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Etude des anomalies isotopiques du soufre et de l'oxygène dans le sulfate d'origine volcanique enregistré dans les archives glaciaires

Abstract : Plinian volcanism modify climate for several years by injecting large quantities of sulfur dioxide directly into the stratosphere, further oxidized to sulfuric acid droplets which reflect solar radiations and change the radiative properties of the atmosphere. Up to now, the study of volcanic signals preserved in glaciological archives was limited to the measurements of sulfate concentrations. We propose the use of new tools which are the sulfur and oxygen isotopic anomalies of volcanic sulfate recorded in Dome C and South Pole, to provide further insights into past volcanism.
A study of the temporal evolution of the sulfur and oxygen isotopic anomalies in the Agung (March 1963) and the Pinatubo (June 1991) volcanic sulfate, has been conducted. The sulfur isotopic anomaly changes in sign with time from an initial positive component to a negative value. This change in sign is accompanied by a significant depletion of heavy isotopes with time. Sulfur isotopic anomaly is created during sulfur dioxide photochemical oxidation to sulfuric acid on a month time scale, indicative of a fast process. The oxygen isotopic anomaly seems to be linked to the quasi-biennal oscillation of the stratosphere.
Twelve volcanic eruptions have been studied over the last millenium, by taking the whole sulfate signal. Sulfur isotopic anomaly allowed the identification of 6 stratospheric volcanic eruptions revealing the power of this tool when the nature of the eruption is unknown.
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Submitted on : Wednesday, November 22, 2006 - 3:17:14 PM
Last modification on : Thursday, November 19, 2020 - 3:54:26 PM

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Melanie Baroni. Etude des anomalies isotopiques du soufre et de l'oxygène dans le sulfate d'origine volcanique enregistré dans les archives glaciaires. Océan, Atmosphère. Université Joseph-Fourier - Grenoble I, 2006. Français. ⟨tel-00115661⟩

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