World Library  

Add to Book Shelf
Flag as Inappropriate
Email this Book

Deep Currents in the Gulf of Guinea: Along Slope Propagation of Intraseasonal Waves : Volume 6, Issue 1 (07/01/2009)

By Guiavarc'H, C.

Click here to view

Book Id: WPLBN0003985000
Format Type: PDF Article :
File Size: Pages 38
Reproduction Date: 2015

Title: Deep Currents in the Gulf of Guinea: Along Slope Propagation of Intraseasonal Waves : Volume 6, Issue 1 (07/01/2009)  
Author: Guiavarc'H, C.
Volume: Vol. 6, Issue 1
Language: English
Subject: Science, Ocean, Science
Collections: Periodicals: Journal and Magazine Collection, Copernicus GmbH
Publication Date:
Publisher: Copernicus Gmbh, Göttingen, Germany
Member Page: Copernicus Publications


APA MLA Chicago

Treguier, A. M., Guiavarc'h, C., & Vangriesheim, A. (2009). Deep Currents in the Gulf of Guinea: Along Slope Propagation of Intraseasonal Waves : Volume 6, Issue 1 (07/01/2009). Retrieved from

Description: Laboratoire de Physique des Oceans, CNRS-IFREMER-IRD-UBO, BP 70, 29280 Plouzané, France. In the Gulf of Guinea, intraseasonal variability is large at the equator and along the coast. Current data on the continental slope near 7.5° S show very energetic biweekly oscillations at 1300 m depth. A high resolution numerical model demonstrates that this deep variability is forced by equatorial winds, through the generation of equatorial Yanai waves that propagate eastward and at depth, and then poleward as coastal-trapped waves upon reaching the coast of Africa. Intraseasonal variability is intensified along the coast, especially in the 500–1500 m depth range, with the largest intensification in the 10–20 day period range. The structure of kinetic energy is well explained at first order by a linear model with six baroclinic modes. Along the equator, eastward intensification of energy and bottom intensification are in qualitative agreement with vertically propagating Yanai waves, although the signal is clearly influenced by the details of the bathymetry. Along the coast, vertical modes 3 to 5 are important close to the equator, and the signal is dominated by lower modes farther south. Additional current meter data on the continental slope near 3° N display an energy profile in the 10–20 day period band that is strikingly different from the one at 7.5° S, with surface intensification rather than bottom intensification and a secondary maximum near 800 m. The model reproduces these features and explains them: the surface intensification in the north is due to the regional wind forcing, and the north-south dissymetry of the deep signal is due to the presence of the zonal African coast near 5° N. A 4 years time series at 7.5° S displays intermittencies of the 10–20 day signal near the bottom. This intermittency is not correlated with fluctuations of the equatorial winds and does not seem to be a simple linear response to the wind forcing.

Deep currents in the Gulf of Guinea: along slope propagation of intraseasonal waves

