Structure and distribution of the benthic macrofauna on a Northwest African sandy beach close to a freshwater river discharge     

Abdellatif Chaouti  Isabella Colombini  Mario Fallaci  Elena Gagnarli  Lorenzo Chelazzi  & Abdellatif Bayed 《Marine Ecology》2008,29(S1):99-107

The effects of the freshwater discharge of the Oued Sebou River on the macroinfauna, was studied on the sandy beach of Mehdia through the analysis of the abiotic parameters and of the macrozoobenthos. In autumn 2002 and spring 2003, three beach sites, each with two transects, localized at 50, 3500 and 5720 m from the river mouth respectively, were studied. Positive correlations were recorded for beach slope and pH whereas negative ones were obtained for organic matter content and salinity at increasing distances from the river mouth. Significant differences between beach sites and seasons occurred for median grain size, organic matter content and pH. For each beach site, mean macroinfauna abundance varied between 30 and 100 ind.·m⁻² and in spring there was a significant correlation between this parameter and the increasing distance from the river mouth. No significant correlation was instead found between species richness and the increasing distance, although the farthest beach site from the mouth had the highest number of species during both seasons. The results indicated the importance of organic matter content and salinity for the macrofaunal abundance whereas the diversity indices were more affected by beach slope and grain size. The results showed that there was no clear spatial trend in compound indices of the macrofauna across the sampled sites and the influence of the river discharge of Sebou River did not seem to be significant and consistent on the macrobenthos of this mesotidal shore. Comparison with microtidal shores revealed the influence of the tidal excursion and swell characteristics on the response of the benthic structures of sandy beaches to discharges of freshwater.  相似文献   

Observations of wave pump efficiency     

Peter Nielsen  Paul A. GuardDavid P. Callaghan  Tom E. Baldock 《Coastal Engineering》2008

Currently available data on wave pump efficiency is reviewed. The obtainable efficiency is an important consideration in the design of practical devices for the extraction of wave energy and the analysis of natural systems (e.g., coral flats and rip currents). We find that the peak efficiency is 0.5 for very steep (∼ 40–45°) ramps where the waves break over the top of the ramp. For flatter (< 30°) ramps, the breaking process is more gradual and the peak efficiency is less than 0.1. We have identified natural atoll lagoon systems where the flushing is wave driven and successfully modeled it as driven by a wave pump. The same is the case for rip currents. For both of these natural systems, the pump efficiency is around 0.035. In addition a numerical swash model is used to estimate wave pump efficiency and is seen to match the experimental results for natural systems or breaking wave scenario.  相似文献   

弱流场调制下的海面微波散射模拟研究     

吕伟艳  赵朝方  杜涛 《海洋科学》2008,32(7):57-61

根据海面微波散射的多尺度模型以及波流相互作用理论,对一维弱流场调制下的海面微波散射截面进行了数值模拟。结果表明,利用数值方法直接求解波作用量方程获得的海浪调制谱并结合多尺度模型可以较好地模拟弱流场引起的雷达散射截面的变化。内波等海洋现象调制了海浪谱,使得雷达散射截面反映出这些海洋特征,整个调制过程的模拟对于分析这些海洋现象并更好地利用其雷达数据具有重要意义。  相似文献   

沙质海岸强浪作用下沿岸输沙问题研究   总被引：1，自引：0，他引：1  

王玉海 《海洋工程》2008,26(4)

在沙质海岸上修建导流堤、丁坝等会引起局部海域水沙动力条件的改变和海床冲淤调整,因此准确预测沿岸输沙率是海岸工程建设前进行优化设计的基础条件之一.首先构建了刻画高强度推移质输沙过程中固-液混合体运动的理论模型,通过寻求模型的特解并推导成1D沿岸输沙率公式.该公式适宜计算强浪作用下的推移质输沙率,已得到了大型波浪水槽、往复流水道和海滩现场实测输沙率资料的良好验证.通过与物理模型试验实测输沙量结果的比较,进一步表明该公式能够较好地预测沙质海岸在寒潮大风浪(或台风浪)作用下的高强度输沙量(骤淤量).  相似文献   

