全球海洋环流模式中上层海洋对表面强迫的响应和调整Ⅰ.年际变率

利用一个较高分辨率的全球海洋环流模式在COADS 1945～1993年逐月平均资料的强迫下对海温和环流场进行了模拟试验,研究了全球热带海洋(主要是热带太平洋)海温和环流场的年际变化特征及模式ENSO冷暖事件演变的控制机理.结果表明,模式成功地再现了和观测一致的海温和环流的年际变化以及ENSO演变特征.其中热带印度洋年际SST变率的主要模态表现为与ENSO相联系的海盆尺度的一致性增暖或变冷现象,次级模态为热带印度洋偶极子模态;热带大西洋的SST年际变率表现为类ENSO的年际振荡现象.在热带太平洋,SST年际变化主要表现为ENSO型,环流的年际变率表现为与ENSO相对应的热带海洋质量循环圈的年际异常.对应于暖(冷)事件,前期赤道海洋垂直环流圈显示出减弱(增强)的特征.其中南赤道流异常的位相较Nino3区海温总体要超前5个月左右的时间;赤道上翻流异常的位相在表层要超前4个月,并随时间由上至下扩展;赤道潜流的异常则显示出东传特征,其中最早的较为显著的异常发生ENSO成熟前3个月180°附近.在模式ENSO冷暖事件的演变过程中,次表层海温异常沿赤道的东传起了关键作用,模式的ENSO模态主要表现为"时滞振子"模态.     

赤道太平洋次表层海温异常年际和年代际变率特征与ENSO循环

用美国马里兰大学提供的海洋同化(SODA)月平均资料,分析了赤道太平洋次表层海温异常年际和年代际变率的演化特征,讨论了它们对ENSO循环的影响.结果指出,赤道太平洋次表层海温异常年际和年代际变率具相似的ENSO模分布和演变过程,二者均以赤道西太平洋暖池次表层海温显著的异常中心与赤道东太平洋表层海温异常中心显著反号为主要分布特征,其演变过程通过赤道西太平洋暖池次表层海温异常中心沿海洋气候温跃层向东向上传播来完成.赤道西太平洋暖池次表层海温异常年际变率决定了ENSO循环,年代际变率对ENSO循环也有重要影响,其影响主要在中太平洋, 造成ENSO模的年代际变化.当年代际变率处于正常状态时,ENSO循环基本上是东部型冷暖事件之间的转换;当年际和年代际变率位相相同时,ENSO事件强度将会加强和持续,并出现中部型ENSO事件;当二者位相相反时, ENSO事件强度将会减弱.     

热带海洋-大气耦合的主模态

依据1948年1月～2005年12月NCEP的海表温度(SST)和大气再分析的月平均资料,利用MCA方法,首次确定了代表全球热带海洋-大气相互作用的最主要信号的热带海洋-大气耦合主模态,该主模态随时间的变化与热带太平洋埃尔尼诺-南方涛动(ENSO)模态非常一致,揭示了该主模态包含以下海洋-大气相互作用物理过程:秋季印度尼西亚海洋-大陆区上空850 hPa出现异常的纬向风辐散和经向风辐合导致赤道东、中太平洋海温正异常,热带印度洋海温则出现东冷-西暖的—"偶极子"型异常;冬季热带太平洋出现典型的ENSO盛期对应的海洋-大气耦合型,在南海和热带远西太平洋出现低空反气旋环流异常,热带印度洋出现海盆一致增暖,而热带大西洋海温异常不明显;冬季热带太平洋和热带印度洋的SST异常可以导致春季赤道中太平洋西风异常,南海冬季风减弱,热带西北太平洋出现更明显的低空反气旋环流异常和赤道东风异常,热带西北大西洋出现西南风异常;该模态对夏季大气环流的影响主要表现为热带印度洋海盆一致模态对东亚季风的影响。     

