Risk management of ship-source oil spill in ice conditions in the Northern Baltic Sea

Polar and sub-polar regions are facing a trend of ice retreating and correspondingly increasing maritime traffic. Consequently, the probabilities of ship accidents and oil spills in ice conditions are likely to increase. Therefore, there is a need to carry out further studies on managing the relevant oil spill risk in ice conditions. The Northern Baltic Sea area is targeted as the study region in this thesis, as one of the typical regions with large amount of shipping in ice conditions. Current research on oil spills in ice conditions is diverse, however still a number of research gaps exist, which pose important limitations to authorities to understand the effectiveness of and to make strategic risk management decisions concerning the response and preparedness to oil spills in ice. There is a lack of models for assessing oil recovery effectiveness, which also results in a lack of integrated system model for evaluating the holistic process of oil spill and recovery in ice conditions. Therefore, this thesis focuses on these. The work is divided into four parts: i) developing a theoretical risk-based framework and method for guiding risk management for a system model; ii) establishing a holistic system model from ship accident to response and recovery; iii) identifying critical factors in the system using the developed framework and method; and iv) providing risk control options. Firstly, the thesis develops a theoretical risk-based framework and method for guiding risk management. More specifically, a risk perspective in line with state-of-the-art risk research is emphasized and a coupled modelling framework with the risk perspective is generated. In addition, based on the aligned risk perspective and coherent risk modelling framework, a risk-based framework and method for identifying the critical factors in a system is developed. Meanwhile, a new oil spill response and recovery model for estimating oil recovery effectiveness in ice conditions is created following the established modelling framework. The model suggests that the recovery effectiveness in ice conditions is relatively low, which further indicates that further risk control on critical factors is necessary. An integrated system model is generated which describes the process from accident to response and recovery, i.e. including ship-ship collision, oil outflow, oil drift and newly established response and recovery model. When applying the developed risk-based framework and method to the established system model, the most critical factors in this holistic system are identified.Finally, developments are made towards one important risk control option in the response system, i.e. response vessel operability in ice. This focuses particularly on dynamic ice, as it is one of the most hazardous ice conditions. A transit model for the response vessel including independent and escort navigation operation modes is developed, which is used to develop a response vessel operability index that can be integrated in decision making processes and operational decision support systems. Both the transit model and response vessel operability index are validated.