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1.
Temperature, salinity and density structures were observed on Sept. 23 and 24, 1986 at one vertical section across the East China Sea shelf edge by an advanced type of towed vehicle with CTD sensors which was developed by the Japan Marine Science and Technology Center. The vehicle was towed at a speed of 2.5 m s−1 down to 150 m depth and at intervals of 170–500 m width. The observed profile was 50 km long on Sept. 23 and 70 km long on Sept. 24 along the cross-shelf section. An on-ship acoustic Doppler current profiler was simultaneously used to measure current velocities at depths of 20, 50 and 100 m.Interesting features were noticed. Firstly, there was a vertical displacement of pycnoclines at the lower edge of the surface mixed layer accompanied by vertical inversion of the salinity and temperature in the vicinity of the shelf edge. Pycnoclines were displaced upward by 12 m toward the outer edge on Sept. 23 and by 20 m on Sept. 24. On Sept. 23, the salinity inversion took place in a layer 20 m thick and 8 km wide, whereas the temperature inversion took place in a layer 8 m thick and 1.5 km wide. These vertical inversions were probably generated by vertical shear of tidal currents which was observed by the Doppler current profiler. These results throw light on understanding the vertical mixing process of stratified water on the continental shelf edge. Secondly, an intrusion of the shelf water into the Kuroshio water was observed along pycnoclines below the surface mixed layer 60 to 70 m deep in the Kuroshio region outer break. The measurement was successful in showing a horizontal mixing process of the shelf water and the Kuroshio water which could not be found out by standard CTD observations.  相似文献   

2.
In order to clarify detailed current structures over the continental shelf margin in the East China Sea, ADCP measurements were carried out in summers in 1991 and 1994 by the quadrireciprocal method (Katoh, 1988) for removing diurnal and semidiurnal tidal flows from observed flows, together with CTD measurements. We discussed the process of the Tsushima Current formation in the East China Sea. The Tsushima Current with a volume transport of 2 Sv (1 Sv=106 m3s–1) was found north of 31°N. A current with a volume transport of 0.4 Sv was clearly found along the 100 m isobath. Between the Kuroshio and the current along the 100 m isobath, southeastward component of velocity was dominant compared to northwestward one. Four eastward to southeastward currents were found over the sea bed shallower than 90 m depth. Total volume transport of these four currents was 1 Sv, and they seemed to be originated from the Taiwan Strait. Intrusion of offshore water into the inner shelf northwest of Amami Oshima was estimated to have a volume transport of 0.6 Sv. It is concluded that the Tsushima Current is the confluence of these currents over the continental shelf margin with the offshore water intruding northwest of Amami Oshima.  相似文献   

3.
黑潮与邻近东海生源要素的交换及其生态环境效应   总被引：2，自引：0，他引：2  
宋金明  袁华茂 《海洋与湖沼》2017,48(6):1169-1177
黑潮与东海生源要素的交换对东海的生态环境有重大影响,交换主要是经台湾东北部海域输送至东海陆架和通过日本九州西南海域由东海陆架向外海的黑潮输出两个通道。中国科学院海洋先导专项对黑潮与邻近东海生源要素的交换特征进行了系统的调查和研究,获得了一些新的认识:(1)在台湾东北部区域,碳主要以表层水-次表层水为载体输入,秋季的输入量高于夏季;黑潮溶解态营养盐的输入占据绝对主导地位,且以黑潮次表层热带水-中层水的输入为主,输入通量春季高于夏、秋季,可为东海春季水华提供一定的物质基础,但输入到东海的黑潮水其氮磷比与Redfield比值(16:1)接近,这些"正常水"——黑潮的输入显然对调和东海异常高的氮磷比有重要的作用,从而对东海的生态环境起到"稳定和缓冲"作用。所以,黑潮水对东海的输入不仅维持补充了东海生态系统运转所需的生源要素,更为重要的是缓冲了受人为影响强烈的东海海水的高氮磷比,使东海本已失常的营养盐结构向合适的氮磷比方向转变。因此,黑潮与东海生源要素的输入在一定程度上起着稳定和缓和东海生态环境的作用。(2)通过构建的海水Ba-盐度新指标体系,定量细致刻画了黑潮对东海生源物质在台湾东北部区域的输入范围和程度,黑潮次表层水从台湾东北陆架坡折处沿底部向北偏西方向入侵东海,其近岸分支可以入侵到浙江近岸,其黑潮次表层水占比仍可达到65%左右。垂直方向上,陆架外侧站位受黑潮次表层水的影响范围更大,黑潮水占50%比例位置可延伸至外侧TW0-1站位(122.59°E,25.49°N)表层,而内侧靠近大陆的站位则只限于陆架中部位置底层。  相似文献   

