PN断面黑潮流速垂直分布特征及机制分析（英文）

本文基于全球海洋再分析模拟GLORYS2(Global Ocean Reanalysis Simulation 2)结果,分析了PN断面(126.0°E-128.2°E,1 000 m以浅)黑潮流速垂直结构的季节和年际变化,探讨了黑潮流速垂直结构形成的动力学机制。结果表明:1)PN断面黑潮夏季流量最大,春季次之,秋、冬季节最小;气候态平均的冬、夏季流速最大值都位于次表层,春、秋季节流速最大值位于表层;夏季相对流速较大、最大值深度较浅;等密线在黑潮主轴区下凹,冬季更为明显。流速最大值深度和密度水平梯度为零的深度均表现出了较大的年际差异,该年际变化甚至超过季节差异;2)流速与密度符合热成风关系。黑潮通量由太平洋大尺度风场及中尺度运动两者共同决定,但局地的热通量和环流对温盐的输运共同影响密度场,调节黑潮流速的垂直分布,影响水通量的分配及营养盐输运;3)有些年份夏季流速最大值出现在表层,可能是夏季西南季风诱导陆架水离岸输运进入黑潮上层导致的结果。非线性、非地转物理过程的影响没有考虑在本研究中,热成风关系能够解释黑潮流速垂直分布形成的部分原因。     

东海PN断面水团分布的季节变化

利用PN断面的高分辨率CTD温度、盐度和密度资料,采用曲线族拟合的水团分析方法分析发现,PN断面处的水团有明显的陆架水和黑潮水的交汇特征,且随着季节的变化PN断面处的水团特征也发生明显的变化.夏季,黑潮水核心离陆架的距离最远且深度较深,陆架水与黑潮的混合水浮置于黑潮水本体之上且向深海拓展的最远,隶属度在PN断面上200 m的分布几乎呈水平状;秋季,黑潮水主体离陆架的距离最近,并将陆架混合水向陆架压迫,使得隶属度等值线由夏季的平直状态向陆地弯曲;冬季,黑潮水团的核心占据了深海区域的整个表层和次表层,且位置相对于秋季更向深海移动,黑潮水与陆架水的交汇处也由秋季的陆架移向陆坡;春季,是唯一可以清楚地看到陆架混合水隶属度分布的季节,此时陆架混合水充满整个陆架海域,而黑潮水的核心进一步远离陆架.海面风场和净热通量场通过改变混合层的深度影响PN断面处黑潮水和陆架水之间的混合,而海面降水对于PN断面上的水团分布特征没有显著影响.     

1992年东海黑潮的变异

基于1992年4个航次的水文调查资料,运用改进逆方法计算了东海黑潮的流速、流量和热通量．计算结果表明：（1）PN断面黑潮在春季和秋季都有两个流核,冬季和夏季则只有一个流核．主核心皆位于坡折处．Vmax值春季最大,冬季和夏季次之,而秋季最小．黑潮以东及以下都存在逆流．（2）TK断面黑潮在冬季为两核,春、夏季为3核．海峡南端及海峡深处存在西向逆流．（3）通过A断面的对马暖流Vmax值在秋季最大,冬季最小．黄海暖流位于其西侧,相对较弱．（4）通过PN断面净北向流量夏季最大,秋季最小,而冬、春季介于上述二者之间,1992年四季平均值为28．0×106m3/s;TK断面的净东向流量也是在夏季最大;A断面净北向流量则在秋季最大．（5）PN断面4个航次的平均热通量为2．03×1015W．TK断面3个航次的平均热通量为2．00×1015W．（6）在计算海区,冬、春和秋季都是由海洋向大气放热;夏季则从大气吸热．冬季海面上热交换率最大,而夏季热交换率最小．关键词##4东海;;黑潮;;季节变化     

