Quasi-isopycnic layer model for large-scale ocean circulation

A hydrothermodynamic model of a multilayer ocean, incorporating the upper mixed layer (UML) is described. The model is based on a system of primitive equations integrated within each layer. All layers are assumed to be horizontally-inhomogeneous, however, the density in each thermocline layer changes within the limits determineda priori by the prescribed basic stratification. It is assumed that the layers may outcrop. Results of the numerical experiment on subduction simulation (downwelling of UML waters toward the main thermocline layers) are given.Translated by V. Puchkin.     

Distribution Characteristics of Mean Seawater Temperature Related to the Thermocline in the Deep-Water Area of Nansha

On the bisis of determining the there elements of themocline ( depth [upper bound depth ], thickness and intensity ) and the maximum vertical temperature gradient of the surveying station, the paper calculates the mean temperature of the Nansha deep-water surveying station within the upper-bound depth layer of thermocline and the mean temperature below the lowerbound depth of thermocline between the 300m and 800m layers,respectively. Analysis indicates that the horizontal distribution of mean seawater temperature shows a distinct trend of the lowtemperature seawater slowly moving from tbe northeast to the southeast of Nansha,which seems to have been driven by the Northeast Monsoon. The larger the vertical temperature radient is, the greater is its capability of preventing the heat of the upper seawater from diffusing into the deeper layers on the vertical direction.     

Modelling of upwelling and downwelling in the ocean

Numerical experiments on the reconstruction of upwelling and downwelling at the eastern boundary of the ocean were carried out in the framework of a multilayer model of the ocean involving the upper mixed layer (UML). The peculiarities of these phenomena when they are formed and attenuated owing to the strong intensification and abatement of the longshore wind have been studied. It is shown that cold waters are always involved from the thermocline to the UML during upwelling. In downwelling, this occurs as a rule. However, during upwelling the abatement of the wind may result in subduction —the inflow of warm waters from the UML to the thermocline.Translated by Mikhail M. Trufanov.     

Modelling of the upper mixed layer in the Tropical Atlantic

A method for the computation of the spatial-temporal variability of the upper mixed layer (UML) within the framework of a model for the multilayer ocean is proposed. Using a three-layer ocean (UML, thermocline, and abyssal regions) as an example, the formation of the UML topography from the state of rest and the current and temperature fields in the Tropical Atlantic are considered.Translated by Mikhail M. Trufanov.     

THE VERTICAL CHARACTERISTICS OF INTERNAL WAVES IN SHALLOW REGION OF THE EAST CHINA SEA ANALYSED FROM CTD DATA

The vertical characters of temperature, salinity and density fluctuations in shallow region of the East China Sea are analysed by using 12 CTD short records with 1-hour intervals. The average S,t and p profiles can be divided into three distinctive layers: the thermocline, and the layers above and below it. The fluctuations of t, S and p are basically caused by internal waves, but there are somewhat intrusions or entrainments at the thermocline boundaries. The vertical displacement of the thermocline centre is up to more than 6.35m and the thermocline thickness changes from 3.5 to 8.0 m. Their varature with time are intermittent and rather irregular. The vertical wavenumber spectra of temperature fluctuations have been estimated by using the maximum entropy method, indicating that energy is mainly contained in the low-wavenumber range (<0.13cpm) with two sharp peaks probably corresponding to the first and second modes of internal waves, whose dependence is estimated to be less than β-2. There exist dep     

南海中部上层海洋温度的短周期振动

南海季风试验(SCSMEX)期间,南海中部投放了3个ATLAS浮标.本文选取3个站点1998年4月13日～1999年4月8日的所有观测水层的温度数据作为研究.通过逐月功率谱分析,发现50-500m深度,温度存在全日和半日2个显著短周期的振动;利用小波分析得出了温度短周期振动的时空变化特点,并结合温度跃层时空结构的分析,发现跃层深度上,温度全日(或半日)周期振动的时空变化与跃层时空结构存在一致性,即在跃层核心深度上,跃层强度越大的时域内,温度全日(或半日)周期的振动就越显著.     

