Anders Damsgaard, Alistair Adcroft, Olga Sergienko

Lagrangian models of sea-ice dynamics have several advantages over Eulerian continuum models. Spatial discretization on the ice-floe scale are natural for Lagrangian models and offer exact solutions for mechanical non-linearities with arbitrary sea-ice concentrations. This allows for improved model performance in ice-marginal zones. Furthermore, Lagrangian models can explicitly simulate jamming processes such as sea ice movement through narrow confinements. Granular jamming is a chaotic process that occurs when the right grains arrive at the right place at the right time, and the jamming likelihood over time can be described by a probabilistic model. While difficult to parameterize in continuum formulations, jamming emerges spontaneously in dense granular systems simulated in a Lagrangian framework. Here, we present a flexible discrete-element framework for approximating Lagrangian sea-ice mechanics at the ice-floe scale, forced by ocean and atmosphere velocity fields. Our goal is to evaluate the potential of simpler models than the traditional discrete-element methods for granular dynamics. We demonstrate that frictionless contact models based on compressive stiffness alone are unlikely to produce jamming, and describe two different approaches based on Coulomb-friction and cohesion which both result in increased bulk shear strength of the granular assemblage. The frictionless but cohesive contact model displays jamming behavior which is similar to the more complex model with Coulomb friction and ice-floe rotation at larger scales, and has significantly lower computational cost.