Greenland Icecap Is Melting Faster Than Thought

Posted: Jan 5 2016, 8:46am CST | by , in News | Latest Science News


Greenland Icecap is Releasing Water Faster than Thought
Meltwater forming on Greenland ice sheet and flowing towards sea. Credit:Dirk van

Near-surface layers of the Greenland ice sheet could cause a huge spike in sea levels as it is losing its ability to store meltwater.

Rise in global temperature is affecting the Greenland ice sheet more severely than what was originally thought. A new study suggests that rapidly melting ice could run off more water into the oceans and could set the stage for a huge spike in sea levels. 

The near-surface layers of the Greenland ice sheet that have not been compressed into glacier ice yet are releasing melting water at a rate that has not been anticipated before. 

This ice cover or firn layer is up to 80 meters thick but it is losing its ability to store water due to atmospheric warming.

"Basically our research shows that the firn reacts fast to a changing climate. Its ability to limit mass loss of the ice sheet by retaining meltwater could be smaller than previously assumed.” Horst Machguth from University of Zurich and lead author of the study said.

To find out the exact impact of recent climate change on the structure of near-surface snow and ice layers, researchers traveled several hundred kilometers across the firn layers and drilled numerous 20 meter deep cores for obtaining samples from the layers. 

Firn layer works like a sponge. The porus firn traps meltwater inside and slowly freezes it into ice before it runs off the surface of the glacier and it is referred to as ‘ice lens.’

Until recently, researchers believed that firn layer is still trapping meltwater but new research shows that this is not the case any longer. Sample collected from lower elevations of Greenland indicate that a surprisingly massive ice layer has formed directly below the ice sheet surface and making it difficult for meltwater to filter through the firn layer – meaning forcing it to release instead.

"It appears that the intensive and repeated entry of meltwater formed numerous ice lenses, which ultimately hindered percolation of further meltwater.” Co-author Dirk Van from Denmark said.

Radar measurements suggest that dense ice layer is not only developed in lower elevations but taking place in higher elevations as well. Due to massive ice layer, excess water is not retaining in ice sheet and flowing toward oceans. Greenland ice sheet is losing billions of tons of ice every year due to rising temperatures and contributing to rise in sea levels. This process could result in making sea level rise even worse.

"In contrast to storing meltwater in porous firn, this mechanism increases runoff from the ice sheet", explains Mike MacFerrin from University of Colorado and co-author of the study. "This process has not previously been observed in Greenland. The total extent of this ice lid capping the ice sheet firn remains unknown. For this reason, the amount of additional ice sheet runoff associated with this newly observed process cannot yet be quantified." 

Nevertheless, the latest study is an important step forward in understanding the effect of climate change on Greenland ice sheet and in making predictions about what will happen to ice sheet in the future. 



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Hira Bashir covers daily affairs around the world.




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