CR – Cryospheric Sciences

EGU22-1321 | Presentations | MAL19 | CR Division Outstanding ECS Award Lecture

Insights of multiple sensors remote sensing techniques for the mapping of subglacial valleys beneath glaciers and ice shelves 

Romain Millan, Jeremie Mouginot, Mathieu Morlighem, Antoine Rabatel, Lucille Gimenes, Nicolas Champollion, Eric Rignot, Lu An, and Anders Bjørk

Accurate mapping of subglacial bedrock topography is of prime importance to correctly simulate the past and future evolution of glaciers and ice sheets. As ocean warming is a major driver of recent changes in Greenland and Antarctica, mapping the bathymetry of the ocean seafloor in fjords and underneath ice shelves is crucial to accurately model warm water pathways up to the ice margins and grounding lines. A good knowledge of this bedrock topography also allows to better understand the past extent of the ice sheets and identify vulnerable regions that are sitting on retrograde bed slopes, hence that might be prone to the marine ice sheet instability. For mountain glaciers, accurately mapping the bedrock topography is mandatory to estimate ice thicknesses, which are used to simulate the contribution of glaciers to sea level rise, but also to quantify the amount of freshwater resources stored in glaciers. Because of their large number, remote locations, and difficult access conditions, only scarce in-situ data exists for bedrock topography. Hence, while being a fundamental variable for glacier modeling, it remains poorly constrained at the time. Here, we present how the use of multiple sensors remote sensing techniques has helped us to unravel the hidden relief beneath glaciers and ice sheets. In Greenland and Antarctica, we use airborne gravimetry measurements along with multibeam and radar echoe sounder to map the bathymetry in fjords and below ice shelves. We show that the use of these new bathymetric products help us to understand the retreat history of glaciers, revealing pathways for warm water, and contributes to better modeling ocean circulation up to the grounding lines of glaciers. For mountain glaciers, we mapped the ice velocity worldwide at an enhanced sampling resolution of 50 m, using massive cross correlation techniques on image pairs from both optical (ESA’s Sentinel-2; USGS/NASA’s Landsat-7/8) and radar imagery (ESA’s Sentinel-1a/b). Finally, we combine this mapping with airborne and ground penetrating radar to recover the ice thickness of all glaciers on Earth. These estimations reveal a different picture of the bedrock topography beneath glaciers, with a modified ice thickness distribution. Using these new estimations as initial state in the Open Global Glacier Model, we show the important impact on the evolution of freshwater resources, and specifically on the timing of the peak water.

How to cite: Millan, R., Mouginot, J., Morlighem, M., Rabatel, A., Gimenes, L., Champollion, N., Rignot, E., An, L., and Bjørk, A.: Insights of multiple sensors remote sensing techniques for the mapping of subglacial valleys beneath glaciers and ice shelves, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1321, https://doi.org/10.5194/egusphere-egu22-1321, 2022.

EGU22-6431 | Presentations | MAL19 | Julia and Johannes Weertman Medal Lecture

Future global glacier mass changes and their impact on sea level and streamflow 

Regine Hock

Concurrent with atmospheric warming, glaciers around the world are rapidly retreating with direct consequences for global sea level and streamflow. Projections indicate considerable mass losses over the 21st century, however, mass losses vary strongly between regions and emission scenarios. In some regions with little ice cover projections forced by high emission scenarios show almost complete deglaciation by the end of the 21st century while in high-polar regions the relative mass losses are generally in the order of a few tenths of percent relative to year 2015. The mass losses alter local runoff regimes and lead to glacier runoff increases in some regions but to decreases in others. Global glacier changes are linearly correlated with global mean temperature increase indicating that limiting global warming has a direct effect on future glacier mass changes.

How to cite: Hock, R.: Future global glacier mass changes and their impact on sea level and streamflow, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6431, https://doi.org/10.5194/egusphere-egu22-6431, 2022.

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

EGU22-53 | Presentations | CR1.1

Future glacier lakes in the Swiss Alps: a projection of their evolution 

Daniel Farinotti, Tim Steffen, Matthias Huss, Rebekka Estermann, and Elias Hodel

With the ongoing, rapid glacier retreat, high-alpine landscapes are poised to change drastically over the coming decades. The newly exposed areas will not only give rise to new environments that can be eventually colonized by plants and organisms, but also to characteristic landforms. Amongst these, future glacier lakes forming in topographical depressions left behind by glacier retreat, have already been in the focus of earlier studies. The interest in these features is given by a number of factors, ranging from the ecological significance of such high-alpine lakes, over the potential hazards posed by such newly emerging water bodies, to their optical appeal in terms of landscape elements.

Here, we add to the existing body of literature dealing with the formation of new glacier lakes, and do so by leveraging both (1) a recently released, measurement-based estimate for the subglacial topography of all glaciers in the Swiss Alps, and (2) the results of a regional-scale glacier evolution model driven by different climate scenarios. Whilst the first point significantly increases the robustness of our projections, the second allows for a first quantification of the timing by which such new glacier lakes are expected to emerge. In this time-dependent analysis, we also include the possibility for newly emerging lakes to disappear again due to re-filling with sediments – a process neglected by studies so far.

Our results indicate that, if glaciers were to disappear entirely from the Swiss Alps, up to 683 new glacier lakes could emerge. These hold the potential of storing up to 1.16 ± 0.16 km3 of water, for a total lake area of 45 ± 9 km2. For a middle-of-the-road climate scenario, we estimate that about 14% of the total volume (i.e. 0.16 ± 0.07 km3) could emerge by 2050. For 2100, the number changes to 57% (0.66 ± 0.17 km3), indicating a substantial increase in the pace by which new lakes will emerge after mid-century. Our first-order assessment of lake re-sedimentation indicates that about 45% of the newly emerging glacier lakes (ca. 260 out of ca. 570) could disappear again before the end of the century, and that between 12 to 20% of the newly emerging lake volume could be lost again due to this process. This suggests that sedimentation processes have to be taken into account when aiming at anticipating how future glacier landscapes will look like.

How to cite: Farinotti, D., Steffen, T., Huss, M., Estermann, R., and Hodel, E.: Future glacier lakes in the Swiss Alps: a projection of their evolution, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-53, https://doi.org/10.5194/egusphere-egu22-53, 2022.

In contrast to the general retreat of glaciers across the globe, the glaciers of the Karakoram (KR) region of Karakoram-Himalayas (KH) have displayed an anomalous divergent response, with some glaciers remaining either stable or surging. This phenomenon is known as the "Karakoram Anomaly." Although many factors are reported to have control over it, the present study tries to decipher the role of Western Disturbances (WDs) in establishing and sustaining the anomaly. These upper-tropospheric extra-tropical cyclones impact the region during the boreal winter. WDs are the major contributor of winter snowfall over KR, dictating the mass-balance variability of the region, as reported by previous studies. Therefore, to achieve the study's objectives, a tracking algorithm is applied to 39-seasons (1980-2019; Nov-Mar) of the ERA5 reanalysis dataset. Initial simulations suggest that the tracking algorithm has the potential to capture nearly ~90% of the reported tracks accurately in terms of their time of occurrence. Furthermore, the associated statistics generated for tracks passing through KR revealed a ~10% increase in the WD-associated precipitation intensity. The results shall be further analyzed to quantify the contribution of WD-associated snowfall in modulating the regional mass-balance anomaly. Additionally, the various mechanisms involved in WDs' formation and intensification will also be investigated.

How to cite: Javed, A. and Kumar, P.: Deciphering the changes associated with Western Disturbances impacting “Karakoram Anomaly”, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-155, https://doi.org/10.5194/egusphere-egu22-155, 2022.

EGU22-366 | Presentations | CR1.1

Surface energy balance and sublimation of the winter snow cover at 4863 m a.s.l. on Chhota Shigri Glacier moraine (western Himalaya, India) between 2009 and 2020 

Arindan Mandal, Thupstan Angchuk, Mohd Farooq Azam, Alagappan Ramanathan, Patrick Wagnon, Mohd Soheb, and Chetan Singh

Surface energy balance (SEB) is the most comprehensive way to explain the atmosphere-glacier interactions but requires extensive data. We analyse an 11-year (2009-2020) record of the meteorological dataset from an automatic weather station installed at 4863 m a.s.l., on a lateral moraine of the Chhota Shigri Glacier in the western Himalaya. The study was carried out over the winter months (December to April) to understand the SEB drivers and snow sublimation. Further, we examine the role of cloud cover on SEB and turbulent heat fluxes. The turbulent heat fluxes were calculated using the bulk aerodynamic method, including stability corrections. The net short-wave radiation is the primary energy source. However, a significant amount of energy is dissipated by the turbulent heat fluxes. The cloud cover plays an important role in limiting the incoming short-wave radiation by up to 75%. It also restricts the turbulent heat fluxes by around 50%, consequently less snow sublimation. During the winter period, turbulent latent heat flux contributed the largest (63%) in the total SEB, followed by net all-wave radiation (29%) and sensible heat flux (8%). Dry air, along with the high snow surface temperature and wind speed, favours sublimation. We also observe that strong and cold winds, possibly through mid-latitude western disturbances, impede sublimation by bringing high moisture content in the region and cooling the snow surface. The estimated snow sublimation fraction is 18 to 42% of the total winter snowfall at the study site, indicating that the snow sublimation is an essential parameter in the surface mass balance and hydrological modelling at the high mountain Himalayan catchments.

How to cite: Mandal, A., Angchuk, T., Azam, M. F., Ramanathan, A., Wagnon, P., Soheb, M., and Singh, C.: Surface energy balance and sublimation of the winter snow cover at 4863 m a.s.l. on Chhota Shigri Glacier moraine (western Himalaya, India) between 2009 and 2020, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-366, https://doi.org/10.5194/egusphere-egu22-366, 2022.

EGU22-777 | Presentations | CR1.1

Topographic controls on ice flow and recession for Juneau Icefield (Alaska/British Columbia) 

Bethan Davies, Jacob Bendle, Jonathan Carrivick, Robert McNabb, Christopher McNeil, Mauri Pelto, Seth Campbell, Tom Holt, Jeremy Ely, and Bradley Markle

Globally, glaciers are losing dramatic volumes of ice, especially in Alaska, which dominates sea-level rise from glaciers. Plateau icefields may be especially sensitive to climate change due to the non-linear controls their topography imparts on their response to climate change. However, Alaskan plateau icefields have been subject to little structural glaciological or regional geomorphological assessment, which makes the controls on their present and former mass balance difficult to ascertain. 

We inventoried 1050 glaciers and 401 lakes of the Juneau Icefield region for the year 2019. We found that 63 glaciers had disappeared since the 2005 inventory, with a reduction of glacier area of 422 km2. We also present the first structural glaciological and geomorphological map for an entire plateau icefield in Alaska. Glaciological mapping of nearly 20,000 features included crevasses, debris cover, foliation, ogives, medial moraines and, importantly, areas of glacier fragmentation, where glaciers either separated from tributaries via lateral recession (n=59), and disconnected within areas of former icefalls (n=281). Geomorphological mapping of >10,000 landforms included glacial moraines, glacial lakes, trimlines, flutes and cirques. These landforms were generated by a temperate icefield during the “Little Ice Age” neoglaciation. These data demonstrate that the present-day outlet glaciers, which have a similar thermal and ice-flow regime, have undergone largely continuous recession since the “Little Ice Age”.

These data document the interactions between topography and glacier change. Importantly, disconnections are occurring within glaciers can separate accumulation and ablation zones, increasing rates of glacier mass loss. We show that glacier disconnections are widespread across the icefield and should be critically taken into consideration when icefield vulnerability to climate change is considered.

How to cite: Davies, B., Bendle, J., Carrivick, J., McNabb, R., McNeil, C., Pelto, M., Campbell, S., Holt, T., Ely, J., and Markle, B.: Topographic controls on ice flow and recession for Juneau Icefield (Alaska/British Columbia), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-777, https://doi.org/10.5194/egusphere-egu22-777, 2022.

EGU22-1170 | Presentations | CR1.1

Glaciers and ice caps under climate change since the Little Ice Age 

Jonathan Carrivick, Jacob Yde, Liss Andreassen, William James, Jenna Sutherland, Ethan Lee, Duncan Quincey, Clare Boston, and Michael Grimes

Mountain glaciers and ice caps are undergoing rapid mass loss but rates of contemporary change lack long-term (centennial-scale) context. Future projections of glacier changes require spin up to present day conditions and thus baseline ice extents and ice volumes are a prerequisite for model validation. Here, we reconstruct the Little Ice Age maximum glacier extent and ice surface of Jostedalsbreen, which is the largest ice mass in mainland Europe. Jostedalsbreen had its largest Little Ice Age (LIA) maximum about 1740 to 1860. The LIA ice-covered area was 568 km2 and the LIA ice volume was between 61 km3 and 91 km3. We show that the major outlet glaciers have lost at least 110 km2 or 19 % of their LIA area and 14 km3 or 18 % of their LIA volume until 2006. The largest proportional changes are associated with the loss of ice falls and consequent disconnection of tributaries. Glacier-specific hypsometry changes suggest a mean rise in ELA of 135 m but there is wide inter-glacier variability. A median date for the LIA of 1755 suggests that the long-term rate of ice mass loss has been 0.05 m w.e. a-1. Comparison of that long-term rate of mass loss with our other published analyses of changes to mountain glaciers and ice caps since the LIA shows that Jostedalsbreen is unusual in not exhibiting an acceleration in mass loss since the LIA. Indeed, we have reported a 23 % acceleration of glacier mass loss in NE Greenland and a doubling for the Southern Alps of New Zealand. Others have reported a doubling of the rate of mass loss for the Vatnajökull ice cap and for Patagonia since the LIA. We have very recently reported a ten-fold increase for ~ 15,000 glaciers across the Himalaya. A synthesis of these long-term analyses reveals a latitudinal effect, regional climate effects and local controls on long-term glacier mass balance. For example, local rates of loss across the Himalaya were enhanced with the presence of surface debris cover (by 2 times vs clean-ice) and/or a proglacial lake (by 2.5 times vs land-terminating). Overall, we highlight the utility of geomorphological-based reconstructions of glaciers for understanding and quantifying long-term (centennial-scale) responses of mountain glaciers and ice caps to climate and hence for understanding of meltwater production and proglacial landscape evolution.

How to cite: Carrivick, J., Yde, J., Andreassen, L., James, W., Sutherland, J., Lee, E., Quincey, D., Boston, C., and Grimes, M.: Glaciers and ice caps under climate change since the Little Ice Age, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1170, https://doi.org/10.5194/egusphere-egu22-1170, 2022.

EGU22-1808 * | Presentations | CR1.1 | Highlight

On the benefit and cost of artificial glacier melt reduction 

Matthias Huss

The artificial reduction of glacier melt is gaining increased attention due to accelerated ice wastage with atmospheric warming. In Switzerland, active coverage of glaciers using geotextiles is performed at currently ten sites and since more than 15 years. The measures represent an efficient method to locally safeguard the operability of ski slopes or other touristic attractions. Furthermore, ideas for large-scale technical interventions to save glaciers using artificially produced snow were proposed, with considerable resonance in the international media.

Here, an assessment of the benefit and applicability, as well as the costs and the drawbacks of different techniques to artificially reduce glacier melt is presented. On the one hand, observational data (in situ and remote sensing) across the Swiss Alps are used to analyze the efficiency and the spatial extent of the applied technical measures in the past. On the other hand, an integrative model approach is presented for investigating the potential of large-scale artificial snow production to limit the retreat of an entire glacier over the 21st century, including an evaluation of the related costs and risks.

Presently, about 0.18 km2, or 0.02% of the total Swiss glacier area, are covered by geotextiles, with a doubling of the covered area since 2012. Up to 350,000 m3 of ice melt per year have been mitigated by this technique. It is estimated that 1 m3 of saved glacier ice comes at a cost of 0.6 to 7.9 CHF m-3 yr-1, depending on the type of installation and its location on the glacier. These relatively high costs are an indication for the considerable economic value attributed to glacier ice.

It is shown that artificial melt reduction is not scalable. Whilst local interventions can be efficient and profitable, climate scenario-based model results for large-scale interventions indicate that saving Alpine glaciers by technological solutions is neither achievable nor affordable. It is a challenge to adequately communicate this gap between feasible local-scale ice-melt reduction, and the impractical technological 'saving' of entire glaciers to a broader public.

How to cite: Huss, M.: On the benefit and cost of artificial glacier melt reduction, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1808, https://doi.org/10.5194/egusphere-egu22-1808, 2022.

EGU22-2367 | Presentations | CR1.1

Which are the largest glaciers in the world outside the ice sheets? 

Michael Zemp, Ann Windnagel, Regine Hock, Fabien Maussion, Frank Paul, Philipp Rastner, and Bruce Raup

Glacier monitoring has been internationally coordinated for more than 125 years. Despite this long history there is no unambiguous answer to the popular question: which are the world’s largest glaciers?

In this study, we present a first scientific assessment of the largest glaciers in the world – distinct from the two ice sheets in Greenland and Antarctica – and in the 19 regions used for the current Randolph Glacier Inventory. Ranking glaciers by size is non-trivial since it depends on how an individual glacier is defined and mapped. It is also important to differentiate between individual glaciers and glacier complexes, which are contiguous glaciers that meet at ice divides and might form an ice cap or ice field.

We find that the largest glacier complexes cover areas larger than ten thousand square kilometres, whereas the largest individual glaciers cover up to several thousand square kilometres. The world’s largest glaciers and glacier complexes are located on the Antarctic Peninsula, on sub-Antarctic Islands, in the Arctic, and in Patagonia. As such, the largest glacier complexes cover areas the size of smaller countries (e.g., Switzerland or Austria) or of smaller US states (e.g. New Jersey or South Carolina), but are still orders of magnitudes smaller than the Greenland and Antarctic Ice Sheets.

In addition, we show that the ranking of glaciers requires not only clear definitions but depends on the availability, quality, and consistency of digital glacier outlines at global scale. Corresponding additional metadata are required in the available inventories to fully automate a glacier ranking by area, and to extend such a study to rankings by length, volume/mass, and other parameters.

How to cite: Zemp, M., Windnagel, A., Hock, R., Maussion, F., Paul, F., Rastner, P., and Raup, B.: Which are the largest glaciers in the world outside the ice sheets?, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2367, https://doi.org/10.5194/egusphere-egu22-2367, 2022.

EGU22-2818 | Presentations | CR1.1

Thermal regime of the Grigoriev ice cap and the Sary-Tor glacier in the Inner Tien Shan, Kyrgyzstan. 

Lander Van Tricht and Philippe Huybrechts

The thermal regime of glaciers and ice caps represents the internal distribution of ice temperatures. Accurate knowledge of the thermal regime is crucial to understand the dynamics and response of ice masses to climate change, and to model their evolution. The ice temperature for example strongly controls the plasticity and the deformation rate of the ice with higher temperatures encouraging movement, and whether a glacier can slide over its base. Although the assumption is that most ice masses in the Inner Tien Shan are polythermal, this has not been examined in appropriate detail so far. In this research, we investigate the thermal regime of the Grigoriev ice cap and the Sary-Tor glacier, both located in the Inner Tien Shan in Kyrgyzstan. A 3D thermo-mechanical higher-order model is applied. Input data and boundary conditions are inferred from a surface energy mass balance model, a historical air temperature and precipitation series, ice thickness reconstructions, and digital elevation models. Calibration and validation of the englacial temperatures is performed using historical borehole measurements on the Grigoriev ice cap, radar measurements for the Sary-Tor glacier and temperature measurements on other glaciers in the area. The results of this study reveal a polythermal structure of the Sary-Tor glacier and a cold structure of the Grigoriev ice cap. The difference is related to the larger amount of snow (insulation) and superimposed ice (release of latent heat) for the Sary-Tor glacier resulting in higher surface temperatures, especially in the accumulation area, which are subsequently advected downstream. Further, ice velocities are much lower for the Grigoriev ice cap compared to the Sary-Tor glacier with consequent lower advection rates. Since the selected ice masses are representative examples of the (Inner) Tien Shan glaciers and ice caps, our findings can be generalised allowing this to improve the understanding of the dynamics and future evolution of the studied ice masses as well as other glaciers and ice caps in the region.

How to cite: Van Tricht, L. and Huybrechts, P.: Thermal regime of the Grigoriev ice cap and the Sary-Tor glacier in the Inner Tien Shan, Kyrgyzstan., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2818, https://doi.org/10.5194/egusphere-egu22-2818, 2022.

EGU22-3021 | Presentations | CR1.1

North Atlantic cooling is slowing down mass loss of Icelandic glaciers 

Brice Noël, Guðfinna Aðalgeirsdóttir, Finnur Pálsson, Bert Wouters, Stef Lhermitte, Jan M. Haacker, and Michiel R. van den Broeke

Icelandic glaciers have been losing mass since the Little Ice Age in the mid-to-late 1800s, with higher mass loss rates in the early 21st century, followed by a slowdown since 2011. As of yet, it remains unclear whether this mass loss slowdown will persist in the future. By reconstructing the contemporary (1958-2019) surface mass balance of Icelandic glaciers, we show that the post-2011 mass loss slowdown coincides with the development of the Blue Blob, an area of regional cooling in the North Atlantic Ocean to the south of Greenland. This regional cooling signal mitigates atmospheric warming in Iceland since 2011, in turn decreasing glacier mass loss through reduced meltwater runoff. In a future high-end warming scenario, North Atlantic cooling is projected to mitigate mass loss of Icelandic glaciers until the mid-2050s. High mass loss rates resume thereafter as the regional cooling signal weakens. 

How to cite: Noël, B., Aðalgeirsdóttir, G., Pálsson, F., Wouters, B., Lhermitte, S., Haacker, J. M., and van den Broeke, M. R.: North Atlantic cooling is slowing down mass loss of Icelandic glaciers, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3021, https://doi.org/10.5194/egusphere-egu22-3021, 2022.

EGU22-4166 | Presentations | CR1.1

Mass loss of mountain glaciers does not translate directly to sea level rise 

Philip Kraaijenbrink, Edwin Sutanudjaja, Roderik van de Wal, Marc Bierkens, and Walter Immerzeel

The excess meltwater that results from climate change induced mass loss of mountain glaciers is an important contributor to sea level rise (SLR). Up to now, large scale glacier observations and models have been used to estimate the amount of generated excess meltwater and its transient contribution to SLR under the assumption that meltwater is added to the ocean instantaneously and in its entirety. However, hydrological processes and water consumption during the transit from glacier to the ocean may affect the amount and timing of glacier runoff that eventually drains into the ocean. We hypothesize that some of the lost glacier ice may not reach the ocean at all or only at a much later stage.

In this study, we assessed the impacts of the hydrological pathway of meltwater from the glacier snouts to the ocean in the Indus Basin. With its large glacier ice reserves, relatively arid climate and large irrigation scheme, this basin provides the optimal case study for such an assessment. We coupled output from a detailed glacier model to the fully distributed hydrological model PCR-GLOBWB 2, and forced the models with bias-corrected historical and future climate data from the third phase of the Inter-Sectoral Impact Model Intercomparison Project (ISIMIP3).

Our findings show that, particularly in (periods of) dry years, considerable fractions of excess glacier meltwater do not enter the ocean. The changes in hydrological stores indicate that much of it is withdrawn for surface water irrigation of cropland and eventually evaporates as a result. The increased surface water availability due to the presence of excess glacier meltwater leads to a lowering of groundwater irrigation and a reduction of the unsustainable depletion of the basin’s groundwater store. In the future, increased availability of excess glacier meltwater and increased water withdrawals due to continued climate change and socioeconomic developments exacerbate these effects. Up to the end of century, depending on the specific climate scenario, around 12% of excess glacier meltwater does not enter the ocean directly.

We conclude that not all glacier mass loss can be assumed to contribute (directly) to SLR, which may lead to overestimation of future sea level rise. Further research is necessary to estimate the breadth of these effects at a global scale, but we hypothesize that this may also play a role in other glacierized basins with semi-arid downstream regions and considerable distances between the glaciers and the ocean.

How to cite: Kraaijenbrink, P., Sutanudjaja, E., van de Wal, R., Bierkens, M., and Immerzeel, W.: Mass loss of mountain glaciers does not translate directly to sea level rise, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4166, https://doi.org/10.5194/egusphere-egu22-4166, 2022.

EGU22-4281 | Presentations | CR1.1

Longitudinal patterns of suspended microbial assemblages in glacier-fed streams. 

Kristýna Jachnická, Tyler J. Kohler, Petra Vinšová, Lukáš Falteisek, Gabriel Singer, Tomáš Vrbický, and Marek Stibal

Glaciers are considered to be a biome with diverse microbial life, and their meltwaters are highly influential to downstream ecosystems by creating a unique riverine habitat template and providing resources such as nutrients and organic matter. Yet, despite unprecedented rates of glacial retreat globally, not much is known about the fate of microbial cells exported from glaciers, despite their potential to colonize and reside in downstream ecosystems. The influence of glacial meltwater on these downstream ecosystems may persist far downstream, but other sources of nutrients, organic matter, and microbial cells within the hydrological catchment likely gain influence with distance from the glacier. These include soils and thawing permafrost - partly via eroding stream banks - and benthic stream biofilms residing both within and outside the glacial environment (e.g. in tributary streams).

In this work, we ask how suspended microbial assemblages change with increasing distance from the source glacier, especially in terms of their composition and corresponding with abiotic environmental factors. We hypothesize that OTU richness will increase with distance from source glaciers as the importance of other catchment sources increase. Specifically, we expect ‘cryospheric’ OTUs to decrease in relative abundance, and more ‘generalist’ freshwater OTUs to increase. We sampled five glacier-fed streams (3 in the Austrian Alps, 1 in Iceland and 1 in Greenland) from the glacier terminus until the ocean or major riverine outlet. DNA was extracted from samples, and 16s rRNA gene amplicons were sequenced to characterize the assemblage structure. These preliminary observations improve our knowledge of the fate of glacially-exported microbial assemblages, and help us to understand the extent of their potential impact for downstream ecosystems, especially in the current age of deglaciation.

How to cite: Jachnická, K., Kohler, T. J., Vinšová, P., Falteisek, L., Singer, G., Vrbický, T., and Stibal, M.: Longitudinal patterns of suspended microbial assemblages in glacier-fed streams., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4281, https://doi.org/10.5194/egusphere-egu22-4281, 2022.

EGU22-4484 | Presentations | CR1.1

The Randolph Glacier Inventory (RGI) version 7 

Fabien Maussion, Regine Hock, Frank Paul, Philipp Rastner, Bruce Raup, Michael Zemp, and the RGI Consortium

The Randolph Glacier Inventory (RGI) is a globally complete collection of digital glacier outlines, excluding the two ice sheets. It has become a pillar of glaciological research at global and regional scales for estimates of recent and future glacier changes, glacier mass balance, glacier contribution to sea-level rise, among others. The latest RGI version (V6) was released in July 2017.


Here, we present a new version of the RGI (version 7.0), which is our best estimate of global glacier outlines around the year 2000. Unlike previous versions which were compiled by an ad-hoc manual process using different sources, RGI7.0 is generated directly from the Global Land Ice Measurements from Space (GLIMS) glacier database, ensuring full traceability of single outlines to their original authors. The dataset is generated automatically with Python scripts parsing the GLIMS database and selecting outlines according to community decisions (based on data availability, quality and closeness to the year 2000). Prior to its release, the dataset was available for open review from the scientific community, and further refined as necessary.


About 70% of the outlines (30% of the total area) in RGI7.0 are obtained from new inventories that were submitted to GLIMS since the last release of RGI6.0 by different groups around the world. This led to considerable quality improvements especially in High Mountain Asia, Northern Canada, northern Greenland, Caucasus and Middle East, South America and New Zealand. RGI7.0 includes updated topographical and geometrical glacier attributes generated with a new community software. The new RGI generation process is open-source, fully reproducible and easily adaptable, making future updates straightforward to generate.

How to cite: Maussion, F., Hock, R., Paul, F., Rastner, P., Raup, B., Zemp, M., and Consortium, T. R.: The Randolph Glacier Inventory (RGI) version 7, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4484, https://doi.org/10.5194/egusphere-egu22-4484, 2022.

EGU22-5099 | Presentations | CR1.1

Sensitivity of Alpine glaciers to anthropogenic atmospheric forcings 

Léo Clauzel, Adrien Gilbert, Martin Ménégoz, and Olivier Gagliardini

European Alpine glaciers have strongly shrunk over the last 150 years in response to climate warming. Glacier retreat is expected to persist and even intensify in future projections. This work aims at evaluating how much of the glacier retreat can be attributed to anthropogenic atmospheric forcings. For this purpose, we quantify the evolution of the Argentière glacier in the Mont Blanc area under different climate reconstructions over the period 1850-present. The different reconstructions are extracted from 4 ensemble experiments conducted with the IPSL-CM6-LR General Circulation Model (GCM), excluding and including natural and anthropogenic atmospheric forcings. These 6-member experiments are statistically corrected and downscaled with a quantile mapping approach that ensures consistent long term tendencies and precipitation-temperature relationship. These data feed a three-dimensional ice flow model coupled with a surface mass balance model to simulate changes in the glacier geometry over time. Over 1850-2014, historical simulations show a significant warming whereas there is no clear trend of precipitation at the annual scale. The glacier appears to be highly sensitive to individual anthropogenic forcings, with a glacier volume loss around 45% in the greenhouse gases-only experiment and a growth of about 5% in the aerosols-only experiment in 2014 relative to 1850, compared to the 32% volume loss over the same period in the historical experiment. Moreover, the natural-only experiment reveals the great impact of anthropogenic forcings with a much lower volume loss of about 10%. The latter also confirms that the end of the Little Ice Age would have occurred even without human activities. Finally, the simulations highlight a strong influence of natural internal variability and show that Argentiere Glacier definitively left its possible natural pathway only during the last decade.

How to cite: Clauzel, L., Gilbert, A., Ménégoz, M., and Gagliardini, O.: Sensitivity of Alpine glaciers to anthropogenic atmospheric forcings, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5099, https://doi.org/10.5194/egusphere-egu22-5099, 2022.

EGU22-5833 | Presentations | CR1.1

Multi-temporal elevation changes of Fedchenko Glacier, Tajikistan (1928-1958-1980-2010-2017-2019) 

Fanny Brun, Astrid Lambrecht, Christoph Mayer, Etienne Berthier, Amaury Dehecq, Janali Rezaei, and César Deschamps-Berger

Fedchenko Glacier, located in the central Pamir in Tajikistan, is the longest glacier in Asia. Due to its prominent location and its large size, it attracted scientific interest over the course of the twentieth and twenty first centuries, providing thus a rare legacy of historical data in Central Asia. In this study, we investigate a series of topographic data from 1928 to 2019. We use topographic maps collected during historical expeditions in 1928 and 1958. We take advantage of modern satellite data, such as KH-9 spy satellite (1980), SPOT5 (2010) and Pléiades (2017 and 2019). We also rely on ICESat campaign of 2003 and numerous GNSS surveys conducted in 2009, 2015, 2016 and 2019, which ensures a proper co-registration of the satellite data.

We calculate a mean rate of elevation change of -0.40 m/yr for 1928-2019, with a maximum thinning at the lowermost locations (approaching -0.90 m/yr). Despite this long-term thinning trend, we observe large contrasts between the sub-periods. The thinning rate of the tongue doubled for two sub-periods (1958-1980 and 2010-2017) compared to the long-term average. The ERA5 reanalysis (1950-2020) and the Fedchenko meteorological station records (1936-1991) reveal a dry anomaly in 1958-1980, followed by a wet anomaly in 1980-2010, which might have compensated for the temperature increase and thus mitigated mass losses. This wet anomaly could be an important feature of the “Pamir-Karakoram” anomaly, characterized by limited glacier mass losses in this region during the early twenty-first century. Our work contributes to better constrain the decadal glacier thickness changes, with unprecedented temporal resolution. This opens the way for more sophisticated approaches that link the glacier response to climate variability over decades.

How to cite: Brun, F., Lambrecht, A., Mayer, C., Berthier, E., Dehecq, A., Rezaei, J., and Deschamps-Berger, C.: Multi-temporal elevation changes of Fedchenko Glacier, Tajikistan (1928-1958-1980-2010-2017-2019), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5833, https://doi.org/10.5194/egusphere-egu22-5833, 2022.

EGU22-6364 | Presentations | CR1.1

The Albedo-Ablation couple: a complex relationship with severe consequences 

Kathrin Naegeli and Martina Barandun

Glaciers in Central Asia provide essential water resources for an increasing socio-economic water demand. However, glacier ablation is spatio-temporally highly heterogeneous, revealing hot-spots of the complex glacier response to climate change. A darkening of glacier surfaces caused by varying sources ranging from light absorbing mineral particles and black carbon to organic matter such as algal bloom, impacts the surface energy balance of glaciers. The albedo of the bare-ice surface is particularly crucial in regard to the ablation magnitude.

In this study, we present across scale results of the dependence of glacier mass balance on surface albedo for a large number of glaciers in the Tien Shan and Pamir Mountains. We used over 3000 surface reflectance scenes from the Landsat suite over the last two decades to produce distributed albedo maps. Annual mass balance time series are modelled using a temperature-index and distributed accumulation model for each glacier and year individually. The modelled estimates are annually calibrated with transient snowlines and further constrained by multiyear geodetic mass balances.

A comprehensive analysis of albedo variability and trends is performed at varying scales, ranging from pixel to catchment. A relationship between the distributed albedo information and the detected trends with the mass balance rates and variabilities is established. We highlight the sensitivity of glacier mass balance on surface albedo and stress the importance of the enhanced albedo feedback that will be amplified due to atmospheric warming and suspected darkening of glacier surfaces in the near future. This feedback will accelerate glacier melt and thus put the availability of melt water to river run off at sustainable risk. 

How to cite: Naegeli, K. and Barandun, M.: The Albedo-Ablation couple: a complex relationship with severe consequences, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6364, https://doi.org/10.5194/egusphere-egu22-6364, 2022.

EGU22-7864 | Presentations | CR1.1

Anthropogenic Influence on Surface Changes at Olivares Glaciers, Central Chile 

Martina Barandun, Claudio Bravo, Bernard Grobety, Theo Jenk, Ling Fang, Kathrin Naegeli, Andrés Rivera, Sebastián Cisternas, Tatjana Münster, and Margit Schwikowski

We have investigated the source and role of light absorbing impurities (LAI) deposited on the glaciers of the Olivares catchment, in Central Chile. LAI can considerably darken (lower ice albedo) the glacier surface, enhancing their melting. We combined chemical and mineralogical analyses of surface ice samples with field-based spectral reflectance measurements and laboratory analysis to investigate the nature and properties of LAI on the glacier surface. Using remote sensing-based albedo maps, we upscaled local information to glacier-wide coverage. We then used a model to evaluate the sensitivity of surface mass balance to a change in ice albedo. The across-scale surface sample analysis revealed a history of over half a century of LAI deposition. We found traces of mining residuals in glacier surface samples. The glaciers with highest mass loss in the catchment present enhanced concentrations of surface dust particles with low reflectance properties. Our results indicate that dust particles with strong light-absorbing capacity have been mobilized from anthropogenic sources and deposited on the nearby glacier surfaces, thus lowering their surface reflectance. Large scale assessment from satellite-based observations revealed darkening (ice albedo lowering) at most investigated glacier tongues from 1989 to 2018. Mass balance is sensitive to ice albedo changes. However, we believe that an accelerated winter and spring snow albedo decrease, triggered by surface impurities, might be responsible for the above-average mass balances encountered in this catchment.

How to cite: Barandun, M., Bravo, C., Grobety, B., Jenk, T., Fang, L., Naegeli, K., Rivera, A., Cisternas, S., Münster, T., and Schwikowski, M.: Anthropogenic Influence on Surface Changes at Olivares Glaciers, Central Chile, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7864, https://doi.org/10.5194/egusphere-egu22-7864, 2022.

EGU22-8724 | Presentations | CR1.1

Comparison of simulated and radar-determined accumulation and melt at a high glacier accumulation site in the Alps 

Astrid Lambrecht, Achim Heilig, and Christoph Mayer

The quantification of snow accumulation and the temporal evolution of the snow pack is essential when investigating the mass balance conditions of mountain glaciers. In particular, accumulation regions become smaller due to the gradual increase of the equilibrium line, thus reducing mass input into the glacier system. This will have severe consequences on ice flux and thus the mass balance conditions across many mountain regions worldwide. The mass redistribution within the accumulation regions is considerably influenced by migration of melt water in the snow and firn pack and the induced mass and density changes. Here, we study snow and firn processes at a high mountain accumulation plateau on 3470 m asl at Vernagtferner, Austria. Vernagtferner is a major glacier in the drainage basin of Rofenache, with an area of about 6.9 km², covering altitudes between 2900 m and 3550 m. A snow monitoring station, including an upward-looking ground penetrating radar (upGPR) was installed at the highest accumulation basin in 2018. This station allows the continuous determination of the snow pack stratigraphy and of the snow water equivalent (SWE) (Heilig et al. (2009, 2010), Schmid et al. 2014, Heilig et al., 2015). We compare numerical simulations of the 1-dimensional snow cover model SNOWPACK (Bartelt and Lehning, 2002), driven by automatic weather station data, with continuous observations of the installed upGPR system and bi-annual in-situ data. The analysed upGPR data enable continuous evaluation of the SNOWPACK simulations over several melt and accumulation seasons. The upGPR data show that even at high elevations frequent melt-freeze crusts develop during the accumulation period. Even though the crusts are several centimetres, melt water rapidly percolates trough these layers, once the snow pack reaches isothermal conditions in late spring. The simulation results demonstrate, that SNOWPACK is able to reproduce this fast advance of the melt front accurately, while the up-GPR measurements provide an independent proof of the model performance. These measurements also show that firn layers (previous summer surfaces) block water infiltration into depth only for a very short period, indicating that SWE measurements of glacier accumulation only provide realistic values, if carried out before or just at the onset of spring melt. This feasibility study provides important indication on how to extend such studies to larger glacier systems, also in less monitored regions, where in-situ data might be sparse.

How to cite: Lambrecht, A., Heilig, A., and Mayer, C.: Comparison of simulated and radar-determined accumulation and melt at a high glacier accumulation site in the Alps, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8724, https://doi.org/10.5194/egusphere-egu22-8724, 2022.

Glaciers are a representative icon of the current climate change. They embody the three main aspects of this global phenomenon. They are (1) victims of the climate change, (2) an instrument of knowledge which allowed to better understand and address what is happening today, and (3) an important source of impact from climate change, both with respect to natural ecosystems and socio-economic activities.

One aspect related to the retreat of glaciers that is currently poorly investigated, is the consequence on the perception of the mountain environment and on our cultural heritage. Our approach to glaciers has deeply changed with time. During the Little Ice Age, they were regarded as a menace capable of destroying pastures and the highest settlements because of their advance. Then the view changes and glaciers became a sublime component of the landscape, interesting to know and study. Finally, glaciers turned into a source of entertainment for alpinists and tourists. Despite these different perspectives have somehow partially survived the passing of time, now the dominant perception of glaciers regards them as an endangered species. This is because of climate change and in many regions of Earth this vision will change soon: from endangered to extinct species (Carey, 2007).

Among the many environmental and socio-economic consequences, there is also the risk that with melting ice we will lose an important part of our culture. Retreating glaciers are sharing with us important messages, significantly contributing to strengthen the environmental awareness, what will happen when glaciers will be completely disappeared from whole mountain ranges? Will we be able to preserve what they have taught?

From this point of view the Dolomite represent an interesting laboratory to explore, ahead of other Alpine sectors, the effects of deglaciation in a renowned mountain range, with emphasis on the cultural impacts of glacier disappearance. These mountains, among the most famous and frequented of the Earth, hosted several small glaciers characterized by a notable morphological variety, but this glaciological heritage will soon disappear, as the Dolomites are expected to be ice-free in a few decades (Santin et al., 2019). There is a real risk that the Dolomite glaciers will vanish into silence and that with them we will also lose the stories of those who discovered, studied and attended those same glaciers. The aim of the present work is to oppose this fate, reviewing the recent history of Dolomitic glaciers and discussing the human and scientific significance of their demise.

 

References

  • Carey (2007) The history of ice: how glaciers became an endangered species, Environmental History 12:497-527.
  • Santin et al. (2019) Recent evolution of Marmolada glacier (Dolomites, Italy) by means of ground and airborne GPR surveys, Remote Sensing of the Environment 235:111442.

How to cite: Baccolo, G. and Varotto, M.: Mountains with no ice: deciphering the disappearance of glaciers in a renowned mountain range, the Dolomite case (Eastern Alps), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9821, https://doi.org/10.5194/egusphere-egu22-9821, 2022.

EGU22-9884 | Presentations | CR1.1

On the use of the ESRI image service for mapping Little Ice Age glacier extents 

Johannes Reinthaler and Frank Paul

Glacier extents are mainly mapped by a semi-automated classification of multispectral satellite images (e.g. Landsat, Sentinel-2) with manual corrections of unmapped regions (e.g. ice in cast shadow or under debris cover). The quality of such corrections improve towards higher spatial resolution sensors, but such data were so far only seldom available for direct digitizing in a GIS. With the increasing availability of web map services (wms) such as the ESRI image service or national services the situation has strongly changed and first studies already analysed the potential of such services in geoscience.

The ESRI wms can be embedded into the professional mapping environment of ArcMap or QGIS. It provides mostly cloud and snow free mosaics of very high-resolution (0.31 - 0.5 m) GeoEye and Worldview images up to a scale of 1:5000. The images can be shown in the background as an information layer, but not further processed. The user has no control over the images provided (e.g. their acquisition date) or how they are mosaiced and orthorectified, locally resulting in snow covered or shifted images. The acquisition date and sensor used for each image part can be extracted using the information tool. Due to its recent availability, the ESRI wms has not yet been widely used and its huge potential especially for geomorphological and paleoglaciological mapping has still to be explored.

In this study, which is performed in the framework of the EU Horizon 2020 project PROTECT (protect-slr.eu) we present (1) a workflow for mapping Little Ice Age (LIA) glacier extents using the ESRI wms, (2) a detailed uncertainty analysis and (3) first results of glacier area changes since the LIA for selected regions in Alaska, Baffin Island, Novaya Zemlya and the tropics. Additionally to the ESRI wms, we used Sentinel-2 images, the ArcticDEM and modern glacier outlines from the Randolph Glacier Inventory (RGI). Geomorphological indicators (trim lines, moraines, vegetation free zones) and glaciological considerations were considered to guide the digitizing. Geolocation uncertainties were determined against independent data sources and the interpretation and reproduction uncertainties were quantified by multiple digitising experiments. The possible timing of the former LIA maximum extents was obtained to the extent possible from the literature, but here large uncertainties remain.

In total, outlines for 371 LIA glaciers were created and compared to today relative area changes of -20%, -15%, -26% and -58% were found for Alaska, Baffin Island, Novaya Zemlya and the tropics, respectively. Reproduction uncertainties were calculated for a sample of 18 glaciers to be on average 1.4 ±1.3%, interpretation uncertainties for a sample of 17 glaciers 1.9 ±10%. The digitization of LIA glacier extents with 10 m Sentinel-2 images is only rarely possible due to the difficulties identifying small scale moraines and resulted in much higher . We conclude that wms such as the ESRI World imagery layer provide, despite their shortcomings, an excellent opportunity to precisely map LIA maximum extents of glaciers around the world.

How to cite: Reinthaler, J. and Paul, F.: On the use of the ESRI image service for mapping Little Ice Age glacier extents, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9884, https://doi.org/10.5194/egusphere-egu22-9884, 2022.

EGU22-11054 | Presentations | CR1.1

Disentangling the debris-cover anomaly in High Mountain Asia 

Evan Miles, Marin Kneib, Michael McCarthy, Stefan Fugger, and Francesca Pellicciotti

Rocky debris covers 30% of glacier ablation areas in High Mountain Asia and generally suppresses melt. However, remote sensing observations have shown no statistical difference in glacier thinning rates between areas with and without debris cover; the ‘debris cover anomaly’. This pattern is apparent at subregional and regional scales, even after controlling for the elevation differences between debris-covered and clean ice. 

Two primary hypotheses to explain this behaviour have interpreted the thinning patterns in terms of melt or ice supply differences. First, rapid melt at supraglacial ponds and ice cliffs could enhance ablation in debris-covered areas, and therefore thinning as well. These features cannot entirely compensate for the melt reduction under debris, so a second hypothesis interprets the anomaly to indicate differences in emergence velocity between debris-covered and clean ice. However, complete understanding of the problem is challenged by a scale gap: the prior process studies have focused on single glaciers, whereas the anomaly has been identified for subregional- to regional spatial scales. Furthermore, these hypotheses neglect numerous other differences between debris-covered and clean glaciers (e.g. topo-climatic situation, accumulation mechanisms), which could bias this comparison.

We overcome these limitations through a direct assessment leveraging diverse large datasets and modelling. We firstly estimate emergence velocities and map ice cliffs and supraglacial ponds on a glacier-by-glacier basis across High Mountain Asia. We additionally assess other factors that could contribute to unexpected specific mass balance patterns: thin debris melt enhancement, distinct topo-climatic settings and the importance of avalanching for debris-covered ice. To determine the contribution of each factor to the debris-cover anomaly, we develop a statistical metric of how anomalous sub-debris ablation rates are, based on the difference in ablation rates between debris-covered and clean ice, as well as its altitudinal pattern. We use this metric and systematically remove the influence of the above hypothesized controls from each glacier’s emergence-corrected thinning data (specific mass balance) in a full-factorial investigation.

Our results firstly demonstrate that although emergence velocity differences between clean and debris-covered ice are systematic across the region, they do not resolve the debris-cover anomaly at the subregional or regional scale (altitudinal ablation rates are more negative for debris than clean ice). We find that accounting for any additional factor reduces the strength of the debris anomaly at regional and subregional scales, and our full-factorial analysis suggests that multiple factors combine to explain the debris cover anomaly.  Our results indicate that both hypotheses are correct in their process understanding at the glacier scale (reduced emergence velocity under debris, substantial ice cliff and pond ablation contribution), but not in their interpretation of the debris cover anomaly. Rather, our results underline previous suggestions that debris-covered glaciers fundamentally differ from clean ice glaciers in terms of mass supply mechanisms (i.e. supported by avalanching) and ablation patterns, leading to distinctive geometric expression and dynamics, and that the debris anomaly results from the integration of these patterns across scales.

How to cite: Miles, E., Kneib, M., McCarthy, M., Fugger, S., and Pellicciotti, F.: Disentangling the debris-cover anomaly in High Mountain Asia, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11054, https://doi.org/10.5194/egusphere-egu22-11054, 2022.

EGU22-12934 | Presentations | CR1.1

Air temperature distribution and structure of katabatic wind on a shrinking mountain glacier 

Lindsey Nicholson, Ivana Stiperski, and Alexander Kehl

The glacier katabatic wind system represents a feedback mechanism (de)coupling the glacier and the overlying atmosphere, altering the glacier microclimate.

Still, there are only a limited number of distributed measurements of the atmospheric conditions above the glacier surface. In August 2018, eight weather stations, partly with turbulence measurements at two levels, were installed in the middle and lower part of the Hintereisferner valley glacier in Austria, yielding three weeks of data on the near-surface spatial pattern of atmospheric conditions. These data are used to (a) quantify the observed properties of the glacier wind with regard to its spatial variability, persistence, and the synoptic conditions that erode it and (b) assess how well methods to extrapolate near-surface air temperature over glacier surfaces are influenced by the existence of the glacier wind and match the available observations on Hintereisferner.

 

Despite data limitations and uncertainties, results show that the glacier wind persists under most synoptic conditions, and deepens and speeds up downglacier. However, significant disturbances such as cold front passages and rain events can cause erosion of katabatic wind for periods from minutes to days. Representations of near-surface temperature distribution over the glacier using classical lapse rates and the along flow-line modified Greuell-Böhm model showed variable agreement to the measured data, with evidence for dependency on ambient atmospheric conditions. However, interpretations of the performance of temperature extrapolations should be viewed with caution due to the absence of observations in the upper glacier. We consider how these findings can be included in surface energy balance models of future glacier evolution, and conceptually how this aspect of the glacier microclimate, and the wider valley circulation, can be expected to evolve with continued glacier shrinkage.

How to cite: Nicholson, L., Stiperski, I., and Kehl, A.: Air temperature distribution and structure of katabatic wind on a shrinking mountain glacier, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12934, https://doi.org/10.5194/egusphere-egu22-12934, 2022.

EGU22-12976 | Presentations | CR1.1

Glacier retreat and debris cover evolution in the Afghan Hindu Kush Himalaya between 2000 and 2020 

Jamal Abdul Naser Shokory and Stuart Lane

Glaciers play a crucial role in the hydrological cycle, providing water in summer when it is most needed for irrigation. Global warming is leading to glacier retreat and enhanced summer runoff in the short-term, which should occur until glaciers become small enough that there is an end to this glacial subsidy and a reduction of summer runoff. However, debris accumulation, as it may alter the surface energy balance, will modify the rate at which this happens and may represent an important negative feedback. For this reason, quantifying and explaining glacier change in the Hindu Kush Himalaya (HKH) region, notably its relation to changing debris cover, is of paramount importance, especially for a country like Afghanistan with water resources highly dependent on glacial meltwater. This study assessed changes in glaciers of Afghanistan using data for 2000, 2007, 2017 and 2020 based upon the analysis of country-wide Landsat data and innovative indices for mapping both ice and debris-covered glacier extent.

Results showed 2862.5±47.8 km2 of total glacier area in the year 2000, decreasing by 45.9 km2to 2007 (i.e. 6.55 km2 per year), by a further 112.0 km2 by 2017 (i.e. 11.2 km2 per year), and by a further 73 km2 (i.e. 24.3 km2 per year) by 2020; that is there is a progressive increase in retreat rates. Of the 231.2 km2 (8.07 %) loss of glacier surface area between 2000 and 2020, almost 81% related to glaciers with a size ≤ 2.01 km2, which accounted for 50% of the total glacier area in the year 2000. Decreases were more dominant in center and northern regions of the country, whilst the northeastern region, the most glaciated part of the country, showed lesser changes. Increases in total debris cover area were found in the northeastern region of the country where there were lower decreases in total glacier area, whilst there were noticeable decreases in total debris cover area observed in southern and southeastern regionss and higher decreases in total glacier area. This suggested that the ability of the glaciers to produce debris cover has regional significance in explaining whether glacier loss occurs.

Ice elevation significantly changed over the time; changes in minimum ice elevations were up to +53 m, higher in the north, south, and southeastern regions. Maximum ice elevations decreased by -88 m, suggesting loss of accumulation zones. However, the northeastern part had a positive increase in maximum accumulation zone heights +23 m, this indicates possibility of increases in accumulation area.  

These results revealed differences in the regional response of Afghan glaciers to climate change. In the next stage of this work, we will link the spatial distributions of glacier response to downstream populations to identify those regions most exposed to the effects of these climate changes.

How to cite: Shokory, J. A. N. and Lane, S.: Glacier retreat and debris cover evolution in the Afghan Hindu Kush Himalaya between 2000 and 2020, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12976, https://doi.org/10.5194/egusphere-egu22-12976, 2022.

EGU22-13209 | Presentations | CR1.1 | Highlight

Attribution of extreme annual glacier mass loss to anthropogenic forcing 

Lauren Vargo, Ruzica Dadic, Brian Anderson, Regine Hock, Huw Horgan, Andrew King, Andrew Mackintosh, and Ben Marzeion

Glaciers in every region on Earth have lost mass over the past two decades as global temperature has risen 0.5C. Retreating glaciers symbolize climate change and present societal challenges across the globe. To better quantify the consequences of climate change, previous studies have established methods to calculate the anthropogenic component of extreme weather and climate events. Previously, we established a framework using existing event attribution methods together with glacier mass balance modeling to determine the increase in probability of extreme annual mass loss of New Zealand glaciers occurring with climate change. Here, we look to expand our developed attribution framework to calculate the change in probability and amount of extreme annual mass loss for glaciers around the world.

 
To do this, we simulate glacier mass balance using a degree-day model, driven with general circulation model (GCM) output from available CMIP6 models and ensemble members. Historical natural simulations define climate without anthropogenic forcing, and SSP5 8.5 simulations define climate with anthropogenic forcing. We use the two different climate forcings to produce scenarios of glacier mass change with and without climate change. The differences in these scenarios are compared with measurements from the highest annual glacier mass loss years.
 

We develop the attribution method though application to several glaciers around the world, including South Cascade Glacier (USA), Gries Glacier (Switzerland), and Brewster Glacier (New Zealand). Our initial results show large increases in probability and amount of annual glacier mass loss occurring due to climate change for all three glaciers. Difficulties in applying the attribution framework to glaciers globally include accessing modern glacier outlines and reconciling differences between glaciological and geodetic measurements of glacier mass change.

How to cite: Vargo, L., Dadic, R., Anderson, B., Hock, R., Horgan, H., King, A., Mackintosh, A., and Marzeion, B.: Attribution of extreme annual glacier mass loss to anthropogenic forcing, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13209, https://doi.org/10.5194/egusphere-egu22-13209, 2022.

EGU22-13295 | Presentations | CR1.1

Glacial drought buffering through the 21st century 

Lizz Ultee, Sloan Coats, and Jonathan Mackay

Global climate model projections suggest that 21st century climate change will bring significant drying in the terrestrial midlatitudes. Recent glacier modeling suggests that runoff from glaciers will continue to provide substantial freshwater in many drainage basins, though the supply will generally diminish throughout the century. In the absence of dynamic glacier ice within global climate models (GCMs), a comprehensive picture of future drought conditions in glaciated regions has been elusive. We evaluate glacial buffering of droughts in the Standardized Precipitation-Evapotranspiration Index (SPEI), which we calculate by combining CMIP5 climate model output with glacial runoff projections from GloGEM.

We find that accounting for glacial runoff tends to increase multi-model ensemble mean SPEI (wetter baseline) and reduce drought frequency and severity, even in basins with glacier cover of <2% by area.  We also find that the strength and future trend of glacial drought buffering depends on basin aridity index and glacial cover, and does not depend on other characteristics such as total basin area or latitude.  Glacial drought buffering persists even as glacial runoff is projected to decline through the 21st century.

How to cite: Ultee, L., Coats, S., and Mackay, J.: Glacial drought buffering through the 21st century, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13295, https://doi.org/10.5194/egusphere-egu22-13295, 2022.

Satellite observations show rapid retreat of many outlet glaciers in West Antarctica, corresponding to a significant proportion of the contributions to global sea level rise in recent years. These changes have not been formally attributed to anthropogenic climate change, primarily because of the potential for positive feedbacks on ice sheet mass loss, which may have been triggered even within the limits of natural variability. This naturally leads to the attribution question: “how much more (or less) likely have anthropogenic changes made a specified contribution to sea level rise?” In this talk, I shall describe a Bayesian framework to address this question, which uses ensembles of many simulations with independent realizations of ice-sheet forcing with, and without, anthropogenic changes. Enhanced melting of ice shelves is thought to be the key forcing contribution responsible for recent retreat of the West Antarctic Ice Sheet; we include a consideration of the accuracy of melt rates in this framework by updating our prediction of sea level rise according to the agreement between the parametrized melt rate in the simulations and the output from a numerical ocean circulation model, at various time points. Experiments in an idealized setup point elucidate the dependence on the forcing timescale in the changes in likelihood of various contributions and demonstrate the feasibility of attribution studies for the Antarctic ice sheet.

How to cite: Bradley, A. T.: A Bayesian Framework for Anthropogenic Attribution of Sea Level Rise Contributions from the West Antarctic Ice Sheet, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1118, https://doi.org/10.5194/egusphere-egu22-1118, 2022.

EGU22-3279 | Presentations | CR1.2

Reduced mass loss from the Greenland ice sheet under stratospheric aerosol injection 

Ralf Greve, John C. Moore, Thomas Zwinger, Fabien Gillet-Chaulet, Chao Yue, Liyun Zhao, and Heiko Goelzer

Stratospheric aerosol injection (SAI) has been proposed as a potential method of mitigating some of the adverse effects of anthropogenic climate change, including sea-level rise from the ice sheets. In this study, we use the SICOPOLIS (www.sicopolis.net) and Elmer/Ice (elmerice.elmerfem.org) dynamic models driven by changes in surface mass balance, surface temperature and ocean temperature (similar to ISMIP6-Greenland; Goelzer et al., 2020, doi: 10.5194/tc-14-3071-2020) to estimate the sea-level-rise contribution from the Greenland ice sheet under the IPCC RCP4.5, RCP8.5 and GeoMIP G4 (Kravitz et al., 2013, doi: 10.1002/2013JD020569) scenarios. The G4 scenario adds 5 Tg/yr sulfate aerosols to the equatorial lower stratosphere to the IPCC RCP4.5 scenario.

We simulate the mass loss of the Greenland ice sheet for the period 2015-2090 under the three scenarios with four earth system models, using SICOPOLIS with hybrid shallow-ice-shelfy stream dynamics and Elmer/Ice in the Elmer/Ice-sheet set-up with shelfy stream dynamics. For atmosphere-only forcing, the results from the two ice-sheet models are very similar. Relative to the constant-climate control simulations (CTRL), the losses from 2015 to 2090 are 64 [53, 80] mm SLE for RCP8.5, 46 [38, 53] mm SLE for RCP4.5 and 28 [18, 39] mm SLE for G4 (mean and full range). Thus, the mean mass loss under G4 is about 38% smaller than that under RCP4.5. For both models, the accumulated SMB is larger than the actual ice loss because, as the ice sheet recedes further from the coast, the mass loss due to calving is reduced. We will also investigate the response of the ice sheet to ocean-only forcing and combined atmospheric and oceanic forcing.

How to cite: Greve, R., Moore, J. C., Zwinger, T., Gillet-Chaulet, F., Yue, C., Zhao, L., and Goelzer, H.: Reduced mass loss from the Greenland ice sheet under stratospheric aerosol injection, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3279, https://doi.org/10.5194/egusphere-egu22-3279, 2022.

EGU22-3838 | Presentations | CR1.2

Errors in Mass Balance estimates of Antarctica from ice mask and input-output inconsistencies, pinpointed by GRACE 

Nicolaj Hansen, Sebastian B. Simonsen, Fredrik Boberg, Rene Forsberg, and Ruth Mottram

Surface mass balance (SMB) is computed from regional climate models (RCM) using reanalysis data. Estimates of the SMB vary between RCMs due to differences such as the model set-up, physical parameterizations, and topography as well as ice mask. The ice mask in a model defines the surface covered by glacier ice. The differences in ice masks appear small, however it is here shown that it leads to important differences in SMB when integrated over the continent. To circumvent this area-dependent bias, intercomparison studies of modelled SMB use a common ice mask (Mottram et al., 2021). The SMB in areas outside the common ice mask is discarded. By comparing the native ice masks with the common ice mask used in Mottram et al. 2021 we find differences in integrated SMB of between 20.1 and 102.4 Gt per year over the grounded ice sheet when compared to the ensemble mean from Mottram et al. 2021. These differences are nearly equivalent to the entire Antarctic ice sheet mass imbalance identified in the IMBIE study.
SMB is particularly essential when estimating the total mass balance of an ice sheet via the input-output method, by subtracting ice discharge from the SMB to derive the mass change. We use the RCM HIRHAM5 to simulate the Antarctic climate and force a newly develop offline subsurface firn model, to simulate the Antarctic SMB from 1980 to 2017. We use discharge estimates from two previously published studies to calculate the regional scale mass budget. To validate the results from the input-output method, we compared the results to the gravimetry-derived mass balance from the GRACE/GRACE-FO mass loss time series, computed for the period 2002–2020. We find good agreement between the two input-output results and GRACE in West Antarctica, however, there are large disagreements between the two input-output methods in East Antarctica and over the Antarctic Peninsula. Over the entire grounded ice sheet, GRACE detects a mass loss of 900 Gt for the period 2002-2017, whereas the two input-output results show a mass gain of 500 Gt and a mass loss of 4000 Gt, depending on which discharge dataset is used. These results are integrated over the native HIRHAM5 ice mask. If we instead integrate over the common ice mask from Mottram et al. 2021, the results change from a mass gain of 500 Gt to a mass loss of 500 Gt, and a mass loss of 4000 Gt to a mass loss of 5000 Gt, over the grounded ice sheet for the period 2002-2017. While the differences in ice discharge remain the largest sources of uncertainty in the Antarctic ice sheet mass budget, our analysis shows that even a small area bias in ice mask can have a huge impact in high precipitation areas and therefore SMB estimates. We conclude there is a pressing need for a common ice mask protocol, to create an accurate harmonized updated ice mask.

How to cite: Hansen, N., Simonsen, S. B., Boberg, F., Forsberg, R., and Mottram, R.: Errors in Mass Balance estimates of Antarctica from ice mask and input-output inconsistencies, pinpointed by GRACE, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3838, https://doi.org/10.5194/egusphere-egu22-3838, 2022.

EGU22-4154 | Presentations | CR1.2

A Tale of Two Ice Sheets, SSPs, CMIPs and global models: future climate and surface mass balance projections for Greenland and Antarctica 

Ruth Mottram, Fredrik Boberg, Nicolaj Hansen, Peter Langen, Shuting Yang, Mathias Larsen, and Christian Rodehacke

Surface Mass Balance (SMB) is the key driver of ice sheet mass budget. It delivers the snow that nourishes ice sheets and the surface melt that balances snowfall and, along with ocean interactions, drives ice flow. We here present alternative future projections for both the Greenland and Antarctic ice sheets, driven by two different earth system models (ESMs), EC-Earth and CESM2, for two different emissions pathways (SSP585, 245) and in the case of EC-Earth for two different CMIP versions (EC-EARTH2 inCMIP5 and EC-EARTH3 in CMIP6).

We use the regional climate model (RCM) HIRHAM5 to downscale the global models to 5.5km resolution over the Greenland ice sheet and 12km resolution over Antarctica. HIRHAM5 output is then used to drive a surface mass budget model for both ice sheets.

The matrix of models and scenarios gives us the opportunity to examine how different factors, including atmospheric circulation indices, model resolution, ocean dynamics, sea ice and SMB components affect mass budget and sea level rise estimates over the course of the 21st century. About half the difference between CMIP5 and CMIP6 SMB estimates is related to differences in the scenarios compared to the SSPs and about half is related to differences in the driving models. In addition, we compare with other published downscaled SMB estimates from different RCMs (MAR and RACMO) to assess the envelope of likely ice sheet evolution out to 2100. Both CESM2 and EC-EARTH3 have high equilibrium climate sensitivity, and our study correspondingly shows high ice sheet mass loss particularly from Greenland by the end of the century, in line with other published estimates under high emissions scenarios. Melt is increasingly important in both ice sheets, but especially Greenland over the course of the 21st century and scales by temperature and therefore emissions pathway. All model projections show an increase in precipitation, but internal variability in circulation in the Southern Ocean still dominates the patterns in Antarctica and masks to some extent climate change signal in SMB.

Future work will extend the ensemble of SMB estimate with a direct statistically based method, that allows fast downscaling of ESM output directly to SMB using the Copenhagen Ice Sheet Surface Energy and Mass Balance modEL (CISSEMBEL) and we also present some early preliminary results comparing different downscaling techniques.

How to cite: Mottram, R., Boberg, F., Hansen, N., Langen, P., Yang, S., Larsen, M., and Rodehacke, C.: A Tale of Two Ice Sheets, SSPs, CMIPs and global models: future climate and surface mass balance projections for Greenland and Antarctica, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4154, https://doi.org/10.5194/egusphere-egu22-4154, 2022.

EGU22-5252 | Presentations | CR1.2

Improving interpretation of sea-level projections through a machine-learning-based local explanation approach 

Jeremy Rohmer, Remi Thieblemont, Goneri Le Cozannet, Heiko Goelzer, and Gael Durand

Sea-level projections are usually calculated from numerical simulations using complex long-term numerical models (or a chain of models) as part of multi-model ensemble studies. Because of their importance in supporting the decision-making process for coastal risk assessment and adaptation, improving the interpretability of these projections is of great interest. Specifically, it is assumed that clear and transparent explanations of projected sea-level changes can increase the trust of the end-users, and ultimately favor their engagement in coastal adaptation. To this end, we adopt the local attribution approach developed in the machine learning community, and we combine the game-theoretic approach known as ‘SHAP’ (SHapley Additive exPlanation, Lundberg & Lee, 2017) with tree-based regression models. We applied our methodology to sea-level projections for the Greenland ice sheet computed by the ISMIP6 initiative (Goelzer et al., 2020) with a particular attention paid to the validation of the procedure. This allows us to quantify the influence of particular modelling decisions and to express the influence directly in terms of sea level change contribution. For Greenland, we show that the largest predicted sea level change, 19cm in 2100, is primarily attributable to >4.5cm (i.e. nearly 25%) to the choice of the model parameter that controls the retreat of marine-terminating outlet glaciers, i.e. to the modelling of the retreat rate of tidewater glaciers; other modelling decisions (choice of global climate model, formulation of the ice sheet model ISM, model grid size, etc.) have only a low-to-moderate influence for this case (with contribution of 1-2cm). This type of diagnosis can be performed on any member of the ensemble, and we show how the aggregation of all local attribution analyses can help guide future model development as well as scientific interpretation, particularly with regard to model spatial resolution or the selection of a specific model formulation.

This study was supported by the PROTECT project, which received funding from the European Union's Horizon 2020 research and innovation program under grant agreement No 869304.

References

Goelzer, H., et al. (2020). The future sea-level contribution of the Greenland ice sheet: a multi-model ensemble study of ISMIP6. The Cryosphere 14, 3071-3096.

Lundberg, S.M., & Lee, S.I. (2017). A unified approach to interpreting model predictions. In Proceedings of the 31st international conference on neural information processing systems (pp. 4768-4777).

How to cite: Rohmer, J., Thieblemont, R., Le Cozannet, G., Goelzer, H., and Durand, G.: Improving interpretation of sea-level projections through a machine-learning-based local explanation approach, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5252, https://doi.org/10.5194/egusphere-egu22-5252, 2022.

Full-Stokes (FS) ice sheet models provide the most sophisticated formulation of ice sheet flow. However, their ap- plicability is often limited due to the high computational demand and numerical challenges. To balance computational demand and accuracy, the so-called Blatter-Pattyn (BP) stress regime is frequently used. Here, we explore the dynamic consequences by solving FS and the BP stress regime applied to the Northeast Greenland Ice Stream. To ensure a consistent comparison, we use one single ice sheet model to run the simulations under identical numerical conditions. A sensitivity study to the horizontal grid resolution (from 12.8 down to 0.1 km) reveals that velocity differences between the FS and BP solution emerge below ∼1 km horizontal resolution and continuously increase with resolution. Over the majority of the modelling domain both models reveal similar surface velocity patterns. At the grounding line of 79° North Glacier the simulations unveil considerable differences whereby BP overestimates ice discharge of up to 50% compared to FS. A sensitivity study to the friction type reveals that differences are stronger for a power-law friction than a linear friction law. Model differences are attributed to topographic variability and the basal drag since neglected stress terms in BP become important.

How to cite: Humbert, A., Kleiner, T., and Rückamp, M.: Comparison of ice dynamics using full-Stokes and Blatter-Pattyn approximation: application to the Northeast Greenland Ice Stream, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5459, https://doi.org/10.5194/egusphere-egu22-5459, 2022.

EGU22-5983 | Presentations | CR1.2

Influence of surface mass balance on the high-end sea-level commitment from the Antarctic Ice Sheet 

Violaine Coulon, Ann Kristin Klose, Christoph Kittel, Frank Pattyn, and Ricarda Winkelmann

Over the last decades, the Antarctic Ice Sheet (AIS) has been losing mass, mainly through ice discharge and sub-shelf melting (Rignot et al., 2019). More specifically, recent observations show that the AIS is currently losing mass at an accelerating rate in areas subject to strong ocean-induced melt. At the same time, no long-term trend in snowfall accumulation changes can be detected in the interior of the ice sheet. Due to these current trends, basal melting has often been considered as the main driver of future Antarctic mass loss. However, even though stronger basal melting of ice shelves is projected to drive future AIS mass loss, recent studies (e.g. Seroussi et al., 2020) have shown that surface mass balance (SMB, the balance of accumulation through snowfall and ablation through erosion, sublimation and runoff) has a strong potential in controlling the future stability and evolution of the Antarctic Ice Sheet. With increasing temperatures, SMB is expected to increase in Antarctica in the future as a result of enhanced snowfall. As long as the warming remains modest, other AIS SMB components (such as runoff) will likely continue to play a minor role in future SMB changes (Lenaerts et al., 2019; Kittel et al., 2021). Under high-emission scenarios, however, future runoff is likely to significantly compensate for mass gain through snowfall (Kittel et al 2021). The balance between these competing processes is still a matter of debate and, as of yet, there is no consensus on estimates of the future mass balance of the Antarctic Ice Sheet (Seroussi et al., 2020).

Here, we investigate the relative importance of SMB changes and ocean-induced melt on the long-term (multi-centennial to multi-millennial) AIS response as well as their associated uncertainties. To do so, we force two ice sheet models (fETISh and PISM) with atmospheric and oceanic projections inferred from a subset of models from the sixth phase of the Coupled Model Intercomparison Project (CMIP6) under the Shared Socioeconomic Pathways (SSP) 5-8.5 and SSP1-2.6. Changes in precipitation rate and air temperature are corrected for elevation changes and used as inputs to a positive degree-day scheme which estimates changes in snowfall, rainfall and surface runoff. Climate projections are used as forcing until the year 2300 and afterwards no climate trend is applied, allowing to investigate the long-term impacts of early-millennia warming (often called sea-level commitment).

Taking into account key uncertainties in both atmospheric and oceanic forcing, our results predict that atmosphere-ice surface interactions will have an important role on the AIS stability under high-end future emission scenarios. We also show the increasingly important role of the melt-elevation feedback for multi-centennial projections of the AIS. Finally, we find that modelling choices regarding the atmosphere forcing have a significant influence on the future sea-level contribution from the AIS under high-end emission scenarios, leading to a spread from a few centimeters to several meters contribution over the coming millennia.

How to cite: Coulon, V., Klose, A. K., Kittel, C., Pattyn, F., and Winkelmann, R.: Influence of surface mass balance on the high-end sea-level commitment from the Antarctic Ice Sheet, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5983, https://doi.org/10.5194/egusphere-egu22-5983, 2022.

EGU22-7420 | Presentations | CR1.2

Overestimation of elevation-melt feedback in uncoupled projections of ice sheet mass loss 

Miren Vizcaino, Uwe Mikolajewicz, and Raymond Sellevold

The elevation feedback on melt has been identified as a key process to explain (Gregoire et al, Nature, 2012) and project (Aschwanden et al., Sci Advances, 2019; Ridley et al, J Clim, 2005; Vizcaino et al, Clim Dyn, 2008) long-term deglaciation. It is also central to the theory of ice sheet evolution hysteresis, deglaciation thresholds/tipping points, and the problem of reversibility (Garbe et al, Nature, 2020; Gregory et al, TC, 2020; Gregory et al, Nature, 2004, Robinson et al, Nature Clim. Change, 2012). Ice-sheet-model-only estimates of this feedback rely on a largely unexplored parameter, the so-called “lapse rate”. This parameter is defined as the rate at which the near-surface atmospheric temperature changes strictly due to surface elevation change.

In this work, we use coupled an uncoupled ice sheet and climate simulations with two different General Circulation/Earth System Models (Vizcaino et al, GRL, 2015; Muntjewerf et al, JAMES, 2019) to estimate the temperature lapse rate over the Greenland ice sheet as it deglaciates. We find that this lapse rate is highly variable over seasons, with much reduced lapse rates during summer over melting surfaces. We propose that uncoupled  state-of-the-art projections are likely overestimating deglaciation rates due to too high summer lapse rates over the ablation area.

How to cite: Vizcaino, M., Mikolajewicz, U., and Sellevold, R.: Overestimation of elevation-melt feedback in uncoupled projections of ice sheet mass loss, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7420, https://doi.org/10.5194/egusphere-egu22-7420, 2022.

Mass loss from the Greenland Ice Sheet ice sheet has increased sixfold since the 1990s. With accelerated ice mass loss rates, it could become the largest contributor to sea-level rise in the 21stcentury. Both the surface mass balance and outlet glacier retreat control this ice mass loss. The latter is decomposed between ice flow changes in the lower trunks of outlet glaciers (discharge) and calving of marine-terminating outlet glaciers. Partitioning between SMB and retreat contributors evolved through the last decade. It is uncertain how much they will contribute individually in the future. While a coupled RCM-ice sheet model helps to improve the SMB contribution, future glacier retreat contribution modelling is in its early stages. Using the RCM MAR, fully coupled to the GISM ice sheet model, we investigate the impact of the surrounding ocean on the outlet glaciers. Our parameterization, based on oceanic basins temperature and subglacial ice sheet runoff changes, simulates individual outlet glacier retreat rate. By forcing our atmosphere – GrIS – ocean-retreat-like model by several CMIP6 GCM models, we assess the 21stcentury Greenland ice mass loss. Partitioning between mass loss from SMB and outlet glacier retreat forced by various CMIP6 SSP scenarios is estimated both at the regional and large Greenland scale.

How to cite: Le clec'h, S., Fettweis, X., and Huybrechts, P.: Quantifying 21st century Greenland ice mass loss from outlet glacier retreat and surface mass balance changes from coupled MAR-GISM simulations., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7883, https://doi.org/10.5194/egusphere-egu22-7883, 2022.

EGU22-7964 | Presentations | CR1.2

The long-term sea-level commitment from Antarctica 

Ann Kristin Klose, Violaine Coulon, Frank Pattyn, and Ricarda Winkelmann

With a sea-level rise potential of 58 m sea-level equivalent, the future evolution of the Antarctic Ice Sheet under progressing warming is of importance for coastal communities, ecosystems and the global economy. Short-term projections of the sea-level contribution from Antarctica in the recent ice sheet model intercomparison ISMIP6 range from a slight mass gain (-7.8 cm) to a mass loss of up to 30.0 cm sea-level equivalent at the end of the century under Representative Concentration Pathway 8.5 (Seroussi et al., 2020, Edwards et al., 2021). However, due to high inertia of the system, the ice sheet response to perturbations in its climatic boundary conditions are rather slow. Consequences of potentially triggered unstable ice loss due to positive feedback mechanisms may therefore play out over long timescales (on the order of millennia).  Projections of the committed sea-level change at a given point in time, that is the sea-level change which arises by fixing the climatic boundary conditions and letting the ice sheet evolve over several millennia, might differ substantially from the sea-level change expected at that point in time (Winkelmann et al., 2022).

Previous assessments of the long-term contribution to sea-level rise from the Antarctic Ice Sheet have been primarily restricted to a single model and have rarely explored the full range of intra- and inter-model parameter uncertainties. Here, we determine the long-term, multi-millennial sea level contribution from mass balance changes of the Antarctic Ice Sheet by means of two ice sheet models, the Parallel Ice Sheet Model (PISM) and the fast Elementary Thermomechanical Ice Sheet (f.ETISh) model. More specifically, we assess the response of the Antarctic Ice Sheet to atmospheric and oceanic forcing conditions derived from state-of-the-art climate model projections available from the sixth phase of the Coupled Model Intercomparison Project (CMIP6) under the Shared Socioeconomic Pathways SSP5-8.5 and SSP1-2.6 available until the year 2300. The sea-level commitment from the Antarctic Ice Sheet is quantified by branching off at regular intervals in time and running the ice sheet models for several millennia under fixed climate conditions. Key uncertainties related to ice dynamics as well as to interactions with the bed, atmosphere and ocean are taken into account in an ensemble approach.

How to cite: Klose, A. K., Coulon, V., Pattyn, F., and Winkelmann, R.: The long-term sea-level commitment from Antarctica, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7964, https://doi.org/10.5194/egusphere-egu22-7964, 2022.

EGU22-8432 | Presentations | CR1.2

Layer Tracing of the Greenland Ice Sheet Interior: A Coupled Model Approach 

Therese Rieckh, Andreas Born, and Alexander Robinson

We are using an ice sheet model that explicitly represents individual layers of accumulation that are fixed in time (isochronal). With progressing time, new layers are added on the top, while older layers subside and become thinner as ice flows towards the margins. This approach eliminates unwanted diffusion and faithfully represents the englacial stratification.

The isochronal model is coupled uni-directionally to a full ice sheet model (“host model”), which provides the ice physics and dynamics. Via the isochronal model’s layer tracking, the host model’s output can be evaluated throughout the interior using the radiostratigraphy data set of the Greenland ice sheet.

We investigate the stability and resolution-dependence of this coupled modeling system in simulations of the last glacial cycle with yelmo as the host model. One key question concerns how frequent updates from the host model must be to ensure a reliable simulation. This could enable offline forcing of the isochronal model with output from a range of existing ice sheet models.

The long-term goal is to make the isochronal model flexible and easily adaptable enough to effectively force it with existing full ice sheet models and to provide it to the community as a new way to assess the models’ performance. 

How to cite: Rieckh, T., Born, A., and Robinson, A.: Layer Tracing of the Greenland Ice Sheet Interior: A Coupled Model Approach, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8432, https://doi.org/10.5194/egusphere-egu22-8432, 2022.

EGU22-8882 | Presentations | CR1.2

Implementation of the Zoet-Iverson basal sliding law in CISM 

Tim van den Akker, William H. Lipscomb, Gunter R. Leguy, Willem Jan van de Berg, and Roderik S.W. van de Wal

There are large uncertainties in model predictions of the Antarctic Ice Sheet (AIS) contribution to future sea level rise. One source of model uncertainty is the description of basal friction. Here, we implement a new basal sliding law, developed by Zoet and Iverson (2020), in an updated version of the Community Ice Sheet Model (CISM). The Zoet-Iverson sliding law combines properties of two previously used sliding laws: power-law behavior in areas with slow-moving ice and coulomb-law behavior in fast-moving ice streams and outlet glaciers. We adress the behavior and performance of the Zoet-Iverson law in CISM using AIS spin-up procedures developed for the Ice Sheet Model Intercomparison Project for CMIP6 (ISMIP6). We invert a non-dimensional coefficient in the Zoet-Iverson law to match modelled and observed thickness for grounded ice. Ocean temperatures are tuned to nudge ice-shelf thickness via the basal melt rates. These tuning processes are Antarctic-wide, but we focus on the Amundsen Sea region. We then advance the model forward to better represent the present-day Thwaites glacier, by inverting for observed ice velocity and by changing the ocean forcing. The main results from this run are the sub-shelf ocean temperature perturbation, thickness, and velocity profile of Thwaites glacier. Results are compared with different sliding laws to demonstrate the effect of the Zoet-Iverson law on the representation of the ongoing retreat. 


Zoet, L.K. & Iverson, N.R. (2020). A slip law for glaciers on deformable beds. In: Science 368 (6486), pages 76-78. DOI: 10.1126/science.aaz1183

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.: Implementation of the Zoet-Iverson basal sliding law in CISM, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8882, https://doi.org/10.5194/egusphere-egu22-8882, 2022.

EGU22-9957 | Presentations | CR1.2

The 1950-2020 variability of the Greenland Ice Sheet surface mass balance 

Uta Krebs-Kanzow, Christian Rodehacke, and Gerrit Lohmann

We use the diurnal Energy Balance Model (dEBM) in combination with ERA5 reanalysis forcings to simulate the surface mass balance (SMB) of the Greenland Ice Sheet (GrIS). The dEBM (Krebs-Kanzow et al., 2021) is based on the energy balance of glaciated surfaces. In contrast to most empirical schemes, it is physics based and accounts for variations in the radiative forcing due to changes in the Earth's orbit and atmospheric composition. The dEBM scheme only requires monthly atmospheric forcing (precipitation, temperature, shortwave and longwave radiation and cloud cover) and is computationally inexpensive, which makes it particularly suitable to investigate the response of ice sheets to long-term climate change. After calibration and validation, we investigate the contribution of individual climate forcings (temperature, precipitation, clouds and radiation) to the interannual SMB variability.                     

Furthermore, we compare 1979-2016 ERA5 and ERA-Interim with respect to the main atmospheric drivers of the melt season over the GrIS. In summer, ERA5 differs remarkably from ERA-Interim: averaged over the lower parts of the GrIS, the mean near-surface temperature is 1 K lower while mean downward shortwave radiation at the surface is on average 15W/m^2 higher than in ERA-Interim. In consequence those methods which hitherto have estimated the GrIS surface mass balance from the ERA-Interim surface energy balance need to be carefully recalibrated before they can be progressed to ERA5 forcing.

Krebs-Kanzow, U., Gierz, P., Rodehacke, C. B., Xu, S., Yang, H., and Lohmann, G., 2021: The diurnal Energy Balance Model (dEBM): a convenient surface mass balance solution for ice sheets in Earth system modeling, The Cryosphere, 15, 2295–2313, https://doi.org/10.5194/tc-15-2295-2021.

How to cite: Krebs-Kanzow, U., Rodehacke, C., and Lohmann, G.: The 1950-2020 variability of the Greenland Ice Sheet surface mass balance, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9957, https://doi.org/10.5194/egusphere-egu22-9957, 2022.

EGU22-10811 | Presentations | CR1.2

The pre-industrial digital elevation model of the Greenland Ice Sheet from the 17th and 18th Centuries  

Rachel Oien, Sophie Nowicki, and Beata Csatho

A large uncertainty surrounding the current state of the Greenland Ice Sheet (GIS) and the predictions for future sea-level change stem from a lack of knowledge in the historical boundary and shape of the ice sheet. Prior to the 1970s, the ice sheet is reliant on aerial imagery and digital photographs. To help improve ice sheet model projections, in particular for the Ice Sheet Model Intercomparison Project for CMIP6 (ISMIP6) group, the focus is to provide a historical perspective of the boundaries and thickness. The digital elevation model is built using trim lines, geomorphic mapping, known points of boundary conditions, early explorer records, through a combination of biogeographical, archaeological and geologic records to amalgamate into a historical DEM. As more numerical simulations are based on the same DEM input yet the response time of the ice sheet is slow enough where a pre-industrial DEM would provide insight into the climate-ice sheet interactions of the recent past. Furthermore, this work will provide an observation-based estimate of change to the GIS and has the potential to lead to a calculation of the spatial ice mass loss from previous centuries. This DEM will increase understanding of the spatial extent of the GIS prior to the 20th century which remains crucial for evaluating the reliability of numerical simulations to predict global sea-level rise.

How to cite: Oien, R., Nowicki, S., and Csatho, B.: The pre-industrial digital elevation model of the Greenland Ice Sheet from the 17th and 18th Centuries , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10811, https://doi.org/10.5194/egusphere-egu22-10811, 2022.

EGU22-11363 | Presentations | CR1.2

Evaluation of CMIP5 and CMIP6 global climate models in the Arctic and Antarctic regions, atmosphere and surface ocean 

Cécile Agosta, Christoph Kittel, Charles Amory, Tamsin Edwards, and Cécile Davrinche

Large efforts are engaged to model climate-ice sheet interactions in order to estimate Antarctic and Greenland ice sheets’ contribution to sea level in the next decades to centuries. Here we present a first-order evaluation of CMIP5 and CMIP6 climate models over both polar regions. We focus on large-scale atmospheric fields and surface ocean variables only. Our goal is to provide a first overview of climate model biases in polar regions, in order to use their outputs on an informed basis. We particularly target the use of climate model outputs for forcing ice sheet models and regional atmospheric models.

We consider 9 (non-independent) variables : 850 hPa and 700 hPa annual and summer temperature, annual integrated water vapor, annual sea level pressure, annual 500hPa geopotential height, summer sea surface temperature, and winter sea ice concentration; over the Arctic (> 50°N) and the Antarctic (<40°S) regions. We use the ERA5 reanalysis as a reference, but we also include 5 other reanalyses in the intercomparison in order to estimate uncertainty coming from this choice. We define two sets of metrics. The first set of metrics, called “scaled rmse”, is the spatial root mean square error (RMSE) of time-mean variables for each region, that we divide by the median RMSE among all CMIP models. The second set of metrics, called “implausible fraction”, is the portion of the region where the difference between time-mean CMIP model and time-mean ERA5 is greater than three times the local interannual standard deviation. We find a strong relationship between the two sets of metrics. In addition, using the implausible fraction, we find that CMIP variables are significantly more implausible in the Antarctic than in the Arctic. It might be because of badly resolved processes or because of higher decadal variability in the South. Further work should include estimates of decadal variability in the implausibility computation.

How to cite: Agosta, C., Kittel, C., Amory, C., Edwards, T., and Davrinche, C.: Evaluation of CMIP5 and CMIP6 global climate models in the Arctic and Antarctic regions, atmosphere and surface ocean, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11363, https://doi.org/10.5194/egusphere-egu22-11363, 2022.

EGU22-12543 | Presentations | CR1.2

Antarctic surface climate in RACMO2.3p3 

Christiaan van Dalum, Willem Jan van de Berg, and Michiel van den Broeke

This study investigates the sensitivity of modeled surface melt and subsurface heating on the Antarctic ice sheet to a new spectral snow albedo and radiative transfer scheme in the Regional Atmospheric Climate Model (RACMO), version 2.3p3 (Rp3). We tune Rp3 to observations by performing several sensitivity experiments and assess the impact on temperature and melt by incrementally changing one parameter at a time. When fully tuned, Rp3 compares well with in situ and remote sensing observations of surface mass and energy balance, melt, near-surface and (sub)surface temperature, albedo and snow grain specific surface area. Near surface snow temperature is especially sensitive to the prescribed fresh snow specific surface area and fresh dry snow metamorphism. These processes, together with the refreezing water grain size and subsurface heating, are important for melt around the margins of the Antarctic ice sheet. Moreover, small changes in the albedo and the aforementioned processes can lead to an order of magnitude overestimation of melt, locally leading to runoff and a reduced surface mass balance.

How to cite: van Dalum, C., van de Berg, W. J., and van den Broeke, M.: Antarctic surface climate in RACMO2.3p3, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12543, https://doi.org/10.5194/egusphere-egu22-12543, 2022.

EGU22-24 | Presentations | CR1.3 | Highlight

Anticipating future ice-dammed lakes across High Mountain Asia 

Loris Compagno, Matthias Huss, Harry Zekollari, Evan Miles, and Daniel Farinotti

Over recent decades, a significant increase in the amount and the size of glacier lakes has been observed. These lakes enhance glacier mass loss but also present societal hazard as they may retain large volumes of water. When large lakes drain, the downstream valleys can severely be impacted by the resulting glacial lake outburst floods (GLOFs), potentially leading to infrastructural damage and ecological impacts. Most studies assessing the future evolution and potential hazards from glacial lakes focus on proglacial lakes, i.e. lakes that are dammed by either moraines or bedrock. Albeit typically more hazardous, ice-dammed lakes including supraglacial lake are generally neglected in such assessments. 

Here, we assess for the first time the formation and development of potential ice-dammed lakes for all glaciers in High Mountain Asia. To do so, we model the geometry of each glacier by linking past digital elevation models to outputs of the combined glacier mass balance, ice flow and debris evolution model GloGEMflow. We identify potential ice-dammed lakes in depressions at the surface and margins of glaciers, and model their geometrical evolution by accounting for the enhanced melt caused by the lakes’ presence. The model is calibrated and evaluated with independent datasets. 

To analyze the ice-dammed lakes’ sensitivity to climate change, we model the evolution of glaciers and their ice-dammed lakes under different Shared Socioeconomic Pathways (SSPs). Our results indicate that the total number of potential ice-dammed lakes will first increase through time, and then diminish as glaciers shrink, reducing confining barriers. Compared to 2000, a moderate warming scenario (SSP126) anticipates approx. 42% more lakes by 2050, whilst in a strong warming scenario (SSP585), the increase is of ~46%. By the end of this century, the number of ice-dammed lakes will diminish compared to the 2050 peak by approx. 16%  (SSP126) and ~42% (SSP585) due to glacier shrinkage. The same pattern is also expected for the lakes’ volume evolution, which is expected to increase compared to 2000 between ~79% (SSP119) and ~87% (SSP585) by 2050, for then diminish by about 8% by the end of the century for SSP585 compared to 2050.  Finally, by investigating the largest ice-dammed lakes, we highlight regions that could be of particular relevance when aiming at anticipating future GLOFs from ice-dammed lakes.

How to cite: Compagno, L., Huss, M., Zekollari, H., Miles, E., and Farinotti, D.: Anticipating future ice-dammed lakes across High Mountain Asia, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-24, https://doi.org/10.5194/egusphere-egu22-24, 2022.

In the northern Japanese Alps, more than 100 perennial snow patches exist (Higuchi and Iozawa, 1971).Recently, several groups measured the ice thickness and horizontal flow velocity of seven perennial snow patches in the region, finding them to be active glaciers (e.g., Arie et al., 2019). As they are less than 0.5 km2 in area, they are classified as very small glaciers (VSGs). According to Arie et al. (2021), who observed the mass balance using geodetic methods from 2015 to 2019, 1) the fluctuation of the annual mass balance of Japanese VSGs was highly dependent on yearly fluctuation in accumulation depth, 2) the mass balance amplitude was the largest of all glaciers in the world recorded by WGMS, 3) VSGs can be formed only in terrains where avalanches and snowdrifts can acquire more than double the snowfall. However, for avalanches and snowdrifts in 3), the specific topographic conditions that indicate the magnitude of these contributions are not clear. Hughes (2009) found that the contribution of avalanches to the glacier is large where the "avalanche ratio," which is the ratio of total avalanche discharge area to total glacier area, is high.
 
In this study, we compared the avalanche ratio, distribution altitude, and slope direction of the seven confirmed VSGs, seven large perennial snow patches (over 10,000 m²), and three small perennial snow patches (under 1000 m²) to show the topographic conditions for the formation of glaciers and perennial snow patches in the northern Japanese Alps. As a result, there was a positive correlation between the average snow depth of VSGs calculated by the geodetic method from 2015 to 2021 and the avalanche ratio. A negative correlation was seen between the avalanche ratio and distribution altitude in the VSGs, and the lower the altitude, the higher the avalanche ratio. In addition, the relationship between avalanche ratio and distribution altitude showed that the avalanche ratio of VSGs and large perennial snow patches were larger than that of small perennial snow patches at the same altitude. The avalanche ratio of Ikenotan Glacier, which is the only glacier on the windward slope with no snowdrift, was more than twice as large as that of VSGs at the same altitude. These results suggest that the magnitude of the contribution of avalanche and snowdrift deposition and the distribution altitude determine the size of glaciers and perennial snow patches.
 
Arie, K., Narama, C., Fukui, K., Iida, H. and Takahashi, K.: Ice thickness and flow of the Karamatsuzawa perennial snow patch in the northern Japanese Alps, Journal of the Japanese Society of Snow and Ice, 81(6), 283–295, doi:10.5331/seppyo.81.6_283, 2019.
Arie, K., Narama, C., Yamamoto, R., Fukui, K. and Iida, H.: Characteristics of mountain glaciers in the northern Japanese Alps, cryosphere, 1–28, doi:10.5194/tc-2021-182, 2021.
Higuchi, K. and Iozawa, T.: Atlas of perennial snow patches in central Japan, Water Research Laboratory. Faculty of Science, Nagoya University., 1971.
Hughes, P. D.: Twenty-first Century Glaciers and Climate in the Prokletije Mountains, Albania, Arct. Antarct. Alp. Res., 41(4), 455–459, 2009.

How to cite: Arie, K. and Narama, C.: Topographic conditions for the formation of glaciers and perennial snow patches in the northern Japanese Alps, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-131, https://doi.org/10.5194/egusphere-egu22-131, 2022.

EGU22-3638 | Presentations | CR1.3 | Highlight

Subglacial channels, climate warming and increasing frequency of alpine glacier snout collapse 

Pascal Egli, Bruno Belotti, Boris Ouvry, James Irving, and Stuart Lane

Alpine glacier retreat has increased markedly since the late 1980s and is commonly linked to the effects of rising air temperature on surface melt. Less considered are processes associated with glacier snout-marginal surface collapse. A survey of 22 retreating Swiss glaciers suggests that collapse events have increased in frequency since the early 2000s, driven by ice thinning and reductions in glacier-longitudinal ice flux.

Detailed measurement of a collapse event at one glacier with Uncrewed Aerial Vehicles and ablation stakes showed 0.02 m/day vertical surface deformation above a meandering main subglacial channel, the planform of which was mapped with Ground Penetrating Radar measurements. However, with low rates of longitudinal flux (<1.3 m/year), ice creep was insufficient to close the channel in the snout marginal zone. We hypothesize that an open channel maintains contact between subglacial ice and the atmosphere, allowing greater incursion of warm air up-glacier, thus enhancing melt from below. The associated meandering of subglacial channels at glacier snouts leads to surface collapse due to erosion and internal melt as well as removal of ice via fluvial processes.

How to cite: Egli, P., Belotti, B., Ouvry, B., Irving, J., and Lane, S.: Subglacial channels, climate warming and increasing frequency of alpine glacier snout collapse, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3638, https://doi.org/10.5194/egusphere-egu22-3638, 2022.

EGU22-4231 | Presentations | CR1.3

Modelling the 3-D evolution of glaciers at regional to global scales: challenges and opportunities 

Harry Zekollari, Matthias Huss, Loris Compagno, Frank Pattyn, Heiko Goelzer, Stef Lhermitte, Bert Wouters, and Daniel Farinotti

Various techniques exist to model the evolution from glaciers at regional to global scales. Whereas pioneering efforts typically relied on volume-area scaling approximations or parameterizations based on observed glacier changes (retreat parameterization), more recent approaches now also explicitly incorporate ice-dynamical processes. In these latter studies, glaciers are typically represented through central flowlines. Such flowline approaches are particularly suited for mountain glaciers that span over a large elevation range, i.e. valley-glaciers with an elongated shape. However, flowline approaches are not ideal to represent the geometry of ice caps (large glaciers) that generally have a dome-shaped geometry. For ice caps, a model representation that explicitly accounts for the glacier’s 3D geometry and that allows for the glacier to lose and gain mass in all directions, both through mass balance and ice dynamic processes, is needed.

Here we present simulations performed with a coupled surface mass balance – ice flow model that explicitly accounts for the 3D geometry of individual glaciers. The model, written in Python, relies on the shallow ice approximation to describe ice flow, allowing to run large ensembles of simulations. The goal is to simulate the temporal evolution of glaciers with distinct shapes and situated in various climatic regimes, i.e. having a model that allows for an automated intialization and that is suited for regional to global-scale applications.

In this contribution, we present simulations performed with this new large-scale model for regions with mountain glaciers (e.g. European Alps and Scandinavia), as well as regions with large ice caps (e.g. Iceland). Through this, we highlight various challenges that relate to model initialization or the choice of model settings, for instance. We also explore how simulated glacier evolutions compare to those simulated with a retreat parameterzation and through flowline modelling, thereby shedding light on the need for a 3D modelling approach.

How to cite: Zekollari, H., Huss, M., Compagno, L., Pattyn, F., Goelzer, H., Lhermitte, S., Wouters, B., and Farinotti, D.: Modelling the 3-D evolution of glaciers at regional to global scales: challenges and opportunities, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4231, https://doi.org/10.5194/egusphere-egu22-4231, 2022.

EGU22-4263 | Presentations | CR1.3

Implementation of calving processes in large-scale ice sheet models 

G. Hilmar Gudmundsson

Concepts and ideas related to implementation of calving in large-scale ice-sheet models are presented and discussed, and new model verification experiments proposed. For unconfined ice shelves, any calving law where the calving rate increases with cliff height (free board) must lead to an unstable advance or retreat. No other solutions are possible and all calving front positions are always unstable. If in contrast, calving rate is a monotonically decreasing function of cliff height, both stable and unstable positions are possible. An example of such a configuration and simple analytical solution for the transient evolution of the calving front is provided, which can be used for numerical verification purposes. It is argued that cliff-height based calving laws are, at least for the case of buttressed ice shelves, arguably unphysical as they can result in a multi-valued function for the calving rate as a function of local state of stress. Implementation of a new variational form of the level-set method, involving forward-and-backward diffusion, for capturing the evolution of calving fronts is discussed and several applications to Pine Island and Thwaites glacier shown.

How to cite: Gudmundsson, G. H.: Implementation of calving processes in large-scale ice sheet models, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4263, https://doi.org/10.5194/egusphere-egu22-4263, 2022.

EGU22-4937 | Presentations | CR1.3

Treatment of Density Variations in Ice-Flow Models using the Shallow Ice Stream Approximation 

Camilla Schelpe and Hilmar Gudmundsson

In most models of large-scale ice-sheet dynamics, horizontal density variations within the ice are largely ignored. Ice-sheets typically comprise a core of meteoric ice, and an overlying layer of lower-density firn of variable thickness. This gives rise to spatial variation in the average density of the ice at each point on the surface, which in principle will modify the glacial dynamics.  A common approach to handle density-variation in the ice is to adjust the thickness of the glacier to the equivalent height of constant-density meteoric ice. We refer to this as the density-to-thickness (D2T) adjustment method. While this approximation preserves the total mass of the ice-column at each spatial coordinate, it introduces additional unwanted terms in the momentum equations, and misses other correction terms. 

In this study, we investigate the D2T adjustment approximation in detail, and consider a number of alternative formulations to handle the density variation in the ice-sheet, based around the modified field equations that we derive in the presence of a variable density field. The alternative formulations include: a static density distribution in which accumulation and compactfication of the firn layer counteracts the advection of the density field so that the time-evolution of the density field can be ignored; or alternatively a time-evolving density distribution with advects with the ice-flow, such that the material derivative of the density field is zero. 

These different formulations are studied in detail within the framework of perturbation analysis. We derive transfer functions for the induced perturbations in both the glacial thickness and velocity, in response to a small perturbation in the density field. We study the frequency profile of the response and its temporal evolution. This helps us gain a deeper understanding of the different formulations, and their impact on glacial dynamics. Within the numerical ice-flow model Úa, we compare the D2T adjustment method to an approach which explicitly includes the density variations, applied to numerical simulations of the Western Antarctic region containing Pine Island and Thwaites Glaciers.

How to cite: Schelpe, C. and Gudmundsson, H.: Treatment of Density Variations in Ice-Flow Models using the Shallow Ice Stream Approximation, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4937, https://doi.org/10.5194/egusphere-egu22-4937, 2022.

EGU22-5781 | Presentations | CR1.3

xDEM - A python library for reproducible DEM analysis and geodetic volume change calculations 

Amaury Dehecq, Erik Mannerfelt, Romain Hugonnet, and Andrew Tedstone

Crunching satellite imagery or Digital Elevation Models (DEMs) is part of your weekly routine?

You are desperate to calculate glacier volume changes despite gappy observations?

Your head blows up just trying to provide those errors bars for your mass balance estimates?

You think science should be fully reproducible?

Python is one of your favourite programming languages?

If you answered yes to any two of those questions, you should definitely attend this presentation!

 

Remote sensing is becoming increasingly important in our understanding of global glacier changes. Dozens of studies each year aim at estimating geodetic glacier mass balance from the regional to the global scale, providing factual numbers behind glacier retreat. But how reliable are those numbers? Current approaches raise several problems:

  • External data, such as glacier outlines can be updated regularly, as is done e.g. with the RGI outlines, potentially making previous estimates obsolete.
  • Data processing techniques, such as DEM coregistration or gap-filling, evolve over time in the community.
  • Many results are not reproducible or cannot even be updated, because access to the data or code is not granted.

All these issues make the comparison and validation of older vs newer studies challenging and questions the reliability of glacier change estimates. Why not team-up and create the tools we all dream of?

 

Here we present xDEM, an open-source, community-built and easy-to-use set of tools for DEMs postprocessing and volume change calculation. The tool is designed as a set of Python modules, built on top of popular libraries (rasterio, geopandas, GDAL). It will ultimately provide all that is needed to turn individual raw DEMs into a geodetic volume change and its uncertainties: coregistration, bias correction, gap-filling, volume change calculation and spatial statistics (e.g. variograms). The concept behind xDEM is:

Ease of use: Python modules developed by glaciologists, (mostly) for glaciologists.

Flexibility and modularity: We offer a set of options, rather than favouring a single method and make it straightforward to combine them.

Reproducibility: Version-controlled; releases saved with DOI; test-based development ensures our code always performs as expected.

The progress of the project can be followed at https://github.com/GlacioHack/xdem.

 

We illustrate the use of xDEM for various test cases and on-going projects to post-process DEMs obtained from ~1930 terrestrial images of the Swiss Alps, American reconnaissance KH-9 satellite images, modern ASTER and Pleiades images or the recent RAGMAC intercomparison experiment.

How to cite: Dehecq, A., Mannerfelt, E., Hugonnet, R., and Tedstone, A.: xDEM - A python library for reproducible DEM analysis and geodetic volume change calculations, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5781, https://doi.org/10.5194/egusphere-egu22-5781, 2022.

EGU22-6030 | Presentations | CR1.3

Future climate and runoff projections in the Naltar Catchment, Upper Indus Basin from CORDEX-South Asia regional climate models and hydrological modelling 

Muhammad Usman Liaqat, Ana Casanueva, Giovanna Grossi, and Roberto Ranzi

Energy budget-based distributed modelling in glacierized catchments is important to examine glaciological-hydrological regimes and compute flow rates in current and projected scenarios. Trends in ablation of snow and glaciers retreat depend upon snow and ice reserves, meteorological parameters and geographical features which vary across sub-basins in Upper Indus Basin. This study attempts to address these issues by employing [1] regional climate models (RCMs) and the Physical based Distributed Snow Land and Ice Model (Ranzi and Rosso 1991; Grossi et al. 2013) in the Naltar catchment (area of 242.41 km2, with 42 km2 glacierized), located in the Hunza river basin (Upper Indus Basin), to project snow and glacier melt and daily streamflow. The calibration and validation of the model were successfully carried out using observed historical meteorological data at hourly time resolution from high altitude meteorological stations (Liaqat et al. 2021). For each of the climate simulations, projections of near future (2040-2059) and far future (2080-2099) under three Representative Concentration Pathways (RCPs) namely RCP2.6, RCP4.5, and RCP8.5 are presented[2]  with respect to corresponding present climate (1991-2010). We used all relevant meteorological variables from an ensemble of 37 simulations in total, which were performed by 3 RCMs driven by 11 different global climate models (GCMs) and were developed under the CORDEX Experiment, (Giorgi et al. 2009)-South Asia initiative. RCMs often present systematic biases and, despite their rather high spatial resolution (here approximately 50km x 50km) they are still too coarse for hydrological impact assessments. In order to produce localized and unbiased climate projections, we scaled the observed climate according to the simulated changes by means of the delta change method as described in Räisänen and Räty (2013) and Räty et al. (2014). Correction factor [3]  in the mean and standard deviation for all for all meteorological variables were obtained for the near and far future periods compared to the historical period (1991-2010) for each simulation. [4] T[5] he joint analysis of climate projections and hydrological modelling, spanning different scenarios and other sources of uncertainty is essential to predict future changes in water resources availability to satisfy mainly irrigation demand in the downstream areas.

 

References

Giorgi F, Jones C, Asrar GR (2009) Addressing climate information needs at the regional level: the CORDEX framework World Meteorological Organization Bulletin 58:175

Grossi G, Caronna P, Ranzi R (2013) Hydrologic vulnerability to climate change of the Mandrone glacier (Adamello-Presanella group, Italian Alps) Advances in water resources 55:190-203

Liaqat MU, Grossi G, Ansari R, Ranzi R Modeling Hydrological Vulnerability to Climate Change in the Glacierized Naltar Catchment (Pakistan) Using a Distributed Energy Balance Model. In: AGU Fall Meeting 2021, 2021. AGU,

Räisänen J, Räty O (2013) Projections of daily mean temperature variability in the future: cross-validation tests with ENSEMBLES regional climate simulations Climate dynamics 41:1553-1568

Ranzi R, Rosso R (1991) Physically based approach to modelling distributed snowmelt in a small alpine catchment IAHS PUBL, IAHS, WALLINGFORD:141-150

Räty O, Räisänen J, Ylhäisi JS (2014) Evaluation of delta change and bias correction methods for future daily precipitation: intermodel cross-validation using ENSEMBLES simulations Climate dynamics 42:2287-2303

How to cite: Liaqat, M. U., Casanueva, A., Grossi, G., and Ranzi, R.: Future climate and runoff projections in the Naltar Catchment, Upper Indus Basin from CORDEX-South Asia regional climate models and hydrological modelling, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6030, https://doi.org/10.5194/egusphere-egu22-6030, 2022.

EGU22-6338 | Presentations | CR1.3 | Highlight

An annual mass balance estimate for each of the world’s glaciers based on observations 

Ines Dussaillant, Romain Hugonnet, Matthias Huss, Etienne Berthier, Frank Paul, and Michael Zemp

The geodetic method has become a popular tool to measure glacier elevation changes over large glacierized regions with high accuracy for multi-annual to decadal time periods. In contrast, the glaciological method provides annually to seasonally resolved information on glacier evolution, but only for a small sample of the world’s glaciers (less than 1%). Various methods have been proposed to bridge the gap on spatio-temporal coverage of glacier change observations and to provide annually-resolved glacier mass balances using the geodetic sample as calibration. Thanks to a new global and near-complete (96% of the world glaciers) dataset of geodetic mass balance observations, this goal has become feasible at the global scale. Inspired by previous methodological frameworks, we developed a new approach to combine the glacier distribution 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). Our results provide a global assessment of annual glacier mass changes and related uncertainties for every individual glacier during the 2000–2020 period. The glacier-specific time series can then be integrated into an annually-resolved global gridded glacier change product at any user-requested spatial resolution, useful for comparison with gravity-based products, calibration or validation of glacier mass balance models operating at a global scale and to improve calculations of the glacier contribution to regional hydrology and global sea-level rise.

How to cite: Dussaillant, I., Hugonnet, R., Huss, M., Berthier, E., Paul, F., and Zemp, M.: An annual mass balance estimate for each of the world’s glaciers based on observations, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6338, https://doi.org/10.5194/egusphere-egu22-6338, 2022.

EGU22-7271 | Presentations | CR1.3

IGM, a glacier evolution model accelerated by deep-learning and GPU 

Guillaume Jouvet, Guillaume Cordonnier, ByungsooKim Kim, Martin Luethi, Andreas Vieli, and Andy Aschwanden

We give an overview of the Instructed Glacier Model (IGM) -- a new framework to model the evolution of glaciers at any scale by coupling ice dynamics, surface mass balance, and mass conservation. The key novelty of IGM is that it models the ice flow by a Convolutional Neural Network (CNN), which is trained from physical high-order ice flow mechanical models. Doing so has major advantages in both forward and inverse modelling.

In forward modelling, the most computationally demanding model component (the ice flow) is substituted by a very cheap CNN emulator. Once trained with representative data, IGM permits to model individual mountain glaciers several orders of magnitude faster than high-order ones on CPU with fidelity levels above 90 % in terms of ice flow solutions leading to nearly identical transient thickness evolution. Switching to Graphics Processing Unit (GPU) permits additional significant speed-ups, especially when modelling large-scale glacier networks and/or high spatial resolutions.

In inverse modelling, the substitution by a CNN emulator does not only speed up but facilitates dramatically the data assimilation step, i.e. the search for optimal ice thickness and ice flow parameter spatial distributions that match spatial observations at best (such as ice flow, surface topography or ice thickness profiles) while being consistent with the high-order ice flow mechanics. The reason is that inverting a CNN can take great benefit from the tools used for its training such as automatic differentiation, stochastic gradient methods, and GPU.

IGM is an open-source Python code (https://github.com/jouvetg/igm), which deals with two-dimensional gridded input and output data. Together with a companion library of trained ice flow emulators, IGM permits user-friendly, computationally highly-efficient, easy-to-customize, and mechanically state-of-the-art glacier forward and inverse modelling at any scale. We illustrate its potential by replicating a simulation of the great Aletsch Glacier, Switzerland, from 1880 to 2100, based on a Stokes model. The complete workflow (data assimilation and 220 years long forward modelling) at 100 m of resolution takes about 1-2 min on the GPU of a laptop and can be replicated and adapted easily using an online Colab notebook.

How to cite: Jouvet, G., Cordonnier, G., Kim, B., Luethi, M., Vieli, A., and Aschwanden, A.: IGM, a glacier evolution model accelerated by deep-learning and GPU, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7271, https://doi.org/10.5194/egusphere-egu22-7271, 2022.

EGU22-7736 | Presentations | CR1.3

Debris cover effect on the evolution of glaciation in the Northern Caucasus 

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

A common disadvantage of almost all global glacier models is that they ignore the explicit description of the debris cover on the heat exchange of the glacier surfaces with the atmosphere. Debris cover plays a key role in the regulation of melt processes. A debris cover more than a few centimeters reduces melting, since it isolates the underlying ice. In this way, debris covered areas are thought to be less exposed to rising temperatures, thereby reducing glacier retreat and mass loss.        

In the foothills of the North Caucasus, an important agricultural region, the problem of expected changes in mountain glaciation is particularly acute, since fluctuations in the flow regime of local rivers depend on the evolution of glaciers: the contribution of glacial runoff to total discharge is very significant.

Here, we present the assessment of debris cover influence on the glacier evolution of the Northern Caucasus on a regional scale (Terek and Kuban river basins). The aim is to determine how much the characteristics of mountain glaciation (its mass balance, area, volume, position of the glacier fronts) of the Northern Caucasus depend on the debris cover evolution. In order to accomplish this goal, we use the GloGEMflow model and a newly created debris cover dynamic module, which is calibrated using newly mapped debris cover outlines. The debris thickness evolution is simulated with a steady deposit model adapted from Verhaegen et al. (2020) and Anderson & Anderson (2016), where debris input onto the glacier is generated from a fixed point on the flow line.

The results reveal that the debris cover evolution pattern differ significantly for Terek and Kuban glacierized basins. Lower elevated Kuban basin glaciers undergo a rapid retreat and lose the debris covered glacier tongues while the Terek basin glaciers experience supraglacial debris expansion with a six times larger effect of debris cover on glacier volume evolution. From 2000 to 2016 the mass loss in the Terek ice basin reached 47834 Mt with an influence of the debris cover module and 50435 Mt  under debris-free conditions. Therefore, we can expect that by the end of the current century the mass loss of the Terek glaciers will be significantly overestimated in case debris cover influence will be ignored in model calculations. On the contrary, in the Kuban basin, calculated mass loss in 2000-2016 with and without debris cover were 1249 Mt  and 1258 Mt  respectfully. Committed loss experiments (constant mean climate for 1990-2015) show that the glaciers of the Terek basin lose ~35% of ice if debris cover is not taken into account and ~29% if debris cover module is turned on (~2  ice volume difference). For the Kuban basin glaciers, the difference of ice volume is only ~0.1  in debris-free vs. debris-covered modes.

The reported study was funded by the RFBR and RS grant 21-55-10003, the work of T. Postnikova was supported by the RFBR grant 20-35-90042.

How to cite: Postnikova, T., Rybak, O., Zekollari, H., Huss, M., Gubanov, A., and Nosenko, G.: Debris cover effect on the evolution of glaciation in the Northern Caucasus, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7736, https://doi.org/10.5194/egusphere-egu22-7736, 2022.

EGU22-7754 | Presentations | CR1.3

The influence of ice-contact lakes and supraglacial debris on glacier change in High Mountain Asia 

Alex Scoffield, Ann Rowan, and Andrew Sole

The number and extent of glacial lakes in mountain regions worldwide has increased over recent decades as glaciers have lost mass. These ice-contact lakes modify the dynamic response of glaciers to climate change, presenting a challenge to projecting their future evolution. In High Mountain Asia (HMA) glacial lakes have expanded by more than 45% in the last 30 years. Previous studies have demonstrated the contrasting dynamic evolution of lake- and land-terminating glaciers in the Eastern Himalaya, although it was previously unclear if this was a localised phenomenon. Using existing and manually derived datasets, we observed glacier surface velocity, surface elevation, terminus position and glacial lake area change across HMA’s differing climatic regimes over a twenty-year period (2000–2020) to investigate the dynamic evolution of ~60 lake- and land-terminating glaciers.

 

Our results show that lake-terminating glaciers in the Himalaya, Karakoram and Pamir experienced faster ice flow in the ablation zone, significant surface thinning and extensive terminus recession in comparison to land-terminating glaciers over the same period. The majority of lake-terminating glacier population experienced a glacier-wide increase in velocity during the twenty-year observation period, including 58% of individual glaciers. In comparison, 62% of land-terminating glaciers experienced a decrease in velocity during the same period. This result suggests that lake-induced dynamic changes are occurring irrespective of the regional climatic regime. Our observations also revealed that lake-terminating debris-covered glaciers experienced a greater magnitude of change in velocity, surface elevation and terminus position, than their clean ice counterparts. These results are important for making projections of future glacier change in HMA where many debris-covered glaciers are pre-disposed to the development of terminal lakes in the next few decades.

How to cite: Scoffield, A., Rowan, A., and Sole, A.: The influence of ice-contact lakes and supraglacial debris on glacier change in High Mountain Asia, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7754, https://doi.org/10.5194/egusphere-egu22-7754, 2022.

Ice flow models include processes which cannot be determined from observational data, but must be represented mathematically in order to simulate the physical system. One such process is the interaction between the ice and the bedrock, basal sliding, which enters models in the form of a sliding law describing the relationship between basal drag and velocity. Basal sliding is a major factor in ice flow, and therefore how it is represented is one of the most important modelling decisions.

 

Several sliding laws have been proposed and used in ice flow models, representing different types of bed. In general, these comprise some combination of a Weertman-style power law and Coulomb friction. The equations for sliding laws contain parameters which are usually given constant, uniform values. The responses to perturbations in the ice flow system differ depending on the sliding law used, and on the parameter choices made.

 

In this study, we use the ice flow model Úa to run experiments for a range of different sliding laws, and different values for parameters within these laws. In each case, we test the response of the model to perturbations in the ice shelf melt rate. We investigate the differences between our model outputs, and assess the relationships between sliding law parameter choices and the resulting changes in ice flow.

 

Our model domain covers the Amundsen Sea Embayment, which we break down into separate catchment areas during our analysis in order to capture localised variation in our results.

How to cite: Barnes, J. and Gudmundsson, H.: The effects of parameter choices in basal sliding laws on a modelled ice flow response to perturbations in forcing, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8658, https://doi.org/10.5194/egusphere-egu22-8658, 2022.

The purpose of the research is to assess the influence of the random weather fluctuations on the estimates of the model-based surface mass balance (SMB) components of the mountain glacier. The common approach in the modeling studies is to use meteorological records (measured or modelled) – surface air temperature and precipitation rate – as weather forcing in numerical experiments. The results of the calculations are normally very sensitive to the parameter choice and the model should be carefully calibrated against measured SMB to obtain correct results. What is usually ignored within the frameworks of this approach is that forcing records at e.g. daily resolution contain internal weather variability which after being integrated by the model can yield in a random walk type trend of SMB.   

To evaluate uncertainty in SMB calculations we force an energy balance model of Djankuat glacier in the Central Caucasus with surrogate series of surface air temperature and precipitation rate. The surrogate series of several model decades duration each are produced by a stochastic weather generator WGEN basing on the observed meteorological series at the weather stations located nearby. In WGEN, precipitation events are simulated by a first-order Markov chain, and the intensity of precipitation is represented using independent gamma distribution. Air temperature is calculated by fitting the appropriate distributions and harmonic functions separately for wet and dry days. Seasonality is reproduced by an estimate of individual sets of model parameters for different periods of the year.

Statistical analysis of the generated ensemble of SMB components revealed that relative standard deviation (RSD) of SMB components (accumulation rate, melting, evaporation, melt water retention) vary within the limits 3-6%, but RSD of the specific mass balance is several times higher.

Our approach enables to filter out reaction of the modeled glaciers induced by the weather noise from systematic reply on climate change.

The reported study was funded by the RFBR and RS grant 21-55-10003.

How to cite: Rybak, O. and Rybak, E.: Evaluating uncertainties in modelled surface mass balance components of a mountain glacier, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8893, https://doi.org/10.5194/egusphere-egu22-8893, 2022.

EGU22-10563 | Presentations | CR1.3

More data and increased automation leads to better quality for GLIMS and RGI glacier data sets 

Bruce Raup, Fabien Maussion, Frank Paul, Etienne Berthier, Tobias Bolch, Jeffrey Kargel, and Adina Racoviteanu

GLIMS, Global Land Ice Measurements from Space, is an initiative that involves ~250 analysts from 34 countries and has the purpose of mapping all glaciers in the world (excluding the Greenland and Antarctic ice sheets) on a periodic basis.  The GLIMS Glacier Database, which became an official product of the NASA NSIDC DAAC (Distributed Active Archive Center) in 2019, contains time series of glacier outlines from different data sources.  Various parts or facies of glaciers are mapped, including the full glacier extent, debris-covered parts, internal rock outcrops, and glacial lakes.  The Randolph Glacier Inventory (RGI) is a snapshot map of glaciers, with one outline per glacier, as close as possible to a target date.

In the last year, GLIMS and the RGI working group have been working closely together to ingest new data into GLIMS and to improve GLIMS and RGI software tools. The goal is to improve data completeness and quality and to make the creation of the RGI smoother and more transparent (Maussion et al., EGU22-4484).  New data include approximately 60,000 outlines from 14 regions in all parts of the Earth, with times ranging from the Little Ice Age to 2018. Software improvements include more quality-control checks and constraints, such as separating multi-polygons into individual ones. 

The presentation will provide an overview on the latest data additions and software developments in GLIMS and the synergy with RGI production.

How to cite: Raup, B., Maussion, F., Paul, F., Berthier, E., Bolch, T., Kargel, J., and Racoviteanu, A.: More data and increased automation leads to better quality for GLIMS and RGI glacier data sets, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10563, https://doi.org/10.5194/egusphere-egu22-10563, 2022.

EGU22-11942 | Presentations | CR1.3

Assessing skill and use of CMIP6 decadal re-forecasts in global glacier mass balance modelling 

Larissa van der Laan, Kristian Förster, Adam Scaife, Anouk Vlug, and Fabien Maussion

Within the earth system, glaciers serve as important indicators of climate change, being principally governed by temperature and precipitation. Additionally, they provide essential freshwater storage on various scales, ranging from long-term in firn and ice, to short-term storage in snow cover. By preventing precipitation from immediately turning into runoff, glaciers fulfill a buffering role within their basins, providing downstream runoff during melt season. With changes in glacier mass balance in response to changes in climate, a glacier's buffering capacity is altered simultaneously. In order to predict the evolution of runoff on temporal scales relevant to water resource management (5-15 years), it is essential to observe and simulate glacier mass balance on the same scale. The current research presents a global modelling approach using the Open Global Glacier Model (OGGM), forced with a multi-model, multi-member retrospective ensemble of monthly temperature and precipitation re-forecasts (hindcasts) from the Decadal Climate Prediction Project (DCPP), part of the Coupled Model Intercomparison Project, phase 6 (CMIP6). The decadal hindcasts are initialized each year in the period 1960-2010 and are bias corrected for model drift, while retaining the period's warming trend, using a lead-time based correction. The hindcasts are then downscaled to the glacier scale and used to compute the climatic mass balance with OGGM, with fixed glacier geometries. The method is validated using 274 reference glaciers, which have a >5 year observational record. It is then applied globally, to all land-terminating glaciers in the Randolph Glacier Inventory (RGI), outside the Greenland Ice Sheet and Antarctica. The results indicate merit in using decadal re-forecasts to model glacier mass balance, paving the way for reliable decadal scale runoff predictions on regional and global scales.

How to cite: van der Laan, L., Förster, K., Scaife, A., Vlug, A., and Maussion, F.: Assessing skill and use of CMIP6 decadal re-forecasts in global glacier mass balance modelling, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11942, https://doi.org/10.5194/egusphere-egu22-11942, 2022.

EGU22-12741 | Presentations | CR1.3

Resolving thermomechanical ice flow on Alpine topography 

Ludovic Räss, Ivan Utkin, and Samuel Omlin

The evolution of glaciers and ice sheets depends sensitively on the processes occurring at their boundaries such as, e.g., the ice-bedrock interface or shear margins. These boundary regions share as common characteristics the transition from flow to no flow over a relatively short distance, resulting in a complex and fundamentally non-hydrostatic stress field. The localised intense shearing may further induce weakening of the ice owing to thermomechanical interactions, ultimately accelerating and potentially destabilising the bulk of the ice. Better understanding the sensitivity of these near-boundary processes is vital and challenging as it requires non-linear and coupled full Stokes models that can afford very high resolution in three-dimensions.

We present recent development of a thermomechanical coupled numerical model that leverages graphical processing units (GPUs) acceleration to resolve the instantaneous stress and velocity fields within ice flow over complex topography in three dimensions. We apply the model to various glaciers of the Swiss Alps resolving the complex flow field in three dimensions and at very high spatial resolution. We further use the model to assess the competition between basal sliding and internal sliding, the latter referring to the formation of a near-basal internal shear zone within the ice owing to thermomechanical feedback. We finally provide some insights in GPU-based high-performance computing model development using the Julia language and the ongoing development of efficient implicit iterative solvers based on the accelerated pseudo-transient method.

How to cite: Räss, L., Utkin, I., and Omlin, S.: Resolving thermomechanical ice flow on Alpine topography, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12741, https://doi.org/10.5194/egusphere-egu22-12741, 2022.

EGU22-649 | Presentations | CR1.4

Quantifying the spatial representativeness of ice core surface mass balance records using ground-penetrating radar data in Antarctica 

Marie G. P. Cavitte, Hugues Goosse, Sarah Wauthy, Brooke Medley, Thore Kausch, Jean-Louis Tison, Brice Van Liefferinge, Jan T.M. Lenaerts, and Frank Pattyn

The future contributions of the Antarctic Ice Sheet to sea level rise will be highly dependent on the evolution of its surface mass balance (SMB), which can offset increased ice discharge at the grounding line. In-situ SMB constraints over annual to multi-decadal timescales come mostly from firn and ice cores. However, although they have a high temporal resolution, ice cores are local measurements of SMB with a surface footprint on the order of cm2. Post depositional processes (e.g. wind driven redistribution) can change the initial snowfall record locally and therefore affect our interpretation of the SMB signal recovered. On the other hand, regional climate models have a high temporal resolution but may miss some of the processes at work as a result of their large spatial footprint, on the order of km2. Comparisons of ice core and model SMB records often show large discrepancies in terms of trends and variability.

We investigate the representativeness of a single shallow core record of SMB of the area surrounding it. For this, we use ice-penetrating radar data, co-located with the ice core records examined, to obtain a multi-annual to decadal radar-derived SMB record. We then compare the radar-derived SMB records to the ice core SMB records to determine the surface area that the ice core record is representative of, in terms of mean SMB as well as SMB temporal variability on historical timescales. We examine ice core records situated over the coastal ice rises of East Antarctica, where SMB is high and spatially heterogeneous, as well as over the interior of the West Antarctic Ice Sheet, where SMB is more uniform spatially. By comparing these two contrasting regions in terms of SMB, we will determine whether a general rule of thumb can be obtained to determine the spatial representativeness of an ice core SMB record.

How to cite: Cavitte, M. G. P., Goosse, H., Wauthy, S., Medley, B., Kausch, T., Tison, J.-L., Van Liefferinge, B., Lenaerts, J. T. M., and Pattyn, F.: Quantifying the spatial representativeness of ice core surface mass balance records using ground-penetrating radar data in Antarctica, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-649, https://doi.org/10.5194/egusphere-egu22-649, 2022.

EGU22-1281 | Presentations | CR1.4 | Highlight

Response of the Wilkes Subglacial Basin Ice Sheet to Southern Ocean Warming During Late Pleistocene Interglacials 

Ilaria Crotti, Aurélien Quiquet, Amaelle Landais, Barbara Stenni, Massimo Frezzotti, David Wilson, Mirko Severi, Robert Mulvaney, Frank Wilhelms, and Carlo Barbante

The growth and decay of marine ice sheets act as important controls on regional and global climate and sea level. The Wilkes Subglacial Basin ice sheet appears to have undergone thinning and ice discharge events during recent decades, but its past dynamics are still under debate. The aim of our study is to investigate ice margin retreat of the Wilkes Subglacial Basin ice sheet during late Pleistocene interglacials with the help of new high-resolution records from the TALDICE ice core. Here we present a multiproxy approach associated with modelling sensitivity experiments.

The novel high-resolution δ18O signal reveals that interglacial periods MIS 7.5 and 9.3 are characterized by a unique double-peak feature, previously observed for MIS 5.5 (Masson-Delmotte et al., 2011), that is not seen in other Antarctic ice cores. A comparison with our GRISLI modelling results indicates that the Talos Dome site has probably undergone elevation variations of 100-400 m during past interglacials, with a major ice thickness variation during MIS 9.3, likely connected to a relevant margin retreat of the Wilkes Subglacial Basin ice sheet. To validate this elevation change hypothesis, the modelling outputs are compared to the ice-rafted debris record (IBRD) and the neodymium isotope signal from the U1361A sediment core (Wilson et al., 2018), which show that during MIS 5.5 and especially MIS 9.3, the Wilkes Subglacial Basin ice sheet has been subjected to ice discharge events.

Overall, our results indicate that the interglacial double-peak δ18O signal could reflect decreases in Talos Dome site elevation during the late stages of interglacials due to Wilkes Subglacial Basin retreat events. These changes coincided with warmer Southern Ocean temperatures and elevated global mean sea level, confirming the sensitivity of the Wilkes Subglacial Basin ice sheet to ocean warming and its potential role in sea-level change.

How to cite: Crotti, I., Quiquet, A., Landais, A., Stenni, B., Frezzotti, M., Wilson, D., Severi, M., Mulvaney, R., Wilhelms, F., and Barbante, C.: Response of the Wilkes Subglacial Basin Ice Sheet to Southern Ocean Warming During Late Pleistocene Interglacials, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1281, https://doi.org/10.5194/egusphere-egu22-1281, 2022.

EGU22-1667 | Presentations | CR1.4

A Path to Quantitative Interpretation of Antarctic Sediment Provenance Records 

Jim Marschalek, Edward Gasson, Tina van de Flierdt, Claus-Dieter Hillenbrand, and Marin Siegert

Tracing the provenance of Antarctic sediments yields unique insights into the form and flow of past ice sheets. However, sediment provenance studies are typically limited to qualitative interpretations by uncertainties regarding subglacial geology, glacial erosion, and transport of sediment both subglacially and beyond the ice sheet margin. Here, we forward model marine geochemical sediment provenance data, in particular neodymium isotope ratios. Numerical ice-sheet modelling predicts the spatial pattern of subglacial erosion rates for a given ice sheet configuration, then ice flow paths are traced to the ice sheet margin. For the modern ice sheet, simple approximations of glacimarine sediment transport processes produce a good agreement with Holocene surface sediments in many areas of glaciological interest. Calibrating our model to the modern setting permits application of the approach to past ice sheet configurations, which show that large changes to sediment provenance over time can be reconstructed around the West Antarctic margin. This first step towards greater integration of Antarctic sediment provenance data with numerical modelling offers the potential for advances in both fields.

How to cite: Marschalek, J., Gasson, E., van de Flierdt, T., Hillenbrand, C.-D., and Siegert, M.: A Path to Quantitative Interpretation of Antarctic Sediment Provenance Records, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1667, https://doi.org/10.5194/egusphere-egu22-1667, 2022.

EGU22-2310 | Presentations | CR1.4

Exploring the sensitivity of modelled sea-level rise projections from the Amundsen Sea Embayment of the Antarctic Ice Sheet to model parameters 

Suzanne Bevan, Stephen Cornford, Adrian Luckman, Anna Hogg, Inés Otosaka, and Trystan Surawy-Stepney

Recent sea-level rise from the Antarctic icesheet has been dominated by contributions from Pine Island and Thwaites Glaciers of the Amundsen Sea Embayment (ASE). Much of the ASE ice is grounded below sea level and is therefore likely to be highly sensitive to ongoing oceanic and atmospheric warming.

Confidence in model-based predictions of the future contributions of the ASE region to sea-level rise requires an understanding of the sensitivity of the predictions to input data, such as bedrock topography, and to chosen parameters within, for example, sliding laws.

We will present results from using the BISICLES adaptive mesh refinement ice-sheet model to explore the sensitivity of modelled ASE 2050 grounded ice loss. We test a regularized Coulomb friction sliding law, varying the regularization parameter, and we test the sensitivity to bedrock elevation by adding gaussian noise of different wavelengths to MEaSUREs BedMachine Version 2 elevations. However, within our experiments, we find the greatest sensitivity in modelled 2050 sea-level contributions is to the imposed ice-shelf thinning or damage rates, which we vary between spatially uniform values of 0 to 15 m/year.

We will also present a comparison of the modelled annual evolution of surface velocity and surface elevation change with observations. Observed surface velocities are based on Sentinel 1 feature tracking, and surface elevation change rates are derived from satellite radar altimetry.

How to cite: Bevan, S., Cornford, S., Luckman, A., Hogg, A., Otosaka, I., and Surawy-Stepney, T.: Exploring the sensitivity of modelled sea-level rise projections from the Amundsen Sea Embayment of the Antarctic Ice Sheet to model parameters, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2310, https://doi.org/10.5194/egusphere-egu22-2310, 2022.

EGU22-4161 | Presentations | CR1.4

Dynamics of East Antarctic glaciers from 1937-2017 analyzed using historical aerial expedition images 

Mads Dømgaard, Flora Huiban, Anders Schomacker, Jeremie Mouginot, and Anders Bjørk

Since the beginning of the 20th century, various countries have carried out expeditions to Antarctica with the aim of claiming territory, reconnaissance as well as capturing aerial images for topographic mapping. Many of these image inventories has since then been forgotten and never used for scientific purposes. We have gained access to a unique dataset of aerial images captured in 1936-1937 as a part of the Norwegian Thorshavn IV expedition surveying and mapping large parts of the East Antarctic coastline. The images have a stereo overlap of approximate 60% and are digitized using a photogrammetry-grade scanner, enabling us to produce the earliest known digital elevation models and orthophotos of Antarctica.

Expanding the observational records of Antarctic glaciers are vital for better understanding and modelling how changes in climatic parameters affects the ice. Currently, we know very little about the behaviour of Antarctic glaciers prior to the 1990s, due to a lack of large-scale observations. Several studies has proven the effectiveness of using digitally-scanned historical aerial images in studying ice mass losses of the pre-satellite era, but very few such studies exist for Antarctica. In this study, we explore Norwegian and Australian historical aerial expedition images collected between 1937 and 1997 to extensively expand the records and provide the earliest regional-scale Antarctic glacier records. The images are processed using structure-from-motion photogrammetry, which enables us to construct accurate, high-resolution digital elevation models and orthophotos. By combining expedition images with modern satellite data, we are creating a unique time-series dataset to study the changes of multiple glaciers along the East Antarctic coastline in Mac Robertson and Kemp Land between 1937 and 2017.

How to cite: Dømgaard, M., Huiban, F., Schomacker, A., Mouginot, J., and Bjørk, A.: Dynamics of East Antarctic glaciers from 1937-2017 analyzed using historical aerial expedition images, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4161, https://doi.org/10.5194/egusphere-egu22-4161, 2022.

EGU22-4786 | Presentations | CR1.4

Simulating the evolution of the Antarctic Ice Sheet including 3D GIA feedback during the Last Glacial Cycle 

Caroline van Calcar, Roderik van de Wal, Bas Blank, Bas de Boer, and Wouter van der Wal

Changes in ice load over time deform the Earth’s crust and mantle. This effect, Glacial Isostatic Adjustment (GIA), induces vertical deformation of the bedrock of the Antarctic continent and impacts the grounding line position which is critical for the dynamical state of the Antarctic Ice Sheet (AIS). GIA introduces a negative feedback and stabilizes the ice sheet evolution, hence GIA modelling is important for transient studies. Most ice dynamic models use a two-layer flat Earth approach with a laterally homogenous relaxation time or a layered Earth approach with a laterally homogenous viscosity (1D) to compute the bedrock deformation. However, viscosity of the Earth’s interior varies laterally (3D) and radially with several orders of magnitude across the Antarctic continent. Here we present a new coupled 3D GIA – ice dynamic model which can run over hundred thousands of years with a resolution of 500 years. The method is applied using various 1D and 3D rheologies. Results show that the present-day ice volume is 3 % lower when using a 1D viscosity of 1021 Pa·s than using a 3D viscosity. However, local differences in grounding line position maybe up to a hundred kilometres around the Ronne and the Ross Ice Shelfs, and ice thickness differences are up to a kilometre for present day conditions when comparing 1D rheologies and 3D rheologies. The difference between the use of various 3D rheologies is significantly smaller. These results underline and quantify the importance of including local GIA feedback effects in ice dynamic models when simulating the Antarctic Ice Sheet evolution over the Last Glacial Cycle.

How to cite: van Calcar, C., van de Wal, R., Blank, B., de Boer, B., and van der Wal, W.: Simulating the evolution of the Antarctic Ice Sheet including 3D GIA feedback during the Last Glacial Cycle, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4786, https://doi.org/10.5194/egusphere-egu22-4786, 2022.

EGU22-5596 | Presentations | CR1.4

Contribution of tropical variability on Antarctic climate changes over the past centuries 

Quentin Dalaiden, Nerilie Abram, and Hugues Goosse

The future evolution of the Antarctic Ice Sheet (AIS), particularly the West Antarctic Ice Sheet (WAIS), will strongly influence global sea-level rise during the 21st century and beyond. However, because of the sparse observational network in concert with the strong internal variability, our understanding of the long-term climate and ice sheet changes in the Antarctic is limited. Among all the processes involved in Antarctic climate variability and change, an increasing number of studies have pointed out the strong relationship between the climate in the tropics and Antarctic (also called tropical-Antarctic teleconnections), especially between the Pacific Ocean and the West Antarctic region. Most of those studies focus only on the past decades, but to fully understand the long-term Antarctic climate changes associated with tropical variability longer time-series are needed. This is achieved here by using annually-resolved paleoclimate records (ice core and coral records) that cover at least the last two centuries to study both the year-to-year and multi-decadal variability of tropical-Antarctic teleconnections. These records are incorporated into a data assimilation framework that optimally combines the paleoclimate records with the physics of the climate model. As data assimilation provides a climate reconstruction that is dynamically constrained – through the spatial covariance in the climate model – the contribution of tropical variability on Antarctic climate changes can be directly assessed. Different sensitivity tests are performed to isolate the contribution of each tropical basin. Additionally, the roles of multi-decadal and year-to-year variability are compared by averaging the annual paleoclimate records at a lower temporal resolution. This new method of combining the two time-scales is proposed in order to preserve the multi-decadal variability in the annual climate reconstruction.

How to cite: Dalaiden, Q., Abram, N., and Goosse, H.: Contribution of tropical variability on Antarctic climate changes over the past centuries, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5596, https://doi.org/10.5194/egusphere-egu22-5596, 2022.

EGU22-7213 | Presentations | CR1.4

Exploring the impact of different past- and present-day climatic forcings on Antarctic Ice sheet evolution 

Christian Wirths, Johannes Sutter, and Thomas Stocker

Simulations of past and future Antarctic ice sheet (AIS) evolution depend, besides the intrinsic model specific uncertainties, on the applied climatic forcing. To model the past, present and future Antarctic Ice Sheet, a large set of different forcings from global and regional climate models, is available. For a more complete understanding of the modeled ice sheet dynamics, it is therefore critical to understand the influence and the resulting model differences and uncertainties associated with climate forcing choices.  

In this study we examine the impact of different climatic forcings onto the equilibrium state of the AIS for past and present-day conditions. We apply past (LGM, LIG, mid-Pliocene warm period) and present-day climatic forcings from regional (RACMO2.3p2, MAR3.10, HIRHAM5 and COSMO-CLM) and global (PMIP4 ensemble) climate models onto the Parallel Ice Sheet Model (PISM v.2.0). Further, we investigate the response of the total ice mass, its distribution and the grounding line dynamics of the modeled equilibrium ice sheet under varying ice sheet sensitivity parameterizations.  

With this analysis, we aim to gain a better understanding of AIS modelling uncertainties due to the applied climatic forcings and parameterizations, which will improve the assessment of modeled past and future ice-sheet evolution.  

How to cite: Wirths, C., Sutter, J., and Stocker, T.: Exploring the impact of different past- and present-day climatic forcings on Antarctic Ice sheet evolution, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7213, https://doi.org/10.5194/egusphere-egu22-7213, 2022.

EGU22-7802 | Presentations | CR1.4

Reversibility experiments of present-day Antarctic grounding lines: the short-term perspective 

Emily A. Hill, Benoit Urruty, Ronja Reese, Julius Garbe, Olivier Gagliardini, Gael Durand, Fabien Gillet-Chaulet, G. Hilmar Gudmundsson, Ricarda Winkelmann, Mondher Chekki, David Chandler, and Petra Langebroek

The stability of the grounding lines of Antarctica is a fundamental question in glaciology, because current grounding lines in some locations are at the edge of large marine basins, and have been hypothesized to potentially undergo irreversible retreat in response to climate change. This could have global consequences and raise sea levels by several metres. If the Antarctic grounding lines in their current configuration are close to being unstable, a small change in external forcing, e.g. a reduction in ice shelf buttressing resulting from an increase in ice shelf melt rates, would lead to continued retreat of the grounding line due to the marine ice sheet instability hypothesis, even after the melt perturbation is reverted. Alternatively, if the system state reverts to its previous value after the perturbation is removed, we can consider the current grounding line positions to be reversible. 

Here, we initialise the ice sheets models Úa and Elmer/Ice to closely replicate the current configuration of the Antarctic Ice Sheet, in particular, the current position of the grounding lines. Under control conditions, state fluxes and ice volume changes are forced to be in balance. Using these quasi-steady state ice sheet configurations, we apply a small amplitude perturbation in ice shelf melt rates by imposing an increase for 20 years in the far-field ocean temperature. After 20 years the melt rate perturbation is returned to zero, and model simulations are continued for a further 80-year recovery period. During this recovery period we examine the trend in ice flux and grounding line position, i.e. do they tend towards their previous values, or do they move further away from their initial state? Our results suggest that the global grounding line around Antarctica begins to reverse to its former state after the perturbation is removed. However, we find the reversibility and response times of grounding lines to a small perturbation in ice shelf buttressing varies between individual basins across the ice sheet.

This work is part of the TiPACCs project and complements an overview presentation on the reversibility of present-day Antarctic grounding lines (EGU22-5176) as well as a presentation exploring long-term reversibility experiments (EGU22-7885).

How to cite: Hill, E. A., Urruty, B., Reese, R., Garbe, J., Gagliardini, O., Durand, G., Gillet-Chaulet, F., Gudmundsson, G. H., Winkelmann, R., Chekki, M., Chandler, D., and Langebroek, P.: Reversibility experiments of present-day Antarctic grounding lines: the short-term perspective, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7802, https://doi.org/10.5194/egusphere-egu22-7802, 2022.

EGU22-7885 | Presentations | CR1.4

Reversibility experiments of present-day Antarctic grounding lines: the long-term perspective 

Ronja Reese, Benoit Urruty, Emily A. Hill, Julius Garbe, Olivier Gagliardini, Gael Durand, Fabien Gillet-Chaulet, G. Hilmar Gudmundsson, Ricarda Winkelmann, Mondher Chekki, David Chandler, and Petra Langebroek

The stability of the grounding lines of Antarctica is a fundamental question in glaciology, because current grounding lines are in some locations at the edge of large marine basins, and have been hypothesized to potentially undergo irreversible retreat in response to climate change. This could have global consequences and raise sea levels by several metres. However, their long-term reversibility for the current ice sheet geometry has not yet been questioned, i.e., if the present-day climatology is kept constant, will the grounding lines remain close to their currently observed position or will they retreat substantially? 

Here we focus on the long-term evolution of Antarctic grounding lines over millennial time scales. Using the Parallel Ice Sheet Model, an initial equilibrium state is created for historic climate conditions around 1850. Then the model is run forward until 2015 with atmospheric and oceanic changes from ISMIP6 to reflect recent trends in the ice sheet. After 2015, we keep the present-day climatology constant and let the ice sheet evolve towards a new steady state, which takes several thousand years. An ensemble over model parameters related to sliding and ocean forcing allows us to analyse the sensitivity of the grounding line evolution to model uncertainties. Since we start from a historic equilibrium state, we can use this approach to assess if the increase from historic to present-day climatology might push Antarctic grounding lines across a tipping point into a different basin of attraction that is characterised by a substantially retreated steady-state grounding line position. 

This work is part of the TiPACCs project and complements an overview presentation on the reversibility of present-day Antarctic grounding lines (EGU22-5176) as well as a presentation exploring the short-term reversibility experiments in more detail (EGU22-7802).

How to cite: Reese, R., Urruty, B., Hill, E. A., Garbe, J., Gagliardini, O., Durand, G., Gillet-Chaulet, F., Gudmundsson, G. H., Winkelmann, R., Chekki, M., Chandler, D., and Langebroek, P.: Reversibility experiments of present-day Antarctic grounding lines: the long-term perspective, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7885, https://doi.org/10.5194/egusphere-egu22-7885, 2022.

EGU22-8215 | Presentations | CR1.4

Ocean temperature forcings in glacial-interglacial Antarctic Ice Sheet simulations 

David Chandler, Petra Langebroek, Ronja Reese, Torsten Albrecht, and Ricarda Winkelmann

Ice shelf basal melt accounts for about half the present-day ice loss from the Antarctic Ice Sheet, and is important for both ice sheet mass balance and as a source of fresh water into the Southern Ocean. In Antarctic Ice Sheet simulations over Quaternary glacial cycle time scales, neither basal melt rate nor its principal oceanographic controls (temperature and salinity of waters adjacent to ice shelves) can be reconstructed directly from proxy records. Given the strong ice-ocean-atmosphere interactions, the ideal solution is a coupled ice-ocean-atmosphere model, but computational demands currently limit this approach to short time scales. Stand-alone ice sheet simulations can cover much longer time scales at reasonable resolution, but require an alternative estimate of ocean temperatures. Here we compare the strengths and weaknesses of three options: (i) proxy reconstructions of North Atlantic and circumpolar deep water temperatures, from marine sediment cores north of 43°S; (ii) an ice sheet air temperature reconstruction, damped and lagged by a linear response function; and (iii) a glacial index method which interpolates between CMIP6 lig127k (interglacial) and lgm (glacial) end-member ocean states. We find considerable differences in the rates and magnitudes of the Antarctic Ice Sheet's contribution to past sea-level changes when applying the three methods in simulations over the last two glacial cycles, particularly during the last interglacial and Holocene. Therefore, the ocean temperature forcing remains as an important but poorly-constrained modelling choice, whether investigating past warm climates or using long simulations as a spin-up for future projections. 

How to cite: Chandler, D., Langebroek, P., Reese, R., Albrecht, T., and Winkelmann, R.: Ocean temperature forcings in glacial-interglacial Antarctic Ice Sheet simulations, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8215, https://doi.org/10.5194/egusphere-egu22-8215, 2022.

EGU22-9447 | Presentations | CR1.4

Assessment of the Antarctic ice-sheet response to ice-shelf collapse as a function of the friction law employed 

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

Sea-level rise projections under climate change exhibit large uncertainty related to the contribution of ice sheets. A major source of uncertainty is the Antarctic Ice-Sheet (AIS) due to the marine-based nature of the West Antarctic Ice-Sheet (WAIS). Part of the WAIS is grounded under sea level and thus in contact with the surrounding ocean via the floating ice shelves. Melting of ice shelves does not directly contribute to sea level rise but it modulates the ice flow towards the sea by controlling the discharge through the grounding line. However, the processes that regulate the dynamics are not fully well understood and represented in state-of-the-art models due to the complexity of the various feedbacks involved. In addition, the basal friction or sliding law that should be employed is not well known. In this context arose the Antarctic BUttressing Intercomparison Project (ABUMIP, Sun et al., 2020) with the aim of studying the response of the AIS to a sudden and maintained collapse of its ice shelves. Here we show the results obtained while performing experiments extending those of Sun et al., (2020) with the thermomechanical ice-sheet model Yelmo and assessing the effect of using different friction laws.

How to cite: Pérez-Montero, S., Blasco, J., Robinson, A., Montoya, M., and Alvarez-Solas, J.: Assessment of the Antarctic ice-sheet response to ice-shelf collapse as a function of the friction law employed, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9447, https://doi.org/10.5194/egusphere-egu22-9447, 2022.

EGU22-9448 | Presentations | CR1.4 | Highlight

Antarctic contribution to future sea-level rise with a three-dimensional ice-sheet model 

Antonio Juárez-Martínez, Javier Blasco, Marisa Montoya, Jorge Álvarez-Solas, and Alexander Robinson

Sea-level rise represents one of the biggest threats that humankind has to face in the
coming centuries. Antarctica hosts today's largest ice sheet on Earth, the Antarctic Ice Sheet
(AIS). In the mid-long term, the AIS could become the main contributor to sea-level rise,
especially as a result of the West Antarctic Ice Sheet (WAIS) being marine-based and
therefore strongly exposed to the ocean. Nonetheless, there is substantial uncertainty in the
future contribution of the AIS to sea-level rise, mainly as a result of poor understanding of
physical processes, such as ice-sheet dynamics or ice-ocean interactions. In order to
overcome the problem of different Antarctic sea-level projections with different experimental
setups, the Ice Sheet Model Intercomparison Project for CMIP6 was organized (ISMIP6).
The first results showed that at higher emission scenarios the AIS melts more. Nonetheless,
the WAIS response to this warming varies widely among the models. We herein investigate
the contribution of the higher-order ice-sheet model Yelmo. Results
with Yelmo show a strong sensitivity of the AIS contribution to sea-level rise to the calibration
of the basal-melting parametrization, particularly remarkable in the WAIS, but being in the
range of the results reached by other ice-sheets models in the context of the ISMIP6
intercomparison project.

How to cite: Juárez-Martínez, A., Blasco, J., Montoya, M., Álvarez-Solas, J., and Robinson, A.: Antarctic contribution to future sea-level rise with a three-dimensional ice-sheet model, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9448, https://doi.org/10.5194/egusphere-egu22-9448, 2022.

Thwaites Glacier in West Antarctica may be the single largest contributor to sea level rise in the coming centuries, but existing projections over such timescales are highly uncertain. A number of factors contribute to this uncertainty and robust predictions involve many complex processes through the interaction between ice, ocean and atmosphere. Here, we use the Úa ice-flow model in conjunction with an uncertainty quantification approach to provide uncertainty estimates for the future (100 years’ time scale) mass loss from Thwaites, and the relative contribution of individual model parameters to that uncertainty. In a first step, we simulate Thwaites glacier from 1997 to present day for a wide variety of uncertain model parameters and compare key outputs from each simulation to observations.  Using a Bayesian probability framework we sample the model parameter space, using informed priors, to build up a model emulator, allowing us to provide uncertainty estimates for a range of future emission scenarios. We show how this framework can be used to quantify the relative contribution of each model parameter to the total variance in our estimation of the future mass loss from the area. This, furthermore, allows us to make clear quantitative statements about different sources of uncertainty, for example, those related to external forcing parameterizations (e.g. surface mass balance) as compared to uncertainties in ice-flow parameters (e.g. basal sliding).    

How to cite: Rosier, S. and Gudmundsson, H.: Estimating the future sea level rise contribution of Thwaites glacier, Antarctica, using an uncertainty quantification approach, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9736, https://doi.org/10.5194/egusphere-egu22-9736, 2022.

EGU22-10547 | Presentations | CR1.4

Projected increases in Antarctic snow accumulation from CMIP6 to 2300 

Natalie Trayling, Daniel Lowry, and Ruzica Dadic

As the atmosphere warms in response to increasing greenhouse gas emissions, snow accumulation over the Antarctic Ice Sheet is projected to increase over the next century. Furthermore, short-term emissions scenarios are also expected to have long-term impacts on ice sheet mass balance for centuries to come. Here, we analysed the extended runs of the Coupled Model Intercomparison Project’s Sixth Phase (CMIP6) to investigate the consequences of emissions scenarios on Antarctic surface mass balance until 2300. Unlike the Arctic, which shows a regime shift from snow-dominated precipitation to rain-dominated precipitation, snow accumulation continues to outpace ablation over the Antarctic Ice Sheet through the year 2300, even under the high emissions Shared Socioeconomic Pathway 5-8.5 scenario. The positive relationship between precipitation and temperature increases through time at both high elevation in the continental interior as well as at the coastal margins of the ice sheet. Under high emissions, although rainfall is projected in some vulnerable regions, such as Thwaites Glacier, overall surface mass balance remains positive and increases through time. In corresponding ice sheet model experiments using the Parallel Ice Sheet Model, the sea level compensation of this increased surface mass balance is as high as 10 cm by 2100 and 1.8 m by 2300, though considerable intermodel spread exists. These model results suggest that mass loss of the ice sheet will continue to be dominated by ocean driven-melting rather than melting of the ice sheet surface for the next centuries.

How to cite: Trayling, N., Lowry, D., and Dadic, R.: Projected increases in Antarctic snow accumulation from CMIP6 to 2300, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10547, https://doi.org/10.5194/egusphere-egu22-10547, 2022.

CR2 – Instrumental and paleo-archive observations, analyses and data methodologies in the cryospheric sciences

EGU22-574 | Presentations | CR2.1

Development of a permittivity sensor for melting probes to explore terrestrial and extraterrestrial cryospheres 

Fabian Becker, Pia Friend, and Klaus Helbing

We will present the design of a permittivity sensor that can be attached to a melting probe and measure the respective ice properties during the melting process, yielding in a comprehensive permittivity profile. Melting probes were already successfully applied in terrestrial cryospheres, such as alpine glaciers and Antarctica. Further applications to cross the ice shield on Dome C in Antarctica or even on icy moons in the outer solar system, such as Europa, are already planned e.g. within the TRIPLE project line funded by the German aerospace center. A sensor measuring the permittivity of the surrounding ice in situ during melting could provide valuable data about the ice properties. The respective density of the ice is correlated with the permittivity, or volcanic ash layers can be identified through permittivity measurements. Another usage of the data could be to correct distance measurements from radar travel times within the ice.

The sensor is designed to operate in the frequency range of 0.1 - 1.5 GHz and works in the range of the near field, which is defined to be within one wavelength, corresponding to the frequency. The concept of this sensor is based on an open coaxial probe, which is connected to the medium of interest. The measurement principle and calibration techniques, as well as first lab measurement results of ice and other materials will be presented. A comprehensive data set on effects of porosity, salinity and impurities of lab-manufactured ice samples on the permittivity will also be given. These data will help to interpret the taken permittivity profiles of glaciers on further missions.

We will also show how the device can be integrated into a melting probe, such as the TRIPLE melting probe. One major challenge is to ensure good contact to the ice during measurement. The diameter of a melting hole often results to be several cm larger in diameter than the melting probe itself. A mechanism that extends the sensors of the melting probe and press it onto the ice for measurements is being developed. 

How to cite: Becker, F., Friend, P., and Helbing, K.: Development of a permittivity sensor for melting probes to explore terrestrial and extraterrestrial cryospheres, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-574, https://doi.org/10.5194/egusphere-egu22-574, 2022.

EGU22-612 | Presentations | CR2.1 | Highlight

Using offsets in airborne radar sounding and laser altimetry to characterize near-surface firn properties over the Greenland ice sheet 

Anja Rutishauser, Andreas P. Ahlstrøm, Robert S. Fausto, Nanna B. Karlsson, Baptiste Vandecrux, Kirk M. Scanlan, Ghislain Picard, and Signe B. Andersen

In recent decades, the Greenland Ice Sheet (GrIS) has experienced a significant increase in surface melting and meltwater runoff, which is now the main contributor to GrIS mass loss. In areas covered by firn, meltwater percolation and refreezing processes can significantly buffer meltwater runoff to the ocean. However, this process leads to the formation of ice layers and an overall firn densification, which is predicted to limit the firns’ meltwater storage capacity in the future. Additionally, the high spatial and temporal variability of ice layer formation and subsequent firn densification can cause large uncertainties in altimetry-derived mass balance estimates. Thus, understanding the spatial and vertical extent of ice layers in the firn is important to estimate the GrIS contribution to sea-level rise.

Due to limited direct observations of firn properties, modeling future meltwater runoff and processes over the rapidly changing GrIS firn facies remains challenging. Here, we present a prospective new technique that leverages concurrent airborne radar sounding and laser altimetry measurements to characterize near-surface firn over spatially extensive areas. We hypothesize that due to their different depth sensitivities, the presence of ice layers in the firn yields an offset between radar sounding- and laser-derived surface elevations (differential altimetry). We compare existing airborne radar and laser measurements to in-situ firn observations and use one-dimensional radar sounding simulations to investigate 1) the sensitivity of the differential altimetry technique to different firn facies, and 2) the techniques’ capability to estimate firn density and firn ice content. Preliminary results over the western GrIS show good correlations between differential altimetry signatures and areas of firn affected by percolation and refreezing processes.

Through this technique, we explore the potential to leverage a wealth of radar sounding measurements conducted at low frequencies (< 200 MHz), that typically do not resolve the firn structure, to derive near-surface firn properties. Finally, we apply the differential altimetry technique to data collected as part of NASA’s Operation IceBridge between 2009-2019 to derive spatio-temporal changes in the GrIS firn in response to climatic conditions, in particular the formation of ice layers and changes in firn ice content. Our results can help reduce uncertainties in satellite-derived mass balance measurements and improve firn models, which both contribute to reducing uncertainties in current and projected GrIS contributions to global sea-level rise.

How to cite: Rutishauser, A., Ahlstrøm, A. P., Fausto, R. S., Karlsson, N. B., Vandecrux, B., Scanlan, K. M., Picard, G., and Andersen, S. B.: Using offsets in airborne radar sounding and laser altimetry to characterize near-surface firn properties over the Greenland ice sheet, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-612, https://doi.org/10.5194/egusphere-egu22-612, 2022.

EGU22-942 | Presentations | CR2.1

Towards assembling the internal ice stratigraphy in coastal regions of Dronning Maud Land, East Antarctica 

Reinhard Drews, Inka Koch, Falk Oraschewski, Mohammadreza Ershadi, Leah Sophie Muhle, Heiko Spiegel, Vjeran Visnjevic, Guy Moss, Jakob Macke, Steven Franke, Daniela Jansen, Daniel Steinhage, and Olaf Eisen

The internal ice stratigraphy as imaged by radar is an integrated archive of the atmospheric- oceanographic, and ice-dynamic history that the ice sheet has experienced. It provides an observational constraint for ice flow modeling that has been used for instance to predict age-depth relationships at prospective ice-coring sites in Antarctica’s interior. The stratigraphy is typically more disturbed and more difficult to image in coastal regions due to faster ice flow. Yet, knowledge of ice stratigraphy across ice shelf grounding lines and further seawards is important to help constrain ocean-induced melting and associated stability.

Here, we present preliminary results of synthesizing information from radar stratigraphic characteristics from airborne and ground-based radar surveys that have been collected for specific projects starting from the 1990s onwards focusing on ice marginal zones of Antarctica. The key data is based on airborne surveys from the German Alfred Wegener Institute’s polar aircrafts equipped with a 150 MHz radar. In the meantime this system has been replaced by an ultra-wide band 150-520 MHz radar. The older data will provide a baseline with extensive coverage that can be used for model calibration and change detection over time. We aim to provide metrics of the radio stratigraphy (e.g. shape and slope of internal reflection horizons) as well as classified prevalent stratigraphy types that can be used to calibrate machine learning approaches such as simulation based inference. The data obtained will be integrated in coordination efforts within the SCAR AntArchitecture Action Group.

How to cite: Drews, R., Koch, I., Oraschewski, F., Ershadi, M., Muhle, L. S., Spiegel, H., Visnjevic, V., Moss, G., Macke, J., Franke, S., Jansen, D., Steinhage, D., and Eisen, O.: Towards assembling the internal ice stratigraphy in coastal regions of Dronning Maud Land, East Antarctica, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-942, https://doi.org/10.5194/egusphere-egu22-942, 2022.

EGU22-1002 | Presentations | CR2.1

Application of cosmic ray snow gauges to monitor the snow water equivalent on alpine glaciers 

Rebecca Gugerli, Darin Desilets, and Nadine Salzmann

Temporally continuous measurements of the snow water equivalent (SWE) are a key variable in many hydrological, meteorological and glaciological studies and are of particular importance in high mountain regions. Obtaining temporally continuous, accurate and reliable SWE observations in these harsh environments, however, remains a challenge. Recently, promising results have been achieved by using a neutronic cosmic ray snow gauge (n-CRSG). The n-CRSG device is deployed below the seasonal snowpack and counts fast neutrons from the secondary cascades of cosmic rays, which are efficiently moderated and absorbed by the hydrogen atoms contained in the snowpack. Based on the exponential relationship between neutrons and hydrogen atoms, we can infer SWE from the neutron count rate. We have installed and evaluated a n-CRSG on the Swiss Glacier de la Plaine Morte. Our validation with 22 manual measurements over five winter seasons (2016/17-2020/21) showed an average underestimation of -2% ±10% (one standard deviation).
In the present study, we explore the use of muons instead of neutrons to infer SWE. To this end, we deployed two muonic cosmic ray snow gauges (µ-CRSG), one below and one above the seasonal snowpack, for the winter season 2020/21 on the same glacier site in Switzerland. The difference in count rates between the top and bottom device can be related to the SWE of the snowpack. We derive a first-cut conversion function based on manual SWE observations by means of snow pits and snow cores. To evaluate the measurements by the µ-CRSG, we also compare them to SWE estimates by the n-CRSG. Over the winter season 2020/21, almost up to 2000 mm w.e. were observed. Overall, the µ-CRSG agrees well with the n-CRSG on the evolution of the snowpack at a high temporal resolution and thus demonstrates its great potential. Also, the inferred SWE measurements lie within the uncertainty of manual observations. Furthermore, the µ-CRSG has several advantages over the n-CRSG; It is cheaper, lighter and promises a higher measurement precision due to the improved counting statistics of the muon count rates. We conclude that the µ-CRSG has even greater potential than the n-CRSG to monitor SWE in remote high mountain environments.

How to cite: Gugerli, R., Desilets, D., and Salzmann, N.: Application of cosmic ray snow gauges to monitor the snow water equivalent on alpine glaciers, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1002, https://doi.org/10.5194/egusphere-egu22-1002, 2022.

EGU22-1021 | Presentations | CR2.1

Best practices for collecting polarimetric data with ApRES for constraining ice-fabric orientation and its spatial variability 

Olaf Eisen, Reza Ershadi, Reinhard Drews, Sophie Berger, Da Gong, Yazhou Li, Carlos Martin, and Ole Zeising

In recent years radar polarimetry has re-surfaced as an ideal tool to determine ice-fabric patterns and linked mechanical ice anisotropy. The leap forward was facilitated by coherent data processing often collected by phase-sensitive Radio-Echo-Sounding (pRES) systems at fixed locations. The polarimetric response can either be synthesized from a set of quad-polarimetric measurements or obtained by manually rotating the antennas. Specifics of the data collection in the field varied between the different surveys, and no set of best practices has yet emerged.  Here we present a systematic study that includes more than fifty different combinations of how polarimetric data can be acquired, including:

  • different distances between the transmitter and receiver (2, 4 and 8 m)
  • different combinations in polarization orientation (22.5 deg)
  • a comparison between discrete full azimuthal data collected every 22.5 degrees and synthesized data collected in a quad-pole setup
  • the effect of 180-degree polarization orientation on repeat measurements, e.g., basal melt rate and polarimetric analysis, e.g., coherence phase
  • definition of Horizontal (H) and Vertical (V) orientation is pRES antenna setup and its impact on synthesizing and analyzing data
  • 90-degree fabric orientation ambiguity in polarimetric data

This study aims to provide best practices, considering that observation time in the field is limited. Ideally, this will lead to a unified setup and nomenclature, facilitating better compatibility from data collected by different groups on ice sheets, shelves, and glaciers.

How to cite: Eisen, O., Ershadi, R., Drews, R., Berger, S., Gong, D., Li, Y., Martin, C., and Zeising, O.: Best practices for collecting polarimetric data with ApRES for constraining ice-fabric orientation and its spatial variability, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1021, https://doi.org/10.5194/egusphere-egu22-1021, 2022.

EGU22-1852 | Presentations | CR2.1

Changes in the internal structure of polythermal glaciers over the last decade: the case study of Fridtjofbreen and Erdmanbreen from 2010 to 2021, Svalbard 

Aleksandr Borisik, Aleksandr Novikov, Ivan Lavrentiev, and Andrey Glazovsky

Glaciers on Svalbard have been shrinking in recent decades in response to current climate change. Most of them have decreased in size, area and surface elevation with stable negative or even accelerated changes in mass balance. Many of them are of the polythermal type, and as they shrink, their thermal regime might also change significantly depending on climate and local parameters, such as distribution of ice facies, firn thickness, and other factors affecting hydrology and glacier movement. In this study, we used data from repeated GPR surveys in 2010/12 and 2020/21 to identify likely changes in the thermal regime of the two polythermal glaciers Fridtjovbreen and Erdmanbreen in the western part of the Nordenskiöldland. These changes we have identified by comparison of changes in the depth of the internal reflection horizon (IRH) which corresponds to the cold-temperate transition surface (CTS) in polythermal glaciers.

Comparison of radio-echo sounding (RES) data obtained along the same transverse and longitudinal transects shows that in the last decade the most prominent CTS changes have occurred in the upper western basin of the Fridtjovbreen, where the mean total ice thickness decreased with rate −0.76 m a-1 (from 151 to 144 m in 9 years), meanwhile the thickness of the temperate ice core decreased with rate −2.52 m a-1 (from 115 to 92 m). As a result, with a general reduction in the thickness of the glacier, its upper cold layer increased from 36 to 52 m. These changes we attribute to the reduction of the firn area in this basin, which resulted in less thermal insulation and water retention and internal refreezing, and, therefore, in the fast cold front penetration into the glacier body with rates more than 3 times higher than the glacier thinning.

How to cite: Borisik, A., Novikov, A., Lavrentiev, I., and Glazovsky, A.: Changes in the internal structure of polythermal glaciers over the last decade: the case study of Fridtjofbreen and Erdmanbreen from 2010 to 2021, Svalbard, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1852, https://doi.org/10.5194/egusphere-egu22-1852, 2022.

EGU22-3030 | Presentations | CR2.1

Arctic Sea-Ice Permittivity Derived from GNSS Reflectometry Data of the MOSAiC Expedition 

Maximilian Semmling, Jens Wickert, Frederik Kreß, Mainul Hoque, Dmitry Divine, Sebastian Gerland, and Gunnar Spreen

Sea ice is a crucial parameter of the Earth’s climate system. Its high albedo compared to water and its insulating effect between ocean and atmosphere influences the oceans’ radiation budget significantly. The importance of monitoring sea-ice properties arises from the high variability of sea ice induced by seasonal change and global warming. GNSS reflectometry can contribute to global monitoring of sea ice with high potential to extend the spatio-temporal coverage of today’s observation techniques. Properties like ice salinity, temperature, thickness and snow cover can affect the signal reflection. The MOSAiC expedition (Multidisciplinary drifting Observatory for the Study of Arctic Climate) gave us the opportunity to conduct reflectometry measurements under different sea-ice conditions in the central Arctic. A dedicated setup was mounted, in close cooperation with the Alfred-Wegener-Institute (AWI), on the German research icebreaker Polarstern that drifted for one year with the Arctic sea ice.

We present results from data recorded between autumn 2019 and spring 2020. The ship drifted in this period from the Siberian Sector of the Arctic (October 2019), over the central Arctic (November 2019 until May 2020) towards Fram Strait and Svalbard (reached in June 2020). Profiles of sea-ice reflectivity over elevation angle (range: 1° to 45°) are derived with daily resolution considering reflection data recorded at left-handed (LH) and right-handed (RH) circular polarization. Respective predictions of reflectivity are based on reflection models of bulk sea ice or a sea-ice slab. The latter allows to include the effect of signal penetration down to the underlying water. Results of comparison between LH profiles and bulk model confirm a reflectivity decrease (about 10 dB) when surrounding open water areas is reduced (by freezing) and the ship drifts in compact sea ice.

Further results comprise estimates of sea-ice permittivity from mid-elevation range reflectivity (10° to 30°). The median of estimated permittivity 2.4 (period of compact sea ice) lies in the expected range of reported old ice type (mostly second-year ice). The retrieved reflectivity in the low-elevation range (1° to 10°) give strong indication of signal penetration into the dominating second-year ice with influence of sea ice temperature and thickness. We conclude that sea-ice characterization in future can profit form GNSS reflectometry observations. The on-going study is currently extended to the further evolution of Arctic sea ice during winter and spring period of the MOSAiC expedition.

How to cite: Semmling, M., Wickert, J., Kreß, F., Hoque, M., Divine, D., Gerland, S., and Spreen, G.: Arctic Sea-Ice Permittivity Derived from GNSS Reflectometry Data of the MOSAiC Expedition, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3030, https://doi.org/10.5194/egusphere-egu22-3030, 2022.

EGU22-3073 | Presentations | CR2.1 | Highlight

Drone-based GPR system for 4D glacier data acquisition 

Bastien Ruols, Ludovic Baron, and James Irving

Thanks to the excellent propagation characteristics of radar waves in ice, ground-penetrating radar (GPR) has been one of the key geophysical methods used in the field of glaciology over the last 50 years. Alpine glacier GPR surveys are typically performed either directly on the glacier surface (e.g., on foot, skis, or with snowmobiles), or by helicopter several tens of meters above the surface. Helicopter-based surveys allow the coverage of large areas safely and efficiently, but this comes at the expense of reduced resolution of glacier internal structures, particularly in the context of 3D surveys. On the other hand, ice-based acquisitions offer high-resolution opportunities, but are very time-consuming, often risky, and can be physically exhausting to perform. Recent advances in the development of drone technologies open new data acquisition possibilities for glacier GPR data, combining the advantages of both ice and air-based methods.

We have developed a drone-based GPR system that allows for safe and efficient high-resolution 3D and 4D data acquisition on alpine glaciers. Our custom-built GPR instrument uses real-time sampling to record traces of length 2800 ns, which corresponds to a depth of over 200 m in glacier ice. Each trace is stacked over 5000 times and acquired using a sampling frequency of 320 MHz, the latter of which is just enough to avoid aliasing with our single lightweight 70-MHz-center-frequency antenna. Traces are recorded at a rate of 14 Hz, meaning that a drone speed of at least 4 m/s can be considered while maintaining a sufficiently high trace density for high-resolution studies. This is at least four times faster than a conventional survey on foot. The total weight of our GPR system plus single transmit/receive antenna is around 2 kg. The drone used in our work has a maximum payload capacity of about 6 kg and is equipped with a radar-based ground sensor which enables us to follow the glacier surface topography during the flights. An independent differential GPS allows us to locate each recorded GPR trace with decimeter precision.

We performed initial testing of the above-described system in August 2021 on the Otemma glacier and successfully acquired around 70-line kilometers of 3D GPR data, over an 8-day period, covering a large portion of the glacier. In September 2021, we undertook additional fieldwork on the Tsanfleuron and Sex-Rouge glaciers and recorded 30-line kilometers of 3D GPR data in less than 3 days. We could then determine and model with high-precision the ice-thickness distribution over the Tsanfleuron pass. These first field results show the concrete benefit of drone-based GPR glacier surveys and motivate further development towards 3D and 4D studies.

How to cite: Ruols, B., Baron, L., and Irving, J.: Drone-based GPR system for 4D glacier data acquisition, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3073, https://doi.org/10.5194/egusphere-egu22-3073, 2022.

EGU22-3192 | Presentations | CR2.1

Strong Ocean Influence on Seasonal Changes in Shallow Shear-Modulus Structure in Alaska 

Toshiro Tanimoto and Jiong Wang

We have developed a method to determine shear-modulus (rigidity) structure for the upper 20-50m of the Earth. The method is based on the analysis of co-located pressure and seismic instruments. We applied this method to about 200 (co-located) stations in Alaska and examined seasonal variation in shallow shear-modulus structure at each site; in this report we quantify this seasonal change by taking the ratio (R) of the highest shear-modulus to the lowest throughout a year and use it as a characteristic feature for each station.

R is smaller than 2 at many stations but there are some stations in and near the Arctic zone that have R larger than 10. Such a large seasonal change implies that there occurs massive melting of shallow permafrost and a significant development of the active layer every summer. As a side product, because of such a huge reduction in near-surface shear-modulus, horizontal amplitudes in seismic noise become 30 times larger in summer than amplitudes in winter.

These seasonal changes may not be surprising because thawing of ice is common every summer in the permafrost region. But regions with large R show a systematic geographic pattern on a large-scale map; large-R stations are typically found near the coast (ocean) and tend to decrease toward the interior of the continent (Alaska and NW Canada). Large R stations are found in the NW Territories in Canada, the North Slope region northern side of the Brooks Range, near the Seaward Peninsula (west), and the Yukon-Kuskokwim Delta (west). These locations suggest a strong influence by the nearby ocean on the climate at each station. Proximity to the ocean (coast) seems to be an important factor in evaluating periglacial hazards.

There are a few exceptions in the northernmost coastal stations as they show small R despite the fact that they are at the coast. But the ICEsat-2 (satellite) data show that sea ice seems to remain thick near the peninsula (near Barrow, Alaska) much longer than other coastal areas in this study; temperature is colder because of thicker sea ice and the amount of melting at these exception sites remains low. This would strengthen the hypothesis that near-coastal ocean has strong influence on the climate of continental interior.

How to cite: Tanimoto, T. and Wang, J.: Strong Ocean Influence on Seasonal Changes in Shallow Shear-Modulus Structure in Alaska, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3192, https://doi.org/10.5194/egusphere-egu22-3192, 2022.

EGU22-3205 | Presentations | CR2.1 | Highlight

Estimation of snow SWE using passive RFID tags as radar reflectors 

Mathieu Le Breton, Éric Larose, Laurent Baillet, Alec van Herwijnen, and Yves Lejeune

Estimation of snow SWE using passive RFID tags as radar reflectors

Mathieu Le Breton(1,2), Éric Larose(1), Laurent Baillet(1), Alec van Herwijnen(3), Yves Lejeune(4)

(1) Univ. Grenoble Alpes, CNRS, ISTerre, Grenoble, France
(2)
Géolithe Innov, Géolithe, Crolles, France
(3)
WSL Institute for Snow and Avalanche Research SLF, Davos, Switzerland
(4)
CEN-CNRM, Météo-France, CNRS, Saint Martin d’Heres, France

 

Passive radio-frequency identification (RFID) tags are used massively to remotely identify industrial goods, and their capabilities offer new ways to monitor the earth’s surface already applied to coarse sediments, landslides, rock fissures and soils (Le Breton et al., 2910, 2020, 2021b). We introduce a method to estimate the variations in snow water equivalent (SWE) of a snowpack using an 865–868 MHz (RFID) system based on commercial off-the-shelf devices. The system consists of a vertical profile of low-cost passive tags installed before the first snowfall, on a structure that is minimally disruptive to the snowpack. The tags are interrogated continuously and remotely by a fixed reader located above the snow. The key measured value is the increase of phase delay, induced by the new layers of fresh snow which slow down the propagation of the waves. The method is tested both in a controlled laboratory environment, and outdoors on the Col de Porte observation site, in order to cross-check the results with a well-documented reference dataset (Lejeune et al., 2019). The experiments demonstrate that SWE can be estimated by this non-contact and non-destructive RFID technique. However, multipath interferences in the snowpack can generate errors up to 40 mm of SWE. This error is mitigated by using multiple tags and antennas placed at different locations, allowing the RFID measurements to remain within +/-10% of the cumulated precipitations (outdoor) and snow weighting (laboratory). In complement, the system can also estimate whether the snow is wet or dry, using temperature sensors embedded in the tags combined with the received signal strength. Using this approach with a mobile reader could allow the non-destructive monitoring of snow properties with a large number of low-cost, passive sensing tags.

 

Publications related to the project:

Le Breton, M., Baillet, L., Larose, E., Rey, E., Benech, P., Jongmans, D., Guyoton, F., Jaboyedoff, M., 2019. Passive radio-frequency identification ranging, a dense and weather-robust technique for landslide displacement monitoring. Eng. Geol. 250, 1–10. http://doi.org/10.1016/j.enggeo.2018.12.027

Le Breton, M., Grunbaum, N., Baillet, L., Larose, É., 2021a. Monitoring rock displacement threshold with 1-bit sensing passive RFID tag (No. EGU21-15305). Presented at the EGU21, Copernicus Meetings. http://doi.org/10.5194/egusphere-egu21-15305

Le Breton, M., Liébault, F., Baillet, L., Charléty, A., Larose, É., Tedjini, S., 2021b. Dense and long-term monitoring of Earth surface processes with passive RFID -- a review. Submitted. Preprint at: https://arxiv.org/abs/2112.11965v1

Lejeune, Y., Dumont, M., Panel, J.-M., Lafaysse, M., Lapalus, P., Le Gac, E., Lesaffre, B., Morin, S., 2019. 57 years (1960–2017) of snow and meteorological observations from a mid-altitude mountain site (Col de Porte, France, 1325 m of altitude). Earth Syst. Sci. Data 11, 71–88. http://doi.org/10.5194/essd-11-71-2019

How to cite: Le Breton, M., Larose, É., Baillet, L., van Herwijnen, A., and Lejeune, Y.: Estimation of snow SWE using passive RFID tags as radar reflectors, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3205, https://doi.org/10.5194/egusphere-egu22-3205, 2022.

EGU22-3248 | Presentations | CR2.1

Annual development of subalpine grassland observed with UAV: how NDVI evolution is controlled by snow melting 

Jesús Revuelto, Javier Sobrino, Daniel Gómez, Guillermo Rodriguez-López, Esteban Alonso-González, Francisco Rojas-Heredia, Eñaut Izagirre, Raquel Montorio-Lloveria, Fernando Pérez-Cabello, and Juan Ignacio López-Moreno

In the Pyrenees, as in other mid latitude mountain ranges, sub alpine areas have a long lasting snow cover that affect different mountain processes, including river discharge timing, soil erosion, primary production or animal and plant phenology. This work presents and analyzes a complete snow depth and Normalized Difference Vegetation Index (NDVI) spatial distribution dataset, generated by Unmanned Aerial Vehicles (UAV) over two years. This study aims to increase the knowledge and understanding of the relationship of the duration and timing of snowmelt and vegetation cover and its annual cycle.

The dataset was obtained in Izas Experimental Catchment, a 55 ha study area located in Central Spanish Pyrenees ranging between 2000 to 2300 m a.s.l., which is mostly covered by grasslands. A total of 18 UAV snow depth and 14 NDVI observations were obtained by a fixed wing UAV equipped with RGB and multispectral cameras during 2020 and 2021. The melt out date for the different areas of the catchment has been obtained from the snow depth distribution dataset, which in turn has been used to analyze the NDVI evolution. The NDVI values for each UAV flight have been correlated with the snow depth distribution observed in previous dates and with different topographic variables as elevation, solar radiation, curvature (through the Topographic Position Index) or slope.

The maximum seasonal NDVI happens throughout the study area simultaneously in the entire study area; however those zones with the latest snow disappearance do not reach NDVI values as high as those observed in areas with earlier snow disappearance. Oppositely areas with the soonest snow melting (in late February) have lower maximum NDVI values that those observed in areas with snow melting occurring later (around May).  NDVI correlations have shown that the snow depth distribution observed about one month prior to each NDVI acquisition has a very important control on pasture phenology. This correlation is particularly evident on the free-snow areas during first melting weeks, with a lower influence in those areas where snow melts at the end of the snow season. This field study exemplifies how intensive UAV acquisitions allow understanding snow processes over extended areas with an unprecedented spatial resolution.

How to cite: Revuelto, J., Sobrino, J., Gómez, D., Rodriguez-López, G., Alonso-González, E., Rojas-Heredia, F., Izagirre, E., Montorio-Lloveria, R., Pérez-Cabello, F., and López-Moreno, J. I.: Annual development of subalpine grassland observed with UAV: how NDVI evolution is controlled by snow melting, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3248, https://doi.org/10.5194/egusphere-egu22-3248, 2022.

EGU22-4179 | Presentations | CR2.1

Hansbreen’s calving-driven ice loss derived from seismic data supported by millimetre-wave radar scans and neural networks 

Wojciech Gajek, William Harcourt, and Dannielle Pearce

Calving of tidewater glaciers is a key driver of glacier mass loss as well as a significant contribution towards sea level rise. However, this dynamic process is still challenging to quantify. In addition, there are very few direct measurements of calving activity in Svalbard at daily to sub-daily resolution due to the requirement of continuous human labour at the calving front for field studies. Seismic instruments in the vicinity of glaciers offer the potential to circumvent this issue since they record ground motion signals, including those generated by calving events, with an unprecedented sub-second resolution. Such data sets are not affected by site conditions like poor visibility or darkness and, in the case of permanent regional seismological stations, already offer long-term datasets. Despite this, a knowledge gap remains which prevents making a direct link between precise calving volumes and seismic records. This study presents our effort made towards obtaining an estimate of volumetric ice loss from integrating seismic records with 3D millimetre-wave radar measurements of a tidewater glacier calving front. In the summer of 2021, an 8-day long time series of integrated measurements was acquired at the calving front of Hansbreen, South Spitsbergen. It included remote sensing observations from a millimetre-wave radar (AVTIS2), Terrestrial Laser Scanner and time-lapse cameras correlated with a seismic dataset from two local arrays deployed at direct vicinity of calving front and a closeby regional permanent seismological station in Hornsund. Integrating these datasets brings an opportunity to correlate visual observations of calving including volumetric ice loss derived from radar scans with seismic signatures registered at nearby seismic arrays. We explore various parameters that characterize observed calving events and develop a model linking chosen parameters with ice loss using machine learning techniques. Local arrays were installed for a limited time and the calibrated parameters are expected to change spatially. Therefore, we further transfer our approach and integrate decade long records from nearby permanent seismological station. Limiting data to a single station record reduces both the accuracy of estimated ice volume and spatial resolution. However, it enables us to apply detection algorithm trained using observed calvings to decade long records and, consequently, to revisit a decade long history of Hansbreen's calving.

How to cite: Gajek, W., Harcourt, W., and Pearce, D.: Hansbreen’s calving-driven ice loss derived from seismic data supported by millimetre-wave radar scans and neural networks, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4179, https://doi.org/10.5194/egusphere-egu22-4179, 2022.

EGU22-4573 | Presentations | CR2.1

Single-frequency GNSS-IR for estimating snowpack height with consumer grade receivers and antennas 

Giulia Graldi, Simone Rover, and Alfonso Vitti

Ground and space based GNSS-IR (Interferometric Reflectometry) has been used in the last 20 years for characterizing the Earth Surface, together with other remote sensing techniques. Among the physical quantities which can be monitored using these techniques, the characterization of the snow cover is of particular interest since it is an important source of freshwater. The increase of the global temperature due to anthropogenic climate changes is threatening the seasonal recharging, and for this reason monitoring the snow cover is crucial. Ground based GNSS-IR can be used for obtaining information on the height of the snowpack, with a precision of 0.04 m by using geodetic-grade GNSS instruments (such those involved in Continuously Operating Reference Stations - CORS). In the present study, the sensitivity of the retrieval of the snowpack height from data acquired with low cost non-geodetic grade instruments with the GNSS-IR technique is evaluated. The analysis is applied to a flat alpine area in the Lavarone plateau in the Province of Trento, Italy (1400 m above sea level), where GNSS field campaigns were carried out in 2018, 2019 for short time periods (90, 120 minutes) due to constraints of the study area. Single-frequency GPS observations were collected with u-blox M8T GNSS receivers and patch u-blox and Tallysman antennas. Leica antenna and receiver were also used for collecting GPS data in double frequency, in order to acquire reference data with geodetic grade instruments. Given the characteristics of the area, it is possible to consider that GPS signals reflect with specular reflection, and thus modelling the Signal to Noise Ratio (SNR) as a function of the distance between the reflecting snow surface above solid ground and the antenna. Multipath frequency associated with snowpack height is retrieved by applying the Lomb Scargle Periodogram on SNR data. The results show that, by applying GNSS-IR technique to data acquired with low-cost receivers and antennas, it is possible to retrieve the height of the snow pack with a standard deviation of about 0.05 m. This demonstrates the feasibility of GNSS-IR also with non-geodetic grade instruments.

How to cite: Graldi, G., Rover, S., and Vitti, A.: Single-frequency GNSS-IR for estimating snowpack height with consumer grade receivers and antennas, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4573, https://doi.org/10.5194/egusphere-egu22-4573, 2022.

Ice thickness is a key parameter for predictive ice sheet modeling, geological interpretation of the underlying bed rock, and site selection for deep ice sheet and bed rock sampling.  However, the uncertainties typically reported are in terms of crossover statistics, and ice thickness uncertainties are generally not formally integrated into ice sheet models.  Here we examine what crossover statistics reveal and conceal for the actual uncertainty in reported ice thickness, examine the impact of system and geometric parameters on uncertainties, and place these parameters in the context of the observed subglacial roughness.  We provide a predictive model for uncertainties as a function of ice thickness, sensor height, and subglacial roughness parameters, evaluate it from the perspective of ground based, airborne and orbital sounding and make recommendations for parameters that should be reported in ice thickness data products.

How to cite: Young, D., Kempf, S., and Ng, G.: Beyond crossovers: Predicting ice thickness uncertainties in ice penetrating radar data from geometric controls, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5506, https://doi.org/10.5194/egusphere-egu22-5506, 2022.

EGU22-5865 | Presentations | CR2.1

Diffraction imaging of alpine glacier GPR data 

Johanna Klahold, Benjamin Schwarz, Alexander Bauer, and James Irving

Over the past decades, ground-penetrating radar (GPR) has become a fundamental tool in glaciological studies thanks to its tremendous capacity to provide high-resolution images in snow and ice. 3D acquisitions in particular can give detailed information on the internal structure, properties, and dynamics of glaciers. For imaging and highlighting important englacial and subglacial features such as meltwater tunnels and voids, an analysis of the spatial distribution of diffractions in the data holds great potential. However, the diffracted wavefield typically has low amplitude and is often masked by more prominent arrivals. Diffraction separation and imaging procedures have already become topics of significant interest in the field of exploration seismology, and may potentially open new possibilities for the analysis of glacier GPR data.

Here, we explore the potential of recent advances in diffraction imaging for the analysis of alpine glacier GPR data. To this end, we consider a 3D data set acquired on the Haut Glacier d’Arolla (Valais, Switzerland) using a 70-MHz single-antenna real-time-sampling GPR system. The approach we use coherently approximates the dominant reflected wavefield and subtracts it from the data. The remaining diffracted wavefield is then enhanced using local coherent stacking. We find that this methodology is highly effective at isolating diffractions in glacier GPR data and provides clean images of the diffracting structures. Current work includes investigation of the correlation between these structures and the englacial and subglacial hydrological network.

How to cite: Klahold, J., Schwarz, B., Bauer, A., and Irving, J.: Diffraction imaging of alpine glacier GPR data, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5865, https://doi.org/10.5194/egusphere-egu22-5865, 2022.

The radar detection of bedrock interface and internal ice layers is a widely used technique for observing interiors and bottoms of ice sheets, which is also an important indicator of inferring the evolution of glaciers and explaining subglacial topographies. The conventional methods, such as the filtering denoise, are limited by the low contrast in ice radar image with noise and interferes and thus the automatic method in tracing and extracting layers' features is trapped. The manual and semiautomatic methods are widely applied but with large time-consuming especially for the large-scale radar image with continuous bedrock and internal layers. To extract and identify the bedrock interface and internal ice layers automatically, we propose EisNet, a fusion system consisting of three sub neural networks. Because of the limitations of conventional manual methods, it is relatively rare that the high-precision extraction of layer features, which can be applied as labels in training. To obtain sufficient radar images with high-quality training labels, we also propose a novel synthetic method to simulate the not only visual texture of the bedrock interface and internal layers but also the artifact noise and interference to match the feature in field data. EisNet is first verified on synthetic data and shows capacity on the extraction of multi types of layer targets. Second, the application on observational radar images reveals EisNet’s generalized performance from synthetic data to the CHINARE data. EisNet is also applied to extract bedrock interfaces from the radar film from the Antarctic. EisNet is now open open-accessing. We hope that EisNet could be applied in more ice radar images from other regions and different forms to promote glacial research.

How to cite: Dong, S., Tang, X., and Fu, L.: Using EisNet to Extract Bedrock and Internal layers from Digital and Analog Radiostratigraphy in Ice Sheets, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6377, https://doi.org/10.5194/egusphere-egu22-6377, 2022.

EGU22-6414 | Presentations | CR2.1

Ice layer detection, distribution, and thickness in the near-surface firn on Devon Ice Cap: a new dual-frequency radar characterization approach 

Kristian Chan, Cyril Grima, Anja Rutishauser, Duncan A. Young, Riley Culberg, and Donald D. Blankenship

Atmospheric warming has led to increased surface melting on glaciers in the Arctic. This meltwater can percolate into firn and refreeze to form ice layers. Depending on their thickness, low-permeability ice layers can act as barriers that inhibit subsequent vertical meltwater infiltration in deeper firn pore space and favor lateral meltwater runoff. Thus, characterizing ice layers in firn is key for understanding the near-surface hydrological conditions that could promote surface meltwater runoff and its contribution to sea level rise.

Airborne ice-penetrating radar (IPR) is a powerful tool for imaging subsurface structure, but only recently have these systems been applied to direct observations of the bulk properties of the near-surface. To evaluate the bulk permeability of the near-surface firn system of Devon Ice Cap (DIC), Canadian Arctic, we use the Radar Statistical Reconnaissance (RSR) technique, originally developed for accumulation studies in West Antarctica. This method utilizes both the coherent and incoherent components of the total surface return, which are predominately sensitive to near-surface permittivity/structure within the system’s vertical range resolution and surface roughness, respectively. Here, we apply RSR to IPR data collected over DIC with the High-Capability Airborne Radar Sounder 2 (HiCARS) system (60 MHz center-frequency, 15 MHz bandwidth), operated by the University of Texas Institute for Geophysics (UTIG). Guided by ground-based ice-penetrating radar data and firn core density measurements, we show that the near-surface heterogeneous firn structure, featuring ice layers, mainly affects the observed coherent component.

We further compare the coherent component of HiCARS with that derived from IPR data collected with the University of Kansas Multichannel Coherent Radar Depth Sounder (MCoRDS) 3 system (195 MHz center-frequency; 30 MHz bandwidth), to evaluate the utility of dual-frequency IPR for characterizing near-surface ice layers. We expect that each radar system is sensitive to a different scale of near-surface bulk properties (i.e., depth and thickness of ice layers of different vertical extents), governed by each radar systems’ center frequency and bandwidth-limited range resolution. We leverage these differences in range resolution to derive ice layer thickness constraints in the DIC firn zone containing meter-thick ice layers, which are consistent with ground-based observations. Our results suggest this dual-frequency approach does indeed show that ice layers are vertically resolvable, spatially extensive, and mostly impermeable to surface meltwater. Thus, we hypothesize that lateral flow over high elevation meter-thick ice layers may contribute to the total surface runoff routed through supraglacial rivers down-glacier in the ablation zone.

How to cite: Chan, K., Grima, C., Rutishauser, A., Young, D. A., Culberg, R., and Blankenship, D. D.: Ice layer detection, distribution, and thickness in the near-surface firn on Devon Ice Cap: a new dual-frequency radar characterization approach, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6414, https://doi.org/10.5194/egusphere-egu22-6414, 2022.

Electrical resistivity tomography (ERT) is a geophysical method that produces an estimate of subsurface resistivity distribution, which can be used to infer the presence and extent of frozen ground. Repeated ERT surveys indicate how subsurface temperature and ground ice conditions are changing over time, which is particularly important for evaluating the changes and risks associated with climate change. However, there is no existing framework for sharing ERT data and datasets are rarely published, making it difficult to find and use historical data to assess subsurface changes. To facilitate data sharing, we are developing a Canadian database for ERT surveys of permafrost.

A key component of this project is the development of an automated ERT data processing workflow to prepare datasets. Establishing best practices for data processing ensures that ERT results are optimized and standardized, which is essential so that changes in subsurface conditions can be reasonably interpreted. We also present our web-based data visualization tool that allows for targeted searching of surveys and plotting of selected results. By storing ERT data in a standardized and accessible way, our goal is to facilitate interpretations of permafrost change on a range of spatial and temporal scales and guide future research in permafrost science.

How to cite: Herring, T. and Lewkowicz, A.: Creating a database of electrical resistivity tomography surveys of permafrost in Canada and establishing best practices for data processing and sharing, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6575, https://doi.org/10.5194/egusphere-egu22-6575, 2022.

EGU22-7154 | Presentations | CR2.1

In-situ measurements of sediment temperature under shallow water bodies in Arctic environments 

Frederieke Miesner, William Cable, Julia Boike, and Pier Paul Overduin

The thermal regime under lakes, ponds, and shallow near shore zones in permafrost zones in the Arctic is predominantly determined by the temperature of the overlying water body throughout the year.   Where the temperatures of the water are warmer than the air, unfrozen zones within the permafrost, called taliks, can form below the water bodies.

However, the presence of bottom-fast ice can decrease the mean annual bed temperature in shallow water bodies and significantly slow down the thawing or even refreeze the lake or sea bed in winter. Small changes in water level have the potential to drastically alter the sub-bed thermal regime between permafrost-thawing and permafrost-forming. The temperature regime of lake sediments is a determining factor in the microbial activity that makes their taliks hot spots of methane gas emission. Measurements of the sediment temperature below shallow water bodies are scarce, and single temperature-chains in boreholes are not sufficient to map spatial variability.

We present a new device to measure in-situ temperature-depth profiles in saturated soils or sediments, adapting the functionality of classic Bullard-type heat flow probes to the special requirements of the Arctic. The measurement setup consists of 30 equally spaced (5cm) digital temperature sensors housed in a 1.5 m stainless steel lance. The lance is portable and can be pushed into the sediment by hand either from a wading position, a small boat or through a hole in the ice during the winter. Measurements are taken continuously and 15 minutes in the sediment are sufficient to acquire in-situ temperatures within the accuracy of the sensors (0.01K after calibration at 0°C). The spacing of the sensors yield a detailed temperature-depth-profile of the near-surface sediments, where small-scale changes in the bottom water changes dominate the temperature field of the sediment. The short time needed for a single measurement allows for fine-meshed surveys of the sediment in areas of interest, such as the transition zone from bottom-fast to free water.

 

Test campaigns in the Canadian Arctic and on Svalbard have proven  the device to be robust in a range of environments. We present data acquired during winter and summer, covering non-permafrost, thermokarst lake and offshore measurements.

How to cite: Miesner, F., Cable, W., Boike, J., and Overduin, P. P.: In-situ measurements of sediment temperature under shallow water bodies in Arctic environments, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7154, https://doi.org/10.5194/egusphere-egu22-7154, 2022.

EGU22-7409 | Presentations | CR2.1

S-wave velocity profile of an Antarctic ice stream firn layer with ambient seismic recording using Distributed Acoustic Sensing 

Wen Zhou, Antony Butcher, J. Michael Kendall, Sofia-Katerina Kufner, and Alex Brisbourne

Measurements of the seismic properties of Antarctic ice streams are critical for constraining glacier dynamics and future sea-level rise contributions. In 2020, passive seismic data were acquired at the Rutford Ice Stream, West Antarctica, with the aim of imaging the near-surface firn layer. A DAS (distributed acoustic sensing) interrogator and 1 km of optic fibre were supplemented by 3-component geophones. Taking advantage of transient seismic energy from a petrol generator and seismicity near the ice stream shear margin (10s of km away from the DAS array), which dominated the ambient seismic noise field,  we retrieve Rayleigh wave signals from 3 to 50 Hz. The extracted dispersion curve for a linear fibre array shows excellent agreement with an active seismic surface wave survey (Multichannel Analysis of Surface Waves) but with lower frequency content. We invert the dispersion curves for a 1D S-wave velocity profile through the firn layer, which shows good agreement with the previously acquired seismic refraction survey. Using a triangular-array geometry we repeat the procedure and find no evidence of seismic anisotropy at our study site. Our study presents challenges and solutions for processing noisy but densely sampled DAS data, for noise interferometry and imaging. 

How to cite: Zhou, W., Butcher, A., Kendall, J. M., Kufner, S.-K., and Brisbourne, A.: S-wave velocity profile of an Antarctic ice stream firn layer with ambient seismic recording using Distributed Acoustic Sensing, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7409, https://doi.org/10.5194/egusphere-egu22-7409, 2022.

EGU22-7447 | Presentations | CR2.1

Investigation of the induced polarization effect in transient electromagnetic soundings to characterize rock glaciers 

Lukas Aigner, Nathalie Roser, Clemens Moser, Theresa Maierhofer, Umberto Morra Di Cella, Christian Hauck, and Adrián Flores Orozco

Geophysical characterization of rock glaciers commonly relies on electrical resistivity tomography (ERT) and seismic refraction tomography (SRT). Yet, large blocks make the installation of geophones and electrodes time consuming, while bad contacts lead to reduced signal-to-noise ratios in both methods. Additionally, ERT and SRT campaigns require rather heavy equipment and need long profiles to reach large depths of investigation. Transient electromagnetic (TEM) measurements offer diverse advantages, as they do not require a galvanic contact with the ground, and can be conducted with light instruments for simplified field procedures. We propose the application of TEM measurements with a single-loop configuration for the collection of extensive data sets in alpine environments. We hypothesize that TEM measurements provide the same information as SRT and ERT, yet field procedures of the TEM method are much more efficient permitting to cover larger areas in reduced time. In particular, we present investigations conducted on the Gran Sometta rock glacier (above Cervinia, Aosta Valley, Italian Alps). The study area consists of a large active rock glacier complex composed of two main lobes with varying ice content. Our surveys aimed at: (i) estimating the depth to the bedrock below the rock glacier, (ii) identifying the degree of weathering in the underlying bedrock, and (iii) evaluating spatial variations of ice content of the rock glacier. We collected TEM data with a TEM-FAST 48 system using 4 A current and a 50 m by 50 m single loop configuration. The experimental setup fits in a single backpack and our 3-person team covered an area of approximately 75’000 m² in 2.5 days, despite the difficult terrain. We measured 28 soundings distributed over the entire site and repeated two sounding locations with a larger 75 m square loop. Complementary spectral induced polarization (SIP) data were measured using 64 electrodes with a separation of 2.5 m between electrodes along two perpendicular profiles to validate our TEM results. We used separated transmitter and receiver instruments as well as cables to reduce EM coupling effects in our SIP data. TEM data reveal sign reversals, which are caused by the induced polarization effect due to the ice content in the rock glacier. We model the TEM response with the open-source algorithm empymod assuming a layered media. We observe that including a layer with a frequency-dependent polarization results in the signal reversals, while the geometry of such a layer also influences the TEM response. Furthermore, we observe that resistivity variations in the layer below the polarizable one can also be detected by the TEM data. Hence, our results demonstrate the applicability of TEM measurements to determine the geometry of the ice-rich layer in an active rock glacier, possible variations in ice content at the study area as well as the electrical properties of the underlying bedrock.

How to cite: Aigner, L., Roser, N., Moser, C., Maierhofer, T., Morra Di Cella, U., Hauck, C., and Flores Orozco, A.: Investigation of the induced polarization effect in transient electromagnetic soundings to characterize rock glaciers, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7447, https://doi.org/10.5194/egusphere-egu22-7447, 2022.

EGU22-7552 | Presentations | CR2.1

Assessment of ESA CryoSat-2 radar altimetry data using GNSSdata at three sites on the Greenland Ice Sheet 

Karina Hansen, Kristine M. Larson, Michael J. Willis, William Colgan, Veit Helm, and Shfaqat Abbas Khan

Ten-year records of ice surface elevation changes derived from three GNSS stations placed on the interior of the Greenland ice sheet are used to assess the ability of CryoSat-2 radar altimetry to capture surface elevation changes during 2010-2021. We use GNSS interferometric reflectometry (GNSS-IR) to derive time series of continuous daily surface elevations. The footprint of GNSS-IR is about 1000 m2 and the accuracy is ±2cm, making it an excellent tool to validate ice surface height from satellite altimetry. We compare GNSS-IR derived ice surface elevations with CryoSat-2 derived surface elevations and find Cryosat-2 performs best at the GNSS site furthest north (GLS3) with a maximum difference of 12cm. The other GNSS sites have a higher residual range because of poorer data availability and local surface variations. The number of Cryosat-2 data points are roughly doubled from GLS1 and GLS2 to GLS3. GLS3 Is located in a very flat area of the ice sheet only moving 55m during 2011-2020. In contrast GLS1 moved 292m in the same period, clearly indicating a steeper slope to the ice sheet at this location, which we have difficulty correcting for because digital elevation models are associated with high uncertainty on the interior of the ice sheet. The strength of this assessment method lies in the continuous daily time series of surface elevation change derived from GNSS, as they clearly capture extreme short-term changes, which otherwise might have been perceived as errors in the radar altimetry measurements.

How to cite: Hansen, K., Larson, K. M., Willis, M. J., Colgan, W., Helm, V., and Khan, S. A.: Assessment of ESA CryoSat-2 radar altimetry data using GNSSdata at three sites on the Greenland Ice Sheet, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7552, https://doi.org/10.5194/egusphere-egu22-7552, 2022.

EGU22-7725 | Presentations | CR2.1

Illuminating the deeper radio-stratigraphy of an alpine glacier using SAR processing 

Falk Oraschewski, Inka Koch, Mohammadreza Ershadi, Jonathan Hawkins, and Reinhard Drews

The internal stratigraphy of alpine glaciers entails information about its past dynamics and accumulation rates. It further can be used for intercalibrating the age-depth scales of ice cores. The internal ice stratigraphy is often imaged using radar, but similar to polar ice sheets the deeper stratigraphy is often difficult to resolve with classical pulsed radar systems. For polar ice sheets, the introduction of phase coherent radars has illuminated this former echo-free zone (EFZ) and now patterns of folded, buckled and disrupted ice stratigraphy are clearly visible. Unfortunately, the new airborne and ground-based radar systems applied in polar regions are typically too heavy to be deployed in an alpine environment.

Here, we transfer the lightweight autonomous phase-sensitive radio-echo sounder (ApRES) to an alpine glacier targeting its echo-free zone (Colle Gnifetti, Italy/Switzerland). The ApRES is a coherent frequency modulated continuous wave radar with an integration time of 1 s per trace which we deployed in combination with a GNSS used in real time kinematic (RTK) mode. The latter allows repositioning of the antennas with sub-wavelength accuracy (approximately 5 cm) required to exploit the coherent signal. Like this, the radio-stratigraphy of the former EFZ at this site could be imaged using a matched filtering SAR method. The resulting radargrams cover former ice core sites (e.g., Ice Memory and KCC) and can be used to harmonize conflicting age-depth scales. This dataset will be analysed further in conjunction with ice-fabric measurements from ice cores to reveal how the anisotropic ice rheology imprints on the flow field of glaciers.

How to cite: Oraschewski, F., Koch, I., Ershadi, M., Hawkins, J., and Drews, R.: Illuminating the deeper radio-stratigraphy of an alpine glacier using SAR processing, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7725, https://doi.org/10.5194/egusphere-egu22-7725, 2022.

EGU22-8245 | Presentations | CR2.1

A passive seismic approach including fiber-optic sensing for permafrost monitoring on Mt. Zugspitze (Germany) 

Fabian Lindner, Krystyna Smolinski, Jonas Igel, Daniel Bowden, Andreas Fichtner, and Joachim Wassermann

As observed elsewhere on a global scale, permafrost at Mt. Zugspitze (German/Austrian Alps) is warming in response to climate change. To monitor permafrost warming and thawing, which affect the rock slope stability and thus the hazard potential, borehole temperature logging and electrical resistivity tomography (ERT) have been employed at Mt. Zugspitze for more than a decade. Furthermore, a recent study shows that the ambient seismic noise recordings of a single seismometer at the same site can be utilized to track permafrost changes over the past 15 years. This passive seismic approach is non-invasive, labour- and cost-effective and provides high temporal resolution. Together with recent advances in instrumentation allowing the measurement of seismic vibrations on a meter scale along a fiber-optic cable (known as distributed acoustic sensing), passive seismology provides unprecedented spatio-temporal resolution for monitoring applications.

 

Starting in July 2021, we extended the single-station deployment on Mt. Zugspitze with three small seismic arrays (six stations each, aperture ~25 m) along the permafrost-affected ridge. The stations are partly installed in a tunnel beneath the surface, which intersects a permafrost body, thus allowing in-situ observations of the frozen rock. We equipped the tunnel facilities with a fiber-optic cable, which we will interrogate on a regular basis, about once per quarter year, to resolve seasonal permafrost dynamics. A first 10-day data set of this monitoring element with seismic channel spacing of 2 m along a cable exceeding 1 km in length is already available and shows that artificial avalanche triggering explosions were successfully recorded. We present data and first results dedicated to permafrost monitoring along the fiber-optic cable and between pairs of seismic stations through cross-correlation of ambient seismic noise. In addition, the seismic arrays are designed to derive rotational ground motions, which we expect to be more sensitive to local subsurface/permafrost changes compared to the classical translational motion measurements. The experiment aims to explore the permafrost monitoring capabilities of passive seismology compared to more classical and established methods as ERT.

How to cite: Lindner, F., Smolinski, K., Igel, J., Bowden, D., Fichtner, A., and Wassermann, J.: A passive seismic approach including fiber-optic sensing for permafrost monitoring on Mt. Zugspitze (Germany), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8245, https://doi.org/10.5194/egusphere-egu22-8245, 2022.

EGU22-8555 | Presentations | CR2.1

Using different seismic approaches to detect submarine permafrost and gas hydrates on the continental Beaufort shelf of the Canadian Arctic 

Henrik Grob, Michael Riedel, Mathieu J. Duchesne, Sebastian Krastel, Jefferson Bustamante Restrepo, Gabriel Fabien-Ouellet, Dirk Kläschen, Jonas Preine, Young Keun Jin, and Jong Kuk Hong

In the Canadian Arctic, permafrost and permafrost-associated gas hydrates formed extensively during the last 1 Ma. After the last glaciation, a marine transgression followed and former terrestrially exposed shelf areas became submerged. Subaerial mean annual temperatures of -20°C or even less changed to present submarine bottom water temperatures near -1°C. The relict submarine permafrost and gas hydrates present in the Beaufort Sea still react to this ongoing thermal change which results in their continued degradation. Thawing permafrost and destabilisation of permafrost-associated gas hydrates may release previously trapped greenhouse gases and can lead to even further gas hydrate dissociation. Moreover, thawing permafrost poses a geohazard in form of landslides and ground collapses. Yet, both the extent of the submarine permafrost and the permafrost-associated gas hydrates are still not well known. Here, we present three different approaches using marine 2D multichannel seismic data to improve the current knowledge of the distribution of offshore permafrost and gas hydrates occurrences in the southern Canadian Beaufort Sea. The acoustic properties of permafrost are determined by the content of ice and unfrozen pore fluids. Changing permafrost conditions affect the elasticity of the medium making seismic methods appropriate for permafrost detection. First, we identify direct and indirect seismic reflection indicators from permafrost and gas hydrates by the presence of cross-cutting, polarity-reversed, and upward-bend reflections as well as velocity pull-ups and shallow pronounced high-amplitude reflections. Second, using diving-wave tomography provides insights into the near-surface permafrost structure by imaging the velocity structure in greater detail than achievable by standard velocity analyses.  And third, diffractions separated from the reflected wavefield yield insights into the sub-wavelength architecture of the permafrost realm on the southern Canadian Beaufort Shelf that may add information about weak phase-boundaries and small-scale heterogeneities. All methods are applied to seismic lines crossing the outer continental margin, where a maximum thermal effect of the transgression is expected, and thus a maximum lateral variation in permafrost and permafrost-associated gas hydrate phase boundaries is expected to be present. 

How to cite: Grob, H., Riedel, M., Duchesne, M. J., Krastel, S., Bustamante Restrepo, J., Fabien-Ouellet, G., Kläschen, D., Preine, J., Jin, Y. K., and Hong, J. K.: Using different seismic approaches to detect submarine permafrost and gas hydrates on the continental Beaufort shelf of the Canadian Arctic, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8555, https://doi.org/10.5194/egusphere-egu22-8555, 2022.

EGU22-8588 | Presentations | CR2.1

3D Spectral Induced Polarization survey to evaluate a thawing permafrost endangered hut in the Italian Alps 

Clemens Moser, Theresa Maierhofer, Elisabetta Drigo, Umberto Morra Di Cella, Christian Hauck, and Adrian Flores Orozco

Due to generally rising air temperatures in the European Alps in context of climate change, large areas of mountain permafrost are thawing, and subsurface pore ice is melting. Consequently, the cohesion of rock masses decreases which can constitute a threat for infrastructure like mountain huts in alpine areas. One directly affected building is the Guide Val d'Ayas al Lambronecca, a hut on a rock ledge in the Italian Alps at 3400 m above sea level. During the last decade the ground directly underneath the hut sank of about 2 m, probably due to the melting of pore ice in the subsurface below the hut. In this study, we investigate the subsurface properties beneath the hut using a 3D geophysical survey. In particular, we deploy the spectral induced polarization (SIP) method, which has emerged as a promising tool to discriminate between ice-rich and ice-poor regions in the subsurface. Our investigation is built on the hypothesis that ice can be identified in electrical images due to its high electrical resistivity and polarization (i.e., capacitive) properties at frequencies above 10 Hz. In our survey, we conducted 2D SIP measurements in summer 2020 (between 0.5 and 225 Hz) along three profiles near the hut, while real 3D SIP measurements (in the range between 1 and 240 Hz) were conducted in summer 2021. For the 3D measurements, we deployed two parallel lines, one on the southern and one on the northern rock wall of the summit where the hut is located. To improve the data quality, we used coaxial cables for the 2D measurements in 2020, while data collected in 2021 were based on the actual separation of the transmitter and receiver (i.e., instrument and cables) to reduce the contamination of the data due to parasitic electromagnetic fields. Processing of the data was based on the statistical analysis of normal and reciprocal misfits. Inversion of the data was performed in 3D using ResIPy which uses complex calculus to simultaneously resolve for the conductive and capacitive properties. Our imaging results evidence a core of ice-filled pores corresponding to high resistivity values (>10 kΩm) directly underneath the hut, this structure is overlain by lower values (<1 kΩm) in near-surface areas representing the active layer. Images of the polarization effect confirm an anomaly due to high values at frequencies above 10 Hz in the center of the rock ledge. Our study demonstrates that 3D SIP measurements can be used to differentiate between ice-rich and ice-poor areas in high mountain permafrost sites with complex topography. Moreover, 3D SIP approaches enable a detection of electrical anomalies in all three dimensions and not only along one certain direction in the case of 2D profiles. This information can be used to assess the impact of permafrost degradation on infrastructure stability in mountain regions and to support restoration actions.

How to cite: Moser, C., Maierhofer, T., Drigo, E., Morra Di Cella, U., Hauck, C., and Flores Orozco, A.: 3D Spectral Induced Polarization survey to evaluate a thawing permafrost endangered hut in the Italian Alps, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8588, https://doi.org/10.5194/egusphere-egu22-8588, 2022.

EGU22-10159 | Presentations | CR2.1

Year-round high-resolution geoelectrical monitoring to improve the understanding of deglaciated soil evolution in the High Arctic 

Mihai O. Cimpoiasu, Harry Harrison, Philip Meldrum, Paul Wilkinson, Jonathan Chambers, James Bradley, Pacifica Sommers, Steven K. Schmidt, Trevor Irons, Dane Liljestrand, Carlos Oroza, and Oliver Kuras

High Arctic regions are experiencing an accelerated rise in temperatures, about three times more than the global average. As a result, the glacier coverage over these landscapes is reducing, uncovering soils which start their development by sustaining emergent microbial communities. These new systems will have a significant impact on the global carbon budget, thus monitoring and understanding their evolution becomes a necessity.

Geoelectrical methods have emerged as a fast, cost-effective and minimally invasive way of imaging soil moisture dynamics in the shallow subsurface. BGS PRIME technology is designed to facilitate low-power remote geoelectrical tomography by using an array of sensor electrodes. We are using such technology to monitor the year-round variability of soil electrical resistivity in 4D on a glacier forefield in the vicinity of Ny-Alesund, Svalbard. Until now, such assessment of soil properties was confined to the summer period due to harsh Arctic winter conditions making site access very difficult.

Two PRIME systems were deployed during the summer of 2021 on Midtre Lovénbreen glacier forefield, which exhibits a soil chronosequence extending from the youngest soils near the glacier snout up to soils of approximately 120 years old. The two geophysical systems are monitoring electrical resistivity within the top 2m of soil of approximately 5 and 60 years of age respectively, recording soil moisture and freeze-thaw dynamics within the active layer above the permafrost.

We present early results, a timeseries of 3D soil electrical resistivity models, that captured several precipitation events during the summer and the progression of the freezing front when soil temperatures dropped below 0 °C in October 2021. These results reveal differences in the hydrodynamic activity between the 5- and 60-year-old sites determined by soil properties and their location on the glacier forefield. In addition, soil cores were sampled from the vicinity of the PRIME systems. These were subsequently subjected to laboratory tests to describe the changes in electrical resistivity as a function of moisture content and during successive freeze-thaw cycles. Furthermore, we are working towards an integrated analysis and a more comprehensive model of soil evolution at our sites by combining geoelectrical measurements with point measurements of environmental parameters and microbiological activity.

How to cite: Cimpoiasu, M. O., Harrison, H., Meldrum, P., Wilkinson, P., Chambers, J., Bradley, J., Sommers, P., Schmidt, S. K., Irons, T., Liljestrand, D., Oroza, C., and Kuras, O.: Year-round high-resolution geoelectrical monitoring to improve the understanding of deglaciated soil evolution in the High Arctic, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10159, https://doi.org/10.5194/egusphere-egu22-10159, 2022.

EGU22-10195 | Presentations | CR2.1

Investigation of ice with geophysical measurements during the transit of cryobots 

Marc S. Boxberg, Anna Simson, Qian Chen, and Julia Kowalski

Several icy moons of our Solar System like Jupiter’s moon Europa have a global ocean of liquid water below their icy crust. These ocean worlds are possible targets for space missions that aim to assess their potential for habitability or even to search for life. Cryobots (or ice melting probes) are suitable tools to reach the subglacial oceans for in-situ investigations. The necessary ice shell transit provides an excellent opportunity to investigate structure and composition of the ice itself by means of geophysical and other in-situ measurements. This will allow us to better understand the evolution of icy moons and their role in our solar system.

We present current ideas as well as first results from terrestrial analogue studies. Acoustic data obtained during a field test on Langenferner Glacier, Italy was used to conduct a travel time tomography, which yields insight into heterogeneities in the local acoustic wave propagation speed through the ice. The acoustic sensor set-up was originally designed for localization of the melting probe rather than an investigation of the ice structure. However, we can still show that such opportunity data can be used to obtain a wave velocity distribution which can be further interpreted with respect to ice properties like porosity.

While we already investigated the acoustic data, we evaluate the potential of other measurements. For example, Radar measurements in combination with the acoustics can be used to identify the ice-water boundary and, in addition, cracks and inclusions in the ice. Conductivity measurements provide information on the salinity. At ice-water interface regions, the salinity is in thermochemical equilibrium with the temperature and porosity of the ice. We present our concept for on-board electrical conductivity measurements and analyze its potential, for example, to constrain ice properties and to predict ice-water interfaces based on existing terrestrial field data and process models. Furthermore, some of the cryobot’s housekeeping data might be of interest for investigating the ambiance, too. For example, the temperature and the density of the ice affect the melting velocity of the cryobot, which constitutes an inverse problem to get further information on the ice.

How to cite: Boxberg, M. S., Simson, A., Chen, Q., and Kowalski, J.: Investigation of ice with geophysical measurements during the transit of cryobots, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10195, https://doi.org/10.5194/egusphere-egu22-10195, 2022.

EGU22-10565 | Presentations | CR2.1

Initiation of an international database of geoelectrical surveys on permafrost to promote data sharing, survey repetition and standardized data reprocessing 

Coline Mollaret, Christin Hilbich, Teddi Herring, Mohammad Farzamian, Johannes Buckel, Baptiste Dafflon, Daniel Draebing, Hannelore Fossaert, Rebecca Gugerli, Christian Hauck, Julius Kunz, Antoni Lewkowicz, Jonas K. Limbrock, Theresa Maierhofer, Florence Magnin, Cécile Pellet, Sebastian Pfaehler, Riccardo Scandroglio, and Sebastian Uhlemann and the IDGSP IPA Action Group

Geoelectrical methods are widely used for permafrost investigations by research groups, government agencies and industry. Electrical Resistivity Tomography (ERT) surveys are typically performed only once to detect the presence or absence of permafrost. Exchange of data and expertise among users is limited and usually occurs bilaterally. Neither complete information about the existence of geophysical surveys on permafrost nor the data itself is available on a global scale. Given the potential gain for identifying permafrost evidence and their spatio-temporal changes, there is a strong need for coordinated efforts regarding data, metadata, guidelines, and expertise exchange. Repetition of ERT surveys is rare, even though it could provide a quantitative spatio-temporal measure of permafrost evolution, helping to quantify the effects of climate change at local (where the ERT survey takes place) and global scales (due to the inventory).

Our International Permafrost Association (IPA) action group (2021-2023) has the main objective of bringing together the international community interested in geoelectrical measurements on permafrost and laying the foundations for an operational International Database of Geoelectrical Surveys on Permafrost (IDGSP). Our contribution presents a new international database of electrical resistivity datasets on permafrost. The core members of our action group represent more than 10 research groups, who have already contributed their own metadata (currently > 200 profiles covering 15 countries). These metadata will be fully publicly accessible in the near future whereas access to the resistivity data may be either public or restricted. Thanks to this open-access policy, we aim at increasing the level of transparency, encouraging further data providers and fostering survey repetitions by new users.

The database is set up on a virtual machine hosted by the University of Fribourg. The advanced open-source relational database system PostgreSQL is used to program the database. Homogenization and standardization of a large number of data and metadata are among the greatest challenges, yet are essential to a structured relational database. In this contribution, we present the structure of the database, statistics of the metadata uploaded, as well as first results of repetitions from legacy geoelectrical measurements on permafrost. Guidelines and strategies are developed to handle repetition challenges such as changing survey configuration, changing geometry or inaccurate/missing metadata. First steps toward transparent and reproducible automated filtering and inversion of a great number of datasets will also be presented. By archiving geoelectrical data on permafrost, the ambition of this project is the reanalysis of the full database and its climatic interpretation.

How to cite: Mollaret, C., Hilbich, C., Herring, T., Farzamian, M., Buckel, J., Dafflon, B., Draebing, D., Fossaert, H., Gugerli, R., Hauck, C., Kunz, J., Lewkowicz, A., Limbrock, J. K., Maierhofer, T., Magnin, F., Pellet, C., Pfaehler, S., Scandroglio, R., and Uhlemann, S. and the IDGSP IPA Action Group: Initiation of an international database of geoelectrical surveys on permafrost to promote data sharing, survey repetition and standardized data reprocessing, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10565, https://doi.org/10.5194/egusphere-egu22-10565, 2022.

EGU22-10835 | Presentations | CR2.1

Combined measurement of snow depth and sea ice thickness by helicopter EM bird in McMurdo Sound, Antarctica 

Wolfgang Rack, Adrian Tan, Christian Haas, Usama Farooq, Aston Taylor, Adriel Kind, Kelvin Barnsdale, and Greg Leonard

Snow on sea ice is a controlling factor for ocean-atmosphere heat flux and thus ice thickness growth, and surface albedo. Active and passive microwave remote sensing is the most promising way to estimate snow depths over large sea ice areas although improved validation is understood as a missing information to support further progress. However, severe limitations in the representative measurement of snow depth over sea ice persist, which exacerbates sea ice mass balance assessments as well as the indirect estimation of consolidated ice thickness from remotely sensed freeboard.

We have designed and flown a snow radar in combination with an electromagnetic induction device for sea ice thickness. The goal was the simultaneous measurement of both the consolidated sea ice thickness and the snow depth on top as a tool to derive snow and ice statistics for satellite validation. The snow radar was integrated into an EM-bird and flown about 15 m above the surface by suspending the instrument from a helicopter. The combination of the applied technologies hasn’t been deployed in this configuration before. The helicopter flight speed was around 70 knots, resulting in a snow measurement about every four meters. The EM instrument can detect ice thickness at 0.1m accuracy, whereas the snow radar is designed to measure snow depth at 0.05m accuracy.

Our field area was the land-fast sea ice and adjacent ice shelf in McMurdo Sound (Antarctica) in November 2021. During this time we found a relatively shallow but variable snow cover (up to about 0.3m) above sea ice of about 2m thickness. Deeper snow was only measured at the transition from the sea ice to the ice shelf, and on the ice shelf itself, where the maximum radar penetration in snow in ideal conditions is estimated to be around 2-3 meters.

We present first results of snow cover statistics in comparison to ground validation and observed snow characteristics, and we compare these results to airphotos and optical satellite imagery. We show that the measurement set-up meets the requirements for level ice and rough fast ice with patchy but dry snow cover. The system still needs to be tested over pack ice with potentially more complex snow morphology.

How to cite: Rack, W., Tan, A., Haas, C., Farooq, U., Taylor, A., Kind, A., Barnsdale, K., and Leonard, G.: Combined measurement of snow depth and sea ice thickness by helicopter EM bird in McMurdo Sound, Antarctica, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10835, https://doi.org/10.5194/egusphere-egu22-10835, 2022.

Ground surface movements and snow cover during freeze/thaw cycles of permafrost are important variables for studying climate change. GPS-IR has emerged as an effective technique to estimate the relative elevation changes of ground surface such as the thaw subsidence of frozen ground and snow depth variations. In permafrost areas, the freezing process of the ground is always accompanied by the snow accumulations, making it hard for GPS-IR to separate these two distinct signals from the estimated elevation changes. In this study, using the Signal to Noise Ratio (SNR) collected by a permafrost GPS site SG27 (Northern Alaska) in 2018, we proposed a physical model-based method to simultaneously estimate the daily snow depths and freezing-ground uplifts with GPS-IR. First, we applied GPS-IR to the SNR data to obtain the daily elevation changes of the ground surface from September 1 in 2018 to August 31 in 2019. The elevation change measurements indicate the onset of snow season on October 18 in 2018 and the end of snow-cover on June 15 in 2019. Second, we used the thermal index Accumulated Degree Days of Freezing (ADDF) calculated from the temperature records to determine the onset of the permafrost freezing season as of September 17 in 2018. Third, we fitted the Stefan function to the estimated elevation changes (i.e. freezing-ground uplifts) from September 17 to October 18 in 2018. The Stefan model agrees with the freezing uplifts with an R2 of 0.65. Forth, we extended the fitted model to the time when the ground was completely frozen (November 1) to estimate daily freezing-ground uplifts up to 1.75 cm under the snowpack. Last, we extracted the snow depths from the estimated elevation changes by subtracting the corresponding freezing-ground uplifts. Our study is the first attempt to simultaneously estimate the daily freezing-ground uplifts and snow depths over the permafrost area with GPS-IR, providing the measurements to understand the coupling effects of the permafrost and snow cover.

How to cite: Hu, Y. and Wang, J.: Simultaneous estimation of snow depth and freezing-ground uplift by GPS Interferometric Reflectometry over a permafrost area, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10858, https://doi.org/10.5194/egusphere-egu22-10858, 2022.

EGU22-12006 | Presentations | CR2.1

Characterising ice sheet properties using Rayleigh wave ellipticity 

Glenn Jones, Ana Ferreira, Bernd Kulessa, Martin Schimmel, Andrea Berbellini, and Andrea Morelli

The physical properties of the ice column are fundamental to the deformation and flow of glaciers and ice sheets. With a warming climate, surface meltwater is ever increasingly being routed and distributed throughout the ice column changing the mechanical and hence thermal properties of the ice and leading to accelerated ice flow and ice mass loss. Since the early 1990s, ice mass loss from the Greenland Ice Sheet (GrIS) has contributed ~10% of the mean global sea level rise. Seismic waves have routinely been used to study the physical characteristics of glaciers and ice sheets due to their sensitivity to both mechanical and thermal properties of ice. Traditionally, reflection seismic surveys have been chosen as the primary seismic approach but this survey method can suffer from difficult logistics in polar regions. Recent advancements in ambient noise methods and the permanent installation of a seismic network in Greenland now permit the long term study of the ice properties of the GrIS.

Rayleigh wave ellipticity measurements (the horizontal-to-vertical ratio of Rayleigh wave particle motions) are particularly sensitive to the subsurface structure beneath a seismic station. Using the polarisation properties of seismic noise, we extract Rayleigh wave ellipticity measurements from the Earth’s ambient noise for on-ice stations deployed in Greenland from 2012-- 2018. For wave periods sensitive to the ice sheet (T ≤ 3.5 s), we observe significant deviation between ellipticity measurements extracted from noise and synthetic fundamental mode calculations using a single ice column. Using a forward modelling approach we show: (1) a slow seismic shear-wave velocity at the near surface, (2) seismic attenuation, quantified as the quality factor Q, is sensitive to the temperature, water content and density of the ice and (3) the excitation of Rayleigh wave overtones plays a leading role in perturbing the ellipticity. Our results highlight how the inclusion of Q and overtone information can fill important gaps in our knowledge of ice sheet temperature, density and water content, which are important for predictions of the future evolution of the GrIS.

How to cite: Jones, G., Ferreira, A., Kulessa, B., Schimmel, M., Berbellini, A., and Morelli, A.: Characterising ice sheet properties using Rayleigh wave ellipticity, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12006, https://doi.org/10.5194/egusphere-egu22-12006, 2022.

EGU22-12082 | Presentations | CR2.1

Snow measurement campaign for snowpack model and satellite retrieval validation in Italian Central Apennines within SMIVIA project 

Edoardo Raparelli, Paolo Tuccella, Annalina Lombardi, Gianluca Palermo, Nancy Alvan Romero, Mario Papa, Errico Picciotti, Saverio Di Fabio, Elena Pettinelli, Elisabetta Mattei, Sebastian Lauro, Barbara Cosciotti, Chiara Petroselli, David Cappelletti, Massimo Pecci, and Frank SIlvio Marzano

The Apennine mountain range is the backbone of the Italian peninsula, crossing it from North-West to South-East for approximately 1200 km. The main peaks are found in Central Apennines, especially in the Gran Sasso d’Italia massif, which hosts the highest Apennines peak, named Corno Grande, with its 2912 m a.s.l. During the winter season, Central Apennines are typically covered with snow, with thickness that can vary between a few centimeters to several meters. Despite the historical presence of snow in these territories, the Apennine snowpack is poorly studied and weather data coming from automatic measurement stations and manual snow measurements hardly coexist. Thus, within the SMIVIA (Snow-mantle Modeling, Inversion and Validation using multi-frequency multi-mission InSAR in Central Apennines) project, we identified the measurement sites of Pietrattina, at 1459 m a.s.l, and Campo Felice, at 1545 m a.s.l., both located in Central Apennines. There we collected automatic measurements using ad hoc installed automatic weather-snow stations (AWSS) and where we performed systematic manual measurements of the snowpack properties, from November 2020 till April 2021. The AWSS measures every 5 minutes air temperature, relative humidity, wind speed, wind direction, incoming short-wave radiation, reflected short-wave radiation, soil surface temperature, snow surface temperature and snow height. The manual part of the campaign included the digging of 10 and 8 snow pits at Pietrattina and Campo Felice sites, respectively, to measure vertical profiles of snow density, temperature, grain shape, grain size and fractional content of light absorbing impurities. Manual snow measurements provide important information on the state of the snowpack, and give the opportunity to reconstruct the history of the snowpack. Their proximity to automatic weather stations let us evaluate the impact of the very local atmospheric conditions on the snowpack evolution. These measurements were performed within the SMIVIA project to: i) evaluate the ability of the snow cover model SNOWPACK to reproduce the observed snow cover properties; ii) verify the possibility to infer snow height and snow water equivalent from the data retrieved with Earth observation satellites; iii) investigate whether the use of a combination of snow numerical models and remote sensing data may provide better results compared to using each of the aforementioned approach, separately. Nevertheless, the data collected during the SMIVIA campaign at the measurement sites of Pietrattina and Campo Felice during season 2020-2021 can also provide precious information for other fields of study, like hydrology, biology and chemistry.

How to cite: Raparelli, E., Tuccella, P., Lombardi, A., Palermo, G., Alvan Romero, N., Papa, M., Picciotti, E., Di Fabio, S., Pettinelli, E., Mattei, E., Lauro, S., Cosciotti, B., Petroselli, C., Cappelletti, D., Pecci, M., and Marzano, F. S.: Snow measurement campaign for snowpack model and satellite retrieval validation in Italian Central Apennines within SMIVIA project, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12082, https://doi.org/10.5194/egusphere-egu22-12082, 2022.

EGU22-12233 | Presentations | CR2.1 | Highlight

Monitoring lake ice with seismic and acoustic sensors 

Cedric Schmelzbach, Daniel May, Christoph Wetter, Simon Stähler, and John Clinton

Seismic monitoring of the thickness and elastic parameters of floating ice on lakes and the sea is of interest in understanding the climate change impact on Alpine and Arctic environments, assessing ice safety for recreational and engineering purposes, studying ice shelves as well as exploring possibilities for the future exploration of the icy crusts of ocean worlds in our solar system. Seismic data can provide an alternative to remote-sensing and ground-based radar measurements for estimation of ice thickness in cases where radar techniques fail. Because of the difficult access to Alpine and Arctic environments as well as seismic sensor coupling issues in ice environments, it is of interest to optimize the use of seismic instruments in terms of sensor type, sensor numbers and layouts.

With the motivation to monitor over time the seismic activity of the lake ice and the ice properties, we conducted a series of seismic experiments on frozen lake St. Moritz in the Swiss Alps during two consecutive winters. Arrangements of sensors ranging in numbers from 96 geophones in mini-arrays to installations of 8, 2 and 1 conventional seismic sensors were used to measure the seismic wavefield generated by ice quakes (cryoseisms), artificial sources like hammer strokes, and ambient vibrations. These data provide an impressive and rich insights into the growth of the ice and variations of seismic activity with time. Even recordings with only a single station enable the determination of ice parameters and location of ice seismicity. Furthermore, we are exploring the value of recording air-coupled waves with microphones as alternative contact-free measurements related to seismic wave propagation in the ice, possibly even with sensors placed on the lake shore.

How to cite: Schmelzbach, C., May, D., Wetter, C., Stähler, S., and Clinton, J.: Monitoring lake ice with seismic and acoustic sensors, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12233, https://doi.org/10.5194/egusphere-egu22-12233, 2022.

EGU22-12490 | Presentations | CR2.1

Exploring the potential of cosmic muon scattering to measure the snow water equivalent 

Aitor Orio, Esteban Alonso, Pablo Martínez, Carlos Díez, and Pablo Gómez

The seasonal snowpack influences the hydrology, ecology and economy of the areas where it is present. However, the real time monitoring of the seasonal snowpack is a still well known scientific challenge. In this study, we have explored the potential of muon scattering radiography (MSR) to infer the snow water equivalent (SWE) of the snowpack. We have used the energy and mass balance model Snowpack to realistically simulate the time evolution and microstructure of the snowpack. The ERA5-Land reanalysis was used as forcing of Snowpack, in a location close to the Monte Perdido massif (Central, Pyrenees) at an elevation of 2041m above sea level. The simulations cover the hydrologic year 2015/2016, approximately reaching up to 700mm of peak SWE. Then, we have coupled the Snowpack numerical simulations with the Geant4 model to simulate the propagation of the muons through the snow layers and to collect the deviation of the muon trajectories. We have measured these deviations with a virtual muon detector based in multiwire proportional chambers, replicating a real detection system designed by us. The obtained distributions of muon deviations have exhibited a strong correlation with the simulated SWE, showing a coefficient of determination of 0.99. This model presents a root-mean-square error (RMSE) of 23.9mm in the SWE estimation. In order to validate the simulation analysis results, we have replicated the numerical experiments under controlled conditions, measuring three artificial snow samples ranging from 0 to 200 mm of SWE in our laboratory. We have measured the samples with an experimental setup composed of the real muon detector whose hardware was virtually replicated for the numerical experiments. Then, we have applied the model derived from the numerical simulations to the muon deviations measured in our laboratory. We have calibrated the real measurements and we have obtained a RMSE of 38.4mm in the SWE estimation. These results show that MSR is a promising non-destructive technique that can be used for the deployment of accurate SWE monitoring networks and can eventually provide information from the internal layered structure of the snowpack.

How to cite: Orio, A., Alonso, E., Martínez, P., Díez, C., and Gómez, P.: Exploring the potential of cosmic muon scattering to measure the snow water equivalent, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12490, https://doi.org/10.5194/egusphere-egu22-12490, 2022.

EGU22-143 | Presentations | CR2.2

Millimetre-wave radar observations of glacier calving at Hansbreen (Svalbard) correlated with TLS, time-lapse camera images and seismic records 

William D. Harcourt, Duncan A. Robertson, David G. Macfarlane, Brice R. Rea, Matteo Spagnolo, Doug I. Benn, Michael R. James, Wojciech Gajek, Danielle Pearce, and Penelope How

The release of icebergs into the ocean through glacier calving is a major source of mass loss from tidewater glaciers across the Arctic. However, there are very few direct measurements of calving activity in Svalbard at daily to sub-daily resolution which impedes our understanding of how these processes influence ice discharge and therefore regional patterns of mass balance. Quantifying ice loss from Svalbard is important because the archipelago contains ~10% of the total Arctic glacier area and holds a sea-level equivalent of ~1.5 cm. In this contribution, we generate an 8-day time series from August 2021 of calving activity at sub-daily resolution for the Hansbreen tidewater glacier in Svalbard using a suite of state-of-the-art remote sensing instruments. Millimetre-wave radar at 94 GHz (called AVTIS2) was used to map the 3D structure of the Hansbreen frontal ice cliff, so that terminus change could be tracked and the volume of ice released through calving quantified. Millimetre-wave radar can map glacier surfaces at high angular resolution and through most weather conditions, hence is not impeded by poor weather conditions unlike instruments such as Terrestrial Laser Scanners (TLS). AVTIS2 mechanically scans across the scene of interest, measures radar backscatter along each Line of Sight (LoS) and generates 3D point clouds by calculating the range to maximum received power along each LoS. In this study, an angular area of 83° (azimuth) x 5° (elevation) was scanned which ensured the entire marine-terminating portions of the ice front were measured throughout the study period. The 3D AVTIS2 point clouds were validated using a coincident survey from a TLS (Riegl LPM-321) and a time-lapse camera deployed at the same location to provide additional validation and knowledge of environmental conditions throughout the study period. Calving events from both datasets were correlated to seismic activity recorded by two networks of geophones deployed in the vicinity of the glacier terminus. We will report on the following: (1) the calving rate of Hansbreen in August 2021, (2) the volume of ice released into the ocean through calving during the 8-day study period, (3) the capabilities of millimetre-wave radar for monitoring glacier calving fronts versus optical approaches (TLS and time-lapse camera images), and (4) calving processes at Hansbreen. This study pushes forward our understanding of frontal ablation processes in Svalbard and demonstrates new possibilities for ground-based remote sensing of ice-ocean interactions.

How to cite: Harcourt, W. D., Robertson, D. A., Macfarlane, D. G., Rea, B. R., Spagnolo, M., Benn, D. I., James, M. R., Gajek, W., Pearce, D., and How, P.: Millimetre-wave radar observations of glacier calving at Hansbreen (Svalbard) correlated with TLS, time-lapse camera images and seismic records, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-143, https://doi.org/10.5194/egusphere-egu22-143, 2022.

EGU22-243 | Presentations | CR2.2

Testing drones and computer vision for acquiring glacier melt observations 

Aaron Cremona, Johannes Landmann, Leo Sold, Joël Borner, and Daniel Farinotti

Climate change is affecting glaciers worldwide, leading to unprecedented melt rates. In this context, establishing systems that provide near-real-time glacier information can be of high interest. However, the effort for acquiring real-time, in situ glacier observations is large.

In a previous study, we investigated the potential for automated acquisition of real-time mass balance readings by using optical cameras installed in-situ and computer vision techniques. The setup proved to be useful for obtaining melt rates with a temporal resolution of 20 minutes. However, it is not feasible to cover an extensive portion of a glacier with such a setup.

In our contribution, we present a method to acquire glacier mass balance readings with a custom drone equipped with a camera. The principle is to acquire images of a color-coded stake, from which surface mass balance can be determined via the glaciological method. To autonomously approach and read the stake, we exploit a combination of computer vision techniques and geometrical triangulation.  The results of off-glacier test flights, as well as four flights on Rhonegletscher, Switzerland, prove that the system is successful in detecting the stake in the videos captured by the drone. The determined stake position has uncertainties of 2.4 - 4.6 m, thus being sufficient to safely approach the stake. We investigate the main factors influencing the performance of the method in more detail, and discuss potential future developments of the system.

