• The Korean Journal of Quaternary Research
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• v.17 no.1
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• pp.7-16
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• 2003

A 31m-long sediment core (SSDP-102) was taken from the inner shelf (about 40m water-depth) off the northwestern coast of the Korea Strait. Detailed lithofacies and organic-geochemical analyses were performed to establish a high-resolution stratigraphy in the Korea Strait shelf and to reconstruct the paleoenvironmental changes associated with the Holocene marine transgression. The stratigraphic framework of the core was primarily established using 6 AMS $^{14}C$ ages. The sedimentary record of the core SSDP-102 allows for the reconstruction of the paleoenvironmental changes during the last 12.1 ka BP. According to the high-resolution seismic reflection profiles, lithofacies and organic-geochemical data, the core SSDP-102 can be divided into three units (III to I in ascending order) above the acoustic basement. The three units reflect distinct changes of depositional environments resulted from the post-glacial marine transgression. Therefore, it is suggested that three phases of sea-level change have occurred within the inner shelf of the Korea Strait following the Holocene marine transgression. (1) estuarine environments from ca. 12.1 to 6.2 ka BP; (2) near-shore environments with a period of decreased rising of sea level between 6.2 and 5.1 ka BP; (3) near-shore to modem marine environments after 5.1 ka BP. In particular, the present marine conditions influenced by the warm Tsushima Current have been gradually established after ca. 5.1 ka BP.

• Ocean and Polar Research
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• v.43 no.4
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• pp.307-320
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• 2021

Udo Rhodolith Beach is a small-scale, mixed sand-and-gravel beach embayed on the N-S trending rocky coast of Udo, Jeju Island, South Korea. This study analyzes the short-term topographic changes of the beach during the extreme storm conditions of four typhoons from 2016 to 2020: Chaba (2016), Soulik (2018), Lingling (2019), and Maysak (2020). The analysis uses the topographic data of terrestrial LiDAR scanning and drone photogrammetry, aided by weather and oceanographic datasets of wind, wave, current and tide. The analysis suggests two contrasting features of alongshore topographic change depending on the typhoon pathway, although the intensity and duration of the storm conditions differed in each case. During the Soulik and Lingling events, which moved northward following the western sea of the Jeju Island, the northern part of the beach accreted while the southern part eroded. In contrast, the Chaba and Maysak events passed over the eastern sea of Jeju Island. The central part of the beach was then significantly eroded while sediments accumulated mainly at the northern and southern ends of the beach. Based on the wave and current measurements in the nearshore zone and computer simulations of the wave field, it was inferred that the observed topographic change of the beach after the storm events is related to the directions of the wind-driven current and wave propagation in the nearshore zone. The dominant direction of water movement was southeastward and northeastward when the typhoon pathway lay to the east or west of Jeju Island, respectively. As these enhanced waves and currents approached obliquely to the N-S trending coastline, the beach sediments were reworked and transported southward or northward mainly by longshore currents, which likely acts as a major control mechanism regarding alongshore topographic change with respect to Udo Rhodolith Beach. In contrast to the topographic change, the subaerial volume of the beach overall increased after all storms except for Maysak. The volume increase was attributed to the enhanced transport of onshore sediment under the combined effect of storm-induced long periodic waves and a strong residual component of the near-bottom current. In the Maysak event, the raised sea level during the spring tide probably enhanced the backshore erosion by storm waves, eventually causing sediment loss to the inland area.

• Journal of Korea Water Resources Association
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• v.51 no.6
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• pp.515-521
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• 2018

Seawater intrusion areas were calculated in Yeosu region considering sea level rise and the effects of countermeasures for seawater intrusion were analyzed using SEAWAT program. The estimated seawater intrusion area was $14.90km^2$ in 2015. When we applied climate change scenarios the area was changed to $19.19km^2$ for RCP 4.5 and $20.43km^2$ for RCP 8.5 respectively. The mitigation effects by artificial recharge with total $50m^3/d$, $100m^3/d$, and $300m^3/d$ are from 3.75% to 10.68% for RCP 4.5, and from 5.82% to 10.77% for RCP 8.5 respectively. If we install barrier wall with the thickness 0.8 m, 1.3 m, and 1.8 m, the mitigation effects are from 6.67% to 12.04% for RCP 4.5, and from 6.17% to 14.98% for RCP 8.5 respectively. The results of this study can be used to be a logical means of quantitative grounds for policy decisions to prevent groundwater contamination by seawater intrusion and subsequent secondary damage in coastal areas.