基于ROMS模型数值研究南海温跃层的季节变化

On the basis of the regional ocean modeling system （ROMS）, the seasonal variations of the thermocline in the South China Sea （SCS） were numerically investigated. The simulated hydrodynamics are in accordance with previous studies： the circulation pattern in the SCS is cyclonic in winter and anticyclonic in summer, and such a change is mostly driven by the monsoon winds. The errors between the modeled temperature profiles and the observations obtained by cruises are quite small in the upper layers of the ocean, indicating that the ocean status is reasonably simulated. On the basis of the shapes of the vertical temperature profiles, five thermocline types （shallow thermocline, deep thermocline, hybrid thermocline, double thermocline, and multiple thermocline） are defined herein. In winter, when the northeasterly monsoon prevails, most shallow shelf seas in the northwest of the SCS are well mixed, and there is no obvious thermocline. The deep region generally has a deep thermocline, and the hybrid or double thermocline often occurs in the areas near the cold eddy in the south of the SCS. In summer, when the southwesterly monsoon prevails, the shelf sea area with a shallow thermocline greatly expands. The distribution of different thermocline types shows a relationship with ocean bathymetry： from shallow to deep waters, the thermocline types generally change from shallow or hybrid to deep thermocline, and the double or multiple thermocline usually occurs in the steep regions. The seasonal variations of the three major thermocline characteristics （the upper bound depth, thickness, and intensity） are also discussed. Since the SCS is also an area where tropical cyclones frequently occur, the response of thermocline to a typhoon process in a short time scale is also analyzed.     

长山群岛海区春季水温垂直结构分析

利用海军大连舰艇学院2006年4月长山群岛海区的CTD调查资料,系统分析了该季节长山群岛海区的温度垂直结构,并探讨了其形成机理。分析指出:4月上、中旬是长山群岛海区季节性温跃层的生成期,群岛东侧和南侧边缘受黄海冷水团形成过程的影响,温跃层的出现概率和跃层强度都远远高于群岛内部;在生成时机上,群岛东侧和南侧边缘海域早于群岛内部水域。中间层和底层海水温度的垂直结构与海流有着很好的相关性,在海洋平流的作用下,海区会产生正跃层、逆跃层、冷中间层、暖中间层等复杂的温度垂直结构。上层海水温度结构主要受海面风场和气温的影响,较强的热辐射和充分的风力搅拌能够加速温跃层的生成。     

Development of lipids during a spring plankton bloom in the northern North Sea: II. Dissolved lipids and fatty acids

During the spring plankton bloom (1976) in the northern North Sea the fatty acid and lipid distribution of the chloroform extractable fraction of seawater was analyzed by gas chromatography and thin-layer chromatography. The fatty acids in the seawater made up about 3% of the total dissolved organic matter. Maximum concentrations during the first phytoplankton bloom were in the range of 5 μmol C dm^?3. Palmitic acid (30.4%) and oleic acid (21.4%) as well as myristic, stearic and palmitoleic acids were the main fatty acids. The concentrations of fatty acids were higher below the thermocline in the deeper layers of the water column. The oleic acid showed large fluctuations, especially below the thermocline and seemed to be bound in a polar fraction. Different lipid classes containing fatty acids were determined by thin-layer chromatography. An estimation showed that the free fatty acid fraction made up the main portion (47.9%), followed by the triacylglycerol fraction (22.8%) and a more polar fraction with 25.1%. The triacylglycerol fraction appears to be more stable than the other fraction in the water column.     

Extraction of Intemal Tidal Currents from A Portion of Sea Current Profile

Internal tide is one of the major oceanic phenomena. Determination of internal tide is important for theoretical study and for ocean engineering research. As an inverse problem, extraction of internal tidal currenls from sea currents is diffi-cult. In this paper, a method is developed to extract internal tidal currents from a portion of the sea current profile based on the fact that the directions of internal tidal currents above and below the thermocline are inverse. Sea current data col-lected from the South China Sea is processed with this method. The internal tidal currents and the depth of the thermocline are successfully extracted. The depth of the thermocline determined is in good agreement with that measured in 1959.     

