Scientists Detect First-Ever ‘Ice Quakes’ Under Greenland’s Rivers — But One Thing Baffled Them
Typically, when scientists imagine going inside the deep bundles of ice in Earth’s polar regions, they think of ice flowing in frozen rivers, like viscous, syrupy honey. But when Andreas Fichtner unrolled a fiber-optic cable into a deep hole carved in Greenland’s ice, he was in for a surprise. The data that the cable sent back to him revealed that rivers in this deep thicket of ice don’t just flow, sometimes they also judder. Just like earthquakes, this icy expanse shudders in “ice quakes.” In a study published in the journal Science, Fichtner and his colleagues described that they discovered thousands of “ice quakes” quivering through Greenland’s ice stream.
Turns out, these invisible quakes are triggered by the hot remnants of a volcano that erupted 7,700 years ago. Fichtner, who is a professor of geophysics at the Swiss Federal Institute of Technology (ETH) in Zurich, and his colleague were performing some experiments in the North East Greenland Ice Stream (NEGIS), the biggest ice stream of the Greenland ice sheet. Before winding up their day, they decided to use their last cable to do one last experiment. They used a mile-deep borehole that other scientists had drilled to extract an ice core. They lowered the cable inside the hole while soaking it up with vegetable oil to prevent it from closing. When they pulled the cable back and analyzed the data, they were baffled.
At first, Fichtner said it was “just some electronic noise,” according to the New York Times. But it was clearly much more than just noise. The cable picked up cascades of tiny “ice quakes,” some of them reverberating hundreds of feet deep into the icy sheet. It was later determined that these quakes seemed to originate from the “impurities in the ice” that were deposited by volcanic eruptions, mainly the eruption of Mount Mazama thousands of years ago. “We were astonished by this previously unknown relationship between the dynamics of an ice stream and volcanic eruptions,” Fichtner said in a press release.
The reason why these ice quakes remained invisible in satellite images till now is because the layer of volcanic particles lingers at a depth of 2,950 feet or more. These impurities are mostly “tiny traces of sulfates” that become lodged between fissures of ice and slowly destabilize the ice’s core over time. This leads to the formation of cracks. Often, one ice quake can trigger another ice quake, leading to a domino of quakes propagating through large distances. This behavior is as mysterious as Earth's plate tectonics.
What makes this discovery so promising is not just the intricate relationship between fire and ice as depicted by the volcanic particles. It also provides valuable ramifications for scientists to understand ice stream behavior and assess global climate change that governs sea level rise. “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,” Olaf Eisen, Professor at the Alfred Wegener Institute and one of the study’s co-authors, said in the press release. Since ice flowing from glaciers usually spills the meltwater into the seas, raising sea levels, this study has caused them to rethink the movement of ice because ice doesn't just flow like honey, it also has a "constant stick-slip motion."