Using seismometers to monitor glaciers.

Seismic instruments could be used to estimate the amount of ice that shears away from glaciers as they flow into the sea, offering a way to better estimate sea level rise due to the breakup of those ice masses.

In 2004 and 2005, Shad O'Neel, a glaciologist at the University of Colorado at Boulder, and his colleagues installed a network of 11 seismometers around the lowermost portions of Alaska's Columbia Glacier. The researchers found that the seismic waves produced by disintegration of the glacier could be distinguished from waves generated by earthquakes because the two phenomena created vibrations at different frequencies, says O'Neel.

Surprisingly, the strength of an ice-quake's vibrations didn't bear any relation to the amount of ice that broke away from the glacier. Instead, the researchers note in an upcoming Journal of Geophysical Research (Earth Surface), it was the duration of an icequake that correlated with the amount of ice shed during the event. That connection could enable scientists to use networks of seismic instruments to monitor ice loss from remote glaciers in Greenland and Alaska, reducing the need for long and costly field trips.