La Jolla , CA 92093 - 0225

The surface of the ocean bulges outward and inward reflecting the topography of the ocean floor. A dense mapping of ocean surface topography from declassified Geosat altimeter data (US Navy), ERS-1 altimeter data (European Space Agency), and repeat-track coverage from the Topex/Poseidon altimeter (NASA and CNES) has provided the first view of the ocean floor structures in many remote areas of the Earth. The spatial resolution of the derived gravity field is limited by travel-time noise from ocean waves and can be improved through additional dense measurements. Altimeter-derived gravity can be used to estimate seafloor topography but only over an intermediate wavelength band (200 < λ < 20 km) and only in areas where sediment cover is thin. The longer wavelength variations in depth are constrained by depth soundings collected by research vessels over the past 30 years. Detailed bathymetry is essential for understanding physical oceanography, marine geophysics, and perhaps even biological oceanography. Currents and tides are controlled by the overall shapes of the ocean basins as well as the smaller sharp ocean ridges and seamounts. Because erosion rates are low in the deep oceans, detailed bathymetry reveals the mantle convection patterns, the plate boundaries, the cooling/subsidence of the oceanic lithosphere, the oceanic plateaus, and the distribution of off-ridge volcanoes.