• Korean Journal of Fisheries and Aquatic Sciences
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• v.24 no.3
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• pp.185-192
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• 1991

The vertical distribution and chemical characteristics of water masses were measured along two south-north transects in the polar front region of the central Korean East Sea. In February, a thermocline was present at depth between 50m and loom at the southern sites of a landward A-transect, and its depth was gradually deepened northward. At an outside B-transect, a thermocline was observed at significantly deep depth of 300m to 400m at two northern stations(Stn. 10 and 11), though the depth of the southward stations was nearly identical to that at the northward stations on a A-transect. In September, there were vertically more various water masses, i.e. the Tsushima Warm surface water(TWSW) or more than $20^{\circ}C$, the Tsushima Middle water(TMW) with a range of $12{\~}17^{\circ}C$, the North Korea Cold Water(NKCW) with $1{\~}7^{\circ}C$ temperature, the Japan Sea Proper Water(JSPW) of less than $1^{\circ}C$, and the mixed water. The North Korea Cold Water could be distinguishable from the other waters, especially from the mixed water of the Tsushima Middle Water and the Japan Sea Proper Water by the pattern of $T-O_2$ diagram. For instance, the North Korea Cold Water had higher oxygen by $1{\~}2ml/l$ than those in the mixed water, although both the two water masses ranged $1{\~}7^{\circ}C$ in water temperature. AOU value was the highest in the JSPW and the lowest in the TWSW. Also, AOU indicated a nearly linear and negative correlation with water temperature. However, AOU data for two masses, the NKCW and the TMW, in September departed remarkably from a regression line. Moreover, the ratio of $$\Delta P/\Delta AOU)$ in September was about $0.45{\mu}g-at/ml$ and higher than the value observed in the open sea. This high value could be elucidated by two factors; intrusion of the NKCW with high oxygen and molecular diffusion of dissolved oxygen from the surface into the lower layer. AOU would be a useful tracer for water masses in the polar front area of the Korean East Sea.

• Journal of the Korean earth science society
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• v.38 no.3
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• pp.194-208
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• 2017

This study analyzed the correlation between tropical cyclone (TC) frequency and the western North Pacific monsoon index (WNPMI), which have both been influential in East China Sea during the summer season over the past 37 years (1977-2013). A high positive correlation was found between these two variables, but it did not change even if El $Ni{\tilde{n}}o$-Southern Oscillation (ENSO) years were excluded. To determine the cause of this positive correlation, the highest (positive WNPMI phase) and lowest WNPMIs (negative WNPMI phase) during an eleven-year period were selected to analyze the mean difference between them, excluding ENSO years. In the positive WNPMI phase, TCs were mainly generated in the eastern seas of the tropical and subtropical western North Pacific, passing through the East China Sea and moving northward toward Korea and Japan. In the negative phase, TCs were mainly generated in the western seas of the tropical and subtropical western North Pacific, passing through the South China Sea and moving westward toward China's southern regions. Therefore, TC intensity in the positive phase was stronger due to the acquisition of sufficient energy from the sea while moving a long distance up to East Asia's mid-latitude. Additionally, TCs occurred more in the positive phase. Regarding the difference in 850 hPa and 500 hPa stream flows between the two phases, anomalous cyclones were strengthened in the tropical and subtropical western North Pacific, whereas anomalous anticyclones were strengthened in East Asia's mid-latitude regions. Due to these two anomalous pressure systems, anomalous southeasterlies developed in East China Sea, which played a role in the anomalous steering flows that moved TCs into this region. Furthermore, due to the anomalous cyclones that developed in the tropical and subtropical western North Pacific, more TCs could be generated in the positive phase.

• Ocean and Polar Research
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• v.34 no.4
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• pp.413-430
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• 2012

To understand the scales of the spatial distribution and temporal duration of the subsurface chlorophyll-a maximum (SCM) observed in the Ulleung Basin of the East Sea, we analyzed physical and chemical data collected during the East Asian Seas Time-series-I (EAST-I) program. The SCM layer occurred at several observation lines from the Korea Strait to $37.9^{\circ}N$ in the Ulleung Basin during August of 2008 and 2011. At each observation line, the SCM layer extended from the coast to about 200 km off the coast. The SCM layer was observed between 30 and 40 m depth in the Ulleung Basin as well as in the northwestern Japan Basin along $132.3^{\circ}E$ from $38^{\circ}N$ to $42.3^{\circ}N$ during July 2009, and was observed around 50 m depth in the northeastern Japan Basin ($135-140^{\circ}E$ and $40-45^{\circ}N$) during July 2010. From these observed features, we hypothesize that the SCM layer observed in the Ulleung Basin may exist in most of the East Sea and may last for at least half-year (from the early May to late October). The nutrient supply mechanism for prolonged the SCM layer in the East Sea was not known, but it may be closely related to the horizontal advection of the nutrient rich and low oxygen waters observed in the Korea Strait between a 50 m depth to near the bottom. The prolonged development of the SCM layer in the Ulleung Basin may result in high primary production and would also be responsible for the high organic carbon content observed in the surface sediment of the region.

