Heat-bearing westerly winds have picked up speed in the past 50 years are likely to be contributing to the melting of Antarctica's Larsen ice shelf, say scientists. Meteorologist Professor John Turner of the British Antarctic Survey says the biggest change in the wind speed occurs in the southern hemisphere summer. "The ice there
is melted most in summer and that is the season when the winds are increased," says Turner, who gave a keynote talk at the Scientific Committee on Antarctic Research meeting in Hobart this week.
Antarctica generally has lower temperatures and pressures than areas at more northern latitudes, like Australia. This differential generates storms that take warm air south and cold air north.
Turner says that over the past 50 years the differential appears to have increased, and this has increased the speed of westerly winds over the Southern Ocean by an average of a few knots. The increase in speed means the westerlies are now blowing over the Antarctic Peninsula rather than around it, bringing destructive warm air onto the Larsen ice shelf to the east of the peninsula, says Turner.
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While the pressure and temperature differential between Antarctica and more northern latitudes goes up and down in natural cycles, Turner says climate models suggest recent changes are "exceptional" when compared to the past 1000 years. "What we've seen over the last 50 years is larger than anything in these models," he says. "That suggests that man is playing a part in this." Turner says an increase in the speed of westerlies ties in with the prediction of more extreme storms in a warming world.
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http://www.abc.net.au/science/news/stories/s1686723.htm
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