Thawing permafrost in the Northern Hemisphere releases “large amounts” of greenhouse gas nitrous oxide, according to a new study from the journal Nature Geoscience.
The study found that under certain conditions thawed permafrost can release as much nitrous oxide as tropical forests, one of the main sources of the gas.
Nitrous oxide, also known as “laughing gas,” is ranked third behind carbon dioxide and methane in contributing to global warming, and is regulated under the Kyoto Protocols. According to the EPA, the gas is 310 times more effective in trapping heat than carbon dioxide. Sixty percent of the nitrous in the atmosphere is produced naturally.
Global warming “wild card”
Twenty-five percent of the land surface in the Northern Hemisphere is underlain by permafrost, and as it thaws it could create a feedback loop that accelerates global warming, because it releases greenhouse gases, like methane and carbon dioxide, which in turn increase warming, spurring more thawing.
Scientists had thought only a little nitrous oxide was released during this process, but the journal study suggests otherwise.
Scientist Bo Elberling led the study, which was conducted on permafrost core samples from Greenland. Thawing and draining the soil from the cores did not increase the production of nitrous oxide, but when the scientists re-saturated the samples with meltwater from the frozen soil — as would happen naturally after thawing — nitrous oxide production was increased 20 times, with a third of it entering the atmosphere.