Mapping the ocean

By 2030, Australia commits to making accessible all existing seabed mapping data, and continuing to map its 8.2-millionsquare-kilometre marine jurisdiction

From lead weights to remote sensing

For centuries, the stars, planets and landforms have served as markers for trade and migration routes. These celestial and terrestrial features are comparatively easy to see and record – but what of those under the water? Curator of Ocean Science and Technology Emily Jateff traces the history of seafloor exploration and mapping.

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01 AusSeabed Bathymetry Coverage 2020. This dataset represents the current extent of bathymetry surveys held by AusSeabed as of March 2020. This dataset is live and will continue to be augmented as coverage is supplied from AusSeabed collaborators. Image courtesy Geoscience Australia, Canberra

02 French chart (c 1775) using the charts produced during James Cook’s Endeavour voyage from Point Hicks to Cape York, including the islands of the Torres Strait, in 1770. Copper engraving by Robert Bernard. ANMM Collection 00000860

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UNDERSTANDING THE COMPOSITION OF THE SEAFLOOR is vital to safe and economically sustainable marine navigation. When Lieutenant James Cook charted the eastern coastline of Australia in 1770, his team of surveyors took ‘soundings’ at intervals to fairly accurately record coastal seabed depth. They accomplished this by throwing a lead weight attached to a rope over the side of the ship and measuring how much line paid out before the lead hit bottom. In 1874, the first recognised Western oceanographic expedition on board HMS Challenger reached the deepest point in the ocean, the 10,500-metreplus Challenger Deep in the Mariana Trench, using a winch and sounding line (this time made of stronger steel wire). Although a slow and arduous process, sounding leads and sextants were the go-to hydrographic tools until the 1920s and the invention of the single beam echosounder, or fathometer. This device ‘sees’ the seafloor in the same way bats visualise where they are going: by pinging sound waves off a point in the distance (in this case, the seafloor) and measuring how long it takes for that ping to return. Using technologies to detect and document our environment remotely is known as remote sensing, and it has changed the way we view our world. Today, ocean bathymetry (seafloor) data are often acquired from satellites. Airborne remote sensing – in particular systems such as laser airborne depth sounding (LADS) – is an excellent means of generating high-resolution bathymetric data for coastal shorelines up to the inner continental shelf, but airplanes can’t fly too far from land without refuelling. Recent innovations in specialised, far-reaching unmanned autonomous vehicles (UAVs) can be used to map by remote command. However, collecting direct (that is, in-water) high-resolution bathymetry data still usually requires access to an ocean-going ship, a means of mapping and a person to process the data. Many research and commercial vessels are now fitted with hull-mounted sidescan and multibeam echosounders (MBES) that are used to conduct hydrographic surveys, either while the ship is under way, or as part of a targeted collection strategy. Once the data are collected, remote sensing specialists postprocess them for multiple uses including Digital Terrain Models and navigation charts. The data are thinned, errors corrected and alterations made to account for differences in wave, tide and temperature. Mounting an ocean-going expedition requires significant investments in time, money and resources. Governments, private industry and scientific bodies usually fund expeditions for specific purposes, including production of information related to chemical, geologic or biological composition of the ocean, or resource extraction. A few expeditions focus on seafloor mapping, but it is more often than not a secondary and opportunistic aspect of any seagoing voyage.

01 GEBCO Digital Atlas, courtesy British Oceanographic Data Centre (BODC), National Oceanography Centre (NOC). 02 On a large ocean-going research vessel, the action happens either at the stern (where most equipment is deployed) or in the Operations Room. This is the Operations Room on board Marine National Facility RV Investigator. Image courtesy CSIRO/Marine National Facility

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How do we have a map of the ocean? As the world globalised in the early 20th century, it became apparent that consistent naming and terms were required for bathymetric charts. The 1903 Commission on Sub-Oceanic Nomenclature determined the need for an internationally recognised general bathymetric chart. Championed by Prince Albert I of Monaco, responsibility for the chart’s production bounced back and forth through various agencies during subsequent years, its production affected by both World Wars and the Cold War. Eventually, oversight of the general bathymetric chart was handed to the Intergovernmental Oceanographic Commission (IOC) of UNESCO, which in turn established The General Bathymetric Chart of the Oceans (GEBCO) as a joint program of the International Hydrographic Organization (IHO) and the Intergovernmental Oceanographic Commission (IOC). The first General Bathymetric Chart of the Oceans, at 1:10 million scale, was published in 1982. GEBCO produces a regularly updated global terrain model map derived from acquired bathymetric data sets. The GEBCO-2019 Grid includes 15 per cent of the ocean floor mapped in 15 arc-second intervals at high vertical (absolute depth) and horizontal (space between points) resolution. This varies significantly based on water depth, with 13.7 per cent of the 0–1500-metre depth interval mapped, but only 2.6 per cent of the world’s seabed mapped at depths exceeding 5750 metres. Below 200 metres, approximately 80 per cent of the data are interpolated or extrapolated, meaning they are derived from statistics. This is what you have to do when you don’t have all the data you need to complete a map: use maths. To interpolate data is to estimate what lies between two known points. To extrapolate data is to extend from known observations to a point in the distance, while operating on the assumption that what lies between them is similar. Interpolated data are generally assumed to be more accurate than extrapolated data, as they are developed from two known points. Extrapolated data, by contrast, can become increasingly less accurate the further they move from the starting data set. One of GEBCO’s goals is to reduce the use of interpolated or extrapolated data and replace this with high-resolution direct bathymetry data.

