The Tarim River Basin, situated in the Eurasia hinterland, serves as the heart of China’s Silk Road Economic Belt. It covers an area of 1.02 million km² and is surrounded by the Tienshan Mountains to the north, the Kunlun Mountains to the south and the Pamir to the west. The runoff is recharged by glacier melt, snow melt, and rainfall. There are large amount of glaciers distributed in the high mountains of Tienshan and the Kunlun Mountains. In recent decades, the glaciers in the Tienshan Mountains are retreating at a faster rate, while glacier in the Kunlun Mountains show less retreat or even advancing trend (i.e., Karakorum anomaly). These changes in glaciers will definitely alter the future runoff.

This study extended the hydrological model SWAT-Glacier by incorporating a degree-day based glacier melt and accumulation module. The hydrological processes of the headwaters of the Tarim River were simulated using SWAT-Glacier model. The model was calibrated and validated using multiple variables, including glacier mass balance, snow cover area, snow water equivalent, daily streamflow and the balance between snowfall, snow melt and sublimation. The hydrological model was forced by the bias-corrected climate from 6 regional climate models in CORDEX. Results indicated that the runoffs of the headwaters originated from the south Tienshan Mountains (i.e., Kaidu River, Aksu River) demonstrated a slight increase or even decrease trend. For the Kaidu River, there will be a slight decrease in runoff under SSP585, as the contribution of glacier melt water is less than 10%. For the Kumarak River, the runoff showed slightly increase and the glacier melt runoff will reach peak point before 2050s. For the rivers originated from the north Kunlun and Karakorum Mountains, the runoff will increase dramatically.

This study provide a basin-scale runoff changes under multiple constraints in the endoreic Tarim River Basin. However, the glacier accumulation and ablation suffers from great uncertainty as the precipitation observation is rare in the high mountains. More efforts should be taken to utilize more state-of-the-art technology in revealing the meteorological and hydrological processes in these alpine catchments.

How to cite: Fang, G. and Chen, Y.: Future changes in runoffs in the headwaters of the Tarim River, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3720, https://doi.org/10.5194/egusphere-egu23-3720, 2023.

Debris-cover representation is rarely included in regional or global glacier models although it plays a key role in the regulation of melt processes. Debris cover that is more than a few centimeters thick reduces melt by insulating glacier ice. However, mass loss and retreat of debris-covered glaciers are not necessarily slower than those of clear ice. Debris-covered glaciers are widespread in the Northern Caucasus. It is important to reliably quantify their evolution because the contribution of glacial runoff to total discharge is significant in the region.

This study assesses the influence of debris cover on the evolution of glaciers in the basins of the Terek and Kuban rivers in the Northern Caucasus in the 21st century and quantifies its effects on glacier mass balance, ice velocity, ice thinning, changes in glacier area, volume, and position of the glacier fronts. We use the GloGEMflow glacier model and introduce a new debris cover dynamic module. The mass balance is calibrated separately for the explicitly modelled debris cover and for clean-ice glaciers (debris cover is implicit in the degree-day factor calibration). The model is calibrated using newly mapped debris cover outlines and ice thickness data from Rounce et al. (2021). The debris evolution is simulated with a steady deposit model adapted from Verhaegen et al. (2020) and Anderson & Anderson (2016), where debris input onto the glacier surface is generated from a fixed point on the flow line.

We compare spatio-temporal changes in glacier geometry including the evolution of debris cover for the explicit and implicit debris-cover formulation for five SSP scenarios from CMIP6. The debris-cover evolution patterns differ significantly between the Terek and the Kuban basins. In the Kuban basin, glaciers located generally at lower elevations, retreat rapidly and lose ice at the debris-covered glacier tongues. On the contrary, the supraglacial debris of the Terek basin glaciers may, under certain climate scenarios, expand and play an increasingly-important role in glacier evolution with time. However, under the high-end warming scenario SSP5-8.5, the ice loss by 2100 overwhelms the debris-cover effects in both regions.

The maximum difference in glacier length, area and volume depending on the explicit or implicit mode of debris-cover modeling occurs before 2100, but by the end of the century it is eliminated due to the retreat of debris-bearing parts of the glaciers or due to the elevation-stabilization effect. In general, explicitly accounting for debris cover in the projections only has a minor effect on the overall projected regional mass loss, but improves the representation of processes on the intra-glacier scale.

