Efficient tools for marine operational forecast and oil spill tracking

A quantified risk analysis for oil spill during crude oil loading operation on tanker ship under improved Z-number based Bayesian Network approach

Crude oil cargo operation poses significant oil spill risk although utmost care is exercised by ship and shore crew. This paper focuses on quantitative risk analysis for oil spill incidents in crude oil tanker ships to enhance safety at the operational level and prevent potential pollution. To achieve this purpose, the Bayesian network (BN) is used under the improved Z-numbers theory. While BN provides a powerful tool based on cause and effect network between the variables, the improved Z-numbers are capable of handling uncertainty and improving the reliability of qualitative expert judgments. The findings show that the occurrence probability of oil spill risk in crude oil tanker ships is found 2.90E-02 during the cargo loading operation. The findings of the research are expected to contribute ship crew, safety inspectors, ship owners, HSEQ managers, and terminal managers in risk management decision-making, improving operational safety, taking control actions, and minimizing oil spills.

Modeling the Agia Zoni II tanker oil spill in Saronic Gulf, Greece

We employed GNOME to simulate the oil spill due to the sinking of the tanker "Agia Zoni ΙΙ" in September 2017 in Saronic Gulf. We performed simulations using various combinations of wind and current input, and values of the GNOME parameters, and compared the simulated oil spill trajectories with coastal pollution and satellite data. The best scenario, i.e., the combination that showed the most satisfactory agreement with field data, uses wind data from one of the closest meteorological stations, calculated currents by a hydrodynamic model and default values of the parameters, except for the windage and the refloat half-life whose proposed values are 3-4 % and 6 h, respectively. Neglecting the effect of the wind in the best scenario worsened the agreement. Mass balance results depicted that approximately 47 % of the total 500 tons of the oil spill ended up on the coastline of Attica peninsula and Salamina Island.

Combined oil spill modelling and shoreline sensitivity analysis for contingency planning in the Irish Sea

Offshore oil spills often result in severe environmental and socio-economic consequences. This work focuses on a busy, yet poorly studied part of NW Europe, the Irish Sea, to assess the impact of future oil spills on the nearby coast. By integrating numerical models and shoreline sensitivity analyses for two confined areas, Liverpool Bay and Milford Haven, this work acknowledges wind direction and speed as principal controls on the movement of oil under winter/storm conditions and in shallow waters. Ocean currents play a secondary role, but are significant in deeper waters and in low-wind summer conditions. The temporal elements used in the modelling thus stress that when the spill occurs is just as important as where. As a corollary, the fate of spilled oil is determined in this work for distinct scenarios and types. Response strategies are recommended to minimise the impact of future spills on coastal populations.

Persistent meanders and eddies lead to quasi-steady Lagrangian transport patterns in a weak western boundary current

The Brazil Current (BC) is a weak western boundary current flowing along the Southwestern Atlantic Ocean. It is frequently described as a flow with intense mesoscale activity and relatively low volume transport between 5.0 and 10.0 Sv. We use a 13-year eddy-resolving primitive-equation simulation to show that the presence of persistent meanders and eddies leads to characteristic quasi-steady Lagrangian transport patterns, aptly extracted through climatological Lagrangian Coherent Structures (cLCS). The cLCS position the surface expression of the BC core along the 2000-m isobath, in excellent visual agreement with high resolution satellite sea-surface temperature and the model Eulerian mean velocity. The cLCS deformation pattern also responds to zonally persistent cross-shelf SSH transition from positive (high) values near coastline to low (negative) values between 200- and 2000-m and back to positive (high) offshore from the 2000-m isobath. Zonally-paired cyclonic and anticyclonic structures are embedded in this transition, also causing the cLCS to deform into chevrons. An efficient transport barrier is identified close to the 200-m isobath confirmed by limited inshore movement of drogued drifters and accurately indicated by an along slope maxima of climatological strength of attraction. We also show that the persistent cyclonic and anticyclonic structures may induce localized cross-shelf transport. Regions of low climatological strength of attraction coincide with large shelves and with stagnant synthetic trajectories. We also show that cLCS accurately depict trajectories initiated at the location of Chevron’s spill (November 2011) as compared to synthetic and satellite-tracked trajectories, and the outline of the oil from that accident. There is also an agreement between the large-scale oil slicks reaching the Brazilian beaches (from August 2019 to February 2020) and the strength of climatological attraction at the coast. Our work also clarifies the influence of persistent mesoscale structures on the regional circulation. The identification and quantitative description of climatological Lagrangian coherent structures is expected to improve the effectiveness of future emergency response to oil spills, contingency planning, rescue operations, larval and fish connectivity assessment, drifter launch strategies, waste pollutant and marine debris dispersion and destination.

