Published: July 23, 1998

CU-Boulder researchers are participating in a major international field experiment to understand climate change trends in the Arctic and whether the Arctic Ocean ice pack is thinning as fast as climate models are predicting.

The Surface Heat Budget of the Arctic Ocean project, known as SHEBA, was designed to understand how the Arctic Ocean, the atmosphere and the ice cap interact to affect the climate of both the Arctic region and the globe. Three Boulder institutions -- the University of Colorado at Boulder, the National Center for Atmospheric Research and the National Oceanic and Atmospheric Administration -- are playing major roles in the project.

"There was an early onset of melt of Arctic snow and ice this year," said Judith Curry, a CU-Boulder professor of aerospace engineering and atmospheric and oceanic sciences participating in SHEBA as a project scientist. Once the Arctic snow and ice start melting, water puddles on the ice and accelerates the creation of ice cracks known as "leads," she said. This increases solar radiation melt on the sides and top of Arctic ice.

"When the snow and ice start melting depends on what is going on with the clouds in terms of how much of the sun's radiation they are reflecting and when precipitation switches over from snow to rain," she said.

Normally about 7 meters thick at the end of September, the Arctic ice cap was measured at less than 2 meters thick in September 1997, according to SHEBA researchers. But even though there was significant melt occurring -- likely tied to El Niño -- it is difficult to separate human-caused climate changes from natural variation, she said.

Curry is the principal investigator on the NCAR C-130 research aircraft making overflights of the Arctic ice. By the end of July, the team will have made 16 flights with C-130 planes, documenting changes in the clouds and surface features, including melt ponds and leads.

The SHEBA project involves aircraft, satellites, a ship, submarines, and even scuba-diving scientists. The effort is funded by the National Science Foundation, the Office of Naval Research, the Department of Energy and NASA, as well as the countries of Japan, Canada and Russia.

A SHEBA icebreaker ship equipped with high-tech instruments has been drifting with the sea ice in the Arctic for the past eight months as part of the project, measuring ice, atmospheric and ocean conditions.

The C-130 flights Curry coordinates has been flying out of Fort Wainright in Fairbanks. Because the SHEBA ship has drifted so far north, it has taken the C-130 three hours to reach the research area from Fairbanks.

"The primary goal is to improve our climate models of the Arctic," said Curry. "The aircraft we use provide a data set that is an intermediate scale between satellite images and information gathered from ships, helping us to fill in additional pieces of the puzzle."

Interactions between sea ice, atmospheric radiation and clouds in the Arctic appear to exert a strong influence on both global and regional climate sensitivity, said Curry. But the effects of clouds are a big question, she said. While clouds may prevent some solar radiation from reaching the ice, the clouds also trap heat and warm the ice.

SHEBA researchers have been testing and implementing models involving Arctic air, atmosphere and sea-ice processes to better understand climate variability since 1997. About 10 CU-Boulder researchers and graduate students are involved in the project.

The SHEBA project will continue until October 1998, said Curry, who is returning to Boulder July 25. It will take scientists about five years to fully analyze the data and improve the climate models in the Arctic, she said.