The UN Decade of Ocean Science

One of the drivers for the global push to map the oceans is the upcoming United Nations Decade of Ocean Science for Sustainable Development 2021–2030. The decade’s vision is to ‘develop scientific knowledge, build infrastructure and foster relationships for a sustainable and healthy ocean’ in line with the UN Sustainable Development Goals. Sustainable Development Goal (SDG) 14: Life Below Water, which strives ‘to conserve and sustainably use the oceans, seas and marine resources for sustainable development’, is the goal that connects science, policy, economics and growth in the ocean space.

Global coverage of the seafloor has increased as much in the last two years as it had in the previous 115 years

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The Ocean Decade will be delivered through six research and development themes that cover everything from understanding biodiversity to marine hazards to pollution. One of these themes is ‘A Predicted Ocean’: ‘Whereby society has the capacity to understand current and future ocean conditions, forecast change and impact on wellbeing and livelihoods.’ This is perfect for our story, as you cannot accurately predict if you don’t have a map.

Seabed 2030

At the UN Ocean Conference in 2017, Mr Yohei Sasakawa, Chairman of The Nippon Foundation, declared that it would financially support a global mapping project in partnership with GEBCO. This collaborative international project aims to produce a complete map of the world’s ocean floor by 2050. Titled Seabed 2030, its target is to bring together all data currently available within the GEBCO grid, as well as other publicly and privately held data sets, to identify and support future mapping operations for previously unmapped areas. As part of this initiative, regional centres were established at the Alfred Wegner Institute in Germany (Southern Ocean), Stockholm University in Sweden (Arctic and North Pacific), Lamont Doherty Earth Observatory at Columbia University in the United States (Atlantic and Indian Oceans) and the National Institute of Water and Atmospheric Research in New Zealand (South and West Pacific Ocean). As a result, global coverage of the seafloor has increased as much in the last two years as it had in the previous 115 years. Nations, private citizens and organisations have stepped up to the challenge, collaborating between government, research, exploration, recreation and industry to do their part to produce a comprehensive global map of the ocean. By 2030, Australia commits to making accessible all existing seabed mapping data and to continue mapping the gaps in its 8.2 millionsquare-kilometre marine jurisdiction. This mission, dubbed AusSeabed, is to ‘improve the quality of awareness, coverage, quality, discoverability and accessibility of seabed mapping data through coordination and collaboration in the Australian region’. AusSeabed is a multi-sector initiative headed by Geoscience Australia with the support of the Australian Hydrographic Office, the CSIRO and many other governmental, industry and research bodies. The CSIRO Marine National Facility research vessel Investigator conducts multibeam surveys on all voyages. All data are included within the publicly accessible AusSeabed Marine Discovery Portal. With more than 25 per cent of the Australian marine estate now mapped, we are well on our way – and Australia will soon gain another vessel capable of mapping our Southern Ocean estate, the ice-breaker Nuyina. In December, Schmidt Ocean Institute became the latest of more than 100 scientific research institutions to sign a memorandum of understanding with GEBCO. Its research vessel Falkor visited the museum in January and is currently completing a circumnavigation of Australia using its deepwater work-class remotely operated vehicle (ROV) SuBastian to visualise and sample deepwater canyons off our coasts (see Signals 130).

01 North-looking 3D view of Osprey Reef in Australia’s Coral Sea Marine Park. Airborne lidar data collected over the shallow reef and lagoon by the Australian Hydrographic Office, and multibeam sonar data collected around the deeper flanks by the Schmidt Ocean Institute’s RV Falkor. Image provided by Dr Robin Beaman, James Cook University under CC 4.0 licence 02 All crowdsourced vessel data recovered along a section of the Great Barrier Reef. Image courtesy Dr Rob Beaman, James Cook University.

