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Arctic Sea-Ice Shrinking while Antarctic Sea-Ice Grows

Satellite sea-ice measurements have revealed dramatic changes in sea-ice cover over the past 35 years. “The late-summer Arctic sea-ice coverage has shrunk by three million square kilometres since 1979,” said lead investigator Prof Ian Simmonds of the University of Melbourne.

“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.

“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,” Simmonds said.

Overall, however, sea-ice around the world is shrinking by about 35,000 km2/year, which is concerning 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,” Simmonds said. “There is strong evidence to indicate changes in the concentration of greenhouse gases in the atmosphere are leading to region-specific changes in climate.

“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 study was published in the Annals of Glaciology.