Environmental Engineering Reference
In-Depth Information
Figure 5.
Left panel. Potential temperature-salinity diagram for the data shown in Figure 4a,
b. (from Knorr 2001; Leg 1 Stn 1 (Bosporus) and Stn 6 (Central Western Gyre); Right panel.
Combined temperature-salinity for Black Sea and Bosporus. The Bosporus data are open circles
and the densest water hasS=36andT=14
◦
C.
and salty water is the Bosporus Plume and S and T increase all the way to the
bottom. Based on the salinity balance for the deep Black Sea (50 m to 2200 m)
the ventilating water is composed of an average CIL to Bosporus entrainment
ratio of
4:1 [39]. Thus, on average the composition of the Bosporus Plume
resembles a mixture of 4 parts CIL with 1 part high salinity Bosporus inflow
from the Mediterranean.
In detail this ratio is higher in the upper few 100 m and lower in the deeper
water. Buesseler et al. [7] used Cs isotope data to estimate an entrainment ratio
of 10 for depths shallower than 200 m. Lee et al. [30] used chlorofluorocarbon
(CFC) data to model the decrease in ventilation and increase in residence time
with depth over the upper 500 m. The entrainment ratio of CIL to Bosporus
inflow decreases from
∼
10 in the suboxic layer to 3.8 for depths near 500 m.
The residence time of water increases from 4.8 yr in the suboxic zone to 625
yr at 500 m over the same interval.
Microstructure profiles have been used to study mixing in the Black Sea.
Diapycnal diffusivities (K
ρ
) calculated from microstructure measurements of
turbulent dissipation were only (1-4) x 10
−
6
m
2
s
−
1
in the lower part of the CIL
and in the suboxic zone with no apparent dependence on (the density gradient
or N) [17]. Consequently, turbulent fluxes are too slow to replace the oxygen
consumed by respiration. Thus the Black Sea has an oxygen containing surface
layer and a sulfide containing deep layer.
∼
