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

Abstract

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 ~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 Niño/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 Niño/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.

Quaternary rainfall variability is governed by insolation in northern China and ice-sheet forcing in the South

“…Such discrepancies probably result from the differences between the domain of the model box, and the region that can be covered by these rainfall proxies, as well as from the age bias between modeling and rainfall reconstructions. Besides, relatively wet glacial periods in southern China have also been observed in reconstructions based on pollen databases [54][55][56] and magnetic investigations 57 (Supplementary Fig. 5), as well as in LGM topsoil moisture and net precipitation simulations based on fully coupled climate models 58,59 .…”

Variation in humidity and the forcing mechanism in Asian monsoon-influenced regions indicated by hematite/goethite from Baxian Lake, southern China, since AD 800

“…The magnetic minerals in lake sediments are generally considered to be terrestrial detrital minerals brought into the lake by surface run-off or eolian processes (Chen et al, 2013; Wei et al, 2020), and usually respond well to the climatic environment. However, post-depositional processes, for instance, the formation of biomagnetosome and authigenic iron sulfide, may change the sedimentary characteristics and thus interfere with the interpretation of the original environmental information (Roberts et al, 2018; Snowball and Thompson, 1988).…”