How can satellites reveal the shape of the ocean floor?

Satellites reveal the shape of the ocean floor primarily through the use of radar altimeters, which measure the distance between the satellite and the sea surface with extreme precision.12

While the deep seafloor is opaque to light, the ocean surface is not perfectly flat; it is warped by the gravitational pull of underwater features. Massive seamounts exert a gravitational attraction that causes the sea surface to bulge slightly upward over them, while deep-sea trenches create corresponding downwarps.2

By mapping these subtle variations in the ocean surface, scientists can compute the gravity field of the seafloor. This data allows researchers to identify and visualize previously uncharted features, such as ridges and fracture zones, providing a comprehensive view of the ocean basin that is often more complete than what can be achieved through ship-based sonar soundings alone. Notable missions like Seasat were instrumental in demonstrating the effectiveness of this technique for global ocean mapping.21