• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.17 no.4
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• pp.243-251
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• 2012

Real-time monitoring for environmental factors(temperature, salinity, chlorophyll, etc.) and carbonate components( pH and $fCO_2$) was conducted during 5-6th of July, 2012 at a seaweeds farm in Gijang, Busan. Surface temperature and salinity were ranged from $12.5{\sim}17.6^{\circ}C$ and 33.7~34.0, respectively, with highly daily and inter-daily variations due to tide, light frequency(day and night) and currents. Surface $fCO_2$ and pH showed a range of $381{\sim}402{\mu}atm$ and 8.03~8.15, and chlorophyll-a concentration in surface seawater ranged 0.8~5.8 ${\mu}g\;L^{-1}$. Environmental and carbonate factors showed the highest/lowest values around 5 pm of 5th July when the lowest tidal height and strongest thermocline in the water column, suggesting that biological production resulted in decrease of $CO_2$ and increase of pH in the seaweed farm. Processes affecting the surface $fCO_2$ distribution were evaluated using a simple budget model. In day time, biological productions by phytoplankton and macro algae are the main factors for $CO_2$ drawdown and counteracted the amount of $CO_2$ increase by temperature and air-sea exchange. The model values were a little higher than observed values in night time due to the over-estimation of physical mixing. The model suggested that algal production accounted about 14-40% of total $CO_2$ variation in seaweed farm.

• Journal of the Korean Society of Marine Environment & Safety
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• v.15 no.4
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• pp.315-328
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• 2009

Long-term trends and distribution patterns of water quality were investigated in the Garolim coastal areas of Yellow Sea, Korea from 1998 to 2007. Water samples were collected at 3 stations and physicochemical parameters were analyzed including water temperature, salinity, suspended solids(SS), chemical oxygen demand(COD), dissolved oxygen(DO) and nutrients. Spatial distribution patterns were not clear among stations but the seasonal variations were distinct except pH and ammonia. The trend analysis by principal component analysis(PCA) during twenty years revealed the significant variations in water quality in the study area. Annual water qualities were clearly classified into 4 clusters by PCA; year cluster 1997, 1998 and 2000-2002, 1999 and 2003-2006/2008. By this multi-variate analysis the annual trends were summarized as follows; In recent years, salinity increased, whereas dissolved inorganic nitrogen, nitrate nitrogen and COD decreased and water quality generally continued to be in good condition in Gsrolim coastal areas without inflow of freshwater from land. Garolim coastal areas are required to be conserved continuously as important coastal areas for fisheries.

• Journal of Wetlands Research
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• v.10 no.3
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• pp.9-26
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• 2008

To clarify the reed (Phragmites australis) stand's effects on the sediment properties and its increasing pattern, breaths of reed stands in 1999 and 2000, and sediment properties - water, salt, organic matter, sulphur, nitrogen, carbon and hydrogen contents - along th depth at the three stands in 2007 were surveyed at Suncheon Bay. Regardless of reed stand, the more distance from the land was long, the more water and salt contents of sediment were high. Organic matter content of sediment was high and increased with the reed biomass at the upper layer but low regardless of biomass at the lower layer. Sulphur content of sediment was higher at old reed stand (0.33%) than at new stand (0.21%) or non-vegetated stand (0.23%). Carbon, nitrogen and hydrogen contents of sediment were similar at three stands in mean values. However, their contents were high at upper layer and low at lower layer in a stand. Therefore, the changing pattern of organic matter content with the depth was similar to but not coincided to the inorganic nutrients' ones. The mean breadth of reed stands increased $2.33{\pm}0.73m$ in 1999 and $3.65{\pm}1.64m$ in 2000. However, the increase of reed stands' breadth a year varied along the direction, year or stands, so that there was not a trend in increasing pattern. It was thought that this increasing pattern made the reed's patch round. The height and density of reed shoot in newly formed stand decreased with the distance from the center of stand. In the newly formed peripheral area of a reed stand, the shoot density was not related with the land (north) or sea (south) direction, however, the shoot height was higher in the sea (south) than in the land (north) direction.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.48 no.1
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• pp.16-24
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• 2011

The sound speed of seawater can be calculated by the empirical formula as a function of temperature, salinity and pressure. It is little affected by salinity because the average salinity is 34 psu and varies within a few psu seasonally and spatially in the ocean. Recently, low-salinity water of 24 psu flows into the western sea area of Jeju Island due to the flood of the Yangtze River in China during summer, affecting sound speed profile. In this paper, it was analyzed how environmental changes affected to the underwater communication - the sound speed of low-salinity water was calculated, and the communication channel was estimated by the simulated acoustic rays while the transmitting and receiving depth and the range were varied with and without the low-salinity layer. And The BER (Bit error rate) was calculated by BPSK(Binary phase shift key) modulation and the effects of the low-salinity water on the BER was investigated. The sound speed profile was changed to have positive slope by the low-salinity layer at the sub-surface up to 20 m of depth, forming acoustic wave propagation channel at the sub-surface resulting in the decrease of most of the BER Consequently, this paper suggests that it is important to consider changes of the ocean environment for correctly analyzing the underwater communication and the detection capability.

