Characteristics of the Bottom Convective Layer of the Black Sea Based on in-situ Data (July, 2016)

A. N. Morozov✉, E. V. Mankovskaya

Marine Hydrophysical Institute of RAS, Sevastopol, Russian Federation

✉ e-mail: anmorozov@mhi-ras.ru

Abstract

Purpose. The purpose of the work is to detail the vertical structure of thermohaline characteristics near the upper boundary of the bottom convective layer based on the CTD measurements, to estimate the heat and salt fluxes, and to study variability of various layer characteristics depending on the geographic location of the stations.

Methods and Results. The data of the SBE 911plus CTD probe obtained in the 87th cruise of the R/V Professor Vodyanitsky which took place in June 30 – July 18, 2016 in the central sector of the northern Black Sea were used. The depth of the bottom convective layer upper boundary was revealed to be variable (1713–1922 m), on the average 1800 ± 60 m. Noted was a tendency for the upper boundary to rise by 150–200 m during transition from the western gyre to the eastern one. But at two stations, the layer was not observed up to the depths exceeding 1900 m. The variation range of potential temperature in the layer was 1.6 ⋅ 10−3°C, and that of salinity – 1.2 ⋅ 10−3 psu. Decrease both of the potential temperature and salinity in the bottom convective layer with increasing longitude and of potential temperature with the layer thickness increase was revealed. The coefficient of vertical turbulent diffusion at 150 m above the layer upper boundary was 1.1 ⋅ 10−5 m2/s. The calculated values of the heat and salt vertical fluxes in 150 m above the bottom convective layer upper boundary constituted 1.6 mW/m2 and 2.9 ⋅ 10−7 g/(m2⋅s), respectively.

Conclusions. Having been analyzed, the data of contact deep-sea thermohaline measurements showed that the Black Sea bottom convective layer was unstable and spatially inhomogeneous, and the location of its upper boundary was variable. The data obtained permit to assume that the eddies penetrate to the deep layers of the sea and manifest themselves in significant deepening of the bottom convective layer upper boundary. In the western part of the sea, the bottom convective layer waters are warmer and saltier than those in its eastern part. Almost the entire geothermal heat flux is dissipated in the bottom layer. To maintain salt balance in the bottom convective layer, there should be a mechanism for replenishing salt in the lower layers of the seabottom convective layer, bottom layer, spatial variability, vertical mixing, vertical heat flux, vertical salt flux, Black Sea.

Keywords

bottom convective layer, bottom layer, spatial variability, vertical mixing, vertical heat flux, vertical salt flux, Black Sea

Acknowledgements

The study was carried out within the framework of the state assignment on themes No. 0555-2021-0003 and No. 0555-2021-0005.

Original russian text

Original Russian Text © A. N. Morozov, E. V. Mankovskaya, 2022, published in MORSKOY GIDROFIZICHESKIY ZHURNAL, Vol. 38, Iss. 5, pp. 548-561 (2022)

For citation

Morozov, A.N. and Mankovskaya, E.V., 2022. Characteristics of the Bottom Convective Layer of the Black Sea Based on in-situ Data (July, 2016). Physical Oceanography, 29(5), pp. 524-535. doi:10.22449/1573-160X-2022-5-524-535

DOI

10.22449/1573-160X-2022-5-524-535

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