Low-latitude forcing on 4.2 ka event indicated by records in the Asian monsoon region

The 4.2 ka event is an important climatic event of the Holocene that is expected to considerably influence the development of human civilizations. However, the forcing mechanism of the 4.2 ka event remains unclear, with current evidence being divided between high-latitude and low-latitude forcings. The Asian climate system contains strong summer and winter monsoon circulations, and thus the region is ideal for studying high- and low-latitude climate forcings on 4.2 ka event. In this study, we present a high-resolution pollen record of the past 5000 years from Wudalianchi Crater Lake in northeastern China in the East Asian monsoon region. An evident decrease in broadleaf trees occurred during the 4.2 ka event, suggesting a decrease in summer monsoon rainfall. Well-dated high-resolution pollen, stalagmite δ18O, and winter monsoon records were collected to study the possible transportation of high- and low-latitude signals. Most of the pollen records showed significant changes during the 4.2 ka event, while no apparent change was found in winter monsoon records. Meanwhile, more obvious changes in stalagmite δ18O records were observed in lower- rather than the higher-latitude regions around 4.2 ka. Our results suggest that the signal of the 4.2 ka event might be transported by low-latitude processes, thus corresponding to a low-latitude forcing.