Editor’s Note: Call to Earth is a CNN initiative in partnership with Rolex. Michel Andre is a Rolex Awards Laureate.
Snap, crackle, pop: the sound of a glacier. The large bodies of densely packed ice may look like motionless masses, but they flow and fracture and grow and shrink, and these processes are anything but silent.
In fact, glacial ice is famously fizzy. Cubes of it have long been used on cruise ships in Alaska, added to a Scotch or a gin and tonic, as the ice gives off a unique hiss when it slowly releases the highly pressurized air that has been trapped there for hundreds and sometimes thousands of years.
But the sounds made by glaciers can be used for more than just novelty ice cubes. With many glaciers around the world shrinking because of the climate crisis, scientists are looking to analyze these noises to predict exactly how quickly ice is melting and what that could mean for sea-level rise.
“Glaciers are undergoing rapid retreat as the atmosphere and the ocean warms,” says Grant Deane, research oceanographer at Scripps Institution of Oceanography in San Diego, California. “If we want to (forecast) sea-level rise … we need a way of monitoring these glacial systems and underwater sound could be an important and interesting way of doing it.”
Deane, who has worked in the field of underwater sound for more than two decades, explains that there are two main processes by which glaciers retreat, both of which make a distinct noise. There is the “bright, energetic sound of bubbles exploding into the water as ice melts,” he says, which he compares to fireworks or sizzling bacon. And there is the “deep, ominous rumble” of a calving event, when a block of ice breaks off from the end of a glacier, which he says sounds like extended thunder.
Both events happen in the boundary where the ice meets the ocean, typically a very dangerous area for humans. That’s one reason why acoustics, which can be monitored from afar, could be so valuable.
Using underwater sound to predict ice melt is still a relatively new field. In 2008, distinguished oceanographer Wolfgang Berger co-authored a piece in the scientific journal Nature Geoscience that proposed using hydroacoustics (sound in water) to monitor Greenland’s ice sheets. That inspired Deane – who was already listening to the ocean’s breaking waves to understand how gases transfer from sea to air – to turn his ears to glaciers.
“As the ocean rises, it’s going to impact so much of our civilization. We need to be able to forecast the stability of these ice sheets so that we can plan well and live well as our environment changes,” he says.
Using underwater microphones to record the sound of calving events in Hans Glacier, at Svalbard, northern Norway, along with time lapse photography, Deane and Oskar Glowacki from the Polish Academy of Sciences demonstrated th