Quantcast

Scientists Study Ice Shelf by Listening to Its Changing Sounds

Science
The Ross Ice Shelf at the Bay of Whales. Michael Van Woert, NOAA

By Marlene Cimons

Researchers monitoring vibrations from Antarctica's Ross Ice Shelf were flabbergasted not long ago to hear something unexpected—the ice was "singing" to them. "We were stunned by a rich variety of time-varying tones that make up this newly described sort of signal," said Rick Aster, professor of geosciences at Colorado State University, one of the scientists involved in the study.


Researchers set out to study low-frequency vibrations that arose from earthquakes and ocean waves. They were surprised to hear the ice sheet "singing" after examining the higher frequencies. The sound, which resembled a low moan, turned out to be a valuable tool. "The tones in these signals shift when the surface of the ice shelf is disturbed by changes in surface dunes or near-surface melt," Aster said.

Changes in the ice shelf's seismic hum could alert scientists when "melt ponds" or cracks appear in the ice, indicating that the ice may become vulnerable to breaking off—a mounting concern as climate change fuels extensive melting. Ice shelves all over Antarctica are becoming thinner, and some have collapsed or retreated due to rising ocean and air temperatures. In the past, these shelves have sometimes collapsed suddenly, without notice.

Climate scientists are concerned about ice shelves on the edge of Antarctica because they hold back large inland glaciers, "like a cork in a bottle," Aster said. Those glaciers then melt into the ocean, raising sea levels. Scientists watched that happen after the Larsen B ice shelf collapsed in 2002—glaciers behind the ice sheet began to thin. All told, Antarctica is home to roughly 7 million cubic miles of ice which, if it melted, would raise sea levels around 200 feet.

When ice shelves disintegrate, glaciers move out to sea. Ted Scambos & Michon Scott, National Snow and Ice Data Center

Melting ice doesn't just add water to the sea. It also changes how that water is distributed. That's because the Antarctic ice sheet exerts a gravitational pull over surrounding waters. "The ice sheet is so massive that it attracts a bulge of ocean close to the continent," Aster said. "When the icecap melts, this bulge relaxes and sea level goes up on the other side of the planet." This produces more coastal flooding in the northern hemisphere.

Researchers studied the Ross Ice Shelf, a Texas-sized plate of ice that floats atop the Southern Ocean. The Ross Ice Shelf—Antarctica's largest ice shelf—is covered in thick blankets of snow, often several meters deep, that are topped with massive snow dunes, like sand dunes in a desert. This snow layer insulates the underlying ice from heating when temperatures rise.

Rick Aster, professor of geosciences at Colorado State UniversityRick Aster

The newly discovered noises are the result of winds blowing across snow dunes on the Rise Ice Shelf. This causes the ice surface to vibrate, producing near-constant seismic "tones" that researchers can use to monitor melting and other changes from afar. The study appears in Geophysical Research Letters, a journal of the American Geophysical Union.

Scientists currently use a variety of methods to monitor an ice shelf—analyzing snow pits, for example, or gathering satellite data. According to Aster, "we may eventually be able to model critical elements of its structure using seismology alone," meaning scientists could track the melt of the ice sheet by listening to its song, using other tools to confirm what they found.

The Ross Ice Shelf. SourceJosh Landis

"We can also see the rearrangement of drifted snow, that is, dunes at the surface, or instances where new snow is deposited or blown away," he added. "This tool provides site-specific information about the ice shelf that can be monitored continuously, which is something you can't do digging snow pits."

The researchers buried 34 extremely sensitive seismic sensors under the snow across the ice shelf for two years, from late 2014 to early 2017, which allowed them to monitor its vibrations, structure and movements. They discovered that the shelf nearly continuously sings at frequencies of five or more cycles per second, stimulated by winds that blow across its dune‐like landscape.

Researchers studying the Ross Ice ShelfRick Aster

They also found changes in frequency whenever storms whipped up the snow dunes, or when the air got warmer or colder. "It's kind of like you're blowing a flute, constantly, on the ice shelf," said Julien Chaput, a geophysicist and mathematician at Colorado State University and lead author of the study. "Either you change the velocity of the snow by heating or cooling it, or you change where you blow on the flute, by adding or destroying dunes. And that's essentially the two forcing effects we can observe."

As the ice shelf changes its tune, "we can track extremely sensitive details about it," Chaput added. "Basically, what we have on our hands is a tool to monitor the environment and its impact on the ice shelf."

Reposted with permission from our media associate Nexus Media.

EcoWatch Daily Newsletter

MStudioImages / E+ / Getty Images

By Jillian Kubala, MS, RD

Backpacking is an exciting way to explore the wilderness or travel to foreign countries on a budget.

Read More Show Less
Tim P. Whitby / 21st Century Fox / Getty Images

The beauty products we put on our skin can have important consequences for our health. Just this March, the U.S. Food and Drug Administration (FDA) warned that some Claire's cosmetics had tested positive for asbestos. But the FDA could only issue a warning, not a recall, because current law does not empower the agency to do so.

Michelle Pfeiffer wants to change that.

The actress and Environmental Working Group (EWG) board member was spotted on Capitol Hill Thursday lobbying lawmakers on behalf of a bill that would increase oversight of the cosmetics industry, The Washington Post reported.

Read More Show Less
Sponsored
A protest march against the Line 3 pipeline in St. Paul, Minnesota on May 18, 2018. Fibonacci Blue / CC BY 2.0

By Collin Rees

We know that people power can stop dangerous fossil fuel projects like the proposed Line 3 tar sands oil pipeline in Minnesota, because we've proved it over and over again — and recently we've had two more big wins.

Read More Show Less
Scientists released a study showing that a million species are at risk for extinction, but it was largely ignored by the corporate news media. Danny Perez Photography / Flickr / CC

By Julia Conley

Scientists at the United Nations' intergovernmental body focusing on biodiversity sounded alarms earlier this month with its report on the looming potential extinction of one million species — but few heard their calls, according to a German newspaper report.

Read More Show Less
DoneGood

By Cullen Schwarz

Ethical shopping is a somewhat new phenomenon. We're far more familiar with the "tried and tested" methods of doing good, like donating our money or time.

Read More Show Less
Sponsored
Pixabay

Summer is fast approaching, which means it's time to stock up on sunscreen to ward off the harmful effects of sun exposure. Not all sunscreens are created equally, however.

Read More Show Less
Mark Wallheiser / Getty Images

The climate crisis is a major concern for American voters with nearly 40 percent reporting the issue will help determine how they cast their ballots in the upcoming 2020 presidential election, according to a report compiled by the Yale Program on Climate Change Communication.

Of more than 1,000 registered voters surveyed on global warming, climate and energy policies, as well as personal and collective action, 38 percent said that a candidate's position on climate change is "very important" when it comes to determining who will win their vote. Overall, democratic candidates are under more pressure to provide green solutions as part of their campaign promises with 64 percent of Democrat voters saying they prioritize the issue compared with just 34 percent of Independents and 12 percent of Republicans.

Read More Show Less
Flooding in Winfield, Missouri this month. Jonathan Rehg / Getty Images

President Donald Trump has agreed to sign a $19.1 billion disaster relief bill that will help Americans still recovering from the flooding, hurricanes and wildfires that have devastated parts of the country in the past two years. Senate Republicans said they struck a deal with the president to approve the measure, despite the fact that it did not include the funding he wanted for the U.S.-Mexican border, CNN reported.

"The U.S. Senate has just approved a 19 Billion Dollar Disaster Relief Bill, with my total approval. Great!" the president tweeted Thursday.

Read More Show Less