While the edges of the glaciers are melting, the ice sheets in Greenland’s interior are getting thicker, according to satellite data collected over the last 11 years. On average the ice sheets have got thicker by about six centimetres each year, the researchers say. The researchers, based at Norway’s Nansen Environmental and Remote Sensing Center (NERSC), say that this is probably because snowfall in the region has increased, due to a weather pattern known as the North Atlantic Oscillation (NAO). The research was conducted using the European Space Agency’s ERS satellites. These carry radar altimeters that send 1800 radar pulses to Earth each second, and record how long they take to return to the satellite. The sensor can time this journey down to the nanosecond, ESA says, meaning that the instrument is accurate to within two centimetres.