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Scientists Warn of Melting Ice Sheet, Rising Sea Level – WSJ.com

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Scientists Warn of Melting Ice Sheet, Rising Sea Level

Melt Happening Faster Than Expected; Researchers Point to Broad Climate Change as Cause

 

By

Robert Lee Hotz

Updated May 12, 2014 7:34 p.m. ET

Thwaites Glacier is one of the six rapidly melting glaciers leading to the shrinking of the West Antarctic Ice Sheet. AFP/Getty Images

Six rapidly melting glaciers in Antarctica are destabilizing one of the world’s largest ice sheets, a process which, if unchecked, could release enough water to raise sea levels world-wide significantly in centuries to come, two groups of scientists said Monday.

On the basis of decades of satellite measurements and aircraft observations, researchers at the National Aeronautics and Space Administration’s Jet Propulsion Laboratory and the University of California at Irvine calculated that the glaciers’ retreat may have already “reached the point of no return.”

An ice sheet is part of a vast, continent-size ice cap—often miles thick—that is drained by flowing glaciers the way a lake is drained by streams.

By themselves, the Antarctic coastal glaciers already contribute as much to sea-level rise every year as, for example, the melting Greenland ice sheet in the Arctic. All told, melt water from the Antarctic glaciers could raise sea level by four feet, the researchers said at a news conference held by NASA. Their findings have been accepted for publication in Geophysical Research Letters.

“Ice is going to retreat in this sector for decades and centuries to come and we can’t stop it,” said NASA glaciologist Eric Rignot, who led the study. “It is quite likely the retreat of these glaciers will accelerate in the future rather than slow down.”

The researchers said that the rapid melting was caused by broad patterns of climate change, including rising regional temperatures, warming ocean currents, and changing wind patterns.

In recent years, overall global surface temperatures haven’t risen as quickly as in the past, even as emissions of so-called greenhouse gases have continued to grow, leading some skeptics to suggest that global warming has already peaked. In their view, predictions of dire future climate consequences—such as the ice melts and sea-level rises projected in the latest findings —are overblown.

In all, Antarctica holds about 60% of the planet’s fresh water, locked into the millions of cubic miles of polar ice. Polar-ice experts worry about how the changes in these glaciers will affect the stability of the continent’s vast West Antarctic Ice Sheet, which contains enough fresh water in its ice to increase sea levels around the world by 10 feet or so.

Until now, polar experts were confident that the coastal glaciers, which were anchored to the sea floor, held the ice sheet in place. As the glaciers have been undercut in recent years by warming ocean water, they have floated free of the sea bottom and melted more rapidly.

Dr. Rignot and his colleagues relied on radar observations captured between 1992 and 2011 by the European Earth Remote Sensing satellites to track the ice. The Pine Island Glacier, for example, retreated 19 miles since 2005, according to the researchers, while the Smith and Kohler glaciers retreated 21 miles inland.

“In West Antarctica, the situation is particularly bad,” said Sridhar Anandakrishnan, a glaciologist at Pennsylvania State University, who has studied the ice sheet but wasn’t involved in the current research. “The ice is flowing faster, which puts more water into the ocean.”

That makes the entire region unstable, according to the scientists.

In an independent computer study released Monday, researchers at the University of Washington concluded that the coastal melting may have already set in motion the slow collapse of the West Antarctic ice sheet.

By their calculations, to be published this week in Science, it could take from 200 to 900 years for the entire ice sheet to melt, they said.

via Scientists Warn of Melting Ice Sheet, Rising Sea Level – WSJ.com.