Where is the Southern Ocean?

The recent announcement from the National Geographic on the 8th June 2021 that the Southern Ocean will be recognised as the world’s fifth ocean, alongside the Atlantic, Pacific, Indian and Arctic, has caused quite a stir amongst scientists who have specialised their research in this unique and mesmerising environment. The reason for this is that they have classified the Southern Ocean as the waters below 60°S.

Regardless of this controversial geographic definition, many have wondered why it has taken the National Geographic so long to recognise this important body of water. In fact, the recognition of the Southern Ocean has proved to be problematic for quite some time now. Whilst organisations such as the National Oceanic and Atmospheric Administration (NOAA) have recognised the Southern Ocean since 1999, the International Hydrographic Organisation (IHO) has not. This intergovernmental organisation is considered an authority in the delineation and classification of the global oceans and seas within them.

The history of the Southern Ocean boundary has been ever changing, James Cook implied New Caledonia bordered it whereas others drew the boundary as between Cape Horn, the Cape of Good Hope, Van Diemen’s Land and the South of New Zealand. Within the IHO the boundary has become increasingly southward since 1928 and in 1953 it was omitted from IHO official publications. In 2000, the boundaries of the Southern Ocean were proposed to IHO again but not all member states ratified this agreement. Member states proposed boundary definitions of 60°S, 50°S and even as far north as 35°S, with Australia arguing that the Southern Ocean extends all the way to their southern coastline. As such it is still up to local hydrographic offices to use their own definition. If we are to agree with the National Geographic definition, rather than more conventional definitions such as 40°S, that’s a difference of over 2000km, with many observational programmes including are own and SOCCOM that are excluded from being ‘Southern Ocean’ programmes.

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Many scientists would argue for different definitions of the Southern Ocean, and this debate rages on today about which is the most appropriate method of classifying the Southern Ocean. Regardless of which classification is used, there is a growing movement to no longer think of separate water bodies, and instead recognise the interconnectedness of the global oceans. Which is why, on the same day as the National Geographic recognition, the UN World Oceans Day was renamed to World Ocean Day. With a message being conveyed of one ocean, one climate and one future. This is an important message to be passed onto the next generation of scientists, if we are to understand the effects of climate change, we cannot look at these systems in isolation. If we do consider there to be only one global ocean, it is the Southern Ocean and Antarctica that sits in the middle, connecting all of us.