Greenland rising faster as ice loss acceleratesWe have several independent lines of evidence that Greenland is losing ice at an accelerating rate. Satellite altimetry find glaciers are sliding faster downhill and dumping more ice into the ocean. Altimetry data also find the ice sheet is thinning. An overall picture is obtained by satellites measuring the gravity around the ice sheet. Another line of evidence has now been added to this picture with GPS measurements finding that Greenland is losing ice so quickly, the land is now rising up at an accelerating rate.These results are published in Accelerating uplift in the North Atlantic region as an indicator of ice loss Jiang 2010. The study looks at high-precision global positioning system GPS data that measure the vertical motion of the rocky margins around Greenland, Iceland and Svalbard. The weight of ice sheets push down on the bedrock it rests on. As the ice sheets lose mass, the bedrock rises. This process, known as Glacial Isostatic Adjustment GIA, has been happening since the planet came out of an ice age around 17,000 years ago. How do we know whether current uplift might be a delayed response to glacial retreats from thousands of years ago? To avoid the effect of past events, this study focuses on vertical acceleration rather than velocities. The results are therefore insensitive to GIA-related motions from past ice mass changes.What they find is crustal uplift in Greenland, Iceland and Svalbard is accelerating. Extrapolating the acceleration backwards in time finds the acceleration began after 1990. The acceleration of uplift over the past decade represents an essentially instantaneous, elastic response to recent accelerated melting of ice throughout the North Atlantic region.
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