The researchers said an important aspect of the study was that it identified significant monsoon cycles linked to solar activity. Representational file image.
| Photo Credit: V RAJU
A recent study conducted by the Central University of Kerala has provided crucial insights into the historical behaviour of the Indian Summer Monsoon over the past 15,000 years.
By analysing ocean sediments from the Bay of Bengal and the Andaman Sea, researchers have shed light on how changes in monsoon activity have influenced water conditions in these regions, particularly affecting salinity and marine productivity.
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The study, which involved the examination of fossil shells of planktonic forminifera, tiny marine organisms, demonstrates that monsoon patterns have fluctuated significantly over millennia. These variations have had a profound impact on both oceanic and terrestrial ecosystems.
The study’s lead researcher, prof. A.V. Sijinkumar of the Department of Geology, explained that while previous research primarily focused on Andaman Sea sediments, the inclusion of data from the Bay of Bengal has provided a more comprehensive understanding of monsoon dynamics.
According to the findings, monsoon intensity peaked during the early Holocene epoch, between 11,000 and 7,000 years ago. In this period, heavy rainfall led to a significant influx of freshwater into the Bay of Bengal, drastically lowering its salinity. The phenomenon occurred due to higher river discharge from major water systems such as the Ganga and the Brahmaputra. The resulting lack of vertical mixing of waters restricted the upwelling of nutrient-rich waters, diminishing primary productivity.
In colder climatic phases when monsoon activity weakened, on the other hand, river discharge declined, leading to better vertical mixing. This process facilitated nutrient upwelling, promoting higher marine productivity and more robust marine ecosystems.
The researchers said an important aspect of the study was that it identified significant monsoon cycles linked to solar activity, suggesting that variations in solar radiation have modulated rainfall over extended periods of time. The researchers also warned that ongoing global warming could amplify summer monsoon intensity in the coming decades, with potential consequences for regional agriculture, water resources, and biodiversity.
S.J. Gayatri, a scientist in the Department of Geology, said a better understanding of past monsoon responses to changes in climate can improve future climate projections and planning.
Together with scientist K. Sandeep in the same department, the study coauthors included experts from the National Institute of Oceanography, Goa, and the National Centre of Polar and Ocean Research, Goa.
It was funded by the Anusandhan National Research Foundation under the Government of India. The study is to be published in the April 25 issue of the journal Quaternary International.
Published – March 24, 2025 10:49 am IST
