The marine heat wave that hit the Mediterranean this summer, with temperatures locally approaching 30 °C in July, was not just an anomaly. It is part of a global warming, and worrying, documented by a study published on September 16 in the scientific journal Geophysical Research Letters, which analyzed data recorded from 1950 to 2025.
Its authors show that the temperature and salinity of the Mediterranean are increasing almost everywhere, at an increasingly sustained rate. Since the beginning of the century, the surface waters of the Mediterranean have warmed by about 0.5 °C per decade, two to three times faster than the surface of the world’s oceans. In most of the basin, during the second half of the 20th century, warming was below the 0.1 °C per decade.
« What worries us is the speed at which these changes occur, and the depth at which they are felt, » Elena Terzić, oceanographer at the Ruđer-Bošković Institute in Zagreb (Croatia) and lead author of the study, said in a statement. Warming and salinization are statistically significant up to 3,000 m deep, she continues.
The warming of the Mediterranean is deeply shaking the ecosystem. It can promote the movement and installation of new species, such as the rabbit fish, which decimates herbariums and species that live there. Marine heat waves can lead to massive mortality, especially among gorgons. These corals are so-called « engineer » species, which offer other animals shelters where to lay, feed or hide. In the summer of 2022, when the temperature rose to 30 °C in the northwest of the basin, massive mortality was deplored up to 30 m deep.
