热带太平洋月平均海平面低频变化的循环传播规律及其与埃尔尼诺的关系

本文对赤道东太平洋表层水温和热带太平洋月平均海平面变化进行了长时间序列分析,揭示了它们的准周期低频振荡特性,其中20°N～20°S区域月平均海平面低频变化的显着周期在43.5～50.0个月之间,与47.6个月的埃尔尼诺显着周期颇为接近;引入空间谱分析的概念与方法,分析阐明了热带太平洋月平均海平面低频变化遵从下列逆时针循环传播规律:东太平洋(墨西哥近海)→北赤道流区域→西赤道太平洋→北赤道逆流区域→东太平洋,该循环与埃尔尼诺循环过程存在密切的一一对应关系;根据上述分析结果,初步建立了依据典型区域月平均海平面变化预报埃尔尼诺的八元逐步回归模型,预报值与实测值序列的相关系数达0.89.     

南海表层水温的长周期振荡及其与埃尔尼诺的关系

本文对南海西沙海洋站(16°50'N、122°20'E)1961～1987年间的表层水温月平均资料、秘鲁与厄瓜多尔外海(5°N、80°～90°W)的表层水温月平均资料,进行水温功率谱分析,并计算了其表层水温异常的强度和指数.计算结果表明,南海、秘鲁与厄瓜多尔外海的表层水温存在着3.3年的长周期变化,且秘鲁与厄瓜多尔外海的表层水温比南海提前变化约5个月,变化是同相的.在1960～1987年间,每当东太平洋沿岸海区发生一次正、反埃尔尼诺现象,南海也相应出现一次强度相当的暧、冷事件.     

太平洋海平面变化特征及影响因素分析

采用经验模态分解法对太平洋沿岸验潮站的月平均海平面资料进行处理,结合T/P高度计资料、Church(2004)重构SSH资料、Ishii(2005)月均海温资料,研究太平洋海平面年际、年代际变化以及资料长度内海平面变化趋势。太平洋沿岸海平面总体呈上升趋势,平均上升速率为1.4 mm/a,趋势项分布有明显的区域性和纬度特征。ENSO对太平洋地区海平面年际变化有显著影响,海平面年际变化与Nino3指数在西(东)太平洋为负(正)相关,海平面年际变化与Nino3指数的相关性在热带太平洋最大,并随着纬度升高相关性减弱,且不同地区年际变化有滞后ENSO时间不等的最大相关。海平面年际变化与PDO指数在西(东)太平洋为负(正)相关,海平面与PDO的相关性分布有区域性和随时间演变特征。年代际变化对目前使用卫星高度计资料分析海平面长期趋势项的预测有直接影响,可能完全掩盖海平面长期变化趋势。     

赤道东太平洋水温的低频振荡与埃尔尼诺形成

本文对赤道东太平洋水温异常作了分析,发现热带太平洋地区的水温存在3-5年的低频振荡和准两年周期振荡.前者具有自东向西传播的趋势,而后者却具有相反的趋势.当两者在赤道东太平洋同位相增温时会形成埃尔尼诺事件.     

近赤道西太平洋低空纬向风异常对ENSO事件的指示性

本文计算了近赤道西太平洋Ponape岛1961～1986年历年逐月850hPa矢量风的纬向与经向分量及其距平值,并分析了其与ENSO事件的关系.结果发现,当该岛纬向风距平(3个月滑动平均)值达到+2m·s-1并持续2～3个月时,则其后东太平洋多即有埃尔尼诺现象发生.进一步分析该岛纬向风距平与西太平洋Truk岛海面水位距平和东太平洋赤道SST距平之间的时滞关系,结果发现,三者之间依次存在着十分显着的时滞相关,表明在西太平洋低纬大气与东太平洋赤道海温之间可能存在着一种由动力异常导致热力异常的物理过程.利用中美西太平洋海气联合考察获得的1986～1988年埃尔尼诺期间165°E断面CTD和ADCP等实测资料,对这种可能过程做了分析和讨论.     

