The Ross Ice Shelf in Antarctica has a haunting voice. Winds washing its chilly snow hills create waves of surface vibrations; these produce near-nonstop seismic tones that resemble a sad song, scientists recently discovered
While the ice shelf’s “music” is played at a frequency that isn’t audible to human ears, the researchers were able to overhear using seismic sensors, they wrote in a new study.
When they listened to recordings gathered over two years on the ice shelf, they found that the ice was almost constantly “singing” at a frequency of 5 Hz — five cycles per second — its miserable hum generated by the blowing of regional and local winds. They also learned that features of its song changed in response to events that affected the surface snow and ice, such as storms that shifted snow hills’ positions, or excessive melting.
Scientists detected the vibration unexpectedly; they had installed 34 seismic sensors, on the Ross Ice Shelf from 2014 to 2017, to monitor other aspects of ice shelf behavior. But when they reviewed the readings, they noticed that the highest snow layer was vibrating almost all the time from the active winds that whipped over its uneven surface, causing a seismic hum.
“It’s kind of like you’re blowing a flute, constantly, on the ice shelf,” lead study author Julien Chaput, a geophysicist and mathematician at Colorado State University in Fort Collins, said in a statement.
The pitch of the hum also changed subtly under certain conditions; after powerful storms changed the shape of the snow hills, and when a warming event in January 2016 led to surface melt, they reported in the study.
Monitoring the “song” of the ice shelf could allow scientists to track shifts in surface ice distantly, and practically in real time. This could help them piece together a more complete picture of ice shelf stability, and it could raise an early red flag if the shelf becomes vulnerable to collapse, the study authors concluded.
The findings were published online Oct. 16 in the journal Geophysical Research Letters.