东海温度锋的分布特征及其季节变异

根据１９３４－１９８８年东海水文观测资料，重点分析东海温度锋的分布特征及其季节变异，并结合近期中日黑潮合作调查研究成果，初步探讨温度锋季节变异和水团演变的关系，所得主要结论是：（１）东海不仅常年存在浙闽沿岸锋，东海北部陆架锋和黑潮锋，而且、春、夏两季，在东海南部还出现一条东海中部出架锋。（２）江海温度锋季节变化的特点是：冬季，锋的宽度和强度皆是表层最强，夏季，表层温度锋仅出现在浙江近岸小范围海域。     

The numerical simulation of the Kuroshio frontal eddies in the East China Sea using a hybrid coordinate ocean mode

A hybrid coordinate ocean model (HYCOM) is used to simulate the Kuroshio frontal eddies in the East China Sea (ECS). The research area is located (20°-32°N, 120°-132°E). Using the simulating data, it is figured out that the Kuroshio frontal eddies occur in summer as well as in the other season in this area. The life cycle of the Kuroshio and its frontal eddies is different with the position. The life-cycle of the Kuroshio frontal eddies of the northwest Diaoyu Islands is about 14 d; and the life cycle of the Kuroshio frontal eddies of southwest Yakushima about 20 d. This result extends the in situ researching results greatly. In addition, the vertical impact depth of the Kuroshio frontal eddies is also changing with the position. On the whole, in the ECS, the maximum impact depth of the Kuroshio frontal eddies of the northwest Taiwan Islands is about 75 m; the maximum impact depth of the Kuroshio frontal eddies of the northwest Diaoyu Islands is more than 125 m, but no more than 200 m; and the maximum impact depth of the Kuroshio frontal eddies of southwest Yakushima is up to 100 m.     

Spatial and temporal variation of particulate organic carbon in the PN section of East China Sea

1 IntroductionThe carbon cycle in the ocean, related to theglobal warming and human food, is of great scientificsignificance. Studies for the carbon transfer and trans-formation in the ocean, including the assimilative andmetabolic capacity, have become one of key researchfoci in global biogeochemical studies (Tsunogai et al.,1997; Hu and Yang, 2001; Hansell et al., 2003; Wei etal., 2003; Yang et al., 2004; Yuan et al., 2004).As is known, POC is composed of living fractionsand organic debr…     

Spring phytoplankton bloom in the fronts of the East China Sea

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 1^st and 10^th, 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.     

东海海洋锋的波动及演变特征

本文利用近十年来获得的ＮＯＡＡ卫星红外影像，较为系统地分析了东海海洋锋（黑潮锋、对马暖流锋和浙江沿岸锋）的波动谱特征以及形态的演变。同时还利用浮标测流结果分析了锋面波动中的流态。分析结果表明：东海黑潮锋通常存在４～５个折叠波形，其波长平均约２００ｋｍ，波动随黑潮流向东北方向传播，速度约１６ｃｍ／ｓ。浙江沿岸锋的波动多呈锯齿形，其波长较短，波数多。在浙江沿岸锋波动发展过程中，其波长从开始的２０～４０ｋｍ发展成３０～６０ｋｍ，它们约以１８ｃｍ／ｓ的速度向东北方向传播。东海海洋锋波动演变形态复杂，其中黑潮锋的波动可能演变成锋面涡旋、暖丝和暖环。     

Study on interaction between the coastal water, shelf water and Kuroshio water in the Huanghai Sea and East China Sea

The main processes of interaction between the coastal water, shelf water and Kuroshiowater in the Huanghai Sea (HS) and East China Sea (ECS) are analyzed based on the observation and study results in recent years. These processes include the intrusion of the Kuroshio water into the shelf area of the ECS, the entrainment of the shelf water into the Kuroshio, the seasonal process in the southern shelf area of the ECS controlled alternatively by the Taiwan Strait water and the Kuroshio water intruding into the shelf area, the interaction between the Kuroshio branch water, shelf mixed water and modified coastal water in the northeastern ECS, the water-exchange between the HS and ECS and the spread of the Changjiang diluted water.     