• Asia-Pacific Journal of Atmospheric Sciences
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• v.54 no.4
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• pp.545-561
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• 2018

Over the North East Asia, extreme anomalous precipitation were observed in 2013 and 2014. During 2013 summer the precipitation was found to be higher (two standard deviation) than the climatological mean of the region; whereas during 2014, which was a borderline El Ni?o year, precipitation was found to be lower (one standard deviation). To understand the differences of these two anomalous years the Global/Regional Integrated Model system (GRIMs) has been used. The study found that low landsurface temperature and high sea-surface temperature over ocean caused a smaller land-sea contrast of surface temperature between East Asia and North West Pacific Ocean in 2014, which could have caused an eastward shift of mean monsoon circulation in that year compared to the circulation in 2013. Due to a change in the lower level circulation and wind field over East Asia the evaporation and moisture transport patterns became very different in those two years. In 2013, this study found high latent heat flux over Eastern China, which implies an increased surface evaporation over that region, and the moisture transported to the north by the mean monsoon circulation; whereas, there was no correlated transport of moisture to the North East Asia during 2014. The precipitable water over North East Asia has a stronger correlation with the latent heat flux over southern land region than that from Ocean region in the eastern side in both the years. A new approach is proposed to estimate the sub-grid scale hydrometeors from GRIMs, overestimated in the existing model.

• Journal of Ecology and Environment
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• v.45 no.4
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• pp.264-276
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• 2021

Background: Salt marshes provide a variety of ecosystem services; however, they are vulnerable to human activity, water level fluctuations, and climate change. Analyses of the relationships between plant communities and environmental conditions in salt marshes are expected to provide useful information for the prediction of changes during climate change. In this study, relationships between the current vegetation structure and environmental factors were evaluated in the tidal flat at the southern tip of Ganghwa, Korea, where salt marshes are well-developed. Results: The vegetation structure in Ganghwa salt marshes was divided into three groups by cluster analysis: group A, dominated by Phragmites communis; group B, dominated by Suaeda japonica; and group C, dominated by other taxa. As determined by PERMANOVA, the groups showed significant differences with respect to altitude, soil moisture, soil organic matter, salinity, sand, clay, and silt ratios. A canonical correspondence analysis based on the percent cover of each species in the quadrats showed that the proportion of sand increased as the altitude increased and S. japonica appeared in soil with a relatively high silt proportion, while P. communis was distributed in soil with low salinity. Conclusions: The distributions of three halophyte groups differed depending on the altitude, soil moisture, salinity, and soil organic matter, sand, silt, and clay contents. Pioneer species, such as S. japonica, appeared in soil with a relatively high silt content. The P. communis community survived under a wider range of soil textures than previously reported in the literature; the species was distributed in soils with relatively low salinity, with a range expansion toward the sea in areas with freshwater influx. The observed spatial distribution patterns may provide a basis for conservation under declining salt marshes.

• Spatial Information Research
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• v.20 no.3
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• pp.39-50
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• 2012

The objective of this study is the quantitative analysis of climate change effects by performing several statistical analyses with hydrometeorological data sets for past 30 years in Geum river watershed. Temperature, precipitation, relative humidity data sets were collected from eight observation stations for 37 years(1973~2009) in Geum river watershed. River level data was collected from Gongju and Gyuam gauge stations for 36 years(1973~2008) considering rating curve credibility problems and future long-term runoff modeling. Annual and seasonal year-to-year variation of hydrometeorological components were analyzed by calculating the average, standard deviation, skewness, and coefficient of variation. The results show precipitation has the strongest variability. Run test, Turning point test, and Anderson Exact test were performed to check if there is randomness in the data sets. Temperature and precipitation data have randomness and relative humidity and river level data have regularity. Groundwater level data has both aspects(randomness and regularity). Linear regression and Mann-Kendal test were performed for trend test. Temperature is increasing yearly and seasonally and precipitation is increasing in summer. Relative humidity is obviously decreasing. The results of this study can be used for the evaluation of the effects of climate change on water resources and the establishment of future water resources management technique development plan.

• Korean Journal of Remote Sensing
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• v.38 no.5_1
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• pp.447-460
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• 2022

