Nutrient transport from an artificial upwelling of deep sea water

The transport of nutrient-rich, deep sea water from an artificial upwelling pipe has been simulated. A numerical model has been built within a commercial Computational Fluid Dynamics (CFD) package. The model considers the flow of the deep sea water after it is ejected from the pipe outlet in a negatively buoyant plume (densimetric Froude number = −2.6), within a stably stratified ocean environment subject to strong ocean current cross flow. Two cross-flow profiles were tested with momentum flux ratios equal to 0.92 and 3.7. The standard k-ε turbulence model has been employed and a range of turbulent Schmidt and Prandtl numbers tested. In all cases the results show that the rapid diffusion of heat and salinity at the pipe outlet causes the plume to attain neutral buoyancy very rapidly, preventing strong fountain-like behavior. At the higher momentum flux ratio fountain-like behavior is more pronounced close to the pipe outlet. The strong cross-current makes horizontal advection the dominant transport process downstream. The nutrient plume trajectory remains largely within one relatively thin stratified layer, making any ocean cross-flow profile less important. Very little unsteady behavior was observed. The results show that the nutrient is reduced to less than 2% of its inlet concentration 10 meters downstream of the inlet and this result is largely independent of turbulent Prandtl or Schmidt number. Initial results would suggest that if such an artificial upwelling were to be viable for an ocean farming project, a large number of upwelling pipes would be necessary. Further work will have to determine the minimum nutrient concentration required to sustain a viable phytoplankton population and the required spacing between upwelling pipes.     

Artificial upwelling in regular and random waves

Mathematical modeling conducted in this study evaluated the hydrodynamic performance of a wave-driven artificial upwelling device in ocean waves off the Hawaiian islands. The device consisted of a buoy (4.0 m in diameter) and a tail pipe (1.2 m in diameter, 300 m in length) with a flow controlling valve. Random ocean waves off the Hawaiian islands used in the device's modeling analysis were synthesized from a wave spectrum obtained from available data. For comparison, the device's performance was also evaluated in regular waves whose height and period are the same as the significant wave height and wave period of random Hawaiian waves. Modeling results indicated that an upwelling flow of 0.95 m³/sec can be generated by this device in random Hawaiian waves and an upwelling flow rate of 0.45 m³/sec can be generated in regular waves. A simple mathematical model which assumed that the device exactly follows the incident waves was used in previous studies. Analysis results also indicated that the simple model cannot satisfactorily simulate the relative velocity and acceleration of the water column in the device. Since the relative velocity and acceleration are important factors in determining the rate of upwelling flow, the simple model must be applied with caution.     

Discussion: a critique of “Modeling suspended sediment distribution in continental shelf upwelling/downwelling settings”

A recent one-dimensional numerical model, the so-called GJ model, neglected horizontal advection and diffusion terms and used vague physical definition for its boundary conditions. An alternative two-dimensional numerical model, which corrects the GJ model’s deficiencies, is proposed to evaluate the physical effects of upwelling/downwelling on suspended sediment concentration (SSC) on continental shelves. The general SSC patterns derived from the two models are similar. However, in the case where settling velocity is larger than the maximum upwelling/downwelling velocity, the GJ model shows a homogeneous distribution of SSC, whereas the two-dimensional model identifies a distinct maximum SSC in the middle of the water column in combined upwelling and downwelling systems, and a SSC gradient in upwelling settings. Furthermore, when the maximum upwelling velocity is larger than the settling velocity, the GJ model shows a maximum SSC at the water surface, whereas the SSC is lower at the water surface when using the two-dimensional model.     

不同布设间距和来流速度下方型人工鱼礁上升流效应的数值模拟

合理的人工鱼礁组合可以有效改善投放水域的流场效应,提高投放水域底层与上层水体之间的扰动。通过使用并行大涡模拟模式及被动示踪物模块,并通过调整人工鱼礁布设间距,研究了在不同背景流速条件(0.1、0.5、0.6和1.0 m/s)下,在不同的横向间距(1L、2L、3L)(L表示人工鱼礁的边长)或纵向间距(1L、2L、3L、4L、5L)情况下,方型人工鱼礁对上升流体积、营养盐的抬升和垂向涡黏系数的影响。研究结果表明,在同一布置条件下,单排布置下的三块人工鱼礁形成的上升流体积大小与来流速度成正相关,体积随来流流速增加而增大6.4%～80.5%;在同一流速条件下,上升流体积大小与纵向布置的间距成正比,与横向布置的间距成反比;在横向布置条件下,当来流速度为1.0 m/s、布设间距为1L时,上升流体积参数最佳。总体来说,上升流体积参数、示踪物浓度差和垂向涡黏性系数均显示横向布置优于纵向布置,相较于布设间距,来流速度是影响上升流体积最重要的因素。     

