Insider

Going with the floe

Research aboard ice-bound ship will provide key data on polar clouds

By SUSAN DIETERLE

Scientists don’t usually need shotgun training before embarking on a field experiment. But when the research site is home to polar bears, it helps to be prepared.

Jim Liljegren, a scientist in atmospheric research who recently joined Ames Lab’s Nondestructive Evaluation Program, is scheduled to spend May 13-June 23 on the Des Groseilliers, a Canadian icebreaker that has been frozen into an arctic ice pack as part of a 13-month mission to study the region’s role in global climate change.

The ship is about 400 miles north of Barrow, Alaska, and will continue to slowly drift west with the ice pack until it is freed from the ice in October.

As part of the preparations for the six-week excursion, Liljegren traveled to U.S. Department of Energy’s (DOE) Sandia National Laboratory in New Mexico for shotgun training in case of a polar bear attack.

"Our first line of defense is to pay attention to what’s going on around us and, if possible, to vacate the area whenever a polar bear is sighted on the horizon," Liljegren explains. "But it isn’t always possible to do that."

Although Liljegren thinks he has little chance of encountering a polar bear, the training "is a better-safe-than-sorry measure."

The research being conducted on the icebreaker is part of a five-year, international project known as the Surface Heat Budget of the Arctic Ocean (SHEBA), aimed at providing scientists with a better understanding of polar climates and they are affected by global change. Among the participants in SHEBA is the DOE’s Atmospheric Radiation Measurement (ARM) Program, a broad-based effort to develop better models for predicting the effect of clouds on the Earth’s climate.

For the past six years, Liljegren has been responsible for ARM’s microwave radiometers – instruments that measure the amount of water vapor and liquid water in clouds. One of the radiometers is aboard the ship to gather much-needed data about the nature of polar clouds.

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

Researchers need this data to fully understand how polar clouds affect the rate of heat transfer between the Earth’s surface and the atmosphere. This is crucial because most of the Earth’s heat is lost at the poles. "If the climate models don’t treat the processes near the arctic very well, then their estimate of the impact of global warming may be incorrect," Liljegren says.

Global warming remains an issue where – for now – there are many questions but relatively few solid answers. Some experts predict that the increased burning of fossil fuels will double the amount of carbon dioxide in the Earth’s atmosphere in 20 years, trapping more solar radiation near the ground and raising the surface temperature of the Earth. Because three-fourths of the planet’s surface area is water, a higher surface temperature would increase water evaporation. More water vapor would mean more clouds to trap the heat, causing the warming cycle to continue – melting the polar ice and unleashing massive climate changes.

But other experts point out that clouds also deflect heat from the sun. If there are more clouds, they reason, less solar heat would reach the Earth – possibly allowing the climate to balance itself.

At this time, though, researchers say the current climate models aren’t accurate enough to predict what might happen. Climate models are complex because they deal with three main components – atmosphere, ocean and land – that experience change on widely varying timetables, Liljegren says. The atmosphere can change in a few seconds, while change in the deep ocean takes centuries. Developing a model that accurately represents the interactions of the components is difficult.

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

One of Liljegren’s planned improvements is rewriting software to enable the radiometer to make faster measurements, thus improving coordination between the radiometers and ARM’s new cloud radars. He is also developing an algorithm that combines infrared measurements of cloud temperature with the microwave measurements in order to determine the liquid-water content of clouds more accurately than the current algorithm, which uses microwave measurements alone.

Liljegren became involved with ARM while working at the DOE’s Pacific Northwest National Laboratory in Washington. He has been at the Ames Lab since October.

ARM has radiometers around the world: at the Southern Great Plains site in Oklahoma and Kansas; in Barrow, Alaska; near Papua, New Guinea; and now on the icebreaker.

Liljegren has visited the Southern Great Plains site several times, and jumped at the chance to spend time aboard the Des Groseilliers. Because Liljegren wants to see the clouds his equipment is measuring, he chose to go during the late spring when the sun is up continuously. "It’s also not quite so cold," he adds with a laugh.

The frigid temperatures and hazards of arctic life aren’t chilling Liljegren’s enthusiasm for the trip. "I’m eager to go because, as an experimentalist, it really helps to go to the field and actually be there as the data are collected so that you get a reality check rather than simply being an armchair commando."

Published: February 1998

Last revision: 4/17/98 sd

Home | Comments | Search | Disclaimer