Published in Nature Climate Change: Dr Jessica Ernakovic from the CSIRO co-authored a large international study revealing CO2 as the biggest player in the thawing of permafrost.
The study found that CO2 emissions from dry and oxygen-rich environments will likely strengthen the climate forcing impact of thawing permafrost on top of methane that is released from oxygen-poor wetlands in the Arctic
The research by the international Permafrost Carbon Network analysed data from 25 Arctic soil incubation studies, and undertook laboratory studies to better understand the impact of temperature and soil conditions.
It found that both these factors affect the quantity of carbon released from thawing permafrost. A 10 ℃ increase in soil temperature releases twice as much carbon into the atmosphere, and drier, aerobic soil conditions releases more than three times more carbon than wetter, anaerobic soil conditions.
Most of that carbon is in the form of CO2, mixed with a surprisingly small amount of methane - only 5% of the total anaerobic products.
Methane packs 34 times the climate warming punch of CO2. The ratio of the released CO2 and methane gas therefore affects the strength of a permafrost carbon feedback loop, which determines how rising temperatures lead to even more thawing and carbon release.
Accordingly, the research indicates that the permafrost carbon feedback will be stronger when a larger percentage of the permafrost zone undergoes thaw in a dry and oxygen-rich environment.
Underlying this effect are microbes that begin digesting the newly available remains of ancient plants and animals stored as carbon in the soil, producing either CO2 or methane, depending on soil conditions.
The Arctic permafrost acts as a vast underground storage tank of carbon, holding almost twice as much as the atmosphere. Thus, small changes in how the carbon is released will have big effects.
The problems remains, though, that at this stage it is unclear whether wet or dry soils will dominate the future Arctic permafrost zone.
As this new research highlights, there is a need to monitor changes in wetness associated with permafrost thaw. These changes will also ultimately sculpt the topography of waterlogged depressions and dry uplands across the Arctic landscape.