• 수산해양기술연구
• /
• 제56권2호
• /
• pp.114-125
• /
• 2020

In order to understand the currents around Hampyung Bay and Haeje Peninsula, 2D numerical simulations for tidal currents and tide-induced residual currents were carried out. Dominant semidiurnal tidal currents have reversing form and flow NNE-SSW from northern Haeje Peninsula to Songi Island, E-S at northern Haeje Peninsula and NNW-SSE in Hampyung Bay. In flood, a part of currents from Imja Island~Nakwhol Island flow along the main stream flowing northeast at offshore region and the rest flow into Hampyung Bay flowing east along the northern coast of Haeje Peninsula. In ebb, currents from Hampyung Bay flow west along the northern coast of Haeje Peninsula and run together with the main stream flowing southeast at offshore region. The currents create an anticyclonic circulation in flood and a cyclonic circulation in ebb around Haeje Peninsula including Hampyung Bay. Tidal currents are accumulated on Doripo which located at the entrance of Hampyung Bay and show high current velocities. Tidal currents and tide induced residual currents are weak at the inside of Hampyung Bay which has narrow entrance, shallow water depth and wide intertidal zone. An anticyclonic eddy is formed around Gaksi Island as a result of tide induced residual currents. In northern coast of Haeje Peninsula, slow constant currents flow east. It is expected that a gradual change of sediment and an increase of flushing time for suspended materials are carried by tidal currents occurring in Hampyung Bay.

• International Journal of Naval Architecture and Ocean Engineering
• /
• 제11권2호
• /
• pp.662-670
• /
• 2019

Tanker cargo tanks are equipped with the means of raising and maintaining the cargo discharge temperature to a suitable level. In this paper, a new heating coil design is proposed and analyzed. Contrary to conventional designs, wherein the heating coils are evenly distributed over the tank bottom, the proposed design arranges the heating coils in the central part of the tank bottom, in a vertical direction. Due to the intensive cargo circulation generated, a forced convection is superimposed on a buoyancy-driven natural convection, providing a more efficient mixed convection heat transfer mechanism. Numerical simulations performed by using a finite volume method show that in the case of 7-bar steam Bunker C heavy fuel oil heating, a five-hour circulation phase average heat transfer coefficient equals 199.2 W/m²K. This result might be taken as an impetus for the more thorough experimental examination.

• Fisheries and Aquatic Sciences
• /
• 제1권2호
• /
• pp.260-268
• /
• 1998

A flow pattern and water exchange in Sagami Bay is examined using a barotropic hydraulic model. In the model experiments, the volume transports of the Kuroshio Through Flow were changed with time. The results of the model experiments show that when the volume transport is increased with time, water mass and vorticity are transferred to the inner part of the bay by wakes from the western part of the bay. In the case of decrease, as the wakes are ceased, the inner cyclonic circulation water is discharged to the outside of the bay by its southward extension through the Oshima eastern channel. It is found that the water exchange by the short-term variation of volume transport in time is about 20% of all the bay water.

• Ocean and Polar Research
• /
• 제34권2호
• /
• pp.239-251
• /
• 2012

The food web dynamics in a coastal ecosystem of Korea were predicted with Ecosim, a trophic flow model, under various scenarios of primary productivity due to ocean warming and ocean acidification. Changes in primary productivity were obtained from an earth system model 2.1 under A1B scenario of IPCC $CO_2$ emission and replaced for forcing functions on the phytoplankton group during the period between 2020 and 2100. Impacts of ocean acidification on species were represented in the model for gastropoda, bivalvia, echinodermata, crustacean and cephalopoda groups with effect sizes of conservative, medium and large. The model results show that the total biomass of invertebrate and fish groups decreases 5%, 11~28% and 14~27%, respectively, depending on primary productivity, ocean acidification and combined effects. In particular, the blenny group shows zero biomass at 2080. The zooplankton group shows a sudden increase at the same time, and finally reaches twice the baseline at 2100. On the other hand, the ecosystem attributes of the mean trophic level of the ecosystem, Shannon's H and Kempton's Q indexes show a similar reduction pattern to biomass change, indicating that total biomass, biodiversity and evenness shrink dynamically by impacts of climate change. It is expected from the model results that, after obtaining more information on climate change impacts on the species level, this study will be helpful for further investigation of the food web dynamics in the open seas around Korea.

