台湾东北部黑潮表层水入侵东海陆架的季节变化规律

基于1998～2011 年进入台湾东北部的WOCE-SVP(World Ocean Circulation Experiment -Surface Velocity Programme)计划的Argos 浮标运行轨道数据, 分析了台湾东北部的环流特征、黑潮表层水入侵东海陆架的季节变化规律。结果表明: 在春夏季, 黑潮表层水入侵仅限于陆架外缘, 而在秋冬季, 黑潮表层水可深入东海陆架或进入台湾海峡。自黑潮区入侵至100 m 和150 m 等深线的浮标数量在秋冬季较多, 春夏季较少。台湾海峡的浮标轨迹在春夏季几乎皆为北向, 在秋冬季皆为南向。在秋季, 东海中部和南部陆架会在黑潮西侧出现逆流和涡旋。可见, 台湾东北部环流具有显著的季节特征; 黑潮表层水入侵东海陆架在秋冬季较强, 春夏季较弱。本研究采用最新的Argos 浮标数据, 揭示了台湾东北部黑潮入侵东海陆架的季节变化规律。     

黑潮水入侵东海陆架及陆架环流的若干现象

利用WOCE-SVP和中国近海环流观察项目的卫星跟踪表层测流浮标资料，详细分析了黑潮及其入侵东海陆架和东海陆架上层环流的分布状况，结果表明：黑潮从台湾东部进入东海后，明显入侵陆架，并在复杂地形的作用下使其流路呈现多种变化，分析结果还显示，对马暖流不仅仅是黑潮的延续，而是多支流合成的结果，通过资料分析发现：秋节东海黑潮西侧100m等深线处可能存在一支与黑潮反向的逆流，关于它存在的季节变化和动力机制有待进一步的深入研究。     

东海东北部春季若干重要水文结构的分析

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。     

黑潮主流径海域海水中的无机碳及其对东海陆架区的影响

基于2014年5—6月对黑潮主流径及毗邻东海陆架海区的调查,研究了该区域水体中无机碳体系参数(p H、总碱度TAlk、溶解无机碳DIC及DIC/TAlk)的垂直与水平分布,在此基础上定量评估了黑潮输入对东海陆架海区无机碳收支的影响。结果表明,黑潮水体中DIC、TAlk与DIC/TAlk总体而言随水深增加而升高,p H降低,综合体现了浮游植物生产、海-气界面交换、有机物降解及Ca CO3溶解等过程的影响;上升流中心站位无机碳参数均受较深层水体上涌影响,与黑潮主流径其它站位略有不同。东海陆架海区外侧站位表层、30m层无机碳主要受台湾海峡暖流影响,高p H、低DIC/TAlk的黑潮表层水影响区域局限于东南部;而在底层,低p H、高DIC/TAlk的黑潮入侵流离开黑潮主流径向正北方延伸并抬升至钱塘江口附近;上升流对无机碳的影响持续至表层,其携带的黑潮中层水因此也可能进入陆架海区。水量模型估算黑潮水在5—10月间跨域陆架边缘向东海陆架区输入溶解无机碳总计58798.9×109mol,净输入达37382.9×109mol,而东海向外输出的无机碳绝大部分经由对马海峡进入日本海。     

台湾东北海域冷涡-上升流系统冬、夏季温度三维结构

利用美国国家海洋大气管理局(NOAA)2007年发布的全球海域温度多年月平均数据库资料(WOA 05),研发计算机数值分析和图形可视技术,对台湾东北海域冬、夏季的温度分布进行数值分析,展示台湾东北海域冷涡-上升流系统冬、夏季温度分布的三维结构,分析黑潮、台湾暖流以及东海陆架水的影响,得出以下结论.(1) 夏季(8月)冷涡主要存在于13-100m深度以及138-150m深度;冬季(2月)冷涡主要存在于109-150m深度之间.(2)夏季(8月)上升流的拱形结构从表层向下都存在,其中由于台湾暖流与东海陆架底层水的影响,造成在深度100-138m之间的等温线不闭合;冬季(2月)上升流的拱形结构主要存在于100m水深以下.(3)在黑潮向西北方向入侵东海陆架的区域,冷涡-上升流系统消失.在冷涡-上升流系统作用的区域,黑潮向东北方向入侵东海陆架的程度越强,冷涡-上升流系统的势力也越强.     

