11 Applications of an Oil Drift and Fate Model for Fairway Design
411
effects at the ship’s hull, and advancing or adverse circulation conditions. In this
sense the combined all-year-round designs outperform their seasonal counterparts
which favour more near-coastal waters along the northern and southern coasts of the
Gulf of Finland. They mostly represent offshore designs which are less hampered
by resistance effects. They are both economically beneficial and environmentally
advantageous. That makes them recommendable for future fairway design studies
of cost efficient networks in the Gulf of Finland.
Our studies have also revealed some aspects of the joint impact of wind, waves
and currents on the oil drift and fate. In order to highlight the potential impact of
waves on oil advection one year of drift simulations (1992) were repeated using
the wave-driven drift currents. Interestingly, the impact of waves is very localized.
Both its sign and amplitude vary over sea areas on a scale of 10 km. This effect
in the study area (the Gulf of Finland) is apparently caused by the complicated
bathymetric and geometrical features that lead to strong local wave energy gradients
and variations in other wave properties owing to shadowing effects. Wave energy
gradients that actually drive the spatially varying currents lead to differences of
up to ≈1 cm/s, at instances even ≈3 cm/s compared to the cases when waves are
ignored. These additional currents may prevent or advance onshore oil propagation,
according to particular topography and wind and wave conditions. Under average
conditions, local residence time differences of up to −2.2 to 1.3 days and differences
in the probability of oil landing of up to ±20 % have been found.
An obvious drawback of this method is that a maritime accident, and, by consequence, an oil spill, is supposed to take place with the same likelihood, independent
of geographical position or weather conditions. In reality, some weather and ocean
conditions (high winds and waves, fog, sea ice, or icebergs in other parts of the
world) are riskier than others, and some waters are more difficult to navigate than
others. Merging sea traffic towards the same pathways would in itself enhance the
risk of collision. It would be highly interesting to continue efforts in this direction,
for example, towards introduction of realistic collision and accident risk into the
mode, equivalently, to introduce site- or weather-dependent weights to the spill simulations.
Acknowledgements The underlying studies were performed in the framework of the BalticWay
project, in which the DMI was jointly supported by the funding from the Danish Ministry of
Science, Innovation and Higher Education and the European Commission’s Seventh Framework
Programme (FP 2007–2013) under grant agreement No. 217246 made with the joint Baltic Sea research and development programme BONUS. The models were run using meteorological forcing
kindly provided by the Danish Climate Centre (DKC).
References
Andrejev O, Myrberg K, Alenius P, Lundberg PA (2004) Mean circulation and water exchange
in the Gulf of Finland—a study based on three-dimensional modelling. Boreal Environ Res
9:1–16
Andrejev O, Sokolov A, Soomere T, Värv R, Viikmäe B (2010) The use of high-resolution
bathymetry for circulation modelling in the Gulf of Finland. Est J Eng 16:187–210
411
effects at the ship’s hull, and advancing or adverse circulation conditions. In this
sense the combined all-year-round designs outperform their seasonal counterparts
which favour more near-coastal waters along the northern and southern coasts of the
Gulf of Finland. They mostly represent offshore designs which are less hampered
by resistance effects. They are both economically beneficial and environmentally
advantageous. That makes them recommendable for future fairway design studies
of cost efficient networks in the Gulf of Finland.
Our studies have also revealed some aspects of the joint impact of wind, waves
and currents on the oil drift and fate. In order to highlight the potential impact of
waves on oil advection one year of drift simulations (1992) were repeated using
the wave-driven drift currents. Interestingly, the impact of waves is very localized.
Both its sign and amplitude vary over sea areas on a scale of 10 km. This effect
in the study area (the Gulf of Finland) is apparently caused by the complicated
bathymetric and geometrical features that lead to strong local wave energy gradients
and variations in other wave properties owing to shadowing effects. Wave energy
gradients that actually drive the spatially varying currents lead to differences of
up to ≈1 cm/s, at instances even ≈3 cm/s compared to the cases when waves are
ignored. These additional currents may prevent or advance onshore oil propagation,
according to particular topography and wind and wave conditions. Under average
conditions, local residence time differences of up to −2.2 to 1.3 days and differences
in the probability of oil landing of up to ±20 % have been found.
An obvious drawback of this method is that a maritime accident, and, by consequence, an oil spill, is supposed to take place with the same likelihood, independent
of geographical position or weather conditions. In reality, some weather and ocean
conditions (high winds and waves, fog, sea ice, or icebergs in other parts of the
world) are riskier than others, and some waters are more difficult to navigate than
others. Merging sea traffic towards the same pathways would in itself enhance the
risk of collision. It would be highly interesting to continue efforts in this direction,
for example, towards introduction of realistic collision and accident risk into the
mode, equivalently, to introduce site- or weather-dependent weights to the spill simulations.
Acknowledgements The underlying studies were performed in the framework of the BalticWay
project, in which the DMI was jointly supported by the funding from the Danish Ministry of
Science, Innovation and Higher Education and the European Commission’s Seventh Framework
Programme (FP 2007–2013) under grant agreement No. 217246 made with the joint Baltic Sea research and development programme BONUS. The models were run using meteorological forcing
kindly provided by the Danish Climate Centre (DKC).
References
Andrejev O, Myrberg K, Alenius P, Lundberg PA (2004) Mean circulation and water exchange
in the Gulf of Finland—a study based on three-dimensional modelling. Boreal Environ Res
9:1–16
Andrejev O, Sokolov A, Soomere T, Värv R, Viikmäe B (2010) The use of high-resolution
bathymetry for circulation modelling in the Gulf of Finland. Est J Eng 16:187–210