External and Internal Forcings Controlled the Precipitation Patterns in eastern China Over the Past Millennium

Hai Li ^1* Jianhui Tang ² Yi Zhong ³ Liang Ning ⁴ Jiabo Liu ⁵ Chijun Sun ⁶ Weijie Zhang ³ Yu-Min Chou ³ Qingsong Liu ³

• ¹ Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), Guangzhou, China
• ² Key Laboratory of Coastal Zone Environmental Processes and Ecological Remediation, Yantai Institute of Coastal Zone Research, Chinese Academy of Sciences (CAS), Yantai, Shandong Province, China
• ³ Department of Ocean Science and Engineering, Southern University of Science and Technology, Shenzhen, China
• ⁴ Key Laboratory for Virtual Geographic Environment, Ministry of Education, Nanjing Normal University, Nanjing, China
• ⁵ Paleomagnetism and Planetary Magnetism Laboratory, School of Geophysics and Geomatics, China University of Geosciences, Wuhan, China
• ⁶ Department of Earth and Planetary Sciences, University of California Davis, Davis, United States

The Asian Summer Monsoon provides critical water source to over a billion people.However, there is mounting evidence regarding how precipitation associated with the Asian Summer Monsoon varies spatially and temporally, prompting further exploration of the underlying mechanisms. Here, we present a ~2900-year summer precipitation history using a sediment core from the Bohai Sea in China. Our records indicate that the warm (cold) phase of the Atlantic Multidecadal Variability significantly increases (decreases) summer precipitation in North China through atmosphere-ocean feedback and circum-global teleconnection. Over the past millennium, eastern China exhibited a distinctive tripole pattern of summer precipitation. During the Medieval Climate Anomaly, it exhibited a positive-negative-positive structure in North, Central, and South China, respectively. In contrast, during the Little Ice Age, the pattern flipped to a negative-positive-negative structure. These patterns were influenced by external forcings, including solar activity and volcanic eruptions, which directly influenced atmospheric circulation patterns and modulated internal climate variability. Our study provides an improved understanding of the summer precipitation variability in East Asia, and emphasizes the external and internal forcings in shaping the spatial patterns of monsoon precipitation.