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

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 summer monsoon (EASM) then. Based on well-established chronologies using precise Th-230 dates and annual-band counting results, the two-cave delta O-18 profiles of similar to 7-yr resolution match well at decadal timescales. Both of the two-cave records document an abrupt weakening (2%. of delta O-18 rise within 20 yr) in the EASM at similar to 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 Inter-tropical 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 EASM intensity, rising atmospheric CO2 and weakening Atlantic Meridional Overturning Circulation between the MI 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. (C) 2014 University of Washington. Published by Elsevier Inc. All rights reserved.