First estimation of the diffusive methane flux and concentrations from Lake Winnipeg,a large,shallow and eutrophic lake |
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| Authors: | Rachel R Mandryk David W Capelle Cara CM Manning Philippe Tortell Ross D McCulloch Tim Papakyriakou |
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| Affiliation: | 1. Centre for Earth Observation Science, University of Manitoba, Winnipeg, MB, Canada;2. Department of Earth, Ocean and Atmospheric Sciences, University of British Columbia, Vancouver, BC, Canada;3. Department of Botany, University of British Columbia, Vancouver, BC, Canada;1. Environment and Climate Change Canada, 867 Lakeshore Rd., Burlington, Ontario L7S 1A1, Canada;2. Centre for Ecology and Hydrology, Wallingford, Oxfordshire OX10 8BB, UK;3. Department of Biology, University of Waterloo, Waterloo, Ontario, N2L 3G1, Canada;4. Wilfrid Laurier University, Faculty of Science, Biology, 75 University Ave West, Waterloo, ON N2L 3C5, Canada;1. Centre for Limnology, Institute of Agricultural and Environmental Sciences, Estonian University of Life Sciences, 61117 Rannu, Tartu County, Estonia;2. Institute of Geology, Tallinn Technical University, Ehitajate tee 5, 12618 Tallinn, Estonia;1. Environment and Climate Change Canada, Watershed Hydrology and Ecology Research Division, Victoria, BC V8W 3R4, Canada;2. Department of Civil Engineering, University of Manitoba, Winnipeg, MB R3T 5V6, Canada;3. University of Victoria, Department of Geography, Victoria, BC V8P 5C2, Canada;4. Environment and Climate Change Canada, Watershed Hydrology and Ecology Research Division, Saskatoon, SK S7N 1K2, Canada;5. Department of Food, Agricultural and Biological Engineering, the Ohio State University, Columbus, OH 44691, USA;6. Department of Geography, University of Calgary, ESB 458, 2500 University Drive NW, Calgary, AB T2N 1N4, Canada;1. Canadian Rivers Institute, University of New Brunswick, Fredericton, New Brunswick, Canada;2. Environment and Climate Change Canada, Cold Regions Research Centre, Wilfrid Laurier University, Waterloo, Ontario, Canada;3. University of Western Ontario and Canadian Rivers Institute, Department of Geography, London, Ontario, Canada;4. Environment and Climate Change Canada, National Hydrology Research Centre, Saskatoon, Saskatchewan, Canada |
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| Abstract: | Freshwater lakes are increasingly recognized as significant sources of atmospheric methane (CH4), potentially offsetting the terrestrial carbon sink. We present the first study of dissolved CH4 distributions and lake-air flux from Lake Winnipeg, based on two-years of observations collected during all seasons. Methane concentrations across two years had a median of value of 24.6 nmol L-1 (mean: 41.6 ± 68.2 nmol L-1) and ranged between 5.0 and 733.8 nmol L-1, with a 2018 annual median of 24.4 nmol L-1 (mean: 46.8 ± 99.3 nmol L-1) and 25.1 nmol L-1 (mean: 38.8 ± 45.2 nmol L-1) in 2019. The median lake-air flux was 1.1 µmol m?2 h?1 (range: 0.46–70.1 µmol m?2h?1, mean: 2.9 ± 10.2 µmol m?2 h?1) in 2018, and 5.5 µmol m?2h?1 (range: 0.0–78.4 µmol m?2 h?1, mean: 2.7 ± 8.5 µmol m?2 h?1) in 2019, for a total diffusive emission of 0.001 Tg of CH4-C yr?1. We found evidence of consistent spatial variability, with higher concentrations near river inflows. Significant seasonal trends in CH4 concentrations were not observed, though fluxes were highest during the fall season due to strong winds. Our findings suggest Lake Winnipeg is a CH4 source of similar mean magnitude to Lake Erie, with lower concentrations and fluxes per unit area than smaller mid- to high-latitude lakes. Additional work is needed to understand the factors underlying observed spatial variability in dissolved gas concentration, including estimations of production and consumption rates in the water column and sediments. |
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| Keywords: | Methane Carbon Cycling Lake Winnipeg Greenhouse Gases |
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