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1.
The American physical oceanographer Henry Stommel and co-workers proposed “the perpetual salt fountain” and suggested the possibility of upwelling deep seawater without an energy source. In the open ocean, deep seawater containing rich nutrients becomes a source of primary production. Previously, we have tested Stommel's hypothesis by numerical simulations and in ocean experiments, and confirmed the upwelling of a perpetual salt fountain. In the present study, we conducted an open-ocean experiment in the Philippines Sea, and succeeded to demonstrate an increase in chlorophyll concentration. The chlorophyll concentration at the pipe outlet was much greater than that in the surrounding seawater. Satellite ocean-color image around the pipe was analyzed, and the signal of artificial upwelling is investigated. Composite analysis of satellite chlorophyll image indicates an increased surface chlorophyll distribution in the vicinity of pipe position, in which the increasing signal is much larger than the expected production based on nutrient supply. Although the problem must be further discussed, this increased signal is shown to be statistically significant. This mechanism may contribute to effective utilization of fishery resources in subtropical oligotrophic region.  相似文献   

2.
文章建立了基于真实场驱动的三维物理—生态耦合模型, 利用模型定量分析了夏季南海北部上升流和羽状流过程对浮游植物生物量空间分布的影响程度及作用机制。首先, 利用2006—2008年卫星遥感数据及2006与2008年夏季观测数据对模型进行了验证, 结果表明, 模型能较好地再现夏季南海北部上升流和羽状流过程, 较好地反映出浮游植物的空间分布特征。模拟分析结果显示, 夏季南海北部浮游植物主要分布在50m等深线以内。琼州海峡东部海域和汕头海域浮游植物垂向分布较为均匀, 上升流的贡献均达到90%以上, 表层水平平流输送是浮游植物主要的汇, 生物过程是浮游植物的源。珠江口和汕尾海域浮游植物存在表层和次表层两个高值区, 羽状流贡献35%~40%, 主要促进表层浮游植物生长, 而上升流贡献60%~65%, 主要促进中底层浮游植物的生长。粤西海域上升流对浮游植物的贡献占92%, 主要促进中底层浮游植物生长, 而表层浮游植物浓度极低。整体上, 夏季南海北部上升流和羽状流主要是通过输送营养盐的方式影响浮游植物的生长。上升流对营养盐的输送作用是向岸方向的爬升输送和平行于等深线的沿岸流输送共同作用的结果。跃层的存在改变了营养盐的垂向输送过程, 是导致上升流和羽状流过程对不同水层浮游植物贡献差异的关键因素之一。整体而言, 夏季南海北部浮游植物空间分布差异是以上升流、羽状流主导, 环流—营养盐—生物过程共同作用的结果。  相似文献   

3.
A perpetual salt fountain can draw up deep sea water without any artificial energy source. This is one of the ideal ways to draw up deep sea water for nutrient enhancement application. A perpetual salt fountain experiment was carried out in May 2004. The estimated average velocity of the upwelling after 48 h from the start of the experiment was about 7 mm/s, and it continued for about 3 days. The flow rate with a single pipe was estimated as approximately 45 m3/day. The amount of upwelled deep sea water by this single pipe seems too small to be of benefit, but we can easily increase the amount by deploying a number of pipes.  相似文献   

4.
Specific features of the turbulent transfer of the momentum and heat in stably stratified geophysical flows, as well as possibilities for including them into RANS turbulence models, are analyzed. The momentum (but not heat) transfer by internal gravity waves under conditions of strong stability is, for example, one such feature. Laboratory data and measurements in the atmosphere fix a clear dropping trend of the inverse turbulent Prandtl number with an increasing gradient Richardson number, which must be reproduced by turbulence models. Ignoring this feature can cause a false diffusion of heat under conditions of strong stability and lead, in particular, to noticeable errors in calculations of the temperature in the atmospheric boundary layer. Therefore, models of turbulent transfer must include the effect of the action of buoyancy and internal gravity waves on turbulent flows of the momentum. Such a strategy of modeling the stratified turbulence is presented in the review by a concrete RANS model and original results obtained during the modeling of stratified flows in the environment. Semiempirical turbulence models used for calculations of complex turbulent flows in deep stratified bodies of water are also analyzed. This part of the review is based on the data of investigations within the framework of the large international scientific Comparative Analysis and Rationalization of Second-Moment Turbulence Models (CARTUM) project and other publications of leading specialists. The most economical and effective approach associated with modified two-parameter turbulence models is a real alternative to classical variants of these models. A class of test problems and laboratory and full-scale experiments used by the participants of the CARTUM project for the approbation of numerical models are considered.  相似文献   

