​Greenlands Ice Sheet May Threaten Sea Levels

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December 24, 2013

The Greenlands ice sheet, a massive lake that could have major implications for understanding sea-level rise, measures 27 square miles. The ice sits on a large body of water. The study was published online Sunday, Dec. 22, in the journal Nature Geoscience.

Researchers at the University of Utah say the lake, known as a “perennial firn aquifer,” remains liquid year-round despite the otherwise perpetually frozen ice sheet on the landscape.

“Large amounts of snow fall on the surface late in the summer and quickly insulates the water from the subfreezing air temperatures above, allowing the water to persist all year long,” said Rick Forster, lead author and professor of geography at the University of Utah.

The Greenland Ice Sheet is vast, covering roughly the same area as the states of California, Nevada, Arizona, New Mexico, Colorado and Utah combined. The average thickness of the ice is 5,000 feet. In 2012, the ice sheet lost volume of 60 cubic miles — a record for melt and runoff.”Of the current sea level rise, the Greenland Ice Sheet is the largest contributor — and it is melting at record levels,” said Forster.

“So understanding the aquifer’s capacity to store water from year to year is important because it fills a major gap in the overall equation of meltwater runoff and sea levels.”

Since 2010, Forster’s team has measured snow accumulation Greenland and how it varies from year to year. The area they study covers 14 percent of southeast Greenland yet receives 32 percent of the entire ice sheet’s snowfall, but there has been little data gathered.

In 2010, the team drilled core samples in three locations on the ice for analysis. Team members returned in 2011 to approximately the same area, but at lower elevation. Of the four core samples taken then, two came to the surface with liquid water pouring off the drill while the air temperatures were minus 20 degrees centigrade.

The water was found at about 10 meters below the surface at the first hole and at 25 meters in the second hole.

“This discovery was a surprise,” Forster says. “Although water discharge from streams in winter had been previously reported, and snow temperature data implied small amounts of water, no one had yet reported observing water in the firn that had persisted through the winter.”

The consequences of losing the Greenland Ice Sheet could be catastrophic. If all the water retained in the ice sheet melted, it is estimated that the global sea level would rise about 6 meters, says Forster.Although no one is predicting a total meltoff all at once, keeping an eye on ice formation, runoff amounts and how the water is moving is critical to accurately predicting sea level changes.

Until now, calculations of the ice sheet mass changes did not include a year-round storage mechanism for liquid water.Forster says the reservoir’s exact role is unknown. “It might conserve meltwater flow and thus help slow down the effects of climate change. But it may also have the opposite effect, providing lubrication to moving glaciers and exacerbating ice velocity and calving increasing the mass of ice loss to the global ocean.”