Physical Oceanography, Vol.
INTERNAL WAVES IN THE SHELF ZONE AND NEAR THE SHELF EDGE
IN THE BLACK SEA
V. A. Ivanov and A. D. Lisichenok
The data accumulated by a measuring complex equipped with a gradient-distributed temperature
sensor in the course of towing in the shelf zone near the South Coast of the Crimea and in the re-
gion where the flow of the Rim Current crosses the shelf edge are used to analyze the energy and
space characteristics of internal waves formed when the flow runs through the shelf edge and to
study the process of their propagation both to the coast and to the open part of the sea.
At present, the idea that the processes of mixing in the ocean can be described by using average coefficients
of turbulent diffusion is replaced by the concept of existence of regions with high activity of the dynamic pro-
cesses responsible for the effective mixing of waters and their exchange with waters of the open ocean. Most
likely, the role of these regions can be well played by the shelf zones . Thus, they have numerous specific
features from the viewpoint of generation, propagation, and dissipation of wave motions.
According to the existing theoretical concepts, barotropic tidal waves generate baroclinic wave motions in
the region of the shelf edge in the ocean [2, 3]. The latter then propagate both to the coast and to the open ocean.
In the process of propagation to the coast, their characteristics are affected by the decrease in depth and various
inhomogeneities of the bottom topography and the density field. As a result of the interaction with these inho-
mogeneities, one may observe the formation of internal “bores” and trains of intense internal waves. As the
waves approach the coast, the cross section of water and, hence, the phase and group velocities of waves de-
crease. The results of the interaction with frontal zones can be more complicated depending on the frequency of
waves, mutual orientation of the vectors of phase velocity, inclinations of the isopycnic surfaces in the frontal
zones, and the presence of currents with velocity shifts [3–5]. The internal baroclinic waves of tidal nature prop-
agating to the open regions of the ocean are detected at distances of hundreds and sometimes even thousands of
kilometers from the coast [6, 7]. Thus, they carry energy from the sites of generation to absolutely different re-
gions with velocities quite high for oceanic processes and then lose their energy. Quite often the shape of intense
internal waves of tidal nature is nonlinear and, just as shelf waves, they are frequently accompanied by trains of
intense short-period waves.
In the Black Sea, the amplitudes of barotropic tides are insignificant and, thus, the baroclinic tidal waves
are practically absent. At the same time, near the shelf edge, there exists a flow of the Rim Current with a veloc-
ity of about
and even higher. The presence of meanders and inertial oscillations creates situations in
which the component of the current velocity perpendicular to the coast can be as large as
larger), which is comparable with the velocities of tidal currents in tidal seas [1, 7]. The presence of intense
short-period internal waves appearing with inertial periods enables us to make a conclusion concerning the ne-
cessity of investigation of the mechanisms of generation of internal waves connected with the interaction be-
tween the Rim Current and the shelf edge in the Black Sea .
The aim of the present work is to study specific features of short-period internal waves in the shelf zone of
the South Coast of the Crimea and directly at the shelf edge in order to reveal possible sources of their genera-
Marine Hydrophysical Institute, Ukrainian Academy of Sciences, Sevastopol. Translated from Morskoi Gidrofizicheskii Zhurnal,
58–64, November–December, 2002. Original article submitted March 13, 2001; revision submitted April 23, 2001.
0928-5105/02/1206–0353 $27.00 © 2002 Plenum Publishing Corporation 353