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Woods Hole Oceanographic Institution


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Publications
»Sc.D. Thesis
»Recirculation gyres in a beta-plane jet
»Forcing and sampling of ocean models
»Thermohaline circulation - sea ice feedback
»Recirculation forced by an unstable jet
»Tidal dissipation over rough topography
»Dynamics of ocean heat transport variability
»Deep ocean currents from GRACE
»Estimates of tidally-driven mixing
»Millennial climate variability
»Oceanic eddy heat transport
»Ocean heat content from GRACE
»Tidally-driven mixing in an ocean model
»Ocean bathymetry and Earth's climate
»Bathymetry from space
»Subtropical mode water during KESS
»North Atlantic Ocean circulation from GRACE
»Subtropical mode water in the Kuroshio Extension
»Tidal mixing during the Last Glacial Maximum
»Kuroshio northern recirculation gyre
»Bottom pressure in KESS and GRACE
»Ocean model metrics
»Abyssal mixing in CCSM
»Kuroshio Extension jet and transport
»The Morphology of Steve


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D. T. Sandwell, W. H. F. Smith, S. Gille, E. Kappel, S. Jayne, K. Soofi, B. Coakley, and L. Geli , Bathymetry from space: Rationale and requirements for a new, high-resolution altimetric mission , Comptes Rendus Geoscience, 2006

Bathymetry is foundational data, providing basic infrastructure for scientific, economic, educational, managerial, and political work. Applications as diverse as tsunami hazard assessment, communications cable and pipeline route planning, resource exploration, habitat management, and territorial claims under the Law of the Sea all require reliable bathymetric maps to be available on demand. Fundamental Earth science questions, such as what controls seafloor shape and how seafloor shape influences global climate, also cannot be answered without bathymetric maps having globally uniform detail. Current bathymetric charts are inadequate for many of these applications because only a small fraction of the seafloor has been surveyed. Modern multibeam echosounders provide the best resolution, but it would take more than 200 ship-years and billions of dollars to complete the job. The seafloor topography can be charted globally, in five years, and at a cost under $100 M. A radar altimeter mounted on an orbiting spacecraft can measure slight variations in ocean surface height, which reflect variations in the pull of gravity caused by seafloor topography. A new satellite altimeter mission, optimized to map the deep ocean bathymetry and gravity field, will provide a global map of the world’s deep oceans at a resolution of 6–9 km. This resolution threshold is critical for a large number of basic science and practical applications, including:
  • determining the effects of bathymetry and seafloor roughness on ocean circulation, mixing, climate, and biological communities, habitats, and mobility;
  • understanding the geologic processes responsible for ocean floor features unexplained by simple plate tectonics, such as abyssal hills, seamounts, microplates, and propagating rifts;
  • improving tsunami hazard forecast accuracy by mapping the deep-ocean topography that steers tsunami wave energy;
  • mapping the marine gravity field to improve inertial navigation and provide homogeneous coverage of continental margins;
  • providing bathymetric maps for numerous other practical applications, including reconnaissance for submarine cable and pipeline routes, improving tide models, and assessing potential territorial claims to the seabed under the United Nations Convention on the Law of the Sea.
Because ocean bathymetry is a fundamental measurement of our planet, there is a broad spectrum of interest from government, the research community, industry, and the general public. Mission requirements. The resolution of the altimetry technique is limited by physical law, not instrument capability. Everything that can be mapped from space can be achieved now, and there is no gain in waiting for technological advances. Mission requirements for Bathymetry from Space are much less stringent and less costly than typical physical oceanography missions. Long-term sea-surface height accuracy is not needed; the fundamental measurement is the slope of the ocean surface to an accuracy of ~1 μrad (1 mm km−1). The main mission requirements are:
  • improved range precision (a factor of two or more improvement in altimeter range precision with respect to current altimeters is needed to reduce the noise due to ocean waves);
  • fine cross-track spacing and long mission duration (a ground track spacing of 6 km or less is required. A six-year mission would reduce the error by another factor of two);
  • moderate inclination (existing satellite altimeters have relatively high orbital inclinations, thus their resolution of east–west components of ocean slope is poor at low latitudes. The new mission should have an orbital inclination close to 60o or 120o so as to resolve north–south and east–west components almost equally while still covering nearly all the world’s ocean area);
  • near-shore tracking (for applications near coastlines, the ability of the instrument to track the ocean surface close to shore, and acquire the surface soon after leaving land, is desirable).


FILE » Sandwell_2006.pdf


» Sandwell_whitepaper.pdf
White paper in support of a high-resolution, ocean altimeter mission, in Report of the High-Resolution Ocean Topography Science Working Group Meeting, ed. D. B. Chelton.


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