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Annu Oikkonen University of Helsinki Mesoscale dynamic- thermodynamic modelling of sea ice Supervisor Prof. Matti Leppranta Slide 2 Mesoscale dynamic-thermodynamic modelling of sea ice The coupling of dynamics and thermodynamics is very important in regional and global climate research for ice climatology, air sea fluxes and ecology of ice- covered seas, and also in short term questions for forecasting of ice drift, ice loads, and transport and dispersion of pollutants, in particular oil spills. The project aims at developing a next generation dynamic-thermodynamic mesoscale (100 km) sea ice model with established scaling laws from the floe size scales to basin scales. The problems to be investigated are the mechanical behaviour of ice in different scales, iceocean interaction, and ice thickness redistribution. The key feature in the scaling is a proper understanding of the rheology of sea ice and its dependence of ice thickness, compactness and state of motion. Also downscaling of the ice stress into the inside-floe scales will be considered Slide 3 The Baltic Sea is the main study region. The product of the project will be used for basic research in earth and environmental sciences, ice engineering applications for scaling of the stresses, short-term ice forecasting of oil spills, and in regional ice climate research. Also the findings of the project may be utilised in developing the sea ice code in global climate models. I concentrate on ice - ocean interaction, that is presently oversimplified in mesoscale models and a more advanced treatment is needed Both field work and modelling Slide 4 R.V. Aranda in the Bothnian Bay, 1.-12.3.2009 Slide 5 Turbulence measurements of velocity (8 Hz), salinity and temperature (1 Hz) CTD profiles ADCP current profiling (0-10 m) Ice drift from Aranda GPS Slide 6 In S3 ice drift was very close to free drift: - Deviating right from the wind direction, drift speed 1-2% of wind speed Ice drift in Station 2 and 3 Slide 7 Aranda drift Drifting buoys in the Sea of Okhotsk, Japan Ice velocity spectrum In the Baltic Sea synoptic time scales dominating Tidal and inertial signals significant in the oceans Slide 8 Thank you!