Numerical experiment on the circulation in the Japan Sea

By using a rectangular basin of uniform depth with inflow and outflow openings, the circulation in the Japan Sea is investigated numerically. Heat flux through the sea surface is determined from the annual mean atmospheric conditions for the Japan Sea, but no wind stress is considered.In the transient state, the warm water supplied through an inflow opening travels cyclonically along the coast as a density-driven boundary current in a rotating system. In the quasi-steady state, the warm water flows northward as a western boundary current which corresponds to the East Korean Warm Current and gradually separates from the coast as it flows northward. No strong boundary current corresponding to the nearshore branch of the Tsushima Current exists.Under annual mean atmospheric conditions, formation of the deep water characteristic of the Japan Sea and of the thermal front corresponding to the Polar Front do not take place.     

Short-Term Thermal Effects of a Power-Generating Plant on Zooplankton in the Swartkops Estuary, South Africa

Abstract. The short-term effect of elevated water temperatures (Δ t = 5–10°C after passing through the cooling circuit of an electricity generating plant) on plankton in a warm temperate estuary. South Africa, was investigated. Phytoplankton entrained on the flood tide was more severely affected than that entrained on the ebb, but chlorination of cooling water was probably a major factor affecting phytoplankton assemblages. Abundance of zooplankton of marine origin was significantly reduced after passing through the cooling circuit. The effect of thermal stress on the curyhalinc zooplankton was not clear, as the origin of the water canal to the generators is located at the extreme seaward limit of spatial distribution of cstuarinc plankton at low tide. Estuarinc species of zooplankton were therefore infrequently sampled and in low numbers only. Other factors which increase mortality are discussed.     

海口湾的台风及其对海水水质的影响机制分析

海口湾受台风影响全年以7～10月为盛行时期,尤以8～10月最盛.我们于1996年台风季节前、后在海口湾海域布设了10个监测站,进行了pH,DO,COD,PO₄-P,NO₂-N,NO₃-N和SiO₃-Si的监测,分析了它们在台风前后的变化,结合台风暴流的数值计算,初步探讨了因台风引起水质变化的机制,结果表明,台风、大浪和风暴流掀起海底沉降物或促使底层高营养盐的水体与表层强烈地混合,尤其是风暴流在湾顶辐聚,强烈的流速悬浮湾顶主要由生活污水排污口附近海域受污染的沉积物,一些污染物溶解于水体,伴随着台风而来的暴雨也将陆源污染物通过南渡江搬运到海口湾,使COD,PO₄-P,NO₂-N,NO₃-N和SiO₃-Si的含量台风后高于台风前.台风大浪和风暴流强烈的水交换作用使外海高DO的海水与湾内海水进行充分的交换,又使空气中的氧充分溶解于水体,使DO在该次台风后反而比台风前高,风暴流的水交换作用也使pH值在该次台风前后没有明显变化.     

海平面长期变化对推算多年一遇极值水位的影响

利用乳山口24a的年极值高、低水位和年平均海平面,分析讨论了平均海平面长期变化对推算多年一遇极值水位的影响.同时讨论了消除平均海平面中长期变化的途径.比较了消除平均海平面长期变化和保留这种变化情况下推算出的两种多年一遇极值水位,可以发现,对多年一遇高水位来说,保留平均海平面长期变化所得结果高于消除了的,而对多年一遇低水位而言,情况正好相反.     

Enzyme activities in the water column and in shallow permeable sediments from the northeastern Gulf of Mexico

