2001年冬春转换期间南海东北部水文和环流特征

根据2001年3月份南海东北部航次调查温、盐资料,分析了2001年冬末春初南海东北部温、盐结构和环流的特征.分析结果表明:观测期间南海东北部环流主要受一次海盆尺度气旋型冷环流支配,冷环流呈现双核结构,垂向尺度接近1000 m.吕宋海峡内侧断面的水交换在600 m以浅海水流入南海,在断面南部(20°N以南)中层和深层有流出,断面法向地转流向西净输运量为6.9×106m3/s;直接的黑潮入侵不超过120.5°E,但有部分的黑潮水沿陆坡达到台湾岛西南部海域,并更有一部分逸入东沙岛以西海域,与南海水混合变性.     

南海中尺度海洋现象研究概述

南海是一个地形复杂的半封闭海盆，受季风，黑潮等因素的作用南海呈现独特的中尺度变异特征，一些中尺度信号的强度可以和南海定常环流的强度相比拟，甚至更强，本文回顾了近20a来南海中尺度海洋现象研究的进展，并就南海的黑潮入侵，黑潮涡环，次海盆尺度多涡环流，浅海亚潮波动，近岸陷波，海洋锋等中尺度现象做若干探讨。     

黑海西北部涡旋与环流对跨陆架水交换的影响

涡旋对海洋中的能量传递和物质交换有重要作用。黑海西北部陆坡边缘是长生命周期涡旋经常发生的海域,但涡旋引起的陆架和海盆之间水交换通量的季节性特征,以及海盆边缘环流对跨陆架水交换的作用等方面的研究还不是很充分。本文对黑海西北部陆架区与深海盆区间的跨陆架水交换进行了研究,利用高分辨率三维原始方程模式模拟的温、盐、流等资料,结合涡旋自动探测方法,统计了黑海西北部海域的涡旋活动,研究了涡致跨陆架水交换的季节性特征,计算对比了2002年到2010年间海盆边缘环流与涡旋对跨陆架水交换通量的各自贡献。结果表明:黑海西北部地区海盆边缘环流强度与跨陆架进、出通量的相关系数分别为0.57和0.67,海盆边缘环流位置与跨陆架交换量的相关系数为0.52;海盆边缘环流强度与位置的季节性变化导致了黑海西北部跨陆架通量的季节性变化。黑海西北部地区表层3月到8月之间涡旋所引起跨陆架交换量约占了跨陆架交换总量的16%~31%;涡致跨陆架通量也具有季节性特征。文中对单个涡旋进行了详细研究:2005年5月5日到2005年7月20日之间在黑海西北部存在一个直径最大值时达到120 km的反气旋式涡旋,涡旋存在期间完成了从陆架区向深海区的水体传输,相当于黑海西北陆架区水体积的30.9%。     

南海上层环流观测研究进展

回顾了近50a来南海环流研究的进展，重点介绍了近期有关南海上层总环流的观测研究成果，并就南海季风急流、南海暖流、南海南部的次海盆尺度环流，以及南海东北部环流的几个问题进行了专门讨论。     

盛夏南海的水文与环流特征:2000年8月航次再探

在国家重点基础研究发展规划的支持下,2000年8月在南海组织了1次多船同步海洋学调查,是迄今为止盛夏期间唯一一次全海盆准同步水文观测。航次间遭遇的多种困难虽被及时化解,然而观测数据的质量已受影响。此前虽已有若干相关研究发表,但未见对观测数据进行质量控制和全面的分析。本文在对CTD和ADCP原始数据仔细校正的基础上,分析和讨论了盛夏期间南海海盆的水文和环流特征,冀留下尽可能完整的记录。分析表明,盛夏期间以海盆SW-NE向轴线为界,南海展现出不同的物理特征。轴线东南受季节性反气旋环流控制,其中次海盆尺度的南沙反气旋环流尤其强大;轴线西北则受各种中尺度现象支配,未见明显的大尺度环流结构。研究证实南沙反气旋环流的水平尺度超过400 km,垂直尺度达近千米,最大流速近1 m/s,是夏季南海最突出的环流特征,但发现其位置和强度存在显著的年际变化。研究并发现,不同于以往的认识,观测期间民都洛海峡交换呈"三明治"结构,表明随强迫条件变化,民都洛海峡交换可出现不同模态。     

