• Journal of the Korea Institute of Military Science and Technology
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• v.10 no.4
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• pp.52-61
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• 2007

Temporal and spatial variations of sea water largely affect on the pattern of underwater sound propagation. Acoustic environmental changes and their effects on underwater sound propagation in the northern part of the East Sea, which have been poorly studied mainly due to lack of observations, are investigated by analyzing the hydrographic data acquired since 1993. Severe changes in acoustic environments are associated with various physical processes such as deep convection, thermal fronts, and eddies in the northern part of the East Sea. Spatio-temporal variations of sound speed field and the layer of the maximum sound speed are categorized into six typical cases. Using a sound source of 5 kHz, acoustic transmission losses are calculated range-independently for the six typical cases. Significant differences among the patterns of transmission loss in the six cases suggest that a different tactics are required when we operate in the northern part of the East Sea.

• Asian Journal of Turfgrass Science
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• v.19 no.2
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• pp.131-140
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• 2005

This study was conducted to compare cold tolerances and growth rates of 5 basic species, commercial lines, and breeding lines of zoysiagrass. Total 41 zoysiagrasses were tested at the northern part (Jeokseong-myeon) and the middle part (Cheonan) of South Korea. Cold tolerance (survival rate during winter), growth rate, green-up speed, and density data were collected visually. Four types of zoysiagrasses (Z. matrella, Z. tenuifolia, USm, and S4M2) with genetic characteristics of Z. matrella died during winter cold, while the others survived. Midium leaf type zoysiagrasses, such as Anyang1, Samdeock1, Anyang2, SJ21, and Pyeongdong, with genetic characteristics of both Z. sinica and Z. macrostachya showed vigorous growth rate one year after planting at the northern part (Jeokseong-myeon). Twenty nine ($70.7\%$) zoysiagrasses showed vigorous growth rate, but the other twelve ($29.3\%$) zoysiagrasses died by cold and drought condition at the middle (Cheonan) part of S. Korea. Anyang2, AJ9-7, Samdeock1, Samdeock2, Samdeock3, and Zenith-C showed vigorous growth rate even though cold and drought environmental condition were artificially provided at these region. But, SJ2-19, NSm, 88Mey, 88Mey-7S, 88Mey-9S, SJ2l-10, ASm, and DBm which did not die at the northern part, showed serious injury at the middle part of S. korea. From this results, we can conclude that drought is as important factor as low temperature for zoysiagrasses during winter.

• Korean Journal of Ichthyology
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• v.34 no.2
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• pp.102-112
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• 2022

This study investigated dietary habits and intra- and inter-specific food resource partitioning of co-occurring walleye pollock (Gadus chalcogrammus) and Pacific cod (G. macrocephalus) from the waters off the north-eastern coast of South Korea using stomach contents and stable isotopes (δ¹³C and δ¹⁵N) analyses. Both species are mesopelagic carnivores that consumed mainly benthopelagic crustaceans, but teleosts were also abundant in the diet of Pacific cod. Non-metric multidimensional scaling (nMDS) ordination and permutational multivariate analysis of variance (PERMANOVA) of dietary data revealed significant intra- and inter-specific dietary differences, i.e., food resource partitioning. Nitrogen stable isotope values (δ¹⁵N) were similar between walleye pollock and Pacific cod, but carbon stable isotope values (δ¹³C) were significant different, suggesting different trophic positioning. Canonical analysis of principal coordinate (CAP) ordination plot further demonstrated that differences in the type and range of prey ingested by the two species contributed such an inter-specific difference in the diet compositions. Ontogenetic changes in diet compositions were evident. As walleye pollock, they preyed more upon carid shrimps and cephalopods, but no such trend was observed in the diets of Pacific cod. While stable isotope values indicated that large-sized specimens of both species were significantly enriched in ¹⁵N relative to smaller conspecifics thus supporting these data. Consequently, in this study, both methodologies, i.e., stomach contents and stable isotope analyses, provided evidence of inter- and/or intra-specific dietary segregations and trophic niche partitioning between co-occurring walleye pollock and Pacific cod off eastern Korean waters.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.28 no.1
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• pp.1-18
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• 2023

