Nonequilibrium thermodynamics of kinetic metamorphism in snow

A numerical model applied nonequilibrium thermodynamics to depth hoar formation at the grain scale. Entropy production rate relations were developed for an open system of ice and water vapor subjected to heat and mass flow. Heat conduction in the bonds had the highest specific entropy production rate, indicating it was the most inefficient part of the snow system at transferring heat. As the metamorphism advanced, the bond sizes grew to enhance the conduction pathways through the snow and increase the heat transfer. This spontaneous microstructural evolution moved the system and the surroundings toward equilibrium by reducing the local temperature gradients across the bonds and increasing the entropy production rate density.