• 한국해양학회지
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• v.30 no.4
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• pp.288-301
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• 1995

Rates of the sedimentation and particle mixing have been estimated by applying uranium-series disequilibrium techniques to three sediment cores collected from the korea Deep Ocean Study (KODOS) site between the clarion and Clipperton Fracture Zones (CCFZ) of the Equatorial Pacific. Sedimentation rates based on the profiles of excess /SUP 230/Th activity and /SUP 230/ Th/SUB xs//SUP 232/ Th activity ratios at the southeastern part of the study area were estimated to be in the order of a few millimeters per thousand year, while at the northwestern part a factor of ten lower. Excess activities of /SUP 230/Th and /SUP 230/Th ratios showed intervals of constant values in the upper part of the sediment cores, probably generated by biological particle mixing. A "two-box" advection-diffusion steady state mixing model was employed in order to estimate particle mixing rates in the upper and the lower layers, based on the distribution profiles of excess /SUP 210/Pb activities. Particle mixing coefficients were estimated to be in the order of 10$^1$ cm$^2$/y in the upper layer and 10/SUP -1/-10/SUP 0/ cm$^2$/y in the lower layer.

• 한국해양학회지
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• v.25 no.4
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• pp.240-244
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• 1990

To solve two problems, temperature shock to the man and difficulty in exchanging the air in the glove box into N2 gas, during the subsampling of Suboxic and cold core sediments, a portable glove box with a refrigerating machine and a gas exchanging bag was constructed for subsampling of sediment cores on board. The refrigerator of the glove box can cool down 200 litter air at 30$^{\circ}C$ to 2$^{\circ}C$${\pm}$2$^{\circ}C$ within 5 minutes. The box was successfully operated during the second KORDI's deep sea research cruise of 1989 in the North equatorial Pacific. Pore water data obtained from the cruise show no evidence for artifacts caused by warming up or oxidation of sediments during subsampling.

• 한국해양학회지
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• v.21 no.2
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• pp.92-100
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• 1986

Laboratory investigations of physical (density and porosity), acoustic (velocity and velocity anisotropy), and electrical (resistivity and resistivity anisotropy) properties in deep-sea carbonate sequences at DSDPsites 288 and 289 in the western equatorial Pacific were made and correlated as a function of diagenesis. Profile of resistivity shows almost a mirror image of velocity indicating that electrical resistivity can be a useful variable to determine the diagenetic stage. Some fluctuations in acoustic and electrical properties near the zones of cherty and siliceous limestones for both sites imply significant changes in pore geometry due to interbedded silica. The significantly reduced pore throat size by the presence of silica which provides excess calcium carbonate to adjacent pore spaces is partly responsible for several jumps in acoustic and electrical properties of the zones. These observed geophysical data are interpreted as the result of silica diagenesis influencing carbonate diagenesis.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.54 no.2
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• pp.180-187
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• 2021

This study was conducted to investigate the reproductive characteristics of the Neon damselfish Pomacentrus coelestis in Chuuk lagoon (7°27' N, 151°53' E), Micronesia, Equatorial Pacific Ocean. The specimens used in this study were collected from August 2009 to September 2010 from around the coral reef area at a depth of 3-10 m in the northwest coast of Weno Island. Overall, 228 individuals were collected over 14 months from this area, of which 115 were females and 108 were males. Among 108 males, 30 were found to be hermaphrodites and the sex of 5 individuals could not be determined. The overall sex ratio was approximately 1.06:1 (female:male), and the ratio of sexually active individuals was 0.79:1. The gonadosomatic index (GSI) fluctuated and showed the highest value of 8.43±1.21 in December 2009 and the lowest value of 3.36±0.71 in September 2009 in sexually active females. Males showed the highest GSI value of 2.64±0.93 in June 2010 and the lowest value of 0.35±0.06 in July 2010. Based on the fluctuation of GSI, the trends in the appearance of monthly sexually active individuals, and biopsy of the gonads, P. coelestis was found to be a hermaphrodite species of protogynous type and is considered to be reproductively active throughout the year.

