Korea Strait Research Articles

대한해협에서의 수온 및 염도변화를 고려한 선박의 저항성능 예측을 위한 기초 연구

Recently, shipping operators have been making efforts to reduce the fuel cost in various ways, such as trim optimization and bulb re-design. Furthermore, IMO restricts the hydro-dioxide emissions to the environment based on the EEDI (Energy Efficiency Design Index), EEOI (Energy Efficiency Operational Indicator), and SEEMP (Ship Energy Efficiency Management Plan). In particular, ship speed is one of the most important factors for calculating the EEDI, which is based on methods suggested by ITTC (International Towing Tank Conference) or ISO (International Standardization Organization). Many shipbuilding companies in Korea have carried out speed trials around the Korea Straits. However, the conditions for these speed trials have not been exactly the same as those for model tests. Therefore, a ship’s speed is corrected by measured environmental data such as the seawater temperature, density, wind, waves, swell, drift, and rudder angle to match the conditions of the model tests. In this study, fundamental research was performed to evaluate the ship resistance performance due to changes in the water temperature and salinity, comparing the ISO method and numerical simulation. A numerical simulation of a KCS (KRISO Container ship) with a free-surface was performed using the commercial software Star-CCM+ under three conditions that were assumed based on the water temperature and salinity data in the Korea Straits. In the simulation results, the resistance increased under low water temperature & high salinity conditions, and it decreased under high water temperature & low salinity conditions. In addition, the ISO method showed the same result as the simulation.

지구물리 탐사에 의해 발견된 제주도 용암동굴의 특징과 의미

제주도에서 기존에 알려진 동굴 이외에 새로운 지하동굴의 존재를 확인하기 위해 제주시 구좌읍 일대에서 지구물리탐사(전기비저항탐사, GPR탐사, ZHF탐사)를 실시하였다. 탐사결과 여러 지점에서 동굴로 추정되는 이상대가 발견되었고, 이상대의 위치와 규모가 일치하는 27개 지점을 선별하여 시추조사를 실시하였다. 그러나 예상과 달리 이상대의 대부분은 용암의 상하부에 형성된 클링커층이거나 용암 사이에 협재된 고토양층이었으며, 5곳에서만 동굴이 발견되었다. 클링커층과 고토양층은 용암과 다른 암석의 물리적 특징으로 인해 이상체로 반응한 것으로 해석된다. 한편 동굴이 확인된 5개 지점 중 2공은 기존에 알려진 용천동굴을 관통하였고, 3공에서 새로운 동굴이 확인되었다. 용천동굴을 관통한 시추공은 시추당시 동굴의 존재가 확인되지 않았던 구간이었으나 용천동굴이 관통됨에 따라 기존 측량도의 오류를 수정하였다. 한편 시추조사로 새롭게 발견된 석회장식 용암동굴은 길이가 약 180 m이며, 상류방향으로 당처물동굴(약 110 m)과 연결되어 있다. 또한 동굴내부에는 용암곡석, 용암제방, 밧줄구조 등이 발달해 있으며, 탄산염 동굴생성물로는 종유관, 종유석, 석순, 석주, 동굴산호 등이 잘 보존되어 있다. 특히 동굴에서 발견되는 탄산염 동굴생성물은 식물 뿌리를 따라 유입된 지표수에 의해 성장하여 독특한 형태를 띠게 된 것으로 추정된다. Geophysical exploration using electric resistivity, ground penetrating radar (GPR), and impedance high-frequency (ZHF) surveys was conducted in Gujwa-eup, Jeju City, Jeju Island, an island in the Korea Strait, to confirm the existence of new caves near known caves. The exploration revealed a number of anomaly zones, presumed to be caves; 27 sites at suitable locations and depth ranges were selected for drilling and further surveys. However, contrary to predictions, most of the anomaly zones were clinker layers or paleosols intercalated with lavas. Only five boreholes intersected caves. The clinker layers and paleosols were possibly detected as anomalies owing to their different physical properties from the other rocks. Two of the five cave-finding boreholes penetrated Yongcheon Cave; a new cave was found at the other. The two boreholes that penetrated Yongcheon Cave were drilled in areas where the cave has not been previously reported, and thus helped correct an error in the cave distribution map. The cave newly discovered in this boring exploration is 180 m long, and it is connected to the upstream part of Dangcheomul Cave (110 m). The cave contains well-developed lava helictites, lava levees, and ropy structures; carbonate speleothems such as soda straws, stalagmites, columns, and curtain shawls are also well preserved. Notably, the unique shape of the carbonate speleothems is attributed to their growth in relation to the cavern water that flowed into the cave along plant roots.

