Of the five oceans—the Southern Ocean became official in 2000 joining the Atlantic, Pacific, Indian, and Arctic—this is the fourth largest and one that few mariners will ever sail through. The Southern Ocean encircles the Antarctic continent, forming a virtual moat that helps to isolate and keep frozen the sixth largest continent that is only 2% ice free.
While all other oceans are bounded by continental masses, a subtle band of sea surface temperature change called the Antarctic Convergence defines this one. It is an irregular boundary varying from 48° to 60° south latitude, where sea surface temperature drops from 5° to 10° F over a distance of 20 to 30 miles. While this does not seem like a great change in temperature, it is a significant gradient in the oceans. This zone is also an eco-boundary with different bird and marine life being found on each side of it.