Kuroshio

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Kuroshio

(Also called Japan current.) One of the western boundary currents of the North Pacific subtropical gyre.

A deep, narrow, and swift current, it continues from the Philippines Current in a northeastward direction from Taiwan along the continental rise of the East China Sea, through Tokara Strait, and close to the eastern coast of Japan. At 35°N it separates from the coast and flows eastward into the Pacific as a free jet known as the Kuroshio Extension. It forms a marked temperature and salinity front with the Oyashio, which meets the Kuroshio Extension from the north and then flows parallel to it. Like all other western boundary currents, the Kuroshio develops instabilities and sheds eddies. Its unique characteristic is that south of Honshu it switches between three quasi- stable paths across the Izu Ridge at irregular intervals of 18 months to several years. Volume transport in the Kuroshio increases downstream and reaches 57 Sv (57 × 106 m3s-1) in the Kuroshio Extension, increasing seasonally by 15% during summer. The current's path in the extension is characterized by large meridional excursions in the so-called First and Second Crest at 145° and 152°E. On approaching the Shatsky Rise at 157°E, the Kuroshio Extension divides into several paths that tend to recombine before the Emperor Seamounts near 170°E cause the current to split again and disintegrate. The flow then continues as the North Pacific Current.

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