冬季闽浙沿岸上升流的数值研究

采用a坐标下三维斜压非线性的浅海陆架数值模式,研究风、边界力流(台湾暖流、黑潮、长江冲淡水)及地形等因子对上升流形成的影响。结果表明,风、台湾暖流是影响冬季闽浙沿岸上升流形成的最重要因子,其中风对浙江沿岸上升流的形成影响较大;台湾暖流对福建沿岸及其远海域上升流的形成影响较大;长江冲淡水对长江口附近上升流有一定的影响,对闽浙沿岸上升流影响不大;地形对闽浙沿岸上升流的形成作用显著;潮对闽浙沿岸上升流形成的影响也很显著。M2分潮对近海岸区域及台湾东北附近海域上升流的形成影响较大。     

闽浙沿岸上升流的数值模拟

本文将闽浙沿岸作为研究海区,采用坐标下三维斜压非线性的浅海陆架模式,综合考虑风、边界流(台湾暖流、黑潮、长江冲淡水)及地形等动力因子对上升流形成的影响,较好地模拟了闽浙沿岸上升流的分布。得出夏季闽浙沿岸近海岸区域有三个比较强的上升流中心,分别位于2520′N,12000′E、2640′N,12015′E、2720′N,12045′E附近,并且在对闽浙沿岸水文结构的模拟中,同样得出夏季沿岸的低温高盐区与计算出的三个较强的上升中心一致。冬季沿岸上升流的强度和范围都明显减弱,但在2520′N,12000′E和2600′N,12030′E及2830′~3000′N,12200′E附近仍有相对较强的上升流存在。     

东海和南黄海夏季环流的斜压模式

基于拉格朗日余流及其输运过程的一种三维空间弱非线性理论，引进了黑潮边界力及长江径流，给出了东海和南黄海的夏季环流及上升流区的分布。计算结果表明：在黑潮西侧存在着台湾－对马暖流系统；进入朝鲜海峡的对马暖流来自台湾暖流、黑潮、东海混合水和西朝鲜沿岸流；黄海暖流主要来源于东海混合水，表面有部分来自对马暖流；闽浙沿岸存在上升流区且构成一带状区域；在长江口外、东海东北部和陆坡上也存在在上升流式；陆坡处上升流     

风和台湾暖流引起东海沿岸上升流数值计算

运用三维数值模型,首先计算了夏季风和台湾暖流引起的东海沿岸上升流。结果表明,风和台湾暖流的作用都可产生顺岸呈带状分布的上升流,风生上升流在２０ｍ至３０ｍ水层速度较大,其值一般为１．０×１０－３ｃｍ／ｓ;而台湾暖流形成的上升流则在３０ｍ以下速度较大,其值在浙南和闽北一般为１．０×１０－３ｃｍ／ｓ,在舟山近海为０．５×１０－３ｃｍ／ｓ。此外,运用Ｅｕｌｅｒｉａｎ－Ｌａｇｒａｎｇｉａｎ方法数值探讨了东海沿岸上升流区海水的源地。逆追踪结果表明,潮因子和风因子对沿岸上升流的贡献都是局地的,即仅能将上升流区附近下层的海水带到沿岸上层;台湾暖流则可将台湾海峡北口的深层水带到闽浙沿岸上层,使闽浙沿岸出现低温、高盐水。     

台湾暖流水和长江冲淡水在32°N断面和PN断面上的分布及其变化

<正>台湾暖流和长江冲淡水是东海西部环流的两个关键分量。台湾暖流起源于台湾海峡和黑潮,通常沿福建和浙江海岸向北流动(翁学传等,1984a;Su et al.,1987;Guan,1994)。与已形成于长江口外的长江冲淡水为特征的沿岸水相遇后,台湾暖流转向东北,甚至转向东(Hu,1994)。冬季,长江冲淡水在一个非常窄的范围内沿海岸线向南流动,但在江河径流     

