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1.
Environmental qualities of coastal water and bottom sediment were assessed at Jordan's northernmost tip of Gulf of Aqaba to evaluate possible impacts of the bordering fish pen cages in Eilat. Results showed significant differences between surface and bottom water in the chemical and physical variables in the different months of the year (2004-2005). Chlorophyll a was also significantly higher in bottom water when compared to that of the offshore water. Nitrate and ammonia were significantly higher in bottom water than the surface water at each individual station. The upper 2 cm of sediment sample recorded higher values of total phosphorus and organic matter. Seasonality affected the content of total phosphorus, organic matter, redox potential and color especially at the sediment layer below 3 cm of the sediment core. The present investigation showed slight modification of water and sediment qualities but no clear sign of eutrophication was observed. However, to maintain sustainability of healthy environmental conditions at the northern tip of Gulf of Aqaba potentials of any possible environmental risks arising from the fish farms or any other coastal investment should be carefully considered.  相似文献   

2.
This study was focused on analysis of the horizontal and vertical current components with correspondence to tide variation, heat flux, seiches and relative backscatter intensity in coastal waters of the northern Gulf of Aqaba during the summers of 2001–2004. Spectrum analysis has shown eight distinguishable peaks of the tide measurements. In addition to semidiurnal and diurnal barotropic tides, signal periods of 8.13, 5.89–6.32 and 4.06 h were related to shallow water compound and overtides of the principal solar and lunar constituent and to seiches (second and third mode) generated in the Red Sea, whereas seiches of the first mode might enhance the semidiurnal tide signal. The shortest periods of 1.02–1.05, 0.50 and 0.36 h were related to seiches (first, second and third mode, respectively) generated in the Gulf of Aqaba. The spectrum analysis and cross-correlation tests of the horizontal and vertical current components and relative backscatter intensity suggested that the vertical motion at the diurnal period was either due to migration of zooplankton or to water convection. Both of which were of the same order as vertical motion induced by horizontal motions of water particles projected parallel on the bottom gradient line. On the other hand, semidiurnal and diurnal periods detected in the vertical currents were caused by the strong signal in the cross-shore current component, first mode seiches generated from the Red Sea and tide. This could be considered as an indicator of the dominant force influencing the currents, such as winds, thermocline depth, seiches and tidal forcing. A permanent convection during summer is likely to occur in the shallow coastal waters due to relatively high inclined bottom, high evaporation and blowing of dry air, as well as the observed dominance of the downward vertical currents in coastal waters.  相似文献   

3.
This study is devoted to oceanographic features of the semi-enclosed Gulf of Aqaba, Red Sea. The data were recorded in winter—spring 1999 on the R/V Meteor cruise leg 44/2. Temperature and salinity profiles were measured at six positions (I—VI). The shipboard NarrowBand Acoustic Doppler Current Profiler (NB ADCP) 150 kHz continuously recorded current profiles down to 350 m en route. The research revealed that the current near the Strait of Tiran front (position VI) represents a semidiurnal signal of an internal tide wave (∼12 h period; 0.2 ms−1 amplitude) that might be generated by the barotropic tide at the sill of the Strait. A sequence of cyclonic and anticyclonic eddy pairs is found along the axis of the Gulf of Aqaba during winter-spring seasons. These sub-mesoscale signals are dominant above the main thermocline and might be caused by wind forcing and the narrowness of the Gulf; it might remain in other seasons with different dimensions in relation to the depth of thermocline. The total diameter of each pair was twice the baroclinic Rossby radius (R ≈ 10 km). A single anti-cyclonic eddy was observed in the upper 300 m in the northern tip of the Gulf with a diameter of about 5–8 km.  相似文献   

