Greenhouse gas emissions from physical permafrost thaw disturbance and subsidence, including the formation and expansion of thermokarst (thaw) lakes, may double the magnitude of the permafrost carbon feedback this century. These processes are not accounted for in current global climate models. Thermokarst lakes, in particular, have been shown to be hotspots for emissions of methane (CH4), a potent greenhouse gas with 32 times more global warming potential than carbon dioxide (CO2) over a 100-year timescale. Here, we synthesize several studies examining CH4 dynamics in a representative first-generation thermokarst lake (Vault Lake, informal name) to show that CH4 production and oxidation potentials vary with depth in thawed sediments beneath the lake. This variation leads to depth-dependent differences in both in situ dissolved CO2:CH4 ratios and net CH4 production responses to additional warming. Comparing CH4 production, oxidation, and flux values from studies at Vault Lake suggests up to 99% of produced CH4 is oxidized and/or periodically entrapped before entering the atmosphere. We summarize these findings in the context of CH4 literature from thermokarst lakes and identify future research directions for incorporating thermokarst lake CH4 dynamics into estimates of the permafrost carbon feedback.
Bibliographical noteFunding Information:
We thank: P. Anthony, S. Billings, N. Haubenstock, F. Horn, T. Howe, A. Saborowski, and B. Van Veldhuizen for assistance in data collection and/or analysis and S. Skidmore for granting access to Vault Lake. Funding for J.K. Heslop, K.M. Walter Anthony, A. Sepulveda-Jauregui, G. Grosse, and A. Bondurant was provided by DOE DE-SC0006920, NSF OPP-1107892, and ARC-1304823. Funding for K. Martinez-Cruz was provided by Conacyt 330197/233369. K.M. Walter Anthony was supported by NASA ABoVE NNX15AU49A . Additional funding for M. Winkel and K. M. Walter Anthony was provided by the NSF ARCSS-1500931 and for G. Grosse by ERC 388335. The Helmholtz Young Investigator Group of S. Liebner is funded by the Helmholtz Gemeinschaft (HGF) (VH-NG-919). Additional funding for J. Heslop was provided by a GFZ Discovery Fellowship. a UAF Center for Global Change Student Research Grant with funds from the UAF Center for Global Change, and STAR Fellowship Assistance agreement no. FP-91762901-0 awarded by the US Environmental Protection Agency (EPA). This manuscript has not been formally reviewed by EPA. The views expressed in this presentation are solely those of J. Heslop, and the EPA does not endorse any products or commercial services mentioned.
© 2020 Elsevier B.V.
Copyright 2020 Elsevier B.V., All rights reserved.
- Methane oxidation
- Permafrost carbon feedback
- Rapid thaw
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