The variability of ocean circulation and sea surface temperature (SST) in the tropical Atlantic, especially in the Gulf of Guinea (GG), defines this region as exceptionally rich from an oceanographic perspective. The Guinea Current (GC), as the major surface current, plays a significant role in marine productivity and coastal upwelling in the GG. This coastal upwelling is known to influence the climate of the surrounding region, primary productivity and local fisheries. Studies on GC variability and its impact on this coastal upwelling have highlighted that the upwelling downstream of Cape Palmas is influenced by GC detachment, topographic variations and advective processes leading to significant vertical mixing. This study aims to analyze the interannual variability of the GC and its impact on coastal upwelling using the Coastal and Regional Ocean COmmunity model (CROCO). The model’s evaluation is conducted using observational data, specifically Geostrophic and EKman Current Observatory (GEKCO) and Ocean Surface Current Analysis (OSCAR) for currents, and Air-sea Fluxes for the global Tropic ocean-description (TROPFLUX) and Optimum Interpolation-Sea Surface Temperature (OI-SST) for temperature. Thus, the model evaluation indicates that it accurately replicates ocean circulation and SST patterns in the tropical Atlantic and the GG. The joint analysis of upwelling indices (surface and intensity) and the position of the GC core allowed us to conclude that the displacement of the GC core does indeed influence the upwelling indices in the northern part of GG. However, other oceanic and atmospheric mechanisms such as vertical diffusion and horizontal advection as proposed by previous studies may also affect the year-by-year variability of coastal upwelling in the northern GG.
References
[1]
Ekman, V. (1905) On the Influence of the Earth’s Rotation on Ocean currents. Arkiv för Matematik, Astronomy Och Fysik, 2, 1-53.
[2]
Wilson, L.J., Fulton, C.J., Hogg, A.M., Joyce, K.E., Radford, B.T.M. and Fraser, C.I. (2016) Climate-Driven Changes to Ocean Circulation and Their Inferred Impacts on Marine Dispersal Patterns. Global Ecology and Biogeography, 25, 923-939. https://doi.org/10.1111/geb.12456
[3]
Bosson, K., Aman, A., Toualy, E. and Arnault, S. (2023) The Surface Guinea Current Variability from Satellite Data. Regional Studies in Marine Science, 64, Article ID: 103045. https://doi.org/10.1016/j.rsma.2023.103045
[4]
Kumagai, N.H., García Molinos, J., Yamano, H., Takao, S., Fujii, M. and Yamanaka, Y. (2018) Ocean Currents and Herbivory Drive Macroalgae-to-Coral Community Shift under Climate Warming. Proceedings of the National Academy of Sciences, 115, 8990-8995. https://doi.org/10.1073/pnas.1716826115
[5]
Ramesh, T., Bolan, N.S., Kirkham, M.B., Wijesekara, H., Kanchikerimath, M., Srinivasa Rao, C., et al. (2019) Soil Organic Carbon Dynamics: Impact of Land Use Changes and Management Practices: A Review. Advances in Agronomy, 156, 1-107. https://doi.org/10.1016/bs.agron.2019.02.001
[6]
Picaut, J. (1983) Sur Les Mécanismes Des Variations Thermiques Dans Le Golfe de Guinée (Du Semi-Diurne à l’interannuel). Ph.D. Thesis, Université de Bretagne Occidentale.
[7]
Aman, A., Testut, L., Woodworth, P.L., Aarup, A. AND Dixon, D.J. (2007) Seasonal Sea Level Variability in the Gulf of Guinea from Altimetry and Tide Gauge. Revue Ivoirienne des Sciences et Technologie, 9, 105-118.
[8]
Arnault, S. (1987) Tropical Atlantic Geostrophic Currents and Ship Drifts. Journal of Geophysical Research: Oceans, 92, 5076-5088. https://doi.org/10.1029/JC092iC05p05076
[9]
Lumpkin, R. and Garzoli, S.L. (2005) Near-surface Circulation in the Tropical Atlantic Ocean. Deep Sea Research Part I: Oceanographic Research Papers, 52, 495-518. https://doi.org/10.1016/j.dsr.2004.09.001
[10]
Stramma, L. and Schott, F. (1999) The Mean Flow Field of the Tropical Atlantic Ocean. Deep Sea Research Part II: Topical Studies in Oceanography, 46, 279-303. https://doi.org/10.1016/s0967-0645(98)00109-x
[11]
Djakouré, S., Penven, P., Bourlès, B., Koné, V. and Veitch, J. (2017) Respective Roles of the Guinea Current and Local Winds on the Coastal Upwelling in the Northern Gulf of Guinea. Journal of Physical Oceanography, 47, 1367-1387. https://doi.org/10.1175/jpo-d-16-0126.1
[12]
Ingham, M.C. (1970) Coastal Upwelling in the Northwestern Gulf of Guinea. Bulle-tin of Marine Science, 20, 1-34.
