Articles | Volume 14, issue 5
https://doi.org/10.5194/os-14-971-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/os-14-971-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Research article
| 
10 Sep 2018
Research article |
| 10 Sep 2018
| 10 Sep 2018
A model perspective on the dynamics of the shadow zone of the eastern tropical North Atlantic – Part 1: the poleward slope currents along West Africa
Lala Kounta
CORRESPONDING AUTHOR
Laboratoire de Physique de l'Atmosphère et de l'Océan Siméon Fongang, ESP
/UCAD, Dakar, Senegal
LOCEAN Laboratory, CNRS-IRD-Sorbonne Universités-MNHN, Paris, France
Xavier Capet
LOCEAN Laboratory, CNRS-IRD-Sorbonne Universités-MNHN, Paris, France
Julien Jouanno
LEGOS Laboratory, IRD-Univ. Paul Sabatier-Observatoire Midi-Pyrénées, Toulouse, France
Nicolas Kolodziejczyk
Laboratoire d'Océanographie Physique et Spatial, IFREMER-IRD-CNRS-UBO, IUEM, Plouzané, France
Bamol Sow
Laboratoire d'Océanographie, des Sciences de l'Environnement et du Climat, UASZ, Ziguinchor, Senegal
Amadou Thierno Gaye
Laboratoire de Physique de l'Atmosphère et de l'Océan Siméon Fongang, ESP
/UCAD, Dakar, Senegal
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Cited articles
Alpers, W., Brandt, P., Lazar, A., Dagorne, D., Sow, B., Faye, S., Hansen,
M. W., Rubino, A., Poulain, P.-M., and Brehmer, P.: A small-scale oceanic
eddy off the coast of West Africa studied by multi-sensor satellite and
surface drifter data, Remote Sens. Environ., 129, 132–143, 2013. a
Bakun, A. and Nelson, C. S.: The seasonal cycle of wind-stress curl in
subtropical eastern boundary current regions, J. Phys. Oceanogr., 21,
1815–1834, 1991. a
Barton, E. D.: Eastern boundary of the North Atlantic: Northwest Africa and
Iberia, Coastal segment (18, E), in: The sea: The Global Coastal Ocean, edited by: Robinson, A. R. and Brink, K. H., 11, 633–657, 1998. a
Blanke, B., Arhan, M., Madec, G., and Roche, S.: Warm water paths in the
equatorial Atlantic as diagnosed with a general circulation model, J. Phys. Oceanogr., 29, 2753–2768, 1999. a
Brandt, P., Hormann, V., Körtzinger, A., Visbeck, M., Krahmann, G.,
Stramma, L., Lumpkin, R., and Schmid, C.: Changes in the ventilation of the
oxygen minimum zone of the tropical North Atlantic, J. Phys. Oceanogr., 40,
1784–1801, 2010. a
Brandt, P., Bange, H. W., Banyte, D., Dengler, M., Didwischus, S.-H.,
Fischer, T., Greatbatch, R. J., Hahn, J., Kanzow, T., Karstensen, J.,
Körtzinger, A., Krahmann, G., Schmidtko, S., Stramma, L., Tanhua, T., and
Visbeck, M.: On the role of circulation and mixing in the ventilation of
oxygen minimum zones with a focus on the eastern tropical North Atlantic,
Biogeosciences, 12, 489–512, https://doi.org/10.5194/bg-12-489-2015, 2015. a, b
Brandt, P., Claus, M., Greatbatch, R. J., Kopte, R., Toole, J. M., Johns,
W. E., and Böning, C. W.: Annual and semiannual cycle of equatorial
Atlantic circulation associated with basin-mode resonance, J. Phys. Oceanogr., 46, 3011–3029, 2016. a
Brink, K., Halpern, D., Huyer, A., and Smith, R.: The physical environment of
the Peruvian upwelling system, Prog. Oceanogr., 12, 285–305, 1983. a
Cabanes, C., Grouazel, A., von Schuckmann, K., Hamon, M., Turpin, V.,
Coatanoan, C., Paris, F., Guinehut, S., Boone, C., Ferry, N.,
de Boyer Montégut, C., Carval, T., Reverdin, G., Pouliquen, S., and
Le Traon, P.-Y.: The CORA dataset: validation and diagnostics of in-situ
ocean temperature and salinity measurements, Ocean Sci., 9, 1–18, 2013. a
Capet, X., Marchesiello, P., and McWilliams, J. C.: Upwelling response to
coastal wind profiles, Geophys. Res. Lett., 31, L13311,
https://doi.org/10.1029/2004GL020123, 2004. a
Capet, X., Colas, F., Penven, P., Marchesiello, P., and McWilliams, J. C.:
Eddies in eastern-boundary subtropical upwelling systems, in: Ocean Modeling
in an Eddying Regime, edited by: Hecht, M. and Hasumi, H., Geophys. Monog. Ser., vol. 177, Am. Geophys. Union,
2008. a
Capet, X., Estrade, P., Machu, E., Ndoye, S., Grelet, S., Lazar, A., Marié,
L., Dausse, D., and Brehmer, P.: On the dynamics of the southern Senegal
upwelling center: observed variability from synoptic to super-inertial
scales, J. Phys. Oceanogr., 47, 155–180, 2017. a
Chelton, D. B. and Schlax, M. G.: Global observations of oceanic Rossby
waves,
Science, 272, 234–238, 1996. a
Clarke, A. J. and Shi, C.: Critical frequencies at ocean boundaries, J.
