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Diagnosing scale-dependent energy cycles in a high-resolution isopycnal ocean model
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  • Nora Loose,
  • Scott Bachman,
  • IAN GROOMS,
  • Malte Jansen
Nora Loose
University of Colorado Boulder, University of Colorado Boulder

Corresponding Author:[email protected]

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Scott Bachman
National Center for Atmospheric Research, National Center for Atmospheric Research
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IAN GROOMS
University of Colorado Boulder, University of Colorado Boulder
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Malte Jansen
The University of Chicago, The University of Chicago
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Abstract

Energy exchanges between large-scale ocean currents and mesoscale eddies play an important role in setting the large-scale ocean circulation but are not fully captured in models. To better understand and quantify the ocean energy cycle, we apply along-isopycnal spatial filtering to output from an isopycnal 1/32$^\circ$ primitive equation model with idealized Atlantic and Southern Ocean geometry and topography. We diagnose the energy cycle in two frameworks: (1) a non-thickness-weighted framework, resulting in a Lorenz-like energy cycle, and (2) a thickness-weighted framework, resulting in the Bleck energy cycle. This paper shows that (2) is the more useful framework for studying energy pathways when an isopycnal average is used. Next, we investigate the Bleck cycle as a function of filter scale. Baroclinic conversion generates mesoscale eddy kinetic energy over a wide range of scales, and peaks near the deformation scale at high latitudes, but below the deformation scale at low latitudes. Away from topography, an inverse cascade transfers kinetic energy from the mesoscales to larger scales. The upscale energy transfer peaks near the energy-containing scale at high latitudes, but below the deformation scale at low latitudes. Regions downstream of topography are characterized by a downscale kinetic energy transfer, in which mesoscale eddies are generated through barotropic instability. The scale- and flow-dependent energy pathways diagnosed in this paper provide a basis for evaluating and developing scale- and flow-aware mesoscale eddy parameterizations.
Jan 2023Published in Journal of Physical Oceanography volume 53 issue 1 on pages 157-176. 10.1175/JPO-D-22-0083.1