By Susan Dieterle
The popping and exploding Jim Liljegren heard on July 4, 1998, didn't come from fireworks.
It came from arctic ice being crushed beneath the hull of an icebreaker that was carrying Liljegren toward the solid footing of the North American mainland for the first time in eight weeks -- two weeks past his scheduled June 23 departure date.
The ice pack surrounding the ship where he had been stationed was cracking and melting, making it impossible for the scheduled plane to land safely. He was forced to wait until a second icebreaker, the Polar Sea, could pick him up along with the 13 scientists and 18 crewmen due to leave with him.
Extreme vigilance had been a necessary part of his life for the past two months. Before taking each step, he had carefully probed the ice in front of him to make sure he didn't sink into a slushy hole where the underlying ice was only a few inches thick. And he had warily watched for polar bears prowling the ice in search of seals -- or anything else -- to feed on.
Those two months had given him a firsthand view of both the harshness and the wonder of nature. As the Polar Sea bucked through the expansive ice pack, propelling itself on top of the ice until the sheer weight of the ship crushed through the 12- to 16-foot-thick floe, Liljegren thought about the ups and downs of his experience.
"It was hard not knowing when we would be able to leave," he says. "But it was wonderful to see all of the things you'd read about or modeled actually occurring. It was fantastic."
Liljegren, an atmospheric researcher at Ames Laboratory, was one of several scientists from throughout the world who volunteered for a six-week shift aboard the Des Groseilliers, a Canadian icebreaker intentionally frozen into the arctic ice pack for 13 months to study polar climate conditions. The Des Groseilliers mission is at the heart of a five-year climate study funded by the National Science Foundation and the Office of Naval Research. Data collected during the mission will be used to improve the accuracy of climate models in order to make better predictions of how global warming might affect Earth's climate.
Polar data is crucial; most of the sun's heat strikes Earth at the equator and is then carried toward the poles where it dissipates back into space. Unless the models contain accurate information on the interactions of water, air and ice at the poles, their predictions will be faulty. Prior to the Des Groseilliers mission, it had been more than 100 years since the last long-term study of the arctic climate.
Liljegren's involvement with climate research began seven years ago when DOE was looking for volunteers for its Atmospheric Radiation Measurement (ARM) program, which studies the role played by clouds in maintaining a balance between incoming heat from the sun and outgoing heat radiating from Earth. Liljegren, then a mechanical engineer at Pacific Northwest National Laboratory in eastern Washington, was intrigued.
He began working with ARM's microwave radiometers, sensitive radio receivers tuned to the frequencies at which water vapor and liquid water emit tiny amounts of energy. The strength of the signals indicates the amount of water vapor in the atmosphere and liquid water in clouds. Clouds play a critical role in climate models and in the ongoing debate over global warming. Liljegren notes that although carbon dioxide is the trigger for the so-called "greenhouse effect," water vapor is the controlling factor in the phenomenon.
"Doubling the carbon dioxide concentrations produces only a slight warming in Earth's atmosphere, but because most of Earth is covered with water, this warming will cause more water to evaporate into the air," he says. "Water vapor blocks heat from escaping to space, so this causes additional warming, which causes additional evaporation, and so on.
"But sooner or later, water vapor condenses into clouds, which are made of liquid-water droplets or ice crystals or both. Liquid-water clouds are very effective at keeping heat from escaping Earth's surface, but they also tend to cool the planet."
For now, scientists don't know whether an increased cloud cover would enable Earth's climate to balance itself or cause atmospheric temperatures to escalate. To gather the needed cloud data from a variety of longitudes, ARM has radiometers at three strategic sites: the Great Plains in Kansas and Oklahoma; in the equatorial region near New Guinea; and at Barrow, Alaska.
When the National Science Foundation began planning an in-depth study of the arctic climate, they wanted ARM to participate. The study is known as the Surface Heat Budget of the Arctic Ocean, or SHEBA. As part of the overall five-year SHEBA project, one year would be spent on the ice pack gathering polar climate data, and the next four years would be spent analyzing the data and applying the findings to climate models.
Among the instruments ARM sent to the SHEBA site was a microwave radiometer, which made Liljegren eligible for a six-week shift. Even though cold temperatures aren't his favorite ("I put on a sweater when the air conditioner is on," he says with a laugh), he eagerly signed on.
He wanted a shift in the early summer when the sun is up continuously so he could see the clouds the radiometer was measuring. Fortunately for him, that also meant relatively warmer temperatures and a better chance of spotting polar bears that might be lurking near the ship. He and the other scientists received gun-safety training in case of a polar bear attack.
