'Ice-Quakes' Breaking Records

In a presentation Thursday at the Seismology Society of America’s annual meeting in Anchorage, the audience saw Glacier seismology, a relatively new area of science, including long-ignored data within Alaska’s  earthquake records capture “ice-quakes” and dynamic change occurring above ground: ice breaking off of glaciers, falling into water - calving.  

The audience also saw data proving that over 99 percent of Alaska’s low-lying glaciers are retreating.

Sensors also captured several thousand “ice-quakes,” according to Alaska’s state seismologist Mike West, as reported in the Daily Climate. 

“Hundreds happen annually along the south-central coast of Alaska, where glaciers reach the sea. Records at the center, located at the University of Alaska, Fairbanks, date back to the 1970s, when seismologists first recognized that calving glaciers created unmistakable seismic signals hundreds of kilometers away, West said. But after the Alaska earthquake network’s hardware was upgraded in 2007, the number of ice-quakes picked up by the sensors increased.

“We have a half-dozen years of really high-quality glacier data,” West said. “We’re in the early stages of being able to look [at what has happened] over a period of years.”

Glacier seismology is a relatively new area of science, with growing interest due to the possibilities for detecting the extent of global warming’s impact in vibrations it causes beneath the Earth’s surface.

Atmospheric measurements, from below ground

As incredible as it might seem, atmospheric change can be measured below ground, and seismic sensors record all types of surface movement – even delineating day from night, or weekends from weekdays when placed near cities.

“It doesn’t matter if it’s an earthquake, or a train going by, or an animal, or a nuclear explosion, or glaciers,” West said. “Our sensors don’t know any better – they just measure how the ground shakes.”

West said that Columbia is the best example to date of an Alaska glacier with a clear change in ice-quake production in recent years. After retreating into shallow waters and became grounded in 2009 and 2010, the end of the glacier rose high enough above sea level that it led to “tall icebergs that fall over, smacking the water” – and a corresponding increase in seismic signals.

Alaska is the most glaciated U.S. state, with glaciers covering about 29,000 square miles, about 5 percent of its surface. More than 99 percent of the state’s low-lying glaciers are retreating. This means a bonanza for the oil and gas industry, and more misery ahead for humans and the planet.

Read more about this fascinating ice-quake story here on the Daily Climate.