A section of the West Antarctic Ice Sheet has melted to a point of no return, according to a new study released by researchers from NASA and the University of California, Irvine. Warmer sea temperatures are melting the ice much faster than previously predicted and new modeling shows that the melt could be complete within 200 years. The ice sheet in question has the potential to release enough water to raise sea levels by four feet (1.2 meters).
The study has focused on an area of glacial land ice (as opposed to seasonally variable sea ice) in the Amundsen Sea Embayment. Three separate lines of evidence are indicating that the rate of melt has reached a point that cannot be reversed. Scientists focused on the ‘grounding line,’ the point where a land-based glacier comes into contact with the sea as it moves downhill. Scientists studied the changes in the flow speed of the ice melt, how high in the water the glacial ice was resting, and the angle of the ground the glaciers were moving over and how far above or below sea level that was. Most glacial melting occurs at the point where the glacier meets warmer sea water, and all three areas of study indicated that the rate of melt was increasing. They attribute the initial spark for the situation to increasing sea temperatures.
As the land ice in this area is generally at least 1,000 meters thick at the grounding line, scientists have been using satellite radar data gathered between 1992 and 2011 to track changes in glacier behavior. They have observed that as the glacier melts and thins, it rests higher in the water. This allows sea water to flow in under the raised glacier, moving the grounding line further inland. The particular problem with this section of West Antarctic ice is that much of the land just onshore is below sea level, allowing the sea to flow in more easily and further under the ice, pooling and compounding the problem.
NASA’s Operation IceBridge will focus closely on this area during this year’s Antarctic study period, beginning in October. But as glaciologist and lead author of the study Eric Rignot says: “The collapse of this sector of West Antarctica appears to be unstoppable…The fact that the retreat is happening simultaneously over a large sector suggests it was triggered by a common cause, such as an increase in the amount of ocean heat beneath the floating sections of the glaciers. At this point, the end of this sector appears to be inevitable.”
Photos by NASA