Glacial Fjords Produce One of the Loudest Natural Marine Environments

Researchers investigate how bubbles escape from melting ice that's found underwater glacial fjords.

Scientists have recently discovered that the prominent sounds provided by one of the loudest natural marine environments is the sizzle of glacier ice as it melts into the sea. The noise created by the trapped air bubbles could help provide clues regarding the rate of glacier melt. It may also help researchers better monitor fast-changing polar environments. 

Lead study author Erin Pettit, a resarcher at the University of Alaska, discusses the sound hear by many researchers--involving poppling, cracking sounds while kayacking in the frigid northern waters. 

"If you were underneath the water in a complete downpour, with the rain pounding the water, that's one of the loudest natural ocean sounds out there," she said, via a press release. "In glacial fjords we record that level of sound almost continually."

As Pettit further examines how the din is caused by melting ice, she notes that she was unable to confirm her hypothesis without research in a more controlled experiment. With the help of other researchers from the University of Texas, they studied chunks of a glacier that was mounted in a tank of chilled water. They also recorded the ice as it melted and were able to match sounds by recording the escape of bubbles from the ice. 

"Most of the sound comes from the bubbles oscillating when they're ejected," Lee said, via the release. "A bubble when it is released from a nozzle or any orifice will naturally oscillate at a frequency that's inversely proportional to the radius of the bubble," he said, meaning the smaller the bubble, the higher the pitch. The researchers recorded sounds in the 1 - 3 kilohertz range, which is right in the middle of the frequencies humans hear.

Though scientists have known for decades about the sounds, the researchers hope that their findings could be used monitor seasonal changes via sound through hydrophone recordings found in glacial fjords. 

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More information regarding this study can be found via the 166th Meeting of the Acoustical Society of America.