圆筒型鱼礁体纵横布设间距下的水动力特性研究

应用计算流体力学(Computational Fluid Dynamics,CFD)软件数值计算了圆筒型人工鱼礁体在不同纵向和横向布设间距下的水动力特性,实测了圆筒型人工鱼礁体在纵向布设间距1.0L和2.0L (L为礁体长度)下的流场及受力特性,验证了物理模型实验中各个测点的流速值和阻力值,计算值与实验值吻合较好.研究...     

Artificial upwelling induced by ocean currents —Theory and experiment

A submerged apparatus, which consists of a buoy, several horizontal contraction and expansion tubes (Venturi-type tubes) and a long pipe, is expected to be used to pump the subsurface sea-water (200–300 meter depth) containing abundant nutrients to surface layer (50–100 m) by the dynamic of ocean currents. i.e. an artificial upwelling without energy cost. A preliminary experiment and analysis are undertaken and shows that the capacity of pumping the nutrient-rich sea-water is worth to build a pilot prototype model.     

Continuous measurement of an artificial upwelling of deep sea water induced by the perpetual salt fountain

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.     

渤、黄海风生流场季节循环时空模态与变异

根据1978—2015年渤、黄海沿岸观测风应力场与二维非线性垂直平均风生流模式,以及旋转经验正交函数（REOF）、调和分析等方法,研究了渤、黄海月平均风生流速度势、流函数场季节循环时空模态与年际变异.渤、黄海月平均风生流速度势、流函数场主要有两种时空模态,季节周期分量是时空模态的主要分量.由于风应力场季节循环变异,渤海流函数场季节时空循环变异程度大于速度势场,速度势、流函数场第二模态是季节变异的主要分量,黄海速度势场季节时空循环变异程度大于流函数场,速度势场第二模态是季节变异的主要分量.由于月平均风应力场强度年际变化显著线性减弱,渤、黄海季节平均风生流场强度年际变化也显著减弱.渤、黄海暖流与冷水团季节生消是风生流水平环流与垂直对流对冷 暖水体输送与汇集共同作用的结果,渤、黄海春、夏季辐合上升环流延缓及减弱了浅层暖水向深层传播,是春、夏季冷水团与温跃层形成的重要动力因素,因此,速度势是研究渤、黄海风生流场十分重要的因素.冬季渤海中部、黄海东部反气旋型及辐散下沉环流与黄海中部气旋型环流、辐合上升环流是黄海暖流季节转换与强度的主要动力控制因素,夏季黄海东部气旋型环流、辐合上升环流与黄海中部反气旋型环流、辐散下沉环流是黄海冷水团季节转换与强度的主要动力控制因素.     

Numerical modelling and analysis of temperature controlled density currents in Tomales Bay, California

The coastal region adjacent to Tomales Bay, California is dominated by wind-driven upwelling during spring and summer and the cold, upwelled water is moved towards Tomales Bay, entering the estuary with the flood tide. If the tidal excursion is ≥6 km and the cold water subducts beneath the warmer, less dense estuarine water, a temperature controlled density current may form and intrude towards the head of the estuary as a thermally stratified bottom layer. The numerical modelling was aimed at determining the capability of the Delft3D-FLOW model to reproduce the cold ocean water intrusion events, the response (development and progression) of these intrusions to differing physical scenarios and the comparative importance of the parameters to the intrusions. The numerical model successfully reproduced the density intrusions and showed that the persistence and break down of the density intrusions were affected by a number of physical parameters, to varying degrees. The sensitivity analysis showed that density intrusion formation is controlled by tidal conditions and ocean water temperature. The strength and persistence of the developed density intrusions are influenced by wind, insolation and estuary depth. Fresh water inflow at the head of the estuary had no impact on the density intrusions. Three-dimensional numerical modelling is thus a valuable tool in understanding the estuary and its functioning.     

