Impact of non-normal flow rule on linear kinematic features in pan-Arctic ice-ocean simulations

Abstract. One important conclusion of the Sea Ice Rheology Experiment (SIREx) is that continuum based sea ice models, with different spatial discretizations and/or sea ice rheologies, all simulate intersection angles between linear kinematic features (LKFs) that are too wide compared to observations. The peak of the probability density function (PDF) of simulated intersection angles is around 90° while the PDF for observed angles rather exhibits a peak around 45°. Ringeisen et al. 2021 proposed to remedy this issue for viscous-plastic (VP) and elastic-VP (EVP) models by introducing a non-normal flow rule specified by a plastic potential. We implemented the plastic potential approach of Ringeisen et al. 2021 in the CICE sea ice model. In pan-Arctic simulations, the non-normal flow rule also leads to a peak of the PDF around 90°. We show that this peak at 90° is at least partly a consequence of many LKFs that are aligned with the computational grid. Nevertheless, the non-normal flow rule brings an interesting capability: it could be used to independently optimize simulated LKFs and more generally deformations while parameters defining the yield curve could serve for modifying simulated landfast ice and to a lesser extent sea ice drift.