[13]
Longhurst, A. (1962) A Review of the Oceanography of the Gulf of Guinea. Deep Sea Research and Oceanographic Abstracts, 24, 633-663. https://doi.org/10.1016/0011-7471(63)90443-1
[14]
Kolodziejczyk, N. (2008) Analyse de La Circulation de Subsurface et de Sa Variabilité Dans Le Golfe de Guinée. Ph.D. Thesis, Université de Bretagne Occidentale.
[15]
Djakouré, S., Penven, P., Bourlès, B., Veitch, J. and Koné, V. (2014) Coastally Trapped Eddies in the North of the Gulf of Guinea. Journal of Geophysical Research: Oceans, 119, 6805-6819. https://doi.org/10.1002/2014jc010243
[16]
Bakun, A. (1978) Guinea Current Upwelling. Nature, 271, 147-150. https://doi.org/10.1038/271147a0
[17]
Colin, C. (1988) Coastal Upwelling Events in Front of the Ivory-Coast during the Focal Program. Oceanological Acta 11, 125-138.
[18]
Colin, C., Gallardo, Y., Chuchla, R. and Cissoko. S. (1993) Environnement Climatique et océanographique du plateau continental de Côte d’Ivoire. In Environnement et ressources aquatiques de Côte d’Ivoire. Tome I: le milieu marin, Ed., Orstom, Paris, 76-110.
[19]
KORANTENG, K.A. and MCGLADE, J.M. (2001) Climatic Trends in Continental Shelf Waters off Ghana and in the Gulf of Guinea, 1963-1992. Oceanologica Acta, 24, 187-198. https://doi.org/10.1016/s0399-1784(01)01140-9
[20]
Gu, G. and Adler, R.F. (2004) Seasonal Evolution and Variability Associated with the West African Monsoon System. Journal of Climate, 17, 3364-3377. https://doi.org/10.1175/1520-0442(2004)017<3364:seavaw>2.0.co;2
[21]
Brandt, P., Caniaux, G., Bourlès, B., Lazar, A., Dengler, M., Funk, A., et al. (2010) Equatorial Upper-Ocean Dynamics and Their Interaction with the West African Monsoon. Atmospheric Science Letters, 12, 24-30. https://doi.org/10.1002/asl.287
[22]
Koné, V., Lett, C., Penven, P., Bourlès, B. and Djakouré, S. (2017) A Biophysical Model of S. Aurita Early Life History in the Northern Gulf of Guinea. Progress in Oceanography, 151, 83-96. https://doi.org/10.1016/j.pocean.2016.10.008
[23]
Amemou, H., Koné, V., Aman, A. and Lett, C. (2020) Assessment of a Lagrangian Model Using Trajectories of Oceanographic Drifters and Fishing Devices in the Tropical Atlantic Ocean. Progress in Oceanography, 188, Article ID: 102426. https://doi.org/10.1016/j.pocean.2020.102426
[24]
Debreu, L., Marchesiello, P., Penven, P. and Cambon, G. (2012) Two-Way Nesting in Split-Explicit Ocean Models: Algorithms, Implementation and Validation. Ocean Modelling, 49, 1-21. https://doi.org/10.1016/j.ocemod.2012.03.003
[25]
Marchesiello, P. and Estrade, P. (2010) Upwelling Limitation by Onshore Geostrophic Flow. Journal of Marine Research, 68, 37-62. https://doi.org/10.1357/002224010793079004
[26]
Hilt, M., Auclair, F., Benshila, R., Bordois, L., Capet, X., Debreu, L., et al. (2020) Numerical Modelling of Hydraulic Control, Solitary Waves and Primary Instabilities in the Strait of Gibraltar. Ocean Modelling, 151, Article ID: 101642. https://doi.org/10.1016/j.ocemod.2020.101642
[27]
Marchesiello, P., Auclair, F., Debreu, L., McWilliams, J., Almar, R., Benshila, R., et al. (2021) Tridimensional Nonhydrostatic Transient Rip Currents in a Wave-Resolving Model. Ocean Modelling, 163, Article ID: 101816. https://doi.org/10.1016/j.ocemod.2021.101816
[28]
Sandrine, D. (2015) Analyse numérique de la circulation océanique de la région Nord du Golfe de Guinée. Ph.D. Thesis, Université d’Abomey-Calavi.
