The SWOT satellite (Surface Water and Ocean Topography), launched into orbit in 2022 and the result of the collaboration between NASA and the French National Center for Space Studies (CNES), allowed you to get a new one very detailed map of the ocean floor. This was possible thanks to its particularly advanced technology, which overcomes the limits of previous satellites dedicated to ocean observation and those of exploration by oceanographic ships. In the new map they stand out abysmal hills And underwater mountains never identified before and are represented in detail i submerged margins of continents. This data is fundamental for the study of plate tectonics, the trend of ocean currents and marine ecosystems.
The map of the ocean floor obtained from the SWOT satellite: what it shows
Our knowledge of the morphology of the ocean floor today is still rather limited, despite the fact that in recent years oceanographic ships have contributed significantly to increasing the information available to us (in particular in the context of the project Seabed 2030which aims to obtain a complete high-resolution seabed map by 2030). The satellites used to date for this purpose provided images at resolutions that were too low. The resolution obtained from the SWOT satellite, however, is much higher than those provided previously.
The result of a year of SWOT surveys was a map of the ocean floor which shows the distribution of structures such as:
- abysmal hillsridges parallel to each other a few hundred meters high, whose direction has changed over time due to the movements of the lithospheric plates;
- underwater mountainsthe so-called seamountsancient extinct cone-shaped volcanoes which constitute an important habitat for many marine organisms and which influence the trend of ocean currents;
- continental marginswhich do not correspond to the coastline, but are found on the seabed along the base of the continental slope, and which sometimes coincide with the margins of lithospheric plates.
Knowing the topography of these structures in detail allows researchers to reconstruct the movements that affected the lithospheric plates and better define their limits, study the characteristics of the continental margins, better understand the trend of ocean currents and how they transport nutrients, identify risks to navigation.
The technology and objectives of the SWOT satellite
The SWOT satellite is located orbiting at 891 km altitude and covers the planet’s oceans, lakes and rivers a 21 day intervals. Its goal is not only to create high-resolution maps of the ocean floor, but also to monitor the levels of rivers and lakes.
SWOT uses the KaRIn tool (Ka-band Radar Interferometer), a radar interferometer high precision which includes two antennas mounted at the ends of a 10 m long arm: one sends radar signals towards the water surface, which reflects them, and both receive the reflected signals. The reflected signals present a phase difference due to the different position of the two antennas. By analyzing it it is possible to calculate precisely the heights of water bodies and their variation. The surface of the ocean, in particular, has protuberances and depressions that imitate the topography of the ocean floor and therefore allow it to be reconstructed. An advantage of this instrument is also that it can take measurements regardless of weather conditions or time of day.
The data obtained with SWOT will be used to quantify the volumes of water stored in different water bodies and their variations over time. For the ocean, SWOT also monitors the distribution of heat and ocean currents at depth. All this information is fundamental in the study of climate change and in the management of water resources.
