Physical Oceanography, Vol. 13, No. 6, 2003
THERMOCHALINE CONVECTION IN THE EDGE-ICE ZONE IN THE
BARENTS SEA TO THE EAST OF SPITSBERGEN
V. M. Kushnir, E. Hansen, V. K. Pavlov, and A. N. Morozov UDC
The analysis of the thermochaline (double-diffusive) convection in the edge-ice zone of the Ba-
rents Sea to the east of Spitsbergen was performed by using the data of two hydrological surveys
of the Norwegian Polar Institute in 1999 and 2000. The Turner’s model, where the critical Ray-
leigh number is determined by using the empirical relationship between the Nusselt number and
the Rayleigh number normalized to its critical value, was used for analysis. The results of cal-
culation of thickness of the convective layer were compared with the data of supervision. The
estimates of the vertical convective velocity were obtained.
Thermochaline or double-diffusive convection is often encountered in marine environments. It is caused by
the gradients of temperature and salinity (taken with different coefficients of molecular diffusion k
These gradients exert the opposite influence on the vertical stability of the water environment. Under certain
conditions, this influence results in the development of convective instability and effective mixing of water lay-
ers with different thermochaline parameters. The mechanism of double-diffusive convection is determined by
the fact that the vertical propagation of heat occurs faster than the propagation of salt.
Double-diffusive convection can appear, in particular, if a cold and less salty water layer lies above a layer
of warmer water with higher salinity. The processes of rather fast heating of the bottom boundary of the contact
zone and cooling of the top boundary of this zone can lead to the development of vertical convective instability.
A thermohydrodynamical model of a system of this sort and the conditions of its stability for linear temperature
and salinity gradients were considered in . It was shown that the basic parameters determining the boundary
of stability are the Rayleigh number
and the stability number (density ratio)
are the drops of temperature and salinity in the contact zone,
is the coefficient of linear
thermal expansion, and
β is the coefficient of salinity compression. Some specific features of convective pro-
cesses of this sort were studied in [2–13] and many other works (see, e.g., the surveys [14, 15]). The confirma-
tion of the fact of formation of convective layers in lakes, seas and oceans (including arctic regions) in the pre-
sence of positive vertical gradients of temperature and salinity can be found in [7, 9, 16–20].
The thermochaline structures in the form of contact zones between cold less salty water of melting ice,
and warmer (salty and dense)
waters of the North-Atlantic origin with
are typical of the edge-
ice zone in the Barents Sea located to the east of Spitsbergen.
Marine Hydrophysical Institute, Ukrainian Academy of Sciences, Sevastopol. Norwegian Polar Institute, Tromsö, Norway . Translated
from Morskoi Gidrofizicheskii Zhurnal, No.
54–66, November–December, 2003. Original article submitted July 2, 2002; revi-
sion submitted July 29, 2002.
0928-5105/03/1306–0361 $25.00 © 2003 Plenum Publishing Corporation 361