and occasionally reach the Antarctic Ice Sheet. Despite occurring only ~1% of the time, Antarctic ARs contribute 10% of the annual precipitation and are major drivers for heatwaves, foehn events, and surface melting on ice shelves. While snowfall is currently the dominant impact of ARs over the grounded Antarctic Ice Sheet, the relative contribution of ARs to snowfall, rainfall, and surface melt may change in a warming climate, along with the frequency and intensity of AR events themselves. Here, we use the Community Earth System Model version 2 (CESM2) Large Ensemble to detect ARs during the current period (1980–2014) and future climate (2015–2100) under the SSP370 radiative forcing scenario. We use an AR detection threshold for the current period based on the 98th percentile of the meridional component of integrated vapor transport (vIVT). To account for projected future increases in atmospheric moisture content (Clausius-Clapeyron effect) and its impacts on vIVT, we scale our AR detection threshold for the future period by the relative change in integrated water vapor compared to the present-day climatology. We then describe how the frequency, intensity, and year-to-year variability in Antarctic ARs changes by the end of the 21st century by region, with links to changes in the large-scale atmospheric circulation accompanying ARs. Finally, we quantify AR-attributed precipitation, precipitation variability, and trends in the future climate, ultimately providing an early assessment of future AR-driven changes to Antarctic surface mass balance.

How to cite: Maclennan, M., Winters, A., Shields, C., Barthelemy, L., Thaker, R., and Wille, J.: Antarctic Atmospheric Rivers in Present and Future Climates, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3671, https://doi.org/10.5194/egusphere-egu24-3671, 2024.

EGU24-4327 | ECS | Orals | AS1.13 | Highlight

Ground-based Remote Sensing of Aerosol, Clouds, Dynamics, and Precipitation in Antarctica - First results from a one-year campaign at Neumayer Station III in 2023 

Martin Radenz, Ronny Engelmann, Silvia Henning, Holger Schmithüsen, Holger Baars, Markus M. Frey, Rolf Weller, Johannes Bühl, Cristofer Jimenez, Johanna Roschke, Lukas Muser, Nellie Wullenweber, Sebastian Zeppenfeld, Hannes Griesche, Ulla Wandinger, and Patric Seifert

Novel ground-based remote sensing observations of aerosols and clouds have been carried out in Antarctica at the German Neumayer Station III (70.67°S, 8.27°W) for a whole year. The deployment of the mobile exploratory platform OCEANET-Atmosphere brought full ACTRIS aerosol and cloud profiling capabilities next to meteorological, radiation, and air chemistry in-situ observations at the Antarctic station. Neumayer III is currently the only station on a floating ice shelf that is manned throughout the year, providing excellent conditions for studying atmospheric effects on the Antarctic ice shelf.

For that deployment the standard instrumentation of OCEANET-Atmosphere (PollyXT Raman polarization Lidar, a HATPRO microwave Radiometer, a Cimel sun and lunar photometer, and Radiation sensors) was extended by a Mira-35 cloud radar, a scanning LITRA-S Doppler lidar and a Parsivel² optical disdrometer. Together, these instruments brought the full ACTRIS aerosol and cloud profiling capabilities to a region where sophisticated ground-based observations were not available. The synergy of the different instruments allows for detailed retrievals of aerosol and cloud properties, such as cloud-relevant aerosol properties, liquid droplet properties and ice crystal concentrations.

While data analysis is ongoing, three scientific highlights have already been identified during austral fall and winter, namely:

  • Observations of a persistent shallow mixed-phase cloud embedded in a plume of advected marine aerosol. State of the art microphysical retrievals are used to obtain aerosol and cloud microphysical properties. Closure between cloud-relevant aerosol particles and precipitating ice crystals was achieved, demonstrating that the cloud formed in an aerosol-limited environment.
  • Two extraordinary warm air intrusions: One with intense snowfall produced the equivalent of 10% of the yearly snow accumulation, a second one with record high temperatures and heavy icing due to supercooled drizzle.
  • Omnipresent aerosol layers in the stratosphere, contributing almost 50% to the aerosol optical depth of around 0.06 at 500nm. Lidar-derived optical signatures revealed sulphate aerosol in the stratosphere - most likely linked to the Hunga Tonga eruption in 2022.

We will present an overview of the campaign, the three highlights and provide an outlook on potential future usage of the dataset.

How to cite: Radenz, M., Engelmann, R., Henning, S., Schmithüsen, H., Baars, H., Frey, M. M., Weller, R., Bühl, J., Jimenez, C., Roschke, J., Muser, L., Wullenweber, N., Zeppenfeld, S., Griesche, H., Wandinger, U., and Seifert, P.: Ground-based Remote Sensing of Aerosol, Clouds, Dynamics, and Precipitation in Antarctica - First results from a one-year campaign at Neumayer Station III in 2023, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4327, https://doi.org/10.5194/egusphere-egu24-4327, 2024.

EGU24-4752 | ECS | Orals | AS1.13

Open Water in Sea Ice Causes High Bias in Polar Low-Level Clouds in GFDL CM4 

Xia Li, Zhihong Tan, Youtong Zheng, Mitchell Bushuk, and Leo Donner

Global climate models (GCMs) struggle to simulate polar clouds, especially low-level clouds that contain supercooled liquid and closely interact with both the underlying surface and large-scale atmosphere. Here we focus on GFDL's latest coupled GCM–CM4–and find that polar low-level clouds are biased high compared to observations. The CM4 bias is largely due to moisture fluxes that occur within partially ice-covered grid cells, which enhance low cloud formation in non-summer seasons. In simulations where these fluxes are suppressed, it is found that open water with an areal fraction less than 5% dominates the formation of low-level clouds and contributes to more than 50% of the total low-level cloud response to open water within sea ice. These findings emphasize the importance of accurately modeling open water processes (e.g., sea ice lead-atmosphere interactions) in the polar regions in GCMs.

How to cite: Li, X., Tan, Z., Zheng, Y., Bushuk, M., and Donner, L.: Open Water in Sea Ice Causes High Bias in Polar Low-Level Clouds in GFDL CM4, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4752, https://doi.org/10.5194/egusphere-egu24-4752, 2024.

EGU24-5220 | ECS | Posters on site | AS1.13

Clouds and precipitation in the initial phase of marine cold air outbreaks as observed by airborne remote sensing 

Imke Schirmacher, Sabrina Schnitt, Marcus Klingebiel, Nina Maherndl, Benjamin Kirbus, and Susanne Crewell

During Arctic marine cold air outbreaks (MCAOs), cold and dry air flows from the central Arctic southward over the open ocean. There, cloud streets form that transform to cellular convection downstream under extreme surface heat fluxes. MCAOs strongly affect the Arctic water cycle through large-scale air mass transformations and can lead to extreme weather conditions at mid-latitudes. The description of air mass transformations is still challenging partly because previous observations do not resolve fine scales and lack information about cloud microphysical properties. Therefore, we focus on the crucial initial phase of development within the first 170 km over open water of two MCAO events with different strengths observed during the HALO-(AC)3campaign. Both times the POLAR 5 and 6 aircraft flew several legs along the same track perpendicular to the cloud streets crossing the sea ice edge several times to allow a quasi-Lagrangian perspective. Based on high-resolution remote sensing and in-situ measurements, the development of the boundary layer, formation of clouds, onset of precipitation, and riming are studied. We establish a novel approach based on radar reflectivity measurements only to detect roll circulation that forms cloud streets.

For the event with the stonger contrast between surface and 850 hPa potential temperature (MCAO index), cloud tops are higher, more liquid-topped clouds exist, the liquid layer at cloud top is wider, and the liquid water path, mean radar reflectivity, amount of rime mass, precipitation rate and occurrence are larger compared to the weaker event. However, the width of the roll circulation is similar for both MCAO events. All parameters, moreover, evolve with distance over open water, as the boundary layer deepens and cloud top heights rise. Cloud streets form after traveling 15 km over open water. After 20 km, cloud cover increases to just below 100 % and after around 30 km, precipitation forms. We find that maxima in the rime mass have the same horizontal scale as the roll circulation. The presentation will highlight how cloud macro- and microphysical parameters vary with distance over open water and explain the differences between both MCAO events.

How to cite: Schirmacher, I., Schnitt, S., Klingebiel, M., Maherndl, N., Kirbus, B., and Crewell, S.: Clouds and precipitation in the initial phase of marine cold air outbreaks as observed by airborne remote sensing, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5220, https://doi.org/10.5194/egusphere-egu24-5220, 2024.

EGU24-6156 | ECS | Posters on site | AS1.13

Ice crystal numbers in Arctic clouds over sea ice and ocean: satellite retrievals and cloud-resolving modelling 

Iris Papakonstantinou Presvelou and Johannes Quaas

Mixed-phase and ice clouds are prominent parts of the Arctic climate system. In particular, boundary layer clouds and their interactions with local aerosols may play an important role in the amplified warming that has been observed in the Arctic during the recent years. These aerosols which are known as ice nucleating particles (INPs) are necessary for the heterogeneous ice formation in temperatures above -38oC. Several in-situ observations have measured a high number of effective ice nucleating particles, possibly related to biological activity in the open ocean. In contrast, in our previous study analyzing the novel active remote sensing dataset DARDAR-Nice for ten years in the Arctic region (Papakonstantinou-Presvelou et al., 2022), we found an increased ice number in low-level clouds over sea ice compared to the open ocean, suggesting other possible factors that might contribute to this difference. Here we perform several sensitivity experiments with the ICON model at kilometer-scale resolution in order to investigate the effect of these factors to the ice number, namely the contribution of local INPs, blowing snow and secondary ice production.

How to cite: Papakonstantinou Presvelou, I. and Quaas, J.: Ice crystal numbers in Arctic clouds over sea ice and ocean: satellite retrievals and cloud-resolving modelling, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6156, https://doi.org/10.5194/egusphere-egu24-6156, 2024.

EGU24-6664 | Orals | AS1.13 | Highlight

Antarctic precipitation: distributed observations during the POPE and AWACA campaigns 

Alexis Berne and Alfonso Ferrrone

Although the deployment of ground-based remote sensing instruments has made possible significant progress, Antarctic precipitation remains poorly understood, in particular away from the scientific stations where most field campaigns have taken place in the past. The PEA Orographic Precipitation Experiment (POPE) campaign took place at the Princess Elisabeth Antarctica station (Queen Maud Land, East Antarctica) during the austral summer 2019-2020. In this framework, a transect of three Doppler vertically profiling precipitation radars (MRR-PRO) was deployed from 20 to 30 km away from the station, in complete autonomy in the complex terrain of the Sor Rondane Mountains. The measurements collected during this campaign highlighted the complex interactions between the terrain and a dry layer likely due to katabatic winds, modulating the occurrence of precipitation in the area.
This POPE campaign also served as a test of the idea of deploying complex instruments dedicated to cloud and precipitation monitoring in complete autonomy to access relevant information away from stations, in areas poorly covered so far. This is a strong motivation for the AWACA project (ERC Synergy), which aims to study the atmospheric branch of the water cycle over Antarctica. AWACA started in September 2021 with the design and construction of autonomous observation platform units (4 in total) sheltering various sensors: surface meteorology, isotopic composition of water vapor and precipitation, and remote sensing of clouds and precipitation. The main deployment along a 1100-km transect between the Dumont d'Urville station at the coast and the Concordia station on the inner Plateau, is scheduled for the austral summer 2024-2025.
In this presentation, I will summarize the main results about precipitation from the POPE campaign as well as the main objectives of the AWACA project.

How to cite: Berne, A. and Ferrrone, A.: Antarctic precipitation: distributed observations during the POPE and AWACA campaigns, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6664, https://doi.org/10.5194/egusphere-egu24-6664, 2024.

EGU24-8702 | ECS | Posters on site | AS1.13

Assessing the Performance of the Weather Research and Forecasting (WRF) Model in Simulating Atmospheric In-Cloud Icing Over Fagernesfjellet, Norway 

Pravin Punde, Yngve Birkelund, Muhammad Virk, and Xingbo Han

Atmospheric icing ensues when water droplets in the atmosphere freeze upon interacting with diverse objects, presenting substantial hazards to infrastructure and leading to disruptions in both road and air traffic. 

This study introduces a detailed analysis of in-cloud icing conducted specifically over Fagernesfjellet, Norway. Utilizing the Weather Research and Forecasting (WRF) model, ERA-5 data was employed for both initial and lateral boundary conditions. The simulation covers a three-month period from October 1, 2022, to December 31, 2022, with a grid spacing of 9,3,1 km.

Acknowledging the substantial influence of local terrain on icing conditions, the analysis prioritizes the highest model resolution. The determination of the icing load involves the utilization of a Makkonen ice accretion model, and the resultant values, alongside surface parameters, undergo validation against field measurements taken at Fagernesfjellet, Norway. The representation of supercooled liquid water (SLW) in numerical weather prediction (NWP) models is crucial for precise atmospheric icing forecasts. Hence, we conduct a comprehensive evaluation of the Thompson scheme's performance in simulating liquid water content (LWC) and, consequently, the icing load, along with general weather parameters associated with icing.

From our preliminary analysis, the WRF model showcases effectiveness in simulating in-cloud icing conditions. WRF adeptly reproduces crucial surface parameters such as temperature, pressure, relative humidity, wind speed, and direction. Nevertheless, there are discernible differences between the observed data and WRF results, particularly noticeable in the case of wind speed and direction.

How to cite: Punde, P., Birkelund, Y., Virk, M., and Han, X.: Assessing the Performance of the Weather Research and Forecasting (WRF) Model in Simulating Atmospheric In-Cloud Icing Over Fagernesfjellet, Norway, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8702, https://doi.org/10.5194/egusphere-egu24-8702, 2024.

EGU24-9122 | Posters on site | AS1.13

Microphysical cloud properties in the initial phase of Arctic cold air outbreaks 

Marcus Klingebiel, Evelyn Jäkel, Michael Schäfer, André Ehrlich, and Manfred Wendisch

Cloud streets are a common feature of cold air outbreaks in the Arctic region. These are long, parallel bands of cumulus clouds that form perpendicular to the wind direction. They are caused by the interaction between the cold air mass and the warm ocean surface. Within the framework of (AC)³, the HALO-(AC)³ campaign was performed in spring 2022 involving several research aircraft to study cold air outbreaks and their belonging cloud streets. In this study we use a spectral imaging instrument, called AISA Hawk, to retrieve cloud microphysical properties in the very initial phase of these cloud streets and therefore focus on their development over the leads in the marginal sea ice zone. 

How to cite: Klingebiel, M., Jäkel, E., Schäfer, M., Ehrlich, A., and Wendisch, M.: Microphysical cloud properties in the initial phase of Arctic cold air outbreaks, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9122, https://doi.org/10.5194/egusphere-egu24-9122, 2024.

A fundamental divide exists between previous studies which conclude that polar amplification does not occur without sea ice and studies which find that polar amplification is an inherent feature of the atmosphere independent of sea ice. We hypothesise that a representation of climatological ocean heat transport is key for simulating polar amplification in ice-free climates. To investigate this we run a suite of targeted experiments in the slab ocean aquaplanet configuration of CESM2-CAM6 with different profiles of prescribed ocean heat transport, which are invariant under CO2 quadrupling. In simulations without climatological ocean heat transport, polar amplification does not occur. In contrast, in simulations with climatological ocean heat transport, robust polar amplification occurs in all seasons. What is causing this dependence of polar amplification on ocean heat transport? Energy-balance model theory is incapable of explaining our results and in fact would predict that introducing ocean heat transport leads to less polar amplification. We instead demonstrate that shortwave cloud radiative feedbacks can explain the divergent polar climate responses simulated by CESM2-CAM6. Targeted cloud locking experiments in the zero ocean heat transport simulations are able to reproduce the polar amplification of the climatological ocean heat transport simulations, solely by prescribing high latitude cloud radiative feedbacks. We conclude that polar amplification in ice-free climates is underpinned by ocean-atmosphere coupling, through a less negative high latitude shortwave cloud radiative feedback that facilitates enhanced polar warming. In addition to reconciling previous disparities, these results have important implications for interpreting past equable climates and climate projections under high emissions scenarios.

How to cite: England, M. and Feldl, N.: Robust polar amplification in ice-free climates relies on ocean heat transport and cloud radiative effects , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9946, https://doi.org/10.5194/egusphere-egu24-9946, 2024.

EGU24-10621 | ECS | Orals | AS1.13 | Highlight

Arctic Warm and Moist Air Intrusions in ICON Simulations 

Jan Landwehrs, Sofie Tiedeck, Sonja Murto, and Annette Rinke

Warm and moist air intrusions (WAI) contribute strongly to extreme warm events in the central Arctic and deliver a major part of the moisture transport into this region, with significant impacts on cloud formation and the surface energy balance. Within the PolarRES EU-project we use the ICON model to study such events both in case studies for the MOSAiC expedition and climate simulations.

MOSAiC provided comprehensive observations of two WAIs in mid-April 2020 when near-surface air temperatures reached the melting point for the first time in this spring. We evaluate different ICON-LAM set-ups, including a pan-Arctic domain with 11km horizontal resolution, as well as more confined domains at convection-permitting 2.5km resolution with varying cloud microphysics settings. A better agreement with local observations is found on the smaller model domains at higher resolution. Additionally, the representation of liquid water is improved by using a more complex two-moment cloud microphysics scheme, where a scenario with higher CCN (cloud condensation nuclei) concentration is found to be more suitable for the aerosol-rich intrusion around April 16.

In a climatological perspective we demonstrate the tracking of moisture intrusion events in decadal-scale climate simulations with ICON-LAM at 11km resolution in a pan-Arctic domain. We drive the regional model with ERA5 and selected CMIP6 GCMs to obtain vertically integrated water vapor transport at high spatial and temporal resolution. This is then used to identify, track and classify WAIs, to study their climatological characteristics, impacts and long-term trends under climate change.

How to cite: Landwehrs, J., Tiedeck, S., Murto, S., and Rinke, A.: Arctic Warm and Moist Air Intrusions in ICON Simulations, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10621, https://doi.org/10.5194/egusphere-egu24-10621, 2024.

EGU24-11947 | ECS | Orals | AS1.13

Boundary-layer cloud modeling challenges on the North Slope of Alaska 

Kyle Fitch, Zachary Cleveland, McKenna Stanford, and Lindsay Dedrickson

The accurate modeling and prediction of cloud base heights is critical for energy balance calculations and aviation operations, alike. Low-level (i.e., boundary-layer) Arctic clouds can be difficult to model, making prediction of formation and dissipation challenging. Primarily mixed-phase, these clouds typically contain low quantities of supercooled liquid water and often slowly precipitate relatively small amounts of moderately and heavily rimed snow particles. While this appears to be the predominant cloudy state on the North Slope of Alaska (NSA), the delicate balance of microphysical, dynamical, radiative, surface coupling, and advective processes can rapidly shift to heavy snow (with various degrees of riming) or to a complete dissipation of the cloud layer without any precipitation, depending on the dominant processes. Here we strive to disentangle these various processes. First, we compare the predictive performances of four different numerical weather models in forecasting the presence and base-heights of low-level clouds: the High-Resolution Rapid Refresh - Alaska (HRRR-AK) model, the Polar Weather Research and Forecasting (Polar WRF) model, the Unified Model (UM), and the European Centre for Medium-range Weather Forecasting (ECMWF) model.  Initial results comparing model output at two U.S. Department of Energy Atmospheric Radiation Measurement (AMT) NSA sites, during the fall season in 2019 and 2022, show that the UM slightly outperforms the HRRR-AK in terms of accurately forecasting the presence of a low-level cloud layer (89% of the time). All models have a significant bias of 300 to 800 meters in forecasting cloud base height (lower than is observed); however, the UM and ECMWF models have the lowest biases. Finally, a case study for a particularly challenging April 2017 thin-cloud event is presented, wherein we compare the performance of four different bulk microphysical parameterization schemes using a higher-resolution large eddy simulation (LES) model, the WRF-LES. Initial results show that the Thompson scheme was the only one able to reproduce and sustain a substantial supercooled liquid layer, but it was unable to reproduce the transition from a deep, liquid-rich cloud to a thin layer with moderately and heavily rimed precipitation. This is the first step in linking simulated LES-scale riming processes with those parameterized at a coarser mesoscale model scale. This has important implications for forecasting low-level clouds in an operational environment, given the efficiency of the riming process.

How to cite: Fitch, K., Cleveland, Z., Stanford, M., and Dedrickson, L.: Boundary-layer cloud modeling challenges on the North Slope of Alaska, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11947, https://doi.org/10.5194/egusphere-egu24-11947, 2024.

EGU24-13193 | Posters on site | AS1.13

Atmospheric Rivers vis-à-vis the Summer Seasonal Cycle and Regional Greenland Surface Melt 

William Neff, Christopher Cox, Mathew Shupe, and Michael Gallagher

Recent analysis [Mattingly et al., 2023] suggests that Atmospheric Rivers (ARs) in combination with planetary scale dynamics and coupled orographic processes (e.g., foehn effect), could lead to enhanced melting in northeast Greenland and could, in turn, be linked to increasing mass loss from outflow glaciers there [Khan et al., 2022]. The importance of large-scale dynamics, which is supported by other studies too (e.g., Neff et al., 2014), led us to examine more generally the patterns of summer melt over the whole of Greenland as influenced by factors such as the seasonal cycle, the frequency of ARs, and general synoptic influences.

Our AR detection method used ERA-5 reanalysis daily data at 65oN, 55oE and 850 hPa from 2000 through 2022, JJA, and for wind directions between 112.5o and 225.0o.  We carried out linear analysis correlation between integrated water vapor, IWV; tropospheric temperature, T850 hPa; tropospheric wind speed, WS 850 hPa; and melt fraction (MF) in an area over the southwest coast near where the typical AR track first encounters the ice sheet between 62-67oN and 50-47o E.  We found high correlation between high IWV and temperature; good correlation between IWV, coastal MF and T850 hPa; and  weak dependence of MF on southerly wind speed.

A consideration in quantifying the effects of ARs on total surface melt is the fact that their influence can extend over multi-day periods. The effect continues along the west coast after the warm front has passed over the ice sheet at the end of the AR life cycle when residual moist, warm air remains trapped in the downstream low along the 3-km high ice sheet, affecting surface energy budgets and where smaller less-ordered mesoscale circulations remain. In addition, because the initial northward transport occurs in concert with a strong ridge centered just east of the center of the ice sheet.  In our analysis we will show results associated with four melt areas: 1) near coastal to the west, 2) over the lower accumulation region such as in the area of the old Dye-2 radar site, 3) at the Summit of Greenland where melt is historically low but of increasing frequency of late, and 4) in the far northeast which was of interest in Mattingly et al. (2023). ARs directly affect the southwest ice sheet and their frequency can modulate MF near the shoulder seasons. Secondary effects along the east coast as the ridge passes, which may include subsidence (Mattingly et al. 2023), are weak but detectable. The frequency of ARs is less influential in the southwest in mid-summer when mean temperatures are warmer throughout the region. Melting in the northeast is only weakly related to ARs and generally follows to the seasonal cycle of warming.

 

Neff, W., et al. (2014, JGR, doi:10.1002/2014JD021470).

Khan, S. A., et al. (2022), E, Nature, doi:10.1038/s41586-022-05301-z.

Mattingly, K. S.,  et al.(2023), , Nature Communications, 14(1), 1743, doi:10.1038/s41467-023-37434-8.

How to cite: Neff, W., Cox, C., Shupe, M., and Gallagher, M.: Atmospheric Rivers vis-à-vis the Summer Seasonal Cycle and Regional Greenland Surface Melt, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13193, https://doi.org/10.5194/egusphere-egu24-13193, 2024.

EGU24-13345 | ECS | Posters on site | AS1.13 | Highlight

Precipitation in the Arctic and Southern Ocean: new insights from aircraft and ship-borne measurements 

Larry Ger Aragon, Yi Huang, Peter May, Jonathan Crosier, Paul Connolly, Estefania Montoya Duque, and Keith Bower

Precipitation is an important component of the hydrologic cycle and sea ice mass balance in polar regions. However, precipitation products in high latitudes constitute the highest uncertainties among satellite retrievals and numerical models. These uncertainties arise from limited in-situ observations of high-latitude precipitation and the fundamental differences between the Arctic and Southern Ocean/Antarctic environments that complicate the key precipitation properties and associated processes. To help address this knowledge gap, this study uses recent aircraft and ship-borne measurements to understand better the microphysical properties of precipitation over the Arctic and Southern Ocean/Antarctic regions. For the Arctic case, select summertime precipitation events are examined using aircraft measurements from precipitation imaging probes. We present the microphysical properties of Arctic precipitation in terms of the dominant ice precipitation type, particle size distributions, and important bulk properties. For the Southern Ocean/Antarctic case, we use recent measurements from ship-borne disdrometer and dual-polarimetric radar and present the distinctive polarimetric signatures and surface precipitation properties of seven synoptic types across the Southern Ocean. We also demonstrate an improved radar rainfall retrieval algorithm for the region, considering the dominance of small raindrop sizes of less than one millimeter in Southern Ocean rainfall. This research is leading toward more accurate, high-resolution estimates of precipitation properties in high-latitude regions, crucial in advancing the understanding of a range of climatological and meteorological processes as well as in evaluations of weather and climate models.

How to cite: Aragon, L. G., Huang, Y., May, P., Crosier, J., Connolly, P., Montoya Duque, E., and Bower, K.: Precipitation in the Arctic and Southern Ocean: new insights from aircraft and ship-borne measurements, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13345, https://doi.org/10.5194/egusphere-egu24-13345, 2024.

EGU24-14866 | Orals | AS1.13

Coordinated observations of the water cycle of marine cold-air outbreaks in the European Arctic during the ISLAS 2022 field campaign 

Harald Sodemann, Iris Thurnherr, Andrew Seidl, Alena Dekhtyareva, Aina Johannessen, Marvin Kähnert, Mari B. Steinslid, Sander Løklingholm, Lars R. Hole, Paul Voss, Lukas Papritz, Marina Dütsch, Robert O. David, Tim Carlsen, David M. Chandler, Patrick Chazette, Julien Totems, Alfons Schwarzenboeck, Franziska Hellmuth, and Julien Delanoe and the ISLAS2022 Team

Marine cold-air outbreaks (mCAOs) are a characteristic type of high-impact weather in the European Arctic and are characterized by an intense water cycle where polar cloud processes play an important role. Model simulations and weather forecasts of mCAO events are challenging and associated with poor predictability. One reason is that processes related to the water cycle interact with one another on a wide range of scales. In regional models, some of these processes are resolved and others are fully or partly parameterised. To test and improve numerical weather prediction models, additional observations and novel types of measurements of water vapour are highly demanded. Stable water isotopes are an increasingly available measurement, allowing to trace sub-grid scale processes, and providing the potential to constrain the mass budget of the atmospheric water cycle during mCAO events. During the ISLAS2022 field experiment (21 March to 10 April 2022), the stable isotope composition of water vapour and liquid samples, cloud structures, and other meteorological parameters were collected between Svalbard and Northern Scandinavia on various measurement platforms. Airborne survey flights to Svalbard provided the ocean evaporation signature and subsequent processing of water vapour during mCAO conditions. During a number of flights, mCAO airmasses were repeatedly sampled over a course of hours to days, allowing to characterize their thermodynamic evolution as clouds were first forming, then glaciating and precipitating. In addition, vapour isotope and sea water isotope measurements were taken continuously onboard R/V Helmer Hanssen between Tromsø and the Greenland west coast. Finally, coordinated land-based measurement activity over Northern Norway and Sweden allowed collection of precipitation samples, thus closing the mass budget of the mCAO events. Furthermore, using buoyancy-controlled meteorological balloons launched from Ny Ålesund, we additionally obtained continuous in-situ measurements of the boundary-layer evolution during the mCAO. We provide an overview over the airborne and ground-based measurement activities during the campaign and provide several examples to highlight the potential of the stable water isotope measurements to constrain the water budget of mCAOs in conjunction with traditional meteorological observations.

How to cite: Sodemann, H., Thurnherr, I., Seidl, A., Dekhtyareva, A., Johannessen, A., Kähnert, M., Steinslid, M. B., Løklingholm, S., Hole, L. R., Voss, P., Papritz, L., Dütsch, M., David, R. O., Carlsen, T., Chandler, D. M., Chazette, P., Totems, J., Schwarzenboeck, A., Hellmuth, F., and Delanoe, J. and the ISLAS2022 Team: Coordinated observations of the water cycle of marine cold-air outbreaks in the European Arctic during the ISLAS 2022 field campaign, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14866, https://doi.org/10.5194/egusphere-egu24-14866, 2024.

EGU24-14968 | ECS | Orals | AS1.13

Insights into cloud biases over high-latitude oceans from a cloud-controlling factor framework 

Joaquin Blanco, Rodrigo Caballero, Steven Sherwood, and Lisa Alexander

A long-standing and pervasive problem within the modelling community is the proper representation of cloud albedo over the Southern Hemisphere (SH) oceanic region. Errors persist despite the extensive evidence that these are related to the unique microphysical characteristics of the austral clouds. In this study we investigate additional causes of cloud albedo biases over the 50˚–65˚ oceanic band using CMIP6 simulations and a cloud-controlling factor (CCF) approach on daily timescales. We gain further insight by replicating our method over the equivalent oceanic region in the Northern Hemisphere (NH).

Cloud albedo, computed from upwelling and downwelling shortwave radiation at surface and top of the atmosphere, is averaged into bins of vertical velocity, surface wind, and sea-surface temperature. The performance of fifteen models in both atmospheric-only and ocean-coupled configurations is evaluated against CERES satellite retrievals in combination with ERA5 reanalysis for the 2000–2014 period.

When averaging cloud albedo by vertical velocity bins, we find that shallow boundary-layer (deep convective) clouds are consistently underpredicted (overpredicted) over the high-latitude oceans of the SH. We repeat the method for the 50˚–65˚ band in the North Atlantic and Pacific oceans and find that similar compensating errors exist.

Another important result is that the SH cloud biases occur for sea-surface temperatures below 4°C. We show that a connection exists between this empirical finding and the biases as determined from microphysical effects, i.e.: a deficit of cloud albedo is due to models producing glaciated rather than supercooled liquid water clouds. Our CCF method allow us to see that in such cases, models tend to simulate NH clouds for the SH.

We also find that the positive sign of the cloud albedo hemispheric asymmetry (SH-NH difference over the 50°–65° band) is consistently predicted by nearly all models, many of which also predict a similar magnitude to observations. However, this is a consequence of compensating errors as individually most models tend to either overpredict or underpredict cloud albedo in both hemispheres.

How to cite: Blanco, J., Caballero, R., Sherwood, S., and Alexander, L.: Insights into cloud biases over high-latitude oceans from a cloud-controlling factor framework, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14968, https://doi.org/10.5194/egusphere-egu24-14968, 2024.

Cold air outbreaks (CAOs) are a key component of the Arctic climate system, featuring intense convective cloud fields embedded in cold, dry air masses over relatively warm surfaces. Large-Eddy Simulation (LES) is a technique often used to investigate CAOs at high spatial and temporal resolutions, resolving the intricate processes involved and providing a wealth of virtual data. A complication with LES studies of CAOs is the typical absence of suitable observational data to fully constrain the simulations, and thus anchor them in reality. This study aims to use observational data from the recent airborn HALO-(AC)³ campaign in the Atlantic sector of the Arctic to drive LES experiments exclusively with observations. To this purpose data from Research Flights 10 and 11 are used, which probed a weak CAO in the Fram Strait on 29 and 30 March 2022. A Lagrangian model framework is adopted, making use of observations along the two-day low-level trajectory that stretched from close to the North Pole to the sea-ice free area Southwest of Svalbard. HALO observations are integrated into the reanalysis-based model forcing in an incremental way, yielding a suite of forcing datasets. These observational data consist of vertical soundings of thermodynamic state, pressure gradients, mesoscale divergence and advective tendencies, as
well as surface properties to act as boundary conditions. The LES code incorporates advanced representations for mixed-phase microphysical processes and radiative transfer, to allow a realistic representation of clouds and turbulence in the transforming low-level airmass. LES results obtained with
this setup are evaluated against independent HALO datasets on clouds and other boundary-layer properties. Inter-comparing the suite of LES runs with different forcing datasets elucidates the impacts of individual forcing components on the air mass transition and associated cloud evolution. 

How to cite: Paulus, F. and Neggers, R.: Studying Cloud Transformations in Cold Air Outbreaks using Large-Eddy Simulations Exclusively Driven by HALO-(AC)³ Campaign Data, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15625, https://doi.org/10.5194/egusphere-egu24-15625, 2024.

EGU24-16011 | ECS | Posters on site | AS1.13

Differential absorption G-band radar for Arctic clouds and water vapor observations 

Sabrina Schnitt, Mario Mech, Jens Goliasch, Davide Ori, Thomas Rose, and Susanne Crewell

The Arctic climate is changing at fast pace. The contribution of low-level clouds to Arctic amplification feedback processes remains challenging to quantify as model evaluation requires continuous, high-quality observations in a demanding environment. Advancing the understanding of governing processes in mixed-phase clouds, ubiquitous in the Arctic, calls for temporally high-resolved measurements of cloud and precipitation microphysical properties as well simultaneous quantification of water vapor amount and profiles in all-weather conditions.

We present the novel and worldwide unique G-band Radar for Water vapor profiling and Arctic Clouds (GRaWAC) system, suitable to deliver these measurements. GRaWAC is a FMCW G-band radar with Doppler-resolving capabilities and simultaneous dual-frequency operation at 167 and 175GHz. The Differential Absorption Radar technique is applied to the measurements to derive temporally continuous water vapor profiles in cloudy and precipitating conditions, which closes a current gap in observational state-of-the-art instrumentation.

