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An Ear to Ocean Temperature
Controversial Project Will Shut Down at End of ’99

The Acoustic Thermometry of Ocean Climate project uses two speakers, one off the coast of California, the other off Hawaii, to send out sound waves. Receivers dotted through the north Pacific Ocean pick up those faint sounds. By measuring how long it takes the sound to travel, scientists can calculate the ocean temperatures. (ABCNEWS.com)

By Kenneth Chang
ABCNEWS.com
June 24 — A controversial project to track ocean temperatures using sound has proven it works—the measurements are precise within one-fiftieth of a degree Fahrenheit. Its findings will revise our understanding of the oceans.
    But the next step is to shut it down.


     The Acoustic Thermometry of Ocean Climate project will unplug and remove its transmitter off the California coast at the end of the year. A second transmitter, off Hawaii, will operate through the end of 1999 before getting pulled from the water.
     ATOC’s original goal—extending the system to every ocean to track the progress of global warming—remains unrealized. Even a modest follow-up to the $40 million project appears unlikely. Researchers say they don’t have the money. They also appear weary, and wary, of the effort needed to obtain another round of permits.

When Environmental Issues Collide
ATOC is the story of what happens when a scientific project to collect data on one high-profile environmental issue (global warming) runs headlong into a second, hot-button environmental issue (saving the whales).
     In the early 1990s, scientists proposed the ATOC project—essentially the world’s largest thermometer.
     The idea is simple: Put a loudspeaker on the ocean floor and play a sound. Then listen for the sound thousands of miles away. Sound travels faster in warmer water, slower in cooler water. By measuring the time between when a sound is made and when it’s heard, scientists can determine the average water temperature along the sound’s path.
     A few months before the transmitters were to be installed in 1994, the project became a topic on a marine mammal forum on the Internet. The resulting maelstrom stirred up the media and Congress.
     “It was a shock to us,” says Robert Spindel, director of the Applied Physics Laboratory at the University of Washington and member of the ATOC team. “The power of the Internet has a very dangerous side.”
     Part of the problem was a misunderstanding of how loud the speakers are.
     “It’s not that loud,” Spindel says of the ATOC sound source. ”There are whales that make sounds louder than this.”
    Part of the problem was ignorance, on everyone’s part. No one really knows what marine mammals hear, which frequencies are damaging or how sensitive their ears are.
     The resulting wrangling between ATOC scientists and the environmentalists delayed the project by a year.

Reaching a Compromise
Environmentalists and scientists compromised in June 1995. Marine mammal studies were added to the project, and the scientists agreed to go through the entire permitting process again if they wanted to continue the project after two years.
     Preliminary results from the marine mammal research indicate that whales largely ignore the loudspeakers—whales have been observed swimming toward them—although there is, on average, a slight tendency to swim away. According to Spindel, there appear to be “no biologically significant effects.”
     As for the ocean temperatures, Spindel presented some of the first results Monday at the Acoustical Society of America meeting in Seattle. “We’ve really shown what we originally hypothesized we could do,” he says.

Disagreement With Satellite Data
The ATOC results also give scientists something ponder. To date, researchers have deduced ocean temperatures indirectly from satellite data on sea levels. Warm water expands, meaning a higher sea level. However, ATOC data indicates that only about half of the change in sea levels can be attributed to temperature change, much less than had been thought.
     “There are some striking differences,” Spindel says. “The explanation for the differences is not clear.” Other effects, such as converging currents pushing up water levels, or changing salt concentrations, might be playing greater roles, he says.
     “This is the first time anyone has made an independent measurement that you can compare to the satellite,” Spindel says. “You should be able to reconcile them eventually.”

Uncertain Future
The environmental groups have not said whether they would oppose a continuation or expansion of ATOC.
     “We agreed to withhold judgment until we saw whether we could tell the (sound) source’s impact on marine mammals,” says Ann Notthoff, a senior planner with the National Resources Defense Council.
     While the scientists may attempt a new ATOC project—Spindel hints at enlisting other countries to avoid the bureaucratic hassles in the United States—the agreement with the environmentalists calls for an end to the preliminary study.
     “We’ll just turn it off,” Spindel says, “and take it out of the water.”


In This Series
Fish Hums for a Mate

Distorted Music Is an Art

Ultrasound to Kill Tumors?

Too Noisy for Newborns

Is Your Computer Really Listening?

The Power of Sound

Related Links
How to Make a Sound

How You Hear






By measuring how long it takes sound to travel through the ocean, scientists can measure its temperature to within one-fiftieth of a degree Fahrenheit.

W E B  L I N K

ATOC



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