France has seen searing temperatures in successive heatwaves over the past few weeks, but it’s not only on land that temperatures are insufferably high. The Mediterranean Sea’s surface temperature reached a record high 30.7°C in late July, and marine heatwaves are becoming increasingly common because of climate change – with dramatic consequences for biodiversity.
As Europe battles wildfires and record drought on land, rising sea temperatures pose another kind of threat. On July 24, the temperature in the Mediterranean reached a peak of 30.7°C off the coast of Alistro in eastern Corsica, according to the Keraunos meteorological observatory. The next day, in the bay of Villefrance-sur-Mer – an idyllic beach town a few miles from Nice – a researcher at the local oceanographic laboratory recorded a temperature of 29.2°C.
“It’s unprecedented,” said the researcher, Jean-Pierre Gattuso. The Mediterraean’s temperature is usually between 21° and 24°C at this time of year.
“What we’re seeing is a marine heatwave,” Gattuso said. “Like the heatwaves we get on land, it’s characterised by unusual temperatures for the season and can go on for several days or even weeks.”
In this case, Gattuso said, record temperatures have been continuing since the end of June and are affecting the entire western Mediterranean, from the heel of the Italian boot to Spain.