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|$B9V1i||Dr. Patrice Klein
Wind ringing of the ocean in presence of mesoscale eddies: $B!!(B
a possible route to mixing.
We analyse the horizontal and vertical propagation of wind-forced
near-inertial motions in a fully turbulent mesoscale eddy field with
a primitive equations numerical model. One result is that the vertical
kinetic energy of the near-inertial motions penetrates into the ocean
interior more quickly and much deeper than the horizontal kinetic
energy. Two maxima of near-inertial vertical velocity (both with r.m.s.
values reaching 60 m/day) appear, one around 100 m and another
unexpected one around 3000 m. The shallower maximum involves vertical
motions with the inertial frequency (f) and a spatial heterogeneity
that resembles the eddy vorticity gradient field.
The deeper maximum involves a dominant frequency of twice the inertial
frequency and smaller space scales. The emergence of the two maxima
results from the phase shift of the lower vertical modes from the
higher ones. A consequence of the appearance of the 2f frequency at
large depths is that parametric subharmonic instability may then work.
As such these result reveal a pathway by which the wind energy quickly
penetrates into the deep interior where it would be available to mixing.