Warmer seas fuelled increase in hurricane strengths, study finds
Hurricane wind speeds around Bermuda have more than doubled because of a rise in sea temperatures, new research has revealed.
The study by the University of Southampton and the UK National Oceanic Centre found the average wind speed of storms near Bermuda increased from 35 to 73mph - an increase of more than 6mph every decade - between 1955 and 2019.
The sea surface and sub-surface water temperature in the region increased by up to 1.1°C over the same time - which could add strength to storms.
Mark Guishard, the director of the Bermuda Weather Service and a co-author of the paper, said the research highlighted the major role that “upper ocean heat” - the temperature of the water in the top 50m - played.
He added: “Near-surface ocean heat provides the fuel for hurricane strength and the potential for storms near Bermuda to be more intense has accordingly been gradually increasing, as our study demonstrates.”
Dr Guishard emphasised: “This research does not represent a prediction of the likelihood of storm impacts in any given year, but it reveals a trend in the intensity of those storms that do come through our area.”
He said that there were “peaks and troughs” that explained variability in hurricane numbers year-to-year, but rising water temperatures had been a longer-term trend.
Dr Guishard added: “One of these multi-decadal trends is that the upper ocean surrounding Bermuda has been warming steadily, as shown by ship-based measurements undertaken by the Bermuda Institute for Ocean Science since the mid-1950s.”
He said the study would also help researchers to develop ways to improve forecasts for storms near the island.
Dr Guishard added: “Preliminary testing with the recent passage of Hurricane Paulette shows promising results that this technique could be further developed into an additional operational tool for forecasters locally.”
Samantha Hallam, the lead author of the paper, said the researchers used a range of records to record conditions in and around hurricanes that passed inside 100km of Bermuda over the past 65 years, including direct hits and near-misses.
She said: “The approach we used could provide a better way to predict Bermuda storm intensity than current theory or operational methods alone.
“It could also be use elsewhere in the subtropical Atlantic where there is a shallow mixed layer depth, typically north of twenty five degrees north.”
The 2020 hurricane season was the busiest on record, with a total of 30 named storms including 13 hurricanes and six major hurricanes.
Bermuda escaped major damage, despite one direct hit and two near misses over the season.
Hurricane Paulette struck the island as a strong Category 1 hurricane last September and caused major power cuts.
It was followed a week later by Hurricane Teddy, which grazed the island as a Category 2 hurricane.
Hurricane Epsilon threatened the island last October, but steered clear of the island, although it brought Bermuda high winds.