Effect of tide in oil spill prediction during Hebei spirit accident in Korea

Multi-nested operational prediction system for the Yellow Sea (YS) has been developed to predict the movement of oil spill. Drifter trajectory simulations were performed to predict the path of the oil spill during the Hebei Spirit accident. The oil spill trajectories at the surface predicted by model with tidal forcing were comparable to the observation for one month experiment, whereas the speed of drifter predicted from the simulation without tidal forcing was remarkably faster than the observation. The bottom current flowing northward from the simulation without tidal forcing was also faster than that with tidal forcing in the interior of the YS. Increased bottom friction by strong tidal current induces increase of vertical mixing and decrease of vertical shear between the surface and bottom currents. Without tidal mixing the relatively strong bottom northward current, which could act as a compensation flow, may enhance the southward surface current. Strong tide might reduce upwind flow along the deep central trough in the YS.