On the internal structure of the Kuril current anticyclonic rings

Data of Argos drifters, XBT and acoustic sections show that anticyclonic rings of the Kuril current contain enhanced near-inertial disturbances. The near-inertial period is significantly increased and reaches the value of the diurnal tide in the ring 86B. XBT and acoustic data show that the dominant wave length in the two anticyclonic rings in equal to 25-60 km. These observations also show the amplitude of internal tide of 50 m within the Strait of Freez and the western boundary of the ring 86B during the tropic tide, and 60 m inside the ring off Paramushiru Island. We show that the diurnal tide can be a plausible generation mechanism for near-inertial oscillations inside the rings. Negative vorticity of the anticyclonic eddy and Doppler frequency shift provide resonance with the tide and trapping of near-inertial waves inside the rings. Resonant high amplitude inertial oscillations are typical not only to the surface layer but they are also observed down to the depths of 800 m.