Air mass origin signals in δ (18)O 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 δ 18O archives. To stress the influence of air mass origins on widely used δ 18O tree-ring chronologies, we conducted correlation analyses between six annually resolved δ 18O tree-ring cellulose (\(\delta ^{18}\textit {O}_{TC}\)) 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 δ 18O values (\(\delta ^{18}\textit {O}_{P}\)) were conducted with the ERA Interim and Laboratoire de Meteorologie Dynamique General Circulation Model (LMDZiso) data, respectively. Particularly the southernmost study sites are influenced by a distinct amount effect. Here, air package origin \(\delta ^{18}\textit {O}_{TC}\) 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 to be influenced stronger by air mass origin than tree-ring isotope values at semi-humid sites. That implies that the local hydroclimate history inferred from \(\delta ^{18}\textit {O}_{TC}\) archives is better recorded at semi-humid sites.