We reveal first measurements from a mid-latitudinal ground site and airborne test flights to illustrate GraWAC’s potential for water vapor, cloud and precipitation profiling. Based on instrument simulations, we outline the benefits of such observations at an Arctic ground-based supersite, such as AWIPEV station, Ny-Alesund, Spitsbergen. There, the G-band radar measurements will be embedded in a synergy of remote sensing instruments, including an operational microwave radiometer and a Ka- and W-band cloud radar, respectively. We highlight future applications of these synergistic measurements, and therein especially the multi-frequency radar space, for model evaluation studies targeting an improved representation of mixed-phase clouds in the Arctic.

How to cite: Schnitt, S., Mech, M., Goliasch, J., Ori, D., Rose, T., and Crewell, S.: Differential absorption G-band radar for Arctic clouds and water vapor observations, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16011, https://doi.org/10.5194/egusphere-egu24-16011, 2024.

EGU24-16088 | ECS | Orals | AS1.13 | Highlight

Investigating potential sources of Ice Nucleating Particles around the Antarctic peninsula 

Floortje van den Heuvel, Mark Tarn, Benjamin Murray, and Thomas Lachlan-Cope

Clouds are a major source of uncertainty in climate model projections, especially in the Southern Ocean where the large model biases in short and long wave radiative fluxes affect the model representation of sea surface temperatures, sea ice and ultimately large scale circulation in the Southern Hemisphere. Evidence suggests that the poor representation of mixed phase clouds and the role of Ice Nucleating Particles (INPs) in these clouds are likely to be responsible for the model biases in this region. To understand how clouds will respond in a future climate we need to both better understand the effects and sources of INPs in the present, and attempt to anticipate the importance of new sources of INPs which could be revealed in a warming climate and by a reduction in glacial coverage.

In order to achieve this, we have dispersed samples of dusts from the Antarctic peninsula and James Ross Island in the Leeds aerosol chamber to characterise the size-resolved ice-nucleating activity of Southern high latitude dusts and to determine the heat lability of the INPs as a potential indicator for biogenic ice nucleators. We’ve also created suspensions from a number of Antarctic mosses and lichen to measure the ice-nucleating activity of these potential sources of INPs. Preliminary results indicate that the collected dusts nucleated ice at temperatures between -18 ºC and -14 ºC while mosses and lichen nucleated ice at temperatures ranging from -18 ºC to -6 ºC, depending on the source. Future work will include a comparison with ambient air filter samples collected around Rothera (Antarctic peninsula) and in the Arctic.

How to cite: van den Heuvel, F., Tarn, M., Murray, B., and Lachlan-Cope, T.: Investigating potential sources of Ice Nucleating Particles around the Antarctic peninsula, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16088, https://doi.org/10.5194/egusphere-egu24-16088, 2024.

EGU24-16503 | ECS | Posters on site | AS1.13

Investigating Arctic Clouds and Water Vapor over Sea Ice: Airborne Passive Microwave Observations during HALO-(AC)3 

Nils Risse, Mario Mech, Catherine Prigent, and Susanne Crewell

Clouds and water vapor play a critical role in the water and energy balance of the Arctic. However, few field observations of these quantities over sea ice exist. Passive microwave observations provide high sensitivity to clouds and water vapor with high spatial and temporal coverage in polar regions. However, retrievals of atmospheric quantities from satellites and aircraft require a description of the variable sea ice emissivity, which depends on the properties of sea ice and snow. Recently, improved retrieval methods that derive sea ice and atmospheric properties simultaneously allowed for improved exploitation of the information from passive microwave observations.

This work presents liquid water path (LWP), ice water path (IWP), and integrated water vapor (IWV) retrieved from the HALO Microwave Package (HAMP) operated onboard the HALO aircraft during the HALO-(AC)3 field campaign in spring 2022 in the Fram Strait. The nadir-viewing HAMP measures along two water vapor bands (22.24 and 183.31 GHz), two oxygen bands (50-60 and 118.75 GHz), and the atmospheric windows at 31 and 90 GHz over different surface types. The retrieval accounts for variable surface emission through a joint surface-atmosphere optimal estimation scheme with the Passive and Active Microwave Radiative Transfer (PAMTRA) model.

The high spatial coverage of the HALO flights allows for assessing the spatial and temporal variability of the retrieved IWV, LWP, and IWP under various atmospheric and surface conditions. A particular focus lies on the warm air intrusion events and their related poleward changes in cloud properties and water vapor over sea ice that HALO captured. Furthermore, the hectometer-scale airborne observations allow statistical comparison with operational satellite products, reanalysis, and model simulations along the flight track. The HAMP observations will improve the characterization of clouds and water vapor in the Arctic and potentially improve the use of passive microwave satellite observations over sea ice.

How to cite: Risse, N., Mech, M., Prigent, C., and Crewell, S.: Investigating Arctic Clouds and Water Vapor over Sea Ice: Airborne Passive Microwave Observations during HALO-(AC)3, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16503, https://doi.org/10.5194/egusphere-egu24-16503, 2024.

EGU24-17876 | Posters on site | AS1.13 | Highlight

How can the proposed  WIVERN satellite mission improve global snowfall measurements? 

Maximilian Maahn, Alessandro Battaglia, Anthony Illingworth, Pavlos Kollias, Stef Lhermitte, Filippo Emilio Scarsi, and Frederic Tridon

Snowfall is an important climate change indicator affecting surface albedo, glaciers, sea ice, freshwater storage, and cloud lifetime. Accurate snowfall measurements at high latitudes are particularly important for the mass balance of ice sheets and for sustaining healthy ecosystems, including fish and wildlife populations. Yet, snowfall remains a quantity which is hard to measure due to high spatial variability, the remoteness of polar regions and challenges associated with in situ measurements of snowfall. The recently decommissioned NASA CloudSat mission provided invaluable information about global snowfall climatology from 2006 to 2023. The CloudSat-based estimates of global snowfall are considered the reference for global snowfall estimates, but these data sets suffer from poor sampling and the inability to see shallow precipitation, which limits their use, for example, as input to surface mass balance models of the major ice sheets. WIVERN (WInd VElocity Radar Nephoscope) is one of the two remaining ESA Earth Explorer 11 candidate missions equipped with a conical scanning 94 GHz radar and a passive 94 GHz radiometer. The main objective of the mission is to measure global in-cloud winds using the Doppler effect, but can also quantify cloud ice water content and precipitation rate. 

 

This presentation discusses the potential of the WIVERN mission to provide improved estimates of global snowfall measurements. Compared to CloudSat, WIVERN's 800 km swath provides 70 times better coverage and its 42 degree angle of arrival significantly reduces the radar blind zone near the surface (especially over the ocean). In addition, WIVERN's radar is accompanied by a radiometer, which can further improve the estimation of snowfall rates. The improved sampling is demonstrated for specific regions ( Antarctica, Greenland) by computing the sampling error at different spatial and temporal scales via simulations of WIVERN vs. CloudSat orbits based on the snowfall rates produced by ERA5 reanalysis. Clutter and signal to clutter ratio simulations are performed for oceanic surfaces and orographic terrains by using a geometric–optics approach and the WIVERN illumination geometry.  Our results show that the WIVERN sampling strategy significantly reduces the uncertainty in polar snowfall estimates, making it a valuable product for climate model evaluation and as an input to surface mass balance models of the major ice sheets.

How to cite: Maahn, M., Battaglia, A., Illingworth, A., Kollias, P., Lhermitte, S., Scarsi, F. E., and Tridon, F.: How can the proposed  WIVERN satellite mission improve global snowfall measurements?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17876, https://doi.org/10.5194/egusphere-egu24-17876, 2024.

EGU24-18277 | ECS | Posters on site | AS1.13

Investigating the role of air mass history of Arctic black carbon in GCMs 

Roxana S. Cremer, Paul Kim, Sara M. Blichner, Emanuele Tovazzi, Ben Johnson, Zak Kipling, Thomas Kühn, Duncan Watson-Parris, David Neubauer, Phillip Stier, Alistair Sellar, Eemeli Holopainen, Ilona Riipinen, and Daniel G. Partridge

Black Carbon (BC) aerosols are known to be important for the Earth’s climate, yet their exact role to the changing of the Earth’s climate and Arctic amplification remains unclear. An accurate description of the BC life cycle in general circulation models (GCMs) can help reduce the uncertainties due to BC aerosols and specify BC's role in the Arctic.

In this study, several GCMs (ECHAM6.3-HAM2.3, ECHAM6.3-HAM2.3-P3, ECHAM6.3-HAM2.3-SALSA2 and UKESM1.0) are compared in terms of their representation of BC mass in the Arctic within the AeroCom project GCM Trajectory. A novel Lagrangian framework is employed to examine the history of air masses reaching the observational station Zeppelin, Svalbard. Therfore the removal processes were analysed along the trajectory and the GCMs compared with each other. The analysis emphasises the impact of remote emissions on local BC concentrations in the Arctic, indicating a longer BC lifetime compared to the global average. This underlines the importance of dry and wet scavenging parametrisations in the GCMs.

 

 

 

How to cite: Cremer, R. S., Kim, P., Blichner, S. M., Tovazzi, E., Johnson, B., Kipling, Z., Kühn, T., Watson-Parris, D., Neubauer, D., Stier, P., Sellar, A., Holopainen, E., Riipinen, I., and Partridge, D. G.: Investigating the role of air mass history of Arctic black carbon in GCMs, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18277, https://doi.org/10.5194/egusphere-egu24-18277, 2024.

EGU24-18940 | Posters on site | AS1.13

Liquid water path derived from airborne observations over the sea-ice-free Arctic ocean 

Mario Mech, Maximilin Ringel, Nils Risse, and Susanne Crewell

Arctic Amplification is most evident in the rise of the near-surface air temperature observed in the last decades, which has been at least twice as strong as the global average. The mechanisms behind that are widely discussed. Many processes and feedback mechanisms still need to be better understood, especially those connected to clouds and their role in the water and energy cycle. Thereby, the cloud liquid water path (LWP) is an important cloud parameter, and it is important to know its occurrence and spatial variability. However, observing LWP is prone to high uncertainties, especially in the Arctic, leading to about a factor of two difference in satellite retrievals between microwave and near-infrared retrievals. Moreover, weather and climate models show significant differences in Arctic regions.

Within this contribution, we will present LWP observations over the sea-ice-free Arctic ocean from measurements conducted during four airborne campaigns conducted within the framework of the "Arctic Amplification: Climate relevant atmospheric and surface processes and feedback mechanisms (AC)3" during the last years over the Fram Strait West of Svalbard. The LWP has been derived by statistical retrieval approaches based on brightness temperature measurements of the Microwave Radar/radiometer for Arctic Clouds (MiRAC) operated onboard the Polar 5 research aircraft of the Alfred-Wegener Institute for Polar and Marine Research (AWI). The consistent LWP product has been used in a comparison study to validate satellite estimates from the Moderate Resolution Imaging Spectroradiometer (MODIS) and the Advanced Microwave Scanning Radiometer 2 (AMSR2) and the one from the ERA5 reanalyses. It could be seen that the various products reveal a characteristic shape of the LWP distribution, but their overall performance varies with season and synoptic situations, i.e., ERA5 does not produce larger LWP values and an over- or under-estimation for specific flights and too high LWP values for MODIS and too low for AMSR2 during cold air outbreak events.

How to cite: Mech, M., Ringel, M., Risse, N., and Crewell, S.: Liquid water path derived from airborne observations over the sea-ice-free Arctic ocean, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18940, https://doi.org/10.5194/egusphere-egu24-18940, 2024.

EGU24-22016 | ECS | Posters virtual | AS1.13

Snowfall particle size distribution and precipitation observations in the Southern Ocean and coastal Antarctica 

Claudio Durán Alarcón, Irina Gorodetskaya, Diogo Luis, Alexis Berne, Michael Lehning, and Katherine Leonard

Snowfall is a key component to the Antarctic region, contributing significantly to the surface mass balance and influencing mean sea level changes. The intricate nature of ice particle microphysics, encompassing type, size, and structure, presents a great challenge in comprehending the processes of solid precipitation in Antarctica. The characteristics of individual ice crystals as they fall from clouds are crucial for understanding their formation and evolution along the vertical profile. Mechanisms such as aggregation, fragmentation, and riming play a pivotal role in accurately representing precipitation in numerical weather prediction models [1]. Despite their importance, the scarcity of observations for evaluating and validating these processes, particularly in the Southern Ocean and Antarctica, adds complexity. To address this gap, a comprehensive set of precipitation observations occurred during the Antarctic Circumnavigation Expedition (ACE) in the austral summer of 2016-2017 was carried out, utilizing diverse sensors aboard the research vessel Akademik Tryoshnikov. The observational toolkit included a snow particle counter (SPC), two total particle counters (Wenglors), vertical precipitation profiles from 24-GHz micro rain radar (MRR) observations, and manually collected Formvar samples. The Formvar technique, preserving ice particle shapes, offers insights into microphysical properties of ice crystals and snowflakes. SPC and Formvar were employed for particle size distribution (PSD) characterization and quantitative precipitation estimations (QPE) [2]. Precipitation was derived from MRR using the existing reflectivity (Ze)-snowfall (S) relationship for Antarctica [3,4,5]. During ACE, primary observations related to snowfall were near the coasts of the Antarctic Peninsula, Western Antarctica, and Adélie Land (Eastern Antarctica). In the last region, a large-scale event was observed by both the ACE expedition and a Multi-angle Snowflake Camera (MASC) at Dumont d’Urville station. Results showed good agreement between Formvar, SPC (size < 500µm), and MASC (size > 500µm) PSDs. Notably, the 20-µm resolution Formvar images exhibited significantly better performance for particles smaller than 500µm compared to MASC (35-µm resolution). Regarding QPE, all sources exhibited a large spread, particularly MRR estimations, sensitive to Ze-S relationship parameters. The use of PSD observations proved useful in making informed choices about these parameters. In monitoring snowfall precipitation, developing a multi-instrumental approach to overcome individual system limitations is crucial, reducing uncertainty.

References:

[1] Grazioli, J. et al. MASCDB, a database of images, descriptors and microphysical properties of individual snowflakes in free fall. Sci Data 9, 186 (2022).

[2] Sugiura, K. et al., Application of a snow particle counter to solid precipitation measurements under Arctic conditions. CRST, 58: 77-83, 2009.

[3] Grazioli, J. et al., Measurements of precipitation in Dumont d'Urville, Adélie Land, East Antarctica. TC 11, 1797–1811, 2017.

[4] Souverijns, N. et al., Estimating radar reflectivity – snowfall rate relationships and their uncertainties over Antarctica by combining disdrometer and radar observations. AR, 196: 211–223, 2017.

[5] M.S. Kulie and R. Bennartz, Utilizing Spaceborne Radars to Retrieve Dry Snowfall. JAMC, 48, 2564-2580.

Acknowledgements: PROPOLAR APMAR-2024, FCT ATLACE (CIRCNA/CAC/0273/2019) and ANR-APRES3. ACE was made possible by funding from the Swiss Polar Institute and Ferring Pharmaceuticals.

How to cite: Durán Alarcón, C., Gorodetskaya, I., Luis, D., Berne, A., Lehning, M., and Leonard, K.: Snowfall particle size distribution and precipitation observations in the Southern Ocean and coastal Antarctica, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-22016, https://doi.org/10.5194/egusphere-egu24-22016, 2024.

EGU24-93 | ECS | PICO | AS3.9

Late Pleistocene East Asian monsoon intensity variations and driving mechanisms: Evidence from a multi-proxy analysis of loess deposits on an East China Sea island 

Zhigang Wang, Laurent Marquer, Yuanyu Cheng, Xiuxiu Ren, Hao Long, Shaofang Ren, Peng Qian, and Xiangmin Zheng

Shengshan Island (SSD), located in East China Sea, contains loess deposits that serve as an excellent carrier for recording environmental changes in the eastern subtropical region of China. Different from the continental Loess Plateau, SSD loess possesses distinctive characteristics due to its coastal location. Here we conducted the first pollen analysis to reconstruct vegetation dynamics in the SSD region during the middle to late Late Pleistocene period (75-40 ka). Biological indicators (i.e., total organic concentration and δ13Corg), along with geochemical proxies (i.e., quartz grain size, magnetic susceptibility, iron oxide ratios, clay minerals, and trace elements), were employed to reconstruct climatic dynamics in the SSD area. The study identified two stages in the evolution of the East Asian Monsoon. In Stage I (75-60 ka), various indicators (i.e., pollen concentration, Pinus concentration, magnetic susceptibility, C4 abundance, K/(I+Ch), Illite crystallinity, CII, Hm/Gt, quartz median grain size, Zr/Rb) increased, suggesting a strengthening of both winter and summer monsoons. In Stage II (60-40 ka), some indicators (i.e., pollen concentration, Pinus concentration, quartz median grain size, Zr/Rb) continued to increase while others (i.e., magnetic susceptibility, C4 abundance, K/(I+Ch), Illite crystallinity, CII, Hm/Gt) decreased, indicating a continued intensification of the winter monsoon but a weakening of the summer monsoon. Further, we explored the driving forces behind variations in monsoon intensity, analyzing changes in various δ18O proxies and sea-level fluctuations. The findings suggest that different mechanisms influence the winter and summer monsoons. Summer monsoon intensity is linked to changes in summer solar radiation at mid-latitudes in the Northern Hemisphere, while winter monsoon dynamic is affected by changes in ice volume and ice sheets. These insights contribute to our understanding of environmental changes related to the East Asian Monsoon, offering valuable perspectives on how these mechanisms could respond to future climate changes.

How to cite: Wang, Z., Marquer, L., Cheng, Y., Ren, X., Long, H., Ren, S., Qian, P., and Zheng, X.: Late Pleistocene East Asian monsoon intensity variations and driving mechanisms: Evidence from a multi-proxy analysis of loess deposits on an East China Sea island, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-93, https://doi.org/10.5194/egusphere-egu24-93, 2024.

EGU24-430 | ECS | PICO | AS3.9

West African dust load modeling and its impact on solar radiation forecast during the dry season 

Léo Clauzel, Sandrine Anquetin, Christophe Lavaysse, Guillaume Siour, Gilles Bergametti, Béatrice Marticorena, Christel Bouet, Rémy Lapere, and Jennie Thomas

The expected growth of solar photovoltaic (PV) production in West Africa over the coming decades poses challenges to the electrical network requiring accurate solar forecasts for both energy producers and power grid managers. Furthermore, solar radiation is affected by dust aerosols which play a significant role in West African meteorology, due to the proximity of this region to the Sahara desert, which is the world's largest source of mineral dust aerosols emissions.

In this general context, our research aims at identifying the impact of mineral dust on solar energy production. Thus, this study focuses on evaluating the influence of dust aerosols on solar radiation forecasts for the Zagtouli solar plant in Burkina Faso. 

Employing a coupled approach between a meteorological model (WRF) and a chemical transport model (CHIMERE), two dust events that are representative of the dry season are simulated in line with West African climatology. While one event is linked to dust emissions from the Bodélé plateau (Chad), the other is related to dust sources located within the South Atlas area.

The model undergoes rigorous assessment in regards to dust life cycle parameters (Aerosol Optical Depth (AOD), PM10, size distribution) and variables essential for solar energy production (Global Horizontal Irradiance (GHI), temperature) using in-situ measurements from long-term observatories (AERONET, INDAAF, AMMA-CATCH) and from the solar farm (GHI), satellite observations (AQUA/TERRA-MODIS, CALIPSO-CALIOP), and reanalysis data (CAMS). This evaluation shows a robust performance of the model.

In addition, sensitivity studies are implemented to evaluate the respective impacts of direct and indirect effects of dust aerosols on the amount of solar radiation available at the surface.

Overall, this study provides strong support for a modeling approach that couples meteorological processes with the dust life cycle to refine solar forecasts in the West African region.

How to cite: Clauzel, L., Anquetin, S., Lavaysse, C., Siour, G., Bergametti, G., Marticorena, B., Bouet, C., Lapere, R., and Thomas, J.: West African dust load modeling and its impact on solar radiation forecast during the dry season, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-430, https://doi.org/10.5194/egusphere-egu24-430, 2024.

EGU24-989 | ECS | PICO | AS3.9 | Highlight

Atmospheric radioisotopes in cryoconite from the Flade Isblink ice cap, NE Greenland 

Dylan Beard, Giovanni Baccolo, Caroline Clason, Geoffrey Millward, Edyta Łokas, Sally Rangecroft, Dariusz Sala, Przemysław Wachniew, and William Blake

Under climatic warming and increased melting, glaciers and ice caps are becoming secondary sources of contaminants deposited decades ago. Cryoconite, an organic-rich material found on the surface of many glaciers, is particularly efficient at accumulating airborne contaminants due to biogeochemical exchanges with the organic matter within cryoconite. Atmospherically derived radioactive isotopes, commonly referred to as fallout radionuclides, have now been found to accumulate in cryoconite globally. However, data from the polar regions, especially ice sheets and ice caps, is scarce. This study helps to address this regional gap in understanding fallout radionuclide accumulation in glacial settings. We present the first radioactivity dataset from cryoconite on a Greenlandic ice cap and assess the role of cryoconite in the distribution of radioactive species in the High Arctic. Forty-six cryoconite samples were collected from the Flade Isblink ice cap (NE Greenland) in August 2022. These samples were analysed via alpha and gamma spectrometry for atmospheric radionuclides, including 137Cs, 241Am, 210Pbexc., 207Bi, 7Be, and several plutonium isotopes. The results of this study confirm cryoconite's exceptional ability to accumulate fallout radionuclides, even in remote and relatively pristine regions such as Northern Greenland. The activities of radionuclides in cryoconite from Flade Isblink are among the highest reported across the High Arctic and the highest ever reported from Greenland. Flade Isblink's radioactivity source is compatible with the stratospheric reservoir established during atmospheric nuclear tests and with weapon-grade fissile fuel, likely originating from Novaya Zemlya. Our findings emphasise the necessity for continued research efforts on the release of legacy contaminants from glaciers, particularly given accelerated global warming and consequent glacier retreat.

How to cite: Beard, D., Baccolo, G., Clason, C., Millward, G., Łokas, E., Rangecroft, S., Sala, D., Wachniew, P., and Blake, W.: Atmospheric radioisotopes in cryoconite from the Flade Isblink ice cap, NE Greenland, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-989, https://doi.org/10.5194/egusphere-egu24-989, 2024.

EGU24-1776 | PICO | AS3.9 | Highlight

Assessment of the Impact of Coarse and Fine Dust on Solar Devices in the Middle East 

Suleiman Mostamandi, Georgiy Stenchikov, Ahmed Balawi, Illia Shevchenko, Dania Kabakebji, and Thomas Altmann

Dust in the Middle East (ME) significantly impacts regional climates and negatively affects the operation of solar farms in the ME region. Suspended dust particles attenuate downward short wave (SW) radiation, while dust deposited on the solar devices decreases effectiveness. This study theoretically assesses dust's attenuation and soiling effects on solar panels within the ME, employing a Weather Research Forecasting Model coupled with the aerosol-chemistry module, WRF-Chem, constrained by observed dust depositions. By analyzing the size distribution of dust deposition samples, we found that a major part of the deposited mass resulted from the deposition of dust particles with radii > 10 um. However, the models usually consider only particles with radii < 10 um.

We corrected this deficiency and conducted a year-long simulation using WRF-Chem. We found that the dust (primarily fine particles with radii < 3 m) reduces the downward SW radiation near the surface by 5-10%. Meanwhile, dust deposition (mostly coarse dust particles with radii > 6 m) imposes soiling losses of 12 to 36 % in different parts of the ME, assuming a weekly cleaning cycle.

Our findings unveil a complex interplay between dust size and its multifaceted impact on solar energy production. This novel insight could lead to optimized maintenance strategies and novel mitigation approaches tailored to the unique dust burden of the Middle East. Ultimately, this study aims to advance solar energy resource assessment and pave the way for enhanced photovoltaic efficiency in dust-prone regions.

How to cite: Mostamandi, S., Stenchikov, G., Balawi, A., Shevchenko, I., Kabakebji, D., and Altmann, T.: Assessment of the Impact of Coarse and Fine Dust on Solar Devices in the Middle East, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1776, https://doi.org/10.5194/egusphere-egu24-1776, 2024.

EGU24-1827 | PICO | AS3.9

Investigation of the mineralogical composition of desert dust particles during a transboundary pollution episode in the UK and implications for health effects  

Stavros Solomos, Christina Mitsakou, Samuel Thompson, Helen Macintyre, Karen Exley, Stuart Aldridge, Christos Zerefos, Nikolaos S. Bartsotas, Christina Kalogeri, and Christos Spyrou

Toxicological and epidemiological studies have supported links between desert dust particles and health impacts, such as worsened asthma, hospitalization for respiratory infections, and seasonal allergic rhinitis. Airborne desert dust particles could serve as a medium for interacting with chemicals on their surfaces, potentially enhancing the bioreactivity of fine particles during episodes of dust storms. The role of the different mineralogical composition (e.g. quarz, iron, feldspars) on the biological effects of mineral dust remains to be determined. In this work we analyze the severe dust event that affected the UK on 15 and 16 March 2022 in terms of the synoptic situation leading to this event, the spatiotemporal distribution of the dust plumes over UK and the chemical/mineralogical composition of the particles. We employ the METAL-WRF model to investigate the atmospheric properties and the quantification of particle concentrations in ambient air but also in dry and wet depositions of dust. The METAL-WRF model includes prognostic fields for ten (10) minerals: illite, kaolinite, smectite, calcite, quartz, feldspar, hematite, gypsum, phosphorus and iron. We also investigate the health impacts linked to the desert dust transport on the population in UK regions. Our results are discussed across similar findings at more frequently dust-affected regions such as the Mediterranean.  

Acknowledgment This study is partially supported by the Hellenic Foundation for Research and Innovation project Mineralogy of Dust Emissions and Impacts on Environment and Health (MegDeth - HFRI no. 703) and the project Bioclimatic urban design for the sustainability and resilience of the urban environment in the context of climate change (BIOASTY)

How to cite: Solomos, S., Mitsakou, C., Thompson, S., Macintyre, H., Exley, K., Aldridge, S., Zerefos, C., Bartsotas, N. S., Kalogeri, C., and Spyrou, C.: Investigation of the mineralogical composition of desert dust particles during a transboundary pollution episode in the UK and implications for health effects , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1827, https://doi.org/10.5194/egusphere-egu24-1827, 2024.

EGU24-2280 | ECS | PICO | AS3.9

Different orbital rhythms in loess grain-size records across the Chinese Loess Plateau 

Deai Zhao, Guoqiao Xiao, Qingzhen Hao, Shaohua Tian, Zhipeng Wu, Hao Lu, Gaowen Dai, Shuzhen Peng, Chunjv Huang, and Qiuzhen Yin

The thick loess-paleosol sequences on the Chinese Loess Plateau (CLP) are among the best terrestrial archives for the understanding of the global paleoenvironment and East Asian monsoon changes. In particular, orbital-scale variations characterized by major periodicities of ~100 kyr, ~40 kyr and ~20 kyr are recorded by various proxies in the loess, which is often suggested to reflect the orbital control on East Asian climate. However, whether these climate periods could be affected by the signals from the dust source areas remains unknown. Here we present the spectrum results of grain size records from the Baoji loess section spanning the past 400 ka in the southeastern part of the CLP, and compare with the previous results in the western CLP (to the west of the Liupanshan Mts.), including Gulang, Menyuan, Lanzhou, Linxia, Jingyuan loess sections, and loess sections in the eastern CLP (to the east of the Liupanshan Mts.), including Luochuan, Xifeng, Lantian, and Weinan sections. The results show that the dominant periods in different sections are spatially different, and the ~20-kyr precession cycle from the western CLP is significantly stronger than that in eastern CLP. Albeit dust accumulation rates in the Jingbian loess section from the eastern CLP are very high, the lack of precession signal suggests that high sedimentation rate is not the main factor for occurrence of precession cycle in grain size records. The results also suggest that the dust source areas for the eastern and western CLP are different, specifically, the loess deposits in western CLP were mainly sourced from the NE Tibetan Plateau, while the loess deposits in eastern CLP were significantly fed by the deserts to the north CLP (including deserts in Northern China and Southern Mongolia). As the dust production and transportation in NE Tibetan Plateau and the deserts to the north CLP were significantly driven by the ~20-kyr local summer insolation and the ~100-kyr ice age cycle, respectively, we argue that the climate cycle in loess grain size of the CLP indeed reflects the climate signals of their source areas, rather than the deposition areas. Our results suggest that caution should be taken when explaining the meaning of the loess grain size records.

How to cite: Zhao, D., Xiao, G., Hao, Q., Tian, S., Wu, Z., Lu, H., Dai, G., Peng, S., Huang, C., and Yin, Q.: Different orbital rhythms in loess grain-size records across the Chinese Loess Plateau, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2280, https://doi.org/10.5194/egusphere-egu24-2280, 2024.

EGU24-3106 | PICO | AS3.9 | Highlight

African dust transport and deposition modelling verified through a successful citizen science campaign in Finland   

Outi Meinander, Rostislav Kouznetsov, Andreas Uppstu, Mikhail Sofiev, Anu Kaakinen, Johanna Salminen, Laura Rontu, Andre Welti, Diana Francis, Ana A. Piedehierro, Pasi Heikkilä, Enna Heikkinen, and Ari Laaksonen

On 21–23 February 2021, dust from a sand and dust storm (SDS) in northern Africa was transported to Finland, north of 60°N. The episode was predicted 5 days in advance by the Finnish Meteorological Institute (FMI) global operational SILAM forecast (silam.fmi.fi), and its key features (e.g., spatial distribution of wet and dry deposition amounts and particle sizes) were confirmed and detailed by a retrospective analysis. SILAM is among the dust forecast models included in the Word Meteorological Organization Sand and Dust Storm Warning Advisory and Assessment System WMO SDS-WAS.  

Dust deposition was observed on 23 February over a large area in the Southern and Central Finland from 60°N to >63.8°N. The ground was covered with snow making dust more easily detectable. The coloured snow caused people to contact FMI asking what is happening. FMI launched a citizen science campaign on Saharan dust with the help of social media, and people were asked to report their observations and to collect dust-containing snow and to extract the dust according to the guidelines. The campaign gained wide national interest in television, radio, newspapers and social media, and resulted in success in receiving citizen samples from 525 locations, with one to over ten samples in each.

The amounts of deposition calculated from the citizen samples were found to be up to 1.1 g/m2 and such maximum amounts per unit area agree with the SILAM calculations. The SILAM model and particle magnetic properties confirmed that dust came from a wide Sahara and Sahel area, from 5000 km away. The median diameters of the dust particles were in the modes of <10 µm and >20 µm. The mineral composition was dominated by quartz, feldspars, and soft phyllosilicates such as micas and clay minerals.

To extract dust from snow, Meinander et al. (2023) protocol recommends: 1. Collect snow samples within one week of the deposition event to minimize post-deposition changes. 2. Evaporate snow under 75oC to preserve the magnectic properties (particles should not be subjected to temperatures higher than 90oC). 3. Keep the remaining particles in the container in which the evaporation took place (e.g., a sheet of aluminium folio on a large oven tray and evaporating the snow in the oven) to best preserve all the particle sizes. 

Reference: Meinander, O., Kouznetsov, R., Uppstu, A. et al. African dust transport and deposition modelling verified through a citizen science campaign in Finland. Sci Rep 13, 21379 (2023). https://doi.org/10.1038/s41598-023-46321-7. 

 

 

How to cite: Meinander, O., Kouznetsov, R., Uppstu, A., Sofiev, M., Kaakinen, A., Salminen, J., Rontu, L., Welti, A., Francis, D., A. Piedehierro, A., Heikkilä, P., Heikkinen, E., and Laaksonen, A.: African dust transport and deposition modelling verified through a successful citizen science campaign in Finland  , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3106, https://doi.org/10.5194/egusphere-egu24-3106, 2024.

Dust storms are severe and disastrous weather events that typically occur in arid and semi-arid desertification areas. The frequent occurrences of spring dust storms in East Asia in recent years have drawn widespread attention in the context of the significant achievements in ecological management and sand prevention. Identifying the source and transport of dust storms in East Asia is key to comprehending the ecological environment and climate. In this study, the MODIS annual product MCD12C1 is used as labels to classify the land cover of Landsat 8/9 images using the Random Forest method in order to obtain the dynamic distribution of dust source areas. The land cover results are processed to the WRF model to provide the meteorological field, after which a Lagrangian transport model FLEXPART-WRF is used to simulate the horizontal and vertical transport of particles from five dust source regions in East Asia during the March 22, 2023 dust storm event. The source apportionments for regions on the transmission path of different dust sources are revealed by an online tracer-tagged of air quality model NAQPMS. The results show that the total area of the East Asian dust source regions in March 2023 is 1.5×106 km2. Cold high pressure from Siberia and the Mongolian cyclone are key synoptic situations for dust emission and transport from dust source areas. The Taklimakan Desert and the Tarim Basin mainly affect northwestern China. The Badain Jaran Desert and Horqin Sandy Land have a greater impact on northern China, with longer transmission distances, and can even affect southeast and Northeast China. The Gobi Desert affects northern China by influencing the dust source areas in Inner Mongolia. The vertical transport height is up to 500m from the ground. The PM2.5 source apportionments show that the Badain Jaran Desert contribution of Beijing-Tianjin-Hebei and its surrounding areas accounted for 45.5 %, while the Gobi Desert accounted for 1.4 %.

How to cite: Li, Y. and Wu, Q.: How dust sources affect downstream regions in East Asia during a dust storm event, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3981, https://doi.org/10.5194/egusphere-egu24-3981, 2024.

