CR1.1 | Glaciers and Ice Caps under Climate Change
EDI
Glaciers and Ice Caps under Climate Change
Convener: Ines DussaillantECSECS | Co-conveners: Harry Zekollari, Lander Van TrichtECSECS, Lindsey Nicholson, Matthias Huss
Orals
| Tue, 16 Apr, 14:00–15:45 (CEST), 16:15–17:55 (CEST)
 
Room 1.61/62
Posters on site
| Attendance Mon, 15 Apr, 16:15–18:00 (CEST) | Display Mon, 15 Apr, 14:00–18:00
 
Hall X5
Posters virtual
| Attendance Mon, 15 Apr, 14:00–15:45 (CEST) | Display Mon, 15 Apr, 08:30–18:00
 
vHall X5
Orals |
Tue, 14:00
Posters on site |
Mon, 16:15
Posters virtual
Mon, 14:00
Glaciers and ice caps are major contributors to sea-level rise and have large impacts on runoff from glacierized basins. Major mass losses of glaciers and ice caps have been reported around the globe for the recent decades. This is a general session on glaciers outside the Greenland and Antarctic ice sheets, emphasizing their past, present and future responses to climate change. Although much progress in understanding the link between glaciers and climate and the impacts of their wastage on various systems has recently been achieved, many substantial unknowns remain. It is necessary to acquire more direct observations, both applying novel measurement technologies and releasing unpublished data from previous years, as well as combining in situ observations with new remote sensing products and modelling. In order to improve our understanding of the processes behind the observed glacier changes, the application of models of different complexity in combination with new data sets is crucial. We welcome contributions on all aspects of glacier changes – current, past and future – based on field observations, remote sensing and modelling. Studies on the physical processes controlling all components of glacier mass balance are especially encouraged, as well as assessments of the impact of retreating glaciers and ice caps on sea-level rise, runoff and other downstream systems.

Orals: Tue, 16 Apr | Room 1.61/62

Chairpersons: Ines Dussaillant, Harry Zekollari, Lander Van Tricht
14:00–14:05
5-minute convener introduction
Glacier change observations
14:05–14:25
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EGU24-1758
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ECS
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solicited
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On-site presentation
Five years of change of two debris-covered glaciers monitored by unmanned aerial system 
Philip Kraaijenbrink and Walter Immerzeel

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

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

14:25–14:35
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EGU24-12833
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On-site presentation
Western North American and Switzerland glaciers experience unprecedented mass loss over the last three years 
Brian Menounos, Matthias Huss, Shawn Marshall, Mark Ednie, and Caitlyn Florentine

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

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

14:35–14:45
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EGU24-920
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ECS
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On-site presentation
Increased up-glacier thinning in four major glaciers of High Mountain Asia revealed by geodetic mass balance estimates 
Arindan Mandal, Anshuman Bhardwaj, Mohd Farooq Azam, Bramha Dutt Vishwakarma, and Thupstan Angchuk

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

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

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

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

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

14:45–14:55
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EGU24-16774
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ECS
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On-site presentation
Combining ground-penetrating RaDAR, unmanned aerial vehicle photogrammetry and borehole thermal data to investigate the evolution of hanging glaciers in the western European Alps 
Ben Robson, Christophe Lambiel, Ludovic Ravanel, James Irving, Ludovic Baron, and Jérémie Gentizon

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

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

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

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

14:55–15:05
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EGU24-6253
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On-site presentation
Local cooling and drying induced by Himalayan glaciers under global warming 
Franco Salerno, Nicolas Guyennon, Kun Yang, Thomas E. Shaw, Changgui Lin, Nicola Colombo, Emanuele Romano, Stephan Gruber, Tobias Bolch, Andrea Alessandri, Paolo Cristofanelli, Davide Putero, Guglielmina Diolaiuti, Gianni Tartari, Sudeep Thakuri, Evan S. Miles, Sara Bonomelli, and Francesca Pellicciotti

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

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

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

15:05–15:15
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EGU24-20828
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ECS
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On-site presentation
Regional ice flow piracy following the collapse of Midgaard Glacier in Southeast Greenland
(withdrawn)
Flora Huiban, Romain Millan, Kristian Kjeldsen, Camilla Andresen, Mads Dømgaard, Amaury Dehecq, Stephen Brunt, Abbas Khan, Jérémie Mouginot, and Anders Bjørk
Understanding glacier processes
15:15–15:25
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EGU24-12014
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ECS
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Highlight
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On-site presentation
The dark zone of an alpine glacier - considering albedo impacts of firn loss 
Lea Hartl, Martin Stocker-Waldhuber, Federico Covi, Anna Baldo, and Kathrin Naegeli