The activities of extracellular enzymes that initiate the microbial remineralization of high molecular weight organic matter were investigated in the water column and sandy surface sediments at two sites in the northeastern Gulf of Mexico. Six fluorescently labeled polysaccharides were hydrolyzed rapidly in the water column as well as in permeable sediments. This result contrasts with previous studies carried out in environments dominated by fine-grained muds, in which the spectrum of enzymes active in the water column is quite limited compared to that of the underlying sediments. Extracts of Spirulina, Isochrysis, and Thalassiosira were also used to measure hydrolysis rates in water from one of the sites. Rates of hydrolysis of the three plankton extracts were comparable to those of the purified polysaccharides. The broad spectrum and rapid rates of hydrolysis observed in the water column at both sites in the northeastern Gulf of Mexico may be due to the permeable nature of the sediments. Fluid flux through the sediments is sufficiently high that the entire 1.5 m deep water column could filter though the sediments on timescales of a few days to two weeks. Movement of water through sediments may also transport dissolved enzymes from the sediment into the water column, enhancing the spectrum as well as the rate of water column enzymatic activities. Such interaction between the sediments and water column would permit water column microbial communities to access high molecular weight substrates that might otherwise remain unavailable as substrates.     

Density currents in the two-layer flow: an example of Dardanelles outflow

Observations from hydrographic surveys are used to describe the density current flowing through the Dardanelles strait into the Marmara Sea. Aegean water plunges below the surface and flows into the Marmara Sea. This flow joins into the Marmara Sea as a negatively buoyant plume and sinks through the deeper parts. Seasonal variation in the incoming water density results in the observing mainly two different forms of the density current in this area. These two forms are boundary currents and intrusion. Boundary currents were observed as a dense bottom current during the winter when the inflowing water density attains to annual maxima and as an overflow during the autumn when the inflowing water density drops to annual minimum. Intrusion form of the density current was observed during the summer.     

Numerical Study on the Vertical Water Exit of A Cylinder with Cavity

When a high-speed body with cavity passes through water-air free surface and exits water, its mechanical environment and dynamic characteristics change significantly due to the great difference in density and viscosity between water and air. With focusing on this problem, the Computational Fluid Dynamics (CFD) method is applied to perform numerical calculation on the process of this vapor-liquid-gas flow during the water exit of a high-speed cylinder, with the Volume of Fraction (VOF) multiphase flow interface-capturing techniques and the overset grid technology. After the verification and validation of the CFD model through mesh convergence study and a water-entry experiment, cavity evolution and flow characteristics including pressure and velocity distribution during the water exit are analyzed. The effects of different initial velocities on the pressure distribution and drag characteristics of the cylinder are investigated. Calculated results show that the cavity collapse during water exit causes strong pressure fluctuation on the cylinder; when the cylinder exits water enveloped in a supercavity, the pressure distribution on its wall surface and surrounding water region is relatively uniform, and the drag changes gently, and thus the cylinder has good motion stability.

     

巽他海峡的水交换过程研究

巽他海峡是爪哇海与东印度洋进行水交换的重要西部通道,其水交换过程与两侧水团性质和环流有密切关系。本研究基于巽他海峡及其附近海域的观测和遥感再分析数据,分析了爪哇海与印度洋通过巽他海峡进行水交换的多时间尺度变化规律,并探讨了局地和大尺度过程对水体输运的影响。研究表明,巽他海峡贯穿流主要由流出爪哇海的年均南向流与随季风南北转向的季节反向流组成,并存在显著的季节内变化。2008—2016年期间,巽他海峡贯穿流3次观测的年均流量分别为(-0.31±0.34),(-0.27±0.43)和(-0.49±0.31)Sv(负号代表流出爪哇海)。巽他海峡贯穿流与局地风和海峡两侧海表面高度梯度密切相关,因此采用多元回归重构了1993—2017年水体输运时间序列,并计算出25 a的平均流量为(-0.37±0.43)Sv。研究也表明,巽他海峡水体输运的年际变化异常与ENSO,IOD相关。     

基于PHC3.0数据集的北冰洋水团分析

基于PHC3.0极地科学中心水文气候数据集(简称PHC3.0数据集)的温度和盐度资料,使用聚类分析和Bayes判别分析的方法,对北纬70°以北海域的水团结构进行了分析,在北冰洋区域划分出4个水团:北冰洋表层水(ASW)、大西洋中层水(AIW)、太平洋水(PW)和北冰洋深层水(ADW)。北冰洋表层水(ASW)遍布于欧亚海盆和加拿大海盆,以低温低盐为特征。大西洋中层水(AIW)位于约200～900m深度,在北冰洋环极边界流的作用下,其影响可达到加拿大海盆。太平洋水(PW)受经白令海峡进入北冰洋的海水影响,相对高温低盐,夏季时影响显著。北冰洋深层水(ADW)在海盆中相当均匀,几乎没有季节变化,盐度约在34.95psu,温度在加拿大海盆约为-0.3℃,欧亚海盆约为-0.7℃。     

