** Authors:**
ALEC GAINES, GRAHAM M. COPELAND, YEŞİM ÇOBAN-YILDIZ, EMİN ÖZSOY, A. S. DAVIE, SERGEYI K. KONALOV

** Abstract: **
The Rhodes Gyre, a prominent feature of the oceanography of
the eastern Mediterranean, is modelled as a vertical, continuous flow,
cylindrical reactor illuminated during the day at its upper end. If
the Gyre is supposed to be in a steady state whilst the
concentrations, C, of a chemical are being measured, the nett rate of
formation or consumption of the chemical is given by -w \delta
C/\delta z + u \delta C/\delta r, where w is the upward velocity of
the water in the vertical, z , direction and u is the velocity of the
water in the radial, r, direction. The behaviour of w and u is
analysed to show that the Gyre may be used as a field laboratory in
which rates of chemical change may be derived from depth profiles
together with values of the surface velocities of the Gyre waters.
In contrast, the central Black Sea is modelled as an ideal, strongly
stratified sea in which the nett rates of formation or consumption of
chemicals under steady state conditions are given by D_{\sigma}
d^2C/d\sigma ^2, where \sigma is the water density and D_{\sigma} is
an eddy diffusion coefficient. Computations reveal that, given better
knowledge of its eddy diffusion coefficients, the Black Sea can also
be treated as a field laboratory where rates of reaction mediated by
bacteria may be derived from depth profiles.

** Keywords: **
Rhodes Gyre, Black Sea, Modelling, Rates of reaction, Water
density

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