EGU24-4003 | ECS | PICO | AS3.9

New insights into the atmospheric dust dynamics in the Carpathian and Wallachian Basin during MIS 1-MIS 2 

Zoran Perić, Helena Alexanderson, Slobodan Marković, Milica Radaković, Petar Krsmanović, and Cathal Ryan

Fine-grained windblown deposits, known as loess, in which fossil soils (palaeosols) are preserved, serve as excellent records of past climate. However, paleoclimate reconstruction studies on loess-palaeosol sequences (LPS) in Southeastern Europe have primarily focused on climate changes during the last one or two glacial-interglacial cycles. Surprisingly, little attention has been given to the climate of the current interglacial, the Holocene. This oversight may be attributed to the prevailing notion that, based on ice core and marine isotope records, the Holocene is considered a climatically stable period. Additionally, the scarcity of LPS with well-preserved Holocene loess has contributed to this lack of attention until now. Three recently discovered loess-palaeosol sequences in the Eastern Carpathian and the Wallachian Basins present fully preserved loess covering MIS 1-MIS 2 offering the potential to unveil new and detailed information about Holocene climate. In this study, we present initial results from two of these LPS: Kisiljevo (44°44′0'' N and 21°25′0'' E) in the Carpathian Basin, and Velika Vrbica (44°35’1.70’’N, 22°43’15.97’’E) in the Wallachian Basin. For both sequences, detailed optically stimulated luminescence (OSL) chronologies using 63-90 µm quartz have been constructed. Age models based on the OSL ages were constructed using the r.bacon software (Blaauw & Christen, 2011), following which dust accumulation rates (MAR) for the last approximately 30,000 years were calculated. The initial results from Kisiljevo reveal a significant loess accumulation during the Holocene, amounting to approximately 120 cm. The highest MARs were observed between 10 and 12 ka (10,000-8,000 BC) with a mean value of 148 g m2 a-1. A similar trend is evident at the Velika Vrbica LPS, where the average calculated MARs during the early Holocene (8 – 11.7 ka) were 189 g m2 a-1, showing a decreasing trend toward the later part of this period (3.1 – 8 ka) with average values reaching 132.1 m2 a-1. Interestingly, at this site, the mean MARs during Marine Isotope Stage 1 (MIS) were higher than during the cold, stadial MIS 2, where the recorded values averaged 177 g m2 a-1. These initial results suggest that the Holocene dust dynamics in this region was more variable than what generally accepted models suggest.

References: Blaauw & Christen (2011). Flexible paleoclimate age-depth models using an autoregressive gamma process. Bayesian Analysis, 6(3), 457–474.

How to cite: Perić, Z., Alexanderson, H., Marković, S., Radaković, M., Krsmanović, P., and Ryan, C.: New insights into the atmospheric dust dynamics in the Carpathian and Wallachian Basin during MIS 1-MIS 2, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4003, https://doi.org/10.5194/egusphere-egu24-4003, 2024.

Colour is a fundamental morphological feature commonly documented during the description of loess layers and soils developed on loesses – both contemporary and fossil. These colours are typically identified directly in the field, matching specific hues from the Munsell Soil Colour Chart. However, this method is highly subjective, with accuracy hinging on the observer's expertise and weather conditions. Introducing digital spectrometers for colour analysis, conducted in the lab on powdered samples, enhances objectivity. This approach was applied to samples from the Middle-Upper Pleistocene loess-palaeosol sequences (L2-S1-L1-S0) in Ukraine's Dnieper basin.

The laboratory work aimed to pinpoint chromatic parameters that typify each loess layer, considering their distinct features and stratigraphic positions, as well as various soil horizons, each with unique degrees of pedogenic alteration. Key colour metrics included lightness (L*), redness (a*), yellowness (b*), chroma (c*), and the R-index. The resultant database of spectrophotometric data helps identify colour patterns characteristic of different sequence components.

Our analysis revealed considerable variation across all measured parameters, yet maintained the distinct coloration typical of loess and soils. We also created a digital colour record corresponding with the analogue Munsell scale, lending further objectivity to colour descriptions. Notably, digital colour identification often markedly differs from traditional, "analogue" methods. Applying RGB tuning, we devised models that realistically replicate colours observed in the field.

The documented chromatic parameters enable geological profile analysis in both vertical and spatial dimensions – following the Dnieper valley's sub-meridian and sub-latitudinal orientations across the river basin. These colour profiles mirror the diverse litho-, pedo-, and diagenetic processes across different genetic stages. Crucially, we identified diagnostic colour characteristics unique to primary loesses (L2 vs. L1), various soil types, their development stages (full-profile vs. reduced), and preservation forms (modern vs. ancient).

Thanks to the high resolution and sensitivity of our spectrophotometric analysis, we detected nuanced chromatic shifts, often abrupt. This revealed otherwise invisible erosional surfaces and concealed boundaries, shedding light on changes in loess lithology or the progression of pedogenic processes. The documented colour shifts illustrate the dynamic evolution of the natural environment, from loess accumulation (cold phases) to soil formation (warm periods).

It should be noted that primary loesses of varying ages, collected from different geological sites, which are primarily described as light yellow, show significant differences in the L*, a*, b*, c* parameters in light of spectrophotometric analyses. This variability aligns well with the findings of geochemical analyses.

Research carried out as part of the grant of National Science Centre, Poland as the project no. 2018/31/B/ST10/01507 entitled “Global, regional and local factors determining the palaeoclimatic and palaeoenvironmental record in the Ukrainian loess-soil sequences along the Dnieper River Valley - from the proximal areas to the distal periglacial zone”.

How to cite: Mroczek, P., Łanczont, M., and Komar, M.: Loess chromaticity as an environmental change recorder: spectrophotometric study of aeolian dust and its role in paleoclimate studies, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4619, https://doi.org/10.5194/egusphere-egu24-4619, 2024.

EGU24-4749 | PICO | AS3.9 | Highlight

Recent developments in dust electrification research  

Keri Nicoll and R. Giles Harrison

Electrification of dust in the atmosphere is abundant, observed by helicopter blades glowing from corona discharge in dusty environments, and sparks from barbed wire fences during the US Dust Bowl.  Electrification of particles in blowing sand, dust devils and dust storms can result from contact charging/triboelectrification during dust generation or through its atmospheric transport, causing particles to accumulate large amounts of charge on their surface.  Strong electrostatic forces can affect the lofting of dust particles from the ground, as well as the transport of dust particles, however the details of such effects are still largely unexplored.  The charging of dust particles, and separation of the charge by mechanical processes yields large electric fields (E-fields, up to tens of kV m1).  Satellite remote sensing of dust is based on measurements of electromagnetic wave propagation, which can be attenuated by large electric fields, thereby the accuracy of dust measurements can be affected by electric fields arising from charge separation in dusty environments. Such E-fields are also expected to alter the orientation of dust particles, changing the effective optical depth of dust layers, existing calculations for which assume randomly oriented particles.

Although the existence of dust electrification has been known about for over a century, the details of the electrification mechanisms, and impact of dust electrification on particle behaviour are not yet fully understood.  This is partly due to a lack of observations of coincident space charge, E-field and particle measurements in dusty regions, particularly at altitudes above the surface.  This presentation will discuss recent research in understanding dust electrification processes, including surface observations of dust electrification in the United Arab Emirates (UAE), and measurements of charge in high altitude dust layers above the surface.

How to cite: Nicoll, K. and Harrison, R. G.: Recent developments in dust electrification research , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4749, https://doi.org/10.5194/egusphere-egu24-4749, 2024.

EGU24-4799 | ECS | PICO | AS3.9

Modeling the Mercury Cycle in the Sea Ice Environment: A Buffer between the Polar Atmosphere and Ocean 

Shaojian Huang, Feiyue Wang, Tengfei Yuan, Zhengcheng Song, Peipei Wu, and Yanxu Zhang

Sea ice (including overlying snow) is a dynamic interface between the atmosphere and the ocean, influencing the mercury (Hg) cycling in polar oceans. However, a large-scale and process-based model for the Hg cycle in the sea ice environment is lacking, hampering our understanding of regional Hg budget and critical processes. Here, we develop a comprehensive model for the Hg cycle at the ocean–sea ice–atmosphere interface with constraints from observational polar cryospheric data. We find that seasonal patterns of average total Hg (THg) in snow are governed by snow thermodynamics and deposition, peaking in springtime (Arctic: 5.9 ng/L; Antarctic: 5.3 ng/L) and minimizing during ice formation (Arctic: 1.0 ng/L, Antarctic: 0.5 ng/L). Arctic and Antarctic sea ice exhibited THg concentration peaks in summer (0.25 ng/L) and spring (0.28 ng/L), respectively, governed by different snow Hg transmission pathways. Antarctic snow-ice formation facilitates Hg transfer to sea ice during spring, while in the Arctic, snow Hg is primarily moved through snowmelt. Overall, first-year sea ice acts as a buffer, receiving atmospheric Hg during ice growth and releasing it to the ocean in summer, influencing polar atmospheric and seawater Hg concentrations. Our model can assess climate change effects on polar Hg cycles and evaluate the Minamata Convention’s effectiveness for Arctic populations.

How to cite: Huang, S., Wang, F., Yuan, T., Song, Z., Wu, P., and Zhang, Y.: Modeling the Mercury Cycle in the Sea Ice Environment: A Buffer between the Polar Atmosphere and Ocean, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4799, https://doi.org/10.5194/egusphere-egu24-4799, 2024.

EGU24-5430 | PICO | AS3.9

A near-global multiyear climate data record of the fine-mode and coarse-mode components of atmospheric pure-dust 

Emmanouil Proestakis, Antonis Gkikas, Thanasis Georgiou, Anna Kampouri, Eleni Drakaki, Claire L. Ryder, Franco Marenco, Eleni Marinou, and Vassilis Amiridis

Dust aerosols play a key role in the Earth’s radiation budget, in climate system, environmental conditions, and human health. However, the complex role of dust depends not only on the physical and chemical properties, but in addition to the particle size distribution, spanning from less than 0.1 μm to more than 100 μm in diameter. Larger mineral dust particles are more efficiently removed through dry deposition close to the source regions and act more efficiently as CCN and/or IN than fine-mode dust particles, whereas fine dust particles are more prominent to long-range transport, resulting to degradation of air-quality and induced negative disorders on human health.
Here, a new four-dimensional, multiyear, and near-global climate data record of the submicrometer and supermicrometer (in terms of diameter) components of atmospheric pure-dust, is presented. The separation of the two modes of dust is based on a combination of (1) the total pure-dust product provided by the ESA-LIVAS database and (2) the supermicrometer-mode component of pure-dust provided by the first-step of the two-step POLIPHON technique, developed in the framework of EARLINET. The submicrometer-mode component of pure-dust is extracted as the residual between the LIVAS total pure-dust and the supermicrometer-mode component of pure-dust. The decoupling scheme is applied to CALIPSO observations at 532nm. The final products consist of the submicrometer-mode and supermicrometer-mode of atmospheric pure-dust, of quality-assured profiles of backscatter coefficient at 532nm, extinction coefficient at 532nm, and mass concentration. The datasets are established primarily with the original L2 horizontal (5 km) and vertical (60 m) resolution of CALIOP along the CALIPSO orbit-path, and secondly in averaged profiles of seasonal-temporal resolution, 1o×1o spatial resolution, and with the original vertical resolution of CALIPSO, between 70oS and 70oN and covering more than 15-years of Earth Observation (06/2006-12/2021).
The climate data record is unique with respect to a wide range of potential applications, including climatological, time-series, and trend analysis over extensive geographical domains and temporal periods, validation of atmospheric dust models and reanalysis datasets, assimilation activities, and investigation of the role of airborne dust on radiation and air quality.

How to cite: Proestakis, E., Gkikas, A., Georgiou, T., Kampouri, A., Drakaki, E., Ryder, C. L., Marenco, F., Marinou, E., and Amiridis, V.: A near-global multiyear climate data record of the fine-mode and coarse-mode components of atmospheric pure-dust, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5430, https://doi.org/10.5194/egusphere-egu24-5430, 2024.

EGU24-5573 | ECS | PICO | AS3.9

Stronger early-spring dust outbreaks across the Northern Hemispheric mid-latitudes in a warmer climate 

Yiting Wang, Yan Yu, Ji Nie, and Paul Ginoux

This research focuses on changes in early-spring dust emissions from Northern Hemispheric mid-latitudes, in the context of global warming. Our study was motivated by the abnormally early and strong dust storms across East Asia in March 2021 and March 2023. These two recent dust extremes opposed the decadal decline of East Asian dust activities. Past studies have attributed this dustiness decline to expanded vegetation cover and resultant weaker near-surface winds in April and May; while in March, dust source regions in the Northern Hemispheric mid-latitudes have been mainly covered by snow or frozen soil instead of vegetation. Inspired by the abnormally warm and snow-free conditions associated with both the 2021 and 2023 early-spring dust extremes, our study examines an alternative hypothesis on dust regimes over the Northern Hemispheric mid-latitudes: in a warmer climate, earlier snow melt may cause stronger early-spring dust outbreaks. Here, using multiple observational datasets and model simulations, we show a 10-35% increase in March dust emission across the East Asian, Central Asian and North American drylands, from the 1980s towards the end of the 21st century, bringing ~20% extra PM10 to Beijing and Denver. This hemispherical enhancement in early-spring dust emission is primarily caused by reduced snow cover in response to warming, and further promoted by dynamical coupling between snow, wind, and soil moisture changes. The increased amount of dust, a light absorbing aerosol, may in turn accelerate larger-scale snow melt when it deposits, thereby triggering positive feedbacks between snow melting, dust emission, and warming. Our findings call for adaptation to the anticipated stronger early-spring dust storms across the North Hemispheric mid-latitudes in the upcoming decades.

How to cite: Wang, Y., Yu, Y., Nie, J., and Ginoux, P.: Stronger early-spring dust outbreaks across the Northern Hemispheric mid-latitudes in a warmer climate, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5573, https://doi.org/10.5194/egusphere-egu24-5573, 2024.

EGU24-6384 | PICO | AS3.9

Trade-offs of simplified versus comprehensive representation of mineralogy when studying dust impacts on Earth’s climate systems 

Paul Ginoux, Qianqian Song, María Gonçalves Ageitos, Ron L. Miller, Vincenzo Obiso, and Carlos Pérez García-Pando

The intensity and direction of dust impacts on Earth’s climate systems depend on mineral composition. For example, the presence or absence of a few percent of iron oxides in dust will determine if dust is warming or cooling the atmosphere. Similarly, feldspar will enhance ice cloud formation, while acid gases in the atmosphere will react on the surface of dust calcite limiting acid rain. Still, most climate models use a simplified representation of dust mineralogy. They assume a fixed composition at emission which stays invariant during transport and removal. Such simplification assumes spatially and temporally constant physical and chemical properties of dust, and appears to provide satisfactory results when comparing some properties with observations. The trade-off is their lack of spatial gradients, which will fail to induce circulation, cloud and precipitation changes. The two reasons to omit mineral variations are the uncertainty of current atlases of soil mineral composition in arid regions, and, more practically, an improved runtime efficiency. The former reason is losing ground with the recent launch (July 2022) of a dedicated mission (NASA/JPL EMIT) to retrieve global soil mineralogy of dust sources at high spatial resolution.

While the EMIT science team is finalizing a satisfactory global map of mineral composition of dust sources, we analyzed the interaction of dust mineralogy on radiation and its impact on the fast temperature response using different representations of mineral composition from detailed and spatially varying to simplified and globally uniform, assuming different hematite contents and methods to calculate optical properties.  

Our results show that resolving dust mineralogy reduces dust absorption, and results in improved agreement with observation-based single scattering albedo (SSA), radiative fluxes from CERES (the Clouds and the Earth’s Radiant Energy System), and land surface temperature from CRU (Climatic Research Unit), compared to the baseline bulk dust model version. It also results in distinct radiative impacts on Earth’s climate over North Africa. From our 19-year simulation, we will show that it leads to a reduction of over 50% in net downward radiation at top of atmosphere (TOA) across the Sahara and an approximately 20% reduction over the Sahel. We will explain how the surface temperature response affects the monsoon flow from the Gulf of Guinea.

Interestingly, we find similar results by simply fixing the hematite content of dust to a globally uniform value of 0.9% by volume. We will discuss the underlying reasons for such results and show that they may be unrelated to the distribution of soil mineralogy. Still, an accurate representation of soil mineralogy is necessary to better understand dust impacts on the Earth’s climate systems.

How to cite: Ginoux, P., Song, Q., Gonçalves Ageitos, M., Miller, R. L., Obiso, V., and Pérez García-Pando, C.: Trade-offs of simplified versus comprehensive representation of mineralogy when studying dust impacts on Earth’s climate systems, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6384, https://doi.org/10.5194/egusphere-egu24-6384, 2024.

EGU24-7235 | ECS | PICO | AS3.9

Quantifying dust emission following wildfires on the global scale 

Xianglei Meng, Yan Yu, and Paul Ginoux

Wildfires can reduce vegetation cover and soil adhesivity, thus expanding bare grounds susceptible to wind erosion. Although in situ observations have confirmed dust emission following wildfires, a quantitative and mechanistic understanding of post-fire dust emissions is limited. Here, on the basis of satellite observations of active fires, aerosol abundance, vegetation cover and soil moisture from 2003 to 2020, we found that 91% and 54% of large wildfires are followed by reduced vegetation cover and enhanced dust emission, leaving intensive dust loadings for 1-25 days over normally dust-free regions. Furthermore, small wildfires, which naturally occur more widespread and frequently than large wildfires, lead to more considerable post-fire dust emissions, mostly global semi-arid regions. The occurrence and intensity of post-fire dust emission are regulated primarily by the extent of precedent wildfires and resultant vegetation anomalies, and modulated secondarily by pre-fire drought conditions. Despite the episodic nature of post-fire dust events, the amount of post-fire dust emission has shown an upward trend over the past two decades, especially over the Northern Hemispheric mid-latitudes, where droughts and wildfires are intensifying. These post-fire dust events impose greater socioeconomic and health impacts than dryland dust, due to the closer location of the former to populated areas. With an ongoing enhancement of extreme wildfires and concurrent droughts under global warming, our results emphasize the emerging importance of post-fire dust emissions on global and regional scales.

How to cite: Meng, X., Yu, Y., and Ginoux, P.: Quantifying dust emission following wildfires on the global scale, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7235, https://doi.org/10.5194/egusphere-egu24-7235, 2024.

EGU24-7871 | ECS | PICO | AS3.9

Wind erosion in Western Sahel : Quantifying the impact of land use and land management 

Paul-Alain Raynal, Caroline Pierre, Béatrice Marticorena, Jean-Louis Rajot, Abdourahmane Tall, Issa Faye, Diouma Cor Fall, Bineta Amar, Antoine Couedel, Gatien Falconnier, Jean-Alain Civil, Olivier Roupsard, and Sidy Sow

It is currently estimated that around 15% of the global mineral dust load comes from the Sahel. In this area, rainfed agriculture and livestock grazing play a crucial role in the livelihood of its rapidly growing population. Cropland is likely to be a main source of anthropogenic dust emissions in this region, as this land use type can favor wind erosion if land management deprives the soil of vegetation cover.

Yet, in situ measurements of wind erosion fluxes are scarce in the Sahel, and usually monitor only one type of land use and an associated land management (eg. whether or not to harvest crop residues, intercropping, etc.). Thus, there is room to improve the assessment of the Sahelian anthropogenic contribution to the global dust load, especially through a regional modelling approach relying on field measurements.

In this study, we combined in situ measurements from Sahelian Senegal with a modelling approach to estimate the effect of the main Sahelian land uses on wind erosion. Furthermore, we monitored contrasting land management per land use, representative of the last decades (1960-2020). Here we present the results for one groundnut field over two years (2020-2021), four different fallowed fields over one year (2022/2023), four millet fields over one year (2023/2024). All 1ha-plots were located near the town of Bambey in central Senegal (Groundnut Basin). The observations included sand-traps monitoring (for each 1ha-plot, 5 masts of 5 « Modified Wilson And Cooke » or MWAC sand traps each; collected every 2 weeks), meteorological data (e.g., wind and temperature profiles, and rainfall; at 5-minutes resolution) and vegetation monitoring (aboveground biomass, surface cover, height; weekly to monthly).

For each land use and land management, we estimated the aerodynamic surface roughness length and the wind friction velocity to simulate the horizontal flux of aeolian sediments using a dedicated model (the Dust Production Model – DPM). We then combined the wind erosion model (DPM) with vegetation models (STEP for fallows and STICS for crops) to simulate the vegetation growth and the associated horizontal flux of aeolian sediment. These simulations are compared to the in situ monitoring from the sand traps. Finally, we used ERA5 meteorological time series from the ECMWF to simulate the horizontal flux for the 1960–2020 period over a typical plot from the study area, for different realistic scenarios of land uses and land management.

Our study revealed the variability of wind erosion horizontal flux for the main Sahelian land use types (400 kg/m/yr for bare soil, 200 kg/m/yr for cropland, less than 10kg/m/yr for fallows), as well as slighter differences related to land management for a same land use. These results help to understand the link between wind erosion and agropastoral practices in Sahelian conditions over multi-decadal periods of time.

How to cite: Raynal, P.-A., Pierre, C., Marticorena, B., Rajot, J.-L., Tall, A., Faye, I., Fall, D. C., Amar, B., Couedel, A., Falconnier, G., Civil, J.-A., Roupsard, O., and Sow, S.: Wind erosion in Western Sahel : Quantifying the impact of land use and land management, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7871, https://doi.org/10.5194/egusphere-egu24-7871, 2024.

EGU24-8628 | PICO | AS3.9 | Highlight

Impact of Saharan mineral dust layers on cloud formation and cloud properties 

Silke Gross, Martin Wirth, and Florian Ewald

Mineral dust contributes strongly to the global aerosol load. The largest source region of mineral dust is the Sahara. But mineral dust cannot be treated as a regional phenomenon. Once lifted in the air, it can be transported thousands of kilometers over several days. The main transport pathway spans over the Atlantic Ocean from Africa towards the Caribbean; with its peak season during the summer months. But transatlantic dust transport can also happen during wintertime, however with less frequency. In addition, the dust particles can be transported northward over the Mediterranean and Europe. In rare events, it can even reach the Arctic region. All the way during transport the dust layer has an impact on the Earth’s radiation budget, by direct interaction with the incoming and outgoing radiation by scattering and absorption, and by indirect interaction as dust can impact cloud formation and cloud properties.

To study long-range transported Saharan dust as well as the dust’s impact on cloud formation and properties, airborne lidar measurements with the WALES lidar system onboard the German research aircraft HALO have been performed over the western sub-tropical North-Atlantic Ocean during NARVAL-II in August 2016 and EUREC4A in January/February 2020. We observed dust transport during the summertime in the clearly separated and well-defined Saharan Air Layer (SAL) as well as during wintertime, when dust transport happens at lower altitudes and the SAL is less separated. In addition, we were also able to capture an event of dust long-range transport into the Arctic during the HALO-(AC)3 campaign in spring 2022. From our measurements we could show, that small amount of water vapor embedded in the SAL has a strong impact on the atmospheric stability and thus also impacts the formation and properties of clouds during long-range transport. Additionally, dust particles are known to act as ice nuclei and with that lead to ice formation at different environmental conditions, changing the ice cloud’s microphysical properties.

In our presentation we will give an overview of the performed WALES measurements. We use these measurements to study dust long-range transport and its impact on the atmospheric stability, cloud formation and cloud properties.

How to cite: Gross, S., Wirth, M., and Ewald, F.: Impact of Saharan mineral dust layers on cloud formation and cloud properties, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8628, https://doi.org/10.5194/egusphere-egu24-8628, 2024.

EGU24-8749 | ECS | PICO | AS3.9

Influence of aerosol deposition on snowpack evolution in simulations with the ORCHIDEE land surface model  

Sujith Krishnakumar, Samuel Albani, Martin Ménégoz, Catherine Ottlé, and Yves Balkanski

Simulating seasonal snow with state-of-the-art global general circulation models (GCMs) is still challenging. Snow provides fresh water to billions of people and plays an important role in the energy budget of the earth through albedo, which affects not only local but also remote and global climate/hydrological patterns. Therefore, changes in snow amount and length of the season are crucial when investigating climate variability.  One key aspect often overlooked in GCMs is the inclusion of Light Absorbing Particles (LAPs) in snow simulations. LAPs dramatically reduce snow albedo, particularly for visible solar radiation, leading to considerable implications for climate modeling. The intention is to lay the foundations for addressing the issues across different climate conditions through simulations, by adding the snow darkening effect to a multilayered intermediate complexity scheme within ORCHIDEE, the land surface model embedded in the IPSL Earth System Model.

LAPs are commonly deposited on the surface of fresh snow and progressively become embedded into deeper layers of the snowpack.  The LAP species taken into account include four log-normal modes of dust, soot, and organic carbons. These tracers allow for the movement of LAPs through different layers of the snowpack, adjusting with snow accumulation or melting. In order to simulate the movement of LAPs, ORCHIDEE has been enhanced with a tracer flow mechanism that carry LAPs from the top snow layer following deposition and move through various layers as snow thickens or flushes with meltwater flow. Our approach to snow albedo deviates from the default method in ORCHIDEE as a function of snow aging through an exponential decay function with dependence on the degree of water saturation and the occurrence of fresh snow deposition. Instead, it integrates the Warren and Wiscombe snow radiative transfer scheme with Kokhanovsky's single scatter properties of snow crystals and the optical properties of LAPs to compute the albedo of impure snow. This study conducted site-level offline ORCHIDEE simulations using observed atmospheric conditions and MERRA2 aerosol deposition data. The integration of LAPs and related processes has led to improved simulations of seasonal snow, achieving more realistic representations of snow albedo compared to pure snow. Our results also show that LAPs play an important role in determining the local snow season length.

How to cite: Krishnakumar, S., Albani, S., Ménégoz, M., Ottlé, C., and Balkanski, Y.: Influence of aerosol deposition on snowpack evolution in simulations with the ORCHIDEE land surface model , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8749, https://doi.org/10.5194/egusphere-egu24-8749, 2024.

EGU24-8796 | PICO | AS3.9 | Highlight

Potential environmental impacts of natural and mining related dust in Greenland and Svalbard 

Jens Søndergaard, Christian Frigaard Rasmussen, Hanne Hvidtfeldt Christiansen, and Christian Juncher Jørgensen

Dispersion and deposition of mineral dust from natural or anthropogenic sources such as proglacial rivers, mines and haul roads can have both positive and negative effects on the environment, depending on the geochemical and mineralogical composition of the dust. Some elements in dust may act as nutrients for, for example, plants, lichens and soil communities, while other elements may act as pollutants with negative impacts on growth or reproduction or cause diseases in animals and plants.

To support the sustainable development of environmentally safe mining in sensitive Arctic land areas and reduce airborne environmental pollution, an improved understanding of processes leading to the dispersion of mineral dust in a changing Arctic is needed. This involves improved methods for monitoring dust emissions and dust deposition in a cold environment as well as analytical tools and methods to source trace and differentiate between natural and mining related dust. Accurate identification of individual dust sources subsequently makes it possible to mitigate emissions and target the regulation of mining activities towards these sources.

In this study, we present preliminary results from two new arctic dust monitoring stations in West Greenland and Svalbard. In Kangerlussuaq, West Greenland, mineral dust has been collected using a wide array of passive and active dust samplers, including a continuously operated high volume dust sampler at a weekly sampling frequency over 2022/2023. In Svalbard, mineral dust has been collected in Adventdalen using passive dust collectors in a transect along the haul road to the active coal mines. Samples have been collected on a weekly sampling frequency in the period September to November 2023 to investigate the temporal and spatial variations in dust deposition rates, as well as the impact of haul road traffic relative to the natural dust emissions and depositions.

How to cite: Søndergaard, J., Frigaard Rasmussen, C., Hvidtfeldt Christiansen, H., and Juncher Jørgensen, C.: Potential environmental impacts of natural and mining related dust in Greenland and Svalbard, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8796, https://doi.org/10.5194/egusphere-egu24-8796, 2024.

EGU24-9570 | ECS | PICO | AS3.9

On the importance of Mongolian cyclones to East Asian dust storm activities 

Feifei Mu and Stephanie Fiedler

Desert-dust aerosols affect the climate, human health, and socio-ecomomic activities. In East Asia, the passage of Mongolian cyclones induce dust-emitting winds in the Gobi Desert. While cyclones are known as driver of dust outbreaks, the relative contribution of Mongolian cyclones to the total East Asian dust emission amount and the dust aerosol optical depth has not been quantified from a climatological perspective. To address this gap in knowledge, the present study systematically assesses the co-occurrence of Mongolian cyclones and dust aerosols in East Asia for 2001 to 2022. This study pairs output of the automated detection algorithm for extra-tropical cyclones in ERA5 re-analysis from the ETH Zürich with data for dust aerosols from multiple sources. Through the use of multiple dust data sets, we account for the substantial data uncertainty for dust aerosols in term of the spatial pattern and the absolute emission magnitudes, which can differ by an order of magnitude. The climatological analysis shows a high frequency and intensity for the occurrence of Mongolian cyclones in the lee of the Altai-Sayan Mountains (100Eo–125Eo and 37No–53No), favouring the seasonal dust activity in the Gobi Desert. The results highlight a tight constraint on the mean Mongolian cyclone contribution to the total dust emission amount of 39-47% in the spatial mean for spring based on data from MERRA-2 and Wu et. al. (2022), despite substantial differences in the absolute emission magnitudes. The dust-laden air from the Gobi Desert during such events typically moves southeastwards over China in the wake of the cyclones affecting the aerosol optical depth. For southern Mongolia and Northeastern China (105Eo–130Eo and 37No–52No), we estimate 34% (MERRA-2) to 43% (CAMS) of the dust aerosol optical depth (DOD) being associated with Mongolian cyclones. A decrease in dust emission fluxes and dust storm frequencies have been reported for Northern China in the past two decades and is thought to be connected to decreasing near-surface winds. Our results point to a negative trend in the dust emission flux and DOD associated with the occurrence of Mongolian cyclones. However, our results also point to the co-occurrence of particularly intense Mongolian cyclones, measured by the 99th percentile of the wind speed, with exceptionally strong dust storms in recent years, e.g., in March 2021, despite a mean negative trend in dust activity. Given the connection of Mongolian cyclone to high-impact dust storms in East Asia, the potential future development of such events should be addressed in future research.

How to cite: Mu, F. and Fiedler, S.: On the importance of Mongolian cyclones to East Asian dust storm activities, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9570, https://doi.org/10.5194/egusphere-egu24-9570, 2024.

Water-soluble organic carbon (WSOC) and its brown carbon (BrC) components in the cryosphere have significant impact on the biogeochemistry cycling and snow/ice surface energy balance. In this study, snow samples were collected across regional area of northern Xinjiang, China to investigate the chemical composition, optical properties, and radiative forcing (RF) of WSOC. Based on the geographic differences and proximity of emission sources, the sampling sites were grouped as urban (U), remote (R), and soil-influenced (S) sites, for which WSOC concentrations were measured as 1968±953 ng g-1 (U), 885±328 ng g-1 (R), and 2082±1438 ng g-1 (S), respectively. The S sites showed the higher mass absorption coefficients at 365 nm (MAC365) of 0.94±0.31 m2 g-1 compared to those of U and R sites (0.39±0.11 m2 g-1 and 0.38±0.12 m2 g-1, respectively). Molecular-level characterization of WSOC using high-resolution mass spectrometry (HRMS) provided further insights into chemical differences among samples. Specifically, much more reduced S-containing species with high degree of unsaturation and aromaticity were identified in U samples, suggesting an anthropogenic source. Aliphatic/proteins-like species showed highest contribution in R samples, indicating their biogenic origin. The WSOC components from S samples showed high oxygenation and saturation levels. The WSOC-induced RF were estimated as 0.04 to 0.59 W m-2, which contribute up to 16% of that caused by BC, demonstrating the important influences of WSOC on the snow energy budget. Furthermore, the molecular composition and light-absorbing properties of BrC chromophores were unraveled by application of a high-performance liquid chromatography (HPLC) coupled to photodiode array (PDA) detector and HRMS. The chromophores were classified into five major types, i.e., (1) phenolic/lignin-derived compounds, (2) flavonoids, (3) nitroaromatics, (4) oxygenated aromatics, and (5) other chromophores. Identified chromophores account for ~23% – 64% of the total light absorption measured by the PDA detector in the wavelengths of 300 – 370 nm. In the representative U and R samples, oxygenated aromatics and nitroaromatics dominate the total absorbance. Phenolic/lignin-derived compounds are the most light-absorbing species in the S sample. Chromophores in two remote samples exhibit ultraviolet-visible features distinct from other samples, which are attributed to flavonoids. Identification of individual chromophores and quantitative analysis of their optical properties are helpful for elucidating the roles of BrC in snow radiative balance and photochemistry.

How to cite: Zhou, Y., Wang, X., and Laskin, A.: Molecular composition, optical properties, and radiative forcing of water-soluble brown carbon in seasonal snow samples from northern Xinjiang, China, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9995, https://doi.org/10.5194/egusphere-egu24-9995, 2024.

EGU24-10547 | ECS | PICO | AS3.9

Development of a dusty cirrus calendar based on satellite data 

Samaneh Moradikian, Sanaz Moghim, and Gholam Ali Hoshyaripour

Mineral dust particles have the potential to serve as natural nuclei for cirrus cloud formation in the upper troposphere. Several studies demonstrate that dust aerosol plays a pivotal role in initiating cirrus clouds and forming extended optically thick cirrocumulus decks known as “dusty cirrus”. Despite this, our ability to accurately identify and predict these climatically significant clouds is still limited. In this work, we propose an algorithm to identify dusty cirrus clouds based on satellite data over the Aral Sea region between 2006 and 2021. The algorithm uses the CALIOP Vertical Feature Mask (VFM) to verify the coexistence of dust particles and cirrus clouds and determine the occurrence of dusty-cirrus. To enhance the accuracy of the algorithm, temperature obtained from an external source (the GEOS-5 data product supplied to CALIPSO) is also incorporated as a constraint for cirrus cloud identification. A random selection of identified dusty cirrus events (5% of the data, 90 events) is cross-validated against other data sources including cloud top temperature (MODIS), cloud top height (MODIS), and AOD (MODIS and VIIRS). The cross-validation confirms approximately 97% of the events to be associated with dusty-cirrus. This confirms that the developed algorithm can be used for developing a dusty cirrus calendar using available CALIOP data. This calendar reveals different facts about the dusty-cirrus occurrence in the study area. Out of the 4407 available samples, 2709 cirrus cloud events are identified, with approximately 65% (1790 events) of them being associated with dusty cirrus. The average values obtained for summer, fall, winter, and spring are 54%, 63%, 66% and 75%, respectively. Annual and seasonal trend analysis reveals different increasing rates for this region. Despite the important uncertainties, our analysis and results suggest that the proposed algorithm can be used for first-order identification and statistical analysis of dusty cirrus.

