Greenland ice cap melting accelerates

Greenland's ice cap is breaking up and melting at an accelerated rate, the results of a satellite study released today reveal, suggesting current sea level rise predictions are too low.

The flow speed of enormous tongues of ice that drain the ice shelf into the sea has roughly doubled over the last five years, NASA scientists found. Three times more ice is lost from the ice sheet each year than previously thought, as melt water flows down crevasses in the ice, causing it to slide faster towards the sea.

“It takes a long time to build and melt an ice sheet, but glaciers can react quickly to temperature changes. Greenland is probably going to contribute more and faster to sea level rise than predicted by current models,” said one of the study’s authors, Eric Rignot from NASA’s Jet Propulsion Laboratory.

Because current climate models do not take glacial flow into account, “current estimates of global sea level rise over the next century, of about 0.5 +/- 0.4 m, may be underestimated,” Cambridge glaciologist Julian A. Dowdeswell commented the findings in today’s issue of Science.

“The changing mass of the great ice sheets of Greenland and Antarctica represents the largest unknown in predictions of global sea-level rise over the coming decades,” he wrote.

Greenland’s ice sheet is up to up to 3km thick and would raise sea levels by 7m if it melted completely. If only melting were considered, without the dynamic effects of glacier flow, this would take at least 1000 years.

The results of the new study, published in the journal Science, show that the movement of glacier tongues cannot be neglected. Their flow speed has doubled in the last five years, and now reaches over 12 km per year, the study found.

The Greenland ice sheet is now losing 220 cubic km of ice per year – around 200 times that used by a city like Los Angeles.

“In a warming world, it is likely that the contribution to sea level rise from Greenland is set to grow further,” Julian Dowdeswell commented.

By Goska Romanowicz

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