An iceberg twice the size of Manhattan broke free from one of Greenland's largest glaciers, illustrating another dramatic change to the warming island.
For several years, scientists had been watching a long crack near the tip of the northerly Petermann Glacier. On Monday, NASA satellites showed it had broken completely, freeing an iceberg measuring 46 square miles.
The same glacier spawned an iceberg twice that size two years ago. Together, the breaks made a large change that has gotten the attention of researchers.
"It's dramatic. It's disturbing," said University of Delaware professor Andreas Muenchow, who was one of the first researchers to notice the break. "We have data for 150 years and we see changes that we have not seen before."
Researchers suspect global warming is to blame, but can't prove it. Glaciers do calve icebergs naturally, but what has happened in the last three years to Petermann is unprecedented, Muenchow and other scientists say.
Ohio State University ice scientist Ian Howat said there is still a chance it could be normal calving, but any further loss would show it's not natural: "We're still in the phase of scratching our heads and figuring out how big a deal this really is."