• Journal of the Korean Institute of Navigation
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• v.25 no.1
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• pp.77-91
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• 2001

According to the many ancient literatures, it is said to be that Merchant Prince, Chang Pogo in unification Silla had traded with not only China, Japan but also Arab-Islam Countries, but unfortunately there is no definite records about this. Therefore in this study the writer would like to presume the sea routes of Merchant Prince, Chang Pogo in a unification Silla. For the purpose of this study the writer would like to study the reference books and materials regarding to the sea routes of prehistoric age and ancient three countries of Kingdoms and unification Silla. Especially the writer consider “The Work of Routes and Kingdoms” of Ibn Khurdarhbih regarding to the ancient sea routes of Korea, China, Arab-Islam Countries, and also the writer consider the ancient sea routes of Tang Dynasty in China and Ryukyu Kingdom in Japan. About this methodology of this study, the writer believe that the sea routes of today is the results of ancient sea routes, and this ancient sea routes could not be changed forever except special circumstance. According in this study the writer would like to persume the sea routes of Merchant Prince, Chang Pogo using like this methodologies. This presumption of the writer is originated on the basis of The Work of Routes and Kingdoms written by ancient Arabian Geographer, Ibn Khurdadhbih in the early years of 9th century. The Work of Routes and Kingdoms is geography, and the principal contents of this geography are the activities of Arab-Islam merchants and Chinese Merchants between Arab-Islam countries and China from 9th century to 11th century by ancient sea routes. But surprisingly in this geography, Silla was marked, and another ancient Arabian geogrpher, Al-Biruni marked Silla on his map, Qanun Al-mas'udi in the 9th century, and also another ancient Arabian geographer, Al-Idrisi marked Silla on his map in the 11th century. Especially Al-Biruni expressed the longitude and latitude of Silla on his map, he expressed Silla as following. “at the extreme end of China toward the East and few people travelled to it by sea”. Therefore the writer would like to presume that Arab-Islam merchants had traded with unification Silla in the 9th century, and also Merchant Prince, Chang Pogo had traded with not only China, Japan but also Arab-Islam Countries using above ancient sea routes in the 9th century.

• Ocean and Polar Research
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• v.25 no.1
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• pp.31-40
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• 2003

In August-September 2001, 15 samples of bottom sediments were collected in the inner, middle and open parts of Amursky Bay near Vladivostok, Russia, and barfin plaice Pleuronectes pinnifasciatus was sampled from the inner and the middle locations of the bay. In the sediments from all three sites elevated concentrations of several heavy metals, i.e. Zn ($102-115{\mu}/g$ dry weight), Ni $(70-73{\mu}g/g)$ and Cu $(27-35{\mu}g/g)$ were discovered. The contents of oil hydrocarbons were very close to or slightly higher than the maximal normal environmental background level, $100{\mu}g/g$ dry weight. The sediments contained negligible amounts of hexachlorocyclohexane, while DDT concentrations were quite high (1.7-16.3ng/g dry weight). Generally, there were no substantial differences in the pollution levels of the locations studied and our results resembled those reported for Amursky Bay in the 1990s. Surprisingly, in 2001 'fiesh' DDT comprised 70-85% of the total DDT content in sediment from all the locations studied. In fish liver total DDTs concentrations were 212.8 and 122.54 ng/g wet weight for the inner and the middle locations, respectively, and 'fresh' DDT comprised 35 and 64% of DDTs, respectively. These results provide evidence of recent input of DDT from an unknown source into the ecosystem of Amursky Bay. Histopathological changes revealed in the plaice liver (vacuolization of hepatocytes, coagulative necrosis of hepatocytes, inflammatory reaction, and necrosis of epithelial cells of bile ducts) are probably connected with an intensive metabolism of DDT in the fish organism. No histological and histomorphometric differences were found in the state of the interrenal tissue. Similar condition of the liver and the interrenal tissue in barfin plaice sampled from the inner and the middle locations of Amursky Bay may be explained by the absence of great differences in the pollution levels of these sites.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.14 no.4
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• pp.239-252
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• 1981

The East China Sea is an important region as nursery and spawning grounds for pelagic fishes such as jack mackerel, common mackerel etc. , and thus constitutes a major fishing area for purse-seine fishery. The environment surrounding in this region is under the influence of the Yellow Sea Cold Water, China Coastal Water and Kuroshio Current. The purpose of this study was to clarify the effects of oceanographic conditions and thermal fronts on the formation of the fishing grounds for the mackerels in the East China Sea. Through the analyses of fisheries statistics during 1968-1976 and temperature data, the following facts are found: 1) Approximately $70\%$ of the total mackerel(common) catches appeared to be come from the Tsushima Current region which includes Sakai coast of the Japan Sea, eastern Tsushima and Shirase Island, and Jeju Island of Korea. This area covers only about $8\%$ of the East China Sea. 2) Main fishing grounds for the jack mackerel are also centered around the area of southwestern Goto, Shirase and eastern Tsushima Island where the catches accounted for about $54\%$ of the total jack mackerel catches. 3) Fluctuations in annual catches are relatively small in the Tsushima Current region, compared to other regions such as Yellow Sea, southwestern coast of Kyushu and mid-western part of the East China Sea, where the fisheries yields varied considerably due to unstable fishing conditions. 4) It appears that the fishing grounds for the jack mackerel are mainly distributed along the warmer region ($15-20^{\circ}C$) of the thermal front, and those for the common mackerel are in somewhat colder region ($13-16^{\circ}C$) in the Tsushima Current.

