琉球群岛附近海域中尺度涡的初步研究

采用1977年1月至2006年12月高分辨率全球大洋环流模型OFES输出结果对琉球群岛附近海域的中尺度涡进行了研究分析。结果表明:(1)尺度较大的涡旋的分布密集区主要有台湾以东海域、琉球海沟上层海域和四国以南海域。(2)琉球海流流经海域的反气旋涡旋占优势,有利于琉球海流的发展。(3)琉球海流受中尺度涡的影响十分显著,纬度越低,其受中尺度涡的影响越明显,而黑潮相对比较稳定,受中尺度涡的影响并不显著。(4)四国以南海域暖涡从黑潮脱落之后向西南移动,该涡旋的移动对琉球海流和黑潮产生特别显著的影响。文章的最后还讨论了中尺度涡与黑潮弯曲以及琉球海流可能存在的联系。     

琉球群岛以东的西边界流与东海黑潮流量时空特征的研究

通过最新的高分辨率再分析海洋数据资料,对于东海黑潮以及琉球群岛以东海域的海流进行了研究。结果表明琉球群岛以东西边界流最大流速出现在600~1200 m深度的地形坡度最大处,大小约为0.2 m/s。由于冲绳岛以南庆良间水道的水交换对于东海黑潮流量有重要的影响,东海黑潮的平均流量从南向北逐渐递增,平均流量为28×106~35×106m3/s;琉球群岛以东的西边界流流量则比东海黑潮小一个量级,平均值小于其变化的方差;由于受庆良间水道海流的影响,冲绳岛东侧的流量要远小于奄美大岛东侧的流量。同一纬度大洋中西传的Rossby波对琉球群岛以东的西边界流有较大影响,因此琉球群岛以东西边界流的流量有大约100 d的显著变化周期。庆良间水道以南的东海黑潮由于主要受台湾以东黑潮流量的控制,也有大约100 d的显著变化周期,庆良间水道以北的东海黑潮则没有该特征。     

琉球海流的研究进展

文章对近期有关琉球海流的研究进行了综述。指出琉球海流是北太平洋一支重要的西边界流,具有如下特征:琉球海流的表层部分受中尺度涡影响强烈,其流速和流量存在有较稳定的次表层极大值,琉球海流在冲绳岛和奄美大岛间得到了显著增强,是一支可和黑潮相匹敌的海流。有关琉球海流的以下几方面内容有待今后更深入研究:(1)琉球海流的起源,其形成的动力学机制及琉球海流在冲绳岛以南的时空变化;(2)琉球海流次表层极大值形成、维持及在冲绳岛以北得到显著增强的动力学机制;(3)琉球海流对东海的影响及其水和热流量在黑潮中所起的作用。     

2002年4～5月琉球群岛两侧海流的研究

基于日本气象厅“长风丸”调查船在2002年4～5月航次期间的CTD资料,结合卫星风场资料,采用改进逆方法计算了琉球群岛两侧海域各断面的流速和流量分布,并分析卫星跟踪浮标资料和同期的卫星高度计资料,得出下面一些主要结论:(1)黑潮流速在PN断面上只有一个流核.通过断面PN的净东北向流量约为34.7×106m3/s,此流量包括台湾暖流、东海黑潮和黑潮以东的反气旋涡的流量.(2)黑潮流速在断面TK上有两个流核,通过断面TK净东向的流量为25.6×106m3/s,黑潮通过海峡后流向断面ASUKA.(3)冲绳岛东南海区琉球海流的流量约为8.8×106m3/s,并流向断面AM.(4)奄美大岛以东的北向海流的流量为12.7×106m3/s,并流向断面ASUKA.在断面ASUKA东南部出现一个中尺度反气旋涡,直径约240 km,其流量约为28.5×106m3/s.(5)四国以南黑潮第一层水体基本来源于通过吐噶喇海峡的黑潮,第二、三层水体来自吐噶喇海峡和奄美大岛以东海域的流量大致相当,而第四层的流量则主要来自于奄美大岛以东海域.(6)浮标资料显示,奄美大岛以东的海流部分来自于断面AM以东海区,并通过断面ASUKA.     

