Reconstruction of the upper ocean 3D dynamics from high-resolution sea surface height
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The present study investigates the reconstruction of the 3D dynamics of a turbulent mesoscale eddy field driven at a depth by a baroclinic instability of the Phillips type. It uses a high-resolution primitive equation simulation as a testbed. The method of reconstruction is based on potential vorticity principles and extends an earlier approach (Lapeyre and Klein, J Phys Oceanogr 36:165–176, 2006) to a regime where the signature of surface density anomalies on the dynamics is weak. The crux and the originality of the reconstruction lie in the estimation from sea surface height and surface density anomalies of the interior quasigeostrophic potential vorticity (PV) anomalies and its subsequent inversion. The estimation of PV anomalies relies on the vertical correlation between PV anomalies and on the knowledge on stratification and horizontal gradients of background PV. PV anomalies are accurately estimated over the first 500 m of the water column and over a wide range of wavenumbers. Density anomalies play a minor role in the PV estimation, though their omission leads to an overestimation of PV by a factor of less than 2 at scales of order 20 km and less. Inversion of the estimated PV leads to a geostrophic streamfunction which in turn provides reliable reconstructions of the relative vorticity and vertical velocity (via the omega equation).
KeywordsAltimetry Potential vorticity inversion Quasigeostrophy
This work is supported by IFREMER, CNRS (FRANCE), the Agence Nationale pour la Recherche (contracts nos. ANR-05-CIGC-010 and ANR-09-BLAN-0365-02). Simulations reported here were done on the Earth Simulator (Yokohama, Japan) through a M.O.U. signed between IFREMER and JAMSTEC. This work is part of the Labex Mer, axe 1: “the ocean engine at very high resolution.”
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