• Korean Journal of Ecology and Environment
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• v.34 no.3 s.95
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• pp.206-214
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• 2001

Water quality and Pollution state of Lake Chungcho were evaluated during three years from 1998 to 2000. We surveyed physicochemical parameters, and TSI (trophic state index) was calculated using TP, Chl. a, and SD (secchi disc transparency) data of growing season average. Water samples were collected bimonthly except freezing season. During the study period, total annual precipitation in 1998, 1999 and 2000 year was 1,797,1,722 and 1,345 mm, respectively. Salinity and conductivity were high($29.3{\pm}5.5\;ppt$, and $45,105{\pm}7,585\;{\mu}S/cm$) then other lagoons in the Eastern Coast of Korea. Chemocline was formed by salinity at $0.5{\sim}1.5\;m$ water depth. As a result of this, DO concentration of hypolimnion was below $3.0\;mgO_2/L$. Especially, when intense chemocline was formed, temperature of hypolimnion was higher than epilimnion. Secchi disc transparency, chlorophyll a, and COD were $1.8{\pm}0.3\;m$, $15.7{\pm}20.7\;mg/m^3$, and $3.1{\pm}0.8\;mgO_2/L$, respectively. Most of TN/TP ratios below 20, but concentration of TN and TP was high. Values of TSI ranged between 59 and 77, indicating a eutrophic condition in this system.

• Journal of the Korean Society for Marine Environment & Energy
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• v.10 no.4
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• pp.193-200
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• 2007

The purpose of this study is investigate to water quality, pH, turbidity, salinity, nutrients, SS, DO, COD, ${NH_4}^+$-N, ${NO_2}^-+{NO_3}^-$-N, TN, TP, ${PO_4}^{3-}$-P in ditches and seawater of the Hwawon, southwestern coastal area of Korea. Two stations of the ditch, one station at outfall from reservoir of the coastal development and 15 stations of seawater were measured in August just after a 96.5 mm rainfall and in dry season of November 2006. The sampling time were divided into a rainy and dry season based on turbidity, SS, salinity and nutrients difference of distributions that was evidence as a inflow of pollutants from the developing coastal land area. The pH, turbidity, salinity and SS were high and showed different from between surface and bottom in near the developing of coastal land than the other stations after a strong rainfall over 90 mm while it were not varied in vertical and horizontal concentration profile in dry season. The other nutrients were showed the same concentrations gradient patterns. In opposition to expectations, the SS in dry season was higher than in the rainy season due to upwelling by the wind and strong current. It appears that the researched coastal seawater qualities were mainly effected by the inflow of freshwater from the ditches and drain from the reservoir of the developing land area during strong rainfall while the seawater qualities were mainly effected by the wind and strong current in dry season.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.8 no.2
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• pp.138-150
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• 2003

In the mid-west coast of Korea where Mankyung and Dongjin rivers discharge fresh water, Saemangeum tidal dyke of 33 km long is under construction to reclaim the very shallow estuary region of 41,000ha. Main source of freshwater in this coastal area is Keum River locating closely north of the dyke. At present, the dyke connected with Gogunsan-Gundo separates this area into three regions; northwestern, southwestern and eastern (Saemangeum) region of the dyke, and the water in Saemangeum region is exchanged through one gap in the northern dyke and two gaps in the southern dyke. We have observed distributions and structures of temperature and salinity to examine the summer circulation related with low-salinity water in this coastal area in 1998 and 1999. In the surface layer off the northern dyke a tongue-like distribution of low-salinity extends 60 km long from Keum River estuary mouth to the northwest, forming plume front bounded by offshore water. In the inner region of Saemangeum dykes salinity distributions show that two river waters are merged together and the low salinity water is deflected toward northern gap of the dyke. In the surface layer off the southern dyke we observed small tongue-like distribution of another low-salinity water extending to the north from Gomso Bay. Based on the analysis of distributions of low-salinity water and frontal structures, we can suggest an anticlockwise circulation of coastal water around the dyke, composed by the estuarine water outgoing from the inner region of the dyke through the northern dyke's gap and the inflow through two gaps of southern dyke from offshore. After completing the dyke construction, this coastal circulation around the dyke will be, however, changed because fresh water discharge of Mankyung and Dongjin rivers will be routed artificially and directly into the area offshore of the southern dyke.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.28 no.4
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• pp.121-132
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• 2023

