A Nonlinear Steady-State Model of the North Water Polynya, Baffin Bay

Abstract

A nonlinear, steady-state model of the North Water (NOW), the Arctic's largest polynya, is presented. The model follows in the spirit of the recently developed latent and sensible heat polynya model of Mysak and Huang, but extends it in several important ways: finite amplitude displacements of the upper-layer thickness are allowed; the channel walls diverge to the south; the sensible-heat flux from the lower layer is physically well defined in terms of a vertical entrainment velocity; and the free-drifting frazil ice to the north of the NOW ice edge is allowed to move to the right of the northerly winds. An important result found here is that with the exception of late spring, the asymptotic southern ice edge position of the NOW can be simulated in terms of a latent heat model alone. In this case, the observed equatorward curvature of the ice edge in the region adjacent to the west Greenland coast can be produced by a combination of a channel that widens in the equatorward direction, together with free-drift frazil ice motion that is to the right of the northerly winds. However, in late spring, when the heat loss to the atmosphere is reduced, the sensible heat flux plays an important role in determining the position and shape of the ice edge, particularly in the region adjacent to the west Greenland coast.