Environmental Engineering Reference
In-Depth Information
A certain view of the ITW dynamics in the Arctic Ocean may be obtained using the
model results for the baroclinic component of tidal velocity, defined as the difference between
the predicted velocity and its barotropic value. In Figure 8d, the spatial distribution along the
above section of the maximum baroclinic tidal velocity (major semi-axis of the velocity
ellipse) is depicted. We notice that the baroclinic tidal velocity in the deep stratified Arctic
Ocean is almost uniform: it is 0 - 2 cm/s both at the continental shelf and in the deep ocean.
Another remarkable feature of the baroclinic tidal velocity field is its near-one-mode
(corresponding to the first baroclinic mode) vertical structure with opposite (in sign)
velocities in the surface and deep layers and almost zero velocities at intermediate horizons.
There are no observational evidence, which might support or rule out this feature.
4. Conclusion
A modified version of the 3D finite-element hydrothermodynamic model QUODDY-4
has been applied to simulate the M 2 surface and internal tides in the Arctic Ocean. This
version differs from the original one by implementing the rotated coordinate system, which
makes it possible to obviate “the pole problem”, and considering the effects of the
equilibrium tide. It is shown that the qualitative results for the M 2 surface tide are close to
those obtained by other authors and that the ITW in the Arctic Ocean are slighter expressed
than in other oceans. The ITW in the Arctic Ocean are of nature of trapped waves, localized
near the continental slope or large-scale topographic irregularities. The ITW generation site is
spaced at a small region of the continental slope to the north-west off the New Siberian
islands. The ITW amplitudes are ~ 4 m near the generation region and decrease with distance
from it. The field of the averaged (over a tidal cycle) integrated (in depth) baroclinic tidal
energy density, like the fields of the maximum baroclinic tidal velocity and the diapycnal
mixing coefficient, also attests that the ITW in the Arctic Ocean are of nature of trapped
waves. The diapycnal mixing coefficient can significantly exceed the canonic value of the
vertical eddy viscosity, implying that the ITW may contribute to the formation of the Arctic
Ocean climate.
The vertical profiles of the averaged local baroclinic tidal energy dissipation differ in
magnitude at troughs and ridges in the deep Arctic Ocean. Its value increases with
approaching the bottom, like at Mid-Atlantic and Hawaiian Ridges . In this respect, the Arctic
Ocean is not an exception. The Arctic Ocean is not the exception as applied to the ITW decay
scale, too. It turns out that the ITW decay scale for the section going across the ITW
generation site is ~ 300 km, what is not beyond the range of its values (100 - 1000 km) for
oceans of moderate and low latitudes.
The depth-integrated total (barotropic + baroclinic) tidal energy dissipation rate in the
Arctic Ocean as a whole is ~ 1.4 × 10 10 W. It is incommensurable with the global tidal energy
dissipation rate (~2.5 × 10 12 W) following from the data of satellite altimetry [Kagan and
Sündermann, 1996]. The contribution of tidal energy dissipation in the Arctic Ocean is
negligible, even smaller than the conversion rate of barotropic and baroclinic tidal energy
(~1 × 10 12 W) in the deep World Ocean [Egbert and Ray, 2000, 2001]. For comparison:
according to Kowalik (1981), the rate of tidal energy dissipation in the Arctic Ocean is
~ 1.3 × 10 10 W for the horizontal eddy viscosity, varying from 5 × 10 8 cm 2 /s to 5 × 10 10 cm 2 /s,
and ~ 1.5 × 10 10 W for the horizontal eddy viscosity, varying from 5 × 10 10 cm 2 /s to
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