The Role of a Weakened Atlantic Meridional Overturning Circulation in Modulating Marine Heatwaves in a Warming Climate

Abstract

AbstractWe explore the effect of Atlantic meridional overturning circulation (AMOC) slowdown on global marine heatwaves (MHWs) under anthropogenic warming by maintaining AMOC strength in climate model simulations throughout the 21st century. The AMOC slowdown has an insignificant effect on global MHWs during the past four decades, except those over the North Atlantic warming hole (NAWH) where the weakened AMOC reduces the occurrence and duration of MHWs by about half by creating a cooler mean‐state sea surface temperature. As the AMOC continues weakening in current century, its effect becomes significant on MHWs in the North Atlantic and Pacific Oceans. The weakened AMOC induces a bipolar‐seesaw‐like change in MHW frequencies, with more frequent MHWs in the Southern Hemisphere but less frequent MHWs in the North Hemisphere except over the NAWH. The reason for the exception is that the NAWH region would enter a near‐permanent MHW state without an AMOC slowdown.