Study of the Kuroshio/Ryukyu Current system based on satellite-altimeter and <Emphasis Type="Italic">in situ</Emphasis> measurements

Data from satellite altimeters and from a 13-month deployment of in situ instruments are used to determine an empirical relationship between sea-level anomaly difference (SLA) across the Kuroshio in the East China Sea (ECS-Kuroshio) and net transport near 28°N. Applying this relationship to the altimeter data, we obtain a 12-year time series of ECS-Kuroshio transport crossing the C-line (KT). The resulting mean transport is 18.7 ± 0.2 Sv with 1.8 Sv standard deviation. This KT is compared with a similarly-determined time series of net Ryukyu Current transport crossing the O-line near 26°N southeast of Okinawa (RT). Their mean sum (24 Sv) is less than the mean predicted Sverdrup transport. These KT and RT mean-flow estimates form a consistent pattern with historical estimates of other mean flows in the East China Sea/Philippine Basin region. While mean KT is larger than mean RT by a factor of 3.5, the amplitude of the KT annual cycle is only half that of RT. At the 95% confidence level the transports are coherent at periods of about 2 years and 100–200 days, with RT leading KT by about 60 days in each case. At the annual period, the transports are coherent at the 90% confidence level with KT leading RT by 4–5 months. While the bulk of the Kuroshio enters the ECS through the channel between Taiwan and Yonaguni-jima, analysis of satellite altimetry maps, together with the transport time series, indicates that the effect of mesoscale eddies is transmitted to the ECS via the Kerama Gap southwest of Okinawa. Once the effect of these eddies is felt by the ECS-Kuroshio at 28°N, it is advected rapidly to the Tokara Strait.     

Surface distribution of alkalinity and specific alkalinity and their application to water mass tracing in Kuroshio area of the East China Sea

Surface distribution and seasonal variation of alkalinity and specific alkalinity in Kuroshio area of the East ChinaSea and their application to the water mass tracing are discussed in this paper. Results show a distinct seasonal variation of the alkalinity, which is concerned with the process of vertical mixing. Different specific alkalinity in various water masses has been found. On the basis of the difference of the specific alkalinity and the distribution of alkalinity, two water fronts in summer season, located at 27°-30°N and 124°-1 27°E, (Ⅰ), and at the northern waters about one latitude from the Taiwan Island, (Ⅱ); one in winter season at about one longitude from coast of mainland of China and 26°-30°N were found. In summer season, about 1-2 longitudes eastward shift of front (Ⅰ) is found by comparison of data in May and August. And the high alkalinity of the northern East China Sea in summer season may be caused by the Huanghe River runoff flowing southward along with the Huanghai Sea     

Splitting of the subtropical gyre in the western North Pacific

Examined here is a hypothetical idea of the splitting of the subtropical gyre in the western North Pacific on the basis of two independent sources of data,i.e., the long-term mean geopotential-anomaly data compiled by the Japanese Oceanographic Data Center and the synoptic hydrographic (STD) data taken by the Hakuho Maru in the source region of the Kuroshio and the Subtropical Countercurrent in the period February and March 1974. Both of the synoptic and the long-term mean dynamic-topographic maps reveal three major ridges, which indicate that the western subtropical gyre is split into three subgyres. Each subgyre is made up of the pair of currents, the Kuroshio and the Kuroshio Countercurrent, the Subtropical Countercurrent and a westward flow lying just south of the Countercurrent (18°N–21°N), and the northern part of the North Fquatorial Current and an eastward flow at around 18°N. The subgyres are more or less composed of a train of anticyclonic eddies with meridional scales of between 300 and 600 km, so that the volume transport of the subgyres varies by a factor of two or more from section to section. The upper-water characteristics also support the splitting of the subtropical gyre; the water characteristics are fairly uniform within each subgyre, but markedly different between them. The northern rim of each subgyre appears as a sharp density front accompanied by an eastward flow. The bifurcations of the sharp density fronts across the western boundary current indicate that the major part of the surface waters in the North Equatorial Countercurrent is not brought into the Kuroshio. The western boundary current appears as a continuous feature of high speed, but the waters transported change discontinuously at some places.     

