Asian monsoon hydrometeorology from water isotopes: implications for speleothem climate record interpretation

Previous studies have documented high correlations between speleothem δ18Op and millennial timescale climate forcings. From LMDZ model analysis, we show that δ18Op at cave sites over southern China is weakly correlated with upstream precipitation in the core of the Indian monsoon region rather than local precipitation, but it is well-correlated with the δ18Op over large areas of southern and central China, consistent with coherent speleothem δ18Op variations over different parts of China. We suggest that the high correlation between insolation and speleothem δ18Op in southern China reflect the variations of hydrologic processes over Indian monsoon region on millennial and orbital timescales. The δ18Op in the drier part (north of ~30N) of China, on the other hand, has consistently negative correlations with local precipitation and may capture local hydrologic processes related to changes in the extent of the Hadley circulation.