Elevation of Antarctic ice sheets, computer artwork. The highest areas are shown in red, with yellow, green and turquoise showing progressively lower elevations. Dark blue areas are at sea level. The western side of Antarctica (towards the left) is lower than the east. It is feared that glacial flow has accelerated on the west of the continent and the West Antarctic ice sheet is thinning. This artwork is based on data from NASA's Ice, Cloud, and Land Elevation Satellite (ICESat). This device is designed to measure the mass balance of Earth's ice sheets, to determine whether the processes that produce ice are balanced by the processes that remove it. An imbalance would have implications for global sea levels.