동해 독도 주변해역에서의 혼합

Abstract

Dok Island (Dokdo) is located at the northeastern corner of Ulleung Basin in the East Sea. The hydrography around Dokdo is very complex influenced by warm waters from the meandering of the East Korean Warm Current (EKWC), cold waters from the Northern Korean Cold Water (NKCW), the size and location of the Ulleung Warm Eddy (UWE) and variability of the subpolar front. In November 2006, the Korea Ocean Research and Development Institute (KORDI) conducted hydrographic survey around Dokdo using the R/V Eardo. Figure 2 shows horizontal distributions of temperature at 4 m and 100 m depths, respectively. Surface temperature is lower near the coast of Dokdo than the outer area, which is an indication of the island mixing. Temperature at 100 m is higher in the southwest probably due to the Tsushima Warm Current (TWC) carrying warm and saline water.Shown in Fig. 3 are vertical distributions of potential temperature, salinity and dissolved oxygen (DO) along Line A from the west of Dokdo to the east. The East Sea Intermediate Water (ESIW) below the TWC, which affects the hydrographic condition in the upper layer around Dokdo is observed at 200 ~ 300 m with low salinity and high dissolved oxygen. It is noticeable that temperature and salinity at the stations in the vicinity of Dokdo is further lowered by about 1.0 °C and 0.1 psu, respectively. The dissipation rate of turbulent kinetic energy (ε) is fundamental to understand of mixing in the ocean and is used to estimate the diapycnal eddy diffusivity (Kz). Microstructure profiling measurements were carried out at 10 stations between Ulleungdo and Dokdo in March 8-10, 2007. The vertical distribution of ε measured by a microstructure profiler (TurboMAP) is shown in Fig. 4b excluding the upper 10 m. The highest level of ε ( W/kg) was observed near Dokdo associated with shear instabilities. Since the stability in the thermocline is very strong, it takes much more energy to displace a particle of water. It is characterize