北太平洋副热带逆流区海流的准90天振荡

根据 POCM模式输出的流场资料 (1993年 1月 1日～ 1998年 12月 31日 ) ,运用小波分析方法分析北太平洋副热带逆流区海流的季节内振荡特征 ,并用功率谱方法作了验证。结果表明 :在以 19.81°N为中心 ,18～ 2 2°N,16 0°E以西的西太平洋海域 ,海流具有显著的准 90 d振荡特征 ;该振荡对应的波长约为 86 5 km,沿 19.81°N该振荡信号自东向西传播的相速度约为 0 .0 9m/ s。从能量角度看 ,该振荡信号主要存在于 15 0 m以内的海洋次表层 ,2 2 2 .5 m深度能量是 6 2 .5 m能量的13%。     

热带太平洋障碍层厚度的时空特征分析

利用中国Argo实时数据中心提供的9 a(2000—2008年)网格化Argo剖面浮标温、盐数据(G Argo),分析热带太平洋障碍层厚度的气候态分布和低频变化特征。气候平均结果表明,较厚的障碍层主要出现于西太平洋暖池区,并有3条纬向障碍层带状分布,从暖池出发向东延伸至120°W,分别位于以15°N,5°N和12°S为中心的纬度带上。经验正交函数(EOF)基本模态分析表明,热带太平洋障碍层低频振荡以季节和年际变化为主,在季节尺度上主要表现为15°N和12°S障碍层纬度带呈反相变化,都在当地冬季最大,夏季最小;在年际尺度上则主要表现为暖池东边界附近障碍层与厄尔尼诺南方涛动(ENSO)相关的变化,以及暖池中部障碍层与热带准2 a周期振荡(TBO)相关的变化。     

基于再分析数据的黄岩岛及邻近海域气象条件分析

采用美国NCEP-CFSR数据库资料,提取了1979—2010年的海平面大气要素场,在中国南海区域(0°～25°N、105°～125°E)和黄岩岛附近点(15°N、118°E),按日、月、年统计了32 a间海平面气压、海面2 m气温、海面2 m相对湿度、海面10 m风场基本气象要素特征。分析发现:黄岩岛及邻近中国南海区域属于赤道带、热带海洋性季风气候,其气候特征是:(1)海平面气压呈北高南低、冬季高夏季低的分布形势;黄岩岛日平均海平面气压冬季约为1 012 hPa,其他季节约为1 008 hPa,年平均海平面气压变化具有准5 a的周期;(2)全年平均气温较高,分布呈现北低南高,大陆低海面高,冬季低夏季高的特点;黄岩岛海面2 m气温日变化较小,年平均值约为27～28℃,年际变化上具有整体增加的趋势;(3)全年相对湿度较大,基本在60%以上,随季节变化明显,冬季较小,夏季较大;黄岩岛日平均相对湿度为80%,总体也具有略微增大的年际变化趋势;(4)受季风影响明显,冬季盛行东北季风,平均风速约为10～12 m/s,夏季盛行西南季风,平均风速约为4～8 m/s;黄岩岛海面风速的变化具有2.5～5 a的变化周期,年平均风速在5.3 m/s上下波动。     

赤道太平洋海域上层海洋热含量及其变化机制的诊断分析

基于1992—2015年国际共享的ECCO v4 (Estimating the Circulation and Climate of the Ocean Version 4)同化产品,利用热含量控制方程定量地诊断赤道太平洋(118°E—75°W, 5°S—5°N, 0～300m)和Ni?o 3.4区(170°W—120°W, 5°S—5°N,0～80m)这两块区域热含量变化机制。对于去掉季节平均后的年际变化,在赤道太平洋地区,时间趋势项主要由经向输送和海表热通量项共同驱动。通过5°N断面的输送决定了时间趋势项的幅值和正负符号。在Ni?o3.4区,时间趋势项主要由海表热通量项和热量输送项共同驱动,其中垂向输送对总输送贡献最大。赤道太平洋地区经向热量输送异常领先于Ni?o3.4区垂向热量输送异常,这解释了在年际尺度上赤道太平洋热含量异常领先Ni?o3.4指数变化的原因。尽管EP(Eastern Pattern)型El Ni?o和CP(Central Pattern)型El Ni?o有许多不同之处,合成分析表明,两类El Ni?o的共同点为:在赤道太平洋地区,两类El Ni?o事件的热量输送异常在发展期和衰退期由经向输送主导;在Ni?o 3.4区, EP型El Ni?o和CP型El Ni?o的热量输送在发展期和衰退期由垂向输送主导。     

并矢相关谱分析方法在非线性资料分析中的应用

本文利用到率并矢相关谱估计方法,对青岛月平均气温（1896年1月—1992年12月）足赤道局部地区日表层水温（0°±0．5°S,165°±0．5°E;1986年12月6日—1991年11月16日）进行了谱分析,结果表明：青岛气温除具有1年周期的主频振荡和二倍峰频处0．5年周期二阶非线性耦合效应外,还隐含有2年周期的低频耦合振荡及0．4年周期的高频耦合振荡;赤道局部地区日表层水温含有90天,63天,50天,40天和29天等几个主要的低频周期振荡。     

基于Argo浮标资料的西北太平洋模态水的空间结构及年际变化

基于国际Argo资料中心提供的从2004年1月至2007年10月的浮标剖面资料,对西北太平洋模态水的时空变化特征进行分析.结合WOA01(the World Ocean Atlas 2001)资料,选定模态水主要形成区(30°～35°N,140°～155°E)作为研究区域,利用3月份的平均资料,给出西北太平洋模态水的空间结构为:北边界位于34.5°N附近,南边界可达30°N以南,东边界位于151.5°E,西边界可达140°E以西,深度为350 m以浅.通过对模态水核心区的逐月资料分析,揭示了其温度、盐度等的季节变化,并提出一种判别模态水范围的盐度判别法.结合海平面高度异常变化,初步分析了涡旋对模态水的影响,发现涡旋只能暂时改变核心区模态水的温盐结构,之后该区域模态水将基本恢复到正常状态.根据模态水2004-2007年的水文数据特点,发现在过去4 a中模态水性质基本稳定,变化很小.     