How to cite: Cremona, A., Landmann, J., Sold, L., Borner, J., and Farinotti, D.: Testing drones and computer vision for acquiring glacier melt observations, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-243, https://doi.org/10.5194/egusphere-egu22-243, 2022.

EGU22-1480 | Presentations | CR2.2

Momentum- & heat- flux parameterization over the Greenland Ice Sheet 

Maurice van Tiggelen, Paul C. J. P. Smeets, Carleen H. Reijmer, Michiel R. van den Broeke, Dirk van As, Jason E. Box, and Robert S. Fausto

The turbulent exchange of heat at the surface, including the sensible heat flux (SHF), is an important component of the surface energy balance (SEB) over glaciers and ice sheets. Yet, the turbulent heat fluxes are parameterized in all SEB models, which makes their contribution to the modelled ice ablation uncertain.

In this study, we present several years of continuous, daily, in situ observations of SHF (eddy-covariance) and ice ablation, taken at multiple contrasting sites across the ablation area of the Greenland ice sheet. We then compare these measurements to several SEB models with different settings for the surface roughness lengths.

We show that it is possible to accurately model the SHF and the daily ice ablation, provided that the prescribed surface roughness lengths, for both heat and momentum, are accurate. We propose a simple parameterization of these roughness lengths, based on both in-situ measurements and remotely sensed data (UAV, ICESat-2).  This updated parameterization can be implemented in SEB- and climate- models for improved simulations of ice sheet ablation and surface mass balance.

How to cite: van Tiggelen, M., Smeets, P. C. J. P., Reijmer, C. H., van den Broeke, M. R., van As, D., Box, J. E., and Fausto, R. S.: Momentum- & heat- flux parameterization over the Greenland Ice Sheet, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1480, https://doi.org/10.5194/egusphere-egu22-1480, 2022.

EGU22-2286 | Presentations | CR2.2

Precision description for remote sensing glacier velocity data 

Bas Altena, Andreas Kääb, and Bert Wouters

A large amount of velocity data is now becoming available through portals, pipelines and repositories. Typically the error characterisation for these individual velocity fields or mosaics is done through sampling statistics, resulting in a proxy of precision for the whole dataset. However even within a scene pair, the appearance can change considerably, or be stable at nearby locations. For example, think of regions close to the transient snowline, or an elongated moraine band, a  crevasse train after a bump or a shear zone. Here the precision of localising an exact image match is clearly anisotropic. If such anisotropic precision estimates are taken into account, it is possible to provide a more correct error-propagation. The merit of velocity data can be found in the help for inversion for thickness estimates (as it is related to the fourth power), or shear and strain rates. Here we introduce a simple and fast methodology to generate an individual dispersion estimate, based upon the similarity surface of an image match. A linear least squares adjustment of the neighbouring similarity scores is sufficient to fit an oriented gaussian peak. This setup makes the computation fast and is easy to implement into already available processing pipelines. We demonstrate its effectiveness on two glaciers, Sermeq Kujalleq, a large outlet glacier of the Greenland icesheet, with strong shear margins and Malaspina Glacier a piedmont glacier with looped moraines. We find directionality within an image subset to be the dominant factor influencing the correlation dispersion. This stems from crevasses and moraine bands within the imagery, while a relation to differential flow, such as shear, is less pronounced. It is our hope, this methodology will narrow the integration gap between models and measurements.

How to cite: Altena, B., Kääb, A., and Wouters, B.: Precision description for remote sensing glacier velocity data, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2286, https://doi.org/10.5194/egusphere-egu22-2286, 2022.

EGU22-2317 | Presentations | CR2.2

Correcting UAV derived winter snow depth on glaciers by modelling the evolution of the No-Snow glacier surface 

Bernhard Hynek, Anton Neureiter, Gernot Weyss, Elke Ludewig, and Wolfgang Schöner

Spatially distributed winter snow accumulation over glaciers is an important information for a lot of purposes. Typically, snow depth on glaciers is measured by manual snow probing or ground penetrating radar. The point measurements of snow depth and snow density are then used to calculate the winter mass balance of the glacier.

In the last decade remote sensing techniques such as LIDAR and structure from motion (sfm) photogrammetry in combination with unmanned aerial vehicles (UAVs) have become more frequent to reconstruct snow surfaces providing a better spatial coverage and spatial resolution. Snow depth is calculated by DEM differencing of a No-Snow surface (summer surface) and the snow surface (winter surface).

However, using DEM differencing to extract snow depth over glaciers introduces the problem, that the No-Snow surface is not constant, as (1) the glacier is moving between the survey dates and (2) the surface possibly undergoes surface lowering due to melt after the summer survey.

In this study we present measurements on two small mass balance glaciers in the Austrian Alps (Goldbergkees and Kleinfleißkees). We account for the evolution of the No-Snow surface by (1) applying a simple model of the vertical ice movement and by (2) calculating the surface lowering due to melt using a distributed mass balance model.  The effect of both corrections is then validated using a dense network of manual snow depth measurements across the glacier.

How to cite: Hynek, B., Neureiter, A., Weyss, G., Ludewig, E., and Schöner, W.: Correcting UAV derived winter snow depth on glaciers by modelling the evolution of the No-Snow glacier surface, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2317, https://doi.org/10.5194/egusphere-egu22-2317, 2022.

EGU22-3376 | Presentations | CR2.2 | Highlight

Maturity of worldwide glacier data sets – history and future ambitions 

Isabelle Gärtner-Roer, Samuel U. Nussbaumer, Bruce Raup, Frank Paul, Ethan Welty, Ann Windnagel, Florence Fetterer, and Michael Zemp

The creation and curation of environmental data present numerous challenges and rewards. In this study, we reflect on the maturity of freely available glacier data sets (inventories and changes), as well as on related demands by data providers, data users, and data repositories in-between. The amount of glacier data has increased significantly over the last two decades, especially as remote-sensing techniques have developed quickly. The portfolio of observed parameters has increased as well, which presents new challenges for international data centers, and fosters new expectations from users.

We assess the services of the Global Terrestrial Network for Glaciers (GTN-G) as the central organization for standardized data on glacier distribution and changes. Within GTN-G, different glacier data sets are consolidated under one umbrella, and the glaciological community supports this service by actively contributing their data sets and by providing strategic guidance via an Advisory Board. To assess each GTN-G data set, we present a maturity matrix and summarize achievements, challenges, and future ambitions.

Most challenges can only be overcome in a financially secure setting for data services and with the help of international standardization. Therefore, dedicated support and long-term commitment for certified data repositories build the basis for the successful democratization of data. In the field of glacier data, this balancing act has so far been successfully achieved through joint collaboration between data repositories, data providers, and data users. However, we also note an unequal allotment of funds for data creation and projects using the data, and data curation. Considering the importance of glacier data to answering numerous key societal questions (from water availability to global sea-level rise), this imbalance needs to be adjusted. In order to guarantee the continuation and success of GTN-G in the future, basic funding schemes, flexible adaptation measures, and regular evaluations are required.

How to cite: Gärtner-Roer, I., Nussbaumer, S. U., Raup, B., Paul, F., Welty, E., Windnagel, A., Fetterer, F., and Zemp, M.: Maturity of worldwide glacier data sets – history and future ambitions, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3376, https://doi.org/10.5194/egusphere-egu22-3376, 2022.

EGU22-3609 | Presentations | CR2.2

GNSS-IR for snow studies at PROMICE automatic weather station in Greenland 

Trine Dahl-Jensen, Shfaqat Abbas Khan, Michele Citterio, Jakob Jakobsen, and Andreas Ahlstrøm

The PROMICE project runs 27 Automatic Weather Stations (AWSs) in Greenland. Most of these are located in the ablation zone of the Greenland ice sheet. From March to September 2020 a multi-frequency Global Navigation Satellite System (GNSS) antenna was installed on the AWS NUK-K at a small local glacier outside Nuuk with the purpose of testing the setup for high precision positioning. Due to the remote location, power supply is limited and the GNSS setup is constructed to minimize the power consumption. Therefore, data collection is limited to three hours each day, the antenna is passive and the data is stored on a local drive and not transmitted.

This study tests if the setup is feasible for GNSS Interferometric Reflectometry (GNSS-IR) measurements of snow depth. The method estimates the average snow depth over an area on the order 10-20 • 103 m2. GNSS-IR analysis shows good reflections during most of the covered time period. A sonic ranger is mounted on the PROMICE AWSs and used for measurement of snow depth. The GNSS reflector heights are compared to measurements from the sonic ranger. Though some differences are present, the GNSS-IR estimates capture the snow melt, as measured by the sonic ranger, well. The quality of the reflections decreases towards the end of the data series when the snow is melted. We expect that this is due to a rougher ice surface. However, useful reflections are still obtained but the uncertainty on the daily estimates increase significantly. The transition from snow to ice surface is confirmed by an albedo estimate based on measurements of shortwave radiation at the AWS.

How to cite: Dahl-Jensen, T., Khan, S. A., Citterio, M., Jakobsen, J., and Ahlstrøm, A.: GNSS-IR for snow studies at PROMICE automatic weather station in Greenland, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3609, https://doi.org/10.5194/egusphere-egu22-3609, 2022.

EGU22-4008 | Presentations | CR2.2

Detection of snow cover dynamics with a long range permanent TLS system at Hintereisferner (Austria) – possibilities and limitations 

Annelies Voordendag, Brigitta Goger, Christoph Klug, Rainer Prinz, Martin Rutzinger, and Georg Kaser

A permanent long-range terrestrial laser scanning (TLS) system is installed at Hintereisferner, Ötztal Alps, Austria to validate snow cover dynamics such as simulated by high-resolution atmospheric models.

Snow cover dynamics include several processes such as snow fall, compaction, metamorphism, snow redistribution by wind, avalanches and melt manifested in specific magnitudes and frequencies. To be able to quantify these surface changes, the smallest possible magnitude that can be measured by the TLS needs to be known.

An uncertainty analysis of the system has been conducted acquiring its limitations. It was known before that atmospheric conditions, the scanning geometry and mechanical properties contribute to the total uncertainty, but so far, these error sources and the total uncertainty had not been quantified.

It was assumed that the position of the TLS was stationary and thus, the georeferencing of the scan was automated with an unchanged transformation matrix. A case study of 29 hourly scans during 5 and 6 November 2020, with no surface changes due to external conditions, showed vertical differences between -0.62 m and +0.47 m relative to a selected reference scan. These deviations are related to ongoing minor movements of the scanner over the scope of day and result in errors of a few decimetres due to the long range acquisition.

The accuracy of the scans improves after manual georeferencing (RiSCAN PRO), resulting in smaller deviations between -0.15 and +0.04 m relative to the selected reference scan.

The total accuracy of the TLS system is ±10 cm (vertical direction) after manual georeferencing, but strongly depends on the range between target surface and TLS. This makes it possible to detect snow fall events, snow redistribution, melt, and avalanches with changes larger than one decimeter. Snow compaction and metamorphism are processes, which are over hourly to daily time steps too small to be detected by the TLS at Hintereisferner.

Over all, the determined accuracy of the TLS shows the suitability of the system setup for validating high-resolution atmospheric models that explicitly compute snow redistribution by wind and thus significantly will improve the treatment of snow cover dynamics in future glacier mass balance research.

 

How to cite: Voordendag, A., Goger, B., Klug, C., Prinz, R., Rutzinger, M., and Kaser, G.: Detection of snow cover dynamics with a long range permanent TLS system at Hintereisferner (Austria) – possibilities and limitations, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4008, https://doi.org/10.5194/egusphere-egu22-4008, 2022.

EGU22-4217 | Presentations | CR2.2

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

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

We have derived the glacier-specific Østrem curve to quantify the influence of a supraglacial debris cover on the mass and surface energy balance components of the Djankuat Glacier, a northwest-facing and partly debris-covered temperate valley glacier in the Caucasus region, 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, are 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. For very thin debris, a slight relative melt-enhancement occurs due to a decreased surface albedo. If debris, however, further thickens, the insulating effect becomes dominant and reduces the melt and runoff of the underlying ice significantly, as thermal conduction becomes the dominant process to induce ice melt beneath such thick debris layers. The above-mentioned effects are modelled 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.

How to cite: Verhaegen, Y., Rybak, O., Popovnin, V., and Huybrechts, P.: Deriving the Østrem curve to quantify supraglacial debris-related melt-altering effects on the Djankuat Glacier, Caucasus, Russian Federation, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4217, https://doi.org/10.5194/egusphere-egu22-4217, 2022.

EGU22-4377 | Presentations | CR2.2

Monitoring the Calderone glacieret in Central Italy from COSMO-SkyMed synthetic aperture radar at X band 

Nancy Alvan Romero, Gianluca Palermo, Edoardo Raparelli, Paolo Tuccella, Pino D'Aquila, Tiziano Caira, Massimo Pecci, and Frank Marzano

In recent decades, snowfalls, snow cover and duration over Central Italy have decreased and there have been some extreme snowfall events followed by extreme avalanche activities. In this regard, the Calderone Glacier (hereinafter Calderone) represents a geographical and geomorphological element of great interest and is defined as a sentinel of climate change in central Italy, as it is going through a strong phase of reduction, it is the only glacier in the Apennines,  and the southernmost in Europe, and for its position on the summit of the Italian Gran Sasso (2912 m asl), a mountain group located in the center of the Apennine belt in the Mediterranean area.

The Italian Glaciological Committee (Comitato Glaciologico Italiano (CGI) )  every year with ad hoc in-situ inspections in late spring and early autumn monitor the Calderone mass balance. The mass balance of a glacier depends on the interplay between the mass gains and losses associated with climate and those associated with the inherent flux, its monitoring is essential because it can contribute to the knowledge of the current ongoing evolution of glaciers. 

Continuation of the traditional type of monitoring, like the one performed by CGI, based on direct measurements of accumulation and ablation by means of a network of stakes, appears to be an unlikely prospect, because in-situ data gathering usually implies expensive field campaigns and with difficult access to the sites, resulting in limited spatial and temporal resolution.  In contrast, techniques based on remotely sensed data, among several techniques, those relying on Synthetic Aperture Radar (SAR) demonstrated to be very effective due to the instrument's capability of operating day and night independently of the weather conditions.

Differential interferometry or DInSAR is a tool for accurate displacement measurements, and it is useful in identifying footprints of progressing movement. DInSAR is interferometry itself, the only difference is that topographical effects are compensated by using a Digital Elevation Model (DEM) of the area of interest, creating what is referred to as a differential interferogram.

In this work we propose the mass balance for the Calderone through the DInSAR results and its comparison with CGI in-situ measurements for the winter period 2018-2020. The data used in this study consist of COSMO-SkyMed satellite X-band single-look complex images in slant geometry (SCS, level 1A product),  Stripmap Himage mode (HH polarization) at 3 m per pixel of spatial resolution, and acquisition geometry Right Descending. The processing of this satellite data was applied over the entire area covered by the images and then refined to Calderone area, it includes a pre-processing first step that include: coregistration, interferogram formation, filtering and speckle; and a second part focused on obtaining the average values, active area and total area for the calculation of the mass balance.

How to cite: Alvan Romero, N., Palermo, G., Raparelli, E., Tuccella, P., D'Aquila, P., Caira, T., Pecci, M., and Marzano, F.: Monitoring the Calderone glacieret in Central Italy from COSMO-SkyMed synthetic aperture radar at X band, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4377, https://doi.org/10.5194/egusphere-egu22-4377, 2022.

EGU22-4654 | Presentations | CR2.2

Short-term surface velocity variations of the Argentière glacier monitored with a high-resolution continuous GNSS network 

Anuar Togaibekov, Andrea Walpersdorf, and Florent Gimbert

The motion of glaciers with a temperate base is highly variable in time and space as a result of glacier basal sliding being strongly modulated by subglacial hydrology. Here we investigate short term (diurnal to multi-diurnal) changes in horizontal velocity and vertical displacement caused by melt and rain water input events on the Argentière Glacier (French Alps). We use up to 13 permanent GNSS stations that have been operating continuously over three full years (since April 2019). We report observations of strong surface acceleration events occurring in response to late summer storms, during which a velocity pulse propagates from up to down glacier at a migrating speed of about 0.1 m/s, which is typical of flow drainage speeds in the distributed system. We thus suggest that transient changes in the surface velocity field during intense and short-term water input events reflect transient changes in the distributed system flow properties. Although the efficient drainage system is expected to be well developed at this time of the year, this latter does not appear to play a primary role in our observations. Using concomitant observations of subglacial flow discharge and seismic tremor amplitudes we are able to estimate the average height of cavities and the associated cavity-drainage conductivity. Examination of the vertical displacement suggests that a vertical motion of the glacier (uplift) is largely controlled by the volume increase in subglacial water cavities rather than by the vertical strain rate change. These observational constraints may be crucial to test subglacial drainage and transient friction theories.

How to cite: Togaibekov, A., Walpersdorf, A., and Gimbert, F.: Short-term surface velocity variations of the Argentière glacier monitored with a high-resolution continuous GNSS network, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4654, https://doi.org/10.5194/egusphere-egu22-4654, 2022.

EGU22-5467 | Presentations | CR2.2

Recent evolution of debris-covered glaciers in the Manaslu region of Nepal (1970 - 2019): the case of Ponkar Glacier 

Adina E. Racoviteanu, Neil F. Glasser, Benjamin A. Robson, Stephan Harrison, Romain Millan, Rijan B. Kayastha, and Rakesh Kayastha

Debris-covered glaciers in the Manaslu region of Nepal have been scarcely studied. Here we aim to fill this gap using new, multi-sensor, freely available 2019 Planet high-resolution (3 to 5 m) imagery, 1970 Corona declassified imagery and UAV and stake ablation data acquired in the field to characterize the surface and evolution of these glaciers over the last five decades. We report regional area changes, glacier thickness, geodetic glacier mass balance and surface velocity changes and focus on Ponkar Glacier and Thulagi Glacier and Lake for an in-depth assessment of surface geomorphology and surface feature dynamics (ponds, vegetation and ice cliffs).

Glaciers in the Manaslu region experienced a mean area loss of -0.26 ± 0.0001 % a-1 between 1970 and 2019, with a mean surface lowering of -0.20 ± 0.02 ma-1 over the period 1970 to 2013, corresponding to a regional geodetic mass balance of -0.17 ± 0.03 m w.e.a−1. Overall, debris-covered glaciers had higher thinning rates compared to clean ice glaciers. During the period 1970 to 2013, the debris-covered Ponkar Glacier had a geodetic mass balance of -0.06 ± 0.01 m w.e.a−1, with parts of the central trunk thickening and a nine-fold increase in the thinning rates over the lower parts of the glacier tongue in the recent years (2013 to 2019). Ice-surface morphology changes between 1970 and 2019 include a decrease in ogives and open crevasses, an increase in ice cliffs and ponds and the expansion of the supraglacial debris and ice-surface vegetation, suggesting reduced ice-dynamic activity.

How to cite: Racoviteanu, A. E., Glasser, N. F., Robson, B. A., Harrison, S., Millan, R., Kayastha, R. B., and Kayastha, R.: Recent evolution of debris-covered glaciers in the Manaslu region of Nepal (1970 - 2019): the case of Ponkar Glacier, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5467, https://doi.org/10.5194/egusphere-egu22-5467, 2022.

EGU22-6163 | Presentations | CR2.2

Sub-seasonal evolution of ice cliffs captured with time-lapse photogrammetry 

Marin Kneib, Evan S. Miles, Pascal Buri, Stefan Fugger, Michael McCarthy, Chuanxi Zhao, Thomas E. Shaw, Martin Truffer, Matthew Westoby, Wei Yang, and Francesca Pellicciotti

Ice cliffs are important contributors to the mass balance of debris-covered glaciers, especially in High Mountain Asia where they can account for one sixth of the melt of  debris-covered glacier tongues, despite covering less than 10% of their area. These features have been shown to evolve, appear and disappear rapidly from year to year, with high variability in relative area and number. It has been hypothesized that ice cliffs expand and melt more rapidly during the monsoon (June-September), but there are very few observations during this period. Here, we use arrays of time-lapse cameras to reconstruct the geometry of four ice cliffs at a weekly timestep over a period of four to six months at two monsoon-affected sites: Langtang Glacier in Nepal, and 24K Glacier in South-Eastern Tibet. We use Structure-from-Motion photogrammetry to derive point clouds and Digital Elevation Models (DEMs) of the glacier surface, using the stable background terrain to constrain viewing geometries and DEM errors. This technique (time-lapse photogrammetry) enables a high accuracy, quantitative measurement of processes occurring at the cliff-scale (elevation uncertainties stay below 30cm at a distance of 300m from the cameras) and at high temporal resolution over the monsoon season, when dense cloud cover and intense precipitation prevent field- or satellite-based observations. We derive the melt patterns of these cliffs from the differencing of the weekly DEMs by accounting for glacier flow. We compare the observed melt patterns with the modeled energy-balance at the cliff surface and use these observations to quantify the influence of debris slumping and redistribution, as well as supraglacial ponds and streams on the melt patterns of these cliffs. The results highlight the seasonal variations of cliff melt, which occurs at up to 8 cm/day during the monsoon, twice as high as observed in the pre- and post-monsoon period. Our energy-balance results indicate that melt rates are driven by incoming long- and shortwave radiation, and are thus highly dependent on the cliff slope and aspect, as substantiated by our photogrammetric measurements. The observations also demonstrate the competitive influence of debris, which progressively reburies the cliff by accumulating at its surface, and supraglacial streams and ponds, which maintain the cliff slope by preventing debris accumulation at the base. These results will help in understanding the surface evolution of debris-covered glaciers and enable a better representation of ice cliff melt and evolution in glacio-hydrological models.

How to cite: Kneib, M., Miles, E. S., Buri, P., Fugger, S., McCarthy, M., Zhao, C., Shaw, T. E., Truffer, M., Westoby, M., Yang, W., and Pellicciotti, F.: Sub-seasonal evolution of ice cliffs captured with time-lapse photogrammetry, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6163, https://doi.org/10.5194/egusphere-egu22-6163, 2022.

EGU22-6853 | Presentations | CR2.2

Quantifying glacier area changes using object-based image analysis in Google Earth Engine 

Asim Ali, Paul Dunlop, Sonya Coleman, Dermot Kerr, Robert W McNabb, and Riko Noormets

Glaciers are an important component of the cryosphere and are key indicators of climate change. Observations of temporal changes in glacier extent are essential for understanding the impacts of climate change, but these observations are not widely available in many parts of the world. Research indicates that climate change has had a significant impact on glacier recession, particularly in the Arctic, where glacier meltwater is an important contributor to global sea-level rise. Therefore, it is important to accurately quantify glacier recession within this sensitive region. In this study, we mapped 480 glaciers in Russian Arctic, Novaya Zemlya, using object-based image analysis (OBIA) applied to multispectral Landsat satellite imagery in Google Earth Engine (GEE) to quantify the area changes between 1986-89 to 2019-21.  Our results confirm that in 1986-89, the total glacierized area was 22958.98 km2 and by 2019-21 there was an 5.56% reduction in glacier area to 21680.63 km2.  Comparison between manually corrected glacier outlines taken from the Randolph Glacier Inventory (RGI) and the mapped glacier outlines derived using the OBIA method shows there is a 90.26% similarity between both datasets. This confirms that OBIA, combined with the GEE platform, is a promising method for accurately mapping glaciers, reduces the time required for manual correction, and can be applied in other glacierized regions for rapid assessment of glacier change.

How to cite: Ali, A., Dunlop, P., Coleman, S., Kerr, D., W McNabb, R., and Noormets, R.: Quantifying glacier area changes using object-based image analysis in Google Earth Engine, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6853, https://doi.org/10.5194/egusphere-egu22-6853, 2022.

EGU22-7501 | Presentations | CR2.2

Understanding the recent evolution of a small Alpine glacier: from geodetic mass balance reconstruction (1991-2020) to local variability of glaciers retreat. 

Luca Mondardini, Paolo Perret, Simone Gottardelli, Marco Frasca, and Fabrizio Troilo

High Alpine environments are rapidly changing in response to climate change, and understanding the evolution of small glaciers is a crucial step to investigate future water availability for populations that inhabits these areas. With an average loss of 1.6 km2 of regional glacier area every year, Aosta Valley is predicted to lose most of its glaciers before the end of the century. With this study, we present a comprehensive analysis of a small glacier’s recent mass balance evolution (1991-2020) where no specific previous mass balance data was available. To do so, we combined historical data (topographic surveys and LiDAR DEMs of the area) with newly acquired satellite stereo imagery and aerophotogrammetric surveys to reconstruct different digital elevation models of the Thoula glacier (0.52 Km2), located on the Italian side of the Mont-Blanc Massif. The ice volume loss that occurred over this period was assessed by accomplishing two GPR surveys to investigate the ice thickness and the underlying bedrock. The Thoula glacier shows a significantly lower loss of volume in comparison to other glaciers located in the Aosta Valley region as well as most of the WGMS (Word Glacier Monitoring Service) reference glaciers for Central Europe. Particular weather-climatic conditions of the Mont Blanc Massif area, generally characterized by a greater amount of snowfall, could explain the observed differences, however, the present study shows how understanding spatio-temporal local variability of small glaciers can significantly contribute to recognizing different regional patterns developing in response to climate change.

How to cite: Mondardini, L., Perret, P., Gottardelli, S., Frasca, M., and Troilo, F.: Understanding the recent evolution of a small Alpine glacier: from geodetic mass balance reconstruction (1991-2020) to local variability of glaciers retreat., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7501, https://doi.org/10.5194/egusphere-egu22-7501, 2022.

EGU22-8240 | Presentations | CR2.2

The jökulhlaup from the subglacial lake Grímsvötn, beneath Vatnajökull ice cap, in November-December 2021, revealing new insight in to slowly rising jökulhlaups 

Eyjólfur Magnússon, Vincent Drouin, Finnur Pálsson, Krista Hannesdóttir, Joaquín M. C. Belart, Gunnar Sigurðsson, Jan Wuite, Tómas Jóhanneson, Benedikt G. Ófeigsson, Thomas Nagler, Magnús T. Gudmundsson, Thórdís Högnadóttir, Michelle Parks, Matthew J. Roberts, and Etienne Berthier

The subglacial lake Grímsvötn, beneath Vatnajökull ice cap, has been an important study area since the first attempts to explain the physics of jökulhlaups. The lake, covered by an up to 300 m thick ice shelf, is situated within a caldera of an active central volcano. It collects meltwater produced by geothermal and volcanic activity, in addition to meltwater from the glacier surface. During most of the 20th century the period of water accumulation was typically 4-6 years, collecting 1-3 km3 of water. The jökulhlaups, as  observed in the river at the glacier terminus ~50 km south of the lake, typically reached peak discharge of 2,000-10,000 m3s-1 after approximately exponential increase over 2-3 weeks. In October 1996, 3.2 km3 of meltwater from an eruption north of Grímsvötn were collected in the lake. This resulted in hydrostatic uplift of the lake ice dam and sudden release of the accumulated water, reaching a peak flow of ~50,000 m3s-1 at the glacier terminus in less than a day. Due to damage to the lake ice dam during the 1996 jökulhlaup and further undermining from geothermal activity near the dam, the water accumulation and release has been different after this event. Between 1996 and 2018, smaller jökulhlaups typically occurred at 1-2 year intervals with the largest volume of ~0.6 km3 in 2004 and 2010. The jökulhlaup discharge still resembled an exponentially rising discharge, but faster, reaching a peak discharge at the glacier front in 3-5 days after detection of flood water in the river. In 2004 and 2010 the peak discharge was ~3,000 m3s-1. From autumn 2018 until November 2021, ~1 km3 of water accumulated in Grímsvötn. The lake level has been monitored since the 1990s, but now with increased accuracy using online GNSS stations located on the floating ice shelf and repeated glacier surface mapping using Pléiades stereo images. Around mid-November 2021 the GNSS instruments started subsiding, revealing that the lake had started draining. In 3 weeks, the discharge from the lake, estimated from the subsidence rate and the lake hypsometry, gradually increased from a few m3s-1 to a peak discharge of ~3500 m3s-1 on 4 December. A few days later, the lake had drained completely. We present the data showing the development at the lake prior to and during the jökulhlaup, and we report on: a) discharge measurements near the glacier front, which combined with the lake discharge allows for an estimate of the temporal subglacial floodwater storage, b) horizontal and vertical ice motion in the vicinity and above the subglacial flood route during the jökulhlaup, from ICEYE and Sentinel-1 radar images obtained with InSAR (24 hour repeat) analysis and amplitude offset tracking, showing the distribution of flood water and the widespread effect of the jökulhlaup on the horizontal ice motion, c) ice surface motion measured by a GNSS station located half-way between the lake and the glacier margin, spanning the entire jökulhlaup. All this provides new insight into the physical processes occurring during a slow, exponentially rising jökulhlaup from Grímsvötn.

How to cite: Magnússon, E., Drouin, V., Pálsson, F., Hannesdóttir, K., Belart, J. M. C., Sigurðsson, G., Wuite, J., Jóhanneson, T., Ófeigsson, B. G., Nagler, T., Gudmundsson, M. T., Högnadóttir, T., Parks, M., Roberts, M. J., and Berthier, E.: The jökulhlaup from the subglacial lake Grímsvötn, beneath Vatnajökull ice cap, in November-December 2021, revealing new insight in to slowly rising jökulhlaups, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8240, https://doi.org/10.5194/egusphere-egu22-8240, 2022.

EGU22-8327 | Presentations | CR2.2

Ice cliff mass-loss of debris-covered Trakarding Glacier, Rolwaling region, eastern Nepal Himalaya 

Yota Sato, Pascal Buri, Evan Miles, Marin Kneib, Sojiro Sunako, Akiko Sakai, Francesca Pellicciotti, and Koji Fujita

Glaciers in High Mountain Asia have been shrinking in the recent decades. They are a valuable indicator of climate change, and their meltwater plays an important role for regional water resources. Debris-covered glaciers, which are prevalent throughout the Himalayas, exhibit complex melt processes due to their heterogeneous surface.  Previous studies have demonstrated that ice cliffs disproportionally contribute to glacier melt, but their importance at the glacier scale has been quantified for only a few sites. In this study, we exploit measurements taken since 2016 on the lake-terminating Trakarding Glacier (27.9°N, 86.5°E; 2.9 km2 spanning 4,500–5,000 m a.s.l.; ~5% ice cliff cover), eastern Nepal Himalaya, to investigate the importance of cliffs for debris-covered ice melt at the glacier scale from a remote-sensing inversion and energy-balance modeling. We generated super-high-resolution (0.2 m) terrain data from aerial photographs (UAV and helicopter-borne photogrammetry) during 2018-2019 and manually delineated ~500 ice cliffs to derive surface velocity, elevation change, and specific mass balance, providing an observational estimate of ablation across the debris-covered tongue and attributable to ice cliffs. Further we employed a process-based 3D-backwasting model to estimate continuous ice cliff mass-loss over the study period. The model calculates the energy balance of ice cliff surfaces and reproduces their evolutions (cliff expansion, shrinkage, and reburial), based on the characteristics of the glacier surface and location of individual ice cliffs. This method, forced with in-situ meteorological and terrain data and evaluated against the observed changes, provides ice cliff mass-loss from the scale of individual features to the entire Trakarding Glacier.

How to cite: Sato, Y., Buri, P., Miles, E., Kneib, M., Sunako, S., Sakai, A., Pellicciotti, F., and Fujita, K.: Ice cliff mass-loss of debris-covered Trakarding Glacier, Rolwaling region, eastern Nepal Himalaya, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8327, https://doi.org/10.5194/egusphere-egu22-8327, 2022.

EGU22-8606 | Presentations | CR2.2 | Highlight

First results of the RAGMAC glacier elevation change intercomparison exercise 

Matthias Braun, Michael Zemp, and Fanny Brun

The intercomparison exercise by the IACS Working Group on Regional Assessments of Glacier Mass Change (RAGMAC) aims to provide an overview of good practises as well as spread of different processing approaches for assessing glacier volume changes from geodetic methods. It is composed of two experiments with mandatory and optional tasks. Participants are encouraged to contribute to all tasks.

Experiment 1 targets a comparison of spaceborne elevation changes to high-quality, high-resolution airborne data (either from laser scanning or aerial photogrammetry) as well as to in-situ surface glacier mass balance data. Test sites are Aletsch Glacier and Hintereisferner in the Alps as well as Vertisen in Norway. The expected outcome of the first experiment (with validation data) is to see how the participants account for the mismatch between DEM acquisition dates and to assess quantitatively the divergence between estimates as a function of this mismatch.

Experiment 2 is setup for regions (Northern Patagonian Icefield, Karakoram, Franz Joseph Land) where not direct validation data is available. The challenge posed here is on the intercomparison and influence of different processing steps and approaches on the elevation and volume change results. Observation periods are pre-defined and participants deliver different versions of the processing results.

The presentation will provide an overview of the exercise and the experiments and outline first results of the endeavour.

How to cite: Braun, M., Zemp, M., and Brun, F.: First results of the RAGMAC glacier elevation change intercomparison exercise, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8606, https://doi.org/10.5194/egusphere-egu22-8606, 2022.

EGU22-8742 | Presentations | CR2.2

What does steady state mean for debris-covered glaciers? 

Christoph Mayer and Carlo Licciulli

Debris-covered glaciers accumulate supra-glacial debris on the glacier surface in the ablation zone. As long as this debris layer is not at least partly removed, it can be expected that glaciers continue to grow in length, because the thickening debris layer continuously reduces surface melt rates. Removal of the debris layer, on the other hand, is a complicated process, which depends on a number of parameters, like surface slope, debris thickness, grain size distribution and water content to name just a few. However, the way how supra-glacial debris is removed might strongly influence the dynamic reaction of the glacier itself.

A realistic study of these interactions can only be performed, if the ice flow and the debris-influenced melt is treated with a high degree of detail. In our study, we coupled a 2-D full Stokes ice dynamic and surface debris transport model with a sophisticated description of energy transfer through the debris layer. This approach ensures that ice flow and surface melt rates are simulated at high detail, including the enhanced melt rates for very thin debris cover just below the equilibrium line. We restricted our experiments to rather simple initial conditions, in order investigate the fundamental feedback mechanisms between melt rates and glacier dynamics. Therefore, we introduced rather simple, but realistic formulations of debris unloading at the glacier front. The coupled experiments show that steady-state conditions are highly unlikely for glaciers with the debris layer remaining on the glacier. However, a balance of the debris budget and the glacier mass flux is possible, when introducing debris removal from the glacier tongue. We focussed on an as realistic as possible representation of the snout geometry, in order to allow a physically sensible debris discharge. The results show that for some removal processes debris-covered glaciers have an inherent tendency to enter an oscillating state, where glacier mass balance and debris balance are out of phase. In specific experiments glacier advance periods end with the separation of the heavily debris-loaded lowermost glacier tongue, at time scales of decades to centuries, followed by an advance of the remaining clean glacier. In such cases we assume that long-term “mean-steady-state” conditions modulated by oscillations in glacier length exist and are independent from climatic variations. This makes it difficult to interpret short-term geometry observations of debris-covered glaciers in the context of climate impact.

How to cite: Mayer, C. and Licciulli, C.: What does steady state mean for debris-covered glaciers?, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8742, https://doi.org/10.5194/egusphere-egu22-8742, 2022.

EGU22-10033 | Presentations | CR2.2

Fusion of multi-sensor, multi-temporal velocity observations to study intra-annual glacier dynamics 

Laurane Charrier, Yajing Yan, Emmanuel Trouvé, Elise Colin Koeniguer, Silvan Leinss, Jeremie Mouginot, and Romain Millan

Intra-annual glacier velocities are key parameters to study glacier basal conditions or short-term events such as glacier surges. However, intra-annual glacier velocities remain poorly understood at a global scale, especially in mountains areas. Indeed, many ice velocity maps are now available on-line or on-demand at a temporal resolution up to 2 days and a spatial sampling up to 50 m (Millan et al., 2019) all over the world. However, these products contain gaps, noise and artefacts especially where image-matching algorithms fail because of strong surface changes, surface locking, shadow casting, clouds, or feature-less regions. Moreover, this amount of data is complex to analyse since velocities span different temporal baselines, are derived from different sensor images using different algorithms. Therefore, there is a need to fuse the available multi-temporal and multi-sensor glacier velocity observations in order to study intra-annual glacier dynamics with a high temporal resolution.

The proposed approach relies on an inversion based on the temporal closure of displacement observation networks. Because the observations have different uncertainties, not necessarily known, the inversion is solved using an Iterative Reweighted Least Square. This approach results in velocity time series which have a complete temporal coverage, a uniform temporal sampling without overlapping time intervals (i.e. without redundancy) by tacking advantage of all available velocity observations without a priori on the displacement behavior. The temporal sampling of these velocity time series can be selected. To select an optimal temporal sampling based on a compromise between temporal resolution and uncertainty, we propose to minimize Root Mean Square Error (RMSE) over stable areas and maximize Velocity Vector Coherence (VVC) over fast moving areas. The proposed approach is illustrated with both mono-sensor and multi-sensor datasets, on two different glaciers: 1) Sentinel-1 velocity observations from (Round et al., 2017) over the Kyagar glacier which is a surge glacier situated in the Karakoram range 2) Sentinel-2 and Venµs velocity observations from (Millan et al., 2019) over the Fox glacier, a temperate maritime glacier with a strong seasonality, situated in Southern Alps of New Zealand. The results reveal strong intra-annual variations of velocity with a reduced uncertainty for both glaciers: RMSE over stable areas is lower for the results than for the original velocities: 1) from 22% lower for 12-days temporal sampling to 67% lower for 36-days temporal sampling over the Kyagar glacier 2) from 78% lower for 5-days temporal sampling to 40% lower for 60-days temporal sampling over the Fox glacier.

This approach is not dataset dependent and can be applied to any available velocity observations derived from any sensors.

How to cite: Charrier, L., Yan, Y., Trouvé, E., Colin Koeniguer, E., Leinss, S., Mouginot, J., and Millan, R.: Fusion of multi-sensor, multi-temporal velocity observations to study intra-annual glacier dynamics, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10033, https://doi.org/10.5194/egusphere-egu22-10033, 2022.

Various interdisciplinary studies have shown substantial discrepancies between modeled and remotely sensed glacier surface elevation change.It is therefore crucial to better understand and quantify uncertainties associated to both methods. We design a probabilistic framework with the aim to filter outliers, fill data voids and estimate uncertainties in glacier surface elevation changes computed from Digital Elevation Model (DEM) differentiation. The technique is based on a Bayesian formulation of the DEM difference problem and specifically targets surging and debris-covered glaciers, both at glacier and regional scales. We first define a set of physically admissible surface elevation changes as an elevation-dependent probability density function.

In a second step, terrain roughness is defined as the main descriptor for DEM uncertainty. Each surface elevation change pixel is a probability distribution. We present validation experiments in High Mountain Asia and show that the model produces results consistent with conventional DEM differencing, while avoiding the caveats of already existing methods. We further demonstrate that accounting for unstable glacier dynamics is crucial for accurate outlier filtering and robust uncertainty estimation. The technique can be applied to other types of remotely sensed glacier quantities (surface velocity etc.) and would provide more reliable characterization of uncertainty associated with changes in glacier mass and dynamics.

How to cite: Guillet, G. and Bolch, T.: Probabilistic estimation of glacier surface elevation changes from DEM differentiation: a Bayesian method for outlier filtering, gap filling and uncertainty estimation with examples from High Mountain Asia, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10073, https://doi.org/10.5194/egusphere-egu22-10073, 2022.

Around 10% of glacier area in the Himalaya is debris-covered with heterogeneous distribution. Debris distribution, as a function of its thickness, induces differential melting and may lead to characteristic slope inversion. The spatial distribution of debris thickness is poorly quantified in the Himalaya with limited field-based measurements. In the present study we conducted a field expedition on the Panchi Nala Glacier (4.50 km2, 60% debris-covered), western Himalaya during September 2021 and measured debris thickness at 73 points using a DGPS. Debris thickness ranges from <1 cm to 50 cm and reaches upto 1 m over extreme margins. In general, the debris is thicker (>25 cm) in the lower reaches (upto 1.5 km from snout) and decreases with increasing distance from snout. This generalization is, however, not always true as some patches of thin debris cover (<3.5 cm) in the lower portion and some patches of thick debris cover (~13 cm) at upper portion were also found. To assess the influence of debris thickness on melting, elevation difference data from Shean et al. (2020) is obtained. The correlation between debris thickness and elevation changes over corresponding pixels is negative (R = −0.58), suggesting that variation in surface elevation changes can partially be explained by the distribution of debris thickness. Spatially, the wastage is comparatively low (−0.69 m/y) around glacier snout where debris cover is thick (~15 cm) and higher (−1.14 m/y) at higher reaches (~3 km from snout) where debris cover is thin (~5 cm). Comparison of profiles derived from SRTM DEM and ASTER DEM along the central flowline for 2000 and 2020, respectively suggests that owing to differential melting, the concavity is developing on the glacier. Thus, debris thickness is playing an important role in regulating the melt and modifying the overall morphology of the Panchi Nala Glacier. 

How to cite: Garg, P. K. and Azam, M. F.: Impact of debris distribution on glacier morphology: a case study of Panchi Nala Glacier, western Himalaya using field and remote sensing measurements, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10142, https://doi.org/10.5194/egusphere-egu22-10142, 2022.

EGU22-10238 | Presentations | CR2.2

Modelling the complex transient response of debris-covered glaciers to climate change and interaction with debris production 

James C. Ferguson, Tobias Bolch, Argha Banerjee, and Andreas Vieli

Numerical modelling studies examining the transient behaviour of debris-covered glaciers have typically varied either the equilibrium line altitude, which is a proxy for climate, or the rate of debris deposition. Since the rate of debris production from headwall erosion is believed to be an increasing function of temperature, a more faithful representation of debris-covered glacier evolution should include a coupling between debris source strength and climate.

In this study, we examine the transient response of debris-covered glaciers to the combined effect of a warming climate and a related increasing debris source using a numerical model that couples ice flow with englacially transported debris. This allows for a debris melt-out concentration in the ablation zone that varies in time and space, depending on the evolving glacier dynamics and the debris deposition history.

We find that debris-covered glaciers in a warming climate exhibit a complex transient response with aspects of both retreat and advance, though these distinct responses occur on different timescales. This suggests that the observed present-day retreat of debris-covered glaciers may be followed by an eventual advance despite a continued increase in global mean temperature.

How to cite: Ferguson, J. C., Bolch, T., Banerjee, A., and Vieli, A.: Modelling the complex transient response of debris-covered glaciers to climate change and interaction with debris production, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10238, https://doi.org/10.5194/egusphere-egu22-10238, 2022.

EGU22-10241 | Presentations | CR2.2 | Highlight

Remote sensing tools for monitoring supraglacial debris cover features and their fluctuations 

Adina E. Racoviteanu

High mountain environments are characterized by highly glacierized, complex, dynamic topography, often exhibiting a heterogeneous debris mantle comprising ponds and exposed ice cliffs, associated with differing ice ablation rates. These has been an increased interest in understanding these supraglacial surface features, i.e., the formation and expansion of supraglacial ponds and implications for glacier hydrology and glacier-related hazards, notably glacier lake outburst flood (GLOF) events. Until recently, supraglacial debris surfaces and their features have received less attention compared to mapping of debris-cover extents due to methodological challenges posed by their ephemeral nature. As a result, they remain poorly quantified in global glacier databases including the Global Land Ice Measurements from Space (GLIMS) and the Randolph Glacier Inventory (RGI). Furthermore, remote sensing studies used to generate these datasets generally rely on traditional “whole pixel” image classification techniques, which do not allow decomposition of a pixel into constituting materials. In this talk I summarize the state-of-art remote sensing techniques to characterize supraglacial features, such as debris material, ice cliffs, supraglacial ponds and vegetation. I particularly highlight the potential of spectral unmixing routines multi-temporal Landsat and Sentinel data combined with high-resolution multispectral imagery to quantify the composition of debris cover at multiple scales across the Himalaya with an emphasis on supraglacial ponds. I summarize the current strengths and limitations of these methods and discuss steps needed such as automation and open-source tools.

How to cite: Racoviteanu, A. E.: Remote sensing tools for monitoring supraglacial debris cover features and their fluctuations, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10241, https://doi.org/10.5194/egusphere-egu22-10241, 2022.

EGU22-11134 | Presentations | CR2.2

‘Dancing around the Östrem curve’: High-resolution monitoring of a supraglacial rockslide on Brenndalsbreen, Norway 

Gernot Seier, Jakob Abermann, Siri H. Engen, Marthe Gjerde, Thomas Scheiber, Karina Löffler, Jonathan L. Carrivick, Liss M. Andreassen, and Jacob C. Yde

Landslides or rockslides occur in unstable slopes around the world, of which many cases are related to changes in the cryosphere. They can result in natural hazards and are an indicator of climate change. Due to their inherent non-linearity, they are difficult to predict and often remain unobserved. Appropriate documentation allows for assessing their consequences and long-term impacts on ecosystems or the hydrological cycle.

We report on a particularly well-documented case of a supraglacial rockslide that occurred on Brenndalsbreen, an outlet glacier of Jostedalsbreen, Norway, in the period November 2009-June 2010. We assess its consequences on local glacier mass balance derived from surface elevation changes and explore potential changes in flow velocities. The rockslide occurred unobserved and did not obviously impact humans or the environment, yet, satellite imagery and aerial photogrammetrical surveys allow for a spatial and temporal quantification of the event. Furthermore, a series of digital elevation models from 2012-2021 is used to determine spatial heterogeneity in ablation rates, however, this is complicated due to the motion of the ice mass. According to the widely used Östrem curve, a debris-cover exceeding a certain threshold thickness protects the ice below from ablation, while a thin debris or dirt layer increases ablation rates. In fact, we find that during the first years after the rockslide, locally, ablation was reduced below the debris layer, while a recent high-resolution LiDAR survey that got complemented with a UAV survey a year later, clearly indicates increased ablation rates relative to the debris-free surroundings. Clear trends in surface velocities have not been found based on satellite remote sensing data. We discuss the significance of the observations on surface energy balance and geomorphological changes in the proglacial area.

How to cite: Seier, G., Abermann, J., Engen, S. H., Gjerde, M., Scheiber, T., Löffler, K., Carrivick, J. L., Andreassen, L. M., and Yde, J. C.: ‘Dancing around the Östrem curve’: High-resolution monitoring of a supraglacial rockslide on Brenndalsbreen, Norway, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11134, https://doi.org/10.5194/egusphere-egu22-11134, 2022.

EGU22-11900 | Presentations | CR2.2

Structurally controlled englacial origin of supraglacial debris cover and relief at a debris-covered Alpine glacier 

Darrel Swift, Andrew Jones, Matthew Westoby, Robert Bryant, and Remy Veness

It is common for temperate glaciers in mountainous regions to exhibit an extensive ablation-zone supraglacial debris cover. Although secondary reworking of surface debris and its role in modifying rates of glacier melt is receiving increasing attention, debris origin and primary distribution is poorly understood. Arguably, studies have tended to uncritically assume that debris supply is dominated by the passive transport of rockfall material that is dispersed within the ice (englacially) or is deposited onto the surface directly. We show that a substantial portion of the debris cover at Miage Glacier, Italy, can be attributed to release from medial moraine (MM) structures that can be observed englacially in debris-free ice cliffs and as supraglacial ‘melt out’ ridges containing vertically oriented clasts, occasionally supported by a fine matrix. Two MM types displaying contrasting debris characteristics were observed: one arising from the tributary confluences located near or below the equilibrium line position, and another derived from accumulation basin confluences. The former were reasonably continguous supraglacial features that in the upper- and mid-ablation area develop considerable relief that clearly acts as a primary control on debris redistribution across the glacier surface. The latter type are traceable for limited distances, and form more isolated areas of high topography in the mid-ablation area. We argue that ablation area debris cover and relief complexity in the upper- and mid-ablation area largely reflects debris entrainment at the point of medial moraine origin, though additional factors include the recent detachment of tributaries, the decline in mass contributed by specific accumulation basins, and the stochastic nature of headwall debris supply. Secondary debris redistribution processes appear to increase as glacier surface elevation declines, meaning in the lower ablation area surface relief decreases as debris distribution complexity increases.

How to cite: Swift, D., Jones, A., Westoby, M., Bryant, R., and Veness, R.: Structurally controlled englacial origin of supraglacial debris cover and relief at a debris-covered Alpine glacier, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11900, https://doi.org/10.5194/egusphere-egu22-11900, 2022.

EGU22-11904 | Presentations | CR2.2

DCG-MIP: The Debris-Covered Glacier melt Model Intercomparison exPeriment 

Francesca Pellicciotti, Adria Fontrodona-Bach, David R Rounce, Catriona L. Fyffe, Mike McCarthy, Evan Miles, and Thomas E. Shaw

As glaciers respond to climate change, the scientific community has dedicated increasing attention to the development of melt models for debris-covered glaciers. Here, we present an intercomparison aimed at advancing our understanding of the skills of models of different complexity to simulate ice melt under a debris layer. We compare 14 models with different degrees of complexity at nine sites in the European Alps, Caucasus, Chilean Andes, Nepalese Himalaya and the Southern Alps of New Zealand, over one melt season. We run the models with meteorological data from automatic weather stations and estimated or measured debris properties. Model performance is evaluated using on-site measurements of sub-debris melt (for all models) and surface temperature (for models based on the surface energy balance) at each site. We find that the two main categories of models considered, physically-based energy balance (EB) models and empirical temperature index (TI) models perform in a distinct manner. Temperature index models are reliably accurate when they are recalibrated, and show a range of results when parameters are uncalibrated. The most accurate energy balance models are those with the highest degree of complexity at the atmosphere-debris interface. However, we also find that additional complexity within the debris and at the debris-ice interface does not improve performance, which results from a lack of data to accurately force the models to represent these processes. The difficulty to properly estimate the physical properties of debris layers and within-the-debris processes are a likely cause. One of our main conclusions is thus that sophisticated models need high quality input data. An important data gap emerged from our experiment: the poor performance of all models at three sites was related to poor knowledge of debris properties; specifically, of thermal conductivity. Since debris properties are a major control on melt model simulations, we demonstrate that consistent data acquisition efforts are required to more rigorously evaluate existing models and support new model developments. Future work should seek to advance models by improving how they account for processes such as debris-snow interactions, moisture in the debris and refreezing. We suggest that a systematic effort of model development using a single model framework could be carried out in phase II of the Working Group.

How to cite: Pellicciotti, F., Fontrodona-Bach, A., Rounce, D. R., Fyffe, C. L., McCarthy, M., Miles, E., and Shaw, T. E.: DCG-MIP: The Debris-Covered Glacier melt Model Intercomparison exPeriment, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11904, https://doi.org/10.5194/egusphere-egu22-11904, 2022.

EGU22-12672 | Presentations | CR2.2

Mapping debris thickness on alpine glaciers using UAV thermography and photogrammetry 

Alexander Raphael Groos and Jérôme Messmer

Supraglacial debris covers the tongue of many mountain glaciers. In the course of ongoing climate change and the rapid melting of glaciers, debris extent and thickness will continue to increase. The thickness and other inherent properties of the debris layer control sub-debris melt rates and influence how glaciers respond to climate change. It is therefore essential to consider the impact of supraglacial debris on ablation in glacier surface mass balance models and glacier evolution models. However, this requires detailed knowledge on the debris thickness distribution. As debris thickness is spatially very variable, it remains a challenge to map debris thickness across the entire ablation zone of a glacier. Here we present the preliminary results of a feasibility study on the Kanderfirn in the Swiss Alps, where we deployed an Unoccupied Aerial Vehicle (UAV) with a visible and thermal infrared camera to map and analyse spatial variations in debris surface temperature, debris thickness, and sub-debris melt rates. Two independent approaches originally developed for satellite data were tested and compared to map debris thickness in high resolution. First, we used the statistical relationship between spatial UAV observations and in-situ point measurements (mapped surface temperature vs. measured debris thickness) to derive spatial debris thickness variations from mapped surface temperature variations. Second, we calculated distributed sub-debris melt rates from UAV-based elevation-change maps and quantified debris thickness through the inversion of a sub-debris ice melt model. Both methods deliver promising results. Despite the remaining challenges, the results emphasise the potential of UAVs equipped with visible and thermal infrared cameras for glacier-wide debris thickness mapping.

How to cite: Groos, A. R. and Messmer, J.: Mapping debris thickness on alpine glaciers using UAV thermography and photogrammetry, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12672, https://doi.org/10.5194/egusphere-egu22-12672, 2022.

EGU22-13196 | Presentations | CR2.2

Air temperature variability inside crevasses in the accumulation area of a maritime glacier in the Southern Alps, New Zealand 

Heather Purdie, Peyman Zawar-Reza, Benjamin Schumacher, Marwan Katurji, and Paul Bealing

In mountain regions around the world, crevasses in glacier accumulation areas undergo cycles of burial and re-exposure between one melt season and the melt season that follows. However, climate warming is extending the length of the ablation season meaning that crevasses are now exposed at the glacier surface for longer.  An analysis of air temperature inside crevasses in the accumulation area of a maritime glacier has found that air temperature inside crevasses can at times be higher than the overlying air temperature. Here we combine measurements of air temperature and wind-speed from inside crevasses with adjacent meteorological data to demonstrate that open crevasses trap incoming shortwave radiation and have complex relationships with wind shear. Results show that crevasse morphology influences warming with the effect more pronounced at wider (more open) crevasses. This highlights the potential of crevasses to enhance glacial melt by acting as heat source through positive radiative and sensible heat feedback. Therefore we hypothesis that energy balance models that treat glacier accumulation areas as smooth surfaces will be underestimating snow melt and possibly overestimating mass balance on alpine glaciers. 

How to cite: Purdie, H., Zawar-Reza, P., Schumacher, B., Katurji, M., and Bealing, P.: Air temperature variability inside crevasses in the accumulation area of a maritime glacier in the Southern Alps, New Zealand, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13196, https://doi.org/10.5194/egusphere-egu22-13196, 2022.

EGU22-11 | Presentations | CR2.3

The Copernicus Imaging Microwave Radiometer (CIMR): A new view of the Cryosphere 

Craig Donlon, Rolv Midthassel, Marcello Sallusti, Mariel Trigganese, Benedetta Fiorelli, and Christophe Accadia

This presentation describes the Copernicus Imaging Microwave Radiometer (CIMR) Sentinel expansion mission. The mission is designed to provide measurement evidence in support of developing, implementing, and monitoring the impact of the European Integrated Policy for the Arctic. Since changes in the Polar regions have profound impacts globally, CIMR will provide a new view of the cryosphere using a suite of unique low-frequency, yet high spatial resolution, microwave radiometer measurements over the high latitudes and the entire global domain. Products will be provided within 3 hours of sensing and for specific operational activities, within 1 hour over specific regions. CIMR will serve users in the Copernicus Ocean, Land and Climate Services fueling down-stream cryosphere applications. The primary instrument is a conically scanning low-frequency, high spatial resolution multi-channel microwave radiometer. A dawn-dusk orbit and large swath width of ~2000 km ensures 95% global coverage each day with a single satellite. Channels centred at L-, C-, X-, Ku- and Ka-band are fully polarised with effective spatial resolution of ≤60 km, ≤15km, ≤5 km and <5 km (goal:4km) respectively. On-board processing provides robustness against radio frequency interference and enables the computation of modified 3rd and 4th Stokes parameters for all channels. This paper reviews the CIMR mission, anticipated performances and the expected Level-2 products that will be provided including sea ice concentration, sea surface temperature, thin sea ice thickness, sea surface salinity and wind speed over the ocean amongst others . In addition, synergies with other Copernicus missions, notably the CRISTAL mission, will be highlighted for cryosphere applications.

How to cite: Donlon, C., Midthassel, R., Sallusti, M., Trigganese, M., Fiorelli, B., and Accadia, C.: The Copernicus Imaging Microwave Radiometer (CIMR): A new view of the Cryosphere, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11, https://doi.org/10.5194/egusphere-egu22-11, 2022.

EGU22-888 | Presentations | CR2.3

Bridging the gap in polar altimetry 

Andrew Shepherd, Sinead Farrell, and Sara Fleury

With the accelerated melting of the ice sheets and the sea ice cover, Earth’s Polar Regions are major witnesses to global warming. Arctic Amplification already modifies lifestyles, economies, ecologies, industries, and transportation across the region. But as a result of teleconnections with the climate system, the Polar Regions also impact on a global scale, affecting sea level rise, ocean circulation and weather patterns, which, in turn, disrupt the natural environment and society. Because of their scale and inaccessibility, observation of the Polar Regions requires a collection of space-based techniques.  Satellite altimetry provides a unique capability to monitor changes in the thickness of land ice and sea ice, and in the Polar Oceans. This information is essential for charting the response of the Polar Regions to climate change, and for predicting their future interactions with, and impacts on, the global climate system.

Although at least 7 satellite altimeters are in orbit today, only two reach polar latitudes: CryoSat-2 and ICESat-2.  CryoSat-2 was launched in 2010 and although it is still operational, it is projected to reach end of life between 2024 and 2026 due to known fuel leakage and battery degradation. ICESat-2 was launched in 2018 with a design-life of 3 years. Other satellite altimeters in lower inclination orbits, including Sentinel-3, survey only minor fractions of the Arctic sea ice pack and the polar ice sheets, and are therefore unable to provide observations of their overall imbalance. The European Commission has initiated the CRISTAL polar altimeter as a high priority candidate mission in partnership with the European Space Agency, in view of their Arctic policy, and based on user requirements. The earliest launch date for CRISTAL is in the final quarter of 2027.

Without successful mitigation, there will be a gap of between 2 and 5 years in our polar satellite altimetry capability. This gap will introduce a decisive break in the long-term records of ice sheet and sea ice thickness change and polar oceanography and this, in turn, will degrade our capacity to assess and improve climate model projections. These capabilities are of major societal importance. In order to ensure the continuity of polar altimetry, there is an urgent need to consider mitigation measures. This paper aims to stimulate a community discussion and position on possible solutions, including extending the lifetime of CryoSat-2 or ICESat-2, manoeuvring an alternative satellite into a high-inclination orbit, accelerating the launch of CRISTAL, and initiating a systematic airborne measurement programme as a bridging capability. 

 

 

 

How to cite: Shepherd, A., Farrell, S., and Fleury, S.: Bridging the gap in polar altimetry, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-888, https://doi.org/10.5194/egusphere-egu22-888, 2022.

EGU22-1867 | Presentations | CR2.3

Application of Remote Sensing and GIS to Assess Snow Cover and its Dynamics: A Case Study of Uttarakhand Himalaya, India 

Arvind Pandey, Deepanshu Parashar, Sarita Palni, and Ajit Partap Singh

The cryosphere plays a vital role in the climate system by changing the energy and mass transfer between the atmosphere and the surface, and it is the most important land cover type in the Himalayan and Polar Regions, which act as an important source of freshwater for rivers. This study examines Snow-Covered Area (SCA) and Snowline variations in the Uttarakhand Himalaya using the Normalized Difference Snow Index (NDSI). Three Landsat series imagery for 1990, 2000, 2010, and Sentinel Data from 2015 to 2021 were processed and analyzed through open-source software. In order to estimate the average elevation of the snowline, a digital elevation model was used and an area estimation study using multispectral imagery. The research focuses on the snowline and snow cover variations over the Uttarakhand Himalaya from 1990 to 2021 and the average snow line-height, respectively. This study shows that in the years 1990, 2000, 2010, and 2015 to 2021, snow line variations and area estimation differences in Uttarakhand, Central Himalaya, and snow line at above sea level (a.s.l.) in the western and eastern part of the study area. This study deals with the analysis of snow line shifting and cover. It suggests that the snow cover area in the Uttarakhand, Central Himalaya, is depleting steadily, which will have adverse impacts, especially upon water resources causing various economic and social disruptions in the near future.

How to cite: Pandey, A., Parashar, D., Palni, S., and Singh, A. P.: Application of Remote Sensing and GIS to Assess Snow Cover and its Dynamics: A Case Study of Uttarakhand Himalaya, India, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1867, https://doi.org/10.5194/egusphere-egu22-1867, 2022.

EGU22-2394 | Presentations | CR2.3

West Greenland surface runoff extent, mapped from daily MODIS imagery 2000 to 2021 

Horst Machguth, Andrew Tedstone, and Enrico Mattea

Streams and lakes develop each summer over the marginal regions of the Greenland ice sheet. These hydrological systems reach well into the accumulation area and indicate that surface runoff of meltwater is an important component of the mass balance of the Greenland ice sheet. Here we map the slush limit, a proxy for the extent of surface runoff, using daily MODIS data (500 m spatial resolution) for the 22 melt seasons from 2000 to 2021. We develop an automated algorithm capable of detecting daily slush limits, provided sufficient image quality. The algorithm is applied to Greenland's west coast. Albeit MODIS' spatial resolution is too coarse to resolve streams, slush fields or lakes, the results highly agree to surface runoff mapping from better resolution satellite imagery. The data document the evolution of the slush limit across latitudes and during the individual melt seasons. We find significant increasing trends in slush limits until the year 2012, but not thereafter. We show that the slush limit typically rises quickly early in the melt season, but upward migration halts before melting ceases. The reasons behind this behaviour remain somewhat enigmatic. For the year 2012, we are able to demonstrate that upward migration of surface runoff stopped early in the melt season, at the upper margin of the ice slabs. These thick and continuous ice layers are located close to the surface, in the firn, and prevent percolation of melt into the otherwise porous firn. Had the ice slabs extended further into the accumulation area, the summer 2012 saw sufficient energy to raise the slush limit by another ~300 m in elevation.

How to cite: Machguth, H., Tedstone, A., and Mattea, E.: West Greenland surface runoff extent, mapped from daily MODIS imagery 2000 to 2021, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2394, https://doi.org/10.5194/egusphere-egu22-2394, 2022.

EGU22-2491 | Presentations | CR2.3

Observing the Disintegration of the A68A Iceberg from Space 

Anne Braakmann-Folgmann, Andrew Shepherd, Laura Gerrish, Jamie Izzard, and Andy Ridout

Icebergs impact the physical and biological properties of the ocean along their drift trajectory by releasing cold fresh meltwater and nutrients. This facilitates sea ice formation, fosters biological production and influences the local ocean circulation. The intensity of the impact depends on the amount of meltwater. A68 was the sixth largest iceberg ever recorded in satellite observations, and hence had a significant potential to impact its environment. It calved from the Larsen-C Ice Shelf in July 2017, drifted through the Weddell and Scotia Sea and approached South Georgia at the end of 2020. Finally, it disintegrated near South Georgia in early 2021. Although this is a common trajectory for Antarctic icebergs, the sheer size of A68A elevates its potential to impact ecosystems around South Georgia through release of fresh water and nutrients, through blockage and through collision with the benthic habitat.

In this study we combine satellite imagery data from Sentinel 1, Sentinel 3 and MODIS and satellite altimetry from CryoSat-2 and ICESat-2 to chart changes in the A68A iceberg’s area, freeboard, thickness, volume and mass over its lifetime to assess its disintegration and melt rate in different environments. We find that A68A thinned from 235 ± 9 to 168 ± 10 m, on average, and lost 802 ± 35 Gt of ice in 3.5 years. While the majority of this loss is due to fragmentation into smaller icebergs, which do not melt instantly, 254 ± 17 billion tons are released through melting at the iceberg’s base - a lower bound estimate for the fresh water input into the ocean. Basal melting peaked at 7.2 ± 2.3 m/month in the Northern Scotia Sea. In the vicinity of South Georgia we estimate that 152 ± 61 Gt of freshwater were released over 96 days, potentially altering the local ocean properties, plankton occurrence and conditions for predators. The iceberg may also have scoured the sea floor briefly. Our detailed maps of the A68A iceberg thickness change will be useful to investigate the impact on the Larsen-C Ice Shelf, and for more detailed studies on the effects of meltwater and nutrients released off South Georgia. Our results could also help to model the disintegration of other large tabular icebergs that take a similar path and to include their impact in ocean models.

How to cite: Braakmann-Folgmann, A., Shepherd, A., Gerrish, L., Izzard, J., and Ridout, A.: Observing the Disintegration of the A68A Iceberg from Space, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2491, https://doi.org/10.5194/egusphere-egu22-2491, 2022.

EGU22-3624 | Presentations | CR2.3

Mapping newly emerging islands and nunataks in Greenland improves existing bed elevation datasets 

Anders Bjørk, Enze Zhang, Mathieu Morlighem, Mathilde Dunk, Amanda Fleischer, Kathrine Thage, Jeremie Mouginot, and Shfaqat Abbas Khan

While great improvements in our understanding of the subglacial landscape has occurred in recent years, the majority of the land beneath the Greenland Ice Sheet is still unmapped. With this study we map newly emerging land masses using Landsat 8 and Planet Scope satellite imagery. By including new islands, nunataks, and ice-contact outcrops in the current bed elevation model BedMachine we are able to improve the reliability of both pro glacial bathymetry as well as subglacial topography in all areas where new land is emerging.

The previous official Greenland wide mapping occurred in 1978-1987 and was done on the basis of aerial photographs recorded at scale 1:150.000. Here, we manually update new island - and ice contact bedrock outcrops using false color pan-sharpened Landsat 8 (15m) from 2019 and verifying our results with Planet Scope satellite images (3m) from 2019 and 2021. With the mapping of newly emerged islands and bedrock outcrops, existing bathymetric and ice thickness products can be updated. As existing models (eg. BedMachineV3) is limited by the available input, it is common to see large assumed ice sheet thicknesses where nunataks are now exposed. Likewise, many newly mapped islands are appearing in places where fjord depths were expected to be several hundreds of meters.

While traditional methods fcor collecting bedrock elevations below the ice and ocean surfaces are associated with extremely high logistical costs, our approach can in a quick and affordable manner update existing med models with valuable data. This addition will result in more accurate ice flow and fjord circulation models, which will ultimately give us better predictions of future sea-level rise. We argue that with the ongoing retreat and downwasting, these systematic mapping efforts should ideally take place on a biannual basis.  

How to cite: Bjørk, A., Zhang, E., Morlighem, M., Dunk, M., Fleischer, A., Thage, K., Mouginot, J., and Abbas Khan, S.: Mapping newly emerging islands and nunataks in Greenland improves existing bed elevation datasets, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3624, https://doi.org/10.5194/egusphere-egu22-3624, 2022.

EGU22-5343 | Presentations | CR2.3

Tracking blue ice in time: deriving Antarctic blue ice fraction from MODIS images using spectral unmixing 

Zhongyang Hu, Peter Kuipers Munneke, Stef Lhermitte, Mariel Dirscherl, Chaonan Ji, and Michiel van den Broeke

Antarctic Blue Ice Areas (BIAs) are a sensitive indicator for climate change. They can be formed either by wind and sublimation or by surface melt, and vary over time. In this regard, distinguishing different blue ice types and observing their change over time can enhance our understanding of climate change in Antarctica. Presently, the areal extent of BIA is retrieved using Earth observation satellites. However, such products rarely provide time series of BIA extent over the entire continent. To fill this gap, we derived blue ice fraction over Antarctica from the moderate resolution imaging spectroradiometer (MODIS) using spectral mixture analysis. Blue ice fraction is defined as the fraction of each MODIS pixel that is covered by blue ice. The results provide a continuous time series of blue ice fraction during the austral summers 2000 to 2021. This time series shows Antarctic blue ice abundance and exposure over time, and indicates that melt-induced BIAs are more variable in time than wind-induced.  According to the accuracy assessment based on high-resolution Sentinel-2 images over six selected test sites in coastal East Antarctica, the blue ice fraction results have an overall uncertainty of around 15% and 25% in wind- and melt-induced BIAs, respectively. The uncertainties mainly arise due to the very similar spectral profiles among melt streams, lakes, and ponds. Overall, our results show great potential in (1) generating annual BIA maps, (2) separating wind-and melt-induced BIAs, (3) evaluating (regional) climate model outputs, and (4) deriving temporal variations in blue ice abundance and exposure.

How to cite: Hu, Z., Kuipers Munneke, P., Lhermitte, S., Dirscherl, M., Ji, C., and van den Broeke, M.: Tracking blue ice in time: deriving Antarctic blue ice fraction from MODIS images using spectral unmixing, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5343, https://doi.org/10.5194/egusphere-egu22-5343, 2022.

EGU22-5913 | Presentations | CR2.3

Interest of the Assimilation of Surface Melt Extent Derived From Passive and Active Microwave Satellites Into the Regional Climate Model MAR Over the Antarctic Peninsula 

Thomas Dethinne, Christoph Kittel, Quentin Glaude, Xavier Fettweis, and Anne Orban

Melting ice sheets are a major contributor to the rising sea level. At the Liège University, the Regional Climate Model MAR (Modèle Atmosphérique Régional) has been developed to monitor and study the current and future evolution of various properties of ice sheets. However, uncertainties remain on the surface melt extent upon Antarctic ice sheets as models are subject to error propagation and need some external data to model the climate.

In Antarctica, unlike Greenland, the produced surface meltwater does not leave the ice sheet through visible rivers in which the quantity of meltwater can be estimated. Remote sensing is then the only product able to provide an estimation of the surface melt extent with a satisfying spatial and temporal coverage. The assimilation of melt spatial extent estimated by remote sensing allows the mitigation of the uncertainties linked to the models as well as a better quantification of the melt quantity.

In this research, active (Sentinel-1) and passive (AMSR2 & SSMIS) microwave satellite data are assimilated into MAR model over the Antarctic Peninsula, where surface melt has caused hydrofracturing and destabilization of ice shelves in the past. The assimilation of the different satellite products is also conducted to study the effect of spatial resolution on melt detection, Sentinel-1 having a pixel size of a few meters while passive satellites are at the 10km scale. This difference can be crucial upon the Peninsula as Foehn effects are occurring locally and can generate local surface melt, not detectable while using a coarser resolution.

How to cite: Dethinne, T., Kittel, C., Glaude, Q., Fettweis, X., and Orban, A.: Interest of the Assimilation of Surface Melt Extent Derived From Passive and Active Microwave Satellites Into the Regional Climate Model MAR Over the Antarctic Peninsula, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5913, https://doi.org/10.5194/egusphere-egu22-5913, 2022.

EGU22-5932 | Presentations | CR2.3

Three different glacier surges at a spot: What satellites observe and what not 

Frank Paul, Livia Piermattei, Désirée Treichler, Lin Gilbert, Luc Girod, Andreas Kääb, Ludivine Libert, Thomas Nagler, Tazio Strozzi, and Jan Wuite

In the Karakoram, dozens of glacier surges occurred in the past two decades, making the region one of the global hotspots. Detailed analyses of dense time series from available optical and radar satellite images revealed a wide range of surge behaviours in this region: from slow advances characterized by slow ice flow over periods longer than a decade to short, pulse-like advances with high velocity over one or two years.

In this study, we present an analysis of three glaciers that are currently surging in the same region of the central Karakoram: North Chongtar, South Chongtar and an unnamed glacier referred to as NN9. A full suite of optical and SAR satellite sensors and digital elevation models (DEMs) are used to (1) obtain comprehensive information about the evolution of the surges between 2000 and 2021 and (2) to compare and evaluate capabilities and limitations of the different satellite sensors for monitoring small glaciers in steep terrain. 

The analysis for (1) reveals a contrasting evolution of advances rates and flow velocities for the three glaciers, while the elevation change pattern is more similar. South Chongtar Glacier showed advance rates of more than 10 km y-1, velocities up to 30 m d-1 and surface elevations raised by 200 m. In comparison, the three times smaller North Chongtar Glacier has a slow and almost-linear increase of advance rates (up to 500 m y-1), flow velocities below 1 m d-1 and elevation increases of up to 100 m. The even smaller glacier NN9 changed from a slow advance to a full surge within a year, reaching advance rates higher than 1 km y-1, but showing the typical surface lowering higher up only recently. It seems that, despite a similar climatic setting, different surge mechanisms are at play in this region and that the surge mechanisms can change in the course of a single surge. 

On topic (2) we found that sensor performance is dependent on glacier characteristics (size, flow velocity, amplitude of changes). In particular velocities derived from Sentinel-1 performed poorly on small, narrow glaciers in steep environment. The comparison of elevation changes revealed that all considered DEMs have a sufficient accuracy to detect the mass transfer during the surges and that elevations from ICESat-2 ATL06 data fit neatly. 

How to cite: Paul, F., Piermattei, L., Treichler, D., Gilbert, L., Girod, L., Kääb, A., Libert, L., Nagler, T., Strozzi, T., and Wuite, J.: Three different glacier surges at a spot: What satellites observe and what not, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5932, https://doi.org/10.5194/egusphere-egu22-5932, 2022.

EGU22-6961 | Presentations | CR2.3

GravIS Portal: User-friendly Ice Mass Variations in Greenland and Antarctica from GRACE and GRACE-FO 

Ingo Sasgen, Eva Boergens, Christoph Dahle, Thorben Döhne, Andreas Groh, Henryk Dobslaw, Sven Reißland, and Frank Flechtner

The German Research Centre for Geosciences (GFZ), together with the Technische Universität Dresden and the Alfred-Wegener-Institute (AWI), maintains the ‘Gravity Information Service’ portal (GravIS, gravis.gfz-potsdam.de). GravIS facilitates the dissemination of user-friendly data of mass variations in the Earth system, based on observations of the GFZ and NASA/JPL satellite gravimetry mission GRACE (Gravity Recovery and Climate Experiment, 2002-2017) and its successor mission GRACE-FO (GRACE-Follow-On, since 2018).

The portal provides mass changes of the Greenland and Antarctic ice sheets on a regular 50 km by 50 km Polar stereographic grid and as basin averages accompanied by empirical uncertainties. Both ice mass balance products rely on the same input data of GRACE/GRACE-FO spherical harmonic coefficients, generated and post-processed by GFZ. Corrections applied to the data include the insertion of estimates of the geocentre motion, replacement of the C20 and C30 coefficients, and the correction for glacial isostatic adjustment with the ICE-6G model.

The gridded data product is processed with sensitivity kernels, tailored explicitly to resolving mass changes of the ice sheets. A regional integration applies these sensitivity kernels to the unfiltered GRACE and GRACE-FO spherical harmonic coefficients. The sensitivity kernels optimise a trade-off between leakage errors and propagated GRACE solution errors.

The basin-average product consists of continent-wide estimates of ice sheet mass changes, and basin averages for seven basins in Greenland and 25 basins in Antarctica. The regional time series are calculated using a forward-modelling  inversion approach, which considers the typical spatial anomalies of the surface-mass balance and dynamic ice discharge.

In addition to the ice mass change data, GravIS provides terrestrial water storage (TWS) variations over the continents and ocean bottom pressure (OBP) variations from which global mean barystatic sea-level rise can be estimated. These data sets are provided either on 1° grids or as regional averages.

The data sets of all Earth system domains can be interactively displayed with the portal and are freely available for download. This contribution aims to show the features and possibilities of the GravIS portal to cryosphere researchers.

How to cite: Sasgen, I., Boergens, E., Dahle, C., Döhne, T., Groh, A., Dobslaw, H., Reißland, S., and Flechtner, F.: GravIS Portal: User-friendly Ice Mass Variations in Greenland and Antarctica from GRACE and GRACE-FO, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6961, https://doi.org/10.5194/egusphere-egu22-6961, 2022.

EGU22-7013 | Presentations | CR2.3

A comparison of Backscatter Intensity of Icebergs in C- and L-band SAR Imagery 

Laust Færch, Wolfgang Dierking, Anthony P. Doulgeris, and Nick Hughes

Images from satellite Synthetic Aperture Radar (SAR) systems are widely used for iceberg monitoring. Normally, icebergs are detected in SAR images by utilizing constant false alarm rate (CFAR) filters, which compare each pixel or cluster of pixels against its background and adaptively set a threshold based on several assumptions regarding the statistical distribution of the background clutter. CFAR algorithms are currently being applied on images from the C-band SAR Sentinel-1 and RADARSAT missions by the operational ice services responsible for Canadian and Greenland waters. Previous studies have shown that imagery from wide-swath C-band SAR is unsuitable for detecting icebergs surrounded by sea ice, but other studies have indicated that icebergs in sea ice may be detected in high-resolution L-band SAR images. Additionally, it is well known that L-band SAR is less sensitive to sea surface roughness than C-band SAR. Therefore, a future operational L-band SAR mission is currently being investigated by the European Space Agency (ESA) since it is expected that L-band images are valuable complements to current C-band imagery for iceberg detection in areas with drift ice and in rough windy seas.

In this project, we investigate the backscatter intensity contrast between icebergs and their surroundings using ALOS-2 PALSAR-2 (L-band) ScanSAR, and Sentinel-1 (C-band) extra wide swath imagery. The investigations are concentrated on SAR images from two test sites, one in the Labrador Sea, where we – for further analysis - identified 256 icebergs in open water, and another site in the region of Belgica Bank with 1013 icebergs embedded in fast ice. The investigation shows that the two SAR sensors performed similarly for the open water site, with a backscatter intensity contrast between icebergs and the background of 5-6 dB in both the HH and HV band.  But for icebergs surrounded by sea ice, the contrast between icebergs and background at both C- and L-band is greatly reduced to around 2 dB for the HH channel and 4-5 dB for the HV channel.  By further manually classifying the sea ice types around the icebergs, we show that the backscatter contrast between icebergs and background is similar at C- and L-band for icebergs embedded in smooth sea ice. However, for rough sea ice, the C-band contrast is decreasing, while remaining high at L-band. Our results indicate that L-band data will lead to better performance for detecting icebergs surrounded by sea ice.

How to cite: Færch, L., Dierking, W., Doulgeris, A. P., and Hughes, N.: A comparison of Backscatter Intensity of Icebergs in C- and L-band SAR Imagery, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7013, https://doi.org/10.5194/egusphere-egu22-7013, 2022.

EGU22-7452 | Presentations | CR2.3

Landsat-1 mosaic of Antarctica from the 1970s 

Bertie Miles and Rob Bingham

The Landsat-1 satellite provides sporadic coverage of coastal Antarctica between 1972 and 1975.  This dataset is a highly valuable scientific resource but has yet to be utilized to its full potential. The imagery are of reasonable quality and have a spatial resolution of 60 m, but are often difficult to process owing to their poor geolocation accuracy, where most images are displaced by >10 km. This requires a time-consuming manual correction which can be especially tricky over the featureless sections of the ice sheet (e.g. Ross Ice Shelf). Here we report on progress towards creating a geolocated mosaic over coastal Antarctica that preliminary analysis indicates will have near-complete coverage with only limited cloud cover. Potential glaciological uses for the mosaic include coastline change both in terms of fast flowing outlet glaciers and the slower flowing regions of the coastline, ice shelf damage, basal channel evolution and migration, changes in ice rises and also any changes in bedrock exposure. We highlight these potential uses with a few small-scale examples.

How to cite: Miles, B. and Bingham, R.: Landsat-1 mosaic of Antarctica from the 1970s, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7452, https://doi.org/10.5194/egusphere-egu22-7452, 2022.

EGU22-7584 | Presentations | CR2.3

Sea ice characterization from combined passive microwave, scatterometers and altimeters observation and radiative transfer modelling. 

Clément Soriot, Catherine Prigent, Frédéric Frappart, and Ghislain Picard

The Copernicus Imaging Microwave Radiometer (CIMR) [Kilic et al. 2018] is a wide-swath conically-scanning multi-frequency microwave radiometer from 1.4 to 36 GHz. It will to provide a wide range of sea-ice information, including sea ice concentration, thin sea ice thickness and snow depth over sea ice. 
The Copernicus Polar Ice and Snow Topography Altimeter (CRISTAL) [Kern et al. 2020] will carry a multi-frequency radar altimeter and microwave radiometer to monitor sea ice thickness and overlying snow depth. Both missions are Copernicus high priority to respond to the Integrated European Union Policy for the Arctic. At the same time, MetOp-SG will carry the ASCAT instrument, that shows sensitivity to sea ice properties, especially the ice type.
Here, we propose to analyze the potential synergies of these instruments, using existing observations with similar characteristics (although less optimal). 

The combination of AMSR2 and SMAP can mimic CIMR, SARAL and Sentinel-3 are proxies for CRISTAL, and ASCAT is already available on MetOp-A and -B. A data set of coincident AMSR2, SMAP, SARAL, Sentinel-3 and ASCAT observations is constructed, over the Poles, over a year. It includes both the Level 1 and Level 2 products. We concentrate first on the study of the complementarity between the observations, at Level 1. It has been previously shown that the exploitation of the observation synergy at Level 1 is more efficient than a posteriori combinations of products, independently estimated from different instruments [Aires 2011]. Then, in order to analyze results of this database, the Snow Microwave Radiometric Transfer (SMRT) [Picard et al. 2018] model is used.  It is an up-to-date radiative transfer model that is tailored to handle snow and sea ice in a plane-parallel configuration, and it can simulate both passive and active microwave responses.

A first study [Soriot et al. 2021] has shown that the use of CIMR-like data with the SMRT model can explain temporal and spatial distribution of microwave signatures over the whole North Pole during all year long. From this interpretation, a realistic characterization of the sea ice and its snow cover has been provided. Correlation and causalities, between microwave signatures and geophysical properties (such as sea ice type, sea ice thickness, snow depth or snow microstructure), have been classified. 

Here, we extend this study to the Austral Ocean and to altimetric data, southern sea ice being more covered by current altimeters than northern sea ice.
Both height and radiometric signals are exploited from the altimeters, using a unique dataset altimetric points space-time colocated. 
Recent developments in SMRT have made it able to simulate altimetric signal [Larue et al. 2021, Sandells et al. 2021], and are used to interpret CRISTAL-like data. Synergies between CIMR-like and CRISTAL-like data are highlighted for an improved sea ice and snow characterization.

How to cite: Soriot, C., Prigent, C., Frappart, F., and Picard, G.: Sea ice characterization from combined passive microwave, scatterometers and altimeters observation and radiative transfer modelling., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7584, https://doi.org/10.5194/egusphere-egu22-7584, 2022.

EGU22-7646 | Presentations | CR2.3

Impact of satellite image pairs selection when deriving ice velocities trends 

Paul Halas, Jeremie Mouginot, Basile de Fleurian, and Petra Langebroek

When assessing ice velocity trends in Greenland, optical feature-tracking has previously been used to derive one-year velocity averages. Indeed, this technique requires pairs of images separated by approximately one year, and usually all possible pairs are used in order to achieve the best spatial coverage for every year. But this implies averaging pairs that start at different time in the year, and it is common to also use pair of images that are separated by shorter or longer time (ranging from 336 days up to 400 days between images).

Since ice velocities display strong seasonal variations, we argue that combining all pairs may impact the yearly ice velocities estimations by sampling differently summer and winter velocities, and therefore impacting the long-term trends.

Here we assess this impact by reproducing the work done from previous studies (Tedstone et al. 2015, Williams et al. 2020) using optical feature-tracking on Landsat-5, 7 and 8 as well as Sentinel-2 constellation, focusing on land-terminating parts of the Southwest of Greenland Ice sheet, and by comparing obtained velocity trend maps with trends of the same area obtained when operating a precise selection of the data.

 

How to cite: Halas, P., Mouginot, J., de Fleurian, B., and Langebroek, P.: Impact of satellite image pairs selection when deriving ice velocities trends, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7646, https://doi.org/10.5194/egusphere-egu22-7646, 2022.

EGU22-7677 | Presentations | CR2.3

Monitoring of Key Climate Variables on Glaciers and Ice Sheets using Sentinel-1 SAR 

Jan Wuite, Thomas Nagler, Markus Hetzenecker, Ludivine Libert, Stefan Scheiblauer, and Helmut Rott

The limited availability of Synthetic Aperture Radar (SAR) data over glaciers and ice sheets in the past, which formed a major obstacle for obtaining consistent climate data records, has been overcome by the Copernicus Sentinel-1 (S-1) mission, launched in 2014. S-1 SAR data in Greenland, Antarctica and other polar regions have since been regularly acquired every 6 to 12 days, allowing for the operational monitoring and time series analysis of key climate variables at a high spatial and temporal resolution. Exploiting the extensive archive of S-1 acquisitions, we have developed algorithms for retrieving dense time series of glacier and ice sheet velocities, ice discharge and surface melt processes, facilitated by the ESA Climate Change Initiative (ESA CCI), ESA Polar Science Cluster (ESA POLAR+) and EU Copernicus Climate Change Service (C3S) programs.

In order to improve existing ice velocity products, we have implemented an InSAR processing line for generation of high-resolution velocity fields from crossing orbits and included a tide correction module to the offset-tracking processing line which accounts for the vertical motion of floating ice shelves and ice tongues due to ocean tides and pressure differences. We present synergistic InSAR and offset tracking ice velocity products, derived from repeat pass S-1 Interferometric Wide (IW mode) swath data, for the Greenland Ice Sheet and report on the performance of the products using in-situ GPS data. Additionally, we show velocity variations of major outlet glaciers in Greenland and Antarctica and other polar ice bodies. The generated ice velocity maps, complemented with ice thickness and other Earth observation datasets, form the basis for deriving ice flow and discharge fluctuations and trends at sub-monthly to multi-annual time scales.

To evaluate snowmelt dynamics in Greenland and Antarctica, we have also developed an algorithm for generating maps of snowmelt extent based on multitemporal S-1 SAR and Advanced Scatterometer (ASCAT) data. The dense backscatter time series yields a unique temporal signature that is used to identify the different stages of the melt/freeze cycle and to estimate the melting intensity of the surface snowpack. The high-resolution melt maps form the main input for deriving value-added products on annual melt onset, ending and duration. Intercomparisons with in-situ weather station data and melt products derived from regional climate models (RCMs) and passive microwave radiometers confirm the ability of the algorithm to detect short-lived and longer melt events.

Our results demonstrate the excellent capability of the S-1 mission in combination with other sensors for comprehensive monitoring of key climate variables on glaciers and ice sheets, providing essential input for various applications such as ice dynamic and climate modelling.

How to cite: Wuite, J., Nagler, T., Hetzenecker, M., Libert, L., Scheiblauer, S., and Rott, H.: Monitoring of Key Climate Variables on Glaciers and Ice Sheets using Sentinel-1 SAR, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7677, https://doi.org/10.5194/egusphere-egu22-7677, 2022.

EGU22-8267 | Presentations | CR2.3

Unsupervised detection and quantification of iceberg populations within sea ice from dual-polarisation SAR imagery 

Ben Evans, Andrew Fleming, Anita Faul, Scott Hosking, Jan Lieser, and Maria Fox

Accurate estimates of iceberg populations, disintegration rates and iceberg movements are essential to fully understand ice sheet contributions to sea level rise and freshwater and heat balances. Understanding and prediction of iceberg distributions is also of paramount importance for the safety of commercial and research shipping operations in polar seas. Despite their manifold implications the operational monitoring of icebergs remains challenging, largely due to difficulties in automating their detection at scale.  

Synthetic Aperture Radar (SAR) data from satellites, by virtue of its ability to penetrate cloud cover and strong sensitivity to the dielectric properties of the reflecting surface, has long been recognised as providing great potential for the identification of icebergs. Many existing studies have developed algorithms to exploit this data source but the majority are designed for open water situations, require significant operator input, and are susceptible to the substantial spatial and temporal variability in backscatter characteristics within and between SAR scenes that result from meteorological, geometric and instrumental differences. Further ambiguity arises when detecting icebergs in dense fields close to the calving front and in the presence of sea ice. For detection to be fully automated, therefore, adaptive iceberg detection algorithms are required, of which few currently exist. 

Here we propose an unsupervised classification procedure based on a recursive implementation of a Dirichlet Process Mixture Model that is robust to inter-scene variability and is capable of identifying icebergs even within complex environments containing mixtures of open water, sea ice and icebergs of various sizess. The method exploits freely available dual-polarisation Sentinel 1 EW imagery, allowing for wide spatial coverage at a high temporal density and providing scope for near-real-time monitoring.  It overcomes many of the limitations of existing approaches in terms of environments to which it may be applied as well as requirements for labelled training datasets or determination of scene-specific thresholds. Thus it provides an excellent basis for operational monitoring and tracking of iceberg populations at a continental scale to inform both scientific and navigational priorities. 

How to cite: Evans, B., Fleming, A., Faul, A., Hosking, S., Lieser, J., and Fox, M.: Unsupervised detection and quantification of iceberg populations within sea ice from dual-polarisation SAR imagery, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8267, https://doi.org/10.5194/egusphere-egu22-8267, 2022.

EGU22-9837 | Presentations | CR2.3

Monitoring ice-calving at the Astrolabe glacier (Antarctica) with seismological and optical satellite 

Floriane Provost, Dimitri Zigone, Jean-Philippe Malet, Emmanuel Le Meur, and Clément Hibert

Better understanding the behaviour of tidewater outlet glaciers fringing marine ice sheets is of paramount importance to simulate Antarctica‘s future response to global warming. Addressing the processes underlying these glaciers dynamics (ice motion, crack propagation, basal melting, sea ice interaction, calving events, etc) is a mean of constraining their ice discharge to the sea and hence the ice sheet global mass balance. We here focus on the Astrolable glacier located in Terre Adélie (140°E, 67°S) near the Dumont d'Urville French research station. In January 2019, a large crack of around 3km length was observed in the western shore of the glacier potentially leading to a calving of ca. 28 km2.The fissure has progressively grown until November 2021 when an iceberg of 20km2 was eventually released. 

The location of the glacier outlet at the proximity of the Dumont DUrville French research station is an asset to collect in-situ observations such as GNSS surveys and seismic monitoring. Satellite optical imagery also provides numerous acquisitions from the early nineties till the end of 2021 thanks to the Landsat and Sentinel-2 missions. We used two monitoring techniques: optical remote sensing and seismology to analyze changes in the activity of the glacier outlet. We computed the displacement of the ice surface with MPIC-OPT-ICE service available on the ESA Geohazards Exploitation Platform (GEP) and derived the velocity and strain rates from the archive of multispectral Sentinel-2 imagery from 2017 to the end of 2021. The images of the Landsat mission are used to map the limit of the ice front in order to retrieve the calving cycle of the Astrolabe. We observe that the ice front had significantly advanced toward the sea (4 km) since September 2016 and such an extension has not been observed in the previous years (since 2006) despite minor calving episodes.

The joint analysis of the seismological data and the velocity and strain maps are discussed with the recent evolution of the glacier outlet. The strain maps show complex patterns of extension and compression areas. The number of calving events detected in the seismological dataset significantly increased during 2016-2021 in comparison with the period 2012-2016. Since the beginning of 2021, both datasets show an acceleration. The number of calving events increased exponentially from June 2021 until the rupture in November 2021 and the velocity of the ice surface accelerated from 1 m.day-1 to 4 m.day-1 in the part of the glacier that detached afterward. This calving event is the first one of this magnitude ever documented over the Astrolabe glacier.

How to cite: Provost, F., Zigone, D., Malet, J.-P., Le Meur, E., and Hibert, C.: Monitoring ice-calving at the Astrolabe glacier (Antarctica) with seismological and optical satellite, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9837, https://doi.org/10.5194/egusphere-egu22-9837, 2022.

EGU22-10065 | Presentations | CR2.3

A Regional Mass Balance Assessment of the Northwest Sector of the Greenland Ice Sheet 

Inès Otosaka, Andrew Shepherd, Andreas Groh, Jeremie Mouginot, and Xavier Fettweis

About a third of Greenland’s total ice losses come from the Northwest sector, a sector that includes a large number of marine-terminating outlet glaciers, which have all experienced widespread retreat triggered by ocean-induced melting. Here, we measure changes in surface elevation in the Northwest sector of the Greenland Ice Sheet from CryoSat-2 between July 2010 and July 2021 and find that the surface has lowered at a rate of 21.9 ± 1.1 cm/yr on average over this period, with rapid thinning occurring at the ice sheet margins at a rate of 46.9 ± 5.9 cm/yr. We further compute mass change by combining our CryoSat-2 surface elevation change dataset with firn densities from a regional climate model, and we show that the Northwest sector lost 456 ± 5.7 Gt of ice between July 2010 and July 2021.

To evaluate our altimetry-based mass balance solution, we compare our solution to independent estimates derived from satellite gravimetry and the mass budget method. We show that our altimetry estimate is the least negative for the Northwest sector as a whole, in contrast, the mass budget method leads to the largest ice losses. However, when partitioning these three estimates into sub-regions of the Northwest sector, we show that the spatial pattern of differences between mass balance estimates is complex, suggesting that discrepancies between techniques do not solely originate from one single region or technique.

Thanks to the higher spatial resolution afforded by satellite altimetry retrievals and the mass budget method, we examine the mass balance of the Northwest sector within its 74 glacier basins and find that differences between the two techniques greater than 0.5 Gt/yr  are recorded in 19 basins, with the largest disagreement recorded at Steenstrup-Dietrichson and Kjer Gletscher.

Comparing altimetry, gravimetry and the mass budget estimates at different spatial scales is critical to isolate the differences between geodetic techniques as well as the drivers of these differences. Previous studies, such as the Ice Sheet Mass Balance Inter-comparison Exercise (IMBIE), have demonstrated that combining independent estimates of ice sheet mass balance can lead to greater certainty. Here, aggregating the altimetry, gravimetry and mass budget method estimates results in a rate of mass loss of 55.6 ± 1.5 Gt/yr for the Northwest sector between June 2010 and June 2019.

How to cite: Otosaka, I., Shepherd, A., Groh, A., Mouginot, J., and Fettweis, X.: A Regional Mass Balance Assessment of the Northwest Sector of the Greenland Ice Sheet, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10065, https://doi.org/10.5194/egusphere-egu22-10065, 2022.

EGU22-11674 | Presentations | CR2.3

Monitoring Frost Heave and Thaw Settlement of Permafrost Using Timeseries InSAR Measurements 

Yoon Taek Jung, Yeji Lee, and Sang-Eun Park

Due to large temperature variations between the summer and winter seasons the active layer of permafrost undergoes repetitive thawing and freezing, and the increase of global temperature has accelerated permafrost degradation related to surface deformation seasonally and annually. Repeated freezing and thawing causes frost heave and thaw settlement, which results in displacement in the activity layer of permafrost. This surface displacement is also associated with ground ice and soil moisture content, and these factors in permafrost region could be observed through timely-dense SAR data. In particular, since the revisit time of Sentinel-1 (C-band) is relatively dense, timeseries SAR interferometry could be useful tools for monitoring and mapping subsurface soil properties over such a wide area. In this study, since the degree of freezing and thawing is very different spatially and temporally, we propose the method to indirectly estimate the ground ice content of the freezing period and the moisture content of the thawing period by quantifying the displacement using timeseries InSAR measurements in the Lena-river floodplain, Siberia.

How to cite: Jung, Y. T., Lee, Y., and Park, S.-E.: Monitoring Frost Heave and Thaw Settlement of Permafrost Using Timeseries InSAR Measurements, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11674, https://doi.org/10.5194/egusphere-egu22-11674, 2022.

EGU22-11829 | Presentations | CR2.3

Mapping Arctic sea ice surface roughness with Multi-angle Imaging Spectro-radiometer. 

Thomas Johnson, Michel Tsamados, Jan-Peter Muller, and Julienne Stroeve

Surface roughness is a crucial parameter in climate and oceanographic studies, constraining momentum transfer between the atmosphere and ocean, providing preconditioning for summer melt pond extent, while also closely related to ice age and thickness. At a local scale, roughness in the form of ridges, hummocks, rafted ice can slow down and hinder safe transport on the ice as well as be a hazard for ice strengthened vessels and structures. High resolution roughness estimates from airborne laser measurements are limited in spatial and temporal coverage while pan-Arctic satellite roughness have remained elusive and do not extend over multi-decadal time-scales. The MISR (Multi-angle Imaging SpectroRadiometer) instrument acquires optical imagery from nine near-simultaneous camera view zenith angles sampling specular anisotropy, since 1999. Extending on previous work to model sea ice surface roughness from MISR angular reflectance signatures, a training dataset of cloud-free pixels and coincident roughness from coincident operation IceBridge (OIB) airborne laser data is generated. Surface roughness, defined as the standard deviation of the within-pixel lidar elevations to a best-fit plane, is modelled using several techniques and Support Vector Regression with a Radial Basis Function kernel selected. Hyperparameters are tuned using grid optimisation, model performance is assessed using blocked k-fold cross-validation. We present a derived sea ice roughness product at 1.1km resolution over the period of operation (April 2000 – 2020) and a corresponding time series analysis. To demonstrate the validity of the derived product, we first evaluate our roughness product against independent LiDAR characterisations of surface roughness consistent with our training data. We also evaluate our derived roughness product with known proxies of surface roughness on a pan-Arctic basis (AWISMOS CS2-SMOS sea ice thickness.) Both our instantaneous swaths and pan-Arctic monthly mosaics show considerable capacity in detecting newly formed smooth ice from polynyas, and detailed surface features such as ridges and leads.

How to cite: Johnson, T., Tsamados, M., Muller, J.-P., and Stroeve, J.: Mapping Arctic sea ice surface roughness with Multi-angle Imaging Spectro-radiometer., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11829, https://doi.org/10.5194/egusphere-egu22-11829, 2022.

EGU22-12059 | Presentations | CR2.3

Satellite investigations of glacial meltwater plumes 

Laura Edwards

Calving at marine terminating glaciers accounts for at least 40 % of mass loss from the Greenland ice sheet, the current largest land ice sea level rise (SLR) contributor. Research suggests that glacier meltwater plumes play an important role in glacier calving front retreat and so studying their extent (2D and 3D) and temporal and spatial variability is critical for estimating potential SLR.

This work presents the novel use of satellite synthetic aperture radar (SAR) to study glacial meltwater plume extent and compares this approach to the more standard use of cloud and light-limited multispectral data for observations of plume extent. SAR data have often been used in oceanography to isolate ocean fronts, large-scale upwelling and estuarine plumes but have not thus far been used for studying glacial meltwater plumes. A SAR intensity image is retrieved from the backscatter signal which is a function of wind, wave and current interactions on a water surface, therefore, any ocean or river features which modify these have the potential to be identified within the SAR image. Higher resolution SAR data have more recently become available providing the opportunity to study meltwater plumes which present as an upwelling in the glacier fjord or lake in front of the glacier.

An initial study location of Breiðamerkurjökull glacier and Jökulsárlón proglacial lake, in Iceland, was chosen for the study which will involve fieldwork in 2022 to allow 3D analysis of plumes. This location is logistically easier and less expensive than Greenland yet provides an ideal analogue for study of Greenland glacier meltwater plumes in fjord-ocean systems. This is due to the connection of Jökulsárlón glacial lake water with the North Atlantic Ocean via a channel through which all tidal and residual flows in and out of the lake occur (Brandon et al., 2017) much like a glacier-fjord system in Greenland. Breiðamerkurjökull glacier calving front terminates in Jökulsárlón just like a marine terminating glacier in Greenland terminates in a fjord. Here initial results from quantifying the 2D extent of surface plumes using SAR are presented. 

How to cite: Edwards, L.: Satellite investigations of glacial meltwater plumes, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12059, https://doi.org/10.5194/egusphere-egu22-12059, 2022.

EGU22-12244 | Presentations | CR2.3

Maximizing the use of remote sensing to quantify Greenland ice sheet runoff 

Louise Sandberg Sørensen and the 4DGreenland team

Our ability to monitor and quantify ice sheet runoff is essential for a better understanding of the hydrology of the Greenland Ice Sheet and its contribution to global sea-level rise in a future warming climate. The amount of liquid water at the surface of the Greenland Ice Sheet has particularly increased due to large regional warming that this region has experienced over the last decades.

Here, we present the initial results of monthly runoff estimates from the Watson drainage basin in West Greenland, developed within the 4DGreenland project. 4DGreenland is a 2-year project funded by  the European Space Agency (ESA), which is focused on quantifying and analyzing the dynamic variations in the hydrological components of the ice sheet, while maximizing the use of Earth Observation (EO) data. 

The basin scale runoff estimate is derived from adding each component of the hydrological cycle: We have used a Random Forest approach (Supervised Learning algorithm) to map supraglacial hydrology ice sheet wide from optical imagery, and used ICESat-2 derived lake bathymetry as calibration to derive storage volumes. To map meltwater we have developed algorithms for generating maps of surface melt extent from high-medium resolution C-band backscatter measurements, and Low resolution PMW data. The subglacial melt is inherently difficult to monitor. The melt produced by friction heat though is derived from a model run of an ice sheet model (Elmer/Ice) which is tuned to assimilate observed ice velocities. Lastly, we have further developed a firn model to quantify the amounf of the meltwater that is retained in the snow/firn column.

By adding these component we are able to present monthly estimated of runoff from the drainage basin, and specifically show how each of the hydrologically components change over time. 

How to cite: Sandberg Sørensen, L. and the 4DGreenland team: Maximizing the use of remote sensing to quantify Greenland ice sheet runoff, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12244, https://doi.org/10.5194/egusphere-egu22-12244, 2022.

EGU22-12419 | Presentations | CR2.3

Gap-filled snow cover fraction from Sentinel-1 and Sentinel-2 constellations 

Cemal Melih Tanis, Kari Luojus, Miriam Kosmale, Simon Gascoin, Gabriele Schwaizer, Markus Hetzenecker, Lina Zschenderlein, Michäel Ablain, and Joel Dorandeu

Copernicus Land Monitoring Service has recently launched a group of high-resolution snow cover products which are derived from Sentinel-1 and Sentinel-2 constellations. High- Resolution Snow and Ice Monitoring (HRSI) products include Fractional Snow Cover (FSC) from the Sentinel-2 constellation and Wet and Dry Snow (WDS) covering Europe and SAR Wet Snow (SWS) products for selected mountain regions derived from the Sentinel-1 constellation. The FSC and WDS products have gaps in the snow cover data due to cloud presence and the SWS product provides only information on the melting snow extent, but dry snow areas and snow-free areas cannot be discriminated by means of SAR data. In the same portfolio, we provide the daily cumulative Gap-filled Fractional Snow Cover (GFSC) product, which is a fusion of those three products. In this product, we gap-fill the FSC product using the wet snow presence detected by the SWS in the spatial domain. In the temporal domain, all recent data in the last 7 days are used for gap-filling by temporal composition. The product aims to have a complete snow cover map of Europe. 

The quality of the product is assessed using in-situ data and gap simulation, for the period of 09.2017 - 08.2018 for mountain ranges in the Pyrenees, Alps, Scandinavia , East Turkey and Corsica, covered by 34 Sentinel-2 tiles. In-situ snow depth information is converted to binary snow cover information using a snow depth threshold. For the gap simulation method, as first step, FSC products with observed snow information are selected. Then, an artificial cloud mask is overlaid on these products, and the gap-filling method is run to generate GFSC products. The resulting GFSC products are compared with the corresponding observed FSC products, considering them as reference data. This comparison shows the agreement between the FSC product and the gap-filling methods. For both comparison methods, FSC values in GFSC and FSC products are converted to binary snow cover information using an FSC threshold. Resulting binary snow cover information is used in contingency tables and performance metrics are calculated for the product and for different gap-filling methods. 

We have found that the gap-filling provides 5 times more pixels with snow cover information and the quality is fairly good. The comparison with in-situ data shows an accuracy over 88% in temporal gap-filling and precision over 87% in spatial gap-filling. The comparison of the gap simulated GFSC and the FSC products shows an accuracy over 97% in temporal gap-filling and precision over 83% in spatial gap-filling. Temporal gap-filling performance is consistent throughout the seasons, although it is less accurate in the accumulation season for the spatial gap-filling, which is expected as the wet snow algorithm is developed for the melting season conditions. The assessment shows that the methods are working well and 7 days old FSC, WDS and SWS data are still valid to fill the gaps in the data. 

How to cite: Tanis, C. M., Luojus, K., Kosmale, M., Gascoin, S., Schwaizer, G., Hetzenecker, M., Zschenderlein, L., Ablain, M., and Dorandeu, J.: Gap-filled snow cover fraction from Sentinel-1 and Sentinel-2 constellations, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12419, https://doi.org/10.5194/egusphere-egu22-12419, 2022.

EGU22-12911 | Presentations | CR2.3

Validation of Cloud Reduction Algorithms Over MODIS Snow Products on Andes Mountain 

Freddy Saavedra, Ana Hernandez, Daniela Gonzalez, Yael Aguirre, Valentina Contreras, Alexis Caro, and Carlos Romero

The Andes Mountains span a length of 7000 km and are important for sustaining regional water supplies in South America. Rivers flow from the west side of the Andes to the Pacific Ocean and are the main source of water supply for energy generation, irrigation, and drinking water. Snow variability across this region has not been studied in detail due to sparse and unevenly distributed instrumental climate data. The optical remote sensing approach has been developed as a great tool to avoid this limitation. However, cloud cover reduces the ability to use it in the northernmost and southernmost portions of the Andes and the winter and spring in the central part of the Andes. We tested the performance of temporal, spatial algorithms in consecutive and simultaneous steps over daily MODIS snow cover products (Aqua and Terra). We evaluated the cloud reduction (effectiveness) and accuracy using simulated experiments from MODIS data by selecting low cloud cover images (“truth”) and cover with artificial clouds, then we ran all the algorithms and tested them based on the “truth” dataset. On clear sky days, we include higher spatial remote sensing data (Landsat and Sentinel) and in-field data from UAV. The combination of Aqua and Terra reduced the cloud cover by 10-15% on a yearly scale. The temporal combination with previous and following days yielded a substantial improvement in cloud removal but is usually less effective for large-area cloud cover. Developing a new dataset with cloud reduction can help to increase the performance of the snowmelt runoff model and extend a large latitude range across the Andes Mountains to use optical remote sensing data for seasonal snow studies. The use of machine learning, fusion with other snow products (e.g. radar), and more intense use of UAVs point to the next research.

How to cite: Saavedra, F., Hernandez, A., Gonzalez, D., Aguirre, Y., Contreras, V., Caro, A., and Romero, C.: Validation of Cloud Reduction Algorithms Over MODIS Snow Products on Andes Mountain, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12911, https://doi.org/10.5194/egusphere-egu22-12911, 2022.

EGU22-993 | Presentations | HS6.4 | Highlight

Modeling future Snow Line Elevation dynamics in the Alps based on long remote sensing time-series 

Jonas Köhler, Andreas Dietz, and Claudia Kuenzer

The inter and intra-annual dynamics of seasonal snow are of key interest in the tourism-based economies of many Alpine regions as well as for millions of people in the adjacent European lowlands when it comes to freshwater supply and electricity generation. However, accurate snow observations over long periods of time and at large spatial scales are especially challenging in inaccessible mountainous areas. This can be overcome by using data from Earth Observation satellites, which have been constantly monitoring the Earth’s surface for almost 40 years. On a catchment basis, we derive the Snow Line Elevation (SLE) from Landsat data for the entire Alpine region and model the spatio-temporal dynamics in monthly time-series ranging from 1984 to today. Based on the historical observations we model future SLE dynamics comparing different uni-variate and multi-variate approaches and assess them for their ability to generate multi-year forecasts from EO-derived time series data. These forecasts can enable local and regional stakeholders to adapt to a potentially changing snow regime under climate change.

How to cite: Köhler, J., Dietz, A., and Kuenzer, C.: Modeling future Snow Line Elevation dynamics in the Alps based on long remote sensing time-series, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-993, https://doi.org/10.5194/egusphere-egu22-993, 2022.

Rationale: After the Tropical Rainfall Measuring Mission (TRMM) was successfully launched by NASA and JAXA in 1997, NASA released the first GPM-era global precipitation product (IMERG) in April 2014, aiming to obtain precipitation data with ultra-fine temporal and spatial resolution around the world. Examining the key precipitation data in different climatic areas influenced by the monsoon can effectively help users and algorithm developers maximise the accuracy and characteristics of new satellite remote sensing products. Objective: To this end, this study used the upper and middle Lancang River basin (UMLRB), a transnational river with complex climatic conditions, as the research area to explore the applicability and precipitation distribution of IMERG and TRMM, and evaluate their accuracy. Methods: In this study, various performance indexes were used to comprehensively evaluate the retrieval accuracy of IMERG and TRMM remote sensing precipitation data in UMLRB; these indexes can be divided into two categories according to the evaluation objectives. One type of indexes mainly evaluates the amplitude consistency of precipitation, and the other type of indexes is mainly used to evaluate the occurrence consistency of precipitation. Results: The results indicated that: (1) The temporal distribution of precipitation in different climatic regions was correctly detected by IMERG and TRMM in the UMLRB, and the dry and wet seasons in the climate transition zone were distinct. (2) IMERG and TRMM tended to overestimate moderate rain (1.0-20 mm/d) while underestimating heavy rain (20-50mm/d) and extreme precipitation (> 50mm/d). (3) In terms of the amplitude consistency of precipitation, the detection results of IMERG in the alpine climate zone were not completely consistent with those of TRMM, while those in the climate transition zone were consistent with TRMM. (4) The stronger the precipitation intensity, the worse the accuracy of IMERG and TRMM, especially between heavy rain (20-50 mm/d) and extreme precipitation (> 50mm/d). (5) The IMERG, which had greater application potential in complex climatic conditions, had higher accuracy than TRMM.” Conclusions/Recommendations: Therefore, before using remote sensing precipitation data to study watershed hydrometeorology in monsoon-affected areas, their seasonal distribution, precipitation intensity, and the type of remote sensing data should be carefully considered to verify their accuracy.

How to cite: Lu, C., Fang, G., Ye, J., and Yang, Z.: Accuracy assessment of IMERG and TRMM remote sensing precipitation data under the influence of monsoon over the upper and middle Lancang River basin, China, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2078, https://doi.org/10.5194/egusphere-egu22-2078, 2022.

Remotely sensed MODIS (Moderate Resolution Imaging Spectroradiometer) data and the NDSI (Normalized Difference Snow Index) based approach have been applied globally for snow cover mapping. However, this method displays severe omission errors in forested areas, due to the forest canopy shading of snow. In this study, we developed a new forest snow mapping algorithm based on MODIS reflectance data, time-lapse observations of forest snow, and a random forest model. We built a time-lapse camera network in the eastern Qilian Mountains in northwestern China to monitor the forest snow processes and obtain the ground truth data. The random forest (RF) model seems to be powerful in capturing the relationships between the MODIS surface reflectance bands and the forest snow presence. The presented approach significantly improved the accuracy of binary snow cover (BSC) mapping in forests. We evaluated the performance of the proposed algorithm with the traditional NDSI-based method. The results show that the new algorithm has a superior performance in forest BSC mapping, compared to the NDSI-based BSC. The proposed RF-BSC can retrieve ~70% of all real forest snow pixels, while the NDSI-BSC can only detect 8-14%. We further investigated the geographical influence (e.g. topography, forest coverage, and solar illumination) of the algorithm performance. This study suggests that the fusion of optical remote sensing data and ground-based observations using machine learning techniques has a great potential in improving the accuracy of land cover mapping.

How to cite: Dong, C. and Luo, J.: Development of a new forest snow mapping algorithm using MODIS data, machine learning and time-lapse photography, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3473, https://doi.org/10.5194/egusphere-egu22-3473, 2022.

EGU22-4520 | Presentations | HS6.4

Snow extend and snow change mapping with Sentinel-1 imaging using SVM 

Flora Weissgerber, Céline Monteil, and Alexandre Girard

Snow dynamics is a key parameter for the hydrological model predicting the river flow rate used in dam management. In the MORDOR model used by EDF, the information of the daily snow extent is an input to improve the flow prediction. This information is extracted from MODIS NDSI daily product. Due to cloud cover, this information can be lacking or imprecise for multiple consecutive days over one catchment, reducing the precision of the prediction.

The goal of this study is to detect the snow extent using SAR data, since it can acquire images through clouds. We focus over the Guil catchment in the French Alps. Sentinel-1 interferometric stacks from June 2018 to August 2019 are used for three different orbits.

Previous studies showed the capacity of the ratio between the current image and a reference image acquired in summer to detect wet snow [Nagler2016], or that the ratio between VH and VV could be linked to the height of snow [Lievens2019]. Interferometry has be shown capable to detect snow since the snow covered area can exhibit a lower coherence [Singh2008].

To compare these parameters using a ground truth, we projected the MODIS NDSI data on our S1-stack using a 1m DEM and considered pixels as snowy if the NDSI is above 0.4.

As pointed in other studies [Löw2002, Wang2015], it is very hard to set a threshold for these parameters, mostly because the vegetation exhibits volume scattering and changes the same way as snow. Using SVM, we investigated the capability of these parameters to detect snow in two setups:
- snow detection: the goal is to classify the pixels as snow or snow-free for all the image, using Nagler parameter in VV and VH, the ratio between VH and VV at each date and the polarimetric coherence at each date. For Nagler parameter, the reference image is the temporal average of the images over July and August 2018.
- change detection: the goal is to classify the pixels into 4 classes, snow-free to snow-free, snow to snow, snow-free to snow and snow to snow-free. Considering two consecutive images, this was done using the variation of the VV and VH ratio, the interferometric coherence between these images, and the ratio between the polarimetric coherences of the images.
For each setup, the learning and the testing were done on two samples of 20000 randomly selected pixels, equally distributed between the classes.

For the snow detection method, between 54% and 59% of the pixels are correctly classified, for the three orbits. This result is stable with the choice of the learning sample. For the change detection setup only 30% of the pixels are correctly classified. Moreover, the per-class metrics vary widely from one experience to the other. This variability as well as the low classification results underline the difficulty of the task but can also be linked to the resolution difference between MODIS used as ground truth and S1. To robustify the detection, spatial and temporal regularization seems necessary.

How to cite: Weissgerber, F., Monteil, C., and Girard, A.: Snow extend and snow change mapping with Sentinel-1 imaging using SVM, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4520, https://doi.org/10.5194/egusphere-egu22-4520, 2022.

EGU22-5117 | Presentations | HS6.4

Development of a snow reanalysis pipeline using downscaled ERA5 data: application to Mediterranean mountains 

Laura Sourp, Simon Gascoin, Mohamed Wassim Baba, and César Deschamps-Berger

The Snow Water Equivalent (SWE) is a key variable to characterize water resource availability in mountain catchments. Despite its hydrological significance, the snow cover is poorly monitored in many regions due to a lack of in situ measurements. 

Global climate reanalysis products provide increasingly accurate data but are too coarse to be used directly in mountain regions to reconstruct snow related variables. However these reanalyses have been successfully used to generate high resolution meteorological forcing and run a snowpack model in the central Andes and the High Atlas mountain ranges (Mernild et al. 2017; Baba et al. 2018). 

The method is based on the MicroMet/SnowModel package (Liston and Elder 2006a; 2006b). MicroMet performs spatial interpolation of meteorological variables using the digital elevation model (downscaling) and the other routines of SnowModel computes the snowpack energy and mass balance. We have implemented a tool to improve the automation and scalability of this method to simulate the snow cover distribution in other regions using ERA5 or ERA5-Land. Our snow simulation tool only requires a digital elevation model as input. The land cover is extracted from the Copernicus global land cover map and the meteorological data are retrieved from either ERA5 or ERA5-Land over the period of interest.  

We used three catchments under the influence of Mediterranean climate to evaluate the performance of this tool: Tuolumne (USA), Bassies (France) and Yeso (Chile). For each catchment either the modeled SWE depth or snow depth are compared with the validation data, over periods going from 3 to 8 years.  In the Tuolumne basin, where the dataset is the most accurate with several SWE maps per year, we find a very good agreement at the basin scale (RMSE 40 mm w.e.). However, the mean RMSE in the highest elevation band (3500-4000 m asl) can exceed 500 mm w.e., which we attribute to the  lack of gravitational transport in SnowModel and errors in the spatial distribution of precipitation. To reduce these errors in particular, we are implementing a non-deterministic representation of the precipitation input data to eventually allow the assimilation of globally available remote sensing data. 

This tool will allow us to compute snow reanalyses in key mountain ranges around the Mediterranean sea over the past two decades (Pyrenees, Atlas and Mount Lebanon) and study the influence of topography and climate on the snow cover variability.

How to cite: Sourp, L., Gascoin, S., Baba, M. W., and Deschamps-Berger, C.: Development of a snow reanalysis pipeline using downscaled ERA5 data: application to Mediterranean mountains, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5117, https://doi.org/10.5194/egusphere-egu22-5117, 2022.

EGU22-7319 | Presentations | HS6.4

SnowPEx+: The International Snow Products Intercomparison and Evaluation Excercise 2015-2020 

Thomas Nagler and the SnowPEx Team

Satellite observations are the only means for timely and complete observations of the global snow cover. A range of different satellite snow products is available, the performance of which is of vital interest for the global user community. We provide an overview on goals and activities of the SnowPEx+ initiative, dedicated to the intercomparison of northern hemispheric and global satellite snow products, derived from data of long-term operational as well as recently launched satellites. SnowPEx+ is the continuation of SnowPEx (2014-2017), carried out as an international collaborative effort under the umbrella of Global Cryosphere Watch / WMO and funded by ESA.

SnowPEx+ focuses on two parameters of the seasonal snowpack, the snow extent (SE) from medium resolution optical satellite data (Sentinel-3, VIIRS, MODIS, AVHRR, etc.) and the snow water equivalent (SWE) from passive microwave satellite data. Overall, 15 hemispheric and global SE products (binary and fractional SE) and two SWE products are participating in the experiment. For intercomparison, daily SE products are transformed to a common map projection and standardized SnowPEx protocols are applied, elaborated by the international snow product community. The SE product evaluation applies statistical measures for quantifying the agreement between the various products, including the analysis of spatial patterns. Validation of SE products uses as benchmark high resolution snow maps from about 150 globally distributed Landsat scenes acquired in different climate zones, under different solar illumination conditions and over various land cover types. This snow reference data set, based on various retrieval algorithms, is generated and evaluated by the SnowPEx+ High Resolution Snow Products Focus Group. In-situ snow data from several organisations in Europe, North America and Asia are also used for validating the satellite SE and SWE products. SWE products are also inter-compared with gridded snow products from land surface models driven by atmospheric reanalysis data. In addition, the multi-year trends of the various SE and SWE products are evaluated. We provide an overview on the snow products, discuss the validation and intercomparison protocols, and report on preliminary results from the intercomparison and validation of various snow products.

How to cite: Nagler, T. and the SnowPEx Team: SnowPEx+: The International Snow Products Intercomparison and Evaluation Excercise 2015-2020, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7319, https://doi.org/10.5194/egusphere-egu22-7319, 2022.

EGU22-9744 | Presentations | HS6.4

Snow depth mapping over large, high-alpine regions by airplane photogrammetry 

Leon Bührle, Mauro Marty, Lucie Eberhard, Andreas Stoffel, and Yves Bühler

Abstract.

Snow depths are traditionally determined by point measurements at automatic weather stations or field observations, which cannot capture the complexity of snow depth distribution in alpine terrain. Therefore, remote sensing techniques have become key tools for spatially continuous snow depth mapping. Only satellites, airborne laser scanners (ALS) or photogrammetry from piloted aircrafts are capable of covering large regions of more than 100 km². However, the accuracy of satellite data does not match/achieve the requirements for exact snow depth mapping yet. In comparison to ALS, photogrammetric methods are considerably more economic, but have the disadvantages of light and weather dependence as well as the lacking ability to penetrate high vegetation. Nevertheless, previous studies of photogrammetric snow depth mapping on a large scale have already proven the accurate implementation, but those studies were either limited to only one recording or characterized by a spatial resolution of around 2 m. These properties limit the comparison of snow depth distribution and the analysis of small-scale features.

In our study we apply airborne imagery from the current state-of-the-art survey camera Vexcel Ultracam acquired during the annual peak of winter for the five years from 2017 to 2021 in an area of approximately 300 km2 around Davos, Switzerland. This enables the calculation of outstandingly improved annual snow depth maps. The high spatial resolution of the snow depth maps (0.5 m) in combination with the high-resolution orthophoto (0.25 m) enables the identification of small-scale snow depth features. Additionally, the development of masks for high-vegetated and settled areas in combination with the high accuracy of the unmasked snow depth values (root mean square error of around 0.15 m) represents a significant step forward for reliable snow depth mapping of large alpine regions with photogrammetric methods. Our study focuses on the consistent workflow used for processing the snow depth maps, demonstrates the special characteristics of the snow depth distribution and presents the potential for investigations and applications based on this unique snow depth time-series.

How to cite: Bührle, L., Marty, M., Eberhard, L., Stoffel, A., and Bühler, Y.: Snow depth mapping over large, high-alpine regions by airplane photogrammetry, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9744, https://doi.org/10.5194/egusphere-egu22-9744, 2022.

EGU22-9932 | Presentations | HS6.4

Fractional snow cover estimation through linear spectral unmixing of Sentinel-2 and Sentinel-3 optical satellite data using local endmembers 

Lars Keuris, Thomas Nagler, Nico Mölg, and Stefan Scheiblauer

Precise snow cover estimations are relevant for many fields of research applications, such as for hydrological and meteorological modelling. Furthermore, snow plays an important role in hydropower management and flood prediction. Snow cover monitoring from satellite imagery has received increasing attention over the past decades. Nowadays, improvements in estimation methodologies and better availability of augmented satellite imagery provide an excellent basis for reliable estimations of fractional snow cover.

In this work we exploit the available spectral information of the Sentinel-2 MSI and Sentinel-3 OLCI for automatic estimation of fractional snow coverage. This is achieved through linear spectral unmixing with local endmembers. Similar implementation of methods that employ spectral unmixing use a reflectance model or a spectral library with pre-selected endmembers. Our approach selects the spectral endmembers from the data itself and applies them depending on the distance from the query point assuming spectral similarities of ground reflectance nearby. Endmembers are found through a pre-classification step based on conservative thresholds in combination with a similarity measure. The linear unmixing problem is solved several times for each query point using different combinations of endmembers detected in the vicinity of the query point; accounting for different illumination conditions and shaded areas. Finally, a careful selection of accurate fractional snow cover estimations is performed. This approach is globally applicable, adjusts to the local environment and illumination conditions and avoids costly endmember modelling or the provision of an external spectral library. The method was tested in different regions in the world using different satellite data including Sentinel-2, Landsat and Sentinel-3 OLCI and were inter-compared with snow information from other sources. In the presentation we will present the method, and examples of fractional snow cover maps. The performance of the method will be shown in comparison with other data and the limitations and capabilities will be discussed.

How to cite: Keuris, L., Nagler, T., Mölg, N., and Scheiblauer, S.: Fractional snow cover estimation through linear spectral unmixing of Sentinel-2 and Sentinel-3 optical satellite data using local endmembers, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9932, https://doi.org/10.5194/egusphere-egu22-9932, 2022.

EGU22-10725 | Presentations | HS6.4 | Highlight

Global Snow Water Equivalent Observations from Space 

Ana Barros, Carrie Vuoyvich, Michael Durand, Leung Tsang, Paul Houser, and Hans-Peter Marshall

Global snow water equivalent (SWE) data are required for understanding the role of snow in the Earth’s water, energy and carbon cycles, and are critical for informing water resource and snow-related hazards. While exciting progress has been made in recent decades, there are currently no global SWE data at the required frequency, resolution and accuracy to address scientific and operational requirements. These data are needed to inform science and application areas and, taken as a whole, are critical to global water and food security. New higher-resolution microwave instruments can provide this information, especially when combined with modeling.  We now have the capability to put these instruments in space to monitor SWE and volume at the required resolution for improved and useful water prediction globally.  This presentation will describe the requirements of a spaceborne SWE mission, review progress in snow remote sensing technology and algorithms, and describe a potential path forward to meet identified snow data needs.

How to cite: Barros, A., Vuoyvich, C., Durand, M., Tsang, L., Houser, P., and Marshall, H.-P.: Global Snow Water Equivalent Observations from Space, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10725, https://doi.org/10.5194/egusphere-egu22-10725, 2022.

EGU22-11519 | Presentations | HS6.4

Synthesizing Daily Snow Cover Maps Using Satellite Images and Climate Information 

Fatemeh Zakeri and Gregoire Mariethoz

Daily snow cover is an essential parameter in hydrology, climate, and environmental studies. Although remote sensing images provide valuable information on snow, they are restricted by clouds, clouds’ shadows, and temporal and spatial coverage. This study synthesizes daily snow cover maps based on climate and near clear sky Sentinel-2 and Landsat images. The motivation of this study is that snow patterns are repeatable between years with similar meteorological characteristics. Accordingly, a distance metric based on climate information is computed, including temperature and precipitation (1km resolution) as well as auxiliary data such as daily MODIS snow cover. This distance quantifies the mismatch between the days when clear sky Landsat or Sentinel-2 data is available, learning days, and days when there is no clear sky satellite data or test days. The proposed methodology is applied on a subset of the Alpine belt called the Western Swiss Alps and on the Jonschwil sub-basin, both located in Switzerland. We have synthesized daily snow cover maps for each of our regions of interest for 20 years since 2000.

To evaluate synthesized snow cover maps, we use leave-one-out cross-validation, comparison with a random selection process, and a degree-day snow model. The leave-one-out assessment shows a good agreement between the actual Landsat and the synthesized one. The synthesized snow cover maps also show that the proposed method output agrees with physical concepts as the physical features have been used along with satellite data in the proposed model. Considering physical features in synthesizing Landsat images is an innovation that allows us to use the methodology to synthesize images for the pre-satellite period. Moreover, random selection assessment shows that considering a metric based on climate and auxiliary data can synthesize snow cover as repeatable patterns depending on meteorological data.

How to cite: Zakeri, F. and Mariethoz, G.: Synthesizing Daily Snow Cover Maps Using Satellite Images and Climate Information, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11519, https://doi.org/10.5194/egusphere-egu22-11519, 2022.

EGU22-12576 | Presentations | HS6.4 | Highlight

Climate change-driven seasonal snow cover variations in Central Asia 

Abror Gafurov, Olga Kalashnikova, Djafar Niyazov, Adkham Mamaraimov, Akmal Gafurov, and Uktam Adkhamov

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., Kalashnikova, O., Niyazov, D., Mamaraimov, A., Gafurov, A., and Adkhamov, U.: Climate change-driven seasonal snow cover variations in Central Asia, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12576, https://doi.org/10.5194/egusphere-egu22-12576, 2022.

EGU22-12801 | Presentations | HS6.4

Quantifying the role of mixed pixels in snow cover distribution in semiarid regions: A study case in Sierra Mountain (Spain) 

Rafael Pimentel, Javier Aparicio, Pedro Torralbo, Eva Contreras, Fátima Moreno-Pérez, Cristina Aguilar, and María José Polo

Observations worldwide identify snow cover persistence together with snowfall occurrence as the most affected variables by global warming. In particular, Mediterranean mountain areas are pointed as climate warming hotspots. The characteristic snow-patched distribution shown over these areas, which result in different accumulation-ablation cycles during the cold season, usually makes spatial resolution the limiting factor for its correct representation. Remote sensing is the only feasible data source for distributed quantification of snow in mountain regions on medium to large scales, due among other to the limited access to these areas together with the lack of dense ground monitoring stations for snow variables. Among the numerous remote sensing sources, the Landsat constellation is those that better fit both basic requirements for studying snow over these areas, to cover a long period with observation and to have an high spatial resolution. However, the traditional classification algorithms for snow detection are usually based on normalized indexes that  provide a binary classification as snow and no-snow pixels throughout the study area; this simple classification may result in large error in heterogeneous and transitional areas within the snow-dominated domain. Alternatively, the spectral mixture analysis (SMA) approach provides a fraction of snow cover within each pixel and thus, constitutes a step forward to characterize heterogeneous and patchy snow areas in semiarid regions. 

This work analysed the role of mixed pixels, defined as pixels made up of different types of surfaces, in snow cover distribution over Mediterranean mountains. Sierra Nevada Mountain Range in southern Spain has been chosen as representative of a Mediterranean mountain area, which is characterized by strong altitudinal gradients with marked differences between the south (directly affected to the sea) and the north faces are found in the area. The fractional snow cover maps, at 30×30 m and 16 days spatial and temporal resolution respectively, derived from SMA of Landsat TM and ETM+ validated using as high resolution terrestrial photography (Pimentel et al., 2017) has been used for mixed pixel analysis. On the one hand, the results show the importance of mixed pixels, which can constitute more than 50% of the total pixels in some areas of the mountainous range and season of the year. On the other hand, the analysis carried out has allowed the identification of areas more prone to allocate this type of pixels, linking that fact to climatic drivers. 

This work has been funded by project MONADA - "Hydrometeorological trends in mountainous protected areas in Andalusia: examples of co-development of climatic services for strategies of adaptation to climatic change", with the economic collaboration of the European Funding for Rural Development (FEDER) and the Andalusian Ministry of Economic Transformation, Industry, Knowledge and Universities. R+D+i project 2020.

How to cite: Pimentel, R., Aparicio, J., Torralbo, P., Contreras, E., Moreno-Pérez, F., Aguilar, C., and Polo, M. J.: Quantifying the role of mixed pixels in snow cover distribution in semiarid regions: A study case in Sierra Mountain (Spain), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12801, https://doi.org/10.5194/egusphere-egu22-12801, 2022.

EGU22-241 | Presentations | G3.2

Inferring Near-Surface Density and Surface Roughness from Satellite-Based Radar Altimetry over Greenland 

Kirk Michael Scanlan and Sebastian B. Simonsen

Estimates of mass balance across the Greenland Ice Sheet (GrIS) are commonly based on the joint interpretation of satellite radar altimetry measurements and the outputs of climate models. Conventional radar altimetry measurements, such as those produced by ESA’s CryoSat-2 platform, provide an observational constraint on the physical dimensions of the ice sheet (i.e., surface height), while climate models attempt to constrain relevant mass fluxes (i.e., precipitation, run-off, and evaporation/sublimation). However, this approach provides no direct observational insight into the large-scale state and temporal evolution of near-surface density across the ice sheet; a critical quantity through which surface deformation and mass flux estimates are linked to overall mass balance.

To date, the analysis of space-based radar altimetry measurements over the GrIS has been predominantly concerned with determining the range between the satellite and the surface as a means of quantifying changes in ice column thickness. While some studies have investigated the relative shape of the measured return echo, little attention has been paid to its actual recorded strength. Radar Statistical Reconnaissance (RSR), originally developed for use with radar reflections from the surface of Mars, provides a framework for the interpretation of backscattered surface echo powers and the quantitative estimation of near-surface properties. The RSR method relies on using the distribution of a set of observed echo strengths in order to determine their coherent and incoherent components. These decomposed reflection components are then assumed to be related to near-surface density (coherent) and wavelength-scale surface roughness (incoherent) respectively.

In this study, we present the first attempt to apply the RSR methodology to Ku-band (SIRAL; on-board ESA CryoSat-2) and Ka-band (ALtiKa; on-board ISRO/CNES SARAL) radar altimetry measurements acquired over the GrIS. In continual operation since July 2010 and March 2013 respectively, the longevity of these spacecraft along with their dense spatial coverage of the GrIS provides a tantalizing opportunity to produce long-term trends in near-surface density. Surface echo powers are extracted from recorded waveforms contained in CryoSat-2 SARin FBR data products as well as SARAL SGDR data products and organized by month. We focus on waveforms in the CryoSat-2 SARin FBR data products in lieu of those from LRM Level 1B data products in order to increase the spatial density of surface echo power measurements and therefore, the spatial resolution of the RSR results. Estimates of coherent and incoherent power are then produced on a month-by-month basis for a constant set of grid points (5 km by 5 km spacing) across the GrIS. We calibrate the coherent component of the CryoSat-2 and SARAL surface echoes to near-surface density using in situ measurements from the SUMup dataset.

This research into leveraging the radiometric information previously ignored in radar altimetry measurements to determine near-surface densities across the GrIS is a new frontier in Earth Observation. The capability to observationally determine near-surface density across the GrIS represents a fundamental contribution to refining surface mass balance estimates and understanding the evolution of the ice sheet in face of a changing climate.

How to cite: Scanlan, K. M. and Simonsen, S. B.: Inferring Near-Surface Density and Surface Roughness from Satellite-Based Radar Altimetry over Greenland, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-241, https://doi.org/10.5194/egusphere-egu22-241, 2022.

EGU22-538 | Presentations | G3.2

Exploring Coastal Altimetry Datasets for Indonesian Seas in relation to Local Tide Gauges 

Zulfikar Adlan Nadzir, Luciana Fenoglio-Marc, Bernd Uebbing, and Jürgen Kusche

Satellite Altimetry has been continuously providing precise sea level for the last 28 years. However, the conventional altimetry is not at its best for the coast because it is hampered by mixed returns of electromagnetic waves due to disturbance from lands and inconsistencies of corrections. Since coastal regions are a vital part of human societies, improving methods to understand the coastal ocean topography, sea level, and its change is essential. In the last seven years alone, there are several specifically-designed coastal retracker that aimed to overcome the disturbance that occurred on the coasts. However, until now, there are only a few extensive studies have compared the accuracy and precision of retrackers and range corrections combination with regards to tide gauges on the coast of Indonesia. A region where the oceanographic condition and land and sea interaction is challenging, mainly due to the existence of shallow seas, narrow straits, and bays.

In this study, we compare sea level heights obtained using six processing schemes mostly dedicated to coastal areas. Three of them are for conventional altimetry (ALES, X-TRACK, and X-TRACK/ALES) and the other for SAR altimetry (STARS, SAMOSA++ in SARvatore and SINCS in TUDaBo). The first covers 20 years and corresponds to the repeat-track phase of Jason-1, Jason-2, and Jason-3. The second covers 10 years and corresponds to the SAR-mode measurements of Cryosat-2, Sentinel-3A/3B, and Sentinel-6. We apply similar state-of-the-art corrections designed for coastal areas.

On the other hand, a set of Indonesian tide gauge stations are being evaluated and selected in terms of their time series and their relationship with the GNSS station near it, identifying the effect of vertical land motion. Those tide gauges are considered as reference and used to assess which combination of retrackers and range corrections provide the sea level height which best agrees with in-situ data.

The results will have implications for understanding the goodness of altimetry processing schemes and of the corrections in the coastal zone, at less than 10 km. Moreover, the result is also will be used to determine precise MDT and in turn, gravity anomaly of Indonesian seas.

How to cite: Nadzir, Z. A., Fenoglio-Marc, L., Uebbing, B., and Kusche, J.: Exploring Coastal Altimetry Datasets for Indonesian Seas in relation to Local Tide Gauges, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-538, https://doi.org/10.5194/egusphere-egu22-538, 2022.

EGU22-2834 | Presentations | G3.2

Increased variability in Greenland Ice Sheet runoff detected by CryoSat-2 satellite altimetry 

Thomas Slater, Andrew Shepherd, Malcolm McMillan, Amber Leeson, Lin Gilbert, Alan Muir, Peter Kuipers Munneke, Brice Noël, Xavier Fettweis, Michiel van den Broeke, and Kate Briggs

Runoff from the Greenland Ice Sheet has increased over recent decades affecting global sea level, regional ocean circulation, and coastal marine ecosystems. Runoff now accounts for most of Greenland’s contemporary mass imbalance, driving a decline in its net surface mass balance as the regional climate has warmed. Although automatic weather stations provide point measurements of surface mass balance components, and satellite observations have been used to monitor trends in the extent of surface melting, regional climate models have been the principal source of ice sheet wide estimates of runoff. To date however, the potential of satellite altimetry to directly monitor ice sheet surface mass balance has yet to be exploited. Here, we explore the feasibility of measuring ice sheet surface mass balance from space by using CryoSat-2 satellite altimetry to produce direct measurements of Greenland’s runoff variability, based on seasonal changes in the ice sheet’s surface elevation. Between 2011 and 2020, Greenland’s ablation zone thinned on average by 1.4 ± 0.4 m each summer and thickened by 0.9 ± 0.4 m each winter. By adjusting for the steady-state divergence of ice, we estimate that runoff was 357 ± 58 Gt/yr on average – in close agreement with regional climate model simulations (root mean square difference of 47 to 60 Gt/yr). As well as being 21 % higher between 2011 and 2020 than over the preceding three decades, runoff is now also 60 % more variable from year-to-year as a consequence of large-scale fluctuations in atmospheric circulation. In total, the ice sheet lost 3571 ± 182 Gt of ice through runoff over the 10-year survey period, with record-breaking losses of 527 ± 56 Gt/yr first in 2012 and then 496 ± 53 Gt/yr in 2019. Because this variability is not captured in global climate model simulations, our satellite record of runoff should help to refine them and improve confidence in their projections.

How to cite: Slater, T., Shepherd, A., McMillan, M., Leeson, A., Gilbert, L., Muir, A., Kuipers Munneke, P., Noël, B., Fettweis, X., van den Broeke, M., and Briggs, K.: Increased variability in Greenland Ice Sheet runoff detected by CryoSat-2 satellite altimetry, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2834, https://doi.org/10.5194/egusphere-egu22-2834, 2022.

Measuring river water level is essential for the global freshwater system monitoring, water resource management, hydrological model development, and climate change assessment. Despite its importance, the number of in-situ gauges has decreased over the recent decades. Moreover, many of the river systems are monitored either sparsely or not long enough to investigate their long-term evolution. Satellite altimetry is a unique technique that has enabled quantifying river levels for more than 25 years. Single mission altimetric water level time series can be obtained at the intersection of the satellite ground tracks and the river. For operational hydrology, however, single mission satellite altimetry is limited in its spatial and temporal sampling governed by the orbit configuration. This study proposes a framework to estimate the long-term sub-monthly river water level over the entire river using Least-Squares Collocation (LSC) by benefiting from multi-mission altimetric water levels (both interleaved and repeat orbit missions). The proposed method allows us to obtain dense water level observations both in time and space.  We present the results over the Mackenzie River basin, located in Canada, and validate against in-situ data.

How to cite: Saemian, P., Tourian, M. J., and Sneeuw, N.: A least-squares collocation approach to densifying river level from multi-mission satellite altimetry; Case study Mackenzie River basin, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3699, https://doi.org/10.5194/egusphere-egu22-3699, 2022.

EGU22-4221 | Presentations | G3.2

Influence of environmental factors on the accuracy of the Sentinel-3A altimetry over Polish rivers 

Michał Halicki and Tomasz Niedzielski

Satellite altimetry is a technique of measuring height. Originally developed to observe sea level dynamics, altimetry has proven its usefulness in monitoring inland waters. Over the recent years these observations became an important supplement to the classical river gauge records. Due to the improvement of the accuracy of altimetric measurements, river water levels are being used in numerous hydrological projects, aiming to calculate water storage or to predict water levels and river discharges. Despite the improving quality of altimetric data, the accuracy of river stage measurements is still in the decimetre range, an order of magnitude lower than altimetry-based sea level observations. This is due to several factors that can lead to the deterioration of altimeter readings.

Our study is the first attempt to assess the accuracy of water levels measured by the Sentinel-3A altimetry at virtual stations (intersections of a satellite ground tracks and a river channel, hereinafter abbreviated as VS) located along Polish rivers. Further, this study aims to investigate the influence of the environmental factors on the data accuracy. The study is conducted on six biggest Polish rivers (Vistula, Odra, Warta, Bug, Narew, San) which drain predominantly lowlands, and – based on width – can be classified as small and medium rivers (40–610 m in width).

In order to assess the accuracy of measurements at virtual sites, we compare water level anomalies of these readings with stages from two adjacent gauges: one downstream and one upstream a VS. In this study we used Sentinel-3A water levels from the Hydroweb database (http://hydroweb.theia-land.fr/ – last access 09.01.2022). The time span of gauge and altimetry data ranges from April 2016 to August 2019. Since the virtual sites are located up to 73 km away from the adjacent gauges (with mean distance of 20.12 km), we decided to calculate the time shift occurring between the analysed stations. Such a unification of times is based on a two-gauge relationship, calculated for each of the satellite measurements.

We found that the root mean square error ranges from 0.12 to 0.44 m, with mean of 0.22 m. The Nash–Sutcliffe efficiency (NSE) varies between 0.40 and 0.98 (with mean of 0.84) for 67 pairs of time series, out of 68 considered. We found no correlation between the accuracy of Sentinel-3A water levels and the river width, neither for the small nor medium river sections. Likewise, land cover (determined using the Corine Land Cover 2018 data) has not been identified as an environmental factor to constrain the data accuracy. However, we found that complex river channel morphology (i.e. the occurrence of sandbars) and the unfavourable geographical setting of the VS (river channel parallel to satellite ground track or its multiple crossing) occur more often at VS with lower NSE (⩽0.8).

This study confirms the usability of the Sentinel-3A altimetry over Polish rivers and identifies factors to constrain its accuracy. The research is supported by the National Science Centre, Poland, through the project no. 2020/38/E/ST10/00295. Our results were recently published in Journal of Hydrology (https://doi.org/10.1016/j.jhydrol.2021.127355).

How to cite: Halicki, M. and Niedzielski, T.: Influence of environmental factors on the accuracy of the Sentinel-3A altimetry over Polish rivers, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4221, https://doi.org/10.5194/egusphere-egu22-4221, 2022.

EGU22-4946 | Presentations | G3.2

Systematic errors in Cryosat-2 swath elevations and their impacts on glacier mass balance estimates 

Jan Haacker, Bert Wouters, and Cornelis Slobbe

Almost ten years ago, the first elevation estimates based on swath processing of interferometric CryoSat-2 altimeter observations were published, mapping the surface of Devon ice cap. The new method holds a great potential to provide dense data coverage, in space and time. Indeed, ESA recently started releasing digital elevation models at a 2 by 2 km resolution for a rolling 3 month data aggregation cycle. Such spatiotemporal resolutions are especially valuable in versatile and dynamic regions as mountain glaciers. In this presentation, we describe systematic errors on the order of 10 m with about yearly periodicity that arise in the proximity of hills and valleys. One error is caused by the superposition of multiple signals, the other is caused by the Fourier-transformation in the SAR beam-forming process. Both are intrinsic to the measuring concept, but their effect can potentially be limited by data filtering strategies. We report the influence of the commonly used coherence and power threshold based filtering on derived elevation change rates. For data users, awareness of these issues is especially important to interpret the observations correctly and to understand that there is a large systematic part in the overall uncertainty.

How to cite: Haacker, J., Wouters, B., and Slobbe, C.: Systematic errors in Cryosat-2 swath elevations and their impacts on glacier mass balance estimates, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4946, https://doi.org/10.5194/egusphere-egu22-4946, 2022.

EGU22-7598 | Presentations | G3.2

Validation of conventional and retracked Sentinel-3 observations along the Norwegian coast 

Matea Tomic, Gholamreza Joodaki, Kristian Breili, Christian Gerlach, and Vegard Ophaug

Satellite altimetry is one of the fundamental techniques for Earth observation, which provides precise measurements with frequent sampling and global coverage. However, its performance is degraded in coastal areas due to different factors, such as land contamination, erroneous tropospheric corrections or complex tidal patterns. In order to improve performance of satellite altimetry in the coastal zones, an increasing number of dedicated coastal altimetry products have been developed and validated in specific areas in later years. Those products are based on the improved analysis of backscattered signals in order to increase accuracy of altimetry observations in the coastal zones. One such product is the Adaptive Leading Edge Subwaveform (ALES) retracker, specifically aimed at the issue of land contamination. As of yet, it has not been validated along the whole, complex Norwegian coastline, with thousands of small islands, narrow fjords, and rough topography.  Thus, this study aims to validate the ALES retracker along the Norwegian coast, comparing conventional and ALES-retracked Sentinel-3 A/B observations with tide gauge observations. Altimetry-tide gauge comparison pairs are found by considering altimetry observations within optimum radii around each tide gauge, determined by minimizing the root mean square of differences (RMSD) for a range of candidate radii. It was found that the optimum radii for tide gauges located towards the open ocean are smaller than for those located inside fjords, because the observation accuracy degrades in the latter areas. Thus, it was necessary to increase radii, i.e. to include more points on the open-sea, for tide gauges inside fjords in order to minimize the RMSD. It was concluded that the ALES dataset generally gave better results (in terms of RMSD and correlation to the tide gauges) than conventional datasets, as well as giving a larger number of valid observations. The results are promising for future optimal combination of altimetry observations with other available sea-level observations in the coastal zone, e.g., from tide gauges, ships, unmanned surface vehicles (USVs) or airborne LiDAR. A prerequisite for such a combination is a reliable error description of each data type, to which the current study serves as a contribution. 

How to cite: Tomic, M., Joodaki, G., Breili, K., Gerlach, C., and Ophaug, V.: Validation of conventional and retracked Sentinel-3 observations along the Norwegian coast, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7598, https://doi.org/10.5194/egusphere-egu22-7598, 2022.

EGU22-10723 | Presentations | G3.2

Impact analysis of surface water level and discharge from the new generation of altimetry observations 

Luciana Fenoglio-Marc, Hakan Uyanik, Jiaming Chen, and Jürgen Kusche

Surface water level and river discharge are key observables of the water cycle and among the most sensible indicators that integrate long-term change within a river basin. Satellite altimetry provides valuable information on water level variation in rivers, lakes and reservoirs and once combined with satellite imagery, river discharge and lake storage changes can be estimated. Over the last decade, a two-dimensional observational field is derived by merging innovative space and in-situ data. The new generation of spaceborne altimeters includes Delay Doppler since 2010 with CryoSat-2, laser technique since 2018 with ICESAT-2 and bistatic SAR altimeter techniques with SWOT planned to be launched late this year. This shows a potential for monitoring the impact of water use and to characterize climate change. The mission SWOT will provide river discharge innovatively derived from contemporaneous river slope, height and width observations.

Our hypothesis is that the new space missions provide (a) surface water levels of higher accuracy and resolution compared to previous altimetric and in-situ observations and (b) new parameters to estimate river discharge and water storage change. A better sampling of flood event detection and of the long-term evolution is expected. We discuss here methodology and applications for satellite altimetry in the fields of hydrology and consider the two open research questions: (1) How can we fully exploit the new missions to derive best estimates of water level and storage change and river discharge and (2) can we separate natural variability from human water use.

For the first goal, we derive a multi-sensor database in an automatic processing which identifies the virtual gauge location and constructs the water height and water extension time-series. Water heights of the official release and of enhanced processing in project Hydrocoastal and in-house are used. Discharge and storage change time-series are derived from hydraulic equations using water extension and slope. First river basin considered is the Rhine river basin, where we obtain at 20 virtual stations a mean accuracy of 15 cm comparing altimeter and river height data. The derived discharge agrees within 18% with the in-situ discharge estimate.

For the second goal, we study past and present discharge and storage change, which are responses to both anthropogenic (deforestation, land use change, urbanization, reservoirs) and natural (climate modes, climate variability, rainfall, glacier and snow melting) processes. We discuss potential and limitations of satellite altimetry constellations for monitor recent river extremes and long-term changes. The work is part of Collaborative Research Centre CRC1502 “Regional Climate Change: Disentangling the role of Land Use and water management” of the German Research Foundation DFG.

How to cite: Fenoglio-Marc, L., Uyanik, H., Chen, J., and Kusche, J.: Impact analysis of surface water level and discharge from the new generation of altimetry observations, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10723, https://doi.org/10.5194/egusphere-egu22-10723, 2022.

Multi-Frequency and multi-Satellite Approaches for enhanced snow, ice and elevation in the polar oceans: updates from Polar+ and Cryosat+ ESA projects

We propose new methods for multi-frequency snow, ice and sea surface retrievals building on the legacy of the Arctic+ Snow project where we developed two products: the dual-altimetry Snow Thickness (DuST) and the Snow on Drifting Sea Ice (SnoDSI) and on the recent ESA projects: Polar+ Snow on Sea Ice and CryoSat+ Antarctic Ocean.  

The primary objective of the Polar+ Snow of Sea Ice ESA project is to investigate multi-frequency approaches to retrieve snow thickness over all types of sea ice surfaces in the Arctic and provide a state-of-the-art snow product. Our approach follows ESA ITT recommendations to prioritise satellite-based products and will benefit from the recent "golden era in polar altimetry" with the successful launch of the laser altimeter ICESat-2 in 2018 complementing data provided by the rich fleet of radar altimeters, CryoSat-2, Sentinel-3 A/B, AltiKa. Our primary objective is to produce an optimal snow product over the recent "operational" period. This will be complemented by additional snow products covering a longer periods of climate relevance and making use of historical altimeters (Envisat, ICESat-1) and passive microwave radiometers for comparison purposes (SMOS, AMSRE, AMSR-2).

The CryoSat+ Antarctic Ocean ESA project aims at exploring alternative methods to derive sea ice thickness and sea surface height measurements over the Antarctic Ocean. The potential of CryoSat-2 to retrieve information on mesoscale features over the area is also explored.  Exciting new results include (i) a detailed inter-comparison of all processing options along-track; (ii) novel optimal interpolation techniques; (iii) dual frequency approaches tested in the SO for snow retrieval; (iv) Lagrangian drift snow products for the SO. This work is supporting the progress of the gridded product development during. Complementing this project, a new ESA project looking at tides in the Southern Ocean (ALBATROSS) started and will offer a clear pathway to impact to the new algorithms developed as part of CSAO. 

We will present exciting methods explored to validate our results against in situ, airborne and other satellite data, including from NASA’s ICESat-2.

How to cite: Tsamados, M. and the POLAR+ Snow on Sea Ice team: Multi-Frequency and multi-Satellite Approaches for enhanced snow, ice and elevation in the polar oceans: updates from Polar+ and Cryosat+ ESA projects, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12366, https://doi.org/10.5194/egusphere-egu22-12366, 2022.

EGU22-13067 | Presentations | G3.2

Applications of Satellite Altimetry Observations 

Margaret Srinivasan, Vardis Tsontos, and Faisal Hossain

Thirty years of altimetry satellite observations have provided important information that enables research discoveries and aids in the development of user-driven applications. National and international space and operational agencies have committed substantial resources to developing and continuing observations of the ocean and large water bodies (lakes, reservoirs, large rivers) through collaboration in these missions. Over the next few years, NASA and other agencies will launch new research missions with technologies that will extend, expand, and evolve observations of ocean, coastal and inland waters. New discoveries and advances in societally relevant applications can be leveraged with increased spatial, temporal and spectral resolutions. We will highlight the use of data from these existing and planned missions for operational and applied user-driven applications and their societal benefits. Topics may include the use of existing, retrospective, and expected time series that contribute to applications such as marine operations, marine biology and biodiversity, coastal studies, hurricanes and other hazards, as well as hydrologic assessments, water resources management, and other surface water applications.

How to cite: Srinivasan, M., Tsontos, V., and Hossain, F.: Applications of Satellite Altimetry Observations, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13067, https://doi.org/10.5194/egusphere-egu22-13067, 2022.

EGU22-13466 | Presentations | G3.2

Monitoring SAR-altimeter missions at non-dedicated tide gauge stations in the German Bight 

Saskia Esselborn and Tilo Schöne

Sea level variations from satellite altimetry need to be consistently calibrated and monitored when used for climate studies. Here, we focus on the estimation of biases and the monitoring of precision and drifts of three SAR-altimeter missions (Sentinel-3A, Sentinel-3B and Sentinel-6MF) at eleven tide gauge stations in the German Bight (Southeastern North Sea). The corresponding operational GNSS-controlled tide gauge stations are partly located in open water, partly at the coast close to mudflats and deliver data every minute in the period 2016 to 2021. Instantaneous sea level (total water envelope) from altimetry is extracted at virtual stations in close vicinity to the gauges (2 to 24 km) and for different retrackers. The processing is optimized for the region and empirically adjusted for the comparison with the nearby tide gauges readings. The precision of the altimeters is depending on location and mission and is shown to be better than 3 cm. The relative drifts between tide gauges and altimetry are discussed.

How to cite: Esselborn, S. and Schöne, T.: Monitoring SAR-altimeter missions at non-dedicated tide gauge stations in the German Bight, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13466, https://doi.org/10.5194/egusphere-egu22-13466, 2022.

EGU22-2255 | Presentations | CR2.7

Bromine, Iodine and Mercury on the East Antarctic plateau: preliminary results from sampling along a traverse. 

Giuditta Celli, Warren R.L. Cairns, Joel Savarino, Barbara Stenni, Massimo Frezzotti, Niccolò Maffezzoli, Clara Turetta, Claudio Scarchilli, Barbara Delmonte, Rita Traversi, and Andrea Spolaor

Sunlit snow is highly photochemically active and plays a key role in the exchange of gas phase species between the cryosphere and the atmosphere. Bromine (Br), Iodine (I) and Mercury (Hg) can be photoactivated by the UV radiation and, in certain circumstances, released from the snowpack into the atmosphere. Mercury is a heavy metal with a known toxicity present in the environment in several different chemical forms. Once present in the snowpack, Hg is very labile and, thanks to the UV light, it can be reduced back to elemental Hg (Hg(0)) and undergo dynamic exchange with the atmosphere. Similar to mercury, iodine can undergo photochemical activation in surface snow resulting in its presence in the surrounding atmosphere where it plays a crucial role in new particle formation. Bromine  has a central role in the mercury cycle in polar regions (through the Atmospheric mercury depletion events) as well as contributing to the tropospheric ozone cycle in the polar region causing the so-called Ozone depletion events. However, compared to Iodine and Mercury, it seems to be more stable after deposition into the snow pack. 

Here we present measurements of bromine, iodine and mercury performed by ICP-MS, on snow pit and shallow core samples taken over a 2100 km traverse in East Antarctica from the coast to the interior (Talos Dome – Dome C traverse 2016 and East Antarctic International Ice Sheet Traverse, EAIIST 2019). The shallow core and the snow pit samples at each site are estimated to cover about 10 to 20 years of snow accumulation, giving us a deposition record from approximately the late 90s, to around the early 21st century. The concentrations determined in different  sampling sites show a rather clear decrease trend from the coast with the minima as we approach the inner part of the Antarctic plateau. In addition, the analysis of surface and bulk samples from EAIIST show a decrease of concentrations toward the inland except for the sites characterised by a strong snow metamorphosis caused mainly by the wind friction. In almost all the sampling sites of the EAIIST traverse the concentrations of Br, I and Hg increase with sample depth, possibly due to snowpack photochemical activation in the upper part of the snowpack. Future studies are planned to  investigate the possible link between the determined concentration profile and the variation of the solar radiation reaching the Antarctic Plateau during spring caused by the ozone hole formation. 

How to cite: Celli, G., Cairns, W. R. L., Savarino, J., Stenni, B., Frezzotti, M., Maffezzoli, N., Turetta, C., Scarchilli, C., Delmonte, B., Traversi, R., and Spolaor, A.: Bromine, Iodine and Mercury on the East Antarctic plateau: preliminary results from sampling along a traverse., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2255, https://doi.org/10.5194/egusphere-egu22-2255, 2022.

EGU22-2266 | Presentations | CR2.7

Trace analysis of organic aerosol markers and lignin in samples from Alpine ice core Colle Gnifetti covering the 20th century using UHPLC-HRMS 

Anja Beschnitt, Johanna Schäfer, Margit Schwikowski, and Thorsten Hoffmann

Ice cores are valuable climate archives preserving organic compounds from atmospheric aerosols over long time ranges. Different approaches of dating are available like annual layer counting, radioactive decay and stratigraphic markers like tephra from volcanic eruption. In combination, they enable accurate dating back to 800,000 years. Secondary organic aerosols (SOA) are formed in the atmosphere by condensation of oxidized highly volatile organic compounds and their chemical profile is highly complex due to the variety of emission sources and reactions in the atmosphere.

Well-known SOA markers include pinic acid, pinonic acid or terebic acid from monoterpene oxidation. Another class of important atmospheric markers are biomass burning products. During combustion of cellulose levoglucosan, an anhydrosugar is formed while the combustion of lignin results in the formation of phenolic compounds like vanillic acid, cinnamic acid, or p-hydroxybenzoic acid. While the lignin burning products provide important information on paleo-fire history, intact polymeric lignin offers a deeper insight into the type and abundance of vegetation. By alkaline oxidation, the polymeric lignin is degraded into the lignin oxidation products (LOP) and the ratios of these products are related to wooden and non-wooden, as well as angiosperm and gymnosperm vegetation.

In this work, an analytical approach is presented covering a variety of SOA markers, biomass burning markers, and polymeric lignin, using UHPLC-HRMS and an elaborate sample preparation procedure. The method was applied to samples from Colle Gnifetti in the Swiss-Italian Alps, a part of Grenzgletscher, covering the time between 1920 and 1994. We present first data on polymeric lignin in ice core samples and an examination of correlations with known organic proxies to emphasize the relevance of lignin not only in climate archives like speleothems and sediments but also in ice core samples.

How to cite: Beschnitt, A., Schäfer, J., Schwikowski, M., and Hoffmann, T.: Trace analysis of organic aerosol markers and lignin in samples from Alpine ice core Colle Gnifetti covering the 20th century using UHPLC-HRMS, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2266, https://doi.org/10.5194/egusphere-egu22-2266, 2022.

EGU22-3462 | Presentations | CR2.7

Insights from 3D Firn Microstructure into Near-Surface Snow Melt Conditions 

Dorothea Elisabeth Moser, Johannes Freitag, and Elizabeth R. Thomas

Coastal low-elevation ice caps of the (Ant-)Arctic and mountain glaciers are at the forefront of climate change. Retrieving ice core records from these regions is crucial to assess current, and predict future, environmental changes.  However, climate reconstruction from melt-affected ice cores is challenging. It requires a comprehensive understanding of the site-specific, near-surface melt conditions, which are fundamental to consequent melt-induced alteration of climate proxies.

Here, we use core-scale microfocus X-ray computer tomography to investigate melt layer microstructure in firn core sections from three (sub-)Antarctic sites (Young Island, Smyley Island, and Sherman Island) at 120-µm resolution. We present density, pore and grain cluster size of 3D melt features and discuss how the secondary imprint of the melt-refreeze process is visible in firn microstructure. We further show that the appearance of melt features varies both within profiles and from site to site. Given that local climate drives the near-surface snow properties and melt conditions, we suggest that melt layer microstructure could be further developed as a useful climate proxy itself.

How to cite: Moser, D. E., Freitag, J., and Thomas, E. R.: Insights from 3D Firn Microstructure into Near-Surface Snow Melt Conditions, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3462, https://doi.org/10.5194/egusphere-egu22-3462, 2022.

EGU22-4226 | Presentations | CR2.7

Optimization of ’cold’ laser ablation sampling for water isotopic analysis on ice cores 

Eirini Malegiannaki, Vasileios Gkinis, Carlo Barbante, and Dorthe Dahl-Jensen

The Beyond EPICA project for retrieving the Oldest Ice Core (1.5 Myr) in Antarctica aims at obtaining high resolution climate records and water isotopes will be one of the most important parameters investigated. Given the extremely thin nature of the annual ice core layers, as we get deep down to the core, analysis of such an ice core requires new adopted techniques on water isotopes with high accuracy and precision. Laser ablation (LA) is an established powerful technique used in various fields and it can also be applied in ice sampling serving a dual purpose: a.direct solid-gas transition and b. the smallest amount of sample possible is used for analysis and that makes LA a micro-distructive process. A new instrument which couples LA sampling with the established Cavity Ring Down Spectroscopy (CRDS) for water isotopic analysis is developed. This novel design will allow both fast gas phase sample collection directly from the ice sample and high quality water isotopic measurements. Particular focus was given in the LA system which consists of a High Energy femtosecond IR LASER and the optical elements that focus the LASER beam into the ice surface. The focusing lens system is placed inside a freezer, up above a motorized stage that accomodates the ice sample. An enclosure supplied with dry air flow was build around the optics and tested by the means of humidity experiments. Subsequent series of experiments with varying laser ablation parameters: pulse energy, repetition rate, ablation time, together with the ablated crater characterization allow the evaluation of LA efficiency in ice and thus the optimization of the parameters controlling the ablation mechanism. Understanding the LA mechanism will provide the knowledge to further develop the sampling procedure and efficiently control and guide the vaporized ice into a CRDS instrument for detection.

How to cite: Malegiannaki, E., Gkinis, V., Barbante, C., and Dahl-Jensen, D.: Optimization of ’cold’ laser ablation sampling for water isotopic analysis on ice cores, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4226, https://doi.org/10.5194/egusphere-egu22-4226, 2022.

EGU22-4492 | Presentations | CR2.7

Glacio-chemical signature of grain boundaries and insoluble particle aggregates in ice core 2D impurity imaging 

Pascal Bohleber, Nicolas Stoll, Barbara Delmonte, Marcello Pelillo, Marco Roman, Kaleem Siddiqi, Barbara Stenni, Sebastiano Vascon, Ilka Weikusat, and Carlo Barbante

Identifying, understanding, and constraining post-depositional processes altering the original layer sequence in ice cores is especially needed in order to avoid misinterpretation of the oldest and most highly thinned layers. The record of soluble and insoluble impurities represents an important part of the paleoclimate proxy set in ice cores but is known to be affected post-depositionally through interaction with the ice matrix, diffusion and chemical reactions. Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) has been recognized for its micron-scale resolution and micro-destructiveness in ice core impurity analysis. Important added value comes from employing LA-ICP-MS for state-of-the-art 2D chemical imaging. The latter has already revealed a close relationship between the ice grain boundary network and impurity signals with a significant soluble component, such as Na. Here we show the latest improvements in 2D chemical imaging of ice with LA-ICP-MS, by increasing the spatial resolution from 35 to 20 and even 10 µm and extending the simultaneous analysis to cover also mostly insoluble impurity species, such as Al. The latter reveal clear signals of insoluble particle aggregates in samples of Greenland ice cores. Combining the chemical images with computer vision-based image analysis allows to separate the geochemical signals of grain boundaries and insoluble particles. Considering intensities as well as elemental ratios, this classification further highlights important differences in the geochemical signals depending on the location of the impurities in the ice matrix. Ultimately, we discuss how this refined approach may serve to investigate post-depositional changes occurring with increasing depth to the soluble and insoluble impurity components, based on grain growth and chemical reactions, respectively.

How to cite: Bohleber, P., Stoll, N., Delmonte, B., Pelillo, M., Roman, M., Siddiqi, K., Stenni, B., Vascon, S., Weikusat, I., and Barbante, C.: Glacio-chemical signature of grain boundaries and insoluble particle aggregates in ice core 2D impurity imaging, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4492, https://doi.org/10.5194/egusphere-egu22-4492, 2022.

EGU22-5031 | Presentations | CR2.7

Deep ice and mineral dust: the case of the TALDICE ice core 

Barbara Delmonte, Giovanni Baccolo, Valter Maggi, and Massimo Frezzotti

Mineral dust archived in polar ice cores can be used to document past atmospheric circulation variability and past climate conditions over the dust source areas. Thanks to its relative immobility and stability, eolian dust concentration has been used to synchronize deep ice cores as well as ice stratigraphies and marine sediment records. However, mineral impurities in deep ice can be affected by post-depositional physical and chemical alterations, deriving from small-scale relocation of dust grains and subsequent alteration in acidic micro-environments.

By applying a set of different techniques spanning from dust concentration and grain size to iron mineralogy and elemental composition, here we provide evidence of in situ dust physical and chemical alterations observed below 1000 m depth in the 1620-m deep TALDICE ice core drilled at Talos Dome (peripheral East Antarctica, 72°49’S, 159°11’E; 2315 m a.s.l.). Results highlight significant dust aggregation and alteration of Fe-minerals with englacial precipitation of neo-formed jarosite, occurring in parallel with the decline of ferrous minerals and depletion of some major elements. Therefore, below 1000 m depth the TALDICE dust record can be considered partly affected by acidic-oxidative weathering resulting from the interaction of dust particles with highly saline acidic brines. Although limited to only one specific site, this study opens new issues concerning the interpretation of climate signals in the deepest part of ice cores.

How to cite: Delmonte, B., Baccolo, G., Maggi, V., and Frezzotti, M.: Deep ice and mineral dust: the case of the TALDICE ice core, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5031, https://doi.org/10.5194/egusphere-egu22-5031, 2022.

EGU22-5683 | Presentations | CR2.7

Halogens in sub-Antarctic ice cores modulated by wind forcing, sea ice and primary productivity 

Delia Segato, Elizabeth R. Thomas, Amy King, Dieter Tetzner, Dorothea Elisabeth Moser, Clara Turetta, Alfonso Saiz-Lopez, Bradley Markle, Joel Pedro, and Andrea Spolaor

Over the last four decades, the Southern Ocean has been characterized by now-persistent stronger westerly winds, with consequences for the Antarctic region climate, including variations in sea ice extent and primary productivity. Here we present the first ever bromine, sodium and iodine records, tracers of sea salt aerosols, sea ice and primary productivity, from five sub-Antarctic ice cores, retrieved from Bouvet, Young, Peter I and Mount Siple Island and Mertz glacier. The aim of the study is (1) to assess if halogens deposited in sub-Antarctic regions are influenced by recent changes in wind forcing and (2) to better understand the underlying processes of halogens emission from ocean/sea ice, their transport and deposition over the Antarctic region.

The trends of sodium and bromine, emitted and transported with sea salt aerosols, suggest that wind strengthening leads to more halogens deposited in the sub-Antarctic. Also, we find that bromine is depleted with respect to the bromine-to-sodium sea-water ratio at all sites, indicating that bromine species are sustained in the marine boundary layer by halogen chemistry and are less prone to be deposited. Iodine records show a positive correlation with marginal sea ice and primary productivity variability, suggesting that iodine species emitted at the edge are deposited more efficiently than bromine species.

How to cite: Segato, D., Thomas, E. R., King, A., Tetzner, D., Moser, D. E., Turetta, C., Saiz-Lopez, A., Markle, B., Pedro, J., and Spolaor, A.: Halogens in sub-Antarctic ice cores modulated by wind forcing, sea ice and primary productivity, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5683, https://doi.org/10.5194/egusphere-egu22-5683, 2022.

EGU22-5847 | Presentations | CR2.7

Insights from the first analysis of Antarctic water stable isotope simulations for the historical period 

Sentia Goursaud Oger, Louise Sime, and Max Holloway

The historical period  (from 1850 to present) yields a window when ice core  and good historical data are both available. It thus represents an important period over which to test the relationship between ice core measurements, here stable water isotopes, and Antarctic climate.  Water stable isotopes from ice cores from Antarctica have traditionally been used to infer past surface air temperatures. Here we run an ensemble over the period 1850-2004 using the UK Met Office HadCM3 general circulation model equipped with water stable isotopes.  Simulations of water stable istopes from general circulation model can help in the interpretation of Antarctic ice cores.  This ensemble captures observed temperature and precipitation trends. Interestingly however the water isotopes exhibit little trend. This appears to be explained by compensating effect of two modes of atmospheric dynamics throughout the period. Further we use these results to examine the relationships used in Last Millienium reconstructions based on Antarctic stable water isotopes data from ice cores.  

How to cite: Goursaud Oger, S., Sime, L., and Holloway, M.: Insights from the first analysis of Antarctic water stable isotope simulations for the historical period, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5847, https://doi.org/10.5194/egusphere-egu22-5847, 2022.

EGU22-6443 | Presentations | CR2.7

The problem of signal loss for the upcoming Beyond EPICA Little Dome C (BELDC) ice core. 

Vasileios Gkinis, Thomas Laepple, Eirini Malegiannaki, and Fyntan Shaw

The recently commenced drilling operation at the Beyond EPICA Little Dome C (BELDC) site will attempt to recover an ice core that reaches back to 1.5 Ma, a time during which the enigmatic Mid-Pleistocene Transition (MPT) took place. While the ice flow and heat flux regime at the drilling site will largely determine the age, as well as the nominal temporal resolution of the deeper parts of the BELDC core, molecular diffusion in solid ice will play a significant role in the effective temporal resolution of the δ18O signal. Here we look into the expected diffusion characteristics of the BELDC ice core by firstly addressing a previously reported problem, that of the δ18O signal loss in the deeper parts of the Dome-C ice core, particularly over Marine Isotope Stage 19 (MIS-19). By using isotope diffusion modelling in combination with high resolution δ18O data, we show the importance of the ice flow thinning function for the estimation of the diffusion length. We also comment on the large uncertainty imposed by the poor knowledge of the diffusivity coefficient. Based on recently published results on the dating of the BELDC site we provide a first order estimate of the effective resolution of the δ18O signal over the MPT transition.

How to cite: Gkinis, V., Laepple, T., Malegiannaki, E., and Shaw, F.: The problem of signal loss for the upcoming Beyond EPICA Little Dome C (BELDC) ice core., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6443, https://doi.org/10.5194/egusphere-egu22-6443, 2022.

EGU22-6818 | Presentations | CR2.7

Chronostratigraphy of Larsen blue ice, East Antarctica, and a tentative reconstruction of surface temperature and accumulation rate during the last deglaciation 

Giyoon Lee, Jinho Ahn, Hyeontae Ju, Florian Ritterbusch, Ikumi Oyabu, Christo Buizert, Songyi Kim, Jangil Moon, Sambit Ghosh, Kenji Kawamura, Zheng-Tian Lu, Sangbum Hong, Chang Hee Han, Soon Do Hur, Wei Jiang, and Guo-Min Yang

Ice coring in blue ice areas (BIAs) serves as an alternative to deep ice core drilling, allowing collection of large-sized old ice samples in a cost-effective way because old ice samples are outcropped to the surface. However, the stratigraphy in many blue ice areas can be complicated due to complex ice flows. Based on ice layers defined by dust bands and ground penetration radar (GPR) surveys, we show that Larsen BIA has a surface transect of ice with an undisturbed horizontal stratigraphy from mid- to downstream side ice. However, the upstream ice exhibits a potential repetition of ages on scales of tens of meters. Correlating δ18Oice, δ18Oatm, and CH­4 records of Larsen ice with existing ice core records indicates that the analyzed gas age and ice age ranges between 9.2–23.4 ka BP and 5.6–24.7 ka BP, respectively. Radiometric 81Kr dating of one of the cores confirms the estimated gas ages within uncertainty. A tentative reconstruction based on a simple analytical framework suggests a warming of 15 ± 5 ℃ during the last deglaciation that we attribute to the retreat of the Ross Ice Shelf, and an increase in snow accumulation by a factor of 1.7–4.6 that we attribute to the increased penetration of snow-bearing storms. Exact estimation of the original deposition site and updated ice ages may enhance the tentative climate reconstructions in future studies. Our study shows that BIAs in Northern Victoria Land may contribute to obtain high-quality paleoclimate proxy records through the last deglaciation.

How to cite: Lee, G., Ahn, J., Ju, H., Ritterbusch, F., Oyabu, I., Buizert, C., Kim, S., Moon, J., Ghosh, S., Kawamura, K., Lu, Z.-T., Hong, S., Han, C. H., Hur, S. D., Jiang, W., and Yang, G.-M.: Chronostratigraphy of Larsen blue ice, East Antarctica, and a tentative reconstruction of surface temperature and accumulation rate during the last deglaciation, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6818, https://doi.org/10.5194/egusphere-egu22-6818, 2022.

EGU22-7601 | Presentations | CR2.7

Snow surface water isotope variability driven by vapor-snow exchange 

Sonja Wahl, Hans Christian Steen-Larsen, Abigail G. Hughes, Alexandra Zuhr, Anne-Katrine Faber, Tyler R. Jones, Laura J. Dietrich, Melanie Behrens, Joachim Reuder, and Maria Hörhold

Observed variability in summer surface snow isotopic composition (δ18O, δD) cannot solely be explained by precipitation events. This variability however, influences the overall summer isotope signal that is archived in ice cores. It is therefore important to explain the origin of such post-depositional modifications of the snow isotope signal to ensure an optimal interpretation of ice core isotope records. The continuous exchange of humidity between the atmospheric vapor reservoir and the snow surface through sublimation and deposition could be a key process. Yet, in the past, the surface humidity flux has been disregarded as influential for the formation of the isotope signal in snow based on the assumption of the absence of isotopic fractionation during sublimation. Here we show evidence of isotopic fractionation during snow sublimation through a combination of laboratory experiments, in-situ observations from the Greenland Ice Sheet, and snow surface modeling. We document substantial isotopic enrichment in the uppermost centimeters of snow induced by sublimation and find that the in-situ observed summer season temporal evolution of the snow surface isotopic composition (in between precipitation events) can be attributed to surface humidity fluxes. We further discuss the nature and the underlying physical process of fractionation during sublimation. Our results lead to an improved process understanding and necessitate the implementation of fractionation during the sublimation process in isotope-enabled climate models.

How to cite: Wahl, S., Steen-Larsen, H. C., Hughes, A. G., Zuhr, A., Faber, A.-K., Jones, T. R., Dietrich, L. J., Behrens, M., Reuder, J., and Hörhold, M.: Snow surface water isotope variability driven by vapor-snow exchange, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7601, https://doi.org/10.5194/egusphere-egu22-7601, 2022.

The West Antarctic Ice Sheet (WAIS) may have collapsed during the last interglacial period, between 132,000 and 116,000 years ago. The changes in topography resulting from WAIS collapse would be accompanied by significant changes in Antarctic surface climate, atmospheric circulation and ocean surface conditions. Evidence of these changes may be recorded in water-isotope ratios in precipitation archived in the ice. We conducted high-resolution simulations with an isotope-enabled version of the Weather Research and Forecasting Model over Antarctica, using boundary conditions provided by climate-model simulations with both present-day and lowered WAIS topography. The results show that while there is significant spatial variability, WAIS collapse would cause detectable isotopic changes at several locations where ice-core records have been obtained or could be obtained in the future. The most robust signals include lower δ18O at Mount Moulton Blue Ice Area and higher δ18O at SkyTrain Ice Rise in West Antarctica, and higher deuterium excess at Hercules Dome, East Antarctica. A combination of records from multiple sites would provide the strongest constraint on the timing and magnitude of past WAIS collapse.

How to cite: Duetsch, M., Blossey, P. N., Pauling, A. G., and Steig, E. J.: Response of water isotopes in precipitation to a collapse of the West Antarctic Ice Sheet in high resolution simulations with the Weather Research and Forecasting and Community Atmosphere Models, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8361, https://doi.org/10.5194/egusphere-egu22-8361, 2022.

EGU22-9900 | Presentations | CR2.7

Analysis of impurities from Talos Dome ice core to assess the solubility of different elements  using INAA and ICP-SFMS 

Elena Di Stefano, Giovanni Baccolo, Paolo Gabrielli, Barbara Delmonte, and Valter Maggi

Antarctic ice cores play a central role in paleoclimatic reconstructions, as they provide a high resolution archive of past climatic and environmental processes. This study focuses on the TALDICE ice core drilled at Talos Dome (East Antarctica, 72°49’S, 159°11’E), which covers more than 343k years of climate history. A comparison is presented between samples analyzed through two different techniques: low background instrumental neutron activation analysis (INAA) and inductively coupled plasma mass spectrometry (ICP-SFMS). While the former is used to investigate only the insoluble fraction of dust, as it can only be applied to solid samples, the latter is used to assess the elemental composition of both the total and the soluble fraction of dust. We thus observe how different elements partition between soluble and insoluble phase at different depths of the ice core and link the geochemical patterns of the considered elements to the main climatic oscillations covered in the Talos Dome ice core.

We determined 45 elements through ICP-SFMS and 39 through INAA, with a good overlapping of the elements between the two techniques. Besides the determination of major elements (Na, Mg, Al, Si, K, Ca, Ti, Mn, Fe), which is important in the assessment of the impact of dust on the ecosystem (e.g. source of nutrients in the Southern Ocean), the high sensibility of both techniques also permitted the determination of trace elements. Among these, rare earth elements (REE) are of particular importance as they have been widely used as a geochemical tracer of aeolian dust sources.

We present enrichment factors and correlation matrices to assess the crustal or non-crustal origin of the considered elements. The high correlations and low enrichment factors found among insoluble elements confirm a prevalent crustal composition for mineral dust. Regarding solubility, the majority of elements exhibits a minimum in solubility during the last glacial maximum. This is the result of higher fluxes of mineral dust transported to the Antarctic continent during cold climate periods and is consistent with the crustal origin we documented for most of the elements considered.

 

 

How to cite: Di Stefano, E., Baccolo, G., Gabrielli, P., Delmonte, B., and Maggi, V.: Analysis of impurities from Talos Dome ice core to assess the solubility of different elements  using INAA and ICP-SFMS, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9900, https://doi.org/10.5194/egusphere-egu22-9900, 2022.

EGU22-10188 | Presentations | CR2.7

What is driving the isotopic composition of surface snow in East Antarctica? - Insights from a multi-year time series of surface snow at Dome C 

Alexandra Zuhr, Amaëlle Landais, Mathieu Casado, Bénédicte Minster, Frederic Prié, Romilly Harris-Stuart, Ghislain Picard, Laurent Arnaud, Marie Dumont, Inès Ollivier, and Thomas Laepple

The isotopic composition (d18O, dD) of surface snow on an ice sheet is primarily seen as a recorder of the air temperature and is used to reconstruct past climatic conditions from ice cores. The second order parameters d-excess and 17O-excess can preserve climatic signals from the moisture origin and are indicative for kinetic fractionation processes in the water cycle between the source and the deposition site. Fractionation is especially important for the surface snow which can exposed to the atmosphere for a long time during periods without snowfall. The resulting effect of this process on the isotopic composition and the second order parameters in the interior of Antarctica is, however, unclear. In order to better understand the contribution of secondary processes on the isotopic signature and to disentangle the climate characteristics at the moisture source region and at the ice core site, we study both the isotopic composition and the second order parameters of surface and subsurface snow at Dome C on the East Antarctic Plateau. For this, we make use of an extensive data set of isotopic data (d18O, dD, dexcess and 17O-excess) from surface (0 - 1.5 cm) and subsurface snow (1.5 - 4.5 cm) covering continuously the period from 2016 to 2020. This data set is complemented with previously published isotopic data of surface snow and precipitation data back to 2011. For additional comparisons and analyses, we use data from a nearby weather station, the ERA5 reanalysis data set, a satellite-derived grain index estimate and simulations from the detailed snowpack model CROCUS.

We observe a good (weak) correlation between the ambient temperature and the surface (subsurface) layer. Most years are characterised by a strong increase in the isotopic composition towards the summer and a gentle decrease towards winter while d-excess shows a contrary behaviour. We suggest that the strength of the summer increase is related to the amount of precipitation and the magnitude of metamorphism at the surface. The degree of metamorphism can (to some degree) be approximated from observational data (e.g. the grain index) or from model output (e.g. latent heat flux from CROCUS). In addition to presenting possible mechanisms leading to strong or weak increases in the isotopic composition in summer, we developed a simple model using temperature and snowfall data from ERA5 to analyse the contribution of temperature and other parameters to the observed isotopic signals.

How to cite: Zuhr, A., Landais, A., Casado, M., Minster, B., Prié, F., Harris-Stuart, R., Picard, G., Arnaud, L., Dumont, M., Ollivier, I., and Laepple, T.: What is driving the isotopic composition of surface snow in East Antarctica? - Insights from a multi-year time series of surface snow at Dome C, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10188, https://doi.org/10.5194/egusphere-egu22-10188, 2022.

EGU22-10784 | Presentations | CR2.7

Ice fabrics and textures in coastal East Antarctica reveal seasonal variations 

Veronica Tsibulskaya and Jean-Louis Tison

The fabric and texture evolution with depth was investigated on several firn/ice cores from ice rises on Princess Ragnhild Coast, East Antarctica. Results at 5 m sampling resolution show important variations in the crystal orientation fabrics as well as in the grain size, on centimetric to decimetric scale. Further analysis on continuous sections spanning several meters of firn core brings to light periodic variations in the fabric clustering. The fabric’s decimetre-scale periodicity displays a clear correlation with the seasonal variability of δ18O and ECM conductivity in the ice. It also reveals a previously unobserved fabric shape. This constitutes an opportunity for a close-up look of the climatic signal burial through the transition from firn to ice.

How to cite: Tsibulskaya, V. and Tison, J.-L.: Ice fabrics and textures in coastal East Antarctica reveal seasonal variations, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10784, https://doi.org/10.5194/egusphere-egu22-10784, 2022.

EGU22-12025 | Presentations | CR2.7

Oxygen in the trapped air: identifying primary atmospheric signals and secondary bubble close-off fractionation 

Yuzhen Yan, Michael Bender, and John Higgins

Ice cores offer a unique opportunity to study past atmospheric composition because the trapped gases are ultimately derived from ancient atmosphere. This distinctive ability has motivated some pioneering efforts in the late 1980s to measure the elemental composition of the trapped air. The goal at that time was to reconstruct past atmospheric O2 concentration variations (PO2), the primary (atmospheric) signal. However, these measurements quickly revealed that oxygen, argon, and nitrogen concentrations in the ice (expressed as δO2/N2 and δAr/N2) are altered by gas-trapping processes. This is the secondary (and confounding) signal formation process.

Such alterations have long thwarted the application of ice core δO2/N2 to reconstruct true PO2. Empirically though, δO2/N2 in the trapped air has a high coherency with local summer insolation, but the cause is not well understood. Presumably, the intensity of sunlight on the surface of the ice sheet determines the extent and nature of snow metamorphism, which in turn modulates the magnitude of O2 and Ar losses relative to N2 at the “bubble close-off depth” (typically 70-120 m in polar regions).

Here, we discuss recent efforts to identify the secondary signals in δO2/N2 and extract the primary, atmospheric PO2 signals. First, using δAr/N2 as a proxy for insolation, we show that PO2 remained stable prior to the Mid-Pleistocene Transition (MPT), the shift from 40- to 100-kyr glacial cycles. After the MPT, however, PO2 began to decline, possibly linked to enhanced to weathering as a result of glacier expansion and, to a lesser degree, more exposed areas of the continental shelves.

Next, we proceed to exploit the secondary signal itself. That is, δO2/N2 and δAr/N2 could be used as a direct proxy of local insolation. By examining the relationship between elemental ratios and temperature proxies, we explore the relationship between high-latitude southern hemisphere insolation and Antarctic temperature in three time slices in the Pleistocene. The implications for the nature of 40-kyr glacial cycles will be discussed.

How to cite: Yan, Y., Bender, M., and Higgins, J.: Oxygen in the trapped air: identifying primary atmospheric signals and secondary bubble close-off fractionation, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12025, https://doi.org/10.5194/egusphere-egu22-12025, 2022.

EGU22-13161 | Presentations | CR2.7 | Highlight

Water Isotopic Signature of Surface Snow Metamorphism in Antarctica 

Mathieu Casado, Alexandra Zuhr, Amaëlle Landais, Ghislain Picard, Laurent Arnaud, Giuliano Dreossi, Barbara Stenni, and Frederic Prié

Water isotope ratios of ice cores are a key source of information on past temperatures. Through fractionation within the hydrological cycle, temperature is imprinted in the water isotopic composition of snowfalls. However, this signal of climatic interest is modified after deposition when snow remains at the surface exposed to the atmosphere. Comparing time series of surface snow isotopic composition at Dome C with satellite observations of surface snow metamorphism, we found that long summer periods without precipitation favor surface snow metamorphism altering the surface snow isotopic  composition. Using excess parameters (combining dD, d17O, and d18O fractions) allow the identification of this alteration caused by sublimation and condensation of surface hoar. The combined measurement of all three isotopic compositions could help identifying ice core sections influenced by snow metamorphism in sites with very low snow accumulation.

How to cite: Casado, M., Zuhr, A., Landais, A., Picard, G., Arnaud, L., Dreossi, G., Stenni, B., and Prié, F.: Water Isotopic Signature of Surface Snow Metamorphism in Antarctica, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13161, https://doi.org/10.5194/egusphere-egu22-13161, 2022.

EGU22-1294 | Presentations | CR2.8

What determines the location of Antarctic blue ice areas? A deep learning approach 

Veronica Tollenaar, Harry Zekollari, Devis Tuia, Benjamin Kellenberger, Marc Rußwurm, Stef Lhermitte, and Frank Pattyn

The vast majority of the Antarctic ice sheet is covered with snow that compacts under its own weight and transforms into ice below the surface. However, in some areas, this typically blue-colored ice is directly exposed at the surface. These so-called "blue ice areas" represent islands of negative surface mass balance through sublimation and/or melt. Moreover, blue ice areas expose old ice that is easily accessible in large quantities at the surface, and some areas contain ice that extends beyond the time scales of classic deep-drilling ice cores.

Observation and modeling efforts suggest that the location of blue ice areas is related to a specific combination of topographic and meteorological factors. In the literature, these factors are described as (i) enhanced katabatic winds that erode snow, due to an increase of the surface slope or a tunneling effect of topography, (ii) the increased albedo of blue ice (with respect to snow), which enhances ablative processes, and (iii) the presence of nunataks (mountains protruding the ice) that act as barriers to the ice flow upstream, and prevent deposition of blowing snow on the lee side of the mountain. However, it remains largely unknown which role the physical processes play in creating and/or maintaining  blue ice at the surface of the ice sheet.

Here, we study how a combination of environmental and topographic factors lead to the observation of blue ice. We also quantify the relevance of the single processes and build an interpretable model aiming at not only predicting blue ice presence, but also explaining why it is there. To do so, data is fed into a convolutional neural network, a machine learning algorithm which uses the spatial context of the data to generate a prediction on the presence of blue ice areas. More specifically, we use a U-Net architecture that through convolutions and linked up-convolutions allows to obtain a semantic segmentation (i.e., a pixel-level map) of the input data. Ground reference data is obtained from existing products of blue ice area outlines that are based on multispectral observations. These products contain considerable uncertainties, as (i) the horizontal change from snow to ice is gradual and a single threshold in this transition is not applicable uniformly over the continent, and (ii) the blue ice area extent is known to vary seasonally. Therefore, we train our deep learning model with a loss function with increasing weight towards the center of blue ice areas.

Our first results indicate that the neural network predicts the location of blue ice relatively well, and that surface elevation data plays an important role in determining the location of blue ice. In our ongoing work, we analyze both the predictions and the neural network itself to quantify which factors posses predictive capacity to explain the location of blue ice. Eventually this information may allow us to answer the simple yet important question of why blue ice areas are located where they are, with potentially important implications for their role as paleoclimate archives and for their evolution under changing climatic conditions.

How to cite: Tollenaar, V., Zekollari, H., Tuia, D., Kellenberger, B., Rußwurm, M., Lhermitte, S., and Pattyn, F.: What determines the location of Antarctic blue ice areas? A deep learning approach, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1294, https://doi.org/10.5194/egusphere-egu22-1294, 2022.

EGU22-2726 | Presentations | CR2.8 | Highlight

Dissecting Glaciers - Can an Automated Bio-Medical Image Segmentation Tool also Segment Glaciers? 

Nora Gourmelon, Thorsten Seehaus, Matthias Braun, Andreas Maier, and Vincent Christlein

The temporal variability of glacier calving front positions provides essential information about the state of marine-terminating glaciers. These positions can be extracted from Synthetic Aperture Radar (SAR) images throughout the year. To automate this extraction, we apply deep learning techniques that segment the SAR images into different classes: glacier; ocean including ice-melange and sea-ice covered ocean; rock outcrop; and regions with no information like areas outside the SAR swath, layover regions and SAR shadow. The calving front position can be derived from these regions during post-processing.   
A downside of deep learning is that hyper-parameters need to be tuned manually. For this tuning, expert knowledge and experience in deep learning are required. Furthermore, the fine-tuning process takes up much time, and the researcher needs to have programming skills.
    
In the biomedical imaging domain, a deep learning framework [1] has become increasingly popular for image segmentation. The nnU-Net can be used out-of-the-box. It automatically adapts the U-Net, the state-of-the-art architecture for image segmentation, to different datasets and segmentation tasks. Hence, no more manual tuning is required. The framework outperforms specialized deep learning pipelines in a multitude of public biomedical segmentation competitions.   
We apply the nnU-Net to the task of glacier segmentation, investigating whether the framework is also beneficial in the domain of remote sensing. Therefore, we train and test the nnU-Net on CaFFe (https://github.com/Nora-Go/CaFFe), a benchmark dataset for automatic calving front detection on SAR images. CaFFe comprises geocoded, orthorectified imagery acquired by the satellite missions RADARSAT-1, ERS-1/2, ALOS PALSAR, TerraSAR-X, TanDEM-X, Envisat, and Sentinel-1, covering the period 1995 - 2020. The ground range resolution varies between 7 and 20 m2. The nnU-Net learns from the multi-class "zones" labels provided with the dataset. We adopt the post-processing scheme from Gourmelon et al. [2] to extract the front from the segmented landscape regions. The test set includes images from the Mapple Glacier located on the Antarctic Peninsula and the Columbia Glacier in Alaska. The nnU-Net's calving front predictions for the Mapple Glacier lie close to the ground truth with just 125 m mean distance error. As the Columbia Glacier shows several calving front sections, its segmentation is more difficult than that of the laterally constrained Mapple Glacier. This complexity of the calving fronts is also reflected in the results: Predictions for the Columbia Glacier show a mean distance error of 635 m. Concludingly, the results demonstrate that the nnU-Net holds considerable potential for the remote sensing domain, especially for glacier segmentation.
    
[1] Isensee, F., Jaeger, P.F., Kohl, S.A.A. et al. nnU-Net: a self-configuring method for deep learning-based biomedical image segmentation. Nat Methods 18, 203–211 (2021). https://doi.org/10.1038/s41592-020-01008-z 

[2] Gourmelon, N., Seehaus, T., Braun, M., Maier, A., Christlein, V.: Calving Fronts and Where to Find Them: A Benchmark Dataset and Methodology for Automatic Glacier Calving Front Extraction from SAR Imagery, In Prep.

How to cite: Gourmelon, N., Seehaus, T., Braun, M., Maier, A., and Christlein, V.: Dissecting Glaciers - Can an Automated Bio-Medical Image Segmentation Tool also Segment Glaciers?, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2726, https://doi.org/10.5194/egusphere-egu22-2726, 2022.

EGU22-2904 | Presentations | CR2.8

Automated mapping of Eastern Himalayan glacial lakes using deep learning and multisource remote sensing data 

Saurabh Kaushik, Tejpal Singh, Pawan Kumar Joshi, and Andreas J Dietz

The Himalayan glacierized region has experienced a substantial rise in number and area of glacial lakes in the past two decades. These glacial lakes directly influence glacier melt, velocity, geometry, and thus overall response of the glacier to climate change. The sudden release of water from these glacial lakes poses a severe threat to downstream communities and infrastructure. Thereby, regular monitoring and modelling of these lakes bear significance in order to understand regional climate change, and mitigating the anticipated impact of glacial lake outburst flood. Here, we proposed an automated scheme for Himalayan glacial lake extent mapping using multisource remote sensing data and a state-of-the-art deep learning technique. A combination of multisource remote sensing data [Synthetic Aperture Radar (SAR) coherence, thermal, visible, near-infrared, shortwave infrared, Advanced Land Observing Satellite (ALOS) DEM, surface slope and Normalised Difference Water Index (NDWI)] is used as input to a fully connected feed-forward Convolutional Neural Network (CNN). The CNN is trained on 660 images (300×300×10) collected from 11 sites spread across Himalaya. The CNN architecture is designed for choosing optimum size, number of hidden layers, convolutional layers, filters, and other hypermeters using hit and trial method. The model performance is evaluated over 3 different sites of Eastern Himalaya, representing heterogenous landscapes. The novelty of the presented automated scheme lies in its spatio-temporal transferability over the large geographical region (~8477, 10336 and 6013 km2). The future work involves Intra-annual lake extent mapping across High-Mountain Asian region in an automated fashion.

Keywords: Glacial Lake, convolutional neural network, semantic segmentation, remote sensing, Himalaya, SAR and climate change

How to cite: Kaushik, S., Singh, T., Joshi, P. K., and Dietz, A. J.: Automated mapping of Eastern Himalayan glacial lakes using deep learning and multisource remote sensing data, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2904, https://doi.org/10.5194/egusphere-egu22-2904, 2022.

EGU22-3446 | Presentations | CR2.8

The AI-CORE Project - Artificial Intelligence for Cold Regions 

Andreas Dietz and Celia Baumhoer and the AI-CORE Team

Artificial Intelligence for Cold Regions (AI-CORE) is a collaborative approach for applying Artificial Intelligence (AI) methods in the field of remote sensing of the cryosphere. Several research institutes (German Aerospace Center, Alfred-Wegener-Institute, Technical University Dresden) bundled their expertise to jointly develop AI-based solutions for pressing geoscientific questions in cryosphere research. The project addresses four geoscientific use cases such as the change pattern identification of outlet glaciers in Greenland, the object identification in permafrost areas, the detection of calving fronts in Antarctica and the firn-line detection on glaciers. Within this presentation, the four AI-based final approaches for each addressed use case will be presented and exemplary results will be shown. Further on, the implementation of all developed AI-methods in three different computer centers was realized and the lessons learned from implementing several ready-to-use AI-tools in different processing infrastructures will be discussed. Finally, a best-practice example for sharing AI-implementations between different institutes is provided along with opportunities and challenges faced during the present project duration.

How to cite: Dietz, A. and Baumhoer, C. and the AI-CORE Team: The AI-CORE Project - Artificial Intelligence for Cold Regions, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3446, https://doi.org/10.5194/egusphere-egu22-3446, 2022.

EGU22-3701 | Presentations | CR2.8 | Highlight

Snow accumulation over the world's glaciers (1981-2021) inferred from climate reanalyses and machine learning 

Matteo Guidicelli, Marco Gabella, Matthias Huss, and Nadine Salzmann

The scarcity and limited accuracy of snow and precipitation observation and estimation in high-mountain regions reduce our understanding of climatic-cryospheric processes. Thus, we compared the snow water equivalent (SWE) from winter mass balance observations of 95 glaciers distributed over the Alps, Canada, Central Asia and Scandinavia, with the cumulative gridded precipitation data from the ERA-5 and the MERRA-2 reanalysis products. We propose a machine learning model to downscale the gridded precipitation from the reanalyses to the altitude of the glaciers. The machine learning model is a gradient boosting regressor (GBR), which combines several meteorological variables from the reanalyses (air temperature and relative humidity are also downscaled to the altitude of the glaciers) and topographical parameters. Among the most important variables selected by the GBR model, are the downscaled relative humidity and the downscaled air temperature. These GBR-derived estimates are evaluated against the winter mass balance observations by means of a leave-one-glacier-out cross-validation (site-independent GBR) and a leave-one-season-out cross-validation (season-independent GBR). The estimates downscaled by the GBR show lower biases and higher correlations with the winter mass balance observations than downscaled estimates derived with a lapse-rate-based approach. Finally, the GBR estimates are used to derive SWE trends between 1981 and 2021 at high-altitudes. The trends obtained from the GBRs are more enhanced than those obtained from the gridded precipitation of the reanalyses. When the data is regrouped regionwide, significant trends are only observed for the Alps (positive) and for Scandinavia (negative), while significant positive or negative trends are observed in all the regions when looking locally at single glaciers and specific elevations. Positive (negative) SWE trends are typically observed at higher (lower) elevations, where the impact of rising temperatures is less (more) dominating.

How to cite: Guidicelli, M., Gabella, M., Huss, M., and Salzmann, N.: Snow accumulation over the world's glaciers (1981-2021) inferred from climate reanalyses and machine learning, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3701, https://doi.org/10.5194/egusphere-egu22-3701, 2022.

EGU22-5317 | Presentations | CR2.8

Point Mass Balance Regression using Deep Neural Networks: A Transfer Learning Approach 

Ritu Anilkumar, Rishikesh Bharti, and Dibyajyoti Chutia

The last few years have seen an increasing number of studies modeling glacier evolution using deep learning. Most of these techniques have focussed on artificial neural networks (ANN) that are capable of providing a regressed value of mass balance using topographic and meteorological input features. The large number of parameters in an ANN demands a large dataset for training the parameter values. This is relatively difficult to achieve for regions with a sparse in-situ data measurement set up such as the Himalayas. For example, of the 14326 point mass balance measurements obtained from the Fluctuations of Glaciers database for the period of 1950-2020 for glaciers between 60S and 60N, a mere 362 points over four glaciers exist for the Himalayan region. These are insufficient to train complex neural network architectures over the region. We attempt to overcome this data hurdle by using transfer learning. Here, the parameters are first trained over the 9584 points in the Alps following which the weights were used for retraining for the Himalayan data points. Fourteen meteorological from the ERA5Land monthly averaged reanalysis data were used as input features for the study. A 70-30 split of the training and testing set was maintained to ensure the authenticity of the accuracy estimates via independent testing. Estimates are assessed on a glacier scale in the temporal domain to assess the feasibility of using deep learning to fill temporal gaps in data. Our method is also compared with other machine learning algorithms such as random forest-based regression and support vector-based regression and we observe that the complexity of the dataset is better represented by the neural network architecture. With an overall normalized root mean squared loss consistently less than 0.09, our results suggest the capability of deep learning to fill the temporal data gaps over the glaciers and potentially reduce the spatial gap on a regional scale.

How to cite: Anilkumar, R., Bharti, R., and Chutia, D.: Point Mass Balance Regression using Deep Neural Networks: A Transfer Learning Approach, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5317, https://doi.org/10.5194/egusphere-egu22-5317, 2022.

EGU22-5612 | Presentations | CR2.8

Retrieving freeze/thaw-cycles using Machine Learning approach in Nunavik (Québec, Canada) 

Yueli Chen, Lingxiao Wang, Monique Bernier, and Ralf Ludwig

In the terrestrial cryosphere, freeze/thaw (FT) state transition plays an important and measurable role for climatic, hydrological, ecological, and biogeochemical processes in permafrost landscapes.

Satellite active and passive microwave remote sensing has shown its principal capacity to provide effective monitoring of landscape FT dynamics. Many algorithms have been developed and evaluated over time in this scope. With the advancement of data science and artificial intelligence methods, the potential of better understanding the cryosphere is emerging.

This work is dedicated to exploring an effective approach to retrieve FT state based on microwave remote sensing data using machine learning methods, which is expected to fill in some hidden blind spots in the deterministic algorithms. Time series of remote sensing data will be created as training data. In the initial stage, the work aims to test the feasibility and establish the basic neural network based on fewer training factors. In the advanced stage, we will improve the model in terms of structure, such as adding more complex dense layers and testing optimizers, and in terms of discipline, such as introducing more influencing factors for training. Related parameters, for example, land cover types, will be included in the analysis to improve the method and understanding of FT-related processes.

How to cite: Chen, Y., Wang, L., Bernier, M., and Ludwig, R.: Retrieving freeze/thaw-cycles using Machine Learning approach in Nunavik (Québec, Canada), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5612, https://doi.org/10.5194/egusphere-egu22-5612, 2022.

EGU22-5910 | Presentations | CR2.8

Learning and screening of neural networks architectures for sub-grid-scale parametrizations of sea-ice dynamics from idealised twin experiments 

Tobias Finn, Charlotte Durand, Alban Farchi, Marc Bocquet, Yumeng Chen, Alberto Carrassi, and Veronique Dansereau

In this talk, we propose to use neural networks in a hybrid modelling setup to learn sub-grid-scale dynamics of sea-ice that cannot be resolved by geophysical models. The multifractal and stochastic nature of the sea-ice dynamics create significant obstacles to represent such dynamics with neural networks. Here, we will introduce and screen specific neural network architectures that might be suited for this kind of task. To prove our concept, we perform idealised twin experiments in a simplified Maxwell-Elasto-Brittle sea-ice model which includes only sea-ice dynamics within a channel-like setup. In our experiments, we use high-resolution runs as proxy for the reality, and we train neural networks to correct errors of low-resolution forecast runs.

Since we perform the two kind of runs on different grids, we need to define a projection operator from high- to low-resolution. In practice, we compare the low-resolution forecasted state at a given time to the projected state of the high resolution run at the same time. Using a catalogue of these forecasted and projected states, we will learn and screen different neural network architectures with supervised training in an offline learning setting. Together with this simplified training, the screening helps us to select appropriate architectures for the representation of multifractality and stochasticity within the sea-ice dynamics. As a next step, these screened architectures have to be scaled to larger and more complex sea-ice models like neXtSIM.

How to cite: Finn, T., Durand, C., Farchi, A., Bocquet, M., Chen, Y., Carrassi, A., and Dansereau, V.: Learning and screening of neural networks architectures for sub-grid-scale parametrizations of sea-ice dynamics from idealised twin experiments, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5910, https://doi.org/10.5194/egusphere-egu22-5910, 2022.

EGU22-6948 | Presentations | CR2.8

Mapping Glacier Basal Sliding with Beamforming and Artificial Intelligence 

Josefine Umlauft, Philippe Roux, Albanne Lecointre, Florent Gimbert, Ugo Nanni, Andrea Walpersdorf, Bertrand Rouet-LeDuc, Claudia Hulbert, Daniel Trugman, and Paul Johnson

The cryosphere is a highly active and dynamic environment that rapidly responds to changing climatic conditions. In particular, the physical processes behind glacial dynamics are poorly understood because they remain challenging to observe. Glacial dynamics are strongly intermittent in time and heterogeneous in space. Thus, monitoring with high spatio-temporal resolution is essential.

In course of the RESOLVE (‘High-resolution imaging in subsurface geophysics : development of a multi-instrument platform for interdisciplinary research’) project, continuous seismic observations were obtained using a dense seismic network (100 nodes, Ø 700 m) installed on Glacier d’Argentière (French Alpes) during May in 2018. This unique data set offers the chance to study targeted processes and dynamics within the cryosphere on a local scale in detail.

 

To identify seismic signatures of ice beds in the presence of melt-induced microseismic noise, we applied the supervised ML technique gradient tree boosting. The approach has been proven suitable to directly observe the physical state of a tectonic fault. Transferred to glacial settings, seismic surface records could therefore reveal frictional properties of the ice bed, offering completely new means to study the subglacial environment and basal sliding, which is difficult to access with conventional approaches.

We built our ML model as follows: Statistical properties of the continuous seismic records (variance, kurtosis and quantile ranges), meteorological data and a seismic source catalogue obtained using beamforming (matched field processing) serve as features which we fit to measures of the GPS displacement rate of Glacier d’Argentière (labels). Our preliminary results suggest that seismic source activity at the bottom of the glacier strongly correlates with surface displacement rates and hence, is directly linked to basal motion. By ranking the importance of our input features, we have learned that other than for reasonably long monitoring time series along tectonic faults, statistical properties of seismic observations only do not suffice in glacial environments to estimate surface displacement. Additional beamforming features however, are a rich archive that enhance the ML model performance considerably and allow to directly observe ice dynamics.

How to cite: Umlauft, J., Roux, P., Lecointre, A., Gimbert, F., Nanni, U., Walpersdorf, A., Rouet-LeDuc, B., Hulbert, C., Trugman, D., and Johnson, P.: Mapping Glacier Basal Sliding with Beamforming and Artificial Intelligence, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6948, https://doi.org/10.5194/egusphere-egu22-6948, 2022.

EGU22-8945 | Presentations | CR2.8

Ice Lead Network Analysis 

Julia Kaltenborn, Venkatesh Ramesh, and Thomas Wright

Ice lead analysis is an essential task for evaluating climate change processes in the Arctic. Ice leads are narrow cracks in the sea-ice, which build a complex network. While detecting and modeling ice leads has been performed in numerous ways based on airborne images, the dynamics of ice leads over time remain hidden and largely unexplored. These dynamics could be analyzed by interpreting the ice leads as more than just airborne images, but as what they really are: a dynamic network. The lead’s start, end, and intersection points can be considered nodes, and the leads themselves as edges of a network. As the nodes and edges change over time, the ice lead network is constantly evolving. This new network perspective on ice leads could be of great interest for the cryospheric science community since it opens the door to new methods. For example, adapting common link prediction methods might make data-driven ice lead forecasting and tracking feasible.
To reveal the hidden dynamics of ice leads, we performed a spatio-temporal and network analysis of ice lead networks. The networks used and presented here are based on daily ice lead observations from Moderate Resolution Imaging Spectroradiometer (MODIS) between 2002 and 2020 by Hoffman et al. [1].
The spatio-temporal analysis of the ice leads exhibits seasonal, annual, and overall trends in the ice lead dynamics. We found that the number of ice leads is decreasing, and the number of width and length outliers is increasing overall. The network analysis of the ice lead graphs reveals unique network characteristics that diverge from those present in common real-world networks. Most notably, current network science methods (1) exploit the information that is embedded into the connections of the network, e.g., in connection clusters, while (2) nodes remain relatively fixed over time. Ice lead networks, however, (1) embed their relevant information spatially, e.g., in spatial clusters, and (2) shift and change drastically. These differences require improvements and modifications on common graph classification and link prediction methods such as Preferential Attachment and EvolveGCN on the domain of ice lead dynamic networks.
This work is a call for extending existing network analysis toolkits to include a new class of real-world dynamic networks. Utilizing network science techniques will hopefully further our understanding of ice leads and thus of Arctic processes that are key to climate change mitigation and adaptation.

Acknowledgments

We would like to thank Prof. Gunnar Spreen, who provided us insights into ice lead detection and possible challenges connected to the project idea. Furthermore, we would like to thank Shenyang Huang and Asst. Prof. David Rolnick for their valuable feedback and support. J.K. was supported in part by the DeepMind scholarship, the Mitacs Globalink Graduate Fellowship, and the German Academic Scholarship Foundation.

References

[1] Jay P Hoffman, Steven A Ackerman, Yinghui Liu, and Jeffrey R Key. 2019. The detection and characterization of Arctic sea ice leads with satellite imagers. Remote Sensing 11, 5 (2019), 521.

How to cite: Kaltenborn, J., Ramesh, V., and Wright, T.: Ice Lead Network Analysis, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8945, https://doi.org/10.5194/egusphere-egu22-8945, 2022.

EGU22-9753 | Presentations | CR2.8

Using LSTM on surface data to reconstruct 3D Temperature & Salinity profiles in the Arctic Ocean 

Mathias Jensen, Casper Bang-Hansen, Ole Baltazar Andersen, Carsten Bjerre Ludwigsen, and Mads Ehrhorn

In recent years, the importance of dynamics in the Arctic Ocean have proven itself with respect to climate monitoring and modelling. Data used for creating models often include temperature & salinity profiles. Such profiles in the Arctic region are sparse and acquiring new data is expensive and time-consuming. Thus, efficient methods of interpolation are necessary to expand regional data. In this project, 3D temperature & salinity profiles are reconstructed using 2D surface measurements from ships, floats and satellites. The technique is based on a stacked Long Short-Term Memory (LSTM) neural network. The goal is to be able to reconstruct the profiles using remotely sensed data.

How to cite: Jensen, M., Bang-Hansen, C., Andersen, O. B., Ludwigsen, C. B., and Ehrhorn, M.: Using LSTM on surface data to reconstruct 3D Temperature & Salinity profiles in the Arctic Ocean, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9753, https://doi.org/10.5194/egusphere-egu22-9753, 2022.

EGU22-10386 | Presentations | CR2.8

Arctic sea ice dynamics forecasting through interpretable machine learning 

Matteo Sangiorgio, Elena Bianco, Doroteaciro Iovino, Stefano Materia, and Andrea Castelletti

Machine Learning (ML) has become an increasingly popular tool to model the evolution of sea ice in the Arctic region. ML tools produce highly accurate and computationally efficient forecasts on specific tasks. Yet, they generally lack physical interpretability and do not support the understanding of system dynamics and interdependencies among target variables and driving factors.

Here, we present a 2-step framework to model Arctic sea ice dynamics with the aim of balancing high performance and accuracy typical of ML and result interpretability. We first use time series clustering to obtain homogeneous subregions of sea ice spatiotemporal variability. Then, we run an advanced feature selection algorithm, called Wrapper for Quasi Equally Informative Subset Selection (W-QEISS), to process the sea ice time series barycentric of each cluster. W-QEISS identifies neural predictors (i.e., extreme learning machines) of the future evolution of the sea ice based on past values and returns the most relevant set of input variables to describe such evolution.

Monthly output from the Pan-Arctic Ice-Ocean Modeling and Assimilation System (PIOMAS)  from 1978 to 2020 is used for the entire Arctic region. Sea ice thickness represents the target of our analysis, while sea ice concentration, snow depth, sea surface temperature and salinity are considered as candidate drivers.

Results show that autoregressive terms have a key role in the short term (with lag time 1 and 2 months) as well as the long term (i.e., in the previous year); salinity along the Siberian coast is frequently selected as a key driver, especially with a one-year lag; the effect of sea surface temperature is stronger in the clusters with thinner ice; snow depth is relevant only in the short term.

The proposed framework is an efficient support tool to better understand the physical process driving the evolution of sea ice in the Arctic region.

How to cite: Sangiorgio, M., Bianco, E., Iovino, D., Materia, S., and Castelletti, A.: Arctic sea ice dynamics forecasting through interpretable machine learning, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10386, https://doi.org/10.5194/egusphere-egu22-10386, 2022.

EGU22-10637 | Presentations | CR2.8

A deep learning approach for mapping and monitoring glacial lakes from space 

Manu Tom, Holger Frey, and Daniel Odermatt

Climate change intensifies glacier melt which effectively leads to the formation of numerous new glacial lakes in the overdeepenings of former glacier beds. Additionally, the area of many existing glacial lakes is increasing. More than one thousand glacial lakes have emerged in Switzerland since the Little Ice Age, and hundreds of lakes are expected to form in the 21st century. Rapid deglaciation and formation of new lakes severely affect downstream ecosystem services, hydropower production and high-alpine hazard situations. Day by day, glacier lake inventories for high-alpine terrains are increasingly becoming available to the research community. However, a high-frequency mapping and monitoring of these lakes are necessary to assess hazards and to estimate Glacial Lake Outburst Flood (GLOF) risks, especially for lakes with high seasonal variations. One way to achieve this goal is to leverage the possibilities of satellite-based remote sensing, using optical and Synthetic Aperture Radar (SAR) satellite sensors and deep learning.

There are several challenges to be tackled. Mapping glacial lakes using satellite sensors is difficult, due to the very small area of a great majority of these lakes. The inability of the optical sensors (e.g. Sentinel-2) to sense through clouds creates another bottleneck. Further challenges include cast and cloud shadows, and increased levels of lake and atmospheric turbidity. Radar sensors (e.g. Sentinel-1 SAR) are unaffected by cloud obstruction. However, handling cast shadows and natural backscattering variations from water surfaces are hurdles in SAR-based monitoring. Due to these sensor-specific limitations, optical sensors provide generally less ambiguous but temporally irregular information, while SAR data provides lower classification accuracy but without cloud gaps.

We propose a deep learning-based SAR-optical satellite data fusion pipeline that merges the complementary information from both sensors. We put forward to use Sentinel-1 SAR and Sentinel-2 L2A imagery as input to a deep network with a Convolutional Neural Network (CNN) backbone. The proposed pipeline performs a fusion of information from the two input branches that feed heterogeneous satellite data. A shared block learns embeddings (feature representation) invariant to the input satellite type, which are then fused to guide the identification of glacial lakes. Our ultimate aim is to produce geolocated maps of the target regions where the proposed bottom-up, data-driven methodology will classify each pixel either as lake or background.

This work is part of two major projects: ESA AlpGlacier project that targets mapping and monitoring of the glacial lakes in the Swiss (and European) Alps, and the UNESCO (Adaptation Fund) GLOFCA project that aims to reduce the vulnerabilities of populations in the Central Asian countries (Kazakhstan, Tajikistan, Uzbekistan, and Kyrgyzstan) from GLOFs in a changing climate. As part of the GLOFCA project, we are developing a python-based analytical toolbox for the local authorities, which incorporates the proposed deep learning-based pipeline for mapping and monitoring the glacial lakes in the target regions in Central Asia.

How to cite: Tom, M., Frey, H., and Odermatt, D.: A deep learning approach for mapping and monitoring glacial lakes from space, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10637, https://doi.org/10.5194/egusphere-egu22-10637, 2022.

EGU22-12785 | Presentations | CR2.8

Machine learning tools for pattern recognition in polar climate science 

William Gregory

Over the past four decades, the inexorable growth in technology and subsequently the availability of Earth-observation and model data has been unprecedented. Hidden within these data are the fingerprints of the physical processes that govern climate variability over a wide range of spatial and temporal scales, and it is the task of the climate scientist to separate these patterns from noise. Given the wealth of data now at our disposal, machine learning methods are becoming the tools of choice in climate science for a variety of applications ranging from data assimilation, to sea ice feature detection from space. This talk summarises recent developments in the application of machine learning methods to the study of polar climate, with particular focus on Arctic sea ice. Supervised learning techniques including Gaussian process regression, and unsupervised learning techniques including cluster analysis and complex networks, are applied to various problems facing the polar climate community at present, where each application can be considered an individual component of the larger sea ice prediction problem. These applications include: seasonal sea ice forecasting, improving spatio-temporal data coverage in the presence of sparse satellite observations, and illuminating the spatio-temporal connectivity between climatological processes.

How to cite: Gregory, W.: Machine learning tools for pattern recognition in polar climate science, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12785, https://doi.org/10.5194/egusphere-egu22-12785, 2022.

EGU22-12882 | Presentations | CR2.8

Inverse modelling techniques for snow and ice thickness retrievals from satellite altimetry  

Joel Perez Ferrer, Michel Tsamados, Matthew Fox, Tudor Suciu, Harry Heorton, and Carmen Nab

We have recently applied an objective mapping type approach to merge observations from multiple altimeters, both for enhancing the temporal/spatial resolution of freeboard samples and for analyzing crossovers between satellites (Gregory et al, 2021). This mapping provides optimal interpolation of proximal observations to a location in space and time based on the covariance of the observations and a priori understanding of their spatiotemporal correlation length scales. This offers a best linear estimator and error field for the observation (radar freeboard or snow depth), which can be used to better constrain pan-Arctic uncertainties. 

 

In addition we will explore here a newly developed inverse modelling framework  to synchronously retrieve the snow and ice thickness from bias corrected or calibrated radar freeboards from multiple satellite retrievals. The radar equations expressed in section can be rearranged to formulate the joint forward model at gridded level relating measured radar freeboards from multiple satellites (and airborne data) to the underlying snow and ice thickness. In doing so we have also introduced a penetration factor correction term for OIB radar freeboard measurements. To solve this inverse model problem for  and  we use the following two methodologies inspired from Earth Sciences applications (i.e. seismology):  

 

Space ‘uncorrelated’ inverse modelling. The method is called `space uncorrelated' inverse modelling as the algorithm is applied locally, for small distinct regions in the Arctic Ocean, multiple times, until the entire Arctic ocean is covered. To sample the parameter space  we use the publicly available Neighbourhoud Algorithm (NA) developed originally for seismic tomography of Earth’s interior and recently by us to a sea ice dynamic inversion problem (Hoerton et al, 2019).   

 

Space ‘correlated inverse modelling. For the second method of inverse modelling, we used what we call a `space correlated' approach. Here the main algorithm is applied over the entire Arctic region, aiming to retrieve the desired parameters at once. In contrast with the previous approach, in this method we take into account positional correlations for the physical parameters when we are solving the inverse problem, the output being a map of the Arctic composed of a dynamically generated a tiling in terms of Voronoi cells. In that way, regions with less accurate observations will be more coarsely resolved while highly sampled regions will be provided on a finer grid with a smaller uncertainty. The main algorithm used here to calculate the posterior solution is called `reverse jump Monte Carlo Markov Chain' (hereafter referred to as rj-MCMC) and its concept was designed by Peter Green in 1999 (Green, 1995). Bodin and Sambridge (2009) adapted this algorithm for seismic inversion, which is the basis of the algorithm used in this study.  

 

How to cite: Perez Ferrer, J., Tsamados, M., Fox, M., Suciu, T., Heorton, H., and Nab, C.: Inverse modelling techniques for snow and ice thickness retrievals from satellite altimetry , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12882, https://doi.org/10.5194/egusphere-egu22-12882, 2022.

EGU22-753 | Presentations | CR2.9

3D sequential data assimilation in Elmer/Ice with Stokes 

Samuel Cook and Fabien Gillet-Chaulet

Providing suitable initial states is a long-standing problem in numerical modelling of glaciers and ice sheets, as well as in other areas of the geosciences, due to the frequent lack of observations. This is particularly acute in glaciology, where important parameters such as the underlying bed may be only very sparsely observed or even completely unobserved. Glaciological models also often require lengthy relaxation periods to dissipate incompatibilities between input datasets gathered over different timeframes, which may lead to the modelled initial state diverging significantly from the real state of the glacier, with consequent effects on the accuracy of the simulation. Sequential data assimilation using an ensemble offers one possibility for resolving both these issues: by running the model over a period for which various observational datasets are available and loading observations into the model at the time they were gathered, the model state can be brought into good agreement with the real glacier state at the end of the observational window. The mean values of the ensemble for unknown parameters, such as the bed, then also represent best guesses for the true parameter values. This assimilated model state can then be used to initialise prognostic runs without introducing model artefacts or a distorted picture of the actual glacier.

In this study, we present a framework for conducting sequential data assimilation and retrieving the bed of a glacier in a 3D setting of the open-source, finite-element glacier flow model, Elmer/Ice, and solving the Stokes equations rather than using the shallow shelf approximation. Assimilation is undertaken using the open-source PDAF library developed at the Alfred Wegener Institute. We demonstrate that the set-up allows us to accurately retrieve the bed of a synthetic glacier and present our plans to extend it to a real-world example.

How to cite: Cook, S. and Gillet-Chaulet, F.: 3D sequential data assimilation in Elmer/Ice with Stokes, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-753, https://doi.org/10.5194/egusphere-egu22-753, 2022.

EGU22-896 | Presentations | CR2.9

Uncertainty quantification for melt rate parameters in ice shelves using simulation-based inference 

Guy Moss, Vjeran Višnjević, Cornelius Schröder, Jakob Macke, and Reinhard Drews

Mass loss from the Antarctic ice sheet is dominated by the integrity of the ice shelves that buttress it. The evolution and stability of ice shelves is dependent on a variety of parameters that cannot be directly observed, such as basal melt and ice rheology. Constraining these parameters is of great importance in making predictions of the future changes in ice shelves that have a quantifiable uncertainty. This inference task is difficult in practice as the number of unknown parameters is large, observations are often sparse, and the computational cost of ice flow models is high.

We aim to develop a framework for inferring joint distributions of mass balance and rheological parameters of ice shelves from observations such as ice geometry, surface velocities, and radar isochrones. Here, we begin by inferring a posterior distribution over basal melt parameters in along-flow sections of synthetic and real world ice shelves (Roi Baudouin). We use the technique of simulation-based inference (SBI), a machine learning framework for performing Bayesian inference when the likelihood function is intractable. The inference procedure relies on the availability of a simulator to model the dynamics of the ice shelves. For this we use the Shallow Shelf Approximation (SSA) implemented in the Python library Icepack.  First, we show that by combining these two tools we can recover the underlying parameters of synthetic 2D data with meaningful uncertainty estimates. In a second step, we apply our method to real observations and get estimates for the basal melt rates which are coherent with the data when running the forward model over a centennial timescale.



How to cite: Moss, G., Višnjević, V., Schröder, C., Macke, J., and Drews, R.: Uncertainty quantification for melt rate parameters in ice shelves using simulation-based inference, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-896, https://doi.org/10.5194/egusphere-egu22-896, 2022.

EGU22-2061 | Presentations | CR2.9

Assimilation of CryoSat-2 radar Freeboard data in a global ocean-sea ice modelling system. 

Aliette Chenal, Charles-Emmanuel Testut, Florent Garnier, Parent Laurent, and Garric Gilles

Sea ice is a key element in our climate system, and it is very sensitive to the current observed climate change. Sea ice volume is a sensitive indicator of the health of Arctic although very challenging to estimate precisely since it is a combination of sea ice area and sea ice thickness. Arctic sea ice volume has decreased by as much as 75% at the end of the summer season if compared with the conditions 40 years ago. The ongoing decline of Arctic sea ice exposes the ocean to anomalous surface heat and freshwater fluxes that can have potential implication for the Arctic region and beyond, for the general oceanic circulation itself.

For more than a decade, Mercator Ocean International develops and produces Global Ocean Reanalysis with a 1/4° resolution system. Based on the NEMO modelling platform, observations are assimilated by a reduced-order Kalman filter. In-situ CORA database, altimetric data, sea surface temperature, and sea ice concentration are jointly assimilated to constrain the ocean and sea ice model.

In previous reanalysis, long-term sea ice volume drift has been observed in the Arctic. To obtain a better constraint on the sea ice thickness, Cryosat-2 radar Freeboard data are assimilated jointly with the sea ice concentration in a multidata/multivariate sea ice analysis. The coupled ocean and ice assimilation system runs on a 7-day cycle, using IAU (Incremental Analysis Update) and a 4D increment. The “white ocean” is modelled with the multi-categories LIM3.6 sea ice numerical model. The aim of this study is to initiate the development of the future operational multi-variate and multi-data sea ice analysis system with freeboard radar assimilation.

After describing this global sea ice reanalysis system, we present results on the abilities of this configuration to reproduce sea ice extent and volume interannual variability in both hemispheres. Comparisons between experiments with and without assimilation show that the joint assimilation of CryoSat-2 radar freeboard and sea ice concentration reduces most of model biases of sea ice thickness, e.g., in the north of the Canadian Arctic Archipelago and in the Beaufort Sea in the Arctic. Moreover, radar freeboard assimilation does not hinder the good results in simulating sea ice extent previously obtained with the assimilation of only sea ice concentration. Validation with non-assimilated satellite data and in-situ data supports these findings. Lastly, snow depth significantly influences the Freeboard measurement: this study also reveals the importance of including snow information on freeboard retrieval and on the ice volume assimilation methodology.

These experiments take place in a context of increasing interest in polar regions and prepare the launch of Copernicus Sentinel expansion satellite missions.

How to cite: Chenal, A., Testut, C.-E., Garnier, F., Laurent, P., and Gilles, G.: Assimilation of CryoSat-2 radar Freeboard data in a global ocean-sea ice modelling system., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2061, https://doi.org/10.5194/egusphere-egu22-2061, 2022.

EGU22-2535 | Presentations | CR2.9

Quantifying Holocene Accumulation Rates from Ice-Core Dated Internal Layers from Ice-Penetrating Radar Data over the West Antarctic Ice Sheet 

Julien Bodart, Robert Bingham, Duncan Young, Donald Blankenship, and David Vaughan

Modelling the past and future evolution of the West Antarctic Ice Sheet (WAIS) to climate and ocean forcing is challenged by the availability and quality of observed palaeo boundary conditions. Aside from point-based geochronological measurements, the only available proxy to query past ice-sheet processes on large spatial scales is Internal Reflecting Horizons (IRHs) as sounded by ice-penetrating radar. When isochronal, IRHs can be used to determine palaeo-accumulation rates and patterns, as previously demonstrated using shallow, centennially dated layers. Whilst similar efforts using deeper IRHs have previously been conducted over the East Antarctic Plateau where ice-flow is slow and ice thickness has been stable through time, much less is known of millennial-scale accumulation rates over the West Antarctic plateau due to challenging ice dynamical conditions in the downstream section of the ice sheet. Using deep and spatially extensive ice-core dated IRHs over Pine Island and Thwaites glaciers and a local layer approximation model, we quantify Holocene accumulation rates over the slow-flowing parts of these sensitive catchments. The results from the one-dimensional model are also compared with modern accumulation rates from observational and modelled datasets to investigate changes in accumulation rates and patterns between the Holocene and the present. The outcome of this work is that together with present and centennial-scale accumulation rates, our results can help determine whether a trend in accumulation rates exists between the Holocene and the present and thus test to what extent these glaciers are controlled by ice dynamics rather than changes in accumulation rates.

How to cite: Bodart, J., Bingham, R., Young, D., Blankenship, D., and Vaughan, D.: Quantifying Holocene Accumulation Rates from Ice-Core Dated Internal Layers from Ice-Penetrating Radar Data over the West Antarctic Ice Sheet, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2535, https://doi.org/10.5194/egusphere-egu22-2535, 2022.

EGU22-3743 | Presentations | CR2.9

Numerical modelling of ice stream fabrics: Implications for recrystallization processes and basal slip conditions 

Daniel Richards, Sam Pegler, and Sandra Piazolo

Accurately predicting ice crystal fabrics is key to understanding the processes and deformation in ice-sheets. Here we use SpecCAF, a continuum fabric evolution model validated against laboratory experiments, to predict the fabric evolution with an active ice stream. This is done by predicting the fabrics at the East Greenland Ice core Project (EGRIP) site. We do this using satellite data and inferred particle paths, combined with the shallow ice approximation (with basal slip) to infer a leading order approximation for the deformation through the ice sheet. We find that SpecCAF is able to predict the patterns observed at EGRIP - a girdle/horizontal maxima fabric perpendicular to the flow direction. By reducing the rate of rotational recrystallization in the model we are also able to predict the fabric strength at EGRIP. This suggests the effect of rotational recrystallization on the fabric may be primarily strain-rate/stress dependent. These results show SpecCAF can be applied to real-world conditions and provide insights into the deformation and basal-conditions of the ice sheet. As the model only considers deformation and recrystallization through dislocation creep, the results imply that - for the ice stream modelled - no other process is significantly influencing both the produced ice fabric and the deformation. We find that the model gives best results for full slip at the base of the ice sheet, implying that the level of sliding at the base of the ice sheet in the North Greenland Ice stream may be very high. The methodology used here can be extended to other ice core locations in Greenland and Antarctica.

How to cite: Richards, D., Pegler, S., and Piazolo, S.: Numerical modelling of ice stream fabrics: Implications for recrystallization processes and basal slip conditions, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3743, https://doi.org/10.5194/egusphere-egu22-3743, 2022.

EGU22-4027 | Presentations | CR2.9

Basal Properties of the Filchner-Ronne Sector of Antarctica from Inverse Modeling and Comparison with Ice-Penetrating Radar Data 

Michael Wolovick, Lea-Sophie Höyns, Thomas Kleiner, Niklas Nickel, Veit Helm, and Angelika Humbert

Lubrication by subglacial water or saturated subglacial sediments is crucial to controlling the movement of fast-flowing outlet glaciers and ice streams.  However, the subglacial environment is difficult to observe directly.  Here, we combine inverse modeling with ice-penetrating radar observations to characterize the ice sheet bed in the Filchner-Ronne sector of Antarctica, with a specific focus on the Recovery Glacier catchment.  First, we use the Ice Sheet System Model (ISSM; Larour et al., 2012) to assimilate satellite observations of ice sheet surface velocity (Mouginot et al., 2019) in order to solve for basal drag and ice rheology across the Filchner-Ronne sector of Antarctica.  Next, we compare these results with ice-penetrating radar observations sensitive to the presence of ponded water at the ice sheet base (Humbert et al., 2018; Langley et al., 2011), along with remotely sensed observations of active lakes (Smith et al., 2009) and putative large subglacial lakes inferred from the ice sheet surface slope (Bell et al., 2007).  We find that the main fast-flowing region of Recovery Glacier is mostly low-drag, with the exception of localized sticky spots and bands.  The boundary between rugged subglacial highlands and a deep subglacial basin near the onset of the ice stream is associated with a sharp reduction in basal drag, although surface velocity changes smoothly rather than abruptly across this transition.  An upstream shear margin, visible in satellite radar images of the ice surface, is associated with low basal drag.  The putative large lakes have low drag but are not strongly distinguished from their surroundings, and radar evidence for ponded subglacial water within them is weak.  The active lakes identified from satellite altimetry are similarly situated in areas of low basal drag, but have limited radar evidence for ponded subglacial water.  An L-curve analysis indicates that our inverse model results are robust against changes in regularization, yet the radar-identified lake candidates do not have a clear relationship with low-drag areas in the fast-flowing ice stream.  We conclude that the deep-bedded regions of Recovery Glacier are underlain by saturated subglacial sediments, but classic ponded subglacial lakes are much more rare.  Isolated sticky spots and bands within the ice stream are either due to protrusions of bedrock out of the sediments or to localized areas of frozen and/or compacted sediments.

How to cite: Wolovick, M., Höyns, L.-S., Kleiner, T., Nickel, N., Helm, V., and Humbert, A.: Basal Properties of the Filchner-Ronne Sector of Antarctica from Inverse Modeling and Comparison with Ice-Penetrating Radar Data, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4027, https://doi.org/10.5194/egusphere-egu22-4027, 2022.

EGU22-5113 | Presentations | CR2.9

Estimating large scale dynamic mountain glacier states with numerical modelling and data assimilation 

Patrick Schmitt, Fabien Maussion, and Philipp Gregor

Ongoing global glacier retreat leads to sea-level rise and changes in regional freshwater availability. For an adequate adaptation to these changes, knowledge about the ice volume and the current dynamic state of glaciers is crucial. At regional to global scales, sparse observations made the dynamic state of glaciers very difficult to assess. Thanks to recent advances in global geodetic mass-balance and velocity assessments, new ways to initialize numerical models and ice thickness estimation emerge. In this contribution, we present the COst Minimization Bed INvErsion model (COMBINE), which aims to be a cheap, flexible global data assimilation and inversion method. COMBINE uses an existing numerical model of glacier evolution (the Open Global Glacier Model, OGGM) rewritten in the machine learning framework PyTorch. This makes the model fully differentiable and allows to iteratively minimize a cost function penalizing mismatch to observations. Thanks to the flexible nature of automatic differentiation, various observational sources distributed in time can be considered (e.g. surface elevation and area changes, ice velocities). No assumption about the dynamic glacier state is needed, releasing the equilibrium assumption often required for large scale ice volume computations. In this contribution, we will demonstrate the capabilities of COMBINE in several idealized and real-world applications, and discuss its added value and upcoming challenges for operational application.

How to cite: Schmitt, P., Maussion, F., and Gregor, P.: Estimating large scale dynamic mountain glacier states with numerical modelling and data assimilation, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5113, https://doi.org/10.5194/egusphere-egu22-5113, 2022.

EGU22-5425 | Presentations | CR2.9

Modeling the Greenland englacial stratigraphy 

Andreas Born, Alexander Robinson, and Alexios Theofilopoulos

Radar reflections from the interior of the Greenland ice sheet contain a comprehensive archive of past accumulation rates, ice dynamics, and basal melting. Combining these data with dynamic ice sheet models may greatly aid model calibration, improve past and future sea level estimates, and enable insights into past ice sheet dynamics that neither models nor data could achieve alone.

In this study, we present the first three-dimensional ice sheet model that explicitly simulates the Greenland englacial stratigraphy. Individual layers of accumulation are represented on a grid whose vertical axis is time so that they do not exchange mass with each other as the flow of ice deforms them. This isochronal advection scheme does not influence the ice dynamics and only requires modest input data from a host thermomechanical ice sheet model.

Using an ensemble of simulations, we show that direct comparison with the dated radiostratigraphy data yields notably more accurate results than calibrating simulations based on total ice thickness. We show that the isochronal scheme produces a more reliable simulation of the englacial age profile than Eulerian age tracers. Lastly, we outline how the isochronal model can be linearized as a foundation for inverse modeling and data assimilation.

How to cite: Born, A., Robinson, A., and Theofilopoulos, A.: Modeling the Greenland englacial stratigraphy, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5425, https://doi.org/10.5194/egusphere-egu22-5425, 2022.

EGU22-8605 | Presentations | CR2.9

Coupling modelling and satellite observations to constrain subglacial melt rates and hydrology 

Martin Wearing, Daniel Goldberg, Christine Dow, Anna Hogg, and Noel Gourmelen

Meltwater forms at the base of the Antarctic Ice Sheet due to geothermal heat flux (GHF) and basal frictional dissipation. Despite the relatively small volume, this meltwater has a profound effect on ice-sheet stability, controlling the dynamics of the ice sheet and the interaction of the ice sheet with the ocean. However, observations of subglacial melting and hydrology in Antarctica are limited. Here we use numerical modelling to assess subglacial melt rates and hydrology beneath the Antarctic Ice Sheet. Our case study, focused on the Amery Ice Shelf catchment, shows that total subglacial melting in the catchment is 6.5 Gt yr-1, over 50% larger than previous estimates. Uncertainty in estimates of GHF leads to a variation in total melt of ±7%. The meltwater provides an extra 8% flux of freshwater to the ocean in addition to contributions from iceberg calving and melting of the ice shelf. GHF and basal dissipation contribute equally to the total melt rate, but basal dissipation is an order of magnitude larger beneath ice streams. Remote-sensing observations, from CryoSat-2, indicating active subglacial lakes and ice-shelf basal melting constrain subglacial hydrology modelling. We observe a network of subglacial channels that link subglacial lakes and trigger isolated areas of sub-ice-shelf melting close to the grounding line. Building upon this Amery case study, we expand our analysis to quantify subglacial melt rates and hydrology beneath the entire Antarctic Ice Sheet.

How to cite: Wearing, M., Goldberg, D., Dow, C., Hogg, A., and Gourmelen, N.: Coupling modelling and satellite observations to constrain subglacial melt rates and hydrology, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8605, https://doi.org/10.5194/egusphere-egu22-8605, 2022.

EGU22-8938 | Presentations | CR2.9

Constraining Soil Freezing Models using Observed Soil Freezing Characteristic Curves 

Élise Devoie, Stephan Gruber, and Jeffrey McKenzie

Objective: Estimate Soil Freezing Characteristic Curves (SFCCs) and uncertainty bounds based on a compilation of existing measured SFCCs.

