February 3, 2012
Spectacular Photos Show Birth Of World’s Biggest Iceberg
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Breathtaking images taken from outer-space by NASA's Operation IceBridge -- the largest airborne survey of Earth's polar ice ever flown -- reveal a 19-mile long, 195 ft.-deep crack across a floating ice shelf in Antarctica that could produce the world´s largest iceberg.The rift was first discovered last October, but IceBridge scientists returned soon after to obtain the first-ever detailed airborne measurements of the 310 square mile iceberg calving in progress.
The images, which were taken in November by NASA's Terra spacecraft, were only released this week, and clearly show how fast the rift in the Pine Island Glacier in western Antarctica is growing — having increased from 18 to 19 miles in just one month.
Pine Island Glacier is a vast 30-mile section of ice reaching out from the Hudson Mountains into the Amundsen Sea. The slow-moving river of ice drains the West Antarctic Ice Sheet, and has not calved a major iceberg since 2001.
The glacier has long attracted the attention of scientists because it is both large and unstable. In fact, experts call it the largest source of uncertainty in global projections of rising sea levels.
Until the IceBridge flight last October of NASA's DC-8, no one had ever seen any evidence of the ice shelf beginning to break apart.
However, the calving underway is the result of a cyclical process, not climate change, scientists say.
The Pine Island Glacier rift is 260 feet wide along most of its length, although in some places it is as much as 800 feet wide. By the time the iceberg breaks free it will cover about 350 square miles of surface area.
Radar measurements suggest the ice shelf in the region of the rift is about 1,640ft thick, with roughly 160ft of that floating above water and the rest submerged.
Image Caption: NASA's DC-8 flew over the Pine Island Glacier Ice Shelf on Oct. 14, 2011 as part of the agency's Operation IceBridge. A large, long-running crack was plainly visible across the ice shelf. The DC-8 took off on Oct. 26, 2011, to collect more data on the ice shelf and the crack. The area beyond the crack that could calve in the coming months covers about 310 square miles (800 square kilometers), IceBridge project scientist Michael Studinger said. Credit: NASA/GSFC/Michael Studinger
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