Those familiar with the Southern Ocean, the body of water encircling Antarctica, know it’s unlike any other.
“Anyone who has been there will struggle to explain what’s so mesmerizing about it, but they’ll all agree that the glaciers are bluer, the air colder, the mountains more intimidating, and the landscapes more captivating than anywhere else you can go,” says Seth Sykora-Bodie, a marine scientist at the National Oceanic and Atmospheric Administration (NOAA) and a National Geographic Explorer.
Since National Geographic began making maps in 1915, it has recognized four oceans: the Atlantic, Pacific, Indian, and Arctic Oceans. Starting on June 8, World Oceans Day, it will recognize the Southern Ocean as the world’s fifth ocean.
“The Southern Ocean has long been recognized by scientists, but because there was never agreement internationally, we never officially recognized it,” says National Geographic Society Geographer Alex Tait.
Geographers debated whether the waters around Antarctica had enough unique characteristics to deserve their own name, or whether they were simply cold, southern extensions of the Pacific, Atlantic, and Indian Oceans.
“It’s sort of geographic nerdiness in some ways,” Tait says. He and the National Geographic Society’s map policy committee had been considering the change for years, watching as scientists and the press increasingly used the term Southern Ocean.
The change, he adds, aligns with the Society’s initiative to conserve the world’s oceans, focusing public awareness onto a region in particular need of a conservation spotlight.
“We’ve always labeled it, but we labeled it slightly differently [than other oceans],” Tait says. “This change was taking the last step and saying we want to recognize it because of its ecological separation.”
While the other oceans are defined by the continents that fence them in, the Southern Ocean is defined by a current.
Scientists estimate that the Antarctic Circumpolar Current (ACC) was established roughly 34 million years ago, when Antarctica separated from South America. That allowed for the unimpeded flow of water around the bottom of the Earth.
The ACC flows from west to east around Antarctica, in a broad fluctuating band roughly centered around a latitude of 60 degrees south—the line that is now defined as the northern boundary of the Southern Ocean. Inside the ACC, the waters are colder and slightly less salty than ocean waters to the north.
Scientists are currently studying how human-driven climate change is altering the Southern Ocean. Ocean water moving through the ACC is warming, scientists have learned, but it’s unclear how much this is impacting Antarctica. Some of the most rapid melting of the continents ice sheets and shelves have been where the ACC is closest to land.
What’s more, the Southern Ocean has ecological effects elsewhere as well. Humpback whales, for example, feed on krill off Antarctica and migrate far north to winter in very different ecosystems off South and Central America. Some seabirds migrate in and out too.
By drawing attention to the Southern Ocean, the National Geographic Society hopes to promote its conservation. Tait says National Geographic’s new policy will have an impact on how children using maps in school learn to see the world.
“I think one of the biggest impacts is through education,” he says. “Students learn information about the ocean world through what oceans you’re studying. If you don’t include the Southern Ocean then you don’t learn the specifics of it and how important it is.”
(National Geographic)