High-resolution mapping confirms rate of Greenland ice sheet melting

The Guardian : Greenland’s ice sheet is one of the largest on Earth. Malcolm McMillan of the Center for Polar Ice Observing and Modeling in the UK and his colleagues recently used the satellite Cryosat-2 to map Greenland with a resolution of 5 km. The satellite uses radar altimetry to measure the height of the surface. By taking images over time, the researchers were able to measure changes in height; an increase in height corresponds to an increase in ice thickness. However, those measurements don’t account for changes in density (the top layer could be ice or snow), surface roughness, water content, and other factors. McMillan’s team examined the satellite imagery collected between 2011 and 2014 and accounted for all the variations. The scientists calculated that 270 billion tons of ice was lost per year, closely matching previous measurements from other groups using different measurement techniques. They also found that the western part of the sheet experienced more ice loss than the eastern side, and that a region less than 1% of the area of the sheet was responsible for 10% of the ice loss.