Subannual-to-biannual-resolved travertine record of Asian Summer Monsoon dynamics in the early Holocene at the eastern margin of Tibetan Plateau

Abstract

In this study, we present a subannual–biannual-resolved (0.9–2 years) ASM intensity record spanning from 11.6 to 10.0 ka BP (before 1950 AD) inferred from a 230Th-dated travertine δ18O record at Zhangjia Ravine on the eastern margin of the Tibetan Plateau. The ZJG-1 δ18O sequence is characterized by high-frequency fluctuations at decadal to centennial scales. Fluctuating between −11.15‰ and −14.78‰ over the δ18O sequence, the fluctuation range gradually decreased from 11.6 to 10.0 ka BP. There are several abrupt changes in the δ18O sequence, which indicate that the ASM in the early Holocene was highly unstable. Comparison with marine records suggests that the Preboreal oscillation (PBO) event could be triggered by a freshwater outburst which led to/resulted in a sudden release of thousands of cubic kilometers of the meltwater to the North Atlantic Ocean. Furthermore, the climate oscillations during the PBO were associated with the complex interplay of solar activity and freshwater outburst, the freshwater outburst may amplify the effect of solar activity when it was in the minima. The rapid warming after the PBO event may be controlled by the common mechanism that induced the Dansgaard–Oeschger warming events during the last glacial period. The further pronounced increases of the travertine δ18O values occurred at about 10.3 ka BP, coinciding roughly with Bond 7 event, also caused by the freshwater outburst and solar activity. This study is not only important to understand the primary driving force of the ASM intensity in the early Holocene, but also essential for evaluate the probability of abrupt climate changes in the future.