How does the climate in the Baltic Sea vary now and in the future?

How has the climate in the Baltic Sea varied over the past 150 years? How will it develop up to the year 2100? A new research project will analyse how the climate in the Baltic Sea has varied since 1850 and simulate future scenarios for the Baltic Sea.

There is insufficient knowledge on how climate changes affect the marine environment, even though studies show that a changed climate could have a major impact on the marine ecosystem. It is feared that problems with eutrophication which lead to increased algal blooms and oxygen-poor sea beds could become worse in a warmer, wetter climate.

“Recreating historic climate and environmental developments in the Baltic Sea provides us with knowledge so that we can better understand possible future developments. We need improved sea models to support the work on environmental measures in the Baltic Sea,” says Markus Meier, an oceanography scientist at SMHI.

Marine environments have a ‘long memory’, as it can take up to 40 years for nutrients to be transported through the sediments and out into the sea. This means that the effect of a reduction in the amount of nutrients added to the ocean is delayed.

“We do not currently have models that can reliably recreate historically observed eutrophication and increased algal blooms,” says Markus Meier.

To have an effective decision-support system for measures to counter eutrophication, projection models which take into account the ‘long memory’ are needed to avoid making measures time-restricted and thereby not improving the marine ecosystem in the longer term.

Data from lightships and future scenarios

Measurements were taken by the lightship Finngrundet over various periods between 1860 and 1969.  Ph
Measurements were taken by the lightship Finngrundet over various periods between 1860 and 1969. Photo: The Maritime Museum Foto Sjöhistoriska museet

In order to acquire better knowledge of how climate changes affect the marine ecosystem, scientists from SMHI will carry out a three-year project which begins by analysing data from Swedish lightships. The data have been collected from the mid-19th century onwards and have just recently become digitally available.
Projections will be carried out using a fine-scale three-dimensional ocean model which takes account of both physical and bio-geochemical properties, and model experiments will be used to examine how changes in the atmosphere and water flows affect the Baltic Sea’s ecosystem and oceanography.

Finally, simulations will be carried out for the whole period 1850-2100. This will increase knowledge about changes in the ocean environment and the importance of altered temperature, salt level and circulation conditions, and the probable increased significance of human impact on the future marine environment.

The project to reconstruct and predict future scenarios for the Baltic Sea’s climate variations for 1850-2100 will be carried out by scientists from SMHI and be funded by the Swedish Research Council. The project will run 2013-2015.