Obliquity forcing of Late Pliocene–Early Pleistocene aridification in the Qaidam Basin, NE Tibetan Plateau

Abstract

Knowledge of the variations of aridification during past warm periods can help predict future aridification trends. However, the variation of aridity during the warm Pliocene epoch, a potential analog for the future climate, has not been sufficiently studied due to the lack of high-resolution records. Here, we present high-resolution (∼7 kyr) oxygen and carbon isotope records spanning the Late Pliocene–Early Pleistocene from the Qaidam Basin, northwestern China. We interpret enriched carbonate δ18O value as indicating stronger evaporation, based on the general correlation between the enrichment of carbonate δ18O and an increased sedimentary halite content. Our results reveal that the Qaidam Basin was already an extremely arid environment no later than ∼3.9 Ma, and that aridification was further intensified at ∼2.6 Ma. Interestingly, the Qaidam Basin experienced decreased aridity or climate wetting during the high insolation intervals within the middle Piacenzian warm period, in contrast with the intensified aridity in the semi-arid Chinese Loess Plateau. Strikingly, the Qaidam Basin experienced intensified aridification during high-obliquity intervals, with smaller global ice sheets, during 3.6–2.5 Ma. We attribute this obliquity signal of Asian aridification to the effects of insolation and possibly glacial forcing, via their impacts on regional evaporation and reduced monsoon precipitation. Using the Late Pliocene as an analogue, our findings suggest that future aridification variations in Central Asia during the next ∼100 kyr may be dominated by 40-kyr cycles, under natural climatic forcing.