European seas regionally up to six degrees warmer than usual: Study identifies climate change as the main driver

According to the researchers, affected areas included parts of the Mediterranean, the Bay of Biscay, and waters around Ireland. In some of these zones, surface temperatures had at times been several degrees above comparative values, and in extreme cases anomalies of around six degrees were recorded.

John Bruno, one of the scientists involved, described the finding as a warning signal for the stability of marine ecosystems. The warming interferes with food webs and increases the risk of mass die-offs of species as well as the spread of warmth-loving organisms into previously cooler waters.

Consequences for ecosystems

Climate scientist Friederike Otto, who also co-authored the study, said regarding the handling of rising temperatures: „Wir können uns nicht aus dieser Situation herauswinden, indem wir uns einfach anpassen." Protecting ecosystems is important in its own right, but in addition, many people and industries depend on the sea not warming as quickly as currently observed.

Economic risks

On the coast of Ireland, researcher Claire Bergin warned of the consequences for fisheries and aquaculture. Warmer water alters the distribution of commercially used species and could noticeably reduce yields in the coming years, she said, citing measurements from Maynooth University.

In Western Europe as well, those involved see economic risks. Tourism in coastal regions depends on intact beaches and stable water temperatures; heat periods in the sea could also increase demand for cooling and water and put utilities under pressure.

The study distinguishes between a short-term response to individual heat waves and a longer-term warming trend. Without a significant reduction in greenhouse gas emissions, a further increase in such anomalies is to be expected, the authors write.

Recommendations and outlook

For the coming summer months, the researchers recommend stronger monitoring of sea temperatures and closer coordination between authorities, fisheries, and nature conservation. Early warning systems for marine heat waves are to be expanded in order to better prepare affected industries and protected areas.

The World Meteorological Organization (WMO) has also pointed out for some time that marine heat waves are increasing in Europe. The new findings fit into this picture, the agency emphasized, referring to ongoing international programs for observation and early warning.

Parts of the scientific community, including co-author John Bruno, are calling for the expansion of marine protected areas and for limiting additional stresses such as over-fertilization and pollution, which further weaken the resilience of warming ecosystems.

If the trends continue, the researchers expect noticeable changes in commercial fisheries, coastal tourism, and energy supply during hot summers. The coming months and years will show how well Europe is prepared for marine heat waves, the study concluded.