The extent of Arctic ice has shrunk by 40% since the late 1970s, when satellite measurements began. But getting comprehensive data on the thickness of the ice, rather than just its area, was difficult until the European Space Agency launched the Cryosat satellite in 2010.
The satellite’s 88 million measurements, analysed in Nature Geoscience, show that from 2010-12 the Arctic ice volume fell by 14%, in step with the warming trend of the last few decades. But in 2013, the ice volume jumped up by 41% .... http://www.theguardian.com