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

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

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

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

15:25–15:35
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EGU24-12488
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ECS
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On-site presentation
Distributed surface mass balance of the avalanche-fed Argentière glacier, French Alps 
Marin Kneib, Amaury Dehecq, Adrien Gilbert, Auguste Basset, Evan S. Miles, Etienne Ducasse, Luc Béraud, Jérémie Mouginot, Jérémie Mouginot, Guillaume Jouvet, Olivier Laarman, Bruno Jourdain, Fanny Brun, and Delphine Six

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

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

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

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

15:35–15:45
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EGU24-8481
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On-site presentation
Observed weakening of glacier ice-bed interface caused by climatic and hydro-mechanical feedbacks: towards glacier-wide acceleration? 
Thomas Vikhamar Schuler, Ugo Nanni, Coline Bouchayer, Henning Åkesson, Pierre-Marie Lefeuvre, Erik Mannerfelt, Andreas Köhler, Louise Steffensen Schmidt, John Hulth, and Francois Renard
 
Stronger and more widespread surface melt may alter the flow of glaciers and ice sheets and trigger instability. However, observational deficiencies hamper our ability to better understand and thus predict such responses. We deployed surface and borehole seismometers along the centerline of a High Arctic glacier in Svalbard. The records span over six years and are analyzed in relation to the measured increase of surface velocity. We complement our seismic analysis (icequakes and seismic noise) with long-term measurements of glacier-surface velocity, surface-elevation changes, and runoff modeling. Since 2000, we observe glacier thinning and steepening, coinciding with acceleration of up to 1000%. In response, new crevasses have opened and provide access pathways for surface melt water to the base of the glacier, affecting the ice-bed coupling. This mechanism represents a positive hydro-mechanical feedback that fuels further acceleration and crevassing. This feedback may have wider implications for triggering of glacier-wide instabilities, increasing short-term sea-level rise and local hazards. Beyond the Arctic, we suggest that, under a warming atmosphere, glaciers may transition from stable to unstable flow through such a mechanism.
 

 

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

Coffee break
Chairpersons: Lindsey Nicholson, Lander Van Tricht
16:15–16:25
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EGU24-14899
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ECS
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On-site presentation
Quantifying Basal Melt of Swiss Glaciers 
Leo Hösli, Matthias Huss, Mauro Werder, and Daniel Farinotti

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

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

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

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

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

16:25–16:35
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EGU24-1505
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ECS
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On-site presentation
Surge initiation at the terminus of Borebreen (Svalbard): Drivers and impact on calving 
William D. Harcourt, Wojciech Gajek, Danni Pearce, Richard Hann, Adrian Luckman, Brice R. Rea, Douglas I. Benn, Mike R. James, Matteo Spagnolo, and Ugo Nanni

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

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

16:35–16:45
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EGU24-13473
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On-site presentation
Monitoring the physical processes driving the mass loss of Tapado Glacier, Desert Andes of Chile 
Álvaro Ayala, Benjamin Robson, Shelley MacDonell, Gonzalo Navarro, Nicole Schaffer, Alexis Segovia, Michal Petlicki, Christophe Kinnard, Simone Schauwecker, Gino Casassa, Sebastián Vivero, and Augusto Lima

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

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

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

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

16:45–16:55
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EGU24-10112
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ECS
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On-site presentation
Poleward shift of the subtropical highs drives Patagonian ice fields mass loss 
Brice Noël, Michiel van den Broeke, Stef Lhermitte, Bert Wouters, and Xavier Fettweis

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

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

Glacier change modeling
16:55–17:15
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EGU24-5843
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ECS
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solicited
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Highlight
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On-site presentation
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Irreversible glacier change and trough water for centuries after overshooting the Paris Agreement temperature goal 
Lilian Schuster, Fabien Maussion, Patrick Schmitt, David R. Rounce, Lizz Ultee, Fabrice Lacroix, and Thomas Frölicher

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

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

Discussion Post a comment
17:15–17:25
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EGU24-8944
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ECS
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Highlight
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On-site presentation
Global ice-thickness inversion using a deep-learning-aided 3D ice-flow model with data assimilation 
Samuel Cook, Guillaume Jouvet, Romain Millan, Antoine Rabatel, Fabien Maussion, Harry Zekollari, and Inès Dussaillant

