Monsoon to get wetter in coming years

The Monsoons, which are crucial to South Asia’s agrarian economy, are going to be wetter and more dangerous, according to a new study. For the past many years, climate change is known to have adverse effect on Monsoons, disrupting the monsoon season.

Science Advances journal published the findings.

The researchers made the assessment by looking back over the past million years to give a sense of monsoons to come. Earlier, the scientists used computer models to show the world how global heating caused by green house gases and increased moisture in warm atmosphere results in wetter monsoons.

DATA OVER 9,00,000 years

Lead author Steven Clemens (professor of geological sciences (research) at Brown University) said  “we show that over the last 9,00,000 years, higher CO2 levels along with associated changes in ice volume and moisture transport were associated with more intense monsoon rainfall (monsoon wetter).”

“That tells us that CO2 levels and associated warming were major players in monsoon intensity in the past, which supports what the models predict about future monsoons — that rainfall will intensify with rising CO2 and warming global temperature,” he said.

The monsoon season in South Asia is generally from June to September. The Monsoon rains , crucial to the region’s agrarian economy, affect the lives of a fifth of the world’s population. The rains can nourish or destroy crops, and even cause devastating flooding. The scientists point out that changes in Monsoon pattern could reshape the region, and history.

MUD FROM SOIL BED

The researchers mainly used mud from the ocean floor to determine the changes and to show monsoon wetter. They drilled core samples in the Bay of Bengal, in the northern Indian Ocean, where the runoff from monsoon seasons drains away from the subcontinent. Clemens has been working with an international team of researchers for several years to understand the major drivers of monsoon activity.

The rainwater caused by the monsoons each summer eventually drains off the Indian subcontinent into the Bay of Bengal. The run off creates a layer of dilute seawater in the bay that rides atop the denser, more saline water below. The surface water is a habitat for microorganisms called planktonic foraminifera, which use nutrients in the water to construct their shells, which are made of calcium carbonate (CaCO3). When the creatures die, the shells sink to the bottom and become trapped in sediment. By taking core samples of sediment and analyzing the oxygen isotopes in these fossils, scientists can divine the salinity of the water in which the creatures lived. The salinity signal can be used as an indicator of changing rainfall amounts over time.

Clemens said that they could reconstruct rainfall over time using these proxies, thereafter look at other paleoclimate data to see what might be the important drivers of monsoon activity. He mentioned that this helped in answering several important questions about the factors driving the monsoons.

 

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