Noisy 'Icequakes' from Melting Icebergs Louder than Man-made Ocean Noise
The noise created by icebergs melting in the ocean equals or exceeds the sounds of man-made ocean noise, according to researchers, who suggest that the naturally occurring phenomena could potentially affect some marine species.
Oregon State University marine geologist Robert Dziak and his colleagues traveled to the Antartic and used hydrophones to track the sounds produced by an iceberg throughout its lifecycle. As an iceberg calved away from a glacier in the Weddell Sea and eventually dissipated into the ocean, the research team tracked the noise it made, finding that it produced surprisingly high noise levels.
"During one hour-long period, we documented that the sound energy released by the iceberg disintegrating was equivalent to the sound that would be created by a few hundred supertankers over the same period," Dziak said in a statement, adding that the noise was not the result of the iceberg scraping the bottom of the ocean floor.
"It was from its rapid disintegration as the berg melted and broke apart. We call the sounds 'icequakes' because the process and ensuing sounds are much like those produced by earthquakes."
Dziak, who has monitored ocean sounds using hydrophones for nearly two decades, said the results of the latest research were surprising because such a large amount of sound energy being generated without the iceberg doing any sort of colliding or scraping into the seafloor defied expectations.
"But think of what happens why you pour a warm drink into a glass filled with ice. The ice shatters and the cracking sounds can be really dramatic. Now extrapolate that to a giant iceberg and you can begin to understand the magnitude of the sound energy," he said, adding, that the noise icebergs make as they melt in the ocean travels a long way.
"In fact, the sounds produced by ice breakup near Antarctica are often clearly recorded on hydrophones that we have near the equator," Dziak said.
Possible impacts the "icequakes" can have on marine species are unknown, but recent studies on the effects of shipping noise, solar blasts and noise created from oil exploration have frequently resulted in clear effects on marine life.
"The breakup of ice and the melting of icebergs are natural events, so obviously animals have adapted to this noise over time," Dziak said.
But, Dziak added that if the atmosphere continues to warm and the breakup of ice is magnified, the volume of ocean noise may be cranked up in polar areas.
"We don't know what impact this may have," Dziak added, "but we are trying to establish what natural sound levels are in various parts of the world's oceans to better understand the amount of anthropogenic noise that is being generated."
Dziak and his colleagues' research will be published this month in the journal Oceanography.