Mitigation-driven global heat imbalance in the late 21st century

Abstract

While the changes in ocean heat uptake in a warming climate have been well explored, the changes in response to climate mitigation efforts remain unclear. Using coupled climate model simulations, here we find that in response to a hypothesized reduction of greenhouse gases in the late 21st century, ocean heat uptake would significantly decline in all ocean basins except the North Atlantic, where a persistently weakened Atlantic meridional overturning circulation results in sustained heat uptake. These prolonged circulation anomalies further lead to interbasin heat exchanges, characterized by a sustained heat export from the Atlantic to the Southern Ocean and a portion of heat transfer from the Southern Ocean to the Indo-Pacific. Due to ocean heat uptake decline and interbasin heat export, the Southern Ocean experiences the strongest decline in ocean heat storage therefore emerging as the primary heat exchanger, while heat changes in the Indo-Pacific basin are relatively limited. Climate mitigation efforts will decrease ocean heat uptake in all ocean basins, except the North Atlantic, where weakened Atlantic Meridional Overturning Circulation leads to sustained heat uptake, according to results from climate simulations to analyze changes in global ocean heat due to a projected greenhouse gas reduction.