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1.
Seasonal variations of the surface currents in the Tsushima Strait were investigated by analyzing the monthly mean surface currents measured with HF radar. Several new features of the surface currents have been found. One notable feature is the large, complicated seasonal variation in the current structure in the eastern channel of the strait. For example, in the southeastern and northwestern regions of the channel, southwestward countercurrents are found in summer while southeastward acrossshore currents are found in autumn and winter. The wind-driven flow (Ekman flow) as well as surface geostrophic currents are responsible for these complicated variations of the surface currents. To quantify each variation of the flow and current, the wind-driven flow was calculated from the monthly wind (more precisely, the friction velocity) using the monthly speed factor and deflection angle estimated in our previous study, and the surface geostrophic currents were then estimated by subtracting the wind-driven flow from the measured surface currents. It was found that the acrossshore currents are the wind-driven flow, and that the surface geostrophic currents flow almost in the along-shore direction, indicating the validity of the decomposition of the surface velocity into the wind-driven flow and the geostrophic currents using the speed factor and deflection angle. A real-vector empirical orthogonal function (EOF) analysis of the surface geostrophic currents shows a pair of eddies in the lee of Tsushima and Iki Islands as the first mode, which indicates that the southwestward countercurrents in the eastern channel are formed primarily by the incoming Tsushima Warm Current.  相似文献   

2.
A review is made of circulation and currents in the southwestern East/Japan Sea (the Ulleung Basin), and the Korea/Tsushima Strait which is a unique conduit for surface inflow into the Ulleung Basin. The review particularly concentrates on describing some preliminary results from recent extensive measurements made after 1996. Mean flow patterns are different in the upstream and downstream regions of the Korea/Tsushima Strait. A high velocity core occurs in the mid-section in the upstream region, and splits into two cores hugging the coasts of Korea and Japan, the downstream region, after passing around Tsushima Island located in the middle of the strait. Four-year mean transport into the East/Japan Sea through the Korea/Tsushima Strait based on submarine cable data calibrated by direct observations is 2.4 Sv (1 Sv = 106 m3 s−1). A wide range of variability occurs for the subtidal transport variation from subinertial (2–10 days) to interannual scales. While the subinertial variability is shown to arise from the atmospheric pressure disturbances, the longer period variation has been poorly understood.Mean upper circulation of the Ulleung Basin is characterized by the northward flowing East Korean Warm Current along the east coast of Korea and its meander eastward after the separation from the coast, the Offshore Branch along the coast of Japan, and the anticyclonic Ulleung Warm Eddy that forms from a meander of the East Korean Warm Current. Continuous acoustic travel-time measurements between June 1999 and June 2001 suggest five quasi-stable upper circulation patterns that persist for about 3–5 months with transitions between successive patterns occurring in a few months or days. Disappearance of the East Korean Warm Current is triggered by merging the Dok Cold Eddy, originating from the pinching-off of the meander trough, with the coastal cold water carried Southward by the North Korean Cold Current. The Ulleung Warm Eddy persisted for about 20 months in the middle of the Ulleung Basin with changes in its position and spatial scale associated with strengthening and weakening of the transport through the Korea/Tsushima Strait. The variability of upper circulation is partly related to the transport variation through the Korea/Tsushima Strait. Movements of the coastal cold water and the instability of the polar front also appear to be important factors affecting the variability.Deep circulation in the Ulleung Basin is primarily cyclonic and commonly consists of one or more cyclonic cells, and an anticyclonic cell centered near Ulleung Island. The cyclonic circulation is conjectured to be driven by a net inflow through the Ulleung Interplain Gap, which serves as a conduit for the exchange of deep waters between the Japan Basin in the northern East Sea and the Ulleung Basin. Deep currents are characterized by a short correlation scale and the predominance of mesoscale variability with periods of 20–40 days. Seasonality of deep currents is indistinct, and the coupling of upper and deep circulation has not been clarified yet.  相似文献   

