Earth's surface mass transport derived from GRACE, evaluated by GPS, ICESat, hydrological modeling and altimetry satellite orbits

Abstract

The Gravity Recovery and Climate Experiment (GRACE) delivered the most accurate quantification of global mass variations with monthly temporal resolution on large spatial scales. Future gravity missions will take advantage of improved measurement technologies, such as enhanced orbit configurations and tracking systems, as well as reduced temporal aliasing errors. In order to achieve the latter, sub-monthly to daily innovative models are computed. In addition, non-conventional methods based on radial basis functions (RBFs) and mascons will give the ability to compute models in regional and global representations as well. We show that the RBF modeling technique can be used for processing GRACE data yielding global gravity field models which fit independent reference values at the same level as commonly accepted global geopotential models based on spherical harmonics. The present study compares for the first time a complete global series of solutions in order to quantify recent ice mass changes. We further compare the ice-induced crustal deformations due to the dynamic loading of the crustal layer with the Global Positioning System (GPS) uplift measurements along Greenland's coastline. Available mass change estimates based on Ice, Cloud, and land Elevation Satellite (ICESat) laser altimetry measurements both in Greenland and Antarctica are used to assess the GRACE results. A comparison of GRACE time series with hydrological modeling for various basin extensions reveals overall high correlation to surface and groundwater storage compartments. The forward computation of satellite orbits for altimetry satellites such as Envisat, Jason-1 and Jason-2 compares the performance of GRACE time-variable gravity fields with models including time variability, such as EIGEN-6S4.