• Korean Journal of Remote Sensing
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• v.13 no.1
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• pp.1-12
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• 1997

The western equatorial Pacific Ocean, where sea surface temperature is the warmest on the globe, is characterized by numerous convective systems and large annual precipitation. In this region, the cloudiness data with tops higher than 8km level obtained from the GMS-IR data are used to investigate the diurnal variation of cloudiness. The amplitude and phase of diurnal and semi-diurnal cycles are mainly investigated to examine details on the temporal and spatial structure of clouds. Cloudiness variation has typical cycles and each cycle is associated with the air-sea interactive phenomena. Spectral analysis on the cloudiness time series data indicates that 30-60 day, 17-20day, 7-8 day, diurnal and semi diurnal cycle are peaked. During Northern Winter and Southern Summer, the large cloudiness exsists over New Guinea, the adjacent seas of North Australia, and the open oceanic regions east of $160^{\circ}$E. Cloudiness diurnal variability over the lands and their adjacent seas is about 2.0 times larger than that over the open sea regions. That may be due to the difference of specific heat between the land and sea. The maximum and minimum cloudiness appeared at 18:00 and 09:00 hours over the land, and at noon and 21:00 hours over the sea, respectively. The amplitude of diurnal component over the land is 4,7 times larger than that of semi-diurnal component, and 1.5 times over the sea.

• Journal of the Korean Geographical Society
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• v.28 no.2
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• pp.112-122
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• 1993

Since more than 50${\%}$ of annual precipitation in Korea falls during Changma, the rainy season of early summer, and Late Changma, the rainy season of late summer, forcasting the onset days Changmas, and the amount related rainfalls would be necessary not only for agriculture but also for flood-control. In this study the authors attempted to build a prediction model for the forecast of the onset date of Changmas. The onset data of each Changma was derived out of daily rainfall data of 47 stations for 30 years(1961~1990) and weather maps over East Asia. Each station represent any of the 47 districts of local forecast under the Korea Meteorological Administration. The average onset dates of Changma during the period was from 21 through 26 June. The dates show a tendency to be delayed in El Ni${\~{n}}o years while they come earlier than the average in La Nina years. In 1982, the year of El Ni${\~{n}}o, the date was 9 Julu, two weeks late compared with the average. The relation of sea surface temperature(SST) over Pacific and Northern hemispheric 500mb height to the Changma onset dates was analyzed for the prediction model by polynomial regression. The onset date of Changma over Korea was correlated with SST in May(SST${_(5)}{^\circ}$C) of the district (8${^\circ}$~12${^\circ}S, 136${^\circ}~148${^\circ}W)of equatirial middle Pacific and the 500mb height in March (MB${_(3)}$"\;"m)over the district of the notrhern Hudson Bay. The relation between this two elements can be expressed by the regression: Onset=5.888SST${_5}"\;"+"\;"0.047MB${_(3)}$"\;"-251.241. This equation explains 77${\%}$ of variances at the 0.01${\%}$ singificance level. The onset dates of Late Changma come in accordance with the degeneration of the Subtro-pical High over northern Pacific. They were 18 August in average for the period showing positive correlation(r=0.71) with SST in May(SST)${_(i5)}{^\circ}$C) over district of IndiaN Ocean near west coast of Australia (24${^\circ}$~32${^\circ}$S, 104${^\circ}$~112${^\circ}$E), but negativ e with SST in May(SST${_(p5)}{^\circ}$ over district (12${^\circ}$~20${^\circ}$S,"\;"136${^\circ}$~148${^\circ}$W)of equatorial mid Pacific (r=-0.70) and with the 500mb height over district of northwestern Siberia (r=-0.62). The prediction model for Late Changma can be expressed by the regression: Onset=706.314-0.080 MB-3.972SST${_(p5)}+3.896 SST${_(i5)}, which explains 64${\%}$ of variances at the 0.01${\%}$ singificance level.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.13 no.3
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• pp.200-209
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• 2008

Particle fluxes were measured with a time-series sediment trap from July 2003 to June 2005 at the St. KOMO(KOMO; Korea Deep-Sea Environmental Study Long-Term Monitoring Station, $10^{\circ}30'N,\;131^{\circ}20'W$) in the northeastern Pacific. Total mass fluxes at a depth of 4,960 m showed distinct seasonal variations with high values in the winter(December-February) and spring(March-May) and low values in the summer(June-August) and fall(September-November). Biogenic origin fluxes also displayed distinct seasonal variations similar to total mass fluxes. Particularly, calcium carbonate fluxes in winter and spring were more than two times greater than those in summer and fall. The prominent seasonal variations of total mass and biogenic fluxes were closely related with the seasonal changes of primary production in the surface waters; in winter and spring, primary production increased due to the enhanced supply of nutrients below the surface mixed layer by strong wind and less stratification, whereas it decreased as a result of the less supply of nutrient by reduced wind speed and strong stratification in summer and fall. The seasonal variations of total mass and biogenic fluxes in this study were higher than the differences of total mass and biogenic fluxes caused by the environmental changes such as El $Ni\tilde{n}o$ and La $Ni\tilde{n}a$ events in the previous studies. In order to understand the effects of El $Ni\tilde{n}o$ and La $Ni\tilde{n}a$ on the particle flux, therefore, the seasonal variation of particle flux in the northeastern equatorial Pacific needs to be well defined.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.13 no.3
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• pp.210-221
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• 2008