声学方法监测悬浮物浓度的定标技术研究

海洋中特别是河口海岸中存在着大量的悬浮物，其中，包含有内陆河流夹带的大量泥沙、海洋内浮游生物及残骸，以及大陆倾倒的大量废水废渣，造成对海洋的污染。研究悬浮物随深度剖面的变化关系，即它的时空特性，将给河口和港湾的疏浚、泥沙综合治理、沿岸工程建设、环境污染防止等方面提供可靠的理论依据和直观方便的监测手段。所以，对悬浮物浓度的定标的研究有着十分重要的现实意义。     

Chemical studies on organic matter and carbon cycle in the ocean

Chemistry of organic materials of the suspended and sinking particles, and the evaluation of the particulate materials for the carbon cycle of the ocean are described in this paper. Organic carbon (POC) and nitrogen (PON) of the suspended particles collected from various areas of the North through South Pacific were determined with considerably high variabilities in their concentration. Higher values of the POC and PON were obtained in the surface water of the higher latitudinal areas of both northern and southern hemispheres and the equatorial Pacific, while the lower values of these organic elements were measured in the middle latitudinal areas of the Pacific. These facts clearly indicate that inorganic nutrients supply to the surface water layers from the underlying water is primarily determinative factor to govern the concentration of the POC and PON in the surface water layer. POC and PON concentrations in the intermediate through deep waters, however, are much less variable in time and space. Carbohydrates, free and combined amino acids and lipid materials were major organic constituents of the suspended particles. The organic composition of the particles was extensively variable in region, time and depth. Such change in the organic composition was mainly caused by the production and decay of the free and combined amino acids, lipid materials and water extractable carbohydrate. Sinking particle which has high sinking rate over 100 m day⁻¹ and can be collected only by sediment trap, also consists of carbohydrates, free and combined amino acids and lipid materials. A detailed analysis of the particle indicate that the sinking particle was much different from the suspended particle from the intermediate through deep waters in terms of the abundance of the biologically susceptible organic materials such as unsaturated hydrocarbon, fatty acid and water extractable carbohydrate often found in phytoplankton. These facts clearly indicate that the sinking particle plays an important role on the vertical transport of the biologically susceptible organic materials from the surface water to the deep water. Vertical flux of organic materials in various water depths was extensively measured in the North Pacific and Antarctic Ocean using the depth-series sediment trap system to collect the sinking particles from various depths of the waters. Regional and seasonal variabilities of the organic carbon flux at the various depths were obviously observed, however the attenuation rate of the organic carbon flux in the intermediate through deep water was not changed so much irrespective of the sampling time and region. The time-series sediment trap system was also using to determine the seasonal variation of the organic carbon flux. An average organic carbon flux at 1 km depth from this trap system was almost comparable to the amount of organic carbon degraded in the water deeper than 1 km depth, which was calculated from oxygen consumption rate of the deep water. Thus, it is clear that the sinking particle must play an important role in the carbon cycle of the deep water.     

