Environmental Engineering Reference
In-Depth Information
Vlasenko (1991) was employed to simulate the ITW generation and propagation in western
adjacent seas of the arctic continental shelf. The ITW were assumed to be plane and
propagate to coast or continental slope at a right angle. This assumption is justified by the
incommensurability of the ITW-induced variability in the normal and transversal directions:
the variability in the first case is much more than in the second one. The mere fact of the
incommensurability of the ITW-induced variability in the normal and transversal directions is
true. This does not rule out the necessity of simulating the ITW three-dimensional structure,
precisely which it is in the reality. Moreover, there is evidence [Craig, 1988, Holloway, 1996,
2000; Cummings and Oey, 1997; Katsumata, 2006] that the conversion of barotropic tidal
energy into the baroclinic one and back depends radically on the dimension of the model in
use (whether the model is two-dimensional (2D) or three-dimensional (3D)). We shall stress
once again that the cited investigations are mainly concerns with western adjacent seas of the
Arctic Ocean, whereas the Central and Kanadian Arctics and eastern adjacent seas of the
Siberian continental shelf still remain unstudied in both experimental and theoretical respects.
Otherwise, the issue as to the ITW climatology in the Arctic Ocean has not been solved.
There is an additional motivation for studies on the ITW in the Arctic Ocean. We bear in
mind the necessity of evaluating a mixing rate and developing an adequate scheme of its
parameterization. As known, observed values of the vertical eddy viscosity can vary from
0.1 cm
2
/s in the thermocline [Ledwell et al., 1993, 1998] to 10 cm
2
/s in the abyssal over rough
topography [Polzin et al., 1977; Ledwell et al., 2000]. The maintenance of such an intensity of
vertical eddy mixing requires a large supply of mechanical energy. One of sources of this
energy is the interaction of barotropic tidal waves with bottom and/or coastline irregularities.
Usually, the global supply of energy to the ITW is evaluated using measurements and tidal
models [Egbert and Ray, 2000, 2001; Jaine and St. Laurent, 2001; Niwa and Hibiya, 2001].
However, because a direct relationship between forcing and the mixing rate in the deep ocean
has not been established, we shall be forced to base on experimental data only.
From these data, it is evident that the mixing rate is enhanced in the ITW generation sites
[Ledwell et al., 2000; Kunze and Toole, 1997; Lueck and Mudge, 1997; Polzin et al., 1997;
Lien and Gregg, 2001; Pinkel et al., 2000; Kunze et al., 2002; Moum et al., 2002] and
attenuated outside these sites. Another possibility to evaluate the vertical eddy mixing
intensity in the deep ocean is related to an analysis of the global tidal energy dissipation
budget. To maintain the observed density stratification, corresponding to the rate of
thermohaline conveyor overturning, there is a need to dissipate ~ 2 × 10
12
W [Munk and
Wunsch, 1998]. An independent analysis of tides, performed using analytical methods,
satellite altimetry and model results, showed that the consumption of barotropic tidal energy
for the ITW generation was about ~1 × 10
12
W [Egbert and Ray, 2000, 2001; Jaine and St.
Laurent, 2001]. In the end, this energy should be dissipated and maintained the intensity of
diapycnal mixing. Thus, the IW (in particular, the ITW) are one of basic sources of energy in
oceans and, if this source is not considered, an understanding of the present-day state of
oceans and its changes in the future, like the climatic system as a whole, is impossible in
principle. Attempts at developing the global ocean circulation models with tidally induced
mixing are available [Jaine and St. Laurent, 2001; Simmons et al., 2004].
The aim of the present article is to simulate the poorly known ITW dynamics and
energetics in the Arctic Ocean for winter conditions and show distinctive features of the
Arctic Ocean ITW. The tasks of the article are:
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