SO 2 Oxidation Kinetics Leave a Consistent Isotopic Imprint on Volcanic Ice Core Sulfate

• Published in: Journal of Geophysical Research: Atmospheres
• Main Authors: Gautier, Elsa, Savarino, Joel, Erbland, Joseph, Farquhar, James
• Other Authors: Observatoire des Sciences de l'Univers de Grenoble (OSUG ), 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 Grenoble Alpes 2016-2019 (UGA 2016-2019 ), Université Grenoble Alpes 2016-2019 (UGA 2016-2019 ), Department of Geology College Park, University of Maryland College Park, University of Maryland System-University of Maryland System, ANR-16-CE01-0011,EAIIST,Projet International d'exploration de la calotte polaire de l'Antarctique de l'Est(2016)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2018
• Subjects: [SDU.OCEAN]Sciences of the Universe [physics]/Ocean; Atmosphere; Antarctic; Antarc*; Ice cap; ice core; Polar Ice Cap
• Online Access: https://hal.science/hal-02350364; https://hal.science/hal-02350364/document; https://hal.science/hal-02350364/file/AGU-SMIF-article%20file-2nd_submission_plaintext.pdf; https://doi.org/10.1029/2018JD028456

International audience This work presents measurements of time-resolved mass-independently fractionated sulfate of volcanic origin from Antarctic ice core records that cover the last 2,600 years. These measurements are used to evaluate the time dependence of the deposited isotopic signal and to extract the isotopic characteristics of the reactions yielding sulfate from stratospheric volcanic eruptions in the modern atmosphere. Time evolution of the signal in snow (years) with respect to the fast SO 2 oxidation in the stratosphere suggests that photochemically produced condensed phase is rapidly and continuously separated from the gas phase and preserved during transportation and deposition on the polar ice cap. On some eruptions, a nonzero isotopic mass balance highlights that a part of the signal can be lost during transport and/or deposition. The large number of volcanic events studied allows the Δ 33 S versus Δ 36 S and δ 34 S versus Δ 33 S slopes to be constrained at À1.56 (1σ = 0.25) and 0.09 (1σ = 0.02), respectively. The Δ 33 S versus Δ 36 S slope refines a prior determinations of Δ 36 S/Δ 33 S = À4 and overlaps the range observed for sulfur seen in early Earth samples (Archean). In recent volcanogenic sulfate, the Δ 33 S versus δ 34 S differs, however, from the Archean record. The similitude for Δ 36 S/Δ 33 S and the difference for Δ 33 S/δ 34 S suggest similar mass-independently fractionated sulfate processes to the Archean atmosphere. Using a simple model, we highlight that a combination of several mechanisms is needed to reproduce the observed isotopic trends and suggest a greater contribution from mass-dependent oxidation by OH in the modern atmosphere. Plain Language Summary Large volcanic eruptions inject sulfurous gases in the stratosphere, where they rapidly form sulfuric acid aerosols. These aerosols can reside in the stratosphere for years, cover the entire globe, and profoundly modify the climate by scattering and absorbing solar radiation. Sulfuric acid aerosols formed by this process ...