According to the National Oceanic and Atmospheric Administration (NOAA), only 10 percent of the 140 million square miles of the planet’s seafloor has been “adequately mapped” (emphasis added). Other online sites mention a range of between 5 and 20 percent. Some of the measurement differences relate to the dates of the estimates and how they were calculated.
“Adequately” is an important word. It refers to the ability to resolve sea bottom features. For example, if resolution is 3 miles, it means that any features smaller than that will not be seen. Since the beginning of the 20th century, maps of the seafloor have been made by interpolating between sparse “soundings” (either from lead-lines or single-beam echo sounders) with very limited resolution and spatial coverage. Toward the end of the 20th century, techniques were developed to estimate seafloor depth from satellite-based measurements, producing the first seafloor maps with global coverage but with a resolution of only 12.4 miles. By 2016, this resolution had increased to 3.1 miles, but this is hardly a detailed map.
By comparison, NASA has been able to map the surface of Venus to 328 feet resolution and Mars to 66 feet. And closer to home, the best moon map resolution is 7 feet. The overused saying, “We know more about the Moon’s behind than the oceans’ bottom,” has a ring of truth.
Highest resolution knowledge of seafloor topography is vital to support commercial, scientific, and military use of the oceans. So, how can this vast, somewhat unknown area be mapped with sufficient detail? The classical and prevailing means is with oceanographic research vessels and specialized hydrographic survey ships. It is estimated that one ship would need 350 years to accomplish 93 percent coverage (the remaining 7 percent is inshore) with current state-of-the-art mapping systems.
The cost of such an effort is large—somewhere between $3 to $5 billion—but this is not much different than the cost of one or two Mars missions, and perhaps a small price to pay to have detailed maps of our own planet. New technology, however, may significantly reduce the cost.
An attractive partial solution is to use fleets of long-duration underwater drones programmed to do multibeam acoustic mapping. They would be large autonomous untethered vehicles (AUVs), essentially unmanned submersibles. Large numbers of them (“swarms’) could be controlled and coordinated by ships. Some AUV users claim they could do surveys with the required precision 60 percent faster than shipboard systems.
Some experimental AUVs already have made test voyages across the Atlantic and Pacific Oceans. But the idea of “autonomy” is not exactly correct. All survey AUVs will require mother ships for voyage monitoring, control of navigation, recharging on-board power, and downloading survey data. A properly configured mother ship could control and service several AUV hydrographic survey submersibles. This would multiply the amount of seafloor mapping per unit of time compared with what can be done by a single hydrographic survey ship. At some future time, the mother ship might even be another type of drone designed to control its own fleet of AUVs. In 2019, a prototype unmanned surface vessel (USV) was tested as a mother ship for a single AUV, and the results were promising.
Developing new data collection platforms such as spacecraft and AUVs and USVs is but one path to greater productivity. Another is more aggressive global collection and management of existing data through international cooperation. Such data harvesting can be anecdotal from private and commercial sources, or professional, from hydrographic survey ship operators.
Today, there is a major international effort to produce a publicly available global seafloor topographic map by 2030. It represents continuation of the historic work of the General Bathymetric Chart of the Oceans (GEBCO) activity that began at the start of the 20th century. In 2016, it was accelerated by Japan’s Nippon Foundation, which joined and provided startup funding to organize the effort. The new project is the Nippon Foundation–GEBCO Seabed 2030 Project. Management is provided by the International Hydrographic Office in Monaco and the U.N.’s International Oceanographic Commission in Paris. For more information, please see www.gebco.net/about_us/overview/.