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- Title
Influences of Mesoscale Ocean Eddies on Flow Vertical Structure in a Resolution‐Based Model Hierarchy.
- Authors
Yankovsky, Elizabeth; Zanna, Laure; Smith, K. Shafer
- Abstract
The understanding and representation of energetic transfers associated with ocean mesoscale eddies is fundamental to the development of parameterizations for climate models. We investigate the influence of eddies on flow vertical structure as a function of underlying dynamical regime and grid resolution. We employ the GFDL‐MOM6 in an idealized configuration and systematically consider four horizontal resolutions: 1/4°, 1/8°, 1/16°, and 1/32°. We analyze the distributions of potential and kinetic energy, decomposed into barotropic and baroclinic, and eddy and mean parts. As resolution increases and baroclinically unstable modes are better captured, kinetic energy increases and potential energy decreases. The dominant trend in vertical structure is an increasing fraction of kinetic energy going into the barotropic mode, particularly its eddy component, as eddies are increasingly resolved. We attribute the increased baroclinicity at low resolutions to inaccurate representation of vertical energy fluxes, leading to suppressed barotropization and energy trapping in high vertical modes. We also explore how the underlying dynamical regime influences energetic pathways. In cases where large‐scale flow is dominantly barotropic, resolving the deformation radius is less crucial to accurately capturing the flow's vertical structure. We find the barotropic kinetic energy fraction to be a useful metric in assessing vertical structure. In the highest‐resolution case, the barotropic kinetic energy fraction correlates with the scale separation between the deformation scale and the energy‐containing scale, that is, the extent of the eddy‐driven inverse cascade. This work suggests that mesoscale eddy parameterizations should incorporate the energetic effects of eddies on vertical structure in a scale‐aware, physically informed manner. Plain Language Summary: Ocean eddies with scales of 10–100s of kilometers are highly energetic features which have a significant influence on the ocean state. Eddies are notoriously challenging to fully capture in modern climate models as they require grid resolutions finer than current computational resources allow for. Our goal is to study the effect of eddies in a simplified model. In particular, we focus on how eddies shape flow vertical structure and redistribute energy. By using a simplified model, we are able to perform high‐resolution simulations where eddies are fully resolved and compare against resolutions that barely permit eddies. In the latter case, the vertical structure of the flow is adversely affected. Eddies transfer energy and information from the ocean surface to depths of thousands of meters. Under‐resolving them leads to energy trapping near the surface and within small vertical scales, altering the ocean energy cycle. We also investigate the influence of the underlying flow regime; for weak and nonuniform with depth flows resolving eddies is crucial to obtaining the correct vertical structure. Our results may guide how to improve eddy representation in more complex and realistic climate models. Key Points: We use idealized modeling to study mesoscale eddy influences on vertical structure as a function of grid resolution and dynamical regimeWhen eddies are unresolved, particularly in weak mean flow regions, the flow fails to barotropize and energy is trapped in baroclinic modesWe identify scalings characterizing barotropic to baroclinic kinetic energy ratios and discuss implications for improving parameterizations
- Subjects
BAROCLINICITY; MESOSCALE eddies; NON-uniform flows (Fluid dynamics); OCEAN energy resources; KINETIC energy; EDDIES
- Publication
Journal of Advances in Modeling Earth Systems, 2022, Vol 14, Issue 11, p1
- ISSN
1942-2466
- Publication type
Article
- DOI
10.1029/2022MS003203