Marine heatwaves in Bay of Bengal most intense from 2016-20

KOLKATA: With an average of three marine heat waves per year in the Bay of Bengal between 1982 and 2021, a study published in Scientific Reports journal last month has revealed that climate change has been increasing this number at a rate of 1.1 heatwaves per decade. The most intense events have happened between 2016 and 2020.
The study, compiled by IIT-Kharagpur researchers from the Centre for Ocean, River, Atmosphere and Land Sciences, observed that the rate of warming in this region is much greater than in other marine regions.Out of the total 107 marine heat waves in the last four decades, the longest — 91 days — was in 2020, between June and September. The most intense one was in 2016, when the water heated up to a maximum of 5.3°C above normal and continued for 69 days.
“The understanding of marine heatwave events across the globe is increasing rapidly. However, the studies in the North Indian Ocean are very limited, and this paper is an effort to understand and analyze the events in the North Indian Ocean, mainly focusing on the Bay of Bengal region,” said the study. “Also, it is observed that the rate of warming in this region is much higher than in other regions. An increasing trend in marine heatwaves is observed over the Arabian Sea and the Bay of Bengal regions. So it is extremely necessary to understand the patterns of these events,” it added.
An increased duration and intensity of marine heatwaves in both the Arabian Sea and Bay of Bengal implies severe consequences on peninsular India. “Depending on three factors — duration, frequency and intensity — there are two direct consequences: one is the increased probability of cyclones in Bengal and the adjoining regions and the second is the displaced migration trends of communities of fish,” said Sugata Hazra, former director of oceanography at Jadavpur University. The consecutive four years of large-scale coastal cyclones are testament to the heating of the water over the last decade. Additionally, the interplay of the Indian Ocean Dipole with Arabian Sea heatwaves can result in severe fluctuation in temperatures in India, possibly leading to drought.
The Nature Journal’s study was published two weeks after the World Meteorological Organisation (WMO) agency announced that the global marine heatwaves occuring now may extend until February 2024. Currently, 27% of global oceans are experiencing a heatwave. Both WMO and the Nature Journal study attributed oceanic heating to the fact that about 90% of excess heating from global warming is absorbed by oceans.