Moisture sources and rainfall water stable isotopes during the recent triple-dip La Niña in coastal Argentina

Abstract

This study explores the influence of meteorological conditions on the water stable isotopic composition of precipitation (δ18O and δ2H) and identifies key moisture sources in the South Atlantic Coastal Region of Argentina during the recent triple-dip La Niña (2020–2023). Using daily rainwater isotopes and HYSPLIT backtrajectory models, five primary sources were determined, with the Sub-tropical Atlantic (44%) as the dominant contributor. Isotopic signatures reveal significant variations in precipitation driven by La Niña’s impact on regional circulation. Unlike previous studies, results show minimal Amazon-sourced recycled moisture and a strong ENSO influence on oceanland moisture ratios. Daily sampling captured enriched isotopic signatures during this event and seasonal shifts in d-excess values. These findings enhance understanding of ENSO-driven hydrological variability and underscore the value of high-resolution sampling for assessing precipitation variability, with implications for groundwater recharge studies and drought resilience in this agriculturally important region.