Geophys. Res., 96, 10731–10738, 1991. a
Clarke, A. J. and Liu, X.: Observations and dynamics of semiannual and annual
sea levels near the eastern equatorial Indian Ocean boundary, J. Phys. Oceanogr., 23, 386–399, 1993. a
Colas, F., Capet, X., McWilliams, J. C., and Shchepetkin, A.: 1997–98 El
Nino
off Peru: a numerical study, Prog. Oceanogr., 79, 138–155, 2008. a
Connolly, T. P., Hickey, B. M., Shulman, I., and Thomson, R. E.: Coastal
trapped waves, alongshore pressure gradients, and the California
Undercurrent, J. Phys. Oceanogr., 44, 319–342, 2014. a
Crépon, M., Richez, C., and Chartier, M.: Effects of coastline geometry
on upwellings, J. Phys. Oceanogr., 14, 1365–1382, 1984. a
Da Silva, M. P. and Chang, P.: Seasonal variation of the subtropical/tropical
pathways in the Atlantic ocean from an ocean data assimilation experiment,
Geoph. Monog. Series, 147, 305–318, 2004. a
Dee, D., Uppala, S., Simmons, A., Berrisford, P., Poli, P., Kobayashi, S.,
Andrae, U., Balmaseda, M., Balsamo, G., Bauer, P., et al.: The ERA-Interim
reanalysis: Configuration and performance of the data assimilation system,
Q. J. Roy. Meteor. Soc., 137, 553–597, 2011. a
de Szoeke, R. A. and Chelton, D. B.: The modification of long planetary waves
by homogeneous potential vorticity layers, J. Phys. Oceanogr., 29,
500–511, 1999. a
Dewitte, B., Ramos, M., Echevin, V., Pizarro, O., and duPenhoat, V.: Vertical structure
variability in a seasonal simulation of a medium-resolution regional model of
the Eastern South Pacific, Prog. Oceanogr., 79, 120–137, 2008. a
Ding, H., Keenlyside, N. S., and Latif, M.: Seasonal cycle in the upper
equatorial Atlantic Ocean, J. Geophys. Res., 114, 2009. a
Djakouré, S., Penven, P., Bourlès, B., Veitch, J., and Koné, V.:
Coastally trapped eddies in the north of the Gulf of Guinea, J. Geophys. Res.-Oceans, 119, 6805–6819, 2014. a
Dussin, R., Barnier, B., and Brodeau, L.: The making of Drakkar forcing set
DFS5, 14, C09016, https://doi.org/10.1029/2009JC005418, 2014. a
Elmoussaoui, A., Arhan, M., and Treguier, A.: Model-inferred upper ocean
circulation in the eastern tropics of the North Atlantic, Deep-Sea Res., 52,
1093–1120, https://doi.org/10.1016/j.dsr.2005.01.010, 2005. a
Fraga, F.: Distribution des masses d'eau dans l'upwelling de Mauritanie,
Tethys, 6, 5–10, 1974. a
Gaillard, F., Reynaud, T., Thierry, V., Kolodziejczyk, N., and
Von Schuckmann,
K.: In situ–based reanalysis of the global ocean temperature and salinity
with ISAS: Variability of the heat content and steric height, J. Climate, 29,
1305–1323, 2016. a
Garzoli, S. L. and Katz, E. J.: The forced annual reversal of the Atlantic
North Equatorial Countercurrent, J. Phys. Oceanogr., 13, 2082–2090, 1983. a
Glessmer, M. S., Eden, C., and Oschlies, A.: Contribution of oxygen minimum
zone waters to the coastal upwelling off Mauritania, Prog. Oceanogr., 83,
143–150, 2009. a
Gómez-Valdivia, F., Parés-Sierra, A., and Laura Flores-Morales, A.:
Semiannual variability of the California Undercurrent along the
Southern California Current System: A tropical generated
phenomenon, J. Geophys. Res., 122, 1574–1589, https://doi.org/10.1002/2016JC012350,
2017. a, b
Hagen, E.: Northwest African upwelling scenario, Oceanol. Acta, 24,
113–128, 2001. a
Hsieh, W. W., Davey, M. K., and Wajsowicz, R. C.: The free Kelvin wave in
finite-difference numerical models, J. Phys. Oceanogr., 13, 1383–1397,
1983. a
Hurlburt, H. and Thompson, J. D.: Coastal upwelling on a β-plane, J.
