Abstract

A diverse array of records now exists from the dry central Andes. Overall, these records indicate that during the late Glacial-early Holocene the area experienced millennial-scale changes in the frequency and magnitude of rainfall that have been linked to ENSO-like variability in the tropical Pacific. Sub-millennial precipitation anomalies have been detected in several records from the Atacama Desert throughout the latest Holocene, but the timing, magnitude and causes of these fluctuations have remained poorly defined. Here, we used a regional climate proxy network to reconstruct rainfall patterns over the last 2 ka, encompassing the Medieval Climate Anomaly (MCA) and the Little Ice Age (LIA). Our dataset includes 122 records of hydrological change such as rainfall anomalies estimates from Abrocoma cinerei fecal-pellets, relict tree mounds found onto abandoned fluvial terraces and radiocarbon dates from archeological sites located at hyperarid core of the Atacama. Our results point to important precipitation variability on centennial timescales across the Atacama Desert over the past two millennia. We identified three wet/dry cycles of different duration. Major hydroclimatic shifts occurred during the MCA (1.4-0.6 ka) and LIA (0.15-0.3 ka) stages, represented by positive and negative rainfall anomalies, respectively. Marine records from the eastern Tropical Pacific suggest negative (positive) SST anomalies during MCA (LIA). This implies that positive (negative) precipitation anomalies during the latest Holocene were likely related to periods of sustained La Niña-like (El Niño-like) conditions. Hence, the tropical Pacific SST gradient seems to be the primary mechanism responsible for centennial precipitation fluctuations in the central Andes.