Environmental Engineering Reference
In-Depth Information
Figure 16.
Long term variations in a) winter sea surface temperature (SST) (
◦
C) averaged over
the interior basin of the Black Sea, and b) the mean temperature (
◦
C) of the Cold Intermediate
Layer for the May-November period. The Cold (C) and Warm (W) periods since 1880 are
indicated. Positive periods of the North Atlantic Oscillation (NAO) correspond to colder, dryer
climate in the Black Sea region (C periods). Negative NAO periods are warmer and wetter (W
periods). Modified from Oguz and Dippner [44].
Recently Podymov (O.I. Podymov, Ph.D. Thesis Abstract, Shirshov Institute
of Oceanology RAS, Moscow, Russia, 2005) identified similar changes in the
boundary of the anoxic zone in the northeastern part of the Black Sea near
Gelendzhik. This part of the Sea is far from the influence of the inputs of
the Bosporus plume and Danube River. Therefore the vertical structure in this
region reflects “integrated”, rather than local, forcing.
Data from individual stations from 1989 to the present are shown in Fig. 17.
The results show that the density of first appearance of hydrogen sulfide oc-
curred from
σ
θ
=16.15-16.25 kg/m
3
from 1991 - 1998 (Fig. 17a). In 1999-2000
this boundary appeared to shoal by about
σ
θ
= 0.05-0.15 kg/m
3
(corresponding
to about 5-15 m). After 2000 the density was more stable. The same tendency
can be seen for the increase of ammonium, total manganese and methane (Fig.
17 b, c, d). These changes appear related to the two warm winters that occurred
in 1998-1999. This probably affected the balance between the input of fresh
water from rivers and saline water from the Bosporus and the winter formation
of the oxygen-rich CIL. In these same years there was an increase in sea surface
temperature, an increase of temperature of the CIL [44], and shoaling of CIL in
