Numerical investigations of future ice conditions in the Baltic Sea

Global climate change is expected to have an effect on the physical and eco logical characteristics of the Baltic Sea. Estimates of future climate on t he regional scale can be obtained by using either statistical or dynamical downscaling methods of global AOGCM scenario results. In this paper, we use 2 different coupled ice-ocean models of the Baltic Sea to simulate present and future ice conditions around 100 years from present. Two 10-year time slice experiments have been performed using the results of atmospheric clim ate model simulations as forcing, one representing pre-industrial climate c onditions (control simulation), and the other global warming with a 150% in crease in CO2 greenhouse gas concentration (scenario simulation). Present-d ay climatological ice conditions and interannual variability are realistica lly reproduced by the models. The simulated range of the maximum annual ice extent in the Baltic in both models together is 180 to 420.10(3) km(2) in the control simulation and 45 to 270.10(3) km(2) in the scenario simulation . The range of the maximum annual ice thickness is from 32 to 96 cm and fro m 11 to 60 cm in the control and scenario simulations, respectively. In con trast to earlier estimates, sea ice is still formed every winter in the Nor thern Bothnian Bay and in the most Eastern parts of the Gulf of Finland. Ov erall, the simulated changes of quantities such as ice extent and ice thick ness, as well as their interannual variations are relatively similar in bot h models, which is remarkable, because the 2 coupled ice-ocean model system s have been. developed independently. This increases the reliability of fut ure projections of ice conditions in the Baltic Sea.