States the size of Rhode Island and Delaware could easily fit on some of the monstrous icebergs adrift near Antarctica.
"We're currently tracking three bergs in the southern Weddell Sea that measure more than 2,070 square miles," says Franklin E. Kniskern of the Joint Ice Center operated by the Navy and the National Oceanic and Atmospheric Administration in this Washington suburb. "None of them currently poses a threat to the research vessels that visit the area."The icebergs form just a small part of the frosty mosaics that the little-known center produces each week for a wide variety of users, including scientists, fishermen, ship captains and wildlife experts.
The center's main responsibility is to map and monitor the massive blanket of ice - most of it in the polar regions - that covers more than 20 million square miles of water. Ice conditions in the Great Lakes are also monitored.
"Two polar-orbiting satellites send back the images that provide the bulk of our data," Capt. Donald E. Hinsman, the center's director, told National Geographic. "Drifting buoys, ship reports, worldwide meteorological information and aerial reconnaissance flights supplement the satellite information."
The center sends out satellite anal-yses and other ice information. It goes worldwide by facsimile, telecopier, telex, radio and direct mail.
Aerial reconnaissance flights are especially busy in the arctic each spring, when ships head for the North Slope of Alaska to resupply military installations. "The flights usually operate each spring through June, while the ice is breaking up, and then again in October and November, when the water starts refreezing," says Hinsman.
Trained observers on reconnaissance flights map the locations and concentrations of ice and try to gauge its age and thickness. The information is quickly relayed back to the center.
The information provided by the center is especially helpful to firms such as Ocean Routes, a California company that tries to advise ship captains on the safest and most economical way to their destinations.
"The seas around Antarctica would be a ghastly blank without the ice center's charts," says George Carlsgaard, Ocean Routes manager of Atlantic and Southern Hemisphere routings. "Without them we would have no idea of the extent of ice boundaries down there."
Fishermen in the Bering Sea between Alaska and the Soviet Union are concerned with ice boundaries, too. "They use our information to get as close to the edge of the sea ice as possible, because that's where the crabs concentrate," Kniskern says.
The ice and snow cover in the arctic also affects birds and, indirectly, hunters. "During June we study the satellite information sent out by the center to determine the extent of the snow and ice covering goose-breeding areas in the high arctic," says Robert J. Blohm, a population assessment expert with the U.S. Fish and Wildlife Service Office of Migratory Bird Management.
A particularly harsh spring that discourages nesting can come home to roost in the fall. "We do a flyby and match those sightings with the broad satellite picture," says Blohm. "Then we let our waterfowl managers know if breeding is likely to suffer so they can establish reasonable quotas in the fall hunting season."
Sea ice also may influence events far above the Earth's surface. Recent studies in the arctic indicate that leads - giant cracks - in the ice allow vast quantities of heat to rise from the ocean into the frigid polar atmosphere. The leads, often spotted by the center, appear when violent windstorms create stress between the ice attached to the land and the sea ice, causing open water to appear.
"No studies have been done in Antarctica but we speculate the same thing may be happening there," says Roger Barry, director of the National Snow and Ice Data Center at the University of Colorado.
It has been estimated that areas where leads occur account for as much as 90 percent of the total energy entering the arctic atmosphere. A slightly warmer arctic climate could increase the size and number of leads, and this might further raise temperatures.
"Any process that disturbs the ice and creates more open water would tend to have a warming effect on the atmosphere and could affect climate in lower latitudes," Barry cautions.
To help scientists such as Barry, the ice center hopes soon to relay ice information by computer to key users. The program, known as the Digital Ice Forecasting Analysis System, will give the users complete ice data almost instantly.