Exploration and Monitoring of the Continental Shelf Underwater Environment

By Iftikhar B. Abbasov

There is still so much about the oceans that scientists do not know, and exploring the continental shelves of the world is a huge part of finding out more about these underwater environments.  Further to that, it is extremely important that, while scientists and engineers explore and monitor the continental shelf, no damage is done to these precious environments. That is the needle that this study intends to thread, giving scientists and engineers a better method and processes for exploring these underwater mysteries, while protecting the environment and wildlife thriving beneath.

Written by a proven scientist in this area, this book is dedicated to the unique developments of hydroacoustical equipment to monitor the coastal shelf. The results of the original experimental sonar studies with application of the parametric antenna are presented.  The book presents a survey of the modern methods and technical monitoring facilities of the coastal aqueous environment. The basic characteristics of the parametric antennas are given considering propagation of the acoustic waves in the environments with dispersion and acoustical absorption.  The author and his colleagues consider the questions of formation of the parametric antenna field in layered-heterogeneous media and the peculiarities of sounding of the interfaces and bottom sediments. Ecological monitoring methods of the basic parameters of quality and condition of the aqueous environment are analyzed. The peculiarities of diagnostics of the underwater engineering constructions when monitoring the offshore strips are described.

For both veteran engineers and students in the field alike, this breakthrough study is a must-have for any scientific library concerned with studying the oceans and especially the continental shelf.

• Language: English
• Publisher: Wiley
• Release date: Sep 12, 2018
• ISBN: 9781119488286

Book preview

Preface

At the beginning of the third millennium human civilization is faced with a multitude of global problems, including scarcity of raw material resources inland. Under these circumstances many researchers pay attention to the World Ocean, in the interior of which there is a huge raw mineral potential. Complexity in studying the World Ocean and its wealth cannot stop man on the way toward their development. Ocean development is a labor-intensive and sophisticated process. In these depths difficulties are to be expected, as with the development of the space environment. This book is dedicated to the questions of the experimental development of the shelf zone for the purpose of conservation of ecology of the marine environment.

The first chapter is dedicated to a survey of the modern methods and technical monitoring facilities of the coastal aqueous environment. The overall approach to the ecological monitoring and existing varieties of diagnostic facilities are presented. Possibilities of satellite-referenced aids of monitoring of the marine medium monitoring, searching for fish basin have been considered. We have considered the questions of monitoring and modeling of the marine ecological systems using underwater engineering facilities for analyses and predicting of dynamic of ecosystems. The survey of the modern hydro acoustical systems using autonomous underwater vehicles, their specific features and development prospects, is given.

In the second chapter we considered the questions concerning formation of the field characteristics of the hydro acoustical parametric antenna in the environments with hydro physical inhomogeneities. The generalized schemes of interaction of the elements in the adaptive hydro acoustical system with parametric antenna are demonstrated. Experimental measurement results of the basic characteristics of the parametric antenna in the environment with hydro physical inhomogeneities near field are given. Time dependencies of acoustic pressure amplitude of the differential frequency wave in the environment with unsteady structure of gas bubbles.

The third chapter presents experimental studies of spatial distribution of amplitude and phase of the acoustic pressure of the differential frequency waves of nonlinear acoustic radiators. We considered the influence of the various forms of acoustic radiators on formation of the structure of the acoustic fields of the differential frequency waves. The results of measurement of radiator parameters for graduation of sound detectors in the limited volume basin are given.

The fourth chapter is dedicated to conditions of formation of the field of hydro acoustical parametric antenna when resting of layered structures in the field of nonlinear interaction of the initial waves of pumping. Theoretically and in experiments we consider the influence of the various kinds of layered-discrete ranges and layers with diffuse interfaces. The experimental results of study when presenting the different interfaces of mediums in the region of the nonlinear interaction of the acoustical parametric antenna are given.

In the fifth chapter we consider the questions of anomalous increase of penetrating the inhomogeneous plane waves through the interface water-air. The experimental results concerning measuring transmission coefficient for the spherical waves are given, as well as the coefficient dependency on the source radiation frequency, depth of the source location and its geometrical dimensions.

The sixth chapter is dedicated to questions of nonlinear interaction of the narrow beams of the acoustical parametric antenna at vertical and inclined incidence to the interface "water – bottom sediments". The results of the basic field characteristics received in the experiments, being created with acoustic parametric antenna in water and in bottom sediments for different angles of incidence are given. As a result we have established the fact of the effective generation and transmission of P waves and transverse waves of differential frequency in the bottom sediments at vertical bottom sounding.

