Wille P.C. Sound Images of the Ocean in Research and Monitoring

Springer, 2005. — 504 p.The particular fascination evoked by many of the sound images of the sea floor presented in this book has changed its character since the 26th December 2004. Formations of scientific and general interest, where large parts of the sea floor, the tectonic plates, are being subducted under adjacent tectonic plates have now become a frightening subject of another dimension. The mechanisms of destruction of human settlements by tectonic processes were known before: the majority of earthquakes and volcanism happen at or near plate margins. History reports of giant waves, propagating at enormous speed, which devastated coastal areas. The Japanese, overrun by the largest number of this kind of deluge, generated by a sudden uplift of the overriding tectonic plate, named them Tsunami. Through the last four centuries nearly two dozen giant Tsunamis have been recorded, each of which killed from more than 2 000 up to 40 000 people. The Sumatra Tsunami of December 2004, when presumably more than 300 000 died and millions became homeless, is unparalleled in history however: an apocalyptic catastrophe. The earthquake magnitude 9.0 is one of the highest ever recorded and corresponds to the energy of 32 000 Megatons TNT. The disaster, unimaginable before, has created an overwhelming response in charity worldwide, but has made us aware again that we are living on the cool but fragile skin of a glowing globe of which we still know only little. The need for a global Tsunami warning system has become strikingly evident. Though earthquakes cannot be predicted, they can be detected, localized and measured in magnitude, and the arrival of resulting Tsunamis, propagating oceanwide, can be made known in advance to save human lives.
The compilation and preparation of this book was completed before the date that shocked the world. However, the publisher has agreed to insert an image of the sea floor relief with the epicenter area in the Indian Ocean. This image, on short notice personally prepared and provided by the Director of the Center for Coastal and Ocean Mapping, L. Mayer, USA, is based on the Sandwell and Smith predicted topography data from NGDC, available prior to the Sumatra Tsunami. Scientific evaluation of actual seismic records in detail and subsequent mapping of the area in near future by high resolution sound imaging will throw light on the origin of this tragedy.
This book is the first attempt to publish a comprehensive overview of the wide variety of acoustic applications in the fields of research, of utilization, surveillance and protection of the ocean. This sound image collection covering a large number of subjects and sites of the world’s oceans and coastal waters is both interdisciplinary and international. It has been enabled by the generous support of more than 120 experts and sound image authors from 22 countries. The images have been selected as representative of the work of the image authors and their subjects. These subjects range from the evidence of plate tectonics and continental shift and from methanehydrate deposits, containing more than twice the amount of all other carbon hydrates on Earth, to indications of ocean warming imaged by acoustic tomography; from submerged cities to historic ship wrecks; from large submarine canyons to huge landslides; from sea lane surveillance and biomass monitoring to images and sound tracks of whale echosounding and communication; from sub-polar ice imaging to steering of the Gulf stream by undersea topography; and from the Arctic Ocean to Antarctica. Unlike the continents and islands inhabited and shaped by man, the deep sea, much more than the continental shelf, is the exclusive territory of nature with marginal human impact hitherto, apart from relics of ship disasters and wars through the centuries and communication cables in the last few decades.
The book is not a high-resolution sound imaged atlas of the world’s sea floor. Two-thirds of the globe is ocean, and only a low percentage of ocean floor has been sound imaged by advanced technology so far. Nevertheless, the book does provide a global atlas of the hidden side of the Earth, albeit in less detail. All available echosounder data – the sparse sounding lines in remote areas of the world as well as the denser measurements near coasts and sea lanes – has been merged with satellite radar data of the sea surface relief, providing a coarse copy of the sea floor beneath. The weak bulges and dents are generated by gravity anomalies which attract the sea volume above a submarine mountain slightly more than above a valley. The merger of these two independent data sets, combined to form a complete globe – a pioneering work by leading experts – is the best possible overview at present of the nearly infinite variety of sea floor formations. This overview has become indispensable as a guide for site selection of follow-on high resolution acoustic close-ups of the outer relief and the structure below, to reveal the details of processes for further on-site research. The CD included with the book allows zooming and turning of the relief globe, as well as of very large sound images.
The book demonstrates the capability of the various technologies of sound imaging as diagnostic tools – similar to ultrasonics in medicine – but the aesthetic appearance of many of these images evokes appreciation beyond mere information. The book is intentionally written for the non-expert who may be a scientist from a neighboring faculty. All comments and textual documentation accompanying the image collection, as well as the introduction to the basic facts of ocean acoustic imaging, have been reviewed and supplemented by the respective experts. The intention is to raise and maintain interest in those formations and processes of the ocean which are beyond the access of photography – by far the majority.The Basic Facts of Imaging the Ocean
Preliminary Remarks
Alternatives to Imaging the Sea by Sound and First Acoustic Trials
Acoustic Features of the Sea
Technical and Physical Characteristics of High Resolution Echosounders
Applications of Acoustic Imaging the Ocean
The Sea Floor – Natural Formations
The Ocean Volume
Man-made Matter
Final Remarks