白令海和鄂霍次克海的海冰偶极子及其对大气环流的影响

基于海冰历史资料的分析表明,白令海和鄂霍次克海的海冰密集度分布在某些年份表现出反位相变化的特征,尤其以冬季最为明显.合成分析的结果表明这种偶极子型海冰异常可能对大气环流(气温和位势高度)产生一定的影响.利用大气环流模式,在给定理想化的白令海、鄂霍次克海偶极子型海冰异常的情况下,通过20个冬季(1-2月)大气环流模式的集合强迫试验,研究了大气环流对这种偶极子型海冰异常的响应特征,数值试验结果与基于观测资料的合成分析比较一致:低空气温对于偶极子型海冰强迫表现为比较明显的对称性响应,气温变化具有垂直斜压的结构,气温变化主要集中在低空;高空大气温度和各层的位势高度的变化均具有显著的非对称性特征,位势高度的变化具有垂直正压结构.参考已有的理论和模拟研究结果,指出高纬地区低空大气的温度变化受直接热力学调整过程的影响明显,对称性响应分量明显,而高层大气温度和各层的大气位势高度变化是由直接热力学调整和间接动力过程响应所共同控制,非对称分量占主导.     

1990～1991年冬季渤海海冰冰情及其数值预报(Ⅰ)——渤海冰情及其天气成因

本文根据1990～1991年冬季渤海海冰的实况和历史资料,通过对冰期、冰厚、结冰范围等几个方面的对比分析,描述了该年度海冰的变化过程,并确定该年度黄、渤海海冰属于轻年。通过气温场、海温场及500hPa高度的分析,总结了该年度辽东湾海冰的特点及成因。     

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。     

北半球中高纬度大气环流主模态的季节演变及其与北极海冰变化的联系

利用31a(1979—2009)气候月平均的海平面气压(SLP)资料,提出1种与北半球中高纬度环流转变相适应的分季法。并根据这个客观分季方法,通过SEOF分析,发现大气环流主模态的季节演变有着典型的北极涛动(AO)空间结构,其时间系数在1990年代中期发生转型。500hPa上纬向波的涡度有着南北反位相的分布特征,冬季正涡度的区域对应着气旋性环流,其覆盖范围广,而夏季正涡度区域更偏北,可见AO在冬季增强,夏季减弱。北半球SLP异常的EOF分解第一模态为北极涛动(AO),第二模态是偶极异常(DA);将这2个模态称之为北半球中高纬度大气环流异常的优势模态。通过计算优势模态与海冰面积的超前滞后相关性,发现AO依然是控制海冰变化的前期大气环流异常的模态,而DA则可能是海冰快速变化后期大气环流的主导模态。     

台湾以东黑潮流量变异与冬季西北太平洋海洋-大气相互作用

通过对历史资料进行奇异值分解、合成分析及相关分析,揭示了对应冬季台湾以东黑潮流量增强(减弱)时,西北太平洋海区异常失热(得热),北太平洋(北纬20°N以北)上空500hPa位势高度负异常(正异常);进一步证实了冬季西北太平洋海洋-大气相互作用是一个正反馈过程;发现了冬季台湾以东黑潮的暖平流作用可能是维持该正反馈过程进行的一个必要条件;通过超前和滞后相关及合成分析,提出从10月开始,台湾以东黑潮流量异常形成的暖平流作用会对冬季西北太平洋海区海洋-大气相互作用有贡献。     

乌拉尔阻塞与巴伦支-喀拉海海冰的季节特征及其相关关系

本文采用经验正交函数分析、线性回归、相关性分析等方法对1982—2017年乌拉尔阻塞(UB)与巴伦支-喀拉海(BKS)海冰季节特征及其相关关系进行分析发现,UB活动频率与BKS海冰密集度均有较强的季节性周期变化,且不同季节BKS海冰与UB相关性不同。进一步对秋季UB与冬季BKS海冰的相关关系分析发现:秋季UB频率在BKS及其周边区域增多的年份里,秋季到冬季结冰期内,局地BKS海域500hPa位势高度持续增加、低层大气温度持续升高;同时,秋季BKS海域海表面温度异常增暖持续至冬季。上述海洋、大气条件不利于结冰期BKS海冰的冻结,因此这些年份里冬季BKS海冰密集度减少。此外,秋季BKS海冰减少也伴随着冬季UB高纬度频率增加。     

