Punctuated ASM strengthening in late Heinrich Stadial from speleothem records, southern China

The dynamical adjustment process (DAP) is a requisite for climate system to arrange for a new equilibrium state. To evaluate the detailed structure of DAP during Heinrich Stadial (HS), high-resolution speleothem-based Asian summer monsoon (ASM) variability was reconstructed, separately covering HSs 5 to 1. In these calcite δ¹⁸O records, a gradual increase of ASM intensity is evident in each mid-HS, followed by a centennial-scale ASM stability lasting on average 590 years during late HS. At this time, δ¹⁸O values decrease by 1%, about 50% of the total HS, compared with maximum values in early HS. This structure of monsoonal HS in speleothem records is not reflected in temperature variations at the Greenland, but is well mirrored in middle- to low latitudes within the northern hemisphere, and even southern oceanic records. It suggests that southern and low-latitude climate conditions are likely important for the termination of HS. Thus, a DAP of about 400–600 years is a precondition for the ASM sub-system to prepare for a new equilibrium.