Precisely constrained 134-ka strong monsoon event in the penultimate deglaciation by an annually laminated speleothem from the Asian monsoon domain

The penultimate deglaciation was characterized by a sub-millennial-scale warm event in the Heinrich Stadial 11(HS11), termed the 134-ka event. However, its precise timing and structure remain poorly constrained due to the lack of high-resolution and precisely dated records. We present an oxygen isotope record of a speleothem with well-developed annual lamina from Zhangjia Cave, located on the north margin of the Sichuan Basin, characterizing Asian summer monsoon (ASM) changes in the 134-ka event, which included an increase excursion of ca. 149 years and decrease excursion of ca. 200 years, inferred from 3.3 & PTSTHOUSND; d(18)O variations. This event also divided the weak ASM interval-II (WMI-II), corresponding to HS11, into two stages, the WMI-IIa 132.8-134.1 ka and WMI-IIb 134.4-136.4 ka. With a comparable climatic pattern globally, the 134-ka event is essentially similar to the millennial-scale events in last glacial-deglacial period. Particularly, the observed weak-strong-weak ASM sequence (138.8-132.8 ka) is largely controlled by changes in the Atlantic Meridional Overturning Circulation (AMOC) forced by the meltwater of northern high-latitude ice sheets. Moreover, our results underpin that AMOC, rather than the global ice volume, is more critical to ASM variations during the last two deglaciations.

Automated summary

The oxygen isotope record of a speleothem from Zhangjia Cave reveals the changes in the Asian summer monsoon during the 134-ka event. This event divided the weak Asian summer monsoon interval-II into two stages and was influenced by the Atlantic Meridional Overturning Circulation.