Brief communication: Impact of the recent atmospheric circulation
change in summer on the future surface mass balance of the
Greenland ice sheet
Abstract. Since the 2000's, a change in the atmospheric circulation over North Atlantic has favored warmer and sunnier weather conditions over the Greenland Ice sheet (GrIS) in summer enhancing the melt increase. This circulation change is not represented by General Circulation Models (GCMs) of the 5th Coupled Model Intercomparison Project (CMIP5) which do not predict any circulation change for the next century over the Atlantic. The goal of this study is to evaluate the impact of an atmospheric circulation change (as currently observed) in a warmer climate on future projections of the GrIS surface mass balance (SMB). We compare GrIS SMB estimates from the regional climate model MAR forced by warmer reanalysis (ERA-Interim with a temperature correction of +1 °C, +1.5 °C and +2 °C at the MAR lateral boundaries) over 1980–2016 to future projections of GrIS SMB from MAR simulations forced with three GCMs over a future period for which a similar temperature increase of +1 °C, +1.5 °C and +2 °C is projected by the GCMs in comparison to 1980–1999. Mean SMB anomalies produced with warmer reanalysis over the climatologically stable period 1980–1999 is similar to those produced with MAR forced with GCMs over future periods characterized by a similar warming over Greenland. However, over the two last decades (2000–2016) when a circulation change has been observed in summer, MAR forced with warmer reanalysis suggests that the SMB decrease could be amplified by a factor of two if such atmospheric conditions will persist compared to future projections forced by GCMs for the same temperature increase but without any circulation change.