As Glaciers Melt, They Hum Too

Posted by on Nov 4, 2014

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Researchers discovered a humming sound coming from the Gorner Glacier next to Gornersee (the tiny lake in blue) in Switzerland. (silent7seven/Flickr)

Researchers discovered a humming sound coming from the Gorner Glacier next to Gornersee (the tiny lake in blue) in Switzerland. (silent7seven/Flickr)

The hills are alive with the sound of… humming? Scientists from the U.S., France and Switzerland recently found that as glaciers melt, they make a low humming sound as water passes through them, according to a new study appearing last month in the journal Geology.

The phenomenon was first observed in the Swiss Alps when a research team placed seismometers near a glacial lake dammed by the Gorner Glacier on the side of the Monte Rosa Massif in an effort to monitor signs of glacier lake outburst floods (GLOFs). As the water from the lake drained through the glacier, the seismometers picked up tiny “harmonic tremors” in the mountain glacier, as well as similar humming sounds made by icequakes near the glacier’s base.

Sliding Fourier transforms (SFT) of 2007 data at the station nearest lake Gornersee, Switzerland (double triangle in Fig. 1), reveal gliding harmonic tremor during a 15 h period on 13 July 2007. The sudden step changes in harmonic tremor frequencies are indicative of hydrofracturing at englacial water-fi lled fractures. A: SFT of data collected from 12 July to 15 July 2007 (7/12–7/15). B: Enlargement of the 13 July record reveals tremor signal in detail. (source: David S. Heeszal, et al./Geology)

Sliding Fourier transforms (SFT) of 2007 data at the station nearest lake Gornersee, Switzerland (double triangle in Fig. 1), reveal gliding harmonic tremor during a 15 h period on 13 July 2007. The sudden step changes in harmonic tremor frequencies are indicative of hydrofracturing at englacial water-filled fractures. (source: David S. Heeszal, et al./Geology)

Part of the reason for the humming is that glaciers aren’t just big solid blocks of ice. Water moves through glaciers in an ever-evolving and complex series of tiny cracks, crevasses and channels (hydrofractures) within the glaciers themselves. Small pockets of water open and close within glaciers all the time as water flows from one part to another. Though how exactly this englacier water (that is, water within a glacier) moves isn’t yet fully understood.

The seismographs were able to measure the hums as water-filled cracks within the glacier opened and closed, but the humming noises were often at such a low frequency that a human ear could not detect them.

Humming glaciers are more than just a curious scientific phenomenon. The paper’s authors state that further research into the hums at the Gorner Glacier might lead to the development of an early warning system against GLOFs. In other words, glaciers may have a built-in alarm systems. GLOFS are difficult to predict because water draining from the lakes can follow a number of different paths over, under or through a glacier that is acting as a boundary or border for the lake, holding the lake water in place. Just watching the surface of the lake isn’t enough to predict when a massive flood will occur. Fortunately, when glaciers go, they don’t go quietly.

Switzerland's Gorner Glacier as seen from space. (NASA)

Switzerland’s Gorner Glacier as seen from space. (NASA)

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