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U.S.: Study Documents Increase in Ocean Noise |
| September 17, 2006 |
 | | Increasing noise from shipping poses a threat to marine life such as killer whales, pictured, by interfering with their ability to communicate and navigate using sound. Photo: Doug Sandilands |
With human populations increasing around the globe in recent decades, no one would be surprised by an increase in the amount of noise on land.
Now, a unique study involving researchers at Scripps Institution of Oceanography at the University of California, San Diego, has shown that the underwater world also is becoming a noisier place, with unknown effects on marine life.
New research published in the August issue of the Journal of the Acoustical Society of America (JASA) has shown a ten-fold increase in underwater ocean noise off Southern California's coast, compared with the 1960s. Mark McDonald of WhaleAcoustics in Bellvue, CO and John Hildebrand and Sean Wiggins of Scripps Oceanography accessed acoustic data recorded in 1964-1966 through declassified U.S. Navy documents. They compared the historical data against acoustic recordings made in 2003-2004 in the same area off San Nicolas Island, one of the Channel Islands more than 160 miles west of San Diego.
The results showed that noise levels in 2003-2004 were 10-12 decibels higher than in 1964-66, an average noise increase rate of three decibels per decade. The culprit behind the increase, according to Hildebrand, appears to be a byproduct of the vast increase in the global shipping trade, the number of ships plying the world's oceans and the higher speeds and propulsion power for individual ships. The noise detected off Southern California originates from ships traveling across the entire North Pacific Ocean.
"We've demonstrated that the ocean is a lot noisier now than it was 40 years ago. The noise is more powerful by a factor of 10," says Hildebrand, a professor of oceanography in the Marine Physical Laboratory at Scripps. "If we've doubled the number of ships and we've documented 10 times more noise, then the noise increase is due to both more ships and noisier individual ships than in the '60s. And that may be because the ships are now bigger, faster and have more propulsion power.”
Hildebrand says the impact of the increased noise on marine animals is unknown. "If impacts are shown to exist, what can be done to protect marine animals? For instance, it may be appropriate to move shipping lanes away from areas where there are concentrations of marine animals," he says. "The impact of ocean noise pollution may be minimized by diminishing the noise source or by separating the noise from things that are sensitive to it."
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