Juxtaposition of Western Pacific Subtropical High on Asian Summer Monsoon Shapes Subtropical East Asian Precipitation

Increasing lines of evidence question the homogenous response of Asian Summer Monsoon (ASM) precipitation patterns, requiring rethinking of the forcing mechanisms. Here we show a ~15,000-year quantitative precipitation history based on well-dated lake levels at Lake Chenghai, subtropical China. Lake levels and the inferred precipitation were high during the Bølling-Allerød, early and late Holocene, but low during the middle Holocene. The orbital scale precipitation trend is out of phase with boreal summer insolation, the later has been widely suggested as the driver of ASM precipitation. Lake Chenghai long-term lake levels are synchronous with trends in tropical Pacific sea surface temperatures, the related zonal sea surface temperature gradients, and interhemispheric temperature gradients. We propose that changes in either the interhemispheric or zonal Pacific temperature gradients modulate the intensity and location of the western Pacific subtropical high, which is juxtaposed on the ASM, leading to heterogeneous hydroclimatic conditions over subtropical East Asia.