Origin of Mediterranean heatwaves discovered

The origin of the waves has been reconstructed marine heat in the Mediterranean, the phenomenon that has affected the record in 2022 and is characterized by surface temperatures of the anomalous sea. The research, published in the journal Nature Geoscience, was conducted by the Euro-Mediterranean Centre for Climate Change (CMCC) which is based in Bologna, with the coordinated by Giulia Bonino. The result now allows us to predict the phenomenon with greater precision. The researchers analyzed data collected over a period of 40 years, from 1982 to 2022, and relating to 123 major events marine heat waves over an area of more than 100,000 square kilometers. It thus emerged that heat waves marines become four to five times more likely when coincide with light winds in the Mediterranean. The research focused in particular on the phenomenon of the intrusions of hot air that are directed from Africa towards Europe (subtropical ridges), informally called 'African anticyclones'. Although these intrusions occur especially in summer, with a frequency of about 2 days, it is the their persistence in determining the formation of waves of marine heat. The high pressure system associated with the dorsal becomes stationary, interrupting the normal eastward movement of weather systems. When these ridges settle on the pelvis of the Mediterranean for five consecutive days or more, cause the cessation of the prevailing winds, which causes the sea to stop to spread heat and the surface waters to warm up quickly. "Our study identifies favorable conditions that lead to marine heatwaves and reveals that they are triggered from persistent subtropical ridges that weaken the strong winds in the area," says Ronan McAdam, researcher at CMCC and co-author of the study.