A new study led by CMCC, the Euro-Mediterranean Center on Climate Change, clarifies some aspects related to the increase in marine heatwaves in the Mediterranean over recent decades.
It is not heat itself that triggers marine heatwaves, but its persistence.
The new study shows that persistent subtropical ridges have far more significant effects than the rise in atmospheric temperatures.
It is their persistence that creates the conditions for the formation of marine heatwaves. At the onset of these events, the ridges become stationary, interrupting the normal eastward movement of weather systems.
When these ridges settle over the Mediterranean basin for five consecutive days, prevailing winds calm down, the sea stops dispersing heat, and surface waters warm rapidly.
According to Ronan McAdam, CMCC researcher and co-author of the study: “Our study identifies the favorable conditions that precede marine heatwaves and reveals that they are triggered by persistent subtropical ridges that weaken strong winds in the area. These results are essential to improve forecasting systems and Earth system models, and represent a key step towards effective early warning and mitigation strategies in the basin.”
The discovery of this statistical relationship lays the foundation for more accurate forecasting systems, which could help protect marine ecosystems and the industries that depend on them from future extreme events. For example, in the Gulf of Lion, underwater temperatures increased by nearly 7°C in just two days during the most extreme events, highlighting how quickly marine heatwaves can develop and the need for accurate forecasts and effective responses.