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BirdGuano
02-07-2009, 01:12 PM
http://www.ctv.ca/servlet/ArticleNews/story/CTVNews/20090205/sea_levels_090205/20090205/

Ice shelf collapse could shift axis of Earth, study says
Updated Thu. Feb. 5 2009 2:13 PM ET

CTV.ca News Staff

A new study from Toronto researchers suggests that the collapse of a large portion of the Antarctic ice sheet would shift the very axis of the Earth.

Geophysicists at the University of Toronto explored the effects on North America and the globe, if sea levels were to rise due to the collapse of the West Antarctic Ice Sheet.

One of the most jarring predictions contained in the report, to be published in the Feb. 6 issue of the journal Science, is that the sea-change could shift the Earth's rotation.

"The melting of the West Antarctic Ice Sheet will actually cause the Earth´s rotation axis to shift rather dramatically -- approximately 500 metres from its present position if the entire ice sheet melts," states a release from U of T's physics department.

There is a widespread belief among scientists that the ice sheet is especially vulnerable to rising global temperatures, and may be prone to collapse, which could trigger a rise in sea levels.

Some analysts have predicted sea levels will rise by five metres -- a value arrived at by taking the total volume of the ice sheet, converting it to water and spreading it evenly across the globe's oceans.

But the new report suggests that is too simplistic an approach, and some areas -- North America and nations in the southern Indian Ocean in particular -- would see much higher sea-level rises than other areas.

"We´ve been able to calculate that not only will the rise in sea levels at most coastal sites be significantly higher than previously expected, but that the sea-level change will be highly variable around the globe," said physics graduate student Natalya Gomez.

The research suggests the melting of the sheet would change the balance of the globe -- similar to tsunamis that move massive amounts of water from one area to another.

Water would migrate from the southern Atlantic and Pacific Oceans northward toward North America and into the southern Indian Ocean.

"The net effect of all of these processes is that 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," said geophysicist Jerry Mitrovica.

"That´s a lot of additional water, particularly around such highly populated areas as Washington, D.C., New York City, and the California coastline."

The study pointed out three factors that are likely to have an effect on the disbursement of water from the melting shelf.

It suggests that as an ice sheet collapses, water actually moves away from it because the sheet's gravitational pull lessens. The result is that the sea level in the area of the shelf actually drops, while other areas see dramatic increases.

Secondly, the research suggests a massive depression in the bedrock that is currently underneath the ice shelf, will fill with water if the sheet collapses. But as the sheet melts and its weight disperses, the depression will rebound, thereby pushing water into other areas.

http://images.ctv.ca/archives/CTVNews/img2/20090205/160_icesheet_090205.jpg

Thirdly, the shift in the Earth's rotation will cause water north, towards North America and the Southern Indian Ocean.

The research is to be published in a paper titled "The Sea Level Fingerprint of West Antarctic Collapse."