West Korea Research Articles

Observation of the West Korea Coastal Current in the Eastern Yellow Sea During Summer

Observation of the West Korea Coastal Current in the Eastern Yellow Sea During Summer

Preliminary Results of Cloud Seeding Experiments for Air Pollution Reduction in 2020

In previous studies, cloud seeding has been primarily used to increase precipitation; however, its use for the purpose of reducing particulate matter concentration has not yet been adequately addressed. In this study, we investigated the effect of cloud seeding on the reduction of fine dust concentration by conducting two airborne experiments in west Korea along the Yellow Sea coast on November 1, 2020. Numerical simulations showed that the seeding material diffused in Seoul, Gyeonggi-do, and Chungcheongnam-do as observed from the prevailing wind direction. We also observed enhanced radar reflectivity in these areas, and analysis of aircraft observation data revealed that the average concentration of cloud, drizzle, and precipitation particles increased after seeding as compared with the observations before and during seeding. Further, the precipitation particles had large diameters after seeding; particularly, PM10 (particulate matter with size ≤ 10 µm) concentration tended to decrease owing to precipitation in the areas affected by cloud seeding; however, it remained unchanged in the unaffected areas. Although it is necessary to conduct further experiments to obtain more comprehensive results, the findings of this study highlight the possibility of reducing fine dust concentration in the atmosphere via cloud seeding.

Effects of spatial bottom friction parameterization scheme on the tidal dynamics in the macrotidal East China Seas

In this study, the effects of different bottom friction coefficient (BFC) parameterization schemes on the modelling of four principal tidal constituents (M2, S2, K1, O1 tides) in the macrotidal East China Seas were investigated by using a high-resolution model based on FVCOM (Finite Volume Community Ocean Model). The applied BFC schemes include: the empirical constant (EC-BFC), sediment-dependent form (SD-BFC), and spatial varying BFC obtained from adjoint data assimilation (SV-BFC). The comparisons between the simulated results and the observations from satellite altimeters and tidal gauge stations indicated that the SV-BFC scheme is superior to others. The locations of amphidromic points calculated with EC-BFC and SD-BFC were in the northwest of those from SV-BFC. The variations in tidal dynamics between different BFC schemes were closely related to the spatial distributions of BFCs, especially in high-valued BFC areas, e.g., the West Korea Bay, the South Yellow Sea, and the eastern coasts of Jiangsu, Zhejiang and Fujian provinces. The tidal energy flux transporting into Bohai and Yellow Seas increased under the SV-BFC scheme, while smaller tidal energy flux transporting from the Korea Strait was generated by SV-BFC as compared to those from EC-BFC and SD-BFC. The high-valued BFC areas in the SV-BFC scheme dissipated larger amounts of tidal energy, and the average values of Simpson-Hunter numbers were lower than those with the other two schemes. However, the values of Simpson-Hunter numbers increased in the West Korea Bay and Jianghua Bay with high-valued BFCs because of the decreasing current velocity under the headland-shaped topography.

Tritium and stable isotope content variation in precipitation at Hongseung: West Korea Region

Tritium and stable isotope content variation in precipitation at Hongseung: West Korea Region

3차원 중력 모델링에 의해 예측된 황해 북부 서한만 분지 석유 저류층의 공간적 분포

북한의 서한만 분지 내에는 경제성이 있는 석유 자원이 존재할 것이라는 것이 여러 경로를 통해서 보고되고 있으나, 북한의 비밀주의 원칙에 의해서, 이 지역의 지질 및 지구물리학적인 연구를 위한 데이터가 공개된 적은 극히 드물었다. 그렇기 때문에 인공위성으로부터 제공되는 중력장 데이터는 서한만 퇴적분지의 구조를 밝혀내고, 이를 통해서 서한만 퇴적분지 내의 석유 부존자원 연구를 위해서 차선책으로 매우 유용하게 이용될 수 있다. 본 연구는 인공위성 데이터를 기반으로 만들어진 TRIDENT 중력장 데이터의 해석과 더불어 서한만 분지 내에서 지금까지 수행된 지질 및 지구물리 데이터를 이용하여 서한만 퇴적분지의 3차원적인 밀도 구조를 밝혀내고자 수행되었다. 본 연구 결과, 서한만 분지 중, 2 군데의 지역에서 약 2,000 kg/㎥의 매우 낮은 밀도를 특징으로 하는 저밀도 지층이 존재한다는 것을 확인하였으며, 이는 이 지역 퇴적분지 내에 석유 부존자원이 존재할 가능성이 매우 높다는 것을 시사한다. 한 곳은 서한만 중앙분지(Central basin) 남쪽 지역 약 3,000 m 깊이 백악기/쥐라기(Cretaceous/Jurassic) 층 속에 존재하며 그 부피는 약 250 ㎦으로 판단된다. 다른 곳은 중앙분지의 북쪽 지하 약 2,500 m에 위치하며, 그 부피는 약 300 ㎦으로 판단된다. 최근에 확보한 서한만 분지의 해상 측정 중력 데이터는 위의 연구 결과가 신빙성이 매우 높다는 것을 보여줌과 동시에 중앙분지 북서쪽 보하이만 방향으로 또 다른 저밀도 지층이 존재할 가능성이 매우 높다는 것을 보여준다.

