SATELLITE ALTIMETRY, THE MARINE GEOID, AND THE OCEANIC GENERAL-CIRCULATION

For technical reasons, the general circulation of the ocean has histor ically been treated as a steady, laminar flow field. The recent availa bility of extremely high-accuracy and high-precision satellite altimet ry has provided a graphic demonstration that the ocean is actually a r apidly time-evolving turbulent how field. To render the observations q uantitatively useful for oceanographic purposes has required order of magnitude improvements in a number of fields, including orbit dynamics , gravity field estimation, and atmospheric variability. With five yea rs of very high-quality data now available, the nature of oceanic vari ability on all space and time scales is emerging, including new findin gs about such diverse and important phenomena as mixing coefficients, the frequency/wavenumber spectrum, and turbulent cascades. Because the surface elevation is both a cause and consequence of motions deep wit hin the water column, oceanographers soon will be able to provide gene ral circulation numerical models tested against and then combined with the altimeter data. These will be complete three-dimensional time-evo lving estimates of the ocean circulation, permitting greatly improved estimates of oceanic heat, carbon, and other property fluxes.