Ice-volume and insolation influences on hydroclimate changes in central eastern China during the antepenultimate glacial period

The rainfall changes in East Asian summer monsoon (EASM) regions on the orbital timescale remain controversial due to the lack of reliable rainfall records. Here, we present new multiproxy records (delta O-18, delta C-13, Sr/Ca and Mg/Ca) of a Th-230-dated stalagmite from Hulu Cave in central eastern China. Multiproxy records reconstruct a regional hydroclimate history from 340 to 261 kyr BP (thousand years before present), approximately covering the antepenultimate glacial period. The delta O-18 record is dominated by the precessional cycles, suggesting that EASM responds to changes in Northern Hemisphere summer insolation (NHSI) on the orbital timescale. Significant correlations amongst the delta C-13, Sr/Ca and Mg/Ca suggest that a common factor, i.e., the local hydrological cycle, controlled their variability, and their leading principal component can be used as a proxy linked to regional rainfall. This composite record bears a good similarity to those from the Chinese Loess Plateau, showing a gradually decreasing rainfall during the antepenultimate glacial period, consistent with changes in global ice volume. Superimposed on the long-term trend, three relative wetter intervals were responding to the higher NHSI periods, suggesting that EASM rainfall variability was induced by integrated effects of global ice volume and NHSI. The increased ice sheets and lower NHSI resulted in an increased meridional temperature gradient and southward shift of the westerlies, which shortened the duration of Meiyu and midsummer rainfall. The differences between the rainfall record and the stalagmite delta O-18 record indicate that the latter represents the overall EASM intensity linked to monsoon circulation, but does not directly reflect the rainfall changes at the cave sites.