Massive Iceberg Peels Off From Antarctic Ice Shelf

The iceberg has begun peeling away from the main ice sheet only 200 miles east of the National Science Foundation (NSF)'s McMurdo Station as measured from the berg's western edge. Among the largest ever observed, the iceberg is approximately 170 miles long x 25 miles wide. Its 4,250 square-mile area is nearly as large as the state of Connecticut.

The iceberg was formed from glacial ice moving off the Antarctic continent and calved along pre-existing cracks in the Ross Ice Shelf near Roosevelt Island. The calving of the iceberg essentially moves the northern boundary of the ice shelf about 25 miles to the south, a loss that would normally take the ice shelf as long as 50-100 years to replace.

Cracks in the Antarctic ice shelf have been closely observed since the advent of remote sensing by satellite and are of particular interest to scientists studying the potential effects of global warming. The breakoff of this iceberg is believed to be part of a normal process in which the ice sheet maintains a balance between constant growth and periodic losses.

Such a berg might bounce against the main ice shelf for several days, sometimes breaking apart, before drifting to sea. NSF supported researcher Doug MacAyeal at the University of Chicago is already at work modeling the potential path of the iceberg, based on the science of iceberg drift dynamics. Polar scientists are concerned that it could drift into McMurdo's shipping lanes, which are used to supply the scientific research station at McMurdo during the austral summer, which begins in October. The rate and direction of drift and the breakup of an iceberg depend primarily on the ocean tides in the area.

NSF, through the United States Antarctic Program, coordinates most U.S. scientific research in the Antarctic. McMurdo Station is the largest of three U.S. Antarctic stations and serves as a "gateway" for field teams studying astronomy, atmospheric sciences, biology, earth science, environmental science, geology, glaciology, marine biology, oceanography and geophysics.

-NSF-

For satellite photos of the iceberg, see: http://uwamrc.ssec.wisc.edu/amrc/iceberg.html