• Journal of the Korean Society for Marine Environment & Energy
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• v.18 no.3
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• pp.189-206
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• 2015

The present study was conducted to investigate the oceanic characteristics of the northern East China Sea through identification of long-term variation patterns of oceanic environment factors, for the objective of gaining understanding of oceanic environment characteristics of the northern waters of East China Sea, which closely influence the oceanic environments of waters nearby South Korea. The study methodology included the use of oceanographic data (water temperature, salinity, dissolved oxygen, nutrients, and chlorophyll-a) on the northern East China Sea from the Korea Oceanographic Data Center (KODC), collected by season for 20 years between 1995 and 2014. Moreover, for the study on the distribution of nutrients, chlorophyll-a. The main water masses that affected the northern East China Sea during the study period were classified as Changjiang diluted water (CDW), Tiawan current warm water (TCWW), Yellow Sea cold water (YSCW), and Kuroshio source water (KW). The forces of CDW and TCWW that forms on the surface and sub-surface layers had weakened for 20 years and the force of KW that forms on the intermediate layer showed a distinctively decreasing trend. However, YSCW showed a trend of expanding its force. Phosphate and silicate exhibited a decreasing tendency and phosphate showed a pattern of being depleted on the surface layer after 2009. It is determined that one of the reasons for this is the concentration of nutrients introduced through CDW and TCWW being too low. The concentration of chlorophyll-a exhibited an increasing tendency during the study period, the reasons for which are determined to be the influences of increase in water temperature, supply of nutrients via YSCW, and increases in light transmission from decrease in suspended solid due to the construction of the Three Gorges Dam.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.3 no.4
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• pp.175-182
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• 1998

Recently it is reported that anomalously low saline surface waters (salinity < 32) occurred at the Ulleung Basin in the East Sea-Japan Sea, during early September to November 1996. Apparent source of such a low saline watermass seems remotely linked to the Changjiang Dilute Water (CDW), which expands to the vicinity of Cheju Island during a flood season. Based on the assumption that waters passing through the Western Channel of the Korea Strait are formed by a mixing of Kuroshio Water and CDW, simplified two end-member mixing model using $^{228}Ra/^{226}Ra$ as a conservative tracer is applied to calculate the contribution of each end member for the formation of low saline surface seawater. Model calculations show CDW contributes $58{\pm}3%$ in September 1996 (S=32.17) and $10{\pm}3%$ in February 1997 (S=34.53) in the formation of surface water flowing into the Western Channel of the Korea Strait. Although results arc deduced from a simplified model with limited data, this study demonstrates that Changjiang discharge is clearly traceable to the interior of the East Sea-Japan Sea in fall season. Undergoing Three Valley Dam construction in the Changjiang River would invoke inevitable changes in the nature and discharge of CDW and its impacts on the marine environment might be significant in the northern East China Sea and even in the Ulleng Basin for coming decades.

• The Journal of the Acoustical Society of Korea
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• v.42 no.1
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• pp.16-24
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• 2023

The salinity of sea water is known as a less influencing variable in the calculation of the sound speed of the sea water. This study investigated how the low salinity of sea water affects the vertical structure of the sound speed near the mouth of the Yangtze (Changjiang) River when the diluted fresh water extends toward the East China Sea in the summer. As a result of comparing two types of sound speeds considered measured and fixed salinity, sound speeds appeared distinguishable when the halocline formed steeper than the thermocline due to Yangtze-River Diluted Water (YRDW). In addition, unlikely with fixed salinity conditions, when measured salinity was considered, an underwater sound channel appeared in the middle of the thermocline of which the source depth is located. Accordingly, considering the salinity, this study suggests using Expendable Conductivity Temperature Depth (XCTD) and Expendable Sound Velocimeter (XSV) rather than Expandable Bathy Thermograph (XBT) when calculating sound speed because of the strong halocline due to YRDW in the summer.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.27 no.1
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• pp.17-32
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• 2022

