Huvudinnehåll

State of the ocean

Eutrophication, acidification, oxygen depletion, and marine heatwaves are some of the threats facing our oceans. SMHI’s researchers investigate how the marine environment around Sweden is changing and what society can do to ensure a vibrant and sustainable sea - now and in the future.

Research questions

Research

The sea surrounding Sweden is not in good condition. The Baltic Sea and the North Sea together form one of the most complex and vulnerable oceanographic regions in the world. Eutrophication, hazardous substances, and fishing have long affected the ecosystems. In addition, the sea is becoming increasingly warm as a result of climate change, which also influences marine life.

Calm as a mirror or churned by restless waves - the sea fascinates. We enjoy it and use it in many ways: for recreation, transport, commercial fishing, and other activities within the blue economy.

You are probably already aware that certain algal blooms are a consequence of eutrophication and can ruin a planned swim. Unfortunately, they can cause more serious problems. Some algae and cyanobacteria (formerly called blue-green algae) are toxic to varying degrees. And when they - and other algae - eventually die and sink to the seabed, large amounts of oxygen are consumed as they decompose. This leads to expanding oxygen-free bottoms, making it nearly impossible for plants and animals to survive. Today, areas of oxygen-depleted seafloor in the Baltic Sea are larger than ever.

There are, however, many types of algae, and they also contribute positively and are a vital part of the marine ecosystem. They form the base of the marine food web and serve as nourishment for many other sea-dwelling species. Through photosynthesis, algae also produce nearly half of all the oxygen on our planet.

Current Research for a Sustainable Sea

In SMHI’s research and development, we primarily work with the marine areas around Sweden: the Baltic Sea, the Kattegat/North Sea, and the Arctic Ocean, as well as the Southern Ocean.

When it comes to eutrophication and cyanobacterial blooms, we monitor how conditions in the sea are changing. This enables us, for example, to build warning systems for blooms that are intense enough to be harmful even to humans. In our models, we can also study how different emission reductions would affect the sea in the long term. But of course, we do much more than that.

Sea Levels, Extreme Weather, Crabs, eDNA Techniques, and Offshore Wind Power

Climate change is causing sea levels to rise. How will this affect Swedish ports, particularly when combined with extreme weather such as cloudbursts and storm winds? We explore this in one of our projects.

SMHI’s research also shows that climate change amplifies the effects of eutrophication in the Baltic Sea, and that climate change alone - by the end of the century - will affect marine habitats and ecosystems as much as all other environmental pressures combined.

We also investigate how these changes in marine habitats make it easier for invasive species to establish themselves in Swedish waters - for example, various crab species. This helps us minimize the negative impacts that invasive species can have on the marine environment. Studies of plankton biodiversity are conducted using eDNA techniques.

The Baltic Sea will become warmer in the future, and ice cover will be reduced. How its salinity will change is more uncertain, as a warmer world introduces changes that can both increase and decrease salinity.

We also conduct research on how offshore wind farms affect the marine environment.

Investigate how the marine environment will change in the future

To SMHI's climate scenario service

Models Show the Effects Before Important Decisions Are Made

Much of our oceanographic research on the marine environment takes place in front of our computers. One of our most important tools is the numerical modelling systems we develop. These are models that describe physical processes in the ocean - such as currents and variations in salinity, temperature, and ice cover - and biogeochemical processes that affect concentrations of nutrients, algae, and oxygen.

As our research increases our understanding, we update the models so they can provide more detailed answers to our questions about the sea. You can think of the models as our laboratory, where we input numerous values to study the effects of different scenarios. For example, we can examine how various policy decisions might influence the marine environment. This makes SMHI’s research an essential foundation for decisions being made today that will affect the marine environment far into the future.

There is potential to reduce the problems we have caused in the sea. Ocean warming is linked to climate change - and must be reduced in order to limit rising water temperatures. When it comes to cyanobacterial blooms and oxygen depletion in the Baltic Sea, it is important to continue reducing nutrient emissions. But the sea responds slowly.

Of the nutrient-reduction measures implemented in the 1980s, only small improvements can be seen - and only in coastal zones. In the open Baltic Sea, no improvements are yet visible. Our model results indicate that improvements in the open Baltic Sea will not appear until the end of this century - if we continue implementing eutrophication-reduction measures and succeed in limiting climate change.

If we see and understand what exists and happens beneath the surface, our ability to care for our remarkable sea increases.