Ocean sediments from Bay of Bengal reveal insights into Indian Monsoon patterns, climate change

Researchers analyze ocean sediments to understand monsoon impact on water conditions, marine productivity, and ecosystem changes over millennia.

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.