Diagnosing the thickness-weighted averaged eddy-mean flow interaction in
an eddying North Atlantic ensemble, Part I: The Eliassen-Palm flux
Quentin Jamet

Laboratoire de Glaciologie et Geophysique de l'Environnement, CNRS, Laboratoire de Glaciologie et Geophysique de l'Environnement, CNRS, Laboratoire de Glaciologie et Geophysique de l'Environnement, CNRS, Laboratoire de Glaciologie et Geophysique de l'Environnement, CNRS, Laboratoire de Glaciologie et Geophysique de l'Environnement, CNRS
Author ProfileThierry Penduff

Laboratoire de Glaciologie et Geophysique de l'Environnement, CNRS, Laboratoire de Glaciologie et Geophysique de l'Environnement, CNRS, Laboratoire de Glaciologie et Geophysique de l'Environnement, CNRS, Laboratoire de Glaciologie et Geophysique de l'Environnement, CNRS, Laboratoire de Glaciologie et Geophysique de l'Environnement, CNRS
Author ProfileAbstract
The thickness-weighted average (TWA) framework, which treats the
residual-mean flow as the prognostic variable, provides a clear
theoretical formulation of the eddy feedback onto the residual-mean
flow. The averaging operator involved in the TWA framework, although in
theory being an ensemble mean, in practice has often been approximated
by a temporal mean. Here, we analyze an ensemble of North Atlantic
simulations at mesoscale-permitting resolution
(1/12$^\circ$). We therefore recognize means and
eddies in terms of ensemble means and fluctuations about those means.
The ensemble dimension being orthogonal to the temporal and spatial
dimensions negates the necessity for an arbitrary temporal or spatial
scale in defining the eddies. Eddy-mean flow feedbacks are encapsulated
in the Eliassen-Palm (E-P) flux tensor and its convergence indicates
that eddy momentum fluxes dominate in the separated Gulf Stream. The
eddies contribute to the zonal meandering of the Gulf Stream and a
northward migration of it in the meridional direction. Downstream of the
separated Gulf Stream in the North Atlantic Current region, the
interfacial form stress convergence becomes leading order in the E-P
flux convergence.