3.
Hydrographic conditions in the Tsushima Strait revisited   总被引：1，自引：1，他引：0  
Long-term averaged temperature and salinity distributions in the Tsushima Strait are investigated on the basis of a concurrent dataset of the eastern and western channels during 1971–2000. Both temperature and salinity show a clear seasonal variation with weak and strong stratifications in December–April and June–October, respectively. The largest standard deviations occur in summer around the thermocline for temperature and in the surface layer for salinity. This indicates large interannual variability in the development of a thermocline and low salinity water advection from the East China Sea. The water masses in both channels are distinctly different from each other; the water in the western channel is generally colder and fresher than that in the eastern channel throughout the year. Baroclinic transport based on the density distributions shows a seasonal variation with a single peak in August for the eastern channel and double peaks in April and August for the western channel. However, this cannot explain the seasonal variation in the total volume transport estimated from the sea level differences across the channels. The spatial distribution of baroclinic transport shows a year-round negative transport towards the East China Sea behind the Iki Island in the eastern part of the eastern channel. This negative transport reflects the baroclinic structure between the offshore Tsushima Current Water and cold coastal water. The corresponding southwestward currents are found in both Acoustic Doppler Current Profiler (ADCP) and high frequency (HF) radars observations.  相似文献   

4.
The connectivity between the interannual salinity variations in the Tsushima and Cheju Straits has been investigated on the basis of historical hydrographic data. Salinity in the Cheju Strait correlates positively with that in the western channel of the Tsushima Strait, but does not show a significant correlation with that in the eastern channel. Empirical orthogonal function (EOF) and singular value decomposition (SVD) analyses of temperature and salinity in the Cheju Strait revealed that salinity in the strait is associated with the cold bottom water in summer. Drastic freshening in the Cheju Strait occurs in a period when the Cheju Current intensifies. The results allow us to hypothesize that the mechanism of interannual salinity variations in the Cheju Strait and western channel of the Tsushima Strait is as follows. The intrusion of cold bottom water into the Cheju Strait in summer intensifies the Cheju Current by increasing the baroclinicity. Since colder bottom water develops a stronger eastward surface current, the larger volume of the Changjiang diluted water is drawn into the strait, which results in a lower salinity condition in the Cheju Strait. As the water in the Cheju Strait flows into the western channel of the Tsushima Strait, salinity in the western channel varies synchronously. This hypothesis is supported by SVD analysis of temperature in the Cheju Strait and salinity in the Tsushima Strait. The salinity condition in the East China Sea is suggested to be another important influence on salinity in the western channel of the Tsushima Strait.  相似文献   

5.
卡里马塔海峡水体交换的季节变化   总被引：2，自引：0，他引：2  
Four trawl-resistant bottom mounts, with acoustic Doppler current profilers(ADCPs) embedded, were deployed in the Karimata Strait from November 2008 to June 2015 as part of the South China Sea-Indonesian Seas Transport/Exchange and Impact on Seasonal Fish Migration(SITE) Program, to estimate the volume and property transport between the South China Sea and Indonesian seas via the strait. The observed current data reveal that the volume transport through the Karimata Strait exhibits significant seasonal variation. The winteraveraged(from December to February) transport is –1.99 Sv(1 Sv=1×10~6 m~3/s), while in the boreal summer(from June to August), the average transport is 0.69 Sv. Moreover, the average transport from January 2009 to December2014 is –0.74 Sv(the positive/negative value indicates northward/southward transport). May and September are the transition period. In May, the currents in the Karimata Strait turn northward, consistent with the local monsoon. In September, the southeasterly trade wind is still present over the strait, driving surface water northward, whereas the bottom flow reverses direction, possibly because of the pressure gradient across the strait from north to south.  相似文献   

