Abstract
Prior to the 24-26 March 2015 extreme precipitation event that impacted northern Chile, the scenarios for Pleistocene and Holocene wetter paleoclimate intervals in the hyperarid core of the Atacama Desert had been attributed to eastern or southwestern moisture sources. The March 2015 precipitation event offered the first modern opportunity to evaluate a major regional precipitation event relative to those hypothetical paleoclimate scenarios. It was the first opportunity to determine the 18O and 2H composition of a major precipitation event that might eventually be preserved in geological materials. The driver for the March 2015 event was a synoptic-scale weather system, a cutoff cold upper-level low system that traversed the Pacific Ocean at a time of unusually warm temperatures of Pacific surface water. Ground-based precipitation data, stable isotopes in precipitation and river samples, NCEP/NCAR reanalysis atmospheric data and air mass tracking are utilized to connect the Earth surface processes to atmospheric conditions. The δ18O and δ2H of the precipitation and ephemeral rivers were significantly heavier than the rain, snow and ephemeral rivers fed by more frequent but less voluminous precipitation events registered prior to March 2015. Consistent with the atmospheric analyses, the rain isotopic compositions are typical of a water vapor whose source was at more equatorial latitudes of the Pacific and which moved southward. The late March 2015 system was an unforeseen scenario even for El Niño Pacific ocean conditions. Furthermore, the late summer season warmth led to greater potential for erosion and sediment transport than typical of more common moderate precipitation scenarios which usually include widely distributed snow. A comparison of the March 2015 scenario to the spatial distribution of wetter paleoclimate intervals leads to the hypothesis that the March 2015 scenario likely better fits some parts of the paleoclimate record of the continental interior hyperarid Atacama Desert than do the eastern or southwestern moisture source paleoclimate scenarios deduced previously.
Highlights
An uncommon precipitation event impacted northern Chile from 24-26 March 2015 (Fig. 1), at the end of the southern hemisphere summer season and at the onset of El Niño conditions in the Pacific Ocean
North of 26° S heavy rain spanned over 150 km from the Pacific to the Andean highlands. This included the core of the hyperarid Atacama Desert
Isotopic values of rain water and river samples demonstrate that the March 2015 precipitation event supplied water that was outside the isotopic range expected for the western slope of the Andes between 23°-30° S, and similar past events should be recognizable in paleohydrological records
Summary
An uncommon precipitation event impacted northern Chile from 24-26 March 2015 (Fig. 1), at the end of the southern hemisphere summer season and at the onset of El Niño conditions in the Pacific Ocean. Because of the warm season, much of the precipitation fell as rain even in the high mountains where snowfall historically dominates. The impacts included severe flooding of river valleys that drain the Andes to the Pacific coast with associated debris flows, tens of deaths, and widespread property damage (e.g., cities of Chañaral and Copiapó, Fig. 2) (Wilcox et al, 2016). For regions of low relief or internal drainage there was little change of the land surface materials despite high rain totals (Jordan et al, 2015; Tapia et al, 2015; Wilcox et al, 2016; Scott et al, 2017). It is anticipated that groundwater was recharged, though spatial variations in recharge amount are not known
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
