Science

The Dynamics of Glacial earthquakes and their Significance

Scientists who have been studying glacial earthquakes in Greenland have discovered the dynamics involved in this event.

The results of this study which were published in the journal Science, allows scientists to monitor the loss of the Greenland Ice Sheet.

Unlike earthquakes that occur in an instant, glacial earthquakes span minutes.  These also contribute to the loss of glacial ice that occurs in the context of rising sea levels and climate change.

Scientists explain, “Nearly half of Greenland’s mass loss occurs through iceberg calving, but the physical mechanisms operating during calving are poorly known and in situation observations are sparse.”

Scientists surmise  that glacial earthquakes were related to these calving events, however  available data is limited and may not be sufficient to support this theory.  Scientists placed a wireless network of GPS sensors around the margin of Helheim Glacier (a major outlet of the Greenland Ice Sheet).  They observed this for 55 days. The two cameras which were pre-positioned in front of the calving border gave them pictures on an hourly basis.  From these data, researchers  reconstructed a three-dimensional model of the glacier’s front and the calved icebergs.

The researchers then ran a series of simulations in the laboratory  to mimic the movement of a calving iceberg and measure the forces it generated in the water.

Researchers share their discovery. They explained: “As the calving ice fell, it flipped backward and pushed the glacier back, making it into a reverse direction, and prompting the earthquakes’ horizontal motion. When it sank into the water, the water pressure behind it would plummet and caused the main glacier to go down 10 centimeters.  This action pulls the Earth upward.  Scientists  liken this to the  vertical forces observed in glacial earthquakes.

They explain their findings in greater detail. “These forces are the source of glacial earthquakes, globally detectable seismic events whose proper interpretation will allow remote sensing of calving processes occurring at increasing numbers of outlet glaciers in Greenland and Antarctica,” the authors wrote.

Since calving events are sporadic, building a network of  quake detectors, allows  scientists to catch and  obtain information about these unpredictable events and the amount of ice lost from glaciers worldwide.

 

Image: http://blogs.ei.columbia.edu/

Source: http://www.smh.com.au/environment/climate-change/glacial-earthquakes-help-researchers-track-massive-ice-loss-as-planet-warms-20150626-ghz5fm.htm