Cold Intermediate Layer of the Black Sea according to the Data of Field Research in 2016–2019

A. N. Morozov*, E. V. Mankovskaya

Marine Hydrophysical Institute of RAS, Sevastopol, Russia

* e-mail: anmorozov@mhi-ras.ru

Abstract

This paper aims at presenting and discussing the cold intermediate layer averaged characteristics obtained from a preliminary analysis of the data of twelve expeditions carried out by the Marine Hydrophysical Institute in 2016–2019 in the northern and north-eastern regions of the Black Sea. The study uses data of CTD-measurements and current velocity profiles measurements obtained in 2016–2019 expeditions. Vertical profiles of temperature, potential density, buoyancy frequency, and velocity and direction of currents are considered and analyzed. The relationship between the average monthly air temperature and average values of minimum water temperatures is considered. The dependence of the average salinity in the cold intermediate layer core on the minimum water temperature is obtained. Isopicnically averaged dependences of water temperature and buoyancy frequency were obtained and analyzed. For 2017, the vertical turbulent diffusion coefficient in the cold intermediate layer core was estimated. The water temperature less than 8 °C in the cold intermediate layer core was observed only in the 2017 expeditions. After a cold winter of 2016–2017, the relaxation time of exponential recovery of the layer core temperature was one year. The minimal water temperature of the cold intermediate layer is observed at a potential density of 14.5–14.6 kg/m3 in the vicinity of buoyancy frequency local minimum between the seasonal thermocline and the main halocline. Disturbances of the vertical thermal structure caused by a cold winter of 2016–2017 can be traced to the depth of the isopycnic with a potential density of 15.7 kg/m3. During the observation time, the lower boundary of the layer at a temperature of 8.6 °C was rising at an average speed of 10 m per year. Indirect estimates of the vertical turbulent diffusion coefficient in the cold intermediate layer core were about 6·10-6 m2/s.

Keywords

cold intermediate layer, Black Sea, vertical turbulent mixing

Acknowledgments

The research is performed under state order on topics No. 0827-2019-0002 “Operational oceanology” and No. 0827-2019-0004 “Coastal studies”.

For citation

Morozov, A.N. and Mankovskaya, E.V., 2020. Cold Intermediate Layer of the Black Sea according to the Data of the Expedition Field Research in 2016–2019. Ecological Safety of Coastal and Shelf Zones of Sea, (2), pp. 5–16. doi:10.22449/2413-5577-2020-2-5-16 (in Russian).

DOI

10.22449/2413-5577-2020-2-5-16

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