Moisture Sources and Climatic Controls of Precipitation Stable Isotopes Over the Tibetan Plateau in Water-Tagging Simulations

Understanding the climate controls of precipitation delta O-18 in the Tibetan Plateau (TP) is crucial for paleoclimate reconstructions from a wealth of regional archives. We use the outputs of iCAM5 model to quantify the different moisture contribution to local precipitation delta O-18 and to understand the climate controls of precipitation delta O-18 in the TP based on water-tagging. The model shows some deficiencies in simulating the spatial and temporal characteristics of precipitation delta O-18 and the local climatic controls across the TP. Among all the tagged source regions, South Asia and the Indian Ocean contribute the most to the precipitation delta O-18 in the monsoon-controlled domain, followed by the East Asia source region. The westerlies are identified as major moisture sources to the precipitation delta O-18 in the westerlies-controlled domain. South Asia and the Indian Ocean also contribute substantially for the westerlies-controlled domain. On interannual time scales, summer precipitation delta O-18 in the monsoon-controlled domain is dominated by rainout processes occurring along the moisture transport pathway, indicating that precipitation delta O-18 variations here potentially record changes in the regional upstream convection. The delta O-18 signal can be altered by changes in the moisture source location, which implies that enhanced moisture delivery from remote source regions leads to more negative precipitation delta O-18 due to an increase in the rainout effect during transport. Our results have implications for the interpretation of past variations of archives with precipitation stable isotopes, such as ice cores, tree rings, lake sediments, and speleothems in the TP and surrounding regions.

Automated summary

Understanding the climate controls of precipitation delta O-18 in the Tibetan Plateau is crucial for paleoclimate reconstructions. This study uses a model to quantify the different moisture contributions to precipitation delta O-18 and identifies the major moisture sources for different regions. The model shows some deficiencies in simulating the characteristics of precipitation delta O-18 and the local climatic controls across the Tibetan Plateau.