Primary Study of the Mechanism of Eddy Shedding from the Kuroshio Bend in Luzon Strait

The mechanism of the anticyclonic eddy's shedding from the Kuroshio bend in Luzon Strait has been studied using a nonlinear 2 1/2 layer model, in a domain including the North Pacific and South China Sea. The model is forced by steady zonal wind in the North Pacific. Energy analysis is adopted to detect the mechanism of the eddy shedding. Twelve experiments with unique changes of wind forcing speed (to obtain different Kuroshio transports at Luzon Strait) were performed to examine the relationship between the Kuroshio transport (KT) and the eddy shedding events. In the reference experiment with KT of 22.7 Sv (forced with zonal wind idealized from the annual mean wind stress from the COADS data set), the interval of eddy shedding is 70 days and the shed eddy centers at (20°N, 117.5°E). When the Kuroshio bend extends westward, the southern cyclonic perturbation grows so rapidly as to form a cyclonic eddy (18.5°N, 120.5°E) because of the frontal instability in the south of the Kuroshio bend. In the evolution of the cyclonic eddy, it cleaves the Kuroshio bend and triggers the separation of the anticyclonic eddy. In statistical terms, anticyclonic eddy shedding occurs only when KT fluctuates within a moderate range, between 21 Sv and 28 Sv. When the KT is larger than 28 Sv, a stronger frontal instability south of the Kuroshio bend tends to generate a cyclonic eddy of size similar to the width of the Luzon Strait. The bigger cyclonic eddy prevents the Kuroshio bend from extending into the SCS and does not lead to eddy shedding. On the other hand, when the KT decreases to less than 21 Sv, the frontal instability south of the Kuroshio bend is so weak that the size of corresponding cyclonic eddy is smaller than half the width of the Luzon Strait. The cyclonic eddy, lacking power, fails to cleave the Kuroshio bend and cause separation of an anticyclonic eddy; as a result, no eddy shedding occurred then, either.     

Intrusion of the Kuroshio into the South China Sea,in September 2008

Using widespread conductivity–temperature–depth (CTD) data in the Philippine Sea and northern South China Sea near the Luzon Strait together with altimeter data, we identified an intrusion of water from the Kuroshio into the South China Sea (SCS) through the Luzon Strait in September 2008. The Kuroshio water obviously intruded into the SCS from 20 to 21°N, and existed mainly in the upper 300 m. The intrusion water extended as far west as 117°E, then looped around in an anticyclonic eddy and returned to the Philippine Sea further north. The dynamics of the Kuroshio intrusion are discussed using a 1.5-layer nonlinear shallow-water reduced-gravity model. The analysis suggests that the strong cyclonic eddy to the east of the Kuroshio in September 2008 was of benefit to the intrusion event.     

Temporal variations of the net Kuroshio transport and its relation to atmospheric variations

Temporal variations of the net Kuroshio transport are investigated using long-term hydrographic data from repeat section of the 137°E meridian from the south of Japan (34°N) to New Guinea (1°S) conducted by the Japan Meteorological Agency. In this study, boundaries of the Kuroshio and the Kuroshio Counter Current (KCC) are defined based on the sea surface dynamic height distribution. Westward flows associated with the KCC and cold-core eddy north of the Kuroshio are removed from the eastward flow associated with the Kuroshio in order to estimate the net Kuroshio transport strictly. The net Kuroshio transport reveals low-frequency variations: significant signals on a decadal (about 10-year) timescale. The variations of net Kuroshio transport are predominantly caused by changes in the magnitude of oceanic current speed fields associated with a vertical movement of the main pycnocline depth around the southern boundary of the Kuroshio: deepening of the main pycnocline around the southern boundary of the Kuroshio forms a sharp northern upward-tilting slope of the isopycnal surfaces at the Kuroshio region, and eventually the net Kuroshio transport increases together with the Kuroshio eastward transport. By using a wind-driven hindcast model, it is found that the main pycnocline depth variation results from the first-mode baroclinic Rossby waves attributable to two types of Aleutian Low (AL) changes: a change in the magnitude of AL and meridional movement of AL.     

东海黑潮强度与东亚冬季风关系的分析研究

利用卫星高度计资料和再分析资料,本文分析研究了东海黑潮强度与东亚冬季风的关系,并初步探讨了二者相互作用的可能机制。结果表明,位置相近的断面,其流强变化具有相似的特征;在年际尺度上,冬季风与东海黑潮存在相互作用。当冬季风偏强,将削弱次年2-4月SC、SD断面的流强,弱冬季风年的情况相反。冬季风对流强影响的动力过程主要通过改变Ekman输送来实现;热力过程则表现为强（弱）冬季风增大（减少）了黑潮向大气释放的热通量,从而削弱（增强）流强,这一过程主要为冬季风对黑潮的影响。当冬季风偏强时,次年10-12月黑潮中下游流强偏弱,弱冬季风年的情况相反。这一过程与2-4月情况不同,其热力过程主要表现为黑潮对冬季风的影响。强冬季风通过准两年振荡对次年冬季的黑潮流强产生影响,由此构成了一个包含海洋和大气耦合过程的正反馈机制。黑潮流域的海气相互作用过程可能受冬季风和黑潮流强相对强弱的调制,海洋过程和大气过程主导一方的转换中存在一个“临界值”。     

