New twist for obtaining grants: listen to sounds of glaciers to determine how much they shrink

From the AGU and the “why use direct measurements when we can get a grant to study a proxy” department. You can bet they’ll say things like “this glacier sounds distressed”.

Scientists could potentially use the racket made by melting glaciers to estimate how fast they are disappearing, according to a new study of audio recordings captured in the waters of an Arctic fjord.

As glaciers melt, air bubbles trapped in the ice make popping or crackling sounds when they meet seawater, the same way ice cubes sizzle when placed in a warm drink.

New underwater recordings taken from Hornsund fjord in Svalbard, Norway, show melting icebergs make more noise the faster they melt. The recordings also distinguish melting sounds from grounded glaciers and floating icebergs.

The results suggest scientists could potentially use acoustics to track how fast Arctic glaciers are melting, according to a new study detailing the findings in Geophysical Research Letters, a journal of the American Geophysical Union.

Scientists typically measure glacier retreat by analyzing satellite data, but acoustic recordings would allow scientists to better understand what’s happening where the ice meets ocean water, an area difficult to observe with satellites.

Estimating glacier melt would help scientists better understand the effects of sea level rise, according to the researchers. The Arctic is warming at an unprecedented pace, and the melting of Arctic ice contributes to global sea level rise, which is currently about 3.4 millimeters (one-eighth of an inch) per year, according to NOAA.

“There is great possibility to use noise produced by bubbles trapped in glacier ice to study changing climate associated with iceberg melt and glacier melt,” said Oskar Glowacki, a geophysicist at Scripps Institution of Oceanography at the University of California San Diego and lead author of the new study.

“These tiny air bubbles are singing songs, and these songs are the songs of the changing climate.”

Listening for sounds of change

Pockets of air between snowflakes get trapped and compressed over time as layers of snow build up and condense into ice to form glaciers. Icebergs break off glaciers where the ice meets the sea.

Acoustic recordings made near drifting icebergs in the early 1970s showed ice “sizzles” when it melts, as the air bubbles trapped in the ice explode into seawater. Research published in 2015 showed melting glaciers are the loudest places in the ocean and scientists could potentially use this noise to study the melting ice.

In the new study, Glowacki and colleagues from Scripps and the Polish Academy of Sciences in Warsaw placed microphones that can record underwater in Hornsund fjord during the summers of 2013, 2015 and 2016. They wanted to capture sounds of melting glaciers within the fjord to see if they could use the noise as a proxy for how fast the glaciers were melting. They also wanted to see if they could distinguish between sounds made by melting icebergs and those made by the glaciers themselves.

The researchers found the hiss of melting icebergs is slightly different than the sound of melting glaciers. Recordings of the glaciers revealed the explosions of bubbles into seawater were continuous, like rain hitting the surface of a lake.

More here

via Watts Up With That?

May 17, 2018 at 11:30AM

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