China Sea Area Research Articles

Spatiotemporal Profiling of Tropical Cyclones Genesis and Favorable Environmental Conditions in the Western Pacific Basin

AbstractWe analyze the spatiotemporal variations of tropical cyclone (TC) genesis and associated environmental conditions over the western North Pacific with a series of data science techniques, including Gaussian kernel estimator, wavelet, cross‐wavelet coherence, and regression analyses. There are significant semiannual and annual variations of TC genesis over the northern South China Sea and oceanic areas east of the Philippines. Variations on the El Niño–Southern Oscillation timescale are prominent between 5–10°N, 155–160°E. With reconstructed TC series on those frequencies, we further quantify the influences of environmental variables on the primary TC signals over western North Pacific. Over northern South China Sea and oceanic areas east of the Philippines, 40% of the reconstructed TC variance can be explained by vertical shear of zonal wind, relative humidity, and absolute vorticity. The reconstructed TC series near (160°E, 7°N) has strong but varying in‐phase relationships with El Niño–Southern Oscillation, which provides deeper insight into their nonstationary and nonlinear relations than their modest correlation.

Harmful Dinoflagellate Prorocentrum donghaiense Lu is Widely Distributed Along the East China Sea and Korean Coastal Area

There have been controversies regarding the taxonomy of Prorocentrum donghaiense, however Zhang et al. (2016) recently developed a probe with a quantitative real-time PCR (qPCR) assay that targets the D1–D2 region of the large subunit (LSU) rDNA of this species. We used this qPCR assay to determine the spatial distribution and abundance of P. donghaiense along the East China Sea (ECS) and Korean coastal area. During 15–22 May 2017, surface water samples were collected to extract genomic DNA and subsequent qPCR at 29 stations of the ECS and Korean coastal area, and the water temperature and salinity were also recorded at the time of sampling. The morphological features of P. donghaiense collected from the study area were identical to those of P. shikokuense and P. donghaiense reported in previous studies. Higher cell densities were recorded at water temperatures of 14.8 to 19.3°C and at salinity of 32.3 to 34.0, indicating that P. donghaiense can grow in a broad range of water temperatures. In addition, relatively higher cell densities were generally observed within stations that are affected by the Changjiang Diluted Water and Taiwan Warm Current flows, and low cell densities were prominent near the Japanese coast that is affected by the Tsushima Current flow and in the southwest coast of Korea. These results suggest that P. donghaiense occurs throughout a broad area of the ECS and Korean coastal area, and the current flows in the ECS may stimulate P. donghaiense blooms.

Strategi Indonesia dalam Mewujudkan Poros Maritim Dunia di Tengah Kebijakan Jalur Sutra Maritim China

<p><em>Global Maritime Fulcrume </em><em>Policy initiated by President Joko Widodo became one of the main focuses of national development during the Jokowi - JK presidency. The vision of the </em><em>Global Maritime Fulcrume</em><em> is triggered in the direction of Indonesia's national development based on marine activities. The enforcement of the sovereignty of the maritime territory of NKRI, the revitalization of the maritime economic sectors, the strengthening and development of maritime connectivity, the rehabilitation of environmental degradation and the conservation of biodiversity, as well as the enhancement of the quality and quantity of marine human resources are the main programs in the administration of President Jokowi to realize Indonesia as the </em><em>global maritime fulcrum</em><em>. Before the policy of the Global Maritime Fulcrume was initiated, in 2013 the Chinese Government under Xi Jinping will re-establish the concept of "The Silk Road" in its foreign policy agenda. Maritime Silk Road which is promoted to become China's new slogan in various international forums become one of the factors that can be utilized for Indonesia or also become one of the obstacle factor to towards the vision of maritime axis of the world considering China is a country that has made unilateral claim of South China Sea area which will surely stand against the stability of the maritime territory of Indonesia. Of course this makes Indonesia take special care in its maritime strategy.</em><em></em></p><p><em><br /> Keywords: </em><em>Global Maritim Fulcrum</em><em>, Maritime Silk Road, Maritime Strategy</em></p>