Phys. Oceanogr., 3, 16–32, 1973. a
Huyer, A.: Coastal upwelling in the California Current system, Prog.
Oceanogr.,
12, 259–284, 1983. a
Jouanno, J., Hernandez, O., and Sanchez-Gomez, E.: Equatorial Atlantic
interannual variability and its relation to dynamic and thermodynamic
processes, Earth Syst. Dynam., 8, 1061–1069,
https://doi.org/10.5194/esd-8-1061-2017, 2017 a
Junker, T., Schmidt, M., and Mohrholz, V.: The relation of wind stress curl
and
meridional transport in the Benguela upwelling system, J. Mar. Sys., 143,
1–6, 2015. a
Killworth, P. D.: On the propagation of stable baroclinic Rossby waves
through
a mean shear flow, Deep-Sea Res., 26, 997–1031, 1979. a
Kirchner, K., Rhein, M., Hüttl-Kabus, S., and Böning, C. W.: On the
spreading of South Atlantic Water into the northern hemisphere, J. Geophys.
Res., 114, C05019, https://doi.org/10.1029/2008JC005165, 2009. a
Large, W. D. and Yeager, S.: Diurnal to decadal global forcing for ocean and
sea-ice models: the data sets and flux climatologies, NCAR Tech Note
TN–460+STR, 105 pp., 2004. a
Luyten, J., Pedlosky, J., and Stommel, H.: The ventilated thermocline, J.
Phys. Oceanogr., 13, 292–309, 1983. a
Machu, E., Capet, X., Estrade, P., Ndoye, S., Lazar, A., Beaurand, F., Auger,
P.-A., and Brehmer, P.: First evidence of denitrification in the southern
part of the Canary Upwelling System, submitted to Geophys. Res. Lett., 2018. a
Malanotte-Rizzoli, P., Hedstrom, K., Arango, H., and Haidvogel, D. B.: Water
mass pathways between the subtropical and tropical ocean in a climatological
simulation of the North Atlantic ocean circulation, Dynam. Atmos. Oceans, 32,
331–371, 2000. a
Masina, S., Storto, A., Ferry, N., Valdivieso, M., Haines, K., Balmaseda, M.,
Zuo, H., Drevillon, M., and Parent, L.: An ensemble of eddy-permitting
global ocean reanalyses from the MyOcean project, Clim. Dynam., 49, 1–29,
https://doi.org/10.1007/s00382-015-2728-5, 2015. a
McCalpin, J. D.: Rossby wave generation by poleward propagating Kelvin waves:
The midlatitude quasigeostrophic approximation, J. Phys. Oceanogr., 25,
1415–1425, 1995. a
McCreary, J., Kundu, P., and Chao, S.: On the dynamics of the California
Current System, J. Mar. Res., 45, 1–32, 1987. a
Mittelstaedt, E.: Der hydrographische Aufbau und die zeitliche
Variabilität
der Schichtung und Strömung im nordwestafrikanischen Auftriebsgebiet im
Frühjahr 1968, Meteor Forsch.-Ergebn., 11, 1–57, 1972. a
Molemaker, M. J., Mc Williams, J. C., and Dewar, W. K.: Submesoscale
instability and generation of mesoscale anticyclones near a separation of the
California Undercurrent, J. Phys. Oceanogr., 45, 613–629, 2015. a
Philander, S. and Pacanowski, R.: The generation of equatorial currents, J.
Geophys. Res., 85, 1123–1136, 1980. a
Polo, I., Lazar, A., Rodriguez-Fonseca, B., and Arnault, S.: Oceanic Kelvin
waves and tropical Atlantic intraseasonal variability: 1. Kelvin wave
characterization, J. Geophys. Res., 113, C07009, https://doi.org/10.1029/2007JC004495, 2008. a, b, c
Ramos, M., Pizarro, O., Bravo, L., and Dewitte, B.: Seasonal variability of
the
permanent thermocline off northern Chile, Geophys. Res. Lett., 33, L09608,
https://doi.org/10.1029/2006GL025882, 2006. a, b, c
Rao, R., Kumar, M. G., Ravichandran, M., Rao, A., Gopalakrishna, V., and
Thadathil, P.: Interannual variability of Kelvin wave propagation in the wave
guides of the equatorial Indian Ocean, the coastal Bay of Bengal and the
southeastern Arabian Sea during 1993–2006, Deep-Sea Res., 57, 1–13, 2010. a
Rhein, M. and Stramma, L.: Seasonal variability in the Deep Western Boundary
Current around the Eastern tip of Brazil, Deep-Sea Res., 52, 1414–1428,
https://doi.org/10.1016/j.dsr.2005.03.004, 2005. a
Risien, C. M. and Chelton, D. B.: A global climatology of surface wind and
wind stress fields from eight years of QuikSCAT scatterometer data, J.
