• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.4 no.4
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• pp.305-311
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• 1999

This study aims to decipher surface water mass interaction in summer in the South China Sea and East China Sea by radium isotope distribution pattern. Salinity and activity ratio of radium ($^{228}Ra/^{226}Ra$) showed gradual changes, which were adequate to apply simple two end-member mixing between Kuroshio surface water and Changjiang Dilute Water for the East China Sea and the former and Nearshore Diluted Watermass (NDW) for the South China Sea. Two tracer methods, salinity and Ra isotope ratio, were compared for East China Sea. Results showed remarkable consistency for waters near Kuroshio, however, discrepancy were noticeable after Tsushima Warm Current branching. Mixing with subsurface waters may cause the discrepancy. When mixed with subsurface waters, salts and radium isotope ratio are expected to be biased in opposite direction, i. e. prone to underestimate the fraction of less saline water in the case of salts and vice versa for Ra isotope ratio. Taking the mean values of two different results seems more realistic to estimate fraction of end-members.

• Ocean and Polar Research
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• v.30 no.3
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• pp.361-372
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• 2008

A satellite tracked drifter experiment was conducted to observe thermal structure and surface circulation in the northeastern East China Sea. For this experiment, four ADOS buoys, assembled with surface float and thermister chain, were deployed on August 2007 in southern Jeju-do, where the Kuroshio Branch Current is separated from the main stream. Thermal structure in the upper layer of the northeastern East China Sea was successfully observed during the following $1{\sim}3$ months. Strong thermo-haline front in a northeast-southwest direction was observed. In the frontal zone, warm and saline Kuroshio origin water intermixes with fresher coastal water and flows toward the Korean Strait. Typhoon Nari, which passed over the East China Sea 20 days after commencement of study, caused distinct signals in the thermal structure and trajectory of buoys. During the typhoon, surface temperature abruptly dropped to about $4^{\circ}C$, while the thermocline formed at $30{\sim}50$ m depth vanished due to strong vertical mixing. Internal inertial oscillation occurred several days after the typhoon. The fortuitous occurrence of typhoon Nari showed that ADOS buoys can provide useful and accurate air-sea interaction data during typhoons.

• Proceedings of the KSRS Conference
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• v.2
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• pp.831-835
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• 2006

NOAA/AVHRR data were used to analyze sea surface temperatures (SSTs) and thermal fronts (TFs) in the Korean seas. Temporal and spatial analyses were based on data from 1993 to 2000. Harmonic analysis revealed mean SST distributions of $10{\sim}25^{\circ}C$. Annual amplitudes and phases were $4{\sim}11^{\circ}C$ and $210{\sim}240^{\circ}$, respectively. Inverse distributions of annual amplitudes and phases were found for the study seas, with the exception of the East China Sea, which is affected by the Kuroshio Current. Areas with high amplitudes (large variations in SSTs) showed 'low phases' (early maximum SST); areas with low amplitudes (small variations in SSTs) had 'high phases' (late maximum SST). Empirical orthogonal function (EOF) analyses of SSTs revealed a first-mode variance of 97.6%. Annually, greater SST variations occurred closer to the continent. Temporal components of the second mode showed higher values in 1993, 1994, and 1995. These phenomena seemed to the effect of El $Ni{\tilde{n}}o$. The Sobel edge detection method (SEDM) delineated four fronts: the Subpolar Front (SPF) separating the northern and southern parts of the East Sea; the Kuroshio Front (KF) in the East China Sea, the South Sea Coastal Front (SSCF) in the South Sea, and a tidal front (TDF) in the West Sea. Thermal fronts generally occurred over steep bathymetric slopes. Annual amplitudes and phases were bounded within these frontal areas. EOF analysis of SST gradient values revealed the temporal and spatial variations in the TFs. The SPF and SSCF were most intense in March and October; the KF was most significant in March and May.