热带太平洋气候变率的三类模态及与ENSO强度变化的关系

基于Kaplan等重建的1856—2001年全球海表水温距平(SSTA)资料，用小波变换分析了热带太平洋SSTA的气候变率，对热带太平洋SSTA分别进行2—8、8—30和30—100a带通滤波，然后进行EOF分解。结果发现，ENSO模态具有5a左右的年际变化和15a左右的年代际变化2种显著周期，当二者位相相同时，ENSO事件加强，当二者位相相反时，ENSO事件减弱，当年际变化不明显时，显著的年代际变化也可单独导致ENSO事件；热带太平洋SSTA气候态变率以西太平洋暖池和赤道两侧的热带中东太平洋明显海温同号异常为主要特征，具60a左右的周期，其相位变化与气候跃变及El Nifio事件的类型有密切联系；长期增温倾向加大了El Nifio事件的振幅。文章最后指出，ENSO事件强度变化是由年际、年代际和气候态等3类模态变率共同作用的结果，在ENSO预报模式中考虑并引入年代际和气候态变化对ENSO循环的影响，是提高ENSO预测水平的有效途径之一。     

印度洋-太平洋海表温度年际变化的联合模态

利用1870～2004年的HadiSST的月平均海表面温度(SST)资料,对去除了全球增暖趋势的印度洋-太平洋海表温度异常(SSTA)作季节经验正交函数(Season-reliant Empirical Orthogonal Function, S-EOF)分解,得到了印度洋-太平洋海表温度年际变化的2个联合模态,并且分析了与之相对应的大气环流特征.结果表明:低频的厄尔尼诺/南方涛动(ENSO)是控制印度洋-太平洋的主导模态,能使赤道印度洋维持一异常反气旋性环流,削弱印度洋夏季风的作用并且将东印度洋暖池的暖水输送到西印度洋,印度洋SSTA在一年四季中都出现全海盆同号变化,因此,第一主模态是ENSO的低频模与印度洋海盆一致模的联合模态;第二模态表现为太平洋上准2 a的ENSO位相转换模与印度洋偶极子模的联合模态,ENSO的位相转换发生于春季,与季风的异常转换有关,印度洋上出现异常的气旋性环流,叠加在印度洋夏季风上,增大东西印度洋的温差,在秋季出现西低东高的偶极子型海温分布,印度洋夏季风和这个模态的产生发展有很大的联系.     

海温距平的ENSO模和类ENSO模的三维结构

用美国马里兰大学提供的海洋同化(SODA)月平均资料,深入揭示了ENSO模的海洋三维结构及其年际和年代际变率。研究结果指出,ENSO海洋模随深度呈明显规律变化。在热带太平洋,它由热带中东太平洋表层显著海温异常分布型随深度增加逐渐过渡为热带西太平洋次表层显著反号海温异常分布型;在赤道太平洋以赤道西太平洋暖池次表层海温显著异常与赤道中东太平洋表层海温反号显著异常为主要特征。El Nino期间,热带中东太平洋表层为强海温正距平中心,西太平洋暖池次表层为强海温负距平中心,在年际尺度上,160°E以西的西北太平洋副热带海域还存在一个与西太平洋海温异常变化反号、与热带东太平洋同号的区域;La Nina期间正好相反。ENSO循环主要由ENSO年际变率所决定,年际ENSO模具有东部型ENSO事件的海温异常分布特征,其循环是东部型冷暖事件之间的转换,在200m以浅,它具ENSO模相同的三维结构和3-5年的显著年际变化周期;年代际类ENSO模具有中部型ENSO事件的海温异常分布特征,年代际ENSO循环是中部型冷暖事件之间的转换,其影响主要限制在200m以浅的海洋上层,具有ENSO模相似的三维结构和9-23年的显著周期。     

