Environmental Engineering Reference
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the entire abyssal plain, is the largest known example of bottom convection in
the world ocean [67].
Distribution of dissolved sulphide in the bottom layer varies between differ-
ent parts of the sea as shown in Fig. 7 and can be explained by spatial differences
in the bottom heat flux [45]. Eremeev and Kushnir [22] have found that the
width of the bottom convective layer is directly proportional to the intensity
of heat flux from the bottom. Transects covering the area opposite to Sochi
show higher dissolved sulphide concentrations in water layers below 1650 m
(Fig. 7a, c) compared to other transects (Fig. 7b, d). The upper boundary of the
bottom convective layer at the terminal stations of the Sochi transect shoal up
to 1650-1680 compared to its location at 1750-1800 m close to Sochi, which
corresponds to the local maximum of the surface heat flow observed in this
region [45].
Figure 6. Vertical distributions of potential temperature θ (continuous line) and dissolved
hydrogen sulphide ( H 2 S) (circles) in the bottom convective layer (data are from 2002 R/V
Akvanavt expedition, station locations are shown in Fig. 2).
A relative increase in the H 2 S vertical gradient is observed at the boundary
between the intermediate water mass and bottom waters below 1640-1750 m
in the zone of 20-50 m (Fig. 6 and Table 1 last column; 106, 107]. Higher
vertical gradients of thermohaline and chemical parameters are typical in this
zone. The H 2 S concentrations in bottom waters increase with the increased
heat flux at the bottom and with larger volume of the bottom convective layer.
The existence of the bottom homogeneous layer has important implications
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