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渤海动力对黄河入海泥沙输移的影响 总被引：7，自引：0，他引：7
海洋动力过程对黄河入海泥沙的淤积和扩散具有决定性作用，利用三维斜压动力－泥沙模型分析了黄河口外海域潮流动力变化与黄河入海泥沙淤积，扩散特性之间的响应关系，季节环流以及涨落潮的分布和变化很好地解释了黄河口南北浮泥的形成和消长变化以及黄河入海泥沙向海扩散的机理，结果表明，入海泥沙在洪季，枯季和表底层都具有不同的输移特性。 相似文献
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根据河口海岸水沙输移的特点,建立了一个新的二维分组数学模型,用来预测该区域的水沙输移过程。该模型耦合了水动力模块、泥沙输移模块和床面演变模块。其中水动力模块基于浅水方程组,综合考虑了柯氏力、床面切应力以及表面风应力的影响,引入干湿判断法处理动边界。泥沙输移模块首先将泥沙按照粒径分组,针对不同泥砂性质,对各组泥沙分别进行建模求解。床面演变模块基于质量守恒方程,实时更新床面高程以及床沙级配变化,并传递给水动力模块,更新底部边界。该模型被应用在了英国塞汶(Severn)河口,其预测的泥沙浓度和实测数据以及不分组的模型的预测结果进行了比较,结果显示,文中建立的分组模型预测的结果要明显好于不分组模型。 相似文献
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在长江河口北槽抛泥过程中，应用ASSM－Ⅰ型声学悬浮泥沙观测系统观测悬沙浓度的时空分布规律，结合多普勒流速剖面仪走航式断面流速测量。研究发现：（1）泥沙浓度垂向分布形成至少三种结构类型，即上小下大的“L”型和指数型，上大下小的“漂浮”型；（2）受抛泥泥沙输移的影响，断面流场形成低流速区，或分布在水体表、中层，或贯穿整个水体，形成流速切变锋，它们的强度随抛泥泥沙输移扩散逐渐减弱；（3）在落潮流和颗粒重力共同作用下，抛泥泥沙同时存在输移扩散和沉降过程。小潮型抛泥泥沙主要就近扩散和沉降，中潮和大潮型抛泥泥沙输移扩散范围较远。 相似文献
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黄河在调水调沙影响下的入海泥沙通量和粒度的变化趋势 总被引：1，自引：0，他引：1
《海洋地质前沿》2015,(7)
基于1950—2013年的黄河水文泥沙资料,系统研究了黄河实施调水调沙以来入海泥沙在通量、粒度组成和时间分布上的变化特征,揭示了调水调沙影响下黄河入海泥沙的变化趋势。在2002年黄河实施调水调沙以来,6—11月平缓均衡的持续性高水沙量取代了调水调沙之前7—10月峰值尖瘦的汛期特征,汛期与非汛期差异减小,入海水沙通量的季节性特征显著改变。随着调水调沙的逐年实施,河床泥沙颗粒粗化,临界起动功率不断增大,而调水调沙期间的径流量峰值基本稳定,径流对下游河床冲刷效率不断降低,导致入海泥沙通量持续降低、泥沙颗粒变细。可以预见,黄河河口的淤积将会大大减缓,入海的泥沙将更多地沉积在远离河口的区域,维持河口三角洲叶瓣冲淤平衡的临界泥沙量将会加大。 相似文献
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现行黄河入海泥沙分布与海洋动力要素的关系 总被引：7，自引：0，他引：7
在整理分析实测滨海地区地形和海水动力资料的基础上，对现行河口入海泥沙分布与海洋动力因素间的关系进行初步探讨，其目的是根据过去和现在黄河入海泥沙分布规律，展望将来黄河泥沙分布规律，以及它对海岸带开发利用的影响。 相似文献
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1976年黄河改道以来三角洲近岸区变化遥感监测 总被引：16，自引：1，他引：16
通过对黄河三角洲沿岸10个河口、潮汐汉道的23景陆地卫星影像高潮线的解译与对比，探讨自1976年黄河改道以来，三角洲岸线的变化特征；同时，利用GIS软件处理1976年和1992年滨海区水深测量数据，并与黄河利津站同期入海沙量进行对照分析。结果表明：1)目前黄河三角洲总体处于侵蚀破坏阶段，侵蚀岸线长相当于淤积岸线的2倍；2)人类活动对三角洲岸线变化的影响不断增强，人工海岸长度大幅度增加，总岸线长度缩短，岸线趋于平直；3)52．6％的黄河入海泥沙堆积于入海口附近，其中92％的泥沙堆积在15m水深线以内，向外迅速减少，20m水深线以外出现侵蚀；4)87％黄河入海泥沙往东、东南方向扩散与沉积，往南、东北方向扩散与沉积的泥沙很少，河口的北、西北方向整体上处于侵蚀状态。海岸侵蚀与河口泥沙的输移密切相关。 相似文献
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Arne Schnack-Friedrichsen Angela M. Davis Jim D. Bennell Dei G. Huws 《Marine Georesources & Geotechnology》2001,19(4):221-243
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. 相似文献
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Shigehisa Nakamura 《Marine Geodesy》2000,23(1):55-61
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. 相似文献
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The effect of different fixation and storage protocols on the flow cytometric (FCM) simultaneous analysis of bacterioplankton and phytoplankton in coastal seawater samples (Mediterranean coastal lagoons) was investigated. FCM measurements (cell number, fluorescence and scatter characteristics) were obtained through DAPI staining. Three fixatives [glutaraldehyde (GA), formaldehyde (FA) and paraformaldehyde (PFA)] and two storage (3 months duration) methods (5 °C and −196 °C) were tested. Two dominant populations were detected in studied samples: bacteria and eukaryotic picophytoplankton. Adding fixatives (2% final concentration) appears necessary to obtain FCM exhaustive counts of all the bacteria and phytoplanktonic cells. This was related to the permeation effect of fixatives which allowed a better DAPI staining of the cells. Maximum fluorescence, i.e. optimal staining of the cells was obtained with FA or PFA, and significant lower fluorescences with GA. Fixed samples stored at 5 °C induced rapid cell loss. Only storage in liquid nitrogen of samples fixed with FA or PFA, allows mid-term (≥4 months) preservation of bacteria or picophytoplankton cell numbers, and limited evolution of DAPI-induced fluorescence and scatter characteristics. 相似文献
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《海洋学报(英文版)》2014,(9):F0003-F0003
<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, 相似文献
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The relationship between the flux of exotic benthic foraminiferal tests (i.e. tests which are supplied from open-sea sources alone) in a tidal inlet and that of bulk sediment was analysed, which can be expressed as two first-order linear equations. According to this relationship, in order to determine net sediment transport directions in the entrance, the test concentration in surficial sediments of the tidal basin can be compared against a ‘ critical level ’. The critical level is determined for the conditions that no net transport of bulk sediment is present within the entrance. If the observed concentration (averaged over the tidal basin) is higher than the simulated critical level, then the net sediment transport is directed to landward. This method is applied to the analysis of net sand transport at Christchurch Harbour, a tidal inlet system located in southern