NASA’s latest observations from the Surface Water and Ocean Topography (SWOT) satellite have revealed thousands of previously undetected underwater mountains—some less than half the size traditionally required for detection. This breakthrough in seafloor mapping marks a major leap forward in oceanography, offering scientists a far more detailed and accurate picture of the ocean floor than ever before.
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Launched in December 2022 through a partnership between NASA and the French space agency CNES (Centre National d’Études Spatiales), SWOT was originally designed to measure water surface heights across Earth’s lakes, rivers, and oceans. But thanks to its cutting-edge radar technology, the satellite is now uncovering hidden features that could double the number of known seamounts and reshape how we study Earth’s underwater terrain.
Rethinking How We Map the Ocean Floor
For decades, seafloor mapping has relied mainly on sonar technology from ships, capturing direct measurements by bouncing sound waves off the seabed. While accurate, this method is time-consuming and expensive, limiting its reach to just 25 % of the ocean floor. The remaining 75 % has been approximated using satellite data with much lower resolution, leaving massive gaps in our understanding of undersea terrain.
This patchwork view has limited researchers’ ability to fully grasp the structure and dynamics of the ocean floor. With such a large portion still uncharted, the need for a more efficient, large-scale mapping solution has become increasingly urgent.
SWOT’s Approach: Seeing the Ocean Floor from Space
SWOT addresses this problem using radar interferometry, a technique that allows scientists to observe subtle variations in water surface height from orbit. These surface variations are not random—they’re often shaped by gravitational differences caused by features on the seafloor. In other words, underwater mountains, ridges, and valleys slightly alter the gravity field, which in turn creates tiny—but measurable—bumps or dips in the sea surface above.
At the heart of this capability is SWOT’s Ka-band Radar Interferometer (KaRIn). This instrument uses a pair of radar antennas to scan wide swaths of Earth’s surface with centimeter-level accuracy. By sending radar pulses toward the planet and recording how long they take to return, KaRIn can detect extremely small shifts in sea surface elevation—shifts that hint at what’s hidden far below.
Complementing KaRIn is SWOT’s dual-frequency Poseidon altimeter, which adds another layer of data critical to interpreting these gravitational signals. Together, these instruments allow SWOT to observe nearly 90 % of Earth’s surface every 21 days, building a dynamic and high-resolution dataset of sea surface—and seafloor—influences over time.
Early Findings: A New Map Emerges
Initial analysis of SWOT data has already started to reshape our understanding of the ocean’s structure. The satellite is revealing underwater features like seamounts and abyssal hills, which are estimated to cover about 70 % of the ocean floor. These features are geologically significant—they provide insights into plate tectonics, help explain the movement of ocean currents, and serve as crucial habitats for marine life.
A particularly striking discovery is SWOT’s ability to detect smaller seamounts—some less than 700 meters tall—compared to the 1.5-kilometer threshold needed by previous satellites. This new sensitivity could increase the number of known seamounts from 44,000 to around 100,000, dramatically expanding our inventory of the seafloor’s most prominent features.
This is more than a scientific curiosity. Seamounts play an essential ecological role, concentrating nutrients and attracting biodiversity. The ability to detect them more reliably and at smaller scales helps biologists and conservationists better understand and protect marine ecosystems.
Broader Impacts: From Cables to Climate Models
SWOT’s mapping capabilities extend beyond academic research. Accurate, high-resolution seafloor data has practical value in several areas: guiding undersea cable placement, supporting mineral and energy exploration, improving maritime navigation, and helping to model tsunami behavior.
Moreover, the interaction between underwater topography and deep ocean currents is a key component of Earth’s climate system—affecting heat transport, nutrient distribution, and even atmospheric conditions. By offering a clearer view of how these physical features shape ocean dynamics, SWOT’s data will contribute to more accurate climate models and long-term forecasting.
As researchers continue to process SWOT’s data, the focus is shifting to refining measurements of seafloor features—calculating their depth, size, and structure with greater precision. These insights will be integrated with traditional ship-based sonar surveys, advancing the broader global effort to fully map the seafloor by 2030.
SWOT isn’t replacing sonar—it’s enhancing it, offering a fast and scalable way to fill in the blind spots. In doing so, it’s not just giving us a better map of the ocean floor; it’s helping answer long-standing questions about the forces shaping our planet.
Conclusion
The SWOT satellite represents a major leap forward in our ability to observe the ocean floor. By combining advanced radar technology with global coverage, it offers an unprecedented view of underwater features that were previously beyond reach. The implications are wide-ranging—from marine ecology and geology to navigation and climate science.
As the data keeps coming in, so too will discoveries. And with much of the ocean still unexplored, SWOT is helping scientists unlock a deeper, more detailed understanding of Earth’s last frontier.