5.
Effects of Stokes production on summer ocean shelf dynamics   总被引：1，自引：0，他引：1  
A two-dimensional numerical model,which is configured on the basis of Princeton ocean model（POM）,is used to study the effect of Stokes production（SP） of the turbulent kinetic energy on a density profile and Ekman transport in an idealized shelf region in summer.The energy input from SP is parameterized and included into the Mellor-Yamada turbulence closure submodel.Results reveal that the intensity of wind-driven upwelling fronts near the sea surface is weakened by the SP-associated turbulent kinetic energy input.The vertical eddy viscosity coefficient in the surface boundary layer is enhanced greatly owing to the impact of SP,which decreases the alongshore velocity and changes the distribution of upwelling.In addition,the SP-induced mixing easily suppresses the strong stratification and significantly increases the depth of the upper mixed layer（ML） under strong winds.  相似文献   

6.
1997年冬季南海南部海区不同天气过程下的湍流通量输送   总被引：9，自引：0，他引：9  
利用“九五”南沙群岛及其邻近海区综合科学考察 1 997年 1 1月 3— 2 6日期间的走航和定点连续观测获得的大气和海洋资料 ,探讨了调查海区的气象特征 ;使用考虑风速和大气稳定性影响并经高度订正的整体通量输送动力学公式 ,计算了动量、感热和潜热的湍流通量。结果表明 ,与其它天气过程相比 ,降水过程期间无论是大气向海洋输送的动量通量 ,还是海洋向大气输送的感热和潜热通量 ,其值都是最大的。  相似文献   

7.
Comprehensive sea surface surveys of the partial pressure of carbon dioxide (pCO2) have been made in the upwelling system of the coastal (0–200 km from shore) southeastern tropical Pacific since 2004. The shipboard data have been supplemented by mooring and drifter based observations. Air–sea flux estimates were made by combining satellite derived wind fields with the direct sea surface pCO2 measurements. While there was considerable spatial heterogeneity, there was a significant flux of CO2 from the ocean to the atmosphere during all survey periods in the region between 4° and 20° south latitude. During periods of strong upwelling the average flux out of the ocean exceeded 10 moles of CO2 per square meter per year. During periods of weaker upwelling and high productivity the CO2 evasion rate was near 2.5 mol/m2/yr. The average annual fluxes exceed 5 mol/m2/yr. These findings are in sharp contrast to results obtained in mid-latitude upwelling systems along the west coast of North America where the average air–sea CO2 flux is low and can often be from the atmosphere into the ocean. In the Peruvian upwelling system there are several likely factors that contribute to sea surface pCO2 levels that are well above those of the atmosphere in spite of elevated primary productivity: (1) the upwelling source waters contain little pre-formed nitrate and are affected by denitrification, (2) iron limitation of primary production enhanced by offshore upwelling driven by the curl of the wind stress and (3) rapid sea surface warming. The combined carbon, nutrient and oxygen dynamics of this region make it a candidate site for studies of global change.  相似文献   

