Evolution of Meridional Heat Transport by Subtropical Western Boundary Currents in a Warming Climate Predicted by High-Resolution Models

Abstract

Abstract Subtropical western boundary currents (WBCs) are among the most energetic currents in the global circulation system and play an important role in the oceanic meridional heat transport (OHT). Based on nine high-resolution global coupled climate models, this study investigates the change of OHT by subtropical WBCs (WHT) under global warming. We found that WHT in both hemispheres depicts a weakening trend during 1950–2050, primarily caused by the transport change of WBCs. In the Northern Hemisphere, weakening of the Gulf Stream resulting from the slowing AMOC leads to the hemispheric WHT weakening. In the Southern Hemisphere, the WHT decrease is mainly induced by the sharp decline of Agulhas Current transport, associated with the change in wind field in the southern Indian Ocean and Indonesian Throughflow. Compared to the mean flow, the contribution of mesoscale eddies to OHT change is negligible along with WBCs but is important in their extension regions.