Figaro Nautisme: For several days, the temperatures of the Mediterranean have been abnormally high. How does it be explained?
Cyrille Duchesne: “Since June 10, an intense heat wave hit the Mediterranean basin. These high and persistent temperatures have led to a significant warming of the sea, which began to accumulate heat. On July 1, there were already temperatures of 29-30 ° C on the buoys located between Corsica and the Côte d’Azur, an unprecedented situation so early in season with excess. +8 ° C to normal. “
FN: Is this the first time that we have observed such temperature anomalies?
CD: “These water temperatures in 2023 and 2024 were observed in August or September but such temperatures at the very beginning of summer are exceptional. Note that temperatures are a little lower on the Lion Gulf, around 26 ° C in connection with the episodes of Mistral and Tramontane that have occurred in recent days.”
FN: The whole Mediterranean is concerned or are there specific areas?
CD: “It is especially the western and central part of the large Mediterranean basin which is affected by very high water temperatures. Temperatures are closer to normal on the eastern part of the Mediterranean, between Greece, Turkey and Crete with frequent episodes of Meltem which temper the Aegean Sea.”
FN: Is there a link between earthly heat and water temperature?
CD: “Absolutely. The heat of the air gradually warms water. If air temperatures reach 35 ° C or more for several days without wind, the water warms more. In the absence of water movement, this warming is even more pronounced, leading to record temperature anomalies currently observed.”
FN: What are the consequences for underwater life and the climate?
CD: “The impacts are numerous. The corals, although little present in the Mediterranean, suffer from whitening because of the temperature increases, affecting marine biodiversity. Fish, preferring cold waters, move towards deeper areas, making fishing more difficult. Regarding the climate, the oceans, which absorb 20 to 30% of CO2 produced by human activity, risk More able to capture this gas effectively, leading to an acidification of the oceans.
FN: Is the Mediterranean the only sea concerned by this phenomenon?
CD: “No, the Atlantic and the Channel also experience overheated waters even if the temperature anomalies are less than in the Mediterranean (+2 to +5 ° C). This is explained by the recurrences of very hot air lifts on the western facade of the European continent for several weeks.”
FN: Will it still last until the end of the summer? Beyond ?
CD: “Our seasonal forecasts are considering a significantly warmer summer than normal with recurrent periods of heat. The water from the Mediterranean are therefore likely to remain very hot throughout the summer if periods of Mistral and Tramontane and Libeccio in Corsica are not too frequent.”
FN: What could help reduce sea temperature?
CD: “No more water brewing, wind, and thunderstorm depressions could help cool the sea but these are rare in the middle of summer. It will probably be necessary to wait for Cévenols thunderstorms from the beginning of autumn, for example, could pour torrential rains and thus reduce the temperature of the water.”
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