浙江沿岸春季上升流的数值研究

采用三维斜压非线性数值模式ROMS(Regional Ocean Modeling System),在浙江沿岸特殊地形的基础上综合考虑风场、台湾暖流、潮流以及长江径流等可变因子,对春季浙江沿岸上升流进行了数值研究。研究结果表明,浙江沿岸春季存在上升流,且上升流以带状分布在浙江近岸海域,在渔山列岛附近(28.40°N,122.00°E)以及舟山群岛附近(30.70°N,122.60°~123.00°E)存在2个上升流中心。风、台湾暖流和潮动力是影响浙江沿岸春季上升流的重要因子,其中风和台湾暖流对浙江沿岸整条上升流带均有影响;潮动力仅对28.60°N 纬度线以北至舟山群岛附近的上升流以及2个上升流中心的强度存在影响;长江径流对2个上升流中心、舟山群岛及长江口附近的上升流有一定影响。通过对浙江沿岸海域流场的分析可以发现,舟山群岛附近底层各等深线上水体向岸运动的速度比周围海域的大,跨越底层各等深线向上涌升的趋势更明显,间接反映了舟山群岛附近的上升流强度相对较强。对于舟山群岛附近的上升流而言,30 m深度以浅的海域,科氏力、水平平流作用与垂直粘性力是上升流形成的主要动力, 30 m深度以深的海域,上升流形成的主要动力为科氏力与压强梯度力,此时水平平流作用和垂直粘性力对上升流的影响较弱。     

浙江和琼东沿岸上升流的成因分析

本文用相关和对比分析的方法分别对浙江和琼东沿岸上升流形成原因作了进一步分析。结果表明,浙江沿岸上升流与台湾暖流的相关关系较之与风的相关关系更为密切。上升流的月际和年际间变化趋势与台湾暖流的变化趋势基本一致,结合浙江沿岸海底地形特征,本文认为,台湾暖流与地形的共同作用是该上升流形成的主要因子;风的影响一般不是主要的。关于琼东沿岸上升流,由于它与琼东沿岸西南风出现频率的月间变化趋势相当一致,从而进一步证实,该上升流主要由西南风作用形成。     

福建沿岸上升流数值研究Ⅱ.台湾海峡上升流的三维数值模拟

用有限差分法结合新sine-σ坐标变换和三次样条函数性质,建立了适用于台湾海峡上升流计算的三维数值模型.为考察海峡内潮、风、北上的海峡暖流和地形等因子对上升流形成的影响,设计了多种实验方案.结果表明,潮的非线性效应对海峡内上升流的形成有相当重要的影响.潮流和海峡暖流的存在是台湾浅滩上升流形成的主要原因,也是非季风期福建沿岸上升流形成之主因.西南季风盛行期,福建沿岸上升流得以加强,范围扩大,台湾浅滩上升流中心位置南移;东北季风期,福建沿岸上升流在上、中层基本消失,但海坛岛和东山岛近岸下层仍有上升运动存在,台湾浅滩上升流出现范围向北扩展.由于东北风的连续吹刮,台湾西岸亦出现了范围较窄的上升流迹象.计算还表明,海峡内各上升流有明显的季节性和区域性差异.风对海峡内上升流的中、上层结构起主导作用,而潮和海峡暖流则对中、下层上升流的形成起支配作用,因而导致上升流垂向结构的上下异性.     

渤、黄、东海夏季环流的数值模拟

在POM的基础上 ,建立一个σ坐标系下的三维斜压预报模式 ,考虑了海底地形、外来流、长江径流、海面风应力、海面热交换等多方面因素的影响 ,较好地模拟了夏季东中国海环流的情况。其结果表明 ,黑潮在流经东海时沿东海陆坡流动 ,其途径随陆坡等深线走向而变 ,在其两侧出现一些涡旋。夏季台湾暖流上层水主要来自台湾海峡 ,底层水主要由台湾东面黑潮的次表层水入侵陆架生成。夏季进入朝鲜海峡的对马暖流的来源是多方面的 ,其中有 :台湾暖流、黑潮分支、长江冲淡水与西朝鲜沿岸流的混合水。长江冲淡水在出长江口后 ,很快转向北流动 ,到34°N附近转向东南方向。在长江口东北面存在两个中尺度的涡旋。夏季黄海冷水环流由南北两部分组成 ,表层流速大 ,底层流速小。在青岛 石岛附近还存在一个中尺度的反气旋型涡旋     