基于HYCOM再分析数据研究琉球海流的形成与起源

The origin of the Ryukyu Current(RC) and the formation of its subsurface velocity core were investigated using a 23-year(1993–2015) global Hybrid Coordinate Ocean Model(HYCOM) dataset. The volume transport of the RC comes from the Kuroshio eastward branch(KEB) east of Taiwan and part of the North Pacific Subtropical Gyre(pNPSG). From the surface to 2 000 m depth, the KEB(p-NPSG) transport contributes 41.5%(58.5%) to the mean total RC transport. The KEB originally forms the subsurface velocity core of the RC east of Taiwan due to blockage of the subsurface Kuroshio by the Ilan Ridge(sill depth: 700 m). Above 700 m, the Kuroshio can enter the East China Sea(ECS) over the Ilan Ridge, meanwhile, the blocked Kuroshio below 700 m turns to the right and flows along the Ryukyu Islands. With the RC flowing northeastward, the p-NPSG contribution strengthens the subsurface maximum structure of the RC owing to the blockage of the Ryukyu Ridge. In the surface layer, the pNPSG cannot form a stable northeastward current due to frequent disturbance by mesoscale eddies and water exchange through the gaps(with net volume transport into ECS) between the Ryukyu Islands.     

Structure and Transport of the Agulhas Current and Its Temporal Variability

Using a year-long moored array of current meters and well-sampled synoptic sections, we define the variability and mean structure and transport of the Agulhas current. Nineteen current meter records indicate that time scales for the temporal variability in the alongshore and offshore velocities are 10.2 and 5.4 days, respectively. Good vertical correlation exists between the alongshore or onshore velocity fluctuations, excluding the Agulhas Undercurrent. The lateral scale for the thermocline Agulhas current is about 60 km and the onshore velocity correlations are positive throughout the Agulhas Current system. Mean velocities from the array determine that the offshore edge of the Agulhas Current lies at 203 km and the penetration depth is 2200 m offshore of the Undercurrent. Hence, daily averaged velocity sections, determined by interpolation and extrapolation of current meter locations, for a 267-day period, from the surface to 2400 m depth and from the coast out to 203 km offshore encompass the main features of the Agulhas Current system. The Agulhas current is generally found close to the continental slope, within 31 km of the coast for 211 of 267 days. There are only five days when the core of the current is found offshore at 150 km. Total transport is always poleward, varying from −121 to −9 Sv, with maximum transport occurring when the core is 62 km from the coast. Average total transport for the 267 day period is −69.7 Sv; the standard deviation in daily transport values is 21.5 Sv; and the mean transport has an estimated standard error of 4.3 Sv. The Agulhas Undercurrent, which hugs the continental slope below the zero velocity isotach, has an average equatorward transport of 4.2 Sv, standard deviation of 2.9 Sv and an estimated standard error of 0.4 Sv. Transports from the moored array are in reasonable agreement with transport results from synoptic sections. Based on time series measurements at about 30° latitude in each ocean basin, the Agulhas Current is the largest western boundary current in the world ocean.     

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.     

琉球群岛以东海域表层沉积物元素地球化学特征

对琉球群岛以东海域134个站位表层沉积物的化学元素含量进行了系统测试,结合矿物学资料等,对研究区的表层沉积物元素地球化学特征进行了分析。结果表明:(1)琉球群岛以东海域沉积物具有半深海沉积物的地球化学特征;(2)通过元素因子分析,把25种元素或氧化物分为4种组合,每一种组合对应不同的物质来源,分别为陆源成因组合(SiO2,K2O,Zr,TiO2,Y,Sc,Na2O,La,Al2O3,P2O5,Ce),生物成因组合(Sr,CaO,L.O.I,CaCO3),火山源成因组合(MgO,V,Fe2O3,Cr,Li,Co),自生源成因组合(Ni,MnO,Cu,Ba);(3)控制本区元素分布的因素主要是水深、物质来源以及生物和铁锰物质的自生作用。     

