资源环境科技发展态势分析平台

Although present-day precipitation variability in the southern Altiplano and adjacent Andean margins (15-25°S) is well understood, past drivers and mechanisms remain little-explored. We analysed 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°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 CE 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 ENSO variability.