Variation of the Asian summer monsoon since the last glacial-interglacial recorded in a stalagmite from southwest China

Abstract

A number of studies proposed a close link between the climate changes in the Asian summer monsoon (ASM), the Southern Hemisphere (SH), and high latitudes of the Northern Hemisphere (NH). But the mechanisms is still an open question. Although speleothems δ18O records have displayed excellent values in the reconstruction of paleoclimate change at centennial - millennial to orbital timescales, the significance of speleothems δ18O and δ13C is still debatable. Here, a high-precise 230Th dated stalagmite from southwestern China was used to reconstruct the changes of ASM and regional hydrological conditions since the last interglacial (3.6–118.1 ka BP) by the coupled δ18O and δ13C. We found: (1) The EASM and ISM are synchronous changing on the orbital timescale, responding to the change of North Hemisphere summer insolation (NHSI) and high latitude climate change. There is a teleconnection between Antarctic temperature change and ASM through the Mascarene High and the Somali Jet. (2) During MIS 5d, the stalagmite δ18O in Yangzi Cave is nearly 1.5‰ higher than that in MIS 2, the maximum of last glacial. This should be attributed to the different isotopic compositions in moisture source of ISM and EASM, and the dynamic changes of monsoon circulations. (3) From MIS 3 to MIS 2, the ASM showed a “stepped” pattern in weakening, consistent with the decreasing NHSI and increasing global ice volume. (4) The changes in stalagmite δ13C indicated the changes of local hydrological conditions and closely correlated with climate changes revealed by stalagmite δ18O. The effective humidity, which determined by temperature, evaporation, and precipitation, dominated the regional hydrological conditions. The change of effective humidity recorded in stalagmite δ13C by influencing surface biomass and soil CO2-production.