Listen to the Antarctic ice sheet sing a song of melting ice
The Ross ice shelf reverberates with a hum that can help foretell it's fate
The low hum of the Ross Ice Shelf, Antarctica's largest ice shelf, could be used as a diagnostic tool for researchers to monitor its health and surface melt.
"The ice shelves in the Antarctic play a critical role in helping to restrain the glaciers in the interior from flowing rapidly into the ocean," said Rick Aster, who led the team that made the discovery of the ice's song.
If they melt, sea level could rise precipitously, and cause devastating flooding in coastal countries.
The wind in Antarctica can create snow dunes up to a few meters in height. It applies a force to the snow as it whips across the surface, and that generates seismic waves that excite the top snow layer of the ice shelf, making it "sing."
Sensitive seismic sensors deployed by Aster and his team across the Ross Ice Shelf back in 2016 picked up the small vibrations. To make it audible to the human ear, they had to speed it up over 40 times.
While analyzing the seismic records, they noticed an interesting relationship between the air temperature and the tones generated by the snow layer. As the temperature rises, the snow softens and the tone gets lower.
As the ice melts, the tone gets lower and the "song" gets quieter. But if the water refreezes again later, the noise will bounce back, but the pitch will have changed.
This is caused by a change in the properties of the snow, according to Aster, which changes the propagation speed of waves and thus, its tone.
He thinks this could be an invaluable tool to monitor the health of the snow layer and the ice underneath.
If the blanket layer deteriorates, says Aster, it could mean the processes involved could percolate downward and reach the ice underneath, leading to possible cracks in the ice shelf.
"We hope that eventually we'll be able to use them to understand directly what's happening to the snow column in enough detail that we won't have to dig snow pits and other invasive techniques. We can monitor features of the snow and ice just by listening."