Centennial-scale monsoon climate fluctuations from a stalagmite record during the mid-Holocene Epoch in Fulu cave of Huaping, Yunnan, China

Abstract

The mid-Holocene dynamics of the East Asian Monsoon (EAM) and Indian Monsoon (IM) are important for understanding the Holocene climate system. To clarify the relationship between EAM and IM subsystems during the mid-Holocene, a 2085-year (6,270–4,185 a BP) high-resolution record from stalagmite (FL4) in Yunnan, China was reconstructed using ICP-MS-230Th series dating and carbon and oxygen isotope analysis (δ13C and δ18O). In the study period, successive positive δ18O trends revealed a generally weakening Asian monsoon, with the monsoon climate tending toward gradual drying, especially during three centennial-scale drought events in 6,270–6,126 a BP, 5,347–5,140 a BP, and 4,810–4,620 a BP. On the other hand, the uninterrupted negative trend in δ13C signified natural improvements in vegetation overlying the cave, and a serious deficit (~2.5 ‰) in δ13C during 5,519–5,345 a BP implied a heavy rainfall event, in precise phase with δ18O, demonstrating an enhanced Indian Monsoon subsystem. The dense sawtooth-shaped pattern of the carbon and oxygen isotope records indicates that a series of decadal-scale abrupt climate changes were superimposed on the centennial-scale monsoon climate changes. FL4 stalagmite records in the mid-Holocene reflect a gradually weakening monsoon climate with superimposed decadal–centennial events, but natural improvements in local vegetation through self-adjustment.