Sea ice concentration and motion assimilation in a sea ice−ocean model

Abstract

A sea ice concentration and motion assimilation scheme has been developed using the Met Office Forecasting Ocean Assimilation Model (FOAM). FOAM has been upgraded to include a more realistic sea ice rheology and a sea ice thickness distribution. The sea ice data assimilation scheme uses Special Sensor Microwave Imager (SSMI) and QuikSCAT satellite observations to provide ice concentration and motion. A number of 1‐year test integrations have been undertaken, and the resulting sea ice analysis has been examined in detail. The assimilation is able to significantly reduce the model sea ice concentration error and is able to address the model biases. Owing to the faster response times of the elastic‐viscous‐plastic (EVP) sea ice rheology in the model compared to the viscous‐plastic used in previous studies, a novel approach to sea ice motion assimilation using increments to the ice stress has been developed. The sea ice motion assimilation scheme is able to reduce the model sea ice velocity errors by approximately 50% when compared to independent data. Ice velocity assimilation was found to have little impact on the ice concentration, and ice concentration assimilation is found to have little impact on ice velocities. This implies that ice concentrations are primarily thermodynamically controlled and ice velocities are primarily dynamically driven. During the summer, model biases and poor‐quality observations impair the performance of the assimilation.