A record of ozone variability in South Pole Antarctic snow: Role of nitrate oxygen isotopes

• Published in: Journal of Geophysical Research
• Main Authors: Mccabe, Justin R., Thiemens, Mark H., Savarino, Joel
• Other Authors: Department of Chemistry and Biochemistry, University of California Los Angeles (UCLA), University of California (UC)-University of California (UC), Laboratoire de glaciologie et géophysique de l'environnement (LGGE), Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB Université de Savoie Université de Chambéry )-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB Université de Savoie Université de Chambéry )-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), European Science Foundation (ESF) under the EUROCORES Programme EuroCLIMATE, contract ERAS-CT-2003-980409 of the European Commission
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2007
• Subjects: nitrate; isotopes; ozone; [SDU.STU.GL]Sciences of the Universe [physics]/Earth Sciences/Glaciology; Antarctic; South Pole; Antarc*; South pole
• Online Access: https://hal-insu.archives-ouvertes.fr/insu-00377182; https://hal-insu.archives-ouvertes.fr/insu-00377182/document; https://hal-insu.archives-ouvertes.fr/insu-00377182/file/2006JD007822.pdf; https://doi.org/10.1029/2006JD007822

International audience The information contained in polar nitrate has been an unresolved issue for over a decade. Here we demonstrate that atmospheric nitrate's oxygen isotopic composition (Δ17O-NO3) reflects stratospheric chemistry in winter and tropospheric chemistry in summer. Surface snow isotope mass balance indicates that nitrate oxygen isotopic composition is the result of a mixture of 25% stratospheric and 75% tropospheric origin. Analysis of trends in Δ17O-NO3 in a 6 m snow pit that provides a 26-year record reveals a strong 2.70-year cycle that anticorrelates (R = −0.77) with October–November–December column ozone. The potential mechanisms linking the records are either denitrification or increased boundary layer photochemical ozone production. We suggest that the latter is dominating the observed trend and find that surface ozone and Δ17O-NO3 correlate well before 1991 (R = 0.93). After 1991, however, the records show no significant relationship, indicating an altered oxidative environment consistent with current understanding of a highly oxidizing atmosphere at the South Pole. The disappearance of seasonal Δ17O-NO3 trends in the surface layer at depth remain unresolved and demand further investigation of how postdepositional processes affect nitrate's oxygen isotope composition. Overall, the findings of this study present a new paleoclimate technique to investigate Antarctic nitrate records that appear to reflect trends in stratospheric ozone depletion by recording tropospheric surface ozone variability.