Buzz
With the help of seismometers, UChicago researchers, including Becky Goodsell (pictured), documented hundreds of thousands of 'ice quakes,' a phenomenon that could provide insights into glacier melt. Alison Banwell/University of ChicagoIn a secluded section of the icy Antarctic, the ice itself reportedly 'shivers' at night, according to a study published in the journal Annals of Glaciology in December 2018.
From late November 2016 to mid-January 2017, lead author Douglas R. MacAyeal and his team collected seismic data from the McMurdo Ice Shelf, a frozen expanse that borders part of Antarctica's Ross Sea.
Out on the frozen expanse, the team established two seismograph stations. One, known as the "wet station," was positioned in an area with meltwater lakes both on and beneath the surface. The other, referred to as the "dry station," was set up on a solid snow surface about 20 kilometers (12.4 miles) away.
These locations produced drastically different results. Every night, between late November and mid-December, the wet station's instruments recorded what MacAyel describes in a press release as "tens, hundreds, [or] thousands" of tiny seismic events, each lasting less than a second.
In contrast, the dry station did not detect such events but mostly picked up man-made noises from nearby field vehicles. However, the wet station quakes were unmistakably natural in origin. MacAyel and his team believe they are linked to the area's underground water deposits.
MacAyel explains in the same press release, "In these ponds, there’s often a layer of ice on top of liquid water, much like the surface of a lake that’s frozen at the top. As nighttime temperatures drop, the ice contracts and the water beneath it expands as it freezes. This causes the ice lid to warp until it finally snaps."
For years, researchers have been aware that ice can produce seismic events, many of which are small in scale. A well-known instance of this would be the disturbing "frost quakes" that reportedly occurred in the Chicago area earlier this year.
When most liquids freeze, they typically shrink in volume. However, water is an exception; freezing actually causes H2O to expand. Frost quakes occur when groundwater that has seeped into soil or rock freezes rapidly. As the liquid water turns into ice, it expands quickly, generating pressure that can crack the surrounding material, sometimes with a loud noise similar to a shotgun blast.
Frost quakes are a type of event within the broader category known as "ice quakes." This term is also used to describe earthquake-like events triggered by glaciers moving over underlying pools of liquid water.
However, MacAyel's team’s findings suggest that the surface of an ice shelf itself can generate quakes — a concept that has not been proposed before. They hope future researchers will use these tremors to track Antarctic melting patterns.