基于Argo历史观测的南海海盆尺度中层流场研究

针对南海海域海流环境复杂、中层实测数据量少的现状,本文基于2006-2016年布放在南海海域的114个Argo剖面浮标的卫星定位等信息,采用基于背景流和惯性流外推的最小二乘方法,获取南海海域1 200 m深中层流场信息,并采用Divand变分插值的方法形成网格化季节流场。结果表明:（1）针对南海中层（1 200 m）流场,单个Argo浮标可以刻画出具体的中尺度结构,如越南沿岸的反气旋涡,半径约为120 km,最大流速约为9.6 cm/s,平均流速为5.3 cm/s;（2） Argo网格化流场表明海盆尺度中层流场南海南部为反气旋环流结构,北部为气旋式环流,同时在吕宋海峡口存在从南海至太平洋的水体交换;（3）将该流场信息与HYCOM和YoMaHa'07两种资料对比,吻合度较高,与HYCOM再分析资料的偏差分布趋近于正态分布,海流的东西向分量的均方根误差为3.28 cm/s,南北向分量的均方根误差为3.26 cm/s。总体而言,利用Argo轨迹资料能够有效地反演出南海地区海盆尺度的中层环流特征。     

南海上层海洋环流两层半模式的数值模拟Ⅰ.闭边界海盆季节性环流

本文应用一个包含动力学和热力学的热带海洋两层半模式,模拟南海上层海洋闭边界条件下的季节性环流.模式海洋由不同密度的上混合层、季节性温跃层和静止的深水层组成.模式考虑挟卷(卷入entrainment和卷出detrainment)引起海洋上下活动层间的质量、动量与热量的交换,在海面月平均气候风场动力强迫和通过海面热通量的热力影响下,计算了封闭海盆假定下的南海上层海洋的季节环流.用数值试验的方法讨论了非线性效应、摩擦阻尼、侧向混合对大尺度环流的影响,并得出有关模式稳定性的结论.模拟结果与南海海洋实测和动力诊断的环流趋势吻合较好,显示了模式对南海海盆尺度的环流系统有较好的模拟能力.     

卫星跟踪浮标和卫星遥感海面高度中的南海涡旋结构

选择4个南海卫星跟踪Argos漂流浮标及同期的TOPEX／Poseidon卫星遥感海面高度资料，研究了南海海域涡旋的活动及空间结构。这4个Argos漂流浮标的轨迹除了基本符合各季节海盆尺度环流趋势外，分别在菲律 宾以西、越南外海、南海中部等海域呈现出中尺度旋转轨迹。这些尺度涡旋现象在同期的TOPEX卫星遥感海面高度异常（SSHA）分布中得到了准确印证，并在诊断得到的地转流场中对应了一系列瞬变的中尺度涡旋运动。     

南海相对涡度的时空变化特征分析

本文使用2014—2017年间逐日平均的法国Mercator中心全球高分辨率海洋数据集PSY4,探讨南海海域相对涡度与海盆尺度环流的时空变化特征。依照涡度的年平均剖面,在垂向上将南海分为:涡度为正的上层、涡度为负的中层和涡度为正的深层,对应了南海海盆尺度的"气旋式-反气旋式-气旋式"垂向环流。最为显著的相对涡度季节变化出现在南海的上层,最大冬、夏季差异达6.3×10~(-7) s~(-1),为该层内年平均相对涡度值1.7×10~(-7) s~(-1)的3.7倍。在该层的内部,依照季节变化的幅度大小可以进一步划分为3个子层,其中季节变化幅度最大的为上200 m层。在中、深层,深度积分的涡度与海盆尺度环流分别具有"冬强夏弱"和"冬弱夏强"的季节变化特征,而涡度的年际差异可以与季节差异同等重要;逐月的涡度时间序列与吕宋海峡不同断面的水通量变化具有统计相关。     