Velocity structures and transports of the Kuroshio and the Ryukyu current during fall of 2000 estimated by an inverse technique

An inverse calculation using hydrographic section data collected from October to December 2000 yields velocity structure and transports of the Kuroshio in the Okinawa Trough region of the East China Sea (ECS) and south of central Japan, and of the Ryukyu Current (RC) southeast of the Ryukyu Islands. The results show the Kuroshio flowing from the ECS, through the Tokara Strait (TK), with a subsurface maximum velocity of 89 cm s⁻¹ at 460 dbar. In a section (TI) southeast of Kyushu, a subsurface maximum velocity of 92 cm s⁻¹ at 250 dbar is found. The results also show the RC flowing over the continental slope from the region southeast of Okinawa (OS) to the region east of Amami-Ohshima (AE) with a subsurface maximum velocity of 67 cm s⁻¹ at 400 dbar, before joining the Kuroshio southeast of Kyushu (TI). The volume transport around the subsurface velocity maximum southeast of Kyushu (TI) balances well with the sum of those in TK and AE. The temperature-salinity relationships found around these velocity cores are very similar, indicating that the same water mass is involved. These results help demonstrate the joining of the RC with the Kuroshio southeast of Kyushu. The net volume transport of the Kuroshio south of central Japan is estimated to be 64∼79 Sv (1 Sv ≡ 10⁶ m³s⁻¹), of which 27 Sv are supplied by the Kuroshio from the ECS and 13 Sv are supplied by the RC from OS. The balance (about 24∼39 Sv) is presumably supplied by the Kuroshio recirculation south of Shikoku, Japan.     

Variability of Current Structure Due to Meso-Scale Eddies on the Bottom Slope Southeast of Okinawa Island

The relationship between the vertical profile of current on the bottom slope southeast of Okinawa Island and the offshore meso-scale eddy propagated from the east was examined by combined use of the data obtained by a moored upward-looking ADCP (Acoustic Doppler Current Profiler), PIES (Inverted Echo Sounder with Pressure gauge), hydrographic surveys and satellite altimetry during a period from November 2000 to August 2001. The variability of current component parallel to the isobath in the layer over 600 m is found to be markedly different from that in the layer below 600 m. The current variability in the upper and the lower layer can be well explained by the first and second modes of the EOF (Empirical Orthogonal Function) decomposition. The PIES and the sea surface height anomaly data suggest that the first mode represents the surface-trapped current associated with the approach of the offshore meso-scale eddy from the east, whereas the second mode has a bottom-intensified structure. The second mode velocity tends to delay to the first mode. The hydrographic data derived from CTD (Conductivity-Temperature-Depth meter) and PIES data along the line across the isobath suggest that the second mode component is generated by the interaction between the meso-scale eddy and the bottom topography.     

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。     

基于20a卫星高度计数据的黑潮变异特征

黑潮作为一支典型的西边界流,其路径变化特征及其相关的物理现象对于渔业和航海有着不可忽视的影响。本文基于改进的特征线方法,利用1992~2012年的高度计绝对动力地形数据提取了整个黑潮流区逐月的黑潮主轴和边界位置,并对沿轴速度、主流宽度、表层水体输运以及路径标准差等黑潮特征量进行了分析研究。结果表明,黑潮整体的沿轴速度在夏秋季较大,最大值可达0.95 m/s,而在冬季的速度较小;黑潮主流宽度在10、11月份达到最大值;黑潮表层水体输运在夏季最大,春秋两季次之,冬季最小。沿黑潮流路分区域对黑潮特征进行分析,结果表明,越往黑潮下游,其沿轴速度、主流宽度和表层水体输运越大,同时沿轴速度和表层水体输运量最大值出现的时间也越晚,黑潮主轴位置相对于其多年平均的偏离程度越大,且随时间波动也越强烈。     