Key Findings

  • Uncertainty in measured SFCCs is estimated based on measurement technique, water content, and soil disturbance
  • An open-source tool for estimating and constraining SFCCs is developed for use in parameterizing freeze/thaw models

Abstract

Cold-regions landscapes are undergoing rapid change due to a warming climate. This change is impacting many elements of the landscape and is often controlled by soil freeze/thaw processes. Soil freeze/thaw is governed by the Soil Freezing Characteristic Curve (SFCC) that relates the soil temperature to its unfrozen water content. This relation is needed in all physically based numerical models including soil freeze/thaw processes. A repository of all collected SFCC data and an R package for accessing and processing this data was presented in "A Repository of 100+ Years of Measured Soil Freezing Characteristic Curves".

This rich SFCC dataset is synthesized with a focus on potential sources of error due to the combination of measurement technique, data interpretation, and physical freeze-thaw process in a specific soil. Particular attention is given to combining sources of error and working with datasets given incomplete and missing metadata. A tool is developed to extract an SFCC for a soil with specified properties alongside its uncertainty bounds. This tool is intended for use in freeze/thaw models to improve freeze/thaw estimates, and better represent the ice and liquid water content of freezing soils. As phase change accounts for a vast majority of the energy budget in freezing soils, accurately representing the process is essential for realistic predictions. In addition, SFCC type curves are provided for the common sand, silt, clay, and organic soil textures when additional data is unavailable to define the SFCC more precisely.

How to cite: Devoie, É., Gruber, S., and McKenzie, J.: Constraining Soil Freezing Models using Observed Soil Freezing Characteristic Curves, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8938, https://doi.org/10.5194/egusphere-egu22-8938, 2022.

EGU22-9143 | Presentations | CR2.9

Assessing the continuity of englacial layers across the Lambert Glacier catchment. 

Rebecca Sanderson, Neil Ross, Louise Callard, Kate Winter, Felipe Napoleoni, Robert Bingham, and Tom Jordan

The analysis of englacial layers using ice penetrating radar enables the characterisation and reconstruction of current and past ice sheet flow. To date, little research has been undertaken on the ice flow and englacial stratigraphy of the upper catchment of the Lambert Glacier. The Lambert Glacier catchment is one of the largest in East Antarctica, discharging ~16% of East Antarctica’s ice. Quantitative analysis of the continuity of englacial stratigraphy and ice flow has the potential to provide insight into the present-day and past flow regimes of the upper catchment of Lambert Glacier. Radar data from the British Antarctic Survey Antarctica’s Gamburtsev Province Project North (AGAP-N) aerogeophysical survey was analysed using the Internal Layer Continuity Index (ILCI). This approach identified, and characterised, a range of englacial structures and stratigraphy, including buckled layers in areas of increased ice velocity (>20ma-1) and continuous layering across subglacial highlands with low ice velocity adjacent to the central Lambert Glacier trunk. Overall, the analysis is consistent with the present-day ice-flow velocity field and long-term stability of ice flow across the Lambert catchment. However, disrupted layer geometry at the onset of the Lambert Glacier suggests a past shift in the position of the onset of ice flow. These results have implications for the future evolution of this major ice flow catchment, and East Antarctica, under a changing climate. The ILCI method represents a valuable tool for rapidly characterising englacial stratigraphy, and the study demonstrates the transferability of the method across Antarctica. The use of quantitative tools such as ILCI for the analysis of large radar datasets will be critical for projects such as AntArchitecture (https://www.scar.org/science/antarchitecture/home/) which aims to investigate the long-term stability of the Antarctic ice sheets directly from the internal architecture of the ice sheet.

How to cite: Sanderson, R., Ross, N., Callard, L., Winter, K., Napoleoni, F., Bingham, R., and Jordan, T.: Assessing the continuity of englacial layers across the Lambert Glacier catchment., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9143, https://doi.org/10.5194/egusphere-egu22-9143, 2022.

EGU22-9262 | Presentations | CR2.9

Assimilating Cyrosat2 freeboard into a coupled ice-ocean model  

Imke Sievers, Lars Stenseng, and Till Rasmussen
This presentation introduces a method to assimilate freeboard from radar satellite observations.
Many studies have shown that the skill and memory of sea ice models using sea ice thickness as initial condition improve compered to model runs only initializing sea ice concentration. The only Arctic wide sea ice thickness data which could be used for initialization is coming from satellite observations. Since sea ice can’t directly be measured from space freeboard data is used to derive sea ice thickness. Freeboard is converted under assumption of hydrostatic equilibrium to sea ice thickness. For this conversion snow thickness is needed. Due to a lack of Arctic wide snow cover observations most products use a snow climatology or a modification of one. This has proofed to introduce errors. To avoid the errors introduced by this method the presented work aims to assimilate freeboard directly. This presentation will introduce the method and show first results. The assimilation period overlaps with ICESat2 mission. We present a comparison between the presented freeboard assimilation and ICESat2 sea ice thickness products of a first winter season.

How to cite: Sievers, I., Stenseng, L., and Rasmussen, T.: Assimilating Cyrosat2 freeboard into a coupled ice-ocean model , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9262, https://doi.org/10.5194/egusphere-egu22-9262, 2022.

EGU22-9886 | Presentations | CR2.9

Automated Tracking of Glacial Lake Outburst Floods in Norway 

Jogscha Abderhalden and Irina Rogozhina

No continuously updated glacier and glacial lake inventories exist for Norway. Previous inventories have been developed for the time periods of 1947-1985, 1988-1997 and 1999-2006 for glaciers and 1988-1997, 1999-2006, 2014 and 2018 for glacial lakes, by manual digitization, and semi-automated mapping. However, these methods are both time consuming and do not allow for an analysis of glacial lake behaviour on shorter timescales or on a seasonal basis. Therefore, one aim of this study is to present consistent inventories for glaciers and glacial lakes in Norway using semi-automated mapping and machine learning techniques applied on satellite imagery of different spatial and temporal resolution (Landsat 30m, 16 days, and Sentinel 10m, 5 days). An automated method that allows frequent monitoring of glacier variables can provide essential knowledge for the understanding of glacial lake dynamics in a changing climate.

In addition to glacial lake inventories, smaller ice caps with active glacial lakes are investigated more closely, aiming at following the development of glacial lakes throughout seasons. Here we are also analyzing the suitability of PlanetScope imagery compared to the Sentinel and Landsat imagery to detect the known glacial lake outburst flood events and identify currently unrecognized hazard-prone glacial lakes. Since the field-based investigations of glacial lake changes (especially of the ice-dammed lakes) are sparse in Norway, developing methods for remote-sensed, automated monitoring of glacial lake changes and glacial lake outburst floods is essential in order to develop early warning systems, detect potentially hazardous lakes and prevent human losses and damages to infrastructure and local businesses.

How to cite: Abderhalden, J. and Rogozhina, I.: Automated Tracking of Glacial Lake Outburst Floods in Norway, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9886, https://doi.org/10.5194/egusphere-egu22-9886, 2022.

EGU22-10509 | Presentations | CR2.9

A probabilistic analysis of permafrost temperature trends with ensemble modeling of heat transfer 

Brian Groenke, Moritz Langer, Guillermo Gallego, and Julia Boike

Over the past few decades, polar research teams around the world have deployed long-term measurement sites to monitor changes in permafrost environments. Many of these sites include borehole sensor arrays which provide measurements of ground temperature as deep as 50 meters or more below the surface. Recent studies have attempted to leverage these borehole data from the Global Terrestrial Network of Permafrost to quantify changes in permafrost temperatures at a global scale. However, temperature measurements provide an incomplete picture of the Earth's subsurface thermal regime. It is well known that regions with warmer permafrost, i.e. where mean annual ground temperatures are close to zero, often show little to no long-term change in ground temperature due to the latent heat effect. Thus, regions where the least warming is observed  may also be the most vulnerable to rapid permafrost thaw. Since direct measurements of soil moisture in the permafrost layer are not widely available, thermal modeling of the subsurface plays a crucial role in understanding how permafrost responds to changes in the local energy balance. In this work, we explore a new probabilistic method to link observed annual temperatures in boreholes to permafrost thaw via Bayesian parameter estimation and Monte Carlo simulation with a transient heat model. We apply our approach to several sites across the Arctic and demonstrate the impact of local landscape variability on the relationship between long term changes in temperature and latent heat.

How to cite: Groenke, B., Langer, M., Gallego, G., and Boike, J.: A probabilistic analysis of permafrost temperature trends with ensemble modeling of heat transfer, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10509, https://doi.org/10.5194/egusphere-egu22-10509, 2022.

EGU22-11310 | Presentations | CR2.9

Layer geometry as a constraint on the physics of sliding onset 

Elisa Mantelli, Marnie Bryant, Helene Seroussi, Ludovic Raess, Davide Castelletti, Dustin Schroeder, Jenny Suckale, and Martin Siegert

Transitions from basal no slip to basal sliding are a common feature of ice sheets, yet one that has remained difficult to observe. In this study we leverage recent advances in the processing of radar sounding data to study these transitions through their signature in englacial layers. Englacial layers encode information about strain and velocity, and the relation between their geometry and the onset of basal sliding has been demonstrated in ice flow models (the so-called "Weertman effect"). Here we leverage this relation to test the long-standing hypothesis that sliding onset takes the form of an abrupt no slip/sliding transition. By comparing the modeled signature of an abrupt sliding onset in englacial layer slopes against slope observations from the onset region of a West Antarctic ice stream (Institute Ice Stream), we conclude that observed layer geometry does not support an abrupt no slip/sliding transition. Our findings instead suggest a much smoother sliding onset, as would be consistent with temperature-dependent friction between ice and bed. Direct measurements of basal temperature at the catchment scale would allow us to confirm this hypothesis.

How to cite: Mantelli, E., Bryant, M., Seroussi, H., Raess, L., Castelletti, D., Schroeder, D., Suckale, J., and Siegert, M.: Layer geometry as a constraint on the physics of sliding onset, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11310, https://doi.org/10.5194/egusphere-egu22-11310, 2022.

EGU22-13501 | Presentations | CR2.9

Investigating basal thaw as a driver of mass loss from the Antarctic ice sheet 

Eliza Dawson, Dustin Schroeder, Winni Chu, Elisa Mantelli, and Hélène Seroussi

Contemporary mass loss from the Antarctic ice sheet primarily originates from the discharge of
marine-terminating glaciers and ice streams. The rate of mass loss is influenced by warming ocean
and atmospheric conditions, which lead to subsequent thinning or disintegration of ice shelves and
increased outflow of upstream grounded ice. It is currently unclear how the basal thermal state of
grounded ice could evolve in the future - for example as a result of accelerated ice flow or changes
in the ice sheet geometry - but a change in the basal thermal state could impact rates of mass loss
from Antarctica. Here, we use a combination of numerical simulations and ice-penetrating radar
analysis to investigate the influence of basal thawing on 100yr simulations of the Antarctic ice
sheet’s evolution. Using the Ice-sheet and Sea-level System Model, we find that thawing patches
of frozen bed near the ice sheet margin could drive mass loss extending into the continental
interior, with the highest rates of loss coming from the George V - Adélie - Wilkes Land coast and
the Enderby - Kemp Land regions of East Antarctica. This suggests that the thawing of localized
frozen bed patches is sufficient to cause these East Antarctic regions to transition to an unstable
mass loss regime. We constrain model estimates of the basal thermal state using ice-penetrating
radar surveys and analyze radar characteristics including bed reflectivity and attenuation. In
combination, our work identifies critical regions of Antarctica where the ice-bed interface could
be close to thawing and where basal thaw could most impact mass loss.

How to cite: Dawson, E., Schroeder, D., Chu, W., Mantelli, E., and Seroussi, H.: Investigating basal thaw as a driver of mass loss from the Antarctic ice sheet, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13501, https://doi.org/10.5194/egusphere-egu22-13501, 2022.

EGU22-64 | Presentations | G3.1

Surface loading on GNSS stations in Africa 

Saturday Ehisemhen Usifoh, T.Nhung Le, Benjamin Männel, Pierre Sakic, Dodo Joseph, and Harald Schuh

Surface loading on GNSS stations in Africa

Usifoh Saturday E1,2,3, Nhung Le Thi1,2, Benjamin Männel1, Pierre Sakic1, Dodo Joseph3, Harald Schuh1,2
1GFZ German Research Centre for Geosciences, Potsdam, Germany, 2Institut für Geodäsie und Geoinformationstechnik Technische Universität, Berlin, Germany, 3Centre for Geodesy and Geodynamics, Toro, Bauchi State, Nigeria.

 Corresponding author: parker@gfz-potsdam.de

Abstract

The global navigation satellite systems (GNSS) have revolutionalized the ability to monitor the Earth’s system related to different types of natural processes. This includes tectonic and volcanic deformation, earthquake-related displacements, redistribution of oceanic and atmospheric mass, and changes in the continental water storage. As loading affects the GNSS cordinates, we investigated the effect and assessed the impact of applying dedicated corrections provided by the Earth System Modeling group of German Research Center for Geosciences (GFZ). However, loading caused by mass redistribution results in displacement, predominantly with seasonal periods. Significant temporal changes in mass redistribution (e.g caused by climate change) will result to further trends in the station coordinate time series.

In this contribution, we will compare the PPP coordinate time series with the loading-corrected PPP time series by looking at the amplitude and the correlation between the GNSS time series and the model corrections. Also we will compare the PPP coordinate time series with the loading time series by assessing the RMS reduction and change of amplitude.The result shows that loading-induced displacement varies considerably among GNSS stations and applying corrections to the derived time series has favourable impacts on the reduction in the non-linear motion in GNSS height time series of the African stations.

How to cite: Usifoh, S. E., Le, T. N., Männel, B., Sakic, P., Joseph, D., and Schuh, H.: Surface loading on GNSS stations in Africa, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-64, https://doi.org/10.5194/egusphere-egu22-64, 2022.

EGU22-246 | Presentations | G3.1

Benchmarking Amazonian GPS stations: an improved way to model hydrological changes 

Grzegorz Leszczuk, Anna Klos, Jurgen Kusche, Artur Lenczuk, Helena Gerdener, and Janusz Bogusz

Hydrological loading is one of the main contributors into seasonal displacements of the Earth’s crust, as derived from the Global Positioning System (GPS) permanent stations. Recent studies proved that hydrological signatures may be also observed in GPS displacements outside seasonal band. Such estimates may be, however, biased, since (1) total character of GPS displacements is generated by a set of geophysical phenomena combined with GPS-specific signals and errors and (2) the exact sensitivity of GPS for individual components has not yet been properly recognized. In this study, we propose a completely new approach to establish a set of benchmarks of GPS stations, for which sensitivity to geophysical phenomena is identified. We focus on hydrological changes within the Amazon basin, but the same approach could be employed to analyze other phenomena. Analysis is performed for vertical displacements from 63 GPS stations provided by the Nevada Geodetic Laboratory (NGL), collected between 1995 and 2021. Results are compared to data from GRACE (Gravity Recovery and Climate Experiment) and GRACE Follow-On missions (2002-2021), provided by GFZ (GeoForschungsZentrum) as RL06 solution in a form of spherical harmonic coefficients truncated to d/o 96, filtered with DDK3 decorrelation anisotropic filter. We also utilize GLWS (Global Land Water Storage) datatset provided by University of Bonn, as a result of assimilation of GRACE Total Water Storage (TWS) anomalies into WaterGAP Global Hydrological Model (WGHM). We make also use of two hydrological models: pure WGHM and GLDAS (Global Land Data Assimilation System), for which TWS values are provided. Both GRACE and TWS data are converted to vertical displacements of Earth’s crust using load Love numbers, while GPS displacements are reduced for non-tidal atmospheric and oceanic changes. We find the largest values of trends and annual signals for GPS stations proximate to Amazon river. GRACE, GLWS and hydrological models disagree at the level of 8 mm, at maximum. This is mainly caused by the GLDAS model which lacks in the contribution of surface water. Supplementing GLDAS with surface water layer employed from WGHM reduces this difference to 1 mm. Benchmarks of GPS stations are established by using a wavelet decomposition with Meyer’s mother wavelet. We divide both the GPS, GRACE and GLWS displacement time series into 4 decomposition levels, defined by exact periods they contain. Then, we compute correlation coefficients between individual levels of details. We show that the number of 32%, 64%, 97%, 89% and 68% out of 63 GPS stations is significantly correlated to GRACE for periods, respectively, from 2 to 5 months, from 4 to 9 months, from 7 months to 1.4 years, from 1.1 to 3.0 years and from 3.0 years onwards. These numbers change into: 48%, 73%, 100%, 81% and 50% out of 63 GPS stations, when GRACE is replaced with GLWS. 12 or 21 out of 63 GPS stations correlate positively with GRACE or GLWS within entire frequency band, which means that a character of these GPS displacement time series is generated mostly by hydrological changes.

How to cite: Leszczuk, G., Klos, A., Kusche, J., Lenczuk, A., Gerdener, H., and Bogusz, J.: Benchmarking Amazonian GPS stations: an improved way to model hydrological changes, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-246, https://doi.org/10.5194/egusphere-egu22-246, 2022.

EGU22-1449 | Presentations | G3.1

Efficiency of different signal processing methods to isolate signature characteristics in altimetric water level measurements 

Siavash Iran Pour, Annette Eicker, Kyriakos Balidakis, Hamed Karimi, Alireza Amiri-Simkooei, and Henryk Dobslaw

Observed time-series of water transport in rivers can be perceived mathematically as a superposition of non-linear long-term trends, periodic variations, episodic events, colored instrument noise, and other components. Various statistical methods are readily available to extract and quantify both stationary and non-stationary components in order to subsequently attribute parts of the signal to underlying causal mechanisms. However, the available algorithms differ vastly in terms of computational complexity and implicit assumptions, and may thus have their own individual advantages and disadvantages. By employing a suite of time-series analysis methods for 1D (Wavelets, Singular Spectrum Analysis, Empirical Mode Decomposition) and additional statistical assessments like Pruned Exact Linear Time (PELT) tests for change point detection, we will analyze data from two virtual stations at Elbe River (Germany) and Urmia Lake (Iran) that are representative for the central European region with a rather humid climate, and the more arid conditions of Central Asia with much smaller hydrological signal variations, respectively. It is in particular the latter region with a much less developed in situ hydrometeorological observing system, where we expect that carefully processed geodetic data might contribute most to the monitoring of large-scale terrestrial water dynamics. This contribution will highlight the benefits of more advanced signal analysis methods for extracting relevant hydrometeorological information over more conventionally applied algorithms.

How to cite: Iran Pour, S., Eicker, A., Balidakis, K., Karimi, H., Amiri-Simkooei, A., and Dobslaw, H.: Efficiency of different signal processing methods to isolate signature characteristics in altimetric water level measurements, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1449, https://doi.org/10.5194/egusphere-egu22-1449, 2022.

Global and interactively coupled climate models are important tools for projecting future climate conditions. Even though the quality and reliability of such models has increased during the most recent years, large model uncertainties still exist for various climate elements, so that it is crucial to continuously evaluate them against independent observations. Changes in the distribution and availability of terrestrial water storage (TWS), which can be measured by the satellite gravimetry missions GRACE and GRACE-FO, represent an important part of the climate system in general, and the terrestrial water cycle in particular. However, the use of satellite gravity data for the evaluation of interactively coupled climate models has only very recently become feasible. Challenges mainly arise from large model differences with respect to land water storage-related variables, from conceptual discrepancies between modeled and observed TWS, and from the still rather short time series of satellite data.

This presentation will highlight the latest results achieved from our ongoing research on climate model evaluation based on the analysis of an ensemble of models taking part in the Coupled Model Intercomparison Project Phase 6 (CMIP6). We will focus on long-term wetting and drying conditions in TWS, by deriving several hot spot regions of common trends in GRACE/-FO observations and regions of large model consensus. However, as the observational record currently only covers about 20 years, observed trends may still be obscured by natural climate variability. Therefore, to further attribute the wetting or drying in the identified hot spot regions to either interannual/decadal variability or anthropogenic climate change, we investigate the influence of dedicated climate modes (such as ENSO, PDO, AMO etc.) on TWS variability and trends. Furthermore, we perform a numerical model investigation with 250 years of CMIP6 TWS data to quantify the degree to which trends computed over differently long time intervals can be expected to represent long-term trends, and to discriminate regions of rather robust trends from regions of large fluctuations in the trend caused by decadal climate variability.

How to cite: Jensen, L., Eicker, A., and Dobslaw, H.: Attributing land water storage trends from satellite gravimetry to long-term wetting and drying conditions with global climate models, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2335, https://doi.org/10.5194/egusphere-egu22-2335, 2022.

EGU22-2586 | Presentations | G3.1

Contributions of ocean bottom pressure and density changes to regional sea level change in the East Indian Ocean from GRACE, altimetry and Argo data 

Alisa Yakhontova, Roelof Rietbroek, Jürgen Kusche, Sophie Stolzenberger, and Bernd Uebbing

Understanding variations in the ocean heat content is tightly linked to understanding interactions of the global energy cycle with the regional water cycle. Mass, volume, temperature and density changes of  the ocean water column can be estimated with complimentary observations of sea surface height from radar altimetry, ocean bottom pressure from Gravity Recovery and Climate Experiment (GRACE), temperature and salinity from Argo floats. These three techniques have their specific deficiencies and advantages, which can be exploited in a joint inversion framework in order to improve temporal and spatial coverage of oceanic temperature and salinity estimates as well as regionally varying sea level contributions. Solving an inverse problem for temperature and salinity, forward operators are formulated linking the satellite observations to temperature and salinity at depth. This is done by (1) parametrization of temperature and salinity profiles over the full depth of the ocean with B-splines to reduce dimensionality while keeping complexity of the data intact and (2) linearization of the integrated density from parameterized T/S curves. We apply forward operators in the East Indian Ocean to resolve for sea surface height, ocean bottom pressure, temperature and salinity, and assess the regional importance of these factors. We explore the stability of a joint inversion using these forward operators in combination with along-track radar altimetry, GRACE and temperature and salinity by exploring a closed-loop inversion.

How to cite: Yakhontova, A., Rietbroek, R., Kusche, J., Stolzenberger, S., and Uebbing, B.: Contributions of ocean bottom pressure and density changes to regional sea level change in the East Indian Ocean from GRACE, altimetry and Argo data, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2586, https://doi.org/10.5194/egusphere-egu22-2586, 2022.

EGU22-3415 | Presentations | G3.1

Trends in Africa’s Terrestrial Water Storage 

Eva Boergens and Andreas Güntner

The German-American satellite missions GRACE (Gravity Recovery and Climate Experiment) and its successor GRACE-Follow-On (GRACE-FO) observed the unique data set of total water storage (TWS) variations over the continents since 2002. With this nearly 20 years of data, we can investigate trends in water storage beyond the strong declining trends of the ice sheets and glaciers. Unlike all other continents, Africa exhibits an overall positive trend in TWS. This contribution will take a detailed look into Africa's water storage changes and trends. Further, we attempt to explain these trends by comparison to other hydrological observations such as precipitation.

The long-term TWS increase in Africa is most pronounced in the East-African rift centred around Lake Victoria and the Niger River Basin. Other regions such as Madagaskar exhibit a (statistically significant) negative TWS trend. Furthermore, the trends are not monotonous over time. For example, the increasing trend in East Africa only started around the year 2006 and accelerated after 2012. On the other hand, South Africa wetted until 2012 and dried again since then.

This study divides the African continent into climatically similar regions and investigates the regional mean TWS signals. They are more complex than a linear trend and sinusoidal annual and semiannual seasonality; thus, we employ the STL method (Seasonal Trend decomposition based on Loess). In this way, turning points are identified in the so-called trend component to mark significant trend changes.

The observed TWS changes in Africa are caused mainly by changing precipitation patterns, as observed, for example, with the GPCP (Global Precipitation Climatology Project) data set. In some regions, such as South Africa, the correlation between precipitation and TWS change is evident, whereas other areas show a more complex relationship between these two variables.

 

How to cite: Boergens, E. and Güntner, A.: Trends in Africa’s Terrestrial Water Storage, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3415, https://doi.org/10.5194/egusphere-egu22-3415, 2022.

EGU22-3734 | Presentations | G3.1

Closing the water balance of large watersheds using satellite gravimetry 

Roelof Rietbroek, Marloes Penning de Vries, Yijian Zeng, and Bob Su

At the level of a watershed, the conservation of mass imposes that the net moisture transport through the atmospheric boundaries is balanced by the river discharge and an accumulation/depletion in terrestrial sources such as the soil, surface waters and groundwater.

There are considerable uncertainties connected with modelled water balance components, especially since most models only simulate part of the system: either the atmosphere, the surface or the subsurface. Uncertainties in boundary conditions propagate as biases in the simulated results. For example, not accounting for anthropogenic groundwater extraction potentially introduces biases in arid regions, where groundwater is a non-negligible source of moisture for the atmosphere. The use of observations is therefore an important aid to evaluate model performances and to detect possible biases in water balance components.

In this contribution, we compare total water storage changes derived from the Gravity Recovery Climate Experiment (GRACE) and its follow-on mission, with modelled components of the water balance. We use ERA5 reanalysis data to compute (net) atmospheric transports, and river discharge from GloFAS (Global Flood Awareness System). Furthermore, we use precipitation estimates (e.g. from GPCC) together with evapotranspiration from the Surface Energy Balance System (SEBS). We finally perform an accounting of the water balance components for the world’s largest watersheds and show to what extent we can find agreements, inconsistencies and biases in the data and models.

How to cite: Rietbroek, R., Penning de Vries, M., Zeng, Y., and Su, B.: Closing the water balance of large watersheds using satellite gravimetry, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3734, https://doi.org/10.5194/egusphere-egu22-3734, 2022.

EGU22-4918 | Presentations | G3.1

Drought Identification in NLDAS Data using Machine Learning Methods 

Corinne Vassallo, Srinivas Bettadpur, and Clark Wilson

Though machine learning (ML) methods have been around for decades, they have only more recently been adopted in the geosciences. The availability of existing long data records combined with the capability of ML algorithms to learn highly non-linear relationships between data sources means there is even more potential for the replacement or augmentation of existing scientific analyses with ML methods. Here, I give an example of how I used a convolutional neural network (CNN) for the task of pixelwise classification of the North American Land Data Assimilation System (NLDAS) Total Water Storage data into their corresponding drought levels based on the Palmer Drought Severity Index (PDSI). Promising results indicate there is much to be explored in the application of ML to drought identification and monitoring.

How to cite: Vassallo, C., Bettadpur, S., and Wilson, C.: Drought Identification in NLDAS Data using Machine Learning Methods, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4918, https://doi.org/10.5194/egusphere-egu22-4918, 2022.

EGU22-5765 | Presentations | G3.1

Water mass impacts of the main climate drivers over Australia by satellite gravimetry 

Guillaume Ramillien, Lucia Seoane, and José Darrozes

We propose a spatial characterization of the hydrological contributions of several climate drivers that impact continental water mass storage of Australia determined by remote sensing techniques over the period 2002 - 2021. For this purpose, the Slepian functions help for recognizing the signatures of such important changes in the varying gravity field solutions provided by GRACE and GRACE-FO satellite missions such as mascon solutions of 400-km resolution. Time series of 25 Slepian coefficients that correspond to ~99.9% of the eigenvalue spectrum are used to be analyzed and compared to the profiles of climate indexes i.e. El Niño Southern Oscillation (ENSO), Indian Ocean Dipole (IOD) and South Annular Mode (SAM). The best correlations enable to extract specific Slepian coefficients, and then reconstruct the regional hydrological structures that concern each climate driver, in particular for the southeastern basins strongly influenced by the important flooding during La Niña episode of 2010.

How to cite: Ramillien, G., Seoane, L., and Darrozes, J.: Water mass impacts of the main climate drivers over Australia by satellite gravimetry, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5765, https://doi.org/10.5194/egusphere-egu22-5765, 2022.

EGU22-6390 | Presentations | G3.1

A new method for the attribution of breakpoints in segmentation of IWV difference time series 

Khanh Ninh Nguyen, Olivier Bock, and Emilie Lebarbier

In recent years, the detection and correction of the non-natural irregularities in the long climatic records, so-called homogenization, has been studied. This work is motivated by the problem of identification of origins of the breakpoints in the segmentation of difference series (difference between a candidate series and a reference series). Several segmentation methods have been developed for the difference series, but many of them assume that the reference series is homogenous. However, the homogeneity of the reference series, in reality, is uncertain and unproven. In our study, we applied the segmentation method GNSSseg (Quarello et al., 2020) on the difference between the Integrated water vapour estimates of the CODE REPRO2015 GNSS data set and the ERA5 reanalysis. About 36.5% of change points can be validated from the GPS metadata, and the origins of the remaining 64.5% are questionable (Nguyen et al., 2021). The ambiguity can be leveraged when there is at least one nearby GPS station with respect to which the candidate series can be compared. The proposed method uses weighted t-tests combining the candidate GPS and ERA series and their homologues (denoted GPS' and ERA') from each nearby station. If sufficient consistency emerges from the six tests for all the nearby stations, a decision can be made whether the breakpoint detected in the candidate GPS-ERA series is due to GPS or, alternatively, to ERA. For each quadruplet (GPS, ERA, GPS', ERA'), six t-tests are performed, and the outcomes are combined. In a set of 81 globally distributed GNSS time series spanning more than 25 years, 56 series have at least one nearby station, where 171 breakpoints are detected in segmentation, in which 136 breakpoints are attributed to the GPS. Among those, 94 breakpoints have consistent results between all the nearby stations. GPS-related breakpoints are used for the correction of the mean shift in the difference series. The impact of the breakpoint correction on the GNSS IWV trend estimates is then evaluated. 

Quarello A, Bock O, & Lebarbier E. (2020). A new segmentation method for the homogenisation of GNSS-derived IWV time-series. arXiv: Methodology.

Nguyen KN, Quarello A, Bock O, Lebarbier E. Sensitivity of Change-Point Detection and Trend Estimates to GNSS IWV Time Series Properties. Atmosphere. 2021; 12(9):1102. https://doi.org/10.3390/atmos12091102

How to cite: Nguyen, K. N., Bock, O., and Lebarbier, E.: A new method for the attribution of breakpoints in segmentation of IWV difference time series, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6390, https://doi.org/10.5194/egusphere-egu22-6390, 2022.

EGU22-6800 | Presentations | G3.1

Intensifying hydrologic drought in California 

Donald Argus, Hilary Martens, Adrian Borsa, David Wiese, Ellen Knappe, Stacy Larochelle, Mackenzie Anderson, Athina Peidou, Ashlesha Khatiwada, Nicholas Lau, Alissa White, Zachary Hoylman, Matthew Swarr, Qian Cao, Ming Pan, Kristel Chanard, Jean-Philippe Avouac, Gardner Payton, and Felix Landerer

Drought has struck the southwest U.S. for the fourth time this millennium, reducing freshwater available to agriculture and urban centers.  We are bringing new insight by quantifying change in water in the ground using GPS elastic displacements, GRACE gravity, artificial reservoir levels, and snow models. Precipitation in Water Year 2021 was half of normal; the rise in total water in autumn and winter is 1/3 of the seasonal average (estimated using chiefly GPS); water was parched from the ground in the spring and summer, bringing water in the ground to its historic low (estimated using primarily GRACE).  In the Central Valley, soil moisture plus groundwater each year increases by 11 km3 and is maximum in April.  Only half of groundwater lost during periods of drought is replenished in subsequent years of heavy precipitation.  The Central Valley has lost groundwater at 2 km3/year from 2006 to 2021, with 2/3 of the loss coming from the southern Valley.

How to cite: Argus, D., Martens, H., Borsa, A., Wiese, D., Knappe, E., Larochelle, S., Anderson, M., Peidou, A., Khatiwada, A., Lau, N., White, A., Hoylman, Z., Swarr, M., Cao, Q., Pan, M., Chanard, K., Avouac, J.-P., Payton, G., and Landerer, F.: Intensifying hydrologic drought in California, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6800, https://doi.org/10.5194/egusphere-egu22-6800, 2022.

EGU22-7081 | Presentations | G3.1

GPS-based multi-annual variation of the precipitable water over Poland territory 

Andrzej Araszkiewicz, Michał Mierzwiak, Damian Kiliszek, Joanna Nowak Da Costa, and Marcin Szołucha

Earth's visible environmental changes, both natural and man-made, are influencing climate change on a global scale. For this reason, it is necessary to continuously monitor these changes and study the impact of human activities on them. One of the parameters indicating climate change is the systematic increase in temperature for the last 80 years. It causes more evaporation of water from natural and artificial water bodies. Consequently, the water content in the atmosphere is also increasing. Precipitable water is therefore one of the most important parameters when studying climate change. 

The aim of this study was to analyze long-term precipitation water data from a dense GNSS network over Poland. Twelve-year observations from over a hundred ASG-EUPOS stations were used to estimate changes in precipitation water values. These data were verified by comparison with available radio sounding data. Analysis of GPS-based PW values showed a clear increasing trend in PW values by 0.078 mm/year. The spatial-temporal distribution of mean PW values and their fluctuations over the years have been investigated. The obtained results confirm the fact that Poland lies on the border of continental and oceanic climate influence, and are in agreement with climate research concerning this region. 

How to cite: Araszkiewicz, A., Mierzwiak, M., Kiliszek, D., Nowak Da Costa, J., and Szołucha, M.: GPS-based multi-annual variation of the precipitable water over Poland territory, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7081, https://doi.org/10.5194/egusphere-egu22-7081, 2022.

EGU22-7583 | Presentations | G3.1

Using satellite geodesy for carbon cycle research 

Alexandra Klemme, Thorsten Warneke, Heinrich Bovensmann, Matthias Weigelt, Jürgen Müller, Justus Notholt, and Claus Lämmerzahl

To assess realistic climate change mitigation strategies, it is important to research and understand the global carbon cycle. Carbon dioxide (CO2) and methane (CH4) are the two most important anthropogenic greenhouse gases. Their atmospheric concentrations are affected by anthropogenic emissions as well as exchange fluxes with oceans and the terrestrial biosphere. For the prediction of future atmospheric CO2 and CH4 concentrations, it is critical to understand how the natural exchange fluxes respond to a changing climate. One of the factors that impact these fluxes is the changing hydrological cycle.        
In our project, we combine information about the hydrological cycle from geodetic satellites (e.g. GRACE & GRACE-FO) with carbon cycle observations from other satellites (e.g. TROPOMI & OCO-2). Specifically, we plan to investigate the impact of a changing water level in soils on CH4 emissions from wetlands and on the photosynthetic CO2 uptake of plants. Details of our approach and first results will be presented.

How to cite: Klemme, A., Warneke, T., Bovensmann, H., Weigelt, M., Müller, J., Notholt, J., and Lämmerzahl, C.: Using satellite geodesy for carbon cycle research, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7583, https://doi.org/10.5194/egusphere-egu22-7583, 2022.

EGU22-7903 | Presentations | G3.1

Identification of conceptual rainfall-runoff models of large drainage basins based on GRACE and in-situ data 

Karim Douch, Peyman Saemian, and Nico Sneeuw

Since 2002, estimates of the spatio-temporal variations of Earth’s gravity field derived from the Gravity Recovery and Climate Experiment (GRACE and now GRACE-FO) mission measurements have provided new insights into large scale water redistributions at inter-annual, seasonal and sub-seasonal timescales. It has been shown for example that for many large drainage basins the empirical relationship between aggregated Terrestrial Water Storage (TWS) and discharge at the outlet reveals an underlying dynamic that is approximately linear and time-invariant.

In this contribution, we further analyse this relationship in the case of the Amazon basin and sub-basins by investigating different physically interpretable, lumped-parameter models for the TWS-discharge dynamics. To this end, we first put forward a linear and continuous-time model using a state-space representation. We then enhance the model by introducing a non-linear term accounting for the observed saturation of the discharge. Finally, we reformulate the model by replacing the discharge by the river stage at the outlet and add a prescribed model of the rating curve to obtain the discharge. The suggested models are successively calibrated against TWS anomaly derived from GRACE data and discharge or river stage records using the prediction-error-method. It is noteworthy that one of the estimated parameters can be interpreted as the total amount of drainable water stored across the basin, a quantity that cannot be observed by GRACE alone. This quantity is estimated to be on average 1,750 km³ during the period 2004-2009. These models are eventually combined with the equation of water mass balance, in order to obtain a consistent representation of the basin-scale rainfall-runoff dynamics suited to data assimilation.

How to cite: Douch, K., Saemian, P., and Sneeuw, N.: Identification of conceptual rainfall-runoff models of large drainage basins based on GRACE and in-situ data, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7903, https://doi.org/10.5194/egusphere-egu22-7903, 2022.

EGU22-8525 | Presentations | G3.1

Combining space gravimetry observations with data from satellite altimetry and high resolution visible imagery to resolve mass changes of endorheic basins and exorheic basins. 

Alejandro Blazquez, Etienne Berthier, Benoit Meyssignac, Laurent Longuevergne, and Jean-François Crétaux

Continuous monitoring of the Global Terrestrial Water Storage changes (TWS) is challenging because of the large surface of continents and the variety of storage compartments (WCRP, 2018). The only observing system which provides global TWS mass change estimates so far is space gravimetry. Unfortunately, most storage compartments (lakes, groundwater, glaciers…) are too small to be resolved given the current spatial resolution of gravimetry missions. This intrinsic property makes gravimetry-based TWS changes estimates difficult to attribute and to interpret at individual basin scale.

In this context, combining gravimetry-based TWS estimates with other sources of information with higher spatial resolution is a promising strategy. In this study, we combine gravimetry data with independent observations from satellite altimetry and high resolution visible imagery to derive refined estimates of the TWS changes in hydrological basins containing lakes and glaciers (See Data used). The combination consists in including independent observations of glacier (Hugonnet et al., 2021) and lake (Cretaux et al., 2016) mass changes in the conversion process from gravity L2 data to water mass changes data. The combination is done for all regions of the world on a monthly basis.

This approach allows to split properly glacier and TWS changes at interannual to decadal time scales, and derive glacier-free estimates of TWS in the endorheic basins and the exorheic basins. We find that for the period from 2002 to 2020, the total TWS trend of 0.23±0.25 mm SLE/yr is mainly due to a mass loss in endorheic basins TWS of 0.20±0.12 mm SLE/yr. Over the same period, exorheic basins present a non-significative trend of 0.03±0.14 mm SLE/yr. On the contrary, the interannual variability in the TWS change of 4 mm SLE is mainly due to the exorheic basins TWS change.

How to cite: Blazquez, A., Berthier, E., Meyssignac, B., Longuevergne, L., and Crétaux, J.-F.: Combining space gravimetry observations with data from satellite altimetry and high resolution visible imagery to resolve mass changes of endorheic basins and exorheic basins., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8525, https://doi.org/10.5194/egusphere-egu22-8525, 2022.

Satellite gravity missions are unique observation systems to directly observe mass transport processes in the Earth system. Since 2000, CHAMP, GRACE, GOCE, and GRACE-FO have almost continuously been observing Earth’s mass changes and have improved our understanding of large-scale processes such as the global water cycle, melting of continental ice sheets and mountain glaciers, changes in ocean mass that are closely related to the mass-related component of sea-level rise, which are subtle indicators of climate change, on global to regional scale. The existing observation record of more than two decades is already closing in on the minimum time series of 30 years needed to decouple natural and anthropogenic forcing mechanisms according to the Global Climate Observing System (GCOS).

Next Generation Gravity Missions (NGGMs) are expected to be implemented in the near future to continue the observation record. The Mass-change And Geoscience International Constellation (acronym: MAGIC) is a joint investigation of ESA with NASA’s MCDO study resulting in a jointly accorded Mission Requirements Document (MRD) responding to global user community needs. These NGGM concepts have set high anticipation for enhanced monitoring capabilities of mass transports in the Earth’s system with significantly improved spatial and temporal resolution. They will allow an evaluation of long-term trends within the Terrestrial Water Storage (TWS), which was adopted as a new Essential Climate Variable in 2020.

This study is based on modeled mass transport time series of components of the TWS, obtained from future climate projections until the year 2100 following the shared socio-economic pathway scenario 5-8.5 (SSP5-8.5). It evaluates the recoverability of long-term climate trends, annual amplitude, and phase of the TWS employing closed-loop numerical simulations of different current and NGGM concepts up to a spatial resolution of 250 km (Spherical Harmonic Degree 80). The assumed satellite constellations are GRACE-type in-line single-pair missions and Bender double-pair missions with realistic noise assumptions for the key payload and ocean-tide background model errors. In the interpretation and discussion of the results, special emphasis will be given on the dependence of the length of the measurement time series and the quantification of the robustness of the derived trends, systematic changes, as well as possibilities to improve the trend parameterization.

How to cite: Schlaak, M., Pail, R., Jensen, L., and Eicker, A.: Closed Loop Simulations on Recoverability of Climate-Related Mass Transport Signals in Current and Next-Generation Satellite Gravity Missions, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8529, https://doi.org/10.5194/egusphere-egu22-8529, 2022.

EGU22-9943 | Presentations | G3.1

Geodetic climate research in the Austrian Alps 

Christian Ullrich, Olivier Francis, Sajad Tabibi, and Helmut Titz

The Federal Office of Metrology and Surveying (BEV) in Austria is responsible for the geodetic reference system like gravity and height reference frame. Some of these gravity reference stations are monitored regularly by different geodetic terrestrial techniques. The gravity data on some stations show variations and/or changes in gravity. In this presentation, the alpine geodetic reference stations Obergurgl and Franz-Josefs- Höhe in the Austrian eastern Alps will be presented. Both stations are investigated with different geodetic terrestrial techniques in a cooperation of the University of Luxemburg with BEV.

Global warming and associated climate change during the last century and recent decades are among the main reasons for glacier retreat in the Alps. Absolute gravity measurements have been regularly performed in the Austrian Eastern Alps since 1987 in the Ötztal Valley at Obergurgl. In addition, absolute gravity has been regularly observed at Obergurgl from 1987 to 2009 with the absolute gravimeter JILAg6. From 2010, the absolute gravity measurements were continued with the highest accurate absolute gravimeters FG5 from BEV and FG5x from University of Luxemburg. The newest gravity data show again a small increase of gravity. Additionally, a permanent GNSS station was established in 2019 to record information about the assumed vertical uplift at this station.

A second alpine research station was established near the Pasterze Glacier at Großglockner Mountain in 2019. The Pasterze Glacier is one of the largest glaciers in the eastern Alps and is in the vicinity of the highest mountain of Austria, the Großglockner. The station is monitored by repeated absolute gravity measurements and is equipped with a permanent GNSS station. In addition, precise leveling measurements were also tied to this station. In this contribution, initial results of the geodetic research like the gravity results, precise leveling and GNSS measurements will be presented. In the future, gravity data will be quantitively compared to ice mass balance information derived from glacier inventories. A Geodetic Global Navigation Satellite System reflectometry (GNSS-R) antenna will also be installed to study glacier-ice change. A third station at an altitude of 3300 m is planned and will be checked for operating absolute gravity measurements there. The geodynamical processes like vertical uplift and postglacial deformation will be investigated together with glacier retreat on these stations.

How to cite: Ullrich, C., Francis, O., Tabibi, S., and Titz, H.: Geodetic climate research in the Austrian Alps, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9943, https://doi.org/10.5194/egusphere-egu22-9943, 2022.

EGU22-10152 | Presentations | G3.1

GNSS observations of the land uplift in South Africa: Implication for water loss estimation 

Christian Mielke, Makan Karegar, Helena Gerdener, and Jürgen Kusche

Global Navigation Satellite System (GNSS) networks in South Africa indicate a spatially coherent uplift. The cause of this uplift is not clear, but one hypothesis is a crustal deformation due to mantle flow and dynamic topography (Hammond et al., 2021, JGR Solid Earth). We provide an alternative evidence based on elastic loading modelling and independent observations, suggesting that land water loss due to multiple drought periods is a dominant driver of land uplift in South Africa.

The use of continuously measuring GNSS stations has proven to be a successful method for quantifying terrestrial water mass changes, by inverting the observed vertical displacements of the Earth’s crust. Depending on the density of the GNSS network, this method has the potential to derive not only temporal but also spatial higher-resolution total water storage change (TWSC) than the Gravity and Climate Experiment (GRACE) and GRACE Follow-On (GRACE-FO) missions. Since vertical displacements in GNSS data are not only affected by water mass changes, extensive time series analyses are required to reduce or eliminate non-hydrology-related deformations, such as non-tidal oceanic and atmospheric loading. In this way, GNSS also offers an alternative method to monitor the frequently occurring droughts in South Africa, like the severe “Day Zero” drought in Cape Town from 2015-2017.

In this study, daily GNSS time series of vertical displacements (2000-present) are analysed. A long-term trend as well as annual and semi-annual signals are separated from the noisy observations using Singular Spectral Analysis (SSA). The final time series of all stations are inverted into water mass loading over a uniform grid, with the deformation properties of the Earth’s crust being defined by the Preliminary Reference Earth Model (PREM). An experimental approach shows that a 2° x 2° grid resolution of the GNSS-derived TWSC provides appropriate solutions over most of South Africa. The GNSS solution agrees with a GRACE-assimilated solution and a hydrological model at monthly scale over different provinces, with correlations up to 93% and 94%, respectively. The long-term trend averaged over the entire country is correlated with 80% and 54%, respectively. Negative long-term TWSC trends are evident in all data sets and provide compelling evidence that long-term land uplift in South Africa has a hydrological origin.

How to cite: Mielke, C., Karegar, M., Gerdener, H., and Kusche, J.: GNSS observations of the land uplift in South Africa: Implication for water loss estimation, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10152, https://doi.org/10.5194/egusphere-egu22-10152, 2022.

EGU22-10986 | Presentations | G3.1

How changes in compartments of water storage affect the vegetation? 

Srinivas Pernati, Komali Bharath Narayana Reddy, and Balaji Devaraju

The relationship between water storage and vegetation growth differs with changes in different water
compartments such as total water storage, soil moisture and groundwater. This relationship can be
established between variations in water storage and Normalized Difference Vegetation Index (NDVI)
values. The compartments of water storage anomalies were computed with Gravity Recovery and Climate
Experiment (GRACE) and Global Land Data Assimilation System (GLDAS) data sets. NDVI data from
Global Inventory Monitoring and Modeling System (GIMMS) was used to compare with water storage
anomalies. These water storage anomalies and NDVI values were aggregated over each sub-basin of the
Ganga catchment. A correlation analysis was made between water storage components and NDVI values,
which helped to determine how vegetation growth depends on changes in different water compartments.
Initial computations of auto-correlation and cross-correlation between water storage components and
NDVI show different lags for different sub-basins. 

How to cite: Pernati, S., Bharath Narayana Reddy, K., and Devaraju, B.: How changes in compartments of water storage affect the vegetation?, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10986, https://doi.org/10.5194/egusphere-egu22-10986, 2022.

EGU22-12642 | Presentations | G3.1 | G Division Outstanding ECS Award Lecture

Geodesy: a sensor for hydrology 

Kristel Chanard

Understanding how the Earth’s shape, gravity field and rotation change in response to shifting hydrological, atmospherical and oceanic mass loads at its surface has great potential for monitoring the evolving climate. Recent advances in the field, namely hydrogeodesy, have required hand-in-hand development and improvement of the observing techniques and of our understanding of the solid Earth-climate interactions. 

In particular, measurement of the spatial and temporal variations of the Earth's gravity field by the GRACE and GRACE-Follow On satellite missions offer an unprecedented measurement of the evolution of water mass redistribution, at timescales ranging from months to decades. However, the use of GRACE and GRACE-FO data for hydrological applications presents two major difficulties. First, the mission design and data processing lead to measurement noise and errors that limit GRACE missions to large-scale applications and complicates geophysical interpretation. Moreover, temporal observational gaps, including the 11 month-long gap between missions, prevent the interpretation of long-term mass variations. Secondly, disentangling sources of signals from the solid Earth and continental hydrology is challenging and requires to develop methods benefiting from multiple geodetic techniques. 

To reduce noise and enhance geophysical signals in the data, we develop a method based on a spectral analysis by Multiple Singular Spectrum Analysis (M-SSA) which, using the spatio-temporal correlations of the GRACE-GRACE-FO time series, can fill observational gaps and remove a significant portion of the distinctive noise pattern while maintaining the best possible spatial resolution. This processing reveals hydrological signals that are less well or not resolved by other processing strategies. We discuss regional hydrological mass balance, including lakes, aquifers and ice caps regions, derived from the GRACE-GRACE-FO M-SSA solution. Furthermore, we discuss methods to separate sources of gravity variations using additional in-situ hydrological data or geodetic measurements of the Earth’s deformation. 

How to cite: Chanard, K.: Geodesy: a sensor for hydrology, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12642, https://doi.org/10.5194/egusphere-egu22-12642, 2022.

EGU22-12684 | Presentations | G3.1

Twenty years of volume transport from satellite gravimetry in the Atlantic and Southern Ocean 

Andreas Kvas, Katrin Bentel, Saniya Behzadpour, and Torsten Mayer-Gürr

With an observation period of almost twenty years and global data coverage, satellite gravimetry has become a crucial tool for monitoring the state of our planet in a changing climate. Gravimetry-derived mass change has seen numerous applications in different geoscientific disciplines and has fundamentally improved our understanding of the Earth system. One such application is the determination of meridional and zonal volume transport variability based on ocean bottom pressure (OBP) variations, which can provide key insights into climate-relevant ocean currents like the Atlantic Meridional Overturning Circulation (AMOC) or the Antarctic Circumpolar Current (ACC). However, the limited spatial resolution, signal leakage from other geophysical subsystems like the hydrosphere, cryosphere or solid Earth make satellite gravimetry-derived transport estimates difficult to interpret. In this study we investigate geostrophic volume transport variability based on observations of the Gravity Recovery and Climate Experiment (GRACE) and GRACE Follow-On (GRACE-FO) for selected cross sections in the Atlantic and Southern Ocean. We focus on interannual transport variations in the deep ocean, where the more moderately sloping topography poses less stringent requirements on the spatial resolution of the OBP fields, and the lower temporal resolution reduces the impact of observation noise by providing longer averaging periods. Basis for the derived transport variations are high-resolution OBP fields determined in an ensemble Kalman filter approach. This allows us to also propagate the inherent observational noise to transport level and together with glacial isostatic adjustment (GIA) und hydrological model statistics quantify the uncertainty and sensitivity of the derived transport time series. We further contrast results for the Atlantic and Southern Ocean and show the different impact of the satellite observation geometry on meridional and zonal transport estimates.

How to cite: Kvas, A., Bentel, K., Behzadpour, S., and Mayer-Gürr, T.: Twenty years of volume transport from satellite gravimetry in the Atlantic and Southern Ocean, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12684, https://doi.org/10.5194/egusphere-egu22-12684, 2022.

EGU22-279 | Presentations | GM2.7

Assessment of sensor pre-calibration to mitigate systematic errors in SfM photogrammetric surveys 

Johannes Antenor Senn, Jon Mills, Claire L. Walsh, Stephen Addy, and Maria-Valasia Peppa

Remotely piloted airborne system (RPAS) based structure-from-motion (SfM) photogrammetry is a recognised tool in geomorphological applications. However, time constraints, methodological requirements and ignorance can easily compromise photogrammetric rigour in geomorphological fieldwork. Light RPAS mounted sensors often provide inherent low geometric stability and are thus typically calibrated on-the-job in a self-calibrating bundle adjustment. Solving interior (lens geometry) and exterior (position and orientation) camera parameters requires variation of sensor-object distance, view angles and surface geometry.

Deficient camera calibration can cause systematic errors resulting in final digital elevation model (DEM) deformation. The application of multi-sensor systems, common in geomorphological research, poses additional challenges. For example, the low contrast in thermal imagery of vegetated surfaces constrains image matching algorithms.

We present a pre-calibration workflow to separate sensor calibration and data acquisition that is optimized for geomorphological field studies. The approach is time-efficient (rapid simultaneous image acquisition), repeatable (permanent object), at survey scale to maintain focal distance, and on-site to avoid shocks during transport.

The presented workflow uses a stone building as a suitable 3D calibration structure (alternatively boulder or bridge) providing structural detail in visible (DJI Phantom 4 Pro) and thermal imagery (Workswell WIRIS Pro). The dataset consists of feature coordinates extracted from terrestrial laser scanner (TLS) scans (3D reference data) and imagery (2D calibration data). We process the data in the specialized software, vision measurement system (VMS) as benchmark and the widely applied commercial SfM photogrammetric software, Agisoft MetaShape (AM) as convenient alternative. Subsequently, we transfer the camera parameters to the application in an SfM photogrammetric dataset of a river environment to assess the performance of self- and pre-calibration using different image network configurations. The resulting DEMs are validated against GNSS reference points and by DEMs of difference. 

We achieved calibration accuracies below one-third (optical) and one-quarter (thermal) of a pixel. In line with the literature, our results show that self-calibration yields the smallest errors and DEM deformations using multi-scale and oblique datasets. Pre-calibration in contrast, yielded the lowest overall errors and performed best in the single-scale nadir scenario. VMS consistently performed better than AM, possibly because AM's software “black-box” is less customisable and does not allow purely marker-based calibration. Furthermore, we present findings regarding sensor stability based on a repeat survey.

We find that pre-calibration can improve photogrammetric accuracies in surveys restricted to unfavourable designs e.g. nadir-only (water refraction, sensor mount). It can facilitate the application of thermal sensors on surfaces less suited to self-calibration. Most importantly, multi-scale survey designs could potentially become redundant, thus shortening flight time or increasing possible areal coverage.

How to cite: Senn, J. A., Mills, J., Walsh, C. L., Addy, S., and Peppa, M.-V.: Assessment of sensor pre-calibration to mitigate systematic errors in SfM photogrammetric surveys, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-279, https://doi.org/10.5194/egusphere-egu22-279, 2022.

EGU22-344 | Presentations | GM2.7

A sensitivity analysis of Rillstats for soil erosion estimates from UAV derived digital surface models. 

Josie Lynch, Derek McDougall, and Ian Maddock
Fertile topsoil is being eroded ten times faster than it is created which can result in lowered crop yields, increased river pollution, and heightened flood risk (WWF 2018). Traditional methods of soil erosion monitoring are labour-intensive and provide low resolution, sparse point data not representative of overall erosion rates (Báčová et al., 2019). However, technological advances using Uncrewed Aerial Vehicles (UAVs) obtain high-resolution, near-contactless data capture with complete surface coverage (Hugenholtz et al., 2015).  
 

Typically, analysing UAV-Structure-from-Motion (SfM) derived soil erosion data requires a survey prior to the erosion event with repeat monitoring for change over time to be quantified. However, in recent years the ability of soil erosion estimations without the pre-erosion data has emerged. Rillstats, which is specifically designed to quantify volume loss in rills/gullies, has been developed by Báčová et al., (2019) using the algorithm and Python implementation in ArcGIS to perform automatic calculations of rills. Although this technique has been developed, it is not yet tested. 

This research evaluates the sensitivity of Rillstats to estimate soil erosion volumes from Digital Surface Models (DSM) obtained using a DJI Phantom 4 RTK UAV. The aims of the research were to test i) the influence of UAV-SfM surveys with varying flight settings and environmental conditions and ii) the effect of the size and shape of the boundary polygon. Results will be presented that analyse the sensitivity of estimations of soil erosion to changes in DSM resolution, image angle, lighting conditions, soil colour and texture to develop recommendations for a best practice to optimize results. 

How to cite: Lynch, J., McDougall, D., and Maddock, I.: A sensitivity analysis of Rillstats for soil erosion estimates from UAV derived digital surface models., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-344, https://doi.org/10.5194/egusphere-egu22-344, 2022.

EGU22-2513 | Presentations | GM2.7

Evaluation of UAV-borne photogrammetry and UAV-borne laser scanning for 3D topographic change analysis of an active rock glacier 

Vivien Zahs, Lukas Winiwarter, Katharina Anders, Magnus Bremer, Martin Rutzinger, Markéta Potůčková, and Bernhard Höfle

Recent advances in repeated data acquisition by UAV-borne photogrammetry and laser scanning for geoscientific monitoring extend the possibilities for analysing surface dynamics in 3D at high spatial (centimeter point spacing) and temporal (up to daily) resolution. These techniques overcome common challenges of ground-based sensing (occlusion, heterogeneous measurement distribution, limited spatial coverage) and provide a valuable additional data source for topographic change analysis between successive epochs.

We investigate point clouds derived from UAV-borne photogrammetry and laser scanning as input for change analysis. We apply and compare two state-of-the-art methods for pairwise 3D topographic change quantification. Our study site is the active rock glacier Äußeres Hochebenkar in the Eastern Austrian Alps (46° 50’ N, 11° 01’ E). Whereas point clouds derived from terrestrial laser scanning (TLS) have become a common data source for this application, point clouds derived from UAV-borne sensing techniques have emerged only in recent years and their potential for methods of 3D and 4D (3D + time) change analysis is yet to be exploited.

We perform change analysis using (1) the Multi Scale Model to Model Cloud Comparison (M3C2) algorithm [1] and (2) the correspondence-driven plane-based M3C2 [2]. Both methods have shown to provide valuable surface change information on rock glaciers when applied to successive terrestrial laser scanning point clouds of different time spans (ranging from 2 weeks to several years). The considerable value of both methods also lies in their ability to quantify the uncertainty additionally to the associated change. This allows to distinguish between significant change (quantified magnitude of change > uncertainty) and non-significant or no change (magnitude of change ≤ uncertainty) and hence enables confident analysis and geographic interpretation of change.

We will extend the application of the two methods by using point clouds derived using (1) photogrammetric techniques on UAV-based images and (2) UAV-borne laser scanning. We investigate the influence of variations in measurement distribution and density, completeness of spatial coverage and ranging uncertainty by comparing UAV-based point clouds to TLS data of the same epoch. Using TLS-TLS-based change analysis as reference, we examine the performance of the two methods with respect to their capability of quantifying surface change based on point clouds originating from different sensing techniques.

Results of this assessment can support the theoretical and practical design of future measurement set-ups. Comparing results of both methods further aids the selection of a suitable method (or combination) for change analysis in order to meet requirements e.g., regarding uncertainty of measured change or spatial coverage of the analysis. To ease usability of a broad suite of state-of-the-art methods of 3D/4D change analysis, we are implementing an open source Python library for geographic change analysis in 4D point cloud data (py4dgeo, www.uni-heidelberg.de/3dgeo-opensource). Finally, our presented study provides insights how methods for 3D and 4D change analysis should be adapted or developed in order to exploit the full potential of available close-range sensing techniques.

[1] https://doi.org/ 10.1016/j.isprsjprs.2013.04.009

[2] https://doi.org/10.1016/j.isprsjprs.2021.11.018

How to cite: Zahs, V., Winiwarter, L., Anders, K., Bremer, M., Rutzinger, M., Potůčková, M., and Höfle, B.: Evaluation of UAV-borne photogrammetry and UAV-borne laser scanning for 3D topographic change analysis of an active rock glacier, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2513, https://doi.org/10.5194/egusphere-egu22-2513, 2022.

The main type of research material is multi-season aerial photography of the oil mining karst river basin was carried out by unmanned aerial vehicle.

Visual photo delineation revealed the consequences of mechanical transformations, some hydrocarbon inputs (bitumization) and salts (technogenic salinization) were also identified. The last processes were verified using materials from direct geochemical surveys (chemical analyses of soils, surface waters and sets of ordinary photo of sample plots).

It has been established that mechanical transformations, as a rule, is detected by the color and shape of objects. Less often, it is necessary to additionally analyze indirect photo delineation signs: shape of the shadow, configuration of the borders, traces of heavy vehicle tracks. Photo delineation signs of technogenic salinization are turbidity of water and the acquisition of a bluish-whitish color; the change of the color of the water body to green-yellow; white ground salt spots. The bituminization process is sufficiently reliably identified only in the presence of open oil spills on the surface of soil or water. Despite the difficulty of photo delineation, the use of orthophotos allows to identify 13 new sites (26 in total in the studied area) of the processes of bitumization and technogenic salinization, which had not been noted during previous large-scale field survey.

The use of orthophotos to detect the processes of bitumization and technogenic salinization is effective, especially in combination with direct field studies. Conditions for using aerial photography to identify the consequences of oil mining technogenesis: pixel resolution should be equals or more precise than 20 cm / pixel (more desirable – equals or more precise than 10 cm / pixel), snowless shooting season, lack or low level of cloud cover, relatively low forest cover percent. The spatial distribution of the identified areas of all types of technogenesis indicates a close relationship with the location of oil mining facilities.

A promising direction for the development of the research is associated with the use of multispectral imaging, the improvement of attend field surveys, as well as the expansion of the experience of aerial photography of oil fields located in other natural conditions.

The reported study was funded by Russian Foundation for Basic Research (RFBR) and Perm Territory, project number 20-45-596018.

How to cite: Sannikov, P., Khotyanovskaya, Y., and Buzmakov, S.: Applicability of aerial photography for identifying of oil mining technogenesis: mechanical transformations, bitumization, technogenic salinization, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2643, https://doi.org/10.5194/egusphere-egu22-2643, 2022.

EGU22-3163 | Presentations | GM2.7

Comparison of 3D surfaces from historical aerial images and UAV acquisitions to understand glacier dynamics: The Aneto glacier changes in 40 years 

Ixeia Vidaller, Jesús Revuelto, Eñaut Izagirre, Jorge García, Francisco Rojas-Heredia, and Juan Ignacio López-Moreno

Pyrenean glaciers have shown a marked area and thickness decrease in the last century, especially in the last decades, and currently are highly threatened by climate change. Out of the 39 glaciers existing in the Pyrenees in 1984, 23 very small glaciers remain in this mountain range, from which only four have more than 10 ha. Probably, the most emblematic glacier of these four is Aneto glacier as it is located in the North-East face of the highest summit in the Pyrenees, the Aneto peak (3404 m a.s.l.). This work presents the Aneto glacier surface reconstruction from aerial images obtained in 1981, and its comparison with the glacier surface obtained in 2021 with Unmanned Aerial Vehicles (UAV) images.

The 1981 and 2021 images have been processed with Structure from Motion (SfM) algorithms to reconstruct the Digital Surface Model (DSM) of the glacier and nearby terrain. Taking advantage of the accurate geolocation of the UAV images in 2021 (GPS with RTK/PPK surveying), the DSM obtained has a precise representation of the glacier surface. Oppositely the aerial images of 1981 lack precise geolocation and thus require a post-processing analysis. The aerial images of the '80s have been firstly geolocated with Ground Control Points (GCPs) of known coordinates within the study area (summits, crests, and rock blocks with unaltered position). After this initial geolocation, the DSM of 1981 was generated with SfM algorithms. Nevertheless, this DSM still lacks a geolocation accuracy. To allow a comparison between the 1981 and the 2021 DSMs, the glacier surface in 1981 was registered to the 2021 surface with an Iterative Close Point (ICP) routine in the surrounding area of the glacier. The technique described in this work may be applicable to other historical aerial images, which may allow studying glacier evolutions all over the world for dates without field observations.

The surface comparison generated with images that have a temporal difference of 40 years has shown the dramatic area and thickness loss of this glacier, with areas decreasing more than 68 m, and an average thickness reduction of 31.5 m. In this period, the glacier has reduced its extent by about a 60%. There is a recent acceleration in the rate of shrinkage if we compare these data with the obtained for the period 2011-2021, in which area loss reaches 15% and thickness reduction almost reaches 10 m. During the 1981-2021 period the shrinkage rate is 0.78 m thickness/year and 1.5% area/year, meanwhile, during the 2011-2021 period the shrinkage rate is 0.99 m thickness/year and 2.7% area/year.

How to cite: Vidaller, I., Revuelto, J., Izagirre, E., García, J., Rojas-Heredia, F., and López-Moreno, J. I.: Comparison of 3D surfaces from historical aerial images and UAV acquisitions to understand glacier dynamics: The Aneto glacier changes in 40 years, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3163, https://doi.org/10.5194/egusphere-egu22-3163, 2022.

EGU22-3516 | Presentations | GM2.7

Uncertainty of grain sizes from close-range UAV imagery in gravel bars 

David Mair, Ariel Henrique Do Prado, Philippos Garefalakis, Alessandro Lechmann, and Fritz Schlunegger

Data on grain sizes of pebbles in gravel-bed rivers are a well-known proxy for sedimentation and transport conditions, and thus a key quantity for the understanding of a river system. Therefore, methods have been developed to quantify the size of gravels in rivers already decades ago. These methods involve time-intensive fieldwork and bear the risk of introducing sampling biases. More recently, low-cost UAV (unmanned aerial vehicle) platforms have been employed for the collection of referenced images along rivers with the aim to determine the size of grains. To this end, several methods to extract pebble size data from such UAV imagery have been proposed. Yet, despite the availability of information on the precision and accuracy of UAV surveys, a systematic analysis of the uncertainty that is introduced into the resulting grain size distribution is still missing.

Here we present the results of three close-range UAV surveys conducted along Swiss gravel-bed rivers with a consumer-grade UAV. We use these surveys to assess the dependency of grain size measurements and associated uncertainties from photogrammetric models, in turn generated from segmented UAV imagery. In particular, we assess the effect of (i) different image acquisition formats, (ii) specific survey designs, and (iii) the orthoimage format used for grain size estimates. To do so, we use uncertainty quantities from the photogrammetric model and the statistical uncertainty of the collected grain size data, calculated through a combined bootstrapping and Monte Carlo (MC) modelling approach.

First, our preliminary results suggest some influence of the image acquisition format on the photogrammetric model quality. However, different choices for UAV surveys, e.g., the inclusion of oblique camera angles, referencing strategy and survey geometry, and environmental factors, e.g., light conditions or the occurrence of vegetation and water, exert a much larger control on the model quality. Second, MC modelling of full grain size distributions with propagated UAV uncertainties shows that measured size uncertainty is at the first order controlled by counting statistics, the selected orthoimage format, and limitations of the grain size determination itself, i.e., the segmentation in images. Therefore, our results highlight that grain size data are consistent and mostly insensitive to photogrammetric model quality when the data is extracted from single, undistorted orthoimages. This is not the case for grain size data, which are extracted from orthophoto mosaics. Third, upon looking at the results in detail, they reveal that environmental factors and specific survey strategies, which contribute to the decrease of the photogrammetric model quality, also decrease the detection of grains during image segmentation. Thereby, survey conditions that result in a lower quality of the photogrammetric model also lead to a higher uncertainty in grain size data.

Generally, these results indicate that even relative imprecise and not accurate UAV imagery can yield acceptable grain size data for some applications, under the conditions of correct photogrammetric alignment and a suitable image format. Furthermore, the use of a MC modelling strategy can be employed to estimate the grain size uncertainty for any image-based method in which individual grains are measured.

How to cite: Mair, D., Do Prado, A. H., Garefalakis, P., Lechmann, A., and Schlunegger, F.: Uncertainty of grain sizes from close-range UAV imagery in gravel bars, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3516, https://doi.org/10.5194/egusphere-egu22-3516, 2022.

Near-continuous time series of 3D point clouds capture local landscape dynamics at a large range of spatial and temporal scales. These data can be acquired by permanent terrestrial laser scanning (TLS) or time lapse photogrammetry, and are being used to monitor surface changes in a variety of natural scenes, including snow cover dynamics, rockfalls, soil erosion, or sand transport on beaches.

Automatic methods are required to analyze such data with thousands of point cloud epochs (acquired, e.g., hourly over several months), each representing the scene with several million 3D points. Usually, no a-priori knowledge about the timing, duration, magnitude, and spatial extent of all spatially and temporally variable change occurrences is available. Further, changes are difficult to delineate individually if they occur with spatial overlap, as for example coinciding accumulation processes. To enable fully automatic extraction of individual surface changes, we have developed the concept of 4D objects-by-change (4D-OBCs). 4D-OBCs are defined by similar change histories within the area and timespan of single surface changes. This concept makes use of the full temporal information contained in 3D time series to automatically detect the timing and duration of changes. Via spatiotemporal segmentation, individual objects are spatially delineated by considering the entire timespan of a detected change regarding a metric of time series similarity (cf. Anders et al. 2021 [1]), instead of detecting changes between pairs of epochs as with established methods.

For hourly TLS point clouds, the extraction of 4D-OBCs improved the fully automatic detection and spatial delineation of accumulation and erosion forms in beach monitoring. For a use case of snow cover monitoring, our method allowed quantifying individual change volumes more accurately by considering the timespan of changes, which occur with variable durations in the hourly 3D time series, rather than only instantaneously from one epoch to the next. The result of our time series-based method is information-rich compared to results of bitemporal change analysis, as each 4D-OBC contains the full 4D (3D + time) data of the original 3D time series with determined spatial and temporal extent.

The objective of this contribution is to present how interpretable information can be derived from resulting 4D-OBCs. This will provide new layers that are supporting subsequent geoscientific analysis of observed surface dynamics. We apply Kalman filtering (following Winiwarter et al. 2021 [2]) to model the temporal evolution of individually extracted 4D-OBCs. This allows us to extract change rates and accelerations for each point in time, and to subsequently derive further features describing the temporal properties of individual changes. We present first results of this methodological combination and newly obtained information layers which can reveal spatial and temporal patterns of change activity. For example, deriving the timing of highest change rates may be used to examine links to external environmental drivers of observed processes. Our research therefore contributes to extending the information that can be extracted about surface dynamics in natural scenes from near-continuous time series of 3D point clouds.

References:

[1] https://doi.org/10.1016/j.isprsjprs.2021.01.015

[2] https://doi.org/10.5194/esurf-2021-103

How to cite: Anders, K., Winiwarter, L., and Höfle, B.: Automatic Extraction and Characterization of Natural Surface Changes from Near-Continuous 3D Time Series using 4D Objects-By-Change and Kalman Filtering, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4225, https://doi.org/10.5194/egusphere-egu22-4225, 2022.

EGU22-4522 | Presentations | GM2.7

Morphological evolution of volcanic crater through eruptions and instabilities: The case of Ol Doinyo Lengaï since the 2007-08 eruption 

Pierre-Yves Tournigand, Benoît Smets, Kate Laxton, Antoine Dille, Michael Dalton-Smith, Gian Schachenmann, Christelle Wauthier, and Matthieu Kervyn

Ol Doinyo Lengaï (OL) in north Tanzania is the only active volcano in the world emitting natrocarbonatite lavas. This stratovolcano (2962 m a.s.l) is mostly characterized by effusive lava emissions since 1983. However, on the 4th of September 2007, explosive events marked the beginning of a new eruptive style that lasted until April 2008. This new phase involved short-lived explosive eruptions that generated volcanic ash plumes as high as 15 km during its paroxysmal stage. This explosive activity resulted in the formation of a 300 m wide and 130 m deep crater in place of the growing lava platform that had filled the crater since 1983. Since then the effusive activity at OL resumed within the crater and has been partially filling it over the last 14 years. Due to the remote location of the volcano there is a lack of monitoring of its activity and, hence, its eruptive and morphological evolution over the last years is not well constrained (e.g., emission rates, number of vents, unstable areas). This absence of monitoring, preventing the detection of features, such as instabilities of the summit cone, could have hazard implications for the tourists regularly visiting the summit area.

In this study, we quantify the evolution of OL crater area over the last 14 years by reconstructing its topography at regular time interval. We collated several sources of optical images including Unoccupied Aircraft Systems (UAS) images, videos and ground-based pictures that have been collected over the period 2008-2021 by scientists and tourists. Those data have been sorted by year and quality in order to reconstruct the most accurate topographical models using Agisoft Metashape Pro, a software for Structure from Motion (SfM) photogrammetry, and CloudCompare a 3D point cloud processing software. This enables estimating the emitted volume of lava, the emission rate and the remaining crater volume available before crater overflow. It also allows identifying punctual events, such as hornito formation or destruction, and partial crater collapses. Our results indicate that the main lava emission area has repeatedly moved over the years within the crater floor and that OL’s effusion rate has been increasing over the last few years, with more than two times higher lava emission in the period 2019-2021 compared to 2017-2019. Assuming a similar lava effusion rate in the coming years, the crater could again be filled within the next decade leading to new lava overflows. There is thus a need for periodic assessment of the situation at OL. New cost- and time-effective photogrammetry techniques, including UAS and SfM processing, offer a solution to improve the monitoring of such remote volcanoes.

How to cite: Tournigand, P.-Y., Smets, B., Laxton, K., Dille, A., Dalton-Smith, M., Schachenmann, G., Wauthier, C., and Kervyn, M.: Morphological evolution of volcanic crater through eruptions and instabilities: The case of Ol Doinyo Lengaï since the 2007-08 eruption, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4522, https://doi.org/10.5194/egusphere-egu22-4522, 2022.

EGU22-4763 | Presentations | GM2.7

Using high-resolution topography to solve “periglacial puzzles”: A semi-automated approach to monitor solifluction movement 

Marije Harkema, Jana Eichel, Wiebe Nijland, Steven de Jong, Daniel Draebing, and Teja Kattenborn

Solifluction is the slow downslope movement of soil mass due to freeze-thaw processes. It is widespread on hillslopes in Polar and Alpine regions and contributes substantially to sediment transport. As solifluction lobe movement is in the order of millimeters to centimeters per year, it is tricky to measure with a high spatial and temporal resolution and accuracy. We developed a semi-automated approach to monitor movement of three solifluction lobes with different degrees of vegetation cover along an elevational gradient between 2,170 and 2,567 m in Turtmann Valley, Swiss Alps. Subsequently, we compared movement rates and patterns with environmental factors.

  • For solifluction movement monitoring, we applied a combination of the Phantom 4 Pro Plus and Phantom 4 RTK (Real Time Kinematic) drones, image co-alignment and COSI-CORR (Co-registration of Optically Sensed Images and Correlation) to track movement on orthophotos between 2017 and 2021. This drone data acquisition and co-alignment procedure enable a simple, time-saving field setup without Ground Control Points (GCPs).
  • Our high co-registration accuracy enabled us to detect solifluction movement if it exceeds 5 mm with sparse vegetation cover. Dense vegetation cover limited feature tracking but detected movement rates and patterns still matched previous measurements using classical total station measurements at the lowest, mostly vegetated lobe.
  • In contrast to traditional solifluction monitoring approaches using point measurements, our monitoring approach provides spatially continuous movement estimates across the complete extend of the lobe. Lobe movement rates were highest at the highest elevations between 2,560 and 2,567 m (up to 14.0 cm/yr for single years) and lowest at intermediate elevations between 2,417 and 2,427 m (up to 2.9 cm/yr for single years). We found intermediate movement rates at lowest elevations between 2,170 and 2,185 m (up to 4.9 cm/yr for single years). In general, movement had the highest rates at the solifluction lobes center and the lowest rates at the front of solifluction lobes.
  • We linked observed movement patters to environmental factors possibly controlling solifluction movement, such as geomorphic properties, vegetation species and coverage, soil properties determined from electrical resistivity tomography (ERT), and soil temperature data. The least movement at the lobe front is characterized by coarse material and plant species stabilizing the risers or plant species growing here due to the stable risers. Most movement at the lobe center is characterized by fine material and no vegetation or plant species promoting movement. The soil temperature data further suggests that snow cover reduced freezing rates at solifluction lobes and potentially decreased solifluction movement at the lobe between 2,417 and 2,427 m.

This study is the first to demonstrate the use of drone-based images and a semi-automated method to reach high spatiotemporal resolutions to detect subtle movements of solifluction lobes at timescales of years at sub-centimeter resolution. This provides new insights into solifluction movement and into drivers of and factors controlling solifluction movement and lobe development. Therefore, our semi-automated approach may have a great potential to uncover the fundamental processes to understand solifluction movement.

How to cite: Harkema, M., Eichel, J., Nijland, W., de Jong, S., Draebing, D., and Kattenborn, T.: Using high-resolution topography to solve “periglacial puzzles”: A semi-automated approach to monitor solifluction movement, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4763, https://doi.org/10.5194/egusphere-egu22-4763, 2022.

EGU22-6894 | Presentations | GM2.7

Rapid formation of a bedrock canyon following gravel mining in the Marecchia River, Northern Apennines. 

Manel Llena, Tommaso Simonelli, and Francesco Brardinoni

River canyons are characteristic features of transient fluvial systems responding to perturbations in base level and/or sediment supply. Investigating the dynamics of canyon formation and development is challenging due to the typically long time scales and the possible experimental confounding involved. In this context, the lower portion of the Marecchia River, with a history of gravel mining on alluvial deposits resting on highly erodible (i.e., claystones and poorly consolidated sands) bedrock, offers the opportunity to set up a natural experiment and investigate the onset of canyon incision and its subsequent stages of development across five decades (1955-1993). To these ends, we evaluate decadal geomorphic changes of 10-km valley segment of the Marecchia River between Ponte Verucchio and Rimini (Northern Italy) through analysis of Digital Elevation Models derived from the application of Structure from Motion to archival aerial imagery (i.e., 1955, 1969, 1976, 1985, 1993) and from a reference-LiDAR survey (i.e. 2009), in conjunction with analysis of planimetric changes in active channel width and lateral confinement.

During the 1955-2009 period, fluvial incision led to the formation of a 6-km canyon, with average vertical incision of about 15 m (in places exceeding 25 m) and a corresponding annual knickpoint migration rate of about 100 m/yr. In volumetric terms, canyon formation and evolution has involved 6.1 106 m3 (95%) of degradation and 0.29 106 m3 of aggradation (5%), with a corresponding net volume loss of 5.8 106 m3. As a result of canyon development, the active channel has narrowed by about 80%, and channel pattern has drastically changed from braided unconfined to single-thread tightly confined one. These processes were especially important during the 1955-1993 period. Since 1993 to the present, main channel is characterized by a general stability of the active channel width with evidences of a slight recovery through mass wasting processes within it. Local disturbance associated with ongoing canyon development have propagated and are still propagating upstream, posing immediate threat to infrastructures.

How to cite: Llena, M., Simonelli, T., and Brardinoni, F.: Rapid formation of a bedrock canyon following gravel mining in the Marecchia River, Northern Apennines., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6894, https://doi.org/10.5194/egusphere-egu22-6894, 2022.

EGU22-7374 * | Presentations | GM2.7 | Highlight

Expanding glacier time series of Antarctica and Greenland using Soviet Era KFA-1000 satellite images 

Flora Huiban, Mads Dømgaard, Luc Girod, Romain Millan, Amaury Dehecq, Jeremie Mouginot, Anders Schomacker, Eric Rignot, and Anders Bjørk

Long-term records of glaciers are more than ever crucial to understand their response to climate change. High-quality photogrammetric products, Digital Elevation Models (DEMs) and orthophotographs from early satellites are essential, as they offer a unique high-resolution view on the historical glacial dynamics. However, obtaining and producing high-resolution datasets from historical imagery can be a challenge.

In our study, we are extending available satellite images time series using images from Soviet Era KFA-1000 satellite cameras. Each KFA-1000 has a 1000 mm objective, holding 1800 frames in its magazine. Each frame is typically 18x18 cm or 30 × 30 cm, with an 80 km swath width, providing panchromatic images. They supplement the very sparse data period between aerial images and high-resolution modern satellites, giving us high-resolution insight of Antarctica and Greenland dating from 1974 to 1994. Since these images have been largely underused, they have the potential to improve our knowledge of glaciers and open new scientific perspectives. They could help us improve models in studies regarding, for instance the frontal position, the flow-velocity (by doing feature tracking), the surface elevation or the grounding line of the glaciers, etc. With a spatial resolution up to 2 m and images recorded in stereo geometry, they offer a valuable complement to other historical satellite archives such as the declassified American KH imagery. Here, we use structure-from-motion (SfM) to reconstruct former glacier surfaces and flow of main outlet glaciers in both Antarctica and Greenland. We compare and assess the quality of the results by comparing the produced DEMs with recent high-resolution imagery from Worldview’s ArcticDEM. We combine the historical DEMs with recent satellite imagery of the ice elevation and reconstruct the comprehensive history of volume change over southeast and northeast Greenland glaciers since the 90s. Mostly lost from sight for 50 years, we are now resurrecting these highly valuable records and will make them freely available to science and the public.

 

How to cite: Huiban, F., Dømgaard, M., Girod, L., Millan, R., Dehecq, A., Mouginot, J., Schomacker, A., Rignot, E., and Bjørk, A.: Expanding glacier time series of Antarctica and Greenland using Soviet Era KFA-1000 satellite images, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7374, https://doi.org/10.5194/egusphere-egu22-7374, 2022.

EGU22-7686 | Presentations | GM2.7

Comparison of deep learning methods for colorizing historical aerial imagery 

Shimon Tanaka, Hitoshi Miyamoto, Ryusei Ishii, and Patrice Carbonneau

Historical aerial imagery dating back to the mid-twentieth century offers high potential to distinguish anthropogenic impacts from natural causes of environmental change and reanalyze the long-term surface evolution from local to regional scales. However, the older portion of the imagery is often acquired in panchromatic grayscale thus making image classification a very challenging task.  This research aims to compare deep learning image colorisation methods, namely, , the Neural Style Transfer (NST) and the Cycle Generative Adversarial Network (CycleGAN), for colorizing archival images of Japanese river basins for land cover analysis. Historical monochrome images were examined with `4096 x 4096` pixels of three river basins, i.e., the Kurobe, Tenryu, and Chikugo Rivers. In the NST method, we used the transfer learning model with optimal hyperparameters that had already been fine-tuned for the river basin colorization of the archival river images (Ishii et al., 2021). As for the CycleGAN method, we trained the CycleGAN with 8000 image tiles of `256 x256` pixels to obtain the optimal hyperparameters for the river basin colorization. The image tiles used in training consisted of 10 land-use types, including paddy fields, agricultural lands, forests, wastelands, cities and villages, transportation land, rivers, lakes, coastal areas, and so forth. The training result of the CycleGAN reached an optimal model in which the root mean square error (RMSE) of colorization was 18.3 in 8-bit RGB color resolution with optimal hyperparameters of the dropout ratio (0.4), cycle consistency loss (10), and identity mapping loss (0.5). Colorization comparison of the two-deep learning methods gave us the following three findings. (i) CycleGAN requires much less training effort than the NST because the CycleGAN used an unsupervised learning algorithm. CycleGAN used 8000 images without labelling for training while the NST used 60k with labelling in transfer learning. (ii) The colorization quality of the two methods was basically the same in the evaluation stage; RMSEs in CycleGAN were 15.4 for Kurobe, 13.7 for Tenryu and 18.7 for Chikugo, while RMSE in NST were 9.9 for Kurobe, 15.8 for Tenryu, and 14.2 for Chikugo, respectively. (iii) The CycleGAN indicated much higher performance on the colorization of dull surfaces without any textual features, such as the river course in Tenryu River, than the NST. In future research work, colorized imagery by both the NST and CycleGAN will be further used for land cover classification with AI technology to investigate its role in image recognition. [Reference]: Ishii, R. et al.(2021) Colorization of archival aerial imagery using deep learning, EGU General Assembly 2021, EGU21-11925, https://doi.org/10.5194/egusphere-egu21-11925.

How to cite: Tanaka, S., Miyamoto, H., Ishii, R., and Carbonneau, P.: Comparison of deep learning methods for colorizing historical aerial imagery, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7686, https://doi.org/10.5194/egusphere-egu22-7686, 2022.

EGU22-7967 | Presentations | GM2.7

Time-lapse stereo-cameras and photogrammetry for continuous 3D monitoring of an alpine glacier 

Francesco Ioli, Alberto Bianchi, Alberto Cina, Carlo De Michele, and Livio Pinto

Photogrammetry and Structure-from-Motion have become widely assessed tools for geomorphological 3D reconstruction, and especially for monitoring remote and hardly accessible alpine environments. UAV-based photogrammetry enables large mountain areas to be modelled with high accuracy and limited costs. However, they still require a human intervention on-site. The use of fixed time-lapse cameras for retrieving qualitative and quantitative information on glacier flows have recently increased, as they can provide images with high temporal frequency (e.g., daily) for long-time spans, and they require minimum maintenance. However, in many cases, only one camera is employed, preventing the use of photogrammetry to compute georeferenced 3D models. This work presents a low-cost stereoscopic system composed of two time-lapse cameras for continuously and quantitatively monitoring the north-west tongue of the Belvedere Glacier (Italian Alps), by using a photogrammetric approach. Each monitoring station includes a DSLR camera, an Arduino microcontroller for camera triggering, and a Raspberry Pi Zero with a SIM card to send images to a remote server through GSM network. The instrumentation is enclosed in waterproof cases and mounted on tripods, anchored on big and stable rocks along the glacier moraines. The acquisition of a defined number of images and the timing can be arbitrary scheduled, e.g., 2 images per day acquired by each camera, around noon. A set of ground control points is materialized on stable rocks along the moraines and measured with topographic-grade GNSS receivers at the first epoch to orient stereo-pairs of images. From daily stereo-pairs, 3D models are computed with the commercial Structure from Motion software package Agisoft Metashape, and they can be used to detect morphological changes in the glacier tongue, as well as to compute daily glacier velocities. The work is currently focused on improving the orientation of stereo-pairs: the use of computer vision algorithms is under study to automatize the process and increase the robustness of consecutive orientation of stereo-images, e.g., by including images coming from different epochs in the same bundle block adjustment and dividing them afterwards for dense 3D reconstruction. Change detection can be then computed from 3D point clouds by using M3C2 algorithms. Although the stereoscopic system is already installed on the Belvedere Glacier and it is properly taking daily images of the glacier tongue, the processing workflow of stereo-pairs needs to be tuned and automatized to enable high-accurate continuous 3D photogrammetric monitoring of an alpine glacier, computing short-term and infra-seasonal ice volume variations and velocities, as well as detecting icefalls.

How to cite: Ioli, F., Bianchi, A., Cina, A., De Michele, C., and Pinto, L.: Time-lapse stereo-cameras and photogrammetry for continuous 3D monitoring of an alpine glacier, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7967, https://doi.org/10.5194/egusphere-egu22-7967, 2022.

EGU22-8738 | Presentations | GM2.7 | Highlight

Review on the processing and application of historical aerial and satellite spy images in geosciences 

Camillo Ressl, Amaury Dehecq, Thomas Dewez, Melanie Elias, Anette Eltner, Luc Girod, Robert McNabb, and Livia Piermattei

Historical aerial photographs captured since the early 1900s and spy satellite photographs from the 1960s onwards have long been used for military, civil, and research purposes in natural sciences. These historical photographs have the unequalled potential for documenting and quantifying past environmental changes caused by anthropogenic and natural factors.

The increasing availability of historical photographs as digitized/scanned images, together with the advances in digital photogrammetry, have heightened the interest in these data in the scientific community for reconstructing long-term surface evolution from local to regional scale.

However, despite the available volume of historical images, their full potential is not yet widely exploited. Currently, there is a lack of knowledge of the types of information that can be derived, their availability over the globe, and their applications in geoscience. There are no standardized photogrammetric workflows to automatically generate 3D (three-dimensional) products, in the form of point clouds and digital elevation models from stereo images (i.e. images capturing the same scenery from at least two positions), as well as 2D products like orthophotos. Furthermore, influences on the quality and the accuracy of the products are not fully understood as they vary according to the image quality (e.g. photograph damage or scanning properties), the availability of calibration information (e.g. focal length or fiducial marks), and data acquisition (e.g. flying height or image overlap).

We reviewed many articles published in peer reviewed journals from 2010 to 2021 that explore the potential of historical images, covering both photogrammetric reconstruction techniques (methodological papers) and the interpretation of 2D and 3D changes in the past (application papers) in different geoscience disciplines such as geomorphology, cryosphere, volcanology, bio-geosciences, geology and archaeology. We present an overview of these published studies and a summary of available image archives. In addition, we compare the main methods used to process historical aerial and satellite images, highlighting new approaches. Finally, we provide our advice on image processing and accuracy assessment.

How to cite: Ressl, C., Dehecq, A., Dewez, T., Elias, M., Eltner, A., Girod, L., McNabb, R., and Piermattei, L.: Review on the processing and application of historical aerial and satellite spy images in geosciences, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8738, https://doi.org/10.5194/egusphere-egu22-8738, 2022.

EGU22-9799 | Presentations | GM2.7

Coastal erosion dynamics of high-Arctic rock walls: insights from historical to recent orthoimages and DEMs 

Juditha Aga, Livia Piermattei, Luc Girod, and Sebastian Westermann

The thermal regime of permafrost, as well as the retreat of sea ice, influence coastal erosion in Arctic environments. Warming permafrost temperatures might lead to enhanced instabilities, while shorter periods of sea ice expose coastal cliffs to waves and tides for longer periods. Although most studies focus on erosion rates in ice-rich permafrost, coastal cliffs and their permafrost thermal regime are still poorly understood.

In this study, we investigate the long-term evolution of the coastline along Brøgger Peninsula (~30 km2), Svalbard. Based on high-resolution aerial orthophotos and, when available, digital elevation model (DEMs) we automatically derive the coastline from 1936 (Geyman et al., 2021), 1970, 1990, 2011 and 2021. Therefore, we quantified coastal erosion rates along the coastal cliffs over the last 85 years. Due to their high spatial resolution and accuracy, the two DEMs from 1970 and 2021 are used to calculate the erosion volumes within this time. Elevation data and coastline mapping from 2021 is validated with dGPS measurements from August 2021 along three transects of the coastline. In addition, we measured surface temperature of the coastal bedrock from September 2020 to August 2021.

Our preliminary results show erosion rates along the coastal cliffs of Brøgger Peninsula. Uncertainties remain due to mapping issues, which include resolution of aerial images and DEMs, and shadow effects. Overall, historical aerial images combined with recent data provide insight into coastal evolution in an Arctic environment where permafrost temperatures are close to the thaw threshold and might become prone to failure in future.

 

Geyman, E., van Pelt, W., Maloof, A., Aas, H. F., & Kohler, J. (2021). 1936/1938 DEM of Svalbard [Data set]. Norwegian Polar Institute. https://doi.org/10.21334/npolar.2021.f6afca5c

How to cite: Aga, J., Piermattei, L., Girod, L., and Westermann, S.: Coastal erosion dynamics of high-Arctic rock walls: insights from historical to recent orthoimages and DEMs, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9799, https://doi.org/10.5194/egusphere-egu22-9799, 2022.

EGU22-10060 | Presentations | GM2.7

Automated mapping of Soil Surface Components (SSCs) in highly heterogeneous environments with Unoccupied Aerial Systems (UAS) and Deep Learning: working towards an optimised workflow 

Eva Arnau-Rosalén, Ramón Pons-Crespo, Ángel Marqués-Mateu, Jorge López-Carratalá, Antonis Korkofigkas, Konstantinos Karantzalos, Adolfo Calvo-Cases, and Elias Symeonakis

Pattern recognition remains a complex endeavour for ‘structure/function’ approaches to ecosystem functioning. It is particularly challenging in dryland environments where spatial heterogeneity is the inherent functional trait related with overland flow redistribution processes. Within this context, the concept of Soil Surface Components (SSCs) emerged, representing Very-High-Resolution (VHR) hydrogeomorphic response units. SSCs are abstraction entities where spatial patterns of the soil surface and erosional functional processes are linked, according to a large pool of experimental evidence.  

Τhis abstraction complexity, particularly in the abiotic domain, has  so far mandated the use of on-screen visual photointerpretation for the mapping of SSCs, thus limiting the extent of the study cases and their potential for providing answers to the ongoing research discourse. Although significant advances have been achieved with regards to the VHR mapping of vegetation traits with either shallow or deep machine learning algorithms, mapping the full range of SSCs requires bridging the existing gap related with the abiotic domain.

The current confluence of technical advances in: (i) Unoccupied Aerial Systems (UAS), for VHR image acquisition and high geometric accuracy; (2) photogrammetric image processing (e.g. Structure from Motion, SfM), for accurately adding the third dimension, and (3) Deep Learning (DL) architectures that consider the spatial context (i.e. Convolutional Neural Networks, CNN), offers an unprecedented opportunity for achieving the pattern recognition quality required for the automated mapping of SSCs.

We decompose this complex issue with a stepwise approach in an attempt to optimise protocols across all stages of the entire process. For the initial step of image acquisition, we focus on the design of optimal UAS flight parameters, particularly with regards to flight height and image resolution, as this relates to the scale of the analysis: a critical issue for hillslope and catchment scale surveys. At the core of the methodological framework, we then approach the challenge of mapping the patchy mosaic of SSCs as a hierarchical image segmentation problem, decomposed into classification (i.e. discrete) and regression (i.e. continuous fields) tasks, required for dealing with the biotic (e.g. vegetation) and abiotic (e.g. fractional cover of rock fragments) domains, respectively.

Our pilot study area is a hillslope transect near Benidorm, a representative case in semi-arid environment of SE Spain. In this area, the mapping of SSCs was previously undertaken via visual image interpretation. We obtain satisfactory results that allow for the differentiation of plant physiognomies (i.e. annual herbaceous, shrubs, perennial tussock grass and trees). Regarding the abiotic SSCs, in addition to the identification of rock outcrops, we are also able to quantify the fractional cover of rock fragments (RF): an improvement to the visual photointerpretation of only three intervals of RF coverage. A number of challenges remain, such as the position of RF and the transferability of our methodological framework to sites with different lithological and climatological properties.

How to cite: Arnau-Rosalén, E., Pons-Crespo, R., Marqués-Mateu, Á., López-Carratalá, J., Korkofigkas, A., Karantzalos, K., Calvo-Cases, A., and Symeonakis, E.: Automated mapping of Soil Surface Components (SSCs) in highly heterogeneous environments with Unoccupied Aerial Systems (UAS) and Deep Learning: working towards an optimised workflow, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10060, https://doi.org/10.5194/egusphere-egu22-10060, 2022.

EGU22-10190 | Presentations | GM2.7 | Highlight

Historical Structure From Motion (HSfM): An automated historical aerial photography processing pipeline revealing non-linear and heterogeneous glacier change across Western North America 

Friedrich Knuth, David Shean, Chistopher McNeil, Eli Schwat, and Shashank Bhushan

Mountain glaciers are responding in concert to a warming global climate over the past century. However, on interannual to decadal time scales, glaciers show temporally non-linear dynamics and spatially heterogeneous response, as a function of regional climate forcing and local geometry. Deriving long-term geodetic glacier change measurements from historical aerial photography can inform efforts to understand and project future response. 

We present interannual to decadal glacier and geomorphic change measurements at multiple sites across Western North America from the 1950s until present. Glacierized study sites differ in terms of glacial geometry and climatology, from continental mountains (e.g., Glacier National Park) to maritime stratovolcanoes (e.g., Mt. Rainier). Quantitative measurements of glacier and land surface change are obtained from Digital Elevation Models (DEMs) generated using the Historical Structure from Motion (HSfM) package. We use scanned historical images from the USGS North American Glacier Aerial Photography (NAGAP) archive and other aerial photography campaigns from the USGS EROS Aerial Photo Single Frames archive. 

The automated HSfM processing pipeline can derive high-resolution (0.5-2.0 m) DEMs and orthomosaics from scanned historical aerial photographs, without manual ground control point selection. We apply a multi-temporal bundle adjustment process using all images for a given site to refine both extrinsic and intrinsic camera model parameters, prior to generating DEMs for each acquisition date. All historical DEMs are co-registered to modern reference DEMs from airborne lidar, commercial satellite stereo or global elevation basemaps. The co-registration routine uses a multi-stage Iterative Closest Point (ICP) approach to achieve high relative alignment accuracy amongst the historical DEMs, regardless of reference DEM source. 

We examine the impact of regional climate forcing on glacier elevation change and dynamics using downscaled climate reanalysis products. By augmenting the record of quantitative glacier elevation change measurements and examining the relationship between climate forcing and heterogeneous glacier response patterns, we aim to improve our understanding of regional glacier mass change across multiple temporal scales, as well as inform management decisions impacting downstream water resources, ecosystem preservation, and geohazard risks.

How to cite: Knuth, F., Shean, D., McNeil, C., Schwat, E., and Bhushan, S.: Historical Structure From Motion (HSfM): An automated historical aerial photography processing pipeline revealing non-linear and heterogeneous glacier change across Western North America, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10190, https://doi.org/10.5194/egusphere-egu22-10190, 2022.

EGU22-10513 | Presentations | GM2.7

Using UAS-based LiDAR data to quantify oyster reef structural characteristics for temporal monitoring 

Michael C. Espriella, Vincent Lecours, H. Andrew Lassiter, and Benjamin Wilkinson

Given the global decline in oyster reef coverage, conservation and restoration efforts are increasingly needed to maintain the ecosystem services these biogenic features offer. However, monitoring and restoration are constrained by a lack of continuous quantitative metrics to effectively assess reef health. Traditional sampling methods typically provide a limited perspective of reef status, as sampling areas are just a fraction of the total reef area. In this study, an unoccupied aircraft system collected LiDAR data over oyster reefs in Cedar Key, FL, USA to develop digital surface models (DSMs) of their 3D structure. Ground sampling was also conducted in randomly placed quadrats to enumerate the live and dead oysters within each plot. Over 20 topographic complexity metrics were derived from the DSM, allowing relationships between various geomorphometric measures and reef health to be quantified. These data informed generalized additive models that explained up to 80% of the deviation of live to dead oyster ratios in the quadrats. While topographic complexity has been associated with reef health in the past, this process quantifies the relationships and indicates what metrics can be relied on to efficiently monitor intertidal oyster reefs using DSMs. The models can also inform restoration efforts on which surface characteristics are best to replicate when building restored reefs.  

How to cite: Espriella, M. C., Lecours, V., Lassiter, H. A., and Wilkinson, B.: Using UAS-based LiDAR data to quantify oyster reef structural characteristics for temporal monitoring, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10513, https://doi.org/10.5194/egusphere-egu22-10513, 2022.

EGU22-10597 | Presentations | GM2.7

Semantic segmentation of historical images in Antarctica with neural networks 

Felix Dahle, Roderik Lindenbergh, Julian Tanke, and Bert Wouters

The USGS digitized many historical photos of Antarctica which could provide useful insights into this region from before the satellite era. However, these images are merely scanned and do not contain semantic information, which makes it difficult to use or search this archive (for example to filter for cloudless images). Even though there are countless semantic segmentation methods, they are not working properly with these images. The images are only grayscale, have often a poor image quality (low contrast or newton’s rings) and do not have very distinct classes, for example snow/clouds (both white pixels) or rocks/water (both black pixels). Furthermore, especially for this archive, these images are not only top-down but can also be oblique.

We are training a machine-learning based network to apply semantic segmentation on these images even under these challenging conditions. The pixels of each image will be labelled into one of the six different classes: ice, snow, water, rocks, sky and clouds. No training data was available for these images, so that we needed to create it ourselves. The amount of training data is therefore limited due to the extensive amount of time required for labelling. With this training data, a U-Net was trained, which is a fully convolutional network that can work especially with fewer training images and still give precise results.

In its current state, this model is trained with 67 images, split in 80% training and 20% validation images. After around 6000 epochs (approx. 30h of training) the model converges and training is stopped. The model is evaluated on 8 randomly selected images that were not used during training or validation. These images contain all different classes and are challenging to segment due to quality flaws and similar looking classes. The model is able to segment the images with an accuracy of around 75%. Whereas some classes, like snow, sky, rocks and water can be recognized consistently, the classes ice and clouds are often confused with snow. However, the general semantic structure of the images can be recognized.

In order to improve the semantic segmentation, more training imagery is required to increase the variability of each class and prepare the model for more challenging scenes. This new training data will include both labelled images from the TMA archive and from other historical archives in order to increase the variability of classes even more. It should be checked if the quality of the model can be further improved by including metadata of the images as additional data sources.

How to cite: Dahle, F., Lindenbergh, R., Tanke, J., and Wouters, B.: Semantic segmentation of historical images in Antarctica with neural networks, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10597, https://doi.org/10.5194/egusphere-egu22-10597, 2022.

EGU22-10943 | Presentations | GM2.7

High-resolution topography project on the rock walls of the Mont-Blanc massif to reconstruct volume change 

Daniel Uhlmann, Michel Jaboyedoff, Marc-Henri Derron, Ludovic Ravanel, Joelle Vicari, Charlotte Wolff, Li Fei, Tiggi Choanji, and Carlota Gutierrez

Before modern remote sensing techniques, quantifying rock wall retreat due to rockfall events in the high alpine environment was limited to low-frequency post-event measurements for high-magnitude events. LiDAR and SFM now provide precise and accurate 3D models for computing 3D volume changes over time. Otherwise, mid- and low-sized events can remain unobserved due to the remoteness of the rockwalls and the lack of remnant evidence due to the rapid sequestration of ice in surrounding valley and cirque glaciers. To extend rockfall event measurement an initial measurement (t0) is necessary. The Mont-Blanc Massif (MBM, European Alps) High Resolution Topography Project is currently completing high-precision 3D models in the MBM using ground-based and aerial LiDAR, and drone-based structure-from-motion (SFM). In 2021, we began acquisition with initial measurements of 11 major sectors of the massif, representing about 80 km2 of rock and ice slopes, between 1700m - 4810m in elevation. By choosing a study area with robust existent photographic and film archives, such as the MBM, it is possible to extend 3D models back in time for comparison with current datasets. Despite existent high-quality image archives, SFM processing is more challenging and error-prone than from contemporary images due to a lack of metadata, such as camera and lens type, precise dates of images, and the general degradation of the original material.  Despite these limitations, the use of historical-image-based SFM in combination with modern LiDAR data can allow the reconstruction of significant slopes of the MBM over several decades in order to i) obtain estimates of erosion rates, ii) to document rockfall events, and iii) to quantify the extent change and volume loss of hanging glaciers and ice aprons. We thus explore geomorphic processes in the high mountain environment in context of warming climate, as well as the limits of input data (image sets) in terms of practical output resolution.

How to cite: Uhlmann, D., Jaboyedoff, M., Derron, M.-H., Ravanel, L., Vicari, J., Wolff, C., Fei, L., Choanji, T., and Gutierrez, C.: High-resolution topography project on the rock walls of the Mont-Blanc massif to reconstruct volume change, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10943, https://doi.org/10.5194/egusphere-egu22-10943, 2022.

EGU22-11081 | Presentations | GM2.7

Extraction of geomorphological entities from unstructured point clouds – a three-dimensional level-set-based approach 

Reuma Arav, Florian Poeppl, and Norbert Pfeifer

The use of 3D point clouds has become ubiquitous in studying geomorphology. The richness of the acquired data, together with the high availability of 3D sensing technologies, enables a fast and detailed characterisation of the terrain and the entities therein. However, the key for a comprehensive study of landforms relies on detecting geomorphological features in the data. These entities are of complex forms that do not conform to closed parametric shapes. Furthermore, they appear in varying dimensions and orientations, and they are often seamlessly embedded within the topography. The large volume of the data, uneven point distribution and occluded regions present even a greater challenge for autonomous extraction. Therefore, common approaches are still rooted in utilising standard GIS tools on rasterised scans, which are sensitive to noise and interpolation methods. Schemes that investigate morphological phenomena directly from the point cloud use heuristic and localised methods that target specific landforms and cannot be generalised. Lately, machine-learning-based approaches have been introduced for the task. However, these require large training datasets, which are often unavailable in natural environments.

This work introduces a new methodology to extract 3D geomorphological entities from unstructured point clouds. Based on the level-set model, our approach does not require training datasets or labelling, requires little prior information about existing objects, and wants minor adjustments between different types of scenes. By developing the level-set function within the point cloud realm, it requires no triangulated mesh or rasterisation. As a driving force, we utilise visual saliency to focus on pertinent regions. As the estimation is performed pointwise, the proposed model is completely point-based, driven by the geometric characteristics of the surface. The result is three-dimensional entities extracted by their original points, as they were scanned in the field. We demonstrate the flexibility of the proposed model on two fundamentally different datasets. In the first scene, we extract gullies and sinkholes in an alluvial fan and are scanned by an airborne laser scanner. The second features pockets, niches and rocks in a terrestrially scanned cave. We show that the proposed method enables the simultaneous detection of various geomorphological entities, regardless of the acquisition technique. This is facilitated without prior knowledge of the scene and with no specific landform in mind. The proposed study promotes flexibility of form and provides new ways to quantitatively describe the morphological phenomena and characterise their shape, opening new avenues for further investigation.

How to cite: Arav, R., Poeppl, F., and Pfeifer, N.: Extraction of geomorphological entities from unstructured point clouds – a three-dimensional level-set-based approach, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11081, https://doi.org/10.5194/egusphere-egu22-11081, 2022.

EGU22-12200 | Presentations | GM2.7

Terrain Change Detection with ICESat-2: A Case Study of Central Mountain Range in Taiwan 

Pin-Chieh Pan and Kuo-Hsin Tseng

Ice, Cloud, and land Elevation Satellite 2 (ICESat-2), part of NASA's Earth Observing System, is a satellite mission for measuring ice sheet elevation as well as land topography. ICESat-2 is equipped with the Advanced Topographic Laser Altimeter System (ATLAS), a spaceborne lidar that provides topography measurements of land surfaces around the globe. This study intends to utilize ICESat-2 ATL03 elevation data to identify the outdated part in Taiwan’s Digital Elevation Model (DEM). Because the update of DEM takes time and is relatively expensive to renew by airborne LiDAR, a screen of elevation change is crucial for planning the flight route. ICESat-2 has not only a dense point cloud of elevation but also a short revisit time for data collection. That is, ICESat-2 may have a chance to provide a reference for the current condition of terrain formation.

In this study, we aim to verify the 20-meter DEM from the Ministry of the Interior, Taiwan, by ICESat-2 elevation data. The goal is to find out the patches that have experienced significant changes in elevation due primarily to landslides. We select a typical landslide hillside in southern Taiwan as an example, and compare the DEM with ICESat-2 ATL03 photon-based heights before and after the occurrence of landslide events. In our preliminary results, the comparison of DEM and ICESat-2 ATL03 heights has a high degree of conformity inaccuracy (within meter level), indicating ICESat-2’s ability for DEM renewal.

How to cite: Pan, P.-C. and Tseng, K.-H.: Terrain Change Detection with ICESat-2: A Case Study of Central Mountain Range in Taiwan, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12200, https://doi.org/10.5194/egusphere-egu22-12200, 2022.

CR3 – Snow and ice: properties, processes, hazards

EGU22-184 | Presentations | CR3.1

Changes in the frequency and extremity of rain-on-snow events in the warming climate 

Ondrej Hotovy and Michal Jenicek

Seasonal snowpack significantly influences the catchment runoff and thus represents an important input for the hydrological cycle. A shift from snowfall to rain is expected in the future due to climate changes, as well as changes in the precipitation distribution and intensity. As a result, changes in the frequency and extremity of rain-on-snow events, which are considered to be one of the main causes of floods in winter and spring, may occur.

The objective of this study is 1) to evaluate the frequency, extremity, and trends in occurrence of rain-on-snow events in the past based on existing measurements, and 2) to simulate and evaluate the effect of predicted increase in air temperature on the occurrence of rain-on-snow events in the future. We selected several near-natural mountain catchments in Czechia and Switzerland with significant snow influence on runoff and with available long-time series of daily hydrological and meteorological variables. A semi-distributed conceptual model, HBV-light, was used to simulate the individual components of the water cycle at a catchment scale. The model was calibrated for each of study catchments by using 100 calibration trials which resulted in respective number of optimized parameter sets. The model performance was evaluated against observed runoff and snow water equivalent. Each study catchment was divided into several elevation zones by 100 m, for which all data at a daily resolution were distributed by the model. Rain-on-snow events definition by threshold values for air temperature, rain intensity and snow depth allowed us to analyze inter-annual variations and trends in rain-on-snow events during the study period 1965-2019 and in the future.

The results show that a change of rain-on-snow events related to increasing air temperature differs among individual study catchments and individual elevation zones during winter season. Since both air temperature and elevation seem to be an important rain-on-snow drivers, there is an increasing rain-on-snow events occurrence due to a decrease in snowfall fraction. In contrast, a decrease in total number of events was observed due to the shortening of the period with existing snow cover on the ground. Modelling approach also opened further questions related to model structure and parameterization, specifically how individual model procedures and parameters represent the real natural processes. To understand potential model artefacts might be important when using HBV or similar bucket-type models for impact studies, such as modelling the impact of climate change on catchment runoff.

How to cite: Hotovy, O. and Jenicek, M.: Changes in the frequency and extremity of rain-on-snow events in the warming climate, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-184, https://doi.org/10.5194/egusphere-egu22-184, 2022.

EGU22-560 | Presentations | CR3.1

Simulating radio propagation in ice with Parabolic Equations: applications to terrestrial glaciers and ice moons 

Alexander Kyriacou, Gianluca Boccarella, Pia Friend, and Klaus Helbing

We investigate the use of Parabolic Equation (PE) simulations in modelling the propagation of radio waves in inhomogeneous ice environments, such as the firn layer of terrestrial glaciers in the Alps and Antarctic. In particular PEs allow for an accurate and efficient means to simulate pulsed radar on a multi-km scale for depth-dependent permittivity profiles, and inhomogeneities that are the targets of radar scans.

PEs are an approximate solution to Maxwell's equations which are valid within a cone that is perpendicular to the source, which defines the 'paraxial direction'. For monochromatic (single-frequency) radio emission, the electric field can be solved using a numerical step-wise solver, where the next range increment can be solved from the previous step. The emission profile of the source is used to define the starting condition. To solve in the time-domain for pulses, the pulse is decomposed into its Fourier spectrum, and the electric field throughout the geometry is solved for each frequency. By sampling the frequency dependent field amplitude at a given range and depth in the geometry, one can reconstruct the pulse and measure the time of flight. We implement a two-stage PE solver which first models propagation in the forwards direction from a transmitter, and then solves in the 'backwards' direction in order to calculate reflected signals. 

We present a Python based PE solver which simulates emission from a high frequency (300 MHz to 2000 MHz) radar transmitter into ice on a multi km-scale, using depth dependent permittivity profiles and a list of objects, such as boulders, crevasses and aquifers, which cause scattering. We find that we can accurately solve pulsed radar emission, and test target reconstruction techniques. We compare radar images for targets with constant permittivity and varying permittivity. We apply our simulation method to the firn layer of numerous real-world glaciers, with their permittivity estimated from density profiles, and observed birefringence and wave-guide-like behaviour between bands of solid ice, caused by melting and refreezing of the firn. 

Additionally we apply PE simulations to assess the viability of a future melting probe mission on Saturn's ice moon Enceladus, in which the melting probe would seek a near surface water pocket, which it localized with a combined orbital and surface radar scan.

How to cite: Kyriacou, A., Boccarella, G., Friend, P., and Helbing, K.: Simulating radio propagation in ice with Parabolic Equations: applications to terrestrial glaciers and ice moons, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-560, https://doi.org/10.5194/egusphere-egu22-560, 2022.

EGU22-615 | Presentations | CR3.1

Adaptation of a snow cover scheme for complex topography areas: regional calibration over High Mountain Asia and application in global models 

Mickaël Lalande, Martin Ménégoz, Gerhard Krinner, and Catherine Ottlé

Snow cover strongly modulates the energy fluxes between the atmosphere and the Earth's surface. Indeed, snow has generally a much higher albedo compared to other surfaces and therefore reduces the amount of solar radiation absorbed by the surface. Moreover, because of its low conductivity, snow isolates the ground from the atmosphere, impacting soil surface temperatures and energy balance (Zhang 2005). In general circulation models (GCMs) the snow cover fraction (SCF) is usually a diagnostic variable derived from other snow quantities, as for instance, the snow water equivalent (SWE) or the snow depth (SD). The relationship between SWE and SCF varies from simple linear relationships to more advanced parameterizations taking into account the snow density allowing to represent the hysteresis effect between the accumulation phase and the more disparate melting phase (e.g., Niu and Yang 2007). Swenson and Lawrence (2012) highlighted strong differences of snow cover extents between plains and mountainous areas, which may be explained by the persistence of snow on the summits whereas a faster melting occurs in the valleys. However, the dependency of SCF on the topography is considered only in a reduced number of GCMs, whereas mountainous areas represent nearly 1/5 of the world's surface area (Huddlestone et al., 2003). In this study, we designed three new snow parameterizations that include the impact of the sub-grid topography on the SCF in the ORCHIDEE land surface model (LSM) coupled to the LMDZ atmospheric model (part of the French GCM of IPSL). This model shows a strong cold bias and an excess of SCF over the High Mountains of Asia (HMA)  (Lalande et al., 2021). The new SCF parameterizations are based on the following existing ones: Swenson and Lawrence (2012; hereafter SL12), Roesch et al. (2001; hereafter R01), and a modified version of Niu and Yang (2007; hereafter NY07). These new parameterizations were calibrated over HMA using a high-resolution snow reanalysis (Liu et al., 2021), and compared to a deep learning model trained on the reanalysis dataset. The calibrated parameterizations SL12, R01, and the modified version of NY07 were then tested in coupled ORCHIDEE/LMDZ simulations. Preliminary results show improvements in simulated snow cover in HMA but slight deterioration in other areas. They suggest also that calibration should be extended to other snow-covered areas and should include other parameters such as the type of vegetation in particular.

How to cite: Lalande, M., Ménégoz, M., Krinner, G., and Ottlé, C.: Adaptation of a snow cover scheme for complex topography areas: regional calibration over High Mountain Asia and application in global models, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-615, https://doi.org/10.5194/egusphere-egu22-615, 2022.

EGU22-1145 | Presentations | CR3.1

Why does the heated needle probe method underestimate snow thermal conductivity? 

Kevin Fourteau, Pascal Hagenmuller, and Florent Domine

Thanks to its ease of use, the heated needle probe method is broadly employed to measure snow thermal conductivity, both in the field and in laboratory. However, recent studies have highlighted that when compared to other measurement techniques, the needle probe shows a systematic underestimation bias. Here, we examine the theory at the base of the needle probe method and show that for a light and insulating material such as snowthe standard measurement protocol using heating times around 100 s leads to underestimations, as observed. Moreover, the damage done to the snow microstructure when manually inserting the probe leads to a further underestimation, that can exceed 50%. Nonetheless, needle probes remain the only easily deployed technique to measure snow thermal conductivity in remote areas. We thus propose a new measurement protocol to correct this underestimation and to obtain reasonably reliable values of snow thermal conductivity.

How to cite: Fourteau, K., Hagenmuller, P., and Domine, F.: Why does the heated needle probe method underestimate snow thermal conductivity?, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1145, https://doi.org/10.5194/egusphere-egu22-1145, 2022.

EGU22-2326 | Presentations | CR3.1

Snow water equivalents from snow depths: improvements of the DeltaSNOW model 

Michael Winkler and Harald Schellander

Snow water equivalent (SWE) is probably the most important snowpack property, but due to various reasons it has been measured by far less frequently and continuously than, e.g., snow depth (HS). Recent modelling efforts led to ΔSNOW, a semi-empirical approach to derive daily SWE exclusively from consecutive HS series.

The ΔSNOW model - freely available as part of the R-package “nixmass” - builds on basic snow physics and needs seven parameters. If available, those should be fitted using SWE measured at the respective HS observation site(s), otherwise a standard set of parameters is provided, which was calibrated with data from the Alps. In the current model version, the parameters are kept unchanged over time. New-snow density and the maximum density model layers can reach are among the parameters. For natural snow, those vary significantly from day to day and during the winter season, also site specifics like, e.g., altitude influence them.

With this contribution the restriction of fixed density parameters in the ΔSNOW model is probed. Improvements might be achieved if new-snow density was made dependent on the amount of freshly fallen snow, rather than on altitude, date or region. The model-intrinsic maximum snow density could probably be improved if it was increased by the age of the respective snow layers as well as the overburden mass of snow. All validation experiments were performed with SWE and HS data from the Alps and from Germany. The latter comprising a huge high quality data set not only from mountainous regions but also from lowlands and maritime regions. The ΔSNOW model`s ability to simulate daily SWE outperforms other models of comparable complexity also in these areas, even more with adjusted density parameters.

How to cite: Winkler, M. and Schellander, H.: Snow water equivalents from snow depths: improvements of the DeltaSNOW model, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2326, https://doi.org/10.5194/egusphere-egu22-2326, 2022.

EGU22-2460 | Presentations | CR3.1

Retrieving fractional snow cover in Central Apennines from Sentinel 2 and 3 visible-infrared spectroradiometer data and random forest learning techniques 

Eleftheria Tetoula Tsonga, Gianluca Palermo, Edoardo Raparelli, Paolo Tuccella, Maria Paola Manzi, and Frank Marzano

Seasonal snow cover is the largest cryospheric component of in areal extent, covering more than 50 million square kilometers of the Earth surface (more than 31% of its land area) every year. Snow cover area (SCA) and its local properties, in terms of snowpack height and snowpack density, are the main parameters characterizing the snow accumulation in mountainous regions. Such parameters result in particular importance in meteorology, hydrology, and climate monitoring applications. Anyway, in the general case, the considerable geographical extension of snow layers and their typical spatial heterogeneity makes it impractical to monitor the above three parameters regularly (i.e., with a high spatial and temporal resolution) by means of direct or indirect in situ measurements, suggesting the exploitation of satellite technologies for the provision of such data. Snow cover patterns are governed by the effects of topography, land cover, wind redistribution, solar irradiance, and air temperature. On the other hand, in the last few decades, a general back-scaling of snow observation networks occurred worldwide. Based on the above considerations, space-borne SAR sensors are particularly suitable for the analysis of snow deposits, providing data with resolutions up to some meters, with global coverage and a few days revisit time.

In this study, we introduce a satellite-based technique for mapping snow cover fraction balancing the requirements between spatial and temporal resolution, and using data from the European Sentinel constellation. The available current fractional snow cover (FSC) products, provided by Sentinel-2 MSI (Multispectral imager) cloud-gap-filled (CGF) products and Terra MODIS (Moderate-resolution Infrared Spectroradiometer) snow cover products, may suffer either of relatively poor spatial resolution and/or temporal resolution (e.g., FSC at 25-m spatial resolution every 5 days from Sentinel-2 MSI products or 500-m spatial resolution every day from Terra MODIS). For this purpose, we explore the use of the Sentinel-3 optical sensors, OLCI (Ocean Land Color Imager), and SLSTR (Sea-Land Surface Temperature Radiometer), showing a 300-m and 500-m spatial resolution with 2-3 and 1-2 days temporal resolution.

Using as a reference the Sentinel-2 FSC product and employing a DEM (Digital Elevation Model) at 90 m spatial resolution, a machine learning Snow-Cover-Area Random Forest (SCARF) approach has been developed. The proposed algorithm takes, as inputs, both DEM as well as OLCI and SLSTR data, linearly up-sampled at 90-m, and can provide as output FSC product at 90-m spatial resolution every 1-2 days. Input data are derived from NASA SRTM 3-arc-second DEM, OLCI multi-band reflectances, and SLSTR multi-band reflectance and brightness temperatures at nadir and oblique view. After creating 2 datasets (nadir and oblique), we have introduced a distinction between the complete dataset and a subset leaving only the pixel with an elevation higher than 1000 m. As a classification method, we used an RF gradient-boosting classifier (called XGBoostClassifier). In this work, we will illustrate the results of the proposed SCARF algorithm using area-of-interest the Italian Central Apennines and period-of-interest winter 2019-20. Statistical performances, potential developments, and critical issues of the SCARF algorithm will also be discussed.

How to cite: Tetoula Tsonga, E., Palermo, G., Raparelli, E., Tuccella, P., Manzi, M. P., and Marzano, F.: Retrieving fractional snow cover in Central Apennines from Sentinel 2 and 3 visible-infrared spectroradiometer data and random forest learning techniques, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2460, https://doi.org/10.5194/egusphere-egu22-2460, 2022.

EGU22-2736 | Presentations | CR3.1

Snow dunes orientation in East Antarctica 

Marine Poizat, Ghislain Picard, Laurent Arnaud, and Charles Amory

Wind drives the formation, shape and dynamics of aeolian snow dunes. Depending on the wind regime, different bedforms are formed such as as erosional shape (sastrugi) or linear dunes, which are straight or slightly sinuous dunes. Constraining the relationship between snow dunes and wind regimes, notably orientation, is essential for a better understanding of snow redistribution and therefore local surface mass balance. Snow dunes are widely spread in the windy polar regions and have an influence on the surface energy balance. However, relative to their sand analogues there have been few investigations relating snow bedforms orientation to wind direction. In Antarctica where snow bedforms are widely spread, wind direction has been inferred from sastrugi direction, but the relationship between the orientation of dunes and wind regime remains unclear.

In this study, we present a large-scale investigation of linear dune orientation in East Antarctica related to wind direction. We used optical Sentinel-2 images to identify linear dune fields location during summer with a 10-m resolution and retrieved their orientation. Inferring wind direction and speed from ERA5 reanalysis, at 0.25° resolution, we demonstrate that linear snow dunes are found even in areas with weak mean annual wind speed, providing some insights about the conditions of their formation. In addition, the comparison between wind direction statistics (prevailing direction and constancy) and dune orientations provides new insight into the relationship between linear snow dunes and the local wind regimes.

How to cite: Poizat, M., Picard, G., Arnaud, L., and Amory, C.: Snow dunes orientation in East Antarctica, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2736, https://doi.org/10.5194/egusphere-egu22-2736, 2022.

EGU22-3463 | Presentations | CR3.1

Linking snow optical properties to snow microstructure 

Alvaro Robledano, Ghislain Picard, Marie Dumont, Laurent Arnaud, and Frédéric Flin

Snow plays a crucial role in the climate system, as its high albedo is unique among the Earth’s surface materials. Several microstructural properties such as the snow specific surface area strongly modulate the optical properties of snow. Light penetration and scattering by ice particles are also impacted by other microstructural parameters, such as the grain shape. Nevertheless, most radiative transfer models still treat snow as a medium composed of idealized and simplified geometries, which limits the understanding of how the snow microstructure impacts the snow optical properties. Assuming geometric optics and weak ice absorption, only two parameters are needed to describe the snow grain shape in the diffusion regime. These are the absorption enhancement parameter B and the geometric asymmetry factor gG. Here we aim to understand the relationship between the snow microstructure properties and the shape parameters, B and gG.

 

To do so, we combine ray-tracing Monte Carlo methods with 3D images of the actual microstructure of snow, obtained with X-ray imaging and computed microtomography (µCT). The existing Rough Surface Ray-Tracer (RSRT) model, originally designed to simulate snow albedo over rough surfaces, has been adapted to trace light propagation in microstructure 3D images. This approach allows getting rid of the simplified representation of snow in radiative transfer models, and benefits from the accurate ray-tracing calculations. We present here our initial findings and results, which compare well with the results of the advanced radiative transfer theories that relate snow optical properties to the chord length distribution in snow microstructure.

How to cite: Robledano, A., Picard, G., Dumont, M., Arnaud, L., and Flin, F.: Linking snow optical properties to snow microstructure, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3463, https://doi.org/10.5194/egusphere-egu22-3463, 2022.

EGU22-3550 | Presentations | CR3.1 | Highlight

MASCDB: a database of images, descriptors and microphysical properties of individual snowflakes in free fall 

Jacopo Grazioli, Gionata Ghiggi, Anne-Claire Billault-Roux, and Alexis Berne

Snowfall information at the scale of individual particles is rare, difficult to gather, but fundamental for a better understanding of solid precipitation microphysics.

We present a dataset, MASCDB, (and a dedicated python software) of in-situ measurements of snow particles in free fall collected by a multi-angle snowflake camera. The dataset, includes gray-scale (255 shades) images of snowflakes, co-located surface environmental measurements, a large number of geometrical and textural snowflake descriptors as well as the output of previously published retrieval algorithms. Noteworthy examples include: hydrometeor classification, riming degree estimation, identification of melting particles, discrimination of wind-blown snow, as well as estimates of snow particle mass and volume. The measurements were collected in various locations of the Alps, Antarctica and Korea for a total of 2'555'091 snowflake images (or 851'697 image triplets). MASCDB aims to accelerate reproducible research on precipitation microphysics and to address longstanding scientific challenges on snowflake research. Given the large amount of snowflake images and associated descriptors, MASCDB can be exploited by the computer vision community for the training and benchmarking of image processing systems. MASCDB can be accessed on Zenodo (DOI: https://doi.org/10.5281/zenodo.5578920), while the pymascdb package at https://github.com/ltelab/pymascdb.

 

How to cite: Grazioli, J., Ghiggi, G., Billault-Roux, A.-C., and Berne, A.: MASCDB: a database of images, descriptors and microphysical properties of individual snowflakes in free fall, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3550, https://doi.org/10.5194/egusphere-egu22-3550, 2022.

EGU22-3839 | Presentations | CR3.1

Snow height monitoring in coastal Greenland – datasets, scales and climatic drivers 

Jakob Abermann, Kerstin Rasmussen, Kirsty Langley, Jorrit van der Schot, Tiago Silva, Michael Winkler, Harald Schellander, and Wolfgang Schöner

In this contribution we compile hitherto little or unused snow height data for Greenland. We present time-series of autonomously measured snow heights at around 10 locations in different parts of Greenland dating back to 1997. This data was largely measured and archived by Asiaq, Greenland Survey, for varying applications. We show the wide variability of snow heights and determine snow water equivalent using a recently developed model approach. The performance of the model to reproduce manually measured snow water equivalent is striking given the simplicity of input (solely snow depth) and the complexity of the different snow climates. We assess the hydrological significance of seasonal snow cover for very varying climatological conditions in Greenland and evaluate that the hysteresis between snow depth and snow water equivalent formation and depletion differs in shape and strength depending on the general climatological conditions.

In a further step we analyze the drivers of the observed variability relating snow height anomalies to climate oscillation indices (such as NAO, GBI). We hypothesize that the impact of climate oscillations on snow height anomalies is spatially variable in coastal Greenland. Furthermore, we assess to which extent the timing of spring onset determines snow depletion rates.

Finally, given the spatial heterogeneity of snow measurements, we assess the capability of a regional climate model to reproduce snow height and snow water equivalent and relate its performance to topography.

How to cite: Abermann, J., Rasmussen, K., Langley, K., van der Schot, J., Silva, T., Winkler, M., Schellander, H., and Schöner, W.: Snow height monitoring in coastal Greenland – datasets, scales and climatic drivers, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3839, https://doi.org/10.5194/egusphere-egu22-3839, 2022.

EGU22-4509 | Presentations | CR3.1

Experimental and numerical study of heat and mass transport in snow in case of strong temperature gradient conditions. 

Lisa Bouvet, Neige Calonne, Christian Geindreau, and Frédéric Flin

A new experiment has been conducted to characterize experimentally heat and mass transport as well as metamorphism evolution during temperature gradient conditions. To be able to appreciate fine scale as well as larger scale processes, the experimentation lasted 3 weeks with a strong gradient of 100 K m-1 and a mean temperature of -9.5°C. The studied snow layer was 12 cm thick and had a horizontal surface of 0.5 m2. Temporal monitoring of the snow was made through 17 micro-tomographies at specific spots with a resolution of 8 μm and 9 micro-tomographies on full vertical profiles at 21 μm. The layer was also instrumented using 10 temperature and humidity sensors and 7 precise temperature sensors recording at different locations during the whole process. This experiment showed precisely the development of facets and depth hoar in the snow matrix, and leads to interesting results concerning the evolution of heat and mass fields during a strong temperature gradient. The results of this experiment are finally compared to numerical results predicted by coupled heat and mass transport models such as the one of Calonne et al., 2015.

How to cite: Bouvet, L., Calonne, N., Geindreau, C., and Flin, F.: Experimental and numerical study of heat and mass transport in snow in case of strong temperature gradient conditions., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4509, https://doi.org/10.5194/egusphere-egu22-4509, 2022.

EGU22-5111 | Presentations | CR3.1

Local trends of snow water equivalents in the Alps 

Harald Schellander, Michael Winkler, and Anna-Maria Tilg

The spatial and temporal snow mass variation is clearly indicated as knowledge gap by the “IPCC Special Report on the Ocean and Cryosphere in a Changing Climate”, thus impeding current efforts to quantify historic and future trends. This is especially true for the Alps, which are very rich in snow depth (HS) records (both in number and length), but notoriously lack the same for snow water equivalent (SWE) observations.

The ∆SNOW model - freely available as part of the R-package “nixmass” - improved by temporally varying density parameters (cf. EGU22-2326), is used to estimate SWE at more than 2000 stations with continuous, daily HS records in and around the Alps from flatlands to very high Alpine regions with 130 stations above 2000 m.

In this contribution first results of a trend analysis of historical SWE observations of this very large number of stations is presented. The very high station density and large elevation range covered opens the opportunity for a climatologically detailed and elevation dependent analysis of historic trends of seasonal mean and peak SWE at an unprecedented local scale.

How to cite: Schellander, H., Winkler, M., and Tilg, A.-M.: Local trends of snow water equivalents in the Alps, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5111, https://doi.org/10.5194/egusphere-egu22-5111, 2022.

EGU22-5179 | Presentations | CR3.1

Quasi-dynamically downscaled snowpack simulation in Penalara Massif (Sierra de Guadarrama, Central Spain) 

Álvaro González Cervera and Luis Durán

The snowpack over mountains represents an important source of water both in these areas and in adjacent lowlands. It also has a large impact on their economy since it affects tourism, communications, logistics and risks associated with its recreational use. Snow cover in mid elevations is experimenting a significant decrease as a consequence of climate change (IPCC-2021) and it is becoming an important issue in the water management agenda. Despite its importance there is a lack of understanding of its dynamics, due to the scarcity of properly distributed temporally and spatially mountain snowpack observations and the availability of specific simulation tools. With the aim of overcoming this scarcity, we present a new processing chain that couples ERA5 atmospheric reanalysis (ECMWF) with the Intermediate Atmospheric Research model (ICAR, from NCAR) and the Flexible Snow Model (FSM2, University of Edinburgh) in order to assess the snowpack in a small area in Penalara Massif, a mountain region in Central Spain. The 2021-2022 winter season have been simulated with a resolution of 2 m for the snowpack output. Several sensitivity experiments have been conducted in order to assess the impact of the uncertainties on the input forcing data. Also, automatic and manual meteorological observations have been used to validate the model and draw future lines of improvement. First results are very promising. This system has been able to explain the main features of the dynamics of the snowpack and future improvements are foreseen like the impact of snow redistribution of fresh snow due to wind drift and a better knowledge of the transformation of the snow pack and melting process.

How to cite: González Cervera, Á. and Durán, L.: Quasi-dynamically downscaled snowpack simulation in Penalara Massif (Sierra de Guadarrama, Central Spain), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5179, https://doi.org/10.5194/egusphere-egu22-5179, 2022.

EGU22-5541 | Presentations | CR3.1

Dust particles size distributions in snow and its importance for optical properties of snow 

didier voisin, Celine Voiron, Hervé Denis, Sophie Darfeuil, Patrick Ginot, Marie Dumont, Marion Reveillet, and Simon Gascoin

Light absorbing particles (LAPs) from various origins get deposited to the snow where they greatly influence its physical evolution, and most particularly its melt by changing the energy absorbed from solar radiation. Black Carbon and Dust are the most important such particles. How those particles change snow physics depends on their optical properties, which are a function of their chemical composition and size distribution.

In European mountain ranges, part of the deposited dust comes as sporadic Saharan dust outbreaks, which cause important dust layers in the snowpack. One such event was the object of a citizen science collaborative sampling campaign, which resulted in 150 samples collected over the Pyrenees, the Jura, and the French and Swiss Alps.

Dust in these samples was filtered out and weighted, in order to get total deposition fluxes. Size distributions were measured between 4 and 60 µm. This size fraction represents less than 10% of the total mass measured in those samples. Assuming lognormal distributions to extend the measured size distributions beyond 60 µm only explained a fraction of the missing mass.

The relative importance of the particles not measured between 4 and 60 µm for the optical properties of the snowpack depend strongly on their size. A rough estimate of the importance of the missing fraction was attempted by assuming that the overall optical effect scales with the surface area of the particles. Depending on the assumed diameter of particles in this fraction, the missing mass (~90% of the total mass) overall optical impact is estimated between 80 and 40% of the estimated total optical impact of the dust present in the snow.

A limited set of samples was used to assess the size of this missing fraction, using different methods. This preliminary assessment suggests the potential importance of grain aggregation in natural snow and the importance of unbiased size distribution measurements for dust in snow.

How to cite: voisin, D., Voiron, C., Denis, H., Darfeuil, S., Ginot, P., Dumont, M., Reveillet, M., and Gascoin, S.: Dust particles size distributions in snow and its importance for optical properties of snow, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5541, https://doi.org/10.5194/egusphere-egu22-5541, 2022.

EGU22-5717 | Presentations | CR3.1 | Highlight

Evolution of the Antarctic firn layer until 2100 under two climate change scenarios. 

Sanne Veldhuijsen, Willem Jan van de Berg, Max Brils, Peter Kuipers Munneke, and Michiel van den Broeke

Firn covers ~99% of the Antarctic ice sheet, providing pore space in which nearly all of the surface meltwater refreezes or is retained in liquid form. For now, this prevents most of the surface melt to contribute to sea level rise, however as atmospheric warming continues, changes in precipitation, temperature, melt and refreezing will cause the firn layer to evolve. Surface melt and densification rates are expected to increase, which will lead to firn air content depletion and increased firn saturation. Such conditions are extremely important for the Antarctic ice sheet: saturation of firn layers can lead to hydrofracturing induced ice shelf disintegration. On the other hand, snowfall is expected to increase as well, which will add additional pore space to the firn. Firn models can be used to simulate such firn processes and identify future firn conditions.

       In this study, we force the recently improved version of the IMAU Firn Densification model (IMAU-FDM v1.2A) with outputs of the regional atmospheric climate model RACMO2.3p2 at resolution of 27 km covering the period 1950-2100. RACMO2.3p2 is forced with CESM2, which includes the historical period 1950-2015 followed by two climate change scenarios for the period 2015-2100 (SSP126 and SSP585). The historical performance is evaluated by comparing the outputs to a run in which IMAU-FDM v1.2A was forced with RACMO2.3p2, which was forced with ERA-5, a climate model reanalysis nudged towards surface and satellite observations. After evaluation, we present how the firn layer will evolve over the coming century under these scenarios, and identify which areas will potentially become susceptible to ice shelf disintegration.

How to cite: Veldhuijsen, S., van de Berg, W. J., Brils, M., Kuipers Munneke, P., and van den Broeke, M.: Evolution of the Antarctic firn layer until 2100 under two climate change scenarios., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5717, https://doi.org/10.5194/egusphere-egu22-5717, 2022.

EGU22-6092 | Presentations | CR3.1

Evaluating modeled snow cover dynamics over Fennoscandia using Earth observations 

Yeliz A. Yılmaz, Kristoffer Aalstad, Simon Filhol, Simon Gascoin, Norbert Pirk, Janneke Remmers, Frode Stordal, and Lena M. Tallaksen

The snow cover is an essential part of the climate system in cold regions through its effects on the terrestrial water, energy, and carbon balance. Due to the high spatiotemporal variability of snow, it is challenging to resolve snow cover dynamics in models. Thus, our ability to improve the representation of these dynamics in Earth System Models (ESMs) leans heavily on the accuracy and representativeness of the observational data sets used for model evaluation.

The big picture provided by the long-term climate data record from satellites helps us to monitor changes in land cover over large areas. At the same time, rapidly developing drone and terrestrial imaging technology provides higher resolution information over specific areas. This complimentary information from spaceborne, airborne, and terrestrial Earth observations is invaluable for better understanding the complex processes in the climate system. In our work, we are currently exploiting estimates of snow-covered area from different optical sensors onboard polar orbiting satellites that are imaging the Nordic region. Drone and terrestrial images are being explored as a source of validation and calibration data for the satellite products. 

Having representative snow cover maps enables us to better evaluate the terrestrial component of the Norwegian Earth System Model (NorESM), namely the Community Land Model (CLM5). With a focus on snow processes, we are conducting an analysis using satellite-based estimates of snow-covered area (MODIS, Sentinel-2, and Landsat 8), snow simulations from CLM5, snow variables from several climate reanalyses (ERA5, ERA5-Land, and MERRA-2), and in-situ data from eddy covariance stations (LATICE flux sites). Two offline CLM5 simulations are conducted with different atmospheric forcing, namely the default data set (GSWP3) and ERA5. We are investigating trends in the snow cover phenology, which we characterize using snow cover duration, first and last days of the snow cover, and consecutive snow cover days for each snow season over the last two decades. This work illuminates a path to integrate Earth observations with Earth system modeling in cold environments to both identify and constrain sources of uncertainty.

Acknowledgement: This ongoing study is supported by the LATICE (Land-ATmosphere Interactions in Cold Environments) strategic research initiative funded by the University of Oslo, and the project  EMERALD (294948) funded by the Research Council of Norway.

How to cite: Yılmaz, Y. A., Aalstad, K., Filhol, S., Gascoin, S., Pirk, N., Remmers, J., Stordal, F., and Tallaksen, L. M.: Evaluating modeled snow cover dynamics over Fennoscandia using Earth observations, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6092, https://doi.org/10.5194/egusphere-egu22-6092, 2022.

EGU22-7626 | Presentations | CR3.1

Snowmelt dynamics observed by dense X-band time series acquired by COSMO-SkyMed constellation 

Carlo Marin, Francesca Cigna, Giovanni Cuozzo, Claudia Notarnicola, Simonetta Paloscia, Emanuele Santi, and Deodato Tapete

The seasonal snow is one of the largest water reservoirs in nature, storing water during winter, and gradually releasing it in spring during the melt. This guarantees freshwater supply for the lowlands even in the long term, making the mountains the “water towers” of the downstream regions. In fact, the delayed water release from the head watersheds to the forelands is essential for a large number of human activities such as irrigation, drinking water supply and hydropower production. On the other hand, snowmelt may cause natural disasters such as wet-snow avalanches, gliding or release of highly enriched accumulated contaminants able to cause severe impact on water quality.

In recent years, Synthetic Aperture Radar (SAR) has demonstrated capable to provide information about the melting process. In particular, with the launch of the European Commission (EC) Copernicus Programme Sentinel-1 mission, C-band SAR images are regularly acquired every 6 days and delivered free of charge. This opened the possibility to observe a phenomenological relationship between the snow melting process of high altitude snowpacks and the multi-temporal radar backscattering acquired by Sentinel-1. The identification of the temporal signature for each pixel of a Sentinel-1 time series allowed us to detect the onset of the three phases that made up the snowmelt i.e., moistening, ripening and runoff, with a good reliability. However, the mechanisms that drive the snowpack response at microwaves depend on frequency; therefore, different snowpack signatures are expected if using different frequency bands, as the X band available onboard the Italian Space Agency (ASI)’s COSMO-SkyMed (CSK) constellation.

In this work, we analyze a dense X-band time series acquired by the CSK over the Schnalstal catchment in Italy during the snowmelt season. This allows us to point out the similarities and the differences between the electromagnetic interactions using C- and X-band SAR during the snowmelt. Depending on the shorter wavelength, the X-band is more sensitive than C-band to small quantities of liquid water inside the snowpack. Therefore, X band shows an earlier response than C band to the moistening of the surface snow layer (especially for steep local incidence angles), and a more pronounced loss of interaction with deeper layers. X-band is also more sensitive to the increase in the superficial roughness with the consequence of possibly anticipating the runoff onset. However, by comparing the runoff time in the Schnalstal catchment during the melting season 2020-2021, a general agreement between C- and X-band is found even though the characteristic shape of the signature exhibits more variations at X-band than C-band.

This research is part of the 2019-2022 project ‘Development of algorithms for estimation and monitoring of hydrological parameters from satellite and drone’, funded by ASI under grant agreement n. 2018-37-HH.0.

How to cite: Marin, C., Cigna, F., Cuozzo, G., Notarnicola, C., Paloscia, S., Santi, E., and Tapete, D.: Snowmelt dynamics observed by dense X-band time series acquired by COSMO-SkyMed constellation, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7626, https://doi.org/10.5194/egusphere-egu22-7626, 2022.

EGU22-8516 | Presentations | CR3.1

Multiscale tomography of the seasonal evolution of the snow microstructure 

Pascal Hagenmuller, Neige Calonne, Marie Dumont, Julien Brondex, Francois Tuzet, and Jacques Roulle

Due to very active metamorphism, snow on the ground exhibits a wide range of microstructural patterns. Indeed, snow is a very porous material and it exists on Earth close to its melting point, which promotes its structural evolution through vapor transport and melting-refreezing processes. State-of-the-art detailed snowpack models such as SURFEX/Crocus still represent this microstructure in a very rough way. This representation is based on manual observations from the 1990’s using magnification lenses, where the snow grain shape were classified into different types. The descriptors derived from this classification, such as sphericity or grain size, are not based on a sound physical background and cannot be measured, which limits any further improvement of the existing parameterizations. Nowadays, tomography has become a standard technique to capture the 3D snow microstructure at a micrometrical scale in laboratory conditions. Besides, homogenization methods can now numerically estimate several essential but difficult-to-measure snow properties such as thermal conductivity or mechanical viscosity from tomographic images and the ice and air properties. To overcome the limitations of existing snowpack models and to benefit from the wealth of data provided by tomography and numerical homogenization, a new generation of snow models with an explicit and objective representation of the snow microstructure is currently under development. To develop and evaluate these new models, characterization of the snow microstructure evolving in the field is required. The objective of the presented work is to develop a measurement and data processing protocol to be able to conduct these measurements. This represents a challenge because, to date, tomography was mainly limited to small volumes of snow mostly harvested in laboratory conditions. First, we installed a tomograph directly at our snow field site, Col de Porte, 1325 m a.s.l., french Alps. Second, we designed a specific snow cutter to sample snow cores without destroying their very fragile microstructure. Cutters equipped with a sharp hole saw and with an inner diameter of 44 mm and a height of 100 mm are sufficiently large to prevent sample failure and small enough to conduct partial tomography at a very high resolution. Last, we combined two types of tomographic scan in order to capture a high-order approximation of the snow microstructure while maintaining the scanning time short enough. In particular, on each snow core, we scanned a sub-volume (15 mm diameter, 15 mm height, 48 min scan duration) at an effective resolution of 10 microns and the whole sample column (25 mm diameter, 100 mm height, 20 min scan duration) at a resolution of 42 microns. Based on a modified two-point correlation function which applies directly to the greyscale tomographic images and the combination of the two scans, we were able to recover physically-based proxies of the snow microstructure of the full core in a reasonable measurement duration. This includes density, specific surface area and mean curvature.

How to cite: Hagenmuller, P., Calonne, N., Dumont, M., Brondex, J., Tuzet, F., and Roulle, J.: Multiscale tomography of the seasonal evolution of the snow microstructure, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8516, https://doi.org/10.5194/egusphere-egu22-8516, 2022.

EGU22-9092 | Presentations | CR3.1

Investigating the influence of local insolation on near-surface snow grain properties to constrain the mechanisms of pore close-off and associated elemental fractionation in polar firn 

Romilly Harris Stuart, Amaëlle Landais, Patricia Martinerie, Marie Dumont, Mathieu Fructus, Anaïs Orsi, Quentin Libois, Laurent Arnaud, C. Max Stevens, Antoine Grisart, and Frédéric Prié

Processes controlling pore closure in deep polar firn are broadly understood, yet defining the physical mechanisms remains ambiguous. Firn densification models predict pore close-off depths which are subsequently used in firn air models to predict the gas-ages of entrapped air bubbles. However, current firn models require observational tuning which causes variable model performance for sites with different characteristics. Furthermore, layering in the deep firn, which is not simulated in many firn densification models, is expected to cause a large distribution of pore lock-in depths. Observations from numerous firn cores have identified neighbouring layers with different physical properties, such as density, grain size and impurities, which experience pore-closure at different depths. These properties are strongly influenced by 1) snow metamorphism due to temperature gradients within the snowpack, and 2) accumulation rate. The relative influence of each of these properties on pore closure remains in question.

Based on current understanding, we propose to quantify the changes in density and snow microstructural properties near the surface as a result of the interplay between accumulation rate and insolation using the Crocus snowpack model. To support the modelling effort, we have compiled δO2/N2 records - a proxy for local summer solstice insolation - from several polar ice cores. The relationship between insolation and δO2/N2 is understood to be linked to near-surface snow metamorphism, which largely determines the properties of deep-firn layers, and thus, the pore-closure process. By first identifying how insolation and accumulation rate influence the near-surface snow properties, we aim to implement this effect into firn models to develop our understanding of the physical mechanisms controlling pore-closure and the associated elemental fractionation.

How to cite: Harris Stuart, R., Landais, A., Martinerie, P., Dumont, M., Fructus, M., Orsi, A., Libois, Q., Arnaud, L., Stevens, C. M., Grisart, A., and Prié, F.: Investigating the influence of local insolation on near-surface snow grain properties to constrain the mechanisms of pore close-off and associated elemental fractionation in polar firn, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9092, https://doi.org/10.5194/egusphere-egu22-9092, 2022.

EGU22-9316 | Presentations | CR3.1

Investigation of the ductile-to-brittle transition in snow with compression tests and tomography monitoring 

Antoine Bernard, Maurine Montagnat, Guillaume Chambon, and Pascal Hagenmuller

Once fallen on the ground, snowflakes evolve quickly and form the snowpack. Under its own weight, the snowpack slowly deforms and settles. On a steep slope, some layers may rapidly deform and fail, which yield to the release of an avalanche. At the macroscopic scale, snow mechanical behavior is highly strain-rate dependent: ductile at low strain rates and brittle at high strain rates. The ductile-to-brittle transition has recently been shown to occur in two stages, with an intermediate regime of intermittent brittle failures, assumed to result from a competition between different time scales. At the micro-scale, this mechanical behavior is controlled by the microstructure and the visco-plastic and sintering properties of the ice skeleton. In this work, we investigate snow brittle-to-ductile transition by conducting displacement-controlled compression tests monitored with X-ray micro-computed tomogaphy.

We specifically designed a loading apparatus to perform displacement-controlled compression tests in cold environment and the constrained space of the tomographic cabin, so that microstructure evolution could be followed by regular scans. Samples (14 mm in diameter, 14 mm in height) were prepared from natural snow, sieved directly into samples holders, in batch of 10 samples and sintered for 72h at -20°C then stored at -50°C to prevent further microstructure evolution. The sample were taken out and placed in the compression device 30min before the first scan. We explored strain rates from 10-6 s-1 to 10-2 s-1 by vertically compressing 30 samples, up to a peak stress of 250 kPa and at a constant temperature of -18.5 °C. At high strain rates, only the initial and final 3D microstructures were scanned and simple radiographs were acquired during loading at a rate of 5 frames per second. At low strain rates, the 3D microstructure was regularly scanned during the loading. The obtained time series comprises one of the most-resolved (8.5 µm, 1h) and complete dataset on snow microstructure evolution near the ductile-to-brittle transition to date.

Results indicate a clear dependency of snow mechanical response on the strain rate. At strain rates larger than about 10-3 s-1, snow samples display heterogeneous deformations with the formation of compaction bands, while the stress-strain curve shows a serrated behavior. To relate this macroscopic behavior to micro-structural evolution, quantitative investigation of local density and specific surface area changes, as well as of bond network evolution, will be presented. These results should help identifying the micro-scale mechanisms at play during deformation of snow through both ductile and brittle range.

How to cite: Bernard, A., Montagnat, M., Chambon, G., and Hagenmuller, P.: Investigation of the ductile-to-brittle transition in snow with compression tests and tomography monitoring, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9316, https://doi.org/10.5194/egusphere-egu22-9316, 2022.

EGU22-9954 | Presentations | CR3.1

Sensitivity of a new hectometric scale snow transport scheme to various parameterizations for sublimation and accumulation/erosion 

Ange Haddjeri, Matthieu Baron, Matthieu Lafaysse, Rafife Nheili, Louis Le Toumelin, Simon Gascoin, and Marie Dumont

SnowPappus, a new wind snow transport model coupled with Crocus snowpack model, was developed to quantify and model snow drift at a hectometric scale. To reproduce the high spatial variability of the snow cover in Alpine regions, we represent the impact of wind and topography on the simulated snowpack properties. The accurate simulation of the impact of wind is key to anticipate natural hazard related to the snow cover and improve  hydrological predictions. Simulations were performed on a 902 km² French Alps region at 250 m resolution. Here we present the comparison of our snow drift model SnowPappus with in situ measurements and Sentinel 2 snow products, using various sublimation parametrizations and different numerical schemes to represent the horizontal divergence of blowing snow fluxes responsible for accumulation/erosion patterns.

How to cite: Haddjeri, A., Baron, M., Lafaysse, M., Nheili, R., Le Toumelin, L., Gascoin, S., and Dumont, M.: Sensitivity of a new hectometric scale snow transport scheme to various parameterizations for sublimation and accumulation/erosion, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9954, https://doi.org/10.5194/egusphere-egu22-9954, 2022.

Snow on Arctic sea ice plays many roles in Arctic climate feedbacks; in particular, through its impact on sea ice. Snow can have many, sometimes contrasting effects on sea ice thickness and extent. For example, during the ice growth season, snow can inhibit ice growth by insulating the ice from the cold atmosphere. Conversely, snow can allow sea ice to persist longer during the melt season, due to its high albedo. Furthermore, estimates of snow depth on Arctic sea ice are a key input for deriving sea ice thickness from satellite lidar altimetry measurements, such as those from ICESat-2. Due to the logistical challenges of making measurements in as remote a region as the Arctic, snow depth on Arctic sea ice is difficult to observationally quantify.

To provide widespread estimates of the depth and density of snow on Arctic sea ice, models such as the NASA Eulerian Snow On Sea Ice Model (NESOSIM) can be used. The latest version of NESOSIM, version 1.1, is a 2-layer three-dimensional model with simple representations of snow accumulation, wind packing, loss due to blowing snow, and redistribution due to sea ice motion. Relative to version 1.0, among other changes, NESOSIM 1.1 features an extended model domain and reanalysis snowfall input from ERA5 scaled to observed snowfall derived from CloudSat satellite radar measurements.

The free parameters in NESOSIM, which dictate the strength of the wind packing (densification) and blowing snow loss processes, cannot be directly constrained to observations. We present an indirect calibration of these free parameters, by calibrating NESOSIM output to observations from airborne snow depth observations from Operation IceBridge and in situ CRREL-Dartmouth snow buoy measurements, as well as historical Soviet drifting station density measurements, using a Metropolis Markov Chain Monte Carlo (MCMC) approach. This approach produces estimates of the free parameters and their uncertainty distributions, from which model snow depth and density uncertainties can be estimated. We find that introducing stricter observational constraints in the calibration produces narrower snow depth uncertainty distributions from NESOSIM. We then examine the impact of these uncertainties on sea ice thickness derived using NESOSIM output and freeboard measurements from ICESat-2.

How to cite: Cabaj, A., Kushner, P., and Petty, A.: Observationally calibrating snow-on-sea-ice model free parameters and estimating uncertainties using a Markov Chain Monte Carlo method, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10534, https://doi.org/10.5194/egusphere-egu22-10534, 2022.

EGU22-10881 | Presentations | CR3.1

Optimal Estimation of Snow Related Parameters in Noah Land Surface Model Using an Evolutionary Algorithm 

Seon Ki Park, Sujeong Lim, and Claudio Cassardo

Snow processes in the land surface models (LSMs) include the snow cover fraction, snow albedo, and snow depth — all interacting with the atmospheric conditions. Most LSMs include parameters based on empirical relations, resulting in uncertainties in model solutions. In addition, such parameters often reflect only the local characteristics where the empirical relations are made. Therefore, the empirical parameters need to be optimized when they are applied to different regions. This study seeks the optimal snow-related parameters over South Korea where heavy snowfall events occur in the winter. The optimization is conducted using a micro-genetic algorithm (micro-GA) and the in situ and satellite observations for the snow depth, snow cover fraction, and snow albedo. The micro-GA is one of the evolutionary algorithms to search for the best potential solution based on natural selection and the survival of fitness. To represent the regional empirical parameters using the single-column model (e.g., Noah LSM), we selected the representative stations over South Korea to cover various vegetation types. Next, we identify which snow-related parameters can be optimized and suggest the optimal parameters using the micro-GA over South Korea. As a result, the Noah LSM simulations, using the optimized parameters, reduced the biases by 45.1% and 32.6 % for the snow depth and snow albedo, respectively, and the root mean square errors by 17.0 %, 8.2 %, and 5.6 % for snow depth, snow cover fraction, and snow albedo, respectively.

How to cite: Park, S. K., Lim, S., and Cassardo, C.: Optimal Estimation of Snow Related Parameters in Noah Land Surface Model Using an Evolutionary Algorithm, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10881, https://doi.org/10.5194/egusphere-egu22-10881, 2022.

EGU22-11474 | Presentations | CR3.1

Physics of snow cover in the climate model INMCM 

Alexey Chernenkov, Evgeny Volodin, and Sergey Kostrykin

Snow cover has a great influence on the energy balance on the surface, in particular ability to reflect solar radiation. As well as radiation, when modeling the climate, it is important to correctly describe the water cycle. During the transitional seasons, when the temperature fluctuates around zero degrees Celsius, some of the melt water can be retained in the snow layer and refreeze. In addition, over time after a snowfall the snow becomes denser. Aged, wet, refrozen snows have different optical properties than new-fallen snow, in particular a lower albedo. Moreover, atmospheric aerosols falling on a snow-covered surface leads to its pollution and, as a consequence, reduces its reflectivity. Aerosols such as mineral dust and black carbon have the greatest effect on the albedo and radiation balance.

In the climatу model INMCM, some physical features of snow cover have been implemented. The porous structure of the snow is taken into account and the calculation of the water content of the snow layer is realized. During snowmelt, the ratio of the water is retained in the pores, and does not go immediately to the upper boundary of the soil. The possibility of refreezing of melt water contained in the snow layer has also been implemented. The change in snow density over time is taken into account. At the same time, it is assumed that the snow layer consists of a mixture of usual and refrozen snow, as well as melt water contained in snow pores. The influence of the composition of the snow layer and its density on the reflectivity is taken into account. The effect on the albedo of impurities contained in snow is also taken into account (for example, black carbon). Computational experiments were carried out with the INMCM model to assess the sensitivity to the realized physical processes.

This work is supported by the Russian Science Foundation, project No. 20-17-00190.

How to cite: Chernenkov, A., Volodin, E., and Kostrykin, S.: Physics of snow cover in the climate model INMCM, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11474, https://doi.org/10.5194/egusphere-egu22-11474, 2022.

EGU22-12019 | Presentations | CR3.1

Analysis of snow water equivalent data needs and capabilities 

Carrie Vuyovich, Ana Barros, Dorothy Hall, Rhae Sung Kim, Eunsang Cho, Melissa Wrzesien, and Sujay Kumar

Global snow cover is an integral part of the Earth’s water and energy cycles, contributing life-giving water resources to billions of people around the world while helping to cool the planet by reflecting solar energy back to space.  Accurate measurements of snow at a regional scale are needed to improve runoff predictions to inform water supply and hydropower needs and to help predict conditions that are associated with floods, drought, and wildfires. Though we can measure the extent of snow cover globally, we cannot yet reliably measure the amount of water stored in a snowpack, or snow-water equivalent (SWE) from space at the resolution and accuracy needed to understand its role in the water cycle. In addition, it is uncertain how the extent and the volume of snow will be changed across the globe in a warmer climate. Here we will review the snow data needs to address our most pressing science questions and operational requirements. We will also present the results of a coverage analysis of SWE data from currently-available and upcoming sensors over the northern hemisphere to identify gaps in current capabilities.

How to cite: Vuyovich, C., Barros, A., Hall, D., Kim, R. S., Cho, E., Wrzesien, M., and Kumar, S.: Analysis of snow water equivalent data needs and capabilities, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12019, https://doi.org/10.5194/egusphere-egu22-12019, 2022.

EGU22-12623 | Presentations | CR3.1

High-speed imaging of snow saltation: wind tunnel experiments using natural snow 

Daniela Brito Melo, Alec Petersen, Filippo Coletti, Benjamin Walter, Matthias Jaggi, and Michael Lehning

Drifting snow is a multi-scale process. It is composed of particles rolling and sliding along the surface, particles in saltation following short ballistic trajectories in the first 10 cm above the surface and particles in suspension at higher regions of the atmosphere. Drifting snow is currently represented in some regional and mesoscale atmospheric models by taking into account its effect on snow height, snow sublimation and snow densification. Snow saltation is a sub-grid process in these models and is therefore parameterized. However, the current parameterizations are based on limited field and wind tunnel measurements and do not take into account the effect of the bed characteristics, as grain size, inter-particle cohesion and snow density, on the saltation dynamics.

In order to improve the current saltation models, we conducted wind tunnel experiments using natural snow at the WSL Institute for Snow and Avalanche Research SLF to measure the kinematics and shape of particles in saltation. The wind tunnel is located at 1670 m above sea level, has a cross section area of 1x1 m2 and a total length of 14 m. Naturally deposited snow is collected in trays after each snowfall and transported to the tunnel without disturbing the snowpack. We used a high speed camera, aquiring images at 5 kHz with backlighting provided by an LED to capture images of saltating snowflakes. We measured wind speed with an array of pitot tubes positioned 2-10 cm above the snowbed. We additionally measured the density and hardness of the snow cover before the experiments using a box density cutter and a Snow Micro Pen (SMP), respectively. We process the images with a 2D Particle Tracking Velocimetry (PTV) algorithm allowing us to obtain Eulerian and Lagrangian statistics of the kinematic quantities as well as estimates of the snowflake characteristics like size, aspect ratio and orientation. In addition, by assuming a constant particle density, we derive particle mass flux profiles.

The results show that the particle size distribution in saltation can indeed be characterized by a lognormal or a gamma distribution. From the analysis of the particle streamwise velocity profiles, it is clear that the assumption of a constant particle speed inside the saltation layer (common in simple saltation models) might not be a good approximation even for low friction velocities. We will present in how far we can assess the influence of the snow properties on mass flux and saltation dynamics as a basis to validate recent model results on the influence of inter-particle cohesion for example. Moreover, this data set will contribute to the development of new parameterizations for snow saltation mass flux and streamwise velocity that would take into account the effect of snow density and hardness.

How to cite: Melo, D. B., Petersen, A., Coletti, F., Walter, B., Jaggi, M., and Lehning, M.: High-speed imaging of snow saltation: wind tunnel experiments using natural snow, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12623, https://doi.org/10.5194/egusphere-egu22-12623, 2022.

EGU22-1764 | Presentations | CR3.2

How investigating the physics of avalanche-obstacle interaction with DEM can help to calculate the avalanche impact pressure on obstacles 

Michael Lukas Kyburz, Betty Sovilla, Johan Gaume, and Christophe Ancey

Calculating snow avalanche impact pressure is an essential task for safe construction and hazard mapping in mountainous regions. Although avalanche-obstacle interaction crucially depends on the flow regime, practitioners mostly assume that impact pressure is similar to the dynamic pressure in inviscid fluids, that is, it is proportional to the square velocity weighted by an empirical drag coefficient. When fitting this coefficient to field measurements, one does not end up with a unique value, but with a range of possible values that cover more than one order of magnitude. In the absence of a physics-based framework, setting the right drag coefficient requires good working knowledge and experience from practitioners. Indeed, even for trained engineers it may be unclear how the impact pressure depends on the expected flow regime, on obstacle width, or on terrain configuration. To address these questions, we simulate the avalanche impact pressure on obstacles of varying geometry for four distinct avalanche flow regimes using the Discrete Element Method and a cohesive contact model. The results allow us to quantify the influence of the obstacle width and shape on the average impact pressure, as well as the detailed pressure distribution on the obstacle surface. Furthermore, we propose a novel method for estimating the drag coefficient based on simple geometrical considerations and key characteristics of avalanche flow. Our results are validated using experimental data from the Vallée de La Sionne test site, and make a step forward in the derivation of a physics-based framework for computing snow avalanche impact pressures for varied flow regimes depending on obstacle shape and dimensions.

How to cite: Kyburz, M. L., Sovilla, B., Gaume, J., and Ancey, C.: How investigating the physics of avalanche-obstacle interaction with DEM can help to calculate the avalanche impact pressure on obstacles, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1764, https://doi.org/10.5194/egusphere-egu22-1764, 2022.

EGU22-2973 | Presentations | CR3.2

Snow mechanical properties variation at slope scale, implication for snowpack stability assessment and snow cover models 

Francis Meloche, Francis Gauthier, and Alexandre Langlois

Snow avalanches represent a natural hazard for infrastructures and backcountry recreationists. Risk assessment of avalanche danger is difficult due to sparse nature of available observations informing on snowpack mechanical and geophysical properties. Spatial variability of these properties also add complexity to the decision-making and route finding in avalanche terrain for backcountry recreationists. Snow cover models simulate snow mechanical properties at fairly good resolution (around 100 m). However, small-scale variability such at the slope scale (5-50 m) remains critical to monitor given that slope stability and the possible size of an avalanche are governed by such scale. In order to better understand and predict the spatial variability at the slope scale, this work explores linkages between snow mechanical properties and microtopographic indicators. First, we compare their covariance models and scaling properties. Then, we predict snow mechanical properties, including point snow stability, using GAM spatial models (Generalized additives models) with microtopographic indicators as covariates. Snow mechanical properties such as snow density, elastic modulus, shear modulus and snow microstructural strength were measured at multiple locations over several studied slopes (20-40 m) using a high-resolution penetrometer (SMP), in Rogers Pass, British-Columbia, and Mt Albert, Québec. Point snow stability such as the skier crack length, critical propagation crack length and a skier stability index were derived using the snow mechanical properties from SMP measurements. Microtopographic indicators such as the topographic position index (TPI), vegetation height and proximity, Winstral index (wind-exposed/sheltered area) and potential radiation index were derived from UAV surveys with sub-meter resolution. We computed the variogram and log-log variogram of snow mechanical properties and microtopographic indicators. The comparison shows some similarities in autocorrelation distances for snow depth, snow density, snow microstructural strength, TPI, vegetation height and the Winstral index. GAM models suggest several significant covariates such as snow depth and snow surface slope, but also TPI, Winstral index, vegetation height and distance to vegetation. The percentage of variance explained is around 50% ranging from 20% to 80%. Models predictions were better for the slab depth and slab density with higher variance explained (around 60/70%) with lower RMSE than point snow stability indicator (around 40%) with higher RMSE. At the slope scale, snow surface slope and snow depth remain the most important spatial indicators of point snow stability for backcountry recreationists in their route-finding decision making. The point snow stability map generated represents a good teaching material in avalanche skill training and awareness course. In future work, assuming that snow cover models simulate the mean snow mechanical properties of a simulation cell, the covariance function of microtropographic indicators could be used to infer the covariance function of snow mechanical properties using a gaussian process/Bayesian framework as a sub-grid parametrization scheme.

How to cite: Meloche, F., Gauthier, F., and Langlois, A.: Snow mechanical properties variation at slope scale, implication for snowpack stability assessment and snow cover models, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2973, https://doi.org/10.5194/egusphere-egu22-2973, 2022.

EGU22-3749 | Presentations | CR3.2

Snow Avalanche Frequency Estimation (SAFE): 32 years of remote hazard monitoring in Afghanistan 

Arnaud Caiserman, Roy C Sidle, Deo Raj Gurung, and Ben Jarihani

Snow avalanches are one of the most predominant natural hazards in mountain areas. Every year throughout the world, they are the cause of much material destruction and loss of life. It is therefore essential for local communities and public authorities to assess areas most vulnerable to avalanches. Here, we propose a new method for automatic avalanche detection from Landsat archives, using a snow index. This open-source and user-friendly model in Google Engine is the first to automatically inventory all the avalanches that have occurred each year across wide catchment areas, over a period of 32 years. The Snow Avalanche Frequency Estimation (SAFE) model was tested in the mountains of Afghanistan - Amu Panj Basin - one of the most remote regions in the world and one of the poorest in terms of avalanche monitoring. SAFE correctly detected 76% of the actual avalanches identified on Google Earth images and in the field. Since 1990, this region of Afghanistan has been impacted by 810,000 avalanches with an average frequency of 0.88 avalanches/km²yr-1. With SAFE, it is now possible to clearly identify villages, roads, and rivers that are frequently affected by avalanches and thus help decision-makers in their investments in avalanche protection infrastructure. It was also found that the frequency of avalanches has not changed over the last 32 years, but SAFE has identified a northeast shift of these hazards, notably due to a slight increase in temperatures in the south at the beginning of winter. SAFE is the first robust model that can be used worldwide and is capable of filling data voids on snow avalanche impacts in inaccessible regions.

How to cite: Caiserman, A., Sidle, R. C., Gurung, D. R., and Jarihani, B.: Snow Avalanche Frequency Estimation (SAFE): 32 years of remote hazard monitoring in Afghanistan, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3749, https://doi.org/10.5194/egusphere-egu22-3749, 2022.

EGU22-4216 | Presentations | CR3.2

On the rheology of dense flow regimes in snow avalanches 

Camille Ligneau, Betty Sovilla, and Johan Gaume

The effect of climate change becomes more and more perceptible in mountain areas. For instance, in low to medium elevations, the avalanche activity is already impacted because of a warmer snow cover. This warming has an important effect on the mechanical properties of snow, especially close to 0°C, where the temperature and the presence of liquid water greatly affects the cohesion and friction. In snow avalanches, the transition from cold (T < -2°C) to warm (T = 0°C) snow generates a variety of dense flow regimes which differ drastically in terms of velocity and shearing profiles. For a cold and loose snow, one can typically observe fast flows with Bagnold-shaped profiles of a few tens of meters per second, while a warm and wet snow exhibits low- or zero-sheared velocity profiles with a magnitude of a few meters per second, over the same topography.

The present work aims to investigate the rheology of flowing snow as a function of its physical properties, with a view to bring more physics into continuum avalanches models based on empirical coefficients. We use a 2D Discrete Element Modeling (DEM) to model snow as a cohesive granular material. The simulated distinct particles interact through a contact model that can be tuned in terms of cohesion and friction, in order to satisfy the four dense flow regimes: cold dense regime, sliding slab regime, warm shear regime and warm plug regime.

First, we calibrate the contact model to find the adequate ranges of cohesion and friction corresponding to the four flow regimes. We also highlight the particular boundary conditions that are required for specific flow regimes to occur, particularly the importance of the ground friction and the initial cohesion of the snow. Second, we extract rheological features such as the friction law μ(I) and the values of θstop for each flow regime and discuss their relevance regarding avalanche dynamics. Finally, the interaction of the flow regimes with an erodible snow cover is explored and discussed qualitatively.

How to cite: Ligneau, C., Sovilla, B., and Gaume, J.: On the rheology of dense flow regimes in snow avalanches, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4216, https://doi.org/10.5194/egusphere-egu22-4216, 2022.

EGU22-5242 | Presentations | CR3.2

Imaging water transport across the soil-snow interface using neutron transmission radiography 

Michael Lombardo, Peter Lehmann, Anders Kaestner, Amelie Fees, Alec van Herwijnen, and Jürg Schweizer

The soil-snow interface plays a critical role in the release of glide-snow avalanches, which threaten life and infrastructure such as houses, roads, and chair lift masts in alpine areas. One of the important factors controlling glide-snow avalanche release is the presence of interfacial water between the ground and snowpack. Several mechanisms, such as percolation of water from the snow surface and geothermal melting of basal snow layers, have been postulated to explain the formation of this interfacial water. These mechanisms remain, however, poorly understood to poor predictability of glide-snow avalanche release. Here, we demonstrate the use of neutron transmission radiography for investigating the transport of water across the soil-snow interface at laboratory scales. We show that neutron transmission radiography is capable of capturing changes in water content during snow melt processes in both the snow and soil phases. Neutron imaging also revealed that the hydraulic properties of the porous interface between the soil and snow (mimicking a vegetation layer) affect the formation of an interfacial water layer. Improved understanding of the water transport across the soil-snow interface should lead to better prediction of glide-snow avalanche releases in the future.

How to cite: Lombardo, M., Lehmann, P., Kaestner, A., Fees, A., van Herwijnen, A., and Schweizer, J.: Imaging water transport across the soil-snow interface using neutron transmission radiography, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5242, https://doi.org/10.5194/egusphere-egu22-5242, 2022.

EGU22-5723 | Presentations | CR3.2

New insights on avalanche release mechanics based on large-scale elastoplastic simulations 

Bertil Trottet, Ron Simenhois, Grégoire Bobillier, Alec van Herwijnen, and Johan Gaume

The release of snow slab avalanches starts with the failure of highly porous weak snow layer buried beneath a cohesive snow slab leading to mixed-mode crack propagation along the slope. The first modelling attempt of the process date back to 1979 with a pure shear weak layer fracture assumption proposed by McClung. Later, Heierli extended the concept of anticrack, to account for weak layer volumetric collapse and subsequent slab bending. Recent advances reconciled these different approaches and have shown the existence of a supershear crack propagation regime leading to intersonic crack propagation speeds in the up and down-slope directions.
    
    In this work, based on the Material Point Method, finite strain elastoplasticy and critical state theory, we report a transition from sub-Rayleigh anticrack to supershear crack propagation involving the Burridge--Andrews mechanism. The existence of this transition is further confirmed by full-scale avalanche analyses. By accounting for slab fracture, we highlight that soft slabs can prevent supershear transitions to occur. In addition, it is shown that crack branching in the slab can either occur from top to bottom in the case of slow propagating anticracks or from bottom to top for supershear cracks. Through a sensitivity analysis, we investigate the conditions for crack arrest or for the so-called 'en échelon' slab fracture mechanism. Finally, full 3D simulations reveal interesting propagation and release patterns related to the interplay between cross-slope and down/up-slope propagation as well as slab tensile failure. This enables to analyse slab fracture modes at crown, flanks and staunchwall of the avalanche. These new findings allow us to reach a next step in our understanding of the avalanche release mechanics in order to predict both avalanche release shapes and sizes.

How to cite: Trottet, B., Simenhois, R., Bobillier, G., van Herwijnen, A., and Gaume, J.: New insights on avalanche release mechanics based on large-scale elastoplastic simulations, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5723, https://doi.org/10.5194/egusphere-egu22-5723, 2022.

EGU22-5830 | Presentations | CR3.2

A Depth-Averaged Material Point Method for the Simulation of Snow Slab Avalanche Release 

Louis Guillet, Bertil Trottet, Lars Blatny, Denis Steffen, and Johan Gaume

Snow slab avalanches release due to crack propagation within a weak snow layer buried below a cohesive snow slab. In 1979, McClung [1] described this process assuming an interfacial and quasi-brittle shear failure for the weak layer. This model fails to explain observations of propagation on low angle terrain and remote avalanche triggering. To address this shortcoming, Heierli et al. [2] adapted in 2008 the anticrack concept developed for porous rocks to weak snow layers. In 2018, Gaume et al. [3] showed that mixed mode shear-compression failure and subsequent volumetric collapse (anticrack) of the weak layer were necessary ingredients to accurately model propagation mechanisms, thus reconciling apparently conflicting theories. More recently, large scale simulations based on the Material Point Method (MPM) and field observations revealed a transition from slow anticrack to fast supershear crack propagation [4]. This transition, which occurs after a few meters suggests that a pure shear model should be sufficient to estimate the release sizes of large avalanche release zones.

Motivated by this new understanding, we developed a depth-averaged MPM for the simulation of snow slab avalanches release. Here, the weak layer is treated as an external shear force acting at the base of the slab and is modeled as an elastic quasi-brittle material with residual friction. We first validate the model based on simulations of the so-called Propagation Saw Test (PST) and comparing numerical results to analytical solutions and 3D simulations. Second, we perform large scale simulations and analyse the shape and size of avalanche release zones. Finally we apply the model to a complex real topography. Due to the low computational cost compared to 3D MPM, we expect our work to have important operational applications for the evaluation of avalanche release sizes required as input in hazard mapping model chains. Finally, the model can be easily adapted to simulate both the initiation and dynamics of shallow landslides.

References

[1] McClung, D.M. Shear fracture precipitated by strain softening as a mechanism of dry slab avalanche release. Journal of Geophysical Research: Solid Earth (1979) 84 3519--3526
[2] Heierli, J., Gumbsch, P. and Zaiser, M. Anticrack nucleation as triggering mechanism for snow slab avalanches. Science (2008) 321(5886):240-3
[3] Gaume, J., Gast, T. and Teran, J. and van Herwijnen, A and Jiang, C. Dynamic anticrack propagation in snow. Nature Communications (2018) 9 3047
[4] Trottet, B., Simenhois, R., Bobillier, G., van Herwijnen, A., Jiang, C. and Gaume, J. Transition from sub-Rayleigh anticrack to supershear crack propagation in snow avalanches. (2021). doi:10.21203/rs.3.rs-963978/v1

How to cite: Guillet, L., Trottet, B., Blatny, L., Steffen, D., and Gaume, J.: A Depth-Averaged Material Point Method for the Simulation of Snow Slab Avalanche Release, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5830, https://doi.org/10.5194/egusphere-egu22-5830, 2022.

EGU22-6416 | Presentations | CR3.2

Investigating the potential of GNSS-modules for inflow avalanche measurements 

Michael Neuhauser, Rene Neurauter, Steffen Tuermer, Johannes Gerstmayr, Marc Adams, Anselm Koehler, and Jan-Thomas Fischer

A detailed knowledge of avalanche dynamics is crucial to optimize flow models that allow avalanche simulation tools to be effectively used for dimensioning mitigation measures or identifying endangered terrain. There are different ways to observe the dynamics in an avalanche during the flow. It can be achieved with remote sensing approaches or fixed sensor systems that interact with the flow. In this Abstract we introduce an inflow sensor system, the so called AvaNodes that are equipped with a variety of sensors, investigating the potential of Global Navigation Satellite System (GNSS) modules.

The AvaNode is a cube with 16 cm side length. It is designed to flow in the avalanche and obtain GNSS position and velocity, inertial measurement unit (IMU) based accelerations, angular velocities and the magnetic flux densities, and temperature by means of an infrared thermometer.

The utilized GNSS modules are from the ublox CAM-M8 series, that have a position accuracy of 2 m and velocity accuracy of 0.05 m/s, according to the datasheet.

To estimate the position accuracy of the AvaNode while covered with snow, experiments were performed with the AvaNode buried in snow at different depths at a known location. Results show that the position accuracy is highly dependent on the number of satellites that the module currently tracks, ranging between 2 and 10 meters.  To estimate the GNSS velocity accuracy while the AvaNode is covered with snow, a dynamic experiment with moving sensors was performed. The AvaNode was transported on a sledge while it was buried in 10 and 20 cm of snow. An accuracy in the range of 0.5 m/s was observed, allowing to potentially investigate the dynamics in real avalanches. The influence of burial or snow cover depth did not show conclusive influence on the results and requires further investigation. In 2021 this inflow sensor system was used in two avalanche experiments, on March 15 and 16, obtaining start and end positions, as well as promising GNSS velocities. On March 15 one AvaNode was transported by an avalanche, where the GNSS velocity shows a maximum of 15 m/s and a duration of 50 seconds of the avalanche. On March 16 two AvaNodes were picked up by an avalanche, both showing similar velocity distributions, with a maximum velocity of 17 and 13 m/s.

How to cite: Neuhauser, M., Neurauter, R., Tuermer, S., Gerstmayr, J., Adams, M., Koehler, A., and Fischer, J.-T.: Investigating the potential of GNSS-modules for inflow avalanche measurements, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6416, https://doi.org/10.5194/egusphere-egu22-6416, 2022.

EGU22-6943 | Presentations | CR3.2

Glide-snow avalanche formation: First insights from soil and snow monitoring 

Amelie Fees, Alec van Herwijnen, Michael Lombardo, and Jürg Schweizer

Glide-snow avalanches release due to a loss of friction at the interface between the snowpack and the ground. As a result, these avalanches can involve large snow volumes and can have a high damage potential. It is hypothesized that glide-snow avalanche release is linked to the presence of liquid water at the snow-soil interface, but the driving physical processes are poorly understood. We therefore monitored soil and snow properties at our Dorfberg field site above Davos, Switzerland. The field site is a south-east facing slope with frequent snow gliding and glide-snow avalanches. Our soil monitoring setup consisted of two parts. First, we installed a grid of 22 combined, water content and temperature sensors just below the soil surface. The grid covered the entire field site to increase the likelihood of avalanche release above a sensor. Second, we installed two vertical sensor profiles in the soil, each measuring matric potential, water content, and temperature at three depths down to -20 cm. These profiles were continued in the snow with water content and temperature sensors at three heights up to 20 cm. This allowed us to detect gradients and the direction of water flow across the snow-soil interface. Initial results from glide-snow avalanche events showed an increase in water content with increasing snow depth in the days preceding the event. In addition, the soil was close to saturation (high matric potential) and the soil temperature across the entire slope was constant and above 0 °C before release. Although more data are required to confirm our findings, these initial data provide a valuable step towards identifying the driving physical processes at the snow-soil interface. This will help to better understand the source of interfacial water and to improve glide-snow avalanche forecasting.

How to cite: Fees, A., van Herwijnen, A., Lombardo, M., and Schweizer, J.: Glide-snow avalanche formation: First insights from soil and snow monitoring, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6943, https://doi.org/10.5194/egusphere-egu22-6943, 2022.

EGU22-7074 | Presentations | CR3.2

Model-based identification of snow properties from full-field measurements 

Philipp Rosendahl, Valentin Adam, Florian Rheinschmidt, Bastian Bergfeld, Alec van Herwijnen, and Philipp Weißgraeber

The accurate measurement of elastic and fracture properties of snow is challenging but crucial for the modeling of avalanche events. We propose the combination of a closed-form model of the mechanical behavior of layered snowpacks with full-field displacement measurements of propagation saw tests (PSTs) for the identification of the elastic properties of all snow layers and of the fracture toughness of weak layers.

The analytical model provides snow cover deformations, weak-layer stresses and energy release rates of cracks within the weak-layer for arbitrarily layered snowpacks. It can be used for real-time analyses of skier-loaded slopes and for stability tests such as the propagation saw test. Its real-time evaluation is particularly important for the present application.

Full-field measurements of snow cover deformations during propagation saw tests can be obtained using digital image correlation. Recordings of a simple handheld camera suffice for the present application.

The elastic material properties of each layer can then be obtained by fitting the modeled displacement field to the recorded field. The solution of this optimization problem requires many evaluations of the model with varied material parameters of all layers but finally yields the elastic properties of each layer of the snow cover.

Finally, the model allows for the calculation of weak-layer fracture toughnesses using the above determined material properties and the critical crack length of the PST experiment. The results indicate an increasing slab stiffness and an increasing weak-layer fracture toughness throughout one winter season.

How to cite: Rosendahl, P., Adam, V., Rheinschmidt, F., Bergfeld, B., van Herwijnen, A., and Weißgraeber, P.: Model-based identification of snow properties from full-field measurements, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7074, https://doi.org/10.5194/egusphere-egu22-7074, 2022.

EGU22-7278 | Presentations | CR3.2

Detrainment and braking of small to medium snow avalanches interacting with forests. 

Louis Védrine, Xingyue Li, and Johan Gaume

Mountain forests provide natural protection against avalanches. They can both prevent avalanche formation in release zones and reduce avalanche mobility in runout areas. Although the braking effect of forests has been previously explored through global statistical analyses on documented avalanches, little is known about the mechanism of snow detrainment in forests for small and medium avalanches. This study investigates the detrainment and braking of snow avalanches in forested terrain, by performing three-dimensional simulations using the Material Point Method (MPM) and a large strain elastoplastic snow constitutive model based on Critical State Soil Mechanics. First, the snow internal friction is evaluated using existing field measurements based on the detrainment mass, showing the feasibility of the numerical framework and offering a reference case for further exploration of different snow types. Then, we systematically investigate the influence of snow properties and forest parameters on avalanche characteristics. Our results suggest that, for both dry and wet avalanches, the detrainment mass decreases with the square of the avalanche front velocity before it reaches a plateau value. Furthermore, the detrainment mass significantly depends on snow properties. It can be as much as ten times larger for wet snow compared to dry snow. By examining the effect of forest configurations, it is found that forest density and tree diameter have cubic and square relations with the detrainment mass, respectively. Finally, through an energetic and mass study, our results suggest that compared to a regular aligned arrangement, forests with random and regular staggered arrangements have better protective effect. The outcomes of this study may contribute to the development of improved formulations of avalanche-forest interaction models in popular operational simulation tools and thus improve hazard assessment for alpine geophysical mass flows in forested terrain.

How to cite: Védrine, L., Li, X., and Gaume, J.: Detrainment and braking of small to medium snow avalanches interacting with forests., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7278, https://doi.org/10.5194/egusphere-egu22-7278, 2022.

EGU22-7403 | Presentations | CR3.2

Automated prediction of wet-snow avalanche activity in Switzerland 

Martin Hendrick, Frank Techel, Michele Volpi, Olevski Tasko, Cristina Pérez-Guillén, Alec van Herwijnen, and Jürg Schweizer

Avalanche hazard forecasting is essential to reduce the risk for people and infrastructure in mountain areas. Among the different types of avalanches, wet-snow avalanches are particularly challenging to predict due to the poor understanding of their release mechanism. We therefore trained a random forest model to predict wet-snow avalanche activity based on weather and snow measurements and downstream SNOWPACK simulations provided by automated weather stations. The model was trained on a database covering 20 years of avalanche observations (avalanche type, size, location, slope aspect) in the context of operational avalanche forecasting in Switzerland. The prediction performance (F1-score: harmonic mean between recall and precision) for wet-snow avalanche active days is around 76% (recall: 73%, precision: 80%), and is 99% for days with no activity.  The model not only well reproduced the onset, but also the end of wet-snow avalanche periods. Operational testing during winter 2021-2022 allow to evaluate differences in model performance between nowcast derived from meteorological measurements and forecast from numerical weather prediction models. Overall, the results are promising and are an important step forward a more reliable forecast of wet-snow avalanche activity.

How to cite: Hendrick, M., Techel, F., Volpi, M., Tasko, O., Pérez-Guillén, C., van Herwijnen, A., and Schweizer, J.: Automated prediction of wet-snow avalanche activity in Switzerland, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7403, https://doi.org/10.5194/egusphere-egu22-7403, 2022.

EGU22-7599 | Presentations | CR3.2

On the origin of the pulsing activity in powder snow avalanches 

Betty Sovilla, Michael Kyburz, Camille Ligneau, Cristina Pérez- Guillén, Pierre Huguenin, Michael Hohl, and Johan Gaume

Powder snow avalanches (PSAs) are a major threat to people and infrastructure in many mountainous regions of the world. Their force is enough to easily destroy mature forests and any infrastructure located along their path. This is to some extent related to the high velocities and flow heights they can develop, but the basic physical mechanisms controlling their destructiveness remain unclear. Part of this insecurity is related to the fact that the structure of a PSA is very complex. In fact, it can be visualized as the superposition of three distinct layers: (i) a dense granular basal layer, (ii) a transition layer in the form of a turbulent flow with strong density stratification, and (iii) a dilute turbulent suspension of finer particles covering the whole.

Experimental data collected at the Vallée de la Sionne avalanche test site (VdlS) in Switzerland suggests that the destructive capacity of PSAs is largely related to high-energy pulses within this complex stratification. This data indicates that there are at least three different physical processes at the origin of the pulses, specifically: (i) waves at the surface of the dense basal layer (e.g roll-waves, erosion-deposition waves), (ii) coherent vertical structures within the transition layer, and (iii) coherent turbulence structures in the suspension layer. All of these processes, which can also coexist, can be associated with maxima in the dynamic pressure measured over a fixed obstacle.

Although the origin of these pulses still remains largely speculative, with this contribution we aim to present experimental evidence for the existence of various mechanisms of pulsing in PSAs and discuss their relevance in terms of dynamic pressure calculations.

How to cite: Sovilla, B., Kyburz, M., Ligneau, C., Pérez- Guillén, C., Huguenin, P., Hohl, M., and Gaume, J.: On the origin of the pulsing activity in powder snow avalanches, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7599, https://doi.org/10.5194/egusphere-egu22-7599, 2022.

EGU22-7745 | Presentations | CR3.2

Are avalanche models correct? An uncertain view on convergence 

Matthias Tonnel, Anna Wirbel, Felix Oesterle, and Jan-Thomas Fischer

At the core of many avalanche simulation tools, numerical kernels are utilized to solve flow model equations. Aside from trying to fit the models as best as possible to the current understanding of actual flow mechanisms, these kernels have to fulfill general mathematical requirements, such as convergence, stability and consistency. The precision of numerical solutions is limited and needs to be determined by appropriate uncertainty quantification approaches. It is also necessary to assess the impact of input variability propagating through the numerical kernel.

To allow kernel testing and uncertainty quantification, the AvaFrame framework provides a suite of test cases as well as analysis tools. This includes tests with known solutions usable to determine the kernel errors (ana1Tests) and idealized/real world topographies to estimate effects of varying simulation setups. By changing numerical settings, flow model setup or input data it is possible to show their effects on simulation results in a quantitative manner. It therefore allows us to relate input variations to the uncertainty in simulation results. Error and uncertainty quantification is done using modules for computing statistical measures (ana4Stats), indicators along an avalanche path (ana3AIMEC) and various visualization routines.

We showcase this for our com1DFA dynamical dense flow avalanche (DFA) module. The kernel of com1DFA is based on depth integrated governing equations (shallow water) and solved numerically using the smoothed particle hydrodynamics (SPH) method. Applying our analysis tools, we evaluate the convergence of the DFA kernel with regard to the numerical parameters time step, SPH kernel size and particles size. We investigate the accuracy and precision of the numerical solution using the similarity solution test, a test with a semi-analytic solution for depth integrated equations. It allows us to establish a suitable relation between time step, SPH kernel size and particles size for the com1DFA kernel.

Using the same approach for an avalanche setup, we can also vary selected input parameters like friction coefficients and/or release thickness and quantify the resulting uncertainties on simulation results, e.g. runout and peak flow variables.

How to cite: Tonnel, M., Wirbel, A., Oesterle, F., and Fischer, J.-T.: Are avalanche models correct? An uncertain view on convergence, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7745, https://doi.org/10.5194/egusphere-egu22-7745, 2022.

EGU22-7747 | Presentations | CR3.2

Numerical and experimental investigation of crack propagation regimes in large-scale snow fracture experiments 

Bobillier Gregoire, Bergfeld Bastian, Gaume Johan, van Herwijnen Alec, and Schweizer Jürg

Dry-snow slab avalanches are the main cause of avalanche fatalities in mountainous regions. Their release is a multi-scale process which starts with the formation of a localized failure in a highly porous weak snow layer underlying a cohesive snow slab, followed by rapid crack propagation within the weak layer. Finally, a tensile fracture through the slab leads to its detachment. The dynamic process of crack propagation, which affects the size of avalanche release zones, is still rather poorly understood. To shed more light on this crucial process, we performed a series of flat field fracture mechanical experiments, up to ten meters long, over a period of 10 weeks from January to March 2019. These experiments were analyzed using digital image correlation to derive high-resolution displacement fields to compute dynamic crack propagation metrics. We then used a 3D discrete element method (DEM) to numerically simulate these experiments to investigate the micro-mechanics. Both in the experiments and in the simulations, we observed a stationary regime after several meters of crack propagation. The DEM simulations showed that in this regime crack propagation is driven by compressive stresses. A parametric DEM study showed that the elastic moduli of the slab and weak layer, as well as weak layer shear strength, are key variables affecting crack propagation. Our results also highlight that these mechanical parameters influence the propagation distance required to attain the steady-state regime. Finally, DEM simulations on steep slopes showed the emergence of a so-called supershear crack propagation regime, driven by shear stresses, in which crack propagation velocity becomes intersonic. These simulations were confirmed by preliminary experimental results obtained on a steep slope. Our experimental and numerical datasets provide unique insight into the dynamics of crack propagation and lay the foundation for comprehensive studies on the influence of snowpack mechanical properties on the fundamental processes of slab avalanche release.

How to cite: Gregoire, B., Bastian, B., Johan, G., Alec, V. H., and Jürg, S.: Numerical and experimental investigation of crack propagation regimes in large-scale snow fracture experiments, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7747, https://doi.org/10.5194/egusphere-egu22-7747, 2022.

EGU22-7909 | Presentations | CR3.2

Simulating avalanche problem types to assess avalanche climate zones in the French Alps 

Benjamin Reuter, Pascal Hagenmuller, and Nicolas Eckert

Snow avalanches result from a complex interaction of weather and terrain, where past weather as well as internal snow cover processes play an important role. Snow cover models account for these processes and simulate the snow cover at a level of detail that allows to describe snow instability. That information on snow instability is required to assess avalanche climates rather than snow climates – which represents a classification based on weather observations. Running the model SURFEX/Crocus with long-term meteorological data (S2M reanalysis) covering the winter seasons between 1958 and 2020, we eventually derived the avalanche problem types for the 23 massifs representing different regions of the French Alps at daily resolution. This allows us to create a climatology based on avalanche problem types and study differences between mountain regions in the French Alps.

In a first step, we applied a commonly used snow climate classification to understand how in the different Alpine regions seasonal characteristics fluctuate under continental or coastal influence. In some regions the majority of the winter seasons had coastal characteristics, whereas in other regions almost half of the seasons were classified continental. In a second step, we add snow instability information by simulating avalanche problem types. This allows us to explore snow instability patterns that result from the meteorological forcing that the snow climate classification summarizes but which the snow climate classification cannot fully capture. Across the regions persistent weak layers and wet snow were the most common avalanche problems types on days when the model expected natural release. Moreover, we applied a k-means clustering to the frequencies of new snow, persistent and wet snow avalanche problem types to identify similarities between in the Alpine regions. We assessed the clustering performance and found that 4 clusters separate well our data which includes information on duration and frequency of avalanche problem types. The clusters coincide with the geographic location of the regions, i.e. Northern, Southern, inner-alpine or front-range regions have specific characteristics that manifest in frequency of avalanche problem types.

We showed how avalanche problem types can be used as an additional descriptor to the snow climate classification to include snow instability specific information. As avalanche problem types identified spatial differences between different snow climate regions, we are now ready to analyze how those changes evolve with time in the different regions.

How to cite: Reuter, B., Hagenmuller, P., and Eckert, N.: Simulating avalanche problem types to assess avalanche climate zones in the French Alps, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7909, https://doi.org/10.5194/egusphere-egu22-7909, 2022.

EGU22-7984 | Presentations | CR3.2

Full three-dimensional simulations of snow-avalanche flow with two-phase, incompressible, granular μ(I) rheology using OpenFOAM / interFoam 

Alexander H. Jarosch, Tómas Jóhannesson, Kristín Martha Hákonardóttir, and Hafþór Örn Pétursson

Protective measures against snow- and landslides are widely used to improve the safety of settlements in avalanche-prone areas. Modelling of granular flow against obstructions is important for the design of catching and deflecting dams and other protective measures in run-out zones and for hazard zoning both below protective measures and in general for avalanche paths with complex terrain geometry. We describe the implementation of a two-phase (granular material and air), incompressible granular-flow rheology for the OpenFOAM / interFoam computational fluid dynamics software system based on the recently developed μ(I) granular rheology. The model has been calibrated with observations from eight large Icelandic avalanches and shown to reproduce the observed shapes of the avalanche deposits in the run-out zones, and some available radar measurements of avalanche velocities, with observed and estimated values for avalanche volume and release depth in the starting areas. Several of the avalanches are from paths with complicated geometries, including deep gullies and ridges that split the avalanche in the run-out zone, which indirectly provides constraints on the simulated flow dynamics. The model represents an important improvement with respect to depth-averaged models for snow-avalanche flow in complicated terrain geometries as it is able to simulate the full three-dimensional flow at impact with obstacles such as catching and deflecting dams and braking mounds, including the formation and time-dependent development of hydraulic jumps. Thus, splashing and airborne jets formed at impact with obstacles and landing of granular material on the terrain below obstacles can be modelled, as well as the formation of wedges behind the upstream face of dams or mounds, variations of the flow direction with depth within the flow and thus shearing overflow of the upper part of avalanches at impact with deflecting dams that deflects the main avalanche flow, the effect of the steepness of the upper face of catching and deflecting dams, and the effect of the curvature of the axis of deflecting dams and many other aspects of the flow against obstructions. Some examples of simulations of the flow of design avalanches against protective dams in Iceland will be shown in the presentation.

How to cite: Jarosch, A. H., Jóhannesson, T., Hákonardóttir, K. M., and Pétursson, H. Ö.: Full three-dimensional simulations of snow-avalanche flow with two-phase, incompressible, granular μ(I) rheology using OpenFOAM / interFoam, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7984, https://doi.org/10.5194/egusphere-egu22-7984, 2022.

EGU22-8220 | Presentations | CR3.2

Vehicle damage and transport and possible shock wave formation in the Flateyri avalanche in January 2020. 

Ragnar Lárusson, Kristin Martha Hakonardottir, and Haukur Elvar Hafsteinsson

Two large dry slab avalanches from the 700 m high mountain above the village of Flateyri, NW Iceland, partly overflowed two deflecting dams on the eve of the 14th of January 2020. While most of the avalanche snow was deflected from the village by two 15-20 m high deflecting dams, approximately 10 % of the total mass overflowed the dams, injuring one person and causing damage to one house, three vehicles and breaking a steel mast, a timber shed and shrub/bush. Radar measurements of the speed of the avalanche, the density of the avalanche deposit, damage to structures, and witness accounts suggest that the avalanche was a transitional avalanche with a 400 m long fluidized head, followed by a denser core, upstream of the dam and the overflow belonged to a fluidized region of intermittent density. It is believed that the sonic speed in such fluidized regions can be one order of magnitude lower than that of air. In such a case the speed of the fluidized region can be comparable to the sonic speed within it, giving rise to the possibility of supersonic shock wave formation.

The aim of the current study is to analyze the dynamics of the part of the avalanches that overflowed the deflecting dams, based on the in-situ damage that the overflow caused, and attempt to distinguish between damage that a shockwave would cause and damage that the kinetic energy in the overflow may cause. The focus is on the three vehicles that were hit by the avalanche overflow and transported 13 to 20 m horizontally, two of them over a three to four meters high pile of snow. We find that aerodynamic forces caused by the overflow could have been large enough and lasted long enough to transport the cars the observed distances. The calculations are simplified and effects of an uneven lateral density distribution are omitted. Supersonic conditions in the overflow are considered unlikely.

A moving supersonic shockwave would not have lasted long enough (order of 10-100 ms) to transport the cars. Weak compression shocks in subsonic avalanche flow may form upstream of stationary obstacles, due to the compressibility of the avalanche front. Those would also be too short-lived to contribute to the transport of the vehicles. Damage to brittle objects (with a resonance period in the same range as the pressure wave period, 2 to 100 ms), such as window glass, doors, and non-reinforced concrete walls, can however be contributed to such short-lived impacts and interactions with moving pressure waves.

Shockwave-turbulence interactions are generally known to cause high-intensity noise radiation of various characteristics. Standing shocks, due to supersonic flow upstream of stationary obstacles (e.g. buildings or high cliffs) could be a cause for impulsive sounds observed prior to the arrival of the avalanche.

How to cite: Lárusson, R., Hakonardottir, K. M., and Hafsteinsson, H. E.: Vehicle damage and transport and possible shock wave formation in the Flateyri avalanche in January 2020., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8220, https://doi.org/10.5194/egusphere-egu22-8220, 2022.

EGU22-9519 | Presentations | CR3.2

Characterization and detection of avalanche signals using a seismo-acoustic array 

Christine Seupel, Cristina Pérez Guillén, and Alec van Herwijnen

Seismic and infrasound monitoring systems have been used for remote detection and characterization of avalanches and their dynamics. Recent studies have shown that seismic and infrasound methods are very complementary. Infrasound signals from avalanches are relatively easy to detect automatically but only contain partial information about the avalanche. Seismic signals, on the other hand, are more difficult to detect automatically but contain more information about the entire avalanche. To exploit the advantages of both wave types, we installed a combined seismo-acoustic array consisting of five seismometers and five infrasound sensors at our field site in Dischma valley above Davos. Additionally, we obtained ground-truth data on avalanches from several automatic cameras, field surveys and drone flights.

Results from data collected over two winter seasons show that both dry- and wet-snow avalanche were detected by our system, and highlight differences in seismic and infrasound wave characteristics depending on the avalanche type and size. Specifically, detection distance increased with avalanche size for both wave types. Furthermore, differences in seismic and infrasound signal characteristics were generally more pronounced for wet-snow avalanches than for dry-snow avalanches. Using array techniques we localized the avalanche paths and extracted seismic and infrasound waveform features. We also trained a machine learning model to automatically identify signals generated by avalanches, with promising results. Overall, our results indicate that combining seismic and infrasound wave characteristics can improve the remote detection and characterization of avalanches.

How to cite: Seupel, C., Pérez Guillén, C., and van Herwijnen, A.: Characterization and detection of avalanche signals using a seismo-acoustic array, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9519, https://doi.org/10.5194/egusphere-egu22-9519, 2022.

EGU22-10346 | Presentations | CR3.2

Modelling forest effects on snow avalanche runout with the Flow-Py simulation tool 

Christopher D'Amboise, Michael Neuhauser, Anne Hormes, Matthias Ploerer, Jan-Thomas Fischer, and Michaela Teich

Forests cover large parts of mountain areas. It is therefore necessary to include their effects in simulations at the regional scale to understand the key role forests have for risk mitigation. Process-based physical models can be used for such simulations, but they often require larger computational resources than statistical models. Flow-Py is a customizable, open-source simulation tool to predict the runout and intensity of gravitational mass flows (GMF). Flow-Py is based on data-driven empirical modeling ideas with automated path identification to solve the routing and stopping of GMFs in three-dimensional terrain, requiring fewer parameters than physical GMF runout models. Here we present the custom-built forest plug-in to the Flow-Py simulation tool which accounts for forest effects in the transit and runout zones of snow avalanches. 

Flow-Py employs the well-known runout angle (α) concept to determine the stopping of a GMF, and routing algorithm consisting of a terrain contribution and persistence contribution. The interaction between forest and avalanches, which can reduce their runout and decrease their intensity can be broken down into two main processes, 1) adding friction and 2) reducing flowing mass or the detrainment of snow. The forest plug-in has the capability to mimic these physical interactions by increasing the runout angle and adjusting the routing flux in forested areas. We present the framework of the forest plug-in for a test case and the results of a sensitivity study on parameters controlling the forest-avalanche interaction.  

The forest plug-in requires the spatial extent of the forest and an estimate of the kinetic energy of the avalanche to compute the forest’s effect on the avalanche movement. Additional information on the structure of the forest (e.g., forest type, stem density, canopy cover, basal area) can be used to amplify or dampen these effects. The forest information is summarized in the forest structure index (FSI), which indicates how developed a forest is with regards to its optimal protective effect against snow avalanches and ranges between 0 (no protection) and 1 (optimal protection), considering, e.g., dominant forest type, elevation band, or the forest development stage. 

Forests located in the starting zones of avalanches have long been used as an efficient mitigation measure to reduce avalanche risk. However, forests located in the transit and runout zones of avalanches also have mitigating properties, but the degree of protection is difficult to quantify without simulation tools and their integrated models. Including forest-avalanche interactions in regional-scale simulations with Flow-Py and its forest plug-in allows to estimate the degree to which forest protects human activity and infrastructure against potential avalanches. That is, by combining simulation results with and without forest it is possible to estimate the forest impact, i.e., how much the forest reduces the magnitude (runout and intensity) of the avalanche. Such regional overviews can be calculated fast with large-scale input data, which is important to, e.g., quantify changes in the protective effect of a forest area caused by disturbance agents such as wind, bark beetles or fire.  

How to cite: D'Amboise, C., Neuhauser, M., Hormes, A., Ploerer, M., Fischer, J.-T., and Teich, M.: Modelling forest effects on snow avalanche runout with the Flow-Py simulation tool, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10346, https://doi.org/10.5194/egusphere-egu22-10346, 2022.

EGU22-11328 | Presentations | CR3.2

An in-flow sensor system for data acquisition in snow avalanches 

Rene Neurauter, Michael Neuhauser, Johannes Blobel, Robert Winkler, Falko Dressler, Jan-Thomas Fischer, and Johannes Gerstmayr

The dynamics of snow avalanches and in particular their rheology is of big importance to develop improved avalanche models and thus increase safety in mountainous areas. Existing measurement systems only allow a limited in situ view of the dynamics of snow avalanches and therefore demand the development of innovative measurement systems. Furthermore, due to the limited measurement capability of existing systems, comprehensible motion reconstruction is currently not possible. Therefore, the aim of this work is to present a measurement system that enables accurate in flow observations of snow avalanches and has the mechanical properties of a typical snow granule. A main objective of the measurement system is to allow a full motion reconstruction regarding translations and rotations with a high sampling rate and without exceeding sensor ranges.

The newly developed system, denoted as AvaNode, has the shape of a concave cube with a variable density to fit typical snow granules in flowing avalanches and their deposits. The AvaNode contains a strapdown inertial navigation sensor capable of measuring accelerations, angular velocities, and magnetic flux densities with up to 400Hz and allows for an estimation of the orientations, velocities, and positions of the AvaNode using state of the art motion reconstruction algorithms. The reconstruction is significantly improved due to precise calibration of all sensors using reference measurements with a 6R robot and onsite magnetic field calibration. In order to get a refined motion trajectory, the AvaNodes are also equipped with radio ranging modules. These modules allow performing time of flight (TOF) measurements, determining the distance between several nodes. A Global Navigation Satellite System (GNSS) module determines longitude, latitude, and altitude, as well as world time, however, with low frequency resolution and larger errors due to snow coverage. To measure the temperature evolution in avalanches, an infrared temperature sensor is attached.  Multiple recovery systems like Recco rescue reflector (passive), Pieps TX600 (active), and Lambda4 Smilla (active) are integrated to allow fast retrieval of the sensors.

As first results, we present the employed sensor calibration approaches for the inertial navigation with corresponding laboratory data signatures. The sensor calibration allows in-depth analysis of motion data, identifying typical data signatures observed in avalanches. Furthermore, we show first data acquired from in-flow snow avalanche measurements, which prove the functionality of the system and allow the first insights into trajectories of snow granules, regarding accelerations, angular velocities, rotations, and position.

How to cite: Neurauter, R., Neuhauser, M., Blobel, J., Winkler, R., Dressler, F., Fischer, J.-T., and Gerstmayr, J.: An in-flow sensor system for data acquisition in snow avalanches, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11328, https://doi.org/10.5194/egusphere-egu22-11328, 2022.

Highly-porous cohesive granular materials such as snow possess complex modes of failure. Apart from classical failure modes, they show microstructural failure and fragmentation associated with densification within a local, narrow zone. Therefore cracks may form and propagate even under compressive load ('anticracks', 'compaction bands'). Such failure modes are of great importance in a range of geophysical contexts. For instance, they may control the release of snow slab avalanches and influence fracturing of porous rock formations. In the snow context, specific failure mechanisms of the ice matrix and their interplay with the microstructure geometry of snow are still poorly understood. Recently, X-ray computed tomography images have provided insights into snow microstructure and capability of directly simulating its elastic response by the finite element method (FEM). However, apart from thermodynamically driven healing processes the inelastic post-peak behaviour of the microstructure is controlled by localized damage, large deformations and internal contacts.  As a result of the well-known limitations of FEM to capture these processes we use Peridynamics (PD) as a non-local continuum method to approach the problem. Due to its formulation, (micro)cracks and damage are emergent features of the problem solution that do not need to be known or located in advance. In this contribution we perform unconfined displacement controlled high strain-rate uniaxial compression simulations of snow microstructures within a peridynamic framework. Computed tomography images of snow specimen serve as a simulation data base. The obtained results show a novel insight into local failure of snow and allow a better comprehension of the underlying failure mechanisms. This study contributes to improve non-local macroscopic constitutive models for snow for future applications.

How to cite: Ritter, J. and Zaiser, M.: High Strain Rate Compressive Failure of Porous Brittle Snow Microstructures Simulated by Peridynamics, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12376, https://doi.org/10.5194/egusphere-egu22-12376, 2022.

During the winter seasons 2019-2020 and 2020-2021 as well as during the current season 26 avalanche infrasound detection systems (IDA®) were used by Parks Canada, the Norwegian Road Administration and Swiss cantons as support for operational decision making to minimize avalanche risk. In this period, more than 800 controlled avalanches and 2700 natural avalanches were detected and delivered in near-real-time to avalanche teams.

Operational efficiency of the Trans-Canada Highway (BC) in the winter months is highly dependent on effective avalanche control. Here the goal of infrasound technology is to provide the Glacier National Park avalanche control team with information on avalanche activity in specific avalanche sectors and paths to reduce avalanche related road closure times. Infrasound technology has also been successfully applied in sparsely vegetated terrain at high altitudes and latitudes such as in Norway, where the Norwegian Public Roads Administration operates infrasound systems along remote road sections where visual observations are difficult to gather. Experiences from regional avalanche forecasting teams in Switzerland where multiple arrays are distributed over a larger area are also presented.

In this work we want to give an overview of results obtained from the use of infrasound technology with particular focus on advantages and limitations encountered in various operational contexts. Recent results of ongoing developments such as multi array processing are also presented.

How to cite: Ulivieri, G., Vezzosi, S., Steinkogler, W., and Dreier, L.: Infrasound detection of avalanches: operational experience from 26 systems in Canada, Switzerland and Norway - individual and multi-array based approaches, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13066, https://doi.org/10.5194/egusphere-egu22-13066, 2022.

EGU22-13133 | Presentations | CR3.2

Force measurements during snow stability tests 

Silke Griesser and Ingrid Reiweger

A very powerful and commonly used method to assess the danger of avalanche release on a slope is the performance of snow stability tests. The present work aims to contribute towards a better understanding of snow stability test results by conducting force measurements during a snow stability test, namely the Compression Test (CT). We were particularly interested in the variability of the force applied to a potential weak layer during the test by different persons and for different snow covers. We therefore focused on the stress levels for the single taps and loading steps of a CT, and how they were influenced by different snow properties (effective depth, compaction depth, and snow hardness) as well as other factors, such as test subjects’ body weight and arm length. We used two capacitive pressure sensors to conduct force measurements during the performance of CTs at two different depths with eleven different people and at seven different locations. The evaluation and analysis of these measurements were conducted with Python. Our results showed that the penetration depth and compaction of the snow above the force sensor significantly influenced the transmission of stress. The stress levels of shoulder taps were in the range of stress levels below a standing skier and decreased non-linearly with penetration depth. Furthermore, we found that stress levels were rising also within distinct loading steps. Moreover, it was possible to confirm the influence of a person’s weight and arm length on stress levels, and consequently, statistically significant differences between different test persons. In terms of avalanche safety, our results indicate a non-linear decrease of the probability of fracture initiation with increasing tap number. Most importantly, we discovered that regardless of what was analysed, the data’s scattering decreased with increasing depth, which means that the significance of a CT result increased considerably with increasing fracture depth.

How to cite: Griesser, S. and Reiweger, I.: Force measurements during snow stability tests, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13133, https://doi.org/10.5194/egusphere-egu22-13133, 2022.

EGU22-752 | Presentations | CR3.4

Increasing the episodic glacial lake outburst flood hazard in response to surge glaciers in the Karakoram 

Nazir Bazai, Peng Cui, Paul Carling, Hao Wang, and Javed Hassan

In contrast to glaciers in other areas of the world, the Karakoram glaciers appear to be stable or increasing mass in response to global climate change, a phenomenon known as the 'Karakoram anomaly.' Many glaciers are experiencing irregular, frequent, and rapid frontal advances (surges), which cause natural hazards by obstructing river channels forming ice-dammed lakes, consequent outburst floods and posing threats downstream over the region. Predicting the phenomenon to protect downstream communities remains challenging around the globe. The determination of the surge characteristics, timing and evolution of lakes and GLOFs is fundamental to flood control and disaster management. This study documents 179 glacial lake outburst floods (GLOFs) that occurred from 1533 to 2020 in five major valleys. Sixty-four of the events took place after 1970, and 37 of these had remote sensing imagery that covered the GLOF formation to breaching sequence. Thirty-six glaciers were associated with GLOFS due to ice-front advance building ice barriers in rivers. The Kayger and Khurdopin glaciers are the most hazardous examples, responsible for 31.8% of major GLOFs in the Karakoram. Using a cross-correlation feature-tracking technique on remote sensing imagery, we analyzed ten surge glaciers and documented six surge events from 1990 to 2019. Results show periodic surge cycles for the Khurdopin, Kyager, Shishper, and Chilinji glaciers of c. 15–20 years, with a surge velocity in the mid-2010s higher than that of the late 1990s for all studied glaciers. The higher velocity of a glacier increases the risk of flooding downstream of the terminus because the transfer of a huge ice mass towards the terminus during the surge is a key factor for conduit development, formation and reformation of a series of ice-dammed lakes, thus determining the magnitude and frequency of outburst flood events. The response of Karakorum glaciers to global warming and climate forcing, comprising a continuum of glacier mass gain, ice thinning, and ice advance has resulted in lake formation and ice dam failures. We predict the frequency of GLOFs will increase in the future. These findings support the increasing anomalous behavior of glaciers in the Karakoram region. A conceptual model of ice-dammed lake formation and GLOF initiation in response to glacier surging is presented to synthesize the detailed observations.

How to cite: Bazai, N., Cui, P., Carling, P., Wang, H., and Hassan, J.: Increasing the episodic glacial lake outburst flood hazard in response to surge glaciers in the Karakoram, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-752, https://doi.org/10.5194/egusphere-egu22-752, 2022.

EGU22-1271 | Presentations | CR3.4 | Highlight

Distribution and controls on the accumulation of fallout radionuclides in cryoconite across the global cryosphere 

Caroline Clason and the Rad-Ice team

Fallout radionuclides (FRNs) are a product of nuclear accidents and weapons testing, and are known environmental contaminants. There has been extensive research into the risks and consequences of FRN deposition for human and ecosystem health, however this has rarely extended to the cryosphere. The results of our international collaboration reveal widespread accumulation of FRNs in cryoconite spanning 30 glacier sites and 477 samples across the Arctic, the Alps, the Caucasus, North America, the Andes, the Himalaya and Antarctica. The activity levels of FRNs found in many samples are orders of magnitude higher than those found in other environmental matrices such as mosses and lichens, and include some of the highest ever recorded outside of nuclear exclusion zones. This raises important questions around the role of glaciers, and specifically cryoconite and its interaction with meltwater, in concentrating - and eventually releasing - FRNs to levels above those historically deposited in the surrounding environment. We compare FRNs in cryoconite with a range of geographical and environmental factors, and find no significant correlation between 137Cs and distance from Chernobyl, and moderate correlations for 241Am and 210Pb which deteriorate to no significant correlation when only Northern Hemisphere sites are considered. We also find no correlation with distance from the sea, or with mean elevation, but a moderate correlation between precipitation and both 137Cs and 241Am, highlighting the importance of scavenging of atmospheric contaminants by snow. Notably, we find a strong correlation between organic matter and activities of both 137Cs and 210Pb, reflecting the capacity of cryoconite to bind FRNs due the presence of extracellular polymeric substances. This research has, for the first time, shed light on the widespread occurrence of FRNs in glacier catchments across the global cryosphere. The potential risks of FRN exposure for water and environmental quality, including uptake of FRNs by flora and fauna, should be a focus of future interdisciplinary research as glaciers continue to retreat and release legacy contaminants into proglacial environments.

How to cite: Clason, C. and the Rad-Ice team: Distribution and controls on the accumulation of fallout radionuclides in cryoconite across the global cryosphere, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1271, https://doi.org/10.5194/egusphere-egu22-1271, 2022.

EGU22-2441 | Presentations | CR3.4

Disruption of the sedimentary environment in Greenland fjords due to enhanced cryosphere melting caused by > 2oC climate warming 

Antoon Kuijpers, Susanne Lassen, Jian Ren, and Gholamreza Hosseinyar

Widespread and fast melting of glaciers and ice sheets as a result of marked climate warming leads to a variety of possible hazards, both in proximal and (sea level) far-field regions. Past melting behavior of the Greenland Ice Sheet (GrIS)  has been strongly controlled by northern hemisphere insolation changes. In the early- and mid-Holocene relatively high insolation led to marked ice sheet retreat. The GrIS extent reached its minimum in NW Greenland  between  5 and 3 ka (ka = 1000 yrs before present) and in southern Greenland between 7 and 4 ka(1). During this regional ‘Holocene Thermal  Maximum’ (HTM) a more humid climate prevailed with summer  temperatures  3o to 5o C higher than in the mid-20th century(2,3). Here we report sediment records from Greenland fjords indicative of drastically enhanced bottom current activity as well as local occurrence of massive silt deposition during above HTM periods. In Ameralik fjord near Nuuk a major sediment hiatus exists for the interval 6.8 to 4.4 ka(4), whereas nearby in this fjord massive deposition of silty melt water sediments subsequently occurred(5). In the outer part of Igaliku Fjord, South Greenland, sedimentation had stopped between approx. 7 and 3.7 ka(6). Nearby lake deposits display record-high accumulation rates of organic-rich sediment associated with a mild, stormy climate between 4.5 and 3.7 ka(7). On the shelf near Nuuk sediment geochemistry confirms significant melt water sediment transport from the adjacent mainland, markedly ceasing after 4 ka(8). Lacking of a hardground underlying the hiatus in the sediment core from Ameralik fjord points to erosion instead of long-term non-depositional conditions. Coastal deposits lack evidence of mid-holocene earthquake-induced tsunami activity, a potential trigger mechanism we thus may exclude. Instead we conclude that widespread glacier melting under a much warmer (> 2o) climate must have led to repeated (sub)glacial  meltwater outburst surges producing high-energy, hyperpycnal  flow processes in the fjords. Sea level high-stand data from far-field regions around the Indian Ocean suggest most prominent melting episodes around 6 ka and near 4.3 ka(9).  Higher temperatures and increased precipitation rates in western Greenland presumably also favored widespread onshore permafrost thawing and consequently local destabilization of fjord slopes. Associated mud- and debris flow processes likewise have had a severe impact on the fjord sedimentary regime and benthic ecosystem. Based on above sedimentary records, we thus conclude that further ongoing global warming will have hazardous effects on the benthic environment of glacial fjords.

1) Young, N.E., J.P. Briner, 2015. Quat Sci Rev 114, 1-17

2) Axford, Y. et al. 2020. Annu Rev Earth Planet Sci, doi.org/10.1146/annurev-earth-081420-063858

3) Levy, L.B. et al. 2018. Arctic, Antarctic, Alpine Res. 2018, 18(1), e1414477, doi.org/10.1080/15230430.2017.1414477

4) Ren, J. et al. 2009. Mar Micropal, doi:10.1016/j.marmicro.2008.12.003               

5) Møller, H.S. et al. 2006.The Holocene 16,5, 685-695

6) Lassen, S.J. et al. 2004.The Holocene 14,2,165-171      

7) Andresen, C.S. et al. 2004. J Quat Sci 19(8) doi:10.1002/jqs.886

8) Madaj, L. et al.2021. EGU Gen. Assem.2020, doi.org/10.5194/egusphere-egu2020-786

9) Hosseinyar, G.et al. 2021. Quat Intern 571, 26–45

How to cite: Kuijpers, A., Lassen, S., Ren, J., and Hosseinyar, G.: Disruption of the sedimentary environment in Greenland fjords due to enhanced cryosphere melting caused by > 2oC climate warming, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2441, https://doi.org/10.5194/egusphere-egu22-2441, 2022.

EGU22-2511 | Presentations | CR3.4

Estimating probabilities of occurrence related to impacts on glacial lakes from large rock-ice avalanches 

Wilfried Haeberli, Simon Allen, and Holger Frey

Worst-case scenarios concerning volumes and hydrographs of sudden, far-reaching  impact/flood waves from existing and future glacial lakes are based on assumed impacts from large, high-energy rock- or rock/ice-avalanches. The probability of occurrence related to such events as a basis for quantitative hazard and risk assessment and intercomparison depends on their expected magnitude and frequency. Magnitude is given by the term “large”  - here defined as volumes of millions of m3 which enable near-instantaneous displacement of lake volumes in the order of millions to tens of millions of m3. Quantitative determination of related frequencies, on the other hand, faces fundamental difficulties for a number of reasons. Rock-ice avalanches are non-repetitive events: Once an event has occurred it cannot occur again in the same way from the exact same site, because the unstable rock mass has definitely been removed from its detachment zone. Destabilisation processes which precede rock- or rock/ice avalanches are cumulative processes: Under conditions of continued global warming, future conditions are not only different from the past, but also from present-day situations. Scenarios of drastic and long-term future glacier vanishing and permafrost degradation/thaw must be taken into consideration, along with changes in atmospheric triggering conditions.

During the past years, first steps towards producing a useful statistical data basis have been achieved concerning regional developments in time of rock- and rock/ice avalanches for selected cold mountain areas of variable sizes. The existing statistical data bases together with indications about effects from warming trends can now be used to rougly determine event recurrence times per unit area of steep icy peaks. This, in turn, opens the possibility to quantitatively estimate expected probabilities of occurrence related to possible future extreme impacts on critical locations, such as involving glacial lakes and process cascades. In view of the still strongly limited statistical data and the complexity of the involved processes, only order-of-magnitude estimates can be achieved. A first preliminary analysis based on quantitative information from the European Alps and Glacier Bay National Park indicates event recurrence times of about 103 to 104 years per km2 of steep icy peaks with an increase of about a factor of 5 as documented for the Alps during the past few decades. Applying these results to the slopes in the catchment of three glacial lakes of high practical interest provides probabilities of ocurrence per year of 0.01 to 0.001 for Laguna Palcacocha (Cordillera Blanca, Peru), 0.1 to 0.01 for Lower Barun Lake (Nepal Himalaya) and 0.1 to 0.01 for the system of lakes which is likely to form during the coming decades at Great Aletsch glacier (Swiss Alps) where presently no lake exists.

Such first estimates indicate important possibilities for quantitative hazard and risk assessments but need further improvement by systematic data collection about large catastrophic mass flows in cold mountains and by analysing the key environmental factors in a more differentiated way.

How to cite: Haeberli, W., Allen, S., and Frey, H.: Estimating probabilities of occurrence related to impacts on glacial lakes from large rock-ice avalanches, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2511, https://doi.org/10.5194/egusphere-egu22-2511, 2022.

EGU22-3113 | Presentations | CR3.4

Tracking mountain geohazards in Uzbekistan with application of remote sensing and advances in data analysis. 

Timur Sabitov, Maxim Petrov, Halim Mamirov, Fahriddin Akbarov, Sarkorbek Suvonqulov, and Naila Sabitova

Climate change is affecting the environment of Central Asia, the high mountains and particularly the paraglacial and glacial environments. Trends shown to affect the state and dynamics of glaciation; a gradual decrease in both area and volume, and the increase in the area of moraine deposits can be observed. Meanwhile, the frequency of occurrence of hazardous geological phenomena's related to glacial dynamics, such as outbursts of glacial lakes (GLOF'S), avalanches, rockfalls, blockages of river channels, as well as mudflows, is increasing. Observations after them are complicated by the inaccessibility of areas due to lack of infrastructure, seasonal restrictions, the required number of people to conduct observations in the field and financial costs. Studies shown that remote sensing technologies allow observation of changes and proved to have sufficient spatial and temporal resolution to assess the transformations taking place. In our study, we propose a method for assessing statistically significant changes occurring in the catchment for each of the image elements (pixel) over time using nonparametric statistics. The novelty of the work is the application of an assessment of the significance of these changes that allows to reduce the influence of human error in the analysis of images thus producing higher quality results and reducing time required. Although the technology is known in the world - and is used to solve the problems of machine learning and deep vision. For the territory of Uzbekistan and in this research area, this method is innovative, and the statistical assessment of significance over time is used for the first time. Thus, the method makes it possible to identify areas where significant changes have occurred due to events mentioned above, and reduces the amount of time and costs required to search for these areas to prevent or reduce further damage.

How to cite: Sabitov, T., Petrov, M., Mamirov, H., Akbarov, F., Suvonqulov, S., and Sabitova, N.: Tracking mountain geohazards in Uzbekistan with application of remote sensing and advances in data analysis., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3113, https://doi.org/10.5194/egusphere-egu22-3113, 2022.

EGU22-4384 | Presentations | CR3.4

Mapping glacial lakes and their changes using cloud processing of optical satellite images 

Varvara Bazilova and Andreas Max Kääb

Glacial lakes are an important component of terrestrial meltwater storage and respond to climate change and glacier retreat. Although there is evidence of rapid worldwide growth of glacial lakes, changes in frequency and magnitude of glacier lake outburst floods (GLOFs) under climatic changes are not yet understood. We refine existing methods of water mapping, based on optical remote sensing images, that can be applicable for the mapping of glacial lakes. We propose and discuss methods for regional-scale glacial lake mapping and GLOF detection using large time series of optical satellite images and the cloud processing tool Google Earth Engine in a semi-automatic way. The methods are presented for various temporal scales, from the 2-week Landsat revisit period to annual resolution. The proposed methods show how constructing an annual composite of pixel values such as minimum or maximum values can help to overcome traditional problems associated with water mapping from optical satellite data like clouds, or terrain and cloud shadows. For annual-resolution glacial lake mapping, our method set only involves two different band ratios based on multispectral satellite images. The elevation range, computed from a digital elevation model is used on the postprocessing step to filter out noise associated with image quality and misclassifications. The study demonstrates various examples of how the proposed methods can be applied to detect GLOFs and to produce a complete regional-scale glacial lake inventory, using the Greater Caucasus as an example. We also discuss limitations of the approaches, finding that for applications where reliable detailed maps are required, visual revision of the results is still recommended owing to the often small size of glacial lakes, combined with their large variability in, for example, topographic setting, turbidity, depth, or temporal occurrence.

How to cite: Bazilova, V. and Kääb, A. M.: Mapping glacial lakes and their changes using cloud processing of optical satellite images, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4384, https://doi.org/10.5194/egusphere-egu22-4384, 2022.

EGU22-4674 | Presentations | CR3.4

The Role of Frictional Melting in Rock/Ice Avalanche Dynamics:  Thermomechanical Modelling of the Piz Cengalo and Chamoli Events 

Perry Bartelt, Jessica Munch, Bühler Yves, and Stefan Margreth

The rock/ice avalanches that occurred in Switzerland (Piz Cengalo, 23.8.2017) and the Indian Himalaya (Chamoli, 7.2.2021) and their subsequent debris flows have highlighted the question of how much water can be generated by frictional melting of glacier ice and entrained snow. The Piz Cengalo event initiated with the release of some 3.2 mio m3 of rock and entrainment of approximately 0.6 mio m3 of glacier ice.  The source of water necessary to trigger the debris flow activity has been attributed in part to frictional melting of ice.  First calculations by Shugar et al. (2017) indicate that the Chamoli event initiated with a total of 27 mio m3 of rock (80% by volume) and glacier ice (20%). Additional entrainment of snow increased the total ice content of the flow.  Meltwater generated by frictional melting has likewise been suggested as the cause of the catastrophic flood wave.

In order to analyze the the Piz Cengalo event, the SLF developed a mathematical model to simulate rock/ice avalanches, including snow, water and soil entrainment (Margreth and Bartelt, 2018).  The model calculates the internal heat energies of the rock, ice and water phases and includes the melting of ice.  Frictional work drives the melting process, but is additionally supplemented by heat exchanges/contact between the rock-ice-water components. The model correctly provides the overall temperature rise of an event, which can be found from simple energy arguments. The numerical model, however, predicts the rate of melting, which depends on when ice and snow are entrained into the flow, as well as terrain features, which influence frictional work rates.   An important result of the model calculations is that meltwater is not spread homogeneously over the depositions, but is concentrated at specific locations in the deposits, facilitating the formation of secondary mass movements.

Using this mathematical model to simulate the Chamoli event we find a total maximum meltwater production of 2.5mio m3 to 3.0 mio m3.  This estimate should not be characterized as small:  during the flow in the upper reaches of the Raunthi Gadhera frictional heating generated 50’000 tons of water every second.  This rate decreased significantly as the flow reached the Dhauliganga river valley.    In the end, only half of the initial glacier ice melted.  From downstream gauge station measurements, Indian government officials have estimated the total volume of the water surge to be approximately 6 mio m3 over a period of one hour (Rautela et al., 2021).  In agreement with the field observations of Rautela and co-authors we find the remaining 3mio m3 of water to come from entrainment of ponded water in the Raunthi Gadhera valley and the subsequent blockage and dam break at the Dhauliganga river inlet.  That is, secondary sources of water are necessary to reproduce the observations.  A similar result is found for the Piz Cengalo case study.  Under extreme assumptions, we find that of the initial 0.6 mio m3 of glacier ice, between 0.08 mio m3 and 0.12 mio m3 melted, leaving significant amounts of ice in the depositions.  

 

How to cite: Bartelt, P., Munch, J., Yves, B., and Margreth, S.: The Role of Frictional Melting in Rock/Ice Avalanche Dynamics:  Thermomechanical Modelling of the Piz Cengalo and Chamoli Events, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4674, https://doi.org/10.5194/egusphere-egu22-4674, 2022.

EGU22-4864 | Presentations | CR3.4

Assessment and inventory of hazardous mountain lakes in Kyrgyz Republic 

Sergey Erokhin, Vitalii Zaginaev, Simon Allen, and Anna Meleshko

More than 90 % of territory of Kyrgyz Republic are mountains.  More than two thousand lakes have formed but only some lakes pose a threat to lives, assets and livelihoods. Many of these lakes are seasonally dynamic, and form in ice-rich permafrost environments that are characteristic of the region. The objective of this study was to describe and implement an evidence-based expert lake hazard assessment criteria, to produce an updated inventory of hazardous lakes, which are susceptible to outburst within the territory of Kyrgyz Republic. A total of 368 lakes susceptible to outburst in Kyrgyzstan were inventoried and classified into 5 classes: ice-dammed, ice-cored moraine-dammed, ice-free moraine dammed, bedrock-dammed and morainedammed, and landslide-dammed lakes. The hazardous lake inventory was most recently updated in 2021 based on field works and remote sensing analysis.

All 368 lakes were described by a number of quantitative and qualitative characteristics and were assigned different levels of outburst susceptibility. All studied lakes are situated within the elevational zone between 1200 m.a.s.l. and 4300 m.a.s.l. All lakes were estimated in terms of their surface area from remote sensing data for different years, which ranges from thousands to millions of square meters. For 47 ice cored moraine dammed lakes bathymetry measurements were conducted, for many of them several times.

The outburst susceptibility was estimated according to 4 hazard categories and each lake is assigned within a certain category depending on current lake characteristics. A particular feature of the non-stationary lakes found in this region is the rapid changes in outburst susceptibility that can occur over short time-periods. A total of 111 lakes, which at least once have been assigned with the highest hazard levels (the 1st or 2nd category) in the period from 2006-2017 were analyzed for their changes over time. According to the analysis, the hazard level of many lakes varies over time and the number of category 1 and 2 lakes has considerably decreased in the recent decade. Lakes of the 1st and 2nd hazard categories decreased since 2006 by 57 % and 45 % respectively (from 21 to 9 and 49 to 27), while the number of lakes of the 3rd and 4th categories increased from 35 to 58 and 1 to 16.

The lake hazard assessment scheme developed for the Kyrgyz Republic may be a valuable tool for scientists and authorities dealing with outburst flood hazards in other similar environments of Central Asia and elsewhere.

How to cite: Erokhin, S., Zaginaev, V., Allen, S., and Meleshko, A.: Assessment and inventory of hazardous mountain lakes in Kyrgyz Republic, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4864, https://doi.org/10.5194/egusphere-egu22-4864, 2022.

EGU22-5835 | Presentations | CR3.4

Process and mechanisms on the occurrence of massive glacier-rock avalanches in the southeastern Tibetan Plateau under anthropogenic warming 

Wei Yang, Chuanxi Zhao, Matthew Westoby, Baosheng An, Guangjian Wu, Weicai Wang, Zhongyan Wang, Yongjie Wang, and Stuart Dunning

Catastrophic mass flows originating from the mountain cryosphere can cause widespread loss of life, destruction of property, and significant geomorphological reworking along flow paths. Based on in-situ field investigations, high-resolution satellite imagery, digital elevation models (DEMs), seismic records, and meteorological data, we present the process reconstruction, triggering mechanism, and downstream implications of a 50 Mm3 ice-rock avalanche and mass flow that originated from 6500 m asl of the Sedongpu basin in southeastern Tibet on 22 March 2021.The avalanche transformed into a highly mobile mass flow which temporarily blocked the Yarlung Tsangpo river. The avalanche flow lasted ~5 minutes and produced substantial geomorphological reworking. This event, and previous ones from the basin (a total of ~50 Mm3 on October 2017 and into 2018 occurring close to the 2021 ice-rock avalanche source region, and the detachment of the low-angle tongue of Sedongpu Glacier in two separate events with a total of ~130 Mm3 on 17/18 October and 29 October 2018), occurred concurrently with, or shortly after periods characterized by record positive air temperature anomalies, which may have contributed to instability of the mountain cryosphere. The occurrence of future large mass flows from the basin under anthropogenic warming cannot be ruled out, and their likelihood and impacts must be carefully considered given potential risks to life and implications for sustainable hydropower and associated socioeconomic development along the Brahmaputra.

How to cite: Yang, W., Zhao, C., Westoby, M., An, B., Wu, G., Wang, W., Wang, Z., Wang, Y., and Dunning, S.: Process and mechanisms on the occurrence of massive glacier-rock avalanches in the southeastern Tibetan Plateau under anthropogenic warming, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5835, https://doi.org/10.5194/egusphere-egu22-5835, 2022.

EGU22-6175 | Presentations | CR3.4

A knowledge and capacity building concept for reducing vulnerabilities from Glacier Lake Outburst Floods in Central Asia. 

Alessandro Cicoira, Simon Allen, Holger Frey, Christian Huggel, Laura Niggli, Manu Tom, Alfred Diebold, Obidjon Kodirov, Zuura Mamadalieva, Bakhtibek Otambekzoda, Zhuldyz Zhurumbetova, Gulnaz Abdaliyeva, Natalya Kim, and Kristine Tovmasyan

Central Asia is facing important challenges to coping with the adverse effects of climate change. Within the Glacier Lake Outburst Floods in Central Asia (GLOFCA) Project, funded by the Adaptation Fund (AF), UNESCO and the university of Zurich, in strong collaboration with numerous local partners, aim at reducing vulnerabilities of populations in the Central Asia region from glacier lake outburst floods. The project is divided into five components: i) strengthening capacity to monitor and assess glacier lake outburst flood (GLOF) hazard, ii) strengthening national and regional policies and approaches to address the needs of vulnerable communities, iii) designing and launching tailored early warning systems (EWS) and risk reduction measures, iv) implementing targeted demonstration projects and defining best practices, and, finally, v) facilitating knowledge exchange, stakeholder engagement, and communication. The fifth component cuts across all others, and across the full 5 year project duration, recognising capacity building as being essential to the harmonious and sustainable outcome of the project.

The core of the Knowledge and Capacity Building Concept (component five) seeks to be a well-rounded education and training programme tailored for communities, stakeholders, scientists, and universities. The essential aim of this effort is to set the basis for institutionalising the project activities, learnings and successes of the project, and ultimately enabling autonomous sustainability and scaling-up of the project by local authorities and communities. At the onset of the project, a needs assessment was undertaken via a questionnaire shared with key stakeholders. Based on results of this survey, local expectations and requirements were clearly identified. State-of-the-art methodologies will be trained, offering an insight into both licensed and open-source software to assist risk assessment and modelling. Ideally, novel methodologies will be developed and established as regional best practices. The sustainability of the capacity building outcomes is key and this is why an important focus will be dedicated to the coordination between the different stakeholders and a teach-the-teachers module. All capacity building material and project-specific output will be exchanged via a web-based knowledge platform, with information regularly communicated through classical and social media. All the activities will be organised in a blended format, using tools such as webinars, distance-learning modules, as well as in-presence classes, workshops and summer schools. Through targeted and timely interventions, the GLOFCA project will help strengthen key institutions, build community resilience, and establish the next generation of hazard and risk management specialists, with the skills needed to support sustainable disaster risk reduction in Central Asia.

How to cite: Cicoira, A., Allen, S., Frey, H., Huggel, C., Niggli, L., Tom, M., Diebold, A., Kodirov, O., Mamadalieva, Z., Otambekzoda, B., Zhurumbetova, Z., Abdaliyeva, G., Kim, N., and Tovmasyan, K.: A knowledge and capacity building concept for reducing vulnerabilities from Glacier Lake Outburst Floods in Central Asia., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6175, https://doi.org/10.5194/egusphere-egu22-6175, 2022.

High-mountain regions are very sensitive to climatic changes, which is particularly visible in the drastic retreat of Alpine glaciers. Concomitant with retreating glaciers, permafrost degradation affects large parts of high-mountain regions. In recent years, the hydrological significance of permafrost ice has therefore increasingly come into focus. However, surprisingly little is known about the current state and size of water resources in alpine permafrost. Moreover, it remains unknown whether the thawing of permafrost is already making a significant contribution to late summer runoff in alpine catchments.