8.
2002年夏季粤东外海的海洋状况   总被引：3，自引：1，他引：3  
本文利用2002年7月22日至8月2日对粤东外海进行的水文观测资料，分析了调查海区的水温、盐度和跃层的分布状况，并对粤东沿岸的上升冷水、海洋锋等海洋现象进行了探讨．结果表明，整个粤东沿岸都存在着下层冷水的涌升现象，该现象在大亚湾外海附近和广东总来外海附近尤为明显，从而导致粤东沿岸水等温线非常密集，产生上升流锋．上升流锋随着深度的增加有向外海扩展的趋势．此外，在台湾浅潍的南部，陆架的坡析处和东沙群岛的东例以及西南部海战似乎也有下层冷水涌升的迹象．东沙群岛的北侧和西部海战有暖水中心存在，该暖水中心可能是离岸的表层水离异一定距离后发生下沉所致．珠江口的东例出现高温低盐水，其低盐水舌向东伸展，可达大亚湾口外海，等盐度线非常密集，是一个非常强的冲淡水羽状锋。  相似文献   

9.
Unusual large-scale phytoplankton blooms in the equatorial Pacific   总被引：1，自引：0，他引：1  
Unusual large-scale accumulations of phytoplankton occurred across 10,000 km of the equatorial Pacific during the 1998 transition from El Niño to La Niña. The forcing and dynamics of these phytoplankton blooms were studied using satellite-based observations of sea surface height, temperature and chlorophyll, and mooring-based observations of winds, hydrography and ocean currents. During the bloom period, the thermocline (nutricline) was anomalously shallow across the equatorial Pacific. The relative importance of processes that enhanced nutrient flux into the euphotic zone differed between the western and eastern regions of the blooms. In the western bloom region, the important vertical processes were turbulent vertical mixing and wind-driven upwelling. In contrast, the important processes in the eastern bloom region were wave-forced shoaling of nutrient source waters directly into the euphotic zone, along-isopycnal upwelling, and wind-driven upwelling. Advection by the Equatorial Undercurrent spread the largest bloom 4500 km east of where it began, and advection by meridional currents of tropical instability waves transported the bloom hundreds of kilometers north and south of the equator. Many processes influenced the intricate development of these massive biological events. Diverse observations and novel analysis methods of this work advance the conceptual framework for understanding the complex dynamics and ecology of the equatorial Pacific.  相似文献   

10.
An attempt is made to examine some observational and theoretical aspects of upper ocean dynamics in regions of strong coastal upwelling. “Upper ocean” is roughly defined as about the upper 10–30 m of the water column for most systems. First, the basic surface Ekman and mixed layers are discussed, including some of the modifications due to upwelling. Next, coastal upwelling fronts and their associated circulation are treated. Finally, areas of strongly three-dimensional upwelling are classified and discussed. Horizontal advection of heat and momentum appear to be generally important for the near-surface dynamics of coastal upwelling, and these phenomena make realistic theoretical treatments especially difficult.  相似文献   

11.
The aim of the current paper is to investigate hydrodynamic characteristics of the artificial upwelling induced by ocean currents. Experiments were performed in a flume at different density difference heads, horizontal current velocities and upwelling pipe diameters. A three-dimensional computational fluid dynamics (CFD) model was employed on wider range of parameters for further analysis. The performance of the numerical model has been confirmed by the experimental findings. The present results show that the volume flow rate of current-induced artificial upwelling is influenced by geometrical parameters and inclination angle of the pipe, the horizontal current velocity and vertical distribution of water density. In ideal two-layer density stratified water, the critical current velocity to generate upwelling linearly increases with the increase of the density difference, and the maximum rising height for upwelling is inversely proportional to the density difference. Feasibility analysis was taken by using current and density profiles of the East China Sea near Dongji Islands, which provides an useful reference for engineering practice.  相似文献   

12.
This paper reviews the dynamics of ocean pipes aspirating fluid and presents a selective review of the research undertaken on it. It focuses on the equations of motion, fluid-solid interaction at the inlet of the free end of the pipe, the stability mechanism of pipes aspirating steady fluid, etc. In particular, some unresolved or partly resolved issues on these important aspects are discussed. Finally, the promising future development in this area is discussed.  相似文献   

