Spatial pattern of Asian stalagmite δ18O over the last millennium shaped by monsoon circulation changes

Abstract

High-resolution stalagmite δ¹⁸O records have been used to study variations in the Asian summer monsoon (ASM) over the last millennium. However, the spatial pattern and climatic significance of these records remain unclear. Based on precise ²³⁰Th dating and annual laminae counts, we present a ∼3-year-resolution stalagmite δ¹⁸O record from Xinglong Cave in North China, covering 731–1698 C.E. and 1832–1937 C.E. Empirical orthogonal function analysis was performed on this new record and 17 other coeval stalagmite δ¹⁸O records in the ASM region. The first spatial pattern displays positive loadings primarily in 'India, Southeast Asia, and North China' (INC) and negative loadings in 'South China' (SC). The first principal component negatively correlates with the reconstructed sea surface temperatures (SST) of the eastern equatorial Pacific, North Indian Ocean (NIO), and tropical North Atlantic. During periods of warming SST in these regions, anomalous tropical western North Pacific anticyclone (WNPAC) enriches δ¹⁸O in precipitation and stalagmites over SC by increasing water vapor transport from the South China Sea and western Pacific. Meanwhile, NIO warming and WNPAC increase precipitation in the Indian Peninsula, depleting δ¹⁸O in water vapor and precipitation. This ¹⁸O-depleted water vapor continues to transport into China, affecting δ¹⁸O in precipitation and stalagmites in regions located outside the WNPAC's northwestern flank. Our study suggests circulation anomalies may drive significant spatial differences in stalagmite δ¹⁸O from the ASM region over the last millennium.