Future weakening of the Atlantic Meridional Overturning Circulation shaped by reduced Labrador Sea winds and salt transport feedback

Abstract Climate models predict a wide range of AMOC weakening, complicating future projections. Using CMIP6 data, this study finds that future AMOC weakening is strongly influenced by increased downward heat flux, especially in the Labrador Sea. Despite substantial heat uptake (10–80 Wm-2), seawater temperatures barely rise due to reduced heat transport linked to AMOC weakening. Changes in seawater temperature minimally affect density, but decreased northward salt flux associated with AMOC weakening reduces density in the Labrador Sea. CMIP6 models suggest that increased heat uptake in the Labrador Sea can initiate AMOC weakening, followed by reduced salinity. Further analysis shows that changes in surface heat flux in the Labrador Sea are dominated by turbulent heat fluxes, strongly influenced by surface winds. These findings suggest that the extent of Labrador Sea wind weakening and the associated reduction in salinity are crucial factors in explaining the future degree of AMOC weakening.