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1.
河口羽流是河口冲淡水在陆架中扩展的主要形式, 其扩展受到诸多动力与地形因素的影响, 口门拦门沙就是其中之一。以一个理想化的河口为例, 采用区域海洋模型(regional ocean modelling system, ROMS), 研究口门拦门沙对河口羽流扩展的影响, 具体包括拦门沙对羽流的出流状态、扩展范围以及远场区沿岸流淡水输运的影响。研究结果表明, 拦门沙增加了口门处的水体分层, 减小了羽流出流速度, 增大了羽流凸出体的半径, 减小了远场区沿岸流宽度, 并进而减少了沿岸流中的淡水输送。本项研究对地形因素对河口羽流的扩展研究以及陆源物质的向海输运等均具有重要意义。 相似文献
2.
FPJ Nehama 《African Journal of Marine Science》2015,37(4):593-604
A model for the Zambezi River plume, the largest on the Indian Ocean coast of Africa, is presented and the results of experiments with different discharges and wind forcings are analysed. Although the river plays an important role in the southern African economy through power generation on large dams, artisanal fisheries, and frequent flooding events that impact greatly on local populations, the plume has not been well studied. Observations during the period 2004–2007, when the winds were mainly easterly or south-easterly, indicated that the plume waters can extend both downstream (equatorwards) and upstream (polewards) of the Zambezi Delta with a recirculating bulge near the river mouth. The model is constructed using the Regional Ocean Modeling System (ROMS), with a 40-km long, 3-km wide river discharging into a rectangular coastal ocean with a linearly sloping bottom. When the model is forced only by a constant river discharge of 1 000?m3 s?1 (typical of observed discharge amounts in summer), the Kelvin and Froude numbers for the resulting plume imply a ‘large-scale’ buoyant discharge with a coastal current that is close to being in geostrophic balance with the across-shore pressure gradient and a recirculating ageostrophic bulge near the mouth. The distributions of the bulge and plume waters are found to be relatively insensitive to the discharge amount. Under constant wind forcing, the plume distribution changes dramatically. Northerly and easterly winds produce the largest changes with the latter able to deflect the plume up to 180° due to Ekman drift. When sea breeze-like winds are imposed, accumulation of water in the bulge occurs with substantial spreading upstream. Stronger sea breezes lead to less downstream spreading of the plume than gentle winds. When the winds are mainly across-shore, Ekman drift dominates, but the dynamics become almost geostrophic when the winds are roughly aligned to the coast. These experiments suggest that the Zambezi River plume is sensitive to the winds on diurnal to synoptic time-scales. 相似文献
3.
《Oceanologica Acta》1998,21(6):887-906
This paper presents an ecological modelling of the Bay of Seine (Eastern Channel) over the last twenty years, chosen as a typical case of eutrophication in a river plume. In the physical sub-model, the Bay is divided into 42 boxes and water fluxes between them are calculated automatically using Ifremer's “Elise” software. A two-layer, vertical thermohaline model is then linked with the horizontal circulation scheme in order to take vertical stratification into account. The biological submodel deals with two chemical elements, nitrogen and silicon, and splits phytoplankton into diatoms and flagellates. Results from this ecological model point out the spatial concordance of highest phytoplanktonic concentrations with the river plume spreading in the bay. Contrary to diatoms, flagellate production appears to be mainly confined to the eastern bay, due to the vertical haline stratification in front of the river mouth. As far as the whole bay is concerned, the interannual fluctuations of diatom production are related to the level of spring insolation, whereas silicon inputs regulate diatom production in the river plume. The flagellate summer production in the plume is enhanced by high water temperature and high N/Si ratios, which appear during dry years with low discharge regimes. Finally, interannual increase of flagellate production could be related to gradual increase of nitrogen loadings, contrasting with silicon loadings, which remained stable for twenty years. 相似文献
4.
1Introduction TheChangjiang(Yangtze)Riverdrainageba sinliesbetween25°and35°N,andbetween91°and122°E,withatotalareaof1.81×106km2anda populationof4×108.Itpassesthroughadensely populatedareawithwell developedindustryandag riculture,includingShanghai,the 相似文献
5.
