NASA Modis Imagery Captures Progress Of 12/08, 1/09 Wilkins Shelf Breakdown

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Mods: Press release.

Changing weather conditions left their mark on sea ice along the Antarctic Peninsula in late 2008 and early 2009. In mid-December 2008, melt water resting on the sea ice colored it sky blue. At the beginning of 2009, however, the sea ice appeared snowy white, and cracks had begun along the ice margin. The MODIS on NASA’s Terra satellite captured these images on December 13, 2008 (main), and January 2, 2009 (visible if you move your mouse over the main image). Both images show the northern portion of the Antarctic Peninsula.

In the image acquired on December 13, a layer of melt water rests on the surface of the sea ice. This sea ice is fast ice that has held fast to the coastline, not moving with winds nor ocean currents. The previous summer on the Antarctic Peninsula had been cold enough to allow this ice to persist, and snowfall may also have accumulated on the ice since that time. The water could result from melted snow, melted ice, or a combination.

In the image acquired on January 2, the sky-blue hue is gone, indicating that the melt water had either drained through cracks in the ice, or refrozen. The full-resolution image of this scene shows the formation of new sea ice in areas to the south, suggesting that refrozen sea ice is more likely. A storm or cold front passing through the region could drop temperatures just enough to form new sea ice. Although the melt water was gone, the sea ice was cracked, and several fissures appeared along the northeastern ice edge.

Along Antarctica’s perimeter, sea ice grows dramatically in the winter and shrinks just as dramatically in the summer. The appearance of melt water on the sea ice in December 2008—late spring in the Southern Hemisphere—was not so much an indication of climate change as an indication of seasonal change. The Antarctic Peninsula has, however, experienced changes suggesting a warming climate. In contrast to sea ice, which may come and go each year, ice shelves are long-lasting slabs of ice attached to coastlines. Historically, the Larsen Ice Shelf on the Antarctic Peninsula has been divided into four sections from north to south: A, B, C, and D. The Larsen A disintegrated in 1995, and the Larsen B disintegrated in 2002. (More recently, the Wilkins Ice Shelf, farther south along the peninsula, experienced both summertime and wintertime breakups.)

When an ice shelf breaks away from a coastline, it often leaves something behind, and a remnant of the Larsen Ice Shelf appears in these images. The remnant shelf is easier to spot in the December 13 image, where it contrasts with the blue melt ponds. The remaining shelf connects with Robertson Island in the east.

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http://modis.gsfc.nasa.gov/gallery/individual.php?db_date=2009-01-12