13.
The Santa Clara River delivers nutrient rich runoff to the eastern Santa Barbara Channel during brief (1–3 day) episodic events. Using both river and oceanographic measurements, we evaluate river loading and dispersal of dissolved macronutrients (silicate, inorganic N and P) and comment on the biological implications of these nutrient contributions. Both river and ocean observations suggest that river nutrient concentrations are inversely related to river flow rates. Land use is suggested to influence these concentrations, since runoff from a subwatershed with substantial agriculture and urban areas had much higher nitrate than runoff from a wooded subwatershed. During runoff events, river nutrients were observed to conservatively mix into the buoyant, surface plume immediately seaward of the Santa Clara River mouth. Dispersal of these river nutrients extended 10s of km into the channel. Growth of phytoplankton and nutrient uptake was low during our observations (1–3 days following runoff), presumably due to the very low light levels resulting from high turbidity. However, nutrient quality of runoff (Si:N:P = 16:5:1) was found to be significantly different than upwelling inputs (13:10:1), which may influence different algal responses once sediments settle. Evaluation of total river nitrate loads suggests that most of the annual river nutrient fluxes to the ocean occur during the brief winter flooding events. Wet winters (such as El Niño) contribute nutrients at rates approximately an order-of-magnitude greater than “average” winters. Although total river nitrate delivery is considerably less than that supplied by upwelling, the timing and location of these types of events are very different, with river discharge (upwelling) occurring predominantly in the winter (summer) and in the eastern (western) channel.  相似文献   

14.
Quantitative data are presented on the distribution of adult and larval stages of the euphausiid Nyctiphanes australis G. O. Sars, in western Cook Strait, New Zealand, an area influenced by an upwelling plume. The behaviour of N. australis in the Kahurangi Point region at different stages of its life history appears to ensure its maintenance, in general, over the continental shelf on an upwelling coast. Population structure at the source of the upwelling near Kahurangi Point differed from that in regions “down stream” from the plume. Nyctiphanes australis was most abundant at the “downstream” eastern end of the upwelling plume, and the evidence suggesting that the dense populations there may be resident is discussed. Possible reasons for low densities of furcilia II and III stages in the eastern plume region are considered.  相似文献   

15.
In this paper, a two-fluid model of turbulent two-phase flow is used to simulate turbulent stratified flows. This is a unified multi-fluid model for the motion of each phase in the flow, whose turbulent transport is closed by a two-phase k– model. The exchanges of mass, momentum and energy between the two phases are fully accounted for in the simulation. For illustration, a case of turbulent stratified flow with strong buoyancy effects, for which extensive experimental data are available, is selected for examination. It is shown that the numerical results agree well with the experimental data.  相似文献   

16.
台湾岛附近海洋对0908号台风“莫拉克”的响应特征   总被引：1，自引：1，他引：0  
在模拟2009年登陆我国东部沿海的台风"莫拉克"的基础上,利用AVHRR/AMSR和SODA再分析数据和模拟结果,初步评估了GRAPES-ECOM海-气耦合模式(上海台风研究所基于GRAPES-TCM区域台风模式和ECOM海洋模式开发而成)模拟台风期间海洋响应的能力,并分析了台风期间台湾岛周围海域的海温、上升流、中尺度冷涡等的变化特点。分析结果表明,GRAPES-ECOM耦合模式较好地模拟了表层海温对台风的响应,与深水海洋响应比较,揭示了近海对台风响应的一些新特征:(1)在台湾以东海域,台风活动改变了黑潮海域海水的垂直运动,诱导黑潮南部沿岸上升流,而北部先于台风存在的上升流减弱,导致不同水深海温的最大降温位置都出现在路径左侧,与深海偏向路径右侧不同;(2)位于台湾岛东北面的彭佳屿冷涡因其形成与大陆架和黑潮有关,当台风在台湾以东洋面活动时,冷涡位于台风右前方,黑潮表层海水辐合流向大陆架,冷涡中心温度上升,强度减弱,当台风转折北上,冷涡位于台风东南侧,表层海水辐散,加强底层冷水上涌,从而增强了该冷涡的强度;(3)台风不仅加深了台湾海峡的混合层深度,还使得海水的垂直热力结构改变,并使整层海温趋于一致。  相似文献   

