Resumen de Isotopic Characteristics and Paleoclimate Implications of the Extreme Rain Event of March 2015 in Northern Chile
Teresa E. Jordan, Christian Herrera Lameli, Linda V. Godfrey, Stephen J. Colucci, Carolina Gamboa, Javier Urrutia, Gabriel González López, Jacob F. Paul
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 rain event relative to those hypothetical paleoclimate scenarios. It was the first opportunity to determine the 18O y 2H of a major precipitation event that might eventually be preserved in geological materials, as well as to examine geomorphological and sedimentological consequences of extended heavy rainfall. 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 isotopes 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 review of the spatial and temporarl distribution of evidence of wetter paleoclimate intervals leads to the hypothesis that the March 2015 scenario likely better fits some parts of the paleoclimate record of the hyperarid Atacama Desert than do the climate scenarios deduced previously.
