Estimating polar marine free-air gravity anomalies from dense radar altimeter data

Geological free-air gravity anomalies of the polar marine areas were estimated from dense ERS1 radar altimeter data. Data processing techniques were developed to deal with data gaps from the seasonal ice coverage, directional variations of the ascending and descending orbital data tracks, and other high-latitude mapping problems. To reduce along-track data distortions, the ERS1 168 altimetry data were geodetically co-phased and spectral correlation filtered. Geoid undulations were first estimated and converted to the free-air gravity anomalies by Brun’s formula and the fundamental equation of geodesy. The results in the open waters of the Barents and Kara Seas of the Russian Arctic show good coherence with global model and shipborne data, whereas along the coastline, strong ocean currents, possible tidal model inaccuracies, and poor data coverage limit the coherence. The approach uses local satellite altimetry to update reference gravity models in the polar regions. It thus has considerable utility for resolving details of the polar marine gravity field as global warming removes the ice cover and the cross-track distance of altimeter missions decreases.