East Asian summer monsoon evolution in northeast China since the mid-Holocene reconstructed from chemical weathering intensity of Lake Jingpo sediments

The chemical index of alteration (CIA) has been used to reconstruct the monsoon rainfall. However, the relationship between the CIA and monsoon rainfall has not been fully understood. In this study, we investigated a sedimentary CIA record from Lake Jingpo during the past 6.1 ka in northeast China. The CIA values ranged from 80 to 88, reflecting the topsoil of basaltic clays in the watershed. The increase in CIA between the mid-1960s and the mid-1980s corresponds to reduced annual (summer) precipitation from the CRU reanalysis datasets, suggesting that the supply of suspended particulates matter into the lake may have resulted from the weakened transport of fresh debris into the river. In other words, the change in chemical weathering intensity in this region is an inverse response to East Asian summer monsoon (EASM) circulation. The results indicate that the EASM precipitation broadly follows the decreasing trend in high-latitude Northern Hemisphere summer insolation, and the abrupt reduction at 4.2 ka may have coincided with the tipping point of the EASM since the mid-Holocene. EASM precipitation increased from 1.5 ka and broadly corresponds to the so-called 2-kyr shift. This shift may be related to Atlantic Meridional Overturning Circulation (AMOC) oscillation. A comparison of the sub-millennial-scale EASM record with the total solar irradiance and El Niño-Southern Oscillation (ENSO) records suggests that the EASM in northeast China was potentially driven by solar activity, whereas the EASM–ENSO teleconnection in this region has become pronounced since the late Holocene ( ca. 4.2 ka). • CIA values of lake sediment are inversely correlated to atmospheric precipitation. • EASM precipitation in northeast China abruptly decreased at 4.2 ka. • The EASM precipitation gradually increased since 1.5 ka, corresponding to 2-kyr shift. • The EASM precipitation was potentially driven by solar acidity since 6.1 ka. • The EASM-ENSO teleconnection became pronounced since 4.2 ka alone.