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

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

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

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

17:25–17:35
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EGU24-2575
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Highlight
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On-site presentation
Projecting the evolution of the Northern Patagonian Ice Field until the year 2200 
Marius Schaefer, Ilaria Tabone, Ralf Greve, Johannes Fürst, and Matthias Braun

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

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

17:35–17:45
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EGU24-9831
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ECS
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On-site presentation
Unravelling the sources of uncertainty in glacier runoff in the Patagonian Andes (40–56° S)  
Rodrigo Aguayo, Fabien Maussion, Lilian Schuster, Marius Schaefer, Alexis Caro, Patrick Schmitt, Jonathan Mackay, Lizz Ultee, Jorge Leon-Muñoz, and Mauricio Aguayo

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

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

17:45–17:55
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EGU24-1173
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ECS
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Virtual presentation
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Modeling the surface mass balance of Penny Ice Cap, Baffin Island, 1959–2099 
Nicole Schaffer

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

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

Discussion Post a comment

Posters on site: Mon, 15 Apr, 16:15–18:00 | Hall X5

Display time: Mon, 15 Apr 14:00–Mon, 15 Apr 18:00
Chairpersons: Ines Dussaillant, Harry Zekollari, Lindsey Nicholson
X5.192
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EGU24-3118
Step-change in supraglacial pond area on Tshojo Glacier, Bhutan, and potential downstream inundation patterns due to pond drainage events.
(withdrawn)
Rachel Carr, Amy Barrett, Sonam Rinzin, and Caroline Taylor
X5.193
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EGU24-3207
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ECS
Contrasting glacier terminus position trend rates between Central-Western Greenland peripheral glaciers and ice sheet:  spatiotemporal patterns and trends (1985 to 2022) 
Josep Bonsoms, Marc Oliva, and Juan Ignacio López-Moreno

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

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

X5.194
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EGU24-5140
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ECS
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Assessing the Influence of Climate Forcing Data Resolution on Simulations of Glacier and Freshwater Dynamics for the Flade Isblink Ice Cap, Northeast Greenland 
Muhammad Shafeeque, Anouk Vlug, and Ben Marzeion

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

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

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

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

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

X5.195
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EGU24-5815
Temperature Decoupling on the World’s Mountain Glaciers 
Thomas Shaw, Evan Miles, Pascal Buri, Michael McCarthy, Nicolas Guyennon, Luca Carturan, Franco Salerno, and Francesca Pellicciotti

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

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

X5.196
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EGU24-6780
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ECS
Effect of climate policies on the long-term equilibration of glaciers 
Harry Zekollari, Lilian Schuster, Regine Hock, Ben Marzeion, Fabien Maussion, and the GlacierMIP3 participants

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

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

 

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

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

X5.197
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EGU24-7118
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ECS
Quantifying runoff variability and Glacier thickness variations from 2011 to 2020 in Gangotri glaciated region, India 
Japjeet Singh, Vishal Singh, and Chandra Shekhar Prasad Ojha

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

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

X5.198
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EGU24-7454
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ECS
Ablation drivers over a cold-based ice cap in the Eastern Alps: a surface energy balance analysis 
Anna Baldo, Lindsey Nicholson, Lea Hartl, and Martin Stocker-Waldhuber

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

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

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

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

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

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

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

X5.199
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EGU24-8865
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ECS
 Estimation of Snow Line Altitude Utilising Satellite Imagery of Alpine Glaciers 
Sobia Ayub, Carlo Camporeale, Luca Ridolfi, Erika Coppola, and Alberto Godio

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

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

X5.200
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EGU24-9185
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ECS
Seasonal speedup of glacier in the southeastern Tibetan Plateau 
Tianzhao zhang, Wei Yang, and Shaoting Ren

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

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

X5.201
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EGU24-8079
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ECS
Global glacier climate disequilibrium from modelling steady state AAR 
Weilin Yang, Wenchao Chu, Yingkui Li, and Andrew Mackintosh

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

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

X5.202
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EGU24-11243
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ECS
Surface Mass Balance of the Cordillera Darwin Icefield, Tierra del Fuego, Chile 
Franziska Temme, Christian Sommer, and Johannes J. Fürst

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

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

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

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

X5.203
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EGU24-12396
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ECS
Reanalysis of the surface mass balance of Mittivakkat Gletsjer (Southeast Greenland): Synthesizing data sources 
Christoph Posch, Simon de Villiers, Niels Tvis Knudsen, Jacob Clement Yde, Anders Anker Bjørk, Wolfgang Schöner, Jakob Abermann, and Kamilla Hauknes Sjursen

