Thermal Convection in Polar Ice Sheets Related to the Various Empirical Flow Laws of Ice

Abstract

Summary A more detailed analysis of the original application of thermal convection theory to polar ice sheets is made. This analysis considers the empirical flow laws of ice for a wide range of stress and temperature. A polynomial flow law based on theoretical creep models gives the best representation of thermal stresses driving convection in polar ice sheets. The flow law also predicts ice viscosities which decrease rapidly with depth, and leads to supercritical Rayleigh numbers for the central portions of the Antarctic ice sheet. Ascending convection flow is visualized as confined to narrow, mushrooming diapirs perhaps regularly dispersed throughout the central portions of the ice sheet. Oriented crystal fabrics defining these diapirs may weaken from the centre toward the edge of the ice sheet; nevertheless the presence of diapirs should be detectable seismically by the vertical alignment of glide planes within them.