In this study we combine UAV-derived volumetric change detection with the hydro-chemical analysis of δ18O and δ2H isotope signatures and the radio nuclide 129I in the discharge from the Kaiserberg rock glacier in the Austrian Alps. The combination of these methods allows a direct and indirect quantification of permafrost degradation. Furthermore, the isotopic signatures help to decipher the relative and absolute permafrost contribution to discharge over the summer months.

First results from the analysis of digital elevation models show an average volume loss of several thousand cubic metres per year between 2017 and 2019. In addition, geochemical data on δ18O- and δ2H-isotopes and the radionuclide 129I indicate an increased contribution of meltwater from the permafrost body of the Kaiserberg rock glacier in the summer months, which is dominant on single days in late summer. 

How to cite: Kraushaar, S. and Bloethe, J. H.: Towards deciphering the contribution of permafrost and active layer to summer runoff in a small alpine catchment, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7052, https://doi.org/10.5194/egusphere-egu22-7052, 2022.

EGU22-7208 | Presentations | CR3.4

Basal thermal regime investigations at Whymper hanging Glacier (Aosta Valley – Italy) 

Fabrizio Troilo, Perret Paolo, Simone Gottardelli, Luca Mondardini, Daniele Giordan, Niccolò Dematteis, Luc Piard, Olivier Gagliardini, Adrien Gilbert, and Christian Vincent

The Grandes Jorasses Massif culminates at 4203m at the Punta Walker summit on the border between France and Italy. The south slope of Grandes Jorasses is widely glaciated and overlies the Val Ferret, a populated and highly frequented area presenting different hamlets, the most important being Planpincieux village. Located at an altitude between 4000 and 4100 m, the Whymper Serac is a hanging glacier that undergoes periodic gravity-driven instabilities. On 1st June of 1998, 150.000m3 of ice fell, and the resulting ice avalanche reached 1750m, at a distance of about 400m from houses of the Le Pont village and the main road. The monitoring activity started in 1997: a  series of boreholes had been drilled to assess the basal thermal regime of the serac and subsequently install a monitoring system for early warning signs and risk assessment

In September 2020, three thermistor chains in three different boreholes were installed on Whymper Serac. Temperature profiles were measured at different periods between October and November 2020. In September 2021 another three thermistor chains were installed and their temperature profile measured in October 2021. During the same survey, temperature profiles of the 2020 thermistors could be measured again on 2 out of 3 boreholes, (one being too close to the serac front was not safe to reach) confirming data acquired on the 2020 field campaign. The outcome of basal temperature measurements of 2020 and 2021 give good spatial coverage of the serac allowing comparison with data from the 1997 measurements, despite on the fact that most of the ice mass fell in 1998.

A warming trend in most of the temperature profiles is evident in comparison whith 1997 data; 5 out of 6 points of measure still show temperatures below 0° C. One point of measure shows evidence of temperate ice at the ice/bedrock interface. Whymper Serac measurements provide evidence that the glacier is still frozen to the bedrock, but one part of the serac shows the beginning of a potential transition from cold based regime to temperate based regime. If, on one hand, surface displacements of the ice mass still show low displacements (typical of a cold based glacier), on the other hand, a velocity anomaly was detected on a small portion of the serac corresponding to the temperate based sector. Further research is needed to better understand the evolution of the thermo-mechanical conditions of the Whymper Serac in the current climate change scenarios. Therefore, thermo-mechanical modeling of the Whymper Serac is underway, based on the Elmer/Ice model.

How to cite: Troilo, F., Paolo, P., Gottardelli, S., Mondardini, L., Giordan, D., Dematteis, N., Piard, L., Gagliardini, O., Gilbert, A., and Vincent, C.: Basal thermal regime investigations at Whymper hanging Glacier (Aosta Valley – Italy), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7208, https://doi.org/10.5194/egusphere-egu22-7208, 2022.

EGU22-7327 | Presentations | CR3.4

Numerical modelling of ice avalanches from the Planpincieux glacier (Italy) 

Paolo Perret, Martin Mergili, Simone Gottardelli, Luca Mondardini, Valerio Segor, and Fabrizio Troilo

Forward simulations of ice avalanches are important to inform risk management. However, the reliability of such simulations often suffers from the dependency of model parameters on the process magnitude, hampering the simulation of unprecedented events in a given area. We suggest a reliable, straightforward and practically applicable work flow for the forward simulation of ice avalanches for the purpose of risk management with regard to the Planpincieux glacier, located on the Italian side of Mont Blanc massif.

Since 2013, the Planpincieux glacier, has been studied to analyse the dynamics of ice collapses in a temperate glacier. Several documented ice avalanches and glacial floods (1929, 1952, 1982, 2005, 2017), which, in some cases, threatened the village of Planpincieux and damaged the municipal road, have been linked to this glacier. Starting from the summer of 2019, a fast moving ice volume, partially separated by the rest of the glacier tongue by a large crevasse, has drastically increased the occurrence of a new collapse with possible implications for the valley floor. Considering the potential risk, a glacier constant monitoring (GbInSAR) and an avalanche early warning system (avalanche Doppler radar) were deployed, and numerical modelling of ice avalanches from this glacier was made.

Thereby, we couple an empirical-statistical model with a physically-based mass flow model: (I) the rules of Alean (1985) for the angle of reach are fed into the software r.randomwalk in order to estimate worst-case reference travel distances for various scenarios of starting volumes, (II) the basal friction angle used in the physically-based tool r.avaflow is optimized against those reference travel distances for each volume scenario, (III) the travel distances and travel times are checked for plausibility against well-documented events, (IV) flow pressures and flow kinetic energies are computed with r.avaflow for each volume scenario.

The model results are well supported by empirical data for smaller events, whereas direct reference data for the larger scenarios are not available. Interpretation of the results further has to take into account that (A) for some scenarios, the empirical relationships had to be extended beyond their known range of validity, introducing additional uncertainty, and (B) the relationships do not work for snow-covered trajectories, that, for example, would decrease the friction and lead to longer travel distances. As a result, the outcomes can be, with some care, considered as worst-case assumptions for ice avalanches in summer, but are not valid for ice avalanches during the other seasons.

How to cite: Perret, P., Mergili, M., Gottardelli, S., Mondardini, L., Segor, V., and Troilo, F.: Numerical modelling of ice avalanches from the Planpincieux glacier (Italy), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7327, https://doi.org/10.5194/egusphere-egu22-7327, 2022.

EGU22-7659 | Presentations | CR3.4

Glacier-permafrost interactions and GLOF’s. Insights from 7 decades of kinematics and elevation changes in the Southern French Alps. 

Diego Cusicanqui, Xavier Bodin, Antoine Rabatel, Pierre Allain Duvillard, Andre Revil, Philippe Schoeniech, and Johan Berthet

The mountain cryosphere is currently undergoing substantial modifications in an unprecedented short period of time. As effects of climate change becomes important, understanding the glacier and periglacial dynamics that lead to complex and delayed responses is timely. The spatial and functional interactions between landforms within these environments may strongly influence their processes (e.g., ablation, accumulation), usually studied in two separate research paths (i.e., glaciology and geomorphology). Very little research has focused on glacial and periglacial systems, where several perennial cryospheric elements (debris-covered glaciers, rock glaciers) are intertwined.

Here, a multidisciplinary approach is proposed combining (i) Structure from Motion on historical, modern aerial images and spaceborne images, (ii) geophysical with Electrical Resistivity Tomograms , and (iii) geomorphological surveys. The purpose is to quantify and describe morphometric changes over seven decades (1940 - 2020) at the Chauvet glacial and periglacial system (Southern French Alps, 44.85°N, 6.84°E). This study site is critical in terms of natural hazards because at least six Glacier Lake Outburst Floods were recorded during the 20th and 21th centuries, likely related to the permafrost degradation, the presence of a thermokarstic lake and an englacial conduit within the ice.

Complex spatio-temporal patterns and functional interactions between different landforms were evidenced. In the upper part of the valley, a small debris-free glacier turns downvalley into a debris-covered glacier occupying most of the central part of the valley. Further downslope, a rock glacier developed. The contrasting developments and landform responses are documented with multi-temporal DEMs and ortho-images. Very low thinning rates and surface velocities (< 0.5 m a-1) were observed on the rock glacier, whereas the adjacent debris-covered glacier presents intermediate thickness losses (> 1 m a-1) and higher surface velocities. However, the contact zone between the dead debris-covered and the rock glacier shows clear signs of mass down-wasting and complex interplay of phenomena such as thermokarst melting of massive ice and the flow towards the topographic depression.

An important speed-up of the horizontal displacements since the 1990s and an important surface lowering have most probably conditioned the dynamics of the observed outburst-floods. Those seem to be a complex combination of several processes affecting the different cryospheric elements. (i) the well-developed thermokarst lake over debris-covered area, on the topographic depression (i.e., bucket shape with barriers damming the lake) which is mainly controlled by the bedrock morphology and evolution of the surface topography. The current capacity of this depression has been estimated to 180,000 ± 350 m3. (ii) the specific glacio-geomorphological dynamics of debris-covered and the rock glacier units, which dynamics influence the opening/enlargement and closure of the englacial conduit. (iii) the hydro-meteorological conditions (e.g., enhanced snow melt in late spring) probably impacts the hydrology, water filling and the lake outflow.

The findings of this study highlight the relationships between glacial and periglacial features and their long-term evolution. The systemic study of GLOF formation processes would lead to a better identification of sites at risk and to the implementation of more robust prevention procedures in order to face the environmental and societal challenges of climate change.

How to cite: Cusicanqui, D., Bodin, X., Rabatel, A., Duvillard, P. A., Revil, A., Schoeniech, P., and Berthet, J.: Glacier-permafrost interactions and GLOF’s. Insights from 7 decades of kinematics and elevation changes in the Southern French Alps., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7659, https://doi.org/10.5194/egusphere-egu22-7659, 2022.

EGU22-7937 | Presentations | CR3.4

A risk analysis framework: Key risks from permafrost thaw in Arctic coastal areas 

Susanna Gartler, Joan Nymand Larsen, Jon Haukur Ingimundarson, Peter Schweitzer, Olga Povoroznyuk, and Alexandra Meyer

This paper presents the results from fieldwork conducted in three focal areas of the “Nunataryuk” EU H2020 permafrost project: the Nordic Area (Greenland and Svalbard), the Beaufort Sea Area in Canada (Northwest Territories/ Inuvialuit Settlement Region and Gwich’in First Nation Traditional Territory) and Northeastern Siberia in Russia. The paper analyzes the entanglement between social and environmental change and presents a risk analysis framework, including the interconnected geo-physical & socio-cultural risks, with the aim to improve adaptation and mitigation strategies of local communities. Guided by a mixed-methods approach, the research outcomes are the result of field-based research, including focus groups, qualitative interviews, participant observation, community workshops – as well as a quantitative survey in three settlements (Qeqertarsuaq in Greenland, Aklavik in Canada and Longyearbyen on Svalbard).

How to cite: Gartler, S., Larsen, J. N., Ingimundarson, J. H., Schweitzer, P., Povoroznyuk, O., and Meyer, A.: A risk analysis framework: Key risks from permafrost thaw in Arctic coastal areas, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7937, https://doi.org/10.5194/egusphere-egu22-7937, 2022.

EGU22-8571 | Presentations | CR3.4

Climate change impacts on snow avalanche risk in alpine regions 

Gregor Ortner, Michael Bründl, Chahan M. Kropf, Yves Bühler, and David N. Bresch

Various studies show that changes in the climate system, such as temperature rise and extreme precipitation events, strongly influence gravity driven hazards. Within the  research program "Climate Change Impacts on Alpine Mass Movements'', we develop a framework to model mass movement risk altered by climate and socio-economic drivers. In a first approach, we've modeled snow avalanche risk in Switzerland for the current climate situation and three avalanche hazard scenarios. For each of these scenarios we've considered different 3-day increases in snow height for avalanche formation, derived from meteorological stations. For the modelling we've applied the RAMMS::LSHIM Large Scale Hazard Indication Mapping algorithm combining the delineation of potential release areas from a high-resolution terrain model with a forest layer to depict the spatial distribution of avalanche impact for each of the chosen scenarios.
To model possible climate change effects on snow avalanche hazard, we use down-scaled data from the CH2018 climate change scenarios as input for the  model "SNOWPACK''. The so-derived changing avalanche hazard disposition is simulated with the RAMMS::LSHIM method and risks are analysed with the probabilistic, Python-based risk assessment platform CLIMADA using high resolution building layers to identify monetary assets and assign vulnerabilities. The results are spatio-temporally explicit risk maps, depicting changes of snow avalanche risks based on the combination of exposure and vulnerability information. These maps allow for the appraisal of appropriate risk management options and thereby contribute to decision support and highlight areas where adaptation measures to climate change might be needed.

How to cite: Ortner, G., Bründl, M., Kropf, C. M., Bühler, Y., and Bresch, D. N.: Climate change impacts on snow avalanche risk in alpine regions, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8571, https://doi.org/10.5194/egusphere-egu22-8571, 2022.

EGU22-9094 | Presentations | CR3.4

Where is Arctic coastal infrastructure at risk? 

Annett Bartsch, Barbara Widhalm, Georg Pointner, Clemens von Baeckmann, Ingmar Nitze, Guido Grosse, Hugues Lantuit, Anna Irrgang, Julia Boike, and Goncalo Vieira

Infrastructure and anthropogenic impacts are expanding across the Arctic. A consistent record of human impact is required in order to quantify the changes and to assess climate change impacts on the communities.
We derived a first panarctic satellite-based record of expanding infrastructure and anthropogenic impacts along all permafrost affected coasts (100 km buffer) within the H2020 project Nunataryuk based on Sentinel-1/2 satellite imagery. C-band synthetic aperture radar and multi-spectral information is combined through a machine learning framework. Depending on region, we identified up to 50% more information (human presence) than in OpenStreetMap. The combination with satellite records on vegetation change (specifically NDVI from Landsat since 2000) allowed quantification of recent expansion of infrastructure. Most of the expanded human presence occurred in Russia related predominantly to oil/gas industry.

The majority of areas with human presence in this coastal zone will be subject to thaw by mid-21st century based on ground temperature trends derived from the ESA CCI+ Permafrost time series (1997-2019). Of specific concern in this context are also settlements located directly at permafrost affected coasts. An efficient erosion rate monitoring scheme needs to be developed and combined with settlement records and permafrost information in order to assess the risk for local communities and infrastructure. Relevant progress in the framework of the ESA EO4PAC project will be discussed.

How to cite: Bartsch, A., Widhalm, B., Pointner, G., von Baeckmann, C., Nitze, I., Grosse, G., Lantuit, H., Irrgang, A., Boike, J., and Vieira, G.: Where is Arctic coastal infrastructure at risk?, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9094, https://doi.org/10.5194/egusphere-egu22-9094, 2022.

EGU22-10026 | Presentations | CR3.4

GLOF risk management experiences and options in a global context 

Laura Niggli, Simon Allen, Holger Frey, Christian Huggel, Murat Kassenov, Bolot Moldobekov, Dmitry Petrakov, Zhanar Raimbekova, John Reynolds, and Weicai Wang

Glacier lake outburst floods (GLOF) are cryospheric hazards of severe destructive potential. GLOFs are prevalent in all glacierized mountain ranges globally and can cause high economic losses and pose a threat to people and livelihoods, potentially impacting agricultural land, lives and infrastructure. This underlines the importance of effective GLOF disaster risk management (DRM). GLOF DRM experiences are reported on in mountain ranges globally. However, there are relevant gaps in their documentation, analysis, and evaluation.

This study compiled GLOF DRM experiences in South and North America, Europe, and Asia. We categorized the different structural and non-structural measures that have been taken and systematically analysed the temporal scope in which they function (i.e., short-term, long-term), as well as the risk component they influence (i.e., hazard, exposure, vulnerability). We analysed for the different DRM measures, in what context they were practiced, what their benefits were, what challenges were faced, as well looking at aspects of sustainability.

We found that the biggest share of DRM measures is based on and applied in a limited spatial context often aiming at the reduction of a physical hazard emerging from a specific glacial lake. Examples of such activities are syphoning and pumping of lakes, drainage channels (with/out sluice gates) and tunnels for lake level regulation, flow channel adaptation, dam reinforcement, etc. Such measures, while generally taken once and aimed at short-term fixes (e.g., lake level lowering by pumping) as well as at long-term fixes (definitive lake level lowering by outflow tunnel), can face issues of sustainability. This can be the case for structural measures, for instance, when structures become unfit due to environmental changes (e.g., climate-related, earthquakes). While there are short-term as well as long-term measures in all three risk management components (hazard, exposure, vulnerability), there is a tendency for hazard reduction measures to be more short-term focused, and for exposure reduction (e.g., early warning systems, spatial planning, relocation, etc.) and vulnerability reduction (e.g., information, governance, preparedness, economic diversification, disaster relief, etc.) to be more mid- and long-term focused. Different challenges were found for all examined DRM measures mostly arising from issues in the technical feasibility (due to harsh climatic and environmental settings), the financial cost (of deploying people and material, and maintaining structures), and social acceptance and appropriation.

While the findings from this study should not be generalized and strictly imposed on all other GLOF DRM cases, the knowledge gained by it is urgently needed to develop recommendations for GLOF DRM based on best practice experiences. GLOF DRM will become increasingly important in warming and increasingly exposed mountain environments globally. It will, thus, be important to further investigate the cost and benefit as well as the effectiveness of different DRM strategies. For sustainable DRM it is important to not look at GLOF hazard in isolation, but to take into account also other physical hazards in the same catchment.It should be considered within the wider context of integrated multi-hazard assessment in order to appropriately tackle/approach the interrelated effects of events that may occur simultaneously, cascadingly or cumulatively.

How to cite: Niggli, L., Allen, S., Frey, H., Huggel, C., Kassenov, M., Moldobekov, B., Petrakov, D., Raimbekova, Z., Reynolds, J., and Wang, W.: GLOF risk management experiences and options in a global context, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10026, https://doi.org/10.5194/egusphere-egu22-10026, 2022.

EGU22-10234 | Presentations | CR3.4

Glacier and permafrost hazard and risk management: from science to policy and implementation 

Holger Frey, Simon Allen, Christian Huggel, and Divya Kashyap Sharma

Glacier and permafrost hazards in cold mountain regions encompass various flood and mass movement processes that are strongly affected by climate change. Rising temperatures cause glacier retreat, permafrost thawing and degradation, with underground warming continuously propagating at greater depths. These cumulative changes, happening at different time scales, generally exacerbate slope stability and increase the probability for destructive mass movement events. Outbursts of glacial lakes, which are newly forming and growing with glacier retreat, are destructive processes with potential reaches of several hundreds of kilometers. These events often involve chains of cascading and interacting mass movement processes, threating mountain communities which are typically highly vulnerable, but also putting at risk critical infrastructure such as roads, buildings, agricultural land and hydropower installations.

Here we present a series of research and cooperation projects, funded by the Global Programme Climate Change and Environment of the Swiss Agency for Development and Cooperation (SDC). These projects supported the development of guidelines for hazard assessment, contributed substantially to the elaboration of risk management guidelines for Glacial Lake Outburst Floods (GLOFs) for India, and eventually led to supporting the design and implementation of a GLOF Early Warning System (EWS) in Sikkim, India.

From 2016 to 2017, a large consortium of international experts from the Standing Group on Glacier and Permafrost Hazards (GAPHAZ) of the International Association of Cryospheric Sciences and International Permafrost Association (IACS/IPA), elaborated a technical guidance document on the assessment of glacier and permafrost hazards in mountain regions. This guidance document reflects the current state-of-the-art of future oriented, scenario based hazard assessment and mapping, supported by physically based, numerical models. Building on that, scientists involved in the elaboration of this document have been invited as international experts in the elaboration of Guidelines for the Management of Glacial Lake Outburst Floods for India, led by the National Disaster Management Authority (NDMA) of the Indian Government. This document builds on the concepts in the GAPHAZ guidelines, but beyond hazard assessment includes also relevant aspects of risk management and DRR, while being specifically tailored to the situation of Indian Himalayan States. Currently efforts are ongoing to implement a multi-lake EWS in the Teesta River Basin in Sikkim, India with the support of NDMA. This project, which also involves the government of Sikkim, local stakeholders, Swiss universities and companies and SDC, is considered by NDMA as a pilot study for the implementation of the new GLOF management guidelines described above.

These continued long-term efforts provide invaluable learnings on collaborative scientific efforts, transdisciplinary work at the science-policy interface, and joint efforts of the academia, public and private sector towards real world applications of disaster risk management under challenging conditions.

How to cite: Frey, H., Allen, S., Huggel, C., and Kashyap Sharma, D.: Glacier and permafrost hazard and risk management: from science to policy and implementation, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10234, https://doi.org/10.5194/egusphere-egu22-10234, 2022.

EGU22-172 | Presentations | HS2.1.5 | Highlight

Aufeis impact on the hydrological cycle in the North-Eastern Russia 

Nataliia Nesterova, Olga Makarieva, Andrey Ostashov, Anastasiya Zemlianskova, Andrey Shikhov, and Vladimir Alexeev

Aufeis are produced annually in the rivers valleys in permafrost environment as the result of layer-by-layer freezing of groundwater flowing to the surface. Aufeis are widespread in the territory of the North-East of Eurasia (including the basins of large rivers in permafrost, such as the Yana, Indigirka, Kolyma, Anadyr, Penzhina Rivers and rivers of the Chukchi Peninsula (total area about 2 mln. km2).  They comprise an important water resource of the study region.

Based on the analysis of Landsat satellite images for the period 2013-2019 the number and total maximum area were estimated. As Landsat images do not always allow correctly assess the maximum area of aufeis, it was adjusted to get the maximum value before the beginning of ablation period for the assessment of aufeis resources. Total number of giant aufeis (>0.1 km2) formed by groundwater reaches 6217 with maximum area of about 4500 km2 (in average 0.22 % of studied area). For each aufeis field the assessment of maximum ice reserves was conducted.  

The aufeis resources of the North-East are at least 10.6 km3 or 5 mm of aufeis runoff. The aufeis resources vary from 0.4 to 4.25 km3 (or 3.7 – 11 mm) for individual basins of large rivers. The greatest aufeis resources in absolute values are found in the Indigirka River basin. The contribution of aufeis runoff to streamflow in different seasons was calculated for 58 hydrological gauges (area 523 – 526000 km2). Aufeis annual runoff varies from 0.3 to 29 mm (0.1 – 22%, average 3.8%) with the share in winter runoff amount about 6 – 712 % (average 112%) and the spring freshet 0.2 – 43% (average 7.1%).

The influence of aufeis and glaciers on the water balance is compared – in general, the aufeis runoff exceeds the glacial runoff. The response of aufeis to climate change depends on different factors of the natural system. The dynamics of aufeis formation is directly related to the winter runoff, which changes are observed in different parts of the cryolithozone. The presented results are relevant for studying the impact of climate change on the hydrological cycle and its components in the permafrost regions of the Northern Hemisphere.

The study was carried out with the support of RFBR (19-55-80028, 20-05-00666) and St. Petersburg State University (project 75295879).

How to cite: Nesterova, N., Makarieva, O., Ostashov, A., Zemlianskova, A., Shikhov, A., and Alexeev, V.: Aufeis impact on the hydrological cycle in the North-Eastern Russia, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-172, https://doi.org/10.5194/egusphere-egu22-172, 2022.

EGU22-528 | Presentations | HS2.1.5

S3M Italy: a real-time, open-source cryospheric-forecasting chain for applications on a large scale 

Francesco Avanzi, Simone Gabellani, Fabio Delogu, Francesco Silvestro, Silvia Puca, Alexander Toniazzo, Pietro Giordano, Marco Falzacappa, Sara Ratto, Hervè Stevenin, Antonio Cardillo, Edoardo Cremonese, and Umberto Morra di Cella

Monitoring the state of the cryosphere in real time is a key to improved risk and water resources management, especially in a warming climate. All around the world, this goal is achieved through forecasting chains combining models with in-situ and remote-sensing measurements. Here, we discuss lessons learned while developing S3M Italy, one such chain delivering hourly estimates of snow water equivalent, density, snow and glacier melt, and bulk liquid water content across the Italian territory (300k+ km2, 200 m resolution1.5 hour turnaround). S3M Italy includes downloaders to ingest input data from automatic weather stations, spatialization tools to convert these data into weather-input maps, blending routines for deriving daily snow-covered-area maps from ESA Sentinel 2, NASA MODIS, and EUMETSAT H-SAF products, mapping algorithms based on multilinear regressions for assimilating on-the-ground snow-depth data, as well as algorithms to manage parallelized runs and then mosaic model outputs. S3M Italy has been developed to support decisions by the Italian Civil Protection Agency and is fully open source, not only in terms of underlying models (https://github.com/c-hydro/s3m-dev), but also in terms of all pre-processing routines (https://github.com/c-hydro/fp-hydehttps://github.com/c-hydro/fp-s3m). 

How to cite: Avanzi, F., Gabellani, S., Delogu, F., Silvestro, F., Puca, S., Toniazzo, A., Giordano, P., Falzacappa, M., Ratto, S., Stevenin, H., Cardillo, A., Cremonese, E., and Morra di Cella, U.: S3M Italy: a real-time, open-source cryospheric-forecasting chain for applications on a large scale, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-528, https://doi.org/10.5194/egusphere-egu22-528, 2022.

EGU22-859 | Presentations | HS2.1.5

On the identification of hydrogeological reservoirs in a proglacial catchment and their future groundwater storage 

Tom Müller, Bettina Schaefli, and Stuart N. Lane

Rapid glacier retreat leads to the emergence of new rocky landscapes. The common assumption of the presence of bare bedrock underlying glaciers and the closely related assumption that glacier and snow melt manifest themselves essentially as surface runoff, is challenged by the rapid sediment accumulation and the formation of geomorphological landforms where water may be infiltrated and stored. Although some studies have provided rough estimates of groundwater storage and release in high elevation catchments, the actual reservoirs providing baseflow discharge are difficult to identify. While the combined effect of future glacier decline and earlier snowmelt are well recognized, it remains unclear how the rapid hydrogeomorphological transformations will modify the potential groundwater stores.

In this study we will provide results of a case study of a glaciated catchment in the Swiss Alps. Firstly, we will discuss, based on a simple modelling approach, the hydrological functioning of different landforms and show to which extend each hydrological unit is currently contributing to groundwater storage. We will then focus on a detailed assessment of the hydrological dynamics of an outwash plain using a 3D Modflow modelling approach. We will show how such a small fluvial aquifer is connected to other landforms and how it can maintain high storage during much longer time scales than other landforms due to strong river-groundwater interactions. Even though the current storage of the outwash plain is limited, we will discuss how glacier retreat may increase its relative contribution in the future. Finally, we will focus on the remaining unidentified storages in our field study and we will provide some geochemical analysis of their potential location and finally conclude with a summary of the hydrogeological functioning of a rapidly deglaciating proglacial catchment.

How to cite: Müller, T., Schaefli, B., and Lane, S. N.: On the identification of hydrogeological reservoirs in a proglacial catchment and their future groundwater storage, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-859, https://doi.org/10.5194/egusphere-egu22-859, 2022.

EGU22-1106 | Presentations | HS2.1.5 | Highlight

Future hydrology of the cryospheric driven Lake Como catchment in Italy under climate change scenarios 

Fuso Flavia, Casale Francesca, Giudici Federico, and Bocchiola Daniele

In this paper we analyse the future hydrology of the Lake Como catchment under climate change scenarios. The management of the lake is extremely important because it is needed both to supply water for the irrigation demand of the Po Valley, and to prevent flood risk along the lake shores. The climate variations are affecting the lake operation with negative impacts both on agriculture and hydropower production. The lake dynamics are link to the cryospheric driven upstream basin, and so the use of a model able to assess the water input as related to snow cover processes is a key issue. Accordingly, we use the physically based hydrological model Poli-hydro able to represent the most important process in the cryospheric driven catchment. We set up and calibrated the model against lake inflows during 2002-2018, resulting in a mean error Bias = +2.15%, and a monthly/daily Nash-Sutcliff efficiency, NSE = 0.77/0.64. We then performed a stochastic disaggregation of 3 Global Circulation Models (GCMs) of the most recent Assessment report 6 (AR6) of the IPCC, under 4 different socio-economic pathways (SSPs), from which we derived daily series of rainfall and temperature to be used as inputs for the hydrological model Poli-Hydro. The climate projections show a potential increase of temperature at the end of the century between +0.61°C and +5.96°C, which would lead to a decrease of the total ice volume in the catchment of -50% and -77%, respectively. Future projections show generally an increase of discharge in autumn and winter (November-March) and a reduction in spring and summer (May-September). This is due to the increase of temperature with an increase of liquid precipitation instead of solid precipitation in winter and an anticipation of the snow melt peak at the beginning of spring. Possible consequences are the increase of flood hazard in the winter period and a scarcity of water availability in summer. A new regulation of Lake Como is essential to satisfy stakeholders requests.

How to cite: Flavia, F., Francesca, C., Federico, G., and Daniele, B.: Future hydrology of the cryospheric driven Lake Como catchment in Italy under climate change scenarios, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1106, https://doi.org/10.5194/egusphere-egu22-1106, 2022.

EGU22-1338 | Presentations | HS2.1.5

Evaluating the hydrological regime of the snow-fed and glaciated Hunza basin in the Hindukush Karakorum Himalaya (HKH) region 

Aftab Nazeer, Shreedhar Maskey, Thomas Skaugen, and Michael E. McClain

In the high altitude Hindukush Karakorum Himalaya (HKH) mountainous region, the complex weather and terrain and sparse measurements make the precipitation distribution and hydrological regime significant unknowns. Recent advances in remote-sensing and reanalysis-based global precipitation products and numerical models may provide more insights on the hydro-climatic regimes for such regions. This study examined the precipitation distribution and snow and glacier melt contributions to river flow in the highly glaciated and snow-fed Hunza basin of the Karakorum mountains. The Distance Distribution Dynamics (DDD), a rainfall-runoff model with its temperature index and an energy balance approach for glacial melt, was used. The model was forced with precipitation estimates based on a newly developed and fine resolution (0.1°×0.1°) gridded product of ERA5-Land. The model calibration and validation were performed from 1997–2005 and 2006–2010, respectively. The mean annual precipitation of the Hunza basin was estimated as 947 mm from 1997–2010. The precipitation distribution analysis showed more precipitation at lower elevations than at higher. The simulated snow cover area (SCA) was in good agreement with MODIS satellite-based SCA. The flow analysis indicated that the Hunza’s flow is strongly controlled by glacier melt (44–47 %) followed by snowmelt (31–32 %) and rainfall (22–23 %). The simulations showed that the DDD model has good potential to simulate hydrological processes satisfactorily for data-scarce basins.

How to cite: Nazeer, A., Maskey, S., Skaugen, T., and E. McClain, M.: Evaluating the hydrological regime of the snow-fed and glaciated Hunza basin in the Hindukush Karakorum Himalaya (HKH) region, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1338, https://doi.org/10.5194/egusphere-egu22-1338, 2022.

EGU22-2690 | Presentations | HS2.1.5

Changes in glacier and snow melt contributions to streamflow in James Ross Island, Antarctic Peninsula 

Michal Jenicek, Ondrej Nedelcev, and Jan Kavan

Antarctica has been significantly warming in the last decades. According to climate projections, the increase in air temperature is likely to continue in the future, which will affect runoff dynamics due to glacier retreat and changes in snow cover. Despite the large changes in glacier volume in some parts of Antarctica, little is known about streamflow dynamics and contribution of different water sources to total catchment runoff. Therefore, the objective of our research was to 1) describe runoff dynamics in six catchments located in the Ulu Peninsula, James Ross Island, which represents one of the largest deglaciated areas in Antarctica and 2) to assess the inter-annual variations in glacier melt, snowmelt and potentially rain contributions to runoff over the years 2015 – 2021. The study catchments have different glaciation, and thus considerable diurnal regime of streamflow. Streamflow measurements performed in 2018 austral summer were used to describe the streamflow dynamics of the six catchments. Additionally, a conceptual bucket-type catchment model has been set-up for two of the six catchments, first partly glacierized and second without glacier coverage. In-situ measurements of glacier ablations (2015–2019) and daily precipitation and air temperature partly measured directly at automatic weather stations located in the catchments and partly derived from ERA5-land reanalysis were used as model inputs. Since water level and streamflow data are limited for the study area, a genetic algorithm procedure was used to calibrate the model.

Direct streamflow measurements performed in 2018 austral summer showed the largest variations in Triangular and Shark Streams, which represent the most glaciated catchments among all study catchments. The less variable streamflow was found in Algal Stream, a completely deglaciated catchment. Highest streamflow was recorded in late afternoon, whereas minimum streamflow was recorded in late night or early morning which suggests the strong diurnal regime. In glacierized catchments, the streamflow responded fast on increased air temperature and solar radiation during day. In contrast, soil water stored in the active layer and snow patches mostly controlled streamflow dynamics in deglaciated catchments. Besides, the runoff response was somewhat delayed in these catchments compared to glaciated catchments due to temporal subsurface storage. The above findings were proved also by model simulations, which extended streamflow data for the period 2015-2021. Besides, the simulations showed different glacier and snow contributions to total runoff in study catchments and also different times of streamflow responses to changes in meteorological inputs in combination with different catchment storages which influence runoff delays.

How to cite: Jenicek, M., Nedelcev, O., and Kavan, J.: Changes in glacier and snow melt contributions to streamflow in James Ross Island, Antarctic Peninsula, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2690, https://doi.org/10.5194/egusphere-egu22-2690, 2022.

EGU22-2805 | Presentations | HS2.1.5

Assessment of streamflow trends in snow and glacier melt dominated catchments of SW Spitsbergen 

Marzena Osuch, Tomasz Wawrzyniak, and Elżbieta Łepkowska

The study focuses on the changes in the regime of the four High Arctic catchments in the last 40 years taking into account different percentages of glacial coverage. The selected catchments include Breelva, Ariebekken, Bratteggbekken and Fuglebekken with glacial coverage of 61%, 11.8%, 5.9% and 0% respectively.

The flow time series in the selected catchments were simulated using a glacio-hydrological model calibrated and validated based on the available archival hydro-meteorological data.

In the second step, the reconstructed flows from the period 1979-2020 were filtered and smoothed. This allowed for delineation of the seasonal pattern by filtering out small scale variability. The changes in flow regime were assessed with trend analysis for each calendar day.

Similar trends of change were detected in all studied catchments due to similar locations in the SW Spitsbergen and climatic conditions. These changes include the earlier onset of snowmelt driven floods, large increases in autumn flows, prolongation of the hydrologically active season (starts earlier and lasts longer), decrease in flows in the latter half of June and the early part of August (except for the Breelva catchment). These changes resulted in the changes of flood regime from snowmelt-dominated to the bi-modal with peaks in both July/August and September.

A comparison of the changes between the four catchments indicated differences in the magnitude of hydrological response depending on the percentage of glacial coverage in the catchments. The larger the glacierized area is, the larger the changes in the flow regime. The estimated changes are larger than observed in lower latitudes due to larger changes in climatic conditions.

How to cite: Osuch, M., Wawrzyniak, T., and Łepkowska, E.: Assessment of streamflow trends in snow and glacier melt dominated catchments of SW Spitsbergen, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2805, https://doi.org/10.5194/egusphere-egu22-2805, 2022.

EGU22-3798 | Presentations | HS2.1.5

Water Towers of the Pamirs: I. Precipitation and temperature trends 

Zulfiqor Khojazoda, Roy Sidle, and Arnaud Caiserman

Precipitation and temperature changes across the Vakhsh and Panj basins are of great importance for Tajikistan, Afghanistan, Turkmenistan, and Uzbekistan for consumption, agricultural, and energy purposes. While studies of precipitation and temperature trends have been conducted in these basins, attention to their heterogenous topography and nature have not been considered and analyzed together with glacial and permafrost melt. Here, we assessed the trends of precipitation and temperature over the last 20 years using remote sensing products. For precipitation, we used research grade daily GPM IMERG V06 Final Run from 2001 to 2020. Similarly, temperature MODIS Land Surface Temperature & Emissivity (LST&E) (MOD11A1) was used to assess temperature trends and separate liquid from solid precipitation. Annual precipitation and temperature trends were also assessed in three elevation bands: low (317-2225m), middle (2225-4500m) and high (4500-7543m).

Positive significant trends for solid precipitation mainly arise in the northern parts of the basins, while slightly positive with more negative trends occurred over the central and southern parts of the Panj basin. A significant solid precipitation trend of +1.30mm y-1 below 2225 m a.s.l. occurred in late spring. Many of the pixels (1 x 1 km) across the study region that exhibited significant trends were increases in temperature, especially in the high elevations in the eastern portion of the basins. There was a significant annual increase of liquid precipitation coupled with a decrease in solid precipitation and an increase in temperature trend in the central Pamirs, implying a shift from solid to liquid precipitation. An increase in rainfall below 4500 m a.s.l. was observed, where the largest increases occurred in the western portions of these basins with nearly no significant temperature trends; thus, potentially having a positive influence on agricultural and community water supplies. However, long-term water supplies in the dry regions of the central and eastern parts of the basins may create supply vulnerabilities.

How to cite: Khojazoda, Z., Sidle, R., and Caiserman, A.: Water Towers of the Pamirs: I. Precipitation and temperature trends, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3798, https://doi.org/10.5194/egusphere-egu22-3798, 2022.

EGU22-4005 | Presentations | HS2.1.5

The surprising weather conditions favoring artificial ice reservoirs (Icestupas) 

Suryanarayanan Balasubramanian, Martin Hoelzle, Michael Lehning, Jordi Bolibar, Sonam Wangchuk, Johannes Oerlemans, and Felix Keller

Since 2014, mountain communities in Ladakh, India have been constructing dozens of ArtificialIce Reservoirs (AIRs) by spraying water through fountain systems every winter. The meltwater from these structures is crucial to meet irrigation water demands during spring. However, there is a large variability associated with this water supply due to the local weather influences at the chosen location. This study compared the ice volume evolution of an AIR built in Ladakh, India with two others built in Guttannen, Switzerland using a surface energy balance model. Model input consisted of meteorological data in conjunction with fountain discharge rate (mass input of an AIR). Validation with drone’s ice volume observations shows the model performs well. Our results show that the conical shape of AIRs significantly reduce solar radiation-induced melt. The location in Ladakh had a maximum ice volume four times larger compared to the Guttannen site. However, the corresponding water losses for all the AIRs were more than three-quarters of the total fountain discharge due to high fountain wastewater. Drier and colder locations in relatively cloud-free regions are expected to produce long-lasting AIRs with higher maximum ice volumes. This is a promising result for dry mountain regions, where AIR technology could provide a relatively affordable and sustainable strategy to mitigate climate change induced water stress.

 

How to cite: Balasubramanian, S., Hoelzle, M., Lehning, M., Bolibar, J., Wangchuk, S., Oerlemans, J., and Keller, F.: The surprising weather conditions favoring artificial ice reservoirs (Icestupas), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4005, https://doi.org/10.5194/egusphere-egu22-4005, 2022.

EGU22-4317 | Presentations | HS2.1.5

Glacier runoff variation since 1981 in the upper Naryn river catchments, Central Tien Shan 

Tomas Saks, Eric Pohl, Horst Machguth, Amaury Dehecq, Martina Barandun, Ruslan Kenzhebaev, Olga Kalashnikova, and Martin Hoelzle

Water resources in Central Asia strongly depend on glaciers, which in turn adjust their size in response to climate variations. We investigate glacier runoff in the period 1981–2019 in the upper Naryn basin, Kyrgyzstan. The basins contain more than 1000 glaciers, which cover a total area of 776 km2. We model the mass balance and runoff contribution of all glaciers with a simplified energy balance melt model and distributed accumulation model driven by ERA5 LAND re-analysis data for the time period of 1981 - 2019. The results are evaluated against discharge records, satellite-derived snow cover, stake readings from individual glaciers, and geodetic mass balances. Modelled glacier volume decreased by approximately 6.7 km3 or 14%, and the majority of the mass loss took place from 1996 until 2019. The decreasing trend is the result of increasingly negative summer mass balances whereas winter mass balances show no substantial trend. Analysis of the discharge data suggests an increasing runoff for the past two decades, which is, however only partly reflected in an increase of glacier melt. Moreover, the strongest increase in discharge is observed in winter, suggesting either a prolonged melting period and/or increased groundwater discharge. The average runoff from the glacierized areas in summer months (June to August) constitutes approximately 23% of the total contributions to the basin's runoff. The results highlight the strong regional variability in glacier-climate interactions in Central Asia.

How to cite: Saks, T., Pohl, E., Machguth, H., Dehecq, A., Barandun, M., Kenzhebaev, R., Kalashnikova, O., and Hoelzle, M.: Glacier runoff variation since 1981 in the upper Naryn river catchments, Central Tien Shan, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4317, https://doi.org/10.5194/egusphere-egu22-4317, 2022.

EGU22-4705 | Presentations | HS2.1.5

Water Towers of the Pamirs: II. Cryosphere dynamics and implications for runoff and livelihoods 

Roy C Sidle, Arnaud Caiserman, Álvaro Salazar, and Zulfiqor T Khojazoda

Cryosphere components in the Pamirs play an important role in the release of water to the Vakhsh and Panj river systems where both mountain and downstream communities rely on sustainable water supplies for their agriculture, potable water, and hydropower. Of the three primary cryosphere sources of water (glacial, snow, and permafrost melt), glacial melt is the most predictable and constitutes and intermediate supply of runoff to streams, while almost no estimates of permafrost contributions are available. Snowmelt is highly variable from year to year and because it is the largest water supply to these rivers, understanding the potential amount and timing of snowmelt is critical for local communities.  

Based on our remote sensing investigations during the past 20 years, we water found wide interannual variations in snow water, snowline elevation, and snow persistence throughout the Vakhsh and Paji basins, but no clear evidence of basin-wide climate change trends. Specific locations of the central Pamirs appear to be shifting from snow to rain due to climate warming, approximately offsetting each other, but likely producing more runoff in late spring to early summer and less in mid to late summer. In the high, glaciated Vakhsh basin, temperature increases have been offset by higher snowfall, resulting in little glacial ice change. By overlaying maps of glaciers on a digital elevation model (Alos Palsar 12.5 m) containing stream networks, we estimated that about 75% of the glaciers were closely connected to first-order or larger channels; however, this may be a liberal estimate because some first-order streams are not connected to major river systems. Based on the TTOP model nearly 24,000 km2 of continuous permafrost terrain exists throughout the Panj and Vakhsh basins, the majority of which is located at elevations > 3577 m. Streamflow contributions from permafrost thaw during the summer were estimated as subsurface flux from streambanks; ≈ 638 x 106 m3 each summer, which represents about 1.5% of the average annual river discharge for both basins.

The climate variability and localized changes we observed pose challenges for predicting runoff from high elevation cold regions due to the altered patterns of the timing of snow, glacier, and permafrost accumulation and melt, including temporal changes, interannual variability, and hydrological connectivity of sources. The various water sources will respond differently in a changing climate, generating complex runoff scenarios and socioeconomic consequences downstream.

How to cite: Sidle, R. C., Caiserman, A., Salazar, Á., and Khojazoda, Z. T.: Water Towers of the Pamirs: II. Cryosphere dynamics and implications for runoff and livelihoods, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4705, https://doi.org/10.5194/egusphere-egu22-4705, 2022.

EGU22-6025 | Presentations | HS2.1.5

Integrating glacier flow in hydrological modelling for water resources management 

Andrea Momblanch, Tejal Shirsat, Anil Kulkarni, and Ian P Holman

The climate emergency will drive changes in the cryosphere and hydrology of high mountain catchments, with subsequent influences on water resources availability. Process-based hydrological and glaciological models require significant amounts of data which are often unavailable in high mountainous catchments, especially in developing countries, and are unable to explicitly integrate human-induced factors on river flows (Momblanch et al. 2019). This can be overcome by water resources systems models that take a more conceptual approach. However, they currently have limited capability to represent glacier evolution and thus river discharge dynamics, especially in long-term simulations required for climate change impact and adaptation analysis. There is, therefore, a clear need for improved representation of the spatio-temporal response of glaciers within water resources systems models to support the strategic water resources planning and management and ensure future water security.

The Water and Evaluation and Planning system (WEAP; Yates et al. 2005) is widely used in water resources management studies by both the scientific and decision-making communities around the world. WEAP includes a glacier module which accounts for ice accumulation and melt using the enhanced temperature-index method, but overlooks other processes such as glacier area change, snow redistribution, sublimation and ice flow. These omissions will severely impact the validity and utility of long-term simulations, especially in regions with very rough topography such as the Himalayas.

This research reports the development and application of an enhanced glacier modelling capability in the WEAP software that introduces ice flow dynamics. Through the integration of elevation bands and remote sensing-derived glacier velocities, a ‘plug-in’ extension into WEAP’s Application Programming Interface allows glacier routing to be represented. The Aleo catchment in the upper reaches of the Indus basin in the Western Himalayas is used as a case study to showcase the ‘plug-in’ and to compare outputs with other process-based models. The results show that the enhanced glacier model significantly improves the simulation of the main glacier variables, i.e. mass balance, depth and volume, with respect to the original glacier model in WEAP. The research outputs contribute to a better understanding of climate change impacts on high mountain hydrology, which is key for regional development.

 

References

Momblanch, A., Holman, I., Jain, S., 2019. Current Practice and Recommendations for Modelling Global Change Impacts on Water Resource in the Himalayas. Water 11, 1303. doi:10.3390/w11061303

Yates, D., Purkey, D., Sieber, J., Huber-Lee, A., Galbraith, H., 2005. WEAP21—A Demand-, Priority-, and Preference-Driven Water Planning Model. Water Int. 30, 501–512. doi:10.1080/02508060508691894

How to cite: Momblanch, A., Shirsat, T., Kulkarni, A., and Holman, I. P.: Integrating glacier flow in hydrological modelling for water resources management, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6025, https://doi.org/10.5194/egusphere-egu22-6025, 2022.

EGU22-6871 | Presentations | HS2.1.5

Dissecting the subseasonal and altitudinal water balance of a high-elevation Himalayan catchment using a land surface model 

Pascal Buri, Simone Fatichi, Thomas E. Shaw, Evan S. Miles, Michael McCarthy, Catriona Fyffe, Stefan Fugger, Shaoting Ren, Marin Kneib, Koji Fujita, and Francesca Pellicciotti

The snow and glacier reservoirs of High Mountain Asia play a key role in sustaining water supply to mountain communities and downstream ecosystems, populations and economic activities. However, little is known about how rain, snow- and ice melt vary sub-seasonally and along the altitudinal gradient in high-elevation watersheds.

We generate detailed simulations of catchment hydrology using a land surface model that constrains energy and mass fluxes using advanced physical representations of both cryospheric and biospheric processes in high detail at 100 m spatial resolution. We use the model to study how snow and glacier processes affect the hydrological cycle and how vegetation can mediate water yield from the high mountains of a glacierized Himalayan catchment downstream. This bridges the modelling gap between snow- and glacier dynamics, which generate the runoff, and vegetation processes, which interfere with runoff production and water uses at lower elevations.

We study the upper Langtang catchment (~4000-7000 m a.s.l.) in the Nepalese Himalayas, and simulate catchment runoff for two hydrological years (2017-2019), revealing the relative importance of precipitation, snow, ice, soil moisture and vegetation for different elevations and seasons. The land surface model is forced with hourly meteorological input data based on the main weather station in the basin and air temperature and precipitation were spatially distributed using observed elevational gradients. 

We calibrate a minimal set of parameters (physical properties of supraglacial debris) and use integrative variables such as catchment runoff or glacier mass balance only for validation. The availability of a rich dataset of field- and remote sensing observations allows validation of numerous physical processes simulated by the model and drastically reduces the probability of internal error compensation.

The model provides detailed insights into the importance of each of the energy and mass balance components in the catchment water budget and shows that evaporative fluxes are non-negligible contributors to mass loss at very high elevations (especially from snow) and in the lower part of the catchment (transpiration from vegetation). Often neglected or derived as a bulk quantity in simpler model approaches, evaporation accounts for about 15% of the water leaving the basin. We show precipitation to be the major source of uncertainty in the simulations and that vegetation is relevant in determining the amount of runoff transferred further downstream even for high elevation, extensively glacierized Himalayan catchments.

How to cite: Buri, P., Fatichi, S., Shaw, T. E., Miles, E. S., McCarthy, M., Fyffe, C., Fugger, S., Ren, S., Kneib, M., Fujita, K., and Pellicciotti, F.: Dissecting the subseasonal and altitudinal water balance of a high-elevation Himalayan catchment using a land surface model, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6871, https://doi.org/10.5194/egusphere-egu22-6871, 2022.

EGU22-7605 | Presentations | HS2.1.5 | Highlight

Future effects of glacier retreat on downstream runoff and hydropower generation in the Alps 

Mario Wallner, Jakob Abermann, Gabriel Bachner, Elisabeth Frei, Wolfgang Schöner, and Karl Steininger

Due to climate change, glaciers are retreating worldwide. Among different consequences, the decline of meltwater in rivers will lead to a reduction in runoff. The aim of this work is to quantify the changes in runoff and the impact on selected hydropower plants in different drainage basins in the Alps until 2100.

Outputs from the Global Glacier Evolution Model (GloGEM), which uses 14 General Circulation Models to compute the future evolution of the glaciers worldwide, were used to determine past and future runoff from glaciers individual hydropower plants’ catchments. Measured runoff data at selected locations along rivers was used to compute the share of glacier runoff in total discharge. The computed river runoff was subsequently applied to determine the reduced electricity production of the hydropower plants.

The results reveal a decrease in summer runoff at all investigated power plants by 2100. However, large differences occur among the different catchments. In particular, geographical characteristics, such as glacier size and altitude, determine the intensity and timing of the decline. Areas located further away from glaciers, particularly in the North of the Eastern Alps, show the strongest reduction in glacier runoff (up to 86% compared to 1986-2015). In contrast, mountainous catchments and the South of the Alps are mostly affected by a decrease in river discharge (up to 33% compared to 1986-2015). Due to the dry summer climate, the summer runoff in these areas is reliant on the glacier discharge. This is also evident in the impact on hydropower production. For the run-of-river plants along the Rhone, one has to expect a decrease in summer production of up to 20%, which corresponds to an annual loss of € 5.3 Million. The losses are even higher for storage power plants located in catchments with a big glacier cover. For these, annual losses of up to € 35.0 Million were determined for the period 2071-2100.

How to cite: Wallner, M., Abermann, J., Bachner, G., Frei, E., Schöner, W., and Steininger, K.: Future effects of glacier retreat on downstream runoff and hydropower generation in the Alps, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7605, https://doi.org/10.5194/egusphere-egu22-7605, 2022.

EGU22-7894 | Presentations | HS2.1.5

Snow/rain source mixing and residence time modeling in a sub-alpine mountainous catchment under global warming 

Aniket Gupta, Didier Voisin, and Jean-Martial Cohard

Mountain catchments behavior is largely governed by snow accumulation and melting regime. These intricate water fluxes sustain the streamflow response for several months and maintain the surface moisture until late summer. The melting snow slowly percolates to the subsurface recharging underground reservoirs which later sustain the ecosystem during the dry periods. During the summer periods in mountainous catchment the rain contributes more to the surface runoff because of steep slopes. In this study, we hypothesise that middle elevation mountain catchments under a warming climate will shift from a snow hydrological recharging behavior to a flash flood behavior. We used ParFLOW-CLM, a fully distributed physical based surface-subsurface coupled integrated hydrological model to show how much water budget partitioning will change on a small subalpine mid-elevation (2000-2200 m) catchment at col du Lautaret (France). With a 10 m hyper-resolution setup, ParFLOW-CLM helps us to distinguish between the Hortonian and Dunian runoff along with the velocity of water movement in the x-y-z direction. Further, we applied a Lagrangian particle tracking model, EcoSLIM, to track the location, movement and residence time of the snow and rain sources. After running the model for the present climate we selected CMIP6 climate model projections that lead to temperature rise from 1 °C to 2.5 °C. The present climate results show that the snowmelt contributes to 90 % of subsurface source particles compared to rain and has a higher residence time in the catchment. These snow particles along with sustaining the streamflow also help in providing water to plants and evapotranspiration during the dry periods. Under warmer climates, the snow to rain ratio decrease leads to more surface runoff and less recharge to the subsurface. The decrease in subsurface recharge leads to reduced surface moisture in the dry season, which directly impacts the evaporation and transpiration through the vegetation. Hence, the rapid global warming leads to a decrease in the snow and subsurface storage which may impact downstream communities in terms of water availability, and at the same time, decrease water availability for the mountain vegetation through reduced surface moisture. In conjunction, the overall mountain ecosystem gets adversely impacted.

How to cite: Gupta, A., Voisin, D., and Cohard, J.-M.: Snow/rain source mixing and residence time modeling in a sub-alpine mountainous catchment under global warming, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7894, https://doi.org/10.5194/egusphere-egu22-7894, 2022.

Central Asia's river systems are largely fed by reliable snow and glacier melt which allows agricultural production in the dry lowlands and hydropower production. However, climate forcing is changing faster than ever and predictions of river discharge relying on past observations (as are currently applied by Central Asia’s Hydrometeorological Agencies) may no longer pass stringent quality criteria for good forecasts. There is a growing need for hydrological models for nexus studies and the feasibility study for small hydropower plants in the region. Central Asia is a large region with a sparse hydrometeorological monitoring network which makes it difficult to calibrate hydrological models with traditional methods. It is therefore good news that the amount of remotely sensed data or data from reanalysis products has been increasing in both quantity, and quality in the past few years. Such data offers a huge potential to improve hydrological modelling efforts but the required pre-processing of such data often exceeds the capacities of local stakeholders in Central Asia which does not allow them to valorize these data. As local workflows being digitized, tools need to be developed to facilitate the integration of improved model forcing and modelling techniques in applied hydrology. 

The present study uses the daily CHELSA-W5E5 v1.1 data set at daily 1km by 1km resolution, which is an ERA5 derivative with corrections for high mountain regions, to force degree-day melt models for glaciers and semi-distributed hydrological models using HBV. We combine the data from the Randolph Glacier Inventory in the region with recently available information on individual glacier elevation change (2000 - 2019), thickness and glacier discharge (2000 - 2016) to calibrate degree-day melt models for glaciers in Central Asia and to estimate daily glacier discharge until the end of the century for the 4 GCM models of the CIMIP6 climate projections with the highest priority for the region and for 4 socio-economic scenarios (i.e. 16 modeling scenarios). We also validate existing glacier volume, length and area scaling relationships for Central Asian glaciers from the literature. 

The glacier discharge time series is used as a source to a semi-distributed hydrological model to estimate the future water availability of the river Koksu,  a tributary to the Shakhimardan catchment in the south of the Fergana valley, and is a key input for the design of a small-hydropower plant. We further demonstrate a workflow to calibrate the snow components of the HBV modules in the hydrological model using the high mountain snow reanalysis product. 

We strive to streamline the use of such novel data products in the hydrological modelling process for Central Asian river basins by developing a suite of publicly available R packages & vignettes that facilitate data processing and modelling. The presented modelling effort is part of the ongoing EU Horizon 2020 project Hydro4U which aims at promoting sustainable small-hydropower solutions in Central Asia. The project's demonstration site of Shakhimardan is especially interesting because of its sensitive transboundary nature and the potential for socio-economic development in this remote enclave which is frequently cut off from power supply.

How to cite: Marti, B., Karger, D., and Siegfried, T.: Using recent public glacier data sets to calibrate glacier melt models and drive hydrological models in Central Asia: Facilitating hydrological modelling workflows, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7983, https://doi.org/10.5194/egusphere-egu22-7983, 2022.

EGU22-8568 | Presentations | HS2.1.5

Simulation of river flow in the Gunt River Basin in Tajikistan 

Ben Jarihani, Anastasia Zemlyanskova, and Olga Makarieva

Mountainous regions of the world are the source of water for large amount of population living downstream. This is also the case for Pamir Mountains in Tajikistan which produces majority of the water for the several countries in the region. Despite increasing impacts of climate change, last several decades, there have been critical decrease of number of monitoring networks in mountainous areas of Central Asia bringing high uncertainty to water resources management and planning. In this study we investigate the possibility to combine the remote sensing data, ground observations and a modelling approach to estimate discharge of Gunt River in the Eastern Pamir, Tajikistan. The Gunt River watershed is of great importance for the region, as about 60 settlements are concentrated along the entire length of the river, including the administrative city of Khorog. Two hydropower stations were built in the lower reaches of the river to provide electricity for the local communities. These headwater glacier-fed basins of Central Asia are particularly vulnerable; as climate change threatens water supply from glacier systems and increases evaporative losses, while demand to irrigation water and electricity is rising. This uncertainty in water supply can result, to a deterioration in the development of the economy and the quality of life in the region. Therefore, for sustainable electricity production and economic development in the region, a better understanding of water availability in the river, is required.

 

The aim of the study is to assess the characteristics of the flow regime of the Gunt River. We used "Hydrograph" hydrological model to simulate daily discharge of the Gunt River. The model algorithms combine physically based and conceptual approaches to describe snow and glacier melting and runoff generation processes. "Hydrograph" model has also successfully used to simulate river flow in Varzob River with similar climatic conditions in Tajikistan. Parametrization of the model including the assessment of precipitation distribution in the high mountainous areas is based on the data from the research watershed of the Varzob River with long term historical data availability. The verification and evaluation of the model was conducted based on the historical data (1970-1980) using data from the Dzhavshangoz and Khorog meteorological stations. The model performance and simulations for the recent period (2000-2020) were also evaluated by using the remote sensing data. The results have shown satisfactory quality with difference between the observed and simulated runoff does not exceed 2%. In general, the results of the paper confirm the possibility of using the deterministic model "Hydrograph" to simulate the daily water runoff in the river which is critical for hydropower and irrigation purposes. However, the lack of accurate information on distribution of precipitation in the catchment, significantly reduces the model results accuracy. The study was carried out with the support of St. Petersburg State University (project 75295879).

How to cite: Jarihani, B., Zemlyanskova, A., and Makarieva, O.: Simulation of river flow in the Gunt River Basin in Tajikistan, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8568, https://doi.org/10.5194/egusphere-egu22-8568, 2022.

EGU22-8570 | Presentations | HS2.1.5 | Highlight

Can fully satellite-products-driven simple models account for snow processes in data scarce regions? 

Dhiraj Raj Gyawali and András Bárdossy

This study investigates satellite-based information driven snow accounting routines to simulate snow processes in mountainous regimes that are inherently associated with data scarcity. Simple, independent and parsimonious snow accounting routines that are fully driven by remote sensing (RS) information such as the land surface temperatures and snow-cover information along with distributed temperature index-based snow-melt models, are presented. RS based snow-cover distribution does not only provide the crucial information on areal extent of snow, but can also be a highly imperative proxy for the precipitation accumulations in these data scarce regions, as the availability and resolution of the data doesn’t depend on the mountainous terrain. These models are calibrated independently on the snow-cover distribution, can be coupled with any rainfall-runoff models to simulate “snow-processes informed” discharge and are flexible enough to be extended to a wide geographical extent. These models, in addition to simulating the snow accumulation and melt processes, also use the timing of snow appearance and disappearance. This accounting of snow can be inverted to obtain seasonal precipitation estimates in data scarce snow dominated regions, which can be a very crucial information for water resources planning. Specific results pertaining to the validation of the models in Switzerland and southern Germany (ungauged scenario) are shown. 

How to cite: Gyawali, D. R. and Bárdossy, A.: Can fully satellite-products-driven simple models account for snow processes in data scarce regions?, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8570, https://doi.org/10.5194/egusphere-egu22-8570, 2022.

EGU22-8896 | Presentations | HS2.1.5

Combining high resolution atmospheric simulations and land-surface modelling to understand high elevation snow processes in an Himalayan catchment 

Achille Jouberton, Yota Sato, Akihiro Hashimoto, Masashi Niwano, Thomas E. Shaw, Evan S. Miles, Pascal Buri, Stefan Fugger, Michael McCarthy, Koji Fujita, and Francesca Pellicciotti

Glaciers are key components of the Asian water towers and provide water to large downstream communities for domestic, agricultural and industrial uses. In the Nepal Himalaya, the Indian Summer Monsoon dominates climate, and results in a complex meteorology and simultaneous accumulation and ablation that complicate the quantification of snow processes. Assessing solid precipitation input, especially in the upper accumulation area (> 6000 m a.s.l.), remains key to understanding recent mass losses. Catchment-scale glacio-hydrological modelling in the Himalaya has to date mostly relied on temperature-index or intermediate-complexity enhanced temperature-index methods, but recent studies have shown that such approaches can lead to inaccurate amounts of melt, especially at high elevations where refreezing, sublimation and avalanches influence the snow depth variability. The Trakarding–Trambau Glacier system experienced significant mass loss over the last decades, and recent field measurements of meteorology and glacier change present the opportunity to examine these problems with physically-based and spatially-resolved atmospheric and glacio-hydrological modelling.

We combine a novel non-hydrostatic atmospheric model (NHM; atmospheric core of the cryosphere-oriented regional climate model NHM-SMAP) and an advanced land surface model at cloud-permitting hyper-resolution (~ 100 m) to explore the role of snow processes in the water balance of this glacierized catchment. We force the land-surface model of the catchment with dynamically downscaled, hourly outputs from  NHM for the 2018-2019 hydrological year. We evaluate the NHM output using available in-situ meteorological observations  and evaluate the land surface model skills and process representation with in-situ mass balance observations, remotely sensed surface elevation change and snow cover. Coupling of the two types of models is unprecedented in the Himalaya, and holds promise to reveal processes that cannot be explicitly assessed by simpler models or forcing data. We investigate the contribution of sublimation and precipitation partition to the glacier mass balance and catchment runoff, and analyze the difference in mass balance and its drivers between the debris-covered and debris free-glaciers. To place this very novel type of simulations into the context of current research, we compare our NHM-forced simulations with simulations forced by station data and ERA5-Land reanalysis.  Finally, we evaluate the effect of spatial resolution (50 m, 100 m, 200 m) on model performance and process representation. 

Our results highlight the potential of sophisticated models based on the calculations of energy and mass fluxes to unravel the complex processes that shape the response of Himalayan catchments, and provide an assessment of their skills as a function of spatial resolution.

How to cite: Jouberton, A., Sato, Y., Hashimoto, A., Niwano, M., Shaw, T. E., Miles, E. S., Buri, P., Fugger, S., McCarthy, M., Fujita, K., and Pellicciotti, F.: Combining high resolution atmospheric simulations and land-surface modelling to understand high elevation snow processes in an Himalayan catchment, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8896, https://doi.org/10.5194/egusphere-egu22-8896, 2022.

EGU22-9049 | Presentations | HS2.1.5

A novel method to understand the interaction between a patchy snow cover and the adjacent atmosphere 

Michael Haugeneder, Michael Lehning, Tobias Jonas, and Rebecca Mott

Late in the ablation season the snow cover gets patchy. The resulting surface temperature gradients and the lateral advection of heat over the partial snow cover engage different atmospheric processes such as the development of stable internal boundary layers (SIBL) or atmospheric decoupling close to the snow surface. Even though lateral advection of heat and the resulting atmospheric phenomena significantly influence the energy balance of the melting snow pack in spring, there is a lack of understanding and, thus, they are not explicitly taken into account in snow melt runoff models yet.
To gain further understanding of those complex near-surface atmospheric processes at the meter to sub-meter scale, we conducted a comprehensive field campaign at an alpine research site. The field campaign included the measurement of meteorological parameters, snow ablation pattern, and turbulence using eddy-covariance sensors. Furthermore, we applied a novel experimental method. Two thin synthetic screens were vertically, in parallel to the prevailing wind direction, deployed across the transition from bare ground to snow covering a horizontal distance of 6m. The screens quickly adapt to ambient temperature and, thus, serve as a proxy for the local air temperature. Using a high resolution thermal infrared camera, a 30Hz sequence of infrared frames was recorded. The recorded air temperature fields capture the dynamics of turbulent eddies adjacent to the surface depending on different parameters such as wind speed or the snow coverage. A thin SIBL develops above the leading edge of snow patches possibly protecting the snow surface from warmer air above. However, sometimes the warm air entrains into the SIBL and reaches down to the snow surface adding further energy to the snow pack.
In an attempt to quantify exchange processes from those dynamics, we developed a method to estimate high-resolution, near-surface 2D wind fields from tracking the air temperature pattern on the screens. A spatial correlation search yields the shift of an eddy or air parcel between two subsequent frames, using air temperature as a passive tracer. From this shift, the wind speed can be calculated at a very high spatial resolution. Vertical profiles of air temperature, horizontal, and vertical wind speeds across the transition from bare ground to snow can be evaluated with the advantage of a high spatial (0.01 m) and temporal (30 Hz) resolution.
The screen measurements and wind speed estimation are validated with 3D short-path ultrasonic anemometer measurements close to the surface, which provide further insights into the turbulence characteristics close to the snow surface.
With the high spatio-temporal resolution data we aim to better understand and quantify small scale energy transfer processes over patchy snow covers and their dependency on the atmospheric conditions. This will allow to improve parameterizations of these processes in coarser resolution snow melt models.

How to cite: Haugeneder, M., Lehning, M., Jonas, T., and Mott, R.: A novel method to understand the interaction between a patchy snow cover and the adjacent atmosphere, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9049, https://doi.org/10.5194/egusphere-egu22-9049, 2022.

The MODIS sensor on the NOAA Terra satellite has been providing daily information on global snow cover with a nominal spatial resolution of 500 m since February 2000. Since July 2022, this sensor is also located on NOAA's Aqua Satellite in orbit. The daily snow cover product of both platforms constitutes the basis for the DLR Global SnowPack (GSP) processor.

In the course of the GSP processing, the daily data of both MODIS sensors are merged and data gaps (e.g., clouds or polar night) are interpolated over 3 days. From a digital elevation model, the snow height (elevation above which only snow occurs), as well as the snow-free height (elevation below which no snow occurs) are determined. Heights above or below these thresholds are filled accordingly. Finally, remaining gaps are gradually filled by the values of preceding days. Since the year 2022, the daily cloud free GSP data has been made available in near real time (3 days delay due to the preprocessing of the NSIDC) via the GeoService Portal of the Earth Observation Center (EOC).

The rapid provision of the information on global snow coverage allows completely new applications of time-critical questions. These include hydrological estimates to what extent the snow conditions in the catchment area influence the drainage behavior. In addition to the satellite data, meteorological and hydrological data of the past 20 years are used to estimate the impact of a changing snow cover on the runoff. In the course of climate change, a delayed onset of snow cover and an earlier snowmelt is likely. Warmer winters also increase the risk of Rain-on-Snow events, which cause a strong increase in the outflow and have more dramatic ecological effects.

We will present results for selected river catchment areas with a special focus on hydrological extreme events (droughts and floods), and when their occurrence has been shown early in the development of seasonal snow coverage. Our goal is to provide an automatic early warning system based on near real time GSP for large river catchments with nival-influenced drainage regimes.

How to cite: Roessler, S. and Dietz, A.: Use of near real-time cloud-free MODIS snow cover data from DLR’s Global SnowPack for the early forecast of extreme hydrological events, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9205, https://doi.org/10.5194/egusphere-egu22-9205, 2022.

EGU22-9453 | Presentations | HS2.1.5

Investigating the impact of temporal resolution on a snow model used for hydrological modelling 

Anne-Lise Véron, François Tilmant, Guillaume Thirel, François Bourgin, Charles Perrin, and Félicien Zuber

Real-time flood forecasting and other hydrological applications in mountainous areas require a good understanding and accounting of snow accumulation and melt. The CemaNeige snow model is currently used with the GRP hydrological model by most regional operational services in France to produce floods forecasts with lead times varying from a few hours to a few days. The snow model is based on a degree-day approach and needs limited inputs (precipitation and air temperature) spatialized on altitude bands over the catchment. It was initially developed on snow-dominated catchments by Valéry et al. (2014) using only streamflow series as calibration information. The model was then adapted by Riboust et al. (2019) to better simulate snow-covered areas as estimated by MODIS satellite images. These data were used as a secondary source of information for parameter calibration. All these developments were made at the daily time step. However, for real-time purposes, the outputs from the snow model are often needed at a finer time step, typically hourly or sub-hourly.

Here the transposability and the consistency of the CemaNeige model were studied across a range of time steps, from hourly to daily, on a set of snow-influenced catchments. This follows previous works on the hydrological model to improve its consistency across time scales (see e.g. Viatgé et al., 2019). Several questions were addressed:

  • To which extent are the outputs of the snow model and its parameters consistent across various time steps?
  • Is the current snow model complexity (structure and parameters) sufficient to simulate the snow influence at the catchment scale at sub-daily time steps?
  • Can we expect better results by running the snow model at sub-daily time steps than by disaggregating the outputs of the snow model run at the daily time?

The answers to these questions will be presented based on a comprehensive testing scheme and a set of numerical criteria. Perspectives in terms of operational use will be discussed.

How to cite: Véron, A.-L., Tilmant, F., Thirel, G., Bourgin, F., Perrin, C., and Zuber, F.: Investigating the impact of temporal resolution on a snow model used for hydrological modelling, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9453, https://doi.org/10.5194/egusphere-egu22-9453, 2022.

EGU22-9540 | Presentations | HS2.1.5

What role do glaciers play in smoothing streamflow during summer rainfall events? A case study from the Swiss Alps. 

Bettina Schaefli, Ladina Binkert, Luca Benelli, Natalie Ceperley, Peter Leiser, Jan Baumgartner, Benjamin Berger, and Kevin Wyss

The retreat of glaciers, particularly in catchments where they were extensive, has important consequences for future water management and in particular for hydropower production. Glaciers store water in liquid or solid form on short- to long-term time scales and thereby affect the precipitation-runoff behavior of heavily glacier-covered catchments from interannual and seasonal to sub-daily time scales. While today reliable predictions can be made about the change in quantity and timing of glacier melt runoff, the consequences of glacier retreat for summer rainfall events remain unclear. By intensively monitoring streamflow during the summer months in an area with a high degree of glacier cover, we can fill this research gap. Our key research question is hereby how strongly the glacier smooths out the observed rainfall peaks and how the smoothing effect evolves over the course of the glacier melt season. The answer to this question is crucial to anticipate potential water and sediment management challenges under intense summer rainfall events in catchments with strongly reduced glacier-cover.

In this presentation, we share results from the Oberaargletscher catchment (10 km2, elevation 2310 - 3630 m a.s.l.) located in the Swiss Alps that was intensively monitored from July to October 2021. The monitored variables include precipitation, streamflow, electric conductivity, stable isotopes of water, water and air temperature. Based on the high resolution streamflow data, we analyze the influence of summer rainfall events on the runoff response, and in particular on the runoff lag time and the hydrograph shape. The obtained results are related to potential driving variables including the extent of snow cover and of the glacial drainage system, the precipitation intensity and air temperature.

We will furthermore discuss to what extent the rainfall fraction in the streamflow can be quantified based on streamflow observations alone, which will give valuable insights for future measurement campaigns at comparable sites.

How to cite: Schaefli, B., Binkert, L., Benelli, L., Ceperley, N., Leiser, P., Baumgartner, J., Berger, B., and Wyss, K.: What role do glaciers play in smoothing streamflow during summer rainfall events? A case study from the Swiss Alps., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9540, https://doi.org/10.5194/egusphere-egu22-9540, 2022.

EGU22-10540 | Presentations | HS2.1.5

Modelling the glacier-hydrology of two large catchments in the Peruvian Andes 

Catriona L. Fyffe, Emily Potter, Andrew Orr, Thomas E. Shaw, Edwin Loarte, Katy Medina, Evan Miles, Florian von Ah, Michel Baraer, Alejo Cochachin, Joshua Castro, Nilton Montoya, Matthew Westoby, Duncan J. Quincey, and Francesca Pellicciotti

Glacier meltwater is a vital component of river discharge in the Peruvian Andes, providing an important source of dry season runoff for communities, agriculture and fragile mountain ecosystems. Previous hydrochemical and modelling studies have identified the importance of glacier meltwater to downstream runoff and analysis of runoff records suggest ‘peak water’ has passed already. These studies, however, have been confined to the Rio Santa basin and the models applied have simplifications in their treatment of glacier melt and evolution. Our objectives are to i) determine the past glacier contribution to streamflow, determining when peak water passed and quantifying the recession of the glacier contribution to runoff; ii) predict future glacier evolution and its consequent impacts on water resources; and iii) to compare the hydrological response of catchments in central and southern Peru and establish their future response to glacier recession.

To meet these objectives we have applied the hourly physically-oriented, glacio-hydrological model TOPKAPI-ETH to two catchments in the Peruvian Andes: the Rio Santa in the Cordillera Blanca (4953 km2) and the Rio Urubamba draining the Cordilleras Vilcanota, Urubamba and Vilcabamba (11048 km2), the two most glacierised catchments in Peru. Past glacier recession has been substantial and future temperature rise is likely to lead to further glacier retreat, threatening water security in both regions. The model is forced with hourly atmospheric inputs from high-resolution (4 km), bias-corrected Weather Research and Forecasting (WRF) model outputs, which are downscaled to the TOPKAPI-ETH model resolution (100 m), using temperature and precipitation lapse rates defined from the WRF data for all sub-catchments of each domain. To reduce equifinality in model parameters we calibrate the model in a stepwise manner, using a combination of in-situ and remotely sensed data. Melt model parameters are calibrated based on full energy balance simulations at five sites across the two domains, with albedo parameters also derived from calibration with measured data. We calibrate the temperature decrease over glacier ice in an iterative manner using the WRF air temperatures, observed weather station data and the energy balance model outputs. Precipitation undercatch is a key unknown but it is constrained by careful comparison of modelled glacier surface mass balances with those inverted from remotely sensed data, while hydrological routing parameters are identified through calibration against hourly runoff records collected within the catchments. 

We use the model outputs to unravel the water balance characteristics of both catchments, their main drivers, including the relative importance of glacier and snow melt components within catchment runoff, and how they vary seasonally, inter-annually and through time due to glacier recession. By applying the model to two catchments with contrasting climatologies and glacier characteristics we are also able to disentangle the reasons for their distinct future trajectories. 

How to cite: Fyffe, C. L., Potter, E., Orr, A., Shaw, T. E., Loarte, E., Medina, K., Miles, E., von Ah, F., Baraer, M., Cochachin, A., Castro, J., Montoya, N., Westoby, M., Quincey, D. J., and Pellicciotti, F.: Modelling the glacier-hydrology of two large catchments in the Peruvian Andes, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10540, https://doi.org/10.5194/egusphere-egu22-10540, 2022.

EGU22-10582 | Presentations | HS2.1.5

A Novel Approach to Estimate Snowfall over an Alpine Terrain via the Assimilation of Sentinel-1 Snow Depth Observations 

Manuela Girotto, Giuseppe Formetta, Shima Azimi, Sara Modanesi, Gabrielle De Lannoy, Hans Lievens, Riccardo Rigon, and Christian Massari

Estimating snowfall over mountain regions is an extremely challenging task due to the high variability of spatial and temporal precipitation gradients. Traditional methods to estimate snowfall include in-situ gauges, doppler weather radars, satellite radars and radiometers, numerical modeling and reanalysis products. Each of these methods, alone, is unable to capture the complex orographic precipitation. For example, in-situ gauges are often too sparse and lead to significant interpolation errors; radar beams are shielded by the complex mountainous terrains; satellite estimates are sub-optimal over snowy mountains regions; while the physical parameterization of mountainous orography remains challenging for estimating precipitation in numerical models. A potential method to overcome model and observational shortcomings in precipitation estimation is land surface data assimilation, which leverages the information content in both land surface observations and models while minimizing their limitations due to uncertainty. Recently, the ESA and Copernicus Sentinel-1 constellation has been used to map snow-depth across the Northern Hemisphere mountains with 1 km spatial resolution by exploiting C-band cross-polarized backscatter radar measurements. This work aims at characterizing and estimating snowfall precipitation errors over an alpine watershed located in Trentino Alto Adige, Italy. We derive the snowfall errors via the data assimilation of 1 km Sentinel-1 snow-depth observations within a numerical model. The data assimilation applies a particle batch smoother to the coupled snow-17 and Sacramento hydrological models.

How to cite: Girotto, M., Formetta, G., Azimi, S., Modanesi, S., De Lannoy, G., Lievens, H., Rigon, R., and Massari, C.: A Novel Approach to Estimate Snowfall over an Alpine Terrain via the Assimilation of Sentinel-1 Snow Depth Observations, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10582, https://doi.org/10.5194/egusphere-egu22-10582, 2022.

EGU22-10735 | Presentations | HS2.1.5

Climate change impact on precipitation-phase partitioning and streamflow for glacierized catchments in Nepal 

Anju Vijayan Nair, Sungwook Wi, Colin Gleason, Rijan Bhakta Kayastha, and Efthymios I. Nikolopoulos

The change in climate, characterized by spatial and temporal variations in precipitation and temperature, significantly impacts the hydrological processes and water resources availability. Quantifying long-term changes in climatic variables and their effect on streamflow are crucial for understanding watershed hydrology and developing effective climate adaptation and water management strategies. In this study, we aim to quantify the changes in precipitation, temperature, and streamflow over the last 70 years (1950-2020) for two glacierized catchments in Nepal: Marsyangdi and Budigandaki River Basins. We utilize a distributed hydrological model (HYMOD_DS) forced by the most recent release of the ERA5 Land reanalysis product. Our investigation focuses on evaluating the impact of spatiotemporal changes in precipitation phases (either snow or rainfall) on streamflow characteristics. Specifically, we analyze the temporal trends and changes in the distribution of snow and rainfall and resulting streamflow separated into surface runoff and baseflow at daily and seasonal scales. The ERA5 Land reanalysis indicates a decrease in mean annual total precipitation for the period 1950-1980 and an increasing trend afterward. Annual mean temperature exhibits a rising trend for the entire period. Streamflow simulations for both basins revealed a significantly increased total flow over the last 20 years, primarily due to an increase in rainfall-induced streamflow. The results from this study will provide critical insight into the hydrology of glacierized basins and serve as a reference for water resources planning under climate change.

How to cite: Vijayan Nair, A., Wi, S., Gleason, C., Kayastha, R. B., and Nikolopoulos, E. I.: Climate change impact on precipitation-phase partitioning and streamflow for glacierized catchments in Nepal, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10735, https://doi.org/10.5194/egusphere-egu22-10735, 2022.

EGU22-11243 | Presentations | HS2.1.5

Modelling blue-green water fluxes in mountain headwaters at the climatic ends of High Mountain Asia 

Stefan Fugger, Pascal Buri, Thomas Edward Shaw, Simone Fatichi, Evan Stewart Miles, Michael McCarthy, Catriona Fyffe, Marin Kneib, Achille Jouberton, and Francesca Pellicciotti

Mountain catchments receive, retain, transport and release water that determines downstream ecology, landforms, hazards and human livelihoods. The hydrological regimes of such catchments are seasonally governed by the storage and release of water by snow and glaciers, and are modulated by the seasonality of liquid precipitation rates and energy fluxes. The wide range of climatic-topographical situations across High Mountain Asia creates a variety of hydrological regimes in this region.

In this study we apply a sophisticated modelling framework in two heavily glacierized catchments at opposite ends of the climatic spectrum in High Mountain Asia: an arid catchment with winter accumulation glaciers (Vaksh headwaters, Northern Pamir) and  a humid catchment with spring-summer accumulation (the Upper Parlung, South-Eastern Tibet). Both catchments span an elevation range of several thousand metres and a number of vegetation zones. To study the concomitant response of the cryosphere and biosphere, we use a land surface model with a mechanistic and energy-balance-based representation of both the cryosphere and biosphere, at 100m spatial and hourly temporal resolution. We force the model with statistically-downscaled and bias-corrected reanalysis data. For model setup and independent validation, we leverage extensive in-situ observations, collected at both sites. We complement those with spatial datasets, such as ice-dynamics-corrected glacier mass balance, snow cover, and vegetation indices.

We analyse the differences in the catchment water balance and flux partitioning between these two study sites in terms of energy fluxes, snow and glacier accumulation and ablation, vegetation distribution and phenology, and give special attention to patterns of evapotranspiration (ET). Using the model we determine the importance of supraglacial debris cover, widespread in the catchments, and its role in modifying the glacier mass balance under different moisture regimes. We also determine the links between snow melt seasonality, glacier mass balance, plant productivity and the responses in catchment runoff. This work presents one of the first applications of hyper-resolution land surface modelling to understand biosphere-cryosphere-hydrosphere interactions in High Mountain Asia, and will provide insights into the skills and drawbacks of such modelling approaches.

How to cite: Fugger, S., Buri, P., Shaw, T. E., Fatichi, S., Miles, E. S., McCarthy, M., Fyffe, C., Kneib, M., Jouberton, A., and Pellicciotti, F.: Modelling blue-green water fluxes in mountain headwaters at the climatic ends of High Mountain Asia, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11243, https://doi.org/10.5194/egusphere-egu22-11243, 2022.

EGU22-11271 | Presentations | HS2.1.5

Climate change impact on rain, snow and glacier melt components of streamflow for the river Rhine: synthesis of a model experiment and relevance for water use 

Kerstin Stahl, Markus Weiler, Marit Van Tiel, Irene Kohn, Andreas Haensler, Daphne Freudiger, Jan Seibert, Greta Moretti, and Kai Gerlinger

Streamflow of the river Rhine and its tributaries consists of rain, snowmelt and glacier ice melt components. The amounts of these components have already changed in the past years due to climate warming. Hydrological modelling until the year 2100 was carried out for the Rhine catchment using an ensemble of downscaled and bias-corrected climate projections and a chain of hydrological models considering cryosphere changes. The modelled daily streamflow components provide unique insight into the hydrological processes of a warmer future at different spatial and temporal scales down to individual events. In the Rhine basin, projected precipitation for the RCP8.5suggest wetter winters and drier summers, but annual net precipitation change differs in the up- and downstream regions with a net increase projected only in the lower basin. The model experiments suggest that the rain component of streamflow will dominate the seasonal variability in the future more than in the past. Snow will provide less seasonal water storage and melt earlier in winter and spring. Glaciers will continue their retreat with differences among individual glaciers and the ice melt component in the main river Rhine is projected to retreat fast with almost no ice melt component left at the end of the century. As a consequence, in particular low flows in downstream reaches will exacerbate due to the lack of buffering snow and ice melt; esp. during hot summer drought years. This change will affect environmental flows, water use for energy production, navigation and other water uses, changes of which can be estimated from the modelled scenarios. Overall, streamflow variability and extremes will increase. Despite propagated uncertainties from a range in the downscaled and bias-corrected climate model input, the projected changes are substantial and are a clear mandate to reconsider water uses and enhance river protection goals.

How to cite: Stahl, K., Weiler, M., Van Tiel, M., Kohn, I., Haensler, A., Freudiger, D., Seibert, J., Moretti, G., and Gerlinger, K.: Climate change impact on rain, snow and glacier melt components of streamflow for the river Rhine: synthesis of a model experiment and relevance for water use, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11271, https://doi.org/10.5194/egusphere-egu22-11271, 2022.

EGU22-11859 | Presentations | HS2.1.5

How are snowmelt rates changing across climates? Insights from a new Northern Hemisphere SWE dataset 

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

Although warming temperatures should intuitively lead to faster snowmelt, some studies suggest that melt rates might be slower in a warming world. This assumes that typically deep snowpacks are thinning and become isothermal earlier in the season when less solar radiation is available for melt. Investigating these changing snow dynamics is challenged by a lack of observations on water content of the snowpack, the Snow Water Equivalent (SWE). However, high quality observations of snow depth are generally more available in both space and time, even at higher elevations. Here we present a new dataset of historical SWE time series over the Northern Hemisphere, including a wide variety of climates. These time series are obtained converting historical ground-based snow depth time series to SWE by using the DeltaSNOW model. For the conversion to work over a range of climates, we apply a regional calibration of model parameters based on climatological data and provide model performance and uncertainty estimates. For >2.000 sites characterised by seasonal snow, we investigate changes in total snow accumulation, timing of snowmelt and melt rates for the period 1980-2020. Large decreases in total melt and earlier melt timing are widely observed. However, trends in snowmelt rates are generally weak and spatially inhomogeneous. Slower snowmelt in a warmer world occurs mostly on deep snowpacks that have been heavily depleted and where the number of days with melt has not significantly changed, making melt rates slower. However, both faster and slower melt are observed on sites where both the amount of melt and number of melt days have decreased. We provide an analysis of the causes for the spatial and temporal variability in trends. We find that trends can differ depending on the definition of melt rate and peak SWE, and that the drivers of the trends differ over different climates. Strong warming generates large melt events during the late accumulation season, challenging the commonly used definition of peak SWE and making it harder to compare the snowmelt dynamics of the past and the current climate. We note that focusing on melt rate change might mask important effects on melt timing and magnitude, because a proportional reduction in total melt and number of melt days can lead to no change in melt rate.

How to cite: Fontrodona-Bach, A., Larsen, J., Woods, R., Schaefli, B., and Teuling, R.: How are snowmelt rates changing across climates? Insights from a new Northern Hemisphere SWE dataset, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11859, https://doi.org/10.5194/egusphere-egu22-11859, 2022.

EGU22-11913 | Presentations | HS2.1.5

Unraveling energy balance partitioning in sub-alpine forests: interplay of canopy structure, topography, and meteorological conditions 

Giulia Mazzotti, Clare Webster, Louis Quéno, Bertrand Cluzet, Richard Essery, and Tobias Jonas

In Alpine regions, forests that overlap with seasonal snow mostly reside in complex terrain. Due to major observational challenges in these environments, the combined impact of forest structure and topography on seasonal snow cover dynamics is still poorly understood. However, recent advances in forest snow process representation and increasing availability of detailed canopy structure datasets now allow for hyper-resolution (<5 m) snow model simulations capable of resolving tree-scale processes. These simulations can shed light on the complex process interactions that govern forest snow cover dynamics.

We present multi-year simulations at 2 m resolution obtained with FSM2, a mass- and energy-balance based forest snow model specifically developed and validated for meter-scale applications. Our 3km2 model domain encompasses forested slopes of a sub-alpine valley in the Eastern Swiss Alps. Simulations thus span a wide range of canopy structures, terrain characteristics, and meteorological conditions typical for the region. We analyze spatial and temporal variations in forest snow energy balance partitioning, aiming to quantify and understand the contribution of individual energy exchange processes at different locations and times.

Our results suggest that snow cover evolution is equally affected by fine-scale canopy structure, terrain characteristics and meteorological conditions. We show that the interaction of these three factors can lead to snow distribution and melt patterns that vary between years. Generally, we find higher snow distribution variability and complexity in slopes that receive solar radiation early in winter. Our process-level insights corroborate and complement existing empirical findings that are largely based on snow distribution datasets only. Hyper-resolution simulations as presented here will thus help us to better understand how ecohydrological regimes sub-alpine regions may evolve as a result of forest disturbances and a warming climate.

How to cite: Mazzotti, G., Webster, C., Quéno, L., Cluzet, B., Essery, R., and Jonas, T.: Unraveling energy balance partitioning in sub-alpine forests: interplay of canopy structure, topography, and meteorological conditions, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11913, https://doi.org/10.5194/egusphere-egu22-11913, 2022.

EGU22-12146 | Presentations | HS2.1.5

Effects of Geologic Heterogeneity on Permafrost Distribution and Catchment Hydrology in Mountain Environments 

Cassandra Koenig, Christian Hauck, Lukas Arenson, and Christin Hilbich

Changes in surface runoff from permafrost thaw in mountain catchments can be estimated using numerical cryo-hydrogeology models. However, such models can be complex from a numerical standpoint due to the need to simulate transient thermo-hydrologic feedbacks in highly heterogenous geological settings. Models that also seek to quantify water movement and water-budget contributions from ground-ice thaw must further account for changes in water/ice saturation to continually estimate and update the physical properties that control heat and water transfer in the ground (i.e., thermal and hydraulic conductivity) during the model execution. This has important implications for permafrost hydrology modelling efforts in arid mountain watersheds like the High Andes, where water security is threatened by climate change and the role of permafrost in the hydrologic cycle is unclear.

In this contribution the coupled finite element codes TEMP/W and SEEP/W are used to illustrate ground thermal and hydrologic dynamics for different geological scenarios within a hypothetical mountain slope, characteristic of the High Andes at an altitude of up to 6000 m. The 3 km-long, two dimensional cross-sectional model was developed based on a simplified topography, and ground temperatures and climate data collected within the region. In the first scenario, a uniform hydraulic conductivity is applied to the full model domain. A second scenario simulates a case where the hydraulic conductivity of the ground in the upper 200 m is an order of magnitude higher than for the rest of the model (i.e., as in fractured bedrock or unconsolidated sediment). The scenarios were subjected to a 1,000-yr seasonally cyclic climate forcing, followed by 1,000 years of warming superimposed on inter-annual variability at an average warming rate of 4 deg/100 year.

Model experiments show that the applied variations in hydraulic conductivity support vastly different permafrost and ground ice-content distributions under identical climate forcing. Compared to the uniform hydraulic conductivity case, the scenario with high hydraulic conductivity upper layer produces an increase in the heterogeneity of ice-rich permafrost under the stable climate forcing, and a slightly accelerated rate of permafrost thaw under climate warming. Higher recharge and discharge fluxes across the model surface are also predicted for the high hydraulic conductivity scenario.

The divergence in the results is attributed to preferential flow paths that develop near the model surface in the higher hydraulic conductivity case, which in turn leads to increased spatial complexity in advective heat transfer. This can have profound effects on predictive models aiming to estimate rates of permafrost thaw and discharge behaviour under climate warming, and highlights the need for awareness of uncertainties associated with estimated or assumed thermal and hydrologic properties in modelling large mountain catchments.

How to cite: Koenig, C., Hauck, C., Arenson, L., and Hilbich, C.: Effects of Geologic Heterogeneity on Permafrost Distribution and Catchment Hydrology in Mountain Environments, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12146, https://doi.org/10.5194/egusphere-egu22-12146, 2022.

EGU22-12251 | Presentations | HS2.1.5

The value of complementary data for physically consistent hydrological models in mountain regions 

Paul Schattan, Benjamin Winter, Larissa van der Laan, Abror Gafurov, Gertraud Meißl, Giovanni Cuozzo, Felix Greifeneder, Valentina Premier, Matthias Huttenlau, Johann Stötter, and Kristian Förster

In the face of climate change and socio-economic developments, water scarcity is a tremendous challenge. In particular, a significant portion of the world’s population rely on water from cryospheric sources such as snow and/or glacier fed mountain rivers. However, the data coverage in mountain regions is often sparse, which substantially hampers the assessment of climate impacts on hydrological systems. Furthermore, the large impact of climate change on snow and glacier hydrology require physically sound hydrological models.

The gap between the growing need for sustainable water resources management, low data availability and uncertain hydrological projections calls for new approaches. To close this gap, a modular modelling framework was developed to foster the use of complementary data sets in hydrological models. The framework enables a flexible combination of remote sensing and in situ data for model calibration and validation providing a multi-model and multi-input ensemble. The additional consideration of data regarding snow covered area, snow water equivalent and soil moisture allows for physically meaningful representations of key hydrological processes, even in the absence of a dense network of meteorological stations and river discharge gauges.

Case studies in the European Alps (Inn and Adige/Etsch) and in Central Asia (Ala Archa and Karadarya) illustrate the high value of this approach for physically meaningful representations of the hydrological processes. Furthermore, a high impact of glacier retreat on future water availability was found for the highly glacierised basins of the Fagge river in the upper part of the Inn basin and the Ala Archa river.

How to cite: Schattan, P., Winter, B., van der Laan, L., Gafurov, A., Meißl, G., Cuozzo, G., Greifeneder, F., Premier, V., Huttenlau, M., Stötter, J., and Förster, K.: The value of complementary data for physically consistent hydrological models in mountain regions, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12251, https://doi.org/10.5194/egusphere-egu22-12251, 2022.

EGU22-3569 | Presentations | GMPV9.3

Volcanically-triggered changes in glacier surface velocity 

Michael Martin, Iestyn Barr, Benjamin Edwards, Elias Symeonakis, and Matteo Spagnolo

Many (~250) volcanoes worldwide are occupied by glaciers. This can be problematic for volcano monitoring, since glacier ice potentially masks evidence of volcanic activity. However, some of the most devastating and costly volcanic eruptions of the last 100 years involved volcano-glacier interactions (e.g. Nevado del Ruiz 1985, Eyjafjallajökull 2010). Therefore, improving methods for monitoring glacier-covered volcanoes is of clear societal benefit. Optical satellite remote sensing datasets and techniques are perhaps most promising, since they frequently have a relatively high temporal and spatial resolution and are often freely available. These sources often show the effects of volcanic activity on glaciers, including ice cauldron formation, ice fracturing, and glacier terminus changes. In this study, we use satellite sources to investigate possible links between volcanic activity and changes in glacier velocity. Despite some studies reporting periods of glacier acceleration triggered by volcanic unrest, the potential of using the former to monitor the latter has yet to be investigated. Our approach is to observe how glacier surface velocity responded to past volcanic events in Alaska and Chile by applying feature-tracking, mostly using optical satellite imagery. The overall aim is to systematically track changes in the glacier velocity, with hope of improving volcano monitoring and eruption prediction. 

How to cite: Martin, M., Barr, I., Edwards, B., Symeonakis, E., and Spagnolo, M.: Volcanically-triggered changes in glacier surface velocity, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3569, https://doi.org/10.5194/egusphere-egu22-3569, 2022.

As loci of the fresh formation of alkaline rock, volcanic islands are hotspots of geochemical activity. Collectively volcanic islands are responsible for approximately one third of the global long term CO2 drawdown from chemical weathering. Glaciers also form environments with substantial chemical weathering activity. Despite zero-degree temperatures, subglacial environments provide both freshly ground down mineral surfaces and highly dilute meltwaters, allowing chemical processes to occur at faster rates than in warmer settings where reactions occur near chemical saturation. Yet, the degree to which glaciation enhances weathering on volcanic islands has received relatively little study.

Beerenberg, Jan Mayen, Norway, is the world´s northernmost active stratovolcano. It is mostly glacierized, with 23 distinctly named glaciers descending from the top of the volcanic cone to the sea. Many of the Beerenberg glaciers release sediment-laden subglacial water, indicative of water-rock interaction in subglacial environments. In August 2021, we did a preliminary survey of the aqueous geochemistry and sediment composition of several subglacial outlets at Beerenberg’s largest glacier, Sørbreen. We also surveyed glacial surface streams, glacial ice and snow, non-glacial melt streams, springs, and proglacial lakes.

The subglacial waters of Sørbreen are strongly enriched in bicarbonate, with little chloride despite the marine location and only trace amounts of other anions. Cation composition is ~60% Na and K and 40% Ca and Mg by mole, suggesting a balance between divalent and monovalent cations reflective of local bedrock. Together this strongly suggests carbonation weathering of silicate minerals as the source of the vast majority of dissolved load in the subglacial waters. Non-glacial waters are more dilute and enriched in sea water derived ions (Cl, SO4, and Na) compared to subglacial waters.  

While a complete geochemical budget is not possible from our initial observations, these results imply that Beerenberg is a hot spot of chemical weathering. If our dissolved CO2 fluxes are representative of long-term averages, then atmospheric CO2 drawdown at Sørbreen is comparable to other glacierized mafic volcanic rock regions, such as those on Iceland and Disko Island. These atmospheric CO2 drawdown rates are approximately double the world average and a factor of five higher than the drawdown in non-glacierized high latitude regions.

How to cite: Graly, J., Engen, S., and Yde, J.: Preliminary Geochemical Assessment of the Subglacial Environment of Beerenberg, the World’s Northernmost Active Stratovolcano, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4743, https://doi.org/10.5194/egusphere-egu22-4743, 2022.

EGU22-6528 | Presentations | GMPV9.3

Pre-Holocene glaciovolcanism in the Katla area, south Iceland 

Rosie Cole, Magnús Gudmundsson, Birgir Óskarsson, Catherine Gallagher, Guðrun Larsen, and James White

The Katla volcanic system is one of the most productive in Iceland. Frequent basaltic and occasional silicic phreatomagmatic eruptions through the ice cap Mýrdalsjökull have provided a rich Holocene tephra record. Understanding of pre-Holocene eruptions and the thickness and extent of ice cover during glacial periods is much more limited.

We present eruption and emplacement models for three formations exposed on the flanks of the Katla volcano. Two are rhyolitic nunataks and one is an alkali basaltic sequence. These formations rise above the surrounding ice and topography, respectively, and show evidence for ice-confined emplacement, indicating their formation at a time when ice cover was thicker and more extensive.

Our models of each formation are based on field study, a photogrammetry survey, and major element geochemical analyses. The basaltic formation of Morinsheiði is an intercalated sequence of volcaniclastic rocks, pillow lavas and pillow breccias, entablature-jointed and lobate lavas, and more massive pahoehoe lava sheets, intruded by several dykes. The top of the sequence is a glacially eroded surface and it is bounded on all sides by deep valleys. The Enta nunatak is a kinked ridge or possibly two en-echelon ridges. A silicic volcaniclastic unit is intercalated with and intruded by fluidal and heavily jointed rhyolite lobes, spines and sheets. This formation is capped by a segment of crater wall composed of scoria. The Kötlujökull nunatak is tabular in shape, has a clastic base and is capped by jointed lava with lobate margins and breakout lobes descending the steep slopes.

Each formation exhibits evidence of multiple eruption styles in varying hydrological conditions, and at least for Morinsheiði a fluctuating water level. These are the preliminary results from the project “SURGE: Uncapping subglacial eruption dynamics and glacier response”, which aims to better understand the relative influences of magma chemistry, eruption style and glacial conditions on meltwater production and retention, glacial response, and the feedback effects for continued eruptions. These models, combined with new 40Ar-39Ar dating of the lavas, will also provide greater insight into the form of Katla and the glacial conditions that prevailed during the late Pleistocene.

How to cite: Cole, R., Gudmundsson, M., Óskarsson, B., Gallagher, C., Larsen, G., and White, J.: Pre-Holocene glaciovolcanism in the Katla area, south Iceland, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6528, https://doi.org/10.5194/egusphere-egu22-6528, 2022.

EGU22-8641 | Presentations | GMPV9.3

The Bláfjall tuya in North Iceland, morphological characteristics and effect of ice flow and icesheet slope on edifice form  

Anna Margrét Sigurbergsdóttir and Magnús Tumi Gudmundsson

Tuyas are basaltic to intermediate glaciovolcanic edifices, formed in a body of meltwater within an ice sheet, in an ocean or a lake. The most common tuya stratigraphy consist of a lowermost layer or a mound of pillow lava, overlain by hyaloclastite tuffs and capped by a layer of subaerially-formed, horizontally bedded, lava flows. The parts of the lava flows more distant from the vent are built on flow-foot breccias, with the transition from subaerially-formed lava flows and breccias being a distinct stratigraphic boundary: the passage zone. The elevation of the passage zone marks the water level in the englacial lake into which the evolving tuya was built. At many locations the elevation of the passage zone appears to vary considerably from one location on a tuya to another. Some tuyas are elongated. One idea is that the elongation is predominantly in the direction of ice flow at the time of eruption.

By studying tuyas through aerial photography, satellite imagery and ground observations, the edifices variations in the elevation of the passage zone can be studied. This provides information on the eruption processes and environmental conditions at the time of formation.  We have analyzed the variation of passage zone elevation with distance along strike of a selected set of tuyas in Iceland. These include Bláfjall, located in Northern Iceland. It was formed within a Pleistocene ice sheet a continuous, prolonged eruption, or in a series of eruptions, closely spaced in time. The lava cap reaches a maximum thickness of approximately 100 m but is only a few meters to a few tens of meters thick on average, showing clear signs of influence from the ice sheet. Apparently, both the thickness of the ice sheet and the direction of ice flow direction exerted major control on the height and elongation of the Bláfjall tuya. The eruption took place well to the north of the ice divide at the time, and the flow of ice was predominantly from south to north, with the elongated structure of the tuya oriented parallel to the flow of the ancient glacier. The thickness of the lava cap is greatest in the north part and generally decreases towards south. This is despite the fact that the elevation of the mountain increases southwards. This indicates that the northern part is mostly formed by an advancing lava delta, propagating in the direction of ice flow and that the level of the water body present at the end of the advancing lava delta become progressively lower towards north. This suggests a sloping ice sheet at the time of formation, or possibly a receding ice sheet, leading to gradual thinning with time as the eruption progressed.   

How to cite: Sigurbergsdóttir, A. M. and Gudmundsson, M. T.: The Bláfjall tuya in North Iceland, morphological characteristics and effect of ice flow and icesheet slope on edifice form , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8641, https://doi.org/10.5194/egusphere-egu22-8641, 2022.

EGU22-8667 | Presentations | GMPV9.3

Tephra layer formed in the 1996 eruption of Gjálp, Iceland 

Irma Gná Jóngeirsdóttir, Magnús Tumi Gudmundsson, and Gudrún Larsen

Gjálp is a hyaloclastite ridge situated beneath the western part of the ~8000 km2 Vatnajökull ice cap, located midway between the subglacial calderas of Grímsvötn and Bárdabunga volcanoes. The tephra erupted at Gjálp has affinities fitting with the Grímsvötn volcanic system while the associated seismicity and unrest preceding the eruption suggest that the eruption was caused by lateral magma flow from Bárdarbunga.  Eruptions occurred at Gjálp in 1938 and 1996 but only the 1996 eruption is thought to have broken through the ice. The 1996 eruption was first detected on the 30th of September at about 22:00 GMT by the onset of seismic tremor; the following day heavily crevassed ice cauldrons were noticed. Around 30 hours after detection of the tremor the eruption broke through the ice sheet. The eruption lasted for 13 days, during which a 6-7 km long subglacial, hyaloclastite ridge was formed. The subglacial eruption melted large volumes of ice that accumulated within the Grímsvötn caldera until early November, when it was released in a major jökulhlaup, destroying bridges and damaging roads. In comparison with the subglacial eruption the subaerial part was relatively modest. The style of activity was mostly Surtseyan and the tephra erupted is mildly intermediate in composition.

The tephra fall began on October 2 and continued intermittently until October 13. The first tephra was seen at 05:18 on October 2. By 08:50 the largest explosions threw tephra about 1 km above the ice surface and the plume rose to 4-4.5 km above sea level. This tephra was carried north and north-northeast across North and Central Iceland and was detected as far as 250 km from source. On October 3 the plume was reported to have reached 8-9 km a.s.l. Tephra was also dispersed to the east and south and most of the tephra accumulated on the Vatnajökull glacier. During the eruption, repeated snow fall caused layering within the tephra deposit. In the following year samples were collected from the tephra fall area on the glacier. These consist mostly of snow cores with tephra thickness ranging from dm to mm. The samples were processed to estimate the tephra volume and to create a dispersal and isopach map. The tephra layer deposited on the glacier is volumetrically only a few percent of the bulk volume (~0.7 km3) of the subglacial ridge formed in the 1996 eruption.

How to cite: Jóngeirsdóttir, I. G., Gudmundsson, M. T., and Larsen, G.: Tephra layer formed in the 1996 eruption of Gjálp, Iceland, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8667, https://doi.org/10.5194/egusphere-egu22-8667, 2022.

EGU22-8751 | Presentations | GMPV9.3 | Highlight

The causes of unexpected jökulhlaups, studied using geothermal reservoir modelling 

Hannah Iona Reynolds, Magnús T. Gudmundsson, and Thórdís Högnadóttir

Jökulhlaups (glacier outburst floods) are considered the most common type of volcanic hazard in Iceland, and result from the accumulation of meltwater during long-term geothermal activity beneath glaciers, or very rapid melting over a short period of time. Jökulhlaups may occur without visible precursors or prior warning, varying in size from being persistent leakage to floods that have caused considerable damage like the jökulhlaups in Múlakvísl and Kaldakvísl in July 2011. Little has been known about the onset time of water accumulation/melting, whether water accumulated before it was released, and how these events are related to intrusion of magma. This study categorises known ice cauldrons within Icelandic glaciers based on their volume, rate of formation, and longevity. Geothermal reservoir modelling was then used to explore possible heat sources which generate the cauldrons. Five scenarios were simulated: (1) Subglacial eruption – freshly erupted magma in direct contact with the ice at the glacier base; (2) Intrusion into homogeneous bedrock - magma intrudes into a bedrock of homogeneous properties; (3) Intrusion into high permeability channel – similar to scenario (2) but a high permeability channel extends from the intrusion to the glacier-bedrock boundary, e.g. zone of high permeability at a caldera fault; (4) Sudden release of pressure – a hot reservoir is topped by caprock, with a high permeability pathway from depth up to the glacier-bedrock boundary, representing a sudden breach of a pressurised reservoir; and (5) Intrusion into a very hot reservoir – similar to scenario (3) but the reservoir is near boiling point, from previous repeated intrusive activity. This work improves our understanding of sudden and unexpected jökulhlaups, which is helpful for hazard assessments and response plans for unrest in glaciers near inhabited areas, tourist spots, and power plants. 

How to cite: Reynolds, H. I., Gudmundsson, M. T., and Högnadóttir, T.: The causes of unexpected jökulhlaups, studied using geothermal reservoir modelling, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8751, https://doi.org/10.5194/egusphere-egu22-8751, 2022.

EGU22-8774 | Presentations | GMPV9.3

The role of volcanic particle thermal conductivity, density, and porosity in influencing ice melt. 

Katie Reeves, Jennie Gilbert, Stephen Lane, and Amber Leeson

Volcanoes can generate pyroclastic material that is deposited on ice and snow surfaces. However, a range of particle properties and spatial distribution of layer thicknesses are associated with deposition of volcanic material1. This can modify the thermodynamic behaviour and optical properties of clean ice. Typically, thin layers of particles (i.e. in ‘dirty’ ice conditions) can increase ice ablation, whilst thick layers of particles (i.e. in ‘debris-covered’ conditions) can hinder ablation2. Therefore, the state of ice is an important control on the energy balance of an ice system. 20.4% of Earth’s known Holocene volcanoes are associated with glacier or permanent snow cover3, and so it is crucial to understand how volcanic material interacts with ice systems to (1) better understand the evolution of debris-covered and dirty ice in general and (2) forecast future ice-melt scenarios at individual ice-covered volcanoes.

We present laboratory experiments that systematically reviewed the impact of volcanic particles of a range of compositions and properties (e.g. thermal conductivity, diameter, density, and albedo) on ice. Experiments assessed single particles and a scattering of particles on optically transparent and opaque ice, subjected to visible light illumination from a light emitting diode in a system analogous to dirty ice. Automated time-lapse images and in-person observations captured the response of particles and ice to radiation. Particles investigated included trachy-andesitic cemented ash particles from Eyjafjallajökull (Iceland), basaltic-andesitic scoria from Volcán Sollipulli (Chile), and rhyolitic pumice from Mount St. Helens (USA).

The experiments provided insight into some of the processes associated with volcanic particle interaction with ice. Results demonstrated that all volcanic particles with varying albedos induced ice melt and drove convection systems within the meltwater. This convection resulted in indirect heating beyond the immediate margins of the particles. The particles additionally lost finer grained fragments to meltwater, further driving ice melt through the addition of multiple absorbing surfaces within the ice system. This demonstrated that volcanic particles have the capability to melt ice very effectively in dirty ice conditions. In all experiments, the particles had a low thermal conductivity (relative to ice), although the density differed between particle types. Our experiments showed that the porosity and density of a volcanic particle can dictate the behaviour of particle-ice interaction; a dense particle can melt downwards through the ice (in similarity with the behaviour of iron-based meteorites4), whilst a less dense particle can become buoyant in meltwater, resulting in an extensive area of surface melt.

1. Möller et al. (2018), Earth Syst. Sci. Data, https://doi.org/10.5194/essd-10-53-2018

2. Fyffe et al. (2020), Earth Surf. Process. Landforms, DOI: 10.1002/esp.4879

3. Curtis and Kyle (2017), Journal of Volc. And Geo. Research http://dx.doi.org/10.1016/j.jvolgeores.2017.01.017

4. Evatt et al. (2016), Nature Comms., DOI: 10.1038/ncomms10679

How to cite: Reeves, K., Gilbert, J., Lane, S., and Leeson, A.: The role of volcanic particle thermal conductivity, density, and porosity in influencing ice melt., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8774, https://doi.org/10.5194/egusphere-egu22-8774, 2022.

EGU22-10002 | Presentations | GMPV9.3

Characterization of alteration minerals in Deception Island (Antarctica): implications for the dynamics of the current hydrothermal system 

Raquel Arasanz, Oriol Vilanova, Adelina Geyer, Meritxell Aulinas, Jordi Ibañez-Insa, Antonio M. Álvarez-Valero, Helena Albert, and Olga Prieto-Ballesteros

Hydrothermal systems, commonly developed in volcanic calderas, play an important role on the type and location of the post-caldera volcanic activity. The hydrothermal alteration and mineral precipitation can modify the physical properties and mechanical behaviour of the affected rocks, with the progressive alteration facilitating the occurrence of phreatic or hydrothermal explosive eruptions. Deception Island (South Shetland Islands) is one of the most active volcanoes in Antarctica, with more than 20 eruptions and three documented unrest periods over the past two centuries. The island consists of a composite volcano with an 8.5 x 10 km centrally located caldera dated at c. 8,300 years, according to paleomagnetic data, and 3,980 ± 125 calibrated years before the present (cal yr BP) based on tephrochronology, sedimentological studies and 14C dating. After the caldera-forming event, volcanic activity has been characterized by monogenetic magmatic and phreatomagmatic eruptions located around the caldera rim. Also, a hydrothermal system developed in the Port Foster area, although no detailed study has been done so far. The aim of this work is to shed further light in the dynamics of Deception Island hydrothermal system by studying several representative samples of magmatic rocks. A detailed petrographic study and a characterization of primary and secondary minerals have been carried out. The presence of secondary minerals and the palagonite alteration in the Fumarole Bay Formation suggest that the alteration of the samples took place under conditions of low water/rock ratios, basic pH and temperatures below 200 °C. The secondary minerals from the Basaltic Shield Formation samples may be indicative of fluids with temperatures higher than 200 °C and richer in CO2. Finally, the physical changes observed in the samples of this study lead to the conclusion that the investigated areas of the Fumarole Bay Formation are more likely to host hydrothermal or phreatic explosive eruptions, compared to the Basaltic Shield Formation zones.

This research is part of POLARCSIC research initiatives and was partially funded by the MINECO grants POSVOLDEC(CTM2016-79617-P)(AEI/FEDER-UE) and VOLGASDEC (PGC2018-095693-B-I00)(AEI/FEDER, UE) and the grant PID2020-114876GB-I00 funded by MCIN/AEI/ 10.13039/501100011033 and, as appropriate, by “ERDF A way of making Europe”, by the “European Union” or by the “European Union NextGenerationEU/PRTR”. This research is also supported by the PREDOCS-UB grant.

How to cite: Arasanz, R., Vilanova, O., Geyer, A., Aulinas, M., Ibañez-Insa, J., Álvarez-Valero, A. M., Albert, H., and Prieto-Ballesteros, O.: Characterization of alteration minerals in Deception Island (Antarctica): implications for the dynamics of the current hydrothermal system, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10002, https://doi.org/10.5194/egusphere-egu22-10002, 2022.

EGU22-10267 | Presentations | GMPV9.3

Pyroclastic Density Currents Over Ice: An Experimental Investigation of Microphysical Heat Transfer Processes 

Amelia Vale, Jeremy Phillips, Alison Rust, and Geoff Kilgour

Pyroclastic density current (PDC) interactions with ice are common at high altitude and latitude stratovolcanoes. When PDCs propagate over ice, melt and steam are generated. The incorporation of melt and steam into PDCs can alter the flow dynamics by reducing friction at the particle-ice interface and between individual particles. Melt incorporation can also transform a PDC into an ice-melt lahar. The hazardous and temporally unpredictable nature of these flows limits field observations. Conceptual models of PDC-ice interactions for hazard assessment and modelling exist, but quantifications of the microscale physical processes that underpin these interactions are limited. We use experiments to characterise the melting and friction reduction that occur when PDCs are emplaced onto ice.

In experiment set one, a heated particle layer was rapidly emplaced onto a horizontal ice layer contained within an insulated beaker 7.3 cm in diameter. The particle types used were glass ballotini, crushed pumice, and Ruapehu PDC samples, covering a diverse range of grain characteristics. The particle layer was varied in thickness up to 45 mm and across temperatures up to 700 °C. In each experiment, the mass of melt and steam were quantified, and the time evolution of temperature through the particle layer was measured.

Across all particle types, increasing particle layer mass (therefore layer thickness) and temperature increased melt and steam production. However, Ruapehu and pumice melt masses showed greater sensitivity than ballotini to particle temperature for any given layer thickness. Conversely, steam production was greater for the ballotini for any given layer thickness and was more sensitive to ballotini particle temperature.

Localised steam escape, fluidisation, capillary action, and particle sinking, were observed to varying extents in the experiments. These phenomena caused melt to be incorporated into the particle layer. The rate of increase in melt generation decreases with increasing particle layer thickness. This is due to increasing steam production, the increasing temperature of incorporated meltwater, energy losses to the atmosphere, and alterations to the bulk particle diffusivity.

Experiment set two characterised the mobility of particles over frozen and non-frozen substrates. Pumice and Ruapehu particles of varying temperature and layer thickness were poured into a 4.5 cm diameter alumina tube, which was rapidly lifted, allowing the particles to radially spread over the substrate. This configuration has been widely studied in experiments on granular flow mobility. The initial and final aspect ratios of the particle layer were measured, and conform to a power-law form previously interpreted as showing that frictional interactions are only important in the final stages of flow emplacement. Enhanced particle layer mobility over ice was only observed for Ruapehu particles above 400 °C, which we interpret to be due to fluidisation of the particles by rising steam. This is consistent with experiment set one, where Ruapehu particles produced more steam than pumice, and were often fluidised above 400 °C.

Experimental data will be used to calibrate surface flow hazard models for PDC runout and lahar generation, enabling prediction of PDC-ice interaction hazards. These models will be tested at Mt. Ruapehu, New Zealand. 

How to cite: Vale, A., Phillips, J., Rust, A., and Kilgour, G.: Pyroclastic Density Currents Over Ice: An Experimental Investigation of Microphysical Heat Transfer Processes, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10267, https://doi.org/10.5194/egusphere-egu22-10267, 2022.

EGU22-12210 | Presentations | GMPV9.3

Characterising ice-magma interactions during a shallow subglacial fissure eruption: northern Laki, Iceland, a case study 

Catherine (Kate) Gallagher, Magnús Tumi Gudmundsson, Thorvaldur Thordarson, Bruce Houghton, Birgir Óskarsson, Robert Askew, Rosie Cole, William Moreland, Valentin Troll, and Guðrún Þorgerður Larsen

Iceland has the largest variety of subglacially formed volcanic edifices worldwide, given the extensive glacial cover during the Pleistocene and its frequent volcanic activity. As substantial parts of the volcanic zones are presently ice-covered, eruptions beneath glaciers are common.

 

Phreatomagmatic activity and flood deposits have been hypothesised for shallow subglacial fissure eruptions, at or within a glacial margin. However, to date, no historical examples that did not immediately break through the ice, resulting in dry magmatic activity, have been directly observed. Also, at dynamic ice-margin settings, no extensive resultant formations from shallow subglacial fissure eruptions formed in older historic eruptions have been studied until now. 

 

The final fissure from the 1783–84 CE Laki basaltic flood lava event in the Síða highlands of Iceland, fissure 10, provides a perfect natural laboratory to understand the eruptive dynamics of a shallow subglacial or intraglacial fissure eruption. Fissure 10 is a 2.5 km long formation, which constitutes the final phase of activity on the 29 km long Laki crater row, formed as eruptive activity from the Laki eruption propagated under Síðujökull, an outlet glacier from the Vatnajökull ice-cap. The resultant eruptive sequences display evidence of the increasing influence of ice when traced along strike from SW to NE, with the eruption transitioning to a predominantly phreatomagmatic phase with increasing degrees of lateral confinement. The sequence is dominated by volcanoclastic units, formed by multiple phreatomagmatic and magmatic phases suggestive of fluctuating water levels, intercalated with hackly jointed intrusions, hackly jointed lobate lava flows and debris flows. Repeating units of agglutinated spatter and spatter-fed lava flows cap the sequence, suggesting decreasing influence of external water with stratigraphic height and towards the end of the fissure’s eruptive activity. A thin layer of glacial till coats the top of the fissure 10 sequences. The margin of Síðujökull has since fully receded from the formation.

 

Our model for the eruptive dynamics of the northern Laki fissure 10 formation is based on field mapping, a drone photogrammetry survey, petrological observations and EMP analysis of glassy tephra and lava selvages to gain a full understanding of the activity and how eruptive activity progressed. The Laki eruption benefits from a wealth of previous studies on the magmatic phases from the other 9 subaerially eruptive fissures, to the SW of fissure 10, allowing for the effects of the glacier on this fissure’s activity to be isolated and defined.

 

Fissure 10 allows for an approximate reconstruction of the ice margin and glacier slope at the time of eruption, adding valuable information on the extent of the glaciers in SW-Vatnajökull in the late 18th century, and during the Little Ice Age. These shallow subglacially erupted deposits are the only fully accessible intraglacial eruptive vents, from a known historical eruption, on Earth. Detailed mapping and petrological analysis of deposits like these is important for interpreting landforms in paleo-ice margins, where transitional activity occurs.

How to cite: Gallagher, C. (., Gudmundsson, M. T., Thordarson, T., Houghton, B., Óskarsson, B., Askew, R., Cole, R., Moreland, W., Troll, V., and Larsen, G. Þ.: Characterising ice-magma interactions during a shallow subglacial fissure eruption: northern Laki, Iceland, a case study, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12210, https://doi.org/10.5194/egusphere-egu22-12210, 2022.

EGU22-12717 | Presentations | GMPV9.3

Volcano-ice interaction:  The empirical constraints derived from eruptions in Iceland in the period 1918-2015 

Magnus Tumi Gudmundsson, Thórdís Högnadóttir, Eyjólfur Magnússon, Hannah I Reynolds, Guðrún Larsen, and Finnur Pálsson

Eruptions where glacier ice has a significant effect on the style of activity occur in some parts of the world, notably the Andes, Alaska, parts of Antarctica and Iceland.  Due to its northerly latitude and considerable ice cover within the volcanically active zones, about 50% of all eruptions in Iceland occur within glaciers, which is about 15 such eruptions per century.  In the last 25 years, six such confirmed eruptions have taken place while only one minor confirmed eruption occurred in the period 1938-1996.  This is due to the episodic nature of activity in the volcanoes covered by the 7900 km2 Vatnajökull ice cap, with a new period of high activity starting with the Gjálp eruption of 1996.   Contemporary observations have therefore provided considerable empirical data on these events.  These data include glacier thickness prior to eruptions, ice cauldron development, glacier flow perturbations, melting rates and transitions from fully subglacial to explosive/partly subaerial eruptions.  In addition, some data exist that constrains the volcano-ice interaction in the eruptions of Katla in 1918, Grímsvötn in 1934 and 1983, Gjálp in 1938 and Hekla in 1947.  The majority of these events were basaltic.  However, at least two eruptions that had an initial fully subglacial phase (Gjálp 1996, Eyjafjallajökull 2010) were of intermediate composition.  The volume of subglacially-erupted magma ranged from a few million m3 to 0.45 km3 (DRE), initial ice thicknesses ranging from 50 to 750 m, and melted ice volumes between 0.01 km3 to 4 km3.  Combined, the data from the eruptions of the last 100+ years, provides important constraints on heat transfer rates, the rate of penetration of eruptions through ice, glacier response to eruption, and the potential for generation of jökulhlaups and lahars.  Post-eruption observations in Grímsvötn have revealed that craters formed in eruptions that break through the glacial cover can be partly built on ice.  These tend to be highly transient features due subsequent melting and ice movement.  Surface melting of ice by pyroclastic density currents has occurred in Iceland, but this type of activity has in the recent past mostly been confined to the occasional sub-Plinian to Plinian eruptions in e.g. Hekla volcano.   However, there are indications that such activity has played an important role in some relatively rare large Plinian eruptions at ice covered volcanoes in Iceland, as observed in e.g. Alaska and the Andes.

How to cite: Gudmundsson, M. T., Högnadóttir, T., Magnússon, E., Reynolds, H. I., Larsen, G., and Pálsson, F.: Volcano-ice interaction:  The empirical constraints derived from eruptions in Iceland in the period 1918-2015, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12717, https://doi.org/10.5194/egusphere-egu22-12717, 2022.

CR4 – lce sheets, ice shelves and glaciers

EGU22-530 | Presentations | CR4.1

The last deglaciation of the Eurasian ice sheet (21,000 - 8,000 yr BP): a sensitivity study to PMIP3/PMIP4 coupled atmosphere-ocean models outputs 

Victor van Aalderen, Sylvie Charbit, Christophe Dumas, and Aurélien Quiquet

Rapid sea-level rise, due to melting and destabilization of present-day ice sheets will likely have important consequences on human societies. Observations provide evidences of increased mass loss in the West Antarctic Ice Sheet (WAIS) over the recent decades, partly due to ocean warming. Despite improvements in both climate and ice-sheet models, there are still significant uncertainties about the future of West Antarctica, due, in part, to our misunderstanding of the process responsible for the marine ice sheet evolution. Paleoclimate studies provide important information on ice-sheet collapse in a warming world.

Our study is based on the Eurasian Ice Sheet (EIS) complex, including the British Island Ice Sheet (BIIS), the Fennoscandian Ice Sheet (FIS) and the Barents Kara Ice Sheet (BKIS). Because large parts of both the BKIS and the WAIS are marine-based, the BKIS at the LGM can be considered as a potential analogue to the WAIS.

To improve our understanding of the mechanisms responsible for the EIS retreat, we performed transient simulations of the last EIS deglaciation (21 000 – 8 000 yr BP) with the GRISLI ice sheet model forced by 5 PMIP3/PMIP4 models, and two transients GCM models, TRACE21K and iLOVECLIM. Our main goal is to investigate the sensitivity of the EIS grounding line retreat to climate forcing, sea-level rise and glaciological processes with a focus on the BKIS evolution during the deglaciation and the behaviour of the large Bjornoyrenna ice stream.  

How to cite: van Aalderen, V., Charbit, S., Dumas, C., and Quiquet, A.: The last deglaciation of the Eurasian ice sheet (21,000 - 8,000 yr BP): a sensitivity study to PMIP3/PMIP4 coupled atmosphere-ocean models outputs, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-530, https://doi.org/10.5194/egusphere-egu22-530, 2022.

EGU22-1501 | Presentations | CR4.1

Hysteresis and orbital pacing of the early Cenozoic Antarctic ice sheet 

Jonas Van Breedam, Philippe Huybrechts, and Michel Crucifix

The early Cenozoic Antarctic ice sheet has grown non-linearly to a continental-scale ice sheet close to the Eocene-Oligocene boundary when environmental conditions were favourable. These favourable conditions included the movement of the continent towards the South Pole, the thermal isolation of the Antarctic continent and declining atmospheric CO2 concentrations.  Once the threshold for ice sheet growth was reached, a series of positive feedbacks led to the formation of a continental-scale ice sheet.

The thresholds for growth and decline of a continental scale ice sheet are different. The ice sheet state is dependent on the initial conditions, an effect called hysteresis. Here we present the hysteresis behaviour of the early Cenozoic Antarctic ice sheet for different bedrock elevation reconstructions. The ice sheet-climate coupler CLISEMv1.0 is used and captures both the height-mass balance and the ice-albedo feedback accurately. Additionally, the influence of the different orbital parameters on the threshold to glaciation and deglaciation is investigated in detail. It appears that the long-term eccentricity cycle has a significant influence on the ice sheet growth and decline and is able to pace the ice sheet evolution for constant CO2 concentration close to the glaciation threshold.

How to cite: Van Breedam, J., Huybrechts, P., and Crucifix, M.: Hysteresis and orbital pacing of the early Cenozoic Antarctic ice sheet, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1501, https://doi.org/10.5194/egusphere-egu22-1501, 2022.

EGU22-1635 | Presentations | CR4.1

The role of the Laurentide ice-sheet topography in the Alpine hydro-climate at glacial times 

Patricio Velasquez, Martina Messmer, and Christoph C. Raible

In this study, we investigate the sensitivity of the glacial Alpine hydro-climate to changes of the Laurentide ice sheet (LIS). Bridging the scale gap by using a chain of global and regional climate models, we perform sensitivity simulations of up to 2 km horizontal resolution over the Alps for the Last Glacial Maximum and the Marine Isotope Stage 4. In winter, we find wetter conditions in the southern part of the Alps during glacial conditions compared to present day, to which dynamical processes, i.e.  changes in the wind speed and direction, substantially contribute. During summer, we find the expected drier conditions in most of the Alpine region during glacial conditions, as thermodynamics suggests drier conditions under lower temperatures. The sensitivity simulations of the LIS changes show that an increase of the ice-sheet thickness leads to a significant intensification of glacial Alpine hydro-climate conditions, which is mainly explained by dynamical processes. The findings demonstrate that the Laurentide ice-sheet topography plays an important role in regulating the Alpine hydro-climate and thus permits a better understanding of the precipitation patterns in the complex Alpine terrain at glacial times.

How to cite: Velasquez, P., Messmer, M., and Raible, C. C.: The role of the Laurentide ice-sheet topography in the Alpine hydro-climate at glacial times, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1635, https://doi.org/10.5194/egusphere-egu22-1635, 2022.

EGU22-1774 | Presentations | CR4.1

Reconstruction of the Patagonian Ice Sheet during the Last Glacial Maximum using numerical modelling and geological constraints 

Franco Retamal-Ramírez, Andrés Castillo, Jorge Bernales, and Irina Rogozhina

During the Last Glacial Maximum (LGM, 23,000 to 19,000 years ago), the Patagonian Ice Sheet (PIS) covered the central chain of the Andes between ~ 38 °S to 55 °S. From limited paleoclimatic evidence, especially that derived from glacial landforms, it becomes clear that maximum ice sheet expansions in the Southern and Northern Hemispheres were not synchronized. However, large uncertainties still exist in the timing of the onset of regional deglaciation as well as its major drivers. Ice sheet modelling combined with glacial geochronology and paleoclimate reconstructions can provide important information on the PIS geometry, ice volume and its contribution to the sea level low during the LGM. It can also help to test different paleoclimate scenarios and identify climate models that capture regional climate responses to the global change in a realistic manner.

Here we present an ensemble of numerical simulations of the PIS during the LGM with an aim to constrain the most likely LGM climate conditions that can explain the reconstructed geometry of the PIS in a satisfactory manner. The PIS model is driven by the climate forcing that fuse near-surface air temperatures and precipitation rates from the ERA5 reanalysis with the paleoclimate model outputs from the Paleoclimate Modelling Intercomparison Project (PMIP2 and PMIP3) and the in-house Community Earth System Model (CESM) experiments. Our analysis suggests a strong dependence of the PIS geometry on the near-surface air temperature forcing. All the ensemble experiments designed with PMIP and in-house CESM experiments fail to reproduce the ice sheet extent between 38 and 42 °S. The most realistic performance for the LGM ice sheet extents south of 38 °S has been derived using those climate models that have a higher spatial resolution. The latter helps these models to capture regional climate conditions in a more physically consistent manner. It should be kept in mind that this analysis is based on the evaluation of the modelled ice sheet extents only, as geological evidence on the former ice sheet thickness is still scarce. Nevertheless, it can be shown that a realistic ice sheet geometry during the LGM is consistent with a regional decrease in air temperature of 7 to 12 °C and an increase in precipitation of 400 to 1500 mm/year along the western sectors of the PIS.

How to cite: Retamal-Ramírez, F., Castillo, A., Bernales, J., and Rogozhina, I.: Reconstruction of the Patagonian Ice Sheet during the Last Glacial Maximum using numerical modelling and geological constraints, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1774, https://doi.org/10.5194/egusphere-egu22-1774, 2022.

EGU22-2516 | Presentations | CR4.1

Coupled Greenland ice sheet-climate simulations with the Norwegian Earth System Model (NorESM2) 

Heiko Goelzer, Petra Langebroek, and Andreas Born

Long-term simulations of ice sheets and their interaction with the climate system require the application of Earth system models with interactive ice sheet components. To this end we present the first experiments performed with the CMIP6-type Norwegian Earth System Model (NorESM2) including a Greenland ice sheet model component. We present our coupling and modelling strategy, which builds on earlier work with the Community Earth System Model and show first results for two NorESM2 version with different resolution of the atmospheric component. We have performed and analyzed pre-industrial spinup and control experiments, historical runs and future projections under scenario ssp585, following the ISMIP6 protocol.

How to cite: Goelzer, H., Langebroek, P., and Born, A.: Coupled Greenland ice sheet-climate simulations with the Norwegian Earth System Model (NorESM2), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2516, https://doi.org/10.5194/egusphere-egu22-2516, 2022.

EGU22-2829 | Presentations | CR4.1

Net effect of ice-sheet-atmosphere interactions reduces simulated transient Miocene Antarctic ice sheet variability 

Lennert B. Stap, Constantijn J. Berends, Meike D.W. Scherrenberg, Roderik S.W. van de Wal, and Edward G.W. Gasson

Benthic δ18O levels vary strongly during the warmer-than-modern early- and mid-Miocene (23 to 14 Myr ago), suggesting a dynamic Antarctic ice sheet (AIS). So far, however, realistic simulations of the Miocene AIS have been limited to equilibrium states under different CO2 levels and orbital settings. Earlier transient simulations lacked ice-sheet-atmosphere interactions, and used a present-day rather than Miocene Antarctic bedrock topography. Here, we quantify the effect of ice-sheet-atmosphere interactions, running IMAU-ICE using climate forcing from Miocene simulations by the general circulation model GENESIS. Utilising a recently developed matrix interpolation method enables us to interpolate the climate forcing based on CO2 levels (between 280 and 840 ppm) as well as varying ice sheet configurations (between no ice and a large East Antarctic ice sheet). We furthermore implement recent reconstructions of Miocene Antarctic bedrock topography. We find that the positive albedo-temperature feedback, partly compensated by a negative feedback between ice volume and precipitation, increases hysteresis in the relation between CO2 and ice volume. Together, these ice-sheet-atmosphere interactions decrease the amplitude of Miocene AIS variability in idealised transient simulations. Forced by quasi-orbital 40-kyr forcing CO2 cycles, the ice volume variability reduces by 21% when ice-sheet-atmosphere interactions are included, compared to when forcing variability is only based on CO2 changes. Thereby, these interactions also diminish the contribution of AIS variability to benthic δ18O fluctuations. Evolving bedrock topography during the early- and mid-Miocene reduces ice volume variability by 10%, under equal 40-kyr cycles of atmosphere and ocean forcing. 

How to cite: Stap, L. B., Berends, C. J., Scherrenberg, M. D. W., van de Wal, R. S. W., and Gasson, E. G. W.: Net effect of ice-sheet-atmosphere interactions reduces simulated transient Miocene Antarctic ice sheet variability, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2829, https://doi.org/10.5194/egusphere-egu22-2829, 2022.

EGU22-2831 | Presentations | CR4.1

Reconstructing Cordilleran Ice Sheet stability in western Canada during the Last Deglaciation 

Christopher Darvill, Brian Menounos, Brent Goehring, and Alia Lesnek

The Cordilleran Ice Sheet in western North America was of comparable size and topographic setting to the modern Greenland Ice Sheet and exhibited similar dynamics. Ice streams channelled rapid flow and the western ice margin terminated in both marine and terrestrial environments. Reconstructing Cordilleran Ice Sheet retreat can therefore provide a helpful analogue for how the Greenland Ice Sheet may respond to changing climate and underlying topography in the future. Moreover, deglaciation in this region controlled routes available for early human migration into the Americas. Here, we present cosmogenic 10Be nuclide exposure ages from glacial erratics and bedrock on the west coast of British Columbia (53.4°N, 129.8°W) that add to existing chronologies along ~600 km of coastal North America. Collectively, these data show deglaciation back to the present coastline by ca. 18–16 ka. Retreat then slowed and ice seemingly stabilised close to the present coastline for several thousand years until ca. 14–13 ka. Ice may still have been lost during this period of relative stability, but through vertical thinning rather than lateral retreat. We attribute initial retreat to destabilisation and grounding line retreat resulting from rising sea level and/or ocean warming in the northern Pacific. Subsequent stability at the present coast was likely due to the transition from marine to terrestrial margins despite increasing temperatures that may have driven ice sheet thinning. Hence, we show the importance of understanding both climatic and non-climatic drivers of ice sheet change through time. We also show that hundreds of kilometres of coastline were free of ice prior to an important period of early human migration into the Americas.

How to cite: Darvill, C., Menounos, B., Goehring, B., and Lesnek, A.: Reconstructing Cordilleran Ice Sheet stability in western Canada during the Last Deglaciation, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2831, https://doi.org/10.5194/egusphere-egu22-2831, 2022.

EGU22-3080 | Presentations | CR4.1

Could the Laurentide Ice Sheet have exhibited internal oscillations? 

Daniel Moreno, Jorge Alvarez-Solas, Marisa Montoya, Javier Blasco, and Alexander Robinson

It is well known that the climate during the last glacial period was far from stable. The presence of layers of ice-rafted debris (IRD) in deep-sea sediments has been interpreted to reflect quasi-periodic episodes of massive iceberg calving from the Laurentide Ice Sheet (LIS). Several mechanisms have been proposed, yet the ultimate cause of these events is still under debate. From the point of view of ice dynamics, one of the main sources of uncertainty and diversity in model response is the choice of the basal friction law. Therefore, it is essential to determine the impact of basal friction on ice-stream surges. Here we study the effect of a wide range of basal friction parameters and laws for the LIS under constant LGM boundary conditions by running ensembles of simulations using a higher-order ice-sheet model. The potential feedbacks among till mechanics, basal hydrology and thermodynamics are also considered to shed light on the behaviour of the ice flow. Our aim is to determine under what conditions, if any, physically-based internal oscillations are possible in the LIS. Increasing our understanding of both basal friction laws and basal hydrology will improve not only reconstructions of paleo ice dynamics but also help to constrain the potential future evolution of current ice sheets.

How to cite: Moreno, D., Alvarez-Solas, J., Montoya, M., Blasco, J., and Robinson, A.: Could the Laurentide Ice Sheet have exhibited internal oscillations?, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3080, https://doi.org/10.5194/egusphere-egu22-3080, 2022.

EGU22-3293 | Presentations | CR4.1

Simulations of North American ice sheet at the LGM with FAMOUS-BISICLES and its sensitivity to global temperatures 

Sam Sherriff-Tadano, Niall Gandy, Ruza Ivanovic, Lauren Gregoire, Charlotte Lang, Jonathan Gregory, and Robin Smith

Understanding the response of ice sheets to global temperature changes is a critical issue for the climate community. To accurately simulate future ice sheet evolution, we need to know the strength of feedbacks between the climate and ice sheets. Testing the ability of coupled climate-ice sheet models to simulate past ice sheet extent can provide a way to evaluate the models and ground truth projections. One example is the Last Glacial Maximum (LGM), when huge ice sheets covered the Northern Hemisphere, especially over the North America. Here, we performed simulations of the North American ice sheet and climate of the LGM with a recently updated ice sheet-atmosphere coupled model Famous-Ice (Smith et al. 2021, Gregory et al. 2020). The model consists of a low-resolution atmospheric general circulation model Famous (Smith et al. 2008) and an ice sheet model BISICLES (Cornford et al. 2013). It calculates the surface mass balance over ice sheets based on an energy budget scheme and incorporates an updated albedo scheme, which accounts for albedo changes associated with modifications in surface air temperature, grain size and density of the snow. The atmospheric model reproduces the surface mass balance of the modern Greenland ice sheet reasonably well (Smith et al. 2021). Simulations of projections of future sea-level rise (Gregory et al. 2020) and the LGM (Gandy et al. in prep) have also been performed with Famous-Ice using a different ice sheet model GLIMMER.

We present simulations of the LGM with interactive ice sheets in North America and Greenland using FAMOUS-BISICLES. Uncertain input parameters controlling the surface temperatures and ice albedo are varied in our simulations. The global temperature is specified by applying fixed sea surface temperature in the atmospheric model producing a global cooling that ranges from -3K to -6.5K in the simulations. The bare ice minimum albedo is varied from 0.2 to 0.7, which corresponds to the range in PMIP3 models. Our results show a better representation of North American ice sheet when forced with a colder LGM (-6.5K) and high bare ice albedo. We will further discuss potential roles of model biases and compare our results with simulations performed with FAMOUS-GLIMMER (Gandy et al. in prep).

How to cite: Sherriff-Tadano, S., Gandy, N., Ivanovic, R., Gregoire, L., Lang, C., Gregory, J., and Smith, R.: Simulations of North American ice sheet at the LGM with FAMOUS-BISICLES and its sensitivity to global temperatures, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3293, https://doi.org/10.5194/egusphere-egu22-3293, 2022.

EGU22-4740 | Presentations | CR4.1

Antarctic-climate multi-millenia coupled simulations under different pCO2 levels with the iLOVECLIM-GRISLI model 

Gaelle Leloup, Aurélien Quiquet, Christophe Dumas, Didier Roche, and Didier Paillard

Ice sheets and the rest of the climate system interact in various ways, notably via the atmosphere, ocean and solid earth. Atmospheric and oceanic temperatures and circulations affect the evolution of ice-sheets, and conversely ice-sheet evolution impacts the rest of the climate system via various processes, including albedo modification, topographic changes and freshwater flux release into the ocean. To correctly model the evolution of the climate system and sea level rise, these feedbacks therefore need to be considered.

Under the highest emission scenario, temperature is expected to reach levels comparable to the Eocene epoch in a few centuries [1]. At this time, there was no widespread glaciation in Antarctica.

The work of Garbe et al [2] has shown that the Antarctic ice sheet has a hysteresis behavior and gave different temperature thresholds leading to committed Antarctic mass loss. For example, between 6 and 9 degrees of warming (a global temperature increase comparable to the one expected in 2300 for the most emissive scenario), the loss of 70% of the present-day ice volume is triggered. However, the modelling study used idealized perturbations of the climate fields based solely on global mean temperature. More specifically, global mean temperature is translated into local changes of ocean and surface air temperature and increased until a complete deglaciation of the Antarctic ice-sheet is reached. In addition the study did not take into account the ice sheet change feedback on the climate system.

In our work we intend to go a step further by taking into account both the influence of atmosphere and oceanic temperature and circulations on the ice sheet in a physical way, as well as the influence of the ice sheet on the rest of the climate system.

To do so, we use the coupled ocean-atmosphere-vegetation intermediate complexity model iLOVECLIM [3], fully coupled to the GRISLI ice-sheet model for Antarctica [4, 5].

We perform several multi-millenia equilibria simulations for different pCO2 levels, thanks to the relative rapidity of both the iLOVECLIM and GRISLI models. These simulations lead to different atmospheric and oceanic temperatures and Antarctic mass loss. 

These coupled simulations allow us to explore the impact of the ice sheet feedback on the climate and to investigate the differences compared to cases where these feedbacks are not included. The influence of the model parameters linked to the ice sheet coupling is also studied.

 

References :

[1] Westerhold et al 2020, “An astronomically dated record of Earth’s climate and its predictability over the last 66 million years”

[2] Garbe et al 2020 “The hysteresis of the Antarctic Ice Sheet”

[3] Quiquet et al 2018, “Online dynamical downscaling of temperature and precipitation within the iLOVECLIM model (version 1.1)”

[4] Quiquet et al 2018, “The GRISLI ice sheet model (version 2.0): calibration and validation for multi-millennial changes of the Antarctic ice sheet”

[5] Quiquet et al 2021 “Climate and ice sheet evolutions from the last glacial maximum to the pre-industrial period with an ice-sheet–climate coupled model”

How to cite: Leloup, G., Quiquet, A., Dumas, C., Roche, D., and Paillard, D.: Antarctic-climate multi-millenia coupled simulations under different pCO2 levels with the iLOVECLIM-GRISLI model, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4740, https://doi.org/10.5194/egusphere-egu22-4740, 2022.

EGU22-5016 | Presentations | CR4.1

Antarctic sub-shelf melt during the present and the last interglacial and its impact on ice sheet dynamics 

Maxence Menthon, Pepijn Bakker, Aurélien Quiquet, and Didier Roche

The response of ice sheets to climate changes can be diverse and complex. The amplitude, speed and irreversibility of the melting of the ice sheets due to current anthropogenic emissions remain largely uncertain after 2100. Being able to reconstruct the evolution of the ice sheets during the past climate changes is a possible approach to constrain their future evolution in time scales further than the end of the century.

Here we aim to reconstruct the evolution of the Antarctic ice sheet during the Last Interglacial (LIG, ~ 130 to 115 kyr BP). The LIG was 0.5 to 1˚C warmer than the pre-industrial era with a sea-level between 6 to 9 m above present level. In other words, the Antarctic ice sheet during the LIG can be considered as an analogue to its future evolution. Moreover, it is the interglacial on which we have the most geological records to compare with simulation results.

Knowing that the oceanic forcing is the main driver of the Antarctic ice sheet retreat, we introduced the sub-shelf melt module PICO (Reese et al. 2018) in the ice sheet model (GRISLI, Quiquet et al. 2018) in order to physically compute the melt. We use outputs from the Earth Sytem Model (iLOVECLIM, Roche et al. 2014) to force idealized experiments. Several time periods will be covered: present-day, last glacial maximum and LIG. This work is a first step towards a fully coupled iLOVECLIM-GRISLI-PICO simulation to explicitly take into account the ice sheet climate - interactions in a physical way in simulations of the Antarctic ice sheet during the LIG and future centuries.

How to cite: Menthon, M., Bakker, P., Quiquet, A., and Roche, D.: Antarctic sub-shelf melt during the present and the last interglacial and its impact on ice sheet dynamics, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5016, https://doi.org/10.5194/egusphere-egu22-5016, 2022.

EGU22-5261 | Presentations | CR4.1

Simulating the Last Glacial Cycle using a Glacial Index and Climate Matrix Method 

Meike D.W. Scherrenberg, Roderik S.W. van de Wal, Constantijn J. Berends, and Lennert B. Stap

For simulating ice sheet – climate interactions on multi-millennial time-scales, a set-up that uses a two-way coupled Earth System Model would be ideal. However, running these simulations over multi-millennium time-scales while including ice sheets, is not feasible. Alternatively, ice sheet models can be forced by interpolating climate time-slices, allowing for a transient forcing to an ice sheet model at limited computational costs.

Here, we compare two methods that interpolate between climate time-slices to create a transient forcing for ice sheet simulations. Firstly, we use a glacial index method, in which the climate is linearly interpolated between time-slices based only on prescribed atmospheric CO2 concentrations. Secondly, we use a climate matrix method in which the interpolation is not only dependent on the prescribed CO2 concentration, but also on internally generated thickness, volume and albedo. As a result, the climate matrix method captures ice-sheet atmosphere feedbacks.

Here we present ice sheet simulations of the Last Glacial Cycle using IMAU-ICE forced with Last Glacial Maximum (LGM) and Pre-Industrial time-slices. For the time-slices we use the output from nine Paleoclimate Modelling Intercomparison Project Phase III (PMIP3) GCMs. Our aim is to compare and to evaluate the differences in ice sheet evolution and LGM volume and extent resulting from the different PMIP3 models and the interpolation method used for transient simulations.

For most PMIP3 forcings, both the North-American and Eurasian ice sheets build up quicker in the climate matrix method compared to the glacial index method, which is in better agreement with paleo-observations. This is mostly a result from precipitation differences between the two interpolation methods: In the climate matrix method the interpolation of precipitation is dependent on internally generated ice thickness instead of only CO2. Therefore, when ice thickness is smaller than LGM, the interpolation tends to shift more towards pre-industrial in the climate matrix method compared to the glacial index method. As precipitation is larger during pre-industrial compared to LGM in most Eurasian and North-American regions, this leads to a larger precipitation in the climate matrix method, increasing ice sheet volume. Similarly, the climate matrix method results into warmer temperatures in ice-free areas as the interpolation is dependent on both CO2, albedo and insolation. However, for most PMIP3 models, this ice sheet-temperature feedback does not cancel-out the increased precipitation in the climate matrix method.

How to cite: Scherrenberg, M. D. W., van de Wal, R. S. W., Berends, C. J., and Stap, L. B.: Simulating the Last Glacial Cycle using a Glacial Index and Climate Matrix Method, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5261, https://doi.org/10.5194/egusphere-egu22-5261, 2022.

EGU22-5599 | Presentations | CR4.1

Impact of cumulative anthropogenic carbon emissions, emission duration, and negative emission scenarios on melting of the Greenland ice sheet 

Dennis Höning, Reinhard Calov, Stefanie Talento, Matteo Willeit, and Andrey Ganopolski

Budgets of remaining anthropogenic carbon emissions have been estimated to keep global warming below a limit (IPCC report 2021). A main impact of global warming is the rise of the sea level caused by melting of the Greenland ice sheet. However, the response of the Greenland ice sheet to temperature rise is strongly nonlinear. Melting depends on the time interval at which the ice sheet is exposed to high temperatures and on its rate of change, and a short time interval of high emission would therefore not necessarily result in the same sea level rise as long intervals of low emission. In order to make adequate predictions about sea level rise associated with melting of the Greenland ice sheet at specific times in the future, it is therefore crucial to explore the impact of cumulative emissions in combination with the emission duration.

We simulate Earth’s evolution for the next 20,000 years using CLIMBER-X, a fully coupled Earth System model of intermediate complexity, including modules for atmosphere, ocean, land surface, sea ice and the interactive 3-D polythermal ice sheet model SICOPOLIS, which is applied to the Greenland ice sheet at a spatial resolution of 16 km. In a first step, we explore equilibrium states of the volume of the Greenland ice sheet using constant partial pressures of atmospheric CO2. We also explore tipping points related to these states, i.e. unstable states of the ice volume where smaller values would lead to further melting until the associated stable state is reached. Next, we investigate the critical cumulative carbon emission to cross these tipping points. Finally, we assess the influence of the emission duration on crossing the tipping points and on the convergence rate towards the associated equilibrium states. We also investigate to what extent future negative emissions could limit sea level rise.

Our results show how high carbon emission rates, even throughout a short time interval, cause the Greenland ice sheet system to rapidly approach equilibrium states of smaller ice volume. This convergence cannot completely be offset by future negative emissions. In contrast, a quick decrease of global emissions, even if in combination with an extended time period of small net emissions in the future, would substantially delay sea level rise and could even prevent the system from crossing the tipping points.

How to cite: Höning, D., Calov, R., Talento, S., Willeit, M., and Ganopolski, A.: Impact of cumulative anthropogenic carbon emissions, emission duration, and negative emission scenarios on melting of the Greenland ice sheet, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5599, https://doi.org/10.5194/egusphere-egu22-5599, 2022.

EGU22-6242 | Presentations | CR4.1

Sensitivity of Heinrich-type ice sheet surges and their implications for the last deglaciation 

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

Transitions from a stable, periodically oscillating ice-sheet system to a perpetual ice stream has potentially far-reaching implications for the timing of the onset of the last deglaciation as well as for climate transitions such as the Younger Dryas. These periodical ice-sheet oscillations known as Heinrich-type ice sheet surges are among the most dominant signals of glacial climate variability. They are quasi-periodic events during which large amounts of ice are discharged from ice sheets into the ocean. The addition of freshwater strongly affects the ocean circulation, resulting in a pronounced cooling in the North Atlantic region. In addition, changes in the ice sheet geometry also have significant effects on the climate. Here, we use a coupled ice sheet-solid earth model that is driven with forcing from a comprehensive Earth System Model that includes interactive ice sheets to identify key drivers controlling the surge cycle length of Heinrich-type ice-sheet surges from two main outlet glaciers of the Laurentide ice sheet. Our simulations show different surge initiation behaviour for the land-terminating Mackenzie ice stream and marine-terminating Hudson ice stream. For both ice streams, the surface mass balance has the largest effect on the surge cycle length. Ice surface temperature and geothermal heat flux also influence the surge cycle length, but to a lesser degree. Ocean forcing and different frequencies of the same forcing have a negligible effect on the surge cycle length. The simulations also highlight that a certain parameter space exists under which stable surge oscillations can be maintained. This parameter range is much narrower for the Mackenzie ice stream than for the Hudson ice stream. Leaving the stable regime results in a dynamical switch that turns the system from periodically oscillating system into a perpetual ice stream system. This transition can lead to a volume loss of up to 36% for the respective ice stream drainage basin under otherwise glacial climate conditions.

How to cite: Schannwell, C., Mikolajewicz, U., Ziemen, F., and Kapsch, M.-L.: Sensitivity of Heinrich-type ice sheet surges and their implications for the last deglaciation, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6242, https://doi.org/10.5194/egusphere-egu22-6242, 2022.

EGU22-6247 | Presentations | CR4.1

The influence of proglacial lakes on climate and surface mass balance of retreating ice sheets – An Investigation of the Laurentide and Fennoscandian ice sheets,13 ka BP 

Lianne Sijbrandij, Paul Gierz, Sebastian Hinck, Uta Krebs-Kanzow, Gerrit Lohmann, and Lu Niu

This study investigates how large proglacial lakes affected regional climate and surface mass balance (SMB) of retreating ice sheets during the last deglaciation. For this purpose we have modified the atmosphere model ECHAM6. The approach is here to limit the surface temperature of proglacial lakes to values below 4°C, while other lakes in ECHAM6 can freely evolve according to a mixed layer scheme.

As a first application we investigate the impact of proglacial lakes during the Allerød interstadial at 13 ka (ka is thousand years before present) with three atmosphere stand-alone experiments:

(i) with 13ka land surface boundary conditions (GLAC1d, Ivanovic et al., 2016) and a modern lake configuration

(ii) same as (i) but with additional lakes around the North American and Fennoscandian Ice Sheets

(iii) same as (ii) but the additional lakes are treated according to our proglacial lake approach.

Over the ocean we use boundary conditions taken from a 15ka coupled climate simulation. These three simulations were evaluated with respect to the regional climate response and the SMB was calculated using the diurnal Energy Balance Model (dEBM, Krebs-Kanzow et al., 2021). Preliminary results are indicating an overall positive effect of regular lakes, and in particular proglacial lakes, on the SMB of the great ice sheets over Northern America and Scandinavia during the Allerød interstadial.

 

References:

Ivanovic, R. F., Gregoire, L. J., Kageyama, M., Roche, D. M., Valdes, P. J., Burke, A., Drummond, R., Peltier, W. R., and Tarasov, L.: Transient climate simulations of the deglaciation 21–9 thousand years before present (version 1) – PMIP4 Core experiment design and boundary conditions, Geosci. Model Dev., 9, 2563–2587, https://doi.org/10.5194/gmd-9-2563-2016, 2016.

Krebs-Kanzow, U., Gierz, P., Rodehacke, C. B., Xu, S., Yang, H., and Lohmann, G., 2021: The diurnal Energy Balance Model (dEBM): a convenient surface mass balance solution for ice sheets in Earth system modeling, The Cryosphere, 15, 2295–2313, https://doi.org/10.5194/tc-15-2295-2021.

How to cite: Sijbrandij, L., Gierz, P., Hinck, S., Krebs-Kanzow, U., Lohmann, G., and Niu, L.: The influence of proglacial lakes on climate and surface mass balance of retreating ice sheets – An Investigation of the Laurentide and Fennoscandian ice sheets,13 ka BP, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6247, https://doi.org/10.5194/egusphere-egu22-6247, 2022.

EGU22-6624 | Presentations | CR4.1

A transient glacial cycle simulation with the coupled CESM1.2-PSUIM climate-ice-sheet model 

Kyung-Sook Yun and Axel Timmermann

Here we present first results from a series of transient glacial cycle simulations which were conducted with the Community Earth System model (CESM, version 1.2) coupled to the Penn State University ice sheet-ice-shelf Model (PSUIM). The coupling is achieved by applying CESM-simulated surface air temperature, precipitation, surface shortwave radiation and subsurface-ocean temperatures to the PSUIM. CESM is forced in return by PSUIM-simulated ice sheet cover, topography, and freshwater fluxes. The coupled model, which uses a ~ 4 degree horizontal resolution in the atmosphere and ocean and ~ 40 km for the ice-sheets in both hemispheres, includes representations of the lapse-rate, desert-elevation and albedo-dust feedbacks. The coupled model, which uses moderate bias corrections for temperature and precipitation, reproduces the ice sheet evolution over the last glacial cycle in reasonable agreement with paleo-climate data. In this presentation we will further highlight the sensitivity of simulated glacial variability to changes in key surface parameters as well to the individual orbital and greenhouse gas forcings. Our results reveal that only the combination of orbital and CO2 forcings can generate the full glacial/interglacial amplitude. Single forcings are insufficient to generate glacial variability, which emphasizes the need to understand the mechanisms that led to the orbital pace-making of CO2 during the Pleistocene.

How to cite: Yun, K.-S. and Timmermann, A.: A transient glacial cycle simulation with the coupled CESM1.2-PSUIM climate-ice-sheet model, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6624, https://doi.org/10.5194/egusphere-egu22-6624, 2022.

EGU22-7293 | Presentations | CR4.1

Antarctic Ice Sheet  simulations using Yelmo ice sheet model and a series of IPSL CM5A2 climate simulations between 17 Ma and 14 Ma 

Diane Segalla, Javier Blasco Navarro, Gilles Ramstein, Frédéric Fluteau, Alexander James Robinson, Jorge Alvarez-Solas, Marisa Luisa Montoya Redondo, and Florence Colleoni

The mid-Miocene Climatic Optimum (MMCO, ~17-15 Ma) and the mid-Miocene Climatic Transition (MCT, ~15-13.5 Ma),  represents a period of high policy relevance because of the high atmospheric pCO2 concentrations. Exploring this period offers the opportunity to investigate the Antarctic Ice Sheet (AIS) response to CO2 forcings that are close to those projected in the medium to worse case emission scenarios. A set of equilibrium simulations with the 3D ice sheet model Yelmo allows us to study the envelope of the AIS volume and extent during the MMCO (17 Ma) and MCT (14 Ma). These simulations are forced off-line with equilibrium climatic conditions  obtained with the Atmosphere-Ocean General Circulation Model (AOGCM) IPSL CM5A2.  Two values of the reconstructed atmospheric pCO2, i.e. 420 ppm and 700 ppm, are prescribed, for an orbital configuration corresponding to minimum and maximum insolation values at 75°S each (9 climate simulations in total). Thanks to these different configurations we simulated the AIS dynamics. Results show that at 17 Ma, warmer conditions produce an AIS that is drastically reduced with respect to today’s configuration. At 14 Ma, cooler climatic conditions allow the AIS to expand again. This is in agreement with the geological records of the AIS dynamics that reveal a substantial expansion of the ice sheet at the end of the MCT. Since Antarctica is the only ice sheet at this time, our set of climate and ice-sheet simulations capture the envelope of ice volume and extent of the AIS. Moreover, such studies contribute to a better understanding of the 𝛿18O records and of the evolution of deep ocean temperature versus ice volume and global mean sea level change.

How to cite: Segalla, D., Blasco Navarro, J., Ramstein, G., Fluteau, F., Robinson, A. J., Alvarez-Solas, J., Montoya Redondo, M. L., and Colleoni, F.: Antarctic Ice Sheet  simulations using Yelmo ice sheet model and a series of IPSL CM5A2 climate simulations between 17 Ma and 14 Ma, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7293, https://doi.org/10.5194/egusphere-egu22-7293, 2022.

EGU22-7563 | Presentations | CR4.1

Sea ice dynamics in the Labrador Sea across Heinrich events during MIS 3 

Henrieka Detlef, Mads Mørk Jensen, Marianne Glasius, and Christof Pearce

The most prominent events of ice-sheet collapse in the recent geological past are so-called Heinrich events observed during millennial-scale climate oscillations of the last glacial period. They are characterized by the dispersal of ice(berg) rafted debris and freshwater across the North Atlantic, with the Hudson Strait suggested as the predominant source region. One potential mechanism triggering iceberg release invokes cryosphere-ocean interactions, where subsurface warming destabilizes the Laurentide ice sheet. In this scenario, the build-up of a subsurface heat reservoir is caused by an extensive sea ice cover in the Labrador Sea in combination with a reduced overturning circulation in the North Atlantic, preventing the release and downward mixing of heat in the water column.

Here we present high-resolution reconstructions of sea ice dynamics in the outer Labrador Sea between 30 ka and 60 ka at IODP Site U1302/03, located on Orphan Knoll. Sea ice reconstructions are based on a suite of sympagic and pelagic biomarkers, including highly branched isoprenoids and sterols. These results suggest a transition from reduced/seasonal to extended/perennial sea ice conditions preceding the onset of iceberg rafting associated with Heinrich event 3, 4, 5, and 5a by a couple of hundred to a thousand years. Our preliminary results thus support the importance of sea ice in the Labrador Sea for triggering Heinrich events. Future results from the same core will have to confirm the timing and extent of subsurface warming and ocean circulation dynamics.  

How to cite: Detlef, H., Mørk Jensen, M., Glasius, M., and Pearce, C.: Sea ice dynamics in the Labrador Sea across Heinrich events during MIS 3, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7563, https://doi.org/10.5194/egusphere-egu22-7563, 2022.

EGU22-7694 | Presentations | CR4.1

Sensitivity of the Eurasian Ice Sheet: Improved model-data comparison routines 

Rosie Archer, Jeremy Ely, Timothy Heaton, and Chris Clark

At the Last Glacial Maximum, the Eurasian Ice Sheet (EIS) was one of the largest ice masses, reaching an area of 5.5 Mkm2 at its maximum. Recent advances in numerical ice sheet modelling hold significant promise for improving our understanding of ice sheet dynamics, but remain limited by the significant uncertainty as to the appropriate values for the various model input parameters. The EIS left behind a rich library of observational evidence, in the form of glacial landforms and sediments. Integrating this evidence with numerical ice sheet models allows inference on these key model parameters, leading to a better understanding of the behaviour of the EIS and a framework for advancing numerical ice sheet models. To quantify how successfully a particular model run matches the available data, model-data comparison tools are required. Here, we model the EIS using the Parallel Ice Sheet Model (PISM), a hybrid shallow-ice shallow shelf ice sheet model. We perform sensitivity analyses to reveal the most important parameters controlling the evolution of our modelled EIS. Results from this analysis allow us to reduce the parameter space required for a future ensemble experiment. This ensemble experiment will utilise novel model-data comparison tools which compare ice-free timings to geochronological evidence and modelled flow directions with drumlins. Unlike previous model-data comparison routines, our tools provide a more nuanced, and probabilistic, assessment of fit than a simple pass-fail. This offers significant benefits for future parameter selection.

How to cite: Archer, R., Ely, J., Heaton, T., and Clark, C.: Sensitivity of the Eurasian Ice Sheet: Improved model-data comparison routines, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7694, https://doi.org/10.5194/egusphere-egu22-7694, 2022.

EGU22-9235 | Presentations | CR4.1

Tipping Points in the Amundsen Sea Sector, a comparison between 2D and 3D ice-sheet models 

Cyrille Mosbeux, Olivier Gagliardini, Nicolas Jourdain, Benoit Urruty, Mondher Chekki, Fabien Gillet-Chaulet, and Gael Durand

Ice mass loss from Antarctic Ice Sheet is increasing, accelerating its contribution to global sea level rise. Interactions between the ice shelves (the floating portions of the ice sheet that buttress the grounded ice) and the ocean are key processes in this mass loss. The most rapid recent observed mass loss from the Antarctic Ice Sheet is in the Amundsen Sea, where buttressing is declining as small ice shelves are being thinned rapidly by melting driven by inflows of warm Circumpolar Deep Water, leading to important grounding line retreats. Recent research indicates that ice sheets, especially the parts that rest on a bed below sea level such as most of the Amundsen sector, are particularly prone to an unstable and irreversible retreat that might lead to an important and fast global sea level rise.

As part of the European Horizon 2020 research project TiPACCs that assesses the possibility of near-future irreversible changes, so-called tipping points, in the Southern Ocean and the Antarctic Ice Sheet, we conduct numerical simulations perturbating the current conditions of the ice-ocean system in the Amundsen Sea Sector. More particularly, we use the Stokes flow formulation of the open-source ice flow model Elmer/Ice, forced with melt parametrization under the ice shelves to determine the effect of ocean warming on the ice-sheet evolution –eventually looking for the existence of future tipping points in the region. Since 3D-Stokes models can be numerically expensive, using the same Elmer/Ice framework (datasets, ocean and climate forcing), we compare our results to the more efficient but sometimes less accurate 2D-shallow–shelf(y)-Approximation (SSA). This methodology allows us to entangle the differences between the two models and better constrain the uncertainty linked to TiPACCs pan-Antarctic simulations based on the SSA.

How to cite: Mosbeux, C., Gagliardini, O., Jourdain, N., Urruty, B., Chekki, M., Gillet-Chaulet, F., and Durand, G.: Tipping Points in the Amundsen Sea Sector, a comparison between 2D and 3D ice-sheet models, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9235, https://doi.org/10.5194/egusphere-egu22-9235, 2022.

EGU22-9983 | Presentations | CR4.1

Antarctica’s x-factor: How does Antarctic precipitation change with temperature? 

Lena Nicola, Prof. Dirk Notz, and Prof. Ricarda Winkelmann

Snowfall is by far the most important positive contributor to the overall mass balance of the Antarctic Ice Sheet, potentially buffering temperature-induced dynamical ice loss in a warming climate. Previous studies have proposed that Antarctic snowfall will increase along the Clausius-Clapeyron relationship, describing the saturation water vapour pressure as a function of temperature (7% change for 1°C of warming). Due to cold temperatures and continentality in the interior, this general, first-order explanation may not hold true for snowfall changes across the ice sheet. In this study, we investigate how this first-order approximation can be modified to more reliably represent snowfall changes in a warming climate for simulations of the Antarctic Ice Sheet.

To characterise the present-day precipitation pattern, we use reanalysis data and make use of state-of-the-art model data from the CMIP6 modelling project as well as regional model data. We analyse how the sensitivity of Antarctic precipitation to temperature changes is represented in models and how it potentially changes in the future. We use least-squares linear regression to determine the sensitivity factor, Antarctica’s x-factor, that is used in ice-sheet models to scale precipitation. 

With our statistical analyses, we show that sensitivities of column-integrated water vapour, precipitation, snowfall, net precipitation, and surface mass balance to temperature changes are fairly similar under present-day conditions; implying that the exponential relationship of saturation water vapour pressure to temperature could generally lead to additional mass gains of the Antarctic Ice Sheet with warming. However, we find that the relationship of Antarctic precipitation to temperatures across the ice sheet is not constant, but decreases with ongoing warming. Taking these changes into account could give a more reliable estimate of future precipitation changes than existing approaches. We demonstrate that a linear approximation of the exponential relationship between Antarctic precipitation and temperature becomes more and more imprecise in a warming climate, both for computing the sensitivity factor and to scale Antarctic precipitation in models.

We propose a new way to extract the sensitivity factor of Antarctic precipitation to temperature which takes regional variations and the temperature dependence into account. The temperature dependence becomes more important the higher the warming becomes. Considering local warming rates, we show the necessity of introducing a temperature-dependent scaling factor in ice-sheet models, especially for high-end or long-term sea-level projections.

How to cite: Nicola, L., Notz, P. D., and Winkelmann, P. R.: Antarctica’s x-factor: How does Antarctic precipitation change with temperature?, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9983, https://doi.org/10.5194/egusphere-egu22-9983, 2022.

EGU22-10008 | Presentations | CR4.1

The evolution of future Antarctic surface melt using PISM-dEBM-simple 

Julius Garbe, Maria Zeitz, Uta Krebs-Kanzow, and Ricarda Winkelmann

With a volume of 58 m sea-level equivalent, the Antarctic Ice Sheet represents the largest potential source of future sea-level rise under global warming. While the ice sheet gains mass through snowfall at the surface, it loses mass through dynamic discharge and iceberg calving into the ocean, as well as by melting at the surface and underneath its floating ice shelves.

Already today, Antarctica is contributing to sea-level rise. So far, this contribution has been comparatively modest, but is expected to increase in the future. Most of the current mass losses are concentrated in the West Antarctic Ice Sheet, mainly caused by sub-shelf melting and ice discharge. Because air temperatures are low and thus surface melt rates are small, any significant melting at the surface is restricted to the low-elevation coastal zones. At the same time, most of the mass loss is offset by snowfall, which is projected to further increase in a warming atmosphere.

As warming progresses over the coming centuries, the question arises as to how long the mass losses on the one side will be compensated by the gains on the other. In 21st-century projections, increasing surface mass balance is outweighing increased discharge even under strong warming scenarios. However, in long-term (multi-century to millennium scale) warming simulations the positive surface mass balance trend shows a peak and subsequent reversal. Owing to positive feedbacks, like the surface-elevation or the ice-albedo feedback, this effect can be enhanced once a surface lowering is triggered or the surface reflectivity is lowered by initial melt.

Here, we implement a simplified version of the diurnal Energy Balance Model (dEBM-simple) as a surface module in the Parallel Ice Sheet Model (PISM), which extends the conventional positive-degree-day (PDD) approach to include the influence of solar radiation and parameterizes the ice albedo as a function of melting, implicitly accounting for the ice-albedo feedback.

Using a model sensitivity ensemble, we analyze the range of possible surface mass balance evolutions over the 21st century as well as in long-term simulations based on extended end-of-century climatological conditions with the coupled model. The comparison with the PDD approach hints to a strong overestimation of surface melt rates of the latter, even under present day conditions. The dEBM-simple further allows us to disentangle the respective contributions of temperature- and insolation-driven surface melt to future sea level rise.

How to cite: Garbe, J., Zeitz, M., Krebs-Kanzow, U., and Winkelmann, R.: The evolution of future Antarctic surface melt using PISM-dEBM-simple, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10008, https://doi.org/10.5194/egusphere-egu22-10008, 2022.

EGU22-10758 | Presentations | CR4.1

Kill dates from re-exposed black mosses constrain past glacier advances along the western Antarctic Peninsula 

Dulcinea Groff, David Beilman, Zicheng Yu, and Derek Ford

Glaciers retreating along the western Antarctic Peninsula (AP) reveal previously entombed soils and plants. We collected black (dead) mosses to constrain the timing of late Holocene glacier advances at four sites along the AP from ice-free terrain and from rapidly retreating ice margins. The results of radiocarbon measurements from 39 black mosses were used to infer glacier activity over the past 1500 years along with established criteria for sample collection. The criteria ensure robust estimates of when plant growth ended, referred to hereafter as “kill date”. From these kill dates we report distinct periods of ice advance during ca. 1300, 800, and 200 calibrated calendar years before 1950 (cal yr BP) and the first estimates of glacier rate of advance around 800 cal yr BP of 2.0 and 0.3 meters per year from Gamage and Bonaparte Points (southern Anvers Island), respectively. Kill dates reveal a narrow range of ages within a region, suggesting that multiple glacier termini advanced together, and that the rate of local advances may have varied by an order of magnitude. Other evidence for glacier advances in the northern AP ca. 200 cal yr BP and ages of penguin remains (a proxy for penguin colony abandonment) centered ca. 800 cal yr BP from several sites across the AP coincide with our kill dates. Combining several lines of terrestrial evidence for past glacier activity is critical to improving our understanding of the regional synchroneity of glacial dynamics and cryosphere-biosphere connections.

How to cite: Groff, D., Beilman, D., Yu, Z., and Ford, D.: Kill dates from re-exposed black mosses constrain past glacier advances along the western Antarctic Peninsula, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10758, https://doi.org/10.5194/egusphere-egu22-10758, 2022.

A leading contender for explaining the mid-Pleistocene transition (MPT) from small 40 kyr glaciations to large, abruptly terminating 100 kyr ones is a shift to high friction bed under the Northern hemisphere ice sheets – the North American ice sheet in particular. The regolith hypothesis posits that this occurred with the removal of deformable regolith – laying bare higher-friction bedrock under ice sheet core domains. Is the regolith hypothesis consistent with the physics of glacial removal of mechanically weak surface material?                

                                                                        

Self-consistency of the regolith hypothesis has not been tested for a realistic, 3D North American ice sheet, capturing the transition from soft to hard bedded and 40 to 100 kyr cycles, fully considering basal processes and sediment production. To test self-consistency, we simulate the pace and distribution of regolith removal in a numerical ice sheet model incorporating the relevant glacial processes and their uncertainties. Specifically, the Glacial Systems Model includes: fully coupled sediment production and transport, subglacial hydrology, glacial isostatic adjustment, 3D thermomechanically coupled hybrid ice physics, and internal climate solution from a 2D non-linear energy balance model. The sediment model produces sediment via quarrying and abrasion while transporting material englacially and subglacially. The subglacial hydrology model employs a linked-cavity system with a flux based switch to tunnel drainage, giving dynamic effective pressure needed for realistic sediment and sliding processes. Deflection and rebound of the Earth's surface are calculated for a range of solid Earth visco-elastic rheologies.  The coupled system is driven only by prescribed atmospheric CO2 and orbitally derived insolation.

                                                                         

Starting from a range of initial sediment distributions and simulating an ensemble of model parameter values, we model the rate and spatial distribution of regolith dispersal and compare this against the inferred range of Pliocene regolith thickness, the present day sediment distribution, and the timing of the MPT. A first order fully coupled representation of ice, climate and sediment interactions captures the transition within parametric and observational uncertainty. The system gives the shift from 40 to 100 kyr glacial cycles while broadly reproducing the present day sediment distribution, inferred early Pleistocene extent, LGM ice volume and deglacial margin locations.

How to cite: Drew, M. and Tarasov, L.: A test of the Regolith Hypothesis with fully coupled glacial sediment and ice sheet modelling, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10821, https://doi.org/10.5194/egusphere-egu22-10821, 2022.

EGU22-11345 | Presentations | CR4.1

New ice margin chronology for the last deglaciation of the North American Ice Sheet Complex 

Martin Margold, April S. Dalton, Jakob Heyman, Helen E. Dulfer, and Sophie L. Norris

The North American Ice Sheet Complex (comprising the Laurentide, Cordilleran and Innuitian ice sheets) was the largest ice mass in the Northern Hemisphere that grew towards and waned after the Last Glacial Maximum. The existing ice margin chronology available for the North American Ice Sheet Complex is based on radiocarbon data only and does not reflect other geochronometric information constraining the last deglaciation, such as cosmogenic exposure- or optically stimulated luminescence ages. Here we present a series of newly produced ice margin isochrones from 25 ka to present, in a time step of 500 years. For each isochron, we draw maximum, best estimate, and minimum ice margin position in an attempt to capture the existing uncertainty. The ice margin isochrones are based on (i) an up-to-date dataset of radiocarbon ages (~5000), (ii) 10Be and 26Al cosmogenic nuclide data that directly date ~80 ice-marginal features over North America, (iii) ~350 optically stimulated luminescence ages dating the deposition of an aeolian cover immediately post-deglaciation, (iv) the ice-sheet scale glacial geomorphology record. Our effort brings the information on the last North American Ice Sheet Complex deglaciation on par with that for the Eurasian Ice Sheets and should serve the broad community of Quaternary research from archaeology to numerical ice sheet modelling.

How to cite: Margold, M., Dalton, A. S., Heyman, J., Dulfer, H. E., and Norris, S. L.: New ice margin chronology for the last deglaciation of the North American Ice Sheet Complex, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11345, https://doi.org/10.5194/egusphere-egu22-11345, 2022.

EGU22-11407 | Presentations | CR4.1

Effects of extreme melt events on the Greenland ice sheet 

Johanna Beckmann and Ricarda Winkelmann

Over the past decade, Greenland has experienced several extreme melt events, the most pronounced ones in the years 2010, 2012 and 2019. With progressing climate change, such extreme melt events can be expected to occur more frequently and potentially become more severe. So far, however, projections of ice loss and sea-level change from Greenland typically rely on scenarios that only take gradual changes in the climate into account. 
Here we investigate the effect of extreme melt events on the ice dynamics and overall mass balance of the Greenland Ice Sheet in simulations using the Parallel Ice Sheet Model (PISM). While the extremes generally lead to thinning of the ice sheet by enhanced melting, they partly also decrease the overall ice surface velocities due to a reduced driving gradient. In our simulations, we find that taking extreme events into account leads to additional ice loss compared to the baseline scenario without extremes. We find that the sea-level contribution from Greenland could increase by up to 45 cm by the year 2300 if severe extreme events are considered in future projections. We conclude that both changes in the frequency and intensity of extreme events need to be taken into account when projecting the future sea-level contribution from the Greenland Ice Sheet.

How to cite: Beckmann, J. and Winkelmann, R.: Effects of extreme melt events on the Greenland ice sheet, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11407, https://doi.org/10.5194/egusphere-egu22-11407, 2022.

EGU22-11503 | Presentations | CR4.1

De-tuning a coupled Climate Ice Sheet Model to simulate the North American Ice Sheet at the Last Glacial Maximum 

Lauren Gregoire, Niall Gandy, Lachlan Astfalck, Ruza Ivanovic, Sam Sherriff-Tadano, Robin Smith, and Daniel Williamson

Coupled climate-ice sheet models are crucial to evaluating climate-ice feedbacks' role in future ice sheet evolution. Such models are calibrated to reproduce modern-day ice sheets, but current observations alone are insufficient to constrain the strength of climate-ice feedbacks. The extent of the Northern Hemisphere ice sheets during the last glacial maximum, ~20,000 years ago, is well known and could provide a benchmark for calibrating coupled climate-ice sheet models. We test this with the FAMOUS-ice coupled Climate-Ice Sheet model (Smith et al., 2020), a fast GCM coupled to the Glimmer ice sheet model. We ran Last Glacial Maximum simulations using FAMOUS-ice with interactive North American Ice Sheet, following the PMIP4 protocol (Kageyama et al., 2018). We find that the standard model setup, calibrated to produce a good present-day Greenland (Smith et al., 2020), produced a collapsed North American ice sheet at the Last Glacial Maximum. We ran ensembles of hundreds of simulations to explore the influence of uncertain ice sheet, albedo, atmospheric, and oceanic parameters on the ice sheet extent. The North American continent deglaciated rapidly in most of our simulations, leaving only a handful of useful simulations out of 280. We thus developed a method to efficiently identify regions of the parameter space that can produce a reasonable ice-sheet extent. This involved emulating the equilibrium ice volume and area as a function of the surface mass balance at the start of our simulations. We then ran three waves of short simulations for 20-50 years to identify parameter values and surface mass balance conditions potentially suitable to grow a realistic ice sheet. This enabled us to find ~160 simulations with good ice extent.

Through analysis of these simulations, we find that albedo parameters determine the majority of uncertainty when simulating the Last Glacial Maximum North American Ice Sheets. The differences in cloud cover over the ablation zones of the North American and Greenland ice sheet explains why the ice sheets have different sensitivities to surface mass balance parameters. Based on our work, we propose that the Last Glacial Maximum can provide an “out-of-sample” target to avoid over calibrating coupled climate-ice sheet models to the present day.

References:

Kageyama, M. et al. The PMIP4 contribution to CMIP6 – Part 4: Scientific objectives and experimental design of the PMIP4-CMIP6 Last Glacial Maximum experiments and PMIP4 sensitivity experiments. Geosci. Model Dev. 10, 4035–4055 (2017).

Smith, R. S., George, S., and Gregory, J. M.: FAMOUS version xotzt (FAMOUS-ice): a general circulation model (GCM) capable of energy- and water-conserving coupling to an ice sheet model, Geosci. Model Dev., 14, 5769–5787, https://doi.org/10.5194/gmd-14-5769-2021, 2021.

 

How to cite: Gregoire, L., Gandy, N., Astfalck, L., Ivanovic, R., Sherriff-Tadano, S., Smith, R., and Williamson, D.: De-tuning a coupled Climate Ice Sheet Model to simulate the North American Ice Sheet at the Last Glacial Maximum, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11503, https://doi.org/10.5194/egusphere-egu22-11503, 2022.

EGU22-11929 | Presentations | CR4.1

Evaluation of a coupled climate ice sheet model over the Greenland ice sheet and sensitivity to atmospheric, snow and ice sheet parameters 

Charlotte Lang, Victoria Lee, Sam Sherriff-Tadano, Niall Gandy, Jonathan Gregory, Ruza Ivanovic, Lauren Gregoire, and Robin S. Smith

As part of a project working to improve coupled climate-ice sheet modelling of the response of ice sheets to changes in climate across different periods since the Last Glacial Maximum, we present simulations of the modern Greenland climate and ice sheet using the FAMOUS-BISICLES model.

FAMOUS-BISICLES, a variant of FAMOUS-ice (Smith et al., 2021a), is a low resolution (7.5°X5°) global climate model that is two-way coupled to a higher resolution (minimum grid spacing of 1.2 km) adaptive mesh ice sheet model, BISICLES. It uses a system of elevation classes to downscale the lower resolution atmospheric variables onto the ice sheet grid and calculates surface mass balance using a multilayer snow model. FAMOUS-ice is computationally affordable enough to simulate the millennial evolution of the coupled climate-ice sheet system, and has been shown to simulate Greenland well in previous work using the Glimmer shallow ice model (Gregory et al., 2020).

The ice sheet volume and area are sensitive to a number of parametrisations related to atmospheric and snow surface processes and ice sheet dynamics. Based on that, we designed a perturbed parameters ensemble using a Latin Hypercube sampling technique and ran simulations with climate forcings appropriate for the late 20th century. The ice sheet area and volume are most correlated to parameters that set the snow/firn albedo while the relationship is less simple for parameters related to clouds and precipitation.

We compare FAMOUS-ice SMB and coupled behaviour against the more sophisticated, higher resolution, CMIP6-class UKESM-ice coupled climate ice sheet model for a late 20th century simulation as well as an abrupt 4XCO2 experiment.

Our simulations produce a large range of climate and ice sheet behaviours, including a stable control state for the modern Greenland, and we have been able to highlight the sensitivity of the system to other sets of parameters and future changes in climate.

How to cite: Lang, C., Lee, V., Sherriff-Tadano, S., Gandy, N., Gregory, J., Ivanovic, R., Gregoire, L., and Smith, R. S.: Evaluation of a coupled climate ice sheet model over the Greenland ice sheet and sensitivity to atmospheric, snow and ice sheet parameters, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11929, https://doi.org/10.5194/egusphere-egu22-11929, 2022.

EGU22-12018 | Presentations | CR4.1

Uncertainties of Surface Mass Balance in Greenland for the mid-Holocene as derived from CMIP6/PMIP4 simulations. 

Rebekka Neugebauer, Christian B. Rodehacke, Gerrit Lohmann, and Uta Krebs-Kanzow

The temporal evolution of Greenland’s surface mass balance (SMB) exerts an essential control on its volume, geometry, and sea-level contribution. Surface mass balance simulations based on future climate projections reveal considerable uncertainties. Here, we investigate Greenland’s SMB during past climate periods and assess the uncertainties due to model dependent climate forcing. Specifically we analyse the SMB of the pre-industrial climate and the mid-Holocene warm period.

 

We study the surface mass balance of the Greenland ice sheet with respect to uncertainties due to model dependent climate forcing. For this purpose, we create an ensemble based on the output of climate models of the sixth phase of the Coupled Model Intercomparison Project (CMIP6) and the fourth phase of the Paleomodel Intercomparison Project (PMIP4) (Brierley et al., 2020). This ensemble is used to simulate the SMB with the diurnal energy balance model (dEBM) (Krebs-Kanzow et al, 2021). As part of the analysis, we inspect anomalies and inter-model deviations of the mid-Holocene climate forcing, and evaluate the spread of spatial patterns of SMB anomalies in CMIP6/PMIP4. Our results indicate that the model-dependent climate forcing adds considerable uncertainty to SMB estimates over Greenland during the Holocene.

 

References

Brierley, C. M., Zhao, A., Harrison, S. P., Braconnot, P., Williams, C. J. R., Thornalley, D. J. R., Shi, X., Peterschmitt, J.-Y., Ohgaito, R., Kaufman, D. S., Kageyama, M., Hargreaves, J. C., Erb, M. P., Emile-Geay, J., D'Agostino, R., Chandan, D., Carré, M., Bartlein, P. J., Zheng, W., Zhang, Z., Zhang, Q., Yang, H., Volodin, E. M., Tomas, R. A., Routson, C., Peltier, W. R., Otto-Bliesner, B., Morozova, P. A., McKay, N. P., Lohmann, G., Legrande, A. N., Guo, C., Cao, J., Brady, E., Annan, J. D., and Abe-Ouchi, A., 2020: Large-scale features and evaluation of the PMIP4-CMIP6 midHolocene simulations, Clim. Past, 16, 1847–1872, doi:10.5194/cp-16-1847-2020, 2020. 

Krebs-Kanzow, U., Gierz, P., Rodehacke, C. B., Xu, S., Yang, H., and Lohmann, G., 2021: The diurnal Energy Balance Model (dEBM): a convenient surface mass balance solution for ice sheets in Earth system modeling, The Cryosphere, 15, 2295–2313, https://doi.org/10.5194/tc-15-2295-2021.

How to cite: Neugebauer, R., Rodehacke, C. B., Lohmann, G., and Krebs-Kanzow, U.: Uncertainties of Surface Mass Balance in Greenland for the mid-Holocene as derived from CMIP6/PMIP4 simulations., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12018, https://doi.org/10.5194/egusphere-egu22-12018, 2022.

EGU22-12930 | Presentations | CR4.1

Dynamic glaciers improve LGM simulation in High Mountain Asia 

Qiang Wei, Yonggang Liu, and Yongyun Hu

Glaciers on Tibetan Plateau and its surrounding areas were much more extensive during Last Glacial Maximum (LGM) when global mean temperature was 5-8 K lower than today. Accurately reconstructing glaciers on and around Tibetan Plateau remains vital towards understanding glaciers’ sensitivity against climate change, and vice versa.

Previous simulations on glaciers in High Mountain Asia during LGM are usually forced with prescribed climatology without considering the bi-directional feedbacks. We instead coupled a climate model (CESM) to an ice-sheet model (ISSM). Our results show that the interactions between HMA glaciers and climate was significant. Uncoupled runs that ignore such interaction yielded glacial coverage roughly 10% more than coupled runs. Regional glacial features change considerably in coupled simulation. Glaciers on the mid-west Tibetan Plateau decreased while those in Qilian Mountains, Tianshan Mountains and Pamir Plateau saw pronounced increase. Compared with uncoupled simulations, our coupled results is in better agreement with reconstructions of LGM glaciers.

 

 

 

 

 

 

KEY WORDS: Glacier; Ice-sheet; Tibetan Plateau; High Mountain Asia; Numerical simulation; Climate modelling

 

How to cite: Wei, Q., Liu, Y., and Hu, Y.: Dynamic glaciers improve LGM simulation in High Mountain Asia, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12930, https://doi.org/10.5194/egusphere-egu22-12930, 2022.

EGU22-13289 | Presentations | CR4.1

Effects of future freshwater forcing from ice sheet mass loss in a high-resolution climate model 

André Jüling, Dewi Le Bars, Erwin Lambert, Marion Devilliers, and Sybren Drijfhout

The Greenland and Antarctic ice sheets are losing mass to the ocean. This additional freshwater flux to the ocean is only expected to increase in the future, but it is usually not included in current climate model simulations as ice sheets are not modelled interactively. However, this freshwater flux will influence multiple aspects of the climate response. We develop a plausible, future freshwater forcing scenarios for both ice sheets and use a high-resolution, eddy-permitting version of EC-Earth3 to simulate the response to a high emission scenario. We investigate the effect of this additional freshwater on sea ice, ocean circulation, surface temperatures, and sea level by comparing the simulations to the HighResMIP EC-Earth3 simulations without ice sheet mass loss.

How to cite: Jüling, A., Le Bars, D., Lambert, E., Devilliers, M., and Drijfhout, S.: Effects of future freshwater forcing from ice sheet mass loss in a high-resolution climate model, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13289, https://doi.org/10.5194/egusphere-egu22-13289, 2022.

EGU22-50 | Presentations | G3.3

Towards an improved understanding of vertical land motion and sea-level change in eastern North America 

Soran Parang, Glenn A. Milne, Makan A. Karegar, and Lev Tarasov

Many coastal cities are an early casualty in climate-related coastal flooding because of processes resulting in land subsidence and thus enhanced relative sea-level (RSL) rise. Much of the Atlantic coast of North America has been sinking for thousands of years, at a maximum rate of ~20 cm per century as a consequence of solid Earth deformation in response to deglaciation of the Laurentide ice sheet (between ~18,000 and ~7,000 years ago) [e.g. Love et al., Earth's Future, 4(10), 2016]. Karegar et al. [Geophysical Research Letters, 43(7), 2016] have shown that vertical land motion along the Atlantic coast of the USA is an important control on nuisance flooding. A key finding in this study is that while glacial isostatic adjustment (GIA) is the dominant process driving land subsidence in most areas, there can be large deviations from this signal due to the influence of anthropogenic activity impacting hydrological processes. For example, between Maine (45°N) and New Hampshire (43°N), the GPS data show uplift while geological data show long-term subsidence. The cause of this discrepancy is not clear, but one hypothesis is increasing water mass associated with the James Bay Hydroelectric Project in Quebec [Karegar et al., Scientific Reports, 7, 2017].

The primary aim of this study is to better constrain and understand the processes that contribute to contemporary and future vertical land motion in this region to produce improved projections of mean sea-level change and nuisance flooding. The first step towards achieving these aims is to determine a GIA model parameter set that is compatible with observations of past sea-level change for this region. We make use of two regional RSL data compilations: Engelhart and Horton [Quaternary Science Reviews, 54, 2012] for northern USA and Vacchi et al. [Quaternary Science Reviews, 201, 2018] for Eastern Canada, comprising a total of 1013 data points (i.e., sea level index points and limiting data points) over 38 regions distributed throughout our study region. These data are well suited to determine optimal GIA model parameters due to the magnitude of other signals being much smaller, particularly in near-field regions such as Eastern Canada. We consider a suite of 32 ice history models that is comprised mainly of a subset from Tarasov et al. [Earth and Planetary Science Letters, 315–316, 2012] as well as the ICE-6G and ANU models. We have computed RSL for these ice histories using a state-of-the-art sea-level calculator and 440 1-D Earth viscosity models per each ice history model to identify a set of Earth model parameters that is compatible with the observations.

How to cite: Parang, S., Milne, G. A., Karegar, M. A., and Tarasov, L.: Towards an improved understanding of vertical land motion and sea-level change in eastern North America, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-50, https://doi.org/10.5194/egusphere-egu22-50, 2022.

EGU22-852 | Presentations | G3.3

The inclusion of ice model uncertainty in 3D Glacial Isostatic Adjustment modelling: a case study from the Russian Arctic 

Tanghua Li, W. Richard Peltier, Gordan Stuhne, Nicole Khan, Alisa Baranskaya, Timothy Shaw, Patrick Wu, and Benjamin Horton

The western Russian Arctic was partially covered by the Eurasian ice sheet complex during the Last Glacial Maximum (~26 ka BP) and is a focus area for Glacial Isostatic Adjustment (GIA) studies. However, there have been few GIA studies conducted in the Russian Arctic due to the lack of high quality deglacial relative sea-level (RSL) data. Recently, Baranskaya et al. (2018) released a quality-controlled deglacial RSL database for the Russian Arctic that consists of ~400 sea-level index points and ~250 marine and terrestrial limiting data that constrain RSL since 20 ka BP. Here, we use the RSL database to constrain the 3D Earth structure beneath the Russian Arctic, with consideration of the uncertainty in ice model ICE-7G_NA, which is assessed via iteratively refining the ice model with fixed 1D Earth model to achieve a best fit with the RSL data. Also, the uncertainties in 3D Earth parameters and RSL predictions are investigated.

 

We find an optimal 3D Earth model (Vis3D) improves the fit with the deglacial RSL data compared with the VM7 1D model when fixed with the ICE-7G_NA ice model. Similarly, we show improved fit in the White Sea area, where 1D model shows notable misfits, with the refined ice model ICE-7G_WSR when fixed with VM7 Earth model. The comparable fits of ICE-7G_NA (Vis3D) and ICE-7G_WSR (VM7) implies that the uncertainty in the ice model might be improperly mapped into 3D viscosity structure when a fixed ice model is employed. Furthermore, fixed with refined ice model ICE-7G_WSR, we find an optimal 3D Earth model (Vis3D_R), which fits better than ICE-7G_WSR (VM7), and the magnitude of lateral heterogeneity decreases significantly from Vis3D to Vis3D_R.  We conclude that uncertainty in the ice model needs to be considered in 3D GIA studies.

How to cite: Li, T., Peltier, W. R., Stuhne, G., Khan, N., Baranskaya, A., Shaw, T., Wu, P., and Horton, B.: The inclusion of ice model uncertainty in 3D Glacial Isostatic Adjustment modelling: a case study from the Russian Arctic, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-852, https://doi.org/10.5194/egusphere-egu22-852, 2022.

EGU22-918 | Presentations | G3.3

Regional GIA: modelling choices and community needs 

Riccardo Riva

GIA is a global process, because of gravitational effects, its interplay with earth rotation, and the large spatial extent of ice-sheet and ocean loading. However, mainly due to the presence of heterogeneities in the structure of crust and upper mantle, modelling of GIA signals often requires a regional approach. This is particularly true in the light of continuous advances in earth observation techniques, that allow increasingly accurate determination of land deformation, coastal sea level change, and mass balance of glaciers and ice sheets.

This talk will address a number of open issues related to regional GIA models, such as the effect of transient and non-linear rheologies, and the complementary role of forward and semi-empirical approaches, with an eye on the needs of the geodetic, sea level and cryosphere communities.

How to cite: Riva, R.: Regional GIA: modelling choices and community needs, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-918, https://doi.org/10.5194/egusphere-egu22-918, 2022.

EGU22-1343 | Presentations | G3.3

Resolving the Influence of Ice Stream Instability on Postglacial Relative Sea-Level Histories: the case of the St Lawrence River Channel Ice Stream 

Richard Peltier, Tanghua Li, Gordan Stuhnne, Jesse Velay-Vitow, Matteo Vacchi, Simon Englehart, and Benjamin Horton

A challenge to understanding Late Quaternary glaciation history is the mechanism(s) responsible for the asymmetry in an individual glaciation cycle between the slow pace of glaciation and the more rapid pace of deglaciation (e.g., Broecker and Van Donk, 1970). It is increasingly clear that a major contributor to the rate of global deglaciation is the instability of marine terminating ice streams. Recent analyses by Velay-Vitow et al. (2020) suggest that these instabilities were often triggered by ocean tides of anomalously high amplitude. Examples include the Hudson Strait Ice Stream responsible for Heinrich Event 1 (H1) and the Amundsen Gulf Ice Stream. Here, we analyse the instability of the Laurentian Channel and St Lawrence River Channel ice stream system. Our analysis begins with the recognition of highly significant misfits of up to 60 m at ~9,000 calendar years ago between deglacial relative sea-level histories inferred by Vacchi et al. (2018) at sites along the St Lawrence River Channel and those predicted by the ICE-6G_C (VM5a) and ICE-7G_NA (VM7) models of the Glacial Isostatic Adjustment process. We suggest that these disagreements between models and data may be due to the St Lawrence River Channel ice stream becoming unstable during the deglaciation of the Laurentide Ice Sheet (LIS) due to the hypothesized tidal mechanism for ice stream destabilization. We investigate a sequence of scenarios designed to provide a best estimate of the timing of this event. Since this ice stream penetrated deeply into the interior of the LIS and was connected to the Laurentian Channel ice stream, the instability of the latter was required in order for destabilization of the St Lawrence River channel ice stream to be possible. We explore the consistency of the implied sequence of events with the observational constraints.

How to cite: Peltier, R., Li, T., Stuhnne, G., Velay-Vitow, J., Vacchi, M., Englehart, S., and Horton, B.: Resolving the Influence of Ice Stream Instability on Postglacial Relative Sea-Level Histories: the case of the St Lawrence River Channel Ice Stream, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1343, https://doi.org/10.5194/egusphere-egu22-1343, 2022.

EGU22-1447 | Presentations | G3.3 | Highlight

Benchmark of numerical GIA codes capable of laterally heterogeneous earth structures 

Volker Klemann, Jacky Austermann, Meike Bagge, Natasha Barlow, Jeffrey Freymueller, Pingping Huang, Erik R. Ivins, Andrew Lloyd, Zdeněk Martinec, Glenn Milne, Alessio Rovere, Holger Steffen, Rebekka Steffen, Wouter van der Wal, Maryam Yousefi, and Shijie Zhong

During the last decade there has been an increasing demand to improve models of present-day loading processes and glacial-isostatic adjustment (GIA). This is especially important when modelling the GIA process in tectonically active regions like the Pacific Northwest, Patagonia or West Antarctica. All these regions are underlain by zones of low-viscosity mantle. Although one-dimensional earth models may be sufficient to model local-scale uplift within these regions, modeling of the wider-scale deformation patterns requires consideration of three-dimensional viscosity structure that is consistent with other geophysical and laboratory findings. It is this wider-scale modeling that is necessary for earth-system model applications as well as for the validation or reduction of velocity fields determined by geodetic observation networks based on GNSS, for improving satellite gravimetry, and for present-day sea-level change as paleo sea-level reconstructions.

There are a number of numerical GIA codes in the community, which can consider lateral variations in viscoelastic earth structure, but a proper benchmark focusing on lateral heterogeneity is missing to date. Accordingly, ambiguity remains when interpreting the modelling results. The numerical codes are based on rather different methods to solve the respective field equations applying, e.g., finite elements, finite volumes, finite differences or spectral elements. Aspects like gravity, compressibility and rheology are dealt with differently. In this regard, the set of experiments to be performed has to be agreed on carefully, and we have to accept that not all structural features can be considered in every code.

We present a tentative catalogue of synthetic experiments. These are designed to isolate different aspects of lateral heterogeneity of the Earth's interior and investigate their impact on vertical and horizontal surface displacements, geocenter and polar motion, gravity, sea-level change and stress. The study serves as a follow up of the successful benchmarks of Spada et al. (2011) and Martinec et al. (2018) on 1D earth models and the sea-level equation. The study was initiated by the PALSEA-SERCE Workshop in 2021 (Austermann and Simms, 2022) and benefits from discussions inside different SCAR-INSTANT subcommittees, the IAG Joint Study Group 3.1 “Geodetic, Seismic and Geodynamic Constraints on Glacial Isostatic Adjustment", the IAG Subcommission 3.4 “Cryospheric Deformation" and PALSEA.

References:

Austermann, J., Simms, A., 2022 (in press). Unraveling the complex relationship between solid Earth deformation and ice sheet change. PAGES Mag., 30(1). doi:10.22498/pages.30.1.14

Martinec, Z., Klemann, V., van der Wal, W., Riva, R. E. M., Spada, G., Sun, Y., Melini, D., Kachuck, S. B., Barletta, V., Simon, K., A, G., James, T. S., 2018. A benchmark study of numerical implementations of the sea level equation in GIA modelling. Geophys. J. Int., 215:389-414. doi:10.1093/gji/ggy280

Spada, G., Barletta, V. R., Klemann, V., Riva, R. E. M., Martinec, Z., Gasperini, P., Lund, B., Wolf, D., Vermeersen, L. L. A., King, M. A. (2011). A benchmark study for glacial isostatic adjustment codes. Geophys. J. Int., 185:106-132. doi:10.1111/j.1365-246X.2011.04952.x

How to cite: Klemann, V., Austermann, J., Bagge, M., Barlow, N., Freymueller, J., Huang, P., Ivins, E. R., Lloyd, A., Martinec, Z., Milne, G., Rovere, A., Steffen, H., Steffen, R., van der Wal, W., Yousefi, M., and Zhong, S.: Benchmark of numerical GIA codes capable of laterally heterogeneous earth structures, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1447, https://doi.org/10.5194/egusphere-egu22-1447, 2022.

EGU22-1479 | Presentations | G3.3

Peripheral and near field relative sea-level predictions using GIA models with 3D and regionally adapted 1D viscosity structures 

Meike Bagge, Volker Klemann, Bernhard Steinberger, Milena Latinovic, and Maik Thomas

Glacial isostatic adjustment (GIA) describes the viscoelastic response of the solid Earth to ice-sheet and ocean loading. GIA models determine the relative sea-level based on the viscoelastic deformations of the Earth interior including self-gravitation due to the loading of the water redistribution between ocean and ice and rotational effects. Choosing an Earth structure that adequately reflects the viscoelastic behavior of a region remains a challenge. For a specific region, the viscosity stratification can be inferred from present-day geodetic measurements like sea-level, gravity change and surface displacements or from paleo observations of former sea level. Here, we use a suite of geodynamically constrained 3D Earth structures that are derived from seismic tomography models and create regionally adapted 1D Earth structures to investigate to what extent regional, radially symmetric structures are able to reproduce the solid Earth response of a laterally varying structure. We discuss sea-level variations during the deglaciation in the near field (beneath the former ice sheet) and peripheral regions (surrounding the ice sheet) with focus on North America and Antarctica as well as Oregon and Patagonia. The suite of 3D Earth structures vary in transfer functions from seismic velocity to viscosity, i.e., in Arrhenius law and viscosity contrast between upper mantle and transition zone. We investigate how the relative sea-level predictions of the model suite members are affected due to the simplification of the Earth structure from 3D to 1D.

In general, our results support previous studies showing that 1D models in peripheral regions are not able to reproduce the 3D models’ predictions, because the response depends on the deformational behavior beneath the adjacent ice sheet and the local structure (superposition). Furthermore, the analysis of the model suite members shows different response behaviors for the 1D and 3D cases, e.g., suite members with weaker dependence of viscosity on seismic velocity can predict lowest RSL for the 3D case, but largest RSL for the 1D case. This indicates the relevance of the 3D structure in peripheral regions. 1D models in the near field are more capable to reproduce 3D model response behavior. But also here, deviations indicate that the lateral variations in the Earth structure beneath the ice sheet influence local relative sea-level predictions. 

How to cite: Bagge, M., Klemann, V., Steinberger, B., Latinovic, M., and Thomas, M.: Peripheral and near field relative sea-level predictions using GIA models with 3D and regionally adapted 1D viscosity structures, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1479, https://doi.org/10.5194/egusphere-egu22-1479, 2022.

Further understanding of Antarctic Ice Sheet responses to global climate changes requires an accurate and continuous reconstruction of the AIS changes. However, the erosive nature of ice-sheet expansion and sea-level drop and the difficulty of accessing much of Antarctica make it difficult to obtain field-based evidence of ice-sheet and sea-level changes before the Last Glacial Maximum. Limited sedimentary records from the Indian Ocean sector of East Antarctica demonstrate that the sea level of Marine Isotope Stage 3 was close to the present level despite the global sea-level drop lower than −40 m. Although previous GIA-derived sea levels hardly explain these sea-level observations, we demonstrate glacial isostatic adjustment modeling with refined Antarctic Ice Sheet loading histories. Our experiments reveal that the Indian Ocean sector of the Antarctic Ice Sheet would have been required to experience excess ice loads before the Last Glacial Maximum in order to explain the observed sea-level highstands during Marine Isotope Stage 3. We also conduct a sensitivity test of the small Northern American Ice Sheet during Marine Isotope Stage 3, suggesting that this small ice sheet is not enough to achieve sea-level highstands during Marine Isotope Stage 3 in the Indian Ocean sector of East Antarctica. As such, we suggest that the Indian Ocean sector of the East Antarctic Ice Sheet reached its maximum thickness before the global Last Glacial Maximum.
 
Reference
Ishiwa, T., Okuno, J., and Suganuma, Y., 2021. Excess ice loads in the Indian Ocean sector of East Antarctica during the last glacial period. Geology, 49, 1182–1186. https://doi.org/10.1130/g48830.1

How to cite: Ishiwa, T., Okuno, J., and Suganuma, Y.: Excess ice loads prior to the Last Glacial Maximum in the Indian Ocean sector of East Antarctica derived from sea-level observations and GIA modeling, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1568, https://doi.org/10.5194/egusphere-egu22-1568, 2022.

EGU22-1807 | Presentations | G3.3

Three-dimensional velocity variations due to ice mass changes in Greenland – Insights from a compressible glacial isostatic adjustment model 

Rebekka Steffen, Holger Steffen, Pingping Huang, Lev Tarasov, Kristian K. Kjeldsen, and Shfaqat A. Khan

The lithospheric thickness beneath and around Greenland varies from a few tens of kilometres in offshore regions to several tens of kilometres (up to 200 – 250 km) in land areas. But, due to different datasets and techniques applied in geophysical studies, there are large differences between the different geophysical lithosphere models. As an example, lithosphere models from seismological datasets show generally larger values (above 100 km), while models using gravity or thermal datasets tend to be thinner (values mostly below 100 km). To model the deformation associated with the melting of the Greenland Ice Sheet a detailed lithosphere model is required. Nevertheless, seismologically obtained lithosphere models are the ones usually applied in these so-called glacial isostatic adjustment (GIA) models. Besides, GIA models can be used to provide additional constraints on the lithospheric thickness.

Results from most 3D GIA models are compared to observed vertical velocities only, while horizontal velocities are known to be sensitive to the lateral variations of the Earth (e.g., lithospheric thickness). But, horizontal velocities from incompressible GIA models, which are commonly used, are not suitable due to the neglect of material parameter changes related to the dilatation. Compressible GIA models in turn can provide more accurate estimates of the horizontal and vertical viscoelastic deformations induced by ice-mass changes. Here, we use a variety of lithospheric thickness models, obtained from gravity, thermal, and seismological datasets, in a three-dimensional compressible GIA Earth model. The GIA model will be constructed using the finite-element software ABAQUS (Huang et al., under review in GJI) and applying recent ice history models Huy3 and GLAC-GR2a for Greenland in combination with the Little Ice Age deglaciation model by Kjeldsen et al. (2015). We will compare various lithosphere models, including their impact on the modelled 3D velocity field, and compare these against independent GNSS (Global Navigation Satellite System) observations.

References:

Huang, P., Steffen, R., Steffen, H., Klemann, V., van der Wal, W., Reusen, J., Wu, P., Tanaka, Y., Martinec, Z., Thomas, M. (under review in GJI): A finite element approach to modelling Glacial Isostatic Adjustment on three-dimensional compressible earth models. Geophysical Journal International. Under review.

Kjeldsen, K., Korsgaard, N., Bjørk, A. et al. (2015): Spatial and temporal distribution of mass loss from the Greenland Ice Sheet since AD 1900. Nature 528, 396–400, https://doi.org/10.1038/nature16183.

How to cite: Steffen, R., Steffen, H., Huang, P., Tarasov, L., Kjeldsen, K. K., and Khan, S.: Three-dimensional velocity variations due to ice mass changes in Greenland – Insights from a compressible glacial isostatic adjustment model, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1807, https://doi.org/10.5194/egusphere-egu22-1807, 2022.

EGU22-4475 | Presentations | G3.3

The effect of uncertain historical ice information on GIA modelling 

Reyko Schachtschneider, Jan Saynisch-Wagner, Volker Klemann, Meike Bagge, and Maik Thomas

When inferring mantle viscosity by modelling the effects of glacial isostatic adjustment (GIA) a necessary constraint is the external forcing by surface loading. Such forcing is usually provided by a glaciation history, where the mass-conserving sea-level changes are considered solving the sea-level equation. The uncertainties of glaciation history reconstructions are quite large and the choice of a specific history strongly influences the deformation response obtained by GIA modelling. The reason is that any history is usually based on a certain Earth rheology, and mantle viscosity inversions using such models tend to resemble the viscosity structure used for the glaciation history (Schachtschneider et al., 2022, in press). Furthermore, uncertainties of glaciation histories propagate into the respective GIA modelling results. However, to quantify the impact of glaciation history on GIA modelling remains a challenge.

In this study we investigate the effect of uncertainties in glaciation histories on GIA modelling. Using a particle-filter approach we study the effect of spatial and temporal variations in ice distribution as well as the effect of total ice mass. We quantify the effects on a one-dimensional viscosity stratification and derive measures to which extent changes in sea-level pattern and surface deformation depend on variations in ice loading.

 

References:

Schachtschneider, R., Saynisch-Wagner, J., Klemann, V., Bagge, M., Thomas, M. 2021. Nonlin. Proc. Geophys., https://doi.org/10.5194/npg-2021-22

How to cite: Schachtschneider, R., Saynisch-Wagner, J., Klemann, V., Bagge, M., and Thomas, M.: The effect of uncertain historical ice information on GIA modelling, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4475, https://doi.org/10.5194/egusphere-egu22-4475, 2022.

EGU22-4969 | Presentations | G3.3 | Highlight

Sea level response to Quaternary erosion and deposition in Scandinavia 

Gustav Pallisgaard-Olesen, Vivi Kathrine Pedersen, Natalya Gomez, and Jerry X. Mitrovica

The landscape in western Scandinavia has undergone dramatic changes through numerous glaciations during the Quaternary. These changes in topography and in the volumes of offshore sediment deposition, have caused significant isostatic adjustments and local sea-level changes, owning to erosional unloading and de- positional loading of the lithosphere. This geomorphic mass redistribution also has the potential to perturb the geoid, resulting in additional sea-level changes. However, the combined sea-level response from these processes is yet to be investigated in detail for Scandinavia.

In this study we estimate the total sea-level change from i) late Pliocene- Quaternary onshore bedrock erosion and erosion of sediments on the coastal shelf and ii) the subsequent deposition in the Norwegian Sea, northern North Sea and the Danish region. We use a gravitationally self-consistent global sea- level model that includes the full viscoelastic response of the solid Earth to surface loading and unloading. In addition to total late Pliocene-Quaternary geomorphic mass redistribution, we also estimate transient sea-level changes related specifically to the two latest glacial cycles.

We utilize existing observations of offshore sediment thicknesses of glacial origin, and combine these with estimates of onshore glacial erosion and of erosion on the inner shelf. Based on these estimates, we define mass redistribution and construct a preglacial landscape setting as well as approximate a geomorphic history of the last two glacial cycles.

Our results show that erosion and deposition has caused a sea-level fall of ∼50-100 m along the southern coast of Norway during the last two glacial cycles reaching ∼120 m in the offshore Skagerak region. The total relative sea-level fall during the Quaternary reach as much as ∼350 m in Skagerak. This highlights the importance of accounting for geomorphic sediment redistribution in glacial isostatic-adjustment modelling when interpreting ice sheet histories and glacial rebound.

How to cite: Pallisgaard-Olesen, G., Pedersen, V. K., Gomez, N., and Mitrovica, J. X.: Sea level response to Quaternary erosion and deposition in Scandinavia, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4969, https://doi.org/10.5194/egusphere-egu22-4969, 2022.

EGU22-5146 | Presentations | G3.3

The use of Non-Linear Geometry (NLGEOM) and gravity loading in flat and spherical Finite Element models of Abaqus for Glacial Isostatic Adjustment (GIA) 

Jesse Reusen, Pingping Huang, Rebekka Steffen, Holger Steffen, Caroline van Calcar, Bart Root, and Wouter van der Wal

In geodynamic studies, most Finite-Element (FE) models in the commercial FE software Abaqus use elastic foundations at internal boundaries. This method works well for incompressible and so-called material-compressible material parameters but it is unclear if it works sufficiently well for implementing compressibility, especially in a 3D spherical model. The latter is of importance in investigations of glacial isostatic adjustment (GIA). A possible alternative method is based on a combination of explicit gravity loading with non-linear geometry (NLGEOM parameter in Abaqus) (Hampel et al., 2019). This method would remove the need to make a stress transformation to get the correct GIA stresses, and automatically accounts for the change in internal buoyancy forces that arises when allowing for compression, according to the Abaqus Documentation. We compared the method for (in)compressible flat (~half-space) FE models with existing numerical half-space and spherical (in)compressible codes and tested the applicability of this method in a spherical FE model. We confirm that this method works for multi-layer incompressible flat FE models. We furthermore notice that horizontal displacement rates of incompressible flat FE models match those of spherical incompressible GIA models below the current GNSS (Global Navigation Satellite System) measurement accuracy of 0.2-0.3 mm/a, but only for ice sheets that are smaller than 450 km in extent. For compressible models, disagreements in the vertical displacement rates are found between the flat NLGEOM model and the compressible Normal Mode code ICEAGE (Kaufmann, 2004). An extension of the NLGEOM-gravity method to a spherical FE model, where gravity must be implemented in the form of body forces combined with initial stress, leads to a divergence of the solution when viscous behaviour is turned on. We thus conclude that the applicability of the NLGEOM method is so far limited to flat FE models, and in GIA investigations for flat models the applicability further depends on the size of the load (ice sheet, glacier).

References:

Hampel, A., Lüke, J., Krause, T., & Hetzel, R., 2019. Finite-element modelling of glacial isostatic ad-
justment (GIA): Use of elastic foundations at material boundaries versus the geometrically non-linear
formulation, Computers & geosciences, 122, 1–14.

Kaufmann, G. (2004). Program Package ICEAGE, Version 2004. Manuscript. Institut für Geophysik der Universität Göttingen.

How to cite: Reusen, J., Huang, P., Steffen, R., Steffen, H., van Calcar, C., Root, B., and van der Wal, W.: The use of Non-Linear Geometry (NLGEOM) and gravity loading in flat and spherical Finite Element models of Abaqus for Glacial Isostatic Adjustment (GIA), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5146, https://doi.org/10.5194/egusphere-egu22-5146, 2022.

EGU22-6013 | Presentations | G3.3 | Highlight

A finite element approach to modelling Glacial Isostatic Adjustment on three-dimensional compressible earth models 

Pingping Huang, Rebekka Steffen, Holger Steffen, Volker Klemann, Wouter van der Wal, Jesse Reusen, Yoshiyuki Tanaka, Zdeněk Martinec, and Maik Thomas

A new finite element method called FEMIBSF is presented that is capable of modelling Glacial Isostatic Adjustment (GIA) on compressible earth models with three-dimensional (3D) structures. This method takes advantage of the classical finite element techniques to calculate the deformational and gravitational responses to the driving forces of GIA (including body forces and pressures on Earth’s surface and core-mantle boundary, namely CMB). Following Wu (2004) and Wong & Wu (2019), we implement the GIA driving forces in the commercial finite element software Abaqus and solve the equation of motion in an iterative manner. Different from those two studies, all formulations and calculations in this study are not associated with spherical harmonics but are performed in the spatial domain. Due to this, FEMIBSF is free from expanding the load, displacement, and potential into spherical harmonics with the short-wavelength components (of high degree and order) neglected. We compare the loading Love numbers (LLNs) generated by FEMIBSF with their analytical solutions for homogeneous models and numerical solutions for layered models calculated by the normal-mode approach/code, ICEAGE (Kaufmann, 2004), the iterative body force approach/code, IBF (Wong & Wu, 2019) and the spectral-finite element approach/code, VILMA-C (Martinec, 2000; Tanaka et al., 2011). We find that FEMIBSF agrees well with analytical and numerical LLN results of these codes. In addition, we show how to compute the degree-1 deformation directly in the spatial domain with the finite element approach and how to implement it in a GIA model using Abaqus. Finally, we demonstrate that the CMB pressure related to the gravitational potential change in the fluid core only influences the long-wavelength surface displacement and potential such as the degree-2 component.

 

References

 

Kaufmann, G. (2004). Program Package ICEAGE, Version 2004. Manuscript. Institut für Geophysik der Universität Göttingen.

 

Martinec, Z. (2000). Spectral–finite element approach to three-dimensional viscoelastic relaxation in a spherical earth. Geophysical Journal International142(1), 117-141.

 

Tanaka, Y., Klemann, V., Martinec, Z. & Riva, R. E. M. (2011). Spectral-finite element approach to viscoelastic relaxation in a spherical compressible Earth: application to GIA modelling. Geophysical Journal International184(1), 220-234.

 

Wong, M. C. & Wu, P. (2019). Using commercial finite-element packages for the study of Glacial Isostatic Adjustment on a compressible self-gravitating spherical earth–1: harmonic loads. Geophysical Journal International217(3), 1798-1820.

 

Wu, P. (2004). Using commercial finite element packages for the study of earth deformations, sea levels and the state of stress. Geophysical Journal International, 158(2), 401-408.

 
 
 

How to cite: Huang, P., Steffen, R., Steffen, H., Klemann, V., van der Wal, W., Reusen, J., Tanaka, Y., Martinec, Z., and Thomas, M.: A finite element approach to modelling Glacial Isostatic Adjustment on three-dimensional compressible earth models, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6013, https://doi.org/10.5194/egusphere-egu22-6013, 2022.

EGU22-6236 | Presentations | G3.3

Identifying geographical patterns of transient deformation in the geological sea level record 

Karen M. Simon, Riccardo E. M. Riva, and Taco Broerse

In this study, we examine the effect of transient mantle creep on the prediction of glacial isostatic adjustment (GIA) signals. Specifically, we compare predictions of relative sea level change from GIA from a set of Earth models in which transient creep parameters are varied in a simple Burgers model to a reference case with a Maxwell viscoelastic rheology. The model predictions are evaluated in two ways: first, relative to each other to quantify the effect of parameter variation, and second, for their ability to reproduce well-constrained sea level records from selected locations. Both the resolution and geographic location of the relative sea level observations determine whether the data can distinguish between model cases. Model predictions are most sensitive to the inclusion of transient mantle deformation in regions that are near-field and peripheral relative to former ice sheets. This sensitivity appears particularly true along the North American west coast in the region of the former Cordilleran Ice Sheet, which experienced rapid sea-level fall following deglaciation between 14-12 kyr BP. Relative to the Maxwell case, Burgers models better reproduce this rapid phase of regional postglacial sea level fall. As well, computed goodness-of-fit values in this region show a clear preference for models where transient deformation is present in the whole or lower mantle, and for models where the rigidity of the Kelvin element is weakened relative to the rigidity of the Maxwell element. In contrast, model predictions of relative sea-level change in the far-field show little or weak sensitivity to the inclusion of transient deformation.

How to cite: Simon, K. M., Riva, R. E. M., and Broerse, T.: Identifying geographical patterns of transient deformation in the geological sea level record, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6236, https://doi.org/10.5194/egusphere-egu22-6236, 2022.

EGU22-6829 | Presentations | G3.3

Dependence of GIA-induced gravity change in Antarctica on viscoelastic Earth structure 

Yoshiya Irie, Jun'ichi Okuno, Takeshige Ishiwa, Koichiro Doi, and Yoichi Fukuda

The Antarctic ice mass loss is accelerating due to recent global warming. Changes in Antarctic ice mass have been observed as the gravity change by GRACE (Gravity Recovery and Climate Experiment) satellites. However, the gravity signal includes both the component of the ice mass change and the component of the solid Earth response to surface mass change (Glacial Isostatic Adjustment, GIA). Evaluating the GIA-induced gravity change requires viscoelastic Earth structure and ice history from the last deglaciation.

Antarctica is characterized by lateral heterogeneity of seismic velocity structure. West Antarctica shows relatively low seismic velocities, suggesting low viscosity regions in the upper mantle. On the other hand, East Antarctica shows relatively high seismic velocities, suggesting thick lithosphere. Here we examine the sensitivities of GIA-induced gravity change in Antarctica to upper mantle viscosity and lithosphere thickness using spherically symmetric Earth models.

Results indicate that the gravity field change depends on both the upper mantle viscosity profile and the lithosphere thickness. In particular, the long-wavelength gravity field changes become dominant in the adoption of viscoelastic models with a low viscosity layer beneath the elastic lithosphere. The same trend is also shown in the adoption of viscoelastic models with a thick lithosphere, and there is a trade-off between the structure of the low viscosity layer and the thickness of the lithosphere. This trade-off may reduce the effect of the lateral variations in Earth structure beneath Antarctica on the estimate of Antarctic ice sheet mass change.

How to cite: Irie, Y., Okuno, J., Ishiwa, T., Doi, K., and Fukuda, Y.: Dependence of GIA-induced gravity change in Antarctica on viscoelastic Earth structure, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6829, https://doi.org/10.5194/egusphere-egu22-6829, 2022.

EGU22-7609 | Presentations | G3.3

Deglaciation of the Antarctic Ice Sheet modeled with the coupled solid Earth – ice sheet model system PISM-VILMA 

Torsten Albrecht, Ricarda Winkelmann, Meike Bagge, and Volker Klemann

The Antarctic Ice Sheet is the largest and most uncertain potential contributor to future sea level rise. Understanding involved feedback mechanisms require physically-based models. Confidence in future projections can be improved by models that can reproduce past ice sheet changes, in particular over the last deglaciation. The complex interaction between ice, bedrock and sea level plays an important role in ice sheet instability with a large variety of characteristic response time scales dependent on the heterogeneous Earth structure underneath Antarctica and the ice sheet dynamics.

We have coupled the VIscoelastic Lithosphere and MAntle model (VILMA) to the Parallel Ice Sheet Model (PISM v2.0, www.pism.io) and ran simulations over the last two glacial cycles. In this framework, VILMA considers both viscoelastic deformations of the solid Earth by considering a three-dimensional rheology and a gravitationally self-consistent mass redistribution in the ocean by solving for the sea-level equation. PISM solves for the stress balance for a changing bed topography, which is updated in 100 years coupling intervals and which can directly affect ice sheet flow and grounding line dynamics.

Here, we show first results of coupled PISM-VILMA simulations scored against a database of geological constraints including sea level index points. We discuss sensitivities of model parameters and climatic forcing in preparation for a larger parameter ensemble study. This project is part of the German Climate Modeling Initiative PalMod.

 

How to cite: Albrecht, T., Winkelmann, R., Bagge, M., and Klemann, V.: Deglaciation of the Antarctic Ice Sheet modeled with the coupled solid Earth – ice sheet model system PISM-VILMA, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7609, https://doi.org/10.5194/egusphere-egu22-7609, 2022.

EGU22-7906 | Presentations | G3.3

Glacial Isostatic Adjustment in Antarctica : a rheological study 

Alexandre Boughanemi and Anthony Mémin

 The Antarctic Ice Sheet (AIS) is the largest ice sheet on Earth that has known important mass 
 changes during the last 20 kyrs. These changes deform the Earth and modify its gravity field, 
 a process known as Glacial Isostatic Adjustment (GIA). GIA is directly influenced by the mechanical
 properties and internal structure of the Earth, and is monitored using Global Navigation Satellite 
 System positioning or gravity measurements. However, GIA in Antarctica remains poorly constrained  
 due to the cumulative effect of past and present ice-mass changes, the unknown history of the past
 ice-mass change, and the uncertainties of the mechanical properties of the Earth. The viscous 
 deformation due to GIA is usually modeled using a Maxwell rheology. However, other geophysical
 processes employ Andrade (tidal deformation) or Burgers (post-seismic deformation) laws that could 
 result in a more rapid response of the Earth. We investigate the effect of using these
 different rheology laws to model GIA-induced deformation in Antarctica.  

Employing the ALMA and TABOO softwares, we use the Love number and Green functions formalism to
compute the surface motion and the gravity changes induced by the past and present ice-mass redistributions.
We use the elastic properties and the radial structure of the preliminary reference Earth model (PREM) and the
viscosity profile given by Hanyk (1999). The deformation is computed for the three rheological laws mentioned
above using ICE-6G and elevation changes from ENVISAT (2002-2010) to represent the past and present changes
of the AIS, respectively. 

We obtain that the three rheological laws lead to significant Earth response within a 20 kyrs time interval since
the beginning of the ice-mass change. The differences are the largest between Maxwell and Burgers rheologies
during the 500 years following the beginning of the surface-mass change. Regarding the response to present
changes in Antarctica, the largest discrepancies are obtained in regions with the greatest current melting rates,
namely Thwaites and Pine Island Glacier in West Antarctica. Uplift rates computed twelve years after the end of
the present melting using Burgers and Andrade rheologies are five and two times larger than those obtained
using Maxwell, respectively. 

How to cite: Boughanemi, A. and Mémin, A.: Glacial Isostatic Adjustment in Antarctica : a rheological study, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7906, https://doi.org/10.5194/egusphere-egu22-7906, 2022.

EGU22-8112 | Presentations | G3.3

Investigating the Sensitivity of North Sea Glacial Isostatic Adjustment during the Last Interglacial to the Penultimate Deglaciation of Global Ice Sheets 

Oliver Pollard, Natasha Barlow, Lauren Gregoire, Natalya Gomez, Víctor Cartelle, Jeremy Ely, and Lachlan Astfalck

The Last Interglacial (LIG; MIS 5e) period (130 - 115 ka) saw the last time in Earth’s history that polar temperatures reached 3 - 5 °C above pre-industrial values causing the Greenland and Antarctic ice sheets to shrink to sizes smaller than those of today. Similar polar temperature increases are predicted in the coming decades and the LIG period could therefore help to shed light on ice-sheet and sea-level responses to a warming world. 

LIG estuarine sediments preserved in the North Sea region are promising study sites for identification of the Antarctic ice sheet's relative contribution to LIG sea level, as well as for the reconstruction of both the magnitude and rate of LIG sea-level change during the interglacial. For these purposes, sea-level records in the region must be corrected for the impacts of glacial isostatic adjustment (GIA) which is primarily a consequence of two components: the evolution of terrestrial ice masses during the Penultimate Deglaciation (MIS 6), predominantly the near-field Eurasian ice sheet, and the viscoelastic structure of the solid Earth. 

The relative paucity of geological constraints on characteristics of the MIS 6 Eurasian ice sheet makes it challenging to evaluate its effect on sea level in the North Sea region. In order to model the Eurasian ice extent, thickness, and volume during the Penultimate Deglaciation we use a simple ice sheet model (Gowan et al. 2016), calibrated against models of the Last Glacial Maximum. By employing a gravitationally consistent sea-level model (Kendall et al. 2005), we generate a large ensemble of GIA outputs that spans the uncertainty in parameters controlling both the viscoelastic earth model and the evolution of global ice sheets during the Penultimate Deglaciation. By performing spatial sensitivity analysis with this ensemble, we are able to demonstrate the relative importance of each parameter in controlling North Sea GIA. Our comprehensive approach to exploring uncertainties in both the global ice sheet evolution and solid earth response provides significant advances in our understanding of LIG sea level.

How to cite: Pollard, O., Barlow, N., Gregoire, L., Gomez, N., Cartelle, V., Ely, J., and Astfalck, L.: Investigating the Sensitivity of North Sea Glacial Isostatic Adjustment during the Last Interglacial to the Penultimate Deglaciation of Global Ice Sheets, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8112, https://doi.org/10.5194/egusphere-egu22-8112, 2022.

EGU22-8350 | Presentations | G3.3 | Highlight

Reconstructing large scale differential subsidence in the Netherlands using a spatio-temporal 3D paleo-groundwater level interpolation 

Kim de Wit, Roderik S.W. van de Wal, and Kim M. Cohen

Subsidence is a land use problem in the western and northern Netherlands, especially where both shallow soft soil subsidence and deeper subsidence components, including glacio-isostatic adjustment (GIA), add up. The aim of this study is to improve the estimation of the GIA component within the total subsidence signal across the Netherlands during the Holocene, using coastal plain paleo-water level markers. Throughout the Holocene, the GIA induced subsidence in the Netherlands has been spatially and temporally variant, as shown by previous studies that used GIA modelling and geological relative sea-level rise reconstructions. From the latter work, many field data points are available based on radiocarbon dated coastal basal peats of different age and vertical position. These reveal Holocene relative sea-level rise to have been strongest in the Wadden Sea in the Northern Netherlands. This matches post-glacial GIA subsidence (forebulge collapse) as modelled for the Southern North Sea, being located in the near-field of Scandinavian and British former ice masses.

In this study, geological data analysis of RSL and other paleo-water level data available from the Dutch coastal plain for the Holocene period is considered in addition. The analysis takes the form of designing and executing a 3D interpolation (kriging with a trend: KT), where paleo-water level Z(x,y,age) is predicted and the field-data points are the observations (Age, X, Y and Z as knowns). We use a spatio-temporal 3D grid that covers the Dutch coastal plain, and reproduces and unifies earlier constructed sea level curves and high-resolution sampled individual sites (e.g. Rotterdam). The function describing the trend part of the interpolation separates linear and non-linear components of relative water level rise, i.e.: long-term background subsidence and shorter-term GIA subsidence signal and postglacial water level rise. The kriging part then processes remaining subregional patterns. The combined reconstruction thus yields a spatially continuous parameterization of regional trends that (i) allows to separate subsidence from water level rise terms, and (ii) is produced independently of GIA modelling to enable cross-comparison. Results are presented for the coastal plain of the Netherlands ([SW] Zeeland – Rotterdam – Holland – Wadden Sea – Groningen [NE]). The percentage of the total coastal-prism accommodation space that appears due to subsidence, from the south to the north of the study area increases by 20%. Holocene-averaged subsidence rates from the first analysis ranged from ca. 0.1 m/kyr (Zeeland) to 0.4 m/kyr (Groningen), which is 5-10 times larger than present-day GPS/GNSS-measured rates.

The research presented in this abstract is part of the project Living on soft soils: subsidence and society (grantnr.: NWA.1160.18.259). 

How to cite: de Wit, K., van de Wal, R. S. W., and Cohen, K. M.: Reconstructing large scale differential subsidence in the Netherlands using a spatio-temporal 3D paleo-groundwater level interpolation, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8350, https://doi.org/10.5194/egusphere-egu22-8350, 2022.

EGU22-9485 | Presentations | G3.3

An adaptive-triangular fully coupled 3D ice-sheet–sea-level model 

Jorjo Bernales, Tijn Berends, and Roderik van de Wal

Regional sea-level change and the deformation of the solid Earth can lead to important feedbacks on the long- and short-term evolution and stability of ice sheets. A rigorous manner of accounting for these feedbacks in model-based ice-sheet reconstructions and projections, is to establish a two-way coupling between an ice-sheet and a sea-level model. However, the individual requirements of each of these two components such as a global, long ice sheet load history or a high ice-model resolution over critical sectors of an ice sheet are at present not easy to combine in terms of computational feasibility. Here, we present a coupling between the ice-sheet model UFEMISM, which solves a range of approximations of the stress balance on a dynamically adaptive irregular triangular mesh, and the gravitationally self-consistent sea-level model SELEN, which incorporates the glacial isostatic adjustment for a radially symmetric, viscoelastic and rotating Earth, including coastline migration. We show global simulations over glacial cycles, including the North American, Eurasian, Greenland, and Antarctic ice sheets, and compare its performance and results against commonly used alternatives.

How to cite: Bernales, J., Berends, T., and van de Wal, R.: An adaptive-triangular fully coupled 3D ice-sheet–sea-level model, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9485, https://doi.org/10.5194/egusphere-egu22-9485, 2022.

EGU22-9968 | Presentations | G3.3

Interacting melt-elevation and glacial isostatic adjustment feedbacks allow for distinct dynamic regimes of the Greenland Ice Sheet 

Maria Zeitz, Jan M. Haacker, Jonathan F. Donges, Torsten Albrecht, and Ricarda Winkelmann

Interacting feedbacks play an important role in governing the stability of the Greenland Ice Sheet under global warming. Here we study the interaction between the positive melt-elevation feedback and the negative feedback from glacial isostatic adjustment (GIA), and how they affect the ice volume of the Greenland Ice Sheet on long time scales. We therefore use the Parallel Ice Sheet Model (PISM) coupled to a simple solid Earth model (Lingle-Clark) in idealized step-warming experiments. Our results suggest that for warming levels above 2°C, Greenland could become essentially ice-free on the long-term, mainly as a result of surface melting and acceleration of ice flow. The negative GIA feedback can mitigate ice losses and promote a partial recovery of the ice volume.

Exploring the full factorial parameter space which determines the relative strength of the two feedbacks reveals that four distinct dynamic regimes are possible: from stabilization, via recovery and self-sustained oscillations to the irreversible collapse of the Greenland Ice Sheet. In the recovery regime an initial ice loss is reversed and the ice volume stabilized at 61-93% of the present day volume. For certain combinations of temperature increase, atmospheric lapse rate and Earth mantle viscosity, the interaction of the GIA feedback and the melt-elevation feedback leads to self-sustained, long-term oscillations in ice-sheet volume with oscillation periods of tens to hundreds of thousands of years and oscillation amplitudes between 15-70% of present-day ice volume. This oscillatory regime reveals a possible mode of internal climatic variability in the Earth system on time scales on the order of 100,000 years that may be excited by or synchronized with orbital forcing or interact with glacial cycles and other slow modes of variability.

How to cite: Zeitz, M., Haacker, J. M., Donges, J. F., Albrecht, T., and Winkelmann, R.: Interacting melt-elevation and glacial isostatic adjustment feedbacks allow for distinct dynamic regimes of the Greenland Ice Sheet, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9968, https://doi.org/10.5194/egusphere-egu22-9968, 2022.

Geodetic time series from autonomous GNSS systems distributed across Antarctica are revealing unexpected patterns and startling rates of crustal deformation due to GIA.  Linked with seismic mapping and derived rheological properties of the Antarctic crust and mantle, and with new modeling capabilities, our understanding of the timescales of GIA response to ice sheet change is swiftly advancing.  Rapid GIA response allows for cryosphere-solid earth interactions that can alter ice sheet behavior on decadal and centennial timescales.  Continued progress in understanding how such feedbacks may influence future contributions of polar ice sheets to global sea level change requires continuing and expanding our geodetic observations. What frameworks can lead to implementation of this goal?  U.S. and international science vision documents pertaining to geodynamics, the changing cryosphere and sea level, all point to international collaborative efforts as the way to achieve ambitious science goals and extend observational capacities in polar regions.  SCAR research programmes facilitated the network vision and collaborative relations that led to the POLENET (POLar Earth observing NETwork) network of geophysical and geodetic instruments during the International Polar Year 2007-08. Can the SCAR INSTANT programme provide a framework for collaborative initiatives between national Antarctic programs to form a sustainable model to support acquisition of the observations required to meet community science objectives?  Let’s consider the ‘grass roots’ actions by the science community needed to push international, interdisciplinary science frameworks forward.

How to cite: Wilson, T. J.: GNSS Observations of Antarctic Crustal Deformation – International Framework for Future Networks?, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10610, https://doi.org/10.5194/egusphere-egu22-10610, 2022.

EGU22-10884 | Presentations | G3.3

Effect of Icelandic hotspot on Mantle viscosity in southeast Greenland 

Valentina R. Barletta, Wouter van der Wal, Andrea Bordoni, and Shfaqat Abbas Khan

Recent studies suggest the hotspot currently under Iceland was located beneath eastern Greenland at ~40 Ma BP and that the upwelling of hot material from the Iceland plume towards Greenland is ongoing. A warm upper mantle has a low viscosity, which in turn causes the solid Earth to rebound much faster to deglaciation. In the area of the Kangerlussuaq glacier, a large GPS velocities residual after removing predicted purely elastic deformations caused by present-day ice loss suggests the possibility of such fast rebound to little ice age (LIA) deglaciation. Here we investigate the lithospheric thickness and the mantle viscosity structure beneath SE-Greenland by means of model predictions of solid Earth deformation driven by a low viscosity mantle excited by the LIA deglaciation to the present day. From the comparison of such modeled deformations with the GPS residual, we conclude that 1) a rather thick lithosphere is preferred (90-100 km) 2) and the upper mantle most likely has a viscosity that changes with depth. Assuming a two layer upper mantle, it is not well constrained which part of the upper mantle has to be low, with a preference for low viscosity in the deeper upper mantle.

To understand such results we implemented forward modelling with more realistic earth models, relying on improvements in seismic models, petrology and gravity data. This yields 3D viscosity maps that can be compared to inferences based on the 1D model and forms the basis for 3D GIA models. The conclusion based on the 1D model can be explained with 3D Earth models. In the area of the Kangerlussuaq glacier the seismic derived viscosities prefer a higher viscosity layer above a lower viscosity one. This stems from the slow decrease in viscosity with depth. The layer that is characterized as shallow upper mantle still contains shallow regions with low temperatures, while the deeper upper mantle reaches low viscosities. Generally, for GIA earth models the “higher above lower” viscosity layering is unusual. However, the analysis of the 1D model clearly shows this to be one of the preferred model regions, in combination with a large lithosphere thickness of 100 km. This is a notable result that draws attention to the importance of shallow layering in GIA models. 

How to cite: Barletta, V. R., van der Wal, W., Bordoni, A., and Khan, S. A.: Effect of Icelandic hotspot on Mantle viscosity in southeast Greenland, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10884, https://doi.org/10.5194/egusphere-egu22-10884, 2022.

EGU22-10942 | Presentations | G3.3

Separating of Glacial Isostatic Adjustment (GIA) across Antarctica from GRACE/GRACE-FO observations via Independent Component Analysis (ICA) 

Tianyan Shi, Yoichi Fukuda, Koichiro Doi, and Jun’ichi Okuno

The redistribution of the near-surface solid Earth due to glacial isostatic adjustment (GIA), which is the ongoing response of the solid Earth due to changes in the ice-ocean load following the Last Glacial Maximum, has a direct impact on the inferred Antarctic Ice Sheet (AIS) mass balance from gravimetric data acquired during the Gravity Recovery and Climate Experiment (GRACE) and GRACE Follow-On (GRACE-FO) missions.