热带印度洋SST海盆模态的“充电/放电”作用——对夏季南亚高压的影响

根据观测资料和海气耦合模式初值试验结果,通过比较分析热带太平洋SST主模态(ENSO模)和热带印度洋SST主模态(海盆模)对夏季南亚高压的影响,揭示了印度洋海盆模的"充电/放电"作用:赤道中东太平洋海温异常首先对印度洋进行"充电",形成热带印度洋SST对太平洋EN-SO的响应模态——海盆模。该模态在ENSO发生翌年春季达到峰值位相,而且有很好的持续性,可以从春季持续到夏季,该暖(冷)模态可以引起大气的"Matsuno-Gillpattern"响应,并通过亚洲夏季平均西南季风的异常水汽输送等使得夏季南亚高压偏强(弱),即为"放电"过程。而赤道中东太平洋海温异常对夏季南亚高压的直接影响并不显著,并指出了夏季南亚高压和超前3~12个月Nio3指数之间高的显著正相关关系只是一个表象,并不是太平洋海温异常对南亚高压的直接影响结果,而是通过印度洋海盆模态的"充电/放电"作用引起的。     

季风转换期印度洋经向热输运的年际变异及其机理

本文采用SODA3.4.2再分析数据和POP2海洋模式研究了季风转换期间（春季和秋季）热带印度洋经向热输运异常（Meridional Heat Transport Anomaly, MHTA）的年际变异特征。春季MHTA存在两个主要模态,即一致模态和辐合辐散模态:一致模态表现为热带印度洋上层一致的向北输运,受热带印度洋海温一致模相关的赤道反对称风场（赤道以北/南为东北风/西北风异常）调控;辐合辐散模态则呈现关于赤道对称的表层辐散次表层辐合特征,受控于赤道以南的热带西南印度洋和副热带东南印度洋海温偶极子。然而,秋季MHTA仅表现为辐合辐散模态,受到印度洋偶极子期间赤道东风和赤道外反气旋式风应力异常影响。此外,POP2敏感性试验也验证了印度洋海温模态影响下异常风场对MHTA的调控作用,即反对称的风引起一致向北的MHTA,赤道东风异常引起MHTA表层辐散、次表层辐合现象。因此,热带印度洋海气耦合模态年际变化对印度洋上层热量再分配有着重要的意义。     

全球海洋环流模式中上层海洋对表面强迫的响应和调整Ⅱ.年代际变率

利用一个较高分辨率的全球海洋环流模式在COADS 1945～1993年逐月平均资料的强迫下对海温和环流场进行了模拟,分析了北太平洋海温和环流场的年代际变化特征,同时诊断了1976-77年代际跃变过程中海温场变化的机制.模式模拟出了北太平洋海温年代际异常的主要模态以及1976-77年跃变前后的演变特征,模拟的北太平洋中部、加州沿岸和KOE区的海温异常的强度和演变趋势均和观测比较一致;同时,模式重现了分别始于20世纪70和80年代的中纬度海温异常信号沿等密度面向低纬地区的两次潜沉过程.在表层,流场的异常主要表现为与风应力异常基本符合Ekman关系的一个异常海洋涡旋,而整个上层海洋平均的流场异常则表现为两个海洋涡旋的异常,其中副热带海洋涡旋的异常的强度要显著于副极地海洋涡旋的异常,而副极地海洋涡旋异常出现的时间比副热带海洋涡旋晚3a左右的时间.对1976-77年前后3个区域上层海温各贡献项的诊断结果表明,北太平洋中部变冷主要是水平平流和热通量异常贡献的结果;而加州沿岸变暖主要归因于热通量的贡献;在KOE区,垂直平流、热通量和水平平流三者都起了重要作用,其中水平平流异常对这一区域海温年代际跃变出现的时间起了至关重要的作用.     

