The exceptional warming in the Mediterranean Sea during 2024

In 2024,the year with the warmest global temperature since 1850 (Copernicus Climate Change Service), very high temperatures were observed at regional scale.In the Mediterranean Sea,the measured sea temperature locally displayed values that were never recorded before. Satellite and in situ observationsindicate that during 2024 the Mediterranean Sea has experienced a sequence of strong marine heat waves, occurring in the months of February, April, June, and  August.  Thesurface temperature anomalies with respect to the 1990-2020 climatology reached about 3° C in the Algerian and Levantine basins in February, and 4-5° C in the northern part of the western Mediterranean and in the Adriatic Sea in August. Moreover, in situ observations incoastal areas oftheTyrrhenian Sea, gathered through aCitizen Scienceactivity  (MEDFEVER initiative), indicated strong warming even on the seafloor, as a result of rapid heat transfer from  the sea surface to the bottom.  Satellite data show that surface temperature anomalies were strongly modulated by large gyres and eddies. We find that these dynamical structures control the anomalous warming induced by air-sea interactionsin regions such as the Algerian Basin, the Tyrrhenian Sea, and the Levantine basin. Estimates of mean and eddy kinetic energy from altimeter data suggest that mesoscale structures were particularly energetic during 2024 and favored warming in regions where eddy activity was intense. Model data show that themain quasi-permanent anticyclonic structures throught the basin were very effective in transferringsurface heat anomalies into the deep layers.  Finally, we analyze the 2024 Mediterranean summer temperature anomaliesin relationto local and global patterns of atmospheric circulation.