In the seventh chapter the results of development of the measuring equipment to develop the continental shelf are discussed. Monitoring systems demand for measurement of the force impact of the waves on the onshore facilities, offshore oil and gas platforms and sea terminals. The original suggestions for modernization of the sonar detection equipment of the navigation system based on the acoustical wave meter are given.

In the eighth chapter the results of research regarding eutrophication of the waters of the north-east part of Gulf of Taganrog of Azov Sea are presented. Geo-ecological space-time evaluation of contents of biogenes, saltiness and trophicity value was performed. We created map charts of the aquatic area, demonstrating visually distributions of the values under research. We made analysis of the ecologically allowable concentrations and reserves of different substances of waters of the study aquatic area.

The ninth chapter is dedicated to application of the parametric profilograph together with side-scanning sonar in the tasks of geology, in geo-acoustics and seismoacoustics on the sea shelf. We made analysis of bottom structures, with the purpose of searching for mineral products, construction of the engineering hydraulic structures, and evaluation of sludge contaminations for ecological control. The results of experimental works concerning investigation of the engineering structures and monitoring of the aquatic area are presented.

Editor

Prof. Iftikhar B. Abbasov

Chapter 1

Monitoring of Aqueous Environment of the Continental Shelf: The Current State

Iftikhar B. Abbasov

Southern Federal University, Engineering Technological Academy, Department of Engineering Graphics and Computer Design, Taganrog, Russia

Corresponding author: [e-mail]

Abstract

This chapter is dedicated to a survey of the modern state of the methods and diagnostic facilities of the aqueous environment of offshore strips. General approaches to the ecological monitoring of the natural environment and existing varieties of diagnostic facilities are described. The possibilities of satellite monitoring facilities of alga bloom in the areas of seas and oceans have been considered. The remote sounding methods of the effective search for fish basins, hydrological parameters: temperature of the sea surface, color of the ocean and oceanic currents are given.

We have considered the questions of monitoring and modeling of the sea ecological systems with use of underwater engineering facilities for analysis and predicting dynamics of ecosystems. The survey of modern hydro acoustical monitoring systems of underwater environment with use of autonomous underwater vehicles, their peculiarities, and development prospects are given. Developments in the area of autonomous underwater vehicles will play an important role in monitoring and studying of offshore areas.

Keywords: diagnostic facilities, aqueous environment, ecological monitoring, satellite monitoring, hydrological parameters, underwater engineering facilities, autonomous underwater vehicles, hydro acoustical monitoring systems.

1.1 Introduction

Development of sea resources of shelf zone requires use of the modern facilities and methods of ecological monitoring of the anthropogenic influence on the environment. Let us consider the basic terminology and further proceed to review the literary sources in the field of monitoring.

World Ocean – main part of hydrospace, continuous, but not solid water shell of the Earth, surrounding continents and islands and distinct with similarity of salt composition. World Ocean covers almost 70.8% of the Earth’s surface (Gross, 1972) (Dobroliubov, 2014).

Ocean – (Old Greek Ὠκεανός, by the name of the Old Greek god Ocean) – largest water body, comprising the part of the World Ocean, located among the continents, having system of water circulation and other specific features.

Continental shelf, shelf – aligned part of underwater continent edge, adjoining to dry land and characterizing of the geological structure common with it, includes sea bottom and subsoil of submarine areas, as a rule, considered within the range of 200-mile economic zone.

Marine natural environment – aggregate of components of the natural environment, natural and natural/man-made features, located within the range of continental shelf and water space over it.

Aquatic area – water air surface within the range of the natural, artificial or conventional borders.

Environment monitoring – integrated environment observations, including its components, natural ecological systems, over the processes occurring within them, phenomena, evaluation and prediction of change of the environmental state.

Within the context of this chapter the review was performed and the analysis of the modern state of studies was made in the field of monitoring of the aqueous environment of the onshore continent shelf. As a result of performed review of literature on monitoring of the shelf of the World Ocean, current studies can be conventionally classified into the topics as follows:

common monitoring and diagnostics tasks;

satellite data use for the remote diagnostics;

seismic activity monitoring of sea bottom;

fish stock monitoring;

submarine technical facilities for the archeological research;

underwater vehicles for geological exploration;

monitoring of ecosystems with use of underwater vehicles;

modern state of underwater monitoring vehicles;

hydro acoustical systems of remote shelf diagnostics.

