Monsoon and hydroclimate evolution during Heinrich Stadial 3 as revealed by stalagmite from Central China

Of the six Heinrich Stadials (HSs) that occurred during the last glaciation, HS3 was situated in the period of Northern Hemisphere summer insolation maximum and larger ice cover, which had a special climatic background. Concurrently, the transition characteristics and mechanism of HS3 in the East Asian Summer Monsoon (EASM) region remain unclear. In this study, we present a high-resolution (11 a) and precisely dated speleothem (YX350) δ¹⁸O and δ¹³C records spanning Marine Isotope Stages 3–2 from Yongxing Cave, Central China. The stalagmite δ¹⁸O record is generally consistent with published stalagmite sequences from the EASM domain. The timing of HS 3 in our record (30.64–29.14 ka BP) agrees well with spatially-separated cave records (30.78–28.74 ka BP) in the EASM region. The gradual transition, as observed in other southern Chinese stalagmite records, differs from the mutation observed in Greenland. The gradual transition is more closely aligned with low-latitude processes and Antarctic temperatures. Furthermore, we observed that the calcite δ¹³C generally tracks the δ¹⁸O changes. However, on millennial scales, the δ¹³C during HS3 was relatively depleted, indicating that regional hydrological conditions did not undergo a notable deterioration during this period. This is in contrast to the relatively enriched δ¹⁸O. It has been demonstrated that a significant portion of icebergs, carrying over 2.5 Sv of meltwater from the Hudson Strait, in conjunction with the southward flowing of the Labrador Current, were routed directly to the subtropical Noth Atlantic gyre, bypassing regions of deep-water formation and the North Atlantic “Ruddiman Belt”. As a result, the impact on low-latitude regions was relatively limited, and there was no result in significant deterioration of regional hydrology and ecology in the Yangtze River Valley.