The glacier surface forms a vital boundary where snow and ice mass exchange occurs through climatic processes. In addition to the visible upper surface, glaciers are bounded by other interfaces, including the underlying base of bedrock/sediment, the front of a calving glacier facing an ocean or lake, and the ice-shelf base in contact with sub-shelf seawater. These unseen boundaries are venues of glacial sliding, hydrology, calving and underwater melting, which play critical roles in glacier dynamics and mass change. These processes are also essential for understanding how glaciers affect surrounding environments through erosion, sedimentation, ice and meltwater discharge. Despite their importance, these boundaries are largely unexplored, in contrast to the increasing amount of data available on the glacier surface. As they are covered by ice and water, special techniques and tools are required for direct observation. For example, hot-water drilling and borehole measurements provide crucial information regarding subglacial processes, and in-situ observations of the ice-water interface can be carried out with uncrewed vehicles or underwater survey devices near the calving front. Based on our experiences in the Alps, Patagonia, Greenland and Antarctica, this presentation highlights the importance of the processes taking place at the hidden glacier boundaries.

How to cite: Sugiyama, S.: On the dark side: Exploring hidden boundaries of glaciers and ice sheets, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5296, https://doi.org/10.5194/egusphere-egu25-5296, 2025.

Polar ice sheets and glaciers worldwide are rapidly losing mass, acting as major contributors to global sea-level rise. This mass loss trend is expected to continue and further accelerate in a warming climate. Besides solid ice discharge of calving icebergs, mass loss is driven by a declining glacier surface mass balance (SMB), i.e., the difference between mass gained from snowfall accumulation and lost from meltwater runoff to the ocean. Reconstructions of past and projections of future glacier SMB often rely on global or regional climate models typically running on 5 to 100 km grids. Such spatial resolution remains, however, insufficient to accurately capture local SMB processes over small glaciers and ice caps.

To bridge this resolution gap, statistical downscaling has proven an efficient tool to spatially refine SMB outputs from coarse global and regional climate models to high-resolution (sub-)kilometer grids. In this presentation, we will assess the added value of statistical downscaling to accurately resolve local SMB processes, notably the high accumulation and melt rates generated over rugged mountain ranges and narrow outlet glaciers, respectively. We will discuss how high-resolution products proved essential to reconcile recent in situ and remote sensing mass change records, and to yield reliable future SMB projections. This talk will highlight the role of statistical downscaling in identifying mechanisms that currently drive, and may further accelerate, mass loss of polar ice sheets and glaciers across the globe.

How to cite: Noël, B.: Capturing high-resolution ice sheets and glacier surface mass balance in a changing climate, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5980, https://doi.org/10.5194/egusphere-egu25-5980, 2025.

Climate Change is expected to increase the intensity and frequency of extreme rainfall events in the coastal areas of Patagonia (Southwest Atlantic Ocean, SWAO). These events carry heavy loads of terrestrial materials and nutrients, and minor components such as kaolin and ash, into coastal areas through riverine inputs. The Chubut River estuary was used a reference coastal ecosystem in the SWAO. In its lower course, the river is diverted into irrigation channels that supply water for agricultural activities. These channels are open from spring to early autumn, increasing the runoff of terrestrial material, and are closed during the rest of the year. Furthermore, kaolin mines are located in the upper course of the river and ash deposition coming from volcanos have been registered. A monitoring of terrestrial material of the Chubut River estuary was conducted and the attenuation coefficients of the different components were evaluated, including terrigenous material, kaolin, and ash. The findings show that the terrestrial material, estimated as dissolved organic carbon (DOC), doubles during rainfall conditions and when irrigation channels are open. During extreme rainfall events, DOC concentrations increased by up to fivefold compared to normal conditions, being the main attenuator in the river. This resulted in a PAR attenuation coefficient variable between 1.3 m^-1 under baseline conditions (closed channels, no rainfall) to over 8 m^-1 following extreme rainfall events in the outer regime (seawater side) of the estuary. Further monitoring of the different under-studied estuarine components in the SWAO and their effects on the attenuation coefficient is crucial for primary productivity studies.

How to cite: Vizzo, J. I., Helbling, E. W., and Villafañe, V. E.: Inputs of Terrestrial Material, Kaolin and Ash into Coastal Patagonian Waters and their Effects on the Attenuation Coefficient of the Chubut River Estuary (Argentina), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-434, https://doi.org/10.5194/egusphere-egu25-434, 2025.

A wide range of problems in oceanic mass and energy transport involve learning submesoscale surface flow fields from diurnal geostationary satellite observations. Yet, traditional methods, such as the Maximum Cross-Correlation (MCC) algorithm, suffer from limited spatiotemporal resolution and extensive post-processing. Here, we present the RAFT-Ocean architecture, a deep neural network-based approach for learning submesoscale flow fields in pixel-to-pixel manner, to retrieve submesoscale surface flow fields from geostationary satellite data. Compared to the MCC algorithm, the RAFT-Ocean architecture significantly improves these methods, reducing the end-point error (EPE) uncertainty by more than 65% and the absolute angular error (AAE) by more than 55%. The RAFT-Ocean architecture, when transferred to the geostationary ocean color satellite (GOCI/CMOS and GOCI-II/GK2B) sea surface chlorophyll-a products for diurnal hourly flow field retrieval, produced more realistic, continuous, and refined sea surface flow field data compared to geostrophic flow data from altimeter data. The refined diurnal hourly flow field matched well with the filamentous structure of surface phytoplankton, demonstrating an advantage in spatiotemporal resolution for kinetic energy transfer across scales. This approach enhances flow field retrieval quality and opens new avenues for real-time marine environment monitoring and modeling.

How to cite: Ding, X., Zhao, M., and Li, H.: Deep learning for submesoscale surface flow retrieval from geostationary satellite observations, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2306, https://doi.org/10.5194/egusphere-egu25-2306, 2025.

This study is part of a doctoral research project aimed at characterizing coastal sediments in relation to the presence of microplastics and marine litter. Within this framework, the present research seeks to establish an up-to-date knowledge base regarding the geochemical characterization of sediments across different seasons along the Ferrara coastal area, specifically at Lido degli Estensi (Ferrara, Italy). The objective is to identify potential vulnerabilities and/or critical aspects related to environmental pollution that require further investigation. Building upon the methodology of Aquilano et al. (2023) and adapting it to the experimental requirements of the current study, a research area was selected at Lido degli Estensi, outside zones allocated for tourism-related public concessions. This site is located on the southern side of the Porto Garibaldi navigation channel (Comacchio municipality, Ferrara), in a coastal section experiencing accretion due to the construction of artificial jetties at the port-channel entrance. These jetties trap sediment transported from the south as a result of longshore drift. Given the beach's width (approximately 150 m), a cross-shore profile was divided into five zones based on specific geomorphological characteristics: swash zone, lower backshore, upper backshore, dune scarp, and dune. Along this beach profile, variations in carbonate content, major oxide composition, and heavy metal concentrations were investigated across different seasons using eight sampling points per season. To evaluate sediment quality in terms of heavy metal contamination, the following indices were employed: Enrichment Factor (EF; Reinmann and De Caritat, 2005), Geoaccumulation Index (Igeo; Buccolieri et al., 2006), Contamination Factor (CF; Loska et al., 2004), and Pollution Load Index (PLI; Ferreira et al., 2022). Furthermore, heavy metal concentrations detected in the samples were compared with the limits established by current Italian legislation (Legislative Decree 152/06). This study was conducted as part of the ECS_00000033_ECOSISTER project, funded under the National Recovery and Resilience Plan (NRRP), Mission 04 Component 2 Investment 1.5 – NextGenerationEU (Call for Tender No. 3277, dated 30/12/2021).

How to cite: Buoninsegni, J., Marrocchino, E., Tassinari, R., Tessari, U., and Vaccaro, C.: Geochemical characterization of coastal sediments: a preliminary study of seasonal variations at Lido degli Estensi (Ferrara, Italy), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3582, https://doi.org/10.5194/egusphere-egu25-3582, 2025.

Climate change significantly impacts the hydrology and water resources of any region especially high mountain areas including cryosphere that consist of glaciers. Numerous studies report that glaciers are retreating and losing volume with time causing serious concerns over freshwater availability in the basins they feed water to. Assessment of these changes and their relationship with various climatic aspects are crucial to understand and tackle such challenges. Long-term trends in temperature and precipitation and their spatio-temporal distribution, for the mountainous state of Uttarakhand in India were assessed, utilizing the India Meteorological Department’s gridded precipitation and temperature datasets for the period 1951-2023. Mann-Kendall trend test was performed at 90% significance level, for each grid, to check monthly trends, which gave critical insights upon shifts in seasonal meteorology. Results reveal notable changes in the monthly distribution of precipitation with many grids reporting a decreasing winter precipitation (Oct-Jan) and many showing an increasing precipitation for May and August. Global warming impact is much visible through changes in minimum temperatures for almost all the grids, reporting a strong positive trend for February, March, August, September and November. Importantly, these changes are more prominent for the high-altitude areas, which highlights elevation dependent climate change pattern. Evidently, the precipitation is shifting from winters to summers and the minimum temperatures are increasing towards the end of ablation season (Aug-Sep), decreasing the chances of receiving solid precipitation or snowfall. Consequently, a decrease in snow cover is expected in the future, which from a hydrological perspective, would lead to a reduction in snowmelt discharge and its contribution to streamflow of the Himalayan perennial rivers. Moreover, the increasing temperature and precipitation during summers can generate huge discharges from glacierized catchments due to increased simultaneous contribution of glacier-melt and rainfall, causing destructive flash floods and debris flow events, as being witnessed in the recent past. Combination of decreased precipitation in winter months and increased temperatures overall, can prove detrimental to glaciers’ health as they will melt more, whereas their replenishment will be lesser, leading to negative mass balances. Climate change is certainly having an adverse effect on the mountain hydrology, especially that of the Himalayan cryosphere. The glaciated catchments are expected to have more glacier-melt and rainfall-runoff contribution and less snow-melt contribution in the near-future. The glaciers, present in the region, are expected to retreat and lose mass more rapidly, considering the meteorological changes in the high elevation areas. Small glaciers might deplete faster, which would lead to problems of freshwater availability in the nearer downstream areas dependent on the melt-runoff water. While there seems no immediate solution to the prevailing scenario of climate change, community-based measures can be adopted to tackle problems of water availability. Water conservation and springshed management in the mountainous regions are some focus areas to work upon, in order to ensure water security under the changing climate.

How to cite: Thapliyal, M., Singh, S., and Patel, L.: Climate Change and its Impact on the Hydrology of a Glaciated Mountainous Region, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4832, https://doi.org/10.5194/egusphere-egu25-4832, 2025.

The coastal ecosystems, including estuaries and mangroves, are highly vulnerable to anthropogenic intervention, particularly due to activities such as urbanization, wastewater discharge, and industrial development, which can alter their ecosystem services and affect habitat quality. In order to evaluate the impact of these interventions through the carbon and nitrogen isotopic composition of two macroalgae Boodleopsis verticillata and Bostrychia spp in four coastal ecosystems of the Colombian Pacific (Valencia - VAL, San Pedro - SPE, Chucheros – CHU with low intervention, and Piangüita - PIA with high intervention) were used to understand the sources of these elements. δ¹⁵N values is a commonly used to providing information about nitrogen sources in primary producers. δ¹³C values is used to investigate carbon sources i.e. terrestrial or marine. Samples were collected during 2014, 2015, and 2016, and analyzed by isotope ratio mass spectrometer. The results show that the δ¹³C values ranged from -33.97 to -31.93 ‰ in VAL, -33.78 to -30.09 ‰ in SPE, -31.12 to -28.45 ‰ in CHU, and -33.32 to -21.71 ‰ in PIA. δ¹⁵N values ranged from 0.32 to 3.18 ‰ in VAL, 0.57 to 5.47 ‰ in SPE, 1.82 to 3.39 ‰ in CHU, and 2.32 to 10.16 ‰ in PIA. Significant differences were found among the four areas with mean δ¹³C values by locality (VAL -30.21 ‰, SPE -31.71 ‰, CHU -30.09 ‰, and PIA -30.52 ‰) and δ¹⁵N values (VAL 1.74 ‰, SPE 2.30 ‰, CHU 2.40 ‰, and PIA 4.47 ‰) reflecting the impacts of human activities on the coastal ecosystems. This work contributes to understanding the effects of anthropogenic intervention on pollution and wastewater discharge in coastal ecosystems, providing key tools for the development of environmental management policies that support conservation in the Colombian Pacific.

How to cite: Arce-Sánchez, R. S., Medina-Contreras, D., and Sánchez-Gonzalez, A.: Primary producers as indicators of anthropogenic intervention in the Colombian Pacific, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7292, https://doi.org/10.5194/egusphere-egu25-7292, 2025.

The Mediterranean Sea, with its unique characteristics as a semi-enclosed and highly stratified basin, serves as a natural laboratory for studying oceanic processes of global relevance. Vertical mixing is a fundamental process regulating the transfer of mass, heat, and nutrients between water column layers, influencing dynamical and biogeochemical processes, and controlling the exchange with the overlying atmosphere. Due to its turbulent nature acting on small spatial and temporal scales, vertical mixing remains challenging to simulate in modern ocean circulation models. Moreover, the interaction between vertical mixing and horizontal diffusion/advection is essential in shaping the transport and distribution of heat, nutrients, and pollutants in marine environments. Finding the optimal vertical mixing parameterizations alongside horizontal advection and diffusion schemes in an ocean circulation model, able to simulate the available observations, presents significant challenges due to the need for consistent scaling, numerical stability, and accurate representation of multi-scale processes.

Here, we use the same system setup as the Mediterranean Forecasting System of the Copernicus Marine Service, that is NEMO (v4.2) general circulation model, including tides, coupled with the WaveWatch III wave model. The model features a horizontal resolution of 1/24° (approximately 4 km) and 141 unevenly spaced vertical levels. We investigate the performance of different numerical vertical closure schemes – a Richardson-number-dependent, a one-equation and a two-equation models – as well as the effect of different lateral advection and diffusion schemes. The role played by the enhanced vertical diffusion due to Camarinal Sill at the Strait of Gibraltar in controlling the exchange of water masses between the Atlantic Ocean and the Mediterranean Sea is also investigated. We validate our model by assessing our ability to reproduce physical processes and by comparing it with in-situ data throughout the Mediterranean basin, across varying seasons and years.

How to cite: Gualtieri, L., Borile, F., Burchard, H., Oddo, P., Miraglio, P., Clementi, E., Goglio, A. C., and Pinardi, N.: Investigating vertical mixing and lateral diffusion parameterizations in the Mediterranean Sea, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8649, https://doi.org/10.5194/egusphere-egu25-8649, 2025.

Breaking internal gravity waves cause small-scale turbulent mixing, which changes water mass properties, affects biogeochemical cycles, and contributes to driving the large-scale overturning circulation. Ocean general circulation models do not resolve this process and thus rely on a parameterization. The state-of-the-art IDEMIX (Internal wave Dissipation, Energy and MIXing) model predicts the propagation and dissipation of internal wave energy based on external forcing functions that represent the main generation mechanisms, notably the internal tide generation at the sea floor and the near-inertial wave generation at the sea surface. By linking small-scale mixing to internal wave energetics, IDEMIX allows the consistent parameterization of wave-induced mixing in ocean models. Its basic incarnation treats all internal waves as part of a horizontally homogeneous continuum and was shown to successfully reproduce observed turbulent kinetic energy dissipation rates and internal wave energy levels. In a newer configuration (IDEMIX2), the internal wave field is compartmentalized, distinguishing between a high-mode continuum on the one hand and low-mode near-inertial wave and internal tide compartments, whose horizontal propagation is explicitly resolved in wavenumber angle space, on the other hand. We present the evaluation of the IDEMIX2 model with a particular focus on the impact of applying an anisotropic internal tide forcing. So far, parameterizations of internal tide-driven mixing have not taken the strong anisotropy of the internal tide generation process into account. We demonstrate the need for doing so, showing a notable impact on the modeled internal wave energetics and predicted mixing when changing from the previous isotropic to the new anisotropic tidal forcing in IDEMIX2. 

How to cite: Pollmann, F., Eden, C., Olbers, D., Nycander, J., and Zhao, Z.: Anisotropic internal tide forcing in the consistent internal wave mixing scheme IDEMIX, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8764, https://doi.org/10.5194/egusphere-egu25-8764, 2025.

This study investigates the spatio-temporal variability and long-term warming trends in sea surface temperature (SST) across the Arabian Sea from 2000 to 2019, using daily AVHRR satellite observations with a 1°x1° spatial resolution. Seasonal and interannual SST dynamics reveal patterns shaped by monsoonal processes and global climate phenomena, such as El Niño and La Niña. Wavelet spectrum analysis highlights periodic fluctuations and dominant frequencies associated with interannual climate variability, further emphasizing the influence of seasonal processes. Spring (MAM) exhibits the most pronounced interannual warming, particularly in the central and northern regions, while autumn (SON) demonstrates significant warming trends, especially in the southern basin. Monsoonal processes influence seasonal variability, with winter (DJF) cooling in the northern Arabian Sea and summer (JJA) upwelling along Oman and Somalia, resulting in localized cooling amidst broader warming trends in central and southern regions. Wavelet power spectra from critical regions, including the Gulf of Oman, Balochistan Coast, and Mumbai, indicate dominant periodicities of interannual warming, with variations corresponding to regional oceanographic processes. For instance, the Balochistan Coast displays the highest warming rate (0.0519°C/year), underscored by strong wavelet power at periodicities tied to El Niño–Southern Oscillation (ENSO) cycles. Similarly, the Gulf of Oman and Mumbai exhibit distinct spectral peaks, reflecting localized climate dynamics and variability. Regionally, the warming trend varies significantly. The Gulf of Aden (0.0181°C/year), Gulf of Oman (0.0164°C/year), and Gulf of Kutch (0.0269°C/year) exhibit moderate warming rates, while areas like the Balochistan Coast and South of Salalah (0.023°C/year) highlight significant localized warming. Southwestern Arabian Sea regions west of Kochi (0.0209°C/year) and Mangalore (0.0323°C/year) also demonstrate notable trends. In contrast, regions like Minicoy (0.0162°C/year) and the Male-Maldives area (0.0073°C/year) show relatively weaker warming. These findings underscore the critical role of spatial and seasonal variability in shaping SST changes and their implications for regional climate patterns, monsoonal behavior, marine ecosystems, and fisheries. The pronounced warming in key regions, coupled with insights from wavelet spectrum analysis, highlights the influence of localized oceanographic processes, such as upwelling, heat transport, and climate-induced variability. These results necessitate further study to assess future impacts and develop mitigation strategies for sensitive marine biodiversity and economic resources in the Arabian Sea . 

How to cite: Saha, S. and Mukherjee, A.: Unraveling the Arabian Sea’s Thermal Pulse: Seasonal and Interannual SST Variability Amidst Climate Dynamics, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12429, https://doi.org/10.5194/egusphere-egu25-12429, 2025.

We have previously developed a 12-sample environmental DNA (eDNA) sampler designed for use in the marine surface. The sampler can collect and store eDNA samples on filter cartridges according to scheduled sequences. Communicating via mobile phone networks also makes it possible to collect samples on demand. For the underwater eDNA sample-return missions, we have designed and developed a compact eDNA sampler with an oil-filled (pressure-balanced) configuration, enabling its deployment at various depths. Field trials for the underwater eDNA sampler were performed using underwater platforms such as deep-sea landers. Here, we introduce the newly developed compact eDNA sampler and discuss its potential applications in mid- to deep-ocean layers, focusing on eDNA sample-return missions targeting jellyfish and other marine species.

How to cite: Fukuba, T. and Lindsay, D.: Development of an underwater eDNA sampler and its potential application in jellyfish eDNA detection, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14703, https://doi.org/10.5194/egusphere-egu25-14703, 2025.

Between Sept. 4, 2023, and Sept. 12, 2023, a cyclogenesis develops close to the Greek coast in the Ionian Sea. The evolution of this cyclone is divided into two phases: a strongly baroclinic one with intense orographic precipitation in Greece, and a final barotropic phase with the formation of an intense tropical-like cyclone (TLC) impacting Libya. In this work, we investigate this TLC (named “Daniel”) initially using the standalone WRF model with different sea surface temperature sources,  untile the use of the coupled atmosphere-ocean models. Preliminary results show that SST plays a crucial role in the intensification and tropicalization of the cyclone, with a strong impact not only along the cyclone track but especially in the neighboring areas, where high values of heat transport a precipitable water are found. We also observe how the use of a coupled model as a digital twin, shows strengths in the quality of the simulation and the physics of the process, but highlights some critical issues in the configuration of the marine model, which at small technical variations produces intense changes in the structure of the ocean and atmosphere.

How to cite: Ricchi, A., Ferretti, R., Pantillon, F., Dafis, S., Menna, M., Martellucci, R., Serafini, P., and Carrió, D. S. C.: On the role of air-sea-wave interaction in developing destructive Tropical-Like Cyclones DANIEL, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17499, https://doi.org/10.5194/egusphere-egu25-17499, 2025.

Ice crevasses are pervasive features across the Arctic and Antarctic ice sheets. These deep, open fractures in the ice surface serve as critical conduits for transporting surface meltwater into the englacial system, significantly impacting ice sheet hydrology and stability. Accurate mapping of the spatial and temporal distribution of ice crevasses is vital for advancing our understanding of ice sheet dynamics and their evolution. Remote sensing technology provides a robust platform to achieve this purpose, while the rapid advancement of machine learning algorithms offers substantial benefits for automated crevasse detection, facilitating efficient and large-scale mapping. This study conducts a comprehensive comparison of the performance of various machine learning models, including CNN, U-Net, ResNet, and DeepLab, for ice crevasse extraction. Through quantitative evaluation metrics and visual inspection, the optimal machine learning model was selected to map ice crevasses on Antarctic ice shelves using multi-source remote sensing data, such as SAR and optical satellite imagery. Furthermore, this work explores the strengths and limitations of various machine learning in detecting ice crevasse and proposes potential solutions for further refinement. This study aims to contributes to enhancing ice crevasse detection and offering robust ice crevasse datasets, which is crucial for reliable analyzing the dynamic of the Antarctic ice sheet in the future.

How to cite: Liang, S. and Xiao, X.: Antarctic ice shelf crevasse detection using multi-source remote sensing data and machine learning, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19031, https://doi.org/10.5194/egusphere-egu25-19031, 2025.

SnowMapPy is a Python-based package developed to streamline the collection, preparation, and analysis of MODIS NDSI data, specifically from the Terra and Aqua satellite products. By automating essential steps (data clipping, reprojection, filtering, and time series generation), SnowMapPy improves the efficiency and precision of snow hydrology research. The protocol allows users to work with both local and Google Earth Engine cloud-based datasets, enabling flexible data acquisition and processing tailored to the needs of snow hydrology, water resource management, and climate change studies. Designed for accessibility and flexibility, SnowMapPy supports large-scale, high-resolution snow cover analysis with minimal configuration. The package facilitates customized workflows through its modular structure, making it a valuable tool for researchers aiming to understand snow dynamics and their impact on seasonal water resources. 

How to cite: Elyoussfi, H., Boudhar, A., Belaqziz, S., Bousbaa, M., Bechri, H., Sproles, E. A., and Benzhair, F.: SnowMapPy v1.0: A Python Package for Automated Snow Cover Mapping and Monitoring in Mountain Regions , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20632, https://doi.org/10.5194/egusphere-egu25-20632, 2025.

This study explores the seasonal and lagged correlations between Chlorophyll-a (Chl-a) concentrations and vertical velocity (wT) to elucidate upwelling's role in driving phytoplankton productivity. In Oman (Region III), an immediate response to upwelling was observed, with the strongest correlation (r = 0.7) at lag 0 during peak upwelling months (June–July). In contrast, Iranian regions (I & II) exhibited delayed responses, with maximum correlations (r = 0.7) at lag 1 (occurring about a month later). This delay may result from processes like nutrient mixing and remineralization. Seasonal trends revealed sustained Chl-a concentrations in Oman, peaking at 2.39 mg m^-3 in September, while Iran showed a steady decline after a July peak of 1.37 mg m^-3. Stratification and horizontal currents modulated Chl-a distributions, with weaker stratification in Oman enabling efficient nutrient delivery. These findings reveal the intricate dynamics of upwelling-driven productivity across both semi -enclosed and open marine ecosystems. By examining regional variations in the context of broader oceanographic processes, this study offers valuable insights for the sustainable management of upwelling systems and for anticipating their responses to climate change.

How to cite: A. Ismail, K. and Salim, M.: Unveiling the Impact of Upwelling on Phytoplankton Productivity in the Arabian/Persian Gulf and Sea of Oman, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20989, https://doi.org/10.5194/egusphere-egu25-20989, 2025.

How to cite: Van Tricht, L., Zekollari, H., Huss, M., Rybak, O., Satylkanov, R., and Farinotti, D.: Modelling the impact of mining activities on the dynamics and evolution of a Kyrgyz glacier, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1532, https://doi.org/10.5194/egusphere-egu25-1532, 2025.

Knowledge of glacier ice volumes is crucial for constraining future sea level potential, evaluating freshwater resources, and assessing impacts on societies, from regional to global. Motivated by the disparity in existing ice volume estimates, we developed a global machine learning framework to model the ice thickness of individual glaciers. IceBoost is a gradient-boosted tree regression model, trained with 3.7 million global ice thickness measurements and an array of 34 numerical features. The model's error aligns within 10% of existing models outside polar regions, and is 30% to 40% lower at high latitudes. We find that providing supervision through available thickness measurements can further reduce the error of individual glaciers by up to a factor 2 to 3. A feature ranking analysis reveals that geodetic information is the most informative variable, while incorporating ice velocity improves model performance by 6% at high latitudes. A major feature of IceBoost is its ability to generalize globally, including in ice sheet peripheries. We present the model, discuss the advantages and shortcomings of a machine learning approach, estimate errors, and provide updated regional glacier volumes.

How to cite: Maffezzoli, N., Rignot, E., Barbante, C., Petersen, T., and Vascon, S.: A global machine learning system for glacier ice volumes, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1960, https://doi.org/10.5194/egusphere-egu25-1960, 2025.

We report on the mass balance evolution and climate sensitivities of four glaciers from moderately dry to moderately wet climate zones of High Mountain Asia over the last five decades. We focus on Chhota Shigri Glacier located in the western Himalaya (RGI region: South Asia west), Tuyuksu and Sary Tor glaciers (Northern and Central Tien Shan, Central Asia), and an unnamed glacier (hereafter Glacier No. 4) (Eastern Himalaya, South Asia east). Continentality index indicates Chhota Shigri and Sary Tor as most continental (43 and 41) glaciers, Tuyuksu as intermediate (34) and Glacier No. 4 as the most maritime glacier (22). Using declassified spy satellite imagery from the 1970s and 1980s and recent high-resolution optical satellite images, we estimated glacier mass loss rates ranging from -0.3 ± 0.1 m w.e a^-1 for Chhota Shigri and Tuyuksu glaciers (1971-2020), -0.4 ± 0.1 m w.e. a⁻¹ for Glacier No. 4 (1969–2022), and -0.6 ± 0.1 m w.e a^-1 for Sary Tor Glacier (1973- 2023). We calibrated a mass balance model (SnowModel) coupled with an ice dynamics model to simulate the long-term annual and seasonal mass balance of each glacier. Subsequently, we used the calibrated model to calculate the dynamic mass balance sensitivity of each glacier to the changes in temperature and precipitation. Our results reveal that Sary Tor Glacier is least sensitive to climate changes. However, as this glacier has observed significantly increasing temperature over the last decades, it may witness an increasing mass loss due to its strong sensitivity to temperature changes. Chhota Shigri Glacier’s mass balance is less sensitive to changes in temperature and precipitation compared to Tuyuksu Glacier. In addition, no significant trends in either temperature or precipitation was observed, implying a more stable response of the glacier to climate in near future. Tuyuksu Glacier accumulates mass both in summer and winter, and it is strongly influenced by temperature changes. With no significant increase in precipitation to offset the mass loss due to increased temperature, this glacier will likely experience an increased mass loss in coming decades. Glacier No. 4 has the highest sensitivity to climate. With a warming trend observed in this region, this glacier is expected to witness highest mass loss among the four in the coming years.

How to cite: Bhattacharya, A., Mukherjee, K., Ghuffar, S., King, O., Bolch, T., and Menounos, B.: Variabilities in Climate Sensitivities and Mass Balance of Four High Mountain Asian Glaciers, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4653, https://doi.org/10.5194/egusphere-egu25-4653, 2025.

The Juneau Icefield, Alaska, lost ice at an accelerated rate after 2005, relative to the past 250 years. Rates of area shrinkage were found to be 5 times faster from 2015–2019 than from 1979–1990. The continuation of this trend could push glacial retreat beyond the point of possible recovery.

Climate-driven ice loss from glaciers and icefields has been shown to contribute to rising sea-levels, with Alaska expected to remain the largest regional contributor to this effect up to the year 2100. Alaskan glaciers are particularly vulnerable to changes in the climate because they are often top-heavy (with more area at a higher altitude) and located on plateaus. In addition, these factors make Alaskan glaciers more prone to threshold behaviour, in which exceeding a tipping point could result in an irreversible recession. Longer-term records of Alaskan glacier change are needed to understand how climate change impacts these glaciers.

We used historical records, aerial photographs, 3D terrain maps, and satellite imagery to reconstruct Juneau Icefield glacier behaviour over the past 250 years. We observed steady glacier volume loss at a rate of approximately 0.65 km³ per year between 1770–1979. This rate accelerated to approximately 3 km³ per year between 1970–2010 and then doubled to 5.9 km³ per year between 2010–2020. This ice loss acceleration between 2010–2020 was accompanied by a glacial thinning rate 1.9 times higher than that from 1979–2000 and increased icefield fragmentation. This reduction in icefield accumulation area is contributing to a positive feedback loop, including increasing glacier disconnection and fragmentation. Lowering albedo occurs where surfaces such as darker rock are increasingly exposed, reducing solar reflectivity, and further contributing to the recession.

The findings suggest that a physical mechanism are contributing to this icefield moving towards an irreversible tipping point in glacier recession. This greater understanding of Alaskan glacier ice loss mechanisms could improve projections of near-future sea level rise.

How to cite: Davies, B., McNabb, R., Bendle, J., Carrivick, J., Ely, J., Holt, T., Markle, B., Nicholson, L., and Pelto, M.: Accelerating loss of Alaskan Glaciers, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5778, https://doi.org/10.5194/egusphere-egu25-5778, 2025.

Modeling future glacier evolution is traditionally divided into two steps. The first step, known as inverse modeling, involves estimating "hidden" variables (such as distributed ice thickness) to ensure the model aligns with available observations, thereby reconstructing the current full subglacial and supraglacial states. The second step, forward modeling, uses the initial state derived from the inverse model and simulates its evolution under a given climate forcing. Despite advancements in data availability to constrain inverse modeling and improvements in the representation of physical processes, several challenges persist. These include artificial biases and uncertainties, such as the "initial shock" problem, which arises when ice flow and surface mass balance are not physically balanced. These issues stem largely from the difficulty of reconciling hypothesized physical equations with observational data, especially as the volume of available data increases.
Generalized automatic differentiation (the main tool that permits deep learning) and advancements in parallel computing present unprecedented opportunities to address these challenges. By enabling the exploration of large spaces of glacier states, these technologies make it possible to identify states consistent with both ice physics and observations -- an approach that is computationally infeasible with traditional data assimilation methods. More specifically, physics-informed deep learning is a powerful tool that has the capability to merge the two essential steps (data assimilation by inverse modeling, and forward modeling) into a single framework. In this framework, both observational data as well as physics are seen as constraints that can be enforced in a similar manner, allowing for the discovery of composite, consistent solutions. Most importantly, the intrinsic structure of neural networks makes them highly efficient for computational tasks on GPUs as needed for global modeling, where traditional CPU-based solvers suffer from computational bottlenecks.
This work reviews the latest advancements in the Instructed Glacier Model (IGM), a next-generation glacier evolution model leveraging automatic differentiation and physics-informed deep learning to simulate ice flow and topographical change. IGM, a Python-based framework, integrates ice thermomechanics, surface mass balance, and mass conservation while emphasizing user accessibility, modularity, and reproducibility. The model takes benefit of recent libraries and tools such as: i) TensorFlow for high computational efficiency on GPUs and effective data assimilation, ii) OGGM for enhanced data accessibility, and iii) Hydra for streamlined configuration management. We demonstrate IGM’s versatility through applications in paleo and contemporary glacier modeling. Finally, we illustrate the added value of merging inverse and forward modeling into a unified framework. This approach reduces uncertainties by bridging the gap between data and physics, addressing the persistent challenge of inferring spatially distributed ice thickness while ensuring alignment with observed ice flow.

How to cite: Jouvet, G., Cook, S., Finley, B., Leger, T., and Maussion, F.: Unified forward and inverse glacier modeling with IGM, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7262, https://doi.org/10.5194/egusphere-egu25-7262, 2025.

Glacier retreat and the transition from land to lake termini can accelerate mass loss through various feedback mechanisms. This study examines the dynamic changes during the land-to-lake transition of four neighboring glaciers (Exploradores, Grosse, Reichter and Gualas) located in the maritime-humid climate of the western Northern Patagonian Icefields, where ablation rates on glacier terminal tongues can reach up to 20 m w.e. annually.

We conducted the first bathymetric surveys on the glacier’s proglacial lakes and integrated data on ice velocity, elevation changes, front retreat, and front depth to identify the main controls on glacier retreat. Three transition stages were observed: (i) initial thinning with slow front retreat, (ii) increased glacier velocity and terminus flotation leading to rapid disintegration into large tabular icebergs, and (iii) formation of a stable calving front on prograde or <5º retrograde bedrock slopes, with a slowdown in velocity followed by smaller calving events. One debris-covered glacier left large sections of dead ice, while debris-free glaciers efficiently produced large tabular icebergs (>500 m).

While Grosse, Gualas and Reicher Glacier developed a calving front, Exploradores Glacier is currently in stage (i) to (ii), characterized by increased velocity and flotation. Identifying this stage is critical for Exploradores Glacier not only for glaciological interest, but also due to a rapid increase in lake area in the coming years, which will heighten the risk for tourists accessing the terminal glacier tongue, a major attraction visited by up to 9,000 tourists annually. Due to insufficient ice bedrock information to fully assess flotation conditions, we discuss the potential of using ice velocity (widely available nowadays through satellite), geometry and elevation changes to predict rapid retreat stages.

In the Patagonian Icefields, overdeepened areas currently covered by ice are expected to fill with water as glaciers retreat. Understanding the impacts and processes during glacial lake development will enhance the interpretation of paleo-records and predictions of glacier responses to climate change in future environmental systems.

How to cite: Irarrazaval, I., Somos-Valenzuela, M., Lizama, E., Morales, B., Egli, P., Dussaillant, I., and Reid, B.: Changes in glacier dynamics during land-to-lake glaciers transition in Patagonian glaciers. , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7609, https://doi.org/10.5194/egusphere-egu25-7609, 2025.

Climate warming causes increased glacier ablation around the globe. This leads to decreasing surface albedos, which trigger positive melt-albedo feedbacks, fostering continuous glacier darkening whose intensity depends on glacier-specific, topo-climatic factors. Here, we present an analysis of regional disparities of glacier darkening across the European Alps over the period 2000-2023. We derive temporal means and trends of the summer albedo of 152 glaciers from the MODIS MOD10A1 snow product. Based on this data we introduce and calculate a new measure called "glacier darkening resilience", which combines albedo mean and trend to a theoretical time span needed for the albedo to reduce to zero. Our results reveal negative albedo trends on all glaciers (-0.037±0.012 per decade). On 112 glaciers, these trends are statistically significant. The Silvretta Alps are identified as the hot spot of Alpine glacier darkening, with a decadal albedo trend of -0.059 and a darkening resilience of 69.1 years. The Adamello-Presanella Alps, in contrast, show the highest darkening resilience (215.9 years) with a decadal albedo trend of just -0.021. We find that the mean glacier albedos are primarily governed by local climates, while their trends are rather influenced by topographic factors that differ between Western and Eastern Alps.

How to cite: Möller, M., Möller, R., and Mayer, C.: Regional disparities and topo-climatic controls of glacier darkening across the European Alps since 2000, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10167, https://doi.org/10.5194/egusphere-egu25-10167, 2025.

Mountain glaciers are a major contributor to sea-level rise and serve as an important freshwater resource for many mountainous regions. Accurate mass balance estimates are therefore essential for predicting and managing the global and local impacts of climate change. In a warming climate, glaciers will experience increased liquid precipitation and melt, making it crucial to better understand and model the associated surface processes. In this study, we present a modelling approach developed to investigate the dynamic interaction between surface liquid water and glacier mass balance using the SURFEX-ISBA-Crocus model. As Crocus is primarily a snowpack model, some adaptations were necessary for its application to glacier environments. The research focuses on a specific process: the retention of liquid water at the ice surface, which affects both the mass and surface energy budgets.

Our implementation temporarily retains liquid water from melt or rain events when glacier ice is exposed at the surface. This water impacts the energy balance and can refreeze over time depending on meteorological conditions. To prevent over-accumulation, excess water is drained according to a predefined coefficient. This process has a significant impact on glacier properties, through the presence of liquid water at the surface and the production of refrozen ice, which directly affects the albedo and mass balance.

We applied this new development to Mera Glacier in Nepal to analyse its impact on point mass balance, mass fluxes such as melt and refreezing, and their seasonal variations. The case study highlighted the role of the liquid water reservoir in modulating the effects of melt and rain events. During the pre-monsoon season, the developed model showed greater mass loss due to surface liquid water, which enhanced warming rather than compensating through refreezing. In contrast, during the monsoon and post-monsoon seasons, the behaviour shifted, with the developed version showing less negative mass balance as refreezing increased. The mean annual difference between the two model versions was 0.22m w.e. over the four simulated years, with a larger difference of 0.38 m w.e. observed in 2021-2022. Sensitivity tests on key parameters of the buffer model indicated that the differences are driven not only by the amount of liquid water retained, but also by a positive feedback on albedo, which strongly influences the energy balance.

To further validate and refine the method, future work will focus on comparing this modelling approach with observations and measurements.

How to cite: Goutard, A., Réveillet, M., Brun, F., Six, D., Amory, C., Fettweis, X., Fourteau, K., Lafaysse, M., and Roussel, L.: Impact of surface liquid water retention on glacier mass balance: application to Mera Glacier (Nepal) using SURFEX-ISBA-Crocus, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10188, https://doi.org/10.5194/egusphere-egu25-10188, 2025.

Glaciers and ice caps worldwide are in strong decline, and models project this trend to continue with future warming, with strong natural and socioeconomic implications. The Jostedalsbreen ice cap is the largest ice cap on the European continent (500 km² in 1966, 458 km² in 2019) and occupies 20% of the total glacier area of mainland Norway. Here we simulate the evolution of Jostedalsbreen since 1960, and its fate in a changing climate in the 21st-century and beyond (2300). This ice cap contains glacier units with a great diversity in shape, steepness, hypsometry, and flow speed. We employ a coupled model system annually accounting for the mass-balance elevation feedback, with 3-d ice dynamics and simulated surface mass balance constrained by Bayesian inference. We find that Jostedalsbreen may lose 12-74% of its present-day volume, depending on future emissions. Regardless of scenario, the ice cap is likely to split into three parts during the second half of the 21st century. Our results suggest that Jostedalsbreen will likely be more resilient than many smaller glaciers and ice caps in Scandinavia. However, we show in simulations to the year 2300 that by the year 2100, the ice cap may be committed to a complete disappearance during the 22nd century, under high emissions. Under medium 21st-century emissions, the ice cap is bound to shrink by 90% until 2300. Further simulations indicate that substantial mass losses undergone until 2100 are irreversible. Our study illustrates a model approach for complex ice masses with numerous outlet glaciers such as ice caps, and how tightly linked future mass loss is to future greenhouse-gas emissions. Finally, uncertainties in future climate conditions appear to be the largest source of uncertainty in future evolution of ice caps like Jostedalsbreen.

How to cite: Åkesson, H., Hauknes Sjursen, K., Andreassen, L. M., Vikhamar Schuler, T., Dunse, T., Kusk Gillespie, M., Robson, B. A., Schellenberger, T., and Clement Yde, J.: Recent history and future demise of Jostedalsbreen, the largest ice cap in mainland Europe, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10323, https://doi.org/10.5194/egusphere-egu25-10323, 2025.

Glacial Lake Outburst Floods (GLOFs) are a recurring threat in the Karakorum of Gilgit-Baltistan, Pakistan. Numerous surge-type glaciers in the region periodically advance at time intervals of around 10-25 years and dam up streams to create ice-dammed lakes. These lakes empty in sometimes catastrophic outburst floods one to three times a year for several years once an ice dam has formed. Although the downstream population is aware of the risk, early warning systems are being established by the government, and protection measures are being undertaken, even the most recent outburst floods, e.g. at Shishper Glacier, have caused significant damage to essential infrastructure such as the Karakoram Highway and local settlements.

In summer 2024 a team of four members of the GOTHECA project carried out fieldwork missions at 6 surge-type glaciers in the upper Hunza Valley and at two glaciers in Shigar Valley. We collected repeat UAV data on eight glaciers, UAV data of GLOF lake bathymetry for three locations, GPR data on three glaciers, temperature gradient data together with local students, and established a weather station in Shimshal Valley thanks to collaboration with partners from Pakistan. The aim of this data collection is to provide ground-truth for satellite data, to better understand the current state and characteristics of local surge-type glaciers, and to better quantify and model past and future GLOFs in Gilgit-Baltistan.

We present preliminary results from repeated UAV surveys and from some of the first GPR surveys on these surge-type glaciers in the upper Hunza Valley, providing insights about volumes of former and potential future ice-dammed lakes, ice dynamics, and thermal properties of glacier tongues. With air temperatures of nearly 30 degrees Celsius measured at the tongue of Yazghil Glacier at 3000 m.a.s.l. at noon in summer, daily melt rates were extremely high at more than 0.15 m/day, but the glacier tongue was advancing at several decimeters per day, indicating a potential onset of a surge. Radargrams for three surge-type glaciers indicate alternating zones of warm and cold ice, suggesting polythermal characteristics of these glacier tongues even when not actively surging.

How to cite: Egli, P., Enzenhofer, U., Lappe, R., Hillisch, L., Ayub, G., Hussain, Z., Raza, G., Steiner, J., and Gong, Y.: Insights from fieldwork on surge-type glaciers with GLOF potential in Gilgit-Baltistan: preliminary results from UAV surveys, GPR surveys, and meteorological measurements , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10525, https://doi.org/10.5194/egusphere-egu25-10525, 2025.

Debris-covered glaciers (DCG) are common in most parts of High Mountain Asia (HMA). Existing studies show that DCG have been losing mass at similar or even higher rates than debris-free glaciers (DFG). However, the process driving the response of DCG to climate change are much more heterogenous than those of DFG. Understanding the evolution of DCG is further complicated by the development glacial lakes which have significant impacts on glacier dynamics.

To investigate the characteristics and development of the DCG a long time series of observations is beneficial. Here, we present the mass balance and surface evolution of selected DCGs located in different parts of HMA since the last 60 years using historical KH-4 and KH-9 stereo imagery and contemporary high-resolution stereo images such as Pléiades. In addition, we analyse their velocity changes since the 1980s using available data from ITS_Live and calculated annual and seasonal velocities from Sentinel-1 and 2 data.

Our results show that DCGs have slowed-down on average and the surface of DCGs have become rougher indicating the evolution of ice cliffs and supra-glacial lakes. Most DCG have large stagnant tongues, a reverse elevation change gradient at the distal part of the tongue and no visible signs of retreat (“Khumbu type”). In contrast, others show flow activity throughout the tongue and are retreating. Their surface elevation change gradient is similar to DFG (“Kangshung type”). The lake-terminating DCG are also active throughout, have the highest velocity at the end of the tongue and show the highest mass loss. We found topography to be one of the main drivers of heterogeneity. Work is ongoing to analyse various climate parameters to better understand the reasons for the heterogeneity and investigate the similarities and differences in the seasonal velocity of DCGs.

How to cite: Bolch, T., Baldacchino, F., and Bhattacharya, A.: Variable evolution of debris-covered glaciers in High Mountain Asia during the last several decades, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11329, https://doi.org/10.5194/egusphere-egu25-11329, 2025.

Glacier surges are periods of significantly increased ice flow due to ice-dynamic feedbacks, in contrast to more conventional advances or other responses due to changes in mass balance. In the Arctic, a ring of surging glacier clusters can be found extending from Alaska-Yukon to Novaya Zemlya. The ‘Arctic ring’ encapsulates Svalbard, an archipelago with a long history of glaciological observations and consequently measurements of glacier surges. However, estimates of the number of surge-type glaciers across the archipelago range between 10% and 90% depending on the classification technique used. To better understand the causes, drivers and impacts of glacier surges in Svalbard, improved monitoring is required and new techniques developed to extend the observational record of active surge dynamics. In this contribution, we review the benefits and limitations of different approaches for monitoring and detecting glacier surges in Svalbard. We use this to compile a new database of surge-type glaciers in Svalbard, which also contains data on surge characteristics e.g. terminus change and velocity. We find that 36% of glaciers in Svalbard have displayed surge-type behaviour throughout our observational and landform record, rising to 51% when removing glaciers smaller than 1 km². Of all the glaciers in Svalbard, only 9% have been directly observed to surge in Svalbard. Since the 2000s, satellite monitoring has enabled detection of most surges of glaciers with large catchments, and the launch of the Copernicus Sentinels in 2014 has further enhanced our monitoring capabilities. Current surge detection is based upon tracking the speed of glaciers over time, elevation changes, terminus advances particularly in historical data sets, and more recently automatically detecting surface changes related to a surge such as increased crevassing. Geophysical sensors are critical for observing subglacial conditions and further work is required to improve deployment strategies on heavily crevassed glaciers. Past surge behaviour can be inferred by employing a landsystems approach and using historical archives such as maps, photographs and field notes. Improvements in our ability to detect surges has started to reveal more complex surge dynamics that suggests the binary classification of a glacier as surge-type or not breaks down. This has implications for how we understand the mechanisms through which glaciers build up energy during quiescence which enables ice flow acceleration during a surge.

How to cite: Harcourt, W. D., Pearce, D. M., Gajek, W., Lovell, H., Kääb, A., Benn, D. I., Luckman, A., Hann, R., Kohler, J., Mannerfelt, E. S., Strozzi, T., McCerery, R., and Davies, B.: The distribution of glacier surge behaviour in Svalbard and implications for understanding unstable ice flow, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12624, https://doi.org/10.5194/egusphere-egu25-12624, 2025.

Belvedere Glacier, in Italy, is the Alpine glacier with the highest elevation jump, starting from the East Massif of Monte Rosa over 4,000 m a.s.l., and with an ablation area ending at ca. 1,900 m a.s.l. . The deep debris layer, which covers and insulates the tongue of the glacier is indeed the reason why it still persists at such low altitudes. The modelling of dark glaciers melt and dynamics is made difficult by the changing debris cover layer. Here, thanks to the measurements campaign on Belvedere Glacier of 2024, where we installed a climate station, several thermistors, and ablation stakes, we calibrated an energy balance model to mimic ice melt. We also assessed debris layer thickness by reversing energy balance model using infrared satellite images. Dynamics of the glacier was modelled using Glen flow law and GPR measurements of ice thickness. 
By coupling the energy balance model to Poli-Hydro hydrological model we were able to mimic the evolution of the glacier and the water resources of the area up to 2100 using 6 GCM from AR6.

How to cite: Dezuanni, P., Stucchi, L., Fugazza, D., Barbone, D., and Bocchiola, D.: Physical modelling of the retreat of Belvedere Glacier through the 21st century, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12993, https://doi.org/10.5194/egusphere-egu25-12993, 2025.

Slip at the ice-bed interface (basal motion) dominates the flow of many glaciers, and it is uncertain whether this velocity component will increase or slow in a warmer world. Past results from an idealized flowline glacier model show that declining basal motion induces a two-phase response that initially accelerates glacier retreat in a warming climate on a multidecadal timescale but lessens centennial-scale retreat and mass loss. In the present work, we utilize existing field-collected and remotely-sensed constraints on ice thickness, ice surface velocity, and the change in each of these terms to constrain the current rate of basal motion and its change over the past ~40 years. We focus on the ~1500 global glaciers with higher density of field-based ice thickness measurements in the GlaThiDa dataset (>18 measurements points per glacier). Utilizing these ice thickness and surface velocity constraints, we employ a flow model to estimate the rate of basal motion as the residual between observed surface velocity and modeled ice deformation. We first estimate the contribution of varying basal motion to observed changes in surface velocity across the study glaciers.  We then estimate these glaciers’ retreat and thinning responses to changing velocity and compare these with the magnitudes expected from atmospheric warming, constrained by published point measurements, mass balance models, and snowline observations. These results will constrain the extent to which evolving ice dynamics have amplified or mitigated the response of global glaciers to climate change over past decades. Further, this knowledge will provide insight into the potential importance of varying basal motion on projections of future glacier change, with implications for global sea level rise as well as local water resource and ecosystem management.

How to cite: Armstrong, W., Dehecq, A., Hock, R., Brun, F., Gagliardini, O., Gillet-Chaulet, F., Gilbert, A., Gimbert, F., Millan, R., and Vincent, C.: Investigating the role of evolving basal motion in modulating global glacier change, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13219, https://doi.org/10.5194/egusphere-egu25-13219, 2025.

Glaciers in the European Alps have experienced strong area and volume loss since the end of the Little Ice Age (LIA) around the year 1850. How large these losses were was so far only poorly known, as published estimates of area loss were mostly based on simple up-scaling and alpine-wide reconstructions of LIA glacier surfaces were lacking. For this study, we compiled all digitally available LIA glacier extents for the Alps and added missing outlines for glaciers >0.1 km² by manual digitizing. This was based on geomorphologic interpretation of moraines and trimlines on very high-resolution satellite images available from web-map services in combination with historic topographic maps and modern glacier outlines.

From this dataset we determined glacier area changes for all glaciers with LIA extents at a regional scale and reconstructed glacier surfaces with a Geographic Information System (GIS) to calculate (a) glacier volume changes for the entire region from the LIA until around 2015 and (b) total LIA glacier volume in combination with a reconstructed glacier bed. The glacier area shrunk from 4244 km² at the LIA maximum to 1806 km² in 2015 (-57%) and total volume was reduced from about 280±43 km³ around 1850 to 100±17 km³ (-64%) in 2015, roughly in line with previous estimates. On average, glacier surfaces lowered by 44 m from the LIA until 2015 (-0.26 m a^-1), which is three-times less than observed over the 2000 to 2015 period (-0.82 m a^-1) according to Hugonnet et al. (2021). Many glaciers have now only remnants of their former coverage left and at least 1938 glaciers melted away completely, which led to the deglaciation of entire mountain catchments.

