Mid-Holocene rainfall heterogeneity in subtropical East Asia

Growing lines of evidence reveal an unexpectedly dry mid-Holocene but wetting late Holocene in subtropical East Asia, which is anti-phase/out-of-phase to the widely recognized northern hemisphere solar-insolation-forced Asia summer monsoon precipitation trend. This asynchrony implies that some key processes are missing in the current understanding of the Asia summer monsoon dynamics across different monsoon subsystems. Here we further confirm this spatial rainfall heterogeneity with robust biogeological evidence, corroborated by archeological evidence and simulations of transient climatic models. We propose that the location and intensity of the western Pacific subtropical high (WPSH) are most likely responsible for the observed orbital/suborbital spatial hydroclimatic heterogeneity, while the tropical Indo-Pacific sea surface temperature (SST), the SST gradients between the west-east equatorial Pacific, as well as the temperature gradients between southern-northern hemispheres, are the governing factors that combinedly regulate the WPSH behaviors and ultimately modulate the orbital/suborbital rainfall heterogeneity in subtropical East Asia.