Seasonal cycle of the salinity barrier layer revealed in the northeastern Gulf of Guinea

Type Article
Date 2019-04
Language English
Author(s) Dossa A. N.1, 2, Da-Allada C. Y.1, 3, 4, 5, Herbert G6, Bourles Bernard6
Affiliation(s) 1 : Univ Abomey Calavi, ICPMA UNESCO Chair, Int Chair Math Phys & Applicat, Cotonou, Benin.
2 : Univ Fed Pernambuco UFPE, Dept Oceanog, Lab Oceanog Fis Estuarina & Costeira, Recife, PE, Brazil.
3 : UNSTIM, ENSTP, Abomey, Benin.
4 : IRD, LHMC IRHOB, Cotonou, Benin.
5 : Univ Brest, IUEM, CNRS, IRD LOPS,Inst Francais Rech Exploitat Mer IFREMER, Brest, France.
6 : IRD, Instrumentat Moyens Analyt Observ Geophys & Ocean, Brest, France.
Source African Journal Of Marine Science (1814-232X) (Natl Inquiry Services Centre Pty Ltd), 2019-04 , Vol. 41 , N. 2 , P. 163-175
DOI 10.2989/1814232X.2019.1616612
WOS© Times Cited 5
Keyword(s) mixed layer depth, Niger River discharge, numerical model, oceanography, sea surface salinity, tropical Atlantic, vertical stratification
Abstract

The region located in the far northeast of the Gulf of Guinea (NEGG), eastern tropical Atlantic, remains poorly documented due to a lack of available in situ ocean data. Heavy rainfall and intense river discharges observed in this region induce a strong salinity stratification that may have a significant impact on the mixed layer depth and on sea surface temperatures, through the so-called barrier-layer effect. By using recent in situ data and climatological outputs from a numerical simulation, we reveal the existence of a barrier layer in the NEGG and describe its seasonal occurrence. In the NEGG, the barrier layer limits the mixed layer depth. From January to March, significant values for the barrier-layer thickness are observed mostly due to the horizontal advection of fresh water. From April, vertical mixing along with vertical advection increase the sea surface salinity; hence, the barrier-layer thickness decreases and reaches its minimum in July. During the rest of the year, values for the barrier-layer thickness are again high, mostly under the influence of the Niger River discharge and precipitation, with the highest values recorded in October, when the river discharge and precipitation are at a maximum.

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