Aquatic biomass is a major source to particulate organic matter export in large Arctic rivers ...

• Main Authors: Behnke, Megan I., Tank, Suzanne E., McClelland, James W., Holmes, Robert M., Haghipour, Negar, Eglinton, Timothy I., Raymond, Peter A., Suslova, Anya, Zhulidov, Alexander V., Gurtovaya, Tatiana, Zimov, Nikita, Zimov, Sergey, Mutter, Edda A., Amos, Edwin, Spencer, Robert G. M.
• Format: Text
• Language: English
• Published: ETH Zurich 2023
• Subjects: Arctic; rivers; particulate organic matter; endmember; carbon flux; permafrost
• Online Access: https://dx.doi.org/10.3929/ethz-b-000604581; http://hdl.handle.net/20.500.11850/604581

Arctic rivers provide an integrated signature of the changing landscape and transmit signals of change to the ocean. Here, we use a decade of particulate organic matter (POM) compositional data to deconvolute multiple allochthonous and autochthonous pan-Arctic and watershed-specific sources. Constraints from carbon-to-nitrogen ratios (C:N), δ13C, and Δ14C signatures reveal a large, hitherto overlooked contribution from aquatic biomass. Separation in Δ14C age is enhanced by splitting soil sources into shallow and deep pools (mean ± SD: -228 ± 211 vs. -492 ± 173‰) rather than traditional active layer and permafrost pools (-300 ± 236 vs. -441 ± 215‰) that do not represent permafrost-free Arctic regions. We estimate that 39 to 60% (5 to 95% credible interval) of the annual pan-Arctic POM flux (averaging 4,391 Gg/y particulate organic carbon from 2012 to 2019) comes from aquatic biomass. The remainder is sourced from yedoma, deep soils, shallow soils, petrogenic inputs, and fresh terrestrial production. Climate ... : Proceedings of the National Academy of Sciences of the United States of America, 120 (12) ...