4.
We examined and compared tidal currents and water column structure between a near-shore station (12 km from the coast) and an offshore station (32 km from the coast) adjacent to the Caeté River, Pará Region, Brazil. Although the coastal system of Pará is largely influenced by local tides and wind, we found substantial differences in the dominant forcing agents between stations. Water column dynamics at the near-shore station were largely affected by local tidal processes, while differences between surface and bottom layer flows also indicated the importance of gravitational circulation at this station and a substantial influence of the adjacent Caeté River discharge. In comparison, at the offshore station, water column structure was largely influenced by a semi-diurnal tidal flow, an along-coastal current flow (mainly associated with the North Brazil Current) and the dynamics of local wind flow. The near-shore station at low tide showed a high level of stratification; at high tide such stratification was reduced. In comparison, stratification was only apparent within the upper 6 m at the offshore station, the rest of the water column was relatively well-mixed. The stratification within Station 1 at low tide was a result of the bi-directional movement of water discharged from the Caeté River, with lower salinity surface water and high salinity bottom water resulting in an estuarine-like circulation environment. The spatial variability and lack of correlation in current flow and water column structure between the near-shore and offshore stations suggest that a flow field resulting from differences in local circulation, tidal variability and wind persistence separate areas. We argue that this separation may indicate that the offshore station is located in a transition region between the Caeté River waters and the local coastal area.  相似文献   

5.
2006年冬季粤东沿岸下降流观测分析   总被引：1，自引：0，他引：1       下载免费PDF全文
根据珠江口及其附近海域2006年冬季(2006年12月至2007年1月)航次的CTD调查资料发现,由于表层水体冷却而产生的对流作用,以及东北季风、浪、流等强动力条件下,冬季陆架水体垂向混合均匀,但粤东近岸海域却存在显著的温跃层及逆盐跃层,其原因在于:东北季风的Ekman效应引起了陆架表层高温、高盐海水向岸输送,东北季风还驱动了西南向沿岸流,其底边界层的Ekman效应引起了沿岸底层低温、低盐海水离岸输送,这样就形成了陆架方向的次生环流,在沿岸海域则为下降流,并表现为沿岸海域的逆盐跃层及温跃层现象。在下降流显著的区域,溶解氧垂向分布均匀且浓度较高,这应归因于下降流将溶解氧浓度较高的表层水带入深层所致。  相似文献   

6.
A three-dimensional, nonlinear, primitive equation ocean general circulation model is used to study the response of the Gulf of Mexico to Hurricane Frederic. The model has free surface dynamics and a second order turbulence closure scheme for the mixed layer. Realistic coastlines, bottom topography and open boundary conditions are used in the study. The model has a vertical sigma coordinate with 18 levels, and a horizontal resolution of 0.2°×0.2° for the entire Gulf. The study focuses on hurricane generated sea level, current, and coastally trapped wave (CTW) responses of the Gulf. Time series of sea levels from U.S. coastal tide gauge stations and the numerical model simulation of sea levels and currents on the shelf are used to study sea level, current and CTW responses. Both model sea levels and observations from tide gauge stations show a westward progression of the surge as a CTW response. The results of the study of sea levels and currents indicate that CTW propagate to the west with phase speeds of 7–10 m s–1. There is also a strong nonlinear interaction between the Loop Current and hurricane induced currents. The surface current attains a maximum of 200 cm s–1 in the eastern Gulf. The model surface elevation at several locations is compared with tide gauge data. The current meter data at three moorings are also compared with the model currents. The model simulations show good agreement with observed data for the hurricane induced coastally trapped wave, storm surge, and current distribution in the Gulf.  相似文献   

7.
Physical oceanographic data were collected during September 1975 at stations in the shallow water (max. depth 45 m) embayments of Salonica Bay and Thermaicos Gulf, and comparisons are made with data collected during other seasons. The distribution of temperature and salinity in the water column indicated the following features: fresh surface water predominantly related to river discharge; an intermediate water mass, apparently formed by mixing between the fresh and open sea waters; a thermocline, and deep bottom water open sea characteristics. The summer distribution of density in the surface and bottom waters, and the seasonal variation in the pattern of surface salinity, suggested an anti-clockwise water circulation throughout the embayments.  相似文献   

