Heating UpOne of the most comprehensive studies on the melting of Greenland Ice Sheet has revealed h

Heating UpOne of the most comprehensive studies on the melting of Greenland Ice Sheet has revealed how little we actually know about how warmer climates will effect it. Using satellite and aerial data from NASA’s ICESat spacecraft and field surveys from Operation IceBridge the authors were able to determine the height of the Greenland Ice Sheet at 100,000 locations. The vast amount of data led to new estimates at high spatial resolutions of annual ice loss between 1993 and 2012; this showed that approximately 243 metric gigatons (approximately 277 cubic kilometers) of ice were lost each year and raising sea levels an estimate 0.68 millimeters annually.Not only does the study present the best estimates to date about Greenland ice loss , it also revealed our current model based predictions of future ice loss are woefully inaccurate. Each glacier in the ice sheet reacts differently to warming; some of the glaciers add ice, others lose it, and some flip year to year. These variations might be caused by the surrounding ocean, the bedrock under the glacier, the shape of the fjord, etc. When these factors are taken into account, more accurate models are created.The data collected for this study tried to incorporate all those factors to create better models of individual glaciers. The glaciers were then grouped into seven different categories which can be used to create better models of what the ice sheet, as a whole, will do as the climate warms.Another contribution to better glacier models comes from a report on supraglacial lakes, or lakes formed by the melting of ice and snow on top of glaciers. Not only do these lakes soak up more sun, causing more ice to melt, but they often slip through cracks in the ice until they hit bedrock. When this happens, they act as a lubricant that carries the glacier faster down the fjords.When these lakes drain and carry the glacier down faster, the glaciers themselves flatten out and become thin. Unfortunately, thinner ice is more susceptible to warmer temperatures than thicker ice, therefore increasing the rate of melt. As the rate increases, supraglacial lakes will form farther and farther inland, causing the glaciers to move faster in a feedback loop.The new data from both the studies will hopefully be used to create more accurate models of melt water from Greenland Ice Sheet, providing better estimates that will help coastal cities cope with rising ocean levels.Further reading: http://www.pnas.org/content/early/2014/12/12/1411680112.abstract?sid=ed73a50e-13ee-4ed9-874a-5ba58a610fcdand:http://www.nature.com/nclimate/journal/v5/n1/full/nclimate2463.htmlPhoto Credit: NASA’s Earth Observatory https://www.flickr.com/photos/nasaearthobservatory/6993002080/in/photostream/-Colter  -- source link

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