Introduction to the study of oceanographic influences in the northern East China Sea due to the Three Gorges Dam

The Three Gorges Dam (TGD) as the world’'s largest hydroelectric dam, located at the Three Gorges in the middle of the Changjiang River, have been constructed for primarily preventing flooding downstream until 2009. The Changjiang River contributes about 80% of the total freshwater discharge from rivers supplying into the Yellow and East China Seas. Changiang Diluted Water (CDW) is a mixture of Changjiang freshwater with seawater, and is transported into the South Sea and the East Sea of Korea through the northern East China Sea (ECS). CDW is one of the most important sources of nutrients for marine ecosystem in the ECS. By controlling water flow through the TGD, some fresh water will be prevented from flowing into the ECS , affecting the surrounding ocean environments and their ecosystems. After the completion of the TGD, the variation of the Changjiang River discharge will be changed the oceanographic environments in the adjacent seas. The purpose of the study is to understand long-term variations and to help predict future changes in the marine environments and ecosystems of the East China Sea. We examined the water mass properties of the CDW, the distribution of nutrients and suspended sediments, the effect on the lower trophic ecosystem, and the implications for ocean circulation modeling for the CDW. Water mass structures in the northern ECS show strongly influenced by the high temperature and low salinity of the CDW. The concentrations of nitrate and phosphate in the CDW are characterized by relatively high, but silicate is low due to probably the construction of TGD. Data presented in this study can be used to national marine policies related to the predicted effects of the TGD.1

A study on the shallow gas in Gwangyang-Yeosu Bay

고해상 \\\\'Chirp\\\\' 탄성파자료와 시추퇴적물 자료를 이용하여 광양만과 여수해만의 천부가스층(shallow gas)의 발달분포 및 특성에 대해 연구하였다. 연구지역에서 발달한 천부가스층의 탄성파 음향특성은 가스층 상부경계면이 분명치 않은 음향 혼탁상(acoustic turbidity)과 매우 분명한 음향 덮개상(acoustic blanket)이 특징적으로 발달하였다. 음향 혼탁상은 광양만 전 지역과 여수해만 서쪽지역에 넓게 분포하는 반면, 음향 덮개상은 여수해만 동쪽의 수심이 깊은 수로지역에 일부 나타난다. 또한 해저면에 노출된 음향 혼탁상이 선박항로 지역을 따라 분포하는데 이는 가스 경계층 상부의 퇴적물 준설에 의한 것으로 판단된다. 음향 혼탁상 발달지역의 퇴적물특성은 광양만내 섬진강 델타지역은 뻘질혼합 모래층이 우세하고 그 밖의 지역은 뻘질층이 대부분이다. 이 지역에서 획득한 시추퇴적물에서 가스와 관련된 특별한 퇴적구조는 확인이 안됐다. 음향 덮개상 발달 퇴적층에서 획득한 시추퇴적물은 비교적 단단한 뻘질 퇴적층으로 구성되었으며, 퇴적층을 분리시킨 큰 규모의 수평의 균열구조와 수직의 미세한 선 구조들이 잘 발달하였다. 이는 퇴적물내 포함된 가스 팽창에 의해 형성된 구조로 해석된다. 천부 가스층 발달지역은 홀로세 고해수준 퇴적층(Holocene sea-level highstand deposits)이 두껍게 쌓인 지역과 대부분 일치하여 분포한다. 이 천부 가스층은 해수면이 현 위치에 도달한 후기 홀로세 고해수준 동안 섬진강에서 공급된 퇴적물내 유기물의 분해과정에서 형성된 메탄가스(methane gas)로 해석된다.2

마산만의 고해상 탄성파 퇴적층서 발달특성 연구

2

Green algae detecting and monitoring around the coast of China and Korea using multi-sensor satellite images

