Global warming may take ocean sounds back to dinosaur era

Global warming may be changing ocean sounds, taking them back to the acoustics of more than 100 million years ago when dinosaurs roamed the earth, new research suggests.

Rising temperatures increase the acidity of the oceans and allow sounds near the surface to travel further than they currently do, says Rhode Island acoustician David G. Browning.

He predicts that sounds, such as whale noises in the low-frequency sound range, by the year 2100 will be able to travel twice as far as they do now — similar to during the dinosaur age.

"We call it the cretaceous acoustic effect, because ocean acidification forced by global warming appears to be leading us back to the similar ocean acoustic conditions as those that existed 110 million years ago, during the age of dinosaurs," Browning said in a statement.

He will present his research at a meeting of the Acoustical Society of America in Kansas City next week.

His team analyzed boron, an element that affects sound absorption and transmission of low-frequency sounds, in sediments on the sea floor. This analysis allowed researchers to trace the history of boron levels through the geological record, all the way back to 300 million years ago.

His team concluded that as the ocean becomes more acidic because of rising temperatures, transmission of sounds improved.

"This knowledge is important in many ways," he said in the statement.

"It impacts the design and performance prediction of sonar systems. It affects estimation of low-frequency ambient noise levels in the ocean.

"And it's something we have to consider to improve our understanding of the sound environment of marine mammals and the effects of human activity on that environment."