Abundant pre-industrial carbon detected in Canadian Arctic headwaters: implications for the permafrost carbon feedback

Dean, J. et al. (2018) Abundant pre-industrial carbon detected in Canadian Arctic headwaters: implications for the permafrost carbon feedback. Environmental Research Letters, 13(3), 034024. (doi: 10.1088/1748-9326/aaa1fe)

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Mobilization of soil/sediment organic carbon into inland waters constitutes a substantial, but poorly-constrained, component of the global carbon cycle. Radiocarbon (<sup>14</sup>C) analysis has proven a valuable tool in tracing the sources and fate of mobilized carbon, but aquatic <sup>14</sup>C 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 <sup>14</sup>C content of aquatic CO<sub>2</sub>, 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 to 228 years before sampling date (a 120-125% increase) compared to CO<sub>2</sub>, which rose from 92 to 151 years before sampling date (a 59 63% increase). 'Pre-industrial' aged carbon (assimilated prior 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.

Item Type:Articles
Additional Information: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).
Glasgow Author(s) Enlighten ID:Garnett, Dr Mark
Authors: Dean, J., van der Velde, Y., Garnett, M. H., Dinsmore, K., Baxter, R., Lessels, J. S., Smith, P., Street, L. E., Subke, J.-A., Tetzlaff, D., Washbourne, I., Wookey, P. A., and Billett, M.
College/School:College of Science and Engineering > Scottish Universities Environmental Research Centre
Journal Name:Environmental Research Letters
Publisher:Institute of Physics Publishing Ltd.
ISSN (Online):1748-9326
Published Online:15 December 2017
Copyright Holders:Copyright © 2017 The Authors
First Published:First published in Environmental Research Letters 13(3):034024
Publisher Policy:Reproduced under a Creative Commons License

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