A new study conducted by researchers from the Birbal Sahni Institute of Palaeosciences, an autonomous institute of the Department of Science and Technology, analyzed magnetic minerals accumulated in sediments from Bakhira Lake in Sant Kabir Nagar over 25,000 years to track past changes in climate and their influence on rainfall, weathering, sediment transport, and lake processes in northern India. The research focused on the Central Ganga Plain, which is critically important for agricultural practices and heavily influenced by the Indian Summer Monsoon.
The study investigated environmental magnetic properties preserved in Bakhira Lake sediments, which provide a continuous and reliable archive of monsoon variability dating back to the Last Glacial Maximum. Bakhira Lake, located in the Ghaghara–Rapti alluvial system, represents a perennial oxbow/floodplain wetland formed through the migration and subsequent cut-off of the Rapti River. Designated as a Ramsar Site in 2022, it is one of the largest wetlands in Uttar Pradesh, with floodplain–lacustrine settings that favor sediment accumulation and preservation.
The sediment sequence extends back approximately 25,000 years and is constrained by seven accelerator mass spectrometry radiocarbon dates, providing a well-dated terrestrial archive for investigating Late Quaternary environmental and climatic variability. Using environmental magnetic properties integrated with grain-size, geochemical, and clay mineralogical records, the researchers reconstructed variations in the Indian Summer Monsoon from the Last Glacial Maximum to the present.
The record identifies major climatic events including the Last Glacial Maximum (~25.3–18.1 cal ka BP) marked by cold and dry conditions with weakened monsoon, Heinrich Stadial 1, Bølling–Allerød (~15.3–12.8 cal ka BP) with enhanced monsoon activity, Younger Dryas (~12.8–11.1 cal ka BP) with renewed cooling and weakened monsoon, Holocene Climatic Optimum (~9.2–4 cal ka BP) with enhanced monsoon precipitation and pedogenic activity, and late Holocene droughts (~4–2 cal ka BP) with reduced monsoon strength.
The research, published in Palaeogeography, Palaeoclimatology, Palaeoecology, improves understanding of how the Indian Summer Monsoon has responded to natural climate change before instrumental records existed. The findings provide valuable baseline information for improving climate models, predicting future monsoon behavior, and understanding the response of river and lake systems to changing rainfall patterns. The study supports better planning for water-resource management, agriculture, flood and drought mitigation, and environmental conservation in the Ganga Plain, where millions depend directly on monsoon rainfall.