丁字湾近岸海域潮汐、潮流和余流特征研究

利用丁字湾近岸海域2021年的最新观测资料,研究了潮汐、潮流和余流的基本特征和变化规律。得出如下结论：潮汐为正规半日潮,最大潮差405 cm,最小潮差69 cm,平均潮差248 cm,涨潮历时小于落潮历时。潮流为规则半日浅海潮流,最大涨潮流流速为67 cm/s,最大落潮流流速为72 cm/s。涨潮流历时小于落潮流历时。垂向来看,表层流速最大,中层次之,底层最小。海流的旋转谱分析的结果显示M₂分潮的谱峰值最高,运动形式为逆时针旋转流。余流,整体余流流速小于10 cm/s,表层余流最大,中层次之,底层最小。观测期间,长周期的风向和余流流向相反,因此风不是余流的控制因素。     

长江河口北支上口不规则周期潮流的动力机制

数值模拟和动量分析长江河口北支上口枯季大潮期间 1 d内出现"四涨四落"不规则周期涨落潮流现象。长江河口北支上口 1日内两次涨潮流和两次落潮流为常规涨落潮流,受外海半日潮流控制,两次涨潮流和落潮流为非常规涨落潮流。北支上口非常规的涨潮流处于南支落潮的末期,范围小,流速弱,历时约2 h;表层主要是垂向黏滞项和水平扩散项与正压项间的作用,南向的垂向黏滞项起着决定的作用,底层则是斜压项与正压项间的作用;北支上口非常规涨潮流是北风、盐度锋面产生的南向斜压压强梯度力和南支末期落潮流的牵引作用共同造成的;径流抑制非常规涨潮流的产生,持续时间随径流量的增加呈指数递减,当径流量达到22 300 m3/s时,非常规涨潮流现象消失。北支上口非常规落潮流处于南支涨潮流的初期,由于在北支上口南支的涨潮流早于北支涨潮流,导致南支水体进入北支,形成北支上口第二次落潮流,范围较大,流速较强,历时约2.5 h,从表层至底层主要是垂向黏滞项与非线性平流项和正压项之间的作用。本文揭示了北支上口 1 d内出现"四涨四落"不规则周期涨落潮流的动力过程和机制。     

福建东山湾潮流和余流特征研究

东山湾位于台湾海峡南口的西岸,属于潮控型半封闭海湾.本文章通过对M1站1周年的流速、流向及对应的风速、风向资料进行分析,结果表明:M1站正压流动特征显著,潮流日不等现象较明显,相邻潮次中涨急流速明显小于落急流速.观测期间,M1表、中、底3层实测最大涨潮流速分别为83,78,71 cm/s,实测最大落潮流速分别为152,104,100 cm/s.夏季表层余流流速明显大于中层和底层,冬季各层余流速相差则较小.径流是M1站的余流的主要因子.夏季,径流对表层作用最为明显,其余流流速明显大于中层和底层,中、底层由于受温盐跃层产生的斜压效应作用,出现较长时段的北向余流;冬季东山湾平面和垂向温、盐分布均匀,各层余流流向均为落潮方向,且表层往底层方向,流速变幅不大.由于其半封闭型的海湾形态,风应力对东山湾的余流贡献较小.     

夏秋季泉州湾中部海域潮流和余流的变化特征

在前人大量研究的基础上,通过数据统计、潮流调和分析、低通滤波及谱分析等手段对泉州湾湾中水道上M站3个多月的实测资料进行潮流和余流特征分析.结果表明:该站为规则半日潮流,以半日潮分量M2占绝对优势;各层涨潮流的主导方向均为WNW向,落潮流主导方向表层为SE—ESE向,实测涨、落潮最大流速分别达151 cm/s和138 cm/s.M站河口环流动力过程非常明显;从表层往底层,余流流向沿顺时针方向从WSW向往NW向偏转;水体在落潮时受潮汐张力的作用,盐度的层化结构逐渐增强,而在涨潮时受潮混合的作用,盐度的层化结构逐渐减弱.     

大亚湾海域潮流和余流的三维数值模拟

用三维陆架海模式(HAMSOM)对大亚湾海域的潮汐、潮流和余流进行了数值模拟研究,模拟结果与实测值吻合较好。给出了潮流性质、主要分潮的潮流椭圆和余流。计算结果表明,大亚湾海域的潮流性质以不正规半日潮为主,水平潮流具有明显的往复流性质,主要呈南-北方向,落潮流速比涨潮流速大,其中表层M2分潮最大流速为25.3cm.s-1。流速受地形的影响,在大辣甲和黄毛山岛之间以及两岛与岸之间的区域流速较大,尤其在湾的东北角狭长地形处流最急,流速最大;靠近岸边流速较小,水平速度的垂向变化不大。夏季湾内余流较小,海域自净能力较弱。冬季湾内水体的自净能力随流场强度加强而加强。     