Larval distribution pattern of Muraenesox cinereus (Anguilliformes: Muraenesocidae) leptocephali in waters adjacent to Korea

To understand the transport and recruitment processes of the daggertooth pike conger, Muraenesox cinereus, in the marginal seas of East Asia, we investigated the distribution pattern, estimated spawning areas and periods, and recruitment mechanisms of M. cinereus, based on 51 individuals of leptocephali collected from Korean waters during 2010–2014. Back-calculated hatching dates, determined from the daily incremental growth rates of the otoliths, indicated that the spawning period for M. cinereus was during July–September. The size range of M. cinereus leptocephali collected offshore of Jeju Island and southeast of the Korea-Japan intermediate zone was 16.6–20.9 mm TL (age, 18–23 d). We hypothesize that one of the spawning grounds of M. cinereus is located offshore in the East China Sea. In Korean waters, the ages and body lengths of M. cinereus leptocephali increased northward from latitude 31°30′N to 34°40′N, with metamorphosis occurring at latitude 34°40′N. Therefore, we surmised that the hatched preleptocephali of M. cinereus were transported from offshore areas in the East China Sea to Jeju Island and the Korea Strait (KS) by the Kuroshio and Tsushima Warm Current.

Assessment of precipitation climatology in an ensemble of CORDEX-East Asia regional climate simulations

CR Climate Research Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials CR 64:141-158 (2015) - DOI: https://doi.org/10.3354/cr01302 Assessment of precipitation climatology in an ensemble of CORDEX-East Asia regional climate simulations Bo Huang*, Stefan Polanski, Ulrich Cubasch Institute of Meteorology, Freie Universität Berlin, Carl-Heinrich-Becker-Weg 6-10, 12165 Berlin, Germany *Corresponding author: huangb@zedat.fu-berlin.de ABSTRACT: An ensemble of regional climate simulations from the Coordinated Regional Downscaling Experiment in East Asia (CORDEX-East Asia) was analysed to evaluate the ability of 5 regional climate models (RCMs) and their ensemble mean in reproducing the key features of present-day precipitation (1989-2008). We emphasised (1) an extreme rainfall event, (2) seasonal climatology, (3) annual cycles and inter-annual variability and (4) the monsoon characteristics. We highlighted 4 sub-monsoon regions, viz. South Asian Summer Monsoon (SAS), the East Asian Summer Monsoon (EAS), the Western North Pacific Tropical Monsoon (WNP) and the Australian-Maritime Continent Monsoon (AUSMC). We found that the RCMs showed a reasonable performance to capture the extreme rainfall event in 1998. The RCMs simulated the seasonal mean, annual cycle and inter-annual variability acceptably. However, individual models exhibited significant biases in some sub-regions and seasons. Moreover, most of the RCMs significantly improved their performance in capturing precipitation climatology and monsoon characteristics over the Korean Peninsula, the Korea Strait and southern Japan. Based upon this performance study, we conclude that the present set of RCMs from CORDEX can be used to provide useful information on climate projections over East Asia. KEY WORDS: CORDEX-East Asia · Regional climate model · Ensemble simulations · Precipitation climatology · Monsoon characteristics Full text in pdf format PreviousNextCite this article as: Huang B, Polanski S, Cubasch U (2015) Assessment of precipitation climatology in an ensemble of CORDEX-East Asia regional climate simulations. Clim Res 64:141-158. https://doi.org/10.3354/cr01302 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in CR Vol. 64, No. 2. Online publication date: July 29, 2015 Print ISSN: 0936-577X; Online ISSN: 1616-1572 Copyright © 2015 Inter-Research.

