A Persistent Coast Mode of Precipitation in Southeast China Over the Last Millennium.

Instrumental data set have revealed several summer precipitation patterns in eastern China, being summarized as "tripole," "dipole" and "coast" modes. The former two have been found to persist at different time scales, leaving the latter unclear in geological records. Here we present 1300‐year hydroclimate records in a tropical maar lake in the southern coast of China using archeal lipid GDGTs, which can reflect lower water redox conditions largely regulated by lake water depth. The down‐core GDGTs reveal a relatively drier condition during the medieval climate anomaly compared to the Little Ice Age, in‐phase with other records in southeast coast of China but opposite to the inland region, hence demonstrating a persistent "coast" mode in eastern China. The thermal state of equatorial Pacific is suggested to play an important role in shaping the "coast" mode by modulating the location and strength of the western Pacific subtropical high and tropical typhoons. Plain Language Summary: Summer precipitations in eastern China affect more than 1 billion people's lives and economic development. It is well‐known that summer precipitations in eastern China show spatial differences. A seesaw pattern of summer precipitations between the southeast coast and the inland region of China, called "coast" mode, has been proposed from modern observations. However, whether this "coast" mode persists in the past remains unexplored. Here, we present a 1300‐year lake‐level record based on GDGTs, a suit of archeal lipids, in a coastal lake of southern China. The result shows a dry medieval climate anomaly and wet Little Ice Age. This result is consistent with other records in southeast coast of China, but in contrast with those in the inland region, thereby proving the persistent of the "coast" mode in the last millennium. The movement of western Pacific subtropical high and tropical typhoon associated with thermal state of the equatorial Pacific could result in this "coast" mode. Key Points: A 1300‐year lake level record based on archeal tetraether lipids in a maar lake on southern coast of ChinaA climate pattern of dry medieval climate anomaly and wet Little Ice Age exists in the southeast coast of ChinaThe thermal state of the equatorial Pacific shapes the coast mode of summer precipitations in eastern China during the last millennium [ABSTRACT FROM AUTHOR]