Phys. Oceanogr., 38, 2379–2413, 2008. a
Rouault, M.: Bi-annual intrusion of tropical water in the northern Benguela
upwelling, Geophys. Res. Lett., 39, 2012. a
Schafstall, J., Dengler, M., Brandt, P., and Bange, H.: Tidal-induced mixing
and diapycnal nutrient fluxes in the Mauritanian upwelling region, J.
Geophys. Res., 115, 2010. a
Schneider, T., Bischoff, T., and Haug, G. H.: Migrations and dynamics of the
intertropical convergence zone, Nature, 513, 45–53, 2014. a
Schouten, M. W., Matano, R. P., and Strub, T. P.: A description of the
seasonal
cycle of the equatorial Atlantic from altimeter data, Deep-Sea Res., 52,
477–493, 2005. a
Stramma, L., Hüttl, S., and Schafstall, J.: Water masses and currents in
the
upper tropical northeast Atlantic off northwest Africa, J. Geophys. Res.,
110, c12006, https://doi.org/10.1029/2005JC002939, 2005. a, b, c, d
Sverdrup, H. U.: Wind-driven currents in a baroclinic ocean; with application
to the equatorial currents of the eastern Pacific, P. Natl. Acad. Sci. USA, 33, 318–326, 1947. a
Talley, L. D.: Descriptive physical oceanography: an introduction, Academic
press, London, UK, 2011. a
Thomas, M. D., De Boer, A. M., Johnson, H. L., and Stevens, D. P.: Spatial and
temporal scales of Sverdrup balance, J. Phys. Oceanogr., 44, 2644–2660,
2014. a
Tomczak, M.: Review and commentary to paper “The poleward undercurrent on
the
eastern boundary of the subtropical North Atlantic”, in: Poleward Flows Along
Eastern Ocean Boundaries, 93–95, Springer, New York, NY, USA, 1989. a
Tomczak Jr., M.: An analysis of mixing in the frontal zone of South and North
Atlantic Central Water off North-West Africa, Prog. Oceanogr., 10, 173–192,
1981. a
Townsend, T. L., Hurlburt, H. E., and Hogan, P. J.: Modeled Sverdrup flow in
the North Atlantic from 11 different wind stress climatologies, Dynam. Atmos.
Ocean, 32, 373–417, 2000. a
Vega, A., du Penhoat, Y., Dewitte, B., and Pizarro, O.: Equatorial forcing of
interannual Rossby waves in the eastern South Pacific, Geophys. Res.
Lett., 30, 1197, https://doi.org/10.1029/2002GL015886, 2003. a
Voituriez, B.: Les sous-courants équatoriaux nord et sud et la formation
des dômes thermiques tropicaux, Oceanol. Acta, 4, 497–506, 1981. a
Voituriez, B. and Herbland, A.: Comparaisons des systèmes productifs de
l'Atlantique tropical est: dômes thermiques, upwellings côtiers et
upwelling équatorial, Tech. rep., Rapports et Procès-Verbaux des
Réunions du Conseil International pour l'Exploration de la Mer,
available at: http://www.documentation.ird.fr/hor/fdi:42794 (last access: 18 August 2018), 1982.
a
White, W. B.: The resonant response of interannual baroclinic Rossby waves to
wind forcing in the eastern midlatitude North Pacific, J. Phys. Oceanogr.,
15, 403–415, 1985. a
Wooster, W., Bakun, A., and McLain, D.: Seasonal upwelling cycle along the
eastern boundary of the North Atlantic, J. Mar. Res., 34, 131–141, 1976. a
Wunsch, C.: The decadal mean ocean circulation and Sverdrup balance, J. Mar.
Res., 69, 417–434, 2011. a
Yang, J. and Joyce, T. M.: Local and equatorial forcing of seasonal
variations
of the North Equatorial Countercurrent in the Atlantic Ocean, J. Phys.
Oceanogr., 36, 238–254, 2006. a
Yoon, J.-H. and Philander, S.: The generation of coastal undercurrents, J.
Oceanogr., 38, 215–224, 1982. a
Short summary
The currents along the West African seaboard are poorly known. Based on a carefully evaluated numerical simulation the present study describes these currents in the sector 8–20°N and the physical processes that drive them. Prevailing northward flow with two intensification periods per year is identified. Both local and distant coastal winds (blowing as far as thousands of kilometers away in the Gulf of Guinea) contribute to the circulation in this sector.
The currents along the West African seaboard are poorly known. Based on a carefully evaluated...