Analysis of the effective observation of ocean color satellites of the Yellow and East China Seas

ABSTRACTBased on long time series of merged ocean color products (2003–2016) from the ESA GlobColour dataset, spatial and temporal distributions on effective observation days of ocean color satellites of the Yellow and East China Seas are analyzed. The results show that the average number of effective observation days for the region is 51 ± 6.8 days per year. Large numbers of such days appeared for the West Korea Bay and western Liaodong Bay, at 100 ± 8.3 days per year. Small numbers of days appeared for the southwestern southern Yellow Sea, northwestern East China Sea, and the branch of Kuroshio Current region, at 40 ± 10.1 days per year. Effective observation days of the Yellow and East China Seas had strong seasonal characteristics. The Bohai Sea, northern Yellow Sea, and southern Yellow Sea had two peaks in March and October. The East China Sea had a single peak in July. A lack of effective observation reduces the quality of monthly ocean color products, with greater than 15% bias if the monthly data are averaged from 3 days and 30% bias if the monthly data are from 1 day only.

The only choice is both choices: balancing assurance and coercion in nonproliferation-focused alliance-management strategies

ABSTRACTConventional theories of alliance management often overemphasize the utility of either assurance or coercion in preventing allied nuclear proliferation. Historical analysis reveals that prioritizing either of these two tactics to the exclusion of the other is inadvisable. A strategy that focuses solely on security guarantees or coercive threats is likely to encourage an allied state to pursue a hedging strategy, in which the client state continues to clandestinely develop its own nuclear capabilities while remaining underneath its patron’s defensive “umbrella.” This article introduces a new framework for understanding the effectiveness of nonproliferation-focused alliance-management strategies. By exploring the cases of West Germany and South Korea, the article concludes that the best way to prevent allies from pursuing nuclear weapons is to combine assurance with coercion. This establishes an incentive–punishment relationship that limits an ally’s motivation to develop nuclear weapons. These conclusions have particular salience today, as conversations over nuclear-weapons development have become increasingly normalized in Germany and particularly in South Korea. The United States’s capacity to influence its allies’ nuclear behavior is currently being eroded through the degradation of both patron credibility and client dependence, weakening the long-term viability of the global nonproliferation regime.

탈이념화된 기억 : 러시아혁명 100주년 기념을 돌아보다

탈이념화된 기억 : 러시아혁명 100주년 기념을 돌아보다

Spatial distribution of hydrocarbon reservoirs in the West Korea Bay Basin in the northern part of the Yellow Sea, estimated by 3-D gravity forward modelling

Spatial distribution of hydrocarbon reservoirs in the West Korea Bay Basin in the northern part of the Yellow Sea, estimated by 3-D gravity forward modelling

Risk of Surface Sediment Erosion in the Bohai Sea, North Yellow Sea and Its Indication to Tidal Sand Ridge Occurrence

ABSTRACT Tang, C.; Li, Y. F.; Liu, X.; Zhao, Y., and Zhang, H., 2016. Risk of surface sediment erosion in the Bohai Sea, North Yellow Sea and its indication to tidal sand ridge occurrence. Bottom geomorphological evolution and sediment distribution are under strong control of tidal forcing along China's coast. To quantify and assess the temporal-spatial change of bottom environment, a risk-based probabilistic concept of erosion is applied and maps of erosion risk are constructed. Sediment data categorized into 5 classes, together with hydrodynamic data in a temporal resolution of one hour and a model time of one month, are used to calculate the potential of erosion of surface sediments in the Bohai Sea, North Yellow Sea. Comparison with results of the tidal ellipse and bottom shear stress from model output shows that the highest risk of erosion is located in the Yalujiang Estuary, West Korea Bay, north of the Bohai Bay and in the surroundings of the Laotieshan channel of Bohai Strait, which may explain th...

