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

Abstract

Abstract. 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.

Lake Fluctuations, Plant Productivity, and Long-Term Variability in High-Elevation Tropical Andean Ecosystems

“…This pattern is consistent with an extreme reduction of the Altiplano tree-ring-based precipitation reconstruction during the last three decades (Morales et al, 2012). Drier conditions were also identified in an aridity reconstruction for the central Andes region from southern South America (Boucher et al, 2011). Consistently, a sustained shrinking of small glaciers from the tropical Andes have been recorded since the second half of the 20th century (Ramirez et al, 2001;Francou et al, 2003;Vuille et al, 2008), which was associated with the increasing trend in temperature for JULIETA CARILLA ET AL.…”

Precipitation changes in the South American Altiplano since 1300 AD reconstructed by tree-rings

“…It has been proposed that the negative impact of this persistent centennial drought on local agricultural-based societies triggered social conflicts and a period of wars in the Altiplano during the 14th and 15th centuries (Nielsen et al, 2002). A persistent drought has also been recorded during the 14th century in the Palmer Drought Severity Index (PDSI) field reconstruction, mainly based on the Quelccaya, Huascarán and Sajama ice-cores for the Altiplano region (Boucher et al, 2011). Our reconstruction presents milder to wet conditions prevailing from the 1410s to the 1520s with a particularly humid interval at the end of the 15th century.…”

“…Drier conditions from 1780 to 1820 were also recorded in the PDSI reconstruction for the South American subtropical region (Boucher et al, 2011). Based on historical documents, Gioda and Prieto (1999) recorded severe droughts in Potosí (southern Bolivia) during this period, with two extreme dry events lasting consecutively 10-(1777-1786) and 5-yr (1801-1805).…”

Modelling and climatic interpretation of the length fluctuations of Glaciar Frías (north Patagonian Andes, Argentina) 1639–2009 AD

“…Villalba et al, 1997Villalba et al, , 2003 and precipitation (e.g. Villalba et al, 1998;Lara et al, 2008;Boucher et al, 2011) exist. Neukom et al (2010Neukom et al ( , 2011 have compiled a temperature and precipitation reconstruction for southern South America on a 0.5 • × 0.5 • grid from a selection of the available proxy records.…”