How to cite: Moradikian, S., Moghim, S., and Hoshyaripour, G. A.: Development of a dusty cirrus calendar based on satellite data, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10547, https://doi.org/10.5194/egusphere-egu24-10547, 2024.

EGU24-11462 | ECS | PICO | AS3.9

Seasonal effects of wind-blown dust emissions on size-resolved aerosol acidity over the U.S 

Stylianos Kakavas, Evangelia Siouti, Athanasios Nenes, and Spyros Pandis

Wind-blown dust emitted by the Earth’s surface is one of the major sources of dust emissions especially in non-vegetated areas like deserts and can affect both climate and human health. Acidity is an important property of atmospheric aerosols impacting a series of related processes and can be affected by these emissions of alkaline dust. In this work, we use a wind-blown dust emissions model to quantify the wind-blown dust emissions over the continental United States during February and July 2017. The modeling domain covers a region of 4752 × 2952 km2 including northern Mexico and southern Canada with a horizontal grid resolution of 36 × 36 km. Then, the hybrid version of aerosol dynamics in PMCAMx (Particulate Matter Comprehensive Air-quality Model with Extensions) chemical transport model is used to simulate size-resolved aerosol acidity. In this version of PMCAMx for fine (PM1) particles, bulk equilibrium is assumed, while for larger particles a dynamic model is used to simulate the mass transfer to each size section. Two cases of simulations are performed. The first is the base case simulation and includes the wind-blown dust emissions for both months. The second one neglects these emissions in order to study their effects on aerosol acidity during a wintertime and a summertime period as a function of particle size and altitude.

How to cite: Kakavas, S., Siouti, E., Nenes, A., and Pandis, S.: Seasonal effects of wind-blown dust emissions on size-resolved aerosol acidity over the U.S, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11462, https://doi.org/10.5194/egusphere-egu24-11462, 2024.

EGU24-11544 | ECS | PICO | AS3.9

Abundance of giant mineral dust particles: Insights from measured emitted dust size distributions during the J-WADI campaign 

Hannah Meyer, Andres Alastuey, Sylvain Dupont, Vicken Etyemezian, Jessica Girdwood, Cristina González-Flórez, Adolfo González-Romero, Tareq Hussein, Mark Irvine, Konrad Kandler, Peter Knippertz, Ottmar Möhler, George Nikolich, Xavier Querol, Chris Stopford, Franziska Vogel, Frederik Weis, Andreas Wieser, Carlos Pérez García-Pando, and Martina Klose

Gaining a precise understanding of the particle size distribution (PSD) of mineral dust at emission is critical to assess its climate impacts. Despite its importance, comprehensive measurements at dust sources remain scarce and usually neglect part of the super-coarse (particle diameter d between 10 and 62.5 μm) and the entire giant (d > 62.5 μm) particle size ranges. Measurements in those size ranges are particularly challenging due to expected relatively low number concentrations and low sampling efficiencies of instrument inlets.

This study aims to better constrain the abundance of super-coarse and giant dust at emission as part of the Jordan Wind erosion And Dust Investigation (J-WADI, https://www.imk-tro.kit.edu/11800.php) field campaign conducted north of Wadi Rum in Jordan in September 2022. The goal of J-WADI is to improve our fundamental understanding of the emission of desert dust, in particular its full-range size distribution and mineralogical composition.

To capture the dust PSD across the entire size spectrum, we deployed multiple aerosol spectrometers, including active, passive, and open-path devices, such that in combination, a size range from approximately 0.4 to 200 μm was covered. Here we investigate the variability of the PSD in the super-coarse and giant ranges from observed dust events, address instrumental uncertainties and the impact of different inlets on the resulting PSDs. Our preliminary results reveal a mass concentration peak at around 30 μm, potentially limited toward larger sizes by substantially reduced inlet efficiencies. Giant dust particles were generally detected during active dust emission starting from friction velocities larger than around 0.2 m s-1.

Based on our results, we will investigate the mechanisms facilitating super-coarse and giant dust particle emission and transport. Quantifying the conditions for and the amount of super-coarse and giant dust at emission will lay the foundation to incorporate its impacts in weather and climate models.

How to cite: Meyer, H., Alastuey, A., Dupont, S., Etyemezian, V., Girdwood, J., González-Flórez, C., González-Romero, A., Hussein, T., Irvine, M., Kandler, K., Knippertz, P., Möhler, O., Nikolich, G., Querol, X., Stopford, C., Vogel, F., Weis, F., Wieser, A., Pérez García-Pando, C., and Klose, M.: Abundance of giant mineral dust particles: Insights from measured emitted dust size distributions during the J-WADI campaign, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11544, https://doi.org/10.5194/egusphere-egu24-11544, 2024.

EGU24-12203 | ECS | PICO | AS3.9

Black Carbon and Dust in the snow of Chilean Central Andes: From albedo reductions to radiative forcing 

Maria Florencia Ruggeri, Ximena Fadic, Gonzalo Barcaza, and Francisco Cereceda-Balic

The cryosphere, a vital component of the Earth's climate system, holds substantial importance in both the hydrological cycle and the energy balance. Current apprehension turns around alterations in the cryosphere linked to the reduction in Surface Snow Albedo (SSA).

The decrease in SSA is primarily attributed to the presence of light-absorbing particles (LAPs) and the growth of snow grain size (SGS). The quantitative assessment of these SSA reductions' climatic impact is reflected through their Radiative Forcing (RF), indicating the change they induce in the net radiative flux at the tropopause or the top of the atmosphere. LAPs, mainly composed of Black Carbon (BC) and Mineral Dust (MD), contribute to albedo reduction at visible wavelengths. BC originates from the incomplete combustion of fossil fuels and biomass, while MD primarily emanates from arid and semi-arid regions with low vegetation cover. Precise RF calculations resulting from SSA reductions gain significance, particularly in regions where snow cover governs freshwater availability. Chile exemplifies such a concern, possessing the largest portion of the Andean cryosphere, highly responsive to climate change. This has significant implications for water resources, impacting freshwater availability for Chile's residents and key economic activities.

To quantify the Radiative Forcing RF generated by LAPs in the Chilean Central Andes, snow samples were collected at Portillo, from 2017 to 2022. NUNATAK-1 is a portable, flexible, collaborative scientific platform belonging to the Centre for Environmental Technologies (CETAM-UTFSM), specially designed for research campaigns under extreme conditions, equipped with different automatic and real-time monitoring instruments to measure meteorology, net albedo, solar radiation, gases and aerosols, among others. The samples underwent analysis to determine BC and MD concentrations, following the methodologies outlined in Cereceda-Balic et al. (2022). Snow albedo was modeled using the SNow, ICe, and Aerosol Radiation (SNICAR). Evaluating the singular and combined effects of LAPs, snow albedo was simulated for four scenarios: clean snow (without LAPs), BC only, dust only, and BC + dust. RF represents the variance in absorption between LAP-influenced scenarios and clean snow. For RF calculation, measured solar irradiance specific to each sampling date at the designated site was used. BC concentrations ranged from 2.6 to 717.2 ng g-1, while MD concentrations varied between 1.6 and 181.3 mg kg-1, leading to SSA reductions of up to 21% relative to clean snow. Notably, it was observed that the absorption produced by BC and MD could be comparable, underscoring the significant role of MD in this semiarid location. Moreover, even with relatively moderate or low LAP concentrations in the snow, substantial RF values are generated, emphasizing the heightened climatic influence of LAPs in the region.

Acknowledgments: ANID-Fondecyt Projects 11220525 and 1221526, ANID ANILLO ACT210021, FOVI 230167.

How to cite: Ruggeri, M. F., Fadic, X., Barcaza, G., and Cereceda-Balic, F.: Black Carbon and Dust in the snow of Chilean Central Andes: From albedo reductions to radiative forcing, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12203, https://doi.org/10.5194/egusphere-egu24-12203, 2024.

EGU24-12289 | ECS | PICO | AS3.9

Image-based nowcasting of dust storms by predicting SEVIRI desert dust RGB composites 

Kilian Hermes, John Marsham, Martina Klose, Franco Marenco, Melissa Brooks, and Massimo Bollasina

Dust storms are frequent high-impact weather phenomena that directly impact human life, e.g., by disrupting land and air traffic, posing health threats, and affecting energy delivery from solar-energy systems. Timely and precise prediction of these phenomena is crucial to mitigate negative impacts.

Currently operational numerical weather prediction (NWP) models struggle to reliably reproduce or resolve dynamics which lead to the formation of convective dust storms, making short-term forecasts based on observations (“nowcasts”) particularly valuable. Nowcasting can provide greater skill than NWP on short time-scales, can be frequently updated, and has the potential to predict phenomena that currently operational NWP models do not reproduce.  However, despite routine high frequency and high resolution observations from satellites, as of January 2024, no nowcast of dust storms is available.

In this study, we present an image-based nowcasting approach for dust storms using the SEVIRI desert dust RGB composite. We create nowcasts of this RGB composite for a large domain over North Africa by adapting established optical-flow-based methods as well as a machine learning approach based on a U-net. We show that our nowcasts can predict phenomena such as convectively generated dust storms (“haboobs”) which currently operational NWP may not reliably reproduce. Furthermore, we show that a machine learning model offers crucial advantages over optical-flow-based nowcasting tools for the application of predicting complete RGB images.

Our approach therefore provides a valuable tool that could be used in operational forecasting to improve the prediction of dust storms, and indeed other weather events. Due to the technical similarity of RGB composite imagery from geostationary satellites, this approach could also be adapted to nowcast other RGB composites, such as those for ash, or convective storms.

How to cite: Hermes, K., Marsham, J., Klose, M., Marenco, F., Brooks, M., and Bollasina, M.: Image-based nowcasting of dust storms by predicting SEVIRI desert dust RGB composites, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12289, https://doi.org/10.5194/egusphere-egu24-12289, 2024.

Two billion tons of dust are annually transported in our atmosphere all around the world. High latitudes include active desert regions with at least 5 % production of the global atmospheric dust. Active High Latitude Dust (HLD) sources cover > 1,600,000 km2 and are located in both the Northern (Iceland, Alaska, Canada, Greenland, Svalbard, North Eurasia, and Scandinavia) and Southern (Antarctica, Patagonia, New Zealand) Hemispheres. Recent studies have shown that HLD travels several thousands of km inside the Arctic and > 3,500 km towards Europe. In Polar Regions, HLD was recognized as an important climate driver in the IPCC Special Report on the Ocean and Cryosphere in a Changing Climate in 2019. In situ HLD measurements are sparse, but there is increasing number of research groups investigating HLD and its impacts on climate in terms of effects on cryosphere, cloud properties and marine environment.

Long-term dust in situ measurements conducted in Arctic deserts of Iceland and Antarctic deserts of Eastern Antarctic Peninsula in 2018-2023 revealed some of the most severe dust storms in terms of particulate matter (PM) concentrations. While one-minute PM10 concentrations is Iceland exceeded 50,000 ugm-3, hourly PM10 means in James Ross Island, Antarctica exceeded 300 ugm-3 in 2021-22. The largest HLD field campaign was organized in Iceland in 2021 where 11 international institutions with > 70 instruments and 12 m tower conducted dust measurements (Barcelona Supercomputing Centre, Darmstadt, Berlin and Karlsruhe Universities, NASA, Czech University of Life sciences, Agricultural University of Iceland etc.). Additionally, examples of aerosol measurements from Svalbard and Greenland will be shown. There are newly two online models (DREAM, SILAM) providing daily operational dust forecasts of HLD. DREAM is first operational dust forecast for Icelandic dust available at the World Meteorological Organization Sand/Dust Storm Warning Advisory and Assessment System (WMO SDS-WAS). SILAM from the Finnish Meteorological Institute provides HLD forecast for both circumpolar regions. 

Icelandic dust has impacts on atmosphere, cryosphere, marine and terrestrial environments. It decreases albedo of both glacial ice/snow similarly as Black Carbon,  as well as albedo of mixed phase clouds via reduction in supercooled water content. There is also an evidence that volcanic dust particles scavenge efficiently SO2 and NO2 to form sulphites/sulfates and nitrous acid. High concentrations of volcanic dust and Eyjafjallajokull ash were associated with up to 20% decline in ozone concentrations in 2010. In marine environment, Icelandic dust with high total Fe content (10-13 wt%) and the initial Fe solubility of 0.08-0.6%, can impact primary productivity and nitrogen fixation in the N Atlantic Ocean, leading to additional carbon uptake.

Sand and dust storms, including HLD, were identified as a hazard that affects 11 of the 17 Sustainable Development Goals. HLD research community is growing and Icelandic Aerosol and Dust Association (IceDust) has > 110 members from 57 institutions in 22 countries (https://icedustblog.wordpress.com, including references to this abstract). IceDust became new member aerosol association of the European Aerosol Assembly in 2022. New UArctic Thematic Network on HLD was established in 2023.   

How to cite: Dagsson Waldhauserova, P., Meinander, O., and members, I.: High Latitude Dust (HLD) measurements in Iceland, Antarctica, Svalbard, and Greenland, including HLD impacts on climate and HLD networking, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13103, https://doi.org/10.5194/egusphere-egu24-13103, 2024.

EGU24-13462 | ECS | PICO | AS3.9

Local anthropogenic factors contributing to constrasting glacier response in two mountain glaciers, located in Central Andes, Chile 

Felipe McCracken, María Florencia Ruggeri, Gonzalo Barcaza, Ximena Fadic, and Francisco Cereceda-Balic

Contrasting behaviour of neighbouring mountain glaciers, sharing similar mass balance gradients, have been observed, suggesting the influence of local anthropogenic factors altering the surface energy balance and then explaining larger down-wasting trends in glacier response. It is in this context that for this work the comparison of two contrasting glaciers was used to analyze these differences: considering the Paloma Norte Glacier (PNG), exposed to anthropogenic emissions from local mining activities, and the Yeso Glacier (YG), isolated of these sources. The objective of this research is to combine the remote analysis of light-absorbing particles, such as Black Carbon (BC), Organic Carbon (OC), as well as the estimation of area and albedo, together with the analysis of local climatic trends of each glacier according gridded data, in order to evaluate their differences and the influence of each of these parameters on the surface variation of each glacier.

We determined glacier shrinkage, interannual albedo reduction and black carbon estimates using satellite images over the last 22 years for the Paloma Norte and Yeso glaciers. The results show that in the range 2000-2022, the GPN experienced a 27.11% greater surface loss than the GY, 83.49% higher albedo change rates, and almost 23 times higher BC+OC concentrations compared to the GY. Furthermore, the multivariate regression analysis identified that the most influential parameters was BC-OC, which is consistent with the disparities in glacial retreat observed in this period.

These results are part of an ongoing research, where, in addition, it is intended to contrast these values with measured data at ground stations, where we will use the data from NUNATAK-1 (-32,844, -70,129) and 2 (- 33,665, -70,086) refuge laboratories in the Central Andes. NUNATAK-1 is a portable, flexible, collaborative scientific platform belonging to CETAM, specially designed for research campaigns under extreme conditions equipped with different automatic and real-time monitoring instruments to measure meteorology, net albedo, solar radiation, gases and aerosols, among others. Which are parameters that will also be used to compare with glacial ablation and radiative transfer models, to evaluate the scenarios of albedo change under a pristine environment and another under the scenario of aerosol deposition on the surfaces of the glaciers of interest. All the above mentioned is being carried out to determine to whether these differences are purely due to the orientation of each glacier or the local anthropogenic influence to which they are exposed, and thus decouple the natural effect of climate change from the local anthropogenic effect.

In summary, the results of this work will aim to guide decision-makers, to guarantee greater protection and awareness of the effects that local emissions may (or may not) have on the conservation of these important reservoirs of drinking water, which will allow for a decoupling of the influence and/or impact of local anthropogenic activity from the natural effect of climate change.

Acknowledgments: This research has been carried out with the financial support of CETAM-UTFSM, and the ANID projects: Fondecyt Initiation 11220525, Fondecyt Regular N° 1221526, ANID Anillo ACONCAGUA Project N°ACT210021 and FOVI230167.

How to cite: McCracken, F., Ruggeri, M. F., Barcaza, G., Fadic, X., and Cereceda-Balic, F.: Local anthropogenic factors contributing to constrasting glacier response in two mountain glaciers, located in Central Andes, Chile, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13462, https://doi.org/10.5194/egusphere-egu24-13462, 2024.

EGU24-14539 | ECS | PICO | AS3.9

Exploring the effects of mineral dust acidification on oxidative potential and limiting nutrient solubility 

Andrea Baccarini, Carolina Molina, Christos Kaltsonoudis, Katerina Seitanide, Maria Georgopoulou, Ali Waseem, Georgia Argyropoulou, Adolfo Gonzalez-Romero, Xavier Querol, Carlos Pérez García-Pando, Dimitrios Papoulis, Satoshi Takahama, Kalliopi Violaki, Spyros N. Pandis, and Athanasios Nenes

Mineral dust aerosol particles are ubiquitous in the atmosphere; they contribute to more than half of the total atmospheric aerosol burden and have far-reaching impacts on biogeochemical cycles, air quality and Earth’s radiative budget. Much of the impact of dust is linked to its mild alkalinity and metal content, which directly influence atmospheric reactivity. However, metals and other trace nutrients (TN), such as phosphorous, are largely insoluble in freshly emitted dust and exhibit limited bioavailability for ecosystems upon deposition. The same metals can induce considerable oxidative stress upon inhalation, but mostly if in soluble form. Previous studies have found that atmospheric processing and, in particular, acidification of dust (caused by reactions with sulfuric, nitric, hydrochloric and organic acids) can promote TN solubility and increase the adverse health effects of population exposure to dust. Atmospheric processing also influences dust hygroscopicity and cloud-forming ability, directly affecting Earth’s radiative budget and deposition patterns.

Previous experiments investigating the effect of atmospheric processing on mineral dust properties were mainly conducted in bulk materials and samples. The dissolution kinetics of metals and TN remains poorly constrained under real atmospheric conditions. To address this issue, we have developed an atmospheric simulation chamber facility where mineral dust particles from a wide range of soils can be generated and aged by any mechanisms relevant to the atmosphere (e.g., acidification through photooxidation and/or nocturnal chemistry).

This study provides a detailed characterization of the chamber facility and explores how acidification alters the properties of mineral dust. In particular, we examine the effect of nitrate and sulfate aging on the solubility of TN and the oxidative potential (measured with a DTT assay) of the dust, under atmospherically relevant conditions. We conclude by relating these findings to field observations and discussing the implications for biogeochemical cycles and air quality.

How to cite: Baccarini, A., Molina, C., Kaltsonoudis, C., Seitanide, K., Georgopoulou, M., Waseem, A., Argyropoulou, G., Gonzalez-Romero, A., Querol, X., Pérez García-Pando, C., Papoulis, D., Takahama, S., Violaki, K., N. Pandis, S., and Nenes, A.: Exploring the effects of mineral dust acidification on oxidative potential and limiting nutrient solubility, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14539, https://doi.org/10.5194/egusphere-egu24-14539, 2024.

EGU24-16299 | PICO | AS3.9 | Highlight

Diverse and high pollution of microplastics in seasonal snow across Northeastern China 

Xin Wang and Hanxuan Wen

Snow scavenging is recognized as one of the major sinks for atmospheric microplastics (MPs). However, little is known about the properties of MPs in large-scale surface snow. Using Nile Red staining and micro-Fourier transform infrared spectroscopy, we identified the shapes, sizes, and polymer components of MPs in seasonal snow across northeastern (NE) China, a major industrial area. The average concentration of MPs was (4.52 ± 3.05) × 104 MPs L−1 , and the highest contamination (6.65 ± 3.89) × 104 MPs L−1 was observed in Changbai Mountains, which was the highest concentration observed in surface snow to the extent of literature. The majority of snow MPs were smaller than 50 μm and composed primarily of fragments. Ethylene vinyl acetate and polyethylene were the dominant contributors to their chemical components. Investigation with positive matrix factorization revealed that the MPs were primarily generated by debris from packaging materials, followed by industrial and construction activities. In addition, the winter atmospheric circulation over the northwestern Siberian and Mongolian plateaus likely dominated the wide-range dispersion and deposition of the MPs across NE China. These results provide a first comprehensive perspective of MPs from sources to removal associated with snow in a large geographic region.

How to cite: Wang, X. and Wen, H.: Diverse and high pollution of microplastics in seasonal snow across Northeastern China, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16299, https://doi.org/10.5194/egusphere-egu24-16299, 2024.

EGU24-16833 | ECS | PICO | AS3.9

Cumulative and relative impact of aerosol species on snowmelt runoff from the Hindu Kush Himalayan glaciers 

Sauvik Santra, Shubha Verma, and Shubham Patel

Himalayan glaciers are a significant contributor to the global supply of snowmelt water and serve as the primary source for major rivers in South Asia. In this study, we have evaluated the effect of aerosol species on glaciers in the Hindu Kush Himalayan (HKH) region and identified the glaciers most affected, as well as the relative and cumulative impact of different aerosol species, including black carbon (BC). We estimate the surface concentration of organic carbon (OC), sulfate (Sul), and dust aerosols in the HKH region. We also measured the concentration of these aerosol species in the snow of nine glaciers and investigated their influence on annual glacier runoff. Furthermore, we identified the source regions and sectors that are responsible for aerosol loading in the region. In this study, we combined free-running (freesimu) and constrained (constrsimu) aerosol simulations with an atmospheric general circulation model, an aerosol-snow radiative interaction model, and a novel hypsometric glacier energy mass balance model. The freesimu estimates of aerosol species concentrations were more accurate at high-altitude (HA) stations than at low-altitude (LA) stations. However, the constrsimu estimates performed significantly better at LA stations. A hotspot location of high concentration of aerosol species was identified near Manora Peak, located almost at a central location in the HKH region. Although the concentration of other aerosol species was 2 to 5 times higher than BC (< 70 μg kg-1), they caused significantly less reduction in snow albedo than BC over the HKH glaciers. The cumulative snow albedo reduction (SAR) due to all aerosol species, including BC, was estimated to be as much as 7 to 8% over the Gangotri and Chorabari glaciers, with Gangotri being one of the most important glaciers responsible for the formation of the Ganges River. The Pindari glacier was found to have the highest annual runoff increase (ARI) of all glaciers studied despite having a lower aerosol-induced SAR than the Gangotri and Chorabari glaciers. Five of the nine glaciers (Pindari, Sankalpa, Milam, Gangotri, and Chorabari) had ARI higher than 300 mm w.e. y-1 due to aerosol-induced SAR. Glaciers located in the HKH region were found to be two to three times more sensitive to SAR than cold Tibetan glaciers. This, combined with the recent increase in temperature due to global warming, paints a worrying picture for the future. Analysis of the fractional contribution of aerosol species revealed that BC aerosols, although having a less than 15% contribution to the total aerosol loading, contribute 55 to 70% of total aerosol-induced ARI, followed by dust (20 to 30\%), Sul and OC aerosols respectively. Analysis of region- and source-tagged simulation data revealed that the main sources of OC and Sul aerosols south of 30°N were biomass burning and open burning (for OC), and fossil fuel burning (for Sul) from the nearby Indo-Gangetic plain. For regions located north of 30°N and for dust aerosols, the main contributor was identified as long-range intercontinental transport from far-off regions of Africa and West Asia.

How to cite: Santra, S., Verma, S., and Patel, S.: Cumulative and relative impact of aerosol species on snowmelt runoff from the Hindu Kush Himalayan glaciers, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16833, https://doi.org/10.5194/egusphere-egu24-16833, 2024.

EGU24-16834 | ECS | PICO | AS3.9

Characterisation of algal blooms on seasonal snowfields through a combination of field spectrometry, drone imagery and radiative transfer modeling at Hardangerjøkulen (Hardanger glacier), Southern Norway 

Lou-Anne Chevrollier, Adrien Wehrlé, Joseph M. Cook, Alexandre M. Anesio, Liane G. Benning, and Martyn Tranter

Pigmented microalgae bloom on glaciers and snowfields worldwide, contributing to carbon storage and enhanced surface melt through surface darkening. The darkening impact of snow algal blooms is being increasingly studied on terrestrial glaciers and ice sheets but less attention has been given to seasonal snowfields, despite their ecological and climatic relevance. Algal blooms are typically widespread but heterogeneously distributed and therefore high resolution airborne observations provide important insights to better understand the spatial patterns and impact of the blooms. Here, we present 130 field spectra colocated with low-cost and light-weight drone imagery acquired over 6 different snowfields in July and August 2023 around Hardangerjøkulen (Hardanger glacier), Southern Norway. We combine these high-resolution measurements with radiative transfer modeling to provide estimates of abundance, carbon storage and albedo impact of snow algal blooms on seasonal snowfields.

How to cite: Chevrollier, L.-A., Wehrlé, A., M. Cook, J., M. Anesio, A., G. Benning, L., and Tranter, M.: Characterisation of algal blooms on seasonal snowfields through a combination of field spectrometry, drone imagery and radiative transfer modeling at Hardangerjøkulen (Hardanger glacier), Southern Norway, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16834, https://doi.org/10.5194/egusphere-egu24-16834, 2024.

EGU24-17044 | PICO | AS3.9

Inaugural dust and climate model simulations with the new EMIT global mineral abundance maps 

María Gonçalves Ageitos and the EMIT team

Minerals in dust shape the interaction of this ubiquitous aerosol with relevant components of the Earth system. Iron oxides absorb short-wave radiation, while quartz or k-feldspars act as efficient ice nuclei, contributing to the formation of mixed-phase clouds. In addition, iron and phosphorus containing minerals transport nutrients to terrestrial and marine ecosystems. Other minerals, like calcite, affect aerosols’ pH and intervene in atmospheric chemistry processes. Incorporating these complex effects into Earth System Models (ESM) has proven challenging due to our limited knowledge about the mineralogy of dust sources and its particle size distribution at emission.

The ongoing NASA Earth Surface Mineral Dust Source investigation (EMIT) project has produced a first version of a global mineral abundance map at an unprecedented resolution based on spaceborne imaging spectroscopy observations from the International Space Station. Using this new product, we have conducted multi-annual simulations with several ESMs that explicitly represent dust mineralogy. Our study characterizes the relevance of the new map in the ESM results by comparison with our previous baseline simulations. We conduct a thorough evaluation against a global mineral fraction compilation derived from concentration and deposition measurements. Our results are also compared against single scattering albedo (SSA) retrievals from dusty AERONET sites. Our focus is primarily iron oxides, hematite and goethite, which, together with particle size, control the dust SSA in the short-wave.

By providing a first set of simulations with the new EMIT mineral abundance maps and their evaluation, our work contributes to advancing the representation of this key aerosol within ESMs and to further assessing its significance within the global climate system.

How to cite: Gonçalves Ageitos, M. and the EMIT team: Inaugural dust and climate model simulations with the new EMIT global mineral abundance maps, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17044, https://doi.org/10.5194/egusphere-egu24-17044, 2024.

EGU24-17082 | PICO | AS3.9

Underestimation of desert dust ingested by aircraft from the CAMS reanalysis compared to CALIOP retrievals 

Claire Ryder, Clement Bezier, Helen Dacre, Rory Clarkson, Vassilis Amiridis, Eleni Marinou, Emmanouil Proestakis, Zak Kipling, Angela Benedetti, Mark Parrington, Samuel Remy, and Mark Vaughan

Atmospheric mineral dust aerosol constitutes a threat to aircraft engines from deterioration of internal components. Here we fulfil an outstanding need to quantify engine dust ingestion at worldwide airports.  The vertical distribution of dust is of key importance since ascent/descent rates and engine power both vary with altitude and affect dust ingestion. We use representative jet engine power profile information combined with vertically and seasonally varying dust concentrations to calculate the ‘dust dose’ ingested by an engine over a single ascent or descent. Using the Copernicus Atmosphere Monitoring Service (CAMS) model reanalysis, we calculate climatological and seasonal dust dose at 10 airports for 2003-2019. Dust doses are mostly largest in summer for descent, with the largest at Delhi (6.6 g). Beijing’s largest dose occurs in spring (2.9 g). Holding patterns at altitudes coincident with peak dust concentrations can lead to substantial quantities of dust ingestion, resulting in a larger dose than the take-off, climb and taxi phases. We compare dust dose calculated from CAMS to spaceborne lidar observations from two dust datasets derived from the Cloud–Aerosol Lidar with Orthogonal Polarization (CALIOP). In general, seasonal and spatial patterns are similar between CAMS and CALIOP though large variations in dose magnitude are found, with CAMS producing lower doses by a mean factor of 2.4±0.5, particularly when peak dust concentration is very close to the surface. We show that mitigating action to reduce engine dust damage could be achieved, firstly by moving arrivals and departures to after sunset and secondly by altering the altitude of the holding pattern away from that of the local dust peak altitude, reducing dust dose by up to 44% or 41% respectively.

How to cite: Ryder, C., Bezier, C., Dacre, H., Clarkson, R., Amiridis, V., Marinou, E., Proestakis, E., Kipling, Z., Benedetti, A., Parrington, M., Remy, S., and Vaughan, M.: Underestimation of desert dust ingested by aircraft from the CAMS reanalysis compared to CALIOP retrievals, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17082, https://doi.org/10.5194/egusphere-egu24-17082, 2024.

EGU24-17880 | PICO | AS3.9

Unveiling the provenance of dust in the EPICA Dronning Maud Land Ice Core (Antarctica) throughout the Last Deglaciation (7–27 kyr BP): A Quantitative Record Using a Novel Rare Earth Element Mixing Model 

Steeve Bonneville, Aubry Vanderstraeten, Laruelle Goulven, Sibylle Boxho, Bory Aloys, Gabrielli Paolo, Gili Stefania, and Nadine Mattielli

Antarctic ice cores have provided valuable insights into the intricate interplay between dust and climate dynamics in the Southern Hemisphere. However, until now, a continuous and quantitative record detailing the origin of dust during the last deglaciation is lacking. In this study, we utilized a novel database comprising 207 Rare Earth Element (REE) patterns obtained from dust and fine sediment/soil fractions collected from well-known potential source areas (PSA) in the Southern Hemisphere. By combining this comprehensive dataset of REE patterns, we developed a robust statistical model to best match the REE patterns measured in the Epica Dronning Maud Land (EDML) ice core in East Antarctica. Among the 398 samples analyzed in the EDML core, 386 have been un-mixed with statistical significance. When coupled with data on total atmospheric deposition, our findings enable the first quantification of the dust flux from the various PSA reaching the EDML region between 7,000 and 27,000 years before present (kyr BP). Our results unveil that, despite a substantial decrease in atmospheric deposition at the onset of deglaciation around 18,000 years ago, the dust composition remained relatively uniform throughout the Last Glacial Maximum (LGM, 18-27 kyr BP) and Heinrich Stadial 1 (HS1, between 14.7-18 kyr BP). During this period, approximately 68% of the total dust deposition was coming from Patagonian sources, with the remaining contributions originating from Australia (14-15%), Southern Africa (~9%), New Zealand (~3-4%), and Puna-Altiplano (~2-3%). A significant shift in dust provenance occurred around 14.5 kyr BP, marked by a drop in Patagonian contribution to below 50%, while low-latitude PSAs increased their contributions, accounting for 21-23% from Southern Africa, 13-21% from Australia, and ~4-10% from Puna-Altiplano. We propose that this shift is linked to enduring alterations in the hydrology of Patagonian rivers, including Atlantic-Pacific drainage reversals and the decline of braided planform, along with the sudden submersion of the Patagonian shelf. Indeed, between 15 and 14.0 kyr BP, the PAT shelf surface area was halved and by ∼13 kyr BP, it had shrunk by 70% from to its former maximum glacial expansion, with most of the PAT shelf south of 40°S submerged. The drastic reduction of the area subjected to aeolian deflation coupled with the reduction of fine sediment supply of eastern plains in PAT induced an overall decline in dust emission from Patagonian sources. Our finding emphasizes an important feedback between dust composition in Southern Hemisphere and eustatic sea level during the Last Glacial-Interglacial Transition. The early Holocene dust composition reveals heightened variability, with a prevalent contribution from Patagonia at ~50%. Post 11.5 kyr BP, as Puna-Altiplano experienced persistent aridity, our records demonstrate a noticeable increase in dust contribution. Leveraging a comprehensive coverage of both local and distal PSA, our statistical model, based on REE patterns, provides a straightforward and cost-effective method for tracing dust sources in ice cores.

How to cite: Bonneville, S., Vanderstraeten, A., Goulven, L., Boxho, S., Aloys, B., Paolo, G., Stefania, G., and Mattielli, N.: Unveiling the provenance of dust in the EPICA Dronning Maud Land Ice Core (Antarctica) throughout the Last Deglaciation (7–27 kyr BP): A Quantitative Record Using a Novel Rare Earth Element Mixing Model, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17880, https://doi.org/10.5194/egusphere-egu24-17880, 2024.

