Indian Ocean Heatwaves Are On the Rise, And Are Altering Monsoon Rains Across India, Shows IITM Study

Global ocean temperatures are also rising due to excessive absorption of heat trapped by greenhouse gas emissions. Such ocean warming drives unprecedented changes in marine ecosystems, sea levels, and even weather patterns

Marine heatwaves in the Indian Ocean alters the rainfall patterns

One such devastating consequence of ocean warming is marine heatwaves, which subsequently affect global weather patterns. A first-of-a-kind study led by renowned climate scientist Roxy Mathew Koll from the Indian Institute of Tropical Meteorology (IITM), Pune, has now demonstrated how marine heatwaves in the Indian Ocean alters the rainfall patterns during the southwest monsoon season.

“Climate model projections suggest further warming of the Indian Ocean in the future, which will very likely intensify the marine heatwaves and their impact on the monsoon rainfall. Since the frequency, intensity, and area covered by the marine heatwaves are increasing, we need to enhance our ocean observational arrays to monitor these events accurately and update our weather models to skillfully predict the challenges presented by a warming world,” explains Dr Koll.

 Marine heatwave events occurring across the Indian Ocean studied

The IITM researchers specifically studied such marine heatwave events occurring across the Indian Ocean for this analysis. The researchers say that marine heatwaves used to be rare in the tropical Indian Ocean, but such episodes are now on the rise. In fact, heat waves have been occurring almost every year, triggered mainly by rapid warming in the Indian Ocean and strong El Niño. Moreover, a peak in solar radiation and weaker winds also lead to local marine heatwaves in the region.

Marine heatwaves are now on the rise

In 36 years, from 1982 to 2018, the western Indian Ocean recorded 66 heatwave events, while the Bay of Bengal reported startling 94 such events, says the research. This implies a sharp increase in marine heatwaves to the tune of 1.5 events per decade over the western Indian Ocean and 0.5 events per decade over the north Bay of Bengal.

Another key outcome of this study was the impact of marine heatwaves on the Indian monsoon season.

Heatwaves in the Indian Ocean leading to dry weather conditions over the central Indian subcontinent

As per its findings, the marine heatwaves in the Indian Ocean are leading to dry weather conditions over the central Indian subcontinent. Simultaneously, the study notes an increase in the rainfall pattern over south peninsular India due to heatwaves in the North Bay of Bengal.

Even the monsoon 2021 witnessed a similar pattern continued, with the southern peninsula registering 11% excess rainfall during the southern monsoon season, followed by repeated flooding episodes in October and November as well.