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.