Modeling the 3D structure of the ocean : Status and perspectives
Centre Européen de Recherche et de Formation Avancée en Calcul Scientifique42, Avenue Gaspard Coriolis
31057 Toulouse Cedex
Tel : 05 61 19 31 31 - Fax : 05 61 19 30 00
MODELING THE 3D STRUCTURE OF THE OCEAN: STATUS AND PERSPECTIVES
Christian Le Provost
(Laboratoire d'Etudes en Geophysique et Oceanographie Spatiales, LEGOS - UMR CNES/CNRS/UPS, Toulouse)
Tuesday May 19, 11.00 a.m. CERFACS Conference Room
The three dimensional structure of the ocean and the multiplicity of the space and time scales which characterize the many physical processes taking place in the "blue" ocean and over the continental shelves impose to address their simulation through a large variety of models. The presentation will be divided in two parts, considering first "short" time scale phenomena, and then "longer" time scale ocean processes, the usual partition being the Coriolis frequency f (i.e. periods of typically 24h at 30 deg. latitude, 17h at 45 deg. latitude, and 12.42h at 75 deg. - the period of the main lunar tidal component-).
Modeling the major high frequency phenomena will be first reviewed, related to tides and meteorologically forced long gravity waves, at global and regional scales. Their dynamics is governed by gravity, although topographically trapped waves also occur at high latitude, which are controlled by vorticity conservation. Examples of simulations based on finite difference numerical methods will be presented.
Modeling the general ocean circulation will then be addressed, from large scale thermohaline and basin scale circulation to the mesoscale, and their interactions. At time scales larger than f-1 distinct dynamical regimes exist, in which the rotation of the earth is dominant. Geostrophic turbulence is typically considered at 100 days and 100km. At longer periods, the oceanic motions are dominated by the seasonal cycle, and the variability can often be described in term of Rossby and Kelvin waves. Finally, the oceanic circulation shows also long term variability at decadal to centenial scales, and larger, associated with slow deep currents. Some typical examples will be presented to illustrate the usual numerical approaches developed over the last decade to address the scientific questions associated to these movements, focusing on the geostrophic turbulence and basin-scale circulations.
The continuous increase of the computing facilities allows now to run experiments which were previously impossible to think about. The presentation will point towards these exciting perspectives.
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