Snow in the sea ice system: friend or foe?

Snow is a crucial and integral component of the sea ice system. It insulates the ice to retard the rate of thermodynamic ice thickening. At the same time, it contributes directly to sea-ice thickening through snow-ice formation, which can occur where the weight of the snow overburden leads to surface flooding. Snow has unique optical properties that reduce the amount of light penetrating to the underlying ice and ocean water, while raising the albedo of the ice in a way that retards melting. Seals also rely on snow drifts on the ice for denning purposes, and snow presence and quality affect human travel across the ice. Moreover, the snow significantly modifies the visual and microwave signals of sea ice in remote sensing. Here, we review the properties of sea ice snow cover and ramifications of that cover for the sea ice system.