The ocean still holds many secrets. Despite technological advancements, the underwater relief remains less known than the surface of the Moon. However, a satellite designed by NASA and CNES has just unveiled the details with unprecedented precision.
The SWOT (Surface Water and Ocean Topography) satellite, launched in December 2022, has mapped the seabed in just one year. This map, achieved with an 8-kilometer (approximately 5-mile) resolution, surpasses 30 years of data collected by previous satellites. Researchers have discovered thousands of abyssal hills and underwater volcanoes previously invisible.
Until now, most underwater surveys were based on satellite altimetry. This technique involves deducing seabed topography from height variations on the ocean's surface. Seamounts, for instance, alter local gravity, causing water to accumulate above them.
SWOT introduces innovation by measuring these variations in two dimensions. The more precise surveys have made it possible to discern previously unknown geological structures. While studying abyssal hills, scientists noticed shifts in the alignment of ridges. This suggests that the tectonic plates responsible for these features have changed their movement over time.
The SWOT data also revealed thousands of small underwater volcanoes less than 1,000 meters (approximately 3,280 feet) tall. These formations influence ocean currents and host remarkable biodiversity. Some of these volcanoes were buried under sediments or located in areas previously deemed to have no significant relief.
Continental margins, also targeted by SWOT, play a critical role in coastal ecology and ocean dynamics. Located at the junction between continents and ocean floors, these zones consist of gentle or steep slopes extending to great depths.
They act as dynamic interfaces where currents, tides, and biological activities transport and redistribute nutrients and sediments. This process is essential for coastal marine ecosystems, promoting biodiversity and supporting local food chains. The surveys have improved mapping of these sensitive areas, often distorted by less accurate measurements.
The team led by Yao Yu, a researcher at the Scripps Institution of Oceanography, plans to continue using SWOT's data for another three years. With more surveys, it may be possible to study variations in the marine gravitational field caused by underwater volcanic eruptions or tectonic movements.
By refining seabed mapping, the SWOT mission opens new perspectives for oceanic geology. The gathered data will help better understand tectonic plate dynamics and assess the state of marine ecosystems.
Article author: Cédric DEPOND