Abstract
Abstract Deep-ocean high-resolution moored temperature data are analyzed with a focus on superbuoyant frequencies. A local Taylor hypothesis based on the horizontal velocity averaged over 2 h is used to infer horizontal wavenumber spectra of temperature variance. The inertial subrange extends over fairly low horizontal wavenumbers, typically within 2 × 10−3 and 2 × 10−1 cycles per minute (cpm). It is therefore interpreted as a stratified inertial subrange for most of this wavenumber interval, whereas in some cases the convective inertial subrange is resolved as well. Kinetic energy dissipation rate ε is inferred using theoretical expressions for the stratified inertial subrange. A wide range of values within 10−9 and 4 × 10−7 m2 s−3 is obtained for time periods either dominated by semidiurnal tides or by significant subinertial variability. A scaling for ε that depends on the potential energy within the inertio-gravity waves (IGW) frequency band PEIGW and the buoyancy frequency N is proposed for these two cases. When semidiurnal tides dominate, ε ≃ (PEIGWN)3/2, whereas ε ≃ PEIGWN in the presence of significant subinertial variability. This result is obtained for energy levels ranging from 1 to 30 times the Garrett–Munk energy level and is in contrast with classical finescale parameterization in which ε ∼ (PEIGW)2 that applies far from energy sources. The specificities of the stratified bottom boundary layer, namely a weak stratification, may account for this difference.
Highlights
Large-scale down to submesoscale variability in the ocean is strongly influenced by the earth’s rotation and vertical density stratification
In the case of low energy levels corresponding to the Garrett–Munk model (Garrett and Munk 1972, hereinafter GM72), vertical wavenumber spectra inferred from observations in the main thermocline show that there is an intermediate spectral range, a stratified inertial turbulent subrange referred to as ‘‘buoyancy subrange’’ or ‘‘saturated inertio-gravity waves (IGW)’’ subrange, between the IGW domain and that of small-scale turbulence (e.g., Gregg 1987)
The analysis of temperature variance spectra reveals a transition to an inertial range at a frequency of about twice the buoyancy frequency, for various dynamical regimes of high or low energy levels
Summary
Large-scale down to submesoscale variability in the ocean is strongly influenced by the earth’s rotation and vertical density stratification. In the case of low energy levels corresponding to the Garrett–Munk model (Garrett and Munk 1972, hereinafter GM72), vertical wavenumber spectra inferred from observations in the main thermocline show that there is an intermediate spectral range, a stratified inertial turbulent subrange referred to as ‘‘buoyancy subrange’’ or ‘‘saturated IGW’’ subrange, between the IGW domain and that of small-scale turbulence (e.g., Gregg 1987). As far as could be judged from these profiles, the temperature–salinity (TS) relationship was reasonably tight (Fig. 3)
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
