There is only one ocean. The vast body of water that covers 71 percent of the Earth is continuous, but it has been divided into named regions — and where those divisions fall has changed over time, for historical, cultural, geographical and scientific reasons.
Four oceans, then five
Historically there were four named oceans: the Atlantic, the Pacific, the Indian and the Arctic. Most countries, including the United States, now also recognize a fifth, the Southern (Antarctic) Ocean. The Pacific, Atlantic and Indian are the best known.
The newest ocean
The Southern Ocean is the most recently named. The U.S. Board on Geographic Names recognizes it as the water reaching from the coast of Antarctica to the line of latitude at 60 degrees South.
Its boundaries were proposed to the International Hydrographic Organization in 2000. Not every country agrees with them, though, so IHO members have yet to ratify them. The United States is a member of the IHO, represented by the National Ocean Service's Office of Coast Survey.
Sources
Based on "How many oceans are there?" from NOAA's National Ocean Service, a work of the United States government in the public domain.
ライセンス： CC0 1.0（パブリックドメイン） · 出典 oceanservice.noaa.gov
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