The 2.8 ka abrupt climate event in East Asian Monsoon region: High-resolution stalagmite records from southern China

Using 15 ²³⁰Th dating of a stalagmite (SN33) from Shennong Cave, Jiangxi Province, southeastern China, along with 140 δ¹⁸O results, we reconstructed the evolution of the East Asian Summer Monsoon (EASM) during the Late Holocene between 3.2 and 2.5 ka B.P., with an average resolution of 4 yrs. During this interval, a pronounced positive δ¹⁸O excursion was observed between 2.97 and 2.68 ka B.P., marking the occurrence of the 2.8 ka weak monsoon event in southeastern China. This event began at 2965 ± 13 a B.P. and ended at 2677 ± 47 a B.P., characterized by an asymmetric "double-plunging" structure. Through centennial-scale variations in δ¹³C, trace elements, δ²³⁴U, and growth rate of stalagmite SN33, we infer that southeastern China was in a wetter state during 2.8 ka event. Comparison with other geological records further supports that, while southeastern China indeed experienced humid conditions during this period, other regions were in a state of drought. The 2.8 ka B.P. climatic anomaly had profound impacts on agriculture, population migration, and cultural transitions in the East Asian monsoon region. In China, populations migrated to the warmer and more humid region in southeastern of lower reaches of the Yangtze River Valley (YRV), facilitating the development of agriculture and culture in this region. Meanwhile, the collapse of the Zhou Dynasty in China and the decline of the Songguk-ri culture in Korea were also responses to the cooler and drier climate conditions during the 2.8 ka event.This precipitation pattern may have been influenced by a strengthened westerly jet stream and the Western Pacific Subtropical High (WPSH) during 2.8 ka B.P..  The internal dynamics and transitional characteristics between the 2.8 ka and 8.2 ka events suggest that both weak monsoon events in the Holocene may have been driven by a common mechanism, likely associated with a weakening of the Atlantic Meridional Overturning Circulation (AMOC). Additionally, the significant decline in solar activity during the latter phase of the 2.8 ka event indicates that centennial-scale variations in East Asian monsoon circulation were likely co-driven by solar activity and high-latitude climatic changes in the Northern Hemisphere.