Wilkins Ice Bridge Collapse

Credit: Jeff Schmaltz; MODIS team; NASA , Posted on: Tuesday, 14 April 2009, 06:33 CDT Download full size image

This image, captured by the MODIS on the Aqua satellite shows the Wilkins Sound, a seaway on the southwest side of the Antarctic Peninsula. The interesting thing in this image, besides the lovely wavy shape of the icy coastline, is that in it, you can see the breakup of a the narrow ice bridge that connects Charcot Island and Latady Island. This is the last remnant of the northern part of Antarctica’s Wilkins Ice Shelf. The remains of the ice bridge are near the image top center, beneath that top jutting peninsula of ice.

In this linked image, taken by the MODIS on the Terra satellite on March 31, 2009, the ice bridge was still intact. The ice appears to be smooth, an unbroken surface. Less than a week later, late on April 6, the MODIS on the Aqua satellite captured the image you see above. The smooth bridge is gone, replaced by chunks of ice. The breakup was initially observed in radar imagery by the European Space Agency.

The pieces of the former ice bridge join multiple other chunks of ice formed as the northern portion of the ice shelf broke apart throughout the previous decade. The broken pieces of the shelf have remained frozen in place since 1998, but now that the ice bridge no longer provides a barrier, the remnants of the ice shelf may flow out into the Southern Ocean. A careful comparison of the two images reveals that some of the ice nearest the bridge shifted between March 31 and April 6.

Many factors contributed to the collapse of the northern portion of the ice shelf, including brine on the ice, physical stresses on the shelf, and warming temperatures, says Scambos. Throughout 2008, parts of the ice shelf (formerly to the left of the bridge) broke away. The ice bridge had been the last intact portion of the northern edge of the ice shelf. The southern portion of the Wilkins Ice Shelf (part of which appears in the lower right corner of the images) is still intact, but may be more vulnerable now that the northern edge has disintegrated.

What is the significance of the disintegration of the northern portion of the Wilkins Ice Shelf? The collapse of the ice shelf will not contribute to sea level rise, since the ice had already been floating on the water. When other ice shelves such as the Larsen, have collapsed, they allowed glaciers to pump more ice into the ocean at a faster rate, which did contribute to sea level rise. The Wilkins Ice Shelf, however, does not buttress any major glacier, says Scambos. The Wilkins Ice Shelf is the tenth major ice shelf to collapse in recent times, another sign that warming temperatures are impacting Earth’s fragile cryosphere.

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