Petroleum system analysis of West Korea Bay Basin, North Korea

북한의 서한만 분지는 상당량의 석유가 발견된 것으로 알려지고 있으나, 석유탐사에 대한 정보가 많지 않기 때문에 석유 산출에 대해서 정확하게는 알 수가 없다. 그러나 서한만 분지에 대한 지질과 광역층서, 그리고 수집된 탐사와 시추정보를 바탕으로 하여, 석유 생성 및 이동·집적에 대한 석유시스템을 수치 모델링 방법에 의하여 분석하였다. 서한만 분지는 고생대 탄산염암과 선캠브리아기의 변성암을 기반암으로 하며, 중생대층과 신생대층이 중첩되어 두껍게 퇴적되어 있는 열개분지(rift basin)이다. 석유시스템 모델링 결과, 주요 근원암층인 상부 쥬라기층에서 생성된 석유와 가스는 근원암으로부터 배출되어, 이 근원암층 내의 사질암층 지역과, 상부 쥬라기층 하위에 존재하는 탄산염 기반암층으로 이동하는 것이 관찰된다. 이 모델링 결과와 기존의 시추정보를 종합하여 해석하면 다음과 같은 석유생성, 이동, 집적에 대한 석유시스템이 추정된다. 즉, 서한만 분지의 석유와 가스를 생성한 주요 근원암은 심호환경에서 퇴적된 후기 쥬라기의 셰일층이다. 서한만 분지발달 과정에서 장기간의 융기와 무퇴적 기간이 존재함에 따라 이 근원암층은 지속적으로 매몰이 진행되지 못하였고, 이에 따라 근원암층에서 석유와 가스가 생성은 되었으나 다량의 석유와 가스가 배출되지는 못하였다. 일부 배출된 석유와 가스는 상위의 하부 백악기층(Lower Cretaceous strata)과 제3기층으로 이동하였을 뿐만 아니라, 하위의 탄산염 기반암층으로도 이동한 것으로 추정된다. 서한만 분지에는 광역적인 덮개암층은 존재하지 않는다. 따라서 석유와 가스는 고생대, 중생대, 신생대층 각각의 퇴적층 내 암상변화와 관련된 층서트랩의 형태로 집적되어 있을 가능성이 많다. 이 연구는 제한된 정보와 자료를 바탕으로 수행된 석유시스템 분석이므로, 추후에도 서한만 분지에 대한 지속적인 정보와 자료의 확보가 요구되며, 이들 자료와 정보를 바탕으로 재해석이 필요하다.

당진 지역 제4기 진관단층의 운동 특성과 단층비지의 ESR 연령

In order to outline the kinematics and movement history of a new Quaternary fault, Jingwan Fault in Dangjin, West Korea, we analyzed the geometry of the fault zone composed of a few gouge zones, and made ESR dating for fault gouge materials. The striking Jingwan Fault is a normal fault and exhibits a gradual change in dip (gentle in the lower part, steep in the upper part), indicating a listric fault. As for the fault gouge zone, its thickness varies and reaches 2~3 cm in the lower part or between basement rocks, and 20~30 cm in the middle-upper part or between the basement and Quaternary deposit. It is observed in the latter case that more than three gouge zones develop with different colors, and branch out and re-merge, or they are partly superimposed, indicating different movement episodes. The cumulative displacement is estimated to be about 10 m using the geological cross-sections, from which it is inferred that the total length of fault may be about 2.5 km on the basis of the empirical relation between cumulative displacement and fault length. Therefore, a more study would be needed to verify the entire fault length. The results of ESR dating for three gouge samples at different spots along the fault yields ages of , , and , indicating at least two movement episodes. Slickenlines observed on the fault planes indicate a pure dip slip (normal faulting), which suggests that the ENE-WSW trending Jingwan Fault was presumably moved under a NNW-SSE extensional environment.

