Influence of the representation of landfast ice on the simulation of the Arctic sea ice and Arctic Ocean halocline

Landfast ice is near-motionless sea ice attached to the coast. Despite its potential for modifying sea ice and ocean properties, most state-of-the-art sea ice models poorly represent landfast ice. Here, we examine two crucial processes responsible for the formation and stabilization of landfast ice, namely sea ice tensile strength and seabed–ice keel interactions. We investigate the impact of these processes on the Arctic sea ice cover and halocline layer using the global coupled ocean–sea ice model NEMO-LIM3. We show that including seabed–ice keel stress improves the seasonality and spatial distribution of the landfast ice cover in the Laptev and East Siberian Seas. This improved landfast ice representation sets the position of flaw polynyas to new locations approximately above the continental shelf break. The impact of sea ice tensile strength on the stability of the Arctic halocline layer is far more effective. Incorporating this process in the model yields a thicker, more consolidated, and less mobile Arctic sea ice pack that further decouples the ocean and atmosphere. As a result, the available potential energy of the Arctic halocline is decreased (increased) by \(\sim \)30kJ/m\(^2\) (\(\sim \)30kJ/m\(^2\)) in the Amerasian (Eurasian) compared to the reference simulation excluding sea ice tensile strength and seabed–ice keel stress. Our findings highlight the need to better understand landfast ice physical processes conjointly with the subsequent influences on the ocean and sea ice states.