How satellite remote sensing of the ice sheets can contribute to studies of sea level change
During the last decades, the contribution of the ice sheets to sea level rise has increased relative to the thermal expansion of the oceans and to the melting of mountain glaciers and icecaps. Crucial for estimating and forecasting the contribution of the ice sheets is the determination of their mass balance, i. e. of mass gain caused by accumulation of snow and mass loss due to melting and iceberg calving. As a complement to field measurements and model simulations of ice sheet dynamics (the latter dependent on the environmental conditions), satellite data are needed for interpolating between sparse field sites and for the validation of model results. In addition, they are mandatory for observations of sudden events such as the collapse of ice shelves and the break-off of huge icebergs. Parameters derived from satellite data cover different spatial scales, ranging from ice sheet mass changes at horizontal resolutions between 300 and 500 km (obtained from measurements of the hemispherical gravity field) to local velocity fields of moving glaciers with 100 m to 1 km resolution. Satellites are also useful to record changes of extent and elevation of the ice sheets, for the determination of snow accumulation, and for the detection of melting processes and iceberg calving. Satellite data products do not yet exactly meet the requirements of climate studies in all cases. However, satellite mission concepts and parameter retrieval methods are being continuously improved, increasing their usefulness in climate research. In this presentation, an overview will be given concerning the different methods to observe processes characterizing ice sheet dynamics and to evaluate their impact on sea level change.