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TitleMicrobial greenhouse gas dynamics associated with warming coastal permafrost, western Canadian Arctic
AuthorLapham, L L; Dallimore, S R; Magen, C; Henderson, L C; Powers, L C; Gonsior, M; Clark, B; Côté, M; Fraser, P; Orcutt, B N
SourceFrontiers in Earth Science vol. 8, 582103, 2020 p. 1-15, https://doi.org/10.3389/feart.2020.582103 (Open Access)
Year2020
Alt SeriesNatural Resources Canada, Contribution Series 20200296
PublisherFrontiers Media
Documentserial
Lang.English
Mediapaper; on-line; digital
File formatpdf; html
ProvinceNorthwest Territories
AreaTuktoyaktuk Island; Beaufort Sea
Lat/Long WENS-133.0417 -132.9917 69.4583 69.4500
Subjectssurficial geology/geomorphology; environmental geology; geochemistry; Nature and Environment; Science and Technology; climate; temperature; permafrost; ground ice; periglacial features; ice lenses; massive ice; organic carbon; microorganisms; atmospheric geochemistry; methane; carbon dioxide; coastal erosion; biogeochemistry; core samples; carbon geochemistry; stable isotope studies; carbon isotopes; sediment geochemistry; climate change; permafrost thaw; active layer thickness; greenhouse gases; atmospheric emissions; cumulative effects
Illustrationslocation maps; satellite images; time series; photographs; profiles; geoscientific sketch maps; bar graphs
ProgramEnvironmental Geoscience, Arctic impacts
Released2020 12 15
AbstractPermafrost sediments contain one of the largest reservoirs of organic carbon on Earth that is relatively stable when it remains frozen. As air temperatures increase, the shallow permafrost thaws which allows this organic matter to be converted into potent greenhouse gases such as methane (CH4) and carbon dioxide (CO2) through microbial processes. Along the Beaufort Sea coast in the vicinity of the Tuktoyaktuk Peninsula, Northwest Territories, Canada, warming air temperatures are causing the active layer above permafrost to deepen, and a number of active periglacial processes are causing rapid erosion of previously frozen permafrost. In this paper, we consider the biogeochemical consequences of these processes on the permafrost sediments found at Tuktoyaktuk Island. Our goals were to document the in situ carbon characteristics which can support microbial activity, and then consider rates of such activity if the permafrost material were to warm even further. Samples were collected from a 12 m permafrost core positioned on the top of the island adjacent to an eroding coastal bluff. Downcore CH4, total organic carbon and dissolved organic carbon (DOC) concentrations and stable carbon isotopes revealed variable in situ CH4 concentrations down core with a sub-surface peak just below the current active layer. The highest DOC concentrations were observed in the active layer. Controlled incubations of sediment from various depths were carried out from several depths anaerobically under thawed (5°C and 15°C) and under frozen (-20°C and -5°C) conditions. These incubations resulted in gross production rates of CH4 and CO2 that increased upon thawing, as expected, but also showed appreciable production rates under frozen conditions. This dataset presents the potential for sediments below the active layer to produce potent greenhouse gases, even under frozen conditions, which could be an important atmospheric source in the actively eroding coastal zone even prior to thawing.
Summary(Plain Language Summary, not published)
Permafrost sediments contain a large reservoir of organic carbon that is stable when frozen. As permafrost thaws, this organic matter may be converted into greenhouse gases through microbial processes. Along the Beaufort coast, warming temperatures are causing the active layer to deepen and erosion of permafrost is occurring. In this paper, we consider the biogeochemical consequences of these processes using a 12 m permafrost core from Tuktoyaktuk Is. Variable methane (CH4) concentrations were measured with a peak just below the active layer and the highest dissolved organic carbon concentrations were in the active layer. Incubation experiments of sediment resulted in production rates of CH4 and carbon dioxide (CO2) that increased upon thawing, as expected, but also showed appreciable production rates under frozen conditions. This demonstrates the potential for frozen sediments to produce greenhouse gases, which could be an atmospheric source along the eroding coast.
GEOSCAN ID326905