An Abrupt Aging of Dissolved Organic Carbon in Large Arctic Rivers

Schwab, M.S.; Hilton, R.G.; Raymond, P.A.; Haghipour, N.; Amos, E.; Tank, S.E.; Holmes, R.M.; Tipper, E.T.; Eglinton, T.I.

doi:10.1029/2020gl088823

An Abrupt Aging of Dissolved Organic Carbon in Large Arctic Rivers

Schwab, M.S.; Hilton, R.G.; Raymond, P.A.; Haghipour, N.; Amos, E.; Tank, S.E.; Holmes, R.M.; Tipper, E.T.; Eglinton, T.I.

Authors

M.S. Schwab

R.G. Hilton

P.A. Raymond

N. Haghipour

E. Amos

S.E. Tank

R.M. Holmes

E.T. Tipper

T.I. Eglinton

Abstract

Permafrost thaw in Arctic watersheds threatens to mobilize hitherto sequestered carbon. We examine the radiocarbon activity (F14C) of dissolved organic carbon (DOC) in the northern Mackenzie River basin. From 2003‐2017, DOC‐F14C signatures (1.00 ± 0.04; n = 39) tracked atmospheric 14CO2, indicating export of “modern” carbon. This trend was interrupted in June 2018 by the widespread release of aged DOC (0.85 ± 0.16, n = 28) measured across three separate catchment areas. Increased nitrate concentrations in June 2018 lead us to attribute this pulse of 14C‐depleted DOC to mobilization of previously frozen soil organic matter. We propose export through lateral perennial thaw zones occurred at the base of the active layer weakened by preceding warm summer and winter seasons. Although we are not yet able to ascertain the broader significance of this “anomalous” mobilization event, it highlights the potential for rapid and large‐scale release of aged carbon from permafrost.

Citation

Schwab, M., Hilton, R., Raymond, P., Haghipour, N., Amos, E., Tank, S., …Eglinton, T. (2020). An Abrupt Aging of Dissolved Organic Carbon in Large Arctic Rivers. Geophysical Research Letters, 47(23), Article e2020GL088823. https://doi.org/10.1029/2020gl088823

Journal Article Type	Article
Acceptance Date	Oct 14, 2020
Online Publication Date	Dec 8, 2020
Publication Date	Dec 8, 2020
Deposit Date	Nov 10, 2020
Publicly Available Date	Mar 2, 2021
Journal	Geophysical Research Letters
Print ISSN	0094-8276
Electronic ISSN	1944-8007
Publisher	Wiley
Peer Reviewed	Peer Reviewed
Volume	47
Issue	23
Article Number	e2020GL088823
DOI	https://doi.org/10.1029/2020gl088823