Coupled Atmosphere-Ice-Ocean Models

As described in Section 19.2.3.8, regional models, such as a Baltic Sea model, can get the boundary values for the calculation of surface fluxes from simulations with atmosphere models, which have been carried out previously. This is possible, because the influence of the Baltic Sea on the Northern Hemisphere weather system is only important for local phenomena, and inaccuracy in the feedback from the Baltic Sea to the atmosphere is of minor importance, Schrumm and Backhaus (1999). Widely used datasets, such as the ERA-40 reanalysis data, are improved by assimilation of observations. If surface variables calculated by the ocean model tend to drift away, this is compensated to a large extent by the calculated surface fluxes. For this reason numerical simulations with standalone ocean-ice models can be successful. 

However, such an approach decreases the predictive capability and Emits the value for hindcasting of the regional climate of the last centuries. For this purpose atmosphere, ice, and ocean state variables must be simulated jointly, because they require each other mutually for the calculation of surface fluxes. This can be accomplished by coupled atmosphere-ice-ocean simulations, supplemented by a land model to compute the runoff of rivers from the Baltic catchment area. Such coupled model configurations are under development and have been applied for case studies (see Lehmann et al., 2004 Kjellstrom et al., 2005). 

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Schrum, C., Hiibner, U., Jacob, D., Podzun, R., 2003. A coupled atmosphere/ice/ocean model for the North Sea and the Baltic Sea. Climate Dynamics, 21, 131-151. 

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