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

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

X5.204
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EGU24-12617
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ECS
Do Grenzgletscher's Dynamics Shift? Insights from Terrestrial Radar Interferometry and Comparative Analyses 
Leah Sophie Muhle, Christian Thomas Wild, Reinhard Drews, and Elisa Mantelli

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

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

X5.205
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EGU24-13526
Glacier area changes on Baffin Island from 2000 to 2019 derived from Landsat and Sentinel-2 satellite images 
Frank Paul and Philipp Rastner

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

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

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

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

X5.206
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EGU24-15836
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ECS
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The rapid retreat of two lake-terminating outlet glaciers of the Northern Patagonian Ice Sheet and underestimation of mass loss due to subaqueous ice volume 
Pascal Emanuel Egli, Inés Dussaillant, Iñigo Irarrazaval, Marcelo Somos-Valenzuela, Benjamín Sotomayor González, Elizabet Lizama, Bastián Morales, and Joaquín Fernandez

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

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

Discussion Post a comment
X5.207
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EGU24-16009
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ECS
Enhancing Flood Preparedness: Modeling the Shishper glacier's Glacial Lake Outburst Flooding in Pakistan using Satellite Data and 2D Hydraulic Modeling 
Aleš Urban, Falak Naz, Hossein Azadi, Babar Naeem, and Arjumand Zaidi

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

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

X5.208
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EGU24-16092
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ECS
Satellite altimetry derived glacier mass changes over High Mountain Asia during 2003‒2022 
Fanyu Zhao, Di Long, Pengfei Han, Yiming Wang, Yifei Cui, and Xingwu Duan

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

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

X5.209
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EGU24-19339
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ECS
Monitoring high resolution variations in proglacial lake area using an Uncrewed Aerial Vehicle (UAV) at Fjallsjökull, Iceland 
Ameila Andrews, Nathaniel Baurley, Jadu Dash, and Jane Hart

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

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

X5.210
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EGU24-19184
Glacial meltwater plume extent from multispectral and SAR satellite data 
Laura Edwards

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

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

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

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

X5.211
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EGU24-16523
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ECS
The retreat of the Adamello Glacier (Italy) in a changing climate from snow and meteorological measurements, remote sensing observations and surface mass balance modelling 
Paolo Colosio, Muhammad Usman Liaqat, Giovanna Grossi, and Roberto Ranzi

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

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

X5.212
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EGU24-20265
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ECS
Deriving the Østrem curve to quantify supraglacial debris-related melt-altering effects on the Djankuat Glacier, Caucasus, Russian Federation 
Yoni Verhaegen, Philippe Huybrechts, Oleg Rybak, and Victor Popovnin

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

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

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EGU24-20299
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ECS
Quantifying parameter uncertainty in projections of glacier mass change in Iceland under GlacierMIP3 experiments  
Megan James

 

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

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

Posters virtual: Mon, 15 Apr, 14:00–15:45 | vHall X5

Display time: Mon, 15 Apr 08:30–Mon, 15 Apr 18:00
Chairpersons: Lander Van Tricht, Matthias Huss
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EGU24-930
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ECS
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Projections of Elbrus glaciers, proglacial lakes and dead ice areas. 
Taisiya Postnikova, Oleg Rybak, Afanasy Gubanov, Harry Zekollari, and Matthias Huss

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

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

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

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

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

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vX5.12
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EGU24-1728
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ECS
6 Years in-situ mass balance study of Pensilungpa Glacier from 2016 to 2022 in Suru River Valley, Ladakh Himalaya, India.  
Pankaj Kunmar, Manish Mehta, Vinit Kumar, Ajay Rana, and HC Nainwal

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

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

vX5.13
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EGU24-16984
How to balance the voids? Tackling rapid ice loss in western Austria 
Andrea Fischer, Martin Stocker-Waldhuber, Lea Hartl, Bernd Seiser, Kay Helfricht, Andreas Gschwentner, and Giulia Bertolotti

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

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

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

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

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

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EGU24-20043
Glacier Mass Balance Observation in Barkrak Glacier, Western Tian Shan: Implications for Water Availability in Central Asia
(withdrawn)
Gulomjon Umirzakov, Halimjon Mamirov, Fakhriddin Akbarov, Sarkorbek Suvankulov, Gabit Zulpikharov, Davron Eshmuratov, Timur Khismatullin, Maxim Petrov, Tomas Saks, Martina Barandun, and Martin Hoelzle