CHINA–NORTH KOREA RELATIONS IN THE POST-COLD WAR ERA AND NEW CHANGES IN 2009

In the late 1990s, China established “strategic cooperative relations” with North Korea, which mixed elements of alliance and practical cooperative relations, in the process of dismantling the Cold War. However, in the summer of 2009, that is, in the wake of the second nuclear test and the serious illness of Kim Jong Il, this relations changed into “new strategic cooperative relations” with “increased elements of alliance.” This new relations between the two countries were characterized by the strengthened bond in politics and security and by the establishment of systematic economic connections. Due to this new relation, the future of North Korea is less likely to follow the scenario envisaged by some in the Western countries who have anticipated the “collapse of the North Korean regime.” This new relations will render the economic sanctions imposed on North Korea rather useless, thus having a great influence on the effort to resolve the North Korean nuclear issue. And the West will find it more difficult to resort to economic sanctions. The expansion of the economic cooperation between China and North Korea created an ironic situation where South Korea’s sanctions against North Korea make it lose its share of North Korean market. To conclude, the new relations between China and North Korea have made it unavoidable for the West and South Korea to modify their respective North Korea policy to adjust to the changing policy environment.

Comparison of Tidal Sand Ridges between the Subei Shoal and the West Korea Bay

In the Yellow Sea, two large terrains of tidal sand ridges developed, respectively, in the Subei Shoal and the West Korea Bay. Sediment supply, hydrodynamics and bedforms are critical factors to form them. In this paper, sediment composition, morphology of sand ridges, etc. are analyzed in terms of relevant factors and subsequently their formation mechanisms and evolution processes are careful compared.

Implications of Dam Obstruction for Global Freshwater Fish Diversity

Dams are obstructing rivers worldwide, impairing habitat and migration opportunities for many freshwater fish species; however, global data linking dam and fish distributions have been limited. Here, we quantify dam obstruction at the biogeographic scale of freshwater ecoregion, which provides the spatial framework necessary to assess the risk of fish species loss due to dams and allows us to identify both ecoregions and genera at risk. Nearly 50% of the 397 assessed freshwater ecoregions are obstructed by large- and medium-size dams, and approximately 27% face additional downstream obstruction. A synthesis of obstruction data and fish traits indicates that taxa such as lampreys (Lampetra spp.), eels (Anguilla spp.), and shads (Alosa spp.) are at particular risk of species loss. Threatened ecoregions with heavy dam obstruction and above-average counts of total, diadromous, or endemic species are found on all continents and include the Murray—Darling Province, Southern Italy, the Lower and Middle Indus Basin, West Korea, the South Atlantic region of the United States, the Upper Paraná, and Mobile Bay ecoregions.

Development of polymorphic microsatellite markers for Cymbidium goeringii (Orchidaceae)

Microsatellite markers were developed in Cymbidium goeringii to investigate its genetic diversity and population genetic structure. From a microsatellite-enriched genomic library, 21 novel polymorphic microsatellites were isolated. The polymorphic patterns were verified in four populations (East Korea, West Korea, China, and Japan). The number of alleles per locus ranged from 11 to 29 with a mean of 20.29. The observed and expected heterozygosities varied from 0.272 to 0.799 and from 0.461 to 0.911, respectively. These microsatellite markers will be useful tools for understanding genetic variation and population ecogenetic structure in C. goeringii.

Phylogeny and divergence time estimation of Coreoleuciscus splendidus populations (Teleostei: Cypriniformes) endemic to Korea based on complete mitogenome sequences

We determined the complete mitogenome sequences for four Coreoleuciscus splendidus strains (Teleostei: Cypriniformes) inhabiting the Han and Geum river drainages in the West Korea Subdistrict, and the Seomjin and Nakdong river drainages in the South Korea Subdistrict in the Korean peninsula. The gene contents and arrangement of C. splendidus were homogeneous to those of typical vertebrates. Phylogenetic analysis with the partitioned nucleotide matrix of concatenated mitochondrial genes revealed that C. splendidus formed a monophyletic group with gobionine species in the cyprinid lineage. The four river strains separated into two phylogenetically distinct groups, which were in accordance with the biogeographical distribution pattern in Korea according to subdistrict. The estimated divergence time among western and southern subdistrict populations was 37.9 ± 6.5 million years ago (Mya), whereas those between the two river strains in each subdistrict were estimated to be 3.2–3.4 Mya. The presence of such distinct historical lineages has great implications for biogeography of ichthyofauna in Korea and future management and conservation plans of C. splendidus populations.