8.
北部湾东北部水团分布及季节变化分析   总被引：2，自引：0，他引：2  
基于2016年9月—2017年8月北部湾海域棕囊藻调查9个航次的温度、盐度和密度等水文数据,通过K-mean动态聚类分析方法分析了研究海域水团的分布及季节变化过程。根据温盐资料将研究海域的海水类型分为低温高盐的陆架底层水团、陆架表层混合水团和低盐沿岸水团。通过20°10′N断面上多期次的温盐分布特征揭示了北部湾整体上逆时针环流在北部湾东侧陆坡的存在;通过大面水文调查的结果揭示琼州海峡的余流特征,并结合卫星漂流浮标运动轨迹揭示了珠江冲淡水对研究海区水团分布的影响。本研究丰富了对北部湾东北部水团分布和季节变化的认知,对研究该海域赤潮发生、发展规律有指导意义。  相似文献   

9.
为研究黄河入海径流变化条件下河口附近海域盐度扩散特征,以更好地保护河口海域生物资源多样性,本文以黄河下游利津水文站的长序列实测径流数据资料为基础,利用近海水动力模型FVCOM,分析径流变化对黄河口海域盐度的影响规律。结果表明：黄河口与莱州湾之间存在顺时针的环流系统,在余流作用以及涨落潮方向的影响下,黄河冲淡水长期向莱州湾扩散;丰水期黄河冲淡水几乎影响了整个莱州湾,27盐度锋可以到达莱州湾中部,27等盐线的表层包络面积为2 665.61 km2,占莱州湾的1/4左右,枯水期低盐度水只有向南扩散的趋势,27以下的低盐度水集中分布在黄河口门附近,27等盐线的表层包络面积只有199.65 km2;5月份,随着入海径流量增加,27等盐线扩散的范围、距离、方向都会发生明显变化。在对近海生物资源有迫切保护需求的情景下,适当减少其他用水户供水量以增加入海生态径流量,可以有效改善黄河口海域附近的盐度情况,为生物资源的生长繁殖创造良好条件。  相似文献   

10.
赵紫涵  宋贵生  赵亮 《海洋学报》2020,42(10):144-154
溶解氧(DO)是海洋生物生存不可缺少的要素。随着人类活动的增加，全球近岸海域低氧情况愈发严重，已经成为威胁海洋生态系统健康的重要因素。通过对2017年5?9月秦皇岛外海区域的观测调查，探讨了该海域低氧与酸化的形成机制并计算了月平均耗氧速率。结果表明，5月秦皇岛外海水体混合较为均匀，表、底层DO浓度一致，均大于8 mg/L；6月开始形成密度跃层，与此同时底层DO浓度和pH开始下降；8月底层呈现明显的低氧和酸化状态，DO浓度下降至2～3 mg/L，pH下降至7.8以下；9月随着层化消失，底层水体DO浓度和pH逐渐升高。相关性分析显示，DO和叶绿素a (Chl a)以及pH具有良好的耦合性，说明秦皇岛外海区域的低氧发生过程主要为局地变化。同时表明DO浓度和pH主要受水体中浮游植物的光合作用和有机物有氧分解的影响。通过箱式模型计算得到2017年6?8月密度跃层以下水体及沉积物耗氧速率为951～1193 mg/(m2·d)[平均为975 mg/(m2·d)]。综合来看，水体分层是秦皇岛外海低氧和酸化发生的先决条件，跃层以下的有机物分解耗氧则是底层水体发生低氧和酸化的重要原因。  相似文献   

11.
琼州海峡东部水进入北部湾对广西沿海环流的影响   总被引：1，自引：0，他引：1  
本文通过对琼州海峡东部水域温盐资料和沿岸海洋站同步观测资料的对比发现：夏季，广西涠洲岛盐度变化规律和琼州海峡东部、中部变化规律一致，广西北海略受影响，而远离琼州海峡的龙门和白龙尾两站，则更多反映夏季陆地水文规律。同时，采用琼州海峡多年海流资料和涠洲岛定点站及近期测流站的海流观测资料对比看出，琼州海峡冬夏季余流方向仍然是自东向西。结合数值模拟计算结果，同样得出琼州海峡东部水自东向西进入北部湾的事实。这些温盐分布特征和余流观测结果进一步证实：粤西沿岸流是琼州海峡水向西输运的主要来源，形成粤西沿岸流这种现象的根源在于珠江冲淡水的西向流，它们通过琼州海峡进入北部湾，加强了北部湾北部气旋式环流的形成。夏季，在强的西南风作用下，产生较强北部湾西岸北向沿岸流，促使低盐冲淡水向外海输运，然后在东部涠洲岛附近形成更大范围内气旋式环流。琼州海峡东部水进入北部湾对广西沿海环流影响的研究，直接向琼州海峡冬夏季水体输运方向的传统结论提出了新的挑战。  相似文献   