1993和1994年东海黑潮的变异

基于“长风丸”1993～1994年共8个航次的水文调查资料,采用改进逆方法计算了东海黑潮的流速、流量和热通量.计算结果表明:(1)PN断面黑潮流速在秋季时均呈双核结构;而在其他季节,有时为单核,有时为双核;黑潮主核心皆位于坡折处.黑潮以东及黑潮以下都存在南向逆流.(2)TK断面较复杂,可出现单、双或三核结构.在吐噶喇海峡中部、北部出现流核的机率较高.海峡南端及海峡深处都存在西向逆流,而且海峡南端的逆流在秋季较强.(3)在A断面,对马暖流核心位于陆坡上,但有时偏西或偏东.Vmax值的变动范围为26～46cm/s.黄海暖流位于其西侧,流速则相对减小.(4)东海黑潮流量在这两年中,在春季均出现最小值,在夏季出现最大或较大值.黑潮流量,以PN断面为例,每年四季平均流量值1994年与1993年几乎相同,但略小于1992年的平均流量值.8个航次中通过PN、TK断面的平均净流量分别为27.1×106和25.0×106m3/s.(5)8个航次中,通过PN、TK断面的热通量的平均值分别为1.99×1015和1.78×1015W.(6)在计算海域秋季和冬季均是由海洋向大气放热;夏季则均从大气吸热;春季则不确定.海面上热交换率在冬季最大,而春、夏季较小.     

基于Argos漂流浮标的东海黑潮特征分析

基于1979—2008年的表面漂流浮标资料,在选定区域(21°～33°N,120°～132°E)内对3个东海黑潮特征断面上的表层流速结构进行分析。选取的特征断面分别是位于台湾东北东海黑潮南段的SS断面,位于黑潮所流经东海的中央地段的PN断面和位于日本九州与奄美群岛之间的TT断面。Argos漂流浮标资料的统计结果能够较好地反映东海黑潮不同流段的主要特征及其季节变化。东海黑潮中段相对于其他流段流速强、流幅宽、流量大的特征最为显著,也最为稳定。     

台湾岛以东黑潮热输运的季节及年际变化特征

黑潮热输运对我国沿海区域气候变化及海洋生态环境具有重要影响。基于JCOPE2(Japan Coastal OceanPredictabilityExperiment2)模式1993—2016年的高分辨率数值模拟结果,计算了通过台湾岛以东24°N KET(Kuroshio East of Taiwan Island)断面的黑潮热输运,分析了其季节及年际变化特征,结合ONI指数(Oceanic Nino Index)探讨了其与ENSO(厄尔尼诺-南方涛动)事件的关系。研究结果表明, KET断面黑潮热输运具有显著的季节变化,春夏季较大,秋冬季偏小;年均值为1.98 PW(1 PW=10~(15) W),标准差为0.18 PW,热输运强年为1996—1997年和2015年,热输运弱年为2000年, 2002年和2013年。超强ENSO过程对黑潮热输运有显著影响。受超强厄尔尼诺事件影响,台湾岛以东黑潮热输运明显增加,热输运极大值超前ONI指数极大值约5～10个月。利用方差分析得到流速方差项对KET断面黑潮热输运总时域方差贡献最大,解释了热输运总方差最大值的77%,其次是温度与流速协方差项以及温度方差项,分别解释了热输运总方差的15%和6%。     

太平洋海气界面净热通量的季节、年际和年代际变化

根据 COADS资料 ,使用经验正交分解 (EOF)等分析方法 ,研究了北太平洋海气热通量的季节、年际和年代际变化特征。分析结果表明 :北太平洋海洋夏季净得热 ,冬季净失热 ,且黑潮及其延伸体区失热最大。净热通量年际变化较明显 ,北太平洋西部模态水形成区冬季净热通量和副热带失热区春季净热通量的年际变化都主要依赖于潜热和感热通量的年际变化。夏季净热通量的低频变化中心在热带 ,冬季低频变化中心在黑潮及其延伸体区。冬季赤道东、西太平洋净热通量异常的年际变化相反 ;在热带北太平洋中部年际变化达到最大。夏季热带太平洋是净热通量异常的年际变化最大的海域 ,沿赤道两侧在 16 5°E处呈偶极子型分布。     