It is well known that satellite synthetic aperture radar interferometry (InSAR) has been widely used for the observation of surface displacement owing to earthquakes, volcanoes, and subsidence very precisely. In wetlands where vegetation exists on the surface of the water, it is possible to create a water level change map with high spatial resolution over a wide area using the InSAR technique. Currently, a number of imaging radar satellites are in operation, and most of them support a ScanSAR mode observation to gather information over a large area at once. The Cienaga Grande de Santa Marta (CGSM) wetland, located in northern Colombia, is a vast wetland developed along the Caribbean coast. The CGSM wetlands face serious environmental threats from human activities such as reclamation for agricultural uses and residential purposes as well as natural causes such as sea level rise owing to climate change. Various restoration and protection plans have been conducted to conserve these invaluable environments in recognition of the ecological importance of the CGSM wetlands. Monitoring of water level changes in wetland is very important resources to understand the hydrologic characteristics and the in-situ water level gauge stations are usually utilized to measure the water level. Although it can provide very good temporal resolution of water level information, it is limited to fully understand flow pattern owing to its very coarse spatial resolution. In this study, we evaluate the L-band ALOS-2 PALSAR-2 ScanSAR mode to observe the water level change over the wide wetland area using the radar interferometric technique. In order to assess the quality of the interferometric product in the aspect of spatial resolution and coherence, we also utilized ALOS-2 PALSAR-2 stripmap high-resolution mode observations.

• The Korean Journal of Petroleum Geology
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• v.9 no.1_2 s.10
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• pp.1-15
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• 2001

Hierarchically controlled sequence stratigraphic analysis shows that the Lower Ordovician mixed carbonatesiliciclastic Mungok Formation, Korea consists of three depositional sequences: T1, T2, and T3 in ascending order. Sequence boundaries are generally marked by abrupt transition from coarse-grained shallow-water carbonates to finegrained deeper-water carbonates mixed with fine-grained siliciclastics, and show indication of subaerial exposure such as karstification. Within this sequence stratigraphic framework, facies characteristics indicate that the Mungok sequences were mostly deposited on a subtidal ramp without slope break. The Mungok ramp had been under the influence of frequent tropical storm activity during deposition. The difference in lithology of tempestites seems to have been controlled by the nature of substrates and by proximality. High-frequency cycles consist of upward-shallowing facies successions. Cycles of shallow-water and basinal deposits are not well represented, probably due to cycle amalgamation. Cycle stacking patterns do not show a consistent thickness change that is usually associated with a large-scale sea-level change probably because of unfilled accommodation space.

• Journal of the korean society of oceanography
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• v.35 no.3
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• pp.129-152
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• 2000

The Cheju Current (CC), defined here as a mean eastward flow in the Cheju Strait, mostly carries water of high temperature and salinity originating from the Kuroshio in winter and spring, the Cheju Warm Current Water (CWCW). The strong core of the eastward component of the CC is found close to Cheju Island (Cheju-Do, hereafter) in winter and spring with a peak speed of about 17.0 cm/s. The eastward flow weakens towards the northern Cheju Strait, and a weak westward flow occurs occasionally close to the southern coast of Korea. The volume transport ranges from 0.37 to 0.45 Sv(1 Sv=10$^6$ m$^3$/s) in winter and spring. Seasonal thermocline and harocline are formed in summer and eroded in November. The occurrence of the CWCW is confined in the southern Cheju Strait close to Cheju-Do below the seasonal thermocline in summer and fall, and cold water occupies the lower layer north of the CWCW which is thought to be brought into the area from the area west of Cheju-Do along with the CWCW. Stratification acts to increase both the speed of the CC with a peak speed of greater than 30 cm/s and the vertical shear of the along-strait currents. The strong core of the CC detached from the coast of Cheju-Do and shifted to the north during the stratified seasons. The volume transport in summer and fall ranges 0.510.66 Sv, which is about 1.5 times larger than that in winter and spring. An annual cycle of the cross-strait sea level difference shows its maximum in summer and fall and minimum in winter and spring, whose tendency is consistent with the annual variability of the CC and its transport estimated from the ADCP measurements. Moored current measurements west of Cheju-Do indicate the clockwise turning of the CC, and the moored current measurements in the Cheju Strait for 1530 days show the low-frequency variability of the along-strait flow with a period of about 37 days.

• Journal of Navigation and Port Research
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• v.37 no.5
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• pp.511-517
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• 2013

UNFCCC was adopted in 1992 in order to prevent global warming. However, as a lack of concrete reduction goal and implementation plan, UNFCCC could not have effectiveness. In 1997, Kyoto Protocol to UNFCCC was adopted and UNFCCC regime started practically binding on the parties. Global warming takes the leading role in changing marine environment such as the rising of water level and sea water temperature. Also, Ocean plays the vital role in storing carbon to prevent global warming. Meanwhile ships which get the propulsion generated by consuming the fossil fuel are identified as GHG source and the discussions regarding the control of GHG emitted from ships are still in progress in IMO. IMO instrument has some legal conflicts with UNFCCC in principle. Therefore, this paper reviews the present UNFCCC regime and UNCLOS. Also, it surveys activities of IMO and analyze the Amendment to MARPOL73/78 Annex VI which entered into force on January 1, 2013. Finally, conclusions suggest the improvements in order to ensure effectiveness the new Amendment to MARPOL73/78 practically.