The new datasets are made freely available to support a wide range of studies related to the determination of climate change impacts in the Alps. We will present the different input datasets and their uncertainties, the method applied to reconstruct glacier surfaces and the spatial variability of glacier area and volume changes in the Alps since the LIA.

How to cite: Reinthaler, J. and Paul, F.: Reconstructed glacier area and volume changes in the European Alps since the Little Ice Age, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13294, https://doi.org/10.5194/egusphere-egu25-13294, 2025.

Glacier-climate models are crucial for understanding and predicting climate change impacts on snow and glacier-fed regions. However, their accuracy depends heavily on the quality of climate input data. While general circulation models (GCMs) provide broad-scale insights, their coarse spatial resolution limits their ability to capture fine-scale climatic variability, especially in complex mountainous regions. We integrate high-resolution Regional Climate Models (RCMs) and Convection-Permitting Models (CPMs) into a glacier-climate coupled model namely Open Global Glacier Model (OGGM) to improve equilibrium line altitude (ELA) projections for the glaciers of Aosta valley. We calibrate OGGM using the snow line altitude (SLA) dataset. SLA at the end of the ablation season is an indicator of climate change and a proxy to equilibrium line altitude (ELA). We compute SLA by incorporating satellite imagery of Landsat data for calibration period through image segmentation. K-Means Clustering is utilizing to divide the image into three classes: snow, ice and barren. By computing snow cover ratio across various elevations, the SLA is computed. The clustered classes are validated with manual segmentation while the SLA time series is by the dataset provided by the World Glacier Monitoring Service (WGMS). Historical ELA is constructed based on the Historical Instrumental climatological Time series of the greater Alpine region (HISTALP) for the calibration period. The calibration period gives Pearson’s correlation coefficient of 0.69. We force the high resolution RCMS and CPMs for both the historical period (1985-2005) and future period (2006-2100). The reason is to validate the model for both periods and to analyze whether the provided models perform well in the historical period or not. The RCMs and the CPMs offer advantages over the GCMs by resolving finer-scale atmospheric processes, such as orographic precipitation and temperature gradients, crucial for accurate glacier modeling. Our results indicate that the RCM and the CPM  reduce biases in the ELA predictions, aligning more closely with observational data compared to GCM-driven simulations. These advancements highlight the transformative potential of high-resolution climate models in glacier research, offering more reliable projections of glacier mass loss, water resource availability, and climate-driven hazards in alpine regions.

How to cite: Ayub, S., Camporeale, C., Ridolfi, L., Coppola, E., and Godio, A.: Enhancing Glacier-Climate Modeling: Integrating High-Resolution Climate Models for Improved Equilibrium Line Altitude Projections in the Alpine Glaciers, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15055, https://doi.org/10.5194/egusphere-egu25-15055, 2025.

In the Southern Volcanic Zone of the Andes (~33°S - ~46°S), glaciers occur only on the highest peaks of active volcanoes. Many of these glaciers, hence, are located within craters or calderas that have a bowl-shaped basal geometry atypical to other mountain glaciers. Volcán Sollipulli, located at about 39° S, hosts a massive glacier that fills a caldera (diameter of ~4 km), with a relatively flat surface elevation of ~2060 m in 2023/2024. Ground-penetrating radar data from 2013 suggested a maximum ice thickness of approximately 750 m, making it the deepest measured body of ice in Chile, north of the Patagonian Ice Fields, thus harboring a vast amount of freshwater. Glaciers in the southern Andes are undergoing unabated retreat, resulting in reduced freshwater storage, increasing contribution to sea-level rise, and leading to the formation of glacial lakes, which implies the potential risk of glacial lake outburst floods (GLOFs).

We present a glaciological study of the caldera Sollipulli glacier, investigating the glacier surface elevation over the last decades using remote sensing data and field measurements, and discuss potential effects of the atypical geometry on its future evolution. While the glacier was already losing mass in the 2000 – 2015 period, our results show a nearly two-fold increase in melt rates since then, resulting in more than 60-m glacier thinning during the 21st century. The increasing melt coincides with observations of late summer snow absence on the entire glacier. This indicates that the freezing level has risen above the maximum glacier surface altitude, leading to shrinkage of the accumulation zone to a minimum or its disappearance. In consequence, the surface-lowering induced melt-elevation feedback is now further enhancing mass loss, in addition to the increased climate forcing. The evolution of existing and new marginal glacial lakes is providing hints on glacier hydrology and provides insights on the potential future lake formation that could affect the glacier’s role as a freshwater reservoir and GLOF risk.

How to cite: Arndt, J. E., Somos, M., Farías, D., Navas, S., Rivera, A., Xie, H., and Fernández, A.: Evolution of the caldera-filling glacier at Volcán Sollipulli, Chile, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15883, https://doi.org/10.5194/egusphere-egu25-15883, 2025.

The existence of cold firn and ice within the European Alps provides an invaluable source of paleoclimatic data with the capability to reveal the nature of anthropogenic forcing in Western Europe over the preceding centuries. Unfortunately, continued atmospheric warming has initiated the thermal degradation of cold firn to that of a temperate firn facie, where infiltrating meltwater compromises this vital archive. However, there is currently limited knowledge regarding the physical transition of firn between these different thermal regimes.

We present the application of a modified version of the spatially distributed Coupled Snow and Ice Model in Python (COSIPY) to the high-altitude glacierised saddle of Colle Gnifetti (4,450 m a.s.l.) of the Monte Rosa massif, Swiss/Italian Alps. Forced by an extensively quality-checked meteorological time series from the Capanna Margherita (4,560 m a.s.l.), with a distributed accumulation model to represent the prevalent on-site wind scouring patterns, the evolution of the cold firn’s thermal regime is investigated between 2003 and 2023. Our results show a continuation of previously identified trends of increasing surface melt at a rate of 0.54 cm w.e. yr ⁻², representing a doubling over the 21-year period. This influx of additional meltwater and the resulting latent heat release from refreezing drives englacial warming at a rate of 0.045 °C yr ⁻¹, comparable to in-situ measurements. Since 1991, a measured warming of 1.5 °C (0.046 °C yr ⁻¹) has been observed at 20 m depth with a marked inversion in the temperature gradient developing in the 15-30 m depth range. While this remains below the local rate of atmospheric warming (0.073 °C yr ⁻¹), in lower altitude regions (∼ 4,300 m a.s.l.) simulated warming is considerably greater suggesting a rapid transition from cold to temperate firn is occurring – potentially indicative of future conditions at Colle Gnifetti. However, uncertainty is high in this region as the simulation is particularly sensitive to changes to the model’s parameterisations – principally those controlling albedo and percolation – and crucially the length and simulated depth of the model spin-up.

Our research also greatly contributed to the development of the latest version 2.0 of the COSIPY model which includes critical bug fixes, the addition of new parameterisations and performance enhancements to benefit the wider modelling community.

How to cite: Gastaldello, M., Mattea, E., Hoelzle, M., and Machguth, H.: Modelling Cold Firn Evolution at Colle Gnifetti, Swiss/Italian Alps, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17699, https://doi.org/10.5194/egusphere-egu25-17699, 2025.

Due to ongoing glacier shrinkage caused by anthropogenic climate change, Col de Tsanfleuron (2803 m a.s.l.) in the western Swiss Alps, a former ice pass separating two neighbouring small mountain glaciers (Glacier de Tsanfleuron and Glacier du Sex Rouge), became ice-free in September 2022. The question arose as to whether or not the pass had – until 2022 – always been ice-covered throughout the Holocene. Both bedrock lithology of the now ice-free pass and anthropogenic disturbance likely impedes the application of surface exposure dating to answer this question. Therefore, the glaciers’ evolution was modelled from 11.5 ka until 2100 CE using the Instructed Glacier Model (IGM). Model calibration was carried out based on available glacier mass balance data. Due to the different quality and spatiotemporal resolution of available climate data, two different model runs were performed for the past (one from 11.5 ka to 2000 CE, and a second one from the Little Ice Age maximum (1850) to 2020). In addition, the future evolution of both glaciers was modelled until 2100 using an ensemble of 10 different GCM-RCM model chains for three different RCP scenarios. The three model runs were initialised with reconstructed or observational data for glacier extent, surface elevation and ice thickness. Validation of the modelling results was performed based on known evidence of Holocene glacier fluctuations in the Alps as well as using available 1850-present glacier area and volume data.

Even though the modelled fluctuations of Glacier de Tsanfleuron and Glacier du Sex Rouge show high temporal coherence with known advance and retreat phases for other alpine glaciers, modelled glacier extents and volumes are larger for the entire Holocene compared to in-situ measurements in 2019. According to preliminary modelling results, Col de Tsanfleuron was likely ice-covered throughout the Holocene until 2022. These results partly contrast with other studies, suggesting for instance that in the Alps various summits at higher altitude had been ice-free during the Holocene Thermal Maximum (~10.2 to ~4.2 ka). On the other hand, there is evidence that individual small alpine glaciers persisted during the entire Holocene. Our modelling results are subject to various uncertainties, e.g. related to the initial glacier area, surface elevation and volume, related to the climate data sets used, or related to the melt parameters applied and the modelling approach itself. For the period 1850-2020, our model is able to realistically trace the glaciers’ evolution at high spatiotemporal scale. Modelling results for the future predict the ultimate disappearance of both glaciers. Glacier du Sex Rouge will have completely vanished by around 2040, whereas, depending on the modelled climate scenario, the latest remnants of Glacier de Tsanfleuron will disappear between 2060 and 2080.

How to cite: Schild, J., Fischer, M., and Jouvet, G.: Modelling the fluctuations of two small alpine glaciers (Glacier de Tsanfleuron and Glacier du Sex Rouge, western Swiss Alps) throughout the Holocene (11.5 ka – 2100 CE), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18463, https://doi.org/10.5194/egusphere-egu25-18463, 2025.

Observed glacier melt is a hallmark of modern climate change, yet a comprehensive attribution of industrial-era glacier retreat to human-caused warming remains to be settled. This challenge stems from difficulties in accurately simulating individual glacier behavior, which depends on poorly constrained factors like local geometry and historical climate conditions.  Here, we adapt methodologies that have previously been applied to industrial-era temperature attribution, and apply them towards climate metrics of specific relevance to glacier mass balance. We use historical and natural-forcing-only simulations from the CMIP5 and CMIP6 climate-model archives, along with observational products of near-surface temperature (e.g. Berkeley Earth) to create a global map of anthropogenic melt-season temperature change. These temperature changes are translated into shifts in equilibrium line altitude (ELA), the boundary between a glacier’s accumulation and ablation zones.  By applying these ELA shifts to example glacier profiles that match known Little Ice Age extents, we estimate the changes in ablation area and rates resulting from anthropogenic activity.  This approach offers fresh insights on quantifying the impact of anthropogenic emissions on modern glacier retreat globally.

How to cite: Berdahl, M., Christian, J., Steig, E., and Roe, G.: Adapting temperature-attribution methodologies to understand industrial-era glacier retreat, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20608, https://doi.org/10.5194/egusphere-egu25-20608, 2025.

The surface mass balance (SMB) of glaciers represents the link between glaciers and their local climate. Quantifying the SMB is essential for calibrating glacier mass-balance models, improving our understanding of the glacier’s response to a changing climate, which affects freshwater availability, sea-level rise, and the risk of natural hazards, among others.

While the SMB cannot be measured directly from space, it can be derived from observations of elevation change, ice velocity, and ice thickness (gradients). Such approaches have been successfully applied in detailed studies of individual glaciers with high spatial and temporal data coverage. However, extending these efforts to regional or global scales present significant challenges due to inconsistent temporal data coverage, coarse spatial resolution, and large uncertainties linked to regional datasets. As a result, many regional glacier evolution models continue to rely on single glacier-wide average mass-balance estimates from long-term geodetic elevation change measurements for model calibration. However, this can lead to model overparameterization and equifinality problems, which are major sources of uncertainty in projections. With the advent of extensive remote sensing datasets and machine learning approaches, there is now an unprecedented opportunity to estimate spatial SMB patterns across glaciers, on regional to global scales.

In this study, we estimate spatial SMB patterns on glaciers in the Swiss Alps with a generalised approach that does not rely on high spatial coverage from in-situ measurements, but rather on datasets with a regional availability. More specifically, we use observational datasets of ice thickness and ice velocity fields derived from remote sensing to calculate the ice flux divergence and combine this with the continuity equation for ice thickness and observations of elevation change to estimate spatial SMB patterns. To optimize the calculation of the ice flux divergence, which relies on non-local ice flow behaviour, we employ a machine learning approach to determine the best filtering (smoothing) parameters for the spatial velocity and thickness gradients. The performance of the method is assessed by comparing SMB estimates with in-situ SMB values derived from stake measurements. This study aims at providing a scalable framework for estimating spatially resolved SMB patterns, with potential applications at the global scale.

How to cite: Izeboud, M., Van Tricht, L., and Zekollari, H.: Glacier Blueprints: Deriving Spatial Surface Mass Balance from Remote Sensing at a Regional Scale with Machine Learning, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-200, https://doi.org/10.5194/egusphere-egu25-200, 2025.

Alpine glaciers are analogues to remote polar ice streams and serve as accessible natural 
laboratories for understanding the key processes driving ice flow. Here, we capture temporal 
variability of surface velocities as a proxy for processes at the glacier bed using a terrestrial radar 
interferometer (GPRI, GAMMA Portable Radar Interferometer). We conducted two field 
campaigns in October 2023 and June 2024 to measure velocity variability over several days at a 
temporal resolution of three minutes. We focus on a steep icefall zone in which the onset of basal 
sliding is hypothesized. A common challenge in processing terrestrial radar data is the 
contribution of atmospheric turbulence to the measured interferometric phase. To reduce this 
effect, we stack 2653 (1420) one-hour interferograms for each of the two field campaigns. After 
stacking, displacement on fixed rock walls is minimal compared to the mean ice velocity. Across 
both time series, we captured velocity variability on daily as well as seasonal time scales. On the 
steep ice fall, mean velocity differences between the fall and spring campaigns show ~30% faster 
flow in the spring season, when more surface meltwater may lubricate the glacier bed leading to 
seasonally accelerated glacier flow. This research highlights the effectiveness and challenges of 
terrestrial radar interferometry and provides valuable information for understanding glacier 
dynamics in alpine environments.

How to cite: Konietzko, J., Wild, C. T., Muhle, L. S., Drews, R., and Mantelli, E.: Glacier Flow Dynamics from Terrestrial Radar Interferometry: Grenzgletscher, Switzerland , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-943, https://doi.org/10.5194/egusphere-egu25-943, 2025.

The retreat of glaciers has received considerable attention due to its implications for water availability and hydropower generation, thereby raising significant concerns for both the environment and society. Consequently, understanding the impact of climate on glacier evolution has become essential. In the present study, we investigate the application of various Machine Learning/Deep Learning models, specifically Linear Regression, Neural Networks, XG Boost, and Random Forest, to predict surface mass balance across two geographically distinct regions: the Swiss Alps and Svalbard. We also compared and analyzed different input datasets, such as ERA5, ERA5-Land (higher resolution), and a downscaled climate dataset to understand the impact of selecting different climate datasets and spatial resolutions. The performance of these models is evaluated based on different combinations of input variables to ascertain their impact on prediction accuracy.

How to cite: Moudgil, P. S., Bij de Vaate, I., Hock, R., and Guillet, G.: Predicting Surface Mass Balance of Valley Glacier using Machine Learning, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3927, https://doi.org/10.5194/egusphere-egu25-3927, 2025.

Melting glaciers are icons of the climate crisis and severely impact local geohazards, regional freshwater availability, and global sea levels. Well-constrained observations of glacier mass change and associated uncertainties are required to assess these downstream impacts and provide the baseline for calibrating and validating models for future projections. Previous assessments of global glacier mass changes were hampered by spatial and temporal limitations and the heterogeneity of datasets from different observation methods. The Glacier Mass Balance Intercomparison Exercise (GlaMBIE; https://glambie.org) set out to tackle these challenges through a community effort to collect, homogenise, combine, and analyse glacier mass changes from in situ and remote-sensing observations.

This presentation summarises the results and lessons learned from the first GlaMBIE (2022−24) and introduces GlaMBIE-2, which runs from 2025 to 2026. In GlaMBIE-2, we aim to compile additional mass-change estimates to broaden observational coverage from different methods, extend the data series back to 1992 to align with available ice-sheet estimates, and update the time series to 2025 to cover the latest developments. In addition, we are running pilot studies to better understand the apparent bias between digital elevation model (DEM) differencing and altimetry and to increase the spatio-temporal resolution of our estimates to further hydrological applications. We invite the research community to participate in this collaborative effort by contributing their expertise and glacier mass change data, whether from in situ observations, repeat mapping from optical imaging and radar interferometry, laser and radar altimetry, and gravimetry.

How to cite: Zemp, M., Gourmelen, N., Jakob, L., Nussbaumer, S. U., Welty, E., and Berthier, E.: The second Glacier Mass Balance Intercomparison Exercise 2025–26 – a Call for Data & Participation, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5164, https://doi.org/10.5194/egusphere-egu25-5164, 2025.

On-glacier avalanches contribute to non-linear mass balance patterns and, by channeling snow from upper headwalls onto the glacier surface, can maintain glaciers at low elevations despite increasing temperatures. Here we combine a gravitational snow redistribution model estimating avalanching with the Open Global Glacier Model (OGGM) to quantify the current and future contribution of avalanches to glacier mass balance for all mountain glaciers in the world. The avalanche contribution is added as a multiplicative correction factor of solid precipitation per elevation band, and the resulting mass balance is calibrated against global-scale geodetic data based on DEM differencing. The avalanche model is evaluated against a set of remote sensing observations at various spatial scales, including flux inversions and avalanche deposit outlines from Sentinel-1, and the influence of avalanches is quantified using ensemble simulations with CMIP6 climate data until 2100.

The model results show that avalanches can contribute substantially to glacier mass balance, with a strong spatial variability between glaciers and regions. The region most affected is New Zealand, with 19% of the total snow accumulation originating from avalanches on average. At the glacier scale, this avalanche contribution shows a strong variability that depends on glacier area and slope. Some glaciers more than double their snow accumulation while others lose mass by avalanching, and accounting for this contribution leads to more local variability in the mass balance gradients. We find that, at the regional scale and for many individual glaciers, accounting for avalanching has little impact on the simulated future evolution of glacier volume. This is because the effect of avalanching is already implicitly taken into account in the calibration against glacier-specific geodetic mass balance. However, for individual glaciers, explicitly accounting for the effect of avalanches can substantially impact the projected evolution. This is especially relevant for small glaciers at low elevations that, in the model simulations, may survive several decades longer than they would otherwise. We also find indications that removal of snow by avalanching may lead to a higher sensitivity to warming, and therefore faster thinning of steep glaciers at high elevation.

How to cite: Kneib, M., Maussion, F., Carcanade, G., Brun, F., Farinotti, D., Huss, M., van Tiel, M., Jouberton, A., and Champollion, N.: Contributions of avalanches to glacier mass balance at the global scale, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6326, https://doi.org/10.5194/egusphere-egu25-6326, 2025.

Rocky debris layers cover an increasing portion of glacier ablation areas as glaciers thin and retreat in response to climate change, progressively altering surface melt rates. However, determining the thickness and physical properties of supraglacial debris that are required for accurate representation of debris in glacier melt models is challenging, and measurements are scarce. Here, we provide an openly available dataset (DebDab, https://zenodo.org/records/14224835) that compiles physical properties and thickness of supraglacial debris over 83 glaciers in 13 regions of the Randolph Glacier Inventory. The majority of the database (90%) is compiled from 172 sources in the literature, while the remaining 10% has not been published before. DebDab contains 8,286 data entries for supraglacial debris thickness, of which 1,852 include sub-debris ablation rates too, 167 data entries of thermal conductivity of debris, 157 of aerodynamic surface roughness length, 77 of debris albedo, 56 of debris emissivity and 37 of debris porosity. We show regional differences in the distribution of debris thickness measurements, as well as an uneven spatial coverage with well-sampled regions like Central Europe and South Asia, but gaps in the Andes and  Alaska. Additionally, debris thickness measurements are mostly concentrated at lower glacier elevations, leaving mid-glacier areas under-sampled, which may affect the dataset's representativeness. We also provide the most detailed scatter plot of debris thickness and ablation rates yet, with Østrem curves fitted for 19 glaciers, based entirely on observational data, and supporting the well-documented reduction in melt rates after the initial few centimetres of debris and the subsequent minimal reduction in melt rates for thicker debris. DebDab can be used in energy balance, melt and surface mass balance models by incorporating site-specific debris properties, or to evaluate remote  sensing estimates of debris thickness and surface roughness. It can also help future field campaigns on debris-covered glaciers by identifying undersampled regions, glaciers and properties. DebDab is open to new data submissions from the community as more data of supraglacial debris properties become available. 

How to cite: Fontrodona-Bach, A., Groeneveld, L., Miles, E., McCarthy, M., Shaw, T., Melo Velasco, V., and Pellicciotti, F.: DebDab: A database of physical properties of supraglacial debris, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10102, https://doi.org/10.5194/egusphere-egu25-10102, 2025.

Globally, mountain glaciers are retreating under the effects of climate change. Many of these mountain glaciers are part of important water tower regions (Immerzeel et al., 2020), and their retreat threatens the water security of local communities and downstream catchments. In the Semi-Arid Chilean Andes, mountain glaciers are particularly important as water from precipitation is limited in this arid climate, which is currently experiencing a ‘mega drought’.   However, estimating the changing ice volume is challenging due to two key reasons. Firstly, a large proportion of the glaciers are small in extent and have a high degree of debris-cover, meaning the ice extent is challenging to measure using satellite remote sensing data. This is most pronounced in the case of rock glaciers, which are numerous in this region. Secondly, there are few in situ observations of ice thickness and extent to validate the multispectral remote sensing observations. Given this context, we present new observations of glacier elevation changes using derived from recently acquired Synthetic Aperture Radar (SAR) observations. This work aims to better understand how glacier mass balance in the Semi-Arid Chilean Andes affects water resources for downstream catchments, and we evaluate the applicability of the SAR data including ESA’s Sentinel-1 in this context. We use DEM differencing and radar backscatter analyses to study glacier changes in order to track retreat and estimate changing ice content. We will present the findings of this work and comment on the possible opportunities and limitations this approach offers.

How to cite: Fox, E., Palmer, S., Rangecroft, S., Harrison, S., and Schwartz-Marin, E.: Glacier elevation changes in the Semi-Arid Chilean Andes from Synthetic Aperture Radar, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11234, https://doi.org/10.5194/egusphere-egu25-11234, 2025.

Quantifying the ongoing retreat of glaciers and ice sheets – and projecting their futures – are major societal concerns due to their contribution to sea-level rise and influence on water resources, natural hazards, and associated socioeconomic impacts. However, our ability to confidently project glacier and ice-sheet mass change is often limited by a severe lack of  observations that reliably constrain both their input (snow) and output (flow) mass fluxes. To address these needs, in April 2024 NASA selected Snow4Flow as an Earth Venture Suborbital (EVS-4) mission. Snow4Flow will capture the spatial variability in snow accumulation and ice volume across 4 Arctic and near-Arctic regions that contain hundreds of rapidly changing glaciers to deliver more reliable, societally relevant projections of land-ice change. Our target areas are Alaska and far western Canada, southeastern Greenland, the Canadian High Arctic, and Svalbard. We will perform spatially extensive multi-frequency airborne radar-sounding surveys in March–May 2027–2029, in conjunction with ground-validation campaigns. Snow4Flow will drive foundational improvements to Northern Hemisphere land-ice boundary conditions and forcing data, including orographic precipitation patterns in alpine environments, ice thickness and subglacial topography, and will directly leverage them into state-of-the-art models and projections. All associated software, datasets and model outputs will be rapidly and openly distributed to enable both independent use and assessment, along with portability to other glacierized regions on Earth.

How to cite: Holt, J. W., MacGregor, J., and Andrews, L. C.: Snow4Flow: A new NASA airborne mission to measure and model the state and fate of Arctic glaciers, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12435, https://doi.org/10.5194/egusphere-egu25-12435, 2025.

Monitoring glacier flow velocity on the Greenland Ice Sheet is crucial for understanding mass balance and assessing its impact on sea level rise. However, the present high temporal resolution velocity primarily derived from Sentinel-1 SAR data, often exhibit gaps during melt seasons due to daily freeze-thaw cycles on the ice surface. 

Here, we constructed a 6-day velocity time series from 2017 to 2021 for six outlet glaciers to comprehensively capture their velocity variations by combining Sentinel-1 and -2 data, including Petermann Glacier, Jakobshavn Isbræ, Helheim Glacier, Kangerlussuaq Glacier, Nioghalvfjerdsfjorden Glacier, and Zachariæ Isstrøm Glacier. The offset-tracking technique was applied to derive initial velocity time series from SAR and optical data separately, pairing each image with its three subsequent acquisitions. A least squares method based on connected components then calculates the time series for Sentinel-1 and Sentinel-2 separately, which were then fused using a weighted least squares method, with weights determined by RMSEs. 

Sentinel-2 data effectively filled the summer gaps of the glacier velocity time series that only generated with Sentinel-1 imagery (such as NSIDC-0766), improving the coverage rates by over 30% in summer. The filled gaps concentrated in the elevation range of 600-1400 meter for Petermann Glacier, Nioghalvfjerdsfjorden Glacier, and Zachariæ Isstrøm Glacier, while for Jakobshavn Isbræ, it was most prominent between 1000-1800 meter. The coverage increase for Helheim Glacier and Kangerlussuaq Glacier is most significant in the elevation of 1500-2000 meter. These improvements are primarily observed in the radar glacier zones of wet snow zone and the percolation zone, where daily freeze-thaw more frequently occurred, leading to decoherent of its surface backscattering. In contrast, improvements are less pronounced at the dry snow zone where no thawing occurs and ice crevasses distributed glacier terminus with abundant features for offset-tracking.

At the groundline, Petermann exhibited relatively stable flow, ranging from 1.17 to 1.20 km/yr. Jakobshavn Isbræ showed significant variability, peaking at 4.39 km/yr in 2019 before declining to 2.52 km/yr in 2021. Helheim displayed lower velocities, ranging from 0.15 to 0.26 km/yr, while Kangerlussuaq maintained consistently high flow rates of 4.16 to 4.57 km/yr. Zachariæ Isstrøm demonstrated a steady increase from 0.68 to 0.74 km/yr, and Nioghalvfjerdsfjorden showed minor variations, ranging from 1.14 to 1.17 km/yr. The velocity map gap filled by Sentinel-2 revealed quicker flow rates during the summer months, especially for Jakobshavn Isbræ, Kangerlussuaq, and Zachariæ Isstrøm , reaching up to 1.0 m/day, indicating a lower estimation of the glacier mass loss with the flux gate method. As for other outlet glaciers, Petermann Glacier, Nioghalvfjerdsfjorden Glacier and Helheim Glacier, the underestimation of velocity using only Sentinel-1 velocity time series was more pronounced further from the glacier terminus. Precision analysis shows the Sentinel-1 offset-tracking precision is approximately 10 times better than that of Sentinel-2, emphasizing the importance of weighted fusion when combining the datasets.

How to cite: Mao, Y., Li, G., and Chen, Z.: Integrating Sentinel-2 and Sentinel-1 Imagery to Analyze Glacier Velocity Variability of Six Outlet Glaciers in Greenland, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15276, https://doi.org/10.5194/egusphere-egu25-15276, 2025.

Glacier surges are spectacular events that lead to surface elevation changes of tens of meters in a period of a few months to a few years, with different patterns of mass transport. They can result in surface elevation changes of more than 100 m in a few months. Recent developments in remote sensing have enabled the estimation of glacier elevation change and surface velocity at monthly resolution. These two variables are crucial to constrain the physical mechanisms responsible for glacier surges.

In this work, we exploit a large archive of Digital Elevation Models (DEMs) over 2000-2019 from the ASTER optical satellite sensor. The time series is filtered and homogenized to monthly elevations, in order to study surging glaciers in the Karakoram (Beraud et al., under review). This workflow implements a LOWESS method – locally weighted polynomial regression for filtering and a B-spline method ALPS-REML as elevation temporal interpolation. Additionally, we use ITS_LIVE glacier surface velocities, regularized to monthly dates using the temporal closure of the displacement measurement network (Charrier et al., 2022).

On the modelling side, Thogersen et al. (2019; 2024) theorised a surge propagation mechanism based on the rate and state approach of basal friction. They found that, first, a surge is triggered when a shear stress is reached over a sufficiently large area and, second, it exists relationship between the velocity of the surge front propagation and the sliding velocity. We then explore over about five glaciers the ability of the two datasets to test Thogersen's theory of surge initiation and propagation.

References:

Beraud, L., Brun, F., Dehecq, A., Hugonnet, R., and Shekhar, P.: Glacier surge monitoring from temporally dense elevation time series: application to an ASTER dataset over the Karakoram region, https://doi.org/10.5194/egusphere-2024-3480, In review.

Charrier, L., Yan, Y., Koeniguer, E. C., Leinss, S., and Trouve, E.: Extraction of Velocity Time Series With an Optimal Temporal Sampling From Displacement Observation Networks, IEEE Transactions on Geoscience and Remote Sensing, 60, 1–10, https://doi.org/10.1109/TGRS.2021.3128289, 2022

Thøgersen, K., Gilbert, A., Schuler, T. V., and Malthe-Sørenssen, A.: Rate-and-state friction explains glacier surge propagation, Nature Communications, 10, 2823, https://doi.org/10.1038/s41467-019-10506-4, 2019.

Thøgersen, K., Gilbert, A., Bouchayer, C., and Schuler, T. V.: Glacier Surges Controlled by the Close Interplay Between Subglacial Friction and Drainage, Journal of Geophysical Research: Earth Surface, 129, e2023JF007 441, https://doi.org/10.1029/2023JF007441, 2024.

How to cite: Béraud, L., Dehecq, A., Brun, F., Gilbert, A., Charrier, L., Hugonnet, R., and Shekhar, P.: Regional observation of glacier surges from space: monthly time series and application to physical theories., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16010, https://doi.org/10.5194/egusphere-egu25-16010, 2025.

Long-term observations of glacier dynamics are crucial for understanding past climatic shifts and assessing current glacier conditions. The Ladakh region, known for its high-altitude arid landscape, amasses about 40% of Indian glacier wealth, which is vital for local communities who rely on meltwater for their water needs. However, human-induced warming has accelerated glacier depletion globally, including in the Trans-Himalayas. Despite its importance, Ladakh remains underrepresented in glaciological research, highlighting the need for continued studies on glacier dynamics in the region. Glacier velocity and mass balance is interlinked with each other and is a manifestation of mass change in the glacier system. This study aims to present inter-annual glacier velocity over the Rulung and Gyama massifs of Karzok range, Ladakh using the global dataset i.e. ITS_LIVE which is available from 1980s to 2018, calculated using multiple satellite missions. Furthermore, mass balance calculations are performed to quantify changes in glacier mass. This study also evaluates the influence of both climatic and topographic factors on glacier dynamics. The Rulung and Gyama massifs contain 52 and 100 glaciers, respectively, covering total areas of 22.2 ± 1.4 km² and 44.9 ± 2.7 km². Notably, the glaciers in both massifs are relatively small, with average sizes of 0.39 km² for Rulung and 0.45 km² for Gyama. Consequently, the magnitude of glacier velocity is also low. The surface velocity of Rulung Glacier ranges from 0.37 ± 0.21 m/y to 8.17 ± 2.80 m/y, with an average of 2.33 ± 1.63 m/y. In contrast, the velocity of Gyama Glacier varies from 0.40 ± 0.11 m/y to 6.53 ± 3.32 m/y, with an average of 1.73 ± 0.70 m/y. Over the study period, the velocity across both massifs exhibited a decreasing trend, with an average slowdown of 0.05 m/y (31%) in Rulung and 0.01 m/y (8%) in Gyama. Both glaciers show a negative mass balance, with rates of -0.17 ± 0.03 m w.e./y for Rulung and -0.07 ± 0.01 m w.e./y for Gyama. The observed slowdown in glacier velocity and the associated mass loss can be attributed to sustained warming in the region and an erratic precipitation pattern, both of which primarily govern glacier dynamics. The decreasing velocity and negative mass balance are interlinked, as reduced flow rates often correlate with a loss of glacier mass, further accelerating the retreat and thinning of glaciers. Additionally, regional heterogeneity in velocity patterns can be explained by topographic factors, which exert a significant influence on glacier dynamics The overall decline in both glacier velocity and mass balance highlights the ongoing depletion of glaciers in the region, posing a substantial threat to water security and increasing the risk of natural hazards to communities living in close proximity to the glaciers. The study recommends timely attention towards depleting glaciers to better manage the important water resources. 

Keywords: Glacier changes, remote sensing, glacier mass balance, glacier velocity, climate change, Karzok Range, Ladakh Himalaya

How to cite: Prajapati, M., Garg, P. K., and Mukherjee, S.: Spatiotemporal glacier dynamics over the Rulung and Gyama massifs, Ladakh (2000–2018): Influences of topographic and climatic factors, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16727, https://doi.org/10.5194/egusphere-egu25-16727, 2025.

World-wide glaciers are losing mass which affects global sea-level, river runoff, freshwater influx to the oceans, glacier-related hazards, and landscape changes, with implications for human livelihoods and ecosystems.

Robust glacier mass balance estimates at a high temporal and spatial resolution are hence essential to effective adaptation strategies. 

We outline a probabilistic formalism, based on a modified particle scheme, for using stake, glacier wide, and geodetic mass balance measurements to infer the parameters of a numerical glacier evolution model - the Python Glacier Evolution Model, PyGEM. The particle method iteratively estimates the posterior probability distribution of the dynamical glacier state vector  while successfully accommodating data gaps as well as model nonlinearity and non-Gaussianity.

Our method is tested on different glaciers representing a broad range of climatic conditions and glacial contexts across Scandinavia. 

The approach leverages the combined strengths of the numerical model’s glacier physics-based predictive capabilities with the observations’ direct representation of glacier conditions, providing a robust estimate of glacier mass balance and its associated uncertainties.

This study underscores the value of Bayesian data assimilation, offering a robust and computationally tractable tool for estimating past, current and future glacier changes with high spatiotemporal coverage.

How to cite: Guillet, G., Aalstad, K., Yilmaz, Y., and Hock, R.: Long-Term Glacier Mass Balance Reanalysis Using Data Assimilation: Case Studies from Scandinavia, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17436, https://doi.org/10.5194/egusphere-egu25-17436, 2025.

Knowledge of ice thickness is essential for understanding past and predicting future changes of glaciers systems in response to climatic changes. Various methods exist on how to best estimate ice thickness from surface information in data sparse regions. These estimates are vital as they serve as starting point for future glacier evolution under different climatic scenarios.

These projections serve to determine future sea-level contribution or to inform adaptation or mitigation strategies required in response to glacier retreat.

Methods for mapping glacier ice thickness typically utilize surface information and combine it with the perfect plasticity assumption, mass-conservation or the stress balance to infer the unknown thickness distribution. In data sparse regions, estimates remain largely unconstrained and might deviate considerably not only on local scales.

Several maps of glacier ice thickness have been presented for Chile. Most of them however had global or at least a larger target region. So often site-specific measurements were not considered or at most for loose validation. This presents the first systematic effort to integrate local field measurements conduced by the Chilean Water Directorate (DGA) between 2012 and 2014 into an ice thickness reconstruction

These measurements of a constant basal shear stress (τy) at the ice-bedrock interface to infer ice thickness and subglacial topography. This approach avoids overly complex parametrization and is particularly well-suited for data-sparse regions. For this study, ice thickness was reconstructed using surface elevation, glacier outlines and extensive GPR measurements.

Validation results demonstrated achieving root mean square errir of 0.47 meters and a bias of 0.65 meter compared These findings underscore the importance of integrating local measurements with advanced modeling techniques to enhance the accuracy of ice-thickness maps in Chile.

How to cite: Berkhoff, J., Fürst, J., Sommer, C., Farias, D., Schaefer, M., Rodriguez, J. L., Uribe, J., and Ugalde, F.: Mapping glacier ice thickness in Chile, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18678, https://doi.org/10.5194/egusphere-egu25-18678, 2025.

Modelling the evolution of mountain glaciers in response to climate change is essential for accurate projections of global sea level rise and changes in the regional hydrological cycle. Glacier evolution and Earth system models applied at regional to global scales typically rely on simple temperature-index and snow accumulation models to describe spatio-temporal variations in glacier surface mass balance. The major advantage of temperature-index models over more complex energy balance models is their computational efficiency, the limited number of calibration parameters and the global availability of the required basic input data (i.e. air temperature and precipitation). However, temperature-index models based solely on an empirical relationship between melt and air temperature are not suitable for tropical and subtropical regions where incoming shortwave radiation and evaporation have a major control on the energy exchange at the glacier surface. In addition, several studies have shown that these models are oversensitive to air temperature variations and are not robust over time, so they need to be recalibrated for changing climatic conditions. This is problematic for forward modelling. Models of intermediate complexity, such as simplified energy balance models, are thought to be more robust over time and therefore more suitable for long-term modelling. The drawback of more complex models, however, is that they are more computationally expensive, require additional input data and have more degrees of freedom, making them prone to equifinality problems. Most glacier surface mass/energy balance models are now calibrated against geodetic observations available for basically any glacier worldwide. While these observations provide a consistent basis for model calibration, they do not allow the mass balance gradients to be constrained. This uncertainty can lead to large over- or underestimates of ablation and accumulation rates, with consequences for modelling glacier runoff and evolution. Here we present the results of a modelling experiment in which we compared the robustness and spatio-temporal transferability of two surface mass balance models of different complexity, constrained not only with geodetic but also with snowline observations automatically derived from Sentinel-2 data, for all monitored glaciers in the Alps. 

How to cite: Groos, A. R., Sommer, C., Tabone, I., and Fürst, J. J.: Surface mass balance modelling of the Alps constrained by geodetic and snow line observations, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20803, https://doi.org/10.5194/egusphere-egu25-20803, 2025.

The Southern Patagonian Icefield has been observed to exhibit one of the highest mass loss rates globally. However, the individual glaciers within this icefield show significant variations in their contributions to these loss rates, both in terms of space and time. This phenomenon is particularly evident in the glaciers Perito Moreno, Viedma, and Upsala, the latter being the largest glaciers in Argentina with its adjacent basins. Since the climatic sensitivity of lake-terminating glaciers can be strongly influenced by the bedrock topography, we surveyed these three glaciers for the first time with a 25 MHz helicopter-borne radio-echo sounding system.  The data was then incorporated into an state-of-the-art reconstruction approach to derive basin-wide ice thickness information and, subsequently, information regarding the subglacial bedrock topography. This enables the investigation of the potential of future glacier retreat due to the role of buoyancy-driven glacier calving. Furthermore, we analyzed the elevation changes from 2000 to 2024 based on SRTM and TanDEM-X microwave satellite data, the surface velocity evolution of these glaciers, and incorporated bathymetric measurements.

How to cite: Koch, M., Sommer, C., Blindow, N., Fürst, J. J., and Braun, M. H.: Unveiling the role of the bedrock topography on glacier evolution in Patagonia, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-21894, https://doi.org/10.5194/egusphere-egu25-21894, 2025.

The rapid shrinkage of glaciers in recent years is a result of global warming. Long-term, worldwide observations of glacier mass balance—excluding the Antarctic and Greenland ice sheets—based on satellite data indicate that estimated mass loss between 2000 and 2019 accounts for about 21 ± 3% of observed sea-level rise (Hugonnet et al., 2021). The retreat of glaciers is expected to have major environmental and social impacts; therefore, predicting future glacier responses to a changing climate is crucial for anticipating and mitigating these impacts (Bolibar et al., 2022).

One way to quantify glacier responses to climate change is by monitoring the equilibrium line altitude (ELA) (e.g., Zemp et al., 2007). The ELA is defined as the spatially averaged altitude on the glacier surface where the climatic mass balance is zero at a given time. Moreover, it represents the lowest boundary of climatic glacierization (Ohmura et al., 1992). Hence, analyzing changes over time in glacier ELA is important for predicting future glacier behavior. However, field-based ELA observations (the glaciological method) are limited to only a few hundred glaciers due to the considerable labor and time required. It is also possible to detect the ELA using optical satellite images (Rastner et al., 2019), but these observations are often restricted at the end of the snowmelt season by cloud cover or the polar night.

In contrast, synthetic aperture radar (SAR) is largely insensitive to weather conditions and can observe glaciers regardless of solar illumination or cloud cover. Additionally, glacier zones (such as firn, superimposed ice, and ice) could be distinguished using SAR images (Barzycka et al., 2023). The lower boundary of the firn area is referred to as the firn line. In temperate glaciers without superimposed ice, the altitude of the newly formed annual firn line can be considered equivalent to that year’s ELA. However, the firn line does not exhibit strong year-to-year variability because the previous year’s firn remains in place. Instead, multiple consecutive years of negative (or positive) mass balance will cause the firn line to retreat (or advance). Consequently, firn line variations tend to smooth out annual fluctuations, revealing long-term trends of ELA (König et al., 2002).

In this study, we investigated long-term changes in the firn line altitude (FLA) of two temperate glaciers (Taku glacier, Kesselwandferner) with extensive ELA observation records using a time series of L-band SAR images (JERS-1, ALOS, and ALOS-2). We then compared the SAR-derived FLA with ELA recorded in the long-term. The results indicate that the FLA is consistent with long-term ELA changes, suggesting that the SAR-derived FLA effectively captures the long-term trends in glacier ELA.

How to cite: Arie, K. and Tadono, T.: The detection of long-term changes in the glacial firn line using L-Band SAR, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3010, https://doi.org/10.5194/egusphere-egu25-3010, 2025.

Temporal variations of glacier velocity estimation are essential to understanding glacier dynamics and predicting glacier hazards. Therefore, in the current study, the continuous glacier velocities were estimated from 2014 to 2023 in the Nathorstbreen Glacier System (NGS), Svalbard, where a recent surge event was observed. Also, the study identified and quantified the factors controlling variations in annual glacier velocity. Using Landsat 8 OLI imageries, Cossi-corr, an advanced Fourier-based image-matching tool, was utilized to estimate the velocity of the NGS. After that, a multivariate regression analysis preceded by the backward stepwise selection method to identify the controlling factors of annual glacier velocity variations, considering temperature, precipitation, snowfall, and terminus fluctuations. The result indicates that the highest and lowest average yearly velocity of NGS was observed in 2021 and 2018 with a magnitude of 0.86 ± 0.11 m/day and 0.34 ± 0.18 m/day, respectively. An overall decline in velocity was observed between 2014 and 2018, followed by a resurgence between 2020 and 2022 and a final decline in 2023. The terminus of the glaciers show retreat and advancement annually, with an overall retreat of 2.9 km through the study period. Terminus fluctuations were identified as a key driver of annual glacier velocity, with a strong correlation between terminus movement in one year and velocity changes in the next. A 100-meter retreat increased the following year’s yearly velocity by around 9.2 meters, whereas a 100-meter advancement of terminus slowed down the following year's velocity with the same magnitude.

How to cite: Kim, H.-C. and Guha, S.: Temporal Glacier Velocity Variations and Their Controlling Factors in the Nathorstbreen Glacier System, Svalbard, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3886, https://doi.org/10.5194/egusphere-egu25-3886, 2025.

Glacier flow is a sensitive indicator of mass balance and dynamics. Monitoring changes in glacier flow at high temporal resolutions enables understanding of the glacier’s sensitivity to short term climate variability. Previous studies have found that the glaciers in High Mountain Asia (HMA) are in tendency slowing down concomitant to losing mass at an accelerating rate. However, only few investigated seasonal velocity variations and the difference between debris-covered and debris-free glaciers flow dynamics. We focus on four debris-covered and four debris-free glaciers across HMA, which have different climates, glaciological, topographic and terminating environments. The four debris-covered glaciers include Kekesay, Satopanth, Khumbu and Xibu glaciers. The four debris-free glaciers include Tuyuksu, Abramov, Petrov and Yanong glaciers. Sentinel-1 and -2 images were selected to calculate the glacial velocities using the feature tracking module provided by CARST (Cryosphere And Remote Sensing Toolkit) (Zheng et al., 2021). We then developed a novel statistical method to extract the seasonally resolved glacial velocity time series. We found clear seasonal signals in the velocities for some of the glaciers and suggest that changes in the subglacial drainage system are driving the seasonal variations in velocities. This mechanism will likely continue in the future due to increased surface melt rates and changes in precipitation patterns across HMA. We also highlight that icefalls may alter the glaciers dynamics by blocking the development of subglacial drainage channels, and thus seasonal propagation of velocities. Our novel methodology enables further understanding of short term dynamics of debris-covered and debris-free glaciers, which is crucial to capture in order to study the response of glaciers today, and in the future to climate change in HMA.

Zheng, W., Durkin, W. J., Melkonian, A. K., & Pritchard, M. E. (2021, March 9). Cryosphere And Remote Sensing Toolkit (CARST) v2.0.0a1 (Version v2.0.0a1). Zenodo. http://doi.org/10.5281/zenodo.3475693

How to cite: Baldacchino, F., Bolch, T., and Zheng, W.: Investigating seasonal velocity variations of debris-covered and debris-free glaciers in High Mountain Asia, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4317, https://doi.org/10.5194/egusphere-egu25-4317, 2025.

Denman Glacier is one of the largest outlet glaciers in Antarctica. Despite its potential significance for sea level change, its geometry and dynamics remain poorly constrained, making predictions of its response to the changing climate challenging. Seismic signals arise from internal stress and interaction with the subglacial landscape, however, seismic methods are still an often underutilised tool for investigating glacial characteristics. In fact, seismology provides one of the few tools for directly observing the processes and properties that control outlet glacier stability and flow.

We present an overview of the seismic data acquired from a transect across Denman Glacier during the Denman Terrestrial Campaign (2023/24). The transect is located 50 km upstream from the grounding line, where the glacier is 13 km wide, and modelling studies suggest a very deep subglacial trough.  

We employ a combination of passive and active seismic techniques to study the glacier’s geometry, internal structure, and dynamics. Our findings reveal constraints on the glacier's geometry, providing an independent view of the depth extent of the main trough. The recorded seismicity also offers preliminary insights into the glacier's dynamics, the baseline for the monitoring of changing environmental forcing.

How to cite: Stål, T., Reading, A. M., Askey-Doran, N., Cook, S., Gradl, J., Hudson, T., Kelly, I., Kulessa, B., Kupis, S., Lösing, M., Magyar, J., Manassero, M. C., Scheiter, M., Selway, K., Thompson, S., and Turner, R.: Seismicity of Denman Glacier: Constraints on Geometry and Dynamics, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5279, https://doi.org/10.5194/egusphere-egu25-5279, 2025.

The High Mountain Asia (HMA) hosts the most significant number of glaciers outside the polar region, called the "Third Pole."  Glacier meltwater is vital for 1.5 billion inhabitants in the HMA. The Yarlung Zangbo–Brahmaputra (YB), a transboundary river flowing from China through India and Bangladesh into the Bay of Bengal supporting more than 80 million people, is fed by over 15,000 pieces of glaciers. However, glacier melt contribution to the runoff in the YB by sub–basins is still unclear. In this study, we presented an updated glacier inventory for debris–free glaciers in the YB for 2020, calculated geodetic mass balance by glacier surface elevation difference, using NASADEM and GLO30 DEMs from 2000 to 2013, laser altimetry data from ICESat–2 from 2018 to 2023, and available elevation difference datasets from 2000 to 2020. Additionally, we studied nine individual glaciers to verify our geodetic glacier mass balance results with available in–situ observations and to better understand the glacier dynamics in the basin. Our study shows that (1) the glacier area decreased from 12,638.3±758.3 km² in the 1970s to 9,081±12.09 km² in 2020, with a loss of 28.15% of debris–free glacier area at –0.56 % a^–1 in the past fifty years; (2) glacier mass balance (GMB) was –0.49 ± 0.02 m w.e.a^–1 from 2000 to 2013, with glacier mass change (GMC) at –4.61 ± 0.41 Gt a^–1; (3) based on ICESat–2 and GLO30 from 2013 to 2023, the GMB was –0.47 ± 0.02 m w.e.a^–1, and GMC was –4.44 ± 0.38 Gt a^–1; (4) the GMB was consistently negative in the YB from 2000 to 2020 at five–year intervals, with –0.36 m w.e.a^–1 (–3.95 Gt a^–1) in 2000 – 2005, and –0.64 m w.e.a^–1 (–7.07 Gt a^–1) in 2015 – 2020; (5) the GMB contribution to runoff increased from 0.05 % a^–1 during 2000 – 2005 to 0.86 % a^–1 during 2015 – 2020, with an average of 0.59% a^–1 in the YB from 2000 to 2023.

How to cite: Ali, N., Ye, Q., Cuo, L., Zhang, X., Hu, Y., Ji, X., Lei, W., Junbo, W., and Liping, Z.: The glacier geodetic mass balance and its hydrological contribution to runoff in the Yarlung Zangbo-Brahmaputra basin, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5481, https://doi.org/10.5194/egusphere-egu25-5481, 2025.

The surface elevation of the Greenland Ice Sheet undergoes continuous changes driven by the interaction of surface mass balance processes and ice dynamics, each displaying distinct spatial and temporal characteristics. In this study, we utilize satellite and airborne altimetry data with high spatial (1 km) and temporal (monthly) resolution to examine these changes from January 2003 to August 2023. Our analysis highlights the complex and evolving elevation change patterns of Jakobshavn Isbræ (JI). Specifically, we document thinning near the JI terminus from 2003 to 2015, followed by thickening of approximately 25 meters between 2015 and 2018, thinning of around 20 meters from 2018 to 2022, and slight thickening during 2022–2023.

To validate these findings, we compare surface elevation changes derived from satellite and airborne altimetry with GPS observations from bedrock-based monitoring stations near the JI margins. These GPS stations capture bedrock displacement due to ongoing land uplift in response to current ice mass changes, with the glacial isostatic adjustment (GIA) signal removed. The GPS data, providing continuous daily estimates of mass changes, corroborates the intricate and evolving elevation change patterns observed in JI.

How to cite: Khan, S. A., Berg, D., Cheng, G., Morlighem, M., Barlatta, V., Seroussi, H., and Hassan, J.: Complex evolving elevation change pattern of Jakobshavn Isbræ during 2003-2023, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6055, https://doi.org/10.5194/egusphere-egu25-6055, 2025.

