Latest news with #AndreasFichtner
Yahoo
13-02-2025
- Science
- Yahoo
Scientists record never-before-seen 'ice quakes' deep inside Greenland's frozen rivers
When you buy through links on our articles, Future and its syndication partners may earn a commission. In a first, researchers have recorded countless "ice quakes" that sporadically shake the Greenland Ice Sheet. These quakes may explain the jerky way that the island's frozen rivers move downstream toward the sea, the scientists say. Researchers detected these quakes by lowering a fiber-optic cable into a 1.7-mile-deep (2.7 kilometers) borehole in the Northeast Greenland Ice Stream — Greenland's largest frozen river that serves as the main artery through which ice is discharged from the ice sheet's interior into the North Atlantic Ocean. Similar to earthquakes, ice quakes are seismic events that can happen in ice when it fractures and two slabs grind against each other. Ice quakes in Greenland have gone undetected until now because they are blocked from reaching the surface by a layer of volcanic particles buried 2,950 feet (900 meters) beneath the ice, the researchers said in a statement. These particles originated from a huge eruption of Mount Mazama, in what is now Oregon, about 7,700 years ago, they said. Related: Greenland's ice sheet — the second biggest in the world — is cracking open at alarming speed, scientists discover Not only do volcanic particles prevent seismic waves from traveling to the surface, but they may also be directly responsible for the quakes, Andreas Fichtner, a professor of geophysics at the Swiss Federal Institute of Technology (ETH) in Zurich and the lead author of a new study published Feb. 6 in the journal Science, said in the statement. The ice quakes probably start from impurities in the ice, such as sulphates and other particles, which may destabilize the ice and lead to the formation of small cracks. "We were astonished by this previously unknown relationship between the dynamics of an ice stream and volcanic eruptions," Fichtner said. Ice quakes can trigger other ice quakes like dominoes, and thereby propagate horizontally over large distances, according to the statement. Researchers are interested in ice streams — and the role ice quakes play in the way these streams move ice — because they dump large amounts of ice from glaciers into the sea, contributing to sea level rise. Uncertainties about how exactly ice streams transport their load lead to errors in computer models that help scientists assess the future impacts of climate change. Previously, scientists thought that the ice only flows slowly through these rivers like thick honey. But the new finding, along with previous research, has forced scientists to rethink the way ice moves. "The assumption that ice streams only flow like viscous honey is no longer tenable," Fichtner said. Instead, the new data confirm that tiny quakes deep inside the Greenland Ice Sheet cause ice streams to "also move with a constant stick-slip motion," Fichtner said. RELATED STORIES —Greenland is losing so much ice it's getting taller —Giant viruses discovered living in Greenland's dark ice and red snow —Scientists discover hidden 'plumbing' that's driving Antarctic ice sheet into the ocean The Greenland Ice Sheet is the largest ice sheet in the Northern Hemisphere, covering approximately 80% of Greenland's landmass. Meltwater from the Greenland Ice Sheet is already the biggest global source of sea level rise, accounting for a 0.6-inch (1 centimeter) increase since the 1990s. Scientists estimate there is enough ice locked inside Greenland to raise sea levels by 23 feet (7 m). "The fact that we've now discovered these ice quakes is a key step towards gaining a better understanding of the deformation of ice streams on small scales," study co-author Olaf Eisen, a professor of glaciology at the Alfred Wegener Institute for Polar and Marine Research in Germany, said in the statement.
New York Times
06-02-2025
- Science
- New York Times
In Greenland, the Ice Doesn't Just Flow, It Quivers and Quakes
When Andreas Fichtner unspooled a fiber-optic cable into a deep hole in Greenland's ice, he wasn't expecting to discover a whole new way that glaciers move. Even when the cable started sending back data, his first reaction was skeptical. 'Rubbish,' Dr. Fichtner, a professor of seismology and wave physics at the Swiss university ETH Zurich, remembers thinking. 'Just some electronic noise.' This was August 2022. The field season in Greenland was almost over. The cold, the altitude, the long hours — all of it was wearing on Dr. Fichtner and his fellow researchers. But they'd been saving one of their cables for one last experiment, one that would let them measure tiny movements deep within the vast river of ice as it flowed toward the sea. What they found raises questions about scientists' assumptions about how the ice sheets of Greenland and Antarctica are moving and adding to sea levels worldwide. That last cable picked up cascades of tiny 'ice quakes,' some of them reverberating hundreds of feet, Dr. Fichtner and his colleagues reported on Thursday in the journal Science. These quakes seemed to start near impurities in the ice that were deposited by volcanic eruptions, Dr. Fichtner said. Where these particles sit, the ice is weaker, more prone to cracking. Along these cracks, the ice sticks and slips and quivers as it moves, creating tiny seismic disturbances. This isn't what scientists usually imagine is going on inside the deep piles of ice that cover Earth's polar regions. Typically, they think of this ice as flowing like syrup: slowly, smoothly, fluidly. But if the ice were really moving like a uniform mass of honey, then Dr. Fichtner's cable would have picked up 'complete silence,' he said. Instead, it recorded these 'really, really curious events,' he said. 'That was the surprise here.' By sending laser pulses through fiber-optic cable and measuring how they scatter, scientists can reconstruct fine movements along the cable's entire length. This has proved useful for monitoring seismic activity, deep-sea currents, glacial ice and more. In Greenland, Dr. Fichtner and a colleague lowered a cable by hand nearly a mile down a borehole, one that other scientists had drilled to extract an ice core. There the cable lay for 14 hours, picking up vibrations. If winding and unwinding a cable doesn't sound especially challenging, let Dr. Fichtner be the first to inform you: It was 'serious physical work.' The borehole was filled with a special kind of vegetable oil to keep it from closing up, so the cable was slow to sink and heavy to lift back out. Plus, the subzero cold made the cable brittle, meaning they had to handle it with utmost care. When Dr. Fichtner started looking at the readings that came back, he had to convince himself they weren't 'rubbish.' What if they showed vibrations coming from within the cable itself? Or from cracks forming in the borehole wall? In time, he and his team concluded that they'd recorded something intrinsic to the ice. Still, Dr. Fichtner acknowledged that only by making more measurements in more places can scientists really say how commonly these quakes occur within ice sheets. Getting enough measurements is a constant challenge for polar scientists, said Hélène Seroussi, an engineering professor at Dartmouth College in New Hampshire who wasn't involved in the new research. When oceanographers want to collect data, they can drop instruments into the deep sea in a matter of hours. Glacier researchers have to drill deep into the ice, which takes months, even years. 'That's why we keep finding all these new principles and mechanisms that seem relatively fundamental,' Dr. Seroussi said. 'Each time you have a new observation, a new ice core, a new way of measuring, you learn something new.' Andy Aschwanden, a glaciologist at the University of Alaska Fairbanks, said Dr. Fichtner and his colleagues' discovery offered an interesting glimpse into the intricacies of ice physics. But he said it was too early to know whether it can help scientists better predict how quickly the melting ice sheets will lift global sea levels. The ice still holds other mysteries that, if unraveled, are likely to improve the modeling much more, Dr. Aschwanden said. The new findings could someday help scientists better understand the way ice sheets break apart at their edges, said Richard B. Alley, a professor of geosciences at the Pennsylvania State University. Pre-existing flaws or damage in the ice can cause it to crack up rapidly once it flows off the land and out to sea, Dr. Alley said. It's the same reason a fast-food ketchup packet is easy to open if you do it from the little notch, but very difficult if you try to tear it anywhere else, he said. 'All of us who study ice,' Dr. Alley said, 'will be building on this new paper for a long time to come.'
