sea levels rise worse than expected

Sea level rise may be worse than expected

1 hour ago

WASHINGTON (AP) — Melting ice from global warming may raise sea levels even more than had been expected, an analysis suggests. Long-term melting of ice in Antarctica and other areas could raise sea levels by 16 feet to 17 feet, previous studies have indicated. But a report in Friday's edition of the journal Science warns that factors not previously considered could boost that increase to up to 21 feet in some areas.

Earlier research has focused on melting ice adding water to the oceans and on thermal expansion of sea water in a warmer climate.

In the new report geophysicist Jerry X. Mitrovica and physics graduate student Natalya Gomez of the University of Toronto, Canada, and Oregon State University geoscientist Peter Clark, say other factors need to be considered.

_When an ice sheet melts, its gravitational pull on the ocean is reduced and water moves away from it. That means sea levels could fall near Antarctica and rise more than expected in the northern hemisphere.

_Antarctic bedrock that currently sits under the weight of the ice sheet will rebound from the weight, pushing some water out into the ocean.

_The melting of the West Antarctic ice sheet will cause the Earth's rotation axis to shift, potentially moving water northward.

"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," Mitrovica said in a statement.
On the Net:

* Science: http://www.sciemcemag.org

Antarctic ice sheet collapse may swamp U.S. coasts
Thu Feb 5, 2009 8:27pm GMT



By Will Dunham

WASHINGTON (Reuters) - North America's coastlines would be hit especially hard by rising sea levels if the huge West Antarctic Ice Sheet collapses and melts in a warming world as some experts fear, scientists said on Thursday.

The loss of that ice sheet alone would inundate some coastal areas, swamping New York, Washington D.C., south Florida, Los Angeles, San Francisco and Seattle, with sea levels in some places higher by 21 feet or more than today, the researchers wrote in the journal Science.

Factors including changes in the Earth's rotation from the loss of the huge ice sheet would make sea level changes highly variable around the globe, they said. The southern Indian Ocean region also would be heavily affected, they added.

"You pay the price in North America," University of Toronto geophysicist Jerry Mitrovica said in a telephone interview.

"The peak sea level rise occurs on the coasts of the United States -- the New York area and down the coast, the eastern seaboard of the United States," Mitrovica added. "On the West coast, it's even just a little bit bigger."

The West Antarctic Ice Sheet covers about 350,000 square miles (900,000 square km), the size of U.S. states Texas and Oklahoma combined. Its volume equals about 100 times the amount of water in all of North America's Great Lakes, said Natalya Gomez of the University of Toronto, another researcher.

Mitrovica said this is not imminent, but rather: "It's a time scale of hundreds of years."

The United Nations Intergovernmental Panel on Climate Change estimates a loss of the ice sheet would raise sea levels around the world on average by about 16.5 feet.