Clim. Past Discuss., 7, 153-198, 2011
© Author(s) 2011. This work is distributed
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This discussion paper has been under review for the journal Climate of the Past (CP). Please refer to the corresponding final paper in CP.
A millennial multi-proxy reconstruction of summer PDSI for Southern South America
É. Boucher1, J. Guiot1, and E. Chapron2
1Centre Européen de Recherche et d'Enseignement des Géosciences de l'Environnement (CEREGE), UMR 6635, Europôle Méditerranéen de l'Arbois, 13545 Aix-en-Provence cedex 4, France
2ISTO UMR 6113 Université d'Orléans, 1A rue de la Férollerie, 45071 Orléans cedex 2, France

Abstract. We present the first highly resolved millennial reconstruction of the summer (DJF) Palmer Drought Severity Index (PDSI) for the Southern Hemisphere. Our multi-proxy reconstruction focuses on Southern South-America (SSA, south of 20° S) and is based on a novel spectral analogue method that aims at reconstructing the low frequencies of PDSI series independently from higher frequencies. The analysis of past regimes and long-term fluctuations in the PDSI reveals considerable geographical and temporal variations over the last millennia in SSA. Hence, recent changes, although some were very significant, were rarely exceptional over the last thousand years. However, from the point of view of extremes, recent PDSI values associated to extreme droughts (e.g. in the Andes) or wet spells (e.g. in the Pampas) were unequalled over the last thousand years. A major feature of our reconstruction is that it highlights that low frequency water availability fluctuations in Patagonia were generally in antiphase with those found on the rest of the sub-continent. We show that such antiphases within SSA's hydroclimate could be attributed the Antarctic Oscillation (AAO). The AAO was an important climatic driver during the calibration period (1930–1993) in SSA, and possibly over the last millennia as well. ENSO and PDO signals are also embedded, to a lesser extent, within the PDSI series, but the influence of these forcings has considerably varied through time and space over the last thousand years. Our results therefore highlight the complexity of water-availability fluctuations in SSA and their important dependence on external ocean-atmospheric forcings.

Citation: Boucher, É., Guiot, J., and Chapron, E.: A millennial multi-proxy reconstruction of summer PDSI for Southern South America, Clim. Past Discuss., 7, 153-198, doi:10.5194/cpd-7-153-2011, 2011.
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