A 16 ka record of high-amplitude precipitation events from the southern part of the hyperarid Atacama Desert.

The Atacama Desert in Chile is known to be one of the driest deserts on Earth, with dominating hyperaridity since the Miocene. During recent times, however, especially the southern part of the Atacama repeatedly experienced exceptional precipitation events, like in 2015 and 2017. Locally, these events with rainfall rates of >50 mm within 48 hours caused catastrophic floods with significant destruction and human fatalities. Although the meteorological drivers of these heavy rains are widely understood, only little is known about the frequency and amplitude of similar events on geological timescales.

Here we present the results of a study in an endorheic claypan from the southern edge of the hyperarid core of the Atacama, an area with mean annual precipitation of 5 mm/a. A modern ground-truthing approach applying remote-sensing and meteorological as well as climate-modelling data indicate that during the past 30 years, the claypan reacted very sensitive to local precipitation, with events >20 mm of rain causing sufficient surface run-off in the catchment to partially flood the basin. A short sediment core recovered from the center of the claypan covers approx. the past 16,000 years.  First sedimentological, mineralogical, and geochemical findings imply strong variations in the amplitude of the recorded precipitation events over time, with a clear shift from more intense to lower-amplitude events from the late Pleistocene to the Holocene. The results of the study shed new light on the glacial-interglacial precipitation variability in the Atacama Desert and its driving mechanisms.