Abstract

Although present-day precipitation variability in the southern Altiplano and adjacent Andean margins (15-25 degrees S) is well understood, past drivers and mechanisms remain little-explored. We analyzed the pollen assemblages of 31 fossil rodent middens to reconstruct precipitation change during the most recent millennium in the highlands of the Atacama Desert (22 degrees S), on the western foothills of the Altiplano. Variations in low and high elevation pollen types reveal reduced (increased) precipitation between 930 and 550 BP (510 and 440 BP) (BP = before present; taken as Common Era 1950). Variable pollen assemblages prevailed from 390 to 90 BP, followed by a drying trend that persists until present times. Similarities with proxy records from the Altiplano, the tropical Andes and the equatorial Pacific suggest that centennial-scale wet/dry phases in the Atacama highlands were associated with changes in the strength of the South American monsoon system, most likely influenced by changes akin to modern El Nino Southern Oscillation variability.