Permafrost Thaw Does Not Offset Arctic Carbon Emissions

The extending growing season in the Arctic that has come along with a warming climate does not offset carbon emissions from permafrost thaw, according to the Woods Hole Research Center (WHRC).

Writing in the journal Ecology, WRCH researcher Sue Natali and her colleagues report on their first-of-its-kind field experiment to determine net gains and losses in carbon emissions that come from thawing permafrost.

"Our results show that while permafrost degradation increased carbon uptake during the growing season, in line with decadal trends of 'greening' tundra, warming and permafrost thaw also enhanced winter respiration, which doubled annual carbon losses," Natali said in a news release.

Carbon levels captured in permafrost are three to seven times greater than the amount sequestered in tropical forests, according to WHRC, which notes that as historically cold climates get warmer it will cause a release of methane and carbon dioxide into the atmosphere - thus creating more warming and more permafrost thaw.

Natali said that prior to this study "the understanding of permafrost feedbacks to climate change had been limited by a lack of data examining warming effects on both vegetation and permafrost carbon simultaneously."

The researchers conducted experiments during summer and winter, measuring CO2 emissions from permafrost and the impact on carbon balance in the ecosystem.

"There is 100 times more carbon stored belowground than aboveground in the arctic, so observed changes in plant productivity are only a very small component of the story. Given the amount of carbon stored belowground in the arctic, it is very unlikely that plant growth can ever fully offset carbon losses from permafrost thaw," Natali said.

Within the next century researchers expect permafrost to decline by as much as 70 percent, which may lead to an effect on global warming.

"The only way we can accurately project future climate is to understand the responses of both plants and microbes to a warming climate," Natali said. "This study was the first to simulate whole ecosystem warming in the Arctic, including permafrost degradation, similar to what is projected to happen as a result of climate change. There is a strong potential for significant global carbon emissions if rates calculated here become typical for permafrost ecosystems in a warmer world."