象山港内湾潮汐应变对横向流及其余环流垂向空间结构的调控研究

横向流 (垂直于海湾主轴方向的流动) 对横向动量以及物质分布具有重要影响。已往研究表明,潮汐应变对横向流的垂向空间结构具有重要的调控作用。但这种认识仅局限于强层化海区,弱层化条件下潮汐应变对于横向流空间结构的影响仍未可知。为此,本文以象山港为例,基于实测数据阐释了弱层化条件下潮汐应变对横向流及其余环流垂向空间结构的调控作用。结果显示,象山港内湾横向流的垂向空间结构随大小潮呈现出明显的变化规律。大潮时,潮汐应变现象明显,涨潮时较强的垂向混合使得横向流在高潮阶段呈现出一层结构;落潮时垂向混合较弱,横向流在低潮时呈现两层结构。小潮时,潮汐应变受到抑制,垂向混合在涨落潮时均较弱,因此横向流在高低潮阶段均呈现出两层结构。经过潮时均进一步得到的横向余环流呈现出上层向南、下层向北的两层结构。由于潮汐应变的大小潮变化,横向余环流的反转深度反转点自大潮到小潮呈现出上升的趋势。     

江苏盐城近岸海域水动力特征

通过2018年对江苏盐城近岸海域(射阳港至大丰港之间)布设的4个测流站位夏冬两季连续25 h海流、悬沙浓度的观测资料,对该地区的水动力特征进行了初步分析,结果表明:新洋港到四卯酉河口沿岸的潮流主轴的方向基本与等深线走向一致,呈现明显的往复流特征,射阳港附近站位(JS-YWPY01站)涨潮流以SW向为主,落潮流以NNE向为主;JSYWPY02、JS-YWPY03和JS-YWPY04 3站涨潮流均以SE向为主,落潮流均以NW向为主,JS-YWPY03站和JS-YWPY04站涨潮流流速大于落潮流流速;25 h内出现2次涨落潮,落潮历时大于涨潮历时,而涨潮流速大于落潮流速,最大流速一般发生在中潮位时刻,最小流速均发生在高潮或低潮时刻,测区一带潮汐属于正规半日潮,潮流在观测周期内呈现显著的变化特征。     

珠江河口磨刀门水道枯季盐水入侵特性分析

为探讨磨刀门水道潮流和盐度的三维分布特性,本文建立了磨刀门水道的三维潮流和盐度数值模型,采用2009年枯季磨刀门水道实测潮流和盐度资料对模型参数进行率定和验证。结果显示,枯季由于上游径流量小,磨刀门水道总体涨、落潮流速都不大,表层总体涨潮平均流速都在0.5 m/s以内,总体落潮平均流速在0.8 m/s以内;底层总体涨落潮平均流速都在0.5 m/s以内;从盐度的平面分布来看,磨刀门水道近口门河段总体呈现涨潮时水道东侧盐度高于西侧,落潮时东侧盐度小于西侧的趋势。大潮和中潮期间,落潮时盐水向上游的入侵距离反而较涨潮时更远,主要原因是,落潮时的底层盐水向上游的补偿流动以及地形阻拦形成更为强烈的紊动扩散。潮汐动力弱(小潮)时,整个水道内水流流速很小,流态平缓,紊动较弱,总体仍呈现涨潮时入侵距离大于落潮,显示枯季磨刀门水道盐水入侵的主要影响因素取决于地形和潮动力。     

基于FVCOM的泉州湾海域三维潮汐与潮流数值模拟

基于FVCOM海洋数值模式,采用非结构的三角形网格和有限体积法,建立了泉州湾海域高分辨率(26 m)的三维潮汐、潮流数值模型。模拟结果同2个验潮站和3个连续测流站的观测资料符合良好,较好地反映了泉州湾内潮汐、潮流运动的变化状况和分布特征,给出了M₂、S₂、K₁、O₁ 4个主要分潮的同潮图、表层潮流椭圆分布,以及模拟区域内最大可能潮差、表层最大可能潮流流速和潮余流分布。分析表明,4个分潮的最大潮汐振幅和迟角差分别为219 cm和19°,85 cm和25°,26 cm和12°,26 cm和9°;石湖港以东海域的潮波为逆时针旋转的驻波,以西海域为前进波;最大可能潮差由湾口的8.0m向湾内增加至8.8 m。湾内潮流类型为规则半日潮流,落潮最大流速大于涨潮最大流速,北乌礁水道为强流区,表层最大可能潮流流速为2.4 m/s;湾口潮流运动以逆时针方向的旋转流形式为主,湾内的潮流运动以往复流形式为主,长轴走向主要沿着水道方向,与等深线和海岸线平行;四个分潮流表层最大流速分别为1.4 m/s,0.58 m/s,0.12 m/s,0.10 m/s。余流流速大小与潮流强弱有密切的联系,表、中、底层最大余流流速分别为26 cm/s,20 cm/s,16 cm/s,三者在水平方向基本呈北进南出的分布形态。     

象山港余流特征数值研究

基于Delft3D-Flow模块建立了象山港海域的三维斜压潮流数值模型,结合实测水文资料,研究了象山港的潮(余)流特征,对欧拉余流场的时空分布进行了定量的比较和分析,并与潮流测站计算分析得到的欧拉余流分布对比,很好的模拟了象山港的余流特征。结果表明:由湾外至湾顶,余流呈减小的趋势,湾外余流最大为33 cm/s,湾顶最小,余流平均仅5 cm/s。垂向上,表层余流大于底层余流,表层余流指向湾外,而底层余流则指向湾内。对比斜压、正压两种模式下的欧拉余流分布,可以看出湾顶附近主要受径流控制,两种模式得到的结果基本一致,口门至西沪港区域受径流和潮流的共同影响,斜压模式更准确地模拟出了水体层化和垂向余环流结构。     

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,