Abstract

Friction of sea ice plays a fundamental role in a variety of geophysical and engineering scenarios. Examples include ridging and rafting, ice-induced loads on offshore structures and the physics of brittle compressive failure. In this paper attention is focused on the characteristics of static friction and frictional sliding of ice upon ice at velocities of around 0.1 m s-1 (~10 km/day) and lower, at homologous temperatures greater than around Th =0.85 (>-40 o C). The coefficients of both static and kinetic friction are described and then discussed in terms of the underlying physical processes. At root is creep deformation of asperities. Creep leads to an increase in contact area and thus to an increase in the coefficient of static friction with increasing time under load. Creep leads also to an increase in the coefficient of kinetic friction with increasing velocity at lower speeds. At higher speeds, localized melting of asperities sets in, via frictional heating, and this leads to a decrease in the kinetic coefficient with increasing velocity. Modeling indicates that the velocity that marks the transition scales as $V_t \propto a \Delta T^2$ where $a$ denotes asperity size and $\Delta T$, the difference in temperature between the melting point and the body of ice. Implications for sea ice mechanics are discussed.