Drought in the Asian summer monsoon region is liked to a weakened inter-hemispheric temperature gradient

Understanding the causes of abrupt hydrologic declines in the Asian summer monsoon region may help limit the adverse effects of such events on the region's economy and ecology. Here, we provide a high-resolution record of hydrological evolution in the East Asian monsoon margin region since the last deglaciation. Our synthesis of hydrological records in the East Asian monsoon region reveals that northern and southern China were generally wet during the early Holocene, while two significant drought events occurred in northern China under the suppressive effect of Northern Hemisphere ice sheets. The hydrological pattern of "southern drought–northern floods" developed during the middle Holocene, and the southward withdrawal of the Intertropical Convergence Zone, which was controlled by the inter-hemispheric temperature gradient, along with the enhanced suppression of the East Asian monsoon by the Hadley Circulation, combined to cause synchronous extreme droughts during the mid- to late-Holocene. Since the early Holocene, China has experienced wet conditions with two significant droughts in northern regions, followed by synchronous extreme droughts due to inter-hemispheric temperature gradient and enhanced Hadley Circulation, according to synthesis of a high-resolution hydrological record.