Maltese waters are experiencing the longest marine heatwave on record, according to a professor of geosciences.

Marine heatwaves occur when warmer sea temperatures above the climatological average persist for more than five consecutive days.

While the climatic norm for sea surface in August is under 28°C, temperatures from the start of the month were, on average, 2°C above this threshold, according to university professor Aldo Drago, coordinator of the Physical Oceanography Research Group at the University of Malta.

“We use climate models to look into the past data and I am confident that, although the marine heatwave this year has not ended yet, it is definitely the longest one with this intensity on record,” he said.

Temperatures began exceeding climatological averages in July and peaked at the weekend at above 30°C in Marsalforn and Xlendi, he explained.

In comparison, during the same period last year the average sea surface temperature was 27.10°C and the year before that 27.45°C, he said.

Data from a surface buoy in proximity of Marsalforn showing a strong positive trend in sea surface temperature during the first half of August. Credit: Physical Oceanography Research Group at the University of Malta

Although the marine heatwave recorded in 2017 topped the current one, temperature-wise, this heatwave has persisted for over two weeks and is ongoing, he pointed out. He described this as another blow for marine life,  explaining that the rise in sea temperatures was devastating for the ecosystem.

He noted that 27°C is the threshold for many marine species but, since 1987, the island had been observing an increase in the intensity and frequency of marine heatwaves, which was putting significant stress on aquatic life.

Warmer waters could lead to some species dying while mobile fish species could move to more favourable regions.

It could also provide an ideal environment for alien species to thrive, he added.

“Some of the effects are irreversible, as our ecosystem is a complex system of dynamic equilibria which can be altered permanently,” he said. 

He added that climate change was at the root cause of the rise in marine heatwaves, with the flux of solar radiation associated with the high air temperatures causing the sea surface temperatures to go up.

“We need to take action to curb climate change and to curb the stressors on marine life. Such effects are cumulative and eventually lead to tipping points, wreaking havoc in an already fragile marine ecosystem,” he said. 

The university’s Physical Oceanography Research Group specialises in the real-time monitoring of the marine environment.

It provides essential marine data services for research and for operational use by local stakeholders and to enable climatological assessments.

Adam Gauci is responsible for running field observations.