Impact of Greenland Ice Sheet Melt on the Atlantic Meridional Overturning Circulation in GFDL ESM2Mb

Abstract:

Observations show an increase in the melting of the Greenland Ice Sheet (GIS) since the early 20^th century with a significant acceleration over the past decade. Located next to two critical areas of deep water formation, the GIS has the potential to directly impact the Atlantic Meridional Overturning Circulation (AMOC) via the freshening of surface waters in these regions. All the Earth System Models part of the Coupled Model Intercomparison Project Phase 5 (CMIP5) project a significant decline in AMOC strength over the next 100 to 200 years under increased greenhouse gas concentrations; however none of these projections consider the impacts of the GIS. Previous modelling studies have investigated the response of AMOC to freshwater input in various hosing experiments, but the magnitude of the change in AMOC strength varies significantly between these studies. The uncertainty is likely a result of the wide range of experimental design, including various methods for imposing the freshwater forcing in the simulations and use of different global climate models which do not simulate realistic melt from the GIS. Here, we present results from experiments in which GFDL ESM2Mb is forced with realistic projections of freshwater discharge from the GIS under the RCP 8.5 scenario in order to investigate the impact of future melt of the GIS on the AMOC. The results presented here are a contribution to the AMOC Model Intercomparison Project (AMOCMIP), a community effort to investigate the impacts of GIS melt on AMOC.