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| Titel |
Arctic catchment releases mostly young aquatic carbon despite complete thawing of old organic-rich permafrost soils during growing season. |
| VerfasserIn |
Joshua F. Dean, Michael F. Billett, Kerry J. Dinsmore, Mark H. Garnett, Ype van der Velde |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250145179
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| Publikation (Nr.) |
 EGU/EGU2017-9093.pdf |
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| Zusammenfassung |
| Radiocarbon (14C) dating of dissolved organic carbon (DOC) in Arctic freshwaters has been
used as a crucial tool for detecting old C mobilised from thawing permafrost, but DO14C in
major Arctic rivers is usually quite young. New methods for the collection of both CO2 and
CH4 from inland waters allow novel observation of dissolved 14CO2 and 14CH4
alongside DO14C, and provide a more sensitive method than aquatic OC alone –
published Arctic freshwater 14C studies to date focus only on DOC, particulate OC, or
ebullition CH4/CO2. The mobilisation of old C sourced from deepening permafrost soil
active-layers into Arctic freshwaters has the potential to form a significant positive climate
feedback.
We compare 14C in DOC, dissolved CO2 and dissolved CH4 at five time points over a
single growing season from streams, ponds and lakes underlain by continuous permafrost in
the western Canadian Arctic. Using age distribution analysis based on atmospheric 14CO2
records, we estimated the age of aquatic C that would otherwise be labelled as “modern”
due to the 14C bomb peak. We then calculated the vertical and lateral C fluxes in
the study systems, and estimated the proportion derived from old permafrost C.
The upper organic-rich soils are the dominant hydrologic pathway, which were
completely thawed by late season, and we hypothesised that mobilisation of older,
deeper organic soil C would be visible in the aquatic 14C by late in the growing
season.
Early in the season, median aquatic DO14C and CO2 ages were 65-131 years old (all 14C
ages reported here are years before sampling date). By the end of the season, DO14C was
156-271 years old, while CO2 was 113-161 years old, demonstrating that aquatic C ages
reflect the mobilisation of thawing older permafrost C. CH4 concentrations were
generally low throughout and only two dates were obtained: 202 and 1,970 years
old.
Overall there was limited evidence of very old permafrost organic C, which comprised
0-10% of vertical and lateral aquatic fluxes. Our results demonstrate that permafrost thaw will
result in the mobilisation of old C into the aquatic phase as DOC, CO2 and CH4, but also
indicate potential resilience within these systems in response to climate change. |
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