南海北部近岸海域风场特征分析与预报研究

南海北部近岸海域北靠东亚大陆,南面广阔的南海海域,地理位置十分独特,具有典型的季风特征.本文对南海北部近岸海域风场与大尺度大气环流特征的相关分析,阐述大气环流异常对南海北部近岸海域风场的影响.研究表明,南海北部近岸海域风场分布具有较强的区域性和季节性;因气候年际变化的强弱,如厄尔尼诺与南方涛动(ENSO)循环、南海暖池...     

Microbial Biomass and Organic Nutrients in the Deep-Sea Sediments of the Central Indian Ocean Basin

In order to assess the impact of deep-sea mining on the in situ benthic life, we measured the microbial standing stock and concentration of organic nutrients in the deep-sea sediments of the Central Indian Ocean Basin in the Indian pioneer area. Sediments were collected using box core and grab samples during September 1996. The total bacterial numbers ranged from 10 10 -10 11 cells per g -1 dry weight sediment. There was a marginal decrease in the number of bacteria from surface to 30 cm depth, though the subsurface section registered a higher number than did the surface. The highest numbers were encountered at depths of 4-8 cm. The retrievable number of bacteria were two orders less in comparison with the direct total counts of bacteria. An almost homogeneous distribution of bacteria, total organic carbon, living biomass, and lipids throughout the depth of cores indicates active microbial and benthic processes in the deep sea sediments. On the other hand, a uniform distribution of total counts of bacteria, carbohydrates, and total organic carbon in all the cores indicates their stable nature and suggests that they can serve as useful parameters for long-term monitoring of the area after the benthic disturbance. Further studies on temporal variability in this region would not only verify the observed norms of distribution of these variables but would also help to understand restabilization processes after the simulated benthic disturbance.     

海上大直径钢管桩打桩过程中桩周土强度弱化研究

海上大直径钢管桩打桩过程中,桩周土体受到强烈扰动而发生强度弱化,掌握桩周土体强度弱化规律对于准确预测打桩过程、保证工程安全具有重要意义。为研究土体强度弱化规律,开展了环剪试验模拟打桩对桩周土体的扰动,测试土体强度随剪切速率的变化规律,建立了描述土体强度弱化规律的拟合公式,引入到打桩分析软件中。研究结果表明：土体的强度折减程度不仅与土体本身的性质有关还受到土体的埋深和剪切速率的影响,埋深越深土体强度折减程度越低,剪切速率越高土体强度折减越高,在打桩分析中可采用这里推荐的线性折减方法来模拟不同深度处土体强度的折减规律。     

Geoacoustic Inversion via Genetic Algorithm and Its Application to Manganese Sediment Identification

An acoustic inversion method using a wide-band signal and two near field receivers is proposed and applied to multiple layered seabed models including a manganese sediment. The inversion problem can be formulated into a probabilistic model comprised of signals, a forward model, and additive noise. The forward model simulates wide-band signals, such as chirp signals, and is chosen to be the source-waveletconvolution plane wave modeling method. The wavelet matching technique, using weighted least-squares fitting, estimates the sediment sound-speed and thickness on which determination of the possible numerical ranges for a priori uniform distribution is based. The genetic algorithm is applied to a global optimization problem to find a maximum a posteriori solution for determined a priori search space. Here the object function is defined by an L 2 norm of the difference between measured and modeled signals. Not only the marginal pdf but also its statistics are calculated by numerical evaluation of integrals using the samples selected during importance sampling process of the genetic algorithm.     

