Satellites have been invaluable in calculating how much ice is bound in the ice sheets of Greenland and Antarctica and how much they gain or lose every year, as they are far too big to survey in any other way. NASA’s ICESat satellite, for example, collects high-resolution elevation data, the idea being that changes in surface height indicate changes in ice volume, and therefore mass. Louise Sandberg Sørensen and her colleagues use this data to calculate changes in the quantity of ice stored in the Greenland ice sheet.

They find that dramatic thinning has taken place at the ice-sheet margins while interior areas have thickened – but the team also have to take into account layers of firn and snow on top of the ice. If these become compacted, an elevation change occurs even though the total mass does not change, so they have to model firn extent and the rates at which these layers shrink. This ensures that their 5-year estimate of mass loss from the ice sheet is as accurate as possible, aiding predictions of how the ice sheet will contribute to future sea-level rise.

Ice2sea Work Package: WP3.4

Publication: Sandberg Sørensen, L., S. B. Simonsen, K. Nielsen, P. Lucas-Picher, G. Spada, G. Adalgeirsdottir, R. Forsberg, and C. Hvidberg (2011), Mass balance of the Greenland ice sheet (2003–2008) from ICESat data – the impact of interpolation, sampling and firn density, The Cryosphere, 5, 173 – 186.