Rapid northwestward extension of the East Asian summer monsoon over the last deglaciation: evidence from mollusk record

The magnitude and rate of spatial expansion of the East Asian summer monsoon (EASM) rain belt as the climate warms remains unclear. Existing assessments still lack the ecological records that are more sensitive to the EASM rainfall to quantify the spatial extension during the past warming scenarios. Here, the spatiotemporal extension of EASM intensity since the last glacial maximum (LGM) is reconstructed using six well-dated mollusk fossil sequences from Chinese loess sections located at the northern part of the EASM. The abundant occurrence of typical dominant mollusk species indicative of EASM intensity gradually delayed from southeast to northwest since the last deglacial warming. The estimated expansion rate of EASM intensity accelerated markedly during the ~12-9 ka (~50 km/ka), which corresponded with the early-Holocene rapid warming period, shifting northwestward ~150 km compared to present. This imply that northern fringe of EASM in northern China will become wetter as the climat...