Impact of Greenland Ice Sheet disintegration on atmosphere and ocean disentangled

Abstract. We analyze the impact of a disintegrated Greenland Ice Sheet (GrIS) on the climate through steady-state simulations with the global Max Planck Institute for Meteorology Earth System Model (MPI-ESM). This advances our understanding of the intricate feedbacks between the GrIS and the full climate system. Sensitivity experiments enable the quantification of the individual contributions of altered Greenland surface elevation and properties (e.g., land cover) to the atmospheric and oceanic climate response. Removing the GrIS results in reduced mechanical atmospheric blocking, warmer air temperatures over Greenland and thereby changes in the atmospheric circulation. The latter alters the wind stress on the ocean, which controls the ocean-mass transport through the Arctic gateways. Without the GrIS, the upper Nordic Seas are fresher, attenuating deep-water formation. In the Labrador Sea, deep-water formation is weaker despite a higher upper-ocean salinity, as the inflow of dense overflow from the Denmark Strait is reduced. Our sensitivity experiments show that the atmospheric response is primarily driven by the lower surface elevation. The lower Greenland elevation dominates the ocean response through wind-stress changes. Only in the Labrador Sea do altered Greenland surface properties dominate the ocean response, as this region stores excessive heat from the Greenland warming. The main drivers vary vertically: the elevation effect controls upper-ocean densities, while surface properties are important for the intermediate and deep ocean. Despite the confinement of most responses to the Arctic, a disintegrated GrIS also influences remote climates, such as air temperatures in Europe, the Atlantic Meridional Overturning Circulation (AMOC) and the subtropical gyre. These interactions and feedbacks between ice sheets and the other climate components highlight the necessity of including dynamic ice sheets in climate models that are used for future projections.