Modeling the Influence of Grounded Landfast Ice on Nearshore Sediment Transport

Grounded landfast ice is common along mid to high latitude coasts in the northern hemisphere, but its geomorphic impact is poorly understood due to a lack of targeted studies and conflicting observations of ice as both a protective and erosive feature. Uncertainty in the net impact of grounded landfast ice on sediment budgets may lead to inaccurate predictions of how these cold coasts will evolve, especially in response to changing climate. Previous field studies lack a systematic assessment of ice's role in sediment transport and the variables that influence it. This study applied a physics-based coastal model, XBeach, to simulate ice-induced hydrodynamic scour for varying ice extents, wave conditions, and nearshore slopes. Results showed a nonmonotonic response of sediment transport to ice grounding depth that explains previous discrepancies related to the role of ice in coastal erosion. Grounded ice presence displaced the focus of erosion offshore in all simulations, and increased sediment transport compared to no-ice runs for nearshore slopes of 0.001, 0.01 and 0.02. Geomorphic changes persisted through subsequent wave activity after the ice was removed. This study puts forth the first systematic examination of the role of ice-induced hydrodynamics on nearshore erosion, which facilitates the prediction of coastal evolution associated with changing ice conditions.