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Newly mapped Greenland valleys up risk of faster glacier melting

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Scientists have found new evidence that indicates Greenland may be an even larger contributor to rising sea levels than previously thought. The discovery of very long valleys underneath the Greenland ice sheet may be evidence that these glaciers are actually more sensitive to global warming.

The new evidence was discovered by researchers from NASA and the University of California Irvine. These previously unknown valleys underneath Greenland can extend up to several dozen miles and many of them connect the ocean to Greenland's ice cap. The researchers published their findings in the online journal Nature Geoscience.

These deep valleys are situated even lower than current sea levels. The presence of these valleys may mean that the seaside edges of Greenland's glaciers can melt much faster when they come into contact with the warm waters of the Atlantic. This accelerated melting of the edges of Greenland glaciers can dump large amounts of water into the ocean, further accelerating the rise of global sea levels. It was initially thought that the melting of Greenland's ice sheet would slow down in the coming years once ocean waters hit higher ground. However, the presence of the newfound canyons shows that these older models may be wrong.

"That turns out to be incorrect. The glaciers of Greenland are likely to retreat faster and farther inland than anticipated -- and for much longer -- according to this very different topography we've discovered beneath the ice," said UC Irvine associate project scientist Mathieu Morlighem. "This has major implications, because the glacier melt will contribute much more to rising seas around the globe." Morlighem is also the lead author of the study.

To conduct the study, the researchers used a novel technique that had the capability of gathering large amounts of data regarding the edges of Greenland's glaciers. While NASA's Operation IceBridge has been sending aircraft over Greenland to gather topographical information about the island, there were still large gaps in the data and Morlighem compensated for this by using a "mass conservation algorithm." This algorithm used data regarding the thickness of ice in Greenland and other data such as surface melt, amount of snowfall and ice movement to help scientists fill in the gaps. Their calculations showed that the glaciers on the periphery of Greenland are a lot longer compared with previous estimates. Some parts of these glaciers are now known to extend as much as 65 miles (100 kilometers) deep into Greenland's interior. Previous techniques made it difficult for scientists to map out ice underneath Greenland's surface.

"Operation IceBridge vastly improved our knowledge of bed topography beneath the Greenland Ice Sheet," said co-author Eric Rignot of UC Irvine and NASA's Jet Propulsion Laboratory.

With the data from Operation IceBridge and the predictions provided by the "mass conservation algorithms," scientists can soon construct even more accurate models that can predict the effect of Greenland's ice loss on global sea levels.

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