Airborne lidar measurements for Cryosat validation

Airborne laser measurements provide a detailed capability to measure the geometry of an ice surface with an accuracy of 5-25 cm over a large range of spatial scales (1 m to 100´s of km), either as along-track profiles or scanning lidar swath mapping transects, thus providing a useful calibration and validation tool for Cryosat measurements. The lidar measurements are based on precise GPS positioning and inertial attitude data, with accuracy currently limited by long-range kinematic GPS performance. Over marine areas measured sea-ice topography may be converted into ice thickness using models of sea-surface height (geoid) variations and equilibrium assumptions. Over glaciers and ice sheets the varying radar penetration into the snow and ice complicates understanding of radar satellite data, and similarly snow thickness and snow density provides uncertainty in recovering ocean ice thickness from ice free-board measurements. We describe in the paper some recent campaigns using single-profile and scanning lasers to map sea-ice in the Arctic Ocean north of Greenland, as well as some results of comparing radar measurements to laser data in selected areas over the Greenland ice sheet.