Physical Oceanography, Vol. 19, No. 3, 2009
ANALYSIS OF OBSERVATIONS AND METHODS FOR CALCULATING
HYDROPHYSICAL FIELDS IN THE OCEAN
CLIMATIC AND HYDROPHYSICAL CONDITIONS OF THE DEVELOPMENT OF
HYPOXIA IN WATERS OF THE NORTHWEST SHELF OF THE BLACK SEA
V. V. Ukrainskii and Yu. I. Popov
The data of meteorological and oceanographic observations on the northwest shelf of the Black
Sea for 1973–2000 are used to compute the characteristics of the entire area in the presence of
hypoxia of waters under the pycnocline in the summer–autumn period and the area of surface
waters with a level of salinity lower than
The time of onset of the spring warm-
ing of air (stable transition through a temperature of
A statistically significant
positive trend of the air temperature
is revealed in Odessa.
The process of
warming was observed mainly for the winter
riods and became especially intense since the beginning of the 1990s. On the basis of the data of
correlation analyses, we establish a statistically significant relationship between the large-scale
atmospheric processes [the index of North Atlantic Oscillation (NAO) and the wind conditions],
the area of surface waters whose salinity is lower than
and the total area with hypoxia in
the summer–autumn periods. For positive mean values of the NAO index (in January–March),
we most often observe early spring with elevated repetition of the south and west winds with
subsequent development of hypoxia in large areas of the northwest shelf. We propose an empir-
ical regression model for the prediction of the total area of summer–autumn hypoxia of waters
with predictors: the onset of the spring warming of air and the area of propagation of waters
whose salinity is lower than
in May. The maximum error of prediction of the area with
hypoxia does not exceed
i.e., less than
of the total area of the northwest shelf
in the Black Sea (to the north of
The processes of hypoxia in seawater are developed as a result of the consumption of oxygen in the pro-
cesses of oxidation of substances present in water under the conditions of absent or restricted supply of oxygen
from external sources. It is known [1, 2] that the most intense consumption of oxygen occurs in the process of
oxidation of organic substances and, first of all, of their readily oxidizable forms (phytoplankton). The weakly
oxidizable organic substances are deposited in the bottom sediments in the process of sedimentation, and their
subsequent decay runs mainly under the conditions of reduction.
The conditions of evolution of gases in waters of the abyssal layer in the summer–autumn period are mainly
determined by the following two principal characteristics: the intensity of vertical and horizontal exchange of
waters (and oxygen contained in these waters) and the conditions specifying the intensity of development, death,
and oxidation of phytoplankton.
Ukrainian Scientific Center of Ecology of Sea, Ukrainian Ministry for Environmental Protection, Odessa, Ukraine.
Translated from Morskoi Gidrofizicheskii Zhurnal, No.
19–29, May–June, 2009. Original article submitted January 16, 2008;
revision submitted May 26, 2008.
140 0928-5105/09/1903–0140 © 2009 Springer Science+Business Media, Inc.