General introduction

The East Sea (Japan Sea) is a semi-enclosed marginal sea surrounded by the East Asian continent and Japanese Islands in the northwestern Pacific. It is topographically isolated from the North Pacific which allows only a small portion of the Kuroshio penetrating into the sea. In spite of its small basin size of about 10⁶ km² and semi-isolated topography, many unique open ocean processes have been observed and identified, especially the existence of its own thermohaline circulation. Early oceanographic survey in the East Sea dates back to mid-19th century followed by numerous basin- or subbasin-scale regular and/or processoriented observations conducted by surrounding countries, independently or cooperatively, and also by overseas countries. The advent of satellite-tracked drifters and floats and the availability of various satellite-derived products have greatly contributed to understanding and finding important oceanographic processes. Mooring technology used in the East Sea has made progress for establishing some long-term local and global time-series stations.