EGU24-17990 | ECS | PICO | AS3.9

Impactor-Based Size Fractionation of Aerosol Particles over the Tropical Atlantic Ocean: Source Identification using Nd, Sr, and Pb Isotopes  

Oriol Teruel-Cabello, Leo Pena, Ester Garcia-Solsona, Eduardo Paredes, Isabel Cacho, Antoni Rosell-Melé, and Joan Villanueva

Airborne mineral dust is a significant constituent of the Earth's climate system that warrants detailed investigation to comprehend its impact on climate processes. This work presents a comprehensive multiproxy approach, utilizing Sr-Nd-Pb isotopes, to discern mineral dust source areas from North Africa, a region contributing approximately 55% of the global annual dust load. Our research not only focuses on identifying provenance but also explores the relationship between climate processes in source areas and aerosol properties at remote locations. We collected samples during three oceanographic campaigns in the tropical Atlantic Ocean conducted in 2020, 2021, and 2022, spanning late winter and entire spring periods. The interannual aspect allows us to capture variations, enhancing our understanding of dust emission and transport dynamics. The implementation of a sampling device that separates aerosol particles of different sizes allows for the detailed isotopic characterization of particles in each size range. Our results indicate the existence of diverse origin and transport patterns depending on the particle size. Differentiation based on particle size uncovers compelling insights into the dynamics of dust dispersion, revealing size-dependent variations in dust behavior. Notably, we observe distinctive pathways for the mass of elements at each size, elucidating the complex interplay between Nd, Sr, and Pb. 

How to cite: Teruel-Cabello, O., Pena, L., Garcia-Solsona, E., Paredes, E., Cacho, I., Rosell-Melé, A., and Villanueva, J.: Impactor-Based Size Fractionation of Aerosol Particles over the Tropical Atlantic Ocean: Source Identification using Nd, Sr, and Pb Isotopes , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17990, https://doi.org/10.5194/egusphere-egu24-17990, 2024.

Vegetation fires represent a major, mostly anthropogenically-driven, component of the Earth system that are affecting different landscapes in multiple regions of the globe and are supposed to increase further in number and severity with the ongoing climate change. Measurements and conceptional model studies have already shown that the fire-induced disturbance of the near-surface wind patterns allow for the mobilization of soil dust particles and their injection into the atmosphere through the pyro-convective updrafts related to the fires. However, the dust emission schemes of the current generation of aerosol-climate models do not consider this fire-related emission pathway and focus on wind-driven dust emissions of mostly unvegetated landscapes such as deserts only. This can result in an underrepresentation of dust particles in the fire-affected regions with consequences regarding a correct representation of aerosol-atmosphere interactions such as the radiation budget.

Therefore, the present study aims to provide more insights concerning the importance of fire-driven dust emissions in the climate system. In order to achieve this, the process was implemented as a new emission pathway into the aerosol module HAM (Hamburg Aerosol Module) of the newly coupled aerosol-climate model ICON-HAM. Information about the behavior of the fire-affected wind fields and their potential to overcome typical emission thresholds have been used to set the dust emission fluxes in relation to data of the global fire activity, expressed by the fire radiative power (FRP), and to land-surface characteristics such as soil type and surface roughness.

Multi-year global simulations of ICON-HAM were analyzed to quantify the impacts of the additional dust emissions caused by the fire activity and their injection parameterization on a seasonal and continental scale. It was found that the strength of the fire-related dust emissions strongly depends on the region where the fire occurs, which is determined by the local soil-surface conditions and not only by the fire strength. However, the vegetation fires can lead to an increase of the atmospheric dust load even in regions far away from those commonly known as dust source areas, highlighting that fire-driven dust emissions can substantially contribute to the total aerosol load and in particular its composition within fire-prone regions or also within a fire-prone climate.

How to cite: Wagner, R. and Schepanski, K.: Fire-driven dust emissions – applying a newly developed parameterization scheme in a global aerosol-model, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18339, https://doi.org/10.5194/egusphere-egu24-18339, 2024.

EGU24-18556 | PICO | AS3.9

EMIT Global Dust Source and Emission Mineral Abundance Maps for Dust and Climate Modeling 

Carlos Pérez García-Pando and the EMIT Team

Soil dust aerosols, comprised of diverse minerals with varying relative abundances, particle size distribution (PSD), shape, surface topography, and mixing state, exert a significant influence on climate. Despite this complexity, conventional Earth System Models tend to assume a globally uniform dust aerosol composition, overlooking well-documented regional variations in the mineralogy of their sources. Existing models addressing dust mineralogical variations often rely on mineral abundance maps extrapolated from an insufficient and non-uniform set of soil sample analyses, especially scarce in arid and semiarid regions.

This study introduces the first version of a series of global dust source and emission mineral abundance maps for dust and climate modelling built upon data from the Earth Surface Mineral Dust Source Investigation (EMIT) imaging spectrometer that is currently operational on the International Space Station (ISS). EMIT measures the spectral range from 0.38 to 2.50 microns through 285 contiguous spectral channels at a high spatial resolution of approximately 60 meters per pixel and ~77 km swath width. The EMIT ground system, utilizing Tetracorder, enables material identification and mapping on mineral spectra. EMIT provides quantitative maps for 10 critical minerals over dust sources pivotal for understanding interactions with the Earth System, with a specific emphasis on mapping iron oxides (hematite and goethite) to constrain the dust direct radiative effect.

Our study offers a comprehensive overview of the diverse methods explored, challenges faced, and key assumptions made to provide quantitative dust source mineralogy. Notably, addressing the absence of information on quartz and feldspar, whose absorption features extend beyond the measured spectral range, poses a significant challenge. Methodologies range from a model that linearly relates mineral abundance to absorption-feature band depth, to more advanced models solving the non-linear multiple scattering radiative transfer problem, providing abundances across a broader range of conditions.

Furthermore, the study provides insights into key assumptions guiding the derivation of mineral abundance maps for both clay and silt fractions of the soil. It also details methods rooted in brittle fragmentation theory, essential for estimating emitted size-resolved mineralogy, which is the critical input for Earth System Models.

This research contributes to advancing our understanding of soil dust aerosols, laying the foundation for improved climate models that account for nuanced regional variations in mineralogical composition.

How to cite: Pérez García-Pando, C. and the EMIT Team: EMIT Global Dust Source and Emission Mineral Abundance Maps for Dust and Climate Modeling, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18556, https://doi.org/10.5194/egusphere-egu24-18556, 2024.

EGU24-18893 | ECS | PICO | AS3.9

Size segregation process along the soil-saltation-dust continuum: observations in southern Tunisia  

Rizewana Marécar, Béatrice Marticorena, Gilles Bergametti, Jean Louis Rajot, Christel Bouet, Servanne Chevaillier, Anais Féron, Bouthaina Khalfallah, Stéphane Alfaro, Mohamed Taieb Labiadh, Thierry Henry des Tureaux, Saad Sekrafi, and Mohsen Lifti

The particle size segregation processes occurring between the soil, the saltation layer and the dust layer close to the surface are not well described while they are key steps for a precise assessment of dust emission. Improving our understanding and quantifying the role of the processes acting in these three compartments should significantly enhance the consistency of dust emission models.

Data obtained during the WIND-O-V (WIND erOsion in presence of sparse Vegetation) field campaign that took place in spring 2017 in southern Tunisia have been analyzed. Eight saltation events of durations from 1 to 4 hours were sampled and corresponded to a range of wind friction velocities between 0.28 and 0.46 m s-1. The dispersed and non-dispersed size distributions of the soil and of the saltation fluxes were characterized and the micrometeorological conditions were also analyzed. Simultaneous measurements of size resolved saltation fluxes and size-resolved vertical dust fluxes were carried out. The combined analysis of size distributions of the parent-soil and of the horizontal and vertical fluxes reveals an enrichment of fine particles that increases with height. A consistent behavior is observed when comparing the particle size distribution of the saltation and of the vertical dust fluxes. Moreover, we observe changes in the size distributions from one event to another that are similar for the saltation and the dust fluxes. This strongly suggests that the processes controlling the saltation significantly affect the dust size distribution. The roles of the vertical transfer and of the micrometeorological conditions on the size distributions are also discussed.

How to cite: Marécar, R., Marticorena, B., Bergametti, G., Rajot, J. L., Bouet, C., Chevaillier, S., Féron, A., Khalfallah, B., Alfaro, S., Labiadh, M. T., Henry des Tureaux, T., Sekrafi, S., and Lifti, M.: Size segregation process along the soil-saltation-dust continuum: observations in southern Tunisia , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18893, https://doi.org/10.5194/egusphere-egu24-18893, 2024.

EGU24-19326 | PICO | AS3.9

Why does it rain in the desert? The dust record in Tunisia. 

Anna Bird, Ian Millar, Doris Wagner, Kaja Fenn, Rachel Smedley, Barbara Mauz, Moez Mansoura, Michael Rogerson, Marc Luetscher, Mahjoor Lone, and Noureddine Elmejdoub

North Africa is one of the regions identified by UNESCO as experiencing severe water stress, and further drying could be devastating for region that is also insecure. Tropical semi-arid regions, such as North Africa are highly sensitive to climate change, and climate predictions for this area suggest that this region will experience drying in the next decades and centuries. This contrasts with findings from palaeo-studies which show that, during the Pleistocene, global warming often correlates to humid phases. This project uses speleotherm records with palaoedust (loess) archives to assess the climate record over humid and dry periods to improve our understanding of past climate change in the sensitive but under-represented central northern Africa region. This presentation will focus on findings from the most important loess deposit in northern Africa, at Matmata in Tunisia.

The loess sections within the Matmata Plateau have loess and soil horizons relating to a series of humid and arid phases during the Quaternary, a sequence that provides valuable insight into the origins and dynamics of desert deposits and the interplay between continental and maritime weather systems. Previous work, in the 1990s, on the Matmata loess has shown onset of loess deposition to be during a humid phase (~70 ka) with loess deposition continuing as the climate becomes more arid into the Upper Holocene. It is currently assumed that the source of this material is the Grand Erg Orient, based on a relatively old study (1987). However, new OSL data presented here shows that the onset of loess deposition was much older than previously thought (~300 ka), with the top of the sections dated at ~24 ka. It appears that deposition was not continuous with a large gap in the record from 143 – 45 ka. Gaps in sedimentation for the section older than ~140 ka are difficult to determine due to limited reliability of older OSL ages.

Provenance analysis has been undertaken on many of the dated samples to establish past transport directions. Detrital zircon U-Pb data suggest that there is dominant Algeria-type source with some input from the north. The amount of this input varies over time with samples older than 200 ka showing a larger input from the north. 87Sr/86Sr and 143Nd/144Nd isotopes from different grainsize fractions tell a similar story, with a dominant west African source.

How to cite: Bird, A., Millar, I., Wagner, D., Fenn, K., Smedley, R., Mauz, B., Mansoura, M., Rogerson, M., Luetscher, M., Lone, M., and Elmejdoub, N.: Why does it rain in the desert? The dust record in Tunisia., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19326, https://doi.org/10.5194/egusphere-egu24-19326, 2024.

EGU24-20434 | ECS | PICO | AS3.9

Forcing factors behind primary productivity variabilities in Western Arabian Sea  since the Last Glacial Maximum: an important role of mineral dust supplies 

Alice Karsenti, Charlotte Skonieczny, Stéphanie Duchamp-Alphonse, Xinquan Zhou, Kara Labidi, Nicolas Musial, Ana Alves, Maxime Leblanc, Julius Nouet, Amélie Plautre, Sébastien Bertrand, Eva Moreno, Annachiara Bartolini, Catherine Kissel, and Franck Bassinot

Located in the Northwestern part of the Indian Ocean, the Arabian Sea (AS) is surrounded by vast arid regions (e.g. Arabian Peninsula, Pakistan, Iran), regularly swept by regional winds, that supply important amounts of mineral dust to the sea. This oceanic area is also under the influence of Indian monsoon surface winds that create a coastal upwelling off Somalia and Oman during summer and a convective mixing north of 15°N during winter. Consequently, mineral dust, coastal upwelling and convective mixing bring important amounts of nutrients to the euphotic zone, making the AS one of the most productive oceanic regions in the world. Although older studies usually highlight the coastal upwelling as a major factor behind primary productivity (PP) patterns in the AS, more recent studies have demonstrated that mineral dust inputs and convective mixing could have a significant influence on PP as well, at least since the Last Glacial Maximum (LGM). This time interval encompasses a glacial-interglacial transition with rapid fluctuations of ice sheet volume and atmospheric CO2 concentration, and represents therefore, a perfect case study to explore the impact of key Earth’s climate forcing mechanisms on the PP for both, past and future climate conditions. Yet, mineral dust component is still poorly documented by proxy data in the AS and direct reconstruction of PP are rare, which limit our understanding of how fertilization of the euphotic zone either by dust, coastal upwelling and/or convective mixing, impacts PP in the past. In this study, we combine high resolution bulk geochemical composition, detrital fraction grain-size distribution and clay mineralogy composition, together with coccoliths counting and carbon organic analyses from sediment cores MD00-2354 and MD00-2355, both retrieved on the Owen ridge. The aim is to reconstruct high-resolution mineral dust and PP patterns over the western part of the AS since the LGM. Both sites are located under the direct influence of dust plumes and among the seasonal latitudinal shift of monsoonal winds. They are therefore willing to register nutrient inputs from mineral dusts, winter convective mixing and/or summer coastal upwelling. Combined with previous paleoclimate records from the area, they will provide for the first time, an unprecedented overview of the forcing factors behind PP distribution in the past. Preliminary results show decreasing PP at both sites through the last 20 ka, suggesting a regional pattern of nutrient distribution in the western AS. Particularly, a strong correlation between PP and mineral dust signals reinforces the hypothesis of a key role of mineral dust on PP in the area. 

How to cite: Karsenti, A., Skonieczny, C., Duchamp-Alphonse, S., Zhou, X., Labidi, K., Musial, N., Alves, A., Leblanc, M., Nouet, J., Plautre, A., Bertrand, S., Moreno, E., Bartolini, A., Kissel, C., and Bassinot, F.: Forcing factors behind primary productivity variabilities in Western Arabian Sea  since the Last Glacial Maximum: an important role of mineral dust supplies, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20434, https://doi.org/10.5194/egusphere-egu24-20434, 2024.

EGU24-20949 | PICO | AS3.9

Radiative Forcing Assessment of Black Carbon in Snow from the Antarctic Peninsula  

Francisco Cereceda-Balic, María Florencia Ruggeri, Gonzalo Barcaza, Ximena Fadic, and Hans Moosmüller

The pristine Antarctic environment, despite its remoteness, is not immune to the influence of anthropogenic
pollutants. This study focuses on quantifying the Radiative Forcing (RF) resulting from Black Carbon (BC)
concentrations in snow samples collected from various points on the Antarctic Peninsula during the austral summer
of 2023, aiming to assess the impact of BC on the snowpack albedo and, consequently, on the regional climate. To the
best of our knowledge, in most of the locations studied, BC concentrations in snow have never been measured before.
Snow samples were meticulously collected from different locations on the Antarctic Peninsula, covering a diverse
range of environments, including base surroundings, remote locations, and icebergs. This effort was undertaken as
part of the ECA59 campaign, funded by the Chilean Antarctic Institute (INACH). The sampling constituted the initial
phase of a project involving three distinct sampling periods. Specifically, the collection sites were situated in the
eastern sector of the peninsula, known for its minimal human presence and limited prior research, making it a
relatively unexplored region. BC concentrations in our snow samples were measured following the method described
in Cereceda-Balic et al. (2022, https://doi.org/10.1016/j.envres.2022.113756). To understand the BC RF, the SNICAR
(SNow, ICe, and Aerosol Radiation) model was employed to simulate snow albedo for measured BC concentrations.
This methodology allowed for an assessment of the potential BC-induced changes in albedo and the resulting RF. The
analysis revealed a significant range of BC concentrations in Antarctic snow samples, spanning from 2.4 to 1157 ng g-1. Simulating snow albedo using the SNICAR model indicated BC-induced albedo reductions of up to 20% relative to clean snow. The calculated BC-induced RF reached up to 38 W m-2, indicating a substantial climatic impact of BC in the Antarctic Peninsula region.

Our findings underscore the influence of BC on the radiative properties of snow in the Antarctic Peninsula. The diverse
BC concentrations observed here suggest varying sources and highlight the need for continued monitoring. The results
reveal the vulnerability of the Antarctic Peninsula to the impacts of anthropogenic pollutants, even in its seemingly
pristine surroundings. Acknowledging and addressing these influences is essential for assessing the broader
implications of climate change in polar regions. Continued research at these little-explored sites is crucial for refining
climate models and informing mitigation strategies to preserve the integrity of the Antarctic environment.


Acknowledgments: INACH Project RT_34-21, and ANID Project: Fondecyt Projects N°1221526 andN°11220525, ANILLO ACONCAGUA N°ACT210021, and FOVI230167

How to cite: Cereceda-Balic, F., Ruggeri, M. F., Barcaza, G., Fadic, X., and Moosmüller, H.: Radiative Forcing Assessment of Black Carbon in Snow from the Antarctic Peninsula , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20949, https://doi.org/10.5194/egusphere-egu24-20949, 2024.

EGU24-22132 | ECS | PICO | AS3.9

Reading dust provenance record in Epica Dome C Ice Core (EDC) of Antarctica reveals a shift from Patagonian to African sources through the last deglaciation (2.9 – 33.7 kyr) 

Sibylle Boxho, Nadine Mattielli, Aubry Vanderstraeten, Goulven G. Laruelle, Aloys Bory, Paolo Gabrielli, Stefania Gili, and Steeve Bonneville

Epica Dome C (EDC) ice core is invaluable and highly-resolved record of Earth’s climate. Within the database of climate proxies in deep ice core, quantifying the contribution of the various sources of dust has been very challenging and, so far, no continuous record of dust provenance has been established. Here, we developed an algorithm that combines the REE patterns from a large database (from 207 sediments/soils in well-known Potential Source Areas - PSA - in the Southern Hemisphere) to fit the REE patterns measure in EDC data[1]. Complemented by Monte Carlo simulations to account for analytical uncertainties and by evaluation of goodness-of-fit, our model quantifies the respective contribution of the dust sources (regrouped by large PSA like Patagonia, Africa, S-E Australia, New Zealand and Puna-Altiplano) deposited in EDC ice core between 2.9 and 33.7 kyr at a centennial resolution.

Our provenance record reveals that a major shift in dust provenance occurred at ~14.5-kyr BP during which the contribution of Patagonia (PAT – the main supplier of dust of the Last Glacial Maximum -LGM) declined from   ̴55% to 35% (% of total dust deposition) while African dust (SAF) became more prevalent from   ̴20% during LGM to   ̴40% after 14.5 kyr BP. As a matter of fact, the main supplier of dust in EDC during the Holocene is Southern Africa. We ascribe this abrupt shift to (i) long-lasting changes in the hydrology and of Patagonian rivers and (ii) to a sudden acceleration of sea-level rise between 14 and 15 kyr BP that submerged vast swathes of Patagonian continental shelf, triggering a decline in PAT dust supply to Antarctica. In turn, this induced a steep increase – in relative term - of SAF dust contribution in EDC.

Importantly,our record for EDC is very much consistent with our previous results for Epica Dronning Maud Land (EDML)[2] ice core showing the exact same shift (PAT for SAF dust) between 14 and 15 kyr BP. Yet, compared to EDML, EDC record shows generally larger contribution for SAF and lower PAT dust which seems logical considering the respective localization of EDML and EDC. Our results for EDC thus confirms the relationship between dust composition and eustatic sea level and also highlight the importance of African dust deposition in the Southern Indian ocean and in the adjacent sector of the Southern Ocean since 14 kyr. Our tracing method using REE patterns offers a new, high-resolution tool for the reconstruction of atmospheric paleo-circulation and paleoclimate in the Southern Hemisphere.

[1]Gabrielli et al., (2010), Quaternary Science Review 29, 1-2.

[2]Vanderstraeten et al., (2023), Science of the Total Environment 881, 163450

How to cite: Boxho, S., Mattielli, N., Vanderstraeten, A., Laruelle, G. G., Bory, A., Gabrielli, P., Gili, S., and Bonneville, S.: Reading dust provenance record in Epica Dome C Ice Core (EDC) of Antarctica reveals a shift from Patagonian to African sources through the last deglaciation (2.9 – 33.7 kyr), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-22132, https://doi.org/10.5194/egusphere-egu24-22132, 2024.

EGU24-3624 | ECS | Orals | ITS2.8/AS4.10

Discriminators of Antarctic Atmospheric River Environments             

Rebecca Baiman, Andrew C. Winters, Benjamin Pohl, Vincent Favier, Jonathan D. Wille, and Kyle R. Clem

Although rare, atmospheric rivers (ARs) substantially influence the interannual variability of Antarctic surface mass balance. We identify characteristics unique to AR environments by comparing (1) AR, (2) Analog (environments that feature high-low pressure couplets, similar to AR environments, but no AR), and (3) Top AR (high-precipitation AR timesteps) during 1980–2019 around Antarctica. We find significant differences between AR and Analog environments including more intense and poleward-shifted mid-tropospheric geopotential height couplets as well as larger atmospheric moisture anomalies. We find similar significant enhancement in synoptic-scale dynamic drivers of Top ARs compared to AR environments, but no significant difference in local integrated water vapor anomalies. Instead, our results highlight the importance of large-scale dynamic drivers of Top AR timesteps, including connections between high-precipitation ARs and Rossby waves excited by tropical convection. This deeper understanding of Antarctic AR environments provides context for interpreting future changes to the Antarctic surface mass balance.

How to cite: Baiman, R., Winters, A. C., Pohl, B., Favier, V., Wille, J. D., and Clem, K. R.: Discriminators of Antarctic Atmospheric River Environments            , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3624, https://doi.org/10.5194/egusphere-egu24-3624, 2024.

EGU24-3880 | ECS | Orals | ITS2.8/AS4.10 | Highlight

Future Atmospheric Rivers in Antarctica using CMIP6-IPSL model : intensity and impacts 

Léonard Barthelemy, Francis Codron, Vincent Favier, and Jonathan Wille

Atmospheric Rivers (AR) are extreme hydrological events that have strong impacts on the different components of the Antarctic ice sheet surface mass balance (SMB), through both snow accumulation and surface melt due to heating and rain. Their evolving characteristics are therefore important to understand for an accurate prediction of future SMB changes.

We use here an ensemble of simulations of the mid-21st century climate using the IPSL-CM6 model. The future Antarctic ARs are identified using a detection algorithm adapted to the region, and taking into account in the detection threshold (based on moisture fluxes) the rising background moisture in a warmer climate. While a constant detection threshold leads to a continuous increase of the number of ARs detected, the use of this adaptative threshold leads instead to a relatively stable frequency of occurence, but with a larger penetration over Antarctica (+5% occurence over the continent). In addition, a wave number 3 component appears in the future change in frequency, as well as in AR-related snowfall.

While the number of ARs does not change much, their intensity, as measured by the associated water vapor transport, increases in line with the Clausius-Clapeyron relation. Their different impacts on the SMB also become larger, with both increasing snowfall, and surface melt and rainfall in the coastal regions. The direct effect on the SMB is however dominated by the increase in snow accumulation.

How to cite: Barthelemy, L., Codron, F., Favier, V., and Wille, J.: Future Atmospheric Rivers in Antarctica using CMIP6-IPSL model : intensity and impacts, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3880, https://doi.org/10.5194/egusphere-egu24-3880, 2024.

EGU24-6344 | Orals | ITS2.8/AS4.10

Characteristics of surface melt potential over Antarctic ice shelves based on regional atmospheric model simulations of summer air temperature extremes from 1979/80 to 2018/19 

Andrew Orr, Pranab Deb, Kyle Clem, Ella Gilbert, David Bromwich, Fredrik Boberg, Steve Colwell, Nicolaj Hansen, Matthew Lazzara, Priscilla Mooney, Ruth Mottram, Masashi Niwano, Tony Phillips, Denis Pishniak, Carleen Reijmer, Willem Jan van de Berg, Stuart Webster, and Xun Zou

We calculate a regional surface “melt potential” index (MPI) over Antarctic ice shelves that describes the frequency (MPI-freq, %) and intensity (MPI-int, K) of daily maximum summer temperatures exceeding a melt threshold of 273.15 K. This is used to determine which ice shelves are vulnerable to melt-induced hydrofracture and is calculated using near-surface temperature output for each summer from 1979/80 to 2018/19 from two high-resolution regional atmospheric model hindcasts (using the MetUM and HIRHAM5). MPI is highest for Antarctic Peninsula ice shelves (MPI-freq 23-35%, MPI-int 1.2-2.1 K), lowest (2-3%, < 0 K) for Ronne-Filchner and Ross ice shelves, and around 10-24% and 0.6-1.7 K for the other West and East Antarctic ice shelves. Hotspots of MPI are apparent over many ice shelves, and they also show a decreasing trend in MPI-freq. The regional circulation patterns associated with high MPI values over West and East Antarctic ice shelves are remarkably consistent for their respective region but tied to different large-scale climate forcings. The West Antarctic circulation resembles the central Pacific El Niño pattern with a stationary Rossby wave and a strong anticyclone over the high-latitude South Pacific. By contrast, the East Antarctic circulation comprises a zonally symmetric negative Southern Annular Mode pattern with a strong regional anticyclone on the plateau and enhanced coastal easterlies/weakened Southern Ocean westerlies. Values of MPI are 3-4 times larger for a lower temperature/melt threshold of 271.15 K used in a sensitivity test, as melting can occur at temperatures lower than 273.15 K depending on snowpack properties.

How to cite: Orr, A., Deb, P., Clem, K., Gilbert, E., Bromwich, D., Boberg, F., Colwell, S., Hansen, N., Lazzara, M., Mooney, P., Mottram, R., Niwano, M., Phillips, T., Pishniak, D., Reijmer, C., van de Berg, W. J., Webster, S., and Zou, X.: Characteristics of surface melt potential over Antarctic ice shelves based on regional atmospheric model simulations of summer air temperature extremes from 1979/80 to 2018/19, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6344, https://doi.org/10.5194/egusphere-egu24-6344, 2024.

EGU24-6416 | ECS | Posters on site | ITS2.8/AS4.10 | Highlight

Modelling the Impacts of Summer Extreme Precipitation Events on Surface Mass Balance in Southern Greenland 

Nicole Loeb, Alex Crawford, and Julienne Stroeve

The warming Arctic climate drives an increased potential for extreme precipitation events. Here, extreme precipitation is defined as the top 5% of daily accumulations where at least 1 mm occurred. Case studies have shown that these events can have substantial impacts on the regional surface mass balance (SMB) of the Greenland Ice Sheet. Depending on the precipitation phase and timing, mass may be added via the precipitation, or melt may be enhanced from rainfall, driving increased runoff and ice discharge. Southern Greenland is an area undergoing substantial change in terms of both intense precipitation occurrence and SMB, so it is essential to understand their relationship as the climate warms.

Observations of extreme precipitation are limited due to its rare nature and sparse observational networks. Modelling studies can shed light on broader changes by filling in data gaps and providing future projections, allowing for a deeper look into physical linkages and changes. Here, historical and future simulations of the Regional Atmospheric Climate Model (RACMO) and Variable-Resolution Community Earth System Model (VR-CESM) are used. Representation of summer extreme precipitation events in southern Greenland in VR-CESM and RACMO is explored and compared through case studies. Key variables, including precipitation phase, runoff, and overall SMB are evaluated to discern potential impacts in each model. Events in the historical and future (following SSP5-8.5) periods are investigated to determine whether the response to events of similar magnitude and seasonal timing differs in a warmer climate.

Furthermore, an approximation of how these extreme precipitation events influence seasonal SMB is presented by assessing the ratio of the event-related anomaly to the cumulative seasonal SMB anomalies. Comparisons of event-specific contributions with broader seasonal variations shed light on the connection between short-term meteorological events and longer-term climatic shifts in shaping Greenland's SMB.

How to cite: Loeb, N., Crawford, A., and Stroeve, J.: Modelling the Impacts of Summer Extreme Precipitation Events on Surface Mass Balance in Southern Greenland, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6416, https://doi.org/10.5194/egusphere-egu24-6416, 2024.

EGU24-7689 | ECS | Posters on site | ITS2.8/AS4.10

Quantification of the Greenland ice sheet surface mass balance using high-resolution CARRA data and in-situ observations 

Verena Mülder, Maurice van Tiggelen, and Carleen Tijm-Reijmer

This project contributes to the understanding of the surface mass and energy balance of the Greenland ice sheet, by evaluating the accuracy of the Copernicus Arctic Regional Reanalysis (CARRA) dataset against in-situ observations collected from automatic weather stations (AWS) positioned along the K-transect on the Greenland ice sheet.  Additionally, the results are compared with the Regional Atmospheric Climate Model 2.3p2 (RACMO2.3p2), containing a spatial resolution of 11 km against CARRA’s 2.5 km horizontal resolution. This research thereby emphasizes the improvements and shortcomings of the new CARRA dataset for reproducing the near surface climatology on the Greenland ice sheet.

The validated CARRA dataset is then used as forcing in a surface energy balance model, enabling the determination of the surface mass and energy balance components of the Greenland ice sheet at higher spatial resolution. The modelled surface mass balance is evaluated against in-situ measurements along the K-transect, and to other regions where in situ measurements are available. 

Preliminary results show that the CARRA dataset accurately reproduces radiative fluxes, such as short- and longwave radiation components, as well as turbulent fluxes, including temperature and wind gradients. These accurate representations provide updated, high-resolution gridded fields of the Greenland ice sheet’s climate, and are crucial for precise modelling of the melt and runoff dynamics of the Greenland ice sheet through the surface energy balance model.

This research thereby presents an updated high-resolution depiction of the Greenland ice sheet climate and energy balance, which can be used as a foundation for future projections of the Greenland Ice Sheet in forthcoming studies.

How to cite: Mülder, V., van Tiggelen, M., and Tijm-Reijmer, C.: Quantification of the Greenland ice sheet surface mass balance using high-resolution CARRA data and in-situ observations, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7689, https://doi.org/10.5194/egusphere-egu24-7689, 2024.

EGU24-10419 | Posters on site | ITS2.8/AS4.10

Unraveling the Forcings behind West Antarctic Summer Melt: CMIP6 Perspectives on Remote Climate Drivers 

Yingfei Fang, James Screen, Song Yang, Xiaoming Hu, and Shuheng Lin

The circulation pattern conducive to summer surface melt over the Ross Ice Shelf in West Antarctica is intricately linked to sea surface temperature anomalies in the tropical central-eastern Pacific associated with El Niño, along with atmospheric heating anomalies over western Australia. Our study utilizes 61 models within the Coupled Model Intercomparison Project (CMIP6) and reveals their ability to effectively simulate these primary drivers that influence the circulation pattern over West Antarctica.

El Niño emerges as a crucial force shaping atmospheric circulation anomalies over the Ross Sea, inducing two distinct wave trains toward West Antarctica—one originating from the central Pacific and the other from the Maritime Continent. Furthermore, irrespective of El Niño, anomalous atmospheric heating over western Australia emerges as another significant forcing, initiating a Rossby wave train that extends from subtropical Australia to the Ross Sea.

This comprehensive assessment advances our understanding of the remote forcings steering climate variability in West Antarctica during the austral summer. Moreover, it instills confidence in the predictability of future climate changes in this region.

How to cite: Fang, Y., Screen, J., Yang, S., Hu, X., and Lin, S.: Unraveling the Forcings behind West Antarctic Summer Melt: CMIP6 Perspectives on Remote Climate Drivers, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10419, https://doi.org/10.5194/egusphere-egu24-10419, 2024.

EGU24-10663 | ECS | Orals | ITS2.8/AS4.10 | Highlight

Contribution of blowing snow sublimation to the surface mass balance of Antarctica 

Srinidhi Gadde and Willem Jan van de Berg

Blowing snow transport is an essential polar boundary layer process and constitutes the major ablation term in the Antarctic ice sheet's surface mass balance (SMB). Here, we present an update to the blowing snow model in the Regional Atmospheric Climate Model (RACMO), version 2.3p3, to include the effect of blowing snow sublimation and transport in the prognostic equations for temperature and water vapour. Updates rectify the numerical artefacts in the modelled blowing snow flux variation with wind speed. Updates include the replacement of uniformly distributed ice particle radius, which limited the maximum ice particle radius to ≤ 50 μm, with an exponentially increasing ice particle radius distribution to include all the relevant range of radii between 2 to 300 μm without any additional computational overhead. We compare the model results against the observations from site D47 in Adèlie Land, East Antarctica. These updates correct the numerical artefacts observed in the previous model results, and RACMO successfully predicts the power-law variation of the blowing snow transport flux with wind speed. Updates also improve the prediction of the magnitude of the blowing snow fluxes. In addition, at site D47, we obtain an average blowing snow layer depth of 230±116 μm, which falls within the range of values obtained from satellite observations. A qualitative comparison of the simulated blowing snow frequency from RACMO with CALIPSO satellite observations shows that the simulated frequency matches well with the satellite product. Compared to the previous model version for the period 2000–2010, the contribution of integrated blowing snow sublimation is increased by 30%, with a yearly average of 176±4 Gt yr-1. The increase amounts to 1.2% reduction in the integrated SMB of the Antarctic ice sheet. The updates also introduce changes in the climatology of blowing snow in Antarctica. Specifically, we observe significant changes in the sublimation of interior regions of the escarpment zone of Antarctica.

How to cite: Gadde, S. and van de Berg, W. J.: Contribution of blowing snow sublimation to the surface mass balance of Antarctica, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10663, https://doi.org/10.5194/egusphere-egu24-10663, 2024.

EGU24-11814 | Posters on site | ITS2.8/AS4.10 | Highlight

Large-scale drivers of the exceptionally low winter Antarctic Sea Ice Extent in 2023 

Monica Ionita-Scholz

The year 2023 marked a turning point for the Antarctic region, as the Southern Hemisphere experienced a significant reduction in its sea ice cover, with a record-breaking sea ice minimum in July 2023 of ~2.4 million square kilometers below the long-term mean. This study investigates the drivers behind this exceptional event, by combining observational, satellite and reanalysis data. Throughout the year, the Antarctic Sea ice extent broke record after record, ranking as the lowest sea ice on record from January to September, with the exception of March and April. The exceptionally low sea ice extent from May to August was mainly driven by the prevalence of a zonal wave number 3 pattern, with alternating surface high- and low-pressure systems, which favored the advection of heat and moisture, especially over the Ross Sea (RS), Weddell Sea (WS), and Indian Ocean (IO). From May 2023 to August 2023, record-breaking low sea ice extent and high temperatures were recorded, and the most affected regions were RS, WS, and IO. Over the Weddell Sea, temperature anomalies of up to 10°C have been observed from May to July, whereas over the Ross Sea, temperature anomalies of up to 10°C have been observed, especially in July and August. A regime shift in the Antarctic Sea ice, as well as in the average mean air temperature and subsurface ocean temperature over the Weddell Sea, was detected around 2015. The analysis revealed complex interactions between atmospheric circulation patterns, oceanic processes, and their implications for variability and change in Antarctic Sea ice. Understanding the underlying mechanisms of these extreme events provides crucial insights into the changing dynamics of Antarctic Sea ice and its broader climatic significance.

