On June 8 people around the globe celebrated World Oceans Day. National Geographic magazine had a special reason for celebration: The frigid waters that flow around Antarctica have long been known as the Southern Ocean because its properties are relatively uniform throughout.

Embedded in the Southern Ocean is the Antarctic circumpolar current, or ACC, which circles the globe around the Antarctic continent, although until now it has lacked an official designation.

The ACC is a major factor in carrying heat from the Atlantic, Pacific and Indian oceans into the cold southern waters. There the cold waters of the ACC also store carbon in their depths, making them of significant environmental importance.

Although the U.S. Board on Geographic Names has recognized the Southern Ocean since 1999, only in 2021 did National Geographic and the National Oceanic and Atmospheric Administration add the ocean to the official map.

Southern Ocean’s unique properties

The Southern Ocean joins the Arctic, Indian, Atlantic and Pacific oceans. The addition is important for many reasons. One of the biggest impacts is educational: Students learn about the ocean world through the waters being studied. Officially recognizing it underscores its importance to the planet.

The cold waters of the Southern Ocean are distinct because their current connects Indian, Atlantic and Pacific waters, thereby mixing water from the other oceans.

Most of the Southern Ocean is made up of deep water, with only a few shallow areas. The typical depth of the Southern Ocean ranges from 13,000 to 16,000 feet. Its deepest point lies at 60 degrees south and 24 degrees west at the South Sandwich Trench — at 23,740 feet, it is one of the deepest points of any ocean in the world.

Because there is no land around 60 degrees south, the waters of the Southern Ocean can circulate around the entire globe. This allows warmer waters moving southward in undersea masses in the Atlantic to transport much heat from the Northern Hemisphere. Caught in the ACC, the deep circulating water that travels all the way from Greenland in the North Atlantic gives up its heat to the ACC, which then disperses into the sea.

The ACC flows from west to east around Antarctica in a broad fluctuating band roughly centered around a latitude of 60 degrees south, 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.

Region only recently explored

The Southern Ocean’s floor has not been extensively explored, although scientists suspect that there are huge deposits of oil and natural gas, particularly around the continental margins. Manganese nodules also exist in great quantities on the seafloor.

The Southern Ocean, geologically the youngest of the oceans, was formed when Antarctica and South America moved apart roughly 30 million years ago, opening the Drake Passage and allowing the formation of the ACC.

Antarctica was the last region on Earth to be discovered, unseen until 1820 when the Russian expedition of Fabian Gottlieb von Bellingshausen and Mikhail Lazarev sighted the Fimbul ice shelf. The continent remained largely neglected for the rest of the 19th century because of its harsh environment, lack of easily accessible resources and isolation.

In January 1840, land in Antarctica was seen for the first time, almost simultaneously, by a U.S. exploring expedition under Lt. Charles Wilkes and a separate French expedition under Jules Dumont d’Urville. The first confirmed landing was by a team of Norwegians in 1895.

Richard Brill is a retired professor of science at Honolulu Community College. His column runs on the first and third Fridays of the month. Email questions and comments to brill@hawaii.edu.