Vertical structure and variation of currents observed in autumn in the Korea Strait

To observe vertical structure and temporal variations of currents in the Tsushima Warm Current region of the Korea Strait, a moored buoy system was deployed in autumn 2009. The moored buoy system measured vertical profiles of current, temperature, and salinity for 24 days and a background hydrographic survey was performed. Along-strait northeastward currents were dominant in the upper layer (8–35 m). The mean current veers counterclockwise from 48 m to 74 m as much as 50°, and its speed is reduced with depth. There were distinct northward onshore currents near the bottom (65–80 m). It was demonstrated that thermal wind relation holds in the inclined pycnocline layer, which generates the counterclockwise veering current structure. Density gradient along the strait is a main factor producing the cross-strait onshore current component below the upper-layer and the cross-strait density gradient reduces the along-strait current component with depth. Previous studies have never focused on the effect of the along-strait density structure on current structure. The first Empirical Orthogonal Function mode (CM1) of current variability explains 70% of local current variations and its vertical structure is close to the mean current structure. The correlation analysis among variations of CM1 current, slope of sea level anomaly (SSLA) and local wind anomaly revealed that the variation of CM1 current is mainly related to the variation of SSLA across the strait (c-SSLA), which is known to be controlled by remote and local wind forcing. Similarity between vertical structures of mean and CM1 current suggests that thermal wind relation is the main dynamics maintaining the counterclockwise turning of CM1 current below the upper layer although the upperlayer CM1 current is controlled by c-SSLA through barotropic geostrophic relation. Time series of temperature and salinity indicate that the thermohaline front between Korean Coastal Water and Tsushima Warm Current Water meanders in time and migrates over the mooring station back and forth. The front meandering and migration also affect the local SSLA and CM1 current variations in autumn in the Korea Strait.

Population panmixia and the Pleistocene demographic expansion of spotty belly greenling Hexagrammos agrammus in the East Sea and Northwest Pacific

The population genetic structure and historical demography of spotty belly greenling, Hexagrammos agrammus, which has limited distribution in the Northwest Pacific, was assessed with partial sequences of the mitochondrial DNA (mtDNA) cytochrome b and the control region (D-loop). A total of 103 individuals were collected from four sites located at the Korea Strait (Southern coast of Korea) and the East coast of Korea and two places in the Pacific coast of Japan. For all the populations, nucleotide diversities were low (0.006–0.009) while the haplotype diversities were as high as 0.92 to 0.97, indicating that the fish has undergone a recent population expansion after experiencing bottleneck. Star-shaped patterns of haplotype networks as well as the significant negative values of Tajima’s D and Fu’s F S corroborate the recent population expansion. Mismatch distribution analysis reveals that the demographic expansion of the species started during the 2nd half of the Middle Pleistocene Series approximately 141,000–406,000 years ago. Hierarchical analysis of molecular variance (AMOVA), the pairwise population statistics (F ST), and the exact test of haplotype differentiation demonstrate no significant genetic differentiation among populations investigated, suggesting that spotty belly greenling is panmictic in the East Sea and the Pacific coast of Japan.

Molecular evidence reveals a closer relationship between Japanese and mainland subtropical specimens of a widespread tree species, Acer mono

Clarifying the evolutionary relationship between island organisms and those of the adjacent mainland is critical in understanding the dispersal and evolution of species. Considerable research has been conducted on the relationship between plants of the East Asian mainland and the Japanese archipelago as well as the roles of the East China Sea and the Korea (Tsushima) Strait in plant evolution. However, most previously studied species have limited range distributions, which may preclude a comprehensive understanding. Acer mono is a widespread deciduous tree in East Asia. By integrating chloroplast DNA sequences and nuclear microsatellite data, we identified a close genetic relationship between Japanese and subtropical mainland populations. However, different details are revealed by chloroplast DNA sequences and nuclear microsatellite data. The chloroplasts from the northwestern part of the eastern subtropical populations were more closely related to the archipelago populations (CP2 clade), but no shared haplotypes were found, which may indicate an ancestral connectivity. Contrarily, plants from the eastern part of the eastern subtropics and the archipelago populations were assigned into the same gene pool based on nuclear microsatellite data (K = 6), which probably reflects a recent glaciation connection via pollen dispersal. Our study implies that the Korea (Tsushima) Strait may have been a long-term barrier for A. mono, while the East China Sea may have served as a corridor for pollen dispersal.

