Interpreting precipitation δ18O over eastern China for the Asian summer monsoon: Results from the last millennium simulations

Abstract

AbstractThe Asian summer monsoon (ASM) plays a major role in the Asian climate system, affecting nearly half of the world's population. The oxygen isotopes of speleothem calcite (δ18Oc) records in China provide important insights into past ASM changes; however, it remains controversial whether the δ18Oc records over eastern China (EC) mainly reflect the Indian summer monsoon (ISM) or East Asian summer monsoon (EASM). In this study, we estimate the relationships between precipitation‐weighted oxygen isotopes (δ18Opw) and various ASM indices over the last millennium based on the isotope‐enabled Community Earth System Model. The δ18Opw in EC mainly characterizes the intensity of the ISM and, to some extent, reflects the meridional wind component of the EASM, but it has an opposite relationship with the zonal wind component of the EASM. Although the limitations of various EASM definitions lead to the contrary relations between the δ18Opw and EASM indices, the δ18Opw in EC is accompanied by consistent EASM footprints. Moreover, although the meridional wind‐based EASM indices are negatively correlated with δ18Opw over EC, the relationships are much weaker than that with the ISM indices. The widespread negative δ18Opw signals extending from the Indian Peninsula to East Asia are closely coupled with the low‐level circulation over the ISM region. When considering the relationship between the EASM and δ18Opw over EC, the positive contribution from the Northwest Pacific offset the negative contribution from the remote Indian Ocean, leading to the insignificant correlation between the EASM indices and δ18Opw over EC.