Oceans cover more than 70 percent of our planet, so it’s not surprising that naming conventions differ around the world. In the United States, we’re taught that there are four great oceans: the Atlantic, Pacific, Indian, and Arctic Oceans. Some in the Southern Hemisphere, however, claim a fifth: the Southern Ocean (or Great Southern Ocean), also called the Antarctic Ocean.

Our article “Australia’s Dry Run” in the April issue included a map showing the Murray River draining into the Indian Ocean. That prompted several queries from Australian readers who wondered why we didn’t label it Southern Ocean.

Like many mapmakers, the National Geographic Society does not officially recognize the Southern Ocean. According to our Maps Division, “The Atlantic, Indian, and Pacific Oceans merge into icy waters around Antarctica. Some define this as an ocean—calling it the Antarctic Ocean, Austral Ocean, or Southern Ocean—but there is no international agreement on the name and the extent of a fifth ocean.”

Of course, that doesn’t stop others from using Southern Ocean, and occasionally we’ve included the term in our magazine. Since the majority of our readers aren’t familiar with the term, when we do use it, we add an explanation: “He sailed through what Australians call the Southern Ocean”; “the circumpolar sea, which some scientists call the Southern, or Antarctic, Ocean.”

The tide may be turning, though. One tireless advocate for oceans in general—and for a fifth ocean designation in particular—is eminent oceanographer Sylvia Earle. A National Geographic explorer-in-residence, Earle co-authored the new Ocean: An Illustrated Atlas, published by National Geographic. That atlas includes an entire chapter on the Southern Ocean and notes: “Nations are actually voting on the existence and naming of a separate Southern Ocean. Whatever the outcome of this great geographic debate, there are unquestionably distinct currents, water characteristics, and biological communities in the ocean surrounding Antarctica.”

—David Brindley

Satellite image of Antarctica and surrounding waters: NASA

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