17.
A computational fluid dynamics (CFD) model was developed to simulate the turbulent flow and species transport of deep-sea high temperature hydrothermal plumes. The model solves numerically the density weighted unsteady Reynolds-averaged Navier–Stokes equations and energy equation and the species transport equation. Turbulent entrainment and mixing is modeled by a k–ε turbulence closure model. The CFD model explicitly considers realistic vent chimney geometry, vent exit fluid temperature and velocity, and background stratification. The model uses field measurements as model inputs and has been validated by field data. These measurements and data, including vent temperature and plume physical structure, were made in the ABE hydrothermal field of the Eastern Lau Spreading Center. A parametric sensitivity study based on this CFD model was conducted to determine the relative importance of vent exit velocity, background stratification, and chimney height on the mixing of vent fluid and seawater. The CFD model was also used to derive several important scalings that are relevant to understanding plume impact on the ocean. These scalings include maximum plume rise height, neutrally buoyant plume height, maximum plume induced turbulent diffusivity, and total plume vertically transported water mass flux. These scaling relationships can be used for constructing simplified 1-dimensional models of geochemistry and microbial activity in hydrothermal plumes. Simulation results show that the classical entrainment assumptions, typically invoked to describe hydrothermal plume transport, only apply up to the vertical level of ~0.6 times the maximum plume rise height. Below that level, the entrainment coefficient remains relatively constant (~0.15). Above that level, the plume flow consists of a pronounced lateral spreading flow, two branches of inward flow immediately above and below the lateral spreading, and recirculation flanking the plume cap region. Both turbulent kinetic energy and turbulence dissipation rate reach their maximum near the vent; however, turbulent viscosity attains its maximum near the plume top, indicating strong turbulent mixing in that region. The parametric study shows that near vent physical conditions, including chimney height and fluid exit velocity, influence plume mixing from the vent orifice to a distance of ~10 times the vent orifice diameter. Thus, physical parameters place a strong kinetic constraint on the chemical reactions occurring in the initial particle-forming zone of hydrothermal plumes.  相似文献   

18.
A three-dimensional numerical model is developed and used to study the coastal upwelling processes and corresponding seasonal changes in the sea level along the west coast of India. The upwelling and associated sea level variations are seen as a response of coastal ocean to pure wind stress forcing. The model is designed to represent coastal ocean physics by resolving surface and bottom Ekman layers as realistically as possible. The prognostic variables are the three components of the velocity field, temperature, salinity and turbulent energy. The governing equations together with their boundary conditions are solved by finite-difference techniques. Experiments are performed to investigate sea level fluctuations associated with the thermal response and alongshore currents of the coastal waters. The model is forced with mean monthly wind stress forcing of January, May, July and September representing northeast monsoon and different phases of the southwest monsoon. It is known from the observational study that the upwelling process reaches to the surface waters by May along the coastal waters of the extreme southwest peninsular region. The process is more intense in July compared to May and September and its strength decreases from south to north. However, during the northeast monsoon season, which is represented by January wind stress forcing in the model, downwelling is simulated along the coast. The model simulations of the coastal response are compared with the observations and are found to be in good agreement. The maximum computed vertical velocity of about 2.0 ×10 -3 cm s -1 is predicted in July in the southern region off the coast.  相似文献   

19.
石湘  陈健仁  尹崇达  张宇 《海洋工程》2019,37(1):127-133
针对用于单元管件的非自应力灌浆卡箍和膨胀式自应力灌浆卡箍,讨论了灌浆卡箍水下安装的几个吊装和安装设计问题。首先介绍灌浆卡箍水下安装的总体设计及其安装步骤;然后进行了下水吊装时保持卡箍进浆口在下、出浆口在上的姿态分析和设计,计算出了合适的吊装悬挂距离;对帮助卡箍两瓣自动包拢受损管件的一个辅助闭合机构进行了力学分析和液压系统设计;介绍了卡箍对中及端部密封装置的工作原理;最后介绍了卡箍安装的海上试验情况,列出了各工序安装时间。为灌浆卡箍水下安装技术走向实际工程应用提供了设计和试验经验。  相似文献   

20.
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   

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