Evaluation of the flushing rates of Apalachicola Bay, Florida via natural geochemical tracers 总被引：4，自引：0，他引：4
We used naturally occurring radium isotopes as tracers of water exchange in Apalachicola Bay, a shallow coastal-plain estuary in northwestern Florida. The bay receives fresh water and radium from the Apalachicola River, and mixes with Gulf of Mexico waters through four inlets. We deployed moored buoys with attached Mn-fibers at several stations throughout the estuary during two summer and two winter periods. After deployment for at least one tidal cycle we measured the ratio of the two short-lived radium isotopes 223Ra (half-life = 11 d) and 224Ra (3.6 d) to estimate “radium ages” of the water in the bay.During our four seasonal deployments the river discharge ranged from 338 to 1016 m3 s− 1. According to our calculations the water turnover time in the bay during these samplings ranged from 6 to 12 days. Age contours in the bay showed that winds and tides as well as river discharge influence the water movement and the residence time of freshwater in the bay. We also calculated the mean age of river water in the bay which was between 5 to 9 days during the studied periods. We suggest that this approach can be used to quantify transport processes of dissolved substances in the bay. For example, soluble nutrient or pollutant transport rates from a point source could be examined. We conclude that the radium age technique is well suited for flushing rate calculations in river dominated shallow estuaries. 相似文献
6.
Kaushik Sasmal Eiji Masunaga Adrean Webb Oliver B. Fringer Edward S. Gross Matthew D. Rayson Hidekatsu Yamazaki 《Journal of Oceanography》2018,74(2):169-186
The three-dimensional numerical model SUNTANS is applied to investigate river plume mixing in Otsuchi Bay, an estuary located along the Sanriku Coast of Iwate, Japan. Results from numerical simulations with different idealized forcing scenarios (barotropic tide, baroclinic tide, and diurnal wind) are compared with field observations to diagnose dominant mixing mechanisms. Under the influence of combined barotropic, baroclinic and wind forcing, the model reproduces observed salinity profiles well and achieves a skill score of 0.94. In addition, the model forced by baroclinic internal tides reproduces observed cold-water intrusions in the bay, and barotropic tidal forcing reproduces observed salt wedge dynamics near the river mouths. Near these river mouths, vertically sheared flows are generated due to the interaction of river discharge and tidal elevations. River plume mixing is quantified using vertical salt flux and reveals that mixing near the vicinity of the river mouth, is primarily generated by the barotropic tidal forcing. A 10 ms?1 strong diurnal breeze compared to a 5 ms?1 weak breeze generates higher mixing in the bay. In contrast to the barotropic forcing, internal tidal (baroclinic) effects are the dominant mixing mechanisms away from the river mouths, particularly in the middle of the bay, where a narrow channel strengthens the flow speed. The mixing structure is horizontally asymmetric, with the middle and northern parts exhibiting stronger mixing than the southern part of the bay. This study identifies several mixing hot-spots within the bay and is of great importance for the coastal aquaculture system. 相似文献
7.
基于高精度海洋动力模型FVCOM (finite-volume community ocean model), 模拟分析了1999—2010年珠江口羽状流的季节和年际变化规律, 并结合经验正交函数(empirical orthogonal function, EOF)分析探讨了影响珠江口羽状流扩展变化的主要动力因子。采用模拟时段内的现场观测数据对多年模拟结果进行验证, 结果表明模型具有较高的精度, 能够较好地模拟珠江口羽状流的扩展变化规律。模拟结果显示, 珠江口羽状流存在显著的季节变化。夏季, 受大径流和西南风的影响, 羽状流的扩展呈现双向特征, 即粤西沿岸扩展和粤东离岸扩展同时存在, 扩展范围最大; 冬季, 径流衰减为最小值, 风场转变为强烈的东北风, 羽状流被紧紧挤压在西岸, 形成狭窄的条带状, 扩展范围最小; 春、秋两季属于过渡季节, 羽状流扩展情况类似, 均表现为沿岸向粤西扩展。年际变化层面, 夏季羽状流的年际变化最为显著, 呈现粤东扩展占优型、近似对称型和粤西扩展占优型三种形态; 春季羽状流的年际变化次之, 羽状流的差异主要体现在珠江口和粤西海域; 秋、冬两季羽状流的年际变化较小, 尤以冬季最小。EOF分析的第一模态可以解释整体变化的91.2%, 反映了径流量对珠江口羽状流的影响; 第二模态可以解释整体变化的4.1%, 反映了盛行风对珠江口羽状流的影响。 相似文献
8.
