Scientists track noisy icebergs across world's oceans

CORVALLIS, Ore., July 11 (UPI) -- Icebergs drifting from Antarctica to warmer waters produce levels of noise as they melt that could potentially affect some ocean dwellers, researchers say.

The breakup of ice sheets and the calving and grounding of icebergs can create enormous sound energy, they said, but even floating icebergs can be the source of noise.

Oregon State University researchers used hydrophones to track the sound produced by an iceberg through its life cycle, from its origin in the Weddell Sea to its eventual demise in the open ocean.

"During one hourlong 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," marine geologist Robert Dziak said in an OSU release Thursday.

"This wasn't from the iceberg scraping the bottom," he noted. "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."

The researchers followed the iceberg for two months until it broke up.

"You wouldn't think that a drifting iceberg would create such a large amount of sound energy without colliding into something or scraping the seafloor," Dziak said. "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."

Sounds, both natural and human-caused, may affect marine life, especially animals that use sound for activities such as feeding, breeding and navigation, the researchers said.

"The breakup of ice and the melting of icebergs are natural events, so obviously animals have adapted to this noise over time," Dziak said. "If the atmosphere continues to warm and the breakup of ice is magnified, this might increase the noise budget in the polar areas.

"We don't know what impact this may have."