Mediterranean Marine Heatwave
The Mediterranean Sea is experiencing an unprecedented marine heatwave in 2025. Temperatures are up to eight degrees Celsius above normal for this time of year. Scientists describe this as a one-in-a-billion event driven by human-induced climate change. This extreme warming threatens marine ecosystems and may cause severe weather in Europe in the coming months.
What Is a Marine Heatwave?
A marine heatwave occurs when sea surface and sub-surface temperatures remain much higher than usual for extended periods. This disrupts marine life and oceanic processes. The current Mediterranean heatwave is the most intense on record with sea surface temperatures six standard deviations above average.
Causes of the Mediterranean Heatwave
The main cause is a heat dome—a large high-pressure system causing sinking air and increased temperatures. This reduces wind and water mixing, trapping heat in the sea. The Mediterranean heat dome is linked to a broader high-pressure ridge over the Atlantic. Climate change likely strengthens these heat domes by altering atmospheric circulation and reducing aerosol cooling.
Impacts on Marine Ecosystems
Rising sea temperatures harm marine biodiversity and fisheries. The western Mediterranean, including the Balearic and Tyrrhenian Seas, is most affected. Studies show marine heatwaves have tripled in frequency and last 50 percent longer in the last 40 years. Mass mortality events have devastated marine habitats along thousands of kilometres of coastline.
Effects on Weather Patterns
Warmer seas increase atmospheric moisture, raising dew points and fuel for storms. This can intensify rainfall and lead to catastrophic floods and landslides in coastal and mountainous areas. Past events, such as the deadly floods in Spain in 2024, demonstrate the human cost of such extreme weather amplified by warm seas.
Future Risks and Monitoring
The Mediterranean heatwave is expected to worsen as summer progresses. Continuous monitoring is essential to predict autumn rainfall and storm severity. The interaction between marine and atmospheric heatwaves magnifies risks to ecosystems, economies, and communities dependent on the Mediterranean region.
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