Vertical ocean mixing in the Jeju Strait of Korea

Abstract

Hydrographic survey were carried out in the Jeju Strait in the northern East China Sea, where the Cheju Warm Current (CWC) flows eastward carrying warm and saline water, in June and November 2015 to study small scale hydrographic structureand vertical mixing. The data collected show the seasonal variation in distribution of three major water masses, the CWS water, surface coastal water and deep cold water, both in vertically and in laterally. It is observed that colder and fresher water intrusions in the upper pycnocline depth in the frontal zone lead to the generation of turbulent patches indicating an active mixing process. The subsurface Chlorophyll-a maximum layer (SCML) appears in all observation sections. The turbulent energy dissipation rates and corresponding vertical eddy diffusivities are relatively higher in the thermocline/pycnocline in many places and they match with the SCML. This means that mixing within the thermocline/pycnocline is a key physical process to drive vertical nutrient flux into the SCML from the lower layer.