Wednesday, June 2, 2021

Flow of slushy sea ice predicts glacier calving

A view of Illusiat Glacier shows the ice melange (in the foreground) and the sheered off edge of the glacier where a massive ice sheet just broke away. (Jason Amundson)

Ice mélange, the mass of floating sea ice that buttresses many tidewater glaciers, plays a major role in the timing of calving icebergs, finds a new study published in Nature Geoscience

Scientists measured how just a tiny shift in the flow of a mélange, from smooth to slightly more chaotic, can predict up to one hour in advance that a massive hunk of ice will break off from a glacier, then crash into the ocean to form a new iceberg. 

“As a gateway to the ocean, ice mélange is critical to predictions of sea-level rise,” says Justin Burton, associate professor of physics at Emory University and co-author of the paper. “We’ve provided what may be the best, most high-resolution data ever on the dynamics of a mélange leading up to a major calving event. That helps us understand the forces determining how much ice melts into the ocean, and how fast it happens.” 

Ryan Cassotto, a glaciologist from the University of Colorado, Boulder, is lead author of the paper. Co-authors include Jason Amundson from the University of Alaska Southeast, Juneau; and Mark Fahnestock and Martin Truffer, both from the University of Alaska Fairbanks. 

The study’s data was drawn from Ilulissat, a World Heritage Site and the most productive tidewater glacier in Greenland, also known as Jakobshavn Glacier. Kilometer-sized icebergs that calve from Ilulissat often capsize, leading to glacial earthquakes and small tsunamis. 


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