• Journal of the korean society of oceanography
• /
• v.33 no.4
• /
• pp.196-204
• /
• 1998

$^{14}$C uptake experiments were carried out in and around the cold water mass in the southern part of the Korean East Sea in August and October 1995 to assess spatial and seasonal variability of primary productivity and its relation to physical and chemical factors. The cold and high saline water mass in the bottom layer extended upward to the surface layer and developed along the eastern coast of Korea in August. Chlorophyll-a concentration was maintained high in the cold water mass through August to October and its maximum concentration was 6.3 ${\mu}$g 1$^{-1}$ at Stn. 209-4 in August. Primary productivity and daily primary productivity ranged from 0.29 to 8.02 mgC m$^{-3}$ hr$^{-1}$ and from 58.3 to 63.1 mgC m$^{-2}$ d$^{-1}$, respectively, throughout the study period. Primary productivity of the cold water mass was higher than that of offshore waters in both summer and autumn seasons. P$_{max}$ and I$_{max}$ of the cold water mass in August were higher than those in October, except Stn. 208-5. These results suggest that high primary productivity in the cold water mass may be established by the upwelled nutrients and light adaptaion to convected phytoplankton due to upwelling of the bottom waters.

• Journal of the korean society of oceanography
• /
• v.31 no.2
• /
• pp.64-74
• /
• 1996

Numerical experiments of OAT (Ocean Acoustic Tomography) are carried out in the East Sea of Korea where the canonical ocean has been perturbed by a mesoscale warm eddy and a thermal front. In order to estimate the horizontal and vertical structure of water temperature of the perturbed ocean, the experimental area is divided into 16 cells with 8 pairs of sources and receivers for a horizontal slice and the water column is divided into 8 layers for a vertical slice. The inversely estimated temperature field by using SVD (Singular Value Decomposition) method reveals the eddy and frontal structure clearly. The rms errors of the two horizontal slices are less than $0.4^{\circ}C$ and $1.7^{\circ}C$ at 400 m and 200 m depths, respectively, while the error in the vertical slice is less than $1.0^{\circ}C.$ For better estimation of temperature by OAT method, particularly for the East Sea, a range-dependent ray model should be used to solve the forward problem. At the same time, improvement in computing the refracted ray path between vertical layers is required to obtain more accurate travel time information. The results of the present experiment give rise to a possibility of application of OAT in remote sensing of the ocean thermal structure.

• Asia-Pacific Journal of Atmospheric Sciences
• /
• v.54 no.4
• /
• pp.575-585
• /
• 2018

In the case study of this paper, sensitivity experiments are carried out using the mesoscale non-hydrostatic Weather Research and Forecasting (WRF) model to investigate the impact of tropical cyclone (TC) Soudelor (2003) on the East Asian subtropical upper-level jet (EASJ) before TC Soudelor transformed into an extratropical cyclone. The physical mechanism for changes in the EASJ intensity and position caused by TC Soudelor is explored. Results indicate that TC Soudelor would warm the air in the middle and upper troposphere over the Japan Sea and the adjacent areas through stimulating northward propagating teleconnection pattern as well as releasing large amounts of latent heat, which led to increase (decrease) the meridional air temperature gradient to the south (north) below the EASJ axis. As a result, the geopotential height abnormally increased in the upper troposphere, resulting in an anomalous anticyclonic circulation belt along the EASJ axis. Correspondingly, the westerly winds to the north (south) of the EASJ axis intensified (weakened) and the EASJ axis shifted northward by one degree. The case study also suggests that before the extratropical cyclone transition of TC Soudelor, the TC activities had exerted significant impacts on the EASJ through thermodynamic processes.

