Synoptic variability of the acoustic characteristics in tropical Atlantic waters

Synoptic variability of the sound speed and parameters of the SOFAR channel in the tropical Atlantic are considered. The synoptic component of the temporal and spatial dispersions of sound speed is singled out. The synoptic processes are shown to essentially affect the vertical hydroacoustic structure on a 1-month scale. It has been found that synoptic variations in the sound speed field penetrate as far as the SOFAR channel axis and deform it considerably.Translated by V. Puchkin.     

Oceanic sound channels around New Zealand

Configuration of major sound channels in the ocean around New Zealand is derived from the temperature and salinity data available from the region between latitudes 28°S and 56°S and between 158°E and 174°W. The “SOFAR channel” is established throughout the area northwards of the Antarctic Convergence, with its axis in a depth of about 1,300 m. Little variation in the depth of this axis was found except in the southern part of the subantarctie zone, where the weak vertical temperature stratification cannot maintain a velocity minimum; the axis of the SOFAR channel tends to decrease in depth as it loses its identity. In the northern part of the subantarctie region, a second channel was found at a depth of about 100 m. The depth of the axis of this “subantarctie channel” increases to about 500 m under the surface outcrop of the Subtropical Convergence. It loses its identity at about 400 m in the stronger vertical temperature stratification of the subtropical region. To the south of the Antarctic Convergence, an “antarctic channel” was found with its axis at a depth of some 400 m in a temperature inversion between Antarctic Winter Water and the underlying Pacific Deep Water.

Sound velocity on the surfaces defined by the channel axes is mapped. A ridge of maximum SOFAR velocity is defined extending east and west of the northern part of New Zealand. This feature does not seem to appear in the north Pacific and has been tentatively associated with the dynamics of east‐flowing subtropical currents in this region.     

The range-averaged intensity model: a tool for underwater acousticfield analysis

The range-averaged intensity model (RAIM) long known as a powerful method for transmission loss estimation in waveguides, is extended to other aspects of the acoustic field: impulse response and angular pattern estimations at a receiver, general time spreading in a waveguide, signal fluctuations, reverberation levels, and ambient noise structure. An example of its application to a SOFAR propagation and detection case is presented. This method appears to be a very efficient and reliable analysis tool for many underwater acoustics configurations: particularly long-range horizontal telemetry and shallow-water sonar     

VLF source localization with a freely drifting acoustic sensorarray

The source localization and tracking capability of the freely drifting Swallow float volumetric array is demonstrated with the matched-field processing (MFP) technique using the 14-Hz CW data collected during a 1989 float experiment conducted in the northeast Pacific. Initial MFP of the experimental data revealed difficulties in estimating the source depth and range while the source azimuth estimate was quite successful. The main cause of the MFP performance degradation was incomplete knowledge of the environment. An environment adaptation technique using a global optimization algorithm was developed to alleviate the environmental mismatch problem, allowing the ocean-acoustic environment to be adapted to the acoustic data in a matched-field sense. Using the adapted environment, the 14-Hz source was successfully localized and tracked in azimuth and range within a region of interest using the MFP technique at a later time interval. Two types of environmental parameters were considered, i.e., sound speed and modal wave number. While both approaches yield similar results, the modal wave number adaptation implementation is more computationally efficient     

Experimental measurements of the complex motion of a suspended axisymmetric floating body in regular and near-focused waves

Numerical models which account for the multiple response modes of floating wave energy converters (WECs) in operating conditions require experimental data for validation. Measurement and observation of complex hydrodynamic mechanisms are also required to inform the development of modelling tools suitable for the simulation of response to extreme waves. Experimental measurements are reported of the motion of an axisymmetric float to regular and near-focused waves. The mechanical system, incident wave conditions and response in a 2D vertical plane are detailed to facilitate comparison to numerical simulations. The system comprises a heaving float connected to a counterweight by an inextensible cable over two pulleys to provide a simplified representation of the slowly varying surge constraint of a mooring system. Translation of the float is measured using an optical encoder. Motion in heave, surge and pitch are also determined by a position identification method based on analysis of video footage. For low frequency regular waves, the float prescribes an elliptical trajectory and the variation of response amplitude with wave amplitude is linear. At higher frequencies, drift of up to one-third of the float radius is observed and the float oscillates along an arc. More complex motions are observed due to the three large amplitude waves of a near-focused wave group. During these waves the upper surfaces of the float are partly immersed and motion occurs in heave, surge and pitch.     

