The song of climate change: Antarctic ice caps sing

The vast pack ice of Ross in Antarctica has been captured "singing" in remarkable new observations – which could help scientists monitor its changes from afar.

Winds blowing over the snow dunes on the plateau rattle the surface of an ice slab of Texas size, producing an almost constant set of seismic "tones" described in a recently published study.

The ice platform – on which land aircraft bound for New Zealand's Scott base during the summer season – is the largest in Antarctica and is fed from inside the icy continent that floats over the Southern Ocean.

Most of this was in Ross's dependence, claimed by New Zealand.

It has reinforced adjacent ice sheets on the Antarctic continent, preventing ice from flowing from the ground into the water, like a cork in a bottle.

When the ice fell, the ice sank more quickly from land to sea, raising the sea level.
The ice shelves in Antarctica have been thinning and, in some cases, have broken or retreated due to rising temperatures of the ocean and the air.

Previous observations have shown that Antarctic ice floes can collapse sharply and without obvious warning signs, which occurred during the abrupt collapse of the Larsen B ice shelf on the Antarctic Peninsula in 2002.

To better understand the physical properties of the plateau, researchers buried 34 sensitive seismic sensors under its snow-covered surface.

The sensors allowed the researchers to monitor the pack ice vibrations and study its structure and movements for more than two years, from late 2014 to early 2017.

The ice floes are covered with a thick layer of snow, sometimes reaching several meters deep, topped with huge snow-covered dunes, like sand dunes in a desert.

This layer of snow acts as a fur coat for the underlying ice, isolating the ice from the heat and melting even as the temperature increases.

When the researchers started analyzing seismic data on a shelf, they noticed something strange: his fur coat vibrated almost constantly.

Looking more closely at the data, they realized that winds blowing over the huge snow dunes caused the roar of the ice sheet, like the sound of a colossal drum.

They also noted that the height of this seismic buzz was changed as weather changed the surface of the snow cover.

They discovered that the ice vibrated at different frequencies when strong storms rearranged the snow dunes or that the temperature of the air at the surface rose or fell, which changed the speed at which the seismic waves propagated in the sea. snow.

"It's a bit like you're constantly blowing on the pack ice," said Julien Chaput, a geophysicist and mathematician at Colorado State University, and lead author of the new study.

Just as musicians could change the pitch of a note on a flute by changing the holes in which the air was going through or how fast, weather conditions on the ice could alter the frequency of its vibrations by altering its dune-shaped topography, explained Chaput.

"Either you change the speed of the snow by heating it or cooling it, or you change the place where you blow into the flute, adding or destroying dunes," he said.

"And these are essentially the two forcing effects that we can observe."

The buzz was too infrequent to be heard by human ears, but new findings suggest that scientists could use seismic stations to continuously monitor conditions on ice platforms in near real time.

According to Douglas MacAyeal, a glaciologist at the University of Chicago, studying the vibrations of the insulating snowpack from an ice floe could give scientists an idea of ​​how it reacted to climate change.

Changes in the seismic snoring of ice could indicate whether melt ponds or ice cracks are forming, which could indicate whether the ice is likely to break.

"The reaction of the pack ice tells us that we can follow extremely sensitive details about it," Chaput said.

"Basically, what we have in our hands is a tool to monitor the environment, really, and its impact on the pack ice."

If the ice sheet of Ross collapsed, scientists believe that this would have major consequences on the rise of the sea level.

The wider pack ice of West Antarctica stores an equivalent rise of 3.2 m sea level, while the much larger ice sheet of East Antarctica contains 58 m of sea level. equivalent rise in sea level.

Prior to 2012, Antarctica was losing ice at a steady rate of 76 billion tonnes per year – a contribution of 0.2 mm per year to sea level rise.

But since then, there has been a big triple increase.

Between 2012 and 2017, the continent lost 219 billion tonnes of ice a year, a contribution of 0.6 mm per year at sea level.

And between 1992 and 2017, the Antarctic ice sheet lost about 3 trillion tons of ice, which equates to about 8 mm of average sea level rise.

Over this 26-year period, the melting of the oceans has tripled the rate of West Antarctic ice loss from 53 billion to 159 billion tonnes per year.

The rate of ice loss from the Antarctic Peninsula has risen from about 7 billion to 33 billion tonnes a year as a result of the collapse of the sea ice.

In western Antarctica, the waters of the sea were gnawing ice trays, while those of the Amundsen and Bellingshausen seas were up to 18% thinner than in the early 1990s .

In the Antarctic Peninsula, where the temperature of the air had risen sharply, pack ice collapsed as a result of the melting of their surfaces.

A total of 34,000 km 2 of ice has been lost since the 1950s.