Marine oil spill detection using Synthetic Aperture Radar over Indian Ocean

Four oil spill events over the Indian Ocean including Chennai, Sharjah, Al Khiran and Mubarak Village are analyzed using Sentinel-1 satellite data. General National Oceanic and Atmospheric Administration (NOAA) Operational Modeling Environment (GNOME) model is utilized for oil spills trajectory production, whereas oil spills weathering processes are modeled using Automated Data Inquiry for Oil Spill (ADIOS). Synthetic Aperture Radar (SAR) based oil spill detection technique provided reliable results at the wind speed between 3 to 9 m/s for all events. Maximum oil spill movement (33 km) from the source point is observed in the Al Khiran, whereas evaporation rate of crude (degraded) oil is observed as high (low). The Near Real Time (NRT) detection of oil spill using SAR imagery needs high computational power, however, provides better results. This study concludes that SAR based oil spill detection is a cost-effective technique and can be utilized for mapping of oil spills.

The oil spill transport across the shelf-estuary interface

Oil spills caused by ship collisions and offshore oil wells are an ongoing risk for estuaries in the northern Gulf of Mexico. The fate and transport of the oil spill across the interface between a bar-built estuary and the adjacent coast are influenced by multi-scale forcing mechanisms and their corresponding interactions. Of primary interest are the alongshore currents on the shelf encountering strong tidal flows at the estuary entrance. A new cross-scale model was developed for Galveston Bay to reproduce the multi-scale flows. The model was employed in regionally-distributed numerical Lagrangian experiments to investigate the oil spill transport across the shelf-estuary interface. The influence of the multi-scale flows on the oil spill transport was characterized in terms of Lagrangian connectivity and Lagrangian flushing. The new Galveston Bay model was also used to evaluate the Texas City "Y" spill and resulted in a reasonable agreement with the NOAA observations. This research enhances our understanding of the oil transport across the threshold between two contiguous water systems and highlights the importance of resolving the multi-scale flows for the purpose of oil spill predictions.

Innovative Approaches for Geometric Uncertainty Quantification in an Operational Oil Spill Modeling System

Reliable and rapid real-time prediction of likely oil transport paths is critical for decision-making from emergency response managers and timely clean-up after a spill. As high-resolution hydrodynamic models are slow, operational oil spill systems generally rely on relatively coarse-grid models to provide quick estimates of the near-future surface-water velocities and oil transport paths. However, the coarse grid resolution introduces model structural errors, which have been called “geometric uncertainty”. Presently, emergency response managers do not have readily-available methods for estimating how geometric uncertainty might affect predictions. This research develops new methods to quantify geometric uncertainty using fine- and coarse-grid models within a lagoonal estuary along the coast of the northern Gulf of Mexico. Using measures of geometric uncertainty, we propose and test a new data-driven uncertainty model along with a multi-model integration approach to quantify this uncertainty in an operational context. The data-driven uncertainty model is developed from a machine learning algorithm that provides a priori assessment of the prediction’s confidence degree. The multi-model integration generates ensemble predictions through comparison with limited fine-grid predictions. The two approaches provide explicit information on the expected scale of modeling errors induced by geometric uncertainty in a manner suitable for operational modeling.

An online platform for rapid oil outflow assessment from grounded tankers for pollution response

The risk of oil spills is an ongoing societal concern. Whereas several decision support systems exist for predicting the fate and drift of spilled oil, there is a lack of accurate models for assessing the amount of oil spilled and its temporal evolution. In order to close this gap, this paper presents an online platform for the fast assessment of tanker grounding accidents in terms of structural damage and time-dependent amount of spilled cargo oil. The simulation platform consists of the definition of accidental scenarios; the assessment of the grounding damage and the prediction of the time-dependent oil spill size. The performance of this integrated online simulation environment is exemplified through illustrative case studies representing two plausible accidental grounding scenarios in the Gulf of Finland: one resulting in oil spill of about 50 t, while in the other the inner hull remained intact and no spill occurred.

