A Review of Climatic Controls on δ18o in Precipitation over the Tibetan Plateau: Observations and Simulations
Thursday, 18 December 2014: 8:30 AM
Located at the convergence of air masses between the westerlies and monsoon, the Tibetan Plateau (TP) undergoes complex water cycle processes, which need to be documented and understood through a combination of variant methodologies. The stable oxygen isotope ratio (δ18O) in precipitation is an integrated tracer of the atmospheric processes and has been used worldwide. Since the 1990s, an intensive effort has been dedicated to studying precipitation isotopic composition at more than 20 stations in the TP. Based on these observations, we establish a database of precipitation δ18O and use different models to evaluate the climatic drivers of present-day precipitation δ18O over the TP. The spatial and temporal patterns of precipitation δ18O and their relationships with temperature and precipitation reveal three distinct domains, respectively associated with the influence of the westerlies (Northern TP), Indian monsoon (Southern TP) and transition in between. The seasonal patterns of precipitation δ18O are diverse in different domains. High-resolution atmospheric models equipped with stable isotopes capture the spatial and temporal patterns of precipitation δ18O and their relationships with moisture transport from the westerlies and Indian monsoon. Only in the westerlies domain are atmospheric models able to represent qualitatively and quantitatively the relationships between climate and precipitation δ18O. More significant temperature effect exists when either the westerlies or Indian monsoon is the sole dominant atmospheric process. The observed and simulated altitude-δ18O relationships strongly depend on the season and the domain (monsoon or westerlies). Our results have crucial implications for the interpretation of the abundant stable isotope information derived from natural climatic archives over the TP such as ice cores, lake sediments or tree rings, and for the application of atmospheric simulations to quantifying paleo-climate and paleo-elevation changes.