Paleoclimatic evolutions during the Holocene: A stalagmite δ18O record from Majiaping Cave, Guizhou, China

Speleothemoxygen isotope records from East Asia have been utilized to reconstruct Asian summer monsoon (ASM) variability over the last several hundred thousand years. However, what the isotope variation represents on orbital to annual timescales remains greatly debated. The high-resolution speleothem records combined with modern meteorological observation are essential for better understanding this debate. Here, we report a stalagmite δ¹⁸O (δ¹⁸Oc) record of the highest resolution (average of ~1-yr) between 1730 to 8590 yr BP from Majiaping (MJP) Cave, Guizhou Province, southwest China. This record is precisely dated based on the ¹⁴C dating method combined with ²³⁰Th/U, ²¹⁰Pb, and lamination counting dating methods. The result shows that the ¹⁴C dating method can establish a reliable chronology for stalagmites that cannot be dated by ²³⁰Th/U. The comparisons of the precipitation δ¹⁸O with the local temperature, rainfall amount, and moisture sources show that the δ¹⁸Oc record from southwest China is mainly controlled by the “amount effect” on annual to decadal timescale modified by ENSO. The consistent long-term δ¹⁸Oc trends among all monsoonal regions in the low latitudes of the northern hemisphere indicate that on the orbital timescale the δ¹⁸Oc trend reflects changes in the large-scale spatial circulation of the atmosphere, which is controlled by the changes of northern hemisphere summer insolation. Ensemble Empirical Mode Decomposition (EEMD) and Bernaola-Galvan Segmentation Algorithm (BGSA) analyses reveal that on the semi-millennium timescale, the δ¹⁸Oc record of the MJP stalagmite shows 8 weak East Asian summer monsoon events during 8.2ka BP, 7.3 ka BP, 5.9 ka BP, 5.5 ka BP, 4.2 ka BP, 3.1 ka BP, 2.4 ka BP and 1.9 ka BP. The comparisons of the structural feature and forcing factor of the first 7 events with the 1.9 ka event indicate that the first 7 events correspond to the changes in total solar irradiance and the 1.9 ka event may be related to the internal forcing of the Earth system controlled by the ENSO. On the interannual-multidecadal timescale, the δ¹⁸Oc record shows the high-frequency cyclicities of 3~7-yr and 30~70-yr which are related to ENSO and PDO according to modern instrumental records. However, the relationships among ENSO, PDO, and the δ¹⁸Oc are not constant during the Holocene.