Sunset over sea ice off the coast of Antarctica captured from the Nathaniel B. Palmer, an NSF research icebreaker ship, during an Antarctic oceanography research cruise. Click on image for full size (55 Kb) NOAA Corp Collection, Photographer Michael Van Woert

The Southern Ocean is a bit different. Many mapmakers do not even recognize it as an ocean. The Southern Ocean (sometimes known as the Antarctic Ocean or South Polar Ocean) surrounds Antarctica in the South Polar Region, extending to 60°S latitude.

In general, the boundaries of any ocean are usually the surrounding continents. For example, the Atlantic Ocean is bound by the North American and European continents in the north and the South American and African continents in the south. But the Southern Ocean does not have continents that define its boundaries.

So what makes the Southern Ocean an ocean?

According to the International Hydrographic Organization (IHO), because of its distinct circulation pattern, the waters of the Southern Ocean are somewhat separated from other oceans even without continents to form borders. The Antarctic Circumpolar Current is the strong ocean current that circles eastward around Antarctica. Because of this ocean circulation pattern, the seawater in the Southern Ocean is colder. The colder and isolated water supports a unique marine ecosystem in the Antarctic.