Physical Oceanography, Vol. 18, No. 6, 2008
ANALYSIS OF OBSERVATIONS AND METHODS FOR CALCULATING
HYDROPHYSICAL FIELDS IN THE OCEAN
EXPERIMENTAL ESTIMATION OF THE COEFFICIENT OF VERTICAL
TURBULENT EXCHANGE IN A STRATIFIED LAYER OF
THE BLACK SEA NEAR THE CONTINENTAL SLOPE
A. S. Samodurov and A. M. Chukharev
On the basis of the data of field measurements, we present the results of numerical analysis of the
intensity of vertical turbulent exchange in stratified layers of the Black Sea in the region of the
shelf–continental-slope boundary depending on the local stratification. The experiments were
carried out within the framework of the GEF/BSERP and Black Sea-2004 international pro-
jects. The data were obtained by using a probing version of the Sigma-1 measuring complex.
In processing the data of measurements, we apply a procedure of evaluation of the coefficient of
vertical turbulent diffusion depending on the external conditions based on the analysis of the
spectra of the gradient of temperature fluctuations. For the two studied regions of the shelf, the
coefficients of turbulent exchange turn out to be much higher (by about an order of magnitude)
than for the open sea under similar conditions. This can be explained by the specific features of
the bottom topography affecting the dynamics of quasiinertial waves playing to role of the main
causes of small-scale mixing and vertical diffusion.
The processes of vertical turbulent exchange in the upper layers of the Black Sea play an important role in
the redistribution of heat, salt, and various dissolved chemical admixtures. The experience accumulated in the
last decades in the development and verification of the models used to describe the processes of exchange shows
that it is impossible to get good qualitative and quantitative agreement between the model and field data without
the detailed knowledge and proper analysis of the basic physical mechanisms guiding these processes. The aim
of the present work is to determine the coefficients of vertical turbulent exchange according to the experimental
data on the small-scale structure of the upper stratified layer in the region of continental slope in the northwest
and northeast parts of the Black Sea. The shear instability and local mixing in the system of quasiinertial internal
waves are regarded as the main mechanisms responsible for the vertical exchange in the investigated region.
One of the analyzed data arrays was accumulated in the course the cruise of the R/V (research vessel) Aka-
demik of the Bulgarian Academy of Sciences realized within the framework of the GEF/BSERP project in May
Marine Hydrophysical Institute, Ukrainian Academy of Sciences, Sevastopol, Ukraine.
Translated from Morskoi Gidrofizicheskii Zhurnal, No.
14–24, November–December, 2008. Original article submitted May 29,
308 0928-5105/08/1806–0308 © 2008 Springer Science+Business Media, Inc.