How to cite: Ionita-Scholz, M.: Large-scale drivers of the exceptionally low winter Antarctic Sea Ice Extent in 2023, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11814, https://doi.org/10.5194/egusphere-egu24-11814, 2024.

EGU24-12356 | ECS | Orals | ITS2.8/AS4.10

Understanding local and large-scale changes in the Arctic and the effect on Cyclone activity 

Chelsea Parker, Melinda Webster, Priscilla Mooney, Elina Valkonen, and Linette Boisvert

The Arctic is warming four times faster than the rest of the globe, with a concurrent rapid loss of sea ice extent and thickness. Cyclones are synoptic weather events that transport heat and moisture into the Arctic, and have complex impacts on sea ice, marine ecosystems, and socio-economic activities. However, the effect of a changing climate on Arctic cyclone behavior remains poorly understood. This study uses a combination of reanalysis data, cyclone tracking techniques, and high-resolution numerical modeling to explore the effect of recent and future climate change on Arctic cyclone behavior across seasons.

This work first examines the relative importance of changes in local surface conditions and turbulent fluxes and broader changes in pressure patterns, steering flow, and baroclinicity with recent climate change in governing cyclone frequency, intensity, and trajectories. Our analysis suggests that cyclone activity is shifting throughout the autumn with competing effects of turbulent fluxes and large-scale conditions. With recent climate change, sea ice is declining, and surface temperatures and turbulent fluxes are increasing, resulting in slight increases in Autumn cyclone intensity. In early autumn, cyclone frequency and trajectories are strongly governed by the large-scale flow despite increases in surface turbulent fluxes and baroclinicity. By late autumn, land-sea temperature contrast is increasing with sea ice loss, and changes in baroclinicity and large-scale flow work in concert to increase cyclone activity in the Arctic.

This work then uses regional, high resolution, convection-permitting Weather Research and Forecasting (WRF) model simulations to demonstrate the sensitivity of cyclone characteristics to recent and future climate change. Simulations with downscaled CMIP6 global climate projections reveal that future sea ice loss and increasing surface temperatures by the year 2100 drive large increases in the near-surface vertical temperature gradient, sensible and latent heat fluxes into the atmosphere, and deep convection during spring cyclone events. The changes in the future (warmer) climate alter cyclone trajectories and increase and prolong intensity, with significantly increased wind speeds, temperatures, and precipitation. Such changes in cyclone lifecycles and characteristics may exacerbate sea ice loss and Arctic warming through positive feedback mechanisms. The increasing extreme nature of weather events such as Arctic cyclones has important implications for atmosphere-ice-ocean interactions in the new Arctic.

How to cite: Parker, C., Webster, M., Mooney, P., Valkonen, E., and Boisvert, L.: Understanding local and large-scale changes in the Arctic and the effect on Cyclone activity, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12356, https://doi.org/10.5194/egusphere-egu24-12356, 2024.

EGU24-12942 | Orals | ITS2.8/AS4.10 | Highlight

Abrupt increase in Greenland melt governed by atmospheric wave change 

Rune Grand Graversen, Tuomas Heiskanen, Richard Bintanja, and Heiko Goelzer

Recent Greenland ice-sheet melt constitutes an alarming contribution to global sea-level rise. Observations indicate an approximate balance of the ice sheet until the late 1990s, after which a strong increase in melting occurred. This cannot be attributed linearly to gradually-increasing global warming. Instead the abrupt shift is suggested to be linked to atmospheric circulation changes, although causality is not fully understood. Here we show that changes of atmospheric waves over Greenland have significantly contributed to the shift into a strong melting state. This is evident from applying a newly-developed methodology effectively decomposing atmospheric flow patterns into parts associated with Rossby waves and smaller perturbations. A westerly-flow reduction, consistent with anthropogenic Arctic warming, affected transports by atmospheric waves and led to a decrease in precipitation and an increase in surface warming, contributing to ice-sheet mass loss, in particular over the southwestern regions. Hence the Greenland ice-sheet melt is an example of a climate response non-linearly coupled to global warming.

How to cite: Graversen, R. G., Heiskanen, T., Bintanja, R., and Goelzer, H.: Abrupt increase in Greenland melt governed by atmospheric wave change, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12942, https://doi.org/10.5194/egusphere-egu24-12942, 2024.

EGU24-13437 | Orals | ITS2.8/AS4.10

Atmospheric river brings warmth and rainfall to the northern Antarctic Peninsula during the mid-austral winter of 2023 

Deniz Bozkurt, Jorge F. Carrasco, Raul R. Cordero, Francisco Fernandoy, Alvaro Gómez, Benjamin Carillo, and Bin Guan

Recent research has extensively analyzed summertime atmospheric river (AR) events in the Antarctic Peninsula (AP) using ground-based and atmospheric observations, yet a significant gap remains in understanding the occurrence and impacts of ARs during the Antarctic winter. This study focuses on an extraordinary warming event in the AP between 1 and 3 July 2023, utilizing data from recent wintertime field campaigns and ERA5 reanalysis. On 2 July, the Frei station in northern AP recorded a remarkable daily maximum near-surface air temperature of 2.7°C, significantly higher than the mean winter value of -3.8°C and surpassing the winter 99th percentile of 1.8°C. On 2-3 July, at least 6 hours of liquid precipitation were recorded, as corroborated by ERA5 data, leading to notable rain-on-snow and melt events. This occurrence challenges conventional expectations, as liquid precipitation during the depths of the southern winter is exceedingly rare in Antarctica. Radiosonde observations indicated a substantial elevation of the freezing level to about 650 meters, a stark contrast to the 20 meters observed before the event. These observations also revealed a moist and nearly saturated atmospheric profile. The event was synoptically characterized by a distinct trough over the Bellingshausen Sea and a pronounced northwest-southeast oriented blocking ridge from the southwestern Atlantic to the Weddell Sea, resulting in a dipole-like pressure pattern around the AP. These conditions were instrumental in the development of an AR with a north-to-south flow. This flow was marked by maximum integrated vapor transport values exceeding 500 kg m-1 s-1, channeling warm, moisture-laden air from continental South America towards the AP. A long-term winter trend analysis reveals a significant strengthening of the dipole pattern, which correlates with increased frequencies of ARs and consequently leads to notable warm temperature anomalies over the northern AP. The study underscores the importance of understanding the complex relationship between local, synoptic conditions, and the dynamics of ARs in influencing winter climate patterns in the AP. This study's ongoing high-resolution simulations and isotope analysis aim to uncover the detailed characteristics and isotopic signatures of this extraordinary warming event, enhancing our understanding of its origins and impacts.

How to cite: Bozkurt, D., Carrasco, J. F., Cordero, R. R., Fernandoy, F., Gómez, A., Carillo, B., and Guan, B.: Atmospheric river brings warmth and rainfall to the northern Antarctic Peninsula during the mid-austral winter of 2023, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13437, https://doi.org/10.5194/egusphere-egu24-13437, 2024.

EGU24-14236 | ECS | Posters on site | ITS2.8/AS4.10

Visibility and Fog Synoptic and Mesoscale Variability over Marambio Base, Antarctic Peninsula 

Mauricio Jimenez Garcia, John Mejia, Juan Jose Henao, Noemi Troche, Alvaro Rafael Martinez, and Kevin Alexander Chicaeme

Summertime aviation, research, and field campaigns in Marambio Base, Antarctic Peninsula (AP), and surrounding areas, are frequently affected by low visibility and fog.  Additionally, upper-air soundings in the area are launched weekly, limiting the study of the synoptic time scale variability of these hazards. A special field campaign was designed to fill this observational gap, and to examine the drivers of fog events.  A three week-long intensive observation campaign during February 2023 successfully captured the evolution and vertical structure of two multiday fog episodes that were later interrupted by westerly Foehn winds, favoring sudden warming, drying, and clear skies over eastern flank of the AP.  This dataset is also used to evaluate and assess the skill of regional climate simulations using the Global Forecasting Systems data and the Polar-WRF model.  We carried out the later modeling activities to examine the mesoscale characteristics of the interplay between the fog episodes and the Foehn winds.  This study shows the analyses of the special upper-air observations and modeling simulations, with emphasis in the description of the observable and predictable mesoscale ingredients and their relationship with synoptic forcings. We found a cycle that modulates visibility and fog: (i) low visibility ahead of the synoptic trough bringing a deep northerly moistening and warming dominating warm advection fog on the northeastern side of the AP; (ii) an enhanced mid-level inversion is formed by adiabatic warming due to westerly winds on the lee side of the AP limiting mixing; (iii) visibility increases as Foehn winds warm up and dry out the low-level atmosphere west of the AP; (iii) a meso-low (heat-low) developed on the lee side of the AP that later moved eastward with the synoptic trough, bringing cooler southerly air masses that lower visibility and favoring cold advection fog; finally (iv) cooling is maintained ahead of the synoptic ridge sustaining cold advection fog.  Polar-WRF helped us diagnose the mechanistic nature of the fog events, while providing intricate multiscale connections modulating visibility in the region.

How to cite: Jimenez Garcia, M., Mejia, J., Henao, J. J., Troche, N., Martinez, A. R., and Chicaeme, K. A.: Visibility and Fog Synoptic and Mesoscale Variability over Marambio Base, Antarctic Peninsula, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14236, https://doi.org/10.5194/egusphere-egu24-14236, 2024.

EGU24-15041 | ECS | Posters on site | ITS2.8/AS4.10

Comparison of Atmospheric Large-scale Patterns during two Warming Periods in Greenland in the last 100 years  

Florina Roana Schalamon, Jakob Abermann, Sebastian Scher, Andreas Trügler, and Wolfgang Schöner

The air temperature (AT) increased during the Early 20th Century Warming (ETCW), especially in the Arctic, with a similar trend as during the present warming period. This AT increase is observed while investigating the annual AT anomaly of historic observations provided by the Danish Meteorological Institute (DMI) and of the zonal average of Greenland based on reanalysis data (NOAA 20CRv3). 

We define two distinct warming periods (1922–1932 and 1993–2007) for Greenland with a continuous increase in the AT anomaly. The increase is the largest at the northernmost observations in Upernavik and the smallest at the easternmost observations in Tasiilaq. The zonal average trend (Sen's slope) of AT increase in Greenland is 0.1°C/year in both periods, exceeding the global AT trend. Examining the spatial distribution of the AT trend in the reanalysis data during the warming periods reveals a warming hotspot in the sea in front of the West Coast of Greenland, which is more dominant in the second period. Nonetheless, the positive trend is rather homogeneous over Greenland, indicative of large-scale influences rather than localized phenomena. This motivates our study to analyse and compare the structure of atmospheric large-scale patterns (LSP) during these two warming periods. 

To do this, we use an unsupervised self-organizing maps (SOM) algorithm to highlight prevalent LSPs based on the reanalysis of the geopotential height of 500hPa. SOM is an artificial neural network used for clustering data into distinct groups, so-called nodes, by reducing its dimensionality. In the first approach to compare both periods, the frequency of the nodes is evaluated, meaning comparing how often a specific prevalent LSP defined by SOM occurs in the one and the other warming periods. A preliminary result is that there are significant differences in the occurrence of the nodes. Further exploration of the difference in node frequency and setting them into a meteorological context are the primary objectives of this study. 

Additionally, we aim to establish links between LSP and anomalies of atmospheric variables (such as air temperature) to investigate whether similar LSP are accountable for similar deviations. This will deepen our understanding of the atmospheric dynamics during Greenland's warming periods, which affect the cryosphere.  

How to cite: Schalamon, F. R., Abermann, J., Scher, S., Trügler, A., and Schöner, W.: Comparison of Atmospheric Large-scale Patterns during two Warming Periods in Greenland in the last 100 years , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15041, https://doi.org/10.5194/egusphere-egu24-15041, 2024.

EGU24-16074 | ECS | Posters on site | ITS2.8/AS4.10

Correcting uncertainty estimations of  20th-century reanalysis with independent historic datasets in the arctic 

Sebastian Scher, Florina Schalamon, Jakob Abermann, and Andreas Trügler

20th-century reanalysis datasets are an invaluable tool for understanding the climate from the beginning of the last century up to the present. They provide a best guess of the atmospheric state, based on a combination of observations and numerical modeling. Contrary to other reanalysis datasets, however, 20th-century reanalysis uses solely surface observations and is thus much less constrained. Consequently, the uncertainty of the analysis is high compared to reanalysis datasets for the satellite era. In the Arctic, where observations are even more sparse than in other parts of the globe, this issue is especially severe. Therefore, a robust estimation of the uncertainty of the reanalysis product is essential. While state of the art 20th-century reanalysis datasets provide some measures of uncertainty, they do not cover the whole uncertainty. We test whether historic independent measurements – that were not assimilated in the reanalysis – can be used to get a more reliable uncertainty estimation of temperature time-series over the last century. For this aim, we use recently digitized in-situ measurements from Alfred Wegener’s last Greenland expedition.  Finally, we assess how the outcome of testing typical hypotheses – such as warming trends or comparison of different periods - is affected when considering the new uncertainty estimations 

How to cite: Scher, S., Schalamon, F., Abermann, J., and Trügler, A.: Correcting uncertainty estimations of  20th-century reanalysis with independent historic datasets in the arctic, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16074, https://doi.org/10.5194/egusphere-egu24-16074, 2024.

EGU24-16268 | ECS | Orals | ITS2.8/AS4.10

Atmospheric drivers of the rapid decline of Novaya Zemlya's glaciers 

Jan Haacker, Bert Wouters, Xavier Fettweis, Jason Box, and Isolde Glissenaar
The glaciers on the High Russian Arctic archipielago Novaya Zemlya have been losing roughly 10 Gt/yr over the past decade, 5 Gt/yr more than in the one before. While earlier research pointed to ocean discharge as driver of the acceleration, we present new results that show that foehn events, triggered by atmospheric rivers, led to the most severe melt events in the recent times. We use output of the regional atmospheric model MAR, together with geodetic observations from CryoSat-2, and reanalysis data (CARRA, ERA5, MERRA-2) to show that roughly 70 % of the melt occurs during atmospheric rivers episodes. Between 1990 and 2022, 45 of the 54 days with more than 1 Gt melt were accompanied by foehn winds. We conclude that the representation of atmospheric rivers and foehn winds in models is crucial for accurate projections of the future glacier evolution.

How to cite: Haacker, J., Wouters, B., Fettweis, X., Box, J., and Glissenaar, I.: Atmospheric drivers of the rapid decline of Novaya Zemlya's glaciers, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16268, https://doi.org/10.5194/egusphere-egu24-16268, 2024.

EGU24-18137 | ECS | Orals | ITS2.8/AS4.10 | Highlight

Melt ponds and atmosphere-ice-ocean exchange in the UK Met Office Unified Model during the Arctic Summertime Cyclones field campaign 

Christopher Barrell, Ian Renfrew, John Methven, and Andrew Elvidge

Melt ponds play a key role in the Arctic sea-ice surface energy budget. Their reduced albedo compared to the surrounding ice and snow surfaces increases the absorption of short-wave radiation and enhances ice melt. Further, melt ponds affect atmosphere-ice-ocean surface turbulent exchanges of heat, moisture and momentum, which influence the structure of the overlying boundary layer. 

Simulation of melt ponds and surface exchange over sea ice in coupled numerical weather prediction models depends on parameterization schemes that need further development. However, the relationship between sea ice surface conditions and the overlying boundary layer is difficult to constrain due to the lack of in-situ observations in Arctic regions. 

We carried out the Arctic Summertime Cyclones project field campaign in July-August 2022 to make observations of sea-ice surface exchange and cyclone dynamics. Using the British Antarctic Survey MASIN Twin Otter aircraft we observed a range of sea ice surface types, some with a very high melt pond fraction during warm melt conditions, and the overlying atmospheric boundary layer. 

Using these observations to evaluate forecasts from the UK Met Office Unified Model, we show that a combination of deficiencies in the model sea ice field, melt pond representation and surface exchange parameterizations are linked to errors in the simulated boundary layer structure. In particular, the model consistently exhibits surface temperature and albedo biases over sea ice with melt ponds that act as sources of error in the surface energy budget.

How to cite: Barrell, C., Renfrew, I., Methven, J., and Elvidge, A.: Melt ponds and atmosphere-ice-ocean exchange in the UK Met Office Unified Model during the Arctic Summertime Cyclones field campaign, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18137, https://doi.org/10.5194/egusphere-egu24-18137, 2024.

EGU24-18598 | ECS | Posters on site | ITS2.8/AS4.10

Projection of near-surface winds in Antarctica using ESMs downscaled by a regional atmospheric model (MAR) 

Cécile Davrinche, Cécile Agosta, Charles Amory, Christoph Kittel, and Anaïs Orsi

Antarctica's climate is unique, partly due to strong westerlies on the ocean and strong easterlies at the ice sheet margins. On the continent, near-surface winds play a major role in shaping the climate of the continent as they influence sea-ice formation, the amount of precipitation reaching the ground or the stability of the boundary layer. They result from both large-scale and surface forcings, whose relative magnitude and future evolution is yet uncertain.

We show an evaluation at present day of a selection of Earth System Models (ESMs) from CMIP6 and their downscalings by the regional atmospheric model MAR. The ESMs have been selected based on their demonstrated ability to represent fairly well the southern hemisphere general atmospheric circulation. They are thus expected to have a good representation of the large-scale forcing of near-surface wind. We present a framework for evaluating against field observations how accurately different CMIP6 products are able to represent near-surface winds over Antarctica. We also present the selection process for the automatic weather stations to use and the metrics for the evaluation.

Then, we investigate the future evolution of near-surface winds on the Antarctic continent as projected by the ESMs and their downscalings. We show maps of their projected changes up to 2100 and investigate whether these changes are significant with regards to the internal variability of the ESMs and their historical biases. This evaluation provides us with a first step towards characterizing the future evolution of near-surface winds in Antarctica. Further work will then be undertaken to provide a more comprehensive analysis of their potential drivers, including the evolution of both large-scale and surface forcings.

How to cite: Davrinche, C., Agosta, C., Amory, C., Kittel, C., and Orsi, A.: Projection of near-surface winds in Antarctica using ESMs downscaled by a regional atmospheric model (MAR), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18598, https://doi.org/10.5194/egusphere-egu24-18598, 2024.

EGU24-18912 | Posters on site | ITS2.8/AS4.10

Evaluating a state of the art, internationally coordinated pan-Arctic regional climate model ensemble 

Priscilla Mooney, Alok Samantaray, Chiara De Falco, and Ruth Mottram and the PolarRES regional climate modellers

Within the Horizon 2020 project PolarRES, a new ensemble of regional climate simulations has been developed using the latest generation of regional climate models (RCMs) for the Arctic. These state-of-the-art RCMs downscale the ERA5 reanalysis over the period 2001-2020, covering the entire Arctic region at a grid spacings of approximately 12km. Furthermore, all simulations follow the Polar CORDEX protocol for the next generation of regional climate projections of the polar regions. This new ensemble of high-resolution climate simulations offers considerable opportunities to advance our understanding of the present-day climate of the Arctic. However, a first step to realising this potential is to evaluate the performance of the regional climate models, highlighting their strengths and limitations. This is also necessary for understanding and interpreting the future projections that will be generated by these RCMs using a novel storylines approach to downscale CMIP6 models.

The work presented here will focus on the simulations of the present-day climate driven by the ERA5 reanalysis. As part of the evaluation process, a clustering technique is applied to reanalysis data to identify regions with similar annual and seasonal characteristics of surface temperature and precipitation. This approach allows for a better understanding of the regional climates of the Arctic, provides a more physically consistent basis for model evaluation, and eases the investigation of model deficiencies in simulating regional scale forcings. This work will focus on the regionalisation of the Arctic for model evaluation and present preliminary results of the application of this regionalisation to the aforementioned Arctic climate simulations.

How to cite: Mooney, P., Samantaray, A., De Falco, C., and Mottram, R. and the PolarRES regional climate modellers: Evaluating a state of the art, internationally coordinated pan-Arctic regional climate model ensemble, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18912, https://doi.org/10.5194/egusphere-egu24-18912, 2024.

EGU24-20816 | Orals | ITS2.8/AS4.10

Surface melt over the Antarctic Peninsula: targeted observations capturing recent extreme events 

Irina V. Gorodetskaya, Claudio Durán-Alarcón, Penny Rowe, Xun Zou, Sangjong Park, and Vincent Favier

The recent two years have been marked by many regional climate-state extremes particularly over the southern polar region including record-high surface melt over the Antarctic Peninsula in February 2022 (Gorodetskaya et al., 2023; Zou et al., 2023), the strongest heatwave ever recorded over East Antarctica bringing extreme inland snowfall and coastal surface melt in March 2022 (Wille et al., 2024), and an extremely low Antarctic sea ice area observed in winter 2022 outpaced by the lowest record in winter 2023 (Purich and Doddridge, 2023). Increased magnitude and probability of occurrence of extreme events, along with their high impacts on the Antarctic surface mass balance require detailed understanding of the underlying large-scale, regional and local drivers, using comprehensive and high-resolution observations and modeling. Here we will present analysis of extreme surface melt events and their drivers based on targeted observations conducted during 2022-2023 over the northern Antarctic Peninsula, including two austral summer campaigns and the winter Year of Polar Prediction in the Southern Hemisphere (YOPP-SH) enhanced observational period. Cloud and precipitation profiles using radar and lidar measurements are analyzed together with thermodynamic state of the troposphere from radiosonde observations and surface radiative fluxes with a specific focus on the extreme warm events characterized by surface melt and/or rainfall. In particular, the February 2022 extreme warm event showed very high downwelling longwave flux (up to 350 W/m2) due to the low warm-base liquid-containing clouds. Frequent occurrence of supercooled liquid water with low and warm cloud-bases is characteristic of the site during both summer and winter seasons and plays an important role in surface melt events. Another key factor during warm events is the transition from snowfall to rainfall (both with height in the vertical column, indicated by melt layer height derived from the precipitation radar measurements, and with time over the course of the event). Using radiosonde profiling, we identify layers of maximum moisture and heat transport into the Antarctic Peninsula, which showed an outstanding magnitude during the hot spell in February 2022 associated with an intense atmospheric river and which we further compare to other observed warm events. Significant differences are found for cloud and precipitation properties between ground-based measurements and ERA5 reanalysis, prompting the use of state-of-art high-resolution observations to improve representation of relevant processes in the models particularly during surface melt events.

Funding acknowledgements: Portuguese Polar Program projects APMAR/TULIP/APMAR2; FCT projects MAPS and ATLACE; ANR project ARCA; KOPRI; NSF awards 2127632 and 2229392.

References:

Gorodetskaya et al. (2023): Record-high Antarctic Peninsula temperatures and surface melt in February 2022: a compound event with an intense atmospheric river. npj Clim Atmos Sci, https://doi.org/10.1038/s41612-023-00529-6

Purich and Doddridge (2023): Record low Antarctic sea ice coverage indicates a new sea ice state. Commun Earth Environ, https://doi.org/10.1038/s43247-023-00961-9

Wille et al (2024): The Extraordinary March 2022 East Antarctica “Heat” Wave. Part I: Observations and Meteorological Drivers. J. Climate, https://doi.org/10.1175/JCLI-D-23-0175.1.

Zou et al (2023): Strong warming over the Antarctic Peninsula during combined atmospheric River and foehn events: Contribution of shortwave radiation and turbulence. J. Geophys. Res. Atmos., https://doi. org/10.1029/2022JD038138 

 

How to cite: Gorodetskaya, I. V., Durán-Alarcón, C., Rowe, P., Zou, X., Park, S., and Favier, V.: Surface melt over the Antarctic Peninsula: targeted observations capturing recent extreme events, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20816, https://doi.org/10.5194/egusphere-egu24-20816, 2024.

CR8 – Short courses, Outreach, Communication

EGU24-337 | ECS | Posters on site | EOS2.4

Exploring the Depths: 3D Modeling of Ukraine's Caves through Terrestrial Laser Scanning and Digital Photogrammetry 

Mariia Oliinyk, Ihor Bubniak, Andrij Bubniak, Yevhenii Shylo, Anatolii Vivat, Valerii Mandzuk, and Taras Marko

This study presents a comprehensive exploration of Mlynky Cave in Ternopil Region and Medova Cave in Lviv, Ukraine, utilizing advanced geospatial technologies for 3D modeling. In the investigation of Mlynky Cave located in the Ternopil region, terrestrial laser scanning and digital photogrammetry techniques were employed. Concurrently, for the exploration of Medova Cave situated in the city of Lviv and renowned as a unique tourist attraction, a combination of terrestrial laser scanning and manual scanning using the Stonex X120 handheld laser scanner was implemented.

The application of terrestrial laser scanning and digital photogrammetry to Mlynky Cave facilitated the capture of high-resolution point clouds, resulting in a detailed three-dimensional representation of the cave's interior. The generated 3D model offers an immersive and navigable experience, allowing for remote exploration and analysis.

In contrast, the exploration of Medova Cave, being a distinctive tourist landmark in Lviv, involved a dual scanning approach. Terrestrial laser scanning contributed to the overall mapping of the cave, while the Stonex X120 handheld laser scanner was specifically employed for targeted and detailed scanning of intricate features. This combination of technologies resulted in a holistic 3D model that preserves the unique geological formations and historical significance of Medova Cave.

The findings from this research highlight the effectiveness of integrating various scanning methodologies, including terrestrial laser scanning and manual scanning with devices like the Stonex X120. The comprehensive 3D models not only contribute to scientific research and geological analysis but also serve as valuable tools for conservation efforts and educational purposes.

This study sets a precedent for the application of advanced scanning techniques in cave exploration, showcasing the adaptability of technology in addressing the diverse challenges encountered during fieldwork. As the boundaries of geospatial technology in subterranean environments continue to expand, this research contributes to the evolving methodologies in cave exploration, emphasizing the importance of a multi-faceted approach to documentation and preservation.

How to cite: Oliinyk, M., Bubniak, I., Bubniak, A., Shylo, Y., Vivat, A., Mandzuk, V., and Marko, T.: Exploring the Depths: 3D Modeling of Ukraine's Caves through Terrestrial Laser Scanning and Digital Photogrammetry, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-337, https://doi.org/10.5194/egusphere-egu24-337, 2024.

EGU24-646 | ECS | Orals | EOS2.4

A multidisciplinary and multi-institutional fieldwork in the Indian Himalaya for glacio-hydro-climatological studies 

Saurabh Vijay, Irfan Rashid, Argha Banerjee, and Chandan Sarangi

Himalaya is the longest mountain range in high-mountain Asia. The Himalaya is a home of thousands of glaciers that provide freshwater to a large population living in these countries. Glaciers are also a key indicator of regional and global climate change. Therefore, they are studied by a diverse set of researchers including glaciologists, climate scientists and hydrologists. Although satellite remote sensing and modelling communities have grown to address past, present and future changes in glaciers, field based studies are still vital. As the Himalayan range is shared by many bordering countries including India, China, Pakistan and Nepal, the strategies of conducting fieldwork vary depending on financial resources and trained manpower. As the fieldwork is time-consuming and expensive, new approaches are required.   

In this work, we show how we formed a  glaciological community of early-career permanent faculty or scientists in India to plan and conduct extensive fieldwork in a cost-effective manner. In the last three years, this group has conducted more than 5 joint field expeditions in the Indian Himalaya. Here, we highlight the challenges of multi-disciplinary and multi-institutional fieldwork. India is a huge country with diverse cultures, habits and languages. Different institutions have different policies of sharing field equipment. Proper planning and time management are critical, but not everyone, especially first-timers, do not understand their role in practice, which makes it very difficult for the field managers. Consistent measurements at the benchmark locations are very important, but this is often challenging as the institute/principal investigator-wise funding is limited and time-varying. Overcoming this scenario, this group developed a multi-institutional funding with efficient and resource sharing plan to set up a benchmark site in the Himalaya, which can be used for consistent monitoring for more than 10 years and address key science questions related to glaciology, hydrology and micro-climate. Such a project can be joined by any institute across the world and the partnering institute may add value by adding measurement plans and science objectives as well as benefit from existing capacities at the benchmark location. This group has previously hosted research partners from Germany and Australia. Some group members worked with several research groups and acted as a bridging partner between Indian and non-Indian researchers. A bridging partner played an important role to handle aspects related to expectations, working culture and training. 

In short, this study highlights the successes and challenges of such an efficient consortium that promote international collaboration, consistent monitoring and training of students in the field as well as knowledge and manpower exchange.     

How to cite: Vijay, S., Rashid, I., Banerjee, A., and Sarangi, C.: A multidisciplinary and multi-institutional fieldwork in the Indian Himalaya for glacio-hydro-climatological studies, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-646, https://doi.org/10.5194/egusphere-egu24-646, 2024.

EGU24-1090 | ECS | Posters on site | EOS2.4

Coming in from the cold: addressing the challenges experienced by women conducting remote polar fieldwork  

Elaine Runge, Maria Dance, Rebecca Julianne Duncan, Marjolein Gevers, Eleanor Maedhbh Honan, Florina Roana Schalamon, and Daniela Marianne Regina Walch

Title: Coming in from the cold: addressing the challenges experienced by women conducting remote polar fieldwork 

Authors:

1. Runge, Elaine – Danish Hydrological Institute, Marine & Coastal Field Services, Agern Allé 5, Hørsholm, Denmark

2. Dance, Maria - School of Geography and the Environment, University of Oxford, S Parks Rd, Oxford, UK

3. Duncan, Rebecca Julianne - School of Life Sciences, University Technology Sydney, Broadway Rd Ultimo, Sydney, Australia and Department of Arctic Biology, University Centre in Svalbard, Longyearbyen, Norway

4. Gevers, Marjolein - Institutes des dynamiques de la surface terrestre (IDYST), Université de Lausanne, Géopolis Mouline, 1015 Lausanne, Switzerland

5. Honan, Eleanor Maedhbh - Department of Geography, Durham University, Durham, DH1 3LE, UK

6. Schalamon, Florina Roana- Department of Geography and Regional Sciences, University of Graz, Heinrichstraße 36, 8010 Graz, Austria

7. Walch, Daniela Marianne Regina - Département de Biologie, Chimie et Géographie, Université du Québec à Rimouski, 300 Allée des Ursulines, QC G5L 3A1, Rimouski, Canada

Abstract:

Remote fieldwork is an important component of polar research within the physical and social sciences. Yet there is increasing recognition that the inherent logistical, physical, psychological, and interpersonal challenges of remote polar fieldwork are not felt equally across the polar research community, with minority groups often disproportionately affected. Although historically lacking diversity, the demographics of polar researchers have shifted and the way polar research is conducted has been changing in response. However, there are still barriers to equal participation. Removing these barriers would attract scientists from more diverse backgrounds and improve scientific outcomes. 

We explored the lived experiences of those who identify as women in polar fieldwork through a review of current literature and an anonymous survey, using existing networks to connect with women working in polar research. We synthesised and evaluated the literature and survey responses with regards to topics such as harassment, hygiene, inefficient communication, and gendered work expectations and responsibilities to form a holistic understanding of the key fieldwork challenges faced by women.  The majority of survey respondents (80%, n=373) had encountered negative experiences during fieldwork, with the most common and impactful issues relating to field team dynamics and communication, sexism, rest, and weather. Many other issues including fieldwork preparation, work expectations, harassment, and personal space and privacy were also raised by respondents. 

From the recent developments and critical points of action that we identified in the literature and the survey, we propose strategies to remove barriers to participation and improve the experiences of women in polar fieldwork. These include strategies that are applicable on both an individual and organisational level. A diverse polar research community is imperative in order to address the challenges presented by current unprecedented climate change. Although we focussed on women’s experiences, through this study, we seek to advance the discourse on challenges faced by minorities in polar research. 

How to cite: Runge, E., Dance, M., Duncan, R. J., Gevers, M., Honan, E. M., Schalamon, F. R., and Walch, D. M. R.: Coming in from the cold: addressing the challenges experienced by women conducting remote polar fieldwork , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1090, https://doi.org/10.5194/egusphere-egu24-1090, 2024.

EGU24-2116 | Posters on site | EOS2.4

Virtual geology and virtual field trips 

Sara Carena, Anke Maria Friedrich, and Apoorv Avasthy

3D visualization skills are essential in geology, but although virtual 3D tools have been available for years, we have yet to fully integrate them in our courses. In addition, physical field trips not only present accessibility problems for students with limited mobility but can be a considerable financial burden on everyone. Covid restrictions accelerated and expanded a project we were already working on: creating a collection of 3D models of rocks and outcrops to be used as a training aid in the classroom. Travel restrictions, which at our institution included a yearlong complete ban of all field courses (including one-day trips), spurred us to expand the original concept to include also a full 3D virtual environment for students to carry out field trips and mapping exercises. In choosing our tools, we considered three factors: costs, time, and level of difficulty. That meant finding commercial software and hardware that was affordable, did not require programming or engineering skills, or special licenses (e.g. pilot license for large drone), using areas for which we already had a significant amount of material, and storing our 3D models on public platforms.

