Meghalaya cave stalagmite reveals 6,000-year history of monsoon changes
A study of a cave deposit in Mawsmai Cave shows how solar activity and ocean currents influenced ancient rainfall.
Researchers have used an 11-cm-long stalagmite from Meghalaya's Mawsmai Cave to reconstruct 6,000 years of monsoon history in northeastern India, according to The Assam Tribune. The study examined changes in the Indian Summer Monsoon (ISM) between 11,807 and 5,622 years ago.
The research, published in the journal Palaeogeography, Palaeoclimatology, Palaeoecology, found that the monsoon was much stronger during the early Holocene, specifically between 11,807 and 7,700 years ago. This period was marked by lower oxygen isotope values in the cave deposit. Rainfall intensity then decreased gradually from 7,700 to 5,622 years ago.
The team, led by Yachna Verma and Anil K Gupta of IIT Kharagpur, along with Prasanta Sanyal of IISER Kolkata, identified links between regional rainfall and global systems. They noted that monsoon fluctuations matched North Atlantic Bond events, suggesting a connection to the Atlantic Meridional Overturning Circulation (AMOC).
The study also found climate cycles repeating every 110 and 118 years, which align with Gleissberg solar cycles. Scientists stated that solar variability, the Pacific Decadal Oscillation (PDO), and temperature differences between the Indian Ocean and the Tibetan Plateau helped regulate monsoon strength.
The stalagmite was recovered from a chamber 300 metres inside the cave in the East Khasi Hills district, where humidity was over 95 per cent. The researchers noted that combining mineralogical analysis with geochemical indicators offers a new way to understand prehistoric climate conditions.