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An anti-phased relationship between Greenland Dansgaard-Oeschger (DO) and Antarctic temperature was revealed by ice core records, and the "bipolar see-saw" mechanism has since been proposed in explanation for the interhemispheric thermal redistribution. However, limited by chronology uncertainties of ice cores, particularly the ice age-gas age differences, the exact phase relationship and triggers for millennial-scale events are still in debate. Searching for proxies that could reflect both boreal and austral signals in one geological archive is therefore, a potential solution for the phase dilemma. Here, high-resolution paleoclimatic records from 55.2 to 36.5 ka BP were reconstructed using 21 230Th/U dates and 647 sets of δ18O and δ13C data by one stalagmite HJ1 from Huangjin Cave, Hebei Province, northern China. Robust millennial-scale fluctuations are found in δ18O and δ13C time series, corresponding to DO events 8 to 14 and Heinrich 4 and 5 events within dating errors. Discrepancies exist in the structures and onsets in δ18O and δ13C records; that is, abrupt DO onsets in δ13C data and gradual onsets in δ18O. Timing of DO onsets in δ13C are prior to (e.g. DO12 and DO14) or synchronous with (e.g. DO8 to DO11) those in δ18O. Comparison of HJ1 δ18O and bipolar ice core records suggests that the East Asian summer monsoon (EASM) is influenced by both hemispheres, but better mimics the Antarctic temperature. This suggests that the EASM is controlled by the cross equatorial airflows, and further indicates an important role of the Atlantic Meridional Overturning Circulation (AMOC) in modulating the inter-hemispheric heat gradient. However, our δ13C profile strongly resembles with the Greenland δ18O record on the millennial timescale, in terms of the "sawtooth" structure and the abrupt transition. This indicates that northern high-latitude climate could modulate hydro-thermal conditions in northern China, possibly via the mid-latitude westerly jet and/or the Silk Road teleconnection, which influences the vegetation/biomass changes and thereby controls stalagmite δ13C values. Therefore, HJ1 δ18O receives climatic signals from the Southern Hemisphere (SH) to a larger extent, while δ13C captures largely the changes in the Northern Hemisphere (NH). Furthermore, comparison between calcite and ice core records shows that during DO14, temperature increases in the NH leads the SH cooling by ∼120 years. However, during short-term DO events, the SH may start cooling ∼150 years before the NH warming. These findings demonstrate two possibilities for the NH-SH phase relationship which are dependent on the trigger location of the AMOC recovery and the "bipolar see-saw" mode is likely controlled by the oceanic processes. • Greenland-type sawtooth structure is found in stalagmite δ13C in northern China. • Hydrothermal condition in northern China linked to the northern high-latitude via westerly jet. • Antarctica -type triangle shape revealed in Chinese stalagmite δ18O. • Two types of Greenland-Antarctica phase relationship depend on the trigger location. [ABSTRACT FROM AUTHOR]

In this study, a 140 kyr stack (MT2022) of 95 stalagmite δ18O records from Southern China was synthesized using the error weighted mean method and the linear weighted mean method. This stack record was derived from approximately 1100 U/Th dating and 40000 δ18O data points. On orbital scale, MT2022 agrees with the variation of the summer (21 July) insolation at 65°N and restores as much detail as possible of the actual variability of Asian Summer Monsoon (ASM) from stalagmite records. The age model of MT2022 was established according to the dating results of each sample record, and the start and end periods of each weak monsoon event were constrained by at least five stalagmite sample records, with average errors of less than 0.2 kyr. By comparison, we find that MT2022 was generally consistent with the Speleothem Interstadial Onset Compilation data set (SIOC19) and had more sample records from the ASM domain, which is more suitable to represent the ASM evolution. Furthermore, comparing MT2022 to three Greenland ice core timescales, we discovered that MT2022 was quite consistent with NGRIP (GICC05) over the last 60 kyr and differed from GRIP (ss09sea) and GISP2 (Meese-Sowers). The main discrepancy between MT2022 and GRIP occurs around Dansgaard-Oeschger (DO) events 14 and 20–23, whereas MT2022 and GISP2 start to deviate prominently beyond 40 kyr BP. The high degree of consistency between GICC05 and MT2022 allows their accuracy to be validated against each other, thus, MT2022 may provide a new chronological reference for climatic events in the last glacial-interglacial cycle as well as an age calibration standard for other palaeoclimate archives. [ABSTRACT FROM AUTHOR]

The Heinrich Stadial 2 (HS2) event is poorly defined in the Greenland δ18O 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 δ18O 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 δ18O 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 Dansgaard-Oeschger 2 event in the Greenland δ18O 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. • An ~16-year-resolution East Asian summer monsoon (EASM) history covering the onset of Heinrich Stadial 2 event. • Statistical analyses of timing for Heinrich Stadial 2. • Globally pervasive twofold structure during Heinrich Stadial 2. [ABSTRACT FROM AUTHOR]