This study was carried out under Governmental Order to Water Problems Institute, Russian Academy of Sciences, subject no. FMWZ- 2022-0001, and was funded by the RSF grant number 22-17-00133.

How to cite: Postnikova, T., Rybak, O., Zekollari, H., Huss, M., and Gubanov, A.: Future evolution of glaciers in the Caucasus: focus on debris-cover evolution., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-893, https://doi.org/10.5194/egusphere-egu23-893, 2023.

It is essential to test the potential impact of processes missing in the global-scale models that are used to project on glacier mass balance in the glacier models, such as the modification of the mass balance through debris-cover. In this study, we evaluate the impact of a parameterization of debris cover on glacier mass change projections using the Open Global Glacier Model (OGGM). The assessment of uncertainties about the potential impact of debris cover on global scale modeling is complicated by the scarcity of suitable data on debris-covered glaciers for validation (e.g., mass balance measurements for individual elevation bins on debris-covered glaciers). To calibrate and validate the mass balance module, we rely on glacier-wide geodetic volume changes. Debris cover can enhance ice melting if less than a few centimeters thick, or decrease ice melting through insulation of the underlying ice by a thick layer of debris. Ice cliffs, supraglacial ponds and streams associated with debris cover may increase the absorption of heat and increase ice melting. In OGGM, the effects of debris cover are parameterized by a simple modification of the mass balance module, through introducing an elevation-dependent temperature sensitivity parameter (“degree-day factor”) and including a debris-related melt correction factor. While debris cover plays only a minor role on glacier mass change on the global scale, this becomes important on regional and individual glacier scales. Our results show the effect of debris cover could improve model performance on the mass balance gradient, not the overall mass balance. To validate our results on the mass balance gradient, we rely on the geodetic mass balance for each elevation band.

How to cite: Mojtabavi, S., Rounce, D., Maussion, F., and Marzeion, B.: Uncertainty assessment of modeling the impact of debris cover on global glacier mass change: challenges and solutions, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9828, https://doi.org/10.5194/egusphere-egu23-9828, 2023.

A recent large-scale glacier model intercomparison revealed a strong influence of model design choice on glacier projections. Here we examine the influence of various temperature-index mass-balance models and calibration options. With the Open Global Glacier Model (OGGM) framework, we compare the performance and projections of model options such as the use of surface-type dependent degree-day factors as well as varying temporal climate resolution (daily, monthly) and downscaling strategies (temperature lapse rates, temperature and precipitation correction). We focus on 88 glaciers with long term observations of mass-balance profiles and seasonal mass-balance, allowing us to assess the added value of using multiple mass-balance statistics in the calibration process. We find that using interannual mass-balance variability to calibrate otherwise fixed parameters generally leads to an improved representation of the mass-balance gradient, which in turn is a crucial explanatory variable for future glacier evolution. Therefore, we also find a strong influence of the calibrated temperature lapse rates on future glacier volume. Using different degree-day factors for snow, firn, and ice leads to nonlinear sensitivities, where future glacier loss depends on how the accumulation area changes compared to the calibration period. Our study illustrates the strong impact of temperature-index model choice on projected glacier volume and runoff. But it cannot clearly demonstrate the added value of additional model complexity due to the lack of independent observations.

How to cite: Schuster, L., Rounce, D., and Maussion, F.: Glacier projections sensitivity to temperature-index model and climate downscaling parameter calibration choices, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11983, https://doi.org/10.5194/egusphere-egu23-11983, 2023.

We partitioned Antarctic ice mass changes (2003-2020) into the contributions of surface mass balance (SMB) and ice discharge over 27 drainage basins, based on the combined estimates of satellite gravimetry and altimetry observations and a numerical SMB model. Our analysis indicates that the ice discharge has played a dominating role in ongoing ice mass losses and accelerations, especially in the glaciers near Amundsen and Bellingshausen Sea in West Antarctica. In particular, the mass losses in the Thwaites and Pine Island Glaciers have been mostly controlled by ice discharge, while the contribution of SMB has been minor. On the other hand, SMB contributed large portions of ice mass imbalance in East Antarctica, such as glaciers near the Dronning Maud Land and Wilkes Land. An inaccurate GIA model is a potential source of uncertainty in our estimates.