Formation, Distribution and Volume Transport of the North Pacific Intermediate Water Studied by Repeat Hydrographic Observations

In order to examine the formation, distribution and transport of North Pacific Intermediate Water (NPIW), repeated hydrographic observations along several lines in the western North Pacific were carried out in the period from 1996 to 2001. NPIW formation can be described as follows: (1) Oyashio water extends south of the Subarctic Boundary and meets Kuroshio water in intermediate layers; (2) active mixing between Oyashio and Kuroshio waters occurs in intermediate layers; (3) the mixing of Oyashio and Kuroshio waters and salinity minimum formation around the potential density of 26.8σ_θ proceed to the east. It is found that Kuroshio water flows eastward even in the region north of 40°N across the 165°E line, showing that Kuroshio water extends north of the Subarctic Boundary. Volume transports of Oyashio and Kuroshio components (relative to 2000 dbar) integrated in the potential density range of 26.6–27.4σθ along the Kuroshio Extension across 152°E–165°E are estimated to be 7–8 Sv (10⁶ m³s⁻¹) and 9–10 Sv, respectively, which is consistent with recent work. This revised version was published online in July 2006 with corrections to the Cover Date.     

The structure of the kuroshio front in the vicinity of separation point where the Kuroshio leaves the Japanese coast

By using existing data obtained in the offshore area from the Boso Peninsula to the Joban Coast, it was shown that the double structure of the Kuroshio Front — which is usually found along the northern edge of the Kuroshio Extension to the east 143°E (Nagataet al., 1986 ; Shinet al., 1988) — is hardly found at the edge of the Kuroshio when it is flowing along the Japanese coast or in the area to the west of 142°E. It was suggested that the cold and fresh water core beneath the density front of the double structure originates from the fresh and cold Oyashio Water which is captured beneath the Kuroshio Front just off the Kashima Coast. The double structure of the Kuroshio Front would be generated and developed very rapidly in the region between 142°E and 143°E just after the Kuroshio leaves the Japanese coast.     

Statistical features of eddies approaching the Kuroshio east of Taiwan Island and Luzon Island

This study examined the statistical features of eddies approaching the Kuroshio east of Taiwan Island and Luzon Island. In total, 315 eddies (138 anticyclonic and 177 cyclonic eddies) were detected from 19.5 years of satellite altimeter sea-level data, with more than 95% of these eddies being generated in the ocean west of the Mariana Islands. Eddy trajectory statistics indicated that eddies frequently intrude into the Kuroshio regime at two latitude bands, namely 18°N–19°N and 22°N–23°N, with periods of 146 ± 62 and 165 ± 46 days, respectively. The interaction time is longer within the two active bands (33 ± 10 days at 18°N–19°N and 45 ± 17 days at 22°N–23°N) than at other latitudes. These two eddy-intrusion bands are associated with the northern and southern Subtropical Countercurrents (STCCs). These STCCs have a vertically reversed sign of the meridional potential vorticity gradient, thus providing a key energy source for eddy generation. In addition, when westward-propagating eddies approach the Ryukyu Islands, the southwestward recirculation flow east of the island chain as well as topographic effects cause some eddies to head southwestward to the east of Taiwan and intrude into the Kuroshio at 22°N–23°N, rather than to dissipate directly. Therefore, we suggest that the STCCs play a key role in inducing the eddies to frequently intrude into the Kuroshio at 18°N–19°N and 22°N–23°N. In addition, the Ryukyu Islands are responsible for concentrating the eddies within 22°N–23°N.     