Study on the best calculation scheme of equivalent evaporation duct feature

In view of the lack of applicability of the existing equivalent evaporation duct feature calculation scheme in China's sea area and the requirement of the evaporation duct model test, this study used the actual sounding data in China's coastal areas and studied the applicability of the three computational schemes proposed by J.F. Howell, S.P. Oncley, and G.J. Steeneveld in different sea areas and different seasons by comparing the error and standard deviation. The applicability of the sea area shows that the best calculation scheme for the equivalent evaporating duct feature in the South China Sea is the scheme proposed by G.J. Steeneveld et al., while the optimal calculation method for the East China Sea is the scheme proposed by S.P. Oncley et al.; the seasonal applicability shows that the scheme proposed by G.J. Steeneveld et al. has the best-fitting results in the spring, while in the summer and winter, the scheme proposed by S.P. Oncley et al. fits best. These results provide a theoretical basis for the follow-up study.

Improving the Definition and Algorithms of China’s Coastline Considering the Diversity of Tidal Characteristics

Two commonly used definitions of coastline are compared and analyzed in this article. To build a more perfect digital tide-coordinated coastline model in China, we should first solve the problems of the existing definition and unclear algorithms of China’s coastline. On the basis of defining the coastline in China as the intersection of coastal land and the mean high water spring (MHWS), it should be further revised, and defined either as an intersection of coastal land and the MHWS or as a mean higher high water level (MHHWL) considering the diversity of tidal characteristics in China Sea areas. Since MHWS is related to the extreme of the lunar phase and MHHWL is related to the extreme of the angle of the lunar declination elevation, the algorithms to obtain them are more complicated than that of mean high water (MHW) used in the United States. We should consider the specific law of tidal movement in different tide types of the predominantly semidiurnal or diurnal sea areas in China when studying the precise algorithms for MHWS and MHHWL. Several experiments show that the difference between the two types of calculations of coastal height, such as water level observations and tidal predictions, is within centimeter level. The research results of this article have a certain reference value for countries with similar coastline features as in China.

Influence of the Kuroshio Interannual Variability on the Summertime Precipitation over the East China Sea and Adjacent Area

AbstractMuch attention has been paid to the climatic impacts of changes in the Kuroshio Extension, instead of the Kuroshio in the East China Sea (ECS). This study, however, reveals the prominent influences of the lateral shift of the Kuroshio at interannual time scale in late spring [April–June (AMJ)] on the sea surface temperature (SST) and precipitation in summer around the ECS, based on high-resolution satellite observations and ERA-Interim. A persistent offshore displacement of the Kuroshio during AMJ can result in cold SST anomalies in the northern ECS and the Japan/East Sea until late summer, which correspondingly causes anomalous cooling of the lower troposphere. Consequently, the anomalous cold SST in the northern ECS acts as a key driver to robustly enhance the precipitation from the Yangtze River delta to Kyushu in early summer (May–August) and over the central ECS in late summer (July–September). In view of the moisture budget analysis, two different physical processes modulated by the lateral shift of the Kuroshio are identified to account for the distinct responses of precipitation in early and late summer, respectively. First, the anomalous cold SST in the northern ECS induced by the Kuroshio offshore shift is likely conducive to the earlier arrival of the mei-yu–baiu front at 30°–32°N and its subsequent slower northward movement, which may prolong the local rainy season, leading to the increased rain belt in early summer. Second, the persistent cold SST anomalies in late summer strengthen the near-surface baroclinicity and the associated strong atmospheric fronts embedded in the extratropical cyclones over the central ECS, which in turn enhances the local rainfall.

Seawater quality criteria derivation and ecological risk assessment for oil pollution in China

The establishment of water quality criteria (WQC) for oil pollutants is the basis for ecological risk assessment of marine oil pollution. Ecotoxicity data of oil pollutants to marine organisms in China were collected and toxicity test of oil to nine Chinese marine organisms were performed. Based on the WQC guidelines of the United States, the sea WQC of oil pollutants in China were studied. Then, the ecological risk of oil in 7 sea areas of China was assessed. Results showed that the long-term and short-term criteria of oil pollutants in China are 7.3 μg/L and 36 μg/L, respectively. Except for Qinhuangdao and Xiamen sea areas, the highest oil concentration in the other five sea areas exceeded the long-term WQC by >10 times, and the highest oil concentration in the Pearl River Estuary exceeded the long-term WQC by >100 times, indicating serious ecological risk.

