Washington: Despite warmer air and oceans, there`s more sea ice in Antarctica now than in the 1970s, a new study suggests.
The latest numbers suggest that the Antarctic sea ice may be heading toward a record high this year.
While changes in weather may play a big role in short-term changes in sea ice seen in the past couple of months, changes in winds have apparently led to the more general upward sea ice trend during the past few decades, according to University of Washington research.
The new modeling study shows that stronger polar winds lead to an increase in Antarctic sea ice, even in a warming climate.
"The overwhelming evidence is that the Southern Ocean is warming," author Jinlun Zhang, an oceanographer at the UW Applied Physics Laboratory, said.
"Why would sea ice be increasing? Although the rate of increase is small, it is a puzzle to scientists," the researcher said.
His new study shows that stronger westerly winds swirling around the South Pole can explain 80 percent of the increase in Antarctic sea ice volume in the past three decades.
The polar vortex that swirls around the South Pole is not just stronger than it was when satellite records began in the 1970s, it has more convergence, meaning it shoves the sea ice together to cause ridging.
Stronger winds also drive ice faster, which leads to still more deformation and ridging.
This creates thicker, longer-lasting ice, while exposing surrounding water and thin ice to the blistering cold winds that cause more ice growth.
In a computer simulation that includes detailed interactions between wind and sea, thick ice - more than 6 feet deep - increased by about 1 percent per year from 1979 to 2010, while the amount of thin ice stayed fairly constant.
The end result is a thicker, slightly larger ice pack that lasts longer into the summer.
The study is set to be published in the Journal of Climate.