Kuroshio

(oceanography) A fast ocean current originating off the southeast coast of Luzon, Philippines, and flowing northeastward off the coasts of China and Japan into the upper waters of the north Pacific Ocean. It carries large quantities of warm water from the tropics into the midlatitude regions, and is an important agent in redistributing global heat.

A swift, intense current flowing northeastward off the coasts of China and Japan in the upper waters of the North Pacific Ocean. The Kuroshio is the western portion of a giant clockwise, horizontal circulation known as the North Pacific subtropical gyre. This circulation extends from 15° to 45°N across the entire width of the Pacific Ocean. It is driven by the large-scale winds—the trades in the south and the westerlies in the north. As with all other western boundary currents, such as the Gulf Stream, the effect of the Earth's rotation and its spherical shape is to concentrate the Kuroshio flow into a current that is only about 100 km (62 mi) wide with speeds up to 2 m/s (4 mi/h). See also Coriolis acceleration; Gulf Stream; Pacific Ocean.

The Kuroshio (Japanese, meaning “Black Current”) has an apparent blackness resulting from the water clarity, which is a consequence of the low biological productivity of seawater in the area. It originates off the southeast coast of Luzon, the main island of the Philippines. For the first 1000 km (620 mi), the Kuroshio flows northward along the east coasts of Luzon and Taiwan, until it enters the East China Sea. For the next 1000 km, it flows northeastward near the edge of the continental shelf off eastern China, until it exits the East China Sea through the Tokara Strait. During its final 1000 km, it flows east-northeastward off the southern coast of Japan (where it is sometimes called the Japan Current). Finally, it leaves the Asian coast near Tokyo and travels into the interior of the North Pacific Ocean as a slowly expanding jetlike current known as the Kuroshio Extension. Here it merges with the Oyashio, a cold current with high biological productivity, and becomes the North Pacific Current.

Like the Gulf Stream in the North Atlantic, the Kuroshio rapidly carries large quantities of warm water from the tropics into midlatitude regions. It is consequently an important agent in redistributing global heat. North of 30°N, where prevailing winds are westerlies, the North American climate is strongly affected by the warmth of these waters.