Over a 35-day period from January 31 to March 7, 2002, Antarctica's Larsen B ice shelf lost a total of about 1,255 square miles (3,250 square kilometers), one of the largest shelf retreats ever recorded. This image, captured by NASA's MODIS satellite sensor on February 23, shows the shelf mid-disintegration, spewing a cloud of icebergs adrift in the Weddell Sea. In December 2007, a team of National Geographic explorers will begin a five-week expedition across the continent's Larsen ice shelf to study how global warming is changing the topography of Antarctica.