However, sparse in-situ observation networks across Antarctica have led to the inability to effectively constrain the GIA effect. Here, we analyze the mass change patterns across Antarctica via independent component analysis (ICA), a statistics-based blind source separation method to extract signals from complex datasets, in an attempt to reduce uncertainties in the glacial isostatic adjustment (GIA) effects and improve understanding of AIS mass balance.

The results reveal that GIA signal could be directly separated from GRACE/GRACE-FO observations without introducing any external model.  Although the GIA signal cannot be completely isolated, the correlation coefficients between ICA-separated GIA, and the ICE-5G and ICE-6G models are 0.692 and 0.691, respectively. The study demonstrates the possibility of extracting GIA effects directly from GRACE/GRACE-FO observations.

How to cite: Shi, T., Fukuda, Y., Doi, K., and Okuno, J.: Separating of Glacial Isostatic Adjustment (GIA) across Antarctica from GRACE/GRACE-FO observations via Independent Component Analysis (ICA), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10942, https://doi.org/10.5194/egusphere-egu22-10942, 2022.

EGU22-11569 | Presentations | G3.3

The influence of Earth’s hypsometry on global sea level through a glacial cycle and into the future 

Vivi Kathrine Pedersen, Natalya Gomez, Gustav Pallisgaard-Olesen, Julius Garbe, Andy Aschwanden, Ricarda Winkelmann, and Jerry Mitrovica

Earth’s topography and bathymetry is shaped by a complex interplay between solid-Earth processes that deform the Earth from within and the surface processes that modify the outer shape of the Earth. At the surface, an ultimate baselevel set by global sea level marks the defining transition from erosion to deposition. Over geological time scales, this baselevel has resulted in a distinct hypsometric distribution (distribution of surface area with elevation), with the highest concentration of surface area focused in a narrow elevation range near present-day sea level.

This particular feature in Earth’s hypsometry makes the global land fraction very sensitive to changes in sea level. Indeed, a sea-level change will result in a significant change in the land fraction as dictated by the hypsometric distribution, thereby modulating the very same sea-level change. However, it remains unexplored exactly how sea-level changes have modified the global land fraction over past glacial cycles and into the future.

Here we analyse how Earth’s hypsometry has changed over the last glacial cycle as large ice sheets waxed and waned particularly in Scandinavia and North America. These changes in global ice volume resulted in a significant global excursion in sea level, modulated regionally by solid-Earth deformation, gravitational effects, and effects from Earth’s rotation. These changes modified Earth’s hypsometry, and therefore the global land fraction at any given time. Consequently, we can map out how Earth’s hypsometry has influenced global mean sea level (GMSL) over time. To examine this relationship between Earth’s hypsometry and sea level further, we look to the deep future, to a scenario where both the Greenland Ice Sheet and the Antarctic Ice Sheets will melt away completely over multi-millennial timescales. This scenario is not meant to represent a realistic future scenario per se, but it allows us to define the hypsometric GMSL correction needed for any GMSL that the Earth has experienced recently or will experience in the future.

How to cite: Pedersen, V. K., Gomez, N., Pallisgaard-Olesen, G., Garbe, J., Aschwanden, A., Winkelmann, R., and Mitrovica, J.: The influence of Earth’s hypsometry on global sea level through a glacial cycle and into the future, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11569, https://doi.org/10.5194/egusphere-egu22-11569, 2022.

EGU22-12689 | Presentations | G3.3

Improving past and future relative sea-level constraints for the Norwegian coast 

Thomas R. Lakeman, F. Chantel Nixon, Anders Romundset, Matthew J.R. Simpson, John Inge Svendsen, Kristian Vasskog, Stein Bondevik, Glenn Milne, and Lev Tarasov

New research aims to improve relative sea-level (RSL) projections for the Norwegian coast. The main objectives are to: i) collect observations of past RSL changes, ranging from the end of the last ice age to the last century, ii) develop a high-quality database of post-glacial sea-level index points (SLIPs) for the Norwegian coast, and to iii) improve our understanding of past and future vertical land motion using glacial isostatic adjustment (GIA) modelling. To now, our collection of new empirical data has focussed on three significant, but enigmatic RSL histories that are not adequately reproduced in existing GIA models: very recent stillstands and transgressions documented by historical tide gauge records, rapid transgressions during the early- to mid-Holocene Tapes period, and abrupt transgressions during the latest Pleistocene Younger Dryas chronozone. Ongoing field sampling is focussed on developing high-resolution RSL trends from salt marshes, isolation basins, and raised beaches, using multiple biostratigraphic and geochemical proxies (i.e. micropaleontology, macrofossils, x-ray fluorescence, C/N) and dating techniques (i.e. Pb-210, Cs-137, C-14, tephrochronology, geochemical markers). Results from various localities spanning the Norwegian coast provide robust constraints for the timing and rate of RSL change during the Younger Dryas and Tapes chronozones. Additional results providing new estimates of very recent RSL trends in southwest Norway are presented by Holthuis et al. (Late Holocene sea-level change and storms in southwestern Norway based on new data from intertidal basins and salt marshes; Session CL5.2.2). These new and emerging constraints are being integrated into a post-glacial RSL database that incorporates high-quality data from the entire Norwegian coastline. Over 1000 SLIPs have been assembled from published studies. These existing data were updated using current radiocarbon calibration curves, high-resolution digital elevation models, new field observations, and new quantitative estimates of relevant uncertainties. Ongoing GIA modelling is utilizing the new RSL database, a glaciological model that freely simulates ice sheet changes, as well as geodetic and ice margin chronology constraints, to develop rigorous uncertainty estimates for present and future GIA along the Norwegian coast.

How to cite: Lakeman, T. R., Nixon, F. C., Romundset, A., Simpson, M. J. R., Svendsen, J. I., Vasskog, K., Bondevik, S., Milne, G., and Tarasov, L.: Improving past and future relative sea-level constraints for the Norwegian coast, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12689, https://doi.org/10.5194/egusphere-egu22-12689, 2022.

Uncertainty in present-day glacial isostatic adjustment (GIA) rates represent at least 44% of the total gravity-based ice mass balance signal over Antarctica. Meanwhile, physical couplings between solid Earth, sea level and ice dynamics enhance the dependency of the spatiotemporally varying GIA signal on 3D rheology. For example, the presence of low-viscosity mantle beneath melting marine-based ice sheet sectors such as the Amundsen Sea Embayment may delay or even prevent unstable grounding line retreat. Improved knowledge of upper mantle thermomechanical structure is therefore required to refine estimates of current and projected ice mass balance.

Here, we present a Bayesian inverse method for mapping shear wave velocities from high-resolution adjoint tomography into thermomechanical structure using a calibrated parameterisation of anelasticity at seismic frequency. We constrain the model using regional geophysical data sets containing information on upper mantle temperature, attenuation and viscosity structure. The Globally Adaptive Scaling Within Adaptive Metropolis (GASWAM) modification of the Metropolis-Hastings algorithm is utilised to allow efficient exploration of the multi-dimensional parameter space. Our treatment allows formal quantification of parameter covariances, and naturally permits us to propagate uncertainties in material parameters into uncertainty in thermomechanical structure.

We find that it is possible to improve agreement on steady state viscosity structure between tomographic models by approximately 30%, and reduce its uncertainty by an order of magnitude as compared to a forward-modelling approach. Direct access to temperature structure allows us to estimate lateral variations in lithospheric thickness, geothermal heat flow, and their associated uncertainties.

How to cite: Hazzard, J., Richards, F., Roberts, G., and Goes, S.: Reducing Uncertainty in Upper Mantle Rheology, Lithospheric Thickness and Geothermal Heat Flow Using a Bayesian Inverse Framework to Calibrate Experimental Parameterisations of Anelasticity, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12967, https://doi.org/10.5194/egusphere-egu22-12967, 2022.

This article presents a comprehensive benchmark study for the newly updated and publicly available finite element code CitcomSVE for modeling dynamic deformation of a viscoelastic and incompressible planetary mantle in response to surface and tidal loading. A complete description of CitcomSVE’s finite element formulation including calculations of the sea-level change, polar wander, apparent center of mass motion, and removal of mantle net rotation is presented. The 3-D displacements and displacement rates and the gravitational potential anomalies are solved with CitcomSVE for three benchmark problems using different spatial and temporal resolutions: 1) surface loading of single harmonics, 2) degree-2 tidal loading, and 3) the ICE-6G GIA model. The solutions are compared with semi-analytical solutions for error analyses. The benchmark calculations demonstrate the accuracy and efficiency of CitcomSVE. For example, for a typical ICE-6G GIA calculation with a 122-ky glaciation-deglaciation history, time increment of 100 years, and ~50 km (or ~0.5 degree) surface horizontal resolution, it takes ~4.5 hours on CPU 96 cores to complete with about 1% and 5% errors for displacements and displacement rates, respectively. Error analyses shows that CitcomSVE achieves a second order accuracy, but the errors are insensitive to temporal resolution. CitcomSVE achieves the parallel computation efficiency >75% for using up to 6,144 CPU cores on a parallel supercomputer. With its accuracy, computing efficiency and its open-source public availability, CitcomSVE is a powerful tool for modeling viscoelastic deformation of a planetary mantle in response to surface and tidal loading problems. 

How to cite: Zhong, S., Kang, K., Aa, G., and Qin, C.: CitcomSVE: A Three-dimensional Finite Element Software Package for Modeling Planetary Mantle’s Viscoelastic Deformation in Response to Surface and Tidal Loads, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13136, https://doi.org/10.5194/egusphere-egu22-13136, 2022.

EGU22-13323 | Presentations | G3.3

Mantle viscosity derived from geoid and different land uplift data in Greenland 

Mohammad Bagherbandi, Hadi Amin, Linsong Wang, and Masoud Shirazian

The Earth’s mass redistribution due to deglaciation and recent ice sheet melting causes changes in the Earth’s gravity field and vertical land motion in Greenland. The changes are because of ongoing mass redistribution and related elastic (on a short time scale) and viscoelastic (on time scales of a few thousands of years) responses. These signatures can be used to determine the mantle viscosity. In this study, we infer the mantle viscosity associated with the glacial isostatic adjustment (GIA) and long-wavelength geoid beneath the Greenland lithosphere. The viscosity is determined based on a spatio-spectral analysis of the Earth’s gravity field and the land uplift rate in order to find the GIA-related gravity field. We used and evaluated different land uplift data, i.e. the vertical land motions obtained by the Greenland Global Positioning System (GPS) Network (GNET), GRACE and Glacial Isostatic Adjustment (GIA) data. In addition, a  combined land uplift rate using the Kalman filtering technique is presented in this study. We extract the GIA-related gravity signals by filtering the other effects due to the deeper masses i.e. core-mantle (related to long-wavelengths) and topography (related to short-wavelengths). To do this, we applied correlation analysis to detect the best harmonic window. Finally, the mantle viscosity using the obtained GIA-related gravity field is estimated. Using different land uplift rates, one can obtain different GIA-related gravity fields. For example, different harmonic windows were obtained by employing different land uplift datasets, e.g. the truncated geoid model with a harmonic window between degrees 10 to 39 and 10 to 25 showed a maximum correlation with the GIA model ICE-6G (VM5a) and the combined land uplift rates, respectively. As shown in this study, the mantle viscosities of 1.6×1022 Pa s and 0.9×1022 Pa s for a depth of 200  to 650  km are obtained using ICE-6G (VM5a) model and the combined land uplift model, respectively, and the GIA-related gravity potential signal.

How to cite: Bagherbandi, M., Amin, H., Wang, L., and Shirazian, M.: Mantle viscosity derived from geoid and different land uplift data in Greenland, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13323, https://doi.org/10.5194/egusphere-egu22-13323, 2022.

EGU22-138 | Presentations | CR4.3

Spatial and Temporal Variability of Basal Melt Rate beneath Getz Ice Shelf 

Salar Karam, Elin Darelius, Keith Nicholls, and Anna Wåhlin

Basal melting of ice shelves in the Amundsen Sea – caused by inflows of relatively warm and salty ocean water – has caused widespread thinning and acceleration of their tributary glaciers. In this study, we present novel time series from 2016 with sub-weekly resolution of direct measurements of basal melt rate from four sites on the western Getz Ice Shelf, including one site close to a grounding line. We examine spatial differences between the sites and complement these time series with mooring records from outside the cavity to investigate driving mechanisms of the basal melt rate from sub-seasonal down to tidal time scales. Far from the grounding line, melt rates display strong variability at fortnightly frequencies, caused by spring-neap tidal cycles increasing turbulence and subsequently mixing up heat towards the ice base. No variability at fortnightly frequencies is visible close to the grounding line, implying that well-mixed conditions there reduce the effect of the spring-neap tidal cycle. On longer time scales, the melt rate appears to show sensitivity to the depth of the thermocline, which previous studies have linked to wind forcing at the shelf break. As glaciers in West Antarctica are rapidly thinning, contributing significantly to sea level rise, it is becoming increasingly urgent to understand driving mechanisms of the basal melt rate.

How to cite: Karam, S., Darelius, E., Nicholls, K., and Wåhlin, A.: Spatial and Temporal Variability of Basal Melt Rate beneath Getz Ice Shelf, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-138, https://doi.org/10.5194/egusphere-egu22-138, 2022.

Terra Nova Bay in the western Ross Sea of Antactica has received increasing attention recently by international oceanographic and sea ice observation campaigns.  In Terra Nova Bay strong katabatic events create one of the most intense sea ice producing polynyas in Antarctica.  The associated deep convection drives the formation of HSSW, the precursor of AABW. It also facilitates the oceanic heat exchange with the adjacent ocean cavity beneath the Nansen Ice Shelf (NIS).  Terra Nova Bay presents us with the unique opportunity of studying many of the primary interactive processes of atmosphere, ocean, ice shelves and sea ice, in a relatively confined region. 
In this talk we will show results of a high resolution, coupled ocean-ice shelf modeling study that synthesizes and contextualizes available data sets from various recent observation campaigns. Our results include the first tidal model of Terra Nova Bay and the NIS cavity, the seasonal heat budget of the cavity and the formation of meso-scale eddies inside the polynya. We have also investigated the oceanographic role of erosion features at the base of the NIS, associated ice shelf melt rates and the impact of fresh water outflow in preconditioning the onset of winter polynya activity as well as the large scale circulation in Terra Nova Bay. 

How to cite: Jendersie, S., Dow, C., Paul, S., and Gwyther, D.: A cold  cavity? Results of a high resolution ice-shelf ocean coupled model of Terra Nova Bay and the ocean cavity beneath the Nansen Ice Shelf., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-647, https://doi.org/10.5194/egusphere-egu22-647, 2022.

EGU22-1158 | Presentations | CR4.3

The vertical structure and entrainment of subglacial melt water plumes 

Hans Burchard, Karsten Bolding, Adrian Jenkins, Martin Losch, Markus Reinert, and Lars Umlauf

Basal melting of marine-terminating glaciers, through its impact on the forces that control the flow of the glaciers, is one of the major factors determining sea level rise in a world of global warming. Detailed quantitative understanding of dynamic and thermodynamic processes in melt-water plumes underneath the ice-ocean interface is essential for calculating the subglacial melt rate. The aim of this study is therefore to develop a numerical model of high spatial and process resolution to consistently reproduce the transports of heat and salt from the ambient water across the plume into the glacial ice. Based on boundary layer relations for momentum and tracers, stationary analytical solutions for the vertical structure of subglacial non-rotational plumes are derived, including entrainment at the plume base. These solutions are used to develop and test convergent numerical formulations for the momentum and tracer fluxes across the ice-ocean interface. After implementation of these formulations into a water-column model coupled to a second-moment turbulence closure model, simulations of a transient rotational subglacial plume are performed. The simulated entrainment rate of ambient water entering the plume at its base is compared to existing entrainment parameterizations based on bulk properties of the plume. A sensitivity study with variations of interfacial slope, interfacial roughness and ambient water temperature reveals substantial performance differences between these bulk formulations. An existing entrainment parameterization based on the Froude number and the Ekman number proves to have the highest predictive skill. Recalibration to subglacial plumes using a variable drag coefficient further improves its performance.

How to cite: Burchard, H., Bolding, K., Jenkins, A., Losch, M., Reinert, M., and Umlauf, L.: The vertical structure and entrainment of subglacial melt water plumes, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1158, https://doi.org/10.5194/egusphere-egu22-1158, 2022.

EGU22-2364 | Presentations | CR4.3

Uncertainties in marine ice-sheet retreat are dominated by basal melt 

Tijn Berends, Lennert Stap, and Roderik van de Wal

The loss of ice in Antarctica is dominated by the melting of floating ice shelves due to warming oceans. However, the relation between changing ocean temperatures and rates of sub-shelf melt is poorly constrained. Ice-sheet models currently employ a range of different approaches to this problem, varying in complexity from simple parameterizations based on linear temperature-melt relations to fully coupled ocean models. While several studies have compared two or more parameterisations, such efforts are complicated by the complex geometry of the Antarctic ice-sheet, as well as the uncertainty in (future) patterns of ocean circulation and atmospheric forcing.

The MISMIP/ISOMIP/MISOMIP family of experiments (Asay-Davis et al., 2016) provides a framework for intercomparing basal melt parameterisations in an idealized geometry, reducing the many difficulties of applying them in a realistic setting. Here, we present results of the MISOMIP1 experiment with the ice-sheet model IMAU-ICE. We show that the differences in simulated ice-sheet retreat caused by the use of different basal melt models are much larger than those arising from other model uncertainties such as the formulation of basal sliding, stress balance approximations, and model resolution. This suggests that basal melt is likely the largest source of uncertainty in future projections of Antarctic ice-sheet retreat.

How to cite: Berends, T., Stap, L., and van de Wal, R.: Uncertainties in marine ice-sheet retreat are dominated by basal melt, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2364, https://doi.org/10.5194/egusphere-egu22-2364, 2022.

EGU22-2764 | Presentations | CR4.3

Towards interpretation of the radio-stratigraphy of Antarctic ice shelves from modeling and observations: A case study for the Roi Baudouin Ice Shelf, East Antarctica  

Vjeran Visnjevic, Reinhard Drews, Clemens Schannwell, Inka Koch, Steven Franke, and Daniela Jansen

Ice shelves surrounding the Antarctic perimeter buttress ice flow from the continent towards the ocean, and their disintegration leads to an increase in ice discharge and sea level rise. The evolution and integrity of ice shelves is governed by surface accumulation, basal melting, and ice dynamics. We find history of these processes imprinted in the ice-shelf stratigraphy, which is mapped using isochrones imaged with radar. As an observational archive, the radar obtained stratigraphy combined with ice flow modeling has high potential to assist model calibration and reduce uncertainties in projections for the ice-sheet evolution. In this study we use a simplistic and observationally driven ice-dynamic forward model to predict the ice-shelf stratigraphy. We validate this approach with the full Stokes ice-flow model Elmer/Ice, and present a test-case for the Roi Baudouin Ice Shelf (East Antarctica) - where our model predictions agree well with radar obtained observations. The presented method enables us to investigate whether ice shelves are in steady-state, as well as to map spatial variations of how much of the ice-shelf volume is determined by its local surface mass balance. In the case of Roi Baudouin, we find the ice-shelf volume in the western part to be dominated by ice inflowing from the ice sheet, while the eastern part of the ice shelf is dominated by ice locally accumulated on the shelf. Such analysis serves as a metric for the susceptibility of ice shelves to climate change. We further apply our approach to other ice shelves in Antarctica.

How to cite: Visnjevic, V., Drews, R., Schannwell, C., Koch, I., Franke, S., and Jansen, D.: Towards interpretation of the radio-stratigraphy of Antarctic ice shelves from modeling and observations: A case study for the Roi Baudouin Ice Shelf, East Antarctica , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2764, https://doi.org/10.5194/egusphere-egu22-2764, 2022.

EGU22-2903 | Presentations | CR4.3

Understanding the melting of Greenland's largest glacial ice tongue with high-resolution modelling and adaptive coordinates 

Markus Reinert, Marvin Lorenz, Knut Klingbeil, and Hans Burchard

Melting of the Greenland ice sheet has a big influence on the climate system. Therefore, it is important to understand how the ice melts. Since direct measurements at the underside of floating ice tongues are sparse, high-resolution models for the interaction of ocean and glacial ice are needed to determine sub-glacial melt rates and to understand melt processes. A common problem is that model resolution is often too low, so that the meltwater plume is only represented by one or two layers, and thus the entrainment of warmer water into the plume is not well captured. However, this heat transport towards the ice is crucial for the sub-glacial melt rate.

In this talk, we show how we solve this problem with the General Estuarine Transport Model (GETM). GETM features adaptive vertical coordinates that zoom automatically to areas of interest, in particular strong density gradients. A high density contrast exists in the entrainment layer between the relatively fresh and cold meltwater of the plume, and the ambient ocean water. By zooming towards this interface, our adaptive vertical coordinates resolve the meltwater plume with several layers, while keeping the total number of model layers at a modest level to ensure a feasible computation time. In addition, the coordinate levels align to the moving isopycnals – they “follow” the plume, which strongly reduces numerical mixing and pressure gradient errors.

We present this for the fjord of the 79°N-Glacier (79NG), which has the largest floating ice tongue in Greenland. In our idealized 2D-setup, we obtain layers as thin as 0.2 m to 1 m in the meltwater plume, for only 100 levels over a water column of several 100 m depth. Thanks to this high resolution of plume and entrainment layer, our model reproduces the overturning circulation in the glacier cavity correctly; in particular, it shows that the salinity stratification of the adjacent ocean determines the level at which the meltwater plume detaches from the ice tongue. Almost all sub-glacial melting occurs before this detachment, i.e., where the plume is directly at the ice–ocean interface. Furthermore, we can confirm that the highest melt rates exist near the grounding line of the glacier. Finally, our simulated melt rates are consistent with observations at 79NG.

Our model, developed in the GROCE (Greenland ice sheet–ocean interaction) project, will form the basis of a realistic 3D-model of the 79NG-fjord in the future.

How to cite: Reinert, M., Lorenz, M., Klingbeil, K., and Burchard, H.: Understanding the melting of Greenland's largest glacial ice tongue with high-resolution modelling and adaptive coordinates, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2903, https://doi.org/10.5194/egusphere-egu22-2903, 2022.

EGU22-2997 | Presentations | CR4.3

Satellite Remote Sensing Investigations into Changing Ice-shelf Extents in the eastern Weddell Sea Sector of Antarctica 

Nick Homer, Julien Dowdeswell, and Frazer Christie

Contemporary glaciological research is increasingly focussed on the long-term stability Antarctic Ice Sheet under different climate change scenarios, where changes to atmospheric and oceanic processes are forecast. The floating ice shelves which extend from the ice sheet are of particular research interest because they exert considerable control over the flow of inland ice and respond relatively rapidly to external forcing mechanisms.

In this study, new ice-shelf extent mapping is undertaken by delineating the calving front of the eastern Weddell Sea Sector of the East Antarctic Ice Sheet, where four of Antarctica’s ten largest ice shelves are located. Calving fronts and other lengths of coastline were mapped using an adapted edge-extraction coastline delineation method, entirely within a GIS computing environment, from a suite of remotely-sensed satellite optical (Landsat-series) and synthetic aperture radar (Sentinel-1) imagery. Combined with pre-existing coastline products, a timeseries of ice-shelf areal extent is presented and discussed in the context of known and theorised ice-ocean-atmosphere interactions occurring in the region. In contrast to what is occurring in other regions of the Antarctic Ice Sheet, ice shelves are found to have been synchronously advancing since the 1960s, with only the occasional detachment of large, tabular icebergs causing ice-shelf retreat on sub-decadal timescales. Most recently, total ice-shelf area along the eastern Weddell Sea coastline from Filchner to Fimbul ice shelves, inclusive, has been increasing by c. 550 km2 yr-1 between 2009 and 2019.

Examination of climate reanalysis and sea-ice observations suggests that increasing southward surface wind-speed anomalies along the eastern Weddell Sea coastline are facilitating increased sea-ice concentrations at the margins of the ice shelves and it is argued that this may be increasing the ice-shelves’ structural integrity, limiting iceberg calving activity. Ulimately, however, the ice shelves in this region are still primarily governed by bed-geometry and internal ice dynamical properties. Although this evidence is indicative of a region of the ice sheet in relative mass balance, the future continuation of identified surface air warming trend will increase the likelihood of increased iceberg calving, or indeed ice-shelf retreat or collapse, aping that perviously observed in the Antarctic Peninsula. Further research is, however, needed to assess what effect warming might have on the large-scale atmospheric processes governing changes to the surface winds and related sea-ice concentration anomalies, so that better predictions as to the future evolution of these ice shelves and their inland feeder ice streams may be made.

How to cite: Homer, N., Dowdeswell, J., and Christie, F.: Satellite Remote Sensing Investigations into Changing Ice-shelf Extents in the eastern Weddell Sea Sector of Antarctica, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2997, https://doi.org/10.5194/egusphere-egu22-2997, 2022.

EGU22-3246 | Presentations | CR4.3

Pre-breakup drawdown and ice cliff formation on two Larsen B tributaries, 1968-2008 

Naomi Ochwat, Ted Scambos, Sarah Child, and Mike Willis

The major tributary glaciers of the former Larsen B Ice Shelf have undergone significant changes in the time leading up to, and following, the collapse of the ice shelf in March 2002. Crane and Hektoria-Green-Evans Glaciers (hereafter, Crane; Hektoria) experienced multiple periods of rapid velocity increases and intervening decreases, and dramatic surface lowering and mass loss. Initial results of early (late 1960s) U.S. Navy Trimetrogon aerial image analysis for elevation indicates large elevation losses in the decades prior to the disintegration event. Following the ice shelf collapse, both glaciers developed significant ice cliff fronts, but with markedly different calving styles and ice front heights at different times after the event. Rapid collapse with indications of arcuate listric faulting began at Hektoria almost immediately after ice shelf loss, while Crane also experienced rapid retreat during this time. Maximum elevation of the cliff fronts in the Hektoria collapsed region ranged between 60 and 100 meters. Peak ice cliff height at Crane was approximately 105 m, occurring in late 2004. These cliff heights correspond with periods of very high flow speed, thinning, and rapid ice front retreat that is characteristic with modeled ice cliff failure events. Here we present our analysis of the characteristics that defined the retreat periods. We assess ice velocity changes from optical satellite imagery, hypsometry, and ice cliff front heights from stereo-image DEMs and altimetry data, and use bed topography and bathymetry data. Ice cliff failure that could lead to Marine Ice Cliff Instability (MICI) has never been observed either in situ or through remote sensing. Using the observed dynamics of Crane and Hektoria, we aim to improve our understanding of the parameters that modeling results show as the drivers of ice cliff failure. In doing so, impacts of ice cliff failure on outlet glacier stability in numerical modeling will be better constrained, which will increase predictive sea level rise accuracy.

How to cite: Ochwat, N., Scambos, T., Child, S., and Willis, M.: Pre-breakup drawdown and ice cliff formation on two Larsen B tributaries, 1968-2008, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3246, https://doi.org/10.5194/egusphere-egu22-3246, 2022.

EGU22-3402 | Presentations | CR4.3

IceLines – A new service to monitor Antarctic ice shelf front dynamics 

Celia A. Baumhoer, Andreas J. Dietz, Konrad Heidler, and Claudia Kuenzer

Antarctica`s coastline is constantly changing by moving ice shelf margins and glacier tongues. This can influence the discharge of the Antarctic Ice Sheet if ice shelf areas with buttressing forces are involved. By now, glacier and ice shelf front changes are not tracked continuously due to time-consuming manual work. Hence, dynamics of the calving front position are often simplified by using the steady-state-calving assumption for modelling. To provide modelers with frequent and continuous time series of calving front change, we introduce the ice shelf front monitoring service “IceLines”. IceLines monitors major Antarctic ice shelf fronts based on Sentinel-1 radar imagery. The data set is automatically updated on a monthly basis and can be accessed via the EOC GeoService (geoservice.dlr.de) hosted by DLR. IceLines automatically downloads and pre-processes Sentinel-1 data for 36 selected shelves and glaciers, extracts the calving front based on a deep neural network and optimizes the result by post-processing. The processing chain of IceLines presents unprecedented dense time series of calving front change during the era of Sentinel-1 (2014-today). Whereas many previous challenges for automatic calving front detection were tackled (e.g. various glacier morphologies, backscatter changes, different polarizations), some limitations exist for ice shelves with excessive surface melt during summer or dry snow facies close to the front. We will present the current implementation, the derived calving front time series and validation results of IceLines. Discussions with the modelling community are welcome to further improve the IceLines data set for ice sheet and ice shelf modelling applications.

How to cite: Baumhoer, C. A., Dietz, A. J., Heidler, K., and Kuenzer, C.: IceLines – A new service to monitor Antarctic ice shelf front dynamics, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3402, https://doi.org/10.5194/egusphere-egu22-3402, 2022.

EGU22-3613 | Presentations | CR4.3

Ice rise and ice rumple dynamics, and the consequences for ice sheet evolution 

Clara Henry, Clemens Schannwell, Vjeran Višnjević, and Reinhard Drews

The Antarctic contribution to sea level projections remains poorly constrained, particularly due to the complex dynamical response of the ice sheet to changes in external forcing in coastal regions. In our study we investigate ice rises and ice rumples, features which form in ice shelves where ice is locally grounded due to elevated bed topography. As a consequence, upstream ice is buttressed, regulating the flow of ice. Ice rises and ice rumples differ from one another in their characteristic flow regimes, with ice rises having a local, radial flow regime and ice rumples having a flow regime predominantly aligned with that of the surrounding ice shelf. Ice rises cause the surrounding ice shelf to flow either side of the feature and thereby cause a greater degree of buttressing.

Using a three-dimensional, isothermal,  full Stokes, idealised model setup (Elmer/Ice), we investigate the response of ice rises and ice rumples to sea level change, mimicking a glacial cycle. During sea level increase, a transition from ice rise to ice rumple occurs, and with a subsequent decrease in sea level, hysteretic behaviour is observed, i.e. the current grounded area, dome position and flow regime are dependent on the past state of the system. The hysteretic behaviour seen in the ice rise-rumple system is reflected in the upstream ice shelf and is likely to have an effect on continental grounding line dynamics. These findings have important implications for the initialisation and transient simulation of ice rises and ice rumples within continental-scale ice sheet models given that the evolution of these features is important for the timing and magnitude of sea level projections.

How to cite: Henry, C., Schannwell, C., Višnjević, V., and Drews, R.: Ice rise and ice rumple dynamics, and the consequences for ice sheet evolution, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3613, https://doi.org/10.5194/egusphere-egu22-3613, 2022.

EGU22-3951 | Presentations | CR4.3

Annual estimates of basal melting and calving from Antarctic ice shelves during 2010-2019 

Benjamin Davison, Anna Hogg, Noel Gourmelen, Julia Andreasen, Richard Rigby, Jan Wuite, and Thomas Nagler

Ice shelves play a crucial role in controlling rates of ice discharge across Antarctica’s grounding lines. Mass loss from ice shelves, predominately due to basal melting and calving, can reduce the buttressing force provided by ice shelves, leading to increased grounded ice discharge. Despite the importance of ice shelves, existing estimates of calving and freshwater fluxes from ice shelves have utilised disparate datasets valid for inconsistent time periods or have relied on simplifying assumptions, resulting in a limited account of the health of many ice shelves and little indication of processes driving ice shelf mass imbalance.

Here, we quantify calving and basal melt fluxes at annual temporal resolution during 2010 to 2019. Our annual measurements account for annual variations in ice velocity and basal melt rate for 183 ice shelves, and annual variations calving front position for 34 major ice shelves (accounting for ~90% of the ice shelf area). On average during the study period, a calving flux of 1283±109 Gt yr-1 is roughly equal to a melt flux of 1247±149 Gt yr-1. Inter-annual variations in the fluxes of both basal meltwater and calving mean that the melt contribution to ice shelf mass loss varies between 35% and 62%, with the lowest contributions in years with large calving events. These large (>100 Gt) calving events are rare (8 events during 2010-2019), yet account for 35% of the total ice shelf calving flux, highlighting the importance of large calving events for ice shelf mass balance over short time scales. Eighty percent of ice shelves, including many in East Antarctica, are melting at or faster than their balance rates, indicating that ocean-driven erosion of ice shelf grounding lines is widespread around Antarctica. Furthermore, we find a significant and strong positive correlation (R=0.68) between basal melt flux and grounding line discharge, implying that ocean-driven melt may pace grounded ice loss from Antarctica.

How to cite: Davison, B., Hogg, A., Gourmelen, N., Andreasen, J., Rigby, R., Wuite, J., and Nagler, T.: Annual estimates of basal melting and calving from Antarctic ice shelves during 2010-2019, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3951, https://doi.org/10.5194/egusphere-egu22-3951, 2022.

On timescales longer than several months, ice flow is treated as a non-Newtonian fluid, which viscosity depends on the second invariant of the strain-rate tensor and the temperature-dependent ice-stiffness parameter. This power-law dependence is known as Glen's flow law. Although results of laboratory experiments and inferences from in situ observations suggest a range of the power-law exponent n  from 1 to 5, the value of 3 is widely used. In studies focused on ice-shelf dynamics, the traditional approach is to use remote-sensing observations to infer the ice-stiffness parameter by means of inverse methods assuming a constant value of n=3. Focusing on the floating tongue of Pine Island Glacier, the inversions of the ice-stiffness parameter are performed for various constant as well as spatially variable values of n using present-day observations. Using the inferred parameters and basal melting derived from remote-sensing observations, the Pine Island Glacier Ice Shelf flow is simulated for hundred years. Results of simulations indicate that the effects of rheological parameters are of the order of 5%. The difference between results of hundred years simulations with observationally derived  and spatially uniform basal melting are of the order of 40%. These results indicate that on centennial timescales the ice-shelf flow is more sensitive to details of basal melting than to rheological parameters, provided the latter are constrained by observations.

How to cite: Sergienko, O.: The effects of rheological parameters on ice-shelf flow on centennial time scales., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4904, https://doi.org/10.5194/egusphere-egu22-4904, 2022.

EGU22-5266 | Presentations | CR4.3

Impact of sliding laws and surface mass projections on Greenland outlet glacier dynamics at 100-year timescales 

Rachel Carr, Emily Hill, and Hilmar Gudmundsson

The Greenland Ice Sheet (GrIS) contributed to 10.6 mm of global sea level rise between 1992 and 2018 (Shepherd et al., 2020), which is forecast to increase to 90±50 mm by 2100, under RCP8.5 forcing (Goelzer and others, 2020). Thus, it is crucial that we accurately forecast near future ice losses from the GrIS and assess the relative contribution of surface mass balance (SMB) and accelerated discharge from outlet glaciers. Uncertainties in forecasts of GrIS mass loss, which stem from model uncertainties, climate modelling projections, ocean forcing and the calving process.

Here, we assess the relative importance of two major sources of uncertainty, namely the choice of sliding law and SMB forecasts. To do this we use the ice flow model Úa to perform a series of model experiments using different formulations of the sliding law, and different projections of future SMB. Úa is vertically integrated, uses the shallow ice stream / shelf approximation and has an adaptive mesh. We conducted this work at three major Greenland outlet glaciers: Kangerdlugssuaq (KG), Humboldt (HU) and Petermann (PG) glaciers. These glaciers were selected as they are major sources of ice loss from the GrIS and have a diverse range of characteristics (e.g. terminus type, speed and catchment geometry), meaning that we can assess the variability in the importance of sliding laws and/or SMB forecasts between different types of glacier.

First, we initialised the models for each study glacier using remotely sensed data from 2014/15. We then performed a series of model inversions using four different sliding laws (Weertman, Budd, Tsai and Cornford laws), to all closely match the observed ice flow velocities. For each sliding law, we then ran a forward-in-time model simulation using the rheology and basal slipperiness fields derived from each inversion and compared the difference in ice loss after 100 years between each sliding law. Our results demonstrated that the impact of using different sliding laws varied between our study glaciers, resulting in limited differences at HU and substantially variation at KG and PG. To test the impact of SMB projections we use SMB projections from the Modèle Atmosphérique Régional (MAR) for ISMIP6, which utilised six CMIP5 and five CMIP6 models (Hofer et al., 2020). We then run forward simulations for 100 years for each study glacier, using each of the SMB forecasts, and using the rheology and basal slipperiness fields from each inversion. Initial results demonstrate that the impact of the difference SMB forecasts is far greater than the impact of the choice of sliding law.

References:

Goelzer, H., et al., 2020. The future sea-level contribution of the Greenland ice sheet: a multi-model ensemble study of ISMIP6. The Cryosphere, 14(9), pp.3071-3096.

Hofer, S. et al., 2020. Greater Greenland Ice Sheet contribution to global sea level rise in CMIP6. Nature communications, 11(1), pp.1-11.

Shepherd, A. et al., 2020. Mass balance of the Greenland Ice Sheet from 1992 to 2018. Nature, 579(7798), 233-239.

How to cite: Carr, R., Hill, E., and Gudmundsson, H.: Impact of sliding laws and surface mass projections on Greenland outlet glacier dynamics at 100-year timescales, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5266, https://doi.org/10.5194/egusphere-egu22-5266, 2022.

EGU22-5462 | Presentations | CR4.3

Seasonal ice velocity variability of Western Antarctic Peninsula tidewater glaciers from high temporal resolution Sentinel-1 imagery 

Benjamin Wallis, Anna Hogg, Benjamin Davison, and Michiel van den Broeke

In Antarctica dynamic ice loss dominates the continent’s contribution to sea level rise and the magnitude of dynamic ice loss depends in part on the ice speed at marine-terminating glacier grounding lines. Long term dynamic ice speed variations in Antarctica have been observed on multi-year timescales, most notably in ice speed increases in the Amundsen Sea sector, Getz basin and Antarctic Peninsula. Glacier and ice sheet speed can also be variable on seasonal timescales, due to surface meltwater-induced variations in basal water pressure and changes in the force balance at the terminus due to terminus advance and retreat. While these seasonal changes are well documented on the Greenland Ice Sheet, observations of seasonal ice speed changes in Antarctica are sparse and poorly resolved.

In this study, we show widespread seasonal ice speed fluctuations near the termini of 106 tidewater outlet glaciers across Western Antarctic Peninsula North of 70° S by exploiting the full Sentinel-1 record from 2014 to 2021. The seasonal speed variations were consistent each year, and are characterised by a summertime speed-up, with speed variability on average 13 ± 6.5% of the annual mean. There is good agreement between our observations of seasonal ice speed changes and time-series of potential forcing mechanisms, including surface water flux, terminus position change and reanalyses of ocean temperature. Our results demonstrate that the glaciers of the Western Antarctic Peninsula are sensitive to forcing in the ice-ocean-atmosphere system on seasonal timescales.

By observing widespread seasonal ice speed variations on the Antarctic Peninsula for the first time, we demonstrate a previously unknown sensitivity of part of the Antarctic Ice Sheet to external forcing over short timescales. This is particularly relevant for mass balance calculations by the input-output method, which typically rely on annual estimates of ice speed that do not capture these seasonal changes. Our dataset covers the Sentinel-1 epoch (2014-present), however the Antarctic Peninsula has undergone the greatest warming of any Southern Hemisphere terrestrial area in the latter twentieth century and atmospheric temperatures are projected to rise further in a 1.5°C warming scenario. Therefore, it is essential to understand the historic prevalence of seasonal speed changes on the Peninsula and to determine the impact of these seasonal variations on annual ice motion, to improve future projections of the Antarctic response to continued warming and its contributions to sea level rise.

How to cite: Wallis, B., Hogg, A., Davison, B., and van den Broeke, M.: Seasonal ice velocity variability of Western Antarctic Peninsula tidewater glaciers from high temporal resolution Sentinel-1 imagery, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5462, https://doi.org/10.5194/egusphere-egu22-5462, 2022.

EGU22-5859 | Presentations | CR4.3

Fenics_ice framework applied to three West Antarctic ice streams: Smith, Pope and Kohler Glaciers. 

Beatriz Recinos, Daniel Goldberg, James Maddison, and Joe Todd

Fenics_ice is a finite element model framework written in Python that quantifies the initialization uncertainty for time-dependent ice sheet models. Here, we apply for the first time this framework to real ice streams in the Amundsen basin: Smith, Pope and Kohler Glaciers. We quantify the degree to which observational uncertainty translates to parametric uncertainty (posterior uncertainty of inversions for basal drag and ice stiffness fields) and to uncertainty in projected quantities of interest (QoIs) such as sea level contribution. The framework implements the Shallow Shelf Approximation (SSA), and implements a control methods approach to invert for the basal drag and ice stiffness fields. Beginning with a cost function optimization which can allow for either gridded or point-cloud velocities, we generate a low-rank approximation to the posterior covariance of the parameters through the use of the cost function Hessian. In our work, the Hessian is calculated through algorithmic differentiation (AD) using the “complete” Hessian rather than the Gauss–Newton approximation. We then project the covariance on a linearization of the time-dependent ice sheet model (again using AD to generate the linearization) to estimate the growth of QoI uncertainty over time. We then show the model framework and capabilities when applied to these ice streams and our future plans to scale our framework into a larger domain.

How to cite: Recinos, B., Goldberg, D., Maddison, J., and Todd, J.: Fenics_ice framework applied to three West Antarctic ice streams: Smith, Pope and Kohler Glaciers., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5859, https://doi.org/10.5194/egusphere-egu22-5859, 2022.

EGU22-6193 | Presentations | CR4.3

The response of the Larsen C Ice Shelf to changes in ice-shelf buttressing 

Tom Mitcham, G. Hilmar Gudmundsson, and Jonathan L. Bamber

The future viability of the Larsen C Ice Shelf (LCIS) has been called into question following the collapse of its more northerly, neighbouring ice shelves on the Antarctic Peninsula, and the calving of the A68 iceberg in July 2017. Initially, using the ice-flow model Úa, we conduct time-independent experiments and find that the vast majority of the buttressing capacity of the LCIS is generated in the regions of the ice shelf just downstream of the grounding line. We also find that the Bawden and Gipps Ice Rises provide a negligible proportion of the total buttressing capacity of the ice shelf, as determined by modelled instantaneous changes in grounding line flux (GLF) in response to their removal.

We then conduct time-dependent experiments to examine the transient evolution of the LCIS and its tributary glaciers to changes in ice-shelf buttressing. We present, for the first time, simulations of the transient response of the system to the loss of basal contact at the Bawden and Gipps Ice Rises.  We find that the instantaneous increase in ice-shelf velocities is sustained throughout the 100-year model run, with associated dynamic thinning of the ice shelf on the order of tens of metres during this period. However, we find that the impact on the grounded ice dynamics, GLF and ice volume above flotation (VAF) is limited.

Through idealised calving experiments we show that the instantaneous response in GLF to a reduction in ice-shelf buttressing decays rapidly in the first few years following the calving event. We also find an increasing, but non-linear, relationship between the reduction in ice-shelf buttressing and the loss of VAF after 100 years, largely controlled by the bedrock topography of the tributary glaciers. With our model setup, using the BedMachine Antarctica v2 ice thickness and bedrock topography data, we find that the dynamic mass loss 100 years after the complete collapse of the LCIS is ~0.6 mm SLE.

How to cite: Mitcham, T., Gudmundsson, G. H., and Bamber, J. L.: The response of the Larsen C Ice Shelf to changes in ice-shelf buttressing, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6193, https://doi.org/10.5194/egusphere-egu22-6193, 2022.

EGU22-6203 | Presentations | CR4.3

The evolution of a basal melt channel on the southern Filchner Ice Shelf 

Ole Zeising, Julia Christmann, Hugh F. J. Corr, Veit Helm, Lea-Sophie Höyns, Coen Hofstede, Ralf Müller, Niklas Neckel, Keith W. Nicholls, Timm Schultz, Daniel Steinhage, Michael Wolovick, and Angelika Humbert

Basal melt channels of ice shelves influence ice-ocean interaction and thus the current and future dynamics of ice sheets and ice shelves. Understanding their evolution is necessary to assess their influence on ice shelves’ stability. In this study, we investigate the evolution of a basal channel, up to 330 m high, located in the southern Filchner Ice Shelf where the ice thickness is between 1150 and 1400 m. Observations with a phase-sensitive Radio Echo Sounder (pRES) reveal decreasing melt rates within the channel, from 1.8 m/a to freezing with increasing distance from the grounding line of Support Force Glacier. At a distance of 20 km from the grounding line, melt rates within the channel fall below those of the ambient ice and the height of the channel starts to decrease. Calculating the evolution of this channel over 250 years, under present-day melt rates, reveals a mismatch when compared with its present geometry: the melt rates would have needed to have been twice as high as those of the present day to form today's channel geometry. In contrast, the present-day melt rates result in a closure of the channel. These results were confirmed by simulations with a viscoelastic model: while the present-day melt rates led to a closure of the channel, higher melt rates reproduced the current channel geometry. The type of melt channel in this study diminishes with distance from the grounding line and is therefore not a destabilizing factor for ice shelves.

How to cite: Zeising, O., Christmann, J., Corr, H. F. J., Helm, V., Höyns, L.-S., Hofstede, C., Müller, R., Neckel, N., Nicholls, K. W., Schultz, T., Steinhage, D., Wolovick, M., and Humbert, A.: The evolution of a basal melt channel on the southern Filchner Ice Shelf, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6203, https://doi.org/10.5194/egusphere-egu22-6203, 2022.

EGU22-6500 | Presentations | CR4.3

First steps for a 3d flexible, unstructured finite element ocean model for flow under ice shelf cavities: an ISOMIP+ case study 

William Scott, Stephan Kramer, Benjamin Yeager, Paul Holland, Keith W. Nicholls, Martin Siegert, and Matthew Piggott

Accurate modelling of basal melting beneath ice shelves is key to reducing the uncertainty in forecasts of ice-shelf stability and, thus, the Antarctic contribution to sea level rise. However, the lack of flexibility inherent to traditional ocean models can pose problems.

Obtaining accurate melt estimates requires capturing the turbulent exchange of momentum, heat and salt at the ice-ocean interface, which may be modulated by the competing effects of stratification and basal slope. There are still significant uncertainties surrounding the trade-off between the simplicity of the melt parameterisation and the processes that need to be resolved by the numerical ocean model near the boundary.

Real ice-shelf cavity geometries are complicated. Bathymetric valleys are common and provide pathways for warm circumpolar deep water. The ice base is marked by channels, crevasses and terraces. These features will affect the boundary flow, with an added complication that melting plays a role in their formation. It is very difficult to model such flow regimes using a traditional ocean model not only because of the resolution constraints imposed by inflexible grids, but also due to the inbuilt assumptions of large aspect ratio processes and domains that may be violated when flow occurs past these features.

Ice flow models are very sensitive to how they are forced by melting at the grounding line, where the ice starts to float. The grounding line is precisely the region where ocean models are most questionable due to insufficient resolution imposed by limitations on the grid. Subglacial outflow into the cavity will likely break the inherent physical assumptions of hydrostatic, non-negligible vertical accelerations in large aspect ratio domains.

To model these effects requires the use of an ocean model that contains a flexible, unstructured mesh, is applicable at a range of length scales and, crucially, is still valid when the vertical-to-horizontal grid aspect ratio approaches order one. We are developing such a model for simulating flow under ice shelf cavities using the Firedrake finite element framework, primarily because it enables adjoint sensitivities to be calculated automatically. We present our 3d simulations of ISOMIP+ experiments alongside simulations using the MITgcm ocean model, a commonly used z-layer (constant vertical resolution) model. We have found that the ability to vary the mesh resolution flexibly in the horizontal and vertical, even in a relatively simple ISOMIP+ domain (i.e., no channels or crevasses) is very useful to investigate how melt rate depends on grid resolution, which ultimately must be the first aim of any study using a numerical model.

How to cite: Scott, W., Kramer, S., Yeager, B., Holland, P., Nicholls, K. W., Siegert, M., and Piggott, M.: First steps for a 3d flexible, unstructured finite element ocean model for flow under ice shelf cavities: an ISOMIP+ case study, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6500, https://doi.org/10.5194/egusphere-egu22-6500, 2022.

EGU22-6634 | Presentations | CR4.3

Shear-margin melting causes stronger transient ice discharge than ice-stream melting according to idealized simulations 

Johannes Feldmann, Ronja Reese, Ricarda Winkelmann, and Anders Levermann

Basal ice-shelf melting is the key driver of Antarctica’s increasing sea-level contribution. In diminishing the buttressing force of the ice shelves that fringe the ice sheet the melting increases the solid-ice discharge into the ocean. Here we contrast the influence of basal melting in two different ice-shelf regions on the time-dependent response of an idealized, inherently buttressed ice-sheet-shelf system. Carrying out three-dimensional numerical simulations, the basal-melt perturbations are applied close to the grounding line in the ice-shelf’s 1) ice-stream region, where the ice shelf is fed by the fastest ice masses that stream through the upstream bed trough and 2) shear margins, where the ice flow is slower. The results show that melting below one or both of the shear margins can cause a decadal to centennial increase in ice discharge that is more than twice as large compared to a similar perturbation in the ice-stream region. We attribute this to the fact that melt-induced ice-shelf thinning in the central grounding-line region is attenuated very effectively by the fast flow of the central ice stream. In contrast, the much slower ice dynamics in the lateral shear margins of the ice shelf facilitate sustained ice-shelf thinning and thereby foster buttressing reduction. Regardless of the melt location, a higher melt concentration toward the grounding line generally goes along with a stronger response. Our results highlight the vulnerability of outlet glaciers to basal melting in stagnant, buttressing-relevant ice-shelf regions, a mechanism that may gain importance under future global warming.

How to cite: Feldmann, J., Reese, R., Winkelmann, R., and Levermann, A.: Shear-margin melting causes stronger transient ice discharge than ice-stream melting according to idealized simulations, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6634, https://doi.org/10.5194/egusphere-egu22-6634, 2022.

EGU22-6747 | Presentations | CR4.3

Antarctic grounding line retreat enhanced by subglacial freshwater discharge 

Jamin S. Greenbaum, Christine Dow, Tyler Pelle, Mathieu Morlighem, Helen Fricker, Susheel Adusumilli, Adrian Jenkins, Anja Rutishauser, Donald Blankenship, Richard Coleman, Benjamin Galton-Fenzi, Won Sang Lee, Jason Roberts, and Seung-Tae Yoon

Accurate prediction of sea level rise requires detailed understanding of processes contributing to ice sheet mass loss. Antarctica’s ice shelves are thinning, resulting in enhanced flow of grounded ice due to weakened ice shelf buttressing. Glaciers feeding ice shelves with the highest melt rates are also experiencing some of the most rapid grounding zone retreat. However, these ice shelf melt rates reach values that cannot be explained by ocean forcing alone and are not reproduced in ocean models. We present subglacial hydrology model outputs for four major Antarctic glaciers (Pine Island, Thwaites, Totten and Denman), which flow through the deepest and most extensive Antarctic marine subglacial basins and feed rapidly thinning ice shelves. We show that the areas of high ice shelf melting rates and grounding line retreat coincide closely with areas of high subglacial discharge. We posit that the subglacial discharge provides the missing component driving the high melt rates, and identify positive feedbacks between ice dynamics, steepening of ice shelf basal slope, and subglacial outflow. If surface temperatures increase as expected in Antarctica over the coming decades, surface meltwater could flow to the ice sheet base, as observed in Greenland. The surface meltwater hydrological cycle could therefore contribute to seasonal variations in subglacial meltwater and ice shelf basal melt, leading to accelerated grounding line retreat into Antarctica’s deepest subglacial basins. Invoking these feedbacks could reconcile sea level records and ice sheet model simulations that remain overly stable in warmer periods.

How to cite: Greenbaum, J. S., Dow, C., Pelle, T., Morlighem, M., Fricker, H., Adusumilli, S., Jenkins, A., Rutishauser, A., Blankenship, D., Coleman, R., Galton-Fenzi, B., Lee, W. S., Roberts, J., and Yoon, S.-T.: Antarctic grounding line retreat enhanced by subglacial freshwater discharge, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6747, https://doi.org/10.5194/egusphere-egu22-6747, 2022.

EGU22-6965 | Presentations | CR4.3

Importance of landfast ice for ice shelves melt rate projection under future climate conditions in the Totten area, East Antarctica 

Guillian Van Achter, Thierry Fichefet, and Hugues Goosse

The Totten Glacier in East Antarctica is of major climate interest because of the large fluctuation of its grounding line and of its potential vulnerability to climate change. The Totten ice shelf melt rate is predicted to increase under future climate conditions, but this increase may differ on whether the landfast ice is represented in the model or not. Using a series of high-resolution, regional NEMO-LIM-based experiments, including an explicit treatment of ocean – ice shelf interactions and a landfast ice representation, we simulate the ocean – ice interactions in the Totten Glacier area for both historical (1995-2014) and future (end of the 21 st following RCP 4.5) periods. We show major changes between historical and projection runs as increased ice shelf melt rate, loss in sea ice production or intensified ocean circulation. Moreover, the representation of landfast ice dampens the ice shelf melt rate increase. The Totten ice shelf melt rate is increased between the two periods by either +41% when landfast ice is taken into account, or by 58% when it is not taken into account. This highlights the importance of including a landfast ice representation in our ocean models in order to predict realistic ice shelf melt rate increase in East Antarctica.

How to cite: Van Achter, G., Fichefet, T., and Goosse, H.: Importance of landfast ice for ice shelves melt rate projection under future climate conditions in the Totten area, East Antarctica, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6965, https://doi.org/10.5194/egusphere-egu22-6965, 2022.

EGU22-7254 | Presentations | CR4.3

Uncovering basal melt channels on the Dotson Ice Shelf 

Ann-Sofie Priergaard Zinck, Bert Wouters, and Stef Lhermitte

Like most of the ice shelves in the Antarctic Amundsen Sea Embayment, intrusion of warm circumpolar deep water onto the continental shelf causes basal thinning to the Dotson Ice Shelf (DIS). Studies on other ice shelves have shown how Digital Elevation Models (DEM) of high spatial resolution can reveal basal melt patterns that are crucial in understanding the dynamics of basal melting and the underlying ocean circulation. In this study we aim to achieve high spatial and temporal resolution basal melt rates of the DIS to try to uncover new basal melt patterns which products of coarser resolution do not capture. This will be done by using the high spatial resolution Reference Elevation Model of Antarctica (REMA) and a method based on the Google Earth Engine (GEE). This allows for fast co-registration and subsequent thinning and basal melt rate analysis of the 2-m resolution REMA strips from 2010-2017. Ice shelf thinning is calculated both in a Eulerian and Lagrangian framework, the latter providing information to the basal melt rate analysis. In agreement with other studies of the DIS a melt channel is found on the western side of the ice shelf. Furthermore, our study indicates a second smaller channel, which has not been revealed by existing altimetry studies.  This suggests that high-resolution basal melt rate products could be of great importance. Furthermore, it enlightens the difficulties in coupling ocean and ice models, since such models often run on a coarser grid and therefore, they will not capture the small-scale variabilities.

How to cite: Zinck, A.-S. P., Wouters, B., and Lhermitte, S.: Uncovering basal melt channels on the Dotson Ice Shelf, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7254, https://doi.org/10.5194/egusphere-egu22-7254, 2022.

EGU22-7731 | Presentations | CR4.3

A crevasse-depth calving law accounting for submarine melt undercutting 

Donald Slater and Doug Benn

The impact of submarine melting on calving is thought to be central in the response of marine-terminating glaciers to climate, yet we currently have no settled parameterisation that can represent this process in ice sheet models. The crevasse-depth calving law has been widely applied with arguable success, but in its present form accounts only for depth-mean stresses. As such, it does not account for the bending stresses induced by undercutting that may be key to the impact of submarine melting on calving.

Here, we combine elastic beam theory with linear elastic fracture mechanics to study the propagation of surface and basal crevasses near the front of tidewater glaciers in response to melt undercutting. We check our results against a numerical approach involving 2D elastic simulations and the displacement correlation method for estimating fracture depth. Our results suggest that bending stresses can play a significant role in modifying crevasse depth, with undercutting promoting the opening of surface crevasses and protruding ‘ice feet’ promoting the opening of basal crevasses. Lastly, we seek a revised crevasse-depth calving law that accounts for these effects.

How to cite: Slater, D. and Benn, D.: A crevasse-depth calving law accounting for submarine melt undercutting, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7731, https://doi.org/10.5194/egusphere-egu22-7731, 2022.

EGU22-7822 | Presentations | CR4.3

Complex basal motion of a Greenland Ice Sheet tidewater glacier 

Robert Law, Poul Christoffersen, Emma MacKie, Samuel Cook, Marianne Haseloff, and Olivier Gagliardini

Uncertainty tied to the mechanics of the fast motion of the Greenland Ice Sheet plagues sea-level rise predictions. Much of this uncertainty arises from imperfect representations of physical processes in constitutive relationships for basal slip and internal ice deformation, with continued misalignment between model output and borehole field data. To investigate further, we model two isolated cuboid domains from the fast-moving Sermeq Kujalleq (a.k.a Store Glacier), incorporating temperate ice rheology (softer ice at the melting point) and statistically realistic variogram-generated bed topography. Our results indicate a hitherto unappreciated complexity in ice-sheet basal motion over rough beds. Realistic topographic variability leads to highly variable basal slip rates (from <10 to >70% of surface velocity over ~1km), complex and variable deformation patterns, and a basal temperate ice layer that varies greatly in thickness in agreement with borehole observations (from <10 to >150 m). Velocity variations at the relatively smooth upper boundary of the temperate ice layer are significantly less variable, indicating that the slim basal temperate ice layer is an important control on ice motion. These results suggest that inversion procedures for basal traction over rough beds (including parts of Antarctica) may also be accounting for deformation within a temperate ice layer, which is problematic if the inclusion of a temperate ice layer and rough topography means commonly used basal slip relationships are no longer applicable. 

How to cite: Law, R., Christoffersen, P., MacKie, E., Cook, S., Haseloff, M., and Gagliardini, O.: Complex basal motion of a Greenland Ice Sheet tidewater glacier, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7822, https://doi.org/10.5194/egusphere-egu22-7822, 2022.

EGU22-8336 | Presentations | CR4.3

Icebergs slow glacier retreat in a Greenland fjord 

Karita Kajanto and Kerim Nisancioglu

The interface between ice and ocean in Greenlandic fjords is the main source of uncertainty in the sea level contribution estimates from the Greenland ice sheet in the coming century. So far, research has shown tight coupling between the glacier and the water column in the fjord, but several main processes remain unclear. The role of icebergs in narrow fjords is poorly understood, and until recently research has focused mostly on the buttressing effect iceberg melange can have on the calving front. However, icebergs provide a substantial fresh water flux in the fjord that can exceed subglacial discharge annually. Iceberg melt is distributed at depth and produced throughout the year, and contributes to the stratification of the fjord, impacting the glacier terminus.

We model the high-silled Ilulissat Icefjord in Western Greenland with the MITgcm ocean model, using IceBerg package to study the effect different iceberg distributions have on this fjord. We compare our results to available XCTD profiles from the fjord. Our results demonstrate that including icebergs is essential to correctly understand the stratification of the fjord. We show that larger icebergs with drafts close to, or deeper than sill depth cool the fjord basin at depth. More specifically, we show that — while the inflowing water looses heat as it passes icebergs — a significant part of this iceberg-induced cooling at depth is due to entrainment of iceberg-cooled intermediate waters into the basin. Furthermore, we demonstrate that icebergs affect glacier melt rate by modifying the melt rate distribution along the glacier face both in shape and magnitude.

How to cite: Kajanto, K. and Nisancioglu, K.: Icebergs slow glacier retreat in a Greenland fjord, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8336, https://doi.org/10.5194/egusphere-egu22-8336, 2022.

EGU22-8440 | Presentations | CR4.3

Impact of ice shelf crevasses on Grounding line flux 

Cristina Gerli, Sebastian Rosier, and Hilmar Gudmundsson

Antarctic Ice shelves are fundamentally important components of the cryosphere and key to predictions of global sea level rise. Thinning and fracturing of ice shelf systems can reduce back-stress forces exerted on grounded glaciers upstream, increasing mass flux across their grounding lines (GL). In recent years it has been suggested that a number of ice shelves around Antarctica have rapidly broken apart as a result of hydrofracturing.  Hydrofracture is the process whereby surface crevasses are filled up with meltwater and the resulting hydrostatic pressure cause outward propagation of the crevasse fracture.

Recent work assessed the impact of ice shelf thickness change and crevasse hydrofracturing on the vulnerability of ice shelves and on ice drainage. Using a deep convolutional neural network, high-resolution crevasses and fractures were mapped throughout Antarctica, revealing that 60 ± 10 % of ice shelves are vulnerable to fracturing, if inundated with water.

Here we use these crevasse maps to evaluate their impact on the flow of upstream glaciers, quantifying the change in flux at the GL. We employ a finite element ice flow model, Ua, which solves the vertically integrated shallow shelf approximation with an unstructured mesh, that allows refined resolution in complex areas, such as at the GL. In the absence of information on crevasse depth, we make the assumption that crevasses propagate through the entire thickness, meaning our results represent the maximum possible effect that these crevasses may have on ice flow. We present results for many of the most important ice shelves in East and West Antarctica.

We find that incorporating crevasses in the ice shelf always increases the mass flux of upstream glaciers across their GLs, however, there is substantial variability in flux change among ice shelves. Small increases in flux due to crevassing (7-15%) were detected for Fimbul, Shackleton, Pine Island, Larsen C, and Brunt Ice Shelves, with a more considerable increase for the Dotson & Crosson Ice shelves (38%). The increase in flux due to crevassing was extremely large for the Totten Ice Shelf (248%). The large differences in sensitivity between ice shelves may be a result of various factors, most notably the proximity of the features identified as crevasses to important pinning points. More work investigating these factors is needed in order to have a more complete understanding of the effects of crevasse hydrofracturing on inland glaciers.

How to cite: Gerli, C., Rosier, S., and Gudmundsson, H.: Impact of ice shelf crevasses on Grounding line flux, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8440, https://doi.org/10.5194/egusphere-egu22-8440, 2022.

EGU22-8546 | Presentations | CR4.3

Coastal retreat doubles previous estimates of Antarctic ice shelf loss 

Chad Greene, Alex Gardner, Nicole-Jeanne Schlegel, and Alexander Fraser

Ice shelves tend to grow through a steady influx of glacial ice and retreat in discrete calving events that occur on subannual to multidecadal timescales. The impacts of ice shelf calving and retreat are far-reaching, but the evolution of Antarctica’s coastline has not been well characterized, owing to the difficulty of delineating ice fronts in limited satellite data. To create an annual coastline dataset that spans the past quarter century, we combine data from multiple satellite sensors, and we use the known physics of ice flow to constrain ice front positions and fill gaps in the data record. We find that since 1997, Antarctica’s coastlines have retreated by 37,000 km2, led by major calving events from the Ross and Ronne ice shelves in the early 2000s, and sustained by countless loss events from smaller ice shelves ever since. Calving losses total nearly 6000 Gt, which is roughly equivalent to the total mass that has been lost to ice shelf thinning over the same period. Using an ice sheet model, we examine the impacts of observed coastal changes on the buttressing strength of Antarctica’s ice shelves.  

How to cite: Greene, C., Gardner, A., Schlegel, N.-J., and Fraser, A.: Coastal retreat doubles previous estimates of Antarctic ice shelf loss, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8546, https://doi.org/10.5194/egusphere-egu22-8546, 2022.

EGU22-9198 | Presentations | CR4.3

Observing iceberg size distributions and implications for calving processes 

Connor Shiggins, James Lea, William Harcourt, Siddharth Shankar, Stephen Brough, and Dominik Fahrner

Icebergs are a key component of the ice-ocean interface, and provide the opportunity to gain insight into calving processes, and freshwater budgets in fjords and oceans amongst others. Iceberg area and volume distributions have been characterised for a handful of sites across the Greenland Ice Sheet, though a greater spatial and temporal range of data are required to understand how iceberg dynamics vary between different glaciers. Here we present iceberg area and volume distributions from 141 ArcticDEM scenes from 2010-2017 for 19 marine-terminating glaciers in Greenland, with 588,856 icebergs automatically detected.

The data show emerging evidence for more positive power law slope values (i.e. glaciers with larger icebergs) at glaciers with mean terminus depths exceeding 230 meters. However, the range of these values are generally consistent once a depth of 230 metres is exceeded. Glaciers with shallower depths can generate similar iceberg distributions, though typically these provide more negative exponents (i.e. are dominated by smaller icebergs).

Our results allow a characteristic range of iceberg size distributions to be defined for glaciers with mean terminus depths greater than 230 metres, which is likely controlled by a change in dominant calving processes at/near these depths. While shallower glaciers can in some cases provide similar distributions, most observations show distributions dominated by smaller icebergs. Together these suggest that mean terminus depth exerts a fundamental control on calving processes and the resulting iceberg size distributions.

Having the capability to constrain expected iceberg distributions from these data will be useful for understanding controls on calving processes, how fjord freshwater fluxes may evolve, and characterising how the size of icebergs that are exported from fjords will change as Greenland’s marine-terminating glaciers continue to retreat.

How to cite: Shiggins, C., Lea, J., Harcourt, W., Shankar, S., Brough, S., and Fahrner, D.: Observing iceberg size distributions and implications for calving processes, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9198, https://doi.org/10.5194/egusphere-egu22-9198, 2022.

EGU22-9275 | Presentations | CR4.3

Impacts of variability in fjord circulation on glacier dynamics in Cumberland Bay, South Georgia  

Joanna Zanker, Emma Young, Ivan Haigh, and Paul Brickle

South Georgia is a mountainous and heavily glaciated sub-Antarctic island in the Southern Ocean, lying in the path of the Antarctic Circumpolar Current. Cumberland Bay is the largest fjord on the island, split into two arms, Cumberland East and West Bay, with a large marine-terminating glacier at the head of each arm. Water circulation in such fjords, and associated transport and exchange of heat, directly governs the stability of glaciers at the ice-ocean interface and the subsequent glacier dynamics. Over the past century there has been a markedly different behaviour in the retreat rate of Nordenskjöld glacier in East Bay, compared with that of Neumayer glacier in West Bay. Fjord circulation patterns are complex with influencing factors including winds, meltwater runoff, bathymetry and coastal current systems. Precise understanding of the variability in ocean circulation and exchange in Cumberland Bay cannot be understood from limited observational data alone. Here, we use observations together with a new high-resolution numerical model built using the NEMO4 framework to determine the dominant physical drivers of variability. Nordenskjöld and Neumayer glaciers are represented as a vertical wall with a theoretical annual cycle of freshwater discharge injected at the depth of neutral buoyancy. The model is used to investigate how variability in the circulation regime couples with the associated heat transport within the two fjord arms, and to elucidate the role of such variability on glacier dynamics and rate of retreat. The sensitivity of the system to sill depth, fjord geometry and wind direction will be demonstrated through a series of model experiments, gaining a stronger understanding of the key drivers of the different retreat rates of these glaciers. 

How to cite: Zanker, J., Young, E., Haigh, I., and Brickle, P.: Impacts of variability in fjord circulation on glacier dynamics in Cumberland Bay, South Georgia , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9275, https://doi.org/10.5194/egusphere-egu22-9275, 2022.

EGU22-9920 | Presentations | CR4.3

Short-term dynamics of Sermeq Kujalleq in Kangia (Jakobshavn Isbræ), Greenland derived from TRI and GNSS measurements 

Adrien Wehrlé, Martin P Lüthi, Ana Nap, Guillaume Jouvet, and Fabian Walter

Sermeq Kujalleq in Kangia (Jakobshavn Isbræ), Greenland has been extensively investigated over the past decades due to its recent retreat associated with extremely fast ice stream flow and high solid ice discharge. However, its short-term dynamics still remain poorly understood as they consist in transient states that can only be captured by high spatial and temporal in situ measurements. In the new COEBELI project, we aim at combining high resolution field data sets from seismic arrays, global navigation satellite system (GNSS) receivers, long-range uncrewed aerial vehicles and terrestrial radar interferometers (TRI) to achieve a comprehensive and detailed study of the short-term ice stream dynamics. Here, we present TRI and GNSS retrievals of surface velocity and elevation acquired during the first, exploratory field campaign of the COEBELI project in summer 2021. Seven kilometers away from the calving front, we specifically identified a slowdown of 1.12 m d-1 within a single day in the main trunk of the ice stream. While the absolute slowdown is larger in the main trunk than in the outer area of the shear margin (1.12 m d-1 versus 0.75 m d-1), it corresponds to a larger fraction of the pre-slowdown velocity in the latter zone (-4.48% versus -7.94%). We further discuss the challenges associated with the acquisition, processing and analysis of high-resolution data sets for the study of such complex and dynamic environments.

How to cite: Wehrlé, A., Lüthi, M. P., Nap, A., Jouvet, G., and Walter, F.: Short-term dynamics of Sermeq Kujalleq in Kangia (Jakobshavn Isbræ), Greenland derived from TRI and GNSS measurements, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9920, https://doi.org/10.5194/egusphere-egu22-9920, 2022.

EGU22-10208 | Presentations | CR4.3

Extension of marine ice-sheet flux conditions to effective-pressure-dependent and hybrid friction laws 

Thomas Gregov, Frank Pattyn, and Maarten Arnst

Marine ice sheets are complex systems with a highly non-linear behavior. There remains a large uncertainty about how various physical processes such as the basal friction and the subglacial hydrology affect the dynamics of the grounding line (GL). One possibility to better understand their mechanical behavior consists in adopting a boundary-layer analysis close to the GL. Specifically, one can derive a so-called flux condition, which is an analytical expression for the amount of ice that flows through this GL per unit time. In turn, this flux condition can provide useful information about the grounding-line dynamics, including the presence of hysteresis (Schoof, 2007b).

Several studies have introduced hybrid friction laws to model friction between the grounded part of the ice sheet and the bedrock (Schoof, 2005, Gagliardini et al., 2007). These friction laws behave as power-law friction laws far from the GL and plastically closer to it. Recent experiments have shown that these models are more realistic than the usual power-law friction (Zoet and Iverson, 2020). In parallel, sophisticated models for the subglacial hydrology have been developed (Bueler and van Pelt, 2015).

In this presentation, we show that the flux conditions previously derived for the Weertman friction law (Schoof, 2007a) and the Coulomb friction law (Tsai et al., 2015) can be extended to a flux condition for the general Budd friction law, with two different simple effective-pressure models for the subglacial hydrology. Using asymptotic developments, we provide a justification for the existence and uniqueness of a solution to the boundary-layer problem. Finally, we generalize our results to hybrid friction laws, based on a parametrization of the flux condition.

How to cite: Gregov, T., Pattyn, F., and Arnst, M.: Extension of marine ice-sheet flux conditions to effective-pressure-dependent and hybrid friction laws, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10208, https://doi.org/10.5194/egusphere-egu22-10208, 2022.

EGU22-10439 | Presentations | CR4.3

A new ice shelf melt model that accounts for freshwater discharge and application to Denman Glacier, East Antarctica 

Tyler Pelle, Adrian Jenkins, Christine Dow, and Jamin Greenbaum

Ice shelf basal melting is the primary mechanism by which the Antarctic Ice Sheet loses mass. While ocean forcing is the principal driver of basal melting, recent evidence suggests that localized melt maxima are located along deep grounding lines where large quantities of subglacial water are being discharged into sub-ice shelf cavities. As any change in the configuration of the grounding line can drastically influence the stress regime of the entire upstream grounded glacier, it is crucial we resolve this subglacial discharge-driven melting in a basal melt rate parameterization that can be used in standalone ice sheet models. Here, we extend the application of a 1D ocean and subglacial discharge driven melt parameterization into a 2D ice sheet model and apply it in forward simulations of Denman Glacier, East Antarctica.  Using subglacial hydrology model outputs to constrain the discharge inputs, we find that this parameterization resolves both local maxima and the large-scale spatial distribution of melt beneath the ice shelves buttressing Denman, Totten, Thwaites, and Pine Island glaciers. In the forward simulations of Denman Glacier, the melt contribution from subglacial discharge is required to reproduce contemporary patterns of grounding line retreat and rates volume loss. Under realistic 21st century ocean and subglacial forcing scenarios, Denman and Scott glaciers undergo largescale retreat and Denman Glacier retreats upstream to a ~10 km prograde section of bed topography upon which the grounding line stabilizes. However, under enhanced forcing, it is possible that Denman’s grounding line can overcome this topographic high and retreat inland into the deepest submarine trench on Earth beyond 2100

How to cite: Pelle, T., Jenkins, A., Dow, C., and Greenbaum, J.: A new ice shelf melt model that accounts for freshwater discharge and application to Denman Glacier, East Antarctica, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10439, https://doi.org/10.5194/egusphere-egu22-10439, 2022.

EGU22-10529 | Presentations | CR4.3

Characteristic buttressing of Antarctic ice shelves 

Simon Schöll, Ronja Reese, and Ricarda Winkelmann

The increasing dynamical loss of grounded ice in response to thinning of surrounding ice shelves is the main driver of the current sea level rise contribution of Antarctica. The observed acceleration of the ice streams is caused by reduced buttressing of the ice shelves connecting the grounded ice flow to the warming ocean. Several methods have been used to analyze the back-stress of the ice shelves at individual grounding line locations, however none of those quantify the state of the whole shelf. Here we present shelf-wide definitions of buttressing for major Antarctic ice shelves, based on the stress-balance at the grounding line, that respond consistently to ocean warming. We use the Parallel Ice Sheet Model (PISM) at 8km grid resolution and diagnostic output from Úa with a resolution of 200m at the grounding line. We show an increase in buttressing for more confined ice shelves and a decrease under idealized ocean warming. With the shelf-wide buttressing, the role of buttressing in the (de-)stabilizing capabilities of ice shelves on marine ice streams can be investigated.

How to cite: Schöll, S., Reese, R., and Winkelmann, R.: Characteristic buttressing of Antarctic ice shelves, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10529, https://doi.org/10.5194/egusphere-egu22-10529, 2022.

EGU22-10979 | Presentations | CR4.3

Evaluating Petermann Gletscher ice-shelf basal melt and ice-stream dynamics from high-resolution TanDEM-X elevation data. 

Enrico Ciracì, Eric Rignot, Pietro Milillo, and Luigi Dini

Petermann Gletscher drains 4% of the Greenland Ice Sheet that contains an estimated volume of ice equivalent to a 0.5 m global sea-level rise. It terminates in the longest floating ice shelves in the Northern Hemisphere. A significant portion of the glacier’s drainage basin is grounded below sea level on a downsloping bed, hence prone to rapid retreat if the glacier was pushed out of equilibrium by climate warming. Previous studies documented near-zero mass balance and a steady grounding line position during the last three decades. However, more recent observations revealed the transition to a new phase characterized by rapid grounding line retreat and accelerated ice flow after 2016. Increased basal melt due to warming ocean temperatures has been identified as the physical mechanism driving the retreat process. Nonetheless, a comprehensive evaluation of the magnitude and spatial variability of basal melt has not been performed yet. Its contribution to the ice mass loss remains, for this reason, poorly constrained.

In this study, we achieve this goal by employing high-resolution digital elevation models acquired by the German Aerospace Centre (DLR) TanDEM-X mission between 2011 and 2021. We derive basal melt estimates from ice elevation changes computed in a Lagrangian framework. The extended temporal coverage provided by TanDEM-X data allows mapping changes in basal malt over different temporal scales with unprecedented resolution and highlights increased melt rates during the second part of the observation period. The melt rate spatial distribution is consistent with the recent inland migration of the grounding line with peak values above 60 meters per year measured along with the western, central, and eastern sectors of the grounding zone.

How to cite: Ciracì, E., Rignot, E., Milillo, P., and Dini, L.: Evaluating Petermann Gletscher ice-shelf basal melt and ice-stream dynamics from high-resolution TanDEM-X elevation data., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10979, https://doi.org/10.5194/egusphere-egu22-10979, 2022.

EGU22-11427 | Presentations | CR4.3

Comparison of different calving laws using a level set method 

Cruz Garcia-Molina, Fabien Gillet-Chaulet, Mondher Chekki, Gael Durand, and Olivier Gagliardini

Calving is one of the most important processes that induce mass loss in Greenland and Antarctic ice shelves. These major ice discharges modify the calving front position with an impact over the whole stress regime of these glaciers. Because the calving rate depends on several physical parameters, having an empirical parameterization for simulations over long periods is a big challenge. We study the calving front position using the open-source finite element, Elmer/Ice (http://elmerice.elmerfem.org/) code. We use a time constant mesh coupled with a time-evolving signed distance to the front (level-set function Φ) that activates or masks nodes as needed. We study the front position (given as the 0 level set value) evolution by solving

 

with w=c+v, where c is the calving rate and v is the velocity of the ice normal to the front. By using a realistic synthetic configuration, based on the intercomparison models (MISMIP), we validate our level-set method, we study the numerical sensibility, and the impact of different calving laws reported in the literature.

How to cite: Garcia-Molina, C., Gillet-Chaulet, F., Chekki, M., Durand, G., and Gagliardini, O.: Comparison of different calving laws using a level set method, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11427, https://doi.org/10.5194/egusphere-egu22-11427, 2022.

EGU22-11758 | Presentations | CR4.3

Idealized high resolution modelling of plume dynamics and basal melting at Ryder Glacier 

Jonathan Wiskandt, Inga Koszalka, and Johan Nilsson

Using a two dimensional, high resolution, non-hydrostatic regional model, this study explores the melt induced circulation under the floating ice tongue of Ryder Glacier (RG) and the influence of different aspects of the simulation, like ambient water temperature and ice base geometry, on the circulation.

RG is located at the southern tip of Sherard Osborn Fjord (SOF) in the north of Greenland, which was for the first time surveyed oceanographically in 2019. Low grounding-line water temperatures, complex ice-tongue and sill geometries, and permanent sea-ice cover outside the fjord, potentially make the ice-ocean interactions in SOF rather different from those in the more well-studied nearby Petermann Fjord. 

The control simulation uses 2019 hydrographic observations as initial conditions. A set of model experiments is conducted to analyze the dependency of the plume behavior on the slope of the ice base and the temperature forcing from the in-flowing Atlantic water. 

 The simulated circulation and melt rates are qualitatively similar to previous modelling studies of North Greenlandic fjords. Based on observed ice-thickness transects along RG, two idealized ice tongue profiles are examined: one steeper and one shallower. The simulations with shallower slopes have a greater net basal melt and a stronger overturning fjord circulation, even though the melt plume initially is faster on the steeper slope. The results further suggest a direct relationship between the thermal forcing and the melt rate and resulting overturning time scale.

Additionally we discuss the possible numerical and physical implications of these results for future model experiments targeting the influence of basal melt on fjord circulations.

How to cite: Wiskandt, J., Koszalka, I., and Nilsson, J.: Idealized high resolution modelling of plume dynamics and basal melting at Ryder Glacier, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11758, https://doi.org/10.5194/egusphere-egu22-11758, 2022.

EGU22-11865 | Presentations | CR4.3

A new Finite Elements Framework for Fjord-Iceshelf Interaction (FEFFII) 

Stefano Ottolenghi, Jonathan Wiskandt, and Josefin Ahlkrona

Modeling interactions between ice sheets and ocean has proved of significant importance in order to properly understand larger-scale phenomena such as ice sheet melting and ocean circulation. We introduce the Finite Elements Framework for Fjord-Iceshelf Interaction (FEFFII), a new simulation framework for fjord dynamics. Open source and Python-based, it employs the full non-hydrostatic Navier-Stokes equations to account for the ocean evolution, while ice shelf behavior is accounted by the 3-equations parametrization. Even though some its features are still under experimentation, FEFFII is already capable of simulating realistic scenarios and handling relatively complex geometries, as well as moving boundaries. The model has been tested against several benchmarks from literature.

How to cite: Ottolenghi, S., Wiskandt, J., and Ahlkrona, J.: A new Finite Elements Framework for Fjord-Iceshelf Interaction (FEFFII), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11865, https://doi.org/10.5194/egusphere-egu22-11865, 2022.

EGU22-11898 | Presentations | CR4.3

Modelling the reversibility of Pine Island Glacier 

Bradley Reed, Hilmar Gudmundsson, Mattias Green, and Adrian Jenkins
Pine Island Glacier (PIG), in West Antarctica, has undergone dramatic changes in the last few decades, where flow speeds have increased by 75% and grounding lines have retreated over 30km. These recent changes are part of a long term trend of mass loss, believed to have been initiated following climate anomalies in the 1940s and 1970s. The ice shelf cavity first opened around 1945, shortly after a strong El Niño event, and PIG eventually ungrounded from a submarine ridge in the early 1970s, following another notable warm period. Observational records show that intermittent periods of cooler ocean conditions likely slowed the subsequent retreat but were not enough to reverse its progress. 
 
Here we use the ice-flow model Úa to study the recent transient evolution of PIG over the last several decades with the aim of identifying the drivers of observed changes in geometry and grounding line position. We use a depth-dependent melt rate parameterisation driven by present day melt values to represent warm conditions, while experimenting with various cold parameterisations. We ask what happens when the model is forced with alternating periods of cool and warm conditions when PIG is grounded at the submarine ridge. We hypothesise that warm ocean conditions will force the ice stream off the ridge and cooler conditions will slow but not stop the retreat. This work will improve the understanding of how glaciers respond to short, intense warm intervals particularly as El Niño events become more frequent in a warming future. We present the results from the initial investigations into how PIG responds to ocean forcing using an ice flow model. 

How to cite: Reed, B., Gudmundsson, H., Green, M., and Jenkins, A.: Modelling the reversibility of Pine Island Glacier, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11898, https://doi.org/10.5194/egusphere-egu22-11898, 2022.

EGU22-12017 | Presentations | CR4.3

Damage and Dynamic Activity on the Thwaites Glacier Ice Tongue: 2015 to 2021 

Trystan Surawy-Stepney, Anna E Hogg, Stephen L Cornford, and Benjamin J Davison

The majority of ice mass loss in West Antarctica is due to the ejection of grounded ice into the sea via ice-dynamic processes. Structural changes that impact the flow speed of marine-terminating glaciers can, therefore, impact their contribution to global sea level rise. Thwaites Glacier is among those for which these considerations are particularly important, due to its potential connection to the stability of the West Antarctic ice sheet, and the structural changes that have been observed at its terminus in recent years. However, the interactions between ice structural properties and flow speed are not well established, partly due to the limited availability of coincident observations.

We present weekly ice velocity measurements, derived using Sentinel-1 radar data, showing the recent onset of episodic dynamic variability in the form of two large-magnitude ~30%-45% acceleration/deceleration events between 2017 and 2021, occurring across the majority of the remnant of Thwaites Glacier's floating ice tongue, before a relaxation to the 2015/16 mean speed. Using deep learning methods, we measured a synchronous decrease in the structural integrity of the ice tongue and its eastern shear margin during the study period, and the upstream propagation of these regions of damaged ice. The pattern of change seen in the concurrent damage and ice velocity observations suggests a link between the two, which we explore in the work. The existence of this link is further supported by ice flow modelling, carried out using the BISICLES ice sheet model, in which the spatial pattern and concentration of observed damage are closely reproduced when forced with the observed speed changes.

Our results add to the growing body of evidence that the extent and degree of damaged ice has a significant distributed effect on ice velocity, and further demonstrate that damage processes must be integrated in ice sheet models in order to make accurate predictions of long-term behaviour and sea level contribution.

How to cite: Surawy-Stepney, T., Hogg, A. E., Cornford, S. L., and Davison, B. J.: Damage and Dynamic Activity on the Thwaites Glacier Ice Tongue: 2015 to 2021, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12017, https://doi.org/10.5194/egusphere-egu22-12017, 2022.

EGU22-12145 | Presentations | CR4.3

Multi-method based characterization of calving events at Salajiegna glacier - Northern Sweden 

Martin Schulthess, Nina Kirchner, and Peter Sigray

Sea level rise concerns millions of people in coastal areas across the globe. One of the largest uncertainties to project future sea level rise is the frontal ablation (accounting for calving and submarine melt) at marine ice margins, around the Greenland and Antarctic Ice Sheet. High rates of frontal ablation have been observed to imply, through loss of the buttressing effect but not limited to it, increased mass loss from marine terminating glaciers and hence, associated sea level rise. This study focuses on calving processes at a freshwater lake in northern Sweden, which represents a simpler environment to study calving processes than the marine one, because impacts of tides, salinity, and circulation (all known to be relevant at marine ice-ocean boundaries) can be neglected. A multi-method approach to quantify and characterize calving events is presented here, exploring and analysing the underwater acoustic soundscape at a calving glacier front, in connection with optical, image-based methods such as timelapse photography, and photogrammetry based on footage acquired by an uncrewed aerial vehicle (UAV). An acoustic detector is developed, tested and applied to a data set acquired during 2020, and results indicate that the acoustic detector can be an important complement in the range of tools used to observe, and quantify, calving. Applied in remote locations, where continuous monitoring is difficult and where optical methods are of limited use, collecting acoustic data and monitoring calving by means of its acoustic signature could render insights previously not available (because of lacking data and methodology).

How to cite: Schulthess, M., Kirchner, N., and Sigray, P.: Multi-method based characterization of calving events at Salajiegna glacier - Northern Sweden, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12145, https://doi.org/10.5194/egusphere-egu22-12145, 2022.

EGU22-12173 | Presentations | CR4.3

LADDIE: a one-Layer Antarctic model for Dynamical Downscaling of Ice-ocean Exchanges 

Erwin Lambert, Andre Jueling, Roderik van de Wal, and Paul Holland

A major source of uncertainty in future sea-level projections is the ocean-driven basal melt of Antarctic ice shelves. Remote sensing estimates of basal melt shows kilometer-scale features, and ice sheet models require kilometer-scale resolution to realistically resolve ice shelf stability and grounding line migration. Yet 3D numerical ocean models are computationally too heavy to produce melt rates at this resolution. To bridge this resolution gap, we here present the 2D numerical model LADDIE which allows for computationally efficient downscaling of basal melt rates, based on coarse 3D ocean model output. As a test case, we apply the model to downscale basal melt rates of the Crosson-Dotson ice shelf in the fast-melting Amundsen Sea region. Due to the model’s computational efficiency, parameters can be tuned extensively. We have tuned the model to a range of parameters, namely average basal melt, melt in the Kohler West grounding zone, melt along the Dotson Ice Shelf Channel, and the overturning circulation of the cavity waters. These tuning targets are taken from a range of remote sensing products and in situ ocean observations. We show that the model can be tuned to agree with all observations, providing confidence that the model contains the essential physical processes governing basal melt. We propose that (sub-)kilometer resolution basal melt rates can be used to improve the realism of ice sheet models and their simulations of contemporary and future mass loss. Here we show that LADDIE can provide these boundary conditions in a computationally efficient way.

How to cite: Lambert, E., Jueling, A., van de Wal, R., and Holland, P.: LADDIE: a one-Layer Antarctic model for Dynamical Downscaling of Ice-ocean Exchanges, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12173, https://doi.org/10.5194/egusphere-egu22-12173, 2022.

EGU22-12225 | Presentations | CR4.3

Phase field viscoelastic fracture models for ice sheet dynamics 

Jakub Stocek, Robert Arthern, and Oliver Marsh

Antarctic ice sheets grounded under the sea level can break apart if the ice cliffs at the edge of ice shelves collapse under their own weight. The process is known as the marine ice cliff instability and could lead to a rapid retreat of ice shelves, acceleration of the ice sheets, and subsequent increase in global sea levels.
A classical treatment of fracture by Griffith [3] introduced the energy release rate for brittle elastic materials, the energy required for crack propagation, and created the energetic fracture criterion. Unfortunately such theories are insufficient as they cannot reproduce curvilinear cracks, kinks, crack branching, crack arrest, or crack nucleation. One can overcome issues of the classical Griffith theory with a diffusive crack modelling by variational approaches based on energy minimisation [1, 4].
In this talk we present a thermodynamically consistent phase field viscoelastic fracture models relevant for ice sheet dynamics that allows to incorporate additional rheological properties such as creep. By identifying the relevant free energy and dissipation potential functions of interest one can derive relevant viscoelastic models. In the case of Maxwell rheology with Glen's flow law [2], one arrives at two possible systems, one better suited for short timescales and another for longer timescales.
We present robust adaptive numerical schemes that allow to treat both compressible and incompressible materials with pure Dirichlet or Neumann, as well as mixed boundary conditions. 
Computational experiments demonstrate the robustness of the numerical solvers and importance of inclusion of fracture mechanisms into ice sheet models.

[1] B. Bourdin, G.A. Francfort, J.J. Marigo, Numerical experiments in revisited brittle fracture. Journal of the Mechanics and Physics of Solids, Vol. 48, pp. 797--826, 2000.
[2] J.W. Glen, The creep of polycrystalline ice. Proceedings of the Royal Society London A, Vol. 228, pp. 519--538, 1955.
[3] A.A. Griffith, The phenomena of rupture and flow in solids. Philosophical Transactions of the Royal Society London A, Vol. 221, pp. 163--198, 1921.
[4] C. Miehe, F. Welschinger, and M. Hofacker, Thermodynamically consistent phase‐field models of fracture: Variational principles and multi‐field FE implementations. International journal for numerical methods in engineering, Vol. 83, pp. 1273--1311, 2010.

How to cite: Stocek, J., Arthern, R., and Marsh, O.: Phase field viscoelastic fracture models for ice sheet dynamics, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12225, https://doi.org/10.5194/egusphere-egu22-12225, 2022.

EGU22-12475 | Presentations | CR4.3

Historical buttressing effects on present-day Dotson and Crosson Ice Shelf dynamics 

Sarah F. Child, Ted Scambos, Winnie Chu, Ella Stewart, and Karen Alley

For almost three decades, the Dotson and Crosson Ice Shelves have withstood various degrees of velocity increases, basal melt, weakening shear margins, and grounding line retreat. The two ice shelves, located along the Amundsen Sea Embayment, are fed primarily by Kohler, Smith, and Pope Glaciers. The ice shelves were once thought to be separated by a landmass connecting Bear Island to the mainland, but there is no evidence from 75 years of available data supporting this partition. Recent research shows that the changes in dynamics undergone by both ice shelves and their outlet glaciers are due largely to basal melt driven by warm circumpolar deep water (CDW); however, the scope of those changes varies between the two sectors with the Crosson Ice Shelf experiencing the more extreme transformation. Observations from trimetrogon aerial imagery (late-1940s) and Landsat Thematic Mapper data (mid-1980s) reveal the northern edge of the Crosson Ice Shelf terminating at Holt Glacier and its southeastern edge buttressing against Haynes Glacier. Studies show that in the mid-1980s, a decrease in sea ice concentrations led to the migration of the detached Thwaites Ice Tongue which, with fast ice, aided in containing fragments of Thwaites Glaciers—around this time the retreat of Haynes Glacier’s ice tongue also began. We hypothesize it is this decrease in buttressing from ~35 years ago that began a continuous trend (still observed today) in ice shelf thinning, initiation of rifts, and outlet glacier speed increases and grounding line retreats. In contrast, the Dotson Ice Shelf is flanked by Bear Island and Martin Peninsula and has undergone less dramatic alterations in dynamics than the Crosson Ice Shelf. We quantify the impact of buttressing on the two connected ice shelves with the following analyses: extended temporal scale of outlet glacier hypsometry from 1960-the present; detailed 16-year study of grounding line migrations and hydrostatic equilibrium boundaries using CReSIS MCoRDS/2 level one data; estimated shear stresses from multi-year velocities; modeled back stresses acting on both ice shelves. Results of this study will help to improve modeling ocean-ice sheet interactions and better constrain CDW impacts.

How to cite: Child, S. F., Scambos, T., Chu, W., Stewart, E., and Alley, K.: Historical buttressing effects on present-day Dotson and Crosson Ice Shelf dynamics, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12475, https://doi.org/10.5194/egusphere-egu22-12475, 2022.

EGU22-12729 | Presentations | CR4.3

Modelling the ocean-ice interactions at the broken state of ice shelves 

Dorothée Vallot, Nicolas Jourdain, Anna Crawford, Jan Åström, Doug Benn, and Pierre Mathiot

Below ice shelves, complex interactions between the ice and the ocean are at stake that have large implications for future sea level rise. Basal melting from the ocean is recognised to have large impacts on the stability. Many studies focus on theses interactions in coupled models at different spatio-temporal scales. However, most of them consider the basal topography of the shelf as smooth ignoring its irregular state due to basal crevassing or channel-like features. We propose to investigate the impact of these features on basal melt and ice shelf stability by using a discrete particule model and an ocean model applied at the ice shelf of Thwaites glacier.

How to cite: Vallot, D., Jourdain, N., Crawford, A., Åström, J., Benn, D., and Mathiot, P.: Modelling the ocean-ice interactions at the broken state of ice shelves, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12729, https://doi.org/10.5194/egusphere-egu22-12729, 2022.

EGU22-13009 | Presentations | CR4.3

A semi-analytical model for marine ice sheet dynamics 

Ian Hewitt

Marine ice sheets have the greatest potential to contribute to rapid sea-level change because of the potential for rapid transfer of grounded ice (with thickness above flotation) to floating ice shelves or icebergs.  Ice loss occurs when this transfer (the 'grounding-line flux') is larger than the rate at which ice accumulates over the grounded ice sheet.  It is well known that the balance between accumulation and grounding-line flux can result in both stable and unstable ice-sheet states, and that this leads to the potential for 'marine-ice-sheet-instability' (MISI).   Various reduced mathematical models have been used to examine the stability of steady states, accounting for different parameterisations of basal drag, lateral buttressing and ice-shelf melting/calving.  However, real-world ice sheets are (presumably) rarely in a steady state, since the timescales taken for an ice-sheet to reach steady state are typically thousands of years, longer than the timescales on which the forcing changes.  The time-dependent dynamics are therefore important. 

Here, we detail a simple depth- and width- integrated model for a marine ice sheet that yields insight into the time-dependent dynamics that result from changing climate forcing.  The model - which reduces to a relatively simple dynamical system - demonstrates how gradual changes in forcing (surface accumulation, ocean temperature, for example) cause changes in the 'landscape' through which the ice-sheet evolves.  It reproduces some existing results for how the stability of steady states depends on the topography, as well as new results for the pace of groundling advance and retreat.  Investigating fundamental aspects of the time-dependent dynamics in a simplified model like this is important in order to understand the extent to which ice-sheet changes are 'irreversible' (or not). 

How to cite: Hewitt, I.: A semi-analytical model for marine ice sheet dynamics, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13009, https://doi.org/10.5194/egusphere-egu22-13009, 2022.

Mass loss at the Greenland Ice Sheet is influenced by atmospheric processes controlling its surface mass balance, and by submarine melt and calving where glaciers terminate in fjords. There, an ice mélange – a composite matrix of calved ice bergs and sea ice – may provide a buttressing force on a glacier terminus, and control terminus dynamics as a function of mélange dynamics and strength. Kangerlussuaq Glacier is a major outlet of the Greenland Ice Sheet, for which recent major retreat events in 2004/2005 and 2016-2018 coincided with the absence of an ice mélange in Kangerlussuaq Fjord. To better understand the response of Kangerlussuaq Glacier to climatic and oceanic drivers, a 2D flowline model is employed. Results indicate that an ice mélange buttressing force exerts a major control on calving frequency and rapid retreat: when an ice mélange forms in Kangerlussuaq Fjord, it provides stabilizing forces and conditions favorable for winter terminus re-advance. When it fails to form during consecutive years, modeled retreat of Kangerlussuaq Glacier occurs into the large overdeepenings in Kangerlussuaq Fjord, and to terminus positions more than 30 km farther inland, necessitating to anticipate excessive mass loss from Kangerlussuaq Glacier by the year 2065.

How to cite: Barnett, J., Holmes, F., and Kirchner, N.: Modelled dynamic retreat of Kangerlussuaq Glacier, southeast Greenland, strongly influenced by the consecutive absence of an ice mélange in Kangerlussuaq Fjord, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13179, https://doi.org/10.5194/egusphere-egu22-13179, 2022.

EGU22-13292 | Presentations | CR4.3

Simulating seasonal dynamics of Jakobshavn Isbrae through advancing the Elmer/Ice calving model 

Iain Wheel, Anna Crawford, Joe Todd, Doug Benn, Eef Van Dongen, and Tom Cowton

Jakobshavn Isbrae, the largest outlet glacier in Greenland, accounts for over 20% of the mass loss from the Greenland Ice Sheet. The calving of such large, marine-terminating glaciers is an important yet largely unconstrained contributor to global sea level rise. Understanding the influence of changing environmental conditions on calving at influential glaciers is critical for projections of glacier retreat and sea level rise. This understanding remains poor, in part due to the inability of 3D calving models to robustly simulate calving dynamics and large-scale retreat at fast-flowing glaciers such as Jakobshavn Isbrae. It is important to overcome these modelling challenges, as modelling calving in 3D is necessary to understand the role of geometry and internal glacier dynamics on calving and identify the key environmental forcers at individual glaciers.

We present results from a new calving algorithm implemented in the 3D full-Stokes continuum model Elmer/Ice and applied at Jakobshavn Isbrae, West Greenland. Elmer/Ice fully resolves the glacier velocity and stress fields, whilst recent developments in the calving algorithm allow the modelled glacier to advance and retreat limitlessly along the fjord. A positional crevasse depth calving law is implemented within the calving algorithm, which we use to investigate the dominant processes behind large scale calving and retreat at Jakobshavn Isbrae. Furthermore, we investigate the robustness of the crevasse depth calving law to simulate terminus position. Preliminary results suggest the current incarnation of the crevasse depth law underestimates calving and the crevasse depth required to calve needs to be reduced to accurately simulate terminus change at Jakobshavn Isbrae. Additionally, the inclusion of an ice mélange backstress in winter simulations is key to seasonal terminus advance.

How to cite: Wheel, I., Crawford, A., Todd, J., Benn, D., Van Dongen, E., and Cowton, T.: Simulating seasonal dynamics of Jakobshavn Isbrae through advancing the Elmer/Ice calving model, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13292, https://doi.org/10.5194/egusphere-egu22-13292, 2022.

EGU22-13408 | Presentations | CR4.3

Iceberg meltwater intrusions observed in Sermilik Fjord, Southeast Greenland 

Margaret Lindeman, Fiamma Straneo, Hanumant Singh, Claudia Cenedese, David Sutherland, Kristin Schild, and Dan Duncan

As much as half of the freshwater flux from the Greenland Ice Sheet enters the ocean through calving of icebergs into glacial fjords. Remote sensing studies have shown that substantial iceberg melt occurs within fjords, and models indicate that the resulting heat and freshwater fluxes affect fjord circulation and the properties of waters reaching the glacier terminus. Observations are needed to evaluate whether these models accurately represent the distribution of iceberg melt.

Repeat oceanographic surveys around a large iceberg in Sermilik Fjord show anomalously cold, fresh layers consistent with the expected properties of submarine ice melt. We interpret these features as intrusions of iceberg melt and characterize their properties and vertical distribution. We find that iceberg melt drives significant upwelling, with the vertical scale set by the ambient stratification, as predicted by theory and numerical simulations. Our results agree with recent studies suggesting that the typical melt parameterization likely underestimates melt rates in this setting.

How to cite: Lindeman, M., Straneo, F., Singh, H., Cenedese, C., Sutherland, D., Schild, K., and Duncan, D.: Iceberg meltwater intrusions observed in Sermilik Fjord, Southeast Greenland, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13408, https://doi.org/10.5194/egusphere-egu22-13408, 2022.

EGU22-247 | Presentations | CR4.4

Ice-flow history and observations from the ice base of Jutulstraumen drainage basin (Antarctica) 

Steven Franke, Niklas Neckel, Tamara Annina Gerber, Hannes Eisermann, Jölund Asseng, Daniel Steinhage, Veit Helm, Olaf Eisen, Reinhard Drews, Graeme Eagles, Heinrich Miller, Dorthe Dahl-Jensen, and Daniela Jansen

Future sea-level predictions require that the history of the Antarctic Ice Sheet is well understood and constrained by observations. Much of the ice sheets’  ice-dynamic properties are governed by processes at the ice-bed interface which can be imaged with radar sounding surveys. Here we use a combination of ultra-wideband radio-echo sounding data, satellite radar and laser altimetry data, as well as electromagnetic waveform modeling to characterize the properties of the ice base and the evolution of the subglacial morphology of the Jutulstraumen drainage basin (western Dronning Maud Land, Antarctica). Based on the classification of the bed topography, we reconstruct the step-by-step modifications the subglacial landscape has experienced since the beginning of the glaciation of Antarctica, 34 million years ago. Between 2017 and 2020, we find evidence of active episodic cascade-like subglacial water transport along the subglacial valley network. In addition, our high-resolution radio-echo sounding data reveal a cluster of anomalous basal ice units whose material properties we constrain by electromagnetic waveform modeling. Through this, we aim to derive the physical conditions at the ice base, and establish a link to the subglacial hydrology system. The combination of these observations will represent an important step towards a better understanding of large-scale ice-sheet dynamics in western Dronning Maud Land.

How to cite: Franke, S., Neckel, N., Gerber, T. A., Eisermann, H., Asseng, J., Steinhage, D., Helm, V., Eisen, O., Drews, R., Eagles, G., Miller, H., Dahl-Jensen, D., and Jansen, D.: Ice-flow history and observations from the ice base of Jutulstraumen drainage basin (Antarctica), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-247, https://doi.org/10.5194/egusphere-egu22-247, 2022.

EGU22-424 | Presentations | CR4.4

Modelling Subglacial Hydrology under Future Climate Scenarios in Wilkes Subglacial Basin, Antarctica 

Kevin Siu, Christine Dow, Mathieu Morlighem, Felicity McCormack, and Tim Hill

The Greenland and Antarctic ice sheets have differing climates, which makes surface melt a significant hydrological source in Greenland but not currently in Antarctica. Due to changing climate and warming air temperatures, Antarctica is predicted to experience more surface meltwater in the future. This will likely lead to surface features common in Greenland today, such as supraglacial lakes and moulins, to also form over grounded ice in Antarctica. Moulins in particular are important because they will route this surface melt into basal drainage networks. The resulting change in subglacial drainage characteristics and water volumes will potentially have far-reaching impacts on ice dynamics, ice shelf melt, grounding line stability, and ultimately global sea level rise. To examine this, we model the hydrological system in Wilkes Subglacial Basin, East Antarctica with the future climate in mind by incorporating moulins and surface melt to try to understand the impact that this will have on ice sheet and ice shelf dynamics. We use predictive data generated by the Community Climate System Model 4 (CCSM4) for surface runoff in Antarctica for the year 2100 as inputs to the Glacier Drainage System (GlaDS) subglacial hydrology model. We compare the modelling results from two different Representative Concentration Pathway (RCP) scenarios, RCP 2.6 and RCP 8.5. Moulin locations are predicted using current strain rates along preferential surface hydrology flow pathways and we also compare modelling results with different numbers and locations of moulins. Preliminary results show that even under the lower RCP 2.6 scenario, surface water input significantly alters basal drainage rates, channel extent, and water pressure near the grounding line. The changes are focussed during the modelled summer melt season with the hydrological system settling towards its current state over winter. This demonstrates that the future state of the climate will have an impact on the subglacial hydrology of Antarctica and, in turn, on ice flow speeds and ice shelf melt rates near the grounding line.

How to cite: Siu, K., Dow, C., Morlighem, M., McCormack, F., and Hill, T.: Modelling Subglacial Hydrology under Future Climate Scenarios in Wilkes Subglacial Basin, Antarctica, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-424, https://doi.org/10.5194/egusphere-egu22-424, 2022.

EGU22-512 | Presentations | CR4.4

Oil in glacial till as drivers of ice streaming and surging 

Rebecca McCerery, John Woodward, Glen McHale, Kate Winter, Onoriode Esegbue, and Martin Jones

The driving mechanisms of glacier fast flow and the cyclical instability inherent in ice streams and surging glaciers are not fully understood, with current theories of sliding and basal deformation being insufficient in explaining glacier dynamics. Previous work on soil water repellency and interfacial physics shows that the incorporation of a lubricating oil into a sediment enhances the water repellent and water shedding properties. This can form a Slippery Liquid-Infused Porous Surface (SLIPS), whereby a liquid-liquid interface is created when the sediment is exposed to water resulting in extreme water shedding.

In Alberta, Canada, oil sands material has been detected in surficial sediment and in glacial sediments south of the Alberta Oil Sands deposits. It has been hypothesised that this material was eroded and transported subglacially during the Laurentide Glaciation. Here, sediments from the Central Alberta Ice Stream flow track in the former Laurentide Ice Sheet were analysed and compared to samples of the Alberta Oil Sands from mines and natural exposures using oil-oil correlation by gas chromatography-mass spectrometry. The results show evidence of Alberta Oil Sands throughout the Central Alberta Ice Stream flow track, in particular at the terminating margins to the east of Calgary and in the Cooking Lake area to the southeast of Edmonton. These results indicate glacial erosion and long-distance mobilisation of oil sands deposits from Northern Alberta. Three scenarios of SLIPS at the ice-bed interface caused by the presence of a lubricating oil at the bed can be assumed from these results; (i) an oil-wet macroscale SLIPS, (ii) a water-wet macroscale SLIPS, and (iii) a microscale SLIPS.  These SLIPS mechanisms would influence the degree of ice-bed coupling and therefore the proportion and rates of sliding and basal deformation. By understanding the physics occurring at the ice-bed interface it is possible to better predict glacier flow conditions. It is therefore critical that properties affecting wettability and water shedding of sediments such as the presence of an oil are considered in our understanding of transient flow conditions.

How to cite: McCerery, R., Woodward, J., McHale, G., Winter, K., Esegbue, O., and Jones, M.: Oil in glacial till as drivers of ice streaming and surging, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-512, https://doi.org/10.5194/egusphere-egu22-512, 2022.

EGU22-731 | Presentations | CR4.4

Large interannual variability in supraglacial lakes around East Antarctica 

Jennifer Arthur, Chris Stokes, Stewart Jamieson, Rachel Carr, Amber Leeson, and Vincent verjans

Antarctic supraglacial lakes (SGLs) have been linked to ice shelf collapse and the subsequent acceleration of inland ice flow. These processes are difficult to capture in numerical ice sheet models, but those that include them project higher sea-level contributions from Antarctica. However, observations of SGLs in Antarctica remain relatively scarce and their seasonal variability is largely unknown, making it difficult to assess whether some ice shelves are close to thresholds of stability under climate warming. Here, we quantify the variability in SGL distributions and volumes across the entire East Antarctic Ice Sheet around the peak of seven consecutive melt seasons (2014-2020). We investigate potential climatic controls on SGL development and near-surface (i.e. firn) conditions generated by ERA5 climate reanalysis and the Community Firn Model forced by the regional climate model MARv3.11. Interannual variability in SGL volume is >200% on some ice shelves, but patterns are highly asynchronous. More extensive, deeper SGLs correlate with higher summer (December-January-February) air temperatures, but comparisons with modelled melt and runoff are complex. However, we find that modelled January melt and the ratio of November firn air content to summer melt are important predictors of SGL volume on some potentially vulnerable ice shelves, suggesting large increases in SGLs should be expected under future atmospheric warming. 

How to cite: Arthur, J., Stokes, C., Jamieson, S., Carr, R., Leeson, A., and verjans, V.: Large interannual variability in supraglacial lakes around East Antarctica, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-731, https://doi.org/10.5194/egusphere-egu22-731, 2022.

EGU22-820 | Presentations | CR4.4

Antarctic Ice Shelf Aquifers:Characteristics and Potential Contributions to Ice Shelf Loss 

Ted Scambos, Julie Miller, Riley Culberg, Christopher Shuman, Lynn Montgomery, Clément Miège, Marco Brogioni, and David Long

Water-saturated firn layers, or firn aquifers, have recently been identified from satellite microwave image time-series data in some western Antarctic Peninsula ice shelves. Subsequent field work on the Wilkins Ice Shelf (this work) and Müller Ice Shelf (MacDonell et al., 2021) has proven the existence of these perennial ice shelf firn aquifers. Most of the aquifer areas are maintained by seasonal meltwater recharge. Brine aquifers have been known for many decades in certain slow-moving ice shelves with shorter or absent melt seasons (e.g., McMurdo Ice Shelf). We present both satellite evidence of meltwater firn aquifers in several areas of the Antarctic Peninsula, and radar profile evidence consistent with extensive brine infiltration in the Abbott, Nickerson, and Shackleton Ice Shelves. These latter ice shelves had been previously identified as likely sites of widespread brine infiltration (Cook et al., 2018).

The hydrofracture-driven disintegration of the Wilkins Ice Shelf in February-March of 2008, and subsequent rapid calving events extending into the winter season, justify a closer look at the relative potential for fresh-water aquifers, brine aquifers, and surface melt ponds for inducing hydrofracture in ice shelves. The destructive impact of surface or near-surface meltwater on floating ice is now well-established and is implicated in the loss of the Larsen A and Larsen B ice shelves, and rapid late-stage disintegrations of several tabular icebergs. Brine-aquifer-induced disintegration was suspected for the Wilkins breakup (Scambos et al., 2009), but now appears to be related to the effects of a freshwater system. A question remains regarding the vulnerability of ice shelves with significant brine infiltration in an aquifer.

We will present field measurements from the Wilkins Ice Shelf and discuss the relative hydrofracturing potential of fresh water and brines under various scenarios pertinent to ice shelf stability. The potential for future expansion of fresh-water aquifers under warming coastal conditions, and the characteristics of a hypothetical transitioning from a cold brine aquifer to a fresh-water aquifer will be discussed.

 

Cook, S., Galton-Fenzi, B.K., Ligtenberg, S.R. and Coleman, R., 2018. Brief communication: widespread potential for seawater infiltration on Antarctic ice shelves. The Cryosphere12(12), 3853-3859, doi: 10.5194/tc-12-3853-2018.

MacDonell, S., Fernandoy, F., Villar, P. and Hammann, A., 2021. Stratigraphic analysis of firn cores from an antarctic ice shelf firn aquifer. Water, 13(5), 731, doi:10.3390/w13050731.

Scambos, T., Fricker, H.A., Liu, C.C., Bohlander, J., Fastook, J., Sargent, A., Massom, R. and Wu, A.M., 2009. Ice shelf disintegration by plate bending and hydro-fracture: Satellite observations and model results of the 2008 Wilkins ice shelf break-ups. Earth and Planetary Science Letters, 280(1-4), 51-60, doi:10.1016/j.epsl.2008.12.027.

How to cite: Scambos, T., Miller, J., Culberg, R., Shuman, C., Montgomery, L., Miège, C., Brogioni, M., and Long, D.: Antarctic Ice Shelf Aquifers:Characteristics and Potential Contributions to Ice Shelf Loss, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-820, https://doi.org/10.5194/egusphere-egu22-820, 2022.

EGU22-1236 | Presentations | CR4.4

SUHMO: an AMR SUbglacial Hydrology MOdel 

Anne Felden, Daniel Martin, and Esmond Ng

Water flowing under ice sheets and glaciers can have a strong influence on ice dynamics, particularly through pressure changes, suggesting that a comprehensive ice-sheet model should include the effect of basal hydrology. Modeling subglacial hydrology remains a challenge however, mainly due to the range of spatial and temporal scales involved - from subglacial channels to vast subglacial lakes. Additionally, subglacial drainage networks dynamically evolve over time. To address some of these challenges, we have developed an Adaptive Mesh Refinement (AMR) model based on the Chombo software framework. We extend the model proposed by Sommers and others, (2018) with a few changes to accommodate the transition from unresolved to resolved elements. We handle the strong non-linearities present in the equations by resorting to an efficient non-linear Full Approximation Scheme (FAS-MG) algorithm.  We outline the details of the algorithm and present convergence analysis results demonstrating its effectiveness. Additionally, we present results validating our approach, using test cases from the SHMIP inter-comparison project (2018). We finish by discussing ongoing work related to the coupling of SUHMO with the BISICLES AMR ice-sheet model.

How to cite: Felden, A., Martin, D., and Ng, E.: SUHMO: an AMR SUbglacial Hydrology MOdel, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1236, https://doi.org/10.5194/egusphere-egu22-1236, 2022.

EGU22-1801 | Presentations | CR4.4

Quantifying subglacial soft bed sedimentary processes 

Jane Hart, Kirk Martinez, Nathaniel Baurley, and Benjamin Robson

An understanding of subglacial processes are a vital component of ice-sheet models for sea level rise prediction as the use of different sliding laws can result in very different outcomes. In particular, the West Antarctic ice streams, are potentially unstable, and are underlain by soft (unconsolidated) beds, which have rarely been studied. Innovative in situ wireless subglacial experiments and web connected RTK GPS data from Iceland have shown that stick-slick motion can occur at different time scales throughout the whole year, and this allowed the quantification of different sedimentary processes. We investigate the results from four soft bedded glaciers. We compare the similarities and differences; and in particular describe the relationship with subglacial hydrological processes and temperature rise. We discuss the implications for ice sheet models and reconstructions of Quaternary sedimentary processes.

How to cite: Hart, J., Martinez, K., Baurley, N., and Robson, B.: Quantifying subglacial soft bed sedimentary processes, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1801, https://doi.org/10.5194/egusphere-egu22-1801, 2022.

EGU22-2197 | Presentations | CR4.4

Investigating the influence of increased meltwater runoff on basal sliding in Northeast Greenland. 

Ilaria Tabone, Johannes Fürst, and Thomas Mölg

One of the consequences of rising temperatures observed in Northeast Greenland during the last decades is the increase in surface melting. Meltwater runoff can reach the bed and influence the ice flow regime through changes in basal conditions. Yet, depending on the drainage system, meltwater increase can have opposite effects on basal sliding and there is no consensus yet on the mechanisms that govern this hydrological switch. Here we present some advances in understanding the effects of surface meltwater percolation on ice dynamics at the Northeast Greenland Ice Stream (NEGIS) by investigating surface melt-basal sliding interactions at various temporal scales. To this end, we make use of a fully coupled model approach, comprising the finite-element ice-flow model Elmer/Ice and the hydrological scheme GlaDS. The latter is capable of representing the water drainage at all levels of the ice column. High resolution daily surface mass balance reconstructions available for the years 2014-2018 and simulated by the surface energy balance model COSIPY are used to force the ice-flow model. After first sensitivity tests aiming to explore the parameters of the ice-flow-hydrology system model, a fully coupled simulation for the period 2014-2018 is performed. This advanced modelling framework allows us to tackle the response of the NEGIS ice flow to seasonal and multi-annual variations in surface melt through changes in the drainage system.

How to cite: Tabone, I., Fürst, J., and Mölg, T.: Investigating the influence of increased meltwater runoff on basal sliding in Northeast Greenland., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2197, https://doi.org/10.5194/egusphere-egu22-2197, 2022.

EGU22-2296 | Presentations | CR4.4

Increasing surface runoff from Greenland's firn areas 

Andrew Tedstone and Horst Machguth

Most of the Greenland ice sheet (∼78% to 92%) is underlain by porous snow and firn, into which meltwater can percolate and refreeze, or run off. However, the fate of meltwater in firn areas is poorly constrained. We identified the ice sheet’s annual visible runoff limits by mapping surface hydrological features in >25,000 Landsat satellite scenes. Between 1985–1992 and 2013–2020, the visible runoff limits along the west and north margins rose by 58–329 metres, expanding the visible runoff area by ~29%. Estimates using two different regional climate models suggest that the enlarged area has contributed from 190–264 Gt to 320–491 Gt of runoff since 1985, equivalent to as much as ∼10% of recent annual runoff from the west and north margins. However, the spread highlights that runoff processes in the percolation zone are a source of considerable uncertainty among the major models. We demonstrate that sustained excess melting since the 1990s has provided favourable conditions for anomalous near-surface firn densification. Much of the expanded visible runoff area is underlain by relatively impermeable and persistent ice slabs that have previously been identified by airborne radar campaigns. These slabs have recently enabled sustained runoff from higher elevations even in cooler summers. Our findings highlight that lateral runoff over densified near-surface firn is pervasive in several sectors of the ice sheet and therefore must be incorporated into future runoff projections.

How to cite: Tedstone, A. and Machguth, H.: Increasing surface runoff from Greenland's firn areas, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2296, https://doi.org/10.5194/egusphere-egu22-2296, 2022.

EGU22-2467 | Presentations | CR4.4

Subglacial topography and landscape evolution from radio-echo sounding data in the Evans-Rutford Region, southern Antarctic Peninsula. 

Charlotte Carter, Michael Bentley, Stewart Jamieson, Neil Ross, Tom Jordan, and Julien Bodart

Understanding the subglacial bed topography of the Antarctic ice sheet is important for the boundary conditions of ice sheet modelling and the assessment of basal hydrological conditions. Moreover, inferring landscape evolution from the geomorphology can also provide insight into ice sheet inception and history. We utilise radio-echo sounding data from the BAS GRADES-IMAGE and TORUS radar surveys to geomorphologically interpret the bed topography in the Evans-Rutford Region of Antarctica, between the Ellsworth mountains and the southern Antarctic Peninsula. The GRADES-IMAGE survey is a legacy radar survey that has not yet been examined in detail in terms of subglacial bed topography and consists of 11,500 line kilometres of data along 22 lines. We have updated the subglacial bed picks to develop a new Digital Elevation Model of the region. Here we report preliminary results of the mapped subglacial landscape, with potential interpretations of the topographic patterns and landscape evolution. Geomorphological observations of the key features include identification of flat plateau surfaces at similar elevations, sitting between deep incised glacial troughs, some of which have potential tectonic controls.

How to cite: Carter, C., Bentley, M., Jamieson, S., Ross, N., Jordan, T., and Bodart, J.: Subglacial topography and landscape evolution from radio-echo sounding data in the Evans-Rutford Region, southern Antarctic Peninsula., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2467, https://doi.org/10.5194/egusphere-egu22-2467, 2022.

EGU22-2884 | Presentations | CR4.4 | Highlight

Monthly Antarctic-wide surface meltwater evolution between 2006 and 2021, and its links to climate 

Peter Tuckett, Jeremy Ely, Andrew Sole, Stephen Livingstone, James Lea, and Julie Jones

Understanding the distribution and evolution of surface meltwater on the Antarctic Ice Sheets is vital in enabling us to predict how the ice sheet will respond to a warming climate. The majority of Antarctic surface meltwater studies have typically been limited by either spatial or temporal scale. We have overcome these limitations by using a fully automated method to map surface meltwater across the entire Antarctic continent between 2006 and 2021 at a monthly temporal resolution. Furthermore, by accounting for variability in both cloud cover and satellite image coverage, we have generated the first consistent and continuous multi-year time series of Antarctic-wide surface meltwater to date. Here, we present results from analysis of this dataset, including long-term trends in surface meltwater extent, comparison between surface meltwater area and modelled melt, and associations between surface meltwater area and climatic factors. Regression analysis shows strong correlations between surface meltwater area and modelled snowmelt around the ice sheet margin, increasing our confidence in regional climate models to predict future melt conditions. Synoptic scale climate regimes, such as the Southern Annular Mode, exert a strong controlling factor on surface meltwater area totals on an annual basis. However, regional climatic processes and melt-albedo feedbacks can have strong second-order influences on localised melt rates, resulting in high variability in meltwater coverage, especially in parts of East Antarctica. This multi-year dataset offers the opportunity to explore surface meltwater evolution at local, catchment and continental scales, and will be of widespread use in understanding the operation of surface hydrological systems.

How to cite: Tuckett, P., Ely, J., Sole, A., Livingstone, S., Lea, J., and Jones, J.: Monthly Antarctic-wide surface meltwater evolution between 2006 and 2021, and its links to climate, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2884, https://doi.org/10.5194/egusphere-egu22-2884, 2022.

EGU22-3004 | Presentations | CR4.4 | Highlight

Shallow Fracture Buffers High Elevation Runoff in Northwest Greenland 

Riley Culberg, Winnie Chu, and Dustin Schroeder

The growth of shallow, low-permeability ice slabs in Greenland’s firn is known to increase surface meltwater runoff by hindering vertical percolation. However, the partitioning of meltwater between local impoundment, downslope runoff, and drainage to the ice sheet bed is still poorly constrained. Northwest Greenland is a particularly interesting study area for understanding the role of englacial hydrology because ice-penetrating radar surveys have identified coexisting ice slabs and firn aquifers in this region. These results suggest that ice slabs may not necessarily preclude local firn water storage. However, the mechanism that would allow these two distinct facies to develop together is unclear.

               To examine the relationship between firn aquifers and ice slabs in Northwest Greenland, we analyzed six-years of NASA Operation IceBridge radar data between 2011 and 2017. These observations show that isolated, short-lived water pockets frequently develop beneath the ice slabs and over time refreeze to form kilometer-scale ellipsoidal buried ice masses. These ice blobs covered ~14% of the 1176 radar line-kms flown in 2017 and analysis of Landsat imagery between 2000 and 2016 shows they are spatially correlated with visible runoff in supraglacial lakes, streams, or massive slush swamps. High-resolution optical satellite imagery also shows that surface crevassing is widespread in this region and that many of the ice blobs are associated with moulins or lake drainage events in the 2012 melt season. This suggests that ice blobs form where fractures create high permeability pathways through the ice slab through which surface meltwater can drain into the relict firn. In the short term, this process impounds water and heat in the upper 30 meters of the ice column, reducing surface runoff and limiting the immediate impact of surface melt on local ice dynamics. However, on longer timescales, this efficient filling of pore space beneath supraglacial flow paths may lead to more efficient surface hydrology and full ice thickness hydrofracture at high elevations. 

How to cite: Culberg, R., Chu, W., and Schroeder, D.: Shallow Fracture Buffers High Elevation Runoff in Northwest Greenland, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3004, https://doi.org/10.5194/egusphere-egu22-3004, 2022.

EGU22-3047 | Presentations | CR4.4

Satellite detection of firn aquifers in the Antarctic Peninsula 

Lena Buth, Sanne Veldhuijsen, Bert Wouters, Stef Lhermitte, and Michiel van den Broeke

In recent years, the existence of firn aquifers in the Antarctic Peninsula (AP) has been confirmed by in situ observations. Due to their importance for understanding the hydrology of the Antarctic ice sheet, a more spatially comprehensive assessment of AP firn aquifers is desirable. The purpose of this study is to map firn aquifers in the AP from space using C-band Synthetic Aperture Radar imagery from ESA's Sentinel-1 mission. This product enables the detection of firn aquifers at 1 km2 resolution for the period 2017 to 2020. The method is based on quantifying the characteristic shape of the backscatter curve over time during the (partial) refreezing of the liquid water in the firn layer after each peak melt season. In this context, both seasonal aquifers and perennial aquifers are detected together, acknowledging that their backscatter signature in any given year is indistinguishable with the given method. With the new method, seasonal firn aquifers are being detected in the north and northwest of the AP, as well as on the Wilkins Ice Shelf and the George VI Ice Shelf. Imposing the aquifers to occur during all available years, as a proxy for perennial firn aquifers, limits their extent to the north and northwest AP. Both distributions agree well with model simulations. Further in situ and modelling studies and longer time series of satellite observations are needed to validate the results of this study.

How to cite: Buth, L., Veldhuijsen, S., Wouters, B., Lhermitte, S., and van den Broeke, M.: Satellite detection of firn aquifers in the Antarctic Peninsula, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3047, https://doi.org/10.5194/egusphere-egu22-3047, 2022.

EGU22-3182 | Presentations | CR4.4

Terrestrial biomarkers in sediments from the continental slope of Nordaustlandet, Svalbard reveal unprecedented subglacial meltwater drainage during the Last Termination 

Alessio Nogarotto, Riko Noormets, Teena Chauhan, Florence Colleoni, Gesine Mollenhauer, Francesco Muschitiello, Lucilla Capotondi, Claudio Pellegrini, Simon Belt, and Tommaso Tesi

The subglacial environment and its characteristics are of primary importance for the behaviour and the stability of ice sheets; however, the mechanisms that take place beneath ice sheets still need to be accurately quantified. Here we present the results of a multi-proxy, biogeochemical analysis carried out on a marine sediment core (HH11-09GC) from the northern Svalbard continental slope, encompassing the last 30 ka. During Termination I, our results suggest a persistent polynya-like environment with significant input of terrigenous organic matter. Indeed, the amount of land-derived material during this period is comparable to that found in the immediate proximity of the major Siberian river mouths during modern times. Alkenone fingerprint suggests that the origin of the terrigenous material could be related to an as yet unidentified freshwater body located in the White Sea/Pechora Basin region, at the margin of the Svalbard Barents Sea Ice Sheet; therefore, the environmental conditions at the base of the ice sheet were suitable for the existence of a large subglacial water drainage. According to our data, this drainage network was able to carry huge amounts of water and sediments beneath the ice sheet and, subsequently, discharge them thousands of kilometres away from their origin. This could represent the first evidence of a pervasive, highly connected subglacial drainage network in the Barents Sea region. Our results may shed new insights on the magnitude of subglacial drainage systems, and thus have important implications with regards to ice sheet modelling.

How to cite: Nogarotto, A., Noormets, R., Chauhan, T., Colleoni, F., Mollenhauer, G., Muschitiello, F., Capotondi, L., Pellegrini, C., Belt, S., and Tesi, T.: Terrestrial biomarkers in sediments from the continental slope of Nordaustlandet, Svalbard reveal unprecedented subglacial meltwater drainage during the Last Termination, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3182, https://doi.org/10.5194/egusphere-egu22-3182, 2022.

EGU22-3812 | Presentations | CR4.4

Spatial patterns in seasonal coupling between ice sheet hydrology and motion in west Greenland 

Andrew Sole, Benjamin Davison, and Stephen Livingstone

Ice motion within the land-terminating ablation zone of west Greenland typically follows a seasonal pattern with fastest flow in the spring as surface meltwater first accesses the hydraulically inefficient subglacial drainage system, followed by a gradual reduction in ice motion over the summer as efficient subglacial channels evacuate water stored over wide swathes of the subglacial environment. Minimum speeds occur in autumn, when surface meltwater delivery to the bed ceases, then, over winter, ice flow gradually recovers before the cycle repeats once again. This understanding is principally derived from high temporal resolution field observations with limited spatial coverage. It is now, however, possible to measure these seasonal patterns in detail over large spatial scales, enabling basin-scale comparisons between meltwater supply, subglacial hydrology and ice motion.

We present near continuous time-series of ice motion for a ~60,000 km2 portion of predominantly the land-terminating western margin of the Greenland Ice Sheet (with coverage extending up to 150 km from the margin in winter and 25 km in summer) between 2016 and 2022 at up to 12-day temporal resolution derived from Sentinel-1, Sentinel-2 and Landsat 8 imagery. We compare ice motion with surface melt magnitude and timing (derived from meteorological observations and a positive degree day model), theoretical subglacial water routing, and glaciological context (e.g. ice thickness).

Our results reveal clear spatial patterns in seasonal coupling between ice sheet hydrology and motion. Overall, the amplitude of the seasonal cycle of ice motion is generally greater closer to the ice margin as has been shown previously by field observations. There is, however, distinct variability between subglacial hydraulic catchments. Subglacial catchments whose principal drainage pathway has a high hydraulic potential gradient typically experience smaller peaks in summer ice motion, but more prominent autumn ice flow minima. Subglacial water flow in such catchments has more potential to create hydraulically efficient channels, which can both accommodate spikes in meltwater delivery with muted ice flow acceleration, and also reduce basal water pressure across a wider area of the ice bed as surface meltwater delivery declines.

As ice sheet surface mass balance becomes more negative and marginal ice thins fastest (where the ice is land-terminating), subglacial hydraulic gradients and subglacial discharge will both increase. Based on our findings, these changes may lead to smaller summer ice flow accelerations and bigger winter slow-downs, driving an overall decrease in mean annual ice motion. Our results also highlight the importance of careful selection of field sites for measuring ice motion and caution against scaling up from spatially limited observations.

How to cite: Sole, A., Davison, B., and Livingstone, S.: Spatial patterns in seasonal coupling between ice sheet hydrology and motion in west Greenland, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3812, https://doi.org/10.5194/egusphere-egu22-3812, 2022.

EGU22-3854 | Presentations | CR4.4

Subglacial export of coarse sediment from temperate Alpine glaciers by meltwater 

Matthew Jenkin, Davide Mancini, Floreana Miesen, Margaux Hofmann, Bryn Hubbard, Frédéric Herman, and Stuart N. Lane

Proglacial measurements of subglacial sediment export by meltwater are commonly used to estimate glacial erosion rates. Such estimates generally assume that subglacial meltwater flow is the dominant agent driving export and that eroded sediment is rapidly conveyed through subglacial drainage networks to the glacier outlet in efficient channels with large and generally-unsatisfied transport capacities. However, understanding of sediment transport processes under glaciers is limited, especially in the thin, snout-marginal zones of retreating temperate Alpine glaciers.

A growing body of field and model-based research from such systems challenges the theory that eroded sediment is rapidly evacuated. Conversely, Alpine glaciers develop intense diurnal and seasonal discharge variation leading to highly variable sediment transport competence and the moderation of sediment export by associated cycles of alluviation. This has important consequences for the timescales over which sediment export can be used as a reliable proxy for glacial erosion, though the problem remains that very little is known about when and under what conditions a glacier margin is capable of evacuating the sediment supplied to it.

This study attempts to elucidate sediment transport mechanisms and timescales in the main snout-marginal subglacial channel of glacier d’Otemma, Switzerland, by tracking 324 cobble-sized particles tagged with 433 MHz active radio transponders over the mid-to-late 2021 melt season. Tagged particles were injected into the channel via a 48 m deep borehole and were then tracked over a 350 m subglacial reach and a 150 m proglacial reach with a mobile antenna and stationary antenna arrays.

Only 86 particles (27%) were exported in 2021. Preliminary analyses indicate that cobble-sized particles generally have extended residence times in snout marginal zones (weeks to months), with no clear effect of particle size, shape or density on overall transport velocities. Ongoing work involves the daily localisation of particles using a signal strength-based algorithm, providing a unique record of the down-glacier transport of coarse particles in a subglacial channel. Repeat measurements will follow in 2022.

How to cite: Jenkin, M., Mancini, D., Miesen, F., Hofmann, M., Hubbard, B., Herman, F., and Lane, S. N.: Subglacial export of coarse sediment from temperate Alpine glaciers by meltwater, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3854, https://doi.org/10.5194/egusphere-egu22-3854, 2022.

Earth Observation (EO) provides a wealth of data for the monitoring of the Antarctic continent. In this context, data of the Sentinel-1 Synthetic Aperture Radar (SAR) and optical Sentinel-2 satellite missions of the European Copernicus programme deliver valuable information on key ice sheet parameters including the location of the calving front and grounding line, the ice velocity and elevation as well as the Antarctic surface hydrological network. The monitoring of the latter is crucial for an improved understanding of processes such as hydrofracture triggering ice shelf collapse and ultimately ice flow accelerations and increased ice discharge. To establish a monitoring service for supraglacial lake extent delineation in Sentinel-1 SAR and optical Sentinel-2 imagery, a fully automated processing chain based on machine learning and deep learning was developed and integrated within the internal processing infrastructure of the German Aerospace Center (DLR).

Here, we present first results of the implemented machine learning processing pipeline over six major Antarctic ice shelves. In particular, the full archive of Sentinel-1 and Sentinel-2 was exploited to provide bi-weekly supraglacial lake extent mappings during 2015-2021 at unprecedented 10 m spatial resolution. The results over Antarctic Peninsula ice shelves reveal comparatively low lake coverage in 2015-2018 and high lake coverage during summers 2019-2020 and 2020-2021. Over East Antarctic ice shelves, supraglacial lake extents fluctuated more substantially with comparatively high lake coverage during most of 2016-2019 and low lake coverage throughout melting season 2020-2021. Further, the data reveal a coupling between supraglacial lake formation and the near-surface climate, the local glaciological setting and large-scale atmospheric modes.

The final data products on Antarctic supraglacial lake extent dynamics during 2015-2021 are available via the GeoService of the Earth Observation Center (EOC) at DLR. To establish a near-real-time monitoring service on supraglacial lake dynamics in the future, the full processing pipeline is currently refined and data products will be made readily available for download via the EOC GeoService. In this context, we are building upon the expertise of the Polar Monitor project and IceLines, a processor for automated calving front extraction over the Antarctic coastline.

How to cite: Dirscherl, M., Dietz, A., and Kuenzer, C.: Artificial intelligence for the monitoring of Antarctic supraglacial lake dynamics in 2015-2021 using Sentinel-1 SAR and optical Sentinel-2 data, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4526, https://doi.org/10.5194/egusphere-egu22-4526, 2022.

The Totten Glacier is the main conduit for ice leaving the Aurora Subglacial Basin in East Antarctica. During December 2018 and January 2019, we deployed a 12 station broadband seismic array near the grounding zone of the Totten Glacier. Here we report on subglacial sedimentary structure and seismic activity recorded by this network. Previous gravity studies indicated the possibility that erosion had removed most of the subglacial sediments in the region. We use the receiver function analysis to reveal that 100-200 meters of subglacial sediment remain near the grounding zone. We also will summarize a range of glacier generated seismic activity recorded by the array. We find significant occurrence of tidally modulated near surface crevasse related events as well as basal stick-slip seismic activity. We will provide an overview into both the temporal and spatial variability of seismic activity and discuss implications for fast flow in the region.

How to cite: Winberry, P.: Seismic activity and subglacial sedimentary structure near the grounding zone of the Totten Glacier, East Antarctica, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4867, https://doi.org/10.5194/egusphere-egu22-4867, 2022.

EGU22-4909 | Presentations | CR4.4

Assessing firn water storage from a multi-data firn-model inversion 

Sebastian B. Simonsen, Nicolaj Hansen, Inès Otosaka, Baptiste Vandecrux, and Louise Sandberg Sørensen

The ESA 4DGreenland project has the objective of performing an integrated assessment of Greenland’s hydrology through maximizing the use of Earth observation (EO) data. However, as meltwater is activated on the surface of the Greenland ice sheet and percolates into the firn, the firn water storage and delayed runoff are unobservable from EO, and we must resort to modeling to quantify this component. 

The DTU-firn model has previously been used to quantify the change in firn air volume as a leading component of altimetric mass balance estimates and was initially tuned using firn core density observations. Here, we revisit the fundamentals of the model and perform model inversion using as many observational datasets as possible. This observational data ranges from direct measurements of firn compaction derived from “coffee-can” experiments, over traditional observation of densities and temperature from firn cores to regional observation of firn stratigraphy from airborne radar surveys. This large diversity in the data sources ensures the best possible constraints for capturing as many aspects as possible of the firn dynamics.  

One important model feature of the DTU-firn model is its ability to resolve individual precipitation events as model layers. This feature promotes the capability of retaining water and shows promising results in line with the in-situ observation. The updated DTU-firn model is therefore used within the 4DGreenland project to provide updated estimates of meltwater retention and delayed runoff as a function of the available water at the surface of the firn. Combined with results obtained by the HIRHAM- and MAR-firn models, it also enables better quantification of firn model uncertainties. Having built confidence in the model we can treat the retention and delayed runoff as a function of the available water at the surface of the firn. This then gives the possibility of using the observed surface melt, also acquired within 4DGreenland from satellite microwave data, in the assessments of Greenland’s hydrology and thereby increasing the useability of EO data.

How to cite: Simonsen, S. B., Hansen, N., Otosaka, I., Vandecrux, B., and Sandberg Sørensen, L.: Assessing firn water storage from a multi-data firn-model inversion, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4909, https://doi.org/10.5194/egusphere-egu22-4909, 2022.

EGU22-4926 | Presentations | CR4.4

Is longer or warmer melt season a more important driver of ice dynamics. 

Basile de Fleurian, Richard Davy, and Petra M. Langebroek

In recent years, temperatures over the Greenland ice sheet have been rising, leading to an increase in surface melt. This increase however can not be reduced to a simple number. Throughout the recent years we have seen some extreme melt seasons with melt extending over the whole surface of the ice sheet (2012) or melt seasons of lower amplitudes but with a longer duration (2010). The effect of those variations on the subglacial system and hence on ice dynamic are poorly understood and are still mainly deduced from studies based on mountain glaciers.

Here we apply the Ice-sheet and Sea-level System Model (ISSM) to a synthetic glacier with a geometry similar to a Greenland ice sheet land terminating glacier. The forcing is designed such that it allows to investigate different characteristics of the melt season such as its length or intensity. Subglacial hydrology and ice dynamics are coupled within ISSM allowing to study the response of the system in terms of subglacial water pressure and the final impact on ice dynamics. Of particular interest is the evolution of the distribution of the efficient and inefficient component of the subglacial drainage system which directly impacts the water pressure evolution at the base of the glacier. We note that the initiation of the melt season and the intensity of the melt at this period is a crucial parameter when studying the dynamic response of the glacier to different melt season characteristics.

From those results, we can infer a more precise evolution of the dynamics of land terminating glaciers that are heavily driven by their subglacial drainage system. We also highlight which changes in the melt season pattern would be the most damageable for glacier stability in the future.

How to cite: de Fleurian, B., Davy, R., and Langebroek, P. M.: Is longer or warmer melt season a more important driver of ice dynamics., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4926, https://doi.org/10.5194/egusphere-egu22-4926, 2022.

EGU22-5140 | Presentations | CR4.4

Basal hydrofractures near sticky patches 

Hanwen Zhang, Timothy Davis, Richard Katz, Laura Stevens, and Dave May

Basal crevasses are macroscopic structural discontinuities at the base of ice sheets and glaciers. Sticky patches (also referred to as sticky spots) are regions of high basal shear stress caused by low subglacial water pressure or topographic high of the bedrock. Motivated by observations, we hypothesise that in the presence of basal water pressure, spatial variations in basal shear stress on the sticky patches can promote and localise basal crevassing. In the theoretical context of linear elastic fracture mechanics, we develop a model evaluating the effect of shear stress variation on the growth of basal crevasses, finding that the existence of sticky patches can promote mixed-mode basal crevassing on the downstream end. By simulating the quasi-static growth of such mixed-mode basal crevasses, we find that such crevasses tend to incline upstream and propagate along a specific path, which can be approximated by the principal stress trajectories in the uncracked ice. A detailed exploration on the dimensionless parameter space indicates that the crevassing is controlled by three parameters—the flotation fraction, the relative magnitude of excess shear stress, and the relative size of the sticky patch. Inspired by the crevassing in the elastic model, we also explore the propagation of basal crevasses using the viscoelastic rheology.

How to cite: Zhang, H., Davis, T., Katz, R., Stevens, L., and May, D.: Basal hydrofractures near sticky patches, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5140, https://doi.org/10.5194/egusphere-egu22-5140, 2022.

EGU22-5463 | Presentations | CR4.4

Earth Observation for Surface Melt Monitoring over Antarctic Ice Shelves: Opportunities and Challenges 

Sophie de Roda Husman, Zhongyang Hu, Stef Lhermitte, Bert Wouters, and Peter Kuipers Munneke

Surface meltwater is becoming an increasing driver for ice shelf disintegration and consequent mass loss from the AIS. In this regard, monitoring surface melt over Antarctic ice shelves can enhance our understanding of their stability. Earth Observation (EO) satellites provide decadal records of land dynamics over Antarctica, and have been applied in surface melt monitoring. Thereby, they hold a potential to monitor the spatiotemporal evolution of surface melt over the entire AIS. Among the wealth of EO satellites, scatterometer and radiometer observations are most frequently used for surface melt detection, followed by SAR and optical data. Most studies used observations from a single satellite to study surface melt, while specific sensor characteristics (e.g., spatial resolution, overpass time, penetration depth) largely influence the potential for detecting surface melt. Therefore, we compare differences in melt detection between radiometer, scatterometer, SAR and optical sensors to assess the opportunities and challenges in observing surface melt for different EO satellites. We apply state-of-the-art melt detection algorithms to radiometer (Special Sensor Microwave Imager/Sounder, SMMIS), scatterometer (Advanced Scatterometer, ASCAT), Synthetic Aperture Radar (SAR; Sentinel-1), and optical (Moderate Resolution Imaging Spectroradiometer, MODIS) data over the Larsen B+C and Amery Ice Shelves for the 2015-2020 melt seasons. We construct melt timeseries and spatial maps using the melt detection algorithms. and intercompare the spatiotemporal patterns of detected melt. Finally, we compare areas with different melt patterns with auxiliary data sets (i.e., Regional Atmospheric Climate Model (RACMO2), Digital Elevation Models (DEM), high resolution optical imagery). Our results show that the largest differences in detected melt between the EO satellites can be linked to physical properties of the surface, sensor properties and atmospheric conditions. Over the blue ice areas, MODIS indicates more surface melt than the other sensors, as they miss blue ice areas due to either a coarse spatial resolution or the applied detection algorithms. However, over the ice shelves, MODIS detects significantly less surface melt, which can be attributed to the very high cloud obstruction frequency over AIS. Based on this intercomparison, we discuss the opportunities and challenges for melt detection across the AIS regarding the choice of different sensors and the chosen melt detection algorithms. We conclude that merging observations from different satellites (e.g. using machine learning) would further strengthen our knowledge on the presence of surface melt across the AIS, since this combines the strengths of specific sensors based on their sensor characteristics and the area of interest.

How to cite: de Roda Husman, S., Hu, Z., Lhermitte, S., Wouters, B., and Kuipers Munneke, P.: Earth Observation for Surface Melt Monitoring over Antarctic Ice Shelves: Opportunities and Challenges, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5463, https://doi.org/10.5194/egusphere-egu22-5463, 2022.

EGU22-7222 | Presentations | CR4.4

Improved monitoring of subglacial lake activity in Greenland 

Rasmus Bahbah Nielsen, Louise Sandberg Sørensen, Sebastian Bjerregaard Simonsen, Natalia Havelund Andersen, Anne Munck Solgaard, Nanna Bjørnholt Karlsson, Jade Bowling, Amber Leeson, Jenny Maddalena, Malcolm McMillan, Noel Gourmelen, Alex Horton, and Birgit Wessel

Subglacial lakes may form beneath ice sheets and ice caps, given the availability of water and appropriate bedrock and surface topography to capture the water. On a regional scale, these lakes can modulate the freshwater output to the ocean by acting as reservoirs that may periodically drain and recharge. Several such active subglacial lakes have been documented under the Antarctic ice sheet, while only a few are observed under the Greenland ice sheet. The small size of the hydrologically active subglacial lakes in Greenland compared to those in Antarctica, puts additional demands on our mapping capabilities to resolve in great detail the evolving surface topography over these lakes to document their temporal behavior. Here, we explore the potential of combining CryoSat-2 swath data and high resolution DEMs generated from TanDEM-X scenes and ArcticDEM strips to improve our knowledge of the evolution of four active subglacial lake sites previously documented in the literature. We find that the DEM data complement each other well in terms of time and resolution and thus provide new information about the subglacial lake activity, though the small size of the collapse basins is challenging for CS2, and we are only able to derive useful CS2 data for the two largest of the four investigated lakes. Based on these data sets we can e.g. conclude that the collapse basin at Flade Isblink was actually as deep as 95 m when it formed, which is 30 m deeper than previously documented.  We also present evidence of a new active subglacial lake in Southwest Greenland.

How to cite: Bahbah Nielsen, R., Sandberg Sørensen, L., Bjerregaard Simonsen, S., Havelund Andersen, N., Munck Solgaard, A., Bjørnholt Karlsson, N., Bowling, J., Leeson, A., Maddalena, J., McMillan, M., Gourmelen, N., Horton, A., and Wessel, B.: Improved monitoring of subglacial lake activity in Greenland, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7222, https://doi.org/10.5194/egusphere-egu22-7222, 2022.

EGU22-7234 | Presentations | CR4.4

CUAS-MPI - A parallelised version of the confined-unconfined aquifer system model applied to the Greenland Ice Sheet 

Thomas Kleiner, Yannic Fischler, Raban Emunds, Lennart Oestreich, Christian Bischof, Jeremie Schmiedel, Roiy Sayag, and Angelika Humbert

Simulating the hydrological systems underneath ice sheets and glaciers is important for estimating the freshwater flux into the ocean as well as inferring the characteristics of the hydrological system and its impact on ice sheet dynamics. In particular, simulations of the subglacial hydrological system in high temporal and spatial resolution and coupled to ice sheet models are needed to investigate the formation of ice streams. In order to be able to run simulations efficiently, both codes need to be parallelised. To this end, we present our approach for a parallelised version of the confined-unconfined aquifer system (CUAS) model (Beyer et al., 2018) that was established as a python code. CUAS is simulating an effective porous medium layer, in which the transmissivity indicates if the flow is channelised. Transmissivity is evolving by melt, creep and cavity opening. A fully implicit finite difference scheme is used for the hydraulic head while an explicit Euler time step is used for the transmissivity. 

The new CUAS-MPI version is written in C++ and instrumented for performance measurements. The parallelisation is done with MPI, where we take advantage of PETSc data structures and linear equation system solvers. The code has been designed to be coupled to the Ice Sheet and Sea-level system Model (ISSM) using preCICE (precice.org). 

Pumping tests that are widely used in applied groundwater hydrology are performed to test the model implementation including the boundary conditions and to compare with the analytical solutions. We further present test applications to the Greenland Ice Sheet, with the major focus on performance, rather than on characteristics of the hydrological system.

How to cite: Kleiner, T., Fischler, Y., Emunds, R., Oestreich, L., Bischof, C., Schmiedel, J., Sayag, R., and Humbert, A.: CUAS-MPI - A parallelised version of the confined-unconfined aquifer system model applied to the Greenland Ice Sheet, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7234, https://doi.org/10.5194/egusphere-egu22-7234, 2022.

EGU22-7594 | Presentations | CR4.4

What can high resolution ice surface observations tell us about the bed topography of Pine Island Glacier, West Antarctica? 

Helen Ockenden, Rob Bingham, Andrew Curtis, Daniel Goldberg, and Antonios Giannopoulos

The West Antarctic Ice Sheet has the potential to contribute up to 3m of sea level rise over the next few centuries. There is considerable uncertainty over the rate at which ice loss will occur, caused in part by a lack of knowledge about the bed topography beneath the ice sheet, which influences ice flow and retreat. Since direct bed topography observations are often further apart than ice sheet models require, we explore instead what we can learn about bed topography from high resolution observations of the ice surface, which are openly available. We apply an inversion methodology based on linear perturbation theory and developed by Gudmundsson (2003, 2008) to ice surface data from Pine Island Glacier, and present the bed topography results. Comparison to high-resolution radar sounding of the bed topography of Pine Island Glacier from the iSTAR 2013-14 ground surveys allows us to assess the success of the inversion methodology. We identify regions of the glacier where the landforms we see are likely to be artefacts, and regions where unknown and interesting landforms are likely to exist. This methodology has the potential to be extremely useful in regions where direct observations of bed topography are sparse, and for identifying areas where more observations would be of particularly high benefit.   

How to cite: Ockenden, H., Bingham, R., Curtis, A., Goldberg, D., and Giannopoulos, A.: What can high resolution ice surface observations tell us about the bed topography of Pine Island Glacier, West Antarctica?, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7594, https://doi.org/10.5194/egusphere-egu22-7594, 2022.

EGU22-7675 | Presentations | CR4.4

A comparison of supraglacial lake characteristics and drainage dynamics in Southwest Greenland between an extreme high, and an extreme low, melt season 

Emily Glen, Alison Banwell, Jennifer Maddalena, Amber Leeson, Diarmuid Corr, and Mal McMillan

Mass loss from the Greenland Ice Sheet (GrIS) is predicted to contribute up to 10 cm to global sea level rise by 2100. This mass loss is due to both increased meltwater production and therefore increased runoff, which is occurring at higher elevations on the ice sheet, as well as ice-dynamical feedback processes such as supraglacial lakes (SGLs) draining rapidly to the ice sheet bed; enhancing basal sliding. Therefore, the specific processes through which SGLs drain has an important control on mass loss from the GrIS. This highlights the need for high-resolution, integrated datasets that provide a comprehensive view of supraglacial hydrological networks, including SGL drainage events, on the GrIS.

Here, we compare SGL characteristics and drainage dynamics of a southwestern sector of the GrIS throughout both an extreme high melt season (2019) and an extreme low melt season (2018). SGLs are delineated throughout both the summer seasons from Sentinel-2 and Landsat 8 optical imagery using threshold-based normalized difference water index (NDWI) methods followed by extensive manual enhancement to increase accuracy. SGL depths are calculated using a radiative transfer model and individual lake volume is determined. The resulting meltwater maps have a spatial resolution of 10 to 30 m and have a temporal resolution of weekly to fortnightly. The following SGL characteristics are determined: i) area; ii) volume; iii) elevation; iv) ice surface slope; and v) solidity. SGL drainage dynamics are analysed by tracking lakes through the duration of each melt season and determining if a lake drains rapidly by hydrofracture, slowly drains via channel incision and overflow, or does not drain and instead refreezes at the end of the melt season. To do this, we use the Fully Automated supraglacial lake area and volume tracking at enhanced resolution (FASTER) algorithm, developed by Williamson et al. (2018).

As temperatures continue to increase, the frequency of high melt years like 2019 will also increase. As such, it ever more important to understand supraglacial meltwater characteristics and dynamics in high melt seasons, especially compared to years with limited melt.

How to cite: Glen, E., Banwell, A., Maddalena, J., Leeson, A., Corr, D., and McMillan, M.: A comparison of supraglacial lake characteristics and drainage dynamics in Southwest Greenland between an extreme high, and an extreme low, melt season, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7675, https://doi.org/10.5194/egusphere-egu22-7675, 2022.

EGU22-8007 | Presentations | CR4.4

Simulated formation of grounding-zone wedges and implications for ice-sheet stability 

Anders Damsgaard, Jenny Suckale, and Jan Piotrowski

Glacier flow has the potential to mobilize subglacial till, resulting in till deposition and subglacial landforms in glaciated areas. The subglacial till transport occurs when sedimentary beds are thawed and sufficiently weak relative to the glacial driving stress. As a consequence of till mobilization, soft-bedded and marine-terminating ice sheets are known to produce grounding-zone wedges. It has been hypothesized that these wedges may stabilize grounded ice in spite of rising sea level.

In order to test this hypothesis, we develop a fully coupled framework for simulating ice flow, glacier hydrology, and till advection. Ice flow and hydrology is handled with PISM, the three-dimensional, thermomechanical, parallel ice sheet model (Bueler and Brown, 2009; Winkelmann et al 2011). Till advection is computed with the cohesive non-granular fluidity method with pore-water pressure, which is consistent with Coulomb-frictional mechanics and stress-dependent shear-zone thickness (Damsgaard et al., 2020). We apply the model to various bed geometries and forcing scenarios, and show how subglacial landforms evolve and grounding-zone wedges form. The grounding-zone wedges prove to contribute conditional stabilization to the ice sheet, and this mechanism could limit the marine-ice sheet instabilities that may occur on reverse sloping beds.

 

References:

Bueler, E. and Brown, J. 2009 “Shallow shelf approximation as a “sliding law” in a”. J. Geophys. Res. Earth Surf. 114(F3)

Damsgaard, A., L. Goren and J. Suckale 2020 “Water pressure fluctuations control variability in sediment flux and slip dynamics beneath glaciers and ice streams”. Commun. Earth Environ. 1(66), 1–8. doi: 10.1038/s43247-020-00074-7

Winkelmann, R., M. A. Martin, M. Haseloff, T. Albrecht, E. Bueler, C. Khroulev and A. Levermann 2011 “The Potsdam Parallel Ice Sheet Model (PISM-PIK) - Part 1: Model description”. 5(3), 715–726. doi: 10.5194/tc-5-715-2011

How to cite: Damsgaard, A., Suckale, J., and Piotrowski, J.: Simulated formation of grounding-zone wedges and implications for ice-sheet stability, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8007, https://doi.org/10.5194/egusphere-egu22-8007, 2022.

EGU22-8644 | Presentations | CR4.4

Using artificial moulins to characterise englacial R-channels 

Annegret Pohle, Mauro A. Werder, Dominik Gräff, and Daniel Farinotti

The englacial and subglacial drainage system exerts key controls on glacier dynamics.  However, due to its inaccessibility, it is still only poorly understood and more detailed observations are important, particularly to validate and tune physical models describing its dynamics.

By creating artificial glacier moulins - boreholes connected to the subglacial drainage system and supplied with water from surface streams - we present a novel method to monitor the evolution of englacial hydrological systems with high temporal resolution.  Here, we use artificial moulins as representations for vertical, pressurised, englacial R-channels.  From tracer and pressure measurements we derive time series of the hydraulic gradient, discharge, flow speed and channel cross-sectional area.  Using these, we compute the Darcy-Weisbach friction factor, obtaining values which increase from 0.1 to 13 within five days of channel evolution (corresponding to a Manning friction factor of 0.03 to 0.3 s m-1/3).

Furthermore, we simulate the growth of the channel cross-sectional area using different temperature gradients.  The comparison to our measurements largely supports the common assumption that the temperature follows the pressure melting point.  The deviations from this behaviour are analysed using various heat transfer parameterisations to assess their applicability.

Finally, we discuss how artificial moulins could be combined with glacier-wide tracer experiments to constrain parameters of subglacial drainage more precisely. The presented approach allows to accurately quantify the englacial transit time of the tracer and thus, in turn, to quantify the subglacial transit time; something which has not been achieved to date.

How to cite: Pohle, A., Werder, M. A., Gräff, D., and Farinotti, D.: Using artificial moulins to characterise englacial R-channels, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8644, https://doi.org/10.5194/egusphere-egu22-8644, 2022.

EGU22-9202 | Presentations | CR4.4

Temporal relationship between meltwater discharge and CH4 and CO2 emissions from the Greenland Ice Sheet. 

Christian Juncher Jørgensen, Sarah Elise Sapper, Thomas Blunier, Vasileios Gkinis, and Jesper Riis Christiansen

Emission of CH4 and CO2 was recently discovered at the western margin of the Greenlandic Ice Sheet (GrIS) 1,2. While knowledge on both carbon sources, extent and magnitude of these emissions are still very limited, the previous studies indicate that a primary driver for emission is degassing of dissolved and pressurized gases in the meltwater as it reaches the glacial margin. In this way we suggest that glacial hydrology plays a key role in regulating emission on both temporal and spatial scale.

In our studies of subglacial CH4 and CO2 emissions we have so far observed that the seasonal variations in meltwater discharge is correlated to both the magnitude of gas concentrations as well as timing of emissions3,4. We propose that the seasonal variations in the connectivity of subglacial channels to both 1) pockets of sediment with CH4 and CO2 production from both anaerobic and aerobic biological processes and 2) supraglacial meltwater via englacial conduits could be a mechanism, which could explain the overall temporal and seasonal patterns of gas concentrations observed at the glacial margin.

We hypothesize that by observing hydrological and geochemical processes at the margin together with CH4 and CO2 in high frequency over the melt season it can be inferred how subglacial hydrological processes regulate biogeochemical and carbon turnover processes. Knowledge on these mechanism and processes are important for future upscaling CH4 and CO2 emission to seasonal periods and larger spatial scales through modeling as well as the assessment of the potential importance of subglacial carbon emissions to the climate system.

Here, we will present data that couples meltwater discharge to measurements of dissolved CH4 and gaseous CH4 and CO2 as well as campaign measurements of water geochemistry and its isotopic composition. Preliminary data shows that CH4 and CO2 export display a clear diurnal signal in response to variations in the composition of melt water discharge. EC measurements and isotopic composition of melt water show a dominance of surface meltwater to subglacial meltwater, but clear diurnal trends in the mixing between these two water sources can be deduced from both isotope and elemental geochemistry of the meltwater.

1. Christiansen, J. R. & Jørgensen, C. J. First observation of direct methane emission to the atmosphere from the subglacial domain of the Greenland Ice Sheet. Sci. Rep. 8, 16623 (2018).

2. Lamarche-Gagnon, G. et al. Greenland melt drives continuous export of methane from its bed. Nature 73–77 (2018). doi:10.1038/s41586-018-0800-0

3. Jørgensen, C. J., Mønster, J., Fuglsang, K. & Christiansen, J. R. Continuous methane concentration measurements at the Greenland Ice Sheet-atmosphere interface using a low-cost low-power metal oxide sensor system. Atmos. Meas. Tech. Discuss. 13, 3319–3328 (2020).

4. Christiansen, J. R., Röckmann, T., Popa, M. E., Sapart, C. J. & Jørgensen, C. J. Carbon emissions from the edge of the Greenland Ice sheet reveal subglacial processes of methane and carbon dioxide turnover. J. Geophys. Res. Biogeosciences 1–13 (2021). doi:10.1029/2021jg006308

How to cite: Jørgensen, C. J., Sapper, S. E., Blunier, T., Gkinis, V., and Christiansen, J. R.: Temporal relationship between meltwater discharge and CH4 and CO2 emissions from the Greenland Ice Sheet., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9202, https://doi.org/10.5194/egusphere-egu22-9202, 2022.

EGU22-9915 | Presentations | CR4.4 | Highlight

Mapping the bed in challenging radar environments on alpine glaciers and ice sheets using radar polarimetry 

M.Reza Ershadi, Reinhard Drews, Inka Koch, Falk Oraschewski, Rainer Prinz, Carlos Martin, and Olaf Eisen

Mapping the ice bed interface with radar is challenging in many alpine glaciers where the ice is temperate, and in-ice absorption is high. It is also difficult in selected regions of polar ice sheets such as near grounding zones and in ice streams where clutter and rough beds increase incoherent volume scattering. The lack of information for the ice geometry impedes our process understanding, e.g., basal sliding (requires knowledge about the basal roughness) and the routing of subglacial water flow (requires knowledge on basal smoothness). The lack of observations to constrain variations in ice thickness on the sub-kilometre scale is thus still a bottleneck to confidently predict ice dynamics and expected rates of sea-level rise.

A recent development in radioglaciology, namely the application of phase-coherent polarimetric radar, provides an excellent opportunity to overcome these limitations. Radar polarimetry has made significant strides in the last few years to constrain internal ice structure and their impact on the deformation of ice sheets, including the reconstruction of ice micro-structure parameters previously obtained from ice cores. Here, we suggest that the ice-bed interface can be identified in characteristic patterns of the polarimetric coherence phase. This new metric provides information in areas where the backscattered power amplitude does not show any signatures of the ice-bed interface. We provide examples for this across a wide range of glaciological settings, including cold (Colle Gnifetti, Switzerland) and temperate (Hintereisferner, Austria) alpine glaciers, thin grounding zones (Ekström Ice Shelf, East Antarctica) and thick ice domes (Dome C, East Antarctica). If this holds, then the ice thickness mapping in challenging glaciological settings should preferably be done using a quad-polarimetric acquisition geometry. For ground-based surveys, this can be done using an autonomous ice rover, for which we provide a proof-of-concept study on the Ekström Ice Shelf in Antarctica.

How to cite: Ershadi, M. R., Drews, R., Koch, I., Oraschewski, F., Prinz, R., Martin, C., and Eisen, O.: Mapping the bed in challenging radar environments on alpine glaciers and ice sheets using radar polarimetry, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9915, https://doi.org/10.5194/egusphere-egu22-9915, 2022.

EGU22-10584 | Presentations | CR4.4

Cascading supraglacial drainage observed to cause large-scale acceleration and uplift during winter in Greenland 

Nathan Maier, Jonas Andersen, Jeremie Mouginot, Florent Gimbert, and Olivier Gagliardini

On land-terminating regions of ice sheets, large and transient changes in surface motion are not expected outside of summer due to the lack of concurrent melt forcing.  Here, we document the dynamic response to a cascading lake drainage that occurred during winter in Greenland using a high-resolution DInSAR timeseries (6-day) acquired from Sentinel-1 and optical imagery from Landsat-8 and Sentinel-2. A total of fifteen supraglacial lakes and several smaller supraglacial water features were identified to have drained during the event resulting in a velocity wave that propagates from the inland regions to the margin. Along the wave path, speeds increase up to three times pre-drainage velocities as the wave passes. Bifurcation of the velocity wave during the event implies at least two distinct subglacial flood pathways develop which drain from the margin over 100 km apart. By tracking the wavefront, we estimate the wave velocity through the event which we infer to be similar to the drainage velocity. Wave speeds of between 0.04 and 0.28 m s-1 suggests the subglacial flood propagates mainly through an inefficient drainage system. Using temporally overlapping portions of two DInSAR velocity maps which have an accuracy of greater than 0.1 m yr-1, we decompose the signal and demonstrate some of the motion is a result of surface uplift which constrains locations of likely flow pathways. Overall, our results demonstrate a sustained dynamic response to melt forcing can occur in the absence of surface melt. This indicates melt-induced ice motion changes are not limited to summer and transient winter dynamics might commonly occur as stored meltwater is released.

How to cite: Maier, N., Andersen, J., Mouginot, J., Gimbert, F., and Gagliardini, O.: Cascading supraglacial drainage observed to cause large-scale acceleration and uplift during winter in Greenland, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10584, https://doi.org/10.5194/egusphere-egu22-10584, 2022.

The Greenland ice sheet (GrIS) is currently losing mass, as a result of complex mechanisms of ice-climate interaction that need to be understood for reliable projections of future sea level rise. Previous authors have intensively investigated the total GrIS mass balance, Surface Mass Balance (SMB), and ice discharge at different temporal scales. However, knowledge of the remaining mass variations due to supra-, en- and sub-glacier meltwater retention, is limited. In this study, we make a first attempt to quantify the temporal pattern of meltwater retention at different locations within the GrIS by analyzing the bedrock’s elastic response caused by meltwater mass variations. To that end, we use vertical displacements observed by Global Positioning System (GPS) stations. We estimate, for the first time, the evolution of meltwater storage variations at both the seasonal and inter-annual time scale. We find, among others, that the annual cycle of vertical displacements, after subtracting the signals related to SMB and other known mass transport processes, demonstrates at many GPS stations a consistent subsidence from May to July. This is an indication of a mass gain, which starts in May and peaks in July. We infer that this mass gain signal is due to the meltwater accumulation within the ice sheet. An in-depth investigation of this process by Geodetic data is critical for better understanding the hydrological cycle and the further evolution of the GrIS.

How to cite: Ran, J. and Ditmar, P.: GPS data reveal the evolution of liquid water  retention within the Greenland Ice Sheet at the seasonal and inter-annual time scale, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10904, https://doi.org/10.5194/egusphere-egu22-10904, 2022.

EGU22-11291 | Presentations | CR4.4

Properties and High-Resolution Topography of Subglacial Bedforms Beneath a West Antarctic Ice Stream 

Rebecca Schlegel, Alex Brisbourne, Tavi Murray, Adam Booth, Andrew Smith, Roger Clark, and Edward King

Subglacial bedforms such as mega-scale glacial lineations and drumlins are commonly thought to form during active ice flow. They are often present in deglaciated areas with various elongation ratios, consisting of different materials , information which led to the development of different formation theories. However, these exposed examples were formed not only by subglacial processes during glaciation but also altered by processes during and after deglaciation. Here, we analyse in-situ properties and topography beneath Rutford Ice Steam, a fast flowing ice stream in West Antarctica to evaluate current theoretical models of bedform formation. We present a combination of seismic and radar data, including high-resolution 3D radar topography covering the upstream end of a bedform. Data acquisition and processing of the high-resolution 3D radar dataset result in a horizontal resolution of 24 m along- and across-track and a vertical resolution of 12 m. Using seismic acoustic impedance and calibrated radar reflectivity subglacial properties of the bedforms as well as the surrounding area are identified.

A depression around the upstream end of a 360 m wide, 50 m high and more than 13 km long bedform was observed for the first time analysing the high-resolution 3D radar topography.  The depression consists of a deepening up to 45 m deep and 360 m wide and is seen to extend around 10.5 km downstream. Radar reflectivity reveals that the material the depression is excavated into at least partly consists of low porosity material. Radar reflectivity and seismic acoustic impedance  along the bedform imply a stiffer upstream end which softens along flow. The subglacial topography and properties give evidence that the bedform and the depression are formed by a combination of  erosional and depositional processes. Both processes are likely interlinked, as implied by the comparable volume of the moat and the bedform at the upstream end of the bedform. Based on these observations we support or reject common bedform formation theories beneath Rutford Ice Stream.

How to cite: Schlegel, R., Brisbourne, A., Murray, T., Booth, A., Smith, A., Clark, R., and King, E.: Properties and High-Resolution Topography of Subglacial Bedforms Beneath a West Antarctic Ice Stream, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11291, https://doi.org/10.5194/egusphere-egu22-11291, 2022.

EGU22-11677 | Presentations | CR4.4 | Highlight

A time-dependent sliding law for granular till 

Kasia Warburton, Duncan Hewitt, and Jerome Neufeld

The dynamics of soft-bedded glacial sliding over water-saturated tills are poorly constrained and difficult to realistically capture in large scale models. While experiments characterise till as a plastic material with a pressure dependent yield stress, large scale models rely on a viscous or power-law description of the subglacial environment to efficiently constrain the basal sliding rate of the ice. Further, the subglacial water pressure may fluctuate on annual to daily timescales, leading to transient adjustment of the till.

Here, we construct a continuum two-phase model of coupled fluid and solid flows, using Darcy flow to describe the movement of water through the pore space of the till that deforms according to a granular-inspired rheology. After calibrating our model against steady-state experiments, we force the model with a fluctuating effective pressure at the ice-till interface to infer the resulting relationships between basal traction, solid fraction, rate of deformation, and till flux. Shear dilation introduces internal pressure variations and transient dilatant strengthening emerges, leading to hysteretic behaviour in low-permeability materials.

Our model predicts a time-dependent effective sliding law, with permeability-dependent lag between changes in effective pressure and the sliding speed. This deviation from traditional steady-state sliding laws may play an important role in a wide range of transient ice-sheet phenomena, from glacier surges to the tidal response of ice streams. 

How to cite: Warburton, K., Hewitt, D., and Neufeld, J.: A time-dependent sliding law for granular till, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11677, https://doi.org/10.5194/egusphere-egu22-11677, 2022.

EGU22-12228 | Presentations | CR4.4

Borehole-based insights into the nature and timing of hydrological-regulation at a fast-moving Greenlandic outlet glacier 

Bryn Hubbard, Samuel Doyle, Poul Christoffersen, Thomas Chudley, and Robert Law

Enhanced ice velocity around the margins of the Greenland Ice Sheet is facilitated by the presence and pressure of subglacial meltwater. However, annual and longer-term velocity may be moderated by hydrological regulation, which reduces late melt-season and winter ice velocities following summers with relatively high surface melting and associated meltwater flux to the bed. While detail is lacking, hydrological regulation is likely driven by variations in the efficiency of subglacial drainage pathways and by associated variations in post-melt-season water retention at the glacier bed. Spatial variations in these processes may be viewed in terms of domains of differing degrees of hydrological connection to large subglacial meltwater channels. To date, a ‘well connected’ domain and an ‘isolated’ domain have been characterized, and an intermediate ‘weakly connected’ domain proposed. Generally, changes in the extent and/or pressurisation of the isolated domain are proposed as the driver of hydrological regulation. Yet, identifying the precise nature and timing of hydrological regulation, as well as the role of the weakly-connected domain, remain elusive.

             Here, we investigate the nature of the onset of hydrological regulation through a field experiment ~30 km from the terminus of Sermeq Kujalleq/Store Glacier, a fast-moving Greenlandic outlet glacier. We recorded simultaneous high-resolution time series of surface meltwater discharge, surface ice velocity and subglacial water pressure in two boreholes drilled at different distances from a substantial moulin. Analysis of the magnitude and timing of diurnal cycles and longer-term trends in all four records reveals that initially, in July, one borehole intersected the isolated subglacial domain and the other a ‘weakly-connected’ domain, with the latter showing a gradual decline in water pressure through the summer melt season. Transition to a winter state over the period ~10th – 20th August was marked by (i) a decrease in surface melting; (ii) a decrease in the amplitude of diurnal water pressure cycles in both boreholes, and (iii) a decrease in surface velocity. This transition was accompanied by an almost instantaneous (<1 d) switch in the borehole hitherto intersecting the weakly-connected domain to the isolated domain, evidenced by a 180° phase shift in the timing of its diurnal water pressure cycle. After this transition, diurnal cycles in all records diminish and both subglacial water pressure and ice surface velocity increase gradually through the winter.

                We conclude that ice velocity at our study location is at least partly governed by water pressure within a weakly-connected subglacial drainage domain. Water pressure here declines gradually through the melt season but increases after transition to hydraulic isolation, a transition that occurs over a period of only some days in the autumn. At the scale represented by records from individual boreholes the transition can occur over just some hours.

How to cite: Hubbard, B., Doyle, S., Christoffersen, P., Chudley, T., and Law, R.: Borehole-based insights into the nature and timing of hydrological-regulation at a fast-moving Greenlandic outlet glacier, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12228, https://doi.org/10.5194/egusphere-egu22-12228, 2022.

Subglacial flow routing, which simply routs water down the Shreve potential (i.e. the hydraulic potential assuming that water pressure equals a fraction of ice overburden pressure), is probably the most widely used subglacial drainage model.  It is easy to use via many ready-to-use implementations, does not suffer from numerical issues, such as non-convergence, and is fast.

Here I present two improvements to this venerable model: (1) the spatial uncertainties in the input fields (surface and bed topography, water input) and the model parameter (fraction between water pressure and floation pressure) are taken into account by representing them as Gaussian random fields. This a allows to assess the impact of these uncertainties by running Monte Carlo simulations.  (2) the dependence of the ice melting point on the pressure (leading to the so-called supercooling effects) can lead to deflections in the flow directions where descending flow-paths are favoured over ascending ones.  I present a framework on how this effect can be taken into account in subglacial flow routing.

To showcase the improved model, I present results from applying it to catchments of Antarctica which show that the sizes of sub-catchments can have uncertainties of several order of magnitudes.  This demonstrates the need of using such an improved model to make predictions of fluxes, including their uncertainties, into subglacial lakes or at the grounding line.

How to cite: Werder, M.: Subglacial water flow routing v2.0: taking uncertainties and supercooling effects into account, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12718, https://doi.org/10.5194/egusphere-egu22-12718, 2022.

CR5 – Frozen ground, debris-covered glaciers and geomorphology

EGU22-429 | Presentations | CR5.2

Permafrost thawing and changes on peat biological activity of palsa mire in Western Siberia 

Stanislav Chuvanov, George Matyshak, Victoria Trifonova, and Maria Timofeeva

Peatlands comprise 19% of the permafrost area in the subarctic zone, they store 277 Pg of organic carbon. Peatlands in that area are represented by palsa mire. The palsa mire consists of frozen peat mounds (palsa), thermokarst depression and the wet bog without permafrost.

Climate change and thawing of permafrost leads to a change in soil moisture, both drying and wetting. This can lead to a change in the carbon balance of the ecosystem and increase or decrease the emission of greenhouse gases (CO2 and CH4).

The aim of the work was to study the effect of changes in soil moisture on the biological activity of palsa mire peat soils in the north of Western Siberia (65°18'52"N, 72°52'32"E). The studies were conducted in 2018-2021 in the northern taiga in the discontinuous permafrost zone.

The two palsas (Cryic Histosol) and the surrounding bog (Fibric Histosol) were examined. Palsa soils were characterized by high variability of the studied parameters; active layer thickness was 0.66±0.07 m, soil moisture - 30.98±2.49%, soil temperature - 8.31±0.45°C. The soils of the bog were characterized by the absence of permafrost, a higher soil temperature - 13.58±0.26°C and soil moisture - 74.59±0.26%. Despite the difference in the studied parameters of these ecosystems, no significant differences in biological activity were found (185.97±30.51 mgCO2/m2/h).

Based on field measurements, 3 plots were identified with the same type of vegetation and soil temperature, but significantly differ in soil moisture. Depending on soil moisture, the plots were named “Dry” (25.73±1.89%), “Wet” (38.44±0.70%) and “Moist” (53.09±1.06%). Biological activity did not vary significantly between the studied sites but had a multidirectional dynamic in different years. This shows the complexity of palsa, their multifactorial nature and an ambiguous response to changes in moisture.

An added experiment was set up to change soil moisture - transplantation. Measured of CO2 emissions from undisturbed peat soil of a large volume transferred from dry palsa to a wetting bog. And vice versa. The biological activity of the soils did not differ considerable both during wetting and draining. In different years, there was a vary dynamics in CO2 emissions.

According to the results of the study, with climate change, thawing of permafrost and palsa degradation, there will be no significant CO2 flux. This may be due to the multifactorial nature of ecosystems, a wide optimum of soil moisture for peat soils. The influence of additional factors is also significant: the size of the methanotrophic barrier, the transport of CO2 with solutions over the surface of the palsa permafrost.

How to cite: Chuvanov, S., Matyshak, G., Trifonova, V., and Timofeeva, M.: Permafrost thawing and changes on peat biological activity of palsa mire in Western Siberia, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-429, https://doi.org/10.5194/egusphere-egu22-429, 2022.

EGU22-431 | Presentations | CR5.2

Effects of temperature and moisture manipulation on biological activity of Northern and Southern taiga peat soils 

Viktoriia Trifonova, Irina Ryzhova, George Matyshak, Stanislav Chuvanov, and Matvey Tarkhov

Wetland ecosystems play a significant role in organic carbon conservation; one meter layer of peat soils store over 30 percent of terrestrial organic carbon (Lal, 2008). Ecosystems have different sensitivity to climate change in different nature zones (IPCC, 2014) due to various moisture and temperature regime.

The aim in this work is to define effect of temperature and moisture on mineralization rate in peat soils in Northern and Southern taiga.

The samples of Cryic Histosol (WRB, 2014) were taken from Northern Taiga (65°18'52" N, 72°52'32" E). The samples of Fibric Histosol (WRB, 2014) were taken from Southern Taiga (55°40'04" N 36°42'49" E). In laboratory conditions, samples were brought to certain soil moisture (SM): 30, 60, 80, 100 % (Gritsch, 2015), temperature of incubation was ranging from 5 to 25 ◦C (equal-time method).

In all the cases basal respiration (BR) was growing with increasing of temperature. Samples of Cryic Histosol are more sensitive to changes both in temperature and moisture. BR varies from 0.58 ±0.26 (30% SM and 5 ◦C) to 13.53±0.22 mg C-CO2/g/h (100% SM and 25 ◦C). Q10 coefficient varies from 4.64 to 2.82 respectively (this coefficient demonstrates differences in the temperature sensitivity of soil respiration (Kirschbaum, 1995)). For samples of Fibric Histosol BR varies from 0.75±0.01 (30% SM and 5 ◦C) to 6.14±0.26 mg C-CO2/g/h (100% SM and 25 ◦C). Q10 coefficient varies from 2.70 to 2.18 respectively.

Influence of moisture and temperature on biological activity in all of the cases was statistically confirmed, but interaction of factors is significant only for Cryic Histosol. According to the results, Cryic Histosol is more sensitive to temperature and moisture change, than Fibric Histosol. Peat soils in the northern area are subjected to more rapid organic carbon mineralization after a change of hydrothermal regime, than southern peat soils. In conclusion, Q10 coefficient variation indicates that soils with low soil moisture are more sensitive to temperature changes.

How to cite: Trifonova, V., Ryzhova, I., Matyshak, G., Chuvanov, S., and Tarkhov, M.: Effects of temperature and moisture manipulation on biological activity of Northern and Southern taiga peat soils, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-431, https://doi.org/10.5194/egusphere-egu22-431, 2022.

Subsurface hydrology in regions dominated by permafrost is expected to change as a response to global climate change. Groundwater transports energy as well as dissolved solutes such as contaminants and carbon. To investigate the changes in advected energy as well as potential implications for solute transport, we created a permafrost hillslope modeling study that simulates current day active layer hydrology as well as future conditions based on climate projections.

Simulations are conducted with a state-of-the-art physically based numerical model (ATS) and combine a generic modeling approach with site-specific boundary conditions representative of the Adventdalen valley in Svalbard. We find that in the current climate, the subsurface hydrothermal state of the active layer along the hillslope transect is affected by lateral groundwater flow through differences in moisture distribution up- and downhill. Although lateral heat advection along the transect was found to be negligible, we show that the moisture distribution by gravitationally-driven seepage flow along the hillslope leads to unexpected temperature differences between the uphill and downhill parts of the transect. A non-negligible warming effect is observed uphill, resulting in deeper active layer depths than downhill.

Additionally, preliminary results based on transport modeling indicate that solute migration is mostly longitudinal and slow due to low liquid saturation of the active layer in summer. Under warmer conditions (increased air temperatures), lateral heat advection is expected to increase with more available energy, but solute migration may be partially counteracted by a greater volume of unfrozen soil in summer caused by less saturated conditions closer to the surface.

Furthermore, we discuss the potential implications this has for subsurface transport of solutes and dissolved constituents, and highlight challenges for numerical modeling of these systems.

How to cite: Hamm, A. and Frampton, A.: Modeling groundwater flow and solute transport in the active layer of hillslope system in permafrost environments, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2251, https://doi.org/10.5194/egusphere-egu22-2251, 2022.

Zero Emissions Commitment (ZEC), the expected change in global temperature following the cessation of anthropogenic greenhouse gas emissions has recently been assessed by the Zero Emissions Commitment Model Intercomparison Project (ZECMIP). ZECMIP concluded that the component of ZEC from CO2 emissions will likely be close to zero in the decades following the cessation of emissions. However, of the 18 Earth system models that participated in ZECMIP only two included a representation of the permafrost carbon feedback to climate change. To better assess the potential impact of permafrost carbon decay on ZEC a series of perturbed parameter experiments were conducted with an Earth system model of intermediate complexity. The experiment suggest that the permafrost carbon cycle feedback will directly add 0.06 [0.02 to 0.14]oC to the benchmark ZEC value assesses 50 years after 1000 PgC of CO2 has been emitted to the atmosphere. An additional 0.04 [0 to 0.06]oC is likely to been added relative to the benchmark ZEC value from the thaw-lag effect unaccounted for in the ZECMIP experiment design. Overall we assess that the permafrost carbon feedback is unlikely to change the assessment that ZEC is close to zero on decadal timescales, however the feedback is expected to become more important over the coming centuries.

How to cite: MacDougall, A. H.: Estimated effect of the permafrost carbon stability on the zero emissions commitment to climate change, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2539, https://doi.org/10.5194/egusphere-egu22-2539, 2022.

EGU22-2733 | Presentations | CR5.2

Fate of pyrogenic and organic matter in permafrost-affected soils: A two years in-situ incubation 

Marcus Schiedung, Severin-Luca Bellè, and Samuel Abiven

Permafrost-affected mineral soils store large amounts of the soil organic matter (SOM) in high-latitude regions. These regions are large terrestrial carbon reservoirs and highly vulnerable to the global climate change. Global warming will cause rapid permafrost thaw and potentially accelerate decomposition of SOM. High-latitude regions, such as boreal and arctic ecozones, are regularly affected by wildfires with increasing intensity and frequency caused by global climate change. Wildfires produce pyrogenic organic matter (PyOM) during incomplete combustion of the fuel biomass. Little is known about the cycling of SOM and especially PyOM in permafrost-affected mineral soils, which limits our understanding of potential shifts in cycling and interaction with the soil mineral phase over time.

Here we study the fate of highly 13C-labelled (2-3 atm%) ryegrass organic matter and PyOM from the same feedstock (pyrolyzed at 400°C for 4h) during two years of in-situ incubation in boreal forest mineral soils. Soil cores (10 cm length and 6 cm diameter) were buried in the upper 10 cm of mineral soils under continuous and discontinuous to sporadic permafrost conditions at eleven forest locations (with six replicates) in Northern Canada. At the same locations, litter bags (green and rooibos teabags) were buried and soil temperatures were recorded. The soils cores were separated in three depth (0-3, 3-6 and 6-10 cm) to trace the vertical allocation of the applied organic matter. Density and particle fractionations are applied to identify mineral interactions of the ryegrass and pyrolyzed organic matter.

Preliminary δ13C results from the soil cores show a more extensive vertical allocation of ryegrass organic matter and PyOM in continuous permafrost-affected soils within the cores. This can be associated to the importance of freeze and thaw cycles for the carbon dynamics of permafrost-affected mineral soils. Tracing the labelled ryegrass organic matter and PyOM offers not only the opportunity to quantify the translocated fraction but also the decomposed proportion of the freshly added organic matter and thus understand short-term carbon dynamics. Preliminary results from the litter bags indicate a larger mass loss of slow cycling woody organic matter (rooibos tea) in discontinuous to sporadic permafrost-affected mineral soils, while larger mass losses of fast cycling organic matter (green tea) were observed in continuous permafrost-affected soils. These initial results indicate a complex cycling of organic matter in soils under different permafrost conditions.

How to cite: Schiedung, M., Bellè, S.-L., and Abiven, S.: Fate of pyrogenic and organic matter in permafrost-affected soils: A two years in-situ incubation, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2733, https://doi.org/10.5194/egusphere-egu22-2733, 2022.

EGU22-3437 | Presentations | CR5.2

Compositions and origins of greenhouse gas species in permafrost ice wedges at the Batagay megaslump, Yana Uplands, Northeast Siberia 

Hansu Park, Na-Yeon Ko, JeongEun Kim, Thomas Opel, Hanno Meyer, Sebastian Wetterich, Alexander Fedorov, Andrei Shepelev, and Jinho Ahn

Permafrost has a huge potential as a source for greenhouse gas release under global warming. In this context, it is very important to understand biogeochemical mechanisms of permafrost-related greenhouse gas formation and capacity. As ice wedges are an essential component of ice-rich permafrost and often occupy a large volume fraction of permafrost deposits, it is necessary to study the their gas chemistry. The Batagay megaslump (Yana Uplands, Northeast Siberia) exposes ice-rich permafrost deposits (Ice Complex) that have formed in the Middle and Late Pleistocene. Previous studies suggest the ages of these deposits as MIS 4-2 and at least MIS 16 for the Upper and Lower Ice Complexes, respectively. In this study, we analyzed mixing ratios of gas in air bubbles occluded in ice wedges of both ice complexes. We extracted gas by both, wet and dry extraction methods that connected with a gas chromatography system to analyze CO2, N2O, and CH4 concentrations. We observe CO2 concentrations of 1.9–10.3%, N2O of 0.1–8 ppm, and CH4 of 30–170 ppm for the Lower Ice Complex, and CO2 of 0.03–8.89%, N2O of 0.3–70 ppm, and CH4 of 5–980 ppm for the Upper Ice Complex. Greenhouse gas mixing ratios higher than atmospheric level indicate active microbial activity. This is supported by the δ(O2/Ar) values, which range from –89.01 to –67.43% and from –98.07 to –47.06% for the Lower and Upper Ice Complexes, respectively. The highly depleted δ(O2/Ar) values may indicate strong oxidation reactions by microbial activity and/or non-biological oxidation reactions. Even though there is no significant correlation between CO2 and CH4, abiotic CH4 formation might be negligible because it is unlikely to occur under permanently frozen conditions. Interestingly, CH4 and N2O show a weak negative correlation in both ice complexes, which can be explained by the nitrogen compounds’ inhibitory effect for methanogenesis. The δ(N2/Ar) values range from –8.06% to 33.86% for the Lower Ice Complex and from –5.49% to 30.64% for the Upper Ice Complex. Since nitrogen is more soluble in water than argon, this might indicate that ice wedges may have formed without a major contribution of snowmelt but mainly by dry snow compaction, which is also supported by the spherical shape of gas bubbles within the wedge ice. Furthermore, in ice the argon permeation coefficient is higher than that of nitrogen. Thus, high δ(N2/Ar) values (>10%) are due to argon’s diffusion through ice. Our future research will focus on deciphering the biogeochemical process of greenhouse gas formation for both ice complexes by comparison with ice wedges from other Siberian locations which have experienced different biogeochemical conditions in the past.

How to cite: Park, H., Ko, N.-Y., Kim, J., Opel, T., Meyer, H., Wetterich, S., Fedorov, A., Shepelev, A., and Ahn, J.: Compositions and origins of greenhouse gas species in permafrost ice wedges at the Batagay megaslump, Yana Uplands, Northeast Siberia, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3437, https://doi.org/10.5194/egusphere-egu22-3437, 2022.

EGU22-3779 | Presentations | CR5.2

A multi-isotopic approach to the reconstruction of palsa hummock formation: the case study from the Central Siberia 

Anatoly Prokushkin, Elena Novenko, Sergey Serikov, and Daria Polosukhina

In northern palsa mires stable isotopes of C and N of peat organic matter (OM) and O and H of segregated ice may serve as an important conduit of information about variability of environment conditions and OM turnover in the past millennia and modern time. In our study we applied the multi-isotopic record to distinguish variation in the development of palsa peatlands located in forest-tundra ecotone of Central Siberia.

The study sites are located in vicinity of Igarka settlement (67o31’ N, 86o38’E) within the area underlain discontinuous permafrost. The peat cores were obtained in the central intact parts of perennial frost hummocks located in basins of the Gravijka and Little Gravijka rivers (depth 8.6 and 2.7 m, respectively). Thawed and frozen peat samples were collected at 1.0-5.0 cm step depending on the amount of peat and ice material. Peat (solid) samples were analyzed for C and N content and stable isotopic composition (δ13C and δ15N) by TOC Macro cube (Elementar, Germany) paralleled with Isoprime 100 IRMS (UK). Water stable isotope composition (δ18O and δ2H) of segregated ice samples (melted) were obtained by Picarro L-2120-i (Picarro Inc. USA).

The age of studied peatlands ranged between about 6200 cal yr BP (Gravijka site) and 4300 cal yr BP (Little Gravijka site). Meanwhile, there was the large loss of organic matter in the upper active layer of peat deposits as at 15 cm depth the age of OM was ca. 1800 cal yr BP. These findings suggest OM removal during wildfires and likely erosion processes following fires, and specific isotopic composition mirrors an enhanced OM decomposition in active layer. The large variations in composition of analyzed stable isotopes in frozen peat core captured the changes occurred during the past epochs in an input of OM (changes in vegetation and productivity), peat decomposition rates, nitrogen cycle perturbations as well as hydrothermal regimes and permafrost processes like aggradation (e.g. hummock uplift and cryoturbation) and degradation (e.g. hummock collapse, shifts from minerotrophic to ombrotrophic conditions and vice versa).

This work was supported by the Russian Science Foundation, project № 20-17-00043.

How to cite: Prokushkin, A., Novenko, E., Serikov, S., and Polosukhina, D.: A multi-isotopic approach to the reconstruction of palsa hummock formation: the case study from the Central Siberia, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3779, https://doi.org/10.5194/egusphere-egu22-3779, 2022.

EGU22-4024 | Presentations | CR5.2

Does vegetation shift in Arctic tundra upon permafrost degradation influence mineral element recycling in the topsoil? 

Maëlle Villani, Elisabeth Mauclet, Yannick Agnan, Arsène Druel, Briana Jasinski, Meghan Taylor, Edward A.G. Schuur, and Sophie Opfergelt

Climate change affects the Arctic and Subarctic regions by exposing previously frozen permafrost to thaw, unlocking nutrients, changing hydrological processes, and boosting plant growth. As a result, Arctic tundra is subject to a shrub expansion, called “shrubification” at the expense of sedge species. Depending on intrinsic foliar properties of these plant species, changes in foliar fluxes with shrubification in the context of permafrost degradation may influence topsoil mineral element composition. Despite the potential implications for the fate of organic carbon in the topsoil, this remains poorly quantified. Here, we investigate vegetation foliar and topsoil mineral element composition (mineral elements that influence organic carbon decomposition: Si, K, Ca, P, Mn, Zn, Cu, Mo and V) from a typical Arctic tundra at Eight Mile Lake (Alaska, USA) across a natural gradient of permafrost degradation. Results show that foliar element concentrations are higher (up to 9 times; Si, K, Mo, and for some species Zn) or lower (up to 2 times; Ca, P, Mn, Cu, V, and for some species Zn) in sedge than in shrub species. This induces different foliar flux with permafrost degradation and shrubification. As a result, a vegetation shift over ~40 years from sedges to shrubs has resulted in lower topsoil concentrations in Si, K, Zn and Mo (respectively of 52, 24, 20 and 51%) in poorly degraded permafrost sites compared to highly degraded permafrost sites. For other mineral elements (Ca, P, Mn, Cu and V), the vegetation shift has not induced a marked changed in topsoil concentrations at this stage of permafrost degradation. This observed change in topsoil composition involving beneficial or toxic elements for decomposers is likely to influence organic carbon decomposition. These data can serve as a first estimate to assess the influence of other shifts in vegetation in Arctic tundra such as sedge expansion with wildfires.

How to cite: Villani, M., Mauclet, E., Agnan, Y., Druel, A., Jasinski, B., Taylor, M., Schuur, E. A. G., and Opfergelt, S.: Does vegetation shift in Arctic tundra upon permafrost degradation influence mineral element recycling in the topsoil?, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4024, https://doi.org/10.5194/egusphere-egu22-4024, 2022.

EGU22-4211 | Presentations | CR5.2

Long lasting greenhouse gas emissions beyond abrupt permafrost thaw event in permafrost peatlands 

Hanna Lee, Casper Christiansen, Inge Althuizen, Anders Michelsen, Peter Dörsch, Sebastian Westermann, and David Risk

Abrupt permafrost thawing is expected to release large amounts of greenhouse gasses to the atmosphere, creating a positive feedback to climate warming. There is, however, still large uncertainty in the timing, duration, magnitude, and mechanisms controlling this process, which hampers accurate quantification of permafrost carbon climate feedback cycles. The current understanding supports that abrupt permafrost thaw will lead to surface inundation and create anaerobic landscapes, which dominantly produce methane during the decomposition process. Over time, natural succession and vegetation growth may decrease methane release and increase net carbon uptake. We investigated how rapid permafrost thawing and subsequent natural succession over time affect CO2, CH4, and N2O release at a field site in northern Norway (69ᵒN), where recent abrupt degradation of permafrost created thaw ponds in palsa peat plateau-mire ecosystems. The site exhibits a natural gradient of permafrost thaw, which also corresponds to a strong hydrological gradient (i.e. dry peat plateau underlain by intact permafrost, seasonally inundated thaw slumps, thaw ponds, and natural succession ponds covered by sphagnum and sedges). Since 2017, we used a range of manual and automated techniques to measure changes in vegetation, soil and water microclimate, biogeochemistry, and soil CO2, CH4, and N2O concentrations and fluxes across the permafrost thaw gradient. In the three-year observations, we show that abrupt permafrost thaw and land surface subsidence – both intermediate slumping and pond formation – increase net annual carbon loss. Permafrost thaw accelerated CO2 release greatly in thaw slumps (177.5 gCO2 m-2) compared to intact permafrost peat plateau (59.0 gCO2 m-2). During the growing season, peat plateau was a small sink of atmospheric CH4 (-2.5 gCH4 m-2), whereas permafrost thaw slumping and pond formation increased CH4 release dramatically (ranging from 9.7 to 36.1 gCH4 m-2). Furthermore, CH4 release continues to increase even in natural succession pond likely due to aerenchyma transport of CH4 from deeper soil. The overall N2O release was negligeable except in the bare soil peat plateau. The net radiative forcing of ecosystem carbon balance will depend on the carbon uptake from the natural succession of vegetation, but we show that greenhouse gas emissions continue to increase beyond abrupt permafrost thaw event towards natural succession.

How to cite: Lee, H., Christiansen, C., Althuizen, I., Michelsen, A., Dörsch, P., Westermann, S., and Risk, D.: Long lasting greenhouse gas emissions beyond abrupt permafrost thaw event in permafrost peatlands, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4211, https://doi.org/10.5194/egusphere-egu22-4211, 2022.

EGU22-4672 | Presentations | CR5.2

Investigating the impact of active layer thickening on vertical soil moisture distribution in the Tibetan Plateau 

Huiru Jiang, Yonghong Yi, Wenjiang Zhang, Deliang Chen, and Rongxing Li

Permafrost degradation caused by climate warming has potentially large impact on the hydro-eco environment in the Tibetan Plateau (TP) through affecting soil water redistribution, and it is critical to investigate the soil moisture changes and estimate their response to future climate conditions. In this study, we first analyzed the in-situ soil temperature and moisture data to examine the impact of active layer thickening on soil moisture redistribution. There is generally a “water-rich zone” around the bottom of the active layer at sites with the active layer thickness (ALT) greater than ~2 m, and a relative low soil moisture zone occurs approximately between the bottom of the root zone (~ 0.4 m) and the bottom of the active layer. However, at shallower-ALT sites (e.g., ALT< 2 m), a “soil water rich zone” occurs at the upper active layer rather than at the bottom of the active layer, and soil moisture at the deeper active layer generally shows a decreasing trend along soil depth. We used a process-based permafrost hydrology model to represent the above effects of active layer thickening on soil moisture redistribution through modifying the soil hydraulic profile. Model sensitivity runs indicate that soil moisture redistribution with active layer thickening is largely due to dramatic changes of hydraulic conductivity between the root zone and deeper layers (>~ 1m). The saturated hydraulic conductivity tends to increase a little in the root zoon and then show a sharp exponential decline along soil depth, while the pedo-transfer functions that are commonly used in models cannot reproduce this process well.

Our results indicate that shallower ALT helps to retain soil moisture in the soil root zone; however, when ALT increases to a certain depth, the root-zone soil layer tends to lose water because of little recharge from deeper (>~1m) soils due to the dramatical decreases in soil hydraulic conductivity. Therefore, active layer thickening may exacerbate soil drying in the root-zone, which will have negative impacts on the vegetation growth and performances of ecosystem functioning. We will further investigate the soil moisture changes under different climate scenarios in order to better project the future hydro-eco response in the TP permafrost region.

How to cite: Jiang, H., Yi, Y., Zhang, W., Chen, D., and Li, R.: Investigating the impact of active layer thickening on vertical soil moisture distribution in the Tibetan Plateau, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4672, https://doi.org/10.5194/egusphere-egu22-4672, 2022.

EGU22-6418 | Presentations | CR5.2

Role of iron-carbon interactions in the release of greenhouse gases from permafrost systems 

Prachi Joshi, Monique Patzner, Ankita Chauhan, Eva Voggenreiter, Katrin Wunsch, Casey Bryce, and Andreas Kappler

As permafrost thaws, vast stocks of organic carbon previously accumulated within these systems are vulnerable to microbial decomposition and may be released as the greenhouse gases CO2 and CH4. The release of carbon from permafrost systems is expected to lead to runaway positive feedbacks. The timescale and magnitude of the permafrost-climate feedback is highly uncertain as knowledge gaps remain regarding the rate of decomposition of permafrost organic carbon. These knowledge gaps stem, in part, from poor understanding of the association between organic carbon (in the form of organic matter) and minerals, especially high surface area iron minerals. In this work, we investigated the coupling of iron and carbon cycles in permafrost peatlands and its effect on greenhouse gas release. We first showed that up to 20% of the organic carbon in intact permafrost sites may be associated with iron(III) (oxyhydr)oxides and thereby protected from microbial decomposition. At the onset of thaw, this association is broken down, likely due to the microbial reduction of iron(III), and previously protected carbon is thus released. Using microbiological and molecular biological tools, we linked this breakdown to an increase in the abundance of methanogenic microorganisms and concentrations of methane. Preliminary work also suggests that part of the released organic carbon may re-associate with dissolved iron in thaw ponds to form flocs. Currently, we are investigating the molecular composition of organic matter as it undergoes these redox processes with the goal of linking bioavailability to composition. We complement this work with enrichment experiments and microbial community analyses to determine the microbial key players controlling iron(III) reduction and the potential for subsequent microbial Fe(II) oxidation. Collectively, the results of this project suggest that upon thawing, organic matter previously associated with minerals is mobilized and is likely susceptible to microbially-mediated release as CO2 and CH4.

How to cite: Joshi, P., Patzner, M., Chauhan, A., Voggenreiter, E., Wunsch, K., Bryce, C., and Kappler, A.: Role of iron-carbon interactions in the release of greenhouse gases from permafrost systems, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6418, https://doi.org/10.5194/egusphere-egu22-6418, 2022.

EGU22-6825 | Presentations | CR5.2

Biogeochemical and Ecological Responses to Warming Climate in High Arctic Polar Deserts 

Mitsuaki Ota, Amanda Muller, Gurbir Dhilon, and Steven Siciliano

High Arctic polar deserts cover 26% of the Arctic and are predicted to transform dramatically with rapidly rising temperatures. Previous studies found that polar deserts store larger amounts of soil organic carbon (SOC) in the permafrost than previously expected and can emit greenhouse gases (GHGs) at rate comparable to mesic Arctic ecosystems. However, the mechanism of the GHG production is not clear, which contributes to a great source of uncertainty regarding ecological feedbacks to the warming climate. Extreme climate conditions thaw the uppermost part of the permafrost, and the accumulated soil nutrients are ejected into the overlying soil layers where the subsurface nutrient patches (diapirs) form to increase carbon and nitrogen (N) contents by 7% and 20%, respectively. Previous mechanical models suggest that the ejection is facilitated by the increase in soil viscosity in the overlying soil layer. We previously found that diapirs developed about 30% of sorted circles in our study site and that the dominant vascular plant (Salix arctica) increased root biomass and nitrogen uptake from diapirs. To understand a GHG-feedback to the warming climate, we collected 40 soil samples with diapirs and 40 without diapirs during July and August 2013 to investigate gross N transformation rates and GHG emissions associated with diapirs in laboratory. Our study site encompasses two Canadian High Arctic polar deserts and is located near Alexandra Fjord (78°51′N, 75°54′W), Ellesmere Island, Nunavut, Canada. To deal with small amounts of nitrous oxide (N2O) emissions near or below the detection limit, we employed the hurdle models including (1) a Bernoulli component that models whether the data cross the detection limit based on covariates and (2) generalized linear model component that models the data above the detection limit. Our results showed that diapirs decreased gross N mineralization up to 48% and slowed carbon dioxide and methane emissions. Consistently, we found that diapirs contained more recalcitrant SOC using attenuated total reflectance Fourier transformed mid-infrared (ATR-FTIR) spectroscopy. ATR-FTIR also showed higher amounts of polysaccharides known to raise soil viscosity. The hurdle model approach showed that diapirs increased the estimated N2O emissions by up to 49% under wet conditions and suggested that the increase links to the increase in the probability of N2O emissions. On the other hand, under dry conditions, the hurdle models suggested that the increase in the estimated N2O emissions from diapirs links to the increase in the magnitude of the N2O emissions. The higher abundance of polysaccharides and recalcitrant SOC may indicate that biological factors are involved in forming diapirs and that diapirs supply vascular plants with nutrients as a result of a mutualistic relationship. Our study showed that diapirs altered GHG emissions and suggest that future research should include plant-microbe relationship in diapirs and other factors such as occlusion in soil aggregates for a more robust evaluation of diaper-GHG production. Furthermore, we suggest that the hurdle model may be a useful tool for evaluating N2O emissions that are locally small but could be critical in total in the Arctic.

How to cite: Ota, M., Muller, A., Dhilon, G., and Siciliano, S.: Biogeochemical and Ecological Responses to Warming Climate in High Arctic Polar Deserts, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6825, https://doi.org/10.5194/egusphere-egu22-6825, 2022.

EGU22-7559 | Presentations | CR5.2

Who dealt it? Mechanistic modeling of microbial functional types in anaerobic permafrost soils. 

Lara Kaiser, Christian Knoblauch, and Christian Beer

The release of CH4 and CO2 from thawing permafrost soils will substantially impact the global carbon budget. During anaerobic conditions, these emissions are caused by a complex web of microbes. Depending on their interactions, differing ratios of CH4 to CO2 are produced. In order to predict these emissions, mechanistic modeling of microbial processes is essential but is largely omitted in current climate models. 

We present a new, process-based model for CH4 and CO2 production in anaerobic permafrost soils after thaw, incorporating key microbial functional types. Each microbial functional type is represented by a specific chemical pathway, allowing the calculation of substance utilization and production stoichiometrically for each time step. To the best of our knowledge, this is the first model incorporating a microbial type utilizing alternative electron acceptors, specifically Fe3+. These microbes out-compete acetoclastic methanogens for acetate as long as Fe3+ is sufficiently abundant, thereby suppressing CH4 production via this pathway. In addition, fermentation can be inhibited by the accumulation of its end product acetate, as has been observed in experiments.  We optimize the model parameters against data from an anaerobic permafrost soil incubation experiment over seven years.   

How to cite: Kaiser, L., Knoblauch, C., and Beer, C.: Who dealt it? Mechanistic modeling of microbial functional types in anaerobic permafrost soils., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7559, https://doi.org/10.5194/egusphere-egu22-7559, 2022.

Permafrost thaw may stimulate microbial degradation of large soil organic carbon (SOC) stocks, releasing greenhouse gases into the atmosphere. Projecting this feedback to the global carbon (C) balance is urgent, but remains highly uncertain, because complex interactions between soil and microbes make it difficult to capture C dynamics accurately in models. How much CO2 will be respired is to a high degree dependent on C stabilization and persistence in the soil. SOC may be adsorbed to minerals and thereby unavailable to microbes. Common land surface models ignore this process, potentially overestimating C release from thawing permafrost.

This study investigates the effect of this stabilization mechanism on the decomposition process by applying a process-orientated model approach. We fit a microbial-explicit model, which includes mineral adsorption, to a four-year dataset of aerobic incubations of soils from the Lena River Delta, Siberia. We compare this model to a more conceptual first-order decay model, and to a version without mineral adsorption.

Preliminary results suggest that the mechanistic representation of mineral adsorption is crucial for extrapolations into the future, to avoid depletion of organic C pools or the introduction of artificially long C residence times.  We further emphasize the importance of long-term incubation studies.

How to cite: Schröer, C., Knoblauch, C., and Beer, C.: Stabilization in the fate of destabilization: Improving the representation of C stabilization when modeling C decomposition in permafrost-affected soils, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7837, https://doi.org/10.5194/egusphere-egu22-7837, 2022.

EGU22-9286 | Presentations | CR5.2

Thermokarst lake size controls greenhouse gases production but not its temperature sensitivity 

Tianpeng Li, Lichao Fan, Rinat Manasypov, Yakov Kuzyakov, Klaus-Holger Knorr, and Maxim Dorodnikov

Thermokarst lakes formed form permafrost thawing under the global warming are an important source of greenhouse gases (GHG). However, the driving mechanisms and temperature sensitivity (Q10) of GHG emissions from the sediments of thermokarst lakes require deeper understanding. From existing studies of organic matter (OM) turnover and thermodynamic theory, it is known that more refractory OM has a higher temperature sensitivity of decomposition. To test the relevance of such effects in thermokarst lakes, sediments of two differently sized lakes (small = young, DOC rich; large = mature, DOC poor) from Western Siberia were anoxically incubated under three temperatures (4, 10, 16°C) for 49 days. We hypothesized that the Q10 of CO2, CH4 and N2O production increases with lake size as OM becomes increasingly refractory. Rates of CO2 production increased exponentially with temperature in sediments from lakes of both sizes, whereas the highest rates were observed for sediments of the small lake (4.2-9.7 μg C g-1 day-1), as expected for the more labile OM. However, the Q10 of CO2 production (1.8-2.2) was unexpectedly similar between two lakes. The small lake sediment emitted 2-3 orders of magnitude larger amount of CH4 (20-583 ng C g-1 day-1) as compared with large lake. The Q10 values and activation energy (Ea) of CH4 production in small lake sediment significantly decreased from 4-10°C (Q10 = 6.7; Ea = 124 kJ mol-1) to 10-16°C (Q10 = 3.1; Ea = 76 kJ mol-1). This suggests that methanogenesis is a strongly temperature-dependent process that is more sensitive in the low-temperature range. However, Q10 of CH4 production in the large lake did not reveal a sensitivity to temperature probably due to too low CH4 concentrations. In contrast to low CH4 production, the N2O emission rates were dramatically high (0.1-1.3 μg N g-1 day-1) in the sediment of the large lake. Interestingly, there was no N2O detected in the small lake sediment. Presumably, intensive denitrification in the large lake sediment outcompeted methanogenesis for substrate and energy, or enhanced CH4 oxidation occurred with NO3- as the electron acceptor. In summary, the temperature sensitivity of GHG production in thermokarst lake sediments depended more on gas species than on lake size. Nevertheless, the size of thermokarst lakes can serve as an indicator of biogeochemical processes in the sediments, as the small lakes are hotspots of CH4 and the large lakes are hotspots of N2O production.

How to cite: Li, T., Fan, L., Manasypov, R., Kuzyakov, Y., Knorr, K.-H., and Dorodnikov, M.: Thermokarst lake size controls greenhouse gases production but not its temperature sensitivity, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9286, https://doi.org/10.5194/egusphere-egu22-9286, 2022.

EGU22-9369 | Presentations | CR5.2

Biogeochemical responses of plants, soils and microbes to permafrost degradation in a subarctic peatland 

Oriol Grau, Olga Margalef, Joosten Hans, Richter Andreas, Canarini Alberto, Dorrepaal Ellen, Keuper Frida, Sardans Jordi, Peñuelas Josep, and Janssens Ivan

Permafrost peatlands are particularly sensitive to climate warming. The thawing of permafrost in these ecosystems accelerates the decomposition of old organic matter in deep soil layers and re-activates the cycling of carbon (C) and nutrients. Several studies showed that the thawing of permafrost in subarctic peatlands increases nitrogen (N) availability, ecosystem productivity as well as methane (CH4) and C dioxide (CO2) emissions. The mobilisation of other nutrients like phosphorus (P) or potassium (K) and the stoichiometric changes occurring in plants, soils and microbes in these fragile ecosystems are nevertheless poorly understood. In June 2018 we collected plant and soil samples across several permafrost thaw gradients in a palsa mire complex at Stordalen (Abisko, 68°N, Sweden). We selected three contrasting situations across the gradients: a) peat mounds with an intact permafrost core (‘palsa’ areas), b) semi-degraded palsas (‘transition’ area), and c) completely degraded palsas with no permafrost (‘collapsed’ area). For each situation we collected samples of the aboveground vegetation and soil samples at 5-10, 40-45, 70-75 and 95-100 cm (layers A-D), encompassing peat (A and B) and mineral soil layers (C and D). We determined total C, N, P and K, extractable organic C (EOC), total extractable N (TEN), extractable organic N (EON), ammonium (NH4+), nitrate (NO3-), extractable organic and inorganic P (EOP and EIP), microbial enzymatic activity, microbial C, N and P and pH in soil samples at each of the four depths across the gradient. We also determined total C, N, P and K in aboveground vegetation samples. The uppermost soil layer A showed the most statistically significant changes across the gradient of permafrost thaw, namely a 2-fold increase of total N and total P, 3- fold increase of EIP, 4-fold increase of EOP and 5-fold increase of NH4+, along with an increase of potential extracellular enzymatic activity. The fraction of total P immobilised by microbes was highest in the uppermost soil layer of palsas, where microbial P reached 33% of total P. In layer B, there were also several significant changes, such as a 4-fold increase of EOC and TEN and 12-fold increase of NH4+ in transition areas, and a 4-fold increase of EOP in collapsed areas. In addition, foliar chemistry changed significatively across the gradient of permafrost thaw, with a generalised increase of N, P and K, and a decrease of the CN and NP ratios. Along with these changes in foliar chemistry there was an increase of the stocks of N, P and K in biomass across the gradient. The biogeochemical and stoichiometric changes observed in plants, soil and microbes at different soil layers and across the gradient of permafrost thaw evidence that ongoing and future environmental changes will have a major impact on the functioning of these fragile ecosystems in the Subarctic.

How to cite: Grau, O., Margalef, O., Hans, J., Andreas, R., Alberto, C., Ellen, D., Frida, K., Jordi, S., Josep, P., and Ivan, J.: Biogeochemical responses of plants, soils and microbes to permafrost degradation in a subarctic peatland, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9369, https://doi.org/10.5194/egusphere-egu22-9369, 2022.

EGU22-9891 | Presentations | CR5.2

Spatial variability shapes microbial communities of permafrost soils and their reaction to warming 

Cornelia Rottensteiner, Victoria Martin, Hannes Schmidt, Leila Hadžiabdić, Julia Horak, Moritz Mohrlok, Carolina Urbina Malo, Julia Wagner, Willeke A'Campo, Luca Durstewitz, Rachele Lodi, Niek Jesse Speetjens, George Tanski, Michael Fritz, Hugues Lantuit, Gustaf Hugelius, and Andreas Richter

Climate change threatens the Earth’s biggest terrestrial organic carbon reservoir: permafrost soils. With climate warming, frozen soil organic matter may thaw and become available for microbial decomposition and subsequent greenhouse gas emissions. Permafrost soils are extremely heterogenous within the soil profile and between landforms. This heterogeneity in environmental conditions, carbon content and soil organic matter composition, potentially leads to different microbial communities with different responses to warming. The aim of the present study is to (1) elucidate these differences in microbial community compositions and (2) investigate how these communities react to warming.

We performed short-term warming experiments with permafrost soil organic matter from northwestern Canada. We compared two sites characterized by different glacial histories (Laurentide Ice Sheet cover during LGM and without glaciation), three landscape types (low-center, flat-center, high-center polygons) and four different soil horizons (organic topsoil layer, mineral topsoil layer, cryoturbated soil layer, and the upper permanently frozen soil layer). We incubated aliquots of all soil samples at 4 °C and at 14 °C for 8 weeks and analyzed microbial community compositions (amplicon sequencing of 16S rRNA gene and ITS1 region) before and after the incubation, comparing them to microbial growth, microbial respiration, microbial biomass and soil organic matter composition.

We found distinct bacterial, archaeal and fungal communities for soils of different glaciation history, polygon types and for different soil layers. Communities of low-center polygons differ from high-center and flat-center polygons in bacterial, archaeal and fungal community compositions, while communities of organic soil layers are significantly different from all other horizons. Interestingly, permanently frozen soil layers differ from all other horizons in bacterial and archaeal, but not fungal community composition.

The 8-week incubations led to minor shifts in bacterial and archaeal community composition between initial soils and those subjected to 14 °C warming. We also found a strong warming effect on the community compositions in some of the extreme habitats: microbial community compositions of (i) the upper permanently frozen layer and of (ii) low-center polygons differ significantly for incubations at 4 °C and 14 °C. Yet, the lack of a community change in horizons of the active layer suggests that microbes are adapted to fluctuating temperatures due to seasonal thaw events.

Our results suggest that warming responses of permafrost soil organic matter, if not frozen or water-saturated, may be predictable by current models. Process changes induced by short-term warming can be rather attributed to changes in microbial physiology than community composition.

This work is part of the EU H2020 project “Nunataryuk”.

How to cite: Rottensteiner, C., Martin, V., Schmidt, H., Hadžiabdić, L., Horak, J., Mohrlok, M., Urbina Malo, C., Wagner, J., A'Campo, W., Durstewitz, L., Lodi, R., Speetjens, N. J., Tanski, G., Fritz, M., Lantuit, H., Hugelius, G., and Richter, A.: Spatial variability shapes microbial communities of permafrost soils and their reaction to warming, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9891, https://doi.org/10.5194/egusphere-egu22-9891, 2022.

EGU22-10683 | Presentations | CR5.2

Organic matter decomposition and stabilization in Siberian tundra soils affected by thermokarst processes 

Christian Knoblauch, Janet Rethemeyer, Carsten W. Mueller, Pavel A. Barsukov, and Christian Beer

Thawing of permafrost like the wide spread  ice-rich Yedoma deposits in northern Siberia release large quantities of organic matter that may be decomposed to the greenhouse gases (GHG) CO2 and CH4. Since Yedoma deposits store up to 130 Pg of organic carbon (OC), the release of GHG from these thawing deposits might be of global relevance. The degradability of released organic matter is unclear. Current estimates on how fast the organic matter from thawing Yedoma may be transferred into CO2 range between 66% in one summer thaw season and 15% in 100 years. To reduce uncertainties about the degradability of Yedoma organic matter and to quantify the carbon pool that rapidly may be released a CO2, we incubated samples from different thermokarst affected soils and fractionated the organic matter by density fractionation. One set of soils originated from a vegetated thermokarst depression, the second set from a retrogressive thaw slump without vegetation. The total release of CO2 after 500 days at 4°C was significantly higher from soils of the vegetated thermokarst depression (4.0 ± 4.1% of OC) than from the retrogressive thaw slump (2.1 ± 0.9 % of OC), likely due to the input of fresh organic matter by the vegetation. Most of the organic carbon was bound to the mineral fraction (45 ± 24%), while the free particulate organic matter (fPOM) and the occluded organic matter (oPOM) contributed almost equally (26.8 ± 20.9% and 27.8 ± 12.0% of OC, respectively). The amount of carbon in the mineral fraction did not correlate with the CO2 formation, indicating stabilization of organic matter. Surprisingly, the oPOM fraction was stronger correlated with released CO2 than the fPOM fraction. However, the strongest correlation was found between CO2 production and the C/N ratio of total OC.

How to cite: Knoblauch, C., Rethemeyer, J., Mueller, C. W., Barsukov, P. A., and Beer, C.: Organic matter decomposition and stabilization in Siberian tundra soils affected by thermokarst processes, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10683, https://doi.org/10.5194/egusphere-egu22-10683, 2022.

EGU22-11774 | Presentations | CR5.2

The long-term Net Ecosystem Exchange of a remote Siberian high arctic site 

Geert Hensgens, Jorien Vonk, Roman Petrov, Sergey Karsanaev, Torifm Maximov, and Han Dolman

The arctic is warming at double the average global rate. This raises the concern that permafrost is beginning to thaw and could release large amounts of stored carbon, parts of which can be centuries old. If the total carbon release exceeds the carbon uptake the net ecosystem exchange (NEE) shifts from carbon sink to source, amplifying global warming. Here we present long-term eddy covariance (EC) data of a tundra ecosystem in northeast Siberia, showing the current NEE and its drivers in one of the most remote and coldest EC sites of the northern hemisphere. During the growing season the site is an overall carbon sink. The start of the carbon uptake quickly follows snowmelt and total growing season uptake is positively correlated with an earlier timing of the carbon uptake. While snowfall and the timing of snowmelt is highly variable no discernible trend can be seen in long-term data. In general, increased temperatures yield higher net carbon uptake during the growing season, although this effect levels off at roughly 20°C, likely due to the steadily decreasing solar radiation throughout the growing season. Because of the remoteness and extremely low temperatures, no winter measurements exist. However, machine learning gap filling suggests the site is a small net carbon source during most of the winter. This is in accordance with some of the recent findings at other sites and potentially offsets large parts of the growing season uptake. Thus, while the growing season initially might see increased terrestrial carbon uptake at higher regional temperatures, constraining yearly budgets with winter measurements is indispensable to get a full picture of changes in the total carbon budget of arctic tundra sites in Siberia.

How to cite: Hensgens, G., Vonk, J., Petrov, R., Karsanaev, S., Maximov, T., and Dolman, H.: The long-term Net Ecosystem Exchange of a remote Siberian high arctic site, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11774, https://doi.org/10.5194/egusphere-egu22-11774, 2022.

EGU22-11958 | Presentations | CR5.2

Past decomposition dynamics in Arctic terrestrial environments revealed by shotgun sedaDNA 

Kathleen Stoof-Leichsenring, Amedea Perfumo, Sichao Huang, Lars Harms, Luidmila Pestryakova, Boris Biskaborn, and Ulrike Herzschuh

Dynamics of litter decomposition in Arctic terrestrial environments control about carbon storage in permafrost soils and release of CO2 into the atmosphere. Climate warming can accelerate litter decomposition because degradational processes increase, due to shifts in types of labile organic matter available and the composition of decomposing taxa. How litter decomposition changed in former interglacial and glacial periods is rarely studied, because time-series data is lacking, but highly needed to foresee consequences of decomposition and carbon cycling for warming Arctic ecosystems. Innovative shotgun ancient DNA sequencing on sediment core samples provide a snapshot of entire components of past biotic ecosystems and deliver qualitative data on organismal and functional compositional shifts. Our study, for the first time, investigates sedimentary ancient DNA shotgun data in a 52ka sediment core from Far North-Eastern Russia, Lake Ilirney, that recovers former glacial and interglacial periods with pronounced shifts in taxonomic composition in terrestrial vegetation, microbial and fungal diversity. At the same time, the ancient DNA data provides information on gene functions, like degrading enzymes that support variation in functional composition through time. With this data, we aim to understand how litter quality, based on vegetational composition, alters the taxonomic (bacteria, fungi) and functional (enzymes involved in decomposition) community of decomposers. Our result show that glacial times are characterized by tundra vegetation, mainly herbs, accompanied with a dominance of cryophilic soil degraders and relatively lower abundance of enzymes degrading plant organic material. Interglacial periods (like late Holocene) are typified by shrub-tree and heath dominated vegetation with microbes more specialized to degrade plant material, which is supported by an increase of the relative abundance of cellulose and ligninolytic enzymes. Our preliminary results support that under future warming the expansion of shrubs and trees and the increase of specified degraders in Arctic terrestrial environments might lead to enhanced degradation of plant litter resulting in a potential increase of CO2 emissions.

How to cite: Stoof-Leichsenring, K., Perfumo, A., Huang, S., Harms, L., Pestryakova, L., Biskaborn, B., and Herzschuh, U.: Past decomposition dynamics in Arctic terrestrial environments revealed by shotgun sedaDNA, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11958, https://doi.org/10.5194/egusphere-egu22-11958, 2022.

EGU22-1095 | Presentations | BG3.7

Radiocarbon and Stable Isotope Constraints on the Sources and Cycling of Organic Carbon in Mackenzie Delta Lakes 

Julie Lattaud, Lisa Bröder, Negar Haghipour, Liviu Giosan, and Timothy Eglinton

The Arctic is undergoing accelerated changes in response to ongoing alterations to the climate system (Arctic report card 2019), and there is a need for local to regional scale records of past climate variability in order to put these changes into historical context. The Mackenzie Delta region (Northwestern Territories, Canada) is populated by numerous small shallow lakes. They are classified as no-, low- and high-closure lakes, reflecting varying degrees of connection to the river main stem, and as a result, have different sedimentation characteristics. As for much of the Arctic region, the Mackenzie Delta is expected to undergo marked environmental perturbations such as earlier melting of river ice. As a consequence, the annual flood pulse (freshet) may decline, potentially resulting in the disconnection of some lakes from the river, leading to their subsequent desiccation (Lesack et al., 2014; Lesack & Marsh, 2010). In contrast, abrupt permafrost thaw and enhanced thermokarst-related processes might lead to additional lake formation and deepening of already formed lakes.

In this study, we used sediment cores originating from several lakes within the Mackenzie Delta, representing the three types of connectivity to the river (Lattaud et al., 2021). Radiocarbon and stable carbon isotopic signatures of two groups of compounds - fatty acids and isoprenoid and branched glycerol dialkyl glycerol tetraethers (GDGTs) - are employed as tracers of carbon supply to, and cycling within the different lakes. Short-chain fatty acids as well as GDGTs serve as putative tracers of microbial production while long-chain fatty acids originate from higher terrestrial plants. The carbon isotopic signatures are used to distinguish between the relative importance of carbon inputs derived from in situ production, as well as from proximal (lake periphery) and distal (Mackenzie River) sources to the different lakes in the context of their degree of connectivity. Down-core molecular 14C measurements provide insights into the temporal evolution of the lakes, providing context for their response to past and future climate change.

How to cite: Lattaud, J., Bröder, L., Haghipour, N., Giosan, L., and Eglinton, T.: Radiocarbon and Stable Isotope Constraints on the Sources and Cycling of Organic Carbon in Mackenzie Delta Lakes, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1095, https://doi.org/10.5194/egusphere-egu22-1095, 2022.

EGU22-5257 | Presentations | BG3.7

The long-term  biogeochemical fate of C in Subarctic thawing peat plateaus 

Sigrid Trier Kjær, Nora Nedkvitne, Sebastian Westermann, and Peter Dörsch

Global warming causes permafrost to thaw at an unprecedented rate. In Northern Scandinavia, permafrost peat plateaus have been found to decline rapidly during the last decades, releasing old organic carbon to decomposition and runoff. Thawing peat plateaus can partly turn into thermokarst ponds, with consequences for the biogeochemical fate of the released carbon. We investigated carbon degradation of thawing permafrost peat by incubating permafrost peat and thermokarst sediments from three peat plateaus in Northern Norway. The samples were incubated field moist at 10oC for almost one year. Initial decomposition was dominated by CO2 production which strongly responded to oxygen availability, while methane (CH4) production was small. Methane production increased drastically after more than ten months, indicating that thawed permafrost peat has a considerable potential to produce CH4 after a time lag. The cumulative CH4 production of thawed permafrost peat after one year of incubation exceeded that of overlaying active layer peat by up to 641 times, illustrating the potential of thawing subarctic permafrost to act as an additional CH4 source. Comparing laboratory thawed permafrost peat to thermokarst peat revealed remarkable differences in CH4 production, with much higher CH4 production potentials in thermokarst sediments during the first months of incubation and in some samples exceeding CH4 production measured in permafrost peat after one year. This suggests that the potential to produce CH4 increases dramatically with thermokarst formation. Interestingly, thawed permafrost peat produced more DOC over the period of one year than gaseous C (CO2 and CH4), which suggests that hydrological conditions are key to the understanding of the fate of C released from thawing peat plateaus.

How to cite: Kjær, S. T., Nedkvitne, N., Westermann, S., and Dörsch, P.: The long-term  biogeochemical fate of C in Subarctic thawing peat plateaus, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5257, https://doi.org/10.5194/egusphere-egu22-5257, 2022.

EGU22-7422 | Presentations | BG3.7

Using O2/Ar ratios as a proxy for biological productivity determinations in an Arctic river. 

Karel Castro-Morales, Anna Canning, Sophie Arzberger, Samuel Sellmaier, Simon Redlich, Will A. Overholt, Nikita Zimov, Alina Marca, Jan Kaiser, Thomas Wichard, Kirsten Küsel, and Arne Körtzinger

The biogeochemical cycling of carbon in Arctic rivers is perturbed as more terrestrial organic carbon and nutrients are released upon active layer and permafrost thaw. The majority of the carbon dioxide (CO2) in rivers is emitted into the atmosphere, but it can also be utilized during photosynthesis, especially with more availability of nutrients, influencing the carbon flow and aquatic ecosystem metabolism. However, the timing and amount of photosynthetic primary production in Arctic rivers are unknown.

Water samples from the Kolyma River in Northeast Siberia were collected in June (late freshet) and August (summer) 2019. For the first time in an Arctic river, we measured biological oxygen supersaturations using the relative oxygen-to-argon ratio above equilibrium, Δ(O2/Ar), which is an indicator of the presence of biologically produced oxygen. This ratio is influenced in approximately equal parts by physical processes, while biological processes unilaterally influence the oxygen content.

In addition, we measured the partial pressure of CO2, p(CO2), dissolved oxygen and inorganic nutrients concentrations. Mass spectrometry was employed to chemically characterize the composition of dissolved organic matter (DOM) and better understand its origin. Microbial communities were elucidated using 16S and metagenomic based sequencing approaches.

In June, the oxygen saturation in turbid and warm waters (average: 14 °C) in the main river channel was on average 10% above atmospheric equilibrium. The p(CO2) values were well above equilibrium (2000 µatm). Unlike oxygen saturation, Δ(O2/Ar) was negative (undersaturation); thus, physical processes contributed most to the total oxygen supersaturation (up to 20%), apparently due to contributions of freshet cold gas-rich meltwater, while the net biological oxygen concentration was between –10 and –15%.

In August, the water was colder (3 °C drop), and the total oxygen was mostly undersaturated (up to –10%). However, lower p(CO2) and a decrease in the biological oxygen deficit (between 0 and –5%) indicated net biological oxygen input. At the confluence of the main river channel and some tributaries, an algal bloom was observed resulting in up to 6.4% supersaturation in Δ(O2/Ar) and p(CO2) near atmospheric equilibrium.

Concentrations of nitrate and silica were higher in August than in June. Dissolved phosphate concentrations were low at both sampling times, but apparently did not limit primary productivity. The microbial community composition varied greatly between sampling times, with differential shifts across the transect. Compared to June, the DOM pattern in August was less diverse in the river due to more stable stream conditions and defined hydrologic connectivity between land and river, promoting also nutrient supply for biological productivity.

Unlike anticipated, the O2/Ar ratios suggested that net biological oxygen production in the river did not profit during the late freshet, despite unlimited light and CO2 availability and warm temperatures. Contrastingly, the summer low-flow allowed for photosynthetically-driven oxygen production and CO2 uptake in some sites. We conclude that the O2/Ar ratios were essential for quantifying the contribution of biological production, and understand better the fate of CO2 in an Arctic river influenced by thawing permafrost, as well as the land-aquatic-continuum in the context of climate change.

How to cite: Castro-Morales, K., Canning, A., Arzberger, S., Sellmaier, S., Redlich, S., Overholt, W. A., Zimov, N., Marca, A., Kaiser, J., Wichard, T., Küsel, K., and Körtzinger, A.: Using O2/Ar ratios as a proxy for biological productivity determinations in an Arctic river., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7422, https://doi.org/10.5194/egusphere-egu22-7422, 2022.

EGU22-8694 | Presentations | BG3.7

Tracing the footprint of permafrost carbon supply to the Canadian Beaufort Sea 

Lisa Bröder, Julie Lattaud, Bennet Juhls, Antje Eulenburg, Taylor Priest, Michael Fritz, Atsushi Matsuoka, André Pellerin, Thomas Bossé-Demers, Daniel Rudbäck, Matt O'Regan, Dustin Whalen, Negar Haghipour, Timothy Eglinton, Paul Overduin, and Jorien Vonk

The Canadian Beaufort Sea receives large quantities of sediment, organic carbon and nutrients from rapid coastal erosion and permafrost degradation. In addition, the Mackenzie River, the largest North American Arctic river, discharges great amounts of freshwater, dissolved solids and suspended sediments to the Beaufort Sea. Current changes in these fluxes in response to the warming climate have uncertain consequences for the carbon budget on the shelf and in the deep ocean. To investigate the movement and transformation of organic matter along the land-ocean continuum, we collected water and surface sediment samples along five major transects across the Beaufort Sea during the 2021 expedition of the Canadian Coast Guard Ship Amundsen. Sampling locations span from shallow, coastal, sites with water depths ≤ 20 m, to shelf-break and deep-water settings on the continental slope (water depths of ≥1000 m). For this study, we use stable and radiocarbon isotopic (δ13C and Δ14C) analyses of dissolved inorganic (DIC), dissolved organic (DOC) and particulate organic carbon (POC) for surface and bottom waters, as well as surface sediments, in order to compare, contrast and constrain the relative source contributions and ages of these different forms of carbon. Our results will help to better understand the fate of permafrost organic matter in the marine environment and to ultimately improve assessments of the Canadian Beaufort Sea shelf as a carbon source or sink and its potential trajectory with ongoing environmental changes.

How to cite: Bröder, L., Lattaud, J., Juhls, B., Eulenburg, A., Priest, T., Fritz, M., Matsuoka, A., Pellerin, A., Bossé-Demers, T., Rudbäck, D., O'Regan, M., Whalen, D., Haghipour, N., Eglinton, T., Overduin, P., and Vonk, J.: Tracing the footprint of permafrost carbon supply to the Canadian Beaufort Sea, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8694, https://doi.org/10.5194/egusphere-egu22-8694, 2022.

EGU22-9445 | Presentations | BG3.7

Investigating hydrology and carbon cycling connections in peatland permafrost, northern Norway. 

Jacqueline Knutson, François Clayer, Peter Dörsch, Sebastian Westermann, and Heleen A. de Wit

Permafrost in northern Norway is characterized by peat plateaus and palsas and is among the fastest degrading permafrost areas in the world. Changes in these ecosystems with sporadic permafrost can be viewed as possible future states for currently stable permafrost regions. The thawing of permafrost at large scale has the potential to release stored carbon into atmospheric cycling and becomes a source of greenhouse gases. Lateral export of dissolved organic matter (DOM) from thawing permafrost could be an important pathway for loss of formerly stable organic matter (OM), and is controlled by temperature, soil moisture and local hydrology. We aim to study thermokarst ponds and the lateral flux of water, heat, organic carbon and greenhouse gases from a rapidly thawing permafrost peat plateau using high-frequency sensors, floating chambers, measurements of dissolved gases and water chemistry, and assessment of DOM. We analyzed water chemistry and extracted gas samples on 5 sampling campaigns of the Iškoras peat plateau located in the Finnmarksvidda in northern Norway between Sept 2020 and Oct 2021. We investigated production and consumption rates of gases at 3 campaigns by dark incubations between 36-50 hours. We present early data of the peat plateau and the hydrologically connected adjacent wetland.

We explore three hypotheses to better understand the role of hydrology and biogeochemistry in lateral transport of organic matter from the active peat plateau area to the larger catchment. First, there is seasonal changes in the lability of DOM in thermokarst ponds. Second, there is seasonal connection and transport of OM from the peat plateau to the wetland stream that connects to the catchment. Finally, we focus on identifying the areas in the landscape that are hotspots for greenhouse gas production and transport.

The thermokarst ponds were very acidic and high in dissolved gases and TOC compared with the wetland stream system. High emissions from the thermokarst ponds are a key source of CO2 and CH4. Aquatic processing of DOM and turbulence in streams both affect level of GHG emissions. There are also differences in parameters such as CO2 evasion and DIC concentration when there is connection of the wetland stream to the peat plateau. The early data indicate high rates of DOM processing and GHG production in the thermokarst ponds and high variability in DOM export from the peat plateau.

How to cite: Knutson, J., Clayer, F., Dörsch, P., Westermann, S., and de Wit, H. A.: Investigating hydrology and carbon cycling connections in peatland permafrost, northern Norway., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9445, https://doi.org/10.5194/egusphere-egu22-9445, 2022.

EGU22-9657 | Presentations | BG3.7

Particulate organic carbon composition and landscape characteristics in the Peel River Watershed, Canada 

Kirsi Keskitalo, Niek Speetjens, Paul Overduin, Sebastian Westermann, Frederieke Miesner, Torsten Sachs, Ingmar Nitze, Lisa Bröder, Negar Haghipour, Timothy Eglinton, and Jorien Vonk

Rapid warming of the Arctic is accelerating thaw of permafrost, which mobilizes organic carbon (OC). Remineralization of this carbon can contribute to further climate warming. The Peel River watershed is underlain by continuous and discontinuous permafrost and covers a diverse set of landscapes from wetlands to barren mountainous areas. Part of the watershed undergoes abrupt permafrost thaw that releases particulate OC (POC) to the fluvial system. In this study, we couple landscape characteristics to river POC to better understand its spatial variability and the changes imposed on the watershed by permafrost thaw. We sampled POC in July-August 2019 in the Peel River main stem and its tributaries (total n=~120) and used carbon isotopes and lipid biomarkers to characterize its composition and trace its sources. Our first results indicate a compositional diversity within the watershed as POC ranges between <0.1 and 2.1 mg L-1, δ13C-POC from -36.7 to -26.5‰ and Δ14C-POC from -906.4 to -43.5‰. Ongoing changes in the watershed can be traced within its waters, and may help us to decipher how it is changing and may change in the future.

How to cite: Keskitalo, K., Speetjens, N., Overduin, P., Westermann, S., Miesner, F., Sachs, T., Nitze, I., Bröder, L., Haghipour, N., Eglinton, T., and Vonk, J.: Particulate organic carbon composition and landscape characteristics in the Peel River Watershed, Canada, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9657, https://doi.org/10.5194/egusphere-egu22-9657, 2022.

EGU22-9760 | Presentations | BG3.7

Transport and Composition of Terrestrial Organic Matter at the Sediment-Water Interface of the Kara, Laptev and East Siberian Shelf Seas 

Lina Madaj, Kirsi Keskitalo, Örjan Gustafsson, Tommaso Tesi, Igor Semiletov, Oleg Dudarev, Jannik Martens, and Jorien Vonk

Around 65% of the Arctic coastline consists of permafrost soils which are currently thawing on an accelerating rate due to rising global air temperatures. The uncontrolled and rapid thaw of permafrost soils leads to increased coastal erosion and input of large amounts of organic carbon (OC) into the coastal ocean. Here, the OC can either be degraded (leading to production and emission of greenhouse gases that strengthen climate warming) or be sequestered over short or long timescales (attenuating climate warming). A major proportion of permafrost-derived OC quickly settles upon coastal release and therefore the sediment-water interface is the crucial zone for determining the trajectory of thawed OC and whether it deposits or remains in suspension. However, there is little data available from these so-called flocculation (i.e. nepheloid) layers, particularly in the Arctic shelf seas.

