2001: Non-tidal oceanic contributions to gravitational field changes

Abstract. This study examines the nontidal contributions of the oceans to the Earth's gravitational field variations as predicted by a global ocean general circulation model: the Parallel Ocean Climate Model. Such variations in the gravitational field Stokes coefficient are determined up to spherical harmonic degree and order 20 and compared with satellite laser ranging (sLR) data from LAGEOS I and LAGEOS II. For most Stokes coefficients except the lowest-degree ones, this investigation indicates that he application f sea level adjustment to reduce the effects of the model's lack of mass conservation due to the Boussinesq approximation has a negligible effect on timescales l s than a few years. Predicted gravitational changes show strong seasonal variability and account •or a portion of the variations e timated from SLR. We conclude that, in addition to the atmosphere, the oceans are an important contributor to the temporal variations inthe Earth's gravitational field. The Stokes coefficients are useful in examining oceanic mass tran. sport between hemispheres and ocean basins. The estimated oceanic power spectrum has a spectral shape similar to the atmosphere and is well above the noise level of planned satellite missions like the Gravity Recove • and Climate Experiment (GRACE)