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J. Murawski and J. Woge Nielsen
has been accounted for in the solution. Although current-induced pollutant transport
normally dominates its subsurface propagation, wind-induced transport is at least of
the same order of magnitude at the surface (Chap. 4) and wave impact definitely
plays a role in the transport at the sea surface (Ardhuin et al. 2009).
In this chapter we shall expand this analysis towards accounting for these basic
factors that affect the oil spills in the real marine environment and in many occasions
govern the oil drift characteristics. Namely, we shall employ an operational oil drift
and fate model (from now on referred to as the drift model) for approximately solving the inverse problem of oil spill propagation. The model in use has been proven
to be largely reliable, given the local topography is well resolved and an adequate
forcing is applied. The general idea is, however, the same as in Chap. 10: to identify offshore areas, from where the propagation of an oil spill to vulnerable areas is
unlikely or takes a long time.
This approach to the fairway design is not only quite new but also computationally demanding as it requires numerous simulations of a highly complicated model
that handles not only the oil drift (as the above research has been doing) but also
the complex physics and chemistry of oil at sea. To our knowledge no similar attempts have been undertaken before. The option of using realistic oil drift and fate
simulations to estimate the effects of oil weathering, winds and waves in combination with the technology developed in the previous chapters provides a synthesis of
the different processes that determine the fate of oil at sea, and makes it also possible to evaluate their relative importance for accurate forecasts and low-risk fairway
designs.
The chapter starts with an introduction into the characteristic processes that determine the drift (Sect. 11.2.2) and fate of oil at sea (Sect. 11.2.3). These sections
introduce the basic concepts of operational oil spill models and sketch the basic theoretical ideas of how to describe the behaviour of oil in sea water. The reader is next
provided with an overview of the implementation of the oil drift model (Sect. 11.3),
with focus on the particular model used in this study and methods of calculations of
drift trajectories and a subsequent overview of the setup of the model for the target
area, the Gulf of Finland (Sect. 11.3.2). This basin is chosen as study area because
its highly variable hydrodynamic regime is partially constrained by Baltic Sea inflows and also strongly impacted by the riverine input. The estimates of the general
features of oil propagation in this water body (Sect. 11.4) are based on a sequence
of simulations in which a grid of potential oil spill sites has been stretched across
the gulf. The simulations are repeated many times with the same pattern of spills in
order to estimate characteristic drift patterns from a large number of single trajectories of oil parcels. The calculated trajectories, pathways and characteristic oil drift
patterns serve as the basis for the further analysis. Methods have been devised to
develop optimum fairways, similar to those described above and in Andrejev et al.
(2011).
Following the concept developed in the previous chapters, we identify and evaluate various optimum fairway designs that minimize the exposure of coastal areas
to pollution from specific sites along the fairway. The gridded risk maps are used to
identify environmentally safe pathways through the gulf. Optimum fairways minimize aggregated risks along the routes and also account for the potential increase
J. Murawski and J. Woge Nielsen
has been accounted for in the solution. Although current-induced pollutant transport
normally dominates its subsurface propagation, wind-induced transport is at least of
the same order of magnitude at the surface (Chap. 4) and wave impact definitely
plays a role in the transport at the sea surface (Ardhuin et al. 2009).
In this chapter we shall expand this analysis towards accounting for these basic
factors that affect the oil spills in the real marine environment and in many occasions
govern the oil drift characteristics. Namely, we shall employ an operational oil drift
and fate model (from now on referred to as the drift model) for approximately solving the inverse problem of oil spill propagation. The model in use has been proven
to be largely reliable, given the local topography is well resolved and an adequate
forcing is applied. The general idea is, however, the same as in Chap. 10: to identify offshore areas, from where the propagation of an oil spill to vulnerable areas is
unlikely or takes a long time.
This approach to the fairway design is not only quite new but also computationally demanding as it requires numerous simulations of a highly complicated model
that handles not only the oil drift (as the above research has been doing) but also
the complex physics and chemistry of oil at sea. To our knowledge no similar attempts have been undertaken before. The option of using realistic oil drift and fate
simulations to estimate the effects of oil weathering, winds and waves in combination with the technology developed in the previous chapters provides a synthesis of
the different processes that determine the fate of oil at sea, and makes it also possible to evaluate their relative importance for accurate forecasts and low-risk fairway
designs.
The chapter starts with an introduction into the characteristic processes that determine the drift (Sect. 11.2.2) and fate of oil at sea (Sect. 11.2.3). These sections
introduce the basic concepts of operational oil spill models and sketch the basic theoretical ideas of how to describe the behaviour of oil in sea water. The reader is next
provided with an overview of the implementation of the oil drift model (Sect. 11.3),
with focus on the particular model used in this study and methods of calculations of
drift trajectories and a subsequent overview of the setup of the model for the target
area, the Gulf of Finland (Sect. 11.3.2). This basin is chosen as study area because
its highly variable hydrodynamic regime is partially constrained by Baltic Sea inflows and also strongly impacted by the riverine input. The estimates of the general
features of oil propagation in this water body (Sect. 11.4) are based on a sequence
of simulations in which a grid of potential oil spill sites has been stretched across
the gulf. The simulations are repeated many times with the same pattern of spills in
order to estimate characteristic drift patterns from a large number of single trajectories of oil parcels. The calculated trajectories, pathways and characteristic oil drift
patterns serve as the basis for the further analysis. Methods have been devised to
develop optimum fairways, similar to those described above and in Andrejev et al.
(2011).
Following the concept developed in the previous chapters, we identify and evaluate various optimum fairway designs that minimize the exposure of coastal areas
to pollution from specific sites along the fairway. The gridded risk maps are used to
identify environmentally safe pathways through the gulf. Optimum fairways minimize aggregated risks along the routes and also account for the potential increase