Applications of satellite altimetry to oceanography and geophysics |
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Authors: | Robert E Cheney Bruce C Douglas David T Sandwell James G Marsh Thomas V Martin John J McCarthy |
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Institution: | (1) National Ocean Service, NOAA, 20852 Rockville, MD, USA;(2) NASA Goddard Space Flight Center, 20771 Greenbelt, MD, USA;(3) EG&G Washington Analytical Services Center, 20737 Riverdale, MD, USA |
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Abstract: | Satellite-borne altimeters have had a profound impact on geodesy, geophysics, and physical oceanography. To first order approximation,
profiles of sea surface height are equivalent to the geoid and are highly correlated with seafloor topography for wavelengths
less than 1000 km. Using all available Geos-3 and Seasat altimeter data, mean sea surfaces and geoid gradient maps have been
computed for the Bering Sea and the South Pacific. When enhanced using hill-shading techniques, these images reveal in graphic
detail the surface expression of seamounts, ridges, trenches, and fracture zones. Such maps are invaluable in oceanic regions
where bathymetric data are sparse. Superimposed on the static geoid topography is dynamic topography due to ocean circulation.
Temporal variability of dynamic height due to oceanic eddies can be determined from time series of repeated altimeter profiles.
Maps of sea height variability and eddy kinetic energy derived from Geos-3 and Seasat altimetry in some cases represent improvements
over those derived from standard oceanographic observations. Measurement of absolute dynamic height imposes stringent requirements
on geoid and orbit accuracies, although existing models and data have been used to derive surprisingly realistic global circulation
solutions. Further improvement will only be made when advances are made in geoid modeling and precision orbit determination.
In contrast, it appears that use of altimeter data to correct satellite orbits will enable observation of basin-scale sea
level variations of the type associated with climatic phenomena. |
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