Baltic Breakfast: Ocean warming – from global change to Baltic Sea impacts

On 21 October 2026, Ocean Community attended a breakfast seminar hosted by Stockholm University’s Baltic Sea Centre, bringing together perspectives on ocean warming at the global scale and its consequences for the Baltic Sea.

Professor Fabien Roquet from the University of Gothenburg and Norman Göbeler from Tvärminne Zoological Station at the University of Helsinki explored how rising temperatures are changing the ocean, from processes beneath the surface to the effects of marine heatwaves on regional ecosystems. The seminar was moderated by Gun Rudquist, Head of Policy at Stockholm University’s Baltic Sea Centre.

Beyond the Surface: Understanding a Warming Ocean

When we think about ocean warming, we often imagine rising temperatures at the surface. But much of the story takes place below it.

Fabien Roquet’s presentation offered a deeper look into the ocean and how warming affects its internal structure. One important process is stratification: the layering of water masses with different densities. As the ocean warms, these layers can change, influencing how heat, nutrients and oxygen move between the surface and deeper waters.

These processes matter far beyond temperature alone. Changes in stratification can influence ocean circulation and the conditions that marine organisms depend on. In regional seas such as the Baltic Sea, where oxygen availability and nutrient dynamics are already major environmental concerns, understanding what happens beneath the surface is essential to understanding the wider consequences of climate change.

The ocean is not simply warming from the top down. Its changing internal structure also shapes how marine environments respond to a changing climate.

When Heatwaves Reach the Baltic Sea

While ocean warming is a global phenomenon, its effects are experienced differently across regions. The Baltic Sea has warmed at approximately twice the rate of the global ocean average, making marine heatwaves an increasingly important part of the region’s changing climate.

Norman Göbeler’s presentation focused on marine heatwaves in the Baltic Sea and their effects on marine life.

The summer of 2018 stands out as a record-breaking heat event in the region, illustrating the intensity that extreme temperatures can reach.

Marine heatwaves are more than short periods of unusually warm water. Their ecological consequences depend on how high temperatures rise, how long they persist and how organisms respond to the additional stress. Extreme heat can affect marine species, disrupt ecological relationships and, under severe conditions, contribute to mortality events and sudden ecosystem changes.

In the Baltic Sea, these impacts occur alongside existing pressures such as eutrophication and oxygen depletion. Warming can interact with these challenges, making it important to understand not only individual stressors but also how they influence one another.

Looking at marine heatwaves therefore adds an important dimension to our understanding of ocean warming. Long-term temperature trends show how the climate is changing, while extreme events help reveal how marine ecosystems may respond to increasingly challenging conditions.

One Changing Ocean, Regional Consequences

The two presentations approached ocean warming from different perspectives: one explored the physical processes shaping the ocean beneath its surface, while the other examined the consequences of extreme temperatures for life in the Baltic Sea.

Together, they highlight why understanding ocean warming requires more than monitoring average surface temperatures. Changes in stratification, the distribution of heat and oxygen, and the frequency and intensity of marine heatwaves are all part of a broader picture of ecosystem change.

For the Baltic Sea, this knowledge is particularly relevant. Its fragile ecosystem is already under pressure from human activities, and climate change adds another layer of complexity. Understanding how these pressures interact is an important step towards more effective marine protection and informed decision-making.

But knowledge alone is not enough. Translating scientific understanding into practical solutions also requires collaboration between researchers, policymakers, industry, innovators and the wider community.

Where Do We Go Next as Ocean Community?

The challenges facing the Baltic Sea are interconnected, and addressing them requires different forms of expertise and action. Scientific research helps us understand what is changing, while innovation and collaboration can help turn that understanding into solutions.

This is one of the ideas behind Ocean Community’s Baltic Sea Challenge, launching in 2026. The initiative aims to bring together people and organisations working towards solutions for the Baltic Sea, supporting ecosystem resilience and the transformation towards a more sustainable blue economy.

Submission window opens November 25, 2026.

There are different ways to contribute. Whether you are developing a solution, offering scientific or professional expertise, helping bring visibility to promising initiatives, or providing resources and strategic support, your contribution can help connect knowledge with action.

Could you contribute to a healthier Baltic Sea?

Explore the Baltic Sea Challenge to discover how you can get involved as a Solution Builder, Solution Guide, Solution Champion or Solution Partner. The Baltic Sea’s future depends on our ability to understand its changing conditions and work together across disciplines and sectors. By connecting knowledge, people and solutions, we can help turn the challenges facing this unique ecosystem into opportunities for meaningful action.