Purpose. The work is purposed at summarizing the results of studies both of the spatio-temporal variability of water density stratification and the internal wave characteristics in the Barents, Kara, Laptev, East Siberian, Chukchi and Beaufort seas.

Methods and Results. Based on the World Ocean Atlas data, the average monthly profiles of buoyancy frequency were calculated at the 0.25° × 0.25° grid points for 1959–2020. To study the vertical structure and dispersion characteristics of internal waves, the eigenvalues and eigenfunctions of the main boundary value problem of the Sturm – Liouville type were found at the fixed values of a wave number. The regional features of vertical structure and intra-annual variability of the Väisälä – Brunt frequency were revealed. The relationship between the water density vertical structure and the free internal wave characteristics in the seas under consideration was analyzed.

Conclusions. It is shown that maximum water stability in the Barents Sea takes place in July – August, in the Kara Sea – in September and November, in the Laptev Sea – from June to November, in the East Siberian and Chukchi seas – in July, and in the Beaufort Sea – in June. In the same months, the smallest values of the amplitude of vertical velocity component as well as the smallest own periods of internal waves are noted. The depth of maximum values of the vertical component amplitude of internal wave velocities exceeds that of the density gradient maximum values by about 10–20 m.