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Politics : Formerly About Advanced Micro Devices
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To: TimF who wrote (358529)11/14/2007 4:11:53 PM
From: longnshort   of 1573132
 
Ocean Circulation Influence on Arctic Climate Underestimated
Interesting report just released from NASA Tuesday............

A team of NASA and University of Washington scientists have detected an ongoing reversal in the Arctic Ocean circulation which is triggered by atmospheric circulation changes that vary on decade-long time scales. What does this mean? It means that the scientists have determined that not all off the large changes in the Arctic climate that we have seen in recent years are a result of long-term trends associated with global warming.

The study was done by looking at data from 2002-2006 which measured changes in weight of columns of Arctic Ocean water from the surface to the bottom. The weight is influenced by factors such as the height of the ocean's surface and its salinity. A saltier ocean is heavier and circulates differently than one with less salt.

The results of the study suggested that the Arctic Ocean circulation (AO) changed from the counter-clockwise pattern exhibited in the 1990s to the clockwise pattern, which by the way was the dominant circulation prior to 1990. The authors of the study attributed the reversal to a weakened AO, which is a large atmospheric circulation pattern in the far northern hemisphere. The weakening AO reduced the salinity of the upper ocean near the north pole, decreasing its weight and thus changing the ocean's circulation.

"Our study confirms many changes seen in upper Arctic Ocean circulation in the 1990s were mostly decadal in nature, rather than trends caused by global warming," said team leader James Morison.

"The winter of 2006-2007 was another high AO year and summer sea ice extent reached a new minimum," he said. "It is too early to say, but it looks as though the Arctic Ocean is ready to start swinging back to the counterclockwise circulation pattern of the 1990s again."

Here is the link to the story on the NASA news website. It is worth the read, as I only touched on a few of the points.
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