Interhemispheric Monsoon Response to Bipolar Forcing During Heinrich Stadial 4

Heinrich Stadial 4 (HS4) the most prominent iceberg collapse event of the Last Glacial and a key example for studying millennial-scale events. Based on an improved chronological, we present high-resolution, annually laminated speleothem record from southeastern China. Our data suggests that during the onset of HS4, the East Asian Summer Monsoon (EASM) and northern high-latitude climate tightly coupled by the rapid southward migration of the Intertropical Convergence Zone. In contrast, low temperatures in Antarctica strengthened cross-equatorial flow, leading to a gradual weakening of the Indian Summer Monsoon (ISM). Our records precisely date the onset of Heinrich Event 4 (HE4) at 39.70 ± 0.06 ka BP, narrowing the uncertainty in Greenland ice cores. At the onset of HE4, northern high-latitude cooling weakened the EASM and intensified the South American Summer Monsoon (SASM), whereas the ISM declined significantly occurred only at the HE4 maximum, likely triggered by subsequent Antarctic warming.