Leading role of outer-Arctic circulation transport in AMOC response to global warming over a century

Abstract

Abstract Using the Alfred Wegener Institute Climate Model (AWI-CM 1.1 LR), we explored how Arctic and extra-Arctic warming affect the response of Atlantic meridional overturning circulation (AMOC) to quadruple carbon dioxide (4 × CO2) forcing. The results suggest that AMOC weakening is mainly affected by circulation adjustment caused by extra-Arctic warming, while Arctic warming has a limited local impact and a relatively small contribution to AMOC weakening. Due to the warming outside the Arctic, the increase in northward advective heat transport dominates the weakening of deep convection in Nordic Seas. While in the Labrador Sea, the decrease in advection heat transport is compensated by a more significant decrease in ocean heat loss to the atmosphere, leading to an enhancement of the upper ocean stratification. Besides, the weakening of deep convection associated with AMOC response under global warming is more pronounced in Nordic Seas than in Labrador Sea.