黑潮对东海网采浮游植物群落组成与分布的影响

黑潮入侵深刻影响东海生态环境,但对其如何影响浮游植物群落组成与分布仍知之甚少。为此,于2011年四季对东海(26°～33°N,121°～128°E)共164个站位进行浮游植物拖网采集和环境因子测定,分析了浮游植物丰度和优势种组成及其对黑潮入侵的响应。调查共检出浮游植物9门509种(含变种、变型和未定种),其中硅藻305种、甲藻154种,蓝藻、定鞭藻、金藻、裸藻、绿藻、隐藻和黄藻种类数较少。秋季浮游植物细胞丰度最高(30 496.91×10³ cells/m3),高值区位于黑潮与长江冲淡水交汇形成的锋面处;夏季次之(28 911.28×10³ cells/m³),高值区分布与秋季相似;春季较少(19 180.76×103 cells/m3),高值区位于舟山群岛东南部;冬季最低(472.36×10³ cells/m³),高值区位于东海南部。冬季受黑潮表层水入侵影响,主要优势种为铁氏束毛藻(Trichodesmium thiebautii);春、夏季主要优势种为骨条藻(Skeleto...     

Characteristics of outer shelf water in the East China Sea

Water mass properties along cross-sections of the Kuroshio in the East China Sea (ECS) are investigated in detail. We used temperature, salinity and dissolved oxygen data from 2000 and 2002, together with historical temperature and salinity data from 1987 to 2004. Water properties were divided into two groups: high and low salinities or oxygen at temperatures warmer than 15 and 12 °C, respectively. We found the existence of outer shelf water W2, as defined by clear modes in frequency distributions of salinity and oxygen within various temperature segments. The outer shelf water was different from both Kuroshio Tropical Water (KTW) and coastal water. We mapped horizontal and vertical distributions of W2, along with W1 and KTW. The outer shelf water was distributed with density σ _t = 22.5–25.5 over a relatively broad area, from the outer continental shelf to the continental slope, particularly in autumn. Vertical distribution of the water suggests that W2 spread from the outer shelf to just the shelf side of the Kuroshio Current velocity maximum. Seasonal variations are examined with historical data along PN section over 17 years, and suggest that the appearance of W2 is distinct in summer and autumn. By comparing temperature–salinity (T–S) diagrams from Taiwan Strait and east of Taiwan, the outer shelf water (W2) originates from South China Sea Tropical Water (SCSTW), as suggested by Chen, J Geophys Res 110:C05012 (2005). The present study of the ECS clearly shows that SCSTW is transported along the east coast of Taiwan or through the Taiwan Strait into the ECS. It then spreads over a relatively wide area from the outer shelf to just the shelf side of the Kuroshio axis, and there is some horizontal mixing between SCSTW and KTW around the shelf break.     

2010年7月至2015年5月黑潮对邻近中国海的影响和琉球海流在中国研究的进展

黑潮对邻近中国海的影响和琉球海流研究在物理海洋学是一个很重要的、有趣的课题。为了深入地阐明由中国科学家自2010年7月至2015年5月期间所作研究的进展,本文在以下三个方面进行评述。第一方面是关于黑潮入侵南海以及在吕宋海峡周围的环流,分为以下二个很重要论题做阐述:黑潮入侵的季节和年际变化以及黑潮入侵的机制;黑潮对吕宋海峡海流和南海北部环流的影响。第二方面是关于黑潮及其对东海相互作用的变化,分为以下四个有趣的论题来阐述:东海黑潮研究的评述;黑潮入侵东海,水交换以及动力因子;由于黑潮作用营养物质通量在下游增加;从卫星遥感的应用对黑潮入侵东海对陆地物质通量的影响。第三方面,琉球海流与东海黑潮相互作用也被讨论。最后本文主要点作了总结,对今后进一步需要研究也被讨论。     

The Kuroshio East of Taiwan and in the East China Sea and the currents East of Ryukyu Islands during early summer of 1996

Using hydrographic data and moored current meter records and the ADCP observed current data during May–June 1996, a modified inverse method is applied to calculate the Kuroshio east of Taiwan and in the East China Sea and the currents east of Ryukyu Islands. There are three branches of the Kuroshio east of Taiwan. The Kuroshio in the East China Sea comes from the main (first) and second branches of the Kuroshio east of Taiwan. The easternmost (third) branch of the Kuroshio flows northeastward to the region east of Ryukyu Islands. The net northward volume transports of the Kuroshio through Section K₂ southeast of Taiwan and Section PN in the East China Sea are 44.4×10⁶ and 27.2×10⁶ m³s⁻¹, respectively. The western boundary current east of Ryukyu Islands comes from the easternmost branch of the Kuroshio east of Taiwan and an anticyclonic recirculating gyre more east, making volume transports of 10 to 15×10⁶ m³s⁻¹. At about 21°N, 127°E southeast of Taiwan, there is a cold eddy which causes branching of the Kuroshio there.