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Measuring Ocean Currents: Tools, Technologies, and Data covers all major aspects of ocean current measurements in view of the implications of ocean currents on changing climate, increasing pollution levels, and offshore engineering activities. Although more than 70% of the Earth is covered by ocean, there is limited information on the countless fine- to large-scale water motions taking place within them. This book fills that information gap as the first work that summarizes the state-of-the-art methods and instruments used for surface, subsurface, and abyssal ocean current measurements. Readers of this book will find a wealth of information on Lagrangian measurements, horizontal mapping, imaging, Eulerian measurements, and vertical profiling techniques. In addition, the book describes modern technologies for remote measurement of ocean currents and their signatures, including HF Doppler radar systems, satellite-borne sensors, ocean acoustic tomography, and more. Crucial aspects of ocean currents are described in detail as well, including dispersion of effluents discharged into the sea and transport of beneficial materials—as well as environmentally hazardous materials—from one region to another. The book highlights several important practical applications, showing how measurements relate to climate change and pollution levels, how they affect coastal and offshore engineering activities, and how they can aid in tsunami detection. Coverage of measurement, mapping and profiling techniques Descriptions of technologies for remote measurement of ocean currents and their signatures Reviews crucial aspects of ocean currents, including special emphasis on the planet-spanning thermohaline circulation, known as the ocean's "conveyor belt," and its crucial role in climate change
This book provides a comprehensive overview of ocean electronics, energy conversion, and instrumentation. As remote (satellite) sensing becomes increasingly important, this text provides readers with a solid background of wireless sensor networks and image-processing for oceans and ocean-related energy issues. Features: * Focuses on wind energy, ocean wave, ocean tidal, and ocean thermal energy conversion * Discusses the measurements of ocean monitoring parameters such as ocean color, sediment monitoring methods, surface currents, surface wind waves, wave height and wind speed, sea surface temperature, upwelling, wave power and the ocean floor * Discusses sensors like scanner sensor systems, weather satellites sensors, synthetic aperture radar sensors, marine observation satellite(MOS) sensors, micro sensors for monitoring ocean acidification * Includes material on underwater acoustics and underwater communication * Assesses the environmental impact of generating energy from the ocean * Explores the design of applications of marine electronics and oceanographic instruments
Of all of the physical parameters of the ocean realm, the speed and direction of the movement of ocean water, otherwise referred to as ocean "current," is one of the most problematic to characterize. Currents influence the global climate, used for producing power, are crucial in determining the oil spill trajectories and ocean contaminant control, can either work against or with the movement of ships at sea and govern the movements of icebergs. Icebergs are a threat to offshore industries and marine transportations, particularly in places like the Northwest Atlantic, because of damages they can cause once they strike the oil platforms or ship hulls. They are steered by the near-surface current and not the surface current. Therefore, measurment of the real-time ocean currents at desired depths is valuable for the industries or researchers who are dealing with or studying the oceanographic data. Ocean current measurment methods that are currently being employed for ocean monitorings, are not able to measure the real-time current at certain desired depths over a larg area of the ocean. Thus, the existing current measurement methods need improvements. Limitations of the existing methods are as follows. Acoustic dopler current profilers (ADCP), are one of the most popular methods employed by most of the industries dealing with the oceanograghy. ADCPs are capable of measuring the current at any desired depth; however, their measurement method is of a point nature and they cannot measure an area averaged current data. Other techniques such as high frequency radio detecting and ranging systems (HF-RADAR) are also used to measure the surface currents (down to 15 m). These shore-based current meters with radio antenna, follow the same premise of the ADCP. In other words their measurement is dependant on the Doppler effect to determine the direction and velocity of the currents; however, they are capable of evaluating only the surface currents and not the near-surface currents (70-100 meter of depth is considered in this thesis as this is the depth oil structures are deployed in the Northwest Atlantic Ocean). Another group of instruments used for current measurement are floats and drifters which report their data to a centre device which is usually a satelite. The current data obtained with these instruments are fed into modeling systems, e.g. in (Chassignet, Hurlburt et al. 2006), for the ocean forcasting. The problems that exist with the available real-time current data from the satelite is that it is the very shallow current data (down to 15m that can be called surface). The data from other devices like floats is very sparse to include the horizontal information. Hence, Chassignet et al. use data assimilation of the past knowledge and ocean dynamics in order to predict the ocean features. Therefore, it is important to develop a method by which adequate data could be provided for the ocean prediction and modeling system. Thus, the focus of this thesis is on designing a method which is real-time and measures the near-surface current. On the other hand, energy suplies to the instruments in open water is limited as they work mainly rely on batteries and it is difficult to access the instruments in harsh condition to replace the batteries. Moreover, in cold regions the solar power is very limitted and thus using solar cells is not practical. Therefore, in order to measure the ocean current in real time, a novel method along with a sustainable architechture design is being proposed in this dissertation. The new method is based on transit time with the difference that in transit time method waves need to travel in both directions; up- and down-stream. But with a modification in the newly designed architecture; which is adding an extra node in the center of the network's cells, sound waves need to travel on only one direction. This helps with saving a great amount of energy and covering a larger area in comparison with the networks which are developed using transit time method. Experimental results as well as simulations verify that the new proposed method is both efficient and practical.