Analysis of the scientific and technological innovation efficiency and regional differences of the land–sea coordination in China's coastal areas

The overall strategy for land-sea coordination is important for scientific and technological innovation efficiency in China's coastal areas. In this paper, the country's mixed land and sea regions were selected for study, including two land and ocean subsystems with input and output index systems. Based on the variation coefficient method, the global Malmquist–Luenberger (GML) index was used to calculate the scientific and technological development efficiency of coordinated plans for China's coastal land and sea areas from 2006 to 2015 and to analyze the regional differences among these plans. The conclusions are as follows. First, the total factor productivity growth rate of science and technology innovation efficiency in China's coastal areas is primarily larger than 1 and at the frontier of efficiency. The efficiency of mixed areas is higher than that of separated land and sea areas, and the differences in regional technological innovation efficiencies has gradually narrowed. The change in technical efficiency is consistent with changes in the GML index, and the financial crisis of 2008–2009 had a significant positive impact on pure technical efficiency. Second, the coordinated plans for land and sea areas are realized and spatial differences in scientific and technological innovation efficiency in China's coastal areas are classified according to scientific and technological innovation in China's coastal areas. Hebei and Liaoning are classified according to the land efficiency type; Jiangsu and Zhejiang are classified as the marine efficiency-driven type; and the Shandong, Tianjin, Shanghai, and Pan-Pearl River Delta regions are classified as the efficiency of mixed land and sea areas type. Drivers of regional differences mainly include economic development levels, differences in industry structure, the personnel structure of scientific and technological systems, and the state of production and the influence of the government.

Reservoir forming conditions and key exploration technologies of Lingshui 17-2 giant gas field in deepwater area of Qiongdongnan Basin

On September 15, 2014, China National Offshore Oil Co., Ltd announced that a high production of oil and gas flow of 1.6 × 106 m3/d was obtained in Well LS17-2-1 in deepwater area in northern South China Sea, which is the first great oil and gas discovery for self-run deepwater exploration in China sea areas, and a strategic breakthrough was made in natural gas exploration in deepwater area of Lingshui sag in Qiongdongnan Basin. Under the combined action of climax of international deepwater exploration, high oil prices, national demands of China, practical needs of exploration, breakthroughs in seismic exploration and testing technologies, innovations in geological cognition and breakthroughs in deepwater operation equipment, Lingshui 17-2 gas field is discovered. Among these factors, the innovation in reservoir forming geological cognition directly promotes the discovery. The quality of seismic data in the early time is poor, so key reservoir forming conditions such as effective source rocks, high quality reservoirs and oil-gas migration pathways are unable to be ascertained; with support of new seismic acquisition and processing technology, some researches show that Lingshui sag is a successive large and deep sag with an area of 5000 km2 and the maximum thickness of Cenozoic stratum of 13 km. In the Early Oligocene, the Lingshui sag was a semi-closed delta-estuarine environment, where the coal-measure and marine mudstones in Lower Oligocene Yacheng Formation were developed. The Lingshui sag is a sag with high temperature, and the bottom temperature of source rocks in Yacheng Formation can exceed 250 °C, but the simulation experiment of hydrocarbon generation at high temperature indicates that the main part of this set of source rock is still in the gas-generation window, with resources of nearly 1 trillion cubic meters, so the Lingshui sag is a hydrocarbon-rich generation sag. In the Neogene, the axial canyon channel from the Thu Bon River in Vietnam passed through the Lingshui sag, and five stages of secondary channels were developed in the axial canyon channel, where four types of reservoirs with excellent physical properties including the axial sand, lateral accretion sand, natural levee sand as well as erosion residual sand were developed, and lithologic traps or structural-lithologic traps were formed. The diapiric zone in the southern Lingshui sag connects deep source rocks in Yacheng Formation and shallow sandstones in the channels, and the migration pattern of natural gas is a T-type migration pattern, in other words, the natural gas generated from Yacheng Formation migrates vertically to the interior of the channel sandbody, and then migrates laterally in the channel reservoirs and forms the reservoirs. Innovations of geophysical exploration technologies for complicated geological conditions of deepwater areas are made, such as the detuning comprehensive quantitative amplitude hydrocarbon detection technology, which greatly improves the success rate of deepwater exploration; key technologies of deepwater safety exploratory well testing represented by the platform-dragged riser displacement technology are developed, which greatly reduces the drilling test cost. The above key exploration technologies provide a strong guarantee for the efficient exploration and development of Lingshui gas field.

