Mapping Oil Spill Hazard in the Coastal Mediterranean Sea

The Mediterranean region is one of the largest maritime traffic routes in the world.Large accidental spills have declined considerably, but smaller, routine spills from operational activities continue to occur and have a cumulative impact on the coasts. Assessing operational oil discharge coastal impacts requires not only modelling oil dispersion and transformation but also statistical approaches to address system uncertainties. This study follows the Oil Spill Risk Analysis (OSRA) framework (Sepp-Neves et al., 2016), simulating large ensembles of hypothetical spills under diverse meteo-oceanographic conditions to capture the full range of variability. Unlike previous studies, in which virtual spill release points were placed in high-traffic shipping zones (Liubartseva et al., 2015, 2023), release points were distributed homogeneously along the Mediterranean coast , in order to isolate the influence of oceanographic mesoscale dynamics on hazard mappig for the beached oil. The oil spill hazard is quantified following the methodology developed by Sepp-Neves et al., (2020), which demonstrated that beached oil concentration patterns are well described by a Weibull distribution. Using this methodology, Weibull distributions of beached oil concentrations were computed for all Mediterranean coastal states, together with the associated mean beached oil and hazard index. Three characteristic regimes are identified based on the relationship between Weibull mean values and beaching event frequency. A combination of low mean and low frequency, observed for example along the Turkish coast, is indicative of mesoscale current dynamics that predominantly keep the oil away from the coast. A low mean associated with high frequency, as found for Syria, suggests that currents frequently advect oil toward the coast under divergent flow conditions, resulting in repeated beaching events at low concentrations. In contrast, a high mean beached oil concentration coupled with low frequency, observed for Cyprus, reflects current dynamics that funnel oil toward the coast under convergent flow conditions, leading to extreme oil pollution events. Seasonal variations in hazard were also considered.Across nearly all Mediterranean coastal states, autumn generally shows the lowest beached oil pollution hazard, followed by winter and summer, while spring is associated with the highest beached oil hazard. This pattern is generally observed across the Mediterranean region, with only minor exceptions.

References

Sepp-Neves, A.A., Pinardi, N. &  Martins, F. (2016). IT-OSRA: applying ensemble simulations to estimate the oil spill risk associated to operational and accidental oil spills, Climate dynamics, 66:939–954. 

Sepp-Neves, A. A., Pinardi, N., Navarra, A., & Trotta, F. (2020). A general methodology for beached oil spill hazard mapping. Frontiers in Marine Science, 7.

Liubartseva, S., Dominicis, M. D., Oddo, P ., Coppini, G., Pinardi, N., & Greggio, N. (2015). Oil spill hazard from dispersal of oil along shipping lanes in the southern Adriatic and northern Ionian Seas. Marine Pollution Bulletin, 90, 259–272.

Liubartseva, S., Coppini, G., Verdiani, G., Mungari, T., Ronco, F., Pinto, M., ... Lecci, R. (2023). Modeling chronic oil pollution from ships. Marine Pollution Bulletin, 195.