Gravimetric Mass Balance
The Gravity Recovery and Climate Experiment (GRACE) twin satellites have been measuring changes in the Earth’s gravitational field since 2002. Time-variable gravity fields can be used to infer mass changes and mass redistributions in the Earth’s subsystems (e.g. the cryosphere). The mass balance of the Greenland Ice Sheet (GIS) can be measured with an accuracy of around 20 Gt/yr. The Greenland Ice Sheet cci produces Gravimetric Mass Balance (GMB) products for the Greenland Ice Sheet from GRACE measurements. These products comprise monthly mass change time series for the entire GIS and different drainage basins as well as gridded mass change trends over different 5-year periods between.
We use the ITSG-Grace2016 release provided by TU Graz (www.tugraz.at/institute/ifg/downloads/gravity-field-models/itsg-grace2016), which includes spherical harmonic coefficients up to degree 90.
Different processing algorithms exist in order to derive the required information from the available data for the GIS. The round robin (RR) exercise carried out by TU Dresden has confirmed that the mass inversion and spherical harmonic filtering methods give comparable results. Therefore the GIS GMB setup is primarily based on the inversion method applied by DTU Space, where a direct estimate of mass changes are done in a direct least-squares generalized inverse processing. In addition, a second GMB product based on the regional integration approach using tailored sensitivity kernels is provided by TU Dresden.
Products by TU Dresden are also available directly from https://data1.geo.tu-dresden.de/gis_gmb/.