Preprints
https://doi.org/10.5194/os-2020-78
https://doi.org/10.5194/os-2020-78

  12 Aug 2020

12 Aug 2020

Review status: this preprint is currently under review for the journal OS.

Impact of the current feedback on kinetic energy over the North-East Atlantic from a coupled ocean/atmospheric boundary layer model

Théo Brivoal1,2, Guillaume Samson1, Hervé Giordani2, Romain Bourdallé-Badie1, Florian Lemarié3, and Gurvan Madec4,3 Théo Brivoal et al.
  • 1Mercator Océan, Ramonville-Saint-Agne, 31520, France
  • 2Université de Toulouse, Centre National de Recherches Météorologique (CNRM), Météo-France, CNRS, Toulouse, France
  • 3Univ. Grenoble Alpes, Inria, CNRS, Grenoble INP, LJK, 38000 Grenoble, France
  • 4Sorbonne Universités, CNRS, UPMC, IRD, MNHN, LOCEAN, Paris, France

Abstract. A one-dimensional Atmospheric Boundary Layer (ABL1D) is coupled with the NEMO ocean model and implemented over the Iberian–Biscay–Ireland (IBI) area at 1/36° resolution to investigate the retroactions between the surface currents and the atmosphere, namely the Current FeedBack (CFB) in this region of low mesoscale activity. The ABL1D-NEMO coupled model is forced by a large-scale atmospheric reanalysis (ERA-Interim) and integrated over the period 2016–2017.

The mechanisms of eddy kinetic energy damping and ocean upper-layers re-energization are realistically simulated, meaning that the CFB is properly represented by the model. In particular, the dynamical coupling coefficients between the curls of surface stress/wind and current are in agreement with the literature.

The effects of CFB on the kinetic energy (KE) are then investigated through a KE budget. We show that the KE decrease induced by the CFB is significant down to 1500 m. Near the surface (0–300 m), most of the KE decrease can be explained by a reduction of the surface wind work by 4 %. At depth (300–2000 m), the CFB induce a reduction of the pressure work (i.e: the PE to KE conversion) associated with a reduction of KE which is significant down to 1500 m. We show that this reduction of KE at depth can be explained by CFB-induced Ekman pumping above eddies that weakens the mesoscale activity and this over the whole water column.

Théo Brivoal et al.

 
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Théo Brivoal et al.

Data sets

ASCAT ON METOP LEVEL 4 DAILY GRIDDED MEAN WIND FIELDS IN 0.25° GEOGRAPHICAL GRID A. Bentamy and D. Croize Fillon https://doi.org/10.1080/01431161.2011.600348

Model code and software

NEMO ocean engine NEMO System Team https://doi.org/10.5281/zenodo.1464816

Théo Brivoal et al.

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Short summary
We investigate the interactions between near-surface winds and oceanic surface currents on the north-east atlantic region using a simplified lower atmosphere model coupled with an ocean model. we show that the upper ocean kinetic energy is significantly reduced due to these interactions, but in a smaller amplitude than if the wind feedback is ignored. We also show that wind-current interactions affect the deeper ocean by modifying its vertical structure and consequently the pressure field.