Increased Arctic Temperatures Could Speed Up Global Warming

The study found that artificially elevating summer temperatures by about 2 degrees Celsius (3.6F) on plots of arctic tundra increased the CO2 emissions by 26 to 38 percent under normal snowfall. When snowfall on some plots was increased -- which is one possibility under global warming -- CO2 emissions increased 112 to 326 percent.

“We found significant losses of carbon dioxide from the soil of the tundra,” said Michael Jones, a post-doctoral researcher in evolution, ecology and organismal biology at Ohio State University. “Anticipated global warming may increase this carbon loss.”

The study appears in a recent issue of the journal Arctic and Alpine Research.

The arctic, which covers about one-fifth of the globe, contains nearly one-third of the earth’s stored soil carbon. Researchers have found that arctic carbon loss from respiration of CO2 by plants and soil micro-organisms far surpasses the amount taken in by plants each growing season. Carbon dioxide is a major player in global warming.

“The arctic has the most rapidly changing climate of any region on earth,” Jones said. He and his colleagues measured CO2 emissions from moist and dry tundra surrounding Toolik Lake, Alaska. Researchers believe carbon dioxide loss may be different in moist and dry tundra areas. They manipulated winter precipitation in each area by setting up a large snow fence on each tundra type. These fences provided increased snow accumulation and also helped simulate potential changes in environment and climate.

“We know there will be more snow accumulation with increasing winter temperatures,” Jones said. “If the snow takes longer to melt, that shortens the growing season, and that may influence how much carbon dioxide is released.”

The study found that the deep snow sites took about four weeks longer to completely melt than the normal-snow sites.

The researchers also increased summer temperatures in both tundra sites. They used small open-top fiberglass chambers -- much like mini greenhouses -- to warm the air. They used a temperature recording device to take air and soil temperatures in three warmed and three unwarmed plots every 48 minutes from the end of May to mid-August.

Both air and soil temperatures in the open-top chambers were about 2C (3.6F) higher than the temperatures in the unmanipulated sites.

Carbon dioxide concentrations were measured in all plots using an infrared gas analyzer attached to a Plexiglas box. Measurements were taken every four hours for a 24-hour period once a week from early June to late August.

The results showed that moist tundra emitted more carbon dioxide than dry tundra, although losses at both types of sites were significant. The researchers found that in both tundra types, seasonal CO2 loss was higher in the experimentally warmed plots, regardless of the amount of snowfall the previous winter.

Under experimental warming, carbon dioxide emissions were greater from deep-snow plots than those with normal snowfall. However, under normal temperatures, CO2 emissions were lower in deep-snow plots compared to plots with normal snowfall.

“Our results show there is already carbon dioxide loss under current climate conditions, and we expect this will only increase under global warming,” Jones said.

Other researchers included Jace Fahnestock and Jeff Welker of the Department of Renewable Resources, University of Wyoming at Laramie; and Donald Walker and Marilyn Walker of the Institute of Arctic and Alpine Research at the University of Colorado at Boulder. The research was supported by a grant from the Office of Polar Programs at the National Science Foundation.