Numerical Analysis of the Effect of Active Wind Speed and Direction on Circulation of Sea of Azov Water with and without Allowance for the Water Exchange through the Kerch Strait

The effect of seawater movement through the Kerch Strait for extreme deviations in the level and speed of currents in the Sea of Azov caused by the action of climate wind fields has been studied using the Princeton ocean model (POM), a general three-dimensional nonlinear model of ocean circulation. Formation of the water flow through the strait is caused by the long-term action of the same type of atmospheric processes. The features of the water dynamics under conditions of changing intensity and active wind direction have been studied. Numerical experiments were carried out for two versions of model Sea of Azov basins: closed (without the Kerch Strait) and with a fluid boundary located in the Black Sea. The simulation results have shown that allowance for the strait leads to a significant change in the velocities of steady currents and level deviations at wind speeds greater than 5 m/s. The most significant effect on the parameters of steady-state movements is exerted by the speed of the wind that generates them; allowance for water exchange through the strait is less important. Analysis of the directions of atmospheric circulation has revealed that the response generated by the movement of water through the strait is most pronounced when a southeast wind is acting.     

Analysis of the influence of water exchange through the Kerch Strait on the surge processes and currents in the Azov Sea

We present the results of numerical modeling of the influence of water exchange through the Kerch Strait on the stationary motions in the Azov Sea. We use a three-dimensional nonlinear numerical model to perform the analysis of extreme deviations of the sea level and the surface and deep-water currents depending on the direction and velocity of constant wind with and without regard for the water exchange through the strait. It is shown that the influence of water exchange with the Black Sea leads to the increase in the maximum deviations of the sea level and the velocities of stationary currents. Thus, in particular, it is shown that, for a wind velocity of 10 m/sec, the maximum values of the surge and current velocities in the presence of the strait are higher than in the absence of the strait by 36 and 42%, respectively. In this case, the highest current velocities are induced by the south wind.     

Monsoonal impact on circulation pathways in the Indian Ocean

Monsoon driven water mass exchange between the Bay of Bengal(Bo B) and Arabian Sea(AS) is the common experience. However, it is not yet firmly confirmed that the exchange pathway is either passing through southern tip of Sri Lanka or Palk Strait. Local circulation patterns impact the pathways followed by the East Indian Coastal Currents(EICC) that drive exchange, thereby modulating mixing and water mass transformation in the Bay of Bengal around Sri Lanka. In this study, observations from surface drifters were incorporated with the satellite derived data to understand the monsoonal impact on circulation patterns in the Indian Ocean. This was the first multi-national scientific effort which was conducted in the Bo B and AS during 2013 to 2015 to understand the monsoonal impact on circulation patterns in the complex region. The results indicated that seasonally reversing monsoonal currents of southern Sri Lanka, traced by the wintertime freshwater export pathways of the EICC. The deflection of monsoon currents running along the east coast of Sri Lanka by forming cyclonic and anti-cyclonic eddies, which influence the mixing and stirring associated with these flows. Results further indicate the low salinity cold water flows from the Bo B to AS along the western boundary of the Bo B during northeast monsoon. In the same way, reverses the phenomena during southwest monsoon, transporting high salinity warm water from AS to the Bo B. This maintain the bay status which occurred due to freshwater influx from large rivers and high saline water from AS. However, no evidences were observed for the exchange through Palk Strait during the study.Also, there are some mis-matches in in-situ and remotely sensed measurements which imply the necessity of systematic observation system for the complex region as an alternative approach.     

A discussion on typhoon occurred in the Haikou Bay and impact mechanism on seawater quality

INTRODUIONThe Haikou Bay is an imPOrtant hay in Hainan Pmeince. Investigatnin of water qualitywas carried out three times every y6ar to understand the vatying trend of water quality fOr tak-ing pmpr countereres. betimes we may ee comParison conclustons of poIluting degreein Water Quality Monitoring Bulletin Of HaikOu Bay. But the comParison conclusbo is notreareable because the ocean is a complicated system with the interaction of wind, current,wave, tide, biolOgy, chemistry and so …     

A model for the estimation of water filtration and nutrient regeneration by exposed sandy beaches

Exposed sandy beaches filter huge volumes of sea water daily as a result of wave and tide action. A regression model is developed which predicts the volume of water filtered daily by a beach as a function of tide range, beach slope and sand particle size. From these parameters estimates are also made of intertidal distance, the degree of expansion of the intertidal above the still water tide range by wave action and the average path length through the sand interstices percolated by filtered sea water. An equation is derived relating the degree of mineralisation of organic matter in the filtered sea water to the distance filtered through the sand and the sand particle size. Employing all this information, a simple model is used to estimate the volumes of sea water filtered and the amounts of inorganic nitrogen regenerated by intertidal sandy beaches over a range of physical conditions. The implications of this nutrient generation for the inshore zone are discussed.     

