Speleothem evidence of solar modulation on the south Asia monsoon intensity

Abstract The influence of solar variation on climate has long been debated. Here, we utilize a decadal-resolved speleothem δ 18 O record from Vietnam, spanning 32.5 to 27.5 kyr BP, as a proxy for regional precipitation levels. Our results show a general coherence between Total Solar Irradiance (TSI) and regional precipitation, supporting a positive climate response consistent with conventional monsoon theory. Spectral analysis on studied datasets reveals an approximately 180-year periodicity coinciding with the de Vries cycle of solar activity. Further comparing our record with 35 other speleothem records, we demonstrate the importance of sufficient age control points in capturing solar-related periodicities. Model simulation shows that TSI could enhance monsoonal circulation and regional precipitation. Also highlighted are the implications of chronology control for detecting climate events in proxy records. The new findings underscore the significance of relatively minor radiative forcing in regional climate dynamics over monsoonal Asia on decadal to centennial timescales.