6.
本文全面地分析了此段海流的流路与流速结构，首次提出研究海域近底层的环流示意图。指出在夏季，韩国南岸和日本九州北岸均存在着一支南下的逆流，九州西岸出现两种或多种形式的流路。对马暖流在源地流速很弱，流向不稳定，流路时隐时显不明显，只有离开源地后才逐渐显示出一支海流轮廓；强流区在朝鲜海峡附近。该海流可明显地划分为三段。流速夏强冬弱，夏季流幅宽约８０ｋｍ。  相似文献   

7.
The Korea (Tsushima) Strait is an important seaway through which the warm Tsushima Current flows into the East Sea (Japan Sea). A paleogeographic map constrained by a regional sea-level curve developed on the basis of a number of recent 14C radiocarbon dates suggests that the Korea Strait was not closed during the last glacial period. Rather, it was open as a channel-like seaway linking the western North Pacific and the East Sea. Some fraction of the paleo-Tsushima Current inflow presumably continued at that time through the Korea Strait. The activity of the paleo-Tsushima Current is evidenced by the distribution pattern of river-derived lowstand deposits, consisting of a beach/shoreface complex and lowstand deltaic wedges. Received: 16 April 1999 / Revision accepted: 25 February 2000  相似文献   

8.
Kyungsang-Namdo Fisheries Experimental Station released 620 drift bottles in the west strait of the Tsushima Strait from 1932 to 1939. Among them 183 were recovered. Fukuoka Prefectural Fisheries Experimental Station also released 1930 bottles in the east strait between 1954 and 1969. Recovered bottles were 442.The bottles drifted to the south in winter owing to a northwesterly wind, and drifted to the northeast in spring and summer with the Tsushima warm current. Bottles released at the west strait drifted to the north along the east shore of Korea, went around the Ullung Island, and then to the northeast. Drift bottles released at the east strait drifted to the north along the shore of Japan and washed ashore on the coast.  相似文献   

9.
Seasonal Variation of the Cheju Warm Current in the Northern East China Sea   总被引：1，自引：1，他引：1  
The Cheju Warm Current has been defined as a mean current that rounds Cheju-do clockwise, transporting warm and saline water to the western coastal area of Cheju-do and into the Cheju Strait in the northern East China Sea (Lie et al., 1998). Seasonal variation of the Cheju Warm Current and its relevant hydrographic structures were examined by analyzing CTD data and trajectories of satellite-tracked drifters. Analysis of a combined data set of CTD and drifters confirms the year-round existence of the Cheju Warm Current west of Cheju-do and in the Cheju Strait, with current speeds of 5 to 40 cm/s. Saline waters transported by the Cheju Warm Current are classified Cheju Warm Current water for water of salinity greater than 34.0 psu and modified Cheju Warm Current for water having salinity of 33.5–34.0 psu. In winter, Cheju Warm Current water appears in a relatively large area west of Cheju-do, bounded by a strong thermohaline front formed in a "" shape. In summer and autumn, the Cheju Warm Current water appears only in the lower layer, retreating to the western coastal area of Cheju-do in summer and to the eastern coastal area sometimes in autumn. The Cheju Warm Current is found to flow in the western channel of the Korea/Tsushima Strait after passing through the Cheju Strait, contributing significantly to the Tsushima Warm Current.  相似文献   

10.
Spatiotemporal characteristics of interannual temperature variations in the Tsushima Strait are investigated on the basis of historical hydrographic data applying the same procedures as Senjyu et al. (2006). Empirical orthogonal function (EOF) analysis revealed that the most energetic mode of variation (the EOF first mode), which accounts for about 31.5% of the total variance, is the in-phase temperature change for the entire strait. The wintertime temperature variation described by the first mode is associated with the wintertime heat flux in the northern East China Sea, while they are poorly correlated in other seasons. The large standard deviation in the time coefficient of the first mode in August suggests a relationship with the horizontal heat advection in summer in the northern East China Sea. On the other hand, the EOF second mode, which explains about 12.6% of the total variance, is associated with the stratification and baroclinicity in the strait. The time coefficient of the EOF second mode negatively correlates with the baroclinic volume transport through the strait in summer. Comparison of temporal variations among the leading EOF modes for temperature and salinity shows no significant correlations. This indicates that the principal modes of variation in temperature and salinity vary independently within an interannual timescale.  相似文献   

