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11 June 2009

The Greenland ice sheet is melting faster than expected according to a new study led by a University of Alaska Fairbanks researcher and published in the journal Hydrological Processes.

Study results indicate that the ice sheet may be responsible for nearly 25 percent of global sea rise in the past 13 years.

The research also shows that seas are now rising more than 3 millimeters a year - a 50 percent faster rate than the average for the 20th century.

University of Alaska Fairbanks researcher Sebastian Mernild and colleagues from the United States, United Kingdom and Denmark discovered that from 1995 to 2007, overall precipitation on the ice sheet decreased, while surface ablation, the combination of evaporation, melting and calving of the ice sheet, increased.

Greenland's ice sheet may be responsible for nearly 25 percent of global sea rise during the last 13 years.

Since 1995 the ice sheet lost an average of 265 cubic kilometers per year, which has contributed to about 0.7 millimeters per year in global sea level rise.

The sea level rise could be up to twice this contibuting amount, because the quantity does not include thermal expansion of the ice volume in response to heat.

The Greenland ice sheet has been of considerable interest to researchers over the last few years as one of the major indicators of climate change. In late 2000/early 2001 and in 2007, major glacier calving events sent up to 44 square miles of ice into the sea at a time.

Researchers are studying these major events as well as the less dramatic ongoing melting of the ice sheet through runoff and surface processes.

Ice melt from a warming Arctic has two major effects on the ocean.  Increased water contributes to global sea-level rise, which affects coastlines across the globe.

And fresh water from melting ice changes the salinity of the world’s oceans, which can affect ocean ecosystems and deep water mixing.

“Increasing sea level rise will be a problem in the future for people living in coastal regions around the globe,” said Mernild. “Even a small sea level rise can be a problem for these communities.”

Right: A satellite image of 26 June 2008, when the summer melt season had begun along the west coast of Greenland.  Image: NASA
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Below: The Greenland Ice Sheet calving directly into the sea on the northern west Greenland coast.
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The world's fastest moving glacier .....

The Jakobshavn Glacier, appearing as a prominent white strip in the centre of the satellite image shown below, reaches from the Greenland Ice Sheet to a terminus at the sea in Ilulissat Icefjord.

On the ice sheet upstream from the glacier, crevasses or cracks have colored the ice pale gray, and ponds of melt water dot the edge of it.

Jakobshavn is the world's fastest glacier, moving at roughly 14 kilometres/year. More than 6 percent of Greenland's ice sheet is carried away by the glacier.

It produces 10 percent of Greenland's icebergs, each year calving off 35 billion tonnes of ice into the fiord. Some massive icebergs are up to 1,000 metres high, and become grounded in the shallow areas of the fiord.