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This study has reconstructed the Holocene environmental history of central Tibetan Plateau, a transitional area between monsoon-dominated Asia and Westerlies-dominated Asia, to examine the interplay between the two circulation systems and effects of other potential mechanisms on the temporal variability of Holocene climatic conditions in the study area. Specifically, this study has produced a twin record of palaeo-hydrology and palaeotemperature from an alpine wetland sediment sequence using two sets of lipid-based biomarker indices: n-alkanes and branched glycerol dialkyl glycerol tetraethers (bGDGTs). The results show that (1) the Asian summer monsoon has supplied moisture that helped initiate the wetland habitat around 8000 cal. yr BP, about 2000 years later than locations along the southeastern edge of the plateau; (2) a significant decline in moisture supply is evident since the Medieval Warm period; (3) the Westerlies have transmitted variability of the North Atlantic climate to the study area, resulting in periodic increases in evaporation and causing short-term expansion or contraction of the wetland and (4) the palaeo-air temperature change follows closely that of global sea level and sea surface temperature, implying a link to global ice volume change throughout the Holocene. This study concludes that the Holocene climate history of central Tibetan Plateau is a result of monsoonal moisture supply interacted with the Westerlies variability, while the palaeo-temperature has followed changes in global ice volume during the present warm interglacial. [ABSTRACT FROM AUTHOR]

The uplift of the Tibet Plateau (TP) during the Miocene is crucial to understanding the evolution of Asian monsoon regimes and alpine biodiversity. However, the northern Tibet Plateau (NTP) remains poorly investigated. We use pollen records of montane conifers (Tsuga, Podocarpus, Abies, and Picea) as a new paleoaltimetry to construct two parallel midrange paleoelevation sequences in the NTP at 1332 ± 189 m and 433 ± 189 m, respectively, during the Middle Miocene [~15 million years ago (Ma)]. Both midranges increased rapidly to 3685 ± 87 m in the Late Miocene (~11 Ma) in the east, and to 3589 ± 62 m at ~7 Ma in the west. Our estimated rises in the east and west parts of the NTP during 15 to 7 Ma, together with data from other TP regions, indicate that during the Late Miocene the entire plateau may have reached a high elevation close to that of today, with consequent impacts on atmospheric precipitation and alpine biodiversity. [ABSTRACT FROM AUTHOR]