Semidiurnal Internal Tide North and South of the Critical Latitude in the Kara Sea

Temperature measurements data are analyzed from two moorings in the Kara Sea, north of the critical latitude for semidiurnal internal tides (74°30′ N) at a point at 74°54.3′ N, 69°43.6′ E, and south of the critical latitude at a point at 71°14.2′ N, 65°36.3′ E. The moorings operated over one year from 15 October 2021 to 15 September 2022. However, only the data from ice-free months were analyzed. Temperature fluctuations measured on the moorings reflect vertical motions associated with internal waves. The estimated temperature fluctuation spectra were either characterized by a reliable peak related to semidiurnal internal tide (period 12.4 h) or this peak was absent. The semidiurnal spectral peak appeared when the spectrum was calculated from the temperature measurements on the moorings when mean vorticity in the mooring region, derived from satellite altimetry data, was anticyclonic (negative). Those without peaks were related to the periods of cyclonic vorticity. High-resolution SAR data showed numerous packets of short-period internal solitary waves in the vicinity of moorings when peaks at the M2 frequency were present. At such periods, anticyclonic vorticity permitted free propagation of internal tidal waves from the slope regions, and generation of high-frequency waves could have resulted from internal tide evolution.