In 1995, President Clinton signed an order declassifying all intelligence satellite photography taken before 1972. The CIA's Corona satellites carried large spools of film into space. After photographs were taken, the satellites jettisoned the exposed film, which was then snared in midfall by military planes. During 1963, the CIA photographed giant rivers of ice, called ice streams, which drain into the Ross Ice Shelf. Up to 80 kilometers across and hundreds of kilometers long, ice streams flow 10 to 100 times faster than the ice along their banks.
Scientists consider the streams critical to the stability of the ice sheet covering West Antarctica.
Bindschadler and Patricia Vornberger of General Science Corp. in Laurel, Md., compared satellite images to measure how far key features had moved over the decades. Researchers on the ice in 1984 and 1985 observed that the ice was then moving at only 471 m per year, less than half as fast. Over this same period, the ice stream widened by 4 km, much more than researchers had anticipated. The relatively slow-moving banks of the ice stream are thought to restrict its flow. As the stream widens, the banks move away from the center of the stream and the ice there should flow faster, says Charles F. Raymond of the University of Washington in Seattle.