Greenland Icecap Region Melting Faster than Previously Thought
Greenland is losing ice from part of its territory at an accelerating rate - faster than previously thought - suggesting that the icecap is growing increasingly unstable, according to a study in Nature Climate Change.
The northeast sector of the Greenland ice sheet - the largest terrestrial mass of ice in the northern hemisphere - is undergoing what glaciologists call "dynamic thinning." Meltwater is draining into the sea, contributing to the sea level rise.
Oceanographers already knew this, but updated measurements are making them think twice about their previous shallow projections.
Scientists behind the study, led by Shfaqat Khan from the Technical University of Denmark, used more than 30 years of surface elevation measurements including the 370-mile-long Zachariae ice stream in the northeast to discover that overall loss is accelerating. Previous studies had identified melting of glaciers in the island's southeast and northwest, but biologists had assumed that the northeast region was a safe zone from glacial melting.
"It was stable, at least until about 2003," author Tim Radford wrote on Climate News Network. "Then higher air temperatures set up the process of so-called dynamic thinning. Ice sheets melt every Arctic summer, under the impact of extended sunshine, but the slush on the glaciers tends to freeze again with the return of the cold and the dark, and since under historic conditions glaciers move at the proverbial glacial pace, the loss of ice is normally very slow."
Researchers calculate that between April 2003 and April 2012, the northeast was losing ice at the rate of 10 billion tons a year.
The researrchers report global warming is to blame for Greenland's quickening melting pace, noting the rising levels of greenhouse gases in the atmosphere that have contributed to the melt.
Greenland's southerly glaciers have been in retreat and one of them, Jakobshavn Isbrae, is now flowing four times faster than it did in 1997.
Scientists now grow even more worried about melting Greenland, as the one area they seemingly could rely on has
"Northeast Greenland is very cold. It used to be considered the last stable part of the Greenland ice sheet," said Michael Bevis of Ohio State University, part of the Danish-led team. "So now it seems that all of the margins of the Greenland ice sheet are unstable."