1.2 General Monitoring Tasks

General approach to the ecological monitoring of the natural environment provides the measures as follows (Israel, 1984), (Shavykin et al., 2012):

revelation and analysis of the specific anthropogenic sources and interaction factors on the natural environment;

comprehensive analysis of the environment in the regions of possible impact;

ecological monitoring of the natural facilities and processes, exposing to impact.

Monitoring structure of the anthropogenic changes of the natural environment shall include the following basic blocks (Figure 1.1):

observance of the sources and factors of impact;

evaluation and prediction of the actual state of the natural environment.

Figure 1.1 Overall structure of monitoring of the anthropogenic changes.

In the article (Petukhov et al., 2011) the methods and results of comprehensive sea experimental studies on evaluation of the ecological state of the area of sea area are considered. The new method of ecological studies allows localizing the places and areas of soil dumping, as well as evaluates their spacious sizes to the high accuracy extent and snapping to the geographic coordinates. The contemporary information analysis has revealed stable direct dependency between availability at bottom of soil dumping and considerable growth of quantitative characteristics of the control values of the sea ecosystem contamination.

1.3 Remote Monitoring with the Help of Satellites

The need for more efficient ecological ocean monitoring has resulted lately in the noticeable achievements in the studies of algorithms of processing of color satellite photos. Data of satellite photos are widely used to reveal, map and monitor phytoplankton in the ocean. Alga blooming is an indicator of the health state of sea ecosystems. So their monitoring refers to the key parameters of the effective control of onshore and oceanic resources.

The review presented in the article (Blondeau-Patissier et al., 2014) reflects details of development of algorithms in the field of multispectral analysis of the ocean color. To understand space-time regularities of alga blooming some parameters of the environments are important such as water temperature, turbidity, solar radiation and bottom topography. In the review we also discuss the use of statistic methods of processing of satellite data to characterize the factors influencing alga blooming in the onshore and open oceanic spaces.

In view of geographic snapping of some studies in this book to the water area of the Gulf of Taganrog of Sea of Azov, let us consider some works on satellite analysis of alga blooming of this basin. The work (Shavykin et al., 2012) represents the results of the ecological studies of the Gulf of Taganrog of Sea of Azov with help of satellite spectral radiometers. The Gulf of Taganrog has very high chlorophyll phytoplankton concentration, for monitoring we worked out technology and performed the measurements in the near surface layer of chlorophyll concentration with fluorometric method. It is shown that in the Gulf of Taganrog we observe strong time and space variability of chlorophyll plankton concentration in the summer season. As per the results of the measurements chlorophyll concentration in the near surface layer of the Gulf changed up to ten times. The spots of increased contents of chlorophyll concentration were observed with size from several kilometers to half a dozen kilometers. Strong temporary variability of chlorophyll concentration is revealed in the eastern region of the Gulf of Taganrog; for several hours it changed by 20–30%.

Lately considerable success was achieved in the field of development of the airspace methods and processes of remote ocean sounding. Their application perspectives to solve the monitoring tasks of the onshore aquatic areas are based on possibility of registration with the modern remote equipment of the wide spectrum of the important parameters of the aquatic environment. The work (Bondur, 2004) considers possibilities of applying space facilities for monitoring of the onshore areas of seas and oceans. The basic parameters of the aquatic environment have been analyzed, registered with modern space facilities. They include, first of all, as follows:

variations of hydro-optic characteristics, color and turbidity of water;

changes of hydrodynamic parameters (flow fields, internal waves, turbulence, circulating flows), leading to deformations of the surface variation and changes of characteristics of the near surface ocean layer;

temperature variations in the areas of the flow fields, upwelling, interaction of turbulence and the internal waves with water surface;

fluctuations of parameters of the physical and chemical fields of the ocean, leading to temperature change, saltiness, dielectric penetration, concentration of heavy metals;

variations of the biological parameters, concentration of the basic biogene elements (nitrogen, oxygen, phosphor), acidity, phytoplankton state in the ocean;

appearance of the oil films and change of concentration of the films of the surface active agents owing to dissolved organics, leading to change of color, temperature, amplitude and frequency waving characteristics;

variation of the ocean level, caused by the tidal processes, geo-strophic currents, prevention of the catastrophic processes in the offshore strips (tsunami, seaquakes) and evaluation of their consequences.

The tasks, solved by the space means of remote ocean sounding indicate their wide possibilities. So space methods and means even today play a considerable role in ocean monitoring and its coastal zones.

