Fate, transport and risk of potential accidental release of hydrocarbons during arctic shipping

Abstract

Arctic shipping may present risks to the Arctic marine ecosystem. One of the potential sources of risk is accidental oil spills which require mitigation. In order to reduce this risk, there is a need to respond to oil spills in a timely manner. This requires models to evaluate the fate, transport and risk of oil spills in ice-covered waters. Modeling the fate and transport of oil spills is difficult, and the presence of ice makes it complicated. The focus of this study is the application of the models to potential oil spills during Arctic shipping. This study is carried out through a scenario based analysis of potential accidental releases during Arctic shipping accidents. The main application of the work in this thesis is for contingency planning and providing guidance to policies for Arctic shipping operations. This thesis presents a series of studies that review oil weathering and transport models for open and ice-covered waters, update current open water weathering and transport algorithms to make them ice-covered water capable, develop a fugacity based partition model, integrate aforementioned models as well as source models in an ecological risk assessment framework, and develop an accident forecasting methodology. The review shows that current oil spill models are inadequate for predicting the behaviour of oil in ice-covered waters. It also highlights missing algorithms for encapsulation and de-encapsulation processes which are very critical for oil behaviour in ice-covered waters. A refined weathering and transport model is applied to a hypothetical case study involving a potential Arctic shipping accident. The outcome shows that the predictions of the refined models agree reasonably well with oil in ice data from the area under study. The partition model presented is also applied to a hypothetical case study of a shipping vessel passing through the North-West passage. The results predict the level of contamination of the different compartments. The compartments include air, water, ice and sediments. The ecological risk assessment framework developed is applied to a case study in the Kara Sea. The Kara Sea was chosen mainly to draw attention to a potential site for Arctic shipping accidents. The results show acceptable level of risk in the water column since the Risk Quotient (Ratio of predicted concentration and predicted no effect concentration from ecotoxicological studies) is less than 1. An accident forecasting methodology based on the Bayesian approach is presented. This is illustrated with a ship-ice-berg collision scenario. The fate and transport models are used for assessing the consequences of a potential oil spill, while the Arctic shipping forecasting methodology is used for the probability of occurrence. The methodology may also be useful for choosing potential scenarios for the application of the fate and transport models developed. A sensitivity analysis is performed to identify the most critical parameters of the occurrence of the scenario. This information is useful for prioritization of resources during mitigation.