Air mass signals in δ18O of tree-ring cellulose revealed by back-trajectory modeling at the monsoonal Tibetan plateau

A profound consideration of stable oxygen isotope source water origins is a precondition for an unambiguous palaeoenvironmental interpretation of  terrestrial δ18O archives. To stress the influence of air mass origins on widely used δ18O tree-ring chronologies, we conducted correlation analyses between six annually resolved δ18O tree-ring cellulose (δ18OTC) chronologies and  mean annual air package origins obtained from backward trajectory modeling.
This novel approach has been tested for a transect at the southeastern Tibetan plateau (TP), where air masses with different isotopic composition overlap.  Detailed examinations of daily precipitation amounts and monthly precipitation
δ18O values (δ18OP ) were conducted with the ERA Interim and Laboratoire de M´et´eorologie Dynamique General Circulation Model (LMDZiso) data, respectively. Particularly the southernmost study sites are influenced by a distinct amount effect. Here, air package origin δ18OTC relations are generally weaker in contrast to our northern located study sites. We found that tree-ring isotope signatures at dry sites with less rain days per year tend tobe influenced stronger by air mass origin than tree-ringisotope values at semi-humid sites. That implies that the local hydroclimate history inferred from δ18OTC archives is better recorded at semi-humid sites.