Marine heatwaves, or prolonged periods of warm ocean temperatures, can "supercharge" tropical cyclones as part of its rapid intensification before landfall, which can lead to 60 per cent more billion-dollar disasters compared to cyclones free from the influence of marine heatwaves, a study has found.
Damages can come from higher maximum wind speeds, precipitation rates, and storm surges.
Researchers, including those from The University of Alabama, US, found that more tropical cyclones are undergoing a 'rapid intensification' process whereby wind speed increases by 30 knots or about 55 kilometres per hour, carrying potentially devastating consequences for humans and infrastructure upon landfall.
They suggested that the increasing number of intensified cyclones may be related to the growing pervasiveness of marine heatwaves.
The study, published in the journal Science Advances, analysed over 40 years' data (1981-2023) of global records of daily sea surface temperatures along with a global database of landfalling cyclones, and found that storms exposed to marine heatwaves have a higher likelihood of rapidly intensifying.
The authors "use four decades of global data to demonstrate that TCs (tropical cyclones) experiencing RI (rapipd intensification) during MHWs (marine heatwaves) resulted in 60 per cent more billion-dollar disasters compared to those without heat wave influence".
The average marine heatwave frequency in active tropical cyclone basins is typically between 1-1.5 events per year, with localised hotspots exceeding two events per year, most prominently in the Bay of Bengal and Arabian Sea of the North Indian Ocean, among other ocean regions, the researchers said.
"Upward trends in marine heatwave-related tropical cyclones are clear in the East Pacific, North Atlantic, and North Indian (Ocean) basins, while the Southwest Indian and Southwest Pacific basins show little or insignificant change," they said.
The North Indian Ocean basin also showed a significant upward trend in tropical cyclones not associated with a marine heatwave, coinciding with a marked increase in overall tropical cyclone activity since 2005, the authors said.
The unique pattern is tightly linked to rising sea surface temperatures and increased levels of moisture in both the Arabian Sea and the Bay of Bengal, a direct consequence of global warming, they said.
The team found that for billion-dollar tropical cyclones, even after accounting for similar levels of coastal development, marine heatwave tropical cyclones cause significantly higher damages than their counterparts.
The result confirms that enhanced intensity characteristics can amplify economic impacts beyond what would be expected from exposure alone, the authors said.
The findings underscore the critical need for an improved disaster preparedness as marine heatwaves increasingly supercharge tropical cyclones' intensity, leading to more frequent billion-dollar disasters, they said.