Increased water vapor supply in winter and spring leading to the arid Central Asian wetting in last 6000 years

Paleoclimate reconstructions show that the arid Central Asia(ACA)is characterized by a wetting trend from the midHolocene(MH)to the Preindustrial period(PI),which has been acknowledged to be a result of increased mean precipitation.However,a systemic understanding of its governing dynamics remains elusive.Based on model outputs from 13 climate models from the Paleoclimate Model Intercomparison Project phase 4(PMIP4)and proxy records from ACA,here we show that increase in mean precipitation in ACA can be attributed to changes in water vapor source and its transport intensity in winter(December,January,and February)and spring(March,April,and May).In particular,the increase in water vapor supply in winter is associated with the southerly wind anomaly over the northwestern Indian Ocean and Central Asia,caused by an overall weakening of the Asian winter monsoon.This is conducive to water vapor transport from the upwind regions(e.g.,Mediterranean)to ACA.Meanwhile,water vapor supply from the eastern Iceland is also enhanced due to a negative North Atlantic Oscillation-like(NAO-like)atmospheric circulation pattern caused by sea ice expansion in the North Atlantic.In spring,evaporation over land and inland lakes is enhanced by increased insolation in the Northern Hemisphere,which increases atmospheric humidity that fuels midlatitude westerlies to enhance ACA precipitation.In addition,weakened atmospheric subsidence over ACA in winter and spring also contributes to the increased precipitation.Overall,our results indicate that paleoclimate modeling is of great importance for disentangling governing dynamics accounting for reconstructed climate phenomena that might be a synergic consequence of several processes operating in different seasons.