Determination of Gravity Anomaly Using Satellite Altimeter Data in the Great Lakes

In this paper, the determination of gravity anomalies in the Great Lakes using satellite altimeter data of GEOSAT Geodetic Mission (GM) and TOPEX/Poseidon is discussed. The seasonal change of lake level was observed from TOPEX/Poseidon satellite altimeter data. This analysis of lake level change was made to determine the mean lake surface profiles along the TOPEX/Poseidon repeat tracks. The least squares collocation was used to predict gravity anomalies. The gravity anomalies are determined by using mean lake surface profiles derived from TOPEX altimeter data and along-track slopes and azimuth derived from lake surface heights measured by the GEOSAT altimeter. To remove influences of the cycle-to-cycle time variation of lake level, along-track slopes of altimeter height are used. These results are compared to the exisiting surface gravit data measured in the Great Lakes. The gravity anomaly in the Lake Huron derived from the altimeter data using the least squares collocation shows slightly better comparison with the surface gravity anomaly than that implied by the EGM-96 gravity model.