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Melting Greenland Ice Could Accelerate Sea Level Rise, Researchers Say

Jan 06, 2016 11:45 AM EST
Meltwater Rivers
An exceptionally warm summer in 2012 resulted in excess meltwater that filled up the sponge-like pores in the top layer of the Greenland ice sheet. This meltwater hardened into a solid layer of ice, making it more difficult for liquid water to percolate through and causing the water to run off into the sea, instead.
(Photo : Dirk van As, Geological Survey of Denmark and Greenland (GEUS), Copenhagen, Denmark.)

Rising global temperatures are impacting the Greenland ice sheet in more ways than scientists previously thought. While this massive body of ice is often regarded as a "sponge" for glacier meltwater, a recent study suggests climate change is impeding its ability to store excess water, meaning melting ice could boost sea level rise.

In the latest study, researchers from York University examined ice cores drilled into West Greenland's firn between 2009 and 2015. Firn is basically a porous layer of built-up snow that slowly freezes into ice over time, but is not as dense as glacier ice. This layer is particularly important because it traps and stores excess water before it ultimately runs off into the sea. For their analysis, researchers drilled a series of shallow firn cores about 20 meters deep. 

"We were interested in the thin porous near-surface firn layer, and how its physical structure is changing rapidly with climate change," Professor William Colgan, co-author of the recent study, explained in a news release. "The study looked at very recent climate change on the ice sheet, how the last couple of years of melt have really altered the structure of the ice sheet firn and made it behave differently to future melt."

In the last century alone, scientists believe the Greenland ice sheet has lost more than nine trillion tons of ice. However, the ice sheet's melting rate continues to increase as temperatures warm - NASA estimates the vast body of ice loses nearly 287 billion tons of ice every year. If, and when, the entire ice sheet melts, global sea levels could increase by as much as 23 feet.

Based on the recent study, researchers discovered greater amounts of meltwater from an exceptionally warm summer in 2012 filled up the firn's pores and hardened into a solid layer of ice, making it more difficult for liquid water to percolate into the firn. 

"In subsequent years, meltwater couldn't penetrate vertically through the solid ice layer, and instead drained along the ice sheet surface toward the ocean," Colgan added in York's release. "It overturned the idea that firn can behave as a nearly bottomless sponge to absorb meltwater. Instead, we found that the meltwater storage capacity of the firn could be capped off relatively quickly."

Their study was recently published in the journal Nature Climate Change

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