Tropical climate responses to projected Arctic and Antarctic sea-ice loss

Abstract

Arctic and Antarctic sea-ice extent are both projected to dramatically decline over the coming century. The effects of Arctic sea-ice loss are not limited to the northern high latitudes, and reach deep into the tropics. Yet little is known about the effects of future Antarctic sea-ice loss outside of the southern high latitudes. Here, using a fully coupled climate model, we investigate the tropical response to Antarctic sea-ice loss and compare it with the response to Arctic sea-ice loss. We show that Antarctic sea-ice loss, similar to Arctic sea-ice loss, causes enhanced warming in the eastern equatorial Pacific and an equatorward intensification of the Intertropical Convergence Zone. We demonstrate that Antarctic sea-ice loss causes a mini global warming signal comparable to the one caused by Arctic sea-ice loss, and reminiscent of the response to greenhouse gases. We also show that ocean dynamics are key to capturing the tropical response to sea-ice loss. In short, we find that future Antarctic sea-ice loss will exert a profound influence on the tropics. Combined Arctic and Antarctic sea-ice losses will account for 20–30% of the projected tropical warming and precipitation changes under the high-emissions scenario Representative Concentration Pathway 8.5. Antarctic sea-ice loss causes enhanced warming in the eastern equatorial Pacific, and together with Arctic sea-ice loss accounts for 20–30% of projected warming and rainfall changes in the tropics, suggest climate model simulations.