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3/22/2007

Southern Ocean current faces slowdown threat

Breaking Earth News: Antarctica


Global Warming Alert
March 22, 2007

Photo: Ice on the surface of the southern ocean off the Antarctic coast is seen from the window of a U.S. military plane flying from Christchurch, New Zealand, to McMurdo Station, the biggest U.S. science base in Antarctica, in this December 7, 2006 file photo. The impact of global warming on the vast Southern Ocean around Antarctica is starting to pose a threat to ocean currents that distribute heat around the world, Australian scientists say, citing new deep-water data. (Deborah Zabarenko/Reuters)


Report
HOBART (Reuters) - The impact of global warming on the vast Southern Ocean around Antarctica is starting to pose a threat to ocean currents that distribute heat around the world, Australian scientists say, citing new deep-water data.
Melting ice-sheets and glaciers in Antarctica are releasing fresh water, interfering with the formation of dense "bottom water," which sinks 4-5 kilometers to the ocean floor and helps drive the world's ocean circulation system.
A slowdown in the system known as "overturning circulation" would affect the way the ocean, which absorbs 85 percent of atmospheric heat, carries heat around the globe.
"If the water gets fresh enough ... then it won't matter how much ice we form, we won't be able to make this water cold and salty enough to sink," said Steve Rintoul, a senior scientist at the Australian government-funded CSIRO Marine Science.
"Changes would be felt ... around the globe," said Rintoul, who recently led a multinational team of scientists on an expedition to sample deep-basin water south of Western Australia to the Antarctic.

FYI
The Great Ocean Conveyor Belt: Abrupt Climate Change?

The global ocean is not a static pond, but a body in constant motion. Winds blow across its surface, generating waves and currents, while the pull of gravity gently sloshes it back and forth in a lunar rhythm of tides. But beneath these familiar surficial motions lies an enigmatic process which has profound implications for climate: the Great Ocean Conveyor (also called the thermohaline circulation). The Conveyor is one of the great unknowns in humanity's unintentional climate change experiment.



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