An ocean ill-defined


In 2006, I was in the kitchen when I learned from an NPR broadcast that the International Astronomical Union redefined “planet” and that Pluto no longer qualified. I’d reached my late 30s secure in my understanding of three fundamental geographic certainties I learned in school: nine planets, seven continents, four oceans. Now Pluto was no longer one of the planets in our solar system. I took a deep breath and resolved to move on: eight planets, seven continents, four oceans — got it.

My worldview remained largely intact until the fall of last year, when I interviewed sailor and solo-circumnavigator Jeanne Socrates. She made repeated references to the Southern Ocean. I nodded, I thought I knew what she and other mariners meant by Southern Ocean: it’s that area somewhere below the Roaring Forties — maybe around the Furious Fifties? — where bergy bits, growlers, and icebergs loom. It’s where gales and monster seas are the norm.

But it got me thinking. It couldn’t be a real ocean, right? People use the term all the time, but a Southern Ocean would make five, in addition to the four I knew: Pacific, Atlantic, Indian, and Arctic Oceans. Are there four oceans or five?

To get a definitive answer, I talked to Michel Huet, assistant director of the International Hydrographic Organization (IHO).

No simple answer
I learned that the question cannot be answered simply, that the story of the Southern Ocean is a tangled web of science and politics. And while I was taught there are only four oceans, had I been in school 30 years earlier, I’d have been told there are five. Kids today can justifiably be learning it either way. But let’s back up.

In 1937, the IHO (then called the International Hydrographic Bureau) released the 2nd edition of Publication S-23, Limits of Oceans and Seas. This document assigned names and boundaries to all the world’s channels, bays, gulfs, seas, and oceans. Five oceans were listed: Pacific, Atlantic, Indian, Arctic, and Southern Ocean, the last defined as the body of water that circled the planet below 60 degrees south and around Antarctica.

In 1953, an updated 3rd edition of Publication S-23, Limits of Oceans and Seas, was approved by all member states. A primary change to this edition was the elimination of the Southern Ocean.

IHO Publication S-23, Limits of Oceans and Seas (1953) states, “The Antarctic or Southern Ocean has been omitted from this publication as the majority of opinions received since the issue of the 2nd Edition in 1937 are to the effect that there exists no real justification for applying the term Ocean to this body of water… The limits of the Atlantic, Pacific, and Indian Oceans have therefore been extended south to the Antarctic Continent.”


The lonely, windswept waters around Antarctica generally have more icebergs than people.


Then in 1977, the IHO began drafting a revised, 4th edition of Publication S-23. One of the key updates was the inclusion, once again, of the Southern Ocean. None of the IHO member states (81 at last count) objected to redefining a Southern Ocean.

But despite this consensus to recognize a fifth ocean, despite 35 years and several drafts of a 4th edition of Publication S-23, in 2012 the IHO halted further revision work on S-23. The key sticking point is not the Southern Ocean, but political intransigence over the naming of the sea between the Korean Peninsula and the Japanese archipelago (currently the Sea of Japan).

And so the 1953 version of Limits of Oceans and Seas remains the official word.

Unofficially official
But most countries and organizations have moved forward anyway, accepting the existence of the Southern Ocean as defined in the latest Limits of Oceans and Seas draft (2002):

“The limits of the Southern Ocean are the parallel of 60°S to the north (the common limit with the South Atlantic Ocean, the Indian Ocean, and the South Pacific Ocean) and the coast of Antarctica, including the Antarctic Peninsula, to the south.”

Of course, there are more than political considerations. The scientific community is mostly resolved that there is a basis for a distinct definition for this body of water, but there is disagreement among oceanographers about its northern boundary.

The Southern Ocean is distinct in that its longest boundary is not a landmass, but a line of latitude separating it from three other oceans. The geographic feature that distinguishes it from abutting waters is the Antarctic Circumpolar Current. This current is the largest and longest in the world, moving Antarctic Bottom Water (an especially cold, highly saline seawater that forms under sea ice) 13,000 miles around the planet, in an easterly rotation with a volume equal to 125 times the flow of all the world’s rivers.

While the composition of the water in this current is different from anything else in the Southern Hemisphere, the northern boundary of the current changes seasonally. This is the primary reason some oceanographers dispute the 60°S designation as the northern boundary of the Southern Ocean.

The National Geographic Society takes a more nuanced view that reflects both political and scientific considerations. Citing the lack of a ratified international agreement, Juan Valdes, director of editorial and research, says that in general the Society recognizes the Southern Ocean as a scientific term and not an oceanographic feature. Cartographically, the Southern Ocean only appears on physical or oceanic maps produced by National Geographic.

An imprecise term
Because the boundaries and very existence of the Southern Ocean are defined by de facto acceptance of an agreement that was never ratified, the term is often used loosely or imprecisely. Journalists tend to be the biggest offenders, using the moniker without regard to any boundary. In late January, French solo-circumnavigator Alain Delord was picked up by an Antarctic cruise ship after he’d spent three days in his life raft. This dramatic rescue was widely reported by news organizations around the world as having happened in the Southern Ocean. But while Delord was adrift in a remote spot on the planet, he was hundreds of miles north of the 60th parallel.

Also this year, boating media attention to the Vendée Globe increased during the final months of the yacht race. The fleet spent most of January approaching and rounding Cape Horn. Nearly all the media reports talked about these sailors battling it out in the Southern Ocean. Yet like Delord, not one racer in this event sailed within 300 miles of the Southern Ocean’s northern boundary.

But while the boating media are no more precise in their use of the term, perhaps they can be excused since mariners have traditionally used it without respect to political and scientific considerations. For hundreds of years they were the only ones to venture into this region of the planet and needed a way of distinguishing the very real differences in conditions they encountered.

I just hope that the historical, cultural, geographical, and scientific interests remain settled for the time being, at least while I adjust to my new world view: eight planets, seven continents, five oceans. Got it.

Michael Robertson lives aboard his Fuji 40 Del Viento with his family and is a freelance writer.

By Ocean Navigator