• Journal of the korean society of oceanography
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• v.37 no.3
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• pp.169-177
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• 2002

An eddy-resolving free-surface primitive-equation model with nonlinear terrain-following coordinates is established to study the exchange of water masses among the Asian marginal seas and their adjacent waters. A curvilinear coordinate system is used to generate the horizontal grid with a variable resolution for the regional oceans from $5^{\circ}$S to $45^{\circ}$N and $100^{\circ}$E to $155^{\circ}$E. The higher resolution region has about a 10 km by 10 km grid covering the complex geometry of the coastal marginal seas, while the lower resolution region has about a 30 km by 30 km grid covering the eastern Pacific. The model is initialized by the Levitus annual climitology and forced by the monthly mean air-sea fluxes of momentum, heat, and freshwater derived from the Comprehensive Ocean-Atmosphere Data Set. High-resolution and low-viscosity are identified as the key factors for a better representation of the exchange of waters through narrow straits and passages between the marginal seas and their adjacent waters. The dynamics of the loop currents and eddies in the South China Sea and Celebes Sea are examined in detail. It has found that the anticyclonic loop and detached eddies from the Kuroshio through the Luzon Strait play an important role in transporting warm and salty water into the South China Sea, while the cyclonic circulation of the Mindanao Current in the Celebes Sea plays a role in contributing cold water to the Indonesian throughflow. The deep undercurrent of the western Pacific is shown to provide fresher water to the South China Sea and Celebes Sea. These modeling results suggest that the exchange processes via the narrow straits and passages are of fundamental importance to the maintenance of water masses for the marginal sea region.

• 한국해양학회지
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• v.28 no.1
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• pp.24-34
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• 1993

In order to study the seasonal characteristics of species composition and abundance, zooplankton samples were collected from April 1987 to June 1988 with bimonthly intervals in the Mid-Eastern part of the Yellow sea. Among the 24 species of 18 genera occurred in this study area, 17 species are copepods. Noctiluca scintillant has greatly influenced on the distribution of the zooplankton in the coastal area and some copepods may be excluded by its great occurrence. the seasonal variation of abundance of copepods accounting for 30-63.4% of total zooplankton were more varied among stations in the coastal area than in the offshore. It suggests that environmental factors are more variable in the coastal area than in the offshore. In the Copepod community, Acartia omorii, Paracalanus parvus and Corycaeus affinis were predominant in April and June, from August to December and in December, respectively. Sagita enflata as a Kuroshio indicator species, occurred in the study area from August to December. The great occurrence of warm water species, Doliolum sp. in October and the occurrence of Sagitta enflata from August to December suggested that there is a influx of the tributaries of Kuroshio current into the study area. It appeared that the seasonal characteristics of species composition and abundance of zooplankton were affected by the seasonal variation of water mass.

• Journal of the korean society of oceanography
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• v.35 no.4
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• pp.161-169
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• 2000

A seasonal circulation in the East China Sea and the Yellow Sea and its possible cause have been studied with CSK data during 1965-1989. Water mass distributions are clear in winter, but not in summer because the upper layer waters are quite influenced by atmosphere. To solve the problem, a water mass analysis by mixing ratio is used for the lower layer waters. The results show that the distribution of Tsushima Warm Current Water expands to the Yellow Sea in winter and retreats to the East China Sea in summer. It means that there is a very slow seasonal circulation between the East China Sea and the Yellow Sea: Tsushima Warm Current Water flows into the Yellow Sea in winter and coastal water flows out of the Yellow Sea in summer. By the circulation, the front between Tsushima Warm Current Water and coastal water moves toward the shelf break in summer so that the flow is faster in the deeper region. The process eventually makes the transport in the Korea Strait increase. The Kuroshio does not seem to influence the process. A possible mechanism of the process is the seasonal change of sea surface slope due to different local effects of surface heating and diluting between the East China Sea and the Yellow Sea.

• Journal of the Korean earth science society
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• v.25 no.1
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• pp.1-9
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• 2004

The clay minerals of thirty-four bottom sediments collected from the northwestern continental shelf of the East China Sea have been determined by X-ray diffraction analysis. The clay mineral distribution is mainly controlled by the sediment source and the dominant circulation pattern. The predominant clay mineral in our study area is illite comprising more-than 70% of whole clay fraction. The highest concentration of illite (>72%) is found in the southeastern offshore parts beyond the reach of terrigenous input from the Cheju Island. It means that these illites are largely transported by the Kuroshio Current from the South China Sea. Smectite is highly concentrated in the northwest middle part and in the outer-shelf mud patch. It seems to be due to the high supply of smectite transported from China where the fine-grained sediments are discharged from the modern and ancient Huanghe River. The relatively high abundance of kaolinite is likely derived from the Changjiang River via Taiwan ·Warm Current. In contrast, the large amounts of chlorite and high chlorite/kaolinite ratios occur in the northwestern are, reflecting the transportation by the Huanghai Sea Coastal Current from the southern Yellow Sea.

