Sea ice in the Arctic is disappearing quickly, but the opposite is happening in Antarctica, where the reaches of frozen water have actually been growing. Counterintuitive as it may seem, global warming is driving very different changes at each pole, cooling the south while heating the north. Two recent studies in Nature Geosciencesought to tease out which mechanisms are spurring the cooling and sea ice expansion. Richard Bintanja and colleagues at the Royal Netherlands Meteorological Institute report that deep warm water is melting ice shelves that extend from the continent; cold water from the melted ice, in turn, insulates the surface water, keeping it cooler. Yet a group led by Paul Holland of the British Antarctic Survey says that another mechanism is at work: Fierce winds blasting the South Pole are pushing the ice farther north. While the answer isn’t yet clear, the groups agree that cooler waters will mean more sea-level rise, since less moisture will evaporate. Understanding what’s driving the cooling will strengthen sea-level forecasts. Says Bintanja, “Identifying climate mechanisms helps to make these climate models more accurate.”
This story originally ran in the July-August 2013 issue as "Antarctica on the Rocks."