Paleohydrological reconstructions based on sedimentological, geochemical, and isotopic records from a lake transect in the central-southern Altiplano (18degrees-26degreesS) indicate abrupt moisture fluctuations during the last 500 years. A change to modem conditions occurred in the late 19th century in all the records, from northern Chile (Lago Chungara, 18degrees15'S) and the Atacama (Laguna Miscanti, 23degrees45'S) to the southern tip of the Altiplano (Laguna El Peinado, NW Argentina, 26degrees30'S). A previous drier period shows different patterns of timing, duration, and intensity. In Chungara, the and period was shorter and occurred during the late 19th and early 20th centuries, while in Miscanti, it occurred earlier and ended at the beginning of the 20th century. In El Peinado, conditions were wetter during the 17-19th centuries and the and period occurred prior to the 17th century. Other records from the region show abrupt paleohydrological and paleoclimatic changes synchronous with the termination of the Little Ice Age. Despite local differences and dating uncertainties, the Little Ice Age stands out as a significant though complex climatic event in the Andean Altiplano. The discrepancies between the northern and southern Altiplano records during the last few centuries may reflect contrasting responses to external forcing in two areas with different climatic regimes. (C) 2003 Elsevier Science B.V. All rights reserved.

The research work in Laguna Miscanti and Chungará was part of the Swiss National Science Foundation Project ‘Global Change in the Arid Andes’ (SNF-20-36382.92) led by the University of Bern, Switzerland. The Universidad Nacional de Catamarca (Argentina) and the Departamento de Relaciones Internacionales, CSIC (Spain) financially supported the fieldwork in Argentina.

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