How to cite: Kupis, S., Stål, T., and Reading, A.: Seismic reconnaissance of firn structure in Denman Glacier region, East Antarctica, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6229, https://doi.org/10.5194/egusphere-egu25-6229, 2025.

High-altitude lakes across High Mountain Asia (HMA) are one of the critical freshwater reservoirs and sensitive indicators of climate change due to their remote locations and limited human disturbances. However, the ongoing climate change and enhanced glacier melt represent a substantial risk of outburst floods. We present an updated estimate of changes in water level of 239 lakes across HMA from 2010 to 2023 using satellite altimetry data from the CryoSat-2 mission. Examining lake levels, we observe a decline until 2015, followed by a rapid increase until 2023. About 42% of the lakes located above 4000 m a.s.l. are within glaciated catchments. Increased lake levels are particularly notable in glaciated catchments by 0.22 ± 0.01 m a-1, which is slightly faster than those in non-glaciated catchments (0.17 ± 0.01 m a-1). Elevated lake levels in glaciated catchments enhance the risk of glacial outburst floods.

How to cite: Hassan, J., Nielsen, K., Colgan, W., Kayastha, R., Khadka, M., and Khan, S.: Rising Lake Levels Across High Mountain Asia, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7485, https://doi.org/10.5194/egusphere-egu25-7485, 2025.

Glacier albedo is a key driver of glacier energy and mass balance. In recent years, multi-annual firn and summertime snow cover has decreased on Alpine glaciers, exposing larger areas of ice at increasingly high elevations. This reduces glacier albedo and contributes to feedback mechanisms that lead to increased melt. To understand and better predict mass loss in former accumulation areas under conditions of rapid glacier recession, it is important to constrain the possible range of ice albedo that occurs in these newly snow and firn free regions, the duration of ice exposure, and the correlation and causal connection of these factors with ablation at point and glacier scales. Using a unique dataset from an on-ice weather station (3492 m.a.s.l.), ablation stakes, and remote sensing derived albedo, we provide a quantitative overview of albedo and ablation in the summit region of Weißseespitze, the high-point of Gepatschferner (Austria) from 2018 to 2024. We contextualize the observational data with modeling experiments quantifying the sensitivity of surface mass balance to the observed albedo. In the continuous time series of in situ albedo, the seasonal minimum is reached between late July and early September. From 2018 to 2021, minimum albedo values were about 0.30. In 2022, 2023, and 2024 the minima were considerably lower at 0.16-0.17. Prior to 2022, albedo dropped below 0.4 on 3 to 8 days per year. In 2022, 37 days of low albedo conditions (<0.4) were recorded. Ice ablation at the stakes generally increased with increased duration of ice exposure and ranged from zero ablation in years with mostly continuous summer snow cover (e.g. 2020) to more than -1.5 m w.e. in high-melt years like 2022 and 2024. Sentinel-2 derived albedo captures the range and variability of albedo measured in situ well and shows that ice albedo near the summit of Weißseespitze dropped to values similar to those of the surrounding rock in 2022. For average July-September conditions, an albedo decrease from 0.4 to 0.15 results in 10-15 mm w.e. of additional modeled surface melt per day. The impact of ice exposure on melt varies seasonally, with highest sensitivities early in the season. A five day period of very low albedo conditions (<0.2) results in 26% more modeled surface melt if it occurs in late July compared to early September. The albedo decrease at the AWS since 2022 may be related to the exposure and melting of impurity rich firn and ice layers and the accumulation of impurities at the surface, increased presence of meltwater, and the state of the weathering crust. Our extensive dataset sheds light on upcoming changes to be expected at the highest elevations of alpine glaciers in many regions worldwide and provides a starting point for further studies aimed at linking cause and effect of ice albedo variability across scales.

How to cite: Hartl, L., Covi, F., Stocker-Waldhuber, M., Baldo, A., Fugazza, D., DiMauro, B., and Naegeli, K.: Losing the accumulation zone: Exploring albedo and ablation in the summit region of Gepatschferner, Austria, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9169, https://doi.org/10.5194/egusphere-egu25-9169, 2025.

Central Asia hosts a high density of surge‑type glaciers (locally known as pulsating), which exhibit heterogeneous surge characteristics and poorly understood driving mechanisms. Historical monitoring of glacier dynamics in the region is scarce, particularly in the transitional area of the Hissar‑Alay (Pamir-Alay): there, as few as five surging glaciers are reported in existing inventories since the 1970s, and only the Abramov glacier pulsation of 1972 was studied in situ. However, a high prevalence of pulsating glaciers was postulated by Glazirin and Schetinnikov (1980), who used a Bayesian classification model of glacier morphology to predict around 200 occurrences in the Hissar‑Alay – almost 25% of the investigated sample.

Here, we systematically investigate pulsating behavior of glaciers in the Hissar-Alay, using a newly compiled dataset of optical satellite imagery from 1964 to present. We include data from film-based reconnaissance satellites (Key Hole program), SPOT 1 to 7, RapidEye, and Pléiades: these provide superior spatial resolution and temporal coverage compared to the commonly used Landsat and ASTER datasets.

Our analysis reveals asynchronous terminus advances and surge‑like patterns of ice thickness, within an overall context of mass loss. These findings confirm the occurrence of widespread glacier pulsation in the region, despite challenges in the differentiation of actual surge events from glacier advances. We note that existing inventories of surge-type glaciers are highly incomplete and biased towards larger glaciers. The model of Glazirin and Schetinnikov (1980) accurately predicted pulsating behavior at several previously unobserved glaciers; however, we also find a comparable number of misclassifications (both false positive and false negative), confirming that glacier morphology is an imperfect predictor of surging behavior.

Pulsations can induce rapid changes in glacier geometry and surface properties: these may undermine representativity of the computed glacier‑wide mass balance trends, including at reference glaciers like Abramov. Frequently updated topographic data are essential for large-scale modeling and geodetic studies in the region. However, even at pulsating glaciers, point measurements of mass balance remain valuable for calibration and validation of energy and mass balance models. Further investigation of spatio-temporal patterns of the found glacier pulsations will contribute to a better understanding of the drivers of surge behavior in Central Asia.

How to cite: Mattea, E., Barandun, M., Bhattacharya, A., Dehecq, A., Ghuffar, S., and Hoelzle, M.: Six decades of satellite remote sensing reveal widespread glacier pulsations in the Hissar-Alay (Central Asia), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9212, https://doi.org/10.5194/egusphere-egu25-9212, 2025.

Over the past two decades, glaciers in the Himalaya-Karakoram (HK) region have exhibited heterogeneous but accelerated mass loss. Factors driving this loss, such as atmospheric warming and snowfall variability, have been extensively studied by analyzing precipitation and air temperature data, often derived from meteorological reanalysis data. However, reanalysis data such as ERA5 exhibit significant biases and uncertainties, resulting in large spread in glacier mass balance estimates across studies. To address this, we propose to use thermal remote sensing data from the MODIS satellite, which provides glacier surface temperature (GST) at an 8-day temporal and 1 km spatial resolution.

This study leverages 24 years (2000–2024) of MODIS land surface temperature data to analyze GST characteristics, seasonality, and trends across HK subregions. Since temperature modulates glacier mass balance, remote-sensing-based GST is likely to be a superior dataset for mass balance modelling. We demonstrate this by obtaining a strong correlation (r: -0.47; p-value: 0.02) between GST and mass balance for ~6000 glaciers in the HK region. We also show that MODIS-derived GST outperforms ERA5 surface temperature when validated against in-situ surface temperature data measured on glaciers (R²: 0.88, RMSE: 3.57 °C vs. R²: 0.38, RMSE: 8.01 °C).

Our analysis of the spatiotemporal behaviour of GST reveals that during the ablation season, GST has been increasing at an average rate of +0.25 °C dec^-1across the HK region, with the Eastern Himalaya experiencing the highest warming (+0.44 °C dec^-1). Ablation months, August and September, exhibit more pronounced GST warming compared to other months. Comparisons between the decadal averages (2001-2010 vs. 2011-2020) indicate a marked increase in GST, on average +0.18 °C higher in the second decade across the HK subregions, with the Karakoram showing a threefold higher warming rate than others. Altitudinally, GST warming is strongest in mid-glacier areas (4300-5300 m), predominantly clean-ice zones, which warmed +0.30 °C more than debris-covered areas.

In the Eastern Himalaya, rising GST has significantly increased the annual positive GST area ratio (fraction of glacierised area with > 0 °C GST) by ~3% of total glacierised area, contributing to the region's steeper glacier mass loss than other subregions. Overall, the Eastern Himalaya stands out as a hotspot for GST warming, with significant increases annually, during the ablation season, and across altitudinal zones, making it highly vulnerable to persistent and accelerated glacier mass loss.

This study highlights the utility of satellite-derived GST for assessing glacier thermal states and their mass loss characteristics, offering valuable insights into glacier-surface-atmosphere interactions.

How to cite: Mandal, A. and Vishwakarma, B. D.: Glacier surface temperature warming in the Himalaya-Karakoram: Implications for glacier mass loss, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9239, https://doi.org/10.5194/egusphere-egu25-9239, 2025.

The Getz Glaciers, situated near the Amundsen Sea in West Antarctica, represent the third-largest source of freshwater discharge from the Antarctic Ice Sheet. Understanding the physical mechanisms driving ice loss in this region is essential for refining projections of future ice loss and its contributions to global sea-level rise. Subglacial hydrology has recently been recognized as a critical factor influencing long-term glacial mass balance. However, the inland regions of the Getz Glaciers remain relatively understudied compared to other parts of Antarctica. This study utilizes CryoSat-2 satellite altimetry data to detect active subglacial lakes across the Getz Glacier region from 2010 to 2024. The findings reveal a significant number of active subglacial lakes, indicative of vigorous meltwater generation, consistent with observations from other West Antarctic glaciers, such as the Thwaites Glacier and Ross Ice Stream. Further research is required to investigate the potential connections between subglacial hydrology, ocean circulation, and its impact on ice shelf destabilization.

How to cite: Kim, B.-H., Lee, C.-K., Lee, W. S., and Seo, K.-W.: Active subglacial lakes in the Getz glaciers revealed by CryoSat-2 radar altimetry, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9283, https://doi.org/10.5194/egusphere-egu25-9283, 2025.

Glacier inventories serve as critical baseline data for understanding and assessing past, current, and possible future conditions of the local, regional, and global environment. In this study we present a manually mapped inventory of glaciers in the sub-Antarctic Heard Island, for 1947, 1988, and 2019, derived from large-scale topographical maps (1:50,000), cloud-free medium-resolution SPOT, and high-resolution PLEIADES satellite orthoimages.

The total glacier area has reduced from 289.4±6.1 km² in 1947 to 260.3±6.3 km² in 1988, which further decreased to 225.7±4.2 km² in 2019. The mean glacier area has also reduced from 10 km² to 8.7 km² and to 6.4 km² respectively, during the same period. The rate of annual glacier area loss was almost doubled (−0.43% yr⁻¹) in the second investigated period (1988-2019), then it was (−0.25% yr⁻¹) in the first period (1947-1988). Glaciers on the eastern slopes has experienced much higher decrease and retreat rates than the rest of the glaciers. The maximum retreat we observed between 1947 and 2019 was ~5.8 km for the east-facing Stephenson Glacier.

The findings of our study may provide information on how glaciers on Heard Island respond to climate change, potentially reducing uncertainty for further climate and glaciological modelling in this sub-Antarctic region.

How to cite: Tielidze, L., Mackintosh, A., and Yang, W.: Glacier inventory of the sub-Antarctic Heard Island, Australian external territory, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10618, https://doi.org/10.5194/egusphere-egu25-10618, 2025.

Loss of glacier ice is contributing substantially to rising sea levels, and is negatively impacting up to 1.9 billion people globally who rely on meltwater for agriculture, drinking water, hydropower and other ecosystem services. Quantifying how glaciers are responding to ongoing climate change therefore has far-reaching implications, though a global observational assessment of this at an individual glacier scale is currently lacking. 

Here, we leverage the Randolph Glacier Inventory v7.0 (RGI) dataset (baseline date: 2000), and imagery from the Sentinel-2 archive between 2020 and 2024 to establish the change in extent of the 181,402 small ice masses (area <= 2 km2) globally that are most vulnerable to climate change. We achieve this through developing a simple, highly automated approach to glacier extent identification in Google Earth Engine, analysing all cloud free imagery for the end of the melt season in each RGI region. 

Our workflow derives thresholded Normalised Difference Snow Index (NDSI) glacier masks for each Sentinel-2 image where at least 95% of the RGI outline area is visible, with the area of each contiguous ice/snow patch calculated using object based connected component analysis. To minimise potential false positives associated with ephemeral snow cover, the resulting masks for each glacier are ranked smallest to largest by the largest ice patch observed, before a final glacier mask is obtained from the areas identified as ice in at least two out of the three top ranked images. Results are compared to custom ERA5-Land reanalysis baselines to highlight the likely climate drivers of these changes, while CMIP6 climate simulations are used to project potential future change. 

Our results highlight that significant global glacier loss and fragmentation has already occurred since 2000, and is likely to continue with future projected warming. This demonstrates recent glacier vulnerability to climate change and that negative impacts arising from glacier loss will likely become more acute on timescales much shorter than a human lifespan. In the International Year of Glacier's Preservation, this analysis therefore has tangible use for establishing the sensitivity of glaciers to future climate change, communicating the global vulnerability of glaciers, and motivating calls for action.

How to cite: Lea, J., Brough, S., Chudley, T., Davies, B., Ely, J., King, O., Lamantia, K., Larocca, L., and Maussion, F.: Significant global loss and fragmentation of glaciers since 2000, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12214, https://doi.org/10.5194/egusphere-egu25-12214, 2025.

Glaciers terminating in lakes typically flow, thin and lose mass more rapidly than those that terminate on land. This is due to a range of thermomechanical processes exerted at the lake-ice interface, where lake waters drive melt-induced undercutting, enable flotation and facilitate calving. In Greenland, ice marginal lakes (IMLs) have increased in size and number over recent decades and now occupy more than 10% of the ice sheet margin. Despite this, very few observations of their effects on ice dynamics exist, meaning they remain largely unaccounted for in models of ice sheet change.

Here, we use ITS_LIVE ice surface velocity data and the How et al. (2021) IML inventory to compare the flow characteristics of 102 lake-terminating outlet glaciers and 102 neighboring land-terminating outlet glaciers across the Greenland Ice Sheet (GrIS) during 2017. We find that along-flow decelerations are much less pronounced at lake- versus land-terminating glaciers, and that some lake-terminating glaciers (n = 33) even speed up towards the ice margin. In turn, lake-terminating glaciers are on average 4.6 times faster than their land-terminating counterparts within the terminus region. Moreover, the fastest flowing glaciers are found to terminate in the largest lakes, suggesting that lake influence evolves with lake development. Ultimately, these observations demonstrate the capacity of IMLs to enhance the surface velocity of Greenlandic outlet glaciers, highlighting their potential to accelerate future mass loss from the GrIS.

How to cite: Harpur, C., Smith, M., Carrivick, J., Quincey, D., and Taylor, L.: Ice marginal lakes enhance outlet glacier velocities across Greenland, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12360, https://doi.org/10.5194/egusphere-egu25-12360, 2025.

How to cite: Rutishauser, A., Hillerup Larsen, S., Karlsson, N. B., Citterio, M., Binder, D., and Hynek, B.: 12 years of snow accumulation from ground-penetrating radar surveys on AP Olsen Ice Cap, northeast Greenland, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12445, https://doi.org/10.5194/egusphere-egu25-12445, 2025.

Tropical glaciers are highly vulnerable to climate change, with their mass balance influenced by temperature and precipitation, affecting the snow accumulation area (SCA). This study aimed to develop an open-source, cloud-based tool to identify the SCA using Landsat imagery and analyse annual variations in the Cordillera Blanca (CB), Peru, from 1988 to 2023. The total glacier area was obtained using MapBiomas - Peru data. Automatic classification was performed using spectral indices, slope gradient filtering, and morphological filtering, and the Otsu method was applied to identify the accumulation area. A scaling factor of 0.9, applied to the Otsu method's threshold, is proposed for the identification of the SCA in the CB. Statistical analyses assessed trends and correlations between the annual SCA and factors like temperature, sea surface temperature, precipitation, snowfall, El Niño events, and the Pacific Decadal Oscillation (PDO). The SCA series were validated through field data and manual mapping of glaciers (Artesonraju, Shallap, and Yanamarey), yielding correlation values of 0.69, 0.72, and 0.89, respectively. The correlation between automated SCA and mass balance reached 0.88. Comparisons between PlanetScope and Landsat imagery showed differences of <5%, with larger discrepancies observed in glaciers with debris cover or small glaciers (<1 km²). Glacier area loss for the Amazonian and Pacific-facing sectors ranged from 21.3% to 22% between 1988 and 2022, with lower rates of loss between 1998/99 and 2007/08, coinciding with a reduced temperature increase in the Pacific. The Amazonian sector experienced a significant decrease in the SCA in the period 1999 - 2023 (S: -97, Z: -2.5354, ρ: 0.011232). For the Pacific sector, this trend is observed in the period 1988 - 1998 (S: -35, Z: -2.6469, ρ: 0.0081), followed by an increase in the values until 2008 and post resumption of lower SCA values. A more pronounced decrease in snowfall after 2000 was observed in the Pacific sector. During the 1997/98 El Niño event, the average SCA variation was -25.49% for the Pacific and -17.43% for the Amazon. El Niño events showed higher correlations with SCA during the wet season (up to -0.68), with a stronger influence on the Pacific sector. SCA was strongly correlated with temperature in the Amazon (-0.76), while in the Pacific, the correlations with snowfall (0.47) and temperature (-0.46) were more similar. The highest correlations with the meteorological parameters for SCA were observed during the dry season, suggesting that even small changes in temperature or precipitation during this period can significantly impact the accumulation area. The automation of image processing for the CB provided spatial and temporal details about the variations of the glaciers in each sector and the cloud-based tool allowed the continuity of glacial facies monitoring in the region over time.

How to cite: Lopes Lorenz, J., Kellem da Rosa, K., da Rocha Ribeiro, R., Cruz Encarnación, R., Racoviteanu, A., Aita, F., Hillebrand, F. L., Gomez Lopez, J., and Cardia Simões, J.: Cordillera Blanca glacier snow cover area estimation and its response to climate forcing during 1988 - 2023, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13296, https://doi.org/10.5194/egusphere-egu25-13296, 2025.

The World Glacier Monitoring Service (WGMS) and its global network of collaborators maintain a comprehensive programme of ongoing glacier change, resulting in an unprecedented dataset that serves as an increasingly important basis for fundamental glacier research and various applications at local, regional, and global scales. Knowledge of glacier distribution and quantification of glacier change is crucial for assessing the impact of glacier shrinkage on regional freshwater availability, local geohazards, tourism, sites of cultural significance, and global sea levels. Therefore, glacier monitoring is essential for the development of sustainable adaptation strategies in regions wherever glaciers (still) exist.

In this presentation, we assess the status of glacier monitoring in each country in 2025 and compare it to the 2015 baseline (Gärtner-Roer et al., Mountain Research and Development, 2019). During this time, surface elevation changes derived from satellite data reached nearly global coverage. In addition, temporal but also spatial gaps could be filled by adding new glaciological in situ series thanks to data rescue efforts. For each country, we describe the number of observed glaciers and total number of observations available in the WGMS Fluctuations of Glaciers (FoG) database for the following observation types: front variation, glaciological surface mass balance, and geodetic surface elevation change. In addition, we review the availability of glacier outline inventories and the annual mass-balance trend in each country.

Finally, we discuss the role of glacier monitoring in international research and policy-making to place our results in the context of global climate-change monitoring. With the advent of new datasets, such as those derived from satellites, information on glaciers transcends national boundaries. However, limited funding often hampers the long-term monitoring of glaciers, regardless of data source. In view of the International Year of Glaciers’ Preservation in 2025 and the United Nations (UN) Decade of Action for Cryospheric Research in 2025–2034, we establish a 2025 baseline and make recommendations for the future of glacier research.

How to cite: Nussbaumer, S. U., Gärtner-Roer, I., Saibene, G., Welty, E., and Zemp, M.: National and global glacier monitoring efforts – a comparative assessment, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13593, https://doi.org/10.5194/egusphere-egu25-13593, 2025.

With around 46 km², Nevado Coropuna (NC, (15°32’S, 72°39’W; 6377 m) is the largest tropical icecap in the world. NC is situated on a stratovolcano structure with six peaks over 6000 meters, in the arid border of the Andean plateau, Southern Peru. NC is a vital source of freshwater for the communities within the Majes valley and for the vast irrigation plans located in the same valley and on the arid coastal strip. Here we present the 1955-2024 glacier surface evolution, which was retrieved from aerial photography and topographic maps for the initial stage in 1955 and from satellite imagery photogrammetry (SPOT, Worldview, PeruSAT-1 and Pleiades), backed by in-situ GPS-RTK measurements for the last 11 years.

Results show that the glacier lost an average of -0.15 m a^-1 of ice between 1955 and 2013. The ice loss subsequently accelerated to a rate of -0.18 m a^-1 between 2013 and 2018 and -0.44 m a^-1 between 2018 and 2023. During the last year the ice loss rate has been -0.15 m a^-1.

Ice loss has not been even across the glacier, but it primarily concentrated on the largest northern outlets, where it approached -1.9 m a^-1 between 2018 and 2024 with a much lower ice reduction (-0.9 m a^-1) in the southern outlets. Ice loss at the peaks is also reported, as a difference between a negligible ice change in the 1955-2013 timeframe contrasts a -0.7 m a^-1 ice loss at the central part of the NC top plateau during the 2018-2024 timespan. The extensive debris-covered and rock glacier area features a much more stable behaviour, with ice loss/gain values within the error limit between 2013 and 2024. Likewise, the northwestern section of NC seems quite stable, possibly because of its comparatively higher elevation.

Results in NC show a continuous and consistent glacier retreat, but the mass loss pace is less accelerated than other Peruvian glaciers. Glaciers in the Vilcanota range, in the humid margin of the Andes, show a -0.5 m a^-1 ice loss between 2000 and 2020 and there is an even stronger ice loss acceleration in the Central Andes area after 2013, with an average mass change of -1.067 m a^-1.

How to cite: Pellitero Ondicol, R., Llanto Verde, J., Úbeda Palenque, J., and Atkinson Gordo, A. D.: Recent evolution and present situation of the world’s largest tropical icefield: the Nevado Coropuna (Peru). , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13743, https://doi.org/10.5194/egusphere-egu25-13743, 2025.

Glacier AX010 in the Shorong region is an iconic glacier in the Nepal Himalaya, observed since 1978. We conducted a drone photogrammetry survey in November 2023 and evaluated its volume change since 2008 as –1.3 m yr^–1, one of the fastest (and accelerating) shrinking rates in the Himalayas. We reconstructed the annual mass balance using the ERA5 reanalysis climate data and a glacier mass balance model, GLIMB. We first evaluated the ERA5 meteorological variables with our recent in-situ observational data of a nearby site (2022-2023). Secondly, we calibrated the ERA5 precipitation to yield the observed geodetic mass balance and reconstructed the annual mass balance over the past 83 years (1940-2023). The estimated mass balance and calibrated temperature were validated with the observational data in the 1970s and 1990s. We also estimated the ideal temperature by which the glacier could maintain equilibrium states. Trend and breakpoint analyses revealed that the temperature warming and glacier shrinkage started in the mid-1970s while precipitation has been rather stable throughout the entire period. These results suggest that temperature warming is the main driver for the glacier shrinkage.

How to cite: Fujita, K. and Kayastha, R. B.: Finding the turning point and main driver of a disappearing Himalayan glacier, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13997, https://doi.org/10.5194/egusphere-egu25-13997, 2025.

Glaciers in México have been present for the last decades on the highest mountains of México: Iztaccíhuatl,Popocatépetl and Citlaltépetl.

In 1964 the size of twelve glaciers was measured at Iztaccíhuatl volcano using aerial photographs resulting in an extension of 1.4 km². At the time of this review, El Pecho is the only remaining glacier on this mountain which exceeds the projections proposed earlier. Although much of the glacial retreat is related to climate change, in situ observationssuggest that geothermal heat fluxes and hydrothermal flows in the crater area should also be considered.

About the glaciers of Popocatépetl the glacial area in 1964 was 0.72 km² and consisted of three glaciers. Before 1994, the retreat of glaciers was in the order of ~10,000 m²/year. On December 21, 1994, an eruptive period began atPopocatépetl volcano characterized by volcanic explosions alternating with lava dome construction-destruction phases.An increase in heat flow under the glacial ice, the fall of tephra on its surface, and pyroclastic flows that moved over the glacier surface, caused its irregular thinning, retreat and, in the final stage, its fragmentation between1994-2001.

At Citlaltépetl volcano the existence of 9 glaciers was established, covering an area of 2.04 km². In 2007 they covered an area of 0.62 km², and by 2019 the bedrock was exposed, faster than anticipated previously. The accumulation zone of the glacier system is not existent ever since. Exposure of the bedrock increases solar energy transference as heat to the adjacent ice and snow, causing an increasing melting. At the same time, it prevents the flow of ice towards the ablation zone, causing an accelerated retreat of the glacier front. So, the surface of the glacier in 2019 was ~0.46 km², and the current extension for 2024 is only ~0.37 km².

How to cite: Delgado Granados, H., Lorenzo, J. L., Julio Miranda, P., Cortes-Ramos, J., Ontiveros-González, G., and Soto, V.: ~70 years of glacier monitoring in Mexico, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14192, https://doi.org/10.5194/egusphere-egu25-14192, 2025.

The retreat of tropical glaciers is a visible effect of climate change, which is evident in Peru. These glaciers are sensitive to global and local temperature increases, causing accelerated glacier mass loss. From 1962 to 2020, there has been a decrease in glacier cover at the national level, with a loss of approximately 1,280.95 km². This phenomenon significantly affects local ecosystems and water availability, putting at risk the supply of water for human consumption, agriculture and other essential activities, particularly during dry seasons.

The research was carried out on the Shallap and Llaca glaciers, located in the Cordillera Blanca in Ancash, Peru. The Shallap glacier is characterized by two clearly differentiated zones: one covered by debris and the other with a clean surface. While the Llaca glacier has a glacial tongue completely covered by debris which terminates in a proglacial lake. This distinction in the surface characteristics of both glaciers allows for detailed comparisons, providing insights into the role of supraglacial debris in modifying glacier melt rates, processes which have been rarely studied in the Peruvian Andes.

Repeat Unmanned Aerial Vehicle (UAV) imagery conducted in 2019 and 2024 allowed the calculation of mass and area changes of both glaciers, and the assessment of morphological changes between the time periods. Imagery was co-registered to reduce the planimetric errors in the Digital Elevation Models (DEMs).

Much lower mass losses were found over Shallap glacier in the debris-covered compared to clean ice zones, with the debris-covered zone retreating by a maximum of 36 meters, with an area loss of 8,257 m² (equivalent to -14,202 m³ of ice). On the other hand, the debris-free zone retreated by a maximum of 165 meters, with an area loss of 24,439 m², representing a volume of -61,160 m³. However, the Llaca glacier showed a maximum retreat of 122 meters, with an area loss of 21,144 m² (equivalent to -397,813 m³ of ice). This difference in volume loss compared to Shallap glacier, could be due to the presence of the proglacial lagoon, which is still in contact with Llaca glacier and that would be contributing to a greater glacial melting.

Another factor that modulates glacial behavior is the supraglacial debris layer, according to the results obtained from the loss of glacier volume considering the movement recorded between June and November 2024, it was observed that the debris layers of 1.5 cm and 5.5 cm were associated with ice losses of 3.6 m and 2.5 m, respectively. In contrast, the 33 cm and 50 cm thick debris layers showed considerably smaller ice losses of only 0.4 m and 0.2 m. It can be seen that the thicker the debris layer, the lower the ice thickness loss. 

How to cite: Granados, H., Santiago, A., Curo, Y., Dávila, L., Celmi, G., and Fyffe, C.: Influence of the debris layer on the behavior of the Shallap and Llaca glaciers, Cordillera Blanca, Ancash, Peru, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14455, https://doi.org/10.5194/egusphere-egu25-14455, 2025.

Changing glaciers are definite indicators, warning lights, contemporary witnesses and memorials of climate change, as they are accessible beauties and related impacts on the environment, economies, and societies are relatively easy to understand. While these immediate impacts are mainly relevant on local and regional scales, related measures to preserve them need to be taken on the global scale. Therefore, the United Nations have declared 2025 the International Year of Glaciers’ Preservation (IYGP; https://www.un-glaciers.org) to raise global awareness of glaciers' importance and to ensure that those relying on them or affected by their vanishing have access to the necessary data and information services.

The World Glacier Monitoring Service (WGMS) – together with the United Nations Educational, Scientific and Cultural Organization (UNESCO) and the World Meteorological Organization (WMO) – helped to coordinate the implementation of the international glacier year, the World Day of Glaciers (from 2025 on the 21^st of March) and the United Nations Decade of Action for Cryospheric Research 2025−2034. The contributions have focused on the communication of the scientific basis by explaining the basic processes of glacier dynamics, giving insights into in-situ and remote-sensing techniques to quantify glacier changes and by presenting the latest numbers of glacier mass changes. The WGMS has been actively supported by its network of National Correspondents and Principle Investigators, who highlighted individual or regional glacier changes in workshops, exhibitions, and innovative outreach projects.

Based on the experiences gained so far from national and international outreach events, we want to carefully assess the effect and benefits of these science-based activities on the international glacier monitoring and beyond. This analysis should help to prepare upcoming activities during United Nations Decade of Action for Cryospheric Research 2025−2034 as well as negotiations with decision makers at various levels.

How to cite: Gärtner-Roer, I., Nussbaumer, S. U., and Zemp, M.: WGMS contribution to the International Year of Glaciers’ Preservation 2025 – experiences and first conclusions, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14985, https://doi.org/10.5194/egusphere-egu25-14985, 2025.

The elevation bias due to signal penetration in bistatic InSAR DEMs is recognized as a main error source together with co-registration for estimating glacier mass balance with the DEM differencing method. For TanDEM-X DEMs, the elevation processed from X-band (9.65 GHz) SAR data can lie up to 4-8m lower than the actual snow/ice surface in alpine accumulation areas [1]. However, this bias can often be mitigated by differencing TanDEM-X acquisitions from the same season with unchanged SAR geometry, reducing penetration differences between DEMs. The relative importance of SAR signal penetration for accurate mass balance measurements also reduces with the length of the observation period.

Notably, methods have been developed to correct for SAR signal penetration bias, including estimating volumetric coherence and inverting it [2,3]. However, correction methods have rarely been tested and validated across entire TanDEM-X scenes with coincident ground truth measurements of the actual ice surface. [4] calculated signal penetration based on inversion of volumetric coherence on Union Glacier, Antarctica and validated the results against the optical REMA DEM mosaic over temporally stable surfaces.

A recent study on Aletsch Glacier has observed the elevation bias due to signal penetration in a time stamped TanDEM-X DEM by comparing it to a coincident DEM acquisition from Pléiades optical imagery [1]. Moreover, during an inter-comparison experiment on glacier elevation changes, airborne lidar validation DEMs were produced for Aletsch Glacier enabling a comparison of volumetric changes with TanDEM-X measurements [5].

We use these results to analyse the circumstances under which a signal penetration correction layer associated to the individual processed TanDEM-X DEMs can be used to generate bistatic X-band DEMs that reflect the actual ice/snow surface. We will assess the impact of a signal penetration correction on mass balance measurements similar to [6].

References

[1] Bannwart, Jacqueline, Livia Piermattei, Inés Dussaillant, Lukas Krieger, Dana Floricioiu, Etienne Berthier, Claudia Roeoesli, Horst Machguth, and Michael Zemp. 2024. “Elevation Bias Due to Penetration of Spaceborne Radar Signal on Grosser Aletschgletscher, Switzerland.” Journal of Glaciology, April, 1–15. https://doi.org/10.1017/jog.2024.37.

[2] Weber Hoen, E., and H.A. Zebker. 2000. “Penetration Depths Inferred from Interferometric Volume Decorrelation Observed over the Greenland Ice Sheet.” IEEE Transactions on Geoscience and Remote Sensing 38 (6): 2571–83. https://doi.org/10.1109/36.885204.

[3] Dall, Jørgen. 2007. “InSAR Elevation Bias Caused by Penetration Into Uniform Volumes.” IEEE Transactions on Geoscience and Remote Sensing 45 (7): 2319–24. https://doi.org/10.1109/TGRS.2007.896613.

[4] Rott, Helmut, Stefan Scheiblauer, Jan Wuite, Lukas Krieger, Dana Floricioiu, Paola Rizzoli, Ludivine Libert, and Thomas Nagler. 2021. “Penetration of Interferometric Radar Signals in Antarctic Snow.” The Cryosphere 15 (9): 4399–4419. https://doi.org/10.5194/tc-15-4399-2021.

[5] Piermattei, Livia, Michael Zemp, Christian Sommer, Fanny Brun, Matthias H. Braun, Liss M. Andreassen, Joaquín M. C. Belart, et al. 2024. “Observing Glacier Elevation Changes from Spaceborne Optical and Radar Sensors – an Inter-Comparison Experiment Using ASTER and TanDEM-X Data.” The Cryosphere 18 (7): 3195–3230. https://doi.org/10.5194/tc-18-3195-2024.

[6] Abdullahi, Sahra, David Burgess, Birgit Wessel, Luke Copland, and Achim Roth. 2023. “Quantifying the Impact of X-Band InSAR Penetration Bias on Elevation Change and Mass Balance Estimation.” Annals of Glaciology 64 (92): 396–410. https://doi.org/10.1017/aog.2024.7.

How to cite: Krieger, L., Ibarrola Subiza, N., Floricioiu, D., Fischer, G., and Abdullahi, S.: Assessing the TanDEM-X elevation bias due to SAR signal penetration for glacier mass balance measurements, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16658, https://doi.org/10.5194/egusphere-egu25-16658, 2025.

Meltwater from Andean glaciers sustains river flow heavily relied on by ecosystems and communities downstream, particularly during periods of drought. However, contemporary rates of glacier recession in the Andes are accelerating and the yield of freshwater from the high mountain environment here is forecast to decline in coming decades, increasing water stress in the region. Water resource management policies rely on robust hydrological and glacier modelling, which themselves require accurate, long-term records of glacier ice loss rates. Prior to the contemporary satellite era (2000-today), records of glacier mass balance are patchy in the Andes, with available data lacking temporal resolution or covering small glacier samples and our knowledge of glacier behaviour during this period can be improved. Here, we have assembled geodetic glacier mass balance records for 10 glacierised river catchments containing ~3200 glaciers and spanning different climatic zones between 9°S (Rio Santa) and 50°S (Rio Santa Cruz). We have generated glacier surface elevation change data using DEMs generated from regional aerial photography surveys, from three archives of declassified American spy satellite imagery (Corona KH4, Hexagon KH9 mapping camera and Hexagon KH9 panoramic camera) and from contemporary optical stereo archives (ASTER). Our geodetic time series captures considerable inter-catchment variability in glacier mass loss rates across different climatic zones, but clearly indicates accelerating glacier mass loss rates throughout the Andes since the 1960s. These results will be used to calibrate glacier and hydrological models which will simulate meltwater flux from the same 10 catchments towards 2150 as part of the NERC Highlights Project ‘Deplete and Retreat: the Future of Andean Water Towers’.

How to cite: King, O., McNabb, R., Ghuffar, S., Falaschi, D., Dussaillant, I., Carrivick, J., Bhattacharjee, S., Davies, B., and Ely, J.: Andean glacier mass balance through the last six decades, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16893, https://doi.org/10.5194/egusphere-egu25-16893, 2025.

The Pamir Mountains are an important target of current research: they constitute a crucial mountain water tower that is highly vulnerable to future climatic, environmental, and social change; and they contain glaciers experiencing limited early 21st-century mass loss despite climate warming. Due to geopolitical factors, the in-situ records in the region were interrupted during this period, and current assessments of glacier volume and mass change in this region are highly uncertain. A global assessment of geodetic mass balance from ASTER images has suggested a change in the mass balance regime in the region toward declining glacier health, but its uncertainties are very high. In this study, we leverage high-resolution (<5m) optical stereo images that compensate for the scarcity of in-situ snow and glacier observation to provide a mass balance estimate entirely independent of the ASTER dataset.

We analyze high-resolution SPOT5, SPOT6, and Pléiades stereo satellite images acquired since the 2000s over the Sangvor glacierized catchment in the Pamir mountains as a case study. We adopt a stereo image analysis workflow from the Ames Stereo Pipeline to process these data, including coregistration and bias correction, and to remove erroneous artifacts such as jitter-induced undulations. In addition to approximating and subtracting the undulation errors using Fourier transforms, for the results with insufficient correction, we adopt an empirical method that calculates the average value of the error in the cross-track direction of the image from the estimated satellite orbit and directly subtracts the averaged error in each along-track direction. We evaluate the elevation change uncertainty based on the patch approach and then quantify glacier mass balance spanning twenty years over our study domain. In order to empirically estimate the error in the spatially averaged elevation change in the study area, we sampled the area into a certain area, calculated the median of the elevation change in the stable terrain, and then calculated the mean of the absolute difference of these tiled median errors. Finally, we compare our results to those derived from ASTER DEMs for this period. Our results demonstrate the potential of very high-resolution satellite imagery for snow and glacier monitoring despite the challenge of short-interval observations and highlight the value of multiple independent, high-quality geodetic mass balance estimates to resolve changes over shorter periods.

How to cite: Hagiwara, H., Miles, E., Jouberton, A., and Pellicciotti, F.: Glacier mass changes in the Western Pamirs 2003-2024 from high-resolution stereo satellite images, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17900, https://doi.org/10.5194/egusphere-egu25-17900, 2025.

Extensive databases of satellite imagery are now available and can be used to undertake assessments of the mass balance of glaciers. Previous studies have mapped the end-of-season snowlines (ESS) on glaciers from satellite imagery to find their snowline altitudes (SLA) and used these as proxies for the glacier equilibrium-li ne altitudes (ELA). This approach is advantageous because it can be implemented at a large scale and may employ automated methods. The veracity of using remotely measured SLAs as a proxy for in-situ measured ELAs however, has not yet been robustly demonstrated.

We have undertaken a systematic mapping of ESSs on 20 glaciers with existing measured mass balance records to determine the errors associated with remotely measured SLAs. Glaciers are selected from the World Glacier Monitoring Service (WGMS) Fluctuations of Glacier (FoG) database. For each ELA record, we identify the Landsat image closest in date to the original ELA measurement (where cloud cover is minimal) and the image with the highest altitude snowline for the year. For each image, the snowline is mapped, and its corresponding SLA is extracted from the ASTER Global Digital Elevation Map (ASTERGDEM). We find that the reliability of this method is variable, as it is often limited by satellite revisit periods, cloud cover, and late-summer snowfall events. We specifically investigate further the complexities associated with distilling the range of elevation values comprising a mapped snowline into a single elevation value, for example, taking the mean and median elevations along the full width of the glacier and within a fixed buffer of the central flowline and the effect patchy and irregular snowline segments might have on the calculations. Where snow cover is patchy, a greater length of snowline is mapped in order to trace the boundary than is required for smoother segments. This is regardless of whether it contributes a larger area of snow cover or not. Consequently, the SLA calculations are prone to oversampling from areas of irregular snow cover. These results highlight a need to better define the end-of-season SLA and how best to calculate it.

How to cite: Hallford, M., Rea, B. R., Mullan, D., Spagnolo, M., Sam, L., and Singh, S.: Complexities of Using Satellite Imagery for Defining Snowline Altitudes, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19578, https://doi.org/10.5194/egusphere-egu25-19578, 2025.

The Little Ice Age (LIA) is crucial for understanding the pre-industrial state of the cryosphere. Reconstructions often extend modern glacier inventories to LIA moraines, assuming minimal changes in high-altitude regions— a questionable premise for plateau icefields and other ice masses with top-heavy hypsometries. Using geomorphological mapping based on a wide range of high-resolution remote sensing data, including Sentinel-2 satellite imagery, we mapped the LIA extent of the Folgefonna icefield, Western Norway, in the highest attainable detail, distinguishing its geomorphological signature from earlier Holocene advances. A notable distinction was the contrast between densely vegetated pre-LIA surfaces and sparsely vegetated areas characteristic of the LIA. In steep topographical regions, talus cones outside the LIA boundary remained glacially undisturbed, while those within were often reworked into glacial drift, losing their original form. Other key indicators of the LIA boundary included fresh glaciofluvial fans below moraines. The identification of these distinguishing features may improve the accuracy of LIA reconstructions, which in turn may contribute to better glacier inventories and provide a more reliable foundation for assessing long-term glacier dynamics and changes in the cryosphere.

How to cite: Weber, P., Andreassen, L. M., Boston, C. M., and Tvede, A.: High-Resolution Glacier Mapping of Folgefonna, Western Norway, During Its ‘Little Ice Age’ Maximum and Subsequent Retreat, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20005, https://doi.org/10.5194/egusphere-egu25-20005, 2025.

The glaciers of North Sikkim, located in the Central Himalaya, serve as crucial indicators of climate change, shedding light on cryospheric processes and hydrological impacts. This study utilizes feature tracking-based remote sensing techniques to analyze glacier velocity trends from 1990 to 2022, examining 679 glaciers categorized as clean glaciers (CG), debris-covered glaciers (DG), glaciers associated with lakes (GL), rock glaciers (RG), and smaller glaciers (SG, <0.5 km²). Landsat imagery reveals velocity values ranging from -20.17 m/year to 21.99 m/year, with a mean velocity of 0.49 m/year. spatial-temporal analysis identifies three velocity phases for the glaciers like moderate variability (1990–2000), stabilization (2001–2010), and acceleration (2011–2022). The latest phase shows a sharp rise in mean velocity to 0.75 m/year, correlating with increased warming trends. Smaller glaciers exhibited the highest climate sensitivity, with extreme velocities reaching 21.9 m/year, while debris-covered glaciers showed periodic accelerations exceeding 10 m/year in 1996 and 2022. Spatial analysis highlights the influence of glacier size and elevation, with higher-altitude glaciers (>5000 m) moving faster due to steeper gradients.

Class-wise analysis reveals distinct behaviors. Clean glaciers remained stable (-0.5 to 1.5 m/year), while lake-associated glaciers experienced significant velocity surges, peaking at 19.4 m/year in 2021–2022 due to hydrological influences. Debris-covered glaciers recorded the highest mean velocity (0.66 m/year), whereas rock glaciers were the most stable (-0.08 m/year). High-velocity glaciers clustered near the Teesta basin, suggesting localized drivers like increased precipitation and glacial lake expansion. This study provides crucial insights into Himalayan glacier dynamics, informing hydrological modeling, disaster risk assessment, and water resource management. Future research should incorporate climate datasets and advanced modeling to predict glacier responses under varying climate scenarios, ensuring effective cryospheric monitoring amid rapid environmental change.

How to cite: Dutta, S., Ranjan, R. K., and Gaddam, V. K.: Deciphering Glacier Velocity Dynamics in North Sikkim, India (1990–2022) through Geospatial Investigation, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20954, https://doi.org/10.5194/egusphere-egu25-20954, 2025.

Understanding glacier changes during the Holocene provides key insights into climate variability and cryosphere dynamics. Villarrica volcano (39°S), situated within the Southern Volcanic Zone (SVZ) of Chile, preserves a well-defined record of past glacial extents, with moraines marking post-Last Glacial Maximum (LGM) glacial extents. Despite its potential, the glacial history of Villarrica and the SVZ still remains poorly constrained, limiting our understanding of glacier-climate interactions during the last deglaciation and Holocene.

We present new cosmogenic ³He surface exposure ages from 25 olivine-bearing moraine boulders to better constrain the glacial chronology at Villarrica during the late Holocene. Our chronology reveals multiple phases of moraine formation, including Neoglacial advances at 3350 ± 140 years (n=3) and 1740 ± 225 years (n=3), Little Ice Age (LIA; n=7) advances between 720 ± 340 and 370 ± 220 years, and the onset of modern retreat at 100 ± 50 years (n=12). These advances correlate with shifts in the Southern Westerly Winds (SWW), with Neoglacial advances driven by enhanced moisture delivery, while LIA advances reflect reduced ablation during cooler temperatures. Our findings also demonstrate extended ice positions during the industrial era until the early-to-mid 1900s which corresponds with regional evidence of delayed industrial era warming in Patagonia. Furthermore, the historical volcanic activity at volcanoes like Villarrica can significantly influence glacial landscapes and the preservation of moraines. This study provides a unique opportunity to reconstruct glacial behavior in a highly active volcanic region and offers valuable context for understanding the interactions between volcanic activity, climate, and glacial dynamics in the Southern Hemisphere throughout the Holocene.

How to cite: Orellana-Salazar, Y., Marcott, S. A., Tremblay, M. M., Moreno-Yaeger, P., Romero, M., and Mixon, E. E.: A 3He-based Holocene glacial chronology from Villarrica volcano, Chile, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-320, https://doi.org/10.5194/egusphere-egu25-320, 2025.

Glacial erosion shapes alpine landscapes, produces chemically reactive mineral surfaces integral to the carbon cycle, and informs glacier dynamics applied in ice sheet models. Quantifying primary bedrock erosion has remained elusive due to the inaccessibility of the ice-bed interface. Many erosion estimates thereby rely on basin-wide sediment accumulation rates that can include reworked sediment, potentially causing overestimates of glacial erosion. Here, we quantify glacial erosion of primary bedrock using 60 paired cosmogenic in situ ¹⁴C-¹⁰Be measurements from new and published bedrock samples spread across 10 glacier forefields from 60° N to 16° S. We apply a Monte Carlo forward model that tests millions of scenarios of glacier exposure, burial, and erosion to identify scenarios capable of replicating the measured nuclide concentrations. Our new data are from a glacier in southeast Alaska where samples were collected at two scales: landform-scale along a single roche moutonnée to investigate abrasion versus plucking and valley-scale from the modern glacier terminus to its pre-industrial moraine to constrain glacier length fluctuations. The other 9 sites are across-valley transects abutting the terminus of the modern glacier. We compare our results to modeled erosion rates from a power-based abrasion law and Elmer/Ice glacier model simulations. The cosmogenic nuclide-based erosion rates are consistent across scales and sites, overlapping with the modeled erosion rates that are concentrated below 0.3 mm yr^-1. These findings suggest glacial erosion rates of primary bedrock are much lower than predicted from modern sediment supply studies that reach up to 10 mm yr^-1. Our millennial-scale glacial erosion estimates of crystalline bedrock support a modern bias in erosion estimates (e.g. Ganti et al., 2016) with implications for landscape evolution and sediment delivery models.

How to cite: Jones, A., Brooks, J., Marcott, S., Zoet, L., Lifton, N., Gorin, A., Shakun, J., Helanow, C., and Caffee, M.: Glacial erosion rates of primary bedrock from in situ 14C-10Be measurements are low, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-321, https://doi.org/10.5194/egusphere-egu25-321, 2025.

To date, the Icelandic Ice Sheet (IIS) and Patagonian Ice Sheet (PIS) have been poorly understood with regard to their configuration, dynamics, and evolution during the last glacial cycle. The few glaciological modelling studies of the IIS and PIS to date have placed minimal attention on addressing model uncertainties. As such, their inferential value is poorly interpretable.

To address this, we present the results of history matchings of the 3D Glacial Systems Model (GSM) against curated sets of paleo constraints for the last glacial cycle IIS and PIS. History matching identifies a set of model simulations that are not ruled out given available data constraints and robust uncertainty analysis (including both model and data uncertainties). As such, it aims to “bracket reality” as opposed to the much more difficult task of determining a meaningful most likely chronology.

The GSM is a thermo-mechanically coupled glaciological model with hybrid shallow ice and shallow shelf/stream physics. The climate forcing consists of a fully coupled energy balance climate model and glacial indexed climate forcing using the results of PMIP3 (Paleo Model Intercomparison Project). Approximate 30 GSM ensemble parameters partially account for uncertainties in climate, basal drag, and marine ice processes. The GSM configuration includes fully coupled visco-elastic glacio-isostatic adjustment enabling physically self-consistent relative sealevel predictions. Our presentation focuses on bracketing chronologies for the last glacial cycle IIS and PIS as well as disentangling the relative contribution of atmospheric and marine forcings on mass loss during the deglaciation.

How to cite: Goffin, A., Tarasov, L., Benediktsson, Í. Ö., Licciardi, J., Rivera, A., and Lambert, F.: History Matching of the Last Glacial Cycle Model for the Icelandic and Patagonian Ice Sheets, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-501, https://doi.org/10.5194/egusphere-egu25-501, 2025.

During the Last Glacial Maximum (26,000-19,000 years B.P.; Clark et al. 2009), the Patagonian Ice Sheet (PIS) formed a contiguous ice cap over the southern Andes from 38° to 55° S, with a sea level equivalent to 1.5 m (Davies et al., 2020). Despite recent progress in reconstructing the PIS configuration during the last glacial cycle (Davies et al., 2020), constraints on the timing of PIS retreat and thinning during the last deglaciation remain limited. In order to understand how the PIS responds to centennial and millennial scale changes in climate, we provide geologic constraints to reconstruct the timing of its past area and volume changes and apply numerical ice sheet models to test the sensitivity of the PIS to past climate change. To do this, we apply cosmogenic nuclide dating of exposed bedrock surfaces across the Southern Volcanic Zone in northern Patagonia to document the rates of ice sheet thinning during the last deglaciation. Our data are from elevations of 200-2000 m and span a ~400 km latitudinal transect. Transient model simulations of the PIS with the Ice Sheet and Sea-level System Model (ISMM) were performed to test the sensitivity of the northern PIS to changing climatological inputs driven by the Trace-21ka experiment (He, 2011). Our cosmogenic nuclide ages document the onset of rapid ice sheet thinning that initiated at ~18,000 years B.P. with accelerated and widespread deglaciation occurring after 15,000 years, which is in good agreement with our model simulations (Cuzzone et al. 2024). Together, our data and model simulations show that ice sheet thinning and retreat occurred earlier in the northern sector of the PIS than in the south (Cuzzone et al., 2024), which we attribute to a reduction in wintertime precipitation driven by a poleward migration of the westerly winds. Our work highlights the important, but often overlooked, role of precipitation in modulating both the timing of and magnitude of surface mass balance changes of mid-latitude ice sheets at the millennial-scale following the last glacial period.

How to cite: Romero, M., Marcott, S., Cuzzone, J., Tremblay, M., and Jones, A.: A Data-Model Comparison of Ice Sheet Demise in Northern Patagonia During the Last Deglaciation, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-774, https://doi.org/10.5194/egusphere-egu25-774, 2025.

