High-Resolution Modelling of Landfast Ice Formation and Midseason Breakout on the Siberian Shelf

Abstract. Substantial amounts of landfast ice form over the Siberia shelf seas during winter. Under certain conditions, midseason break out may occur, affecting local ecology and human activities. This study employed a 2 km resolution coupled ocean-ice model incorporating a basal stress parameterization to simulate landfast ice in the Siberian Seas. The high- resolution model yields realistic simulations of landfast ice distribution in the Siberian Seas. The contribution of the grounding mechanism to landfast ice stability varies regionally and depends strongly on local geography. Grounded fast ice accounts for 56% of the total simulated landfast ice on the Siberia shelf, with the East Siberia Sea having the largest proportion (70%), followed by the Laptev Sea (54%) and the Kara Sea (41%). The simulated midseason breakout events primarily occurred along the outer edge of the landfast ice in the East Siberia Sea, where the basal stress was ineffective. Further analysis reveals that all the midseason breakouts were associated with the passage of cyclones, whose offshore winds fractured the landfast ice into floating ice.