Causes for the recent increase in sea surface salinity in the north-eastern Gulf of Guinea

  • CY Da-Allada
  • G Alory
  • Y du Penhoat
  • J Jouanno
  • MN Hounkonnou
  • E Kestenare

Abstract

In situ sea surface salinity (SSS) observations showed an increase >0.5 over the period 2002–2009 in the Gulf of Guinea, off the Niger Delta. Observed changes in the Niger River runoff were not consistent with this increase in SSS, but the increase was reproduced in a regional numerical simulation with climatological river runoff. The simulated mixed-layer salinity budget was used to identify the mechanisms responsible for the increase. When comparing the period 2002–2009 with the period 1993–2001, significant changes in the salt budget were identified. The increase in SSS in the more recent period appeared to be driven by changes in the atmospheric freshwater flux, mainly attributed to a regional decrease in precipitation. Horizontal advection partly compensated for the effect of freshwater flux through changes in zonal currents and zonal SSS gradients.

Keywords: mixed-layer salt budget, precipitation, SSS trend

African Journal of Marine Science 2014, 36(2): 197–205

Author Biographies

CY Da-Allada
International Chair in Mathematical Physics and Applications [ICMPA – UNESCO Chair], Université d’Abomey-Calavi, Cotonou, Bénin; Université de Toulouse; Université Paul Sabatier [UPS]; Laboratoire d’Etudes en Géophysique et Océanographie Spatiales [LEGOS]; Edouard Belin, Toulouse, France; Institut de Recherche pour le Développement [IRD], LEGOS, Toulouse, France
G Alory
Université de Toulouse; Université Paul Sabatier [UPS]; Laboratoire d’Etudes en Géophysique et Océanographie Spatiales [LEGOS]; Edouard Belin, Toulouse, France; Conseil National Astronomes et Physiciens [CNAP], LEGOS, Toulouse, France
Y du Penhoat
International Chair in Mathematical Physics and Applications [ICMPA – UNESCO Chair], Université d’Abomey-Calavi, Cotonou, Bénin; Institut de Recherche pour le Développement [IRD], LEGOS, Toulouse, France; Institut de Recherches Halieutiques et Océanologiques du Bénin [IRHOB], Cotonou, Bénin
J Jouanno
Institut Pierre-Simon Laplace [IPSL], Laboratoire d’Oceanographie et du Climat [LOCEAN], Paris, France; Departamento de Oceanografia Fisica, Centro de Investigación Cientifica y de Educación Superior de Ensenada [CICESE], Baja California, Mexico
MN Hounkonnou
Université de Toulouse; Université Paul Sabatier [UPS]; Laboratoire d’Etudes en Géophysique et Océanographie Spatiales [LEGOS]; Edouard Belin, Toulouse, France
E Kestenare
Institut de Recherche pour le Développement [IRD], LEGOS, Toulouse, France
Published
2014-07-30
Section
Articles

Journal Identifiers


eISSN: 1814-2338
print ISSN: 1814-232X