The Use of the Geocenter as a Kinematic Reference Point for Large Scale Geophysical Studies

Because the relative motion between the tracking site polyhedron (located on the solid earth only) and the center of mass of the entire Earth (lithosphere/hydrosphere/atmosphere/cryosphere) system is a proxy for hemisphere-scale mass distribution, it has, along with other low degree spherical harmonic changes and Earth rotation variations, been used to constrain large scale oceanographic and atmospheric models of mass transport. However, with the advent of the Gravity Recovery and Climate Experiment (GRACE) scheduled to launch soon, thousands of harmonic terms will be observed routinely, and therefore this application of the geocenter will likely be less interesting. However, the geocenter remains important as a kinematic reference point. For example, recent papers by the authors have indicated the importance of correcting for frame translational rates in interpreting site verticals for postglacial rebound studies. In this presentation, we will review these results and extend them to the study of the sea level from altimetric satellites by demonstrating the effect on inferred sea level from long period and secular terms in the geocenter affecting the satellite orbit reference frame.