Climate change increases eutrophication in the Baltic Sea

Model projections of the Baltic Sea show that changes will occur in the marine environment in a future climate. Nutrient load reductions to the Baltic Sea are of even higher importance in a warmer climate. A modeling tool has been developed to support decision making.

New climate-change scenarios for the Baltic Sea show that the water temperature will increase and the salinity will decrease. Warmer water changes the oxygen saturation concentrations and turnover rates of biogeochemical processes, enhancing the eutrophication effects.

This means increased bottom areas with missing higher forms of life due to too low oxygen levels, so-called hypoxic areas, reduced biodiversity and increased risk for acidification.

These are the findings in research project ECOSUPPORT, where a multi-model system tool has been developed to assess the combined effect of climate change and nutrient loads to the Baltic Sea. The tool is intended to support decision makers in assessing the human-induced impact of the state of the marine environment.

Examples of changed oxygen saturation concentrations at sea bottom areas, with today´s climate compared to future climate. The maps are based on different nutrients loads. Left map with today´s nutrient load, middle map reduced nutrient loads, and right map highly increased nutrient loads.

Nutrient load reductions necessary

“Nutrient load reductions to the Baltic Sea are of even higher importance in a warmer climate. To keep water quality targets set in the HELCOM Baltic Sea Action Plan in the future, the results indicate that even further load reductions are necessary” says Helén Andersson, oceanographic researcher.

The new advanced modeling tool produces scenario simulations of the whole marine ecosystem that can underpin and inform design strategies to ensure water quality standards, biodiversity and fish stocks.

A large database of climate and environmental model data and observations that describe past and future climates of the Baltic Sea region will be publicly available. The database can be used for policymaking concerning a Baltic Sea unaffected by eutrophication and the adaptation to climate change.