• 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 Society for Marine Environment & Energy
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• v.5 no.4
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• pp.27-40
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• 2002

The circulation of sea water was simulated by two dimensional tide model using the main four tidal components and permanent current driven by inflow/outflow across open boundaries. According to the residt of tide model, the maximum speed of eastward flow on the Cheju Strait is twice higher than that of westward flow. According to the result of permanent current, the flow of permanent current showing semi-circle pattern in the southern part of Kojedo was due to variation of topography. According to the result of circulation model in the Cheju Strait, eastward flow entering in the southern waters from the Yellow Sea of Korea were dominant, but outflows westward were weak. These results suggest that it was difficult to move for suspended particulate matter into the Yellow sea from the southern waters through Cheju Strait.

• Journal of the Korean Geographical Society
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• v.48 no.3
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• pp.321-335
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• 2013

High resolution data for the coastal sand beach during short-term in Jinbok-ri, Uljin-gun, Gyeongsangbuk-do are obtained by terrestrial LiDAR. The micro-geomorphological changes of 8 times before and after the strong low-pressure events during June to September, 2009 and changes under the various environments of wave-energy are investigated in the study. The obvious geomorphological changes between the northern and southern sand beach in Jinbok-ri are revealed by terrestrial LiDAR as well as by grain size analysis. The strong waves by the typhoons decrease the area and volume of the beach, and especially the area is largely influenced. The erosive and depositional processes dominate the northern and southern sand beach, respectively, after high wave in September. These results suggest that lots of sand grains in the beach are largely re-transported within the beach rather than offshore.

• Korean Journal of Remote Sensing
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• v.15 no.1
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• pp.61-71
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• 1999

Several physical phenomena on the sea surface are analyzed from SAR images of South Sea areas, Korea. Strong wave patterns propagating in southerly direction are seen in ERS-1 SAR image on October 11, 1994, and a wave directional spectrum is calculated from this image using the SAR modulation transfer function. RADARSAT SAR image of August 15, 1996 reveals internal waves in northern coastal waters of Cheju Island. Analysis indicates that the internal waves may have been generated by the tidal currents traveling over the shallow bottom of the stratified water in the summer during the tidal changeovers fro ebb to flood and shows patterns of trains of solitons. RADARSAT SAR image taken 3 days after the oil spill accident near Goeje Isalnd on April 3, 1997 detects distinct oil slicks from the accident area but also shows slicks near the coast caused by wind sheltering of coastal mountains and chemical-biological activities.

• Economic and Environmental Geology
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• v.45 no.5
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• pp.513-523
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• 2012

The upper sedimentary layer of the Ulleung Basin in the East Sea shows stacked mass-flow deposits such as slide/slump deposits in the upper slope, debris-flow deposits in the middle and lower slope, and turbidites in the basin plain. Shallow gases or gas hydrates are also reported in many area of the Ulleung Basin, which are very important in terms of marine resources, environmental changes, and geohazard. This paper aims at studying acoustic characteristics and distribution pattern of gas-related structures such as acoustic column, enhanced reflector, dome structure, pockmark, and gas seepage in the upper sedimentary layer, by analysing high-resolution chirp profiles. Acoustic column shows a transparent pillar shape in the sedimentary layer and mainly occurs in the basin plain. Enhanced reflector is characterized by an increased amplitude and laterally extended to several tens up kilometers. Dome structure is characterized by an upward convex feature at the seabed, and mainly occurs in the lower slope. The pockmark shows a small crater-like feature and usually occurs in the middle and lower slope. Gas seepage is commonly found in the middle slope of the southern Ulleung Basin. These gas-related structures seem to be mainly caused by gas migration and escape in the sedimentary layer. The distribution pattern of the gas-related structures indicates that formation of these structures in the Ulleung Basin is controlled not only by sedimentary facies in upper sedimentary layer but also by gas-solubility changes depending on water depth. Especially, it is interpreted that the chaotic and discontinuous sedimentary structures of debris-flow deposits cause the facilitation of gas migration, whereas the continuous sedimentary layers of turbidites restrict the vertical migration of gases.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.2 no.2
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• pp.151-159
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• 1997

