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Role of Mixed‐Layer Instabilities in the Seasonal Evolution of Eddy Kinetic Energy Spectra in a Global Submesoscale Permitting Simulation
Author(s) -
Khatri Hemant,
Griffies Stephen M.,
Uchida Takaya,
Wang Han,
Menemenlis Dimitris
Publication year - 2021
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 - 10.1029/2021gl094777
Subject(s) - geostrophic wind , enstrophy , kinetic energy , spectral line , mixed layer , power law , turbulence , physics , flattening , atmospheric sciences , turbulence kinetic energy , scaling , climatology , geology , mechanics , meteorology , classical mechanics , vorticity , vortex , statistics , geometry , mathematics , astronomy
A submesoscale‐permitting global ocean simulation is used to study the upper ocean turbulence in high kinetic energy (KE) regions. Submesoscale processes peak in winter so that the geostrophic KE spectra tend to be relatively shallow in winter ( ∼k − 2 ) with steeper spectra in summer ( ∼k − 3 ). This transition in KE spectral scaling has two phases. In the first phase (late autumn), KE spectra show the presence of two spectral regimes: ∼k − 3power‐law in mesoscales and ∼k − 2power‐law in submesoscales. The first phase appears with the onset of mixed‐layer instabilities, which convert available potential energy into KE, and this process results in a flattening of KE spectra at submesoscales. However, KE spectra at longer wavelengths follow ∼k − 3scaling associated with a forward enstrophy transfer. In the second phase (late winter), KE produced through mixed‐layer instabilities is transferred to larger scales, andk − 2power‐law also develops in mesoscales.