黑潮营养盐输入对东海陆架浮游生态系统影响的模型研究

黑潮是东海陆架主要的外源营养盐来源之一。本文建立了一个物理-生化耦合的三维生态动力学模型,通过敏感性实验分析了黑潮营养盐输入对东海浮游生态系统的影响,分区域、水层和季节对黑潮输入营养盐的贡献进行了统计分析。主要得到如下结论:(1)黑潮对东海陆架营养盐的影响主要集中在整个外陆架和中陆架的中北部,从垂向分布来看,对外陆架影响主要在50m以深的中下层,而对中陆架的影响在次表层(20—50m)和中下层都较为显著,黑潮对东海陆架营养盐输入的总量,冬季略高于夏季。(2)黑潮对东海浮游植物的贡献冬夏两季存在较大差异,冬季叶绿素的增量主要集中在外陆架的中北部和中陆架的中部,分布在表层(0—20m)和次表层;而夏季则主要在外陆架的中部、中陆架的中北部和内陆架的北部,除了内陆架北部以外都以次表层为主。     

东海陆架环流季节变化的模拟与分析

在改进POM模式基础上,建立1个中国东部海域斜压准预报模式,利用全球海洋模式结果并结合实测资料以及高精度卫星遥感SST资料,进行了东海陆架海域温盐及环流年循环的数值模拟,并系统分析了东海陆架环流系统及其季节变化、各暖流的路径等广为关注的问题。模式结果表明：黑潮主轴主体沿陆架坡折走向,中段黑潮流幅由南至北增宽,流速变大,流核所达深度变浅。浙闽沿岸流是一典型的季风环流,台湾暖流终年表现出东、北两分支结构,其分支表现出明显的季节性变化特征。在东海东北部陆架海域,冬季黑潮以其分支形式向北入侵,夏季则主要以大陆边缘流的形式向北进入陆架。论文对各暖流的水源也进行了相应的分析。     

黑潮跨陆架入侵东海年际变化的数值模拟

为了研究黑潮跨过200m等深线对东海入侵的年际变化特征,本文基于ROMS(Regional Ocean Modeling System)海洋模式,对西北太平洋海域进行了高分辨率的数值模拟,模式水平分辨率高达4km,该分辨率可以很好地分辨黑潮以东区域的中尺度涡旋等过程。模式首先进行了6年的气候态模拟,然后进行了1993到2015年的后报模拟。模式很好地再现了东海陆架已知的环流结构,模拟出的对马海峡和台湾海峡的年平均流量和观测结果也比较一致。基于模式结果,利用旋转经验正交函数(REOF)的方法,对黑潮跨过200m等深线流量的年际变化进行分析。REOF的主要模态表明,黑潮跨过200m等深线对东海陆架的入侵主要发生台湾东北,并且入侵主要集中在黑潮次表层水中。主要模态的时间系数表明,黑潮入侵东海陆架的年平均流量存在一个8年的变化周期。相关性分析表明,黑潮入侵东海陆架的年际变化和太平洋年代际振荡PDO(Pacific Decadal Oscillation)指标具有显著的负相关,其相关系数达–0.63。该相关可以通过如下过程解释:PDO会导致东太平洋风应力涡度异常,由Sverdrup关系可知向赤道的体积输运也会相应地产生异常,根据质量守恒,向赤道体积输运的异常必然通过西边界流-黑潮的异常来平衡,从而导致黑潮入侵东海陆架强烈的年际变化。     

