Importance of strains in kinetic energy flux for submesoscale processes from an anisotropic perspective

Yang, Jun, Wang, Dongxiao, Qiu, Chunhua, Zhai, Xiaoming, Chen, Ru, Qiao, Jiawei and Hong, Bo (2025) Importance of strains in kinetic energy flux for submesoscale processes from an anisotropic perspective. Journal of Geophysical Research - Oceans, 130 (10). ISSN 2169-9275

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Abstract

Submesoscale fronts and filaments are jet-like motions, associated with cross-scale kinetic energy (KE) flux through eddy-mean flow interaction. However, the diagnostic method for KE flux in jets with a steady zonal flow axis is not suitable for submesoscale processes with arbitrary axes. Based on a high-resolution ocean model and observations, we propose a method for diagnosing KE flux via mesoscale strains and submesoscale stresses from an anisotropic perspective. Furthermore, we develop a three-dimensional anisotropic KE flux algorithm under the hydrostatic assumption, which is important for diagnosing the energy sources and distributions of submesoscale vertical instabilities. Horizontally, we find that the inverse KE cascade mainly arises from shear strain throughout the filament’s lifespan, triggering anisotropic frontogenesis and ageostrophic secondary circulations (ASCs). In ASCs, the cross-filament shear strain provides an energy source for the geostrophic shear production (GSP) and causes the forward flux through the symmetric instability. Meanwhile, the forward KE flux caused by the centrifugal instability can reach 35% of GSP which is regulated by the anisotropic eddy KE but has been neglected in previous studies. This finding effectively explains the directional dependence of strains, stresses and instabilities, broadening our understanding of energy balance and providing a foundation for improving submesoscale parameterizations.

Item Type:	Article
Additional Information:	Data Availability Statement: The sea level anomaly from the AVISO satellite altimeter is available at https://data.marine.copernicus.eu/product/SEALEVEL_GLO_PHY_L4_MY_008_047/services from Ducet et al. (2000). The ETOPO1 data are freely available at https://www.ngdc.noaa.gov/mgg/global/relief/ETOPO1/data/ice_surface/grid_registered/binary/ from Amante and Eakins (2009). The HYCOM data are available at https://ncss.hycom.org/thredds/catalogs/GLBy0.08/expt_93.0.html from Bleck (2002), Chassignet et al. (2003), and Halliwell (2004). The ERA5 data are available at https://rda.ucar.edu/datasets/d633000/ from Soci et al. (2024). The ocean model ROMS 4.1 is obtained from the ROMS website (https://github.com/myroms/roms/tree/develop/ROMS). The sea level anomaly from Ducet et al. (2000), the SST from Bessho et al. (2016), the model inputs, and the plot data for reproducing the results of this work are available from Yang et al. (2025). All data were processed using MATLAB Mathworks (2022). Funding information: This study was supported by the National Natural Science Foundation of China (Nos. 42227901, 42376011).
Faculty \ School:	Faculty of Science > School of Environmental Sciences
UEA Research Groups:	Faculty of Science > Research Groups > Centre for Ocean and Atmospheric Sciences
Depositing User:	LivePure Connector
Date Deposited:	17 Sep 2025 09:30
Last Modified:	23 Oct 2025 00:09
URI:	https://ueaeprints.uea.ac.uk/id/eprint/100421
DOI:	10.1029/2024JC022186

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