Decadal to centennial scale hydroclimate oscillations on the western Loess Plateau during the past 1400 years

Climate change exerts a profound influence on human activities, geopolitical reorganization, and ecosystem evolution across the western Loess Plateau (WLP). Here, we present a reconstruction of decadal to centennial hydroclimate variability on the WLP over the past ∼1400 years using speleothem record from Yanwu Cave with precise chronology. Based on speleothem stable isotopes (δ¹⁸O and δ¹³C) and trace elements (Sr/Ca, Mg/Ca, and Ba/Ca) analyses, we found that the stable isotopes are affected by kinetic fractionation effects and reflect a more complex climate signal, while the PC1 component of trace elements demonstrates coherent variations with regional hydroclimate records and is thus interpreted as a robust indicator of hydroclimate variability. Our reconstruction reveals that the hydroclimate variability and agricultural activity jointly dominated the vegetation evolution on the WLP. The warm-wet climate and enhanced human activities during the Medieval Climate Anomaly (MCA) may have led to reduced vegetation cover, whereas the agricultural abandonment during the early stage of the Little Ice Age (LIA) marked a transition to a cold-dry climate that led to vegetation recovery. Furthermore, severe droughts evident in both historical and proxy records likely triggered geopolitical conflicts through subsistence crises. This ecological fragility amplified societal vulnerability to hydroclimate extremes via crop failure and forced migration. Our record further demonstrates a decreased hydroclimate variability during the MCA in contrast to progressively amplified variability throughout the LIA on the decadal to multidecadal timescales, synchronizing with the increase in flood/drought frequency as documented in historical literature.