Benthic respiration and chemical fluxes were measured at the sediment-water interface underlying the marine fish cages floating on the open coastal waters off Tong-Young, the South Coast of Korea. The effects of cage farming on coastal benthic environment and on mass balance of organic carbon in the benthic boundary layer under the marine fish cages are addressed. In a growing season of caged fishes of June, 1995, benthic chambers and sediment traps were deployed on the sediment-water interfaces of the two sites chosen for this study: 1) Cage Site, directly underlying the fish cages of the farm at 18 m water depth, and 2) Control Site, about 100 m away from the farm at 32 m water depth. Benthic respiration rates and chemical fluxes were calculated from the evolution of dissolved oxygen and chemicals in the chamber water, and mass balance of organic carbon in the benthic boundary layer was constructed based on the vertical flux of particulate organic matter (POM) and chemical fluxes out of the sediment. High organic dumping (6400 mg C $m^{-2}d^{-1}$) and high benthic respiration (230 mmol $O_2\;m^{-2}d^{-1}$) were observed at the Cage Site. Equivalent to 40% of vertical flux of organic carbon into the Cage Site seemed to be decomposed concurrently and released back to overlying waters (2400 mg C $m^{-2}d^{-1}$). Consequently, up to 4000 mg C $m^{-2}d^{-1}$ of organic carbon could be buried into the farm sediment (equivalent to 60% of organic carbon flux into the Cage Site). At the Control Site, relatively less input of organic carbon (4000 mg C $m^{-2}d^{-1}$) and low benthic respiration rate (75 mmol $O_2\;m^{-2}d^{-1}$) were observed despite short distance away from the cages. The influence of cage farming on benthic chemical fluxes might be restricted and concentrated in the sea bottom just below the fish cages in spite of massive organic dumping and high current regime around the fish cage farm.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.28 no.5
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• pp.677-697
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• 1995

The analysis of long- period sea level variations with tidal record data around Korea, Japan, and Russia shows that about half of the variations are due to atmospheric influences. The sea level variation by water movements is the largest in the coasts along the Tsushima Current, and becomes smaller in the distant areas. It suggests that the sea level varications are related with the Tsushima Current. The effect of sea level variations to ocean circulation has been studied with a numerical model allowing barotropic sea level fluctuations, like the result with GCM (Semtner) model by Pang et al.(1993), the present model also shows that waters basically flow along isobaths over the last China Sea after geostyophic adjustment around Taiwan. However, barotropic sea level fluctuation makes the basic circulation in the Yellow Sea, which waters flow into the central Yellow Sea and out along the west coast of the Korean Peninsula. Besides this, barotropic sea level fluctuation makes long period waves over the shelf area as the Kuroshio varies. By the waves, the basic circulation in the Yellow Sea is disturbed, so that the flow pattern of oppositely flowing into the Yellow Sea along the west roast of the Korean Peninsula appears. In the Yellow Sea circulation, it seems that northwest winds strengthen the basic circulat ion In winter, and southeast winds strengthen the disturbed circulation in summer. Another point appeared by the long period wave is that the Tsushima Current possibly originates in different areas. There have been two opposing argues on the area in which the Tsushima Current originates the southwest sea of Kyushu Island and the adjacent sea of Taiwan. Through this study, we found that both of them seem to be important areas for the origin of the Tsushima Current, and one of them is possibly strengthened by long period waves. The long period waves given by the variation of the Kuroshio Current in the adjacent sea of Taiwan propagate to the Korea Strait as forced waves. The wave continuously propagates to the last Sea through the eastern channel, but reflects in the western channel due to bottom topography. The reflected waves propagate southwestward along the last China Sea as free waves and determine the sea level variations with forced waves.

