The response of circulation and salinity in a micro-tidal estuary to sub-tidal oscillations in coastal sea surface elevation     

Joanne O’Callaghan  Charitha Pattiaratchi  David Hamilton 《Continental Shelf Research》2007

Conceptual models of circulation theorise that the dominant forces controlling estuarine circulation are freshwater discharge from the riverine section (landward), tidal forcing from the ocean boundary, and gravitational circulation resulting from along-estuary gradients in density. In micro-tidal estuaries, sub-tidal water level changes (classified as those with periods between 3 and 10 days) with amplitudes comparable to the spring tidal range can significantly influence the circulation and distribution of water properties. Field measurements obtained from the Swan River Estuary, a diurnal, micro-tidal estuary in south-western Australia, indicated that sub-tidal water level changes at the ocean boundary were predominantly from remotely forced continental shelf waves (CSWs). The sub-tidal water levels had maximum amplitudes of 0.8 m, were comparable to the maximum tidal range of 0.6 m, propagated into the estuary to its tidal limit, and modified water levels in the whole estuary over several days. These oscillations dominated the circulation and distribution of water properties in the estuary through changing the salt wedge location and increasing the bottom water salinity by 7 units over 3 days. The observed salt wedge excursion forced by CSW was up to 5 km, whereas the maximum tidal excursion was 1.2 km. The response of the residual currents and the salinity distribution lagged behind the water level changes by ∼24 h. It was proposed that the sub-tidal forcing at the ocean boundary, which changed the circulation, salinity, and dissolved oxygen in the upper estuary, was due to a combination of two processes: (1) a gravity current generated by a process similar to a lock exchange mechanism and (2) amplified along-estuary density gradients in the upper estuary, which enhanced the gravitational circulation in the estuary. The salt intrusions under the sub-tidal forcing caused the rapid movement of anoxic water upstream, with significant implications for water quality and estuarine health.  相似文献   

20世纪2次最强El Nino事件珠江口SST变化的差异   总被引：5，自引：8，他引：5  

汤超莲  游大伟  邓松  郑兆勇  邓文君 《广东气象》2007,29(2):11-13

比较分析20世纪2次最强El Nino事件(1982/1983年与1997/1998年)珠江口表层海温(SST)的变化差异,发现造成其差异的原因:一是到达地面的太阳总辐射1982/1983年高于1997/1998年;二是南海高压势力1982/1983年弱于1997/1998年;三是1982/1983年冬季风速比1997/1998年大1~2 m/s。  相似文献   

长江口冲积岛浅滩演变的可视化分析     

胡红兵  胡光道  程和琴 《地理与地理信息科学》2007,23(4):85-88

为了解剧烈开发背景下长江口浅滩的演变特征,运用GIS技术建立1879年以来长江口地区水下数字高程模型(DEM),再现百余年来长江口长兴岛—横沙岛和九段沙浅滩的演变过程,并计算浅滩的面积、体积、冲淤量和冲淤厚度。结果表明:百余年来长兴岛—横沙岛和九段沙浅滩总体上呈淤涨趋势,并沿东南方向向海推进;长江流域中上游的开发和保护以及河口地区重大工程对浅滩演变的影响越来越大。  相似文献   

黄河口水沙过程变异及其对河口海岸造陆的影响   总被引：16，自引：4，他引：16       下载免费PDF全文

张治昊  胡春宏 《水科学进展》2007,18(3):336-341

采用实测资料分析和理论探讨的方法,研究了黄河口海岸造陆与水沙过程变异的关系.研究结果表明:黄河口陆域来水来沙是海岸造陆的基础,来水来沙越大,造陆面积越大,水沙过程变异后,由于水沙的急剧减少,黄河口海岸造陆速度减缓,典型岸段严重蚀退造陆面积也大幅减小;尾闾河道萎缩对海岸造陆影响较大,萎缩越严重,越不利于海岸的造陆发育.运用多元回归分析建立了黄河口海岸造陆水沙临界综合关系式,可供科学调控来水来沙实施黄河口海岸防护过程中参考.  相似文献   

