From process-based snow modelling to spatially distributed glacier mass balance estimates

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.