11.
燕杰  侯一筠  刘泽 《海洋与湖沼》2021,52(4):813-822
通过对比2017年9月和2019年9月的温盐大面观测数据,发现东海陆架上黑潮近岸分支流的路径在两次观测中存在显著差异。2019年9月黑潮近岸分支流中上游的路径相较2017年9月明显的东向偏移,造成黑潮次表层水入侵东海近岸海域的强度较弱。为了探究黑潮近岸分支流的上述显著年际差异的原因,利用卫星高度计数据和再分析风场数据,通过分析大面观测同期的绝对海表动力高度、地转流场以及海表风场的差异,阐述了黑潮近岸分支流路径产生显著年际差异的动力机制。2019年8—9月东海海表较2017年8—9月盛行更强的西南向沿岸季风,强的西南向沿岸风通过埃克曼输运促使水体向岸堆积并在近岸区域沿岸西南向堆积。因此, 2019年8—9月东海近岸海域的跨岸方向压力梯度与2017年8—9月相比较小而沿岸压力梯度则较大。2019年8—9月,受压力梯度分布的影响,东海近岸海域产生西南向的沿岸地转流和离岸地转流。其中西南向的沿岸地转流会在底部生成离岸的底埃克曼流,离岸底埃克曼流和离岸地转流共同抑制了黑潮近岸分支流的向岸入侵。这导致2019年9月黑潮近岸分支流的路径向东偏移,黑潮次表层水入侵浙江近海及长江口区域的强度随之减弱。通过分析研究实际观测案例,阐述了风影响黑潮近岸分支流入侵东海近岸海域的动力机制,同时明确指出海表风场会从黑潮近岸分支流的中上游区域改变其路径,进而对黑潮入侵东海近岸海域产生重要影响。  相似文献   

12.
Variability of Sea Surface Circulation in the Japan Sea   总被引：3，自引：0，他引：3  
Composite sea surface dynamic heights (CSSDH) are calculated from both sea surface dynamic heights that are derived from altimetric data of ERS-2 and mean sea surface that is calculated by a numerical model. The CSSDH are consistent with sea surface temperature obtained by satellite and observed water temperature. Assuming the geostrophic balance, sea surface current velocities are calculated. It is found that temporal and spatial variations of sea surface circulation are considerably strong. In order to examine the characteristics of temporal and spatial variation of current pattern, EOF analysis is carried out with use of the CSSDH for 3.5 years. The spatial and temporal variations of mode 1 indicate the strength or weakness of sea surface circulation over the entire Japan Sea associated with seasonal variation of volume transport through the Tsushima Strait. The spatial and temporal variations of mode 2 mostly indicate the temporal variation of the second branch of the Tsushima Warm Current and the East Korean Warm Current. It is suggested that this variation is possibly associated with the seasonal variation of volume transport through the west channel of the Tsushima Strait. Variations of mode 3 indicate the interannual variability in the Yamato Basin.  相似文献   

