Konrad Steffen: The Global Warming Prophet

"I couldn't get the Ski-Doo started," he says, "and my leg was hanging loose. I dragged myself to a place where we had put an aluminum stake to mark a measuring point. I pulled out the stake and used it to straighten my leg. Then I pushed the snowmobile on its side to get some shelter. I had to get up on my good leg every half hour to jump around, to keep the circulation going. Smoking was out of the question, because I knew that if you smoke, you open your blood vessels; I would freeze to death."

When the storm died down, eight hours later, his research partner, Karl Schroff, began searching for him on foot. (Their other snowmobile had broken through the sea ice and sunk a few days earlier, dunking Steffen in 30F water.)

"Karl was on the top of the ice sheet," Steffen recalls, "and he could hear something like krrrack, krrrack. He knew this kind of a bird did not exist there, so he followed the sound. It was me yelling his name, with no voice left."

Schroff left Steffen with a piece of chocolate and went back to their camp to radio for help. After no one replied to his first round of mayday calls, he fell asleep from exhaustion. A few hours later, he woke and tried again. This time he reached a U.S. Air Force plane, flying toward Thule AFB. A Canadian rescue party eventually plucked Steffen off the ice, 24 hours after he was knocked off his snowmobile. In his pocket was a farewell letter to his then girlfriend, now his wife. "I still have it," he says. "I never gave it to her."

"Anyway," Steffen says, stubbing out his cigarette, "it was good to know that I could quit if I really needed to."

THE SECRET LIFE OF ICE SHEETS
For the past 14 years, NASA glaciologist Jay Zwally has been Steffen's regular partner on the Greenland ice cap. When they were young scientists, conventional wisdom held that ice sheets, unlike glaciers, respond extremely slowly to warming, losing substantial mass only over hundreds of years as meltwater runs off the top or evaporates. But as Zwally and Steffen looked at their data trends, they suspected that another process must be at work. "This is not just melting," Steffen says. "You cannot melt this much ice this quickly."

They theorized that meltwater on the surface of the ice cap was draining through fissures down to the bedrock nearly 4,000 feet below. To test the theory, they installed a network of GPS transceivers, accurate to a few centimeters. They compared the GPS measurements with data from satellites, ground-penetrating radar and other instruments. Then, in a 2002 paper that jolted the scientific community, they concluded that ice-sheet flow accelerates with surface melting, similar to glaciers.

"We call this phenomenon 'dynamic response,' " Steffen says. "What happens is that the melting accelerates as meltwater funnels down to the bedrock. At the bottom, the water acts as a lubricant, flowing under the outlet glaciers and allowing the ice to slip into the sea more quickly. We hadn't expected that ice sheets could react to warming so quickly. But that is the kind of feedback we are coming to understand in the Arctic; it's a very sensitive environment."

The current acceleration could be a short-term adjustment to the warmer temperatures, Steffen says, or it might last much longer. But some scientists, including lead NASA climatologist James Hansen, believe that Zwally and Steffen's observations, coupled with new data from Antarctica, suggest that a major polar melt may be commencing. They point to a phenomenon called the albedo effect, in which melting ice exposes more land and water, causing the earth's surface to become less reflective, and to absorb more of the sun's energy.