On the Mechanisms of Variability of the Atlantic Meridional Overturning Circulation (AMOC)

In this paper we investigate the relationship between the long-term variability of the Atlantic Meridional Overturning Circulation (AMOC) and the intensity of deep convection in the Greenland, Labrador, and Irminger seas, as well as with the intensity of wind induced upwelling in the Southern Ocean. This goal is achieved by extending the AMOC time series back to the 1950s using the AMOC ensemble index. The time variability of the intensity of deep convection over the 60-year study period is estimated using indices of deep convection, while upwelling in the Southern Ocean is estimated from the mean intensity of the divergence of Ekman transport. The contribution of each of the processes is assessed using cross-correlation and multiple regression analyses. The results suggest that during recent decades, the AMOC variations in the North Atlantic were mostly governed by the intensity of deep convection in the Irminger Sea and of upwelling in the Southern Ocean. Among these factors, the intensity of convection in the Irminger Sea has the largest impact on the observed variations in the AMOC.