Evaluation study for phosphorus mobilisation-release behaviour on different marine sediments: focus on phosphate sorption characteristics

Environmental contextPhosphorus is a key nutrient element associated with eutrophication in aquatic ecosystems. We studied phosphate sorption processes, which play a key role in phosphorus cycling, in sediments collected from 23 sites including estuary, coastal sea and aquaculture areas in China. The results show the influence of sediment type on phosphorus buffering capacity and allow better interpretation of phosphorus migration in aquatic ecosystems. AbstractPhosphorus is well known as an important nutrient element associated with eutrophication in the marine ecosystem, and its sorption on sediments plays a key role in its immobilisation in the bio-geochemical cycle. In this paper, the sorption behaviour of phosphorus onto sediments collected from 23 different sites in estuary, coastal sea and aquaculture areas of China was studied. The main aim is to determine the phosphorus sorption characteristics of these sediments thereby assessing their phosphorus buffering capacities. Both kinetic and equilibrium isotherms of the sorption and desorption of phosphorus were assessed. The resultant sorption and desorption kinetic curves fit well to a two-compartment first-order equation. The equilibration time was considered as 48h. The isotherms agreed well with the Freundlich and Langmuir equations. The hysteresis coefficient values showed an obvious sorption-desorption hysteresis. Decreasing salinity was favourable for the sorption ability in the range from 30 to 3. The mean values of the phosphorus sorption-desorption equilibrium concentration and the maximum phosphorus sorption capacity were 0.098mgL−1 and 0.086mgg−1 for sediments in the Changjiang Estuary and East China Sea shelf, and 0.138mgL−1 and 0.067mgg−1 for the sediments in the aquaculture area. The fractions of clay, calcite and organic matter influenced the sorption and retention abilities and the effects were different for sediments obtained from different origins.

Distribution and pollution assessment of heavy metals in the intertidal zone environments of typical sea areas in China

The heavy metals (Cu, Cr, Zn, Cd, Pb) were analysed for 217 surface sediment samples collected across 14 typical intertidal zone areas in China. The data reveals the heavy metals spatial distribution patterns and correlations among their concentrations. Cu, Zn, Cd and Cr showed similar trends of spatial variation and the correlations between the concentrations of every two heavy metals were significantly positive except for the correlation between Pb and Cr concentrations. By using Nemerow index method, Enrichment factor and Sediment Quality Guidelines, it is found that Hangzhou Bay and Jiulong River Estuary were polluted, Yingluo Bay and Dongzhaigang Bay were Cd-rich areas. Except Beidaihe shoal, Sishili Bay and Yingluo Bay that were not exposed to any ecological risk of heavy metals and had no adverse biotoxic effects, the other 11 typical intertidal zone areas were exposed to moderate ecological risk of heavy metals in the sediment with potential adverse biotoxic effects.

Improved simulation–optimization approach for identifying critical and developable pollution source regions and critical migration processes for pollutant load allocation

Simulation–optimization approaches are widely used in land-based pollutant load allocation and management. However, existing simulation–optimization approaches do not optimize the entire pathway of pollution (i.e., generation, transportation, and emission). Thus, the selected allocated load scheme and its reduction management are incomplete and non-optimal in supporting effective reduction measures to set in further. This study aims to establish a simulation–optimization load allocation approach covering the entire pathway of pollution and construct separate allocated loads for each migration process. By comparing the allocated loads to the actual pollutant loads, the critical and developable pollution source regions (CPSRs and DPSRs) and the critical pollution migration processes (CPMPs) are identified, and specific pollution management indicators are established for each pollution source region. This approach is applied to the Bohai Rim, which is currently a major economic development center with a most seriously deteriorating sea area in China. The CPSRs, DPSRs, and CPMPs for total nitrogen are identified, and comparisons of the management indicators with existing approaches are made. Water quality under the allocated load emissions is simulated via a simulation water quality model and compared with that of the actual pollutant loads. Quantitative results indicate that the new approach combines the specific mitigation indicators for each CPSR and CPMP when allowing the extra generation of allocated loads for DPRSs while keeping the water quality of the Bohai Sea under control.

