The effects of sea-surface height variations on the long-period gravity changes

he effects of sea-level variations may be one of the noise sources of some of the solid-earth observations. Since the effects are so smal1 as to be usually neglected for conventional observations, they have not been studied in detail so far. However, the recent observation using superconducting gravimeters (SG) has the potential to detect such a very weak gravity signal. Our preliminary estimation using TOPEX/Poseidon altimeter data showed that the induced gravity signal reached a few micro Gals in peak to peak amplitude. The estimation, however, may contain some errors due to inclusion of steric components of sea surface height (SSH) variation, which actually produce no gravity effect. In this study, we thus recalculate the gravity effects by removing the steric components from SSH. The data sets employed are POCM (Paral1el Ocean Climate Model) SSH and the steric components are evaluated from SST (sea surface temperature) which used to calculate the POCM SSH. To investigate the characteristic of the gravity changes obtained, we applied the EOF analysis to both SSH data and induced gravity changes. The results show that one of the EOF components is strongly correlated to ENSO like SSH variations. The amplitude of expected gravity changes in the pacific equatorial regions may reache 2 to 3 μGal. This amount of amplitude could be detectable enough through a careful gravity observation of ground base and/or through satellite gravity missions now being planed.