Global climate events in the last 3,200 years have brought changes in the Indian summer monsoon

Global climate events in the last 3,200 years have brought changes in the Indian summer monsoon

New Delhi: Global climatic events such as the Roman climatic period, medieval climate anomaly and scant ice age may have had a significant impact on India’s landscape, vegetation and socio-economic development, with a sudden change in the Indian Summer Monsoon (ISM). Along with these climatic events, a study conducted by Indian researchers has found.
The study by the Wadia Institute of Himalayan Geology, an institute of the Department of Science and Technology, shows the wet monsoon conditions between 1200 and 550 BCE in the northwestern Himalayas.
This situation persisted until 450 AD, which coincided with the Roman warm period. It had low rainfall and a weak ISM until 950 AD and then strengthened during the medieval climate anomaly between 950 and 1350 AD.
During the short ice age, there was a clear decrease in monsoon rainfall.
Studies conducted along lake sediments from Lake Rewalsar, a freshwater lake in Mandi district of Himachal Pradesh, may resolve a long debate among scientists over whether such incidents were local or global.
The sediments of this lake preserve signatures that can be used as proxies to understand monsoon variability in the past.
In a recent study published in the journal ‘Quaternary International’, researchers obtained data on grain size, stable isotopes of carbon and nitrogen, total organic carbon (TOC), and total nitrogen data from lake sediments.
They retrieved a sediment core with a length of 15 m from the center of the lake at a water depth of about 6.5 m using a piston corer, which was used as a specimen.
The chronology of the Rewalser Lake sediment was then established based on accelerator mass spectrometry (a form of mass spectrometry to distinguish a rare isotopic from an abundant neighboring mass), 14C radiocarbon dates and ages of fourteen samples from about 2950 years. Ranging from 200 years ago. .
Calculation of total organic carbon TOC, total nitrogen TN, and low carbon isotope ratio values ​​during the 1200–550 BC interval in wet monsoon conditions in the northwestern Himalayas.
This situation persisted until 450 AD, which coincided with the Roman warm period. This was followed by low rainfall and a weak ISM by 950 AD. The ISM became comparatively stronger during the medieval climate anomaly between 950 and 1350 AD. During the Little Ice Age, there was a clear decrease in ISM precipitation, as indicated by the relatively low C / N ratio and decreased TOC content.
The findings pointed to a revival of wet climatic conditions with a strong ISM around 1600 AD following a slight ice age, which prevails at the present time.
The study stated that the variability of ISM in the historical past needs to be understood in the present, and that the future behavior of ISM as climate change and water supply has determined the rise and demise of ancient civilizations.

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