K-Ar dating of illites for time constraint on tectonic burial metamorphism of the Jurassic Nampo Group (West Korea)

The timing of tectonic burial metamorphism of the early Mesozoic Nampo Group (western Korea) related to the Jurassic Daebo orogeny was first constrained by K-Ar dating of illite in sedimentary rocks. Two shale samples show a clear decreasing trend of both the amount of detrital component and K-Ar age of illites with decreasing grain size from >4 μm to 4–2 μm, and to <2 μm fractions. This observation most likely reflects a binary mixture of old detrital 2M1 and young authigenic 1Md illites, usually seen in argillaceous sedimentary rocks. In this sense, the latest illitization attributable to the crustal loading can be estimated to be 157–140 Ma, the extrapolated illitic age inferred from a linear regression between the amount of detrital component and apparent K-Ar age of different size fractions. This result suggests that the maximum tectonic burial metamorphism of the Nampo Group has occurred in the last stage of the Daebo orogeny.

Erratum to: Genetic variation of coreoleuciscus splendidus populations (Teleostei; Cypriniformes) from four major river drainage systems in South Korea as assessed by AFLP markers

Amplified fragment length polymorphism (AFLP) technique was used to assess genetic variation and population structuring of Coreoleuciscus splendidus (Teleostei; Cypriniformes) from four major river drainage systems in South Korea (i.e. the Han and Geum Rivers belonging to the West Korea Subdistrict and the Seomjin and Nakdong Rivers belonging to the South Korea Subdistrict). Four combinations of selective primers generated 152–186 DNA fragments, of which 45–59 were polymorphic. The Geum River population had the lowest genetic variation in terms of average heterozygosity. The pairwise genetic differentiation (FST) estimates showed that the four populations of C. splendidus were genetically differentiated (P < 0.05). The FST values were higher between population groups of the West and South Subdistricts than between populations from the two river systems within each subdistrict. A dendrogram based on the distance matrix revealed that all C. splendidus individuals bifurcated into two subdistrict population groups and were further divided into two river populations within each subdistrict. Individuals from each population consistently clustered together with high statistical support. The analysis of molecular variance after partitioning of C. splendidus populations into two groups (i.e. the West and South Korea Subdistricts) revealed very strong geographic structuring between them with 74.01% of total variance (P < 0.001). Taken together, the AFLP markers clearly distinguished not only between two population groups of the West and South Subdistricts but also between populations from two river systems within each subdistrict. Morphological differences between the two subdistrict population groups in body color and the presence of black array(s) on dorsal, anal, and caudal fin rays agreed with their high degree of genetic variation. Our findings strongly indicate that restricted dispersal and gene flow are apparent among four geographically separate populations of C. splendidus, and each population should be treated as an evolutionarily significant unit; this should be an a priori consideration for developing their conservation strategies.

Dynamics of the cross-shelf circulation in the Yellow and East China Seas in winter

A general ocean circulation model is used to study the dynamics of the cross-shelf circulation in the Yellow and East China Seas in winter. The model results show that the shelf circulation in winter is induced primarily by the northerly monsoonal winds. Compared with the wind-driven circulation, the Kuroshio-forced circulation over the shelf is very weak. The westward shift of the Yellow Sea Warm Current is produced by the northerly winds through the generation of a sea-level trough off the Subei coasts and a sea-level ridge along the center of the Yellow Sea topographic trough. The sea-level trough off the Subei coasts is produced because the sea level at the coast is tied to the depression in the northern Yellow Sea and is moderated by the surface Ekman transport of the northerly monsoon. The sea-level ridge along the center of the Yellow Sea topographic trough is produced because the sea level along both the east China and the west Korea coasts decreases. The structure of the sea level gives rise to a geostrophic intrusion against the wind along the western side of the Yellow Sea trough and southward movement of the Korean coastal currents along the eastern side of the trough. Under the northerly wind forcing, the currents over the East China Sea shelf flow southward in an opposite direction to the Yellow Sea Warm Current. The resulting divergence, therefore, forces the Yellow Sea Coastal Current to move offshore to form the East China Sea Current. At the head of the submarine canyon off the Changjiang mouth, a northward intrusion is produced by downwind pile-up of sea level and by the wind-curl forcing. The Yellow Sea Warm Current and the canyon intrusion then extend southward through the propagation of topographic Rossby waves to reverse the wind-driven currents over the East China Sea shelf, generating the offshore and inshore branches of the Taiwan Warm Current, both of which serve to raise the sea level over the East China Sea shelf. The final adjustment to the northerly wind forcing is a sea-level tilt to the south, which forces the East China Sea Current to flow cross the continental shelf and slope into the Okinawa Trough. The numerical experiments thus suggest that both the inshore and offshore branches of the Taiwan Warm Current are forced primarily by the northerly winds in winter.