The ocean's currents do not just run in straight lines; the biggest and most lasting of them join into vast rotating systems. These are gyres, and there are five major ones.
The world ocean's five major gyres. Credit: NOAA.
How gyres form
Wind, tides and differences in temperature and salinity drive the ocean's currents, and the ocean churns up many kinds: eddies, whirlpools and deep ocean currents. The larger, sustained currents have names of their own — the Gulf Stream, for example. Together, these large and permanent currents make up the systems called gyres.
The five major gyres
- the North Pacific Subtropical Gyre
- the South Pacific Subtropical Gyre
- the North Atlantic Subtropical Gyre
- the South Atlantic Subtropical Gyre
- the Indian Ocean Subtropical Gyre
A word with a second meaning
"Gyre" is now often used for something else: the collections of plastic waste and other debris found in higher concentrations in some parts of the ocean. That use is increasingly common, but traditionally the word means only one thing — a large system of rotating ocean currents.
Sources
Based on "What is a gyre?" 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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