12.
Coastal marine environments are important links between the continents and the open ocean. The coast off Mangalore forms part of the upwelling zone along the southeastern Arabian Sea. The temperature, salinity, density, dissolved oxygen and stable oxygen isotope ratio (δ18O) of surface waters as well as those of bottom waters off coastal Mangalore were studied every month from October 2010 to May 2011. The coastal waters were stratified in October and November due to precipitation and runoff. The region was characterised by upwelled bottom waters in October, whereas the region exhibited a temperature inversion in November. The surface and bottom waters presented almost uniform properties from December until April. The coastal waters were observed to be most dense in January and May. Comparatively cold and poorly oxygenated bottom waters during the May sampling indicated the onset of upwelling along the region. δ18O of the coastal waters successfully documented the observed variations in the hydrographical characteristics of the Mangalore coast during the monthly sampling period. We also noted that the monthly variability in the properties of the coastal waters of Mangalore was related to the hydrographical characteristics of the adjacent open ocean inferred from satellite-derived surface winds, sea surface height anomaly data and sea surface temperatures.  相似文献   

13.
伴随广西北部湾经济区的建立与开发,北部湾海域污染加剧,赤潮灾害愈发严重。文章综述1984—2015年广西北部湾海域赤潮演变趋势,结果表明:①赤潮发生频率和发生面积逐年增加;②赤潮种类呈现增多趋势。通过分析赤潮演变趋势,提出防控的思路:①加强广西北部湾入海流域及沿海地区污染防治和近岸海域环境保护;②利用生物技术进行赤潮生物防控;③加强科技支撑和提升赤潮科学研究能力。  相似文献   

14.
In this study we used two stable isotopes, δ13C and δ18O, for water mass classification in the coastal region off eastern Hokkaido. δ13C* values, which were corrected for the biological effect, and δ 18O values up to 300 m depth suggested that the isotopic character of the onshore and offshore water in the southern Okhotsk Sea, the Nemuro Strait and the western North Pacific could be explained by the mixing of three source waters: the Oyashio water (OYW), Soya Warm Current water (SWCW) and East Sakhalin Current water (ESCW). In summer, δ 13C*-δ 18O plots indicated mixing between SWCW from the southern Okhotsk Sea and OYW in the Pacific coast of southeastern Hokkaido, while temperature-salinity plots of the onshore water showed minimal difference from the offshore OYW. In winter, on the other hand, the mixed water of ESCW and OYW (or SWCW) appeared in the Pacific coastal region, distributed as cold, low salinity onshore water. Finally, we estimated mixing ratios of OYW, SWCW and ESCW in the coastal region of western North Pacific using their mean values of δ 13C* and δ 18O as endmembers. These results suggest seasonal and yearly changes of water mass combination en route from the southern Okhotsk Sea to the western North Pacific.  相似文献   

15.
The coastal waters of the Great Barrier Reef (GBR) are hypersaline (salinity ∼37) during the dry season as a result of evaporation greatly exceeding rainfall, of shallow waters, and of the presence of numerous bays along the coast preventing rapid flushing. These hypersaline waters are not flushed out by salinity-driven baroclinic currents because these waters are vertically well-mixed. Instead these waters are transported by a longshore residual current and thus form a coastal boundary layer of hypersaline waters. As a result the hypersalinity distribution is 2-D with both cross-shelf and longshore gradients of salinity. The cross-shelf gradients are largely controlled by turbulent diffusion, while the longshore gradients are controlled by the residual currents that transport hypersaline waters longshore south ward in the central and southern regions of the GBR. Because every bay supplies hypersaline waters, the width of the coastal hypersaline layer increases southwards. Steady state is reached in about 100 days, which is the typical duration of the dry season. The dynamics of the GBR hypersaline coastal boundary layer thus differ from the classical inverse hypersaline systems, e.g. in Saloum River Estuary, Laguna San Ignacio, Mission Bay, Tomales Bay, San Diego Bay, Hervey Bay, Shark Bay, Coorong Coast Lagoon, Spencer Gulf, Gulf of California and many others where the salinity gradient is mainly 1-D with a dominant along-channel salinity gradient.  相似文献   