Tunnel valleys are impressive erosional landforms and may attain extreme depths of almost 600 m. Open and buried tunnel valleys have been mapped in many formerly glaciated sedimentary basins. Characteristics of tunnel valleys include undulating basal profiles, abrupt terminations and steep flanks, all indicative of subglacial incision by pressurised meltwater discharge. Tunnel-valley formation is primarily controlled by climatic and glaciological factors. However, the structural inventory, such as faults and salt structures, have been invoked as controlling the location and orientation of tunnel valleys. To identify correlations that may indicate such a structural control, we compare the distribution and orientations of buried Pleistocene tunnel valleys in the North German Basin to the regional structural inventory.  

Our analysis shows that deep tunnel valleys are restricted to areas with thick erodible Cenozoic deposits. The correlation between the trends of tunnel valleys, faults and salt structures varies between the analysed structural regions. The orientations of tunnel valleys commonly follow the trends of faults and salt structures in regions where the structural trend is NNW-SSE to E-W and ice-flow directions were approximately parallel to this trend. However, correlations are rarely observed if the regional structural trend is NW-SE to WNW-ESE and ice advances occurred thus normal or oblique to the regional fault trend. Faults active under the present-day stress field typically are NNW-SSE to NE-SW trending normal faults. Therefore, the strikes of neotectonically active faults were commonly favourable for tunnel-valley incision and may have promoted subglacial erosion. No clear correlation between the orientations of tunnel valleys and elongated salt structures can be identified.

A major motivation for this study was the potential impact of future glaciations and tunnel-valley incision on the long-term safety of radioactive waste repositories. Our results demonstrate that the presence and orientations of faults and salt structures, however, do not provide consistent indicators for future tunnel-valley incision.

How to cite: Lang, J., Bebiolka, A., Noack, V., Schützke, J., Weihmann, S., and Breuer, S.: Does the structural inventory control tunnel-valley formation? – Insights from the North German Basin, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3674, https://doi.org/10.5194/egusphere-egu25-3674, 2025.

The Laurentide Ice Sheet (LIS) covered vast areas of North America during the Wisconsinan period. The melting of the LIS resulted in the release of a substantial volume of freshwater into the Labrador Sea, thereby affecting the strength of the Atlantic Meridional Overturning Circulation (AMOC), a critical component of the global climate system. Consequently, the investigation of the dynamics of the LIS provides a framework for predicting the melting of analogous ice sheets, such as the Greenland Ice Sheet, in the future. This study presents an updated Quaternary stratigraphy of the Labrador Shelf, based on 2D multi-channel seismic reflection data from three glacial cross-shelf troughs: Okak, Hopedale and Cartwright. Seven different seismic units are described and interpreted in terms of their origin and deposition processes. We observe de- and interglacial deposits between glacial till layers for the first time on the Labrador Shelf. Additionally, sets of incised channels at three different depth intervals have been discovered. The data gathered indicates that these channels are of subglacial origin. Finally, the observations are combined into a shelf evolution model consisting of eight stages and spanning two glacial-interglacial cycles. Our study demonstrates that the cross-shelf troughs of the Labrador Shelf were not fully excavated by the LIS during the Wisconsinan glaciation. Instead, deeper sediment layers contain evidence of older glacial-interglacial cycles. Consequently, the sedimentary succession can be used as an archive to reconstruct the dynamics of glaciations during Quaternary glacial-interglacial cycles.

How to cite: Lenz, K.-F., Gross, F., Gebhardt, C., Lohrberg, A., Schneider, R., Kolling, H., Riefstahl, F., Bautista, O. M., Thamm, V., and Krastel, S.: Reconstructions of the Laurentide Ice Sheet based on Quaternary sediment architecture and buried glacial channels on the Labrador Shelf, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4144, https://doi.org/10.5194/egusphere-egu25-4144, 2025.

The seafloor geomorphology of glaciated continental margins occasionally hosts relict glacial landforms that serve as proxies of the ice sheet dynamics. The Baltic Sea is a relatively shallow, epicontinental, young sea whose formation after the last deglaciation was modulated by global sea-level fluctuations and isostatic adjustments. During the last glaciation, the Baltic Basin (BB) was one of the major advance corridors of the Fennoscandian Ice Sheet (FIS) towards the Central European Plain. It hosted the Baltic Ice Stream Complex – a zone of potentially highly dynamic, warm-based, fast-flowing ice that drained central parts of the ice sheet. Therefore, BB is a key region for reconstructing the dynamics of the last FIS southern sector. However, the availability of high-resolution bathymetric data which may better constrain BB’s geomorphology is still limited. In particular, the southern part of the BB suffers from a lack of high-resolution bathymetry, which leaves glacial landforms, potentially preserved at the seafloor, largely unrecognized. 

Here, we present the results of mapping relict glacial landforms in some areas of the southern BB. The landforms were mapped in ArcGIS based on bathymetric models obtained from the Polish Navy Hydrographic Office, the Swedish Maritime Administration, the General Inspectorate of Environmental Protection, and the Rhenish-Westphalian Power Plant as 0.5 to 10 m grids. We identified individual glacial landforms such as subglacial lineations, subglacial ribs, moraine ridges, grounding line landforms, crevasse-squeeze ridges, meltwater channels, eskers and ploughmarks. The mapping was performed by on-screen digitizing at various scales, depending on landform dimensions. The outcome is a GIS map of glacial geomorphological features preserved at the seafloor. This is the first map displaying the distribution and morphology of relict glacial landforms based on high-resolution bathymetric data in the southern BB. 

This work was supported by the National Science Centre, Poland (grant no. 2021/41/B/ST10/01086).

How to cite: Tylmann, K., Grinbauma, I., Greenwood, S. L., Piotrowski, J. A., and Kasuła, M.: Relict glacial landforms in the southern Baltic Sea Basin, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5689, https://doi.org/10.5194/egusphere-egu25-5689, 2025.

This study advances our understanding of the glacial history of the Putorana Plateau, Central Siberia, by expanding beyond cirque analyses to encompass a broader suite of geomorphological features. Using high-resolution Arctic DEM (2 m) data, this research systematically maps and assesses key glacial landforms, including moraines, cirques, ice-scoured basins, streamlined bedforms, and other large-scale features indicative of past ice dynamics. The focus spans multiple glacial periods, from the Last Interglacial through the Last Glacial Maximum (LGM), with particular emphasis on the major advances during MIS5b and MIS4.

The mapping builds on the recently completed cirque inventory of the Western Putorana by, incorporating larger features to comprehensively reconstruct the glacial history of the region. Detailed geomorphological analysis aims to delineate ice flow patterns, quantify ice extent, and identify variations in glacial behaviour across different stadials and interstadials. By integrating these findings with existing palaeoclimate data and previous studies on wider Siberian glaciations, this research provides critical insights into the extent and timing of glaciations in the region.

Initial results highlight the Putorana Plateau as a dynamic ice-marginal environment, shaped by successive glacial advances and retreats. The largest glacial extent occurred during the Late Saalian (MIS 6) and was followed by substantial glaciations during MIS 5b (90–80 ka) and MIS 4 (60–50 ka) connected to the Fennoscandian Ice Sheet, to form the wider Eurasian Ice Sheet. These advances, pre-date the more globally recognised LGM at 30–22 ka, revealing a complex history of ice-sheet behaviour influenced by regional climatic and topographic factors.

This study fills a critical gap in the palaeoglacial research of Siberia, where previous investigations have primarily concentrated on the Ural or Kamchatka Mountains and other Weichselian glaciation configurations. By providing the first large-scale geomorphological assessment of the Putorana Plateau, this work not only refines our understanding of Siberian glacial history but also establishes a framework for future studies on palaeoclimate and ice-sheet dynamics in other remote and understudied regions.

How to cite: Oien, R. and Lee, E.: Geomorphological Mapping of the Putorana Plateau: Tracing Glacial Histories from the Last Interglacial to the LGM, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5887, https://doi.org/10.5194/egusphere-egu25-5887, 2025.

The rapid retreat and fragmentation of Alpine glaciers is widely reported as humanity faces dramatic climate change in mountainous regions. This rapid change leads to changes in sedimentary processes, which are exposed in recently deglaciated regions. These Alpine glacier forefields offer a wide spectrum of settings through which the ancient sedimentary record can be interpreted. Glacial valley orientation, slope inclination and lithology, and plumbing of subglacial and englacial meltwater drainage all influence the immediate preservation potential of glacial sediments upon deposition. In this contribution, we explore the geomorphology and sedimentology of the Taschachferner (a valley glacier), presenting a new geological-geomorphological map. This small glacier drains an icefield in the Ötztal Alps, and its current ice margin lies at approximately 2550 m a.s.l. Thus far, the glacial sedimentology and its bedrock geology have not been subject to investigation. The bedrock geology is dominated by E-W striking units of paragneiss and amphibolite, and the latter exhibit a series of well-preserved striations together with meltwater-sculpted bedforms (p-forms). The lower region of the glacier can be divided into two parts: (i) a clean-ice part, on the northern valley side with a low, subdued profile and (ii) a debris covered part at the southern valley side, covered with supraglacial debris. The valley margins are dominated by several generations of lateral moraines, the most prominent of which corresponds to the 1852 Little Ice Age Maximum. A well-developed “hanging sandur” is observed immediately in front of the ice margin. This consists of a series of sand and gravel bars cradled in the lee of an interpreted regional fault cross-cutting the bedrock. Sandur deposition is currently influenced and overprinted by dead ice, influencing the trajectory and location of river channels and gravel bars. This paper provides clear lessons regarding the distribution of ice-margin facies associations, which must be incorporated into models of glacier decay in the context of a rapidly
warming climate.

How to cite: Le Heron, D., Mejias Osorio, P., Heninger, M., and Davies, B.: Sedimentology of a Rapidly Retreating Alpine Glacier: Insights From the Taschachferner, Tirol, Austria, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8572, https://doi.org/10.5194/egusphere-egu25-8572, 2025.

In the past the West Antarctic Ice Sheet (WAIS) extended beyond its present-day limits, sometimes as far as the continental shelf edge during cold periods, such as the Last Glacial Maximum (LGM, ~19-23 ka). Sediment deposited at the base of grounded ice is known as subglacial diamicton (or ‘till’). In addition, diamictons can be formed in a range of other glacimarine depositional environments including sub-ice shelf or seasonally open marine settings, as iceberg rafted and scoured diamictons, or glacigenic debris flows. Whilst there has been some progress in characterising subglacial and iceberg-keel scoured diamictons at both macro- and micro-scales, historically it has been difficult to distinguish between different types of diamictons formed in very different settings. This is particularly true for areas where several glacial and glacimarine processes operate, and thus, overprint each other. However, distinguishing between the different types of diamictons is crucial if we are to reliably reconstruct the maximum extent of the WAIS in the past and the timing of its retreat. This information is urgently needed for ice sheet and climate models that are used to predict future WAIS changes and resulting global sea-level rise. The aim of this study is to macro- and microscopically examine, and determine the origin of, diamictons from the outer shelves of the Bellingshausen Sea (core GC371) and the Amundsen Sea (cores VC430, VC436), in West Antarctica. Although the three cores examined in this study were retrieved from sea floor areas affected by iceberg-keel scouring, their diamictons may also represent any or all of the other aforementioned diamicton-forming processes. Micromorphological analyses show that diamictons in all three cores have undergone stress resulting in pervasive deformation subsequent to deposition. Cores GC371 and VC430 contain diamictons with more abundant and better developed microstructures than core VC436, which suggests cores GC371 and VC430 have undergone more intense deformation than core VC436. Micromorphological structures and features at all three core sites demonstrate complicated and/or inverse down-core deformation patterns, which often do not complement a traditional strain profile, and are not consistent between core sites. This indicates potential overprinting of structures at several horizons after multiple deformation events. Future research should focus on attempting to identify and unravel separate deformation events in diamictons, and to further distinguish between diamictons formed in different Antarctic depositional settings.

How to cite: Linch, L.: The micromorphology of iceberg-keel scoured diamictons from the Bellingshausen and Amundsen Seas: An approach to improving reconstructions of West Antarctic Ice Sheet extent., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9400, https://doi.org/10.5194/egusphere-egu25-9400, 2025.

During the Late Palaeozoic Ice Age (LPIA), South Africa was part of the Gondwana supercontinent. It therefore offers remarkably well-preserved outcrops (e.g. Nooitgedacht and Oorlogskloof) that show the extensive glacial influence.

Here, we introduce a newly discovered area in the Northern Cape region where glacially sculpted outcrops reveal a complex relationship between hard bedrock and soft-sediment features. The outcrops feature streamlined structures, clast-rich diamictite, as well as striated surfaces and exceptionally well-preserved flutes, among other features.

The area, which experiences flooding at irregular intervals, serves as an outstanding example of Late Palaeozoic glacial influence and likely represents one of the best-preserved outcrops of pre-Quaternary flutes.

Furthermore, comprehensive mapping of the visible structures enables a detailed analysis of the different phases of glaciation, contributing significantly to our understanding of the complex dynamics of ice flows during the LPIA.

How to cite: Wohlschlägl, R., Mejías Osorio, P., Busfield, M., and Le Heron, D.: In tune with the ice: First description of excellently preserved flutes and other glacial structures from the LPIA in a newly discovered area in South Africa, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9495, https://doi.org/10.5194/egusphere-egu25-9495, 2025.

The European Alps were covered by a large interconnected system of valley glaciers during the Last Glacial Maximum (LGM). Many of the glaciers advanced into the Alpine Foreland leaving large latero-frontal moraine complexes suitable for (direct) exposure age dating and correlation of the ice extent at different times. In contrast to large parts of the Alps, valley glaciers flowing to the east did not reach the Alpine Foreland resulting in limited preservation of datable relicts. Fortunately, two localities at the margin of the Enns and Mur Glaciers have been found, where the requirements (quartz-rich blocks resting on latero-frontal moraine ridges) for age dating using cosmogenic 10Be and 26Al are met. 
The Mur Glacier occupied a W-E oriented valley located south of the Niedere Tauern mountain range in Styria. It had several outlets, one of them terminating in the very east at the village Pöls, where a roughly 400 m wide end moraine ridge is preserved. At least two-phases of ice stabilisation are indicated by two to three superimposed ridges. 1.5 m³ Pegmatite-gneiss blocks are embedded in the end moraine ridge, where we collected three samples to determine their exposure age. Age calculation using cosmogenic 10Be and 26Al yields a mean age of 19.6 ± 1.7 ka, whereby the oldest ages were obtained in the outermost part of the ridge following the expected stratigraphic sequence during ice retreat. These ages are in good agreement with other data of end moraines from LGM ice margins around the Alps. More precisely, the age range falls into a second ice re-advance, specified at other locations (especially at the southern alpine rim) but not differentiable at the Mur Glacier.
At the Enns Glacier, which extended north of the Niedere Tauern mountain range, subparallel to the Mur Glacier, a multiphase moraine complex is preserved, however almost all of the  boulders are limestone or dolomite. We managed to scout few conglomerate/breccia blocks that contain 1-2 cm quartz components in a fine matrix. Three of them are embedded in the termination area and two additional boulders are located further proximal. Mean exposure ages calculated using 10Be range between 14 and 17 ka. Ages calculated from the same samples using 26Al are even more scattered. This is surprising given the similarities in location, valley orientation, geographical location, and altitude between both sample locations. Results from Enns Glacier definitely do not fall into the LGM period. But field evidence such as the location and morphological height of the ridges, strongly suggest that they were formed during the LGM and not in a Late-Glacial phase. Implementation of a snow/forest cover correction only has a minor impact on the calculated age. It is possible that the large spread in the Enns glacier exposure ages is caused by the lithological heterogenity of the sampled boulders. Large quartz clasts resist weathering for a longer duration while the matrix is continuously removed until one clast falls out and results in a discontinuous accumulation of cosmogenic radionuclides at the surface. Discussion at the conference is appreciated.

How to cite: Griesmeier, G. E. U., Neuhuber, S. M., Braumann, S. M., Reitner, J. M., Le Heron, D. P., Marchhart, O., and Wieser, A.: Cosmogenic radionuclide exposure ages from the Enns and Mur Glaciers in the Eastern Alps (Styria/Austria), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10580, https://doi.org/10.5194/egusphere-egu25-10580, 2025.

The role of large subsurface landforms produced during glaciations of the Pleistocene is still poorly understood with respect to groundwater flow. In particular, so-called tunnel valleys formed beneath ice sheets, acted as drainage systems of glacial meltwater. Their dimensions (up to 5 km width, 400 m depth, 100s of km length) reflect the massive amount of meltwater that incised into and flushed the subsurface beneath ice sheets.

To understand the potential of tunnel valleys as preferential flow pathways of offshore freshened groundwater (OFG) in the southeastern North Sea, we sailed 320 km of marine time-domain controlled-source electromagnetic surveys on 10 profiles using the surface-towed SWAN system on R/V ALKOR. In particular, we aim to answer the following questions: (1) Does the distribution of electrical resistivities indicate the presence of freshened groundwater in the subsurface of the North Sea? and (2) Can we delineate different resistivity distributions inside tunnel valleys?

Here we show our subsurface electrical resistivity distribution from 2D inversions of the TD-CSEM data with and without structural constraints. We compare these results to a dense net of high-resolution 2D seismic reflection data and additional information from core data in similar geological setting, integrating geophysical and geological data.

The subsurface electrical resistivities show good correlation with the structures prevalent in the 2D seismic reflection data, where correlation is strongest for the upper and lower parts of the tunnel valleys. The electrical resistivity distribution also correlates with deeper Paleogene and Neogene sediments showing low electrical resistivities, likely corresponding to brines. These sediments have been updomed into a large anticline due to salt tectonics in the area, which is reflected in the geometry of electrical resistivities. In between the shallow low resistivity Holocene to Pleistocene sediments and the deeper low resistivity Neogene sediments are regions of significantly increased resistivities in Plio-Pleistocene sediments. These regions are interpreted to represent remnant offshore freshened groundwater from the flushing of meltwater below ice sheets during the Pleistocene, likely to be widespread and not limited to the southeastern North Sea.

How to cite: Lohrberg, A., Haroon, A., Moosdorf, N., and Krastel, S.: The role of buried tunnel valleys of the southeastern North Sea for offshore freshened groundwater: New insights from surface-towed time-domain CSEM measurements, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10687, https://doi.org/10.5194/egusphere-egu25-10687, 2025.

Glacial environments are undergoing rapid transformations due to climate change, which can be observed in the sedimentological processes associated with ice masses. In mountain regions, these can vary within a catchment due to controlling factors such as geological setting and debris sources, slope processes and instability, orientation of the glacier, and glacial dynamics. The Rofental is a valley in the Austrian Alps with a rich history in glaciological research, and hosts several glaciers that exemplify some of these differences. However, until now, there has been no detailed sedimentological work done, in spite of the yearly increase in supraglacial debris on many glaciers, as well as significant ice margin and forefield changes. To address this, we present the results of sedimentological and geomorphological mapping from 2023 and 2024, integrating ground-level observations and drone imagery from fieldwork at 3 different glaciers in the Rofental area: the Hintereisferner, Guslarferner, and Vernagtferner. These glaciers have varying degrees of debris cover and, in some cases, exhibit preservation of delicate sedimentary depositional features on the ice itself. Questions arise regarding transport mechanisms of the debris, including the relative influence of englacial meltout, supraglacial stream deposition and mass wasting (e.g. rockfalls and debris flows). The origins of this debris, its impact on preservation of dead ice over the coming years, and its influence on downwasting rates deserve investigation. By studying these glaciers, we can gain insights into how they will continue to evolve over time, compare them to the previous sedimentary record, and potentially revise some of the established characteristics for retreating glaciers. 

How to cite: Mejías Osorio, P., Wohlschlägl, R., Davies, B. J., Vandyk, T., Karbacher, S., and Le Heron, D. P.: Glaciers in the Rofental, Ötztal Alps, Austria: a sedimentological perspective, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11750, https://doi.org/10.5194/egusphere-egu25-11750, 2025.

The Ediacaran Period (635 Ma to 538.8 Ma) was a crucial transition interval for the Earth System between the Proterozoic and Phanerozoic worlds. Ediacaran rocks preserve evidence for both profound changes to the global carbon cycle via the stable carbon isotope record, and the emergence of ecosystems containing complex macroscopic organisms, including early animals, through the trace and body fossil records. Nevertheless, geological evidence of Earth’s climate through the Ediacaran is poorly constrained and often equivocal, which limits deeper comprehension of how the Earth System functioned during this time, and the possible feedbacks between biotic and climatic evolution.

The Ediacaran Period is sandwiched between the Cryogenian Period (720 Ma to 635 Ma), which may have been characterised at times by extreme ‘Snowball Earth’ icehouse conditions, and the Cambrian Period (538.8 Ma to 486.85 Ma), which was likely a prolonged greenhouse interval. There is abundant geological evidence of glaciation in the mid- to late Ediacaran (~593 to 579 Ma) that, whilst challenging to correlate in detail, appears to break the ‘Snowball Earth’ mould of globally distributed low altitude ice seen during the preceding Cryogenian Period. In particular, a cluster of glacial deposits on palaeocontinental Avalonia and Gondwana are associated with this interval, with glaciation considered to have terminated just prior to the first appearance of early animal fossils.

Here, we critically evaluate the depositional ages and likely glaciogenicity of candidate glacial deposits of plausibly mid-Ediacaran age. Our re-evaluated dataset provides a framework for assessing the geographical and temporal extent of icehouse conditions in the mid-Ediacaran. We combine this framework with new climate and icesheet model simulations to examine the possible nature of the climate system through this interval. Our data-model comparison supports the hypothesis that, in contrast to the preceding Cryogenian-style ‘Snowball Earth’, the mid-Ediacaran icehouse followed the Phanerozoic paradigm of low altitude ice confined to the mid- to high palaeolatitudes, a pattern of glaciation that continues to the present day.

How to cite: Wong Hearing, T. W., Pohl, A., Tindal, B. H., Vandyk, T. M., Fluteau, F., Liu, A. G., Harvey, T. H. P., and Williams, M.: Earth’s first Phanerozoic-style icehouse in the late Neoproterozoic, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12696, https://doi.org/10.5194/egusphere-egu25-12696, 2025.

Yukon has been repeatedly affected by the northern Cordilleran Ice Sheet (NCIS). Although termed an ice sheet, it is better described as an ice complex, with quasi-independent lobes originating from mountainous areas around the border of Yukon. This ice complex produced irregular, digitate horseshoe-shaped glacial limits largely on the plateau area of central Yukon, at the eastern edge of unglaciated Beringia. These limits have broadly followed a pattern of progressively diminished extent. It is likely that variations in precipitation across the source areas of these lobes affected their extent and timing during various glacial cycles. The growth model of the NCIS is contingent on ice from numerous cirques and ice fields in the source areas eventually amalgamating into these large, coalescent ice lobes. What is unclear is the contribution of cirque and valley glaciers from the few mountainous areas near the limits of glaciation. This research describes the contribution of cirques and valley glaciers in two areas at the glacial limits from MIS 6-2.

Central Ruby Range is in southwest Yukon and was affected by the Saint Elias lobe. It encompasses the limits of MIS 2, 4 and 6 glaciations. Stratigraphic analysis paired with ¹⁰Be surface exposure dating indicates extensive local ice production from cirques and plateau surfaces during MIS 2. During early MIS 2, local valley glaciers advance to the edge of the range but had retreated before inundation by the St. Elias lobe, likely due to local precipitation reduction. These alpine ice centres were responsive to deglacial climatic fluctuations and hosted significant re-advances during the Older Dryas, despite their location in the rain shadow of the St. Elias Mountains and during rapid retreat of the St. Elias Lobe. The MIS 4 limit is slightly more extensive than the MIS 6 limit here, likely because local ice contributed to this portion of the St. Elias Lobe. The record and limit of the MIS 6 glaciation is poorly constrained here but 150 km to the NW, MIS 6 is 4 km more extensive than 4.

Granite Creek is in the Gustavus Range in central Yukon at the MIS 2 limit of the Selwyn lobe. During MIS 2 a tongue of the Selwyn lobe occupied the lower portion of Granite Creek, forming a lake. Cirque glaciers near the margin were overrun by the Selwyn lobe. Cirque glaciers terminating in the lake advanced due to floating ice margins, but these maximum limits are not reflected in the geomorphic record; their well-defined moraines are recessional from this maximum. Stratigraphic studies indicate extensive MIS 4 cirque glaciation but no evidence of a proximal Selwyn lobe. During MIS 6, cirque glaciers were extensive early enough that the Selwyn lobe did not inundate local cirque valleys even though the entire area was overrun.

This research indicates peripheral ice accumulation could contribute to the NCIS. However, variations in precipitation imply that peripheral ice sources were largely out of sync with local ice sources.

How to cite: Ward, B., Cronmiller, D., Steinke, J., and Bond, J.: Distal Cirque Contribution to the Northern Cordilleran Ice Sheet, Yukon, Canada, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13259, https://doi.org/10.5194/egusphere-egu25-13259, 2025.

Despite a significant body of work utilizing terrestrial cosmogenic nuclide dating to examine the late Quaternary glacial history of the mid to northern Rocky Mountains, we lack an understanding of alpine glacial and ice cap responses to climate change in the southern Rocky Mountains (SRM) and the Southwestern United States (SWUS). While limited work has examined the timing of glacial advance and retreat in the SRM of New Mexico using relative age dating techniques, only one study to date has examined last glacial maximum glacier extents in a mountain valley in the southern Sangre de Cristo mountains (SdCm). The lack of age control for the southernmost Rocky Mountain glacial sequences limits our understanding of the timing for SWUS glacial retreat in response to late Quaternary warming periods. Additionally, while limited work has suggested an absence of Holocene glaciation in valley glacier systems at the far southern extreme of the SdCm near Santa Fe, New Mexico, the southernmost limit to Holocene glaciation within the United States remains uncertain.

Here, we develop preliminary moraine chronology, model glacier and ice cap extents, and produce a paleoclimate record throughout the late Quaternary at Costilla Massif in the SdCm of New Mexico. We aim to use the glacial and paleoclimatic records to examine variations in climate between Costilla Massif and other glaciated regions of the Rocky Mountains and test the hypothesis that latest Pleistocene and Holocene glaciation occurred in the SRM. We use 10Be terrestrial cosmogenic nuclide exposure dating of quartz monzonite boulders to develop a glacial chronology for six moraines in two glaciated valleys at Costilla Massif. We use the updated glacial energy/mass balance of Plummer and Phillips to (1) model the extent of valley glaciation and (2) determine paleoclimatic deviations from modern conditions required to sustain glaciers at each moraine position. We compare ice cap extents at Costilla Massif with similar small ice caps throughout the southern Sdm to determine changes in extent related to fluctuations in local and regional climate. We then compare our moraine-derived paleoclimate record with similar records elsewhere in the Rocky Mountains and other climatic proxy records throughout the SWUS and SRM regions to provide analysis of warming trends during the Late Quaternary.

Preliminary soil relative age dating techniques indicate glacial landforms at Costilla Massif range in age from MIS6 (~195 – 123 ka) to the Holocene. Given their limited extent and relative lack of soil development, we hypothesize that the youngest cirque glaciers at Costilla Massif are of Holocene age. Additionally, we predict the Costilla Ice Cap persisted into the Holocene. We predict that valley glaciers at Costilla massif began to retreat earlier than occurred in the mid- to northern Rocky Mountains at similar rates to elsewhere in the SdCm. However, the presence of a locally extensive ice cap and local variations in topography and precipitation and temperature regime compared to elsewhere in the SdCm permitted stabilization of cirque glaciation during the early Holocene in contrast to previous studies suggesting a deglaciation of the SdCm by about 15 ka.

How to cite: Feldman, A., Sion, B., Anderson, L., Brugger, K., and Bustard, J.: Quaternary climate inferences for the southernmost Rocky Mountains from cosmogenic dating and glacier modeling at Costilla Massif, New Mexico., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13921, https://doi.org/10.5194/egusphere-egu25-13921, 2025.

Records of ice-rafted detritus (IRD) from the global oceans indicate the expansion of large Northern Hemisphere ice sheets prior to the Plio–Pleistocene transition. Yet, the geometry of these early ice sheets remains unclear due to limited availability of well-dated terrestrial sediments. In the German and Polish sectors of the North European Plain, chronostratigraphic schemes evolved independently to produce a contrasting picture of regional glacial history. The most divergent points hinge upon the timing and number of alleged Middle Pleistocene Eurasian Ice Sheet (EIS) advances to reach as far south as the Central European Uplands (~51°N).

Here we present ¹⁰Be-²⁶Al abundances measured directly in subglacial tills obtained from two locations within ~180 km of the southernmost German-Polish border (Peres, DE; Jaroszów, PL). Using Particle-Pathway Inversion of Nuclide Inventories (P-PINI), we calculate sediment burial ages by matching large arrays of simulated ¹⁰Be-²⁶Al pairs to empirical data, accounting for glaciation-induced complexities in pre-burial sample nuclide ratios. These results are supplemented by U-Pb geochronology of detrital zircons within the tills as a means of inferring source area correlations and interpreting former ice flow pathways.

Our findings suggest equivalency between the lower stadial of the Elsterian glacial stage in the eastern North German Plain and the Sanian 1 in the Polish Silesian Lowlands. Despite their conventional respective assignments to MIS 12 and MIS 16, our data indicate an older concordant age (MIS 36–56) for both deposits. This implies a temporal compression of the Polish pre-glacial series and provides evidence of the disputed Narevian glacial stage below the Nidanian. Dating uncertainties allow correlation with either the floristically-defined Pinnau (Menapian) or the older Lieth (Eburonian) cold phases recognized across Germany and northwest Europe. We further examine these correlations in light of our findings from the well-studied Szczerców lignite mine exposures (central PL), ~200 km east, where dating of Sanian 1 and 2 tills in stratigraphic position suggests that they were emplaced between MIS 16 and 22. Collectively, these results point to an Early Pleistocene advance of the EIS, extending to ~51°N at a time when peak glacial global sea levels were ~50–100 m higher than those of the Last Glacial Maximum.

How to cite: Wagner, K., Yla-Mella, L., Margold, M., Knudsen, M. F., Krzyszkowski, D., Wachecka-Kotkowska, L., Wieczorek, D., Rother, H., Wansa, S., Szuman-Kalita, I., Eriksen, B. L., Andersen, J. L., Olsen, J., Sláma, J., and Jansen, J.: An advance of the Eurasian Ice Sheet to the Central European Uplands preceded MIS 16, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14643, https://doi.org/10.5194/egusphere-egu25-14643, 2025.

The subglacial environment is a key part of glacier dynamics, and the ‘slipperiness’ of the bed has shown to be related to the rate of sea level rise. Investigations of the subglacial hydrological system associated with soft beds are rare. Studies from modern glaciers have revealed there is a continuum in subglacial fluvial behaviour associated with a deforming bed, from channelised to distributed. We use data from wireless in situ subglacial probes, GPR, glacier velocity data from remote sensing and GNSS and drone surveys to investigate this continuum. We then use this data to relate this to the geomorphology and sedimentology from both modern and Quaternary melt-water corridors, in order to reconstruct past subglacial processes.

How to cite: Hart, J., Martinez, K., Baurley, N., Robson, B., and Andrews, A.: Subglacial meltwater corridors and their relationship to the soft-bed subglacial hydrological continuum, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15497, https://doi.org/10.5194/egusphere-egu25-15497, 2025.

Reconstructing the last glaciation of the European Alpine Ice Field via numerical modelling has been challenged by persistent model-data disagreements, including large overestimations of its former thickness. Here, we tackle this issue by applying the Instructed Glacier Model, a three-dimensional, high-order, and thermo-mechanically coupled model enhanced with physics-informed machine learning. This new approach allows us to produce an ensemble of 100, Alps-wide and 17 thousand-year-long (35-18 ka) simulations at 300 m spatial resolution. Unfeasible with traditional models due to computational costs, our experiment substantially increases model-data agreement in both ice extent and thickness. The model-data offset in ice thickness, for instance, is here reduced by between 200% and 450% relative to previous studies. The results yield implications for more accurately reconstructing former ice velocities, ice temperatures, basal conditions, glacial erosion processes, glacial isostatic adjustment, and climate evolution in the Alps during the Last Glacial Maximum. Furthermore, the switch to GPU-based computations enables us, for the first time, to also couple our Alpine Ice Field model with three-dimensional and time-transgressive ice advection of particles (tens of millions). Here, particles are seeded to mimic both the subglacial (e.g. abrasion, plucking) and supraglacial (e.g. rockfall) origins of glacially-transported sediments. Using our ensemble best-fit simulation, we present the results of tracking the sink-to-source transport trajectories of distinct LGM ice-contact deposits (e.g. terminal moraines), and the LGM source-to-sink transport trajectories of specific surface lithologies, throughout the Alps. We find that modelling the Alps-wide glacial transport of particles also helps us better understand the complex internal ice dynamics of the former Alpine Ice Field, including transfluences and the zipping/unzipping behaviours of different tributary glaciers. More generally, this work demonstrates that physics-informed AI-driven glacier models can overcome the bottleneck of high-resolution continental-scale modelling required to accurately describe complex topographies and ice dynamics.

How to cite: Leger, T., Jouvet, G., Kamleitner, S., Mey, J., Herman, F., Finley, B., Ivy-Ochs, S., Vieli, A., Henz, A., and Nussbaumer, S.: A data-consistent, high-resolution model of the last glaciation in the Alps achieved with physics-driven AI , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15931, https://doi.org/10.5194/egusphere-egu25-15931, 2025.

The Late Palaeozoic Ice Age (LPIA) is Earth’s most recent, severe glacial epoch and in Namibia experienced its acme at about 300-298 Ma. The record of the glaciation in southern Africa is exceptional, and many of the deposits consist of poorly-sorted diamictites of the Dwyka Group that were deposited beneath glaciers or at their margins. The study of these deposits has often been neglected, because sedimentologists have tended to regard these deposits as complex, massive, or confusing. New quantitative approaches to oriented samples developed in the course of Quaternary glacial studies is beginning to change this, and thus this study will consist of a detailed evaluation of oriented diamictite samples recovered from northern Namibia (Opuwo) the Aranos Basin (central-southern Namibia) and the Karasburg Basin (Namibia-South Africa border). The aim of this Masters project is to produce a substantial new set of directional data. Previous authors have proposed diverse and often conflicting ice-flow directions from different data sources, and it is hoped that this controversy can be resolved.

Oriented samples were collected during fieldwork in 2019 and 2023 from five different locations. Each was cut in three directions, ie “north-south”-, “east-west”- and “top”-orientations, and thin sections were prepared from these, which were then scanned in high resolution. These scans are being quantitatively analysed using the “microstructural mapping” method proposed by Phillips et al. (2011). Measuring the direction of the longest axis of the grains in each oriented thin section will be achieved using CorelDraw. The data from CorelDraw is then exported to OpenStereo, a program which is used for structural geology analysis, to draw rose diagrams of clast orientation. The rose diagrams from each sample will thus represent three sides of a cube, and this “pseudo cube” will allow the orientation of clasts to be characterised in 3D space. From this, an understanding of the dynamics of sediment deformation, and thereby ice flow orientation, will be determined. At PANGEO, preliminary results will be presented.

The main goal of my thesis is to contribute to a nuanced paleo-reconstruction through a better understanding of glacial dynamics in the LPIA. This will not only improve understanding of ancient glacial environments in Namibia but also further the understanding of contemporary glacial behaviour through exploitation of well-preserved samples. Given the complex issues in unraveling past ice flow in ancient rocks, many datasets have been combined by previous authors to achieve this (striation orientations on bedrock, crossbed orientations etc). By contrast, this will be the first large and significant database of flow directions from the LPIA sedimentary record of Namibia drawn from one single source.

How to cite: Heninger, M. and Le Heron, D.: Bringing Order to Chaos: Micromorphological Analysis of Late Palaeozoic glacial diamictites  , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16663, https://doi.org/10.5194/egusphere-egu25-16663, 2025.

Maladeta Glacier, one of the largest glaciers of the Pyrenees, is located on the Maladeta Massif (Central Pyrenees), close to the highest point of the range, the Aneto peak (42° 37' 52 N, 0° 39' 24 E; 3,404 m a.s.l.).  Maladeta Glacier is one of the most meridional ice masses in Europe, and is considered a very good proxy indicator to study the impact of climatic changes on mediterranean mountains.

This glacier is 650 meters long, occupy an area of 24.8 ha and their maximum altitude is ~3,200 meters. At the end of the last century, due to the retreat, the glacier split into two smaller bodies. The main aim of this research is to present an analysis of the evolution of the glacier since the LIA and examine their shrinking. Based on morphological features, the extent of the glacier, their Equilibrium Line Altitude (ELA) and the temperatures in the study were calculated for the following periods: LIA, 1957, 1983, 2006, 2012 and 2018. To estimate the glacier extension during the LIA, the moraines were mapped by using photo interpretation techniques. For the recent phases digital aerial photographs and satellite images were used.

The preliminary results of the research reveal a retreat of the Maladeta Glacier since the LIA. The length of the glacier has been severely reduced, and its area decreased from 128 ha during the LIA to 24.8 ha in 2018. During this period, the ELA has increased from ~2,894 to ~3,108 m a.s.l. These data reveal a huge retreat of the glacier since the LIA, showing an increase of the temperature in the study area of 1.11-1.39°C from LIA to 2018.

How to cite: Campos, N., Alcalá, J., Emmer, A., Sattar, A., Veettel, B. K., and Le Roy, M.: Evolution of the Maladeta Glacier (Central Pyrenees) since the Little Ice Age, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20001, https://doi.org/10.5194/egusphere-egu25-20001, 2025.

The Weichselian Ice sheet extent during the Last Glacial Maximum has not been thoroughly described for the Danish North Sea. Particularly towards the western sector, where studies have tended to focus on the deeper geology. With offshore activities related to the renewable energy transition, focus on quaternary glacial landscape evolution, its geological history and the associated geotechnical challenges has risen.    

Regional high resolution seismic mapping combined with conventional and high-resolution vintage seismic data has revealed glaciotectonic thrusting in glacio-lacustrine deposits in the western part of the Danish North Sea. The glacio-lacustrine deposits are part of a laterally extensive unit that covers the entire southern part of the western Danish North Sea revealing evidence of a   large ice-dammed lake in front of the Weichselian ice sheet. Deformation of glaciolacustrine sediments has been observed providing geomorphological evidence of the approximate position of the Weichselian ice sheet in the Danish North Sea.  Additionally previous ice sheet positions have been identified, revealing a retreat pattern characterized by at least three phases of ice marginal lake development. The drainage of the glacial lake is recorded in the sediments as erosional channels which appears to drain through a prominent landscape feature known as the Elbe Paleo valley. This study presents the geological landscape evolution from the last glacial maximum to the early Holocene with emphasis on the glacial processes that have shaped the area.

How to cite: Prins, L. T., Allaart, L., Christensen, N., Vangkilde-Pedersen, T., Hansen, K., Lauridsen, B., and Knutz, P.: Last Glacial Maximum to early Holocene - ice sheet extent and landscape development in the Western Danish North Sea, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20816, https://doi.org/10.5194/egusphere-egu25-20816, 2025.

Over the past century, global irrigation extent has expanded nearly fivefold, increasing from approximately 63Mha in the early 1900s to over 306Mha today. This growth has been particularly pronounced in Asia, which accounts for roughly 85% of current global irrigation withdrawals. Irrigation, as one of the most impactful land management practices, substantially influences regional climate by altering precipitation patterns and cooling surface air temperatures. These meteorological changes raise important questions about how irrigation-driven weather modifications might affect glaciers in High Mountain Asia (HMA). This study investigates the impact of irrigation expansion on glaciers in HMA using simulations from the Irrigation Model Intercomparison Project (IRRMIP). IRRMIP provides historical climate simulations (1901-2014) under two contrasting scenarios: (1) the Irr-scenario, representing real-world irrigation trends, and (2) the NoIrr-scenario, modeling a world with irrigation extent fixed at early 20th-century levels. These scenarios are then used as inputs for the Open Global Glacier Model (OGGM) to assess the effects of irrigation expansion-induced climate changes on glaciers. Our results reveal that irrigation expansion had an important impact on glacier changes in HMA. Without irrigation expansion, glaciers would have lost considerably greater volume loss over the 1985-2014 period compared to the real-world case with irrigation expansion. This outcome discovers the buffering effect of irrigation on glaciers in HMA, partially offsetting climate-induced glacier loss and underscores the interconnection between human land management and cryospheric systems.

How to cite: Ponds, M., Aguayo Gutierrez, R., Yao, Y., Thiery, W., and Zekollari, H.: The effect of irrigation on glacier evolution in High-Mountain Asia, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-203, https://doi.org/10.5194/egusphere-egu25-203, 2025.

Glaciers adapt slowly to changing climatic conditions, leading to a time lag between climate change and the resulting impacts, such as sea-level rise, water supply changes, and ecological impacts. While previous projections of all glaciers around the globe have mainly focused on the 21st century, longer timescales are essential to fully understand the glacier response to climate policies and associated warming. 

Using eight glacier evolution models, we simulate global glacier evolution over multi-centennial timescales, allowing glaciers to equilibrate with climate under various constant global temperature scenarios. We estimate that glaciers globally will lose about 40% of their mass, relative to 2020, corresponding to a global mean sea-level rise of more than 10 centimeters even if temperatures stabilized at present-day conditions. The effect of climate policies is very pronounced: under the +1.5°C target of the Paris Agreement, more than twice as much global glacier mass remains at equilibration compared to the mass projected under the warming level resulting from current policies (+2.7°C by 2100 above pre-industrial). 

Long-term global glacier mass loss is highly sensitive to global mean temperature, with each additional 0.1°C warming leading to a ca. 2% additional increase in global glacier mass loss. These long-term losses largely exceed those projected over the 21st century, implying that the most substantial impacts of today's climate policies on glacier mass will unfold after 2100. Notably, regions previously found to experience limited mass loss in the 21st century, such as Arctic Canada, Russian Arctic, and Subantarctic & Antarctic Islands, are projected to lose substantial mass on longer timescales. 

Our findings underscore the necessity of extending the focus of glacier studies beyond the 21st century to fully comprehend the long-term implications of today’s climate policies.

How to cite: Zekollari, H., Schuster, L., Maussion, F., Hock, R., Marzeion, B., Rounce, D. R., and GlacierMIP3 participants, T.: Current climate policies will affect multi-century global glacier change, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-242, https://doi.org/10.5194/egusphere-egu25-242, 2025.

The Himalayan region is experiencing a higher rise in temperature than the global mean, leading to glacier retreat. This retreat is contributing to the rapid formation and expansion of numerous moraine-dammed lakes. Simultaneously, the Himalayan region is witnessing a surge in development activities, including road and tunnel construction, hydropower projects, rapid urbanization, and a booming tourism industry. These changes increase the region's susceptibility to glacial lake outburst floods (GLOFs) by altering the natural ecosystem. However, infrastructure development activities can require significant time, during which retreating glaciers may create new lakes, creating new challenges for risk management. Consequently, regions that appear safe today may become vulnerable in the future. In this context, our study focuses on the Alaknanda basin, an area with a high concentration of glaciers and extensive developmental activity.

In this study, we have identified potential lake sites in the Alaknanda basin and assessed their impact on the infrastructure. We used the Himalayan Glacier Thickness Mapper (HIGTHIM) tool to estimate future glacial lakes. It uses the laminar flow method, which estimates ice thickness by balancing factors such as ice surface slope, glacier geometry, and basal shear stress. This method identifies potential subglacial depressions that may become exposed during glacier retreat, thus predicting the area and volume of future glacial lakes.

We identified 28 potential lake sites with a total area of 471.81 ha and a potential to store 113.4 million m³ of water. A highly susceptible lake in the Vishnuganga sub-basin, with an area of 38 ha and a volume of 14.5 million m³, is assessed to understand the impact of GLOF on the downstream region. This study evaluates a possible GLOF caused by a moraine-dam failure using the hydrodynamic model HEC-RAS. This model uses SRTM DEM to understand the channel geometry and downstream topography. The simulation predicts an average flood depth of 10 m and a flood velocity of 5 ms^-1 within the settlement, located 10 km from the lake. This settlement experiences flooding within 53 minutes with a peak discharge of 6200 m³s^-1 in a high-risk scenario.

Considering the uncertainties in future moraine formations, a sensitivity analysis was conducted by varying the moraine breaching parameters to model different risk scenarios. In addition, the study incorporates hazard, vulnerability, and risk mapping of the downstream flood-affected area to assess potential GLOF impacts comprehensively. These findings highlight the critical role of GLOF prediction in safeguarding downstream communities and guiding future planning efforts. Considering the ongoing and future development activities in this region, it is essential to integrate GLOF risk assessments into development strategies to minimize the potential impact on vulnerable communities and infrastructure.

How to cite: Jadhav, J., Kulkarni, A., and Prasad, V.: Assessing the risks from a potential Glacial Lake Outburst Flood in the Alaknanda Basin, Central Himalaya, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-511, https://doi.org/10.5194/egusphere-egu25-511, 2025.

Permafrost degradation poses a significant threat to the organic carbon (C) pool primarily through regulating microorganisms. However, microbial responses and their associations with C loss across vertical profile remain unclear. Here, we used metagenomic sequencing to investigate bacterial communities in 125 samples from five 15 m-depth permafrost cores, spanning from the active layer to the permafrost layer along a degraded gradient on the Qinghai-Tibet Plateau. We find that α-diversity decreases, while stochastic processes and community stability increase from the active layer to the permafrost layer. Along permafrost degradation, these community attributes follow similar variations within the active layer but remain basically constant within the permafrost layer. The relative abundance and interaction of core taxa play important roles in maintaining community stability in the active and permafrost layers, respectively. Interestingly, degradation strengthens the negative effect of community stability on C storage, with this link being stronger in the active layer than the permafrost layer, further exacerbating C loss. Our findings provide novel insights into the capacity of microbial-mediated permafrost C sequestration and contribute to modeling C dynamic under future warming.

How to cite: Chen, S., Bahadur, A., Wu, T., Wu, Q., and Wei, P.: Divergent responses of bacterial communities to permafrost degradation and their roles in mediating carbon across vertical profile, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2227, https://doi.org/10.5194/egusphere-egu25-2227, 2025.

Ski resorts, as main climate and economic resources, play key roles to achieve UN Sustainable Development Goal 8 (promoting decent work and economic growth) in global ice-snow areas. However, warming is influencing spatial suitability of Chinese ski resorts. The study develops an integrated framework that combines machine learning models (MaxEnt and Random Forest) with multi-model ensemble (MME) CMIP6 climate projections to evaluate ski resort suitability in China under current and future climate scenarios. Results show that current suitable areas are concentrated in Northeast and North China, in which winter temperature (i.e. artificial snow weather conditions) and tourist sources are key indicators. Under low-emission scenarios, suitability slightly increases by 2050 but declines significantly by 2070 under high-emission scenarios (19.90% reduction nationally). Regional differences are significant, with Southern China experiencing the largest decline (55.71%), followed by Northeast (21.23%), North (18.68%), and Northwest (10.42%). The suitability centroid shifts mildly from North China to northwestward with a trend toward higher altitudes and latitudes. 

How to cite: Wang, S. and Zhao, R.: Suitability of Chinese snow resorts: present and future, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2446, https://doi.org/10.5194/egusphere-egu25-2446, 2025.

During the last decades, most glaciers have been retreating and losing mass in all high-mountain regions, where permafrost has also undergone warming, degradation, and ice loss. In this context, rock glaciers, a visual indication of the presence of mountain permafrost, have gained attention because they host shallow groundwater resources. Hence, rock glaciers could represent a contributor for future water supply, especially in arid and semi-arid mountain areas and/or during dry periods. However, a growing body of literature, mostly composed of local scale studies, has reported high concentrations of solutes, including trace elements, in rock glacier-fed waters, with negative implications on water quality. Therefore, the potential for rock glaciers to function as safe sources for drinking water supply may be questioned, although the main drivers of solute export from rock glaciers are still little understood. Here, we investigated how geographical and geological settings, together with cryospheric conditions, influence the water chemistry of intact (containing internal ice) and relict (without internal ice) rock glaciers, and assessed the potential implications for water quality. To do this, we assembled an unprecedented dataset on 201 rock glacier springs from mountain ranges across Europe, North and South America, and we applied a combination of machine learning, multivariate and univariate analyses, as well as geochemical modelling. Several intact rock glacier springs had higher concentrations of sulphate and trace elements (e.g., Ni, Al, U) than relict ones. Accordingly, one third of springs issuing from intact rock glaciers had a water quality that did not meet the requirements of drinking water standards, with respect to only 5 % of relict rock glacier springs. The ice presence combined with specific lithologies (e.g., paragneisses) enhanced solute concentrations in rock glacier springs, due to intense oxidation of sulphide minerals that was also responsible for the elevated trace element concentrations. Since rock glaciers are emerging as key mountain water resources as well as potential threats to water quality, we call for an international effort to investigate the hydrochemistry of rock glacier springs across the globe, especially in understudied mountain ranges (e.g., Himalayas, Caucasus) and where these springs are used for drinking purposes.

Brighenti, S., Colombo, N., et al. Factors controlling the water quality of rock glacier springs in European and American mountain ranges. Science of the Total Environment 953, 175706 (2024). https://doi.org/10.1016/j.scitotenv.2024.175706

NC and SB equally contributed to this work. NC and MF were supported by the project NODES, which has received funding from the MUR – M4C2 1.5 of PNRR funded by the European Union – NextGenerationEU (Grant agreement no. ECS00000036).

How to cite: Colombo, N., Brighenti, S., Wagner, T., Pettauer, M., Guyennon, N., Krainer, K., Tolotti, M., Rogora, M., Paro, L., M. Steingruber, S., Del Siro, C., Scapozza, C., R. Sileo, N., D. Villarroel, C., Hayashi, M., Munroe, J., Trombotto Liaudat, D., Cerasino, L., Tirler, W., Comiti, F., Freppaz, M., Salerno, F., Litaor, M. I., Cremonese, E., Morra di Cella, U., and Winkler, G.: Intact rock glaciers as weathering reactors: influence on spring water quality, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3731, https://doi.org/10.5194/egusphere-egu25-3731, 2025.

