Ice sheet mass balance in central West Greenland

Abstract

Volume changes of the Greenland ice sheet in response to climate change may form a significant contribution to variations in sea level. However, still the sign of the present volume change is unknown. The aim of this project was to increase our understanding of present state of the Greenland ice sheet and of its sensitivity to climate change, with emphasis on the Kangerlussuaq transect (West Greenland, 67 uN). We have performed mass-balance, meteorological and ice-velocity measurements along the transect. With a record length of 10 years, the mass-balance measurements constitute the longest series of this kind on the Greenland ice sheet. A crucial parameter for the determination of the amount of melt is the albedo (this is the fraction of the solar radiation reflected by the surface). Therefore, we have improved the retrieval methods used to estimate the surface albedo from satellite data. For that purpose we have, among others, measured the albedo from a helicopter. The resulting data were used for validation of the satellite-derived albedos. With the satellite-derived albedos and the mass-balance data we have developed a method for estimating the surface mass balance of the Greenland ice sheet from satellite data. Furthermore, we have developed an atmospheric boundary-layer model, specifically designed for glaciers and ice sheets. The model was used to study the relation between the climate of the free atmosphere and conditions near the surface of the ice sheet, which determine the amount of melt.