南海温跃层基本特征及一维预报模式

根据现有1907—1990年南海大面调查资料,按1°×1°网格进行逐月的标准水层的温度统计。在此基础上采用3次样条函数的插值方法计算出整个南海温跃层的深度、厚度和强度并予以相应分析。分析表明,南海温跃层主要分为两种类型:第一类为辐射型,主要分布在南海北部的陆架区内,季节变化显著;第二类为不同水体叠置型,主要分布在广大深水区,它长年存在,季节变化较小。一种温跃层的一维积分预报模式,该模式是基于忽略热平流作用和水平热扩散的前提下,从局部热平衡方程出发,建立了受海面热收支及风混合作用下求解温度垂直分布及温跃层的时空变化。在南海北部水深约300m处进行了单站温跃层后报,结果表明,温跃层的深度、厚度和强度的相对误差均在30％以下。     

潮汐作用下渤海温跃层波动与起伏的数值研究

研究了潮汐(四大分潮 M₂,S₂,K₁,O₁同时输入)作用下渤海温跃层起伏与波动的三维数值模型(将海洋分为3层,即上混和层、跃层和下混和层),揭示了整个海区温跃层上界面处跃层起伏(在文中指每个时刻跃层波高的周期平均值)的地理分布及叠加在起伏之上的潮周期波动的时空变化,模拟出跃层波动与实测基本一致.结果发现大振幅的跃层波动均发生在海峡及近海地形突变之处.一般界面波动的波高大于甚至远远大于同一位置的表层潮波.从位相以及周期来看,潮波和跃层上下界面波动相互之间,有些海域一致,有些地方则相差甚远.跃层上界深度及厚度的梯度,对跃层起伏分布有一定的影响.跃层起伏还可能与海岸海底摩擦有关.     

Extraction of Internal Tidal Currents from A Portion of Sea Current Profile

Internal tide is one of the major oceanic phenomena. Determination of internal tide is important for theoretical studyand for ocean engineering research. As an inverse problem, extraction of internal tidal currents from sea currents is diffi-cult. In this paper, a method is developed to extract internal tidal currents from a portion of the sea current profile basedon the fact that the directions of internal tidal currents above and below the thermocline are inverse. Sea current data col-lected from the South China Sea is processed with this method. The internal tidal currents and the depth of the thermo-cline are successfully extracted. The depth of the thermocline determined is in good agreement with that measured in 1959.     

Seasonal variations in temperature,salinity and density in the southern coastal waters of the Caspian Sea

Variability in water temperature, salinity and density was investigated based on field measurements near Anzali Port, in the Southern Caspian Sea in 2008. Seasonal changes of seawater properties were mainly observed through the upper 100 m layer, while below this layer seasonal variations of the parameters were minor. Vertical structure of the temperature in the southern coastal waters of the Caspian Sea is characterized by a significant seasonal thermocline between 20–50 m depths with vertical variation in temperature about 16°C in midsummer (August). Decrease of the thermocline occurs with the general cooling of the air and sea surface water, and deepening of the mixed layer during late of autumn and winter. Seasonal averages of the salinity were estimated in a range of 12.27–12.37 PSU. The structure of thermocline and pycnocline indicated agreement between changes of temperature and density of seawater. Seasonal pycnocline was observed in position of the thermocline layer.     

A note on average cross-isopycnal mixing in the North Atlantic ocean

Area averaged mixing is inferred from the difference between cross-isopycnal advection and air-sea forcing, using a density budget in isopycnal layers. The results suggest that mixing is weak (indistinguishable from zero) in the thermocline in qualitative agreement with local and regional measurements. Mixing increases in warmer density classes, but becomes indeterminate at low densities, where climatological flux errors are largest. At high density, mixing reappears owing to the heat flux required to balance the formation of dense water and reflects mixing with intermediate and bottom water.     

Hydrothermal mineralization along submarine rift zones,Hawaii

This is the first article to describe mineralization of midplate submarine rift zones and hydrothermal manganese oxide mineralization of midplate volcanic edifices. Hydrothermal Mn oxides were recovered from submarine extensions of two Hawaiian rift zones, along Haleakala and Puna Ridges. These Mn oxides form two types of deposits, metallic stratiform layers in volcaniclastic rocks and cement for clastic rocks; both deposit types are composed of todorokite and bimessite. Thin Fe‐Mn crusts that coat some rocks formed by a combination of hydrogenetic and hydrothermal processes and are composed of δ‐MnO₂. The stratiform layers have high Mn contents (mean 40%) and a large fractionation between Mn and Fe (Fe/Mn = 0.04). Unlike most other hydrothermal Mn oxide deposits, those from Hawaiian rift zones are enriched in the trace metals Zn, Co, Ba, Mo, Sr, V, and especially Ni (mean 0.16%). Metals are derived from three sources: mafic and ultramafic rocks leached by circulating hydrothermal fluids, clastic material (in Mn‐cemented sandstone), and seawater that mixed with the hydrothermal fluids. Mineralization on Haleakala Ridge occurred sometime during the past 200 to 400 ka, when the summit was at a water depth of more than 1,000 m. Hydrothermal circulation was probably driven by heat produced by intrusion of dikces, magma reservoirs, and flow of magma through axial and lateral conduits. The supply of seawater to ridge interiors must be extensive because of their high porosity and permeability. Precipitation of Mn oxide below the seafloor is indicated by its occurrence as cement, growth textures that show mineralizing fluids were introduced from below, and pervasive replacement of original matrix of clastic rocks.     

