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Jeudi 20 septembre - Etude de la circulation méridienne dans l'océan Pacific tropical a l'aide de float Argo

by SEMSOU last modified Feb 12, 2013 12:31 PM
When Sep 20, 2012
from 11:00 AM to 12:00 PM
Where Salle Jules Verne
Attendees Nathalie Zilberman, SCRIPPS
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Nathalie Zilberman, SCRIPPS

 

Etude de la circulation méridienne dans l'océan Pacific tropical a l'aide de float Argo


Abstract : Gridded Argo temperature and salinity profiles and atmospheric reanalysis surface winds are used to study the time-variability of the shallow meridional overturning circulation (MOC) in the South Pacific Ocean between 2004 and 2010. The basin-wide meridional geostrophic transport is computed at several latitudes where the Argo coverage is dense enough to resolve the flow field. An initial level of no motion at 1000 m is used in the tropics, while 2000 m is chosen in the subtropics, and these relative velocities are adjusted using Argo trajectory data. The response of the Pacific heat transport to interannual variations in the wind forcing and the Indonesian Throughflow (ITF) is studied. In the tropical South Pacific Ocean, the poleward Ekman and equatorward geostrophic branches of the MOC exhibit an El Niño-Southern Oscillation (ENSO) signature with strong meridional transport occurring during La Niña and weak meridional transport during El Niño. At 7.5°S, mean basin-wide geostrophic transport from 1000 dbar is 48.5 +/- 2.5 Sv, of which 30.3-38.4 Sv returns to the subtropics in the surface Ekman layer, whereas 10.1-18.2 Sv flows northward feeding the ITF. The major portion of the time-variability in basin-wide geostrophic transport is due to changes in the interior. The mean oceanic heat transport across 7.5°S (including the ITF) is -0.5 +/- 0.15 pW, about half of the air-sea heat flux computed from reanalyses integrated over the region north of 7.5°S. During La Niña, stronger equatorward transport of cooler subsurface water at 7.5°S is accompanied by stronger heat gain by the ocean from the atmosphere north of 7.5°S. The opposite tendencies occur during El Niño.

 

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