Through research, physical oceanography aims to solve the numerous problems stated by thermal, optical and dynamical properties of the oceans. Instrumentation and Metrology in Physical Oceanography describes the means used in oceanography to determine physical properties of the oceans by medium of in situ measurements. This book explores the theoretical functioning of sensors and instruments, as well as different practical aspects of using these tools. The content of this book appeals directly to technicians or engineers wishing to enhance their knowledge of instrumentation and application to environment surveillance. Instrumentation and Metrology in Physical Oceanography details the functioning of sensors and instruments used to assess the following parameters in oceanography: temperature, conductivity, pressure, sound velocity, current in magnitude and direction, time and position with GPS, height of water and tide, waves, optical and chemical properties (turbidity), dissolved gas (O2, CO2), pH, nutrients and other dissolved elements. Furthermore, this book also elaborates on the different means used to obtain measurements at sea (boats, drifting floats, moorings, undersea platforms, gliders...) and techniques currently being developed.
The objective of this project, funded by the Office of Naval Research, was to develop imaging sonar with increasingly higher resolution. With modern advancements in digital electronics, it is now feasible to digitize incoming sonar data at the carrier frequency, in this case, approximately 3 x 50 kHz. Subsequent homodying and data compression can be done using software. The sonar technology was tested on two occasions on the research platform R/V FLIP. On the first occasion it was mounted on FLIP at a depth of 20 meters and operated over a 20-day period with FLIP moored in 200 meters of deep water. In these summer experiments the mixed layer depth was very thin. The sonar was positioned in the upper thermocline, where sound is strongly downward refracted. Thus, the sonar scattered primarily from the sea surface for the first 800-meter range, and subsequently recorded a mix of surface and bottom echoes to ranges greater than 2.5 km. A second data collection opportunity occurred in Sep-Oct 2002, when FLIP was moored off the Hawaiian Island of Oahu, observing large amplitude internal waves generated by tidal flow over the Keana Ridge. Here the depth of the mixed layer was 25 meters and breaking waves, which provide subsurface bubbles as scattering targets, were common. The sonar was operated continuously for about 20 days, achieving ranges of 1.5 km from pure surface scattering. The dominant signal seen was the surface wave field, which was quite energetic during trade wind conditions. When these signals were low-pass filtered in time, images of underlying Langmuir cells emerged. Further filtering has begun to reveal the internal wave signature. The next developmental task is to create a real-time analysis and display capability to match the speed of this sonar, which digitally recorded at a rate of 100 Gigabytes per day.
During the past decade, man's centuries-old interest in marine me teorology and oceanography has broadened. Ocean and atmosphere are now treated as coupled parts of one system; the resulting interest in air-sea interaction problems has led to a rapid growth in the sophistication of instruments and measurement techniques. This book has been designed as a reference text which describes, albng with the instruments themselves, the accumulated practical experi ence of experts engaged in field observations of air-sea interac tions. It is meant to supplement rather than replace manuals on standard routine observations or instnunentation handbooks. At the inception a textbook was planned, which would contain only well tested methods and instruments. It was quickly discovered that for the book to be useful many devices and techniques would have to be included which are still evolving rapidly. The reader is therefore cautioned to take nothing in these pages for granted. Certainly, every contributor is an expert, but while some are back ed up by generations of published work, others are pioneers. The choice of topics, of course, is debatable. The types of observa tions included are not exhaustive and topics such as marine aero sols and radio-tracers are omitted, as was the general subject of remote sensing, which was felt to be too broad and evol ving too rapidly. The guideline adopted in limiting size was maximum use fulness to 'a trained experimentalist new to the field'.