The Southern Ocean,

 

The Antarctic Ocean, as delineated by the draft 4th edition of the International Hydrographic Organization's Limits of Oceans and Seas (2002)

A general delineation of the Antarctic Convergence, sometimes used by scientists as the demarcation of the Southern Ocean

Earth's oceans
Arctic Atlantic Indian Pacific Southern
v t e

The Southern Ocean, which encircles Antarctica, will henceforth be given the same status, and typeface, as the Arctic, Atlantic, Indian and Pacific Oceans

ECONOMIST.COM

Another ocean has been added to the map

How is this decided?