Water covers 71 percent of Earth, and what’s in and underneath it is still largely unknown. Radar doesn’t work in water, and manned explorations are impractical at all but extremely local scales. But acoustical techniques—sonar, echo sounding, and other exploration systems, including the analysis of passively collected underwater sounds—can yield immense quantities of information about the shape and contour of the seafloor terrain and the nature of the soil beneath the water, along with the temperatures, salinity, and life in the water itself.
Although IEEE has sponsored various kinds of conferences concerned with underwater acoustic exploration in Asia, Europe, and North America, South America’s first is taking place this year. Sponsored by IEEE and its Oceanic Engineering Society (OES), the IEEE/OES Acoustics in Underwater Geosciences Symposium will be held in Rio de Janeiro from 24 to 26 July. About 140 attendees from research institutions and private companies are expected.
A SEA OF INFORMATION
The symposium, known as RIO Acoustics 2013, will cover state-of-the-art and emerging techniques to investigate the water column, seafloor, and near-surface sediment of the ocean and inland waters, as well as the techniques’ application in ocean engineering, environmental management, and mineral exploration. Topics to be explored include acoustical oceanography, the characterization of underwater sediments, hydroacoustic techniques for inland waters, and marine geophysical surveys. Other areas include applications in the oil and gas industries, harbor engineering, and underwater archeology and mining. Also on the agenda are fishery acoustics, acoustic biosensing, the impact of underwater sound on marine life, and habitat mapping.
Technologies such as passive acoustical techniques, sensors and transducers, and signal and image processing are also to be discussed. Exploratory papers focus on harvesting signals from underwater ambient noise, not only to monitor shipping traffic, marine life, wave action, volcanic activity, and distant rainfall but also to investigate ocean conditions by analyzing how they transmit these sounds (the so-called inverse problem). Passive techniques are especially useful, IEEE Fellow Jean-Pierre Hermand says, for determining marine sediment properties and studying the ecology, and for determining the distribution and abundance of marine species—mammals, fish, and invertebrates—that use sound for communicating, navigating, locating food, finding mates, and protecting themselves.
More than 70 papers are expected, and plans call for keynote addresses and a special day at which companies demonstrate their technologies, answer questions, and learn about the wants and needs of the symposium’s participants.
THE LOCAL ANGLE
RIO Acoustics grew out of a special session within a more general conference, the 2011 Congress of the Brazilian Geophysical Society. That session, dealing with the techniques of remote underwater acoustic sensing, brought together a group of South American researchers who wanted a standalone event covering a wider spectrum of applications for the techniques, along with a role for equipment makers and survey companies. Arthur Ayres Neto, associate professor for marine geophysics and geoacoustics at Universidade Federal Fluminense in Niterói, near Rio de Janeiro, and invited speaker Hermand, research director for the Environmental Hydroacoustics Lab at the Free University of Brussels (ULB), organized the new symposium, which they cochair. The idea was developed while Ayres visited ULB last year, and the two schools have signed a cooperation agreement for the joint development of research projects and technical exchanges.
The symposium is an international conference, drawing papers and participants from Asia, Australia, Central America, Europe, and the United States, but much of its focus will be on South America.
“Acoustic sensing techniques and their use in underwater geosciences are not yet as widespread in South America as in Asia, North America, or Europe,” Hermand says. “The potential audience is spread all over the South American countries.”
Adds Ayres, “One of the main objectives of the symposium is to build a network of underwater-acoustics professionals in South America. Such networks are well developed in Europe, the United States, and Asia. These tools and techniques are well known in the oil industry, which has lately grown here in importance, but people here are less familiar with them.”
Underwater acoustic applications differ from country to country in South America. On the Pacific coast, thanks to the nutrient-rich upwellings off Peru and Chile, phytoplankton (on which fish feed) is abundant and so fish are plentiful. There, fisheries’ needs predominate, not just for finding fish to catch but also for monitoring fish stocks and their environment to prevent overfishing. On the Atlantic side, mineral interests predominate.
Brazil, with more than 6500 kilometers of waterways and 8000 km of coast, has varied needs. For its offshore oilfields, it wants ways to prospect for resources and determine drilling conditions, both on the continental shelf and in the deep ocean beyond, and to monitor the state of underwater pipelines. It also would like to monitor the sediment piling up behind its many hydroelectric dams—including the Itaipu, one of the world’s largest hydropower producers—and to track and maintain navigability of the shifting sediments and sandbars within the Amazon basin and extending out to sea. It, too, has fisheries, thanks to seasonal upwelling in some ocean regions.
“Oceans are essential,” Hermand says, “and preserving this essential resource will be a challenge for the next generation. Advances in ocean acoustic sensing will be key.”