Western boundary current crossing a ridge

Investigated is a possibility of two-dimensional model in the study of the dynamics of the western boundary current by a numerical experiment. Emphasis is laid on the effect of bottom barrier corresponding to the Izu Ridge.The western boundary current in the model is formed by source and sink of the water prescribed at an artificial eastern wall (600 km offshore). The bottom topographyconsists of a continental slope parallel to the straight western coast, and a ridge protruding from the western coast to 500 km offshore (1,500 m deep and 400 km wide). The grid size of 12 km× 25 km (offshore and longshore directions, respectively) resolves both the western boundary current and the bottom topography.The assumption of homogeneity of the water density makes the western boundary current detour along the isobath of the ridge.A steady state solution is obtained under the assumptions that the horizontal velocity does not change direction vertically (equivalent barotropic), and that the geostrophic relationship holds at the bottom. Homogeneity of the water density is not assumed. The solution shows that most of the volume transport of the western boundary current cross the ridge and the current has cyclonic vorticity near the summit of the ridge. It seems to suggest that the investigation by three-dimensional models is neccesary in order to study the complete dynamics of the western boundary current crossing the ridge.     

Southern Ocean transformation in a coupled model with and without eddy mass fluxes

A coupled air–sea general circulation model is used to simulate the global circulation. Different parameterizations of lateral mixing in the ocean by eddies, horizontal, isopycnal, and isopycnal plus eddy advective flux, are compared from the perspective of water mass transformation in the Southern Ocean. The different mixing physics imply different buoyancy equilibria in the surface mixed layer, different transformations, and therefore a variety of meridional overturning streamfunctions. The coupled‐model approach avoids strong artificial water mass transformation associated with relaxation to prescribed mixed layer conditions. Instead, transformation results from the more physical non‐local, nonlinear interdependence of sea‐surface temperature, air–sea fluxes, and circulation in the model's atmosphere and ocean. The development of a stronger mid‐depth circulation cell and associated upwelling when eddy fluxes are present, is examined. The strength of overturning is diagnosed in density coordinates using the transformation framework.     

Quasi-3D Numerical Simulation of Tidal Hydrodynamic Field

Based on the 2D horizontal plane numerical model,a quasi-3D numerical model is establishedfor coastal regions of shallow water.The characteristics of this model are that the velocity profiles can be ob-tained at the same time when the equations of the value of difference between the horizontal current velocityand its depth-averaged velocity in the vertical direction are solved and the results obtained are consistent withthe results of the 2D model.The circulating flow in the rectangular area induced by wind is simulated and ap-plied to the tidal flow field of the radial sandbanks in the South Yellow Sea.The computational results fromthis quasi-3D model are in good agreement with analytical results and observed data.The solution of the finitedifference equations has been found to be stable,and the model is simple,effective and practical.     

Observations of a cycle of intense coastal upwelling and downwelling at the research site of the Shirshov Institute of Oceanology in the Black Sea

The paper presents the results of joint analysis of the response of vertical temperature and current velocity profile distributions in the coastal zone of the Gelendzhik region of the Black Sea to strong wind forcing in the third ten-day period of September 2013. This forcing was caused by the propagation of an atmospheric cyclone, which first initiated coastal upwelling that was later replaced by downwelling. We formulate a criterion for the development of full coastal upwelling and demonstrate its efficiency. We assume that frequent events of incomplete coastal upwelling and downwelling are associated with changes in the water dynamics (variations in the intensity and direction of the alongshore current) generally not related to local wind forcing.     

东海北部一个夏季气旋型涡旋的初步分析

近十年来,随着海洋探测技术的发展,在世界各大洋里都发现了中尺度涡旋,这是物理海洋学上的重大进展之一。目前所发现的中尺度涡旋,不管是在大洋里,还是在极地区,一般均处于千米以上的深水区。但在陆架浅海区，海底摩擦要消耗大量的能量,是否也会出现这类涡旋,这是一个令人感兴趣的问题。 根据现有文献和我们对近几年东海水文调查资料的初步分析得知,在我国陆架区至少有两个气旋型涡旋,一个在台湾东北的彭佳屿附近海域,另一个在济州岛西南海域。对前者,管秉贤(1978)和M.Uda(1974)等均从冷水团的角度进行过研究,特别是日本学者在此海域进行了多次调査。至于后者,井上尚文(1975)曾根据1969年11月投放的“人工水母”(即底层流示踪器)的资料分析指出:“在黄海暖流和黄海沿岸流两股底层流的中间区域,有黄海冷水伸入。在秋、冬期间,南北流向呈反时针方向旋转。从而可以认为,以调查海区的中部(济州岛南面)海底为中心,有一个范围相当大的环流存在。”由此人们自然会提出这样一个问题:在春、夏两季,这一反时针方向的水平环流是否继续存在。尤其在夏季,自南北上进入黄海和东海的黑潮及其分支(对马暖流和黄海暖流)与黄海、东海沿岸流系交错汇合,盘踞在下层的冷水又极度发展,使得环流结构和水文状况较冬季复杂得多,这时的情况又将变得怎样?本文主要根据1972年7-8月常规水文观测资料,同时参照近几年的水文资料,对此问题作一初步探讨。 本文研究的重点海区的范围是30°30′-33°00′N,124°00′-127°E,如图1阴影部分所示。为了便于资料的分析,在绘制温、盐度等平面分布图时,将其范扩大到28°-34°N之间的大部分海域。 本文引用的资料主要来源于国家海洋局标准断面调查资料,东海渔业资源调査资料，日本气象厅海洋气象观测资料和南朝鲜水产振兴院海洋观测资料。     

