- Jonathan Amos
- BBC News Science Reporter
Scientists have created the most accurate map ever of the mountains, valleys, and plains that make up the ocean floor around Antarctica.
This graph covers 48 million square kilometers, and for the first time shows the new deepest point – a depression at 7,432 meters deep called the Factor Deep.
Knowing the shape of the ocean floor is essential to safe navigation, marine conservation, and an understanding of Earth’s climate and geological history.
But there is still much to learn. Vast areas of land have not been properly observed.
The International Bathymetry Project of the Southern Ocean (IBCSO) took five years to create the first attempt at a comprehensive map, published in 2013.
The IBCSO and other similar projects around the world are gradually bridging the gaps in our rare knowledge of the world’s ocean floor.
Ships and boats are encouraged to routinely operate sonars to take depth measurements. Governments, companies and organizations are urged to share data and put as much of it in the public domain as possible. This pays off.
The new map covers the area from the bottom of the Southern Ocean to 50°S. If you divide the 48 million square kilometers into squares of 500 m grids, then 23% of these cells have passed at least one recent depth measurement. This is a huge improvement over nine years ago.
Previously, the IBCSO started at 60°S, with less than 17% of modern-scale networks.
“You have to understand exactly what it means to change from 60 to 50 degrees; we more than doubled the area of the graph,” says Boris Dorchel of the Alfred Wegener Institute in Germany.
“We’ve increased the coverage for the area, but we’ve also increased the data density, because at the same time we keep getting new data,” he told BBC News.
Much of the information in the graph comes from icebreakers that support science efforts in Antarctica, including the former British Antarctic ship, RRS James Clark Ross. (In the future, this British contribution will come from his successor, RRS Sir David Attenborough, affectionately known as Boaty McBoatface.)
On journeys between the White Continent and countries like Chile, South Africa and Tasmania, their echoes scan the submerged terrain below.
And this activity is increasingly being coordinated, as research organizations from different countries work together to slightly modify the ways their icebreakers work.
More detailed maps of the sea floor are needed for several reasons.
They are essential to safe navigation, but are also essential to fisheries management and conservation, because marine animals tend to congregate around seamounts. Each seamount is the core of biodiversity.
In addition, the rugged seafloor affects the behavior of ocean currents and vertical mixing of water. This is information needed to improve models that predict future climate change – because it is the oceans that play a major role in moving heat around the planet.
“We can also study how the Antarctic ice sheet has changed over thousands of years just by looking at the sea floor,” explains Rob Larter of the British Antarctic Survey.
“There is a record of where the ice flowed and where its grounding areas (places in contact with the sea floor) extended. This is beautifully preserved in the shape of the sea floor.”
Funded by Japan’s Nippon Foundation and supported by SeaBed2030, the new map is made possible, the international effort to map the bottom of the Earth’s ocean by the end of the decade.
Currently, our knowledge of four-fifths of the planet’s underwater terrain comes only from low-resolution satellite measurements that infer the presence of seamounts and deep valleys from the gravitational influence these features have on the sea surface. Water accumulates over a large seamount mass and sinks a little where there is a trench.
An important discovery between the first and second editions of the IBCSO is the identification of the deepest point in the Southern Ocean. This depression is called the Factorian Deep at the southern end of the South Sandwich Trench. It is located at a depth of 7432 m. Texas adventurer Victor Veskovo measured this and visited him with his Limiting Factor submarine in 2019.
The remote and inhospitable nature of the Southern Ocean makes it difficult to map large portions of the bed. There is great hope that an emerging class of robotic crafts will be able to fulfill this task in the coming years.
The depth chart of the Southern International Ocean has been published in Scientific Data.
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