The Sound of Glacial Calving

Listening to the unique creaks and cracks of an arctic fjord, six researchers affiliated with the Polish Academy of Sciences recorded the sounds glaciers make as they break off into water. The recordings are being used in an important effort to better understand this process of breaking off, called calving.

Glacial calving is “poorly understood” according to the researchers who published a new article in the scientific journal, Geophysical Research Letters, titled, Underwater acoustic signatures of glacier calving. However, through their research they successfully identified three distinct ways that glaciers calve, typical subaerial, sliding subaerial, and submarine. Basically, whether the piece of ice breaking off was falling outward from the top of the glacier, like a person jumping off the top, sliding straight down the face of the glacier, like something very slowly sliding off the top, or was actually breaking off underwater and shooting up to the surface, like a person swimming back up after falling in.

An image of three types of glacial calving and their sound signatures.
Types of glacial calving from Glowacki et. al, 2015.

Although glaciers around the world, by definition, are all large masses of ice that last year-round and slowly move, they vary in size, shape, speed, and importantly, location. Eventually, many glaciers terminate at bodies of water. Glaciers that terminate at bodies of water with tidal patterns, like oceans fjords, and sounds, are called tidewater glaciers. Tidewater glaciers are a form of calving glaciers, which break off into chunks as they push forward into bodies of water, creating icebergs.

This new article adds to our understanding of this process in a novel way. By recording the sounds of the calving process the researches overcame previous obstacles in monitoring these events. In the past, keeping track of tidewater glacial calving was difficult due to the lack of sunlight in the poles and the poor quality of satellite imagery. However, using relatively cheap and simple underwater microphones, called hydrophones, attached to a buoy, the researches identified the distinct sound signatures of the ice slowly melting, cracking and expanding, and eventually, breaking off from the glacier altogether. The researchers then combined the calving sound signatures with photographs from a GoPro camera they had set up to monitor the events visually, allowing them to identify and confirm the three distinct types of calving.

They say that by continuing to monitor the underwater sounds glaciers make, scientists will be able collect more data on how, and how much, glaciers around the world are breaking off into the bodies of water in which they terminate. This will help to better understand the calving process itself, as well as allow them to keep better track of how quickly glaciers are melting due to climate change.

This is important, because tidewater glaciers contribute more water to global sea level rise than any other type of glacier, and by some counts, contribute more water to sea level rise than the Antarctic and Greenland Ice Sheets combined.

By establishing the connection between the visual and audio information the researches established that these sound signatures did in fact correspond to these particular types of events, and presumably, could be used on its own in the future– giving scientist a cheap and easy monitoring tool to gauge glacier calving around the world.

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