Monday, March 29, 2010

Polar extremes

The arctic is warming, a lot! Antarctica as a whole is not warming like the arctic. Why the difference?

The arctic is mostly ocean covered in floating ice. It is warming faster than most other places on earth and the sea ice is rapidly melting.

Antarctica is the driest continent on earth. The climate there has been significantly modified by the ozone hole. It's not warming as fast as the arctic, but the glacial melt is contributing to rising sea levels, and could realistically add more than one metre to sea levels within the next 90 years.

Ozone declined rapidly last century and is only now stabilising. It is expected to largely recover to 1980 levels by the middle of this century.

The depletion of ozone has changed the polar vortex, which extends from the surface to the stratosphere and follows the earth's contour lines at the south pole. The loss of ozone from 1980 onwards strengthened the polar vortex winds by 15%. The winds driven by the ozone hole are shielding eastern Antarctica from the warming that is affecting the rest of the world. However, the winds transfer down to the surface and are carrying warm air to western Antarctica, where glaciers are melting.

Low pressure cells over the Amundsen Sea are forcing up deep water, which is warmer than 1°C. This warmer water is getting in under the Pine Island Glacier and melting it from below.

Of 244 Antarctic Peninsula glaciers, 87% have retreated over the last 50 years.

For a comprehensive and up-to-date reading on the Antarctic, see the Turner et al SCAR report of Antarctic Climate Change and the Environment, which was released in November 2009.

A recent slide presentation (Feb 2010) based largely on the above report can be seen here.

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