For decades, the evolution of the Indian monsoon has not been entirely understood. Nor have scientists decoded how it intensified and how it has varied with time, leaving gaps in how they understand a recurring climate phenomena on such a large scale. By analysing sediment from the Bay of Bengal, researchers have found that the present Indian monsoon system, as we have it now, goes back at least 27 million years.
“Previous studies only went as far back as 12 million years. They used wind and vegetation data, but that would not paint a clear picture of monsoon intensity,” corresponding author Sajid Ali from the Birbal Sahni Institute of Palaeontology in Lucknow said. “We analysed sediment from the Bay of Bengal. Change in sediment is directly linked to change in monsoon … The presence of minerals depends on the intensity of monsoon. Different minerals are formed when the monsoon is strong and others when it is weak.”
For the study, to be published in Wiley journal ‘Paleoceanography and Paleoclimatology’, they collected 38 sediment samples under Japan’s International Ocean Discovery Program. Over four years, the study was conducted with resident researchers in Germany.
When they studied nano fossils (plankton which are one thousand millionth of a metre) from the bottom of the sediment deposits, "those were found to be 27 million years old, the age we conclude for the present Indian Monsoon system,” Ali explained.