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 Now a team of U.S. researchers says it has figured out the bizarre
phenomenon and that could help them forecast global sea-level rise.
Vertical shafts in the ice sheet, called moulins, can funnel melt
water beneath parts of the glacier and lift them up. This causes
cracks beneath the so-called supragalcial lakes that can empty them
in days, according to scientists from the Massachusetts Institute of
Technology-Woods Hole Oceanographic Institution (MIT/WHOI) Joint
Program in Oceanography.
Draining lakes can accelerate sea-level rise by suddenly injecting
large volumes of water into the ocean and lubricating the flow of
ice offshore. However, the finding suggests that only lakes at
lower, warmer altitudes on the ice sheet where moulins are more
prevalent are vulnerable, according to the research published in the
journal Nature.
 "The trigger is less likely to occur at lakes at higher elevations
on the ice sheet — even though water volumes in those lakes can be
large," according to the research.
"Our discovery will help us predict more accurately how supraglacial
lakes will affect ice sheet flow and sea level rise as the region
warms in the future," lead author Laura Stevens wrote in a Woods
Hole press release.
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Scientists at Ohio State and Cornell University said last year that
two lakes on the Greenland ice sheet that had previously held
billions of gallons of water had mysteriously disappeared.
The Greenland ice sheet covers more than 600,000 square miles (1.6
million square kilometers) and is expected to be a significant
contributor to sea-level rise as it melts.
(Writing by Richard Valdmanis. Editing by Andre Grenon)
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