The energy spectrum of the current velocity in deep layers of the Black Sea

In 2016-2017, for the first time, nearly year-long measurements of the current velocities were carried out below the thermocline at a depth of 100 m and at a depth of 1700 m that was about 100 m above the seabed by using the mooring station in the deep central part of the Black Sea. Analysis of the new data set allowed us to uncover the followings. In the near-bottom layer, the significant flow velocities were recorded, reaching a peak magnitude of 0.13 m/s. Near the frequency of 1·10^-6 Hz, in the transition region of the energy spectrum, the spectral energy of the deep current was close to that observed in the same range in the subthermocline layer of the sea. In the range of balanced geostrophic motions, the energy spectrum had a slope of -2,8 that should be compared to a spectrum slope of -1,8 obtained for current below the thermocline. The regular strong horizontal currents were observed near the local inertial frequency f_I. There was a “blue shift” of the inertial maximum up to 5% with respect to f_I in the energy spectrum.