Changing tides: Earth’s southe

Image: canva

Changing tides: Earth’s southern seas now officially world’s fifth ocean

Since National Geographic began making maps in 1915, it has recognised four oceans, but as of 8 June 2021, it now recognises five world oceans.

Changing tides: Earth’s southe

Image: canva

National Geographic’s cartographers recently said that the swift current circling Antarctica keeps the waters there distinct and worthy of their own name: The Southern Ocean.

The Southern Ocean

Since National Geographic celebrated World Oceans Day on 8 June 2021, they now recognise the Southern Ocean as the world’s fifth ocean with the other four being the Atlantic, Pacific, Indian, and Arctic oceans.

“The Southern Ocean has long been recognised by scientists, but because there was never agreement internationally, we never officially recognised it,” says National Geographic Society Geographer Alex Tait. 

Since the late 1970s, the National Geographic Society has employed a geographer who oversees changes and tweaks to every map that’s published. Tait has been on the job since 2016. And so, throughout the years, geographers debated whether the waters around Antarctica had enough unique characteristics to deserve their own name, or whether they were simply extensions of the Pacific, Atlantic, and Indian Oceans. 

“It’s sort of geographic nerdiness in some ways,” Tait says. He and the 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, Tait 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 recognise it because of its ecological separation.”

Southern Ocean defined by its current

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. 

Extending from the surface to the ocean floor, the ACC transports more water than any other ocean current. It pulls in waters from the Atlantic, Pacific, and Indian Oceans, helping drive a global circulation system known as the conveyor belt, which transports heat around the planet.

Image: National Geographic

Promote conservation

By drawing attention to the Southern Ocean, the National Geographic Society hopes to promote its conservation. Here, fragile marine ecosystems are home to wonderful marine life such as whales, penguins, and seals.