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Igor Ivichev, Lars Robert Hole, Lev Karlin, Cecilie Wettre and Johannes Röhrs
Six iSPHERE oil spill and current tracking buoys were deployed over the continental shelf of northern Norway (Nordkapp region) during spring-summer 2011. These drifters provide real-time GPS position location information to aid in locating marine oil spills and other leeward drifting objects. In this study we assess the differences between the spreading of the surface drifters and the trajectories forecast by the operational Lagrangian oil drift model at the Norwegian Meteorological Institute (met.no). The study investigates the reason for these differences, and we use a recently established new skill score as a measure of the model accuracy. The differences observed in this study are the consequence of the combined impact of the modeled wind, ocean and current constituents that force the oil drift model. Each numerical model is run on a grid of 4 km resolution, which means that many mesoscale features are either not represented well enough, or not represented at all. A problem with the ocean model, since eddies in the ocean are typically of a much smaller scale than in the atmosphere (40-50 km), and there are few observations to assimilate into the model. Studies such as this, comparing modeled trajectories with observed drifter trajectories are an important way to indirectly validate and improve ocean models, as well as improving the trajectory model itself.