Multi-phased ASM evolution and rainfall response during Heinrich Stadial 5

Abstract Changes in Asian summer monsoon (ASM) circulation and regional precipitation were reconstructed from stalagmite δ 18 O and trace element records from Wulu Cave in southern China, covering Chinese Interstadial (CIS) 13 to Heinrich Stadial (HS) 5. During HS 5, the evolution of δ 18 O-based ASM can be divided into four stages, i.e., an abrupt onset/termination and unstable mid-HS 5 (a slow ASM decline followed by a stepwise ASM strengthening). The extent of ASM weakening in mid-HS 5, relative to the mean δ 18 O value, reaches 58% of the total magnitude of HS 5. In contrast, multi-stage variability is less clear in element-inferred rainfall variations, which feature a stadial/interstadial pattern. During CIS 13, large-amplitude element oscillations are accompanied by a rapid decline at the onset of HS 5, with a limited range of variability in HS 5. The rainfall reduction in mid-HS 5, in comparison with the mean level, approximates 33% of the full event, practically equivalent to that during Chinese Stadial (CS) 14. It suggests a pronounced sensitivity of ASM and an inertial precipitation response to HSs. During HS 5, a cooling in the eastern tropical Pacific could favor a formation of La Niña state and a wetting in southern China. The timing of HS 5 in our record (48.53±0.12 ka, 47.19±0.12 ka) agrees well with the central age of spatially-separated cave records (48.72±0.14 ka, 47.35±0.24 ka). At the onset of HS 5, Asian hydroclimate changes are coeval with bipolar ice-core records, but lead the Greenland warming by 300 years at the termination or are synchronous with Greenland records via atmospheric CH 4 constraints. This at least implicates that the monsoonal rainfall is less sensitive to climate perturbations during HS 5.