The 9.2 ka event during the early Holocene recorded by a stalagmite from Dongge Cave

Abstract

It is important to understand the variability and mechanisms of the Asian summer monsoon during the Holocene, yet the dynamics of the Asian monsoon weakening in response to the 9.2 ka event remain controversial. We reconstructed paleoclimate records with 12 ²³⁰Th/U dates and 199 pairs of δ¹³C and δ¹⁸O from a stalagmite in Dongge Cave, southwestern China, covering from ∼2332 to 9793 a BP. Our records provide new evidence for interpreting centennial-scale monsoon variabilities and environmental changes during the early Holocene. Our sample sensitively captures the 8.2 and 9.2 ka events, exhibiting significantly positive isotopic shifts. Of note is the δ¹³C record, which displays dramatic oscillations during these events, reflecting the rapid response of terrestrial ecosystems and vegetation to abrupt climate changes. Comparison with other geological records suggests that the cause for the 9.2 ka event differs from the 8.2 ka event, the latter of which was dominantly forced by iceberg collapse and freshwater input in the North Atlantic. However, the 9.2 ka event may have been affected by the synergistic effect of solar activity and the Atlantic Meridional Overturning Circulation, which leads to a southward shift of the Intertropical Convergence Zone and triggers sudden changes in the Asian summer monsoon.