钱塘江河口大规模治江围涂后对涌潮高度的影响   总被引：1，自引：0，他引：1       下载免费PDF全文

陈来华 《水科学进展》2007,18(3):385-389

根据钱塘江河口治江围涂前和大规模治江围涂后现场实测的涌潮高度数据,对盐官以下河段大潮期涌潮高度的变化进行分析,结果表明,大规模治江围涂后的涌潮最高河段已由治江围涂前的新湾下移至大缺口段,并且大规模治江围涂后的涌潮最高值比治江围涂前增高了0.4 m,盐官河段增高0.1 m.盐官以上河段治江围涂后的涌潮高度变化,主要与径流对沙坎顶的冲淤密切相关,在其它条件相同时,治江围涂后的涌潮高度有所增大.这一结果与某些年份因涌潮增高,标准堤大量溢流等实例基本相符.  相似文献   

海南岛万泉河口沉积物有机碳、 氮同位素的特征及其环境意义^*   总被引：4，自引：0，他引：4  

葛晨东  王颖  T.F.Pedersen  O.Slaymaker 《第四纪研究》2007,27(5):845-852

对海南岛万泉河口沙美内海柱样K3和K4沉积物进行生物地球化学指标总有机碳(TOC)、总氮(TN)、有机碳同位素(δ¹³ C)、氮同位素(δ¹⁵ N)的分析,以及²¹⁰ Pb定年了解其近代变化特征,追踪沉积物有机质来源的变化,提取沉积环境演变及人类活动的信息。K3中TOC的变化介于0.51 ％ ~1.12 ％ ,K4变化介于0.43 ％ ~1.49 ％ ,而其随时间的变化反映了流域内人类活动的历史。17世纪TOC含量明显增加记录了明末清初开始流域内广泛种植农作物的活动,19世纪以来TOC含量逐渐增加,至现代达最高值,对应了工业革命以来人类活动的增强。K3和K4的δ¹³ C值变化分别在-24.38 ‰ ~-21.02 ‰ 之间和-24.74 ‰ ~-20.17 ‰ 之间,δ¹⁵ N值变化分别在2.20 ‰ ~4.62 ‰ 之间和2.39 ‰ ~5.02 ‰ 之间,映证了本区沉积物有机质是陆源物质和海洋物质混合的特点。明末清初开始流域内广泛种植玉米等农作物造成δ¹³ C值增加和δ¹⁵ N值减少; 自19世纪以来至现在,该区的经济活动增加,人口的持续增长,尤其是近50年来化肥农药的大量使用,造成陆源输入的有机碳含量大幅增加,使δ¹³ C值减少和δ¹⁵ N比值增加。 δ¹³ C值自19世纪以来就逐渐变轻,说明陆源和海洋有机碳的比例发生了变化,较轻的陆源有机碳比例相对增加,较重的海洋有机碳比例相对减少,反映了玉带滩沙坝的增长、沙美内海封闭、海水交换作用减少的状况。C/N比值分别从底部的16.19和17.36到顶部减小为11左右,自19世纪以来呈明显减小的趋势也反映了沙美内海泻湖自生的藻类有机质供应越来越多,也说明了其逐渐封闭、水动力条件越来越弱,与外海的交换作用逐渐减少的状况。  相似文献   

黄河口水体光谱特性及悬沙浓度遥感估测   总被引：10，自引：1，他引：10  

樊辉  黄海军  唐军武 《武汉大学学报(信息科学版)》2007,32(7):601-604

通过黄河口含沙水体野外遥感光谱反射率的观测实验，探讨了黄河口水体表观光谱特性，分析了悬浮体中有机颗粒含量和悬沙粒度对光谱特性的影响。针对Landsat TM／ETM^＋影像波段特性，对黄河口含沙水体在其可见光至近红外4个波段的光谱特性进行了模拟分析，并结合表观光谱观测数据建立了经验回归函数，以估测不同时相黄河口水体表层悬沙的浓度。  相似文献   