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As the world globalised in the early 20th century, it became apparent that consistent naming and terms were required for bathymetric charts

The latest survey, ‘Visioning the Coral Sea’, was the first of a kind, with scientists operating from shore and public delivery of new seabed mapping data within days of returning to port. Schmidt Ocean Institute gives GEBCO open access to past data sets and provides information from mapping operations, including its ongoing ‘Mapping the Gaps’ program in the Pacific. The Nippon Foundation recently announced three new initiatives designed to make it easier for research organisations and private companies and individuals to participate in the Seabed 2030 program. These include providing vessels with data-gathering equipment; funding additional mapping days in remote areas and providing MBES operators where required; and ‘championing’ solutions for increased public participation. These steps have already borne fruit. The Five Deeps Expedition, led by explorer Victor Vescovo, conducted research via the single-crewed Deep Submergence Vehicle Limiting Factor at remote locations in the deepest parts of the five global oceans. The Nippon Foundation allocated additional funding to the project for extended mapping days, and provided access to an experienced MBES operator who monitored acquisition of bathymetric data. This allowed for sustained collection of data, including during transit, and transfer of comprehensive high-resolution bathymetry data into the Seabed 2030 global map of the ocean floor.

Crowd-sourced citizen science

Crowd-sourced bathymetric data doesn’t just come from large organisations – even small recreational vessels can play a part. The ‘Crowd-sourced bathymetry (or depth) on the Great Barrier Reef’ project has been installing small data loggers about the size of a mobile phone on volunteer vessels to record depth and position data from their depth sounder and GPS navigation systems. Over the past year, 10 volunteer vessels – including luxury motor yachts, dive charters, crown-of-thorns starfish control vessels, government watercraft and smaller hire boats – have been automatically logging depth and position data to a USB stick inserted into their data loggers. These data are publicly accessible via the AusSeabed Marine Discovery Portal. Led by Dr Robin Beaman at James Cook University, the project uses innovative citizen science to collect new depth data from remote parts of the Great Barrier Reef where traditional hydrographic surveys may not have already visited, and that lack any modern digital depth data. The new soundings, combined with all other survey data, are used to generate detailed 3D depth models for the Great Barrier Reef. These detailed models reveal the deeper underwater landscape, such as ancient river channels, submerged (drowned) reefs and canyons.

Once it’s mapped, then what? Imagine it is 2030, the drive to map the oceans has resulted in 100 per cent coverage at high resolution, and all data are stored in a publicly accessible archive (with limitations for public safety and national interest, of course). What does this mean for us? A global map has many positive outcomes. First, we’ll know what is down there. At present, Mars and the moon have been mapped at higher resolution than the ocean. Policymakers can use these data to inform future economic decision making for development of the global ‘Blue Economy’ – an emerging concept that encourages better stewardship of our ocean or ‘blue’ resources. Resource managers and scientists can utilise informed ocean circulation patterns data, which rely on the shape of the seabed, to predict weather and climate. Ocean and coastal modelling will assist with hazard awareness, resource management and protection. Data will enhance knowledge of how ecosystems interact and help calculate the locations of such features as deep-water corals, ocean rifts or hydrothermal vents. Finally, we’ll have an accurate and comprehensive bathymetric model, a key outcome of the UN Decade of Ocean Science for Sustainable Development 2021–2030, and a major step forward in our quest to comprehend our ocean. The Australian National Maritime Museum is committed to supporting the UN Decade of Ocean Science for Sustainable Development 2021–2030 through programming, exhibitions and events over the next 10 years. This article is part of an ongoing series on key Decade initiatives.

Ocean Talk on Falkor’s findings

The museum’s free Virtual Ocean Talk on Thursday 1 October will reveal some of the recent findings of the Schmidt Ocean Institute’s research vessel Falkor and its remotely operated vehicle (ROV) SuBastian as they explored Australia’s deep-sea submarine canyons, seamounts and coral ecosystems – bringing to light fascinating new species from coast to coast. Please see page 40 or go to www.sea.museum for further details.

Content on crowd-sourced bathymetry data provided by Dr Robin Beaman of James Cook University and used with sincere appreciation and thanks. Further reading United Nations Decade of Ocean Science for Sustainable Development 2021–2030: en.unesco.org/ocean-decade United Nation Department of Economic and Social Affairs Sustainable Development: sustainabledevelopment.un.org/?menu=1300 AusSeabed Marine Data Portal: marine.ga.gov.au RV Investigator blog: blog.csiro.au/tag/rv-investigator/ Lucy Bellwood’s cartoons from her three-week stint as Artist in Residence aboard RV Falkor: medium.com/@lubellwoo/mappin-the-floor-81a3b0472ca4