Railsback's Some Fundamentals of Mineralogy and Geochemistry
The Black Sea IIIa: Variation with depth
The Black Sea is a strongly stratified body
of water because its deep water is much more
saline than its surface water. This difference
results from inflow of freshwater from rivers to
give the dilute surface waters, and from deep
inflow of seawater through the Bosporus to
supply the salinity of the Black Sea's deep
waters. However, even the deep water of the
Black Sea is much less saline than typical
oceanic seawater, as shown below.
Vertical variation in temperature in the
Black Sea is also very different from that of
the global ocean. Deep water in the Black
Sea, former shallow water of the Aegean, is
relatively warm, but a cold intermediate layer
separates that deep water from the warm
20
22
24
26
28
30
32
34
0
36
2
4
6
8
10
12
1600
A freshwater lake would plot at S = 0.1 to 0.5 ppt
Depth (meters)
1200
0
Typical
oceanic
thermocline
and thus
pycnocline
400
800
14
100 200 300
Another Black Sea oddity:
the Cold Intermediate Layer
Pronounced halocline
and thus pycnocline
Black Sea
Oxygen (O2) (micromoles)
Temperature (°C)
Salinity (ppt)
18
surface water.
The strong pycnocline or density gradient
forced by the halocline means there is little
vertical mixing in the Black Sea. As a result,
little atmospheric O2 reaches the deep water,
which is consequently markedly anoxic. Part
IIIb explores the resulting chemically unique
nature of the Black Sea's deep water.
No significant
halocline
Typical
global
ocean
Typical
global
ocean
Typical oceanic
O2-minimum zone
Black Sea
Note the large difference in salinity:
is the Black Sea a part of the ocean
or a lake with a saltwater influx problem?
Black Sea
Typical
global
ocean
Anoxia at depth
in the Black Sea
2000
Source of Black Sea data: Yakushev, E.V., et al., 2008, Vertical hydrochemical structure of the Black Sea, in Kostianoy,
A.G., and Kosarev, A.N., The Black Sea Environment: Springer Handbook of Environmental Chemistry v. 5Q, p. 277-307.
LBR BlackSeaTSOProfile01 5/2010