A Korean Movie that overcame Japanese Wartime Propaganda? - A Comparison of the Movies “Volunteer” and “Strait of Korea” -

A Korean Movie that overcame Japanese Wartime Propaganda? - A Comparison of the Movies “Volunteer” and “Strait of Korea” -

Ambient seismic noise tomography of the southern East Sea (Japan Sea) and the Korea Strait

This work was funded by the Korean Meteorological Administration and Development Program under Grant CATER 2012-5051.

The Change of the Name for Korea (Joseon) Strait and Its Implication : An Examination of the Japanese Geography Textbooks in Meiji Period

The Change of the Name for Korea (Joseon) Strait and Its Implication : An Examination of the Japanese Geography Textbooks in Meiji Period

Evaluation of a regional ocean reanalysis system for the East Asian Marginal Seas based on the ensemble Kalman filter

This study introduces the East Asian Marginal Seas (EAMS) reanalysis system and evaluates its products from 1982 to 2006. The EAMS reanalysis system consists of an ocean circulation model with 0.25° horizontal grid spacing and a data assimilation module. Temperature profiles taken by ship and Argo floats as well as satellite-borne sea surface temperature (SST) were assimilated into the model by applying the ensemble Kalman filter every 7 days. The reanalyzed oceanic fields were compared with ones by the control run without data assimilation to assess the impact of the data assimilation. The assimilative model significantly improved the horizontal structures of SST, sea surface height (SSH), vertical structure of temperature, and volume transports through the major straits. Root-mean-square error (RMSE) of SST decreased from 1.0 to 0.6°C. Horizontal and vertical distribution of subsurface temperature was corrected close to the observed values. High SSH variability in the south of Japan and in the Kuroshio extension region was partially restored. Overshooting of the Kuroshio Current and the East Korea Warm Current was suppressed to the south by the data assimilation. SSH and surface circulation in the Oyashio region and in the East Sea (also known as the Sea of Japan) recovered, which corrected the sea level difference between the East Sea and the Pacific Ocean and produced realistic transport through the Korea Strait. The reanalysis well resolved transport through the Korea Strait. The correlation coefficient with the transport based on an Acoustic Doppler Current Profiler measurement was 0.70 and the RMSE was 0.37 Sv (106 m3/s), whereas those were 0.59 and 0.43 Sv in the control run, respectively. The EAMS reanalysis dataset may help us to understand circulation variations in the marginal seas and to investigate factors controlling volume and heat transport.

2010년 국내 남해 해역에 출현한 Pseudo-nitzschia cf. brasiliana의 형태 특성

2010년 국내 남해 해역에 출현한 Pseudo-nitzschia cf. brasiliana의 형태 특성

Variability of Residual Currents and Waves in Haeundae Using Long-term Observed AWAC Data

