Quantitative paleoclimate reconstruction in the Yangtze River Delta since the Last Glacial Maximum based on pollen records

The climate dynamics and driving mechanisms of the East Asian Summer Monsoon (EASM) in the Yangtze River Delta (YRD) since the Last Glacial Maximum (LGM) remain uncertain. We reconstruct annual mean temperature (T_ann), mean temperature of the warmest month (MT_wa), and annual mean precipitation (P_ann) since 19.4 ka BP in the Yangtze River Delta (YRD), using pollen records from three sediment cores (LZK1, CSJA6, ZKA4), constrained by AMS ¹⁴C and OSL dating. Reconstructions were performed with a pollen-climate model based on the Locally-Weighted Weighted-Averaging (LWWA) method. Additional sedimentary proxies (grain size and magnetic susceptibility) were integrated to evaluate climate dynamics and forcing factors. Five climatic stages were identified: the LGM (19.4-18.0 ka, cold-dry), deglaciation (18.0-11.7 ka, fluctuating warming), early Holocene (11.7-8.2 ka, warm-humid), mid-Holocene (8.2-4.2 ka, warm-humid), and late Holocene (after 4.2 ka, fluctuating cooling). These stages broadly align with EASM intensity variations. Abrupt events (Heinrich 1, Bølling-Allerød, Younger Dryas, 8.2 ka, and 4.2 ka) were synchronous with Greenland ice core and Yangtze River stalagmite records, reflecting global climate teleconnections. On the millennial scale, EASM variability was controlled by Northern Hemisphere summer insolation, Atlantic Meridional Overturning Circulation (AMOC), and ice-volume/sea-level feedbacks. On the centennial scale, it was influenced by solar activity, volcanic eruptions, and the El Niño-Southern Oscillation (ENSO). These findings provide high-resolution evidence of EASM dynamics and offer a valuable reference for understanding regional climate adaptation in the future.