Chronological features of Heinrich Stadial 2 based on a high-resolution analysis of 818O stalagmite records from China, and possible links to changes in Atlantic Meridional Overturning Circulation

The Heinrich Stadial 2 (HS2) event is poorly defined in the Greenland 818O ice core record; however, it can be identified in stalagmite records from China. In this paper, we reconstruct an absolutely-dated and high-resolution calcite 818O record from Shima Cave, central China, covering the interval from 26.0 to 23.9 ka BP, with a temporal resolution of -16 years. By integrating our newly reported record with all available 818O records of Marine Isotope Stage 2 from China, which are securely 230Th/U-dated, we calculate the timing of the onset, termination and duration of HS2. The statistical results show that the prominent HS2a phase started at -24.4 +/- 0.1 ka BP and ended at -23.6 +/- 0.1 ka BP, lasting approximately 0.8 +/- 0.3 ka. If the onset of the DansgaardOeschger 2 event in the Greenland 818O record is synchronous with the termination of HS2a, then the GICC05 chronology should be adjusted by +230 years to align it with stalagmite results. Further investigation of HS2 shows that Chinese cave records exhibit a distinct two-fold structure, corresponding to HS2a and HS2b, as observed in marine sediment cores, particularly those recovered around the Atlantic Ocean. These records show comparable changes in relative amplitudes during the HS2a and HS2b phases, which could possibly be related to different weakening episodes in the Atlantic Meridional Overturning Circulation.