Deuterium Excess in Bolivian Precipitation: From Short-term Station Data to ice Core Records

We present here deuterium excess (d) variations in current Bolivian precipitation collected at both monthly and daily resolutions from September 1999 in the Zongo Valley. This valley is located on the northeast side of the Bolivian Cordillera Real, 40km northwesterly from the Illimani summit where an ice core has been drilled in 1999. Interestingly, monthly deuterium excess shows a clear seasonal cycle correlated with isotopes whereas at daily resolution this correlation is much less visible, suggesting different controls on d depending on time resolution. We interpret d variations in terms of possible recycling over Amazonia, different moisture sources between wet and dry season and re-evaporation of droplets during fall. We also examine if an "altitude effect" is shown over the andean region by comparing stations at different elevations. Then, we examine how deuterium excess varies in snow and ice at Illimani summit and we discuss the possible post-depositional processes influencing d. At last, we compare our results with simulations from 1- Rayleigh-based simple models and 2- the REMO meso-scale model focused on tropical South America.