The Climatic Characteristics of Surface Salinity in the South China Sea and the Adjacent Northwest Pacific Ocean

Based on the high-resolution SODA oceanographic hydrological reanalysis data, analyzing the climatic characteristics of the surface salinity in the South China Sea and the adjacent Northwest Pacific Ocean during the new climatic baseline period from 1981 to 2010 in this paper. The results showed that: Sea surface salinity (SSS) in the research area could be obviously divided into two areas, the South China Sea and the Northwest Pacific Ocean. The SSS in the South China Sea was lower than that in the Northwest Pacific Ocean. The annual amplitude of SSS in the South China Sea varied in different sea areas, but it was smaller and almost same in the Northwest Pacific Ocean area. The inter-monthly variations of SSS were the same at continental shelf side and the sea area near the island in the South China Sea, however differences existed with that in the central of the South China Sea. The inter-monthly variation of SSS in the Northwest Pacific Ocean varied from low latitude to high latitude and the salinity field showed “high-low-high” distribution. According to the climatic characteristics of salinity, the research area could be divided into five climatic zones. Among them, the South China Sea was divided into areas A and B, and the Northwest Pacific Ocean was divided into areas C, D, and E. As water invading from the Northwest Pacific Ocean to the South China Sea area that caused a higher salinity in area B than in area A. The northern equatorial current influenced on the Northwest Pacific Ocean, that caused the salinity in area D lower than in areas C and E.

Seismic activity characteristics in the East Sea area

Seismic activity characteristics in the East Sea area

東支那海同緯度圏における民家・集落の空間構成に関する比較研究(2)

東支那海同緯度圏における民家・集落の空間構成に関する比較研究(2)

Parameter optimization of gravel packing sand control method for natural gas hydrate production

According to the research on the method of sand control for oil and gas wells at home and abroad, it was considered that gravel packing sand control method was an effective sand control method for gas well mining. In order to solve the problem of large amount of sand out for natural gas hydrate production, related problems of difficult sand control, that technology was explored of sand control and optimization method that was suitable for mud sand reservoir of natural gas hydrate production. Based on the low pressure strata in the northern South China Sea area of our country, characteristics of low cementation, it was initially chosen particle size of 0.150-0.200mm sand control gravel through theoretical calculation, through it, the best gravel size range was 0.200-0.250mm and the thickness was 40mm.

A low-angle normal fault and basement structures within the Enping Sag, Pearl River Mouth Basin: Insights into late Mesozoic to early Cenozoic tectonic evolution of the South China Sea area

The basement structure of the Cenozoic Enping Sag, within the Pearl River Mouth Basin on the northern margin of South China Sea, is revealed by borehole-constrained high-quality 3D seismic reflection data. Such data suggest that the Enping Sag is bounded in the north by a low-angle normal fault. We interpret this low-angle normal fault to have developed as the result of the reactivation of a pre-existing thrust fault part of a pre-Cenozoic thrust system. This is demonstrated by the selective reactivation of the pre-existing thrust and by diffuse contractional deformation recognized from the accurate analysis of basement reflections. Another significant result of this study is the finding of some residual rift basins within the basement of the Enping Sag. Both the thrust system and the residual basins are interpreted to have developed after the emplacement of continental margin arc-related granitoids (J3–K1) that define the basement within the study area. Furthermore, seismic sections show that the pre-existing residual rift basins are offset by the main thrust fault and they are both truncated by the Tg unconformity. These structural relationships, interpreted in the frame of previous studies, help us to reconstruct a six-event structural evolution model for the Enping Sag from the late Mesozoic to the early Cenozoic. In particular, we interpret the residual rift basins to have formed as the result of back-arc extension due to the slab roll-back of the Paleo-Pacific Plate subduction in the early K2. The thrust system has recorded a compressional event in the late K2 that followed the back-arc extension in the SCS area. The mechanism of this compressional event is still to be clarified, and might be related to continuous subduction of the Paleo-Pacific Plate or to the continent-continent collision between a micro-continental block and the South China margin.

