NASA JPL-UC Irvine glaciologist Eric Rignot explains how glaciers in West Antarctica are changing. Most glaciers in West Antarctica sit on a bed that is below sea level. The massive ice sheet’s exposure to ocean water makes it inherently unstable, a fact that scientists have warned about for decades. In recent years, scientists have observed the glaciers that flow into West Antarctica's Amundsen Sea are shedding ice at a faster rate. Now, new research shows there is nothing to stop these glaciers from being lost to the ocean—an event that will likely take centuries to unfold, but raise global sea level by four feet.