Observational energy transfers of a spiral cold filament within an anticyclonic eddy

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  • Chunhua Qiu
    Sun Yat-sen University
  • Zihao Yang
    Sun Yat-sen University
  • Ming Feng
    Commonwealth Scientific and Industrial Research Organization Oceans & Atmosphere, Brisbane
  • Tom Rippeth
  • Xiaodong Shang
    Chinese Academy of Sciences
  • Zhenyu Sun
    Xiamen University, China
  • Chunsheng Jing
    Fujian Provincial Key Laboratory of Marine Physical and Geological Processes, Third Institute of Oceanography, Ministry of Natural Resources
  • Dongxiao Wang
    Sun Yat-sen University
  • Jun Yang
    Sun Yat-sen University
The ocean surface mixed layer represents a critical interface linking the ocean and atmosphere. The physical processes determining the surface mixed layer properties and mediate atmosphere-ocean exchange. Submesoscale processes play a key role in cross-scale oceanic energy transformation and the determination of surface mixed-layer properties, including the enhancement of vertical nutrient transport, leading to increased primary productivity. Herein, we presented observations of the spiral chlorophyll-a filament and its influence on turbulence within an anticyclonic eddy in the western South China Sea during August 2021. The filament had a negative Ertel potential vorticity associated with strong upwelled/downward currents (approximately 20-40 m/day). Across-filament sections of the in-situ profiles showed turbulent dissipation rates enhanced in the filament. We suggested this enhancement values can be attributed to submesoscale processes, which accounted for 25% of the total parameterized turbulent dissipation rates. The present parametrized submesoscale turbulent scheme overestimated the in-situ values. The filament transferred kinetic energy upward to anticyclonic eddy via barotropic instability and gained energy from the anticyclonic eddy via baroclinic instability. After kinetic energy budget diagnostic, we suggested besides symmetric instability, centrifugal instability and mixed layer baroclinic instability should also be included in the turbulence scheme to overcome the overestimation. The observed dual energy transfers between the anticyclonic eddy and filament, and the observed high turbulent energy dissipation within the filament, emphasized the need for these processes to be accurately parameterized regional and climate models.

Keywords

  • barotropic instabilityfilamentturbulencesurface mixed layerSouth China Sea
Original languageEnglish
JournalProgress in Oceanography
Volume220
Early online date2 Dec 2023
DOIs
Publication statusPublished - 1 Jan 2024

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