Contribution of ENSO variability to the East Asian summer monsoon in the late Holocene

Abstract

The Asian monsoon (AM) is an important atmosphere circulation system of the global climate system, acting as a bridge across high-northern latitude and tropic climates. However, dynamical origins of AM variations during the Holocene remain unclear. Here we present stable isotope records (δ18O and δ13C) of a Holocene stalagmite from Niu Cave, central China, to address the nature and causes of East Asian summer monsoon (EASM) changes. Our δ18O record shows a gradual weakening of the EASM intensity from the middle to the late Holocene, corresponding with a decrease in Northern Hemisphere summer insolation and an enhancement of ENSO activity. The δ13C profile exhibits similar variability to δ18O record, suggesting that regional hydrological changes were primarily controlled by the large-scale summer monsoon circulation. Power spectrum analyses of δ18O and δ13C records show that the EASM intensity varies at a dominant periodicity of ~830yr, probably correlated to an ENSO-like cycle. Furthermore, millennial-scale shifts in our records exhibit a strong correlation with that in ENSO proxies over the past 3000years. The EASM-ENSO relationship may be related to the shifts in the mean position of Walker circulation and western North Pacific subtropical high. Our finding suggests that millennial-scale monsoon changes in the late Holocene are primarily modulated by changes in tropical ocean–atmosphere circulation, rather than variations in the North Atlantic thermohaline circulation.