| Summary: | We present new altimetric marine gravity fields of the polar oceans covering the entire Southern Oceans and the Arctic Ocean up to 81.5N derived from the ERS-1 geodetic mission and ERS-1/2 tandem mission. The fields include poorly charted areas which are covered by both seasonal and persistent sea ice. To retrieve gravity measurements over ice covered regions requires reprocessing of the full waveform telemetry data set to correct for errors in surface elevation measurements which occur over ice. In both of the polar oceans the new gravity fields have excellent spatial resolution (approaching 20 km in most areas and 30 km in perpetually ice-covered seas). Hence they provide an unprecedented view of tectonic fabric in polar seafloor. Signatures in the Arctic gravity field, such as that of an apparent fossil spreading ridge in the Canada Basin, provide valuable constraints on the tectonic opening of the basin. In the Antarctic, the gravity field of the Weddell Sea embayment reveals structures which reflect its complex, uncertain history. Gravity over the Amundsen Sea permits a significant, new southward tracing of fracture zones (e.g., the Pahemo, Endeavor) that abut Marie Byrd Land, conjugate to those adjacent to the Campbell Plateau. This result places significant new constraints on the early history of separation between the New Zealand micro-continent and Marie Byrd Land, West Antarctica; it indicates regional extension which is consistent with the Bellingshausen paleo-plate hypothesis.
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