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Research published last week by the American Geophysical Union documents a chaotic, low-frequency buzz on the Ross Ice Shelf, a French-size platform that floats off the coast of West Antarctica.
The launches are caused by the wind that hits the snow dunes, and it's a kind of disturbing song. But, say the researchers, it is also a harbinger of one of the nightmare scenarios of climate change science: the disintegration of the largest ice floe in the Antarctic and the consequent sliding of glaciers into the ocean.
As you can read in the article. at the bottom, the song slows down when the snow begins to melt in the upper layers of the pack ice.
As you can hear in the researcher's audio files, this has already happened.
Ice made its way through centuries: a discordant song whose verses told the story of cold winds and snow-covered dunes vibrating through Antarctica.
It was not music as we think. Days or months may elapse between each change of tone, composed of notes so low and so slow that they are inaudible to the human ear. But if you could stay 1000 years on Ross's big ice shelf and feel every thrill that went through it – if you were the snow itself – then you knew the chorus.
In January 2016, the song fell flat. 19659010] Accelerated thousands of times in the frequency range of human hearing, it seemed that the sliding of the ice had been muted to resemble a tone, a moaning whistle that lasted two weeks among the hottest ever recorded on the polar continent. A song that warned against melting snow.
Listen.
If the worst fears of climatologists come true – if, during a particularly hot month of this century, the Ross Ice Shelf, which stretches for 500 km, collapses like a crumbling border wall, allowing the Antarctic glaciers to flow along it into swollen oceans – we could see a small part of the beginning of the calamity.
When a smaller ice shelf collapsed on the other side of West Antarctic in January 2002, we were.
"Scientists monitoring daily satellite images of the Antarctic Peninsula have observed with astonishment almost the entire Larsen B ice shelf in just over a month," writes NASA in its memorial dedicated to this plate. 10,000 years old. ice cream.
"He collapsed between images of a satellite," said Julien Chaput, a geophysicist at Colorado State University, Washington Post. "A photo, it was there. The next was not the case. "
But the pack ice was sick well before his spectacular death. As Chaput explains, the early stages of disintegration are insidious and largely invisible to satellites.
Repeated heat waves melt and refreeze the snow carpet at the top of the pack ice. With each new frost, the snow becomes harder. Finally, it becomes so hard that puddles form on the surface of the snow and sink into the snow, digging tunnels in the snow to reach the ice below.
The ice weakens like a decaying boat hull under the onslaught of melting water. It crackles. The magnitude of the damage is obvious for the satellites towards the end, when the entire plateau – ice, snow and snow – breaks up and dissolves in the ocean in a few days.
This is, to put it mildly, a poor warning system. for the end of the world we know.
But as Chaput and his team have demonstrated in an article published last week by the American Geophysical Union, an injured pack ice will sing its troubles long before we show them.
[Scientists are slowly unlocking the secrets of the Earth’s mysterious hum]
The discovery was "a complete accident," said Chaput. Nobody expected the ice to sing.
Several years ago, another team of researchers installed dozens of seismic stations on the Ross Ice Shelf. Like many climatologists, they feared that if the French-size floating ice sheet collapsed – as Larsen B did in 2002 – the titanic glaciers behind would be free to escape the Antarctic continent. and to raise the level of the oceans by several feet.
"For now, Ross's pack ice seems to be stable," said Chaput. "But that could change extremely quickly and without notice."
The seismic stations were designed to measure what the Earth's crust and mantle do under ice – mbadive earthquake-scale vibrations.
dataset from late 2014 to 2017, he noticed something in the sine waves: a subtle song, vibrating through the upper layers of the snow.
"You had these heights, these incredibly defined, persistent and defined tones at each station," he said. "They would change all the time, with changes in air temperature, storms and winds."
Even the movement of a snow dune could change frequencies, said Chaput. It was as if all the snow bed had been dug as an old phonograph record, quivering with the rustling of the atmosphere.
The notes hovered around 5 hertz, about four times more than what the human ear can detect. But Chaput could easily speed them up enough to be able to hear – compress rhythms of several days into minutes or seconds
So that 's how he was able to hear what' s going on. happened in early 2016, when a particularly hot summer arrived in Antarctica and the phonograph jumped.
[Scientists stunned by Antarctic rainfall and a melt area bigger than Texas]
Chaput did not discover the great event of the cast of January 2016. As Chris Mooney wrote in the Washington Post, this disrupted the scientists who had taught him the # 39; era.
The two-week merger left nothing so obvious on the surface of the Ross ice floe. On the contrary, it turned a wet, sodden Texas-sized snowpack as the air temperature reached freezing point. Scientists first discovered it through the presence of steam clouds over the sea ice, Mooney explained, before confirming the damage by microwave satellites.
But in the music of the snow, melting was impossible to miss.
At the seismic stations on the other side of the pack ice, the vibrations of the voice were silenced. Notes stretched in a long drone in some places, like a tornado siren. For Chaput, it sounded like a two-week whine.
"It does not seem very happy to me," he said.
The music of the ice, he explains, is made by the pbading wind. snow dunes and vibrations caused by trillions of ice crystals compressed in the snow – called "firn". "The snow is 80% air, with flaky links between the crystals," said Chaput. "As they weaken, the speed of movement of a wave decreases
All this could simply mean that Chaput found a depressing soundtrack for melting an ice cap. But as described in his article, music also has a potential measurement tool – about a sonogram for the health of snow and ice in the years to come, he expects many more.
That does not mean that we will like what we hear.
The Ross Ice Shelf returned shortly after the end of the heat wave at the end of January, when the snow was covered with ice and crystals reforging their links. But on many listening stations, the sound is no longer the same. The warble now has something that looks like a grater.
"You can see the physical impact," said Chaput, who plans to continue his studies on the Arctic as a faculty member at the University of Texas at El Paso. "When it gets cold again, the nicotine will partially heal and rebound in some ways, but not completely."
He does not know if Ross's ice tray will regain its original structure and voice, or it was permanently damaged, as the Larsen B ice shelf was to be long before breaking.
For the moment, even imperfectly, he continues to sing.
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