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The Antarctic is honestly a little scary. He flees from within; he loves to spill bloody liquids into the ocean as a gargantuan stabbed victim; it is a dry hell landscape, though it is covered with a thick layer of literal water (though the frozen variety); and now it turns out that Antarctica is a fervent whistler of strange melodies. Bear with me: A new study published this week in Geophysical Review Letters explains how scientists have detected resonant strange sounds near the surface of Ross' huge ice shelf in Antarctica. While these winter sounds have their place in the winter landscape, you can banish the idea of anything that looks like frozenThese songs are rather inaudible type in the human ear.
"Ice floes are an essential part of the Antarctic ice system," says Rick Aster, a geophysicist at Colorado State University and co-author of the new study. "We value a lot from them because their stability in the coming decades will greatly affect sea level rise and other problems that affect millions of people. This discovery provides a new tool to measure and understand how they are affected by the warming of the atmosphere and oceans. "
The chief investigator, Julien Chaput, a geophysicist at the University of Texas at El Paso, who started this work under Aster at the CSU, describes this study as a "somewhat happy accident," arising from the deployment. of a broadband seismic instrument on the Ross ice floe, which is about the size of Texas, to study the crust and mantle below. Chaput, an expert in ambient noise monitoring, began to notice "strange spectral anomalies that escaped easy explanations," suggesting that some kind of high-frequency seismic waves were constantly trapped in the firn (the first two meters of snow).
"The end result was really the result of the pursuit of an enigmatic puzzle," he says. "Following this trail has given us a unique insight into all the environmental effects that a" pack ice can feel "on a remarkably short time scale."
The team finally discovered that these trapped floods were created by the constant humming of the wind that grazed the snow on the plateau's surface. These sounds have already been recorded in other parts of the world, including Antarctica, but this study revealed that tones changed over time, in direct response to what was happening in the environment.
In Antarctica, surface movements can often result in vibrations spreading all over the ice. The frequency of these waves varies with changes in soft snow in the dwarf, including impacts of high winds or changes in temperature. The team measured the vibrations (seismic waves) that propagated in the shelf for a little over two years and was able to detect how the frequency was shifted according to storms or high winds, seasonal changes or unusual variations in average temperatures, and so on.
"This last point is particularly interesting," says Chaput, "because it could allow us to quantify ice layers with nest layers heavily impacted by repeated warming events, and also give a measure of the resilience of these layers of ice. dwarf".
These effects may have been better crystallized during observations made in January 2016, during a particularly warm period when temperatures rose slightly above 0 ° C and allowed some snow and snow. melting ice. Cast iron slowed the seismic waves and altered their height. But when the temperatures rose again, the waves did not return to their previous state. The fir tree had been permanently modified and the song of the pack ice had also changed permanently.
The study is an excellent illustration of why it would be useful to use seismic observations to monitor areas of the world closely. Scientists generally consider that the melting of Firn is one of the most important factors in the destabilization of an ice floe. And the ice trays themselves are particularly important because their melting accelerates the flow of ice in the ocean from adjacent ice layers. Over the past few years, he has emphasized the role of ice plateaus as "real heavyweights of any potential uplift of the sea," said Chaput. He is encouraged by the idea of using this technique to study melting ice around the world. He hopes that future researchers will perhaps be able to detect pockets or melt cracks that herald the warning signs of a larger shelf break, be it in Antarctica, the United States, or the United States. Greenland or elsewhere.
"Polar environments are more or less the forefront of climate change, but the instrumentation and modeling of these environments have lagged far behind," Chaput said. "We all know that we are in hot water. The problem is that we do not yet know how hot it is. "He cites the collapse of Larsen B in 2002, illustrating how limited we have been tracking and measuring mass loss ice as it occurs.
"In a sense, this way of looking at continuous seismic data could be considered a" canary in the mines "observation, with a temporal resolution almost in real time," he says. "The deployment of a single seismometer on an ice floe could provide a very subtle environmental forcing at a time scale as short as a few minutes, and provide a means to directly understand the sequence of physical changes that occur in the vicinity. event hits. "
Much remains to be done to prove how viable a seismological observation could be used to monitor ice melt, but it is probably a safe bet to follow the buzz. If the ice has to sing aloud, we can either keep a listening ear and listen carefully.
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