Ocean Dynamics

, Volume 63, Issue 8, pp 901–921 | Cite as

The future of the western Baltic Sea: two possible scenarios

  • Ulf Gräwe
  • René Friedland
  • Hans Burchard


Globally coupled climate models are generally capable of reproducing the observed trends in the globally averaged atmospheric temperature. However, the global models do not perform as well on regional scales. Here, we present results from four 100-year, high-resolution ocean model experiments (resolution less than 1 km) for the western Baltic Sea. The forcing is taken from a regional atmospheric model and a regional ocean model, imbedded into two global greenhouse gas emission scenarios, A1B and B1, for the period of 2000 to 2100 with each two realisations. Two control runs from 1960 to 2000 are used for validation. For both scenarios, the results show a warming with an increase of 0.5–2.5 K at the sea surface and 0.7–2.8 K below 40 m. The simulations further indicate a decrease in salinity by 1.5–2 practical salinity units. The increase in water temperature leads to a prolongation of heat waves based on present-day thresholds. This amounts to a doubling or even tripling of the heat wave duration. The simulations show a decrease in inflow events (barotropic/baroclinic), which will affect the deepwater generation and ventilation of the central Baltic Sea. The high spatial resolution allows us to diagnose the inflow events and the mechanism that will cause future changes. The reduction in barotropic inflow events correlates well with the increase in westerly winds. The changes in the baroclinic inflows can be consistently explained by the reduction of calm wind periods and thus a weakening of the necessary stratification in the western Baltic Sea and the Danish Straits.


Regional ocean models Climate change Baltic Sea Baltic inflow 



The Baltic Monitoring Programme (COMBINE) and the stations of the German Marine Monitoring Network (MARNET) in the Baltic Sea are conducted by the Leibniz Institute for Baltic Sea Research Warnemünde (IOW) on behalf of the Bundesamt für Seeschifffahrt and Hydrographie, financed by the Bundesministerium für Verkehr, Bau-und Wohnungswesen. Supercomputing power was provided by “The North-German Supercomputing Alliance”. This work was supported by the Bundesministerium für Bildung, Wissenschaft, Forschung und Technologie (BMBF) of Germany in the project RA:dOst through grant number 01LR0807B. We are grateful to Karsten Bolding (Asperup, Denmark) for the code maintenance of GETM.


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© Springer-Verlag Berlin Heidelberg 2013

Authors and Affiliations

  1. 1.Department of Physical Oceanography and InstrumentationLeibniz Institute for Baltic Sea ResearchWarnemündeGermany

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