Oceanwide gravity anomalies from GEOS‐3, Seasat and Geosat altimeter data

Abstract

Three kinds of satellite altimeter data have been combined, along with 5'×5' bathymetric data, to calculate a 0°.125 ocean wide gridded set of 2.3×106 free‐air gravity anomalies. The procedure used was least squares collocation that yields the predicted anomaly and standard deviation. The value of including the bathymetric data was shown in a test around the Dowd Seamount where the root mean square (rms) difference between ship gravity measurements decreased from ±40 mgal to ±20 mgal when the bathymetry was included. Comparisons between the predicted anomalies and ship gravity data is described in three cases. In the Banda Sea the rms differences were ±20 mgal for two lines. In the South Atlantic rms differences over lines of 2000 km in length were ±7 mgal. For cruise data in the Antarctica region the discrepancies were ±12 mgal. Comparisons of anomalies derived from the Geosat geodetic mission data by Marks and McAdoo [1992] with ship data gave differences of ±6 mgal showing the value of the much denser Geosat geodetic mission altimeter data.