A detailed East Asian monsoon history surrounding the ‘Mystery Interval’ derived from three Chinese speleothem records

摘要

The ‘Mystery Interval’ (MI, 17.5?14.5 ka) was the first stage of the last deglaciation, a key interval for understanding mechanisms of glacial–interglacial cycles. To elucidate possible causes of the MI, here we present three high-resolution, precisely dated oxygen-isotope records of stalagmites from Qingtian and Hulu Caves in China, reflecting changes in the East Asian summermonsoon (EASM) then. Based on well-established chronologies using precise ~(230)Th dates and annual-band counting results, the two-cave δ~(18)O profiles of ~7-yr resolution match well at decadal timescales. Both of the two-cave records document an abrupt weakening (2‰ of δ~(18)O rise within 20 yr) in the EASM at ~16.1 ka, coinciding with the transition of the two-phased MI reconstructed from New Mexico's Lake Estancia. Our results indicate that the maximum southward displacement of the Intertropical Convergence Zone and associated southward shift of polar jet stream may generate this two-phase feature of the MI during that time.We also discover a linear relationship among decreasing EASMintensity, rising atmospheric CO_2 andweakening Atlantic Meridional Overturning Circulation between theMI and Younger Dryas episodes, suggesting a strong coupling of atmospheric/oceanic circulations in response to the millennial-scale forcing, which in turn regulates global climate changes and carbon cycles.