[29]
Dee, D.P., Uppala, S.M., Simmons, A.J., Berrisford, P., Poli, P., Kobayashi, S., et al. (2011) The Era-Interim Reanalysis: Configuration and Performance of the Data Assimilation System. Quarterly Journal of the Royal Meteorological Society, 137, 553-597. https://doi.org/10.1002/qj.828
[30]
Carton, J.A., Chepurin, G.A. and Chen, L. (2018) SODA3: A New Ocean Climate Reanalysis. Journal of Climate, 31, 6967-6983. https://doi.org/10.1175/jcli-d-18-0149.1
[31]
Sudre, J., Maes, C. and Garçon, V. (2013) On the Global Estimates of Geostrophic and Ekman Surface Currents: Global Estimates of Geostrophic and Ekman Surface Currents. Limnology and Oceanography: Fluids and Environments, 3, 1-20. https://doi.org/10.1215/21573689-2071927
[32]
Bonjean, F. and Lagerloef, G.S.E. (2002) Diagnostic Model and Analysis of the Surface Currents in the Tropical Pacific Ocean. Journal of Physical Oceanography, 32, 2938-2954. https://doi.org/10.1175/1520-0485(2002)032<2938:dmaaot>2.0.co;2
[33]
Praveen Kumar, B., Vialard, J., Lengaigne, M., Murty, V.S.N., McPhaden, M.J., Cronin, M.F., et al. (2012) Tropflux Wind Stresses over the Tropical Oceans: Evaluation and Comparison with Other Products. Climate Dynamics, 40, 2049-2071. https://doi.org/10.1007/s00382-012-1455-4
[34]
Reynolds, R.W., Smith, T.M., Liu, C., Chelton, D.B., Casey, K.S. and Schlax, M.G. (2007) Daily High-Resolution-Blended Analyses for Sea Surface Temperature. Journal of Climate, 20, 5473-5496. https://doi.org/10.1175/2007jcli1824.1
[35]
Caniaux, G., Giordani, H., Redelsperger, J., Guichard, F., Key, E. and Wade, M. (2011) Coupling between the Atlantic Cold Tongue and the West African Monsoon in Boreal Spring and Summer. Journal of Geophysical Research, 116, C04003. https://doi.org/10.1029/2010jc006570
[36]
Koné, M., Djakouré, S., Adon, M., Ta, S. and Kouadio, Y. (2022) Marine Heatwaves, Upwelling, and Atmospheric Conditions during the Monsoon Period at the Northern Coast of the Gulf of Guinea. Climate, 10, Article No. 199. https://doi.org/10.3390/cli10120199
[37]
Bourlès, B., Molinari, R.L., Johns, E., Wilson, W.D. and Leaman, K.D. (1999) Upper Layer Currents in the Western Tropical North Atlantic (1989-1991). Journal of Geophysical Research: Oceans, 104, 1361-1375. https://doi.org/10.1029/1998jc900025
[38]
Schott, F.A., Mccreary, J.P. and Johnson, G.C. (2013) Shallow Overturning Circulations of the Tropical-Subtropical Oceans. In: Geophysical Monograph Series, American Geophysical Union, Washington, 261-304. https://doi.org/10.1029/147gm15
[39]
Richardson, P.L. and Walsh, D. (1986) Mapping Climatological Seasonal Variations of Surface Currents in the Tropical Atlantic Using Ship Drifts. Journal of Geophysical Research: Oceans, 91, 10537-10550. https://doi.org/10.1029/jc091ic09p10537
[40]
Morlière, A. (1970) Les saisons marines devant Abidjan. Documents Scientifiques, Centre de Recherches Océanographiques, Abidjan, 1, 1-15.
[41]
Williame, B. (1967) Major Currents in the North and South Atlantic Oceans between 64˚N and 60˚S. Technical Report, United States. Naval Oceanographic Office. https://doi.org/10.5962/bhl.title.47773
[42]
Lemasson, L. and Rébert, J.P. (1973) Les courants marins dans le Golfe ivoirien. Cahier ORSTOM, XI, 67-95.
[43]
Lefèvre, N., Caniaux, G., Janicot, S. and Gueye, A.K. (2013) Increased CO2 Outgassing in February-May 2010 in the Tropical Atlantic Following the 2009 Pacific El Niño. Journal of Geophysical Research: Oceans, 118, 1645-1657. https://doi.org/10.1002/jgrc.20107
[44]
Djakouré, S., Araujo, M., Hounsou-Gbo, A., Noriega, C., and Bourlès, B. (2017) On the Potential Causes of the Recent Pelagic Sargassum Blooms Events in the Tropical North Atlantic Ocean. Biogeosciences. https://doi.org/10.5194/bg-2017-346
[45]
Alory, G., Da-Allada, C.Y., Djakouré, S., Dadou, I., Jouanno, J. and Loemba, D.P. (2021) Coastal Upwelling Limitation by Onshore Geostrophic Flow in the Gulf of Guinea around the Niger River Plume. Frontiers in Marine Science, 7, Article 607216. https://doi.org/10.3389/fmars.2020.607216
[46]
Toualy, E., Stanojevic, G., Kouadio, K.Y. and Aman, A. (2012) Multi-Decadal Variability of Sea Surface Temperature in the Northern Coast of Gulf of Guinea. Asian Journal of Applied Sciences, 5, 552-562. https://doi.org/10.3923/ajaps.2012.552.562