• Fisheries and Aquatic Sciences
• /
• v.2 no.2
• /
• pp.199-209
• /
• 1999

Before investigating the long-term variations in macrobenthic communities sampled in the Chokchon macrotidal flat in Inchon, Korea, from 1989 to 1996, we need to understand how environmental factors in the area vary. As potential governing agents of tidal flat communities, abiotic factors such as mean sea level, seawater, air temperature, and precipitation were considered. Data for these factors were collected at equal intervals from 1976 or 1980 to 1996, and were analyzed using a decomposition method. In this analysis, all the above variables showed strong seasonal nature, and yielded a significant trend and cyclical variation. Positive trends were seen in the seawater and air temperatures, and based upon this relationship, it was found that the biological sampling period of our program has been carried out during warmer periods in succession. This paper puts forth some hypotheses concerning the response of tidal flat macrobenthos communities to the changing environment including mild winters in succession.

• 한국해양학회지
• /
• v.30 no.4
• /
• pp.271-278
• /
• 1995

A study of heavy mineral sands in terms of heavy mineral group and concentration has been carried out by analyzing 88 grab samples from the continental shelf off the southeast coast of Korea. Heavy mineral groups seem to be outlined and classified into four regions in the study area: 1) the western region; high concentrations of stable minerals, such as opaque mineral, magnetite, garnet and ZTR, 2) Korean Trough region; moderate concentrations of stable minerals, 3) the eastern region; abundant altered mineral and amphibole with minor of pyroxene concentration, and 4) the northeastern shelf-break region; low concentration of stable minerals with abundant altered minerals. The sedimentologic natures of four major heavy mineral regions (groupings) seem to be influenced by physical, dynamic and hydraulic milieu and also aerial and/or subaqueous weathering processes. It seems to be, further, plausible that shallow marine waves and currents associated with neritic dynamic condition of transgressive sea might be very effective on the concentration and groupings (sorting) of heavy min-erals in the surficial sediments of the continental shelf. The pyroxene-abundant heavy mineral suite (group), in fact, seems to suggest a sediment source from Japanese Islands.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
• /
• v.4 no.2
• /
• pp.93-100
• /
• 1999

Analyzing the tide data taken at Kunsan inner and Outer ports, non-tidal and mean sea level and harmonic constants of major constituents are investigated to examine the effects of the dyke gate operation on the sea level change in Keum River estuary. Non-tidal and annual mean sea levels decrease at Kunsan Inner and Outer ports after the dyke gate operation, especially showing an abrupt drop of non-tidal sea level at Kunsan Inner port. This non-tidal sea level drop results in the mean sea level gradient change between the inner and outer port, which can be mainly explained in terms of the decrease of river discharge from the dyke. Amplitudes of the $M_2$ and $S_2$ tides at the Inner port increase after the dyke gate operation, showing an abrupt jump, and phases of both tides slightly decrease. Amplitude and phase of the $K_1$ and $O_1$ tides show slight changes after the dyke gate operation. This significant change of semi diurnal tide amplitude is believed as a result of superposition of incident tidal wave and reflected tidal wave from the dyke.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
• /
• v.28 no.1
• /
• pp.51-61
• /
• 2023

Sound can travel a long distance in the ocean; hence, acoustic instruments have been widely used for ocean observations in various fields such as bathymetric survey, object detection, underwater communication, and current measurements. Herein we introduce a pressure-recording inverted echo sounder (PIES) which is one of the most powerful instruments, moored at seafloor for ocean observation in physical oceanography. The PIES can measure various kinds of oceanic phenomena (currents, mesoscale eddies, internal waves, and sea surface height variabilities) and support acoustic telemetry and pop-up data shuttle (PDS) system for remote data acquisition. In this paper, we review uses of PIES and describe present and prospective system of PIES including remote data acquisition toward (quasi) real-time data recovery.

