Self-regulation of deep-ocean internal wave continuum: Observations on related near-inertial shear and high-frequency vertical motions

Abstract

It is shown using detailed yearlong acoustic current observations between 850 and 1350 m that large-scale and small-scale waves in the ocean interior are coupled in a self-regulating fashion. Vertical current shear, a key to vertical mixing, is dominated near the local inertial frequency. Its value follows details of maximum buoyancy frequency 'Nmax' in thin layers of different density. Its frequency however, is determined by the minimum Nmin in the near-homogeneous layers between the Nmax-layers. These weakly stratified layers are maintained by overturning of density surfaces due to high-frequency internal waves guided by the shear-layers. Rare vertical current observations show a spectral continuum between [Nmin, Nmax] of low-mode interfacial waves rather than wave-groups propagating through smooth large-scale stratification. Copyright 2008 by the American Geophysical Union.