Holocene climatic and environmental change on the western Tibetan Plateau revealed by glycerol dialkyl glycerol tetraethers and leaf wax deuterium-to-hydrogen ratios at Aweng Co

Mean annual air temperature (MAAT) and precipitation isotope records for the Holocene were obtained from the analysis of the relative distribution of branched glycerol dialkyl glycerol tetraethers and compound-specific hydrogen isotope ratios of leaf waxes from a sediment core from Aweng Co on the western Tibetan Plateau (WTP). Our results indicate that the Indian monsoon mainly influenced Aweng Co during the Holocene. During the early Holocene, when summer insolation was at a maximum, the monsoonal influence was strong and the climate was warm and wet. Both the summer and winter insolation were relatively weak, and Aweng Co was cool and dry during the middle Holocene (6–3 ka), indicating a weakening of the Indian monsoon. The southward displacement of the Intertropical Convergence Zone and relatively low atmospheric methane content may have contributed to the middle Holocene cooling on the WTP. During the late Holocene, with a further increase in winter insolation and decrease in summer insolation, the summer monsoon weakened and the MAAT on the WTP gradually increased. Depleted leaf wax hydrogen isotope ratios during the late Holocene can be attributed to accelerated glacier melting because of the elevated MAAT.