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Much stronger tundra methane emissions during autumn freeze than spring thaw
Author(s) -
Bao Tao,
Xu Xiyan,
Jia Gensuo,
Billesbach David P.,
Sullivan Ryan C.
Publication year - 2021
Publication title -
global change biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 4.146
H-Index - 255
eISSN - 1365-2486
pISSN - 1354-1013
DOI - 10.1111/gcb.15421
Subject(s) - environmental science , tundra , growing season , atmospheric sciences , context (archaeology) , spring (device) , zoology , arctic , climatology , ecology , geography , biology , geology , mechanical engineering , archaeology , engineering
Warming in the Arctic has been more apparent in the non‐growing season than in the typical growing season. In this context, methane (CH 4 ) emissions in the non‐growing season, particularly in the shoulder seasons, account for a substantial proportion of the annual budget. However, CH 4 emissions in spring and autumn shoulders are often underestimated by land models and measurements due to limited data availability and unknown mechanisms. This study investigates CH 4 emissions during spring thaw and autumn freeze using eddy covariance CH 4 measurements from three Arctic sites with multi‐year observations. We find that the shoulder seasons contribute to about a quarter (25.6 ± 2.3%, mean ± SD ) of annual total CH 4 emissions. Our study highlights the three to four times higher contribution of autumn freeze CH 4 emission to total annual emission than that of spring thaw. Autumn freeze exhibits significantly higher CH 4 flux (0.88 ± 0.03 mg m −2 hr −1 ) than spring thaw (0.48 ± 0.04 mg m −2 hr −1 ). The mean duration of autumn freeze (58.94 ± 26.39 days) is significantly longer than that of spring thaw (20.94 ± 7.79 days), which predominates the much higher cumulative CH 4 emission during autumn freeze (1,212.31 ± 280.39 mg m −2 year −1 ) than that during spring thaw (307.39 ± 46.11 mg m −2 year −1 ). Near‐surface soil temperatures cannot completely reflect the freeze–thaw processes in deeper soil layers and appears to have a hysteresis effect on CH 4 emissions from early spring thaw to late autumn freeze. Therefore, it is necessary to consider commonalities and differences in CH 4 emissions during spring thaw versus autumn freeze to accurately estimate CH 4 source from tundra ecosystems for evaluating carbon‐climate feedback in Arctic.