Researchers monitoring Greenland's Jakobshavn Isbrae glacier report that a 7km² section of the glacier broke up on July 6 and 7, as shown in the image above. The calving front – where the ice sheet meets the ocean – retreated nearly 1,5km in one day and is now further inland than at any time previously observed.

Research teams led by Ian Howat of the Byrd Polar Research Center at Ohio State University and Paul Morin, director of the Antarctic Geospatial Information Center at the University of Minnesota have been monitoring satellite images for changes in the Greenland ice sheet and its outlet glaciers. While this week's breakup itself is not unusual, Howat noted, detecting it within hours and at such fine detail is a new phenomenon for scientists.

"While there have been ice breakouts of this magnitude from Jakonbshavn and other glaciers in the past, this event is unusual because it occurs on the heels of a warm winter that saw no sea ice form in the surrounding bay," said Thomas Wagner, cryospheric program scientist at NASA Headquarters. "While the exact relationship between these events is being determined, it lends credence to the theory that warming of the oceans is responsible for the ice loss observed throughout Greenland and Antarctica."

The researchers relied on imagery from several satellites, including Landsat, Terra, and Aqua, to get a broad view of ice changes at both poles. Then, in the days leading up to the breakup, the team received images from DigitalGlobe's WorldView 2 satellite showing large cracks and crevasses forming.

DigitalGlobe Inc. provides the images as part of a public-private partnership with U.S. scientists. Howat and Morin are receiving near-daily satellite updates from the Jakobshavn, Kangerlugssuaq, and Helheim glaciers (among the islands largest) and weekly updates on smaller outlet glaciers.

Jakobshavn Isbrae is located on the west coast of Greenland at latitude 69°N and has been retreated more than 45km over the past 160 years, out of which 10km is in just the past decade. As the glacier has retreated, it has broken into a northern and southern branch. The breakup this week occurred in the north branch.

Scientists estimate that as much as 10% of all ice lost from Greenland is coming through Jakobshavn, which is also believed to be the single largest contributor to sea level rise in the northern hemisphere. Scientists are more concerned about losses from the south branch of the Jakobshavn, as the topography is flatter and lower than in the northern branch.

Source: NASA