Department of Civil and Resource Engineering, Faculty of Engineering, Dalhousie University, Halifax, NS B3H 4R2, Canada.
Ocean and Ecosystem Science Division, Fisheries and Ocean Canada, Bedford Institute of Oceanography, Dartmouth, NS B2Y 4A2, Canada.
J Hazard Mater. 2022 Sep 5;437:129404. doi: 10.1016/j.jhazmat.2022.129404. Epub 2022 Jun 17.
This study used a combination of Finite-Time Lyapunov Exponent (FTLE) values, residual currents, and tidal excursion lengths to systematically investigate the effects of tidal dispersion on oil spill trajectories in Burrard Inlet, BC, Canada, which is a tidally dominated estuary. The FTLE analysis results showed that tidal type and tidal phase significantly influenced the FTLE fields because the flow structure and the location of saddle points varied as a function of the tidal type and tidal phase. Some transport barriers formed in the Inner Harbour, which blocked the water exchange between the western and eastern parts of the inlet. Moreover, tidal mixing in the wider regions of Burrard Inlet (i.e., the western Outer Harbour) was relatively weak than in the narrower areas (i.e., First Narrows and Second Narrows). The observations from the FTLE analysis agreed well with the residual currents and tidal excursion results. The drifter trajectories were consistent with the Lagrangian coherent structure lines extracted from the FTLE analysis. To verify the tidal dispersion impact on an oil spill trajectory in the inlet, the FTLE fields were compared with a real oil spill that occurred in Burrard Inlet in 2015 (the M/V Marathassa oil spill). The FTLE fields reasonably explained the spilled oil's trajectories from the real event. In addition, a set of stochastic oil spill models were run in this study and found that the FTLE analysis was a reliable tool for oil spill tracking. Overall, the FTLE method would be a valuable addition to practical oil spill response planning.
本研究结合有限时间李雅普诺夫指数（FTLE）值、余流和潮流往返长度，系统研究潮汐弥散对加拿大不列颠哥伦比亚省伯拉德湾（一个潮汐控制型河口）溢油轨迹的影响。FTLE 分析结果表明，潮汐类型和潮汐相位显著影响 FTLE 场，因为流场结构和鞍点位置随潮汐类型和潮汐相位而变化。一些内港形成了运输屏障，阻止了入口西部和东部之间的水交换。此外，伯拉德湾较宽区域（即外港西部）的潮汐混合相对较窄区域（即第一峡湾和第二峡湾）较弱。FTLE 分析的观测结果与余流和潮流往返结果吻合较好。漂流轨迹与从 FTLE 分析中提取的拉格朗日相干结构线一致。为了验证潮汐弥散对入口溢油轨迹的影响，将 FTLE 场与 2015 年在伯拉德湾发生的实际溢油（M/V Marathassa 溢油事件）进行了比较。FTLE 场合理地解释了实际事件中溢油的轨迹。此外，本研究还运行了一组随机溢油模型，发现 FTLE 分析是溢油跟踪的可靠工具。总体而言，FTLE 方法将是实际溢油应急计划的一个有价值的补充。