• Journal of the Korean earth science society
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• v.32 no.4
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• pp.347-359
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• 2011

This study has developed the index for diagnosis on possibility that typhoons (TYs) affect Korea. This index is closely related to the strength of the western North Pacific high (WNPH), which is calculated as a difference in meridional wind between at the highest correlation area (around Korea) and at the lowest correlation area (sea southeast of Japan) through a correlation analysis between TC frequency that affects Korea and 500 hPa meridional wind. In low frequency years that selected from Korea affecting TC index, anomalous northeasterly is strengthened from Korea to the South China Sea because the center of anomalous anticyclonic circulation is located to northwest of Korea. Thus, TCs tend to move westward from the sea east of the Philippines to the mainland China. On the other hand, in high frequency years, anomalous southwesterly serves as steering flow that more TCs move toward Korea because the center of anomalous anticyclonic circulation is located to sea east of Japan. Consequently, this study suggests that if this index is calculated using real time 500 hPa meridional winds that forecasted by dynamic models during the movement of TCs, the possibility that TCs approach Korea can be diagnosed in real time.

• 한국해양학회지
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• v.20 no.3
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• pp.37-54
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• 1985

A description of the "phytohydrography" in the southwestern waters of the East Sea is given from concurrent measurement of temperature, chlorophyll-a, nutrients, and phytoplankton and also from the calculated primary production during the two cruises in May and October, 1984. Past history of water mass is relatively well reflected in the distribution of phytoplankton species, but such a reflection is rarely shown in the distribution of physical and chemical parameters in general. Upper layer of the waters around Ul-gi and Gampo is typically characterized by the high chlorophyll-a, high primary production, and low nanofraction ratio due to the continuing supply of nutrients from the nutrient-rich cold water underneath. Water of Tsushima current shows poor standing crop in terms of cell numbers and chlorophyll-a concentrations, extremely high nanofraction ratio, and very low primary production. The overwhelming importance of the nanofraction is confirmed in phytoplankton cell numbers, chlorophyll-a concentration, and possibly enough in primary production. This emphasizes the exceptionally strong inflow of warm water into the study area from south among all the waters around the whole Korean peninsula.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.57 no.2
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• pp.107-116
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• 2021

The breakdown of the Korea-Japan fishing negotiations since 2016 has made it impossible for many domestic fishing vessels to operate in the Japanese EEZ water, and large purse seine fishing vessels are one of them. Mackerel is a highly migratory fish species, circulating in the East China Sea, South Sea, West Sea and East Coast throughout the year, and goes through a period of wintering, spawning, growth and feeding migration. In this study, in order to find out the dependence of large purse seine fishing vessels on mackerel fishing in the Japanese EEZ waters, we analyzed the characteristics of mackerel by large purse seine fisheries in the Japanese EEZ waters from 2010 to 2016. The catch and fishing details were investigated. The total catch of mackerel by large purse seine fishery, the average catch rate of mackerel in Japanese EEZ is 4 percent per year. The amount is estimated at 10.2 billion won per year. Although there was an effect, it was not judged to be a significant factor, and it was found that the amount of catch and fish price in the domestic waters had a greater influence on the total catch than the Japanese EEZ waters.

• 한국해양학회지
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• v.25 no.1
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• pp.1-7
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• 1990

Seawater temperature, salinity, inorganic nutrients and the standing crop of phytoplankton species of the 841 water samples from the upper 125 m at 15-40 stations on the 6 semiannual cruises in the southwestern waters of the East Sea (Korea) were studied during the period from September, 1981 to October, 1984, Among the 235 taxa identified two pennate diatioms, cylindrotheca closterium and Nitzschia delicatissima, were the most common and dominant species. The multiple regression analyses between net phytoplankton abundance (dependent variable) and associated environmental factors(independent variables) were applied to the samples from the surface mixed-layer. In spring the coefficients for the seawater temperature was 1. to 4.2 times greater than those for salinity, while the coefficients for the salinity was 2.1 to 3.4 times greater than those for seawater temperature in autumn. Distribution seawater temperature in spring, and salinity in autumn. Schematically the zone of high standing crops moved about on the T-S diagram in a cyclic manner. The distribution of phytoplankton standing crop was quite closely associated with the hydrographic conditions among various kinds of environmental factors studied.