Epipelagic nitrous oxide production offsets carbon sequestration by the biological pump

Xianhui S. Wan, Hua Xia Sheng, Minhan Dai, Karen L. Casciotti, Matthew J. Church, Wenbin Zou, Li Liu, Hui Shen, Kuanbo Zhou, Bess B. Ward, Shuh Ji Kao

Research output: Contribution to journalArticlepeer-review

10 Scopus citations

Abstract

The removal of carbon dioxide from the atmosphere by the marine biological pump is a key regulator of Earth’s climate; however, the ocean also serves as a large source of nitrous oxide, a potent greenhouse gas and ozone-depleting substance. Although biological carbon sequestration and nitrous oxide production have been individually studied in the ocean, their combined impacts on net greenhouse forcing remain uncertain. Here we show that the magnitude of nitrous oxide production in the epipelagic zone of the subtropical ocean covaries with remineralization processes and thus acts antagonistically to weaken the radiative benefit of carbon removal by the marine biological pump. Carbon and nitrogen isotope tracer incubation experiments and nitrogen isotope natural abundance data indicate enhanced biological activity promotes nitrogen recycling, leading to substantial nitrous oxide production via both oxidative and reductive pathways. These shallow-water nitrous oxide sources account for nearly half of the air–sea flux and counteract 6–27% (median 9%) of the greenhouse warming mitigation achieved by carbon export via the biological pump.

Original languageEnglish
Pages (from-to)29-36
Number of pages8
JournalNature Geoscience
Volume16
Issue number1
DOIs
StatePublished - Jan 2023

Funding

We greatly appreciate S. S. Hsiao, Y. Wu, M. Xu, M. He, X. Zhang, G. Shao, W. Zhang and Q. Wu’s inputs during on-board sampling and incubation in the research cruises. We also thank T. Huang and Y. Zhu for the on-board measurement of NH, Y. Wu and L. Wang for NO, NO and PO measurements and Q. Hong, Y. Ma and W. Chen for measuring the Th. We are also grateful for the crew of the RV Dongfanghong II and RV Tan Kah Kee for the on-board assistance and providing the CTD data. Comments from T. W. Trull and H. M. Nelson improved earlier versions of the manuscript. This work was supported by the National Natural Science Foundation of China through grants 92058204, 41890802, 922583024, 1721005, 41730533 and 41906040. M.J.C. acknowledges funding from the Simons Foundation via SCOPE (grant 721221). 4 + 3 − 2 − 4 3− 234

FundersFunder number
Simons Foundation721221
National Natural Science Foundation of China41730533, 1721005, 92058204, 922583024, 41906040, 41890802

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