Rapid 21st Century Weakening of the Agulhas Current in a Warming Climate

Abstract The Agulhas Current (AC) is a critical component of the global ocean circulation. Climate models consistently project the AC to decline in the 21st century. Previous studies typically attributed the weakening of AC to changes in Indian Ocean wind and/or a decline of the Indonesian Throughflow (ITF) transport. However, our analysis suggests that changes in local surface wind and ITF can only explain a portion of the model‐simulated AC changes. Using a hierarchy of models, we show that the decline of the Atlantic Meridional Overturning Circulation (AMOC) strength in a warming climate could also contribute substantially to the AC weakening. Following a weakening of the AMOC, the baroclinic structure of the AC is also modified such that the AC is shoaled to a shallower depth, communicated between basins via Kelvin waves. Our results highlight the importance of remote processes in future western boundary current changes.