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Communication incl. Poster: BibTeX citation key:  Jouanno
Jouanno, J., Marin, F., Du Penhoat, Y., Molines, J.-M. & Sheinbaum, J. 2010. Seasonal heat balance in the upper 100 m of the Tropical Atlantic Ocean. Work presented at Atelier AMMA France 2010.
Added by: Fanny Lefebvre 2010-11-08 18:58:17
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Categories: General
Creators: Jouanno, Marin, Molines, Du Penhoat, Sheinbaum
Publisher: African Monsoon Multidisciplinary Analyses
Collection: Atelier AMMA France 2010

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Abstract
The variability of Sea Surface Temperature (SST) in the Tropical Atlantic is characterized by a strong cooling during May-June and a secondary cooling during November-December. We investigate the mechanisms which drive this SST seasonal cycle. A numerical simulation of the Tropical Atlantic is used to diagnose the different contributions to the temperature trends in the upper 100 m. The simulation reproduces adequately the seasonal cycle of equatorial SST. During both cooling events the coolest temperatures are found in the center of the basin, between 20W and 10W. Results indicate that this is due to enhanced diapycnal heat flux in this region. This is somehow counter intuitive since thermocline and Equatorial Under Current (EUC) are much shallow in the eastern part of the basin. We explain that by 1) a strong vertical shear at the upper bound of the EUC in the center of the basin (where the EUC is shallow and still energetic) and 2) a strong stratification in the eastern basin, due to the presence of warm and low saline surface waters, which limits vertical mixing to the upper 20 m depth and disconnects the surface to subsurface dynamics.

Diapycnal heat flux in the center of the basin exhibits a strong semi-annual cycle with two peaks of same intensity. During the first peak, in May-June, vertical mixing drives the SST while during the second peak, in November-December, the atmosphere strongly acts to damp the cooling, resulting in an effective cooling of SST much more weaker than during summer. At seasonal scale, the timing of both cooling events is closely linked to the enhancement of the vertical shear at the upper bound of the EUC. For both seasons this shear appears to be driven not by the strength of the EUC but by the strength and depth of the surface westward current.
Added by: Fanny Lefebvre