Mechanism for enhanced diffusivity in the deep-sea perpetual salt fountain

The mechanism of enhanced diffusivity occurring in the deep-sea perpetual salt fountain has been investigated experimentally and numerically. Some factors which possibly contribute to the enhanced diffusivity were found to be the pipe oscillation with ocean waves and its baffled wall surface. Field experiments in the ocean (Onagawa Bay of Miyagi, Japan) and numerical simulations were performed to study and confirm the dynamics of the flow and heat transport with enhanced diffusivity occurring in upwelling deep-sea water. The agreement between the field experimental data and the numerical solutions of an oscillating-wall boundary condition imposed on the baffled pipe is encouraging, and it indicates the baffled pipe surface subject to the oscillatory motion leads to the enhanced diffusivity. The buoyancy force and then upwelling velocity can be greatly increased by the enhanced diffusivity. The dominant mechanism is the occurrence of complicated vortices and vortex shedding leading to efficient mixing and enhanced diffusion.     

Introduction of accumulation-dispersal coefficient of marine organisms

Avoiding the subject for fish accumulation, the traditional view in fish population dynamics has ascribed immigration and emigration of fish to dispersal of fish. The main purpose of this paper is to find a quantity that represents the time rate of accumulation-dispersal of marine organisms, and also has some relation to the horizontal convergence of current velocity of the surrounding water. For this, the accumulation-dispersal coefficient is introduced not in the form of diffusion, but in the same form as the convergence. Since the accumulation-dispersal of organisms is a factor that changes its distribution density, all factors causing the change are first classified to locate the position occupied by the accumulation dispersal. Each factor corresponds to each coefficient appearing in a linearized equation describing the rate of change in the density, averaged over a region or a group. The immigration-emigration coefficient is divided into three coefficients of passage, accumulation dispersal and diffusion velocity. For the organisms ranging in a nearly horizontal layer, the accumulation-dispersal coefficient is shown to equal the area-averaged horizontal convergence of organismal velocity relative to land, which is the sum of the area-averaged horizontal convergences of swimming velocity relative to water and of current velocity. However, the area-averaged convergence of current velocity associated with the accumulation-dispersal coefficient for a region is shown to be somewhat different from the usual one.     

Numerical study of the behavior of heated water discharged into the ocean

Matsuno and Nagata (1987) showed numerically that the spreading characteristics of the discharged heated water from power plants of existing scale is significantly influenced by the earth's rotation effect. Although the effect of the enhancement of the Coriolis parameter on the spreading characteristics of the formed warm water mass was discussed in order to demonstrate the rotation effect, other parameters such as the density difference between the discharged heated water and ambient water and the vertical eddy viscosity and diffusivity were fixed. In this paper, the dependence of the spreading characteristics on these parameters is examined. Then, it is shown that the overall shape of the formed warm water mass and density and velocity structure strongly depend on these parameters. Also, it is indicated that the behavior of the warm water mass under the rotation effects is too complicated to be described with a few parameters. For example, the internal radius of deformation seems to be one of the determinative parameters, and the increase of the density difference between discharged water and ambient water has a similar effect on the shape of the formed warm water mass as a decrease of the Coriolis parameter. However, a change of the two values has different effects on the detailed density structure and current structure of the warm water mass. The Prandtl number seems to determine some aspects of the veloczty field such as velocity magnitude and width of the southward flowing current zone. However, other features such as the thickness of the warm water mass are not determined by the Prandtl number.     

