TY - JOUR
T1 - Indian summer monsoon variability in southern India during the last deglaciation
T2 - Evidence from a high resolution stalagmite δ18O record
AU - Raza, Waseem
AU - Ahmad, Syed Masood
AU - Lone, Mahjoor Ahmad
AU - Shen, Chuan-Chou
AU - Sarma, Drona Srinivasa
AU - Kumar, Anil
N1 - Funding information: The authors are thankful to Dr. V. M. Tiwari, Director, CSIR-NGRI, Hyderabad. The first author is thankful to Ms. K. Zainab, S. Singh and colleagues at paleoclimate group, CSIR-NGRI for their support. We are also grateful to the Council of Scientific and Industrial Research (CSIR) for financial support provided through 12th plan projects INDIAS IDEA, INDEX and SHORE. U-Th dating was supported by grants from Taiwan ROC MOST (104-2119-M-002-003, MOST-105-2119-M-002-001) and the National Taiwan University (105R7625). We express our gratitude to anonymous reviewers of Palaeo-3 for constructive comments to modify the manuscript.
PY - 2017/11/1
Y1 - 2017/11/1
N2 - We present a high resolution record of Indian summer monsoon (ISM) variability during the last deglacial period. The record is based on high precision measurements of oxygen isotopes (δ18O) in 263 sub-samples from a ~ 18 cm long stalagmite (VSPM1) sample collected from the Valmiki cave in the southern India. The chronological framework is based on high precision U-Th dating in 8 sub-samples at regular intervals. The stalagmite exhibits a variable growth rate ranging from ~ 0.03 to 0.80 mm/yr with 9 years as an average sampling resolution for δ18O. X-ray diffraction analysis shows that the sample is composed of aragonite mineral. The δ18O record provides a strong evidence of abrupt changes in ISM activity between approximately 15,610 and 13,160 yr BP (before 1950 AD). Highly negative δ18O values at ~ 15,610 and 15,250 yr BP are suggestive of a wet climate followed by less negative δ18O at ~ 15,240 to 14,750 yr BP indicating relatively dry climate. These dry and arid conditions are punctuated by two wet events at 15,030 and 14,910 yr BP. A marked increase in δ18O between approximately 14,660 and 14,370 yr BP suggests weakening in ISM activity, followed by a gradual decrease in δ18O between 14,370 and 13,560 yr BP indicating strengthening of ISM. However we cannot rule out the possibility of some past flooding event influencing δ18O of VSPM1. Wavelet analysis of δ18O time series suggests strong influence of solar forcing on ISM activity. The amplitude variance of δ18O reveal decadal to centennial scale variability in monsoonal activity during the last deglaciation.
AB - We present a high resolution record of Indian summer monsoon (ISM) variability during the last deglacial period. The record is based on high precision measurements of oxygen isotopes (δ18O) in 263 sub-samples from a ~ 18 cm long stalagmite (VSPM1) sample collected from the Valmiki cave in the southern India. The chronological framework is based on high precision U-Th dating in 8 sub-samples at regular intervals. The stalagmite exhibits a variable growth rate ranging from ~ 0.03 to 0.80 mm/yr with 9 years as an average sampling resolution for δ18O. X-ray diffraction analysis shows that the sample is composed of aragonite mineral. The δ18O record provides a strong evidence of abrupt changes in ISM activity between approximately 15,610 and 13,160 yr BP (before 1950 AD). Highly negative δ18O values at ~ 15,610 and 15,250 yr BP are suggestive of a wet climate followed by less negative δ18O at ~ 15,240 to 14,750 yr BP indicating relatively dry climate. These dry and arid conditions are punctuated by two wet events at 15,030 and 14,910 yr BP. A marked increase in δ18O between approximately 14,660 and 14,370 yr BP suggests weakening in ISM activity, followed by a gradual decrease in δ18O between 14,370 and 13,560 yr BP indicating strengthening of ISM. However we cannot rule out the possibility of some past flooding event influencing δ18O of VSPM1. Wavelet analysis of δ18O time series suggests strong influence of solar forcing on ISM activity. The amplitude variance of δ18O reveal decadal to centennial scale variability in monsoonal activity during the last deglaciation.
U2 - 10.1016/j.palaeo.2017.07.003
DO - 10.1016/j.palaeo.2017.07.003
M3 - Article
SN - 0031-0182
VL - 485
SP - 476
EP - 485
JO - Palaeogeography, Palaeoclimatology, Palaeoecology
JF - Palaeogeography, Palaeoclimatology, Palaeoecology
ER -