How to cite: Kim, B.-H., Seo, K.-W., Lee, C.-K., Kim, J.-S., and Lee, W. S.: Partitioning the contribution of surface mass balance and ice discharge in Antarctic glacier mass variations (2003-2020), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-676, https://doi.org/10.5194/egusphere-egu23-676, 2023.

Peripheral glaciers (PGs, i.e., glaciers that are dynamically decoupled from the ice sheet) play a significant role in the mass balance and freshwater runoff of Greenland's land ice. Their evolution has implications for the sea level, global climate and ocean circulation, as well as for coastal communities and ecosystems. In order to accurately model the contribution of PGs to Greenland's overall mass balance and freshwater supply, it is necessary to consider their characteristics that set them apart from the main ice sheet. In this study, we used the Open Global Glacier Model (OGGM) to conduct large-scale regional modeling of approximately 19,000 PGs and project future mass losses, freshwater runoff, and sea level contributions under different climate scenarios. Our results show that PGs are likely to experience 29 % to 52 % of mass loss compared to their 2020 levels by the end of the 21st century, resulting in 10 mm to 19 mm of sea level rise under SSP126 and SSP585, respectively. Under the high emission scenario, PGs are expected to contribute 184 Gt yr^-1 of liquid freshwater and 3 Gt yr^-1 of calved solid ice to the ocean during 2020-2100, affecting ocean density, circulation, and mixing. Peakwater is projected for the 2080s under SSP585, after which annual freshwater contributions are expected to decline due to reduced glacier area. Regional mass and freshwater balance differences were found to be influenced by local climate, ocean-ice interaction, proportion of marine-terminating glaciers, and initial glacier volume. The central-west, southeast, and central-east subregions will experience the largest mass losses (79 %, 69 %, and 63 % of mass in 2020), with peakwater occurring earlier than for all PGs considered together under SSP585. The northeast subregion is expected to contribute 35 % of total liquid freshwater, 73 % of solid ice calving, and 37 % of sea level rise, despite lower mass loss (wrt 2020) due to regional conditions (i.e., climate, glacier geometries, and surrounding ocean). Submarine melting is likely to impact the mass balance of marine-terminating PGs, but further research is needed to explore this effect at a regional scale. This study highlights the importance of considering the distinct behavior of PGs in modeling Greenland's freshwater balance and understanding the factors that influence their mass changes.

How to cite: Shafeeque, M., Malles, J.-H., Vlug, A., Marzeion, B., Möller, M., and Eis, J.: Regional modeling of peripheral glaciers in Greenland: Implications for mass balance, freshwater runoff, and sea level rise , EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3329, https://doi.org/10.5194/egusphere-egu23-3329, 2023.

Retreating and thinning glaciers are icons of climate change and impact the local hazard situation, regional runoff as well as global sea level. For past reports of the Intergovernmental Panel on Climate Change (IPCC), regional glacier change assessments were challenged by the small number and heterogeneous spatio-temporal distribution of in situ measurement series and uncertain representativeness for the respective mountain range as well as by spatial and temporal limitations and technical challenges of geodetic methods. Towards IPCC SROCC and AR6, there have been considerable improvements with respect to available geodetic datasets. Geodetic volume change assessments for entire mountain ranges have become possible thanks to recently available and comparably accurate digital elevation models (e.g., from ASTER or TanDEM-X). At the same time, new spaceborne altimetry (CryoSat-2, IceSat-2) and gravimetry (GRACE-FO) missions are in orbit and about to release data products to the science community. This opens new opportunities for regional evaluations of results from different methods as well as for truly global assessments of glacier mass changes and related contributions to sea-level rise. At the same time, the glacier research and monitoring community is facing new challenges related to the spread of different results as well as new questions with regard to best practises for data processing chains and for related uncertainty assessments.In this presentation, we introduce the Glacier Mass Balance Intercomparison Exercise (GlaMBIE) project of the European Space Agency, which is building on existing activities and the network of the International Association of Cryospheric Sciences (IACS) working group on Regional Assessments of Glacier Mass Change (RAGMAC) to tackle these challenges in a community effort. We will present our approach to develop a common framework for regional-scale glacier mass-change estimates towards a new data-driven consensus estimate of regional and global mass changes from glaciological, DEM-differencing, altimetric, and gravimetric methods.

