Improving the simulation of landfast ice by combining tensile strength and a parameterization for grounded ridges

In some coastal regions of the Arctic Ocean, grounded ice ridges contribute to stabilizing and maintaining a landfast ice cover. Recently, a grounding scheme representing this effect on sea ice dynamics was introduced and tested in a viscous‐plastic sea ice model. This grounding scheme, based on a basal stress parameterization, improves the simulation of landfast ice in many regions such as in the East Siberian Sea, the Laptev Sea, and along the coast of Alaska. Nevertheless, in some regions like the Kara Sea, the area of landfast ice is systematically underestimated. This indicates that another mechanism such as ice arching is at play for maintaining the ice cover fast. To address this problem, the combination of the basal stress parameterization and tensile strength is investigated using a 0.25° Pan‐Arctic CICE‐NEMO configuration. Both uniaxial and isotropic tensile strengths notably improve the simulation of landfast ice in the Kara Sea but also in the Laptev Sea. However, the simulated landfast ice season for the Kara Sea is too short compared to observations. This is especially obvious for the onset of the landfast ice season which systematically occurs later in the model and with a slower build up. This suggests that improvements to the sea ice thermodynamics could reduce these discrepancies with the data. Key Points A grounding scheme is not enough to simulate landfast ice in Pan‐Arctic simulations Both uniaxial and isotropic tensile strengths notably improve the simulation of landfast ice in deep coastal regions Simulated landfast ice season in the Kara Sea is still too short suggesting that thermodynamics should be improved