Intensified monsoonal rainstorm events over westerly-dominated Asian interior during the warm mid-Holocene

Abstract

Hydroclimatic change in the Asian interior plays a key role in regulating regional environmental sustainability, water security, and human-nature relationships. However, the influence of the summer monsoon and westerly circulation on the evolution of hydroclimate over the arid Asian interior remains controversial. Here we present newly collected hydroclimate proxies from loess in the Asian interior, together with transient model simulations, to address the coevolution of monsoon-induced extreme rainfall and significant westerly-affected drying during the mid-Holocene. Our results suggest that a drier mid-Holocene in the southern Tarim Basin was associated with a poleward displacement of the westerly jet due to relatively warm boreal summer temperatures in the mid-latitudes. Strengthened water vapor fluxes associated with the boreal summer monsoon facilitated extreme rainfall events and enhanced mountain erosion. Our proxy-model comparison reveals a drier westerly regime superimposed with strengthened rainfall over the Asian interior during the warm mid-Holocene. Our findings suggest that more summer flash rainstorm events are likely to occur in a warmer world, with enhanced drying in the hyper-arid Asian interior. Mid-Holocene dry climate in the Asian interior was associated with the poleward displacement of the westerly jet due to warm boreal summer temperatures at mid-latitudes, according to hydroclimate, radiocarbon and paleoclimate data and transient model simulations.