Glacial lake outburst floods (GLOF) pose a significant risk for settlements and infrastructure in glacierised catchments. Various studies have investigated the current distribution and past evolution of the abundance of glacial lakes and their associated flood risk. Overall, a positive trend in both the number of glacial lakes and the incidence of GLOFs seems to be identifiable as climate change leads to glacier retreat and larger lakes. As climate change is expected to lead to continued substantial glacier retreat worldwide, it is very likely new glacial lakes will continue to emerge and pose risks to downstream populations, infrastructure and ecosystems. To mitigate these risks, the analysis of present and of future glacial lake abundance is therefore crucial. This study aims to detect bedrock depressions that could allow the development of future glacial lakes. The detection is based on a new dataset of subglacial bed topographies from ice-thickness estimates derived using velocity-based inverse modelling in the Instructed Glacier Model (IGM). Using a topographical sink detection algorithm on this new bed topography dataset allows the detection of subglacial depressions worldwide. These depressions have a high potential to evolve into glacier lakes in the future. Contextualising the results of this study with present glacier lake distribution reveals the evolution of GLOF risk in the Randolph Glacier Inventory (RGI) regions with the ongoing retreat of glaciers. As part of a larger project, these first findings lay the basis for estimating the temporal evolution of GLOF hazard in glacierised catchments in a warming climate.

How to cite: Walker, C. and Cook, S. J.: Global catalogue of future glacier lakes using novel bed topography, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4283, https://doi.org/10.5194/egusphere-egu25-4283, 2025.

How to cite: Demirtaş, E. N. and Önol, B.: Temporal and Spatial Snow Variability in the Mountainous Region of the Upper Euphrates Basin, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4521, https://doi.org/10.5194/egusphere-egu25-4521, 2025.

The hydrology of rock glaciers is a complex and poorly understood field, marked by uncertainties in water flow dynamics and the uneven distribution of the frozen substrate. One effective method for identifying permafrost - particularly in marginal permafrost regions like the Southern Carpathians - is measuring the temperature of mountain springs at the end of summer. Once seasonal snow has melted, permafrost becomes the primary factor influencing the low temperatures of the springs.

This study examines the spatial and temporal variability of spring water temperatures in the Retezat Mountains to assess the distribution of permafrost and its impact on spring water temperatures. In mid-August 2024, water temperatures were recorded at 62 springs using a Testo 110 instrument with a resolution of 0.1⁰ C resolution. The springs, situated at elevations between 1770 and 2230 meters and were categorized into four groups: (1) springs emerging from rock glaciers, (2) springs from scree slopes and talus slopes, (3) springs from areas with slopes covered with meadows and (4) springs from cirque or valley floors.

Additionally, continuous temperature monitoring was implemented for six springs originating from rock glaciers, using dataloggers, with data collection starting in the summer of 2021. Due to their greater resilience to climate change compared to glaciers, rock glaciers are expected to play an increasingly significant hydrological role in the face of ongoing climate change, acting as vital long-term water reservoirs thanks to their thick insulating debris cover.

How to cite: Berzescu, O., Ioniță, A., Urdea, P., Ardelean, F., and Onaca, A.: Investigating the influence of permafrost on springs water temperature in the Southern Carpathians: A comparative analysis of different source types, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5903, https://doi.org/10.5194/egusphere-egu25-5903, 2025.

How to cite: Fox, S., Stefánsson, H., and Peternell, M.: Sampling and Quantification of Microplastic Pollution on Vatnajökull Glacier, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5954, https://doi.org/10.5194/egusphere-egu25-5954, 2025.

Rock glaciers (RGs) are morphologically distinct landforms of alpine permafrost prevalent in Austria and act as shallow groundwater bodies. Previous studies have shown that some RG spring waters exhibit unexpected low pH values, high concentration of total dissolved solids as well as elevated concentrations of heavy metals due to natural acid rock drainage (NARD). It can be observed that NARD increases and intensifies as permafrost boundaries are shifting towards higher altitudes.

This study aims to show (i) the extreme hydrochemical variation among several springs at a single RG due to NARD and (ii) the temporal evolution of NARD over several years at another RG spring. For this purpose, the active Wannenkar RG in Tyrol and the inactive Klafferkessel RG in Styria are investigated. At the Wannenkar RG, over 15 springs have been identified with large variations in pH values and electric conductivity (EC), which may be attributed to different flow paths and thus hydrogeochemical reactions within an intact RG that is experiencing NARD. In contrast, the Klafferkessel RG features only one spring where over a span of less than 10 years a decrease in pH and a doubling of EC is observed. A detailed analysis of these hydrochemical variations aids to understand the underlying processes. This provides a foundation for water management in this sensitive environment due to climate change.

How to cite: Kohler, C., Wagner, T., Pettauer, M., Stamm, F. M., and Winkler, G.: Natural acid rock drainage causing hydrochemical variations in rock glacier springs in the Austrian Alps, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6754, https://doi.org/10.5194/egusphere-egu25-6754, 2025.

Drought is a temporary precipitation anomaly that affects other hydrological variables and can impact large areas, causing devastating effects on agriculture, environment, and water supplies. Climate change is increasing the frequency of droughts, and their intensity is expected to rise in the future.
In snow-dominated catchments, monitoring and analyzing meteorological (precipitation) and hydrological droughts (associated with snow cover area) is crucial due to their importance in water resources. These regions are particularly sensitive to climate change and serve as excellent observatories for both current and past climate change effects.
In this study, we compare historical droughts related to precipitation and snow cover area in three semi-arid and three humid catchments. We also assess the impact of future climate change scenarios on droughts in these systems. The semi-arid catchments are located in the Sierra Nevada (Spain), the Southern Rocky Mountains (Colorado), and the Andes (Chile), while the humid catchments are located in the Alps (Italy), the Caucasus Mountains (Georgia), and the Himalayas (Nepal).
Historical climate variables were obtained from the ERA5-Land reanalysis dataset, and snow cover area was modeled using these climate data along with snow cover area data from the MODIS satellite. Gap filling, extension of the historical period, and simulation of future snow cover area under climate change scenarios were achieved using an improved cellular automata algorithm, which utilizes precipitation, temperature, and elevation as driving variables. Future local climate change scenarios were generated using the stochastic weather generator LARS-WG, which incorporates climate projections from the CMIP6 ensemble, as used in the latest IPCC Sixth Assessment Report. Drought analysis was conducted in terms of frequency, duration, intensity, and magnitude of drought periods using runs theory and various thresholds of the corresponding standardized drought index for precipitation and snow cover area.

This research has been partially supported by the project SIERRA-CC (PID2022-137623OA-I00 funded by MICIU/AEI/10.13039/501100011033 and by FEDER, UE); the project SIGLO-PRO (PID2021-128021OB-I00/ AEI/10.13039/501100011033/ FEDER, UE), the project STAGES-IPCC (TED2021-130744B-C21/AEI/10.13039/501100011033/ Unión Europea NextGenerationEU/PRTR).

How to cite: Collados-Lara, A.-J., Hidalgo-Hidalgo, J.-D., Pulido-Velazquez, D., Jiménez-Espinosa, R., and Fassnacht, S.: Impact of historical and future climate change scenarios on meteorological and snow cover droughts in semi-arid and humid snow-dominated catchments, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6844, https://doi.org/10.5194/egusphere-egu25-6844, 2025.

Climate change is projected to substantially reduce snow availability, posing significant challenges for downstream sectors such as ski resort operations, aquatic ecosystems, and hydropower, which are heavily reliant on seasonal snowmelt and streamflow dynamics. This study presents, for the first time, high-resolution (1x1 km²) daily projections of snow cover and snow water equivalent (SWE) for Switzerland under different global warming levels. These projections are derived from an ensemble of over 25 statistically downscaled EURO-CORDEX models, coupled with an operational snow model. We quantify critical thresholds for snow-dependent metrics, including the regional distribution of ephemeral versus seasonal snowpacks, providing new insights into their temporal and spatial evolution. Additionally, we quantify the influence of multivariate versus univariate bias correction techniques on snow simulations and their downstream effects of SWE and snow cover trends. Our results emphasize the importance of methodological choices in climate impact studies and offer actionable insights for managing future snow-dependent resources in a rapidly warming climate.

How to cite: Beria, H., Kotlarski, S., Jonas, T., and Marty, C.: High-resolution snow projections for Switzerland for the 21st century, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6951, https://doi.org/10.5194/egusphere-egu25-6951, 2025.

The Earth's spatial heterogeneity and its climate make certain areas more sensitive to climate change. Its effects in these regions become evident earlier than in others. Snow-dominated catchments, where a significant portion of precipitation falls as snow, are particularly sensitive to climate change and serve as excellent observatories for both current and past climate change effects. These areas act as early warning systems for the rest of the world due to their high sensitivity to climate change.
Recent scientific literature highlights significant reductions in snow across various systems in the context of climate change. However, to our knowledge, a global comparison of the effects of climate change on semi-arid and humid snow-dominated mountains has not yet been conducted. Our objective is to analyze the potential differences in sensitivity to climate change between semi-arid and humid regions.
In this study, we compare historical patterns and trends of precipitation, temperature, and snow cover area in three semi-arid and three humid catchments, using data from long-term series (1950-2023). The semi-arid catchments are located in the Sierra Nevada (Spain), the Southern Rocky Mountains (Colorado), and the Andes (Chile), while the humid catchments are located in the Alps (Italy), the Caucasus Mountains (Georgia), and the Himalayas (Nepal).
Climate variables were obtained from the ERA5-Land reanalysis dataset, and snow cover area was modeled using these climate data along with snow cover area data from the MODIS satellite. Gap filling and extension of the historical snow cover area period were achieved using an improved cellular automata algorithm, which utilizes precipitation, temperature, and elevation as driving variables.
Several statistical indicators (Nash-Sutcliffe efficiency, Kling-Gupta Efficiency and coefficient of determination) were used to assess the goodness-of-fit of the improved cellular automata algorithm. The results demonstrated a very good agreement with observed snow cover data in both semi-arid and humid catchments, with the exception of the Himalayan catchment, where the fit was deemed acceptable. Regarding historical snow cover trend, the findings of this study indicate a negative snow cover trend both in semi-arid and humid catchments.

This research has been partially supported by the project SIERRA-CC (PID2022-137623OA-I00 funded by MICIU/AEI/10.13039/501100011033 and by FEDER, UE); the project SIGLO-PRO (PID2021-128021OB-I00/ AEI/10.13039/501100011033/ FEDER, UE), the project STAGES-IPCC (TED2021-130744B-C21/AEI/10.13039/501100011033/ Unión Europea NextGenerationEU/PRTR).

How to cite: Hidalgo Hidalgo, J. D., Collados-Lara, A.-J., Pulido-Velazquez, D., Jiménez-Espinosa, R., and Fassnacht, S.: Assessing the impact of recent climate change on semi-arid and humid snow-dominated catchments by using a cellular automata model, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6981, https://doi.org/10.5194/egusphere-egu25-6981, 2025.

Japan features a wide variety of snow environments, with significant differences in snow distribution based on region and elevation. The effects of ongoing climate change are expected to alter snow conditions significantly, highlighting the need for a comprehensive understanding of these changes and their implications.

Meteorological observation sites managed by the Japan Meteorological Agency are predominantly concentrated in low-altitude areas, with only a limited number in high-altitude regions. Consequently, the lack of long-term and spatially extensive observational data has hindered the quantitative understanding of snow conditions in Japan's mountainous regions. To address this gap, the Snow and Ice Research Center (SIRC) of the National Research Institute for Earth Science and Disaster Resilience has operated a Snow and Weather Observation Network for over 25 years. This network spans a wide area, from northern to western Japan, monitoring meteorological and snow conditions fluctuations at high elevations. This study utilizes the long-term data collected through the network to analyze trends in snow conditions across Japan's mountainous regions. Particular emphasis is placed on examining the variation characteristics of maximum snow depth and maximum snow water equivalent, including their differences, elevation dependencies, and contrasts between mountainous and flat areas.

Our results indicate that although the trends in maximum snow depth and maximum snow water equivalent are generally consistent, the variability in maximum snow water equivalent is greater than that of maximum snow depth. Additionally, the variation in maximum snow depth shows a distinct dependence on elevation, with different trends observed in mountainous and flat regions. These findings enhance our understanding of the effects of climate change on Japan's snow environments and provide essential insights for improving future projections of snow conditions, as well as for developing strategies to mitigate snow-related disasters.

How to cite: Sunako, S., Yamaguchi, S., Ito, Y., Yamashita, K., Arakawa, H., and Nemoto, M.: Understanding snow conditions in Japanese Mountains through a quarter century of insights, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7858, https://doi.org/10.5194/egusphere-egu25-7858, 2025.

The Himalayan glaciers, crucial reservoirs of freshwater and delicate ecosystems, are confronting an alarming threat from microplastic pollution. Defined as plastic particles smaller than 5 mm, microplastics have been detected in these glaciers, raising significant concerns regarding their potential impacts on environmental integrity, human health, and aquatic biodiversity. Despite the growing awareness of microplastic pollution globally, there is a notable lack of information regarding snow microplastics in the Himalayan region. In this study, we collected surface snow samples from the western and central Himalayan glaciers during the pre-monsoon season of 2023 to quantify the presence and abundance of microplastics. Samples were obtained near two scientific research stations (Chorabari and Lahaul & Spiti) and from 13 field sites extending up to 20 km from these stations. We employed Agilent 8700 Laser Direct Infrared Chemical Imaging System (LDIR) to identify polymer compositions and analysed air mass back trajectories to ascertain the potential origins of the sampled air masses. Our findings revealed a diverse array of microplastics, including polyamide, polyethylene, polypropylene, and polystyrene, basically low-density plastic present in both glacier regions which are predominated by fragments with sized smaller than 100µm in both regions. The distribution and accumulation of microplastics were influenced by hydrological factors, such as glacier melting and runoff, as well as anthropogenic activities, including tourism and trekking. This research adds to the growing body of evidence on microplastic pollution in remote and high-altitude ecosystems, offering critical insights for policymakers, environmental managers, and researchers. The implications of this study are profound, enhancing our understanding of the regional distribution and impacts of microplastic pollution and informing the development of effective strategies to mitigate plastic waste and promote sustainable development. Human Health. This research contributes to a more nuanced perspective on the microplastic cycle and its profound implications for vulnerable ecosystems like the Himalayan Glacier, paving the way for future inquiries into this pressing and pervasive environmental challenge.

How to cite: sundriyal, S., Kang, S., zhang, Y., and Shukla, T.: Microplastics in Himalayan Glaciers: A Comprehensive Study of recent findings on characteristics and potential source, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8037, https://doi.org/10.5194/egusphere-egu25-8037, 2025.

Global warming in Central Asia has primarily led to glacier melting and the degradation of snow cover in mountainous regions. Research conducted by the Central Asian Institute of Applied Geosciences using Landsat data (2013–2016) revealed that glacier areas in the Tien Shan river basins have decreased by 10–47% compared to data from the USSR Glacier Catalog (1940–1970). Over approximately 70 years, Kyrgyzstan's glacier area has decreased by 16%, with large glaciers shrinking by 17%, while the area of small glaciers has increased by 2.5 times.

Field studies conducted on nine representative glaciers in Kyrgyzstan between 2011 and 2023 indicate a negative mass balance for glaciers in the mountain regions, with the exception of certain years for the Golubin Glacier (Ala-Archa River basin) and the Abramov Glacier (southern border of the Fergana Valley).

In addition to Landsat data, the dynamics of snow cover have been analyzed using MODIS data processed through the MODSNOW-Tool program. This tool provides valuable insights into snow cover dynamics and accumulation in the Tien Shan Mountains. Seasonal snow reserves and glacier runoff are the primary sources of water for mountain rivers in the Tien Shan. At altitudes above 2.5–3 km, melting in river basins lasts 5–6 months, contributing 80–90% of the annual runoff.

Snow cover data has also been utilized to forecast river flow in Kyrgyzstan. This forecasting methodology was developed under the Central Asia Water (CAWa) project and transferred to Kyrgyzhydromet for implementation in 2015. Over the past decade, it has been actively employed to predict water inflows into reservoirs. An evaluation of the methodology for the Naryn, Karadarya, Chu, and Talas rivers (2021–2023) demonstrated its high efficiency in operational hydrological forecasting.

How to cite: Kalashnikova, O.: Hydrological forecasting based on remote sensing snow cover and glacier data in the river basins of the Tien Shan, Kyrgyzstan, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8053, https://doi.org/10.5194/egusphere-egu25-8053, 2025.

In recent years, microplastic (MP) pollution has become a global concern, even reaching remote and pristine environments like Antarctica. Antarctica is a sensitive environment, critical to global biodiversity conservation and climate regulation, and therefore has attracted interest for scientific research. Despite its remoteness, King George Island, located in the South Shetland Islands, experiences significant ship traffic due to its strategic location. The island hosts ten permanent research stations and the only airport in the region. Increasing human activity, including tourism and research operations, along with atmospheric and oceanic circulation, has contributed to microplastic contamination in both marine ecosystems and terrestrial soils. In sensitive environments such as the ice-free periglacial zones where most human activities in Antarctica are concentrated, soil plays a critical role in terrestrial ecological processes, such as mediating biological and hydrological processes, as well as nutrient and chemical cycling. The presence of MPs in soil can alter its properties, potentially affecting their ability to perform its essential ecosystem functions. 

Biodegradable plastics have been proposed as a solution to mitigate the environmental impacts of conventional plastics. However, their degradation is highly variable across different environments, with incomplete degradation leading to the formation of MP that still pose a threat to ecosystems.

This study investigates the degradation of conventional and biodegradable MP on Antarctic soils through an incubation experiment using Cambisol collected from a marine terrace in the Admiralty Bay, King George Island (0-10 cm). The experiment was conducted at 25% moisture and 4°C, with two treatments and four replicates each, where the soil was spiked with conventional and biodegradable MPs. A control treatment, consisting of non-spiked soil, and empty jars as blanks, were also included. CO₂ concentration and δ¹³C-CO₂ isotopic signatures were measured using cavity ring-down spectroscopy, additionally phospholipid fatty acids (PLFA) analyses allowed us to distinguish between microbial groups. The carbon and nitrogen concentration including corresponding isotopes were assessed using EA-IRMS. MP degradation was evaluated through FTIR carbonyl index analysis and δ¹³C-CO₂ mixing model. We will present the preliminary results from this controlled incubation experiment assessing the impact and dynamics of conventional and biodegradable MP on soil from Antarctica.

How to cite: Silva Gurgel do Amaral, S., Vezzone, M., Heiling, M., Vieira, R., Dercon, G., and Meigikos dos Anjos, R.: Assessing the Degradation of Conventional and Biodegradable Microplastics in Soil from King George Island, maritime Antarctica, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8316, https://doi.org/10.5194/egusphere-egu25-8316, 2025.

Microplastics (MPs) are widespread across the globe, including remote regions such as Antarctica. Until recently, Antarctic MPs have been primarily considered to originate from external sources via ocean currents. However, the intensification of human activities within the Antarctic Circumpolar Current (ACC) has raised concerns that local sources, including research stations, could become significant contributors to MP pollution. Nevertheless, the impacts of local sources remain unclear due to the lack of observation data and snap-shot study results. Frequent temporal monitoring linking potential pollution sources with surrounding environments can help assess and understand the impacts of research stations. This study aimed to quantify and characterize MP pollution from research station activities. To this end, we conducted seasonal or monthly sampling of multiple compartments at or near the King Sejong Station (KSS; located on Barton Peninsula, King George Island)—aquatic (wastewater, seawater, beach sediment, marine sediment), atmospheric (outdoor and indoor air), and terrestrial (soil and snow)—over three years (2023-2025). Here, we present preliminary results, mainly focusing on aquatic compartments. In 2023, influent and effluent discharged from KSS-wastewater treatment plant (WTP) and surface seawater near the KSS-pier in Marian Cove were collected in January, April, July, and October. Additionally, five beach sediments and three marine sediments were collected along a transect from the outer to the inner part of Marian Cove. There was no correlation between the number of residents and MP abundance in wastewater; However, an increasing trend in MP abundance was observed with daily wastewater discharge. Contrary to typical observations, MPs in the effluent (573,100 ± 394,615 n/m³) were more than twice as high as in the influent. This is presumed to result from sludge re-suspension that concentrated MPs, indicating inadequate treatment efficiency in KSS-WTP. We estimate that 5 billion MP pieces may enter Marian Cove annually from KSS-WTP. Surface seawater contained two or three orders of magnitude lower MPs (1,099 ± 1,269 n/m³) compared to WTP effluents but higher levels than those in some mid-latitude coastal regions or other open oceans. MP abundances in beach (205 ± 190 n/m³) and marine sediments (277 ± 107 n/m³) were highest at the site closest to the WTP outlet, with a significant correlation with distance. The detected polymer types were 22 in wastewater, 16 in seawater, and 10 in sediments. Although PP was the predominant polymer, its percentages were 22.9%, 55.8%, 49%, and 31.7%, respectively. These findings indicate that MPs from KSS-WTP are fractionated across media, with less dense polymers remaining longer in seawater and beach sediments. This study provides baseline data on the impact of research station activities, emphasizing the need for improved environmental protocols and systematic monitoring to mitigate MP pollution in Antarctica.

Acknowledgement: This study was supported by Korea Polar Research Institute (KOPRI, PE24170), and was also partially supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) (No. RS-2024-00356940).

How to cite: Seong, M.-J., Kim, S.-K., Shin, J.-H., Ji, Y.-J., Kim, J.-Y., Kim, J.-H., Choi, S.-H., and Yeom, C.-H.: Contribution of Research Station Activities to Microplastic Pollution in Antarctica: A Case Study of King Sejong Station, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9708, https://doi.org/10.5194/egusphere-egu25-9708, 2025.

Trojena is a ski resort under construction in the Midian mountains in Saudi Arabia (1500m-2600m). In this warm and arid region, snowfalls are very rare. The average snow cover duration as observed with MODIS is less than 2 days per year during the 2000-2022 period, casting doubts on the possibility to develop a ski resort as advertised by the project managers. Low temperatures at high elevation might allow the production of artificial snow in winter. To examine this possibility, we downscaled  ERA5 meteorological data to 100 m resolution over the Trojena area with MicroMet. We used these high resolution meteorological dataset to  simulate the natural snowpack between 1995 and 2014 at the uppermost and lowermost points (respectively 2389 and 2151 m a.s.l.) in the future ski domain using  the Crocus snowpack model with the default parameters used in France. We evaluated the simulations using Landsat observations of the snow cover. With this model configuration, the snow cover duration with Crocus is slightly overestimated. Then, we ran the Crocus-Resort model  to simulate artificial and managed snow (production of artificial snow and grooming processes) with the default parameters used for French resorts. We evaluated the potential number of skiable days and associated water consumption over this period assuming that the domain was fully equipped to produce artificial snow. In this scenario, the number of skiable days would be approximately 60 and a water consumption around 380 kg.m⁻². Finally, we examined the effect of future climate change by applying the projected temperature increases according to the IPCC scenario SSP2-4.5 on the 2040-2060 horizon. The number of skiable days decreased in this scenario, especially at the bottom of the resort where there would be no skiable days every other year. As a result, the possibility of skiing on snow in Trojena is strongly compromised in the near future. The water consumption decreases in this scenario due to the incapacity of producing snow with the increase of temperature. 

How to cite: Sourp, L. and Gascoin, S.: Snow in the desert: sustainability of the Trojena ski resort in Saudi Arabia, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10001, https://doi.org/10.5194/egusphere-egu25-10001, 2025.

Personal care products (PCPs) have become ubiquitous in daily life, resulting in their continuous release into the environment on a global scale. PCPs are organic compounds commonly found in products such as cosmetics, detergents, and deodorants. The growing interest in these substances is primarily driven by their potential to track shifts in human behaviors and consumption patterns. Key characteristics of these compounds include large-scale industrial production, high daily usage volumes, persistence after application, and semi-volatility.

Among these products, fragrances are widely used in cosmetics, shampoos, soaps, and detergents, while UV-filters are key components of sunscreen lotions, outdoor polymers, and paints. Some of these compounds have been included on the EU's watchlist due to their potential harmful effects. Additionally, several countries in the Southern Hemisphere have already implemented regulations to limit the use of PCPs, driven by concerns over their negative impacts on coral reefs and marine ecosystems.

Fragrances, owing to their semi-volatile nature, can easily enter the atmosphere and be transported over long distances, even reaching remote regions such as Antarctica. In these areas, they can be deposited through both dry and wet deposition processes and undergo cycles of fractionation, evaporation, and re-deposition. Local sources of PCPs, such as scientific research stations and tourism activities, contribute to their presence in these environments. Notably, PCPs have already been detected in the sewage of the Mario Zucchelli Station (MZS) in Antarctica.

This study examined the spatial distribution and temporal variations PCPs in Antarctic surface snow collected during the 2021-2022 season, between November 2021 and February 2022, along the Ross Sea coast, with a particular focus on how seasonality may influence deposition processes. Comparison of the average PCPs concentrations revealed higher values in late summer, with a concentration pattern showing salicylates as the dominant compounds, followed by UV-filters, while musks contributed the least to the total concentration. Salicylates predominated at all sampling sites, including the snow pit dug on McCarthy Ridge. This result may be attributed to potential selectivity in atmospheric transport, likely influenced by the prevailing synoptic air-mass circulation during austral summer.

Additionally, the study was able to differentiate between local and long-range sources by analyzing the concentration trends observed in samples from remote regions and the sewage of the Mario Zucchelli Station. These findings provide a broader understanding of the dynamics involved in long-range atmospheric transport, which require further investigation.

How to cite: Genuzio, G.: Seasonal variability of Personal Care Products in Antarctic snow, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10146, https://doi.org/10.5194/egusphere-egu25-10146, 2025.

Snow is an important factor controlling vegetation functions in high latitudes/altitudes. However, due to the lack of reliable in-situ measurements, the effects of snow on vegetation phenology remains poorly understood. Here, we examine the effects of snow cover duration (SCD) on the start of growing season (SOS) for different vegetation types. SOS and SCD were extracted from in-situ carbon flux and albedo data, respectively, at 51 eddy covariance flux sites in the northern mid-high latitudes. The effects of SCD on SOS vary substantially among different vegetation types. For grassland, preseason SCD outperforms other factors controlling grassland SOS. However, for forests and cropland, the preseason air temperature is the dominant factor in controlling SOS. Preseason SCD mainly influences the SOS by regulating preseason air and soil temperature rather than soil moisture. The CMIP6 Earth system models (ESMs) fail to capture the effect of SCD on SOS. Thus, Random Forest (RF) models were established to predict future SOS changing trends considering the effect of SCD. For grassland and evergreen needleleaf forest, the projected SOS advance rate is slower when SCD is considered. These findings can help us better understand impacts of snow on vegetation phenology and carbon-climate feedbacks in the warming world.

How to cite: Wang, X., Li, Z., Xiao, J., Zhu, G., and Che, T.: Snow cover duration delays spring green-up in the northern hemisphere the most for grasslands, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10479, https://doi.org/10.5194/egusphere-egu25-10479, 2025.

Permafrost, widely distributed in the Northern Hemisphere, plays a vital role in regulating heat and moisture cycles within ecosystems. In the last four decades, due to global warming, permafrost degradation has accelerated significantly in high latitudes and altitudes. However, the impact of permafrost degradation on vegetation remains poorly understood to date. Based on active layer thickness (ALT) monitoring data, meteorological data and normalized difference vegetation index (NDVI) data, we found that most ALT‐ monitored sites in the Northern Hemisphere show an increasing trend in NDVI and ALT. This suggests an overall increase in NDVI from 1980 to 2021 while permafrost degradation has been occurring. Permafrost degradation positively influences NDVI growth, with the intensity of the effects varying across land cover types and permafrost regions. Furthermore, based on Mann‐Kendall trend test, we detected abrupt changes in NDVI and environmental factors, further confirming that there is a strong consistency between the abrupt changes of ALT and NDVI, and the consistency between the abrupt change events of ALT and NDVI is stronger than that of air temperature and precipitation. These findings work toward a better comprehending of permafrost effects on vegetation growth in the context of climate change.

How to cite: Yang, Y., Wang, X., and Wang, T.: Permafrost Degradation Induces the Abrupt Changes of Vegetation NDVI in the Northern Hemisphere, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10548, https://doi.org/10.5194/egusphere-egu25-10548, 2025.

Atmospheric transport is a major pathway for microplastics (MP) to reach remote regions, and it plays a significant role in the global distribution of MP. Processes of wet and dry deposition of atmospheric MP are not well understood, but fallouts from atmospheric MP have been previously measured in remote locations. Iceland holds a very strategic location for studying long-range transport of MP, as it is scarcely populated and is located within major oceanic currents and large-scale weather patterns, far from continental Europe and North America.

This study aims to estimate flux rates of atmospheric deposition of MP in Icelandic lakes and to improve the understanding of the atmospheric transport and deposition of MP towards the Arctic. We collected surface sediment from remote crater-like lakes (elevated, with small catchment areas and no apparent main in- or outflows) to minimize contributions from runoff and avoid local sources of MP. A total of six lakes were targeted, located in various locations around Iceland to cover a large scale of mean annual precipitation, ranging from 1000 to 5000 mm. We sampled from the central parts of ice-covered lakes, using a short coring device to preserve the water-sediment interface and prevent loss of easily suspended particles. Only the interface water and upper first centimetre of sediment were collected for the MP study, and additional short cores were retrieved to assess sediment-accumulation rates, and estimate MP flux rates for each lake. MP were extracted using a heavy liquid separation method, followed by organic matter elimination with an enzymatic purification protocol, and identified using micro-FTIR spectroscopy analyses.

As a matter of concern, every sediment sample from every lake contained microplastic particles, with significant variations between lakes. Estimated MP fluxes range from 1 MP/m²/d in Langanes, a peninsula in NE Iceland to 348 MP/m²/d in Skersli, a shield volcano in the highlands, central Iceland. Polymer types PP and PE largely dominate the pollution, and the average MP size decreased with the distance from the coastline. These results emphasize the ubiquity of MP pollution, even in a remote sub-Arctic region, and highlight that MP accumulation in lake sediments is driven by a complex interaction between precipitation, wind patterns and local topography.

How to cite: Blache, M., Saarni, S., Koenders, E., and Mischke, S.: Atmospheric Deposition Of Microplastics Recorded In Icelandic Lake Sediments: Estimating Microplastic Fluxes Using Short Sediment Cores, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11478, https://doi.org/10.5194/egusphere-egu25-11478, 2025.

As researchers we are well-versed at communicating with the scientific community and assessing the “impact” of our work within the context of academic publishing, but generating impact with non-academic groups is something that is becoming increasingly important, especially under continued global heating. Before and after images of the cryosphere, particularly glaciers, is something the public are now used to seeing, but does this imagery produce the response required to affect a response, or even behavioural or policy change? This contribution reflects on the ways in which cryospheric researchers engage with the public and stakeholder groups and the value of that engagement for researchers, participants, and audiences alike. From citizen science to different forms of art-science dissemination, we draw upon examples from our own work and assess the range of possible impacts of those activities. We focus on understanding and communicating glacier retreat and associated water security issues in the rapidly changing Cordillera Blanca of the Peruvian Andes, and critically examine the benefits and challenges of pursuing participatory research and outreach for the generation of impact beyond academia. We also provide insights from our own experiences to encourage researchers to step beyond the norms of communicating cryospheric science.

How to cite: Clason, C. and Rangecroft, S.: Valuing impact beyond academic publishing: communicating cryospheric change, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11913, https://doi.org/10.5194/egusphere-egu25-11913, 2025.

Here we present an interdisciplinary approach to providing a holistic understanding of an environmental challenge by synthesizing existing published studies and data about water quality in a glaciated Peruvian river basin, the Rio Santa. In mountain regions such as the Cordillera Blanca, connecting the impacts of a changing cryosphere with downstream environmental challenges such as water quality is crucially important for water resource management. Poor water quality negatively impacts human health and ecosystems, yet longitudinal, uninterrupted data to assess trends across time and space is rarely available. We focus on the Rio Santa as a proof of concept for our approach, where water security is already a significant challenge, and one that will become more acute under future climate change, glacier retreat, water and land use change, and water governance.

Research on environmental issues that require in-situ data, such as water quality, is usually fragmented, short-term, and focused on specific aspects or locations, making it difficult to establish a wider, holistic perspective in data-scarce regions. Our approach utilises published data to build a more comprehensive understanding of water quality over a greater temporal and spatial scale than individual studies can provide. Data and knowledge about environmental problems are generated by various research projects over time, but these projects are often unconnected and exist in disciplinary silos. By synthesizing data from existing published research, and seeking to include both quantitative and qualitative data where available, we can aim to create a broader understanding of water quality for a catchment or region, and provide different types of insights, context and knowledge.

We compiled water quality data for the Rio Santa basin from the past two decades, focusing on published variables, such as pH and heavy metal content. We then developed methods to integrate these datasets, providing a more comprehensive understanding of water quality for this catchment. Learnings from this research allow us to expand our understanding from individual studies to build an interdisciplinary and holistic view of water quality across the basin over time. The work also helps to provide a knowledge base for current and future research projects to increase the applicability of data and results, maximising impact and meaning.

How to cite: Rangecroft, S., Clason, C., and Matthews, A.: Synthesizing knowledge to provide a holistic understanding of water quality in the glaciated Rio Santa, Peru, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12093, https://doi.org/10.5194/egusphere-egu25-12093, 2025.

Snow is a critical component of the mountain cryosphere and plays a significant role in shaping the hydrology of the snow-fed basins during summer months. The snowpack serves as a vital water reservoir, accumulating during the wintertime and gradually releasing water during the melt season, to sustain the downstream water demands. Snow is highly sensitive to climate change, particularly in low- and mid-elevation mountain regions like the European Alps.

We present an analysis of a long-term (30 years) dataset of snow water equivalent (SWE) in the Po River district, Italy, which partially covers the mountain ranges of Alps and Apennines from 1991 to 2021. The dataset is available at a spatial resolution of 500x500m and at a daily time step. It was created using a hybrid modelling approach called “J-Snow” that integrates the physically based GEOtop model and assimilation of in-situ snow height data and Earth Observation snow products like MODIS snow cover data.

The Po River basin is the largest in Italy and is considered to be the second most sensitive river basin in Europe after the Rhone basin. In recent years, the Po River basin experienced several droughts, including a recent one in 2022. Therefore, these kinds of long-term spatial datasets help to monitor and analyse the spatial and temporal changes in the SWE and provide vital insights for addressing the snow drought alerts in the study region.

In this study, we analysed several snow phenology metrics that includes snow persistence, first snow date (FSD), snow disappearance date (SDD), peak SWE volume, peak SWE timing, and regional snow line elevation. Our initial results show that the long-term spatially averaged volume of water and snow-covered area are 3.34 Gm³ and 15471 Km², respectively.Additionally, elevation-wise analysis of the snow phenology metrics show that most changes occur in the low-elevation bands (0-2000 m a.s.l). Changes in snow-water storage start, snowmelt timing, and its variability can directly affect the water availability in snow-fed basins, with significant implications for both ecosystems and human populations.

How to cite: Rigon, R., Wani, J. M., Roati, G., Dall'Amico, M., Di Paolo, F., Tasin, S., and Gleason, K. E.: Analysing long-term (1991-2021) daily records of Snow Water Equivalent in the Po River District, Italy, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12423, https://doi.org/10.5194/egusphere-egu25-12423, 2025.

Microplastic particles (MP; plastic pieces with length < 5 mm) have already colonized every ecosystem on Earth, including cryospheric regions. The presence of MPs has been reported in the Artic, Antarctic and glaciers and seasonal snow at high mountain ranges from Europe, Asia and America. Still, their capacity to affect snow metamorphism and albedo, as light-absorbing impurities, remains unexplored. During the snow season of 2023/24 (from early February to early May 2024), 6 in situ experiments were conducted at the Spanish Central Pyrenees employing a set of mini-lysimeters containing surface snow doped with different concentrations of MP. In each experiment, a blank that remained exempt of particle addition was also included. Two types of polymers were used, low-density polyethylene (PE; ~300 µm) and polyurethane (PUR; ~450 µm) black pellets. The mini-lysimeters were exposed to atmospheric conditions for 3-4 hours to quantify changes in snow specific surface area (SSA), liquid water content (LWC), hyperspectral albedo (HA) and ultimately the total melted water after exposition. Results were very variable across the season. Thus, effective melting (> 40%) was observed only during the warmer days under high solar radiation on old snow. Still, changes in SSA, LWC and HA (calculated as percentage of change per hour) occurred almost in every experiment. SSA changes were quite variable, ranging from negative (mid-winter and old snow, with the lowest PUR concentrations used) to 33% h^-1 (spring and warmest day, old snow, all PUR concentrations used). Similarly, LWC increased from 0 the coldest day (with all MPs but the highest PE concentration used) to 500% h^-1 (early winter and old snow, with the highest concentration used). Changes in HA were modest, ranging from 1.1% h^-1 (mid-winter and old snow, low PUR concentrations) to 7.5% h^-1 (spring and warmest day, old snow, highest PUR concentration). Up to now, these results are the first evidence of MP’s capacity to act as light absorbing particles, triggering snow metamorphism and eventually snow melting. Forthcoming studies will test other types of MP and concentrations, under a wider range of snow conditions, to allow a more comprehensive spatial-temporal interpretation.

How to cite: Marin-Beltran, I., Brandes, J., Dominguez-Aguilar, P., Pey, J., Revuelto, J., and Lopez-Moreno, N.: On the role of Microplastics as Light Absorbing Particles in seasonal snowpacks: First evidence from the Central Pyrenees, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13476, https://doi.org/10.5194/egusphere-egu25-13476, 2025.

Emperor penguins are an iconic Antarctic species threatened by climate change. The birds are highly reliant on stable fast ice for successful breeding, and some studies project possible quasi-extinction for over 90% of colonies by 2100 due to future sea ice loss. Recent record-low Antarctic sea ice conditions highlight the threat to the species. In order to better model the future response of emperor penguins to climate change, and increasing extreme ice events in sea ice and at the margins of the ice sheet, it is essential to better understand how colonies have responded to past conditions. In this study we identify the location of the Sanae, Astrid, and Mertz colonies in all available Landsat 4-9, ASTER, and Sentinel-2 imagery, spanning the years 1984-2024. We manually record the location of the colonies through and between years, while also recording major calving events, early fast ice break-out, and distance to the fast ice edge. Colonies typically return to approximately the same sheltered sites annually throughout the 35-40 year period, but we observe variations due to major calving events. Following major calving events at Mertz and Sanae that disrupt breeding sites, colonies relocate to different sites where they may be more vulnerable to earlier fast ice break-out, or need to travel longer distances for foraging. In subsequent years the colonies eventually return to sites close to their original location. Additionally, we observe early fast ice break-out events that are likely to impact breeding success at Mertz and Sanae colonies, including as early as September at Mertz in 2016. Such events are related both to regional sea ice conditions and variations in colony location. Notably, we observe all three colonies to move onto the neighbouring ice shelf in some years (and at Mertz, onto icebergs too), including when stable fast ice is available. Observation of these behaviours contributes to broader understanding of emperor penguins’ adaptability and will aid future efforts to model the response of the species to ice loss.

How to cite: Macdonald, G., Jamieson, S., Stokes, C., Fretwell, P., Marochov, M., and Jenouvrier, S.: Response of emperor penguins to changing ice conditions at the Astrid, Mertz, and Sanae colonies using satellite remote sensing (1984-2024), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13841, https://doi.org/10.5194/egusphere-egu25-13841, 2025.

The spatial distribution and evolution of seasonal snow is a first-order control of glacier mass balance, yet most glaciological models represent snow with rather simple approaches. Despite being key drivers of winter accumulation patterns, processes such as wind drift and avalanching are often disregarded. Here, we explore the application of a recent fully distributed snow model based on mass and energy balance and including redistribution processes to glacierized areas. The model FSM2trans is run over six partially glacierized domains of 1-5 km² in the Swiss Alps for the hydrological years 2021-2024. These simulations are, for the first time, evaluated against glaciological datasets, including spatially distributed in-situ measurements of winter accumulation across the glacier surface and point mass balance timeseries reconstructions at selected ablation stakes. Despite differing spatial and temporal resolution of model and observations, their comparison allows detecting accumulation biases and areas with excessive snow transport in the simulations. These results motivate ongoing efforts to use glaciological observations to finetune FSM2trans for applications in high alpine glacierized terrain. Comparison of first FSM2trans simulations with existing, interpolation-based model estimates of glacier accumulation patterns corroborates the added value of process-based snow modelling for characterizing spatiotemporal accumulation dynamics. Enhanced representation of snow accumulation and depletion over glaciers is expected to provide mass balance estimates at higher spatial and temporal resolution than previously available and will thus also improve surface water inputs from cryospheric components to hydrological models applied to mountain areas.  

How to cite: Mazzotti, G., Huss, M., Magnusson, J., Queno, L., Jonas, T., Kneib, M., and Farinotti, D.: From process-based snow modelling to spatially distributed glacier mass balance estimates , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15823, https://doi.org/10.5194/egusphere-egu25-15823, 2025.

Water managers would benefit from high-resolution, distributed snow water equivalent (SWE) estimates, but limited observations and high spatial and temporal variability make SWE difficult to estimate in real-time. For example, in-situ snow measurement stations provide current-year SWE data, but under-sample SWE spatial heterogeneity; and SWE Reanalysis products back-calculate distributed daily SWE once snow has melted to provide more accurate SWE estimates than do real-time models, but don’t provide real-time information. Recent studies have shown that many regions and years have annual snow accumulation patterns that are repeatable, so here we seek to leverage these patterns by combining sparse real-time measurements with distributed historical information to map real-time SWE. We develop and test two methods for calculating SWE, and for each method we test three criteria for deciding which station or collection of stations should be used to estimate SWE at each grid cell. We determine which Western U.S. regions have similar standardized SWE anomalies, and then test our methods in the Upper Colorado River Basin (UCRB). For our two methods, we calculate 1 April 1990 – 2021 SWE using parametric and nonparametric distributions with a leave-one-out approach to map the current-year’s position within an in-situ station’s long-term SWE distribution to the corresponding position within historical distributions at nearby SWE Reanalysis grid cells. In each of these methods, we use our three station selection criteria to calculate SWE such that we calculate six SWE products over the UCRB. These criteria are: i) the nearest-neighbor station, ii) the collection of most-correlated stations, and iii) all in-situ stations within the UCRB. We then compare these to the SWE Reanalysis product from each corresponding year and compare the accuracies of our various methods with the accuracy of SnowModel output relative to the SWE Reanaysis product. The most accurate method used the mean SNV from the collection of most-correlated in-situ stations. This produced distributed 1 April SWE with a median R value of 0.80 and a root mean squared error (RMSE) of 0.13 m, compared to SnowModel results with an R of 0.60 and RMSE of 0.18 m. The methods used here could be applied to additional data, such as updated SWE Reanalysis products that might have higher resolution and improved accuracy over the product used here.

How to cite: Besso, H.: Towards the use of quantile mapping and historical patterns in SWE calculations, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19636, https://doi.org/10.5194/egusphere-egu25-19636, 2025.

Technical interventions on glaciers have emerged as innovative approaches to mitigate the impacts of climate change on vital cryospheric systems. Mountain glaciers play a crucial role in regulating freshwater availability, providing ecosystem services, and supporting economic activities. However, these glaciers are retreating at alarming rates due to rising global temperatures. Geoengineering strategies aim to counteract these losses by preserving glacier mass, reducing ice melt, and managing runoff to protect downstream ecosystems and communities. Key approaches include albedo enhancement using reflective materials to decrease solar absorption and glacier insulation with physical coverings, such as those used on Austrian glacial skiing areas.

While these interventions provide clear benefits for economically utilized glaciers, such as extending ski seasons, they also present significant environmental impacts. Glaciers host diverse microbial communities, which are highly sensitive to external influences. Studies show that covering glacial surfaces reduces bacterial activity by up to 70% and disrupts microbial community structures, with autotrophic organisms struggling to thrive under light-reduced conditions. Additionally, geotextiles made from polypropylene (PP), commonly used for glacier insulation, release microplastic fibers that are dispersed by meltwater and wind. In supraglacial environments, accumulative fiber lengths of up to 3 kilometers per m² of ice have been detected. These fibers are subsequently found downstream, attached to or incorporated into invertebrates, posing risks to aquatic ecosystems.

The Action Plan Microplastics released by the Environmental Agency of Austria emphasizes the urgent need for environmentally friendly alternatives to mitigate such risks in sensitive glacial ecosystems. Recent testing of cellulose-based materials on an alpine glacier has demonstrated comparable performance to PP in reducing ice melt without contributing to chemical leaching or fiber release. Moreover, cellulose-based materials can be integrated into circular processes, enabling upcycling into new fashion products and reducing waste. Collaboration with policymakers and manufacturers to promote a shift toward sustainable materials could enable the continued use of technical interventions on glaciers where needed while minimizing their environmental impact.

How to cite: Sattler, B., Weisleitner, K., Schwenter, P., and Cuzzeri, A.: Rethinking Glacier Insulation in the Alpine Space: Microplastic Concerns and Sustainable Materials, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20707, https://doi.org/10.5194/egusphere-egu25-20707, 2025.

Mountain glaciers provide an irreplaceable water resource in High Mountain Asia, with a significant proportion of water input to rivers coming from glacial meltwater. However, the volume of water held in these glaciers and the predicted evolution of the glaciers over the coming decades is subject to great uncertainty. 

Previous global ice thickness inversion studies have used low-order models (such as the shallow ice approximation, which is known to be locally unreliable on mountain glaciers) to describe the relationship between ice velocity and thickness. Furthermore, the reliability of the resulting thickness products in High Mountain Asia is severely limited, since at the time they were produced, only an extremely small dataset of measured thicknesses in that region was available for constraint and validation. Lastly, time-dependent ice thickness simulation runs often show an initial ‘shock’ in modelling a glacier’s evolution, due to the lack of consistency between the ice flow physics and existing thickness products, leading to unreliable results.

To construct more accurate thickness maps for selected glaciers, we use the Instructed Glacier Model, a novel deep-learning-based high-order ice flow model with the capability to invert observed glacier surface velocity for ice thickness. This inversion method, which utilises gradient-based optimization techniques, additionally allows for the inclusion of observed thicknesses to constrain the thickness field. 

A new airborne radar method for measuring ice thickness has been deployed in the Himalayas near Mount Everest, unlocking new possibilities for thickness inversion in this region, which has historically not been well covered by in-situ observations. Here, we use the data from this aerial survey to constrain the thickness inversion of the Instructed Glacier Model.

After showing that contemporary ice thickness products are generally inaccurate on High Mountain Asia glaciers, we present new inverted thickness maps for the 13 glaciers which have observations in this new dataset. We assess the accuracy of the results using a subset of the available data as validation, and demonstrate that our results show significant improvement over earlier thickness products.

How to cite: Smith, G., Goldberg, D., Jouvet, G., Maddison, J., and Pritchard, H.: Inverting glacier thickness in High Mountain Asia with a deep-learning-based ice flow model, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-357, https://doi.org/10.5194/egusphere-egu25-357, 2025.

In fast-flowing regions of the Antarctic and Greenland ice sheets, most motion occurs through slip at the boundary between ice and its substrate. Glaciologists have developed “slip laws” that describe basal motion as a function of resistive stress (e.g. basal drag) and effective pressure. When implemented in ice sheet models, the choice of slip law affects predictions of grounding-line migration and sea-level rise. Slip laws implemented in ice sheet models assume that the base of the glacier is “clean” (without rock debris) and separated from the bed by a thin frictionless water film, implying that the only source of basal drag is viscous flow and regelation around bed obstacles. However, observations of basal ice indicate that it is “dirty” (debris or sediment-rich) in most glacial environments, suggesting an additional source of drag due to friction between debris-laden basal ice and the bed. Incorporating debris-bed friction into a slip law may lead to significantly different predictions of the magnitude of basal drag and alter the functional form of the slip law.

Here, we report results of laboratory experiments using a geomechanical apparatus (cryogenic ring shear) to slide ice over a rigid bed composed of inclined marble steps at realistic glaciological conditions (e.g. slip velocity, effective pressure, temperature). We conduct a control experiment by sliding clean ice at a range of velocities and recording the resistance to basal motion. We then slide debris-laden basal ice to determine how debris affects the magnitude and functional form of the basal slip law. Our results suggest that slip in clean ice conditions is well described by the commonly used regularized Coulomb slip law. However, debris-bed friction is a significant source of basal drag, raising measured shear stress by ~50-75% despite a sparse areal debris concentration of ~5%. We derive a slip law incorporating debris-bed friction that fits our experimental data within measurement uncertainty with two tuning parameters. The debris-bed friction slip law is composed of three terms: a clean ice term (equivalent to regularized Coulomb), a pressure-dependent debris friction term, and a velocity-dependent debris-friction term. We further validate this slip law for realistic 3-D bed topographies using a finite-element ice flow model (Elmer/Ice). Finally, we implement a parameterized form of the slip law in an ice sheet model (MPAS-Albany Land Ice) and assess the sensitivity of grounding-line migration and ice-mass loss to the choice of slip law.

How to cite: Brooks, J., Zoet, L., Hansen, D., Helanow, C., Hillebrand, T., Hoffman, M., Morgan-Witts, N., and Perego, M.: A glacier slip law incorporating debris-bed friction, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-737, https://doi.org/10.5194/egusphere-egu25-737, 2025.

In the accumulation regions of the Greenland Ice Sheet (GrIS), not all surface meltwater contributes to runoff. A significant portion is retained through refreezing within the underlying firn layer, a process that critically moderates the overall mass loss from the GrIS. The refreezing of percolating meltwater at shallow depths leads to densification of the near-surface and the formation of ice layers. The extent of meltwater refreezing is influenced by firn density and temperature, which together govern the permeability of the near-surface ice layers. The presence of shallow, thick ice layers (> 1m thick, also known as "ice slab") restricts the deeper percolation of meltwater, thereby promoting its conversion into runoff. For example, the formation of ice slab in GrIS has resulted in nearly a 30% increase in the area contributing to runoff generation since 2001. Therefore, modelling ice slab is essential for understanding the total mass loss of the GrIS, both in recent years and in future projections.

In this study, we present a high vertical resolution, physically distributed model that simulates surface mass balance, refreezing, ice layer formation, and runoff. A novel temperature-dependent criterion for ice layer permeability is incorporated that has been rigorously validated against field measurements from the Devon Ice Cap in the Canadian Arctic, where it demonstrates a strong agreement with point-scale observations of surface mass balance and vertical density profiles. We applied the model to the GrIS from 1999 to 2022, using a horizontal spatial resolution of 0.25° × 0.25°, a vertical resolution of 1 cm, and a temporal resolution of 15 minutes. The model simulations are calibrated using the SUMup archive of surface mass balance observations and validated against shallow core measurements of vertical density profiles. The high vertical resolution of the model provides insights into the process of ice slab evolution and impacts on runoff magnitudes and spatial distribution from the accumulation area of the GrIS. We analyze the model results to examine the relationship between the formation of ice slab and the runoff limit across the GrIS exploring sensitivities to changing climate.

