By Sid Perkins
From San Francisco, at a meeting of the American Geophysical Union
Using data gathered by a satellite launched almost 3 years ago, scientists have assembled the most comprehensive high-resolution map of Antarctica that’s ever been made.
The laser altimeter onboard NASA’s ICESat orbiter fires pulses of light down at Earth more than 40 times each second, says John P. DiMarzio, an engineer at NASA’s Goddard Space Flight Center in Greenbelt, Md. The pulses, about 70 meters across when they reach the Earth’s surface, reflect back toward the spacecraft. The time that each pulse takes to make that round trip reveals the elevation of the spot it hit.
ICESat collects elevation measurements down to latitude 86°S, a mere 450 kilometers from the South Pole. DiMarzio and his colleagues have assembled these data into a map that contains more than 100 million grid points spaced an average of 500 m apart. While the rocky fringes of Antarctica lie at sea level, the highest point on the ice sheet covering the continent has an elevation of 4,260 m.
Previous maps of Antarctica covered areas only down to 81.5°S, says DiMarzio. Also, those maps derived from data gathered by satellite-borne radar altimeters that cast a wider spot on Earth’s surface than ICESat does and therefore had lower resolutions.
The new map of Antarctica will be available to the public early next year at http://www.nsidc.org, the Web site of the National Snow and Ice Data Center in Boulder, Colo.
