Resonant Asian Monsoon During Intermediate Conditions of the Last Deglaciation: Insights from Speleothem Records

Extensive research has explored how sweet spot conditions influence climate variability in the nonlinear Earth system. However, their effects throughout deglaciations remain unclear. Based on an annual-laminated speleothem δ18O record with unprecedent chronology precision, we firstly identified a two-step termination of the Asian Heinrich Period-1 at 15.11 and 14.69 ky BP, each marked by a centennial-scale strengthening of the Asian summer monsoon (ASM), in contrast to centennial-scale ASM weakening events observed at 17.8 and 16.09 ky BP. These transitions occurred underintermediate CO2 and ice volume conditions, which dynamically paced the Atlantic Meridional Overturning Circulation (AMOC) fluctuations and the subsequent reoccurrence of ASM events. It highlights the role of stochastic resonance in nonlinear climate system. Additionally, these AMOC/ASM events also resonated with abrupt CO2 risings across various pervasive modes of variability, which account for half of total CO2 rise during last deglaciation. This substantial contribution to CO2 increases played a key role in ice termination.