The mid-depth circulation of the northwestern tropical Atlantic observed by floats     

Matthias Lankhorst  David Fratantoni  Michel Ollitrault  Philip Richardson  Uwe Send  Walter Zenk 《Deep Sea Research Part I: Oceanographic Research Papers》2009,56(10):1615-1632

A comprehensive analysis of velocity data from subsurface floats in the northwestern tropical Atlantic at two depth layers is presented: one representing the Antarctic Intermediate Water (AAIW, pressure range 600–1050 dbar), the other the upper North Atlantic Deep Water (uNADW, pressure range 1200–2050 dbar). New data from three independent research programs are combined with previously available data to achieve blanket coverage in space for the AAIW layer, while coverage in the uNADW remains more intermittent. Results from the AAIW mainly confirm previous studies on the mean flow, namely the equatorial zonal and the boundary currents, but clarify details on pathways, mostly by virtue of the spatial data coverage that sets float observations apart from e.g. shipborne or mooring observations. Mean transports in each of five zonal equatorial current bands is found to be between 2.7 and 4.5 Sv. Pathways carrying AAIW northward beyond the North Brazil Undercurrent are clearly visible in the mean velocity field, in particular a northward transport of 3.7 Sv across 16°N between the Antilles islands and the Mid-Atlantic Ridge. New maps of Lagrangian eddy kinetic energy and integral time scales are presented to quantify mesoscale activity. For the uNADW, mean flow and mesoscale properties are discussed as data availability allows. Trajectories in the uNADW east of the Lesser Antilles reveal interactions between the Deep Western Boundary Current (DWBC) and the basin interior, which can explain recent hydrographic observations of changes in composition of DWBC water along its southward flow.  相似文献   

船载ADCP资料的潮流分离方法在厦门港断面重复走航中的应用   总被引：1，自引：0，他引：1  

黄奖  葛勇 《台湾海峡》2009,28(1):123-129

本文运用Candela等提出的潮流分离方法,选用高斯函数作为基函数,采用Matlab程序,首次对厦门港嵩鼓水道的船载ADCP断面重复走航资料进行潮流分离计算．通过对14个计算点的Candela方法计算结果与引进差比关系准调和分析方法计算结果的分析比较可见：（1）两种方法计算所得余流在大、小潮的相关系数分别为0．9882和0．8521,余流相对误差在大、小潮分别为0．065和0．150,而所得余流方向在大、小潮的相关系数分别为0．9982和0．9865,余流方向相对误差在大、小潮分别为0．023和0．027．两种方法计算的余流及其方向的相关性很高（在样本数为14,置信度为α=1％时,相关系数大于0．6610,结果是可信的）,而平均相对误差也很小．（2）对14个计算点的M2、S2、K1、O1、M4和MS4等6个分潮的计算结果（共有84个样本数据）进行分析比较,两种方法计算所得6个分潮的长轴、长轴方向和短轴在大潮的相关系数分别为0．9838、0．8960和0．2335,而在小潮的相关系数分别为0．9656、0．7555和0．2209．这两种方法计算所得6个分潮的长轴、长轴方向和短轴在大潮的平均相对误差分别为0．375、0．071和0．753,而在小潮的平均相对误差分别为0．287、0．254和0．845．两种方法计算的分潮长轴及其方向的相关性很高（在样本数为84,置信度为α=1％时,相关系数大于0．283,结果是可信的）．相应的分潮长轴的相关性略低,但是在样本数为84,置信度为α=5％时,相关系数均大于0．217．可认为在置信度为α=5％时,计算结果是可信的,而平均相对误差则略显较大．综上所述,我们认为采用Candela等的方法对船载ADCP断面重复走航资料进行潮流分离计算是可行的．  相似文献   

Characteristics and origins of middle Miocene mounds and channels in the northern South China Sea     

Yufeng Li  Gongcheng Zhang  Renhai Pu  Hongjun Qu  Huailei Shen  Xueqin Zhao 《海洋学报(英文版)》2021,40(2):65-80

