An energy balance model for the Greenland ice sheet

Abstract

The sensitivity of the mass balance of the Greenland Ice Sheet is studied by means of an energy balance model. The model calculates the shortwave and longwave radiation and the turbulent fluxes on a grid with a grid point spacing of 20 km. Special attention is given to the parameterization of the albedo. The albedo is calculated as a function of snow depth, ablation, amount of meltwater at the surface and the type of surface. The response of the model to changing climatic input is nonlinear. As a result the ablation drifts to higher values when temporal variability of input is imposed. Climate change experiments reveal a large sensitivity of the mean ablation to small changes in the temperature. A 1K rise in temperature leads to approximately 30% more ablation. Further experiments with this model suggest that the contribution of the Greenland ice sheet to past global sea level rise has been 35 ± 18 mm over the last 120 years. Applying the Bellaggio scenario as a forcing function results in a doubling of the ablation by 2100 AD. The corresponding contribution to global sea level rise is 6 cm over the period 1985-2100 AD.