《Estuarine, Coastal and Shelf Science》2006,66(1-2):267-279
The composition and behavior of allochthonous particulate organic matter (POM) in the northern part of Ise Bay, Japan were investigated to elucidate the short-term variation in POM accompanying changes in river discharge. The behavior of POM was significantly regulated by hydrographic conditions, but behavior was different in the upper layer versus the middle and lower layers. The former showed simple dynamics controlled by the river plume, while the latter showed complex dynamics because of changes in river discharge and subsequent variation in estuarine circulation. During normal discharge, the contribution of riverine materials to POC in the surface water within the bay was negligible because most riverine organic matter is deposited before flowing into the bay. During high discharge, on the other hand, the contribution of riverine organic matter to total POM increased to 50% at ∼10 km from the river mouth. Though riverine organic matter loads increased, the total amount of POC decreased around the river mouth due to flushing of phytoplankton. After river discharge, the contribution decreased rapidly.The behavior of POM in the middle and lower layers differed from that in the surface layer. At normal discharge, the influence of riverine organic matter was weak. During high discharge, high flooding temporarily weakened the bottom inflow, resulting in heavier riverine organic matter distributed from the river mouth to mid regions within the bay in the lower layer. The maximum contribution of riverine organic matter to total POM was estimated to be ∼60% around 25 km from the river mouth. After high discharge, riverine POM in the lower layer was pushed to the bay head by enhanced estuarine circulation and was uplifted to the middle layer. The behavior of riverine POM dynamically changed in relation to river discharge, and exerted a significant influence on bottom water conditions in the bay. 相似文献
9.
一个概化的潮汐河口羽状流动力学的初步研究 总被引：1，自引：0，他引：1
基于区域陆架海水动力-生态耦合模型(COHERENS)中的三维水动力模型,对一个概化的潮汐河口羽状流动力学进行了初步研究。在均一水深和无风的理想条件下,模拟得到了一个潮周期内概化的潮汐河口表层水体:a)羽状流流场和盐度场的平面分布;b)3种不同河流径流量作用下的羽状流流场和盐度场的平面分布;c)4种不同底床粗糙长度下的羽状流流场和盐度场的平面分布。结果分析表明:a)羽状流的长度在潮汐的作用下递增,而其最大宽度近似呈周期性的变化;b)羽状流的长度和最大宽度都随着河流径流量的增大而分别变长和变宽;c)羽状流的长度和最大宽度都随底床粗糙长度的增大而变小;d)无潮情况下羽状流的凸起明显并存在沿岸流,然而在有潮情况下凸起不明显且无沿岸流;e)水平扩散可能限制了沿岸羽状流的发展。 相似文献
10.
大沽河是胶州湾最大的入海河流,每年都会给胶州湾带来大量泥沙。本文利用三维的ECOMSED水动力-泥沙数值模型对洪水期的大沽河进行了数值模拟,得到了洪水存在期间以及洪水结束后胶州湾的余流分布、大沽河河道上中下游各层盐度、泥沙浓度随时间变化的趋势以及入海冲淡水和泥沙对胶州湾的影响。 相似文献
11.
An-Yi Tsai Gwo-Ching Gong Robert W. Sanders Ciou-Jyu Wang Kuo-Ping Chiang 《Estuarine, Coastal and Shelf Science》2010
Variation in the summer nanoflagellate community on the continental shelf ecosystem of East China Sea (ECS) is closely coupled with environmental variation due to extension of the Changjiang River plume. Spatial patterns of nanoflagellate abundance were studied in June and August 2003, June 2006 and July 2007 over the ECS shelf. The Changjiang River plume was smaller during the August 2003 and July 2007 cruises than during the rest other 2 cruises. Total nanoflagellates densities varied between 1 and 120 × 102 cells ml−1 with the highest abundances occurring within the Changjiang River plume during large plume periods. In the small plume periods, the range of nanoflagellates abundance was 3–33 × 102 cells ml−1 and the highest abundances were observed during these periods either within the Changjiang River plume or the Yellow Sea Coastal Water (YSCW). During large plume periods, nanoflagellate abundance closely related to changes in salinity and during the small period, abundance was most related to water temperature. The pigmented nanoflagellate community (PNF) within Changjiang River plume, especially in the <3 μm size class, appears to increase in response to terrestrial or anthropogenic inorganic nutrient loading in the discharge of fresh water from the Changjiang River. The PNF abundance pronounced increase caused the variation of nanoflagellate community of ECS in summer. We suggest that the discharge of fresh water from Changjiang River has significant ecological impacts on spatial variations in nanoflagellate community in the ECS. 相似文献
12.
