Séminaire
Vertical circulation in the ocean is crucial for the transport of heat, salt and biogeochemical tracers between the surface and the ocean interior. In particular it is a key factor for the supply of nutrients to the euphotic zone or the subduction of matter in the deep ocean. The omega equation is a diagnostic most commonly used to reconstruct w from experimental data. Until now, observation capabilities didn’t allowed to sample properties of the ocean synoptically at fine scale so that the omega equation has been used only to infer order of magnitude for w. However in the incoming years we will be able to design observational networks with much higher spatial and temporal resolutions, allowing for the first time to access quantitatively the vertical dynamics of the ocean. This perspective rises the question of understanding what are the critical scales and observables needed for an accurate estimation of w through the omega equation. We address this problem by reconstructing w using a quasi geostrophic and a generalized version of the omega equation in different flow regimes in the North Atlantic ocean in summer and in winter. The ability of the equation to provide information on the vertical circulation at different length scales is found to be very dependent on the local dynamics. Nevertheless we observed that good results are generally obtained on the pattern of the mesoscale vertical circulation while the submesoscale dynamics (< 40 km) remains elusive.
alice.pietri@locean-ipsl.upmc.fr