How to cite: Laha, S. and W. F. Mair, D.: Modelling evolution of Greenland Ice Sheet near-surface ice slab and its impact on runoff  , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1342, https://doi.org/10.5194/egusphere-egu25-1342, 2025.

Time-averaged or snapshot observations of contemporary ice sheet geometry and surface velocity are commonly used in numerical ice-sheet simulations to infer information about ice viscosity and basal sliding. The solution generally depends on the form of the basal sliding law, ice rheology and some form of regularization. On the other hand, close relationships between observed changes in ice sheet geometry and surface velocity are not systematically examined, yet they contain valuable information about the laws that govern ice-sheet dynamics. For example, it can be shown that the functional relationship between perturbations in ice thickness and ice speed depends on the sliding law exponent in a monotonic way. Hence, by harnessing the information contained in successive measurements of ice-sheet geometry and velocity, one can plausibly derive constraints on the form of the sliding law. Here we use a high-resolution numerical setup of the modern-day West Antarctic Ice Sheet to simulate the response of ice speed to contemporary changes in geometry (ice front location and ice thickness between 2000 and 2020). The simulated changes in ice speed are compared to observations over the same period and used in a Bayesian framework to derive constraints on the form of the basal sliding law, ice rheology, and regularization parameters. The a-posteriori distribution of model parameters is used to construct an ensemble of initial states for the whole of the Antarctic Ice Sheet in the year 2000. The ensemble serves as a starting point for hindcast and forecast simulations, with quantified uncertainties for key model parameters.

How to cite: De Rydt, J.: Calibration of an Antarctic Ice Sheet model, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1718, https://doi.org/10.5194/egusphere-egu25-1718, 2025.

Rapid global warming has resulted in substantial mass loss from the Antarctic Ice Sheet, contributing to global sea level rise. This study aims to delineate the future evolution of the Lambert Glacier-Amery lce Shelf system, the largest drainage system in East Antarctica, under the contrasting emission scenarios in Phase 6 of the Coupled Model Intercomparison Project (CMlP6), specifically SSP5-8.5 and RCP8.5. Employing the ice flow model Úa coupled with the basal melt model PlCO, we analyzed the dynamics of the Amery lce Shelf from 2000 to 2100. The ice shelf's thickness and velocity changes are predominantly driven by the distribution of basal melting. Despite thinning across most simulations, the grounding line showed minimal retreat, with the most sianificant retreat occurring only about 20 km downstream in the eastern sector. By the end of the 21st century, while a marked oceanic warming is evident, it is the Surface Mass Balance (SMB) that predominantly dictates the system's response.The coupled model based on Úa and PICO successfully revealed the increasing trend of the potential contribution of the Lambert-Amery basin to the sea level rise. It was found that even under strong basal melting conditions (5 m/a), the grounding line finds it difficult to cross the shallow sills, highlighting the key impact of bedrock topography on the stability and dynamics of the ice shelf.

How to cite: Wang, Q., Cheng, X., and Li, T.: Projections of the Lambert Glacier–Amery Ice Shelf system's change, East Antarctica, from 2000 to 2100, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2127, https://doi.org/10.5194/egusphere-egu25-2127, 2025.

The material behaviour of ice is complex: At short time scales it behaves as a brittle solid in extension, or a plastic material under compression/shear, whereas at longer time scales the visco-elastic behaviour dominates in all deformation modes. Furthermore, as the temperature of ice is close to its melting point, material properties are strongly impacted by small temperature changes (e.g. those induced via plastic dissipation). All these phenomena are also interlinked with fracture propagation: At lower confining pressure cracks form in a purely brittle manner as a response to sudden stress changes, whereas viscous creep will prevent cracks from forming during slower loading. Instead, at higher pressures (e.g. near the base of ice sheets), cracks develop based on the energy dissipated by plastic work.

Here, a modelling framework able to capture these different regimes will be presented, using the phase-field fracture paradigm to allow for complex fracture patterns. Application will be shown to both small-scale tri-axial compression tests, demonstrating the accuracy of the model and its ability to replicate experimental observations, as well as large-scale cliff failure to showcase the impact of using this material model on predictions of ice-cliff failure.

How to cite: Hageman, T. and Martínez-Pañeda, E.: An ice-specific phase-field fracture model for predicting brittle and ductile failure, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2472, https://doi.org/10.5194/egusphere-egu25-2472, 2025.

Rapid ice sheet sliding requires warm basal temperatures and lubricating basal meltwater.  However, ice sheet models often constrain sliding by inverting surface velocity observations with the vertical structure of temperature and rheology held constant.  If the inversion is allowed to freely vary sliding, then this approach can lead to inconsistencies between the basal temperature and sliding fields. In this study, we propose a new method to quantify the inconsistency between a modelled ice temperature field and the ice velocity field obtained when that temperature field is used to constrain an inversion. This method can be used to evaluate the quality of a modelled temperature field without requiring any englacial or subglacial measurements. We use the method to evaluate simulation results for Totten Glacier using an isotropic 3D ice sheet model with eight geothermal heat flux (GHF) datasets and compare our results with inferences on basal thermal state from radar specularity. The rankings of GHF datasets based on internal inconsistency aligns closely with those using independent specularity content data. Moreover, the spatial distribution of overcooling inconsistency for all datasets shows insufficient GHF at the western boundary of Totten Glacier between 70°S-73°S, which is characterized by a bedrock canyon with fast basal ice velocity. The overheating inconsistency reveals that poorly performing GHF datasets tend to overestimate GHF in central Totten Glacier. Our approach opens a new avenue for assessing the reliability of ice sheet model results and GHF datasets, which may be widely applicable.

How to cite: Wang, J., Zhao, L., Wolovick, M., and Moore, J. C.: Using temperature-sliding inconsistency to evaluate eight geothermal heat flux maps for Totten Glacier, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2721, https://doi.org/10.5194/egusphere-egu25-2721, 2025.

Totten Glacier in East Antarctica holds a sea level potential of 3.85 m and is mostly grounded below sea level. It has the third highest annual ice discharge, 71.4±2.6 Gt yr^-1, among East Antarctic outlet glaciers and has been losing mass over recent decades. Recent thinning of the Totten ice shelf is likely to be due to high basal melt rates driven by increasing intrusion of warm Circumpolar Deep Water. Here we simulate the evolution of the Totten Glacier subregion using a full-Stokes model with different basal sliding parameterizations (linear Weertman, nonlinear Weertman, and regularised Coulomb) as well as sub-shelf melt rates to quantify their effect on the projections. The modelled grounding line retreat and decline in ice volume above floatation using the linear Weertman and the regularised Coulomb sliding parameterizations are close, and both larger than that using the nonlinear Weertman sliding parameterization. The simulated grounding line retreats mainly on the eastern and southern grounding zone of Totten Glacier. The change of sub-shelf cavity thickness is dominated by sub-shelf melt rates, yielding strong volume above floatation dependence on melting through the mechanism of reduced buttressing.

How to cite: Zhao, L., Ma, Y., Gladstone, R., Zwinger, T., Wolovick, M., and Moore, J.: Sensitivity of Totten Glacier dynamics to basal sliding parameterizations and ice shelf basal melt rates, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2782, https://doi.org/10.5194/egusphere-egu25-2782, 2025.

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 apply the deep-learning-driven ice-flow 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. Our previous work focused on the European Alps; here we update the method for a global scale and present results. We show that our volumetric estimates at a regional scale are generally consistent with previous global thickness-modelling studies, and provide preliminary forward-modelling results showing the committed ice loss globally at the 2050 horizon.

How to cite: Cook, S., Jouvet, G., Millan, R., Rabatel, A., Maussion, F., Zekollari, H., and Dussaillant, I.: Global ice thickness and committed loss to 2050, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2800, https://doi.org/10.5194/egusphere-egu25-2800, 2025.

The implementation of ice shelf calving in numerical ice models is a recent development in the field of cryospheric modelling. As roughly half of Antarctica's ice mass loss is due to calving a thorough understanding of the process is required to make accurate predictions of the future Antarctic mass balance. As yet, there has been no comprehensive investigation into the capabilities and robustness of these models for simulating the complicated physical process that is ice shelf calving.

CalvingMIP is an ongoing model intercomparison project that seeks to address this with a series of experiments and tests of increasing complexity, starting from simplified, idealised simulations before expanding to real world predictions. We make a clear distinction between calving algorithms (how a model numerically represents the physical process of ice calving) and calving laws (how much ice should calve at a given time). The recently completed phase one of CalvingMIP focussed on calving laws with the next phase investigating calving laws. Results from phase one are shown from ten different modelling groups across the cryospheric community.

How to cite: Jordan, J. and the The CalvingMIP Team:  Results from phase one of CalvingMIP: , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2866, https://doi.org/10.5194/egusphere-egu25-2866, 2025.

The response of the Antarctic ice sheet to climate change and its contribution to sea level under different emission scenarios are subject to large uncertainties. A key uncertainty is the slipperiness at the ice sheet base and how it is parameterized in glaciological projections. Alternative formulations of the sliding law exist, but very limited access to the ice base makes it difficult to select among them. Here, we use satellite observations of ice flow, inverse methods, and a theory of acoustic propagation in granular material to relate the effective pressure, which is a key control of basal sliding, to seismic observations recovered from Antarctica. Together with independent estimates of grain diameter and porosity from sediment cores, this enables a comparison of basal sliding laws within a Bayesian framework. The presented direct link between seismic observations and sliding law parameters can be readily applied to any acoustic impedance data collected in a glacial environment. For rapidly sliding tributaries of Pine Island Glacier, these calculations provide support for a Coulomb sliding law and widespread low effective pressures.

How to cite: Hank, K., Arthern, R. J., Williams, C. R., Brisbourne, A. M., Smith, A. M., Smith, J., Wåhlin, A., and Anandakrishnan, S.: The Antarctic Ice Sheet sliding law inferred from seismic observations, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3221, https://doi.org/10.5194/egusphere-egu25-3221, 2025.

The West Antarctic Ice Sheet (WAIS) is losing ice and its annual contribution to sea level is increasing. The biggest changes are found in the Amundsen Sea sector of WAIS, which contains two of the most rapidly thinning ice streams, Pine Island Glacier (PIG) and Thwaites Glacier (TG). The future behaviour of these glaciers will impact societies worldwide, yet deep uncertainty remains in the expected rate of ice loss. One prominent question is whether the retreat in this region has already passed a tipping point. In ice-sheet projections using the WAVI model, Thwaites Glacier continues to retreat even in an unrealistic scenario of zero oceanic melting, implying that a tipping point has already been passed. Here, we investigate the robustness of this conclusion to the choices made during the ice sheet model initialisation. In particular, we explore the effects of internal ice temperature, ice shelf extent and initial ice damage on forward runs of the WAVI model under the zero-melt scenario (with no evolving damage). We repeat these experiments for initialisations at different time points within the last ~30 years to assess whether the ice damage in this region passed a tipping point within this timeframe.

How to cite: Williams, C. R., Bett, D., Arthern, R., Holland, P., Bradley, A., and Slater, T.: Effect of model initialisation on committed sea level contribution from the Amundsen Sea Sector, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4095, https://doi.org/10.5194/egusphere-egu25-4095, 2025.

The thermal regime of glaciers plays a critical role in their dynamics and potential hazards. In particular, impermeable cold ice can trap and store liquid water leading to the formation of intraglacial water pockets, as in the Tête Rousse Glacier (France), where the sudden drainage of over 100,000 m³ of water in 1892 caused 175 fatalities and significant damage to the village of Saint-Gervais.

The objective of this work is to produce a detailed thermal regime map of Alpine glaciers to identify those most susceptible to host this type of thermic water pockets. To achieve this, we use a thermo-mechanical ice flow model based on the Elmer/Ice code to simulate the thermal structure of synthetic 2D glacier profiles. The model is based on the enthalpy formulation, where the surface boundary conditions are computed by a subgrid model solving for meltwater percolation and refreezing in the firn. The synthetic 2D profiles are chosen to be representative of the morphological and climatic diversity of the Alps with various length, slope, bedrock shape, elevation range, aspect, and snow accumulation distribution.

The outputs of these simulations form a large database of glacier thermal structures, which will serve as the training dataset for a machine learning emulator currently under development. This emulator will provide a tool to infer thermal regimes to the scale of the entire Alpine region, predicting basal temperatures based on glacier morphology.

The results from the 2D simulations suggest that snow accumulation patterns play a dominant role in shaping glacier thermal regimes: (i) upstream over-accumulation promotes percolation and refreezing of liquid water, releasing latent heat and warming the glacier locally, while (ii) exposed ice downstream acts as an impermeable thermal barrier, creating favorable conditions for water storage.

This integrated approach, combining detailed physical modeling with machine learning techniques, provides a way to build a tool that can be easily applied at a large scale while accounting for the complex interactions that determine the thermal regime of glaciers. In the longer term, it seeks to deliver a comprehensive thermal regime map of Alpine glaciers, providing a valuable resource for identifying glaciers most at risk of hosting intraglacial water pockets and improving the prevention and management of glacier-related hazards.

How to cite: Bonnet, J., Gilbert, A., Ozenda, O., and Gagliardini, O.: Regional scale thermal regime mapping of Alpine glaciers inferred from 2D thermo-mechanical modeling, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6245, https://doi.org/10.5194/egusphere-egu25-6245, 2025.

Corridors of fast ice flow, ice streams, dominate the mass discharge of contemporary ice sheets. Ice streams are points of vulnerability for ice sheet instabilities, and so to understand past and future ice sheet change we need to understand ice stream behaviour. Computer simulations can replicate the position and magnitude of palaeo and contemporary ice streams with some skill, but for accurate future projections of ice mass change we need confidence that simulated ice streams will evolve and adjust to a retreating ice sheet in a realistic manner. This is much harder to constrain with empirical evidence, and there is still considerable uncertainty regarding ice stream response to changes in wider ice sheet geometry.

To explore the behaviour of simulated ice streams on a fundamental level, we run simulations of a circular ice sheet on a flat bed using the BISICLES numerical ice sheet model. We simulate a series of idealised circular ice sheets of various radii, finding that plausible ice stream spacing and magnitude is simulated even on a flat bed, and that ice stream size and frequency scales with ice volume. We apply the idealised model to the bed of the Last Glacial Maximum Icelandic Ice Sheet, resulting in a simulation with less frequent ice streams, each with a greater size than would be expected based on the idealised case. The realistic topography makes ice stream position broadly insensitive to changes in topographic roughness and geothermal heat flux. These simulations provide increased confidence in the ability of ice sheet models to simulate dynamic ice stream change and could act as a starting point for more realistic simulations of the advance and retreat of the last Icelandic Ice Sheet.

How to cite: Gandy, N., Veness, R., Ely, J., and Storrar, R.: Simulations of Ice Stream Size and Frequency Scaling with Ice Sheet Radius, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6479, https://doi.org/10.5194/egusphere-egu25-6479, 2025.

Debris cover on glaciers is expanding worldwide as glaciers are retreating. While the impact of debris cover on local mass balance is relatively well-established, the long-term dynamics of these glaciers are more complex and not fully understood. The dynamics are a key factor when trying to establish relationships between erosion rates, debris fluxes, and debris cover thicknesses while all of these properties are either completely unknown or only known locally in space and time.

Numerical modelling can help us better understand the data scarce debris-covered glacier system. While most recent approaches model englacial debris as an advected concentration, we establish a novel approach that exploits Lagrangian particle tracking in the Instructed Glacier Model (IGM). IGM uses deep learning to solve ice flow equations, greatly reducing computation times and enabling long-term model runs with large amounts of particles. In our implementation, a single particle represents a unit volume of debris and can be assigned any other property. The user can define a particle seeding area through either manual mapping or automatic classification based on conditions. Once particles emerge at the glacier surface in the ablation area, they are evaluated to compute debris cover thickness, which is then tied back to surface mass balance through a user-defined function.

As examples to showcase the capabilities of the model we use Zmuttgletscher, Switzerland, and Satopanth Glacier, India. We explore the sensitivities of the model to the use of different seeding strategies, changes in debris input amounts, mass balance functions, and model parameters such as grid size and seeding frequency.

How to cite: Hardmeier, F., Muñoz-Hermosilla, J. M., Miles, E., Jouvet, G., and Vieli, A.: Exploiting Lagrangian particle tracking in the Instructed Glacier Model (IGM) to model coupled debris-covered glacier dynamics, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6707, https://doi.org/10.5194/egusphere-egu25-6707, 2025.

The Antarctic and Greenland Ice Sheets (AIS and GrIS) play a critical role in shaping future sea-level rise (SLR), but their contributions and human greenhouse gas emissions remain the largest sources of uncertainty in SLR projections (Edwards et al., 2021). This uncertainty, along with the risk of potential tipping points leading to rapid ice loss, arises from a limited understanding of key processes that govern ice-sheet behaviour (Fox-Kemper et al., 2021). In the Ice Sheet Model Intercomparison for CMIP6 (ISMIP6), 55% of AIS and 15 to 35% of GrIS future mass loss uncertainty is due to ice-sheet models’ uncertainty (Seroussi et al., 2023; Jager et al., 2024; Goelzer et al., 2020). While modeling the AIS’s and GrIS’s complex interactions with the climate is difficult (Seroussi et al., 2023), one other uncertain process is basal sliding over bedrock. Because this process is not directly observed due to the large thickness, its representation in current models remains rudimentary. The primary goals of Combining Coupled Modelling and Machine Learning to Constrain Antarctica’s Uncertain Future (ICEMAP) project include (i) better quantification of uncertainties related to basal sliding, (ii) comparison of these uncertainties to other sources of uncertainty, and (iii) exploration of how satellite data can help reduce these uncertainties. 

To achieve these goals, we employ the Shallow Shelf Approximation (SSA) implemented in the Elmer/Ice model, an open source finite element software for ice sheets, glaciers and ice flow modelling, which was one of the participants in ISMIP6 (Gagliardini et al., 2013; Seroussi et al., 2023). It uses inverse methods to calibrate the many unknown parameters related to rheology and friction. Here, we take into account various physical and numerical uncertainties to perform multiple calibrations using remote-sensing velocity data to compute basal sliding and basal shear stress. Subsequently, these values and their spatial variations can be compared with the diverse existing theories that have been developed from small-scale physical and numerical experiments (Gagliardini et al., 2007; Zoet and Iverson, 2020).

Our analysis demonstrates that the principal characteristics of these parameterisations, derived from small-scale experiments, are observable at a large scale. However, the values may deviate from expected norms, particularly with regard to the exponent of the Weertman friction law. This investigation enables the quantification of both the parameter values and their associated uncertainties within the friction parameterisations governing the AIS and the GrIS. Furthermore, it highlights the critical influence of basal water presence, which appears to play a pivotal role in the variability of basal sliding. Incorporating this factor into models, whether through varying levels of model complexity or the use of proxies, is deemed essential for accurately capturing the temporal variations in basal sliding.

How to cite: Jager, E., Gladstone, R., Zwinger, T., Uotila, P., and Moore, J.: Friction: what’s going on underneath the Antarctic and Greenland ice sheets?, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6813, https://doi.org/10.5194/egusphere-egu25-6813, 2025.

When modelling ice flows there are a number of properties of the ice which are poorly constrained by observations, in particular the ice rheology and basal slipperiness at the ice bed. Inversion methods are frequently used to estimate the distribution of these 'hidden' fields in computational ice flow models. These methods use surface measurement data in combination with a forward model of the ice dynamics that relate the hidden fields to the surface fields. In this study we use first-order linear perturbation theory to gain insights into our ability to extract information about the ice viscosity at the same time as basal slipperiness, and understand the theoretical limitations of this approach. We frame the typical inversion problem in terms of a Gaussian maximum a-posteriori estimation with explicitly stated priors for the hidden fields. We illustrate the inversion behaviour with perturbations applied to flow down a laterally confined channel, where both viscosity and slipperiness play a significant role in the ice sheet dynamics. Our results indicate that it is possible to extract information about the viscosity field at the same time as estimating the basal slipperiness, and that explicitly recognising uncertainty in the viscosity field is important. 

How to cite: Schelpe, C. and Gudmundsson, G. H.: On the theoretical aspects of joint inversion for basal slipperiness and viscosity in ice-flow models, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8757, https://doi.org/10.5194/egusphere-egu25-8757, 2025.

Many processes that influence the dynamic behaviour of the Antarctic ice sheet, such as basal sliding, ice rheology, and subglacial meltwater production, largely depend on the thermal state and how it evolves. However, significant uncertainties remain regarding the factors influencing basal and englacial temperatures, hindering the predictions of ice sheet models. These uncertainties pertain to geothermal heat flow, past and present surface climatic conditions, and the inherent complexity of ice flow models. In this study, we provide new estimates of englacial and basal thermal conditions and conduct an ensemble of simulations to quantify the impact of these factors on the basal thermal regime and assess their contributions to model uncertainty. We use observational constraints, including deep borehole measurements, englacial temperatures derived from SMOS satellite observations, and the presence of subglacial lakes, to evaluate the ensemble results and determine the most likely simulations. Although we find that geothermal heat flow remains the largest source of uncertainty, recently published heat flow data seem to better fit the observational constraints. Nevertheless, since the englacial temperature field is sensitive to the past climate history, accounting for variations in surface temperatures and accumulation rates over the last glacial-interglacial cycle results in colder temperature profiles and basal thermal conditions, which points to possible overestimation of thermal conditions based on present-day boundary conditions.

How to cite: Raspoet, O. and Pattyn, F.: Assessing uncertainties in modelling the thermal state of the Antarctic Ice Sheet, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9928, https://doi.org/10.5194/egusphere-egu25-9928, 2025.

Basal sliding is a key process that controls the ice discharge of ice into the ocean. Understanding this process is essential for improving the reliability of future projections of ice sheet evolution and sea level rise. The basal sliding law, which governs ice-bed interactions, remains a critical yet poorly understood process in ice sheet models. Recent advances in transient calibration techniques, which incorporate time series of observed surface velocity and elevation, have enhanced the ability of ice numerical models to infer basal conditions. However, relying on the same type of observational datasets for both model calibration and validation limits the ability to independently evaluate model performance, particularly for future projections. In this study, we introduce an independent observational dataset: measurements from the Global Navigation Satellite Systems (GNSS) collected by Greenland GNSS Network (GNET) stations located along Greenland's coastline. By comparing observed uplift signals with modeled mass change, we can validate model behavior and identify sliding laws most consistent with GNSS data. Here, we illustrate this approach by modeling Helheim and Jakobshavn Glaciers from 2007 to 2022 using three different sliding laws. While all sliding laws produce similar surface velocity patterns consistent with InSAR-derived velocity observations, the patterns of mass change, which control bed uplift, differ significantly. Our analysis reveals that all three sliding laws can reproduce uplift signals consistent with GNSS measurements in terms of inter-annual variability. However, only coulomb-limited sliding laws generate uplift signals consistent with GNSS measurements in multi-annual trends. These results highlight the importance of incorporating multiple independent observational data, such as GNSS, into ice sheet models to refine our understanding of basal sliding laws and reduce uncertainties in predicting future sea level rise.

How to cite: Cheng, G., Barletta, V. R., Khan, S. A., Morlighem, M., Seroussi, H., and Berg, D.: Identifying the Basal Sliding Law Using Numerical Modeling and GNSS Observations, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10180, https://doi.org/10.5194/egusphere-egu25-10180, 2025.

In a warming climate, the potential collapse of the West-Antarctic Ice Sheet is a threat for coastal livelihood as it implies a multimeter sea level rise with unprecedented rate. It is a high-dimensional process, since it involves a number of spatio-temporal variables that interact with each other (e.g. the ocean temperature, the ice thickness and the bedrock elevation). To obtain a better understanding of what initiates a collapse, we propose to apply model reduction techniques to simulations of the Antarctic Ice Sheet under warming scenarios and rely therefore on modern machine learning concepts. Based on this reduced-order representation, we propose an early warning signal that predicts the onset of the marine ice sheet instability in the Thwaites region with a lead time of several decades. This is of key importance to develop meaningful adaptation strategies, which can save lives and critical infrastructure. Most importantly, the early warning signal can be projected back onto the full dimensionality of the problem, thus giving insights into the physics underlying the collapse. This implies that the present work can even serve for developing efficient monitoring systems and mitigation strategies.

How to cite: Swierczek-Jereczek, J., Hill, A., Robinson, A., Alvarez-Solas, J., and Montoya, M.: A reduced-order representation of the West Antarctic Ice Sheet, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10371, https://doi.org/10.5194/egusphere-egu25-10371, 2025.

Ice-sheet modelling studies of the Amundsen Sea Embayment (ASE) in West Antarctica have provided estimates of its future impacts on sea level rise. However, many of these have not considered the impacts of ice front movement due to calving, a key process in the dynamics of marine-terminating glaciers. Sensitivity to calving front retreat is not well understood, so we set out to investigate it in a systematic manner using the recently implemented level set method in the ice-sheet model Úa. Here, we quantify the sensitivity of modelled future mass loss to ice front retreat in the ASE, including Pine Island and Thwaites Glaciers. We find that prescribing constant frontal retreat rates from 0.1 to 1 km/yr progressively increases the contribution to sea level rise when compared to experiments with a fixed ice front. The result with our highest rate of retreat is up to 21.4mm additional sea level contribution by 2100, and 239mm by 2300. We identify specific buttressing thresholds where loss of contact with bedrock features causes changes in the ice dynamics. These are reached at different times depending on the retreat rate, and are the main cause of sensitivity to movement of the ice front. We compare variability in the range of our results using different retreat rates to that in the range of ISMIP6 ocean forcing products, as ocean-induced melt is known to be a major factor in determining the future evolution of the Antarctic ice sheet. We find that the variability due to these two factors is similar. We also find that the additional loss of ice due to a prescribed retreat rate is not heavily dependent on ocean forcing, so can be quantified independently of the ocean-induced melt. Our results demonstrate the importance of accurately representing calving processes in models, showing that they can be as important as ocean forcing and therefore deserve a similar amount of attention in future model development work.

How to cite: Barnes, J., Gudmundsson, H., Goldberg, D., and Sun, S.: Modelling the sensitivity of ice loss to calving front retreat in the Amundsen Sea Embayment, West Antarctica, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10964, https://doi.org/10.5194/egusphere-egu25-10964, 2025.

In the last decades, Pine Island Glacier (PIG) and Thwaites Glacier (TG) are observed to be losing ice with increasing rates, contributing to sea-level rise. To estimate their potential sea-level contribution in the future, it’s essential to understand the mechanisms driving the dynamical changes at present. Various processes have been suggested to influence the dynamics of PIG and TG, including ocean driven sub-ice-shelf melting, iceberg calving, basal sliding and ice fracturing/damage. However, the relative importance of these physical processes for past and future changes of the glaciers remains uncertain. In this study, we use the abundant remote-sensing observations acquired in the recent decades (1996-2023) to quantitatively constrain and perturb an ice-sheet model. By simulating the ice discharge and spatial changes in ice thickness of the glaciers through sensitivity experiments, we quantify the relative impact of the above mentioned processes on the dynamics of PIG and TG.

How to cite: Sun, S.: Contribution of ice-shelf melt, calving and damage to the evolution of Pine Island and Thwaites glaciers, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10973, https://doi.org/10.5194/egusphere-egu25-10973, 2025.

The grounding line marks the boundary between grounded and floating ice, and is a critical region for ice-sheet stability and sea-level projections. The complex ice-flow at the grounding line, where the stress regime moves from vertical shear to horizontal extension over a relatively short distance, is prone to numerical instability in transient full-Stokes simulations. Furthermore, boundary conditions change at the grounding line, switching from a friction law in grounded ice to an ocean pressure force at the ice-ocean interface. Grounding-line full-Stokes problems have been successfully stabilised by the sea spring stabilisation scheme in Elmer/Ice (Durand et al., 2009) which mimicks an implicit time-stepping scheme by predicting the surface elevation and corresponding ocean pressure corrections in the next time step. We extend on this stabilisation approach by introducing the Free-Surface Stabilisation Approximation (FSSA) to the ice-ocean interface. FSSA has been proven successful in allowing larger stable time steps in grounded problems with an evolving ice-atmosphere interface (Löfgren et al., 2022; Löfgren et al., 2024). This stabilisation approach incorporates a boundary condition term into the weak-form of the Stokes equations representing the predicted stress adjustment between the current and next time step. Using a synthetic MISMIP set up (Pattyn et al., 2012), we investigate the applicability of FSSA to the ice-ocean interface.

G. Durand, O. Gagliardini, B. de Fleurian, T. Zwinger, and E. Le Meur. Marine ice sheet dynamics: Hysteresis and neutral equilibrium. Journal of Geophysical Research, 114(F3):F03009, 2009. doi: 10.1029/2008JF001170.

A. Löfgren, T. Zwinger, P. Råback, C. Helanow, and J. Ahlkrona. Increasing numerical stability of mountain valley glacier simulations: implementation and testing of free-surface stabilization in Elmer/Ice. The Cryosphere, 18(8):3453–3470, 2024. doi: 10.5194/tc-18-3453-2024.

A. Löfgren, J. Ahlkrona, and C. Helanow. Increasing stable time-step sizes of the free-surface problem arising in ice-sheet simulations. Journal of Computational Physics: X, 16:100114, 2022. doi: 10.1016/j.jcpx.2022.100114.

F. Pattyn, C. Schoof, L. Perichon, R. C. A. Hindmarsh, E. Bueler, B. de Fleurian, G. Durand, O. Gagliardini, R. Gladstone, D. Goldberg, G. H. Gudmundsson, P. Huybrechts, V. Lee, F. M. Nick, A. J. Payne, D. Pollard, O. Rybak, F. Saito, and A. Vieli. Results of the Marine Ice Sheet Model Intercomparison Project, MISMIP. The Cryosphere, 6(3):573–588, 2012. doi: 10.5194/tc-6-573-2012.

How to cite: Henry, C., Zwinger, T., and Ahlkrona, J.: Numerical stabilisation of grounding line dynamics in Stokes problems, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11161, https://doi.org/10.5194/egusphere-egu25-11161, 2025.

Marine ice sheets are essential components of the climate system, with dynamics strongly influenced by interactions with the atmosphere and the ocean. The grounding line, which separates the grounded region of the ice sheet from the floating region, plays a key role in the evolution of marine ice sheets. While numerous studies have focused on grounding-line migration and its sensitivity to physical processes, the influence of localized bedrock features, known as pinning points, remains less well understood. These pinning points can locally ground the floating ice, thereby altering ice flow by providing additional resistance.

Here, we investigate the impact of pinning points on marine ice-sheet dynamics using numerical simulations. The discontinuity in the momentum balance at the grounding line results in a component of the Jacobian matrix for the linearized problem becoming unbounded near pinning points. This behavior is intrinsic to the system and persists regardless of numerical discretization, even over smooth bedrock geometries and with friction laws that vanish at the grounding line. This suggests adopting a regularized approach that ensures a smooth transition between the grounded and floating regions. Based on numerical experiments in idealized setups, we show that a regularized formulation produces results that are qualitatively different from those of the original, unregularized formulation. Hence, the regularization appears a singular perturbation to the equations. This raises interesting questions about the treatment of grounding lines in marine ice-sheet models. Finally, we discuss potential approaches to mitigate this singular behavior and improve the modeling of marine ice sheets and of their grounding lines.

How to cite: Gregov, T., Pattyn, F., and Arnst, M.: Sensitivity of grounding-line migration to ice-shelf pinning, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11628, https://doi.org/10.5194/egusphere-egu25-11628, 2025.

Thwaites and Pine Island glaciers, West Antarctica, are some of the most dynamical areas of the Antarctic Ice sheet and both currently are discharging more ice into the ocean than is replenished through surface snow accumulation. While the current imbalance does not represent a large contribution to global sea level rise, as compared to the Greenland Ice Sheet an Alpine Glaciers, both Thwaites and Pine Island glaciers have rightly received considerable attention by the glaciological community. This interest is related to the suggestion that these glaciers either have already, or are likely to become, dynamically unstable. Here we review the history of ice-dynamical studies of those systems and show how, in recent years, a more detailed picture of the contemporary dynamics of those systems has emerged.  Our new model-based consensus confirms some previously suggested dynamical behaviour, but also points towards a new understanding of the stability regime of those glaciers. The stability regime of marine-type ice sheet cannot be determined based on local geometry alone. In particular, the slope of the bed with respect to flow direction does not determine the stability of grounding lines. Neither Pine Island nor Thwaites glaciers are currently in a dynamically unstable state. However, Pine Island Glacier did go through a phase of unstable retreat during the 1970s. This unstable phase has now come to a halt. Thwaites glacier similarly appears currently to be responding to some past external forcing, which has yet to be fully identified. However, all studies published do indicate that Thwaites will enter a large-scale unstable and irreversible retreat once, or if, the grounding lines retreats about 75 km upstream of its current location. This recent progress can be described using the well-known IPCC confidence levels, as a shift in the confidence in the potential of near-future collapse of Thwaites from low agreement and low evidence to high agreement and medium evidence.  The biggest unknown is now no longer whether Thwaites glacier can in principle become unstable, but when and if this instability will arise.   

How to cite: Gudmundsson, G. H., Morlighem, M., Goldberg, D., Rydt, J. D., Getraer, B., Barnes, J., Sun, S., and Rosier, S.: The stability regimes of Thwaites and Pine Island Glaciers, West Antarctica., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11774, https://doi.org/10.5194/egusphere-egu25-11774, 2025.

The loss of Thwaites Glacier is the most important factor in determining the future stability of the West Antarctic Ice Sheet (WAIS), which contains enough ice to raise global mean sea level by up to 3.4 m. All ice that will terminally calve from a glacier can be shows as a flux, that is a velocity through a cross-sectional area. This flux is partly controlled by the distance between the two lateral shear margins that bound an ice stream. For glaciers unconstrained by topography, margin migration can significantly influence ice discharge to the ocean. This is well illustrated in the case of the eastern shear margin (ESM) of Thwaites.

The initiation of basal slip is determined according to a sliding law. Although regularized Coulomb-style sliding laws can resolve slip over both hard and soft bedded glaciers, they depend on knowledge of the effective pressure (ice overburden minus water pressure) of the ice. Most modeling studies that examine Coulomb style slip laws limit themselves to a constant floatation percentage, a constant melt rate based on thickness, or other hard parametrizations, while inverting for friction coefficient values. Instead, I look to find the effect of the variation of basal hydrology with a constant friction coefficient, and quantify the change in slip initiation under differing upstream water flux scenarios.

To examine hydrological shear margin controls, I implemented two models. First, a regional hydrology model which couples the Glacier Drainage system model (GlaDS) with a shallow shelf flow approximation (SSA) forced by an ITS_LIVE annual velocity mosaic. This model yields a high resolution, near-steady state, regional-trending hydrologic system across the Amundsen Sea Sector of West Antarctica which informs boundary conditions for a finer scale model. The second model is local to the Thwaites ESM. It is a hydro-thermomechanical 3D flow model which melt in the basal elements of the domain from enthalpy. In the local model, I couple this melt and hydrology to slip through a regularized Coulomb-style sliding law to calculate the spatial slip distribution over the shear margin.

This work finds good agreement between flow solutions and current velocity observations at the local model scale. Additional upstream water sources divert excess water to the Thwaites catchment rather than to neighboring Pine Island Glacier, and these increased fluxes drive a widening of Thwaites’ main trunk (a margin drift outwards). Future work should expand this local model to regional and WAIS-wide domains to resolve many ice stream dynamics in prognostic ice flow models to more accurately predict sea level rise contributions.

How to cite: Hehlen, M. and Martin, C.: Modeling Thwaites Glacier shear margin stability by slip initiation due to variation of effective pressure, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12934, https://doi.org/10.5194/egusphere-egu25-12934, 2025.

Ice-dammed lakes expedite glacier retreat, leading to the expansion of lakes and an elevated risk of Glacial Lake Outburst Floods (GLOFs), and delay the freshwater inflow to the ocean. The escalating number of ice-dammed lakes in Greenland, High Mountain Asia, and Patagonia, driven by the swift retreat of glaciers amid rapid warming, poses a significant threat of natural disasters. Despite extensive research on marine-terminating glaciers, the dynamics of lacustrine-terminating glaciers remain poorly understood. Geological evidence indicates the rapid retreat of the Fennoscandian ice sheet, marked by the formation, expansion, and drainage of ice-dammed proglacial lakes. This underscores a comprehensive investigation into ice-dammed lake-glacier interactions spanning both Paleo- and Contemporary ice sheets. The deglaciation and ice-lake interactions of the Fennoscandian Ice Sheet (FIS) provide a valuable analogue for projecting the future retreat of the Greenland ice sheet, where a manifold increase in the number and volume of ice-dammed lakes is anticipated.

One key aspect of proglacial lake damming is that they may episodically drain; and drainage may be more or less instantaneous. Our study investigates first the effect of lake size, and secondly the effect of sudden lake drainage, on the dynamics of lake-terminating ice sheet outlets using the Ice-sheet and Sea-level System Model (ISSM). Our findings reveal significant differences in the dynamics of land- and lake-terminating glaciers without calving, with the magnitude of differences varying with the lake level. Furthermore, we observed abrupt changes in the deviatoric stress at the front during rapid lake drainage, which could potentially trigger cliff collapse and accelerate ice sheet retreat.

How to cite: Pramanik, A., Greenwood, S., Regnéll, C., and Gyllencreutz, R.: Ice-lake interactions: How does it affect the ice sheet retreat?, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14841, https://doi.org/10.5194/egusphere-egu25-14841, 2025.

Glaciers in the European Alps play an important role, e.g. for water storage, water supply and the ecosystem. Here, we model the future evolution of two valley glaciers in the European Alps over the course of the 21st century. The Great Aletsch Glacier is located in the Western Alps (Switzerland), while the Hintereisferner is in the Eastern Alps (Austria). The two different glacier locations allow us to compare glacier development in the Western and Eastern Alps in a changing climate. We use a three-dimensional model that combines the full Stokes ice dynamics and basal friction inversion on a 25m horizontal grid. The coupled energy balance model computes the surface mass balance based on high-resolution regional RCP8.5 and RCP2.6 climate model (RCM) data from the EURO-CORDEX ensemble (a total of 62 different GCM-RCM combinations). In addition, SSP5-8.5 and SSP1-2.6 of the newer CMIP6 generation have been calculated based on the ISIMIP3b ensembles (10 different GCMs in total). All simulations show a dramatic volume loss, with the GAG disappearing in 2100 under the high-emission scenarios (RCP8.5 and SPP5-8.5) and the HEF already disappearing in around 2060. A special feature is that the HEF shows a similar volume loss under SSP5-8.5 and SSP1-2.6. The GAG has the ability to stabilize under SSP1-2.6.

How to cite: Rückamp, M., Gutjahr, K., Möller, M., and Mayer, C.: Future retreat of Great Aletsch Glacier and Hintereisferner – an East-West comparison, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15050, https://doi.org/10.5194/egusphere-egu25-15050, 2025.

Traditional numerical solvers for simulating glacier dynamics are computationally demanding, particularly for large-scale and long-period projections. Recent use of neural networks(NNs) based surrogate models, including data-driven and physics-informed convolutional neural networks (CNNs), have shown considerable success in accelerating simulation while maintaining adequate accuracy. However, conventional NN-based surrogate models typically map finite-dimensional Euclidean spaces, making them confined to particular discretization or resolution. As a result, these models often exhibit limited generalization capabilities and require frequent retraining when applied to new geometries or solution scenarios outside their training domain. Neural operators (NOs) offer a promising alternative. Unlike classical NNs, NOs learn the mapping between functions in infinite-dimensional spaces, making predictions more invariant with regard to resolution. They learn the parametric dependence of solutions across entire families of partial differential equations, making them better at generalization. Despite these advantages, limited existing literature uses neural operators for glacier flow simulation. 

This study presents different versions of a NO-based surrogate model to predict glacier velocity. These implementations will be evaluated against classical NN-based approaches, focusing on their computational efficiency, accuracy, and generalization across varying resolutions. Additionally, the study will explore key hyperparameters that influence the stability and performance of NO models and perform sensitivity analysis to identify the most effective configurations. The first results are promising and give insight into the performance and potential of NO-based surrogate models for ice-flow simulations.

How to cite: K C, M., Köstler, H., and Fürst, J. J.: Predicting Glacier Dynamics with Neural Operator-Based Surrogate Models., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16232, https://doi.org/10.5194/egusphere-egu25-16232, 2025.

Understanding the physical laws governing glacier and ice sheet basal sliding speed is crucial for accurately predicting their dynamics and contribution to sea-level rise. However, basal sliding is controlled by complex processes linked to subglacial hydrology, which remains difficult to constrain. Previous studies based on Argentière glacier (France) suggest a simplification of the law describing the long-term evolution of sliding velocity, by proposing that long-term subglacial water pressure of hard-bedded glaciers is determined by the basal shear stress condition. The applicability of these findings to other glaciers and over long timescales has not been fully explored yet. In this study, we analyze multidecadal timeseries of surface velocities and elevations from various locations on seven Alpine glaciers, spanning from the early 20th century to the present. Using the Elmer/Ice finite element model, we solve for the full-Stokes equations to derive realistic estimates of basal sliding velocities and shear stresses from observed surface velocity and topography. Our analysis of these datasets reveals distinct basal friction behaviors both among glaciers and within different profiles of the same glacier. We identify three types of friction laws governing glacier dynamics. Most sites follow a Lliboutry-type law, where significant variations in sliding velocity occur under minor changes in shear stress. This behavior can be explained by the formation of water-filled cavities that grow as a function of sliding velocity under constant effective pressure. Other sites exhibit a Weertman-type law, characterized by a power-law scaling between shear stress and sliding velocity, implying constant cavity size through time. Finally, only Gébroulaz glacier follows a Coulomb-type law typical of sedimentary beds, where basal velocities increase dramatically beyond a critical shear stress threshold. For each measurement site, we derive a value of maximum shear stress CN and friction coefficient As and find that hard-bedded glaciers in the Weertman and Lliboutry regimes align along a unified friction law with similar values for the friction exponent m and the bed-shape exponent q. Our results show that the basal friction at all sites can be explained by a single friction law where the effective pressure either remains constant through time or scales with the basal shear stress. Further exploration of correlation between these friction laws and glacier geometric parameters, such as surface slope and bedrock roughness, may provide insights into the underlying mechanisms regulating the long-term effective pressure. 

How to cite: Zeller, M., Gilbert, A., and Gimbert, F.: Investigating the basal friction law of Alpine glaciers from multi-decadal up to centennial observations, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16821, https://doi.org/10.5194/egusphere-egu25-16821, 2025.

How to cite: Richards, D., Arthern, R., Marsh, O., and Williams, R.: A viscoelastic phase-field model for calving and fracture in ice, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17134, https://doi.org/10.5194/egusphere-egu25-17134, 2025.

Subtemperate sliding is key to ice stream formation. It has been shown that models without any approximations to the Stokes equations are necessary to capture temporal instabilities at an ice-sheet scale. In this project we analyze the temporal stability of subtemperate regions using a Stokes flow-line model of an ice stream thermodynamically coupled to a continuous water sheet at the bed using Elmer/Ice. We use Newtonian rheology with suitably chosen physical parameters. Subtemperate sliding was modeled through a temperature dependent sliding with strong sensitivity to temperature changes which introduces an additional thermo-frictional feedback. We perform transient perturbation experiments with small variations of the sliding coefficient. We explore the cases of strong and weak temperature dependence of sliding and the effects of a Weertman and a regularized Coulomb sliding law in the temperate region.

How to cite: Brass, S., Mantelli, E., and Zwinger, T.: Temporal stability of subtemperate regions in an ice-sheet scale flow-line model, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17306, https://doi.org/10.5194/egusphere-egu25-17306, 2025.

The acquisition of 1.5 Myr ice cores is a major objective of Antarctic exploration, aiming to enhance our understanding of the causes behind the Mid-Pleistocene Transition. Here, we combine radar observations and ice-flow modeling to investigate the age, basal thermal state and temperature of the ice sheet in the Dome Fuji region, Antarctica, to provide significant information for selecting the drill site.

We use a 3-D ice-flow model to couple the mechanical, thermal and hydrological processes in the ice sheet. Radar internal stratigraphy and the previously identified subglacial waterbodies are incorporated as constraints in the inverse modelling to improve the reliability of the model results. The modelled basal temperature reaches the pressure melting point in most of the study area, while there is a lower modelled basal temperature near the New Dome Fuji (NDF, 77.789° S, 39.053° E) and southeast of the old Dome Fuji drill site (DF, 77.317° S，39.703° E). The relative basal reflectivity, derived from radar bed return power and modelled 3-D ice temperature, is relatively low in these areas as well. This suggests a lower possibility of basal melting, and thus suggests that a longer climate record might be preserved in the ice. The modelled age of of the ice near the base reaches 1.5 Myr near NDF and south of DF. These modelled results enhance the understanding of ice dynamics, age distribution and thermal structure in the Dome Fuji region.

How to cite: Wang, Z., Wolovick, M., Steinhage, D., Dong, S., and Eisen, O.: 3-D thermal structure and age modelling of the ice sheet in the Dome Fuji region, Antarctica, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17432, https://doi.org/10.5194/egusphere-egu25-17432, 2025.

Debris-covered glaciers play an important role in alpine hydrology and surface debris substantially alters glacier processes and evolution. Yet the processes governing the transport and distribution of debris remain poorly understood, and thus poorly included in models of glacier evolution. To address this gap, we are developing a numerical model of debris transport within the framework of the Instructed Glacier Model (IGM), leveraging a newly implemented Lagrangian particle tracking module to simulate the movement of debris across the glacier.

This study focuses on the Oberaletsch Glacier in Switzerland, where we explore different seeding strategies for the debris particles, which involve defining how and where debris particles are introduced into the model to simulate their transport and distribution. These strategies aim to reproduce the spatial and temporal evolution of debris coverage, starting from a debris-free glacier geometry at the end of the Little Ice Age. This negligible-debris known geometry allows us to spin up the model without debris for our initial condition. To reach this pseudo-steady-state, we calibrate the mass-balance model with historic measurements at the nearby Grosseraletschgletscher. We then focus on the debris seeding: by adjusting the debris seeding locations and rates to reproduce the historic changes in debris extent, we assess the influence of initial particle placement and quantity on the debris distribution.

Preliminary results highlight the sensitivity of debris coverage to changes in the seeding strategies. Our simulations also reveal that certain characteristics of the glacier-surface debris coverage —the location and extent of medial moraines— are linked to glacier morphology and arise from the interaction between ice flow dynamics and the structure of the glacier bed, which collectively dictate where debris is transported and deposited on the glacier surface,  irrespective of debris seeding strategy.

This study highlights the potential of integrating Lagrangian particle tracking into glacier models as a robust tool for advancing our understanding of debris-covered glaciers. This approach also provides new insights into the coupling of glacier dynamics and debris transport processes, and offers a framework to understand and characterize the debris inputs to these systems. It is the first step towards developing fully operational models for predictions of glacier evolution in debris-covered glacier systems under changing climatic conditions.

How to cite: Muñoz-Hermosilla, J. M., Miles, E., McCarthy, M., Hardmeier, F., Melo Velasco, V., Jouvet, G., and Pellicciotti, F.: Towards Reconstructing Debris Supply to Reproduce the Historic Changes in Debris Extent at a Swiss Glacier, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17446, https://doi.org/10.5194/egusphere-egu25-17446, 2025.

The aerial extent of supraglacial debris cover is increasing on mountain glaciers as a result of recent climatic warming. A thicker debris cover tends to shield the glacier surface from melting, with important consequences for glacier dynamics and evolution. However, only a few studies have tried to model the impact of a changing supraglacial debris cover on glacier evolution at a regional scale. For nearly all of the existing models, it is difficult to calibrate the individual unknown model parameters, such as the degree-day factors, temperature and precipitation biases, debris supply rate and englacial debris concentration, because of the strong interdependencies between mass balance, ice-flow and debris cover and thickness evolution. In the case of regional  scale modelling of glacier evolution, almost all of these unknown model parameters are tuned with respect to a small set of selected glaciers. As a result, the level of uncertainty in the calculated model outputs varies for those glaciers that are outside the set of glaciers that were used during calibration. On top of that, due to process-based complexities, many of these models have parameterised the evolution of spatial distribution of debris thickness rather than using process-based models. Therefore, we propose using Bayesian inference to calibrate the coupled ice-flow and debris evolution model. Bayesian inference presents a unique way to calibrate the model parameters while taking into account the uncertainty in the observed data. The stochastic calibration of model parameters through Bayesian inference enables a robust uncertainty analysis of the model results. Using Bayesian inference, helps decouple the intertwined complex process that renders model calibration easy.

To demonstrate the above, as a first step, we present a strategy to effectively decouple and separately calibrate the mass-balance and debris cover evolution modules. We first calibrate the unknown parameters of the mass balance model, namely the degree day factor and the temperature and precipitation biases. We use Bayesian inference for calibrating the mass balance model against geodetic mass balance and satellite-derived, maximum annual snowline altitude. Next, we calibrate a debris cover evolution model using the calibrated mass balance model. We first test this approach at the Oberaletsch Glacier in the Swiss Alps. The mass balance model is forced by reanalysis temperature and precipitation, using a degree-day model modified for debris melt effects. Using our strategy, we simulate the 20-year averaged glacier-wide mass balance within 10% uncertainty as compared to existing geodetic mass balance data. In addition, we simulate the evolution of supraglacial debris-cover for every 10 m elevation band within a mean uncertainty of ~11% as compared to satellite-derived debris cover data. In the future, in addition to the mass balance and debris evolution, we also aim to use this strategy to calibrate the ice-flow module. Once calibrated, the coupled model will be used to estimate the future evolution of glaciers located in the Swiss Alps.

How to cite: Gantayat, P., Miles, E., McCarthy, M., Jouberton, A., Melo Velasco, V., and Pellicciotti, F.: A robust strategy to calibrate a coupled ice-flow, mass balance and debris cover evolution model, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18027, https://doi.org/10.5194/egusphere-egu25-18027, 2025.

The Pine Island and Thwaites glaciers in the Amundsen Sea Embayment are losing mass faster than any others in Antarctica, and are crucial for the stability of the West Antarctic Ice Sheet. Here we examine their sensitivity to the treatment of basal effective pressure and sub-ice shelf melting over millennial timescales, using the BISICLES ice sheet model. We carry out 1000-year simulations with melting applied selectively to either the Pine Island or Thwaites catchments. To examine the sensitivity to effective pressure, we apply an explicit bed weakening scheme below a critical height-above-flotation which has been used in previous studies. We apply a simple depth power law parameterisation foe sub-ice shelf melt and vary a melt coefficient to test the melt sensitivity.