How to cite: Jakob, L., Zemp, M., Gourmelen, N., Dussaillant, I., Nussbaumer, S. U., Hock, R., Berthier, E., Wouters, B., Gardner, A. S., Moholdt, G., Brun, F., and Braun, M. H.: GlaMBIE – An intercomparison exercise of regional and global glacier mass changes, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5944, https://doi.org/10.5194/egusphere-egu23-5944, 2023.

 Glacier meltwater is a significant component of the regional runoff In High Mountain Asia (HMA),. However, the majority of the HMA's glaciers are rapidly losing their mass, putting the long-term viability of meltwater as a component of river flow at risk. It is, hence, crucial to comprehend the long-term glacier response to climate change at the regional scale as well as the impact of non-climatic characteristics like morpho-topographic factors on ice loss. We estimate changes for 445 glaciers in the upper Alaknanda basin and neighboring transboundary glaciers using multi-temporal optical satellite images from 1973 to2020. Our measurements indicate a mean annual area change of −1.14 ± 0.07 m a^–1 and a geodetic glacier mass balance of −0.34 ± 0.08 m w.e.a^–1 for the whole period. Before 2000 (1973-2000), the mean regional glacier mass loss rate was -0.30 ± 0.07 m w.e.a^-1, which increased to -0.43 ± 0.06 m w.e.a^-1 during 2000-2020. The mass loss increased further (-0.68 ± 0.09 m w.e.a^-1) in the recent period (2015-2020) and we observed heterogeneous mass loss both in spatial and temporal scales. Our analysis revealed that the current significant glacier imbalance is probably a result of the rising temperature trend as revealed from the ERA5 Land reanalysis data. An extended ablation season due to the strong seasonal temperature increase has further accelerated glacial mass loss. Steep and higher elevation glaciers were less affected by negative mass budget. This can be explained beside the lower average temperatures at higher elevation by a rapid transfer of snow and ice that helped them to readjust their geometry compared to glaciers at lower elevation, having more gentle slopes and lower dynamics. Such low elevation glaciers are unlikely to recover in coming decades if the current trend of warming continues. We also identified a surging glacier draining onto the Tibetan Plateau that advanced rapidly by around 800 m within three months in Sep-Dec 2019. The advance is still ongoing, though at a much-reduced rate. Our temporally detailed measurements of glacier change provide an in-depth view of glacier evolution in the Alaknanda Basin and will improve the estimation of meltwater run-off component of the hydrological cycle. 

How to cite: Bhattacharya, A., Mukherjee, K., King, O., and Bolch, T.: Examining the impact of climatic and non-climatic attributes on glacier mass budget and surging in Alaknanda Basin, India, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12836, https://doi.org/10.5194/egusphere-egu23-12836, 2023.

We present Bedmap3, the first comprehensive and openly available compilation of Antarctic Ice Sheet survey datasets, plus the latest gridded mapping products of ice thickness and the surface and bed topography of the whole Antarctic continent and continental shelf. For 60 years, scientists have strived to understand the past, present and future of the ice sheet, a goal that has become ever more urgent as ice loss accelerates. Key to this research has been the mapping of the bed-topography, surface slope and ice-thickness parameters that are crucial for modelling ice flow, and hence for predicting future ice loss and ensuing sea level rise. Supported by the Scientific Committee on Antarctic Research (SCAR) and data contributions from the international survey community, the Bedmap3 Action Group has now produced substantially updated gridded maps of these parameters and, for the first time, has standardized and made available all underlying geophysical survey data points from all Antarctic ice-thickness survey campaigns since the 1950s. Here, we describe the standardization that makes these and future datasets accessible under the ‘Findable, Accessible, Interoperable and Reusable’ (FAIR) data principles, allowing scientists to re-use these data freely for their own analysis. We also describe the results of our new mapping, and how this changes our view of Antarctica’s hidden landscapes and its potential to dominate future sea level rise.

How to cite: Fremand, A., Pritchard, H., Fretwell, P., and Bodart, J.: Bedmap3: new data and gridded products of Antarctic ice thickness, surface and bed topography, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13665, https://doi.org/10.5194/egusphere-egu23-13665, 2023.