Preprints
https://doi.org/10.5194/bg-2021-81
https://doi.org/10.5194/bg-2021-81

  06 Apr 2021

06 Apr 2021

Review status: this preprint is currently under review for the journal BG.

Field-scale CH4 emission at a sub-arctic mire with heterogeneous permafrost thaw status

Patryk Łakomiec1, Jutta Holst1, Thomas Friborg2, Patrick Crill3, Niklas Rakos4, Natascha Kljun5, Per-Ola Olsson1, Lars Eklundh1, and Janne Rinne1 Patryk Łakomiec et al.
  • 1Department of Physical Geography and Ecosystem Science, Lund University, 223 62, Sweden
  • 2Department of Geosciences and Natural Resource Management, University of Copenhagen, 1165, Denmark
  • 3Department of Geological Sciences and Bolin Centre for Climate Research, Stockholm University, 114 19, Sweden
  • 4Abisko Scientific Research Station, Swedish Polar Research Secretariat, Abisko, 981 07, Sweden
  • 5Centre for Environmental and Climate Science, Lund University, 223 62, Sweden

Abstract. The Artic is exposed to faster temperature changes than most other areas on Earth. Constantly increasing temperature will lead to thawing permafrost and changes in the CH4 emissions from wetlands. One of the places exposed to those changes is the Abisko-Stordalen Mire in northern Sweden, where climate and vegetation studies have been conducted from the 1970s.

In our study, we analyzed field-scale methane emissions measured by the eddy covariance method at Abisko-Stordalen Mire for three years (2014–2016). The site is a subarctic mire mosaic of palsas, thawing palsas, fully thawed fens, and open water bodies. A bimodal wind pattern prevalent at the site provides an ideal opportunity to measure mire patches with different permafrost statuses with one flux measurement system. The flux footprint for westerly winds is dominated by elevated palsa plateaus, while the footprint is almost equally distributed between palsas and thawing bog-like areas for easterly winds. As these patches are exposed to the same climatic conditions, we analyzed the differences in the responses of their methane emission for environmental parameters.

The methane fluxes followed a similar annual cycle over the three study years, with a gentle rise during spring and a decrease during autumn and with no emission burst at either end of the ice-free season. The peak emission during the ice-free season differed significantly for the mire with two permafrost statuses: the palsa mire emitted 24 mg-CH4 m−2 d−1 and the thawing wet sector 56 mg-CH4 m−2 d−1. Factors controlling the methane emission were analyzed using generalized linear models. The main driver for methane fluxes was peat temperature for both wind sectors. Soil water content above the water table emerged as an explanatory variable for the three years for western sectors and the year 2016 in the eastern sector. Water table level showed a significant correlation with methane emission for the year 2016 as well. Gross primary production, however, did not show a significant correlation with methane emissions. Annual methane emissions were estimated based on four different gap-filing methods. The different methods generally resulted in very similar annual emissions. The mean annual emission based on all models was 4.2 ± 0.4 g-CH4 m−2 a−1 for western sector and 7.3 ± 0.7 g-CH4 m−2 a−1 for the eastern sector. The average annual emissions, derived from this data and a footprint climatology, were 3.6 ± 0.7 g-CH4 m−2 a−1 and 11 ± 2 g-CH4 m−2 a−1 for the palsa and thawing surfaces, respectively. Winter fluxes were relatively high, contributing 27–45 % to the annual emissions.

Patryk Łakomiec et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on bg-2021-81', Anonymous Referee #1, 01 May 2021
  • RC2: 'Comment on bg-2021-81', Anonymous Referee #2, 07 May 2021
  • RC3: 'Comment on bg-2021-81', L. Kutzbach, 11 May 2021

Patryk Łakomiec et al.

Patryk Łakomiec et al.

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Short summary
Methane emission from the sub-artic mire with heterogeneous permafrost status was measured for the years 2014–2016. Lower methane emission was measured from the palsa mire sector while the thawing wet sector emitted more. Both sectors have a similar annual pattern with a gentle rise during spring and a decrease during autumn. The highest emission was observed in the late summer. Winter emissions were positive during the measurement period and have a significant impact on the annual budgets.
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