A MODEL FOR THE INFLUENCE OF WIND AND OCEANIC CURRENTS ON THE SIZE OFA STEADY-STATE LATENT-HEAT COASTAL POLYNYA

This paper presents a model for determining the size and shape of a st eady-state latent heat coastal polynya in terms of the following free parameters: I) the frazil ice production rate (F); 2) the wind stress (tau); 3) the surface ocean velocity field (u); 4) the offshore consol idated thin ice transport (T); 5) the coastline shape; and 6) the inte rsection of the polynya ice edge with the coastline, all of which must be prescribed. Frazil ice trajectories are determined via the free-dr ift ice momentum balance. Analytical solutions for the polynya shape a re derived Tor a straight coastline in the special case when u, T, and tau are uniform in the alongshore direction and the rotation of the e arth is neglected. When the latter constraint is relaxed, an expressio n Tor the asymptotic uniform polynya width is obtained. An expression fur the alongshore adjustment length scale of the polynya associated w ith alongshore variations in the coastline shape, u, T. and tau is der ived. with rotation of the earth included. By considering a wedge-shap ed ocean domain in which the ocean velocity is nondivergent and irrota tional it is demonstrated that (Ij a polynya solution doss not always exist and (ii) a point (S, say) can exist where the frazil ice and thi n ice transports are equal. When S exists, all possible polynya ice ed ge curves will pass through this point. The model is applied to simula te the wind-driven polynya that sometimes forms off the northern Green land coast during winter and early spring between the Henrik Kroyer Is lands and the Ob Bank Because of fundamental couplings between the fre e parameters listed above, one should be cautious in drawing inference s on the physical behavior of the polynya. However, the model is usefu l in revealing the sensitivity of the polynya to variations in the pre scribed forcing fields.