我国Argo浮标的设计与研究

自沉浮式剖面探测浮标是一种海洋观测平台,首先应用在国际Argo计划,故又称之为Argo浮标,专用于海洋次表层温、盐、深剖面测量。仪器布放后自行在大海中工作2a以上,直至电源耗尽;2004年11月8日实验的Argo浮标潜入深度已达到1900m,历时两年的浮标研究工作,在下潜深度、上浮水面、剖面测量、数据处理、卫星传递数据等功能上已经达到国际Argo组织的要求。文章详细阐述了剖面浮标的设计与研制内容和各种试验项目及所得数据,不仅为浮标设计提供科学的实测数据,还为今后该仪器产品化进程提供大量可靠依据和检测方法。     

关于发展我国漂流浮标和锚泊浮标技术的建议

本文综述了90年代国外漂流浮标和锚泊浮标技术的发展动态,从战略发展的高度提出了研制多参数表层漂流浮标、多次往返式剖面仪、绷紧式锚泊浮标和水质监测浮标的建议,并分析了国内的需求和相应的研究基础.     

极地冰藻极端海冰生境适应机制及其受气候变化的影响

冰藻是南北极海冰生物群落中最主要的组成部分,通过固定和输出碳、吸收养分、生产释放氧气和有机化合物,推动高纬度生态系统的生物地球化学循环,在南北极海洋生态系统中发挥着重要作用.从宏观到微观综述了近年来在海冰栖息环境特征、冰藻种类组成和群落结构、冰藻对极端环境的适应机制以及气候变化对海冰环境和冰藻的影响等方面的研究进展,并...     

GNSS-Based Sea Level Monitoring

This paper attempts to assess the use of Global Navigation Satellite System (GNSS) as an accurate, reliable, and easy tool for sea level measurement. The GNSS technique was incorporated into a float based tide gauge system. A prototype of such an instrument was developed based on principles of conventional tide gauges, where high frequency noise is reduced mechanically. The ability of the GNSS based tide gauge (GTG) to monitor sea levels was tested in several experiments. The performance of the GTG was compared to that of a traditional tide gauge. The method of data analysis and data comparison between the GPS measurements and the tide gauge data is presented. The results show that the GTG is equal in performance to the traditional float operated tide gauge. It seems that the GTG is capable of delivering the same level of accuracy (1 cm), and its results are as reliable as its competitor, the traditional float tide gauge. The suggested instrument can be easily integrated into the array of permanent GNSS stations and assist in absolute measurements of sea level changes, caused by global warming and the greenhouse effect, for example.     

GNSS-Based Sea Level Monitoring

This paper attempts to assess the use of Global Navigation Satellite System (GNSS) as an accurate, reliable, and easy tool for sea level measurement. The GNSS technique was incorporated into a float based tide gauge system. A prototype of such an instrument was developed based on principles of conventional tide gauges, where high frequency noise is reduced mechanically. The ability of the GNSS based tide gauge (GTG) to monitor sea levels was tested in several experiments. The performance of the GTG was compared to that of a traditional tide gauge. The method of data analysis and data comparison between the GPS measurements and the tide gauge data is presented. The results show that the GTG is equal in performance to the traditional float operated tide gauge. It seems that the GTG is capable of delivering the same level of accuracy (1 cm), and its results are as reliable as its competitor, the traditional float tide gauge. The suggested instrument can be easily integrated into the array of permanent GNSS stations and assist in absolute measurements of sea level changes, caused by global warming and the greenhouse effect, for example.     