Extensive patches of floating algae have appeared since mid-June in coastal waters off Qingdao, China (Hu and He, 2008). The objectives of this study were : (i) to monitor the movement of green algae patch using the Moderate Resolution Imaging Spectroradiometer (MODIS) time series in the East China Sea and Korean Seas, (ii) to analyze and compare the shapes and sizes of green algae patch by using multi-sensor satellites data such as MODIS, ALOS AVNIR-2, Landsat ETM+, Kompsat-2 MSC. Ocean color remote sensing data is efficient for short and fixed term monitoring because of highly temporal resolution. But relatively lower spatial resolution (1,000m <) of ocean color remote sensing data make it difficult to detect the detail shape of green algae. Therefore, we used the MODIS (250m; band 1 and 2), ETM+ (30m), AVNIR-2 (10m) and MSC (4m) data having more high spatial resolution. MODIS-250m normalized difference vegetation index (NDVI) processing is efficient for the detecting of shapes of large-scale green algae patch. Most of the green algae are distributed around the coastal area of Qingdao, and some of them were getting smaller and moved to the southern sea of Korea. MODIS couldn’t detect small size of the green algae distributed around the southern part of Korea because the size of patch is less than 500m height. As compared with the last year data, the green algae distribution highly increased during summer season in 2008. Multi-sensor integration study has the potential to provide synoptic information of coastal environments monitoring.1

A review on the effect of Three Gorges Dam on oceanographic environments

The Yangtze River is the most longest river in Asia and the third longest in the world behind the Nile and the Amazon. Originating from the Tibetan Plateau at an elevation higher than 5000 m, the Yangtze River flows eastwards into the East China Sea (ECS). The Yangtze River freshwater contributes about 80% of the total discharge of fresh water from rivers around the Yellow Sea and ECS. Construction of the Three Gorges Dam (TGD), scheduled in the completion of 2009, is under way on the world&apos;s largest hydroelectric dam at the Three Gorges in the middle of the Yangtze River. Many environmental and sociological problems are included, though the TGD will produce positive effects socio-economically. By reducing the Yangtze discharge after the completion of the TGD, the changes in the physical, chemical, biological, and geological condition in the East China Sea Basin is expected. Besides, the south-to-north water transfer project to divert water from the Yangtze River to the country&apos;s thirsty northern areas was started in 2002. The water diversion the Yangtze River to the north will result more in the reduction of freshwater outflow to the ECS. The study to examine the effects of diminished the Yangtze River outflow on the oceanographic environmental in the ECS is needed immediately.1

Origin of organic carbon for the surface sediments in the Gwangyang Bay

한국 남해에 위치한 광양만의 남쪽은 대마난류수로 영향 받고 있으며, 만의 북쪽에는 섬진강의 담수가 유입되고 있다. 섬진강에서 유입되는 사질 퇴적물은 강 입구에 집중적으로 퇴적되고, 나머지 세립 퇴적물은 광양만 서측과 여수 해만으로 이어지는 남해 해역으로 부유되고 확산된다. 따라서 광양만 표층퇴적물은 육지에서 유입되는 하천의 영향이 우세한 가운데 외해에서 유입된 퇴적물이 복합되어있다. 광양만에서 2001년과 2002년에 총 89점의 표층퇴적물을 채취하여 입도분석을 하였고, 72개 정점에서 채취한 표층퇴적물에서 유기물의 특성(C/N, δ13C)을 분석하였다. 평균 입도는 2 Φ에서 9 Φ까지 다양하게 분포하고 있는데, 사질 퇴적물은 섬진강 하구역에 집중적으로 분포하고 니질 퇴적물은 광양만 서측과 여수해만에서 외해에 이르는 전 지역에 골고루 분포하고 있다. 전유기탄소 (TOC) 함유량은 섬진강 하구와 광양만 서측의 작은 하천이 유입되는 곳에서 가장 높고 여수해만과 외해인 남해가 만나는 지점에서 가장 낮은데 대체적으로 하천에서 멀어질수록 함유량이 낮아지는 경향을 보이고 있다. 전질소(TN) 함유량도 만 안쪽에서 높고 외해 쪽으로 갈수록 낮아지는 경향을 보이고 있다. 유기물의 C/N와 δ13C 값을 측정하여 광양만 표층퇴적물에 보존된 유기물의 기원을 추정하였다. C/N 비와 δ13C 값의 분포를 볼 때, 광양만 표층퇴적물 유기물은 대부분이 해양기원으로 해석할 수 있으나, 육성기원의 영향을 받는 지역들이 확인되고 있다. 섬진강 입구를 포함하여 만의 안쪽 부분은 여수해만을 걸쳐 남해해역으로 멀어지는 지역에 비하여 상대적으로 육성기원의 영향을 많이 받고 있다. 또한 만의 서쪽이 만의 동쪽에 비해 육성기원의 유기물 영향을 많이 받은 것으로 나타나는데, 이는 창조 시 만의 동쪽에 강한 조류가 흐르고, 낙조 시에는 서쪽에 강한 조류가 흐르는 광양만의 조류흐름과 밀접한 관련성을 보인다. 창조 시 외해로부터 만의 동쪽에 해양기원 유기물을 공급하고, 낙조 시에는 섬진강에서 배출되는 퇴적물이 조류를 따라 만의 서쪽에 퇴적된 결과로 판단되어진다.2