Phylogenetic diversity and phenotypic characterization of cultivable bacterioplankton isolated from polar oceans

A set of 27 marine planktonic bacteria isolated from the polar regions was characterized by 16S rDNA sequencing and physiological and biochemical testing. More than half of these bacteria were positive for caseinase, gelatinase and 13-glucosidase, and could utilize glucose, maltose or malic acid as carbon source for cell growth. Twelve isolates expressed nitrate reduction activities. Except for one antarctic isolate BSwlO175 belonging to Actinobacteria phylum, these isolates were classified as γ-Proteobacteria, suggesting that γ-Proteobacteria dominated in cultivable marine bacterioplankton at both poles. Genus Pseudoalteromonas was the predominant group in the Chukchi Sea and the Bering Sea, and genus ShewaneUa dominated in cultivable bacterioplankton in the Prydz Bay. With sequence similarities above 97%, genus Psychrobacter was found at both poles. These 27 isolates were psychrotolerant, and significant 16S rDNA sequence similarities were found not only between arctic and antarctic marine bacteria （ 〉 99% ）, but also between polar marine bacteria and bacteria from other aquatic environments （ ≥ 98.8% ）, including temperate ocean, deep sea, pond and lake, suggesting that in the polar oceans less temperature-sensitive bacteria may be cosmopolitan and have a bipolar, even global, distribution at the species level.     

Deep-Sea Sediment Compression Curves: Some Controlling Factors, Spurious Overconsolidation, Predictions, and Geophysical Reproduction

Oedometer tests have been carried out on 70 undisturbed surficial clays (at approximately 250 mm below the mudline), mostly collected by free-fall corers from sites widely scattered throughout the deep-sea North Atlantic. Acoustic measurements were also made, initially on contiguous samples and ultimately on the same sample using a geophysically instrumented oedometer which also collected electrical resistivity data. Apart from those quiescent areas below the carbonate compensation depth, such as north of the West Indies where very fine clays exist, most of the samples are silty clays whose geotechnical-geophysical properties are dependent on the type of clay minerals present (and their ability to take in moisture), the sand-size fraction, and the quantity of carbonate present. Thus the pure clays have high compressibilities which decrease on the addition of coarse particles, while the converse is true for the acoustic parameters, these increasing with the sand fraction. Using the notion of the intrinsic compression line for all samples, and comparison to it of the measured compression curves, it is clear that, contrary to some previously held ideas, most deep-sea clays are normally consolidated; the addition of carbonate has the effect of creating an open, stronger sediment skeleton. Interestingly, where information is available, the variation with depth of a sample's acoustic velocity follows the void ratio pressure relationship of the compression curve. This allows the construction of an in-situ sediment compression curve using the in-situ geophysical observations.     

INFORMATION FOR AUTHORS

<正>Acta Oceanologica Sinica(AOS)is a comprehensive academic journal edited by the Editorial Committee of Acta Oceanologica Sinica and is designed to provide a forum for important research papers of the marine scientific community which reflect the information on a worldwide basis.The journal publishes scholarly papers on marine science and technology,including physics,chemistry,biology,     

Estimation of Sediment Properties during Benthic Impact Experiments

Sediment properties, such as water content and density, have been used to estimate the dry and wet weights, as well as the volume of sediment recovered and discharged, during benthic impact experiments conducted in the Pacific and Indian Oceans. The estimates show that the weights of dry (355-1332 t) and wet sediment (1651-4888 t) recovered during the experiments, are not only a function of the total duration and distance covered during the experiment, but also depend on water content and density of the sediment. Estimation of dry sediment and its volumetric ratio in the discharge, are key parameters for calculating the discharged volume. The estimated volume of wet sediment recovered (1427-4049 m 3 ) as well as discharged (2693-6951 m 3 ) during the experiments, provide important inputs to evaluate the sediment resettlement and migration. Using these estimates, the average depth of excavation on the seafloor, can also been calculated. However, the stages of sediment recovery and discharge are expressed differently in some of the experiments. In order to standardize these, different stages have been identified, and definitions of certain terms have been suggested, for use in the future. The methods of calculating different properties, as well as weight and volume of discharged sediment are described in the paper for use in other applications concerning deep-sea discharges.