It’s a strange sound, almost extraterrestrial, that manages to escape from ice shelves. Scientists have recorded the intriguing ‘singing’ from the Ross Ice Shelf, the biggest ice shelf in Antarctica.
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The frequency is too low to be able to be heard naturally by the human ear. But by accelerating the frequency 1,200 times, we can hear the strange sound that comes out of the Antarctic ice. It is actually caused by the wind which, by blowing along the surface of the ice dunes, produces various types of seismic hums.
‘It’s kind of like you’re blowing a flute constantly on the ice shelf,’ describes geophysicist and mathematician Julien Chaput from Colorada State University, who recently published a study about this polar singing.
Global warming’s influence
The aim of their research was to learn more about the physical properties of the Ross Ice Shelf during a time when climate change is dramatically reducing the amount of Antarctic ice. With that goal in mind, Julien Chaput and his colleagues buried 34 seismic sensors under the ice, which measured the structure of the ice from the end of 2014, when the sensors were planted, to early 2017.
By analyzing this data, researchers have concluded that the firn (a snowy cover) is constantly moving, due to exposure to the wind. This outer layer is an accumulation of snow that could eventually form a glacier.
They ‘found that the ice was almost constantly ‘singing’ at a frequency of 5 hertz – 5 cycles per second,’ explained the researchers.
‘Features of its song changed in response to events that affected the surface snow and ice, such as storms that shifted snow dune’s positions, or excessive melting.’
According to researchers, this strange seismic singing can also vary in pitch, depending on things such as the speed of the wind, possible storms or even air temperature. All of these factors can have an impact on the cover of snow.
A new method for measuring the movement of ice
By studying the behavior of these vibrations and how they change over time, researchers hope to learn more about the reactions that take place in layers of ice in a world that’s becoming warmer and warmer.
‘Like the thick, hairy hide of the wooly mammoth, the upper skin of the Antarctic ice sheet is the most important protection from the ravages of a warming climate,’ explains glaciologist Douglas MacAyeal, who wasn’t involved in this study.
‘Melting of the firn is broadly considered one of the most important factors in the destabilization of an ice shelf,’ confirms Julien Chaput. This type of research is both crucial and complex, because the ice in the polar regions undergoes changes that glaciologists find difficult to measure, since they change so quickly. Thanks to Julien Chaput and his team, scientists now have a new way to measure these huge developments.