In the work (Ouellette, Getinet, 2016) they consider the questions concerning the use of the processes of remote sounding for integral control and studying of sea coastal environment. The characteristics of remote sounding systems, representing interest to study oceans and coastal ecosystems are given. We determined the conceptual framework, connecting all the important components of remote sounding processes: ecosystem and contamination state, coastal natural dangerous factors, sea environment and its use, use of coastal territories and population growth dynamics. The summary of remote sounding achievements for developing countries is represented, where realization of these processes is complicated due to some technical and management problems. In general, it is assumed that to understand dynamics of sea and coastal environment a multi-disciplinary approach is required. Remote sounding is a part of this approach, which shall be used by the coastal strips in their practice.

Remote sounding methods provide wide space coverage for the sea environment surveillance. In the work (Strong, Elliott, 2017) some recommendations are given concerning effective extrapolation of monitoring results in several space scopes. The evaluation shows that the remote sounding method is the most important part of high-quality values of the ecological state of sea environment.

1.4 Monitoring of Underwater Seismic Activity

The work (Monna et al., 2014) represents data review, received by observatories GEOSTAR (Geophysical and Oceanographic STATION for Abyssal Research), and expanded in the Southern European regions: Western Iberian gulf, Ionic, Marmara and Tyrrhenian Seas. We described the quality procedure of multiple-parameter data; sea bottom is the main area for surveillance over geophysical parameters. Four interesting geophysical phenomena, connected with geo hazard are considered. In the first case, seismic processes and soil slips in the western Ionic sea were identified and localized with the help of sensory analysis based on seismometer.

In the second case, the system of early tsunami prevention checked in the western Iberian basin is described and today it is really acting in the western Ionic area. In the third case, two large volcanoes in the central part of Mediterranean: Etna and underwater mountain Marsalis are considered. Signals from seismometer and gravimeter were registered at sea bottom at depth of 2100 m, some signals from different sensors point to hydrothermal activity. Vector magnetometer at two volcanic areas helps identifying depth of magnetic lithosphere. In the fourth case, the multiple parametric analysis is represented, which was focused on searching for possible correlations between methane leaking and seismic energy outbreak in the Gulf of Izmit of Marmara Sea.

1.5 Fish Stock Monitoring

Sustainable use of sea resources requires effective monitoring and management of the fish stock in the world. In the work (Klemas, 2013) the remote sounding methods are used, contributing managing fishing fleet for more effective search of fish basins. Fish, as a rule, are joined in the ocean regions, having favorable conditions for the specific kind of fish. Some oceanographic conditions, such as sea surface temperature, ocean color and oceanic currents strongly influence the natural vibrations of the fish stock.

These states of the oceanic environment can be found and measured with remote detectors at satellites and airplanes. Remote sounding data is submitted in real time that helps fishermen save fuel and shipment fuel during the search for fish. The article describes acoustic, optical and radar detectors, installed at ships, satellites and air vessel for the purpose of predicting, modeling and controlling fishery resources.

1.6 Monitoring in the Marine Archeology

Over the past few years success has been achieved in engineering diving, which has made it more available, allowing to be loaded to the deep depths. Access is open to the underwater archeological objects in the deeper waters, which were considered inaccessible before. Since these objects are not subject to the potential risk of human interference, to provide protection of submarine cultural heritage the new approaches to monitoring methods are required. The work (Aragón et al., 2018) describes monitoring technology of archaeological objects based on photometric methods. As an example they use research on shipwrecks in the ancient Roman era in the eastern coast of Spain. The offered method gives the possibility of creating a high-precision computer model of a sea bottom map.

1.7 The Use of Underwater Vehicles for Geological Exploration

The work (Ludvigsen, Sørensen, 2016) is dedicated to research of the problems associated with autonomous sea systems, applied to sea shipment, exploration and oil and gas development, for fishing and aqua culture, science of the oceans, sea renewable energy, offshore production (Figure 1.2). Background knowledge is obtained with the help of the interdisciplinary theoretical, numerical and experimental research in the areas of hydrodynamics, structural mechanics, navigation, control and optimization. In the work we perform review of research, connected with map-making and monitoring of sea bottom and oceans. Also, we consider the question of integration of different autonomous facilities (autonomous underwater vehicles, remotely controlled transport facilities, ship systems) for the field tests in the offshore Arctic water areas.

Figure 1.2 Monitoring systems (Ludvigsen, Sørensen, 2016).

1.8 Use of Underwater Vehicles for Monitoring of Ecosystems

In the work (Dulepov et al., 2006) they consider the questions of monitoring and modeling of sea ecological systems using underwater engineering facilities for analysis and predicting of dynamics of ecosystems. The important approach to obtain quantitative information concerning ecosystems is development of the automated data collecting systems of the ecological research. This data is collected using portable recording units, automated beacons and underwater vehicles, equipped with different detectors, video cameras, systems of positioning, collecting, recording and processing of information.