• Journal of the Geological Society of Korea
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• v.54 no.6
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• pp.587-603
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• 2018

3-D petroleum system modeling was performed on the Jeju Basin, offshore southern Korea to analyze the hydrocarbon migration and accumulation as well as the generation and expulsion of the hydrocarbon, based on subsurface structure maps of respective sedimentary formations. The lowermost formation deposited in Eocene time was assigned as a source rock, for which a mixed kerogen of type II and III was input in the modeling of oil and gas generation in consideration of the sedimentary environment of fluvio-lacustrine condition. Initial TOC was 4% as an input, based on the analysis of the well data and sedimentary environment. The modeling results show that a considerable amount of hydrocarbons was generated and expelled from the source rocks at the western Joint Development Zone (JDZ) sub-block 4, where the hydrocarbons was migrated to the above reservoir rocks at 20 Ma. The oil and gas in the reservoir rocks of the JDZ sub-block 4 are accumulated into the prospects with closure structures that has already been formed at the nearby areas. Another generation of hydrocarbon occurs from the source rock at the eastern border area of JDZ sub-block 1 and 2, where the expulsion of the hydrocarbons occurs at 10 Ma from the source rock into the above reservoir rocks, in which the accumulation also is expected. The generation, migration and accumulation were retarded at the eastern area of the JDZ sub-block 1 and 2, compared with the area of the western JDZ sub-block 4. Based on the modeling results, it is estimated that gases migrated laterally and vertically in long distance whereas oil migrated laterally in shorter distance than gases. A substantial amount of hydrocarbon could have seeped out of the reservoir formations to the surface since the migration of oil and gas actively occurred in Miocene time before the formation of seals. However, the modeling shows that the hydrocarbon could be accumulated smoothly into the closed structures that can be formed locally by alternation of sand and shale beds.

• Journal of the Korean Association of Geographic Information Studies
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• v.23 no.3
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• pp.26-67
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• 2020

Synthetic Aperture Radar(SAR) is able to photograph the earth's surface regardless of weather conditions, day and night. Because of its possibility to search for hydrological factors such as soil moisture and groundwater, and its importance is gradually increasing in the field of water resources. SAR began to be mounted on satellites in the 1970s, and about 15 or more satellites were launched as of 2020, which around 10 satellites will be launched within the next 5 years. Recently, various types of SAR technologies such as enhancement of observation width and resolution, multiple polarization and multiple frequencies, and diversification of observation angles were being developed and utilized. In this paper, a brief history of the SAR system, as well as studies for estimating soil moisture and hydrological components were investigated. Up to now hydrological components that can be estimated using SAR satellites include soil moisture, subsurface groundwater discharge, precipitation, snow cover area, leaf area index(LAI), and normalized difference vegetation index(NDVI) and among them, soil moisture is being studied in 17 countries in South Korea, North America, Europe, and India by using the physical model, the IEM(Integral Equation Model) and the artificial intelligence-based ANN(Artificial Neural Network). RADARSAT-1, ENVISAT, ASAR, and ERS-1/2 were the most widely used satellite, but the operation has ended, and utilization of RADARSAT-2, Sentinel-1, and SMAP, which are currently in operation, is gradually increasing. Since Korea is developing a medium-sized satellite for water resources and water disasters equipped with C-band SAR with the goal of launching in 2025, various hydrological components estimation researches using SAR are expected to be active.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.20 no.2
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• pp.152-156
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• 1987

A mixed population of marine bacteria was obtained to catalize the biodegradation of bunker-C fuel oil by means of the enrichment culture technique. Samples used for the enrichment culture were collected from sea water and sediments in the vicinity of Pusan, Chungmu, and Ulsan in Korea. As the biodegradation of bunker-C oil proceeded, the number of bacteria increased from $1.1\times10^6\;to\;8.7\times10^8$ cells per ml when pH was bufferized by 0.1 M Tris-HCl buffer to 7.6, then oil dispersion increased to $OD^{540}$ 2.2 and approximately $48\%$ of the oil was biodegradated in 10 days. Oil dispersion was absolutely dependent on the addition of nitrogen and phosphate sources in sea water. High and low sulfur-containing bunker-C and crude oil could be dispersed similarly. Bunker-C oil was dispersed rapidly at the pH ranging from 7.0 to 8.0 and dispersed to the amount of 7.5 g per liter of sea water medium.