Transport properties of fast ice within the nearshore

Abstract

Fast ice affects many coastlines in high- and mid-latitude regions, shaping the coastal morphology by acting as both a protective barrier from winter storms and as an erosive agent through sediment entrainment and transport. It has been hypothesized that when sediment-rich ice is dislodged and transported beyond the depth of closure by storm waves, sediment is permanently removed from the nearshore, starving the littoral system and facilitating future erosion. However, despite this large potential impact on coastal sediment budgets, the rates and mechanisms of sediment-rich ice transport are poorly constrained. This study investigates the sediment entrainment process by fast ice, the mechanisms needed for ice mobilization, and the force needed to breakup and transport sediment-rich ice. We find that the Coulomb frictional strength of the sediment regulates the fast ice system and that the viscous rheology of the ice has no direct mechanical effect. Importantly, these results show that only the frictional coefficient of the beach sediment needs to be measured to estimate the resistive strength of the fast ice, significantly simplifying the requirements for evaluating the potential for fast ice mobilization and associated sediment transport. • Investigations on sediment entrainment and mobilization processes for fast ice. • Experiments reveal the force needed to breakup and transport sediment-rich ice. • The frictional strength of the sediment, not ice, regulates the fast ice system. • Blocks of ice with adhered sediment can be treated as a Coulomb material.