Presentation Information
[U17-P07]Coupled Climate and Sulfur Photochemistry in the Archean Atmosphere under Variable Volcanic Outgassing
*Tetsuo Taki1, Hiroyuki Kurokawa1 (1.The University of Tokyo)
Keywords:
Planetary atmosphere,Planetary surface,Photochemistry,Sulfur cycle
Sulfur compounds supplied by volcanic activity, such as SO2 and H2S, can influence atmospheric composition and radiative transfer (e.g., Kasting et al., 1989). Sulfur photochemistry forms reservoirs such as elemental sulfur particles and sulfate aerosols (e.g., Kumar & Francisco, 2017) and can produce isotopic fractionation signatures preserved as the sulfur isotope record (e.g., Endo et al., 2019, 2022). Because these products affect radiative balance, sulfur chemistry is inherently linked to climate. Moreover, sulfur chemistry depends on radicals (OH, O) produced by H2O photolysis, and the H2O distribution is set by the temperature profile. Therefore, climate and photochemistry must be treated consistently when evaluating sulfur-driven atmospheric changes.
Observational constraints indicate that volcanic sulfur fluxes can vary substantially with eruption type and the volcanic activity level (e.g., Self et al.; 2006 Carn et al., 2017). Such variability implies that the atmospheric sulfur budget and the resulting aerosol production, radiative balance, and redox environment may fluctuate over time, motivating a systematic characterization of atmospheric responses to changes in sulfur input. This perspective is particularly important for the early Earth, where interpretations of surface environments and sulfur isotope records can depend sensitively on how volcanic outgassing variability modulates coupled photochemistry and climate.
In this study, we use the publicly available one-dimensional climate–photochemistry code Photochem (Wogan et al., 2023, 2024, 2025) to evaluate how variability in sulfur input affects sulfur chemistry and atmospheric composition via climate changes. We systematically vary lower-boundary fluxes of volcanic gases including sulfur species and quantify the resulting changes in vertical profiles of SO2, H2S, and other major species. In this presentation, we show the changes in radiative balance and thermal structure implied by the resulting atmospheric compositions and examine the potential for feedbacks mediated by changes in the H2O distribution. These calculations aim to estimate how variations in sulfur flux can modify the redox environment of a reducing atmosphere and the production of aerosol precursors, providing constraints on interpretations of the sulfur isotope record and on temporal variability in surface environments.
Observational constraints indicate that volcanic sulfur fluxes can vary substantially with eruption type and the volcanic activity level (e.g., Self et al.; 2006 Carn et al., 2017). Such variability implies that the atmospheric sulfur budget and the resulting aerosol production, radiative balance, and redox environment may fluctuate over time, motivating a systematic characterization of atmospheric responses to changes in sulfur input. This perspective is particularly important for the early Earth, where interpretations of surface environments and sulfur isotope records can depend sensitively on how volcanic outgassing variability modulates coupled photochemistry and climate.
In this study, we use the publicly available one-dimensional climate–photochemistry code Photochem (Wogan et al., 2023, 2024, 2025) to evaluate how variability in sulfur input affects sulfur chemistry and atmospheric composition via climate changes. We systematically vary lower-boundary fluxes of volcanic gases including sulfur species and quantify the resulting changes in vertical profiles of SO2, H2S, and other major species. In this presentation, we show the changes in radiative balance and thermal structure implied by the resulting atmospheric compositions and examine the potential for feedbacks mediated by changes in the H2O distribution. These calculations aim to estimate how variations in sulfur flux can modify the redox environment of a reducing atmosphere and the production of aerosol precursors, providing constraints on interpretations of the sulfur isotope record and on temporal variability in surface environments.