风应力桥梁作用下热带太平洋和热带印度洋相互作用的数值试验

利用中等复杂程度全球热带大气和热带海洋模式的数值试验,模拟分析了热带太平洋和热带印度洋通过风应力桥梁的相互作用过程.利用NCEP再分析的1958～1998年SST强迫大气模式得到的风应力与NCEP再分析的同期热通量共同驱动海洋模式,作为控制试验;和控制试验平行,但强迫大气模式的SST在某一海盆取为多年气候平均值的试验作为敏感性试验.比较控制试验与敏感性试验模拟的SST变率,揭示了热带某海盆SST异常通过风应力桥梁作用对其他海盆SST的影响及其过程.数值试验结果表明:热带某海盆SST暖(冷)异常一般总是引起该海盆上空西部西(东)风异常和东部东(西)风异常;热带太平洋SST暖(冷)异常导致年际尺度上印度洋上空东(西)风异常和年代际尺度上热带印度洋风场辐散(合),该风应力导致热带印度洋年际SST暖(冷)异常以及年代际SST冷(暖)异常,但这种异常均较弱;热带印度洋SST暖(冷)异常导致热带太平洋上空东(西)风异常,该风应力异常在年际和年代际尺度上均导致热带太平洋SST冷(暖)异常,但年代际尺度上异常更明显.考虑到热带印度洋SSTA受热带太平洋SSTA影响大,并且热带太平洋SST暖(冷)异常主要通过表面热通量导致热带印度洋SST变暖(冷)的观测事实,文中揭示的热带印度洋SST暖(冷)异常通过风应力桥梁作用导致热带太平洋SST冷(暖)异常的结果表明,热带印度洋SSTA对于热带太平洋SSTA主要起着一种负反馈作用,并且这种负反馈作用在年代际尺度上更为明显.     

Assessing the Validity of Seismo-Acoustic Predictor Equations for Obtaining Seabed and Sub-Surface Sediment Physical Properties

The interdependence between the seismo-acoustic properties of a marine sediment and its geotechnical/physical parameters has been known for many years, and it has been postulated that this should allow the extraction of geotechnical information from seismic data. Though in the literature many correlations have been published for the surficial layer, there is a lack of information for greater sediment depths. In this article, a desktop study on a synthetic seafloor model illustrates how the application of published near-surface prediction equations to subsurface sediments (up to several tens of meters burial depth) can lead to spurious predictions. To test this further, acoustic and geotechnical properties were measured on a number of sediment core samples, some of which were subjected to loading in acoustically-equipped consolidation cells (oedometers) to simulate greater burial depth conditions. For low effective pressures (representing small burial depths extending to around 10 meters subsurface), the general applicability of established relationships was confirmed: the prediction of porosity, bulk density, and mean grain size from acoustic velocity and impedance appears generally possible for the investigated sedimentary environments. As effective pressure increases through, the observed relationships deviate more and more from the established ones for the near-surface area. For the samples tested in this study, in some instances increasing pressure even resulted in decreasing velocities. There are several possible explanations for this abnormal behavior, including the presence of gas, overconsolidation, or bimodal grain size distribution. The results indicate that an appropriate depth correction must be introduced into the published prediction equations in order to obtain reliable estimates of physical sediment properties for greater subsurface depths.     

A Review of Some Environmental Issues Affecting Marine Mining

This article reviews information recently available from existing marine and coastal mining for responses to environmental issues affecting marine mining at different depths. It is particularly but not exclusively concerned with those issues affecting seabed biodiversity impact and recovery. Much information has been gathered in the past 10 years from shallow mining operations for construction aggregate, diamonds, and gold, from coastal mines discharging tailings to shallow and deep water, and from experimental deep mining tests. The responses to issues identified are summarized in a series of eight tables intended to facilitate site-specific consideration. Since impacts can spread widely in the surface mixing layer SML, and can affect the biologically productive euphotic zone, the main issues considered arise from the depth of mining relative to the SML of the sea. Where mining is below the SML, the issue is whether it is environmentally better to bring the extraction products to the surface vessel for processing (and waste discharge), or to process the extraction products as much as possible on the seabed. Responses to the issues need to be sitespecific, and dependent on adequate preoperational environmental impact and recovery prediction. For deep tailings disposal from a surface vessel, there are four important environmental unknowns: (1) the possible growth of "marine snow" (bacterial flocs) utilizing the enormous quantities of fine tailings particles (hundreds or thousands of metric tons per day) as nuclei for growth, (2) the possibility that local keystone plankton and nekton species may migrate diurnally down to and beyond the depth of deep discharge and hence be subjected to tailings impact at depth, (3) the burrow-up capability of deep benthos and their ability to survive high rates of tailings deposition, and (4) the pattern and rate of dispersion of a tailings density current through the deep water column from discharge point to seabed. Actions to obtain relevant information in general and site-specifically are suggested.     

