||Global Surface Mass Variations from GRACE, GPS and ECCO-JPL Ocean Model
Facets of surface mass variations include land hydrology, ice mass imbalance, non-steric sea level changes and geocenter motion. The successful launch and operation of the GRACE gravity mission have marked a revolutionary transition from local and component measurements to global high resolution mass transport monitoring. However, no single geodetic technique currently can provide complete spectral or spatial coverage. GRACE's time-variable gravity, GPS deformation measurements, and a data-assimilated ocean bottom pressure model contain overlapping and complementary information. These different types of data are used separately and in combination to validate and achieve better results. The combination of GRACE/GPS/OBP over 18 months has yielded high-quality monthly degree-1 surface mass estimates with an equivalent precision of 0.5 mm in all three components of annual geocenter motion. This is significantly below the possible 1-mm accuracy limit expected from SLR due to its sparse and shrinking tracking network configuration. Full spectrum results up to degree and order 50 in spherical harmonic and spatial domains including mass variations over the oceans, Antarctica and Greenland will also be presented.