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Friday, February 13, 2009

Collapse of Ice Sheet would Shift the Rotation Axis of Earth

Geophysicists from the University of Toronto in Canada say that it is the coastlines of North America and the nations in the southern Indian Ocean in particular that face the greatest threats from sea level rises if there is a complete collapse of the West Antarctica Ice Sheet, according to their recent study.

The West Antarctic Ice Sheet.

If the West Antarctic Ice Sheet collapses, the rise in sea levels around many coastal regions will be as much as 25 per cent more than expected, for a total of between six and seven metres if the whole ice sheet melts,” says Jerry Mitrovica, a geophysicist.

Why is that?

1. If the West Antarctic Ice Sheet collapses, sea level will fall close to the Antarctic and will rise much more than the expected estimate in the northern hemisphere because when an ice sheet melts, its gravitational pull on the ocean is reduced and water moves away from it.

2. If the ice sheet collapses the depression (hole) in the Antarctic bedrock that sits under the ice sheet will fill with water. But, as the ice disappears, the hole will shrink as the region rebounds from the loss of ice, which will force some of the water out into the ocean.

3. The collapse of the ice sheet will cause the earth's rotation axis to shift 500 meters from its present condition, which will move water from the southern Atlantic and Pacific oceans northward toward North America and into the southern Indian Ocean.

There is still some question as to how much ice would actually disappear if the whole sheet collapses, but even still, the researchers state that the sea-level rise that would occur at many populated coastal sites would be much larger than one would estimate by simply distributing the meltwater evenly.

There is a link to an illustration of the process at the bottom of the University of Toronto press release.

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