• 한국해안·해양공학회논문집
• /
• 제35권6호
• /
• pp.109-120
• /
• 2023

광해역의 표층 해수유동을 준 실시간으로 측정하는 장비인 해양 고주파 레이다(High Frequency Radar, HFR)는 특정 전파대역(HF)의 주파수를 해수면으로 발사하고 후방으로 산란된 전파를 분석하여 표층 유속 벡터를 측정한다(Crombie, 1955; Barrick, 1972). 본 연구에서 사용되는 Codar사의 Seasonde HF radar의 경우, 무지향성 안테나에서 송·수신한 전파의 브래그 피크(Bragg peak)의 강도와 다중신호분류(Mutiple Signal Classification, MUSIC) 알고리즘을 통하여 방사형 해류(Radial Vector)의 속도와 위치를 결정하게 된다. 이때 생산된 해류는 관측 전파 수신 환경의 특성이 고려되지 않은 이상적인 전파환경(Ideal Pattern)이 적용된 자료로써 이를 보정하기 위하여 안테나 패턴 측정(Antenna Pattern Measurement, APM)을 시행하여 보정된 방사해류장(Measured Radial Vector)을 계산하게 된다. APM의 관측원리는 안테나로부터 수신되는 각 위치별 신호 강도값을 측정하여 해류의 위치 및 위상 정보를 수정하는 것으로 일반적으로 선박에 안테나를 설치하여 실험을 진행한다. 하지만 선박을 활용할 시, 기상조건과 해양 상황 등 다양한 환경에 의해 최적의 APM 결과를 산출하기까지 많은 제약이 따른다. 따라서 APM 실험에 대하여 해상 상황에 대한 의존도를 낮추고 경제적인 효율성을 높이기 위하여 무인항공기인 드론을 이용한 APM 활용 가능성을 검토하였다. 본 연구에서는 전남 완도군 당사리 당사도등대에 설치된 고주파레이다를 활용하여 선박을 활용한 APM 실험과 드론을 활용한 APM 실험을 진행하였으며 선박과 드론으로 관측된 결과가 적용된 방사형 해류와 계류된 고정부이를 활용하여 그 결과를 비교 분석하였다.

• Ocean and Polar Research
• /
• 제30권2호
• /
• pp.129-140
• /
• 2008

As a preliminary effort to establish a data assimilative ocean forecasting system, we reviewed the theory of the Ensemble Kamlan Filter (EnKF) and developed practical techniques to apply the EnKF algorithm in a real ocean circulation modeling system. To verify the performance of the developed EnKF algorithm, a wind-driven double gyre was established in a rectangular ocean using the Regional Ocean Modeling System (ROMS) and the EnKF algorithm was implemented. In the ideal ocean, sea surface temperature and sea surface height were assimilated. The results showed that the multivariate background error covariance is useful in the EnKF system. We also tested the sensitivity of the EnKF algorithm to the localization and inflation of the background error covariance and the number of ensemble members. In the sensitivity tests, the ensemble spread as well as the root-mean square (RMS) error of the ensemble mean was assessed. The EnKF produces the optimal solution as the ensemble spread approaches the RMS error of the ensemble mean because the ensembles are well distributed so that they may include the true state. The localization and inflation of the background error covariance increased the ensemble spread while building up well-distributed ensembles. Without the localization of the background error covariance, the ensemble spread tended to decrease continuously over time. In addition, the ensemble spread is proportional to the number of ensemble members. However, it is difficult to increase the ensemble members because of the computational cost.