 应用遥感技术分析韩江河口悬沙的动态特征   总被引：1，自引：0，他引：1  

丁晓英  许祥向 《国土资源遥感》2007,18(3):71-73

利用韩江河口近20多a的卫星影像资料，结合GIS技术，通过对韩江河口流势、流态和水沙输移特征的分析，探讨韩江河口 出口水流动力状况及其对泥沙输移的影响。结果表明，韩江河口区内泥沙含量较低，在河口区内涨落潮流呈西南-东北向运动，在 河口外则易受西南沿岸流影响，具有近岸输沙的特性。  相似文献   

Properties of suspended sediment in the estuarine turbidity maximum of the highly turbid Humber Estuary system, UK   总被引：1，自引：0，他引：1  

Reginald James Uncles  John Anthony Stephens  Carolyn Harris 《Ocean Dynamics》2006,56(3-4):235-247

Measurements are presented of the properties of suspended particulate matter (SPM) in the estuarine turbidity maximum (ETM) of the upper Humber and Ouse estuaries during transient, relatively low freshwater inflow conditions of September 1995. Very high concentrations of near-bed SPM (more than 100 g l⁻¹) were observed in the low-salinity (less than 1), upper reaches. SPM within the ETM consisted largely of fine sediment (silt and clay) that existed as microfloc and macrofloc aggregates and individual particles. Primary sediment particles were very fine grained, and typically, about 20–30% was clay-sized at high water. The clay mineralogy was dominated by chlorite and illite. There was a pronounced increase in particle size in the tidal river, up-estuary of the ETM. The mean specific surface area (SSA) of near-bed SPM within the ETM was 22 m² g⁻¹ on a spring tide and 24 m² g⁻¹ on a neap tide. A tidal cycle of measurements within a near-bed, high concentration SPM layer during a very small neap tide gave a mean SSA of 26 m² g⁻¹. The percentage of silt and clay in surficial bed sediments along the main channel of the estuary varied strongly. The relatively low silt and clay percentage of surficial bed sediments (about 10–35%) within the ETM’s region of highest near-bed SPM concentrations and their low SSA values were in marked contrast to the overlying SPM. The loss on ignition (LOI) of near-bed SPM in the turbid reaches of the estuary was about 10%, compared with about 12% for surface SPM and more than 40% in the very low turbidity waters up-estuary of the ETM. Settling velocities of Humber–Ouse SPM, sampled in situ and measured using a settling column, maximized at 1.5 mm s⁻¹ and exhibited hindered settling at higher SPM concentrations.  相似文献   

Holocene valley aggradation driven by river mouth progradation: examples from Australia     

Paul Rustomji  Jon Olley  John Chappell 《地球表面变化过程与地形》2006,31(12):1510-1524

Since the end of the post‐glacial sea level rise 6800 years ago, progradation of river mouths into estuaries has been a global phenomenon. The responses of upstream alluvial river reaches to this progradation have received little attention. Here, the links between river mouth progradation and Holocene valley aggradation are examined for the Macdonald and Tuross Rivers in south‐eastern Australia. Optical and radiocarbon dating of floodplain sediments indicates that since the mid‐Holocene sea level highstand 6800 years ago vertical floodplain aggradation along the two valleys has generally been consistent with the rate at which each river prograded into its estuary. This link between river mouth progradation and alluvial aggradation drove floodplain aggradation for many tens of kilometres upstream of the estuarine limits. Both rivers have abandoned their main Holocene floodplains over the last 2000 years and their channels have contracted. A regional shift to smaller floods is inferred to be responsible for this change, though a greater relative sea level fall experienced by the Macdonald River since the mid‐Holocene sea level highstand appears to have been an additional influence upon floodplain evolution in this valley. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献