Marine heatwaves (MHWs), referring to anomalously high sea surface temperatures, have drawn significant attention from marine scientists due to their broad impacts on the surface marine ecosystem, fisheries, weather patterns, and various human activities. In this study, we examined the impact of the distribution of Changjiang diluted water (CDW), a significant factor causing oceanic property changes in the East China Sea (ECS) during the summer, on MHWs. The surface salinity distribution in the ECS indicates that from June to August, the eastern extension of the CDW influences areas as far as Jeju Island and the Korea Strait. In September, however, the CDW tends to reside in the Changjiang estuary. Through the Empirical Orthogonal Function analysis of the cumulative intensity of MHWs during the summer, we extracted the loading vector of the first mode and its principal component time series to conduct a correlation analysis with the distribution of the CDW. The results revealed a strong negative spatial correlation between areas of the CDW and regions with high cumulative intensity of MHWs, indicating that the reinforcement of stratification due to low-salinity water can increase the intensity and duration of MHWs. This study suggests that the CDW may still influence the spatial distribution of MHWs in the region, highlighting the importance of oceanic environmental factors in the occurrence of MHWs in the waters surrounding the Korean Peninsula.

• Journal of the Korean Society for Marine Environment & Energy
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• v.15 no.2
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• pp.76-88
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• 2012

In order to investigate the distribution of water masses and spatio-temporal variation of nutrients in the coastal areas of Gangwon province of the Korean East Sea, a survey of the physico-chemical parameters (temperature and salinity) and nutrients ($NO_2$-N, $NO_3$-N, $NH_4$-N, $PO_4$-P, and $SiO_2$-Si) was carried out at 5 locations (Goseong, Sokcho, Yangyang, Gangneung, and Donghae) in February, May, August, and November 2009. The water masses included in the study area were divided into 4 groups; 1) Tsushima Surface Water (TSW), 2) Tsushima Middle Water (TMW), 3) North Korean Cold Water (NKCW), and 4) East Sea Proper Water (ESPW). The distribution of water masses was affected by the change of season. In February, surface water was derived from the TMW. The TSW was not observed in May, but only observed in August. In November, as the influence of the TSW weakened, that of the NKCW strengthened. Considering the vertical profiles of nutrients, the concentrations in all the seasons were very low within the surface water, but increased rapidly near the thermocline. Most of nutrient concentrations, except for dissolved silicate, remained constant below the depth of 200 m. However, the dissolved silicate concentration increased with depth, suggesting that silicate has a delayed regenerative pattern. The ESPW had the highest nutrient concentration, followed by the NKCW, TMW, and TSW. In February, May, and November, the N/P ratio in most of the water masses was similar to or larger than the Redfield ratio, indicating that nitrogenous nutrients did not act as a limiting factor for phytoplankton growth. However, in August, the N/P ratio in the TSW was less than the Redfield ratio, and the concentration of $NO_2$-N+$NO_3$-N was 0.86 ${\mu}m$, indicating that nitrogenous nutrients did act as a limiting factor for phytoplankton growth in the study area.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.14 no.4
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• pp.195-204
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• 2009

In order to estimate sea surface current fields in the East Sea, we examined characteristics of mean dynamic topography (MDT) fields (or mean surface current field, MSC) generated from three different methods. This preliminary investigation evaluates the accuracy of surface currents estimated from satellite-derived sea level anomaly (SLA) data and three MDT fields in the East Sea. AVISO (Archiving, Validation and Interpretation of Satellite Oceanographic data) provides a MDT field derived from satellite observation and numerical models with $0.25^{\circ}$ horizontal resolution. Steric height field relative to 500 dbar from temperature and salinity profiles in the East Sea supplies another MDT field. Trajectory data of surface drifters (ARGOS) in the East Sea for 14 years provide another MSC field. Absolute dynamic topography (ADT) field is calculated by adding SLA to each MDT. Application of geostrophic equation to three different ADT fields yields three surface geostrophic current fields. Comparisons were made between the estimated surface currents from the three different methods and in-situ current measurements from a ship-mounted ADCP (Acoustic Doppler Current Profiler) in the southwestern East Sea in 2005. For offshore areas more than 50 km away from the land, the correlation coefficients (R) between the estimated versus the measured currents range from 0.58 to 0.73, with 17.1 to $21.7\;cm\;s^{-1}$ root mean square deviation (RMSD). For coastal ocean within 50 km from the land, however, R ranges from 0.06 to 0.46 and RMSD ranges from 15.5 to $28.0\;cm\;s^{-1}$. Results from this study reveal that a new approach in producing MDT and SLA is required to improve the accuracy of surface current estimations for the shallow costal zones of the East Sea.