Black Sea vertical circulation and extremes of the hydrochemical and hydrooptical parameters

A statistical evaluation of vertical current velocity profiles w(z) has bee n undertaken using data provided by current meter profilers. The calculatio n of profiles w(z) involves the estimation of the standard deviation of ver tical current at each depth level, and the standard deviation of the statis tical variability of that estimate. Profiles w(z) have been computed for th e northwestern Black Sea, using current meter and CTD data from three surve ys carried out during 1992-1994. The calculations show w(z) to have a two-l ayered structure, with zero values occurring in the main pycnocline. Such v ertical current structures are consistent with a hydrodynamic model, whereb y the current field is induced by buoyancy fluxes through the lateral basin boundaries. Existence of zero vertical current velocities at the pycnoclin es yields the key to understanding the mechanisms responsible for the oxic- anoxic interface, and of the zones with steep vertical gradients in hydroch emical and hydrooptical characteristics. (C) Elsevier, Paris / Ifremer / CN RS / IRD.