Marine heatwaves rising in the Indian Ocean could threaten monsoons and marine life, study says

A new study by climatologists in Pune has traced an upward trend in marine heatwaves in the Indian Ocean region, which they say could affect marine life as well as future monsoons and cyclones.

Over the past few decades, the warming of the Arabian Sea has produced “severe” category cyclones. Warming oceans are also a threat to marine life, including coral reefs that are at risk of bleaching. Fishing-based livelihoods and fishing industries also remain under constant threat due to warming oceans.

The sea surface temperature during a sea heat wave event peaks (above the 90th percentile) and can remain one to two degrees above climatological normal, experts said.

Unlike terrestrial heat waves which can be predicted well in advance, marine heat waves have no specific periodicity. Also, they can vary from a day to a few days or last up to a month.

Recently, a month-long marine heat wave was reported along the Gulf of Mannar off Tamil Nadu.

“With gaps in the network of ocean observations obtained in the Indian Ocean region, observations of sea surface temperatures are limited, making it difficult to predict events. More observations are needed for that it could be input into climate models,” said Roxy Mathew Koll of the Indian Institute of Tropical Meteorology (IITM) who led the study.

Along with IITM, researchers from Cochin University of Science and Technology and Kerala University of Agriculture participated in the research and observed an upward trend of 1.5 marine heat wave events per decade along the western Indian Ocean, as it increased by 0.5 events per decade in the northern Bay of Bengal from 1982 to 2018. The research, published Tuesday in the journal JGR Oceans, found a total of 94 occurrences in the Bay of Bengal and 66 occurrences in the Western Indian Ocean during this period.

Marine heatwaves in the western Indian Ocean could also mean weak monsoon winds reaching the central Indian subcontinent – ​​the central monsoon zone and rainfed agriculture belt.

In addition, El Nino – the abnormal warming phenomenon along the central and equatorial Pacific Ocean – has also contributed to the increased frequency and intensity of marine heat waves along the region of the Indian Ocean, Koll said.

The western Indian Ocean reported peak events during the October-December period, while in the northern Bay of Bengal it was in May and October, the researchers said.

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