Preprints
https://doi.org/10.5194/bg-2021-70
https://doi.org/10.5194/bg-2021-70

  01 Apr 2021

01 Apr 2021

Review status: a revised version of this preprint is currently under review for the journal BG.

Methane in Zackenberg Valley, NE Greenland: Multidecadal growing season fluxes of a high Arctic tundra

Johan H. Scheller1,2, Mikhail Mastepanov1,3, Hanne H. Christiansen2, and Torben R. Christensen1 Johan H. Scheller et al.
  • 1Department of Bioscience, Arctic Research Centre Aarhus University, Roskilde, Denmark
  • 2Arctic Geology Department, The University Centre in Svalbard, Longyearbyen, Norway
  • 3Oulanka research station, University of Oulu, Finland

Abstract. The carbon balance of high-latitude terrestrial ecosystems plays an essential role in the atmospheric concentration of trace gases, including carbon dioxide (CO2) and methane (CH4). Increasing levels of atmospheric methane have contributed to ~20 % of the observed global warming since the pre-industrial era. Rising temperatures in the Arctic are expected to promote the release of methane from Arctic ecosystems. Still, existing methane flux data collection efforts are sparse and highly scattered, and further attempts to assess the landscape fluxes over multiple years are needed.

Here we use multiyear monitoring from automated flux chambers located on the fringe of a fen area in the center of Zackenberg Valley, northeast Greenland, from July and August (2006–2019). Direct measurements of methane fluxes showed high variability, with mean July–August fluxes ranging from 0.26 to 3.41 mg CH4 m−2 h−1. Methane fluxes based on manual chamber measurements are available from campaigns in 1997, 1999–2000, and in shorter periods from 2007–2013 and have been summarized in several published studies. Fluxes from the multiyear monitoring were combined with fluxes from the most common vegetation types, measured in 2007, and a detailed vegetation cover map to assess the methane flux on a landscape-scale and its variability over time.

July–August landscape fluxes, estimated in the current study for the 2006–2019 period, were low compared to previous estimations. For the full study area covering the valley floor, the net methane source during these months was estimated as 0.06 to 0.83 mg CH4 m−2 h−1 and as 0.26 to 3.45 mg CH4 m−2 h−1 for the central fen-rich areas.

A 2017–2018 erosion event indicates that some fen and grassland areas along the river in the center of the valley are becoming unstable following pronounced fluvial erosion and a prolonged period of permafrost warming. Although such physical disturbance in the landscape can disrupt the current ecosystem–atmosphere flux patterns, even pronounced future erosion along the river is unlikely to impact methane fluxes at a landscape-scale significantly. Instead, projected changes in future climate in the valley play a more critical role. The results show that multiyear landscape methane fluxes are highly variable at a landscape-scale and stress the need for long-term spatially distributed measurements in the Arctic.

Johan H. Scheller 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-2021-70', Anonymous Referee #1, 27 Apr 2021
  • RC2: 'Comment on bg-2021-70', Anonymous Referee #2, 03 May 2021

Johan H. Scheller et al.

Johan H. Scheller et al.

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Short summary
Our study presents a time-series of methane emissions in a high Arctic tundra landscape over 14 summers, which shows large variations between years. The methane emissions from the valley are expected to more than double in the late 21st century. This warming increases permafrost thaw, which could increase surface erosion in the valley. Increased erosion could offset some of the rise in methane fluxes from the valley, but this would require large-scale impacts on vegetated surfaces.
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