The Impact of Tides on Simulated Landfast Ice in a Pan‐Arctic Ice‐Ocean Model

The impact of tides on the simulated landfast ice cover is investigated. Pan‐Arctic simulations are conducted with an ice‐ocean (CICE‐NEMO) model with a modified rheology and a grounding scheme. The reference experiment (without tides) indicates there is an overestimation of the extent of landfast ice in regions of strong tides such as the Gulf of Boothia, Prince Regent Inlet and Lancaster Sound. The addition of tides in the simulation clearly leads to a decrease of the extent of landfast ice in some tidally active regions. This numerical experiment with tides is more in line with observations of landfast ice in all the regions studied. Thermodynamics and changes in grounding cannot explain the lower landfast ice area when tidal forcing is included. We rather demonstrate that this decrease in the landfast ice extent is dynamically driven by the increase of the ocean‐ice stress due to the tides. Plain Language Summary Landfast ice is sea ice that is immobile near a coast for a certain period of time. This coastal ice can stay at rest because it is attached to the coast and/or anchored to the sea floor in shallow water. To study landfast ice, we used a numerical model that represents the physical interactions between the atmosphere, the ocean and the sea ice. We compared two simulations done with this model: one without ocean tides and one that includes the tides. The experiment with tides exhibits a lower extent of landfast ice which is more in line with the observations. This decrease in the landfast ice extent when adding the tides is a dynamical process; the strong tidal currents constantly set the sea ice in motion, preventing it to become landfast.