The mesoscale environmental surveys were conducted between $5^{\circ}N\;and\;17^{\circ}N$ mainly along the $131.5^{\circ}W$ meridian from 1997 to 2002 to investigate controlling factors of carbon and nitrogen contents in bottom sediments. Sediments of the study area showed zonal distribution pattern depending on latitudinal position and can be classified into four types; calcareous ooze($5{\sim}6^{\circ}N$), siliceous sediments($8{\sim}12^{\circ}N$), pelagic red clay($16{\sim}17^{\circ}N$), and mixed sediments($7^{\circ}N$). Inorganic carbon(IC) contents varied depending on water depth and carbonate compensation depth(CCD). Carbonate materials were well preserved in the low latitude region, where water depths are shallower than CCD. In contrast, the higher latitude region dominated by siliceous sediment and pelagic red clays has low productivity in water column as well as the water depths deeper than CCD. Thus, most of carbonate materials were dissolved, which resulted in IC contents of less than 0.05% in the sediments. Organic carbon(OC) and total nitrogen contents(TN) in siliceous sediments were higher than in pelagic red clay sediments simply because of higher primary productivity in the siliceous sediment dominated area. The contents of OC and TN were lower in the calcareous ooze than in the siliceous sediments. It is attributed to the high input of calcareous material to the bottom due to relatively shallow water depth of the area, which diluted organic matter contents in the sediment. Overall results indicated that water depth relative to CCD, primary production in water column, and sedimentation rate largely controls the large-scale distribution of carbon and nitrogen contents in the study area.

• Economic and Environmental Geology
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• v.35 no.1
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• pp.1-12
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• 2002

Manus Basin, located in the equatorial western Pacific, is a back arc basin formed by collision between the IndoAustralian and the Pacific Plates. The basin is host to numerous hydrothermal vent fields and ore deposits. The basement rocks of the Manus Basin consist primarily of dacite and basaltic andesite. Some of the minerals that form the hydrothermal chimneys that were dredged on the Manus basin include pyrite, chalcopyrite, marcasite, sphalerite and galena. The chimneys can be classified into chalcopyrite dominant Cu-rich type and sphalerite dominant Zn-rich type. The concentration of Zn shows good positive correlation with that of Sb, Cd and Ag. The content of Cu, on the other hand, positively correlates with that of Mo, Mn and Co. For samples that were taken from Zn-rich chimney, a strong positive correlation is found between Au and Zn contents. The chimney also shows enrichments of Cd, Mn and Sb. On the other hand, the samples from Cu-rich chimney exhibit strong correlation among Au, Zn and Pb, and are enriched in Mo and Co concentration. Average contents of Au in Cu-rich and Znrich chimneys were 15.9 ppm and 29.0 ppm, respectively. Because of high concentration of Au with Ag and Cu, the ore deposit have high economic potential. Homogenization temperatures and salinities of fluid inclusions in anhydrite and amorphous silica from Zn-rich chimney are estimated to be l74-220$^{\circ}$C and 2.7-3.6 equiv. wt. % NaCI, respectively. These value suggest that ore forming processes were occurred at around 200$^{\circ}$C and that the oxygen fugacity changed from 2: 10$^{-39.5}$bar to -s: 10$^{-40.8}$bar and the sulfur fugacity from -s: 10$^{-14.7}$bar to 10$^{-13.4}$bar during the process. It appears that the temperature at which the ores formed on Cu-rich chimney was higher than that on Zn-rich chimney.

• Journal of the Korean earth science society
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• v.35 no.4
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• pp.249-258
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• 2014

Despite the greenhouse gases like carbon dioxide have steadily increased in atmosphere, the overall trend of the global average surface air temperature has stalled during the last decade (2002-present). This phenomenon is often called hiatus or warming pause, which is challenging the prevailing view that anthropogenic forcing causes warming environment. Our study characterized the hiatus by analyzing the HadGEM2-AO (95 yrs) simulation data based on RCP8.5 scenario. The PC2 time series from the EOF of the zonal mean vertical ocean temperature has been defined as the index that represents the warming pause. The relationship between the hiatus, ENSO and the changes in climate system are identified by utilizing the newly defined PC2. Since the La Nina index (defined as the negative of NINO3 index) leads PC2 by about 11 months, it may be possible that the La Nina causes the warming to be interrupted. We also show that the cooling of the climate system closed tied to the heat penetration into the deep ocean, indicating the weakening the warming rate is due to the oceanic heat uptake. Finally, the global warming hiatus is characterized by the anomalous warming in Arctic region as well as the intensification of the trade wind in the equatorial Pacific.