The role of an interactive Greenland ice sheet in the coupled climate-ice sheet model EC-Earth-PISM

Abstract

AbstractIce sheet processes are often simplified in global climate models as changes in ice sheets have been assumed to occur over long time scales compared to ocean and atmospheric changes. However, numerous observations show an increasing rate of mass loss from the Greenland Ice Sheet and call for comprehensive process-based models to explore its role in climate change. Here, we present a new model system, EC-Earth-PISM, that includes an interactive Greenland Ice Sheet. The model is based on the EC-Earth v2.3 global climate model in which ice sheet surface processes are introduced. This model interacts with the Parallel Ice Sheet Model (PISM) without anomaly or flux corrections. Under pre-industrial climate conditions, the modeled climate and ice sheet are stable while keeping a realistic interannual variability. In model simulations forced into a warmer climate of four times the pre-industrial CO2 concentration, the total surface mass balance decreases and the ice sheet loses mass at a rate of about 500 Gt/year. In the climate warming experiments, the resulting freshwater flux from the Greenland Ice Sheet increases 55% more in the experiments with the interactive ice sheet and the climate response is significantly different: the Arctic near-surface air temperature is lower, substantially more winter sea ice covers the northern hemisphere, and the ocean circulation is weaker. Our results indicate that the melt-albedo feedback plays a key role for the response of the ice sheet and its influence on the changing climate in the Arctic. This emphasizes the importance of including interactive ice sheets in climate change projections.