The vast, flat expanse stretching into the background is the Petermann Glacier, well over one-third of which has now broken off. It connects the Greenland ice sheet to the Arctic Ocean. (Professor Andreas Muenchow, University of Delaware)

A chunk of ice twice the size of Manhattan has parted from Greenland’s Petermann glacier, a break researchers at the University of Delaware and Canadian Ice Service attributed to warmer ocean temperatures.

The separation along Greenland’s northwest coast, which took place 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, an associate professor of physical ocean science and engineering at the University of Delaware, 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,” 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.”

These 2010 and 2012 NASA images provided by the University of Delaware show the formation of a crack in northwestern Greenland's Petermann Glacier. On Monday, an iceberg twice the size of Manhattan tore off one of Greenland's largest glaciers, indicated at center right. (AP)

Ted Scambos, the lead scientist for the National Snow and Ice Data Center at the University of Colorado, 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.”

“It’s going to take awhile to understand how significant a loss this is,” Scambos said.

The Petermann glacier’s flow accelerated between 10 and 20 percent after the 2010 calving event, Muenchow said, adding researchers were still waiting to see if that was a short-term increase or would persist over time.

Polar researcher Jason Box of Ohio State University 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.

Box could not be reached for comment Tuesday.

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 Muenchow cautioned against directly linking air temperatures to the glacier’s behavior, noting it has a floating ice shelf.

“Air temperatures are not very important, because 80 percent of the melting of this glacier takes place from below, in the ocean,” he said.