The Ocean still holds many secrets. Despite technological progress, the underwater relief remains less known than the surface of the Moon. A satellite, designed by NASA and Cnes, has just revealed the details with unprecedented precision.
The SWOT (Surface Water and Ocean Topography) satellite, launched in December 2022, made it possible to map the seabed in just one year. This map, obtained with a resolution of 8 kilometers, surpasses 30 years of data collected by previous satellites. Researchers there have discovered thousands of previously invisible abyssal hills and underwater volcanoes.
The majority of underwater records until then came from satellite altimetry. This technique consists of deducing the topography of the seabed from variations in height at the surface of the ocean. Seamounts, for example, modify the gravity local, causing water to accumulate above them.
SWOT innovates by measuring these variations in two dimensions. The more precise surveys made it possible to discern geological structures that were hitherto unknown. By studying the abyssal hills, scientists observed changes in the orientation of the ridges. This suggests that the tectonic plates at the origin of these reliefs have modified their movement over the ages.
SWOT data also revealed thousands of small underwater volcanoes, measuring less than 1,000 meters in height. These formations influence marine currents and shelter remarkable biodiversity. Some of these volcanoes were buried under sediments or located in areas previously considered without notable relief.
Continental margins, also targeted by SWOT, play a critical role in coastal ecology and ocean dynamics. Located at the junction between the continents and the ocean floors, these zones constitute gentle or steep slopes which extend to great depths.
They act as dynamic interfaces where currents, tides and biological activities transport and redistribute nutrients and sediments. This process plays a key role for coastal marine ecosystems, promoting biodiversity and supporting local food chains. The surveys made it possible to improve the mapping of these sensitive areas, often distorted by less precise measurements.
The team led by Yao Yu, a researcher at the Scripps School of Oceanography, plans to continue exploiting SWOT data for another three years. With more surveys, it will be possible to study variations in the marine gravitational field caused by underwater volcanic eruptions or tectonic movements.
By refining the mapping of the seabed, the SWOT mission opens new perspectives for ocean geology. The data collected will be used to better understand the dynamics of tectonic plates, but also to assess the state of marine ecosystems.
