Comparison of surface and shipborne gravity data with satellite-altimeter gravity data in Hudson Bay

Several free satellite-altimetry models in the public domain may be used to study the Earth's gravity field. In this study, we compare the Bouguer anomaly map of the Hudson Bay region calculated from the satellite-derived V18 model of D. Sandwell (Scripps Institution of Oceanography) and W. Smith (National Oceanic and Atmospheric Administration) with one compiled from measurements (GSC data set) made on the ice shelf and by ship. Noise exists in both data sets and takes the form of linear anomalies along ship tracks on the GSC map and of random high-frequency anomalies on the map derived from satellite altimetry. Spectral analysis of both maps indicates a good correspondence for anomalies wider than 15 km. In central Hudson Bay, the mean difference between the two maps is −1.6 mGal indicating only a small offset between the two data sets. Standard deviation of the difference is 2.35 mGal. The correspondence between anomaly shapes on profiles indicates that satellite-derived gravimetry is certainly good enough for regional studies. Our analysis confirms the usefulness of satellite-derived gravity in areas with incomplete gravity coverage such as the Hudson Strait and Foxe Basin north of Hudson Bay.