We find that mass loss rates generally increase with the critical height-above-flotation. The sensitivity is greatest for small values of the critical height-above-flotation. However, we also find that for both Pine Island and Thwaites glaciers, increasing the critical height-above-flotation and the high end of the range actually delays the onset of rapid retreat. We also find that Pine Island glacier is highly sensitive to the sub-shelf melt rate, and projections of future mass loss depend more upon enhanced ocean melting than on the effective pressure. By comparison, Thwaites glacier was relatively insensitive to increases in ocean melting, and the value of the critical height-above-flotation was more important in controlling rates of mass loss compared to Pine Island glacier.

These results are in line with other recent studies, and support the finding that the Pine Island ice shelf provides significant buttressing strength while the Thwaites ice shelf has minimal buttressing strength. They also demonstrate the importance of accounting for effective pressure in ice sheet model-based experiments. We will present and discuss these results.

How to cite: Trevers, M., Cornford, S., and Payne, T.: Millenial-scale sensitivity of Pine Island and Thwaites glaciers to the treatment of effective pressure and melt forcing, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18635, https://doi.org/10.5194/egusphere-egu25-18635, 2025.

Basal sliding and other processes affecting ice flow are challenging to constrain due to limited direct observations. Inversion methods, which typically fit an ice flow model to observed surface velocities, enable the reconstruction of basal properties from readily available data. We present a numerical inversion framework for reconstructing the glacier basal sliding coefficient, applied to both synthetic and real-world alpine glacier scenarios. The framework employs automatic differentiation to generate adjoint code and runs in parallel on graphics processing units (GPUs).

We explore two inversion workflows using the shallow ice approximation (SIA) as the forward model: a time-independent approach fitting to a single snapshot of annual ice velocity and a time-dependent inversion accounting for both ice velocity and changes in geometry. We find that the time-dependent inversion yields more robust and accurate velocity fields than the snapshot inversion. However, it does not significantly improve the problematic initial transients often encountered in forward model runs that employ sliding fields from snapshot inversions. This is likely due to the limitations of the forward model. This methodology is transferable to more complex forward models and can be readily implemented in languages supporting automatic differentiation.

How to cite: Utkin, I., Chen, Y., Räss, L., and Werder, M.: Snapshot and time-dependent inversions of basal sliding using automatic generation of adjoint code on graphics processing units, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18791, https://doi.org/10.5194/egusphere-egu25-18791, 2025.

How to cite: Archer, R., Ely, J., Johnson, J., Oakley, J., Clark, C., Butcher, F., Dulfer, H., Hughes, A., Boyes, B., and Reese, R.: Statistically optimising the input parameter space of a numerical ice sheet model to improve the model fit to observations of palaeo-ice flow direction , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19449, https://doi.org/10.5194/egusphere-egu25-19449, 2025.

Global sea-level rise is significantly influenced by glacier melting and retreat palpable all around the world. Of particular interest are marine- and lake-terminating (MALT) glaciers, which, despite their small number, store a substantial portion of the global glacier ice volume. One key component of the glacier mass budget in MALT glaciers is frontal ablation, which involves mass loss at calving fronts through calving, subaerial melting and sublimation, and subaqueous melting. In order to estimate the impact of frontal ablation on the evolution of MALT glaciers, ice-flow models need to exhibit a calving criterion as well as a tracking algorithm for frontal migration. Most of the regionally or globally applicable glacier evolution models (GEM) either lack explicit tracking of ice fronts or, if at all, rely on simple empiric calving parametrization. Here we equip a regionally applicable GEM with a state-of-the-art calving module with the aim to lift the confidence of projecting MALT glacier evolution under climate changes.

In this calving module, an implicit level-set tracking scheme is implemented. The level set function (LSF) evolves based on the frontal ice velocity, melting and calving rate. While subaerial melting is ignored, the ice velocity is determined from the Instructed Glacier Model (IGM). The model is applied to an idealized synthetic glacier geometry featuring undulating bed topography in a 2-D space is used. These synthetic experiments enabled to test the sanity of the implementation, mass and shape conservations as well as numerical stability. Furthermore, the implementation allows for appropriate ice front advance and retreat.

The second part of calving algorithm involves estimation of the calving rate using Eigen calving. It assumes calving rates to be proportional to along and transversal strain rates. The calving algorithm is integrated with the Instructed Glacier Model and applied to selected glaciers of the Kongsfjorden region, Svalbard. Abundant calibration data is available from remote sensing in form of multi-temporal ice-front positions. This approach provides a robust framework for incorporating calving dynamics into regional glacier evolution models. It addresses key gaps in existing methodologies and enhances the ability to better predict glacier front propagation.

How to cite: Prasad, V., Groos, A., Tabone, I., Hermann, O., Jouvet, G., Jordan, J. R., and Fürst, J. J.: Equipping an ice-flow model with calving and ice-front migration, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19571, https://doi.org/10.5194/egusphere-egu25-19571, 2025.

Numerical models simulating the evolution of the Antarctic Ice Sheet still contain considerable uncertainty.The dynamic instability of the Antarctic ice sheet is one of the most uncertain factors affecting global mean sea level rise. Among the various factors, ice shelf damage is a major challenge and a key focus in current research on the dynamic changes of the Antarctic ice sheet. In this study, we apply a newly developed three-dimensional  thermomechanically coupled higher-order ice flow model PoLaRIS (Polar Land Ice Simulator) to simulate the Antarctic Ice Sheet. First, we conducted initialization simulations of the Antarctic Ice Sheet, which are crucial for future projection studies. We used the Robin inversion algorithm for initialization, constraining and inverting the basal friction coefficient based on the observed surface velocity. The simulation results closely match the observations. Based on the initial conditions we have simulated, we are now focusing on the numerical simulation of pan-Antarctic ice shelf damage. We use different methods to simulate the present state of ice shelf damage, validate the model results with the satellite imagery, and compare these methods to identify the best schemes for  damage simulation. In the future, we will continue predicting the evolution of the Antarctic Ice Sheet by incorporating the ice shelf damage process into the ice sheet model, studying its dynamic instability and its impact on global mean sea level rise.

How to cite: Long, Q. and Zhang, T.: A Comparison of Different Ice Shelf Damage Modeling Schemes in Antarctica, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-21070, https://doi.org/10.5194/egusphere-egu25-21070, 2025.

The relative contributions of anthropogenic climate change and internal variability in sea level rise from the Antarctic Ice Sheet are yet to be determined. This is primarily because of uncertainty arising from poorly constrained model parameters and chaotic forcing as well as a relatively short observation period. Using an established uncertainty quantification framework (known as calibrate-emulate-sample), we have quantified, for the first time, the role of anthropogenic climate change on retreat of a major Antarctic glacier. We find that anthropogenic trends in forcing, beginning in the 1960s, are only responsible for approximately 15% of the retreat of this glacier since its retreat began in the 1940s. Most of the retreat is attributable to the inertia associated with a slow retreat over the Holocene. We also find, however, that trends in forcing dominate retreat beyond the 21st century, with ice sheet retreat stabilized if anthropogenic trends plateau.

How to cite: Bradley, A., Bett, D., Holland, P., Arthern, R., and Williams, R.: To what extent is climate change responsible for retreat of the Pine Island Glacier over the 20th century?, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-118, https://doi.org/10.5194/egusphere-egu25-118, 2025.

The Greenland Ice Sheet (GIS) has been experiencing significant mass loss since the 1990s, driven by the intensifying effects of global warming. However, this global trend is modulated by distinct annual and interannual variations, highlighting the complex interplay between the ice sheet, atmospheric systems, and the ocean. In this study, we analyzed GIS mass changes from early 2002 to late 2023 using data from the GRACE and GRACE-FO missions, focusing on the dominant temporal cycles and their relationships with climatic indices and parameters.

Using Empirical Orthogonal Functions (EOF) applied to mass variation data from the COST-G solution, we identified five leading modes of variability, accounting for 67.5% of the total variance. The primary mode capture both the annual cycle and longer-term periodicities, while subsequent modes highlight interannual oscillations, with cycles ranging from 4 to 11 years.

We examined the interactions between GIS mass changes and six key climatic drivers: the North Atlantic Oscillation (NAO), Greenland Blocking Index (GBI), Atlantic Multidecadal Oscillation (AMO), temperature duration and intensity, precipitation, and surface albedo. Cumulative indices and parameters enabled direct comparisons with the accumulated mass changes since 2002. Through Wavelet Analysis and cross-correlations, we uncovered significant links with varying time lags. They lead to a complete annual cycle and some interannual relationship between them. For instance, a positive NAO phase enhances precipitation, while the AMO displays a surprising 3.5-year delayed response to mass variations.

Additionally, our findings reveal a connection between 11-year cycles in NAO, GBI, and temperature to solar activity, while 4 to 7-year cycles align with potential atmospheric oscillations and Earth’s internal geodynamics.

This study highlights the GIS as a dynamic system modulated by interrelated processes operating on annual to decadal timescales. We have only investigated Greenland in its globality, but we know that the response to external forcing at a scale of a basin or a glacier differs. It will be important to examine this point as the integrations of multi-scale climatic drivers is important to understand past variations and project future changes under a warming climate. Such understanding is vital for assessing global sea-level rise and formulating mitigation strategies.

How to cite: Cambier, F., Darrozes, J., Llubes, M., Seoane, L., and Ramillien, G.: Links between GRACE/GRACE-FO derived temporal mass variations in Greenland and climatic indices, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-332, https://doi.org/10.5194/egusphere-egu25-332, 2025.

The Marine Isotope Stage (MIS) 12-MIS 11 glacial cycle (490-396 Ka) has been recognized as anomalous by researchers due to the longevity of the interglacial interval.  MIS 12 sea level low stand is inferred to be similar to Last Glacial Maximum (LGM), however, due to limited geomorphological data, major uncertainties remain with respect to where the ice was distributed and the relative size of the ice sheets. With the lowest increase in insolation from glacial to interglacial of the past 800 kyrs, MIS 11 was almost twice as long as the other interglacials of the past 500 kyrs. A prevailing hypothesis for the duration of MIS 11 proposes that the large MIS 12 ice sheets, when exposed to a weak insolation increase, gradually released meltwater and deglaciated throughout the interglacial period, contributing to its extended duration. This freshwater influx triggered a positive feedback, promoting the release of oceanic CO₂ into the atmosphere, which amplified insolation-driven warming and further prolonged the interglacial period.

Given the lack of terrestrial paleoclimate data, ice and climate modelling may offer a way to improve the understanding of this curious interval. Previous modeling work of this interval has been with either highly parameterized, low-resolution coupled ice-climate models, climate models with forced ice sheets, snapshot climate models with pre-industrial ice sheets, or ice sheet models with forced climate. Few models span the entire duration of the glacial cycle. For the first time, we transiently simulate the entire interval with the fully coupled ice sheet-climate LCIce model that resolves both atmospheric and ocean circulation. Parametric uncertainties are addressed by ensemble simulation. This presentation focuses on ensemble analysis of the ice sheets and climate of the glacial cycle as well as sensitivity testing of the two hypothesized drivers for length of MIS 11: meltwater flux during deglaciation and atmospheric CO₂ concentration.

How to cite: Parnell, A. and Tarasov, L.: Ensemble simulation of the MIS 12-MIS 11 glacial cycle using a fully coupled climate-ice sheet model, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-577, https://doi.org/10.5194/egusphere-egu25-577, 2025.

During the Holocene, the Greenland Ice Sheet (GrIS) experienced substantial thinning, with some regions losing up to 600 meters of ice.
Ice sheet reconstructions, paleoclimatic records, and geological evidence indicate that during the Last Glacial Maximum, the GrIS extended far beyond its current boundaries and was connected with the Innuitian Ice Sheet (IIS) in the northwest. We investigate these long-term geometry changes and explore several possible factors driving those changes by using the Parallel Ice Sheet Model (PISM) to simulate the GrIS thinning throughout the Holocene period, from 11.7 ka ago to the present. We perform an ensemble study of 841 model simulations in which key model parameters are systematically varied to determine the parameter values that, with quantified uncertainties, best reproduce the 11.7 ka of surface elevation records derived from ice cores, providing confidence in the modeled GrIS historical evolution. We find that since the Holocene onset, 11.7 ka ago, the GrIS mass loss has contributed 5.3±0.3 m to the mean global sea level rise, which is consistent with the ice-core-derived thinning curves spanning the time when the GrIS and the Innuitian Ice Sheet were bridged. Our results suggest that the ice bridge collapsed 4.9±0.5 ka ago and that the GrIS is still responding to these past changes today. Our results have implications for future mass-loss projections, which should account for the long-term, transient trend.

How to cite: Lauritzen, M. L., Solgaard, A. M., Rathmann, N. M., Vinther, B. M., Grindsted, A., Noël, B., Aðalgeirsdóttir, G., and Hvidberg, C. S.: Modeled Greenland Ice Sheet evolution constrained by ice-core-derived Holocene elevation histories, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1396, https://doi.org/10.5194/egusphere-egu25-1396, 2025.

The Greenland Ice Sheet is a key contributor to contemporary global sea-level rise, but its long-term history remains highly uncertain. The landscape covered by the ice sheet comprises ∼79% of Greenland and is one of the most sparsely mapped regions on Earth. However, sub-ice geomorphology offers a unique record of environmental conditions prior to and during glaciation, and of the ice sheet’s response to changing climate.

Here we use ice-surface morphology and radio-echo sounding data to identify, and quantify the morphology of, valley networks beneath the Greenland Ice Sheet. Our mapping reveals intricate subglacial valley networks beneath the ice-sheet interior that appear to have a fluvial origin. By contrast, in the southern and eastern coastal highlands, valleys have been substantially modified by glacial erosion. We use geomorphometric analysis and simple ice-sheet model experiments to infer that these valleys were incised beneath erosive mountain valley glaciers during one or more phases of Greenland’s glacial history when ice was restricted to the southern and eastern highlands.

These inferred early mountain ice masses contained ~0.5 metres of sea-level equivalent (compared to 7.4 metres in the modern Greenland Ice Sheet). We believe the most plausible time for the formation of this landscape was prior to the growth of a continental-scale ice sheet in the late Pliocene, with the possibility of further incision having occurred during particularly warm and/or long-lived Pleistocene interglacials. Our findings therefore provide new data-based constraints on early Greenland Ice Sheet extent and dynamics that can serve as valuable boundary conditions in models of regional and global palaeoclimate during past warm periods that are important analogues for climate change in the 21st century and beyond.

How to cite: Paxman, G., Jamieson, S., Tinto, K., Austermann, J., Dolan, A., and Bentley, M.: Constraining the extent of the Greenland Ice Sheet during warmer climates of the Pliocene and Pleistocene: insights from subglacial geomorphology, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3494, https://doi.org/10.5194/egusphere-egu25-3494, 2025.

This study examines the interactions between the Northern Hemisphere ice sheets and the ocean during the last glacial period. Using the iLOVECLIM climate model of intermediate complexity coupled with the GRISLI ice sheet model, we explore the consequences of an amplification of the melt rates beneath ice shelves on ice sheet dynamics and the associated feedbacks. First, the amplification of oceanic basal melt rates leads to significant freshwater release from both increased calving and basal melt fluxes. Grounding line retreat and dynamic thinning occur over the Eurasian and Iceland ice sheets, while the oceanic perturbation fails to trigger a grounding line migration over the coasts of Greenland and the eastern part of the Laurentide ice sheet. Second, similarly to hosing experiments with no coupling between the climate and the ice sheets, the influx of fresh water temporarily increases sea-ice extent, reduces convection in the Labrador Sea, weakens the Atlantic meridional overturning circulation, lowers surface temperatures in the Northern Hemisphere, and increases the subsurface temperatures in the Nordic Seas. Third, the freshwater release and latent heat effect on ocean temperatures lead to a decrease in ice sheet discharge (negative feedback) for the Greenland and Eurasian ice sheets. In the experiments, the Laurentide ice sheet does not feature significant volume variations. Nonetheless, we show that we are able to trigger a grounding line retreat and a North American ice sheet volume decrease, by imposing ad-hoc constant oceanic melt rates in a second set of perturbation experiments. However, the Hudson Strait ice stream also does not exhibit the past dynamical instability indicated by the presence of Laurentide origin ice rafted debris in the North Atlantic sediment records.  This suggests that the fully coupled model is too stable, specifically in the Hudson Bay region. To help address this issue, different modelling choices regarding the basal ice sheet dynamics are considered. This emphasizes the need for further research using fully coupled models to explore the triggering mechanisms of massive iceberg discharges and to clarify the role of the ocean in these events.

How to cite: Abot, L., Quiquet, A., and Waelbroeck, C.: Ice sheet-ocean interactions at 40 kyr BP : Insights from a coupled ice sheet-climate model of intermediate complexity., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4341, https://doi.org/10.5194/egusphere-egu25-4341, 2025.

The Greenland Ice Sheet (GrIS), a major driver of global sea-level rise, holds approximately 7 meters of sea-level equivalent. Despite its critical role, significant uncertainties remain about its mass balance and response to climate forcing over the past few centuries, particularly before the satellite era. This study aims to address these gaps by reconstructing a high-resolution (1x1 km) monthly surface mass balance (SMB) dataset spanning AD 1421–2024 and quantifying its contributions to historical and contemporary sea-level changes using the Positive Degree Day (PDD) modelling approach. 

The novel SMB dataset integrates long-term climate reanalysis inputs (ERA5 and ModE-RA). They are then validated and corrected against available ice-core records and weather station observations using a Bayesian approach to formally constrain the uncertainties. Preliminary analysis indicates signidficant SMB-driven mass loss due to climatic forcing during recent past, potentially offering new insights into the relative contributions of SMB and ice dynamics to GrIS total mass changes during latter half of the last millennium. 

These results represent a significant advancement in understanding the GrIS’s historical behaviour and links with climate change and can form a valuable baseline for improving the accuracy of future SMB and sea-level rise projections. By addressing critical knowledge gaps, this work enhances our ability to predict the long-term impacts of climate change on the GrIS and global sea levels.

How to cite: Javed, A., Hanna, E., Wake, L., Wilkinson, R., Morlighem, M., and Mcconnell, J.: Greenland Ice Sheet under climate change: Perspective from a high-resolution modelling simulation from 1421-2024  , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4663, https://doi.org/10.5194/egusphere-egu25-4663, 2025.

In this study, surface mass balance (SMB) is estimated from snow accumulation data collected in the nearby area of Concordia Station. Results from the Italian and French stake farms are jointly analyzed. The Italian stake farm is located ~800 m southwest of the Concordia Station and consists of 13 stakes; observations started at the end of 2010 with almost monthly sampling. Some measurements are also available for the 2006-2010 period from a previous stake farm which was located ~300 m east of the current site. The French stake farm is located ~2 km south of the base and consists of 50 stakes; observations started in 2004 with yearly sampling conducted during austral summer. Snow build-up measurements at individual stakes show a strong variability caused by the interaction of wind-driven snow with surface micro-relief. Over the period of common observations, the present Italian stake farm generally underestimates the snow accumulation with respect to the French one, except for three years in which an overestimation is observed. Over the 2011-2023 period, the mean yearly accumulation recorded by the Italian and French stake farms is 7.3±0.2 cm and 8.4±0.1 cm, respectively. Bootstrap simulation has been performed to: (i) assess the significance of the differences between the two datasets; (ii) evaluate the effect of the different size of the stake farms and their distance to the Station on the measurements. Comparison of the observations with reanalysis datasets (ERA5 and MERRA2) and regional models (RACMO, MAR) has been also performed, with the first ones providing the best agreement with the observations. The potential shadowing effect of the station has also been investigated by analyzing the wind direction during the snowfall events, suggesting that buildings may influence accumulation when they are upwind with respect to the stake farms. Additionally, two more stake farms, located 25 km north and south of Concordia Station, are also analyzed to study the accumulation gradient across Dome C, confirming previous results of a continentality effect. On average, yearly accumulation increases by 0.7±0.2 cm over the 50 km span between the southern and northern stake farms. Results should be valuable for validating SMB estimates obtained from reanalysis, regional climate models and remote-sensing data.

How to cite: Stefanini, C., Stenni, B., Masiol, M., Dreossi, G., Frezzotti, M., Favier, V., Becherini, F., Scarchilli, C., Ciardini, V., and Carugati, G.: Snow accumulation rates at Concordia Station from stake farm observations, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5578, https://doi.org/10.5194/egusphere-egu25-5578, 2025.

The importance of employing a two-way coupled climate-ice sheet model for future sea level projection has been revealed by LOVECLIP simulation. However, it still has several limitations. LOVECLIM, the climate model used in LOVECLIP, is unsuitable for short-term simulation. Additionally, LOVECLIM with a low-resolution T21 cannot solve regional-scale changes over the Antarctic region. Therefore, we newly coupled CESM1.2 to the Penn State Ice Sheet Model (PSUIM). CESM1.2 consists of the Community Atmosphere Model (CAM) with a f09 resolution for the atmosphere and Parallel Ocean Program version 2 (POP2) with a gx1v6 resolution for the ocean. Using coupled CESM1.2-PSUIM, we projected the responses of Greenland and Antarctic ice sheets, as well as future climate and sea level rise under the Representative Concentration Pathway scenarios.

How to cite: Park, J.: Coupled CESM1.2 to Penn State University Ice Sheet Model and future sea level projection, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6338, https://doi.org/10.5194/egusphere-egu25-6338, 2025.

Despite ice cores providing high-resolution climate records, few ice cores extracted from the West Antarctic Ice Sheet (WAIS) cover the Holocene, nor extend into the last glacial period. Marine ice-sheet basins, such as those underlying the WAIS, have been shown to be particularly vulnerable to retreat and possible collapse during past warm periods, and thus have significant potential to contribute to global sea-level rise. Dynamic thinning and retreat of ice are underway in the Amundsen Sea and Bellingshausen Sea sectors of the WAIS, yet this Pacific-facing region remains relatively data-poor for informing estimates of past and future retreat rates and sea-level contributions.

In 2010/11, a 136 m ice core was drilled at the three-way ice divide between Ferrigno Ice Stream, Pine Island Glacier, and Evans Ice Stream catchments. To further investigate this region, we analyse the internal structure across this region imaged through three intersecting radar surveys: (1) a 2004/05 UK/BAS survey, conducted with the Polarimetric Airborne Survey INstrument (PASIN), (2) a 2009/10 ground-based survey of Ferrigno Ice Stream, carried out with 3 MHz radar; and (3) NASA Operation Ice Bridge airborne surveys acquired in 2016 and 2018, which utilised the Multichannel Coherent Radar Depth Sounder 2 (MCoRDS2). We provide dating control to the traced englacial stratigraphy from tying it to the age-depth profile provided by the WAIS Divide Ice Core in central West Antarctica.

We then utilise a 1-D numerical ice-flow model, optimised by shallow ice-core data and these dated internal reflection horizons at the three-way ice divide, to infer palaeo-accumulation rates throughout the Holocene, and place age constraints on the age of the oldest ice at a proposed deep ice-core drill site at Ferrigno Ice Stream. We show that the method is robust and effectively synthesises the shallow ice-core data and the dated internal reflection horizons to reconstruct past climate records. The modelled maximum age at the three-way ice divide is around 24.77 ka +/- 6.88 ka, with a resolution of around 0.6 ka m^-1at the depth of the oldest ice, making this an ideal site for a new deep ice core in West Antarctica. In addition, the ice core would be located in a coastal area and may provide key insights glacial extent during deglaciation.

How to cite: Davis, H., Bingham, R., Hein, A., Hogg, A., Martín, C., and Thomas, E.: A combined radiostratigraphy- and ice-core- derived age scale for ice at the divide between the Amundsen, Bellingshausen and Weddell seas, West Antarctica, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6677, https://doi.org/10.5194/egusphere-egu25-6677, 2025.

Modern West Antarctic ice loss is generally driven by warm circumpolar deep water (CDW) reaching ice shelf grounding zones. Understanding what controls CDW delivery remains a challenge, in part because of the multiple scales involved. Most global models are too coarse to capture critical regional processes, while simulations with high-resolution regional models depend on imposed boundary conditions, precluding the possibility of capturing coupled processes across scales.  Here, we analyze a novel multi-member ensemble of global high-resolution (0.1° ocean, 0.25° atmosphere) Community Earth System Model (CESM) simulations over the historical period (1850-2005).   We compare the high-resolution runs to equivalent simulations at ~1 to 2° resolution, as well as to observational products (e.g. ECCO, WOA).  We show that biases in key ocean properties in the Southern Ocean are significantly improved in the high-resolution simulations.  This includes better representation of CDW in the high-resolution runs. We use these comparisons to explore new insights on the atmosphere and ice conditions that promote CDW delivery toward the ice shelves.

How to cite: Berdahl, M., Leguy, G., Steig, E. J., Lipscomb, W. H., and Otto-Bliesner, B. L.: Global High-Resolution Modeling: A New Lens on the Southern Ocean, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7500, https://doi.org/10.5194/egusphere-egu25-7500, 2025.

The accelerated melting of the Greenland ice sheet, driven by recent global warming, has attracted significant attention regarding the long-term variations in its mass balance. While several analyses have utilized snow melting indicators derived from microwave brightness temperatures observed through satellites, there is a lack of studies examining the diurnal behavior of these temperatures during the melting season. The Advanced Microwave Satellite Radiometer 2 (AMSR2) aboard the Global Change Observation Mission – Water (GCOM-W) satellite provides multiple daily observations on the Greenland ice sheet, enabling the investigation of diurnal changes in brightness temperature. This study aims to clarify the short-term relationship between snow melting and spaceborne microwave brightness temperatures during the summer of 2012, a period marked by extensive melting of the Greenland ice sheet. To examine the timing of snowmelt, snow surface temperature data collected by the Automated Weather Station (AWS) at a site on the ice sheet in north-west Greenland were utilized. The time series of snow surface temperatures from July to August 2012 were analyzed, revealing distinct patterns across three periods: Period A (early-July: snow temperature of 0°C only during the day), Period B (mid-July: snow temperature of 0°C throughout the day), and Period C (mid-August: snow temperature below 0°C all day). In the north-west regions, Snow Index (Tb18H − Tb36H: Difference in brightness temperature between 18 GHz-H and 36 GHz-H) values, indicative of snow cover, showed significantly different short-term variations between the periods. During Period A, Snow Index values were positive throughout the day and decreased towards the afternoon. In contrast, during Period B, Snow Index values were negative throughout the day, with no significant diurnal changes observed. During Period C, Snow Index values returned to positive again and, as in the previous period, no significant changes were observed during the day. These results suggest the possibility of monitoring diurnal melting with high temporal resolution through short-term variations in spaceborne microwave brightness temperature. These variations across the Greenland ice sheet, including other frequency channels, will be further discussed during the conference day.

How to cite: Suzuki, T., Shimada, R., Kachi, M., and Tanikawa, T.: Short-term variations of spaceborne microwave brightness temperature on the Greenland ice sheet during the 2012 melting season., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7794, https://doi.org/10.5194/egusphere-egu25-7794, 2025.

How to cite: Wirths, C., Hermant, A., Stepanek, C., Stocker, T., and Sutter, J.: Unravelling abrupt transitions of Antarctic Ice Sheet dynamics during the mid-Pleistocene transition, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8670, https://doi.org/10.5194/egusphere-egu25-8670, 2025.

Anthropogenic climate change poses a challenge to the stability of current ice sheets. Rising atmospheric temperatures accelerate surface melting in Greenland. Increased ocean temperatures can lead to ice loss at the margins of Antarctica, with positive feedbacks facilitating further ice loss. Both processes impact the Earth System by leading to rising sea level, increasing temperatures through albedo feedbacks, and altering global oceanic circulation. Past records indicate that there is a bipolar interaction between the ice sheets of the Northern and Southern Hemispheres modulated by the Atlantic Meridional Overturning Circulation (AMOC) that could ultimately affect their individual stability. Could the future response of the Greenland and Antarctic ice sheets perturb the AMOC in a manner that changes their own stability landscape? Here we will present the first results of the future evolution of the Greenland and Antarctic ice sheets as simulated with the ice-sheet model Yelmo coupled to a box model representing the oceanic circulation. We will show the coupled effects of the shrinking mass of the ice sheets on the AMOC stability and its feedback on the evolution of the ice sheets themselves.

How to cite: Pérez Montero, S., Alvarez-Solas, J., Robinson, A., and Montoya, M.: Stability of the Greenland and Antarctic ice sheets coupled by the Atlantic ocean circulation, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9305, https://doi.org/10.5194/egusphere-egu25-9305, 2025.

The Antarctic Ice Sheet (AIS) could become the largest single contributor to future sea level rise (SLR). However, its response to rising global mean temperature remains highly uncertain, and potential Solar Radiation Modification (SRM) interventions during the 21st century further complicate the projections. Among these interventions, Stratospheric Aerosol Injections (SAI) have been proposed to limit atmospheric warming and potentially moderate or prevent AIS’ impact on SLR. This study examines the dynamic response of Antarctica to such SAI interventions, in the short-term (until the year 2100) and on centennial time scales. We use the Parallel Ice Sheet Model (PISM) forced by the Community Earth System Model 2 (CESM2) to compare the evolution of AIS under SAI scenarios with that under the Shared Socioeconomic Pathway 2-4.5 (SSP2-4.5). Our findings indicate that, on centennial timescales, SAI may be counterproductive in mitigating sea level rise due to the reduced Antarctic surface mass balance compared to the SSP2-4.5 scenario. Ice shelf thinning and grounding line dynamics emerge as dominant factors driving mid- and long-term AIS behavior, where ice dynamics dominate over the effects of constant climate forcing. Variations in the sliding law parameterization further influence simulated outcomes. Unsurprisingly, the results are highly dependent on the individual earth system model employed. To address this, we compare our findings with a suite of the Ice Sheet Model Intercomparison Project for CMIP6 (ISMIP6) scenarios, as well as additional SRM simulations performed using the Hadley Centre Global Environment Model version 2 (HadGEM2-ES).

How to cite: Corrà, M., Hermant, A., Visioni, D., Goddard, P. B., Jones, A., Spezia, E., and Sutter, J.: Modeling Antarctic Ice Sheet Dynamics in Response to Solar Radiation Management, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9630, https://doi.org/10.5194/egusphere-egu25-9630, 2025.

The Antarctic Ice Sheet (AIS) is expected to be one of the dominant contributors to sea level rise in the near future. However, its future sea-level contribution is subject to substantial uncertainties related to modeling of physical processes. One key process is sub-shelf melting, which is particularly important in ice-shelf cavities, where warmer water intrusions could destabilize the corresponding ice shelves. This is of particular interest in the West Antarctic Ice Sheet, where many regions are marine based. Another fundamental process is Glacial Isostatic Adjustment, which is associated with the lithospheric rebound in response to changes in the ice load. Here, we use a 3D ice-sheet-shelf model coupled with a novel isostasy model to analyze the role of interactions between the ice, the ocean and the lithosphere in AIS projections during the next millennium. We combine experiments testing the sensitivity of several parameters concerning basal melting laws and different isostatic adjustment methods, under mean climatic conditions with high and low emissions scenarios. 

How to cite: Juarez-Martinez, A., Swierczek-Jereczek, J., Blasco, J., Alvarez-Solas, J., Robinson, A., and Montoya, M.: Simulated ice-ocean-bedrock interactions in Antarctica until year 3000, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9731, https://doi.org/10.5194/egusphere-egu25-9731, 2025.

Ice sheet models are essential tools for studying ice sheet dynamics in response to the climate evolution during the Quaternary glacial-interglacial cycles. Here, we develop a new version of the Northern Hemisphere ice sheet model (NHISM, Zweck and Huybrechts, 2005) by adding a user-friendly ice shelf module and other new characteristics, such as the configurable horizontal resolution and coupled sea level change. This new ice sheet-ice shelf coupled model is named NHISM1.1. The ice shelf module is based on the shallow shelf approximation, allowing simulation of ice stream advance into the ocean and the transformation between floating and grounded ice. NHISM1.1 is first used to conduct offline equilibrium ice-sheet simulations driven by observed present-day climate. It simulates a reasonable spatial distribution of the Northern Hemisphere ice sheets with a bias of less than 10% in the Greenland Ice Sheet volume compared to observation. We then use NHISM1.1 to perform offline transient ice sheet simulations for two distinct periods in the past, the Last Deglaciation and the entire MIS-11 period. In both cases, NHISM1.1 is driven by climate outputs of transient simulations performed with the LOVECLIM1.3 model. The performance of NHISM1.1 and the influence of various model configurations are evaluated by comparison with proxy reconstructions and other model simulations as well as sensitivity experiments. Our ice sheet simulations show that the NH ice sheets are largely consistent with geological evidence and that the incorporation of an ice shelf module is critical in properly reproducing glacial inception. By combining the analysis of climate simulations from LOVECLIM1.3 and offline ice sheet simulations from NHISM1.1, we propose that insolation plays a dominant role in driving the initial cooling of the Northern Hemisphere and the regrowth of its ice sheets during the MIS-11 glacial inception.

How to cite: Liu, W., Yin, Q., Huybrechts, P., and Goelzer, H.: Modelling the Northern Hemisphere ice sheet evolution during the last deglaciation and MIS-11 with an ice sheet-ice shelf coupled model, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10037, https://doi.org/10.5194/egusphere-egu25-10037, 2025.

Current projections of Antarctic Ice Sheet dynamics during the next centuries are subject to large uncertainties both reflecting the ice sheet model setup as well as the climate pathways taken into consideration. Assessing both, we present ice sheet model projections of the Antarctic Ice Sheet’s evolution during the next centuries using PISM. We employ PISM at continental scale forced by Earth system model data tailored to specific global temperature scenarios via an adaptive greenhouse gas emissions approach. The scenarios reflect a range of transient temperature overshoot (during the 21st and 22nd century) and stabilization trajectories until the year 2500 resulting either in 1.5 °C or 3°C warming. We account for various ice sheet sensitivities and initialize PISM with a present-day state obtained by a paleo thermal spin-up and further tuned on present-day conditions. For each climate scenario, a wide range of physical parameterizations is explored, to consider different ice sheet responses. Comparing the results with a historical baseline control simulation, a relative loss of ice volume proportional to temperature rise is observed across all parameters in the various scenarios. Additionally, tipping points can be identified for certain parameterisations, beyond which no significant differences are observed between stabilization and overshoot scenarios indicating an already destabilised West Antarctic Ice Sheet at present. We compare these results with model projections based on a selection of the CMIP6 scenarios to illustrate the range of Antarctic Ice Sheet responses under uncertain future climate trajectories.

How to cite: Spezia, E., Corrà, M., Bodart, J., Višnjević, V., Lacroix, F. K. M., Frölicher, T., and Sutter, J.: Assessing Antarctic Ice Sheet dynamics under temporary overshoot and long-term temperature stabilization scenarios  , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10066, https://doi.org/10.5194/egusphere-egu25-10066, 2025.

Mass loss from the Antarctic Ice Sheet is the main source of uncertainty in projections of future sea-level rise. These uncertainties essentially stem from the fact that some regions, such as Thwaites Glacier, may reach a tipping point, defined as irreversible mass loss on human time scales, with a warming climate. The exact timing of when these tipping points may occur remains difficult to determine, allowing for a large divergence in timing of onset and mass loss in model projections. Previous studies have emphasized the difficulties assessing the most suitable observable and the record length necessary to predict such an abrupt collapse within the Early Warning Indicators (EWI) framework. In particular, Rosier et al. (2021) showed that EWI robustly detect the onset of the marine ice sheet instability in realistic geometries such as Pine Island Glacier. The goal of this work is to determine the physical processes that influence the rate of grounding-line retreat of Thwaites Glacier and to test the capability of EWI to predict the onset of such a collapse. Ultimately, this study aims at mapping potential safety bands of grounding-line positions where the glacier may still recover or alternatively reach a ‘stable’ state. 

How to cite: Moreno-Parada, D., Coulon, V., and Pattyn, F.: Safety Bands of Thwaites Glacier, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10219, https://doi.org/10.5194/egusphere-egu25-10219, 2025.

The reconstruction of Antarctic surface mass balance (SMB) is essential for understanding ice sheet dynamics and sea level rise, yet existing datasets are limited to the satellite era (1979-present) because little is known about the sea surface conditions (SSCs) before 1979. Using a new SSCs product derived from a particle filtering reconstruction of the southern climate before 1979 to constrain the regional atmospheric model MAR, we expand the known SMB time series up to 1958. The dataset has been evaluated against AWS and SMB measurement campaigns to ensure a good agreement throughout the simulation period, substantially better than when MAR is forced by ERA5 SSCs (HadISST2). We also investigate the influence of the sea ice extent drop on SMB observed between the 70s and the 80s, analogous to the one observed in 2016. This extended dataset offers improved insight into past ice sheet mass changes and highlights the importance of long-term SMB reconstructions for further understanding the role of the Antarctic ice sheet in Earth's climate system.

How to cite: Maure, D., Kittel, C., Lambin, C., Dalaiden, Q., Goosse, H., and Fettweis, X.: Extending our knowledge of Antarctic SMB further back in time, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11215, https://doi.org/10.5194/egusphere-egu25-11215, 2025.

The timing of the Greenland Ice Sheet's retreat from its extent during the Last Glacial Maximum is a key element in constraining the sensitivity of the ice sheet to climate forcing. Although different deglaciation models have been published in previous years (Bennike, 2002; Funder et al., 2011; Sinclair et al., 2016; Leger et al., 2024), these models are limited by the number of samples used or their geographical extent. Therefore, the models have not been able to adequately resolve the deglaciation chronology of the Greenland Ice Sheet.

In this project, we aim to develop a Greenland-wide deglaciation model based on a new compilation of ¹⁴C dates, cosmogenic nuclide dates, OSL dates, and geomorphological evidence. The new compilation of ¹⁴C samples will be provided as an open-access database: GreenDated.

Within GreenDated, we aim to include all published ¹⁴C data from Greenland and the surrounding ocean shelf. All sample entries will as a minimum include information on location, and a categorization of the depositional environment and the sampled material. These steps will ensure accessibility for future users and enable easy extraction of data from the database. We will also recalibrate all the ¹⁴C data using the newest calibration curves (Heaton et al., 2020; Reimer et al., 2020) and adjust for differences in old normalization techniques, enabling easy recalibration of data for future users. Lastly, we will conduct a quality assessment based on the protocol used in the Dated (Hughes et al., 2016) and SvalHola (Farnsworth et al., 2020) databases, with the addition of an automated scoring system, seeking to limit bias from the authors.

Ultimately, the deglaciation model and the accompanying GreenDated database will provide a complete and thorough constraint on the Greenland Ice Sheet’s retreat from the Last Glacial Maximum position.

References:
Bennike, O. (2002) ‘Late Quaternary history of Washington Land, North Greenland’, Boreas, 31(3), pp. 260–272. https://doi.org/10.1111/j.1502-3885.2002.tb01072.x.
Farnsworth, W.R. et al. (2020) ‘Holocene glacial history of Svalbard: Status, perspectives and challenges’, Earth-Science Reviews, 208, p. 103249. https://doi.org/10.1016/j.earscirev.2020.103249.
Funder, S. et al. (2011) ‘The Greenland Ice Sheet During the Past 300,000 Years: A Review’, Developments in Quaternary Science, 15, pp. 699–713. https://doi.org/10.1016/B978-0-444-53447-7.00050-7.
Heaton, T.J. et al. (2020) ‘Marine20—The Marine Radiocarbon Age Calibration Curve (0–55,000 cal BP)’, Radiocarbon, 62(4), pp. 779–820. https://doi.org/10.1017/rdc.2020.68.
Hughes, A.L.C. et al. (2016) ‘The last Eurasian ice sheets – a chronological database and time-slice reconstruction, DATED-1’, Boreas, 45(1), pp. 1–45.  https://doi.org/10.1111/bor.12142.
Leger, T.P.M. et al. (2024) ‘A Greenland-wide empirical reconstruction of paleo ice sheet retreat informed by ice extent markers: PaleoGrIS version 1.0’, Climate of the Past, 20(3), pp. 701–755. https://doi.org/10.5194/cp-20-701-2024.
Reimer, P.J. et al. (2020) ‘The IntCal20 Northern Hemisphere Radiocarbon Age Calibration Curve (0–55 cal kBP)’, Radiocarbon, 62(4), pp. 725–757. https://doi.org/10.1017/rdc.2020.41.
 inclair, G. et al. (2016) ‘Diachronous retreat of the Greenland ice sheet during the last deglaciation’, Quaternary Science Reviews, 145, pp. 243–258. https://doi.org/10.1016/j.quascirev.2016.05.040.

How to cite: Rosenberg, A., Luetzenburg, G., Bennike, O., Kjellerup Kjeldsen, K., and Krog Larsen, N.: A Greenland-wide Holocene deglaciation model and building an accompanying 14C database, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11339, https://doi.org/10.5194/egusphere-egu25-11339, 2025.

The Greenland Ice Sheet (GrIS) has become the single largest contributor to present day sea-level rise, with mass loss driven by changes in Surface Mass Balance (SMB). As the largest component of SMB, snow accumulation is critical to monitor as Arctic warming continues at an accelerated rate. Snowfall patterns across GrIS are influenced by a complex interaction of many interdependent climate variables, leading to high inter-annual spatial variability. As a result, regional climate models (RCMs) often fail to adequately capture this variability and carry substantial uncertainties, leading to biased estimations of ice mass loss. Here, we present a novel method to bias-adjust RCM precipitation output with in-situ SMB records from the SUMup dataset (2024 release), including over two million data points from radar, ice-core, snow pit and stake measurements. RCM output data is first decomposed into Empirical Orthogonal Functions (EOFs), reflecting different modes of spatial variability, and Principal Components (PCs), capturing temporal fluctuations correlating to various climate indices. The SUMup in-situ measurements are used to derive a set of coefficients to scale the model mean climatology and each EOF and PC through least-squares optimisation. We provide monthly bias-adjusted accumulation maps for HIRHAM5-ERA5 output between 1960-2023 and CARRA between 1991-2023, highlighting regional biases in the models through time. 

Preliminary mean bias maps for HIRHAM5 show that the model underestimates accumulation in the south and interiors of the ice sheet by 20-80% or 30-90 mm/year, while the west and east margins of the accumulation zone are overestimated by 20-60% or 30-150 mm/year. In the winter and spring, the model tends to underestimate accumulation overall by 50-100 mm/year, while the reverse is true for the summer and autumn, when accumulation is mostly overestimated, reaching up to 200 mm/year in the north west. 

How to cite: Lindsey-Clark, J., Grinsted, A., and Hvidberg, C.: New monthly maps of accumulation over the Greenland Ice Sheet, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11420, https://doi.org/10.5194/egusphere-egu25-11420, 2025.

Projections of Antarctica's future sea-level contribution are still subject to great uncertainties, especially with respect to changes in surface mass balance and sub-shelf melting. While the climatic forcing used as boundary condition for ice sheet models cover the average trend in mass balance with global warming, extreme events, such as heatwaves, are typically not yet considered. However, a number of record-breaking extreme events have been observed in recent years in Antarctica already and may become more frequent or extreme with ongoing climate change. Here we investigate the effects of heatwaves on ice-sheet dynamics: using a storyline approach for conducting a suite of numerical ice-sheet simulations, we explore the additional Antarctic contribution to future sea-level rise when atmospheric extreme events are considered in projections. We set this into perspective with anomalous freshwater fluxes from ocean-driven melting (and calving) and investigate the potential for abrupt shifts and tipping dynamics, which extreme events may cause or pre-condition.

How to cite: Nicola, L., Beckmann, J., McCormack, F., and Winkelmann, R.: Towards understanding the effects of extreme events on Antarctic ice-sheet dynamics , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11651, https://doi.org/10.5194/egusphere-egu25-11651, 2025.

Bridging the knowledge gap between the recent decades and the preceding centuries of Greenland Ice Sheet (GrIS) history is essential for improving projections of its contribution to future sea-level rise. Evidence from relative sea-level reconstructions from salt marshes in southern Greenland suggests that GrIS mass loss began around 1850, well before significant anthropogenic warming—a pattern not yet captured in existing simulations of late Holocene GrIS evolution. Extending reconstructions of GrIS surface mass balance (SMB) as far back as possible, by leveraging newly available climate datasets from ~AD 1400 is critical to understanding its sensitivity to climate forcings during key periods such as the Little Ice Age. 

By addressing the underrepresentation of dynamic components and calculation of pre-20th century mass changes, this project aims to provide critical insights into GrIS-climate interactions and refine predictions of GrIS contributions to global sea-level rise. To achieve this aim, we will first  develop a 1x1-km resolution monthly SMB dataset using ModE-RA, a new palaeoclimate reanalysis product spanning 1421-2024.  This new SMB dataset will be used as input to ice sheet model simulations to assess the  spatial and temporal interplay between climate, SMB and ice dynamics.

Here we will present initial results of (1) GrIS temperature, precipitation and SMB fields for 1421 to 2024 AD and (2) historical simulations using the ice sheet model Úa to reconstruct ice thickness and margin changes outside of the observational period.

How to cite: Wake, L., Javed, A., Hill, E., Hanna, E., and Gudmundsson, H.: Bridging the gap between the modern and historical: Extending the mass balance reconstruction of the Greenland Ice Sheet from 1421 to 2024 AD, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11803, https://doi.org/10.5194/egusphere-egu25-11803, 2025.

Anthropogenic greenhouse gas emissions and resulting global warming raise uncertainties in the future of currently existing ice sheets. The Antarctic ice sheet, which contains the equivalent of 58 meters of potential sea level rise, is expected to have a relatively small role on sea level rise in this century, but is expected to continue to lose mass afterwards and could become a major driver of sea level rise on longer timescales (Van Breedam et al., 2020; Winkelmann et al., 2015).

The Antarctic ice sheet interacts with the solid Earth, the ocean and the atmosphere, resulting in various positive and negative feedbacks, enhancing or limiting ice sheet growth (Fyke et al., 2018). Positive feedback mechanisms, such as the albedo-melt and elevation-temperature feedbacks, enhance the ice sheet's response to an initial change in forcing, potentially resulting in nonlinear changes, and it is thus crucial to model these feedbacks on long timescales, when significant changes of the ice sheet’s topography can occur. Nonlinear changes can lead to a hysteresis behaviour, with widely different equilibrium states for a given CO₂ level or temperature anomaly, depending on the initial condition (Pollard and de Conto, 2005; Garbe et al., 2020; Van Breedam et al., 2023).

In this study, we explore the hysteresis of the Antarctic ice sheet from the present-day configuration, using an intermediate complexity climate model, iLOVECLIM, representing the atmosphere, ocean and vegetation, coupled to an ice sheet model, GRISLI. Simulations start from either a pre-industrial ice sheet or an ice-free, isostatically rebounded geometry, and different CO₂ levels are applied.

Crucially, the albedo-melt feedback is accounted for in our coupled setting, which strengthens nonlinear behaviour and leads to critical CO₂ thresholds for the ice sheet melt or growth. This enhances the ice sheet hysteresis, with widely different equilibrium ice volumes at a given CO₂ level, depending on the initial ice sheet geometry. The CO₂ thresholds either trigger the complete Antarctic ice sheet loss or near-complete regrowth. The orbital configuration influences these CO₂ thresholds : a higher (lower) summer insolation in the Southern Hemisphere decreases (increases) the CO₂ threshold for Antarctic deglaciation (glaciation).

These findings highlight the importance of ice sheet-atmosphere interactions, notably the albedo-melt feedback, in projecting future long-term ice sheet behavior. Neglecting these feedbacks could lead to an overestimation of CO₂ thresholds for the Antarctic ice sheet destabilization, with implications for future long-term sea level rise under high emission scenarios.

This study has recently been accepted in Geophysical Research Letters.

How to cite: Leloup, G., Quiquet, A., Roche, D., Dumas, C., and Paillard, D.: Hysteresis of the Antarctic ice sheet with a coupled climate-ice-sheet model, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12628, https://doi.org/10.5194/egusphere-egu25-12628, 2025.

Cenozoic climate has evolved through stepwise quasi-equilibrium states in response to declining CO₂ concentration. As a result, terrestrial polar ice sheets developed in Antarctica ~35 million years ago describing relatively large glacial-interglacial changes, prior to an increasing marine-based ice sheet component by ~15 Ma with lower glacial-interglacial variability, before returning to large glacial-interglacial amplitudes in response to the intensification of Northern Hemisphere Ice Sheets (~2.7 Ma). While mean surface temperature scales linearly with the total concentration of carbon in the atmosphere, this is not the case for past variations in global mean sea-level whose amplitudes are climate-state (CO₂)-dependent. By examining past climate drivers (atmospheric CO₂) and the response of ice volume (sea level), polar ice sheets are seen to demonstrate vastly different sensitivities under changing climate states highlighted by the ‘100-kyr’ problem of non-linear ice sheet change.

In this study, a new independent global ice volume (sea-level) record (X-PlioSeaNZ: 3.3 – 1.7 Ma) is used to evaluate the deep-sea oxygen isotope proxy record (δ¹⁸O_benthic).  An empirical, power-law relationship emerges between δ¹⁸O_benthic and sea-level in contrast to long-standing linear δ¹⁸O_benthic calibrations. This relationship suggests relatively higher deep-ocean temperature contribution to δ¹⁸O_benthic signal and correspondingly lower global ice volume estimates under warmer past climates. It also demonstrates the need for variable ice volume-δ¹⁸O_benthic calibrations in response to the evolving bipolar ice sheet geographies over the last ~3 million years (Myr). Consequently, as the Earth system adjusts to 2-3°C of global warming over the coming decades and centuries, a lower paleo-ice sheet sensitivity (compared to the Last Glacial Maximum) is expected for ice sheet configurations where marine based ice sheets act as a buffer to terrestrial based ice sheets and brings geologic reconstructions into agreement with current projections for future sea-level rise.

How to cite: Grant, G.: Climate state dependence of ice sheet variability, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13026, https://doi.org/10.5194/egusphere-egu25-13026, 2025.

Cruise SD041 of the UK research vessel the RRS Sir David Attenborough to the continental shelf offshore of SE Greenland took place in July-August 2024. The cruise was part of the UK NERC-funded ‘Kang-Glac’ project, a large multi-disciplinary, international, research project jointly led by British Antarctic Survey and Durham University, UK. The cruise collected a range of geological, geophysical, oceanographic and biological data from the continental shelf offshore of Kangerlussuaq Fjord, SE Greenland, and in several adjoining fjords. The aim of the Kang-Glac project is to investigate the response of the Greenland Ice Sheet to ocean warming during the last 11,700 years of the Holocene. During the cruise marine geophysical data in the form of multibeam swath bathymetric imagery of seafloor landforms and sub-bottom profiler data of shallow acoustic stratigraphy were collected, in addition to a suite of sediment cores. Data collection targeted a large cross-shelf bathymetric trough (‘Kang-Trough’) which extended from the mouth of Kangerlussuaq Fiord to the edge of the continental shelf, as well as a series of smaller fjords to the northeast. These marine geophysical data and sediment cores provide a clear record of an extensive Greenland Ice Sheet (GrIS) which expanded and retreated across the shelf via Kang-Trough. Landforms comprise well developed streamlined subglacial bedforms which show convergent GrIS flow into the trough, as well as occasional transverse moraines recording episodic retreat. Sediment cores recovered subglacial tills recording a grounded ice sheet in the cross-shelf trough overlain by a range of deglacial glacimarine facies recording retreat by melting and iceberg calving. Cores from the adjacent trough mouth fan on the continental slope targeted glacigenic debris flows which likely were deposited when the GrIS was grounded at the shelf edge and delivered glacigenic debris onto the slope. Collectively the data provide new insights into past GrIS extent, dynamics, and the nature of associated glacigenic sediment delivery from the LGM through the Holocene in the SE sector of the Greenland continental margin.

