Sunday, August 19, 2012

Sudden massive melt of Greenland ice sheet

Bruce Kirkby paddles in Scorsbysund, off the east coast of Greenland.
  

Nearly all of Greenland's massive ice sheet suddenly started melting a bit this month, a freak event that surprised scientists.

Even Greenland's coldest and highest place, Summit station, showed melting. Ice-core records indicate that last happened in 1889 and occurs about once every 150 years.

Three satellites show what NASA calls unprecedented melting of the ice sheet that blankets the island, starting on July 8 and lasting four days. Most of the thick ice remains. While some ice usually melts during the summer, what was unusual was that the melting happened in a flash and over a widespread area.

“You literally had this wave of warm air wash over the Greenland ice sheet and melt it,” Tom Wagner, an ice scientist at the U.S. National Aeronautics and Space Administration, said Tuesday.
The ice melt area went from 40 per cent of the ice sheet to 97 per cent in four days, according to NASA. Until now, the most extensive melt seen by satellites in the past three decades was about 55 per cent.

Mr. Wagner and other scientists said because this Greenland-wide melting has happened before they cannot yet determine whether this is a natural rare event or one triggered by human-caused global warming. But they do know that the edges of Greenland's ice sheets have already been thinning because of climate change.

Summer in Greenland has been freakishly warm so far. That's because of frequent high-pressure systems that have parked over the island, bringing warm clear weather that melts ice and snow, explained University of Georgia climatologist Thomas Mote. He and others say it's similar to the high-pressure systems that have parked over the American Midwest bringing record-breaking warmth and drought.

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