Seasonal variability of currents structure in the Black sea Northern part from field measurements in 2016

Abstract

This paper presents new results obtained during combined processing of the current and the conditional density measurements in three cruises in July, October and November 2016 in Northern part of Black sea. Current velocity profiles were measured using a Lowered Acoustic Doppler Current Profiler. The spatial distributions of current are presented. The specific features of the vertical distribution of kinetic energy averaged for all stations in the sea active layer are discussed. It is shown that the decrease of kinetic energy with depth occurs most rapidly in the layers of seasonal and permanent pycnoclines. It is established that there is an almost linear relation between kinetic energy and conditional density. The seasonal variability of average kinetic energy occurs to depth of isopycnic with the value of conditional density is 16.7 kg/m3 . The profiles of the squared vertical shear of current velocity isopycnically averaged from ensemble of stations are given. In the main pycnocline layer, in the vicinity of the buoyancy frequency maximum, the maximum of squared shear is noted for each expedition. The profiles of vertical turbulent diffusion coefficient in layers of permanent picnocline derived from fine-scale data using G89 parameterization are discussed. According to date of three cruises the increasing of vertical exchange processes with depth growing is observed. The highest value of the coefficient diapycnal exchange occured in the summer season.