TOOLIK LAKE, Alaska — The hours of sunlight have already shortened from 21 to 12 within the last month here on Alaska's North Slope, where the caribou coexist in the tundra wilderness with the Alaskan pipeline. A sense of the coming long winter is already in the air as researchers from San Diego State University store their computers and specialized equipment until spring.
At the first signs of thaw, the scientists will once more take up their unique experiments that could--when completed within eight to 10 years--have implications for the Earth's future. SDSU, in cooperation with the University of Alaska, is looking at what happens to Arctic tundra when the level of atmospheric carbon dioxide is raised.
Levels of carbon dioxide have been accelerating worldwide in the last several decades because of a growing use of fossil fuels for power plants and automobiles, which release the chemical pollutant into the air as a byproduct of burning. A significant rise in carbon dioxide could affect agricultural production because photosynthesis is the primary method, along with ocean absorption, of removing the chemical from the atmosphere.
Scientists further postulate that unchecked increases could raise temperatures in the lower atmosphere. This is the "greenhouse effect," in which atmospheric carbon dioxide allows radiation from sunlight into the atmosphere but blocks the escape of the ground heat that is generated. A worldwide temperature increase conceivably could reduce or melt the polar ice caps, flooding coastal land.
The importance of the SDSU project comes from the fact that the Arctic tundra, a broad, treeless plain with numerous plant species, absorbs one-fourth of the carbon dioxide taken out of the atmosphere each year by plant life. As a consequence, results of the Alaskan experiments will give scientists vital information for devising the next century's possible climatic and agricultural scenarios from a greenhouse effect.
"The Arctic is extremely important to research because of its permafrost, which can store carbon essentially in an indefinite deep freeze," said Walter C. Oechel, director of the systems ecology research group at SDSU and the head of the Alaska project. The permafrost extends from about 18 inches to several thousand feet below the tundra surface.
"It takes the carbon out of circulation for long, long periods of time; in essence it's an open-ended storage system."
So Oechel and his colleagues are studying how the Arctic ecosystem will respond to increases in carbon dioxide levels, which Oechel said are predicted to double by the year 2070. If the tundra could compensate for higher chemical levels by absorbing the increases, the consequences of a rise in atmospheric carbon dioxide might be less than feared. If not--if the permafrost melts--scientists would be warned to begin attempting measures to lessen the effects of climate and other ecological alterations.
"The doubling could be sooner, but the 2070 date is one assumption we make in our studies," Oechel said. The second major assumption involves a temperature rise of 4 degrees that is predicted for the 21st Century from global climate models.
The project, funded by the federal Department of Energy, includes 12 plexiglass greenhouses on the North Slope about 140 miles south of Prudhoe Bay and about 1,500 miles south of the North Pole. Scientists involved in the project come from several institutions, including the University of Alaska and Duke University, and from the French government. With several tons of computer equipment set up in the field to record observations, the scientists' only fears are that an errant bear or a herd of caribou will wander through their cables, measuring devices and fans.
The four experiments being carried out measure carbon dioxide storage with current atmospheric levels and temperatures, with 50% and 100% increases in chemical levels, and with a 100% increase and a four-degree temperature rise.
Some of the questions Oechel's group is asking include: Will higher levels of carbon dioxide lead to more storage by spurring new photosynthesis and greater plant growth? Is there a level at which the amount of nutrients in the soil will be inadequate to support greater plant growth and cause carbon dioxide storage to level off? Will higher temperatures increase the breakdown of plant matter and thaw the permafrost, which would increase the amount of carbon dioxide in the air?
There are no answers to these questions yet. Definitive conclusions are at least five to seven years away, Oechel said.
"Ecosystems that have come into balance over thousands of years aren't going to show us definitive changes in one or two years," Oechel said.
The eventual conclusions will be extremely useful both to climate modelers and to farmers. The modelers will learn how accurate were their estimates of increased carbon dioxide storage by plants. The agricultural community will be able to judge the need for different amounts of water and nutrients in raising crops.