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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-2019-477
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/bg-2019-477
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Submitted as: research article 12 Feb 2020

Submitted as: research article | 12 Feb 2020

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This preprint is currently under review for the journal BG.

Vegetation Influence and Environmental Controls on Greenhouse Gas Fluxes from a Drained Thermokarst Lake in the Western Canadian Arctic

June Skeeter1, Andreas Christen2, Andrée-Anne Laforce3, Elyn Humphreys3, and Greg Henry1 June Skeeter et al.
  • 1Department of Geography, The University of British Columbia, Vancouver, V6T1Z2, Canada
  • 2Environmental Meteorology, Faculty of Environment and Natural Resources, Albert-Ludwigs Universität Freiburg, Freiburg, Germany
  • 3Department of Geography and Environmental Studies, Carleton University, Ottawa, K1S5B6, Canada

Abstract. Thermokarst features are widespread in ice-rich regions of the circumpolar Arctic. The rate of thermokarst lake formation and drainage is anticipated to accelerate as the climate warms. However, it is uncertain how these dynamic features impact the terrestrial Arctic carbon cycle. Methane (CH4) and carbon dioxide (CO2) fluxes were measured during peak growing season using eddy covariance and chambers at Illisarvik, a 0.16 km2 thermokarst lake basin that was experimentally drained in 1978 on Richards Island, Northwest Territories, Canada. Vegetation in the basin differs markedly from the surrounding dwarf-shrub tundra and included patches of tall shrubs, grasses and sedges with some bare ground and a small pond in the centre. During the study period, temperature and wind conditions were highly variable and soil water content decreased steadily. Basin scaled net ecosystem exchange (NEE) measured by eddy covariance was −1.5 [CI95 % ± 0.2] g C-CO2 m−2 d−1; NEE followed a marked diurnal pattern with no trend during the study period. NEE was primary controlled by photosynthetic photon flux density and influenced by vapor pressure deficit, volumetric water content and the presence of shrubs. By contrast, net methane exchange (NME) was low (8.7 [CI95 % ± 0.4] mg CH4 m−2 d−1 and had little impact on the carbon balance of the basin during the study period. NME displayed high spatial variability, sedge areas in the basin were the strongest source of CH4 while upland areas outside the basin were a net sink. Soil moisture and temperature were the main environmental factors influencing NME, having a positive and negative effect respectively.

June Skeeter et al.

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June Skeeter et al.

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Short summary
This study investigates carbon fluxes at Illisarvik, an artificial drained thermokarst lake basin (DTLB) in Canada's Northwest territories. This is the first carbon balance study in a DTLB outside of Alaska. We used Neural Networks to identify the factors controlling fluxes and to model the effects of the controlling factors. We discuss the role of vegetation heterogeneity on fluxes, especially of Methane, and we show how the carbon fluxes differ from Alaskan DTLB.
This study investigates carbon fluxes at Illisarvik, an artificial drained thermokarst lake...
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