Environmental Engineering Reference
In-Depth Information
1. Introduction
Due to reasons of non-scientific character, the surface tides in the Arctic Ocean have
been studied from a theoretical viewpoint better than the internal tides. Really, if about 10
tidal models were developed to simulate the surface tides [Schwiderski, 1979; Kowalik, 1981;
Proshutinsky, 1993a, b; Gjevik and Straume, 1989; Polyakov and Dmitriev, 1994; Lyard,
1997; Padman and Erofeeva, 2004], then the all we know about the internal tides (otherwise,
about the internal tidal waves (ITW)) was obtained using data of individual in-situ
measurements of seawater temperature and conductivity in western adjacent seas of the Arctic
Ocean (Zubov, 1950; Levine, 1983, 1990, Levine et al., 1985, 1987; D'Assaro and Marehead,
1991; Plüddemann, 1992; Pisarev, 1996; Kozubskaya et al., 1999; Konyaev, 2000, 2002;
Konyaev et al., 2000; Serebryannii and Shapiro, 2001; Sabinin and Stanovoy, 2002; Smirnov
et al., 2002; Serebryannii, 2002]. From these data and general considerations, it follows that
the ITW and generally the internal waves (IW) in the Arctic Ocean differ from their images in
other oceans by
a low (more than an order of magnitude) energy level and, hence, smaller ITW
amplitudes than in other oceans. For example, according to Levine et al. (1987), total
energy, integrated over the internal wave frequency band, is 15 - 30 times less than
its observed values in low latitudes;
a horizontal non-isotopic field, as opposed to its isotropicity in low latitudes. This
implies that the IW in the Arctic Ocean differ in generation and propagation from
those observed in other oceans; and
the proximity of the critical latitude (this concerns the ITW with semidiurnal
periods). Its result are the impossibility to propagate the ITW as free waves beyond
the critical latitude, a rapid decay as the distance moves away from generation sites,
when present, and a decrease for critical relative topographic slopes (the definitions
appearing here may be found in Section 3).
The first two ITW dissimilarities of the Arctic Ocean are usually associated with the non-
uniqueness of mechanisms of the ITW generation and dissipation due to the presence of ice
cover [Levine et al., 1987] or different forcings in ice-covered and ice-free seas [D'Assaro
and Morehead, 1991]. These explanations seem contrary to a solution of the problem on the
ITW vertical structure in ice-covered seas [Savchenko and Zubkov, 1976] and modeling data
for the stratified and homogeneous Arctic Ocean [Kowalik, 1981; Kowalik and Proshutinsky,
1991]. The articles outlined above testify that the effect of ice on low-frequency IW (in
particular, on the ITW) can be neglected. A different situation arises for high-frequency IW,
whose parameters depend on whether the ice cover is present or not [Muzylev and
Oleinikova, 2007].
Theoretical studies of the ITW in the Arctic Ocean are more limited than experimental
ones. We managed to find only 3 articles that were devoted to the problem being discussed.
These are the articles of Polyakov et al. (1994), Morozov et al. (2002) and Morozov and
Pisarev (2002). In the first of them, due to a low horizontal resolution, the adopted three-
dimensional finite-difference model eliminates the possibility to simulate the ITW. Whereas,
in the remaining two articles, the two-dimensional (in the vertical plane) nonlinear model of
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