Methane Emissions from Northern Wetlands During the Holocene : A Synthesis Approach to Account for Wetland Expansion and Fen-Bog-Permafrost Transitions (Invited)

• Main Authors: Treat, Claire, Jones, Miriam C., Brosius, Laura, Grosse, Guido, Walter Anthony, Katey M., Frolking, Steve
• Format: Conference Object
• Language: unknown
• Published: American Geophysical Union 2021
• Subjects: permafrost
• Online Access: https://epic.awi.de/id/eprint/55332/; https://epic.awi.de/id/eprint/55332/1/Treat_2021_AGUFM_CH4Reconstruction.zip; https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/865879; https://hdl.handle.net/10013/epic.364fda78-c94b-4da3-aa9a-4cf4d39ad83b; https://hdl.handle.net/

Methane emissions from northern high latitude wetlands constitute a major uncertainty in the atmospheric methane (CH4) budget during the Holocene. To reconstruct northern wetland methane emissions, we used an empirical model based on syntheses of observations of peat initiation from more than 3600 radiocarbon-dated basal peat ages, plant-macrofossil-derived peatland type from more than 250 peat cores from sites across the northern high latitudes, and observed CH4 emissions averaged from modern-day wetland types in order to explore the effects of wetland expansion and changes in wetland type. Peatland basal ages and plant macrofossil records showed the widespread formation of fens in major northern wetland complexes before 8000 BP. After 8000 BP, new fen formation continued, but widespread peatland succession (to bogs) and permafrost aggradation also occurred. Reconstructed CH4 emissions from peatlands increased rapidly between 10,600 BP and 6900 BP due to fen formation and expansion, then stabilized after 5000 BP at 42 ± 25 Tg CH4 y-1, as high methane-emitting fens transitioned to lower methane-emitting bogs and permafrost peatlands. Permafrost formation in northern peatlands after 1000 BP decreased CH4 emissions by 20% to 34 ± 21 Tg y-1 by the present day. Warming temperatures, changes in peatland hydrology, and permafrost thaw will likely change the magnitude of northern peatland emissions in the future.