Thursday, February 2, 2012
An astonishing photograph taken from outer-space illustrates how an iceberg the size of New York is close to breaking off from Antarctica.
A 19-mile crack in Pine Island Glacier's ice is clearly visible, leading some scientists to speculate that the world's biggest berg could soon be on the move.
The picture, taken by NASA's Terra spacecraft in November 2011 but only released today, shows how the crack is quickly growing. Just a month before it was only 18 miles long.
Pine Island is a huge 30-mile 'tongue' of ice snaking out from the Hudson Mountains to the Amundsen Sea.
It drains the West Antarctic Ice Sheet, and last calved a significant iceberg in 2001. The crack was first photographed by NASA's Operation Ice Bridge last year.
Until the IceBridge flight of NASA's DC-8 in October, no one had seen any evidence of the ice shelf beginning to break apart.
Pine Island has scientists' attention because it is both big and unstable - scientists call it the largest source of uncertainty in global sea level rise projections.
But the calving underway is part of a natural process, NASA says. The rift is 260 feet wide along most of its length, but in places it is already 800 feet wide. It is 195ft deep.
When 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 only about 160ft of that floating above water and the rest submerged.
It is likely that once the iceberg floats away, the leading edge of the ice shelf will have receded farther than at any time since its location was first recorded in the 1940s.
Video: Nasa discovers massive Crack in Ice Shelf
Video: Nasa animation shows glacier changes detected in west Antarctica
This animation shows glacier changes detected in the highly dynamic region of West Antarctica. The data allows Nasa to estimate surface height changes throughout the drainage areas of the most important glaciers in the region. Large elevation changes are seen at the coast at the center of the images and large and accelerating elevation changes extending inland from the coast to the left and right of the images.