CHEMICAL AND ISOTOPIC UNIFORMITY OF THE BOTTOM CONVECTIVE WATER LAYER IN THE BLACK SEA

Abstract

The deep anaerobic water column of the Black Sea is composed of two water masses. The upper mass is stratified in terms of temperature, salinity, and potential density. The lower quasi-uniform mass is located below 1680–1800 m [1–4]. The volume of the bottom water (400–500 m thick) is comparable with that of the aerated surface layer. The uniformity of bottom waters is confirmed by measurements of salinity and potential temperature, while in situ temperature measurements show its downward increase. The virtually uniform bottom water mass (bottom convective layer, BCL) is characterized by a neutral or slightly negative thermohaline stability and following hydrological parameters: S = 22.333 psu, θ = 8.885–8.886°C, σθ = 17.235 kg/m3. The position of the upper BCL boundary is laterally variable, although its general topography remained practically stable during repeated measurements over several years.