Arctic tundra stores huge amounts of methane, making it an important contributor to the global carbon cycle. It is this region that heats up the fastest due to climate change. Scientists set out to find out how soil freeze-thaw cycles affect methane emissions in spring and autumn. The research results are published by the journal Global Change Biology.
Over the past century, Arctic tundra has warmed faster than other regions of the world. High temperatures accelerate the decomposition of organic carbon in the region, resulting in increased net methane emissions.
Due to insufficient data, scientists do not know the details of this process. For example, what is common in methane emissions during spring thaw versus freezing in autumn? Does freezing and thawing affect the amount of methane emitted?
Dr. Bao Tao’s team of the Institute of Atmospheric Physics (IAP) of the Chinese Academy of Sciences (CAS) found that the off-season accounts for about a quarter of total annual methane emissions. The soil melts in spring and freezes in autumn, but scientists did not know exactly how these processes affect methane emissions.
The new study highlights that methane emissions are 3-4 times higher in fall than in spring. The soil has higher levels of moisture, microbes and organic carbon during the fall frost than during the spring thaw. It is these conditions that create a favorable environment for the growth of methanogens, which leads to higher greenhouse gas emissions in the fall.
“The new study will improve our understanding of the methane balance in the Arctic over the seasons,” concludes Dr. Xu Xiyang, co-author of the work.