Different response of stalagmite δ18O and δ13C to millennial-scale events during the last glacial, evidenced from Huangjin Cave, northern China

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.