High-resolution mid-Holocene Indian Summer Monsoon recorded in a stalagmite from the Kotumsar Cave, Central India

Abstract

The Indian Summer Monsoon (ISM), a significant part of the global monsoon system, is driven by several climate forcing parameters. With the growing pace of global climate change scenario, there is need to focus on generating more high-resolution records of past monsoon. The ISM reconstructions from Core Monsoon Zone (CMZ) of India, which represents all-India Summer Monsoon Rainfall, are useful for a better understanding of its past variability. Such reconstructions from the CMZ are rather sparse and require detailed study based on various climate proxies. Here, we focus on the reconstruction of ISM variability during the mid-Holocene, based on stalagmite oxygen isotope ratios from the Kotumsar cave, Central India. We show that with decreasing insolation, monsoon started declining at the beginning of the mid-Holocene from 8.5 to 6.5 ka BP, which is also observed in the previous ISM reconstructions with coarser resolutions. However, a gradual increase in the rainfall is observed from 6.5 to 5.6 ka BP, a feature which is also noted in the East Asian Monsoon reconstruction from the Dongge cave. Our record mainly emphasizes on the occurrence of several abrupt weak monsoon events throughout the mid-Holocene. The occurrence of 8.2 and 5.9 ka abrupt weak monsoon events suggest that ISM variability is tightly bound to North-Atlantic Oscillation (NAO). We also demonstrate that ISM during the mid-Holocene was partly sensitive to El-Nino Southern Oscillation (ENSO), and displayed an inverse relationship.