Strong winds may contribute to more sea ice in Antarctica

Stronger winds could explain the growth of sea ice in Antarctica, a University of Washington researcher says. A new modeling study to be published in the Journal of Climate indicates stronger polar winds lead to an increase in Antarctic sea ice, even in a warming climate, the Seattle university said Tuesday in a release. "The overwhelming evidence is that the Southern Ocean is warming," author Jinlun Zhang, an oceanographer at the university's Applied Physics Laboratory, said in the release. "Why would sea ice be increasing? Although the rate of increase is small, it is a puzzle to scientists." Zhang said his study indicates stronger westerly winds swirling around the South Pole could explain 80 percent of the increase in Antarctic sea ice volume over the past 30 years. The polar vortex swirling around the South Pole is not just stronger than it was when satellite records began in the 1970s, it has more convergence, meaning it pushes the sea ice together to cause ridging, Zhang said. Stronger winds also drive ice faster, which leads to more deformation and ridging and creates thicker, longer-lasting ice while exposing nearby water and thin ice to the cold winds that cause more ice growth. In a computer simulation that included interactions between wind and sea, the thick ice increased by about 1 percent a year from 1979 to 2010, while the amount of thin ice remained fairly constant, Zhang said. "You've got more thick ice, more ridged ice, and at the same time you will get more ice extent because the ice just survives longer," Zhang said.