Estimation of regional ice mass trends in Greenland using a global inversion of level-2 satellite gravimetry data

Abstract

A methodology has been developed for an accurate estimation of mass anomalies in the Earth system using level-2 data products from satellite gravimetry GRACE and GRACE Follow-On (GFO) missions. Its key elements are: (i) direct inversion of Spherical Harmonic Coefficients (SHCs)—or SHC trends—into a global distribution of mass anomalies (or their trends); (ii) Spatially-varying regularization that takes into account available information about the behavior of mass anomalies; and (iii) rigorous optimization of the data processing consistently with the target estimates. The methodology is applied to quantify the mass balance of the Greenland Ice Sheet and its individual Drainage Systems (DSs) in Apr. 2002–Aug. 2023 on the basis of GRACE/GFO monthly solutions from the Institute of Geodesy at Graz University of Technology (ITSG). It is found that the rate of the total mass loss in Greenland was 271±10 Gt/yr. It varied between 19±4 Gt/yr in northeast DS and 77±7 Gt/yr in southeast DS. In average, the mass balance of individual DSs is estimated with an accuracy better than 5 Gt/yr. As a consequence, the obtained estimates show a sufficiently high signal-to-noise ratio (between 5 in the northeast DS and 42 in the northwest DS). This opens the door, among other, for using GRACE/GFO data for a comparison, validation, and calibration of physical models describing mass changes in Greenland, including its surface mass balance, at the scale of individual DSs.