Indian summer monsoon variability during the last millennium as recorded in stalagmite from Baratang Mahadev cave, Andaman Islands

This study presents a stable oxygen isotope record of Indian summer monsoon (ISM) variability using cave speleothem carbonate from Baratang Island (Andaman Islands) encompassing the last millennium (from 10th to 19th century CE). The studied interval encompasses two major climatic events; the Medieval Climate Anomaly (MCA) and the Lithe Ice Age (LIA) as well as the Current Warm Period (CWP). Our data suggest generally higher precipitation during the warm MCA when the ISM was relatively strong, and low precipitation during the cold LIA with a few exceptions when wet conditions prevailed. The Baratang cave record shows greater similarity with the records from the Sahiya and Klang caves, and opposite trends relative to those from the northeastern Himalaya owing to the dipolar nature of ISM precipitation. High-frequency sub-decadal to centennial scale pulses of weakened summer monsoons are observed during 16th to 19th century CE. These phases of weak ISM are correlated with severe droughts and famines in the Indian subcontinent owing to deficient monsoon rainfall, which had pronounced effect on South Asian societies. Spectral analysis suggests a strong periodicity of 190 yr (de Vries cycle) indicating strong influence of solar insolation.