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Inside Iowa State
May 1, 1998

The big chill

Ice-bound ship may hold secrets to global warming

by Susan Dieterle, Ames Laboratory Public Affairs

Ames Laboratory scientist Jim Liljegren soon may find out what it's like to live on thin ice. Liljegren, an atmospheric researcher in the lab's nondestructive evaluation program, will spend May 13 to June 23 on the Des Groseilliers, a Canadian icebreaker that was frozen into the ice last September as part of a 13-month mission to study the arctic's role in relation to global climate change.

A variety of instruments are aboard the ship and on the surrounding ice. The ship is about 400 miles north of Barrow, Alaska, and is drifting west with the ice pack.

"I'm eager to go," Liljegren said, "because, as an experimentalist, it really helps to go to the field and be there as the data are collected so that you get a reality check rather than simply being an armchair commando."

Liljegren will be gathering data about polar clouds.

Polar climates studied

The research being conducted on the ship is one component of a five-year, international project known as the Surface Heat Budget of the Arctic Ocean (SHEBA), aimed at providing scientists a better understanding of polar climates and how global change affects them. Among the participants is the U.S. Department of Energy's Atmospheric Radiation Measure- ment (ARM) Program, an effort to develop better models for predicting the effect of clouds on the Earth's climate.

Liljegren is responsible for ARM's microwave radiometers -- instruments that measure the amount of water vapor and liquid water in clouds. One of the ARM radiometers is on the ice pack to gather data about polar clouds.

"Polar clouds are considerably different from what you find at mid-latitudes and aren't anything like what you typically find in the tropics," Liljegren said. "Because of the remoteness of the arctic, the data on polar clouds has been extremely limited."

Rotating shifts scheduled

Polar regions are viewed as key areas in determining the possible effects of global warming. Because the poles are sensitive regions, effects of global climate change are likely to be noticed there first.

Scientists who have equipment aboard the icebreaker have been scheduled for rotating shifts. Liljegren wants to see the clouds his equipment is measuring, so he chose to go during the late spring when the sun is up continuously.

Researchers hope data from the SHEBA experiment will help provide some answers to the questions surrounding global warming. Scientists say current climate models aren't accurate enough to predict what might happen if the Earth's surface temperature grows warmer. Clouds play a dual role in the climate models since they help trap heat in the atmosphere as well as deflect energy from the sun.

"Cloud models are very complicated and very sophisticated, but all of that sophisti-cation cannot be put into these large climate models. The large models have somewhat oversimplified how clouds form and what effect clouds have on the radiative balance," Liljegren said. "My area of research is to try to improve that state of affairs."

Cloud water content determined

One of Liljegren's plans is to rewrite software to enable the radiometer to measure more quickly, thus improving coordination between the radiometers and ARM's new cloud radars. He also is developing an algorithm intended to more accurately determine the liquid water content of clouds.

"Most of science seeks to break things down into finer and finer elements so that you understand the details of that element really, really well," Liljegren said. "The focus in climate research is on the interactions among the different elements and how a change in one affects the others. You really get to see that the global climate system is just that -- a system."

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