The Kuroshio in the East China Sea

Observations of the hydrography and water movements in the East China Sea in areas where the bottom topography interferes with the Kuroshio indicate a vigorous exchange between the Kuroshio and a continental shelf water mass that is relatively cool and fresh. South of about 28°N, the Kuroshio runs into the continental shelf and is uplifted. The resulting onshore intrusion of the Kuroshio is compensated by an offshore flow in the surface layer of continental shelf water which is a part of the horizontal circulation created in part by the intrusion itself. North of about 28°N, the blocking of the Kyushu coastal topography forces a turn of the Kuroshio to the east and a separation of part of the Kuroshio flow on the left-hand side. The separation gives rise to the Tsushima Current and appears confirmed by recently obtained trajectories of World Ocean Circulation Experiment (WOCE) surface drifters. Thus, the surface layer flow along the East China Sea continental margin along which the Kuroshio flows is marked by a convergence in the southern stretches and a divergence in the north. Further confirmation of this surface flow characteristics is found in a high-resolution numerical model of the Kuroshio flow-through. Based upon the model output, the exchange due to these cross-margin flows amounts to a 7% loss in heat and salt to the Kuroshio and a gain of freshwater by the Kuroshio at the rate of about 1.0 Sv.