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  • 1
    Publication Date: 2021-10-07
    Description: Volcanic eruptions are an important climate driver. The impact of Pinatubo-sized eruptions has been observed and is well constrained. The magnitude and duration of volcanic winter effects after supereruptions such as Toba remain disputed due to disagreement between the strong cooling predicted by models and much milder climate perturbations according to the paleodata. Here we present a reevaluated climate impact of a Toba-sized supereruption based on up-to-date GISS ModelE simulations. In this study, we account for all known primary mechanisms that govern the evolution of the volcanic plume and their nonlinear interactions. The SO 2 radiative effects are evaluated for the first time in coupled climate simulations with the interactive atmospheric chemistry module. We found that SO 2 effects on photochemistry, dynamics, and radiative forcing are especially prominent. Due to strong absorption in ultraviolet, SO 2 feedback on photochemistry partially offsets the limiting effect associated with aerosol microphysical processes. SO 2 greenhouse warming soothes the radiative cooling exerted by sulfate aerosols. SO 2 absorption in the shortwave and longwave causes radiative heating and lofting of the volcanic plume, and boosts the efficiency of SO 2 impact on photochemistry. Our analysis shows that SO 2 lifetime and magnitude of effects scale up and increase with the amount of emitted material. For a Pinatubo-sized eruption, SO 2 feedbacks on chemistry and dynamics are relevant only during the initial stage of the volcanic plume evolution, while local SO 2 concentrations are high. For a Toba-sized eruption, SO 2 effects are as important as sulfate aerosols and produce a less extreme volcanic winter.
    Keywords: 551.5 ; supereruption ; Toba ; volcanic winter ; sulfate aerosols ; climate impact ; sulfur dioxide
    Language: English
    Type: map
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  • 2
    Publication Date: 2022-05-26
    Description: Author Posting. © American Geophysical Union, 2007. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geophysical Research Letters 34 (2007): L13701, doi:10.1029/2007GL030017.
    Description: Paleoceanographic data from the low latitude Pacific Ocean provides evidence of changes in the freshwater budget and redistribution of freshwater within the basin during the Holocene. Reconstructed Holocene seawater δ 18O changes compare favorably to differences predicted between climate simulations for the middle Holocene (MH) and for the pre-Industrial late Holocene (LH). The model simulations demonstrate that changes in the tropical hydrologic cycle affect the relationship between δ 18Osw and surface salinity, and allow, for the first time, quantitative estimates of western Pacific salinity change during the Holocene. The simulations suggest that during the MH, the mean salinity of the Pacific was higher because less water vapor was transported from the Atlantic Ocean and more was transported to the Indian Ocean. The salinity of the western Pacific was enhanced further due both to the greater advection of salt to the region by ocean currents and to an increase in continental precipitation at the expense of maritime precipitation, the latter a consequence of the stronger Asian summer monsoon.
    Description: This work was supported by NSF grants ATM-0501241, ATM-0501351, and WHOI’s Ocean and Climate Change Institute.
    Keywords: Holocene ; Tropical Pacific ; Hydrology ; Paleoceanography ; Geochemical tracers ; Insolation forcing
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Format: text/plain
    Format: application/pdf
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