• Ocean and Polar Research
• /
• 제43권4호
• /
• pp.321-334
• /
• 2021

'Marine mammals-based observations' refers to data acquisition activities from marine mammals by instrumenting CTD (Conductivity-Temperature-Depth) sensors on them for recording vertical profiles of ocean variables such as temperature and salinity during animal diving. It is a novel data collecting platform that significantly improves our abilities in observing extreme environments such as the Southern Ocean with low cost compared to the other conventional methods. Furthermore, the system continues to create valuable information until sensors are detached, expanding data coverage in both space and time. Owing to these practical advantages, the marine mammals-based observations become popular to investigate ocean circulation changes in the Southern Ocean. Although these merits may bring us more opportunities to understand ocean changes, the data should be carefully qualified before we interpret it incorporating shipboard/autonomous vehicles/moored CTD data. In particular, we need to pay more attention to salinity correction due to the usage of an unpumped-CTD sensor tagged on marine mammals. In this article, we introduce quality control methods for the marine mammals-based CTD profiles that have been developed in recent studies. In addition, we discuss strategies of quality control specifically for the seal-tagging CTD profiles, successfully having been obtained near Terra Nova Bay, Ross Sea, Antarctica since February 2021. It is the Korea Polar Research Institute's research initiative of animal-borne instruments monitoring in the region. We anticipate that this initiative would facilitate collaborative efforts among Polar physical oceanographers and even marine mammal behavior researchers to understand better rapid changes in marine environments in the warming world.

• 한국해양공학회지
• /
• 제25권3호
• /
• pp.19-27
• /
• 2011

In case of constructing submerged breakwaters for the purpose of preventing coastal erosion, the number of submerged breakwaters, as well as their asymmetry is dependent on the field conditions. The aim of the present study was to examine the 3-D hydrodynamic characteristics (3-D wave field, wave height, mean water level, and mean flow) around the asymmetric submerged breakwaters using a 3-D numerical model, LES-WASS-3D, which was validated through a comparison with existing experimental data and showed fairly nice agreement. From the numerical results, the wave height, mean water level, and mean flow are discussed in relation with the variation in the breakwater length ratio.

• Ocean and Polar Research
• /
• 제23권4호
• /
• pp.401-410
• /
• 2001

Global climate change will alter many such properties of the Southern Ocean as temperature, circulation, stratification, and sea-ice extent. Such changes are likely to influence the species composition and activity of Antarctic marine microorganisms (protists and bacteria) which playa major role in deter-mining the concentration of atmospheric $CO_2$ and producing precursors of cloud condensation nuclei. Direct impacts of climate change on Antarctic marine microorganisms have been determined for very few species. Increasing water temperature would be expected to result in a southward spread of pelagic cyanobacteria, coccolithophorids and others. Growth rates of many species would be expected to increase slightly but nutrient limitation, especially micronutrients, is likely to result in a negligible increase in biomass. The extent of habitats would be reduced for those organisms presently living close to the upper limit of their thermal tolerance. Increased UVB irradiance is likely to favour the growth of those organisms tolerant of UVB and may change the trophic structure of marine communities. Indirect effects, especially those as a consequence of a diminution of the amount of sea-ice and increased upper ocean stratification, are predicted to lead to a change in species composition and impacts on both trophodynamics and vertical carbon flux.

• Fisheries and Aquatic Sciences
• /
• 제19권10호
• /
• pp.45.1-45.5
• /
• 2016

As a novel strategy to remove ${\beta}$-lactam antibiotic residues from fish tissues, utilization of ${\beta}$-lactamase, enzyme that normally degrades ${\beta}$-lactam structure-containing drugs, was explored. The enzyme (TEM-52) selectively degraded ${\beta}$-lactam antibiotics but was completely inactive against tetracycline-, quinolone-, macrolide-, or aminoglycoside-structured antibacterials. After simultaneous administration of the enzyme with cefazolin (a ${\beta}$-lactam antibiotic) to the carp, significantly lowered tissue cefazolin levels were observed. It was confirmed that the enzyme successfully reached the general circulation after intraperitoneal administration, as the carp serum obtained after enzyme injection could also degrade cefazolin ex vivo. These results suggest that antibiotics-degrading enzymes can be good candidates for antibiotic residue depuration.