On May 11, he traveled to Barrow, located on the northernmost tip of Alaska. From there, he boarded a Twin Otter plane along with a fresh rotation of scientists and crewmen and a load of supplies. The plane flew to the SHEBA site every three weeks for personnel exchanges and supply drops and was the sole source of transportation between the ice camp and the mainland.
During the two-hour plane flight, Liljegren was struck by the vastness of the ice pack. "You get this sense of smallness because the ice seems to go on forever," he says. "You realize how very hostile the environment is."
Life in the Arctic took some getting used to. Because the sun never set and because there was so much to learn at first, Liljegren sometimes found himself staying up for 20-22 hours straight. He gradually developed a routine so that he'd know when to sleep. Each day, he would check the data recorded during the night by the various ARM instruments, and then physically inspect each instrument to clear moisture from the lenses, re-level the stands that shifted in the melting ice and make sure they were positioned properly to track the sun. He also helped other SHEBA scientists, sometimes standing guard for polar bears while the researchers checked their instruments on the ice.
Venturing onto the ice was never an easy task. Though temperatures seldom rose above freezing, the wind chill made it as cold as 40 degrees below zero. "You couldn't just take a little walk around the ship," Liljegren recalls. "First, you had to dress appropriately, then you had to check out a radio and a gun and you had to let the bridge know where you were going and stay in contact with them. At first it seemed a little burdensome, but you had to take reasonable precautions to be safe."
Fog and snow frequently shrouded the ice pack, making it difficult for scientists to see the ship from the instrument sites -- and making it difficult to spot an approaching polar bear. There were nopolar bear attacks, although seven bears were sighted during a two-week period beginning in late May.
Anytime a bear got within 1,000 meters of the ship, crewmen set out on either snowmobiles or the helicopter to chase it away. With the scientific staff spending several hours each day out on the ice, a hungry bear would have posed a real threat. By keeping the bears clear of the SHEBA site, neither the bears nor the group members were harmed.
A different kind of danger gurgled beneath their feet. The ice pack melted more rapidly than expected. Large cracks, known as leads, fractured the ice floe. Near the end of May, the crew tied the ship to large mooring posts that had been driven into the outlying ice, a precaution designed to secure the ship and keep the ice from shifting as it started to break up. By mid-June, the ice immediately around the Des Groseilliers' hull had melted, allowing the ship to float within the ice pack.
Melt ponds now covered the ice. Ponds with white bottoms indicated that somewhere below the slush was "multi-year ice" that would never completely melt and would support Liljegren's weight as he stepped on it. Darkened melt ponds, however, indicated that the ice was only a few inches thick.
Life inside the ship was less forbidding. His 8' x 12' cabin was comfortable, and the food was exquisite. The chefs aboard the Des Groseilliers whipped up lavish Sunday brunches and hearty meals. The food served its purpose. The grueling work in frigid temperatures was physically exhausting, so the researchers and crew needed to eat well to keep up their energy levels.
The group also made time for fun. Liljegren visited with his counterparts during the ship's bar nights and attended a few theme parties, including a beach party where he showed off a Hawaiian shirt he'd brought along. "Everybody that I worked with was really nice -- not just professionally, but personally," he says. "All of the people involved were committed to making it a good experience."
At the weekly SHEBA science meetings, Liljegren listened as his fellow scientists explained their work and how the various elements of the arctic ecosystem worked together. He gained a greater appreciation for the way vegetation and animals adapt to the forbidding environment. "The Arctic is prolific in terms of life, although you don't always notice it," he says.
He also managed to find a few moments of solitude. "Every now and then in the evenings, I would go out and just stand on the bow of the ship and look out because it was so unique to see the sun shining at midnight, reflecting off of the melt ponds. It was amazing, really."
Liljegren says he was pleased with the radiometer's performance at SHEBA and is looking forward to analyzing all of the data. "It looks like it's going to give us a really useful picture of the role of polar clouds and of the radiation transfer through the atmosphere," he says. "Everything worked quite well, so we certainly have the data to move forward."
But even as he moves ahead with his work, he looks back with satisfaction at his time in the Arctic. "It was a very unique experience being in a place where almost no one else has been," Liljegren says. "Working and living there for two months was fantastic."
Current research funded by:
DOE Biological & Environmental Research Office
Last revision: 12/17/99 sd
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