Lim, H.S.; Kim, C.S.; Lee, H.J.; Shim, J.S.; Kim, S.J; Park, K.S., and Chun, I., 2014. Variability of residual currents and waves in Haeundae using long-term observed AWAC data.The Haeundae in the southeastern Korean Peninsula is a famous beach which is one of the most popular tourist attractions of Korea in summer. It is about 1.6 km long and 40 m wide facing the southeastern sea of Korea and Korea Strait. During strong winds in winter and severe typhoons in summer, the beach is significantly eroded by waves and nearshore currents in the surf zone. The intensive coastal developments during last 30 years have caused substantial beach erosion and bathymetric changes in the nearshore area, despite various beach restoration projects, including beach nourishments. Recently, the government decided to construct two submerged breakwaters near both ends of the beach to enhance the preservation potential of the beach replenishments. We estimated the seasonal variations in residual currents from one-year flow measurements using the Acoustic Wave and Current (AWAC) meter, at two locations of Haeundae at approximately 15 m and 22 m in depths. Short-term flows were measured in the surf zone during summer and winter. The moving average method was applied fortnightly to estimate the residual currents. In addition, waves measured with the AWAC were analyzed to characterize seasonal variations in the beach environment of Haeundae. The observed residual currents were well matched with the simulated counterpart from a wave and current coupled model. These simulated nearshore currents appear well correlated with seasonal variations in beach erosion and accumulation. The wave and current data were also used to validate an operational coastal modeling system for the prediction of hydrodynamics. These observations will be incorporated in simulations of sediment transport in Haeundae coastal waters for developing coastal erosion control system.

Experimental testing of a hardware and software complex for remote measurement of current velocities and temperatures in shallow sea water areas

We describe a technique and hardware-software implementation for remote monitoring of sea currents and temperature using data from pulsed hydroacoustic sounding on stationary horizontal tracks in shallow sea water areas. As sounding signals, we used complex phase-manipulated signals based on pseudorandom M-sequences. The complex was tested in Posiet Bay in the Korea Strait in the Sea of Japan.

Water quality assessment at Jinhae Bay and Gwangyang Bay, South Korea

A new water quality index for evaluating the water quality of Jinhae Bay and Gwangyang Bay was developed. Four water quality parameters were selected as water quality indicators for the water quality index: dissolved inorganic nitrogen (DIN), dissolved inorganic phosphorus (DIP), chlorophyll-a (Chl-a), and dissolved oxygen (DO). Reference levels of DIN, DIP, and Chl-a were determined as 6.22 μmol L−1, 0.38 μmol L−1, and 2.32 μmol L−1, respectively, on the basis of a long-term dataset that was collected monthly in the Korea Strait over a period of seven years (2006–2012). The water quality index established for Jinhae Bay and Gwangyang Bay is (bottom DO grade × 0.33) + (surface Chl-a grade × 0.33) + (surface DIN grade × 0.17) + (surface DIP grade × 0.17). On the basis of a three-year observation, the water quality of Jinhae Bay was classified as “good” in winter and spring, “poor” in summer, and “fair” in autumn and exhibited large spatial variation, with the lowest-quality water observed in Masan Bay. The water quality of Gwangyang Bay was classified as “good” in winter, “fair” in spring, “poor” in summer, and “fair” in autumn. Unlike Jinhae Bay, the water quality of Gwangyang Bay exhibited minimal spatial variation. In both bays, water quality among the four seasons was worse during summer. It is essential that a survey for water quality evaluation be conducted during summer.

Interannual variations of sea water parameters and chlorophyll a concentration in the Japan Sea in autumn

Studied are the interannual variations of physical (temperature, salinity, and relative density) and chemical (dissolved oxygen and biogenic elements) parameters of sea water and chlorophyll a concentration in the Japan Sea in autumn. It is demonstrated that the increase in the water flow from the East China Sea through the Korea (Tsushima) Strait leads to the temperature rise and decrease in salinity and dissolved oxygen content in the surface water layer of the Japan Sea. It is revealed that in the central part of the Japan Sea from 1978 to 2012 trends were observed towards the increase in the content of dissolved inorganic nitrogen N, decrease in the content of inorganic phosphorus, and decrease in the concentration of chlorophyll a at the level of 50 m and its increase in the layer of 0–30 m. The observed trends are explained by the intensification of the effect of coastal water of the East China Sea subjected to the significant anthropogenic load on the water of the central part of the Japan Sea.

