| blt |
| (Cartographer) |
| 11/18/07 07:49 PM |
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Re: Update - Arctic currents data
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As we noted above, the radical drop in Arctic sea ice extent during the summer of 2007 exceeded the predictions of current climate models implying that something beyond simple warming was at work. New information about Arctic currents has been released by the Polar Science Center at the University of Washington. They report that unusual currents indeed have been at play and they are part of a decade long oscillation between clockwise and counter clockwise currents in the Arctic. The paper makes no claims if this oscillation explains the record levels of loss of Arctic Sea ice.
From a NASA news release
Quote:
The distribution and size of the [data] suggest that Arctic Ocean circulation changed from the counterclockwise pattern it exhibited in the 1990s to the clockwise pattern that was dominant prior to 1990. Reporting in Geophysical Research Letters, the authors attribute the reversal to a weakened Arctic Oscillation, a major atmospheric circulation pattern in the northern hemisphere. The weakening reduced the salinity of the upper ocean near the North Pole, decreasing its weight and changing its 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 Morison.
"While some 1990s climate trends, such as declines in Arctic sea ice extent, have continued, these results suggest at least for the 'wet' part of the Arctic -- the Arctic Ocean -- circulation reverted to conditions like those prevalent before the 1990s," he added.
Fortunately 2007 is international Polar Year: 2007 - 2008 and significant data has been collected which may document the causes of the sea ice decline more concretely.
The chart below shows contours of the trend in ocean bottom pressure from 2002 to 2006. Apparently this may signal a shift to colder conditions in future.
