Mapping Seafloor Tectonics from Satellite Altimetry: Requirements for a Future Mission
David Sandwell(1) and Walter H. F. Smith(2)
Scripps Inst. of Oceanography,
1102 IGPP Scripps Institution of Oceanography,
La Jolla, CA 92093-0225,
(2) U.S. National Oceanic and Atmospheric Administrati, 1315 East West Hwy. Room 5408, Silver Spring MD 20910-3282 , United States
Our current understanding of the topography and tectonics of the ocean basins is largely derived from dense satellite altimeter measurements of the marine gravity field combined with sparse geophysical measurements from research vessels. Data from ERS-1 and Geosat provided not only a spectacular confirmation of plate tectonics but also partly revealed smaller-scale structures including thousands of seamounts, propagating rifts, ridge jumps, and global-scale variations in seafloor roughness. In addition, the dense gravity information was combined with sparse ship soundings to construct global bathymetry maps at ~10 km resolution - a great improvement over hand-drawn maps but still far worse than our current maps of Mars, Venus, and the Moon. While these data filled a huge gap in our understanding of the ocean basins, they also triggered a thirst for more. Research efforts over the past few years have provided a 30-40% improvement in gravity field accuracy by retracking the raw altimeter waveforms using methods optimized for range precision. However, there are three broad areas of earth science that require an additional factor of 5 improvement in gravity accuracy that can only be achieved with third generation altimeters: (1) resolving the fine-scale tectonic structure of the deep ocean floor (e.g., abyssal hills, microplates, propagating rifts, seamounts, meteorite impacts); (2) measuring the roughness spectra of the seafloor on a global basis to better constrain models of tidal dissipation, vertical mixing, and mesoscale circulation of the oceans; and (3) resolving the fine-scale gravity field for research, exploration and navigational needs.