Modelling the impacts of historical and future extreme precipitation days on seasonal surface mass balance in the Eastern Canadian Arctic and Greenland

Abstract. Land ice in the Arctic is losing mass as temperatures increase, contributing to global sea level rise. While this loss is largely driven by melt induced by atmospheric warming, precipitation can alter the rate at which loss occurs depending on its intensity and phase. Case studies have illustrated varied potential impacts of extreme precipitation events on the surface mass balance (SMB) of land ice, but the importance of extreme precipitation to seasonal SMB has not been investigated. In this study, simulations from the Regional Atmospheric Climate Model (RACMO) and Variable-Resolution Community Earth System Model (VR-CESM) are explored over historical (1980–1998) and future (2080–2098, SSP5-8.5) periods to reconstruct and further project seasonal SMB for the Greenland Ice Sheet and ice caps of the Eastern Canadian Arctic. Historically, extreme precipitation days consistently had higher SMB than non-extreme precipitation days throughout the study area in both the cold season (DJFM) and warm season (JJAS). In future simulations, this relationship persists for the cold season. However, for the warm season, projections indicate a shift towards less positive and more variable SMB responses to extreme precipitation days in the future, accounting for a larger portion of cumulative seasonal positive and negative SMB. Mass loss during extreme precipitation days becomes more common, particularly in SW Greenland and Baffin Island. This likely occurs in part because of a shift toward more rainfall during extreme precipitation events. In other words, in a strong warming scenario, extreme warm season precipitation may no longer reliably yield mass gain for the Greenland Ice Sheet and surrounding ice caps.