Subtropical Gyre

Japanese: 亜熱帯循環 - あねったいじゅんかん（英語表記）Subtropical Gyre

Anticyclonic circulations exist in the subtropical regions of each ocean. In the Pacific Ocean, they consist of the North Equatorial Current, Kuroshio Current, Kuroshio Extension, North Pacific Current, and California Current. On a rotating Earth, water is generally transported to the right (northern hemisphere) at a right angle to the wind, but the westerly winds blowing on the northern edge of the circulation and the northeasterly trade winds blowing on the southern edge raise the water level in the center of the circulation, and the current flows around the contour lines (isobars) of the sea surface as a geostrophic current. All subtropical circulations have strong currents in the parts that move toward high latitudes along the west coast, such as the Kuroshio Current in the North Pacific Ocean and the Gulf Stream in the North Atlantic Ocean. This is due to the effect of the latitude change in the way the Coriolis force works (β effect), and is called the phenomenon of west coast strengthening. (Nagata)

Source: Japan Hydrographic Association, Ocean Information Research Center, Encyclopedia of the Sea

Japanese:

各大洋の亜熱帯域に存在する高気圧性の循環。太平洋では北赤道海流・黒潮・黒潮続流・北太平洋海流・カリフォルニア海流からなる。自転している地球上では水は全体として風に対して直角右向き（北半球）に運ばれるが、循環の北縁を吹く偏西風と南縁を吹く北東貿易風により、循環の中央部の水位が高められ、海流は地衡流として海面の等高線（等圧面）に沿ってその周りを巡る。全ての亜熱帯循環は、北太平洋の黒潮や北大西洋の湾流の様に、西岸沿いに高緯度に向かう部分に強大な海流を持つ。これはコリオリの力の働き方の緯度変化の効果（β効果）によるもので、西岸強化の現象と呼ばれる。（永田）

出典　(財)日本水路協会海洋情報研究センター海の事典について　情報

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