EGU2020-5657
https://doi.org/10.5194/egusphere-egu2020-5657
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Kinetic Energy Conversion in A Wind-forced Submesoscale Flow

Song Li1,2, Nuno Serra1, and Detlef Stammer1
Song Li et al.
  • 1Institut für Meereskunde, Centrum für Erdsystemforschung und Nachhaltigkeit (CEN), Universität Hamburg, Hamburg, Germany
  • 2College of Meteorology and Oceanography, National University of Defense Technology, Changsha, China

Despite recent progress in measuring the ocean eddy field with satellite missions at the mesoscale (order of 100 km), containing the major fraction of ocean kinetic energy, many questions still remain regarding the generation, conversion and dissipation mechanisms of eddy kinetic energy (Ke). In this work, we use the output from an idealized 500-m resolution ocean numerical simulation to study the conversion of Ke in the absence and presence of wind stress forcing. In contrast to the result of the unforced run, Ke increased approximately nine times in the mixed layer and considerably in the pycnocline in the forced run. Eddies and filaments were seen to re-stratify the mixed layer and wind-induced turbulence at the base of the mixed layer promoted its deepening and therefore dramatically enhanced the exchange between Ke and eddy available potential energy (Pe). The wind stress forcing additionally affected the conversion processes between Pe and mean kinetic energy (Km). The wind also excited inertial and superinertial motions throughout almost the whole water column. Although those motions played a major role in the conversion between Pe and Ke, the net effect by inertial and superinertial flows was almost null. In addition, we found an asymmetric character in kinetic energy conversion in eddies. Cyclonic and anti-cyclonic eddies showed different behaviour regarding conversion from Pe and Ke, which was positive on the high Ke part in the anti-cyclonic eddy but negative in the cyclonic eddy.

How to cite: Li, S., Serra, N., and Stammer, D.: Kinetic Energy Conversion in A Wind-forced Submesoscale Flow, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-5657, https://doi.org/10.5194/egusphere-egu2020-5657, 2020

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  • CC1: Comment on EGU2020-5657, Quentin Jamet, 04 May 2020

    Hi Song,

    Thank you for your contribution, very interesting. I have two questions:
    1/ Could you give some details on the spatial and temporal structure of the wind forcing?
    2/ Did you evaluate the benefits of relaxing the hydrostatic approximation, i.e. a comparison with hydrostatic simulations at similar resolution?

    Quentin

    • AC1: Reply to CC1, Song Li, 04 May 2020

      Hi Quentin,

      Thank you very much for your comment and questions.

      Answer to Q1:

      The wind forcing is spatially homogeneous (in speed and direction)  and varies temporally according to a sinusoidal function, i.e., the wind direction rotates by 360 degrees within an inertial period. Furthermore, it is applied as single events, each lasting one inertial period.

      Answer to Q2:

      We believe that at the resolution of 500m (horizontal) and 5m (vertical), the non-hydrostatic behavior is increasingly needed to properly simulate internal wave activity and eddie/eddie or filament interaction.

      Song and Nuno

  • CC2: Comment on EGU2020-5657, Anne Marie Tréguier, 04 May 2020

    Hi Song,

    I don't know wether you are aware of the paper https://www.ocean-sci.net/12/743/2016/ (Jouanno et al 2016). I wonder whether yours simulations give results consistent with theirs, or if there are some surprises.

    • AC2: Reply to CC2, Song Li, 04 May 2020

      Hi Anne,

      Thank you very much for your comment.

      We are aware of that study, but still in the process of evaluating are findings against those in Jouanno et al. (2016).

      Song and Nuno

      • CC3: Reply to AC2, Anne Marie Tréguier, 04 May 2020

        Thanks! When you write this up, I'll be interested by a preprint.