Spatial Variability in Winter Balance on Storglaciären Modelled With a Coupled Terrain Based Approach

Abstract: Although most processes governing the surface mass balance on mountain glaciers are well understood, the causes and extent of spatial variability in accumulation remain poorly constrained. In the present study, the EBFM distributed mass balance model is newly coupled to terrain based modelling routines estimating mass redistribution by snowdrift, preferential deposition, and avalanching (ST-EBFM) in order to model winter balance on Storglaciären, Sweden. STEBFM improves the spatial accuracy of winter balance simulations and proves to be a versatile and computationally inexpensive model. Accumulation on Storglaciären is primarily driven by direct precipitation, which seems locally increased due to small scale orographic effects. Wind driven snow transport leads to significant deposition in the accumulation zone and slight erosion in the ablation zone. The pattern is generally consistent from year to year. Avalanching is the smallest contributor to winter balance, but cannot be neglected. The physical complexity of avalanches and high year to year variability render simulations of the process somewhat uncertain, but observations seem to confirm the large impact that the process can have on the glacier at very localised scales. The role of mass transporting processes in maintaining the current mass equilibrium on Storglaciären highlights the necessity to understand the links between climatic predictors and accumulation in order to accurately assess climate sensitivity.