Design, test and numerical simulation of a low-speed horizontal axis hydrokinetic turbine

A small-scale horizontal axis hydrokinetic turbine is designed, manufactured and studied both experimentally and numerically in this study. The turbine is expected to work in most of China's sea areas where the ocean current velocity is low and to supply electricity for remote islands. To improve the efficiency of the turbine at low flow velocities, a magnetic coupling is used for the non-contacting transmission of the rotor torque. A prototype is manufactured and tested in a towing tank. The experimental results show that the turbine is characterized by a cut-in velocity of 0.25 m/s and a maximum power coefficient of 0.33, proving the feasibility of using magnetic couplings to reduce the resistive torque in the transmission parts. Three dimensional Computational Fluid Dynamics (CFD) simulations, which are based on the Reynolds Averaged Navier–Stokes (RANS) equations, are then performed to evaluate the performance of the rotor both at transient and steady state.

A Multi-Objective Partition Method for Marine Sensor Networks Based on Degree of Event Correlation.

Existing marine sensor networks acquire data from sea areas that are geographically divided, and store the data independently in their affiliated sea area data centers. In the case of marine events across multiple sea areas, the current network structure needs to retrieve data from multiple data centers, and thus severely affects real-time decision making. In this study, in order to provide a fast data retrieval service for a marine sensor network, we use all the marine sensors as the vertices, establish the edge based on marine events, and abstract the marine sensor network as a graph. Then, we construct a multi-objective balanced partition method to partition the abstract graph into multiple regions and store them in the cloud computing platform. This method effectively increases the correlation of the sensors and decreases the retrieval cost. On this basis, an incremental optimization strategy is designed to dynamically optimize existing partitions when new sensors are added into the network. Experimental results show that the proposed method can achieve the optimal layout for distributed storage in the process of disaster data retrieval in the China Sea area, and effectively optimize the result of partitions when new buoys are deployed, which eventually will provide efficient data access service for marine events.

First discovery of Eocene coastal-estuarine ostracods from Japan, with the geological history of the migration of estuarine genera in the Far East

AbstractThe genusNeomonoceratina, which dominated the ostracod assemblage in the uppermost part of the Akasaki Formation (Miroku Group) of the Kyushu Island, Japan, is associated with the benthic foraminiferAmmonia cf.beccarii, molluscaTerebralia? sp. andAnomiasp., and the oogonium of Charophyceae, indicating a marine-to-brackish estuarine environment involving inflowing freshwater. This is the first record of Eocene coastal-estuarine ostracods from the eastern margin of the Eurasian continent and demonstrates that different pre-Neogene coastal-estuarine ostracod assemblages flourished in this region. The assemblages comprised five ostracod species (including one novel species) assigned to the generaNeomonoceratina,Paijeiborchella,PropontocyprisandParakrithella. These species exhibited genus-level links with the Eocene borehole cores along the continental shelf of the East China Sea and other areas of Kyushu. Fossil data of characteristic Eocene coastal-estuarine genera collected worldwide indicate that different characteristic genera inhabited each region. For example,Neomonoceratinaoriginated on the Indian subcontinent by the Early Paleocene period at the latest, along with the northern drift of the Indian subcontinent. These species subsequently diversified west and east with the equatorial current and counter-current via the Tethys and reached the eastern margin of the Eurasian continent among the various eastwards-migrating species, where one genus ultimately adapted to the coastal-estuarine environment. Notably, the coastal-estuarine ostracod assemblage of the eastern margin of the Eurasian continent differs completely from that of the Tethys during the Eocene period. Our results suggest that coastal-estuarine ostracod assemblages are a powerful tool for palaeogeographic reconstruction.