In early November, 2013 a large iceberg completed separation from the calving front of Antarctica’s Pine Island Glacier. Scientists first detected a rift in the glacier in October, 2011 during flights for NASA’s Operation IceBridge. By July, 2013 infrared and radar images indicated the crack had cut completely across the ice shelf. New images now show that Iceberg B-31 is finally broken free and is coming away from the coast.
The Moderate Resolution Imaging Spectroradiometer (MODIS) aboard the Terra satellite captured a true-color image of the calving in progress on November 8. In this image, Iceberg B-31 sits at the lower right edge of Pine Island Bay, very nominally connected to the Pine Island Glacier. Fractures, appearing as icy blue lines, appear to completely separate the iceberg from the glacier, but only at the lower edge is there a wide separation, where the dark blue-black waters of the Bay can be easily seen. By November 11 the separation had been completed, and the iceberg had clearly begun to move away from the coast.
Named B-31 by the U.S. National Ice Center, the new iceberg is estimated to be 35 km by 20 km (21 by 12 mi),or roughly the size of Singapore. The shelf of Pine Island Glacier has been moving forward about 4 km per year, so the calving of B-31 is not a surprise. Nor it is unprecedented, as such events occur about every five or six years in this region. The most notable feature of B-31 is its large size – it is about 50 percent larger than previous ones in this area.