The bottom of the ocean is the largest uncharted area on our planet. With water covering approximately 70 percent of the Earth, many areas remain a mystery. There are ecosystems, aquatic life forms, and natural resources that have never been seen by human beings, let alone documented. Several international organizations are joining forces to amend this situation by mapping the 140 million square miles of ocean floor that is 200 m and deeper. The result will be a comprehensive global bathymetric model useful for multiple applications.
The Seabed 2030 Initiative
A gathering of international scientists and oceanographers at the Forum for Future Ocean Floor Mapping, held in Monaco in June 2016, recognized the importance of deep sea mapping and agreed to develop a program called Seabed 2030. A collaboration between the Nippon Foundation and the General Bathymetric Chart of the Oceans (GEBCO) was formed to establish a program with the goal of completely mapping the deep seas by the year 2030 with best-achievable resolution. The Nippon Foundation provided an initial grant of $18.5 million.
“The biggest challenge in achieving the goals of Seabed 2030 is a fiscal one,” said Dr. Larry Mayer, Director of the Center for Coastal and Ocean Mapping, University of New Hampshire. “With an estimated price tag of more than $3 billion, the support of many international organizations and governments is absolutely necessary. Without such support, it will be difficult for GEBCO and its partners to collect the necessary volume of data in the desired timeframe.”
To keep costs down, existing data is being gathered by regional groups, and crowd-sourced data is being used to fill in gaps. In the past, worries about quality and liability constrained the use of crowd sourcing for ocean mapping; however, the value of data collected by many people is increasingly accepted. Norwegian firm Olex AS is contributing to this approach by encouraging its customers, primarily fishermen, to share sea floor data they collect, in exchange for access to a database of depths collected by Olex customers around the world. Researchers also hope to keep crowd-sourced data consistent by designing an authoritative “black box” for each ship to collect data with known specifications.
Applying Geospatial Technology Underwater
Measuring the depth of water and modeling the terrain hidden beneath the surface requires different technology than terrestrial mapping. Only sound waves can achieve sufficient propagation to penetrate depths of 200 m or more. Advances in autonomous underwater vehicle (AUV) technology, multibeam echo sounders, and Simultaneous Location and Mapping (SLAM) navigation methods are all expanding the boundaries of what is possible.
Ships equipped with multibeam echo sounders can crisscross the open ocean collecting overlapping swaths of sound waves, which are used to build bathymetric maps and seabed image data. The deeper the water, the lower the resolution attainable. Coverage at 100-200 m resolution is adequate for numerous applications and would be a vast improvement over the data available in many areas today.
AUVs equipped with multibeam echo sounders collect data at higher resolution but over smaller areas. Both AUVs and surface ship multibeam sonars have explored the deepest known spot in the ocean, the 36,070-foot (nearly 7 miles) Challenger Deep in the Mariana Trench, located in the western Pacific. The first depth measurements in this area were conducted by the HMS Challenger in 1875 using weighted ropes; the numbers have been refined over the years since the introduction of sonar.
“Each technology has particular constraints: aerial lidar works well for shallow water but requires water clarity, as does the calculation of bathymetry from satellite-derived imagery; hull-mounted sonar collects a wide swath, while AUVs collect only a small area,” explained Mayer. “Positional accuracy is also a major issue since AUVs are not in contact with the GNSS satellite constellation and must rely on inertial navigation systems on board.”
While absolute accuracy may not be critical for every application, it becomes important because overlapping swaths must be correctly positioned to maintain the resolution of the bathymetry. Bad navigation data blurs and distorts the lateral resolution. In addition to optimizing inertial navigation systems and running long straight lines, AUV navigation is supplemented by the following:
- Using features to correct positioning drift (a technique known as SLAM)
- Occasionally coming to the surface for a GNSS fix
- Using surface buoys with GPS and acoustic transponders to communicate with the AUV
None of these methods achieve the positional accuracy possible with a constant surface connection to the satellite constellation; however, they allow work to be done within many survey requirements.
Diverse and Competing Interests
Experts expect that new and improved maps of the ocean floor will spur a variety of activities in remote yet valuable marine environments. Although safety for ocean-faring vessels is a primary motivation for mapping the ocean, more detailed maps will also enable the construction of subsea infrastructure and pipelines, the installation of more submarine communications cables, and the exploitation of underwater minerals, oil and biological materials. Better mapping information also facilitates research into many areas, such as tsunamis, ocean currents, climate, marine life and environmental protection.
Overseeing and regulating these competing interests is the responsibility of several international entities. According to the website of the International Seabed Authority, “a principal function of the Authority is to regulate deep seabed mining and to give special emphasis to ensuring that the marine environment is protected from any harmful effects which may arise during mining activities, including exploration.”
The United Nations Law of the Sea Treaty, adopted in 1982 but not yet ratified by the United States, establishes jurisdictional limits on the ocean area that countries may claim and develops regulations and laws to control pollution of the marine environment. On 24 December 2017, more than 140 members of the United Nations voted to convene an intergovernmental conference focused on developing guidelines for the vast areas of the ocean not currently controlled by any individual country. Over the next two years the details of a legally binding treaty will be negotiated to address deep sea fishing, mining, and other activities. These controls will encourage marine conservation and biodiversity.
Cooperative Ocean Mapping
Innovative approaches to ocean mapping are of interest to many countries around the world. The hydrography and ocean mapping program at the Center for Coastal and Ocean Mapping/Joint Hydrographic Center (CCOM/JHC) at the University of New Hampshire includes a Nippon Foundation/GEBCO funded program that focuses on the training of international students. Over time, these students will make up a collaborative global network, and their countries will benefit from sharing knowledge and resources with others. The CCOM/JHC is an active participant in Seabed 2030, and this network of Nippon Foundation/GEBCO scholars will play a critical role in linking Seabed 2030 to regional mapping efforts.
“We look forward to the day when the ocean floor is as well-mapped as Mars and the moon,” said Mayer. “An understanding of all aspects of the ocean is crucial for Earth’s sustainable future.”
By setting the extremely challenging goal of mapping the Earth’s deep seas by 2030, the Seabed 2030 initiative is revolutionizing traditional data collection practices and encouraging crowd sourcing and centralized databases. Necessity is also driving improvements in post-processing and data analysis and stimulating valuable technological advances in areas such as multibeam echo sounders and AUVs.