Saturday, November 16, 2013

Changing winds dampen Antarctic sea-level rise

Nicola Jones in Nature: Shifting, strengthening winds will help to counteract future sea-level rise in Antarctica — and by doing so, they may help stabilize ice sheets on some parts of the southern continent.

The band of westerly winds that encircles Antarctica has been speeding up and creeping southward since the 1950s. The trend, largely driven by the Antarctic ozone hole, is expected to continue thanks to climate change — and could alone cause a drop in sea level of up to 40 cm over 70 years, according to research led by Leela Frankcombe, a geophysicist at the Centre of Excellence for Climate System Science in Sydney, Australia1.

“That’s really significant,” says Aimee Slangen, who studies sea-level variation at the Australian Commonwealth Scientific and Industrial Research Organisation in Hobart and who was not involved with the study.

Along Antarctic shores, the effect of the winds could counteract almost half of the average global sea-level rise expected by the end of the century, which the latest report of the Intergovernmental Panel on Climate Change estimates to be up to 97 cm. That report notes, however, that tens of centimetres of additional rise might be caused by the unpredictable collapse of the western Antarctic ice sheet.

The reason for the sea-level drop is the Coriolis force, a consequence of Earth's rotation. As the Antarctic Circumpolar Current flows clockwise around Antarctica, this causes sea water to slope higher to the north and lower to the south. As the westerly winds strengthen by up to 15% over the next 70 years, both the current and this slope are expected to increase...

A spectacular shot of Adelie penguins on an iceberg in the Ross Sea by Brocken Inaglory, Wikimedia Commons, under the Creative Commons Attribution-Share Alike 3.0 Unported, 2.5 Generic, 2.0 Generic and 1.0 Generic license

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