利用海洋重力数据和水深数据的相关性剔除粗差

在进行海洋重力和水深测量的时候,由于各种原因会造成部分测量数据带有较大的误差或出现错误.根据海洋重力测量时同时进行水深测量的作业方式,通过实际测量数据,利用海洋重力数据和水深数据的相关性,介绍了在数据后处理中海洋重力数据和水深数据的相互参照作用,以判断测量数据的正确与否,便于删除错误数据,提高测量数据的质量.     

海洋测深中的波浪效应改正技术

以GPS海洋测量手段为代表的现代海洋测量技术已经形成,海洋测量的测深、定位两大主题已得到较好的解决。但是,海洋水深测量数据的改正和归算理论与方法还需要进一步改进。本文对海洋测深中的波浪效应问题进行探讨,提出了波浪效应改正技术,为提高精密海底信息场测量与表征的精度,建立了海洋水深测量数据的改正和归算问题中由波浪效应引起的相关测深改正的数学模型。     

一种新型无人船海洋水深测量技术

在海洋测深中,由于波浪和潮汐的影响,调查船或无人船所测量的瞬时水深不能直接作为海图水深。本文提出了一种新型的无人船海洋水深测量技术,以评估搭载RTK和单波束测深仪的无人船用于海洋水深测量的潜能。首先,使用无人船所搭载RTK的厘米级精度高程数据,通过低通滤波剔除波浪信息,而获得海平面高程。然后,基于潮汐表和无人船海平面高程,构建了一种参考椭球面和海图的两个基准面之差的获取方法;在常规的海洋调查中,该基准面差通常需要由长期的验潮获得。最后,利用海图基准和无人船测量的瞬时水深的转换关系,计算出海图水深。在海南省蜈支洲岛周边海域,利用自研发的无人船“USBV”开展了相关海上实验,以验证所提出的技术方法。实验结果验证了该无人船海洋水深测量技术。     

基于RTK的测量艇实时姿态模型研究及应用

当前,小艇挂载单波束测深系统实施水深测量时,易受风、流、涌浪等复杂因素影响,导致水深测量精度偏低。为了探究船体姿态对水深测量数据精度影响机理,提升单波束水深测量精度,基于RTK实时测定船体三点的高程,结合小艇姿态改正模型,确定小艇实时姿态、航向、换能器动态吃水及升沉,重算深度及位置。通过在珠江口某海域设置不同姿态场景实测数据,计算实时小艇姿态等数据,分析不同船姿态对测深精度的影响规律,重算了水深及位置数据,有效地提高了单波束水深数据精度。     

无人水面测量艇技术研究(一):船型及推进方式设计

目前,无人水面舰船代表了海洋测量装备自动化、智能化的发展趋势,是海洋测量技术研究的热点。针对浅水区域水下地形复杂、暗礁众多、涌浪较大的特点,对无人水面测量艇水深测量技术进行研究,涉及的关键技术包括船型及推进方式设计、测量设备加装测试、无线数据传输功能、测量艇吊放回收技术等,本文主要围绕船型及推进方式展开研究,提出三体喷水推进无人水面测量艇设计方案,基于该方案实现的测量模式具有很强的机动性和高效性,必将极大地提高测量部门在浅水区域水深数据的快速获取能力。     

EOF重构声速剖面对深水多波束的声速改正分析

声速误差是多波束水深地形测量主要误差源之一,通常采用现场声速剖面测量的方式加以改正,但在深远海多波束水深地形测量时,现场获取全深度的声速剖面并非易事。针对这一问题,利用东南印度洋海洋调查工作中采集到的17个站位的CTD数据,将所有站位声速剖面拓展到全深度,采用经验正交函数分析法(Empirical Orthogonal Functions,EOF)构建调查区声速剖面场,可获得声速剖面场内任意一点的声速值。然后通过EOF重构声速剖面场获得的声速值对测区内多波束水深地形数据进行改正,并与实测声速剖面对多波束水深地形数据的改正结果进行对比,结果表明,5000 m水深范围内2种声速改正结果相差很小,EOF重构法对深水多波束的声速改正满足水深测量的要求。     

海洋日变数据影响因素分析

日变改正和船磁方位改正是影响海洋磁测数据精度的主要因素,而船磁改正又会受日变改正精度的影响,因此日变改正对于海洋磁力数据精度而言至关重要。主要研究海洋日变数据与陆地日变数据之间的关系,确定海洋日变数据的可靠性。通过计算海洋日变数据随纬度和水深的变化率,并结合变化趋势、日均值等方面对数据进行分析,以期探索海洋日变与纬度、水深之间的关系,为海洋日变用于磁力日变改正奠定基础,从而提高海洋磁测数据精度。     

近海底调查的拖曳式海洋重力仪

目前海洋重力主要为海面和海底测量。海面重力测量受水深影响,观测点远离重力源,其分辨率降低;海底测量分辨率不受水层影响,但由于逐点测量的耗时,其覆盖性较差。我们制作了一个重力测量系统,该系统在近海底具有高分辨率、高速采集重力数据的能力,其探头用船拖曳在海底附近的正上方。     

序统计滤波估计检测海洋测深异常数据

根据海洋水深数据处理的要求，构建了海洋水深数据的序统计滤波模型，并根据水深异常数据的特点，提出了离差法判定水深异常数据，在遵循“舍深取浅”这一基本海洋数据处理原则基础上，设计了海洋水深异常数据检测的序统计滤波方案。实例分析表明，该滤波方案能够有效地检测并剔除零水深、负水深、孤立突跳水深，保留连续（个数多于（含）3个的）异常水深，在序统计滤波异常数据检测的基础上剔除粗差，能大幅提高粗差检测的效率。     

海洋测绘垂直基准的建立与转换

在我国海洋测绘采用的多个基准面的复杂进程中,垂直基准的建立与实现已开始初露端倪并越来越引起大家的重视。就海洋测量垂直基准的现状、垂直基准面间的关系、海岸带地形测量与水深测量基准面转换技术等方面进行探讨,以期实现海岸带地形图和水深图的无缝拼接。     

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.     

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.     

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.     

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.