How to cite: O Cofaigh, C., Hogan, K., Lloyd, J., Hunt, M., Snowman Andresen, C., Larter, R., and Roberts, D.: Geomorphological and sedimentological evidence of past Greenland Ice Sheet advance and retreat on the continental shelf offshore of SE Greenland as revealed by ‘Kang-Glac’ cruise SD041 , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13742, https://doi.org/10.5194/egusphere-egu25-13742, 2025.

Extensive surface melting has been observed during the austral summer, particularly in the Antarctic Peninsula and peripheral regions. A warming climate change is expected to further increase both precipitation and surface melting due to rising air temperatures. The precipitation, including both liquid and solid phases, contributes to maintaining ice mass, whereas surface melting reduces ice thickness and promotes hydrofracturing of ice shelves, resulting in acceleration of ice mass loss. The Surface Energy and Mass balance model of Intermediate Complexity (SEMIC) is a cost-effective and simplified model which emulates surface energy and mass balance processes. However, its application to Antarctica has not yet been fully explored. In this study, we assess the performance of SEMIC, forced with daily and monthly ERA5 reanalysis data, in reproducing current surface mass balance (SMB) and surface melting. Furthermore, we evaluate future projections of SMB and surface melting under the sustainable (SSP1-2.6) and high-warming (SSP5-8.5) climate scenarios from CMIP6, extending to the end of the 21st century. Our results reveal that SEMIC effectively represents current SMB and surface melting when driven by both daily and monthly forcing, although it underestimates the extent of surface melting in internal ice sheet. Projections indicate that total surface melting volume under SSP1-2.6 and SSP5-8.5 scenarios is projected to gradually increase to 170.1 ± 65.1 Gt yr^-1 and 892.4 ± 505.2 Gt yr^-1, respectively, during 2090-2100. Under the warming scenario, the area experiencing surface melting exceeding collapse threshold (> 725 mm yr^-1) increases significantly by the mid-21st century. While total precipitation is projected to increase, this is offset by an increase in surface melting, resulting in minimal net changes in SMB by the end of the 21st century.

How to cite: Park, I.-W., Jin, E. K., Lee, W. S., and Lee, K.-K.: Revisiting Antarctic surface melting under climate change by the end of the 21st century using a simple surface energy balance approach, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14498, https://doi.org/10.5194/egusphere-egu25-14498, 2025.

Version 3 of the Community Ice Sheet Model (CISM) is scheduled for release later this year along with version 3 of the Community Earth System Model (CESM). CISM is a parallel, open-source ice flow code, written in Fortran and Python, which can be run as a standalone ice sheet or glacier model or as a coupled component of CESM and NorESM. The model supports several Stokes-flow approximations and has participated in many community intercomparison projects, including ISMIP6, CalvingMIP, and GlacierMIP3.

CISM3 will include new physics options for basal sliding, basal hydrology, iceberg calving, and extrapolating sub-ice-shelf temperature and salinity. A new initialization procedure allows the rate of ice mass change to match observations at the beginning of a projection simulation.  Coupled CISM–CESM simulations can include two-way climate coupling with multiple ice sheets, including Antarctica. CISM3 also has an exciting new capability to initialize and simulate mountain glaciers.

To improve user experience, CISM3 will include new Python tools for setting up glacier and ice sheet simulations and analyzing ice-sheet-relevant fields from other CESM components. CISM is now more integrated with CESM than ever before, by leveraging the Common Infrastructure for Modeling the Earth (CIME) case control and testing system for verification and validation. 

This presentation showcases examples and results using CISM3’s new tools and capabilities. 

How to cite: Leguy, G., Lipscomb, W., Thayer-Calder, K., Minallah, S., Petrini, M., Goeltzer, H., van den Akker, T., Sacks, B., Vertenstein, M., and Berdahl, M.: Version 3 of the Community Ice Sheet Model, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15073, https://doi.org/10.5194/egusphere-egu25-15073, 2025.

The Nioghalvfjerdsfjorden glacier (NG) and Zachariae Isstrøm (ZI) are major contributors to the mass balance of northeast Greenland, which drain 12% of the Greenland Ice Sheet. Accurate measurements of these two glaciers are crucial to the estimation of the mass balance in northeast Greenland. They also serve as an important parameter for reflecting climate change and predicting future sea level rise. In the past, early ice velocity data were scarce, primarily due to challenges in difficulties in image orthorectification caused by large distortions and low quality in historical remote sensing imagery. We proposed a systematic process for orthorectification of CORONA KH-4A imagery, which has proven to be both efficient and accurate in velocity mapping at a precision of 25m. By employing a hierarchical network densification approach based on ARGON KH-5 and CORONA KH-4A imagery, we have successfully reconstructed the ice flow velocity fields for NG and ZI from 1963 to 1967. Combining with other ice velocity products, we have obtained the ice velocity of NG and ZI spanning a period nearly 60 years. The results indicate that the average ice flow velocity near the grounding line has increased by 12.4% for NG and a substantial 81.4% for ZI from 1963 to 2020. While ZI is experiencing accelerated mass loss, the NG is still in a relatively stable state under the similar climate condition. The slight fluctuations in ice velocity for NG may be due to the unique topography and the hindering effect of ice rises, suggesting the climate change may have a comparatively less impact on it.

How to cite: An, L., Dai, L., Liu, X., and Li, R.: Study on the Instability of Two Large Glaciers in Northeast Greenland in Recent 60 Years, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15269, https://doi.org/10.5194/egusphere-egu25-15269, 2025.

We present the first results of future Antarctic climate simulations with the polar-adapted Regional Atmospheric Climate Model (RACMO2.4p1). As part of the PolarRES project, two climate storylines are explored, examining the response of the Antarctic surface mass balance (SMB) to two plausible future climates with varying degree of Antarctic sea ice loss and changes to upper atmospheric circulation. For this RACMO2.4p1 is run on a 11 km horizontal grid forced with high emission scenario SSP3-7.0 simulations from CESM2 and MPI-ESM for the period 2015-2100. To evaluate the model performance using climate model data, we compare historical simulations (1985-2015) forced by CESM2 and MPI-ESM to those forced by ERA5. We examine shifts in Antarctic precipitation and SMB between the current and future climate, and relate those changes to changes in atmopsheric circulation, atmospheric moisture budget and presence of sea ice.

How to cite: Hofsteenge, M. G., van de Berg, W. J., van Dalum, C. T., Verro, K., van Tiggelen, M., and van den Broeke, M.: Modelling future Antarctic climate and surface mass balance with RACMO2.4p1 (2015-2100), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15319, https://doi.org/10.5194/egusphere-egu25-15319, 2025.

The Miocene epoch was a warm period characterised by elevated atmospheric CO₂ levels compared to the present day. These CO₂ concentrations are similar to those predicted for future climate scenarios, making the Miocene an important period to deepen our understanding of warmer climates. While Greenland ice cores have provided highly valuable data for the late Quaternary, terrestrial palaeoclimate archives extending deeper in time in the Arctic remain sparse, leaving a significant gap in our knowledge of Greenland's climate history.

Speleothems are an excellent archive for obtaining high-resolution terrestrial climate data. During speleothem formation, dripwater can be trapped as fluid inclusions, preserving the isotopic signature of ancient meteoric water. This study focuses on four speleothems from a cave in eastern North Greenland. U-Pb dating indicates that the speleothems were deposited during the middle and late Miocene. We analysed the stable H isotopic composition of primary fluid inclusions to reconstruct the isotopic composition of palaeo-dripwater. Carbon and oxygen isotopes of the speleothem calcite were also measured in order to estimate quantitative temperatures for eastern North Greenland during middle and late Miocene. Our initial results show that during such an elevated CO₂ world, mean annual air temperatures were substantially elevated above modern values.

Macroscopically, all speleothems are comprised of translucent and light brown calcite. Microscopically, the dominant fabric is coarsely crystalline columnar calcite. Fluid inclusion petrography shows the presence of both fluid inclusion-rich and inclusion-poor areas in the late Miocene speleothems, while primary fluid inclusions are abundant in the two middle Miocene speleothems. The mean water content obtained from crushing varies from 0.2 µL to 1.0 µL between the speleothems.

How to cite: Friedrich, L., Koltai, G., Moseley, G. E., Czuppon, G., Demény, A., Wang, J., Cheng, H., Donner, A., Dublyansky, Y., and Spötl, C.: Preliminary insights into Miocene palaeoprecipitation and palaeotemperature using speleothem fluid inclusion isotopes from eastern North Greenland, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15980, https://doi.org/10.5194/egusphere-egu25-15980, 2025.

It is highly challenging to include both the Antarctic and Greenland ice sheets in a state-of-the-art earth system model. Our presentation demonstrates our system's design, the essential steps before coupling the entire system, the challenges faced in the coupling process, and the initial findings from our series of simulations for warming scenarios spanning the next few centuries until 2500.

We will highlight the existing limitations in the computed climate conditions that affect the behavior of ice sheets. These motivate our system's design. For instance, ocean temperature biases in the marginal seas around Antarctica inhibit its direct use to determine basal melting of floating ice shelves fringing Antarctica despite extensive tuning efforts. As a result, we have developed a flexible framework deemed necessary to adequately represent the currently observed ice sheet state. The still delicate integration of ice sheets into climate models directs the spin-up procedure of ice sheet models. The procedure's results and its consequences are presented and discussed. In particular, the available iceberg calving mechanism has been demanding in our simulations because we allow for freely waxing or waning ice shelf edges around Antarctica, unprecedented in coupled climate-ice sheet model systems.

Finally, the first results of our fully coupled simulations complete the presentation. These focus on the interaction between the climate system and Antarctica or Greenland and its influence on primary climatic conditions. In our model system, interacting ice sheets shape the climate state, creating feedback loops that affect the ice sheet state itself. This interaction may ultimately counteract the disintegration of ice sheets. Supposed it is a robust result, it implies that standalone ice sheet simulations may overestimate future sea level contributions.

How to cite: Rodehacke, C., Ackermann, L., Gierz, P., Masoum, A., and Lohmann, G.: Greenland and Antarctica as Interacting Constitutes in AWI-ESM, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16025, https://doi.org/10.5194/egusphere-egu25-16025, 2025.

Understanding how key regional circulation features respond to future global warming is essential for projections of Antarctic Ice Sheet dynamics, and future global sea level rise. The Southern Annular Mode (SAM) influences the strength and location of the mid-latitude tropospheric westerly jet, which controls the transport of warm air and moisture towards the AIS. The Amundsen Sea Low (ASL), a permanent low-pressure system off the coast Antarctica affects regional wind patterns, precipitation and ocean circulation. These features can also impact the exchange of heat and carbon dioxide between the ocean and atmosphere, impacting sea ice extent and the stability of ice shelves. Under global warming scenarios, changes in these atmospheric features may significantly alter surface mass balance, surface melt, temperature and precipitation patterns over the AIS.

This study uses UK Earth System Model (UKESM) overshoot experiments that explore future emission increase, stabilization, and reduction simulations to investigate the interactions between atmospheric circulation features and the Antarctic cryosphere. These idealised simulations are forced only by CO₂ concentrations and currently extend up to 650 years duration, allowing exploration of the response of the AIS to a range of global warming scenarios, and asses potential reversibility under future CO₂ reduction.

This research utilises these simulations to identify trends in the SAM, ASL and westerly jets. Initial results show a deepening of the absolute pressure of the ASL, a poleward shift and strengthening of the westerly jet, with trends increasing and reversibility diminishing with higher global warming scenarios. These simulations are then used to identify any relationship between these features and trends in temperature, precipitation and surface melt over regions of the AIS and ice shelves, providing insights into the long-term stability of the AIS under varying climate scenarios.

How to cite: Taylor, S., Orr, A., Cornford, S., Bracegirdle, T., and Smith, R.: Exploring Antarctic Circulation-Ice Sheet Interactions in UKESM Climate Projections Through 2500 and Beyond, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16564, https://doi.org/10.5194/egusphere-egu25-16564, 2025.

The future evolution of the Antarctic Ice Sheet with progressing warming constitutes one of the, if not the main uncertainty in projections of future sea-level change. As the largest potential source of sea-level rise and one of the key tipping elements in the climate system, robust projections are needed to inform coastal adaptation planning worldwide.

Using historically-calibrated perturbed-parameter ensembles of projections with two ice-sheet models, we assess the response of the Antarctic Ice Sheet and associated uncertainties to a wide range of climate futures extending to the year 2300 and beyond.

We show that the near-term projections of the Antarctic Ice Sheet are strongly influenced by ice-sheet model sensitivities, especially under limited warming, until strong changes in Antarctic climate beyond the end of the century, as projected under unmitigated emissions, clearly dominate the ice-sheet evolution. Irrespective of the wide range of uncertainties explored in our ensembles, large-scale ice loss is triggered in both West and East Antarctica under higher warming scenarios, but can be avoided by reaching net-zero emissions well before 2100. This leads to a multi-meter difference in the committed Antarctic sea-level contribution projected under low and very high emission pathways by the end of the millennium. Our results suggest that the next years and decades are decisive for the multi-centennial fate of the Antarctic Ice Sheet.

How to cite: Klose, A. K., Coulon, V., Edwards, T., Turner, F., Pattyn, F., and Winkelmann, R.: From short-term uncertainties to long-term certainties in the future evolution of the Antarctic Ice Sheet, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16952, https://doi.org/10.5194/egusphere-egu25-16952, 2025.

The mass loss from the Greenland ice sheet has increased over the last two decades, and is now a major contributor to the global mean sea level rise. While the interior of the Greenland ice sheet has remained relatively stable, the mass loss from the ice sheet margins have spread to the north and since 2007 propagated into interior Greenland. We present here an assessment of the interior stability in North Greenland over the last three decades using GPS data, remote sensing data, and climate model output. We compile GPS survey data from interior ice core sites in North Greenland at GRIP (1992-1996), NorthGRIP (1996-2001), NEEM (2007-2015), and EastGRIP (2015-2022), and compare with surface mass balance estimates, and remote sensing observations to assess changes over the last decades. While the surface elevation has remained relatively stable at the northern ice divide sites, an inferred northward migration of the ice divide in Northwest Greenland observed in 2007-2015 coincided with the onset of thinning along the ice margin in the Baffin Bay area. The surface elevation near the summit of the Greenland ice sheet lowered slightly over the last 30 years, during a period of widespread thinning along the western margin. The observations are discussed in relation to regional changes in surface mass balance and the dynamical response to mass loss at the ice margin.

How to cite: Hvidberg, C. S., Grinsted, A., Keller, K., Kjær, H. A., Rathmann, N., Lauritzen, M. L., Dahl-Jensen, D., Mottram, R., Hansen, N., Olesen, M., Simonsen, S., Sørensen, L. S., Solgaard, A. M., and Karlsson, N. B.: Stability of interior North Greenland – an assessment from GPS and satellite data, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17048, https://doi.org/10.5194/egusphere-egu25-17048, 2025.

The Greenland ice sheet (GrIS) formed more than 1 Ma ago and has evolved over many glacial-interglacial cycles. As it still adjusts to past changes, correctly capturing its present-day state is essential to accurately predict its future evolution and contribution to sea level rise. Furthermore, the past offers numerous examples of the GrIS‘ response to warmer climates, possibly analogous to its future fate.

Here, the Parallel Ice Sheet Model (PISM) is utilized to investigate the evolution of the GrIS over past glacial-interglacial cycles. For simulations over such long timescales, the computationally inexpensive PDD scheme is commonly used to calculate surface melt. However, PDD schemes do not capture spatial and temporal differences in surface mass balance sensitivity to temperature and cannot drive glacial-interglacial ice volume changes as they neglect the positive feedback between melt and albedo. To address this, we instead use the Diurnal Energy Balance Model (dEBM-simple) module. It takes into account seasonally and latitudinally varying melt contributions from solar shortwave radiation and changes in albedo in addition to temperature-driven melt to achieve a better representation of orbital timescales.

We calibrate PISM-dEBM-simple with present-day melt rates from the regional climate model RACMO. The calibrated model is then used to investigate the different patterns of growth and retreat of the GrIS over the past glacial-interglacial cycles emerging from using the PDD or the dEBM module in PISM. The enhanced sensitivity of the dEBM to insolation results in an earlier and greater mass loss at the onset of the Holocene, primarily from low-elevation regions and ice shelves.

How to cite: Schwermer, I., Munck Solgaard, A., Langgaard Lauritzen, M., Noël, B., Nuterman, R., and Schøtt Hvidberg, C.: Modelling the evolution of the Greenland ice sheet over glacial-interglacial cycles, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17469, https://doi.org/10.5194/egusphere-egu25-17469, 2025.

How to cite: Menthon, M., Bakker, P., Quiquet, A., and Roche, D.: Does the AMOC strength matter for the Antarctic ice sheet retreat during the penultimate deglaciation? , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17480, https://doi.org/10.5194/egusphere-egu25-17480, 2025.

In the coming century, the Greenland Ice Sheet (GrIS) is expected to be one of the main contributors to global sea-level rise. In addition, it is thought to be a tipping element due to the existence of positive feedbacks governing its mass balance. Previous studies have explored its stability across a range of temperatures, from present-day conditions to a global warming of 4°C, showing a threshold behavior in its response. However, it is known this threshold has already been exceeded in the past. During the Holocene Thermal Maximum, when Greenland temperatures were 2–4°C warmer than today, the ice sheet retreated beyond its present-day margin but did not fully disappear. Ice losses depend on the level of warming, but also on the rate of forcing and how long the forcing remains above the threshold.  Therefore, we propose studying the stability of the ice sheet over a broader temperature range: from the Last Glacial Maximum to a warming of +4°C,  and examining its current state within the bifurcation diagram. For this purpose, we use the ice-sheet model Yelmo coupled with the regional moisture-energy balance model REMBO and a linear parameterization of the oceanic basal melting.

How to cite: Gutiérrez-González, L., Álvarez-Solas, J., Montoya, M., and Robinson, A.: Mapping the stability of the Greenland Ice Sheet, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19292, https://doi.org/10.5194/egusphere-egu25-19292, 2025.

So far, melting of the Greenland Ice Sheet (GrIS) has been the biggest contributor from the Earth’s cryosphere to global sea-level rise. Major uncertainties remain about how oceanic heat is transported across the shelf and through the fjords to the faces of marine-terminating glaciers, and how this affects rates of ice melt and calving. In turn, the increasing supply of meltwater and nutrients to the ocean around Greenland is impacting marine ecosystems as primary productivity rises,  subsequently increasing the potential for  carbon to be buried as “blue carbon” in Greenland’s fjords as warming continues. In July-August 2024, the UK-funded KANG-GLAC project completed a 40-day multidisciplinary research cruise to SE Greenland where the 40-strong scientific party made a suite of integrated geological, ocean and biological observations. The main aims of the project are two-fold. First, it aims to better understand how marine-terminating glaciers respond to oceanic heat on longer timescales (decades to centuries) by reconstructing glacier and ice-sheet behaviour during the Holocene and in particular during the climatic warm period of the Holocene Thermal Maximum. Second, the project will quantify nutrient cycling in the water column and uppermost seafloor sediments in order to improve our knowledge of  marine ecosystem response to meltwater supply from the GrIS.  The cruise on the UK’s premier polar research vessel, the RRS Sir David Attenborough, is the start of a 3.5 year project. Here, we will present an overview of our field observations in this past-to-future project and outline the plans for future data-driven modelling of the Greenland Ice Sheet.

How to cite: Hogan, K., Colm, O. C., Abrahamsen, P., Howe, J., Inall, M., Lloyd, J., Manno, C., März, C., Roberts, D., Tarling, G., Sime, L., Voss, J., Tarasov, L., and Andresen, C. and the SD041 Shipboard Scientific Party: Early Results from KANG-GLAC: A Project to Understand Holocene Ice Sheet-Ocean Interaction and Marine Productivity in SE Greenland, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19646, https://doi.org/10.5194/egusphere-egu25-19646, 2025.

Understanding the dynamic response of the Greenland Ice Sheet (GrIS) during past climate warmings is essential for predicting its behaviour as global warming accelerates. However, detailed reconstructions of GrIS growth and retreat are limited due to lack of long high-resolution sedimentary records in proximity to its major glacial outlets. Here, new osmium isotope data are presented, from IODP Expedition 400 Hole U1604B, obtained from the lower slope of the Melville Bugt Trough Mouth Fan on the northwest Greenland margin. The osmium isotope analyses are integrated with shipboard sedimentary proxies to trace sediment sources and reconstruct glacial meltwater flux. Preliminary results from the studied interval show sediment proxy variations suggesting significant changes in sediment sources and depositional conditions. Between ~29 and 24 m CSF-A ¹⁸⁷Os/¹⁸⁸Os are radiogenic (~2.3 – 2.5). In contrast, immediately above this section between ~24 and 22 m CSF-A depth ¹⁸⁷Os/¹⁸⁸Os are distinctly less radiogenic (~1.3). The latter depth interval is also characterized by a peak in Ca/K ratios, decreased magnetic susceptibility and natural gamma radiation. The current preliminary age-model for Hole 1604B suggests that the studied core interval could represent the end of the Saalian Glacial. As such, we hypothesize the change in the sediment proxies is interpreted to record enhanced glacial meltwater and sediment delivery, potentially following ice sheet break-up at the end of the Saalian glacial and transition into the Eemian interglacial. Our multi-proxy findings provide new insight into the relationship between GrIS, Innuitian/Laurentide Ice Sheets, and regional sedimentation patterns during a significant glacial to interglacial transition, with important implications for understanding of GrIS response to abrupt climate warming.

How to cite: Huang, S., Selby, D., Lloyd, J., and Knutz, P.: Investigating Osmium Isotopes and Sedimentological Records for the end of the Saalian Glacial from Northwest Baffin Bay, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19795, https://doi.org/10.5194/egusphere-egu25-19795, 2025.

The polar ice sheets are melting faster due to climate change, with the contribution of the Greenland and Antarctic ice sheets being the largest uncertainty in projecting future sea level rise. Understanding this is crucial for assessing impacts on the environment and ecosystems. Most of the existing modelling studies focus on ice sheet response to atmospheric and oceanic forcing. However, the ice sheets closely interact with and influence the Earth’s climate. With the goal of better representing ice sheet and climate processes and feedbacks, we aim to integrate Greenland and Antarctic dynamic ice sheet components into the Norwegian Earth System Model (NorESM). NorESM is a global, CMIP-type coupled model for the physical climate system and biogeochemical processes over land, ocean, sea ice and atmosphere. In its latest release, NorESM features interactive coupling with a dynamic Greenland Ice Sheet (GrIS) component, although this coupling does not explicitly include ocean forcing at the marine-terminating margins of the ice sheet. In this presentation, we will show preliminary results of NorESM simulations featuring (1) a new interactive coupling with the Community Ice Sheet Model (CISM) over both the Antarctic and Greenland domains, and (2) a new ocean and ice sheet coupling allowing us to force the ice sheets with horizontally and vertically resolved  NorESM ocean properties. We will discuss work in progress, highlighting recent advances and most pressing challenges of our coupling approach.

How to cite: Petrini, M., Vertenstein, M., Goelzer, H., Lipscomb, W. H., Leguy, G. R., Sacks, W. J., Thayer-Calder, K., Chandler, D. M., and Langebroek, P. M.: Coupling the polar ice sheets to the Norwegian Earth System Model: advances and challenges, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20400, https://doi.org/10.5194/egusphere-egu25-20400, 2025.

As the second largest ice body on Earth, comprising an ice volume of 7.4 m sea level equivalent, the Greenland ice sheet is one of the main contributors to global sea level rise. Though observational and modelling efforts have increased substantially in recent years, major uncertainties remain regarding the ice sheet – climate interactions and feedback mechanisms that drive the ice sheet’s long-term mass loss. To improve sea level projections and the representation of such interactions in model simulations, efforts are currently emerging to couple ice sheet and regional climate models. However, so far, only a few coupled ice sheet – regional climate model simulations have been performed, and these do not extend beyond the centennial timescale. They therefore provide limited insights into the evolution and critical thresholds of the ice sheet – climate system over longer timescales.

As such, to obtain a better understanding of the ice sheet – climate interactions and potential feedback mechanisms over Greenland, we coupled our Greenland Ice Sheet Model (GISM) with a high-resolution regional climate model, the Modèle Atmosphérique Régional (MAR), and performed millennial-length simulations. The global climate model forcing for MAR during these simulations consisted of the IPSL-CM6A-LR model output under the SSP5-8.5 scenario, which was available until 2300. After this date, the climate was held constant, and we prolonged our coupled simulations until the year 3000.

Specifically, we performed three coupled simulations for the period 1990-3000 with differing coupling complexity: full two-way coupling, one-way coupling and zero-way coupling. In the two-way coupled set-up, the ice sheet topography and surface mass balance were communicated yearly between both models, such that ice sheet – climate interactions were fully captured. In the one-way coupled set-up only the surface mass balance – elevation feedback was considered, through interpolation of the yearly SMB onto the changing ice sheet topography. And lastly, in the zero-way coupled set-up the ice sheet – climate interactions were entirely omitted.

The results show that the ice sheet evolution is determined by positive as well as negative feedback mechanisms, that act over different timescales. The main observed negative feedback in our simulations is related to changing wind speeds at the ice sheet margin, due to which the integrated ice mass loss remains fairly similar for all simulations up to 2300, regardless of the differently evolving ice sheet geometries. Beyond this time however, positive feedback mechanisms related to decreasing surface elevation and changing precipitation patterns dominate the ice sheet – climate system and strongly accelerate the integrated ice mass loss. Hence, over longer timescales and for a realistic representation of the evolving ice sheet geometry, it is indispensable to account for ice sheet – climate interactions as was done in our two-way coupled ice sheet – regional climate model set-up.

How to cite: Paice, C., Fettweis, X., and Huybrechts, P.: The role of Greenland ice sheet – climate interactions from 1000-year coupled simulations with MAR-GISM, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20846, https://doi.org/10.5194/egusphere-egu25-20846, 2025.

Atmospheric rivers are transient channels of intense water vapor that account for up to 90% of the poleward moisture transport from mid-latitudes. Though short-lived, these events can deliver extreme amounts of heat and rainfall that have been widely reported to accelerate ablation and ice mass loss across the Arctic. However, the impact of atmospheric river fueled snowfall has received less attention, partly due to the limited availability of empirical evidence and direct observations. Here, we explore the potential of atmospheric rivers to deliver intense snowfall to the Greenland ice sheet and thereby replenish its health through enhanced mass accumulation. Specifically, we use new firn-core isotopic analyses and glacio-meteorological datasets from Southeast Greenland to examine the origin and impact of atmospheric rivers on regional mass balance. To this end, we sampled firn core stratigraphy from the upper accumulation area of Southeast Greenland and related it to meteorological observations, to demonstrate that an intense atmospheric river in mid-March 2022 delivered up to 11.6 gigatons per day of extreme snowfall to this region of the ice sheet. 
We show that this immense snowfall not only recharged the snowpack and offset Greenland ice sheet net mass loss by 8% in 2022, but also raised local albedo thereby delaying the onset of summer bare-ice melt by 11 days, despite warmer than average spring temperatures. Since 2010, synoptic analysis of ERA5 data reveals that snow accumulation across Southeast Greenland increased by 20 mm water equivalent per year, driven by enhanced Atlantic cyclonicity. Depending on their seasonal timing, our study demonstrates that the impact of atmospheric rivers on the mass balance of the Greenland ice sheet is not exclusively negative. Moreover, their capacity to contribute consequential ice mass recharge may become increasingly significant under ongoing Arctic amplification and predicted poleward intrusion of mid-latitude moisture.

How to cite: Bailey, H. and Hubbard, A.: Mass Recharge of the Greenland Ice Sheet driven by an IntenseAtmospheric River, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-21018, https://doi.org/10.5194/egusphere-egu25-21018, 2025.

A major obstacle in both paleo and future simulations of the Antarctic Ice Sheet is that most studies do not include interactive ice sheets. Although this is a current area of development, most studies use stand alone climate models to force separate ice sheet models to study the potential impacts of climate changes on ice sheets; however this method ignores consequent impacts of the ice sheets on the ocean-atmosphere system, leading to simulations that may under or over estimate retreat in a warmer climate. The few model simulations that do include ice sheet-climate feedbacks disagree on the overall sign of the these feedbacks.
Here we are developing a new coupling between an established ice sheet (PSU-ISM) and climate model (HadCM3) that has been used extensively for paleoclimate applications. These models are suitable for performing multiple simulations over thousands of years. The ice sheet model output will be used to update the ice sheet in the climate model. The climate model orography and land sea mask will be modified to match that in the ice sheet model and ice sheet discharge will be added as a freshwater flux, modelled via change in salinity around the Southern Ocean. The models have been coupled offline and we are next automating this process so that simulations can be repeated over shorter timescales. This will allow the model to develop feedbacks more quickly rather than being limited to the length of the run. The model has been developed using pre-industrial idealised simulations. The main focus of the work is on reproducing the AIS response and sea level rise during the middle Miocene warm interval that matches proxy records more closely without having to add unrealistic CO2 forcing.

How to cite: Byrne, L.: Development of a new coupled ice sheet-climate model for simulations of the Antarctic Ice Sheet under a warm climate, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-21116, https://doi.org/10.5194/egusphere-egu25-21116, 2025.

Ice slabs are multi-meter thick layers of refrozen meltwater that form in the Greenland Ice Sheet (GrIS) percolation zone and play a crucial role in modulating surface runoff. The limited permeability of ice slabs restricts the vertical percolation of meltwater into underlying firn, thus accelerating runoff. Improving understanding of ice slab growth and evolution is crucial to improving understanding of GrIS supraglacial hydrology, reducing uncertainty in projections of GrIS surface runoff rates, and improving global sea level rise estimates. Existing maps of ice slab extent have been developed using NASA’s Operation Ice Bridge Accumulation Radar data collected between 2011-2014 and 2017-2018 as well as Soil Moisture Active Passive (SMAP) L-band radar data averaged over 2015-2019, however both of these datasets have some combination of limited spatial resolution, poor spatial coverage, or inconsistent temporal coverage, making it difficult to capture high resolution rates of inland expansion.

Here, we present the first annual time series of ice slab extent from 2015 through 2024, derived from polarimetric Sentinel-1 backscatter measurements. This work yields maps of the full spatial extent and continuity of ice slabs at 500 m² resolution and establishes a comprehensive decade-long record of ice slab behavior in a warming climate. To assess atmospheric drivers of ice slab growth over this time, we compare our observations of inland expansion to hindcasts from two regional climate models: MAR and RACMO. We also compare our time series to the existing MacFerrin and Brils models of ice slab expansion to evaluate whether computationally expensive firn models are needed to predict ice slab expansion. Our work ensures continuous monitoring of ice slab expansion into the 2030s with the arrival of each new year of Sentinel-1 data and provides a basis for improving model predictions of surface mass balance in Greenland’s wet snow zone.

How to cite: Mutter, E. and Culberg, R.: Decade Long Time Series (2015 - 2024) of Ice Slab Expansion in Greenland using Sentinel-1 SAR , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1811, https://doi.org/10.5194/egusphere-egu25-1811, 2025.

Subglacial drainage models sensitively depend on the values of numerous uncertain parameters. However, the computation time associated with running these models makes it difficult to quantify the associated uncertainty in model outputs and to use field data to calibrate parameter values. To overcome these computational limitations, we construct a Gaussian Process (GP) emulator that accelerates subglacial drainage modelling by ~1000x. The GP predicts spatiotemporally resolved water pressure as a function of eight model parameters and is trained using ensembles of up to 512 simulations with the Glacier Drainage System (GlaDS) model applied to the Kangerlussuaq sector of the western Greenland Ice Sheet. The GP reproduces the spatial patterns and daily temporal variations simulated by GlaDS within ~4%, with locally higher errors near moulins and during the early melt season. As an application of the GP, we compute the sensitivity of basal water pressure to each of the eight parameters and find that three parameters (ice-flow coefficient, bed bump aspect ratio and the subglacial cavity system conductivity) explain 90% of the variance in model outputs. Next, we explore using a borehole water-pressure timeseries to calibrate the eight uncertain parameters. We take a Bayesian perspective to quantify the uncertainty in parameter estimates and use the GP in place of the physics-based model to make Markov Chain Monte Carlo sampling computationally feasible. We find meaningful constraints relative to the prior assumptions on most parameters and a factor-of-three reduction in uncertainty of the calibrated model predictions. However, significant differences between the calibrated model and the borehole data suggest that structural limitations of the model, rather than poorly constrained parameters or computational cost, remain the most important constraint on subglacial drainage modelling.

How to cite: Hill, T., Flowers, G., Bingham, D., and Hoffman, M.: Subglacial drainage modelling and Bayesian calibration using Gaussian Process emulators, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3771, https://doi.org/10.5194/egusphere-egu25-3771, 2025.

The flow of Antarctic ice streams is modulated by a subglacial hydrological system, including “shallow” water transported through till and channels as well as “deep” groundwater stored in sedimentary basins. The latter has risen to prominence in recent years as a contributor to subglacial hydrology through the exchange of groundwater with the “shallow” system. These sedimentary basins possess complex geometries and display variations in salinity due to historic seawater intrusion. However, relatively little is known about the hydraulic properties of subglacial sedimentary basins, or their overall contribution to subglacial hydrology. To address these questions, we develop a mathematical model of groundwater flow in a sedimentary basin driven by an overlying marine ice sheet over geological timescales. By comparing modelled seawater intrusion to field observations of groundwater salinity, we  estimate the permeability of sedimentary basins in West Antarctica. We also show that exchange of groundwater between sedimentary basins and the shallow hydrological system is primarily driven by spatial variation in the basin geometry, and discuss implications for the dynamics of the ice stream. 

How to cite: Cairns, G., Hewitt, I., and Benham, G.: Modelling the hydrology of sedimentary basins beneath marine ice sheets, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4180, https://doi.org/10.5194/egusphere-egu25-4180, 2025.

How to cite: Napoleoni, F., Schlegel, R., Brisbourne, A. M., Bodart, J., Ockenden, H., Bingham, R. G., and Ghost, T.: New insights into Hydrology and Lake Dynamics Upstream of Thwaites Glacier, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5167, https://doi.org/10.5194/egusphere-egu25-5167, 2025.

We present a model for water flow at the base of a glacier implemented with the Elmer/Ice Open-Source Finite-Element Software. The model describes subglacial water flow in connection with the emptying of basal water bodies and the subglacial propagation of glacial outburst flood (jökulhlaup) fronts using a visco-elastic model for the overlying glacier combined with a turbulent thin-sheet model for water flow. The visco-elastic model is based on Maxwell-elements¹ combining linear elasticity with the non-linear viscous behaviour described by Glen's ice-flow law, and, by introducing a pressure variable, allowing for incompressibility of the material. The dynamics of the subglacial ice–water interface is implemented as fluid–structure interaction (FSI), utilizing artificial compressibility. The coupled visco-elastic, thin-sheet model aims to represent the propagation of rapidly- and slowly-rising subglacial floods², many of which are inferred from remote-sensing and in-situ observations to involve lifting of the glacier from its sole over large areas³. Dynamically similar subglacial ice–water interactions may be involved in widespread, propagating ice-velocity and surface-elevation disturbances that have been observed by remote sensing during subglacial drainage events in Greenland⁴ and Antarctica⁵, indicating that the dynamics of jökulhlaups may have wider implications for glacier dynamics in general. We will demonstrate the coupled model with simple synthetic examples. The visco-elastic model can simulate the observed geometry of ice-surface depressions formed by the collapse of basal water cupolas and conduits, for which we present simulation results with comparison to observed ice-surface depressions at Vatnajökull ice cap, Iceland.

References

¹Zwinger, T., Nield, G. A., Ruokolainen, J., and King, M. A.: A new open-source viscoelastic solid earth    deformation module implemented in Elmer (v8.4), Geosci. Model Dev., 13, 1155–1164 (2020).

² Jóhannesson, T. Propagation of a subglacial flood wave during the initiation of a jökulhlaup. Hydrol. Sci. J., 47, 417–434 (2002).

³ Magnússon, E., & 13 others. New insights into the development of slowly rising jökulhlaups from the Grímsvötn subglacial lake, Iceland, deduced from ICEYE SAR images and in-situ observations. EGU General Assembly 2024, EGU24-18204, https://doi.org/10.5194/egusphere-egu24-18204.

⁴ Maier, N., Andersen, J.K., Mouginot, J., Gimbert, F., & Gagliardini, O. Wintertime supraglacial  lake drainage cascade triggers large-scale ice flow response in Greenland. Geophys. Res.  Lett., 50(4), p.e2022GL10 (2023).

⁵Neckel, N., Franke, S., Helm, V., Drews, R., & Jansen, D. Evidence of cascading subglacial  water flow at Jutulstraumen Glacier (Antarctica) derived from Sentinel-1 and ICESat-2  measurements. Geophys. Res. Lett., 48(20), p.e2021GL094472 (2021).

How to cite: Zwinger, T., Jóhannesson, T., Råback, P., and Ruokolainen, J.: Numerical modelling of subglacial water flow under a visco-elastic glacier-ice cover, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6255, https://doi.org/10.5194/egusphere-egu25-6255, 2025.

The Greenland Ice Sheet (GrIS) has been losing mass at an accelerating rate, primarily due to meltwater runoff to the ocean. Firn, a porous transition layer between snow and ice, has the potential to buffer the GrIS’s contribution to sea level rise by retaining this meltwater. In regions with low surface accumulation, such as the K-transect in Southwest Greenland, high surface melt leads to the formation of thick, near-impermeable ice slabs which decrease the capacity of firn to retain meltwater. In contrast, in regions with high surface accumulation, such as the Helheim glacier in Southeast Greenland, high surface melt causes the formation of firn aquifers.

In this research, we simulate ice slabs and firn aquifers with a one-dimensional firn model, called Timm’s Firn Model (TFM), along glacier flowlines in different climate forcing scenarios. Instead of the commonly-used, more computationally efficient bucket scheme, the TFM solves the Richards’ equation, which simulates the vertical water transport more physically. We investigate whether the TFM simulates an earlier onset, greater extent, and expansion of ice slabs and firn aquifers towards the interior of the GrIS. In addition, we offer a new detection method for ice slabs based on hydraulic conductivity and volumetric liquid water content, enabled by the modeling of liquid water movement with the Richards’ equation.

The results show that firn aquifers were already forming in the Helheim glacier region before the GrIS started rapidly losing mass. Furthermore, the TFM results indicate that, with warming, firn aquifers form earlier along the flowline, expanding towards the interior of the ice sheet. Firn aquifer formation is highly dependent on surface accumulation, with higher accumulation rates favouring formation.

We further find that ice slabs, though less extensive than firn aquifers, were present along the K-transect in Southwest Greenland before the GrIS’ rapid mass loss. With warming, ice slabs form earlier along the flowline and expand towards the interior, consistent with available observations. Three consecutive years of extensive melt lead to ice slab formation. However, decade-old ice in the subsurface firn leads to ice slab formation as well, by merging with newly refrozen layers.

How to cite: Jovanovic, N., Schultz, T., and Humbert, A.: Simulating Greenland Ice Slabs and Firn Aquifers with a 1D Firn Model, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6766, https://doi.org/10.5194/egusphere-egu25-6766, 2025.

The hydrofracture-driven drainage of supraglacial lakes rapidly introduces large volumes of meltwater to the ice-sheet bed, influencing ice-sheet dynamics on multiple timescales. Immediate ice deformation mainly arises from three sources: the opening of the hydrofracture crack, separation of the ice from the bed, and additional slip at the bed. An understanding of the ice response to drainage requires knowledge of these spatially and temporally varying sources, ideally constrained by observations obtained both on the ice surface and within the ice column. Previous work examining ice dynamics during supraglacial lake drainage relies on ice-surface observations only: aerial and satellite imagery, Global Navigation Satellite System (GNSS) data, and pressure-sensor records from draining lakes. We deployed three autonomous phase-sensitive radio echo sounders (ApRES) near a set of three supraglacial lakes at ~950 m elevation, in the mid-ablation zone of the western Greenland Ice Sheet, to record englacial deformation during lake drainage. The ApRES stations were embedded within a geophysical network including GNSS stations, air-temperature sensors, and a lake pressure logger, and were configured to make repeat measurements every 15 minutes from May 2022 to September 2023. In 2022, two of the lakes adjacent to the ApRES stations drained abruptly via hydrofracture, exhibiting characteristics of inter-lake static-stress triggering; in 2023, all three lakes drained in a similar manner. We demonstrate the capability of the ApRES system to provide estimates of the time-varying change in englacial vertical strain rate that accompanies hydrofracture-driven lake drainage, despite the short durations of the drainages and the wet and variable ice surface that is inevitable during the melt season. At station locations ~1 km away from the hydrofracture cracks, we observe vertical strain rates of magnitude up to ~1 yr^-1 during lake drainages, averaged over the top 500 m of ice and over 15 minutes; background vertical strain rates have magnitudes of ~10^-3 yr^-1 at these locations. As a first step towards incorporating these englacial observations of deformation as constraints on an inverse problem to obtain the spatial and temporal history of the deformation source, we compare the englacial observations to predictions from a source model constructed using only GNSS data. Following previous work, we use an elastic dislocation model and invert the GNSS data to obtain time- and space-varying estimates of the opening of the hydrofracture crack, opening at the ice-bed interface, and excess slip at the bed during lake drainage. We then use this model to predict changes in strain in the ice under the ApRES stations, and compare the resulting timeseries with our observations. We evaluate the additional sensitivity provided by our englacial observations to the deformation source.

How to cite: Lu, G., Nettles, M., Stevens, L., and Larochelle, S.: Observations and models of englacial deformation during supraglacial lake drainage, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6941, https://doi.org/10.5194/egusphere-egu25-6941, 2025.

Greenland’s crevasses are responsible for transferring the majority of seasonal runoff to the bed of the ice sheet in fast-flowing regions, with implications for ice rheology, subglacial hydrology, and ice dynamic feedbacks. However, their drainage mechanics are poorly understood, particularly relative to other transfer mechanisms such as lake drainage and moulins. Here, we use remote-sensing products to identify relationships between strain rates and crevasse drainage at Greenland’s fast-flowing outlet glaciers. We map the time-series evolution of water-filled crevasses by training and applying a convolutional neural network (CNN) to 10 metre resolution Sentinel-2 MSI imagery, and extract contemporaneous logarithmic strain rates from NASA MEaSUREs ITS_LIVE velocity data. We test the time-evolving relationship between strain rates and crevasse ponding across a range of outlet glaciers, and examine whether significant relationships between the two processes can be detected. We find that crevasse drainage displays a unique response to seasonal strain rate evolution not detectable in analogous lake drainage studies, with drainage events occurring following a seasonal transition from compressive to tensile strain rate regimes. We aim to use these relationships to parameterise dynamic controls on crevasse drainage into coupled models of Greenland Ice Sheet hydrology-dynamics.

How to cite: Chudley, T., Stokes, C., Winterbottom, T., Lea, J., and Clason, C.: Seasonal drainage of ponded crevasses in response to dynamics at Greenlandic outlet glaciers, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8763, https://doi.org/10.5194/egusphere-egu25-8763, 2025.

The term "water pocket" is often used as an umbrella term to describe the unknown origin of glacial outburst floods. There is currently no consensus on its definition and the formation and rupture mechanisms of water pockets remain poorly understood. Here, we define a glacial water pocket as an englacial or subglacial water-filled cavity with a volume larger than 1000 m³. Glacier outburst floods originating from the rupture of a water pocket are called water pocket outburst floods (WPOFs). WPOFs are in contrast to glacier lake outburst floods (GLOFs), for which the water giving rise to a flood stems from a detectable reservoir located either in the glacier forefield, at the surface of the glacier, at the glacier margin, or at the glacier base.

Here, we aim to understand the mechanisms behind WPOFs from alpine glaciers by analyzing their spatial and temporal distribution, pre-event meteorological conditions, and the glacio-geomorphic features of the glaciers from which the floods originate. We updated an inventory of known WPOFs in the Swiss Alps to 91 events from 37 individual glaciers. Among all the recorded events, 64 events have direct observations of the flood at the glacier tongue, while 27 events are characterized as speculative because of the lack of direct observations. Infrastructure damage was reported for 43 events, and two WPOFs caused the death of three people. Most WPOFs occurred between June and September, linked to meltwater input. Meteorological data indicate anomalously high temperatures during the days preceding most events and heavy precipitation on 25 % of days for which WPOFs occur, indicating that water pockets typically rupture during periods of high water input.

Based on the collected information, we propose four mechanisms of water pocket formation: temporary subglacial channel blockage, hydraulic barriers, water-filled crevasses, and accumulation of liquid water behind barriers of cold ice (thermal barriers). Overall, our analysis highlights the challenge of understanding WPOFs due to the sub-surface nature of water pockets, emphasizing the need for field-based research to improve their detection and monitoring.

How to cite: Ogier, C., Fischer, M., Werder, M. A., Huss, M., Hupfer, M., Jacquemart, M., Gagliardini, O., Gilbert, A., Hösli, L., Thibert, E., Vincent, C., and Farinotti, D.: Glacier outburst floods originating from glacial water pockets: what do we know?, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9210, https://doi.org/10.5194/egusphere-egu25-9210, 2025.

Antarctic ice shelves, which encircle approximately 75% of the continent, play a pivotal role in moderating global mean sea level rise as their buttressing properties restrict the flow of inland ice. Each ice shelf is subject to distinct glaciological and climatic conditions that influence its susceptibility to partial break-up or total disintegration. One factor compromising the stability of ice shelves is the presence of both surface and sub-surface meltwater, which may accelerate firn-air depletion and induce flexural stresses, possibly leading to fractures within the ice shelf.

While the occurrence of surface meltwater has been studied extensively in recent years – documenting widespread meltwater systems across several ice shelves during the austral summer – our understanding of meltwater storage below the surface remains limited. In some regions, liquid water may persist within the ice-shelf surface throughout the year, insulated by overlying snow, firn, or ice layers. This subsurface meltwater, particularly in the form of buried lakes, represents a potential mechanism for hydrofracture – even outside the melt season. However, buried lakes are typically difficult to detect using optical imagery, complicating efforts to understand their dynamics and their impact on ice-shelf stability.

Here, we aim to evaluate the feasibility of applying machine learning methods, previously employed on the Greenland Ice Sheet, to detect meltwater lakes buried beneath the surface of Antarctic ice shelves. Using a convolutional neural network in a deep learning approach, we seek to classify ice-shelf surface and subsurface features in Sentinel-1 Synthetic Aperture Radar imagery (SAR), enabling the identification of buried lakes. Preliminary qualitative analysis of Sentinel-1 SAR data has revealed several possible buried meltwater lakes near the grounding line of the western Wilkins Ice Shelf near Merger Island. These lake findings provide an opportunity to assess the applicability of machine learning models developed for Greenlandic application in an Antarctic context. Additionally, it allows us to test the use of airborne radar data for validating buried lake identification in SAR imagery.  

How to cite: Suchantke, P., Dell, R., Arnold, N., and Dunmire, D.: Investigating Buried Meltwater Lakes on an Antarctic Ice Shelf with Sentinel-1 SAR Imagery and Machine Learning Methods, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9617, https://doi.org/10.5194/egusphere-egu25-9617, 2025.

Shortwave radiation can penetrate a few metres below the surface of an ice sheet, causing subsurface melting which results in the formation of a surface layer of porous ice, called the weathering crust. The weathering crust evolves in response to changing weather conditions, affecting the albedo, the surface and near-surface melting, and the transport of meltwater across the ice-sheet surface. Here, we extend our existing one-dimensional mathematical model for the vertical structure and temperature of the weathering crust to also account for lateral flow of meltwater through the porous crust. This is done using Darcy’s law and a parametrisation for lateral drainage. Our model successfully reproduces observed temperature, porosity and surface lowering on the south-western Greenland Ice Sheet over several years. This enables our model to be used as a tool for predicting future mass loss and weathering crust evolution in a changing climate. We also explore how two key parameters in our model – representing the partitioning of shortwave radiation between surface and subsurface absorption, and the strength of lateral meltwater drainage – affect the ice structure, temperature and mass loss. From this, we demonstrate the importance of accounting for the weathering crust, particularly subsurface radiation, for correctly reproducing observed surface mass loss.

How to cite: Woods, T. and Hewitt, I.: Modelling surface mass loss from the Greenland Ice Sheet in response to radiation and lateral meltwater drainage, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10272, https://doi.org/10.5194/egusphere-egu25-10272, 2025.

Over 3,300 ice-marginal lakes exist around the Greenland Ice Sheet (GrIS), interacting with ~10% of its perimeter boundary. The number of ice-marginal lakes has increased over the last three decades, likely in response to enhanced meltwater runoff and glacier recession. We describe an ice-dammed, ice-marginal lake drainage event observed north of Isunnguata Sermia Glacier, south west Greenland in which ~1.6 million m³ of water drained from the 100 m deep lake over 4 days during the 2015 melt season. Using the Glacier Drainage System (GlaDS) model, fully-coupled to ice flow dynamics in the Ice-sheet and Sea-level System Model (ISSM), we model this ice-marginal lake drainage as an instantaneous drop in water level at the boundary of our model domain. By modifying the subglacial hydrological inflow/outflow boundary conditions, and tracking the evolution of the system through time in terms of channelised discharge, sheet thickness, effective pressure, and ice velocity we show that ice-marginal lake-drainage of the scale observed in 2015 causes significant reorganisation of the channelised subglacial drainage, both in the short term with a sudden injection of water and channel development, and in the long term with changes in the outlet boundary conditions and basal friction. As the number of ice-marginal lakes and the frequency of their drainage increases going forward we expect these dynamic drainage reorganisations to become more common, with implications for future GrIS dynamics. 

How to cite: Hepburn, A. J. and the SLIDE Team: How do variations in ice-marginal lake water depth impact subglacial hydrology routing and ice dynamics? , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10780, https://doi.org/10.5194/egusphere-egu25-10780, 2025.