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Etude des phénomènes de dépôt et post-dépôt de la neige andine sur un site tropical d'altitude (Illimani - Bolivie - 6340 m) en vue de l'interprétation d'une carotte de glace.

Abstract : The Illimani ice cores, extracted in 1999 in the Bolivian Andes thanks to the GREAT ICE team of IRD and analysed over the following years at LGGE, have shown a strong seasonality in their chemical signal, with stronger concentration peaks during the dry season than during the wet season. A series of experiments has been carried out to inquire into the mechanisms of formation of these peaks, and to study the deposition processes of atmospheric impurities in the region. A multidisciplinary approach based on three types of data over the years 2000 to 2003 has been adopted. These are meteorological data, and the results of chemical composition analyses of snow deposited on the glacier, as well as of aerosols collected at a nearby site (located at a different altitude). The chemical analyses were carried out by ionic chromatography and therefore only deal with the soluble fraction. The study of the archiving phenomena on the glacier shows that deposition occurs by means of abundant precipitation of low ionic concentration during the wet season, whereas a mixture of dry deposition and rare but highly concentrated precipitation characterises the dry season. In contrast to other Andean sites, sublimation occurring during the dry season is not the main reason for the formation of these peaks. Sublimation is responsible for concentration increases in most ionic species at the surface, but its effects are limited. The ionic quantities deposited are conserved, except for some species - in particular acetate, for which losses were observed. We question the importance of the wind as causing the erosion of the signal. Concerning the aerosols, a seasonal pattern is found to characterise the Amazonian contribution with a biomass-burning signal expressed in the organic species at the end of the dry season.
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Submitted on : Friday, May 25, 2012 - 10:47:43 AM
Last modification on : Friday, September 25, 2020 - 9:16:02 AM
Long-term archiving on: : Thursday, December 15, 2016 - 8:59:21 AM

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Hervé Bonnaveira. Etude des phénomènes de dépôt et post-dépôt de la neige andine sur un site tropical d'altitude (Illimani - Bolivie - 6340 m) en vue de l'interprétation d'une carotte de glace.. Glaciologie. Université Joseph-Fourier - Grenoble I, 2004. Français. ⟨tel-00701331⟩

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