Weakening monsoon event during 2.8 ka BP in East China linked to the North Atlantic cooling

Abstract

The timing and structure of the past weakening monsoon events, such as the 2.8 ka BP event, is critical for testing the simulation experiment of extreme climate prediction in the future. But the lack of continuous records with high resolution based on precise chronology during 2.8 ka BP hinders the better understanding of the event. In this study, we present a new annually-resolved stalagmite δ18O record covering the 2.8 ka BP event with precisely independent chronology from Central China. Combined with other 7 well-dated stalagmite δ18O records from East China covering 2.8 ka BP period with resolution less than 10 years, the Asian summer monsoon (ASM) signal has been extracted by the principal component analysis (PCA), and the ASM sequence has been built by the first principal component (PC1) on a decadal scale. Two weakening anomalies of the ASM are presented by PC1 during the 2.8 ka BP event and this event has been identified by 1 standard deviation with an asymmetric two-plunging structure and a duration of ∼310 years. The comparisons between the ASM weakening derived from multiple stalagmite δ18O records in this study and the solar insolation minimum with the North Atlantic cooling, suggest that the synchronous North Atlantic cooling should play an important role on the monsoon weakening in East Asia, while the delayed insolation minimum must be impossible to trigger the 2.8 ka BP event. But low solar radiation may magnify the variation amplitude of the monsoon weakening around 2.7 ka BP, which suggest both internal variability and external forcing impact on the 2.8 ka BP event.