동중국해에 분포하는 뻘질 퇴적체의 음향학적 발달특성연구

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Sediment Characteristics in Gwangyang Bay and Adjacent Sea Area

남해 특별관리해역으로 지정되어 관리되고 있는 광양만 및 주변해역의 퇴적학적 특성을 밝히기 위해 표층퇴적물 시료를 채취하여 입도분석과 저서성유공충 분석을 하였다.2

Using Tintinnid Distribution for Monitoring Water Mass Changes in the Northern East China Sea

Tintinnid species distribution has been monitored in the northern East China Sea (ECS) in the summer of 2006 through 2011. This is used to understand the water mass movements in the northern ECS. The warm oceanic tintinnid species had largely spread in 2007 in the area, indicating that there was greater warm water extension into the northern ECS. However the extension of neritic water within the Changjiang diluted water mass has strengthened in 2008 and 2010 because the neritic species distribution had relatively grown in both years. These annual results based on the biological indicators of tintinnid species are well matched with the salinity change in the area. The warm oceanic species, Dadayiella ganymedes had frequently occurred over the study years and had shown a significant relationship with the salinity change. This is valuable as a key stone species for monitoring the intrusion of the Kuroshio within the northern ECS. Information from tintinnid biological indicators can support physical oceanography data to confirm ambiguous water mass properties.33Nscopuskc

Collapse of summer biological activity in the East China Sea during 1998-2014

The purpose of this study is to investigate climatological variations from the temporal and spatial surface satellite-driven chlorophyll concentration and to understand the physical mechanism that affect the distribution of chlorophyll in the East China Sea (ECS) during 1998-2014. A linear trend analysis of chlorophyll data reveals that, during recent 17 years, the spring bloom was enhanced in the most of the ECS, while summer and fall blooms were weakened. The increased spring (Mar. - May) chlorophyll was associated with strengthened winter (Dec. - Feb.) wind that probably provided more nutrient into the upper ocean from the deep. The causes of decreased summer (Jun. - Aug.) chlorophyll in the northern ECS were related one or more factors such as river runoff, wind pattern, SST (stratification of the water column), and limited nutrient supply. First, although 17-year summer chlorophyll variations were well correlated with the area influenced by the Changjiang River discharge, their variations was not linearly correlated with the river discharge after 2003. Second, spatially different patterns of chlorophyll were better related to spatial variations of wind-direction that the amount of river discharge during the summer season. Third, the decreased summer chlorophyll seemed to be related with the nutrient limitation. However, the decreased fall (Sep. - Nov.) chlorophyll was associated with weakened wind that tends to he East China Sea (ECS) during 1998-2014. A linear trend analysis of chlorophyll data reveals that, during recent 17 years, the spring bloom was enhanced in the most of the ECS, while summer and fall blooms were weakened. The increased spring (Mar. - May) chlorophyll was associated with strengthened winter (Dec. - Feb.) wind that probably provided more nutrient into the upper ocean from the deep. The causes of decreased summer (Jun. - Aug.) chlorophyll in the northern ECS were related one or more factors such as river runoff, wind pattern, SST (stratification of the water column), and limited nutrient supply. First, although 17-year summer chlorophyll variations were well correlated with the area influenced by the Changjiang River discharge, their variations was not linearly correlated with the river discharge after 2003. Second, spatially different patterns of chlorophyll were better related to spatial variations of wind-direction that the amount of river discharge during the summer season. Third, the decreased summer chlorophyll seemed to be related with the nutrient limitation. However, the decreased fall (Sep. - Nov.) chlorophyll was associated with weakened wind that tends to1