Morphological and molecular identification of an introduced alien sea squirt (Tunicata: Ascidiacea) in Korea

Sea squirts were collected from shallow waters of 0.5–5.0 m depth at 27 harbors or ports in Korea: 14 harbors in the East Sea, 10 harbors in the Korea Strait, and three harbors in the Yellow Sea. Ciona intestinalis was identified as an introduced alien species and was compared with the Asian native C. savignyi, which was first reported in Korea. Four distinct morphological differences are recognized between these two species: 1) shape of pigment spots on branchial and atrial siphons, 2) flecks of body, 3) color or shape of the tip of the vas deferens, and 4) thickness and transparency of the body wall. Phylogenetic relationships of these species are examined through molecular analysis based on 720 bp of mtCOI gene sequences. Korean C. intestinalis belong to Type A.

A New Record of Juvenile Chromis mirationis (Perciformes: Pomacentridae) from Korea, Revealed by Molecular Analysis, with a Comparison to Juvenile Chromis notata

A single juvenile pomacentrid specimen (5.9 mm standard length) was collected from the Korea Strait in October 2010. The specimen is characterized by punctate-stellate melanophores scattered on the operculum and dorso-ventral region in front of the caudal peduncle, the lack of melanophores on the posterior end of the anal fin base, the presence of 14 spines and 14 soft rays on the dorsal fin, and the presence of 2 spines and 12 soft rays on the anal fin. A molecular analysis based on mitochondrial DNA 16S rRNA sequences showed that this specimen is closely related to adult Chromis mirationis (d = 0.002), but that it differs from Chromis notata (d = 0.017). Juvenile C. mirationis differ from juvenile C. notata in having no melanophores on the posterior end of the anal fin base. We propose a new Korean name, "tti-ja-ri-dom" for C. mirationis.

Genetic diversity and population structure of the gizzard shad, Konosirus punctatus (Clupeidae, Pisces), in Korean waters based on mitochondrial DNA control region sequences

In this study, we clarified the population structure of the gizzard shad, Konosirus punctatus, in Korean waters. We analyzed 896 base pairs of the mitochondrial DNA control region in 182 individuals, which were sampled from eight localities between the East Sea and the Yellow Sea. The haplotype diversity (h) was very high (0.9662–1.0000) but the nucleotide diversity (π) was very low (0.0061–0.0434). A neighbor-joining tree showed that the population clustered into two reciprocal monophyletic groups, lineages A and B. Lineage A is distributed on all coasts of Korea, from the Yellow Sea to the East Sea, declining to the east, whereas lineage B is distributed in the East Sea and Korea Strait, disappearing completely from middle Korea Strait to the west. Analysis of molecular variance showed strong structuring (F ST = 0.856; P < 0.0001) between the two lineages. Neutrality tests and mismatch distribution analyses showed that a recent rapid expansion event occurred only in lineage A. Our results suggest that the management unit of the Korean gizzard shad may be divided in two, lineage A and lineage B.

Comparison of anchovy biomass estimates measured by trawls, egg production methods and hydro-acoustics in the Chesapeake Bay and the Korea Strait

We compared estimates of anchovy biomass derived from trawl surveys, egg production method (EPM) and acoustic surveys, conducted in two remote regions. Biomass density of bay anchovy Anchoa mitchilli was estimated in Chesapeake Bay, USA, by trawls, EPM and acoustics from 1989 to 2000. Biomass density of Pacific anchovy Engraulis japonicus was estimated in the Korea Strait using EPM, simulation-based daily cohort analysis and acoustics from 1984 to 2006. Most of the existing estimates already had considered body-size-dependent gear selectivity, highlyvariable instantaneous natural mortality of anchovy eggs, and avoidance of trawl nets by adult anchovy. Despite great variability in the ratio of trawl to acoustic biomass estimates (0.034–8.35), annually-averaged biomass density of young-ofthe-year individuals derived by the two methods were similar for bay anchovy in Chesapeake Bay and Pacific anchovy in the Korea Strait (0.83 and 0.70 g m−3, respectively). Results suggested that, despite substantial uncertainty, anchovy biomass estimates are generally compatible between EPM and acoustics. However, reported estimates of biomass density derived from the two acoustic surveys in the Korea Strait differed by a factor of 28, suggesting that further improvements in calibrations are required to reliably estimate anchovy biomass. The comparisons suggested that all biomass estimates could be biased and will require comparison and validation by other, independent sampling methods.