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Swot measurements help in seafloor mapping

Image of the Month - May 2024

Conventional nadir altimetry has improved the global ocean bathymetry maps. The bathymetry of the seafloor represents a large contrast in density between the seawater and the rock.  Bathymetric highs associated with, for example, ridges or seamounts have an extra mass relative to the surrounding seafloor.  This extra mass produces a local increase in the pull of gravity causing a small bump in the ocean surface that can be measured by radar altimetry (see Applications: bathymetry).
Swot is providing a dramatic increase in the accuracy and resolution of the ocean surface topography and thus the seafloor bathymetry. 

A study by the Scripps Institute of Oceanography has begun on the subject, using data from the one-day calibration phase over a region of the South Pacific including the Foundation Seamounts (around 240°E, 37°S). The Swot coverage includes 30 submarine volcanoes in an area where the ocean topography and gravity field are well known from shipboard surveys, and where ocean dynamics are relatively weak so stacking many repeats suppresses the ocean variability signal to reveal the gravity signal. 
The RMS difference between Swot's stacked slopes and reference slopes is comparable to the best in-situ gravity data, and four times better than the best Saral altimetry data after filtering.  
In short, a single KaRIn altimeter swath can produce marine gravity data of a quality comparable to that obtained over 20 years of conventional nadir altimetry. The accuracy and resolution of the Swot-derived marine gravity field should exceed current models after 8 months. 

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