赤道中、东太平洋表层流速20d振荡特征分析

通过对1985年1月1日—1986年12月31日沿赤道5个锚定浮标站表层流速资料的分析,发现在140°W与108°W之间表层流速v存在一周期约为20d的显著振荡。该振荡是由波长约2000km、以1.15-1.23m／s的波速向西传播的波动引起的。该波动被推断为第二斜压模态混合Rossby惯性重力波。带通滤波和低通滤波结果表明,以110°W测站为例,20d振荡流速构方根为21.8cm／s（纬向）和22.1cm／s（经向）;单一流速振幅的特征值为30-50cm／s,最大振幅可达70cm／s;u季节变化的均方根小于17cm／s,v无明显季节变化。年平均流速通常小于5cm／s。以上各统计量表明,20d周期波动引起的v振荡在赤道东太平洋表层流速变化中非常显著。     

ElNio夏季太平洋上空垂直环流特征及我国汛期降水

本文利用NCAR(美国国家大气研究中心)1976年太平洋各层风场资料,计算了0°—50°N,105°E—110°W范围内,7月850hPa,700hPa,500hPa,300hPa,250hPa和200hPa各层上的垂直运动,并与叶笃正等所作的太平洋上空夏季平均环流特征作比较得出:(1)常年Walker环流明显,而E1 Ni(?)o发生年热带西太平洋上升运动减弱,东太平洋空气下沉区变成了强上升区,Walker环流下沉区东移至110°W以东;(2)常年热带西太平洋Hadley环流不明显,沿160°E以东Hadley环流越来越清楚,呈向东递增的趋势,而E1 Ni(?)o年Hadley环流东西变化甚为复杂,Hadley环流的上升支并不在赤道附近,而移至10°N左右,明显较常年偏北,Hadley环流也变成自热带向副热带倾斜的环流圈;(3)E1 Ni(?)o发生年,夏季以淮河为中心的空气上升区变成下沉区,而37°N以北的华北地区仍是上升区,华北多雨,所以出现Ⅰ型降水。     

近30年西北太平洋热带气旋的时空变化及与海洋上层热状态的关系

使用1982—2014年美国国家海洋和大气管理局(National Oceanic and Atmospheric Administration,NOAA)最优插值(1/4)°逐日海温分析资料、美国国家海洋数据中心(National Oceanographic Data Center,NODC)提供的海洋上层700 m热含量数据和美国联合台风警报中心(Joint Typhoon Warning Center,JTWC)的热带气旋(tropical cyclone,TC)最佳路径资料,分析西北太平洋地区(0°~30°N,105°~155°E)TC活动的时空分布特征,探讨TC与海洋上层热状态之间的关系。结果表明:TC频数具有显著的年代际变化特征:1982—1992年和2003—2014年皆为低频期,而1993—2002年则为高频期,33年来TC发生频数表现为缓慢增加—快速增加—减少的特征。最近15年(2000—2014年),TC数量呈现明显下降的趋势。在西北太平洋,TC有3个明显的源地,分别为源地1(10°~22°N、110°~120°E);源地2(8°~20°N、125°~145°E);和源地3(5°~20°N、145°~155°E)。源地1、源地2的频数呈上升趋势,而源地3呈下降趋势。海洋上层热状态的变化给TC带来的影响是多方面的,TC频数对上层热含量(heat content)的响应较明显,而海表面温度(sea surface temperature,SST)不是影响TC数量变化的主要因素。伴随着海洋上层的增暖,TC的年持续时间有减少趋势,TC强度正在增强。在全球变暖背景下,TC活动给西北太平洋沿岸国家带来的潜在威胁极有可能加剧。     

热带西北太平洋0~300 m热含量的年代际变化

太平洋是海表温度年际变化和年代际变化发生的主要区域,但对太平洋海洋热含量变化的研究相对较少。为此, 本文分析了1980—2020年太平洋上层(0~300 m)热含量的时空变化特征。基于IAP数据,本文首先利用集合经验模态分解法(EEMD)提取不同时间尺度的海洋热含量信号,并利用正交经验分解法(EOF)对不同时间尺度的海洋热含量进行时空特征分析,得到了太平洋0~300 m海洋热含量的年际变化、年代际变化以及长期变暖的时空特征。结果表明,除了年际变化之外,热带西北太平洋上层热含量还存在明显的年代际变化和长期变暖趋势。在东太平洋和高纬度西太平洋,热含量的年代际变化特征并不突出。热带西北太平洋热含量的年代际变化在1980—1988年和1999—2013年较高,而在1989—1998年和2014—2020年期间较低。此外,针对热带西北太平洋热含量的经向、纬向和垂向特征分析,发现这种年代际变化主要发生在5°N—20°N,120°E—180°E,次表层50~200 m范围内。热带西北太平洋热含量的年代际变化对全球海表温度的年代际变化有着重要作用。     

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.     

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.     

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.     

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.