Modelling the future evolution of an alpine debris-covered glacier

Debris-covered glaciers can react differently to external forcings than clean-surface glaciers. Depending on its thickness, a supraglacial debris layer impacts the glacier mass balance by either enhancing the surface melt or protecting the underlying ice. Based on previous works focusing on simple flowline geometries, we extended the model setup to three-dimensional complex geometries. The framework is implemented using the Ice-sheet and Sea-level System Model (ISSM) and applied to a typical alpine glacier geometry. Ice dynamics are solved on high-resolution with full-Stokes and coupled to the surface debris transport equation. The employed surface mass balance (SMB) model is capable of describing the melt rate for all debris thicknesses by including turbulent fluxes within the upper debris cover. This SMB formulation resolves the enhanced melt rates for a thin debris cover as well as the decreasing melt rates for thickening debris. To test the sensitivity of future projections of alpine glaciers on the debris layer, simulations are forced with high-resolution regional climate model (RCM) data from the EURO-CORDEX ensemble (RCP2.6 and RCP8.5).