Synchronous changes in the East Asian-Australian summer monsoons around 7.2 ka

Previous evidence has identified the presence of numerous abrupt changes in the East Asian-Australian summer monsoons (EAASMs) on centennial to millennial timescales during the Holocene, which are tightly coupled with high northern latitude cooling anomalies. However, less attention has been paid to spatial characteristics in the EAASMs during the 7.2 ka event. Here a series of hydrological records from the EAASMs region are systematically integrated to improve understanding of the spatial precipitation distributions in the EAASMs region around 7.2 ka. The results show significant dry conditions in northern China, but relatively dry conditions or dry-to-wet shifts in southern tropical China around 7.2 ka, distinctly indicating an abrupt collapse of the East Asian summer monsoon during the 7.2 ka event. A similar pattern is also observed in the Australian summer monsoon region. The precipitation in northern Australia and its adjacent seas abruptly decreases around 7.2 ka, whereas it takes on a slight increase with a dry-to-wet shift near the center of the Indo-Pacific warm pool region. Therefore, it seems that synchronous collapse in the EAASMs occurs during the 7.2 ka event, which is different from a see-saw in the EAASMs during the 8.2 ka event. And it is inferred that synchronous changes in the EAASMs at the 7.2 ka event is probably a response to a low solar irradiance superimposed with influence of the volcanic eruption and ENSO activities.