We know surprisingly little about Earth’s deep oceans. Surprisingly, we have better maps of the Moon than our ocean floor. While ships equipped with sonar provide accurate depth measurements, mapping oceans this way is slow, costly, and often leaves large areas unmapped.
In contrast, satellites can frequently observe vast areas of the Earth. The Surface Water and Ocean Topography (SWOT) mission, a collaboration between NASA and the French space agency CNES, regularly maps about 90% of the planet’s surface waters every 21 days. However, early satellite data didn’t focus on small geological features that are key to understanding ocean physics.
Recently, a NASA-supported team created one of the most detailed maps of the ocean floor to date. This work combines steady satellite observations with advanced physics to reveal hidden structures beneath the waves.
So, how did they map the seafloor? Using data from April 2023 to July 2024, the researchers identified deep-ocean features that were largely unknown before. By using radar interferometry, they could measure the height of the ocean surface, mapping even the tiniest bumps and dips. These imperfections in the sea surface indicate the presence of underwater features like ridges and volcanoes, as greater mass creates slightly stronger gravitational pulls that lift the sea surface ever so slightly.
This process transforms height data into a detailed map of the vertical gravity gradient, which highlights sharp changes in gravity. This is important because such variations often mark significant geological features. Over the past 30 years, previous methods could only map marine gravity at a resolution of about 12-16 kilometers. Now, with newer techniques, scientists can focus on features as small as 8 kilometers wide, revealing structures previously concealed.
Abyssal hills cover large parts of the ocean floor and provide evidence of tectonic activity over millions of years. The new high-resolution maps allow scientists to trace these hills across vast ocean basins, helping refine our understanding of past geological movements.
Meanwhile, smaller underwater volcanoes, or seamounts, can now be detected more easily. Previous satellite techniques typically only identified seamounts over 1 kilometer tall. SWOT can find those below this height, adding crucial information for volcanology and infrastructure planning.
Additionally, SWOT has uncovered hidden tectonic features masked by sediment layers on continental margins. These insights can help reveal how continents split apart or collided, enhancing our understanding of Earth’s geological history.
Understanding the seafloor is not just academic. The insights gained from these maps directly impact climate models, navigation, and even fisheries. By knowing the underwater terrain, researchers can simulate ocean currents more accurately, identify safe routes for submarine cables, and understand where marine life thrives.
While satellites vastly expand our understanding, ships still play a vital role. They provide the depth measurements that anchor bathymetric maps. As SWOT continues its observations, its data will become even more refined, revealing smaller underwater features and improving global bathymetry.
In essence, by listening to the slight shifts in sea surface height, scientists can map the hidden structures of the ocean floor more accurately than ever before. This groundbreaking work paints a clearer picture of our planet’s underwater landscape.
This research reminds us just how much we have left to learn about our oceans and their role in the Earth’s systems. For more details, you can check out the full study published in Science.
