Tags: greenland | disappearing | lakes | cracks | bottoms

Greenland Disappearing Lakes Have Cracks in Their Bottoms

By    |   Thursday, 04 Jun 2015 06:42 AM

Greenland is seeing huge lakes disappear from its ice sheets because of hydro-fractures that form beneath the lakes' basins and then empty billions of gallons of water within hours, a study has discovered.

The sudden loss of big lakes in Greenland had been a mystery since 2006 when 2.2 square-mile North Lake which was created from meltwater lost nearly 12 billion gallons of water in less than two hours, according to LiveScience.com.

Scientists have said the majority of the country's supraglacial lakes drain slowly when water is rerouted into crevasses in a glacier. The new study, published in the latest issue of the science journal Nature, determined after examining GPS images and data that about 13 percent of the lakes can drain within 24 hours from the cracks

"The images would show the lake there one day, and gone the next day," said Laura Stevens, a glaciology doctoral candidate with the Massachusetts Institute of Technology/Woods Hole Oceanographic Institution Joint Program.

While researchers at the Woods Hole Oceanographic Institution knew since 2008 that the glacial cracks could trigger a draining of the lakes, no one knew why and how it was happening, reported Tech Times. Researchers created a ring of 16 GPS units around North Lake to look at ground movement in 2011, 2012 and 2013.

The GPS information from the study show that from six to 12 hours before a drainage event on those dates, the ice would shift and move upward, noted Tech Times. That type of movement, if it got severe, would create the giant cracks needed to cause the hydro-fracturing that would quickly drain the lake.

Researchers said in the Nature study that the cracks could create a water flow faster than water goes over Niagara Falls.

"In some ways, ice behaves like Silly Putty — if you push up on it slowly, it will stretch; if you do it with enough force, it will crack," said Stevens. "Ordinarily, pressure at the ice sheet surface is directed into the lake basin, compressing the ice together. But, essentially, if you push up on the ice sheet and create a dome instead of a bowl, you get tension that stretches the ice surface apart."

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Greenland is seeing huge lakes disappear from its ice sheets because of hydro-fractures that form beneath the lakes' basins and then empty billions of gallons of water within hours, a study has discovered.
greenland, disappearing, lakes, cracks, bottoms
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2015-42-04
Thursday, 04 Jun 2015 06:42 AM
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