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The rapid melting of the frigid Arctic nearly 9,000km away is likely to have caused the extreme rainfall witnessed in the Indian sub-continent over the past few decades, say scientists at the Goa-based National Centre for Polar and Ocean Research (NCPOR).
|| Nikita Bararia

A recent study by researchers from India and Norway found that the periods of increasing extreme rainfall events in India during June to September coincide with rapidly declining summer sea ice in the Arctic. Based on analysis of climate data for the last 100 years, the scientists have established the link between the declining Arctic sea ice and the Indian summer monsoon (ISM), which typically lasts from June-September.

They have found that upper atmospheric circulation changes associated with rapid melting of sea ice in the Arctic ocean can reach further into the tropics and influence extreme rainfall events in India. The findings from the study show that the upper atmospheric circulation changes due to Arctic sea ice loss facilitate enhanced moisture supply and convection over the Indian landmass and cause increased extreme rainfall events. The study has been published in the reputed npj Climate and Atmospheric Science journal.

Led by Sourav Chatterjee and co-authored by M Ravichandran, Nuncio Murukesh, Roshin P Raj and Ola M Johannessen, the study further stressed that detailed numerical modelling studies into the observed link will help shed more light on the potential contributing factors behind extreme weather events in India.

“The study’s findings point to the fact that the variability of extreme events during ISM can at least partly result from upper-level atmospheric circulation changes due to remote sea ice changes in the Arctic and local sea surface temperature changes in the Arabian Sea,” said Chatterjee.Scientists had already observed the increasing frequency of extreme rainfall events over the Indian landmass during ISM in the past few decades. Climate researchers have noticed more “extreme rainfall periods” in 2019 and 2020 as compared to 2018, but large parts of India have also witnessed drought-like conditions due to the unequal distribution of rainfall. The India Meteorological Department (IMD), in its ‘Statement of Climate of India during 2020’, shows that high intensity precipitation events have been on the rise, leading to flooding in Kerala, north Karnataka, Maharashtra (including Mumbai), Assam, Bihar, eastern Uttar Pradesh, south Gujarat and even Punjab.

The sea ice in the Arctic ocean is declining rapidly, potentially influencing global climate and weather patterns, said director of NCPOR, M Ravichandran.A large amount of heat released during the extreme rainfall events in northwest India is known to travel up to the Arctic and reduce sea ice. But in this study, the research team focused on the possible relationship the other way round to see if changes in the Arctic atmospheric condition due to sea ice loss potentially influence the extreme rainfall during ISM,” said Ravichandran.

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