Late-Holocene high-frequency East Asia Winter Monsoon variability inferred from the environmentally sensitive grain size component in the distal shelf mud area, East China Sea

Abstract

The B2 (B2G) and I4 sediment cores recovered from the centre of the distal mud area of the East China Sea (ECS) were analysed for grain size distribution. Proxies for environmentally sensitive grain size components (ESGSC) retrieved from the composite B2 core, namely, variations in the volumetric content and mean grain size of specific grain size fractions, reveal a detailed history of the East Asia Winter Monsoon (EAWM) including centennial to decadal-scale variations spanning the last 2300 calendar years before present (cal. yr BP). The results indicate that EAWM variations are consistent with temperature changes in eastern China (as inferred from historical documents). Additionally, the sea surface temperature (SST) in the Southern Okinawa Trough, the δ18O of stalagmite from the Sanbao cave and the drift ice indices from the North Atlantic, along with strong or weak EAWMs, corresponding to low or high temperatures, respectively. Four periods of EAWM variations were identified, namely, a weak EAWM stage from 2300 to 2050 cal. yr BP; a comparatively enhanced EAWM between 2050 and 1700 cal. yr BP; a return to a weak EAWM from 1700 to 700 cal. yr BP, including the Roman Warm Period (RWP), the Sui–Tang Dynasty Warm Period (STWP) and the ‘Medieval Warm Period’ (MWP) and a strongly developed EAWM between 700 and 100 cal. yr BP, corresponding to a ‘Little Ice Age’. An important abrupt warm to cold climate change event occurred around 678 cal. yr BP. During this period, the climate change was likely related to global scale changes in atmospheric circulation. Spectral analyses of the ESGSC proxies show high-frequency cycles and a close solar–monsoon connection to the EAWM, suggesting that one of the primary controls for centennial to decadal-scale change in EAWM intensity was the variation in solar radiation during that time.