Using satellite altimetry data from SWOT, scientists have created a global map of marine gravity, uncovering thousands of new seamounts. (Eötvös is a unit that measures the ocean’s vertical gravity gradient.) Credit: Yao Yu, Yu et al., 2024, https://doi.org/10.1126/science.ads4472
The Surface Water and Ocean Topography (SWOT) mission instruments have allowed for the clearest satellite-produced map of the seafloor to date, according to a new study in Science. The work could help researchers better understand everything from biodiversity hotspots to plate tectonics to tsunami propagation.
Ship-based sonar has a resolution of about 200-400 meters (650-1,300 feet). The Seabed 2030 project aims to map the entire ocean floor by the end of the decade using this method. However, the relatively time-consuming and expensive technique has imaged only about 25 percent of the seafloor so far.
Most seafloor map images are derived from satellite altimetry, which measures height variations of the ocean’s surface. Scientists use this information to make inferences about seafloor features that influence sea surface level by affecting marine gravity (e.g., sea level is higher over a seamount). During the last 30 years, data gathered by satellite instruments have allowed scientists to map marine gravity at a resolution of about 12-16 kilometers (7.5-9.9 miles).
Jointly developed by NASA and the Centre National d’Etudes Spatiales (CNES, the French national space agency) and launched in 2022, SWOT measures sea surface height in two dimensions rather than one. In the new study, researchers used SWOT data from April 2023 to July 2024 to map marine gravity at a resolution of 8 kilometers (5 miles).
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