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Assessment of fine‐scale parameterizations of turbulent dissipation rates near mixing hotspots in the deep ocean
Author(s) -
Hibiya Toshiyuki,
Furuichi Naoki,
Robertson Robin
Publication year - 2012
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2012gl054068
Subject(s) - internal wave , dissipation , turbulence , wavenumber , geology , latitude , bathymetry , shear (geology) , turbulence kinetic energy , geophysics , atmospheric sciences , mechanics , physics , geodesy , optics , oceanography , petrology , thermodynamics
Shear‐based and/or strain‐based fine‐scale parameterizations of turbulent dissipation rates in the deep ocean become erroneous near topographic features where internal wave spectra deviate from Garrett‐Munk (GM). Although the Gregg‐Henyey‐Polzin (GHP) parameterization incorporates this spectral deviation, the applicability remains uncertain. We evaluate “ α ” and “ β ” representing the local internal wave energy in the high frequency (2 f < ω < N ) and low frequency ( f < ω < 2 f ) bands, respectively, scaled by their corresponding values in GM using fine‐scale vertical shear and strain simultaneously measured near mixing hotspots. The local internal wave spectra are biased toward higher frequencies ( α / β ≫ 1) over rough bathymetry where high frequency internal waves are generated, whereas they are biased toward lower frequencies ( α / β ≪ 1) at latitudes where high vertical wavenumber, near‐inertial shears are created by parametric subharmonic instabilities . Compared with the shear‐based and/or strain‐based parameterizations, GHP more accurately estimates turbulent dissipation rates by compensating for deviations from GM.