August Temperature Reconstruction Based on Tree-Ring Latewood Blue Intensity in the Southeastern Tibetan Plateau

Abstract

Tree-ring blue intensity (BI) has been widely applied for temperature reconstructions in many regions around the globe. However, it remains untested in the southeastern Tibetan Plateau (TP) where a large number of ancient trees are distributed. In this study, we developed earlywood blue intensity (EWBI), latewood blue intensity (LWBI), and delta blue intensity (ΔBI) chronologies based on tree-ring samples collected from Abies spectabilis at two sites in the southeastern TP. Our results reveal that the EWBI and ΔBI chronologies correlated negatively with temperature parameters and LWBI chronology correlated positively with temperature parameters, respectively. Among them, the LWBI chronology was identified most suitable for reconstructing the mean temperature in August. A linear regression model was developed for the August temperature reconstruction, which accounts for 34.31% of the observed variance in the period of 1954–2017. The reconstruction, spanning 1789–2017, is highly consistent with other tree-rings based temperature reconstructions from the neighboring regions. Our findings reveal a potential linkage between the August temperature anomaly in the southeastern TP and the Atlantic Multidecadal Oscillation (AMO), which suggests that the AMO fingerprint in the region is not just evident in winter but also in summer.