Enhanced East Asian summer monsoon circulation during the Early to Middle Bronze Age

Abstract

The Holocene East Asian summer monsoon (EASM) evolution has been extensively investigated, yet proxy records show inconsistent variations during the Bronze Age, and spatial patterns of hydroclimatic conditions remain controversial, limiting our understanding of monsoonal behavior and its potential association with culture development. Here we present multiple biomarker records from the northern coast of the South China Sea, which document the strength of monsoon-induced upwelling/mixing effect, to infer Holocene EASM variability. Our multiple biomarker records consistently indicate enhanced EASM circulation during ∼6000–9000 cal a BP and ∼3300–4500 cal a BP, superimposed on the long-term weakening trend. The enhanced EASM circulation during the Early to Middle Bronze Age challenges the presumed cool/dry climate background and lends support to a tripole pattern of hydroclimatic variability over East China during this period.