Relationship between Cd and PO4 in the Subtropical Sea near the Ryukyu Islands

The relationship between dissolved cadmium (Cd) and phosphate (PO₄) was examined at three stations in the subtropical area near the Ryukyu Islands in May 1999. Preformed PO₄ was obtained using the Redfield ratio in order to separate the surface water and the other layers in this study area. Almost 0 μM (−0.043 μM to 0.094 μM) was estimated in the layers above 300 m and 250 m at Sts. 1 and 3 and at St. 2, respectively. Up to these depths, water was considered to be uniform, and these layers were defined as the surface water in this study area. In the surface water, the slopes of the regression lines of the Cd-PO₄ plot were 0.162, 0.156, and 0.226 (nM/μM) at Sts. 1, 2, and 3, respectively, and these values were much closer to the estimated regenerated ratio of Cd to PO₄ from the Apparent Oxygen Utilization (AOU)-Cd/PO₄ plots, which was 0.197 (nM/μM) in this study area. Below surface layers, the slopes of the Cd-PO₄ plot changed to 0.371, 0.352, and 0.362 (nM//μM) at Sts. 1, 2, and 3, respectively. In the relationships between Cd and PO₄, clear deviations or kinks were observed at three stations at a PO₄ concentration of approximately 0.2 μM in the plot, which was attributable to the discontinuity of surface water and the other layers across the North Pacific subtropical mode water. In studies of the interaction between surface water and biogenic particles concerning the Cd/PO₄ ratio, separate analyses of seawater (surface water and the other layers) should be carried out to obtain the individual surface water ratio because the Cd/PO₄ ratio in the surface water is expected to differ from that of the underlying water. Furthermore, the biological fractionation of these constituents is based on the surface water ratio. This revised version was published online in July 2006 with corrections to the Cover Date.     

Spatial and temporal patterns of seagrass habitat use by fishes at the Ryukyu Islands,Japan

To investigate whether or not regional–temporal patterns of seagrass habitat use by fishes existed at the Ryukyu Islands (southern Japan), visual surveys were conducted in seagrass beds and adjacent coral reefs in northern, central, and southern Ryukyu Islands, in November 2004, and May, August, and November 2005, the northern region having less extensive seagrass beds compared with the central and southern regions. During the study period, the seagrass beds were utilized primarily by 31 species, the densities of some of the latter differing significantly among regions. With the exception of Apogonidae and Holocentridae, all species were diurnal and could be divided into 6 groups based on seagrass habitat use patterns; (1) permanent residents A (10 species, e.g. Stethojulis strigiventer), juveniles and adults living in seagrass beds as well as other habitats; (2) permanent residents B (5 species, e.g. Calotomus spinidens), juveniles and adults living only or mainly in seagrass beds; (3) seasonal residents A (4 species, e.g. Cheilodipterus quinquelineatus), juveniles living in seagrass beds as well as other habitats; (4) seasonal residents B (6 species, e.g. Lethrinus atkinsoni), juveniles living only or mainly in seagrass beds; (5) transients (5 species, e.g. Parupeneus indicus), occurring in seagrass beds in the course of foraging over a variety of habitats; and (6) casual species (1 species, Acanthurus blochii), occurring only occasionally in seagrass beds. Regarding temporal differences, juvenile densities in each group were high in May and August compared with November in each region, whereas adult densities did not differ drastically in each month. For regional differences, juvenile and adult densities of permanent residents A and B were higher in the southern and central regions than in the northern region. Moreover, some seasonal residents showed possible ontogenetic habitat shift from seagrass beds to coral reefs in each region. These results indicated that seagrass habitat use patterns by fishes changed temporally and regionally and there may be habitat connectivity between seagrass beds and coral reefs via ontogenetic migration in the Ryukyu Islands.     

