A millennial multi-proxy reconstruction of summer PDSI for Southern South America

• Published in: Climate of the Past
• Main Authors: Boucher, E., Guiot, Joel, Chapron, Emmanuel
• Other Authors: Centre européen de recherche et d'enseignement des géosciences de l'environnement (CEREGE), Aix Marseille Université (AMU)-Institut national des sciences de l'Univers (INSU - CNRS)-Collège de France (CdF (institution))-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)-Institut National de la Recherche Agronomique (INRA), Institut des Sciences de la Terre d'Orléans (ISTO), Université de Tours-Institut national des sciences de l'Univers (INSU - CNRS)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS), ANR-06-VULN-0010,ESCARSEL,Evolution Séculaire du Climat dans les régions circum-Atlantiques et Réponse de Systèmes Eco-Lacustres(2006)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2011
• Subjects: [SDU.STU.CL]Sciences of the Universe [physics]/Earth Sciences/Climatology; [SDE.MCG]Environmental Sciences/Global Changes; Antarctic; The Antarctic; Patagonia; Pacific; Antarc*
• Online Access: https://hal-insu.archives-ouvertes.fr/insu-00643480; https://hal-insu.archives-ouvertes.fr/insu-00643480/document; https://hal-insu.archives-ouvertes.fr/insu-00643480/file/cp-7-957-2011.pdf; https://doi.org/10.5194/cp-7-957-2011

International audience We present the first spatially explicit field 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 low PDSI frequencies independently from higher frequencies. The analysis of past regimes and trends in extreme wet spells and droughts reveals considerable geographical and temporal variations over the last millennium in SSA. Although recent changes are in some cases notorious, most were not exceptional at the scale of the last thousand years. Our reconstruction highlights that low frequency water availability fluctuations in Patagonia were generally in antiphase with the rest of the subcontinent. Providing the fact that modern patterns of changes are transferable to the past, we show that such antiphases within SSA's hydroclimate could be attributed to the spatially contrasted response of summer PDSI to the Antarctic Oscillation (AAO). However, El Niño Southern Oscillation (ENSO) and Pacific Decadal Oscillation (PDO) signals are also embedded within the PDSI series during the 20th century. All these ocean-atmospheric forcings acted synergically, but the dominant influence appeared highly compartmentalized through space, highlighting clear AAO- (e.g. South Patagonia) and ENSO- (e.g. the Pampas) dominated regions. Our results therefore emphasize the complexity of water-availability fluctuations in SSA and their important dependence on external ocean-atmospheric forcings.