• Fisheries and Aquatic Sciences
• /
• v.16 no.2
• /
• pp.117-124
• /
• 2013

We investigated the short-term and local changes in the thermohaline front in the Jeju Strait, Korea, which is usually formed during winter and spring. To do so, we compared Real-Time Observation System by Ferryboat (RTOSF) data with wind data and routinely collected oceanographic data. During February and April 2007, a thermohaline front formed in the Jeju Strait around the 13-$14^{\circ}C$ isotherms and 33.0-33.5 isohalines. The thermohaline was clearly weakened and began moving southward in mid-March. The variations in the surface temperature and salinity showed a continuous north-south oscillation of the thermohaline front with a period of 3-10 days. The speed of the short-term and local fluctuation of thermohaline front was about 5-30 cm/s. We confirmed these findings by examining the variation in the maximum temperature gradient and $14^{\circ}C$ isotherm during the study period. These short-term and local changes had not been previously detected using serial oceanographic and satellite data. Analysis of local wind data revealed a northerly wind fluctuation with a period of 3-10 days, which was clearly related to the short-term and local changes in the thermohaline front. The short-term and local changes of the thermohaline front in the Jeju Strait originated from local changes in the winter monsoon in this area.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
• /
• v.18 no.4
• /
• pp.163-177
• /
• 2013

An instrumented ferry made two transects per day across two current systems which are the North Korean Cold Current and the East Korean Warm Current over the years 2012-2013 from Gangneung to Ulleungdo in the southwestern East Sea. Seawater properties of these transects were measured with high spatial and temporal resolution for an extended period of time. Here the salinity records from the transects with the oceanographic observation data from East Sea Fisheries Institute of NFRDI, AVISO daily current chart and GOCI Chlorophyll-a image in 2012 and 2013 are used to study the time-series variation of salinity at the surface. The high salinity section with the range of 33.15~34.12 occurred on the transect mainly in the middle of eddy, and western boundary of strong northward current from June to October. We can found low salinity waters in both sides of the high salinity section. It is estimated that the western low salinity waters with the range of 30.58~33.20 accompanied by southward current were derived from the NKCC and the eastern waters with the range of 31.30~33.24 accompanied by northward current were derived from the Tsushima Surface Water. The lowest salinity of NKCC is confirmed in this study as 30.36. It is found that the western waters below 33.00 extended extremely toward the east about 110 km area from Gangneung and toward the south around Jukbyon coastal area as a 5~10 m layer. We can find its volume of low saline waters transport is not neglectable compared with that of Tsushima Current region in the western part of the East Sea. In this study we named it as the North Korean Low Saline Surface Water in summer.