A model for the closure of a two-dimensional coastal latent heat polynya

Abstract

This paper presents a numerical model for the closure of a two-dimensional island polynya, assuming that the pile-up depth H of consolidated new ice at the polynya edge (during opening) and at the coast (during closing) is constant. The polynya closing time T is found to be relatively insensitive to ice drift orientation, and the quotient | U |/| u | , where u and U are the frazil and consolidated ice velocities, respectively. Also, T is weakly dependent on the island length D, except when both the onset of closure occurs significantly before the opening polynya steady-state is reached, and also D≲ L a, the alongshore adjustment length scale. However, T is found to be sensitive to F/ F o, where F and F o are the constant frazil ice production rates during polynya closing and opening, respectively. We exploit the parameter dependence of T as a function of F, F o, D, u , U and H to derive an approximate expression for the closing time that is accurate to within ∼8%, assuming that the polynya closes from an initial area that is close to its steady-state area.