• 한국해양학회지
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• v.23 no.3
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• pp.123-129
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• 1988

The toxicity of bivalves in the Korean waters was investigated during 1987-1988. The toxicity of paralytic shellfish poison (PSP) was found in the sea mussels (Mytilus edulis galloprovincialis, M. corsucus), scallops (Patinopecten yessoensis, Chlamys farreri), tellin (Peronidia venulosa) and venus clam (Ruditapes philippinarum) among the 28 species screened. The toxicity in mussels, scallop (C. farreri) and venus clam was mainly confirmed from the samples collected around Jindong Bay in the southern coast of the peninsula, whereas the toxicities of tellin and scallop (P. yessoensis) were found in the vicinity of Pohang in the east coast. Samples from the west coast showed low levels of toxicity than those from the east arid south coasts. Although it varied with the regions, the toxicity was detected mainly during April to June, exceptionally during May to August in Pohang. The levels of toxicity were generally below the criteria of 4 mouse unit (MU)/g edible portion in foreign countries, with few exceptions.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.573-576
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• 2008

When the concrete structures are in contact with seawater, concentration of chloride for estimating chloride diffusion coefficient can be defined as the chloride concentration of sea water. However, in case the concrete structures, constructed in the seashore, aren't directly in contact with seawater, it is difficult to establish the interface concentration of chloride. In addition, marine concrete structures are greatly affected by salt attack such as rebar corrosion, among the cause of salt attack, airborne chlorides is primary factor. Therefore, in this study, salt attack environment by airborne chlorides was investigated in terms of a seasonal distribution at 72 spots, 27 areas in the East, West, South coast for 3 years from July '03 to June '06. Results indicated that in the East and South coast, the amount of the airborne chlorides is comparatively higher in summer, in the West coast, higher in winter according to the seasonal wind.

• The Journal of the Acoustical Society of Korea
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• v.21 no.4
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• pp.421-429
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• 2002

Sea surface backscattering signal measurements were conducted in the shallow waters off the east coast of Korea to study the acoustic wave scattering from the sea surface. The grazing angles of wave range from 20° to 40° with a frequency of 60 kHz. The wind speed and surface roughness of the experiment area were 3 m/os and below 1 m, respectively. The measured acoustic backscattering strengths greatly exceed the composite roughness predictions at low grazing angles. To account for this discrepancy, the scattering strengths due to a near-surface bubble layer were considered. The prediction with bubble contribution was found to be in good agreement with the experimental measurement.

• The Korean Journal of Quaternary Research
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• v.17 no.2
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• pp.33-38
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• 2003

This study is conducted to examine the data of climate or environmental change in the northeastern Asia during the last glacial maximum. A remarkable feature of the 18,000 BP biome reconstructions for China is the mid-latitude extention of steppe and desert biomes to the modem eastern coast. Terrestrial deposits of glacial maximum age from the northern part of Yellow Sea suggest that this region of the continental shelf was occupied by desert and steppe vegetation. And the shift from temperate forest to steppe and desert implies conditions very much drier than present in eastern Asia. Dry conditions might be explained by a strong winter monsoon and/or a weak summer monsoon. A very strong depression of winter temperatures at LGM. has in the center of continent has influenced in northeast Asia similarly. The vegetation of Hokkaido at LGM was subarctic thin forest distributed on the northern area of middle Honshu and cool and temperate mixed forest at southern area of middle Honshu in Japan. The vegetation landscape of mountain- and East coast region of Korea was composed of herbaceous plants with sparse arctic or subarctic trees. The climate of yellow sea surface and west region of Korea was much drier and temperate steppe landscape was extended broadly. It is supposed that a temperate desert appeared on the west coast area of Pyeongan-Do and Cheolla-Do of Korea. The reconstruction of year-round conditions much colder than today right across China, Korea and Japan is consistent with biome reconstruction at the LGM.

• Atmosphere
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• v.16 no.1
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• pp.33-48
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• 2006

A classification of snowfall type based on development mechanism is proposed using previous snowfall studies, operational experiences, etc. Five types are proposed: snowfall caused by 1) airmass transformation (AT type), 2) terrain effects in a situation of expanding Siberian High (TE type), 3) precipitation systems associated with extratropical cyclones (EC type), 4) indirect effects of extratropical cyclones passing over the sea to the south of the Korean peninsula (ECS type), and 5) combined effects of TE and ECS types (COM type). Snowfall events during 1981-2001 are classified according to the 5 types mentioned above. For this, 118 events, with at least one station with daily snowfall depth greater than 20 cm, are selected. For the classification, synoptic weather charts, satellite images, and precipitation data are used. For TE and COM types, local sea-level pressure chart is also used to confirm the presence of condition for TE type (this is done for events in 1990 and thereafter). The classification shows that 109 out of 118 events can be classified as one of the 5 types. In the remaining 8 events, heavy snowfall occurred only in Ullung Island. Its occurrence may be due to one or more of the following mechanism: airmass transformation, mesoscale cyclones and/or mesoscale convergence over the East Sea, etc. Each type shows different characteristics in location of snowfall and composition of precipitation (i.e., dry snow, rain, and mixed precipitation). The AT-type snowfall occurs mostly in the west coast, Jeju and Ullung Islands whereas the TE-type snowfall occurs in the East coast especially over the Young Dong area. The ECS-type snowfall occurs mostly over the southern part of the peninsula and some east cost area (sometimes, whole south Korea depending on the location of cyclones). The EC- and COM-type snowfalls occur in wider area, often whole south Korea. Precipitation composition also varies with the type. The AT-type has a snow ratio (SR) higher than the mean value. The TE- and EC-type have SR similar to the mean. The ECS- and COM-type have SR values smaller than the mean. Generally the SR values at high latitude and mountainous areas are higher than those at the other areas. The SR value informs the characteristics of the precipitation composition. An SR value larger than 10 means that all precipitation is composed of snow whereas a zero SR value means that all precipitation is composed of rain.

