A Minimal Bonded Discrete Element Model for Sea Ice Breakup

Abstract. Current climate models simulate sea ice as a continuous medium despite the inherent discontinuities at the scale of individual floes. Discrete element models (DEMs) can directly represent these discontinuities, making them valuable tools for understanding subgrid-scale sea ice dynamics. However, DEMs are typically limited by their high computational cost and large parameter spaces, which hinder their validation and interpretability. In this work, we developed, calibrated, and evaluated the performance of a low-complexity, two-dimensional bonded DEM for process-based studies of ice flow and fracture. We modified the linear bonded particle model implemented in the molecular dynamics software, LAMMPS (Large-Scale Molecular Massively Parallel Simulator), to prevent failure in compression because undamaged sea ice is significantly stronger under compression than tension. Through an ensemble of simple shear experiments, we related the effective elastic modulus and shear strength to the bond stiffness, critical strain, and particle size. We further observed that the simulated ice deformation was localized in space and intermittent in time, in agreement with observations. Using a canonical geometry idealizing sea ice flow through the Nares Strait, we demonstrated that the model could reproduce ice arch formation and collapse previously observed in this region and reproduced in higher-complexity models. We found that our model could represent four possible regimes: no fracturing, stable ice arch formation, the formation of an ice arch that subsequently collapses, and the absence of an ice arch buttressing flow through the channel. These regimes collapsed onto a single control parameter given by the product of bond stiffness and critical strain. In summary, this low-complexity DEM offers a computationally efficient framework for evaluating short-timescale, discrete sea ice processes, which may be used in conjunction with more comprehensive models to better understand key ice deformation processes.