Greenland meltwater will slow circulation in the Atlantic, climate model suggests

The key freshwater inputs that drive the Atlantic meridional circulation (AMOC) slowdown and their climate responses remain inconclusive. Using a state-of-the-art global climate model, we conduct freshwater experiments to re-examine the sensitivity of the AMOC and its climate impacts. The Irminger Basin appears to be the most effective area for additional freshwater inflows, causing the greatest weakening of the AMOC. While global temperature and precipitation responses are relatively homogeneous, subcontinental responses—especially in the northern midlatitudes—are heterogeneous. At high latitudes, temperature changes determine the response of sea ice to freshwater fluxes and associated ice-albedo feedbacks. In tropical and extratropical regions, temperature dynamics are shaped by atmospheric circulation and oceanic heat transfer. Precipitation shows seasonal and regional variability due to altered surface turbulent heat flux and the southward movement of the Intertropical Convergence Zone (ITCZ). The extensive heterogeneity in climate extremes underscores the need to monitor areas of freshwater release associated with AMOC deceleration. These findings have major implications for understanding paleoclimate and the future impacts of the AMOC. (Qiyun Ma,  Xiaoxu Shi, Monica Ionita, more at science.org)