March 20, 2019

Hear the ghostly hums of Antarctica's biggest ice shelf

20 October 2018, 05:07 | Dale Webster

Relatively warmer waters eating away at ice

Relatively warmer waters eating away at ice shelves

In 2014, the team placed 34 seismometers in the snow a few meters deep on the Ross Ice Shelf.

When the researchers started analyzing seismic data on the Ross Ice Shelf, they noticed something odd: the vibration was nearly constant.

The team believes that monitoring vibrations could help predict if the ice shelf is about to break.

Relatively warmer waters eating away at ice shelves.

The resulting data showed something odd: the "fur coat" snow layer that protects the ice from heat was constantly "singing", or vibrating.

Turns out the sounds come from powerful winds blowing through snow dunes. "We find that the frequencies and other features of this singing change, both as storms alter the snow dunes and during a (January 2016) warming event that resulted in melting in the ice shelf's near surface".

"Either you change the velocity of the snow by heating or cooling it, or you change where you blow on the flute, by adding or destroying dunes", Chaput said.

In fact, this phenomenon of wind that vibrates the surface of the sea ice in the Antarctic is too low for a human being can hear.

The noise has also allowed researchers to discover how several processes like global warming and winds are affecting the ice. "And that's essentially the two forcing effects we can observe". But, as University of Chicago glaciologist Douglas MacAyeal pointed out, seismic stations could aide near-real-time studies, giving scientists a sense of how that snow jacket responds to climate change. For instance, changes in the hum could indicate the presence of melt ponds or cracks in the ice.

"The response of the ice shelf tells us that we can track extremely sensitive details about it", said lead author Julien Chaput, a geophysicist and mathematician at the Colorado State University. "Basically, what we have on our hands is a tool to monitor the environment, really".

The findings were reported in the journal Geophysical Research Letters. Antartica is experiencing an accelerating loss of mass from its ice shelves, which act as plugs holding back the world's largest stores of ice from flowing uninhibited into the ocean.

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