The Impact of Tropical Indian Ocean Warming on Southern Hemisphere Polar Climate

The impact of two distinct anthropogenic forcings on the Southern Hemisphere's (SH) polar climate is investigated using idealized climate model simulations. Consistent with previous studies, chemical constituent changes are shown to drive a cooling of the polar stratosphere during austral spring and early summer followed by an increase of tropospheric westerlies. Tropical Indian Ocean warming, itself a response to chemical constituent changes, drives a warming of the polar stratosphere and weakening of tropospheric westerlies, opposite to the local radiatively driven cooling. Our model experiments suggest that warming of the tropical Indian Ocean initiates a potent dynamical mechanism for changing high latitude climate, one that must be considered for accurate attribution of SH polar climate change.