4.
Two intensive, high-resolution hydrographic surveys during April 2000 and May 2001 are used to characterize the thermohaline and current structure at the shelfbreak in the South China Sea. In 2000, a strong anticyclonic circulation was present in the northern portion of the South China Sea with strong onshore currents east of Dongsha Island. The flow became polarized along isobaths as it encountered shallow water, with northeastward flows of over 0.9 m/s along steep topography. The flow was driven by strong density contrasts between waters of the outer shelf and upper slope. Shelf water was both cooler and more fresh than the water offshore, which had salinities close to that of Kuroshio water. In contrast, the mean flow in the northern South China Sea was predominantly cyclonic in 2001. Flow over the slope was to the southwest at up to 0.2 m/s. The water mass properties of the outer shelf and upper slope were similar, so that there were not the strong cross-shelf density gradients present as in 2000. A potential difference between the water mass structure of the two years was the difference in cooling during the preceding winters. In December, 1999, unusually strong cooling may have resulted in cooler shelf waters relative to the following year. The ASIAEX study area may be a particularly sensitive region to both seasonal and interannual variability, as it is near a bifurcation point associated with the Kuroshio Intrusion into the South China Sea.  相似文献   

5.
The coast of Zhejiang Province is a zone of maximum tidal ranges in China. One of the causes is the influence of the adjacent continental shelf. A model is presented in this paper, whose theory suggests that the amplitudes of semidiurnal tides should be amplified on the southern continental shelf of the East China Sea, while those of diurnal tides should not. The values computed from the equations are basically in agreement with observations.  相似文献   

6.
The effects of tidal currents (i.e., barotropic and internal tides) are important in the biogeochemistry of a coastal shelf sea. The high-frequency of currents and near-bottom temperatures collected in three consecutive southwest monsoon seasons (May, June, July and August of 2013 until 2015) is presented to reveal the role of the tidal currents to the temperature variability in the coastal shelf sea of the east coast of Peninsular Malaysia (ECPM), south of the South China Sea (SCS). The results of a spectral density and harmonic analysis demonstrate that the near-bottom temperature variability and the tidal currents are influenced by diurnal (O1 and K1) and semidiurnal (M2) tidal currents. The spectral density of residual currents (detided data) at 5, 10 and 16 m depth also shows significant peaks at the diurnal tidal frequency (K1) and small peaks at the semidiurnal tidal frequency (M2) indicating the existence of internal tides. The result of the horizontal kinetic energy (HKE) shows a strong intermittent energy of internal tides in the ECPM with the strongest energy is found at 16 m depth during a sporadic cooling event in June and July. A high horizontal cross-shore heat flux (16 m) also indicates strong intrusions of cooler water into the ECPM in June and July. During the short duration of cold pulse water observed in June and July, a cross-wavelet analysis also reveals the strong relationship between the near-bottom temperatures and the internal tidal currents at the diurnal tidal frequency. The intrusion of this cooler water is probably related to the monsoon-induced upwelling in June. It is loosely interpreted that the interaction between the strong barotropic tides and the steep slope in the central basin of the SCS under the stratified condition in southwest monsoon has generated these internal tides. The dissipation of internal tides from the slope area probably has driven the cold-upwelled water into the ECPM coastal shelf sea when the upwelling intensity is the highest in June and July.  相似文献   

7.
东海东北部春季若干重要水文结构的分析   总被引：7，自引：2，他引：7  
本文主要基于韩国海洋研究所在东海沿岸海洋过程试验中收集的ＣＴＤ资料，分析了１９９５年春季出现在东海东北部的一些重要水文结构。结果表明，一种锋涡状结构出现在黑潮向东转折点附近。它不仅使邻近海域的水文结构变得更复杂，而且诱发黑潮水与陆架水间活跃的交换。在陆架坡折处观测到若干孤立的陆架水块，可能是锋涡的卷挟作用所致；该海域存在４个水团，即黑潮水、对马暖流水、陆架水和混合水。对马暖流水分为上下两层：上层水为变性黑潮水，盐度比黑潮水约低０．１，底层对马暖流水仅位于冲绳海槽区，并有着与黑潮中层水相同的温、盐特性；一种双锋结构出现在邻近黑潮的陆架边缘附近。在内陆架形成的陆架锋，由北向南伸展时，愈来愈偏向陆架边缘。而黑潮锋沿九州以西深槽的陆架边缘向北伸展。在黑潮转折点附近，两锋几乎合并为一条锋。狭窄的锋带由黑潮水及其变性水和陆架水的混合水所占据。  相似文献   

