Speleothem based 1000-year high resolution record of Indian monsoon variability during the last deglaciation

Abstract A high resolution record of the Indian summer monsoon (ISM) is generated using a δ 18 O time series from a stalagmite collected from the Valmiki cave in southern India. This record covers a time span of ~ 1000 years from 15,700 to 14,700 yr BP (before 1950 AD) with an average sampling resolution of ~ 5 years. High amplitude δ 18 O variation in this record reflects abrupt changes in ISM activity during the last deglaciation and suggest an age for the onset of Termination 1a (T1a) at ~ 14,800 yr BP in the Indian sub-continent. This record shows evidence for strong changes in tropical climate during the last deglaciation. Coincident variability in VSPM4 δ 18 O with speleothems from southern China during Termination 1a suggests that these caves reflect fluctuations in ISM activity. The variance in δ 18 O amplitude reveals significant multidecadal variability in ISM activity. Our record reveals intervals of strong monsoon activity during the later phase of Heinrich event 1 (H1) and shows synchronous multidecadal variability between ISM and East Asian monsoon (EAM). Spectral analysis of δ 18 O time series in VSPM4 reveals solar forcing and strong ocean–atmospheric circulation control on ISM dynamics during the studied time interval.