First Signs of Melting Seen in East Antarctica

Earth's last great icy citadel, the East Antarctica Ice Sheet, is beginning to crumble.

Antarctica's western ice sheet has been under siege from global warming for some time, with billions of tons of ice melting into the ocean each year and contributing to sea level rise. By contrast, the east has appeared to hold out, its mass staying stable.

Now a new set of satellite measurements indicate the East may have begun to succumb to warmer temperatures, losing as much as 57 billion tons of ice a year since 2006. There is still a lot of uncertainty in the readings, but if the readings hold up under scrutiny, it would mark an important change in the world's largest ice sheet.

WATCH VIDEO: The Larsen ice shelf at the northern end of the Antarctic Peninsula experienced a dramatic collapse between January 31 and March 7, 2002.

"This could be the beginning of a trend, but whether or not it's a trend or just variability from year to year, we're not sure," Jianli Chen of the University of Texas at Austin said. Chen led a team of researchers on the study, which appeared yesterday in Nature Geoscience.

The team's results in western Antarctica match up well with previous studies, which have found that the region is shedding around 196 billion tons of ice each year.

Related Content:

• BIG PIC: Earth's Fiercest Winds
• Ozone Recovery Could Thaw Antarctica
• HowStuffWorks.com: How Glaciers Works

That's a tiny fraction of the total amount of ice on the continent, which holds enough frozen water to raise sea level a staggering 70 meters (230 feet) if it were to melt. Still, it's enough to cause concern -- much of the western ice sheet lies below sea level, and though air temperatures have remained well below freezing, warmer ocean waters have been eating away at its edges.

The eastern glaciers have comparatively little direct contact with ocean waters, which may explain why they have remained stable in recent years, even growing by some measurements.

But Chen and his team's work, a profile of changes in ice quantity from 2002 through early 2009, suggests the Eastern glaciers began shedding ice in the Wilkes Land area of East Antarctica in 2006. Ice loss also appears to have accelerated in much of Western Antarctica, perhaps indicating a warming trend since then. The team based their studies on data from the Gravity Recovery and Climate Experiment (GRACE) satellite.

Not all scientists are convinced, however. Jay Zwally of NASA's Goddard Space Flight Center noted that the team's findings also show a thickening of ice in another part of eastern Antarctica, which he thinks is evidence that snowfall has merely shifted away from Wilkes Land in recent years.

"You can have a change in precipitation of tens of centimeter during the time period they're looking at," he said. "I don't think what they're seeing is related to changes in ice dynamics. Melt isn't driving this."