Circulations east of Taiwan and in East China Sea and east of Ryukyu Islands during early summer 1985

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Interactions of Mesoscale Eddy and Western Boundary Current: A Reduced-Gravity Numerical Model Study

A reduced-gravity primitive equation eddy resolving model is used to study the interaction of a typhoon-induced eddy and a wind-driven general circulation. A typhoon-induced eddy is characterized by a core with a relative vorticity of the same order as the local Coriolis parameter. This eddy is neutrally stable relative to a disturbance induced by the westward advection of the eddy, due to the planetary β-effect. Hence, its evolution in the open ocean is similar to the classical frontal geostrophic eddy. Within the western boundary flow regime, the eddy is entrained northward by the mean circulation. This northward eddy advection and the mean-vorticity advection due to eddy flow induce another disturbance with a north-south asymmetry into the circular eddy. Together with the zonal asymmetric disturbance, associated with the planetary β-effect, the original circular eddy becomes unstable. The nonlinear eddy-flow interactions in the eastern flank of a western boundary current causes the eddy to deform quickly into an ellipse and lose its waters and energy into the mean circulation.     

1995与1996年夏季琉球群岛两侧海流

基于1995,1996年夏季日本调查船的观测资料,采用P矢量方法对琉球群岛两侧的海流进行了计算.结果表明:黑潮为琉球群岛以西海域的一支东北向强流,1996年夏季的流速比1995年夏季的强,在深层出现南向逆流.黑潮东、西两侧分别存在一个反气旋式暖涡和一个弱的气旋式冷涡.1995年夏季,琉球群岛以东,从表层至以下层都存在一支沿岸北上的海流,即琉球海流.该海流来自黑潮分支,为本海区的一个主要物理特征.琉球海流以下出现弱的南向流.冲绳岛以东海域,在25°～25°30'N,128°30'～129°10'E附近从表层至700m水深存在一个中尺度的反气旋式暖涡.在温、盐水平分布图上,对应的出现一个较高温、低密水块.1996年夏季,冲绳岛西南海域存在一个中尺度的反气旋式暖涡和一个气旋式冷涡,形成一个偶极子,中间为较强的南向流,该现象为本海区的一个重要物理特征,属首次报道.冲绳岛以东表层主要被南向流控制,琉球海流不明显.200m以深在近岸出现北向流,这表明琉球海流的核心位于次表层.琉球海流的下面出现南向流.计算海区东北部从表层到700m水深出现一个中尺度的反气旋式暖涡,与1995年夏季时比较,其位置向北移动.此外在1996年夏季从近表层到深层,垂直方向和水平方向上的等温线、等盐线波动很大,例如在C断面上冷、暖涡相间出现,且暖     

两个西边界流延伸体区域中尺度涡统计特征分析

黑潮和湾流是世界大洋中最典型的两支西边界流,黑潮延伸体（Kuroshio Extention,KE）和湾流延伸体（Gulf Stream Extention,GSE）区域中尺度涡活动十分活跃。本文综合利用卫星高度计资料和Argo浮标资料,对KE和GSE区域中尺度涡的表层特征及其对温盐影响进行了统计研究和对比分析。结果表明:黑潮和湾流主轴附近为涡旋频率的高值区,主轴南北两侧分别以气旋涡和反气旋涡数量占多,主轴附近的涡旋强度明显大于其他区域;两个区域的涡旋以西向移动为主,气旋涡和反气旋涡都具有向南（赤道）偏离的趋势;两个区域的涡旋数量都以夏、秋季较多,涡旋强度都在春、夏季较大,且GSE区域涡旋强度明显大于KE区域;气旋涡（反气旋涡）引起内部明显的温度负（正）异常,KE区域气旋涡（反气旋涡）内部呈"负-正"（"正-负"）上下层相反的盐度异常分布,GSE区域气旋涡（反气旋涡）在各层呈现较为一致的盐度负（正）异常;两个区域中尺度涡对温盐场的平均影响深度可达1 000×104 Pa以上。     

北太平洋西边界流研究综述

综述了近20年来国内外学者在研究北太平洋西边界流的平均结构及NEC分叉动力机制、NM K流系平均输运的分配及变化、NM K流系季节及年际变化规律及其与EN SO之间的关系、NM K流系在热带和亚热带水交换中的作用以及水团的平均分布特征等方面所取得的主要成果。通过分析,发现东亚季风、R ossby波和K e lv in波等是影响北太平洋西边界流的主要因素;而缺乏长期直接的海流观测资料是深入研究北太平洋西边界流遇到的最大障碍。     

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.