File:Puzzle arctic sea ice extents.gif

Summary

These maps of the Northern Hemisphere show the nine regions that were studied by Claire Parkinson of NASA's Goddard Space Flight Center for trend changes in the sea ice cover before and after 1990, when the North Atlantic Oscillation reached a peak in its annual index. The nine regions are: the Arctic Ocean; the Kara and Barents Seas; the Greenland Sea; Baffin Bay/Labrador Sea; the Gulf of St. Lawrence; Hudson Bay; the Bering Sea; the Canadian Archipelago; and the Seas of Okhotsk and Japan.

The white color indicates an expansion in the ice cover in a particular region, while the light blue color depicts a reduction in total ice cover.

The first map depicts the period from1979 to1990 when the North Atlantic Oscillation annual index was generally increasing. This meant an increasing amount of cold air spilling west and south around the semi-permanent Icelandic Low, leading to increased extent of ice (in white) in Baffin Bay/Labrador Sea, Hudson Bay, and the Gulf of St. Lawrence over those regions. Over the same period, to the east of the Low's center, more and more warm air was swept up from the south, reducing ice over the Kara and Barents Seas, the Arctic Ocean, and, to a lesser extent, the Greenland Sea, as designated by the light blue color over those regions.

Conversely, in the second map showing the period from 1990 to 1999, ice cover decreased (depicted in light blue) in Baffin Bay/Labrador Sea, Hudson Bay, and the Gulf of St. Lawrence, but increased (in white) in the Kara and Barents Seas, the Arctic Ocean, and the Greenland Sea.

"This regional pattern of reversals in the ice extent trends is highly suggestive of an Icelandic Low impact, or, more broadly, of an impact from the North Atlantic Oscillation," Parkinson said. "Still, the satellite data reveal an overall decrease in Arctic sea ice extent since 1978."

http://www.gsfc.nasa.gov/topstory/20011001icepuzzle.html

Uploaded by Piotr Flatau

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