Analysis of temporal and spatial variability of phytoplankton by physical-biological models

I reviewed my research on analysis of temporal and spatial variability of phytoplankton by physical-biological models. This paper was prepared for a lecture of the member awarded the Okada Prize for 1991 from the Oceanographical Society of Japan.Temporal change of phytoplankton in a local upwelling was studied by simulated upwelling experiments conducted with natural phytoplankton communities under natural surface light conditions. Results of the culture experiments was explained by a simple model. This model allows to predict the chlorophyll and nutrient concentration changes in a given upwelled water mass.Above model was verified by a local upwelling observed off Izu, Japan, on May, 1982. Phytoplankton growth and nutrient decrease in surface water of the local upwelling were observed within two days followed by decrease of phytoplankton concentration under depleted nutrient environment. The phytoplankton growth and nutrient decrease could explained by the model with phytoplankton removal rate of about half of the growth rate. Centric diatom was the dominant phytoplankton group and pennate diatom showed less abundance in the upwelled water. Pennate diatom showed fast growth rate when nutrient was abundant and fast decreasing rate after nutrient depleted. On the other hand, flagellate and monads showed relatively slow change of biomass under the change of nutrient concentrations. Furthermore, resting spore formation of centric diatom,Leptocylindrus danicus, was observed in a response to nutrient depletion.Temporal and spatial variability of phytoplankton in the southeastern U.S. continental shelf ecosystem was studied by physical-biological models. First, differences of the biological responses to frontal eddy upwelling during spring and to intrusion during summer was considered by Lagrangian particle tracing experiments with optimally-interpolated flow fields. In spring, particles showed residence time of a few days; however, particles in summer intrusion stayed on the shelf nearly 30 days. It was concluded that difference of particle residence time of upwelled water make the difference of plankton communities. Similar flow fields and particle tracing experiments were used to trace the features in chlorophyll distributions during spring of 1980 derived by Coastal Zone Color Scanner (CZCS). Phytoplankton patchness were created and deformed by frontal eddy events. Eularian physical-biological model was constructed to understand the CZCS-chlorophyll distributions. Statistical comparisons with series of numerical experiments indicate that horizontal advection is an important process for the chlorophyll distributions and that upwelling and associated phytoplankton growth are responsible for the across-shelf gradients and maintenance of concentrations. Furthermore, the CZCS data were assimilated to the model to improve the phytoplankton concentrations, and phytoplankton carbon flux across shelf was estimated. Processes causing the time changes of chlorophyll concentrations were estimated with the model and satellite data further indicated that the both physical and biological forcing is important for the time chages. Several other studies conducted presently were mentioned.     

环台湾岛海域冬季水文要素的数值模拟

本文利用POM模式对环台湾岛海域冬季的水文要素进行了数值模拟,对有代表性的水平环流、温度场和上升流三个要素所进行的分析表明:模式再现了台湾岛东岸的高温高盐强流速区即黑潮,黑潮在冬季并无直接进入台湾海峡的分支存在;西岸的东北向流在冬季各个层次上都存在,台湾东北部的冷涡模拟与实况较为一致。温度场和上升流的分布与水平环流有很好的对应关系。本文还进一步验证了前人的一些研究成果,并对一些特殊物理现象的成因进行了定性解释。     

Effect of bottom slope in northeastern North Pacific on deep-water upwelling and overturning circulation

Hydrographic data show that the meridional deep current at 47°N is weak and southward in northeastern North Pacific; the strong northward current expected for an upwelling in a flat-bottom ocean is absent. This may imply that the eastward-rising bottom slope in the Northeast Pacific Basin contributes to the overturning circulation. After analysis of observational data, we examine the bottom-slope effect using models in which deep water enters the lower deep layer, upwells to the upper deep layer, and exits laterally. The analytical model is based on geostrophic hydrostatic balance, Sverdrup relation, and vertical advection–diffusion balance of density, and incorporates a small bottom slope and an eastward-increasing upwelling. Due to the sloping bottom, current in the lower deep layer intensifies bottomward, and the intensification is weaker for larger vertical eddy diffusivity (K _V), weaker stratification, and smaller eastward increase in upwelling. Varying the value of K _V changes the vertical structure and direction of the current; the current is more barotropic and flows further eastward as K _V increases. The eastward current is reproduced with the numerical model that incorporates the realistic bottom-slope gradient and includes boundary currents. The interior current flows eastward primarily, runs up the bottom slope, and produces an upwelling. The eastward current has a realistic volume transport that is similar to the net inflow, unlike the large northward current for a flat bottom. The upwelling water in the upper deep layer flows southward and then westward in the southern region, although it may partly upwell further into the intermediate layer.