Sometimes I forget simple facts that just about everyone who’s had much schooling at all on planet earth knows. I can’t recall why the question came up yesterday, but at some point I asked myself “how many oceans are there?” and had to stop and actually think about the answer. I know my kids already knew how many oceans there were before they were even in kindergarten but I’m sitting here with sheepskins on my wall and have to count out the names: Atlantic, Pacific, Indian, Arctic.

And it turns out I’m still wrong: there are five per science and Encyclopedia Brittanica; it’s just that until 2000ish, we were only taught that there were four. Or just one, if you look at it differently:

Earth’s ocean count depends upon one’s perspective. A collection of scientific organizations, including the International Hydrographic Organization, has considered the existence of the Southern Ocean (also called the Antarctic Ocean) in the waters surrounding Antarctica below 60° S latitude. The separation of the Southern Ocean from the Atlantic, Pacific, and Indian oceans is reasonable when you consider that the Antarctic Circumpolar Current and the winds that circle the outer approaches of the continent create a kind of natural separation, or Antarctic Convergence (in terms of oceanography and meteorology), between Antarctica and the rest of the world. Although some organizations, and even many countries (such as the United States, Australia, and New Zealand), rank the Southern Ocean right alongside Earth’s other oceans, the concept of the Southern Ocean has not yet been universally accepted.

Functionally speaking, however, there is only one ocean, since every ocean is connected to at least two others. The reality of a single ocean is also evidenced by the thermohaline circulation (called the Global Ocean Conveyor or the Great Ocean Conveyor Belt) that passes through all of them. The thermohaline circulation continually replaces seawater at depth with water from the surface and slowly replaces surface water elsewhere with water rising from deeper depths.

Neat! I love encyclopedias and kind of wish they were still a thing, impractical and inefficient as that might be. Anyway, how about some United Soccer Links: