Identification Of A Regionally Coherent Subseasonal Signal Of Stable Isotopes In Tropical Andean Precipitation

Limited observations and the lack of comprehensive understanding of the controls on the isotopic content of precipitation severely limit paleoclimate reconstructions in the outer tropical Andes. This study examines four years of daily observations of stable isotopes in precipitation from ten sites in southern Peru and northern Bolivia and focuses on understanding the controls on the subseasonal spatiotemporal variability in isotopes during the wet season. These data provide new insights into modern isotope variability at high spatial and temporal scales. We identify a robust, regionally coherent subseasonal signal of isotopes in precipitation that occurs each year with a periodicity of around 15 days. This signal reflects variability in precipitation delivery driven by synoptic conditions, and closely relates to variations in the strength and direction of the South American Low Level Jet and moisture availability directly to the east of the Altiplano. Annual layer snowpacks on high Andean glaciers retain this subseasonal signal, allowing the development of snow-pit age models based on precipitation isotope measurements and demonstrating that region-wide synoptic signals are recorded in the snow. This result has implications for improving paleoclimate reconstructions from tropical Andean ice cores and other paleoclimate records.