I am currently the lead PI on an NSF-funded project (Arctic Natural Sciences) investigating N2O cycling in the water-column of the Western Arctic Ocean, which is still poorly constrained despite the special role this region plays for global climate. Water-column samples for N2O isotope and isotopomer analysis were collected in fall (Aug-Oct) as part of the U.S. GEOTRACES 2015, CHINARE 2016, and during a cruise on the R/V Healy in 2017. My research is guided by the overarching hypothesis that productive shelf areas of the Arctic Ocean (e.g., Chukchi and Beauford seas) potentially support significant net fluxes of N2O to the atmosphere via water-column nitrification and in sediments via coupled nitrification-denitrification, and that these sources contribute to offshore transport of N2O toward the central Arctic. However, the magnitude of these potential fluxes is unknown. Both processes can be identified by geochemical signatures in water-column N2O. Results from the U.S. GEOTRACES suggest that Western Arctic sediments is the main N2O source to the water-column.

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Funding: NSF, Arctic Natural Sciences

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Relevant publications:

Lehmann, N., Kienast, M., Granger, J., Bourbonnais, A., Altabet, M. A., and J-É. Tremblay, Remote western Arctic nutrients fuel remineralization in the deep Baffin Bay, submitted to Global Biogeochemical Cycles, November 2018, MS# 2018GB006134.

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Yang, S., Chang, B. X., Warner, M. J., Weber, T. S., Bourbonnais, A., Santoro, A. E., ... & Bianchi, D. (2020). Global reconstruction reduces the uncertainty of oceanic nitrous oxide emissions and reveals a vigorous seasonal cycle. Proceedings of the National Academy of Sciences, 117(22), 11954-11960.