288
T. Soomere
and the Kattegat that supplies the deeper parts of the Baltic Sea with oxygen-rich
waters. The dynamics of water masses in this area is described in more detail in
Sects. 5.2.2, 5.2.5 and 5.3.3.
The interplay of brackish Baltic Sea waters with saline North Sea water masses
results in strong salinity gradients and small values of the baroclinic (internal)
Rossby radius 2 R 1 in this area. This measure usually varies from 1–4 km in the Belt
Sea (Fennel et al. 1991) and is about 5 km in the Arkona Basin and the Pomeranian Bay (Osi´ nski et al. 2010). Therefore most of the medium-resolution circulation
models with a grid step around 2 nautical miles (nm) are barely eddy-permitting
and a finer resolution is needed to properly resolve the dynamics in this domain.
Consequently, the application of the technology of preventive coastal protection for
this region (Lu et al. 2012) presents an intricate challenge for modellers.
9.2.2 The Gulf of Finland
The situation is equally intricate in the Gulf of Finland. The width of its navigable part is at places below 50 km and extensive domains in its eastern part are too
shallow for large ships. The concentration of traffic is exceptionally high in several
narrow passages that can host the largest ships sailing to the eastern end of the gulf
(see Fig. 10.1 in Chap. 10). The major long-haul fairway from the Northern Gotland
Basin (see Fig. 2.1 in Chap. 2 or Leppäranta and Myrberg 2009 for the contemporary partition of the Baltic Sea) to the eastern region of the gulf crosses an intense
fast ferry link between Helsinki and Tallinn. In the recent past more than 50 gulf
crossings took place daily along this route during the high season (Parnell et al.
2008). The traffic flow has decreased to some extent since then but still hosts 30–
40 gulf crossings a day (Kurennoy et al. 2011). The listed circumstances increase
the odds for a release of various adverse impacts (oil or chemical pollution) or hazardous objects into the sea owing either to an accident, to technical problems or to
human mistakes or misbehaviour. The associated impact may be dangerous to both
the environment and to other vessels.
A thorough overview of the physical oceanography of the Gulf of Finland is
presented in Chap. 6. This easternmost prolongation of the Baltic Sea has a total
length of about 400 km, maximum width of 125 km and a mean depth of only 37 m
(Soomere et al. 2008). Similarly to the gateway to the Baltic Sea, this basin also has
complicated geometry and bathymetry, strong gradients, small baroclinic Rossby
radius and extremely complex internal dynamics. The overall nature of its currents is
well known. A traditional view is that the mean circulation (integrated over the entire
water column) is cyclonic with an average speed of a few cm/s (Alenius et al. 1998).
This gyre not necessarily becomes evident on the sea surface where the predominant
2 See Chaps. 2–6 for a definition of this measure and for the discussion of its role in the dynamics.
T. Soomere
and the Kattegat that supplies the deeper parts of the Baltic Sea with oxygen-rich
waters. The dynamics of water masses in this area is described in more detail in
Sects. 5.2.2, 5.2.5 and 5.3.3.
The interplay of brackish Baltic Sea waters with saline North Sea water masses
results in strong salinity gradients and small values of the baroclinic (internal)
Rossby radius 2 R 1 in this area. This measure usually varies from 1–4 km in the Belt
Sea (Fennel et al. 1991) and is about 5 km in the Arkona Basin and the Pomeranian Bay (Osi´ nski et al. 2010). Therefore most of the medium-resolution circulation
models with a grid step around 2 nautical miles (nm) are barely eddy-permitting
and a finer resolution is needed to properly resolve the dynamics in this domain.
Consequently, the application of the technology of preventive coastal protection for
this region (Lu et al. 2012) presents an intricate challenge for modellers.
9.2.2 The Gulf of Finland
The situation is equally intricate in the Gulf of Finland. The width of its navigable part is at places below 50 km and extensive domains in its eastern part are too
shallow for large ships. The concentration of traffic is exceptionally high in several
narrow passages that can host the largest ships sailing to the eastern end of the gulf
(see Fig. 10.1 in Chap. 10). The major long-haul fairway from the Northern Gotland
Basin (see Fig. 2.1 in Chap. 2 or Leppäranta and Myrberg 2009 for the contemporary partition of the Baltic Sea) to the eastern region of the gulf crosses an intense
fast ferry link between Helsinki and Tallinn. In the recent past more than 50 gulf
crossings took place daily along this route during the high season (Parnell et al.
2008). The traffic flow has decreased to some extent since then but still hosts 30–
40 gulf crossings a day (Kurennoy et al. 2011). The listed circumstances increase
the odds for a release of various adverse impacts (oil or chemical pollution) or hazardous objects into the sea owing either to an accident, to technical problems or to
human mistakes or misbehaviour. The associated impact may be dangerous to both
the environment and to other vessels.
A thorough overview of the physical oceanography of the Gulf of Finland is
presented in Chap. 6. This easternmost prolongation of the Baltic Sea has a total
length of about 400 km, maximum width of 125 km and a mean depth of only 37 m
(Soomere et al. 2008). Similarly to the gateway to the Baltic Sea, this basin also has
complicated geometry and bathymetry, strong gradients, small baroclinic Rossby
radius and extremely complex internal dynamics. The overall nature of its currents is
well known. A traditional view is that the mean circulation (integrated over the entire
water column) is cyclonic with an average speed of a few cm/s (Alenius et al. 1998).
This gyre not necessarily becomes evident on the sea surface where the predominant
2 See Chaps. 2–6 for a definition of this measure and for the discussion of its role in the dynamics.