18
T. Soomere
currents, with a typical lifetime from weeks up to a few months have been recently
identified for different areas of the Baltic Sea in terms of Eulerian transport of water
masses (Lehmann et al. 2002; Meier 2007).
These patterns are normally concealed, usually hidden behind the enormous complexity of the instantaneous fields of currents and their short-term variability. Their
existence may essentially modify the transport of potential adverse effects compared
with the classical understanding of the local circulation. Moreover, in certain cases
they predominantly carry water (and pollution ) in a preferred direction that not necessarily matches the downwind or downwave direction (Soomere et al. 2011). On
the one hand, such phenomena obviously have a high potential for the rapid and
systematic transport of both water masses and adverse impacts such as nutrients,
toxic substances or oil pollution between specific sea areas. On the other hand,
their smart use offers a particular solution to the problem of reduction of anthropogenic impacts to vulnerable areas. Namely, if the resulting patterns of transport
are systematic enough, they can be used for placing human activities (such as marine
traffic) in specific regions (areas of reduced risk), from which the pollution transport
to vulnerable or high-cost areas is unlikely (Soomere and Quak 2007).
1.12 Quantification of Offshore Domains
It is heuristically obvious that such current patterns and associated features of (Eulerian or Lagrangian) 8 transport may provide a clear environmental benefit. The optimal solution is a fairway (or location where to tow the damaged ship, etc.) chosen
so that an accident, if it happens, takes place in the most favourable location. To
specify such a location, it is necessary to quantify the potential of different offshore
sites to serve as a source of risk to the vulnerable regions if pollution were to be
released at this site. For ideally homogeneous currents patterns, the most favourable
locations would be the ‘most offshore’ sites.
This picture needs to be modified if some current patterns systematically carry
adverse impacts in a certain direction. Such a transport reflects certain features
of Lagrangian flow and not necessarily coincides with the long-term patterns of
currents calculated from Eulerian velocities. Therefore, in certain areas of seas or
oceans, which host semi-persistent Lagrangian flow patterns, the potential for remote coastal damage may be smaller than it would be expected from purely geometrical arguments (such as the distance to the nearest coast). These areas are called
8 The Eulerian specification of the flow field is a way of treating, measuring or calculation the motion properties for each fixed location in space as time passes. In marine conditions one has to use
fixed moorings in order to properly measure the Eulerian velocities. This framework is mostly used
in circulation modelling. The Lagrangian specification is a way of looking at fluid motion where the
observer follows an individual water particle as it moves through space and time. The transport of
different substances and items in the marine environment is obviously Lagrangian. The Lagrangian
velocity and transport can be directly measured using drifting buoys. An overview of these specifications and their implementation in the developed technology is presented in Chaps. 3, 4 and 7.
T. Soomere
currents, with a typical lifetime from weeks up to a few months have been recently
identified for different areas of the Baltic Sea in terms of Eulerian transport of water
masses (Lehmann et al. 2002; Meier 2007).
These patterns are normally concealed, usually hidden behind the enormous complexity of the instantaneous fields of currents and their short-term variability. Their
existence may essentially modify the transport of potential adverse effects compared
with the classical understanding of the local circulation. Moreover, in certain cases
they predominantly carry water (and pollution ) in a preferred direction that not necessarily matches the downwind or downwave direction (Soomere et al. 2011). On
the one hand, such phenomena obviously have a high potential for the rapid and
systematic transport of both water masses and adverse impacts such as nutrients,
toxic substances or oil pollution between specific sea areas. On the other hand,
their smart use offers a particular solution to the problem of reduction of anthropogenic impacts to vulnerable areas. Namely, if the resulting patterns of transport
are systematic enough, they can be used for placing human activities (such as marine
traffic) in specific regions (areas of reduced risk), from which the pollution transport
to vulnerable or high-cost areas is unlikely (Soomere and Quak 2007).
1.12 Quantification of Offshore Domains
It is heuristically obvious that such current patterns and associated features of (Eulerian or Lagrangian) 8 transport may provide a clear environmental benefit. The optimal solution is a fairway (or location where to tow the damaged ship, etc.) chosen
so that an accident, if it happens, takes place in the most favourable location. To
specify such a location, it is necessary to quantify the potential of different offshore
sites to serve as a source of risk to the vulnerable regions if pollution were to be
released at this site. For ideally homogeneous currents patterns, the most favourable
locations would be the ‘most offshore’ sites.
This picture needs to be modified if some current patterns systematically carry
adverse impacts in a certain direction. Such a transport reflects certain features
of Lagrangian flow and not necessarily coincides with the long-term patterns of
currents calculated from Eulerian velocities. Therefore, in certain areas of seas or
oceans, which host semi-persistent Lagrangian flow patterns, the potential for remote coastal damage may be smaller than it would be expected from purely geometrical arguments (such as the distance to the nearest coast). These areas are called
8 The Eulerian specification of the flow field is a way of treating, measuring or calculation the motion properties for each fixed location in space as time passes. In marine conditions one has to use
fixed moorings in order to properly measure the Eulerian velocities. This framework is mostly used
in circulation modelling. The Lagrangian specification is a way of looking at fluid motion where the
observer follows an individual water particle as it moves through space and time. The transport of
different substances and items in the marine environment is obviously Lagrangian. The Lagrangian
velocity and transport can be directly measured using drifting buoys. An overview of these specifications and their implementation in the developed technology is presented in Chaps. 3, 4 and 7.