7月北极海冰与翌年1月大气环流及亚洲中、高纬地区气温趋势的关系

本文主要通过相关统计分析,研究了7月各海区海冰与同期上空500hPa高度场的关系及其与后期翌年1月北半球500hPa大气环流的联系,对翌年1月亚洲中高纬地区气温趋势的可能影响在此也作了讨论。结果表明:7月北极海冰与其同期上空500hPa高度存在着较好的负相关关系。其中,尤以Ⅰ、Ⅱ海区负相关关系更好。在北极各海区中,以7月第Ⅲ海区海冰与后期翌年1月北半球500hPa大气环流联系较为密切。主要表现为,7月Ⅱ海区海冰M指数高(即冰情重)时,翌年1月北欧低槽及东亚大槽偏弱,并多伴随着乌拉尔山阻塞形势的破坏过程。7月Ⅱ海区海冰M指数低(即冰情轻)时,翌年1月北欧低槽及东亚大槽偏强,多伴随着乌拉尔山阻塞形势的建立过程。7月Ⅱ海区冰情重时,亚洲中、高纬地区1月气温多偏低,反之多偏高。     

冬季北太平洋的温带气旋活动及其与前期秋季北极海冰的关系

基于欧洲中期天气预报中心(ECMWF)的ERA_interim全球再分析数据集,利用客观算法识别和追踪温带气旋,分析了1979—2014年冬季(12月—次年2月)北太平洋(120°E~120°W,20°N~80°N)的温带气旋活动特征及其变化,探讨了冬季风暴路径与秋季北极海冰异常的关系。北太平洋温带气旋活动的气候态显示为自日本以东洋面至阿拉斯加湾北部的风暴路径。对30°N以北气旋活动频率异常的EOF分析显示其第一模态为太平洋气旋活动的南北向偶极子结构,表示风暴路径南北摆动的变化特征,且有向北偏移的趋势。第二模态的空间分布表现为40°N~60°N之间的大陆沿岸和太平洋洋面上呈相反的分布形势。时间系数的回归分析显示,冬季太平洋风暴路径的南北摆动与秋季(9—11月)东西伯利亚海-波弗特海海冰的异常显著相关。该海区秋季海冰减少导致冬季阿留申低压区呈高压异常,西风急流北移,45°N~75°N之间的大气斜压性增强而45°N以南大气斜压性减弱,从而使风暴路径向45°N以北偏移。     

福建春季降水量场预测模型研究

利用1960—2000年福建春季(2—4月)降水量场资料，分析了经验正交函数(EOF)展开得出的特征向量，以反映降水的空间分布特征。研究了前三种分布型的时间系数与前期北半球500hPa、100hPa月高度距平场和北太平洋海温距平场之间的关系，针对不同的分布型分别找出了不同的前期预测信号，以此为预测因子，构建出福建春季降水量场短期气候预测模型。利用该模型对2001、2002年福建春季降水量场进行试预测，取得了较满意的结果。     

2007-2018年黄渤海海冰气候特征及其对气象因子的响应

基于美国国家冰雪数据中心 （NSIDC） 海冰资料、美国国家环境预报中心 （NCEP） 再分析格点数据和黄渤海近岸13个气象站点逐日气温数据,通过相关分析和合成分析,研究了 2007-2018 年黄渤海海冰范围的变化特征,探讨了近 12 年黄渤海海冰范围对近岸陆地气温、大气环流和局地天气过程的响应。结果表明: （1） 黄渤海海冰范围年际振荡明显,近 12 年呈现先增加后减小的趋势,与同期黄渤海近岸气温呈显著负相关关系;每年 1 月下旬至 2 月下旬是一年中海冰范围最大的时期。（2） 海冰范围偏大与偏小年份东亚地区 500 hPa 大气环流形势呈现出近乎相反的分布。 （3） 东亚阻塞形势的建立是黄渤海海冰范围爆发性增大的一个前兆信号,它带来的大风降温天气是造成黄渤海海冰范围爆发性增大的重要原因.     

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.     

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.     

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.     

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.