A detailed comparison of Asian Monsoon intensity and Greenland temperature during the Allerød and Younger Dryas events

An annual layer-counted and ²³⁰Th-dated stalagmite oxygen isotope record from Qingtian Cave in Hubei province, central China, provides an Asian Monsoon (AM) history across the Allerød to Younger Dryas (YD) transition, with an average 2.5-year resolution. Seasonal δ¹⁸O profiles indicate that the calcite δ¹⁸O is a sensitive proxy for AM changes, and the close similarity between the Qingtian and other cave records from eastern China suggests a large-scale regional coherence of monsoonal precipitation δ¹⁸O variations associated with the temperature changes in high-northern latitudes. The annually-resolved chronology with a U-Th age uncertainty of less than 100 yr defines the timing, duration and transition of the early Allerød, the intra-Allerød cold period (IACP), the late Allerød, and the start of the YD. The 160-yr-long IACP, with two brief reversals, is clearly shown in both δ¹⁸O and lamina thickness records. The early and late Allerød, separated by the IACP, are characterized by several decadal to centennial cycles of δ¹⁸O variations, each punctuated by sub-cycles. These decadal to centennial monsoon variations correlate with the Greenland temperature changes, supporting a model simulation that the decadal North Atlantic Oscillation (NAO) and North Pacific Oscillation (NPO) are coupled via atmospheric circulation under glacial boundary conditions, perhaps affecting tropical/subtropical monsoon changes. However, the monsoon transition between the late Allerød and YD lasted 380 yr, longer than the analogous Greenland temperature shift by at least 130 yr [Stuiver, M., Grootes, P.M., GISP2 oxygen isotope ratios. Quat. Res. 53 (2000) 277-284]. This implicates other links besides the direct link between Greenland and the AM, which is now well documented. One possibility is the influence by Southern Hemisphere climate via cross-equatorial air flow [An, Z.S., The history and variability of the East Asian paleomonsoon climate. Quat. Sci. Rev. 19 (2000) 171-187].