Weakening Monsoon due to a rapidly warming Indian Ocean

What is it about?

Our recent research points out a significant decreasing trend in the summer monsoon rainfall over the central Indian subcontinent during the past century. The study suggest that the rapid warming in the Indian Ocean is playing an important role in weakening the monsoon circulation and the rainfall. The study finds that, contradictory to what earlier studies have noted, the land-sea thermal contrast over the South Asian domain has in fact reduced in the past decades. This reduction in land-sea temperature difference is primarily contributed by a strong warming in the Indian Ocean. The surface warming in the Indian Ocean especially that in the western regions have reached values of up to 1.2°C during the past century, much larger than the warming trends in the other tropical oceans. The decrease in the land-sea thermal contrast is also visible in the upper atmosphere, as the warming trends in the ocean surface is transferred to the atmosphere above through convective processes. Apart from the ocean warming, a part of the decrease in land-sea temperature difference is also due to suppressed warming over the Indian land mass, possibly due to increased aerosols or reasons which are still uncertain.

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