Investigation of the shore-based gravity variations caused by the effect of oceanic tidal loads with atomic gravimeter

Gravity measurement in coastal areas is critically affected by ocean tidal loading (OTL). However, the model of OTL is not accurate enough for offshore high-precision gravity measurement at present. In this paper, we carry out the investigation of gravity variations for the measured location that is far from the shore. Theoretically, we found that the existing gravity-corrected model for OTL needs to be further improved. Currently, the OTL model calculates the effect of tidal waves globally. However, the influence of local mass changes on gravity measurement should be taken into account, especially since the observed location is far from the coast. The effect of regional seawater mass on gravity measurement has been analyzed, and a new modified model for OTL has been presented. For further verification, the gravity measurement experiments are carried out based on a homemade atomic gravimeter for the measured location, which is 230 m far away from the shore and surrounded by seawater. Even in the harsh measurement environment of a wharf, the continuous monitoring of gravity has been implemented for about three days, and the measurement sensitivity of our atomic gravimeter is estimated to be 0.76 mGal/√Hz for an interrogation time of 110 ms. Moreover, the gravity changes of approximately 170 μGal have been observed with the variation of regional seawater mass, which agree well with the calculated results based on the new modified model of OTL. The results of this paper may be helpful for the high-precision calibration of marine gravimeters