Within glacial ice sheets, there are streams of ice, sometimes called ice rivers, that move much faster than the surrounding ice. If you’re having trouble imagining how ice moves inside ice, Elizabeth Thomas, a paleoclimatologist at the University at Buffalo, suggests an analogy to help visualize these icebound rivers.
Since the Gulf Stream carries warm water from the tropical Atlantic Ocean up the coast of the Carolinas and then across to Europe, she explains, “the Gulf Stream is essentially a river of water that's flowing faster than the ocean around it.”
The same thing happens in ice sheets. Most of the ice moves very slowly, but in some places, the ice moves much more swiftly than the surrounding ice, and those faster-moving areas are ice streams. And within these streams, researchers have discovered ice quakes.
Read More: What the Mysterious Bloop Taught Us About Antarctica
What Causes Ice Quakes
Recently, an international team of scientists led by Andreas Fichtner of the ETH Zürich, a public research university in Zürich, Switzerland, discovered many little ice quakes deep within the ice rivers on the Northeast Greenland Ice Sheet.
“Inside the ice stream are thin layers of sulfates left over from volcanoes,” explains Fichtner. “These impurities make the ice in these areas a little weaker than the surrounding ice, and the stresses localize near these weak layers, causing them to crack. This is what produces the ice quakes.”
This discovery shows that ice streams move with what Fichtner calls a “stick-slip” motion rather than always flowing smoothly like viscous honey.
Glacier ice flows by means of many different mechanisms, explains Kristin Poinar, a University at Buffalo scientist who studies the Greenland Ice Sheet.
“It can ooze slowly and viscously; it can move rapidly and elastically,” she says. “What we haven’t appreciated before is that these micro-slip events might add up to be fairly significant to the overall amount of flow.”
A Better Understanding of Wild Ice
Fichtner hopes this newly discovered mechanism will be included in simulations of ice sheet evolution. “These simulations of how ice sheets move over 100-year time scales are essential ingredients of sea-level predictions,” he says.
“The ice sheet models we have today are great,” adds Poinar, “and they’re about to get better.”
Thanks to a combination of field and lab studies, scientists have understood the basics of ice flow for almost 100 years, she says, but studies like this one are crucial as scientists hone their understanding of the intricate details of the properties of ice.
“Ice in the wild has these special properties that lab ice does not. And so, if we aren't studying ice in the wild, we're missing the complexities. We're getting the basics right, but we're missing the complexities that make this particular ice stream flow faster than our models currently predict,” says Poinar.
And getting those models just right is more important than you may realize, adds Thomas.
“Most people have never seen a glacier, much less one of the world’s great ice sheets, because they’re so remote,” she says. “But the water from them ends up in our communities.”
Having a precise understanding of ice flow dynamics helps scientists better predict sea-level rise.
“That’s super important because we know that the sea level has already risen by a foot in the past century,” Thomas says. “This rise impacts coastal communities every time there’s a high tide; meanwhile, storm surges are becoming devastating.”
It Takes a Team
Poinar also notes that this project was a collaboration between multiple international scientists and agencies. This is common in many areas of science, but perhaps especially in glaciology, she says. That’s because it takes a lot of international support to be able to survive in the inhospitable regions where you find glaciers.
“Living and working in Greenland for long enough to make a measurement like this — which is several years — takes a lot of international logistical support to keep you fed, warm, and out of the wind.”
Thanks to this kind of support, Fichtner and his team are planning to continue their research on ice quakes. They are now in the process of determining if Alpine glaciers produce similar quakes.
Read More: Loss of Sea Ice in Antarctica Is "Nothing Short of Shocking"
Article Sources
Our writers at Discovermagazine.com use peer-reviewed studies and high-quality sources for our articles, and our editors review for scientific accuracy and editorial standards. Review the sources used below for this article:
Antarctic Glaciers. Ice streams
ETH Zürich: Ice streams move due to tiny ice quakes
Avery Hurt is a freelance science journalist. In addition to writing for Discover, she writes regularly for a variety of outlets, both print and online, including National Geographic, Science News Explores, Medscape, and WebMD. She’s the author of Bullet With Your Name on It: What You Will Probably Die From and What You Can Do About It, Clerisy Press 2007, as well as several books for young readers. Avery got her start in journalism while attending university, writing for the school newspaper and editing the student non-fiction magazine. Though she writes about all areas of science, she is particularly interested in neuroscience, the science of consciousness, and AI–interests she developed while earning a degree in philosophy.
