Paleoaltimetry performance of coupled δ²H_wax-MBT_5ME^′ proxy in semiarid conditions

The multi-proxy approach is becoming an effective means to reduce uncertainties and errors compared to the single proxy approach. In this study, we investigated leaf wax biomarker and brGDGTs in topsoils along a semiarid elevation transect on the Chinese Loess Plateau. We found that both leaf wax n-alkane δ²H_wax values and brGDGTs-derived MBT_5ME^′ decreased significantly with elevation, and thus the coupled δ²H_wax-MBT_5ME^′ proxy can improve correlation coefficients (R² = 0.96) compared to a single proxy (R² = 0.82 and 0.90 for δ²H_wax and MBT_5ME^′, respectively) and reduce the uncertainty (RMSE = 230 m) relative to a single proxy (RMSE = 275 m and 360 m for δ²H_wax and MBT_5ME^′, respectively) in elevation estimates. Then we tested the effectiveness and advantages of coupled δ²H_wax-MBT_5ME^′ proxy from surface soils on the Tibetan Plateau compared to a single proxy. Collectively, the coupled δ²H_wax-MBT_5ME^′ proxy can be used as a potentially advantageous proxy for reconstructing paleoelevation in semiarid conditions.