Why sea ice grows at one pole, but shrinks at the other

While Antarctic sea ice has been expanding at a record-setting pace, sea ice around the world is shrinking by about 35,000 square kilometers a year. "It seems counterintuitive, but the growth in the Antarctic sea ice is consistent with global warming and the effects of increased atmospheric carbon dioxide," says Ian Simmonds. (Credit: Michael Studinger/NASA Earth Observatory)

There have been dramatic, yet differing, changes in sea ice cover at the poles over the past 35 years, according to a new analysis of satellite images.

“The late-summer Arctic sea ice coverage has shrunk by 3 million square kilometers since 1979,” says lead investigator Ian Simmonds, a¬†professor in the School of Earth Sciences at the University of Melbourne.
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“There were significant decreases for every month of the year, with the greatest rate of decrease in September. Some are now suggesting that September sea ice could disappear from the Arctic in as little as 25 years,” adds Simmonds.

“In contrast, Antarctic sea ice has been expanding, and 2013 was a record-breaking year. In September, we saw the greatest coverage of sea ice since satellite records started in 1979.”

Overall, however, sea ice around the world is shrinking by about 35,000 square kilometers a year. These dramatic changes are of concern as the polar regions influence global climate patterns.

“It seems counterintuitive, but the growth in the Antarctic sea ice is consistent with global warming and the effects of increased atmospheric carbon dioxide. There is strong evidence to indicate changes in the concentration of greenhouse gases in the atmosphere are leading to region-specific changes in climate,” Simmonds explains.

“The greenhouse effect is strengthening the westerlies over the Southern Ocean and this could be causing the increase in the Antarctic sea ice zone. Ultimately ocean warming will counteract this but it may be a number of years before that takes place.”

The new analysis is detailed in a paper published in the Annals of Glaciology.

Source: University of Melbourne