The topography of the ocean floor helps determine how water masses and currents move in the oceans and affect our climate. Seafloor structures also influence the biodiversity in the ocean. Therefore, the most accurate information possible on bottom topography is essential for marine and climate science research. With the second version of the International Bathymetric Chart of the Southern Ocean (IBCSO v2), an international research group led by the Alfred Wegener Institute has presented the best and most detailed bottom chart to date of the Southern Ocean, which plays a key role in the Earth system. The chart and the complex methodology were published in the Nature journal Scientific Data.
The Southern Ocean, a key region for the Earth system and the global climate, surrounds the Antarctic continent. Here, the Antarctic Circumpolar Current, driven by strong westerly winds – the famous “Roaring Fourties” – is the central unifying element of the global thermohaline circulation, influencing ocean currents in the Pacific, Atlantic and Indian Oceans. In addition, the cold waters of the Southern Ocean absorb gigantic amounts of CO2 and heat from the atmosphere, temporarily buffering some of the negative effects of man-made climate change. It is also a place of high biological productivity and hosts a unique biodiversity.
Despite this great importance, in the Southern Ocean – as in other oceans – only comparatively few regions of the seafloor have been surveyed and mapped in detail to date. Satellite data provide an area-wide, but only relatively coarse-resolution picture. High-resolution data can currently only be recorded ship-based. This, for example, means that research vessels such as the icebreaker Polarstern repeatedly encounter previously unknown topographic highlights in the Southern Ocean, such as a 1920-meter-high seamount, which they named “Madiba Seamount” after Nelson Mandela’s nickname.
“Wherever you go or work, you need a map to orient yourself. That’s why virtually all marine science disciplines rely on detailed maps of the seafloor,” says Dr. Boris Dorschel-Herr, head of bathymetry at the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI). “For example, the bottom topography in the Southern Ocean is also crucial for understanding many climate-relevant processes. Warm water masses, for example, flow in deep troughs in the continental shelf up to the ice shelves and glaciers of Antarctica and influence their melting. Conversely, the flow of glaciers and the stability of ice sheets also depend significantly on the composition of the subsurface. With IBCSO v2, we are now providing the best and most detailed imaging of the Southern Ocean to date.”
The International Bathymetric Chart of the Southern Ocean (IBCSO) is an international Southern Ocean mapping project coordinated by AWI. Back in 2013, a first IBCSO data grid (IBCSO v1) was published with a high-resolution map for the area south of 60°S. In the following years, the amount of new measurement data has increased significantly.
Since 2017, IBCSO has been part of the Nippon Foundation – GEBCO Seabed 2030 Project, which has set the ambitious goal of surveying the world’s oceans by 2030. “The new version of IBCSO – IBCSO v2 – for the Southern Ocean now covers the entire area south of 50 degrees latitude at a high resolution of 500 by 500 meters – and thus a seafloor area 2.4 times larger than the first version,” explains Boris Dorschel-Herr. “As a result, the Antarctic Circumpolar Current and the oceanographic ‘gateways’ important to its understanding – the Drake Passage and the Tasman Passage – are now fully included. The map incorporates more than 25.5 billion measurements provided by 88 institutions from 22 countries.”
The data grid and a high-resolution map of the Southern Ocean are freely available for download online at the project site www.ibcso.org and at https://doi.org/10.1594/PANGAEA.937574.
Press Release Alfred Wegener Institute for Polar and Marine Research
Link to original publication: Boris Dorschel, Laura Hehemann, Sacha Viquerat et al: The International Bathymetric Chart of the Southern Ocean Version 2. Scientific Data (2022), DOI: https://doi.org/10.1038/s41597-022-01366-7
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