8.
台湾东北部黑潮次表层水入侵的季节变化规律   总被引：5，自引：1，他引：4  
台湾东北部,黑潮次表层水常年入侵东海陆架。但是黑潮次表层水入侵的季节变化规律,尚存在很多不明之处。本文基于2009至2011年间东海4个航次的CTD实测数据,研究了黑潮次表层水入侵东海过程的季节变化规律,发现:黑潮次表层水入侵在春末夏初开始加强,夏季最强,秋季开始减弱,冬季最弱。入侵的黑潮次表层水起源深度也随季节变化有所不同。另外,结果还表明黑潮次表层水入侵存在明显的短期变动。  相似文献   

9.
Sources of water in the Taiwan Strait   总被引：5，自引：0，他引：5  
The conveyor of the source water that feeds into the Taiwan Strait (TS), particularly from the south, is investigated using historical CTD (Conductivity-Temperature-Depth) data and a North Pacific Ocean and East Asian seas coupled model. The modeled currents and drifter trajectories suggest that the Kuroshio Branch Water (KBW) rarely flows directly into the TS from the Luzon Strait (LS) in winter; instead the massive westward movement of the Kuroshio conveys high salinity water to the southeastern TS through a loop-like route. In summer, the modeled flow fields suggest that the Kuroshio surface currents hardly intrude into the TS directly from the LS. Observations and model results show that the monsoon-driven northeastwardflowing currents in the northern South China Sea transport relatively low salinity water through the entire TS.  相似文献   

10.
《Oceanologica Acta》1998,21(5):713-716
Exchanges between the East China Sea (ECS) and the Kuroshio have been recalculated by taking into consideration the intra-annual variation of salinity on the shelf. Flux through the Taiwan Strait, previously unavailable data in the Yellow Sea and in the central and northern ECS, denitrification and ground water fluxes are now also considered. The Kuroshio Intermediate Water remains the major source of nutrients on the East China Sea continental shelf, with slightly more upwelling in the dry season than in the wet season.  相似文献   

11.
The Sofala Bank, a wide shelf located along the central coast of Mozambique, hosts tides with high amplitudes. The Regional Ocean Modelling System (ROMS) was used to analyse the tidal currents on the bank and to investigate their effects on the stratification and generation of tidal fronts. During spring tides, barotropic tidal currents with maximum values ranging from 40 cm s–1 to 70 cm s–1 are found on the central bank. The major axis of the tidal ellipses for M2 and S2 follow a cross-shelf direction with mainly anticlockwise rotation. Similar to observations, three distinct regimes occur: (i) a warm well-mixed region on the inner shelf where the depths are <30 m; (ii) a wellmixed colder region above the shelf edge; and (iii) a stratified region offshore. The model shows that the tides lead to cooling where two criteria are satisfied: the Simpson and Hunter parameter log10(h/U3) <3.2 and the depth h >30 m. The shelf edge of the bank is important for internal tide generation. Two frontal structures result, one offshore between cooler mixed waters and warmer stratified waters and the other in shallow inshore waters, between cooler mixed waters and solar heated mixed waters.  相似文献   

12.
Spring phytoplankton bloom in the fronts of the East China Sea   总被引：2，自引：0，他引：2  
Frontal areas between warm and saline waters of the Kuroshio currents and colder and diluted waters of the East China Sea (ECS) influenced by the Changjiang River were identified from the satellite thermal imagery and hydrological data obtained from the Coastal Ocean Process Experiment (COPEX) cruise during the period between March 1st and 10th, 1997. High chlorophyll concentrations appeared in the fronts of the East China Seas with the highest chlorophyll-a concentration in the southwestern area of Jeju Island (~2.9 mg/m3) and the eastern area of the Changjiang River Mouth (~2.8 mg/m3). Vertical structures of temperature, salinity and density were similar, showing the fronts between ECS and Kuroshio waters. The water column was well mixed in the shelf waters and was stratified around the fronts. It is inferred that the optimal condition for light utilization and nutrients induced both from the coastal and deep waters enhances the high phytoplankton productivity in the fronts of the ECS. In addition, the high chlorophyll-a in the fronts seems to have been associated with the water column stability as well.  相似文献   