T-phases from an earthquake swarm on the mid-Atlantic ridge at 31.6° N

An ocean bottom seismometer array on the Nova Scotia shelf edge recorded T-phases from an earthquake swarm on the mid-Atlantic ridge at about 31.6° N in June 1975. The swarm occured along a segment of the ridge that ruptured similarly 17 yr previously. From 1964 to mid-1979 the worldwide network recorded three other earthquake swarms along this segment of the mid-Atlantic ridge (MAR). A sparse network of sensors in the SOFAR channel, having a lower magnitude threshold, might provide a better means of monitoring the seismicity of both short-length transforms and ridge crests along the MAR than does the worldwide seismic network.     

Principles for operationalizing climate change adaptation strategies to support the resilience of estuarine and coastal ecosystems: An Australian perspective

Effective publicly developed adaptation strategies are crucial in managing the impacts of Climate Change. Adaptation strategy development is particularly complex in estuarine and coastal marine ecosystems because of their diverse environmental values, extensive human utilisation and the complex socio-ecological systems they support. Although many generic adaptation frameworks are available they cannot provide specific guidance for locally relevant strategy development. In contrast, situation-specific tools work well for their intended purpose but are usually unsuitable for a different situation. The gap between generic frameworks and situation-specific tools is addressed in this study by developing a set of general principles to provide guidance for the efficient and robust development of adaptation strategies. The nine principles comprise a conceptualisation of the various factors that are likely to have an effect on the success or otherwise of an adaptation strategy and they apply in any situation. An example ‘adaptation checklist’ that serves as a guide to practitioners in the field, will help ensure that all critical components are covered during the development of an adaptation strategy.     

潜标式海洋探测仪控制系统及模块设计

基于CORTEX M4内核的STM32嵌入式系统,设计并实现了用于长期监测海洋地理环境参数(温度、盐度、湿度等)的潜标式海洋探测仪,给出了主控系统及各个模块的设计方案及选型,通过合理的功能分配,可靠的硬件设计和有效的软件实现,使探测仪具备低功耗、高可靠的特点。海试实验表明,主控系统实现了对探测仪的浮力调节、能源供电及应急处置等状态控制,通过在SOFAR声道工作,完成了对深海海洋要素的实时监测。     

An estimation of the average lifetime of the latest model of APEX floats

Estimating the average lifetime of floats is very important for Argo, because the total cost of maintaining the monitoring network largely depends on float lifetime. However, the actual lifetime of floats used in Argo is currently unknown. An estimate can be made by examining past float survival, but this is complicated by floats still operating at sea and continuous improvements in float hardware. Because APEX (Autonomous Profiling Explorer) floats are the most widely deployed type of float in the world oceans, in this study we estimate the lifetime of the latest model of APEX powered by alkaline batteries. The expected lifetime is estimated with a statistical method that allows for floats that are still active and that failed because of a known and now fixed hardware fault that should not cause failure in the latest model of floats. As an example, we analyzed the APEX fleets managed by the Japan Agency for Marine-Earth Science and Technology (JAMSTEC), because we have access to a JAMSTEC database in which the causes of float failure have been carefully correlated to known hardware problems. Analysis of the JAMSTEC fleet (n = 571, as of 7 May 2008) indicated that the expected lifetime of the latest model of APEX is 134.6 (127.6–141.5, considering standard errors) cycles, equivalent to 3.7 years of 10-day cycles. We conclude that the annual deployment of 813 (773–859) APEX floats is needed to maintain the Argo observational network of 3000 floats. Floats with different hardware configurations (e.g., lithium batteries) or different mission programs (e.g., shallower profiling, deeper profiling every several cycles) may be expected to have an even longer lifetime.     