A method for simulating the entire leaking process and calculating the liquid leakage volume of a damaged pressurized pipeline

The accidental leakage of long-distance pressurized oil pipelines is a major area of risk, capable of causing extensive damage to human health and environment. However, the complexity of the leaking process, with its complex boundary conditions, leads to difficulty in calculating the leakage volume. In this study, the leaking process is divided into 4 stages based on the strength of transient pressure. 3 models are established to calculate the leaking flowrate and volume. First, a negative pressure wave propagation attenuation model is applied to calculate the sizes of orifices. Second, a transient oil leaking model, consisting of continuity, momentum conservation, energy conservation and orifice flow equations, is built to calculate the leakage volume. Third, a steady-state oil leaking model is employed to calculate the leakage after valves and pumps shut down. Moreover, sensitive factors that affect the leak coefficient of orifices and volume are analyzed respectively to determine the most influential one. To validate the numerical simulation, two types of leakage test with different sizes of leakage holes were conducted from Sinopec product pipelines. More validations were carried out by applying commercial software to supplement the experimental insufficiency. Thus, the leaking process under different leaking conditions are described and analyzed.

A dynamical systems perspective for a real-time response to a marine oil spill

This paper discusses the combined use of tools from dynamical systems theory and remote sensing techniques and shows how they are effective instruments which may greatly contribute to the decision making protocols of the emergency services for the real-time management of oil spills. This work presents the successful interplay of these techniques for a recent situation, the sinking of the Oleg Naydenov fishing ship that took place in Spain, close to the Canary Islands, in April 2015.

Assessing pollution-related effects of oil spills from ships in the Chinese Bohai Sea

An analysis of the effects of potential oil spills will provide data in support of decisions related to improving the response to oil spills and its emergency management. We selected the Chinese Bohai Sea, especially the Bohai Strait, as our investigation region to provide an assessment of the effects of pollution from ship-related oil spills on adjacent coastal zones. Ship-related accidents are one of the major factors causing potential oil spills in this area. A three dimensional oil transport and transformation model was developed using the Estuary, Coastal, and Ocean Model. This proposed model was run 90 times and each run lasted for 15days to simulate the spread and weathering processes of oil for each of four potential spill sites, which represented potential sites of ship collisions along heavy traffic lanes in the Bohai Sea. Ten neighboring coastal areas were also considered as target zones that potentially could receive pollutants once oil spilled in the study areas. The statistical simulations showed that spills in winter were much worse than those in summer; they resulted in very negative effects on several specific target zones coded Z7, Z8, Z9, and Z10 in this paper. In addition, sites S3 (near the Penglai city) and S4 (near the Yantai city) were the two most at-risk sites with a significantly high probability of pollution if spills occurred nearby during winter. The results thus provided practical guidelines for local oil spill prevention, as well as an emergency preparedness and response program.

Environmental sensitivity mapping and risk assessment for oil spill along the Chennai Coast in India

Integration of oil spill modeling with coastal resource information could be useful for protecting the coastal environment from oil spills. A scenario-based risk assessment and sensitivity indexing were performed for the Chennai coast by integrating a coastal resource information system and an oil spill trajectory model. The fate analysis of spilled oil showed that 55% of oil out of a total volume of 100m(3) remained in the water column, affecting 800m of the shoreline. The seasonal scenarios show major impact during the southwest (SW) and northeast (NE) monsoons and more fatal effects on marine pelagic organisms during SW monsoon. The Oil Spill Risk Assessment Modeler tool was constructed in a geographic information systems (GIS) platform to analyze the risks, sensitivity mapping, and priority indexing of resources that are likely to be affected by oil spills along the Chennai coast. The results of sensitivity mapping and the risk assessment results can help organizations take measures to combat oil spills in a timely manner.

