Decadal ocean bottom pressure variability and its associated gravitational effects in a coupled ocean- atmosphere model

The launch of the Gravity Recovery and Climate Experiment (GRACE) satellite mission in March 2002 has made timely the study of geophysical processes that redistribute the Earth's mass. This study uses the Hadley Centre coupled oceanatmosphere model HadCMS to examine the ocean's role in mass redistribution on inter-annual to decadal timescales. The leading empirical mode of interannual bottom pressure variability is a striking, basin-wide, oscillation between the Atlantic and Pacific Oceans. Our analysis suggests that this mode is primarily a wind driven phenomenon. We find some evidence for such a mode in a re-analysis of the global ocean, although the indirect nature of this evidence means no certain conclusions can yet be drawn. Thus, we consider the gravitational effects of this mode and the potential of current geodetic missions to detect it. A surprising result is that oceanic mass redistribution can lead to decadal trends in the zonal harmonic J₂, with a slope of approximately one-third that observed in geodetic measurements of J₂, all of which is normally attributed to post glacial rebound.