We created 3D models of hand samples and of key outcrops at several field locations that we normally visit in both Spain and Germany by acquiring photos and movies in the field using hand-held cameras and a small drone (which in Europe only requires insurance and operator's registration). We then processed imagery to produce scaled and georeferenced models with Metashape Pro. We used 3DVista Pro, originally designed for real estate showcasing, to produce immersive and interactive virtual field trips (VFTs). This software allowed us to link 3D models, which are stored on either Sketchfab or V3Geo, with videos, animations, photos, maps, text, and realistic sounds for each field scene. An e-learning module in the form of quizzes and game-like features can be incorporated too. We put together different types of VFT: show-and-tell standard VFTs and VFTs with a specific theme (e.g. unconformities), field exercises where students carry out measurements and observations both virtually and later in in the field, and complementary material for remote mapping courses. The reception from students has been positive, so we have kept using virtual tools after lockdown ended.

How to cite: Carena, S., Friedrich, A. M., and Avasthy, A.: Virtual geology and virtual field trips, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2116, https://doi.org/10.5194/egusphere-egu24-2116, 2024.

EGU24-4152 | Posters on site | EOS2.4

Learning from the past to shape the future: Environmental change, health and ecosystem services of Lake Malawi 

Annett Junginger, Friedemann Schrenk, and Christian Albrecht

Freshwaters and their biodiversity are in a state of crises across the world. Yet, these ecosystems are of global significance and provide resources on which, unlike in Europe, the livelihoods of millions of people depend in sub-Saharan Africa. Academics and African universities, however, lack experts for meeting multifold challenges of saving hotspots of aquatic biodiversity. Two consecutive three-week field schools, funded by Volkswagen Foundation, have been conducted in Malawi between 2022 and 2023 and were based on a sustainable network of African and German partnerships initiated during previous field schools. For the first time, the field schools were initiated and conceptualized by former African participants, who now have been acting as field school lecturers. These field schools aimed at training M.Sc. and Ph.D. students from DR Congo, Zambia, Sierra Leone, Malawi, Tanzania, Uganda and Germany in paleo-limnology, aquatic ecosystem science, human health, sustainable resource use and conservation. All participating countries have important freshwater ecosystems often shared with neighboring countries experiencing strong and multifold anthropogenic pressure. The magnitude of these impacts can only be understood by a combination of paleo-limnological methods with actualistic ecological water analyses. The field schools have covered major aspects ranging from a) reconstructing past conditions, b) assessing the present state to c) planning the future. A One Health framework has been adopted, making use of a citizen science approach to translate our field work findings into public outreach projects. The ultimate goals of the field schools were: a) Establishment of permanent network of interdisciplinary collaboration in paleo-environmental and aquatic sciences between African and German universities, b) Establishment of a sustainable teaching and research program in paleo-environmental and aquatic sciences applicable at African universities such as in Malawi, and c) Initiation of a long-term collaboration and of joint research and teaching projects between African scientific partners in the participating countries. This collaborative approach opens new perspectives on further research for the sake of better management of African inland waters in general. Most importantly, this cooperation exposed and equipped young researcher with skills for further research work in their own countries.

How to cite: Junginger, A., Schrenk, F., and Albrecht, C.: Learning from the past to shape the future: Environmental change, health and ecosystem services of Lake Malawi, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4152, https://doi.org/10.5194/egusphere-egu24-4152, 2024.

The DDE-Outcrop3D plays an important role in the digitization of geological resources. By digitally preserving, presenting, and reconstructing classic geological outcrops worldwide, the DDE-Outcrop3D Project broadens the user’s fieldwork visions and perspectives, allowing convenient access to fieldwork data, and helping users alleviate constraints imposed by time, distance, and financial resources. This project enables users to partake in immersive, online scientific explorations and educational endeavors, which has significance for public education in natural history museums. Firstly, digital outcrops provide scientific and reliable references for the exhibition scene designing of museum galleries related to geological environments and natural ecology. Secondly, digital outcrops visualize geological knowledge in multimedia forms within museum exhibits, enhancing interactivity with visitors and improving the knowledge density and display efficiency per unit area. Lastly, digital outcrops extend beyond museum confines, supporting museum-school collaborative scientific curricula aimed at cultivating autonomous geological research skills among K-12 students. This paper provides an in-depth example of the DDE-Outcrops3D application at the Chengdu Museum of Natural History (also known as the Museum of Chengdu University of Technology), offering a detailed exposition of the technology’s substantial value in public education for natural science museums.

How to cite: Guo, Y.: Visualization of DDE-Outcrop 3D to Promote Public Education in Natural History Museums, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4239, https://doi.org/10.5194/egusphere-egu24-4239, 2024.

EGU24-5166 | Posters on site | EOS2.4 | Highlight

Advancing Chinese Landscape Painting Research with DDE-Outcrop 3D Technology 

Jingwen Luo, Huohua Xiong, Chao Zhang, and Yao Guo

       The article discusses how the DDE Outcrop-3D provides a new perspective on the research and dissemination of ancient Chinese landscape painting.By combining the digital outcrop record with the textbook Painting Manual of the Mustard Seed Garden(1679) 1from Qing Dynasty, artists would explain diverse techniques of “Cun” used in Chinese landscape painting in a more visualized way.With the painting method of rocks (painting technique of “Cun” ) from the textbook and geological features such as rock structures and stratigraphical age shown by DDE Outcrop-3D mixed, artists would create more realistic, detailed and emotional paintings, as well as more artistic expression for the record of geological information.

      In the past, beginners could only learn the techniques of landscape painting with Painting Manual of the Mustard Seed Garden and ancient paintings, while they can have a deeper and more intuitive understanding of the traditional landscape painting expression according to DDE Outcrop-3D nowadays, acquiring more passionate visual feelings and emotional expression than copying ancient paintings when learning and creating. Based on the record of digital outcrop, some conventional Chinese landscape painting teaching and creation tasks can be accomplished indoor with new inspiration.  Traditional Chinese painting techniques can be used to depict the mountains, rivers, lakes and on this planet recorded by DDE Outcrop-3D. New possibilities will be created for artists and scholars to spread Chinese landscape painting culture in a scientific way.

       At the same time, geologists can classify the different rocks and outcrops presented by ancient Chinese painters based on DDE outcrop-3D records, providing new views for the study and appreciation of ancient Chinese paintings.In the past, artists could only interpret Chinese painting from Chinese characterized perspectives such as images, brush manner or ink manner, so the audience could not be personally on the scene and understand the original concept of "enjoyable for traveling and living" in Chinese landscape painting better.

      As a cutting-edge technology providing 3D visualization of geological and other natural phenomena, the application of DDE Outcrop-3D in the interdisciplinary field marks that it can not only play an important role in geological science, but also has significance for research, education and dissemination of traditional Chinese paintin

 1.The book had published in Europe as name of “The Tao of Painting” in 1957 . The book introduces the painting methods of various shaped rocks in Chinese landscape painting in detail, and is a book that systematically summarizes the Chinese painting styles of different dynasties. Since the Qing Dynasty, the book has been one of the preliminary textbooks for Chinese landscape painting and a reference for every beginner who tries to learn Chinese painting.

How to cite: Luo, J., Xiong, H., Zhang, C., and Guo, Y.: Advancing Chinese Landscape Painting Research with DDE-Outcrop 3D Technology, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5166, https://doi.org/10.5194/egusphere-egu24-5166, 2024.

EGU24-5636 | ECS | Posters on site | EOS2.4

Exploration and Application of High-Precision Inclined Photography Technology in Digital Collection of Geological Outcrops 

Zongqi Lin, Bingqian Wang, Yuqing Wu, Wenfeng Zhou, Xueli Peng, Yuhao Xu, Chenyu Wang, and Cai Wang

With the ongoing evolution of unmanned aerial vehicle (UAV) technology in geology, particularly the emergence of oblique photogrammetry, a novel approach for creating high-precision 3D models of geological outcrops has been introduced. This technique offers a more abundant and detailed perspective compared to traditional orthophotography. To guarantee optimal data collection, an extensive preliminary survey of the surrounding area of the geological outcrop was conducted using satellite imagery. We selected the DJI Mavic 3 drone, equipped with a 4/3 CMOS sensor and boasting an effective resolution of 20 million pixels. The incorporation of a Hasselblad lens significantly enhances the image quality. During the photography process, we meticulously controlled critical parameters such as the overlap rate of images, flight altitude, and the angle of photography. The overlap rate was typically maintained between 60-70%, necessitating systematic photography from macroscopic to microscopic levels and the continual adjustment of the drone camera's tilt to capture intricate details of the outcrop from various angles, enabling the construction of a more detailed and comprehensive 3D model.

Our project has digitally captured and modeled over 120 notable geological outcrops across 12 countries, including China, the United Arab Emirates, Italy, France, Germany, Spain, and Namibia, etc. We have amassed over 240,000 drone photos for 3D modeling, in excess of 7,000 panoramic shots, and more than 800 video segments featuring international experts discussing outcrops, culminating in 8000GB of data. The essence of our work is rooted in precise UAV oblique photography, and through extensive experimentation, we've established a systematic approach, achieving centimeter-level resolution.

Looking to the future, our goal is to further the digitalization of classical geological outcrops, field practice bases, and world geoparks. The data and models we produce are invaluable for geological research and education, offering a more vivid and intuitive understanding of complex geological phenomena to both the academic community and the public.

How to cite: Lin, Z., Wang, B., Wu, Y., Zhou, W., Peng, X., Xu, Y., Wang, C., and Wang, C.: Exploration and Application of High-Precision Inclined Photography Technology in Digital Collection of Geological Outcrops, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5636, https://doi.org/10.5194/egusphere-egu24-5636, 2024.

EGU24-8622 | Posters on site | EOS2.4

Optimising airborne research 

Franco Marenco and Claire Ryder

Airborne platforms offer great opportunities for atmospheric research into the upper atmospheric layers, and they range from large and fully-equipped Atmospheric Research Aircraft (ARA) to small Unmanned Aerial Vehicles (UAVs) carrying only a few instruments on-board. Such mobile platforms permit to sample the atmosphere from a unique perspective and can be used to obtain better insight on processes, to map the atmosphere in three dimensions, to validate models and spaceborne sensors, and to assist decision-making during emergencies (e.g. volcanic eruptions). We have had the chance to work closely with the Facility for Airborne Atmospheric Measurements (FAAM) ARA and of developing research closely with the Unmanned Systems Research Laboratory (USRL) of the Cyprus Institute. In this presentation we will discuss some typical challenges of airborne research and how campaigns can be optimised. All platforms are obviously different, and teams work in different ways, but several aspects of the campaign optimisation process are common.

Teamwork and communications are important requisites for success. Moreover, flight planning is a complex process, involving the use of several (often ad hoc) products providing forecasts and situational awareness, but also a knowledge of the operational constrains and a continuous negotiation between the scientific, logistics and technical teams. A thorough preparation is a key to success, and is practiced both before and during a campaign. Unpredicted situations will systematically occur, and they require having a clear prospect of the scientific objectives, the operational processes and limits, and having done a prior “homework” to understand the preferred options. Decisions have to be taken at several stages: when planning a campaign, between flights during a campaign, and whilst a flight is being carried out. Each decision is a compromise between scientific objectives and operational constrains and it is vital to be able to make the right choices. The ultimate goal of this process is to have the aircraft in the right place at the right time, as many times as possible, but without forcing excessively onto the operational limits. For a scientist, learning to understand the technical jargon (e.g. familiarity with altitudes in feet, name of airborne manoeuvres, etc) and the operational processes (e.g. how air traffic control works, how long in advance decisions need to be made, etc) is as important as understanding the scientific objectives of the campaign. To concentrate on the decision-making process rather than on how to locate information, a good prior organisation is required. A “dry run” can help in practicing and simulating the campaign in advance, with uncertainties and decisions to be taken, so as to test the best compromises and solidify the teamwork.

Ultimately, airborne observations are sporadic, and some of them will be intrinsically inefficient because precious flight time can be lost during transits, when instruments fail, or when the targeted atmospheric conditions do not occur. The optimisation process aims to improve the overall efficiency and transform the uncertainties and unforeseen circumstances into a success.

How to cite: Marenco, F. and Ryder, C.: Optimising airborne research, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8622, https://doi.org/10.5194/egusphere-egu24-8622, 2024.

EGU24-8989 | ECS | Orals | EOS2.4

Polar Impact's Guide to Inclusive Fieldwork Experiences 

Amruta Vurakaranam, Emma Robertson, Caleb Walcott, Prem Gill, Mariama C. Dryák-Vallies, Evan Quinter, and Alex Ihle

Fieldwork is a key element in natural sciences, including polar sciences, yet there is a notable lack of representation of minorities in polar field expeditions. Despite the historical involvement of ethnic minorities in such expeditions, their role as contributors and experts in polar scientific knowledge has often been overlooked. In our efforts to promote diversity and inclusivity in the sciences, it is important to reshape fieldwork spaces. This entails providing support to help individuals navigate these spaces, particularly if they are engaging in polar fieldwork for the first time. Establishing resources and support networks is pivotal in this process. We aim to develop a comprehensive fieldwork guide accommodating scientists from underrepresented backgrounds while remaining valuable to a broader audience. Although many fieldwork resources exist, there is an absence of a multi-faceted and inclusive Polar-specific guide. Existing fieldwork guides primarily prioritise physical safety, overlooking crucial aspects such as accessibility, mental health, and insights from underrepresented minority (URM) field scientists. This specialised resource is imperative as exclusionary or negative fieldwork experiences can significantly hinder the retention and career progression of scientists from underrepresented backgrounds. Drawing on our experience as an international volunteer organisation dedicated to promoting inclusivity and accessibility in polar sciences, Polar Impact is uniquely positioned to develop such a fieldwork guide. Our mission focuses on supporting, connecting, and highlighting the experiences of Black, Asian, Indigenous, people of colour, and minority ethnic professionals in the polar research community. It does so by utilising personal experiences from our members and field experts, extensive surveys, and insights from existing guides. Through this expertise, we aim to bridge knowledge and representation gaps, crafting a guide that nurtures a more supportive environment for all scientists in polar research.

How to cite: Vurakaranam, A., Robertson, E., Walcott, C., Gill, P., C. Dryák-Vallies, M., Quinter, E., and Ihle, A.: Polar Impact's Guide to Inclusive Fieldwork Experiences, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8989, https://doi.org/10.5194/egusphere-egu24-8989, 2024.

EGU24-10548 | Orals | EOS2.4

Implementation of UNESCO’s Recommendation on Open Science through Outcrop Modelling in UNESCO Global Geoparks 

Antonio Abreu, Rania Sabo, Kristof Vandenberghe, and Eunhee Lee

Abstract

In 2015, UNESCO adopted its third designation (UNESCO Global Geoparks) to promote the conservation, education, and sustainable development of Earth's geological features, aligning with one of its mandates – geoscience. In a significant development in 2021, UNESCO adopted the Recommendation on Open Science, the first international standard setting instrument on open science. This sparked a growing interest in the potential availability of geological data from Geoparks through open data sources.

Geoparks face different challenges that demand an inclusive solution, and three-dimensional (3D) outcrop modelling emerges as a possible option for some of the issues, while allowing for the implementation of the UNESCO Recommendation on Open Science:

  • It can assist in the conservation and sustainable management of geological resources, through providing an open-source platform for informed decision-making.
  • Addressing educational challenges, 3D models become interactive tools for virtual field trips, extending the reach of UNESCO Global Geoparks to a broader audience.
  • For geotourism, outcrop modelling enhances promotional efforts by showcasing unique geological features, attracting, and retaining visitors.
  • These models offer detailed insights into geological structures, aiding risk management application via proactive mitigation of hazards.
  • 3D modelling overcomes accessibility limitations by enabling virtual exploration of otherwise hard-to-reach locations, fostering a more inclusive understanding of geological heritage.
  • The ease of sharing these models fosters collaboration among geologists and researchers, contributing to a collective knowledge base about geological formations located within UNESCO Global Geoparks.

Developing 3D outcrop modelling in Geoparks will require collaboration with a specialized organisation. Due to its proficient acumen in this domain, Deep-time Digital Earth (DDE) emerges as a compelling collaborator in this project. Working with DDE could allow the preparation of a digital inventory of interesting geological features and land/seascapes for a particular under-represented region, such as Africa. The implementation methodology is set to take place over a few phases, piloting selected UNESCO Global Geoparks. The first phase will include the identification of which UNESCO Global Geoparks are already implementing the technology and what is the interest of Geoparks in using this technology.

Overall, it is expected that 3D outcrop modelling will be instrumental in overcoming various challenges, making Geoparks more accessible, engaging, and sustainable.

How to cite: Abreu, A., Sabo, R., Vandenberghe, K., and Lee, E.: Implementation of UNESCO’s Recommendation on Open Science through Outcrop Modelling in UNESCO Global Geoparks, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10548, https://doi.org/10.5194/egusphere-egu24-10548, 2024.

EGU24-11289 | Posters on site | EOS2.4

GoNorth – Fieldwork in the Arctic Ocean 

Margit Simon and Øyvind Paasche and the GoNorth consortium

In 2009 the United Nations' Shelf Commission supported the Norwegian claim for an extended continental shelf north of Svalbard, into the Nansen Basin.

Given that the scientific knowledge about the new-gained shelf areas is limited, it implied the necessity for new marine fieldwork and data-collection as this would provide expertise required by national authorities to reach sound and science-based decisions about the area in question.Hence the mission of the Norwegian GoNorth consortium was established. It continues to organize and launch a series of scientific expeditions deep into the Arctic Ocean to acquire new and essential knowledge about the oceanic areas, from the sea floor and subsea geology, through the water column, to the surface sea ice. The program is ambitious and strives for scientific excellence while at the same time being economically feasible and a key knowledge-provider. The program seeks, in other words, to bring Norway to the forefront as a responsible manager of the environment and the natural resources.

The first GoNorth expedition was carried out in 2022 with Norwegian research vessel Kronprins Haakon heading for the Nansen Basin and the northern part of the Knipovich Ridge. In 2023, during the summer-expedition with the RV Kronprins Haakon, GoNorth scientists did, in collaboration with scientists onboard the German icebreaker vessel Polarstern, target one of the slowest spreading areas of the global system of mid-ocean ridges: the Gakkel Ridge. An exciting summer-cruise is planned for 2024 in collaboration with the Swedish icebreaker ship Oden with destination Morris Jesup Rise and the Yermak-plateau. Here we will introduce the project history and goals, its recent successful field campaigns and discoveries made as well as present the outlook for future Polar Ocean explorations.

 

How to cite: Simon, M. and Paasche, Ø. and the GoNorth consortium: GoNorth – Fieldwork in the Arctic Ocean, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11289, https://doi.org/10.5194/egusphere-egu24-11289, 2024.

Geological mapping is a cognitively daunting task. In part because field geology is a discipline that largely deals with the invisible. It is through geological mapping that geologists reveal the invisible geology hidden beneath the Earth's surface, as well as the invisible geology that once lay above ground and has been lost to erosion. The geological map lies precisely at the intersection between these two invisible worlds. It is also challenging because it requires advanced 3D thinking skills. Yet, the benefits of learning geological mapping are invaluable for the development of communication skills, critical thinking, resilience, and leadership. Geological mapping also compels students to embrace and navigate uncertainties through iterative hypothesis testing.
However, preparing and delivering high-quality field courses is expensive in terms of time and resources. On the students' side, accessing these courses is a growing challenge, as many of them face clashes with other curriculum commitments, part-time jobs, caregiving responsibilities, or financial constraints. Virtual Reality (VR) is emerging as a transformative technology to teach and learn about our natural world, enhance field experiences, and mitigate accessibility issues.
VR liberates teachers and learners from the tyranny of 2D devices in which our natural world is reduced to planar images. Broadcasting from the metaverse into a Zoom session, I will demonstrate how geological mapping can be effectively learned in VR. The virtual world I'll show replicates the landscape in central NSW, Australia, where our undergraduate students are introduced to geological mapping. At a 1:1 scale, this virtual world features a high-resolution satellite image draped over a lidar DEM (resolution 5 m). Georeferenced to a local magnetic field parallel to the natural prototype, students use a virtual GPS handset to locate themselves and a virtual geological compass to measure structural features. Other virtual tools include field notebooks, geological hammers, and digital cameras to collect geological data and conduct geological mapping. Photogrammetric models of actual outcrops and high-resolution photographs of fossils and microstructures are positioned accurately, providing students with realistic field-like encounters. The immersive experience is enhanced by 3D models of trees, bushes, shimmering waterways, a volumetric soundscape mimicking the real environment, realistic weather conditions, and time-dependent sunlight.
Once immersed in this virtual yet realistic environment, students experience field geology in a manner relatively close to reality. Important missing ingredients include physical and mental fatigue, as well as the anxiety triggered by potential risks such as getting lost, injuries, bee stings, snake bites, etc. Nevertheless, VR offers a very effective way to prepare students for geological mapping, its principles, and workflows. For students returning from the field, it also offers the possibility to revisit some outcrops or check outcrops they may have missed while in the field. Importantly, for students unable to attend field courses, VR offers an invaluable opportunity to grasp the essence of geological mapping principles, bridging the accessibility gap for a diverse student population.

How to cite: Rey, P.: Live From the Metaverse! An Introduction to Geological Mapping in Immersive Virtual Reality, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13374, https://doi.org/10.5194/egusphere-egu24-13374, 2024.

EGU24-15319 | ECS | Posters on site | EOS2.4 | Highlight

Swiss Alps 3D: building a large-scale 3D underground model of the Central European Alps 

Ferdinando Musso Piantelli, Pauline Baland Baland, Anina Ursprung, and Roland Baumberger

The Swiss Geological Survey (SGS) is the competence centre for the subsurface and georesources of the Swiss Confederation. It provides up-to-date, high-quality spatial reference data for the whole of Switzerland in the form of nationwide geological datasets and 3D geological models. Between 2024 and 2030, the SGS is funding the Swiss Alps 3D project, which consists of eight research projects involving multiple universities and aims to develop a consistent large-scale 3D geological model of the main contacts and structures of the Swiss Alps.

In this poster we present the complete workflow that will be used for the construction of this 3D model and the project plan for the next 7 years. The main challenge for 3D modelling in Alpine regions is the lack of subsurface data (seismic, boreholes, etc.). However, the high relief, the sparse vegetation and the large number of scientific studies make these regions an excellent site for advanced surface-based 3D modelling. Based on the new Tectonic Map of Switzerland 1:500'000 (2024, in prep.), the area is divided into eight 3D modelling projects according to their paleogeographic origin and structural evolution. The resulting models will then be merged into a single large-scale 3D model.

At the beginning of each modelling project, a 1:25’000 scale geological map of the main structural and lithostratigraphic contacts will be produced by verifying and harmonising a 2D geological dataset compiled for the study (published maps, strike and dip data, tunnel and seismic data). 3D modelling software packages (e.g., Move™, SKUA-Gocad) will be then used to generate a network of regularly spaced (1000 m) geological cross sections throughout the area. By applying explicit or implicit 3D interpolation and meshing techniques between the cross sections and the surface outcrop lines (i.e., spline curve method), lithological and structural boundaries will be then interpolated to generate 3D surfaces of each horizon of the model. The workflow presented here offers the chance to gain validation approaches for domains only weakly constrained or with no subsurface data available, by generating a 3D model that integrates all accessible geological information and background knowledge.

Swiss Alps 3D will generate key knowledge by establishing an experienced modelling community and 3D visualization of the main structures and lithostratigraphic boundaries of the Central European Alps. The development of such a model will provide a framework model of the area as a basis for higher resolution 3D models to be used for infrastructure planning, groundwater studies, natural hazard assessment, education and research purposes. In addition, such models will provide access to strategic subsurface knowledge for geo-resource and geo-energy management and exploration.

How to cite: Musso Piantelli, F., Baland, P. B., Ursprung, A., and Baumberger, R.: Swiss Alps 3D: building a large-scale 3D underground model of the Central European Alps, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15319, https://doi.org/10.5194/egusphere-egu24-15319, 2024.

EGU24-15882 | ECS | Orals | EOS2.4

Creating welcoming learning environments - towards institutional guidelines for more inclusive field courses in the geosciences  

Floreana Miesen, Léa Rodari, Natalie Emch, Georgina King, and Ian Delaney

Fieldwork is a cornerstone of many geoscience study programmes, enhancing student learning experiences and fostering lasting social bonds. However, field-based courses can impose significant mental, physical, and financial burdens on students. This may inadvertently exclude and discriminate against those who lack the means to participate or deviate from the stereotypical image of field scientists. In designing field courses that support a wide range of students, the geosciences community has the opportunity to create a more welcoming environment and benefit from a more diverse generation of geoscientists. 

We share experiences and insights from our journey to develop institutional guidelines for field courses, which acknowledge and promote diversity, accessibility, and student well-being. We reflect on navigating the hurdles encountered while drafting these guidelines and the means to gain support for them. We explore the cultural shifts needed to challenge more conventional approaches to field-based teaching, along with questioning who traditionally participates and how courses are structured. We contrast bottom-up and needs-based approaches with top-down directives, emphasising effective communication between students and field trip leaders, as well as the impact of hierarchical structures. 

By addressing issues like physical fitness requirements and financial limitations, we propose strategies to lower entry barriers. In doing so, we aim to support and attract students from diverse backgrounds. The presentation also underscores the significance of proper communication, before, during, and after field courses, setting expectations and addressing student's concerns or challenges. Finally, we advocate for a comprehensive approach to safety, including considerations of mental health, harassment, and discrimination in formal risk assessments, accompanied by adequate training for field trip leaders.

How to cite: Miesen, F., Rodari, L., Emch, N., King, G., and Delaney, I.: Creating welcoming learning environments - towards institutional guidelines for more inclusive field courses in the geosciences , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15882, https://doi.org/10.5194/egusphere-egu24-15882, 2024.

EGU24-16189 | ECS | Posters on site | EOS2.4

From theory to real-world geomatics applications: glacier monitoring fieldworks through an innovative teaching program 

Federica Gaspari, Francesco Ioli, Federico Barbieri, Rebecca Fascia, Livio Pinto, and Lorenzo Rossi

Applying skills gained from university courses marks a pivotal step in crafting engaging and innovative teaching methods (Balletti et al., 2023). Over its 10 editions, the Summer School hosted by Politecnico di Milano's Section of Geodesy and Geomatics, within the Department of Civil and Environmental Engineering, has consistently aimed to bridge the divide between theory and practice. Focused on instructing students in the design and execution of topographic surveys, particularly in environmentally challenging alpine regions impacted by climate change, this program ensures hands-on learning experiences.

The Summer School is framed within a long-term monitoring activity of the Belvedere Glacier, a temperate debris-covered alpine glacier, located in the Anzasca Valley (municipality of Macugnaga – Italy). Since 2015 annual in-situ GNSS and UAV photogrammetry surveys have been performed to derive accurate 3D models of surface of the entire glacier, allowing the derivation of its velocity and volume variations over the last decade. In a week-long program, undergraduate and graduate students in Engineering, Geoinformatics and Architecture are encouraged to collaborate, with the supervision of young tutors who are passionate about the topic, to develop effective strategies for designing in-situ measuring surveys, fostering problem solving and team-working. The teaching materials used to introduce key theoretical concepts as well as to guide students through practical exercises with processing software is made openly accessible online with a dedicated website built on top of an open-source GitHub repository (https://tars4815.github.io/belvedere-summer-school/), providing the groundwork for developing collaborative online teaching and expanding the material for other future learning experiences  (Potůčková et al., 2023).

Adding value to the experience, students also contribute to an ongoing project regarding the monitoring of the glacier (Ioli et al., 2021; https://labmgf.dica.polimi.it/projects/belvedere/), providing valuable insights on the recent evolution of the natural site. The 2D and 3D georeferenced products are indeed published in an existing public repository on Zenodo (https://doi.org/10.5281/zenodo.7842348), sharing results with a wider scientific community.

The valuable experience and outcomes from various Summer School editions led the organizing team to secure the EGU 2023 Higher Education teaching grant program. This opportunity facilitated enhancements to the teaching material and bolstered support for in-situ experiences.

Bibliography:

Balletti, C., Capra, A., Calantropio, A., Chiabrando, F., Colucci, E., Furfaro, G., Guastella, A., Guerra, F., Lingua, A., Matrone, F., Menna, F., Nocerino, E., Teppati Losè, L., Vernier, P., Visintini, D. (2023): The SUNRISE summer school: an innovative learning-by-doing experience for the documentation of archaeological heritage, Int. Arch. Photogramm. Remote Sens. Spatial Inf. Sci., XLVIII-M-2-2023, 147–154

Ioli, F., Bianchi, A., Cina, A., De Michele, C., Maschio, P., Passoni, D., Pinto, L. (2021). Mid-term monitoring of glacier’s variations with UAVs: The example of the belvedere glacier. Remote Sensing, 14(1), 28.

Potůčková, M., Albrechtová, J., Anders, K., Červená, L., Dvořák, J., Gryguc, K., Höfle, B., Hunt, L., Lhotáková, Z., Marcinkowska-Ochtyra, A., Mayr, A., Neuwirthová, E., Ochtyra, A., Rutzinger, M., Šedová, A., Šrollerů, A., Kupková, L. (2023): E-TRAINEE: open e-learning course on time series analysis in remote sensing, Int. Arch. Photogramm. Remote Sens. Spatial Inf. Sci., XLVIII-1/W2-2023, 989–996

How to cite: Gaspari, F., Ioli, F., Barbieri, F., Fascia, R., Pinto, L., and Rossi, L.: From theory to real-world geomatics applications: glacier monitoring fieldworks through an innovative teaching program, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16189, https://doi.org/10.5194/egusphere-egu24-16189, 2024.

EGU24-16328 | ECS | Orals | EOS2.4

DDE-Outcrop3D: A new pathway to the Deep-time Earth 

Xia Wang, Hanting Zhong, Jianhua Chen, Zongqi Lin, Bingqian Wang, Mingcai Hou, Yalin Li, and Chengshan Wang

Outcrops are the basics of geosciences. Investigation of geological outcrops is the bedrock of geological research, but the data acquisition based on traditional fieldwork is often limited by the size and accessibility of the outcrops. Especially in a hundreds-meter scale area, geological studies often rely on single-profile analysis, which makes it challenging to reveal the overall characteristics of systems with spatial heterogeneity (e.g., carbonate deposition, reef complex). For geological education, field excursions are necessary for the students, but the accessibility of the outcrops is seriously impacting the global equality of geological education because of regional conflicts or poverty. Geological heritage outcrops, important outcrops such as GSSP (Global Stratotype Section and Point), or outcrops with both scientific and commercial value need to be documented to prevent future destruction; besides the traditional solutions such as photography or videos, 3D digital outcrops can save more diversified geological information.

Utilizing UAVs allows for a cost-effective and highly efficient approach to investigating outcrops. Through close-range photogrammetry employing UAV-captured images, the creation of precise three-dimensional models for outcrops has become feasible, reaching an impressive level of accuracy at the centimeter scale. Under the Deep-time Digital Earth (DDE) framework, the DDE-Outcrop3D platform (outcrop3D.deep-time.org) is an open-access Web platform for real-scene 3D digital outcrops. It is based on the Cesium open-source 3D earth engine, providing functions for multiple data uploading, sharing, information editing, and community outreach. DDE-Outcrop3D platform has 124 digital outcrop models from Asia, Europe, and Africa, all accessible to the public. The latest versions of DDE-Outcrop 3D can provide a new pathway to scientific research and education, and aim to foster broader engagement among researchers, educators, and enthusiasts, providing a valuable resource for immersive exploration and enhanced understanding of geological outcrops.

Here, we present the main features of the DDE-Outcrop3D platform and its application scenarios on geological research and education, scientific communication, and preservation of geological heritages. 

Acknowledgement: This work is funded by “Deep-time Digital Earth”, an IUGS-recognized Big Science Program.

How to cite: Wang, X., Zhong, H., Chen, J., Lin, Z., Wang, B., Hou, M., Li, Y., and Wang, C.: DDE-Outcrop3D: A new pathway to the Deep-time Earth, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16328, https://doi.org/10.5194/egusphere-egu24-16328, 2024.

EGU24-16411 | Posters virtual | EOS2.4

Svalbard Integrated Arctic Earth Observing System: Tools to help you do fieldwork in Svalbard 

Eleanor L. Jones, Ilkka S. O. Matero, Christiane Hübner, Rudolf Denkmann, Ashley Morris, Øystein Godøy, and Heikki Lihavainen

Svalbard Integrated Arctic Earth Observing System (SIOS) is an international consortium in which 28 member institutions from 10 countries cooperate to develop and maintain a regional Earth observing system in and around Svalbard. We will present some of the tools that this consortium uses to facilitate fieldwork within Earth System Science. Firstly, our Logistics Sharing Notice Board is a platform where you can offer spare logistical resources or ask for logistical support with your fieldwork. Secondly, our Observation Facility Catalogue can help you learn about existing infrastructure and measurements in Svalbard, and you can even enter your own instruments and infrastructure. In addition, our e-learning platform is a valuable resource for newcomers to research and fieldwork in Svalbard and our data catalogue provides an overview of and access to relevant existing datasets. Finally, SIOS offers funding to facilitate access to the research infrastructure owned by SIOS member institutions (our Access Programme), as well as to improve infrastructure in and around Svalbard (our Optimisation Programme).

How to cite: Jones, E. L., Matero, I. S. O., Hübner, C., Denkmann, R., Morris, A., Godøy, Ø., and Lihavainen, H.: Svalbard Integrated Arctic Earth Observing System: Tools to help you do fieldwork in Svalbard, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16411, https://doi.org/10.5194/egusphere-egu24-16411, 2024.