Evaluation of the aquatic environment state and distribution of bottom, zooplankton organisms and alga has great theoretical and practical meaning in ecosystem research. Traditional methods of obtaining such data with the help of creepers, sweepers, beacons and divers are usually restricted according to the region’s depth and soil nature; also, they can harm biological diversity. One of the most modern and ecologically safe technologies of biomonitoring is based on using non-habitant underwater vehicles. Underwater works can be used more effectively for ecological monitoring of the aquatic environment in the near bottom layers, including evaluation of hydro chemical water state by means of detectors: oxygen content, salt content, pH, temperature, electrical conductivity, water turbidity, chlorophyll concentration.

In the water column with the help of underwater vehicles we can perform work on evaluation of turbidity, illumination intensity and oxygen content to calculate productive possibilities of plankton communities. With this purpose evaluation of density of microalgae per unit of volume and chlorophyll content is performed. An underwater vehicle, equipped with digital video camera and system of detectors, allows obtaining the objective information of biocenosis and parameters of the aquatic environment. Depending on the kind of research, the underwater vehicle can be equipped with different problem-oriented systems of detectors to solve the tasks of marine culture, ecological monitoring, and video monitoring of underwater landscapes.

The overall scheme of ecological research of sea ecosystem can be presented in the form of several blocks, connected with each other in structure and functions (Figure 1.3). Based on the experimental data, we have obtained data on biology, metabolism, ration, fertility of kind of populations of the Far East seas. Mathematical models of reproduction of Pacific salmon have been developed and studied, allowing an evaluation of the efficiency of the artificial and natural reproduction and possible catching volumes.

Figure 1.3 Ecological research scheme.

The underwater vehicles can be used for ecological monitoring of the aquatic environment in the near bottom layers more effectively. This technology includes exploration of sea bottom, bottom biocenosis, and map-making for evaluation of state of ecosystems. The main tasks concerning studying the state of bottom ecosystems can be determined as (Dulepov, Leluikh, 2007):

monitoring of the aquatic environments in the near bottom layers;

monitoring of bottom biological communities;

monitoring of bottom landscapes.

Technology of investigation of sea bottom ecosystems is based on using data measurement system of the underwater vehicle TSL, created in the Institute of problems of sea technologies of the Far East department of the Russian Academy of Sciences. TSL vehicle allows selecting the set path of travel in real time, equipped with color video camera and digital photo camera. Validation of monitoring technology of bottom ecosystems with the help of the underwater vehicle TSL was performed at range in different time periods.

The work results (color video images of sea bottom, digital photo images, acquisition parameters and measurement data) were recorded in the on-board computer for subsequent processing. Creation of the system of monitoring ranges of bottom ecosystems using underwater robotic engineering allows following the state of ecological systems long term. The landscape’s map-making of shelf zone and monitoring of bottom ecosystems can solve the tasks of the environment protection, maintaining biological diversity of the coastal sea regions.

Autonomous underwater vehicles AUV have a wide range of applications in sea geophysics and they are used increasingly for scientific, applied and commercial purposes (Wynn et al., 2014). Their capability to operate autonomously from the base vessel makes them comfortable for research of extreme conditions, from the deepest dimples up to polar ice sheets. They have transformed mappings of the sea bottom by providing map-making data of higher resolution than from the surface ships.

The main regions of the autonomous underwater vehicles are as follows:

research of underwater volcanoes and hydrothermal sources;

map-making and monitoring of ecosystems;

map-making of benthic habitats under conditions of shallow-water and deep-water basins;

map-making of the morphological composition of sea bottom, ice cover.

The work (Wynn et al., 2014) represents a series of new data, which underline the growing generality of geophysical research with application of the autonomous underwater vehicles, including as follows:

multifrequency acoustic imaging of the underwater environment, coral reefs;

collecting of photos of sea bottom of high resolution.

Future advanced developments in the field of the autonomous underwater vehicles will play an important role in exploration of sea geophysics. In the work (Naumov, Matvienko, 2011) they considered advantages and the main regions of application of the autonomous underwater vehicles. The existing robotic engineering complexes are used when performing prospecting works, at geological survey of sea mineral resources, in the scientific research on hydro acoustics, ecology and sea biology. The state of the autonomous underwater vehicles of being relevant at market of underwater engineering works is provided by their key