Abstract
Ocean-atmosphere CO2 exchange is key in modulating global climate, but the Arctic Ocean’s anthropogenic carbon (Cant) uptake is poorly constrained. Most studies in the Canada Basin using the Transit Time Distribution (TTD) relied on two years of paired gas tracers, CFC-12 and SF6. Here we use nuclear reprocessing products 129I, 236U, and 137Cs to estimate Cant in the Atlantic Water layer by the TTD. We present the evolution of Cant in the Canada Basin from 1993 to 2023, and a high-resolution distribution of Cant across the basin in 2022. We observe a basin-wide inventory increase in the Atlantic Layer (400–1000 m) of 5.5 ± 0.9 Tg C yr−1. Cant content in water entering the Canada Basin tracks increasing atmospheric input, time-lagged by 15-20 years; we anticipate Cant content of up to 65 μmol kg−1 in core Atlantic Water entering the basin by 2050.
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Data availability
The 2022 and 2023 radioisotope data generated in this study are available at Zenodo (2022 at https://doi.org/10.5281/zenodo.18880777, 2023 at https://doi.org/10.5281/zenodo.18880591). Previously published data used in this study are available from the original sources cited in the manuscript. Hydrographic data are from the Beaufort Gyre Exploration Program, and are available at: https://www2.whoi.edu/site/beaufortgyre/data/ctd-and-geochemistry/.
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Acknowledgements
Thanks to the crew and science team onboard the CCGS Louis St Laurent involved in sampling during the 2020–2023 JOIS/BGOS expeditions. Special thanks to Kayley Kündig, Goelle Scacco, Aline Schneuwly and Marguerite Larriere for assistance in sample processing and measurements. This work was supported by the European Research Council (ERC-2020-COG 101001451—TITANICA), awarded to N.C. Additional funding was provided by the Swiss Polar Institute Polar Access Fund (PAF-2022-003), awarded to A.P.
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A.P. and N.C. designed the study. A.P., A.-M.W., W.W. and S.Z. collected the samples from 2020 to 2023. A.P., N.C., C.V., and H.P-T. undertook sample measurements. A.P. L.R. and A.-M.W. performed data analysis. A.P. and L.R. created visualisations. A.P. wrote the text, and all authors contributed to the reviewing and editing.
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Payne, A., Raimondi, L., Wefing, AM. et al. Nuclear waste radionuclides unveil three decades of anthropogenic carbon in the Canada Basin of the Arctic Ocean. Nat Commun (2026). https://doi.org/10.1038/s41467-026-71115-6
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DOI: https://doi.org/10.1038/s41467-026-71115-6
