The Response of the North Atlantic to the Increasing Greenland Ice Sheet Melting: Simulations with a Very High Resolution Ocean Model

The Greenland Ice sheet (GrIS) has experienced an increasing mass loss since the 1990s, consistent with the warming of the Arctic atmosphere in response to global warming. The enhanced freshwater (FW) flux due to both surface melt and outlet glacier discharge has contributed to the acceleration in global sea level rise in the recent decades, and has become an important influence on the changing FW budget of the subarctic Atlantic. There is a concern that increasing FW fluxes from Greenland may strengthen the decline of the Atlantic meridional overturning circulation (AMOC) expected from the projected increases in high latitude temperature and precipitation. However, our understanding of the oceanic response to the actual acceleration in Greenland melting is limited due to idealizations in the FW forcing scenarios and lack of spatial resolution used in previous ocean climate model studies. Here we present an assessment of the impact of the spatially distributed increases in FW fluxes obtained from a recent reconstruction, using a global ocean circulation model with a grid spacing fine enough (about 3 km) to capture the small-scale, eddying transport processes in the subpolar North Atlantic. The model simulations suggests that the invasion of meltwater from the West Greenland shelf has initiated a gradual freshening trend at the surface of the Labrador Sea which will begin to dampen the deep winter convection in the next years; however, the impact on the AMOC will remain small compared to its natural interannual variability at least until the end of the decade. The results imply that reliable projections of the oceanic response to a possible future acceleration of the GrIS melting needs to account for a realistic representation of both the FW input scenario and the ocean transport processes.