Glacial region's melt past 'point of no return,' NASA says

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Although the Amundsen Sea region is only a fraction of the whole West Antarctic Ice Sheet, NASA estimates the region contains enough ice to raise global sea levels by 4 feet.

A glacial region of western Antarctica that’s already melting rapidly has passed “the point of no return,” according to the National Aeronautics and Space Administration.
“The collapse of this sector of West Antarctica appears to be unstoppable,” Eric Rignot, a glaciologist at NASA’s Jet Propulsion Laboratory and the University of California, Irvine, said today in an e-mailed statement.
NASA estimates the glaciers, in the Amundsen Sea region, contain enough water to raise global sea levels by 4 feet (1.2 meters). United Nations researchers in September said sea levels have risen by 19 centimeters (7.5 inches) since the Industrial Revolution, and may rise an additional 26 centimeters to 98 centimeters by 2100.
“This sector will be a major contributor to sea level rise in the decades and centuries to come,” Rignot said in the statement. “A conservative estimate is it could take several centuries for all of the ice to flow into the sea.”
Rignot is lead author of a study that has been accepted for publication in the journal Geophysical Research Letters, NASA said. The team used radar observations from the two European Earth Remote Sensing satellites, ERS-1 and ERS-2, to track the movement of the “grounding lines,” the place where the floating portion of glacier meets land.
Floating ice
They determined that the glaciers have become so thin that they are now floating in areas where they used to be grounded. As the grounding lines retreat inland, there’s more space below the ice for sea water, which accelerates melting. The researchers also found the masses of ice are flowing faster toward the sea, causing further thinning.
Scientists have homed in on the West Antarctic Ice Sheet because the level of melting detected there is greater than the far bigger and more stable Eastern portion of the continent.
“The alarming thing about the glacial evidence is that the rate of change is happening at a human timeframe as opposed to a geological timeframe,” John Skalbeck, a professor of geoscience at the University of Wisconsin-Parkside, said today in a telephone interview. “It’s the rate of change that has geoscientists most alarmed. We’ve not seen these types of rates from the geological past.”
Antarctica’s ice sheets hold enough water to raise sea levels by 187 feet, according to UN estimates, though that’s not likely for thousands of years.

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