• Ocean and Polar Research
• /
• v.45 no.2
• /
• pp.43-55
• /
• 2023

This study was conducted to understand the seasonal patterns and variation of the copepod community in the Anma Islands of Yeonggwang, Yellow Sea, with a focus on seasonal surveys to assess the factors affecting their occurrence. Throughout the survey period, Acartia hongi, Paracalanus parvus s. l., and Ditrichocorycaeus affinis were dominant species, while Acartia ohtsukai, Acartia pacifica, Bestiolina coreana, Centropages abdominalis, Labidocera rotunda, Paracalanus sp., Tortanus derjugini, Tortanus forcipatus occurred differently by season and station. As a results of cluster analysis, the copepod communities were distinguished into three distinct groups: spring-winter, summer, and autumn. The results of this study showed that the occurrence patterns of copepod species can vary depending on environmental conditions (topographic, distance from the inshore, etc.), and their spatial occurrence patterns between seasons were controlled by water temperature and prey conditions. One of the physical mechanisms that can affect the distribution of zooplankton in the Yellow Sea is the behavior of the Yellow Sea Bottom Cold Water (YSBCW), which shows remarkable seasonal fluctuations. More detailed further studies are needed for clear grounds for mainly why to many Calanus sinicus in the central region of the Yellow Sea are seasonally moving to the inshore, what strategies to seasonally maintain the population, and support the possibilities of complex factors.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
• /
• v.5 no.1
• /
• pp.16-26
• /
• 2000

Physical characteristics and nutrient distributions in seawater were investigated to understand the mechanism of red tide outbreak in coastal waters off Kohung area. To identify any physical and chemical differences before, during and after the red tide outbreaks, 6 times of field observations have been carried out from May to October, 1997. We found that major environmental properties of the seawater in the study area were determined not by the local meteoric conditions or nearby-land influences, but by the intrusion of seawater from offshore. In particular, extreme environmental variations in seawater were found during the period of red tide outbreak from August to September. Before the red tide outbreak, high concentrations of DIN(Dissolved Inorganic Nitrogen)were found in seawater, but they decreased during the outbreak. Whereas no significant variations of DIP(Dissolved Inorganic Phosphate) were found. For the water mass in the semienclosed northern part of the study area, local nutrient sources originated from nearby-lands were estimated to cover 70% of total DIN input, but the rest part of the water mass in the study area, sporadic intrusion of offshore water mass could account for the major source of DIN supply. An offshore water mass influenced by Yangtze river effluent was suggested as one of the candidates with its high nitrate contents, high seawater temperature and low salinity. A red tide related phytoplankton, Gyrodinium impudicum, was found in seawater on the 21th day of August and, on the same day, a unique water mass with high temperature and extremely low salinity suddenly appeared in the study area. On the 22th day of September, after one and half month duration of red tide we found that red tide had disappeared simultaneously with the intrusion of new water mass with different characteristics.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.29 no.5
• /
• pp.663-676
• /
• 1996

Physical properties and textural parameters of thirty-five piston tore samples recovered from the southeastern coast of Korea (Korea Strait), were investigated using the autopycnometer. The physical properties (porosity, water content, wet bulk density, dry bulk density, gram density, and void ratio) were measured at rather uniform intervals along each core. Sediment texture (grain size, sand, silt, and clay contents) was also measured at the same subbottom depth. The measured and calculated results are; mean grain size $0.57\~8.09\phi(average:3.67\phi)$, porosity $26\~81\%\;(average:\;55\%)$, water content $16.7\~61.4\%(average:\;31.6\%)$, wet bulk density $1.37\~2.18g/cm^3\;(average:\;1.85g/cm^3)$, dry bulk density $2.55\~3.11g/cm^3\;(average:\;2.35g/cm^3)$, grain density $2.40\~3.10g/cm^3\;(average:\;2.85g/cm^3)$, and void ratio $0.56\~2.54$ (average: 0.94). The sediment texture generally coincides well with the bathymetry indicating the influence of Pleistocene-Holocene sea level changes. Also the contours of physical properties are closely related to the sediment texture. Fluctuation of physical properties are similar to the textural variation. It seems that sediment texture is a significant factor in determining physical property in this study area.