The Effects of Ice Floe‐Floe Interactions on Pressure Ridging in Sea Ice

The mechanical interactions between ice floes in the polar sea‐ice packs play an important role in the state and predictability of the sea‐ice cover. We use a Lagrangian‐based numerical model to investigate such floe‐floe interactions. Our simulations show that elastic and reversible deformation offers significant resistance to compression before ice floes yield with brittle failure. Compressional strength dramatically decreases once pressure ridges start to form, which implies that thicker sea ice is not necessarily stronger than thinner ice. The mechanical transition is not accounted for in most current sea‐ice models that describe ice strength by thickness alone. We propose a parameterization that describes failure mechanics from fracture toughness and Coulomb sliding, improving the representation of ridge building dynamics in particle‐based and continuum sea‐ice models. Plain Language Summary Considerable areas of the polar oceans are covered by sea ice, formed by frozen sea water. The extent and thickness of the ice pack influences local and regional ecology and climate. The ice thickness is particularly important for the ice‐cover survival during warm summers. Wind and ocean currents compress and shear the sea ice, and can break and stack ice into ridges. Current sea ice models assume that the ice becomes increasingly rigid as ridges of ice rubble grow. Modeling sea ice as bonded particles, we show that ice becomes significantly weaker right after the onset of ridge building. We introduce a mathematical framework that allows these physical processes to be included in large‐scale models. Key Points Ice elasticity can provide large resistance during early compression of sea‐ice floes Sea‐ice deformation becomes spatially localized at the onset of ridging due to contact weakening We develop a mathematical framework for simulating the observed sea‐ice ridging in large‐scale sea‐ice models