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  • Impact of surface current a...
    Brivoal, Théo; Samson, Guillaume; Giordani, Hervé; Bourdallé-Badie, Romain; Lemarié, Florian; Madec, Gurvan

    Dynamics of atmospheres and oceans, September 2024, 2024-09-00, Letnik: 107
    Journal Article

    A one-dimensional Atmospheric Boundary Layer (ABL1D) model is coupled with the NEMO ocean model and implemented over the Iberian–Biscay–Ireland (IBI) area at 1/36° resolution to investigate the damping effect of the current and the thermal feedback on the kinetic energy (KE) at the mesoscale. This type of coupling between an ocean model and an ABL1D is a newly proposed approach as an alternative of intermediate complexity between bulk forcing and full coupling with an atmosphere model. In ABL1D, the prognostic tracers are nudged toward large-scale variables and the wind is guided by a low-frequency geostrophic wind provided from the ERA-Interim reanalyses. First, the ABL1D is successfully validated against satellite observations regarding the wind, and the dynamic coupling coefficient (linking the near surface wind and wind-stress to the of the surface currents) are consistent with the literature, over the period 2016–2017. Our results show that the thermal feedback has a negligible impact on kinetic energy (KE) and does not influence the strength of the current feedback in the region. Given the ABL1D physics, this further indicates that the changes in the vertical wind structure caused by CFB are primarily governed by local mechanical mechanisms associated with surface wind-stress condition, rather than by thermodynamic or non-local processes within the planetary boundary layer. The induced KE reduction by the current feedback amounts to 14% at the surface and propagates down to 2000 m, indicating that it can modify the vertical distribution of KE throughout the water column. KE reductions in the surface boundary layer (0 – 300 m) and in the interior (300 – 2000 m) are attributed to a reduction of the surface wind work by 4%, and of the pressure work by 7%, respectively. The Ekman pumping anomalies induced by the current feedback tend to attenuate eddy activity and horizontal pressure gradients at depth, illustrating the potential of the current feedback to induce a geostrophic adjustment on the water column. These results illustrate the relevance of the proposed ABL1D coupling approach for reproducing the wind-current coupling (a.k.a. current feedback effect) which cannot be taken into account straightforwardly with simple bulk forcing. •A one-dimensional Atmospheric Boundary Layer (ABL1D) model is coupled with the NEMO ocean model over the Iberian–Biscay–Ireland area.•Our model is validated against satellite data and used to study current and thermal feedback effects on kinetic energy (KE).•The SST-wind coupling has a negligible impact on KE and on the current feedback (CFB) strength over the study area.•The wind structure is influenced by CFB mainly through local mechanical processes, not thermodynamic or non-local ones.•The CFB reduces surface KE by 14% and extends down to 2000m, altering KE distribution throughout the water column.•Our results highlights the relevance of ABL1D coupling to capture wind-current interaction compared to bulk forcing methods.