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| Titel |
Thermokarst lake methanogenesis along a complete talik profile |
| VerfasserIn |
J. K. Heslop, K. M. Walter Anthony, A. Sepulveda-Jauregui, K. Martinez-Cruz, A. Bondurant, G. Grosse, M. C. Jones |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 12, no. 14 ; Nr. 12, no. 14 (2015-07-24), S.4317-4331 |
| Datensatznummer |
250118031
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| Publikation (Nr.) |
 copernicus.org/bg-12-4317-2015.pdf |
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| Zusammenfassung |
| Thermokarst (thaw) lakes emit methane (CH4) to the
atmosphere formed from thawed permafrost organic matter (OM),
but the relative magnitude of CH4 production in
surface lake sediments vs. deeper thawed permafrost horizons
is not well understood. We assessed anaerobic CH4
production potentials from various depths along a 590 cm long
lake sediment core that captured the entire sediment package
of the talik (thaw bulb) beneath the center of an interior
Alaska thermokarst lake, Vault Lake, and the top 40 cm of
thawing permafrost beneath the talik. We also studied the
adjacent Vault Creek permafrost tunnel that extends through
ice-rich yedoma permafrost soils surrounding the lake and into
underlying gravel. Our results showed CH4 production
potentials were highest in the organic-rich surface lake
sediments, which were 151 cm thick (mean ± SD: 5.95 ±
1.67 μg C–CH4 g dw−1 d−1;
125.9 ± 36.2 μg C–CH4 g C−1org d−1). High
CH4 production potentials were also observed in
recently thawed permafrost (1.18 ± 0.61 μg C–CH4g dw−1 d−1; 59.60±
51.5 μg C–CH4 g C−1org d−1) at the bottom of the
talik, but the narrow thicknesses (43 cm) of this horizon
limited its overall contribution to total sediment column
CH4 production in the core. Lower rates of
CH4 production were observed in sediment horizons
representing permafrost that has been thawing in the talik
for a
longer period of time. No CH4 production was
observed in samples obtained from the permafrost tunnel, a
non-lake environment. Our findings imply that CH4
production is highly variable in thermokarst lake systems and
that both modern OM supplied to surface sediments and ancient
OM supplied to both surface and deep lake sediments by in situ
thaw and shore erosion of yedoma permafrost are
important to lake CH4 production. |
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