Oil drift modeling in pack ice - Sensitivity to oil-in-ice parameters

An improved oil-in-ice parameterization has been implemented in the Seatrack Web oil spill model, tested using data from the Runner 4 oil spill accident, which occurred in high ice concentrations in the Gulf of Finland on 5 March 2006. The model is able to describe the observed transport and spreading of oil reasonably well. The sensitivity of the results towards oil-in-ice parameters and hydrodynamic forcing models has been investigated. Both the mean oil trajectory and the oil spreading are sensitive to a threshold velocity for the withdrawal of oil from below ice floes, and the oil spreading is highly sensitive to the size of the floes. The trajectories for the ice drift and for the water current drift set the limits of the oil drift, and these are in turn highly dependent on the hydrodynamic forcing and the assimilation of ice conditions. In future development of oil spill modeling in ice it is therefore important to focus not only on the ice parameterization but also on the ability to model ice drift, ice floe sizes, and the currents below the ice.