Simulating iceberg drift within sea ice in the Greenland Sea and Barents Sea

Icebergs drifting within sea ice represent a serious hazard to Arctic maritime activities, yet predicting their drift remains highly uncertain. We show that sea ice governs the drift of five icebergs in the Greenland Sea (IB-I to III) and Barents Sea (IB-IV, V) between 2012 and 2025. Those icebergs were either locked in the sea ice drift or were dragged by a combination of sea ice, water and wind. We investigate the simulation error by ocean and sea ice input data and the model formulation of the used Lagrangian iceberg drift model. The error is quantified as the difference between simulated and observed drift distance and direction, and it varies across cases and environmental conditions, with low errors for IB-I and IB-IV and high errors for IB-II and IB-III. A new sea ice drag formulation substantially reduces these large errors, particularly for trajectories in regions with high sea ice concentration. This formulation enables the small Arctic icebergs to follow the sea ice motion more realistically, either through a lowered lock-in concentration threshold of 0.7 or by applying a sea ice concentration dependent drag coefficient. Contributing to the overall simulation error, differences in the ocean and sea ice input led to substantial simulation spread of 0 . 2 to 1 . 5 × the observed drift distance and 13 to 8 5 ∘ drift direction. Parts of this error originate from the input sea ice concentration fields, which, though consistent with operational sea ice charts, show a slight positive bias from local observations. • Sea ice drags or locks in iceberg and is thus essential in iceberg drift simulations. • The drag by sea ice accounts for large parts of the iceberg drift distance. • Uncertain ocean and sea ice input cause large spread in the iceberg simulations. • The simulation error is decreased by a modified sea-ice-drag-equation.