Here, we investigate the composition of suspended sediment within the flocculation layer at the sediment-water interface as well as the shallow surface sediments to shed light on the degradation state and fate of terrestrial OC, and additionally, characterize its lateral and vertical variability upon transport offshore. All samples were collected during ISSS-2020 expedition in late summer (Sept-Oct) of 2020 onboard R/V Akademik Msistlav Keldysh in the Kara Sea (n=2), Laptev Sea (n=8), and East Siberian Sea (n=4). We present first results of elemental, isotopic, and sedimentological analyses of suspended and surface sediments (C/N values, δ13C, Δ14C, surface area). With these data, we want to better understand how transport and degradation processes of terrestrial OC vary across the vast Siberian shelves.

How to cite: Madaj, L., Keskitalo, K., Gustafsson, Ö., Tesi, T., Semiletov, I., Dudarev, O., Martens, J., and Vonk, J.: Transport and Composition of Terrestrial Organic Matter at the Sediment-Water Interface of the Kara, Laptev and East Siberian Shelf Seas, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9760, https://doi.org/10.5194/egusphere-egu22-9760, 2022.

EGU22-10196 | Presentations | BG3.7

Landscape-related ground ice variability on the Yukon coastal plain inferred from computed tomography and remote sensing 

Philip Pika, George Tanski, Mathias Ulrich, Louis-Philippe Roy, Fabrice Calmels, Hugues Lantuit, Daniel Fortier, Michael Fritz, and Jorien Vonk

Warming in the Arctic causes strong environmental changes with degradation of permafrost (permanently frozen ground). Active layer deepening (gradual thaw) and permafrost erosion (abrupt thaw) results in the mobilization and lateral transport of organic carbon, altering current carbon cycling in the Arctic. Ground ice content is a crucial factor limiting our understanding and ability to determine the rates and dynamics of permafrost thaw and its impact on potential thaw subsidence rates, changes in lateral hydrological pathways and its driving mechanisms on a landscape scale.

In this study we investigate ground ice content and its characteristics across the most dominant landscape units of the Yukon coastal plain (Canadian Arctic), using two spatially and technically contrasting approaches. In our bottom-up approach, twelve permafrost cores were collected from moraine, lacustrine, fluvial and glaciofluvial deposits using a SIPRE corer (mean drilling depth of 2 m) in spring of 2019. Ground ice and sediment contents within polygon centers were analyzed and classified using computed tomography and image recognition software (k-means). Our top-down approach quantified ice-wedge volumes from remote sensing imagery tracing the circumference of polygon troughs over the same area. Preliminary results - extrapolated to the entire coastal plain - show that the ground-ice content in polygon centers vary significantly from massive ice in the polygon troughs (wedge-ice). Total ice volume was estimated around 80.2 vol.-%, of which 68.2 ± 18.1 vol.-% was attributed to ground ice in polygon centers, and 12 ± 3.1 vol.-% of the landscape is massive ice in wedge-ice along polygon troughs. Additionally, differences among and between landscape units are also substantial, with highest ice volume contents in moraines landscapes, where polygon centers contain 58.8 vol.-% ground ice and wedge-ice volume is 16.2 vol.-%), while the lowest ice contents are found in glacio-fluvial deposits (22.1 vol.-% resp. 9.1 vol.-%).

Our results reveal a higher average and a larger variability in ground ice contents than previously found, suggesting a need of both ground-based measurements and remote sensing imagery to further our understanding of the future landscape subsidence, but also to avoid a likely under- or overestimation associated with the chosen approach. We conclude that due to the high ground ice contents on the Yukon coastal plain, substantial changes of the permafrost landscape will occur under current warming trends. These will include subsidence, abrupt erosion, changes in hydrology and organic carbon mobilization, degradation and export processes, which will differ between landscape units.

How to cite: Pika, P., Tanski, G., Ulrich, M., Roy, L.-P., Calmels, F., Lantuit, H., Fortier, D., Fritz, M., and Vonk, J.: Landscape-related ground ice variability on the Yukon coastal plain inferred from computed tomography and remote sensing, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10196, https://doi.org/10.5194/egusphere-egu22-10196, 2022.

EGU22-11181 | Presentations | BG3.7

Rapid Permafrost Thaw Removes Nitrogen Limitation Rising the Potential of N2O Emissions 

Rica Wegner, Claudia Fiencke, Christian Knoblauch, Lewis Sauerland, and Christian Beer

Previous research was addressed to carbon emissions after permafrost thaw, but less attention was paid to changes in nitrogen availability and N2O emissions and in particular data from the Russian Arctic are scarce. Rise in water temperature and sea-level contribute to coastal erosion accelerating thaw rates and the release of dissolved nitrogen. Already 78% of the coastal regions of the Laptev Sea are affected by rapid permafrost thaw. This study estimates whether eroded Arctic coasts are hotspots for N availability and N2O emissions and to further understand the impact of NO3- leaching. Therefore, we estimated N-transformation rates and greenhouse gas (GHG) production (CO2, CH4, N2O) by incubating non-vegetated and revegetated soil samples from a retrogressive thaw slump in the Lena River Delta, Siberia. Within the thaw slump we found at exposed thaw mounds a domination of DIN over DON and an accumulation of NO3- with up 110 µg N (g DW)-1 within the growing season and in the presence of vegetation. Those results are contracting to what is normally reported in Arctic regions. Our incubations indicate that thaw mounds are hotspots for N-mineralization and N2O release (up to 390 ng N2O-N (g DW)-1) via denitrification while at the slump floor denitrification was substrate limited. Substrate limitation is rather caused by soil moisture and pH value than by functional limitation, since in our incubation N-mineralization could proceed in all samples. Simulated NO3- leaching removed the substrate limitation of the denitrification and converted the slump floor to a significant N2O hotspot (410 ng N2O-N (g DW)-1).

Our results emphasise that it is necessary to consider geomorphology and landscape processes to identify hotspots of gaseous and dissolved N loss. A higher availability of inorganic nitrogen in coastal zones will have effects on marine ecosystems and more in depth-studies are needed to characterise seasonality of nitrogen leaching by melt water and eroded sediments.

How to cite: Wegner, R., Fiencke, C., Knoblauch, C., Sauerland, L., and Beer, C.: Rapid Permafrost Thaw Removes Nitrogen Limitation Rising the Potential of N2O Emissions, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11181, https://doi.org/10.5194/egusphere-egu22-11181, 2022.

EGU22-11190 | Presentations | BG3.7

The size matters: aerobic methane oxidation in thermokarst lake sediments in Western Siberia 

Maxim Dorodnikov, Rinat Manasypov, Lichao Fan, Oleg Pokrovsky, Michaela A. Dippold, and Yakov Kuzyakov

Thermokarst lakes of permafrost peatlands in Western Siberia are among the most important sources of greenhouse gases (GHG) such as CO2 and CH4 because of current permafrost thawing due to climate change. Field measurements demonstrated the increase of dissolved GHG concentrations with the decreasing lake size due to higher concentration of coastal-derived organic C in water of small lakes. However, the size-dependent mechanisms of the GHG production and consumption (e.g. CH4 oxidation) in the sediments of these lakes remain poorly known. We estimated aerobic CO2 production and CH4 oxidation potentials based on natural 13C abundance and 13C labeling in two layers of upper 20 cm sediments of three thermokarst lakes: small (~ 300 m2), medium (~ 3000 m2) and large (~ 1 km2). We hypothesized that i) specific CO2 production (per gram of sediment) decreases with increasing lake size, but CH4 oxidation increases, and ii) both processes are more intensive in the upper 10 cm of sediments than in deeper 10–20 cm, due to naturally occurring O2 gradients and the available C. As expected, CO2 production in the upper layer was 1.4–3.5 times higher than in the deeper layer and the rate of production increased from large (170 nmol CO2 g-1 d.w. h-1) to medium (182) and small (234) lakes. In contrast to CO2, CH4 oxidation in the uppermost sediment layer was similar between lakes, while the deeper layer in the large lakes had 12- and 73-fold higher oxidation rates (5.1 nmol CH4-derived CO2 g-1 d.w. h–1) than in small and medium lakes, respectively. This was attributed to the fact that the O2 concentration in the water of large lakes is higher than in smaller lakes due to the intense turbulence caused by wind and waves. Due to the ongoing and future thawing of permafrost, smaller lakes will increase in size, so that a large part of the CH4 produced in the sediments will be oxidized. However, this process can be (over)compensated by the increased formation of new small lakes. From an ecological perspective, the sediments of shallow thermokarst lakes in the discontinuous permafrost zone of Western Siberia could oxidize up to 0.48 Tg C as CH4 in the summer period, with the largest contribution coming from the large lakes. This confirms the key role of the thermokarst lake ecosystems as a global hotspot of GHG turnover.

Acknowledgement. This work was supported by RSF grant No. 21-77-10067 and the German Academic Exchange Service (DAAD).

How to cite: Dorodnikov, M., Manasypov, R., Fan, L., Pokrovsky, O., Dippold, M. A., and Kuzyakov, Y.: The size matters: aerobic methane oxidation in thermokarst lake sediments in Western Siberia, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11190, https://doi.org/10.5194/egusphere-egu22-11190, 2022.

The Canadian Beaufort Sea coastline consists of permafrost, permanently frozen soils, that store large amounts of organic carbon (OC). Rising temperatures in the Arctic will lead to thaw of these permafrost soils as well as enhanced coastal erosion. The trajectory of thawing coastal carbon upon thaw will determine the degree of breakdown and greenhouse gas emission, impacting climate warming. However, we still have a poor understanding of the marine fate of sediments and OC from eroding arctic coastlines.

In order to obtain more insight into the fate of the eroding material, we will use hydrodynamic fractionation on a variety of actively eroding coastal cliffs (parent material). Hydrodynamic fractionation accounts for the sediment sorting of particles when exposed to different energy conditions such as waves. With this technique we will fractionate based on density and grainsize to mimic the route in the marine system. Current estimates of sediment and OC input from arctic coastal erosion are only based on bulk measurements.

Samples were collected from eight sites (n=5 at each site) with a wide spatial and geological variation across the Canadian Beaufort Sea. These sites range from peaty and flat islands to muddy slumps and sandy locations. For all sites, parent material was collected onshore, fractionated and separated in five fractions based on density (cut-off 1.8 g/mL) and grainsize (cut-offs 38, 63, and 200mm). All fractions will be analysed for geochemical properties (total OC, total nitrogen, δ13C, and D14C, biomarkers and lipids) in order to determine the quantity and quality of the organic matter. Distribution of sediment fractions based on weight shows large variability between sites (e.g. low density fraction between 2-13% and high density between 9-50% with grainsize 63-200mm) as well as within sites, depending on the characteristics of the coast. Using the spatial variability of these fractions in combination with coastal characteristics assessed with GIS techniques we will attempt to upscale for the Canadian Beaufort Coast. This will hopefully improve our insights on the type and composition of parent material which is released into the marine system as a source of carbon.

How to cite: van Crimpen, F., Madaj, L., Whalen, D., Tesi, T., and Vonk, J.: The hydrodynamic potential of eroding arctic permafrost coasts: fractionation of permafrost parent material in the Canadian Arctic to determine its fate in the marine system, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11429, https://doi.org/10.5194/egusphere-egu22-11429, 2022.

EGU22-12454 | Presentations | BG3.7

Nitrogen isotopic inventory of the Lena River Delta 

Tina Sanders, Claudia Fiencke, Bennet Juhls, Olga Ogneva, Jens Strauss, Robyn Tuerena, and Kirstin Dähnke

Permafrost-affected soils around the Arctic Ocean contain a large reservoir of organic matter including nitrogen, which partly reach the river after thawing, degradation and erosion of permafrost. After mobilization, reactive remineralised nitrogen is either used for primary production, microbial processing or is simply transported to coastal waters. With analyzing the natural abundance of the stable isotope composition in different form of nitrogen components, we aim to unravel the balance of transport and biological nitrogen turnover processes like remineralization or nitrification and in consequent the fate of the nitrogen. 

We have analyzed soil, suspended matter and dissolved inorganic and organic nitrogen for their contents and 15N stable isotope composition to create a baseline for a nitrogen inventory of the Lena River Delta in 2019/2020. We used samples from two transect cruises through the delta in March and August 2019, a monitoring program at Samoylov Island in the central delta (2019/2020), and different soil type samples from Samoylov and Kurunghak Island. Our aim was to determine nitrogen sources, sinks and transformation processes during transport in river and delta.

Our data shows that in winter the nitrogen transported from the delta to the Laptev Sea were dominated by dissolved organic nitrogen (DON) and nitrate, which occur in similar amounts of approx. 10 µmol/L. The load of nitrate, during the transect cruise, increased slightly in the delta, while we observed no changes to the isotope values of DON and nitrate indicating a lack of biological activity in the winter season and the lateral transport from soils was the likely source. In summer, nitrogen was mainly transported as DON and particulate nitrogen in the suspended matter and nitrate was mainly below 1µmol/L. 

The nitrogen stable isotope values of the different nitrogen components ranges between 0.5 and 4.5‰, and were subsequently enriched from the soils via suspended particulate matter (SPM)/sediment and DON to nitrate. These light values indicate soil nitrogen mainly originates from atmospheric nitrogen fixation. During transport and remineralization, biogeochemical recycling via nitrification and assimilation by phytoplankton led to an isotopic enrichment in summer. In the coastal waters of the Laptev Sea, the exported river waters are slowly mixed with marine nitrate containing waters from the Arctic Ocean, and a part of the riverine organic nitrogen is buried in the sediments.

 Our data provides a baseline for isoscape analysis and can be used as an endmember signal for modeling approaches.  

How to cite: Sanders, T., Fiencke, C., Juhls, B., Ogneva, O., Strauss, J., Tuerena, R., and Dähnke, K.: Nitrogen isotopic inventory of the Lena River Delta, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12454, https://doi.org/10.5194/egusphere-egu22-12454, 2022.

EGU22-12622 | Presentations | BG3.7

Groundwater discharge as a driver of methane emissions from Arctic lakes 

Carolina Olid, Valentí Rodellas, Gerard Rocher-Ros, Jordi Garcia-Orellana, Marc Diego-Feliu, Aaron Alorda-Kleinglass, David Bastviken, and Jan Karlsson

Methane (CH4) emissions from Arctic lakes are significant and highly sensitive to global warming. Groundwater inputs to lakes could be substantial and constitute a link between CH4 from melting permafrost to emissions via lakes. Yet, groundwater CH4 inputs and associated drivers are hitherto poorly understood. In this study, we disclose temporal and spatial patterns of groundwater CH4 inputs to Arctic lakes in the discontinuous permafrost zone in northern Sweden. Results show that groundwater discharge is a major source of CH4 to the lakes. Spatial patterns across lakes suggest that groundwater inflow rates are primarily related to lake morphology and land cover. Groundwater CH4 inputs and atmospheric CH4 emissions from lakes were higher in summer than in autumn, reflecting changes in hydrological and biological drivers. This study reveals the large role and the drivers of groundwater discharge in lake CH4 cycling, which may be further exacerbated with the ongoing climate change, as rising temperatures, increasing precipitation, and permafrost thawing are likely to increase groundwater CH4 inputs to lakes.

How to cite: Olid, C., Rodellas, V., Rocher-Ros, G., Garcia-Orellana, J., Diego-Feliu, M., Alorda-Kleinglass, A., Bastviken, D., and Karlsson, J.: Groundwater discharge as a driver of methane emissions from Arctic lakes, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12622, https://doi.org/10.5194/egusphere-egu22-12622, 2022.

EGU22-12968 | Presentations | BG3.7

Inferring permafrost thermal properties from freeze-thaw column experiments and numerical modelling 

Jelte de Bruin, Victor Bense, and Martine van der Ploeg

Cold-regions contain a vast pool of organic carbon in permafrost, which is currently immobilized. As the global air temperatures rise, permafrost active layer depths are increasing. The deepening of the active layer reactivates groundwater transport processes, leading to the release of solutes such as dissolved carbon to streams and the atmosphere. In order to make predictions of the rates of permafrost thaw based upon numerical modeling, we need accurate data on active layer thermal properties.

Active layer thermal properties, thermal conductivity and heat capacity, are strongly coupled to geological properties such as water content, and organic matter content and are therefore highly heterogenous in natural systems. Furthermore, the effective thermal properties vary as a function of temperature through ice-content, especially across the freeze-thaw interval near 0 oC. Direct in-situ observations of active-layer thermal properties are rare because in-situ measurements involves sampling of frozen samples and analysis in a laboratory.

This study uses soil column (1 m high x 0.31 m diameter) experiments to investigate the relation between soil physical properties and thermal properties. A total of nine samples were synthesized using a range of grain sizes and organic matter contents, and were fully saturated with water. The columns were insulated on the sides and top, aiming to create a fully 1D thermal system allowing only vertical heat transport. The columns are subjected to one freeze-thaw cycle, lasting about 20 weeks. Resulting temperature observations were analyzed using a numerical heat transfer model. By fitting the temperature observations to the heat transfer model, thermal properties can be inferred. Initial data shows differences in heat propagation through the soil column, indicating differences in thermal conductivity and heat capacity as a result of varying soil grain size and organic matter content. This research will help to link permafrost soil physical properties to thermal properties, and increase understanding at the dynamic freeze-thaw interval.

How to cite: de Bruin, J., Bense, V., and van der Ploeg, M.: Inferring permafrost thermal properties from freeze-thaw column experiments and numerical modelling, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12968, https://doi.org/10.5194/egusphere-egu22-12968, 2022.

EGU22-532 | Presentations | SSP3.11

Recognising cold-based glaciation in the rock record: striated bedrock surfaces of the > 540 million year old Luoquan Formation of China 

Thomas Vandyk, Xiaoshuai Chen, Yuchong Wang, Zhenrui Yang, Hongwei Kuang, Yongqing Liu, Guanghui Wu, Meng Li, Bethan J. Davies, Graham A. Shields, and Daniel P. Le Heron

When preserved from deep time glaciation, subglacially striated bedrock surfaces allow the interpretation of past ice characteristics that are often elusive from the study of sediments alone. Salient amongst these is the thermal regime, which has a profound influence upon ice behaviour and consequent sediment erosion, transport and deposition. Typically, striated bedrock surfaces are linked to ice at its pressure-temperature melting point, indicating a locally warm-based thermal regime. Conversely, a cold-based thermal regime is defined by ice frozen to the substrate and is linked to minimal erosion. Cold-based erosional forms have been identified in Antarctica but their recognition is next to impossible if imprinted upon a surface previously or subsequently affected by warm-based erosion (e.g. striation). In the ancient record this is especially problematic, as it is typically only through the recognition of characteristic warm-based features that a surface can be confirmed as subglacial at all. Consequently, it is likely that there is an observational bias in the rock record toward warm-based over cold-based ice. This study, through careful geomorphologic analysis of unusually well preserved striated surfaces of the North China Craton from the Ediacaran Period (c. 635 – 540 Ma), presents rare examples that record dominant cold-based and more limited warm-based erosion on the same subglacial surface. It is hoped that this approach may benefit other workers interested in identifying cold-based as well as the more obvious warm-based subglacial conditions from the record of deep time glaciation.

How to cite: Vandyk, T., Chen, X., Wang, Y., Yang, Z., Kuang, H., Liu, Y., Wu, G., Li, M., Davies, B. J., Shields, G. A., and Le Heron, D. P.: Recognising cold-based glaciation in the rock record: striated bedrock surfaces of the > 540 million year old Luoquan Formation of China, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-532, https://doi.org/10.5194/egusphere-egu22-532, 2022.

EGU22-727 | Presentations | SSP3.11

Forward modelling of the completeness and preservation of Quaternary palaeoclimate signals recorded by ice-marginal moraines 

Ann V. Rowan, David Lundbek Egholm, and Chris D. Clark

Glaciers and ice sheets fluctuate in response to climatic change and often record these changes by building ice-marginal (terminal and lateral) moraines. Therefore, glacial landscapes are a potentially valuable archive of terrestrial palaeoclimate change. Typically, a cooling climate causes glaciers to expand and warming causes glaciers to shrink. However, the influence of high-relief mountainous topography on glacier dynamics complicates this behaviour, such that ice-marginal moraines are not always a straightforward palaeoclimate indicator. We used a higher-order ice-flow model to simulate change in glacier erosion, extent, and thickness in the response to climatic change and the resulting formation and preservation of moraines in a synthetic mountain landscape. Our results show that the rate of palaeoclimatic change relative to the glacier’s response time determines the geometry, number and position of ice-marginal moraines. However, glaciers can build distinct moraines in the absence of climate change, and the distance from the glacial maximum may not represent the chronological order of moraine formation. While moraines can be preserved despite erosion during subsequent glaciations, moraine sequences frequently contain gaps that could be misinterpreted as representing more stable palaeoclimates. These results provide theoretical understanding for the interpretation of glacial landforms both in the field and from satellite data (e.g. digital terrain models) to understand Quaternary climate change.

How to cite: Rowan, A. V., Egholm, D. L., and Clark, C. D.: Forward modelling of the completeness and preservation of Quaternary palaeoclimate signals recorded by ice-marginal moraines, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-727, https://doi.org/10.5194/egusphere-egu22-727, 2022.

EGU22-4196 | Presentations | SSP3.11

Paleoclimate archive potential of the possibly former sub-glacial Lake Manicouagan (Canada) 

Kai-Frederik Lenz, Catalina Gebhardt, Patrick Lajeunesse, Arne Lohrberg, Felix Gross, and Sebastian Krastel

Lakes in formerly glaciated areas are prone to provide valuable paleoclimate archives, which contain information about the glacial processes influencing the region in which the lakes formed. The eastern Canadian provinces Québec, Newfoundland and Labrador are key areas to understand climate changes since the Cenozoic. Lake Manicouagan is a 214 Myr old impact crater lake located in the province of Québec, 220 km north of the Saint Lawrence River. This area was directly affected by the waxing and waning of the Laurentide Ice Sheet at least during the last glaciation. Here, we present high-resolution seismic data imaging the glacially excavated thalweg of Lake Manicouagan and a sedimentary sequence filling it. On that basis, we assess the potential of this sedimentary sequence as a paleoclimate archive. Our high-resolution seismic data reveal a varying shape of the valley throughout the lake. A U-shape of the valley suggests that grounded glacial erosion excavated the thalweg, whereas a narrow V-shape in some areas is indicative of pressurized subglacial meltwater erosion. We discuss three different scenarios regarding the deposition of sediment and the evolution of Lake Manicouagan during the Upper Pleistocene and Holocene: (1) the entire sedimentary sequence was deposited during and after the final retreat of the Laurentide Ice Sheet or (2) the deposits are the result of multiple glacial-interglacial cycles or (3) Lake Manicouagan was a subglacial lake during the last glaciation. We favor the third scenario because it explains missing interglacial units and erosional ice contact surfaces in the sedimentary sequence. Lake Manicouagan holds a valuable paleoclimate archive regardless of the scenario. Either the lake is a high-resolution paleoclimate record of the last 7.5 kyr, or the lake sediments contain pre-deglacial information, located in an area which was directly affected by advance and retreat of the Laurentide Ice Sheet during the Wisconsin glaciation.

How to cite: Lenz, K.-F., Gebhardt, C., Lajeunesse, P., Lohrberg, A., Gross, F., and Krastel, S.: Paleoclimate archive potential of the possibly former sub-glacial Lake Manicouagan (Canada), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4196, https://doi.org/10.5194/egusphere-egu22-4196, 2022.

EGU22-4736 | Presentations | SSP3.11

The provenance of the sediment in an overdeepening and its implications for the distribution of glacier ice in the Bern area (CH) 

Michael Schwenk, Fritz Schlunegger, Laura Stutenbecker, Dimitri Bandou, and Patrick Schläfli

The extent and distribution of glaciers on the Swiss Plateau during the Last Glacial Maximum (LGM) can be determined from the geological record. However, similar reconstructions for the glaciations that preceded the LGM are far more difficult to be made due to the inaccessibility of suitable sedimentary records. Here, we explored Quaternary sediments which were deposited during the MIS 8 glaciation at least 250 ka ago, and which were recovered in a drilling that was sunk into an overdeepening W of Bern (Switzerland). We analyzed the sediment-bulk chemical composition of the deposits to investigate the supply of the material to the area by either the Aare Glacier or the Valais Glacier. The potential confluence of these two glaciers in the Bern area makes this location ideal for such an analysis. We determined the sediment-bulk chemical signal of the various lithological units in the central Swiss Alps where the glaciers originated, which we used as endmembers for our provenance analysis. We then combined the results of this fingerprinting study with the existing information on the sedimentary succession and its deposition history. This sedimentary suite is composed of two sequences A (lower) and B (upper), both of which comprise a basal till that is overlain by lacustrine sediments. The till at the base of Sequence A was formed by the Aare Glacier. The overlying lacustrine deposits of an ice-contact lake were mainly supplied by the Aare Glacier. The basal till in Sequence B was also formed by the Aare Glacier. The provenance signal points towards a simultaneous material supply by both the Aare and the Valais Glaciers during the formation of the lacustrine sediments in Sequence B. We use these findings for a paleogeographic reconstruction. During the time when Sequence A and the basal till in Sequence B were deposited, the Aare Glacier dominated the area. This strongly contrasts with the situation during the LGM, when the Aare Glacier was deflected by the Valais Glacier towards the NE. Probably, the Valais Glacier was less extensive during MIS 8. However, part of the lacustrine sediments deposited within Sequence B could only have been supplied by the Valais Glacier, indicating that the glacier did not cover the study area, yet had been in close proximity to the study area. We thus postulate that during the deposition of Sequence B both the Aare Glacier and the Valais Glacier were connected to this lake that had formed at the foot of these glaciers. These glaciers potentially also dammed this lake. In conclusion, we could outline a detailed scenario of sediment supply to the investigated overdeepening during the MIS 8 glacial period based on the provenance and sedimentological data, and that glaciers were arranged in a different way than during the LGM.

How to cite: Schwenk, M., Schlunegger, F., Stutenbecker, L., Bandou, D., and Schläfli, P.: The provenance of the sediment in an overdeepening and its implications for the distribution of glacier ice in the Bern area (CH), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4736, https://doi.org/10.5194/egusphere-egu22-4736, 2022.

EGU22-5362 | Presentations | SSP3.11

Geometry of overdeepenings obtained through three-dimensional gravity modelling 

Dimitri Bandou, Fritz Schlunegger, Edi Kissling, Urs Marti, Michael Schwenk, Patrick Schläfli, Guilhem Douillet, and David Mair

We investigated the formation mechanism of tunnel valleys, by producing 3D models of bedrock topography using gravimetry. We obtained the cross-sectional geometry of tunnel valleys in the Swiss foreland, near Bern. The combination of information about the densities of the sedimentary fill and of the bedrock together with borehole data and gravity surveys along profiles across the valleys served as input for our 3D gravity modelling software, Prisma. This finally allowed us to model the gravity effect of the Quaternary fill of the overdeepenings and to produce cross-sectional geometries of the overdeepenings. We focused on two sections situated in the Gürbe valley and in the Aare valley. We determined a density of 2’500 kg/m3 for the Upper Marine Molasse bedrock, and with Prisma we obtained a bulk density of kg/m3 for the Quaternary infill. Our gravity surveys across the valleys yielded a maximum residual anomaly of -2.9 mGal for the Gürbe valley and -4.1 mGal for the Aare valley. The application of our Prisma model showed that these anomalies can be explained by Quaternary suites with a thickness of 160 m and 235 m for the infill of the Gürbe and Aare valleys, respectively. The high-resolution information about the cross-sectional geometry of the tunnel valley flanks, from the application of Prisma, allowed us to infer a two-step formation process of the overdeepened trough.  A first glaciation, during MIS 6 or before, would have deepened the trough. And a second glaciation, during the Last Glacial Maximum  (MIS 2), would have widened the valleys. We explain this pattern by the differences between the ice thicknesses of the LGM and MIS 6 glaciers and by the relatively low erodibility of the Upper Marine Molasse bedrock. The Molasse units indeed comprise tender and porous sandstones and offer a lower erosional resistance than the Quaternary infill, which consists of cohesive and thus competent glacio-lacustrine marls. This probably offered ideal conditions for the thick and thus erosive MIS 6 glaciers to erode deeply into the Molasse bedrock. In contrast, the lacustrine fill of this trough possibly prevented the thinner and thus less erosive LGM or MIS 2 glaciers to further incise the bedrock. The consequence was that erosion of the LGM glaciers mainly occurred on the lateral sides, thereby resulting in a widening of the tunnel valleys. Finally, we apply this approach to the remaining gravity profiles, to create a 3D model of the geometry of the overdeepening network near Bern.

How to cite: Bandou, D., Schlunegger, F., Kissling, E., Marti, U., Schwenk, M., Schläfli, P., Douillet, G., and Mair, D.: Geometry of overdeepenings obtained through three-dimensional gravity modelling, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5362, https://doi.org/10.5194/egusphere-egu22-5362, 2022.

EGU22-7472 | Presentations | SSP3.11

GIS-based morphostratigraphic analysis of glaciofluvial terrace hypsometry in the North Alpine Foreland using R 

Thomas Pollhammer, Bernhard Salcher, Florian Kober, and Gaudenz Deplazes

The morphology of glaciofluvial terrace staircases is controlled by the interactions of fluvio- and geodynamic factors. Prerequisites for their formation are periodically aggradating rivers (e.g. associated with Quaternary cold periods), in combination with tectonic uplift (e.g. Bridgland & Westaway, 2008). Glaciation can thereby remarkably pronounce this effect where the end of a glacial cycle is typically associated with immediate incision. Abandoned plains represent then a morphologic snapshot, covering a very short period of time. Consequently, they can be highly suitable to act as a morphostratigraphic marker for climatic and geodynamic processes. Especially in this context, regional scale systematic analyses appear very promising and have so far not been subject to intense research.

We present a GIS-based morphostratigraphic method and toolset, using the R programming environment. The toolset can be used to project the full elevation information of a high-resolution digital elevation model (DEM) of a river channel (incl. full valley flanks and/or unconfined outwash plains), to 2D (paleo-) river long-profiles, together with other geodata, if available (e.g. existing terrace maps and outcrop information). DEM data is displayed semitransparently in the profile view, making terrace-tops stand out as more or less dark and flat lines. This allows plausibility/quality analysis of existing maps, as well as mapping procedures. Furthermore, on the basis of the projected data, DEM pixels of corelated terraces can be statistically evaluated and models (regression functions) fitted, which allows the reconstruction and measurement of parameters of paleo-riverbeds (e.g. relative height above local base-level, local slope, concavity).

We applied this method in the North Alpine Foreland to an extensive terraced landscape, representing a large age span until up to Early Pleistocene age, as well as abundant data on terrace stratigraphy (i.e. from geological mapping, drilling campaigns and relative and absolute age constrains), including high resolution digital elevation models. Despite the long history of Quaternary research in the region, a consistent stratigraphic model of the Quaternary period is currently missing. In fact, the last mountain range scale model was proposed more than 110 years ago by Penck and Brückner (1909). Local findings by geologic surveys (Switzerland, Germany and Austria) unveil strong inconsistencies and an updated model is highly needed.

Based on a new code in the R programming environment we evaluate existing stratigraphic models and show how glacio- and geodynamic implications can be statistically derived from terrace hypsometry.

References:

Bridgland, D., Westaway, R. (2008): Climatically controlled river terrace staircases: A worldwide Quaternary phenomenon. Geomorphology 98, S.285-315. Elsevier. doi:10.1016/j.geomorph.2006.12.032

Penck, A., & Brückner, E. (1909): Die Alpen im Eiszeitalter. Leipzig: Tauchnitz. 

How to cite: Pollhammer, T., Salcher, B., Kober, F., and Deplazes, G.: GIS-based morphostratigraphic analysis of glaciofluvial terrace hypsometry in the North Alpine Foreland using R, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7472, https://doi.org/10.5194/egusphere-egu22-7472, 2022.

EGU22-8375 | Presentations | SSP3.11

Glacial erosion rates across the Alps derived from in situ 10Be in river sediments 

Julien Charreau, Apolline Mariotti, Pierre-Henri Blard, Sylvain Breton, and Samuel Toucanne

Glaciers are strong agents of erosion and play a key role in the evolution of mountain ranges. In order to improve our understanding of the influence of glacial erosion dynamics on landscape evolution and mountain building, it is essential to quantitatively constrain glacial erosion rates across multiple topographic and climatic settings.

In situ cosmogenic 10Be concentrations measured in river sediments have been widely used over the last twenty years to infer denudation rates integrated at the catchment scale. This approach was mainly applied to fluvial settings because in this case, the 10Be concentration of detrital sediments is a simple function of denudation. In regions covered by glaciers, river sediments result from a mixture of material produced in the pure fluvial domain and sediments produced by glacier erosion. The 10Be concentration measured in such settings thus results from the mixture of these two sources. Here, we use a simple mass conservation approach to estimate pure glacial erosion rates from the 10Be concentration measured in watersheds combining glacial and fluvial domains. In practice, we first established an empirical power-law linking denudation rates to the mean slope of non-glaciated catchments. For each partially glaciated catchment, this law was used to constrain the pure fluvial 10Be end-member using slopes derived from a DEM. Finally, this input was used to compute the pure glacial erosion rate required to satisfy the 10Be concentration measured in rivers. This new approach was applied to 2 different datasets:

  • Present-day glacier erosion in the Alps. We apply this approach to determine the erosion of modern glaciers across the entire Alps. We used previously published 10Be concentration measured in river sediments covering partially glaciated watersheds. The fluvial denudation power law was constrained from 148 fluvial – glacier free catchments. We then selected 11 watersheds with glaciers bigger than 5 km2 and a glacial cover of at least 5% of their total surface. The so-obtained glacial erosion rates from these 11 watersheds range from 0.2 to 1.5 mm.yr-1. Finally, we compare those values to satellite-derived glaciers' sliding velocity which is thought to be the main factor controlling glacial erosion rates.

 

  • Paleo-erosion in the Var (Southern Alps) setting over the last 75 ka. We apply the same approach to the Var catchment (Southern French Alps) to estimate past glacial erosion rates over the last 75 ka (Mariotti et al., 2021). This basin has been deglaciated since the Holocene and 10Be modern denudation rates were estimated across 9 sub-basins (Mariotti et al., 2019) providing the required dataset to estimate the local fluvial denudation power law. 10Be concentrations were measured in two 75 ka sedimentary cores drilled in the Mediterranean Sea when the Var catchment was previously glaciated (Mariotti et al., 2021). Our findings show that during the LGM, the pure glacial erosion rates were 3 times higher (1.5 +/- 1 mm.yr-1) than during MIS 3-4 (0.4 +/- 0.5 mm.yr-1). This suggests a nonlinear forcing of climate on glacial erosion, mainly controlled by the interplay between glacier velocity, climate, and basin topography.

How to cite: Charreau, J., Mariotti, A., Blard, P.-H., Breton, S., and Toucanne, S.: Glacial erosion rates across the Alps derived from in situ 10Be in river sediments, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8375, https://doi.org/10.5194/egusphere-egu22-8375, 2022.

EGU22-9723 | Presentations | SSP3.11

Feasibility study of quartz ESR dating for sediments in northern Switzerland 

Sumiko Tsukamoto, Gaudenz Deplazes, and Marius Buechi

Fluvial and glaciofluvial sediments in the Northern Alpine Foreland record detailed history of the Quaternary glaciations and climatic changes. These sediments and associated landscapes have been typically classified using the Penck and Brückner’s concept for four terrace levels; the so-called Niederterrasse, Hochterrasse, Tiefere Deckenschotter and Höhere Deckenschotter. Sediments of Niederterrasse and Hochterrasse were dated using quartz and feldspar luminescence dating, however, older sediments (Tiefere and Höhere Deckenschotter) are beyond the upper limit of the method and are difficult to date. In this study we tested the feasibility of quartz electron spin resonance (ESR) dating using the Ti centre for sediments from northern Switzerland.

Eight samples were used in this work; these are two modern river sands from a bank (GRUE1) and a sand bar (GRUE0) of the River Thur at Grüt, fluvial-lacustrine (BER6) and fluvial-fluviglacial (BER3) sediments from Beringen, which have OSL dates of ~25 and ~150 ka, Tiefere Deckenschotter from Hungerbol (HUNE2), and Höhere Deckenschotter from Irchel Hasli (HASE1, HASE2) and from Irchel Steig (STEE2). Quartz ESR dating was conducted using the single aliquot regenerative dose protocol using three aliquots each for the Ti-Li and Ti-H centres. Dose recovery tests were also performed using two young samples (GRUE1 and BER6) by adding ~1000 Gy on top of the natural aliquots. Dose recovery ratios were satisfactory for both samples and for both Ti-Li and Ti-H centres. The apparent ages of samples from Tiefere and Höhere Deckenschotter are in stratigraphic order, ranging from 530 to 890 ka for the Ti-Li centre. However, the residual dose obtained from modern and young samples were significant, with a mean of ~750 Gy for the Ti-Li centre and ~200 Gy for the Ti-H centre. These residual doses are corresponding to ~70 % and ~40 % of the natural equivalent dose of the Deckenschotter samples, which makes the evaluation of actual burial dose very difficult. Ages corrected for the residual dose obtained from modern and young samples result in unreasonably young ages between ~150 and ~320 ka.

How to cite: Tsukamoto, S., Deplazes, G., and Buechi, M.: Feasibility study of quartz ESR dating for sediments in northern Switzerland, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9723, https://doi.org/10.5194/egusphere-egu22-9723, 2022.

EGU22-10224 | Presentations | SSP3.11

Major deglaciation during the Late Glacial in coastal regions of Greenland 

Julia Nieves Garcia de Oteyza de Ciria, Marc Oliva, David Palacios, Jose Maria Fernández-Fernández, Irene Schimmelpfennig, Nuria Andrés, Dermot Antoniades, Laetitia Léanni, Vincent Jomelli, Vincent Rinterknecht, Tim Lane, and Aster Team

The Greenland Ice Sheet (GrIS) is a key component of the global climate system. However, our current understanding of the spatio-temporal oscillations and landscape transformation of the GrIS margins since the last glacial cycle is still incomplete. This work aims to study the deglaciation in the Zackenberg Valley, Greenland, and the origin of the derived glacial landforms. In order to reconstruct the spatial extent and geometry of past glacial phases we carried out extensive fieldwork and high-detailed geomorphological mapping, together with cosmic-ray exposure (CRE) dating to samples from erosive and depositional glacial landforms. Erratic boulders dispersed across the summits suggest that Late Quaternary glaciers filled the valleys and fjords during periods of maximum ice expansion. As glacier thickness decreased, the Zackenberg glacier was confined in the interior of the main valley, leaving several lateral moraine ridges along the slopes. The deglaciation started by ~13.7-12.5 ka and accelerated paraglacial slope processes (e.g. solifluction). By ca. 10.5 ka, the last remnants of glacial ice disappeared from the lower sections of the valley. This deglaciation chronology broadly agrees with what is observed in other sites across Greenland.

How to cite: Garcia de Oteyza de Ciria, J. N., Oliva, M., Palacios, D., Fernández-Fernández, J. M., Schimmelpfennig, I., Andrés, N., Antoniades, D., Léanni, L., Jomelli, V., Rinterknecht, V., Lane, T., and Team, A.: Major deglaciation during the Late Glacial in coastal regions of Greenland, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10224, https://doi.org/10.5194/egusphere-egu22-10224, 2022.

It is undoubtedly the observation of modern European Alps glaciers along with their erosive, transportational and depositional actions shaping the landscapes that first led scientists to reveal the existence of a ‘past ice age’ during which glaciers not so long ago covered northern Europe and North America. Based on similar observations, evidence for much more ancient (Permian, ca. 300 Ma) glaciers were simultaneously discovered in Wales. Since then, others glacial episodes punctuating the Earth history were successively discovered (Eyles, 2008), the oldest of which being the ‘Barberton diamictites of South Africa, dated back to 3.5 Ga (deWit & Furnes, 2016).

The modern glaciation may serve as the basis to decipher past ice ages and associated climate dynamics that remain obscure as growing evidences indicate that these ancient glacial epochs share similarities, but also discrepancies, with the Cenozoic one, in term of tempos (ice ages encompassing periods of contraction-dilatation of ice) or forcing parameters (e.g., Ghienne et al., 2014; Kochhann et al., 2021; Montanez, 2021). Past ice dynamics may therefore be unraveled by the integration in time and space of punctual glacial processes whose interpretation is made on the basis of their modern and recent equivalent. The glacio-isostatic adjustment, for example, is a process well-known for the ultimate glacial cycle, as marked by widespread evidences such as the raised beaches of Scandinavia and Canada. Given its time span of completion however (a few tens of thousands of years), this process is hardly decipherable for ancient epochs, for which temporal resolution is intrinsically too low, therefore hindering our ability to constrain ancient ice-sheet dynamics. A stratigraphic model built upon recent glacial strata has been successfully extrapolated to both the Ordovician and Carboniferous-Permian ice ages, providing clues about pattern of glacial retreat of postglacial relative sea level changes. Similarly, the geomorphic and stratigraphic imprints of fjords nowadays dissecting high-latitude continental margins were used as an analog that permitted the characterization of fossil fjords and associated glacial dynamics tied to the Carboniferous-Permian glaciation in Namibia (Dietrich et al., 2021). On the other hand, strata related to ancient ice ages may provide novel insights into the understanding of modern glacial processes that remain obscure by granting access to sectors otherwise ‘locked’ such as the ice-substrate interface or sediments nowadays on continental margins, covered in great water depths and buried under younger sediments. Finally, the window into deep and long times offered by sedimentary basins hosting deposits tied to ancient glacial epochs may provide clues on the impact of repeated or long-lasting glaciation on the earth surface evolution (Jaeger & Koppes, 2016). The presentation will briefly review how mutual benefits can be obtained from combining the investigation of ancient and recent glacial deposits (Dowdeswell et al., 2019).

 

 

How to cite: Dietrich, P.: A history of glaciations: the perks of combining recent and ancient morphostratigraphic archives, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12523, https://doi.org/10.5194/egusphere-egu22-12523, 2022.

EGU22-45 | Presentations | GM10.3

Fennoscandian Ice Sheet glaciation on the Kola Peninsula and Russian Lapland 

Benjamin Boyes, Lorna Linch, Danni Pearce, and David Nash

Previous reconstructions of the glacial history of the last Fennoscandian Ice sheet (FIS) in northwest Arctic Russia are limited in scope owing to a lack of empirical geomorphological and chronological data. As a result, previous reconstructions suggest the Kola Peninsula was glaciated by either the FIS, the Ponoy Ice Cap, or the Kara Sea Ice Sheet. Utilising new databases of over 245,000 mapped glacial landforms and 209 numerical ages, we present a new time-slice reconstruction of Late Weichselian (c. 40-10 ka) FIS glaciation on the Kola Peninsula and Russian Lapland.

Subglacial bedforms are used to reconstruct ice flow geometry in the region. The relative age sequence of events demonstrates an evolving ice sheet configuration, including ice sheet build-up and retreat stages, and evidence of ice streaming. Moraines and meltwater landforms are used to reconstruct ice margin positions in the region. The Kola Interlobate Complex, stretching almost 400 km, is likely to be a time-transgressive landform assemblage, which formed at an east- and northeast-migrating junction between the warm-based White Sea lobe and cold-based ice on the Kola Peninsula, probably before the Last Glacial Maximum. Reconstructed retreat ice margin positions indicate that FIS retreat is characterised by thinning, resulting in a lobate ice margin.

This new reconstruction provides a framework into which sedimentary and chronological reconstructions can be contrasted and compared. This research also provides crucial empirical data for validating numerical model simulations of the FIS, which in turn will further our understanding of ice sheet dynamics in other Arctic, Antarctic, and Alpine regions.

How to cite: Boyes, B., Linch, L., Pearce, D., and Nash, D.: Fennoscandian Ice Sheet glaciation on the Kola Peninsula and Russian Lapland, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-45, https://doi.org/10.5194/egusphere-egu22-45, 2022.

EGU22-1269 | Presentations | GM10.3

Relict sand wedge sites in Hungary – granulometry and quartz grain microfabrics 

Beáta Farkas and Péter Szabó

Thermal contraction cracks are well-known proxies of frost action, both in recent and relict environments. A sedimentological analysis was carried out on relict sand wedges from two study sites (Kemeneshát and Mogyoród area) in Hungary, in order to investigate past periglacial processes in the Pannonian Basin. After adequate sample preparation, the grain size distribution of sand wedge infillings (N=82) was determined, and descriptive statistical analysis was carried out using GRADISTAT software. 470 quartz sand grains were examined using a scanning electron microscope (SEM). Thereby, the roundness of the grains was determined and grain surface microtextures were analysed. The results show that every sample from the Kemeneshát area exhibits poor sorting values and mainly polymodal distributions, while the Mogyoród samples are exclusively unimodal and moderately sorted. SEM investigation reinforces the abovementioned statements with Krumbein’s scale results. Most of the studied grains are angular, which refers to the short transportation time of the sediment. Crystal overgrowth was often found on the grains, which suggests sandstone or metamorphic origin for the infilling material. Intensively weathered grain surfaces mark lots of changes in the paleotemperature. Fresh, sharp edges, as well as big, unaltered conchoidal fractures and breakage blocks, indicate intensive frost weathering processes during the last damaging cycle of the sediment. These results help us to reduce the arising uncertainties in the paleoenvironmental reconstruction of the Pannonian Basin during Late Pleistocene.

How to cite: Farkas, B. and Szabó, P.: Relict sand wedge sites in Hungary – granulometry and quartz grain microfabrics, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1269, https://doi.org/10.5194/egusphere-egu22-1269, 2022.

EGU22-2889 | Presentations | GM10.3

Andean Permafrost in Taluses and Blockslopes in the Agua Negra Catchment, Argentina - Distribution and Hydrological Significance 

Melanie A. Stammler, Diana A. Ortiz, Tamara Koehler, and Lothar Schrott

Extensive areas in mountain regions are under permafrost conditions with periglacial processes in the arid Andes of Argentina being mostly associated with high mountain permafrost. The most visible expression of creeping mountain permafrost within the periglacial altitudinal belt (between 35º and 27ºS), is the occurrence of rock glaciers. Beside snow and ice melting, active layer thawing and degrading permafrost contribute to river runoff; an essential resource in the arid Andes and their forelands. Halla et al. (2021) calculated for the first time rock glacier ice content using geophysical methods and four-phase modeling. Besides rock glaciers, taluses (including protalus ramparts) and blockslopes are widespread above an altitude of 4000 m a.s.l., with a first quantitative assessment revealing a surface coverage of about 73 %. We hypothesize that beside rock glaciers, taluses and blockslopes present a high potential for ice content, having a comparable or even more significant importance as valuable water reserves. However, taluses and blockslopes have not yet been properly investigated and little research has focused on the permafrost distribution and stratigraphy of these landforms.

This study determines the characteristics and the influence of climatic, topographical, and lithological conditions on the permafrost, using a multi-method approach: Electrical Resistivity Tomography (ERT), Seismic Refraction Tomography (SRT), hydrological monitoring along the course of Agua Negra river (discharge, water sampling), and UAV-, as well as spaceborne remote sensing analysis. While the use of ERT is beneficial due to the contrasting electrical resistivities of lithological media, water and ice, SRT complements the data with detailed p-wave based information on the upper layer. Hydrological monitoring aids in distinguishing different water resources and in estimating their contributions to runoff. In addition, the repeated application of remote sensing techniques allows for an acquisition of high resolution digital elevation models with models of difference providing insight in the magnitude, timing and spatial pattern of vertical and horizontal surface changes.

The possibility of determining with greater precision the distribution of permafrost in the arid Andes will lead to a more accurate estimation of solid-state water reserves stored in periglacial landforms in arid Andean catchments.

Halla, C., Blöthe, J.H., Tapia Baldis, C., Trombotto, D., Hilbich, C., Hauck, C., Schrott, L., 2021. Ice content and interannual water storage changes of an active rock glacier in the dry Andes of Argentina. The Cryosphere, 15, 1187-1213.

How to cite: Stammler, M. A., Ortiz, D. A., Koehler, T., and Schrott, L.: Andean Permafrost in Taluses and Blockslopes in the Agua Negra Catchment, Argentina - Distribution and Hydrological Significance, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2889, https://doi.org/10.5194/egusphere-egu22-2889, 2022.

Rock glaciers are common components of mountain landscapes with strong potential to document past and present environmental changes, and a notable vulnerability to future climatic perturbations.  Recent studies have begun to consider the contribution of rock glaciers to high mountain hydrology, with a particular emphasis on the possible role of internal ice as a source of meltwater.  This project utilized automated samplers to collect water discharging from two representative rock glaciers in the Uinta Mountains of Utah, USA.  Additional samplers were deployed at a non-rock glacier spring and along the main stream in this basin.  All samplers ran continuously from the start of July through early October, 2021.  Water from the automated samplers, and from precipitation collectors, was analyzed for stable isotopes with cavity ring-down spectroscopy and hydrochemistry with ICP-MS.  Our findings reveal that water draining from the rock glaciers in mid-summer has a low solute content and notably negative δ18O, consistent with the melting of lingering snowpack.  As summer progresses, values of δ18O rise and total dissolved load increases as the influence of this snow-derived water wanes.  In late summer and early autumn, nearly all of the rock glacier discharge can be distinguished from snowmelt, summer precipitation, and groundwater by intermediate values of δ18O, elevated d-excess, and high abundances of Ca and Mg.  This water is interpreted to come from internal ice that was vulnerable to melting in this warm summer following a snow-poor winter.  The isotopic and hydrochemical fingerprint of this rock glacier discharge can then be used as an end-member, along with groundwater and summer precipitation, for unmixing of the late summer streamwater composition.  This exercise suggests that September discharge in the stream, with a watershed of ~50 km2 above the sampling point, contains a detectable component derived from melting internal ice of unknown age within rock glaciers.  An important implication of this conclusion is that late summer/ autumn baseflow in high-elevation streams could decrease in the future as this reservoir of subsurface ice is depleted, particularly in summers following low-snow winters.

How to cite: Munroe, J. and Handwerger, A.: Constraining the contribution of rock glaciers to the summer hydrology of a high-elevation watershed, Uinta Mountains, Utah, USA, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3178, https://doi.org/10.5194/egusphere-egu22-3178, 2022.

EGU22-3193 | Presentations | GM10.3

Core drilling in a low altitude permafrost site from temperate regions. Case study: Detunata Goală, Romanian Carpathians 

Razvan Popescu, Alfred Vespremeanu-Stroe, Mirela Vasile, Sabina Calisevici, and Ilie Andrian

Detunata Goală scree is a talus slope-rock glacier system characterized by persistent snow and ice during springtime and summer in spite of a mean annual air temperature of around +7°C. This is a porous talus made of andesitic basaltic columns affected by chimney circulation that seems to allow for a extrazonal permafrost of low altitude in a temperate climate much lower than the regional limit of alpine permafrost. In the postdoctoral project FrozenCORE electrical resistivity tomography (ERT) and seismic refraction tomography (SRT) were applied in October 2020 in order to check permafrost presence at the end of the warm season and to determine the internal structure of the deposit. The two methods indicated contradictory results, as ERT indicated a high resistive layer in the first 10-15 m while the SRT indicated a high velocity layer at depths greater than 15 m. A borehole was drilled in June 2021 in the coldest sector of the scree and the cores recovered indicated that: 1) the talus is relatively thin, less than 13 m; 2) the deposit has a low amount of ice, several lenses were found between 3 and 10 m each of at most a few centimeters thick; 3) the scree porosity is relatively low, much smaller than at the surface. A thermistor chain was installed in the borehole at depths according to the GTN-P recommendations for future monitoring of the temperatures in the underground. Ice samples were collected from the cores for isotopic analyses in order to check if the ice from the greater depths is older than the upper one assumed to be seasonal. The drilling indicated that ERT is a better method for assessing the stratigraphy of such talus deposits.

How to cite: Popescu, R., Vespremeanu-Stroe, A., Vasile, M., Calisevici, S., and Andrian, I.: Core drilling in a low altitude permafrost site from temperate regions. Case study: Detunata Goală, Romanian Carpathians, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3193, https://doi.org/10.5194/egusphere-egu22-3193, 2022.

EGU22-3211 | Presentations | GM10.3

Spatio-temporal variations in rock wall temperature in Norway post the Little Ice Age 

Justyna Czekirda, Bernd Etzelmüller, Sebastian Westermann, Ketil Isaksen, and Florence Magnin

Warming-induced permafrost degradation is believed to be responsible for the increasing number of rock-slope instabilities, such as rockfalls or rock avalanches, over the past few decades. Relationship between permafrost degradation and geomorphological activity, is nevertheless, hard to establish because often little is known about the permafrost distribution in steep slopes. In the present study, we assess spatio-temporal changes in rock wall temperature in Norway post the Little Ice Age, using the two-dimensional ground heat flux model CryoGrid 2D. We create transects across the monitored rock walls in the Western Norway, in the high alpine range of Jotunheimen and in the Northern Norway.

               Our results demonstrate that rock wall temperature at 20 m depth increased by an average of 0.2 °C decade-1 since the 1980s. Therefore, if atmospheric warming rates remain similar, rock wall permafrost currently at -1 °C at 20 m depth could degrade completely at this depth by 2070. Furthermore, we show how rock wall temperature is influenced by: (1) rock wall geometry, (2) rock wall size, (3) magnitude of surface offsets due to the incoming shortwave solar radiation, (4) snow conditions above and below rock walls, (5) blockfield-covered plateaus or glaciers in their vicinity. Multi-dimensional thermal effects are smaller in Norway than in the European Alps due to the dissimilarities in mountain geometry and smaller differences in ground surface temperature between various mountainsides. Rock walls with large surface offsets arising from solar radiation might be warmer than plateaus above or talus slopes below, thus ground heat flux in such rock walls is directed towards colder plateaus or talus slopes. Furthermore, thermal conditions in blockfield-covered plateaus have impact on rock wall temperature and lead to larger warming rates at 20 m depth, whereas large glaciers decrease warming rates at the same depth. Therefore, a potential glaciers retreat would likely increase ground warming rates in the nearby parts of rock walls.  

How to cite: Czekirda, J., Etzelmüller, B., Westermann, S., Isaksen, K., and Magnin, F.: Spatio-temporal variations in rock wall temperature in Norway post the Little Ice Age, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3211, https://doi.org/10.5194/egusphere-egu22-3211, 2022.

EGU22-3663 | Presentations | GM10.3

Rock glaciers in the low Arctic of Greenland: surface and subsurface structure, permafrost conditions, long-term evolution, and present kinematics of a large rock glacier system at Bjørneø Island, SW Greenland 

Andreas Kellerer-Pirklbauer, Jakob Abermann, Felix Bernsteiner, Kirsty Langley, Tazio Strozzi, and Martin Mergili

Active rock glaciers in Greenland have been studied since the 1980s focusing on two regions (Disko Island and Zackenberg) located north of 69°13’N. As judged from permafrost models, widespread existence of permafrost and thus active rock glaciers are also possible south of this latitude. Therefore, research on a large rock glacier on the island of Bjørneø (size: 1 km²; elevation 250-600 m a.s.l.; NNW-exposed) at 64°30’N was initiated in 2016. Research focused until 2020 on repeated differential GPS measurements at several fixed ground control points, on the analysis of the bottom temperature of the winter snow cover, and on the assessment of high-resolution orthophotos and digital terrain models based on UAV campaigns. Results up to 2020 indicate that permafrost influences a large part of the rock glacier and surface displacement takes place in the order of cm per year particularly in the central part.

Within an INTERACT research project we continued and expanded research at this rock glacier in 2021 applying two types of geophysics (electrical resistivity tomography, ground penetrating radar), differential GPS, relative surface dating, geomorphic mapping, clast form analysis, and monitoring of ground, air, and water temperatures. We find that widespread permafrost is likely along the measured geophysical profiles, that ground and water temperatures generally support the assumption of present permafrost conditions, and that the rock glacier evolved over a period of several thousand years, starting to form soon after the recession of the Greenland Ice Sheet from the coast some 10.4 to 11.4 ka BP.

In addition to fieldwork, different types of remote sensing- and modelling based research at this rock glacier were accomplished. Clast size distribution was semi-automatically quantified using a high-resolution digital terrain model. Results reveal distinct clast size-differences along a longitudinal profile of the rock glacier. Analyses of time-series of Sentinel-1 differential SAR interferograms for the period 2016 to 2021 showed minor motion in the uppermost part of the landform during a period of two months, distinct compressive flow (few cm) of two lobes of the landform after several months, and landform-wide movement over a period of 3 years. The terrain surface before the formation of the rock glacier, and thus the rock glacier volume, were reconstructed on the basis of field observations and terrain data. The volume of material relocated due to rock glacier activity was approx. 10 million m³. Finally, the present rock glacier extent and morphology were numerically reproduced as a steadily evolving and slowly moving viscous mass using a model implemented in the GIS-based open-source mass flow simulation framework r.avaflow.

Our chosen multidisciplinary approach is a significant step forward in understanding the long-term evolution and present conditions of large rock glacier systems in the low Arctic region of Greenland.

How to cite: Kellerer-Pirklbauer, A., Abermann, J., Bernsteiner, F., Langley, K., Strozzi, T., and Mergili, M.: Rock glaciers in the low Arctic of Greenland: surface and subsurface structure, permafrost conditions, long-term evolution, and present kinematics of a large rock glacier system at Bjørneø Island, SW Greenland, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3663, https://doi.org/10.5194/egusphere-egu22-3663, 2022.

EGU22-4034 | Presentations | GM10.3

Holocene jökulhlaups along the Hvítá River, Iceland: geomorphology, chronology, and hydrology 

Greta Wells, Sheryl Luzzadder-Beach, Timothy Beach, Thorsteinn Saemundsson, and Andrew Dugmore

Glacial outburst floods (jökulhlaups) have significantly modified landscapes across Earth throughout the Quaternary and are a contemporary geohazard in glaciated regions worldwide. Iceland experiences more frequent jökulhlaups than nearly anywhere on Earth, though research has focused on floods triggered by subglacial volcanic eruptions. However, floods from ice-marginal lakes may be a better analogue for most global jökulhlaups because both occur during rapid global warming. As the Icelandic Ice Sheet retreated in the early Holocene, meltwater lakes accumulated at ice margins and periodically drained in jökulhlaups. One such lake formed in the Kjölur highland region and drained along the Hvítá River in southwestern Iceland, leaving behind abundant geomorphologic evidence including 50-meter-deep canyons, bedrock channels, and boulder deposits. Yet, only one previous publication has investigated these events.

This project uses a suite of field mapping, geochronological, paleohydraulic, and modeling techniques to better constrain flood timing and dynamics. It introduces new lines of geomorphologic evidence, revises drainage route maps, provides estimates of flood magnitude, and discusses ongoing cosmogenic nuclide dating analysis to reconstruct flood chronology. Finally, it interprets results to present hypothesized scenarios of ice margin position, glacial lake formation, and jökulhlaup drainage during Icelandic Ice Sheet deglaciation. The Hvítá jökulhlaups are also an excellent case study for extreme flood impacts in bedrock terrain and drainage processes from ice-marginal lakes, helping to close a research gap in Iceland and advance understanding of links between climate change, ice response, and hydrology in other Arctic and alpine regions.

How to cite: Wells, G., Luzzadder-Beach, S., Beach, T., Saemundsson, T., and Dugmore, A.: Holocene jökulhlaups along the Hvítá River, Iceland: geomorphology, chronology, and hydrology, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4034, https://doi.org/10.5194/egusphere-egu22-4034, 2022.

Knowing the age and evolution of present-day relict rock glaciers help to decipher past landscape evolution. In an Alpine context, this is particularly relevant for the Alpine Lateglacial and early Holocene period. Relative dating of the surface of a relict rock glacier with the Schmidt-hammer exposure-age dating (SHD) approach has the advantage of a cheap, rather easy handling, and fast method in comparison to absolute age dating approaches such as for instance terrestrial cosmogenic nuclides (TCN) using 10Be. A combination of the two methods at identical sampling sites might help to reduce intrinsic uncertainties of both methods. However, there is still a lack of direct comparisons of dating results based on TCN ages to ages based on Schmidt hammer rebound values. In this study, we compared published TCN ages from 34 sampling sites of relict rock glaciers and neighboring landforms taken from Steinemann et al. (2020) with measured SHD data. The TCN-samples have been taken primarily from two rock glacier systems consisting of gneissic rocks named Tandl and Norbert in the Reißeck Mountains, Carinthia, Austria. At each site where Steinemann et al. (2020) took a sample to quantify the absolute age based on 10Be, we carried out 100 individual Schmidt-hammer rebound measurements. The results of the two methods were partly consistent but partly difficult to interpret. At the study site Tandl (n=20), a significant correlation between TCN ages and R-values has been detected. The age calibrating curve for the Tandl site, suitable to calculate absolute ages from the relative R-values, is: age[ka] = -1.128ˑx R + 55.642 with an R² of 0.803. In contrast, no significant correlation between R-values measured at the study site Norbert (n=14) in comparison to ages derived by TCN data was revealed. This might be due to a more complex transport history of the sampled boulders in terms of both glacial as well as periglacial transport elements, the influence of a more complex lithology at Norbert, elevation effects (impacting differences in weathering), block instability or exhumation and erosion effects of the sampled boulders. Furthermore, gneiss is more difficult to measure with the Schmidt-hammer approach due to its common anisotropy compared to, for example, granite, which is the lithology mostly used in previous studies where TCN and SHD was compared. Therefore, our study comprises an interesting case study of both successful and problematic direct comparisons of TCN- and SHD-derived age data.

Steinemann O, Reitner JM, Ivy-Ochs S, Christl M, Synal HA (2020) Tracking rockglacier evolution in the Eastern Alps from the Lateglacial to the early Holocene Quaternary Science Reviews 241:106424. https://doi.org/10.1016/j.quascirev.2020.106424

How to cite: Krisch, P. and Kellerer-Pirklbauer, A.: Comparing Schmidt-hammer rebound values with terrestrial cosmogenic nuclides-derived ages in the Reißeck Mountains, Hohe Tauern Range, Austria, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4080, https://doi.org/10.5194/egusphere-egu22-4080, 2022.

Recent glacier lake formation in mountain areas is a consequence of temperature increase and subsequent glacier melt. These new lakes affect the sediment cascade by collecting great parts of the sediment input by the meltwater streams. A quantification of these trapped sediments can be achieved by assessing changes in the lake bottom surface at different periods in time. Bathymetry changes can be affected by the delayed melting of buried glacier ice, preserved at the lake floor, which lead to an overestimation of sediment volumes.

We analysed bathymetry changes within the proglacial lake Obersulzbach, Hohe Tauern range, Austria over a period of 13 years. Lake floor and delta sediments were investigated using high resolution, multi-temporal geophysical data derived from sub bottom profiling (SBB), echo sounding and ground penetrating radar (GPR). We compared three instances of bathymetry data that document changes of the lake floor attributed to ice melt and sedimentation. SBB and GPR data were applied to detect buried ice underneath the sediments in order to assess the sediment and the ice volume in the lake and delta. 

The proglacial lake Obersulzbach formed in 1998 when the tongue of the Obersulzbach glacier in the Hohe Tauern Range, Austrian Alps, retreated behind a bedrock barrier. The glacier lake evolved in a former confluence zone of four glacier parts that originate in the valley head of the Obersulzbach valley. The lake has a maximum depth of 40 meters and a size of 170,000 m². The glacier ice retreated from the lake area in 2010 to a distance of more than 500 meters from the lake in 2021. Since 2009, a delta started to build up at the distal part of the lake fed by two meltwater streams. Parts of the delta started to sink below lake level in 2019, forming localised depressions. This process continued in 2020 and 2021 when large parts of the delta sunk into the lake increasing the lake area by 30%. In the delta area, the surface sunk by up to 20 m within 2 years. We attribute these changes to a delayed, but rapid melting of buried glacier ice at the lake floor and within the delta more than 10 years after the retreat of the glacier tongue.

How to cite: Otto, J.-C. and Heine, E.: Bathymetry changes due to delayed basal ice melt at the proglacial lake Obersulzbachsee, Hohe Tauern, Austria – Implications for sediment budgeting, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4395, https://doi.org/10.5194/egusphere-egu22-4395, 2022.

EGU22-4668 | Presentations | GM10.3

Regional characterization of rock glacier activity based on DInSAR phase and permafrost extent 

Chiara Crippa, Daniele Codara, and Federico Agliardi

Rock glaciers are bodies of frozen debris and ice that move under the influence of gravity in permafrost areas. They are important climatic proxies and can undergo destabilization related to flow of the frontal sectors over steep topography or acceleration related to permafrost degradation and climate change. As consequence, they evolve with complex mechanisms, mirrored by spatial heterogeneity and extremely variable displacement rates. Although a sound quantification of activity is a key component of the study of rock glaciers, only few of them can be characterized by point-like site investigations and ground-based displacement measurements. Their study is thus widely facilitated by remote sensing applications, which proved to be powerful tools for a spatially distributed and temporally continuous characterization on a regional scale

Here, we developed a novel methodology to exploit the potential of spaceborne DInSAR analyses to characterize the state of activity of 516 rock glaciers mapped by Scotti et al., (2013) over an area of approximately 1000km2 in the north-eastern sector of Valtellina (Italian Central Alps) and we exploited Landsat-8 thermal imaging to explore their regional distribution according to the land surface temperature.

The original rock glacier inventory, based on orthophotos and DSM mapping, provides a morphological and a dynamic classification (active/inactive vs. relict) of the mapped landforms according to surface evidence. To integrate this dataset with information on the present-day state of activity, we developed a semi-automatic procedure in ArcGIS and Matlab TM combining DInSAR products, morphometric data and available permafrost extent information (APIM). To obtain a spatially distributed characterization of rock glacier activity patterns, we processed Sentinel-1 A/B images (2017-2020) with increasing temporal baselines (Bt from 12 to 120 days) and generated 124 interferograms in ascending and descending geometry to account for all the different topographic orientations. We then implemented an analysis of the interferometric phase to achieve a quantification of each rock glacier activity based on four steps: 1) correcting the phase values inside each rock glacier for the modal phase value inside a surrounding stable area; 2) stacking (median phase values) of all the selected interferograms generated with same temporal baselines; 3) extracting frequency distributions of median phase values inside each rock glacier and stable area; 4) calculating the percentage of phase values inside each rock glacier that falls outside the uncertainty ±σ range of the stable area ones. This percentage provides an “Activity Index” that allows defining four classes of rock glacier activity together with the presence (active, inactive) or absence (active debris, relict) of permafrost. Classification results based on DInSAR data at different temporal baselines allow recognizing styles of activity characterized by different ranges of displacement rates and spatial and temporal heterogeneities, possibly correlated with the underlying deformation mechanisms. The integration with land surface temperature finally provides useful insights on the distribution of rock glacier activity classes in different topographic conditions.

Our methodology can be applied to other alpine areas and datasets for a wide-area evaluation of rock glacier activity for climatic studies and possible geohazard hot-spot identification.

How to cite: Crippa, C., Codara, D., and Agliardi, F.: Regional characterization of rock glacier activity based on DInSAR phase and permafrost extent, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4668, https://doi.org/10.5194/egusphere-egu22-4668, 2022.

EGU22-4737 | Presentations | GM10.3

Ice stream dynamics and ice margin retreat of the last Laurentide Ice Sheet in the Northwest Territories, Canada 

Helen E. Dulfer, Benjamin J. Stoker, Martin Margold, Chris R. Stokes, Chris D. Clark, Colm Ó Cofaigh, and David J.A. Evans

The Laurentide Ice Sheet (LIS) was the largest of the ephemeral Pleistocene ice sheets in the Northern Hemisphere, with a Last Glacial Maximum (LGM) ice volume similar to the modern Antarctic ice sheet. A recent inventory of paleo-ice streams across the LIS shows many similarities with present-day ice streaming in Antarctica, where ice streams account for approx. 90% of mass loss. However, in the Mackenzie Lowlands of the Northwest Territories, Canada, the paleo-ice stream record is enigmatic. Previous work has identified a number of large paleo-ice streams, including the Mackenzie Trough, Anderson, Bear Lake and Fort Simpson ice streams, however, their extent, configuration, temporal relationship to each other and spatial evolution over time remains poorly constrained. Consequently, their impact on the rate and style of deglaciation of the northwestern sector of the LIS is poorly understood.

Here we utilise the newly available high resolution Arctic DEM (0.5 m resolution) to re-map glacial landforms across the Mackenzie Lowlands in greater detail (area >800,000 km2). We then use this landform record to reconstruct the ice dynamics in this region following the well-established approaches of flowset mapping and the glacial inversion method. The high resolution data allow us to present a detailed reconstruction of LGM ice flow over the Mackenzie Lowlands and resolve the configuration and evolution of ice streams over time. The landform record suggests that the ice streams operated time-transgressively during deglaciation, switching on and off at different times. While ice contact landforms, such as moraines, lateral and submarginal meltwater channels and ice-contact deltas, show the overall retreat of the LIS towards the Keewatin Dome in the east, in several regions the ice retreat record is complex, suggesting interlobate ice configurations with multiple ice retreat directions.

How to cite: Dulfer, H. E., Stoker, B. J., Margold, M., Stokes, C. R., Clark, C. D., Ó Cofaigh, C., and Evans, D. J. A.: Ice stream dynamics and ice margin retreat of the last Laurentide Ice Sheet in the Northwest Territories, Canada, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4737, https://doi.org/10.5194/egusphere-egu22-4737, 2022.

EGU22-5542 | Presentations | GM10.3

Headwall erosion rates from cosmogenic 10Be in medial moraine debris of five adjacent Swiss valley glaciers 

Katharina Wetterauer, Dirk Scherler, and Leif S. Anderson

Rock walls in high-alpine glacial environments are becoming increasingly unstable due to climate warming. This instability increases the erosion of headwalls above glaciers modifying glacial surface debris cover and mass balance and, thus, affecting the response of glaciers to climate change. As debris is deposited on glaciers, it is passively transported downglacier forming medial moraines where two glaciers join.

We assess headwall erosion by systematic downglacier-debris sampling of medial moraines and by computing headwall erosion rates from their 10Be-cosmogenic nuclide concentrations. Around Pigne d’Arolla in Switzerland, we collected a total of 39 downglacier medial moraine debris samples from five adjacent glaciers. We explicitly chose medial moraines with source headwalls that vary in size, orientation and morphology, to investigate how different debris source area characteristics may express themselves in medial moraine cosmogenic nuclide concentrations. At the same time, the downglacier-debris sampling enables us to derive headwall erosion rate estimates through time, as medial moraine deposits tend to be older downglacier.

Preliminary results reveal systematic differences in 10Be concentrations for the studied glaciers. At Glacier d’Otemma, Glacier du Brenay, and Glacier de Cheilon 10Be concentrations average at 17x103, 31x103, and 4x103 atoms g-1, respectively. Downglacier 10Be concentrations at Glacier d’Otemma vary systematically and headwall erosion rates tend to increase towards the present. At both Glacier du Brenay and Glacier de Cheilon downglacier 10Be concentrations are more uniform, suggesting that headwall erosion rates did not evolve significantly through time. Results for Glacier de Tsijiore Nouve and Glacier de Pièce will follow soon. In addition, samples at Glacier d’Otemma were collected along two parallel medial moraines sourced by different but adjacent headwalls. Yet, their downglacier 10Be concentrations deviate and our analyses suggest that at Glacier d’Otemma both differences in headwall orientation and headwall deglaciation history may account for the deviation of the two medial moraine records. For all five glaciers, we currently explore how lithology, slope angles, exposition, deglaciation, and elevation vary between the debris source areas and how differences therein could result in the observed differences in 10Be concentrations.

How to cite: Wetterauer, K., Scherler, D., and Anderson, L. S.: Headwall erosion rates from cosmogenic 10Be in medial moraine debris of five adjacent Swiss valley glaciers, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5542, https://doi.org/10.5194/egusphere-egu22-5542, 2022.

EGU22-5740 | Presentations | GM10.3

The oldest palaeocryogenic stages in the Quaternary loess-palaeosol sequences of Ukraine 

Olena Tomeniuk and Andriy Bogucki

In the Pleistocene on the territory of Ukraine palaeocryogenic processes left the most noticeable traces in the features of the structure and properties of the periglacial loess-palaeosol sequences (LPSs).

The oldest of the Quaternary palaeocryogenic stages established in Ukraine is associated with the solifluction layer (fossil active layer of the permafrost) in the loess L3 (MIS 8) overlying the Lutsk palaeosol of the regional stratigraphic scheme that corresponds to S3, MIS 9. This stage was first documented in the Boyanychi key section, thus it got the eponymous name Boyanychi. A characteristic feature of this stage is the wide development of plastic deluvial-solifluction deformations. Palaeocryogenic deformations of this stage are described in only two sections of Quaternary LPSs – Boyanychi and Korshiv on Volhynian Upland. In Boyanychi, a large ice-wedge pseudomorph with a vertical size of more than 2 m was described and sampled for engineering and geological research. This is clear evidence of the existence of permafrost at that time. The age of L3 loess in the Boyanychi section is 277±41 ka BP.

Cryogenic deformations of the Yarmolyntsi palaeocryogenic stage (early MIS 6, Yarmolyntsi subhorizon) is most pronounced directly above the Korshiv fossil soils complex (S2, MIS 7) in many sections of Volhynian, Podolian uplands and Forecarpathians. During the Yarmolyntsi palaeocryogenic stage, deluvial-solifluction plastic deformations, mainly associated with the solifluction layer (fossil active layer) overlying the Korshiv palaeosol complex, were widely developed. Ice-wedge pseudomorphs exceed 2.5 m in depth. The age of the Yarmolyntsi subhorizon within the L2 loess of the Boyanychi section is 200.4±26.1 ka BP.

The Ternopil palaeocryogenic stage is associated with the Ternopil subhorizon in L2 loess (MIS 6) and is represented mainly by structural deluvial-solifluction deformations. Occasionally there was a polygonal-vein cracking that left traces in the form of ice-wedge pseudomorphs (Velykyi Hlybochok section, etc.). The age of the Ternopil subhorizon within the L2 loess of the Korshiv section is 159±53 ka BP, 164±34 ka BP, in the Boyanychi section is 162.2±17 ka BP.

Traces of the Lanivtsi palaeocryogenic stage (upper part of MIS 6, Lanivtsi subhorizon) are more widespread in the Quaternary LPSs of Ukraine. They are associated with the upper part of the L2 loess. It is the Lanivtsi (Zbarazh?) fossil active layer of the permafrost. Its development occurred at the end of the Middle Pleistocene. In the sediments of the Lanivtsi palaeocryogenic stage gleyed loams with a well-defined semi-mesh postcryogenic structure, highlighted by films of brown ferruginization, are dominated. Structural deformations of the Lanivtsi palaeocryogenic stage are well-developed in the sections of Zbarazh and Vyshnivets on the Podolian upland. Ice-wedge pseudomorphs are filled with loess and have vertical dimensions of slightly more than 2 m.

Palaeocryogenic deformations are of great importance for the stratigraphic division of the Quaternary LPSs of Ukraine. Clear stratigraphic positions of fossil active layers, their morphological and lithological features are reliable benchmarks for the determination and justification of specific horizons.

Acknowledgements

This study was supported by the project of the National Research Foundation of Ukraine, grant number 2020.02/0165.

How to cite: Tomeniuk, O. and Bogucki, A.: The oldest palaeocryogenic stages in the Quaternary loess-palaeosol sequences of Ukraine, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5740, https://doi.org/10.5194/egusphere-egu22-5740, 2022.

Ice provenance and dynamic behaviour between the British-Irish ice sheet has been subject to controversy in recent years. Several studies of clast lithology and glacial morphology have alluded to the inland extension of the North Sea Lobe into northeast England and the Vale of York. However, the extent that the North Sea Lobe extends into the Vale of York, and its dynamic interactions with the Stainmore and Wensleydale ice masses is as yet unknown. This study aims to reconstruct the complex provenance of the Vale of York ice lobe through clast lithological and matrix geochemical analysis. Multivariate statistical methods were applied to the datasets in the form of a PCA and Cluster Analysis, to aid in the correlation of Vale of York tills to BIIS and NSL type sites. Indicator erratics for NSL (Cheviot volcanics and flint), Scottish (greywacke and metasedimentary lithologies), and Lake District (felsic tuff) provenance were found in several tills and were central to tracing till provenance. Major and trace metal, and clast lithological cluster analyses have identified at least two occasions where the NSL and Eden-Stainmore ice converges at Scorton Quarry in the north of the Vale of York. NSL ice has been traced as far south and west as Norton Mills. Deposits to the west (Marfield Quarry and Lightwater Quarry) are dominated by a local Wensleydale ice signature and lack evidence of North Sea ice.

How to cite: Jenkins, H.: A palaeo-reconstruction of Devensian ice-flow phasing in the Vale of York., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5791, https://doi.org/10.5194/egusphere-egu22-5791, 2022.

EGU22-6055 | Presentations | GM10.3

InSAR-based characterization of rock glacier kinematics in the La Sal Mountains, Utah, USA 

Camryn Kluetmeier, Alex Handwerger, and Jeffrey Munroe

Rock glaciers are perennially frozen bodies of ice and poorly sorted rock debris that flow downslope due to basal shear and deformation of interstitial ice. As common features in high mountain environments, rock glaciers constitute an important component of alpine hydrology and landscape evolution through release of seasonal meltwater and transport of debris downslope. Here, we use satellite-based interferometric synthetic aperture radar (InSAR) from 2015 to 2021 to identify and characterize rock glaciers in the La Sal Mountains of Utah, USA. Following the IPA Action Group guidelines, we created an inventory of 45 active and transitional rock glaciers in the La Sal Mountains based on mean InSAR velocity maps. La Sal Mountain rock glaciers have an average area of 0.09 km2 and are found at a mean elevation of 3187 m, where mean annual air temperature and precipitation are estimated to be 2.44 °C and 1012 mm, respectively. The mean downslope velocity for the inventory is 3.58 ± 1.13 cm yr -1 with individual rock glacier velocities ranging from 1.98 cm yr -1 to 7.54 cm yr -1. Time-dependent deformation of 19 representative rock glaciers shows that rock glacier motion varies seasonally, with rates of up to 38.2 cm yr-1 during the late summer. Average annual rock glacier velocities are also strongly correlated to the overall amount of precipitation received each year (R2 = 0.97). Our results offer insight into environmental factors that may govern rock glacier kinematics, suggesting that rock glacier kinematics are controlled by the availability of liquid water.

How to cite: Kluetmeier, C., Handwerger, A., and Munroe, J.: InSAR-based characterization of rock glacier kinematics in the La Sal Mountains, Utah, USA, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6055, https://doi.org/10.5194/egusphere-egu22-6055, 2022.

EGU22-6195 | Presentations | GM10.3

Analysis of the 20-year long permafrost evolution at the long-term monitoring site Stockhorn, Swiss Alps, by applying a petrophysical joint inversion and a thermal model (Cryogrid3). 

Sarah Morard, Christin Hilbich, Coline Mollaret, Cécile Pellet, Florian Wagner, Sebastian Westermann, and Christian Hauck

The Stockhorn plateau, an east-west oriented crest located at an elevation of around 3’410 m a.s.l. in the Swiss Alps, is a measurement site belonging to the Swiss Permafrost Monitoring Network (PERMOS). In this study we present a combined analysis of thermal and geophysical data by applying the so-called petrophysical joint inversion (PJI) scheme (Wagner et al., 2019). By using the PJI approach with different petrophysical relationships (Archie’s law and Resistivity Geometric Mean model) (see Mollaret et al., 2020), we attempt to quantify the ice and water content changes in the subsurface over the past 20 years and analyse their spatial heterogeneity. The results will be validated with the borehole data.

Many different data sets are available for the Stockhorn plateau and they give evidence of permafrost degradation in the past 20 years. Two boreholes were drilled in 2000 and provide temperature measurements to a depth of 17 m and 100 m, respectively. From 2002 to 2020, the active layer depth has increased by 2 m for the northern borehole and by 3.3 m for the southern borehole. A weather station provides measurements since 2002 (PERMOS, 2021). The meteorological data show an increasing air temperature trend from 2003 to 2018 (Hoelzle et al., 2020). Since 2005, annual geoelectrical surveys (ERT) have been performed with collocated seismic surveys (RST) in almost every year. The geophysical data from 2007 to 2021 show a decreasing trend for specific electrical resistivities and P-wave velocities, but a detailed interpretation of the geophysical data is however not straightforward because of heterogeneous lithology as well as the small-scale topography effects causing a complex thermal regime.

The north-south geophysical profile is hereby situated at the boundary between two different rock formations. This is visible through the occurrence of a conductive anomaly observed in the geoelectrical surveys between the two boreholes. In addition, the plateau is covered by different materials such as fine debris, blocky and fine-grained materials, and bedrock, which implies different porosity values along the geophysical profiles in the subsurface. Due to large spatial heterogeneities in the observed temperature and geophysical data, the impact of permafrost degradation on the ground properties such as water and ice content is unclear. In contrast to the formerly used four-phase model (4PM, Hauck et al., 2011), where ERT and RST inversions are computed individually and a porosity distribution had to be prescribed, the PJI scheme has the advantage of obtaining physically consistent results of water and ice content distributions in the ground by inverting the ERT and RST results simultaneously (Wagner et al., 2019). In addition to the validation of the PJI results with the borehole data, it could be possible to validate the results with the thermal model simulations using Cryogrid3 (Westermann et al., 2016).

How to cite: Morard, S., Hilbich, C., Mollaret, C., Pellet, C., Wagner, F., Westermann, S., and Hauck, C.: Analysis of the 20-year long permafrost evolution at the long-term monitoring site Stockhorn, Swiss Alps, by applying a petrophysical joint inversion and a thermal model (Cryogrid3)., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6195, https://doi.org/10.5194/egusphere-egu22-6195, 2022.

EGU22-7098 | Presentations | GM10.3

Dynamic changes of a large ice-debris complex in the Central Andes of Argentina 

Jan Henrik Blöthe, Carla Tapia Baldis, Christian Halla, Estefania Bottegal, Dario Trombotto Liaudat, and Lothar Schrott

Active rock glaciers and ice-debris complexes constitute important indicators of permafrost in periglacial environments of high mountain regions. Within the permafrost body and the seasonally frozen active layer, these cryogenic landforms potentially store significant amounts of water. Especially in dry mountain belts, such as the central Andes of Argentina, rock glaciers and ice-debris complexes attain several kilometres in length, even outranging glaciers in size and number. This intriguing observation fostered discussions on their importance as water reservoirs in this semiarid part of the Andes, yet studies addressing this issue in the region remain sparse.  

Here we present data on the internal composition, surface velocities and volumetric changes of the Morenas Coloradas ice-debris complex (>2 km2), located close to the City of Mendoza in the central Argentinian Andes that we derive from Electrical resistivity tomography (ERT) measurements and repeated aerial surveys collected in the years of 2016 and 2019. In addition, we compare our newly gathered data with earlier studies as well as aerial imagery from the late 1960ies.

Our geophysical data indicate massive ice in the central upper part of the Morenas Coloradas complex, which is supported by field observations and remote sensing data, showing a zone of active thermokarst development with massive ice capped by a 2-4 m thick layer of debris. In the lower parts of the ice-debris complex, thermokarst phenomena are absent. Still, our geophysical data point to frozen subsurface conditions, but lower resistivities indicate ice-debris mixtures instead of massive ice here.

Between 2017 and 2019, surface velocities of the Morenas Coloradas ice-debris complex largely varied between 0.5 and 4 m yr-1. The highest displacement rates are found in the central upper part of the landform, where two tributaries join the main stem of the complex, as well as in the lower part of the extensive tongue that reaches down to ~3600 m asl. While the landform shows active deformation on the full width of ~500 m in the upper and central parts, active displacement is funnelled into a small band in the lower part approaching the frontal position. Comparing our results to aerial imagery from the late 1960ies, we find surprisingly little variation in the displacement pattern and magnitude, despite the considerable dynamics during more than five decades of warming climate and changes in precipitation patterns. In terms of volumetric changes, however, we find that the Morenas Coloradas ice-debris complex has lost roughly 110,000 m3 between 2017 and 2019 in the lower 2/3 of the landform that is covered by our data. Interestingly, volumetric loss is focused on the central upper part (~80 % of total loss) where large thermokarst ponds attest the rapid degradation. The lateral parts and lower reaches, in contrast, show little absolute volumetric change over observation period from 2017 to 2019.

How to cite: Blöthe, J. H., Tapia Baldis, C., Halla, C., Bottegal, E., Trombotto Liaudat, D., and Schrott, L.: Dynamic changes of a large ice-debris complex in the Central Andes of Argentina, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7098, https://doi.org/10.5194/egusphere-egu22-7098, 2022.

EGU22-7728 | Presentations | GM10.3

Further numerical simulations of subglacial bedform formation: Implications for interpreting palaeo-landscapes 

Jeremy Ely, David Stevens, Chris Clark, and Andrew Fowler

Subglacial bedforms, repetitive landforms formed at the base of an ice-sheet or glacier as a result of the movement of subglacial sediments, are abundant in areas of former glaciation where they are often used to reconstruct past-ice flow conditions. Commonly referred to as one of the following morphotypes, the formation of drumlins, subglacial ribs and mega-scale glacial lineations (MSGL), has been the subject of scientific enquiry for over a century. Understanding subglacial bedform formation has important implications for reconstructions of palaeo ice-sheets, which require assumptions to be made regarding their genesis.

One explanation envisages subglacial bedforms as the result of instabilities in the coupled flow of ice, water, and till at the ice-bed interface. Here, we evaluate the progress of this hypothesis, commonly referred to as the instability theory of subglacial bedform formation. We present numerical solutions of the current version of the instability model, exploring the simulation outcomes for various constrained parameters. In our model, subglacial ribs and drumlins commonly arise, grow to a mature state, and persist. Drumlins are always preceded by subglacial ribs, perhaps explaining their commonly observed banded arrangements in the landscape. The transition from ribs to drumlins is rapid, with transitory intermediate quasi-circular forms - this perhaps explains why they are rarely observed. This evolutionary trajectory is one-way, with no simulations showing drumlins turning into ribs. This is most likely explained by the development of preferential pathways for water and sediment between drumlin ridges as the ice-bed interface evolves. Furthermore, we find that the numerical model is unable to produce MSGL, with previously reported MSGL-like features likely to be a consequence of periodic boundary conditions. This is despite analytical solutions to the model showing features with an MSGL-like wavelength. To resolve this, either a more sophisticated numerical toolkit is required, or the model requires further development.

Using these simulations as a basis of our discussion, we argue that whether the instability theory can be regarded as the fundamental cause of subglacial bedforms likely depends upon your viewpoint. For the mathematician, linear stability analysis of the model produces bedform wavelengths consistent with observations, so perhaps the problem is solved. For a numerical modeller, producing the missing MSGL remains a challenge. For sedimentologists, the model lacks the complexity to replicate the history of processes recorded within subglacial bedforms, and necessarily generalises deformational processes. Thus, many sedimentologically-based questions remain unanswered by this model. Finally, we argue that if subglacial bedforms arise from an instability, then inverting for glaciological conditions (e.g. velocity, thickness) based on the morphology of bedforms alone may be unachievable. The nature of instabilities means that small changes to the system will alter the final bedforms produced, and similar bedforms may occur through combinations of different conditions.

How to cite: Ely, J., Stevens, D., Clark, C., and Fowler, A.: Further numerical simulations of subglacial bedform formation: Implications for interpreting palaeo-landscapes, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7728, https://doi.org/10.5194/egusphere-egu22-7728, 2022.

EGU22-7826 | Presentations | GM10.3

On the dynamics of rock glaciers in marginal mountain permafrost (Retezat Mountains, Romania). 

Flavius Sirbu, Valentin Poncos, Tazio Strozzi, Alexandru Onaca, Delia Teleaga, and Dan Birtas

Active rock glaciers (RG) are associated with mountain permafrost occurrence, and in the last years, remote sensing has been widely used to assess their dynamics. However, the use of remote sensing in determining the dynamics of slow-moving rock glaciers, from areas with patchy permafrost, controlled by site-specific conditions still remains a significant challenge. One such area is the central part of Retezat Mountains in the Southern Carpathians, Romania.

Here we present and discuss the results obtained by using Persistent Scatterer Interferometry (PSI) on Sentinel-1 images between 15.5.2015 and 27.10.2020. The results were validated with 26 in situ measurements with a Topcon Hiper V Differential GPS connected to the ROMPOS network for real-time corrections and millimetric accuracy. Also, the spatial distribution of RG dynamics was compared with a predicted map of permafrost distribution.

The results show that the displacement rates are low, at around 10mm/year. Out of the 48 investigated RGs, only two have displacement rates between 10 and 20mm/year, 14 show displacement of up to 10mm/year, and 32 don’t show any (measurable) displacement. However, the displacement rates are found to cover only part of the RGs, with stable areas being identified on all of them. When comparing the distribution pattern of the displacement rates, there is a good overall agreement with the modelled permafrost distribution, further suggesting that rock glacier dynamics are influenced by permafrost occurrence in marginal conditions.

How to cite: Sirbu, F., Poncos, V., Strozzi, T., Onaca, A., Teleaga, D., and Birtas, D.: On the dynamics of rock glaciers in marginal mountain permafrost (Retezat Mountains, Romania)., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7826, https://doi.org/10.5194/egusphere-egu22-7826, 2022.

EGU22-7928 | Presentations | GM10.3

Geomorphic responses at the permafrost margins: observations from the Swiss Alps 

Hanne Hendrickx, Reynald Delaloye, Jan Nyssen, and Amaury Frankl

The warming and thawing of permafrost creates a multitude of geomorphic responses. Warm permafrost areas, with temperatures between -2° and 0°C, are especially affected because of the occurrence of pressurized water at the bounding of the ice/rock contact, which is very sensitive to any temperature change. In mountain permafrost regions, this implies that geomorphic response will first be observed at lower elevations, close to the permafrost margins, before shifting upwards as the climate changes. In addition, an increased surface summer runoff related to the rising elevation of rain precipitation, more severe rainfall events and a reduced extent of snow patches can be observed. Therefore, there is a need for a detailed monitoring of these critical areas, where climate change induced processes will first occur, to improve our understanding of the landscape evolution in mountainous regions.

For this purpose, four common mountainous periglacial landforms, a rock wall, a debris flow affected talus slope, a rock glacier and a rockslide are monitored in high temporal and spatial resolutions. These landforms are important steps in the alpine sediment cascade, potentially acting as a sediment source or sink depending on their connectivity within the landscape. Several close range sensing techniques were combined (GNSS data, archival aerial photographs, uncrewed aerial vehicles, terrestrial laser scanning, time-lapse photography and seismic data), providing multiple lines of evidence. Limitations related to the sensor and monitoring intervals were overcome by the integration of the different datasets. Especially in the European Alps, where monitoring activities have been ongoing for decades with an increased instrumentation, this approach unlocks interesting research paths.

All four studied landforms show a clear response to the present-day climate change. We observed a 2-year rock wall destabilisation with an unprecedented level of detail, including a precursory deformation of the rock wall, a process already ongoing before the start of the monitoring. The deep permafrost bedrock that was exposed after large cliff falls (104-106 m3) has already been out of equilibrium with the surface temperature for three decades. On the studied talus slope, a high magnitude debris flow event (3 x 104 m3, various surges) was recorded in summer 2019 as a result of several convective thunderstorms, exceeding all historical debris flow events since 1946. Rock glacier acceleration (up to 15 m yr-1) and destabilisation has been observed, in this case delivering a considerable volume of debris to steep torrential gullies where it can be mobilised again in the form of debris flows. The Grabengufer rockslide, one of the only permafrost-affected active rock slide accurately monitored in the Alps, is continuously accelerating (from 0.3 to > 1 m y-1 in a bit more than a decade). Although all our observations are study area specific, similar observations have been made elsewhere in the European Alps. Therefore, the high resolution spatial and temporal data collected in this study deepens the insight in processes increasingly occurring throughout the Alps. By doing so, this research contributes to the understanding of high mountain geomorphology in a changing climate.

How to cite: Hendrickx, H., Delaloye, R., Nyssen, J., and Frankl, A.: Geomorphic responses at the permafrost margins: observations from the Swiss Alps, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7928, https://doi.org/10.5194/egusphere-egu22-7928, 2022.

EGU22-8172 | Presentations | GM10.3

Geometry of LGM polygonal sorted patterns analysed using high-resolution airborne data (Krkonoše Mountains, Czech Republic) 

Tomáš Uxa, Marek Křížek, David Krause, and Tereza Dlabáčková

Relict sorted patterns are valuable indicators of past permafrost and climate evolution, but their detailed terrain explorations are usually challenging due to high time requirements and poor pattern visibility. Here, we test the applicability of high-resolution airborne data to map and analyse the geometry of LGM polygonal sorted patterns at one site in the Krkonoše Mts., Czech Republic. We delineated a total of 2000 sorted patterns using colour contrasts between their elevated centres and bordering troughs discernible on a LiDAR digital elevation model with a resolution of 0.5 m and on true-colour orthogonal aerial photographs with a resolution of 0.2 m. Since the patterns occupy an area of ~1.96 ha, the density of their network accounts for ~1019 cells per hectare. The patterns have a diameter of 3.59±0.95 m, a height of 0.30±0.11 m, and an estimated sorting depth of 1.00±0.26 m. The number of pattern sides ranges between three and ten, but 82 % of the patterns are pentagonal to heptagonal, and their sides mostly meet at three- or four-way intersections at an angle of 120±24°. However, isometric patterns are rather rare as a length-to-width ratio attains 1.48±0.30. Generally, the remotely-sensed pattern attributes are consistent with ground-truth data previously collected at the study site, which proves the utility of high-resolution airborne data to rapidly map and complexly analyse the geometry of large sets of relict landforms over extensive areas that could not be done by conventional terrain surveys. The sorting depth indicates that permafrost superimposed by ~1 m thick active layer occurred at the study site during the LGM, which can be further used for past permafrost and climate modelling. The dataset can also have many other applications such as for validating automated pattern mapping/delineation tools and pattern growth models or for choosing an effective sample size for future surveys.

The research is financially supported by the Czech Science Foundation, project number 21-23196S.

How to cite: Uxa, T., Křížek, M., Krause, D., and Dlabáčková, T.: Geometry of LGM polygonal sorted patterns analysed using high-resolution airborne data (Krkonoše Mountains, Czech Republic), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8172, https://doi.org/10.5194/egusphere-egu22-8172, 2022.

EGU22-9681 | Presentations | GM10.3

Drained lake basins on a circumpolar scale – Updates from the IPA Action Group 

Helena Bergstedt, Benjamin Jones, Guido Grosse, Alexandra Veremeeva, Amy Breen, Anna Liljedahl, Annett Bartsch, Benjamin Gaglioti, Frédéric Bouchard, Gustaf Hugelius, Ingmar Nitze, Juliane Wolter, Kenneth Hinkel, Louise Farquharson, Matthias Fuchs, Mikhail Kanevskyi, Pascale Roy-Leveillee, and Trevor Lantz

Lakes and drained lake basins (DLB) are ubiquitous landforms in permafrost regions. The long-term dynamics of lake formation and drainage is evident in the abundance of DLBs covering 50% to 75% of arctic permafrost lowlands in parts of arctic Alaska, Russia, and Canada. Following partial or complete drainage events, DLBs evolve through time. As the basins age and ground ice enrichment occurs, the surface heaves and vegetation communities evolve, exhibiting spectral and texture differences indicative of these changing conditions. This mosaic of vegetative and geomorphic succession and the distinct differences between DLBs and surrounding areas can be discriminated and used to make a landscape-scale classification employing various indices derived from multispectral remote sensing imagery that, when combined with field sampling and peat initiation timing, can be used to scale across spatial and temporal domains. Previously published local and regional studies have demonstrated the importance of DLBs regarding carbon storage, greenhouse gas and nutrient fluxes, hydrology, geomorphology, and habitat availability. A coordinated pan-Arctic scale effort is needed to better understand the importance of DLBs in circumpolar permafrost-regions. Here we present an update of ongoing work within the Action Group on DLBs supported by the International Permafrost Association (IPA), an effort by the community to develop a first pan-Arctic drained lake basin data product. Comprehensive mapping of DLB areas across the circumpolar permafrost landscape will allow for future utilization of these data in pan-Arctic models and greatly enhance our understanding of DLBs in the context of permafrost landscapes. Utilizing remote sensing imagery (Landsat-8) and freely available DEM data sets (e.g. ArcticDEM) allows us to implement our mapping approach on a circumpolar scale. A previously published prototype of this data product covering the North Slope of Alaska forms the basis of this large-scale mapping effort. Here we present first result working towards a pan-Arctic remote sensing-based DLB data product focussing on selected areas in Canada and Siberia, Russia.

How to cite: Bergstedt, H., Jones, B., Grosse, G., Veremeeva, A., Breen, A., Liljedahl, A., Bartsch, A., Gaglioti, B., Bouchard, F., Hugelius, G., Nitze, I., Wolter, J., Hinkel, K., Farquharson, L., Fuchs, M., Kanevskyi, M., Roy-Leveillee, P., and Lantz, T.: Drained lake basins on a circumpolar scale – Updates from the IPA Action Group, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9681, https://doi.org/10.5194/egusphere-egu22-9681, 2022.

EGU22-9692 | Presentations | GM10.3

Long-term destabilization of retrogressive thaw slumps (Herschel Island, Yukon, Canada) 

Saskia Eppinger, Michael Krautblatter, Hugues Lantuit, Michael Fritz, Josefine Lenz, and Michael Angelopoulos

Retrogressive thaw slumps (RTS) are a common thermokarst landform along Arctic coastlines and provide a large amount of material containing organic carbon to the nearshore zone. The number of RTS has strongly increased since the last century. They are characterized by rapidly changing topographical and internal structures e.g., mud flow deposits, seawater-affected sediments or permafrost bodies and are strongly influenced by gullies. Furthermore, we hypothesize that due to thermal and mechanical disturbance, large RTS preferentially develop a polycyclic behavior.

To reveal the inner structures of the RTS several electrical resistivity tomography (ERT) transects were carried out in 2011, 2012, and 2019 on the biggest RTS on Herschel Island (Qikiqtaruk, YT, Canada), a highly active and well-monitored study area. 2D ERT transects were conducted crossing the RTS longitudinal and transversal, always reaching the undisturbed tundra. Parallel to the shoreline, and crossing the main gully draining the slump, we applied 3D ERT which was first measured in 2012 and repeated in 2019. The ERT data was calibrated in the field using frost probing to detect the unfrozen-frozen transition and with bulk sediment resistivity versus temperature curves measured on samples in the laboratory.

The strong thermal and topographical disturbances by gullies developing into large erosional features like RTS, lead to long recovery rates for disturbed permafrost, probably taking more than decades. In this study we demonstrate that ERT can be used to determine long-lasting thermal and mechanical disturbances. We show that they are both likely to prime the sensitivity of RTS to a polycyclic reactivation.

How to cite: Eppinger, S., Krautblatter, M., Lantuit, H., Fritz, M., Lenz, J., and Angelopoulos, M.: Long-term destabilization of retrogressive thaw slumps (Herschel Island, Yukon, Canada), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9692, https://doi.org/10.5194/egusphere-egu22-9692, 2022.

EGU22-11255 | Presentations | GM10.3

Teleconnections and a holistic Earth Systems approach to a retreating Alpine glacier 

Dan Le Heron, Charlie Bristow, Bethan Davies, Bernhard Grasemann, Christoph Kettler, and Martin Schöpfer

The Gepatschferner in the Öztal Alps is Austria’s second largest glacier and is the subject of a monitoring campaign from 2019 onwards which was initially focussed on sedimentology and geomorphology of the forefield. Emphasis was placed on the styles and rates of sediment cannibalisation, with implications for transcription of the evidence into the deep time sedimentary record. This included the mapping of flutes, crag and tail structures, roches moutonées, fluvial sediments, till and rockfall deposits in the proglacial area. Their evolution over time is documented by repeated fieldwork and drone surveys. However, cognizant of the complexity of the subglacial environment (deforming bed areas, rigid bed areas and shifting meltwater systems) our work has expanded to ground-penetrating radar (GPR) surveys, enabling us to map subglacial conduits, englacial channels, and glacier structure. This structure involves the mapping of foliation, folds and fractures in the glacier, supported by field measurements. Repeated survey of both GPR and drones allows the 4D evolution of surficial glacier drainage, elevation, and forefield to be characterised. This work thus encompasses sedimentology, geomorphology, structural glaciology and bedrock geology. We argue that investigating the temporal and spatial landsystem-scale interactions between cryosphere (glacier and its structure), hydrosphere (meltwater pathways), and lithosphere (geomorphology, bedrock geology, sedimentology) will lead to breakthrough interpretations. These will include (i) controls on the evolution of the meltwater system, (ii) controls on the genesis of subglacial bedforms, (iii) the relationship between geology, geomorphology and glacier structure. Repeated, iterative surveys allow us to explore the teleconnections between cryosphere, hydrosphere and lithosphere, and their predictive capacity.

How to cite: Le Heron, D., Bristow, C., Davies, B., Grasemann, B., Kettler, C., and Schöpfer, M.: Teleconnections and a holistic Earth Systems approach to a retreating Alpine glacier, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11255, https://doi.org/10.5194/egusphere-egu22-11255, 2022.

Boulder-dominated periglacial, paraglacial and related landforms are important elements which can help to improve our knowledge about past climatic conditions and morphodynamic processes. As the formation and stabilization of these landforms can be associated to cold or transitioning climatic conditions from cold to warm, putting them on a solid temporal basis is vital to connect their evolution to changing climatic conditions throughout the Holocene. In this study, Schmidt-hammer exposure-age dating (SHD) was performed at different landforms including sorted polygons, rock-slope failure deposits and a blockfield in and around Breheimen, South Norway. By obtaining an old and a young control point, it is possible to calculate a calibration curve, from which the respective landform ages were estimated. The SHD age estimates ranged from 8.02 ± 0.72 to 3.45 ± 0.70 ka showing their relict character. The sorted polygon ages of 6.55 ± 0.68 and 4.76 ± 0.63 ka point to a stabilization within and towards the Holocene Thermal Maximum (HTM; ~8.0–5.0 ka). Whereas the ages of the investigated rock-slope failures from 8.02 ± 0.72 to 3.45 ± 0.70 ka can be divided in two groups. The first group consists of two rock-slope failures with overlapping ages with a mean age of ~7.6 ka. This timing can be related to the onset of the HTM characterized by warmer temperatures possibly leading to slope weakening due to a variety of factors, such as permafrost degradation and increasing cleft-water pressure. Ages of the second group, with three rock-slope failures, cluster around ~3.7 ka, shortly after a cold climatic period between 4.75–3.85 ka. Therefore, we assume that the occurrences of these rock-slope failures could have been climatically induced by warmer temperatures. The blockfield age of 5.24 ± 0.79 ka is significantly younger than other dated blockfields in South Norway and indicates longer activity of the boulders at the blockfield surface. Surface exposure ages from boulder-dominated landforms stress that these landforms can be valuable elements in improving our knowledge about landform evolution and palaeoclimatic fluctuations within the Holocene in South Norway.

How to cite: Marr, P., Winkler, S., and Löffler, J.: Boulder-dominated periglacial and related landforms as palaeoclimatic and morphodynamic indicators in Breheimen, South Norway, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12371, https://doi.org/10.5194/egusphere-egu22-12371, 2022.

The last Fennoscandian Ice Sheet provides a valuable scenario for testing and evaluating numerical ice sheet models with a large amassed database of landform, stratigraphic and dated evidence of ice sheet activity. In contrast to the core shield area (Norway, Sweden and Finland) of the ice sheet, fewer investigations beyond the shield (Denmark, Germany, Poland, Lithuania, Latvia, Estonia and Russia) attempt to gather local to regional information into ice sheet wide syntheses of ice margin and lobe dynamics. For example, many detailed investigations across these countries remain disconnected with adjacent areas applying varying methods and naming schemes making it difficult to reconcile at the ice sheet scale.

Here we present a systematic and spatially coherent reconstruction of ice margin dynamics for the whole southern and eastern margin, from Denmark to arctic Russia. The landform to reconstruction method allows for a consistent approach to be applied to the 1.2+ million km2 mapping area despite a wide range of glaciological landform and data variability (DEM vary in resolution from 0.4 m-25 m) found in the 1.2+ million km2 study area. We propose this reconstruction as a first-order framework of ice marginal dynamics that can be used to develop second-order and more detailed knowledge of fluctuations when more closely connected to stratigraphic and geochronometric investigations. Rather than a simple concentric retreat pattern often envisaged the landform record and its frequent overprinting forces a solution of complexity with lobe interactions and readvances.

How to cite: Diemont, C. R., Clark, C. D., Livingstone, S. J., and Hughes, A. L. C.: Spatially continuous landform driven reconstruction of marginal retreat dynamics of the Southern and Eastern sectors of the last Fennoscandian Ice Sheet, beyond the hard bedrock shield, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12648, https://doi.org/10.5194/egusphere-egu22-12648, 2022.

EGU22-250 | Presentations | GM7.3

Timing of Glacier Retreat on Mt. Davraz by Cosmogenic Chlorine-36 in the Western Turkey 

Onur Altinay, Mehmet Akif Sarıkaya, Attila Çiner, Cengiz Yıldırım, Manja Žebre, and Uroš Stepišnik

The Taurus Mountain Range extends parallel to the Mediterranean coast of Turkey. It hosts lofty mountains (>3000 m above sea level, a.s.l.) carved by glaciers in the Late Pleistocene. Despite the recent studies in Anatolia, Mt. Davraz (2635 m a.s.l.) has not been studied in detail and its glacial chronology was lacking. This study presents our first findings of the glacial history, origin and geochronology of Mt. Davraz, which is located SW of Eğirdir Lake (915 m a.s.l.), 100 km north of Antalya city. Tectonics, karstification, glaciation, and periglaciation have led a distinctive geomorphology of the area. The main landscape of the area is predominantly shaped by paleoglaciers. Cirques are the dominant glacial erosional landforms, and most of them were developed on the northern slopes of Mt. Davraz. Based on the topographical limitations, cirque paleoglaciers could not to transformed into valley glaciers. Although it is one of the lowest mountains in the Taurus Mountain Range, it has a large hummocky field with an area of about 3 km2 on the northern slope. It was developed by a paleo-ice cap. There is also a smaller hummocky field deformed by a rock glacier advancements on the E-NE slopes of the mountain. In order to understand the timing of paleoglaciations, we obtained 6 cosmogenic 36Cl surface exposure ages from the moraine boulders on hummocky field. Based on the preliminary results, Mt. Davraz hummocky field yielded sequential retreat history; the eastern hummocky field deposited their moraines at 21.7 ± 1.5 ka ago, while the western hummocky field at 17.7 ± 1.2 ka ago. Our results show that the glaciers started to retreat by the Last Glacial Maximum (LGM) and continued to the earlier stages of Late-glacial.

This work was supported by TÜBİTAK 118Y052 and 118C329 projects.

 

How to cite: Altinay, O., Sarıkaya, M. A., Çiner, A., Yıldırım, C., Žebre, M., and Stepišnik, U.: Timing of Glacier Retreat on Mt. Davraz by Cosmogenic Chlorine-36 in the Western Turkey, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-250, https://doi.org/10.5194/egusphere-egu22-250, 2022.

The investigation of Holocene glacier chronologies has been recognised as a key element of research on mountain glaciations in the light of current global change. They can be utilised as high-resolution palaeoclimatic archives for the immediate and more distant geological past. During the past few decades considerable progress has been achieved, in particular due to substantial improvements of the ability to accurately date glacial landforms such as terminal moraines essential for reconstructing past glacier margins and subsequent analysis of glacier advance/retreat periods. The Southern Alps of New Zealand are among the few suitable regions for the investigation of Holocene glacier chronologies in the mid-latitudinal Southern Hemisphere.

Since early studies of Holocene glacier chronologies in the mid-20th century, mapping of the investigated glacier forelands has been an integrated part of almost all scientific approaches regardless of the individual dating methods applied. These mapping attempts serve the identification and positioning of certain glacial or glaciofluvial landforms and allow the reconstruction of former glacier margins. They frequently also provide information on the location of sample sites selected for subsequent dating. If detailed geomorphological mapping schemes are in use, such maps additionally support the interpretation of any chronological data by identifying the genetic origin of any landform investigated. This enables the latter to be causally related to different dynamic stages of the glacier. Additionally, such maps may highlight potential uncertainties such as postdepositional disturbance or unclear morphodynamic connections between landforms and the glacier.

Reviewing recent publications it seems, however, that some appraisal of such detailed geomorphological mapping is often traded-off against the impressive progress with up-to-date dating techniques and high-resolution digital elevation models or satellite/aerial imagery. Unfortunately, the latter do neither qualify as geomorphological maps per se nor fully serve the abovementioned purpose. The widespread applied common GIS software has, furthermore, limitations with respect to its graphic capabilities and unintentionally entails negligence of established and well-suited signatures or geomorphological mapping schemes.

A detailed geomorphological map of the glacier foreland of Mueller Glacier, Southern Alps/New Zealand will be presented. It follows an established geomorphological mapping scheme ("GMK 25") that has been adequately modified to fit both purpose and selected scale. Despite several glacier chronological studies have been conducted on this glacier foreland and the site is considered a regional 'key site', this map constitutes the first of its kind. The detailed geomorphological map is utilised to assess discrepancies among existing chronologies by reviewing the morphometric properties and genetic origin of those landforms that have been dated. It reveals that potential postdepositional modification of some landforms investigated had not been appropriately considered with certain previous studies. As a result, the evidence for some glacier advances needs to be classified as 'weak'.  

Summarising, detailed geomorphological mapping is still essential for the study of Holocene glacier chronologies and should not lose its prominent position - or even disappear.

How to cite: Winkler, S.: Potential of detailed geomorphological mapping for the study of Holocene glacier chronologies: Mueller Glacier, Southern Alps/New Zealand, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1502, https://doi.org/10.5194/egusphere-egu22-1502, 2022.

EGU22-1698 | Presentations | GM7.3

Maximum glacier extent of the Penultimate Glacial Cycle in the Upper Garonne Basin (Pyrenees): new chronological evidence 

Marcelo Fernandes, Marc Oliva, Gonçalo Vieira, David Palacios, José Maria Fernández-Fernández, Magali Delmas, Julia García-Oteyza, Irene Schimmelpfennig, Josep Ventura, and Aster Team

The Upper Garonne Basin constituted the longest glacier of the Pyrenean ice field during the Late Pleistocene. From the peaks of the axial Pyrenees that exceed 2,800-3,000 m, the Garonne palaeoglacier flowed along ~80 km northwards during the major glacial advances reaching only 420-440 m. This palaeoglacier reached the Pyrenean foreland, at the Loures-Barouse-Barbazan basin (LBBB) where it formed a terminal moraine complex that is examined in this work. We have constrained the timing of the maximum glacial extent as well as the onset of the deglaciation from the end of the Last Glacial Cycle (LGC) based on the geomorphological observations and a 12-sample dataset of 10Be Cosmic-Ray Exposure (CRE) ages. There are two moraine systems at the LBBB, where the first is composed of weathered ridges at the outermost part of the basin and the second encompasses well-preserved ridges stretching across the innermost part of the basin. Chronological data shows that the external moraines were abandoned by the ice at the end of the Penultimate Glacial Cycle (PGC) and the onset of the Eemian Interglacial, at ~129 ka. The few existing reliable boulders to date in the internal moraine showed inconsistent ages as they were probably affected by post-glacial processes and therefore, this work adds no evidence of subsequent glacial advances or standstills during the LGC in the LBBB. However, the terminal basin was already deglaciated during the global Last Glacial Maximum (GLGM) at 24-21 ka, as revealed by exposure ages from polished surfaces at the confluence of the Garonne-la Pique valleys, 13 km south of the entrance of the LBBB. This study introduces the first solid CRE database in the Pyrenees for the glacial advance that occurred during the PGC and provides also new evidence from the GLGM when the Garonne palaeoglacier had already significantly shrunk.

How to cite: Fernandes, M., Oliva, M., Vieira, G., Palacios, D., Fernández-Fernández, J. M., Delmas, M., García-Oteyza, J., Schimmelpfennig, I., Ventura, J., and Team, A.: Maximum glacier extent of the Penultimate Glacial Cycle in the Upper Garonne Basin (Pyrenees): new chronological evidence, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1698, https://doi.org/10.5194/egusphere-egu22-1698, 2022.

EGU22-2054 | Presentations | GM7.3

Simulating the surface mass balance at the Monte Sarmiento Massif, Cordillera Darwin, Chile 

Franziska Temme, David Farías-Barahona, Thorsten Seehaus, Tobias Sauter, Ricardo Jaña, Jorge Arigony-Neto, Inti Gonzalez, Christoph Schneider, and Johannes Fürst

Together with the Northern and the Southern Patagonian Icefield, the Cordillera Darwin Icefield (CDI) in Tierra del Fuego experienced strong ice loss during the last decades. In some areas the observed glacier retreat contrasts with findings of recent surface mass balance studies, which implies that the observed losses are partly caused by dynamic adjustments. However, the difficult accessibility of Patagonian glaciers and the harsh conditions result in scarce observational data of glacier mass balances, especially for the CDI. In the westernmost region of the CDI, Monte Sarmiento is located. It hosts an 83 km2 icefield, with Schiaparelli Glacier being the largest glacier, terminating in a proglacial lake.

We focus on reproducing the local meteorological conditions using statistical downscaling of atmospheric reanalysis data to the study site as well as a linear model of orographic precipitation. Subsequently, we concentrate on a best representation of the surface mass balance (SMB) conditions on the local glaciers. For this purpose, we apply four melt models of different complexity: i) a positive degree-day model, ii) a simplified energy balance model using potential insolation, iii) a simplified energy balance model using the actual insolation (accounting for cloud cover, shading effects and diffuse radiation) and iv) a fully-fledged surface energy balance model. For the latter, we rely on the “COupled Snowpack and Ice surface energy and mass balance model in PYthon” (COSIPY). These models are calibrated on Schiaparelli Glacier (24.3 km2), which is the largest and best-studied glacier of the Monte Sarmiento Massif. Observational records comprise in-situ stake, thickness and meteorological measurements as well as remotely sensed elevation changes and flow velocities. After the melt model calibration, we apply them to other adjacent glacier basins and assess their performances against geodetic mass changes. This way, we want to answer the question if it is feasible to apply SMB models, calibrated for one single glacier, to surrounding glaciated areas under these unique climatic conditions. If a single-site calibration showed poor transferability properties, further remotely sensed observables will be considered in the calibration. This way we also hope to answer the question, which melt model can best reproduce the spatial variability in remotely sensed specific mass balances over a larger region.

How to cite: Temme, F., Farías-Barahona, D., Seehaus, T., Sauter, T., Jaña, R., Arigony-Neto, J., Gonzalez, I., Schneider, C., and Fürst, J.: Simulating the surface mass balance at the Monte Sarmiento Massif, Cordillera Darwin, Chile, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2054, https://doi.org/10.5194/egusphere-egu22-2054, 2022.

EGU22-2237 | Presentations | GM7.3 | Highlight

Multidecadal Delay Between Deglaciation and Formation of a Proglacial Lake Sediment Record 

Loic Piret, Sebastien bertrand, and Fernando Torrejón

Proglacial lake sediments are widely recognised as accurate and high-resolution archives of climate and glacier variability. Sediments deposited in proglacial lakes are frequently varved, which offers the possibility to generate precisely-dated records, and their basal ages are often used to constrain deglaciation histories. It is often assumed that lake sedimentation starts immediately after deglaciation. With this in mind, we studied the onset of lake sedimentation in a recently deglaciated lake (Calluqueo Lake, Chilean Patagonia) to investigate the possible delay between proglacial lake formation and establishment of a continuous sediment record. Calluqueo Lake is a 3.5 km long lake composed of a large 220 m deep proximal basin, separated from a smaller 50 m deep distal basin by a 40 m deep sill. The lake is bordered by steep lateral moraines that contain large boulders. Aerial images and historical data show that Calluqueo Glacier entirely covered the lake basin until 1941. Since then, it rapidly receded until it became land-based in 1985. Side Scan sonar images and grab sampling shows that the sediment cover is limited to the small distal basin, which was entirely deglaciated by 1978. By comparison, no sediment was found in the deepest proximal basin although it has been ice free for at least three decades. Varve counting of sediments deposited in the distal basin shows that the stratigraphic record starts in 1996 ± 4 CE, i.e., that the first 20 – 50 years of the glacier’s retreat are not represented in the sediments of Calluqueo Lake. We hypothesize that the fine-grained sediments that are discharged into the lake immediately after its formation first start accumulating between the large boulders that compose the ablation moraine on the lake floor. The continuous stratigraphic record only starts forming after the coarse moraine deposits are buried under fine-grained particles. Our results have important implications for the use of proglacial lake sediments in paleoclimate and paleoenvironmental research. They suggest that proglacial lake sediment records lack the first 20 – 50 years of sedimentation. Although this delay may be negligible for reconstructions of deglaciation histories based on basal radiocarbon ages, it becomes significant for the use of lake sediment records from recently deglaciated environments.

How to cite: Piret, L., bertrand, S., and Torrejón, F.: Multidecadal Delay Between Deglaciation and Formation of a Proglacial Lake Sediment Record, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2237, https://doi.org/10.5194/egusphere-egu22-2237, 2022.

EGU22-2466 | Presentations | GM7.3

Postglacial environment reconstruction of the northwestern USA from the lacustrine record: Bells Lake, northern Idaho 

Avinesh Kumar, Daniel Gavin, and Nicolas Waldmann

Lakes acts as the ubiquitous substitutes of oceans by effectively imprinting the signatures of varying environments in their sediments. A multiproxy sedimentary record from Bells Lake (N Idaho, USA) has been investigated to ascribe the postglacial paleoenvironment of NW USA. It is a 5 m deep, 6.3 ha lateral lake situated on the floodplain of the St. Joe River. It receives its sedimentary input from the central part of the Rocky Mountains. Therefore, perfectly situated for archiving environmental variability related to alpine glacial variability and precipitation fluctuations in relation with millennial-scale latitudinal migrations of the Northern Hemisphere Westerlies (NHW) since the Last Glacial Maximum (LGM). We recovered a continuous 15 m core using a Livingstone corer at the centre of the lake for this study. The core stratigraphy consists of five major units ranging from black organic-rich clay towards the top and clayey sand-silt in the bottom units. The bottom of the core consists of stiff clayey sediments that prevented further penetration and were dated by radiocarbon to 15.2 ka. Therefore, it appears to represent sediments that shortly post-date the last Missoula Flood event. The whole record was framed by seven radiocarbon dates and three tephra isochrons. The record shows that during the early Holocene, an increase in detrital geochemical proxies (Al, K, Fe, and Ti) and a high sedimentation rate (3.72 mm/yr) point towards high terrestrial input in a warm and humid environment, probably inducing high productivity in the lake. These changes likely resulted from intensified weathering conditions and high surface runoff with the latitudinal migration of the NHW, which induced diminishing conditions of the continental alpine glaciers in the Rockies. The Younger Dryas (12.9-11.7 ka) is clearly recorded by several parameters, including paleo-redox proxies (e.g., Mn/Fe), weathering indices (Chemical Index of Alteration), Fe-S plot, a decrease in TOC, and an increase in clay content. This suggests oxic hypolimnion (due to lower lake levels or increased wind strength) and increased fine detrital input (possibly from glacial expansion). Occasional flooding might have been responsible for the deposition of fine sand layers at 11.6-11.2 ka. Following this episode, the 8.2 ka & 4.2 ka events of aridity were also well identified by the sudden drops in the detrital proxies and magnetic susceptibility values, probably pointing to reduced weathering conditions during a short return to a cold and arid phase; later was possibly due to the dramatic warming of North Pacific Ocean might be caused by increased solar irradiance or volcanism disrupting the SST gradient between tropical eastern and the western Pacific Ocean. A thick Mt. Mazama tephra (7.6 ka), a confounding event, is also capsuled in the record likely contributing to the rapid formation of long gun barrel levees that extended into Lake Coeur d'Alene (CDA). A major change in the limnological conditions appear to occur at 6.1 ka and is interpreted as the isolation of Bells Lake basin from the larger Lake CDA, currently occupying the lowlands in the west within the modern mean state Mediterranean type of climate system. 

How to cite: Kumar, A., Gavin, D., and Waldmann, N.: Postglacial environment reconstruction of the northwestern USA from the lacustrine record: Bells Lake, northern Idaho, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2466, https://doi.org/10.5194/egusphere-egu22-2466, 2022.

EGU22-2910 | Presentations | GM7.3

The glacial geomorphology of the Scărișoara Plateau, Godeanu Mountains, Southern Carpathians, Romania 

Cristina-Ioana Balaban, David H. Roberts, David J.A. Evans, and Stewart S.R. Jamieson

Reconstructing the extent, style, timing and drivers of past mountain glaciation is crucial in both understanding past atmospheric circulation and predicting future climate change. Unlike in high-elevation mountains situated in maritime and continental climates, less is known of past glaciation in mid-altitude mountains, located in transitional climates, such as the Southern Carpathians of Romania. Despite these mountains harbouring a rich glacial geomorphology, this has never been systematically mapped according to well-established morphological criteria, nor confidently related to former styles of glaciation. Therefore, filling this gap is important for not only accurately identifying glacial extents, but also for establishing past glaciation styles and relating them to past ice dynamics and climate. We aim to understand the extent and timing of past glaciation in the Godeanu Mountains, Southern Carpathians. We present a new geomorphological map of the area, highlighting landforms associated with glaciation of the Scărișoara plateau and surrounding valleys. Using both remote (orthophotographs and Google Earth) and field mapping techniques, we describe and interpret the origins of glacial erosional landforms (ice-moulded bedrock, ice-marginal meltwater channels), and of depositional discrete debris assemblages of likely glacial (moraines), periglacial (pronival ramparts, protalus lobes, rock glaciers) and paraglacial (rock slope failure) origins. We also hypothesize the relationship of these landforms with former styles of glaciation. The field study results aid the interpretation of the geomorphology in the wider mountain range. Once absolute chronological results have been produced, the mapping will be used as a spatial constraint for numerical ice-flow modelling in the Parallel Ice Sheet Model (PISM).

How to cite: Balaban, C.-I., Roberts, D. H., Evans, D. J. A., and Jamieson, S. S. R.: The glacial geomorphology of the Scărișoara Plateau, Godeanu Mountains, Southern Carpathians, Romania, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2910, https://doi.org/10.5194/egusphere-egu22-2910, 2022.

EGU22-3235 | Presentations | GM7.3

Late Quaternary glacier-based climate reconstruction from the Southern Alps, New Zealand 

Levan Tielidze, Shaun Eaves, Kevin Norton, Andrew Mackintosh, and Alan Hidy

Geochronological dating of glacial landforms, such as terminal and lateral moraines, are useful for determining the extent and timing of past glaciation and for reconstructing the magnitude and rate of past climate changes. Here we report the first dataset of Late Quaternary glacial maximum extent and its deglaciation from the Ahuriri River valley, Southern Alps, New Zealand (44°23'54''S, 169°39'48''E) based on 66 beryllium-10 (10Be) surface-exposure ages from terminal-lateral moraine systems and glaciated bedrock surfaces situated at different sites of the valley. Our results show that the former Ahuriri Glacier reached its maximum extent 19.8±0.3 ka, which coincides with the global Last Glacial Maximum. By 16.7±0.3 ka, the glacier had retreat ~18 km up-valley and this deglaciation was accompanied by the formation of a shallow proglacial lake. Our surface-exposure chronology from the moraines situated upper right tributary of the Ahuriri River valley also indicates that other subsequent advance of the palaeo glacier culminated at 14.5±0.3 ka ago, while the next re-advance or still stand phases occurred at 13.6±0.3 ka. About 1000 yr later (12.6±0.2 ka), the former glacier built another prominent terminal-lateral moraine ridge in the lower section of the upper right tributary valley. In overall, our result supports the hypothesis that climate was ~5°C colder (ELA depression ~880 m) than present at 19.8±0.3 ka, while it was ~4.4°C colder (ELA depression ~770 m) at 16.7±0.3 ka. Furthermore, local air temperature was lower by 3.6°C (ELA depression ~630 m) during the 14.5-13.6 ka and by 2.0°C (ELA depression ~360 m) at 12.6 ka respectively relative to present. Our results clearly demonstrate the structure of last glacial termination in New Zealand such as strong glacier recession during this time-period in accordance of at least five glacier re advances or still stand phases. This new 10Be surface exposure dataset will help us in better understanding of past glacier-climate interactions in the Southern Alps and in the Southern Hemisphere in general.

How to cite: Tielidze, L., Eaves, S., Norton, K., Mackintosh, A., and Hidy, A.: Late Quaternary glacier-based climate reconstruction from the Southern Alps, New Zealand, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3235, https://doi.org/10.5194/egusphere-egu22-3235, 2022.

EGU22-4623 | Presentations | GM7.3

Paleogeographic reconstruction of Segrino Lake area: Southern Alps, Northern Italy 

Laura Simoncelli, Alberto Bosino, Vít Vilímek, Jan Kropáček, and Michael Maerker

The origin of the Southern sub-Alpine lakes was intensively discussed in the past century. Morphological observations, combined with seismic reflection acquisitions provided the fluvio-glacial origin of them. However, the formation and the post-Messinian evolution of the smaller lakes between the two branches of the Como Lake, Southern Alps, Italy, was only marginally investigated so far. This area is regionally named Triangolo Lariano, and several authors hypothesised the post-Messinian evolution of Segrino Lake area connecting its formation with the initial Messinian incision followed by the morainic block during the Last Glacial Maximum (LGM). The proposed study re-evaluates the origin of Segrino Lake as well as the lower Triangolo Lariano area, using morphological observation, orthophoto interpretation, detailed Terrain analysis on high-resolution DEM and finally, the interpretation and correlation of borehole stratigraphy. The results highlight a complex morphological evolution of the area up to the pre-Messinian times. In fact, considering the morphology and the geological characteristics of the bedrock as well as the morphometry of the area, fluvial and glacial phases were observed. Deep incised valleys linked with the Messinian Sea level change, and a complex drainage system are clearly detectable on the field and from detailed Terrain analysis. Finally, to reconstruct the paleogeography and order the chronology of the geological events that have occurred in the area, a set of borehole data were interpreted. These analyses allowed to observe an alternation of strata characterized by heterogeneous and interstratified deposits, that reflected a sequence of lacustrine, fluvial, glacial, lacustrine, and fluvial deposits. In fact, the careful evaluation of the stratigraphy highlights the presence of a pre-Messinian lacustrine phase in the area North of Segrino Lake. In addition, fluvial deposits, suspended valleys and paleo-meanders suggest a strong erosive phase dating back to the Messinian age. During this period, the Lambro River deeply incised into the bedrock forming the actual Segrino Valley. Subsequently, the glaciation phase remodelled the area, depositing erratic boulders and morainic material that caused changes in the drainage settings. In particular, the morainic barrier South of Segrino Lake is responsible for the formation of a new lake in the Segrino-Canzo area as well as in the lower part of the study area were the Pusiano and Alserio Lakes are located nowadays. In the following period the deglaciation and the new hydrological asset of the area led to a shrinking of Segrino-Canzo Lake, and finally a drainage inversion of Segrino Lake, with the outflow directed towards North, and the formation of an alluvial fan which isolated the actual Segrino Lake. Finally, the hypothesis already formulated in the past by some other authors, regarding the presence of a lake that he would fill the study area after the LGM, is therefore supported. New evidence due to the available borehole stratigraphy allowed us to recognize a new and more complex and highly heterogeneous evolution of the study area from Messinian time onwards.

How to cite: Simoncelli, L., Bosino, A., Vilímek, V., Kropáček, J., and Maerker, M.: Paleogeographic reconstruction of Segrino Lake area: Southern Alps, Northern Italy, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4623, https://doi.org/10.5194/egusphere-egu22-4623, 2022.

EGU22-4999 | Presentations | GM7.3

Late-glacial to Neoglacial evolution of glacier extent and surface mass balance in the Cordillera Blanca, Peruvian Andes 

Tancrède Leger, Andrew Hein, Daniel Goldberg, and Derek Fabel

Cordillera Blanca glaciers represent the greatest glacial freshwater reserve in tropical South America and have been shrinking substantially over recent decades, posing a threat to future water resources in the Peruvian Ancash region. A crucial step to better understand the evolution of these glaciers under changing conditions is to establish robust reconstructions of their past response to climate fluctuations. Such reconstructions are limited in the tropical Andes, which inhibits our understanding of the climatic drivers of tropical glacier length and surface mass balance changes. The relative importance of temperature versus precipitation rate changes on glacier length changes is therefore still debated in the region. Here, we present 42 cosmogenic 10Be exposure ages from moraine boulder samples, establishing for the first time a comprehensive chronology for Late-glacial, Holocene and Neoglacial advances of four distinct Cordillera Blanca mountain glaciers. We use this chronology to constrain a series of moraine-matching numerical model-run simulations conducted for each dated glacier advance using a spatially-distributed ice-flow model coupled with a positive degree-day surface mass balance parameterisation. These simulations aim at modelling and estimating former three-dimensional glacier geometries, equilibrium line altitudes, surface mass balance properties and their evolution through time. This analysis also enables us to use glacier surface mass balance as a proxy for past atmospheric temperature and precipitation variations at the time of the reconstructed glacier advances. This new, multi-method glacier reconstruction enables, for the Cordillera Blanca: 1) novel glacio-geomorphological interpretations, 2) an improved understanding of glacier extent, surface mass balance and volume change during the Late-glacial, Holocene and Neoglacial phases of advance, and 3) new estimations of paleoclimate conditions required for the reconstructed glacier events to occur.   

How to cite: Leger, T., Hein, A., Goldberg, D., and Fabel, D.: Late-glacial to Neoglacial evolution of glacier extent and surface mass balance in the Cordillera Blanca, Peruvian Andes, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4999, https://doi.org/10.5194/egusphere-egu22-4999, 2022.

EGU22-5052 | Presentations | GM7.3

Coincident glacier and lake evolution across New Zealand: Past, present, and future 

Jenna Sutherland, Jonathan Carrivick, Matthias Huss, Heather Purdie, Christopher Stringer, Michael Grimes, William James, and James Shulmesiter

Mountain glaciers are rapidly diminishing and causing widespread environmental and socio-economic concern. The stability of mountain glaciers is influenced by the expansion of proglacial landscapes and meltwater impounded as lakes within natural topographic depressions or ‘overdeepenings’. In particular, the relative sensitivity of mid-latitude glaciers to modern climate change makes them especially important to consider. One of the most striking features of South Island, New Zealand, is the sequence of glacial lakes that occupy mountain valleys along the Southern Alps. Our previous work has highlighted that the presence of these lakes is likely to have had an impact on ice-marginal dynamics of their adjacent glaciers, thereby influencing the rate of deglaciation on sub-millennial timescales. This emphasizes the need to incorporate proglacial lakes into palaeoglacier reconstructions and into analyses of future glacier evolution. In this new study we (i) document contemporary loss of glacier ice across the Southern Alps, (ii) analyse ice-marginal lake development since the 1980s, (iii) utilise modelled glacier ice thickness to suggest the position and size of future lakes, and (iv) employ a large-scale glacier evolution model to suggest the timing of future lake formation and future lake expansion rate. In recent decades, Southern Alps glaciers have fragmented both by separation of tributaries and by detachment of ablation zones. Glacier margins in contact with a proglacial lake have experienced the greatest terminus retreat. Our analysis indicates a positive relationship between mean glacier mass balance and rate of lake growth and with length of an ice-contact lake boundary. We project sustained and relatively homogenous glacier volume loss for east-draining basins but in contrast a heterogenous pattern of volume loss for west-draining basins. Our model results show that ice-marginal lakes will increase in number and combined size towards 2050 and then decrease to 2100 as glaciers disconnect from them. Overall, our findings should inform (i) glacier evolution models into which ice-marginal lake effects need incorporating, (ii) studies of rapid landscape evolution and especially of meltwater and sediment delivery, and (iii) considerations of future meltwater supply and water quality.

How to cite: Sutherland, J., Carrivick, J., Huss, M., Purdie, H., Stringer, C., Grimes, M., James, W., and Shulmesiter, J.: Coincident glacier and lake evolution across New Zealand: Past, present, and future, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5052, https://doi.org/10.5194/egusphere-egu22-5052, 2022.

EGU22-6505 | Presentations | GM7.3

Insight into glacier evolution, proglacial lake dynamics, and paleoclimate from Lago Argentino, Patagonia 

Maximillian Van Wyk de Vries, Emi Ito, Mark Shapley, Guido Brignone, Matias Romero, and Andrew D. Wickert

Proglacial lakes provide valuable records of paleoclimate, volcanism, and glaciation. We present results from spatially extensive coring of Lago Argentino, a 1500 km2 proglacial lake on the eastern margin of the Southern Patagonian Icefield (SPI). We recovered forty-seven sediment cores from water depths up to 600 m. Detailed analysis of this sediment reveals annual laminations – known as varves – which we use to build a high-resolution age-depth model for each core.

In this presentation, we discuss the insight gained into varve formation mechanisms, paleoclimate, and glacier change in the Lago Argentino basin of the Southern Patagonian Icefield. Firstly, we show that varves form by three distinct mechanisms across Lago Argentino (~west to east): a seasonal cycle in glacial sediment influx, a seasonal cycle in lake mixing, and a seasonal cycle in fluvial sediment influx. Second, we examine the evidence for recent glacier fluctuations across Lago Argentino. We find evidence that glaciers were locally larger early in the last millennium than during the Little Ice Age. Finally, we examine the periodicity of sediment mass accumulation rate and find dominant decadal to centennial periodicities (35, 80, 150 and 200 years). We relate periodicities in sediment accumulation to periodicities in known climatic drivers, specifically the Southern Annular Mode. These results provide new insight into multiannual glacial change and sedimentation dynamics in a complex glacio-lacustrine system and highlight the value of proglacial lake records for understanding present-day glacier change.

How to cite: Van Wyk de Vries, M., Ito, E., Shapley, M., Brignone, G., Romero, M., and Wickert, A. D.: Insight into glacier evolution, proglacial lake dynamics, and paleoclimate from Lago Argentino, Patagonia, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6505, https://doi.org/10.5194/egusphere-egu22-6505, 2022.

EGU22-7124 | Presentations | GM7.3

Landscape evolution of the Sölk Valleys and adjacent regions from the last Interglacial to today (Niedere Tauern range, Austria) 

Gerit E.U. Griesmeier, Jürgen M. Reitner, and Daniel P. Le Heron

The Gröbminger Mitterberg, an isolated flat hill located within the Enns Valley, consists of fluvial, deltaic and lake bottom sediments on top of bedrock, which are covered by subglacial till. In comparison, the sedimentary succession in the Sölk Valleys, which drain into the Enns Valley, is more divers. The highest peaks reaching 2680 m a.s.l. and cirques are dominated by talus, relict rock glaciers and two groups of moraine ridges. Latero-frontal moraine ridges located higher than 1900 m a.s.l. are remarkable. Frequently, two or three ridges are located close to each other and have a morphologically fresh shape. Further downvalley, single laterao-frontal moraine ridges occur, which are often flattened and less prominent. They appear in different altitudes according to their catchment area. However, they do not reach the main valley floor. The slopes of the main valleys and secondary valleys are often covered by subglacial till and reworked slope deposit,s which are dominated by a silty-sandy matrix and angular to subrounded clasts. Additionally, many slopes have been affected by mass movements. At the valley mouth of secondary valleys, ice marginal sediments occur consisting of very rounded pebbles in a sandy matrix and in some areas, cross bedding can be observed. Slightly above the valley floor of the main valleys, gently sloping terrace bodies interfingering with truncated alluvial fans and slope sediments described above occur. These deposits are diamicts, which consist of sandy or silty matrix with rounded and angular clasts.

An interpretation of these findings suggests the following landscape evolution:

The sedimentological record of Gröbminger Mitterberg suggests aggradation of the Enns Valley floor to at least 850 m a.s.l. (200 m higher than today) prior to the Last Glacial Maximum (LGM). During the LGM, the area was covered by the Enns Glacier with tributary glaciers from the Sölk Valleys. The ice surface reached 1800 m a.s.l. in the northernmost part (in the Enns Valley), roughly 2100 m a.s.l. in the southernmost part at a transfluence pass (Sölkpass) and even higher altitudes in cirques. During that time, large areas were covered by basal till. With the breakdown of the ice mass and ice surface lowering at the onset of the phase of ice-decay, trunk glaciers and cirque glaciers got separated resulting in the formation of ice-marginal lakes. On the already ice-free slopes, reworking of the previously deposited sediment and mixing with talus started. Further, climate warming proceeded and ice retreat resulted in mass movements and rock falls. As soon as the valley floor was ice-free, aggradation started by large river systems accumulating sediment in the valley floor. This was followed by two separate cold stages, the Gschnitz Stadial (Heinrich Event 1, ~16-17 ka) and the Egesen Stadial (Younger Dryas, ~12-13 ka), where cirque glaciers developed in equilibrium with climate oscillations (up to three stabilisation phases recognised during Egesen Stadial). In the Holocene, climate warming led to river incision in the main valleys and resulted in today´s landscape.

How to cite: Griesmeier, G. E. U., Reitner, J. M., and Le Heron, D. P.: Landscape evolution of the Sölk Valleys and adjacent regions from the last Interglacial to today (Niedere Tauern range, Austria), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7124, https://doi.org/10.5194/egusphere-egu22-7124, 2022.

EGU22-7360 | Presentations | GM7.3

Late Pleistocene glacial advances, equilibrium-line altitude changes and paleoclimate in the Jakupica Mt. (North Macedonia) 

Zsófia Ruszkiczay-Rüdiger, Zoltán Kern, Marjan Temovski, Balázs Madarász, Ivica Milevski, Johannes Lachner, and Peter Steier

In the Jakupica Mt. (North Macedonia, Central Balkan Peninsula; ~41.7° N, ~21.4 E; maximum elevation: 2540 m asl) a large plateau glacier was reconstructed. The lowest mapped moraines in the northeastern valleys are at elevations of 1490-1720 m asl and suggest the former existence of glacier tongues of ~3 km length. The maximum ice extent and five deglaciation phases were reconstructed. The equilibrium line altitude (ELA) of the most extended glacial phase is 2073+37/-25 m asl. The 10Be Cosmic Ray Exposure (CRE) age (n=8) of this phase was estimated at 19.3+1.7/-1.3 ka, conformable with the LGM similarly to the nearby Jablanica Mt [1]. CRE ages from the next moraine generation placed the first phase of deglaciation to 18.2+1.0/-3.0 ka (n=8). The samples from the moraine of the penultimate deglaciation phase (n=5) provided CRE ages with large scatter and biased towards old ages, which is probably the result of inherited cosmogenic nuclide concentrations within the rock [2, 3], as it was suggested in the cirques of the Retezat Mt. [4].

Glacio-climatological modelling was performed under constrains of geomorphological evidence in order to make paleoclimatological inferences. The degree-day model was used to calculate the amount of accumulation required to sustain the glaciological equilibrium assuming a certain temperature drop at the ELA for the most extended stage.

If the LGM mean annual temperature and the increased annual temperature range suggested by pollen-based paleoclimate reconstructions [5] are placed into the glaciological model the estimated annual total melt at the LGM ELA implies much wetter conditions compared to the current climate. This is in contrast with the regional LGM annual precipitation reconstructions of the same dataset, which suggests ~25% decrease in the Jakupica Mt. Alternatively, the model can be constrained with the current annual temperature range and the regional estimates of LGM temperature drop at 6-7 °C. This suggests 1.3 to 1.8 times more simulated precipitation than today.

These results support paleoclimate models, which predict increased precipitation in this region and suggest that in the Central Balkan region either the precipitation or the annual temperature amplitude (or both) are inaccurate in the pollen-based paleoclimate reconstruction database.

 

Funding: NKFIH FK124807; GINOP-2.3.2-15-2016-00009; RADIATE 19001688-ST.

 

 

[1] Ruszkiczay-Rüdiger et al. 2020. Geomorphology 351: 106985

[2] Ruszkiczay-Rüdiger et al. 2021. GRA, EGU21-4573

[3] Ruszkiczay-Rüdiger et al. 2021. vDEUQUA2021, Book of Abstracts, DOI: 10.5281/zenodo.5526214

[4] Ruszkiczay-Rüdiger et al. 2021. Geomorphology, 107719.

[5] Bartlein, et al. 2011. Clim. Dyn. 37, 775–802.

How to cite: Ruszkiczay-Rüdiger, Z., Kern, Z., Temovski, M., Madarász, B., Milevski, I., Lachner, J., and Steier, P.: Late Pleistocene glacial advances, equilibrium-line altitude changes and paleoclimate in the Jakupica Mt. (North Macedonia), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7360, https://doi.org/10.5194/egusphere-egu22-7360, 2022.

EGU22-7499 | Presentations | GM7.3

New insights into the last glacial cycle in the south-eastern European Alps from the glacial geomorphological record of the Monte Cavallo (NE Italy) 

Lukas Rettig, Irka Hajdas, Giovanni Monegato, Paolo Mozzi, and Matteo Spagnolo

Recent studies have shown that during the last glacial cycle the extent, timing and style of glaciation was not uniform across the European Alps but influenced by local topographic or climatic factors. In the south-eastern part of the mountain range, for example, glaciers not only developed in the inner-Alpine sectors but also along the pre-Alpine chains, probably fuelled by high orographic precipitation in these regions. Despite their high climatic sensitivity, the evolution of these glaciers throughout the last glacial cycle is still not fully understood and more field data are needed to enable comparisons among different sites. To address this issue, we present new results from the Monte Cavallo Group (Venetian Prealps, NE-Italy), based on detailed geomorphological mapping, glacier reconstructions and Equilibrium Line Altitude (ELA) modelling; then we compare our findings to other paleoglaciers that existed along the fringe of the southern Alps.

The oldest sediments in the Monte Cavallo Group are deposits of a small lake basin, rich in organic macrofossils such as branches and bark remains. These sediments likely date back to at least the earliest part of MIS 3, or potentially even previous interglacial periods. As climate deteriorated towards the Last Glacial Maximum (LGM), glacier tongues advanced from the peak regions into the main valleys. While towards the west, some small tributaries merged with the large Piave glacier, most of the glacial system of the Monte Cavallo remained independent. Its maximum extent is marked by prominent lateral and frontal moraine ridges that allowed reconstructing the geometry and ELA of the glaciers during the LGM. Besides the valley glaciers, also mid-altitude plateaus were at least temporarily covered by ice, however these plateau glaciers probably quickly vanished after the LGM acme, due to their restricted elevation range. Glacial retreat in the valleys, on the other hand, was intermitted by phases of stagnancy or readvance, as indicated by smaller moraine ridges up-valley. Comparing these Late Glacial moraines with other regional records may reveal important patterns regarding the early stages of post-LGM deglaciation in the south-eastern Alps.

How to cite: Rettig, L., Hajdas, I., Monegato, G., Mozzi, P., and Spagnolo, M.: New insights into the last glacial cycle in the south-eastern European Alps from the glacial geomorphological record of the Monte Cavallo (NE Italy), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7499, https://doi.org/10.5194/egusphere-egu22-7499, 2022.

EGU22-8595 | Presentations | GM7.3

Structural-controlled valley morphology of the largest Central Alpine Glacier 

Ferdinando Musso Piantelli, Sandro Truttmann, and Marco Herwegh

The susceptibility of catchment rocks to glacial erosion may control the evolution of valley morphology in high-relief mountain ranges such as the Alps. Non-uniform proneness to bedrock erosion may indeed localize knickpoints and overdeepenings characteristic of glacial valleys. Yet, little is known about the explicit influence of bedrock properties (i.e. lithology, hardness, and geological structures) on glacial erosion processes. In this study, we select the Great Aletsch Glacier (Swiss Alps) as a natural laboratory to document and investigate the relationship between bedrock properties and subglacial erosion mechanisms. The Great Aletsch Glacier with a length of more than 20km and an ice thickness of up to 800m is the largest glacier in Central Europe. The underlying bedrock consists of the crystalline basement units of the Aar massif (gneiss, granite, and granodiorite) and is dissected by a large number of steep faults and former ductile shear zones. Geological and remote sensing lineament mapping combined with 3D geological modelling allowed us to make a large-scale characterization of the lithologies and structures’ spatial frequency over the entire length of the glacier. Additionally, we performed field-based rock hardness analyses (Schmidt hammer) along the glacier’s bedrocks (intact rock and faulted/sheared domains) to testify for structure-controlled erosion behaviour. Obtained results demonstrate that: (i) the typology and distribution of faults and shear zones are not uniform over the entire length of the glacier; (ii) high-frequency structure domains correlate with overdeepenings and/or abrupt glacier flow deflection in the direction of the strike of the structures; (iii) low-frequency structure domains correlate to the absence of overdeepenings and a straight glacier trajectory. In terms of erosive resistance domains of intact rock masses show high hardness values for each of the investigated lithologies without substantial variability between the different basement rocks (rebound values ranging from 45 to 60 N/mm2). On the contrary, faulted or sheared domains show a significant drop in hardness value (rebound values ranging from 10 to 40 N/mm2). Based on these results we propose that, for the case of the Great Aletsch Glacier, differences in crystalline basement lithologies do not exert an important role in glacial erosion. We postulate instead that the non-uniform spatial distribution of geological structures imposes a major control on the development of the glacial valley. The substantially reduced bulk hardness within high-frequency structure domains renders indeed the bedrock to be more prone to efficient glacial erosion process at these sites (i.e. glacial quarrying) and therefore to the development of large-scale overdeepenings, local scouring, or changes in the glacier flow direction. By contrast, the more massive undeformed and therefore less erosive low-frequency structures domains coincide with sections with no knickpoints or overdeepenings. In times of global warming and glacial retreat, such structure-controlled bedrock incisions are prone for further enhanced surface weathering and gravitation-controlled erosion processes, such as rockfalls and landslides, providing sites of enhances natural hazard potential.

How to cite: Musso Piantelli, F., Truttmann, S., and Herwegh, M.: Structural-controlled valley morphology of the largest Central Alpine Glacier, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8595, https://doi.org/10.5194/egusphere-egu22-8595, 2022.

EGU22-9576 | Presentations | GM7.3 | Highlight

Projected increases in climate extremes and temperature-induced drought over the Peruvian Andes, 1980-2100 

Emily Potter, Catriona Fyffe, Andrew Orr, Duncan Quincey, Andrew N Ross, Sally Rangecroft, Katy Medina, Helen Burns, Alan Llacza, Gerardo Jacome, Robert Hellström, Joshua Castro, J Scott Hosking, Alejo Cochachin, Cornelia Klein, Edwin Loarte, and Francesca Pellicciotti

Precipitation, snow and ice melt from Andean river basins provide a crucial water source to mountain and downstream communities equally. Precipitation and temperature changes due to global climate change are likely to affect agriculture, hydropower generation and hazard risks, but are poorly constrained, especially in future projections.

Here we focus on two heavily glacierised regions of the Peruvian Andes, the Cordillera Blanca, and the Cordillera Vilcanota-Urubamba, to assess projected changes in extreme meteorological events and droughts. Previous work suggests increasing temperatures in both regions in the 21st century, with contrasting projections of precipitation trends. There has been little focus, however, on how extremes in precipitation and temperature might vary in the future. Having created a bias-corrected regional climate model from 1980-2018, we use empirical quantile mapping to statistically downscale 30 CMIP5 models. This ensemble is analysed to determine future changes in climate extremes.  

Both minimum and maximum daily temperatures are projected to increase in the from 2018 to 2100. This leads to a large reduction in the number of frost days in both regions, and suggests that under a high-emissions scenario, almost every day in the late 21st century will be in the 90th percentile of temperatures experienced during 1980-2018. The number of wet and dry days is not projected to change, but precipitation falling on very wet days (in the 95th percentile of the 1980-2018 period) is projected to increase significantly.

Lastly, we consider changes in future meteorological droughts using the standardised precipitation evapotranspiration index (SPEI) which considers potential evapotranspiration, as well as precipitation. We estimate potential evapotranspiration from temperature projections, using the Hargreaves method. Despite projected precipitation increases, temperature increases leading to an increase in evaporation may be large enough to increase meteorological droughts in the future, with the total number of drought months projected to almost double under high emission scenarios by the end of the 21st century. In a region that already experiences water stress and hazards, these changes to both extreme rainfall and drought could have a significant impact for communities in the Peruvian Andes, and for the downstream urban areas and industry that rely on mountain river flow.

 

How to cite: Potter, E., Fyffe, C., Orr, A., Quincey, D., Ross, A. N., Rangecroft, S., Medina, K., Burns, H., Llacza, A., Jacome, G., Hellström, R., Castro, J., Hosking, J. S., Cochachin, A., Klein, C., Loarte, E., and Pellicciotti, F.: Projected increases in climate extremes and temperature-induced drought over the Peruvian Andes, 1980-2100, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9576, https://doi.org/10.5194/egusphere-egu22-9576, 2022.

EGU22-9602 | Presentations | GM7.3

Climate transitions during the Late Glacial and the Early Holocene reconstructed from moraine records in the Austrian Alps 

Sandra M. Braumann, Joerg M. Schaefer, Stephanie Neuhuber, and Markus Fiebig

Glaciers provide an excellent natural laboratory for reconstructing the climate of the past as they respond sensitively to climate oscillations with advance or retreat. Therefore, we study glacier systems and their behavior during the transition from colder to warmer climate episodes in glaciated valleys of the Silvretta Massif in the Austrian Alps.  

Using a combination of geomorphological mapping and beryllium-10 surface exposure dating, we reconstruct ice extents of the past and find that glaciers stabilized during the Pre-Bølling to Bølling transition (14.4 ± 1.0 ka, n=3), during the Younger Dryas (ca. 12.9-11.7 ka; n=7), and during the earliest Holocene (ca. 12-10 ka; n=2). The first, (pre)-Bølling age group indicates a stable ice margin that postdates the Gschnitz stadial (ca. 17-16 ka) and predates the Younger Dryas. It shows that local inner-alpine glaciers prevailed until the onset of the Bølling warm phase (ca. 14.6 ka) or possibly even into the Bølling. The second Younger Dryas age group captures the spatial and temporal fine structure of glacier retreat during the Egesen stadial prior to Holocene warming. It evidences ice surface lowering of several tens of meters throughout the Younger Dryas, which is indicative of milder climate conditions at the end of the stadial compared to its beginning. The third age group falls into a period of substantial warming, the Younger Dryas-Holocene transition. The deposition of moraines during a period of abrupt warming implies centennial-scale cold snaps that were probably caused by feedback in the climate system. An explanation proposed in the Younger Dryas-Holocene context is the deglaciation of ice sheets in the Northern hemisphere and resulting freshwater input into the Atlantic ocean, which in turn slowed down ocean circulations and thus reduced heat transport toward (Northern) Europe.

The new geochronologies synthesized with pre-existing moraine records from the Silvretta Massif show that the transition from glacial to interglacial climate conditions occurred within a few centuries and illustrate the sensitive response of Silvretta glaciers to abrupt warming events in the past. Our ice-margin reconstructions provide an example of the response of glaciers and the climate system in a warming world.

How to cite: Braumann, S. M., Schaefer, J. M., Neuhuber, S., and Fiebig, M.: Climate transitions during the Late Glacial and the Early Holocene reconstructed from moraine records in the Austrian Alps, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9602, https://doi.org/10.5194/egusphere-egu22-9602, 2022.

EGU22-9793 | Presentations | GM7.3

Numerical reconstructions of the Patagonian Ice Sheet: Growth and demise through the Late Quaternary 

Andrés Castillo, Matthias Prange, Jorjo Bernales, Franco Retamal-Ramírez, Michael Schulz, and Irina Rogozhina

Glacial geomorphological and geochronological studies suggest that the Patagonian Ice Sheet (PIS) stretched from 38°S to 55°S during the Marine Isotope Stages (MIS) 2-3. While its western margin reached the Pacific Ocean, the easternmost sectors of the PIS were characterized by terrestrial lobes that fed large paleo glacial lakes after its maximum extension towards the end of the MIS 3. An ice-marginal stabilization occurred throughout the global Last Glacial Maximum followed by a rapid deglaciation after 18,000 yr before present.

Here we present an ensemble of transient numerical simulations of the PIS that have been carried out to provide information on its thickness and extents through the MIS 3 and MIS 2. Our aim here is to determine the range of climate conditions that matches the field-derived ice sheet geometries and the timing of local deglaciation, while bracketing the spread in possible ice volumes and sea level contributions originating from uncertainties in the internal parameters and external forcings. The model ensemble makes use of the new higher-order version of the ice sheet model SICOPOLIS forced by combination of present-day atmospheric conditions from the ERA5 reanalysis and outputs from the Paleoclimate Modeling Intercomparison Project (PMIP) and new Community Earth System Model (CESM) experiments. 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 necessity of high spatial-resolution regional modeling. Our results also suggest that in order to realistically simulate the evolution of the PIS in agreement with geological archives, the MIS3 should have witnessed colder regional temperatures in and around Patagonia than those shown by global climate models for the MIS 2.

How to cite: Castillo, A., Prange, M., Bernales, J., Retamal-Ramírez, F., Schulz, M., and Rogozhina, I.: Numerical reconstructions of the Patagonian Ice Sheet: Growth and demise through the Late Quaternary, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9793, https://doi.org/10.5194/egusphere-egu22-9793, 2022.

EGU22-10361 | Presentations | GM7.3

Holocene history of Rio Tranquilo Glacier, Monte San Lorenzo (47°S), Central Patagonia 

Esteban Sagredo, Scott Reynhout, Michael Kaplan, Juan Aravena, Paola Araya, Brian Luckman, Roseanne Schwartz, and Joerg Schaefer

A well-resolved glacial chronology is crucial to compare sequences of glacial/climate events within and between regions, and thus, to unravel mechanisms underlying past climate changes. Important efforts have been made towards understanding the Holocene climate evolution of the Southern Andes; however, the timing, patterns and causes of glacial fluctuations during this period remain elusive. Advances in surface exposure dating techniques, together with the establishment of a Patagonian 10Be production rate, have opened new possibilities for establishing high-resolution glacial chronologies at centennial/decadal scale. Here we present a new comprehensive Holocene moraine chronology from Mt. San Lorenzo (47°S) in central Patagonia, Southern Hemisphere. Twenty-four new 10Be ages, together with three published ages, indicate that the Río Tranquilo glacier approached its Holocene maximum position sometime, or possibly on multiple occasions, between 9860 ± 180 and 6730 ± 130 yr. This event(s) was followed by a sequence of slightly smaller advances at 5750 ± 220, 4290 ± 100 (?), 3490 ± 140, 1440 ± 60, between 670 ± 20 and 430 ± 20, and at 390 ± 10 yr ago. By comparing our results with other glacier chronologies from central and southern Patagonia, we explore the role of the Southern Westerly Winds as a pacemaker of the Holocene glacier fluctuation in southern South America. 

How to cite: Sagredo, E., Reynhout, S., Kaplan, M., Aravena, J., Araya, P., Luckman, B., Schwartz, R., and Schaefer, J.: Holocene history of Rio Tranquilo Glacier, Monte San Lorenzo (47°S), Central Patagonia, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10361, https://doi.org/10.5194/egusphere-egu22-10361, 2022.

EGU22-10632 | Presentations | GM7.3

Deglaciation dynamics of the Rio Cisnes palaeo-outlet glacier (~45°S), former Patagonian Ice Sheet 

Emma Cooper, Varyl Thorndycraft, Bethan Davies, Adrian Palmer, and Juan-Luis García

The former Patagonian Ice Sheet (PIS) expanded and contracted multiple times during the Quaternary, preserving a well-defined geomorphological and sedimentological record of ice extent and dynamics. Influenced by both regional (e.g. Southern Westerly Winds) and interhemispheric climate forcing mechanisms, reconstructions of PIS extent and dynamics through time may yield unique insights into Southern Hemisphere (palaeo-)climate and (palaeo-)glacier dynamics.

An increasing number of palaeoglaciological reconstructions in Patagonia have highlighted spatial asynchrony in the timing of local glacial maxima and deglaciation. This offset in the timing of ice advance/retreat implies that dynamic controls, such as topography or calving mechanisms, played a part in regulating the structure and pace of deglaciation. Assessing the role of these mechanisms is complicated by a general lack of glacial landsystems work in Patagonia, particularly north of the Northern Patagonian Icefield (46 – 47.5 °S).

Here we aim to understand the timing, structure, and style of deglaciation in the Rio Cisnes valley, an eastern outlet glacier of the former Patagonian Ice Sheet. We combine glacial geomorphological mapping, field sedimentology, Uncrewed Aerial Vehicle (UAV) photogrammetry, and a new chronology based on cosmogenic nuclide surface-exposure age dating. These data informed a refined deglacial ice and palaeolake reconstruction. The new 10Be exposure ages constrain the timing of palaeolake level drop to ~16 ka, which indicates that icefield outlet glaciers were retreating back from their zone of confluence in the Cisnes valley into their respective valleys by this time, leaving the main Cisnes valley ice free.

How to cite: Cooper, E., Thorndycraft, V., Davies, B., Palmer, A., and García, J.-L.: Deglaciation dynamics of the Rio Cisnes palaeo-outlet glacier (~45°S), former Patagonian Ice Sheet, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10632, https://doi.org/10.5194/egusphere-egu22-10632, 2022.

EGU22-10709 | Presentations | GM7.3

Geomorphic and sedimentologic impacts of the Big Lost River Floods, east-central Idaho, USA 

Glenn Thackray and Braedon Warner

The Big Lost River Floods impacted the Basin and Range landscape of east-central Idaho during Late Pleistocene time, exerting geomorphic and sedimentologic effects preserved primarily in the flood source and sink areas.  The floods resulted from ice dam rupture in the Pioneer Mountains, traversed the wide tectonic basin of the Big Lost River valley, and terminated in a closed lacustrine basin on the Eastern Snake River Plain. We elucidate the history of multiple floods, their magnitudes, and their timing through surficial geologic mapping, cosmogenic radionuclide dating, and hydraulic modeling. 

The East Fork Big Lost River was dammed by the Wildhorse Canyon glacier at its maximum extent, forming Glacial Lake East Fork (GLEF). Flood-transported boulders extend ca. 20 km downvalley from the dam.  Distinct boulder bars and meso-scale cataracts cover several hundred hectares of basalt plains landscape in the Arco Scablands, 100 km downstream from the source, with isolated boulders from the source area.  Very little flood evidence has been identified in the intervening segment of the floodway. 

In the source area, ice damming occurred only during near-maximum ice extent, with GLEF volume and outburst flood discharge assumed to be correlative with dam thickness. Ages from new 10Be CRN and OSL dating reveal that GLEF was most recently dammed ca. 20.6 ka.  This age is similar to a published 3He chronology from Arco Scabland flood boulders. However, we have conducted additional dating in the Arco Scablands, and a second age mode of 35 ka is clear from the combined 3He datasets, suggesting extensive glaciation of the flood source area at that time. A closed-basin lake in the river-terminating basin further downstream has also yielded unpublished results from other workers, demonstrating correlative MIS 3 and 2 lake highstands.

HEC-RAS 2-D hydraulic modeling constrains likely flood discharges in the Arco Scablands. The results suggest MIS 3 flood discharge of ca. 30,000 m3/s and MIS 2 flood discharge of ca. 10,000 m3/s.

The concentration of apparent flood evidence likely reflects the variability of stream power along the floodway.  In the upstream reach, floodwaters were confined within a 1 km-wide valley, concentrating stream power. Erratic boulders mantle outwash terraces throughout this reach.  Downstream, the valley widens to 3-10 km; the wide valley would have dramatically reduced stream power and, thus, limited the capacity for geomorphic work.  Flood deposits in that reach were presumably either eroded or buried. In this context, it is surprising that flood evidence is dramatic in the Arco Scablands, which occupy low-relief, basalt-mantled Eastern Snake River Plain landscape.  Despite the overall low relief, two factors appear to have focused floodwaters into the Scablands.  First, simple topographic variability amongst individual basalt flows and monogenetic shield volcano slopes appear to have been sufficient to limit the floodway width and concentrate stream power, despite the general low relief.  Second, a ca. 1 km wide structural graben at the mouth of the Big Lost River valley appears to have focused the floodwaters into that low-relief floodway.

How to cite: Thackray, G. and Warner, B.: Geomorphic and sedimentologic impacts of the Big Lost River Floods, east-central Idaho, USA, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10709, https://doi.org/10.5194/egusphere-egu22-10709, 2022.

EGU22-10767 | Presentations | GM7.3

Reconstructed post gLGM glacier recession and climatic variability of the Changme Khangpu valley, Eastern Himalayas, INDIA 

Manasi Debnath, Milap Chand Sharma, Hiambok Jones Syiemlieh, and Arindam Chowdhury

The glaciated Changme Khangpu basin (CKB) covering an area of 767.8 km2, constitutes an important region in the Eastern Himalayas for palaeoclimate research to assess variability over recent geological times. Climatically, this part of the Himalayas is mainly controlled by the Indian Summer Monsoon (ISM). We provide a combination of multiproxy data, i.e., geomorphological, sedimentological, geochemical, Accelerator Mass Spectrometry 14C dating and Schmidt Hammer rebound value dating methods in reconstructing glacier and climatic changes related to the post global Last Glacial Maximum (gLGM) in the Changme Khangpu basin of the Sikkim Himalaya. The four set of well-preserved moraines depicted four advances of this glacier and palaeoclimate has been reconstructed after the Phase-II glacier advances i.e. post gLGM period. The post gLGM glacier recession in the Changme Khangpu (CK) valley witnessed a prolonged humid climate phase from <14.29 ± 0.22 ka to 7.08 ± 0.08 ka cal BP that inferred from the sedimentary log in this valley and incidentally correlate with the monsoonal reactivation (15 ka to 12 ka BP) in Southern Asia. This humid period was succeeded by dry climatic phases from 7.08 ka to 5.4 ka cal BP and from 5.18 to 4.65 ka cal BP, which well correlates with the dry phases in the Chopta valley, west of this area in Sikkim Himalaya. The glacier had receded from its Phase-III advance in between <4 and >1.3 ka BP. This period was followed by the active paraglacial fan formation and witnessed historical outburst events in this valley.

 

Keywords: Changme Khangpu glacier (Sikkim); Eastern Himalayas; Last Glacial Maximum; Palaeoclimate; Glacier geomorphology; 14C AMS dating; Chemical index of alteration.

How to cite: Debnath, M., Sharma, M. C., Syiemlieh, H. J., and Chowdhury, A.: Reconstructed post gLGM glacier recession and climatic variability of the Changme Khangpu valley, Eastern Himalayas, INDIA, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10767, https://doi.org/10.5194/egusphere-egu22-10767, 2022.

EGU22-12198 | Presentations | GM7.3

Glacial fluctuations in the southwestern Wicklow Mountains, Ireland. 

Margaret Jackson, Gordon Bromley, and Brenda Hall

Mapping and dating former glacial margins is a key tool for assessing the sensitivity of glaciers to changing climate conditions, both past and future. However in many regions, such as along the northeastern margins of the North Atlantic, direct chronologic control on past glacier extent can be sparse. In particular, the former extent and elevation of the Irish Ice Sheet (IIS) during the Last Glacial Maximum (LGM; 26-19 ka) and subsequent termination remain a topic of debate - due in part to the coarse resolution of existing (direct) age control on glacial margins. This includes the margins of former valley and cirque glaciers that nucleated in the Irish highlands after local retreat of the IIS. In eastern Ireland, the Wicklow Mountains host numerous valley and cirque moraines that are largely undated, evidence of past glacial fluctuations following the LGM. Here we report new geomorphic mapping and cosmogenic beryllium-10 surface-exposure ages of moraines in the Glen of Imaal in the southwestern Wicklow Mountains. Our preliminary beryllium-10 ages provide new chronologic constraint on the extent of glaciers in the Glen of Imaal following the LGM. We also compare our preliminary glacial chronology with records of wider North Atlantic climate to investigate the response of ice in the Glen of Imaal to changing climate conditions. These data provide new insight on Ireland’s glacial past, and yield vital information on climate and glaciation in the wider North Atlantic region. 

How to cite: Jackson, M., Bromley, G., and Hall, B.: Glacial fluctuations in the southwestern Wicklow Mountains, Ireland., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12198, https://doi.org/10.5194/egusphere-egu22-12198, 2022.

EGU22-13508 | Presentations | GM7.3

Advances on submarine geomorphology at the Fjord system of Gran Campo Nevado (~52°S) 

Mario Veloso-Alarcón, Gazis Iason-Zois, Alessa Geiger, Bertrand Sebastien, and Cristián Rodrigo

The glacial history of Patagonia has been built from paleoclimate records found at the margin of the former Patagonian Ice-sheet. However, current deglaciation models of Patagonia still have spatio-temporal gaps to be filled. In this direction, the study of the submerged paleo-climate records at the Patagonian Fjord system and pro-glacial lakes could fill these gaps and enhance our knowledge on deglaciation in Patagonia. However, the exploration of such remote areas is hindered by logistic challenges and rough weather conditions.

In November of 2018 we collected the first high-resolution swath multibeam echosounder (MBES) bathymetry of Senos Icy and Glacier, the southern section of Canal Gajardo and Estero Portaluppi, which are fjords located at the flanks of Gran Campo Nevado. In this work, we present this new bathymetry and its first geomorphological interpretation. The analysis revealed a heterogeneous seafloor with geomorphological features related to glacial dynamics. The data interpretation is supplemented by shallow sub-bottom profiles that have been also acquired during that survey. We think that such information is the baseline for future exploration of these fjords focused on the already identified submerged glacial bedforms and their chronology.  

How to cite: Veloso-Alarcón, M., Iason-Zois, G., Geiger, A., Sebastien, B., and Rodrigo, C.: Advances on submarine geomorphology at the Fjord system of Gran Campo Nevado (~52°S), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13508, https://doi.org/10.5194/egusphere-egu22-13508, 2022.

CR6 – Sea, Lake and River Ice

EGU22-1181 | Presentations | CR6.1

Sea ice evaluation tool: application to CMIP6 OMIP and the sensitivity of sea ice simulation to atmospheric forcing uncertainties 

Xia Lin, François Massonnet, Thierry Fichefet, and Martin Vancoppenolle

We will introduce the Sea Ice Evaluation Tool (SITool) developed to evaluate the skill of Arctic and Antarctic model reconstructions of sea ice concentration, extent, edge location, drift, thickness, and snow depth. It is a Python-based software and consists of well-documented functions used to derive various sea ice metrics and diagnostics. The SITool version 1.0 is used to evaluate the performance of global sea ice reconstructions from nine models that provided sea ice output under CMIP6 Ocean Model Intercomparison Project with two different atmospheric forcing datasets: the Coordinated Ocean-ice Reference Experiments version 2 (CORE-II) and the updated Japanese 55-year atmospheric reanalysis (JRA55-do). The improved Arctic and Antarctic sea ice areal properties and ice drift simulation have been recognized in OMIP models forced by JRA55-do. The processes contributing to these improvements are assessed and discussed. It is found that improvements in the simulation of summer ice concentration in the interior region are linked, in both hemispheres, to improvements in the downward surface net shortwave radiation flux in JRA55-do. The austral winter ice concentration simulation is improved in the ice edge region relating to the dynamic process dominated by surface wind stress. The obvious improvement of the ice drift magnitude simulation is in the Arctic ice edge region from November to April dominated by the decreased surface wind stress forced by JRA55-do, while the improvement in the Antarctic is much smaller. This study provides clues to improve the atmospheric reanalysis product for a better sea ice simulation in ocean-sea ice models and more attention can be paid to the radiation flux and wind fields.

How to cite: Lin, X., Massonnet, F., Fichefet, T., and Vancoppenolle, M.: Sea ice evaluation tool: application to CMIP6 OMIP and the sensitivity of sea ice simulation to atmospheric forcing uncertainties, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1181, https://doi.org/10.5194/egusphere-egu22-1181, 2022.

EGU22-1209 | Presentations | CR6.1

The atmospheric response to the Weddell Sea Polynya 

Holly Ayres and David Ferreira

The Weddell Sea Polynya is a large opening within the sea ice cover of the Weddell sea sector, typically found sitting over the Maud Rise in its largest occurrences. It has been a rare event in the satellite period, appearing throughout the 1970s and again in 2016/17. Many mechanisms have been suggested to cause the onset of the Weddell Sea Polynya, from deep convection of the ocean and upwelling at the Maud Rise, in addition to increased cyclone activity and the influence of atmospheric rivers. It is thought that with increasing atmospheric greenhouse gasses, the Weddell Sea Polynya will be even less frequent, due to an intensification of the haline stratification within the polynya region. The opening of the polynya creates an ocean to air heat flux in the cooler months, with the potential to influence atmospheric dynamics. The atmospheric response to the polynya and regional ice loss may be observed locally within the low-pressure region of the Weddell Sea or further afield climate. Here, we use high and low resolution AGCM experiments with the HadGEM3 UK Met Office model, alongside PRIMAVERA high-resolution analysis of the polynya, to evaluate the atmospheric response to the polynya and associated features, in addition to the role of model resolution in resolving the polynya and its associated features.

How to cite: Ayres, H. and Ferreira, D.: The atmospheric response to the Weddell Sea Polynya, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1209, https://doi.org/10.5194/egusphere-egu22-1209, 2022.

EGU22-2294 | Presentations | CR6.1

Model predictions of overwash extent into the marginal ice zone. 

Jordan Pitt and Luke Bennetts

Overwash is an important aspect of the dynamics in the marginal ice zone where sea ice and ocean waves interact. Overwash dissipates wave energy, and the presence of water on top of sea ice can drive growth or melting, depending on the local thermodynamic conditions. The presence of water on floes is also important for biologic and chemical processes. While overwash has been observed and investigated under experimental conditions, it has not yet been studied in the marginal ice zone. One reason for this lack of in-situ measurements and observations is due to the marginal ice zone being highly dynamic, and the onset of overwash only occurring under specific and sensitive conditions. To facilitate future observations we have produced a model of the extent of overwash into fields of sea ice by combining a new model of the onset of overwash and a standard attenuation model. This model of overwash extent is validated against experimental observations and is used to provide the extent of overwash for realistic ice and wave field conditions observed during the July 2017 voyage of the South African icebreaker S.A. Agulhas II. 

 

How to cite: Pitt, J. and Bennetts, L.: Model predictions of overwash extent into the marginal ice zone., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2294, https://doi.org/10.5194/egusphere-egu22-2294, 2022.

EGU22-3764 | Presentations | CR6.1

Utilising Cryosat-2 observations of the Arctic sea ice cover to produce a new Arctic sea ice reanalysis 

Nicholas Williams, Nicholas Byrne, Daniel Feltham, Peter Jan Van Leeuwen, David Schroeder, Ross Bannister, and Andrew Shepherd

In this work we present results from a new sea ice reanalysis over the satellite era. We use a newly created sea ice data assimilation system CICE-PDAF, combining the Los Alamos Sea Ice Model (CICE) and the Parallelized Data Assimilation Framework (PDAF), to take advantage of the new observations of the sea ice cover produced in the last decade by Cryosat-2. Sea ice thickness and sea ice thickness distribution observations from Cryosat-2, alongside sea ice concentration observations, are assimilated to explore their effects on our current estimates of the Arctic sea ice cover. In particular we look at its effects on the sea ice thickness distribution. The true state of the Arctic sub-grid scale thickness distribution system is not well known, and yet it plays a key role in the dynamic and thermodynamic processes present in the model to produce a good estimate of the Arctic sea ice state. Thus by combining knowledge from state-of-the-art sea ice models with knowledge from newly developed observations we hope to produce a clearer picture of the Arctic sea ice and its thickness distribution.

How to cite: Williams, N., Byrne, N., Feltham, D., Van Leeuwen, P. J., Schroeder, D., Bannister, R., and Shepherd, A.: Utilising Cryosat-2 observations of the Arctic sea ice cover to produce a new Arctic sea ice reanalysis, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3764, https://doi.org/10.5194/egusphere-egu22-3764, 2022.

EGU22-4719 | Presentations | CR6.1

Satellite Remote Sensingof Melt Ponds and Albedoin the Arctic 

Hannah Niehaus, Larysa Istomina, Aleksey Malinka, Eleonora Zege, Tim Sperzel, and Gunnar Spreen

A wide variety of surface types are present in the Arctic: Ocean, ice, snow and melt ponds cover the surface featuring a strong heterogeneity. Due to the differences in their albedo the composition of these surface types strongly impacts the radiative feedback and hence the energy budget which is crucial in climate models. During the summer period the variability is particularly high because the increased temperatures lead to melt pond formation. The seasonal development of melt ponds features fast and local changes in fraction of surface types and thus in albedo. To study the ice-albedo feedback and its impact on the Arctic climate, large scale and regular information on these characteristics are necessary. This can be facilitated by the use of satellite remote sensing.
In 2016, the Sentinel-3 mission was launched providing full coverage of the Arctic on a daily basis aside from cloud coverage limitations. The devices these satellites carry include the Ocean and Land Colour Instrument (OLCI) and the Sea and Land Surface Temperature Radiometer (SLSTR). Together these two instruments measure 30 spectral bands at wavelengths between 400 nm and 12 μm. We present the available melt pond fraction and surface albedo products retrieved from the optical Setinel-3 satellite data with the Melt Pond Detector (MPD) algorithm developed by Zege and others. However, these measurements cannot resolve surface type heterogeneity beyond the spatial resolution of 1.2 km and require additional information to enable spectral unmixing of these surface types at a sub-pixel scale. To investigate the performance and enable improvements of the established retrieval, higher resolution satellite imagery is used. The Sentinel-2 twin satellites were launched in 2015 and 2017 and provide spectral measurements in the optical and near-infrared range at a resolution of 10 m whereas the temporal and spatial coverage is limited. A classification algorithm developed by Wang et al. is applied to obtain melt pond fractions of this increased accuracy for the years 2018 to 2021. Here, we present the melt pond fraction for selected Sentinel-2 scenes and their correspondence with the allocated MPD results. These show good agreement for landfast ice areas with distinct melt ponds, while in general drift and resolution issues are likely to be responsible for discrepancies. For the period of June and July 2020, the available and cloud free scenes along the MOSAiC (Multidisciplinary drifting Observatory for the Study of Arctic Climate) drift track are evaluated. This observation indicates a melt onset on the MOSAiC floe mid of June, roughly one week prior to the vicinity.

How to cite: Niehaus, H., Istomina, L., Malinka, A., Zege, E., Sperzel, T., and Spreen, G.: Satellite Remote Sensingof Melt Ponds and Albedoin the Arctic, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4719, https://doi.org/10.5194/egusphere-egu22-4719, 2022.

Investigating the temporal and spatial changes in Arctic sea ice freeboard, thickness and volume is crucial for climate and environmental research. In this study, the freeboard, thickness and volume of the Arctic sea ice between 2011 and 2020 were acquired from CryoSat-2 data and it was compared with NASA Operation IceBridge and Alfred Wegener Institue AWI datasets. The effect of wind field and temperature and itscontribution on Arctic sea ice were also investigated. The main steps of our research are as follows. 1) Selecting data points above 66 degrees north latitude and filtering out sea ice by flag value and mask; Using OSI SAF sea ice concentration (SIC) data to further constrict the area; Interpolating the latest mean sea surface data DTU21 into CryoSat-2 data; Calculating the sea ice freeboard via spatial altimetry relationship. 2) Combining with snow density, snow depth, multi-year ice density and first-year ice density to estimate the sea ice thickness respectively from freeboard according to the assumption of hydrostatic equilibrium. 3) Using the area and extent provided by NSIDC to interpret the volume. 4) Utilizing Seasonal and Trend decomposition using Loess(STL) to analyse the seasonal and interannual variations of sea ice. 5) Dividing the Arctic Ocean by its marginal sea, coupled with the HY-2B microwave scatterometer data and NCEP/NCAR reanalysis data, the impact of the Beaufort Sea, the Chukchi Sea, the East Siberian Sea, the Laptev Sea, the Kara Sea, the Barents Sea, the Greenland Sea, and the Baffin Bay wind field on the sea ice were studied. 6) Exploring the correlation between the sea surface temperature and the sea ice freeboard, thickness and volume. The result indicated that (1) the freeboard and thickness was decreasing about 9.748% and 8.80% during 2011-2020,respectively; (2) there are interlunar variations in sea ice freeboard and thickness, the freeboard and thickness of sea ice reach the minimum in August to September each year and the maximum appears in March to April; (3) Arctic sea ice is affected by both thermodynamics and dynamics, the reduction of Arctic sea ice was largely due to the sea surface wind field, one of the dynamic factors is the wind field on the sea surface. The sea ice changes in the various sea areas of the Arctic Ocean are related to the wind field to varying degrees. The changes in the sea surface wind field in recent years have further promoted the reduction of sea ice, making it possible for the Arctic to open to navigation in the summer. Fully understanding the evolution of sea ice change in the Arctic Ocean is helpful for humans to better protect the earth.

How to cite: Zhang, Y.: Spatio-temporal Variablity of Arctic Sea Ice Freeboard, Thickness and Volume from CryoSat-2 and Its Possible Drivers, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7540, https://doi.org/10.5194/egusphere-egu22-7540, 2022.

EGU22-8338 | Presentations | CR6.1

Feedbacks emerging from variable floe size in the Arctic sea ice cover 

Adam Bateson, Daniel Feltham, David Schröder, Jeff Ridley, and Rebecca Frew

Sea ice is not homogenous and is instead made up of individual pieces of ice that are called floes. Observations show that these floes range in size from just metres to tens of kilometres. Sea ice and climate models have historically assumed a fixed floe size, if there is an explicit representation of floe size at all. There have been several recent efforts to include a treatment of variable floe size within sea ice models. These models have included several processes thought to be important in floe size evolution including break-up of sea ice by waves, lateral melt and growth, welding together of floes, and brittle fracture processes. Floe size can have a direct impact on sea ice evolution via several mechanisms including lateral melt rate, momentum exchange between the sea ice, ocean, and atmosphere, and the ice rheology. Floe size distribution (FSD) models have so far been used within sea ice models to primarily explore the direct impact of floe size on the sea ice cover, and there has been little exploration of the possible resulting feedback processes.

In this study we consider a prognostic approach to modelling the FSD within the CICE sea ice model where the shape of the FSD is an emergent characteristic. We consider results from both standalone sea ice simulations and fully coupled climate simulations. These results are used to explore whether an improved representation of sea ice-ocean and sea ice-atmosphere feedbacks modifies the impact of floe size on the sea ice concentration and thickness over both pan-Arctic and localised scales. We will focus on feedbacks that result from changes to the lateral melt rate, considering in particular whether there is a significant impact from the ice-ocean albedo feedback mechanism. Finally, we will discuss the necessary conditions for there to be significant feedbacks resulting from the inclusion of floe size distribution models in sea ice and climate models. 

How to cite: Bateson, A., Feltham, D., Schröder, D., Ridley, J., and Frew, R.: Feedbacks emerging from variable floe size in the Arctic sea ice cover, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8338, https://doi.org/10.5194/egusphere-egu22-8338, 2022.

EGU22-11971 | Presentations | CR6.1

Emergence of a sub-ice platelet layer in mushy-layer sea ice model simulations 

Martin Vancoppenolle, Pat Wongpan, and Pat Langhorne

Sightings have long reported the presence of unconsolidated ice crystals spanning up to several meters in thickness under Antarctic landfast sea ice. This so-called sub-ice platelet layer (SIPL) was until recently considered as exotic and out of the scope of standard sea ice models.

Here we show that a realistic, highly porous and isothermal SIPL emerges in one-dimensional mushy-layer sea ice model simulations, provided appropriate thermal forcing. The model SIPL develops once conductive heat fluxes are insufficient to cause internal freezing of the new, highly porous ice. Sufficiently high snow and ice thicknesses are key to the onset of the SIPL development, whereas high liquid content and isothermal character stabilize the SIPL.

Two model features are necessary to the emergence of the SIPL: an advective formulation of salt dynamics, and a high value for the liquid fraction of new ice. We surmise that large-scale ice-ocean models should capture a SIPL at physically sensible locations and times if the aforementioned issues are properly considered.

How to cite: Vancoppenolle, M., Wongpan, P., and Langhorne, P.: Emergence of a sub-ice platelet layer in mushy-layer sea ice model simulations, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11971, https://doi.org/10.5194/egusphere-egu22-11971, 2022.

EGU22-12055 | Presentations | CR6.1

MISR Arctic and Antarctic Sea Ice Albedo 2000-2019 Product Creation and Trend Analysis 

Laura Aguilar, Jan-Peter Muller, Said Kharbouche, Thomas Johnson, and Michel Tsamados

Sea ice albedo is a key climate variable that affects the Earth’s radiation budget. Spatio-temporal variation of sea ice albedo can be retrieved from pre existing satellite observation processing chains such as the CLARA2-SAL product. However, currently there is only one albedo product which is derived from instantaneous multi-angle measurements and that is from MISR [1]. The accuracy of surface albedo products is usually affected by error accumulation from atmospheric corrections to the top-of-atmosphere bi-directional reflectance factor (BRF) and the modelling of bottom of the atmosphere BRF and subsequent modelling to bi-directional reflectance distribution function (BRDF) using these BRFs. Sea ice surfaces being both anisotropic and dynamic have satellite product accuracies that also depend on the length of deployed time window, thus requiring sufficient numbers of observations over a short period of time. In this study, we present a data fusion method using the high accuracy near simultaneous sampling of the Multiangle Imaging SpectroRadiometer (MISR) generated at the Langley Research Center applying a Rayleigh atmospheric correction, with the MOD35 cloud mask which is part of the MOD29 Surface Temperature and Ice Extent product derived from the Moderate Imaging Spetroradiometer (MODIS), both onboard the Terra satellite. 

We assume that the MISR bi-hemispherical reflectance (BHR) albedo is independent of solar angle, a crucial condition for instantaneous albedo products. As the accuracy of MOD29 cloud mask is assessed at >90% [1], this synergistic method can retrieve an improved BHR of the Arctic sea ice between April and September of each year from 2000 to 2019, and of the Antarctic sea ice between September and March of each year from 2000 to 2019. This study is a follow-on from Kharbouche and Muller (2018), that developed this method and focused on the Arctic region for the time span between March and September from 2000 to 2016. 

For both polar regions, we create four daily sea ice products consisting of different averaging time window (±1 day, ±3 days, ±7 days and ±15 days), each containing the number of samples, mean and standard deviation. For all four MISR cloud-free daily sea ice products, we derive 1km, 5km and 25km spatial resolutions. We perform an assessment of the day-of-year trend of sea ice BHR between 2000 and 2019 for the Arctic, and between 2000 and 2019 for Antarctic, confirming a continuing decline of sea ice shortwave albedo in the Arctic depending on the day of year and length of observed time window, and providing a novel sea ice shortwave albedo product analysis for Antarctica.

Acknowledgements. This work was supported by the QA4ECV project www.QA4ECV.eu, of the European Union’s Seventh Framework Programme (FP7/2007–2013) under grant agreement number 607405. We thank our colleagues at JPL and NASA LaRC for processing the MISR data, especially Sebastian Val and Steve Protack and Jeff Walter, respectively and Richard Frey and Steve Ackerman at CIMMS, SSEC, University of Madison, WI for the analysis of the MOD35 cloud mask using CALIPSO shown in [1].

[1] https://doi.org/10.3390/rs11010009

 

How to cite: Aguilar, L., Muller, J.-P., Kharbouche, S., Johnson, T., and Tsamados, M.: MISR Arctic and Antarctic Sea Ice Albedo 2000-2019 Product Creation and Trend Analysis, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12055, https://doi.org/10.5194/egusphere-egu22-12055, 2022.

EGU22-12506 | Presentations | CR6.1

Arctic sea-ice volume budget from satellite observations and CMIP6 models 

Harry Heorton and Michel Tsamados

Sea-ice floating upon the Arctic ocean is a constantly moving, growing and melting surface. The seasonal cycle of sea ice volume has an average change of 10 000 Km$^3$ or 9 billion tonnes of sea ice. The role of dynamic redistribution of sea ice, the process by which it flows and deforms when blown by winds and floating upon ocean currents, has been observable during winter growth by the incorporation of satellite remote sensing of ice thickness and drift. CMIP6 models contain dynamic sea-ice components that simulate the drift and mass balance of Arctic sea ice.

We combine satellite-derived observations of sea ice concentration, drift, and thickness to provide maps of ice growth, melt and dynamic redistribution. Winter growth and summer melt seasons are analyzed over the CryoSat-2 period between October 2010 and April 2020. We reveal key circulation patterns that contribute to summer melt and minimum sea ice volume and extent. Specifically, we show the importance of ice drift to the interannual variability in Arctic sea-ice volume, and the regional distribution of sea ice growth and melt rates. When comparing these observations to CMIP6 models long term trends are revealed. We show how the divergence and mechanical redistribution of sea ice is a key component in the resilience of central Arctic ice volume to anthropogenic climate change.

How to cite: Heorton, H. and Tsamados, M.: Arctic sea-ice volume budget from satellite observations and CMIP6 models, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12506, https://doi.org/10.5194/egusphere-egu22-12506, 2022.

Brine channel networks and brine inclusions are dominating features of the microstructure of saline ice that determine the physical properties and influence thermodynamic and convective processes within the ice. Similar to sea ice, salinity and the spatial distribution of brine are important properties of sea spray ice. However, their manifestation in the microstructure and their relation to the growth conditions are scarcely investigated for spray ice. Towards a physical understanding of brine inclusion and brine drainage processes in sea spray ice, we characterize microstructures of samples from the field and from systematic experiments in the cold lab under varying growth conditions (temperatures, spray rate, salinity). By means of 3D micro-computed tomography images, we examine main characteristics of the brine features. We will present first results of the microstructure characterization and discuss their relation to the growth conditions.

How to cite: Willibald, C.: Brine channel network and brine inclusions – characterization of the three-phase 3D microstructure of saline spray ice, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12706, https://doi.org/10.5194/egusphere-egu22-12706, 2022.

EGU22-13263 | Presentations | CR6.1

Modelling the wave-induced fragmentation of the sea ice cover 

Nicolas Mokus and Fabien Montiel

Fragmentation of the sea ice cover by wind-generated waves is an
important mechanism impacting ice evolution.
Fractured ice is more sensitive to melt, leading to a local reduction in
concentration, facilitating wave propagation, hence introducing a
positive feedback loop accelerating sea ice retreat.
Although this process and the concept of floe size distribution (FSD)
have been incorporated in several sea ice components of global climate
models (GCM), the physics governing ice breakup under wave action
remains poorly understood, and its parametrisation highly simplified.
We propose a numerical model of wave-induced sea ice breakup to estimate
the FSD resulting from repeated fracture events.
This model, based on linear water wave theory and viscoelastic sea ice
rheology, solves for the scattering of an incoming wave spectrum by the
ice cover and derives the corresponding strain field. Fracture occurs
when the undergone strain exceeds a prescribed threshold.
We find that under realistic wave forcing, lognormal FSDs appear
consistently in a large variety of model configurations.
This result contrasts with the power-law FSD behaviour often assumed by
modellers.
We discuss the properties of these modelled distributions, and
investigate the stochastic processes affecting their emergence.

How to cite: Mokus, N. and Montiel, F.: Modelling the wave-induced fragmentation of the sea ice cover, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13263, https://doi.org/10.5194/egusphere-egu22-13263, 2022.

EGU22-13506 | Presentations | CR6.1

Spatiotemporal evolution of snow depth distribution on Antarctic sea ice 

Ted Maksym, M. Jeffrey Mei, Nander Wever, Ernesto Trujillo, Katherine Leonard, Steve Ackley, Blake Weissling, Guy Williams, and Hanumant Singh

Snow cover is a primary control on Antarctic sea ice mass balance as it controls basal ice growth and snow ice formation. It is also a primary control on the surface energy budget, partitioning of solar radiation, and sea ice biological communities. Finally, knowledge of its distribution is critical for accurate estimation of sea ice thickness from satellite altimeters. The floe-scale distribution of snow is highly variable, driven by wind redistribution over complex sea ice surface topography. Yet, our understanding of the seasonal evolution of snow depth distribution is poor and its representation in models is simple or non-existent.

We present observations of the three-dimensional distribution of snow depth, ice thickness, and surface topography from a suite of cruises in the Weddell, Bellingshausen, Ross, and East Antarctic Seas that span the full growth season – from autumn, through winter, to late spring. The distribution of snow depth changes from a right-skewed distribution in autumn as snow initially accumulates around ridges to a gaussian by spring as snow deepens and ice surface topography roughens. While the distribution is spatially complex, the spectral distribution of snow features is similar across seasons. Using these data we construct a simple statistical model for the seasonal evolution of floe-scale snow depth distribution. We also compare our results to prior observations from drilling transects and larger-scale airborne observations from NASA’s Operation IceBridge. For the latter we use a convolutional neural network to demonstrate that the surface topography can be used as a reliable predictor of the snow depth distribution at regional scales.

How to cite: Maksym, T., Mei, M. J., Wever, N., Trujillo, E., Leonard, K., Ackley, S., Weissling, B., Williams, G., and Singh, H.: Spatiotemporal evolution of snow depth distribution on Antarctic sea ice, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13506, https://doi.org/10.5194/egusphere-egu22-13506, 2022.

EGU22-342 | Presentations | OS1.11

Upper-ocean processes in sea-ice formation season in front of Dotson Ice Shelf 

Yixi Zheng, Benjamin Webber, Karen Heywood, and David Stevens

The upper-ocean processes near ice shelves play crucial roles in the local freshwater budget, carbon take-up, surface albedo, and ice-shelf melting via controlling the air-sea heat exchange and thermocline depth. The upper-ocean processes are particularly complex during the austral autumn when both the air temperature and solar radiation flux drop dramatically, which result in an intense sea-ice formation and further influence the air-sea-ice interactions. However, in regions near the ice shelves like the Dotson Ice Shelf, where sea ice covers the ocean ten months a year, the lack of high-resolution and long-period observations limit our understanding of the upper-ocean processes in this sea-ice formation season. Here we present a dataset of high-frequency (1 Hz) temperature and salinity measurements collected by a recovered seal’s tag. This tag recorded the ocean properties during late summer to autumn (mid-February to mid-April 2014) in a small region (within a 15-km radius circle) in front of the Dotson Ice Shelf, when sea ice formed and mixed-layer depth deepened. During those two months, mixed-layer depth increased from about 25 m to 125 m. The mixed-layer water temperature was always near the freezing point, while the salinity increased from 33.35 to 34.25 g per kg, equivalent to a sea ice formation of about 3.26 cm per day. We compare the changes of the upper-ocean properties with ERA-5 reanalysis atmospheric data and find that the upper-ocean heat content can be largely explained by the air-temperature changes. We run a 1-D upper-ocean model with and without sea-ice formation to explore the effect of sea-ice formation on the processes on the salinification and deepening of the mixed layer during autumn.

How to cite: Zheng, Y., Webber, B., Heywood, K., and Stevens, D.: Upper-ocean processes in sea-ice formation season in front of Dotson Ice Shelf, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-342, https://doi.org/10.5194/egusphere-egu22-342, 2022.

EGU22-346 | Presentations | OS1.11

Observed mixing at the flanks of Maud Rise in the Weddell Sea 

Martin Mohrmann, Sebastiaan Swart, and Céline Heuzé

Maud Rise is a seamount in the eastern Weddell Sea and the location of the Maud Rise halo of reduced sea ice and polynyas. In this region, we present novel in situ data from two profiling floats with up to daily-resolved hydrographic profiles. Over Maud Rise, the mixed layer is especially deep during winter (150-200 m), leaving a thick layer of winter water after re-stratification that persists throughout the year and increases the rate of autumn mixed layer deepening. In contrast, the halo around Maud Rise is characterized by a shallow mixed layer depth and only a thin layer of winter water. Below the mixed layer, the water properties in the Maud Rise region are significantly correlated with bathymetric depth; thus, the Maud Rise flank defines the fronts between the Warm Deep Water of the abyssal ocean and the colder, less stratified Maud Rise Deep Water characteristic of the Taylor cap over Maud Rise. We analyse the curvature of spiciness in density space to quantify observed interleaving, which is substantially higher over and along the flanks of Maud Rise than in the surrounding deeper waters. These intrusions are indicative of enhanced lateral and vertical mixing along heavily sloping isopycnals, creating favorable conditions for thermobaric and double diffusive convection that facilitate the Maud Rise halo and may contribute to the formation of polynyas.

How to cite: Mohrmann, M., Swart, S., and Heuzé, C.: Observed mixing at the flanks of Maud Rise in the Weddell Sea, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-346, https://doi.org/10.5194/egusphere-egu22-346, 2022.

EGU22-572 | Presentations | OS1.11

Interannual variability in the ocean CO2 uptake along the West Antarctic Peninsula: A decade of year-round observations 

Elise Droste, Dorothee Bakker, Hugh Venables, Mario Hoppema, Giorgio Dall'Olmo, and Bastien Queste

The West Antarctic Peninsula (WAP) has warmed rapidly due to global climate change and there is large interannual variability in winter conditions, especially sea ice duration. Sea ice driven changes in the water column stability and marine biogeochemistry are impacting the CO2 uptake in this highly productive region. This work extends the Rothera Oceanographic and Biological Time Series (RaTS) to a decade of year-round observations of surface water carbonate chemistry (2010-2020). This spans considerable sea ice variability, allowing assessment of the air/ice/ocean system across a wide range of conditions, including low sea ice cover as is predicted for the region. It includes rare winter-time data that show an unbiased view of annual carbonate processes and how they might be seasonally interconnected and coupled to sea ice dynamics. Even though the coastal region at Marguerite Bay is a net sink of CO2, the time series is characterised by strong seasonal variability, indicating that this coastal region is a source of CO2 to the atmosphere during the austral winter and a strong CO2 sink in the summer. Additionally, we see differences in the net CO2 uptake between different years. Net annual CO2 uptake increased between 2014 and 2017 compared to previous years due to longer durations of heavier sea ice cover. Annual CO2 uptake decreased again between 2017 and 2020, which are years associated to lower sea ice concentration and shorter duration of sea ice cover. We focus on the interannual differences in sea ice concentration and extent and how they are linked to differences in the water column structure, biogeochemical properties, and air-sea CO2 exchange.

How to cite: Droste, E., Bakker, D., Venables, H., Hoppema, M., Dall'Olmo, G., and Queste, B.: Interannual variability in the ocean CO2 uptake along the West Antarctic Peninsula: A decade of year-round observations, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-572, https://doi.org/10.5194/egusphere-egu22-572, 2022.

EGU22-817 | Presentations | OS1.11

Interannual hydrographic variability beneath Thwaites Eastern Ice Shelf, West Antarctica 

Tiago Dotto, Karen Heywood, Rob Hall, Ted Scambos, Yixi Zheng, Yoshihiro Nakayama, Tasha Snow, Anna Wåhlin, Christian Wild, Martin Truffer, Atsuhiro Muto, and Erin Pettit

Basal melting of the Amundsen Sea ice shelves is caused by relatively warm waters accessing the ice base through turbulent processes at the ice-ocean boundary layer. Here we report hydrographic variability in Thwaites Eastern Ice Shelf (TEIS) from January 2020 to March 2021 using novel subglacial mooring measurements and ocean modelling. The layers ~100 m beneath the ice base warmed considerably (~1˚C) in this period. The meltwater fraction doubled associated with basal melting due to the higher heat, leading to a freshening in the upper layers. The lighter layer contributed to the acceleration of the under-ice circulation, which led to higher basal melting through intensified temperature flux, creating positive feedback beneath the ice. The interannual variability of the water masses in the TEIS cavity is linked to the seasonal strengthening and weakening of the Pine Island Bay gyre. During periods that the sea-ice covers the bay, such as winter 2020 and the 2020-2021 summer season, the momentum transfer from the wind to the ocean surface is less effective and the gyre weakens. The deceleration of the gyre leads to relaxation and shoaling of the isopycnals beneath the TEIS, which brings warmer water upwards closer to the ice base. The results discussed in this work shows that the fate of the Amundsen Sea ice sheet is tightly controlled by adjacent small-scale gyres, which could prolongate warming periods beneath ice shelf cavities and lead to high basal melting rates.

How to cite: Dotto, T., Heywood, K., Hall, R., Scambos, T., Zheng, Y., Nakayama, Y., Snow, T., Wåhlin, A., Wild, C., Truffer, M., Muto, A., and Pettit, E.: Interannual hydrographic variability beneath Thwaites Eastern Ice Shelf, West Antarctica, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-817, https://doi.org/10.5194/egusphere-egu22-817, 2022.

EGU22-1163 | Presentations | OS1.11

Internal tsunamigenesis and mixing driven by glacier calving in Antarctica 

Michael Meredith, Mark Inall, Alexander Brearley, David Munday, Tobias Ehmen, Katy Sheen, Katherine Retallick, Amber Annett, Rhiannon Jones, Filipa Carvalho, Katrien Van Landeghem, Alberto Naveira Garabato, Laura Gerrish, James Scourse, Alison Cook, and Christopher Bull

Ocean mixing around Antarctica is a key process that influences the vertical distributions of heat and nutrients, affecting glacier and ice shelf retreats, sea ice formation and marine productivity, with implications for regional ecosystems, global sea level and climate. Here we show that collapsing glacier fronts associated with calving events trigger internal tsunamis, the propagation and breaking of which can lead to significant mixing. Observations of one such event at the West Antarctic Peninsula, during which 3-20 megatonnes of ice were discharged to the ocean, reveal rapidly-elevated internal wave kinetic energy and upper-ocean shear, with strong homogenisation of the water column. Scaling arguments indicate that, at the West Antarctic Peninsula, just a few such events per summer would make this process comparable in magnitude to winds, and much more significant than tides, in driving shelf mixing. We postulate that this process is likely relevant to all regions with calving marine-terminating glaciers, including also Greenland and the Arctic. Glacier calving is expected to increase in a warming climate, likely strengthening internal tsunamigenesis and mixing in these regions in the coming decades.

How to cite: Meredith, M., Inall, M., Brearley, A., Munday, D., Ehmen, T., Sheen, K., Retallick, K., Annett, A., Jones, R., Carvalho, F., Van Landeghem, K., Naveira Garabato, A., Gerrish, L., Scourse, J., Cook, A., and Bull, C.: Internal tsunamigenesis and mixing driven by glacier calving in Antarctica, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1163, https://doi.org/10.5194/egusphere-egu22-1163, 2022.

EGU22-1259 | Presentations | OS1.11

Open-Ocean Polynyas in the Cooperation Sea, Antarctica 

Qing Qin, Zhaomin Wang, Chengyan Liu, and Cheng Chen

     Extensive studies have addressed the characteristics and mechanisms of open-ocean polynyas in the Weddell and Cosmonaut Seas. Here, we show that more persistent open-ocean polynyas occur in the Cooperation Sea (CS) (60°E-90°E),  a sector of the Southern Ocean off the Prydz Bay continental shelf,  between 2002 and 2019. Polynyas are formed annually mainly within the 62°S-65°S band, as identified by sea ice concentrations less than 0.7. The polynyas usually began to emerge in April and expanded to large sizes during July-October, with sizes often larger than those of the Maud Rise polynya in 2017. The annual maximum size of polynyas ranged from 115.3 × 103 km2 in 2013 to 312.4 × 103 km2 in 2010, with an average value of 188.9 × 103 km2. The Antarctic Circumpolar Current (ACC) travels closer to the continental shelf and brings the upper circumpolar deep water to much higher latitudes in the CS than in most other sectors; cyclonic ocean circulations often develop between the ACC and the Antarctic Slope Current, with many of them being associated with local topographic features and dense water cascading. These oceanic preconditions, along with cyclonic wind forcing in the Antarctic Divergence zone, generated polynyas in the CS. These findings offer a more complete circumpolar view of open-ocean polynyas in the Southern Ocean and have implications for physical, biological, and biogeochemical studies of the Southern Ocean. Future efforts should be particularly devoted to more extensively observing the ocean circulation to understand the variability of open-ocean polynyas in the CS.

How to cite: Qin, Q., Wang, Z., Liu, C., and Chen, C.: Open-Ocean Polynyas in the Cooperation Sea, Antarctica, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1259, https://doi.org/10.5194/egusphere-egu22-1259, 2022.

EGU22-1558 | Presentations | OS1.11

Drivers of Dense Shelf water formation in East Antarctic polynyas 

Esther Portela Rodriguez, Stephen R. Rintoul, Laura Herraiz-Borreguero, Fabien Roquet, Takeshi Tamura, Esmee van Wijk, Sophie Bestley, Clive McMahon, and Mark Hindell

Coastal polynyas are key regions of Dense Shelf Water (DSW) formation that ultimately contributes to the ventilation of the ocean abyss. However, not all polynyas form DSW. In this study, we analyse the main drivers of DSW formation in four East Antarctic polynyas: Mackenzie, Barrier, Shackelton and Vincennes Bay from west to east. Mackenzie and Barrier (in lesser extent) were the only two polynyas where DSW formation was observed while it is absent in Shackelton and Vincennes Bay in the particular years when they were best sampled. We analysed the role of Bathymetry, water-mass distribution and transformation, stratification of the water column, sea-ice production rate and associated salt advection. We found that sea ice production was highest in Mackenzie, particularly in early winter, which likely contributed to reach higher salinity than the other polynyas at the beginning of the sea ice formation season. From April to September, the total salinity change in Mackenzie polynya was lower than in the other polynyas, and the strong contribution of the brine rejection was partly offset by freshwater advection. Overall, the preconditioning in early winter in Mackenzie polynya, likely due to strong SIP in February and March was the main driver determining DSW formation in MAckenzie in contrast with the other East Antarctic polynyas.

How to cite: Portela Rodriguez, E., Rintoul, S. R., Herraiz-Borreguero, L., Roquet, F., Tamura, T., van Wijk, E., Bestley, S., McMahon, C., and Hindell, M.: Drivers of Dense Shelf water formation in East Antarctic polynyas, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1558, https://doi.org/10.5194/egusphere-egu22-1558, 2022.

EGU22-2561 | Presentations | OS1.11

Circulation and water masses on the Bellingshausen Sea continental shelf 

Karen J. Heywood, Ria Oelerich, Peter Sheehan, Gillian Damerell, Andrew Thompson, Michael Schodlok, and Mar Flexas

The circulation of the Bellingshausen Sea has not attracted as much attention as that of its neighbours, the Amundsen Sea and the West Antarctic Peninsula.  Like them, it hosts a wide variety of vulnerable ice shelves, and exhibits inflows of warm deep water onto the continental shelf, and outflows of resulting ice shelf meltwater. Quantifying heat and freshwater transport, and understanding their temporal and spatial variability, is important for understanding the impact of a warming, melting Antarctica on ocean circulation.

First, we identify processes influencing interannual variability in warm deep water on the southern Bellingshausen Sea continental shelf using the GLORYS12V1 1/12° reanalysis from 1993 to 2018. EOFs of potential temperature below 300 m allow separation into warm and cold regimes. The Amundsen Sea Low is more intense and extends further to the east during warm regimes than during cold regimes. Increased Ekman transport results in a stronger frontal jet and Antarctic Coastal Current (AACC) in the cold regime. The warm and cold regimes are also linked to different temperature tendencies.  In the warm regime, a wind-induced reduction of sea ice results in increased heat loss to the atmosphere, convection, and formation of cold dense water in winter associated with a cooling of the southern Bellingshausen Sea and a net northward heat transport. In contrast, conditions of the cold regime favour a gradual warming of the southern Bellingshausen, consistent with a net southward heat transport.

Second, we use high-resolution sections collected from two ocean gliders deployed in the Bellingshausen Sea between January and March 2020 to quantify the distribution of meltwater. We observe a cyclonic circulation in Belgica Trough, whose western limb transports a meltwater flux of 0.46 mSv northwards and whose eastern limb transports a newly-identified meltwater re-circulation (0.88 mSv) southwards. Peak meltwater concentration is located into two layers (~150 m and ~200 m) associated with different density surfaces (27.4 and 27.6 kg m-3). The deeper layer is characterised by elevated turbidity. The shallower layer is less turbid, and is more prominent closer to the shelf break and in the eastern part of Belgica Trough. We hypothesise that these different meltwater layers emanate from different ice shelves that abut the Bellingshausen Sea.

To test the hypothesis of multiple source regions, we perform experiments using a regional set-up of MITgcm (approx. 3 km resolution), in which tracers released beneath ice shelves are used as a proxy for meltwater to diagnose transport pathways. Meltwater at the glider study site originates from ice shelves in the eastern Bellingshausen, particularly from George VI. Meltwater is primarily transported westward in the AACC; a small proportion detaches from the AACC via eddies and lateral mixing and, from the west, enters the cyclonic circulation within Belgica Trough, consistent with the glider-observed northward meltwater flow in the west and the southward re-circulation in the east. Very little meltwater from ice shelves immediately south of Belgica Trough enters this in-trough circulation.

How to cite: Heywood, K. J., Oelerich, R., Sheehan, P., Damerell, G., Thompson, A., Schodlok, M., and Flexas, M.: Circulation and water masses on the Bellingshausen Sea continental shelf, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2561, https://doi.org/10.5194/egusphere-egu22-2561, 2022.

The sensitivity of sea ice to the contrasting seasonal and perennial snow properties in the southeastern and northwestern Weddell Sea is not yet considered in sea ice model and satellite remote sensing applications. However, the analysis of physical snowpack properties in late summer in recent years reveal a high fraction of melt-freeze forms resulting in significant higher snow densities in the northwestern than in the eastern Weddell Sea. The resulting lower thermal conductivity of the snowpack, which is only half of what has been previously assumed in models in the eastern Weddell Sea, reduces the sea ice bottom growth by 18 cm. In the northwest, however, the potentially formed snow ice thickness of 12 cm at the snow/ice interface contributes to an additional 2 cm of thermodynamic ice growth at the bottom. This emphasizes the enormous impact of unappreciated regional differences in snowpack properties on the thermodynamic ice growth.

How to cite: Arndt, S.: Sensitivity of sea ice growth to snow properties in opposing regions of the Weddell Sea in late summer, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2870, https://doi.org/10.5194/egusphere-egu22-2870, 2022.

EGU22-3041 | Presentations | OS1.11

Sensitivity of the relationship between Antarctic ice shelves and iron supply to projected changes in the atmospheric forcing 

Mike Dinniman, Pierre St-Laurent, Kevin Arrigo, Eileen Hofmann, and Gert van Dijken

Previous studies showed that correlations of satellite-derived estimates of chlorophyll a in coastal polynyas over the Antarctic continental shelf with the basal melt rate of adjacent ice shelves are a result of upward advection or mixing of iron-rich deep waters due to circulation changes driven by ice shelf melt, rather than a direct influence of iron released from melting ice shelves.  In this study, the effects of projected changes in winds, precipitation, and atmospheric temperatures on this relationship were examined with a 5-km resolution ocean/sea ice/ice shelf model of the Southern Ocean.  The atmospheric changes are added as idealized increments to the forcing.  Inclusion of a poleward shift and strengthening of the winds, increased precipitation, and warmer atmospheric temperatures resulted in an 83% increase in the total Antarctic ice shelf basal melt, with changes being heterogeneously distributed around the continent.  The total dissolved iron supply to the surface waters over the continental shelf increased by 62%, while the surface iron supply due just to basal melt driven overturning increased by 48%.  However, even though the total increase in iron supply is greater than the increase due to changes in the ice shelf melt, the ice shelf driven supply becomes relatively even more important in some locations, such as the Amundsen and Bellingshausen Seas.  The modified atmospheric conditions also produced a reduction in summer sea ice extent and a shoaling of the summer mixed layers.  These simulated responses to projected changes suggest relief of light and nutrient limitation for phytoplankton blooms over the Antarctic continental shelf and perhaps an increase in annual production in years to come.

How to cite: Dinniman, M., St-Laurent, P., Arrigo, K., Hofmann, E., and van Dijken, G.: Sensitivity of the relationship between Antarctic ice shelves and iron supply to projected changes in the atmospheric forcing, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3041, https://doi.org/10.5194/egusphere-egu22-3041, 2022.

EGU22-3067 | Presentations | OS1.11

Simulated warm water access to the Amundsen Sea continental shelf 

Alessandro Silvano, Paul Holland, Kaitlin Naughten, Oana Dragomir, Pierre Dutrieux, Adrian Jenkins, Yidongfang Si, Andrew Stewart, Beatriz Peña-Molino, and Alberto Naveira Garabato

The West Antarctic Ice Sheet is losing mass at an accelerating rate, contributing to sea level rise. Ocean forcing is considered to be the main driver of this mass loss, associated with warm intrusions of Circumpolar Deep Water onto the continental shelf. Here we describe these intrusions, focussing on the role of the Amundsen Undercurrent. The Amundsen Undercurrent is an eastward, bottom-intensified current located at the shelf break/upper slope that transports warm Circumpolar Deep Water. This current enters the continental shelf through deep canyons that connect the shelf break with ice shelf cavities, bringing oceanic heat to the base of the ice shelves. We use a regional ocean model to introduce the forcing mechanisms of the Amundsen Undercurrent and the drivers of its temporal variability. We conclude by discussing how this variability ultimately influences melting of ice shelves in the Amundsen Sea.

How to cite: Silvano, A., Holland, P., Naughten, K., Dragomir, O., Dutrieux, P., Jenkins, A., Si, Y., Stewart, A., Peña-Molino, B., and Naveira Garabato, A.: Simulated warm water access to the Amundsen Sea continental shelf, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3067, https://doi.org/10.5194/egusphere-egu22-3067, 2022.

EGU22-3373 | Presentations | OS1.11

Antarctic ice shelf open ocean corridors with large swell available 

Nathan Teder, Luke Bennetts, Rob Massom, and Phil Reid

Over the last three decades there have been two catastrophic disintegrations events on the Antarctic peninsula, the Larsen A ice shelf in 1995 and the Larsen B in 2002, alongside the Wilkins ice shelf which underwent multiple partial disintegrations between 1998—2009.  Previous research into these events indicated that there had been prolonged periods where the Larsen and Wilkins Ice Shelves were without a sea-ice buffer to protect them from ocean swell in the leadup to their respective disintegrations. Swell potentially acted as a trigger mechanism to each shelf to disintegrated, as they had already been destabilised by surface flooding, fracturing, thinning and other glaciological factors.

This study will focus on the algorithm we developed which calculates the time where an ice shelf is without a local sea ice buffer (“exposure”), the size of the ocean which could directly propagate waves into the shelf (“corridor”) and the maximum wave height of swell which is directed towards the shelf in the corridor. An analysis of the last forty-one years showed that there was a large variation over individual ice shelves for both exposure and the available swell, due to the impact of polynyas, ice tongues and fast-ice growth which can protect the ice shelf. On a regional scale, the East Antarctic Ice Shelf and West Antarctic Ice Shelf had opposing trends, with the West Antarctic Ice Shelf recording a weak increasing trend of exposure and available swell.

How to cite: Teder, N., Bennetts, L., Massom, R., and Reid, P.: Antarctic ice shelf open ocean corridors with large swell available, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3373, https://doi.org/10.5194/egusphere-egu22-3373, 2022.

EGU22-3444 | Presentations | OS1.11

Drivers and reversibility of abrupt ocean cold-to-warm and warm-to-cold transitions in the Amundsen Sea, Antarctica 

Justine Caillet, Nicolas Jourdain, and Pierre Mathiot

Ocean warming around Antarctica has the potential to trigger marine ice-sheet instabilities. It has been suggested that abrupt and irreversible cold-to-warm ocean tipping points may exist, with possible domino effect from ocean to ice-sheet tipping points (Hellmer et al. 2017). Here we investigate the existence of drivers of ocean tipping points in the Amundsen Sea. This sector is currently relatively warm, but a cold-to-warm tipping point may have occurred in the past. The conditions for an hypothetic abrupt return to a cold state are also investigated. A 1/4° ocean model configuration of the Amundsen Sea, representing interactions with sea-ice and ice-shelves, is used to characterize warm-to-cold and cold-to-warm oceanic transitions induced by perturbations of the atmospheric forcing and their influence on ice-shelf basal melt. We apply idealized perturbations of heat, momentum and freshwater fluxes to identify the key physical processes at play. We find that the Amundsen Sea switches permanently to a cold state for an air cooling of 2.5°C and intermittently for either an air cooling of 0.5°C, precipitations decreased by 30% or a 2° northward shift of the winds. All simulated transitions are reversible, i.e. restoring the forcing to its state before the tipping point is sufficient to restore the ocean to its original state although the recovery time is correlated to the amplitude of the perturbations. Perturbations of the heat and freshwater fluxes modify the properties of the ocean by impacting the buoyancy flux, either through their impact on the sea-ice or, directly, to a lesser extent. Perturbations of the momentum flux involve more complex mechanisms as it combines both an Ekman effect and an indirect effect on the buoyancy flux related to changes in sea-ice advection.

How to cite: Caillet, J., Jourdain, N., and Mathiot, P.: Drivers and reversibility of abrupt ocean cold-to-warm and warm-to-cold transitions in the Amundsen Sea, Antarctica, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3444, https://doi.org/10.5194/egusphere-egu22-3444, 2022.

EGU22-4235 | Presentations | OS1.11

Model Based Polynya: Deep water formation in the Southern Ocean 

Benjamin Barton, George Nurser, and Yevgeny Aksenov

Dense water is formed when sea ice around Antarctica drifts apart leaving open-water areas called polynyas. Both the processes of cooling sea water in contact with the atmosphere and salt accumulation in sea water during sea ice formation, lead to the sea water getting denser. The dense water formation in the oceans surrounding the Antarctic continent contributes to meridional overturning circulation, making it crucial to understand the changes in the Antarctic sea ice and oceans to improve model predictions. Using NEMO output from both a regional configuration and a coupled global configuration we ask how well are polynyas and deep water formation represented in the models? How do regional trends in sea ice affect the polynyas and deep water formation? In the model we find several types of polynya; including the open-water Great Weddell Sea Polynya and coastal polynyas. We have developed and applied an algorithm for classifying coastal polynyas based on sea ice concentration to identify and separate these from the open water polynya areas, in addition, we include sea ice thickness in the classification of coastal polynyas to select areas where the mixed-layer is deep, and surface salt flux is present. In the coastal polynyas the mixed-layer is deep and densification of the upper ocean is strong due to the surface salt flux. The Great Weddell Sea Polynya is also found to deepen the mixed-layer but the strong salt flux, found along the coast, is not present in the open-water polynya suggesting an alternative mechanism is taking place. The favourable ice divergence in the Weddell Sea builds over several years in both models but the Great Polynya itself does not reoccur after the 1980s. Coastal polynyas make up the largest area of the polynyas but show a negative trend in total area, possibly suggesting a diminishing role of these polynyas in future dense water formation. The study asserts different contributions of the two types of polynyas to deep water production.

How to cite: Barton, B., Nurser, G., and Aksenov, Y.: Model Based Polynya: Deep water formation in the Southern Ocean, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4235, https://doi.org/10.5194/egusphere-egu22-4235, 2022.

EGU22-4275 | Presentations | OS1.11

Characterizing the Basal Melting Spatio-Temporal Variability of the Ross Ice Shelf using a Regional Ocean Model 

Enrico Pochini, Florence Colleoni, Andrea Bergamasco, Manuel Bensi, Giorgio Budillon, Pasquale Castagno, Michael Dinniman, Pierpaolo Falco, Riccardo Farneti, Emanuele Forte, Vedrana Kovačević, and Stefanie Mack

The Ross Ice Shelf (RIS) is one of the biggest Antarctic ice shelves and buttresses ice streams draining both the West and East Antarctic ice sheets. Recent  observations indicate that the melting of Antarctic ice-shelves is accelerating with great spatial heterogeneity. However, estimates of basal melting, which rely on indirect methods, are affected by large uncertainties: as for the RIS, the literature includes basal melt rates from 48 to 123 Gt/yr. To improve basal melting predictions we must understand what causes its spatio-temporal variability. Here, we use a regional configuration of the MIT general circulation model (MITgcm) to analyze the interactions between various water masses and the ice shelf, and their connection to local and global climate. The model simulates the ocean circulation in the Ross Sea and inside the RIS cavity from 1993 to 2018. In the actual configuration it does not account for tidal forcing. Basal melting of the RIS is parameterized by the three-equation formulation. The simulated RIS basal averaged melt rate is 78.6 ± 13.3 Gt/yr averaged over 1993-2018.

To better understand which local water mass causes basal melting, we developed a new methodology based on mixing ratios of endpoint-water masses. The endpoints are defined by: the High and Low Salinity Shelf Water (HSSW/LSSW), characterized by high and low salinity respectively and a near-freezing temperature; warm and salty modified Shelf Waters (mSW); warm and fresh Antarctic Surface Water (AASW); and cold and fresh Ice Shelf Water (ISW).

Our analyses show that in the long-term, HSSW causes ~45% of the total basal melting and is found mostly in the Western half of the RIS cavity. It shows a long-term trend due to the increase in the volume of cavity occupied by HSSW at the expense of LSSW. LSSW yields ~20% of the total basal melting and is mostly found in the Eastern half of the RIS cavity. As expected, melting due to mSW (~15% of the basal melting) and AASW (~7% of the basal melting) shows a strong seasonal cycle. Simulated mSW mostly reaches the Central-Eastern RIS during summer. Similarly, AASW intrudes below the RIS near Ross Island exclusively in summer. Melting attributed to ISW is only ~2%. About 11% of the simulated basal melting cannot be clearly attributed to any of the main water masses due to local mixing.

Finally, RIS basal melting and Ross Sea water masses variability inside the cavity are likely driven by a combination of local forcing (katabatic wind), large-scale wind/pressure systems (Amundsen Sea Low, Southern Annular Mode) and teleconnections (El-Niño Southern Oscillation, Pacific Decadal Oscillation), mediated by ocean-sea ice interactions, in particular by sea ice production in Western Ross Sea polynyas, and sea ice import in the Eastern Ross Sea. Identifying such climatic connections can inform which melting mode will be more important in the future climate and which region of the RIS will be more affected.

How to cite: Pochini, E., Colleoni, F., Bergamasco, A., Bensi, M., Budillon, G., Castagno, P., Dinniman, M., Falco, P., Farneti, R., Forte, E., Kovačević, V., and Mack, S.: Characterizing the Basal Melting Spatio-Temporal Variability of the Ross Ice Shelf using a Regional Ocean Model, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4275, https://doi.org/10.5194/egusphere-egu22-4275, 2022.

EGU22-5388 | Presentations | OS1.11

How does the Southern Annular Mode impact ice-shelf basal melt around Antarctica? 

Deborah Verfaillie, Charles Pelletier, Hugues Goosse, Nicolas C. Jourdain, Christopher Y.S. Bull, Quentin Dalaiden, Vincent Favier, Thierry Fichefet, and Jonathan Wille

The climate of the polar regions is characterized by large fluctuations and has experienced dramatic changes over the past decades. In particular, the patterns of changes in sea ice and ice sheet mass are complex in the Southern Hemisphere. The Antarctic Ice Sheet has also lost mass in the past decades, especially in Western Antarctica, with a spectacular thinning and weakening of ice shelves, i.e., the floating extensions of the grounded ice sheet. Despite recent advances in observing and modelling the Antarctic climate, the mechanisms behind this long-term mass loss remain poorly understood because of the limited amount of observations and the large biases of climate models in polar regions, in concert with the large internal variability prevailing in the Antarctic. Among all the processes involved in the mass variability, changes in the general atmospheric circulation of the Southern Hemisphere may have played a substantial role. One of the most important atmospheric modes of climate variability in the Southern Ocean is the Southern Annular Mode (SAM), which represents the position and the strength of the westerly winds. During years with a positive SAM index, lower sea level pressure at high latitudes and higher sea level pressure at low latitudes occur, resulting in a stronger pressure gradient and intensified Westerlies. However, the current knowledge of the impact of these fluctuations of the Westerlies on the Antarctic cryosphere is still limited. Over the past few years, some efforts investigated the impact of the SAM on the Antarctic sea ice and the surface mass balance of the ice sheet from an atmosphere-only perspective. Recently, a few oceanic studies have focused on the local impact of SAM-related fluctuations on the ice-shelf basal melt in specific regions of Antarctica, particularly Western Antarctica. However, to our knowledge, there is no such study at the scale of the whole Antarctic continent. In this study, we performed idealized experiments with a pan-Antarctic regional ice-shelf cavity-resolving ocean - sea-ice model for different phases of the SAM. We show that positive (negative) phases lead to increased (decreased) upwelling and subsurface ocean temperature and salinity close to ice shelves. A one-standard-deviation increase of the SAM leads to a net basal mass loss of 40 Gt yr-1, with strong regional contrasts: increased melt in the Western Pacific and Amundsen-Bellingshausen sectors and the opposite response in the Ross sector. Taking these as a baseline sensitivity, we estimate last millennium and end-of-21st-century ice-shelf basal melt changes due to SAM of -60.7 Gt yr-1 and 1.8 to 26.8 Gt yr-1 (depending on the emission scenario considered), respectively, compared to the present.

How to cite: Verfaillie, D., Pelletier, C., Goosse, H., Jourdain, N. C., Bull, C. Y. S., Dalaiden, Q., Favier, V., Fichefet, T., and Wille, J.: How does the Southern Annular Mode impact ice-shelf basal melt around Antarctica?, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5388, https://doi.org/10.5194/egusphere-egu22-5388, 2022.

EGU22-6053 | Presentations | OS1.11 | Highlight

Tipping of the Filchner-Ronne and other Antarctic ice shelf cavities 

Verena Haid, Ralph Timmermann, and Hartmut Hellmer

Tipping of an ice shelf cavity from a cold to a warm state happens when a sustained inflow of warm Circumpolar Deep Water (CDW) or a modified variant of it replaces High Salinity Shelf Water (HSSW) and Ice Shelf Water (ISW) in a cold-water cavity. HSSW and ISW with temperatures close to or even below the surface freezing point provide little heat for melting glacial ice. CDW derivatives, however, can cause a substantial multiplication of the ice shelf basal melt rates. The increased melt water release may trigger a positive feedback loop that stabilizes the warm state. Therefore, if the outside circumstances  turned back to previous conditions, a reversal from warm to cold would not occur under the same conditions as the switch from cold to warm.

A warm tipping has been found possible for the Filchner-Ronne Ice Shelf (FRIS) cavity in previous studies. In the framework of the EU project TiPACCs, we now reinforce our focus on the conditions which can cause a tipping for the Filchner Ronne and other Antarctic ice shelf cavities. We conducted a series of FESOM-1.4 simulations with different manipulations of the atmospheric forcing variables in order to analyse the common factors of tipping events, opposed to more stable results.

We found that for the Filchner Trough region in a warming world, the crucial balance is between the different rates of warming and freshening of (a) the continental shelf waters in front of the ice shelf and (b) the waters transported with the slope current. While other studies identified an uplift of the pycnocline at the continental shelf break as a necessary condition for warm onshore flow, we deem a tipping more likely to hinge on the density loss of the shelf waters. When density on the continental shelf decreases more rapidly than in the slope current at sill depth, the ice shelf cavity is prone to tip. Reversibility of the tipping is possible within three decades under ERA Interim atmospheric forcing (1979-2017), but our study also confirms that hysteresis effects can cause a bistability of warm and cold state in the FRIS cavity under the 20th century HadCM3 forcing.

How to cite: Haid, V., Timmermann, R., and Hellmer, H.: Tipping of the Filchner-Ronne and other Antarctic ice shelf cavities, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6053, https://doi.org/10.5194/egusphere-egu22-6053, 2022.

EGU22-6237 | Presentations | OS1.11

Influence of anthropogenic forcing and internal climate variability on winds over the Amundsen Sea shelf 

Paul Holland, Thomas Bracegirdle, Pierre Dutrieux, Kaitlin Naughten, David Schneider, Gemma O'Connor, Eric Steig, and Adrian Jenkins

Ocean-driven ice loss from the West Antarctic Ice Sheet (WAIS) is a significant contributor to sea-level rise. In the 20th century, modelled wind trends over the Amundsen Sea imply an ocean warming that could explain this ice loss. In this presentation, climate model simulations are used to separate internal and anthropogenic influences on these wind trends. Tropical Pacific variability is found to be most influential in winter and over the Amundsen Sea continental shelf, while greenhouse gases and ozone depletion are dominant in summer and north of the shelf. Model projections feature strong wind trends that imply future ocean warming. In these projections, moderate greenhouse-gas mitigation has no influence on wind trends near the Amundsen Sea shelf. Internal climate variability creates a large and irreducible uncertainty in winds over the shelf. This complex regional and seasonal interplay between anthropogenic forcing and internal variability may determine the attribution and projection of ice loss from the WAIS.

How to cite: Holland, P., Bracegirdle, T., Dutrieux, P., Naughten, K., Schneider, D., O'Connor, G., Steig, E., and Jenkins, A.: Influence of anthropogenic forcing and internal climate variability on winds over the Amundsen Sea shelf, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6237, https://doi.org/10.5194/egusphere-egu22-6237, 2022.

EGU22-7243 | Presentations | OS1.11

Last Glacial Maximum ice shelf retreat and sea-ice dynamics in the Joides Basin, Ross Sea, Antarctica 

Chiara Pambianco, Lucilla Capotondi, Federico Giglio, Alessio Di Roberto, Simon Belt, Gesine Mollenhauer, Alessio Nogarotto, and Tommaso Tesi

Here we present preliminary results from the Joides Basin, one of the depressions placed on the continental shelf adjacent to the Ross Ice Shelf (RIS) edge during the Last Glacial Maximum (LGM). We studied a south west – north east transect composed of four gravity cores and one piston core collected along the axis of the Joides Basin in order to reconstruct the past-LGM glacial sedimentary facies and provide new stratigraphic information. A suite of organic biomarkers were used to reconstruct sea-ice conditions and retreat of the RIS during the last termination.

The last glacial termination has been broadly targeted as a potential analogue to current/future global warming, and many studies on this timeframe have been conducted in the RIS, which, with its buttressing effect on continental ice, and its connection to the surrounding marine environment, represents a key element in bridging atmosphere and ocean. The RIS balance and behavior, during rapid climate change, however, is still poorly understood. Many questions are still open regarding the RIS retreat and warming effects on both the atmosphere and ocean, and concerns remain about the reliability of the chronology of marine sediments recovered from this region.

Based on radiocarbon dates of bulk organic carbon and foraminifera, our proposed age model provides new results on the paleo-environmental changes in the Joides Basin as the system moved from an ice-sheet dominated environment to a distal ice-sheet-system. Our preliminary results provide new information to better improve our understanding of the RIS modalities of retreat and the related effects to the surrounding marine and glacio-marine environment during the last deglaciation and Holocene.

How to cite: Pambianco, C., Capotondi, L., Giglio, F., Di Roberto, A., Belt, S., Mollenhauer, G., Nogarotto, A., and Tesi, T.: Last Glacial Maximum ice shelf retreat and sea-ice dynamics in the Joides Basin, Ross Sea, Antarctica, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7243, https://doi.org/10.5194/egusphere-egu22-7243, 2022.

EGU22-7257 | Presentations | OS1.11

Drivers of Antarctic sea-ice advance date 

Kenza Himmich, Martin Vancoppenolle, Gurvan Madec, Jean-Baptiste Sallee, Casimir De Lavergne, Marion Lebrun, and Paul Holland

Sea-ice advance is a key moment to the Antarctic climate and ecosystem. Over the last 4 decades, sea-ice advance has been occurring earlier in the Weddell and Ross Seas and later west of the Antarctic Peninsula and in the Amundsen Sea. However, not much is known on the drivers of the observed changes nor on the physical processes determining the date of advance in the Southern Ocean. To progress understanding, we investigate the respective roles of ocean-sea ice processes in controlling the timing of sea-ice advance using observational and reanalysis data. Based on the satellite-based sea-ice concentration budget at the time of advance, we identify two regions with distinct processes. In the outermost ice-covered region, a few degrees of latitude within the winter ice-edge, no ice growth is observed and the ice advance date can only occur by transport of ice from higher latitudes. This is consistent with above freezing reanalysis sea surface temperature (SST) at the time of sea-ice advance. Elsewhere in the seasonal ice zone, ice import is a minor contributor to the sea-ice concentration budget hence sea-ice advance must be due to freezing only. In situ hydrographic observations show that the date of advance is more strongly linked to the seasonal maximum of the mixed layer heat content (MLH) than to the seasonal maximum SST — which reflects that the need for the full mixed layer to approach freezing before sea ice can appear. The relationship is stronger in regions with no contribution of sea-ice transport. Based on these considerations, we suggest that upper ocean hydrographic properties and sea ice drift are key features to determine the timing of sea-ice advance.

How to cite: Himmich, K., Vancoppenolle, M., Madec, G., Sallee, J.-B., De Lavergne, C., Lebrun, M., and Holland, P.: Drivers of Antarctic sea-ice advance date, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7257, https://doi.org/10.5194/egusphere-egu22-7257, 2022.

EGU22-7897 | Presentations | OS1.11

A multidecadal decline of Weddell Sea Bottom Water volume forced by wind-driven sea ice changes 

Shenjie Zhou, Andrew Meijers, Michael Meredith, Povl Abrahamsen, Alessandro Silvano, Paul Holland, Jean-Baptiste Sallée, and Svein Østerhus

Antarctic Bottom Water (AABW) is one of the most important deep water masses contributing to the lower limb of the global overturning circulation, which modulates the deep ocean ventilation and oceanic heat/carbon exchanges on multidecadal to millennial timescales. Weddell Sea Bottom Water (WSBW) is a key precursor of the AABW exported from the Weddell Sea. Its formation involves intense air-sea-ice interaction on the continental shelf that releases brine from sea ice formation, and occurs mostly in the austral winter. Here we report a distinct long-term volume decline of WSBW revealed by data collected along repeat occupations of World Ocean Circulation Experiment (WOCE) hydrographic sections. We estimate a >20% reduction of WSBW volume since the early 1990s and a resultant widespread deep Weddell Sea warming associated with a basin-scale deepening of isopycnal surfaces. With the most significant volume reduction concentrating within the densest classes of WSBW and a concurrent decline of sea ice formation rate (>30%) over the southwestern Weddell continental shelf inferred from remote-sensed sea ice concentration data, we propose that the observed WSBW volume reduction is likely to be driven by a multidecadal weakening of dense shelf water production due to the sea ice changes. Reanalysis atmospheric data and ice drift data suggest that the reduction of sea ice formation rate is predominantly linked to changes in wind-driven sea ice convergence in front of Ronne Ice Shelf and Berkner Bank, as a response to a vigorous Amundsen Sea Low deepening that is teleconnected to tropical Pacific SST variability, and associated with the local radiative forcing from long-term ozone depletion.

How to cite: Zhou, S., Meijers, A., Meredith, M., Abrahamsen, P., Silvano, A., Holland, P., Sallée, J.-B., and Østerhus, S.: A multidecadal decline of Weddell Sea Bottom Water volume forced by wind-driven sea ice changes, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7897, https://doi.org/10.5194/egusphere-egu22-7897, 2022.

EGU22-8256 | Presentations | OS1.11

Oceanic drivers of air-sea-ice interactions: the imprint of mesoscale eddies and ocean heat content on the sea ice, atmosphere, and ice sheet 

Pierre-Vincent Huot, Christoph Kittel, Thierry Fichefet, Sylvain Marchi, Nicole Van Lipzig, Xavier Fettweis, Deborah Verfaillie, François Klein, and Nicolas Jourdain

The Antarctic Climate is characterized by strong interactions between the Southern Ocean, its sea ice cover, and the overlying atmosphere taking place over a wide range of spatio-temporal scales. This coupling constrains our ability to isolate the role of specific components of the climate system on the dynamics of the Antarctic Climate, especially with stand-alone approaches neglecting the feedbacks at play. Based on coupled model simulations, we explore how the ocean can drive the interactions with the cryosphere and atmosphere at two distinct spatio-temporal scales. First, the role of ocean mesoscale eddies is investigated. We describe the imprint of mesoscale eddies on the sea ice and atmosphere in a high-resolution simulation of the Adélie Land sector (East Antarctica) performed with a regional coupled ocean--sea ice--atmosphere model (NEMO-MAR). Specific attention is given to the role of the sea ice in the modulation of the air-sea interactions at mesoscale and to the influence of eddy-driven fluxes on the ocean and sea ice. We show that mesoscale eddies affect near-surface winds and air temperature both in ice-free and ice-covered conditions due to their imprint on the sea ice cover. In addition, eddies promote northward sea ice transport and decrease momentum transfer by surface stress to the ocean. In a second section, we move to larger spatial and temporal scales and delve into the influence of the ocean on the seasonal to interannual variability of the sea ice, atmosphere, and ice shelves basal melt at the scale of the Southern Ocean. This work is based on early results from a new coupled ocean–sea ice--atmosphere--ice sheet configuration with explicit under-ice shelf cavities called PARASO. We focus on subsurface heat content variability and its influence on the interactions between the ocean, the sea ice, the atmosphere, and the Antarctic Ice Sheet.