黑潮与邻近东海生源要素的交换及其生态环境效应

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。     

夏季对马暖流水来源的探讨

主要根据韩国海洋研究所通过东海沿岸海洋过程试验(COPEX-ECS)收集的CTD和卫星跟踪表面漂流浮标观测结果,探讨了夏季对马暖流水的来源.所得主要结论为:(1)对马暖流水的结构有着明显的区域性变化.在九州西侧的冲绳海槽北区,对马暖流水为3层结构;而在陆架和对马-朝鲜海峡,对马暖流水为两层结构.(2)对马暖流表层水以次高盐(33.50～34.10)为特征.它主要是由以长江冲淡水为主体的沿岸水、黑潮表层水和东海南部陆架水汇聚而成.(3)对马暖流中层水由两部分组成.温跃层以下,盐度大于34.50的高盐水,基本为爬升的黑潮水表层水.位于跃层中的对马暖流水则是黑潮水与陆架低盐水的混合水.(4)在对马-朝鲜海峡,由于与陆架低盐水和沿岸水不断混合,来自源区的海水明显变性.盐度大于34.50的高盐水,仅出现在50m以深的底层水中.     

东中国海环流及其季节变化的数值模拟

关于东中国海环流的研究，国内外学者已做了大量的工作。早期科学家们主要依赖于对温盐资料和少数测流资料的分析研究对渤、黄、东海的环流结构有了较系统和深入的认识。东中国海环流是由一个气旋式的“流涡”组成，东侧主要是北上的黑潮-对马暖流-黄海暖流及其延伸部分；西侧为南下的沿岸流系。黑潮对东中国海环流的影响是如此之大，以致于除了某些局部区域外，上述海域主要流系的冬、夏季分布形式比较相似而无本质上的差异(胡敦欣等，1993)。但本文所研究海域正处于世界上最显著的季风区，冬、夏季盛行风向基本相反，过渡季节(春、秋季)风向多变，风力减弱；海洋热盐结构季节变化明显(如冬季混合强，而夏季层化明显等)，这些因素都使得东中国海环流存在着较明显的季节变化。 自20世纪80年代以来，东中国海环流的数值模拟工作逐步展开，并已成为研究环流结构及其形成机制的强有力工具。但由于数值模式本身以及计算方案的缺陷(如有些学者用固定的风场、温盐场对东中国海环流进行诊断模拟等)和观测资料的不足，数值模拟的结果难以得到验证，渤、黄、东海的环流研究中仍有大量的问题存在争议，以待澄清。例如，台湾暖流的来源、流径;对马暖流的来源;夏季黄海暖流的流径以及黄海冷水团环流等均有不同的论述。对黄、东海环流季节变化的数值模拟工作也较少，多用冬、夏典型月份的风场强迫积分至稳定态，给出冬、夏季环流，这种做法值得商榷。三维环流模式很难在1个月内达到稳定态，尤其是夏季层化明显、风力减弱的情况下，非常定风场的影响更应引起人们的重视。 本文采用比较符合实际的计算方案，用年循环风场和海面热通量场为外强迫，对渤、黄、东海的环流及其季节变化进行了模拟，并对一些争议问题进行了探讨。     

A structure of the Kuroshio and its related upwelling on the East China Sea shelf slope

The ADCP on an advanced towed fish with controllable main and tail wings, called DRAKE measured a detailed sectional structure of the Kuroshio flowing to the NE along the East China Sea shelf slope west of Okinawa. At the observation period, a countercurrent directed to the SW formed in near-bottom water on the shelf slope. The horizontal flow perpendicular to the stream axis of the Kuroshio constructed a convergence zone around the boundary between the Kuroshio and the countercurrent. An intensive upwelling with the maximum velocity of 2.8 cm s^–1 was found to distribute on the shelf slope around the convergence zone. A dynamic cause of this intensive upwelling is discussed carefully.     

Shelfbreak circulation and thermohaline structure in the northern south China Sea-contrasting spring conditions in 2000 and 2001

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.     

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.     

The calculation of Kuroshio current structure in the East China Sea—early summer 1986

On the basis of hydrographic data and moored current meter records obtained during an early summer cruise (May 20–June 23) of 1986, a three dimensional diagnostic calculation of the circulation is performed in the survey area, which covers the East China Sea continental shelf, Okinawa Trough and an area east of the Ryukyu Island. The Kuroshio Current condition and structure in the East China Sea, its branches and their interrelationship as well as the eddies around the Kuroshio, are discussed. When the Kuroshio entered the area northeast of Taiwan, there were two branches. The main branch flowed northeastward along the continental slope and the other branch was at the eastern part of the Okinawa Trough. The main axis of the Kuroshio followed the continental slope above the 300 m level, but moved gradually eastward to the Okinawa Trough below the 300 m level.     

