Seatrack Web forecasts and backtracking of oil spills - an efficient tool to find illegal spills using AIS

Abstract

Seatrack Web is a fully operational oil drift forecasting system. It covers the Baltic Sea and part of the North Sea. The system is available over the Internet and has the latest weather and ocean forecasts, thus giving the user the best possible decision tool in an oil combating situation. The drift model calculates the three-dimensional movements of substances or objects at sea, including sinking, stranding and turbulent dispersion. For oils, the evaporation, emulsification and wave-induced vertical dispersion are also calculated. Seatrack Web is the HELCOM system for forecasting of oil drift, and the primary users are oil combating authorities in the countries surrounding the Baltic Sea. It has been in operation since the early 1990s. The system now includes several new features, where a coupling to an AIS (Automatic Identification System) ship track data base is the most important. When finding a spill in the sea, it is possible to make a backtracking calculation with the system. The result shows every hour the location of the oil back in time. Adding AIS data to those oiled areas shows clearly which ships have been close to the oil during the whole calculation period. The system then fetches new ship tracks in space and time depending on the changing positions of the oil. A large number of possible ships are often found, and those can then be deleted successively after analyses and more information about the circumstances. The first year of experience with using AIS in Seatrack Web have led to many suggestions for improvement. It now, for instance, works faster to identify the suspected ships and it is also easier to ignore irrelevant ships. One valuable new feature is that if AIS data are missing it is possible to take those data from the log book and fill in so the ship track will be completed, thus having correct information when analysing the situation. During 2008 satellite information will be shown in the map, which simplifies the identification of illegal polluters even further. The satellite image can also show an ongoing release of a spill, by showing a ship connected to the oil while releasing it. Two radar satellites will be used, RADARSAT 1 and ENVISAT. A case with all information included can also be saved to show as evidence in court at later occasions as animation or special pictures.