Greek Seas Hit Warmest Point in 40 Years, Researchers Say

The seas in Greece hit their warmest point in 40 years this summer, with water temperatures exceeding 28 degrees Celsius, according to a study conducted by three Greek universities.

Researchers at the universities of Thessaloniki, the Aegean and Thrace studied satellite data on the temperature of Greek seas from 1982 until today and concluded that the entire Aegean, Ionian and Cretan Seas have registered the highest temperatures of the last four decades in the summer of 2024.

The temperature rise was particularly evident in deeper waters, as far down as 50 meters in some areas, and that has been of a particular concern to scientists. “This means there is a cumulative phenomenon at work,” Vasilis Kolovoyiannis, one of the researchers at the University of the Aegean’s Department of Oceanography and Marine Biosciences told the Athens News Agency. He also said that researchers observed “changes in the usual mechanics of cooling in the Aegean, such as the inflow of cold waters from the Black Sea, which was low, and the coastal rise of colder masses.”

The role of marine heatwaves

According to another key finding, extended marine heatwaves also played a crucial role in the rise of temperatures. While their frequency was not particularly high in the summer of 2024, the hottest ever recorded in Greece, the duration of marine heatwaves exceeded previous records, especially in the north Aegean, which lasted until August.

Yiannis Androulidakis, another researcher and associate professor at the University of the Aegean’s Department of Oceanography and Marine Biosciences, in an interview with the Athens News Agency, adds that their current research, supported by other studies, shows a constant rise in sea temperatures in Greece every summer, to the rate of 0.5 degrees per decade. In some areas, he said, sea temperature rose to 30 degrees in the summer of 2024. Temperatures are increasing at a faster rate in the north Aegean (particularly in Thessaloniki’s Thermaic Gulf), smaller areas of the Ionian Sea, and regions of the Dodecanese.

The effects on the ecosystem

The combination of high temperatures with long durations is “the worst of the ecosystem,” according to Professor Androulidakis. As an example, he cites the production of mussels in coastal aquaculture farms west of Thessaloniki. Production has been severely damaged due to the thermal shock, causing problems not only to this year’s production but also for the future, since the offspring also died.

Moreover, professors Androulidakis and Kolovoyiannis told the Athens News Agency that the rise in sea temperatures also leads to a change in the oxygen levels in the water and increases the risk of invasion of heat-friendly fish species in the south Aegean and the Cretan Sea. According to the Sea Shepherd, a non-profit marine conservation society, the overall rise of temperatures in the Mediterranean Sea has already led to the destructive extinction of fish both in Greece and in Italy, while it affects the migration patterns of various marine species.

The larger picture in the Mediterranean Sea

The rise in sea temperatures both in Greece and across the Mediterranean Sea is attributed to climate change. The Mediterranean, where Greece is located, is warming up faster than other parts of the world mainly because it is a closed sea. Already severely affected by overfishing, marine life and the sea’s sensitive ecosystem in the Mediterranean are under serious threat because of rising temperatures, which have hit new record highs. According to Sea Shepherd, in August 2024 the water temperature off the shores of Egypt reached a record 31,96 degrees Celsius, the highest ever recorded. Meanwhile the sea’s surface temperature across the Mediterranean rose to 28, 9 degrees Celsius, exceeding the 2023 record of 28,71 degrees Celsius.