13.
We discussed the detailed current structures in the Eastern Channel of the Tsushima Strait, using four sets of acoustic Doppler current profiler (ADCP) data, which were taken by the quadrireciprocal method (Katoh, 1988), for removing tidal currents, in summers of 1987–1989. In the Eastern Channel, diurnally averaged currents balanced almost geostrophically. In the upper layer of the deepest part of the Eastern Channel, there existed a current core which corresponded to one branch of the Tsushima Current. The current direction in this core was between NE and ENE in all observations but the magnitude of velocity in 1987 differed largely from that in 1988. Another current core with lower velocities was found near the north coast of Kyushu. Near the bottom at the deepest part of the Eastern Channel, the velocity was more or less 0.3 kt (15 cm s–1). Along the east coast of Tsushima and in waters northeast of it, countercurrents were observed. The continuity of these countercurrents was interpreted as follows: A part of the current flowing from the Western Channel of the Tsushima Strait into the Japan Sea turns clockwise in waters northeast of Tsushima, and flows southwestward along the east coast of Tsushima. The southwestward current along Tsushima was correlated with the northeastward current in the central part of the Eastern Channel. The transport through the Eastern Channel was between 0.59 and 1.30 Sv (1 Sv=106 m3s–1). The baroclinic component, which was defined as the transport based on calculations of geostrophic current with assuming zero velocity near the bottom, was very small.  相似文献   

14.
ＯｎｔｈｅｏｒｉｇｉｎｏｆｔｈｅＴｓｕｓｈｉｍａＷａｒｍＣｕｒｒｅｎｔＷａｔｅｒ￥ＴａｎｇＹｕｘｉａｎｇａｎｄＨｅｕｎｇ－ＪａｅＬｉｅ（ＦｉｒｓｔｉｎｓｔｉｔｕｔｅＯｆＯｃｅａｎｏｇｒａｐｈｙ，ＳｔａｔｅＯｃｅａｎｉｃＡｄｍｉｎｉｓｔｒａｔｉｏｎ，Ｑ...  相似文献   

15.
Interannual salinity variations in the Tsushima Strait are investigated on the basis of historical hydrographic data. The EOF analysis revealed that the most dominant mode is the in-phase salinity variation between the eastern and western channels. The time coefficients of the EOF first mode in summer show a negative correlation with the Changjiang discharge, which indicates that salinity in the Tsushima Strait tends to decrease over summer, related to a large discharge of the Changjiang. The eigenvectors of the first mode are larger in the eastern channel than those in the western channel, though the low salinity water mainly flows through the western channel. This is because the low salinity water spreads into the eastern channel as well as the western channel over summers with a large discharge of the Changjiang. The out-of-phase salinity variation between the channels is extracted as the EOF second mode; this is the predominant variation in the western channel. The time coefficients of the second mode in summer show no significant correlations to the volume transports through the western channel and the transport differences between channels. A relationship between the EOF second mode and variations in the wind stress over the East China Sea is suggested.  相似文献   

16.
依据自适应数值模型，模拟了东中国海冬、夏季三维斜压Lagrange环流。模拟发现：台湾暖流的上层水来自台湾海峡入流和台湾东北黑潮的表层水；50m以下的深底层水主要由台湾东北黑潮的次表层水入侵陆架生成。冬季对马暖流外海一侧主要由黑潮水构成，而其近陆一侧由台湾暖流和陆架混合水构成，西朝鲜沿岸流在济州海峡汇入对马暖流；夏季它还包含转向后的长江冲淡水。冬季黄海暖流并非对马暖流的直接分支，黄海暖流水是对马暖流水和陆架水混合而成，这与传统观点相悖，而与中韩黄海水循环动力学合作调查结果一致。黄海暖流东西两侧分别为2支向南流动的滑岸流。夏季黄海环流构成基本封闭的逆时针环流。冬季渤海环流主要有一逆时针大环流，但辽东湾的环流是顺时针向的。渤海环流冬强夏弱，水流在渤海海峡北进南出。  相似文献   

