A new ice thickness and bedrock dataset for the Greenland ice sheet

Ice thickness data collected between 1993 and 1999 using a coherent ice penetrating radar system developed at the University of Kansas have been combined with data collected by the Technical University of Denmark in the 1970s to produce a new ice thickness grid for Greenland. Cross-over analysis was used to assess the relative accuracy of the two datasets and they were weighted accordingly and interpolated onto a regular 5 km spacing grid using a kriging interpolation procedure. A high resolution land-ice mask was used to help constrain the interpolation of the ice thickness data near the ice sheet margins where, in the past, the relative errors have been largest. The ice thickness grid was combined with a new digital elevation model of the ice sheet and surrounding rock outcrops to produce a new bed elevation dataset for the whole of Greenland. The ice thickness grid was compared with the currently available dataset. Differences in the centre of the ice sheet, where the ice is thickest, were of the order of a few percent. Near the margins, however, large differences, of as much as a factor ten, were found. The total volume of ice contained in the ice sheet was re-estimated and found to have a value of 2.93 x 10 km. The ice thickness grid was used to calculate the spatial pattern of gravitational driving stress over the ice sheet. Anomalous patterns of stress were found in areas that appeared to be associated with areas of rapid flow. Bamber et. al. New ice thickness data set for Greenland, JGR atmos, (in press) 2