ANCHORAGE - Columbia Glacier has retreated nine miles over the past 20 years in a meltdown punctuated by ice quakes and submarine gushes of water triple the flow of the Mississippi River. "It's 50,000 cubic meters per second ... for seven minutes," said glaciologist Tad Pfeffer early last month from the American Geophysical Union meeting in San Francisco. "It comes out of the bottom of the glacier, and it flows up the front of the ice cliff and spreads out on the surface."
The findings about the Prince William Sound glacier were announced at the annual meeting, where Pfeffer and his team presented three scientific reports about the Columbia's continuing breakup and mysterious dynamics. Columbia Glacier has now pulled back to the halfway point of its expected retreat. But it may be on the cusp of a much faster withdrawal across a broad inner bay, Pfeffer said.
New research during the past two summers has measured powerful ice quakes that shake the glacier when great chunks break into the sea, offering a more accurate way to keep track of the glacier's calving. Understanding how the Columbia changes as it shrinks will help scientists predict what will happen with much larger glacial systems in Greenland and Antarctica in the face of climate warming, Pfeffer said.
Pfeffer and other researchers from the Institute of Arctic and Alpine Research at the University of Colorado in Boulder have been scrutinizing the glacier with seismometers, lasers, and time-lapse and aerial photography for several years. Pfeffer's team took the 130th aerial photograph of the glacier this year, continuing a series that goes back more than 30 years.
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