The buffer capacity of southern Korean waters in summer was quantified using data set of temperature, salinity, dissolved inorganic carbon, total alkalinity obtained from August 2020 cruise. The geographical distribution and variability of six buffer factors, which amended the existing Revelle factor, are discussed their relationship with the hydrological parameters of temperature and salinity. The calculated results of six buffer factors showed the spatial variations according to the distributions of various water masses. The buffer capacity was low in the East Sea Surface Mixed Water (ESMW) and South Sea Surface Mixed Water (SSMW) where upwelling occurred, and showed an intermediate value in the Yellow Sea Surface Water (YSSW). In addition, the buffer capacity increased in the order of high temperature Tsushima Warm Current (TWC) and Changjiang Diluted Water (CDW). This means that the Changjiang discharge water in summer strengthens the buffer capacity of the study area. The highest buffer capacity of CDW is due to its relatively higher temperature and biological productivity, and a summer stratification. Temperature showed a good positive correlation (R²=0.79) with buffer capacity in all water masses, whereas salinity exhibited a poor negative correlation (R²=0.30). High temperature strengthens buffer capacity through thermodynamic processes such as gas exchange and distribution of carbonate system species. In the case of salinity, the relationship with buffer capacity is reversed because salinity of the study area is not controlled by precipitation or evaporation but by a local freshwater input and mixing with upwelled water.

• 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.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.17 no.2
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• pp.59-75
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• 2012

The species composition of plankton is essential to understand the material and energy cycling within marine ecosystem. It also provides the useful information for understanding the properties of marine environments due to its sensitivity to the physicochemical characteristics and variability of water masses. In this study we adopted metagenomics to evaluate eukaryotic plankton species diversity from coastal waters off Busan. Characteristics of water masses at sampling sites is expected to be very complex due to the mixing of various water masses; Nakdong River runoff, Changjiang diluted water (CDW), South Sea coastal water, and Tsushima warm current. 18S rDNA clone libraries were constructed from surface waters at the three sites off Busan. Clone libraries revealed 94 unique phylotypes from 370 clones; Dinophyceae(42 phylotypes), Ciliophora(15 phylotypes), Bacillariophyta(7 phylotypes), Chlorophyta(2 phylotypes), Haptophyceae(1 phylotype), Metazoa(Arthropoda( 17 phylotypes), Chaetognatha(1 phylotypes), Cnidaria(2 phylotypes), Chordata(1 phylotype)), Rhizaria (Acantharea(2 phylotypes), Polycystinea(1 phylotype)), Telonemida(1 phylotype), Fungi(2 phylotypes). The difference in species diversity at the closely located three sites off Busan may be attributed to the various physicochemical properties of water masses at these sites by the mixture of water masses of various origins. Metagenomic study of species composition may provide useful information for understanding marine ecosystem of coastal waters with various physicochemical properties in the near feature.

• Korean Journal of Environmental Biology
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• v.37 no.1
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• pp.93-108
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• 2019

To investigate the temporal-spatial distribution of picophytoplankton in relation to different water masses in the northern East China Sea (ECS), picophytoplankton abundance were investigated using flow cytometry with environmental factors in 2016-2017. The results from the analysis of flow cytometer data showed that Synechococcus appeared across all seasons, exhibiting its minimum abundance in winter and maximum abundance in summer. Furthermore, high abundance was detected in the surface mixed layer during spring and summer when vertical stratification occurs; in particular, Synechococcus exhibited maximum abundance in thermocline layer, indicating a close correlation to water temperature and thermocline formation. In addition, the abundance of Synechococcus indicated a decrease in the western seas in 2017 compared to 2016 under the strong influence of the Changjiang Diluted Water (CDW). This was determined by the significant influence of the CDW on the abundance of Synechococcus during summer in the northern waters of the ECS. In contrast, Prochlorococcus did not appear during winter and spring, and its distribution was limited during summer and autumn in the eastern seas under the influence of the Kuroshio current. The largest range of Prochlorococcus distribution was confirmed during autumn without the influence of the CDW. Thus, the distribution pattern of each picophytoplankton genus was found to be changing in accordance to the extension and reduction of sea current in different seasons and periods of time. This is anticipated to be a useful biological marker in understanding the distribution of sea currents and their influence in the northern waters of the ECS.

• Journal of the Korean Wood Science and Technology
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• v.10 no.3
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• pp.96-108
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• 1982

Pinus is one of the most important species supplying domestic industrial timbers such as constitutional lumber, pulpwood, and mine props. It occupies nearly 50 percent of the total forest resources in Korea. With above conception, to develop this forest resources and to obtain the basic data on the reasonable and effective utilization of Pinus, this study was carried out. Five species (P. koraiensis S. et Z., P. densiflora S. et Z., P. thunbergii Parlat, P. densiflara far erecta, P. rigida Miller) grown in Kwangnoong experimental forest stand, Chungcheongnam-Do, and Gangwon-Do regions were selected as sample trees. Anatomical, physical, mechanical and chemical properties of them were investigated.