16.
The existence of a surface barotropic front-jet system at the confluence region off the eastern tip of Oman (Ras Al Hadd or RAH) is documented for 1994–1995 through advanced very high resolution radiometer (AVHRR) and acoustic Doppler current profiler (ADCP) observations. The thermal signature of this confluence is visible in 1995 between early May and the end of October, i.e., throughout the SW Monsoon and into the transition period between SW and NE Monsoons. The thermal characteristics are those of a NE-oriented front between cooler water of southern (upwelled) origin and warmer waters of northern Gulf of Oman origin. During the period when the thermal front is absent, ADCP data suggest that the confluence takes a more southward direction with Gulf of Oman waters passing RAH into the southeastern Oman coastal region. The thermal gradient is initially small (June–July) but later increases (August–October) into a front that exhibits small-scale instabilities. Surface current velocities within the jet, estimated by tracking these features in consecutive satellite images, are 0.5–0.7 m s−1 and in remarkable agreement with concurrent ADCP retrievals in which the seasonal maximum in velocity is 1 m s−1. ADCP observations collected during several US JGOFS cruises reveal a weakly baroclinic current in the confluence region that drives the waters into the offshore system. The fully developed jet describes a large meander that demarcates two counter-rotating eddies (cyclonic to the north and anticyclonic to the south of the jet) of approximately 150–200 km diameter. The southern eddy of this pair is resolved by the seasonally averaged, sea-level anomaly derived from TOPEX/Poseidon observations. During the SW Monsoon, the RAH Jet advects primarily cold waters along its path, but as soon as the wind system reverses with the transition to the intermonsoonal period, a warm current is rapidly established that advects the surface coastal waters of the Gulf of Oman offshore. In accordance with the interannual variation of the wind forcing phase, the reversal of the currents from NE to SW occurred earlier in 1994 than in 1995, confirming that the RAH Jet is integral part of the East Arabian Current. The transport of the Jet, estimated by combining SST information on the width with ADCP data on the velocity's vertical structure, is found to fluctuate between 2–8×106 m3 s−1 and its thickness between 150–400 m. These significant fluctuations are due to the time-variable partition of horizontal transport between eddies and the RAH Jet and are potentially important to the nutrient and phytoplankton budgets of the Arabian Sea.  相似文献   

17.
首次报道了闽东海域分布的3种石珊瑚,分别为造礁石珊瑚陀螺珊瑚（Turbinaria sp．）、非造礁石珊瑚猩红筒星珊瑚（Tubastrea coccinea Lesson）和1个珊瑚待定种,其中陀螺珊瑚和1个珊瑚待定种为中国新记录．珊瑚分布面积约3．24km2,主要呈零星斑块状分布在岛礁周围水深2—25m近岸岩礁区．2012年5～8月对闽东台山列岛和星仔列岛4km2范围内的55个岛礁近岸海域进行4个航次的调查表明,珊瑚的分布总体上南部的台山列岛海域分布数量多于北部的星仔列岛,海岛东部海域略多于西部．研究认为,闽东海域发现陀螺珊瑚说明其分布主要受台湾暖流的影响,揭示我国大陆沿岸造礁石珊瑚分布北缘可能扩展到台山列岛和星仔列岛．  相似文献   

