Increased arctic temperatures could speed up global warming

An increase in arctic temperatures as a result of global warming could result in significantly higher levels of carbon dioxide being released by arctic tundra into the atmosphere, new research suggests.

The Ohio State University study found that if summer temperatures on plots of arctic tundra were artifically increased by about 2oC, carbon dioxide emissions increased by 26 to 38 percent under normal snowfall.

When snowfall on some plots was increased – which is one possibility under global warming – carbon dioxide emissions increased 112 to 326 percent, according to the study which was first published in the journal Arctic and Alpine Research.

“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.”

Researchers have found that arctic carbon loss from respiration of carbon dioxide by plants and soil micro-organisms far surpasses the amount taken in by plants each growing season.

“The arctic has the most rapidly changing climate of any region on earth,” Jones said. He and his colleagues measured carbon dioxide 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 fibreglass chambers – much like mini greenhouses – to warm the air from the end of May to mid-August.

Both air and soil temperatures in the open-top chambers were about 2oC higher than the temperatures in the unmanipulated sites.

Carbon dioxide concentrations were measured in all plots 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 carbon dioxide 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, carbon dioxide 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.

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