Mediterranean Sea Experiencing Unprecedented Heatwave

Since June 10th, the Mediterranean basin has been gripped by an intense heatwave. These persistently high temperatures have led to a significant warming of the sea, which has been accumulating heat. As of July 1st, buoys between Corsica and the French Riviera were already recording temperatures of 29-30°C, an unprecedented situation so early in the season, with excesses of +5 to +8°C above normal.

Exceptional Temperatures

Water temperatures of this magnitude have been observed in August or September in previous years, but such high temperatures at the very beginning of summer are exceptional. Temperatures are slightly lower in the Gulf of Lion, around 26°C, due to recent Mistral and Tramontane winds.

Geographic Scope

The western and central parts of the Mediterranean basin are most affected by these very high water temperatures. Temperatures are closer to normal in the eastern Mediterranean, between Greece, Turkey, and Crete, where frequent Meltem winds temper the Aegean Sea.

Link Between Land and Sea Temperatures

There is a direct correlation. The heat from the air gradually warms the water. If air temperatures reach 35°C or higher for several days without wind, the water warms even more. In the absence of water movement, this warming is even more pronounced, leading to the record temperature anomalies currently observed.

Consequences for Marine Life and Climate

The impacts are numerous. Corals, though not abundant in the Mediterranean, suffer from bleaching due to rising temperatures, affecting marine biodiversity. Fish, which prefer colder waters, are moving to deeper areas, making fishing more difficult. Regarding the climate, oceans, which absorb 20 to 30% of the CO2 produced by human activity, may no longer be able to capture this gas effectively, leading to ocean acidification. This could trigger a vicious cycle of climate warming and extreme weather events, such as more intense storms and floods.

Other Affected Areas

The Mediterranean is not the only sea affected. The Atlantic and the English Channel are also experiencing overheated waters, although the temperature anomalies are smaller than in the Mediterranean (+2 to +5°C). This is due to the recurring influx of very hot air over the western facade of the European continent in recent weeks.

Duration of the Phenomenon

Seasonal forecasts predict a summer significantly hotter than normal, with recurring periods of intense heat. The waters of the Mediterranean are therefore likely to remain very warm throughout the summer unless periods of Mistral, Tramontane, and Libeccio winds in Corsica become more frequent.

Potential Solutions

Increased water mixing, wind, and storm depressions could help cool the sea, but these are rare in mid-summer. It will likely be necessary to wait for the Cévenol storms of early autumn, for example, which could bring torrential rains and thus lower the water temperature.

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