CR – Cryospheric Sciences

CR1.1 – Glaciers and Ice Caps under Climate Change

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.

EGU22-5099 | 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.

EGU22-7864 | 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.

EGU22-4484 | 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.

EGU22-2367 | 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.

EGU22-10518 | Presentations | CR1.1 | Highlight

Global observations of accelerated glacier change over the past decade using TanDEM-X remote sensing

Philipp Malz, Christian Sommer, David Farías, Thorsten Seehaus, and Matthias Braun

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.

EGU22-11054 | 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.

EGU22-2818 | 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.

EGU22-8724 | 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.

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.

EGU22-1808 * | 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.

EGU22-6364 | 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.

EGU22-5833 | 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.

EGU22-9884 | 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.

EGU22-1170 | 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.

EGU22-777 | 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.

EGU22-12934 | 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.

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.

EGU22-3021 | 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.

EGU22-4281 | 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.

EGU22-12944 | Presentations | CR1.1

Transport of contrasting carbon pools by high latitude rivers and streams – an Icelandic survey

Nora Gallarotti

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.

EGU22-4166 | 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.

EGU22-53 | 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.

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.

CR1.2 – Ice sheet mass balance and sea level: ISMASS/ISMIP6 and beyond

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.

EGU22-10811 | 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.

EGU22-9957 | 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.

EGU22-12543 | 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.

EGU22-3838 | 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.

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.

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.

EGU22-8882 | 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.

EGU22-11363 | 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.

EGU22-4154 | 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.

EGU22-7420 | 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.

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.

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.

EGU22-5252 | 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.

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.

EGU22-7964 | 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.

CR1.3 – Observing and modelling glaciers at regional to global scales

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.

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.

EGU22-11942 | 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.

EGU22-6338 | 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.

EGU22-5781 | 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.

EGU22-10563 | 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.

EGU22-7271 | 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.

EGU22-4263 | 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.

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.

EGU22-24 | 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.

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.

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.

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.

EGU22-12741 | 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.

EGU22-12796 | Presentations | CR1.3

Ice-Ocean-Atmosphere Interactions in the Arctic: Svalbard Case Study

Morag Fotheringham

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.

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.

CR1.4 – The Antarctic Ice Sheet: past, present and future contributions towards global sea level

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.

EGU22-1281 | 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.

EGU22-8215 | 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.

EGU22-4786 | 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.

EGU22-1667 | 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.

EGU22-5596 | 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.

EGU22-4161 | 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.

EGU22-8177 | Presentations | CR1.4

Regional Acceleration of the Antarctic Dynamic Ice Loss from Satellite Gravimetry

Theresa Diener and Ingo Sasgen

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.

EGU22-7802 | 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.

EGU22-9447 | 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.

EGU22-10547 | 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.

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.

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.

EGU22-9448 | 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.

CR2.1 – Geophysical and in situ methods for snow and ice studies

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.

EGU22-10269 | Presentations | CR2.1

Advances in X- and Ku- Band Radar Algorithms for SWE Retrieval

Edward Kim, Jiyue Zhu, Do Hyuk 'DK' Kang, Firoz Borah, and Leung Tsang

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.

EGU22-12490 | 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.

EGU22-4573 | 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.

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.

EGU22-3248 | 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.

EGU22-10835 | 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.

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.

EGU22-7154 | 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.

EGU22-12233 | 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.

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.

EGU22-10195 | 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.

EGU22-612 | 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.

EGU22-6414 | 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.

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.

EGU22-942 | Presentations | CR2.1