Polynyas in a high‐resolution dynamic–thermodynamic sea ice model and their parameterization using flux models |
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| Authors: | H BJORNSSON A J WILLMOTT L A MYSAK M A MORALES MAQUEDA |
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| Institution: | Program in Atmospheric and Ocean Sciences, GFDL, Princeton University, New Jersey, USA;;Department of Mathematics, Keele University, Staffordshire ST5 5BG, UK;;Department of Atmospheric and Oceanic Sciences and Centre for Climate and Global Change, McGill University, Montreal, QC H3A 2K6, Canada;;Potsdam Institute for Climate Impact Research, PO Box 60 12 03 14412 Potsdam, Germany |
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| Abstract: | This paper presents an analysis of the solutions for a steady state latent heat polynya generated by an applied wind stress acting over a semi‐enclosed channel using: (a) a dynamic–thermodynamic sea ice model, and (b) a steady state flux model. We examine what processes in the sea ice model are responsible for the maintenance of the polynya and how sensitive the results are to the choice of rheological parameters. We find that when the ice is driven onshore by an applied wind stress, a consolidated ice pack forms downwind of a zone of strong convergence in the ice velocities. The build‐up of internal stresses within the consolidated ice pack becomes a crucial factor in the formation of this zone and results in a distinct polynya edge. Furthermore, within the ice pack the across‐channel ice velocity varies with the across‐channel distance. It is demonstrated that provided this velocity is well represented, the steady state polynya flux model solutions are in close agreement with those of the sea ice model. Experiments with the sea ice model also show that the polynya shape and area are insensitive to (a) the sea ice rheology; (b) the imposition of either free‐ slip or no‐slip boundary conditions. These findings are used in the development of a simplified model of the consolidated ice pack dynamics, the output of which is then compared with the sea ice model results. Finally, we discuss the relevance of this study for the modelling of the North Water Polynya in northern Baffin Bay. |
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