• Proceedings of the KSRS Conference
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• 2004.10a
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• pp.696-700
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• 2004

In the Korean seas, Sea Surface Temperature (SST) and Thermal Fronts (TF) were analyzed temporally and spatially during 8 years from 1993 to 2000 using NOAA/AVHRR MCSST. As the result of harmonic analysis, distributions of the mean SST were $10~25^{\circ}C,$ and generally SST decreased as latitude increased. SST increased in the order as following; the South Sea $(20\~23^{\circ}C),$ the East Sea $(17\~19^{\circ}C)$, and the West $Sea(13\~16^{\circ}C).$ Annual amplitudes and phases were $4\~11^{\circ}C,\;210\~240^{\circ}$ and high values were shown as following; the West Sea $(A1,\;9\~11^{\circ}C),$ the Northern East Sea $(A5,\;8\~9^{\circ}C),$ the Southern East Sea $(A4,\;6\~8^{\circ}C),$ the South Sea $(A3,\;6\~7^{\circ}C),$ the East China Sea $(A2,\;4\~7^{\circ}C)$ and phases; $A3\;(238\~242^{\circ}),\;A4\;(235\~240^{\circ}),\;A5\;(225\~235^{\circ}),\;Al\;(220\~230^{\circ}),\;A2\;(210\~235^{\circ}),$ respectively, Both of them were related inversely except the area A2, therefore the rest areas were affected by seasonal variations. TF were detected by Soble Edge Detection Method using gradient of SST. Consequently, TF were divided into 4 fronts; the Subpolar Front (SPF) based on the Cold Water Mass (low SST and salinity Subartic Water), resulting from the North Korea Cold Current (NKCC) and the East Sea Proper Cold Water in the middle and low layer, and the Warm Water Mass (high SST and salinity Subtropical Water), resulting from the Tsushima Warm Current (TWC) in area A4 and 5, the Kuroshio Front (KF) based on the Kuroshio Current (KC) and shelf waters in the East China Sea (ESC) in A2, and the South Sea Coastal Front (SSCF) based on the South Sea Coastal Water (SSCW) and TWC in A3. Also, the Tidal Front was weakly appeared in AI. TF located in steep slope of submarine topography. Annual amplitudes and phases were bounded in the same place, and these results should be considered to influence of seasonal variations.

• Journal of Environmental Science International
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• v.19 no.12
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• pp.1385-1395
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• 2010

Harmful dinoflagellate Cochlodinium polykrikoides blooms have been frequently occurred in coastal areas of the East Sea since 1995. We compared the oceanic conditions in years 1995, 2001 and 2003 when the C. polykrikoides bloom was strong, and in years 1998 and 2004 when the C. polykrikoides bloom was not appeared. We studied temporal and spatial variation of upwelling and geostrophic currents on the western channel of Korean Strait, an entrance of the East Sea. The period and occurrence area of C. polykrikoides bloom was depended on variation of upwelling in summer. In the distributions of geostrophic current, southward current was dominant near the coast in August, 1998 and 2000. Whereas northward current was dominant near and off the coast in August, 1995 and 2003 which the C. polykrikoides bloom was strong. When compared dominant phytoplankton of the coastal areas in each year, Kuroshio indicator species Proboscia alata and Chaetoceros affine were dominant, respectively, in 2001 and 2003 at every stations. However, the dominant species was variable at each coastal area in 1998 and 2000. In 2003, the abundance of Sagitta elegans which is known as the cold water indicator was low, but the abundance of S. enflata, warm water indicator, was very high in Gangneung compared to Sokcho. It seemed that the distribution of S. elegans is restricted by strong warm water current. In conclusion, it was estimated that the distribution of C. polykrikoides bloom in the coastal area of the East Sea was closely related with the strength of East Korea Warm Current and upwelling.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.26 no.2
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• pp.184-191
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• 1990

하계 대한해협 서수도에는 연직적으로 특성이 서로 다른 세 개의 수괴가 존재한다. 그 중 표층수에 대하여 인접 해역의 해수 특성과 상호 비교함으로써 그 기원과 유로를 추정하였다. 그 결과, 표층수는 동지나해의 대륙붕 상에서 형성된 Kuroshio수와 중국대륙연안수의 혼합수로써, 중국대륙연안수의 영향을 더 많이 받는 것으로 나타났다. 대부분의 표층수는 Kyushu Island의 서쪽 해역, 경도 126$^{\circ}$E와 127$^{\circ}$E 사이 해역과 제주도 동쪽 해역을 거쳐 유입되고, 한국 연안 부근에 있는 일부 표층수는 제주도 서쪽해협을 거쳐 유입된 것으로 나타났다.