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Biogeosciences An interactive open-access journal of the European Geosciences Union
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https://doi.org/10.5194/bg-2019-437
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/bg-2019-437
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

Submitted as: research article 18 Nov 2019

Submitted as: research article | 18 Nov 2019

Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Biogeosciences (BG).

Environmental controls on ecosystem-scale cold season methane and carbon dioxide fluxes in an Arctic tundra ecosystem

Dean Howard1,2, Yannick Agnan3, Detlev Helmig1, Yu Yang4, and Daniel Obrist2 Dean Howard et al.
  • 1Institute of Arctic and Alpine Research, University of Colorado Boulder, Boulder, CO, USA
  • 2Department of Environmental, Earth and Atmospheric Sciences, University of Massachusetts Lowell, Lowell, MA, USA
  • 3Earth and Life Institute, Université Catholique de Louvain, Louvain-la-Neuve, Belgium
  • 4Department of Civil and Environmental Engineering, University of Nevada, Reno, NV, USA

Abstract. Understanding the processes that influence and control carbon cycling in Arctic tundra ecosystems is essential for making accurate predictions about what role these ecosystems will play in potential future climate change scenarios. Particularly, air–surface fluxes of methane and carbon dioxide are of interest as recent observations suggest that the vast stores of soil carbon found in the Arctic tundra are becoming more available to release to the atmosphere in the form of these greenhouse gases. Further, harsh wintertime conditions and complex logistics have limited the number of year-round and cold season studies and hence too our understanding of carbon cycle processes during these periods. We present here a two-year micrometeorological data set of methane and carbon dioxide fluxes that provides near-continuous data throughout the active summer and cold winter seasons. Net emission of methane and carbon dioxide in one of the study years totalled 3.7 and 89 g C m−2 a−1 respectively, with cold season methane emission representing 54% of the annual total. In the other year, net emission totals of methane and carbon dioxide were 4.9 and 485 g C m−2 a−1 respectively, with cold season methane emission here representing 82 % of the annual total – a larger proportion than has been previously reported in the Arctic tundra. Regression tree analysis suggests that, due to relatively warmer air temperatures and deeper snow depths, deeper soil horizons – where most microbial methanogenic activity takes place – remained warm enough to maintain efficient methane production whilst surface soil temperatures were simultaneously cold enough to limit microbial methanotrophic activity. These results provide valuable insight into how a changing Arctic climate may impact methane emission, and highlight a need to focus on soil temperatures throughout the entire active soil profile, rather than rely on air temperature as a proxy for modelling temperature–methane flux dynamics.

Dean Howard et al.
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Dean Howard et al.
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Soil, snow, and atmosphere exchanges of mercury in the interior Arctic tundra, Alaska Detlev Helmig, Brendan Blanchard, and Daniel Obrist https://doi.org/10.18739/A21Z41S5S

Dean Howard et al.
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Short summary
The Arctic tundra represents a vast store of carbon that may be broken down by microbial activity into greenhouse gases such as CO2 and CH4. Though microbes are less active in winter, the long duration of the cold season makes this period very important for carbon cycling. We show that, under conditions of warmer winter air temperatures and greater snowfall, deeper soils can remain warm enough to sustain significantly enhanced CH4 emission. This could have large implications for future climates.
The Arctic tundra represents a vast store of carbon that may be broken down by microbial...
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