New map shows the Southern Ocean seabed in unprecedented detail


The characteristics of the ocean floor help determine how water masses and ocean currents move and how they affect our climate. Biodiversity is also influenced by the reliefs of the seabed. Therefore, having as accurate information as possible on the topography of the seabed is essential for oceanographic and climate research. With the second version of the International Bathymetric Chart of the Southern Ocean (IBCSO v2), an international group of researchers led by the Alfred Wegener Institute recently presented the best and most detailed seabed maps of the Southern Ocean. , which plays a central role in the Earth system. The map and the complex methods used to create it were published in the journal Nature Scientific data.

Surrounding the Antarctic continent, the Southern Ocean is a key region for the Earth system and global climate. Here, the Antarctic Circumpolar Current, driven by powerful westerly winds – the infamous “Roaring Forties” – represents the key element of the thermohaline circulation on a global scale, influencing ocean currents in the Pacific, Atlantic and Indian. In addition, the cold water of the Southern Ocean absorbs huge amounts of CO2 and the heat of the atmosphere, creating a temporary buffer for many of the negative consequences of anthropogenic climate change. Moreover, these waters are characterized by high biological productivity and harbor a unique diversity of species.

Despite its great importance, in the Southern Ocean – as in many other oceans – only relatively few regions of the seabed have been studied and mapped in detail. Although satellite data covers the entire ocean, it offers relatively low resolution. Currently, high-resolution data can only be collected using on-board methods. As a result, multibeam echosounder readings taken in the Southern Ocean by research vessels like the icebreaker Polarstern often yield previously unknown topographical highlights, such as a 1,920-meter seamount, dubbed the Madiba Seamount in honor of Nelson Mandela’s nickname.

“No matter where you travel or work, you need a map to orient yourself. That’s why virtually all oceanographic disciplines rely on detailed maps of the ocean floor,” says Dr Boris Dorschel- Herr, head of bathymetry at the Alfred Wegener Institute, Helmholtz Center. for Polar and Marine Research (AWI). “For example, the topography of the seabed in the Southern Ocean is key to understanding a range of climate-related processes. Masses of warm water flow through deep troughs in the continental shelf toward the ice shelves and Antarctic glaciers, affecting their melting. Conversely, the stability and calving behavior of glaciers and ice sheets is highly dependent on the characteristics of the underlying ground. With IBCSO v2, we have provided the best and the most detailed map of the Southern Ocean to date.

The International Bathymetric Chart of the Southern Ocean (IBCSO) is an international project coordinated by the AWI and responsible for mapping the Southern Ocean. The first IBCSO digital bathymetric model (IBCSO v1) and high-resolution map of the area south of 60°S were released in 2013. In the years since, the amount of new measurement data has increased dramatically.

Since 2017, IBCSO has been part of the Nippon Foundation –GEBCO Seabed 2030 Project, which has set the ambitious goal of surveying all of the world’s oceans by 2030. “The new version of IBCSO — IBCSO v2 — for Southern Ocean now covers all area south of 50e parallel – which means 2.4 times more seabed than the first version – at a high resolution of 500 meters by 500″, explains Dorschel-Herr. “As a result, the Antarctic Circumpolar Current and the oceanographic ‘gateways’ essential for understand – the Drake Passage and the Tasmanian Passage – are included in their entirety. The graph is based on more than 25.5 billion measurements provided by 88 institutions in 22 countries.

The digital bathymetric model and a high-resolution map of the Southern Ocean are available for free download from the project website www.ibcso.org and https://doi.org/10.1594/PANGAEA.937574.

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