National Ocean Service

About: National Ocean Service is a government organization based out in Silver Spring, Maryland, United States. It is known for research contribution in the topics: Algal bloom & Population. The organization has 500 authors who have published 643 publications receiving 46096 citations.

Marine gravity from Geosat and ERS-1 altimetry in the Weddell Sea

Abstract: 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.

Observing global ocean circulation with SEASAT altimeter data

Abstract: A nondynamic algorithm for correcting the geo‐centric radius of the SEASAT orbit has been developed. This scheme reduces the satellite altitude error to a few decimeters and requires only weak a priori knowledge of sea surface undulations. Application has been made to a single three‐day period during which SEASAT took global altimeter measurements of sea surface topography with geographic resolution of 900 km at the equator. The resulting corrected SEASAT ephemeris then enabled computation of a sea surface largely free of the 2 to 7 m error that would otherwise arise from error in the ephemeris distributed with the SEASAT data. Subsequent subtraction of GEM L2 geoid heights from this sea surface has yielded ocean dynamic heights in reasonable qualitative and quantitative agreement with values obtained from oceanographic data. The fact that results of this quality could be obtained from only one three‐day arc of SEASAT data demonstrates the potential of satellite altimetry for determining global o...