Oct. 2, 1997 Initial images from the first complete radar survey of Antarctica, using the Canadian Space Agency's Radarsat mission, show better-than-expected details of its massive ice streams and crevices, as well as old, buried features of the international South Pole research station established in the late 1950s.
"The quality of these first images is quite stunning," said Dr. Robert Thomas, program manager for polar research in NASA's Office of Mission to Planet Earth, Washington, DC. "Antarctica is the only continent on Earth that has not been properly mapped. Despite many years of research, we still do not know whether this massive ice sheet is growing larger or smaller. Radarsat's Antarctic Mapping Mission should help us answer this question, and many related questions about its potential for affecting global sea levels."
Nearly 70 percent of the Earth's fresh water is contained in the Antarctic region, and changes in this enormous reservoir directly influence world sea levels and climate. As a reference point, if fully melted, this ice would raise the global sea level by about 230 feet (70 meters).
Previous research has revealed that about 90 percent of Antarctic ice flows into the sea via large "ice streams." These rivers of ice are tens of miles wide and about a half-mile thick, and can flow rapidly within the predominantly slow-moving ice sheet. "We know little about why these ice streams form where they do, or what determines their speed," Thomas said. "Most Antarctic ice streams flow into 'ice shelves,' large, floating slabs of ice the size of Texas that rest on the ocean and occupy most of the Antarctic coastline. They move seaward at about a half-mile per year, occasionally 'calving' to form huge icebergs."
Where the seabed beneath an ice shelf becomes sufficiently shallow, the ice shelf runs aground, slows down and thickens to form an "ice rise" which tends to slow the seaward progress of the ice shelf, and ultimately to hinder ice discharge down the ice streams. However, if the ice shelf were to become sufficiently thin, for instance, by increased melting from beneath, the speed of ice discharge would increase, allowing more ice to flow into the ocean, and thus raising the sea level. "Just how quickly this could happen if climate were to change is not known, and would depend heavily on whether the ice sheet is already thinning or, as some evidence suggests, actually thickening," Thomas said. "These unknowns are the prime reasons for this research effort."
The first radar image of Earth's geographic South Pole from the Radarsat Antarctic campaign clearly shows the infrastructure of the Amunsden-Scott Station operated by the U.S. National Science Foundation. The image reveals the modern infrastructure that supports a host of international science programs, but also shows an abandoned aircraft runway and other remains of the old South Pole station, now buried under about 30 feet of snow and ice.
This image and several others, as well as further information on the Radarsat mission, are available on the Internet at the following URL, under the link to the Antarctic Mapping Mission:
The Antarctic Mapping Mission was made possible by rotating the satellite 180 degrees from its normal field of view, which was completed on Sept. 11. Full mapping will require the collection of over 5,000 images.
"Following the successful rotation, 30 percent of the mission's objectives have now been achieved," said Rolf Mamen, Director General of Space Operations at the Canadian Space Agency. "We are extremely pleased with the quality of the radar images being obtained of this unmapped region of our planet, and of the contribution we are making to the scientific community."
The high-resolution digital image mosaic of the ice sheet and exposed portions of the continent to be taken by the Antarctic Mapping Mission will serve as a benchmark for testing the predicted effects of global warming on the interior ice sheet and its bounding ice shelves. This unique data set also will support the development of policies to help preserve Antarctica in its relatively pristine state, through the goals subscribed under the international Antarctic Treaty System.
U.S. partners in the Antarctic portion of the Radarsat mission include the Byrd Polar Research Center of Ohio State University, Columbus, OH; NASA's Alaska Synthetic Aperture Radar Facility in Fairbanks; the Jet Propulsion Laboratory, Pasadena, CA, and the Goddard Space Flight Center, Greenbelt, MD.
"The job of mapping one of the last largely unexplored regions of the Earth is truly a mission of international cooperation, with collaboration that includes scientists from Great Britain, Germany, Japan, and Australia in addition to the United States and Canada," said Dr. Kenneth Jezek, a professor of geological science and director of the Byrd Polar Research Center at Ohio State University. "In that way, the Antarctic Mapping Mission is in keeping with the spirit and intent of the Antarctic treaty, which serves to preserve the continent for peaceful scientific research by any nation."
In exchange for the launch of the Radarsat satellite by NASA in November 1995, Canada agreed to provide access to a proportionate amount of its operational data and to execute the yaw maneuver of the spacecraft twice during the mission to allow the mapping of the Antarctic continental ice sheet.
Operated by the Canadian Space Agency from St. Hubert, Quebec, Radarsat utilizes a sophisticated microwave radar system able to produce images through cloud cover, smog, haze, smoke and darkness. The satellite can be programmed to capture images of an area as wide as 320 miles (500 kilometers), and can detect objects as small as 26 feet (eight meters.)
NASA's involvement in Radarsat is part of the agency's Mission to Planet Earth enterprise, a long-term coordinated research program to study the Earth's land, oceans, air, ice and life as a total system.
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