Abstract
Mobilization of soil/sediment organic carbon into inland waters constitutes a substantial, but poorly-constrained, component of the global carbon cycle. Radiocarbon (C-14) analysis has proven a valuable tool in tracing the sources and fate of mobilized carbon, but aquatic C-14 studies in permafrost regions rarely detect 'old' carbon (assimilated from the atmosphere into plants and soil prior to AD1950). The emission of greenhouse gases derived from old carbon by aquatic systems may indicate that carbon sequestered prior to AD1950 is being destabilized, thus contributing to the 'permafrost carbon feedback' (PCF). Here, we measure directly the C-14 content of aquatic CO2, alongside dissolved organic carbon, in headwater systems of the western Canadian Arctic-the first such concurrent measurements in the Arctic. Age distribution analysis indicates that the age of mobilized aquatic carbon increased significantly during the 2014 snow-free season as the active layer deepened. This increase in age was more pronounced in DOC, rising from 101-228 years before sampling date (a 120%-125% increase) compared to CO2, which rose from 92-151 years before sampling date (a 59%-63% increase). 'Pre-industrial' aged carbon (assimilated prior to similar to AD1750) comprised 15%-40% of the total aquatic carbon fluxes, demonstrating the prevalence of old carbon to Arctic headwaters. Although the presence of this old carbon is not necessarily indicative of a net positive PCF, we provide an approach and baseline data which can be used for future assessment of the PCF.
Original language | English |
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Article number | 034024 |
Number of pages | 11 |
Journal | Environmental Research Letters |
Volume | 13 |
Issue number | 3 |
Early online date | 27 Feb 2018 |
DOIs | |
Publication status | Published - Mar 2018 |
Bibliographical note
This work was primarily supported by the UK Natural Environment Research Council (NERC), grant numbers NE/K000217/1, NE/K000225/1, NE/K000268/1 and NE/K000284/1. JFD acknowledges partial support by the program of the Netherlands Earth System Science Centre (NESSC), financially supported by the Ministry of Education, Culture and Science (OCW). We would like to thank the Aurora Research Institute in Inuvik, Prof Philip Marsh of Wilfrid Laurier University, Dr Oliver Sonnentag of Université de Montréal, and Dr Mark Cooper of the University of Exeter, for support during the field campaigns, Environment Canada for data access, Dr James Weedon of Vrije Universiteit Amsterdam for support with the statistical analyses, and the staff at the NERC Radiocarbon Facility (NRCF010001) and the SUERC AMS Laboratory for the 14C sample processing. The authors declare no competing financial interests. Requests for additional materials and data should be sent to J F Dean.Keywords
- carbon dioxide CO2
- dissolved organic carbon DOC
- methane CH4
- Arctic catchments
- inland waters
- radiocarbon C-14
- dissolved inorganic carbon
- organic-carbon
- climate-change
- active layer
- methane
- thaw
- radiocarbon
- lakes
- peatlands
- dioxide