Abstract
We assess the accuracy and spatial resolution of the Surface Water and
Ocean Topography (SWOT) swath altimeter for measuring marine gravity
anomalies. The analysis is performed at the Foundation Seamounts in the
South Pacific where we developed a highly accurate gravity field by
combining the long-wavelength (> 40 km) gravity field
derived from previous nadir altimeters with the shorter wavelength
gravity field from the seafloor topography as constrained by the ship
gravity. In this region, the slope of the ocean variability is 50-100
times smaller than the gravity/slope signal of the seamounts so can be
ignored in the analysis. Each SWOT cycle can deliver gravity anomaly/SSS
with an accuracy of 2.6 mGal/μrad and a spatial resolution of 14 km,
with accuracy diminishing when significant wave height (SWH) exceeds
~6 meters. Averaging repeated SWOT measurements improves
the accuracy and resolution. For example, we expect that averaging just
10 repeats (7 months) results in accuracy/resolution that matches the
best marine gravity maps based on 230 months of nadir altimetry. With a
mission lasting over a year, SWOT promises a substantial leap in marine
gravity accuracy and resolution, uncovering previously uncharted details
of the seafloor, including thousands of uncharted seamounts.