南海的季节环流─TOPEX/POSEIDON卫星测高应用研究

应用1992～1996年的TOPEX/POSEIDON卫星高度计遥感资料,研究了冬、夏季风强盛期多年平均的南海上层环流结构。研究结果表明,南海上层流结构呈明显的季节变化,在很大程度上受该海区冬、夏交替的季风支配。冬季总环流呈气旋型,并发育有两个次海盆尺度气旋型环流;夏季总环流大致呈反气旋型、但在南海东部18°N以南海域未见明显流系发育。研究还表明,南海环流的西向强化趋势明显,无论冬、夏在中南半岛沿岸和巽他陆架外缘均存在急流,其流向冬、夏相反,是南海上层环流中最强劲的一支。鉴于该海流的动力特征与海洋动力学中定义的漂流不同,有相当大的地转成分,建议称为“南海季风急流(South China Sea MonsoonJet)”.冬季南下的季风急流在南海南部受巽他陆架阻挡折向东北,沿加里曼丹岛和巴拉望岛外海有较强东北向流发育。夏季北上的季风急流在海南岛东南分为两支:北支沿陆架北上,似为传统意义上的南海暖流;南支沿18°N向东横穿南海后折向东北;二者之间(陆架坡折附近)为弱流区。两分支在汕头外海汇合后,南海暖流流速增强。就多年平均而言,黑潮只在冬季侵入南海东北部,并在南海北部诱生一个次海盆尺度的气旋型环流,这时南海暖流只出现在汕头以东海域.夏季南海北部完全受东北向流控制,未见黑潮入侵迹象.用卫星跟踪海面漂流浮标观测进行的对比验证表明,以上遥感分析结果与海上观测一致。     

东海黑潮温盐与中国东部气温和降水的相互关系

采用东海黑湖主流段长时间序列的实测温盐资料，研究了东海黑潮上层温度、上层盐度的变化及其与中国东部降水和地面气温的关系。结果表明，在过去50年内，东海黑潮上层海温呈上升趋势，而上层盐度略呈下降趋势。东海黑潮上层海温和我国东部地面气温的关系在冬季十分密切，呈现出大面积显著的正相关，这与冬季南下冷空气的整体降温作用有关。夏季，长江中下游江水的增多致使大量长江冲淡水入海，导致黑潮上层水盐度下降，此时东海黑潮上层盐度与我国大陆东部降水呈负相关。     

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.     

东中国海拉格朗日环流数值模拟Ⅱ.环流模拟

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。     

Numerical investigation on propulsion of the counter-wind current in the northern South China Sea in winter

The propulsion of the winter counter-wind current in the northern South China Sea (SCS) is investigated with a regional, three-dimensional, primitive equation model. This current is usually called the SCS Warm Current (SCSWC). Model results well reproduced the banded structure of the Guangdong coastal current, the SCSWC and the slope current from the coast to the slope in the northern SCS in the climatological data. The across-shelf flow is active in the shelf break area. Both onshore and offshore flows exist; the net across-shelf transport is shoreward throughout the year, and is larger in winter than in other seasons. The joint effect of baroclinicity and relief (JEBAR) is the dominant forcing of the across-shelf transport in the shelf break area. The major mass source of the SCSWC is the onshore-veered slope current. It is the JEBAR effect that supplies the necessary negative vorticity to maintain the slope current flowing across the isobaths and veering to the right hand to feed the SCSWC. Analyses of the momentum fields indicate that the onshore pressure gradient in the outer shelf balances the Coriolis force induced by the northeastward SCSWC in the frame of geostrophy. In winter, such an onshore pressure gradient is mainly provided by the strong density contrast between waters of the shelf and of the upper slope, which results from the Kuroshio intrusion via the Luzon Strait. The notable intrusion of the Kuroshio in winter is crucial for maintaining the density structure in the shelf break area and facilitates the set-up of the onshore pressure gradient over the outer shelf.