The East Sea, one of the regions where the most rapid warming is occurring, is known to have important implications for the response of the ocean to future climate changes because it not only reacts sensitively to climate change but also has a much shorter turnover time (hundreds of years) than the ocean (thousands of years). However, the processes underlying changes in seawater characteristics at the sea's deep and abyssal layers, and meridional overturning circulation have recently been examined only after international cooperative observation programs for the entire sea allowed in-situ data in a necessary resolution and accuracy along with recent improvement in numerical modeling. In this review, previous studies on the physical characteristics of seawater at deeper parts of the East Sea, and meridional overturning circulation are summarized to identify any remaining issues. The seawater below a depth of several hundreds of meters in the East Sea has been identified as the Japan Sea Proper Water (East Sea Proper Water) due to its homogeneous physical properties of a water temperature below 1℃ and practical salinity values ranging from 34.0 to 34.1. However, vertically high-resolution salinity and dissolved oxygen observations since the 1990s enabled us to separate the water into at least three different water masses (central water, CW; deep water, DW; bottom water, BW). Recent studies have shown that the physical characteristics and boundaries between the three water masses are not constant over time, but have significantly varied over the last few decades in association with time-varying water formation processes, such as convection processes (deep slope convection and open-ocean deep convection) that are linked to the re-circulation of the Tsushima Warm Current, ocean-atmosphere heat and freshwater exchanges, and sea-ice formation in the northern part of the East Sea. The CW, DW, and BW were found to be transported horizontally from the Japan Basin to the Ulleung Basin, from the Ulleung Basin to the Yamato Basin, and from the Yamato Basin to the Japan Basin, respectively, rotating counterclockwise with a shallow depth on the right of its path (consistent with the bottom topographic control of fluid in a rotating Earth). This horizontal deep circulation is a part of the sea's meridional overturning circulation that has undergone changes in the path and intensity. Yet, the linkages between upper and deeper circulation and between the horizontal and meridional overturning circulation are not well understood. Through this review, the remaining issues to be addressed in the future were identified. These issues included a connection between the changing properties of CW, DW, and BW, and their horizontal and overturning circulations; the linkage of deep and abyssal circulations to the upper circulation, including upper water transport from and into the Western Pacific Ocean; and processes underlying the temporal variability in the path and intensity of CW, DW, and BW.

• 한국해양학회지
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• v.26 no.1
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• pp.83-100
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• 1991

A layer of salinity-minimum which characterizes the East Sea intermediate Water (ESIW) is found at an approximate depth of 200 m in three CTD section taken in the Ulleung Basin on May 17-21, 1988. Properties at this layer vary in ranges of $1.1^{\circ}C except at stations near the east coast of Korea where temperature is as high as $4.39^{\circ}C$ and salinity is as low as $33.992{\textperthousand}$. To be distinguished from the ESIW the East Sea Proper Water (ESPW) may be characterized by temperature less than $1^{\circ}C$, Salinity at the saliently-minimum layer and 500db increases southward in general, implying that the cold waters, both ESIW and ESPW, formed in the northern basin of the East Sea are spreading southward below the permanent thermocline in the basin. Hydrography in the Ulleung Basin is very similar to that in the Alboran Sea, suggesting a possibility of an anticyclonic circulation in the Ulleung Basin which is controlled strongly by the shoaling bottom.

• Journal of the Korean Society of Marine Environment & Safety
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• v.20 no.6
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• pp.601-608
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• 2014

The purpose of this study was to explore the long-term variability of sea surface temperature (SST) and cluster analysis derived from in-situ data in the coastal oceanographic observation 8 stations (Sokcho, Jumunjin, Donghae, Jukbyeon, Pohang, Janggigab, Ulgi, Gampo) of the East Sea during 1971-2013. As a result of cluster analysis, SST variations in each area could be divided into two groups, which was a group A of Sokcho, Jumunjin, Donghae, and group B of Jukbyeon, Pohang, Janggigab, Ulgi, Gampo. The SST and SST anomalies at Sokcho, Jukbyeon, Pohang and Gampo during 1971-2013 showed the increase-trend with the variations of decadal-scale. Annual SST values also increased remarkably after 1988. The increases of SST for 43 years showed $2.26^{\circ}C$ at Sokcho, $1.99^{\circ}C$ at Jukbyeon, $1.11^{\circ}C$ at Pohang and $0.89^{\circ}C$ at Gampo. In particular, the SST variations of the northern areas were higher than those of southern areas. The seasonal SSTs increased the order of Sokcho-Jukbyeon-Pohang-Gampo in fall and winter and that of Jukbyeon-Sokcho-Pohang-Gampo in spring and summer.

• Broadcasting and Media Magazine
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• v.11 no.4
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• pp.104-117
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• 2006

In this Paper, we analyze the application of Interactive Data Broadcasting in DMB(Digital Multimedia Broadcasting) in the accordance with convergence of service and technology. With the acceleration of digital convergence in the Ubiquitous period substantial development of digital media technology and convergence of broadcasting and telecommunication industry are being witnessed. Consequently these results gave rise to newly combined-products such as DMB(Digital Multimedia Broadcasting), WCDMA(Wide-band code division multiple access), Wibro(Wireless Broadband Internet), IP-TV (Internet protocol TV) and HSDPA(High speed downlink packet access). The preparatory stage for the implementation of Interactive Data Broadcasting Service will be reached by the end of December, 2006. DMB is the first result of a successful convergence service between Broadcasting and Telecommunication in new media era. Multimedia technology and services are the core elements of DMB. The Data Broadcasting will not only offer various services of interactive information such News, Weather, Broadcasting Program etc, but also be linked with characteristic function of mobile phone such as calling and SMS(Short Message Service) via Return Channel.

