A robust and computationally efficient model of a two-dimensional coastal polynya

A two-dimensional polynya model incorporating a new computationally efficient parameterisation for the collection thickness of frazil ice at the polynya edge, H, is presented. The new parameterisation is designed to overcome the lack of robustness associated with the parameterisation of [Biggs, N.R.T., Morales Maqueda, M.A., Willmott, A.J. 2000. Polynya flux model solutions incorporating a parameterisation for the collection thickness of consolidated new ice. J. Fluid. Mech. 408, 179–204], in which H depends on the relative orientation of the polynya edge with respect to the flow of ice. As a result of this dependence, steady state polynya edge solutions exist that support seemingly unrealistic corners and that cannot be attained by evolving the polynya equations from an initial state in which the polynya is closed. The new parameterisation, removes the dependence of H on the orientation of the polynya edge by averaging the collection thickness of Biggs et al. (2000) along the polynya edge over length scales much smaller than the length of the polynya edge but much larger than the diameter of individual ice floes. The new parameterisation is robust in that steady state two-dimensional polynya solutions can now always be attained starting from a closed polynya state.