Sponsor
We thank T. Bauska (British Antarctic Survey) and S. Shackleton (Massachusetts Institute of Technology) for diligent sampling at the Taylor Glacier main transect, and we thank S. Toyoda and N. Yoshida (TiTech) and J. Mohn (EMPA) for N2O isotopic calibration gases. The University of Bern gratefully acknowledges financial support by the Swiss National Science Foundation (Award 172506 and 200328). Oregon State University gratefully acknowledges financial support from the National Science Foundation (Award 1903681). Open access publishing facilitated by University of Tasmania, as part of the Wiley - University of Tasmania agreement via the Council of Australian University Librarians.
Published In
Global Biogeochemical Cycles
Document Type
Article
Publication Date
5-1-2025
Subjects
N2O production
Abstract
During the transition from the Last Glacial Maximum (LGM) to the Holocene, the atmospheric N2O mole fraction increased by 80 nmol mol−1. Using ice core measurements of N2O isotopomer ratios, we show that this increase was driven by increases in both nitrification and denitrification, with the relative partitioning between both production pathways depending on the assumed isotopic end‐member source signatures. Similarly, we also attribute a 35 nmol mol−1 N2O mole fraction increase during the Heinrich Stadial 4/Dansgaard Oeschger 8 (HS4/DO8) millennial‐scale event to increases in both N2O production pathways. In contrast, the 25 nmol mol−1 N2O mole fraction decrease during the Younger Dryas was driven almost exclusively by a decrease in nitrification. The deglacial and HS4/DO8 increases in N2O production occurred in both marine and terrestrial environments, with the terrestrial source responding faster to warming by about two centuries. Constraints on changes in nitrification and denitrification emissions are robust and consistent with previous studies showing the sensitivity of N2O emissions to abrupt Northern Hemisphere warming. This study demonstrates for the first time the importance of both denitrification and nitrification pathways in driving source changes. Absolute emissions are more uncertain due to uncertainty about source isotopomer signatures. For instance, the contribution of denitrification to emissions at the LGM shifts from (65 ± 10) % to (91 ± 6) % when factoring in isotope enrichment due to partial reduction of N2O to N2 during denitrification. Reducing uncertainty in source signatures will increase the power of ice core N2O isotope records in deducing environmental change.
Rights
© 2025. The Author(s).This is an open access article under theterms of the Creative CommonsAttribution License, which permits use,distribution and reproduction in anymedium, provided the original work isproperly cited.
Locate the Document
DOI
10.1029/2024GB008287
Persistent Identifier
https://archives.pdx.edu/ds/psu/43598
Publisher
American Geophysical Union (AGU)
Citation Details
Menking, J. A., Lee, J. E., Brook, E. J., Schmitt, J., Soussaintjean, L., Fischer, H., Kaiser, J., & Rice, A. (2025). Glacial‐Interglacial and Millennial‐Scale Changes in Nitrous Oxide Emissions Pathways and Source Regions. Global Biogeochemical Cycles, 39(5). Portico. https://doi.org/10.1029/2024gb008287