The birth of an iceberg can be violent. When they have sloughed off glaciers, these calving chunks of ice are accompanied by shotgun cracks of sound and crashing waves. Once loose, icebergs drift out to sea, at the mercy of winds and ocean currents. But it turns out that icebergs might not all go quietly into the night.
In fact, the death of an iceberg is surprisingly loud, according to new research published in the July issue of the journal Oceanography. The amount of energy released during the 20-minute breakup of one of these floating islands of ice in Antarctica is equivalent to the noise produced by about 214 supertankers.
Although previous researchers have recorded the sounds icebergs make when calving or running aground, this is most likely the first time anyone's reported the sounds of an iceberg breaking up over open water, said study leader Bob Dziak, a geophysicist studying earthquakes and volcanoes at Oregon State University and the U.S. National Oceanic and Atmospheric Administration.
The 37-mile-long (60-kilometer-long) iceberg emitted what sounded like tortured groans, shudders, and cracks as it ran aground, spun around, scraped along the seafloor, and then broke up over open water. The noises as the iceberg broke apart, called an icequake, were so loud Dziak first thought he was listening to a volcano.
But when he pinpointed where the noises were coming from, a nearby iceberg, A53, tipped him off to the true source of his acoustic haul. "It surprised me how much energy was being released during these events," Dziak said. "I didn't expect that."