"No place on Earth is more sensitive to global warming than the Arctic, and these satellite images provide scientists with valuable data for understanding how climate change affects this complex region," Gore said in a statement. "By making these satellite images available to the scientific community, we take another important step toward meeting the challenge of global warming," he added.

Recognizing the sensitivity of the polar regions to small changes in climate, the National Science Foundation and the Office of Naval Research funded the Surface Heat Budget of the Arctic Ocean project, or SHEBA, in 1998.

Some 50 scientists made more than 300 types of observations operating from a Canadian ice-breaking ship frozen in the polar ice pack for one year.

A number of SHEBA C-130 aircraft flights coordinated by CU-Boulder aerospace engineering Professor Judith Curry were made over the region in 1998. These photos, combined with the declassified images, should help SHEBA scientists significantly, said Florence Fetterer of the CU-Boulder-based National Snow and Ice Data Center.

Fetterer and Emeritus Professor Norbert Untersteiner of UW had previously used high-resolution reconnaissance imagery when conducting summer sea-ice studies from 1993 to 1995. They later concluded the SHEBA project would benefit from similar imagery.

The National Snow and Ice Data Center is part of the Cooperative Institute for Research in Environmental Sciences, a joint program of CU-Boulder and the National Oceanic and Atmospheric Administration.

"The one-meter reconnaissance imagery seemed an obvious choice because it allows researchers a means of examining pack ice features close-up," said Fetterer of the classified photos being provided to SHEBA scientists. "The imagery also provides a wider view of the ice area around the ship that can be correlated to low-resolution civilian satellite imagery," Fetterer added.

At the request of the NSF, the National Imagery and Mapping Agency officially approved the declassification of 59 days of Arctic spring and summer data. A sample image can be obtained from the U.S. National Reconnaissance Imagery of the SHEBA Site.

The task was aided by the multi-agency Civil Applications Committee, which in 1998 created a means for federal agencies to procure classified remote-sensing data if they could show that their science requirements could not be fulfilled by another conventional data source.