Importance of the Equatorial Undercurrent on the Sea Surface Salinity in the Eastern Equatorial Atlantic in boreal spring

Type Article
Date 2017-01
Language English
Author(s) Da-Allada Casimir Yelognisse1, 2, 3, Jouanno J.4, Gaillard FabienneORCID5, Kolodziejczyk NicolasORCID6, Maes C.1, Reul NicolasORCID5, Bourles B.7
Affiliation(s) 1 : Univ Brest, CNRS, IRD LOPS, IFREMER,IUEM, Brest, France.
2 : IRD, LHMC IRHOB, Cotonou, Benin.
3 : ESTBR UNSTIM, Abomey, Benin.
4 : Univ Toulouse, CNRS, LEGOS, CNES,IRD,UPS, Toulouse, France.
5 : Univ Brest, CNRS, IFREMER LOPS, IRD,IUEM, Brest, France.
6 : Univ Brest, CNRS, IUEM LOPS, IFREMER,IRD, Brest, France.
7 : IRD LEGOS, Brest, France.
Source Journal Of Geophysical Research-oceans (2169-9275) (Amer Geophysical Union), 2017-01 , Vol. 122 , N. 1 , P. 521-538
DOI 10.1002/2016JC012342
WOS© Times Cited 10
Keyword(s) Atlantic Cold Tongue, SMOS SSS, model, EUC salinity maximum, vertical processes
Abstract The physical processes implied in the sea surface salinity (SSS) increase in the equatorial Atlantic Cold Tongue (ACT) region during boreal spring and the lag observed between boreal spring SSS maximum and sea surface temperature (SST) summer minimum are examined using mixed-layer salinity budgets computed from observations and model during the period 2010-2012. The boreal spring SSS maximum is mainly explained by an upward flux of high salinity originating from the core of the Equatorial Undercurrent (EUC) through vertical mixing and advection. The vertical mixing contribution to the mixed-layer salt budget peaks in April-May. It is controlled primarily by i) an increased zonal shear between the surface South Equatorial Current and the subsurface EUC and ii) the presence of a strong salinity stratification at the mixed-layer base from December to May. This haline stratification that is due to both high precipitations below the Inter Tropical Convergence Zone and zonal advection of low-salinity water from the Gulf of Guinea, explains largely the seasonal cycle of the vertical advection contribution to the mixed-layer salt budget. In the ACT region, the SST reaches its maximum in March/April and minimum in July/August. This SST minimum appears one month after the maximum of SSS. The 1-month lag observed between the maximum of SSS in June and the minimum of SST in July is explained by the shallowing of the EUC salinity core in June, then the weakening/erosion of the EUC in June-July which dramatically reduces the lateral subsurface supply of high saline waters. This article is protected by copyright. All rights reserved.
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Da-Allada Casimir Yelognisse, Jouanno J., Gaillard Fabienne, Kolodziejczyk Nicolas, Maes C., Reul Nicolas, Bourles B. (2017). Importance of the Equatorial Undercurrent on the Sea Surface Salinity in the Eastern Equatorial Atlantic in boreal spring. Journal Of Geophysical Research-oceans, 122(1), 521-538. Publisher's official version : https://doi.org/10.1002/2016JC012342 , Open Access version : https://archimer.ifremer.fr/doc/00363/47396/