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A synthesis of upper ocean geostrophic kinetic energy spectra from a global submesoscale permitting simulation
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  • Hemant Khatri,
  • Stephen M Griffies,
  • Takaya Uchida,
  • Han Wang,
  • Dimitris Menemenlis
Hemant Khatri
Princeton University

Corresponding Author:hemantkhatri1091@gmail.com

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Stephen M Griffies
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Takaya Uchida
Institut des Géosciences de l'Environnement
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Han Wang
University of Toronto
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Dimitris Menemenlis
Jet Propulsion Laboratory, California Institute of Technology
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A submesoscale-permitting global ocean model is used to study the upper ocean turbulence. Submesoscale processes peak in winter and, consequently, geostrophic kinetic energy (KE) spectra tend to be relatively shallow in winter (∼k-2) with steeper spectra in summer (∼k-3). This seasonal transition from steep to shallow power-law in the KE spectra indicates a transition from quasi-geostrophic (QG) turbulence in summer to pronounced surface-QG-like turbulence in winter. It is shown that this transition in KE spectral scaling has two phases. In the first phase (late autumn), KE spectra show a presence of two spectral regimes: ∼k-3 scaling in mesoscales (100-300 km) and ∼k-2 scaling in submesoscales (<50 km), indicating the coexistence of QG, surface-QG, and frontal dynamics. In the second phase (late winter), mixed-layer instabilities convert available potential energy into KE, which cascades upscale leading to flattening of the KE spectra at larger scales, and k-2 power-law develops in mesoscales too.
28 Sep 2021Published in Geophysical Research Letters volume 48 issue 18. 10.1029/2021GL094777