基于海洋渔业发展的海洋科考船建造和应用

为提高我国海洋科考船的建造和应用水平,促进远洋和极地渔业发展,文章根据国内外海洋科考船的发展历史和现状,分析我国海洋科考船在海洋渔业发展中存在的问题以及海洋科考船的发展趋势,并提出相关建议。研究结果表明:国际海洋科考船发展早、数量多且装备先进;我国海洋科考船发展较快,但仍需提升数量和技术,在建和研发船舶具有世界领先水平;在促进海洋渔业发展方面,我国海洋科考船存在远洋和极地调查能力以及集成功能较弱的问题;基于海洋科考船在提高极地作业能力等方面的发展趋势以及海洋渔业发展需求,我国海洋科考船的建造和应用应加强顶层设计、技术应用和数据共享。     

海洋牧场生态环境在线监测物联网技术研究

海洋牧场生态环境在线监测网是海洋牧场建设的重要发展方向之一.传统海洋监测系统体积大、功耗大、价格昂贵,受牧场建设的经费限制,无法大量投放组成监测网,迫切需要一种低成本的海洋监测手段,可负担大面积、高空间密度的投放,并以分布式的物联网方式进行组网监测,解决这一难题.本文基于MEMS技术研发可大量"群蜂式"布放、高时空分辨...     

滑模摊铺机在混凝土路面施工中的应用

泰曲路(泰安-曲阜)改造工程三合同段的混凝土路面采用滑模摊铺机进行施工,滑摸摊铺机在不用固定模板的情况下可以连续完成摊铺、振动、刮平、成形、抹光以及打设传力杆等工序,工艺先进,具有一定的推广价值。     

基于机器学习的海洋浮标寿命及轨迹预测

Argo计划(Array or Real-time Geostrophic Oceanography)为海洋和大气研究提供了宝贵的资料,在短期天气预报和长期气候预测中起到了重要作用.为保证Argo观测阵列的正常运转,需要时刻关注浮标的运行状态,以保证研究区域内维持一定数量和密度的浮标.然而Argo浮标投放费用高昂,投放...     

Wave attenuation characteristics of a tethered float system

Wave attenuation characteristics of a tethered float system have been investigated for various wave heights, wave periods, water depths, depths of submergence of floats and float sizes. As the floats are similar in size and shape, only a single tethered spherical float is considered for the theoretical analysis. Float motion is determined through the dynamical equation of motion, developed for a single degree of freedom. From incident and transmitted wave powers, transmission coefficients are computed. The results show that transmission coefficient does not vary with changes in wave height or water depth. When depth of submergence of float increases, wave attenuation decreases, showing that the system performs well when it is just submerged. As float velocity decreases with increase in float size, transmission coefficient increases with increase in float size. The influence of wave period on wave attenuation is remarkable compared to other parameters. The effect of drag on wave attenuation is studied for varying drag coefficient values. Theoretical results are compared with experimental values and it is found that theory overestimates wave attenuation which may probably be due to various linearisations involved in the theoretical formulation.     

有效吸收和传递波浪能的锚泊系统的设计制作

将传统定位浮标加以改进,可以形成一种能有效吸收和传递波浪能的锚泊系统。此系统的最上端是漂浮着的海面浮标,海面浮标下端连着锚泊钢缆,锚泊钢缆下端到海底之间又依次连有张紧锤、储链和重物锚块。锚泊系统中的海面浮标随波浪同步上下起伏,从而带动与其连在一起的由张紧锤绷直的锚泊钢缆上下振动,于是海面浮标吸收波浪能并由引导缆向下传递。20 m长的储链可以保证整个装置在涨潮、退潮的极限水深情况下,仍旧可以有效地传递海表面波浪能;合适的重物锚块可以起到为整个系统定位的功能。最后给出了一个实际应用波浪能的例子。设计制作的锚泊系统可以有效吸收和传递波浪能,为波浪能的利用提供了一种行之有效的方法。