Timing and structure of the short-lived Dansgaard-Oeschger 6 event in the Asian monsoon system

Abstract

The structural features of the Asian monsoon in response to the Dansgaard-Oeschger (DO) event during the last glacial period are important for understanding and investigating the characteristics and dynamical mechanisms of the monsoon climate evolution. Here, based on seven ²³⁰Th dating results and 144 sets of oxygen and carbon isotope (δ¹⁸O and δ¹³C) data from a stalagmite (No. SM5) in Shima Cave, Hunan Province, we reconstruct climatic and environmental evolutions in the East Asian monsoon region, with an average resolution of ∼12 years over the period from 34.1 to 32.6 ka BP. SM5 δ¹⁸O record captures the rapid onset of the DO6 event at ∼33.8 ± 0.1 ka BP, with a negative isotopic bias of ∼1.8 ‰ over several decades, indicative of a fast recovery of the East Asian summer monsoon corresponding to Greenland warming. Considering the published stalagmite records with independent ²³⁰Th dating from the East Asian and the South American monsoon regions, we suggest that the DO6 should have started at ∼33.8 ± 0.1 ka BP and ended at ∼33.4 ± 0.1 ka BP, with a duration of ∼0.4 ± 0.1 ka BP. This further supports the accuracy of GICC05 chronology for Greenland ice cores surrounding this time interval. Besides, a “double peak” structure of DO6 Interstadial is observed in high-resolution mid- to low-latitude geological records and the CH₄ record but is missing in Greenland temperature record. These lines of evidence show that while the Asian monsoon was able to respond rapidly to northern high-latitude climates, it also featured centennial-scale oscillations possibly unique to the mid- to low-latitude regions.