Spatial variation in concentration and sources of organic carbon in the Lena River, Siberia

• Published in: Journal of Geophysical Research: Biogeosciences
• Main Authors: Kutscher, L, Mörth, C, Porcelli, D, Hirst, C, Maximov, T, Petrov, R, Andersson, P
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: Wiley 2017
• Subjects: Arctic; Arctic Ocean; Global warming; lena river; permafrost; Siberia
• Online Access: https://doi.org/10.1002/2017JG003858; https://ora.ox.ac.uk/objects/uuid:b8697d4e-5261-4eb4-b7dc-29a366d5c06e

Global warming in permafrost areas is expected to change fluxes of riverine organic carbon (OC) to the Arctic Ocean. Here OC concentrations, stable carbon isotope signatures (δ 13 C), and carbon-nitrogen ratios (C/N) are presented from 22 sampling stations in the Lena River and 40 of its tributaries. Sampling was conducted during two expeditions: the first in July 2012 in the south and southeastern region and the second in June 2013 in the northern region of the Lena basin. The data showed significant spatial differences in concentrations and major sources of OC. Mean subcatchment slopes were correlated with OC concentrations, implying that mountainous areas in general had lower concentrations than lowland areas. δ 13 C and C/N data from tributaries originating in mountainous areas indicated that both dissolved and particulate OC (DOC and POC) were mainly derived from soil organic matter (SOM). In contrast, tributaries originating in lowland areas had larger contributions from fresh vegetation to DOC, while aquatically produced OC was the major source of POC. We suggest that these differences in dominant sources indicated differences in dominant flow pathways. Tributaries with larger influence of fresh vegetation probably had surficial flow pathways, while tributaries with more SOM influence had deeper water flow pathways. Thus, the future export of OC to the Arctic Ocean will likely be controlled by changes in spatial patterns in hydroclimatology and the depth of the active layers influencing the dominant water flow pathways in Arctic river basins.