Late Quaternary East Asian Summer Monsoon Variability Deduced From Lacustrine Mineral Magnetic Records of Dahu Swamp, Southern China

摘要

The lack of long-term and well-preserved terrestrial archives from southern China largely impedes our understanding of past variability in the East Asian summer monsoon (EASM). In this study, we developed rainfall/precipitation-related records by conducting a systematic mineral-magnetic investigation on Dahu Swamp sediments over the past similar to 47.0 ka. The integrated magnetic results show that the magnetic minerals in the sediments were mainly catchment derived, likely reflecting hydroclimatic changes associated with EASM strength. In combination with other climatic proxies, our magnetic records reveal a relatively wet climate during the middle-late Marine Oxygen Isotope Stage 3 and the Holocene and a relatively dry climate during the Marine Oxygen Isotope Stage 2, which broadly follow the precession-induced summer insolation changes in the middle-low latitudes of the Northern Hemisphere. The regional heterogeneity of the EASM rainfall evolution might be ascribed to the changes in timing and duration of Mei-yu Front in China, which were closely associated with the El Nino/Southern Oscillation activities through its effects on the Western Pacific Subtropical High position. Long-term climatic patterns inferred from Dahu Swamp were broadly similar to those of the Western Pacific Warm Pool region, especially during the mid-Holocene rainfall optimum period, further supporting that the thermal mean states of the tropical Pacific associated with El Nino/Southern Oscillation modes may influence EASM precipitation. Our results highlight the coupled influence of external insolation forcing and internal low-latitude processes on the spatial and temporal EASM variability, and understanding these influences could be critical to the prediction of future monsoon behavior under ongoing and future global warming.