Abstract
Atmospheric nitrogen deposition is an important external nitrogen source to the ocean that can fuel export production, yet its origin and contribution remain uncertain in the nitrogen-limited North Pacific Subtropical Gyre (NPSG). We present aerosol nitrate and reduced nitrogen (RN) concentrations and nitrogen isotopic composition (δ15N), along with air-mass back trajectories, across the NPSG in summer and winter. High δ15N values (–0.4‰ to 3‰) of aerosol nitrate and RN suggest that natural sources dominate in both seasons, contributing only modestly to the local external nitrogen supply. A synthesis of historical observations reveals pronounced zonal gradients in aerosol nitrogen concentrations and δ15N between the NPSG and transition zone, indicating enhanced anthropogenic influence in the latter, where nitrogen limitation is weaker. We estimate that lateral ocean transport from the transition zone increases external nitrogen inputs to the NPSG by 18%, highlighting an indirect pathway linking human emissions to oligotrophic ocean productivity.
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Data availability
The datasets generated and/or analyzed during the current study were deposited into the Zenodo repository64 and are available at the following: https://doi.org/10.5281/zenodo.18871497.
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Acknowledgements
We thank the captain and crew of the R/V Tan Kah Kee (Xiamen University) for their assistance at sea. We thank Li Tian, Wenbin Zou, Yutong Yang, Lifang Wang, Menghao Ma, and Tao Huang for their help with sampling and nutrient measurements. This work was supported by the National Key Research and Development Program of China (2023YFF0805001), the National Natural Science Foundation of China (42476032, 42330401, 42130401), and the Research Grants Council of the Hong Kong Special Administrative Region, China (No. AoE/P-601/23-N).
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L.W. and D.D. analyzed the data and drafted the manuscript. J.Y.T.Y. designed this study and revised the manuscript. W.M., Z.Z., L.L., X.L., H.B., S.J.K., and M.D. discussed the results and contributed to the final manuscript.
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Wu, L., Dai, D., Ma, W. et al. Atmospheric deposition and lateral ocean transport enhance nitrogen supply to the North Pacific Subtropical Gyre. npj Clim Atmos Sci (2026). https://doi.org/10.1038/s41612-026-01388-7
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DOI: https://doi.org/10.1038/s41612-026-01388-7
