Controls on the 14C Content of Dissolved and Particulate Organic Carbon Mobilized Across the Mackenzie River Basin, Canada

The Mackenzie River Basin (MRB) delivers large quantities of organic carbon (OC) into the Arctic Ocean, with significant implications for the global C budgets and ocean biogeochemistry. The amount and properties of OC in the Mackenzie River's delta have been well monitored in the last decade, b...

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Bibliographic Details
Published in:Global Biogeochemical Cycles
Main Authors: Campeau, Aydrey, Soerensen, Anne L., Martma, T, Åkeblom, Staffan, Zdanowicz, Christian
Format: Article in Journal/Newspaper
Language:English
Published: Enheten för miljöforskning och övervakning 2020
Subjects:
arctic rivers
dissolved organic carbon
particulate organic carbon
radiocarbon
Other Earth and Related Environmental Sciences
Annan geovetenskap och miljövetenskap
Arctic
Arctic Ocean
Mackenzie River
Canada
Mackenzie river
permafrost
Online Access:http://urn.kb.se/resolve?urn=urn:nbn:se:nrm:diva-4027
https://doi.org/10.1029/2020GB006671
Description
Summary:The Mackenzie River Basin (MRB) delivers large quantities of organic carbon (OC) into the Arctic Ocean, with significant implications for the global C budgets and ocean biogeochemistry. The amount and properties of OC in the Mackenzie River's delta have been well monitored in the last decade, but the spatial variability in OC sources transported by its different tributaries is still unclear. Here we present new data on the radiocarbon (14C) content of dissolved and particulate OC (Δ14C‐DOC and Δ14C‐POC) across the mainstem and major tributaries of the MRB, comprising 19 different locations, to identify factors controlling spatial patterns in riverine OC sources. The Δ14C‐DOC and Δ14C‐POC varied across a large range, from −179.9‰ to 62.9‰, and −728.8‰ to −9.0‰, respectively. Our data reveal a positive spatial coupling between the Δ14C of DOC and POC across the MRB, whereby the most 14C‐depleted waters were issued from the mountainous west bank of the MRB. This 14C‐depleted DOC and POC likely originates from a combination of petrogenic sources, connected with the presence of kerogens in the bedrock, and biogenic sources, mobilized by thawing permafrost. Our analysis also reveals intriguing relationships between Δ14C of DOC and POC with turbidity, water stable isotope ratio and catchment elevation, indicating that hydrology and geomorphology are key to understanding riverine OC sources in this landscape. A closer examination of the specific mechanisms giving rise to these relationships is recommended. For now, this study provides a road map of the key OC sources in this rapidly changing river basin.

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