连续深度基准面构建及通航水深服务模式研究

通航水深是船舶在某时段沿着一定航线通过特定区域的最浅水深,对船舶的安全航行具有重要意义。海图测绘时将水深归算至深度基准面,由验潮资料求得,而潮汐值是通过临近区域发布的潮汐表来进行推算,由此获得的通航水深精度不 高,且不同港区之间采用深度基准不统一,所以无法为船舶提供精确、连续的通航水深。本文提出了一种基于高精度 GNSS的通航水深测量方法,直接测量海底高程,通过精密数值模型模拟海面高程,由此获得通航水深,并提出了实时通航水深的应用模式。为了建立与陆地地形相衔接的海底地形模型,以 CGCS2000 参考椭球面为垂直参考基准面,深度基准面采用 POM（Princeton Ocean Model） 模式进行潮波数值模拟的方法构建。实验结果显示：数值模型精度较高,构建的深度基准面误差在5 cm 以内。本文提出的方法改变了传统的通航水深测量及服务模式,提供高效率、高精度通航水深、海图水深数据,可为船舶用户提供实时动态水深服务。     

杭州湾南岸浅滩的漫滩潮流数值模拟

在杭州湾浅滩上采用底座式ADCP测得单点的漫滩潮流流速、流向及同步水位的变化过程,并在此基础上建立平面二维潮流数值模型,分析整个潮滩上的漫滩潮流过程及其特征。在模型漫滩边界上采用向上取水位值的处理方法,使得模型计算稳定,并获得了稳定逼真的漫滩潮流模拟结果。模拟结果表明:漫滩潮流模拟过程与实测资料基本一致。因此在漫滩潮流模拟中向上取水位值的边界处理方法是可行的。研究成果为漫滩潮流的数值模拟提供了一种较实用的漫滩边界处理方法。     

Static wave setup with emphasis on damping effects by vegetation and bottom friction

Wave setup can contribute significantly to elevated water levels during severe storms. In Florida we have found that wave setup can be 30% to 60% of the total 100-year storm surge. In areas with relatively narrow continental shelves, such as many locations along the Pacific Coast of the United States, wave setup can be an even larger proportionate contributor of anomalous water levels during major storms. Wave setup can be considered as comprising two components, with the first being the well-known static wave setup resulting from the transfer of breaking wave momentum to the water column. The second, oscillating component, is a result of nonlinear transfer of energy and momentum from the primary (linear) spectrum to waves with length and time scales on the order of the wave groups.Static wave setup is the focus of this paper with emphasis on effects due to internal or surface forces that act on the wave system and cause both dissipation of wave energy and transfer of momentum. In particular, the effects of wave damping by vegetation and bottom friction are considered. Linear wave theory is applied to illustrate these effects and, for shallow water waves, the setup is reduced by two-thirds the amount that would occur if the same amount of energy dissipation occurred in the absence of forces. Effects of nonlinear waves are then considered and it is found, for a shallow water wave of approximately one-half breaking height, that a wave setdown rather than setup occurs due to damping by vegetation and bottom friction.The problem of wave setup as waves propagate through vegetation was stimulated by studies to establish hazard zones associated with 100-year storm events along the shorelines of the United States. These storms can generate elevated water levels exceeding 4 to 6 m and can result in overland wave propagation. As these waves propagate through vegetation and damp, the question arose as to the contribution of this process to elevated mean water levels through additional wave setup.     

南海超百米水深海底油管道泄露修复实例

以2008年惠州油田120 m水深海底管道抢修项目为例,介绍了国内首例深水海底管道维修项目的实施。通过项目实施,积累了一些深水海底管道维修经验,同时对未来深水管道维修技术提出了更高要求。