Energy exchange during river icing formation in a subarctic environment, Yukon Territory

Icings are common hydrologic phenomena in cold subarctic environments. They are formed by the accumulation of repeated overflow layers during winter. The size and thickness of the icing layers, however, are determined by the interaction of surface water hydrologic and microclimatologic systems. This paper examines the energy exchanges associated with icing layers with diff erent thicknesses. In the case of thick layers of overflow, ice layers requ ire a longer time to freeze completely due to greater latent heat stored in larger water volumes. Milder air temperatures will slow growth even furthe r. Under such conditions, flowing water between the top ice cover and the u nderlying ice body provides significant amounts of energy. As much as 60 - 87 % of the energy may be supplied by running water, Under progressively co lder temperature conditions, faster growth rates reduce the time of water f low and, therefore, reducing the relative amount of energy supplied by flow ing water. In this case energy is provided mainly by the latent heat releas ed by the freezing of water contained in the overflow layer. Under certain conditions, the absorption of solar radiation also generates a considerable amount of energy input to the regime. This energy is released mostly throu gh sensible and radiative heat losses. During icing layer formation, latent heat is the least important, accounting for only 6 - 17 % of the total hea t loss.