Modelling the hydrodynamic conditions associated with Dinophysis blooms in Galicia (NW Spain)

The northwestern Iberian coast (Galician Rías and shelf) is frequently affected by toxic harmful algal blooms (HABs) (mainly Dinophysis spp.), leading to lengthy harvesting closures in a region where aquaculture has a strong socioeconomic impact. The project ASIMUTH (http://www.asimuth.eu) aimed to develop forecasting capabilities to warn of impending HABs along the European Atlantic coast. Simulations with the ROMS model (hydrodynamical and ecological simulations complemented with Lagrangian particle tracking simulations) of the Galician coastal circulation have been performed in the framework of the ASIMUTH project to characterize and forecast oceanographic conditions before and during HAB periods. In this work, we present the Galician ASIMUTH forecast system and demonstrate its skill in predicting HAB transport and its usefulness to provide assessment for the management of the areas affected by toxic outbreaks. Experience gained during DSP events in 2005 and 2013 is shown. We also describe the Galician pilot HAB bulletins, aimed at distributing forecasts of HAB events that might induce closures of harvesting areas or, when the areas are already closed, at giving information on forthcoming oceanographic conditions that could favour or hamper the opening of an area. Our results show that the model forecasts and the bulletins can provide early warning of the risk of Dinophysis spp. events and the risk of closures linked to the presence of DSP toxins above regulatory levels in harvesting areas.

Temporal variability of marine debris deposition at Tern Island in the Northwestern Hawaiian Islands

A twenty-two year record of marine debris collected on Tern Island is used to characterize the temporal variability of debris deposition at a coral atoll in the Northwestern Hawaiian Islands. Debris deposition tends to be episodic, without a significant relationship to local forcing processes associated with winds, sea level, waves, and proximity to the Subtropical Convergence Zone. The General NOAA Operational Modeling Environment is used to estimate likely debris pathways for Tern Island. The majority of modeled arrivals come from the northeast following prevailing trade winds and surface currents, with trajectories indicating the importance of the convergence zone, or garbage patch, in the North Pacific High region. Although debris deposition does not generally exhibit a significant seasonal cycle, some debris types contain considerable 3 cycle/yr variability that is coherent with wind and surface pressure over a broad region north of Tern.

Improving environmental assessments by integrating Species Sensitivity Distributions into environmental modeling: examples with two hypothetical oil spills

A three dimensional (3D) trajectory model was used to simulate oil mass balance and environmental concentrations of two 795,000 L hypothetical oil spills modeled under physical and chemical dispersion scenarios. Species Sensitivity Distributions (SSD) for Total Hydrocarbon Concentrations (THCs) were developed, and Hazard Concentrations (HC) used as levels of concern. Potential consequences to entrained water column organisms were characterized by comparing model outputs with SSDs, and obtaining the proportion of species affected (PSA) and areas with oil concentrations exceeding HC5s (Area ⩾ HC5). Under the physically-dispersed oil scenario ⩽ 77% of the oil remains on the water surface and strands on shorelines, while with the chemically-dispersed oil scenario ⩽ 67% of the oil is entrained in the water column. For every 10% increase in chemical dispersion effectiveness, the average PSA and Area ⩾ HC5 increases (range: 0.01-0.06 and 0.50-2.9 km(2), respectively), while shoreline oiling decreases (⩽ 2919 L/km). Integrating SSDs into modeling may improve understanding of scales of potential impacts to water column organisms, while providing net environmental benefit comparison of oil spill response options.

Coastal exposure to oil spill impacts from the Finisterre Traffic Separation Scheme

This study analyzes the coastal exposure to potential oil spills coming from the various corridors that constitute the Finisterre Traffic Separation Scheme (NW Iberia). A Lagrangian model was executed with results from a realistic configuration of an ocean model during 2012, validated here against High-Frequency (HF) radar-derived surface currents. Virtual particles were released each hour and followed during the next 4 days. A series of maps summarize which regions would be impacted and when. We have learnt, for example, that Cape Finisterre is the most affected area under a wide range of scenarios and that a sensitive area such as the National Park of the Atlantic Islands would require protective actions in less than 24 h if oil spills from the south eventually occurred. A complete analysis by corridor and during specific wind events is available through a web tool, which could be useful for decision makers in case of contingency.