AbstractRecent observations document a reduction in Arctic sea ice thickness [e.g. Rothrock et al., 1999; Wadhams and Davis, 2000; Perovich et al., 2003; Yu et al., 2004] and a decrease in its extent during the last two decades, especially in summer [e.g. Cavalieri et al., 2003; Serreze et al., 2003]. Climate scenario simulations with coupled atmosphere ocean general circulation models (AOGCMs) indicate an even more pronounced reduction in summertime Arctic sea ice thickness during the 21st century [e.g. Walsh and Timlin, 2003; ACIA, 2004]. An appropriate description of sea ice thickness and coverage in AOGCMs plays a key role in modelling latent and sensible heat fluxes over the Arctic Ocean where a most accurately characterised sea ice albedo is essential for computing the absorbed solar radiation over the ice-covered ocean. Due to positive albedo feedback effects small changes in absorbed solar radiation can excite large changes in sea ice thickness and coverage on a local scale as well as on up to whole Arctic scales.