2000年8月长江口外海区冲淡水和羽状锋的观测

采用CTD、多参数环境监测系统 YSI等仪器设备 ,于 2 0 0 0年 8月在长江口外海区对长江冲淡水结构、羽状锋等进行了现场观测。 2 0 0 0年 8月长江冲淡水出口门后 ,朝东北偏北流动 ,而当年 8月为长江径流量偏小的月份。通过动力分析指出了近口门段长江冲淡水分布类型与径流量的关系。长江冲淡水主流在近口门附近朝东北偏北扩展后 ,在科氏力作用下朝东南扩展 ,在转向区域为沿水下河谷北上的高盐台湾暖流水。高盐的台湾暖流水和长江冲淡水混合 ,生成口外羽状锋 ,强度大 ,阻挡了长江冲淡水向东扩展 ,并使冲淡水在当年径流量偏小情况下朝东北偏北运动。部分台湾暖流水在中下层能穿越长江口外而向北流动。羽状锋主要存在于长江口外 1 2 2 .6°E附近的 1 5m水层之上。在浙江沿岸、长江口外水下低谷西侧、吕泗近岸存在着上升流现象     

A Review of Some Environmental Issues Affecting Marine Mining

This article reviews information recently available from existing marine and coastal mining for responses to environmental issues affecting marine mining at different depths. It is particularly but not exclusively concerned with those issues affecting seabed biodiversity impact and recovery. Much information has been gathered in the past 10 years from shallow mining operations for construction aggregate, diamonds, and gold, from coastal mines discharging tailings to shallow and deep water, and from experimental deep mining tests. The responses to issues identified are summarized in a series of eight tables intended to facilitate site-specific consideration. Since impacts can spread widely in the surface mixing layer SML, and can affect the biologically productive euphotic zone, the main issues considered arise from the depth of mining relative to the SML of the sea. Where mining is below the SML, the issue is whether it is environmentally better to bring the extraction products to the surface vessel for processing (and waste discharge), or to process the extraction products as much as possible on the seabed. Responses to the issues need to be sitespecific, and dependent on adequate preoperational environmental impact and recovery prediction. For deep tailings disposal from a surface vessel, there are four important environmental unknowns: (1) the possible growth of "marine snow" (bacterial flocs) utilizing the enormous quantities of fine tailings particles (hundreds or thousands of metric tons per day) as nuclei for growth, (2) the possibility that local keystone plankton and nekton species may migrate diurnally down to and beyond the depth of deep discharge and hence be subjected to tailings impact at depth, (3) the burrow-up capability of deep benthos and their ability to survive high rates of tailings deposition, and (4) the pattern and rate of dispersion of a tailings density current through the deep water column from discharge point to seabed. Actions to obtain relevant information in general and site-specifically are suggested.     

Increased Particle Fluxes at the INDEX Site Attributable to Simulated Benthic Disturbance

Particle fluxes were measured 7 m above the sea bottom during the predisturbance, disturbance, and postdisturbance periods by using time series sediment traps attached to seven deep-sea moorings deployed in the INDEX experiment site in the Central Indian Basin. The predisturbance particle fluxes varied between 22.3 to 55.1 mg m -2 day -1 . Increased and variable particle fluxes were recorded by the sediment traps during the disturbance period. The increase observed was 0.5 to 4 times more than the background predisturbance fluxes. The increases in particle fluxes (~4 times) recorded by the sediment trap located in the southwestern direction (DMS-1) were the greatest, which could be the result of preferential movement of resuspended particles generated during the deep-sea benthic disturbance along the general current direction prevailing in this area during the experimental period. Also, the traps located closer to the disturbance area recorded greater fluxes than did the traps far away, across the Deep Sea Sediment Resuspension System path. This variability in recorded particle fluxes by the traps around the disturbance area clearly indicates that physical characteristics such as grain size and density of the resuspended particles produced during the disturbance had an important effect on particle movement. The postdisturbance measurements during ~5 days showed a reduction in particle fluxes of ~50%, indicating rapid particle settlement.     

