Extremes of climate and terrain found on no other continent confront all who venture to Antarctica. Almost a century ago iron men named Admundsen, Shackleton, and Scott raced exhaustion, starvation, frostbite, and each other to the South Pole. Planting Norway's flag, Amundsen won. Today's goal is knowledge: Satellite and ground-based observations help scientists understand the continent and its global climate impacts. The scope and detail achieved by Radarsat's recent Antarctic mapping missions “was once inimaginable,” according to ... NASA. ...
ELEVATION OF THE ICE SHEET - Many mountaintops rise higher than Antarctica's highest point – Vinson Massif, 16,.067 feet – but with an average elevation of 8,000 feet, the continent ranks as Earth's highest. Asia, its closest competitor, averages 3,000 feet. Roughly dome shaped, the ice sheet conceals much of the bedrock relief below. The 1,800-mile-long Transantarctic Mountains rival the Rockies in height, but only the peaks break through the ice.
MEASUREMENTS OF A PARADOX - Ninety percent of the world's ice and 70 percent of the world's fresh water are found here, yet most of Antarctica is truly a desert. The snow equivalent of less than three inches of rain–a precipitation rate close to that of the Sahara–falls over the high interior of the continent each year. But snow and ice have been slowly accumulating on Antarctica for millions of years. More than 15,600 feet deep at tits thickest, the mean depth of the ice exceeds 6,600 feet.
ICE ON THE MOVE - Glaciologists once thought that ice motion in Antarctic's interior was slow and relatively uniform, with just a few fast-moving outlet glaciers and ice streams drawing ice from the interior down to the sea. A computer model based on recent satellite data suggests a more intricate ice-movemnt pattern. Like rivers, coastal ice flows appear to be fed by complex systems of tributaries that penetrate hundreds of miles into major drainage basins.
ULTIMATE WINDS - Katabatic winds–cold air pouring down glacial slopes–often blow at 80 miles and hour and can exceed 180 miles an hour. Offshore, circumpolar winds and currents push against sea ice that rings Antarctica each winter, driving the frozen ocean counterclockwise around the continent.
Shifting Shorelines - Antarctica is a mapmaker's nightmare: By the time its outline is drawn, it is likely to have changed significantly. Less than half of the shoreline is rock or ice firmly grounded on rock. Floating ice shelves and advancing and retreating glaciers make up nearly 60 percent of the coast. Massive icebergs regularly calve from the ice shelves, knocking divots the size of small U.S. states from the outline of the continent. The coastline shown here is based on Radarsat's 1997 Antarctic Mapping Mission. ...
A Sea of Ice - When winter comes, the ocean surface around Antarctica begins to freeze. Spreading over an average of 30,000 square miles a day, the ring of sea ice eventully covers more than seven million square miles, an area larger than the continent itself. Reducing the ocean's absorption of atmospheric carbon dioxide and blocking ocean-atmosphere heat exchange, sea ice plays a role in shaping regional climate that in turn has impacts over much of the globe.
Continent for Cooperation - No single nation rules Antarctica. Since 1959 the terms of a multinational treaty have dedicated the continent to peaceful use and free exchange of scientific information. Some countries make territorial claims, but military activities and mineral exploitation have been prohibited indefinitely. Science is multinational too. Data from automated weather stations, critical to safe operations in this hostile setting, are freely shared. Individual nations maintain bases, but the research projects they support typically involve collaborators from many countries.
Radarsat Fills in the Blanks - Maps of Antarctica's interior remained mostly white blanks into the mid-1980s. Satellites using visible light had produced detailed surface images, but their angles of view excluded more than 1.2 million square miles poleward of about 82º south latitude. Then in 1997 the Canadian Space Agency (CSA) rotated its Radarsat I satellite in orbit, directing its radar sensor toward the South Pole. The first Antarctic Mapping Mission, a joint project of CSA and NASA in the U.S., imaged the entire continent in just 18 days at a resolution many times finer than any other single satellite survey. Compiling Radarsat's 4,500 scans into the digital mosaic seen in this map required two years. Dark areas on the map indicate smooth ice and fine-grained surfaces, like new snow, that don't scatter the radar beam. Coarse surfaces–old granular snow, rough ice, and crevasses–break up the beam and appear bright. During its many passes over the continent the satellite scanned the surface in strips, producing the faint starburst effect that patterns the image. In 2000, Radarsat remapped Antarctica's coast and most of its fast-moving glaciers, astonishing researchers with detailed images of recent change.
