A crescent-shaped crack in the centre-right of this NASA satellite image shows where a massive iceberg broke free of the Petermann Glacier and began drifting downstream. The image was taken by the moderate resolution imaging spectroradiometer, or MODIS, on NASA's Aqua satellite
The images show the massive chunk of ice breaking off of the Petermann Glacier on the northwestern coast of Greenland. The glacier produced a similar ice island twice as large in 2010.
NASA said the crack in the glacier had been visible since 2001, and that its polar-orbiting Aqua satellite had observed the break on July 16-17.
Muenchow said the Atlantic waters melting the glacier appear to be warming, but that records only go back to 2003.
"Some changes are dramatically visible, such as the discharge of large ice islands," he wrote. "Some changes, perhaps more important, are not."