The surfaces of the Moon, Jupiter, and Venus are more thoroughly mapped than the ocean floor, which comprises 71% of the Earth’s surface regions. Only 25% of the seafloor has been surveyed by ship-based sonar instruments, forcing researchers to rely primarily on satellite data and other technologies to penetrate the depths.
Now, NASA and the French space agency CNES‘s Surface Water and Ocean Topography (SWOT) satellite is providing researchers with capabilities to create the most accurate ocean maps yet, improving navigation and knowledge of aquatic ecosystems.
The Importance of Underwater Maps
A University of California San Diego team has helped transform SWOT data into the most complete seafloor map ever created. Underwater navigation and laying communication cables are two essential activities in our increasingly globalized world that can benefit from improved map accuracy.
“Seafloor mapping is key in both established and emerging economic opportunities, including rare-mineral seabed mining, optimizing shipping routes, hazard detection, and seabed warfare operations,” said Nadya Vinogradova Shiffer, head of physical oceanography programs at NASA Headquarters in Washington.
Beyond aiding human activities, the mapping will also illuminate the ocean for natural scientists, identifying underwater mountains called seamounts and the smaller abyssal hills. The maps will increase understanding of tides and currents, the major drivers of marine ecosystems and plate tectonics, as they push heat and nutrients through the deep ocean. Additionally, nutrients can collect on the slopes of such features, attracting marine life and creating ecosystem pockets in barren regions.
NASA’s SWOT Satellite
Since launching in 2021, the satellite developed at NASA’s Jet Propulsion Laboratory has been conducting continual observations with a broader aquatic mission than patrolling the oceans. It also measures the water height of oceans, lakes, reservoirs, and rivers, which researchers can turn into fresh-water and seawater topographic maps. This mapping technology holds significant potential in sea ice and floor tracking.
“The SWOT satellite was a huge jump in our ability to map the seafloor,” said David Sandwell, a geophysicist at Scripps Institution of Oceanography in La Jolla, California.
Covering 90% of the globe every 21 days, SWOT measured centimeter-scale differences in sea surface height over repeated observations. The researchers extrapolated the gravitational pull of deep ocean features like seamounts, abyssal hills, and continental margins where continental and oceanic crust meet from those tiny bumps in the sea surface. From a year’s worth of this data, the team was able to predict features on the ocean floor.
High Resolution
The new work achieved a much finer resolution than earlier attempts to observe bottom features through satellite data. Previous attempts were limited to large seamounts over a kilometer tall. By detecting sea hills less than half a kilometer high, the number of known features climbed from 44,000 to 100,000.
New maps also provide valuable insights into Earth’s geologic history. Abyssal hills occur in parallel ridges at locations where tectonic plates diverge. By studying the extent and location of these feature bands, geologists can identify tectonic movements over time.
Parker Space Probe
“Abyssal hills are the most abundant landform on Earth, covering about 70% of the ocean floor,” said the lead author, Yao Yu, an oceanographer at Scripps Institution of Oceanography. “These hills are only a few kilometers wide, which makes them hard to observe from space. We were surprised that SWOT could see them so well.”
Continuing to Fill in the Ocean Floor
The work continues as researchers push towards mapping the entire seafloor by 2030, originally expected to be accomplished through ship-based sonar. The team hopes to fill more gaps in the international 2030 project by further examining the SWOT measurements.
“We won’t get the full ship-based mapping done by then,” said Sandwell. “But SWOT will help us fill it in, getting us close to achieving the 2030 objective.”
The paper “Abyssal Marine Tectonics from the SWOT Mission” appeared on December 12, 2024, in Science.
Ryan Whalen covers science and technology for The Debrief. He holds an MA in History and a Master of Library and Information Science with a certificate in Data Science. He can be contacted atryan@thedebrief.org, and follow him on Twitter@mdntwvlf.