5 Essential Facts About the Recently Recognized Southern Ocean

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Adding a new geographical feature to the world map is a rare occurrence. For over a hundred years, schoolchildren have been taught that Earth has four primary saltwater bodies: the Arctic, Atlantic, Indian, and Pacific oceans. These oceans are interconnected yet separated by the world's seven continents.

However, scientists have acknowledged a fifth ocean, known as the Southern Ocean, for quite some time. In 1937, the waters surrounding Antarctica were officially recognized by the International Hydrographic Organization (IHO), only to lose this designation in 1953. In the U.S., the National Oceanic and Atmospheric Administration (NOAA) has recognized this fifth ocean since 1999, but now the global scientific community has officially brought the Southern Ocean into the public eye. This recognition, made official on June 8—World Oceans Day—aims to raise awareness about the urgent need for conservation in a region where industrial fishing has nearly decimated endemic fish populations over recent decades.

Here are five key facts about the Southern Ocean:

1. It Was Once Part of the Pacific Ocean

Ever since James Cook ventured into the southern regions during the 1770s, there has been ongoing debate about whether and how to differentiate the Southern Ocean from the adjacent water bodies. Historically, it has been grouped with the Indian and Atlantic oceans, but more recently, it has been associated with the Pacific Ocean.

2. It's the World's Second Smallest Ocean

Positioned at Earth's southern extreme, the Southern Ocean wraps around Antarctica, extending up to 60 degrees south latitude. This means it doesn't reach the southern tip of South America, which lies much farther south. Among the world's oceans, only the Arctic Ocean is smaller in size.

3. It's Defined by Currents, Not Continents

Distinguishing between saltwater bodies is typically achieved by landmasses: if a continent lies between two oceans, they are given distinct names. However, the Southern Ocean is unique because no continent separates it from the Indian, Atlantic, or Pacific oceans.

Instead, the Southern Ocean's boundaries are shaped by the Antarctic Circumpolar Current (ACC), a swift-moving current that flows from west to east around Antarctica. The ACC's waters are notably colder and less salty compared to those of the surrounding oceans.

4. It Hosts a Distinct and Delicate Ecosystem

The Southern Ocean is the exclusive habitat of the Emperor penguin (Aptenodytes forsteri), the Weddell seal (Leptonychotes weddellii), and countless other species found nowhere else on Earth. Additionally, it serves as a crucial feeding area for creatures like the humpback whale(Megaptera novaeangliae), which travels to these waters each summer to feast on krill before returning north.

5. It's Time to Acknowledge the Southern Ocean

Despite its remote location, the Southern Ocean deserves recognition. Climate scientists advocate for its inclusion on maps, as it plays a critical role in the climate crisis. In 2021 alone, two of the largest icebergs ever documented calved from the continent. Additionally, industrial fishing targeting krill and Patagonian toothfish (sold as Chilean sea bass in restaurants) underscores the urgent need to protect and emphasize this fragile region.