Strong coupling between the East Asian summer monsoon and regional hydrological conditions as evidenced by multiproxy stalagmite records for the last deglaciation

Millennial-to centennial-scale abrupt climate events during the last glacial‒interglacial transition have significant relevance to modern-day extreme climate changes, which are occurring more frequently in the context of global warming. However, the regional expression of humidity conditions during the last deglaciation and their possible forcing mechanism in northern China are controversial. Here, combined with published δ¹⁸O data, we report 35-year-resolved δ¹³C and 76-year-resolved Mg/Ca and Sr/Ca records from a stalagmite from 15.3 to 10.9 ka BP from Lianhua Cave, northern China. The LH4 stalagmite δ¹⁸O record clearly records a weak monsoon event during the Younger Dryas (YD) from 12.8 to 11.6 ka BP and a strong monsoon event during the Bølling-Allerød (BA) from 14.6 to 12.8 ka BP. In addition, the δ¹³C and trace element ratio records, which represent local hydroclimatic changes, indicate wetter conditions during the BA and drier conditions during the YD, which appear to match well with the δ¹⁸O variations on the millennial timescale. A comparison of 28 records from 17 sites along the modern margin of the China summer monsoon revealed that the BA was characterized by wet conditions; inversely, the YD was characterized by dry conditions throughout northern China, which is obviously different from the consensus of the wet YD and the dry BA in northern northeastern China. The covariance in northern China suggests that the hydrological variation may be modulated by the advance and retreat of the large-scale East Asian summer monsoon (EASM) circulation. Further comparison revealed an anticorrelated relationship between millennial-scale precipitation changes in northern China and the middle‒lower reaches of the Yangtze River Valley during the last deglaciation. This correlation is analogous to the dipole precipitation mode at present, which is likely associated with the strength and position of the westerly jet and/or the western Pacific subtropical high, both of which play important roles in the spatial distribution of precipitation over eastern China.