Stacked global satellite gravity profiles

Gravity field recovery from satellite altimetry provides global marine coverage but lacks the accuracy and resolution needed for many exploration geophysics studies. The repeating ground tracks of the ERS-1/2, Geosat, and Topex/Poseidon altimeters offer the possibility of improving the accuracy and resolution of gravity anomalies along widely spaced (∼40-km spacing) tracks. However, complete ocean coverage is usually needed to convert the sea-surface height (or along-track slope) measurements into gravity anomalies. Here we develop and test a method for constructing stacked gravity profiles by using a published global gravity grid (Sandwell and Smith, 1997), V7.2, as a reference model for the slope-to-gravity anomaly conversion. The method is applied to stacks (averages) of Geosat/ERM (up to 62 cycles), ERS-1/2 (up to 43 cycles), and Topex (up to 142 cycles) satellite altimeter profiles. We assess the accuracies of the ERS-1/2 profiles through a comparison with a gravity model of the northern Gulf of Mexico (profiles provided by EDCON Inc.). The 40 ERS profiles evaluated have a mean rms difference of 3.77 mGal and full wavelength resolution (0.5 coherence) of 24 km. Our processing retains wavelengths as short as 10 km so smaller, large-amplitude features can be resolved, especially in shallowoceanareas (<1000mdeep).Weprovide an example of combining these higher resolution profiles with lower resolution gravity data in the Caspian Sea.