Impact of ocean-atmosphere current feedback on ocean mesoscale activity : regional variations and sensitivity to model resolution

Swen Jullien (1) , Sébastien Masson (2) , Véra Oerder (3) , Guillaume Samson (4) , François Colas (5) , Lionel Renault (6, 7)

1 LOPS - Laboratoire d'Océanographie Physique et Spatiale
2 NEMO R&D - Nucleus for European Modeling of the Ocean
3 ECAM - Escuela de Ciencias Aplicadas del Mar
4 Mercator Océan
5 PROTEO - Processus et interactions de fine échelle océanique
6 AOS - Department of Atmospheric and Oceanic Sciences [Los Angeles]
7 LEGOS - Laboratoire d'études en Géophysique et océanographie spatiales

Ocean mesoscale eddies are characterized by rotating-like and meandering currents that imprint the low-levelatmosphere. Such a current feedback (CFB) has been shown to induce a sink of energy from the ocean to theatmosphere, and consequently to damp the eddy kinetic energy (EKE), with an apparent regional disparity.In a context of increasing model resolution, the importance of this feedback and its dependence on oceanicand atmospheric model resolution arise. Using a hierarchy of quasi-global coupled models with spatial res-olutions varying from 1/48to 1/128, the present study shows that the CFB induces a negative wind work atscales ranging from 100 to 1000 km, and a subsequent damping of the mesoscale activity by ~ 30% on average,independently of the model resolution. Regional variations of this damping range from ~ 20% in very richeddying regions to;40% in poor eddying regions. This regional modulation is associated with a differentbalance between the sink of energy by eddy wind work and the source of EKE by ocean intrinsic instabilities.The efficiency of the CFB is also shown to be a function of the surface wind magnitude: the larger the wind, thelarger the sink of energy. The CFB impact is thus related to both wind and EKE. Its correct representationrequires both an ocean model that resolves the mesoscale field adequately and an atmospheric model reso-lution that matches the ocean effective resolution and allows a realistic representation of wind patterns. Theseresults are crucial for including adequately mesoscale ocean–atmosphere interactions in coupled generalcirculation models and have strong implications in climate research.

Mots clés: Feedback; Currents; Mesoscale processes; Air-sea interaction; Coupled models; Mesoscale models

Domaines: Géophysique [physics.geo-ph]

Swen Jullien, Sébastien Masson, Véra Oerder, Guillaume Samson, François Colas, et al.. Impact of ocean-atmosphere current feedback on ocean mesoscale activity : regional variations and sensitivity to model resolution. Journal of Climate, 2020, 33 (7), pp.2585-2602. ⟨10.1175/JCLI-D-19-0484.1⟩. ⟨hal-02869856⟩