Spatial pattern and cause of centennial-scale hydroclimatic variability over eastern China during the last millennium

Instrumental and historic records have shown that the hydroclimatic variability on interannual- to decadal-timescales over eastern China is spatially different, with a meridional dipole or even tripole pattern. Yet, how this spatial pattern of hydroclimate change on centennial timescales looks like is still unclear due to the lack of well-reconstructed climate records from South China. Here, we present a precisely-dated, high-resolution δ18O record of stalagmite (JL2) from Jiuluo Cave, Guilin, South China, to elucidate the hydroclimatic variability in South China over the last millennium and thus explore the spatial pattern and cause of centennial-scale hydroclimatic variability across eastern China. Based on the previous results of modern cave monitoring carried out in the Guilin region, the δ18O of JL2 is carefully interpreted as a robust proxy for summer monsoonal rainfall change. It clearly shows that a decrease in monsoonal rainfall over South China occurred during the periods of 941–1250 CE (i.e. the Medieval Warm Period (MWP)) and 1550–1850 CE (late Little Ice Age (LIA)), while intensification of monsoonal rainfall occurred during 1250–1550 CE (early LIA) and since 1850 CE (the Current Warm Period). Comparison of the JL2 record with other well-reconstructed proxy records from different zones along the trajectory of the East Asia summer monsoon (EASM) allows us to depict the spatial variation in centennial-scale monsoonal rainfall over eastern China. We confirmed that a “wet northern and dry southern” pattern existed for the rainfall regime of eastern China during the MWP, and a “dry northern and wet southern” pattern during the early LIA. Furthermore, there was a tripole pattern showing dry conditions in both North and South China but wet condition in the Jianghuai area, central China during the late LIA. These spatial patterns of centennial-scale monsoonal rainfall variability were principally linked to changes in summer monsoon intensity and the long-live state of El Niño–Southern Oscillation (ENSO). We also found that solar activity could influence the monsoonal rainfall to some degrees, and reduced monsoonal rainfall often occurred during intervals of solar minimum. Nevertheless, the monsoonal rainfall change during the 14th century was ascribed to great shift in oceanic and atmospheric circulation rather than to variations in solar activity.