Chinese speleothem evidence of the early-mid Holocene transition and the instability of Asian summer monsoon

Abstract

The Asian summer monsoon circulation during the Holocene is suggested to be controlled by northern hemisphere summer insolation, but the transition from strong to weak monsoon status lagged the insolation peak, and its causes remain unclear. Here, we provide a high-resolution East Asian summer monsoon record, with 14 ²³⁰Th/U dates and 510 δ¹⁸O data on a stalagmite from Shima Cave, central China, spanning the past 14.6 ka. Our record shows a gradual monsoon intensification from the deglaciation to the early Holocene, followed by monsoon deterioration since the mid Holocene. Using 23 cave δ¹⁸O records from China, we obtained an integrated δ¹⁸O record in order to investigate the overall changes in Asian summer monsoon circulation throughout the Holocene. The general pattern and transition of the integrated δ¹⁸O record agree well with the Ti record from Cariaco Basin, both demonstrating a prominent transition at ∼7.5 ka BP and coinciding with worldwide reorganizations of atmospheric circulations. The early-mid Holocene monsoon transition demonstrates that the response of the monsoon to insolation is likely altered by internal changes, including temperature in northern hemisphere and ice-sheet recession. Besides, fluctuating monsoon climate during the early Holocene is well demonstrated in Shima record. Prominent and large-amplitude monsoon weakenings during the 8.2 ka, 9.2 ka and Preboreal Oscillation events, and five small-amplitude events, all related to meltwater injections and cooling in the North Atlantic regions. The close correspondence between these reconstructions suggests that the early Holocene monsoonal changes were sensitive to northern high-latitude climates during the process of ice sheet retreat.