18.
A tracer model with random diffusion coupled to the hydrodynamic model for the Zhujiang River Estuary (Pearl River Estuary, PRE) is to examine the effect of circulations on the transport of completely conservative pollutants. It is focused on answering the following questions: (1) What role does the estuarine plume front in the winter play in affecting the pollutants transport and its distribution in the PRE ? (2) What effect do the coastal currents driven by the monsoon have on the pollutants transport? The tracer experiment results show that: (1) the pollutant transport paths strongly depend on the circulation structures and plume frontal dynamics of the PRE and coastal waters; (2) during the summer when a southwesterly monsoon prevails, the pollutants from the four easterly river inlets and those from the bottom layer of offshore stations will greatly influence the water quality in Hong Kong waters, however, the pollutants released from the four westerly river-inlets will seldom affect the water quality of Hong Kong waters due to their transport away from Hong Kong; (3) during the winter when a northeasterly monsoon prevails, all pollutants released from the eight river gates will be laterally transported seaward inside the estuary and transport westward in the coastal waters along the river plume frontal zone. However, pollutants released from the surface layer of offshore stations near or east of the Dangan Channel will be carried into the coastal waters of Hong Kong by the landward component of the westward coastal current driven by the winter northeasterly monsoon. But the pollutants from the bottom layer of the offshore stations will be carried away from the offshore by the bottom flow driven by the northeasterly monsoon. This implies that only surface-released matter from offshore stations will affect the water quality of the coastal waters around Hong Kong during the winter when a northeasterly monsoon prevails.  相似文献   

19.
在全球气候变化和人类活动加剧的背景下,赤潮、绿潮、褐潮、水母暴发和泥螺入侵等生态灾害已成为近年来海洋生态系统异常的主要表现形式。为科学管理和防治山东近岸海域生态灾害,文章汇总1999-2018年山东近岸海域典型生态灾害的特征和变化趋势。研究结果表明:赤潮是山东近岸海域最主要的生态灾害,研究期内共发生赤潮69起,累计面积为7 141 km2,发生海域主要集中在滨州-东营近岸、潍坊小清河口、莱州近岸、长岛近岸、烟台四十里湾、青岛胶州湾、威海乳山近岸和日照近岸,以夜光藻为主;自2007年以来,绿潮在我国南黄海海域每年均有发生,持续时间70余天,此外烟台套子湾、四十里湾和蓬莱近岸以及潍坊近岸等海域也相继发生绿潮,主要种类包括缘管浒苔、石莼、管浒苔和束生刚毛藻;褐潮是由抑食金球藻引起的生态灾害,山东近岸海域仅2011年和2012年有褐潮发生;水母暴发种主要包括海月水母、沙海蜇和白色霞水母,其中海月水母是山东半岛近岸海域种群数量最大、分布范围最广和暴发频率最高的种类;泥螺入侵是由于2001年的人为引种而导致的生物入侵灾害,近年来泥螺数量大幅减少,目前仅在滨州、东营和潍坊局部潮间带有少量分布。  相似文献   

20.
A tracer model with random diffusion coupled to the hydrodynamic model for the Zhujiang River Estuary (Pearl River Estuary, PRE) is to examine the effect of circulations on the transport of completely conservative pollutants. It is focused on answering the following questions: (1) What role does the estuarine plume front in the winter play in affecting the pollutants transport and its distribution in the PRE? (2) What effect do the coastal currents driven by the monsoon have on the pollutants transport? The tracer experiment results show that: (1) the pollutant transport paths strongly depend on the circulation structures and plume frontal dynamics of the PRE and coastal waters; (2) during the summer when a southwesterly monsoon prevails, the pollutants from the four easterly river inlets and those from the bottom layer of offshore stations will greatly influence the water quality in Hong Kong waters, however, the pollutants released from the four westerly river-inlets will seldom affect the water quality of Hong Kong waters due to their transport away from Hong Kong; (3) during the winter when a northeasterly monsoon prevails, all pollutants released from the eight river gates will be laterally transported seaward inside the estuary and transport westward in the coastal waters along the river plume frontal zone. However, pollutants released from the surface layer of offshore stations near or east of the Dangan Channel will be carried into the coastal waters of Hong Kong by the landward component of the westward coastal current driven by the winter northeasterly monsoon. But the pollutants from the bottom layer of the offshore stations will be carried away from the offshore by the bottom flow driven by the northeasterly monsoon. This implies that only surface-released matter from offshore stations will affect the water quality of the coastal waters around Hong Kong during the winter when a northeasterly monsoon prevails.  相似文献   

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