East Asian summer monsoon precipitation variability since the last deglaciation

TLDR

The absence of a precisely dated, unequivocal climate proxy from northern China hampers understanding of East Asian summer monsoon dynamics. The study presents a well‑dated, pollen‑based, ~20‑year resolution precipitation reconstruction from an alpine lake in North China, providing the first direct record of EASM evolution since 14.7 ka. The reconstruction was derived using a transfer function applied to pollen data from the lake. The record shows a gradual intensification from 14.7–7.0 ka, a peak 30 % above present from ~7.8–5.3 ka, a rapid decline since ~3.3 ka, punctuated by two millennial‑scale weakening events during the Younger Dryas and ~9.5–8.5 ka, and two centennial‑scale intervals of enhanced or weakened monsoon during the Medieval Warm Period and Little Ice Age, indicating strong internal feedback processes.

Abstract

Abstract The lack of a precisely-dated, unequivocal climate proxy from northern China, where precipitation variability is traditionally considered as an East Asian summer monsoon (EASM) indicator, impedes our understanding of the behaviour and dynamics of the EASM. Here we present a well-dated, pollen-based, ~20-yr-resolution quantitative precipitation reconstruction (derived using a transfer function) from an alpine lake in North China, which provides for the first time a direct record of EASM evolution since 14.7 ka (ka = thousands of years before present, where the “present” is defined as the year AD 1950). Our record reveals a gradually intensifying monsoon from 14.7–7.0 ka, a maximum monsoon (30% higher precipitation than present) from ~7.8–5.3 ka and a rapid decline since ~3.3 ka. These insolation-driven EASM trends were punctuated by two millennial-scale weakening events which occurred synchronously to the cold Younger Dryas and at ~9.5–8.5 ka and by two centennial-scale intervals of enhanced (weakened) monsoon during the Medieval Warm Period (Little Ice Age). Our precipitation reconstruction, consistent with temperature changes but quite different from the prevailing view of EASM evolution, points to strong internal feedback processes driving the EASM and may aid our understanding of future monsoon behaviour under ongoing anthropogenic climate change.