Assessing the Validity of Seismo-Acoustic Predictor Equations for Obtaining Seabed and Sub-Surface Sediment Physical Properties

The interdependence between the seismo-acoustic properties of a marine sediment and its geotechnical/physical parameters has been known for many years, and it has been postulated that this should allow the extraction of geotechnical information from seismic data. Though in the literature many correlations have been published for the surficial layer, there is a lack of information for greater sediment depths. In this article, a desktop study on a synthetic seafloor model illustrates how the application of published near-surface prediction equations to subsurface sediments (up to several tens of meters burial depth) can lead to spurious predictions. To test this further, acoustic and geotechnical properties were measured on a number of sediment core samples, some of which were subjected to loading in acoustically-equipped consolidation cells (oedometers) to simulate greater burial depth conditions. For low effective pressures (representing small burial depths extending to around 10 meters subsurface), the general applicability of established relationships was confirmed: the prediction of porosity, bulk density, and mean grain size from acoustic velocity and impedance appears generally possible for the investigated sedimentary environments. As effective pressure increases through, the observed relationships deviate more and more from the established ones for the near-surface area. For the samples tested in this study, in some instances increasing pressure even resulted in decreasing velocities. There are several possible explanations for this abnormal behavior, including the presence of gas, overconsolidation, or bimodal grain size distribution. The results indicate that an appropriate depth correction must be introduced into the published prediction equations in order to obtain reliable estimates of physical sediment properties for greater subsurface depths.     

海上大直径钢管桩打桩过程中桩周土强度弱化研究

海上大直径钢管桩打桩过程中,桩周土体受到强烈扰动而发生强度弱化,掌握桩周土体强度弱化规律对于准确预测打桩过程、保证工程安全具有重要意义。为研究土体强度弱化规律,开展了环剪试验模拟打桩对桩周土体的扰动,测试土体强度随剪切速率的变化规律,建立了描述土体强度弱化规律的拟合公式,引入到打桩分析软件中。研究结果表明：土体的强度折减程度不仅与土体本身的性质有关还受到土体的埋深和剪切速率的影响,埋深越深土体强度折减程度越低,剪切速率越高土体强度折减越高,在打桩分析中可采用这里推荐的线性折减方法来模拟不同深度处土体强度的折减规律。     

Determination of In Situ Sediment Shear Strength from Advanced Piston Corer Pullout Forces

The advanced piston corer (APC) has been used by the Ocean Drilling Program since 1985 for recovering soft sediments from the ocean floor. The pullout force measured on extracting the core barrel from the sediment is shown to correlate with the average shear strength of the sediment core measured in the ship's laboratory. A simple rule of thumb is derived relating the shear strength of the sediment to the pullout force. Multiple APC holes at individual sites allow the consistency of the pullout measurements to be assessed. The effects of different operational procedures during APC coring are also explored. Although generally applicable, the correlation between pullout force and laboratory measurements of shear strength breaks down for some APC holes, possibly because of the disturbance of some sediment types during the APC coring process. A better understanding of the physical process of APC coring, and its effect on the properties of the sediment both inside and immediately outside the core barrel, would indicate what confidence can be put on the measurement of pullout force as a way of evaluating the in situ shear strength of deep sea sediments.     

Interannual Sea Level Variations and Annual Tides in the Northwestern Pacific

Specific properties of the interannual sea level variations and annual tides in the Northwestern Pacific were studied. Several tide stations were monitored. The monthly mean sea level for the year of 1995 was analyzed at each tide station. A seismic event in 1995, some tectonic activity around the subject area, and the Kuroshio (the oceanic western boundary current) may possibly contaminate results which would have occurred from the astronomical annual tide alone.     

《Acta Oceanologica Sinica》Vol. 33(2014) contents

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INFORMATION FOR AUTHORS

<正>Acta Oceanologica Sinica(AOS)is a comprehensive academic journal edited by the Editorial Committee of Acta Oceanologica Sinica and is designed to provide a forum for important research papers of the marine scientific community which reflect the information on a worldwide basis.The journal publishes scholarly papers on marine science and technology,including physics,chemistry,biology,