• Korean Journal of Ichthyology
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• v.32 no.3
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• pp.148-159
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• 2020

This study investigated the seasonal and inter-annual changes in vertical distribution and size spectrum of walleye pollock, Gadus chalcogrammus inhabiting middle eastern coast of Korea (hear after pollock). Pollock was distributed between 50 m and 600 m depth range, and body size (total length) ranged from 16.6 cm to 81.5 cm. The trends of population body size were increased in autumn and winter and decreased in spring and summer. Vertical distribution of pollock showned depth-dependent patterns with distributing smaller individuals mainly in the upper layer (shallower depth), while larger fish in deeper habitats. Those patterns in vertical distribution of pollock population is probably due to be the results of energy-saving strategy, metabolic effects, and changes in prey selections according to pollock growth, derived from spatial and temporal changes in oceanic condition in habitat grounds. When water temperature in upper layer were increased and that of below thermocline depth became decreased in 2017, the ratio of smaller (<35 cm) and larger (≥35 cm) individuals was biased toward larger fishes, extending their distribution into shallow depth, and consequently main fishing ground was formed in far from coastal area. In addition, the ratio of smaller individual distributing between 100~300 m was increased with decreasing temperature gradient between below thermocline and bottom layer. Changes in spatial and temporal distributions of pollock population likely be related with vertical and horizontal changes in oceanic conditions and, consequently food supplies.

• 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.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.25 no.1
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• pp.65-72
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• 1992

It is believed that the lower cold water is formed by winter cooling in the north of the East(Japan) Sea. To examine its effect on the general circulation of the East Sea, we performed a two-layer numerical model with realistic bottom topography. First a circulation is generated by imposing only an inflow and an outflow which is then modified by adding the cooling effect in the north. The interface between the two layers rises due to cooling and propagates along the coast as internal Kelvin waves. About 7 months after the cooling starts, all coastal areas of the basin have higher elevation than that in offshore region. This induces baroclinic currents resulting in clockwise(anticlockwise) circulation in upper (lower) layer of the basin. It is concluded that the East Korean Warm Current strengthens as a result of lower cold water formation.

• Journal of the Korean earth science society
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• v.23 no.5
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• pp.436-441
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• 2002

This study is concerned with the sea breeze criterion and climatological characteristics of the short-time sea breeze in the Gangneung coastal area. The sea breeze criteria in this area are listed here. First, the fact of the sea breeze blowing was considered to be a change of wind direction from land to sea and vice versa without terrain effect like easterly wind. Second, the sea breeze of which continuous time 1-hour or 2-hour was selected. Then the climatological characteristics of the short-time sea breeze were analyzed using the meterological data from a 10-year(1988${\sim}$1997) period. The climatological characteristics which were analyzed for the short-time sea breeze consist of the frequency, onset time, wind direction speed and temperature. Finally, this study will be helpful in meteorological application through the climatological characteristics of sea breeze along the east coast as well as Gangneung Airport.

• Asian Journal of Atmospheric Environment
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• v.10 no.2
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• pp.57-66
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• 2016

Wet deposition fluxes of ions at a coastal site in southwestern Japan in the period 1996-2003 were investigated to quantify the respective contributions of cyclone-, stationary front- and typhoon-associated rains. On average, the deposition fluxes of terrigenous-origin ions, nss-$SO_4{^{2-}}$, $NO_3{^-}$, $NH_4{^+}$ and nss-$Ca^{2+}$ were $37.6{\pm}7.3$, $16.3{\pm}4.2$, $19.0{\pm}3.4$ and $9.6{\pm}4.8meq\;m^{-2}yr^{-1}$, and those of $Na^+$ and $Cl^-$, the major ions in sea water, were $97.0{\pm}38.2$ and $115.2{\pm}48.2meq\;m^{-2}yr^{-1}$, respectively. Cyclone-associated rain constituted more than 50% of the fluxes of the terrigenous ions in almost all years. Stationary front-associated rain also contributed significantly, although the contribution was lower than the contribution by Cyclone-associated rain in almost all years. In particular, the wet deposition flux of nitrogen compounds of $NO_3{^-}$ and $NH_4{^+}$, which are important nutrients for micro-bioactivities in sea surface water, was dominated by cyclone-associated rain. Due to the extreme abundance of $Na^+$ and $Cl^-$ in the rainwater of typhoons, the fluxes of $Na^+$ and $Cl^-$ were contributed substantially by typhoons in years with typhoons' passage although cyclones were still the largest contributor to the fluxes. These results indicate the dominance of cyclones in the wet deposition to the East China Sea areas and the necessity to take rain types into account for a more accurate elucidation of the temporal and spatial variation of the wet deposition.