How to cite: Huot, P.-V., Kittel, C., Fichefet, T., Marchi, S., Van Lipzig, N., Fettweis, X., Verfaillie, D., Klein, F., and Jourdain, N.: Oceanic drivers of air-sea-ice interactions: the imprint of mesoscale eddies and ocean heat content on the sea ice, atmosphere, and ice sheet, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8256, https://doi.org/10.5194/egusphere-egu22-8256, 2022.

EGU22-8960 | Presentations | OS1.11

Antarctic ice tongue collapse triggered by loss of stabilizing land-fast sea ice 

Rodrigo Gomez Fell, Wolfgang Rack, Heather Purdie, and Oliver Marsh

The complete length of Parker Ice Tongue (18 km or 41 km2) calved in March 2020. This event occurred at the same time as repeated full summer break-outs of surrounding land-fast sea ice. Our results showed that periods of continuous ice tongue growth coincided with extended periods of land-fast sea ice coverage for at least the past 60 years. We also found that seasonal variations in the ice tongue dynamics were linked to variations in the local land-fast sea ice extent. A complete Antarctic ice tongue calving right at the grounding line has not been reported before.

Based on the analysis of satellite images and aerial photographs we determined Parker Ice Tongue length variations for the last 65 years. We found that the average growth of Parker Ice Tongue has been ~193 m/y-1. If we assume a constant growth rate, a break-off event of the magnitude observed has not occurred in the last 169 years.

We used a Sentinel-1 SAR image sequence to create a 2017-2020 time series of surface ice velocities. We found a significant inverse correlation between fast ice extent and ice tongue velocities (R= -0.62; R2=0.39). The short summer period, characterized by decreased land-fast sea ice extent, showed around 11% higher velocities compared to winter. This supports the idea that fast-ice extent can influence ice tongue dynamics seasonally.

Here we showcase the vulnerability of Parker Ice Tongue once left exposed to oceanic processes, which poses questions about the fate of other ice tongues if land-fast sea ice decreases more broadly in the future.

How to cite: Gomez Fell, R., Rack, W., Purdie, H., and Marsh, O.: Antarctic ice tongue collapse triggered by loss of stabilizing land-fast sea ice, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8960, https://doi.org/10.5194/egusphere-egu22-8960, 2022.

EGU22-9080 | Presentations | OS1.11

Hydrography, circulation and warm inflow toward the central Getz Ice Shelf: two years of mooring observations 

Vår Dundas, Elin Darelius, Kjersti Daae, Nadine Steiger, Yoshihiro Nakayama, and Tae-Wan Kim

As the melt rates of Getz Ice Shelf (GIS) increase, its grounding line is retreating, possibly destabilizing GIS. Detailed oceanographic observations from all the GIS frontal regions are needed to describe its drivers of basal melt and obtain an accurate projection of its melt rates. We present the first mooring observations from the bathymetrically sheltered trough between Siple and Carney Islands - one of the remaining GIS fronts to be described in detail. Although the ocean is colder in this central trough compared to what is observed in adjacent troughs, temperatures more than 1° above freezing are present throughout the mooring period, with a positive mean heat transport directed towards the ice shelf. Output from a high-resolution regional model indicates that heat is advected to the trough from both the eastern Amundsen Sea and from the continental shelf break in the north. The variability in heat content and heat transport are both affected by ocean surface stress, but while westward stress drives increased heat transport towards the ice shelf, eastward stress drives enhanced heat content. These relationships are most prominent in winter. Anomalously low summertime sea ice concentration and weak winds during the mooring period appear to suppress the effect of a strong positive anomaly in cumulative Ekman pumping, causing relatively low heat content during the mooring period compared to long-term estimates from the regional model.

How to cite: Dundas, V., Darelius, E., Daae, K., Steiger, N., Nakayama, Y., and Kim, T.-W.: Hydrography, circulation and warm inflow toward the central Getz Ice Shelf: two years of mooring observations, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9080, https://doi.org/10.5194/egusphere-egu22-9080, 2022.

EGU22-10311 | Presentations | OS1.11

Twenty-first century projections of ice-shelf melt in the Amundsen Sea, Antarctica 

Nicolas Jourdain, Pierre Mathiot, Justine Caillet, and Clara Burgard

Approximately 10% of the global mean sea level rise over 2005–2010 was attributed to the glaciers flowing into the Amundsen Sea. This was mostly driven by changes in intrusions of Circumpolar Deep Water and subsequent ice shelf melt. Yet, projecting future ice shelf melt remains challenging because of large biases of CMIP models near Antarctica and because resolving the ocean circulation below the relatively small ice shelves in this sector requires a relatively high model resolution. Previously, we built atmospheric projections of the Amundsen sector at 10km resolution constrained by the rcp85 CMIP5 multi-model mean (Donat-Magnin et al. 2021). Here we use this atmospheric forcing to drive an ensemble of three 1/12° NEMO projections of the Amundsen Sea circulation and ice shelf melting. We find that melt rates are typically increased by 50% to 100% at the end of the 21st century compared to present day. Approximately half of this increase is explained by remote ocean changes transmitted through the model boundaries, while increased iceberg discharge does not have a significant effect. We describe the mechanisms at play through the terms of the ocean heat budget equations. We then use these projections to re-discuss some of the ISMIP6 projections (Seroussi et al. 2020, Edwards et al. 2021).

How to cite: Jourdain, N., Mathiot, P., Caillet, J., and Burgard, C.: Twenty-first century projections of ice-shelf melt in the Amundsen Sea, Antarctica, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10311, https://doi.org/10.5194/egusphere-egu22-10311, 2022.

EGU22-10635 | Presentations | OS1.11

Coastal and offshore controls on the variability of the Undercurrent in the Amundsen Sea 

Oana Dragomir, Alessandro Silvano, Anna Hogg, Michael Meredith, George Nurser, and Alberto Naveira Garabato

The marine-terminating glaciers of the Amundsen Sea are experiencing increased basal melting associated with an inflow of warm and salty water from the deep ocean onto the shelf via submarine glacial troughs. Modelling work suggests that variability in the transport of this source of heat across the shelf-break and onto the Dotson Trough in the western Amundsen Sea is regulated by wind-driven changes in an eastward undercurrent that flows along the continental slope.

What controls the strength and variability of the undercurrent, however, is not well documented due to a lack of observations in the region. Here, we use a 5-year mooring record of undercurrent velocity in the Dotson Trough in conjunction with a novel 16-year altimetric sea level product that includes measurements in regions of near-perennial ice cover to describe the connection between undercurrent variability and climate modes on seasonal to interannual time scales.

We find a robust signature of the undercurrent variability that is linked to both a circumpolar coastal sea level signal as well as to the sea level in an offshore region in the Amundsen Sea. We discuss the implications of this undercurrent-sea level covariability in the context of atmospheric climate modes and we further explore what this link conveys about the undercurrent variability on interannual timescales by using of our full altimetry record.

How to cite: Dragomir, O., Silvano, A., Hogg, A., Meredith, M., Nurser, G., and Naveira Garabato, A.: Coastal and offshore controls on the variability of the Undercurrent in the Amundsen Sea, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10635, https://doi.org/10.5194/egusphere-egu22-10635, 2022.

Terra Nova Bay Polynya (TNBP) is one of the representative coastal polynya in East Antarctica. TNBP plays a major role of sea ice producers in the Antarctica, and it influences the regional current circulation and the surrounding marine environment. Therefore, it is important to investigate the influencing factors of TNBP. In this study, time series of TNBP area was estimated from Landsat-8 OLI/TIRS (2013-2016) and Sentinel-1 SAR (2017-2021) images by visually analyzing the boundary of polynya. To analyze the environmental factors influencing the area of ​​TNBP, wind speed, temperature, air pressure, and humidity measured at an automatic weather station installed near the polynya, and sea surface temperature, salinity and heat fluxes predicted by a reanalysis data were compared to the time series TNBP area. The area of TNBP showed a moderate correlation with the wind speed, but it was statistically low correlated with all other environmental factors. Meanwhile, a multiple linear regression between the time series area and all environmental factors showed a much higher correlation coefficient than between the polynya area and wind speed. However, the polynya areas predicted by the multiple linear regression model were largely deviated from those estimated from the satellite images. In future work, we intend to develop a model that retrieve more accurate TNBP area by selecting environmental factors suitable for polynya area estimation and applying them to machine learning techniques.

How to cite: Kim, J. and Han, H.: A study on the influencing factors of Terra Nova Bay Polynya using satellite imagery, AWS, and reanalysis data, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11096, https://doi.org/10.5194/egusphere-egu22-11096, 2022.

EGU22-11231 | Presentations | OS1.11

Water Mass Transformation in the Antarctic shelf 

Fabio Boeira Dias, Petteri Uotila, Ben Galton-Fenzi, Ole Ritcher, Steve Rintoul, Violaine Pellichero, and Yafei Nie

Antarctic Bottom Water (AABW) forms around Antarctica, sinks to the ocean’s abyss and fills more than 30% of the ocean’s volume. The formation of AABW includes mixing of distinct water masses, such as High Salinity Shelf Water (HSSW), Ice Shelf Water (ISW) and Circumpolar Deep Water on the continental shelf. Despite its climatic importance, the mechanisms of AABW formation are poorly known due to the lack of observations and the inability of climate models to simulate those mechanisms. We applied the Water Mass Transformation (WMT) framework in density space to simulations from a circumpolar ocean-ice shelf model (WAOM, with horizontal resolution ranging from 10 to 2 km) to understand the role of surface fluxes and oceanic processes to water mass formation and mixing on the Antarctic continental shelf, including the ice shelf cavities. The salt budget dominates the water mass transformation rates, with only secondary contribution from the heat budget. The buoyancy gain at relatively light density classes (27.2 < σΘ < 27.5 kg/m3) is dominated by basal melting. At heavier densities (σΘ > 27.5), salt input associated with sea-ice growth in coastal polynyas drives buoyancy loss. The formation of HSSW occurs via diffusion of the surface fluxes, but it is advected towards the cavities of large ice shelves (e.g., Ross, Ronne-Filchner), where it interacts with ice shelf through melting and refreezing and forms ISW. The sensibility of those mechanisms to the model horizontal resolution was evaluated. The basal melting and associated buoyancy gain rates largely decrease with increased resolution, while buoyancy loss associated with coastal polynyas are less sensible to resolution as surface fluxes are estimated from sea ice concentration observations. These results highlight the importance of high resolution to accurately simulate AABW formation, where mixing processes occurring below ice shelf cavities play an important role in WMT.

How to cite: Boeira Dias, F., Uotila, P., Galton-Fenzi, B., Ritcher, O., Rintoul, S., Pellichero, V., and Nie, Y.: Water Mass Transformation in the Antarctic shelf, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11231, https://doi.org/10.5194/egusphere-egu22-11231, 2022.

EGU22-11368 | Presentations | OS1.11

Antarctic ice-shelf basal melting in a variable resolution Earth System Model 

Xylar Asay-Davis, Alice Barthel, Carolyn Begeman, Darin Comeau, Matthew Hoffman, Wuyin Lin, Mark Petersen, Stephen Price, Andrew Roberts, Milena Veneziani, Luke Van Roekel, and Jonathan Wolfe

The processes that govern freshwater flux from the Antarctic Ice Sheet (AIS)—ice-shelf basal melting and iceberg calving—are generally poorly represented in current Earth System Models (ESMs). The processes governing ocean flows onto the Antarctic continental and into ice-shelf cavities can only be captured accurately at resolutions significantly higher than those in typical CMIP-class ESMs. The Energy Exascale Earth System Model (E3SM) from the US Department of Energy supports regional refinement in all components, allowing global modeling with high resolution in regions of interest. Here, we present fully coupled results from an ocean/sea-ice mesh that has high resolution (12 km) on the Antarctic continental shelf and much of the Southern Ocean and low resolution (~30 to 60 km) over the rest of the globe. E3SM includes Antarctic ice-shelf cavities with fixed geometry and calculates ice-shelf basal melt rates from the heat and freshwater fluxes computed by the ocean component. In addition, E3SM permits prescribed forcing from a climatology of iceberg melt, providing a more realistic representation of these freshwater fluxes than found in many ESMs. With these new capabilities, E3SM version 2 produces realistic and stable ice-shelf basal melt rates across the continent. We show preliminary results of modeled ice-shelf basal melt rates across a range of Antarctic ice-shelves under pre-industrial and historical climate forcing, as well as the impacts of these added capabilities on the region’s climate. We show that the use of a mesoscale eddy parameterization, tapered with the mesh resolution, reduces biases even in the 12-km region where some eddies are resolved.  The accurate representation of these processes within a coupled ESM is an important step towards reducing uncertainties in projections of the Antarctic response to climate change and Antarctica's contribution to global sea-level rise.

How to cite: Asay-Davis, X., Barthel, A., Begeman, C., Comeau, D., Hoffman, M., Lin, W., Petersen, M., Price, S., Roberts, A., Veneziani, M., Van Roekel, L., and Wolfe, J.: Antarctic ice-shelf basal melting in a variable resolution Earth System Model, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11368, https://doi.org/10.5194/egusphere-egu22-11368, 2022.

EGU22-11440 | Presentations | OS1.11

Millennial-scale interactions of the Antarctic Ice Sheet and the global ocean 

Moritz Kreuzer, Willem Huiskamp, Torsten Albrecht, Stefan Petri, Ronja Reese, Georg Feulner, and Ricarda Winkelmann

Increased sub-shelf melting and ice discharge from the Antarctic Ice sheet has both regional and global impacts on the ocean and the overall climate system. Additional meltwater, for example, can reduce the formation of Antarctic Bottom Water, potentially affecting the global thermohaline circulation. Similarly, increased input of fresh and cold water around the Antarctic margin can lead to a stronger stratification of coastal waters, and a potential increase in sea-ice formation, trapping warmer water masses below the surface, which in turn can lead to increased basal melting of the ice shelves.

So far these processes have mainly been analysed in simple unidirectional cause-and-effect experiments, possibly neglecting important interactions and feedbacks. To study the long-term and global effects of these interactions, we have developed a bidirectional offline coupled ice-ocean model framework. It consists of the global ocean and sea-ice model MOM5/SIS and an Antarctic instance of the Parallel Ice Sheet Model PISM, with the ice-shelf cavity module PICO representing the ice-ocean boundary layer physics. With this setup we are analysing the aforementioned interactions and feedbacks between the Antarctic Ice Sheet and the global ocean system on multi-millenial time scales.

How to cite: Kreuzer, M., Huiskamp, W., Albrecht, T., Petri, S., Reese, R., Feulner, G., and Winkelmann, R.: Millennial-scale interactions of the Antarctic Ice Sheet and the global ocean, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11440, https://doi.org/10.5194/egusphere-egu22-11440, 2022.

EGU22-11967 | Presentations | OS1.11

Development of persistent Southern Ocean biases in HadGEM-GC3.1-MM and implications for modelled ocean-ice interaction in West Antarctica 

Kyriaki M. Lekakou, Ben G.M. Webber, Karen J. Heywood, David P. Stevens, Patrick Hyder, and Helene Hewitt

The ice shelves of the Amundsen Sea are rapidly thinning, and this can be largely explained by basal melting driven by the ocean. However, sparse observational data and poorly known bathymetry contribute to the difficulty of quantifying the key ocean mechanisms that transport warm water onto the Amundsen Sea continental shelf and their variability. These processes should be represented in coupled climate models such as those used for CMIP6. Previously, we leveraged recent observational campaigns and gains in process understanding to assess how well four models, UKESM1 and the HadGEM-GC3.1 family of models, represent the ocean processes forcing warm water onto the Amundsen Sea continental shelf. We identified the medium resolution (1/4°) HadGEM-GC3.1-MM model’s inability to represent warm water intrusion on the continental shelf, revealing substantial biases in sea ice, SST, salinity and circulation in the Southern Ocean. It is important to understand the processes that are driving these biases, to guide the improvement of this and similar models. Here, we study model behaviour during the spin-up, control and historical runs, to identify what is causing this unrealistic behaviour. A key result is the rapid development of biases in temperature and salinity on the Amundsen’s Sea continental shelf, after only 15 years in the spin-up run, entering a state which persists throughout the following runs. By calculating the differences in sea ice concentration between years 0-5 and 10-15 of the spin up-run, we found significant changes across multiple regions of the Southern Ocean and continental shelf, with most of the East Antarctic sector and Bellingshausen Sea showing a considerable decline that exceeds 20% in some places. The differences between years 0-5 and 10-15 Notable freshening takes place in the whole West Antarctic sector and a strong westward slope current appears, which encircles Antarctica. While strong biases in sea ice and salinity develop later in the Weddell Sea, during the first 15 years the largest biases occur in Drake Passage and the west Antarctic sector. We analyse tendencies and the freshwater budget from the spin-up run to quantify the key processes that drive the development of these biases in selected regions.

How to cite: Lekakou, K. M., Webber, B. G. M., Heywood, K. J., Stevens, D. P., Hyder, P., and Hewitt, H.: Development of persistent Southern Ocean biases in HadGEM-GC3.1-MM and implications for modelled ocean-ice interaction in West Antarctica, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11967, https://doi.org/10.5194/egusphere-egu22-11967, 2022.

EGU22-12887 | Presentations | OS1.11

Four year-long observations from a key inflow region onto the southern Weddell Sea continental shelf 

Nadine Steiger and Jean-Baptiste Sallée

The Filchner Trough on the continental shelf in the southern Weddell Sea is the gateway for warm water from off the continental shelf to flow towards the Filchner Ice Shelf. The warm water is steered southward along the eastern slope of the trough, potentially increasing basal melt rates of the ice shelf and leading to the formation of cold and dense Ice Shelf Water that overflows and contributes to the Antarctic Bottom Water. We present mooring time series from 2017 to 2021 in key inflow regions of modified Warm Deep Water onto the eastern continental shelf. Three moorings were placed across the eastern flank of the Filchner Trough close to the shelf break and captured the changes in the thickness of the northward-flowing Ice Shelf Water as well as the overlying southward warmer water. Another mooring was placed over the shallower eastern shelf and allowed a comparison between the two pathways of warm water onto the continental shelf. The four-year-long observations provide a better understanding of the processes that influence the seasonal and interannual variability in temperatures and circulation and possible changes in the flow of warm water towards the ice shelf.

How to cite: Steiger, N. and Sallée, J.-B.: Four year-long observations from a key inflow region onto the southern Weddell Sea continental shelf, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12887, https://doi.org/10.5194/egusphere-egu22-12887, 2022.

EGU22-13276 | Presentations | OS1.11

Investigation Into Antarctic Slope Front Regimes Using an Idealised Isopycnal Model 

Qing Yee Ellie Ong, Matthew England, Andrew Hogg, Navid Constantinou, and Edward Doddridge
The Antarctic Slope Current is a current that flows westward around Antarctica and lies close to the coast on the continental shelf. The slope current region features steeply sloping isopycnals at the continental shelf, characterising the Antarctic Slope Front (ASF). The ASF serves as a barrier between warm Circumpolar Deep Water and the continental shelf. Depending on the local structure of the ASF, Circumpolar Deep Water can flood on to the continental shelf and induce basal melt, with implications for sea level rise globally. Observations in these regions of the ocean are scarce, or even non-existent, and eddy-resolving modelling studies of the ASF are also limited. We have developed a set of idealised configurations with an isopycnal model that can emulate the conditions in different ASF regimes. We investigate how the different ASF regimes are affected by variations in wind forcing, topography and stratification. This aims to identify the different dynamics and the sensitivity of forcings and boundary conditions that allow warm water to reach the shelf in different ASF regimes.

How to cite: Ong, Q. Y. E., England, M., Hogg, A., Constantinou, N., and Doddridge, E.: Investigation Into Antarctic Slope Front Regimes Using an Idealised Isopycnal Model, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13276, https://doi.org/10.5194/egusphere-egu22-13276, 2022.

EGU22-13422 | Presentations | OS1.11

Direct evidence for a 20th Century decline in Southern Ocean sea ice 

David Ferreira and Jonathan Day

Since satellite records began in the 1970s, a small expansion of sea ice area around Antarctica has been observed, in stark contrast with the large decrease seen in the Arctic region. This expansion is difficult to reconcile with the observed rise in global temperatures and appears at odds with the ice loss simulated by climate models over the same period. Efforts to elucidate the driving mechanism are hampered by a short observational record, with little information available prior to the advent of satellite observations. Here we use direct observations recovered from logbooks of early explorers and routine shipping reports (1900 to 1953) to shed new light on the position of the ice edge. The data reveals that the early 20th century sea ice extended 3.1$^\circ$ (2.6$^\circ$-3.3$^\circ$ for 5-95\% confidence interval) further north ($\sim$100\% more extensive) than the present day. This finding re-frames the 20th century as a period of overall long-term sea ice loss in the Antarctic. The extensive sea ice cover, compared to present, goes hand-in-hand with cooler sea surface temperatures and reduced zonal wind speed in the region, consistent with reduced concentrations of anthropogenic forcing agents (greenhouse gas, ozone depletion) in the early 20th century, and may reflect the unperturbed state of Antarctic sea ice.

 

How to cite: Ferreira, D. and Day, J.: Direct evidence for a 20th Century decline in Southern Ocean sea ice, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13422, https://doi.org/10.5194/egusphere-egu22-13422, 2022.

One of the most important phenomena in the Arctic seas, in which all cascades of the scale of variability of oceanological processes are observed, are climatic and seasonal frontal zones. However, despite the climate changes noted by many researchers, so far, the ideas about the long-term dynamics and characteristics of the surface layer in the frontal zones in the Arctic region are fragmentary.

In our work, we considered seasonal and long-term variability of the Polar Frontal Zone (PFZ), the River Plumes Frontal Zone (RPFZ) and the Marginal Ice Zone (MIZ) in the Barents and Kara Seas. The authors evaluated their relationship with eddies structures and atmospheric oscillations. We used satellite data of temperature, salinity and sea level for the period from 2002 to 2020, which we processed using cluster analysis. To isolate the manifestations of eddies structures on the surface, we used radar images of the Envisat ASAR and Sentinel-1A/B. To analyze the relationship between the characteristics of the frontal zones and atmospheric oscillations, we used correlation analysis.

We have shown that the intensity of interannual and seasonal estimates of the SST gradient and the area of the PFZ and RPFZ in the first decade was an order of magnitude higher than in the period from 2011 to 2020. We observe the opposite pattern for the characteristics of the MIZ – in the second decade, the magnitude of the estimates of the SST gradient and area increases. We observe the maximum number of eddies structures in PFZ and RPFZ against the background of a general weakening of the SST gradients. We assume that this is due to the development of intense baroclinic instability in the frontal zones. In our opinion, the intensity of winter meridional transport over Northern Europe affects the growth of summer SST gradients and a decrease in the area of the PFZ and a decrease in SST in the RPFZ. The magnitude of the winter Arctic zonal transfer may increase the characteristics of SST in the RPFZ region. The value of the average seasonal gradient of the SST of the climatic surface PFZ is lower than that of the seasonal RPFZ and MIZ.

The analysis of frontal zone and eddies in this work was supported by RFBR grant 20-35-90053.

How to cite: Konik, A. and Zimin, A.: Seasonal and long-term variability of the characteristics surface frontal zones of the Barents and Kara seas, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-60, https://doi.org/10.5194/egusphere-egu22-60, 2022.

EGU22-571 | Presentations | OS1.6

Validation of the Arctic water and energy cycles in CMIP6 with consistent observation-based estimates 

Susanna Winkelbauer, Michael Mayer, and Leopold Haimberger

This contribution focuses on the Arctic water budget, including its atmospheric, terrestrial, and oceanic components. Oceanic volume fluxes through the main Arctic gateways are calculated, using data from the CMEMS Global Reanalysis Ensemble Product (GREP), and compared to water input to the ocean from atmosphere and land. For this purpose, we use various state-of-the-art reanalyses, including the European Centre for Medium Range Weather Forecast's (ECMWF) latest products ERA5 and ERA5-Land and evaluate them against available satellite (e.g., GRACE) and in-situ river discharge observations.

To obtain a consistent estimate of all physical terms, we combine the most credible estimates of the individual budget terms and perform a variational optimization to obtain closed water budgets on annual and seasonal scales. This up-to-date estimate of the Arctic water cycle is subsequently used to validate historical runs from the Coupled Model Intercomparison Project Phase 6 (CMIP6). Modelled water budget components are analyzed concerning their annual means, seasonal cycles and trends and compared to our observationally constrained data. Results suggest that there remain large uncertainties in the simulation of the Arctic water cycle of the recent decades.

Furthermore, we choose a similar approach to validate the coupled energy budget in CMIP6 models, including oceanic heat transports through the Arctic gateways (where mooring-derived oceanic heat transports are available), atmospheric energy transports and vertical energy fluxes at the surface and top-of-the-atmosphere, as well as Arctic Ocean heat storage.

This assessment helps to understand model biases in typically analyzed quantities such as sea ice extent or volume. It also provides physically based metrics for detecting outliers from the model ensemble which can help to reduce spread in future projections of Arctic change.

How to cite: Winkelbauer, S., Mayer, M., and Haimberger, L.: Validation of the Arctic water and energy cycles in CMIP6 with consistent observation-based estimates, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-571, https://doi.org/10.5194/egusphere-egu22-571, 2022.

EGU22-1414 | Presentations | OS1.6

Identification, characteristics, and dynamics of Arctic extreme seasons in ERA5 and CESM climate simulations 

Katharina Hartmuth, Maxi Boettcher, Heini Wernli, and Lukas Papritz

The Arctic atmosphere is strongly affected by anthropogenic warming leading to long-term trends in surface temperature and sea ice extent. In addition, it exhibits strong variability on time scales from days to seasons. While recent research elucidated processes causing long-term trends as well as synoptic extreme conditions in the Arctic, we investigate unusual atmospheric conditions on the seasonal time scale. We introduce a method to identify extreme seasons – deviating strongly from a running-mean climatology – based on a principal component analysis in the phase space spanned by the seasonal-mean values of surface temperature, precipitation, and the atmospheric components of the surface energy balance. Given the strongly varying surface conditions in the Arctic, this analysis is done separately in Arctic sub-regions that are climatologically characterized by either sea ice, open ocean, or mixed conditions.

Using ERA5 reanalyses for the years 1979-2018, our approach identifies 2-3 extreme seasons for each of winter, spring, summer, and autumn, with strongly differing characteristics and affecting different Arctic sub-regions. Results will be shown for two contrasting extreme winters affecting the Kara and Barents Seas, including their substructure, the role of synoptic-scale weather systems, and potential preconditioning by anomalous sea ice extent and/or sea surface temperature at the beginning of the season.

To statistically quantify and confirm these results, we further apply our method to large ensemble simulations of the CESM climate model, using roughly 1000 years of data in present-day (1990-2000) and end-of-century (2091-2100) climate, respectively. Results show a strong similarity between the characteristics of extreme seasons in ERA5 and CESM for the present-day period. The identified seasons predominantly show the most extreme seasonal-mean anomalies of the applied surface parameters, confirming that our approach captures seasons with extraordinary conditions. Preliminary results will also be shown about our current investigation of possible changes in the characteristics and driving mechanisms of Arctic extreme seasons in the warmer end-of-century climate.

The framework developed in this study and the insight gained from analyzing both, reanalysis and climate model data, will be insightful for better understanding the effects of global warming on Arctic extreme seasons.

How to cite: Hartmuth, K., Boettcher, M., Wernli, H., and Papritz, L.: Identification, characteristics, and dynamics of Arctic extreme seasons in ERA5 and CESM climate simulations, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1414, https://doi.org/10.5194/egusphere-egu22-1414, 2022.

EGU22-1715 | Presentations | OS1.6

Water masses variability in the eastern Fram Strait explored through oceanographic mooring data and the CMEMS dataset 

Carlotta Dentico, Manuel Bensi, Vedrana Kovačević, Davide Zanchettin, and Angelo Rubino

The interaction between North Atlantic and Arctic Ocean waters plays a key role in climate variability and in
driving the global thermohaline circulation. In the past decades, an increased heat input to the Arctic has
occurred which is considered of high climatic relevance as, e.g., it contributes to enhancing sea ice melting.
In this frame, the progressive northward extension of the Atlantic signal within the Arctic domain known as
Arctic Atlantification is one of the most dramatic environmental local changes of the last decades.
In this study we used in situ data and the Copernicus Marine Environment Monitoring Service (CMEMS)
reanalysis dataset to explore spatial and temporal variability of water masses on different time-scales and
depths in the eastern Fram Strait. In that area, warm and salty Atlantic Water (AW) enters the Arctic Ocean
through the West Spitsbergen Current (WSC). Time series of potential temperature, salinity and potential
density obtained from CMEMS reanalysis in the surface, upper-intermediate and deep layers referring to the
period 1991-2019 have been considered. High-frequency observations gathered from an oceanographic
mooring maintained by the National Institute of Oceanography and Applied Geophysics (OGS) in
collaboration with the Italian National Research Council - Institute of Polar Science (CNR-ISP) have been
used to assess the reliability of CMEMS data in reproducing ocean dynamics in the deep layer (ca 900-1000
m depth) of the SW offshore Svalbard area. The mooring system has been collecting data since June 2014.
In this contribution, we will show how the CMEMS data compared with in situ measurements as far as
seasonal and interannual variations as well as long-term trends are concerned. We will also discuss how
CMEMS reanalyses show differences in resolving ocean dynamics at different depths. Particularly, the severe
limitations in reproducing thermohaline variability at depths greater than 700 m. Finally, we will illustrate how
our results highlight strengths and limitations of CMEMS reanalyses, underscoring the importance of
optimizing measurements in a strategic area for studying climate change impacts in the Arctic and sub-Arctic
regions.

How to cite: Dentico, C., Bensi, M., Kovačević, V., Zanchettin, D., and Rubino, A.: Water masses variability in the eastern Fram Strait explored through oceanographic mooring data and the CMEMS dataset, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1715, https://doi.org/10.5194/egusphere-egu22-1715, 2022.

EGU22-1760 | Presentations | OS1.6

Large biases in hydrography and circulation of the Arctic Ocean in CMIP6 models 

Céline Heuzé, Hannah Zanowski, Salar Karam, and Morven Muilwijk

Climate models are our best tools to quantify ongoing changes caused by the climate crisis, but they are not perfect. The Arctic Ocean is particularly challenging to simulate: complex circulation flowing through narrow gateways and around tortuous bathymetry, dense water cascading off the steep shelf break, slow exchanges in canyons, along with known biases in sea ice and neighbouring seas.

We investigate the Arctic Ocean in the historical run of 14 distinct models that participated to the latest Climate Model Intercomparison Project phase 6 (CMIP6) and find large biases in temperature, salinity, density, and depth of critical water masses, both on the shelves and in the deep basins. The biases are consistent throughout the water column and throughout the Arctic, with correlations often exceeding 0.9. However, no significant trend is observed in these biases, suggesting that the deep basins of the Arctic are not correctly ventilated already at the level of the Atlantic Water.

Using the subset of models that submitted the age of water output, we confirm this absence of ventilation by dense water overflows: the overflows occur at too few locations and are diluted at shallow depths.   

Work is ongoing to relate these biases to the relevant processes, the upper water column, and fluxes through the various Arctic Ocean gateways.

How to cite: Heuzé, C., Zanowski, H., Karam, S., and Muilwijk, M.: Large biases in hydrography and circulation of the Arctic Ocean in CMIP6 models, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1760, https://doi.org/10.5194/egusphere-egu22-1760, 2022.

EGU22-1782 | Presentations | OS1.6

Variability of surface transport pathways and how they affect Arctic basin-wide connectivity 

Yevgeny Aksenov, Chris Wilson, Stefanie Rynders, Stephen Kelly, Thomas Krumpen, and Andrew C. Coward

The Arctic Ocean is of central importance for the global climate and ecosystems. It is undergoing rapid climate change, with a dramatic decrease in sea ice cover over recent decades. Surface advective pathways connect the transport of nutrients, freshwater, carbon and contaminants with their sources and sinks. Pathways of drifting material are deformed under velocity strain, due to atmosphere-ocean-ice coupling. Deformation is largest at fine space- and time-scales and is associated with a loss of potential predictability, analogous to weather often becoming unpredictable as synoptic-scale eddies interact and deform. However, neither satellite observations nor climate model projections resolve fine-scale ocean velocity structure. Here, we use a high-resolution ocean model hindcast and coarser satellite-derived ice velocities, to show: that ensemble-mean pathways within the Transpolar Drift during 2004–14 have large interannual variability and that both saddle-like flow structures and the presence of fine-scale velocity gradients are important for basin-wide connectivity and crossing time, pathway bifurcation, and also for predictability and dispersion (the latter are covered in an associated paper [1].

The saddle-points in the flow and their neighbouring streamlines define flow separatrices, which partition the surface Arctic into separate regions of connected transport properties. The separatrix streamlines vary interannually and identify periods when the East Siberian Arctic Shelf, an important source of terragenic minerals, carbon and nutrients, is either connected or disconnected with Fram Strait and the North Atlantic. We explore the implications of this transport connectivity, with our new metric - the Separatrix Curvature Index – which in this context is arguably more informative than either the Arctic Oscillation or Arctic Ocean Oscillation indices.

This work resulted from the Advective Pathways of nutrients and key Ecological sub- stances in the Arctic (APEAR) project (NE/R012865/1, NE/R012865/2, #03V01461), part of the Changing Arctic Ocean programme, jointly funded by the UKRI Natural Environment Research Council (NERC) and the German Federal Ministry of Education and Research (BMBF). This work has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement no. 820989 (project COMFORT). 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. This work also used the ARCHER UK National Supercomputing Service and JASMIN, the UK collaborative data analysis facility. Satellitebased sea ice tracking was carried out as part of the Russian-German Research Cooperation QUARCCS funded by the German Ministry for Education and Research (BMBF) under grant 03F0777A. This study was carried out as part of the international Multidisciplinary drifting Observatory for the Study of the Arctic Climate (MOSAiC) with the tag MOSAiC20192020 (AWI_PS122_1 and AF-MOSAiC-1_00) and the NERC Project “PRE-MELT” (Grant NE/T000546/1). We also acknowledge funding support received from the NERC National Capability programmes LTS-M ACSIS (North Atlantic climate system integrated study, grant NE/N018044/1) and LTS-S CLASS (Climate–Linked Atlantic Sector Science, grant NE/R015953/1). The authors would like to acknowledge the contribution of Maria Luneva to the discussions about the initial idea of the study and for highlighting the historical importance of observations from the Russian North Pole drifting stations. Sadly, Maria passed away suddenly in 2020 before the draft of the reported paper was written.

[1] Wilson, C., Aksenov, Y., Rynders, S. et al. Significant variability of structure and predictability of Arctic Ocean surface pathways affects basinwide connectivity. Commun. Earth. Environ. 2, 164 (2021). https://doi.org/10.1038/s43247-021-00237-0.

How to cite: Aksenov, Y., Wilson, C., Rynders, S., Kelly, S., Krumpen, T., and Coward, A. C.: Variability of surface transport pathways and how they affect Arctic basin-wide connectivity, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1782, https://doi.org/10.5194/egusphere-egu22-1782, 2022.

EGU22-2125 | Presentations | OS1.6

Variability of the Upper Ocean Energy Field in the Amundsen Basin, Arctic Ocean 

Wen-Chuan Wu, Ying-Chih Fang, and Benjamin Rabe

The dynamics of the Arctic Ocean are changing significantly with increasing global greenhouse gas emissions. Under the current warming scenario, the thinning of sea ice could affect Arctic thermohaline dynamics for the foreseeable future, which would affect the development of the energy cascade. Here, we analyze in situ Lagrangian measurements of the wintertime upper-ocean thermohaline field that were taken during the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition. Horizontal wavenumber spectra of density are examined from 13 approximately 100-km long transects from October 2019 – May 2020 to determine the steepness of spectra for different spatial scales. Unlike the relatively well-defined frequency spectra, horizontal wavenumber spectra yield variable patterns depending on the region of observations. This issue motivates us to investigate the current state of horizontal wavenumber spectra in the multiyear ice zone of the central Arctic. Our preliminary results show that the wavenumber spectra are not consistent in space and time, implying an interplay of stratification, mixed layer depth, and external forcing, such as ice dynamics.

How to cite: Wu, W.-C., Fang, Y.-C., and Rabe, B.: Variability of the Upper Ocean Energy Field in the Amundsen Basin, Arctic Ocean, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2125, https://doi.org/10.5194/egusphere-egu22-2125, 2022.

EGU22-2274 | Presentations | OS1.6

Eddies and the distribution of eddy kinetic energy in the Arctic Ocean 

Wilken-Jon von Appen, Till Baumann, Markus Janout, Nikolay Koldunov, Yueng-Djern Lenn, Robert Pickart, Robert Scott, and Qiang Wang

Mesoscale eddies are important for many aspects of the dynamics of the Arctic Ocean. These include the maintenance of the halocline and the Atlantic Water boundary current through lateral eddy fluxes, shelf-basin exchanges, transport of biological material and sea ice, and the modification of the sea-ice distribution. Here we review what is known about the mesoscale variability and its impacts in the Arctic Ocean in the context of an Arctic Ocean responding rapidly to climate change. In addition, we present the first quantification of eddy kinetic energy (EKE) from moored observations across the entire Arctic Ocean, which we compare to output from an eddy resolving numerical model. We show that EKE is largest in the northern Nordic Seas/Fram Strait and it is also elevated along the shelfbreak of the Arctic Circumpolar Boundary Current, especially in the Beaufort Sea. In the central basins it is 100-1000 times lower. Except for the region affected by southward sea-ice export south of Fram Strait, EKE is stronger when sea-ice concentration is low compared to dense ice cover. Areas where conditions typical in the Atlantic and Pacific prevail will increase. Hence, we conclude that the future Arctic Ocean will feature more energetic mesoscale variability.

How to cite: von Appen, W.-J., Baumann, T., Janout, M., Koldunov, N., Lenn, Y.-D., Pickart, R., Scott, R., and Wang, Q.: Eddies and the distribution of eddy kinetic energy in the Arctic Ocean, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2274, https://doi.org/10.5194/egusphere-egu22-2274, 2022.

The average rate of coastal change in the Arctic Ocean is -0.5 m/yr, despite significant local and regional variations, with large areas well above -3 m/yr. Recent data suggest an acceleration of coastal retreat in specific areas due to an increasingly shorter sea ice season, higher storminess, warmer ocean waters and sea-level rise. Moreover, climate warming is inducing the subaerial degradation of permafrost and increasing land to sea sediment transportation. This work consists of the characterization and analysis of the main controlling factors influencing recent coastline change in the Tuktoyaktuk Peninsula, Northwest Territories, Canada. The specific objectives are I. mapping Tuktoyaktuk Peninsula’s coastline at different time-steps using remote sensing imagery, II. quantifying the recent coastal change rates, III., characterizing the coastal morphology, IV. identifying the main controlling factors of the coastal change rates. A very high-resolution Pleiades survey from 2020, aerial photos from 1985 and the ArcticDEM were used. Results have shown an average coastline change rate of -1.06 m/yr between 1985 and 2020. While this number is higher than the Arctic average rate, it neglects to show the significance of extreme cases occurring in specific areas. Tundra cliffs are the main coastal setting, occupying c. 56% of the Tuktoyaktuk Peninsula coast and foreshore beaches represent 51%. The results display an influence of coastal geomorphology on change rates. The coastal retreat was higher in backshore tundra flats (-1.74 m/yr), whereas more aggradation cases exist in barrier beaches and sandspits (-0.81 m/yr). The presence of ice-wedge polygons contributes to increasing cliff retreat. Foreshore assessment may be crucial, as beaches present a hindering impact on coastal retreat (-0.76 m/yr), whereas foreshore tundra flats promote it (-1.74 m/yr). There are 48 areas with retreat rates higher than -4 m/yr, most being submersion cases.

How to cite: Costa, B., Vieira, G., and Whalen, D.: The fast-changing coast of Tuktoyaktuk Peninsula (Beaufort Sea, Canada): geomorphological controls on changes between 1985 and 2020, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2426, https://doi.org/10.5194/egusphere-egu22-2426, 2022.

EGU22-2717 | Presentations | OS1.6

Subduction as Observed at a Submesoscale Front in the Marginal Ice Zone in Fram Strait 

Zerlina Hofmann, Wilken-Jon von Appen, Morten Iversen, and Lili Hufnagel

The marginal ice zone in Fram Strait is a highly variable environment, in which dense Atlantic Water and lighter Polar Water meet and create numerous mesoscale and submesoscale fronts. This makes it a model region for researching ocean frontal dynamics in the Arctic, as the interaction between Atlantic Water and the marginal ice zone is becoming increasingly important in an "atlantifying" Arctic Ocean. Here we present the first results of a front study conducted near the ice edge in central Fram Strait, where Atlantic Water subducted below Polar Water. We posit that the frontal dynamics associated with the sea ice edge also apply beyond, both to the open and the ice-covered ocean in the vicinity. They, in turn, can affect the structure of the marginal ice zone. The study comprises a total of 54 high resolution transects, most of which were oriented across the front. They were taken over the course of a week during July 2020 and include current velocity measurements from a vessel-mounted ADCP. Most of the transects also include either temperature and salinity measurements from an underway CTD, or temperature and salinity measurements and various biogeochemical properties from a TRIAXUS towed vehicle. Additionally, 22 CTD stations were conducted, and 31 surface drifters were deployed. This wealth of measurements gives us the opportunity to follow the temporal and spatial development of the density fronts present at the time. We discuss the dynamics of the frontal development, including the associated geostrophic motion, and the induced secondary ageostrophic circulation with subsequent subduction of Atlantic Water and biological material in a highly stratified region. Beneath the stratified upper ocean, subduction is clearly visible in the biogeochemical properties, and water samples indicate a substantial vertical transport of smaller particles. Surface drifters accumulated in locations of subduction, where sea ice, if present, would likely also accumulate. Our study thus demonstrates the importance of frontal dynamics for the vertical transport of water properties and biological material, and the highly variable development of the marginal ice zone in Fram Strait.

How to cite: Hofmann, Z., von Appen, W.-J., Iversen, M., and Hufnagel, L.: Subduction as Observed at a Submesoscale Front in the Marginal Ice Zone in Fram Strait, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2717, https://doi.org/10.5194/egusphere-egu22-2717, 2022.

EGU22-3069 | Presentations | OS1.6

Atlantic Water properties, transport, and water mass transformation from mooring observations north of Svalbard 

Zoé Koenig, Kjersti Kalhagen, Eivind Kolås, Ilker Fer, Frank Nilsen, and Finlo Cottier

The Atlantic Water inflow to the Arctic Ocean is transformed and modified in the ocean areas north of Svalbard, and influences the Arctic Ocean heat and salt budget. As the Atlantic Water layer advances into the Arctic, its core deepens from about 250 m depth around the Yermak Plateau to 350 m in the Laptev Sea, and gets colder and less saline due to mixing with surrounding waters. The complex topography in the region facilitates vertical and horizontal exchanges between the water masses and, together with strong shear and tidal forcing driving increased mixing rates, impacts the heat and salt content of the Atlantic Water layer that will circulate around the Arctic Ocean.

In September 2018, 6 moorings organized in 2 arrays were deployed across the Atlantic Water Boundary current for more than one year (until November 2019), within the framework of the Nansen Legacy project to investigate the seasonal variations of this current and the transformation of the Atlantic Water North of Svalbard. The Atlantic Water inflow exhibits a large seasonal signal, with maxima in core temperature and along-isobath velocities in fall and minima in spring. Volume transport of the Atlantic Water inflow varies from 0.7 Sv in spring to 3 Sv in fall. An empirical orthogonal function analysis of the daily cross-isobath temperature sections reveals that the first mode of variation (explained variance ~80%) is the seasonal cycle with an on/off mode in the temperature core. This first mode of variation is linked to the first mode of variation of the current. The second mode (explained variance ~ 15%) corresponds to a shorter time scale (6-7 days) variability in the onshore/offshore displacement of the temperature core linked to the mesoscale variability. On the shelf, a counter-current flowing westward is observed in spring, which transports colder (~ 1°C) and fresher (~ 34.85 g kg-1) water than Atlantic Water (θ > 2°C and SA > 34.9 g kg-1). This counter-current is driven by Ekman dynamics. At greater depth (~1000 m) on the offshore part of the slope, a bottom-intensified current is detected, partly correlated with the wind stress curl. Heat loss of the Atlantic Water between the two mooring arrays is maximum in winter, estimated to 300-400 W m-2 when the current speed and the heat loss to the atmosphere are the largest.

 

How to cite: Koenig, Z., Kalhagen, K., Kolås, E., Fer, I., Nilsen, F., and Cottier, F.: Atlantic Water properties, transport, and water mass transformation from mooring observations north of Svalbard, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3069, https://doi.org/10.5194/egusphere-egu22-3069, 2022.

EGU22-3289 | Presentations | OS1.6

Differences in Arctic sea ice simulations from various SODA3 data sets 

Zhicheng Ge, Xuezhu Wang, and Xidong Wang

SODA (Simple Ocean Data Assimilation) is one of the ocean reanalysis data widely used in oceanographic research. The SODA3 dataset provides multiple ocean reanalysis data sets driven by different atmospheric forcing fields. The differences between their arctic sea ice simulations are assessed and compared with observational data from different sources. We find that in the simulation of arctic sea ice concentration, the differences between SODA3 reanalysis data sets driven by different forcing fields are small, showing a low concentration of thick ice and a high concentration of thin ice. In terms of sea ice extent, different forced field model data can well simulate the decline trend of observed data, but the overall arctic sea ice extent is overestimated, which is related to more simulated sea ice in the sea ice margin. In terms of the simulation of arctic sea ice thickness, the results of different forcing fields show that the simulation of arctic sea ice thickness by SODA data set is relatively thin on the whole, especially in the thick ice region. The results of different models differ greatly in the Beaufort Sea, the Fram Strait, and the Central Arctic Sea. The above differences may be related to the differences between the model-driven field and the actual wind field, which leads to the inaccurate simulation of arctic sea ice transport and ultimately to the different thickness distribution simulation. In addition, differences in heat flux may also lead to differences in arctic sea ice between models and observations. In this paper, the differences between the results of arctic sea ice driven by different SODA3 forcing fields are studied, which provides a reference for the use of SODA3 data in the study of arctic sea ice and guidance for the selection of SODA data in the study of sea ice in different arctic seas.

How to cite: Ge, Z., Wang, X., and Wang, X.: Differences in Arctic sea ice simulations from various SODA3 data sets, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3289, https://doi.org/10.5194/egusphere-egu22-3289, 2022.

EGU22-3494 | Presentations | OS1.6

Vigorous Internal Wave Generation at the Continental Slope North of Svalbard 

Till M. Baumann and Ilker Fer

Mixing along the pathway of Atlantic Water in the Arctic Ocean is crucial for the distribution of heat in the Arctic Ocean. The warm boundary current typically flows along the upper continental slope where energy conversion from tides to turbulence and tidally driven mixing can be important; however, observations -and thus understanding- of these spatiotemporally highly variable processes are limited.

Here we analyze yearlong observations from three moorings (W1, W2 and W3) spanning the continental slope North of Svalbard at 18.5°E over 16 km from 400 m to 1200 m isobaths, deployed between September 2018 and October 2019. Full-depth current records show strong barotropic diurnal (i.e., sub-inertial) tidal currents, dominated by the K1 constituent. These tidal currents are strongest at mooring W2 over the continental slope (~700 m isobath) likely due to topographic trapping far north of their critical latitude (30°N). The diurnal tide undergoes a seasonal cycle with amplitudes reaching minima of ~4 cm/s in March/April and maxima of ~11 cm/s in June/July. Associated with the diurnal tide peak at W2 in summer 2019 is a strong baroclinic semidiurnal signal up to 15 cm/s around 4.5 km further offshore at W3 between 500 m and 1000 m depth. This semidiurnal current signal exhibits a fortnightly modulation and is characterized by upward energy propagation, indicative of generation at the bottom rather than the surface.

We hypothesize that the semidiurnal baroclinic waves are generated by the barotropic diurnal tide about 15 km upstream. There, the slope is oriented approximately normal to the major axis of the tidal current ellipses, maximizing the cross-isobath flow and thus the tidal energy conversion potential. The topographic slope angle approaches criticality for frequencies close to the second harmonic of K1 (2K1, with a semidiurnal period of 11.965 h) around the 620 m isobath and may thus facilitate an efficient generation of second harmonic internal waves. Linear superposition of a 2K1 wave with the rather weak (~5 cm/s) ambient M2 tide would explain the observed fortnightly modulation. The super-inertial wave (w2K1>f) propagates freely and its pathway is presently not known.

Although further research on the generation mechanism is needed, the strong baroclinic semidiurnal currents observed at the continental slope have direct implications for deep mixing. Furthermore, energetic diurnal tidal currents impinging on a steep continental slope are also known to generate non-linear internal lee-waves that can also lead to substantial turbulence and consequent mixing.

How to cite: Baumann, T. M. and Fer, I.: Vigorous Internal Wave Generation at the Continental Slope North of Svalbard, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3494, https://doi.org/10.5194/egusphere-egu22-3494, 2022.

EGU22-3595 | Presentations | OS1.6

Present and future influence of ocean heat transport on winter Arctic sea-ice variability 

Jakob Dörr, Marius Årthun, and Tor Eldevik

The recent retreat of Arctic sea ice area is overlaid by strong internal variability on all timescales. In winter, the variability is currently dominated by the Barents Sea, where it has been primarily driven by variable ocean heat transport from the Atlantic. As the loss of winter Arctic sea ice is projected to accelerate and the sea ice edge retreats deeper into the Arctic Ocean, other regions will see increased sea-ice variability. The question thus arises how the influence of the ocean heat transport will change. To answer this question, we analyze and contrast the present and future regional impact of ocean heat transport on the winter Arctic sea ice cover using a combination of observations and simulations from several single model large ensembles from CMIP5 and CMIP6. For the recent past we find a strong influence of the heat transport through the Barents Sea and the Bering Strait on the sea ice cover on the Pacific and Atlantic side of the Arctic Ocean, respectively. There is strong model agreement for an expanding influence of ocean heat transport through these two gateways for high and low warming scenarios. This highlights the future importance of the Pacific and Atlantic water inflows.

How to cite: Dörr, J., Årthun, M., and Eldevik, T.: Present and future influence of ocean heat transport on winter Arctic sea-ice variability, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3595, https://doi.org/10.5194/egusphere-egu22-3595, 2022.

EGU22-3652 | Presentations | OS1.6

High-resolution modelling of marine biogenic aerosol precursors in the Arctic realm 

Moritz Zeising, Laurent Oziel, Özgür Gürses, Judith Hauck, Bernd Heinold, Svetlana Losa, Silke Thoms, and Astrid Bracher

The presence of liquid or ice as cloud phase determines the climate radiative effect of Arctic clouds, and thus, their contribution to surface warming. Biogenic aerosols from phytoplankton production localized in leads or open water were shown to act as cloud condensation nuclei (liquid phase) or ice nuclei (ice phase) in remote regions. As extensive measurements of biogenic aerosol precursors are still scarce, we conduct a modelling study and use acidic polysaccharides (PCHO) and transparent exopolymer particles (TEP) as tracers. In this study, we integrate processes of algal PCHO excretion during phytoplankton growth or under nutrient limitation and processes of TEP formation, aggregation and also remineralization into the ecosystem model REcoM2. The biogeochemical processes are described by two functional phytoplankton and two zooplankton classes, along with sinking detritus and several (in)organic carbon and nutrient classes. REcoM2 is coupled to the finite-volume sea ice ocean circulation model FESOM2 with a high resolution of up to 4.5 km in the Arctic. We will present the first results of simulated TEP distribution and seasonality patterns at pan-Arctic scale over the last decades. We will elucidate drivers of the seasonal cycle and will identify regional hotspots of TEP production and its decay. We will also address possible impacts of global warming and Arctic amplification of the last decades in our evaluation, as we expect a strong effect of global warming on microbial metabolic rates, phytoplankton growth, and composition of phytoplankton functional types. The results will be evaluated by comparison to a set of in-situ measurements (PASCAL, FRAM, MOSAiC). It is further planned that an atmospheric aerosol-climate model will build on the modeled biogenic aerosol precursors as input to quantify the net aerosol radiative effects. This work is part of the DFG TR 172 Arctic Amplification.

How to cite: Zeising, M., Oziel, L., Gürses, Ö., Hauck, J., Heinold, B., Losa, S., Thoms, S., and Bracher, A.: High-resolution modelling of marine biogenic aerosol precursors in the Arctic realm, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3652, https://doi.org/10.5194/egusphere-egu22-3652, 2022.

EGU22-3711 | Presentations | OS1.6

Eddies in the marginal ice zone of Fram Strait and Svalbard from spaceborne SAR observations in winter 

Igor Kozlov, Oksana Atadzhanova, and Sergey Pryakhin

In this work we investigate the intensity of eddy generation and their properties in the marginal ice zone (MIZ) of Fram Strait and around Svalbard using spaceborne synthetic aperture radar (SAR) data from Envisat ASAR and Sentinel-1 in winter 2007 and 2018. Analysis of 2039 SAR images allowed identifying 4619 eddy signatures in the MIZ. While the overall length and the area of MIZ are different in 2007 and 2018, the number of eddies detected per image per kilometer of MIZ length is similar for both years.
Eddy diameters range from 1 to 68 km with mean values of 6 km and 12 km over shallow and deep water, respectively, suggesting that submesoscale and small mesoscale eddies prevail in the record. At eddy diameter scales of 1-15 km, cyclones strongly dominate over anticyclones. However, in the range of 15-30 km this difference is gradually vanishing, and for diameter values above 30 km anticyclones start to dominate slightly.
Mean eddy size grows with increasing ice concentration in the MIZ, yet most eddies are detected at the ice edge and where the ice concentration is below 20%. The fraction of sea ice trapped in cyclones (53%) is slightly higher than that in anticyclones (48%). The amount of sea ice trapped by a single ‘mean’ eddy is about 40 km2. Here we also attempt to give a first-order estimate of the eddy-induced horizontal sea ice retreat using observed values of eddy radii and amount of sea ice trapped in the eddies, and empirical mean values of ice bottom ablation and ice thickness. The obtained average horizontal ice retreat is about 0.2-0.5 km·d–1 ± 0.02 km·d–1. The spatial patterns of the eddy-induced horizontal sea ice retreat derived from SAR data suggest a pronounced decrease in MIZ area and a shift in the edge location that agrees with the observations.
The analysis of the spatial correlation between eddies, currents and winds shows that the intensity of eddy generation/observations and their detectability in the MIZ, and the width of eddy bands correlate with the intensity of northern and northeasterly winds. In some regions, e.g. along the Greenland Sea shelf break, in Fram Strait and over the Spitsbergen Bank the probability values of eddy occurrence in the MIZ seem to correlate with stronger boundary currents, while north of Svalbard and over Yermak Plateau higher eddy probability values are observed under low/moderate currents and winds.
This study was supported by the Russian Science Foundation grant # 21-17-00278 (analysis of sea ice conditions, ice trapping and melting by eddies) and by the Ministry of Science and Higher Education of the Russian Federation state assignment # 075-00429-21-03 (data acquisition & processing).

How to cite: Kozlov, I., Atadzhanova, O., and Pryakhin, S.: Eddies in the marginal ice zone of Fram Strait and Svalbard from spaceborne SAR observations in winter, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3711, https://doi.org/10.5194/egusphere-egu22-3711, 2022.

EGU22-4360 | Presentations | OS1.6

Properties of mesoscale eddies in the Arctic Icean from a very high-resolution model 

Vasco Müller and Qiang Wang

Mesoscale eddies are believed to play a substantial role for the dynamics of the Arctic Ocean, influencing the interaction of the ocean with the atmosphere and sea-ice as well as the transport and mixing of water masses. Especially their effects on the thermohaline structure and stratification could be crucial for better understanding future changes in the Arctic and the ongoing ‘atlantification’ of the Arctic Ocean water masses. Better understanding of Arctic eddy dynamics also allows the improvement of parametrization of eddy processes in models, which is critical for a realistic representation of the Arctic in climate models and understanding the role of the Arctic Ocean in the global climate. However, simulating Arctic Ocean mesoscale eddies in ocean circulation models presents a great challenge due to their small size at high latitudes and adequately resolving mesoscale processes in the Arctic requires very high resolution, making simulations very computationally expensive.
Here, we use the new unstructured‐mesh Finite volumE Sea ice-Ocean Model (FESOM2) with 1-km horizontal resolution in the Arctic Ocean to evaluate properties of mesoscale eddies. This very high-resolution model setup can be considered eddy resolving in the Arctic Ocean and has recently been used to investigate the distribution of eddy kinetic energy in the Arctic. The analysis here is based on automatically identifying and tracking eddies using a vector geometry-based algorithm and focuses on the model’s representation of eddy properties and dynamics. In-situ observations from the year-long MOSAiC expedition give us the unique possibility to assess the model’s representation of eddy properties against direct observations, both in the Arctic summer and winter seasons.

How to cite: Müller, V. and Wang, Q.: Properties of mesoscale eddies in the Arctic Icean from a very high-resolution model, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4360, https://doi.org/10.5194/egusphere-egu22-4360, 2022.

EGU22-5299 | Presentations | OS1.6

Divergence in CMIP6 projections of future Arctic Ocean stratification 

Morven Muilwijk, Lars H. Smedsrud, Igor V. Polyakov, Aleksi Nummelin, Céline Heuzé, and Hannah Zanowski

The Arctic Ocean is strongly stratified by salinity gradients in the uppermost layers. This stratification is a key attribute of the region as it acts as an effective barrier for the vertical exchanges of Atlantic Water (AW) heat, nutrients, and CO2 between  intermediate depths and the surface of the deep Eurasian and Amerasian Basins (EB and AB). Observations show that from 1970 to 2017, the stratification in the AB has strengthened, whereas, in parts of the EB, the stratification has weakened. The strengthening of the stratification in the AB is linked to a freshening and deepening of the halocline. The weakened stratification in parts of the EB is linked to a shoaling, warming, and lack of freshening of the halocline (Atlantification). Future simulations from a suite of CMIP6 models project that under a strong greenhouse-gas forcing scenario (SSP585), the AB and EB surface freshening and AW warming continues. To meaningfully compare hydrographic changes in the simulations, we present a new indicator of stratification. We find that within the AB, there is agreement among the models that the upper layers will become more stratified in the future. However, within the EB models  diverge regarding future stratification. We discuss and detail some mechanisms responsible for these simulated discrepancies.

 

How to cite: Muilwijk, M., Smedsrud, L. H., Polyakov, I. V., Nummelin, A., Heuzé, C., and Zanowski, H.: Divergence in CMIP6 projections of future Arctic Ocean stratification, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5299, https://doi.org/10.5194/egusphere-egu22-5299, 2022.

EGU22-5601 | Presentations | OS1.6

Studying Atlantic Water heat in the Arctic Ocean using the CESM Large Ensemble 

Alice Richards, Helen Johnson, and Camille Lique

Atlantic Water is the most significant source of oceanic heat in the Arctic Ocean, isolated from the surface by a strong halocline across much of the region. However, an increase in Atlantic Water temperatures and a decrease in eastern Arctic stratification are thought to have contributed to Arctic sea-ice loss in recent decades. Investigating how Atlantic Water heat is likely to change and affect the upper ocean during the coming decades is therefore an important part of understanding the future Arctic. In this study, data from the Community Earth System Model (CESM) large ensemble are used to investigate forced trends and natural variability in the Atlantic Water layer properties and heat fluxes over the period 1920-2100, under an RCP 8.5 scenario from 2006.

How to cite: Richards, A., Johnson, H., and Lique, C.: Studying Atlantic Water heat in the Arctic Ocean using the CESM Large Ensemble, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5601, https://doi.org/10.5194/egusphere-egu22-5601, 2022.

EGU22-5807 | Presentations | OS1.6

A multidecadal model estimate of pan-Arctic coastal erosion rates and associated nutrient fluxes 

Stefanie Rynders and Yevgeny Aksenov

Arctic coastal erosion is an environmental hazard expected to increase under climate change, due to decreasing sea ice protection along with increasing wave heights. In addition to the impact on land, this affects the marine environment, as coastal erosion is a source of organic matter, carbon and nutrients for the coastal waters and shelf seas in the Arctic. Following Barnhart et al., we adapted the White model for iceberg melt to calculate pan-coastal erosion rates. The approach combines ice, ocean and wave model output with permafrost model output and geological characteristics from observations. The calculated erosion rates show large spatial variability, similar to observations, as well as a large seasonal cycle. Additionally, it brings to light the increasing trend between the 1980s and 2010s, with a lengthening of the erosion season, plus inter-annual variability. Using observed nutrient ratios, the erosion rates are converted to biogeochemical sources, which can be used for marine ecosystem models. The approach could be used on-line in earth system models, providing both projections of future erosion rates as well as improved biogeochemistry projections. We acknowledge financial support from Advective Pathways of nutrients and key Ecological substances in the Arctic (APEAR) project (NE/R012865/1, NE/R012865/2, #03V01461), as part of the Changing Arctic Ocean programme, jointly funded by the UKRI Natural Environment Research Council (NERC) and the German Federal Ministry of Education and Research (BMBF), and from the European Union’s Horizon 2020 research and innovation programme under project COMFORT (grant agreement no. 820989), for which 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: Rynders, S. and Aksenov, Y.: A multidecadal model estimate of pan-Arctic coastal erosion rates and associated nutrient fluxes, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5807, https://doi.org/10.5194/egusphere-egu22-5807, 2022.

EGU22-6164 | Presentations | OS1.6

Submesoscale dynamics in the central Arctic Ocean during MOSAiC: optimising the use of observations and high-resolution modelling. 

Ivan Kuznetsov, Benjamin Rabe, Ying-Chih Fang, Alexey Androsov, Alejandra Quintanilla Zurita, Mario Hoppmann, Volker Mohrholz, Sandra Tippenhauer, Kirstin Schulz, Vera Fofonova, Markus Janout, Ilker Fer, Till Baumann, Hailong Liu, and Maria Patricia Mallet

Submesoscale features with profound impact on ocean dynamics and climate-relevant fluxes are frequently observed in the upper ocean including Arctic region. Yet, modelling these features remains a challenge due to the difficulties in the parameterization of submesoscale processes and high resolution required, in particular, in the polar regions. The most effective way to study such phenomena is joint modelling and observational work. Several autonomous observation platforms have been deployed as part of Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) experiment within an approximately 50 km radius around the central observatory. Data from these buoys in combination with data from the central observatory provide a unique opportunity to reconstruct 3D water properties and velocity by constraining a numerical model that resolves the dynamics of the (sub-)mesoscale. It turns out that a minimum root mean square error between results of an optimal interpolation and observations indicates a characteristic length scale of about 7.5 km, corresponding approximately the first-mode barolinic Rossby radius in the area of investigation. However, results of the interpolation are questionable at the sub-mesoscale due to the distribution of the buoy observations in time and horizontal space. In order to describe the in-situ data to achieve a better characterization and understanding of (sub-)mesoscale dynamics we developed and applied a modification of the 3D regional model FESOM-C. The observed temperature and salinity were used to nudge the model to obtain an optimized solution at the resolution of the models. A series of simulations with different horizontal resolutions and model parameters make it possible to analyze the ability of models of this type to reproduce the observed dynamics, to estimate eddy kinetic energy and power spectra, and to compare findings with the observations used to nudge the model. We will show the eddy-induced fluxes and characteristics of eddies along the track of the beginning winter MOSAiC drift.

How to cite: Kuznetsov, I., Rabe, B., Fang, Y.-C., Androsov, A., Zurita, A. Q., Hoppmann, M., Mohrholz, V., Tippenhauer, S., Schulz, K., Fofonova, V., Janout, M., Fer, I., Baumann, T., Liu, H., and Mallet, M. P.: Submesoscale dynamics in the central Arctic Ocean during MOSAiC: optimising the use of observations and high-resolution modelling., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6164, https://doi.org/10.5194/egusphere-egu22-6164, 2022.

EGU22-6176 | Presentations | OS1.6

Heat and salt budgets in the Hornsund fjord 

Anna Przyborska, Agnieszka Strzelewicz, Maciej Muzyka, and Jaromir Jakacki

Climate change is affecting all the Svalbard fjords, which are more or less subject to global warming.  In situ observations in the Hornsund fjord indicate that more and more warm Atlantic water is reaching the fjord as well, and this may influence the rate of melting of sea ice and glaciers, which is likely to increase.  

More freshwater enters the fjord in several different ways. Melting glaciers bring freshwater in the form of surface inflows from freshwater sources, in the form of submarine meltwater at the interface between ocean and ice, and in the form of calving icebergs.  Retreating glaciers and melting sea ice allow the warm Atlantic waters to reach increasingly inland fjord basins and more heat stored in the fjords causes increased melting of the inner fjord glaciers.  The increasing amounts of freshwater in the fjord can change the local ecosystem.

Estimates of the heat and the salt fluxes will give a better understanding of how the ocean interacts with the glaciers through submarine melting and vice versa, how glaciers interact with the ocean through freshwater supply.  Budgetary conditions will be calculated from the high resolution model results (HRM) of velocity, temperature and salinity for the interior of the Hornsund fjord.

Calculations were carried out at the Academic Computer Centre in Gdańsk

How to cite: Przyborska, A., Strzelewicz, A., Muzyka, M., and Jakacki, J.: Heat and salt budgets in the Hornsund fjord, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6176, https://doi.org/10.5194/egusphere-egu22-6176, 2022.

EGU22-6421 | Presentations | OS1.6

Evolution of the wintertime salt budget of the Arctic Ocean mixed layer observed during MOSAIC 

Torsten Kanzow, Benjamin Rabe, Janin Schaffer, Ivan Kuznetsov, Mario Hoppmann, Sandra Tippenhauer, Tao Li, Volker Mohrholz, Markus Janout, Luisa von Albedyll, Timothy Stanton, Lars Kaleschke, Christian Haas, Kirstin Schulz, and Ruibo Lei

In wintertime, the Arctic Ocean mixed layer (ML) regulates the transport of oceanic heat to the sea ice, and transfers both momentum and salt between the ice and the stratified ocean below. Between October, 2019, and May, 2020, we recorded time series of wintertime ML-relevant properties at unprecedented resolution during the MOSAIC expedition. Vertical and horizontal salt and temperature gradients, vertical profiles of horizontal velocity, turbulent dissipation of kinetic energy, growth of both level and lead ice, and ice deformation were obtained from both the Central Observatory and the Distributed Network around it.  

We find that the ML deepened from 20 m at the onset of the MOSAIC drift to 120 m at the end of the winter. The ML salinity showed a decrease between early November 2019 and mid-January 2020 followed by a pronounced increase during February and March 2020 - marking the coldest period of the observations. Applying the equation of salt conservation to the ML as a guiding framework, we combine the abovementioned observations, to intercompare the temporal evolutions of the different processes affecting salinity. Overall, brine rejection associated with thermodynamic ice growth turns out to be the largest salt flux term in the ML salt budget. Thereby the observed amplitudes of upward ocean heat fluxes into the mixed layer are too small for them to have a relevant impact on limiting ice growth. Horizontal salt advection in the ML is the second-most important flux term, actually representing a net sink of salt, thus counteracting brine release. It displays considerably larger temporal variability than brine release, though, due to the variable of ocean currents and horizontal salt gradients. Vertical ocean salt fluxes across the mixed layer base represent the third-most important salt flux term, showing particularly elevated values during storm events, when small-scale turbulence in the ML is triggered by the winds. The results presented will be interpreted in the context of the changes in the regional and temporal ocean, atmosphere and sea ice properties encountered during the MOSAIC drift.

How to cite: Kanzow, T., Rabe, B., Schaffer, J., Kuznetsov, I., Hoppmann, M., Tippenhauer, S., Li, T., Mohrholz, V., Janout, M., von Albedyll, L., Stanton, T., Kaleschke, L., Haas, C., Schulz, K., and Lei, R.: Evolution of the wintertime salt budget of the Arctic Ocean mixed layer observed during MOSAIC, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6421, https://doi.org/10.5194/egusphere-egu22-6421, 2022.

The unprecedented warming in the Arctic opens broad prospects for connecting the Northern Sea Route (NSR) to the Maritime Silk Road. Such a "docking" will significantly impact the global economy. The main problems of the Northern Sea Route are the harsh environmental conditions of the North and, most importantly, the presence of sea ice. While, on average, the ice-free period lasts from June to November, the dates of start and end of ice season vary from year to year within a month or even more. Such variability is impossible to capture by numerical weather prediction, limiting predictability for five days. Therefore, currently, there is no specific timeframe when the waterway is free of ice.

Here I show that a long-range forecast for the navigation season is possible for specific locations in Bering and Okhotsk Seas. The approach is fundamentally different from the numerical weather and climate models; it is based on statistical physics principles and recently discovered spatial-temporal regularities in the Asian-Pacific monsoon system [1]. The regularities appear in the form of spatially organized critical transitions in the near-surface atmosphere over the see. The specific locations mean critical areas - tipping elements of the spatial-temporal structure of ice formation, which are identified via data analysis. I rely on the distribution of near-surface air temperature and wind data (NCEP/NCAR re-analyses data set) to reveal conditions for ice formation [2]. I show that a transition from open water to ice season begins when the near-surface air temperature crosses a critical threshold, it is a starting point for forecasting the ice season's start date. The approach provides long-term predictions of the ice season's start in critical areas 30 days in advance.

Furthermore, the transition from water to ice in the Bering and Okhotsk Seas is driven by the Asian-Pacific monsoon air movements. It has the following implications. First, there is a linkage between the onset of ice formation in the northern part of the Bering Sea and the western part of the Sea of Okhotsk. Second, Asian Monsoon, including the Indian monsoon [3], is driven by the same Asian-Pacific system [4]. As a result, the timing of the monsoon is linked with the ice season. These findings show that it is essential to consider these connections to overcome regional forecast limitations. The system approach applied on a continental scale will be relevant for improving the long-term monsoon and ice season forecasts, which we desperately need for climate adaptation.

ES acknowledges the financial support of the EPICC project (18_II_149_Global_A_Risikovorhersage) funded by BMU and the RFBR (No. 20-07-01071).

[1] Stolbova, V., E. Surovyatkina, B. Bookhagen, and J. Kurths (2016): Tipping elements of the Indian monsoon: Prediction of onset and withdrawal. GRL 43, 1–9 [doi:10.1002/2016GL068392]

[2] Surovyatkina, E. and Medvedev, R.: Ice Season forecast under ClimateChange: Tipping element approach, EGU General Assembly 2020, EGU2020-20073, https://doi.org/10.5194/egusphere-egu2020-20073

[3] https://www.pik-potsdam.de/en/output/infodesk/forecasting-indian-monsoon

[4] Surovyatkina, E.: The impact of Arctic warming on the timing of Indian monsoon and ice season in the Sea of Okhotsk, EGU General Assembly 2021, EGU21-13582, https://doi.org/10.5194/egusphere-egu21-13582

How to cite: Surovyatkina, E.: Long-Range Forecast for the Navigation Season: linking the Northern Sea Route and Maritime Silk Road, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6572, https://doi.org/10.5194/egusphere-egu22-6572, 2022.

EGU22-6930 | Presentations | OS1.6

Physical manifestations and ecological implications of Arctic Atlantification 

Karen M. Assmann, Randi B. Ingvaldsen, Raul Primicerio, Maria Fossheim, Igor V. Polyakov, and Andrey V. Dolgov

The Atlantic gateway to the Arctic Ocean is influenced by vigorous inflows of Atlantic Water. Particularly since 2000, the high-latitude impacts of these inflows have strengthened due to climate change driving so-called ‘Atlantification’ - a transition of Arctic waters to a state more closely resembling that of the Atlantic. In this review, we discuss the physical and ecological manifestations of Atlantification in a hotspot region of climate change reaching from the southern Barents Sea to the Eurasian Basin. Atlantification is driven by anomalous Atlantic Water inflows and modulated by local processes. These include reduced atmospheric cooling, which amplifies warming in the southern Barents Sea; reduced freshwater input and stronger influence

of ice import in the northern Barents Sea; and enhanced upper ocean mixing and air–ice–ocean coupling in the Eurasian Basin. Ecosystem responses to Atlantification encompass increased production, northward expansion of boreal species (borealization), an increased importance of the pelagic compartment populated by new species, an increasingly connected food web and a gradual reduction of the ice-associated ecosystem compartment.

How to cite: Assmann, K. M., Ingvaldsen, R. B., Primicerio, R., Fossheim, M., Polyakov, I. V., and Dolgov, A. V.: Physical manifestations and ecological implications of Arctic Atlantification, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6930, https://doi.org/10.5194/egusphere-egu22-6930, 2022.

EGU22-6934 | Presentations | OS1.6

Barents Sea Polar Front dynamics during fall and winter 2020-2021 

Eivind Hugaas Kolås, Till Baumann, Ilker Fer, and Zoe Koenig

The Barents Sea is one of the main pathways by which Atlantic Water (AW) enters the Arctic Ocean and is an important region for key water mass transformation and production. As AW enters the shallow (< 400 m) Barents Sea, it propagates as a topographically steered current along a series of shallow troughs and ridges, while being transformed through atmospheric heat fluxes and exchanges with surrounding water masses. To the north, the warm and salty AW is separated from the cold and fresh Polar Water (PW) by a distinct dynamic thermohaline front (the Barents Sea Polar Front), often less than 15 km in width.

Two cruises were conducted in October 2020 and February 2021 within the Nansen Legacy project, focusing on the AW pathways and ocean mixing processes in the Barents Sea. Here we present data from CTD (Conductivity, Temperature, Depth), ADCP (Acoustic Doppler Current Profiler) and microstructure sensors obtained during seven ship transects and two repeated stations across and on top of a 200 m deep sill (77°18’N, 30°E) at the location of the Polar Front between AW and PW. The ship transects are complemented by five underwater glider missions, two equipped with microstructure sensors. On the sill, we observe warm (>2°C) and salty (>34.8) AW intruding below the colder (<0°C) and fresher (34.4) PW setting up a geostrophic balance where currents exceed 20 cm/s. We observe anomalous warm and cold-water patches on the cold and warm side of the front, respectively, collocated with enhanced turbulence, where dissipation rates range between 10-8 and 10-7 W/kg. In addition, tidal currents on the sill reach 15 cm/s. The variable currents affect the front structure differently in the vertical. While the mid-depth location of the front is shifted by several kilometers, the location of the front near the bottom remains stationary.  The frontal dynamics on the sill result in transformation and mixing of AW, manifested in the troughs north of the sill as modified AW.

How to cite: Hugaas Kolås, E., Baumann, T., Fer, I., and Koenig, Z.: Barents Sea Polar Front dynamics during fall and winter 2020-2021, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6934, https://doi.org/10.5194/egusphere-egu22-6934, 2022.

EGU22-7237 | Presentations | OS1.6 | Highlight

Sea-ice deformation forecasts for the MOSAiC Arctic drift campaign in the SIDFEx database 

Valentin Ludwig and Helge Goessling and the SIDFEx Team

The Sea Ice Drift Forecast Experiment (SIDFEx) database comprises more than 180,000 forecasts for trajectories of single sea-ice buoys in the Arctic and Antarctic, collected since 2017. SIDFEx is a community effort originating from the Year Of Polar Prediction. Forecasts are provided by various forecast centres and collected, and archived by the Alfred Wegener Institute (AWI). AWI provides a dedicated software package and an interactive online platform for analysing the forecasts. Their lead times range from daily to seasonal scales. Among the buoys targeted by SIDFEx are the buoys of the Distributed Network (DN) array which was deployed during the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition. In this contribution, we show to what extent the deformation (divergence, shear and vorticity) of the DN can be forecasted by the SIDFEx forecasts. We investigate the performance of single models as well as a consensus forecast which merges the single forecasts to a seamless best-guess forecast. 

How to cite: Ludwig, V. and Goessling, H. and the SIDFEx Team: Sea-ice deformation forecasts for the MOSAiC Arctic drift campaign in the SIDFEx database, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7237, https://doi.org/10.5194/egusphere-egu22-7237, 2022.

EGU22-7240 | Presentations | OS1.6

Arctic Ocean Heat Content as a Driver of Regional Sea Ice Variability 

Elena Bianco, Doroteaciro Iovino, Stefano Materia, Paolo Ruggieri, and Simona Masina

The Arctic Ocean is transitioning from permanently ice-covered to seasonally ice-free, with thinner and more dynamic sea ice. This strengthens the coupling with the atmosphere and the ocean, which exert a strong influence on sea ice via thermodynamic and dynamic forcing mechanisms. Short-term predictions are met with the challenge of disentangling the preconditioning processes that regulate sea ice variability, as these often trigger a response that is not uniform in time nor in space.  This study assesses the role of ocean heat content (OHC) as a driver of sea ice variability for five different regions of the Arctic Ocean. We choose to focus on a sub-seasonal time frame, with the goal of investigating whether anomalies in ocean heat content offer a source of predictability for sea ice in the following months and whether this coupling varies across different regions and seasons. To account for the different processes that regulate the Arctic Ocean heat budget, we consider ocean heat content in the mixed layer (OHCML) and in the upper 300 m (OHC300), computed from the CMCC Global Ocean Reanalysis C-GLORSv5 for the period 1979-2017. Time-lagged correlations of linearly detrended anomalies suggest a link between heat content and sea ice variability in the following months. This source of predictability is stronger during the melt season and peaks in autumn, with highest correlations in the Kara and Chukchi regions. Consistent with previous studies, a distinctive response is observed for the Barents Sea, where sea ice is more strongly coupled with the ocean during the freezing season.  Our preliminary results support a central role of OHC as a driver of sea ice thermodynamic changes at sub-seasonal scales, a mechanism that is likely to become stronger under ice-depleted conditions.   

How to cite: Bianco, E., Iovino, D., Materia, S., Ruggieri, P., and Masina, S.: Arctic Ocean Heat Content as a Driver of Regional Sea Ice Variability, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7240, https://doi.org/10.5194/egusphere-egu22-7240, 2022.

EGU22-7793 | Presentations | OS1.6

Decadal variability in the transient tracer distribution in the upper Arctic Ocean 

Wiebke Körtke, Maren Walter, Oliver Huhn, and Monika Rhein

The Arctic is warming stronger and faster than other regions during the climate change. Within this development, the Arctic Ocean’s water masses and ventilation processes are changing as well. Transient anthropogenic tracers can be used to track water masses and to investigate ventilation and mixing processes. For these tracers, e.g. chlorofluorocarbons (CFCs), the atmosphere is the only source to the ocean and they are conservative in the water. In this study, we analyse CFC-12 (CCl2F2) along two transects in the Canadian basin of the central Arctic Ocean covered in different decades (T1: 1994 and 2015, T2: 2005 and 2015), with additional hydrographic data for context. We find differences in both the tracer concentration and the hydrographic properties between the years and transects. Along the first transect (located at ~180°W), the difference in saturation between 2015 and 1994 is largest in the layer of the Atlantic Water at high latitudes (> 82°N). A similar strong increase in CFC-12 saturation is observed along the second transect (located at 150°W). In contrast to the saturation increase in the Atlantic Water layer, we find a decrease close to the surface, which is correlated to oversaturations in 2005 in this region. At the same time, the surface waters were more saline in 2005 indicating a mixing event. Oversaturation is present in all years, except in 1994. Existence of oversaturation can be caused by special events, either inside the ocean (by mixing processes) or at the sea ice-ocean-atmosphere interface (by the occurrence of changes in the sea ice concentration or atmospheric forcing). We compare the tracer results with hydrographic properties, as well as with wind and ice conditions present during the time of measurements, to investigate the causes of the observed changes. Further, the time dependent atmospheric concentrations of CFCs are used to determine the age of water masses. Here, we use the simplest possible approach of age determination to identify the age of the Atlantic Water along the transects, assuming no interaction or exchange with the surrounding water masses after the Atlantic Water left the surface in Fram Strait. Due to the decreasing CFC-12 atmospheric concentration after 2003/04, it is necessary to use sulfur hexafluoride (SF6) as an additional tracer for 2015. Along the first transect, the tracer age of CFC-12 for 1994 is compared to the tracer age of SF6 in 2015. In 2015 the tracer age is much higher in the region south of 80°N compared to 1994, while the ages are quite similar at higher latitudes. The higher age in the southern part of the transect indicates a water mass, that is much older in 2015 than it was in 1994, a sign of a possible circulation change. A similar result is found along the second transect, where the new tracer SF6 is available in both years. Along this transect, the water is also older in 2015 than in 2005.

How to cite: Körtke, W., Walter, M., Huhn, O., and Rhein, M.: Decadal variability in the transient tracer distribution in the upper Arctic Ocean, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7793, https://doi.org/10.5194/egusphere-egu22-7793, 2022.

EGU22-8055 | Presentations | OS1.6

Atlantic Water boundary current along the southern Yermak Plateau, Arctic Ocean 

Ilker Fer and Algot K. Peterson

One of the major branches of the warm and saline Atlantic Water supply is the current along the west coast of Spitsbergen in Fram Strait. The Yermak Plateau is a topographic obstacle in the path of this current. The diverging isobaths of the Plateau split the current, with an outer branch following the 1000-1500 m isobaths along the rim of the Yermak Plateau (the Yermak branch). Observation based estimates of the volume transport, structure and variability of the Yermak branch are scarce.

Here we present observations from an array of three moorings on the southern flank of the Yermak Plateau, covering the AW boundary current along the slope, between the 800 m to 1600 m isobaths over 40 km distance, from 11 September 2014 to 13 August 2015. The aim is to estimate the volume transport in temperature classes to quantify the contribution of the Yermak branch, to document the observed mesoscale variability, and identify the role of barotropic and baroclinic instabilities on the variability.

All three moorings show depth- and time-averaged currents directed along isobaths, with the middle mooring in the core of the boundary current. Depth-averaged current speeds in the core, averaged over monthly time scale, reach 20 cm s-1 in March. Temperatures are always greater than 0°C in the upper 800 m, or than 2°C in the upper 500 m. Seasonal averaged volume transport estimates of Atlantic Water defined as temperature above 2°C, are maximum in autumn (1.4 ± 0.2 Sv) and decrease to 0.8 ± 0.1 Sv in summer. The annual average AW transport is 1.1 ± 0.2 Sv, below which there is bottom-intensified current, particularly strong in winter, leading to a substantial transport of cold water (<0°C) with an annual average of 1.1 ± 0.2 Sv.

Mesoscale variability and energy conversion rates are estimated using fluctuations of velocity and stratification in the 35 h to 14-days band and averaging over a monthly time scale.  Time-averaged profiles of horizontal kinetic energy (HKE) show a near-surface maximum in the outer and middle (core) moorings decreasing to negligible values below 700 m depth. HKE averaged between 100-500 m depth increases from about 3×10-3 m2 s-2 in fall to (6-9)×10-3 m2 s-2 in winter and early spring.  Temperature and cross-isobath velocity covariances show substantial mid-depth temperature fluxes in winter. Divergence of temperature flux between the core and outer moorings suggests that heat is extracted by eddies. Depth-averaged energy conversion rates show typically small barotropic conversion, not significantly different from zero, and highly variable baroclinic conversion rates with alternating sign at 1-2 month time scales. Observations suggest that the boundary current is characterized by baroclinic instabilities, which particularly dominate in winter months. 

How to cite: Fer, I. and Peterson, A. K.: Atlantic Water boundary current along the southern Yermak Plateau, Arctic Ocean, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8055, https://doi.org/10.5194/egusphere-egu22-8055, 2022.

EGU22-8234 | Presentations | OS1.6

Towards Late Quaternary sea ice reconstructions in the Arctic with sedimentary ancient DNA. 

Tristan Cordier, Danielle M. Grant, Kristine Steinsland, Katja Häkli, Dag Inge Blindheim, Agnes Weiner, Aud Larsen, Jon Thomassen Hestetun, Jessica Louise Ray, and Stijn De Schepper

Sea ice has a pivotal role in the regulation of the Arctic climate system, and by extension to the global climate. Our knowledge of its historical variation and extent is limited to the satellite records that only cover the last several decades, which considerably hampers our understanding on how past climate has influenced sea ice extent in the Arctic. Latest modelling efforts indicate that the Arctic may be sea ice free in summer by 2050, making the appreciation of the effects that such major change will have on Arctic ecosystems of paramount importance. Here, we will present the first results of the AGENSI project (www.agensi.eu) aiming at reconstructing the past sea ice evolution with sedimentary ancient DNA. Based on a large collection of surface sediments collected along multiple gradients of sea ice cover in the Arctic, we show that plankton DNA sinking to the seafloor can be used to predict the variation of surface sea ice cover. Further, we will present our current efforts to utilize this dataset to reconstruct the past sea ice variation in Late Quaternary sediment cores.

How to cite: Cordier, T., Grant, D. M., Steinsland, K., Häkli, K., Blindheim, D. I., Weiner, A., Larsen, A., Hestetun, J. T., Ray, J. L., and De Schepper, S.: Towards Late Quaternary sea ice reconstructions in the Arctic with sedimentary ancient DNA., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8234, https://doi.org/10.5194/egusphere-egu22-8234, 2022.

EGU22-8941 | Presentations | OS1.6

North Water Polynya Sensitivity to Arctic Warming 

Rajan Patel, Patrick Ugrinow, Alexandra Jahn, and Chris Wyburn-Powell

The North Water Polynya (NOW) in northern Baffin Bay contains nutrient-rich waters which are essential to the biodiversity of the region and the native Inuit people. Over the observational period the size and duration of the NOW in spring has varied considerably, and recent studies suggest the NOW may fail to form in the future. Even small changes to the polynya have the potential to impact local ocean circulation and nutrient cycling. 

To assess the projected changes to the NOW, we look at CMIP5 large ensembles under multiple forcing scenarios. Initial results from CESM1 LE suggest that global temperatures greater than 2.5ºC above pre-industrial levels shift the peak polynya area from June to May. Work is ongoing to assess biogenic and physical impacts of such changes. Implications for climate change are that to avoid large changes to the NOW, warming should be limited.

Additionally, the Polynya area fluctuates with time but decreases as a whole throughout the 21st century.

How to cite: Patel, R., Ugrinow, P., Jahn, A., and Wyburn-Powell, C.: North Water Polynya Sensitivity to Arctic Warming, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8941, https://doi.org/10.5194/egusphere-egu22-8941, 2022.

EGU22-9569 | Presentations | OS1.6

Interplay between subsurface eddies and sea ice over the Arctic Ocean 

Angelina Cassianides, Camille Lique, Anne Marie Treguier, Gianluca Meneghello, and Charly Demarez

The paucity of observations over the Arctic Ocean prevents us from fully understanding the interaction between sea ice and mesoscale dynamics. Previous studies on this interplay have documented the interaction between surface eddies and sea ice, omitting the subsurface eddies. This work focuses on the possible role of these subsurface eddies in shaping the sea ice distribution. First, we perform an extensive eddy census over the period 2004-2020 over the Arctic Basin, based on data from Ice Tethered Profilers (ITP) and moorings from the Beaufort Gyre Exploration Project. About 500 subsurface eddies are detected, including both submesoscale (radius between 2-10 km) and mesoscale (up to 80 km) structures. Second, we investigate the dynamical or thermodynamical signature that these eddies may imprint at the surface. On average, these eddies do not cause significant variations in either the temperature of the mixed layer or the melting of sea ice. However, we estimate that subsurface eddies induce a dynamic height anomaly of the order of a few centimetres, leading to a surface vorticity anomaly of O(10^{-5} - 10^{-4}) s^{-1}, suggesting that they may be a significant local forcing for the sea ice momentum balance. Our results suggest that there is no link between the sea ice evolution and the energy level associated with the presence of subsurface eddies. It suggests that once formed, these structures may evolve at depth independently of the presence of sea ice. 

How to cite: Cassianides, A., Lique, C., Treguier, A. M., Meneghello, G., and Demarez, C.: Interplay between subsurface eddies and sea ice over the Arctic Ocean, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9569, https://doi.org/10.5194/egusphere-egu22-9569, 2022.

EGU22-9777 | Presentations | OS1.6

(Sub-)mesoscale Dynamics in the Arctic and its Impact on the Flux of Nutrients and Carbon: a case study from the MOSAiC expedition 

Alejandra Quintanilla Zurita, Benjamin Rabe, and Ivan Kuznetsov

In this work, we will show the main ideas for studying how the (sub-)mesoscale processes impact the flux of nutrients and dissolved inorganic and organic carbon (DIC/DOC) in the upper layers of the central Arctic Ocean. These fluxes are essential since they are one of the primary mechanisms to connect the deeper layers of the ocean with the upper part: nutrients stored deeper can go to the surface mixed-layer and be used for primary production. On the other side, the Arctic Ocean is considered a carbon sink and contributes to the biological pump. For doing this, we are using the high-resolution numerical model FESOM-C to assimilate the hydrographic observations from the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition (2019-2020) to describe the (sub-)mesoscale dynamics (eddies, fronts). We will make use of the OMEGA equation to disentangle the vertical fluxes due to diabatic and adiabatic processes in the model output. Finally, we will analyse those results with in-situ observations of nutrients and DIC/DOC to estimate associated mass fluxes.

How to cite: Quintanilla Zurita, A., Rabe, B., and Kuznetsov, I.: (Sub-)mesoscale Dynamics in the Arctic and its Impact on the Flux of Nutrients and Carbon: a case study from the MOSAiC expedition, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9777, https://doi.org/10.5194/egusphere-egu22-9777, 2022.

EGU22-9899 | Presentations | OS1.6 | Highlight

Changes in Arctic Halocline Waters along the East Siberian Slope and in the Makarov Basin from 2007 to 2020 

Cécilia Bertosio, Christine Provost, Marylou Athanase, Nathalie Sennéchael, Gilles Garric, Jean-Michel Lellouche, Joo-Hong Kim, Kyoung-Ho Cho, and Taewook Park

The Makarov Basin halocline receives contributions from diverse water masses of Atlantic, Pacific, and East Siberian Sea origin. Changes in surface circulation (e.g., in the Transpolar Drift and Beaufort Gyre) have been documented since the 2000s, while the upper ocean column in the Makarov Basin has received little attention. The evolution of the upper and lower halocline in the Makarov Basin and along the East Siberian Sea slope was examined combining drifting platforms observations, shipborne hydrographic data, and modelled fields from a global operational physical model.

In 2015, the upper halocline in the Makarov Basin was warmer, fresher, and thicker compared to 2008 and 2017, likely resulting from the particularly westward extension of the Beaufort Gyre that year. From 2012-onwards, cold Atlantic-derived lower halocline waters, previously restricted to the Lomonosov Ridge area, progressed eastward along the East Siberian slope, with a sharp shift from 155 to 170°E above the 1000 m isobath in winter 2011-2012, followed by a progressive eastward motion after winter 2015-2016 and reached the western Chukchi Sea in 2017. In parallel, an active mixing between upwelled Atlantic water and shelf water along the slope, formed dense warm water which also supplied the Makarov Basin lower halocline.

The progressive weakening of the halocline, together with shallower Atlantic Waters, is emblematic of a new Arctic Ocean regime that started in the early 2000s in the Eurasian Basin. Our results suggest that this new Arctic regime now may extend toward the Amerasian Basin.



How to cite: Bertosio, C., Provost, C., Athanase, M., Sennéchael, N., Garric, G., Lellouche, J.-M., Kim, J.-H., Cho, K.-H., and Park, T.: Changes in Arctic Halocline Waters along the East Siberian Slope and in the Makarov Basin from 2007 to 2020, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9899, https://doi.org/10.5194/egusphere-egu22-9899, 2022.

EGU22-10044 | Presentations | OS1.6

Sea ice import affects Beaufort Gyre freshwater adjustment 

Sam Cornish, Morven Muilwijk, Jeffery Scott, Juliana Marson, Paul Myers, Wenhao Zhang, Qiang Wang, Yavor Kostov, and Helen Johnson

The Arctic Ocean's Beaufort Gyre is a wind-driven reservoir of relatively fresh seawater, situated beneath time-mean anticyclonic atmospheric circulation, and is covered by mobile pack ice for most of the year. Liquid freshwater accumulation in and expulsion from this gyre is of critical interest to the climate modelling community, due to its potential to affect the Atlantic meridional overturning circulation (AMOC). In this presentation, we investigate the hypothesis that wind-driven sea ice import to/export from the BG region influences the freshwater content of the gyre and its variability. To test this hypothesis, we use the results of a coordinated climate response function (CRF) experiment with four ice-ocean models, in combination with targeted experiments using a regional setup of the MITgcm, in which we apply angular changes to the wind field. Our results show that, via an effect on the net thermodynamic growth rate, anomalies in sea ice import into the BG affect liquid freshwater adjustment. Specifically, increased ice import increases freshwater retention in the gyre, whereas ice export decreases freshwater in the gyre. Our results demonstrate that uncertainty in the cross-isobaric angle of surface winds, and in the dynamic sea ice response to these winds, has important implications for ice thermodynamics and freshwater. This mechanism may explain some of the observed inter-model spread in simulations of Beaufort Gyre freshwater and its adjustment in response to wind forcing.

How to cite: Cornish, S., Muilwijk, M., Scott, J., Marson, J., Myers, P., Zhang, W., Wang, Q., Kostov, Y., and Johnson, H.: Sea ice import affects Beaufort Gyre freshwater adjustment, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10044, https://doi.org/10.5194/egusphere-egu22-10044, 2022.

One of the fastest changing environments of the Arctic is the Barents Sea (BS), located north of Norway between Svalbard, Franz Josef Land and Novaya Zemlja. Although covering only about 10% of the Arctic Ocean area, the BS is of Arctic-wide importance,  as the warm water advected from the North Atlantic cause massive heat fluxes in the atmosphere and sea ice melt, ultimately driving major water mass modifications relevant for the Arctic Ocean circulation  downstream.

We focus on the question whether the observed retreat in sea-ice extent in the BS over the past four decades has enhanced the inflow of warm Atlantic water (AW) into the BS via an ocean-sea-ice-atmosphere feedback contributing to Arctic Amplification, as follows. We start by presenting evidence that the retreating winter sea-ice cover of the Barents Sea has been associated with an increase in ocean-to-atmosphere heat flux that can be observed in a strong rise in near surface air temperature - spatially coinciding with the regions of strong sea-ice retreat. Furthermore, the rising air temperature and the associated convective processes in the atmosphere create a local low sea level pressure (SLP) system over the northern BS that results in additional westerly winds in the vicinity of the Barents Sea Opening (BSO), where the warm and saline AW enters the BS. In case these additional winds enhance the AW inflow into the BS a positive feedback is likely as more heat is available for melting further ice, amplifiying the negative SLP anomaly.

In a set of ocean sensitivity experiments using the sea-ice and ocean model FESOM2.1, we investigate the impact of sea ice-related SLP anomalies and their associated anomalous atmospheric circulation patterns on volume transport through the BSO. The simulations rely on a horizontal grid resolution of approx. 4.5 km in the Arctic and Nordic Seas allowing precise modeling of the BS hydrography and circulation. The model is initially driven with a repeated normal year forcing (CORE1) to isolate the impact of the wind anomalies from high frequency atmospheric variability. After a spin-up phase, the model is perturbed by anomalous cyclones over the BS derived from long term SLP differences in reanalysis datasets associated with the observed sea-ice retreat. The results point indeed to a slight increase in net volume transport into the BS across the BSO. This increase, however, is not caused by an increase in the inflow of AW, but rather a decrease of the outflow of modified AW recirculating back towards Fram Strait. In terms of the feedback, our results indicate that the BS AW inflow is not sensitive to cyclonic wind anomalies caused by the sea-ice retreat. The additional volume and heat transport in the modified AW range may not be sufficient to provide enough heat to melt further sea-ice and hence likely does not close the proposed feedback mechanism in the BS.

How to cite: Heukamp, F. and Kanzow, T.: Investigations on the coupling of the Barents Sea sea-ice retreat on the Atlantic Water inflow via an ocean-ice-wind feedback in the context of Arctic Amplification, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10191, https://doi.org/10.5194/egusphere-egu22-10191, 2022.

EGU22-10689 | Presentations | OS1.6

Air-Sea, Ice-Sea, and Effective Wind Forcing of the Beaufort Gyre 

Elizabeth Webb, David Straub, Bruno Tremblay, and Louis- Philippe Nadeau

Surface heat and momentum fluxes between the atmosphere and ocean are mitigated by sea ice cover, resulting in an effective net forcing that can be very different in character from the wind stress alone. The effective stress is often expressed as a weighted sum of air-sea and ice-sea stresses. This is appropriate for levitating ice. Allowing instead for floating ice, one can rewrite the effective forcing in a way that makes no explicit mention of the ice-ocean stress. Instead, the net forcing becomes a linear sum of air-sea and internal ice stresses. These differences are explored in the context of the Beaufort Gyre. Previous studies have introduced the ice-ocean governor as a regulating mechanism for the gyre, and in this limit, the ice-ocean stress is assumed to vanish. For floating ice, the governor limit can be thought of instead as a balance between the wind stress and the internal ice stress. Note that this balance would seem to be unlikely in that the internal stress is associated with small-scale linear kinetic features, which are very different in character from the mesoscale and synoptic features that determine the wind stress. High-resolution ECCO data will be used to examine the instantaneous and time-averaged spatial structure of the various terms that drive the Beaufort Gyre. Future work will also examine the air-sea-ice interface in different wind and ice regimes, as well as the role of eddy fluxes in the gyre dynamics. 

How to cite: Webb, E., Straub, D., Tremblay, B., and Nadeau, L.-P.: Air-Sea, Ice-Sea, and Effective Wind Forcing of the Beaufort Gyre, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10689, https://doi.org/10.5194/egusphere-egu22-10689, 2022.

EGU22-11202 | Presentations | OS1.6

Upper Arctic Ocean hydrography during the year-round MOSAiC expedition in the context of historical observations 

Myriel Vredenborg, Benjamin Rabe, Sandra Tippenhauer, and Kirstin Schulz and the Team MOSAiC OCEAN

The Arctic Ocean is characterized by complex processes coupling the atmosphere, cryosphere, ocean and land and undergoes remarkable environmental changes due to global warming. To better understand this system of unique physical, biogeochemical and ecosystem processes and their recent changes, the year-round ice drift experiment Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) was conducted from autumn 2019 to autumn 2020.

In this study we analyse temperature and salinity measurements of the upper Arctic Ocean taken during MOSAiC with different devices, i.e. on an ice-tethered profiler, a microstructure profiler and water sampler rosettes operated from the ship as well as through an ice hole on the ice floe. Combining all these measurements provides us an exceptional data resolution along the MOSAiC track. Moreover, we compare these observations with a comprehensive dataset of historical hydrographic data from the region.

Along the MOSAiC track we find signatures of a convective lower halocline (Fram Strait branch), as well as advective-convective lower halocline (Barents Sea branch). We see pronounced changes in the salinity and temperature of the lower halocline in comparison to the historical data, in particular, at the beginning of the drift. Furthermore, we show polar mixed-layer and upper halocline conditions in relation to seasonality and local surface conditions. We put the warm Atlantic Water temperature in the context of historical observations and investigate indications for the presence of Pacific Water.

How to cite: Vredenborg, M., Rabe, B., Tippenhauer, S., and Schulz, K. and the Team MOSAiC OCEAN: Upper Arctic Ocean hydrography during the year-round MOSAiC expedition in the context of historical observations, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11202, https://doi.org/10.5194/egusphere-egu22-11202, 2022.

EGU22-11472 | Presentations | OS1.6

Structure and seasonal variability of the Arctic Boundary Current north of Severnaya Zemlya 

Eugenio Ruiz-Castillo, Markus Janout, Torsten Kanzow, Jens Hoelmann, Kirstin Schulz, and Vladimir Ivanov

We assessed the spatial and temporal variability of the Arctic Boundary Current (ABC) using a high-resolution array of 7 oceanographic moorings, deployed across the Eurasian continental slope north of Severnaya Zemlya in 2015-2018. In particular, we quantified transports and individual water masses based on temperature and salinity recorders and current profilers. The highest velocities (>0.30 ms-1) of the ABC occurred at the upper continental slope and decreased offshore to below 0.03 ms-1 in the deep basin. The ABC shows strong seasonal variability with velocities two times higher in winter than in summer. Compared to the upstream conditions north of Svalbard, the water mass distribution changed significantly within 20 km from the shelf edge due to mixing with- and intrusion of shelf waters. Further offshore, Atlantic Waters remained largely unmodified. The ABC transported 4.2±0.1 Sv across the region with 63-71% of the volume transport constrained within 30-40 km of the shelf edge. Water mass transport was 0.52±0.13, 0.9±0.27, 0.9±0.33 and 0.9±0.35 Sv for Atlantic Waters (AW), Dense Atlantic Water (DAW), Barents Sea Branch Water (BSBW) and Transformed Atlantic Water (TAW), respectively. A seasonality in TAW and BSBW transport was linked with temperature changes, where maximum transports coincided with minimum temperatures. Our results highlight the importance of the Barents Sea for the ABC along the Siberian slopes, and indicate that a continuing Barents Sea warming would directly translate to reductions in the TAW and BSBW cooling effect and thus lead to warmer oceanic conditions in the ABC pathway. 

How to cite: Ruiz-Castillo, E., Janout, M., Kanzow, T., Hoelmann, J., Schulz, K., and Ivanov, V.: Structure and seasonal variability of the Arctic Boundary Current north of Severnaya Zemlya, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11472, https://doi.org/10.5194/egusphere-egu22-11472, 2022.

EGU22-11518 | Presentations | OS1.6

Differential summer melt rates of ridges, first- and second-year ice in the central Arctic Ocean during the MOSAiC expedition 

Evgenii Salganik, Benjamin Lange, Christian Katlein, Ilkka Matero, Julia Regnery, Igor Sheikin, Philipp Anhaus, Knut Høyland, and Mats Granskog

During the melt 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. This summer consolidation is related to refreezing of less saline meltwater, originating from snowmelt and ridge keel melt. We examine the spatial variability of ice melt for different types of ice from in situ drilling, coring, and from multibeam sonar scans of remotely operated underwater vehicle (ROV). Seven ROV scans, performed from 24 June 2020 to 28 July 2020 during the Multidisciplinary drifting Observatory for the Study of the Arctic Climate (MOSAiC) expedition were analyzed. The area investigated by the ROV (400 by 200 m) consisted of several ice ridges, surrounded by first- and second-year ice. Seven ice drilling transects were additionally performed to validate ROV measurements. The maximum keel depth of the ridge investigated by ice drilling was 6.5 m. We show a substantial difference in melt rates of first-year ice, second-year ice, and sea ice ridge keels. We also show how ridge keels decay depending on keel depth, width, steepness, and orientation relative to the ice drift direction. These results are important for quantifying ocean heat fluxes for different types of ice during advanced melt, and for estimation of 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., Regnery, J., Sheikin, I., Anhaus, P., Høyland, K., and Granskog, M.: Differential summer melt rates of ridges, first- and second-year ice in the central Arctic Ocean during the MOSAiC expedition, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11518, https://doi.org/10.5194/egusphere-egu22-11518, 2022.

In September-October 2021 during NABOS-2021 expedition specialized shipborne ice observations were carried following methodological principles developed in AARI. The overall research area for the cruise included Arctic basin area toward north of Laptev and East Siberian seas within 73-82°N 125°E-170°W. Ice conditions were generalized and analyzed along the oceanographic cross-sections in accordance with the ice conditions homogeneousness. Hard ice conditions were unforeseen during the planning period, which made adjustments to the initial expedition plans and several minor northern cross-sections were canceled.

The route fragment with the hardest ice conditions was observed within 78-82°N 160°-172°E. Sea ice concentration was 10 tenths totally, concentration of residual ice varied from 5-7 to 10 tenths directly on the route of the vesse. Prevailing forms of the sea ice were big (500m-2000m) and often vast (2000-10000m) floes with strongly smoothed hummock formations covered with snow 10-15 cm high. The thickness of the residual ice on the route was mainly 50-70 cm (17%), often over 100 cm (6%), in hummocks over 2-3 meters. The water area between the ice fields was captured by young ice, grey and grey-white (3-4 up to 9 tenths).

Several areas were crossed by vessel twice in a time difference of one month. Sea ice formation process during the month long was fixed and analyzed by changes in distribution of ice with different stages of development. In general, 66% of the ship track within the ice during expedition had sea ice concentration of 10 tenths, the residual ice on the route accounted for 26%, young ice was observed for 38%, nilas and new ice 36%.The residual ice thickness varied from 30-50 cm to 160 cm and above, in some cases (hummock formations) over 300 cm. Ice thickness of 30-50 and 50-70 cm accounts for 9% each, thicknesses over 70 cm account for 8% of all thickness ranges observed throughout the entire route of the vessel in the ice.

Key words: shipborne observations, ice conditions of navigation, ice thickness, ice concentration, stage of development of ice.

How to cite: Timofeeva, A.: Navigation in the ice conditions in Arctic basin in September-October 2021, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13087, https://doi.org/10.5194/egusphere-egu22-13087, 2022.

EGU22-13088 | Presentations | OS1.6

An effect of mesoscale and submesoscale eddies on sea ice processes in the Marginal Ice Zone 

Sergey Pryakhin, Igor Bashmachnikov, Igor Kozlov, and Claudia Wekerle

The early study of eddy properties in the Marginal Ice Zone (MIZ) and of their influence on the ice regime in the Greenland Sea, based on the results of the MIZEX project (Johannessen et al., 1987), revealed that eddies may capture and transport a significant amount of ice, enhancing its ablation. Estimates suggest that eddies may provoke the ice edge retreat as fast as 1–2 km per day during summer. However, up to present, the mesoscale dynamics in polar regions, as well as the effect of eddies on ice edge ablation are poorly understood. This is due to sparse in situ observations and to an insufficient spatial resolution of numerical models, typically not resolving the mesoscale processes due to a relatively small Rossby deformation radius in polar regions.
This study aims to better understand the ways eddies affect the sea ice edge and their relative effect on the MIZ position in the East Greenland Current (75-78°N and 20°W-10°E). Pronounced local water temperature gradients and the importance of thermodynamics ablation in the ice dynamics in the Greenland Sea, derived in previous studies (Selyuzhenok et al., 2020), suggest a possibly strong eddy effect on the MIZ. This effect was noted in several case studies, when eddies were observed to trap and transport a significant amount of ice away from the MIZ (see, for example, von Appen et al., 2018). 
We base our results on the output of the very high-resolution Finite Element Sea ice-Ocean Model (FESOM), tested against the remote sensing observations from ENVISAT. We investigate only the warm period of 2007, when ice is actively melting and during which period a data on eddies, detected in SAR data, is available. Comparison of the location and dynamics of the ice edge in FESOM, AMSR-E-based ice concentration products and ENVISAT ASAR data, as well as of eddy properties in FESOM and in SAR satellite images, suggest that the model is in good agreement with the observations and can be used to study mesoscale dynamics of the MIZ in the region.
The analysis showed that eddies affect the ice edge position through an enhanced horizontal exchange across the MIZ. The sea-ice is trapped by eddies and transported east, in the area of a warmer water, while the warmer water is entrained by eddies and transported west, towards the MIZ. Both effects contribute to the accelerated sea ice melt and destruction. The highest temperature gradients, as well as the largest concentration of eddies in the MIZ were detected in the northern part of the study area, adjacent to the Fram Strait. Here eddies were found to play a particular important role in the MIZ dynamics.
This research was financed by the Russian Science Foundation (RSF) project N 21-17-00278.

How to cite: Pryakhin, S., Bashmachnikov, I., Kozlov, I., and Wekerle, C.: An effect of mesoscale and submesoscale eddies on sea ice processes in the Marginal Ice Zone, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13088, https://doi.org/10.5194/egusphere-egu22-13088, 2022.

CR7 – The Cryosphere in the Earth system: interdisciplinary topics

EGU22-80 | Presentations | CR7.1

What determines the ice shelf shape? 

Yoshihiro Nakayama, Toshiki Hirata, and Daniel Goldberg

Ice shelf melt rates near grounding lines are a few orders of magnitude higher than other locations. This intense melting close to
the grounding zone is crucial as it induces ice shelf thinning, further acceleration of ice flow, and grounded ice loss. However,
little is revealed about ice and ocean processes determining peak ice shelf melt rates close to the grounding line because (1) ocean
modelers apply a constant cavity geometry, (2) ice modelers typically assume some parameterizations for determining ice shelf melt rates,
and (3) ice-ocean coupled simulations typically require long model integration, necessitating coarse resolution, and they are not able to
resolve small-scale processes near grounding zones. Here, we develop an idealized high-resolution Pine-Island-like model configuration (250
m, 500m, and 1km horizontal and 10 m vertical grid spacings) and conduct ice-ocean coupled simulation for 20 years after 60 years of
initialization. We show that ice slope and ice shelf melt rate close to the grounding zone increases with higher grid resolution but ice
shelf geometry converges towards the highest resolution solution. We are also able to simulate the formation of sub-ice shelf channels by
applying seasonally varying oceanic conditions. We also present our preliminary results of ice-ocean coupled realistic Pine Island
simulation using unprecedentedly high horizontal and vertical resolution  (200m horizontal and 10 m vertical grid spacings). This is
a step towards understanding the ice-ocean interacting mechanisms determining ice shelf shape and melt rate, which is crucial for
improved projections of future Antarctic ice loss.

How to cite: Nakayama, Y., Hirata, T., and Goldberg, D.: What determines the ice shelf shape?, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-80, https://doi.org/10.5194/egusphere-egu22-80, 2022.

Dynamically coupled ice sheet-ocean models are beginning to be used to study the response of the Antarctic Ice Sheet to fluctuations in ocean temperatures. However, initialising a coupled ice-ocean model for realistic settings is challenging and can introduce nonphysical transients. The extent to which such transients can affect model evolution and projection is unclear. Here, we use a synchronously-coupled model of ice-ocean dynamics to investigate the evolution of Pope, Smith and Kohler Glaciers, West Antarctica, over the next half-century. Two methods of coupled initialisation are used: in one, the ice-sheet model is constrained to fit observed velocities in its initial state; in the other, the model is constrained with both velocities and grounded thinning rates over a 4-year period while forced with simulated ocean melt rates. For each method, two climate scenarios are considered -- one where ocean conditions during this initialisation period persist indefinitely, and one where the ocean is in a permanent ``warm'' state -- as well as two ice-sheet basal sliding laws. At first, the model runs initialised with thinning rates exhibit volume loss much closer to observed values than those initialised with velocity only, but after 1-2 decades the forcing primarily determines rates of retreat. This ``crossover’’ timescale is expected to vary by glacier, however. Under the ``warm’’ scenario, grounding line retreat of ~30 km is simulated for Smith and Kohler, but it is questionable whether this will continue due to narrowing of submarine troughs and limiting of heat transport by controlling obstacles.

How to cite: Goldberg, D. and Holland, P.: The relative impacts of initialisation and climate forcing in coupled ice sheet-ocean modelling: application to Pope, Smith and Kohler glaciers, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1125, https://doi.org/10.5194/egusphere-egu22-1125, 2022.

EGU22-2773 | Presentations | CR7.1

Assessing basal melt parameterisations for Antarctic ice shelves using a cavity-resolving ocean model 

Clara Burgard, Nicolas C. Jourdain, Ronja Reese, Adrian Jenkins, and Pierre Mathiot

Ice shelves at the outskirts of the Antarctic ice sheet are thinning due to warm ocean water intruding into their cavities. Thinning reduces the ice shelves' buttressing potential, which means that the restraining force that they exert on the ice flowing across the grounding line is lower and more ice is discharged into the ocean. Taking into account ocean-induced melt, or basal melt, is therefore crucial for accurate sea-level projections. Still, its current representation in ice-sheet models is the main source of uncertainty associated with the Antarctic contribution to global sea-level rise in climate projections.

An increasing amount of high-resolution ocean models are now able to resolve the circulation in the cavities below the ice shelves. However, running such models on multi-centennial scales or in a large ensemble is computationally expensive, especially when coupled with ice-sheet models. Instead, several parameterisations of varying complexity have been developed in past decades to describe the link between hydrographic properties in front of the ice shelf and basal melt rates. Previous studies have shown that the performance of these parameterisations depends on the ice shelf and that individual adjustments and corrections are needed for each ice shelf when applying them on the circum-Antarctic scale.

In this study, we assess the potential of a range of existing basal melt parameterisations to emulate basal melt rates simulated by a cavity-resolving ocean model on the circum-Antarctic scale, without regional adjustments. To do so, we re-tune the parameters of the different parameterisations using an ensemble of simulations from the ocean model NEMO as our reference. We find that the quadratic dependence of melt to thermal forcing and the plume parameterisation yield the best compromise, in terms of integrated shelf melt rates and spatial melt rate patterns. Parameterisations based on the box model, however, yield basal melt rates further from the reference. Additionally to the newly tuned parameters, we also provide uncertainty estimates for the tuned parameters, for applications in large ensembles.

How to cite: Burgard, C., Jourdain, N. C., Reese, R., Jenkins, A., and Mathiot, P.: Assessing basal melt parameterisations for Antarctic ice shelves using a cavity-resolving ocean model, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2773, https://doi.org/10.5194/egusphere-egu22-2773, 2022.

EGU22-4558 | Presentations | CR7.1

PARASO, a circum-Antarctic fully-coupled ice-sheet - ocean - sea-ice - atmosphere - land model involving f.ETISh1.7, NEMO3.6, LIM3.6, COSMO5.0 and CLM4.5 

Sylvain Marchi, Charles Pelletier, Thierry Fichefet, Hugues Goosse, Konstanze Haubner, Samuel Helsen, Pierre-Vincent Huot, Christoph Kittel, François Klein, Nicole P. M. van Lipzig, François Massonnet, Pierre Mathiot, Ehsan Moravveji, Eduardo Moreno-Chamarro, Pablo Ortega, Frank Pattyn, Niels Souverijns, Guillian Van Achter, Sam Vanden Broucke, Deborah Verfaillie, Sébastien Le Clech, Alexander Vanhulle, and Lars Zipf

How well is the Antarctic climate over the last decades represented in climate models and how predictable is its future evolution? These questions delve into the specificities of the Antarctic climate, a system characterized by large natural fluctuations and complex interactions between the ice sheet, ocean, sea ice and atmosphere. The PARAMOUR project aims at improving our understanding of key processes which control the variability and predictability of the Antarctic climate at the decadal timescale. In this context, we introduce PARASO, a novel fully-coupled regional ocean - sea-ice - ice-sheet - atmosphere climate model over an Antarctic circumpolar domain covering the full Southern Ocean. The state-of-the-art models used are f.ETISh1.7 (ice sheet), NEMO3.6 (ocean), LIM3.6 (sea ice), COSMO5.0 (atmosphere) and CLM4.5 (land), which are run at a horizontal resolution close to 1/4°. One key feature of this tool resides in a novel two-way coupling interface for representing the ocean - ice-sheet interactions, through explicitly resolved ice-shelf cavities. We also consider the impact of atmospheric processes on the Antarctic ice sheet through surface mass exchanges between COSMO-CLM and f.ETISh. Our developments include a new surface tiling approach to combine open-ocean and sea-ice covered cells within COSMO. Using a 30 year-long run, we investigate the model performance and the interannual-to-decadal variability of the simulated Antarctic climate. The focus is on the interactions between the atmosphere, ocean and ice components at the regional scale and the links with larger spatial scales. Specific attention is paid to the mass balance of ice sheets and ice shelves, which influences both the ice sheet dynamics and the changes in the ocean and atmosphere. The system and its performance will be documented in this presentation together with some aspects of decadal variability from a 30-year integration forced with reanalyses (ERA5 and ORAS5). Early results of a 3-member retrospective forecast driven by EC-Earth will also be presented.

How to cite: Marchi, S., Pelletier, C., Fichefet, T., Goosse, H., Haubner, K., Helsen, S., Huot, P.-V., Kittel, C., Klein, F., van Lipzig, N. P. M., Massonnet, F., Mathiot, P., Moravveji, E., Moreno-Chamarro, E., Ortega, P., Pattyn, F., Souverijns, N., Van Achter, G., Vanden Broucke, S., Verfaillie, D., Le Clech, S., Vanhulle, A., and Zipf, L.: PARASO, a circum-Antarctic fully-coupled ice-sheet - ocean - sea-ice - atmosphere - land model involving f.ETISh1.7, NEMO3.6, LIM3.6, COSMO5.0 and CLM4.5, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4558, https://doi.org/10.5194/egusphere-egu22-4558, 2022.

EGU22-4608 | Presentations | CR7.1

A comprehensive Earth System Model (AWI-ESM) with interactive ice sheets and icebergs: A step towards realistic freshwater fluxes for abrupt climate change scenarios 

Lars Ackermann, Thomas Rackow, Kai Himstedt, Paul Gierz, Gregor Knorr, and Gerrit Lohmann

Icebergs play a crucial role in Earth's climate system. They transport large amounts of fresh water and alter ocean salinity, affect sea-ice formation, and can lead to abrupt climate changes in the past. Hence, a proper representation of icebergs in Earth system models (ESMs) is essential to improve the understanding of processes involved in abrupt climate changes. Despite their importance, icebergs are rarely represented in ESMs. Freshwater fluxes are often parameterized, neglecting the transport via ocean currents and the heat loss due to iceberg melting. Other models that use an interactive iceberg component are typically ocean-only models, do not represent ice sheets and the atmospheric component explicitly, or are models of intermediate complexity. One reason for this deficiency is the considerable computational costs related to iceberg modeling.

Here, we present the latest version of the Alfred Wegener Institute-Earth System Model (AWI-ESM) with interactive ice sheets and a Lagrangian iceberg model. The iceberg component runs as a submodel of the ocean–sea-ice model FESOM2 with an asynchronous coupling to enable computationally effective simulations with the iceberg-enhanced coupled model. Total execution times can be strongly reduced compared to a non-overlapping execution of the iceberg model with other components. Iceberg meltwater and the associated heat fluxes are coupled to the ocean. The ice sheet is dynamically coupled to the climate components. A new feature of this model setup is the ice sheet-iceberg coupling: Icebergs are drawn from a specific size distribution to match the calving output of the ice sheet model in regions of iceberg discharge. Therefore, discharge-related freshwater fluxes are represented more realistically than in other ESMs.

How to cite: Ackermann, L., Rackow, T., Himstedt, K., Gierz, P., Knorr, G., and Lohmann, G.: A comprehensive Earth System Model (AWI-ESM) with interactive ice sheets and icebergs: A step towards realistic freshwater fluxes for abrupt climate change scenarios, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4608, https://doi.org/10.5194/egusphere-egu22-4608, 2022.

EGU22-9317 | Presentations | CR7.1

Changes on Aurora basin, East Antarctica, in coupled and uncoupled ice-ocean simulations 

Konstanze Haubner, Guillian Van Achter, Charles Pelletier, Lars Zipf, and Frank Pattyn

Ice mass loss on Greenland and Antarctica is a major contributor to sea level change and will thereby profoundly impact the world's infrastructure (e.g. transport, roads, ground water, housing) over the next decades. In order to react and adjust now accordingly, precise estimates of sea level change are needed. Though, future changes in sea level are provided by Earth system models, which rarely include ice sheet models, or by standalone ice sheet models. Hence, feedbacks between ice and atmosphere-ocean are overseen. Local scale coupled models can help bridging this gap by estimating how feedbacks between the different Earth systems affect global sea level estimates.

Here, we present results from a coupled simulation of the ocean-sea ice model NEMO3.6-LIM3 (1/24° grid ~ less than 2 km grid spacing) and the ice sheet model BISICLES (on 0.5-4km spatial resolution). The coupling routine is done via python code including variable exchange, pre- and postprocessing, done offline every 3 months, following the setup described in Pelletier et al., 2021.

Simulated ice mass changes, grounding line position and ice velocity changes of this high-resolution coupling scheme (between 1993-2014) are compared to observations and results of uncoupled simulations. We further discuss which processes might be neglectable and which are the main drivers of ice velocity acceleration and changes in sub-shelf ocean circulation.

 

Pelletier, C., Fichefet, T., Goosse, H., Haubner, K., Helsen, S., Huot, P.-V., Kittel, C., Klein, F., Le clec'h, S., van Lipzig, N. P. M., Marchi, S., Massonnet, F., Mathiot, P., Moravveji, E., Moreno-Chamarro, E., Ortega, P., Pattyn, F., Souverijns, N., Van Achter, G., Vanden Broucke, S., Vanhulle, A., Verfaillie, D., and Zipf, L.: PARASO, a circum-Antarctic fully-coupled ice-sheet - ocean - sea-ice - atmosphere - land model involving f.ETISh1.7, NEMO3.6, LIM3.6, COSMO5.0 and CLM4.5, Geosci. Model Dev. Discuss. [preprint], https://doi.org/10.5194/gmd-2021-315, in review, 2021.

How to cite: Haubner, K., Van Achter, G., Pelletier, C., Zipf, L., and Pattyn, F.: Changes on Aurora basin, East Antarctica, in coupled and uncoupled ice-ocean simulations, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9317, https://doi.org/10.5194/egusphere-egu22-9317, 2022.

EGU22-9710 | Presentations | CR7.1

Increased warm water intrusions would cause mass loss in East Antarctica within 200 years 

Jim Jordan, Hilmar Gudmundsson, Adrian Jenkins, Bertie Miles, Chris Stokes, and Stewart Jamieson

Increased warm water intrusions would cause mass loss in East Antarctica within 200 years

The East Antarctic Ice Sheet (EAIS) is the single largest potential contributor to future global mean sea level rise, containing 52.2 m of sea level equivalent. Current observations put the mass balance of the EAIS to be approximately stable (albeit with some margin of error), although future climatic conditions have the potential to change this. A warming climate is expected to have both a positive effect on ice sheet mass balance via increased precipitation and a negative effect via increased ice discharge over the grounding line, a process enhanced by ocean driven melting of floating ice reducing the buttressing effect of ice shelves. In addition to a general increase in the ocean temperature surrounding the EAIS there is the potential that future climatic shifts may increase the incidence of intrusions of warm Circumpolar Deep Water (CDW) onto the continental shelf, further increasing basal melting.

Here we show, by using a numerical ice-sheet model, simulations of the future EAIS under different  future climate scenarios, both with and without increased CDW intrusions. We find that without increased CDW intrusions the EAIS will have a negative contribution to sea level rise, with increased precipitation more than compensating increased ice discharge. If melting becomes predominately driven by CDW, however, our simulations find the EAIS to have a positive contribution to sea level rise. All simulations, both those with increased CDW forcing and those without, show an overall reduction in floating ice as well as a reduction in grounded ice area.

How to cite: Jordan, J., Gudmundsson, H., Jenkins, A., Miles, B., Stokes, C., and Jamieson, S.: Increased warm water intrusions would cause mass loss in East Antarctica within 200 years, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9710, https://doi.org/10.5194/egusphere-egu22-9710, 2022.

EGU22-10275 | Presentations | CR7.1

Accelerated oceanic forcing in coupled ice sheet-ocean modelling 

Qin Zhou, Chen Zhao, Rupert Gladstone, Tore Hattermann, David Gwyther, and Benjamin Galton-Fenzi

Coupled ice sheet - ocean models are increasingly being developed and applied to important questions pertaining to processes at the Greenland and Antarctic Ice Sheet margins, and the wider implications of such processes. In particular, ice sheet - ocean interactions have a strong control on ice sheet stability and sea level contribution. One of the challenges of such coupled modelling activities is the timescale discrepancy between ice and ocean dynamics, which, combined with the high cost of ocean models, can limit the timeframe that can be modelled. Here we present an "accelerated oceanic forcing'' approach to the ocean side of the coupling, in which the rates of change passed from ice model to ocean model components are increased by a constant factor and the period for which the  ocean model is run is correspondingly decreased. The ice sheet change over a coupling interval is thus compressed into  a shorter period over which the ocean model is run, based on the assumption that the ocean response time frame is shorter than  the compressed run period. We demonstrate the viability of this approach in an idealised setup based on the Marine Ice Sheet-Ocean Model Intercomparison Project, using the open-source Framework for Ice Sheet-Ocean Coupling (FISOC) combining two different ocean models (FVCOM and ROMS) and the ice-sheet model Elmer/Ice. We also demonstrate that the mean cavity residence time computed from the stand-alone ocean simulations can guide the selection of a suitable enhanced forcing factor for the coupled simulations. 

How to cite: Zhou, Q., Zhao, C., Gladstone, R., Hattermann, T., Gwyther, D., and Galton-Fenzi, B.: Accelerated oceanic forcing in coupled ice sheet-ocean modelling, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10275, https://doi.org/10.5194/egusphere-egu22-10275, 2022.

EGU22-10657 | Presentations | CR7.1

Validation of the North American Ice Service iceberg drift model using a novel database of in-situ iceberg drift observations 

Adam Garbo, Luke Copland, Derek Mueller, Adrienne Tivy, and Philippe Lamontagne

Icebergs calved from high-latitude glaciers and ice shelves pose a threat to vessels and offshore infrastructure at a time when Arctic shipping and offshore resource exploration are increasing. Knowledge of the location of potential ice hazards is therefore critical to ensure safe and efficient operations in this remote region. The Canadian Ice Service provides information to stakeholders on the observed and predicted distribution of icebergs in Canadian waters by combining iceberg observations with forecasts from the North American Ice Service (NAIS) iceberg drift model. The NAIS model estimates the forces acting on an iceberg to predict its future position and velocity and is widely used for the East Coast of Canada. However, the model is unproven for areas >60°N and suffers from insufficient validation due to a lack of reliable in-situ observations of iceberg drift. In this study, we use a newly compiled iceberg tracking beacon database to assess the skill of the NAIS iceberg model's predictions of iceberg drift and investigate sensitivity to morphology and environmental forcing (e.g., ocean currents, winds).

Hindcast simulations of the observed tracks of 44 icebergs over the period 2008-2019 were run using ocean currents from three ocean models (CECOM, GLORYS and RIOPS) and wind and wave inputs from the ERA5 reanalysis. Comparisons of several distance error metrics between observed and modelled drift tracks indicate that the NAIS model produces realistic simulations of iceberg drift in Baffin Bay. The root mean square error after the initial 24-hour hindcast period ranged from 18-22 km and increased at a daily rate of 11-13 km, which is comparable to operational forecasts elsewhere. Improved model performance was observed for longer (>250 m) and deeper-keeled (>100 m) icebergs, which appears to counteract the model’s tendency to overestimate drift by reducing the influence of stronger surface ocean currents acting on the iceberg. Ocean current direction, wind direction, and iceberg keel geometry were identified by a sensitivity analysis as the model parameters and environmental driving forces that have the greatest influence on modelled iceberg drift. These results emphasize the need for accurate environmental information and underscore the importance of properly representing the physical characteristics of icebergs in drift models.

How to cite: Garbo, A., Copland, L., Mueller, D., Tivy, A., and Lamontagne, P.: Validation of the North American Ice Service iceberg drift model using a novel database of in-situ iceberg drift observations, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10657, https://doi.org/10.5194/egusphere-egu22-10657, 2022.

EGU22-12129 | Presentations | CR7.1

Two-timescale response of the Filchner-Ronne Ice Shelf to climate change 

Kaitlin Naughten, Jan De Rydt, Sebastian Rosier, Adrian Jenkins, Paul Holland, and Jeff Ridley

A potentially irreversible threshold in Antarctic ice shelf melting would be crossed if the ocean cavity beneath the large Filchner-Ronne Ice Shelf were to become flooded with warm water from the deep ocean. Previous studies have identified this possibility, but there is great uncertainty as to how easily it could occur. Here, we show, using a coupled ice sheet-ocean model forced by climate change scenarios, that any increase in ice shelf melting is likely to be preceded by an extended period of reduced melting. Climate change weakens the circulation beneath the ice shelf, leading to colder water and reduced melting. Warm water begins to intrude into the cavity when global mean surface temperatures rise by approximately 7°C above pre-industrial, which is unlikely to occur this century. However, this result should not be considered evidence that the region is unconditionally stable. Unless global temperatures plateau, increased melting will eventually prevail.

How to cite: Naughten, K., De Rydt, J., Rosier, S., Jenkins, A., Holland, P., and Ridley, J.: Two-timescale response of the Filchner-Ronne Ice Shelf to climate change, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12129, https://doi.org/10.5194/egusphere-egu22-12129, 2022.

EGU22-12248 | Presentations | CR7.1

Coupled ice-ocean modelling of the Amundsen Sea glaciers 

Jan De Rydt and Kaitlin Naughten

Glaciers in the Pacific sector of West Antarctica are losing mass at an accelerating rate. Superimposed on this long-term trend are interannual variations in mass balance that result from a combination of internal ice dynamics and variability in ocean-induced ice shelf melt rates. We explore the relative importance of these internal and external drivers of change, using a newly developed coupling between the 3D ocean model MITgcm, and the SSA ice flow model Úa. For present-day ocean conditions, we simulate persistent retreat of the Pine Island, Thwaites, Smith and Kohler grounding lines between 2020 and 2150. We demonstrate complex changes in ice shelf melt rates caused by the evolving cavity geometries.

How to cite: De Rydt, J. and Naughten, K.: Coupled ice-ocean modelling of the Amundsen Sea glaciers, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12248, https://doi.org/10.5194/egusphere-egu22-12248, 2022.

EGU22-13099 | Presentations | CR7.1

Modelling the thermal and mechanical interaction of an ice-sheet with a partly frozen bedrock 

Thomas Zwinger, Denis Cohen, Rupert Gladstone, and Peter Råback

In recent years, subglacial hydrological models as well as till deformation models have been coupled to ice-flow models in order to determine mechanical basal conditions underneath ice sheets and glaciers. These models, nevertheless, often ignore the thermo-dynamical aspects, in particular, not including the influence of permafrost in proximity to or underneath glaciers. Here we present a thermo-mechanically coupled ice-sheet bedrock model. The latter includes components of saturated aquifer water transport, soil deformation, salinity transport and – most important – energy balance including phase change of the solvent. Using synthetic flow-line setups we present studies of ice-sheet fronts, advancing either over existing permafrost or largely unfrozen soils. We investigate the heat- and meltwater-transfer between the ice-body and its substrate and discuss their impact on ice-dynamics. As the results suggest that in certain situations the water balance further demands the existence of a hydrological system between ice and bedrock, we currently work to include this third model component in form of a subglacial hydrological model. All model components are implemented in the Finite Element software Elmer, which renders their mutual coupling relatively easy, yet, numerically demanding.

How to cite: Zwinger, T., Cohen, D., Gladstone, R., and Råback, P.: Modelling the thermal and mechanical interaction of an ice-sheet with a partly frozen bedrock, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13099, https://doi.org/10.5194/egusphere-egu22-13099, 2022.

EGU22-297 | Presentations | CR7.2

Sea ice thickness and production in Weddell Sea polynyas 

Lu Zhou, Céline Heuzé, and Martin Mohrmann

Open-ocean and coastal polynyas, the result of high-latitude atmosphere-ocean circulation interannual variability, alter the local air-ocean heat exchange and sea ice production. Yet, the role of the ocean, especially its thermal flux, is rarely discussed. Here we examine the surface heat budget and sea ice changes during open-ocean and coastal polynya events in the Weddell Sea using satellite retrievals, in-situ observations, and the Japanese 55-year Reanalysis (JRA55). We find that the oceanic heat flux amounts to about 57.5±4 and 39±3 W/m2 within the 2016 and 2017 polynyas events, respectively; including these values in sea ice thickness. parameterizations significantly reduced their biases. Moreover, we compare sea ice mass productions within coastal and open-ocean polynyas using three methods. The results suggest that more ice production, albeit thinner ice thickness, occurs within the open-ocean than the coastal polynya. Finally, we find that wind and air temperature directly play a crucial role in controlling sea ice production in open-ocean polynyas, and undirectly via their impact on the polynya extent for coastal polynyas. The presence of wide open-ocean polynya does appear to reduce this influences on the ice production within the coastal polynya.

How to cite: Zhou, L., Heuzé, C., and Mohrmann, M.: Sea ice thickness and production in Weddell Sea polynyas, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-297, https://doi.org/10.5194/egusphere-egu22-297, 2022.

EGU22-2873 | Presentations | CR7.2

Clouds increase uncertainty in surface melt projections over the Antarctic ice shelves 

Christoph Kittel, Charles Amory, Stefan Hofer, Cécile Agosta, Nicolas C. Jourdain, Ella Gilbert, Louis Le Toumelin, Etienne Vignon, Hubert Gallée, and Xavier Fettweis

Recent warm atmospheric conditions have damaged the ice shelves of the Antarctic Peninsula through surface melt and hydrofracturing, and could potentially initiate future collapse of other Antarctic ice shelves. However, model projections with similar greenhouse gas scenarios suggest large differences in cumulative 21st century surface melting. So far it remains unclear whether these differences are due to variations in warming rates in individual models, or whether local surface energy budget feedbacks could also play a notable role. Here we use the polar-oriented regional climate model MAR to study the physical mechanisms that will control future surface melt over the Antarctic ice shelves in high-emission scenarios RCP8.5 and SSP585. We show that clouds enhance future surface melt by increasing the atmospheric emissivity and longwave radiation towards the surface. Furthermore, we highlight that differences in meltwater production for the same climate warming rate depend on cloud properties and particularly cloud phase. Clouds containing a larger amount of liquid water lead to stronger melt, subsequently favouring the absorption of solar radiation due to the snow-melt-albedo feedback. Since liquid-containing clouds are projected to increase the melt spread associated with a given warming rate, they could be a major source of uncertainties related to the future Antarctic contribution to sea level rise.

How to cite: Kittel, C., Amory, C., Hofer, S., Agosta, C., Jourdain, N. C., Gilbert, E., Le Toumelin, L., Vignon, E., Gallée, H., and Fettweis, X.: Clouds increase uncertainty in surface melt projections over the Antarctic ice shelves, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2873, https://doi.org/10.5194/egusphere-egu22-2873, 2022.

EGU22-4757 | Presentations | CR7.2

Orographic Flow Influence on Precipitation During an Atmospheric River Event at Davis, Antarctica 

Josué Gehring, Etienne Vignon, Anne-Claire Billault--Roux, Alfonso Ferrone, Alain Protat, Simon P. Alexander, and Alexis Berne

Snowfall in Antarctica is the main input to ice sheet mass balance, which is heavily influenced by the frequency and intensity of maritime moisture intrusions from lower latitudes. The most intense moisture incursions often occur as narrow corridors of enhanced vapor transport, called atmospheric rivers (ARs). However, the fate of ARs depends on the state of the coastal boundary layer. For instance, katabatic or foehn winds can lead to a subsaturated boundary layer, which can cause total snowfall sublimation. In this study, we use recent data collected during the Precipitation over Land And The Southern Ocean (PLATO) campaign to investigate how the synoptic evolution and the local orography influenced the sublimation of snowfall during an AR event (08 – 10 January 2019) at Davis, East Antarctica. The dataset includes scanning polarimetric and vertically pointing Doppler radar, radiosounding, and Raman lidar measurements. We also make use of simulations from the Weather Research and Forecasting (WRF) model. Our analysis revealed that orographic gravity waves (OGWs), generated by a north-easterly flow impinging on the ice ridge upstream of Davis, were responsible for snowfall sublimation through a foehn effect. Despite the strong meridional moisture advection associated with the AR during this event, almost no precipitation reached the ground at Davis. We found that the direction of the synoptic flow with respect to the orography determined the intensity of OGWs over Davis, which in turn directly influenced the snowfall microphysics. We hypothesize that turbulence induced by the OGWs likely enhanced the aggregation process, as identified thanks to dual-polarization and dual-frequency radar observations. This study suggests that despite the intense AR, the snowfall distribution was determined by local processes tied to the orography. It also stresses the importance of studying local effects when interpreting the impact of ARs on the Antarctic surface masse balance. Finally, the mechanisms found in this case study could contribute to the extremely dry climate of the Vestfold Hills, one of the main Antarctic oases.

How to cite: Gehring, J., Vignon, E., Billault--Roux, A.-C., Ferrone, A., Protat, A., Alexander, S. P., and Berne, A.: Orographic Flow Influence on Precipitation During an Atmospheric River Event at Davis, Antarctica, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4757, https://doi.org/10.5194/egusphere-egu22-4757, 2022.

EGU22-5316 | Presentations | CR7.2

Boundary layer dependence of atmosphere-ocean coupling in operational weather forecast models over the marginal ice zone 

Ambrogio Volonté, John Methven, Suzanne L. Gray, Ben Harvey, and Oscar Martínez-Alvarado

Arctic cyclones are the dominant type of hazardous weather system affecting the Arctic environment in summer. They can also have critical impacts on sea-ice movement, sometimes resulting in ‘Very Rapid Ice Loss Events’ which present a major challenge to coupled forecasts of the Arctic environment from days out to a season ahead. In late summer the marginal ice zone is extensive and wind forcing can move the ice readily; in turn, the dynamic sea ice distribution is expected to feedback on the developing weather systems.

In summer 2022, in concert with ONR-THINICE, we aim to fly two research aircraft from Svalbard into Arctic cyclones passing over the marginal ice zone. We will measure the turbulent exchange fluxes, flying low above the interface between atmosphere and ice, at the same time as measuring the wind and cloud structure of the cyclones above and the properties of the ice below. Combining the observations with numerical modelling experiments using the Met Office NWP model, we aim to deduce the dominant physical processes acting and test theoretical mechanisms for the influence of sea ice on Arctic cyclone dynamics, with a particular focus on form drag and momentum exchange in the boundary layer.

Met Office and ECMWF forecasts that are coupled, or uncoupled, with a dynamic sea ice distribution have been investigated initially for systematic differences in the representation of boundary layer and surface fluxes, composited relative to the warm and cold sectors of Arctic cyclones and conditional on the surface beneath (ice, ocean, land). One of the key differences outlined resides in the increased strength of surface (10m) winds over ice, including marginal ice, in coupled Met Office forecasts when compared against their uncoupled counterparts. Initial analysis links this discrepancy with a difference in the degree of stability of the boundary layer. A more stable profile is observed in the coupled forecasts, associated with lower temperature at 1.5m and smaller wind rotation with height. These findings help us to focus the objectives of the research flights and measurements and, in consequence, inform the flight and observation plans for the field experiment.

How to cite: Volonté, A., Methven, J., Gray, S. L., Harvey, B., and Martínez-Alvarado, O.: Boundary layer dependence of atmosphere-ocean coupling in operational weather forecast models over the marginal ice zone, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5316, https://doi.org/10.5194/egusphere-egu22-5316, 2022.

Measurements of precipitation in inland Antarctica are scarce, with estimates often derived by indirect means. This scarcity contrasts with the importance of snowfall, which constitutes, together with water vapor deposition, the main water mass input to the Antarctic ice sheet.

During the austral summer 2019-2020, a transect of three vertically-pointing K-band Doppler radars (MRR-PRO) was deployed across the Sør Rondane Mountains, directly south of Princess Elisabeth Antarctica (PEA). The instruments have been placed at different stages of the interaction between the typical flow of the precipitation systems and the orography. A vertically-pointing W-band Doppler cloud radar was also deployed at the base.

Using the data collected by these four radars, alongside information derived from the ERA5 reanalysis and a set of high-resolution WRF simulations covering the previous three years, we investigated the behavior of precipitation across the transect.

A significant difference in the proportion of virga and precipitation has been observed between the three locations. One of the three MRR-PRO was deployed in a valley, connecting the plateau to the lower plains, at the lowest elevation among the radars in the transect. At this location we observed the highest amount of virga. This behavior is consistent with the presence of a thick dry layer, whose height has been estimated to approximately 1.2 km above the level of PEA. Its existence was noticed in both the reanalysis and the simulations, and the reflectivity factor recorded by the cloud profiling radar decreases with height for most of the layer.

The other two MRR-PRO were deployed at higher altitudes, and both of them recorded a lower fraction of virga. We hypothetize that the higher elevation implies a shorter time spent by precipitating particles in the dry layer, limiting the sublimation of hydrometeors. However, despite being at a slightly lower elevation than the MRR-PRO on the plateau, the MRR-PRO installed amid the mountains recorded precipitation reaching the ground for a higher amount of time steps. This may be caused by the localized precipitation systems frequently observed near the top of the mountains south of PEA.

This study shows that complex terrain in the vicinity of PEA increases the variability in precipitation occurrence, depending on the relative position with respect to the incoming flow and to the dry katabatic layer. This variability questions the representativity of measurements collected at a few stations in the mountainous regions of Antarctica.

How to cite: Ferrone, A. and Berne, A.: Summer snowfall in the Sør Rondane Mountains, Antarctica: characterization using a transect of K-band Doppler profilers, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5553, https://doi.org/10.5194/egusphere-egu22-5553, 2022.

EGU22-6051 | Presentations | CR7.2

Antarctic Atmospheric River Life Cycles 

Jonathan Wille, Vincent Favier, Christoph Kittel, Benjamin Pohl, Steven Cavallo, Christophe Leroy dos Santos, and Irina V. Gorodetskaya

The mass balance of Antarctica is sensitive to intrusions of extremely warm, moist airmasses from the mid-latitudes in the form of atmospheric rivers (ARs). These storms provide a sub-tropical link to the Antarctic continent and engender extreme atmospheric conditions that are largely consequential to surface melt, snowfall, and ice-shelf stability. Using an AR detection algorithm designed for polar regions, we characterize the AR life cycle and describe the atmospheric conditions conducive for ARs to reach the Antarctic continent.

Despite their rarity of occurrence over Antarctica (maximum frequency of ~3 days per year over a given point), ARs have a relatively large impact on the surface melt processes in West Antarctica and snowfall patterns across the whole continent. During the summer season along the Antarctic Peninsula ice shelves, AR landfalls lead to conditions (i.e. extreme temperatures, rainfall, surface melt, sea-ice clearing, ocean swell enhancement), that act to destabilize the leeward ice shelves. Current research is exploring the origins of AR genesis and moisture pathways with a focus on the relationship between atmospheric blocking in the Southern Ocean and AR behavior over East Antarctica.

When examining the life cycles of ARs and non-AR synoptic analogues occurring at Dumont d’Urville (DDU) Station, Antarctica, the AR events often have moisture sources further north in the Southern Ocean than the non-AR analogues. These more northern moisture sources correspond with enhanced latent heat release over anomalously warm sea surface temperatures in northern regions of the Southern Ocean which trigger Rossby wave propagation that enhances upper-level potential vorticity. A highly amplified wave pattern allows for intense poleward moisture transport towards DDU and downstream ridging from the AR position. Thus, any future changes in atmospheric blocking or tropical-polar teleconnections, which control AR behavior around Antarctica, along with further global warming, may have significant impacts on future mass balance projections and subsequent sea level changes.

How to cite: Wille, J., Favier, V., Kittel, C., Pohl, B., Cavallo, S., Leroy dos Santos, C., and V. Gorodetskaya, I.: Antarctic Atmospheric River Life Cycles, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6051, https://doi.org/10.5194/egusphere-egu22-6051, 2022.

EGU22-6289 | Presentations | CR7.2

Drivers of changes in the permafrost late shoulder season 

Cécile Osy, François Massonnet, and Sophie Opfergelt

The Arctic has been warming two to four times more rapidly than the global mean in the last decades – a phenomenon known as Arctic Amplification. This warming induces changes for the whole cryosphere, including the permafrost. A first-order marker of permafrost health is the timing of snowfall compared to the timing of the freezing of the upper soil layer, which together determine the length of its late shoulder season. The late shoulder season of permafrost is the period after plant senescence and before the freezing of the active layer of the permafrost. Its length depends on the air temperature, but also on the timing of snowfall. The snow insulates the ground from the atmosphere, and snow cover will delay the freezing of the ground if it falls before the air temperature drops below freezing point. On the other hand, if the snowfall occurs after the ground freezing, it is expected that the freezing will be more persistent and will reach deeper soil layers more rapidly.

There is to date no large-scale view of the late shoulder season characteristics in the Arctic permafrost regions and how this shoulder season is evolving in a warming Arctic. Here, a study of the temporal variability of the late shoulder season of the permafrost is proposed. To that end, the temporality of the first relevant snowfall and freeze of the top layer of the ground is studied from 1950 to 2020 in the ERA5-Land reanalysis. The temporal trends will be spatialized to account for the spatial heterogeneity of the study area, and to study which variables other than the snow (vegetation, topography, …) influence the length of the shoulder season. The surface pressure and atmospheric circulation in the ERA5 reanalysis is also looked at to explain punctual extreme events and interannual trends..

How to cite: Osy, C., Massonnet, F., and Opfergelt, S.: Drivers of changes in the permafrost late shoulder season, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6289, https://doi.org/10.5194/egusphere-egu22-6289, 2022.

EGU22-8386 | Presentations | CR7.2

Regional differences in cyclone impacts on Arctic sea ice concentration during winter 

Lars Aue, Mirseid Akperov, Petteri Uotila, Timo Vihma, and Annette Rinke

Cyclone events in the Arctic strongly affect both atmospheric variables, such as wind, air temperature and clouds, and surface variables, including sea ice concentration (SIC) and turbulent heat fluxes. However, despite the progress via recent statistical studies, the overall impact of cyclones on Arctic weather, sea ice, and feedback processes between them is not quantitatively well known.

In this study we built up on previous publications and present further details on cyclone impacts on Arctic sea ice in winter by covering a wider range of timescales than before and evaluating our results separately for three different marginal seas of the Arctic Ocean. Hereby we make use of the ERA5 reanalysis and a storm tracking algorithm to analyze the temporal evolution of SIC up to two weeks around the occurrence of each cyclone and compare it with a non-cyclone reference state.

The results show an initial decrease in SIC associated with the occurrence of a cyclone for the Barents and Kara Seas, which is balanced by an increase during the following days. On the contrary, in the Greenland Sea SIC remains lower after a cyclone event for the whole analyzed time period. For all the marginal seas considered, the impact of cyclones on sea ice is intensified, if SIC at a grid cell is low and if the intensity of a cyclone is high. Ongoing work consists of providing more details about the mechanisms responsible for the identified regional differences in cyclone influence on sea ice.

How to cite: Aue, L., Akperov, M., Uotila, P., Vihma, T., and Rinke, A.: Regional differences in cyclone impacts on Arctic sea ice concentration during winter, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8386, https://doi.org/10.5194/egusphere-egu22-8386, 2022.

EGU22-8466 | Presentations | CR7.2

Climatology of sea ice changes attributed to cyclones, fronts, and cold-air outbreaks 

Franziska Weyland, Clemens Spensberger, and Thomas Spengler

Rapid changes in the sea ice cover are commonly attributed to periods of strong winds, which in turn are often associated with cyclones and their fronts. In addition to geographically redistributing sea ice, and thereby potentially increasing its export from the Arctic, cyclones also transport moist warm air masses into the Arctic which can lead to local sea ice melt while the cyclone’s cold sector might lead to freezing and sea ice formation. Furthermore, cold air outbreaks associated with the withdrawal of cold air masses over the open ocean usually lead to sea-ice formation. The relative contribution of these competing effects of weather events on the sea ice is so far poorly understood.

We climatologically assess these competing effects of cyclones on sea ice using detected cyclones, fronts, and cold-air outbreaks in the coupled ECMWF CERA-SAT reanalyses. We then decompose the climatological sea-ice increases and decreases during the different seasons into the components that occur in the vicinity or at larger distance from the different weather events. Preliminary results indicate that the amplitude of both positive and negative sea ice changes increases around cyclones, with an overall net effect of reducing sea-ice concentration during most seasons. Thus, the effect of the wind and warm intrusions within cyclones dominates over the effect of the cyclone’s cold sector. In contrast, cold-air outbreaks are associated with sea-ice growth at any time of the year, but exhibit a clear seasonality in their frequency of occurrence.

How to cite: Weyland, F., Spensberger, C., and Spengler, T.: Climatology of sea ice changes attributed to cyclones, fronts, and cold-air outbreaks, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8466, https://doi.org/10.5194/egusphere-egu22-8466, 2022.

EGU22-9082 | Presentations | CR7.2

Drivers of surface winds variability in Antarctica 

Cécile Davrinche, Cécile Agosta, Charles Amory, Christoph Kittel, and Anaïs Orsi

Surface winds in Antarctica are amongst the strongest and most persistent winds on Earth. They play a key role in defining the surface climate.
While new proxys are being developed in order to understand their past evolution, it is a crucial to understand the processes controlling their temporal variability. 

Here, we investigate the drivers of surface winds variability in East Antarctica at present-day. To do so, we separate the wind-speed temporal variations from daily outputs of the regional atmospheric model MAR at 35 km resolution into different terms of the dynamic equations.
 Our study focuses on a transect running through Adelie Land, where numerous meteorological measurements are being conducted.  
 
We identify the combination of terms that correlates best in winter to the wind speed in this region.
On the Antarctic plateau, wind speed is controlled by the balance between large-scale pressure gradient acceleration and turbulence.
At mid-slope, the katabatic term is the greatest but does not correlate with wind-speed. One of the reason that explains this result is that increasing positive katabatic forcing is counteracted by increasing turbulence (negative term, deceleration effect). Consequently, the combination of the turbulence and katabatic terms correlates slightly better to wind-speed intensity.

At the coast, wind-speed intensity mainly results from the katabatic and thermal wind terms. 


As a conclusion, the study of a smaller number of contribution terms in the budget equation will help evaluating the drivers of past and future evolution of wind speed in this region.

How to cite: Davrinche, C., Agosta, C., Amory, C., Kittel, C., and Orsi, A.: Drivers of surface winds variability in Antarctica, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9082, https://doi.org/10.5194/egusphere-egu22-9082, 2022.

EGU22-9423 | Presentations | CR7.2

The Polar Regions in the Earth System (PolarRES) project 

Priscilla Mooney

Polar climates in a global context remain poorly understood, as does the interactions between the different components of the Polar climate system. These knowledge gaps are leading to large uncertainties in climate change projections for the Polar regions, which hampers mitigation and adaptation efforts. PolarRES, a new project funded by the European Commission under the Horizon 2020 programme, will address these knowledge gaps in the coming years. The PolarRES consortium consists of more than 50 researchers from 21 different institutions from around the world and began in September 2021. The project will zoom into the climate of both Polar regions at unprecedented resolutions with state-of-the-art regional climate models (RCMs) that will be blended with a comprehensive range of existing and novel ground-based observations (for example from the Year Of Polar Prediction (YOPP) and the MOSAiC expedition) and satellite data  (e.g. ESA Earth Observation Programme) to close knowledge gaps on 1) the atmosphere-ocean-sea ice coupled system, 2) the influence of future changes in the global circulation system on the polar climate, and 3) the influence of the polar regions on the global climate system. In doing so, PolarRES will provide novel, more confident, regional climate projections of the polar regions for impact assessments. This work is being undertaken in a multidisciplinary framework that brings together climate and impact modelers to ensure that climate change projections for both Polar regions are impact relevant. This talk will introduce the PolarRES project (https://polarres.eu), progress to date, and the innovative approaches that will be used in the project.

How to cite: Mooney, P.: The Polar Regions in the Earth System (PolarRES) project, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9423, https://doi.org/10.5194/egusphere-egu22-9423, 2022.

EGU22-11853 | Presentations | CR7.2

Parametrizing drifting snow sublimation in the saltation layer 

Armin Sigmund, Varun Sharma, Daniela Brito Melo, Francesco Comola, Jérôme Dujardin, Franziska Gerber, Hendrik Huwald, and Michael Lehning

Modelling the surface mass balance of Antarctica and snow and ice surfaces in general is challenging, yet it is important for making reliable projections of sea level rise. One of the terms with the largest uncertainties is sublimation (and vapor deposition) of drifting and blowing snow. Large-scale atmospheric models strongly simplify or completely neglect the underlying physical processes. In particular, they do not resolve the vertical profiles of particle concentration and sublimation in the saltation layer, corresponding roughly to the lowest 10 cm of the atmosphere. However, small-scale studies based on large-eddy simulations (LES) demonstrate that most of the sublimation of drifting and blowing snow can take place in the saltation layer, at least for shallow layers of drifting snow. As these events occur very frequently, current large-scale models may strongly underestimate snow sublimation. Even in deep blowing snow layers, the saltation layer may be relevant for the overall moisture exchange because strong vapor deposition may occur in an oversaturated layer with a high particle concentration close to the surface. The goals of this study are to (i) propose a parametrization for sublimation of drifting snow in the saltation layer and (ii) evaluate two parametrization options using LES simulations as a reference. The simulations reproduce four situations with different weather conditions measured at the Syowa and Davis Stations, Antarctica. We focus on a suitable parametrization of air temperature, humidity, and sublimation, not yet the representation of the drifting snow concentration. We implement our parametrization in a simple one-dimensional (1D) model that is inspired by the large-scale model CRYOWRF and can be compared to the LES simulations. The 1D model computes temperature and specific humidity at ten vertical levels between the surface and a height of 9 m, of which six levels are in the lowest 0.1 m. The first option uses a prognostic solver at all levels, accounting for turbulent transport and the exchange of moisture and heat between snow particles and the atmosphere. The second, simpler option, uses Monin-Obukhov bulk formulas to estimate the profiles below a height of 2.25 m. The concentrations of drifting and blowing snow are taken from the LES simulations and assumed to remain constant in time. The parametrization computes sublimation of drifting snow using the common formula of Thorpe and Mason (1966). On the contrary, the LES model applies a more accurate approach based on the transient mass and heat balance equations for Lagrangian particles. Only the lowest 9 m of the LES domain (38 x 19 x 18 m³) are used for comparison with the 1D model to limit undesirable effects of the Neumann upper boundary conditions. The prognostic parametrization option yields satisfactory results, while the bulk formulas can lead to a significant bias. We show how the 1D model performs in different weather conditions and discuss the benefits and remaining challenges of the parametrization.

How to cite: Sigmund, A., Sharma, V., Melo, D. B., Comola, F., Dujardin, J., Gerber, F., Huwald, H., and Lehning, M.: Parametrizing drifting snow sublimation in the saltation layer, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11853, https://doi.org/10.5194/egusphere-egu22-11853, 2022.

EGU22-11895 | Presentations | CR7.2 | Highlight

Atmospheric drivers of Greenland ice sheet surface energy and mass balance changes as a function of elevation and circulation patterns 

Tiago Silva, Jakob Abermann, Brice Noël, Sonika Shahi, Jorrit van der Schot, and Wolfgang Schöner

Recent Greenland Ice Sheet (GrIS) surface mass loss has been attributed to the expansion of the bare ice area following the upward migration of the snowline along with persistent blocking systems. Given the temporal fluctuations and spatial heterogeneity of the ablation zone, the local impacts of atmospheric drivers on the GrIS surface energy and mass balance at different elevations and under various atmospheric circulation patterns remain poorly known.

Based on the 1959-2020 period, we present a new indicator of the North Atlantic influence over Greenland (NAG) as the combination of the North Atlantic Oscillation Index (NAO), the Greenland Blocking Index (GBI) and the vertically integrated water vapor over the GrIS. We explore the NAG monthly frequency and the inter-annual evolution along with large-scale spatial anomalies. With the support of a high-resolution regional climate model (RACMO2.3p2), we investigate the influence of spatio-temporal NAG fluctuations on atmospheric drivers, surface energy and mass balance fluxes, that triggered the expansion of the ablation zone to higher elevations. Finally, we assess NAG performance by comparing its results with NAO and GBI alone.

How to cite: Silva, T., Abermann, J., Noël, B., Shahi, S., van der Schot, J., and Schöner, W.: Atmospheric drivers of Greenland ice sheet surface energy and mass balance changes as a function of elevation and circulation patterns, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11895, https://doi.org/10.5194/egusphere-egu22-11895, 2022.

EGU22-13312 | Presentations | CR7.2

Atmospheric response to reduced Antarctic sea ice drives ice sheet mass and energy flux anomalies 

Luke Trusel, Jessica Kromer, and Jan Lenaerts

The mass balance of the Antarctic ice sheet is intricately linked to the state of the atmosphere and ocean surrounding the continent. As a direct result, improving projections of future sea level change relies on understanding change in the Antarctic atmosphere and Southern Ocean, as well as the processes that couple these systems. Here, we explore the influence of sea ice cover on the overlying atmosphere and subsequently the energy and mass budgets of the adjacent Antarctic ice sheet. We investigate these processes using simulations of the Community Earth System Model 2 (CESM2) developed as part of the Polar Amplification Model Intercomparison Project (PAMIP). Specifically, we explore an ensemble of atmosphere-only time slice experiments where the sea ice cover is altered. Results highlight atmospheric warming in all seasons in response to sea ice loss, but particularly pronounced warming at the surface and during non-summer seasons. Sea ice reductions further drive positive anomalies in atmospheric moisture and liquid-bearing clouds, resulting in both enhanced precipitation and downward longwave radiative fluxes over the ice sheet, particularly in West Antarctica. We furthermore explore the impact of sea ice loss on primary modes of atmospheric variability, including the Amundsen Sea low and Southern Annular Mode. These results highlight the potential impact and importance of proper simulation of the Southern Ocean sea ice cover for determining the surface mass balance of the adjacent Antarctic ice sheet. Given that the current generation of coupled climate models struggle with representing observed sea ice dynamics, our results indicate this may likely contribute to uncertainties in the simulation of recent and future Antarctic ice sheet mass balance.

How to cite: Trusel, L., Kromer, J., and Lenaerts, J.: Atmospheric response to reduced Antarctic sea ice drives ice sheet mass and energy flux anomalies, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13312, https://doi.org/10.5194/egusphere-egu22-13312, 2022.

EGU22-13313 | Presentations | CR7.2

Moisture Budget Closure of Arctic Atmospheric Rivers from Saw-Tooth Flight Pattern – A Feasibility Study in High-Resolution Model Data 

Henning Dorff, Heike Konow, Vera Schemann, and Felix Ament

This study investigates in a synthetic way to what extent saw-tooth flight patterns from long-range research aircrafts can close the moisture budget of arctic atmospheric rivers (ARs). Such ARs dominate the moisture transport into the Arctic. The analysis of the moisture budget in AR corridors is key to understand the spatiotemporal AR evolution, resulting air mass transformations along their pathway and precipitation efficiency of ARs. However, the determination of moisture budget components in arctic ARs is challenging due to sparse observations. Dedicated research flight campaigns require the quantification of divergence of integral water vapour transport (IVT) using dropsondes along AR cross sections and remote sensing capturing internal water vapour load and precipitation rate. However, limited number of dropsondes and curtain-restricted remote sensing may deteriorate the AR moisture budget. Uncertainties in airborne representation of AR moisture components have to be assessed. We consider seven arctic ARs from spring season of last decade. They cover pathways over the North Atlantic and Siberia and a broad range of AR conditions representative for the Arctic. To assess airborne budget closure capabilities, we include outputs from the new C3S Arctic Regional Reanalysis (CARRA) and simulations from an adapted ICON model configuration. Both have a horizontal resolution of around 2.5 km and deliver reasonable AR representation with high spatial variability in moisture budget components. By generating synthetic flights and mirroring airborne observations (e.g. dropsondes) in both gridded datasets, we identify major sources of error that arise in the airborne quantification of IVT variability. We determine the representativeness of total precipitation and hydrometeor content derived from diagonal legs for entire AR sectors. For all ARs, levels where specific humidity and wind speed contribute most to IVT are located below 1500 m. Along horizontal AR transects, maximum IVT values and highest lateral IVT variability are located around low-level jets. Frequent soundings near the low-level jet are fundamental to lower uncertainties in moisture flux convergence that dominate against other budget terms. In CARRA, having less than six soundings within the AR cross-section causes biases of total IVT by more than 10 %. Samples along diagonal flight legs through AR sectors can reproduce mean internal precipitation rate, whereas the statistical distribution of hydrometeor contents for the entire sector differs due to the complex cold-front composition near the AR. Evaporation shows minor budget contributions in arctic ARs. While moisture convergence uncertainties are highest close to the AR centre, uncertainty of precipitation rate increases in the AR outflow region. Moreover, we give first insights on very preliminary observations from the HALO-(AC)³ flight campaign in March and April, 2022.

How to cite: Dorff, H., Konow, H., Schemann, V., and Ament, F.: Moisture Budget Closure of Arctic Atmospheric Rivers from Saw-Tooth Flight Pattern – A Feasibility Study in High-Resolution Model Data, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13313, https://doi.org/10.5194/egusphere-egu22-13313, 2022.

EGU22-13314 | Presentations | CR7.2

Synoptic Drivers of Landfalling Atmospheric Rivers Near Dronning Maud Land, Antarctica 

Rebecca Baiman, Andrew Winters, and Jan Lenaerts

Atmospheric rivers (ARs) that reach the Antarctic Ice Sheet (AIS) transport anomalous moisture from lower latitudes and can impact the AIS via extreme precipitation and increased downward longwave radiation. ARs contribute significantly to the interannual variability of precipitation over the AIS and thus are likely to play a key role in understanding future changes in the surface mass balance of the AIS. While ARs impact the entire coastal AIS, coastal Dronning Maud Land (DML) is one of four East Antarctic maxima in AR frequency. Along with the high frequency of ARs, the variability of large-scale flow patterns associated with ARs around DML motivates further investigation of synoptic regimes favoring ARs in this region.

 

This study utilizes a self-organizing map (SOM) to identify synoptic-scale regimes associated with landfalling ARs in and near DML. The catalogue of ARs used in this research is output from a detection algorithm developed specifically for Antarctic ARs, and AR landfalls are identified at timesteps in which an AR overlaps with the AIS between 30°W and 30°E. To determine synoptic regimes conducive to AR landfall, sea level pressure anomalies between 60°W and 60°E from MERRA-2 at the time of AR landfalls are used to train a 16 node SOM. Analysis of precipitation attributable to each SOM node reveals three out of the 16 synoptic regimes are responsible for 28% of the AR precipitation despite representing only 24% of the AR timesteps. Subsequent analysis of this SOM will provide insight into the synoptic drivers and thermodynamic characteristics of the synoptic regimes conducive to the most impactful ARs in the region.

How to cite: Baiman, R., Winters, A., and Lenaerts, J.: Synoptic Drivers of Landfalling Atmospheric Rivers Near Dronning Maud Land, Antarctica, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13314, https://doi.org/10.5194/egusphere-egu22-13314, 2022.

EGU22-13315 | Presentations | CR7.2 | Highlight

Climatology of West Antarctic Atmospheric Rivers and their Impacts on Surface Mass Balance 

Michelle Maclennan and Jan Lenaerts

Authors:

Michelle L. Maclennan, Jan T. M. Lenaerts, Christine A. Shields, Andrew O. Hoffman, Nander Wever, Megan Thompson-Munson, Erin C. Pettit, Theodore A. Scambos, and Jonathan D. Wille.

While Antarctic Ice Sheet (AIS) mass loss is dominated by accelerated ice discharge from the West Antarctic Ice Sheet (WAIS) due to ocean-induced basal melting, surface mass balance (SMB) processes return mass to the WAIS through snowfall. On Thwaites Glacier (TG) in West Antarctica, snowfall is the primary driver for SMB (125 ± 16 Gt snowfall per year), and extreme snowfall events contribute more than 60% of the total snowfall over TG ice shelf, and 30-50% of the total snowfall over grounded TG. Many of these extreme snowfall events are associated with the landfall of atmospheric rivers (ARs). ARs are long, narrow bands of warm and moist air that contribute intense precipitation and surface melting on the AIS, meaning they contribute both positively and negatively to the SMB. Here, we use an Antarctic-specific AR detection tool combined with MERRA-2 and ERA5 reanalyses to develop a climatology of AR events that made landfall over TG and the WAIS from 1980-2020, including their frequency and duration. We quantify the snowfall and surface melt attributed to AR events to determine their impacts on WAIS SMB. Using two case studies of AR events in December 1999 and February 2020, we illustrate the spatial patterns in snowfall and surface melt associated with AR landfall. We then compare the seasonal and spatial patterns in AR-attributed snowfall to the climatology of all snowfall over the WAIS. Finally, we highlight the interannual and decadal variability of West Antarctic AR events and their relationships to large-scale modes of atmospheric variability. Our results enable us to quantify the past impacts of ARs on WAIS SMB and characterize their interannual variability and trends, enabling a better assessment of future AR-driven changes in SMB.

 

How to cite: Maclennan, M. and Lenaerts, J.: Climatology of West Antarctic Atmospheric Rivers and their Impacts on Surface Mass Balance, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13315, https://doi.org/10.5194/egusphere-egu22-13315, 2022.

EGU22-219 | Presentations | CL4.9

Coupled impacts of sea ice variability and North Pacific atmospheric circulation on Holocene hydroclimate in Arctic Alaska 

Ellie Broadman, Darrell Kaufman, Andrew Henderson, Irene Malmierca-Vallet, Melanie Leng, and Jack Lacey

Arctic Alaska lies at a climatological crossroads between the Arctic and North Pacific Oceans. The modern hydroclimate of the region is responding to rapidly diminishing sea ice driven in part by changes in heat flux from the North Pacific. Paleoclimate reconstructions have improved our knowledge of Alaska’s hydroclimate, but no studies have examined Holocene sea ice, moisture, and ocean-atmosphere circulation in Arctic Alaska, limiting our understanding of the relationship between these phenomena in the past. We present a sedimentary diatom assemblage and diatom isotope dataset from Schrader Pond, located ~80 km from the Arctic Ocean. We interpret these new datasets alongside synthesized regional records of Holocene hydroclimate, and sea ice reduction scenarios modeled by HadCM3. The paleo data synthesis and model simulations suggest the early and middle Holocene in Arctic Alaska were characterized by less sea ice, a greater contribution of isotopically-heavy Arctic-derived moisture, and wetter climate. In the late Holocene, sea ice expanded and regional climate became drier. This climatic transition is coincident with a documented shift in North Pacific circulation involving the Aleutian Low (AL) at ~4 ka, suggesting a Holocene teleconnection between the North Pacific and Arctic. The HadCM3 simulations reveal that reduced sea ice leads to a strengthened AL shifted west, potentially increasing transport of warm North Pacific water to the Arctic through the Bering Strait. Our findings demonstrate the interconnectedness of the Arctic and North Pacific on multi-millennial timescales and are consistent with future projections of less sea ice and more precipitation in Arctic Alaska.

How to cite: Broadman, E., Kaufman, D., Henderson, A., Malmierca-Vallet, I., Leng, M., and Lacey, J.: Coupled impacts of sea ice variability and North Pacific atmospheric circulation on Holocene hydroclimate in Arctic Alaska, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-219, https://doi.org/10.5194/egusphere-egu22-219, 2022.

EGU22-300 | Presentations | CL4.9

Temporal dynamics of the giant Anmangynda aufeis characteristics in changing climate, 1962-2021 (North-Eastern Eurasia) 

Anastasiia Zemlianskova, Vladimir Alexeev, Olga Makarieva, Nataliia Nesterova, Andrey Shikhov, and Andrey Ostashov

Significant changes are observed in the water exchange system of the North-Eastern Eurasia which still is the remote and poorly studied region of the cryosphere. Aufeis which are well recognized from the space may serve as the indicators of such changes. Aufeis are the ice sheets formed in permafrost environment due to the layer-by-layer freezing of discharged underground or surface water, their size may reach tenths of square kilometers. The primary goal of this study is to assess the changes in the dynamics of the characteristics (area and volume) of the giant Anmangynda aufeis based on historical and modern observational data. It is located in the zone of mountainous continuous permafrost of the Magadan region of Russia and was extensively studied in 1962-1992.

We combined and analyzed the data of historical materials (1962-1992) with recent data from Landsat and Sentinel images (2000-2020) and our own ground-based observations on the perennial and annual dynamics of aufeis area (2020-2021). Aufeis volume was measured in 1962-1992 and in 2020-2021, but for the period of 2000-2019 the values were estimated based on the regional formula developed by [Sokolov, Sarkysyan, 1981].

Maximum area of aufeis reached 6.6 km2 (about 1.6% of the basin area) in 1967. According to the data of 1969 its volume may grow up to 15.7 million m3. The greatest amplitude of fluctuations in the size of the aufeis (up to 30% of the average long-term value) was observed in the period up to 1976, then it did not exceed 10-15%. The smallest sizes of aufeis were 4.1 km2 and 5.3 million m3 in 1974, 4.3 km2 and 6.4 million m3 in 1990. Thus, over the thirty-year period of observations, the volume of aufeis has halved.

In the recent period, according to satellite data, these values reached the maximum of 5.8 km2 and 12.4 million m3 (2002). The lowest values were 2 times lower than the historical ones (1.9 km2 and 3.6 million m3, 2014). Now, to study the dynamics of aufeis area and volume, the authors have been using UAV shooting. The thickness of the ice is determined by measuring the height of the surface at different periods of the aufeis development. In 2021, the maximum ice thickness reached 4.4 m, and the historical maximum was 8 m.

The intra-annual dynamics of aufeis has also changed. Now the aufeis gets melted completely by August-September, and in the earlier periods the part of the ice sheet (about 4% of its maximum area) remained and was included in the formation of aufeis for the next year.

According to natural and climatic conditions, the river basin in which the Anmangynda aufeis is formed is representative for the mountainous landscapes of the North-Eastern Eurasia. Comprehensive interdisciplinary observations at this site are important to characterize the impact of climate change on natural processes in this region.

The study was carried out with the support of RFBR (19-55-80028, 20-05-00666), Russian Geographical Society (project 07/2021-I (continue)) and St. Petersburg State University (project 75295776).

How to cite: Zemlianskova, A., Alexeev, V., Makarieva, O., Nesterova, N., Shikhov, A., and Ostashov, A.: Temporal dynamics of the giant Anmangynda aufeis characteristics in changing climate, 1962-2021 (North-Eastern Eurasia), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-300, https://doi.org/10.5194/egusphere-egu22-300, 2022.

EGU22-619 | Presentations | CL4.9

The revised Quaternary climatostratigraphy of the Arctic Ocean: linkages with insolation and sea-level changes 

Claude Hillaire-Marcel, Anne de Vernal, and Michel Crucifix

The revised late Pleistocene chronostratigraphy of the Arctic Ocean based on the pre-2000 magnetostratigraphic interpretation and chronological information from the decay of U-series daughter isotopes in sediments leads to reassigning "warm" vs "cold" climatostratigraphic intervals to distinct interglacial, interstadial, or stadial stages and shows a realistic linkage with high latitude insolation parameters and the global sea-level history. "Warm" episodes then match intervals with summer season insolation and sea-level elevation peaking above those of the early Holocene. Whereas the whole summer season insolation governs heat fluxes towards the Arctic Ocean, in relation with the North Atlantic Water inflow, sea level plays a complementary role as it governs the submergence of the Arctic Ocean shelves and the development of “sea-ice factories”. Sea level also controls the flux of warm and low-salinity Pacific water through the shallow Bering Strait, thus the heat budget of the Western Arctic and the salinity budget of the whole Arctic Ocean. The combination of both parameters indicates that climate conditions during recent interglacials were of distinct amplitude and timing vs those at lower latitudes. From MIS 10 to MIS 1, five short "warm" intervals (MIS 1, 3, 5e, 7, 9) were characterized by sea-ice rafting deposition of smectite and detrital carbonate-rich sediments with 230Th-excesses along major drifting sea-ice routes TransPolar Drift; Beaufort Gyre). These layers alternate with coarser layers linked to sporadic and short-duration, Circum-Arctic glacier surges, deposited during stadials. In contradistinction, the MIS 14 to MIS 10 interval have experienced a thick ice-cover (perennial ice or ice shelf) during long periods, including MIS 11 and possibly MIS 13. These interglacials depict relatively a low summer season insolation in contrast with that of other interglacials. Another feature merging from this revision is the shortness of the intervals with seasonally open sea-ice conditions. Often recorded by a few cm-thick sedimentary layers, these intervals are in phase with the mean summer season insolation (not the June solstice peak) and may have lasted a few ka at most, based on the example of the Holocene. Feedbacks from the Arctic Ocean towards climate/ocean conditions at lower latitudes include i) the effect of its sea-ice on albedo and latitudinal pressure gradients, and ii) the impact of its freshwater export on the Atlantic Meridional Overturning Circulation (AMOC). Due to its specific response to insolation and sea-level changes, the Arctic Ocean may have thus triggered out of phase climate and AMOC fluctuations during interglacials at lower latitudes, but it has globally remained a sediment-starved glacial ocean throughout most of the Brunhes epoch.

How to cite: Hillaire-Marcel, C., de Vernal, A., and Crucifix, M.: The revised Quaternary climatostratigraphy of the Arctic Ocean: linkages with insolation and sea-level changes, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-619, https://doi.org/10.5194/egusphere-egu22-619, 2022.

EGU22-1648 | Presentations | CL4.9 | Highlight

Monthly-resolved Freshwater Flux from the Greenland Ice Sheet on a Glacier-Basin Scale 

Nanna Bjørnholt Karlsson, Kenneth D. Mankoff, Anne M. Solgaard, Signe Hillerup Larsen, Robert S. Fausto, and Louise S. Sørensen

The Greenland ice sheet outputs freshwater into the Greenlandic fjords in the form of icebergs and liquid meltwater. This freshwater flux affects the fjords’ water circulation and ecosystems. In recent decades, the mass loss from the ice sheet has increased causing an increasing volume of liquid and solid freshwater to enter the fjords and ocean around Greenland. The total volume of freshwater is currently challenging to determine on a fjord-basin scale due to disparate products that are difficult to compare and combine into a cohesive product. This entails that the effect of the glacially derived freshwater on fjord circulation and ecosystem is not well constrained.

Here, we present a new glacier-basin scale product that combines three existing products into a shared temporal and spatial framework. We use publicly available datasets of solid ice discharge (icebergs), surface meltwater run-off, and basal melt to present a cohesive overview of the influx of freshwater to the Greenlandic fjords. We then quantify the different dominant term for each glacier. The dataset will be freely available and will be of use to, for example, oceanographic and marine biological research activities.

This work was supported by PROMICE (Programme for Monitoring the Greenland Ice Sheet, GEUS) and ESA Polar+ 4D Greenland.

How to cite: Karlsson, N. B., Mankoff, K. D., Solgaard, A. M., Larsen, S. H., Fausto, R. S., and Sørensen, L. S.: Monthly-resolved Freshwater Flux from the Greenland Ice Sheet on a Glacier-Basin Scale, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1648, https://doi.org/10.5194/egusphere-egu22-1648, 2022.

EGU22-2057 | Presentations | CL4.9

Sea level and the Bering Strait gateway as determinant parameters in the ocean dynamics as illustrated from pan-Arctic Holocene records 

Anne de Vernal, Claude Hillaire-Marcel, Tengfei Song, Yanguang Liu, and Jade Falardeau

The shallow (~ 50 m deep) Bering Strait, which is the unique gateway linking the Pacific Ocean to the Arctic Ocean, deserves special attention as sea-level changes modify considerably the exchanges between the two oceans. Under high sea level, poleward heat transfer and freshwater fluxes from the Pacific impact the Arctic freshwater budget and sea ice distribution. Furthermore, sea level determines the status of the Arctic shelves, submerged or not, which plays a role in sea-ice production, as well as in the latent heat from Atlantic waters flowing northward through Fram Strait and the Barents Sea. Hence, high sea levels result in the connection of the Arctic basin with the Pacific, which modifies the Arctic freshwater and heat budgets and leads to the submergence of shelves, thus the potential development of sea-ice factories. The impacts of sea-level on the Arctic Ocean and subarctic seas are not easily reconstructed from sedimentary records, but radiocarbon-based chronologies and proxy-data covering the present interglacial provide useful information. For example, micropaleontological and geochemical records from the Chukchi Sea show progressive warming in surface water accompanying the increase of Pacific flux during the Holocene, until sea-level reached its present-day limit at ~ 4 ka BP. This contrasts with a trend towards perennial sea-ice cover in the southeastern Arctic and with changes at the eastern gateway of the Fram Strait, where cooling is recorded from early to late Holocene. Hence, we hypothesize that increased freshwater inflow from the Pacific into the Arctic together with enhanced sea-ice formation rates, both linked to sea-level rise, may have played a role in the general cooling trend culminating during the late Holocene.

How to cite: de Vernal, A., Hillaire-Marcel, C., Song, T., Liu, Y., and Falardeau, J.: Sea level and the Bering Strait gateway as determinant parameters in the ocean dynamics as illustrated from pan-Arctic Holocene records, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2057, https://doi.org/10.5194/egusphere-egu22-2057, 2022.

EGU22-3499 | Presentations | CL4.9

The representation of atmospheric processes in northeast Greenland in CMIP6 models 

Carolyne Pickler, Jenny Turton, Thomas Mölg, and Michelle McCrystall

Since the end of the 20th century, Greenland has been the largest contributor to sea level rise.  As temperatures continue to increase, this tendency is projected to continue.  This has resulted in numerous studies which evaluate present and future conditions of the Greenland Ice Sheet, many of which use general circulation models (GCMs). The majority of these focus on sea level rise and/or surface mass balance. While some analyses of atmospheric processes have been undertaken, these have typically been over a larger scale (Arctic or Greenland).  This has led to a lack of regional studies of atmospheric processes and how they are represented in GCMs, particularly over northeast Greenland, an area of increased interest in both its glaciology and atmosphere.

To address this, 67 CMIP6 GCM realizations were subject to the Pickler and Mölg (2021) model selection procedure to determine the most suitable realization over northeast Greenland.  The historical simulation of these realizations were evaluated for: (i) their ability to capture the space-time climatic anomalies over 1979-2014 with respect to ERA5 reanalysis data and (ii) their ability to simulate the mean climatic state of northeast Greenland with respect to four automated weather stations over 2009-2020.  MPI-ESM1-2-HR r6i1p1f1 was found to rank highest and ACCESS-ESM1-5 r10i1p1f1 lowest.

The 67 realizations were then evaluated on their ability to capture two important processes influencing the region: the North Atlantic Oscillation (NAO) and the Greenland blocking (GBI).  All realizations were able to simulate the NAO during boreal winter, while all failed to capture the GBI during boreal summer.  Furthermore, the ability of the top and bottom ranked realizations to simulate precipitation, katabatic winds, sea ice, and warm-air events were examined. This analysis reveals key differences between the representation of regional climates within the GCMs, which highlights the need for a rigorous selection procedure prior to estimating future changes.

How to cite: Pickler, C., Turton, J., Mölg, T., and McCrystall, M.: The representation of atmospheric processes in northeast Greenland in CMIP6 models, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3499, https://doi.org/10.5194/egusphere-egu22-3499, 2022.

EGU22-4347 | Presentations | CL4.9

Retreat of the Northeast Greenland ice stream during the last glacial termination - a case study from Norske Trough 

Adrián López-Quirós, Katrine J. Andresen, Joanna Davies, Tuomas Junna, Tove Nielsen, Christof Pearce, and Marit-Solveig Seidenkrantz

The Greenland Ice Sheet (GIS), the second largest ice sheet on Earth, has experienced a dramatic ice mass reduction during the last decades, coincident with global warming and an increase in atmospheric CO2. About 16% of the GIS is currently drained via marine terminating glaciers, mostly through the Northeast Greenland Ice Stream (NEGIS; with ~12%). Two cross-shelf troughs (Norske and Westwind troughs) served as drainage pathways of the NEGIS. According to numerical ice-sheet models, a whole meltdown of the GIS may cause a global sea−level rise of >7 m, causing permanent damage to the environment and countless economic impacts on our coastal society. In order to better understand the processes driving these present changes, studies of the development of glaciers/glacial troughs and ice sheets in response to past climate changes are required for testing numerical models that seek to predict ice-sheet response to anthropogenic climate change.

In this study, high-resolution INNOMAR sediment subbottom profiler data combined to multi-proxy analyses of gravity core DA17-NG-ST10-117G, obtained from Norske Trough during the NorthGreen17 expedition, are investigated. Multi-proxy data derived from the sediment gravity core include 14C-derived ages, descriptions of sedimentary units, compositional variability of ice-rafted debris, and continuous logging of magnetic susceptibility and micro-XRF core scanning. In Norske Trough, submarine glacial landforms indicate that ice sheet retreat to the outer middle shelf after the Last Glacial Maximum (LGM) was stepwise, with phases of grounding line stabilization, while ice sheet retreat from the middle shelf to the coastline during deglaciation was fast. Sedimentological evidence at our recorded coring site captures the transition from sub–ice stream (subglacial) environments to proximal (proglacial)/distal glaciomarine conditions during the LGM to Holocene recession. In addition, preliminary foraminifera analysis indicates warmer recirculating Atlantic Water on the middle Norske Trough immediately on deglaciation, suggesting that oceanic forcing very likely played a significant role during the retreat of the ice margin. This presentation will include a comprehensive comparison of the spatio-temporal sedimentation patterns across the Norske Trough.

How to cite: López-Quirós, A., Andresen, K. J., Davies, J., Junna, T., Nielsen, T., Pearce, C., and Seidenkrantz, M.-S.: Retreat of the Northeast Greenland ice stream during the last glacial termination - a case study from Norske Trough, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4347, https://doi.org/10.5194/egusphere-egu22-4347, 2022.

EGU22-4935 | Presentations | CL4.9

Abrupt climate changes caused by meltwater pulses in the Labrador Sea during the last glacial termination 

Defang You, Ruediger Stein, and Kirsten Fahl

The last glacial termination is an unstable transition state characterized by abrupt climate changes, while the related physical mechanisms are still not fully understood. Here, we present well-dated high-resolution sedimentary records from the eastern Labrador Sea representing the last 23 ka. Based on our biomarker records, there was seasonal to permanent sea ice cover before 11.7 ka BP. During 11.7 to 8.2 ka BP, ice-free conditions were interrupted by several sea ice expansions, while no sea ice after 8.2 ka BP. Besides Heinrich Event 1, four prominent cold events have been identified during 14 ka to 8.2 ka BP. These abrupt events are marked by increases in sea ice, decreases in sea surface temperature, and weak deep current intensity. We propose that these events were mainly triggered by collapses of the Laurentide Ice Sheet and/or Greenland Ice Sheet, resulting in icebergs/meltwater in pulses into the Labrador Sea. This caused surface freshening, which potentially promoted the stratification of surface water, prevented the northward inflow of Atlantic Water, and limited deep water production in the Nordic Seas, consequently disrupting the climate.

How to cite: You, D., Stein, R., and Fahl, K.: Abrupt climate changes caused by meltwater pulses in the Labrador Sea during the last glacial termination, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4935, https://doi.org/10.5194/egusphere-egu22-4935, 2022.

EGU22-5172 | Presentations | CL4.9

The nature of the Arctic lapse-rate feedback: Spatial distribution, seasonality and trends in ERA5 and CMIP6 data 

Olivia Linke, Johannes Quaas, and Christopher Smith

The Arctic amplification is driven by several intertwined causes including the interplay of locally positive radiative feedbacks. The lapse-rate feedback (LRF) is a dominant driver of Arctic amplification and arises from the vertically non-uniform warming in the troposphere. In the Arctic, the LRF enforces a positive radiative feedback as the warming is most pronounced at the surface, but becomes smaller at higher altitudes which feedbacks positively on the initial greenhouse effect. This stands in contrast to the processes in the tropics, where a stronger warming of the upper troposphere dampens the greenhouse effect.

We investigate the nature of the Arctic LRF by using ERA5 Reanalyses and CMIP6 models to compute the feedback via simplified radiative transfer calculations (radiative kernels).

The Arctic LRF is unique in terms of its geographic distribution, seasonality and time evolution. From a global perspective, the LRF is most positive in Arctic winter, but shows the strongest seasonality as it becomes negative in summer over the sea ice covered ocean. Our trend analysis shows that the positive winter LRF increased strongly during the past 30 to 40 years. This increase during boreal winter mediates the annual response and accounts for all Arctic surface types which we define as sea ice, sea ice retreat, open ocean and land. A special focus lies on regions of retreating sea ice, where the positive LRF is strongest throughout the year.

Our results are embedded in previous studies on the changing Arctic atmospheric energy budget through CO2-driven climate change. They show strongly increasing surface heat fluxes over areas of retreating sea ice which is mostly compensated by a decrease in atmospheric transport convergence, both of which can shape the maximum of the high-latitude positive LRF.

We finally carry out an inter-model comparison of linear trends of the Arctic LRF during the past 30 years of historical CMIP6 simulations. This includes more than 50 models to determine the performance of each model by relating to reanalyses data.

How to cite: Linke, O., Quaas, J., and Smith, C.: The nature of the Arctic lapse-rate feedback: Spatial distribution, seasonality and trends in ERA5 and CMIP6 data, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5172, https://doi.org/10.5194/egusphere-egu22-5172, 2022.

EGU22-5289 | Presentations | CL4.9

Linkages between ocean circulation and the Zachariae Isstrøm in the Early Holocene 

Joanna Davies, Anders Møller Mathiasen, Kristiane Kristiansen, Katrine Elnegaard Hansen, Lukas Wacker, Aage Kristian Olsen Alstrup, Ole Lajord Munk, Christof Pearce, and Marit-Solveig Seidenkrantz

It is unequivocal that the climate is changing; marine terminating glaciers in Northeast Greenland (NEG) have experienced rapid speedup and retreat in recent decades as a result. The Zachariae Isstrøm (ZI) began accelerating in 2000, resulting in the total collapse of its floating ice tongue. This has been partly attributed to basal melting caused by the warming of Atlantic Water (AW). Unfortunately, our understanding of the interaction between these entities is somewhat limited by the length of instrumental records. Examining proxies preserved in marine sediment cores provides an alternative method to understand these changes on longer timescales.

Here we apply a multi-proxy approach (XRF, benthic foraminifera, stable isotopes, grain size, CT scans) to marine sediment core DA17-NG-ST08-092G, collected from the NEG continental shelf, 90km east of the ZI terminus. Our results indicate that the site was free of grounded ice at least as early as 12.5 ka cal BP, and most likely before 13.4 ka cal BP. The inflow of AW onto the continental shelf may have played a role in the seemingly early deglaciation at this site. Between 13.4 and 11.2 ka cal BP the site was overlain by a floating ice tongue, most likely the ZI, with AW and PW flowing beneath. Following this, the ZI briefly retreated westwards (11.2-10.8 ka cal BP) before it re-advanced (10.8-9.6 ka cal BP); there was a strong influx of AW throughout these periods. Between 9.6 and 7.9 ka cal BP the ZI retreated westwards again, before a drastic shift in ocean circulation occurred at 7.9 ka cal BP. At this time, there was a sharp decline in AW corresponding to an increase in PW flowing beneath perennial sea ice. In the final part of the record, AW returns and there was likely a breakup of the perennial sea ice.

How to cite: Davies, J., Møller Mathiasen, A., Kristiansen, K., Elnegaard Hansen, K., Wacker, L., Kristian Olsen Alstrup, A., Lajord Munk, O., Pearce, C., and Seidenkrantz, M.-S.: Linkages between ocean circulation and the Zachariae Isstrøm in the Early Holocene, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5289, https://doi.org/10.5194/egusphere-egu22-5289, 2022.

Several recent cold winters in North America and Western Europe has drawn attention on the possible increase in the frequency and/or intensity of extreme events in the mid-latitude Northern Hemisphere. Whether these could result form a strengthening or weakening of the circumpolar vortex and/or shift in the position of the North Atlantic storm track is still a matter of hot debate. A less known player in this conundrum is the dynamics of the Siberian High, one of the major semi–permanent and quasi–stationary weather systems in the Northern Hemisphere; active in winter and associated with dense and cold air masses over Asia and East Europe. The causes behind the variability of the of the Siberian High (strengthening and south and westwards expansion) are still poorly understood, yet important in the context of future climatic changes expected in the core area of its manifestation. In this context, we present here an overview of the present and past (~5000 years) dynamics of the Siberian High, based on 1) modern climate data from Asia and Eastern Europe and 2) proxy-based reconstructions of winter climatic conditions (temperature and precipitation amount). Our analysis starts with a instrumental-based investigation of the mechanisms behind the onset, strengthening and westward expansion of the high-pressure cell centered over North Asia. We further construct and test several hypotheses behind these mechanisms and test them by analyzing the dynamics of winter conditions during several episodes of particularly cold events in the Northern hemisphere (at 4.2 ka BP, 2.8 ka BP, 1.3 ka BP, 0.8-0.2 ka BP). We tentatively suggest that high insolation gradients between summer and winter in the high–latitudes of the Northern Hemisphere could result in the weakening of the polar vortex and increase in the meandering behavior of the jet that leads to an early onset of winter in North Asia. The expanding snow cover reinforces the strength of the Siberian High, leading to its expansion towards south and west and thus bringing colder conditions in West Asia and Europe. Future Arctic amplification could result in a higher frequency of similar behavior of the climate system, thus leading to more frequent and stronger cold spells across Europe.

How to cite: Perşoiu, A. and Ionita, M.: The Beast from the East - winter atmospheric blocking over Eastern Europe during the Late Holocene and its role in regional climate variability, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5951, https://doi.org/10.5194/egusphere-egu22-5951, 2022.

EGU22-5982 | Presentations | CL4.9

Atmospheric internal variability shapes the Arctic change and its feedback on local and remote circulation 

Peter Yu Feng Siew, Camille Li, Mingfang Ting, Stefan Sobolowski, Yutian Wu, and Xiaodan Chen

Arctic sea ice loss in recent decades has been proposed to influence atmospheric circulation at lower latitudes, producing feedbacks that amplify ice loss via thermodynamic and mechanical forcing. One proposed teleconnection pathway arises from autumn Barents-Kara sea ice reduction and leads to a negative North Atlantic Oscillation (NAO) in winter. The existence of such a pathway could improve predictions of  European weather on subseasonal to seasonal timescales. While autumn sea ice and the winter NAO are significantly correlated in satellite-era observations, this correlation appears to be absent in  coupled climate models, calling into question the underlying mechanism. By subsampling long simulations to create satellite-length records, we find a small number of samples across a range of CMIP5 and CMIP6 models that reproduce the observed correlation. In these samples, we observe similar circulation signals (e.g., weakening of the stratospheric polar vortex) as in the observations, but there is no evidence for a driving role from sea ice changes via turbulent heat fluxes. Rather than sea ice, blocking of the atmospheric circulation by the Ural mountains appears to be the key precursor to the winter NAO signal. Overall, our findings reconcile differences between observations and models in representing this Arctic-midlatitude teleconnection, and highlight the important role of atmospheric internal variability in Arctic change. 

How to cite: Siew, P. Y. F., Li, C., Ting, M., Sobolowski, S., Wu, Y., and Chen, X.: Atmospheric internal variability shapes the Arctic change and its feedback on local and remote circulation, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5982, https://doi.org/10.5194/egusphere-egu22-5982, 2022.

EGU22-6260 | Presentations | CL4.9

Baffin Bay surface flux perspectives on autumn Greenland blocking 

Thomas Ballinger, Daniel Topal, Qinghua Ding, Zhe Li, Linette Boisvert, Edward Hanna, and Timo Vihma

The northwest Atlantic Arctic has been recently characterized by rapid environmental change. Examples in the last two-to-three decades include: accelerated retreat of eastern Canadian Arctic glaciers, melt over high-elevation and latitude areas of the Greenland Ice Sheet (GrIS), and shifts in Baffin Bay ice phenology. Many of these glaciological changes and associated extreme events are linked to atmospheric circulation anomalies over the North Atlantic and surrounding areas, including the frequent, intense, and/or persistent presence of Greenland blocking anticyclones. These mid-tropospheric (i.e., 500 hPa) high-pressure cells are often accompanied by invigorated temperature and moisture advection and cloud radiative processes that are known to provoke widespread melt of the region’s cryosphere, even during periods when melt tends to be uncommon. Blocking characteristics are often associated with melt processes, but how these processes and related air-sea exchanges feedback on this type of upper-level atmospheric pattern largely remain uncertain. Evaluating these processes and their uncertainties is especially relevant in the cold season, when upward surface fluxes persist along the ice edge and through thin sea ice cover. Such system-level interactions deserve attention for their multi-scalar effects on the local climate and cryosphere and impacts on the polar jet stream that influences North American and European weather regimes.

This study focuses on the autumn season (September-December) to evaluate interactions involving Baffin Bay’s ice cover and its turbulent and radiative fluxes, and regional atmospheric circulation and winds. Focus is directed on this season as net surface fluxes climatologically tend to intensify from one month to the next and have increased roughly in tandem with the strength and motion characteristics of the overlying circulation described by the Greenland Blocking Index (GBI), and Greenland Streamfunction Index (GSI), respectively. Using flux data from ERA5 reanalysis and the Atmospheric Infrared Sounder (AIRS), we utilize bi-and-multivariate techniques to examine how individual and collective surface flux terms relate to the autumn GBI/GSI variability and trends since 1979. We then take a process-scale view, and investigate such interactions between the Baffin Bay boundary conditions, associated surface fluxes, and the GBI/GSI patterns in months where extremes occur in the ice cover and GBI/GSI independently as well as in tandem for applicable cases. We further aim to model the interaction between autumn Baffin ice-ocean surface fluxes and upper-level patterns using CAM6 Prescribed SST AMIP Ensembles and wind-nudging CESM experiments to isolate the role of Baffin environmental change on the large-scale atmospheric circulation and vice versa.

How to cite: Ballinger, T., Topal, D., Ding, Q., Li, Z., Boisvert, L., Hanna, E., and Vihma, T.: Baffin Bay surface flux perspectives on autumn Greenland blocking, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6260, https://doi.org/10.5194/egusphere-egu22-6260, 2022.

EGU22-7438 | Presentations | CL4.9 | Highlight

Eurasian wintertime cooling: New perspectives from an updated synthesis 

Stephen Outten and Camille Li

Over a decade ago, researchers noticed that as the Arctic warmed rapidly, there was an apparent cooling over large areas of central Eurasia in the wintertime. Many theories were put forward suggesting that changes in wintertime sea-ice were linked to this observed cooling through some hereto unknown teleconnection. Numerous studies based on observations, reanalyses, and a vast array of modelling experiments have been undertaken to resolve this question. The ongoing debate regarding Arctic to mid-latitude teleconnections over the Eurasian sector has divided the scientific community, as highlighted by the work of Cohen et al. [2020], primarily between those in favour of sea-ice having a key role in giving rise to the cooling, and those who believe the cooling is primarily the result of internal atmospheric variability. While Eurasian cooling itself has mostly ended, the debate continues due to a desire to better understand the teleconnections underlying Northern Hemisphere climate variability.

Here we discuss a new synthesis study into Eurasian cooling, undertaken by an extensive team at the Bjerknes Centre over the past two years. The work breaks down the debate into a simple structure, examining first the findings of the observational-based studies and the modelling-based studies separately. In evaluating this body of literature, we attempt to avoid categorizing studies based on the researchers’ interpretations of their findings, and focus where possible on only the facts of what their analyses and simulations show. This has allowed us to reconcile some of the apparently conflicting results in the literature. To be clear, we do not present a new mechanistic understanding of the processes underlying Eurasian cooling. However, laying out the existing research in an objective and structured manner has allowed us to propose a new framework within which to view the problem, wherein we clarify the distinct roles of internal variability and an external (sea-ice driven) forcing of Eurasian cooling.

How to cite: Outten, S. and Li, C.: Eurasian wintertime cooling: New perspectives from an updated synthesis, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7438, https://doi.org/10.5194/egusphere-egu22-7438, 2022.

EGU22-7950 | Presentations | CL4.9

Sensitivity of stratospheric pathways of Arctic-midlatitude linkages to the modification of the gravity wave drag parameterization in ICON model using deep learning 

Sina Mehrdad, Khalil Karami, Dörthe Handorf, Johannes Quaas, Ines Höschel, and Christoph Jacobi

The global warming has been observed to be more severe in the Arctic compared to the rest of the world. This enhanced warming i.e. Arctic Amplification is not just the result of local feedback processes in the Arctic. The stratospheric pathways of Arctic-midlatitude linkages and large-scale dynamical processes can contribute to the Arctic Amplification. The polar stratospheric dynamics crucially depends on the atmospheric waves at all scales. The winter polar vortex can be disturbed by gravity waves in the middle atmosphere. To investigate the sensitivity of the polar vortex dynamics, large-scale dynamical processes, and the stratospheric pathways of the Arctic-midlatitude linkages to the modification of gravity wave drag, we conduct sensitivity experiments using the global atmospheric model ICON-NWP (ICOsahedral Nonhydrostatic Model for Numerical Weather Prediction). These sensitivity experiments are performed by imposing a repeated annual cycle of the year 1985 for sea surface temperatures and sea ice as lower boundary conditions and for greenhouse gas concentrations as external forcing. This year is selected as both El-Nino Southern Oscillation and Pacific decadal oscillation were in their neutral phase and no explosive volcanic eruption has occurred. Hence, lower boundary and external forcing conditions in this year can serve as a useful proxy for the multi-year mean condition and an estimate of its internal variability. We performed simulations where in the control simulation the sub-grid parameterization scheme for both orographic and non-orographic gravity wave drags are switched on. The other two experiments are identical to the control simulation except that either orographic or non-orographic gravity wave drags are switched off.

    Recently, deep learning has extraordinarily progressed our ability to recognize complex patterns in big datasets. Deep neural networks have shown great capabilities to capture the dynamical process of the atmosphere. Applying deep learning algorithms on experiments’ results, the impact of gravity wave drag modifications on large-scale mechanisms of the Arctic Amplification will be analyzed. Special emphasis will be put on the effects of gravity wave drag modifications on the polar vortex dynamics.

How to cite: Mehrdad, S., Karami, K., Handorf, D., Quaas, J., Höschel, I., and Jacobi, C.: Sensitivity of stratospheric pathways of Arctic-midlatitude linkages to the modification of the gravity wave drag parameterization in ICON model using deep learning, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7950, https://doi.org/10.5194/egusphere-egu22-7950, 2022.

The Lancaster Sound is currently one of the pathways for Arctic water and ice entering Baffin Bay. However, this gateway was blocked by the coalescing Laurentide and Innuitian Ice Sheets during the Last Glacial Maximum and only opened during the early Holocene after the various ice sheets had retreated (Dyke et al., 2002; Dalton et al., 2020). Core GeoB22336-4 is a well radiocarbon-dated sediment record from the Lancaster Sound Trough Mouth. Sedimentological and geochemical (elemental and mineralogical) properties of this core revealed four major units: (i) the deglacial unit (~14.5 – 9.7 ka BP) with a dense, foraminifera-free, gravel-rich diamict (>14.0 ka BP) that captures proximal ice-margin conditions, probably deposited under an extended thick ice-shelf environment, overlain by rapidly deposited gravel-bearing sandy-silty mud with intercalated turbidite layers reflecting strong input of ice-rafted material and mass wasting, likely resulting from the fast landward retreat of bordering ice sheets in response to regional warming; (ii) the early Holocene unit (~9.7 – 8 ka BP) characterized by a drop in sedimentation rate and the absence of ice-rafted material and reduction in detrital carbonates, suggesting a switch from tide-water to predominately land-terminating glaciers during glacial retreat; (iii) the unit deposited contemporaneously with the regional Holocene Optimum (~8 – 5.9 ka BP; Ledu et al., 2010; Jennings et al., 2011; St-Onge & St-Onge 2014) consists of rapidly deposited rather fine-grained sediments (up to 52 cm ka-1) possibly related to enhanced meltwater- and/or sea-ice-driven sediment input; and (iv) the neoglacial unit (<5.9 ka BP) with reduced sedimentation rates, a sediment provenance switch from calcite-dominated to dolomite-dominated detrital carbonates, and an increased organic matter flux to the seafloor, which led to a four-fold increase in bioturbation. This diverse sedimentary record reflects the complex ice-ocean-atmosphere interactions controlling the sedimentary dynamics and sediment provenance in northwestern Baffin Bay from the last deglaciation through the Holocene. It sheds light on the complex interaction between sediments delivered by local meltwater sources, mass wasting, iceberg and sea ice-rafting, the opening of the Arctic gateways through Lancaster Sound and Nares Strait, and the influence of warm Atlantic Water (AW). In addition, the Arctic Oscillation (AO) possibly governs surface waters and primary production in northern Baffin Bay including the development and extension of the North Water Polynya (NOW).

How to cite: Okuma, E., Titschack, J., Weiser, J., Kienast, M., Vogt, C., and Hebbeln, D.: Deglacial to Holocene changes in sediment characteristics and provenance in core GeoB22336-4 from Lancaster Sound Trough Mouth: Implications for environmental conditions in northwestern Baffin Bay, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8403, https://doi.org/10.5194/egusphere-egu22-8403, 2022.

EGU22-8791 | Presentations | CL4.9

Seawater isotopic measurements (δ18O and δD) reveal significant freshwater influxes into the Arctic seas 

Ben Kopec, Eric Klein, Shawn Pedron, Hannah Bailey, Douglas Causey, Alun Hubbard, Hannu Marttila, Kashif Noor, and Jeffrey Welker

As the Arctic warms, one of the fundamental changes has been the freshening of Arctic ocean waters, impacting ocean circulation and marine ecosystems, among many other critical changes. This increase in freshwater is largely the result of increased precipitation and runoff as part of an amplified Arctic water cycle and increased influx of glacial meltwater from around the Arctic, particularly from the Greenland Ice Sheet. Tracing the sources and extent of this freshwater is critical to understanding future changes to the Arctic seas. One way of delineating these water masses is through measuring its isotopic composition (δ18O and δD), where the freshwater varies significantly from older and other ocean water sources.

In order to identify these freshwater influxes, we conducted in-situ measurements aboard the USCGC Healy that transited the Chukchi and Beaufort Seas, the Northwest Passage, and performed numerous transects across Baffin Bay and the Labrador Sea, including detailed examinations of several key fjords and coastal regions of Greenland, during autumn of 2021. Over the length of this 45 day expedition, we continuously measured the isotopic composition (δ18O and δD) of surface seawater allowing us to fingerprint these sources of freshwater and assess the spatial extent of their influence. We also collected discrete samples from over 100 CTD casts, primarily in Baffin Bay, to identify how freshwater is distributed in the ocean water column. Through these measurements, we identified numerous freshwater influxes, including anomalously high proportions of freshwater in sections of the Beaufort Sea north of Alaska and in Uummannaq Fjord along the west Greenland coast. These isotopic measurements also allow for the disentangling of different freshwater sources (i.e., precipitation or glacial meltwater). Additionally, we find that the freshwater pulses along the west coast of Greenland corresponded with relatively high levels of chlorophyll and fluorescence, suggesting a possible link between this increase in biologic productivity and an increase in the proportion of freshwater.

How to cite: Kopec, B., Klein, E., Pedron, S., Bailey, H., Causey, D., Hubbard, A., Marttila, H., Noor, K., and Welker, J.: Seawater isotopic measurements (δ18O and δD) reveal significant freshwater influxes into the Arctic seas, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8791, https://doi.org/10.5194/egusphere-egu22-8791, 2022.

Source-specific highly branched isoprenoids (HBIs) have been recently served as a binary or semi-quantitative biomarker to indicate the sea ice extent in the past. Since the light intensity controlled by overlying snow cover and sea ice thickness has a significant impact on the productivity of photoautotrophic organisms and environmental water is the sole source of the hydrogen for the biosynthesis of these organisms, the hydrogen isotope ratio (2H/1H) of HBIs holds the potential to reveal more characteristics of sea ice. In this study, based on the observation of natural settings underneath sea ice, diatom Pleurosigma intermedium were grown at irradiances from 20 to 300 μmol m-2 s-1 in laboratory conditions and harvested from exponential phase and stationary phase respectively to investigate the effect of light and growth phase on hydrogen isotope fractionation in HBIs. Gas chromatography-mass spectrometry (GC-MS) screening showed that a triene (C25:3) and a tetraene (C25:4) C25 HBI alkene were detected in all samples from varying irradiances. A remarkable decline of the ratio of C25:3/C25:4 from higher to lower irradiances was observed. However, there was no significant change in the concentration of C14 (myristic), C16:1 (palmitoleic) and C16 (palmitic) fatty acids with varying light intensity. In addition, terpenoids such as phytol, squalene and range of sterols were also be identified. Published studies on phytol, fatty acid and sterol from Thalassiosira pseudonana and alkenones from Emiliania huxleyi have shown dramatic changes in hydrogen isotope fractionation and concluded that the source of nicotinamide adenine dinucleotide phosphate (NADPH) and the operation of acetogenic pathway, plastidic methylerythritol phosphate (MEP) and/or cytosolic mevalonic acid (MVA) of lipids are the key factors controlling 2H/1H fractionation. The integration of molecular distribution of HBIs, fatty acids and terpenoids in Pleurosigma intermedium together with our ongoing work on their 2H/1H and 13C/12C compositions will lead to a better understanding of diatom metabolism and biochemistry under different light conditions. This knowledge will be instrumental to a more robust interpretation of stable isotope data from environmental samples and thus will contribute to further developing HBI biomarkers as a tool for estimating not only the absence/presence of sea ice but also the ice type, thickness, and snow cover.

How to cite: Gao, S., Zhao, Y., Zhou, Y., Smik, L., Belt, S., Mock, T., and Pedentchouk, N.: The effect of irradiance on lipids of highly branched isoprenoids (HBIs) producing diatom culture of Pleurosigma intermedium: towards stable isotope proxies for the paleo sea-ice reconstructions, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8979, https://doi.org/10.5194/egusphere-egu22-8979, 2022.

EGU22-9431 | Presentations | CL4.9

Late Glacial paleoceanography in the outer Norske Trough, NE Greenland 

Tuomas Junna, Christof Pearce, Katrine Hansen, Joanna Davies, Adrián Quirós, and Marit-Solveig Seidenkrantz

The NE Greenland shelf, together with the Fram Strait, form the main sea ice and cold-water transport pathway between the Arctic Ocean and the Nordic seas. As such, these regions play a part in the Atlantic meridional overturning cell that is driven by the thermohaline convection taking place in subpolar and Polar regions. The ocean circulation, freshwater export and sea ice extent are heavily influenced by the interplay of oceanography, climate, glacial landforms and bathymetry.

Over the outer NE Greenland shelf, a layer of low salinity, cold Polar Water overlies a body of Atlantic Water (AW) that is either recirculated directly across the Fram Strait or further in the Arctic Ocean from where it returns as colder, modified Arctic-Atlantic Water. The relative contributions of these two types of AW recirculation bear significant implications to the deep-water formation and thus, the global ocean circulation, but little is known about the change in AW source over time and how it affects the local environmental settings.

This study aims to describe the paleoceanographic development of the outer Norske Trough using a multi-proxy approach to sediment gravity core DA17-NG-ST12-135G.  The core was taken on the NorthGreen17 Expedition from the outmost location in an east-west transect of cores along the trough. When combined with the other cores, it can be used to reconstruct the  oceanic forcing on the northeastern Greenland Ice Sheet  and its deglaciation history along the Norske Trough. The data used includes AMS 14C dating, sedimentary description, grain size analysis, µ-XRF core scanning and benthic foraminifera analysis. The preliminary results suggest intermittent early AW water influence and high seasonal productivity just east of the Northeast Greenland Ice Stream grounding line during the early deglaciation. AW influence on the outer NE Greenland Shelf is relatively constant after the deglaciation, but changes in productivity and current strengths are captured by the data.

How to cite: Junna, T., Pearce, C., Hansen, K., Davies, J., Quirós, A., and Seidenkrantz, M.-S.: Late Glacial paleoceanography in the outer Norske Trough, NE Greenland, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9431, https://doi.org/10.5194/egusphere-egu22-9431, 2022.

EGU22-9645 | Presentations | CL4.9

Variability of dissolved organic carbon (DOC) in the 6 largest Arctic rivers estimated using high resolution Sentinel-2 and Landsat-8 imageries over the 2013-2021 period. 

Fabrice Jégou, Gaëtane Jallais, Elodie Salmon, Bertrand Guenet, Pierre-Alexis Herrault, Sébastien Gogo, Laure Gandois, Christophe Guimbaud, Fatima Laggoun-Defarge, Nathalie Moulard, Roman Teisserenc, and Jean-Sébastien Moquet

Climate warming with permafrost thaw will modify lateral carbon export, from terrestrial to aquatic ecosystems with a potential huge impact on the Arctic rivers, draining organic-rich soils and in fine into the Arctic Ocean. The majority of annual DOC fluxes by Arctic rivers are transported during the snowmelt break-up period, which makes field measurements of DOC difficult. Passive spatial remote sensing is a very relevant tool to increase the spatial and temporal coverage of these observed values.

In the framework of the French CNES DOC-Rivers project we proposed to apply the approach consisting in analyzing satellite imageries to evaluate DOC concentrations in the 6 great Arctic Rivers: Lena, Ob’, Yenisey, Yukon, MacKenzie, Kolyma. The algorithm, first, establishes a multi-linear relationship between ground-based chromatic dissolved organic matter (CDOM) observations and specific satellite color bands to construct a complete satellite CDOM database. Another linear regression is used afterward with in-situ data from the Arctic Great Rivers Observatory (ArcticGRO) initiative to correlate CDOM and DOC observations. Using this second linear regression, we can predict the DOC content from the previous construct satellite CDOM database. River discharge measurements from the ArcticGRO database also enable to estimate the evolution of DOC export to the Arctic Ocean from satellite data.

We applied this approach to high-resolution satellite data issued from Sentinel 2 (A 2015-2022, B 2017-2022) and Landsat 8 (2013-2022) to create a multi-instrumental synergy. This new database provides an unprecedented source of information for understanding DOC dynamics of in Arctic rivers and assessing its transfer from large catchments to the Arctic Ocean. This database provides information on the variability of DOC during the whole ice-free season and serve to locate areas with higher concentrations and fluxes during the 2013-2021 period. We plan to complement our database on future period with data from new satellite missions (Landsat 9, Sentinel 2C), on the present time with data from on-going missions (Sentinel 3, MODIS) and on past period with data from low resolution observations as Landsat 5 and Landsat 7. This extension of the database over a longer period of time will furnish insight in response to climate warming.

How to cite: Jégou, F., Jallais, G., Salmon, E., Guenet, B., Herrault, P.-A., Gogo, S., Gandois, L., Guimbaud, C., Laggoun-Defarge, F., Moulard, N., Teisserenc, R., and Moquet, J.-S.: Variability of dissolved organic carbon (DOC) in the 6 largest Arctic rivers estimated using high resolution Sentinel-2 and Landsat-8 imageries over the 2013-2021 period., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9645, https://doi.org/10.5194/egusphere-egu22-9645, 2022.

EGU22-10999 | Presentations | CL4.9

Rectified multiyear warming in high latitudes by interannually varying biomass burning emissions in CESM2 Large Ensemble simulations 

Ji-Eun Kim, Ryohei Yamaguchi, Keith Rodgers, Axel Timmermann, Sun-Seon Lee, Karl Stein, Gokhan Danabasoglu, Jean-Francois Lamarque, John Fasullo, Clara Deser, Isla Simpson, Nan Rosenbloom, Jim Edwards, Jennifer Kay, and Malte Steuker

A merged biomass burning aerosol (BBA) emission dataset of satellite observations with fire proxies and fire models has been used in the Coupled Model Intercomparison Project Phase 6 (CMIP6) simulations. Although this utilizes best estimates of fire emissions based on available observations, it results in inconsistency in interannual variability of BBA forcing in CMIP6 between the period of satellite-based fire emissions (1997-2014) and the periods before and after. Using the Community Earth System Model version 2 Large Ensemble (CESM2-LE) simulations, we identify rectified multiyear mean climate responses to interannually varying BBA emissions. The comparison of 50 ensemble members forced by high BBA variability with 50 members by low BBA variability over a limited time domain provides a unique opportunity to identify a forced climate response to interannual fluctuations of fire emissions with high fidelity. While mean aerosol emissions are nearly conserved between the two sets of ensembles, there is detectable warming in northern high latitudes with regionally distinct seasonal changes in response to variable emissions. We find that the multiyear warming occurs in concert with a net loss of soil ice and moisture in addition to a loss of Arctic sea ice. Our results suggest that the magnitude of interannual variability of aerosol emissions can act as climate forcing over multiple years through nonlinear interactions with the cryosphere and soil processes.

How to cite: Kim, J.-E., Yamaguchi, R., Rodgers, K., Timmermann, A., Lee, S.-S., Stein, K., Danabasoglu, G., Lamarque, J.-F., Fasullo, J., Deser, C., Simpson, I., Rosenbloom, N., Edwards, J., Kay, J., and Steuker, M.: Rectified multiyear warming in high latitudes by interannually varying biomass burning emissions in CESM2 Large Ensemble simulations, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10999, https://doi.org/10.5194/egusphere-egu22-10999, 2022.

EGU22-11174 | Presentations | CL4.9

Late Quaternary deglaciation pattern of Lancaster Sound and Barrow Strait traced by radiogenic isotope records in marine sediments 

Johanna Hingst, Claude Hillaire-Marcel, Friedrich Lucassen, Emmanuel Okuma, and Simone Kasemann

The retreat of the Laurentide and Innuitian Ice Sheets in the Canadian Arctic Archipelago (CAA) during the late Quaternary led to the opening of Arctic gateways and the inflow of low salinity Arctic waters into Baffin Bay. Studies on marine sediments focusing on the timing and deglaciation pattern of Canadian Archipelago straits mainly concentrated on the Holocene. Here we present two marine radiogenic isotope records from the mouth of Lancaster Sound (GeoB22336-4) and from Barrow Strait (PS72/287) that cover the last ~14.5 ka BP, thus encompass the earlier deglaciation stage. The radiogenic isotope composition (Nd, Sr, Pb) of the detrital sediment fraction serves as provenance tracer and provides information on changing position of the ice margin and oceanographic conditions. Data from both sediment cores show contributions from highly variable source areas during deglaciation in response to the dynamics of the glacier termini involved. However, a strong influence of detrital carbonates, likely eroded from carbonate outcrops of the CAA and northern Baffin Island, by retreating ice, constitutes a dominant feature. Later, the post-glacial deposits recorded more uniform radiogenic isotope signatures until the mid/late Holocene transition, indicating relatively stable environmental conditions. In addition to local sources, isotope compositions in Lancaster Sound illustrate an increasing influence of sediments from Barrow Strait and thus the setting of oceanographic conditions enabling sediment transport from the central CAA towards the NW Baffin Bay. According to these observations and based on a preliminary age model, complete deglaciation with subsequent flushing of major channels is assumed to have occurred at approximately 10 ka BP. During the late Holocene, slightly changing Sr, Pb, and Nd isotope signatures in both cores probably indicate renewed regional ice advances in response to the neoglacial cooling.

How to cite: Hingst, J., Hillaire-Marcel, C., Lucassen, F., Okuma, E., and Kasemann, S.: Late Quaternary deglaciation pattern of Lancaster Sound and Barrow Strait traced by radiogenic isotope records in marine sediments, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11174, https://doi.org/10.5194/egusphere-egu22-11174, 2022.

EGU22-11646 | Presentations | CL4.9

Variability of Atlantic Water on shelf of Northeast Greenland: Patterns and Drivers 

Rebecca McPherson, Claudia Wekerle, and Torsten Kanzow

During the last two decades, rising ocean temperatures have significantly contributed to accelerated mass loss of the Greenland Ice Sheet. The melting of the ice sheet is now the single largest contributor to global mean sea level rise. Warming subsurface Atlantic Intermediate Water (AIW) found on the wide continental shelf of Northeast Greenland and in the fjords interacts with marine-terminating glaciers, which until recently were considered stable, and causes their rapid melting and retreat. The main source of these waters is the westward recirculation of subducted Atlantic Water (AW) in Fram Strait, which has shown a warming of up to 1°C over the past few decades.

The variability of the AIW on the Northeast Greenland (NEG) shelf is investigated using historical hydrographic observations and high-resolution numerical simulations with the Finite-Element-Sea ice-Model (FESOM2). There is excellent agreement of both the mean and long-term distribution of AIW on the shelf between the model and observations. The two main circulation regimes of AW in Fram Strait are also well-replicated by the numerical simulations.

The dominant variability of the AIW temperature occurs at interannual timescales. A shelf-wide process drives this variability of AIW temperatures. EOF analysis shows that over 81% of the variance of maximum AIW temperatures is explained by the first mode, which features a monopol-like pattern across the whole NEG shelf. There is a strong co-variability between the maximum AIW temperature and the volume transport of AIW towards the glaciers, which moves through the deep trough system as a bottom intensified jet and recirculates on the shelf. A connection between the AIW temperatures on the shelf and the AW boundary current along the shelf edge suggests the East Greenland Current influences AIW properties. An increase in strength of the current corresponds to greater AIW volume transport through the trough system, and also warmer AIW and AW temperatures on both the shelf and off the continental slope. This suggests that the drivers of variability of AIW temperatures on the NEG shelf may be found further offshore, with a connection to AW circulation in Fram Strait.

How to cite: McPherson, R., Wekerle, C., and Kanzow, T.: Variability of Atlantic Water on shelf of Northeast Greenland: Patterns and Drivers, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11646, https://doi.org/10.5194/egusphere-egu22-11646, 2022.

EGU22-870 | Presentations | CL4.8

Causal evaluation of Arctic-midlatitude processes in CMIP6 model simulations 

Evgenia Galytska, Katja Weigel, Jakob Runge, Dörthe Handorf, Ralf Jaiser, Raphael Köhler, and Veronika Eyring

The impact of various mechanisms that link Arctic and midlatitude processes occurring in conditions of amplified Arctic warming is still under debate. Observational and model studies lead to divergent conclusions. This has spurred a number of research activities aiming to apply innovative approaches to improve process understanding. Therefore, to identify robust relationships in the complex Arctic-midlatitude linkages, we apply a novel method that goes beyond simple correlation analysis, known as Causal Networks or Causal Discovery. This allows us to analyze, characterize, and quantify key processes that contribute to the linkage between the Arctic and midlatitudes on a monthly timescale. In particular, we focus on the causal connections among key actors, such as Arctic near-surface temperature and sea ice, near-surface pressure over central Asia, vertical wave propagation, and its further link to the stratospheric polar vortex. Additionally, we analyze the contribution of remote large-scale processes, such as El Niño–Southern Oscillation, Quasi Biennial Oscillation, and North Atlantic Oscillation. In this study, we summarize the comparisons between historical Coupled Model Intercomparison Project Phase 6 (CMIP6) model runs and observational data. On the one hand, our analysis shows that the majority of historical CMIP6 models agree with observations on the significant causal connection between near-surface air temperature and sea ice extent in the Arctic region. These model results also capture the tropospheric-stratospheric coupling and downward impact from the stratosphere to the troposphere shown by observations. On the other hand, we also focus on discrepancies between model simulations and observations and provide possible explanations of investigated differences. These outcomes provide the basis to investigate changes in the links between Arctic and midlatitudes for simulations with various forcings and future scenarios.

How to cite: Galytska, E., Weigel, K., Runge, J., Handorf, D., Jaiser, R., Köhler, R., and Eyring, V.: Causal evaluation of Arctic-midlatitude processes in CMIP6 model simulations, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-870, https://doi.org/10.5194/egusphere-egu22-870, 2022.

EGU22-2613 | Presentations | CL4.8

Weakening of Western Disturbances in Response to Polar Sea Ice Melt 

Varunesh Chandra, Sandeep Sukumaran, and Kieran Hunt

Arctic sea ice has been declining in recent decades. Further, future projections under strong warming scenarios suggest that sea ice will substantially decline in both poles by the second half of 21st century. The effect of polar sea ice melt on low latitude weather systems is relatively less understood. The changes in equator-to-pole temperature gradient can affect the strength of subtropical jet stream which in turn can modulate transient weather systems such as western disturbances (WDs). WDs play a crucial role in the hydrological cycle of northwestern India and adjoining Himalayan region, so it is essential to know the response of WDs to polar sea ice melt.

     To understand the effects of polar sea ice melt on WD activity, we have run a suite of coupled and uncoupled simulations using NCAR community earth system model (CESM1.2.2). Initially, a control (CTRL) run is performed with the model in a fully coupled configuration for 350 years, with a coarse horizontal resolution (2°x2°). By branching off the CTRL simulation at 300th year, another experiment is carried out in which the albedo of the sea ice is reduced so that the increased absorption of the solar radiation would melt the sea ice. We designate this experiment as sea ice melt experiment (SIME). Transient weather systems may not be adequately resolved in the coarse resolution simulations, so we ran an ensemble of high-resolution Community Atmospheric Model (CAM5) simulations using the sea surface temperature (SST) and sea ice concentration (SIC) annual cycles from the coupled model simulations.

     WDs in the high-resolution CAM5 simulations are tracked using a Lagrangian tracking algorithm. Our analyses reveal that the WD activity weakens in the CAM5 simulations forced with the SST and SIC from SIME experiment. A decrease in the equator-to-pole temperature gradient and a subsequent weakening of the subtropical jetstream were also seen in those simulations.

How to cite: Chandra, V., Sukumaran, S., and Hunt, K.: Weakening of Western Disturbances in Response to Polar Sea Ice Melt, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2613, https://doi.org/10.5194/egusphere-egu22-2613, 2022.

EGU22-4854 | Presentations | CL4.8

Thin and thick ice in the Beaufort Sea: A new regime with enhanced mobility 

Kent Moore, Mike Steele, Axel Schweiger, Jinlun Zhang, and Kristin Laidre

The Arctic Ocean has seen a remarkable reduction in sea ice coverage, thickness and age since the 1980s. These changes are most pronounced in the Beaufort Sea, with a transition around 2007 from a regime dominated by multi-year sea ice to one with large expanses of open water during the summer. Here we show that during the summers of 2020 and 2021, the Beaufort Sea hosted anomalously large concentrations of thick and old ice. We show that ice advection contributed to these anomalies, with 2020 dominated by eastward transport from the Chukchi Sea, and 2021 dominated by transport from the Last Ice Area to the north of Canada and Greenland. Since 2007, cool season (fall, winter, and spring) ice volume transport into the Beaufort Sea accounts for ~45 % of the variability in early summer ice volume - a threefold increase from that associated with conditions prior to 2007.   Impacts of these changes are likely to occur on stressed regional ice-dependent ecosystems.

How to cite: Moore, K., Steele, M., Schweiger, A., Zhang, J., and Laidre, K.: Thin and thick ice in the Beaufort Sea: A new regime with enhanced mobility, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4854, https://doi.org/10.5194/egusphere-egu22-4854, 2022.

EGU22-5436 | Presentations | CL4.8

Future changes in poleward moisture transport variability associated with atmospheric rivers 

Richard Bintanja, Jeroen Sonnemans, Karin van der Wiel, Marlen Kolbe, Kirien Whan, and Imme Benedict

The hydrological cycle in the Arctic is intensifying due to climate change, which could modify the climate locally, but also worldwide. For example poleward moisture transport (PMT) is projected to increase in a future climate as well as its interannual variability, mainly in summer. While the first can be attributed to increased atmospheric moisture content, the cause of the latter is still uncertain. We used the global climate model EC-Earth to examine to what extent PMT variability can be linked to atmospheric rivers (ARs) in present and future climates (2C and 3C warmer than the pre-industrial climate). It is found that most PMT variability is driven by Arctic ARs, especially over the Atlantic Ocean and to a lesser extent over the Bering Strait. In years with high PMT, a relatively large share is transported by ARs, up to 50% in the present-day climate. Moreover, our findings suggest that interannual AR-related PMT variability is more sensitive to variations in AR-intensity compared to AR-frequency in the present as well as in warmer climates. This implies that increasing interannual PMT variability is dominantly driven by the increase in PMT per AR rather than the increase in AR-occurrence. Finally, our results point at a strong contribution of ARs to interannual variability of Arctic precipitation and temperature patterns.

How to cite: Bintanja, R., Sonnemans, J., van der Wiel, K., Kolbe, M., Whan, K., and Benedict, I.: Future changes in poleward moisture transport variability associated with atmospheric rivers, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5436, https://doi.org/10.5194/egusphere-egu22-5436, 2022.

EGU22-5836 | Presentations | CL4.8

Impact of the atmospheric circulation on the Arctic snow cover and ice thickness variability 

Marylou Athanase, Merle Schwager, Jan Streffing, Miguel Andrés-Martínez, Svetlana Loza, and Helge Goessling

The Arctic sea ice cover and thickness have significantly declined since the 1970s, while exhibiting large interannual variability. Snow cover on sea ice, acting as an insulating barrier, was shown to be instrumental in driving the variability and trends in sea-ice thickness. Yet, the Arctic snow depth remains scarcely measured and overlooked in climate models, which translates to “very limited predictive skill” according to the IPCC (Special Report on the Ocean and Cryosphere in a Changing Climate). Moreover, sea-ice thickness initialization has been shown to be an important element for skilful sea-ice forecasts, and it appears plausible that the same holds for the snow layer on top.

Here, we investigate the role of atmospheric circulation anomalies in shaping the Arctic snow-cover and sea-ice thickness anomalies. In this preparatory work, spectral nudging of the large-scale atmospheric circulation towards ERA5 reanalysis data is applied to the fully coupled AWI Climate Model (AWI-CM-3). We examine the variability and trends of Arctic snowfall, snow depth, sea ice cover and thickness over a 42-year period (1979-2021), and in particular the reproduction of observed anomalies. Two nudging configurations are used, differing in strength by their relaxation timescale τ and spectral truncation wavenumber T (namely τ=24 h, T20 and τ=1 h, T159). We demonstrate the importance of atmospheric circulation anomalies in shaping variations of snow and ice thickness at sub-seasonal to interannual scales, and discuss the potential of spectral nudging as a tool to improve the initialization of sea ice forecasts.



How to cite: Athanase, M., Schwager, M., Streffing, J., Andrés-Martínez, M., Loza, S., and Goessling, H.: Impact of the atmospheric circulation on the Arctic snow cover and ice thickness variability, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5836, https://doi.org/10.5194/egusphere-egu22-5836, 2022.

EGU22-5858 | Presentations | CL4.8

Skillful Prediction of Decadal Sea Ice Variability in the Antarctic Seas 

Yushi Morioka, Doroteaciro Iovino, Andrea Cipollone, Simona Masina, and Swadhin Behera

This study examines the prediction skill of decadal sea ice variability in the Antarctic Seas using a coupled general circulation model (SINTEX-F2) developed under the EU-Japan collaboration. A decadal reforecast experiment with both sea surface temperature (SST) and sea ice concentration (SIC) initializations shows higher prediction skills of the SIC in the Weddell Sea during austral autumn compared to an experiment with SST initialization only. The former experiment reproduces decadal SIC increase after the late 2000s, which is associated with anomalous sea ice advection by the strengthened Weddell Gyre. A third experiment with the SST, SIC, and subsurface ocean temperature/salinity initializations shows the highest prediction skills of the SIC in the Ross, Amundsen, and Bellingshausen (RAB) Seas during austral winter and spring. The model captures decadal SIC increase after the late 2000s when a larger number of subsurface ocean observations by Argo floats become available. The decadal SIC increase is found to be linked with anomalous cooling of subsurface ocean by the strengthened Antarctic Circumpolar Current and the associated downwelling anomalies in the RAB Seas. These results indicate that both ocean and sea ice initializations benefit skillful prediction of decadal variability in the Antarctic sea ice.

How to cite: Morioka, Y., Iovino, D., Cipollone, A., Masina, S., and Behera, S.: Skillful Prediction of Decadal Sea Ice Variability in the Antarctic Seas, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5858, https://doi.org/10.5194/egusphere-egu22-5858, 2022.

EGU22-6020 | Presentations | CL4.8

Modified soil hydro-thermodynamics cause large spread in projections of Arctic and subarctic climate 

Norman Julius Steinert, Jésus Fidel González-Rouco, Philipp de Vrese, Elena García-Bustamante, Stefan Hagemann, Johann Jungclaus, Stephan Lorenz, Victor Brovkin, Camilo Andres Melo-Aguilar, Félix García-Pereira, and Jorge Navarro

The representation of the terrestrial thermal and hydrological states in current-generation climate models is crucial to have a realistic simulation of the subsurface physical processes and land-atmosphere coupling. This is particularly important for high-latitude permafrost regions since these areas are prone to the release of substantial amounts of carbon from degrading permafrost under climate-change conditions. Many current-generation climate models still have deficiencies in the representation of terrestrial structure and physical mechanisms, such as too shallow land depth or insufficient hydro-thermodynamic coupling. We therefore introduce a deeper bottom boundary into the JSBACH land surface model. The associated changes in the simulated terrestrial thermal state influence the near-surface hydroclimate when sufficient coupling between the thermodynamic and hydrological regimes is present. Hence, we also assess the influence of introducing various physical modifications for the representation of soil hydro-thermodynamic processes in climate projections of the 21st century. The results show significant impacts on terrestrial energy uptake, as well as changes in global near-surface ground temperatures when introducing the physical modifications. The resulting simulation of high-latitude permafrost extent is subject to large variations depending on the model configuration, reflecting the uncertainty of carbon release from permafrost degradation. We further use the modified model to assess the sensitivity of simulated high-latitude climate dynamics to different hydrological configurations in the coupled MPI-ESM. The differences in soil hydrological representation in permafrost regions could explain a large part of CMIP6 inter-model spread in simulated Arctic climate, with remote effects on subarctic dynamical systems.

How to cite: Steinert, N. J., González-Rouco, J. F., de Vrese, P., García-Bustamante, E., Hagemann, S., Jungclaus, J., Lorenz, S., Brovkin, V., Melo-Aguilar, C. A., García-Pereira, F., and Navarro, J.: Modified soil hydro-thermodynamics cause large spread in projections of Arctic and subarctic climate, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6020, https://doi.org/10.5194/egusphere-egu22-6020, 2022.

EGU22-7134 | Presentations | CL4.8

Frequency Change in Blocking-related Winter Cold Days in Europe between Periods of Low and High Arctic Sea Ice 

Andy Richling, Uwe Ulbrich, Henning Rust, Johannes Riebold, and Dörthe Handorf

Over the last decades the change in the Arctic climate resulted in related sea-ice retreat and a much faster warming of the Arctic compared to the global average (Arctic amplification). These changes in sea ice can affect the large-scale atmospheric circulation over the mid-latitudes, in particular atmospheric blocking, and – mediated by the changes in blocking – the frequency and severity of related extreme events. As a step towards a better understanding of changes in weather and climate extremes over Central Europe (C-EU) associated with Arctic climate change, we study the linkage between periods of low and high Arctic sea ice area and the frequency of winter cold days in C-EU. Since frequency of winter cold days in C-EU is associated with atmospheric blocking, especially over the Ural and Scandinavian region, we investigate frequency changes of cold days with respect to the occurrence of blocking in different Euro-Atlantic regions by composite analysis based on ERA5 reanalysis data. 

To separate the resulting changes from the global warming trend and associated Arctic sea ice loss, monthly sea ice area data is first detrended and then divided by the median into two parts representing either low or high sea ice periods. The frequency of occurrence of cold days with respect to both sea ice periods is then calculated and compared. The same procedure is applied to cold days occurring during a blocked day in certain regions to analyze the change of linkage between atmospheric blocking and cold days induced by different sea ice area periods. Preliminary results indicate an increased occurrence of cold days in Central Europe during low sea ice periods, which is enhanced during the occurrence of Ural Blocking.

How to cite: Richling, A., Ulbrich, U., Rust, H., Riebold, J., and Handorf, D.: Frequency Change in Blocking-related Winter Cold Days in Europe between Periods of Low and High Arctic Sea Ice, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7134, https://doi.org/10.5194/egusphere-egu22-7134, 2022.

EGU22-7219 | Presentations | CL4.8 | Highlight

Evaluating the skill of seasonal forecasts of sea ice in the Southern Ocean: insights from the SIPN South project 2017-2022 

François Massonnet, Phil Reid, Jan Lieser, Cecilia Bitz, John Fyfe, and Will Hobbs

The SIPN South project is an international, coordinated initiative endorsed by the Year Of Polar Prediction (YOPP), that aims at identifying the skill of current seasonal predictions of sea ice around Antarctica. Here, we review and analyze the results of five years of predictions of summer sea ice conducted by 20 groups since 2017, having contributed together more than 1000 forecasts. A wide range of approaches is considered, ranging from statistical data-driven to dynamical process-based models. We evaluate the ability of the forecasts to reproduce observed sea ice area at the circumpolar and regional levels and their skill relative to trivial forecasts (climatology, persistence). We find that a substantial spread exists already at day one in the dynamical forecasts, pointing at problems with the initialization. We also find that the forecasts based on statistical modeling perform generally better than forecasts based on dynamical modeling.

How to cite: Massonnet, F., Reid, P., Lieser, J., Bitz, C., Fyfe, J., and Hobbs, W.: Evaluating the skill of seasonal forecasts of sea ice in the Southern Ocean: insights from the SIPN South project 2017-2022, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7219, https://doi.org/10.5194/egusphere-egu22-7219, 2022.

