NASA reports on The Hidden Meltdown of Greenland "All by itself, Greenland could bump sea levels by 7 meters (23 feet) if its ice melted completely. And … it’s melting."
Rignot’s team found that Greenland's glaciers flowing into the ocean are grounded deeper below sea level than previously measured. This means that the warm ocean currents at depth can sweep across the glacier faces and erode them.
“In polar regions, the upper layers of ocean water are cold and fresh,” he explains. “Cold water is less effective at melting ice.”
“The real ocean heat is at a depth of 350-400 meters and below. This warm, salty water is of subtropical origin and melts the ice much more rapidly.”
Rignot’s research team is providing critical information needed to document this effect and accurately predict where and how fast glaciers will give way. The team gathered and analyzed around-the-clock measurements of the depth, salinity, and temperature of channel waters and their intersection with the coastal edge of Greenland's ice sheet. They found that some of the glaciers balance on giant earthen sills that are protecting them, for now. But other glaciers are being severely undercut out of sight beneath the surface, meaning they could collapse and melt much sooner.