Scientists Warn 'Unstoppable' Polar Melt May Raise Sea Level Four Feet

A large section of the West Antarctic Ice Sheet is rapidly falling apart, and its continued melting appears to be "unstoppable," two groups of scientists reported Monday.

Researchers at NASA and the University of California, Irvine note that these glaciers already contribute significantly to sea level rise, releasing almost as much ice into the ocean annually as the entire Greenland Ice Sheet. With this much ice melt potentially being dumped into the sea, the global sea level could rise by as much as 4 feet (1.2 meters).

About 40 years of observations indicate the glaciers in the Amundsen Sea sector of West Antarctica "have passed the point of no return," glaciologist and lead author Eric Rignot said in a news release.

"This sector will be a major contributor to sea level rise in the decades and centuries to come," he added. "A conservative estimate is it could take several centuries for all of the ice to flow into the sea."

The journal Geophysical Research Letters details the major lines of evidence causing such instability in the ice sheet - something scientists have been fearing for some time.

According to The New York Times, the West Antarctic ice sheet sits in a bowl-shaped depression in the earth, with the base of the ice below sea level. Warm ocean water is causing the ice sitting along the rim of the bowl to thin and retreat. As the front edge of the ice pulls away from the rim and enters deeper water, it can retreat much faster than before.  

The team used radar observations captured by the European Earth Remote Sensing (ERS-1 and -2) satellites to measure just how far the grounding line - the point where the glacier meets the land - had retreated.

Glaciers move horizontally as they flow downstream, the study describes, but their floating portions also rise and fall vertically with changes in the tides. The data revealed that as glaciers flow faster, they stretch out and thin, which reduces their weight and lifts them farther off the bedrock.

This process is a vicious cycle. Accelerating flow speeds and retreating grounding lines reinforce each other, and there is no way to stabilize it, the authors note.

"If we have indeed lit the fuse on West Antarctica, it's very hard to imagine putting the fuse out," climate scientist Dr. Richard Alley, who was not involved in the study, told The Times.