High-Resolution Gravity, Tomography, and Seafloor Roughness

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Intellectual Merit: Over the past 5 years an improved global marine gravity and bathymetry grids has been constructed with 1-minute resolution. Raw satellite altimeter waveforms from 1 year of ERS-1 and 1.5 years of Geosat were re-tracked, which has resulted in a 40% improvement in the accuracy of the global marine gravity field, enabling new scientific investigations of transform faults, seamounts, seafloor fabric, and ocean mixing. The improved gravity, combined with a new assembly of global depth soundings, is resulting in a new global bathymetry grid at 1 minute resolution. The present project involves merging the 1-minute resolution marine gravity model with a soon-to-be-published global gravity model (EGM08) complete to spherical harmonic degree 2160 (5 minute resolution), resultig in a seamless gravity field across the shorelines. A grid of uncertainty in the marine gravity will be constructed, based on altimeter data density, altimeter noise, and comparisons with shipboard gravity. A matching bathymetry/topography grid will be generated, with a focus on shallow ocean (1000 m) areas where new soundings are rapidly becoming available. A 1-minute data source grid will be developed that provides the link to the original sounding data. Web access will be provided to all of these data products including: grids, cleaned soundings, and images/maps. These new data resources will be used to investigate the effects of spreading rate on ridge segmentation, lithospheric strength, and crustal structure. These improvements to the global marine gravity and bathymetry grids will benefit scientific and petroleum exploration studies of continental margins. These data are foundational to many scientific studies supported by NSF and benefit a wide range of ocean science investigations. This project will ensure the data are freely available to everyone.Broader Impacts: Global bathymetric charts are used in many areas outside of the scientific community including: K-12 teaching of earth science and seafloor geography; undergraduate-level earth science and plate tectonics; law of the sea; mineral exploration; planning of fiber-optic cable routing and general interest by the public. This information is available on our web site http://topex.ucsd.edu in a variety of formats for expert, intermediate, and novice users.