Abstract
The precipitation variability associated with the East Asian summer monsoon (EASM) has profound societal implications. Here, we use precisely dated and seasonally-resolved stalagmite oxygen isotope (δ18O) records from Shihua Cave, North China to reconstruct the EASM variability over the last 145 years. Our record shows a remarkable weakening of the EASM strength since the 1880s, which may be causally linked to the warming of the tropical Pacific and Indian Oceans. The δ18O record also exhibits a significant ~30-year periodicity, consistent with the instrumental, historical and proxy-based rainfall records from North China, plausibly driven by the Pacific Decadal Oscillation (PDO). Together, these observations imply that ~30-year periodicity is a persistent feature of the EASM, which remains significant with or without anthropogenic forcing. If indeed, the EASM rainfall in North China might decline significantly in the near future, which may affect millions of people in this region.
Highlights
The East Asian summer monsoon (EASM) is a major source of moisture to eastern China, imposing critical influence on the lives of hundreds of millions of people in the region[1,2,3]
Based on the high-resolution and precise-chronology controlled Shihua δ18O record from North China, we reconstructed the variance in the overall EASM intensity and/or monsoon precipitation over the last 145 years
Our record shows a prominent decrease trend in the EASM since the 1880s, which coincides with a persistent warming in the Pacific and Indian Oceans
Summary
The East Asian summer monsoon (EASM) is a major source of moisture to eastern China, imposing critical influence on the lives of hundreds of millions of people in the region[1,2,3]. Over the past few decades, the EASM has exhibited a weakening trend[4], marking a major climate shift in eastern China since the late 1970s5–11. A number of mechanisms have been proposed to explain this declining trend in EASM rainfall as well at its decadal-multidecadal variability. Tree-ring records and historical accounts have previously been used to reconstruct rainfall variations over monsoonal China[18,19,20,21,22]. Tree-ring and historical records are, in principle, proxies that mainly indicate local climate variations rather than large-scale supra-regional changes in EASM. We present a first seasonally-resolved stalagmite δ18O record from Shihua Cave, Beijing, North China over the last 145 years. Calcite deposition over a glass plate, placed directly above the XMG-1, was observed over a half-year monitoring period, confirming that the stalagmite was actively growing before the collection date
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