Ice-mass-variations from GRACE and SLR data: applicability of different space-geodetic-observations and modeling techniques for monitoring medium- and large-scale glacier systems

In the last decade, temporal variations of the gravity field derived from the Gravity Recovery and Climate Experiment (GRACE) satellite mission have become one of the most ubiquitous and valuable sources of information for Earth system studies. In the context of global climate change, this information is of utmost importance from a scientific but also socio-economic perspective. We developed a sophisticated analysis approach to deduce reliable estimates of mass balances of glacier systems from space-gravimetric data. The innovative methodology approximates the regional gravity field in the vicinity of the investigated glaciers with radial basis functions (point masses) and exploits GRACE on the level of raw inter-satellite measurements (Level-1B). The outcome is compared with results from a spherical harmonic synthesis based on the latest ITSG-Grace2018 release as well as mass balance information of selected glaciers provided by the experts at the World Glacier Monitoring Service (WGMS). Finally, for large areas like the Antarctic ice sheet, we additionally estimated the mass balance based on our Satellite Laser Ranging (SLR) gravity field solutions throughout the period 1992 - 2018.