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1 Geosciences Laboratory, Ocean and Earth Sciences, National Ocean Service, NOAA, Silver Spring, Maryland USA
2 Mullard Space Science Laboratory, University College London
A high-resolution gravity field covering virtually all of the Weddell Sea has been derived using a combination of Geosat and ERS-1 data. This field encompasses the entire Weddell Sea region, including areas which are seasonally, as well as areas which are perpetually, covered by sea ice, but excludes areas covered by ice shelves. Permanent sea-ice cover has precluded exploration of large areas of the Weddell Sea by ships and, until now, by satellite altimeters. Complex radar echoes from sea ice confuse trackers onboard altimeter satellites and produce noisy height estimates. As a result, altimeter data over sea ice have usually been removed before marine gravity is computed. We have now, however, reprocessed or ‘retracked’ sea ice echo waveforms from ERS-1, and determined marine gravity fields over ice-covered as well as ice-free ocean. This new gravity map permits us to view tectonic details imprinted in the ocean floor by the complex history of divergence and relative motion between the South American and Antarctic plates as well as motions between crustal blocks comprising West Antarctica. These details include: (1) gravity lineations which are the gravitational expression of fracture zones that trace the history of seafloor spreading in the Weddell Sea; (2) gravitational expression of an ocean-continent boundary in the western Weddell Sea flanking the east coast of the Antarctic Peninsula (Graham Land); (3) a scarp-like gravity anomaly which coincides with the magnetically expressed ‘Orion anomaly’ at about 71°S; (4) a linear, relative gravity high in the southeastern Weddell Sea which parallels the coast and roughly coincides with the (failed) Weddell Rift/Explora Wedge; (5) adjacent linear gravity lows which directly overlie narrow buried basement ridges known as the Explora and Andenes escarpments.
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This 250-word extract was created in the absence of an abstract.
