Floe-scale ridging in discrete element models for sea ice
Anders Damsgaard(1,2), Olga V. Sergienko(1), Alistair Adcroft(1)
1: Program in Atmospheric and Oceanic Sciences, Princeton University, New Jersey, USA
2: Department of Geoscience, Aarhus University, Aarhus, Denmark
Ridging and rafting through compression and shear increase the thickness and therefore also the melt resilience of sea-ice packs. Present formulations for these mechanisms assume that ice strength is solely governed by ice thickness, and generally treat the ice pack as a continuum where each cell in the spatial discretization includes many individual ice floes. Particle-based sea ice models with granular interactions generally represent the ice on a floe-by-floe basis, meaning that new formulations are required for including ridging. We show through small-scale, high-resolution Discrete Element Method simulations that floe-floe compression encompasses different deformational modes, where elasticity transitions to frictional sliding and resultant strain weakening at the onset of ridging. We present a generalized formulation based on elasticity and Coulomb friction which is suitable for simulating the contact mechanics of ridging in particle-based sea ice models. On a larger scale, this results in ice-pack dynamics prone to stick-slip, strain localization, and limited compressional resistance.
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