13.
Five oceanographic surveys were carried out in the East China Sea (ECS) and Yellow Sea from 1999 to 2003. In all, seven different sections were surveyed, but one section (the PN section) was observed on every cruise. Two time-series stations were also surveyed, one located at the Changjiang River mouth, the other over the continental shelf in the PN section.We identified biogeochemical characteristics for waters close to the Changjiang Estuary and in the Kuroshio waters (KW), respectively. Resuspension is a strong feature near bottom over the ECS continental shelf, with suspended matter values 13 times higher than that for the surface. A model of particulate organic carbon (POC) dynamics based on a rectangle equation reveals that POC concentration close to the Changjiang Estuary varies with a semidiurnal period of ∼13 h, coinciding with the tidal period. The upper limit for POC residence times in the seasons we covered over the shelf are estimated to be on the order of weeks and generally increase seaward from near the Changjiang Estuary to the KW. Short POC residence times suggest that POC in the ECS is rapidly exported from euphotic waters.A nepheloid layer, observed as elevated suspended matter in near the bottom of the water column, is important in particle transfer over the shelf, especially in winter when the residual current flows mainly eastward. Cross-shelf transport of POC via the nepheloid layer is estimated to be 0.22 × 1012 g yr−1. Comparison with other work indicates that POC transport is ∼2% of the Changjiang POC input.  相似文献   

14.
A high-resolution, regional, numerical-model-based, real-time ocean prediction system for the northern South China Sea, called the Northern South China Sea Nowcast/Forecast System (NSCSNFS), has been used to investigate subtidal mesoscale flows during the time period of the Asian Seas International Acoustic Experiment (ASIAEX) field programs. The dynamics are dominated by three influences; 1) surface wind stress, 2) intrusions of the Kuroshio through Luzon Strait, and 3) the large-scale cyclonic gyre that occupies much of the northern South China Sea. Each component primarily drives currents in the upper ocean, so deep currents are rather weak. Wind stress is especially effective at forcing currents over the shallow China shelf. The Kuroshio intrusion tends to flow westward until it meets the northern edge of the large-scale cyclonic gyre. Together, these currents produce an intense, narrow jet directed northwest toward the continental slope, often in the region of the ASIAEX field programs. Upon reaching the slope, the current splits with part flowing northeastward along the slope and part flowing southwestward, producing large horizontal and vertical shears and making this region dynamically very complicated and difficult to simulate. The Kuroshio intrusion tends to be stronger (weaker) when the northeasterly winds are strong (weak) and the large-scale gyre is farther south (north), consistent with conclusions from previous model studies. At the northern boundary, the model produces a persistent northward flow through Taiwan Strait into the East China Sea. Data assimilation in the NSCSNFS model is shown to dampen the system, extracting energy and causing the entire system to spin down.  相似文献   

15.
Barotropic tide in the northeast South China Sea   总被引：2，自引：0，他引：2  
A moored array deployed across the shelf break in the northeast South China Sea during April-May 2001 collected sufficient current and pressure data to allow estimation of the barotropic tidal currents and energy fluxes at five sites ranging in depth from 350 to 71 m. The tidal currents in this area were mixed, with the diurnal O1 and K1 currents dominant over the upper slope and the semidiurnal M2 current dominant over the shelf. The semidiurnal S2 current also increased onshelf (northward), but was always weaker than O1 and K1. The tidal currents were elliptical at all sites, with clockwise turning with time. The O1 and K1 transports decreased monotonically northward by a factor of 2 onto the shelf, with energy fluxes directed roughly westward over the slope and eastward over the shelf. The M2 and S2 current ellipses turned clockwise and increased in amplitude northward onto the shelf. The M2 and S2 transport ellipses also exhibited clockwise veering but little change in amplitude, suggesting roughly nondivergent flow in the direction of major axis orientation. The M2 energy flux was generally aligned with the transport major axis with little phase lag between high water and maximum transport. These barotropic energy fluxes are compared with the locally generated diurnal internal tide and high-frequency internal solitary-type waves generated by the M2 flow through the Luzon Strait.  相似文献   

