Marine oil spill simulation and uncertainty analysis - a case study in the Newfoundland offshore area

Zheng, Xiao (2017) Marine oil spill simulation and uncertainty analysis - a case study in the Newfoundland offshore area. Masters thesis, Memorial University of Newfoundland.

[English] PDF - Accepted Version Available under License - The author retains copyright ownership and moral rights in this thesis. Neither the thesis nor substantial extracts from it may be printed or otherwise reproduced without the author's permission. Download (4MB)

Abstract

Oil spills have been regarded as one of the major contributors to marine pollution. With the rapidly changing environmental conditions and the diverse uncertainties in the data associated with the observation or meteorological and oceanographic data, the simulation of an oil spill is challenging to be accurate and reliable enough for supporting response management. Furthermore, with the different assumptions, structures and translations of various simulation models, results could significantly vary even with the same inputs. The objectives of this research are therefore 1) to compare three widely used models for offshore oil spill simulation and evaluate their capabilities under harsh environmental conditions; and 2) to develop a Design of Experiment (DOE) based approach for analyzing uncertainties associated with the spill modeling input and parameters to help improve offshore oil spill simulation. In this research, the Terra Nova oil spill occurred on November 21, 2004, the largest oil spill in offshore Newfoundland, was chosen as a case study. The models, namely GNOME/ADIOS2 and OSCAR, were employed for the simulation of fate and transport of the spilled oil. During the simulation, ocean currents data from the Hybrid Coordinate Ocean Model (HYCOM) and surface wind data measured by the National Climate Data Center (NCDC) were used. The simulation results indicated that 43.7% of the spilled oil evaporated or dispersed in the first two days. With the model of OSCAR, 87.4% of the total spilled oil was evaporated or dispersed, while 10.8% was biodegraded. Only 1.6% of oil remained on the sea surface after six days, which agreed well with the historical data. The results from GNOME showed a more reasonable match with the observations from the RADARSAT-1 satellite images regarding the spill plume, shape and location as compared to those from OSCAR. But on the other hand, OSCAR showed better performance in simulating weathering process. To facilitate a better understanding of the oil fate and transport, and to improve simulation performance, a DOE aided method was developed for sensitivity analysis, parameter calibration and interaction analysis of key factors during spill simulation. The interactions between wind speed and direction, and the currents have been analyzed and the effects of their interactions have been studied. In this case study, the key factors “Windage” and “Wind speed scale” both had the negative effects on the modeling response, but their interaction showed positive effects. The “Along current uncertainty” and “Diffusion coefficient” caused the negative and positive effects, respectively, but leading to the positive effects by their interaction. The results indicated that when adjusting the primary factors in order to optimize the response, interactions between factors may lead an opposite way and missed the optimal solution. The validation through the case study showed consistency with high values of R² (e.g., 0.93 and 0.95 for deviations of coverage and distance between the observed and simulated spills respectively). The results indicated that this DOE aided parameterization method could potentially be a useful tool for the evaluation of the contribution of multiple parameters and be applied as a new calibration method for other oil spill simulation models.

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