太平洋月平均水位变化中的周期成分

为了研究太平洋月平均水位变化中的周期成分,本文根据作者改进的月平均水位周期信号分析方法,分析了太平洋236个水位站的月平均序列.对其中大于45a的序列进行二阶谱和二阶凝聚谱分析,表明这些序列中有的周期成分相位相关性显着.因此采用考虑非线性效应的混合谱周期分析方法,即重复进行最大熵谱分析及周期检验和最小二乘滤波,逐次检验并滤掉最显着的周期分量,求得序列中的显着周期.结果表明水位序列的振动周期因站而异,并非固定不变.讨论了准2a大气振动周期、与埃尔尼诺事件相关的3～7a周期、太阳黑子、双太阳黑子和25～30a超长振动周期的存在.周期振动的迟角和振幅的区域分布和变化对月平均水位的预测具有重要意义;为此对检验出的显着周期根据物理背景作进一步判别,从中选出较客观合理者作为月平均水位序列的拟合周期.用这样的周期分量加线性趋势项拟合月平均水位序列,求得相应的振幅和初相角及线性趋势项.     

太平洋几种海面要素的升降趋势及其对海平面上升的影响

对ＣＯＡＤＳ资料中１９５０－１９９２年太平洋４°×８°方区的海水表层温度及海面气温、气压、风速序列数据，进行了时间序列分析。分析结果表明：太平洋海表气温和水温年上升率分别为０．００６３℃·ａ（－１）和０．００２６℃·ａ（－１）。两者的变化趋势在赤道太平洋都有一个年上升率高值区；而在东海以北的西北太平洋广大海区，都有一个年下降率的低值区。西太平洋海面气压呈上升趋势，东太平洋则相反。气温和水温的升降区域分布特征与风速分量增强和减弱的变化趋势有关。文章还指出，中国和日本沿岸今后几十年海平面变化趋势的预测模式，应以太平洋或全球海平面上升趋势的预测为基础，加上本海区海平面的局地变化订正。     

厄尔尼诺现象与赤道西太平洋,印度洋,黑潮之间海温变化的相互关系分析

文中采用美国ＣＯＤＡＳ和国家气候中心出版的每月海温资料，对按国家气候中心出版的月监测公报所划分的赤道海区Ｃ区（０－１０°Ｓ，１８０－９０°Ｗ），Ｗ区（０－１０°Ｎ，１８０－１４０°Ｅ）和Ｂ区（０－１０°Ｎ，５０－１５０°Ｅ），以及西太平洋黑流区Ａ区（２５－３０°Ｎ，１３０－１４０°Ｅ；３０－３５°Ｎ，１４０－１５０°Ｅ）裼 海温变化作了互相关分析，海区间互相滞后相关系数、交叉凝聚谱计算表明：Ｃ区与     

太平洋海域海平面变化的灰色系统分析

应用灰色系统理论，对太平洋海域４８个长期验潮站的月均海平面分别建立了ＧＭ（１，１）模型。ＧＭ（１，１）模型能较好地反映太平洋海域的海平面变化的趋势，它除了能给出连续的海平面变化速率外，同时能方便地给出海平面变化的加速率。模拟结果表明，在太平洋地壳均衡假设下，太平洋海域的月均海平面以平均速率０．１７ｃｍ／ａ上升。在太平洋海域所取的４８个长期验潮站中，有４０个站在加速上升，全部站的平均加速度为０．０００２９ｃｍ／ａ２。且加速率逐渐增大。当然这些加速率都很小，但作为一种普遍性的趋势，这已足以说明：太平洋海域的海平面在加速上升     

从全球海平面气压场的变化分析埃尔尼诺形成的大气环流条件

本文根据南北半球(60°N-50°S)月平均海平面气压图,研究了赤道东太平洋(0°-10°S,180°-90°W)海表温度与前期12个月各月大气环流异常的关系,发现无论是南半球还是北半球,均是冬季大气环流对以后的海温变化影响大.又对比了埃尔尼诺年及反埃尔尼诺年前期大气环流的差异,如以接近埃尔尼诺峰值的11月为例,则在此之前的12个月内,大气环流的影响可分为三个阶段.第一个阶段自上一年11月至当年1月,与海温相关最大的地区在北半球的大陆上;第二个阶段自2月至5月,为过渡阶段,相关区不稳定,但大部分显著相关区在南半球;第三个阶段自6月到10月,为加强影响阶段,相关区稳定在南半球,反映出南方涛动的特征.最后对环流异常影响埃尔尼诺的物理过程进行了讨论.     

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.     

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.     

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.     

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.