The steady drift of an incompressible Arctic ice cover

The steady drift of pack ice in an idealized arctic basin has been calculated by assuming that the ice is incompressible and inviscid. The momentum and continuity equations for the ice are solved for the velocity and the ice pressure. The divergence of velocity is assumed to be 0.33×10−8 s−1. The boundary conditions require that no ice flows across coastal boundaries but that ice flows out of the basin into the Greenland Sea and into the basin from the Kara Sea. The patterns of calculated velocities and vorticities are realistic, but their magnitudes are too high. The maximum calculated ice pressure of about 108 dyn cm−1 (pressure integrated through the ice thickness) is marginally able to ridge thick ice, according to the ridging model of Parmerter and Coon (1973). These maximum values occur near Greenland, where Wittmann and Schule (1966) report intense ridging. When the wind stress is reduced to one third of the strength first assumed, realistic speeds and vorticities are obtained, and the maximum pressures are reduced to one third of the above value. Coastal shear zones of the order of 100 km wide can be represented by the added assumption of a shear viscosity of about 6×1012 g s−1 and a no-slip condition on coastal boundaries.