There are so many factors that are entered into oil spill models, including the chemical actions and reactions of the oil, the initial amount of oil, and the factors of the region.
There are facts about the water and its composition and the circulation of the water at the surface and at various levels, including circulation that goes on under the spill. Changing tides and circulation patterns will affect the model.
There is the wind and atmosphere that goes on above the spill field. Wind and atmospheric factors are changeable, so the changes in weather account for changes in the movement and behavior of the oil.
And there is a list of biological, biochemical, physics and chemical factors, including atmospheric weathering of the oil mass:
Oil contains volatile and non volatile compounds that “weather” in oxygenated or surface waters. Gaseous components vent off and evaporate. Other components remain behind to take on a variety of qualities and forms and to move in a host of ways.
Spill spreading and diffusion: Given the extensive use of oil dispersants, spreading can be greatly effected. There is also dispersion and spreading through turbulent diffusion, hydronamic dispersion, natural dispersion, evaporation, dissolution, emulsification.
There is sinking and rising, sedimentation, biodegradation, photo oxidation, and auto oxidation.
When the elements of enough breakdown in the oil, proper water pH, enough oxygen in the water and other factors, oil eating life forms can go to work as they are man made or naturally occurring.
There are issues of oil viscosity, pour point stresses and pressures (does the oil drip, seep, slop out of a container or emit in a high pressure extrusion?) There is vertical mixing and the fact that separate spills or broken down masses of oil can lie at different levels and in different forms and must each be modeled separately and on their own terms as “slicklets”.
Some oil slicklets are actually microscopic in nature and can only be detected through testing of the water at the microscopic level. These factors must be worked with.
With vertical mixing, there are different behaviors that occur at different water levels, where pressure, temperature, circulation and all other factors can change. The changing light zones alone will affect the photo oxidation, oxygen levels, biomass and temperatures.
The complexity of oil spill modeling lies in the fact that everything that is listed above not only is interrelated where one can affect the others, everything must be considered at once.
Add in the wide array of complexities that involve the cause, initial action and sources of spills, and the issues of whether the issue was once and immediate or whether the issue is massive and ongoing for a lengthy time, or whether the issue is seepage, and the model gets even more complicated. Also, the presence or absence of gas is considered. Whether the issue was from a submerged pipeline, the depth of the pipeline, and the size of the pipeline must be considered. For surface spills, there are other factors to be considered.
Much of the above data will never be available. While the most observable components of the oil will be traceable, many components, such as vented gases and molecular components of dispersed oil will hardly be detectable over great distances.
The best hopes for oil slick modeling are to learn more and more about data collection, the qualities of the water, circulation, and the qualities of the oil for future improvements in finding out how to use modeling to forecast the movement of oil slicks and slicklets.
John Gonzo, “A Review Of Modern Approaches To Oil Spill Modeling”, GoArticles, Sept 2009
An example using a dye simulation animated Parallel Ocean Program model
Wikipedia, “Parallel Ocean Program”
Public Access to POP at Los Alamos Climate Ocean Website
