The Cryosphere Discussions www.the-cryosphere-discuss.net 1994-0432 1994-0440 3 3 2009 10.5194/tcd-3-1023-2009 http://www.the-cryosphere-discuss.net/3/1023/2009/ http://www.the-cryosphere-discuss.net/3/1023/2009/tcd-3-1023-2009.html http://www.the-cryosphere-discuss.net/3/1023/2009/tcd-3-1023-2009.pdf 1023 1068 2009-11-24 Polynyas in a dynamic-thermodynamic sea-ice model E. Ö. Ólason einar.olason@zmaw.de I. Harms Centre for Marine and Atmospheric Research, Institute of Oceanography, University of Hamburg, Hamburg, Germany The response of a viscous-plastic dynamic-thermodynamic sea-ice model to a constant wind forcing is tested in an idealised setting. Bjornsson et al. (2001) have shown that the granular model of Tremblay and Mysak (1997) gives good results in such a set-up compared to a polynya flux model. Here it is shown that these results can be duplicated using the computationally more efficient elliptic yield curve approach by Hibler (1979) and modified Coulombic yield curve by Hibler and Schulson (2000). Some care is, however, required regarding the parametrisations of the ellipse. In addition it is shown that the new ice thickness formulation of Mellor and Kantha (1989) does not allow for proper polynya formation in the bay. In contrast the new ice thickness formulation of Hibler (1979) is found to give good results. Finally we propose a parametrisation of the ice demarcation thickness (<i>h</i><sub>0</sub>) in Hibler's formulation, based on wind speed and ice thickness. Backhaus,~J.: Improved representation of topographic effects by a~vertical adaptive grid in vector-ocean-model (VOM). Part I: Generation of adaptive grids, Ocean Model., 22, 114–127, \doi10.1016/j.ocemod.2008.02.003, 2008. 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