Researchers recorded what they believe to be "one of the most prominent sounds of a warming planet."
Scientists identified the ominous sound of glaciers sizzling as they melt and disappear into the sea. These sounds are most likely caused by air bubbles escaping from the ice as it melts, an American Institute of Physics news release reported.
"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," Geophysicist Erin Pettit, a researcher at the University of Alaska, said. "In glacial fjords we record that level of sound almost continually."
Petit had noticed the crackling sounds while kayaking in the Alaska waters. Underwater microphones set up by Petit had also recorded the sounds; she found the sound was much louder underwater.
The researchers hope this discovery will help them learn more about the rate of glacial melt, and "fast-changing polar environments."
Kevin Lee and Preston Wilson, acoustics experts with the University of Texas, helped Petit confirm her suspicions. Petit mailed the duo a piece of glacier. Lee and Wilson set the chunk of ice up in a tub of chilled water and recorded the sounds it made as it melted. The noise matched the sounds Petit had detected.
"Most of the sound comes from the bubbles oscillating when they're ejected," Lee said "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 [one to three] kilohertz range, which is right in the middle of the frequencies humans hear.
The pressurized bubbles form when air gets trapped in the ice and squashed down by heavy snow. These bubbles are normally evenly distributed throughout the glacier. This information coupled with the sound and intensity of the escaping bubbles could help researchers measure the rate at which the glacier is melting.