江苏近岸海域水文气象要素的时空分布特征 总被引：5，自引：0，他引：5
2006～2007年在江苏近岸海域进行水文气象要素(气温、湿度、风速风向、波浪、透明度、水色和海水温盐度等)大面观测。数据分析表明,各水文气象要素具有较大的空间分异,四季变化显著。秋季气温明显高于春季,冬季气温较历史数据偏高。整个海域风速较大,风向受季风控制,有效波高与风速之间显著相关。如东附近海域波浪较大,废黄河口波浪较小;春、夏季有效波高较小,而夏、秋季近岸海域波高较小,离岸波高增大。夏季海水透明度最大,平均为2.3m;冬季透明度最小,平均只有0.6m;水色与透明度呈负指数相关。春、秋季水温分布与气温分布基本一致,冬季大致沿等深线分布。射阳河口与长江口为低盐区,辐射沙脊群外缘为高盐区。与20世纪80年代的调查结果相比,出现了一些新特点。这些新的调查成果可为江苏近岸海域的海洋环境保护和可持续发展提供科学依据。 相似文献
13.
The oceanographic conditions of the Mackenzie River plume in the Arctic Ocean were examined during a 12-day period in August 2007. Field observations in the river channel and the delta region (2–6 m depth), ship-based observations on the shelf and satellite observations of sea surface temperatures indicate that movements of plume density fronts cause changes in water temperatures of over 10 C over a few days. We used a 1D model to compare the strength of stratification versus surface wind stress, and a 3D numerical model to simulate the plume motions under forcing from the river flows, local wind and water level variations from tides and wind-driven surge. The results indicate that the coastal region is stratified with a ∼2 m thick surface plume even in water depths of 3–4 m, resulting in strong vertical variation of horizontal currents. Moderate easterly winds of 5–10 m/s are sufficient to induce offshore transport of the surface plume and onshore transport of the deeper shelf water, leading to large fluctuations in temperature and salinity in the coastal region. This study examined a period of offshore transport and mean water level set-down, and indicates the rapid response of the plume to wind over the shallow delta. 相似文献
14.
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 相似文献
15.
基于遥感反演的莱州湾悬沙分布及其沉积动力分析 总被引：5，自引：3，他引：2
选用1986-2004年不同时期的LandsatTM/ETM+影像,利用2004年黄河口附近实测数据推导的表层悬浮泥沙浓度反演模型,结合水文气象资料、多年水深数据和极端天气数模结果,研究了莱州湾西南近岸海域表层悬浮泥沙分布特征,结果表明,受黄河丰枯水期的影响,莱州湾西南部海域悬浮泥沙高浓度区主要分布于黄河口附近海域和西南沿岸,其枯水期的覆盖范围一般大于丰水期的。受潮流高流速场控制,黄河口外悬沙浓度高值区与海底泥沙堆积区对应较好,泥沙主要来源于陆源输沙和泥沙再悬浮;在西南近岸浅海区悬沙浓度高值区主要形成于泥沙的再悬浮,在近岸出现轻微冲刷。风等其他海洋动力因素,一般情况下对悬浮泥沙扩散的程度和范围具有一定的影响作用,但悬沙受潮流场影响而形成的总体扩散趋势未发生改变;极端条件下,风暴潮流使莱州湾西南部近岸浅海区的悬浮泥沙浓度显著增加。 相似文献
16.
Mooring and hydrographic observations were conducted from September 2012 to May 2014 at the mouth of Otsuchi Bay, a ria along the Pacific coast of Japan. Our observations quantitatively demonstrated that the circulation and the water properties of Otsuchi Bay are strongly influenced by the Tsugaru Warm Current (TWC) and Oyashio Current (OY) at seasonal and subseasonal time scales. Two bottom-mounted velocity profilers and temperature and salinity measurements beneath the near-surface halocline showed a counterclockwise lateral circulation pattern related to the TWC, which was enhanced from summer to autumn. From winter to early spring, the lateral circulation patterns related to the TWC weakened and the influence of the OY occasionally increased. When the OY was weak, surface flows became an overturning structure, with outflows in the upper layer and inflows in the lower layer. When the OY was strong and passed close to the Sanriku coast, the circulation became highly variable and intermittent. Intrusions of the markedly low-salinity OY water were observed on two occasions and persisted for periods of several weeks to several months. Salinity was sometimes less than 33.7, the lower limit of the typical TWC from late summer to autumn even when the TWC dominates. We suggested that this is the seasonal fluctuations of the TWC itself, as the upstream current of the Tsushima Warm Current is freshened in summer as a result of the influence of the Changjiang River. The surface water was generally fresher in the south of the bay than in the north, suggesting the Coriolis deflection of the river plume. 相似文献
17.