Increased Particle Fluxes at the INDEX Site Attributable to Simulated Benthic Disturbance

Particle fluxes were measured 7 m above the sea bottom during the predisturbance, disturbance, and postdisturbance periods by using time series sediment traps attached to seven deep-sea moorings deployed in the INDEX experiment site in the Central Indian Basin. The predisturbance particle fluxes varied between 22.3 to 55.1 mg m -2 day -1 . Increased and variable particle fluxes were recorded by the sediment traps during the disturbance period. The increase observed was 0.5 to 4 times more than the background predisturbance fluxes. The increases in particle fluxes (~4 times) recorded by the sediment trap located in the southwestern direction (DMS-1) were the greatest, which could be the result of preferential movement of resuspended particles generated during the deep-sea benthic disturbance along the general current direction prevailing in this area during the experimental period. Also, the traps located closer to the disturbance area recorded greater fluxes than did the traps far away, across the Deep Sea Sediment Resuspension System path. This variability in recorded particle fluxes by the traps around the disturbance area clearly indicates that physical characteristics such as grain size and density of the resuspended particles produced during the disturbance had an important effect on particle movement. The postdisturbance measurements during ~5 days showed a reduction in particle fluxes of ~50%, indicating rapid particle settlement.     

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。     

Determination of In Situ Sediment Shear Strength from Advanced Piston Corer Pullout Forces

The advanced piston corer (APC) has been used by the Ocean Drilling Program since 1985 for recovering soft sediments from the ocean floor. The pullout force measured on extracting the core barrel from the sediment is shown to correlate with the average shear strength of the sediment core measured in the ship's laboratory. A simple rule of thumb is derived relating the shear strength of the sediment to the pullout force. Multiple APC holes at individual sites allow the consistency of the pullout measurements to be assessed. The effects of different operational procedures during APC coring are also explored. Although generally applicable, the correlation between pullout force and laboratory measurements of shear strength breaks down for some APC holes, possibly because of the disturbance of some sediment types during the APC coring process. A better understanding of the physical process of APC coring, and its effect on the properties of the sediment both inside and immediately outside the core barrel, would indicate what confidence can be put on the measurement of pullout force as a way of evaluating the in situ shear strength of deep sea sediments.     

Interannual Sea Level Variations and Annual Tides in the Northwestern Pacific

Specific properties of the interannual sea level variations and annual tides in the Northwestern Pacific were studied. Several tide stations were monitored. The monthly mean sea level for the year of 1995 was analyzed at each tide station. A seismic event in 1995, some tectonic activity around the subject area, and the Kuroshio (the oceanic western boundary current) may possibly contaminate results which would have occurred from the astronomical annual tide alone.     

Flow Cytometric Analysis of Coastal Lagoon Bacterioplankton and Picophytoplankton: Fixation and Storage Effects

The effect of different fixation and storage protocols on the flow cytometric (FCM) simultaneous analysis of bacterioplankton and phytoplankton in coastal seawater samples (Mediterranean coastal lagoons) was investigated. FCM measurements (cell number, fluorescence and scatter characteristics) were obtained through DAPI staining. Three fixatives [glutaraldehyde (GA), formaldehyde (FA) and paraformaldehyde (PFA)] and two storage (3 months duration) methods (5 °C and −196 °C) were tested. Two dominant populations were detected in studied samples: bacteria and eukaryotic picophytoplankton. Adding fixatives (2% final concentration) appears necessary to obtain FCM exhaustive counts of all the bacteria and phytoplanktonic cells. This was related to the permeation effect of fixatives which allowed a better DAPI staining of the cells. Maximum fluorescence, i.e. optimal staining of the cells was obtained with FA or PFA, and significant lower fluorescences with GA. Fixed samples stored at 5 °C induced rapid cell loss. Only storage in liquid nitrogen of samples fixed with FA or PFA, allows mid-term (≥4 months) preservation of bacteria or picophytoplankton cell numbers, and limited evolution of DAPI-induced fluorescence and scatter characteristics.     

《Acta Oceanologica Sinica》Vol. 33(2014) contents

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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,