We show by using a three-dimensional climate model, which includes a comprehensive representation of polar ice sheets, that on centennial to millennial time scales Antarctic Ice Sheet (AIS) can melt and moderate warming in the Southern Hemisphere, by up to 10°C regionally, in a 4 × CO₂ scenario. This behaviour stems from the formation of a cold halocline in the Southern Ocean, which limits sea-ice cover retreat under global warming and increases surface albedo, reducing local surface warming. Furthermore, we show that AIS melting, by decreasing Antarctic Bottom Water formation, restrains the weakening of the Atlantic meridional overturning circulation, which is a new illustration of the effect of the bi-polar oceanic seesaw. Consequently, it appears that AIS melting strongly interacts with climate and ocean circulation globally. It is therefore necessary to account for this coupling in future climate and sea-level rise scenarios.