河口区域冲淡水锋面及物质输运会对台风产生快速而复杂的响应,并产生显著的生态效应及沉积过程,且不同类型的台风会对水动力及物质输运产生不同影响。本文以长江河口为研究区域,利用盐度锋面附近的浮标站点观测数据,发现在登陆型超强台风“利奇马”的影响下,旋转流特征消失,站点全水深出现持续近两天的北向流;而在转向型强台风“巴威”的影响下,出现持续约三天的全水深南向流。应用覆盖长江口及邻近海域的有限体积海洋模型（FVCOM）对两次台风过程进行模拟,实验对比台风过境前后流场、盐度场并且计算淡水通量,发现台风过境时通过破坏夏季典型的向海扩张的表层平流型羽流结构,从而促进盐度垂向混合,导致大量淡水堆积在靠岸一侧,加强了沿岸的淡水输运,进而形成底部捕获型羽流。对于登陆型台风“利奇马”的影响,淡水输运主要沿苏北海岸向北,而在转向型台风“巴威”偏北风的影响下,淡水则显著沿岸向浙闽海域流动。这两种台风过后,表层淡水开始向海扩展,垂向盐度分层再一次呈现,在2～3天内完全恢复为表层平流型羽流结构。 相似文献
18.
胶州湾海水中悬浮体的分布及其季节变化 总被引：2，自引：0，他引：2
海水中的悬浮体包含有机物和无机物,有机物主要为有机碎屑颗粒,例如植物碎屑、浮游生物等;无机物主要是无机碎屑矿物、粘土矿物,也有少量硅质生物骨骼。海水中无机颗粒物质能通过吸附作用,从海水中有效地富集有机溶解物质。海水中天然有机物的分布、变化与浮游生物的活动密切相关,在海洋食物链中占有重要地位,海水中的颗粒有机物是某些游泳动物和底栖动物的食物,因此,海水中有机物的存在不仅对海洋生物有一定的生态学意义,而且对海洋无机元素的存在形式和地球化学转移过程都有直接影响。
胶州湾是一个典型的半封闭海湾,平均水深7m,面积390km2,自然环境优良,水产资源丰富,因此胶州湾的生态环境、生物资源及生态系统持续发展的研究对胶州湾的综合开发利用具有十分重要的意义。胶州湾海水中悬浮体的分布与变化是胶州湾生态环境研究中的一个重要组成部分。本文根据胶州湾海水中悬浮体的定点观测资料,阐明了胶州湾海水中悬浮体平均含量的分布及其季节变化特征,分析了影响悬浮体含量变化的主要因素。 相似文献
19.
Hee Jun Lee 《Ocean Science Journal》2010,45(3):187-195
This study briefly investigated sediment transport by tidal currents in Gomso Bay, on the mid-west coast of Korea during the summer season. Hydrodynamic measurements with benthic tripods (TISDOSs) show that near-bed suspended sediments are transported toward the bay mouth along the low-water line of tidal flats in the southern part of the bay, while they are directed offshore in front of the major tidal channel at the bay mouth according to tidal asymmetry. However, suspended sediments in the main body of sea water, observed from transect and anchor-site measurements, indicate a consistent incoming toward the uppermost tidal flats. A brief episode of relatively strong winds from the west and southeast displays that wind waves can yield the near-bed suspended sediment concentrations (SSC) overwhelming the SSC by tidal currents alone in the remaining duration. 相似文献
20.
根据径流量,1999年和2006年夏季的长江分别处于显著洪季和旱季.此期间的月平均风向也有显著区别.根据同期的海洋现场观测:相对1999年8月,2006年同期的长江口以东、以南毗邻水域表层盐度显著较高,而在长江口东北部海域则相对偏低;长江口附近海域的底层盐度有所偏高,但在浙江中南部沿海底层盐度则相对偏低.利用Regional Ocean Modelling Systems数值模式,对1999年和2006年实际的径流量、风场和黑潮及其分支变化等3个因素对长江冲淡水扩展的影响进行了一系列模拟试验和对比.对比试验表明:相对1999年8月,2006年夏季长江流量大幅度减小是长江口毗邻海域表层盐度升高的主要原因;风场是导致长江冲淡水相对偏北,并使长江口北部出现表层盐度负异常的主要因素;黑潮及其分支在东海北部入侵相对增强、在东海南部入侵相对减弱,使长江口南部表层盐度正异常海域扩大,并促使长江淡水向江口北部扩散增强、而向东部扩散减弱.长江口毗邻海域环流和水团的变化可能对夏季低氧区位置变化产生一定影响. 相似文献