Abstract

Variations in oxygen isotope ratios (O-18) measured from modern precipitation and geologic archives provide a promising tool for understanding modern and past climate dynamics and tracking elevation changes over geologic time. In areas of extreme topography, such as the Tibetan Plateau, the inter... Show moreVariations in oxygen isotope ratios (O-18) measured from modern precipitation and geologic archives provide a promising tool for understanding modern and past climate dynamics and tracking elevation changes over geologic time. In areas of extreme topography, such as the Tibetan Plateau, the interpretation of O-18 has proven challenging. This study investigates the climate controls on temporal (daily and 6h intervals) and spatial variations in present-day precipitation O-18 (O-18(p)) across the Tibetan Plateau using a 30year record produced from the European Centre/Hamburg ECHAM5-wiso global atmospheric general circulation model (GCM). Results indicate spatial and temporal agreement between model-predicted O-18(p) and observations. Large daily O-18(p) variations of -25 to +5 occur over the Tibetan Plateau throughout the 30 simulation years, along with interannual O-18(p) variations of similar to 2. Analysis of extreme daily O-18(p) indicates that extreme low values coincide with extreme highs in precipitation amount. During the summer, monsoon vapor transport from the north and southwest of the plateau generally corresponds with high O-18(p), whereas vapor transport from the Indian Ocean corresponds with average to low O-18(p). Thus, vapor source variations are one important cause of the spatial-temporal differences in O-18(p). Comparison of GCM and Rayleigh Distillation Model (RDM)-predicted O-18(p) indicates a modest agreement for the Himalaya region (averaged over 86 degrees-94 degrees E), confirming application of the simpler RDM approach for estimating O-18(p) lapse rates across Himalaya. Show less