Relationship between tissue phosphorus and seawater phosphate in the brown alga Hormosira banksii

We measured tissue phosphorus content of high and low intertidal Hormosira banksii to test the hypothesis that tissue phosphorus content would be greater in individuals from the low intertidal because of greater total uptake associated with longer immersion in seawater. Moreover, we predicted that tissue phosphorus would be greater at sites where the seawater contained higher phosphate concentrations. There was a positive, linear relationship between local seawater phosphate concentrations and tissue phosphorus content of H. banksii from high and low intertidal zones at six different sites in winter. However, there were no comparable relationships in summer, even though the range of seawater phosphate concentration was similar in both seasons. The phosphorus contents of low intertidal H. banksii were significantly greater than high intertidal H. banksii in winter, but not in summer. Reasons for these differences may be related to greater access to seawater phosphate in low intertidal algae (than those in the high intertidal) in winter, followed by greater utilisation of the internal phosphorus between winter and summer, due to faster growth rates in the low intertidal.     

地形和层结变化对内潮生成影响的数值模拟研究

基于ROMS(Regional Ocean Modeling System)模式,设计了9组理想数值实验,研究了内潮的产生对地形和背景层结环境的敏感性。结果表明:高斯海脊两侧地形梯度较大的超临界坡面处是内潮的主要源区;地形和层结环境的变化对内潮生成有很大影响;如地形和层结保持不变,不同的网格水平分辨率和垂向层数条件下估算的内潮转换率存在差别;地形和跃层的相对空间关系对内潮生成及其引起的水体混合强度存在影响。高分辨率的地形和合适的背景层结是内潮模拟的关键。该结论对于内潮形成的数值模拟研究有一定参考价值。     

Effect of the Internal Tide on Acoustic Transmission Loss at Midfrequencies

Nonlinear internal waves are a common event on the continental shelf. The waves depress the high-gradient region of the thermocline and thicken the surface mixed layer with consequent effect on acoustic propagation. After the waves have passed, it may take several hours for the thermocline to rise to its prewave level. To examine the effect of the rising thermocline, oceanographic and acoustic data collected during the 2006 Shallow Water Experiment (SW06) are analyzed. Midfrequency acoustic data (1.5–10.5 kHz) taken for several hours at both fixed range (550 m) and along a tow track (0.1–8.1 km) are studied. At the fixed range, the rising thermocline is shown to increase acoustic intensity by approximately 5 dB . Along the tow track, the transmission loss changes 2 dB for a source–receiver pair that straddles the thermocline. Using oceanographic moorings up to 2.2 km away from the acoustic receiver, a model for the rising thermocline is developed. This ocean model is used as input to a broadband acoustic model. Results from the combined model are shown to be in good agreement with experimental observation. The effects on acoustic signals are shown to be observable, significant, and predictable.      

The effect of internal tides on the vertical structure of tidal current in the North Huanghai Sea

The tidal current is generally predominant in China's offshore areas. The vertical structure of the observedtidal current is quite complicated with the presence of seasonal thermocline. The observed tidal current may be divided into two parts, an averaged barotropic tide current and a variation tide current. A method for studying the vertical structure of tidal current is developed from the constitution and distribution of energy, and the vertical structure of the observed tide current in the North Huanghai Sea is studied on the basis of the method. The result shows that the reason why the energy of the tidal current is concentrated on the neighbourhood of the thermocline mainly lies in the internal tides i under certain conditions, the fact that the direction of the internal tide current above the thermocline is opposite to the one below the thermocline will be able to cause the rotary directions of the observed tidal current above and below the thermocline to be in opposite. The interaction between th