England. In this investigation, concentrations of exotic foraminiferal tests in the surficial sediments of the tidal basin and ebb tidal delta area were obtained from the analysis of sea-bed sediment samples. A series of probable critical levels were calculated based upon the data sets with regard to: (1) sediment discharge from the rivers; (2) magnitude of sediment discharge within the entrance during the ebb; (3) the test concentration outside the harbour; (4) the thickness of the moving layer; and (5) two parameters associated with dispersive processes. The results show that the concentration in the tidal basin sediment is higher than a number of simulated critical concentrations for representative cases. Consequently, the high level of the concentration of exotic benthic foraminiferal tests within the harbour should be explained as a result of landward net transport of sands within the entrance. 相似文献
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Rahul Sharma 《Marine Georesources & Geotechnology》2000,18(3):237-250
Observations on seafloor features from subbottom profiling and seabed photography data show that the undisturbed and natural conditions before the benthic disturbance undergo a substantial change after operation of the disturber. The effects can be seen in the form of deep trenches and grooves, formed by the action of the sleds and the pumping of the sediment along its path, as well as sediment piles on either side of the track. Biological traces such as fecal coils, casts, tubes, burrows, and trails get obliterated in the areas of disturbance and resedimentation. The smooth, uniform nature of the seafloor observed in predisturbance phase shows microtopographic changes in and around the disturbed area as a result of sediment excavation and resettlement. Vertical mixing as well as lateral transport of sediment alter the geological, biological, physical, and chemical conditions on the seafloor, which need to be monitored over time to assess the process and the time taken for restoration of environmental conditions. 相似文献
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Vance P. Vicente 《Marine Ecology》1989,10(2):179-191
Abstract. Long-term changes in the distributional patterns of commercial sponges ( Spongia spp. and Hippospongia spp.) within the West Indian Region indicates that: 1) commercial sponges had a widespread distribution throughout the whole West Indian Region and were ubiquitous in very shallow water until about the first half of the present century; 2) they were fished commercially not only in the traditional northern Caribbean sites (Florida, Gulf of Mexico, Bahamas) but also in the Greater ( e. g. , Hispaniola, Jamaica) and Lesser Antilles; and 3) they became extinct throughout most of the Lesser Antilles ( e. g. , Puerto Rico, Vieques, St. Thomas) sometime during the first half of this century. Mortalities of spongiids within the Antilles were found to differ from other marine mortalities in that: 1) species disappeared from a large region; 2) species vanished from different habitats and depths; and 3) natural populations never recovered. Species richness patterns suggest that commercial sponge genera ( Spongia and Hippospongia ) evolved under slightly cooler elimatic conditions than those found at present, and that these extinctions occurred as a direct or indirect effect of positive thermal anomalies in sea surface and atmospheric temperatures between 1900–1950. The concept that species diversity is stable on a regional scale is questioned. 相似文献
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The behaviour of an axially pre-loaded cylindrical member of an offshore structure, hit by a supply ship, has been investigated. The effects of axial pre-loading on the dynamic properties of members, the extent of damage and propagation of dynamic instability in the tubular members have also been investigated. Numerical models have been validated using available experimental data from the literature although these are mostly static with no pre-loading. Axial pre-loading was found to change the dynamic characteristics of some cylindrical members quite dramatically while it had no significant effect on others. The study examined whether there was any change in the behaviour between local and global modes when the loading was dynamic rather than static. The effect of damping on the dynamic instability of axially pre-loaded tubes under lateral dynamic loads was also studied. It was observed that for some geometries the quasi-static response can be used to define the boundary between bounded and unbounded dynamic responses. The main contribution of this study, compared with previous investigations reported in the literature, is that both pre-loading and dynamic effects have been included. 相似文献