Numerous elongated mounds and channels were found at the top of the middle Miocene strata using 2D/3D seismic data in the Liwan Sag of Zhujiang River Mouth Basin(ZRMB) and the Beijiao Sag of Qiongdongnan Basin(QDNB). They occur at intervals and are rarely revealed by drilling wells in the deepwater areas. Origins of the mounds and channels are controversial and poorly understood. Based on an integrated analysis of the seismic attribute, palaeotectonics and palaeogeography, and drilling well encountering a mound, research results show that these mounds are dominantly distributed on the depression centres and/or slopes of the Liwan and Beijiao sags and developed in a bathyal sedimentary environment. In the Liwan and Beijiao sags, the mounds between channels(sub) parallel to one another are 1.0–1.5 km and 1.5–2.0 km wide, 150–300 m and 150–200 m high, and extend straightly from west to east for 5–15 km and 8–20 km, respectively. Mounds and channels in the Liwan Sag are parallel with the regional slope. Mounds and channels in the Beijiao Sag, however, are at a small angle to the regional slope. According to internal geometry, texture and external morphology of mounds, the mounds in Beijiao Sag are divided into weak amplitude parallel reflections(mound type I), blank or chaotic reflections(mound type II), and internal mounded reflections(mound type Ⅲ). The mounds in Liwan Sag, however, have the sole type, i.e., mound type I. Mound type I originates from the incision of bottom currents and/or gravity flows. Mound type II results from gravity-driven sediments such as turbidite. Mound type Ⅲ is a result of deposition and incision of bottom currents simultaneously. The channels with high amplitude between mounds in the Beijiao and Liwan sags are a result of gravity-flow sediments and it is suggested they are filled by sandstone.Whereas channels with low-mediate amplitudes are filled by bottom-current sediments only in the Beijiao Sag,where they are dominantly composed of mudstone. This study provides new insights into the origins of the mounds and channels worldwide.  相似文献   

完全非线性波浪破碎模型沿岸流数值模拟   总被引：1，自引：1，他引：0  

李绍武  连怡贞 《海洋工程》2007,25(3):46-52

探讨一种基于完全非线性Boussinesq方程的波浪破碎模型在沿岸流计算中的应用问题。针对控制方程中的完全非线性项对沿岸流成长过程的影响进行了深入讨论。数学模型计算结果表明,完全非线性项有使平均流局部化的作用;通过数模实验还发现,垂向高阶涡度项可以有效抑制破波区外回流;运用Visser的实验室沿岸流实测资料从沿岸流速度、波高和平均水位几方面对所提模型进行了验证,并给出了紊动参数的计算结果。  相似文献   

渤海的环流、潮余流及其对沉积物分布的影响   总被引：42，自引：2，他引：42  

赵保仁  庄国文  曹德明  雷方辉 《海洋与湖沼》1995,26(5):466-473

阐明渤海环流和潮余流的分布特征及其与沉积物输运之间的关系。本文根据80年代以来的实测海流资料得到：辽东湾的环流是顺时针向的；黄河三角洲外海存在着一支流向东北偏北向流，与辽东湾西部的东北向海流相接；渤海湾内的环流北部为反时针向，南部为顺时针向回转的双环结构。上述环流趋势与渤海沉积物分布相一致。渤海沿岸主要入海河流的特征矿物分布正是上述环流存在的最好佐证。文中进一步讨论了潮余流分布特征及其对渤海环流的贡献。  相似文献   

渤海的环流、潮余流及其对沉积物分布的影响   总被引：16，自引：2，他引：16  

赵保仁  庄国文  曹德明  雷方辉 《海洋与湖沼》1995,26(5):466-473

阐明渤海环流和潮余流的分布特征及其与沉积物输运之间的关系。本文根据８０年代以来的实测海流资料得到：辽东湾的环流是顺时针向的；黄河三角洲外海存在着一支流向东北偏北向流，与辽东湾西部的东北向海流相接；渤海湾内的环流北部为反时针向，南部为顺时针向回转的双环结构。上述环流趋势与渤海沉积物分布相一致。渤海沿岸主要入海河流的特征矿物分布正在上述环流存在的最好佐证。文中进一步讨论了潮余流分布特征及其对渤海环流的  相似文献