Vertical structure of the field of current velocities in the northwest part of the Black Sea based on the LADCP data for May 2004

Abstract

The profiles of absolute current velocity obtained by using a lowered acoustic doppler current profiler (LADCP) are presented. In the course of the BSERP-3 expedition, the measurements were carried out in the regions of the Rim Current, anticyclonic eddy, and northwest shelf. In the core of the Rim Current, a unidirectional motion of waters is traced in layers below the main pycnocline down to depths greater than 500 m. Its characteristic velocity can be as high as 0.08 m/sec. It is shown that the direct action of the eddy is detected in the shelf region at distances larger than 20 km from the outer edge of the shelf in the zone bounded by an isobath of 100 m. The formation of multilayer vertical structures in the field of current velocities is revealed in the region of interaction of the anticyclonic eddy with irregularities of the bottom on the side of the shelf. A two-layer structure of currents with specific features in the layer of formed seasonal pycnocline is observed in the region of the shelf down to an isobath of 100 m. The profiles of the moduli of vertical shears of currents averaged over the casts ensemble are presented for the abyssal and shelf parts of the sea. It is shown that the shears induced by the geostrophic currents and wave processes in the region of the main pycnocline are comparable. Below the pycnocline, the shears are mainly determined by the wave processes.

Structure of the Black Sea Currents Based on the Results of the LADCP Observations in 2004–2014

“…In particular, according to the LADCP data of Expedition 1 kinematic characteristics of the anticyclonic eddy [9] and the spatial scales of the current velocity field variability in the surrounding area were determined. [24] In the continental slope area a pronounced correlation of the vertical current velocity field structure with the vertical distribution of the conditional density is observed. Fig.…”

“…The maximum vertical shifts are registered near the core of the cold intermediate layer (CIL), where there is a break in the density gradient. " Maximal velocity shears, according to [14], are located in layers of 10 -25 m and 50 -300 m. The authors of the paper [24] showed that in the Black Sea, the mean profile of the vertical shears has two well-defined maxima in the layers of the seasonal thermocline/pycnocline and main halocline/pycnocline. Maximal vertical shear in the density contrast layer separating the Azov and Black Sea waters is observed in the southern part of the Kerch Strait [31].…”

“…3, left). Data was collected in Expedition 1 (May 2004) [23,24]. CTD data are supplemented by the current velocity profiles.…”

“…In the Black Sea, the profiles of shears and buoyancy frequencies have a wellpronounced maximum in the main halocline/pycnocline layer [22,24]. Fig.…”

Generation of Vertical Fine Structure by Internal Waves in a Shear Flow

“…The Brunt-Väisälä frequency profile, the two components of the flow velocity and the eigenfunction of the fifteen-minute internal wave of the second mode are shown in Figure 4. The data of soundings of the LADCP (Lowered Acoustic Doppler Current Profiler) [29] are used.…”