Seasonal mass balance drivers for Swiss glaciers over 2010–2024 inferred from remote-sensing observations and modelling

Abstract

Reliable estimates of glacier mass balance for an entire mountain range provide valuable insights into the impact of glacier melt on regional water resources. Here, we derive daily mass balance estimates for every glacier in the Swiss Alps over the period 2010–2024. To do so, we leverage two simplified surface energy-balance models and remote sensing observations, i.e. geodetic volume changes and observations of the snow-covered area fraction (SCAF) of glaciers during summer, together with machine-learning techniques for extrapolation purposes. This allows reproducing the seasonal variability of glacier mass balance for glaciers without in situ observations and determining daily glacier mass balance across Switzerland. Over the study period, the Swiss glaciers lost almost 25 % of their 2010 ice volume, which corresponds to a wastage of -15.2 ± 1.6 km3 of ice. The highest winter snow accumulation is inferred to occur in central and western Switzerland, with up to 1.5–1.9 mw.e. by the end of April, whereas the lowest winter accumulation is detected in Valais and ranges between 0.9 and 1.2 mw.e. Furthermore, winter balances are found to show better correlation in space compared to long-term annual balances, which range between -0.6 and -1.5 mw.e., indicating different dominating mechanisms. Finally, we assessed the spatio-temporal variability of seasonal mass balance to gain in-depth insights into the relation between glacier mass balance and the driving climatic factors in the Swiss Alps.