• Korean Journal of Remote Sensing
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• v.12 no.2
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• pp.126-138
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• 1996

The characteristics of rapid development of the low pressure system over the East Sea from 06 to 08 Nov., 1995 has been analyzed in detail by the synoptic numerical products and satellite observations. The Low system was initially triggered the development of the baroclinic leaf cloud over the border of the northern part of Korea and China and moved eastward and then developed explosively com-ma or lambda type cloud system over the East Sea. To forecast well the general development and movement of the coastal winter cyclone over the East Sea popularly in a numerical simulation by several scientists, the large baroclinicity, continuous support of water vapor, and sequential cold outbreak over the warm sea surface have been more commonly concerned about. The cyclone which the central surface pressure was dropped 40hPa within 24 hours has often accompanied strong wind and heavy snow- or rain-fall in the winter season. In all successive observations with 12-hourly satellite imagery and analyzed meteorological variables in this period, the centers of the sea-level pressure and 500hPa geopotential height associated with this cyclone were typically illustrated by moving farther eastward using GMS combined enhanced IR images. The maxi-mum wind sustained by this system with the intensity and central pressure of tropical storm was about 60 knots with the center pressure drop of 44hPa/day similar to the North American cyclonic bomb and Atlantic storm.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.24 no.2
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• pp.208-225
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• 2019

To understand the mean surface circulation and surface currents in the East Sea, trajectories of surface drifters passed through the East Sea from 1991 to 2017 were analyzed. By analyzing the surface drifter trajectory data, the main paths of surface ocean currents were grouped and the variation in each main current path was investigated. The East Korea Warm Current (EKWC) heading northward separates from the coast at $36{\sim}38^{\circ}N$ and flows to the northeast until $131^{\circ}E$. In the middle (from $131^{\circ}E$ to $137^{\circ}E$) of the East Sea, the average latitude of the currents flowing eastward ranges from 36 to $40^{\circ}N$ and the currents meander with large amplitude. When the average latitude of the surface drifter paths was in the north (south) of $37.5^{\circ}N$, the meandering amplitude was about 50 (100) km. The most frequent route of surface drifters in the middle of the East Sea was the path along $37.5-38.5^{\circ}N$. The surface drifters, which were deployed off the coast of Vladivostok in the north of the East Sea, moved to the southwest along the coast and were separated from the coast to flow southeastward along the cyclonic circulation around the Japan Basin. And, then, the drifters moved to the east along $39-40^{\circ}N$. The mean surface current vector and mean speed were calculated in each lattice with $0.25^{\circ}$ grid spacing using the velocity data of surface drifters which passed through each lattice. The current variance ellipses were calculated with $0.5^{\circ}$ grid spacing. Because the path of the EKWC changes every year in the western part of the Ulleung Basin and the current paths in the Yamato Basin keep changing with many eddies, the current variance ellipses are relatively large in these region. We present a schematic map of the East Sea surface current based on the surface drifter data. The significance of this study is that the surface ocean circulation of the East Sea, which has been mainly studied by numerical model simulations and the sea surface height data obtained from satellite altimeters, was analyzed based on in-situ Lagrangian observational current data.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.17 no.2
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• pp.33-44
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• 2012

Transparent exopolymer particles (TEP) are formed by aggregation of polysaccharide products excreted by phytoplankton and have sticky character like gel. They play important role in the production of marine snow in water column. To study the distribution pattern of TEP concentration and its role in carbon cycle in the surface ocean, we measured pH, Total alkalinity (TA), and chlorophyll-a in addition to physical characteristics of seawater within the surface water column. TEP concentrations ranged from nearly undetectable values to $338{\mu}g\;Xeq\;l^{-1}$. They were considerably lower than previously reported values from costal sites, but showed similar values observed in other oceanic region during phytoplankton bloom periods. The spatial distribution of TEP concentrations were similar to those of chlorophyll-a, which indicate that the production of TEP were closely related to phytoplankton. Calculated total dissolved inorganic carbon ($TCO_2$) from the pH and TA was normalized to 35 psu of salinity ($NTCO_2$) and showed negative linear relationship with temperature. Biological drawdown of $NTCO_2$ ($NTCO_{2bio}$) was estimated from the difference between theoretical $NTCO_2$ values and observed $NTCO_2$. In the warm region located south of $40^{\circ}N$ along the $132.5^{\circ}N$ meridional lines, $NTCO_{2bio}$ showed negative value and TEP concentrations were high. This suggested that negative $NTCO_{2bio}$ may be attributed to the biological processes. At the stations located between 44 and $46^{\circ}N$, TEP concentrations showed high concentration at the chlorophyll-a maximum layer within the water column while they showed low concentration in the surface layer. Carbon content of TEP constituted about 40% of $NTCO_{2bio}$ at the chlorophylla maximum layer. In this study, we could not observe any positive and negative relationship between TEP concentration and $NTCO_2$ or pH. It is obvious that we should consider the importance of TEP in the biological carbon cycling processes within surface layer.