Brink, K H. and Chapman, D C.: Program for computing properties of coastal-trapped waves and wind-driven motions over the continental shelf and slope, Second ed. Woods Hole Oceanographic Institution Technical Reports, WHOI-87-24, 119 pp., 1987.; Bunge, L., Provost, C., Lilly, J., D'Orgeville, M., Kartavtseff, A., and Melice, J L.: Variability of the horizontal velocity structure in the upper 1600 m of the water column on the equator at 10\unit\degree W, J. Phys. Oceanogr., 36, 1287–1304, 2006.; Bunge, L., Provost, C., and Kartavtseff, A.: Variability in horizontal current velocities in the central and eastern equatorial Atlantic in 2002, J. Geophys. Res., 112, C02014, doi:10.1029/2006JC003704, 2007.; Clarke, A J.: Reflexion of equatorial waves from oceanic boundaries, J. Phys. Oceanogr., 13, 1193–1207, 1983.; Clarke, A J. and Battisti, D S.: Identification of the fortnightly wave observed along the Northern Coast of the Gulf of Guinea, J. Phys. Oceanogr., 13, 2192–2200, 1983.; Dai, A. and Trenberth, K. E.: Estimates of freshwater discharge from continents: latitudinal and seasonal variations, J. Hydrometeorol., 3, 660–687, 2002.; Enfield, D., del Pilar Corneijo-Rodrigez, M., Smith, R., and Newberger, P.: The equatorial source of propagating variability along the Peru coast during the 1982–1983 El Nino, J. Geophys. Res., 92(C13), 14335–14346, 1987.; Gent, P R., O'Neill, K., and Cane, M A.: A model of the semiannual oscillation in the equatorial Indian ocean, J. Phys. Oceanogr., 13, 2148–2160, 1983.; Griffies, S M., Biastoch, A., Boning, C., Bryan, F., Danabasoglu, G., Chassignet, E P., England, M H., Gerdes, R., Haak, H., Hallberg, R W., Hazeleger, W., Jungclaus, J., Large, W G., Madec, G., Pirani, A., Samuels, B L., Scheinert, M., Gupta, A S., Severijns, C A., Simmons, H L., Treguier, A M., Winton, M., Yeager, S., and Yin, J.: Coordinated ocean-ice reference experiments (COREs), Ocean Model., 26, 1–2, 1–46, 2008.; Arhan, M., Treguier, A M., Bourles, B., and Michel, S.: Diagnosing the annual cycle of the equatorial undercurrent in the atlantic ocean from a general circulation ocean model, J. Phys. Oceanogr., 36, 1502–1522, 2006.; Barnier, B., Madec, G., Penduff, T., Molines, J M., Treguier, A M., Le~Sommer, J., Beckmann, A., Biastoch, A., Böning, C., Dengg, J., Derval, C., Durand, E., Gulev, S., Remy, E., Talandier, C., Theetten, S., Maltrud, M., McClean, J., and De~Cuevas, B.: Impact of partial steps and momentum advection schemes in a global ocean circulation model at eddy-permitting resolution, Ocean Dynam., 5–6, 543–567, doi:10.1007/s10236-006-0082-1, 2006.; Bentamy, A., Quilfen, Y., and Flament, P.: Scatterometer wind fields : A new release over the decade 1991–2001, Can. J. Remote Sens., 28, 431–449, 2002.; Guiavarc'h, C.: Modelisation haute-resolution des courants dans le Golfe de Guinée: Etude des oscillations bimensuelles, Ph.D. thesis, Universite de Bretagne Occidentale, France, 2007.; Guiavarc'h, C., Treguier, A., and Vangriesheim, A.: Remotely forced biweekly deep oscillations on the continental slope of the Gulf of Guinea, J. Geophys. Res., 113, C06002, doi:10.1029/2007JC004471, 2008.; Han, W., Webster, P J., Lin, J L., Liu, W T., Fu, R., Yuan, D., and Hu, A.: Dynamics of intraseasonal sea level and thermocline variability in the equatorial Atlantic during 2002–2003, J. Phys. Oceanogr., 38, 945–967, 2008.; Houghton, R W.: Characteristics of the fortnightly shelf wave along the Ghana coast, J. Geophys. Res., 84(C10), 10777–10786, 1979.; Houghton, R W. and Beer, T.: Wave propagation during the Ghana upwelling, J. Geophys. Res., 81, 4423–4429, 1976.; Hua, B L., d'Orgeville, M., Fruman, M., Menesguen, C., Schopp, R., Klein, P., and Sasaki, H.: Destabilization of mixed Rossby gravity waves and equatorial jets formation, J. Fluid Mech., 610, 311–341, 2008.; Huthnance, J M.: On coastal trapped waves: analysis and numerical calculation by inverse iteration, J. Phys. Oceanogr., 8, 73–94, 1978.; Illig, S., Dewitte, B., Ayou


Click To View

Additional Books

  • Joint Use of Satellite and In-situ Data ... (by )
  • Intrinsic Variability of the Antarctic C... (by )
  • Oil Spills Prediction in the Bonifacio S... (by )
  • High Frequency Fluctuations in the Heat ... (by )
  • Corrigendum to Biogeography of Planktoni... (by )
  • Influence of Frontal Cyclone Evolution o... (by )
  • A Study on Distribution of Chlorophyll-A... (by )
  • On the Shelf Resonances of the English C... (by )
  • Absolute Salinity, ''Density Salinity'' ... (by )
  • Application of the Gaussian Anamorphosis... (by )
  • A Chemical Ionization Mass Spectrometer ... (by )
  • The Effects of Global Climate Change on ... (by )
Scroll Left
Scroll Right


Copyright © World Library Foundation. All rights reserved. eBooks from Hawaii eBook Library are sponsored by the World Library Foundation,
a 501c(4) Member's Support Non-Profit Organization, and is NOT affiliated with any governmental agency or department.