A chunk of ice twice the size of Manhattan has parted from Greenland's Petermann glacier, a break that University of Delaware and Canadian Ice Service researchers attributed to warmer ocean temperatures.
The separation along Greenland's northwest coast, which happened Monday, represents the second major calving event for the glacier in the past three years. In August 2010, the Petermann glacier lost an area of roughly 97 square miles, compared with the 46 square miles that just split off this week.
Andreas Muenchow, a University of Delaware associate professor of physical ocean science and engineering, said the glacier's end point is now at "a location where it has not been for at least 150 years."
"The Greenland ice sheet is changing rapidly before our eyes," Mr. Muenchow said in an interview, adding that while "no individual glacier will be the canary in the coal mine," recent warming has transformed the overall ice sheet. "The Greenland ice sheet is being reduced not just in size, but in volume," he said. "The big and broader climate change story is what's happening all around Greenland."
Ted Scambos, lead scientist for the University of Colorado's National Snow and Ice Data Center, said scientists will now be monitoring whether the glacier's flow rate will accelerate "because of its loss of this chunk of ice at the front of it." He added, "It's going to take awhile to understand how significant a loss this is."
The Petermann glacier's flow accelerated between 10 percent and 20 percent after the 2010 calving event, Mr. Muenchow said, adding that researchers were still waiting to see if that was a short-term increase or would persist over time.
Ohio State University polar researcher Jason Box noted that the 2010 calving was "the largest in the observational record for Greenland." He correctly predicted last summer that the piece that just broke off, about half the size, was on the brink.
Air temperatures in the region have warmed more than 4.5 degrees Fahrenheit, or 2.5 degrees Celsius, since 1987 -- a rate five times that of the rest of the world. But Mr. Muenchow cautioned against directly linking air temperatures to the glacier's behavior, noting that it has a floating ice shelf.