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 (Fig. 1). 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 (50 nmi) wide with speeds up to 2 m/s (4 mi/h).  See also: Coriolis acceleration; Gulf Stream; Pacific Ocean