Thursday, January 14, 2010

Antarctic Circumpolar Current

Winds and wave heights have decreased and we are now back on track at 55 degrees South, with the ship pointing southwestward at 8 knots. We are now entering the realm of the Antarctic Circumpolar Current, a strong westward flowing current, driven by the westerlies. The westerlies are winds caused by air flowing from the subtropical highs to the low pressure cells at the Polar Frontal Zone. The winds are diverted westward by the Coriolis force. In contrast, cold katabatic winds that descend northward from the high pressure cells centered above the Antarctic ice sheet are diverted eastward, and drive the polar current near the coastline of Antarctica (large blue arrows). Here in the Antarctic Polar Frontal Zone the surface water temperatures decrease rapidly: we should be seeing icebergs soon....

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