16.
The possible origin and cause of the less saline shelf water detected in the Kuroshio subsurface layer around the shelf edge of the East China Sea are investigated using observational results obtained in May 1998–2001 in conjunction with a dataset archived by Japan Oceanographic Data Center and a numerical model. The observations show that subsurface intrusions of less saline water are always detected in May in layers above 24.5σθ isopycnal surface, and that salinity inversions (i.e., areas in which the less saline water lies beneath the saline water) are detected around the trough of the Kuroshio frontal eddy (or wave). Analyses of the archived dataset reveal that the isopycnal surface of 24.5σθ is the deepest layer of the Kuroshio pycnocline outcropping to the sea surface on the shallow shelf in early spring. Outcropping isopycnals above 24.5σθ encounter a less saline water plume originating from the Changjiang, especially in the western East China Sea. Thereafter, the less saline water moves along isopycnal layers and reaches the Kuroshio front around the shelf edge. Numerical models demonstrate that, when the frontal wave captures the less saline water, the shelf water takes the form of a salinity inversion in the trough because isohalines in the frontal wave have a phase lag between the upper and lower layers in consequence of the baroclinic instability.  相似文献   

17.
春季东海不同水域的表层叶绿素含量   总被引：5，自引：0，他引：5  
利用１９９４年春季在东海及台湾海峡首次获得的表层水中绿素含量大面走航连续观测资料，结合温盐分布及以往的有关东海及台湾海峡的海流和上升流的结论，分析了春季东海表层叶绿素含量在不同水域的分布特征。结果表明，叶绿素含量分布与水文结构关系密切。叶绿素含量值随不同海流流域而变，但在各海流流域内基本不变，黑潮表层水的叶绿素含量最低，其次是台湾暖流表层水，长江冲淡水与江浙沿岸流域的叶绿素含量较高；黑潮西侧弱流剧  相似文献   

18.
The reliability of a numerical tide model for detiding acoustic Doppler current profiler (ADCP) data is examined on the East China Sea shelf. The process is adopted for the ADCP data obtained on 12–13 May 2003. The ocean model accompanied by the most precise harmonic constants available to public is used to compute external tides. The root mean square difference is less than 10 cm/s between the detided currents and those using the least squares method, and so the detiding process using the numerical model is available to detect the East China Sea shelf circulation faster than this speed.  相似文献   

19.
综述东海和琉球群岛以东海域若干气旋型和反气旋型涡旋的研究.对东海陆架、200m以浅海域,主要讨论了东海西南部反气旋涡、济州岛西南气旋式涡和长江口东北气旋式冷涡.东海两侧和陆坡附近出现了各种不同尺度的涡旋,其动力原因之一是与东海黑潮弯曲现象有很大关系,其次也与地形、琉球群岛存在等有关.东海黑潮有两种类型弯曲:黑潮锋弯曲和黑潮路径弯曲.黑潮第一种弯曲出现了锋面涡旋,评述了锋面涡旋的存在时间尺度与空间尺度和结构等;也指出了黑潮第二种弯曲,即路径弯曲时在其两侧出现了中尺度气旋式和反气旋涡,讨论了它们的变化的特性.特别讨论了冲绳北段黑潮弯曲路径和中尺度涡的相互作用,着重指出,当气旋式涡在冲绳海槽北段成长,并充分地发展,其周期约在1~3个月时,它的空间尺度成长到约为200km(此尺度相当于冲绳海槽的纬向尺度)时,黑潮路径从北段转移到南段.也分析了东海黑潮流量和其附近中尺度涡的相互作用.最后指出在琉球群岛以东、以南海域,经常出现各种不同的中尺度反气旋式和气旋式涡,讨论了它们在时间与空间尺度上变化的特征.  相似文献   

20.
渤、黄、东海潮汐、潮流的数值模拟与研究   总被引：9，自引：4，他引：5  
基于FVCOM海洋数值模式,采用高分辨率的三角形网格,对渤、黄、东海的潮汐、潮流进行数值模拟,并通过比较120个沿岸验潮站和14个潮流观测站的实测与模拟结果进行模型验证,两者符合较好。根据模拟结果,给出了四个主要分潮的潮汐同潮图和5m层潮流最大流速及最大潮流同潮时分布。渤、黄、东海共有5个半日分潮和3个全日分潮的独立旋转潮波系统,且都呈逆时针方向旋转;半日潮流和全日潮流各有12个圆流点;在冲绳岛和奄美岛两侧的4个半日潮流圆流点分别呈对称分布,其中有3个为本文首次给出;在日本九州岛西侧还新给出2个全日潮流圆流点。有关它们的存在性需要实测资料的进一步检验。  相似文献   

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