EGU24-17802 | ECS | Orals | EOS2.4

ADVANCEing FieldSafety: A new course and toolkit for diverse and inclusive geoscience teams 

Mylene Jacquemart, Alice Hill, Alexandra Padilla, Allison Mattheis, Anne Gold, Alyse Thurber, Blair Schneider, Emily Geraghty Ward, Erika Marín-Spiotta, Kristy Tiampo, Mariama Dryák-Vallies, Meredith Hastings, and Ryan Cassotto

Field-based research is integral to many geoscientific studies. Harassment and discrimination in these settings are not new, but widespread recognition of their prevalence, different facets, and the harm they cause has led to demands for cultural change and increased training and preparation for researchers heading into the field. Here, we present a newly developed, widely accessible training program and resource hub for field researchers in preparation for successful and inclusive  field campaigns. This new collaboration, ADVANCEing FieldSafety, builds on the experiences from field safety trainings developed within the University of Colorado, Boulder's FieldSafe project and workplace climate trainings created by the AdvanceGeo Partnership. The ADVANCEing FieldSafety course offers numerous tools designed to create and maintain a positive team culture. The main elements of the training are informed by an intersectional framework and include strategies for creating and implementing codes of conduct, group dynamics and communication tools, allyship training, bystander intervention techniques, traditional and identity-focused risk assessment strategies, and evidence-based practices for inclusive mentorship in the field setting. The course will be offered as a Massive Open Online Course (MOOC) on coursera.org and will become available in 2024, allowing easy access and broad participation. The MOOC will have two pathways:  a Coursera certification and an ADVANCEing FieldSafety certification. The Coursera certificate is obtained by completing the fully online and self-paced course. The ADVANCEing FieldSafety certificate is obtained by completing the course and by participating in facilitated debriefs/reflections related to course topics. The ADVANCEing FieldSafety certification pathway is designed to help field teams meet the new field safety and harassment-mitigation requirements that have recently been implemented, for instance for field campaigns funded by the United States National Science Foundation. Additionally, an easily adaptable  toolkit is also in development such that references and resources can be easily taken into the field. Finally, we are conducting mixed-methods research to assess the effectiveness of the ADVANCEing FieldSafety training for participants and for implementing the management and support structures in field situations offered through the additional toolkit resources. Our goal is to build a stronger geoscience community that works proactively to create norms of inclusive and safe group behavior equipped with tools that promote anti-harassment and early intervention of exclusionary behaviors. 

How to cite: Jacquemart, M., Hill, A., Padilla, A., Mattheis, A., Gold, A., Thurber, A., Schneider, B., Geraghty Ward, E., Marín-Spiotta, E., Tiampo, K., Dryák-Vallies, M., Hastings, M., and Cassotto, R.: ADVANCEing FieldSafety: A new course and toolkit for diverse and inclusive geoscience teams, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17802, https://doi.org/10.5194/egusphere-egu24-17802, 2024.

EGU24-18133 | Posters virtual | EOS2.4

Can Virtual Field Trips be used to prepare students for real fieldwork? 

Jan van Bever Donker, Delia Marshal, Rudy Maart, Luyanda Mayekiso, Henok Solomon, Matthew Huber, and Nompumelelo Mgabisa

As a result of significantly increased class sizes, heightened safety consciousness, significantly increased health and safety regulations, and limited staff resources, a project was started in 2017 to investigate ways and means to improve the impact of field instruction to undergraduate students.

This allowed us to hit the ground running when COVID-19 hit the world, as the lock down regulations triggered a switch to teaching remotely. This significantly accelerated the development of our Virtual Field Trips (VFTs), in this case to be able to provide suitable field evidence for the students as group travel to the field was not possible, except the fourth year small groups.

VFT’s were therefore developed for use at first year, second year, third year and fourth year level of instruction.  In close collaboration with the instructor responsible for teaching the various courses, three different sets of VFTs were developed:

A set of four VFTs for the first year introductory Earth Sciences course, illustrating sedimentary, structural, and igneous features in outcrops as well as hand specimen. Three VFTs were used during practical teaching sessions followed by a test, after which the VFTs were available on-line for self-study. This was followed by the fourth, more comprehensive tour, which was used as an end of practical course test. Comparison of the two test results demonstrated a significant learning gain.

One multi outcrop tour was prepared to illustrate the features the field geologist needs to look out for when applying structural geology to slope stability assessment in an engineering geological setting in the context of raising an existing storage dam wall to increase the storage lake capacity. This lecture was followed by a test prior to the VFT after which the same test was applied sfter the VFT. Comparing the results of the two tests demonstrated that the learning gain increased significantly in accordance with the level of education of the participants.

Finally, a set of seven tours was built to prepare the fourth-year students prior to going to the field by showing them the various sedimentary features they were to visit in the field. Here we used video explanations on the outcrop, 3D LIDAR specimen and drone videos for the spatial aspect.  In this case the final report prepared by the students after the field excursion was compared with the results of the previous year’s class where no VFT was available and again we could demonstrate a distinct learning gain.

In the last case to show the sedimentological features in preparation for the real field trip,  we could demonstrate a positive impact on the outcomes of the field excursion, thus providing an affirmative answer to the question whether VFTs can be used to prepare students for fieldwork.

How to cite: van Bever Donker, J., Marshal, D., Maart, R., Mayekiso, L., Solomon, H., Huber, M., and Mgabisa, N.: Can Virtual Field Trips be used to prepare students for real fieldwork?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18133, https://doi.org/10.5194/egusphere-egu24-18133, 2024.

EGU24-19026 | Orals | EOS2.4

Exploring the Curriculum Potential of Digital Outcrop Models: Guidance from Geoheritage Sites 

Edward Robeck, Lindsay Mossa, Lauren Brase, and Sequoyah McGee

Digital outcrop models (DOMs) provide a rich set of resources for geoscience education, including DOMs that are primarily developed for scientific purposes. This presentation will illustrate the initial stages of an analytical approach as applied to DOMs that is intended to enhance their use in educational settings. Several resulting principles will be offered for consideration and discussion, with the goal of informing the design and dissemination of DOMs to maximize their use in instruction.

Like other resources that aren’t first and foremost developed for use in education, the instructional applications of DOMs can be enhanced by making use of their inherent curriculum potential. The concept of curriculum potential posits that both materials designed for education and those designed primarily for other uses hold possibilities for instruction that are greater than what was intended by the people who created them. Elements of curriculum potential can be drawn out of resources in a variety of ways. For example, skilled educators often can intuitively recognize ways of using resources in instruction that are both novel and effective—and may extend past the intentions of the designers. Another way to bring curriculum potential to light is through analysis based on curriculum theory, instructional models, and other formal frameworks. Such analyses can identify principles to guide effective pedagogical applications of the materials. In instances where developers are open to the resources they are generating being applied across multiple use cases, such principles can provide guidance for broadening the benefits the materials offer to different user groups simultaneously.

It can be reasoned that one way to recognize possible uses of DOMs in education is to position them as analogs to other resources that are primarily developed for use outside of instruction and for which similar analyses have taken place. For example, geoheritage sites are analogous to DOMs in that geoheritage sites are selected and described for purposes (e.g., recognition, conservation) that are not primarily related to their role as educational resources. Therefore, what has been learned about how information associated with geoheritage sites can be disseminated in ways that facilitate their use in education may be suggestive of ways that DOMs can be presented to enhance their educational uses. This analytical crossover seems especially plausible since many DOMs focus on elements of geoheritage sites.

The education and outreach personnel at the American Geosciences Institute (AGI) have been exploring the curriculum potential of geoheritage sites using concepts from various frameworks in curriculum and instruction—including place-based education, phenomenon-based learning, pedagogical content knowledge, and others. The goal is to inform the dissemination of information about geoheritage sites (e.g., in textual descriptions, web portals) to enable the realization of their curriculum potential. One outcome is the recommendation that information be provided that contextualizes each geoheritage site across multiple values (e.g., aesthetic, educational, cultural, historical, scientific). Such information can be expected to foster both multi-disciplinary and interdisciplinary learning. A similar analytical approach can be applied to DOMs and can benefit from (and perhaps be accelerated by) what has been learned about geoheritage sites.

How to cite: Robeck, E., Mossa, L., Brase, L., and McGee, S.: Exploring the Curriculum Potential of Digital Outcrop Models: Guidance from Geoheritage Sites, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19026, https://doi.org/10.5194/egusphere-egu24-19026, 2024.

EGU24-22115 | Orals | EOS2.4 | Highlight

Gear Hack for women: Polar Gear Revisited for Female FriendlyField Operations 

Leila Nour Johnson and Nighat Johnson-Amin

The Polar Regions have been a male preserve from the earliest exploratory journeys, with little or no possibility for women to participate either in exploration or research until quite recent times.

“Antarctica is often associated with images of masculine figures battling against the blizzard. The pervasiveness of heroic white masculine leadership and exploration in Antarctica and, more broadly, in Science, Technology, Engineering, Mathematics, and Medicine (STEMM) research cultures, has meant women have had lesser access to Antarctic research and fieldwork opportunities, with a marked increase since the 1980s. “

(Meredith Nash et al, PLoS One Published online 2019 . doi: 10.1371/journal.pone.0209983)

The hazardous environmental conditions and the proximity with predominantly male colleagues meant that women were initially only accepted on expeditions as spouses or possibly as support at headquarters.

“The situation is very different today, with many women taking on the challenge of research in the Arctic or Antarctic regions. However, many things have not changed and the expeditions remain largely male dominated. The presence and impact of female Antarctic researchers has increased rapidly. In the 1950s most countries did not allow women to work in Antarctica and there were few female Antarctic scientists.”

SCAR Website


While the number of women researchers in the Polar Regions has increased, women remain subject to the pervading culture. The equipment, and clothing available for the extreme conditions remains largely skewed towards male needs and capabilities. Interviews with female researchers has demonstrated that there exists a need to review the equipment used in the field to avoid difficult situations arising from the handling of biological and physiological needs.


The Gorgoneion Project was set up to address the issues raised by the women polar researchers who felt that their performance in the field and their safety was being compromised by clothing related issues. The lack of adapted clothing also prejudiced scientific performance, and createdgeneral unease.


Most of the women who were interviewed for the Gorgoneion Project reported very similar issues, namely:
Lack of adequate insulation in areas specific to the female anatomy.
Lack of dexterity due to wrongly proportioned protective gear, (e.g. gloves or boots).
Issues related to bodily functions and difficulties encountered in obtaining relief in the field.
Weight of clothing not adapted to the physical capabilities of women.
Difficulty to manage temperature control due to integrated layers which prohibit shedding.
Risks to blood circulation due to improper protection of extremities.


The cost of specialized polar gear can easily rise to 20 KEuros per person.

Consequently, it would be very useful to develop a new range of clothing aimed at women researchers. Solutions would
integrate the following:
Know-how from designers who specialize in women’s wear.
Use a sustainable approach employing natural fibres.
Learning from indigenous practices from the Arctic and Patagonia in the handling of cold weather.
Innovating to address the biological needs of women, in particular with regard to bodily functions and period handling.
Combining innovatory methods to provide targeted heat.

How to cite: Johnson, L. N. and Johnson-Amin, N.: Gear Hack for women: Polar Gear Revisited for Female FriendlyField Operations, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-22115, https://doi.org/10.5194/egusphere-egu24-22115, 2024.

EGU24-3603 | ECS | Posters on site | EOS4.3

Bridging the gap between climate scenarios and law - a roadmap for mutual contributions 

Haomiao Du, Edward Brans, Murray Scown, Hsing-Hsuan Chen, Vassilis Daioglou, Mark Roelfsema, Annisa Triyanti, Dries Hegger, Leila Niamir, Marleen van Rijswick, Liping Dai, Peter Driessen, Yann du Pont, Dennis van Berkel, and Detlef van Vuuren

To bridge the knowledge gap between climate scenarios and law, this presentation is aimed to demonstrate currently demanded mutual contributions by legal professionals and integrated assessment modellers on 1) how legal knowledge can be integrated into climate scenarios and 2) how scientific evidence generated from climate scenarios can better guide climate litigation cases. We expect that this could support judges in making trade-offs in climate-related court cases and could contribute to the acceptance of decisions by judges in such cases. Given the emissions gap and the measures that must be taken to comply with the Paris Agreement, the latter is likely becoming more relevant.

Regarding the first part, the results are based on an empirical research project on Improving the Integration of Legal Knowledge and Scholars in Climate Scenario Assessments (https://www.uu.nl/en/research/sustainability/improving-the-integration-of-legal-knowledge-and-scholars-in-climate-scenario-assessments) and a workshop  (https://www.uu.nl/en/research/sustainability/workshop-report-promoting-the-mutual-understanding-between-legal-and-governance-scholars-and-climate) resulted from this project held in May 2023. Via interviews and focus-group discussions with 24 experts in climate modelling, climate law and politics, and ethics, our research highlights four legal aspects for integration, which are: 1) implementation end enforcement of climate targets, 2) key normative principles, 3) legal uncertainties, and 4) the applicability of scenarios in regional and local legal contexts. Considering the challenges of integration due to epistemic distinctions between disciplines, experts held different opinions on the feasibility of integrating those four aspects. Regarding actionable steps for the short term, revising narratives and a ‘legal reality check’ are the most agreed ones. The former refers to adding legal obligations that safeguard justice, fairness and fundamental human rights - traceable to various treaties - to narratives of the global futures. The latter refers to scrutinising the ‘shared feasibility space’ between law on the one hand and modelled scenarios and emission reduction pathways on the other: it can be the compatibility of legal principles with modelled scenarios based on different assessment criteria (e.g. fair share of burdens), or to compare scenarios with and without regulatory boundary conditions in a specific jurisdiction on a specific mitigation solution (e.g. BECCS scenarios).

Regarding the second part, the currently ongoing research focuses on the adoption of authoritative scientific evidence from climate scenarios - typically the projections referred to in the IPCC reports - in climate litigation cases. First, inspired by the Daubert Criteria, this research explores the possibility of developing guidelines for judges to deal with scientific uncertainties contained in multiple projected futures and determining admissibility of scientific evidence. Second, seeing the increasing reference to ‘open norms’ (e.g. due diligence, fair share) and fundamental human rights (to private life or a healthy environment) in court cases, modelled scenarios could provide information for guiding judges in their interpretation of key concepts such as carbon budgets, fair share, emission gap, appropriate emission reduction obligations, and climate-induced harm and loss and damage. We expect that this could be beneficial to the supportability of judges' decisions in climate cases.

How to cite: Du, H., Brans, E., Scown, M., Chen, H.-H., Daioglou, V., Roelfsema, M., Triyanti, A., Hegger, D., Niamir, L., van Rijswick, M., Dai, L., Driessen, P., du Pont, Y., van Berkel, D., and van Vuuren, D.: Bridging the gap between climate scenarios and law - a roadmap for mutual contributions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3603, https://doi.org/10.5194/egusphere-egu24-3603, 2024.

EGU24-5662 | ECS | Posters on site | EOS4.3

Litigation challenging over-reliance on carbon dioxide removal requires quantitative feasibility assessment 

Oliver Perkins, Peter Alexander, Almut Arneth, Calum Brown, James Millington, and Mark Rounsevell

Carbon dioxide removal (CDR) is an emerging frontier in climate change litigation1. CDR must play an important role in achieving global climate targets, by compensating for hard-to-abate emissions (such as from international transport). Yet, over-reliance on CDR in government and corporate decarbonisation plans may serve as a strategy to commit to climate action on paper, whilst making inadequate present-day emissions’ reductions. Therefore, litigation may be necessary to highlight where CDR commitments contribute to a credible decarbonisation plan, and where they are primarily employed as a delaying tactic. Hence, litigation arguing that a given level of CDR deployment represents an unacceptable risk to the achievement of legal climate targets must have clarity around plausible levels of real-world delivery.

Land-based CDR methods, such as afforestation and bioenergy with carbon capture and storage, frequently appear in both modelled decarbonisation scenarios and government policies. Here, we argue that quantitative assessment of the feasible potential of land-based CDR is vital to the success of CDR-focused litigation. Firstly, we highlight key land system processes that will constrain real-world CDR delivery to levels well-below the techno-economic assessments presented in the IPCC 6th Assessment Report (AR6). These constraining processes include land tenure and food insecurity, monitoring and verification, and impermanence due to biophysical disturbances and policy change. Quantifying the likely impact of such factors can fast-track successful CDR litigation by demonstrating the scale of the gap between CDR pledges and plausible real-world potentials.

Further, after Perkins et al., 2, we outline research frameworks that can deliver a quantified feasible potential for land-based CDR within the IPCC AR7 process, and highlight emerging trans-disciplinary methods making progress towards this goal. These methods include geospatial coupled socio-ecological model ensembles, which can capture interactions and feedbacks between socio-economic and biophysical drivers in the land system at global scale. Typically, such ensembles include coupling of spatial agent-based models of land user behaviour with dynamic global vegetation models and non-equilibrium agricultural trade models - which can represent system shocks such as geopolitical instability and extreme weather events. We conclude by arguing that quantitative feasibility assessment must be made a high priority in CDR research to prevent widespread over-reliance on CDR in decarbonisation policies.

1. Stuart-Smith, R.F., Rajamani, L., Rogelj, J., and Wetzer, T. (2023). Legal limits to the use of CO2 removal. Science 382, 772–774. 10.1126/science.adi9332.

2. Perkins, O., Alexander, P., Arneth, A., Brown, C., Millington, J.D.A., and Rounsevell, M. (2023). Toward quantification of the feasible potential of land-based carbon dioxide removal. One Earth 6, 1638–1651. 10.1016/j.oneear.2023.11.011.

How to cite: Perkins, O., Alexander, P., Arneth, A., Brown, C., Millington, J., and Rounsevell, M.: Litigation challenging over-reliance on carbon dioxide removal requires quantitative feasibility assessment, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5662, https://doi.org/10.5194/egusphere-egu24-5662, 2024.

EGU24-8458 | ECS | Posters on site | EOS4.3

Save the Climate but Don’t Blame Us: Corporate Responses to Climate Litigation 

Noah Walker-Crawford

Fossil fuel companies are no longer denying anthropogenic climate change in recent climate litigation but question the validity of climate science for establishing legal responsibility. Past research on social movement legal mobilization has primarily focused on plaintiffs’ perspectives, showing how they use the judicial process as a site of knowledge production. Drawing attention to the other side, I conduct an analysis of scientific disputes in major climate change lawsuits and develop a typology for studying defendants’ evidentiary arguments. Defendants build evidentiary counter-narratives, challenge the substantive quality of plaintiffs’ claims, and attack the scientific integrity of compromising evidence. Litigants’ legal narratives and factual claims are linked to broader normative concerns about how the underlying issues should be resolved. Fossil fuel companies’ legal arguments reflect broader strategies to evade responsibility for climate change.

How to cite: Walker-Crawford, N.: Save the Climate but Don’t Blame Us: Corporate Responses to Climate Litigation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8458, https://doi.org/10.5194/egusphere-egu24-8458, 2024.

EGU24-12601 | ECS | Posters on site | EOS4.3

Towards Evaluating the Financial Responsibility of Carbon Majors for Climate-Related Damages 

Marina Andrijevic, Carl-Friedrich Schleussner, Jarmo Kikstra, Richard Heede, Joeri Rogelj, Sylvia Schmidt, and Holly Simpkin

In light of the global energy crisis and escalating climate change impacts, the liability of major fossil fuel companies is receiving heightened scrutiny, particularly in the context of climate litigation. This study initially establishes the feasibility of attributing climate damages to these companies. Utilizing the social cost of carbon methodology, we evaluate the damages inflicted by the top 25 oil and gas emitters from 1985 to 2018, comparing these to their financial profits. Our central estimate suggests partial damages of approximately 20 trillion USD, with the companies’ financial gains surpassing this by 50%, totaling around 30 trillion USD. This indicates the potential of carbon majors to cover their attributed damages while maintaining significant profits. In our analysis, we also explore how varying approaches to assigning responsibility and handling uncertainties in climate damages can markedly influence these findings. Additionally, we explore the role of sovereign wealth funds in perpetuating fossil-fuel derived wealth and the ensuing liability questions.

How to cite: Andrijevic, M., Schleussner, C.-F., Kikstra, J., Heede, R., Rogelj, J., Schmidt, S., and Simpkin, H.: Towards Evaluating the Financial Responsibility of Carbon Majors for Climate-Related Damages, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12601, https://doi.org/10.5194/egusphere-egu24-12601, 2024.

EGU24-15814 | ECS | Posters on site | EOS4.3

Quantifying the human-induced climate change impact on heat-related mortality events in Europe with Extreme Event Attribution Methods  

Thessa M Beck, Lukas Gudmundsson, Dominik L Schumacher, Sonia I Seneviratne, Hicham Achebak, and Joan Ballester

Numerous Extreme Event Attribution (EEA) studies have consistently shown that human-induced climate change has increased the likelihood of extreme heat events. The increasing relevance of these studies in the context of climate litigation underscores the demand for the quantification of climate change impacts. Heat, as the primary contributor to weather-related mortality on the European continent, has caused more than 61,000 heat-related deaths in Europe during the 2022 summer. We carry out this proof-of-concept study in which we apply Extreme Event Attribution methods combined with epidemiological models to quantify how anthropogenic warming has influenced extreme heat-related mortality events in Europe. In contrast to most health impact studies, we utilize open-access mortality data from Eurostat, which is available in near-real time.

Because of the complex, non-linear relationship between temperature and mortality, we conduct separate Extreme Event Attribution analyses for (i) temperature extremes and (ii) associated heat-related mortality events in 232 distinct administrative regions spanning over 35 European countries. Our findings reveal that the probability of the maximum weekly values observed in 2022 has increased 12-fold [95th CI 3.51-147.15] for temperature and tripled [95th CI 1.02-18.63] for mortality compared to the pre-industrial baseline. Notably, we identify significant geographical disparities, e.g. in Spain the mortality risk is even 30 times higher [95th CI 3.33 – 1218.14] due to anthropogenic warming.

We find a statistically significant trend in 70% [90%] of the regions at the 0.95 [0.90] significance level, and across all age and sex groups, except for women aged 65 years or less, indicating that anthropogenic warming affects almost the entire European population.

This study establishes a foundation for subsequent analyses, not only for heat-related mortality events observed on different temporal and spatial scales but also for enabling an examination of other weather events and associated health impacts. By combining climate sciences and techniques with epidemiology and health data, it is possible to calculate the contribution of climate change to changes in health risks and mortality burdens by sociodemographic categories, such as sex, age, socioeconomic level, or comorbidities, especially in vulnerable groups. This transdisciplinary work has to potential to provide key information for climate-related health lawsuits and opens the door to inter- and transdisciplinary perspectives on how to integrate geoscience and epidemiology insights in litigation.

How to cite: Beck, T. M., Gudmundsson, L., Schumacher, D. L., Seneviratne, S. I., Achebak, H., and Ballester, J.: Quantifying the human-induced climate change impact on heat-related mortality events in Europe with Extreme Event Attribution Methods , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15814, https://doi.org/10.5194/egusphere-egu24-15814, 2024.

EGU24-16721 | ECS | Posters on site | EOS4.3

Does climate change violate children’s rights? Investigating the use of scientific evidence in child and youth-led climate litigation 

Rosa Pietroiusti, Sam Adelman, Annalisa Savaresi, and Wim Thiery

Climate change is already increasing the frequency, intensity and duration of many extreme weather events around the world, as well as driving impacts on communities through slow-onset changes, and will continue to do so with each additional degree of warming. Young and future generations will face an ever-greater number of such events during their lifetimes, raising concerns regarding the intergenerational inequity inherent in climate change. In response to these concerns, child and youth-led climate litigation is emerging as an avenue to push for more ambitious climate policies at national and regional scales, by applying legal duties and obligations in a forward-looking way and presenting courts with  scientific evidence of observed and projected climate risks and impacts. Recent complaints led by young people, including, for example, Sacchi et al. v. Argentina et al., lodged in 2019 with the United Nations Committee on the Rights of the Child and Duarte Agostinho et al. v. Portugal et al., which was heard in 2023 by the European Court of Human Rights, have broken new ground by bringing the rights of children and future generations to the fore. Based on a review of recent and ongoing cases, we will investigate (i) what harms are claimed by youth plaintiffs, and (ii) whether, how and to what extent scientific evidence is used to support their claims. By comparing the cases in relation to their claims, jurisdictional frameworks, reference to human and/or children’s rights, and status, we will shed light on how youth applicants have addressed the main challenges of this specific category of climate litigation, including meeting the victimhood requirement, and what role evidence from the geosciences and other scientific fields has played.

How to cite: Pietroiusti, R., Adelman, S., Savaresi, A., and Thiery, W.: Does climate change violate children’s rights? Investigating the use of scientific evidence in child and youth-led climate litigation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16721, https://doi.org/10.5194/egusphere-egu24-16721, 2024.

EGU24-17250 | ECS | Posters on site | EOS4.3

From Glaciers to Courtrooms: Translating Natural Science Concepts into Legal Frameworks for Climate Litigation 

Randy Muñoz, Christian Huggel, Wilfried Haeberli, Martin Mergili, Adam Emmer, Lukas Arenson, and Matthieu Sturzenegger

The integration of natural science concepts into climate change litigation, particularly in cases related to glacier lake outburst floods (GLOFs) in mountainous regions like the Andes, faces significant challenges due to the differing nature of scientific and legal frameworks.

Scientific understanding of climate change impacts on phenomena such as GLOFs relies heavily on scenarios, modeling, and projections that evolve over time with advancements in technology and knowledge. These models need to be comprehensive, and consider an array of factors including glacier retreat, temperature changes and various risk factors. However, legal standards often require definitive proof of causation. There may arise a discrepancy creating  a gap in case of prevailing uncertainties inherent to high-mountain processes which may not always meet the exacting evidentiary requirements of litigation.

An illustrative example of this challenge is the case of a citizen in Huaraz, in the Andes of Peru, using a major German energy producer over the risks of a catastrophic flood from a GLOF at Lake Palcacocha. The German court’s decision to admit this case is groundbreaking in climate litigation. It implies a recognition of legal responsibilities of large emitters for potential losses and damages caused by anthropogenic climate change globally, provided a causal relation between emissions and risk can be established. This case exemplifies the challenge in linking complex scientific causation with legal accountability.

In the Palcacocha case, the German court defined to distinguish between i) the hazard and risk posed to the plaintiff in Huaraz, and ii) the attribution to anthropogenic climate change and the emissions produced by the defendant. Here we report on the geoscientific studies undertaken to analyze the hazard situation posed by potential rock and ice avalanches, impacting the glacial lake and producing potentially devastating floods in the city of Huaraz. Critical among other are concepts and methods to quantify probability of occurrence of an event, and the effect of cascading slope and mass flow processes.

In conclusion, the challenges in adapting natural science concepts for climate change litigation, particularly regarding GLOFs, stem from different concepts, standards of proof, and conceptual understandings in science and law. Bridging this gap is essential for effective climate litigation and requires innovative interdisciplinary approaches that facilitate the translation of scientific findings into legally cogent arguments. The framework, methods and standards we applied in the case of Palcacocha could serve for other litigation cases in similar environments, highly impacted and vulnerable to anthropogenic climate change. 

How to cite: Muñoz, R., Huggel, C., Haeberli, W., Mergili, M., Emmer, A., Arenson, L., and Sturzenegger, M.: From Glaciers to Courtrooms: Translating Natural Science Concepts into Legal Frameworks for Climate Litigation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17250, https://doi.org/10.5194/egusphere-egu24-17250, 2024.

EGU24-18367 | ECS | Posters on site | EOS4.3

Contributions of carbon majors to historical heatwaves 

Yann Quilcaille, Lukas Gudmundsson, Thomas Gasser, and Sonia I. Seneviratne

While human-induced climate change shows no sign of slowing down, calls to steer to a more sustainable path grow louder. Countries are sued for their lack of ambitious climate action, and high-emitting companies for their responsibilities. However, climate litigation is often impeded by the lack of scientific evidence directly relevant to the legal cases. Available attribution research can provide support for claims, but some key elements are still missing. First, event attribution studies are limited to a few selected events, depending on available researchers’ time and interests. Second, the contributions of high-emitting companies to recent extreme events has not yet been quantified. Here, we fill in both of these gaps. We present the first collective attribution of 149 historical heatwaves reported over the 2000-2021 period. We apply a well-established extreme weather attribution (Philip et al., 2020) to heatwaves reported in the EM-DAT database (EM-DAT, 2023). For each listed heatwave, we identify the event in observational data (ERA5, BEST) and CMIP6 data, then we estimate its occurrence probabilities for present and pre-industrial climate conditions. Subsequently, we calculate the contributions in global mean surface temperature of 110 fossil fuels and cement companies using their CO2 and CH4 emissions (Heede, 2014) and the reduced-complexity Earth system model OSCAR (Gasser et al., 2017). These contributions combined to the collective attribution allow for the calculation of the contributions of these carbon majors to all of the analyzed historical heatwaves. These carbon majors represent 76% of the CO2 emissions over 1850-2021, and half of this 76% is due to only six actors (nation-state of China for coal & cement; nation-state of the Former Soviet Union for coal, oil and gas; Saudi Aramco; Chevron; ExxonMobil; Gazprom). In terms of global mean surface temperature, these six majors contribute to 0.30°C, while the others contribute to an additional 0.34°C. The majority of heatwaves are made substantially more probable and intense due to these six carbon majors. Though, other carbon majors cannot be neglected, as their sole contribution may be enough to make some heatwaves possible. This attribution of a large number of heatwaves and the link to the contributions of the carbon majors will provide useful resources for climate litigation, paving the way towards their legal responsibility.

 

EM-DAT, CRED / UCLouvain: www.emdat.be, last access: 09.01.2024.

Gasser, T., Ciais, P., Boucher, O., Quilcaille, Y., Tortora, M., Bopp, L., and Hauglustaine, D.: The compact Earth system model OSCAR v2.2: Description and first results, Geoscientific Model Development, 10, 271-319, 10.5194/gmd-10-271-2017, 2017.

Heede, R.: Tracing anthropogenic carbon dioxide and methane emissions to fossil fuel and cement producers, 1854–2010, Climatic Change, 122, 229-241, 10.1007/s10584-013-0986-y, 2014.

Philip, S., Kew, S., van Oldenborgh, G. J., Otto, F., Vautard, R., van der Wiel, K., King, A., Lott, F., Arrighi, J., Singh, R., and van Aalst, M.: A protocol for probabilistic extreme event attribution analyses, Adv. Stat. Clim. Meteorol. Oceanogr., 6, 177-203, 10.5194/ascmo-6-177-2020, 2020.

How to cite: Quilcaille, Y., Gudmundsson, L., Gasser, T., and Seneviratne, S. I.: Contributions of carbon majors to historical heatwaves, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18367, https://doi.org/10.5194/egusphere-egu24-18367, 2024.

EGU24-19683 | Posters on site | EOS4.3

Four roles for geoscientists in climate litigation 

Wim Thiery, Rosa Pietroiusti, Annalisa Savaresi, and Stefaan Smis

The number of climate change lawsuits is exploding,  and so is the need for scientific evidence on climate change in courtrooms. Here we identify four roles that climate researchers can take up in light of these recent developments: expert witness, party support, amicus curiae, and litigation-relevant research. For each role, we highlight recent examples and best practices, as well as pitfalls and their overcoming. These examples overall highlight the urgent need for interdisciplinary research between climate science and legal scholars to bring both research communities closer together. In addition, and in activities where exchange with litigators takes place, it is critical that ingestion of scientific information occurs right from the start of the litigation process.

How to cite: Thiery, W., Pietroiusti, R., Savaresi, A., and Smis, S.: Four roles for geoscientists in climate litigation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19683, https://doi.org/10.5194/egusphere-egu24-19683, 2024.

EGU24-20599 | Posters on site | EOS4.3

How stocks judge COPs: market impacts of climate conferences 

Robin Lamboll and Alaa Al Khourdajie

This study investigates the impact of Conference of the Parties (COP) meetings on the stock prices of oil companies and the broader implications for renewable energy sectors to examine the relationship between international climate negotiations and market responses in the energy sector. The analysis focuses on stock price movements and volatility within the oil and renewable energy industries. We look at the data of the 10 largest stocks in each category and investigate their behaviour during COP. The findings indicate that, with the exception of notable negative stock price movements during COPs 20 and 21 (before and during the signing of the Paris Agreement), COP meetings generally do not significantly influence the value of oil companies. There is also no impact on oil prices during COP itself, though some sign of disturbance in the period immediately afterwards. The study also addresses the renewable energy sector, finding no strong effects from most COP meetings but a notable decrease in stocks during COP6's failure. We conclude that the majority of COPs have not produced market signals indicating a green transition, although these signals are potentially detectable.

How to cite: Lamboll, R. and Al Khourdajie, A.: How stocks judge COPs: market impacts of climate conferences, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20599, https://doi.org/10.5194/egusphere-egu24-20599, 2024.

The Climate Litigation Network supports national organisations that are taking litigation action against their governments in respect of the adequacy and implementation of national climate policies and targets. This presentation will provide an overview of the role in science in climate cases that challenge governments’ overall emissions reductions (“framework cases”) – of which there are more than 100 globally. Drawing from a litigator’s perspective, it will address common legal questions (i.e., harm, causation, foreseeability and remedies) that arise in such cases, and provide examples of how science has been used in case studies. 

Across framework cases, scientific evidence has been critical to success. For example, many cases, including those based on human rights or tort law, require claimants to show how they have been impacted or have suffered harm. In this regard, supporting studies range widely, depending on the facts of the case. These could include studies concerning extreme weather events, flooding, landslides, impacts on crop production and availability to water, and impacts on health or culture. To establish legal liability, claimants typically must show that the government’s actions can be causally linked to the harm, and that the harm was foreseeable. In this regard, attribution science and climate science generally can play a role in evidencing why government action (or lack of action) is contributing to climate change impacts. In terms of remedies, several cases have sought to push governments to adopt emissions reduction targets that reflect their “fair share” of the remaining global carbon budget. Numerous fair share methodologies have been developed by academics, many of which seek to reflect obligations and principles set out in the United Nations Framework Convention on Climate Change and international environmental law. In some cases, there may also be questions concerning loss and damage, which could require detailed analyses of how much damage has been incurred, or could be incurred in future, due to the impacts of climate change.

Drawing on case studies from specific cases, this presentation will highlight the current deployment of science in climate cases against governments and explore new frontiers.

How to cite: Williamson, A.: Challenging governments’ response to the climate crisis: the role of science in climate litigation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21949, https://doi.org/10.5194/egusphere-egu24-21949, 2024.

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