Spatial grain-size differentiation reveals Holocene evolution and forcing of the East Asian winter monsoon on the Chinese Loess Plateau

Abstract The East Asian winter monsoon plays a vital role in shaping regional climate, yet its Holocene variability and spatial heterogeneity remain incompletely understood. In this study, we summarize and compare 42 published records from loess, lake, peat, and marine sediments across East Asia and identify three major evolution patterns: a long-term strengthening (Type 1), a long-term weakening (Type 2), and a mid-Holocene minimum (Type 3). Type 3 is predominantly observed on the Chinese Loess Plateau, where wind-driven grain-size indicators provide a regionally consistent EAWM pattern. We further propose the spatial differentiation of grain size (SDGS) between upwind and downwind loess sites as a robust proxy for regional wind strength. Using records from Xifeng and Weinan, SDGS reconstructions reveal a typical Type 3 pattern, confirming the potential of spatially resolved grain-size indicators in East Asian winter monsoon reconstruction. Comparison with summer monsoon proxies suggests that the mid-Holocene weakening of the East Asian winter monsoon may be linked to enhanced East Asian summer monsoon intensity and reduced latitudinal temperature gradients. These findings underscore a multi-millennial-scale anti-phase relationship between the East Asian winter monsoon and summer monsoon, emphasizing the importance of integrating both systems in future monsoon reconstructions.