Interannual variability in methane and nitrous oxide concentrations and sea-air fluxes across the North American Arctic Ocean (2015–2019)

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Authors

Cara Manning , Zhiyin Zheng, Lindsay Fenwick, Ross McCulloch, Ellen Damm, Robert Izett, William Williams, Sarah Zimmermann, Svein Vagle, Philippe Tortell

Abstract

Between 2015–2018, we collected ~2000 measurements of methane (CH4) and nitrous oxide (N2O) concentrations in the North American Arctic Ocean during summer and early fall from water column profiles. We also obtained 25 measurements of CH4 and N2O concentrations in rivers along the Northwest Passage and Ellesmere Island in mid-summer 2017–2019. Our results show that N2O is generated in the highly productive Bering and Chukchi Seas and transported northeastward, producing a persistent subsurface N2O peak in the Beaufort Sea. The Chukchi and Beaufort Sea sediments are a significant source of CH4 to the water column. These sedimentary sources and associated water column consumption display significant spatial gradients and interannual variability. CH4 isotope data demonstrate the importance of CH4 oxidation across the study region. We find that rivers are not a significant source of CH4 or N2O to the Arctic Ocean at the time of year sampled. The estimated annual sea-air flux across the study region (2.3 million km2) had a median (interquartile range) of 0.009 (0.002, 0.023) Tg CH4 y-1 and −0.003 (−0.013, 0.010) Tg N y-1. These results suggest that the North American Arctic Ocean currently plays a negligible role in global CH4 and N2O budgets. Our expansive dataset, with observations at many repeat stations, provides a synopsis of present-day Arctic CH4 and N2O distributions and their range of variability, as well as a benchmark against which future climate-dependent changes can be evaluated.

DOI

https://doi.org/10.31223/X53G86

Subjects

Physical Sciences and Mathematics

Keywords

methane, climate change, biogeochemistry, nitrous oxide, Arctic Ocean

Dates

Published: 2021-09-07 20:15

Last Updated: 2021-09-08 11:22

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License

CC BY Attribution 4.0 International

Additional Metadata

Conflict of interest statement:
None

Data Availability (Reason not available):
Data are under review at PANGAEA. Please contact the corresponding author for early access.

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