| dethalternate | Date: Wednesday, 10-June-2015, 5:18 PM | Message # 1 |
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| Geoscientists have solved a decade-long mystery of how some of the large lakes that sit atop the Greenland ice sheet can completely drain billions of gallons of water in a matter of hours.
In 2006, Greenland's North Lake, a 2.2 square-mile (5.6 square kilometers) supraglacial meltwater lake, drained almost 12 billion gallons of water in less than two hours. In a study published two years later, researchers determined that this astonishing phenomenon is possible because giant hydro-fractures(water-driven cracks) can form directly beneath the lake basin and stretch down to the bed of the ice sheet, emptying the lake of water. But just how these fractures developed has been unknown — until now.
In the new study, published today (June 3) in the journal Nature, scientists using GPS technology discovered that the hydro-fractures form from tension-related stress caused by movements of the ice sheet. These movements are, in turn, triggered by the trickling meltwater.
The new research may help scientists better understand how much the ice sheet is contributing to sea level rise, researchers say.
Most of Greenland's supraglacial lakes drain slowly when superficial streams route water into nearby, permanent crevasses or moulins (vertical conduits or shafts in a glacier). Fairly recently, however, satellite images showed that about 13 percent of the lakes drain quickly, emptying completely within 24 hours.
Read more/full article/source - http://www.livescience.com/51071-how-greenland-lakes-vanish.html
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