Stacked global satellite gravity profiles

Gravity field recovery from satellite altimetry provides global marine cove rage but lacks the accuracy and resolution needed for many exploration geop hysics studies. The repeating ground tracks of the ERS-1/2, Geosat, and Top ex/Poseidon altimeters offer the possibility of improving the accuracy and resolution of gravity anomalies along widely spaced (similar to 40-km spaci ng) tracks. However, complete ocean coverage is usually needed to convert t he sea-surface height (br along-track slope) measurements into gravity anom alies. Here we develop and test a method for constructing stacked gravity p rofiles by using a published global gravity grid (Sandwell and Smith, 1997) , V7.2, as a reference model for the slope-to-gravity anomaly conversion. T he 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 compa rison with a gravity model of the northern Gulf of Mexico (profiles provide d 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 p rocessing retains wavelengths as short as 10 km so smaller, large-amplitude features can be resolved, especially in shallow ocean areas (<1000 m deep) . We provide an example of combining these higher resolution profiles with lower resolution gravity data in the Caspian Sea.