Antarctica 03/17/08

MODIS image of Antarctica

In late February 2008, the Wilkins Ice Shelf on the Antarctic Peninsula disintegrated, an indication of warming temperatures in the region. The Moderate Resolution Imaging Spectroradiometer (MODIS) sensors on NASA's Terra and Aqua satellites provided some of the earliest evidence of the Wilkins Ice Shelf disintegration. Ted Scambos, lead scientist at the National Snow and Ice Data Center (NSIDC), noticed changes in the shelf in MODIS imagery in March 2008.

Terra acquired these images on February 28 (top) and March 17 (bottom). The top image, acquired just before the breakup, shows the intact ice shelf. The bottom image, taken 18 days later, shows the remnants of the ice shelf becoming frozen in place by surrounding seawater. Whereas the intact ice shelf appears white, the disintegrated shelf appears in varying shades of pale blue indicating small pieces of water-saturated ice mixed with a newly forming veneer of sea ice.

In the March 17 image, amid the pieces of shattered shelf, large blocks of ice cluster along the northern and (especially) southern edges of the shelf. Upstream from the broken shelf, crevasses appear on what remains of the shelf, suggesting that this portion of the shelf remains vulnerable to disintegration. According to Scambos, however, the ice shelf will not likely undergo further breakup until the next Antarctic summer. "The ice has begun to re-freeze, and it's already been snowed on," he stated.

At roughly 70.5 degrees south and 72.5 degrees west, the Wilkins Ice Shelf occupies some 13,680 square kilometers (5,282 square miles), and has a maximum thickness of 200 to 250 meters (656 to 820 feet). Like other ice shelves, the Wilkins floats on the surface of the water, but is also glued to the shore. The shelf's disintegration appeared to result directly from warming temperatures. In the five decades prior to the collapse, the Antarctic Peninsula experienced a temperature increase of 0.5 degrees Celsius (0.9 degrees Fahrenheit) per decade, making it one of the fastest warming places on Earth, according to the National Snow and Ice Data Center.

This map of the temperature trend is based on thermal infrared (heat) observations from National Oceanic and Atmospheric Administration (NOAA) satellite sensors. This image shows trends in skin temperatures-roughly the top millimeter of the land, sea ice, or sea surface, rather than air temperatures-and it shows the long-term change in yearly surface temperature between 1981 and 2007. Warming areas appear in shades of red, and cooling areas appear in shades of blue. One of the most dramatically warmed areas appears at the former location of the Larsen B Ice Shelf, which shattered in 2002. Although some 300 kilometers (185 miles) farther south than the Larsen, the Wilkins Ice Shelf seems to have succumbed in the same fashion in early 2008.

Please see the full article on the Wilkins Ice Sheet at the Earth Observatory:

Text and image courtesy of NASA's Earth Observatory.