EGU22-7468 | Presentations | CL4.8

Characterising reanalysis representation of winds at the interface between Antarctica and the Southern Ocean 

Thomas Caton Harrison, Tom Bracegirdle, John King, and Stavroula Biri

Low-level easterly winds encircle Antarctica, helping drive coastal currents which modify transport of circumpolar deep water to ice shelves as well as the formation and distribution of sea ice. Semi-permanent katabatic winds interact with a highly variable maritime component associated with synoptic forcing, both of which are influenced by the steep orography of the Antarctic margins. In this research, representation of the terrestrial and maritime components of the easterlies in three state-of-the-art reanalyses (ERA5, MERRA2 and JRA55) is evaluated. Variability on daily timescales is analysed using self-organising maps which objectively cluster coastal flow regimes into states with different synoptic and mesoscale influences. Correlation coefficients with station and sonde observations are highest in ERA5 overall but stronger terrestrial winds in MERRA2 and JRA55 reduce biases relative to ERA5 for many states. ERA5 is the least prone to overestimating low wind speeds. Performance is reduced for all reanalyses during states dominated by terrestrial katabatics and at stations near sloping terrain. Wind speeds are consistently underestimated when cyclone activity near the steep coastal orography drives a super-geostrophic low-level jet. These results demonstrate how a characterisation of coastal wind variability on short timescales could help diagnose errors in coarser models used for future projections.

How to cite: Caton Harrison, T., Bracegirdle, T., King, J., and Biri, S.: Characterising reanalysis representation of winds at the interface between Antarctica and the Southern Ocean, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7468, https://doi.org/10.5194/egusphere-egu22-7468, 2022.

EGU22-7636 | Presentations | CL4.8

Vegetation Type is an Important Predictor of the Arctic Terrestrial Summer Surface Energy Budget 

Jacqueline Oehri, Gabriela Schaepman-Strub, Jin-Soo Kim, Raleigh Grysko, Heather Kropp, Inge Grünberg, Vitalii Zemlianskii, Oliver Sonnentag, Eugénie S. Euskirchen, and Merin Reji Chacko and the ArcticSEB - Synthesis Team

The terrestrial Arctic is subject to extreme climatic changes including increases in temperature and changes in precipitation patterns. At the heart of these developments lie changes in the land surface energy budget (SEB), which couples important earth system processes including the carbon and water cycles. However, despite the importance of the SEB, uncertainties in predictions of high-latitude SEBs persist, specifically for the SEB-components sensible and latent heat fluxes.

These uncertainties have in part been attributed to insufficient representation of Arctic vegetation in land surface components of Earth system models. However, to date, a quantitative understanding of the relative importance of Arctic vegetation for the SEB compared to other important SEB-drivers is missing.

Here we harmonize in situ observations from regional and global monitoring networks and provide a quantitative, circumpolar assessment of the magnitude and seasonality of observed SEB-components over treeless land >60°N in the time period 1994-2021. Using a variance partitioning analysis, we identify vegetation type as an important predictor for SEB-components during Arctic summer, in comparison with other SEB-drivers including meteorological conditions, snow cover duration, topography, and permafrost extent. Differences among vegetation types are especially high for mean summer magnitudes of sensible and latent heat fluxes, where they reach up to 8% and 9% of the potential incoming shortwave radiation, respectively. Our comparison with SEB-observations across glacier sites show that importantly, these differences among vegetation types are of similar magnitude as differences between vegetation and glacier surfaces. In our seasonality synthesis we find that net radiation (Rnet), sensible (H) and ground (G) heat fluxes have an unexpected early start of summer-regime (when daily mean values > 0 Wm-2), preceding the end of snowmelt by 56, 33, and 39 days, respectively. An elevated variability among vegetation types in the estimated onset (and end) dates of net positive Rnet and H (and G) relative to snowmelt (and onset) date, suggests that vegetation types differentially affect the distribution, trapping and density of snow cover, with important consequences for the cumulative energy fluxes from and to the atmosphere. Finally, we find that long-term, year-round SEB data series of Arctic tundra are still very scarce, especially in the Arctic regions of Eastern Canada and Western Russia.

In conclusion, we provide quantitative evidence of the importance of vegetation types for predicting Arctic surface energy budgets at circumpolar scale. We highlight that substantial differences among vegetation types are not only found for mean magnitudes but also the seasonality of surface energy fluxes. We contend that the land surface components of Earth system models should account for Arctic vegetation types to improve climate projections in the rapidly changing terrestrial Arctic.

How to cite: Oehri, J., Schaepman-Strub, G., Kim, J.-S., Grysko, R., Kropp, H., Grünberg, I., Zemlianskii, V., Sonnentag, O., Euskirchen, E. S., and Reji Chacko, M. and the ArcticSEB - Synthesis Team: Vegetation Type is an Important Predictor of the Arctic Terrestrial Summer Surface Energy Budget, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7636, https://doi.org/10.5194/egusphere-egu22-7636, 2022.

EGU22-7730 | Presentations | CL4.8

Extreme wintertime surface energy budget anomalies in the high Arctic 

Sonja Murto, Rodrigo Caballero, Gunilla Svensson, Lukas Papritz, Gabriele Messori, and Heini Wernli

In recent decades the Arctic has warmed faster than the global mean, especially during winter. Wintertime Arctic warming has been attributed to various mechanisms, with recent studies highlighting the important role of enhanced downward infrared radiation associated with anomalous influx of warm, moist air from lower latitudes. Here we study wintertime surface energy budget (SEB) anomalies over Arctic sea ice on synoptic time scales, using ERA5 reanalysis data (1979-2020). With a new algorithm introduced here, we identify regions exhibiting large positive daily-mean SEB anomalies, and temporally connect them to form life-cycle events. Using Lagrangian tracers, we show that the majority of these winter events are associated with inflow from the Atlantic or Pacific Oceans, driven by the large-scale circulation. They show similar temporal evolution. The onset stage, located around the marginal ice zone, is characterized by roughly equal contributions of net longwave radiation and turbulent fluxes to the positive SEB anomaly. As the events evolve and move further into the Arctic, SEB anomalies decrease due to weakening sensible heat fluxes as the surface adapts. The magnitude of the surface temperature anomaly is determined by the downward longwave radiative flux and changes little over the life-cycle. As this study highlights the importance of turbulent fluxes in driving SEB anomalies and downward longwave radiation in determining local surface warming, both components need to be properly represented by climate models in order to properly model the Arctic climate.

How to cite: Murto, S., Caballero, R., Svensson, G., Papritz, L., Messori, G., and Wernli, H.: Extreme wintertime surface energy budget anomalies in the high Arctic, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7730, https://doi.org/10.5194/egusphere-egu22-7730, 2022.

EGU22-8442 | Presentations | CL4.8

Internal variability of Arctic surface air temperatures at different levels of global warming 

Céline Gieße, Dirk Notz, and Johanna Baehr

Surface temperatures in the Arctic are increasing more than twice as fast as the global average due to Arctic amplification. This warming gives rise to new types of extreme events that can have particularly large impacts. Here, we study the interplay of mean warming and changes in internal variability to better understand and constrain the intensity and frequency of temperature extremes in the Arctic, both regionally and seasonally.
For this study, we analyze projected mean and extreme surface air temperatures in the Arctic for different levels of global warming based on output data from multiple single-model initial-condition large ensembles, with the Max Planck Institute Grand Ensemble (MPI-GE) at the core of the analysis. We use a time-slice approach to construct representative samples of the pre-industrial climate and the climate at different levels of global warming, including the Paris Agreement targets of 1.5 °C and 2 °C.
Considering pan-Arctic temperatures, we find that the mean warming is strongest in winter (~3.5 times annual mean global warming) and lowest in summer (~1.05 times annual mean global warming), which leads to a weakening of the Arctic seasonal cycle with global warming. Moreover, the change in the return levels of extreme temperatures is particularly strong for cold extremes, rendering extremely cold temperatures seldom in a warming Arctic. The level of global warming is strongly impacting the frequency of extreme events. For example, warm extremes that occur every 100 years at 1.5 °C of global warming, occur more than once in 10 years at 2 °C of global warming, and cold extremes that occur every 10 years at 1.5 °C global warming, occur only about every 200 years at 2 °C of global warming (based on MPI-GE data). The response of Arctic mean temperatures to global warming results from a local temperature response that varies substantially for different regions and types of surfaces (land, ice sheet, open ocean, sea ice). We find the most drastic warming, accompanied by a strong reduction of variability, in winter temperatures over the northern Barents Sea linked to its ‘Atlantification’. Lastly, we also note a considerable difference in the Arctic temperature response for the same level of global warming in a transient versus a quasi-equilibrium climate state.
The results of our study allow us to quantify expected changes in the Arctic temperature range with global warming and also to determine when and where, for example, climate mitigation measures are most likely to be visible.

How to cite: Gieße, C., Notz, D., and Baehr, J.: Internal variability of Arctic surface air temperatures at different levels of global warming, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8442, https://doi.org/10.5194/egusphere-egu22-8442, 2022.

EGU22-8755 | Presentations | CL4.8

Robust trends in the number of winter days with heavy precipitation over Europe are modulated by a weaker NAO variability by the end of 21st century 

Ramon Fuentes-Franco, David Docquier, Torben Koenigk, Filippo Giorgi, and Klaus Zimmermann

We use 14 models participating in the Coupled Model Intercomparison Project phase 6 (CMIP6) to analyse the number of days with extreme winter precipitation over Europe and its relationship to the North Atlantic Oscillation (NAO), for the observed period 1950-2014 and 21st-century that for northern Europe, models project two times more extreme precipitation days by the end of the 21st century compared to the historical period (1950-2014). In contrast, no significant change in the number of extreme precipitation days is detected over the whole period for southern Europe. We find a weakening of the NAO variability in the second half of the 21st century compared to the historical period.  For the second half of the 21st century, models show an intensified correlation between the extreme precipitation and the NAO index in both southern and northern Europe. Models with a reduced variability of the NAO show an increased positive trend of days with extreme precipitation in northern Europe.

How to cite: Fuentes-Franco, R., Docquier, D., Koenigk, T., Giorgi, F., and Zimmermann, K.: Robust trends in the number of winter days with heavy precipitation over Europe are modulated by a weaker NAO variability by the end of 21st century, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8755, https://doi.org/10.5194/egusphere-egu22-8755, 2022.

EGU22-9717 | Presentations | CL4.8

Interannual Variability of Arctic Climate: Seasonal and Regional Disparities 

Marlen Kolbe, Richard Bintanja, and Eveline van der Linden

The future of year-to-year variability of Arctic climate change indicators such as sea ice and precipitation is still fairly uncertain. Alongside climatic changes in means, a thorough understanding of interannual variability (IAV) is needed to accurately distinguish between signal and underlying noise, as well as to describe the likelihood of extreme events. 

In this study we quantify the IAV of Arctic surface air temperature, precipitation, evaporation, and sea ice area from 1851-2100 as a function of time in order to assess the effect of climate change on future variability. By influencing the likelihood of extreme events, changes in the magnitude of IAV can not only influence the surface mass balance of the Greenland Ice Sheet, but also affect regions in lower latitudes. Investigations of global climate model output strongly suggest that intermodel differences in CMIP6 projections of IAV are largely explained by natural variability versus model physics. Our results further highlight the need to distinguish between seasons as well as regions when investigating past, present and future states of IAV of Arctic climate. For example, increases in precipitation variability will become much more significant and intense in winter (after 2040) and most pronounced in coastal regions near the Bering Strait, the GrIS and the Norwegian Sea. Depending on the season, the retreat of sea ice can alter precipitation patterns through the process of enhanced evaporation over open ocean areas. Sea ice variability can therefore explain regional and seasonal changes of the Arctic water cycle, as it shifts from being snow- to rain-dominated.

How to cite: Kolbe, M., Bintanja, R., and van der Linden, E.: Interannual Variability of Arctic Climate: Seasonal and Regional Disparities, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9717, https://doi.org/10.5194/egusphere-egu22-9717, 2022.

In the Arctic, observed decadal mean surface air temperatures (SATs) were 0.70°C–0.95°C lower around 1970 than around 1940. Many of the state-of-the-art climate model in the Coupled Model Intercomparison Project Phase 6 (CMIP6) exhibited Arctic surface cooling trend during 1940–1970, which could be attributed to external forcings. Multimodel means of CMIP6 Detection and Attribution Model Intercomparison Project (DAMIP) historical simulations exhibited Arctic surface cooling of –0.22°C (±0.24°C) in 1970 versus 1940 and showed that anthropogenic aerosol forcing contributed to a cooling of −0.65°C (±0.37°C), which was partially offset by a warming of 0.44°C (±0.22°C) due to well-mixed greenhouse gases. In addition to the anthropogenic aerosol forcings, multidecadal internal variability with a magnitude of 0.47°C was the components primarily contributing to the observed Arctic cooling. The SAT spatial pattern of pan-Arctic multidecadal cooling due to the internal variability was identified by the composite analysis and resembles the obseved Arctic surface cooling pattern during 1940–1970.

How to cite: Aizawa, T., Oshima, N., and Yukimoto, S.: Evaluation of anthropogenic aerosol forcing and multidecadal internal variability contributing to mid-20th century Arctic cooling — CMIP6/DAMIP multimodel analysis, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9781, https://doi.org/10.5194/egusphere-egu22-9781, 2022.

EGU22-10357 | Presentations | CL4.8 | Highlight

Snowmelt timing influences the start of the Arctic-boreal fire season across North America 

Thomas D. Hessilt, Brendan M. Rogers, Stefano Potter, Rebecca C. Scholten, and Sander Veraverbeke

Snowmelt timing influences arctic-boreal ecosystem functioning through influences on surface hydrology and energy balance. Spring snow cover extent in the Northern Hemisphere has declined since the mid-20th century by up to 46 % in June, including a strong decrease after the mid-1980s. Regions of arctic-boreal North America have simultaneously experienced increases in the number and size of fires. With early snowmelt timing, the likelihood of early fire ignitions also increases as fuel is exposed and organic soil can begin to dry. Early fire ignitions can potentially develop into larger fires as a prolonged fire season may extend the period of favourable weather conditions for fire spread. Despite the importance of snowmelt timing, ignition timing, and fire size for predicting future boreal fire regimes across North America, these relationships are not well understood. Here we analysed snowmelt and ignition timing across ecoregions for boreal North America from 2001 to 2019. Using newly developed satellite-based fire products, we retrieved and matched ignitions with snowmelt timing in a spatially explicit manner.

            Results indicate that snowmelt timing has occurred 0.2 ± 0.17 days year-1 earlier in western arctic-boreal North America and 0.27 ± 0.33 days year-1 later in eastern arctic-boreal North America between 2001 and 2019. Similarly, we found that ignitions have occurred 0.61 ± 1.12 days year-1 earlier and 0.3 ± 0.58 days year-1 later for the western and eastern ecoregions. In 13 out of 16 ecoregions, there was a significant positive relationship (p < 0.01) between the timing of snowmelt and ignition. This suggests that snowmelt timing helps controlling the fire season start. The mechanisms behind the spatial gradient in the snowmelt timing over the last two decades are less understood and may result from differences in larger climatic oscillations influencing the polar front jet stream and Arctic sea ice extent. Decades of colder air temperature and higher amounts of winter precipitation may explain the later snowmelt and fire season start in the eastern ecoregions. Our results show that a shift in the snowmelt timing has resulted in earlier fire season starts in western boreal North America and in later fire season starts in eastern boreal North America.

How to cite: Hessilt, T. D., Rogers, B. M., Potter, S., Scholten, R. C., and Veraverbeke, S.: Snowmelt timing influences the start of the Arctic-boreal fire season across North America, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10357, https://doi.org/10.5194/egusphere-egu22-10357, 2022.

EGU22-11018 | Presentations | CL4.8 | Highlight

An  Assessment of Arctic Sea Ice Intra-Annual Probabilistic Prediction Skill Using the Regional Arctic System Model 

Wieslaw Maslowski, Younjoo Lee, Anthony Craig, Robert Osinski, and Jaclyn Clement Kinney

The Regional Arctic System Model (RASM) has been developed and used for modeling of past to present and predicting future Arctic climate change at time scales from weeks to decades. RASM is a fully coupled ice-ocean-atmosphere-land hydrology model. Its domain covers the pan-Arctic region, with the default atmosphere and land components configured on a 50-km horizontal grid. The ocean and sea ice components are configured on a rotated sphere mesh with the default configuration of 1/12o (~9.3km) in the horizontal space and with 45 ocean vertical layers. As a regional climate model, RASM requires boundary conditions along its lateral boundaries and in the upper atmosphere, which are derived either from global atmospheric reanalyses for simulations of the past to present or from global forecasts or from Earth System models (ESMs) for climate projections. The former simulations allow comparison of RASM results with observations in place and time, and their tuning, which is a unique capability not available in global ESMs.

Within this framework, RASM has been used every month for the past 3+ years (from January 2019 to present) to dynamically downscale the global intra-annual (i.e., 7-month) operational forecasts from the National Center for Environmental Predictions (NCEP) Climate Forecast System version 2 (CFSv2). Here we present summary results from analysis of  RASM predictive skill from these forecasts using the common metrics to quantify model skill in predicting sea ice conditions at time scales from weeks up to 6 months. Examples of possible improvements of RASM predictive skill are discussed, related to optimized parameter space, improved initial conditions and higher spatial resolution. An outlook for up to decadal probabilistic predictions using dynamical downscaling is also discussed.

How to cite: Maslowski, W., Lee, Y., Craig, A., Osinski, R., and Clement Kinney, J.: An  Assessment of Arctic Sea Ice Intra-Annual Probabilistic Prediction Skill Using the Regional Arctic System Model, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11018, https://doi.org/10.5194/egusphere-egu22-11018, 2022.

EGU22-473 | Presentations | CL5.3.2

Improving the parameterization of vegetation cover variability in land surface models based on satellite observations 

Fransje van Oorschot, Ruud van der Ent, Markus Hrachowitz, Franco Catalano, Souhail Boussetta, and Andrea Alessandri

Vegetation is highly dynamic at seasonal, inter-annual, decadal and longer timescales. These dynamics are strongly coupled with hydrological, biogeochemical and bio-physical processes. In global land surface models,  this coupling is controlled by  parameterizations of the effective sub-grid vegetation cover that controls amongst others modelled evapotranspiration, albedo and surface roughness. In this study we aim to explore the use of observational satellite datasets of LAI and Fraction of green vegetation Cover (FCover) for an improved model parameterization of effective vegetation cover.
The effective vegetation cover can be described by exponential functions resembling the Lambert Beer law of extinction of light under a vegetated canopy  (1-e-k*LAI), with k the canopy light extinction coefficient. In HTESSEL (i.e. the land surface model in EC-EARTH) k has been set to a constant value of 0.5 so far. However, k varies for different vegetation types as it represents the structure and the clumping of a vegetation canopy. For example tree canopies are more clumped than grasses, resulting in a larger effective coverage. In this study we optimize the canopy extinction coefficient k using the LAI and FCover satellite products for different vegetation types (ESA-CCI land cover), with FCover equivalent to the model effective vegetation cover.  
This effort results in a vegetation dependent relation between LAI and effective vegetation cover that is implemented in HTESSEL. The improved effective vegetation cover parameterization is evaluated using offline model simulations. To evaluate the sensitivity to the new parameterization, modelled evaporation, discharge and skin temperature are compared with station and satellite observations.

How to cite: van Oorschot, F., van der Ent, R., Hrachowitz, M., Catalano, F., Boussetta, S., and Alessandri, A.: Improving the parameterization of vegetation cover variability in land surface models based on satellite observations, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-473, https://doi.org/10.5194/egusphere-egu22-473, 2022.

EGU22-846 | Presentations | CL5.3.2

Investigating 25 years of coupled climate modeling 

Lukas Brunner, Ruth Lorenz, Erich M. Fischer, and Reto Knutti

The Coupled Model Intercomparison Project (CMIP) is an effort to compare model simulations of the climate system and its changes. In the quarter of a century since CMIP1 models have increased considerably in complexity and improved in how well they are able to represent historical climate compared to observations. Other aspects, such as the projected changes we have to expect in a warming climate, have remained remarkably stable. Here we track the evolution of climate models based on their output and discuss it in the context of 25 years of model development. 

We draw on temperature and precipitation data from CMIP1 to CMIP6 and calculate consistent metrics of model performance, inter-dependence, and consistency across multiple generations of CMIP. We find clear progress in model performance that can be related to increased resolution among other things. Our results also show that the models’ development history can be tracked using their output fields with models sharing parts of their source code or common ancestors grouped together in a clustering approach.

The global distribution of projected temperature and precipitation change and its robustness across different models is also investigated. Despite the considerable increase in model complexity across the CMIP generations driven, for example, by the inclusion of additional model components and the increase in model resolutions by several orders of magnitude, the overall structure of simulated changes remains stable, illustrating the remarkable skill of early coupled models.

How to cite: Brunner, L., Lorenz, R., Fischer, E. M., and Knutti, R.: Investigating 25 years of coupled climate modeling, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-846, https://doi.org/10.5194/egusphere-egu22-846, 2022.

EGU22-1448 | Presentations | CL5.3.2

An analogue approach to predicting European climate 

Leonard Borchert, Matthew Menary, and Juliette Mignot

Decadal climate prediction is a scientific endeavour of potentially large societal impacts. Yet such predictions remain challenging, as they predict climate skilfully only under certain circumstances or in specific regions. Moreover, decadal climate prediction simulations rely on dedicated coupled climate model simulations that are particularly expensive. In this study, we build upon earlier research by Menary et al. (2021) in search of a method to make skilful and cheap decadal climate predictions by constructing predictions from existing climate model simulations using the so-called analogue method.

The analogue method draws on the idea that there is decadal memory in the climatic state at the start of a prediction. This method identifies the observed state of the climate system at the start of a prediction and then screens the archive of available model simulations for comparable climatic states. It then selects a number of modelled climate states that are similar to the observed situation, and uses the years after the selected simulated climate states as prediction. Using a simple analogue method based on temperature trends in the North Atlantic basin, Menary et al. (2021) demonstrated skilful prediction of North Atlantic SST on par with dynamical decadal prediction simulations. In this study, we refine the original method by using more sophisticated algorithms to select the analogues, and choosing decadal prediction of seasonal European climate as our target. These new selection algorithms include multivariate regression at different time lags as well as non-linear methods.

 

Menary, MB, J Mignot, J Robson (2021) Skilful decadal predictions of subpolar North Atlantic SSTs using CMIP model-analogues. Environ. Res. Lett. 16 064090. https://doi.org/10.1088/1748-9326/ac06fb

How to cite: Borchert, L., Menary, M., and Mignot, J.: An analogue approach to predicting European climate, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1448, https://doi.org/10.5194/egusphere-egu22-1448, 2022.

EGU22-1817 | Presentations | CL5.3.2

Identifying efficient ensemble perturbations for initializing subseasonal-to-seasonal prediction 

Jonathan Demaeyer, Stephen Penny, and Stéphane Vannitsem

The prediction of weather at subseasonal-to-seasonal (S2S) timescales is affected by both initial and boundary conditions, and as such is a complicated problem that the geophysical community is attempting to address in greater detail. One important question about this problem is how to initialize ensembles of numerical forecast models to produce reliable forecasts1, i.e. initialize each member of an ensemble forecast such that their statistical properties are consistent with the actual uncertainties of the future state of the physical system.

Here, we introduce a method to construct the initial conditions to generate reliable ensemble forecasts. This method is based on projections of the ensemble initial conditions onto the modes of the model's dynamic mode decomposition (DMD), which are related to the procedure used for forming Linear Inverse Models (LIMs). In the framework of a low-order ocean-atmosphere model exhibiting multiple different characteristic timescales, we compare the DMD-oriented method to other ensemble initialization methods based on Empirical Orthogonal Functions (EOFs) and the Lyapunov vectors of the model2, and we investigate the relations between these.

References:

1. Leutbecher, M., & Palmer, T.N. (2008). Ensemble forecasting. Journal of Computational Physics, 227, 3515–3539.

2. Vannitsem, S., & Duan, W. (2020). On the use of near-neutral Backward Lyapunov Vectors to get reliable ensemble forecasts in coupled ocean–atmosphere systems. Climate Dynamics, 55, 1125-1139.

How to cite: Demaeyer, J., Penny, S., and Vannitsem, S.: Identifying efficient ensemble perturbations for initializing subseasonal-to-seasonal prediction, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1817, https://doi.org/10.5194/egusphere-egu22-1817, 2022.

The challenges of climate prediction are varied and complex. On the one hand they include conceptual and mathematical questions relating to the consequences of model error and the information content of observations and models. On the other, they involve practical issues of model and ensemble design, and the statistical processing of data.

A route to understanding the complexity of these challenges is to study them using low-dimensional nonlinear systems that encapsulate the key characteristics of climate and climate change. Doing so facilitates the fast generation of very large ensembles with a variety of designs and target goals. These idealised ensembles can provide a solid foundation for improving the design of ESM/GCM ensembles, making them better suited to evaluating the risks associated with climate change and to providing end-user support through climate services.

The ODESSS project - Optimizing the Design of Ensembles to Support Science and Society - is using low-dimensional nonlinear systems to provide solid foundations for the design of climate change ensembles with climate models. In this presentation I will introduce the project and the concepts behind it.

First I will discuss the essential characteristics required of a low dimensional nonlinear system to be able to capture the process of climate prediction. Results will then be presented from the coupled Lorentz ’84 - Stommel ’61 system; a low-dimensional nonlinear system which has these characteristics. These results will be used to illustrate the dangers of confounding natural variability with the consequences of initial condition uncertainty[1], and to demonstrate why risk assessments require much larger initial condition ensembles than are currently available with today’s ESMs/GCMs.

The difference between micro and macro initial condition ensembles [2,3] will then be introduced, along with an explanation of how this leads to a requirement for ensembles of ensembles: the former exploring macro-initial-condition-uncertainty, the latter micro-initial-conditional-uncertainty. The importance of this distinction will be illustrated with both new results from the Lorentz ‘84 - Stommel ‘61 system, and also a GCM[3]. I will highlight the challenges in designing these ensembles of ensembles to be most informative. These challenges relate closely to the problems of initialization and the optimal use of observations.

Finally the subject of model error, multi-model and perturbed-physics ensembles will be discussed. The impact of model error on climate predictions can only be studied effectively if climate change can be accurately quantified within each model. To begin to explore the consequences of model error for climate predictions therefore requires ensembles of ensembles of ensembles: perturbed-physics or multi-model ensembles which  themselves consist of both macro and micro initial condition ensembles. Some approaches will be presented for how low-dimensional systems can be used to optimise the design of such multi-layered ensembles with ESMs/GCMs where computational constraints are more restrictive.

[1] Daron and Stainforth, On predicting climate under climate change. ERL, 2013.

[2] Stainforth et al., Confidence, uncertainty and decision-support relevance in climate predictions. Phil. Trans Roy. Soc., 2007.

[3] Hawkins et al., Irreducible uncertainty in near-term climate projections. Climatic Change, 2015.

How to cite: Stainforth, D.: Ensembles of ensembles of ensembles: On using low-dimensional nonlinear systems to design climate prediction experiments, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3885, https://doi.org/10.5194/egusphere-egu22-3885, 2022.

EGU22-5377 | Presentations | CL5.3.2

What can the last century teach us about climate models? 

André Düsterhus, Leonard Borchert, Björn Mayer, Vimal Koul, Holger Pohlmann, Sebastian Brune, and Johanna Baehr

Climate models are an important tool in our understanding of the climate system. Among other things, we use them together with initialisation procedures to predict the climate from a few weeks to more than a decade. While the community has demonstrated prediction skill for various climate modes on these time scales in the past years, we have also encountered problems. One is the non-stationarity of prediction skill over the past century in seasonal and decadal predictions. It was shown in multiple prediction systems and for multiple variables that prediction skill varies over time. Potential reasons for this non-stationarity was found in the changing state of the North Atlantic system on multi-decadal scales and the limited representation of physical processes within the model. While on the one side this feature of climate predictions leaves uncertainties for future predictions it also highlights windows of opportunity and challenges within climate models. 

We investigate the past century for this non-stationarity with a special focus on the North Atlantic Oscillation, and how the North Atlantic sector changes during these low prediction skill periods. We will demonstrate the limited predictability of features of the North Atlantic Oscillation, like the movement of its activity centres, as well as its implication for the Signal-to-Noise paradox. We also discuss the implications of non-stationarity model prediction skill for the development on future prediction systems and which processes are most likely the reason for the current challenges the community faces.

How to cite: Düsterhus, A., Borchert, L., Mayer, B., Koul, V., Pohlmann, H., Brune, S., and Baehr, J.: What can the last century teach us about climate models?, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5377, https://doi.org/10.5194/egusphere-egu22-5377, 2022.

EGU22-6756 | Presentations | CL5.3.2

Seasonal-to-decadal variability and predictability of the Kuroshio Extension in the GFDL Coupled Ensemble Reanalysis and Forecasting system 

Youngji Joh, Thomas Delworth, Andrew Wittenberg, William Cooke, Xiasong Yang, Fanrong Zeng, Liwei Jia, Feiyu Lu, Nathaniel Johnson, Sarah Kapnick, Anthony Rosati, Liping Zhang, and Colleen McHugh

The Kuroshio Extension (KE), an eastward-flowing jet located in the Pacific western boundary current system, exhibits prominent seasonal-to-decadal variability, which is crucial for understanding climate variations in northern midlatitudes. We explore the representation, predictability, and prediction skill for the KE in the GFDL SPEAR (Seamless System for Prediction and EArth System Research) coupled model. Two different approaches are used to generate coupled reanalyses and forecasts: (1) restoring the coupled model’s SST and atmospheric variables toward existing reanalyses, or (2) assimilating SST and subsurface observations into the coupled model without atmospheric assimilation.  Both systems use an ocean model with 1o resolution and capture the largest sea surface height (SSH) variability over the KE region. Assimilating subsurface observations appears to be critical to reproduce the narrow front and related oceanic variability of the KE jet in the coupled reanalysis. We demonstrate skillful retrospective predictions of KE SSH variability in monthly (up to 1 year) and annual-mean (up to 5 years) KE forecasts in the seasonal and decadal prediction systems, respectively. The prediction skill varies seasonally, peaking for forecasts initialized in January and verifying in September due to the winter intensification of North Pacific atmospheric forcing. We show that strong large-scale atmospheric anomalies generate deterministic oceanic forcing (i.e., Rossby waves), leading to skillful long-lead KE forecasts. These atmospheric anomalies also drive Ekman convergence/divergence that forms ocean memory, by sequestering thermal anomalies deep into the winter mixed layer that re-emerge in the subsequent autumn. The SPEAR forecasts capture the recent negative-to-positive transition of the KE phase in 2017, projecting a continued positive phase through 2022.

How to cite: Joh, Y., Delworth, T., Wittenberg, A., Cooke, W., Yang, X., Zeng, F., Jia, L., Lu, F., Johnson, N., Kapnick, S., Rosati, A., Zhang, L., and McHugh, C.: Seasonal-to-decadal variability and predictability of the Kuroshio Extension in the GFDL Coupled Ensemble Reanalysis and Forecasting system, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6756, https://doi.org/10.5194/egusphere-egu22-6756, 2022.

EGU22-6767 | Presentations | CL5.3.2 | Highlight

Long-term climate prediction for Ireland and its surrounding 

Stephen Ogungbenro, Catherine O'Beirne, and André Düsterhus

Ireland is bordering the North Atlantic, and its climate is dominated by its climate modes on short to longer timescales. The Atlantic low-pressure systems, Jetstream variabilities and airmasses are features of the atmospheric circulation, which also contribute to the climate this region.  So, a long-term climate prediction of Ireland is majorly controlled by the ocean, and by other atmospheric components.

The Ocean has shown good capabilities for decadal to multi-decadal climate predictions, hence, our study adapted a coupled model to investigate seasonal changes in the climate on annual to multi-annual timescales within the Max Planck Institute for Meteorology Earth System Model (MPI-ESM).  Initialized prediction is extended to multi-decadal timescale up onto twenty lead years, and we study prediction capabilities for common climate variables in and around , by identifying major drivers and documenting their prediction skills.  Our results have shown prediction skill for surface temperature over longer timescales, and we explore these capabilities for other variables of interest.  This study opens new opportunities for better long-term predictions of climate components in the region, and our results are relevant for strategic planning.

How to cite: Ogungbenro, S., O'Beirne, C., and Düsterhus, A.: Long-term climate prediction for Ireland and its surrounding, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6767, https://doi.org/10.5194/egusphere-egu22-6767, 2022.

EGU22-7037 | Presentations | CL5.3.2 | Highlight

Destabilizing the Earth’s thermostat: Riverine alkalinity responses to climate change 

Nele Lehmann, Tobias Stacke, Sebastian Lehmann, Hugues Lantuit, John Gosse, Chantal Mears, Jens Hartmann, and Helmuth Thomas

Alkalinity generation from rock weathering is thought to modulate the Earth’s climate at geological time scales. Here, we use global alkalinity data paired with consistent measurements of erosion rates to develop an empirically-based model for riverine alkalinity concentration, demonstrating the impact of both erosion (i.e. erosion rate) and climate (i.e. temperature) on alkalinity generation, globally. We show that alkalinity generation from carbonate rocks is very responsive to temperature and that the weathering flux to the ocean will be significantly altered by climate warming as early as the end of this century, constituting a sudden feedback of ocean CO2 sequestration to climate. While we anticipate that climate warming under a low emissions scenario will induce a reduction in terrestrial alkalinity flux for mid-latitudes (-1.3 t(bicarbonate) a-1 km-2) until the end of the century, resulting in a temporary reduction in CO2 sequestration, we expect an increase (+1.6 t(bicarbonate) a-1 km-2) under a high emissions scenario, causing an additional short-term CO2 sink at decadal timescales.

How to cite: Lehmann, N., Stacke, T., Lehmann, S., Lantuit, H., Gosse, J., Mears, C., Hartmann, J., and Thomas, H.: Destabilizing the Earth’s thermostat: Riverine alkalinity responses to climate change, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7037, https://doi.org/10.5194/egusphere-egu22-7037, 2022.

EGU22-7652 | Presentations | CL5.3.2

Towards operational climate prediction: ENSO-related variability as simulated in a set of state-of-the-art seasonal prediction systems 

Roberto Suarez-Moreno, Lea Svendsen, Ingo Bethke, Martin P. King, Ping-Gin Chiu, and Tarkan A. Bilge

In the last decade, high demands from stakeholders and policymakers have driven unprecedented research efforts directed to improve climate predictability. Nevertheless, attempts to get operational climate predictions on seasonal time scales have been far from skillful for a long time. Based on sources of predictability from the ocean, atmosphere and land processes, current state-of-the-art prediction systems are approaching operational predictability. This work examines and compares the ability of different prediction systems to simulate the variability of sea surface temperatures (SSTs) associated with El Niño-Southern Oscillation (ENSO) and the ENSO-forced response of hydroclimate variability in the North Atlantic-Europe (NAE) region. Seasonal hindcasts derived from two generations of the Norwegian Earth System Model (NorESM1-ME and NorESM2-MM) are used in addition to C3S data to generate time series of year-to-year variability that are validated against observational data. Our results reveal both the advantages and the limitations of these prediction systems to simulate ENSO-related variability, identifying model biases that prevent skillful predictability. Further efforts must be aimed at mitigating these biases in order to achieve fully operational predictions of paramount importance for the benefit of society.

How to cite: Suarez-Moreno, R., Svendsen, L., Bethke, I., King, M. P., Chiu, P.-G., and Bilge, T. A.: Towards operational climate prediction: ENSO-related variability as simulated in a set of state-of-the-art seasonal prediction systems, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7652, https://doi.org/10.5194/egusphere-egu22-7652, 2022.

EGU22-8031 | Presentations | CL5.3.2

Multi-model comparison of carbon cycle predictability in initialized perfect-model simulations 

Aaron Spring, Hongmei Li, Tatiana Ilyina, Raffaele Bernardello, Yohan Ruprich-Robert, Etienne Tourigny, Juliette Mignot, Filippa Fransner, Jerry Tjiputra, Reinel Sospedra-Alfonso, Thomas Frölicher, and Michio Watanabe

Predicting carbon fluxes and atmospheric CO2 can constrain the expected next-year atmospheric CO2 growth rate and thereby allow to independently monitor total anthropogenic CO2 emission rates. Several studies have established predictive skill in retrospective forecasts of carbon fluxes. These studies are usually backed by perfect-model simulations of single models showing the origins of predictive skill in carbon fluxes and atmospheric CO2 concentration. Yet, a comprehensive multi-model comparison of perfect-model predictions, which can be valuable in explaining differences in retrospective predictions, is still lacking. Moreover, as of now, we don't have sufficient understanding of how well do the models predict their own integrated carbon cycles and how congruent this predictability is across models.

Here, we show the predictive skill of land and ocean carbon fluxes as well as atmospheric CO2 concentration in seven Earth-System-Models. Our first results indicate predictive skill of globally aggregated carbon fluxes of 2±1 years and atmospheric CO2 of 3±2 years. However, the regional patterns, hotspots and origins of predictive skill diverge among models. This heterogeneity explains the regional differences found in existing retrospective forecasts and backs the overall consistent predictability time-scales at global scale.

How to cite: Spring, A., Li, H., Ilyina, T., Bernardello, R., Ruprich-Robert, Y., Tourigny, E., Mignot, J., Fransner, F., Tjiputra, J., Sospedra-Alfonso, R., Frölicher, T., and Watanabe, M.: Multi-model comparison of carbon cycle predictability in initialized perfect-model simulations, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8031, https://doi.org/10.5194/egusphere-egu22-8031, 2022.

EGU22-8038 | Presentations | CL5.3.2 | Highlight

Global carbon budget variations in emission-driven earth system model predictions 

Hongmei Li, Tatiana Ilyina, Tammas Loughran, and Julia Pongratz

Predictions of the variations in anthropogenic global carbon budget (GCB), i.e., CO2 emissions and their redistribution among the atmosphere, ocean, and land reservoirs, is crucial to constrain the global carbon cycle and climate change of the past and facilitate their prediction and projection into the future. Global carbon project assesses the GCB every year by taking into account available datasets and stand-alone model component simulations. The utilization of different data sources leads to an unclosed budget, i.e., budget imbalance. We propose a novel approach to assess the GCB in decadal prediction systems based on emission-driven earth system models (ESMs). Such a fully coupled prediction system enables a closed carbon budgeting and therefore provides an additional line of evidence for the ongoing assessments of the GCB.

As ESMs have their own mean state and internal variability, we assimilate ocean and atmospheric observational and reanalysis data into Max Planck Institute Earth system model (MPI-ESM) to reconstruct the actual evolution of climate and carbon cycle towards to the real world. In the emission-driven model configuration, the carbon cycle changes in response to the physical state changes, in the meanwhile, the feedback of atmospheric CO2 changes to physics are also considered via interactive carbon cycle. Our reconstructions capture the observed GCB variations in the past decades. They show high correlations relative to the assessments from the global carbon project of 0.75, 0.75 and 0.97 for atmospheric CO2 growth, air-land CO2 fluxes and air-sea CO2 fluxes, respectively. Retrospective predictions starting from the reconstruction show promising predictive skill for the global carbon cycle up to 5 years for the air-sea CO2 fluxes and up to 2 years for the air-land CO2 fluxes and atmospheric carbon growth rate. Furthermore, evolution in atmospheric CO2 concentration in comparing to satellite and in-situ observations show robust skill in reconstruction and next-year prediction.  

How to cite: Li, H., Ilyina, T., Loughran, T., and Pongratz, J.: Global carbon budget variations in emission-driven earth system model predictions, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8038, https://doi.org/10.5194/egusphere-egu22-8038, 2022.

EGU22-8624 | Presentations | CL5.3.2 | Highlight

Seasonal prediction of North American wintertime cold extremes in GFDL SPEAR forecast system 

Liwei Jia, Thomas Delworth, Xiaosong Yang, William Cooke, Nathaniel Johnson, and Andrew Wittenberg

Skillful prediction of wintertime cold extremes on seasonal time scales is beneficial for multiple sectors. This study demonstrates that North American cold extremes, measured by the frequency of cold days in winter, are predictable several months in advance in Geophysical Fluid Dynamics Laboratory’s SPEAR seasonal (Seamless system for Prediction and EArth system Research) forecast system. Two predictable components of cold extremes over North American land areas are found to be skillfully predicted on seasonal scales. One is a trend component, which shows a continent-wide decrease in the frequency of cold extremes and is attributable to external radiative forcing. This trend component is predictable at least 9 months ahead. The other predictable component displays a dipole structure over North America, with negative signs in the northwest and positive signs in the southeast. This dipole component is predictable with significant correlation skill for 2 months and is a response to the central Pacific El Nino as revealed from SPEAR AMIP-like simulations. 

How to cite: Jia, L., Delworth, T., Yang, X., Cooke, W., Johnson, N., and Wittenberg, A.: Seasonal prediction of North American wintertime cold extremes in GFDL SPEAR forecast system, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8624, https://doi.org/10.5194/egusphere-egu22-8624, 2022.

EGU22-9618 | Presentations | CL5.3.2

Processes of interannual internal variability of the CO2 flux at the air-sea interface in IPSLCM6A 

Matthew Menary, Juliette Mignot, Laurent Bopp, and Lester Kwiatkowski

In order to improve our ability to predict the near-term evolution of climate, it may be important to accurately predict the evolution of atmospheric CO2, and thus carbon sinks. Following on from process-driven improvements of decadal predictions in physical oceanography, we focus on improving our understanding of the internal processes and variables driving CO2 uptake by the North Atlantic ocean. Specifically, we use the CMIP6 model IPSLCM6A to investigate the drivers of ocean-atmosphere CO2 flux variability in the North Atlantic subpolar gyre (NA SPG) on seasonal to decadal timescales. We find that DpCO2 (CO2 partial pressure difference between atmosphere and ocean) variability dominates over sea surface temperature (SST) and sea surface salinity (SSS) variability on all timescales within the NA SPG. Meanwhile, at the ice-edge, there are significant roles for both ice concentration and surface winds in driving the overall CO2 flux changes. Investigating the interannual DpCO2 variability further, we find that this variability is itself driven largely by variability in simulated mixed layer depths in the northern SPG. On the other hand, SSTs show an important contribution to DpCO2 variability in the southern SPG and on longer (decadal) timescales. Initial extensions into a multi-model context show similar results. By determining the key regions and processes important for skilful decadal predictions of ocean-atmosphere CO2 fluxes, we aim to both improve confidence in these predictions as well as highlight key targets for climate model improvement. 

How to cite: Menary, M., Mignot, J., Bopp, L., and Kwiatkowski, L.: Processes of interannual internal variability of the CO2 flux at the air-sea interface in IPSLCM6A, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9618, https://doi.org/10.5194/egusphere-egu22-9618, 2022.

EGU22-9719 | Presentations | CL5.3.2

Seasonal Forecasting of Horn of Africa’s Long Rains Using Physics-Guided Machine Learning 

Victoria Deman, Akash Koppa, and Diego Miralles

The Horn of Africa is known to be prone to climate impacts; the frequent occurrence of droughts and floods creates vulnerable conditions in the region. Gaining knowledge on (sub-)seasonal weather prediction and generating more reliable long-term forecasts is an important asset in building resilience. Most of the region is characterized by a bimodal precipitation cycle with rainfall seasons in boreal spring (March–May), termed the long rains, and boreal autumn (October–November), termed the short rains. Previous studies on seasonal forecasting focused mostly on empirical linear regression methods using information from ocean–atmosphere modes. To date, the potential of more complex methods, such as machine learning approaches, in improving seasonal precipitation predictability in the Horn of Africa still remains understudied. 

 

In this study, machine learning models targeting precipitation during the long rains are developed. The focus on the long rains is motivated by the fact that it is the main rain season in the region and the sources of predictability have proven to be more difficult to pin down. The long rain season has a weak internal coherence and looking at the months separately has proven to enhance prediction skill. Therefore, machine learning models are constructed for the different months (March, April, and May) separately at lead times of 1–3 months. Following an extensive survey of literature, the predictors of the long rain precipitation at seasonal timescales selected in this study include coupled oceanic-atmospheric oscillation indices (such as MJO, ENSO and PDO), regions of zonal winds over 200mb and 850mb and sea-surface temperature (SST) regions with strong correlation to long rain precipitation. Further, a selection of additional terrestrial and oceanic predictors is guided by Lagrangian transport modeling, used to identify the regions sourcing moisture during the long rains. This set of predictors include soil moisture, land surface temperature, normalized vegetation index (NDVI), leaf area index (LAI) and SST, which are averaged over the climatological source region of long rain precipitation. Finally, we provide new insights into the predictability of long rain precipitation at seasonal timescales by analyzing the relative importance of the different predictors used for developing the machine learning model.

How to cite: Deman, V., Koppa, A., and Miralles, D.: Seasonal Forecasting of Horn of Africa’s Long Rains Using Physics-Guided Machine Learning, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9719, https://doi.org/10.5194/egusphere-egu22-9719, 2022.

EGU22-9921 | Presentations | CL5.3.2

Understanding intermodel differences in land carbon sink projections 

Ryan S. Padrón, Lukas Gudmundsson, Vincent Humphrey, Laibao Liu, and Sonia I. Seneviratne

Over the last decades, land ecosystems have removed from the atmosphere approximately one third of anthropogenic carbon emissions, highlighting the importance of the evolution of the land carbon sink for projected climate change. Nevertheless, the latest land carbon sink projections from multiple Earth system models show large differences, even for a policy-relevant scenario with mean global warming by the end of the century below 2°C relative to preindustrial conditions. We hypothesize that this intermodel uncertainty originates from model differences in the sensitivities of annual net biome production (NBP) to (i) the CO2 fertilization effect, and to the annual anomalies in growing season (ii) air temperature and (iii) soil moisture, as well as model differences in long-term average (iv) air temperature and (v) soil moisture. Using multiple linear regression and a resampling technique we quantify the individual contributions of these five terms for explaining the cumulative NBP anomaly of each model relative to the ensemble mean. Differences in the three sensitivity terms contribute the most, however, differences in average temperature and soil moisture also have sizeable contributions for some models. We find that the sensitivities of NBP to temperature and soil moisture anomalies, particularly in the tropics, explain approximately half of the deficit relative to the ensemble mean for the two models with the lowest carbon sink (ACCESS-ESM1-5 and UKESM1-0-LL) and half of the surplus for the two models with the highest sink (CESM2 and NorESM2-LM). In addition, year-to-year variations in NBP are more related to variations in soil moisture than air temperature across most models and regions, although several models indicate a stronger relation totemperature variations in the core of the Amazon. Overall, our study advances our understanding of why land carbon sink projections from Earth system models differ globally and across regions, which can guide efforts to reduce the underlying uncertainties.

How to cite: Padrón, R. S., Gudmundsson, L., Humphrey, V., Liu, L., and Seneviratne, S. I.: Understanding intermodel differences in land carbon sink projections, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9921, https://doi.org/10.5194/egusphere-egu22-9921, 2022.

EGU22-10228 | Presentations | CL5.3.2

Near-term prediction of the global carbon cycle using EC-Earth3-CC, the Carbon Cycle version of the EC-Earth3 Earth System Model 

Etienne Tourigny, Raffaele Bernardello, Valentina Sicardi, Pablo Ortega, Yohan Ruprich Robert, Vladimir Lapin, Juan C. Acosta Navarro, Roberto Bilbao, Arndt Meier, Hongmei Li, and Tatiana Ilyina

Anthropogenic CO2 emissions are associated with global warming in the late 20th century and beyond. Climate-carbon feedbacks will likely result in a higher airborne fraction of emitted CO2 in the future. However, the variability in atmospheric CO2 growth rate is largely controlled by natural variability and is poorly understood. This can interfere with the attribution  of slowing CO2 growth rates  to reducing emissions during the implementation of the Paris Agreement. There is thus a need to both improve our understanding of the processes controlling the global carbon cycle and establish a near-term prediction system of the climate and carbon cycle.

As part of the 4C (Carbon Cycle Interactions in the Current Century) project, the Barcelona Supercomputing Center is implementing a new system for near-term prediction of the climate and carbon cycle interactions using EC-Earth3-CC, the Carbon Cycle version of the EC-Earth3 Earth System Model. This new system is based on the existing operational climate prediction system developed by the BSC, contributing to the WMO Global Annual to Decadal Climate Update. EC-Earth3-CC comprises the IFS atmospheric model, the NEMO ocean model, the PISCES ocean biogeochemistry model, the LPJ-GUESS dynamic vegetation model, the TM5 global atmospheric transport model and the OASIS3 coupler. The system uses initial conditions from in-house ocean biogeochemical and land/vegetation reconstructions based on global atmospheric/ocean reanalyses. By performing retrospective decadal predictions of ocean and land carbon uptake we are able to evaluate the performance of the system in predicting CO2 fluxes and atmospheric CO2 concentrations.

We will present results from the latest concentration- and emission-driven retrospective predictions (or hindcasts) using our system, highlighting the skill and biases of the carbon fluxes and atmospheric CO2. We will also present future predictions for 2022 and beyond, a prototype for the operational system for prediction of future atmospheric CO2.

How to cite: Tourigny, E., Bernardello, R., Sicardi, V., Ortega, P., Ruprich Robert, Y., Lapin, V., Acosta Navarro, J. C., Bilbao, R., Meier, A., Li, H., and Ilyina, T.: Near-term prediction of the global carbon cycle using EC-Earth3-CC, the Carbon Cycle version of the EC-Earth3 Earth System Model, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10228, https://doi.org/10.5194/egusphere-egu22-10228, 2022.

EGU22-10245 | Presentations | CL5.3.2

Drivers of the natural CO2 fluxes at global scale as simulated by CMIP6 simulations 

Veronica Martin-Gomez, Yohan Ruprich-Robert, Raffaele Bernardello, and Margarida Samso Cabre

The implementation of the Paris Agreement should translate into a decrease of the growth rate of atmospheric CO2 in the coming decades due to the reduction in emissions by signing countries. However, the detection of this decrease and its attribution to mitigation measures will be challenging for two reasons: 1) the internal variability of the Earth system may temporarily offset this signal and 2) countries may not maintain their promises. Unless absolute transparency on emissions is adopted by all signing parties, without a robust estimate of the impact of internal variability on the atmospheric CO2 changes, there is no independent way to verify their claims. 

Historical reconstructions and future predictions of global carbon cycle dynamics with predictive systems based on state-of-the-art Earth System Models (ESMs) represent an emerging field of research. With the continuous improvement of ESMs and of these predictive systems, these tools might have the potential of becoming skillful enough in their predictions to represent a useful instrument for policy makers in their effort to monitor and verify the progress of the Paris Agreement’s implementation. 

Here we analyze the main sources of the atmospheric CO2 concentration variability at inter-annual timescale due to internal climate processes in three ESMs, which are used in carbon cycle prediction systems: EC-Earth3-CC, IPSL-CM6A-LR, and MPI-ESM1-2-LR. These results are then compared to the available CMIP6 simulations database.

Investigating the surface CO2 fluxes, we find that land flux inter-annual variations are 10 times higher than ocean flux variations. This has direct consequences in terms of predictability since the land surface processes are generally less predictable than the ocean ones. The regions contributing the most to the variations are Australia, South America and sub-Saharan Africa, suggesting that those are the most important regions to simulate correctly in order to constrain the atmospheric CO2 variations. Interestingly, all those regions are linked to tropical SST variations resembling El Niño Southern Oscillation variability.

Investigating the ocean CO2 fluxes, we find that the regions contributing the most to the global CO2 variations are the Southern Ocean followed by the tropical Pacific.

Therefore, from the analysis of the CMIP6 simulations, we conclude that the main internal driver of the global atmospheric CO2 fluctuations is the tropical Pacific. If the ratio between land and ocean CO2 variations is realistically simulated by the CMIP6 ESMs, this implies that the predictability of the atmospheric CO2 variations due to internal climate processes is tied to the predictability of the tropical Pacific.

How to cite: Martin-Gomez, V., Ruprich-Robert, Y., Bernardello, R., and Samso Cabre, M.: Drivers of the natural CO2 fluxes at global scale as simulated by CMIP6 simulations, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10245, https://doi.org/10.5194/egusphere-egu22-10245, 2022.

EGU22-10340 | Presentations | CL5.3.2 | Highlight

On the seasonal prediction and predictability of winter temperature swings over North America 

Xiaosong Yang, Tom delworth, Liwei Jia, Nathaniel Johnson, Feiyu Lu, and Colleen MacHugh

A novel temperature swing index (TSI) is formed to measure the extreme surface temperature variations associated with the winter extratropical storms. The seasonal prediction skill of the winter TSI over North America was assessed versus ERA5 data using GFDL’s new SPEAR seasonal prediction system. The location with the skillful TSI prediction shows distinctive geographic pattern from that with skillful seasonal mean temperature prediction, thus the skillful prediction of TSI provides additive predictable climate information beyond the traditional seasonal mean temperature prediction. The source of the seasonal TSI prediction can be attributed to year-to-year variations of ENSO, North Pacific Oscillation and NAO. These results point towards providing skillful prediction of higher-order statistical information related to winter temperature extremes, thus enriching the seasonal forecast products for the research community and decision makers beyond the seasonal mean.

How to cite: Yang, X., delworth, T., Jia, L., Johnson, N., Lu, F., and MacHugh, C.: On the seasonal prediction and predictability of winter temperature swings over North America, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10340, https://doi.org/10.5194/egusphere-egu22-10340, 2022.

In the Northwest Atlantic (NWA), including the Labrador Sea, interactions between the atmosphere, ocean circulation, and sea ice play a critical role in regulating the global climate system. The ocean and climate in this region observe rapid and unprecedented, anthropogenically forced changes to the physical environment and biosphere with downstream effects. Future projections of NWA circulation and sea ice can help address pressing questions about these changes and mitigate their potential impacts on the global carbon cycle, coastal communities, and transportation. However, the spatial resolution of current climate models is often insufficient to accurately represent important features in the NWA, such as the location and strength of the Gulf Stream and Labrador Current and their dynamical interactions. This can lead to biases in the model’s mean state, and a misrepresentation of the temporal and spatial scales of ocean variability, e.g., mesoscale eddies, deep convection. Regional ocean models with grid spacing <10 km, forced by global climate simulations, can be used to improve estimates of historical and future circulation and hydrography. However, given the limited spatial resolution and biases in global climate models, a challenge of downscaling their simulations is the appropriate reconstruction of the forcing fields.

Here, we present preliminary results of future projections of NWA circulation and sea ice based on downscaled global climate simulations. These projections are performed using an eddy-resolving, coupled circulation-sea ice model based on the Regional Ocean Modeling System (ROMS) and the Los Alamos Sea Ice Model (CICE). We will focus on the value of correcting biases in the mean and variance of the forcing. We further explore the need of including missing spatial and temporal scales in the atmospheric forcing that are not captured by the global models. Implications for the design of model experiments for future projections will be discussed.

How to cite: Renkl, C. and Oliver, E.: Bias Correction and Spatiotemporal Scales for Downscaling Future Projections of Northwest Atlantic Circulation and Sea Ice, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10467, https://doi.org/10.5194/egusphere-egu22-10467, 2022.

EGU22-10473 | Presentations | CL5.3.2

Proposal for an international effort aimed at quantifying the impact of a realistic representation of vegetation/land cover on seasonal climate forecasts (GLACE-VEG) 

Andrea Alessandri, Gianpaolo Balsamo, Souhail Boussetta, and Constantin Ardilouze

Several works have been showing the importance of vegetation/land cover in forcing interannual climate anomalies and in modulating the influence from soil moisture and/or snow. The aim of this initiative is to exploit the latest available observational data over land to improve the representation of vegetation and land cover that can positively contribute to skillful short-term (seasonal) climate predictions. However, the lack of observations in the past has often determined diverging representations of the processes related to land cover and vegetation among different land surface models. It is therefore fundamental to use the multi-model approach.

A coordinated multi-model prediction experiment will be designed to demonstrate the improvements of the predictions at seasonal time scale due to the enhanced representation of land cover and vegetation. Building from already established efforts (e.g. SNOWGLACE, LS3MIP, ESM-snowMIP, LS4P, CONFESS) we will involve the climate prediction community to develop a common experimental protocol for a multi-model coordinated experiment for the robust evaluation of the performance effects on state-of-the-art dynamical prediction systems. In addition, the verification of the coordinated multi-model predictions will provide understanding and guidance about the better approaches to pursue in the future to model land-vegetation processes.

The initial group of cooperative institutions include ISAC-CNR, ECMWF, Meteo France, while other relevant modeling groups already expressed interest to join. It is expected that a good representation of the centres previously involved in GLACE-2 initiative will participate in this coordinated effort.

The details of experimental protocol will be implemented during the second half of 2022. Simulations are expected to begin in 2023. To facilitate the spread of the initiative among the prediction community and the engagement with stakeholders, a proposal for a new Community Activity in the framework of GEO has been submitted. The initiative is also supported by the GEWEX-GLASS panel that will push it further within the related community.

How to cite: Alessandri, A., Balsamo, G., Boussetta, S., and Ardilouze, C.: Proposal for an international effort aimed at quantifying the impact of a realistic representation of vegetation/land cover on seasonal climate forecasts (GLACE-VEG), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10473, https://doi.org/10.5194/egusphere-egu22-10473, 2022.

EGU22-10621 | Presentations | CL5.3.2

Some key challenges for subseasonal to decadal prediction research 

William Merryfield, Johanna Baehr, Lauriane Batté, Asmerom Beraki, Leon Hermanson, Debra Hudson, Stephanie Johnson, June-Yi Lee, François Massonnet, Ángel Muñoz, Yvan Orsolini, Hong-Li Ren, Ramiro Saurral, Doug Smith, Yuhei Takaya, and Krishnan Raghavan

The practice of initialized subseasonal, seasonal and decadal climate prediction has matured considerably in recent years, with real-time subseasonal and decadal multi-system ensembles joining those established previously for the seasonal to multi-seasonal range. However, substantial scientific, modelling, and informational challenges remain that must be overcome in order to more fully realize the potential for such predictions to serve societal needs. This presentation will examine five such challenges that the World Climate Research Programme’s Working Group on Subseasonal to Interdecadal Prediction (WGSIP) has identified as crucial for further advancing capabilities for translating the inherent predictability of the Earth system into actionable predictive information. Surmounting these challenges will bring nearer an envisaged future in which global users have access to such information specific to individual needs, across Earth system components and on a continuum of time scales, with degrees of confidence, limitations and uncertainties clearly indicated, as well as tools to guide optimal actions.

How to cite: Merryfield, W., Baehr, J., Batté, L., Beraki, A., Hermanson, L., Hudson, D., Johnson, S., Lee, J.-Y., Massonnet, F., Muñoz, Á., Orsolini, Y., Ren, H.-L., Saurral, R., Smith, D., Takaya, Y., and Raghavan, K.: Some key challenges for subseasonal to decadal prediction research, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10621, https://doi.org/10.5194/egusphere-egu22-10621, 2022.

Over East Asia, reliable forecasts of boreal spring droughts and pluvials can provide time window of opportunities to mitigate their adverse effects. Here, we aim to assess the seasonal prediction skill of boreal spring droughts and pluvials over East Asia (EA), using NMME and atmospheric-only global climate model (AGCM) simulations. Results show that NMME models show a better prediction skill of pluvials than that of droughts, indicating asymmetry in the prediction skill. This asymmetric tendency is also found in the prediction skill of sea surface temperature (SST) during the corresponding drought and pluvial years. Results from the AGCM simulations show asymmetry in the prediction skills of spring droughts and pluvials, indicating the limited predictability of SST-teleconnections in the model physics. The findings of this study prioritize a need to improve the representation of sea-air interactions during drought years in the current climate models.

How to cite: Kim, B.-H. and Kam, J.: Asymmetry in the prediction skills of NMME models for springtime droughts and pluvials over East Asia, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10950, https://doi.org/10.5194/egusphere-egu22-10950, 2022.

EGU22-11562 | Presentations | CL5.3.2

Effects of aerosols reduction on the Asian summer monsoon prediction: the case of summer 2020 

Annalisa Cherchi, Andrea Alessandri, Etienne Tourigny, Juan C Acosta Navarro, Pablo Ortega, Paolo Davini, Danila Volpi, Franco Catalano, and Twan van Noije

Northern Hemisphere anthropogenic aerosols influence Southeast and East Asian summer monsoon precipitation. In the late 20th century, both the East Asian and the South Asian summer monsoons weakened because of increased emissions of anthropogenic aerosols over Asia, counteracting the warming effect of increased greenhouse gases (GHGs). Changes in the anthropogenic aerosols burden in the Northern Hemisphere, and specifically over the Asian continent, may also have affected the sub-seasonal evolution of the summer monsoon. During the spring 2020, when restrictions to contain the spread of the coronavirus were implemented worldwide, reduced emissions of gases and aerosols were detected also over Asia.

Following on from the above and using the EC-Earth3 coupled model, a case-study forecast for summer 2020 (May 1st start date) has been designed and produced with and without the reduced atmospheric forcing due to covid-19 in the SSP2-4.5 baseline scenario, as estimated and adopted within CMIP6 DAMIP covidMIP experiments (hereinafter “covid-19 forcing”). The forecast ensembles (sensitivity and control experiments, meaning with and without covid-19 forcing) consist of 60 members each to better account for the internal variability (noise) and to maximize the capability to identify the effects of the reduced emissions.

The analysis focuses on  the effects of the covid-19 forcing, in particular the reduction of anthropogenic aerosols, on the forecasted evolution of the monsoon, with a specific focus on the performance in predicting the summer precipitation over India and over other parts of  South and East Asia. Changes in the performance of the prediction for specific aspects of the monsoon, like the onset and the length of the season, are evaluated as well.

How to cite: Cherchi, A., Alessandri, A., Tourigny, E., Acosta Navarro, J. C., Ortega, P., Davini, P., Volpi, D., Catalano, F., and van Noije, T.: Effects of aerosols reduction on the Asian summer monsoon prediction: the case of summer 2020, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11562, https://doi.org/10.5194/egusphere-egu22-11562, 2022.

EGU22-12989 | Presentations | CL5.3.2

Skillful Prediction of Barents Sea Phytoplankton Concentration 

Filippa Fransner, Marius Årthun, Ingo Bethke, François Counillon, Annette Samuelsen, Jerry Tjiputra, Are Olsen, and Noel Keenlyside

The predictability of phytoplankton abundance in the Barents Sea is explored in the CMIP6 decadal prediction runs with the Norwegian Climate Prediction Model (NorCPM1), together with satellite data and in situ measurements. The model successfully predicts a maximum in the observed phytoplankton abundance in 2007 up to five years in advance, which is associated with a strong predictive skill of 2007 minimum extent of the summer sea ice concentration. The underlying mechanism is an event of anomalously high heat transport into the Barents Sea that is seen both in the model and in situ observations. These results are an important step towards marine ecosystem predictions.

How to cite: Fransner, F., Årthun, M., Bethke, I., Counillon, F., Samuelsen, A., Tjiputra, J., Olsen, A., and Keenlyside, N.: Skillful Prediction of Barents Sea Phytoplankton Concentration, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12989, https://doi.org/10.5194/egusphere-egu22-12989, 2022.

EGU22-1482 | Presentations | CL3.2.4

Pathways of resilience in complex systems. 

Max Rietkerk

The concept of tipping points and critical transitions helps inform our understanding of the catastrophic effects that global change may have on ecosystems, Earth system components, and the whole Earth system. The search for early warning indicators is ongoing, and spatial self-organization has been interpreted as one such signal. Here, we review how spatial self-organization can aid complex systems to evade tipping points and can therefore be a signal of resilience instead. Evading tipping points through various pathways of spatial pattern formation may be relevant for many ecosystems and Earth system components that hitherto have been identified as tipping prone, including for the entire Earth system.

M. Rietkerk, R. Bastiaansen, S. Banerjee, J. van de Koppel, M. Baudena and A. Doelman. 2021. Evasion of tipping in complex systems through spatial pattern formation. Science 374 (169): abj0359.

How to cite: Rietkerk, M.: Pathways of resilience in complex systems., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1482, https://doi.org/10.5194/egusphere-egu22-1482, 2022.

EGU22-2198 | Presentations | CL3.2.4 | Highlight

Partial tipping in a spatially heterogeneous world 

Robbin Bastiaansen, Henk Dijkstra, and Anna von der Heydt

Many climate subsystems are thought to be susceptible to tipping - and some might be close to a tipping point. The general belief and intuition, based on simple conceptual models of tipping elements, is that tipping leads to reorganization of the full (sub)system. Here, we explore tipping in conceptual, but spatially extended and spatially heterogenous models. These are extensions of conceptual models taken from all sorts of climate system components on multiple spatial scales. By analysis of the bifurcation structure of such systems, special stable equilibrium states are revealed: coexistence states with part of the spatial domain in one state, and part in another, with a spatial interface between these regions. These coexistence states critically depend on the size and the spatial heterogeneity of the (sub)system. In particular, in these systems a tipping point might lead to a partial tipping of the full (sub)system, in which only part of the spatial domain undergoes reorganization, limiting the impact of these events on the system's functioning.

How to cite: Bastiaansen, R., Dijkstra, H., and von der Heydt, A.: Partial tipping in a spatially heterogeneous world, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2198, https://doi.org/10.5194/egusphere-egu22-2198, 2022.

EGU22-3830 | Presentations | CL3.2.4 | Highlight

Cascading tipping in a coupled cryosphere-ocean model 

Sacha Sinet, Anna S. von der Heydt, and Henk A. Dijkstra
In the climate system, many different large-scale components have been identified as tipping elements, i.e., components that may pass a tipping point, with a substantial and definitive impact on earth and societies. These climate components do not stand on their own, but are dynamically coupled, which leads to the issue of cascading tipping. One important example of cascading involves the Greenland Ice Sheet (GIS), the West Antarctica Ice Sheet (WAIS) and the Atlantic Meridional Overturning Circulation (AMOC). While the destabilizing effect of a GIS decline on the AMOC is well established, the effect of a tipping WAIS is still unclear.
 
In this project, we aim at getting a better understanding of the global behaviour of this connected system, at a conceptual level. Accounting for the different nature of both ice sheets, we use two models including their most important feedbacks, namely, the marine ice sheet instability for the WAIS and the height-accumulation feedback for the GIS. The AMOC, depicted by the Rooth model, is coupled to both ice sheets through meltwater fluxes. Finally, we consider the Southern Ocean temperature as the main driver of the marine ice sheet instability.
With this conceptual interhemispheric model, we study the role of the AMOC as mediator of this potential cascading in hosing and/or climate change experiments, as well as the involved time scales. As a new result we find that, in this model, the stability of the AMOC depends on the ratio between the GIS and WAIS tipping rates, as well as their delay in time.

How to cite: Sinet, S., von der Heydt, A. S., and Dijkstra, H. A.: Cascading tipping in a coupled cryosphere-ocean model, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3830, https://doi.org/10.5194/egusphere-egu22-3830, 2022.

EGU22-4425 | Presentations | CL3.2.4 | Highlight

Tipping risks due to temperature overshoots within the Paris range 

Nico Wunderling, Ricarda Winkelmann, Johan Rockström, Sina Loriani, David A. McKay, Paul Ritchie, Boris Sakschewski, and Jonathan F. Donges

Climate tipping elements potentially lead to accelerated and irreversible climate change once their critical temperature threshold is passed. Some of their critical thresholds (tipping points) are at risk to be transgressed already within the temperature guardrails of 1.5-2.0°C above pre-industrial levels. However, it has been suggested at the same time that global mean temperature levels are likely to temporarily overshoot these boundaries.

Therefore, we investigate the tipping risk for a set of four interacting climate tipping elements using a conceptual model. To this end, we study the impact of different peak and long-term saturation temperatures on the Greenland Ice Sheet, the West Antarctic Ice Sheet, the Atlantic Meridional Overturning Circulation (AMOC) and the Amazon rainforest.

We find that overshoot peak temperatures between 2.5-4.0°C increase the risk by 10-55% even if long-term global mean temperature levels are stabilized between 1.5-2.0°C. Furthermore, the interactions between the tipping elements increase tipping risks significantly already at modest to intermediate levels of interaction. Therefore our conceptual study suggests that safe overshoots are only possible for low peak temperatures of the overshoot as well as final saturation temperatures at or below today’s global warming levels.

How to cite: Wunderling, N., Winkelmann, R., Rockström, J., Loriani, S., McKay, D. A., Ritchie, P., Sakschewski, B., and Donges, J. F.: Tipping risks due to temperature overshoots within the Paris range, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4425, https://doi.org/10.5194/egusphere-egu22-4425, 2022.

EGU22-4970 | Presentations | CL3.2.4

Planetary limits to soil degradation 

Clarisse Kraamwinkel, Anne Beaulieu, Teresa Dias, and Ruth Howison

Soils are essential to life on Earth but are rapidly degrading worldwide due to unsustainable human activities. We argue that soil degradation constitutes a key Earth system process that should be added as 10th Earth system process to the planetary boundaries framework.

Soil degradation shares all key traits with the nine Earth system processes already present in the planetary boundaries framework. It is caused by human activity, has the potential to cause unacceptable environmental change, shows tipping point behavior when forced beyond a critical level, is relevant on both local and global scales, and is strongly interrelated with the other Earth system processes. 

Healthy soils have a level of resilience against disturbances but once forced beyond a critical level, they are at risk of entering into a downward spiral of degradation fuelled by strong positive feedback loops. Well-documented examples include the local feedback between loss of soil structure and soil biota and the large-scale feedback loop between soil erosion and climate change. The final degraded state of the soil is unable to sustain human life on earth. The fall of past civilizations has been related to their inability to protect the soil. At present, ~33% of the global soils are moderately to severely degraded as a direct result of human activities such as unsustainable agricultural practices, urban expansion, and industrialization. Estimates show that by 2050, 90% of our soils will be degraded, the majority of our ecosystems will be compromised and the entire human population will be affected.

Soils are essential to life on Earth through the provision of soil functions and ecosystem services such as biomass production (including ~95% of the food we eat), climate regulation, water storage and purification, habitat provision, and nutrient cycling. They play a key role in achieving many of the Sustainable Development Goals (SDGs) including SDG 15: life on land, SDG2: zero hunger, and SDG6: clean water and sanitation. Soil degradation leads to critical disruptions to biosphere integrity, biogeochemical flows, climate change, and land-system change, all processes that have already crossed their planetary boundaries. Hence, in order to improve the planetary boundaries framework and clearly signal the need to protect the soil, we call for soil degradation to be considered the 10th Earth system process in the planetary boundaries framework. 

How to cite: Kraamwinkel, C., Beaulieu, A., Dias, T., and Howison, R.: Planetary limits to soil degradation, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4970, https://doi.org/10.5194/egusphere-egu22-4970, 2022.

EGU22-5176 | Presentations | CL3.2.4

Reversibility experiments of present-day Antarctic grounding lines 

Benoit Urruty, Emily A. Hill, Ronja Reese, Julius Garbe, Olivier Gagliardini, Gael Durand, Fabien Gillet-Chaulet, G. Hilmar Gudmundsson, Ricarda Winkelmann, Mondher Chekki, David Chandler, and Petra Langebroek

The stability of the grounding lines of Antarctica is a fundamental question in glaciology, because current grounding lines are in some locations at the edge of large marine basins, and have been hypothesized to potentially undergo irreversible retreat in response to climate change. This could have global consequences and raise sea levels by several metres. However, their reversibility for the current geometry has not yet been questioned, i.e. if pushed very slightly, are they able to recover their former position? 


Here we approach this question using three state-of-the-art ice sheet models (Elmer\Ice, Úa and PISM) which we initialise to closely replicate the current state of Antarctic ice sheet using inverse methods or spin-up approaches and the latest observations. To assess the reversibility of the Antarctic grounding lines in their current position, we apply a small amplitude perturbation in ice shelf melt rates for 20 years, which leads to a numerically significant grounding line retreat, but does not fundamentally alter it. After reversing the forcing we examine the grounding line evolution over the following 80 to 480 years, which allows us to see the direction of the ice sheet trajectory after removing the perturbation, i.e. recovery or further retreat. However, since ice dynamics adjust over long timescales of millennia, in some cases up to 500 years are not sufficient for the grounding lines to fully recover to their initial positions. To complement these experiments and to investigate the long-term response to small perturbations, we run the lower resolved Parallel Ice Sheet Model towards equilibrium. In this case, the perturbation is the increase from 1850 to present-day climate, and the experiments indicate whether present-day climate can cause Antarctic grounding lines to retreat on the long-term.


This work is part of the TiPACCs project and complements two presentations focusing on the short-term (EGU22-7802) and long-term (EGU22-7885) reversibility experiments of present-day Antarctic grounding lines in more detail.

How to cite: Urruty, B., Hill, E. A., Reese, R., Garbe, J., Gagliardini, O., Durand, G., Gillet-Chaulet, F., Gudmundsson, G. H., Winkelmann, R., Chekki, M., Chandler, D., and Langebroek, P.: Reversibility experiments of present-day Antarctic grounding lines, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5176, https://doi.org/10.5194/egusphere-egu22-5176, 2022.

EGU22-5370 | Presentations | CL3.2.4

Revealing hidden tipping in spatially-resolved Earth system analysis 

Sina Loriani, Boris Sakschewski, Jesse F. Abrams, Markus Drüke, Timothy Lenton, Nico Wunderling, Caroline Zimm, and Ricarda Winkelmann
The assessment of potential tipping elements in the Earth system and their associated tipping thresholds is essential for understanding long-term Earth system change and describing a safe operating space. However, their identification in model outputs and observational data typically requires making assumptions about the spatial extent of individual elements. While the resulting regional to continental aggregates allow for the study of collective time series, they are potentially based on subjective judgement and could mask non-linear behaviour on smaller scales.

In this work, we present a novel method based on a timescale- and variable-independent metric to automatically identify potential tipping elements in the Earth system with a few or no free parameters. Gridded datasets are scanned for abrupt shifts on the grid-cell level, which are subsequently automatically clustered in space and time. This allows for the creation of maps with areas grouped and classified by their dynamical behaviour without an a-priori definition of connected regions.

Applying the presented method to various Earth System model outputs, we detect clusters with different nonlinear responses to future emission scenarios which are otherwise masked. Consequently, our bottom-up approach provides insight into the spatial structures and temporal processes of large-scale tipping elements, and sheds light on ‘hidden’ tipping of their subsystems.

 

How to cite: Loriani, S., Sakschewski, B., Abrams, J. F., Drüke, M., Lenton, T., Wunderling, N., Zimm, C., and Winkelmann, R.: Revealing hidden tipping in spatially-resolved Earth system analysis, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5370, https://doi.org/10.5194/egusphere-egu22-5370, 2022.

EGU22-6786 | Presentations | CL3.2.4

Estimating nonlinear stability from time series data 

Adrian van Kan, Jannes Jegminat, and Jonathan Donges

Basin stability (BS) is a measure of nonlinear stability in multistable dynamical systems. BS has previously been estimated using Monte-Carlo simulations, which requires the explicit knowledge of a dynamical model. We discuss the requirements for estimating BS from time series data in the presence of strong perturbations, and illustrate our approach for two simple models of climate tipping elements: the Amazon rain forest and the thermohaline ocean circulation. We discuss the applicability of our method to observational data as constrained by the relevant time scales of total observation time, typical return time of perturbations and internal convergence time scale of the system of interest and other factors.

How to cite: van Kan, A., Jegminat, J., and Donges, J.: Estimating nonlinear stability from time series data, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6786, https://doi.org/10.5194/egusphere-egu22-6786, 2022.

EGU22-7064 | Presentations | CL3.2.4 | Highlight

Identification and management of climate change induced socio-economic tipping points 

Kees van Ginkel, Marjolijn Haasnoot, Elco Koks, and Wouter Botzen

Global warming may cause abrupt and non-linear climate tipping points, with large impacts to established socio-economic systems [1]. The socio-economic system itself also exhibits many non-linear change processes, and therefore may experience manifold unintentional climate-change induced socio-economic tipping points (SETPs) that could already follow from relatively small changes in climatic conditions. Examples are the gentrification of vulnerable groups or abrupt unplanned retreat from areas of increasing climate risk, abrupt transitions in financial markets, large-scale systematic malfunction of critical infrastructure networks during weather extremes, sudden reconfigurations of insurance markets and house price collapses. Such SETPs are defined as ‘a climate change induced, abrupt change of a socio-economic system, into a new, fundamentally different state’ [2]. It is important for spatial-economic planners and capital investors to know if and under what conditions SETPs may happen, and what can be done to anticipate and manage their causes and effects.

With three model-based case studies we demonstrate a stepwise approach to identify SETPs and to support adaptation and mitigation policy. The first is a house price collapse and radical transformation of long-term flood risk policy in a coastal city like Rotterdam, following rapid sea level rise due to Antarctic ice-sheet instability. Using a model that simulates flood risk, house prices and adaption integrally, we identify abrupt house price collapses in hundred-thousands possible futures spanning the uncertainty in sea level rise, storm surge and house market scenarios. We explicitly explore the long-term impacts of four dynamic adaptive strategies to anticipate flood risk and their successfulness in avoiding a SETP [3]. The second case is the financial collapse of the winter sports industry in the European Alps following a gradually retreating snowline [4]. The third is a large-scale systematic malfunction of national road networks of European countries due to increasing river flood hazards. The focus of our contribution is on showing how decision making can be supported despite the large uncertainties around SETPs. Finally, we discuss how the SETP-concept aligns with socio-ecological regime shifts [5] and deliberate positive social tipping points to achieve large mitigation and adaptation challenges [6,7].

Types of tipping points along the cause-effect chain from increasing GHG, to biophysical changes, to socioeconomic impacts and transformative adaptation and mitigation response. Source [2], CC-BY3.0 license.

Refs (doi): [1] 10.1073/pnas.2103081118; [2] 10.1088/1748-9326/ab6395; [3] 10.2139/ssrn.3935775; [4] 10.1016/j.envsci.2021.09.005; [5] 10.1088/1748-9326/aaaa75; [6] 10.1073/pnas.1900577117 [7] v10.1016/j.ecolecon.2021.107242

How to cite: van Ginkel, K., Haasnoot, M., Koks, E., and Botzen, W.: Identification and management of climate change induced socio-economic tipping points, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7064, https://doi.org/10.5194/egusphere-egu22-7064, 2022.

Soils are a key component of the Critical Zone of continental surfaces, ranging from the atmosphere to bedrock, guaranteeing the functioning of the Earth's ecosystems and ensuring the continuity of life on Earth. Our assumption is that highly biodiverse and functional soils provide the underpinning of indispensable services that ensure the basis for sustainable economic livelihoods and societies. Soils are susceptible to degradation through misuse, leading to a reduction in their functional diversity and redundancy. The adoption of a systemic approach, such as the social-ecological systems (SES) framework, may contribute to the identification of the adaptive capacities of societies to this expected reduction in soil functioning. In a SES framework, humans are embedded in natural systems and are understood to profoundly affect these system’s functions/services, interacting through feedbacks and cascading dynamics at different spatial and temporal scales. A SES framework is a suitable analytical tool that can provide insight on sensitive components and constellations of them, which likely may led to the crossing of a tipping point (TP), resulting in undesired alternative steady states of the system.

We aim to identify potential TPs, via an in-depth characterization and understanding of the SESs in the tri-national MAP region (Southwestern Amazon). For this purpose, we have delimited key underlying interconnected subsystems within the study region: the soil ecosystem, the livelihood system, the regional social system and the regional climate system. In our SES framework, we focus on relevant component’s functions for the tipping dynamics relating land use change and loss of ecosystem services. Our objective is to provide a set of early warning indicators of the impact and legacy damage of disturbances and the regulatory feedback dynamics between the different subsystems. Our hypothesis is that the crossing of a TP as consequence of reduced soil functions may exert pressure on livelihoods, as people shift to a new level of welfare or adapt their land use or income-generating activities. If this process leads to additional deforestation, it will likely lead to the amplification of regional drought events due to the loss of moisture convection that forests provide. Increasing drought due to the loss of forests will (self)amplify and lead to increased forest wildfires and more opportunities for illegal deforestation and land use change. Further, increasing livelihood and income insecurity, combined with insufficient provision of state services and regulation, as well as weak law enforcement, may exert pressure on social systems by e.g. making illegal and criminal activities more attractive, ultimately undermining social cohesion. In addition, a central aspect of our research is to investigate options for counteracting this cascade of detrimental/harmful and potentially self-amplifying positive feedbacks. This might be achieved by interfering with self-enhancing positive feedback loops, the stimulation of negative, stabilizing feedbacks, e.g. forest recovery or reflexive governance, especially on the local to regional level in order to prevent the crossing of TPs or even to stimulate non-linear dynamics towards positive TPs.

How to cite: Andrino, A. and the Prodigy Team: Exploring the emergence of tipping points in the social-ecological system at the border of Peru, Brazil and Bolivia (MAP region), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7867, https://doi.org/10.5194/egusphere-egu22-7867, 2022.

EGU22-11441 | Presentations | CL3.2.4

Detecting ecosystem-relevant crossings of thresholds 

Friederike Fröb, Timothée Bourgeois, Nadine Goris, Jörg Schwinger, and Christoph Heinze

With ongoing climate change, multiple stressors including ocean warming, deoxygenation, ocean acidification and limited nutrient availability are expected to lead to considerable regime shifts within marine ecosystems [1]. However, distinguishing such abrupt shifts from long-term trends in physical and biogeochemical ocean variables may not only be obscured by the natural variability of the system, but also the complexity of the ecosystem itself. Moreover, species-dependent physiological tolerances are likely going to limit the detectability of crossing of thresholds or tipping points of the whole ecosystem. The metabolic index describes temperature-dependent hypoxic tolerances with respect to the oxygen supply [2]. Critical values of the metabolic index indicate the geographical limits of marine species, therefore it is a useful metric to describe the extent of a potential habitat. Here, we assess the spatio-temporal detectability of abrupt changes in such a potential habitat for selected marine species using an environmental time series changepoint detection routine developed by [3]. We compare the number and timing of these abrupt changes in different Shared Socioeconomic Pathways (SSPs) run with the fully coupled Norwegian Earth System Model version 2 (NorESM2), i.e., analysing the SSP1-26, SSP-5-34-OS, and SSP5-85 scenarios. Preliminary results reveal global, regional and local abrupt changes of lost metabolically viable potential habitat in relation to environmental stressors under different evolving climates.

This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 820989 (project COMFORT). 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.

 

[1] Heinze et al., 2020, The quiet crossing of tipping points, PNAS, 118(9)

[2] Deutsch et al., 2020, Metabolic trait diversity shapes marine biogeography, Nature, 585, 557-562

[3] Beaulieu and Killick, 2018, Distinguishing trends and shifts from memory in climate data, Journal of Climate, 31(23), 9519-9543

How to cite: Fröb, F., Bourgeois, T., Goris, N., Schwinger, J., and Heinze, C.: Detecting ecosystem-relevant crossings of thresholds, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11441, https://doi.org/10.5194/egusphere-egu22-11441, 2022.

Concerns are rising that the earth system may reach some critical tipping points in the coming decades. Though, growing evidence also supports the potential of positive social tipping points that could propel transformative changes towards global sustainability. The recently approved ERC Starting Grant “StoRes” (Spatial-Temporal Dynamics of Flood Resilience) proposed a systematic analysis on unique cases of flood resilience, which is expected to demonstrate such a positive perspective over various spatial and temporal scales.

The ERC project focuses on the historical Tea Horse Road area (THR), a mountainous region of the Southeast Tibetan Plateau with well-documented history going back over 600 years. The study first sets up a theoretical framework on the multi-spatial-temporal features of flood resilience at the THR region, which covers the spatial differences (household, community, city and region) over the past 600 years regarding the governance, technology, society, and culture perspectives of flood resilience. A set of quantitative proxy data, historical archives, literature re-analysis, statistical data, observation data and field survey data are integrated into both the empirical study in the case areas and the agent-based modelling across the cases. Preliminary results indicated that, various strong and smart social regulations (governance, institutions, plans, management, motivations, orders, donations, dedication, etc.) enabled a wise development of many water conservancy projects that consequently enhanced the resilience of local communities to hydrological hazards.

The study aims to further 1) establish a theoretical understanding of the spatial-temporal scales of flood resilience; 2) investigate the spatial patterns and temporal evolution of flood resilience at the THR cases; 3) model the spatial-temporal dynamics of flood resilience using agent-based models; 4) transfer and generalize the research findings of the THR cases to the Mekong River basin and beyond. By doing so, the project will present pioneering work to shape the emerging research field of flood resilience, offering new and multi-dimensional knowledge on the dynamic nature of flood-society relations, and providing crucial missing links to understand how flood resilience develops within complex human-environment contexts.

How to cite: Yang, L. E.: Spatial-temporal dynamics of positive social resilience to flood hazards, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12359, https://doi.org/10.5194/egusphere-egu22-12359, 2022.

EGU22-12865 | Presentations | CL3.2.4

Towards a green water planetary boundary 

Lan Wang-Erlandsson, Arne Tobian, Ruud van der Ent, Ingo Fetzer, Sofie te Wierik, Miina Porkka, Arie Staal, Fernando Jaramillo, Heindriken Dahlmann, Chandrakant Singh, Peter Greve, Dieter Gerten, Patrick Keys, Tom Gleeson, Sarah Cornell, Will Steffen, Xuemei Bai, and Johan Rockström

Green water - i.e., land precipitation, evaporation and soil moisture - is fundamental for the functioning of the biosphere and the Earth System, but is increasingly perturbed by continental-to-planetary scale human pressures on land, water and climate systems. The planetary boundaries (PB) framework demarcates a global safe operating space for humanity, but does hitherto not explicitly account for green water. Here, we propose a green-water boundary within the existing PB framework, of which a control variable could be defined as "the percentage of ice-free land area on which root-zone soil moisture deviates from Holocene variability for any month of the year". We provide provisional estimates of baseline departures based on CMIP6 data, and review the literature on soil-moisture induced deterioration in Earth System functioning. The evidences taken together suggest that the green water PB is already transgressed, implying that human modifications of green water need to come to a halt and be reversed. Future research needs to advance our understanding of root-zone water dynamics, including associated large-scale and potentially non-linear interactions with ecohydrology, hydroclimate, biogeochemistry and societies.

How to cite: Wang-Erlandsson, L., Tobian, A., van der Ent, R., Fetzer, I., te Wierik, S., Porkka, M., Staal, A., Jaramillo, F., Dahlmann, H., Singh, C., Greve, P., Gerten, D., Keys, P., Gleeson, T., Cornell, S., Steffen, W., Bai, X., and Rockström, J.: Towards a green water planetary boundary, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12865, https://doi.org/10.5194/egusphere-egu22-12865, 2022.

EGU22-13474 | Presentations | CL3.2.4

Global blue and green water cycles exit from pre-industrial variation – freshwater change planetary boundary exceeded? 

Miina Porkka, Vili Virkki, Lan Wang-Erlandsson, Chinchu Mohan, Tom Gleeson, Dieter Gerten, and Matti Kummu
Cycling of water supports a wide array of Earth system functions ranging from ecosystem provision to regulating greenhouse gas fluxes. While justifiably included in the planetary boundaries framework, the current freshwater planetary boundary fails in recognising the interplay between local and global drivers modifying the water cycle. Building on recent conceptual work and considering an extended selection of Earth system functions, we propose quantitative indicators for blue and green water to measure and monitor water cycle modifications. These indicators can capture changes at local, regional, or planetary scales, offering a robust and easily measurable way of determining alterations in the water cycle.
 
Our data consisted of discharge (blue water) and root-zone soil moisture (green water) simulated by state-of-the-art gridded global hydrological models in ISIMIP 2b. Initiating our analysis at the 30-arcmin grid scale, we set cell-wise dry (5th percentile) and wet (95th percentile) local bounds based on pre-industrial (1681–1860) data, separately for blue and green water. We then determined cell-wise exits from these local bounds of baseline variability and aggregated them at the global scale. This resulted in a time series of the percentage of global land area where blue or green water anomalies exit local bounds of baseline variability. The 95th percentile of these global baseline departures was then set as the safe limit of water cycle modifications. Finally, to estimate the state of the water cycle, we compared the recent past (1881–2005) blue and green water conditions to the pre-industrial conditions. First, we determined cell-wise exits from the local bounds and then aggregated the global baseline departures to compare those with the safe limits.
 
We show that in all aspects - blue and green water and dry and wet anomalies - the global water cycle has undergone substantial changes and transgressed the safe limits. This is a result of a gradual change throughout the 20th century. For blue water, drying conditions dominate along the mid-latitudes, whereas for green water, large-scale wetting prevails in the Northern Hemisphere boreal regions. Major changes in both blue and green water conditions co-occur commonly around regions with the highest anthropogenic pressures. Overall, global changes especially towards drier blue water conditions and wetter green water conditions have gone far beyond the pre-industrial levels - therefore placing the water cycle in a state unknown to modern societies.
 
Our results underline the necessity and urgency to update the freshwater change planetary boundary. As both blue and green water cycles have entered an unprecedented state following a long and gradual change, Earth system functions upkept by the water cycle may already be or become compromised. While further studies are required to assess the status of the freshwater change planetary boundary alongside other boundaries to provide a comprehensive analysis on total Earth system resilience, our results clearly show that the global water cycle is changing towards the unknown.

How to cite: Porkka, M., Virkki, V., Wang-Erlandsson, L., Mohan, C., Gleeson, T., Gerten, D., and Kummu, M.: Global blue and green water cycles exit from pre-industrial variation – freshwater change planetary boundary exceeded?, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13474, https://doi.org/10.5194/egusphere-egu22-13474, 2022.

EGU22-13516 | Presentations | CL3.2.4 | Highlight

Ten new insights in climate science 2021 – a horizon scan 

Maria A. Martin

Since 2017, the 10 new insights in climate science (10NICS, https://10insightsclimate.science/) annually summarize a set of the most critical aspects of Earth’s complex climate system – including physical, biogeochemical and socioeconomic/sociocultural dimensions.

Here we set the context of the 10NICS series as a joint project between Future Earth, the Earth League and the World Climate Research Programme (WCRP), and briefly visit each of the ten insights from the 2021 edition (Martin et al., 2021):  (1) the options to still keep global warming below 1.5 °C; (2) the impact of non-CO2 factors in global warming; (3) a new dimension of fire extremes forced by climate change; (4) the increasing pressure on interconnected climate tipping elements; (5) the dimensions of climate justice; (6) political challenges impeding the effectiveness of carbon pricing; (7) demandside solutions as vehicles of climate mitigation; (8) the potentials and caveats of nature-based solutions; (9) how building resilience of marine ecosystems is possible; and (10) that the costs of climate change mitigation policies can be more than justified by the benefits to the health of humans and nature.

The 10NICS topics are not intended to form a comprehensive scientific assessment. Intentionally limited to 10, each insight is succinct and does not try to cover entire fields.

Martin, M. A., Alcaraz Sendra, O., Bastos, A., Bauer, N., Bertram, C., Blenckner, T., … Woodcock, J. (2021). Ten new insights in climate science 2021: a horizon scan. Global Sustainability, 4(e25), 1–20. https://doi.org/10.1017/sus.2021.25

How to cite: Martin, M. A.: Ten new insights in climate science 2021 – a horizon scan, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13516, https://doi.org/10.5194/egusphere-egu22-13516, 2022.

EGU22-13540 | Presentations | CL3.2.4

Conceptualizing World-Earth System resilience: Exploring transformation pathways towards a safe and just operating space for humanity 

John M. Anderies, Wolfram Barfuss, Jonathan F. Donges, Ingo Fetzer, Jobst Heitzig, and Johan Rockström

We develop a framework within which to conceptualize World-Earth System resilience.  Our notion of World-Earth System resilience emphasizes the need to move beyond the basin of attraction notion of resilience as we are not in a basin we can stay in. We are on a trajectory to a new basin and we have to avoid falling into undesirable basins.  We thus focus on `pathway resilience', i.e. the relative number of paths that allow us to move from the transitional operating space we occupy now as we leave the Holocene basin  to a safe and just operating space in the Anthropocene. We develop a mathematical model to formalize this conceptualization and demonstrate how interactions between earth system resilience  (biophysical processes) and world system resilience (social processes) impact pathway resilience.  Our findings show that building earth system resilience is probably our only chance to reach a safe and just operating space.  We also illustrate the importance of world system dynamics by showing how the notion of fairness coupled with regional inequality affects pathway resilience. 

How to cite: Anderies, J. M., Barfuss, W., Donges, J. F., Fetzer, I., Heitzig, J., and Rockström, J.: Conceptualizing World-Earth System resilience: Exploring transformation pathways towards a safe and just operating space for humanity, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13540, https://doi.org/10.5194/egusphere-egu22-13540, 2022.

EGU22-230 | Presentations | NP2.4

Eddy saturation in a reduced two-level model of the atmosphere 

Melanie Kobras, Maarten H. P. Ambaum, and Valerio Lucarini

Eddy saturation describes the nonlinear mechanism in geophysical flows whereby, when average conditions are considered, direct forcing of the zonal flow increases the eddy kinetic energy, while the energy associated with the zonal flow does not increase. We present a minimal baroclinic model that exhibits complete eddy saturation. Starting from Phillips’ classical quasi-geostrophic two-level model on the beta channel of the mid-latitudes, we derive a reduced order model comprising of six ordinary differential equations including parameterised eddies. This model features two physically realisable steady state solutions, one a purely zonal flow and one where, additionally, finite eddy motions are present. As the baroclinic forcing in the form of diabatic heating is increased, the zonal solution loses stability and the eddy solution becomes attracting. After this bifurcation, the zonal components of the solution are independent of the baroclinic forcing, and the excess of heat in the low latitudes is efficiently transported northwards by finite eddies, in the spirit of baroclinic adjustment.

How to cite: Kobras, M., Ambaum, M. H. P., and Lucarini, V.: Eddy saturation in a reduced two-level model of the atmosphere, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-230, https://doi.org/10.5194/egusphere-egu22-230, 2022.

EGU22-269 | Presentations | NP2.4

Nonlinear Multiscale Modelling of Layering in Turbulent Stratified Fluids 

Paul Pruzina, David Hughes, and Samuel Pegler

One of the most fascinating, and surprising, aspects of stratified turbulence is the spontaneous formation of density staircases, consisting of layers with nearly constant density, separated by interfaces with large density gradients. Within a staircase, there are two key lengthscales: the layer depth, and the interface thickness. Density staircases appear in regions of the ocean where the overall stratification is stable, and can be induced experimentally by stirring a fluid with a stable salt gradient. Staircases also appear as a result of double diffusive convection, in both oceanic and astrophysical contexts. Turbulent transport through staircases is enhanced compared to non-layered regions, so understanding their dynamics is crucial for modelling salt and heat transport.

Progress has been made numerically and experimentally, but the fundamental aspects of the problem are not yet fully understood. One leading theory is the Phillips Effect: layering occurs due to the dependence of the turbulent density flux on the density gradient. If the flux is a decreasing function of the gradient for a finite range of gradients, then negative diffusion causes perturbations to grow into systems of layers and interfaces.

An important extension of the Phillips theory is by Balmforth, Llewellyn-Smith and Young [J. Fluid Mech., 335:329-358, 1998], who developed a k-ε style model of stirred stratified flow in terms of horizontally averaged energy and buoyancy fields. These fields obey turbulent diffusion equations, with fluxes depending on a mixing length. The parameterisation of this lengthscale is key to the model, as it must pick out both layer and interface scales. This phenomonological model parameterises terms based on dimensional arguments, and neglects diffusion for simplicity. This model produces clear density staircases, which undergo mergers where two interfaces combine to form one. Layers take up the interior of the domain, while edge regions on either side expand inwards at a rate of t1/2 , removing layers from the outside in. Eventually the edge regions fill the entire domain, so the long time behaviour of the layers cannot be seen.

We present a similar model for stirred stratified layering derived directly from the Boussinesq equations, including molecular and viscous diffusion, so the model can be tailored to specific conditions to make realistic predictions. We show that the layered  region can evolve indefinitely through mergers, by taking fixed-buoyancy boundary conditions to prevent the expansion of the edge regions. We investigate the effects of diffusion on layer formation and evolution, finding that it acts to stabilise the system, both by decreasing the range of buoyancy gradients that are susceptible to the layering instability, and by decreasing the growth rates of perturbations. The lengthscale of the instability also increases, with larger viscosities and diffusivities producing deeper layers with less sharp interfaces.

This model can be used as a more general framework for layering phenomena. Extending to equations for energy, temperature and salinity can model double diffusive layering. More general parameterisations for the fluxes allow it to be adapted to other settings, including potential vorticity staircases in atmospheres and E×B staircases in plasmas.

How to cite: Pruzina, P., Hughes, D., and Pegler, S.: Nonlinear Multiscale Modelling of Layering in Turbulent Stratified Fluids, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-269, https://doi.org/10.5194/egusphere-egu22-269, 2022.

EGU22-1171 | Presentations | NP2.4

Decomposing the Dynamics of the Lorenz 1963 model using Unstable Periodic Orbits: Averages, Transitions, and Quasi-Invariant Sets 

Chiara Cecilia Maiocchi, Valerio Lucarini, and Andrey Gritsun

Unstable periodic orbits (UPOs) are a valuable tool for studying chaotic dynamical systems, as they allow one to distill their dynamical structure. We consider here the Lorenz 1963 model with the classic parameters' value. We investigate how a chaotic orbit can be approximated using a complete set of UPOs up to symbolic dynamics' period 14. At each instant, we rank the UPOs according to their proximity to the position of the orbit in the phase space. We study this process from two different perspectives. First, we find that longer period UPOs overwhelmingly provide the best local approximation to the trajectory. Second, we construct a finite-state Markov chain by studying the scattering of the orbit between the neighbourhood of the various UPOs. Each UPO and its neighbourhood are taken as a possible state of the system. Through the analysis of the subdominant eigenvectors of the corresponding stochastic matrix we provide a different interpretation of the mixing processes occurring in the system by taking advantage of the concept of quasi-invariant sets.

How to cite: Maiocchi, C. C., Lucarini, V., and Gritsun, A.: Decomposing the Dynamics of the Lorenz 1963 model using Unstable Periodic Orbits: Averages, Transitions, and Quasi-Invariant Sets, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1171, https://doi.org/10.5194/egusphere-egu22-1171, 2022.

On a synoptic time scale, the northern mid-latitudes weather is dominated by the influence of the eddy-driven jet stream and its variability. The usually zonal jet can become mostly meridional during so-called blocking events, increasing the persistence of cyclonic and anticyclonic structures and therefore triggering extremes of temperature or precipitations. During those events, the jet takes unusual latitudinal positions, either northerly or southerly of its mean position. Previous research proposed theoretically derived 1D models of the jet stream to represent the dynamics of such events. Here, we take a data-driven approach using ERA5 reanalysis data over the period 1979-2019 to investigate the variability of the eddy-driven jet latitudinal position and wind speed variability. We show that shifts of the jet latitudinal position occur on a daily time scale and are preceded by a strong decrease of the jet zonal wind speed 2-3 days prior to the shift. We also show that the dynamics of the jet zonal wind speed can be modelled by a non-linear oscillator with stochastic perturbations. We combine those two results to propose a simple 1D model capable of representing the statistics and dynamics of blocking events of the eddy-driven jet stream. The model is based on two stochastic coupled non-linear lattices representing the jet latitudinal position and zonal wind speed. Our model is able to reproduce temporal and spatial characteristics of the jet and we highlight a potential link between the propagation of solitary waves along the jet and the occurrence of blocking events.

How to cite: Noyelle, R., Faranda, D., and Yiou, P.: Modeling the Northern eddy-driven jet stream position and wind speed variability with stochastic coupled non-linear lattices, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1250, https://doi.org/10.5194/egusphere-egu22-1250, 2022.

We run a moist shallow water model with stochastic mesoscale forcing, to simulate the effects of mesoscale forcing on exciting large-scale flow structures. In previous work, we showed how the mesoscale forcing excites a classical -5/3 eddy kinetic energy upscale cascade to planetary scales where the linear tropical modes such as Rossby, Yanai, Intertial Gravity, and Kelvin waves form. In this work, we focus on the arising zonal mean flow.

We present results from ensembles of a few hundred simulations indicating multiple-equilibria in the tropical flow, once latent heat release passes a certain threshold in the first 1000 days. Runs up to one hundred thousand days confirm these results and show abrupt transitions in the dry and moist shallow-water turbulence lasting several thousand days. We will discuss the transient nature of the mean flow and suggest a possible new mechanism for the transition of the wind at the equator to super-rotation in a moist environment.

How to cite: Schröttle, J. and Harnik, N.: Spontaneous transitions between sub- and superrotation in dry and moist shallow-water turbulence on the sphere, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1307, https://doi.org/10.5194/egusphere-egu22-1307, 2022.

EGU22-1514 | Presentations | NP2.4

The Mid-Pleistocene Transition: A delayed response to an increasing positive feedback? 

Anne Willem Omta, John Shackleton, Mick Follows, and Peter Thomas

Glacial-interglacial cycles constitute large natural variations in Earth's climate. The Mid-Pleistocene Transition (MPT) marks a shift of the dominant periodicity of these climate cycles from ~40 to ~100 kyr. Ramping with frequency locking is a promising mechanism to explain the MPT, combining an increase in the internal period with lockings to an external forcing. We identify the strength of positive feedbacks as a key parameter to induce increases in the internal period and allow ramping with frequency locking. Using the calcifier-alkalinity model, we simulate changes in periodicity similar to the Mid-Pleistocene Transition through this mechanism. However, the periodicity shift occurs up to 10 Million years after the change in the feedback strength. This result puts into question the assumption that the cause for the MPT must have operated around the same time as the observed periodicity shift.

How to cite: Omta, A. W., Shackleton, J., Follows, M., and Thomas, P.: The Mid-Pleistocene Transition: A delayed response to an increasing positive feedback?, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1514, https://doi.org/10.5194/egusphere-egu22-1514, 2022.

Heat waves result from large-scale stationary waves and have major impacts on the economy and mortality. However, the dynamical processes leading to and maintaining heat waves are still not well understood. Here we use a nonlinear stationary wave model (NSWM) to examine the role played by anomalous stationary waves and how they are forced during heat waves. We will discuss heat waves in Europe and Asia. We show that the NSWM can successfully reproduce the main features of the observed anomalous stationary waves in the upper troposphere. Our results indicate that the dynamics of heat waves are nonlinear, and transient momentum fluxes are the primary drivers of the observed anomalous stationary waves. We will also discuss the role of anomalous SSTs in influencing heat waves.

How to cite: Franzke, C. and Ma, Q.: The role of transient eddies and diabatic heating in the maintenance of heat waves: a nonlinear quasi-stationary wave perspective, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1571, https://doi.org/10.5194/egusphere-egu22-1571, 2022.

EGU22-1988 | Presentations | NP2.4

Modelling Abrupt Transitions in Past Ocean Circulation to Constrain Future Tipping Points 

Guido Vettoretti, Markus Jochum, and Peter Ditlevsen

Recent observationally based studies indicate that the Atlantic Meridional Overturning Circulation (AMOC) and the Greenland Ice Sheet (GIS) may be approaching critical thresholds or tipping points, although the timing is uncertain. The connection between both Greenland meltwater fluxes and anthropogenic greenhouse gas emissions and their impact on the future state of the AMOC is also uncertain. Here we investigate the role of ocean vertical mixing within the interior and surface boundary layer (the K-Profile Parameterization (KPP)) on past millennial scale climate variability in a coupled climate model. Previous studies have demonstrated a sensitivity of the period of millennial scale ice age oscillations to the KPP scheme. Here we show that small changes in the profiles of vertical mixing under ice age boundary conditions can drive the AMOC through a Hopf bifurcation and result in the appearance of millennial-scale AMOC oscillations. This has implications on whether changes in tidal energy dissipation in the coastal and deep ocean are important for modelling past climate variability. More importantly, the same changes in ocean vertical mixing can impact the stability and hysteresis behaviour of the modern AMOC under freshwater input to the North Atlantic as well as leading to abrupt transitions in AMOC strength under a doubling of carbon dioxide concentrations in the atmosphere. We show how understanding the sensitivity of the AMOC to ocean vertical mixing parameterizations used in coupled Earth System models may be important for constraining future climate tipping points.

How to cite: Vettoretti, G., Jochum, M., and Ditlevsen, P.: Modelling Abrupt Transitions in Past Ocean Circulation to Constrain Future Tipping Points, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1988, https://doi.org/10.5194/egusphere-egu22-1988, 2022.

The directional dependencies of different climate indices are explored using the Liang-Kleeman information flow in order to disentangle the influence of certain regions over the globe on the development of low-frequency variability of others. Seven key indices (the sea-surface temperature in El-Niño 3.4 region, the Atlantic Multidecadal Oscillation, the North Atlantic Oscillation, the North Pacific America pattern, the Arctic Oscillation, the Pacifid Decadal Oscillation, the Tropical North Atlantic index), together with three local time series located in Western Europe (Belgium), are selected. The analysis is performed on time scales from a month to 5 years by using a sliding window as filtering procedure.

A few key new results on the remote influence emerge: (i) The Arctic Oscillation plays a key role at short time (monthly) scales on the dynamics of the North Pacific and North Atlantic; (ii) the North Atlantic Oscillation is playing a global role at long time scales (several years); (iii) the Pacific Decadal Oscillation is indeed slaved to other influences; (iv) the local observables over Western Europe influence the variability on the ocean basins on long time scales. These results further illustrate the power of the Liang-Kleeman information flow in disentangling the dynamical dependencies.

How to cite: Vannitsem, S. and Liang, X. S.: Dynamical dependencies at monthly and interannual time scales in the Climate system: Study of the North Pacific and Atlantic regions, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1994, https://doi.org/10.5194/egusphere-egu22-1994, 2022.

The rise of the global sea-level due to the melting of the Greenland ice-sheet poses one of the biggest threats to human society in the 21st century (IPCC, 2021). The Greenland ice sheet has been hypothesized to exhibit multiple stable states with tipping point behavior when crossing specific thresholds of the global mean temperature (Robinson et al., 2012). In regards to the desultory efforts to reduce the global emissions it becomes more and more unlikely to reach the 1.5°C goal by the end of the century and a crossing of the tipping threshold for the Greenland ice sheet becomes inevitable. First early-warning signals of a possible transition have already been found (Boers&Rypdal, 2021). However, it is known that a short-term overshooting of a critical threshold is possible without prompting a change of the system state (Ritchie et al., 2021). Using a complex ice sheet model, we investigate the effects of different carbon-capture scenarios after crossing the tipping threshold for the Greenland ice sheet. We are able to sketch a stability diagram for a number of emission scenarios and show that temporarily overshooting the temperature threshold for Greenland might be quasi-irreversible for some of the emission scenarios.

IPCC, 2021: Summary for Policymakers. In: Climate Change 2021: The Physical Science Basis. Contribution of
Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change [Masson-
Delmotte, V., P. Zhai, A. Pirani, S.L. Connors, C. Péan, S. Berger, N. Caud, Y. Chen, L. Goldfarb, M.I. Gomis, M.
Huang, K. Leitzell, E. Lonnoy, J.B.R. Matthews, T.K. Maycock, T. Waterfield, O. Yelekçi, R. Yu, and B. Zhou (eds.)].
Cambridge University Press. In Press.

Robinson, A., Calov, R. & Ganopolski, A. Multistability and critical thresholds of the Greenland ice sheet. Nature Clim Change 2, 429–432 (2012).

Boers, N. & Rypdal, M. Critical slowing down suggests that the western Greenland Ice Sheet is close to a tipping point. PNAS 118, (2021).

Ritchie, P. D. L., Clarke, J. J., Cox, P. M. & Huntingford, C. Overshooting tipping point thresholds in a changing climate. Nature 592, 517–523 (2021).

How to cite: Bochow, N.: Overshooting the tipping point threshold for the Greenland ice-sheet using a complex ice-sheet model, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2353, https://doi.org/10.5194/egusphere-egu22-2353, 2022.

EGU22-2396 | Presentations | NP2.4

Cascade of abrupt transitions in past climates 

Denis-Didier Rousseau, Valerio Lucarini, Witold Bagniewski, and Michael Ghil

The Earth’s climate has experienced numerous abrupt and critical transitions during its long history. Such transitions are evidenced in precise, high-resolution records at different timescales. This type of evidence suggests the possibility of identifying a hierarchy of past critical events, which would yield a more complex perspective on climatic history of the than the classical saddle-node two-dimension representation of tipping points. Such a context allows defining a tipping, or dynamical, landscape (Lucarini and Bódai, 2020), similar to the epigenetic landscape of Waddington (1957).

To illustrate a richer structure of critical transitions, we have analyzed 3 key high-resolution datasets covering the past 66 Ma and provided evidences of abrupt transitions detected with the augmented Kolmogorov-Smirnov test and a recurrence analysis (Bagniewski et al., 2021). These time series are the CENOGRID benthic d18O and d13C (Westerhold et al., 2020), the U1308 benthic d18O, d13C and the d18bulk carbonate (Hodell and Channell, 2016), and the NGRIP d18O (Rasmussen et al., 2014) records. The aim was to examine objectively the observed visual evidence of abrupt transitions and to identify among them the key thresholds indicating regime changes that differentiate among major clusters of variability. This identification is followed by establishing a hierarchy in the observed thresholds organized through a domino-like cascade of abrupt transitions that shaped the Earth’s climate system over the past 66 Ma.

This study is supported by the H2020-funded Tipping Points in the Earth System (TiPES) project.

References

Bagniewski, W., Ghil, M., and Rousseau, D. D.: Automatic detection of abrupt transitions in paleoclimate records, Chaos, 31, https://doi.org/10.1063/5.0062543, 2021.

Hodell, D. A. and Channell, J. E. T.: Mode transitions in Northern Hemisphere glaciation: co-evolution of millennial and orbital variability in Quaternary climate, Clim. Past, 12, 1805–1828, https://doi.org/10.5194/cp-12-1805-2016, 2016.

Lucarini, V. and Bódai, T.: Global stability properties of the climate: Melancholia states, invariant measures, and phase transitions, Nonlinearity, 33, R59–R92, https://doi.org/10.1088/1361-6544/ab86cc, 2020.

Rasmussen, S. O., Bigler, M., Blockley, S. P., et al.: A stratigraphic framework for abrupt climatic changes during the Last Glacial period based on three synchronized Greenland ice-core records: refining and extending the INTIMATE event stratigraphy, Quat. Sci. Rev., 106, 14–28, https://doi.org/10.1016/j.quascirev.2014.09.007, 2014.

Waddington, C. H.: The strategy of the genes., Allen & Unwin., London, 1957.

Westerhold, T., Marwan, N., Drury, A. J., et al.: An astronomically dated record of Earth’s climate and its predictability over the last 66 million years, Science, 369, 1383-+, https://doi.org/10.1126/science.aba6853, 2020.

How to cite: Rousseau, D.-D., Lucarini, V., Bagniewski, W., and Ghil, M.: Cascade of abrupt transitions in past climates, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2396, https://doi.org/10.5194/egusphere-egu22-2396, 2022.

EGU22-2689 | Presentations | NP2.4

Data-driven estimation of the committor function for an idealised AMOC model 

Valérian Jacques-Dumas, Henk Dijkstra, and René van Westen

The Atlantic Meridional Overturning Circulation (AMOC) transports warm, saline water towards the northern North Atlantic, contributing substantially to the meridional heat transport in the climate system. Measurements of the Atlantic freshwater divergence show that it may be in a bistable state and hence subject to collapsing under anthropogenic forcing. We aim at computing the probability of such a transition. We focus on timescales of the century and on temporary collapses of the AMOC. Using simulated data from an idealized stochastic AMOC model, where forcing and white noise are applied via a surface freshwater flux, we compute the transition probabilities versus noise and forcing amplitudes.

Such transitions are very rare and simulating long-enough trajectories in order to gather sufficient statistics is too expensive. Conversely, rare-events algorithms like TAMS (Trajectory-Adaptive Multilevel Sampling) encourage the transition without changing the statistics. In TAMS, N trajectories are simulated and evaluated with a score function; the poorest-performing trajectories are discarded, and the best ones are re-simulated.

The optimal score function is the committor function, defined as the probability that a trajectory reaches a zone A of the phase space before another zone B. Its exact computation is in general difficult and time-consuming. In this presentation, we compare data-driven methods to estimate the committor. Firstly, the Analogues Markov Chain method computes it from the transition matrix of a long re-simulated trajectory. The K-Nearest Neighbours method relies on an existing pool of states where the committor function is already known to estimate it everywhere. Finally, the Dynamical Modes Decomposition method is based on a Galerkin approximation of the Koopman operator. The latter is the most efficient one for the AMOC model when using adaptive dimensionality reduction of the phase space.

How to cite: Jacques-Dumas, V., Dijkstra, H., and van Westen, R.: Data-driven estimation of the committor function for an idealised AMOC model, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2689, https://doi.org/10.5194/egusphere-egu22-2689, 2022.

EGU22-2784 | Presentations | NP2.4

Mechanisms behind climate oscillations in last glacial maximum simulations 

Yvan Romé, Ruza Ivanovic, and Lauren Gregoire

Millennial-scale variability has been extensively observed across the last glacial period records (115 to 12 thousand years ago) but reproducing it on general circulation models remains a challenge. In recent years, a growing number of climate models have reported simulations with oscillating behaviours comparable to typical abrupt climate changes, although often relying on unrealistic forcing fields and/or boundary conditions. This may become an issue when trying to review the mechanisms at stake because of glacial climates’ sensitivity to these parameters, notably ice sheets geometry and greenhouse gases concentration.

With the addition of snapshots of the early last deglaciation meltwater history over a last glacial maximum (~21 thousand years ago) equilibrium simulation, we obtained different regimes of climate variability, including oscillations that provides the perfect framework for studying abrupt climate changes dynamics in a glacial background. The oscillations consist of shifts between cold modes with a weak to almost collapsed Atlantic Meridional Ocean Circulation (AMOC) and warmer and stronger AMOC modes, with large reorganisation of the deep-water formation sites, surface ocean and atmospheric circulations. The phenomenon has a periodicity of roughly every 1500 years and can be linked to changes of about 10°C in Greenland. This new set of simulation suggests an intricate large-scale coupling between ice, ocean, and atmosphere in the North Atlantic when meltwater is discharged to the North Atlantic.

Most attempts at theorising millennial-scale variability have involved vast transfers of salt between the subtropical and subpolar gyres, often referred to as the salt oscillator mechanism, that in turn controlled the intensity of the north Atlantic current. We believe that the salt oscillator is in fact part of a larger harmonic motion spanning through all components of the climate system and that can enter into resonance under the specific boundary conditions and/or forcing. Illustrated by the mapping of the main salinity and heat fluxes on the oscillating simulations, we propose a new interpretation of the salt oscillator that includes the stochastic resonance phenomenon as well as the effect of meltwater forcing.

How to cite: Romé, Y., Ivanovic, R., and Gregoire, L.: Mechanisms behind climate oscillations in last glacial maximum simulations, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2784, https://doi.org/10.5194/egusphere-egu22-2784, 2022.

EGU22-3973 | Presentations | NP2.4

A minimal SDE model of D-O events with multiplicative noise 

Kolja Kypke and Peter Ditlevsen

The abrupt transitions in the last glacial period between cold stadial and warmer interstadial climate states found in Greenlandic ice-core records, known as Dansgaard-Oeschger (D-O) events, are a rich topic of study not only due to their potential similarities in time scales and mechanisms to present and near-future climate transitions but also since their underlying physical mechanisms are not fully understood. The dynamics of the climate can be described by a Langevin equation dx = −∂U/∂x dt + η(t) where the potential U(x) has a bimodal distribution to represent the stable stadial and interstadial states and the stochastic process η(t) is usually realized as a Gaussian white noise process that causes jumps between these two states. From the steady-state of the Fokker-Planck equation associated with this Langevin equation, the potential U(x) can be determined from the probability distribution of the ice-core record time series. Thus this minimal model simulates time series with statistics similar to those of the original ice-core record. Novel to this study, we introduce a multiplicative noise term η(t, x) to represent the different statistical properties of the noise in the stadial and interstadial periods. The difference between the Itô and the Stratonovich integration of the Langevin equation with multiplicative noise results in slight differences in the attribution of the drift and diffusion terms for a transformed variable. This is illustrated by performing both.

How to cite: Kypke, K. and Ditlevsen, P.: A minimal SDE model of D-O events with multiplicative noise, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3973, https://doi.org/10.5194/egusphere-egu22-3973, 2022.

Several climate sub-systems are believed to be at risk of undergoing abrupt, irreversible changes as a tipping point (TP) in Greenhouse gas concentrations is reached. Since the current generation of climate models is likely not accurate enough to reliably predict TPs, a hope is to anticipate them from observations via early-warning signals (EWS). EWS have been designed to identify generic changes in variability that occur before a well-defined TP is crossed.

Such well-defined, singular TPs are believed to arise from a single dominant positive feedback that destabilizes the system. However, one may ask whether the large number of spatio-temporal scales in the climate system, and associated second-order feedbacks, could not lead to a variety of more subtle, but discontinuous reorganizations of the spatial climate pattern before the eventual catastrophic tipping. Such intermediate TPs could hinder predictability and mask EWS.

We performed simulations with a global ocean model that shows a TP of the Atlantic meridional overturning circulation (AMOC) due to freshening of the surface waters resulting from increased ice melt. Using a large ensemble of equilibrium simulations, we map out the stability landscape of the ocean circulation in high detail. While in a classical hysteresis experiment only one regime of bistability is found, by very slow increases in forcing we observe an abundance of discontinuous, qualitative changes in the AMOC variability. These are used to initialize smaller-scale hysteresis experiments that reveal a variety of multistable regimes with at least 4 coexisting alternative attractors.

We argue that due to chaotic dynamics, non-autonomous instabilities, and complex geometries of the basins of attraction, the realized path to tipping can be highly sensitive to initial conditions and the trajectory of the control parameter. Further, we discuss the degree to which the equilibrium dynamics are reflected in the transient dynamics for different rates of forcing. The results have implications regarding the expected abruptness of TPs, as well as their predictability and the design of EWS.

How to cite: Lohmann, J.: Abundant multistability and intermediate tipping points in a global ocean model, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4470, https://doi.org/10.5194/egusphere-egu22-4470, 2022.

EGU22-5197 | Presentations | NP2.4

Investigating the 'Hothouse narrative' with dynamical systems 

Victor Couplet and Michel Crucifix

The 'hothouse narrative' states that tipping cascades could lead humanity to a binary choice between a 'governed Earth' and a 'hothouse' with no midway alternative. To investigate this scenario, we construct a toy model of interacting tipping elements and ask the following questions: Given a continuous family of emission scenarios, are there discontinuities in the family of responses, as suggested by the 'hothouse narrative'? How realistic is this given knowledge provided by climate simulations and paleo-climate evidence? The relatively low complexity of our model allows us to easily run it for several thousand years and a large range of emissions scenarios, helping us highlight the fundamental role of the different time scales involved in answering our questions. On the one hand, we find that the near-linear relationship predicted by GCMs between global temperature and GHG emissions for the next century can break up at millennial time scales due to cascades involving slower tipping elements such as the ice sheets. This translates as a discontinuity in the family of responses of our model. On the other hand, we find that different emissions scenarios respecting the same carbon budget could potentially lead to different tipping cascades and thus qualitatively different outcomes.

How to cite: Couplet, V. and Crucifix, M.: Investigating the 'Hothouse narrative' with dynamical systems, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5197, https://doi.org/10.5194/egusphere-egu22-5197, 2022.

EGU22-5268 | Presentations | NP2.4

Transition Probabilities of Wind-driven Ocean Flows 

René van Westen and Henk Dijkstra

The quasi-geostrophic wind-driven double-gyre ocean circulation in a midlatitude rectangular basin is a multi-stable system. Under time-independent forcing, the number of steady states is controlled by the Reynolds number. For a specific range of Reynolds numbers, at least two stable steady states exist. In the quasi-geostrophic model, sub-grid scale processes are usually heavily parameterised, either by deterministic or stochastic representation. In the stochastic case, noise-induced transitions between the steady states may occur.

A standard method to determine transition rates between different steady states is a Monte Carlo approach. One obtains sufficient independent realisations of the model and simply counts the number of transitions. However, this Monte Carlo approach is not well-suited for high-dimensional systems such as the quasi-geostrophic wind-driven ocean circulation. Moreover, when transition probabilities are rare, one needs long integration times or a large number of realisations.

Here we propose a new method to determine transition rates between steady states, by using Dynamically Orthogonal (DO) field theory. The stochastic dynamical system is decomposed using a Karhunen-Loéve expansion and separate problems arise for the ensemble mean state and the so-called time-dependent DO modes. Each DO mode has a specific probability density function, which represents the probability in that direction of phase space. In the case of two steady states, at least one of the DO modes has a bimodal distribution. We analyse transition probabilities using this specific DO mode, which is more efficient compared to the ordinary Monte Carlo approach. We will present the general method and show results for transition probabilities in the quasi-geostrophic wind-driven double-gyre ocean circulation.

How to cite: van Westen, R. and Dijkstra, H.: Transition Probabilities of Wind-driven Ocean Flows, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5268, https://doi.org/10.5194/egusphere-egu22-5268, 2022.

EGU22-5433 | Presentations | NP2.4

Tipping points in hydrology: observed regional regime shift and System Dynamics modeling 

Valentin Wendling, Christophe Peugeot, Manuela Grippa, Laurent Kergoat, Eric Mougin, Pierre Hiernaux, Nathalie Rouché, Geremy Panthou, Jean-Louis Rajot, Caroline Pierre, Olivier Mora, Angeles Garcia-Mayor, Abdramane Ba, Emmanuel Lawin, Ibrahim Bouzou-Moussa, Jerôme Demarty, Jordi Etchanchu, Basile Hector, Sylvie Galle, and Thierry Lebel and the TipHyc Project

River runoff and climate data existing from 1950 to present time in West Africa are analyzed over a climatic gradient from the Sahel (semi-arid) to the Gulf of Guinea (humid). The region experienced a severe drought in the 70s-90s, with strong impact on the vegetation, soils and populations. We show that the hydrological regime in the Sahel has shifted: the runoff increased significantly between pre- and post-drought periods and is still increasing. In the Guinean region, instead, no shift is observed.

This suggests that a tipping point could have been passed, triggered by climate and/or land use change. In order to explore this hypothesis, we developed a System Dynamics model representing feedbacks between soil, vegetation and flow connectivity of hillslopes, channels and aquifers. Model runs were initialized in 1950 with maps of land use/land cover, and fed with observed rainfall (climate external forcing).

The modeling results accurately represent the observed evolution of the hydrological regime on the watersheds monitored since the 50s (ranging from 1 to 50000 km²). The model revealed that alternative stable states can exist for the climatic conditions of the study period. From the model runs, we showed that the drought triggered the crossing of a tipping point (rainfall threshold), which explains the regime shift. We identified domains within the watersheds where tipping occurred at small scale, leading to larger scale shifts. This result supports that tipping points exist in semi-arid systems where ecohydrology plays a major role. This approach seems well suited to identify areas of high risk of irreversible hydrological regime shifts under different climate and land-use scenarios.

How to cite: Wendling, V., Peugeot, C., Grippa, M., Kergoat, L., Mougin, E., Hiernaux, P., Rouché, N., Panthou, G., Rajot, J.-L., Pierre, C., Mora, O., Garcia-Mayor, A., Ba, A., Lawin, E., Bouzou-Moussa, I., Demarty, J., Etchanchu, J., Hector, B., Galle, S., and Lebel, T. and the TipHyc Project: Tipping points in hydrology: observed regional regime shift and System Dynamics modeling, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5433, https://doi.org/10.5194/egusphere-egu22-5433, 2022.

EGU22-5500 | Presentations | NP2.4

Conditions for detecting early warning of tipping. 

Peter Ditlevsen

The warning of tipping to an undesired state in a complex system, such as the climate, when a control parameter slowly approaching a critical value ($\lambda(t) \rightarrow \lambda_0$) relies on detecting early warning signals (EWS) in observations of the system. The primary EWS are increase in variance, due to loss of resilience, and increased autocorrelation due to critical slow down. They are statistical in nature, which implies that the reliability and statistical significance of the detection depends on the sample size in observations and the magnitude of the change away from the base value prior to the approach to the tipping point. Thus the possibility of providing useful early warning depends on the relative magnitude of several interdependent time scales in the problem. These are (a) the time before the critical value $\lambda_c$ is reached, (b) the (inverse) rate of approach to the bifurcation point (c) The size of the time window required to detect a significant change in the EWS and finally, (d) The escape time for noise-induced transition (prior to the bifurcation). Here we investigate under which conditions early warning of tipping can be provided. 

How to cite: Ditlevsen, P.: Conditions for detecting early warning of tipping., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5500, https://doi.org/10.5194/egusphere-egu22-5500, 2022.

EGU22-5725 | Presentations | NP2.4

Arctic summer sea-ice loss will accelerate in coming decades 

Anna Poltronieri, Nils Bochow, and Martin Rypdal

Every year, the area of the Arctic sea-ice decreases in the boreal spring and summer and reaches its yearly minimum in the early autumn. The continuous satellite-based time series shows that the September area has decreased from 4.5 x 106 km2 in 1979, to 2.8 x 106 km2 in 2020. The decline has been approximately linear in global mean surface temperature, with a rate of loss of 2.7 x 106 km2 per degree C of global warming.

In the CMIP6 ensemble, however, we find that the majority of the models that reach an Arctic sea-ice free state in the SSP585 runs show an accelerated loss of sea-ice for the last degree of warming compared to the second last degree of warming, which implies an increased sensitivity of the sea-ice to temperature changes. 

Both in the observational and CMIP6 data, we find that the decline in September sea-ice area is approximately proportional to the area north of which the zonal average temperature in spring and summer is lower than a critical threshold Tc. The Arctic amplification implies that the zonally averaged temperatures increase relative to the global temperatures, and with rates increasing with latitude. Linear extrapolation of the zonally averaged temperatures predicts that, with further warming, the September sea-ice area will depend non-linearly on global temperature, the sensitivity will increase and the September sea-ice area may become less that 1 x 106 km2 for global warming between 0.5 and 1.4oC above the current temperature. 

As a result of accelerated sea-ice loss, the average evolution of the sea-ice area among the CMIP6 models before the complete loss of the summer sea-ice shows an increase in the year-to-year fluctuations in minimum ice cover in the next decade. This implies exceptional accumulation of extreme events with very low or no sea-ice at all even before the final loss of the sea-ice. Likewise, an apparent short-term recovery of the sea-ice loss might be observable due to the increasing fluctuations. 

How to cite: Poltronieri, A., Bochow, N., and Rypdal, M.: Arctic summer sea-ice loss will accelerate in coming decades, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5725, https://doi.org/10.5194/egusphere-egu22-5725, 2022.

EGU22-5928 | Presentations | NP2.4

Commitment as Lost Opportunities 

Marina Martinez Montero, Michel Crucifix, Nicola Botta, and Nuria Brede

In the context of climate change, the word "commitment" was originally used to denote how much extra warming is to be expected eventually given a certain fixed concentration of CO2. The notion has evolved and now it is customary to encounter terms such as "constant emissions commitment", "sea level rise commitment" and "zero emissions commitment". All these notions refer to how much change with respect to the current climate state is expected at a given point in the future considering our current climate state and specified future anthropogenic emissions.

Here, we propose thinking about commitment as available options for future action that will allow future decision makers to avoid harmful futures. The definition requires the identification of unwanted outcomes e.g., too high temperature or too fast sea level rise and the specification of a range of possible future anthropogenic emission/intervention scenarios. Given an initial climate state, the measure of commitment is based on the diagnosis of which of those emission/intervention scenarios yield futures safe from the unwanted outcomes. This new definition of commitment explicitly captures the notion of legacy: It measures the range of options that the next generations have at their disposal to avoid harmful futures.

We illustrate the definition and methodology with a simple model featuring ice sheet tipping points and ocean carbonate chemical balance. After having introduced the model, we specify the considered future anthropogenic emission/intervention options available, along with the considered unwanted outcomes. We show how the safe options available for future generations would change in time if we were to follow some of the most standard emission scenarios used in the literature.

How to cite: Martinez Montero, M., Crucifix, M., Botta, N., and Brede, N.: Commitment as Lost Opportunities, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5928, https://doi.org/10.5194/egusphere-egu22-5928, 2022.

EGU22-5997 | Presentations | NP2.4

A fast-slow model for glacial cycles since the Mid-Pleistocene Transition 

Jade Ajagun-Brauns and Peter Ditlevsen

A new simple approach inspired by MacAyeal (1979) to explain the time-asymmetric ‘saw-toothed’ shape and 100,000-year quasi-period of glacial-interglacial cycles since the Middle Pleistocene Transition, is presented. Using a simple model with fast-slow dynamics, the global ice volume is taken to be a function of two independently varying parameters, the solar insolation and ‘alpha’, a secondary control parameter, the study of which is the focus this research. The steady state of the model is a partially folded surface in three-dimensional space where insolation, ‘alpha’, and global ice volume are orthogonal axes. The pleated surface allows for the gradual increase and sudden decrease in ice volume that is observed in the paleoclimate record. To derive a time series of global ice volume, the Euler integration method is used, producing a time series which replicates the ‘saw-toothed’ pattern of glacial cycles in the late Pleistocene. The second control parameter, ‘alpha’, is proposed to be related to internal dynamics of the climate system, such as ice sheet dynamics.

 

Reference

D. R.  MacAyeal, ‘A Catastrophe Model of the Paleoclimate Record’ , Journal of Glaciology , Volume 24 , Issue 90 , 1979 , pp. 245 – 257.

How to cite: Ajagun-Brauns, J. and Ditlevsen, P.: A fast-slow model for glacial cycles since the Mid-Pleistocene Transition, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5997, https://doi.org/10.5194/egusphere-egu22-5997, 2022.

EGU22-5999 | Presentations | NP2.4

AMOC Early-Warning Signals in CMIP6 

Lana Blaschke, Maya Ben-Yami, Niklas Boers, and Da Nian

The Atlantic Meridional Overturning Circulation (AMOC) is a vital part of the global climate that has been suggested to exhibit bi-stability. A collapse from its current strong state to the weak one would have significant consequences for the climate system. Early-warning signals (EWS) for such a transition have recently been found in observational fingerprints for the AMOC.

Some uncertainty in our understanding of the AMOC and its recent evolution is due to the varying quality of its representation in state-of-the-art models. In this work we examine the historical AMOC simulations in the 6th Coupled Model Intercomparison Project (CMIP6) by analyzing the AMOC strength in the models both directly and through the sea-surface temperature fingerprint. As well as examining the evolution of these AMOC time-series in the models, we calculate their associated EWS and use these to evaluate the models in terms of their representation of the AMOC.

How to cite: Blaschke, L., Ben-Yami, M., Boers, N., and Nian, D.: AMOC Early-Warning Signals in CMIP6, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5999, https://doi.org/10.5194/egusphere-egu22-5999, 2022.

The El Niño Southern Oscillation (ENSO) is the most important driver of interannual global climate variability and affects weather and climate in large parts of the world. Recently, we have developed a dynamical network approach for predicting the onset of El Niño events well before the spring predictability barrier. In the regarded climate network, the nodes are grid points in the Pacific, and the strengths of the links (teleconnections) between them are characterized by the cross-correlations of the atmospheric surface temperatures at the grid points. In the year before an El Niño event, the links between the eastern equatorial Pacific and the rest of the Pacific tend to strengthen such that the average link strength exceeds a certain threshold. This feature can be used to predict the onset of an El Niño with 73% probability and its absence with 90% probability. The p-value of the hindcasting and forecasting phase (1981-2021) for this performance based on random guessing with the climatological average is 4.6*10-5.

To assess whether this predictive feature is also present in coupled general circulation models, we apply our algorithm to historical and control runs of CMIP5 and CMIP6. We find that the predictive performance present in observational data is absent or very low in GCMs. The lack of this feature may explain the difficulties of GCMs to overcome the spring barrier.

How to cite: Ludescher, J., Bunde, A., and Schellnhuber, H. J.: El Niño forecasting by climate networks: comparison of the forecasting performance in observational data and in historical and controls runs of CMIP5 and CMIP6, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6329, https://doi.org/10.5194/egusphere-egu22-6329, 2022.

The potential impact of tipping points for climate dynamics is now widely recognized. Furthermore, paleoclimate records suggest that abrupt climate changes have indeed occurred in Earth’s past, potentially on timescales which do not exceed a decade. Several tipping elements, involving various components of the climate system, such as the ocean circulation, sea-ice, continental ice sheets, vegetation, and their couplings, have been suggested. Yet, it remains virtually unknown whether the large-scale atmospheric circulation, the component of the climate system with shortest response time, may undergo bifurcations that could trigger abrupt climate change.

    In this talk I will discuss the possibility of abrupt transitions of the large-scale circulation in the tropics. Specifically, I will consider potential reversals of the mean zonal winds, from the weak easterlies observed in current climate to a "superrotation" state with prevailing westerly winds. The superrotating state exhibits a strongly reduced Hadley circulation.
    I will discuss positive feedback mechanisms and their relevance for the Earth across a hierarchy of models of increasing complexity. A low-dimensional model based on Rossby wave resonance exhibits bistability, and provides a simple criterion for the region of parameter space where this regime exists. We then study the nature of the transition to superrotation in a dry dynamical core, forced in an idealized manner. The main result is that there exists a parameter regime where the dry primitive equations support two coexisting states, with and without an equatorial jet. We will discuss the role of parameters such as the meridional temperature gradient and the boundary layer friction on the existence of this bifurcation.

How to cite: Herbert, C.: Bistability and hysteresis of the large-scale tropical circulation in idealized GCM simulations, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6519, https://doi.org/10.5194/egusphere-egu22-6519, 2022.

EGU22-7029 | Presentations | NP2.4

Global-scale Changes in Vegetation Resilience Mapped with Satellite Data 

Taylor Smith, Niklas Boers, and Dominik Traxl

It is theorized that the resilience of natural ecosystems – their ability to resist and recover from external perturbations – can be estimated from their natural variability. We test this hypothesis using a global set of recovery rates from large disturbances derived from satellite vegetation data, and find that the expected theoretical relationships between these empirical recovery rates and the lag-1 autocorrelation and variance indeed hold approximately. The spatial pattern of global vegetation resilience reveals a strong link to both precipitation availability and variability, implying that water plays a first-order role in controlling the resilience of global vegetation.

The resilience of vegetation is not, however, static – global changes in temperature, precipitation, and anthropogenic influence will all impact the ability of ecosystems to adapt to and recover from disturbances. We investigate the global spatial and temporal patterns of changes in resilience using the empirically confirmed metrics – lag-1 autocorrelation and variance – and find spatially heterogeneous long-term (1980s-) trends; recent trends (2000s-) in vegetation resilience are strongly negative across land-cover types and climate zones.

How to cite: Smith, T., Boers, N., and Traxl, D.: Global-scale Changes in Vegetation Resilience Mapped with Satellite Data, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7029, https://doi.org/10.5194/egusphere-egu22-7029, 2022.

EGU22-7496 | Presentations | NP2.4

Information flow in complex high-dimensional systems 

Mart Ratas and Peter Jan van Leeuwen
Knowledge on how information flows in complex Earth system models would be of great benefit for our understanding of the system Earth and its components. In principle the Kolmogorov or Fokker-Planck equation can be used to estimate the evolution of the probability density. However, this is not very practical since this equation can only be solved in very low dimensional systems. Because of that, mutual information and information flow have been used to infer information in complex systems. This usually involves integration over all state variables, which is generally numerically too expensive. Here we introduce an exact but much simpler way to find how information flows in numerical solutions that only involves integrations over the local state variables. It allows to infer both magnitude and direction of the information flow. The method is based on ensemble integrations of the system, but because the calculations are local the ensemble size can remain small, of  O(100). 
In this talk we will explain the methodology and demonstrate its use on the highly nonlinear Kumamoto-Sivashinsky model using a range of model sizes and exploring both 1-dimensional and multi-dimensional configurations. 

How to cite: Ratas, M. and van Leeuwen, P. J.: Information flow in complex high-dimensional systems, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7496, https://doi.org/10.5194/egusphere-egu22-7496, 2022.

EGU22-7531 | Presentations | NP2.4

Bifurcation diagram for vegetation patterns model: old ways for new insight 

Lilian Vanderveken and Michel Crucifix

Spatial organization is a well-known feature of vegetation in semi-arid regions. This phenomenon appears in various parts of the world where water is the limiting factor for plants growing. Those patterns can be reproduced by using reaction-diffusion equations. Rietkerk developed a vegetation patterns model where the joint effects of a local reaction and diffusion create heterogeneous solutions.

The existence of those solutions expands the range of precipitation conditions under which vegetation can prevail. The complete region in the bifurcation diagram where such stable patterns exist is called the Busse balloon.

To our knowledge, no full investigation of the Busse balloon in Rietkerk’s model is available. Here we address this gap and dissect this Busse balloon by analysing the patterned solution branches of the bifurcation diagram.

For a given domain length, those branches can be computed starting from the different zero modes at the edge of the Turing zone around the branch of homogeneous solutions. Then, we use a Newton-Raphson method to track each branch for precipitation changes. Two types of branches appear. What we call the main branches have a roughly constant wavenumber along the branch. What we call the “mixed state branches” originate at the transition between stability and instability along one main branch. The corresponding solutions appear as mixing the solutions of two main branches, which is why we call them that way. However, we show that the latter plays a minor role in the dynamics of the system.

The awareness of the various patterned branch sheds new light on the dynamics of wavenumber switching or R-tipping for patterned systems. More generally, this work gives new insights into the behaviour of patterned systems under changing environment.

How to cite: Vanderveken, L. and Crucifix, M.: Bifurcation diagram for vegetation patterns model: old ways for new insight, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7531, https://doi.org/10.5194/egusphere-egu22-7531, 2022.

Confirmation exists for the 1997 revolutionary date of 12.850 cal yr BP established for the Laacher See Eruption (LSE) and introduced to encourage US-research on the P/H-KISS impact with LSE as isochrone and impact volcanism proxy (Bujatti-Narbeshuber, 1997). Bayesian analysis by Wolbach et al. (2018) of 157 dated records of the YD-impact hypothesis of Firestone et al. (2007) confirms impact with 2.854 ± 0.056 ka BP. This now allows to introduce the much larger P/H-KISS paleoceanographic transition scenario relating also to Holocene up to the present global climate change. The Holocene era, because of the thermohaline damped flow scenario, is herein considered as permanent end of the ice age, suggested here as the climatic consequence of an ocean topography and threshold change. Decoded cave art navigation world maps with Pleistocene paleoceanography content from Altamira , La Pasiega and El Castillo document in each one of the three maps specific AMOC stable states for interstadial/ full stadial/ stadial paleoclimate. Each map-thermohaline stable state is differently relating to a geomorphological boundary condition that is the subaerial surface Topography of a large Mid Atlantic Plateau (MAP)-Island. It is modelled in the P/H-KISS scenario as primary Pleistocene thermohaline phase 0 geomorphological threshold. As physical boundary condition it is in interaction with the thermohaline gulfstream current (above /below/at threshold). This results in the 3 distinct AMOC equilibrium stages of interstadial/ full stadial /stadial, as Pleistocene criticality interconnected by their respective further transition thresholds. When the primary  geomorphological threshold is removed the result is the Holocene damped flow, a transition continuum of thermohaline phases 1, 2, 3. Geomorphological proof is first the MAP-Island, invariably shown on all three maps. Furthermore the MAP-Island is identified by its characteristic topography on decorated columns in Göbekli Tepe as a highly abstract island symbol with deeper political-territorial meanings. With paleo-astronomical precession dating on Pillar 43, the LSE 12.850 cal yr BP date was reproduced and the YD (P/H-KISS) impact series from comet fragments in the Taurid stream were decoded by M. Sweatman (2019).  The symbol sequence on Pillar 18, revealed here for the first time, is the (HI-T) = MAP-Island-Dual 90°-Transition-Tsunami Code of the two step Mid Atlantic Ridge MAR & MAP- Island isostatic submersion by the Taurid stream Koefels-comet oceanic-impact fragments: Paleoclimatology thus confirms and now extends the D. Paillard (1998) three equilibria ocean-box-climate-model with 3 thresholds for 3 transitions between the 3 thermohaline stable states of the ice age to the larger P/H-KISS transition scenario of paleo-climate change. It states that the above 3 AMOC states are exclusively based on the existence of the MAP-Island threshold. Isostatic MAR & MAP-Submergence brings their ice age ending collapse into the broad continuum of the Global warming Threshold Triad with thermohaline damped flow in a very long lasting Holocene interstadial.

 

*) Bujatti-Narbeshuber, M. - Pleistocene/Holocene (P/H) boundary oceanic Koefels-comet Impact Series Scenario (KISS) of 12.850 yr BP Global-warming Threshold Triad (GTT). -Climates: Past, Present and Future; Second European Palaeontological Congress Abstracts edited by D.K. Ferguson & H.A. Kollmann; Vienna, 1997.

 

How to cite: Dr. Bujatti-Narbeshuber, M.: Pleistocene/Holocene (P/H) boundary oceanic Koefels-comet Impact Series Scenario (KISS) of 12.850 yr BP Global-warming Threshold Triad (GTT)-Part II *), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8412, https://doi.org/10.5194/egusphere-egu22-8412, 2022.

EGU22-8745 | Presentations | NP2.4

Stochastic Modeling of Stratospheric Temperature 

Mari Eggen, Kristina Rognlien Dahl, Sven Peter Näsholm, and Steffen Mæland

This study suggests a stochastic model for time series of daily zonal (circumpolar) mean stratospheric temperature at a given pressure level. It can be seen as an extension of previous studies which have developed stochastic models for surface temperatures. The proposed model is a combination of a deterministic seasonality function and a Lévy-driven multidimensional Ornstein–Uhlenbeck process, which is a mean-reverting stochastic process. More specifically, the deseasonalized temperature model is an order 4 continuous-time autoregressive model, meaning that the stratospheric temperature is modeled to be directly dependent on the temperature over four preceding days, while the model’s longer-range memory stems from its recursive nature. This study is based on temperature data from the European Centre for Medium-Range Weather Forecasts ERA-Interim reanalysis model product. The residuals of the autoregressive model are well represented by normal inverse Gaussian-distributed random variables scaled with a time-dependent volatility function. A monthly variability in speed of mean reversion of stratospheric temperature is found, hence suggesting a generalization of the fourth-order continuous-time autoregressive model. A stochastic stratospheric temperature model, as proposed in this paper, can be used in geophysical analyses to improve the understanding of stratospheric dynamics. In particular, such characterizations of stratospheric temperature may be a step towards greater insight in modeling and prediction of large-scale middle atmospheric events, such as sudden stratospheric warming. Through stratosphere–troposphere coupling, the stratosphere is hence a source of extended tropospheric predictability at weekly to monthly timescales, which is of great importance in several societal and industry sectors.

How to cite: Eggen, M., Rognlien Dahl, K., Näsholm, S. P., and Mæland, S.: Stochastic Modeling of Stratospheric Temperature, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8745, https://doi.org/10.5194/egusphere-egu22-8745, 2022.

EGU22-8753 | Presentations | NP2.4

Is West-Antarctica’s Tipping Point a Fixed Value? 

Jan Swierczek-Jereczek, Marisa Montoya, Alexander Robinson, Jorge Alvarez-Solas, and Javier Blasco

Given large regions of ice grounded below sea level associated with a retrograde bedrock, the West Antarctic Ice Sheet (WAIS) is believed to be a tipping element whose tipping point could be reached within this century under high emission scenarios. As the WAIS represents the largest and most uncertain source of future sea-level rise, characterising its stability is crucial for defining safe emission pathways and protecting livelihoods in coastal regions. In the present work, we investigate its potential to undergo an abrupt change due to a fold bifurcation. To this end, we use a high-order ice sheet model with 16km spatial resolution. Rather than applying a fixed forcing rate as in previous studies, we apply a forcing scheme that adaptively increases the local temperature while keeping the system near equilibrium, which allows us to obtain a rigorous value for the bifurcation tipping point. More importantly, we show how this threshold can become relevant for much lower warming levels than expected - even within the bounds of relatively conservative emission scenarios. Subsequently, we explain the underlying mechanisms leading the marine ice-sheet instability to possibly arise earlier than suggested by the bifurcation study. We finally question whether the tipping point of the WAIS can be understood as a fixed temperature value and if not, by which information it should be extended to provide an early warning signal.

How to cite: Swierczek-Jereczek, J., Montoya, M., Robinson, A., Alvarez-Solas, J., and Blasco, J.: Is West-Antarctica’s Tipping Point a Fixed Value?, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8753, https://doi.org/10.5194/egusphere-egu22-8753, 2022.

EGU22-9237 | Presentations | NP2.4

Using complex networks to predict abrupt changes in oscillatory systems 

Noemie Ehstand, Reik V. Donner, Cristóbal López, and Emilio Hernández-García

Functional networks are powerful tools to study statistical interdependency structures in extended systems. They have been used to get insights into the structure and dynamics of complex systems in various areas of science. In particular, several studies have suggested the use of precursors based on percolation transitions in correlation networks to forecast El Niño events.

Our aim is to provide a better understanding of the potential of such percolation precursors for the prediction of episodic events in generic systems presenting chaotic oscillations. To this end, we study the behavior of the precursors in a spatially extended stochastic Vallis model, an asymmetric Lorenz-63 type model for the El Niño-Southern Oscillation (ENSO). Our results demonstrate the ability of the largest connected component of the network to anticipate abrupt changes associated with the system's oscillatory dynamics.

This research was conducted as part of the CAFE Innovative Training Network (http://www.cafes2se-itn.eu/) which has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No. 813844.

How to cite: Ehstand, N., Donner, R. V., López, C., and Hernández-García, E.: Using complex networks to predict abrupt changes in oscillatory systems, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9237, https://doi.org/10.5194/egusphere-egu22-9237, 2022.

EGU22-9322 | Presentations | NP2.4

The Antarctic and Greenland response to PlioMIP2 mPWP climatic fields 

Javier Blasco, Ilaria Tabone, Daniel Moreno-Parada, Jorge Alvarez-Solas, Alexander Robinson, and Marisa Montoya

Since the pre-industrial era, global sea level has been rising along with greenhouse gas emissions. Part of the contribution to this sea-level change is the mass lost from continental ice sheets, i.e. the Greenland (GrIS) and Antarctic (AIS) ice sheets, which are shrinking at an accelerated rate. However, how they will respond to future warming is highly uncertain due to our lack of knowledge and associated uncertainty in modelling several physical processes, as well as in warming projections. A way to gain insight into future projections is to study past warm periods that are, to some extent, comparable to the present day (PD) in terms of external forcing. The mid-Pliocene warm period (mPWP, 3.3-3.0 million years ago) offers an ideal benchmark, as it is the most recent period with CO2 levels comparable to PD (350-450 ppmv), showing global mean temperatures 2.5-4.0 degrees higher. Eustatic sea-level reconstructions from that period estimate a sea level 15-20 meters higher than PD, implying ice sheets were much smaller in size. The GrIS was starting to form and the AIS was most likely constrained to land-based regions. The Pliocene Model Intercomparison Project, Phase 2 (PlioMIP2) has brought together over 15 climate outputs from 11 General Circulation models from different institutions. These models have simulated mPWP conditions under 400 ppmv of CO2 concentration over a topography generated from an updated bedrock configuration for that time period. Here we use these model outputs to force offline a higher-order ice sheet model for the Antarctic and Greenland domain. Our aim is to investigate how polar continental ice sheets respond to these different climatic fields to pinpoint their most significant climatic and topographical discrepancies. In addition, several sources of structural dependence, from different dynamic states (i.e. basal friction laws) to different initial boundary conditions (starting from no ice-sheet to the PD configuration) are investigated in this modelling framework to create a comprehensive output database for statistical analysis.

How to cite: Blasco, J., Tabone, I., Moreno-Parada, D., Alvarez-Solas, J., Robinson, A., and Montoya, M.: The Antarctic and Greenland response to PlioMIP2 mPWP climatic fields, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9322, https://doi.org/10.5194/egusphere-egu22-9322, 2022.

EGU22-9340 | Presentations | NP2.4

Measuring Amazon rainforest resilience from remotely sensed data 

Da Nian, Lana Blaschke, Yayun Zheng, and Niklas Boers

The Amazon rainforest has a major contribution to the bio-geochemical functioning of the Earth system and has been projected to be at risk of large-scale, potentially irreversible, dieback to a savanna state. Measuring the resilience of the Amazon rainforest empirically is critical to helping us understand the magnitude and frequency of disturbances that the rainforest can still recover from. Different means to quantify resilience in practice have been proposed. Here we determine the Amazon rainforest resilience based on a space-for-time replacement, and then estimating the average residence time in the forest state. This 'global' notion of resilience is different from local measures based on variance or autocorrelation and thus provides complementary information. We study the dependence of the exit-time-base resilience on total rainfall and, in order to study the evolution of the Amazon rainforest, we also estimate changes in their resilience over the years.

How to cite: Nian, D., Blaschke, L., Zheng, Y., and Boers, N.: Measuring Amazon rainforest resilience from remotely sensed data, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9340, https://doi.org/10.5194/egusphere-egu22-9340, 2022.

EGU22-9504 | Presentations | NP2.4

Synchronization of layer-counted archives using a statistical age-depth model 

Eirik Myrvoll-Nilsen, Keno Riechers, and Niklas Boers

Layer-counted paleoclimatic proxy records have non-negligible uncertainty arising from the dating process. Knowledge of this uncertainty is important for a rigorous propagation to further analyses; for example for identification and dating of abrupt transitions in climate or to provide a complete uncertainty quantification of early warning signals. This dating uncertainty can be quantified by assuming a probabilistic model for the age-depth relationship. We assume that the number of counted layers per unit of depth can be described using a Bayesian regression model with residuals following an autoregressive process. By synchronizing the chronologies with other archives one can constrain the uncertainties and correct potential biases in the dating process. This is done by matching the chronologies to tie-points obtained by analyzing different archives covering the same period in time. In practice, tie-points can be associated with a significant amount of uncertainty which also needs to be accounted for. We present a theoretically consistent approach which, under certain assumptions, allows for efficient sampling from synchronized age-depth models that match the tie-points under known uncertainty distributions. The model and associated methodology has been implemented into an R-package. 

How to cite: Myrvoll-Nilsen, E., Riechers, K., and Boers, N.: Synchronization of layer-counted archives using a statistical age-depth model, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9504, https://doi.org/10.5194/egusphere-egu22-9504, 2022.

EGU22-10031 | Presentations | NP2.4

Early Warning Signals For Climate Tipping Points: Beyond White Noise 

Joseph Clarke, Chris Huntingford, Paul Ritchie, and Peter Cox

Tipping points in the Earth System could present challenges for society and ecosystems. The existence of tipping points also provides a major challenge for science, as the global warming thresholds at which they are triggered is highly uncertain. A theory of `Early Warning Signals' has been developed to 
warn of approaching tipping points. Although this theory uses generic features of a system approaching a Tipping Point, the conventional application of it relies on an implicit assumption that the system experiences white noise forcing. In the Earth system, this assumption is frequently invalid.
Here, we extend the theory of early warning signals to a system additively forced by an autocorrelated process. We do this by considering the spectral properties of both the system and also of the forcing.  We test our method on a simple dynamical system, before applying our method to a particular example from the Earth System: Amazon rainforest dieback. Using our new approach, we successfully forewarn of modelled rainforest collapse in a state-of-the-art CMIP6 Earth System Model.

How to cite: Clarke, J., Huntingford, C., Ritchie, P., and Cox, P.: Early Warning Signals For Climate Tipping Points: Beyond White Noise, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10031, https://doi.org/10.5194/egusphere-egu22-10031, 2022.

EGU22-10128 | Presentations | NP2.4

Nonautonomous dynamics and its applications to paleoclimate 

Michael Ghil

The dynamics of systems with time-dependent forcing or coefficients has become a matter of considerable interest in the last couple of decades in general and in the last dozen years or so in the climate sciences in particular (Ghil, 2019; Ghil & Lucarini, 2020; Ghil, 2021; Tel et al., 2021; and references therein). We shall provide a general introduction to the topic and illustrate it with several paleoclimate-related examples (Crucifix, 2012; Riechers et al., 2022; Rousseau et al., 2022). Perspectives for further applications of the concepts and methods of the theory of pullback and random attractors and of their tipping points to paleoclimate will also be provided.

References

  • Crucifix, M.: Oscillators and relaxation phenomena in Pleistocene climate theory, PTRSA, 370, 1140–1165, 2012.
  • Ghil, M., 2019: A century of nonlinearity in the geosciences, Earth & Space Science, 6, 1007–1042, doi: 1029/2019EA000599.
  • Ghil, M., 2020: Review article: Hilbert problems for the climate sciences in the 21st century – 20 years later, Nonlin. Processes Geophys., 27, 429–451, https://doi.org/10.5194/npg-27-429-2020.
  • Ghil, M., and V. Lucarini, 2020: The physics of climate variability and climate change, Mod. Phys., 92(3), 035002, doi: 10.1103/RevModPhys.92.035002.
  • Riechers, K., T. Mitsui, N. Boers, and M. Ghil, 2022: Orbital insolation variations, intrinsic climate variability, and Quaternary glaciations, Clim. Past Discuss. [preprint], https://doi.org/10.5194/cp-2021-136, in review.
  • Rousseau, D.-D., W. Bagnewski, and M. Ghil, 2021: Abrupt climate changes and the astronomical theory: are they related?, Clim. Past, accepted, doi: 10.5194/cp-2021-103 .
  • Tél, T., Bódai, T., Drótos, G., Haszpra, T., Herein, M., Kaszás, B. and Vincze, M., 2020. The theory of parallel climate realizations. Journal of Statistical Physics179(5), 1496–1530.

How to cite: Ghil, M.: Nonautonomous dynamics and its applications to paleoclimate, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10128, https://doi.org/10.5194/egusphere-egu22-10128, 2022.

EGU22-10628 | Presentations | NP2.4

Loss of Earth System Resilience during Early Eocene Global Warming Events 

Shruti Setty, Margot Cramwinckel, Ingrid van de Leemput, Egbert H. van Nes, Lucas J. Lourens, Appy Sluijs, and Marten Scheffer

The Paleocene-Eocene Thermal Maximum (PETM; 56 Ma) and Eocene Thermal Maximum 2 and 3 (ETM2; 54.06 Ma and ETM3; 52.87 Ma) were three of a series of abrupt climate and carbon cycle perturbations, characterized by massive carbon input into the ocean-atmosphere system and strong global warming. These abrupt events, termed hyperthermals, potentially represent ‘tipping points’ at moments in time when the resilience of the system was low and reinforced by strong internal feedbacks, such as the catastrophic release of carbon from submarine methane hydrates. Alternatively, external mechanisms such as volcanism may have played a pronounced external role during the PETM. Here, we evaluate if the hyperthermals indeed resulted from reduced Earth System resilience and tipping point behaviour through the mathematical analyses of climate and carbon cycle indicators, namely, oxygen and stable carbon isotope ratios of deep ocean foraminifer calcite, across the late Paleocene and early Eocene. Our combined analysis using Dynamic Indicators of Resilience (DIORs) and Convergent Cross Mapping (CCM) reveals a loss of resilience and an increase in the causal interaction between the carbon cycle and climate towards the PETM, ETM2, and ETM3. A novel, windowed CCM approach indicates a tight coupling between carbon and climate across the early Eocene, further supporting dominant climate forcing on carbon cycle dynamics. This indicates that the internal rather than external mechanisms were responsible for the hyperthermals, suggesting a secondary role for endogenic processes such as volcanism. Furthermore, the CCM analysis in conjunction with the absence of major positive feedbacks such as the presence of polar ice caps during early Eocene could be employed to stipulate that these hyperthermal events may be caused by the increase in coupling between the carbon cycle and climate systems, eventually pushing both systems towards a tipping point through increasing positive feedbacks.

How to cite: Setty, S., Cramwinckel, M., Leemput, I. V. D., Nes, E. H. V., Lourens, L. J., Sluijs, A., and Scheffer, M.: Loss of Earth System Resilience during Early Eocene Global Warming Events, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10628, https://doi.org/10.5194/egusphere-egu22-10628, 2022.

EGU22-11671 | Presentations | NP2.4

Abrupt climate events recorded in speleothems from the ante penultimate glacial 

Vanessa Skiba, Martin Trüssel, Birgit Plessen, Christoph Spötl, René Eichstädter, Andrea Schröder-Ritzrau, Tobias Braun, Takahito Mitsui, Norbert Frank, Niklas Boers, Norbert Marwan, and Jens Fohlmeister

Millennial-scale climate variability, especially abrupt stadial-interstadial transitions, are a prominent feature of the last glacial as recorded in Greenland ice core records (Dansgaard-Oeschger events). Event abruptness and presence of statistical early warning signals before these transitions indicate that they involve repeated crossing of a tipping point of the climate system. However, only little information is available for periods before the last glacial period as Greenland ice cores and many other high-resolution records do not extent beyond the last glacial cycle. Given the lack of understanding of the triggering mechanism responsible for glacial millennial-scale variability with palaeoclimate data from the last glacial, it is essential to investigate this phenomenon during earlier glacial periods.

Here, we present a new highly resolved, precisely U-Th-dated speleothem oxygen isotope record from the Northern European Alps, a region which has been previously shown to resemble the glacial millennial-scale climate variability obtained from Greenland ice core records very well. Our new data covers the time interval from the ante-penultimate glacial to the penultimate glacial (MIS8-MIS6) with a high degree of replication. For both glacial periods, we find phases of pronounced millennial-scale variability but also several, ~10 ka long phases with the climate system being exclusively in stadial conditions. We compare our data with conceptual model results and investigate the occurrence and absence of abrupt climate transitions of the last 300,000 a.

How to cite: Skiba, V., Trüssel, M., Plessen, B., Spötl, C., Eichstädter, R., Schröder-Ritzrau, A., Braun, T., Mitsui, T., Frank, N., Boers, N., Marwan, N., and Fohlmeister, J.: Abrupt climate events recorded in speleothems from the ante penultimate glacial, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11671, https://doi.org/10.5194/egusphere-egu22-11671, 2022.

EGU22-12053 | Presentations | NP2.4

Fitting and extrapolation of transient behaviour in the presence of tipping points 

Peter Ashwin, Robbin Bastiaansen, and Anna von der Heydt

One of the key problems in climate science is to understand the asymptotic behaviour of a climate model, such as Equilibrium Climate Sensitivity (ECS), from finite time computations of transients of a model that may be complex and realistic. Typically, this is done by fitting to some simpler model and then extrapolating to an asymptotic state. But how do transients behave in the presence of tipping points? More precisely, how much warning can one get of an approaching tipping point? In this work we highlight an illustrative example showing how a good fit of a transient to a simpler model does not necessarily guarantee a good extrapolation, and discuss some other implicit assumptions that may arise when estimating quantities such as ECS.

How to cite: Ashwin, P., Bastiaansen, R., and von der Heydt, A.: Fitting and extrapolation of transient behaviour in the presence of tipping points, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12053, https://doi.org/10.5194/egusphere-egu22-12053, 2022.

EGU22-12438 | Presentations | NP2.4

Updated assessment suggests >1.5°C global warming could trigger multiple climate tipping points 

David Armstrong McKay, Arie Staal, Jesse Abrams, Ricarda Winkelmann, Boris Sakschewski, Sina Loriani, Ingo Fetzer, Sarah Cornell, Johan Rockström, and Timothy Lenton

Climate tipping points occur when change in a part of the climate system becomes self-perpetuating beyond a forcing threshold, leading to abrupt and/or irreversible impacts. Synthesizing paleoclimate, observational, and model-based studies, we provide a revised shortlist of global ‘core’ tipping elements and regional ‘impact’ tipping elements and their temperature thresholds. Current global warming of ~1.1°C above pre-industrial already lies within the lower end of some tipping point uncertainty ranges. Several more tipping points may be triggered in the Paris Agreement range of 1.5-2°C global warming, with many more likely at the 2-3°C of warming expected on current policy trajectories. In further work we use these estimates to test the potential for and impact of tipping cascades in response to global warming scenarios using a stylised model. This strengthens the evidence base for urgent action to mitigate climate change and to develop improved tipping point risk assessment, early warning capability, and adaptation strategies.

Preprint: https://doi.org/10.1002/essoar.10509769.1

How to cite: Armstrong McKay, D., Staal, A., Abrams, J., Winkelmann, R., Sakschewski, B., Loriani, S., Fetzer, I., Cornell, S., Rockström, J., and Lenton, T.: Updated assessment suggests >1.5°C global warming could trigger multiple climate tipping points, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12438, https://doi.org/10.5194/egusphere-egu22-12438, 2022.

EGU22-12501 | Presentations | NP2.4

Paleoclimatic tipping points and abrupt transitions: An application of advanced time series analysis methods 

Witold Bagniewski, Michael Ghil, and Denis-Didier Rousseau

Paleoclimate proxy records contain abrupt transitions that may represent former instances of the climate system crossing a tipping point (TP). Properly identifying these TPs in the Earth’s past helps determine critical thresholds in present-day climate and better understand the climate system’s underlying bifurcation mechanisms.

Information contained in paleoclimate proxy records is often ambiguous because of the complexity of the system, which includes both deterministic and stochastic processes. Furthermore, paleoclimate time series differ in their time spans and periodicities, and often have high levels of noise and a nonuniform resolution. These combined sources of uncertainty highlight the need for using advanced statistical methods for robustly identifying and comparing TPs.

A recently developed method that uses an augmented Kolmogorov-Smirnov test has been shown to be highly effective for transition detection in different types of records. Here, we apply this method to a set of high-quality paleoproxy records exhibiting centennial-to millennial-scale variability that have been compiled in the PaleoJump database. We thereby detect previously unrecognized transitions in these records and identify potential TPs. Furthermore, we investigate regime changes with recurrence analysis and spectral analysis.

This study is supported by the H2020-funded Tipping Points in the Earth System (TiPES) project.

How to cite: Bagniewski, W., Ghil, M., and Rousseau, D.-D.: Paleoclimatic tipping points and abrupt transitions: An application of advanced time series analysis methods, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12501, https://doi.org/10.5194/egusphere-egu22-12501, 2022.

EGU22-12686 | Presentations | NP2.4

Early warning signals for topological tipping points 

Gisela Daniela Charó, Michael Ghil, and Denisse Sciamarella


The topology of the branched manifold associated with the Lorenz model’s random attractor (LORA) evolves in time. LORA’s time-evolving branched manifold robustly supports the point cloud associated with the system’s invariant measure at each instant in time. 

This manifold undergoes not only continuous deformations — with branches that bend, stretch or compress — but also discontinuous deformations, with branches that intersect at discrete times. These discontinuities in the system's invariant measure manifest themselves in the decrease or increase of the number of 1-holes, thus producing abrupt changes in the branched manifold’s topology.

Topological tipping points (TTPs) are defined as abrupt changes in the topology of a random attractor’s branched manifold. Branched Manifold Analysis through Homologies
(BraMAH) is a robust method that allows one to detect these fundamental changes. 
The existence of such TTPs is being confirmed by careful statistical analysis of LORA’s time-evolving branched manifold, following up on Charó et al. (Chaos, 2021, doi:10.1063/5.0059461). Research is being pursued on early warning signals for these TTPs, concentrating on local fluctuations in the system’s invariant measure.

How to cite: Charó, G. D., Ghil, M., and Sciamarella, D.: Early warning signals for topological tipping points, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12686, https://doi.org/10.5194/egusphere-egu22-12686, 2022.

EGU22-13023 | Presentations | NP2.4

Data-driven Reconstruction of Last Glacials' Climate Dynamics Suggests Monostable Greenland Temperatures and a Bistable Northern Hemisphere Atmosphere 

Keno Riechers, Leonardo Rydin, Forough Hassanibesheli, Dirk Witthaut, Pedro Lind, and Niklas Boers

Multiple proxy records from Greenland ice cores exhibit a series of concomitant abrupt climatic shifts during the last glacial. These so-called Dansgaard–Oeschger (DO) events comprise, among others, warming over Greenland, a sudden retreat of North Atlantic and Nordic Seas’ sea ice, and an atmospheric reorganisation of hemispheric extent. Typically DO events are followed by a phase of moderate cooling, before the climate abruptly transition back to its pre-event state. While the physics behind these dynamics are still subject to a vibrant debate, the idea that at least one of the involved climatic subsystems features bistability is widely accepted.

We assess the stability of Greenland temperatures and the Northern Hemisphere atmospheric circulation represented by δ¹⁸O and dust concentration records from the NGRIP ice core, respectively. We investigate the 27-59 ky b2k period of the combined record which covers 12 major DO events at high temporal resolution. Regarding the data as the realisation of a stochastic process we reconstruct the corresponding drift and diffusion by computing the Kramers–Moyal (KM) coefficients. In contrast to previous studies, we find the drift of the δ¹⁸O to be monostable, while analysis of the dust record yields a bistable drift. Furthermore, we find a non-vanishing 4th-order KM coefficient for the δ¹⁸O, which indicates that the δ¹⁸O time series cannot be considered a standard type Langevin process. In a second step, we treat the joint (δ¹⁸O , dust) time series as a two dimensional stochastic process and compute the corresponding coefficients of the two dimensional KM expansion. This reveals the position of the fixed point of δ¹⁸O to be controlled by the value of the dust. In turn, the drift of the dust undergoes an imperfect supercritical pitchfork bifurcation when transitioning from low to high δ¹⁸O values.

How to cite: Riechers, K., Rydin, L., Hassanibesheli, F., Witthaut, D., Lind, P., and Boers, N.: Data-driven Reconstruction of Last Glacials' Climate Dynamics Suggests Monostable Greenland Temperatures and a Bistable Northern Hemisphere Atmosphere, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13023, https://doi.org/10.5194/egusphere-egu22-13023, 2022.

Many generations of climate general circulation models (GCMs) have suggested that a radical reorganisation (tipping) of the Atlantic Meridional Overturning Circulation is unlikely in the 21st Century in response to the greenhouse gas emissions pathways considered by the Intergovernmental Panel on Climate Change (IPCC). Yet some studies suggest that GCMs as a class may represent an AMOC that is biased towards excessive stability. If this is the case then simply looking at AMOC response in the ensemble of current GCMs may give a misleading picture of the possible future pathways of the AMOC.

In this study we use a simple coupled climate model, including both the thermal and water cycle responses to greenhouse gas increase, to explore beyond the range of the current ensemble of ‘best estimate’ GCMs. What would the climate system need to look like in order for AMOC tipping to be a plausible outcome? We find that tipping behaviour would require key parameters controlling the response of the hydrological cycle to surface warming to be towards the edge of plausible ranges.

While AMOC tipping remains a ‘High Impact, Low Likelihood’ outcome, our results extend current knowledge by showing how AMOC tipping could occur in response to greenhouse gas forcing (as opposed to the common idealisation of ‘water hosing’ experiments). The results also show how monitoring key parameters of the climate system may over time allow the possibility of tipping to be more confidently assessed.

How to cite: Wood, R.: Climate storylines for AMOC tipping in response to increasing greenhouse gases, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13181, https://doi.org/10.5194/egusphere-egu22-13181, 2022.

Sea level change affects hundreds of millions of people living in coastal regions. In addition to measuring the total sea level change via satellite altimetry, it is important to understand individual mass and steric contributors on global and regional scales. Consequently, deriving accurate global and regional sea level budgets is of key interest for understanding the underlying processes and aid in assessing future impacts of sea level rise. Furthermore, steric sea level change is related to the Earth’s Energy Imbalance and thus a key indicator of global warming.

The global fingerprint inversion method (Rietbroek et al., 2016) allows to combine GRACE(-FO) gravity measurements and along-track satellite altimetry observations in order to jointly estimate the individual mass and steric changes in a consistent manner. We use an extended fingerprint approach which allows further separation of the ocean mass variations into contributions from the melting of land glaciers and the Greenland and Antarctic ice-sheets as well as terrestrial hydrology effects and changes of the internal mass transport within the ocean. Furthermore, the updated inversion presented here, aims at splitting the steric sea level change into contributions of the upper 700m and the deeper ocean.

Here, we present the inversion results of a closed global sea level budget (within 0.1 mm/yr) during the GRACE era (2002-04 till 2015-12) attributing 1.68 mm/yr and 1.40 mm/yr to ocean mass and steric changes, respectively. Compared to state-of-the art studies the steric contribution is found to be in line while the mass estimates are slightly lower. We provide budgets for major ocean basins and compare our results to individually processed GRACE, altimetry and ocean re-analysis datasets as well as published estimates. Furthermore, we will show preliminary results when extending the inversion to incorporate additional GRACE-FO data. Finally, we extent our investigations to regional sea level budgets for selected regions of interest, such as the Bay of Bengal or the North Sea, which are dominated by completely different sea level components.

How to cite: Uebbing, B., Rietbroek, R., and Kusche, J.: Investigating global and regional sea level budgets by combining GRACE(-FO) and altimetry data in a joint fingerprint inversion, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2190, https://doi.org/10.5194/egusphere-egu22-2190, 2022.

EGU22-2489 | Presentations | CL3.1.1

Introducing WALIS, the World Atlas of Last Interglacial Shorelines Version 1.0 

Alessio Rovere, Deirdre D. Ryan, Matteo Vacchi, Andrea Dutton, Alexander Simms, and Colin Murray-Wallace

We present Version 1.0 of the World Atlas of Last Interglacial Shorelines (WALIS), a global database containing samples and sea-level proxies dated to Marine Isotope Stage 5 (~70 to 130 ka). The database was built through manuscripts and associated datasets compiled in a Special Issue of the journal Earth System Science data (https://essd.copernicus.org/articles/special_issue1055.html). We collated the single contributions (archived in Zenodo at this link: https://zenodo.org/communities/walis_database/) into an open-access standalone database. Database documentation is available at this link: https://doi.org/10.5281/zenodo.3961544. Version 1.0 of the database contains 4005 sea-level index points and 4390 dated samples connected with several tables containing relevant metadata (e.g., elevation measurement techniques, sea-level datums, and literature references).

How to cite: Rovere, A., Ryan, D. D., Vacchi, M., Dutton, A., Simms, A., and Murray-Wallace, C.: Introducing WALIS, the World Atlas of Last Interglacial Shorelines Version 1.0, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2489, https://doi.org/10.5194/egusphere-egu22-2489, 2022.

EGU22-2577 | Presentations | CL3.1.1

Evidence of acceleration in sea-level rise for the North Sea 

Riccardo Riva, David Steffelbauer, Jos Timmermans, Jan Kwakkel, and Mark Bakker

Global mean sea-level rise (SLR) has accelerated since 1900 from less than 2 mm/year during most of the century to more than 3 mm/year since 1993. At the regional scale, detection of an acceleration in SLR is difficult, because the long-term sea-level signal is obscured by large inter-annual variations with multi-year trends that are easily one order of magnitude larger than global mean values. Here, we developed a time series approach to determine whether regional SLR is accelerating based on tide gauge data. We applied the approach to eight 100-year records in the southern North Sea and detected, for the first time, a common breakpoint in the early 1990s. The mean SLR rate at the eight stations increases from 1.7±0.3 mm/year before the breakpoint to 2.7±0.4 mm/year after the breakpoint (95% confidence interval), which is unprecedented in the regional instrumental record. These findings are robust provided that the record starts before 1970 and ends after 2015.

How to cite: Riva, R., Steffelbauer, D., Timmermans, J., Kwakkel, J., and Bakker, M.: Evidence of acceleration in sea-level rise for the North Sea, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2577, https://doi.org/10.5194/egusphere-egu22-2577, 2022.

EGU22-2605 | Presentations | CL3.1.1

Inverting marine terrace morphology to constrain paleo sea-level 

Gino de Gelder, Navid Hedjazian, Anne-Morwenn Pastier, Laurent Husson, and Thomas Bodin

Quantifying paleo sea-level changes is an important challenge given its intricate relation with paleo-climate, -ice-sheets and geodynamics, but pre-Holocene uncertainties currently span several tens of meters. The world’s coastlines provide an enormous geomorphologic dataset, and recent modelling studies have showed their potential in constraining paleo sea-level through forward landscape evolution modeling. We take a next step, by applying a Bayesian approach to invert the geometry of marine terrace sequences to paleo sea-level. Using a Markov chain Monte Carlo sampling method, we test our model on synthetic profiles and two observed marine terrace sequences. The synthetic profiles – with known input parameters – show that there are optimal values for uplift rate, erosion rate, initial slope and wave base depth to obtain a well-constrained inversion. Both the inversion of synthetic profiles and a terrace profile from Santa Cruz (Ca, US) show how sea-level peaks are easier to constrain than sea-level troughs, but that also solutions for peaks tend to be non-unique. Synthetic profiles and profiles from the Corinth Rift (Greece) both show how inverting multiple profiles from a sequence can lead to a narrower range of possible paleo sea-level, especially for sea-level troughs. This last result emphasizes the potential of inverting coastal morphology: joint inversion of globally distributed marine terrace profiles may eventually reveal not only local relative sea-level histories, but catalyse a better understanding of both global paleo sea-level and glacio-isostatic adjustments.

How to cite: de Gelder, G., Hedjazian, N., Pastier, A.-M., Husson, L., and Bodin, T.: Inverting marine terrace morphology to constrain paleo sea-level, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2605, https://doi.org/10.5194/egusphere-egu22-2605, 2022.

EGU22-3307 | Presentations | CL3.1.1

Drivers for seasonal variability in sea level around the China seas 

Ying Qu, Svetlana Jevrejeva, Joanne Williams, and John Moore

Globally variable ocean and atmospheric dynamics lead to spatially complex seasonal cycles in sea level. The China Seas, that is the Bohai, Yellow, East China and the South China seas, is a region with strong seasonal amplitudes, and straddles the transition between tropical and temperature zones, monsoonal and westerlies, shelf and deep ocean zones. Here we investigate the drivers for seasonal variability in sea level from tide gauge records, satellite altimetry along with output from the NEMO (Nucleus for European Modeling of the Ocean) model including sea surface height and ocean bottom pressure along with meteorological data in the China Seas. The seasonal cycle accounts for 37% - 94% of sea level variability in 81 tide gauge records, ranging from 18 to 59 cm. We divided the seasonal cycles into four types: 1) an asymmetric sinusoid; 2) a clearly defined peak on a flat background; 3) a relatively flat signal; 4) a symmetric co-sinusoid. Type 1 is found in northern China and Taiwan, Korea, Japan and The Philippines where Inverse Barometer (IB) effects dominates seasonality along with a steric contribution. The seasonal monsoon associated with barotropic response and freshwater exchange play important roles in type 2, (eastern and southern Chinese coasts), type 3 (East Malaysia) and type 4 (Vietnam and Gulf of Thailand). IB corrected seasonal cycle amplitudes are larger in continental shelf areas than the deep ocean, with a maximum in the Gulf of Thailand, and NEMO underestimates the seasonal amplitude along the coast by nearly 50%.

How to cite: Qu, Y., Jevrejeva, S., Williams, J., and Moore, J.: Drivers for seasonal variability in sea level around the China seas, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3307, https://doi.org/10.5194/egusphere-egu22-3307, 2022.

EGU22-3342 | Presentations | CL3.1.1

Local and remote forcing of sea-level variation off the northeast US coast 

Tong Lee, Ou Wang, Christopher Piecuch, Ichiro Fukumori, Ian Fenty, Thomas Frederikse, Dimitris Menemenlis, Rui Ponte, and Hong Zhang

The relative contributions of local and remote wind stress and air-sea buoyancy forcing to sea-level variations along the East Coast of the United States are not well quantified, hindering the understanding of sea-level predictability there. Here, we use an adjoint sensitivity analysis together with an Estimating the Circulation and Climate of the Ocean (ECCO) ocean state estimate to establish the causality of interannual sea-level variations near the Nantucket island, the approximate geographic center of the northeast US coast where sea-level fluctuations are coherent. Wind forcing explains 68% of the Nantucket interannual sea-level variance, while wind and buoyancy forcing together explain 97% of the variance. Wind stress contribution is near-local, primarily from the New England shelf northeast of Nantucket. We disprove a previous hypothesis about Labrador Sea wind stress being an important driver of Nantucket sea-level variations and another hypothesis suggesting local wind stress being a secondary driver. Buoyancy forcing, as important as wind stress in some years, includes local contributions as well as remote contributions from the subpolar North Atlantic that influence Nantucket sea level a few years later. Our rigorous adjoint-based analysis corroborates previous correlation-based studies that sea-level variations in the subpolar gyre and the northeast US coast can both be influenced by subpolar buoyancy forcing. Forward forcing perturbation experiments further indicate remote buoyancy forcing affects Nantucket sea level mostly through slow advective processes, although waves can cause rapid Nantucket sea level response within a few weeks. Our results quantifying the spatial distribution of forcing contributions to Nantucket sea-level variations are also useful for the development of machine-learning models for predicting sea-level variation off the northeast US coast.

How to cite: Lee, T., Wang, O., Piecuch, C., Fukumori, I., Fenty, I., Frederikse, T., Menemenlis, D., Ponte, R., and Zhang, H.: Local and remote forcing of sea-level variation off the northeast US coast, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3342, https://doi.org/10.5194/egusphere-egu22-3342, 2022.

EGU22-3512 | Presentations | CL3.1.1

Regionalizing the Sea-level Budget Using a Neural Network Approach 

Carolina Machado Lima de Camargo, Marta Marcos, Ismael Hernandez-Carrasco, Tim H.J. Hermans, Riccardo E.M. Riva, and Aimée B.A. Slangen

Understanding the drivers of present-day sea-level change is vital for improving sea-level projections and for adaptation and mitigation plans against sea-level rise. Sea-level budget (SLB) studies focus on attributing the observed sea-level change to its different drivers (steric and barystatic changes). While the global mean SLB is closed, explaining the drivers of sea-level change on a finer spatial scale leads to large discrepancies. Recent studies have shown that closing the regional budget on a regular 1x1˚ grid is not possible due to limitations of the observations itself, but also due to the spatial patterns and variability of the underlying processes. Consequently, the regional budget has been mainly analyzed on a basin-wide scale.

 In this study we use Self-Organizing Maps (SOM), an unsupervised learning neural network, to extract regions of coherent sea-level variability based on 27 years of satellite altimetry data. The SOM clusters have a higher level of spatial detail compared to entire ocean basins, while being large enough to allow for a consistent sea-level budget analysis. The clusters also show how sea-level variability is interconnected among different ocean regions (for example, due to large-scale climate patterns). We perform the clustering analysis on the Atlantic and Indo-Pacific Oceans separately, obtaining a total of 18 clusters. Preliminary results show that we can close the sea-level budget from 1993-2017 in 67% of the clusters. The regions with discrepancies highlight important regional processes that are affecting sea-level change and have not thus far been included in the sea-level budget. In this way, using neural networks provides new insight into regional sea-level variability and its drivers.

How to cite: Machado Lima de Camargo, C., Marcos, M., Hernandez-Carrasco, I., Hermans, T. H. J., Riva, R. E. M., and Slangen, A. B. A.: Regionalizing the Sea-level Budget Using a Neural Network Approach, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3512, https://doi.org/10.5194/egusphere-egu22-3512, 2022.

EGU22-3934 | Presentations | CL3.1.1

Sea level projections portal for communicating impacts to policymakers 

Andrew Matthews and Sveta Jevrejeva

Small island developing states are particularly at risk from extreme water levels and coastal erosion. Policy makers require information to support decision making on how to improve resilience and adapt to future changes. Here we present a web portal designed to display different sea level projections across the Caribbean Sea, developed as part of our contribution to the UK Government’s Commonwealth Marine Economies (CME) programme and the UK Natural Environment Research Council’s ACCORD programme.

The portal has been designed using free and open-source software, and is self-contained, allowing it to be deployed on local partner websites with minimal effort. The responsive design allows the portal to work as well on as it does on PCs.

Currently the portal displays projected sea level for over 50 locations across the Caribbean, along with sea level data available at the site, but extra sites can be added easily. Quality controlled data has been used where possible; where this is not available, we have used automated software developed earlier in the CME programme to perform basic quality control.

Similarly, the portal provides projections from four sea level scenarios based on earlier National Oceanography Centre work, but other projections can be added by updating configuration files.

The portal can be accessed at https://psmsl.org/accord/projections.html

How to cite: Matthews, A. and Jevrejeva, S.: Sea level projections portal for communicating impacts to policymakers, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3934, https://doi.org/10.5194/egusphere-egu22-3934, 2022.

EGU22-4091 | Presentations | CL3.1.1

How robust are estimates of hydrology–driven global sea level change based on modelling and GRACE data? 

Juergen Kusche, Christan Mielke, Olga Engels, Li Fupeng, and Bernd Uebbing

One of the less well-known contributions to global sea level change is the net mass loss or gain of non-cryospheric land water storage, here abbreviated as hydrology-driven global mean sea level rise (HDGMSL). HDGMSL is due to natural variability in the climate system and direct and indirect anthropogenic processes, such as reservoir building, deforestation and land use change, land glacier mass imbalance,  groundwater depletion, and changes in the atmosphere-ocean water fluxes. It has a large inter-annual variability, as  otherwise only observed in the thermo-steric contribution to sea level, and the sign of its net rate over the last decades is still debated.

Here, we revisit estimates of HDGMSL from GRACE and from global hydrological models. We scrutinize the robustness of estimates in the presence of climate variability within the limited GRACE time-frame, in particular large ENSO modes. To this end we make use of an ensemble of three GRACE solutions and a 32-member ensemble of the WGHM hydrological model where various parameters were realistically perturbed. Moreover we consider two different 40-year reconstructions of terrestrial water storage that were trained on GRACE data, two methods of mode decomposition, and we employ different trend estimators including a state-space parameterization. We conclude that HDGMSL was positive in the GRACE time frame with different estimators pointing to rates between -0.01 and 0.30 mm/a, which is probably not representative for a 40-year span. In addition, all conventional error estimates are found to be over-optimistic.

How to cite: Kusche, J., Mielke, C., Engels, O., Fupeng, L., and Uebbing, B.: How robust are estimates of hydrology–driven global sea level change based on modelling and GRACE data?, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4091, https://doi.org/10.5194/egusphere-egu22-4091, 2022.

EGU22-4228 | Presentations | CL3.1.1

Sea level rise along the coastline of Colombia: A vulnerability assessment 

Hannes Nevermann, Jorge Nicolas Becerra Gomez, Peter Fröhle, and Nima Shokri

Abstract

In recent decades, the sea level has risen notably compared to the most recent millennia. This poses serious threats to environment and human population over the next century especially in coastal zones. Every region has climatic and non-climatic drivers of sea level rise which needs to be considered when adaptation and mitigation policies are implemented. We analyzed the coastal consequences of sea level rise along the Caribbean and Pacific coastlines of Colombia. Sea level rise projections published in August 2021 by the Intergovernmental Panel on Climate Change in the 6th assessment report were used in this study (IPCC, 2021). Five Shared Socioeconomic Pathways for the 21st century (SSP1-1.9, SSP1-2.6, SSP2-4.5. SSP3-7.0, SSP5-8.5) were examined. Our results indicate a sea level rise of 1.04 m in the worst-case scenario (SSP5-8.5) which could cause land loss in an area of 2840.64 km². The area at risk will impact 12 departments or 86 municipalities with different social, environmental, economic, and cultural conditions that need to be considered when implementing mitigation policies. Our results illustrate how the projected sea level changes influence a variety of parameters such as area at the potential risk of inundation, land use of the affected area and general socio-economic impacts along the Caribbean and Pacific coastlines of Colombia.

 

Reference

IPCC (2021), Climate Change 2021: The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change [Masson-Delmotte, V., P. Zhai, A. Pirani, S.L. Connors, C. Péan, S. Berger, N. Caud, Y. Chen, L. Goldfarb, M.I. Gomis, M. Huang, K. Leitzell, E. Lonnoy, J.B.R. Matthews, T.K. Maycock, T. Waterfield, O. Yelekçi, R. Yu, and B. Zhou (eds.)]. Cambridge University Press. In Press.

How to cite: Nevermann, H., Becerra Gomez, J. N., Fröhle, P., and Shokri, N.: Sea level rise along the coastline of Colombia: A vulnerability assessment, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4228, https://doi.org/10.5194/egusphere-egu22-4228, 2022.

EGU22-4414 | Presentations | CL3.1.1

High-resolution climate ensemble reveals low confidence in projected changes in storm surges for the mid-century 

Sanne Muis, Jeroen C.J.H. Aerts, José A. Á. Antolínez, Dewi Le Bars, Job C. Dullaart, Trang Minh Duong, Li Erikson, Rein Haarsma, Maialen Irazoqui Apecechea, Andrea O'Neill, Roshanka Ranasinghe, Malcolm Roberts, Kun Yan, Martin Verlaan, and Philip J. Ward

In the coming decades, regions across the globe will be faced with increases in coastal flooding due to sea-level rise and changes in climate extremes. In a collective effort, we have produced new extreme sea level projections derived from an ensemble of high-resolution climate models. Our approach is based on the Global Tide and Surge Model forced with model outputs from the HighResMIP experiments. The HighResMIP models have a much higher spatial resolution than the previous generation of climate models, and can better resolve storms, including tropical cyclones. The dataset has global coverage and spans the period 1950-2050. The dataset provides: 1) timeseries of storm surges, astronomical tides, and total still water levels; and 2) water level statistics for different time slices, including percentiles and return periods.

In this contribution we focus on storm surges and have a first look at model performance for present-day climate conditions and at projected changes. Comparison of the 1 in 10-year surge levels against the ERA5 reanalysis reveals a large spatial bias for some of the HighResMIP models, highlighting the need for multi-model ensembles and bias correction. Comparison of the 1 in 10-year surge levels between the 1951-1980 and 2021-2050 period, shows that some regions, such as Northwest Europe, Alaska, China, and Patagonia, may be faced with an increase in storm surges (>0.1 m), while other regions, such as the Mediterranean and South Australia may see a decrease in storm surges. Overall, the projected changes are characterized by large intermodel variability due the uncertainties that arise from the climate models, internal variability, and extreme value statistics. Future research should aim to better constrain the uncertainties, which can be achieved by a more in-depth exploration of the changes in the meteorological conditions, enlarging the model ensemble, and the implementation of bias correction methods.

The full datasets will soon become openly available at the C3S Climate Data Store and can be used to inform climate impact assessments.

How to cite: Muis, S., Aerts, J. C. J. H., A. Á. Antolínez, J., Le Bars, D., Dullaart, J. C., Minh Duong, T., Erikson, L., Haarsma, R., Irazoqui Apecechea, M., O'Neill, A., Ranasinghe, R., Roberts, M., Yan, K., Verlaan, M., and Ward, P. J.: High-resolution climate ensemble reveals low confidence in projected changes in storm surges for the mid-century, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4414, https://doi.org/10.5194/egusphere-egu22-4414, 2022.

EGU22-4426 | Presentations | CL3.1.1

Seasonal signal and regional sea level variability over the past 25 years 

Svetlana Jevrejeva and Hindumathi Palanisamy

In this study we have quantified the role of seasonal cycles in globally observed sea level variability from satellite altimetry over 1993-2018. We show the largest seasonal variability, with contribution more than 80% of total variance, is detected in particular regions- the marginal seas over the continental shelf regions in South East Asia and Gulf of Carpentaria, tropical Atlantic along the coastal regions of east Atlantic Ocean, Arabian Sea, regions of Mediterranean, Red Sea with amplitudes greater than 20cm in majority of these locations. The rest of the ocean, mainly deep open ocean, exhibits strong signatures of non-seasonal variability related to interannual and longer scale cycles.

For the regions with large seasonal variability (e.g. South East Asia coastline), analysis of seasonal variability demonstrate a good agreement in amplitude and phase from satellite altimetry and tide gauges records. While steric contribution can explain more than 80% of total variability in the deep ocean areas, in shallow areas we explain a large part of variability though wind driven during the two monsoon seasons, and not attributed to the steric changes.

How to cite: Jevrejeva, S. and Palanisamy, H.: Seasonal signal and regional sea level variability over the past 25 years, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4426, https://doi.org/10.5194/egusphere-egu22-4426, 2022.

EGU22-5156 | Presentations | CL3.1.1

High-resolution projections of extreme sea level changes along the coasts of western Europe 

Alisée Chaigneau, Angélique Melet, Stéphane Law-Chune, Aurore Voldoire, Guillaume Reffray, and Lotfi Aouf

Extreme sea levels (ESLs) are a major threat for coastal and low-lying regions. Climate change induced sea level (SL) rise will increase the frequency of ESLs. Projections of ESLs are thus of great interest for coastal risk assessment and decision-making. SL projections are typically produced using global climate models (GCMs). However, GCMs do not explicitly resolve key processes driving ESL changes at the coast (e.g. waves, tides). In this study, a regional model IBI-CCS is set up to refine SL projections of a GCM over the north-eastern Atlantic region bordering western Europe using dynamical downscaling. For a more complete representation of processes driving coastal ESL changes, tides and atmospheric surface pressure forcing are explicitly resolved in IBI-CCS in addition to the ocean general circulation. Furthermore, to include the wave setup contribution to ESLs, a dynamical downscaling of a wave global model is performed over the same north-eastern Atlantic domain using the currents and sea level outputs of the IBI-CCS regional ocean model. All the regional simulations are performed over the 1950 to 2100 period for two climate change scenarios (SSP1-2.6 and SSP5-8.5).

Comparisons to reanalyses and observations over the 1993-2014 indicate that ESLs are satisfactorily represented in the regional simulations. In a second phase, the projected changes in ESLs are analyzed, particularly in term of changes in return levels and return periods. The coupling effects between the key processes driving ESL changes at the coast are investigated. We notably assess the influence of the wave setup contribution to ESLs and to projected changes in ESLs and to their return periods. In addition, the impact of accounting for hourly sea level changes in the wave regional model on ESLs and projections of ESLs is estimated.

How to cite: Chaigneau, A., Melet, A., Law-Chune, S., Voldoire, A., Reffray, G., and Aouf, L.: High-resolution projections of extreme sea level changes along the coasts of western Europe, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5156, https://doi.org/10.5194/egusphere-egu22-5156, 2022.

EGU22-5203 | Presentations | CL3.1.1

Mediterranean coastal sea level reconstruction based on tide gauge observations 

Jorge Ramos Alcántara, Damià Gomis Bosch, and Gabriel Jordà Sánchez

In order to carry out a proper coastal management it is compulsory to have oceanographic databases that accurately characterize the spatiotemporal variability of sea level along the coast. A first source of sea level observations are tide gauges, which cover different time periods, some of them dating back to the 17th century. Whereas tide gauges generally provide very accurate measurements, their main limitation is that they are point-wise measurements with a heterogeneous spatial distribution and temporal coverage. Therefore, it is difficult to represent the complexity of sea level variability at the coast directly from tide gauge observations. Since 1992, sea level measurements provided by satellite altimetry are also available. This technique has a quasi-global coverage, and by minimising all sources of error affecting the measurements, an accuracy close to 1 cm can be achieved. However, altimetric products have a limited spatial and temporal resolution due to the separation between adjacent satellite ground tracks and to the revisiting time of the satellites. Most important, the accuracy of altimetry observations decreases very rapidly near the coast; despite the advances reached in recent years, standard altimetric data are only available from 5-10 km offshore.

As an alternative to coastal altimetric products, in this work we develop a new methodology to reconstruct coastal sea level from a number of tide gauge observations, which in our case is applied to the western basin of the Mediterranean sea. The reconstruction covers all coastal regions and has the spatial and temporal resolution required to characterise coastal processes. The sea level reconstruction is based on a multiscale optimal interpolation where the spatial correlations between tide gauges and all the coastal points has to be determined prior to the interpolation. In our case, these correlations are computed from the outputs of a high-resolution numerical model. As for observations, for the monthly reconstruction we use PSMSL tide gauge records, which cover the period from 1884 to 2015. For the daily reconstruction we use the series of the GESLA-2 data set, which cover from 1980 to 2015.

A cross-validation test developed to validate the skills of the method shows that our reconstruction clearly outperforms altimetric and modelling products at different time scales, and therefore represents a valuable contribution to the attempts of recovering coastal sea level. Thus, the obtained reconstruction has been used to complement the characterization of open sea level variability in the western Mediterranean previously done by other authors, allowing us to estimate coastal sea level trends, and to examine the correlation between Western Mediterranean coastal sea level and the main North Atlantic climate indices. The limitations and applicability of the method to other regions will also be discussed in the presentation.

How to cite: Ramos Alcántara, J., Gomis Bosch, D., and Jordà Sánchez, G.: Mediterranean coastal sea level reconstruction based on tide gauge observations, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5203, https://doi.org/10.5194/egusphere-egu22-5203, 2022.

EGU22-5281 | Presentations | CL3.1.1

The impact of continuous space and time-resolving vertical land motion on relative sea level change 

Julius Oelsmann, Marta Marcos, Marcello Passaro, Laura Sánchez, Denise Dettmering, and Florian Seitz

Vertical land motion (VLM) is a major contributor to relative sea level change (RSLC). Hence, understanding and estimating VLM is critical for the investigation of contemporary and projected coastal RSLC and the allocation of its uncertainties. However, there are several challenges involved in the determination of the linear component of VLM. Firstly, the sparse and inhomogeneous distribution of point-wise VLM observations hinder the direct analysis of VLM continuously in space along the coastline. Secondly, the commonly applied working-hypothesis that VLM can be generally assumed as ‘linear’, is not entirely valid for regions, which are affected by nonlinear processes such as earthquakes, surface mass loading changes or other phenomena. Thus, in order to overcome the limitations of data-availability and to account for time-variable VLM, we develop a new approach to estimate continuous time- and space-resolving (3D) VLM over the period 1995-2020.

We apply a Bayesian Principal Component Analysis to a global network of quality controlled VLM observations (GNSS data and differences of satellite altimetry and tide gauge observations) to extract common modes of variability and to cope with the incomplete VLM data. The estimated modes represent a superposition of large scale VLM fingerprints. These include linear motion signatures, e.g., associated with the Glacial Isostatic Adjustment (GIA), as well as regional patterns of coherent responses to earthquakes or terrestrial water storage changes, which exhibit inter-annual to decadal variability. To generate the 3D VLM reconstruction, the VLM fingerprints are interpolated in space with a Bayesian transdimensional regression, which automatically infers the spatial resolution based on the distribution of the data.

Our approach not only provides an essential observation-based alternative to previously employed VLM estimates from GIA models or interpolated VLM maps, but also allows to directly attribute VLM trend uncertainties to the temporal variability estimated over the period of observation. We combine the VLM dataset with century-long tide gauge RSLC observations to demonstrate the limitations of extrapolating nonlinear VLM back in time and to identify regional differences (in the order of mm/year) of contemporary absolute sea level (ASL) change (1900-2015) w.r.t. a recent sea level reconstruction, which employs a GIA-VLM signature only. Using the present-day VLM estimates, we disentangle the contributions of VLM and projected ASL change (from CMIP6 models) and uncertainties to RSLC (2020-2150). The regional RSLC error budget analysis enables the identification of regions where robust assessments of future RSLC are feasible and where VLM uncertainties dominate the projected ASL uncertainties, while explaining up to 75% of the combined uncertainties. Besides these applications, the VLM estimate represents a vital source of information for various sea level studies focused on the analysis of tide gauge or satellite altimetry observations in coastal areas.

How to cite: Oelsmann, J., Marcos, M., Passaro, M., Sánchez, L., Dettmering, D., and Seitz, F.: The impact of continuous space and time-resolving vertical land motion on relative sea level change, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5281, https://doi.org/10.5194/egusphere-egu22-5281, 2022.

EGU22-6530 | Presentations | CL3.1.1

Common Era sea-level budgets of North America 

Jennifer Walker, Robert Kopp, Timothy Shaw, Geoff Richards, and Benjamin Horton

A sea-level budget improves understanding of driving processes and their relative contributions. However, most sea-level budget assessments are limited to the 20th and 21st centuries and are global in scale. Here, we estimate the sea-level budget on centennial to millennial timescales of the Common Era (last 2000 years). We expand upon previous analysis of sites along the U.S. mid-Atlantic coast (Walker et al., 2021) and produce site-specific sea-level budgets for all of the eastern and western North American coastlines and Gulf coast. This broader scope further improves understanding of the temporal evolution and variability of driving processes of sea-level changes in the past and present, and which will shape such changes in the future.

To produce the sea-level budgets, we use an updated global database of instrumental and proxy sea-level records coupled with a spatiotemporal model. Using the unique spatial scales of driving processes, we separate relative sea-level records into global, regional, and local-scale components. Preliminary results along the eastern North American coastline reveal that each budget is dominated by regional-scale, temporally-linear processes driven by glacial isostatic adjustment until at least the mid-19th century. This signal exhibits a spatial gradient, ranging from 1.0 ± 0.02 mm/yr (1σ) in Newfoundland to a maximum of 1.6 ± 0.02 mm/yr in southern New Jersey to 0.5 ± 0.02 mm/yr in Florida. Non-linear regional and local-scale processes, such as ocean/atmosphere dynamics and groundwater withdrawal, are smaller in magnitude and vary temporally and spatially. The most significant change to the budgets is the increasing influence of the global signal due to ice melt and thermal expansion since ~1800 CE, which reaches a 20th century rate of 1.3 ± 0.1 mm/yr, accounting for 43-65% of each budget.

How to cite: Walker, J., Kopp, R., Shaw, T., Richards, G., and Horton, B.: Common Era sea-level budgets of North America, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6530, https://doi.org/10.5194/egusphere-egu22-6530, 2022.

EGU22-7733 | Presentations | CL3.1.1

Decadal changes of the Adriatic sea level – exploring the combined effect of sea level rise and climate regime’s shift 

Mia Pupić Vurilj, Jadranka Šepić, and Pave Pilić

In this study, an analysis of the observed Adriatic mean sea level time series has been carried out in order to determine the primary causes of the changes documented during the last 50 years.  Monthly sea level data were downloaded from the Permanent Service for Mean Sea Level for seven stations located along the northern and eastern Adriatic coast: Venice, Trieste, Rovinj, Bakar, Zadar, Split and Dubrovnik. Significant positive sea level trend, related to climate change, was detected at the majority of the stations. Further on, using Rodionov’s regime shift index algorithm, several regime shifts were detected. The first pronounced regime shift occurred in 1989 resulting with mean sea level lower than usual for an average of 4.37 cm; the second regime shift occurred in 1996 when mean sea level increased for an average of 2.07 cm; and the third regime shift, which is still on-going, started in 2009 when mean sea level abruptly increased to 5.3 cm above average.  A relationship between North Atlantic Oscillation (NAO) and sea level data has been explored, using both monthly and yearly data. High and significant correlation between the two was established for all data, and in particular for the winter season (December, January, February, March). All climate shifts were related to pronounced changes of NAO. The negative shift starting in 1989 was related to the positive phase of NAO, i.e. to weaker cyclonic activity over the Mediterranean and the Adriatic Sea. Oppositely, the two latter positive regime shifts were related to significant decrease and negative phases of NAO, with NAO reaching the most negative values of the entire observation period during the shift starting in 2009. Negative phase of NAO corresponds to stronger cyclonic activity over the Mediterranean and the Adriatic Sea. In conclusion, documented rise of the Adriatic sea level during the last 50 years, and in particular accelerated rise during the last 20 years represent a combination of mean sea level rise due to climate change and due to atmospherically induced shift of climate regimes.

How to cite: Pupić Vurilj, M., Šepić, J., and Pilić, P.: Decadal changes of the Adriatic sea level – exploring the combined effect of sea level rise and climate regime’s shift, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7733, https://doi.org/10.5194/egusphere-egu22-7733, 2022.

EGU22-8092 | Presentations | CL3.1.1

Synergistic use of tide gauges, satellite altimetry and GPS data for sea level studies 

Francesco De Biasio and Stefano Vignudelli

The relationship between satellite-derived absolute sea level change rates, tide gauge (TG) observations of relative sea level change and global positioning system (GPS) measurements of vertical land motion (VLM) at local scale has been investigated in previous studies [eg. Vignudelli et al., 2018]. The paucity of collocated TG-GPS data and the lack of a well-established mathematical frame in which simultaneous and optimal solutions can be derived, have emphasized the difficulty of deriving spatially-consistent information on the sea level rates. Other studies have claimed the possibility to set locally isolated information into a coherent regional framework using a constrained linear inverse problem approach [Kuo et al., 2004; Wöppelmann and Marcos, 2012].

The approach cited in the above papers has been recently improved in De Biasio et al. [2020]. A step in advance is now to develop an effective synergistic use of global positioning system (GPS) data, tide gauge measurements and satellite altimetry observations. In this study GPS data are used as a real source of information on the relative Vertical Land Motion (VLM) between pairs of tide gauges, and not as mere term of comparison of the results obtained by differencing relative and absolute sea level observations time series.

Long, consistent and collocated tide gauge and GPS observations time series are extracted for a handful of suitable coastal locations, and used in the original formulation of the constrained linear inverse problem, together with satellite altimetry data. Some experiments are conducted without GPS observations (traditional setup), and with GPS observations (the new proposed approach) Results are compared in order to assess the impact of GPS observations directly into the formulation of the constrained linear inverse problem.

The satellite altimetry data-set used in this study is that offered by the European Copernicus Climate Change Service (C3S) through its Climate Data Store archive. It covers the global ocean since 1993 to present, with spatial resolution of 0.25 x 0.25 degrees. This data set is constantly updated and relies only on a couple of simultaneous altimetry missions at a time to provide stable long-term variability estimates of sea level. Tide gauge data are extracted from the Permanent Service for Mean Sea Level archive and from other local sea level monitoring services. GPS vertical position time series and/or VLM rates are taken from the Nevada Geodetic Laboratory and other public GPS repositories.

REFERENCES

Vignudelli, S.; De Biasio, F.; Scozzari, A.; Zecchetto, S.; Papa, A. In Proceedings of the International Association of Geodesy Symposia; Mertikas, S.P., Pail, R., Eds.; Springer: Cham, Switzerland, 2020; Volume 150, pp. 65–74. DOI: 10.1007/1345_2018_51

Kuo, C.Y.; Shum, C.K.; Braun, A.; Mitrovica, J.X. Geophys. Res. Lett. 2004, 31. DOI: 10.1029/2003GL019106

Wöppelmann, G.; Marcos, M. J. Geophys. Res. Ocean. 2012, 117. DOI: 10.1029/2011JC007469

De Biasio, F.; Baldin, G.; Vignudelli, S. J. Mar. Sci. Eng. 2020, 8, 949. DOI: 10.3390/jmse8110949

How to cite: De Biasio, F. and Vignudelli, S.: Synergistic use of tide gauges, satellite altimetry and GPS data for sea level studies, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8092, https://doi.org/10.5194/egusphere-egu22-8092, 2022.

The last interglacial (LIG), ca. 128-116 ka, is widely considered a process analogue in understanding Earth’s systems in a future warmer climate. In particular, significant effort has been made to better constrain ice sheet contributions to sea level rise through direct field observation of relative sea level (RSL) indicators. In order to extract the RSL, a series of corrections for formational parameters and post-depositional processes need to be applied. Along tropical coastal margins, LIG RSL observations are predominately based on exposed shallow coral reef sequences due to their relatively narrow indicative range and reliable U-series chronological constraints. However, the often-limited sub-stadial temporal preservation of many Pleistocene reef sequences on stable coastlines restrict many reported RSLs to a series of distinct points in within the LIG. This in turn, limits ability to elucidate different commonly reported meter-scale sub-stadial sea level peak patterns and their associated uncertainties. In order to address this shortcoming, lithostratigraphic and geomorphologic traces are often used to place RSLs into a broader context. Unfortunately, this is often subjective, with significant reliance on field observations where missing facies and incomplete sequences can distort interpretations. Stepping back from a conventional approach, in this study we generate a spectrum of synthetic Quaternary subtropical fringing reefs in southwestern Madagascar within the DIONISOS forward stratigraphic model environment. Each reef sequence has been subjected to distinct Greenland and Antarctica melt scenarios produced by a coupled ANICE-SELEN global isostatic adjustment model, matching previously hypothesized LIG sea level curves in the Indo-Pacific Basin. The resulting suite of synthetic reef sequences provides the ability to probabilistically test any number of melt scenarios against the sensitivity of the stratigraphic record. We propose this accessible additional quantitative quality control during the final interpretation phase of establishing emergent reef sequence based LIG RSL indicators can assist in narrowing down the wide uncertainty surrounding inter-stadial ice sheet behaviors.   

How to cite: Boyden, P., Stocchi, P., and Rovere, A.: Assessing Last Interglacial Greenland and Antarctic Ice Sheet melting through forward stratigraphic derived synthetic outcrops: test case from Southwestern Madagascar, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8270, https://doi.org/10.5194/egusphere-egu22-8270, 2022.

EGU22-8462 | Presentations | CL3.1.1

Sensitivity of SSP585 sea-level projections to ocean model resolution in the MPI-ESM climate model 

Chathurika Wickramage, Armin Köhl, Detlef Stammer, and Johann Jungclauss

The existence of reliable coastal sea-level projections is essential for identifying necessary adaptation and mitigation strategies of policymakers and coastal communities over the following decades. However, today only a few ocean components of climate projections can resolve the small-scale processes that affect the Dynamic Sea Level (DSL) change in the open ocean and in coastal areas, predominantly in the eddy rich regions such as Antarctic Circumpolar Current (ACC) and the western boundary currents. Therefore, we investigate the dependence of regional sea-level projections on ocean model resolution using the recent Max Planck Institute Earth System Model (MPI-ESM) for the shared socioeconomic pathway 585 (SSP585, fossil-fuel development). By comparing the climate change scenario from 2080 to 2099 to a historical simulation from 1995 to 2014, our results indicate that the models, from eddy-rich (ER), eddy-permitting (HR) to coarser resolution (LR), successfully produce the previously identified global DSL patterns. However, the magnitude of the DSL increase in the North Atlantic subpolar gyre and the decrease in the subtropical gyre is significantly larger in the ER ocean in contrast to HR and LR; the same holds for the magnitude of the opposite dipole pattern in the North Pacific. In the southern ocean, the DSL increases north of ACC but decreases further to the south, projecting much smaller changes in the ER. We note that the meridional shift of ACC, associated with sea-level change, is smaller in ER than in HR and LR, indicating an accelerated ACC compared to HR simulation, which shows no acceleration at the end of the 21st century.

How to cite: Wickramage, C., Köhl, A., Stammer, D., and Jungclauss, J.: Sensitivity of SSP585 sea-level projections to ocean model resolution in the MPI-ESM climate model, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8462, https://doi.org/10.5194/egusphere-egu22-8462, 2022.

EGU22-8657 | Presentations | CL3.1.1

Long-Term Wind Influence on Sea Level Along the Dutch Coast 

Iris Keizer, Dewi Le Bars, André Jüling, Sybren Drijfhout, and Roderik van de Wal

We studied the wind influence on multidecadal variability and trend of sea level along the Dutch coast. Annual mean sea level for the period 1890 to 2020 is obtained from 6 tide gauges. We compared three widely used multi-linear regression models relating sea level and wind based on either local zonal and meridional wind speed or large-scale pressure patterns. For this purpose, surface wind and pressure data from the ERA5 reanalysis and the twentieth century reanalysis v3 (20CRv3) are used 

 

We find a significant multi-decadal mode of variability with an amplitude of around 1 cm and a period of 40 to 60 years that is related to the Atlantic Multidecadal Variability. We show that this multi-decadal wind variability is responsible for an average drop in sea level of 0.5 mm/yr over the last 40 years which is around a quarter of the total sea level rise of 2 mm/yr over that period. Therefore, wind effects on sea level partly masked sea level acceleration at the Dutch coast. This is important for sea level monitoring supporting decision making. 

 

The same multi-linear regression models are then applied to the CMIP6 historical and future climate scenario data to make projections of future wind impact on sea level along the Dutch coast. Contrary to our expectation based on a previous study in the German Bight (Dangendorf et al. 2014) we find no sign that long term wind changes will increase sea level during the 21st century. 

 

Reference: 

Dangendorf, Sönke, Thomas Wahl, Enno Nilson, Birgit Klein, and Jürgen Jensen. “A New Atmospheric Proxy for Sea Level Variability in the Southeastern North Sea: Observations and Future Ensemble Projections.” Climate Dynamics 43, no. 1–2 (July 2014): 447–67. https://doi.org/10.1007/s00382-013-1932-4. 

 

How to cite: Keizer, I., Le Bars, D., Jüling, A., Drijfhout, S., and van de Wal, R.: Long-Term Wind Influence on Sea Level Along the Dutch Coast, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8657, https://doi.org/10.5194/egusphere-egu22-8657, 2022.

EGU22-8674 | Presentations | CL3.1.1

Noisy Input Generalised Additive Model for Relative Sea Level along the East Coast of North America 

Maeve Upton, Andrew Parnell, Andrew Kemp, Gerard McCarthy, and Niamh Cahill

The 2021 Intergovernmental Panel on Climate Change report highlighted how rates of sea level rise are the fastest in at least the last 3000 years. As a result, it is important to understand historical sea level trends at a global and local level in order to comprehend the drivers of sea level change and the potential impacts. The influence of different sea level drivers, for example thermal expansion, ocean dynamics and glacial – isostatic adjustment (GIA), has changed throughout time and space. Therefore, a useful statistical model requires both flexibility in time and space and have the capability to examine these separate drivers, whilst taking account of uncertainty.

The aim of our project is to develop statistical models to examine historic sea level changes for North America's and Ireland's Atlantic Coast. For our models, we utilise sea-level proxy data and tide gauge data which provide relative sea level estimates with uncertainty. The statistical approach employed is that of extensions of Generalised Additive Models (GAMs), which allow separate components of sea level to be modelled individually and efficiently and for smooth rates of change and accelerations to be calculated.

The model is built in a Bayesian framework which allows for external prior information to constrain the evolution of sea level change over space and time. The proxy data is collected from salt-marsh sediment cores and dated using biological and geochemical sea level indicators. Additional tide gauge data is taken from the Permanent Service for Mean Sea Level online. Uncertainty in dating is extremely important when using proxy records and is accounted for using the Noisy Input uncertainty method (McHutchon and Rasmussen 2011).

By combining statistical models, proxy and tidal gauge data, our results have shown that current sea level along North America’s east coast is the highest it has been in at least the last 15 centuries. The GAMs have the capability of examining the different drivers of relative sea level change such as GIA, local factors and eustatic influences. Our models have demonstrated that GIA was the main driver of relative sea level change along North America’s Atlantic coast, until the 20th century when a sharp rise in rates of sea level change can be seen.

This work is part of the larger nationally funded Irish A4 project (Aigéin, Aeráid, agus Athrú Atlantaigh — Oceans, Climate, and Atlantic Change), funded by the Marine Institute. It aims to examine ocean and climate changes in the Atlantic Ocean. The project targets three aspects of the Atlantic: its changing ocean dynamics; sea level changes; and Irish decadal climate predictions. In the future, we will apply this modelling technique to produce a long term historical record for relative sea level change in Ireland.

How to cite: Upton, M., Parnell, A., Kemp, A., McCarthy, G., and Cahill, N.: Noisy Input Generalised Additive Model for Relative Sea Level along the East Coast of North America, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8674, https://doi.org/10.5194/egusphere-egu22-8674, 2022.

EGU22-9058 | Presentations | CL3.1.1

Prediction of future sea-level rise in land suitability for mangrove rehabilitation and restoration in Indonesia 

Luri Nurlaila Syahid, Raymond D. Ward, Anjar D. Sakti, Dian Rosleine, Ketut Wikantika, and Wiwin Windupranata

Mangroves have many benefits, both for humans and for the surrounding ecosystem. One of the most benefits from mangroves is that mangroves have coastal blue carbon reserves up to five times greater than the total carbon storage of temperate, taiga, and tropical forests. But recently, mangroves have decreased in extent by 20-35% due to both anthropogenic and naturogenic factors. One of the naturogenic factors that impact mangroves is sea-level rise. Mangroves cannot survive if sediment accumulation cannot keep pace with sea-level rise. This can result in mangrove death or zonal shifts in plant communities.

The decline in mangrove areas has resulted in increases in carbon emissions. This increase in carbon costs $US6-24 billion in economic damage annually. Indonesia experienced the highest increase in carbon dioxide emissions in the world in 1990-2010. Whereas in the Paris agreement, 2015, countries in the world including Indonesia have committed to reducing emissions by 29-41% by 2030. Therefore, rehabilitation and restoration of mangroves need to be undertaken, as well as identification of those mangroves most under threat.

The aim of this study is to model future sea-level rise and the impact of its exposure on land suitability for mangrove rehabilitation and restoration in Indonesia. This study uses the integration of remote sensing, statistical, and future climate model data combined with GIS methods to produce a sea-level rise model. This study also uses several scenarios both climate and temporal to predict sea-level rise.

The results of this study indicate that there are several areas that have high exposure caused by sea-level rise. This is exacerbated by low rates of sedimentation or land subsidence in some areas. In contrast, several other areas experienced high rates of accretion and thus are at less risk. Changes in rates of inundation caused by sea-level rise have caused some areas suitable for planting mangroves to become unsuitable. Therefore, if planting is carried out in the area now, it is very likely that the mangrove will be submerged by excessive tidal inundation and any rehabilitation and restoration carried out will fail.

This study is expected to be taken into consideration in driving new policy based on the results of the model. This study can also be used as a guide to consider which areas are suitable for mangrove rehabilitation and restoration without the threat of a sea-level rise in the future.

How to cite: Syahid, L. N., Ward, R. D., Sakti, A. D., Rosleine, D., Wikantika, K., and Windupranata, W.: Prediction of future sea-level rise in land suitability for mangrove rehabilitation and restoration in Indonesia, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9058, https://doi.org/10.5194/egusphere-egu22-9058, 2022.

EGU22-9778 | Presentations | CL3.1.1

GESLA Version 3: A major update to the global higher-frequency sea-level dataset 

Ivan D. Haigh, Marta Marcos, Stefan A. Talke, Philip L. Woodworth, John R. Hunter, Ben S. Hague, Arne Arns, Elizabeth Bradshaw, and Philip Thompson

This paper describes a major update to the quasi-global, higher-frequency sea-level dataset known as GESLA (Global Extreme Sea Level Analysis). Versions 1 (released 2009) and 2 (released 2016) of the dataset have been used in many published studies, across a wide range of oceanographic and coastal engineering-related investigations concerned with evaluating tides, storm surges, extreme sea levels and other related processes. The third version of the dataset (released 2021), presented here, contains twice the number of years of data (91,021), and nearly four times the number of records (5,119), compared to version 2. The dataset consists of records obtained from multiple sources around the world. This paper describes the assembly of the dataset, its processing and its format, and outlines potential future improvements. The dataset is available from https://www.gesla.org.

How to cite: Haigh, I. D., Marcos, M., Talke, S. A., Woodworth, P. L., Hunter, J. R., Hague, B. S., Arns, A., Bradshaw, E., and Thompson, P.: GESLA Version 3: A major update to the global higher-frequency sea-level dataset, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9778, https://doi.org/10.5194/egusphere-egu22-9778, 2022.

EGU22-10973 | Presentations | CL3.1.1

Late Cenozoic sea-level indicators in west Luzon, Philippines 

Kathrine Maxwell, Hildegard Westphal, Alessio Rovere, and Kevin Garas

Using the framework of the World Atlas of Last Interglacial Shorelines (WALIS), we produced a standardized database of Last Interglacial (LIG) sea-level indicators in Southeast Asia after reviewing available studies on relative sea-level (RSL) proxies such as coral reef terraces and tidal notches in the Philippines; Sulawesi; and Sumba, Timor, and Alor regions. In total, we reviewed 43 unique RSL proxies in the region and highlighted sites for future studies. Following this work, we revisited a site in west Luzon, Philippines where LIG coral reef terraces were previously reported. In this paper, we present new geomorphic and stratigraphic data on the fossil coral reef terraces in Pangasinan, west Luzon which adds to the limited sea-level indicators in the region. The low-lying areas of western Pangasinan are underlain by sequences of calcareous sandstone-mudstone with minor pebbly conglomerate and tuffaceous sandstone units belonging to the Sta. Cruz Formation, with tentative age designation of Late Miocene to Early Pliocene. Unconformably overlying the tentatively assigned sandstone unit of Sta. Cruz Formation is the Plio-Pleistocene Bolinao Limestone, the youngest formational unit in the area. Based on previous literature, a sequence of coral reef terraces (possibly LIG) is cut onto the Bolinao Limestone. Rising to about 14 meters above mean sea level (m amsl) along the coast of western Pangasinan are previously dated Holocene coral reef terraces. While additional data is needed to shed more light on the RSL changes in the region, our work proves to be more challenging due to the difficulties of doing field surveys during a global pandemic. Nonetheless, we hope that data from this research will help us further understand the different drivers of past sea-level changes in SE Asia providing necessary geologic baseline data for projections of sea-level change in the future.

How to cite: Maxwell, K., Westphal, H., Rovere, A., and Garas, K.: Late Cenozoic sea-level indicators in west Luzon, Philippines, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10973, https://doi.org/10.5194/egusphere-egu22-10973, 2022.

EGU22-11156 | Presentations | CL3.1.1

Danish Climate Atlas view on sea level change in future 

Jian Su, Elin Andrée, Jacob W. Nielsen, Steffen M. Olsen, and Kristine S. Madsen

Wind patterns projected for the region, together with sea level rise and land rise, call into question our current understanding of extreme storm surges in the Danish coastal area. The Danish Meteorological Institute (DMI) will research changes in the extreme statistics of sea level in the twenty-first century through the 'Danish Climate Atlas,' a new national climate service initiative. The study will make use of multi-scenarios, multi-models and multi-parameters approach to focus on the uncertainty of the projected change in extreme statistics of sea level.  Historical sea level records suggest that the relative sea level (RSL) along the Danish North Sea coast south of Skagerrak has been increasing with the global mean sea level (GMSL) rise. However, RSL has been absent in the central Skagerrak-Kattegat Seas, owing to the Fennoscandian post-glacial land-uplift offsetting the GMSL rise. According to the recent IPCC Special Report on the Ocean and Cryosphere in a Changing Climate (SROCC), due to Antarctic ice sheet dynamics, GMSL would grow more than previously estimated in the IPCC Fifth Assessment Report (AR5) by the end of the twenty-first century under RCP8.5. We regionalized the SROCC sea level forecasts for the "Danish Climate Atlas" dataset. Our findings indicate that sea level projections under RCP8.5 result in a > 40 cm RSL rise in the Skagerrak-Kattegat Seas by the end of the twenty-first century, which may necessitate a new adaptation strategy in this region. Under the RCP8.5 scenario, the rate of mean sea level rise will exceed the rate of land rise earlier than previously estimated by AR5. We emphasize, in particular, the impact of these new predictions on future severe sea levels in this region. Our findings suggest that this more current GMSL prediction should be factored into coastal risk assessments in the Skagerrak-Kattegat Seas in this century.

How to cite: Su, J., Andrée, E., Nielsen, J. W., Olsen, S. M., and Madsen, K. S.: Danish Climate Atlas view on sea level change in future, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11156, https://doi.org/10.5194/egusphere-egu22-11156, 2022.

Cultural heritage not only witnesses past spiritual and aesthetic attitudes of mankind, but also represents a unique means to investigate the intimate relationship between humanity and the environment.  We present an overview and preliminary data of the SPHeritage Project, which investigates evidence of Palaeolithic human occupation and cultural heritage in the NW Mediterranean area in conjunction with Pleistocene sea-level change studies. A tightly interdisciplinary approach is necessary to use cultural heritage as a proxy for sea-level change evidence. The SPHeritage Project (MUR grant: FIRS2019_00040, P.I.: M. Pappalardo) investigates how human populations have responded to environmental changes and sea-level variations over the last 400,000 years in the Ligurian-Provençal coastal area (along the border between Italy and France) using a combination of micro-invasive methods applied to in situ and previously excavated sediments of uttermost archaeological relevance. In this area, particularly in the archaeological area of Balzi Rossi, a unique assemblage of archaeological sites dating to the Palaeolithic can be found in a rocky coast geomorphological setting where sea-level indicators of the last 3 or 4 interglacials are present. They lack reliable dating and a standardized assessment of the palaeo sea level they record. Improved age constraint of the coastal deposits and recording of relative sea-level (RSL) change evidence is necessary for: i) contribution to the standardized inventory of past interglacial sea-leves; ii) investigating changes in the biodiversity of rocky coastal marine ecosystems triggered by different interglacial environmental conditions; iii) the development of a self-consistent Glacial Isostatic Adjustment model capable of including the residual effect of previous interglacials’ rebound on the isostatic response of later interglacials; iv) investigating how RSL change and consequent shoreline fluctuations can drive settlement strategies and human migration/dispersal patterns. This project is challenged by the previous removal of large portions of the local archaeological sequences in earlier investigations beginning at the end of the nineteenth century. The challenge in this Project is that most of the local archaeological sequences have been extensively investigated since the end of the nineteenth century and large part of the deposits were removed. Therefore, we will combine analyses of relict in situ sediments with those of stratigraphically constrained materials preserved in museums and archaeological deposits worldwide. Moreover, traces of past shorelines will be searched for in the sedimentary sequence of the continental shelf through geophysical surveys and, if this will prove possible, through direct sediment coring. Our preliminary data are promising, and suggest that this interdisciplinary and microinvasive approach can provide valuable evidence on sea-level change from archaeological areas without hampering cultural heritage preservation.

How to cite: Pappalardo, M. and the SPHeritage Project members: Investigating Pleistocene sea-level changes along the northern Mediterranean coast through Palaeolithic cultural heritage: perspectives from the S-P-Heritage Project, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11357, https://doi.org/10.5194/egusphere-egu22-11357, 2022.

EGU22-11476 | Presentations | CL3.1.1

Understanding the role of internal climate variability in future sea level trends 

Mélanie Becker, Mikhail Karpytchev, and Aixue Hu

Estimating the magnitude of future sea level rise is among the primary goals of current climate research. Sea level projections contain inherent irreducible uncertainty, which is due to internal climate variability (ICV). This uncertainty is commonly estimated from a spread of sea level projections obtained from Global Climate Models (GCM) under the same forcing but with slightly different initial conditions. Here we analyze the ICV contribution to the sea level variations (1) across the Large Ensembles (LE) of Community Earth System Model (CESM) obtained under different warming scenarios and (2) from an alternative approach based on the power-law statistics theory. The magnitude of the sea level response to ICV is also evaluated by comparison with actual tide gauge data. We show that certain coastal regions of the globe are more sensitive to ICV than others, both in observations and in the GCM results. We identify regions where the sea level change will become significant beyond the ICV, providing useful climate change adaptation guidance.

How to cite: Becker, M., Karpytchev, M., and Hu, A.: Understanding the role of internal climate variability in future sea level trends, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11476, https://doi.org/10.5194/egusphere-egu22-11476, 2022.

EGU22-11672 | Presentations | CL3.1.1

Hourly sea-level change with long-term trends for impact attribution: the HLT Dataset 

Matthias Mengel, Simon Treu, Sanne Muis, Sönke Dangendorf, Thomas Wahl, Stefanie Heinicke, and Katja Frieler

Rising seas are a threat for human and natural systems along coastlines. The relation between global warming and sea-level rise is established, but impacts due to historical sea-level rise are not well quantified on a global scale. To foster the attribution of observed coastal impacts to sea-level rise, we here present HLT, a sea-level forcing dataset encompassing factual and counterfactual sea-level evolution along global coastlines from 1979 to 2015. HLT combines observation-based long-term changes with reanalysis-based hourly water level variation. Comparison to tide gauge records shows improved performance of HLT, mainly due to the inclusion of density-driven sea-level change. We produce a counterfactual by removing the trend in relative sea level since 1900. The detrending preserves the timing of historical extreme sea-level events. Hence, the data can be used in event-based impact attribution to sea-level rise with tuples of impact simulations driven with the factual and counterfactual dataset. The dataset is made available openly through the Inter-Sectoral Impact Model Intercomparison Project (ISIMIP).

How to cite: Mengel, M., Treu, S., Muis, S., Dangendorf, S., Wahl, T., Heinicke, S., and Frieler, K.: Hourly sea-level change with long-term trends for impact attribution: the HLT Dataset, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11672, https://doi.org/10.5194/egusphere-egu22-11672, 2022.

EGU22-12063 | Presentations | CL3.1.1

Sub-hourly sea level quality-controlled dataset to quantify extreme sea levels along the European coasts 

Marijana Balić, Jadranka Šepić, Leon Ćatipović, Srđan Čupić, Jihwan Kim, Iva Međugorac, Rachid Omira, Havu Pellikka, Krešimir Ruić, Ivica Vilibić, and Petra Zemunik

Extreme sea levels can lead to floods that cause significant damage to coastal infrastructure and put people's lives in danger. These floods are a result of physical processes occurring at various time and space scales, including sub-hourly scales. To estimate the contribution of sub-hourly sea level oscillations to extreme sea levels, raw sea level data from about 300 tide gauge stations along the European coasts, with a sampling resolution of less than 20 minutes, were collected. The data were obtained from: (1) the IOC-SLSMF website (290 stations); (2) National agencies (Portugal, Finland, Croatia –24 stations). Portions of the raw dataset had various data quality issues (i.e., spikes, shifts, drifts) hence quality control procedure was required. Out of range values, values with a 50 cm difference from one neighbouring value or a 30 cm difference from both neighbouring values, were automatically removed. The automatic spike detection procedure was carried out by removing values that differed by three standard deviations from a spline fitted with the least squares method. Following the automatic quality control, all remaining data were visually examined and spurious data were removed manually.

The resulting data set contains sea level data from 2007. to 2021., with an average record length of approximately 7 years, however the length varies from a few months at some stations to 13 years at others. Tide gauges with longer records (>10 years) are based in the Baltic region, France and Spain, whereas the ones with shorter records (<3 years) are mostly based in the Eastern Mediterranean. The Western Mediterranean and western Europe have a high station coverage with records of various lengths. Tide gauges mostly provide data with a one-minute sampling frequency, however, some of them still record on a multi-minute scale (i.e., United Kingdom with 15 minutes and Norway and the Netherlands with 10 minutes sampling frequency).

Preliminary statistical analyses were done, resulting with spatial and temporal distribution of contribution of high-frequency sea level oscillations to total sea level extremes along the European coasts.

How to cite: Balić, M., Šepić, J., Ćatipović, L., Čupić, S., Kim, J., Međugorac, I., Omira, R., Pellikka, H., Ruić, K., Vilibić, I., and Zemunik, P.: Sub-hourly sea level quality-controlled dataset to quantify extreme sea levels along the European coasts, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12063, https://doi.org/10.5194/egusphere-egu22-12063, 2022.

EGU22-13026 | Presentations | CL3.1.1

Sea-level rise: from global perspectives to local services 

Gael Durand, Michiel R. van den Broeke, Gonéri Le Cozannet, Tamsin L. Edwards, Paul R. Holland, Nicolas C. Jourdain, Ben Marzeion, Ruth Mottram, Robert J. Nicholls, Frank Pattyn, Frank Paul, Aimée B.A. Slangen, Ricarda Winkelmann, Clara Burgard, Caroline J. van Calcar, Jean-Baptiste Barré, Amélie Bataille, and Anne Chapuis

Coastal areas are highly diverse, ecologically rich, regions of key socio-economic activity, and are particularly sensitive to sea- level change. Over most of the 20th century, global mean sea level has risen mainly due to warming and subsequent expansion of the upper ocean layers and the melting of glaciers and ice caps. Over the last three decades, increased mass loss of the Greenland and Antarctic ice sheets has also started to contribute significantly to contemporary sea-level rise. The future mass loss of these ice sheets, which combined represent a sea-level rise potential of ~65 m, constitutes the main source of uncertainty in long-term (centennial to millennial) sea-level rise projections. Improved knowledge of the magnitude and rate of future sea-level change is therefore of utmost importance. Moreover, sea level does not change uniformly across the globe, and can differ greatly at both regional and local scales. The most appropriate and feasible sea level mitigation and adaptation measures in coastal regions strongly depend on local land use and associated risk aversion. Here, we advocate that addressing the problem of future sea-level rise and its impacts requires (i) bringing together a transdisciplinary scientific community, from climate and cryospheric scientists to coastal impact specialists, and (ii) interacting closely and iteratively with users and local stakeholders to co-design and co-build coastal climate services, including addressing the high-end risks. Following these principles, as also adopted in the EU project “Projecting sea-level rise: from projections to local implications” (PROTECT), we encourage the formation of research consortia that cover the entire knowledge chainIn this way global sea-level science can be linked to effective coastal climate services at the scale of risk and adaptation

How to cite: Durand, G., van den Broeke, M. R., Le Cozannet, G., Edwards, T. L., Holland, P. R., Jourdain, N. C., Marzeion, B., Mottram, R., Nicholls, R. J., Pattyn, F., Paul, F., Slangen, A. B. A., Winkelmann, R., Burgard, C., van Calcar, C. J., Barré, J.-B., Bataille, A., and Chapuis, A.: Sea-level rise: from global perspectives to local services, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13026, https://doi.org/10.5194/egusphere-egu22-13026, 2022.

EGU22-13328 | Presentations | CL3.1.1

Long-term trends and variations in sea level of the Black Sea 

Şehriban Saçu and Olgay Şen

The Black Sea is an almost enclosed basin interacted with the Mediterranean Sea through the Bosporus. It has a large catchment area receiving freshwater from the second longest river in Europe, the Danube, and other rivers spread over Europe and Asia. The total riverine discharge is 350 km3/year where the Danube contributes about 65% of the total discharge. Although evaporation rates (280 km3/year) exceed precipitation rates (200 km3/year), large riverine discharge makes the Black Sea an estuarine type basin.  The main feature of the Black Sea is a basin-wide cyclonic circulation, namely Rim Current. The cyclonic circulation causes a lower sea level in the inner part of the basin and a higher sea level in the shelf region. The freshwater budget and thermal expansion of the water are other factors affecting sea level of the Black Sea.  The North Atlantic Oscillation (NAO) could also influence sea level through changes in atmospheric pressure and the above-mentioned factors.  

 

In this study, firstly we investigated long term trends in sea level of the Black Sea on the basis of the tide gauge measurements, satellite altimetry, and gravity measurements from the Gravity Recovery and Climate Experiment (GRACE). Then, we assessed role of the wind curl, freshwater budget, and NAO on sea level variations through temporal and spatial data analysis. The tide gauge measurements suggest a positive sea level trend of about 1.05 – 2.37 mm/years, for a time period >50 years. Basin mean sea level derived from altimeter and GRACE (years between 2003-2019), does not exhibit a statistically significant trend (p<0.05) which might result from the shift towards a positive NAO condition in the last 30-years. We found that sea level variations both in the coastal and inner part of the basin are significantly correlated (p<0.05) with Danube discharge but these correlations are smaller in the inner part. The agreement between interannual variations of Danube discharge and the NAO index suggests that sea level variations are also associated with NAO index. An Empirical Orthogonal Function (EOF) analysis with associated time series (Principal Components, PC) is applied to the gridded altimeter data to capture space and time features of sea level variability. The first mode of the EOF explained about %81.9 of the total variability and showed the same sign over the basin indicating an in-phase oscillation of the whole Black Sea. The PC1 shows interannual variations in accordance with freshwater budget (r=0.76, p<0.05). The second mode of the EOF accounts for %5.7 of the total variability, has opposite signs in coastal and inner parts, the oscillation implied by this mode could be related to the Rim Current intensity governed by wind curl.

 

How to cite: Saçu, Ş. and Şen, O.: Long-term trends and variations in sea level of the Black Sea, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13328, https://doi.org/10.5194/egusphere-egu22-13328, 2022.

EGU22-13467 | Presentations | CL3.1.1

Effect of Holocene sediment redistributions on the relative sea level at present in the Ayeyarwady delta (aka Irrawaddy delta, Myanmar) 

Céline Grall, Adrien Henry, Mikhail Karpytchev, and Melanie Becker

Under high seasonal monsoon rainfall and active tectonics, the Ayeyarwady delta is a large delta plain characterized by a high sediment supply. Also, the Ayeyarwady river, together with the Sittaung, and the Salween Rivers are bringing ~600 Mt/yr of sediments to the Andaman Sea through the Gulf of Martaban. A recent research effort have allowed characterizing the sedimentation at present and since the mid-Holocene. We here propose to integrate these published observations in a stratigraphic reconstruction and to determine by numerical modelling how much these Holocene massive sediment transfers play on coastal subsidence and relative sea level at present.

The present average sedimentation rate at the front of Ayeyarwady delta is ~10 cm/yr and the delta may be divided in two sectors: an eastern embayed sector and a western open coast sector. During the mid-Holocene, the aerial part of the delta have experimented fast progradation rate, reaching prograding rate of ~ 30 m/yr. When applying this sedimentation pattern on a preliminary (radial) viscoelastic Earth model, we show that sediment isostasy plays on the regional coastal dynamics and subsidence at present. In addition, the Ayeyarwady delta lies in a complex tectonic setting, bounded to the west by the Indo-Burman collision zone, and to the east by the sub-vertical dextral Sagaing Fault. We are integrating this tectonic setting in an earth model that allows lateral vertical discontinuity for exploring how much this significantly changes the modelling results.

How to cite: Grall, C., Henry, A., Karpytchev, M., and Becker, M.: Effect of Holocene sediment redistributions on the relative sea level at present in the Ayeyarwady delta (aka Irrawaddy delta, Myanmar), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13467, https://doi.org/10.5194/egusphere-egu22-13467, 2022.

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