HYCOM模式对东海黑潮的气候态模拟

使用三重嵌套的HYCOM(The HYbrid Coordinate Ocean Model)数值模式模拟气候态东海黑潮。模式水平分辨率从大区模式的1°×1°cosθ提高到小区模式的1/8°×1/8°cosθ。对模拟结果的分析表明:(1)高水平分辨率模式对黑潮特征量的模拟有明显的改进。这些改进主要由两方面的原因引起:地形分辨率的提高和改善的斜压效应。(2)小区模式的模拟结果较好地再现了PN断面的垂向结构。基本反映了PN断面流速和流量的季节变化规律。夏季流速最强、流量最大,秋季流速最弱、流量最小,冬、春两季处于过渡期。(3)模式成功地模拟出东海黑潮东侧的逆流。该逆流流速稳定,夏季流速略大。(4)模式模拟出了PN断面的流速双核结构。     

台湾以东黑潮经向热输送变异及可能的气候效应

基于日本气象厅长序列水文再分析资料,通过估算台湾以东黑潮24°N断面热输送量,分析了该断面黑潮热输送的低频变异特征,并探讨了热输送变异与我国近海海表温度异常变化以及前期(前秋、前冬和春季)和同期(夏季)热输送变异与我国夏季降水异常变化的关联性。小波分析显示,台湾以东黑潮(24°N断面)热输送异常存在着显著的准2 a周期振荡和约16 a的年代际变化,且以上显著周期主要存在于20世纪60年代中期以后,另外,台湾以东黑潮(24°N断面)热输送变异的季节差异明显;50多年来,台湾以东黑潮(24°N断面)热输送呈现出长期增强趋势,但变化幅度不大,且各季节长期趋势也有所不同。相关分析表明,台湾以东黑潮(24°N断面)热输送低频变异可能是我国东部近海SST变化的一个重要因素。另外,回归分析发现,前期及同期台湾以东黑潮(24°N断面)热输送变异对我国东部夏季降水异常变化有显著指示性,可能存在较大影响。     

吕宋海峡水体通量时空变化特征的数值模拟研究

利用区域海洋数值模式(ROMS)建立了南中国海三维海洋环流数值模型。基于2006—2018年逐日平均的数值模拟结果,分析了吕宋海峡断面(120.75°E)的纬向流及通过断面的水体通量的时空变化规律,并采用集合经验模态分解法(EEMD)分别探讨了整层和表、中、底层水体通量的时间变化特征。结果表明:断面处纬向流呈现明显的多核结构,流态分布随季节变化较小,而流速变化受季节影响较大;断面水体通量存在明显的季节、月际变化;其垂向变化在年平均、春季、秋季和冬季时都呈现"三明治"结构,分界点分别在540 m和1 720 m左右,受黑潮分支强度的影响,在夏半年(5—9月)呈现"四层"结构,上表层厚度为45～80 m且存在月变化,5月为发展期,6—8月为成熟期,9月为消亡期;表层水体通量的时间变化对整层的变化影响最大,黑潮入侵的强度是导致整层及表层水体通量变化的主要因素。     

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,     

Evaluation of the Risk of Marine Slope Instability: A Pseudo-3D Approach for Application to Large Areas

This article presents a methodology developed to evaluate the instability of submarine slopes that extend over a large area. Special attention was paid to (1) the complex geometry (bathymetry) and the expanse of the slope, (2) the heterogeneity of the sediment, and (3) the distribution of the pore pressure. The safety factor was considered as a spatially varying quantity. The General Formulation (GLE, Fredlund and Krahn 1977), which fully satisfies equilibrium conditions, was used for evaluating the stability of the marine slope. The submarine slope failure, which occurred on 16 October 1979 during the construction of the new Nice airport, was studied in order to test the developed model. Geotechnical parameters were taken from experimental tests carried out by IFREMER on 19 cores extracted at different depths (from 27 m to 1300 m) (Cochonat, Bourillet, and Savoye, 1993; Mulder et al., 1994). Many scenarios were proposed in order to explain the cause of the Nice slope failure (Habib, 1994). In this article, two of those scenarios were tested. Simulation results are presented and discussed.