9 Statistics of Lagrangian Transport Reveals Hidden Features of Velocity Fields
285
that persist during certain time intervals. Such patterns have been recently identified
for different areas of the Baltic Sea both numerically (Lehmann et al. 2002; Meier
2007; Lu et al. 2012) and experimentally (Osi´ nski and Piechura 2009). Their typical lifetime ranges from a few days to weeks up to a few months, that is, from the
synoptic scale (in the Gulf of Finland and in the south-western Baltic Sea) up to
seasonal scale.
Such more or less regularly occurring patterns of currents may definitely provide a joint effect similar to that of jet currents. They apparently relocate not only
water masses but also transport key components of the ecosystem such as nutrients, oxygen or fish larvae between certain sea areas, and thus are extremely important for the functioning of the entire ecosystem. On top of that, they inherently
cause relatively fast current-driven transport of adverse impacts and thus obviously
have a high potential for the systematic transport of pollution between specific domains, and also from the offshore to vulnerable coastal and protected marine areas
(Delpeche-Ellmann and Soomere 2013).
At present, man is not able to steer or influence this dynamics but it is in our
power to highlight such patterns and to account for their presence. The least we can
do is to avoid the release of adverse impacts in those regions from where such currents may rapidly transport water masses to high-value domains. The smart use of
such patterns is a feasible way towards a reduction of anthropogenic impact to vulnerable areas. This can be achieved, for example, by routing ships along a current
that would rapidly carry a potential oil spill out of a vulnerable domain (Soomere
and Quak 2007). Alternatively, and more interestingly, human activities (such as
marine traffic) might be placed in specific regions (areas of reduced risk), from
which the transport of pollution to vulnerable or high-cost areas is unlikely. Avoiding ship traffic (and associated pollution) in certain offshore domains and time intervals might considerably reduce the consequences of potential accidents .
The presence of such (normally concealed) patterns can be used as an indicator
of the applicability of the method developed in this book. Such patterns eventually
shape the pollution propagation as well as the drift of various items (such as vessels
without propulsion, rescue boats or lost containers). Their presence is a strong argument in favour of the existence of areas of reduced risk. Strictly speaking, achieving
a substantial decrease in industry-induced remote environmental risks is not necessarily directly connected with the presence of such patterns. However, their absence
is a signal that there is little hope to benefit from favourable features of currentdriven transport.
The idea of using favourable patterns of transport of adverse impacts for environmental management, ideally, should be applied to the full three-dimensional (3D)
motions in the entire water column and be combined with the wind- and wave-driven
transport. As explained in more detail in Chap. 1, in this book we focus, however,
on the current-driven transport of adverse impacts that are locked in the uppermost
layer of the sea. Moreover, in this chapter we leave out the impact of wind and
waves. Doing so is partially justified by the fact that the properties of wind and
wave fields and the associated transport are relatively well (albeit not perfectly)
known (ASCE (American Society of Civil Engineers) 1996; Reed et al. 1999; Ardhuin et al. 2009). Compared to this knowledge, the prediction of currents and related
285
that persist during certain time intervals. Such patterns have been recently identified
for different areas of the Baltic Sea both numerically (Lehmann et al. 2002; Meier
2007; Lu et al. 2012) and experimentally (Osi´ nski and Piechura 2009). Their typical lifetime ranges from a few days to weeks up to a few months, that is, from the
synoptic scale (in the Gulf of Finland and in the south-western Baltic Sea) up to
seasonal scale.
Such more or less regularly occurring patterns of currents may definitely provide a joint effect similar to that of jet currents. They apparently relocate not only
water masses but also transport key components of the ecosystem such as nutrients, oxygen or fish larvae between certain sea areas, and thus are extremely important for the functioning of the entire ecosystem. On top of that, they inherently
cause relatively fast current-driven transport of adverse impacts and thus obviously
have a high potential for the systematic transport of pollution between specific domains, and also from the offshore to vulnerable coastal and protected marine areas
(Delpeche-Ellmann and Soomere 2013).
At present, man is not able to steer or influence this dynamics but it is in our
power to highlight such patterns and to account for their presence. The least we can
do is to avoid the release of adverse impacts in those regions from where such currents may rapidly transport water masses to high-value domains. The smart use of
such patterns is a feasible way towards a reduction of anthropogenic impact to vulnerable areas. This can be achieved, for example, by routing ships along a current
that would rapidly carry a potential oil spill out of a vulnerable domain (Soomere
and Quak 2007). Alternatively, and more interestingly, human activities (such as
marine traffic) might be placed in specific regions (areas of reduced risk), from
which the transport of pollution to vulnerable or high-cost areas is unlikely. Avoiding ship traffic (and associated pollution) in certain offshore domains and time intervals might considerably reduce the consequences of potential accidents .
The presence of such (normally concealed) patterns can be used as an indicator
of the applicability of the method developed in this book. Such patterns eventually
shape the pollution propagation as well as the drift of various items (such as vessels
without propulsion, rescue boats or lost containers). Their presence is a strong argument in favour of the existence of areas of reduced risk. Strictly speaking, achieving
a substantial decrease in industry-induced remote environmental risks is not necessarily directly connected with the presence of such patterns. However, their absence
is a signal that there is little hope to benefit from favourable features of currentdriven transport.
The idea of using favourable patterns of transport of adverse impacts for environmental management, ideally, should be applied to the full three-dimensional (3D)
motions in the entire water column and be combined with the wind- and wave-driven
transport. As explained in more detail in Chap. 1, in this book we focus, however,
on the current-driven transport of adverse impacts that are locked in the uppermost
layer of the sea. Moreover, in this chapter we leave out the impact of wind and
waves. Doing so is partially justified by the fact that the properties of wind and
wave fields and the associated transport are relatively well (albeit not perfectly)
known (ASCE (American Society of Civil Engineers) 1996; Reed et al. 1999; Ardhuin et al. 2009). Compared to this knowledge, the prediction of currents and related