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Explaining the Weddell Polynya--a Large Ocean Eddy Shed at Maud Rise

Science  01 Jun 2001:
Vol. 292, Issue 5522, pp. 1697-1700
DOI: 10.1126/science.1059322

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Abstract

Satellite observations have shown the occasional occurrence of a large opening in the sea-ice cover of the Weddell Sea, Antarctica, a phenomenon known as the Weddell Polynya. The transient appearance, position, size, and shape of the polynya is explained here by a mechanism by which modest variations in the large-scale oceanic flow past the Maud Rise seamount cause a horizontal cyclonic eddy to be shed from its northeast flank. The shed eddy transmits a divergent Ekman stress into the sea ice, leading to a crescent-shaped opening in the pack. Atmospheric thermodynamical interaction further enhances the opening by inducing oceanic convection. A sea-ice–ocean computer model simulation vividly demonstrates how this mechanism fully accounts for the characteristics that mark Weddell Polynya events.

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