The Energy Spectrum of the Current Velocity in the Deep Part of the Black Sea

Abstract

In 2016–2017, the yearly long measurements of the current velocities were carried out at 100 m depth below the thermocline and at 1700 m depth for the first time, which was about 100 m above the seabed using the mooring station in the deep central part of the Black Sea. The analysis of this new dataset allowed us to uncover the following. In the near-bottom layer, significant current 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 sea layer below the thermocline. In the range of the balanced geostrophic motions at a depth of 1700 m, the energy spectrum had a slope of –2.8, which should be compared to the spectrum slope of –1.8 obtained for the current below the thermocline at the depth of 100 m. Regular strong currents were observed around 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.