The sounds by bubbles from melting ice make underwater glacial fjords one of the loudest natural marine environments on earth, suggesting glaciers sizzle as they disappear into warmer waters.
Though a lot has been said about how the planet is warming continuously, researchers from the University of Alaska provided the first "sound" evidence of a warming planet - the sizzling sound made by glaciers as they melt into warmer waters. The sound made the bubbles arising from melting ice underwater glacial fjords one of the loudest natural marine environments on earth, a press release reveals.
Researchers noted that this sound can provide clues about the rate of glacier melt and also help in monitoring polar environment changes. University of Alaska researcher Erin Pettit said, she often heard crackling sounds when she went out kayaking in the frigid northern waters. Microphones set up underwater, off the Alaskan coast, picked up such sounds, which were much louder than those recorded on the surface of the coast.
"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 in the statement. "In glacial fjords we record that level of sound almost continually."
Pettit suspected that these sounds were created by melting ice but wasn't able to prove her suspicion until she conducted a more controlled study. Seeking the help of Kevin Lee and Preston Wilson, acoustics experts from the University of Texas, the researcher carried the study further. She sent them chunks of glacier which they mounted in a tank of chilled water. They then recorded audio and video of the glacier as it melted. The sounds made matched the sounds made by the escape of bubbles from ice.
For decades now, scientists have been aware of the fact that bubbles in glaciers form when snow crystals trap pockets of air. This air gets squashed down slowly under the pressure of more ice. This compact arrangement forces the snow to turn into ice, further pressurizing the air bubbles. This method of formation also facilitates an even distribution of air bubbles throughout the ice.
"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 1 - 3 kilohertz range, which is right in the middle of the frequencies humans hear.
