Centennial- to millennial-scale Asian summer monsoon changes during the MIS 5/4 transition revealed by high-resolution stalagmite records from southwestern China

During the Marine Isotope Stage (MIS) 5/4 transition, the global climate changed from an interglacial to a glacial state, and hence it was characterized by high-amplitude climate changes. High-resolution stalagmite records can potentially improve our understanding of climate change during this transition. Here we use a high-precision ²³⁰Th-dated, 50-yr-resolution stalagmite δ¹⁸O record from Yangkou Cave, in Chongqing, southwestern China, to reveal centennial- to millennial-scale changes in Asian summer monsoon (ASM) intensity during the interval of 98.8–59.3 kyr B.P. (thousands of years before 1950 CE). The record reveals five Chinese Interstadial events, namely CIS 18–22, and pronounced centennial-scale oscillations are evident and verified within these millennial-scale events. There are four centennial-scale events of monsoon strengthening in both CIS 21 and CIS 22, corresponding to Greenland Interstadial events GI 21 and GI 22. By contrast, CIS 18, CIS 19 and CIS 20 differ in both structure and onset time relative to the corresponding GI events during MIS 4. During MIS 5, reduced ice sheet and sea-ice cover and strong Atlantic Meridional Overturning Circulation (AMOC) forced the Intertropical Convergence Zone (ITCZ) towards its northern limit, which enhanced the teleconnection between the ASM and climate change in northern high latitudes. During MIS 5, the millennial-scale events (CIS 21 and 22) show a rapid atmospheric teleconnection between the ASM and the climate of northern high latitudes, but this coupling did not exist during MIS 4. The weakening of Northern Hemisphere summer insolation, the expansion of ice sheets and sea ice, combined with the increased influence of Antarctica, may have led to the decoupling of the Asian summer monsoon and climate change in high northern latitudes.