Photo Courtesy: India Today Group
Shillong: A single stalagmite pulled from Meghalaya's Mawsmai Cave reveals 6,000 years of hidden monsoon history. Scientists studied an 11-cm-long deposit from 300 metres inside the cave. The work comes from IIT Kharagpur and IISER Kolkata. It maps the Indian Summer Monsoon between 11,807 and 5,622 years ago.
Researchers Yachna Verma, Anil K Gupta, Prasanta Sanyal, Priyantan Gupta, Som Dutt, Pankaj Kumar, and Abhijit Mukherjee led the project. They found the monsoon roared during the early Holocene. It grew weaker as the middle Holocene arrived. Low oxygen isotope values signaled high intensity until 7,700 years ago. Then, the rains slowed.
The team linked these shifts to North Atlantic events known as Bond events 8, 7, 6, 5b, 5a, and 4. These likely shifted the Atlantic Meridional Overturning Circulation. Solar cycles also left their mark. The team found climate patterns repeating every 118 and 110 years. These track with Gleissberg solar cycles. Pacific Decadal Oscillation and Tibetan Plateau temperatures also played a part.
The study, titled Deciphering Holocene monsoon dynamics in northeastern India, appeared in the journal Palaeogeography, Palaeoclimatology, Palaeoecology. It suggests a new way to study old climates. "The researchers said northeastern India, given its geographical setting and sensitivity to climatic changes, offers an important opportunity to understand long-term monsoon behaviour."
Fieldwork required 95 percent humidity inside the cave. B D Kharpan Daly, Ksan Kupar Mawlong, and Kyrmen Skhembha Rani from the Meghalayan Adventure Association assisted the crew. IIT Kharagpur and IISER Kolkata provided the labs. The findings arrived November 4.
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