Direct flows from the Ulleung Basin into the Yamato Basin in the East/Japan Sea

Using the trajectories of ARGO floats, we report direct flows from the Ulleung Basin into the Yamato Basin through a gap between the Oki Spur and the Yamato Rise over the southern part of the East/Japan Sea. The gap is subdivided into two narrow (northern and southern) passages by a seamount located in the middle. The flows, therefore, are narrow and this explains why this flow was not reported earlier. More than half of the 25 ARGO floats, which operated around the gap, drifted through the gap or area near it. The strength of the throughflow estimated using the trajectories of the floats at parking depth is comparable to the mean deep flow found over the southwestern part of the East/Japan Sea. A high resolution regional ocean model whose overall circulation pattern over the Ulleung Basin is consistent with those from previous studies shows that the flow through the gap is supplied mainly by eastward flows crossing the mouth of the basin, and secondarily by the cyclonic circulation following the outer perimeter of the basin. Thus the throughflow is an important component of the deep circulation over the southern East/Japan Sea, and the narrow gap, where the flow is well confined, would be a good place to study the deep circulation.