Synoptic temperature structure of the East China and southeastern Japan/East Seas

Air-deployed expendable bathythermograph (AXBT) surveys are used to investigate the synoptic temperature structure of the East China Sea (ECS), southern Yellow Sea, and southeastern Japan/East Sea (JES) from 1992–1995, in the depth range 0–400 m. The main results of this study are as follows. The regional winter mixed layer is shallow along the paths of the Kuroshio and Polar Front due to strong advection of warm water, which suppresses vertical mixing. The region where mixing is to the bottom is generally northwest of the 100-m isobath in the ECS and in the Tsushima Strait. Two September surveys reveal two different Kuroshio Front positions: in 1992 this front was far on-shelf of its mean position, preventing the formation of eddies at Mien Hwa Canyon; in 1993, the Kuroshio Front had migrated off-shelf, and eddies along the front had formed. The Kuroshio Current Branch West of Kyushu is not seen in summer at 60 m depth, only winter and spring; however, there is evidence of this branch current in all seasons at 100 m depth. Along the entire length of the ECS in all surveys except winter (where wind mixing had homogenized the water column), cross sections show that cold water (<18 °C) inshore of the Kuroshio reached westward of the 200-m isobath, onto the shelf, and as shallow as 60 m. From 1992–1995, the Nearshore Branch is present in all surveys, and the East Korean Warm Current is generally present in spring–fall, and strongest in each May survey.