Sub-decadally-resolved Asian monsoon dynamics during Chinese interstadial 21 in response to northern high-latitude climate

Greenland Interstadial 21 (GIS 21), one of the longest warm episodes during the last glacial period, occurred at the transition from Marine Isotope Stage (MIS) 5a to 4. Precise determination of the timing and duration of this interstadial can improve our understanding of the hydroclimatic connection between low and high latitudes across this MIS boundary. δ18O records of two stalagmites from Sanxing Cave, Southwest China, provide a sub-decadally resolved record of Asian Summer Monsoon (ASM) evolution from 79.0 ± 0.2 to 75.7 ± 0.2 thousand years before present (kyr BP, before 1950 CE) revealing the detailed structure of the Chinese Interstadial 21 (CIS 21). The replicate Sanxing record, for the first time, captures three centennial-scale intervals of strong monsoon and a 700-yr-long weak monsoon period within the CIS 21 “rebound-type” event, concurrent with its counterpart GIS 21. This synchronicity between SW China and Greenland suggests a rapid atmospheric teleconnection between the North Atlantic and the ASM region. Marked by ∼400 yr-long decrease in ASM, CIS 21 ended at 76.8 ± 0.2 kyr BP, which is 0.5–1.0 kyr younger than the corresponding termination of GIS 21 on AICC2012 and GICC05modelext timescales. Given its high accuracy and precision, the Sanxing stalagmite chronology can serve as a benchmark for chronological refinements for ice-core records.