17.
The 10-year series of observations of currents directed along the Korea/Tsushima Strait, which were measured with an acoustic Doppler current profiler aboard a ferry boat that cruised several times a week between the Hakata (Japan) and Pusan (South Korea) ports, is analyzed. Robust estimation methods are used to separate the tidal signal from the inhomogeneous series of the current data in the problem of the harmonic analysis. The MU2, NO1, PHI1, and J1 constituents have been estimated in addition to the MSF, MF, Q1, O1, P1, K1, N2, M2, S2, and K2 tidal harmonics detected previously. The annual variations in the amplitude of the M2 fundamental harmonic have also been taken into account. The current series cleared from the tidal signal has been processed in order to analyze the spatio-temporal variability of the volume transport through the Korea Strait. The normal annual velocity of the water inflow into the Japan Sea through the Korea Strait was 2.77 × 106 m3 s?1. The ratio of the flow rates in the eastern and western zones of the strait separated by the Tsushima Islands was 2/3. Considerable seasonal variations in the discharge are observed in the western strait zone: the flow rate annual maximum in October is 1.75 times as high as the minimum in February. An insignificant (not more than 0.1 × 106 m3 s?1 on average) southward flow can cross the eastern channel. Mesoscale vortices are generated in the lee of the Tsushima Islands when the northeastern current flows around them. The energy spectrum of the total nonseasonal flow rate through the Korea Strait has been constructed in the frequency range of 8–500 days. The spectrum has three significant maximums near periods of 10, 19, and 64 days. It has been indicated that this spectrum flattens at low frequencies (<0.1 day?1) in the vicinity of the formation of mesoscale vortices behind the Tsushima Islands.  相似文献   

18.
Numerical experiments were performed in order to investigate the effects of variations of the transport through the Korea/Tsushima Strait, an inlet of the Japan/East Sea, on the upper layer circulation in the JES based on a 10-month transport observation from May 1999 to March 2000 (Perkins et al., 2000). All external forcings to the model were annual mean fields, except the transport variation through the Korea Strait. In the experiments where the periodic variation of the transport repeated continuously sinusoidally by several periods, strong variability of sea surface height (SSH) was detected in the region extending from the Korea Strait to the Japanese coast due to the geostrophy of the buoyancy forcing at the Korea Strait. The region along the Korean coast is more sensitive to the long-term variations than the short-term (≤60-day period) ones. In two experiments forced by realistic and monthly mean transport, the difference of rms of sea surface height was largest at the Japanese coast and relatively large at the East Korean Warm Current separation region (128∼130°E, 39∼41°N) and to the east of Yamato Rise. The distribution of difference of eddy kinetic energy at 100 m depth between the two experiments was similar to that of the rms of SSH. In the distributions of mean SSH and mean kinetic energy at 100 m depth the realistic transport invokes eddy variability to interact with mean current resulting in the changes of the mean SSH and the mean kinetic energy at the East Korean Warm Current separation region, but it does not produce conspicuous changes in the mean fields of entire JES compared with the mean fields forced by the seasonal transport.  相似文献   

19.
本文主要根据韩国海洋研究所通过东海沿岸海洋过程试验（即COPEX－ECS）收集的CTD资料,较详细地研究了东海东北部夏季的水文状况．文中首先分析了夏季出现在该海域最重要的几件海洋现象．其中主要包括长江冲淡水的东向扩展,黄海底层冷水南向插入,以及黑潮水的爬升和渗透。然后,使用t－S分析法,并参考有关研究成果,对东海东北部夏季水团进行了划分,并重点探讨了黑潮水和对马暖流水的结构特征。最后,本文讨论了朝鲜／对马海峡东、西水道夏季水文结构的差异问题。  相似文献   

20.
To investigate an mechanism of the seasonal variation of transport through the Tokara Strait, two numerical experiments with real geometry and wind forcing were carried out. The models are linear barotropic models which are a North Pacific Ocean model and a limited-area model with a fine grid. The seasonal variation of volume transport with a maximum in the summer and a minimum in the autumn could be well reproduced by both models. The results demonstrate the wind stress component normal to a gradient vector of bottom topography is crucial for determining the seasonal variation. The similar seasonal variation widely covers the East China Sea and has a large amplitude near the Tokara Strait. Finally, it can be concluded that winds north of 35°N have little influence on the seasonal response of our model at the Tokara Strait.  相似文献   

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