The Arctic is warming two to three times faster than the rest of the globe. As temperatures increase, permafrost melts, releasing carbon dioxide, and the growing season lengthens, absorbing CO2.
However, a study being conducted by the Woods Hole Research Center and published in the journal Ecology, finds that the thawing permafrost emits more carbon dioxide than the tundra’s vegetation can offset.
Dr. Susan Natali is an Assistant Scientist at Woods Hole Research Center and the lead author on the study. She says permafrost covers one-fourth of the Northern Hemisphere’s land area and contains twice the amount of carbon than what currently exists in the atmosphere.
“So the permafrost thaw is putting us at risk, because even if a small portion of this carbon is released into the atmosphere, it’s a significant emission of greenhouse gases,” Natali said.
Natali says most models predicting future greenhouse gas totals do not account for emissions from permafrost. This research provides data on how this massive carbon sink reacts to rising temperatures.
“So our estimates of temperature changes as a result of human input from fossil fuels isn’t yet accounting for these additional carbon inputs that we may see from permafrost thaw,” Natali said. “And this is a really large pool of carbon.”
The permafrost acts as a carbon cache, because during the growing season, plants through photosynthesis remove CO2 from the atmosphere and store it in their tissue. At the end of the season, the plants die and freeze before they fully decay. So for tens of thousands of years, permafrost has been collecting this carbon-rich material.
As long as the permafrost stays frozen, the carbon remains locked. But when the permafrost thaws, microbes begin breaking down that organic matter, releasing CO2 and methane. As these greenhouse gases are emitted, more warming occurs, spurring more thawing and more decay. Dr. Richard Houghton is a Senior Scientist at Woods Hole. He says the cycle creates an amplifying system.
“Just think of it as a layer of organic matter and it’s frozen, not at the surface, but in the permafrost it’s frozen,” Houghton said. “And as you’re warming the earth, the warming keeps penetrating into deeper and deeper depths of this organic carbon. And so it’s a large source ready to be released over time.”
The research is in its fifth year on the Eight Mile Lake Watershed in Alaska’s Northern Interior.