NASA; The Hidden Meltdown of Greenland

Aug. 28, 2015: More than 90 percent of our planet’s freshwater ice is bound in the massive ice sheets and glaciers of the Antarctic and Greenland. As temperatures around the world slowly climb, melt waters from these vast stores of ice add to rising sea levels. All by itself, Greenland could bump sea levels by 7 meters (23 feet) if its ice melted completely.
And … it’s melting.

In August 2014, Eric Rignot, a glaciologist working at the University of California, Irvine and NASA's Jet Propulsion Laboratory, led a team in mapping ice cliffs at the front edges of three outlet glaciers in Greenland. The researchers found cavities that undercut the base of these leading edges that can destabilize the ice front and enhance iceberg calving, the process where parts of the glacier break off and float away.

“In Greenland we have melt rates of a few meters a day in the summer months,” says Rignot.
What’s causing this ‘big thaw’?

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 ...................... more


http://science.nasa.gov/science-news/science-at-nasa/2015/28aug_greenland/