Climate Dynamics

, Volume 43, Issue 11, pp 2985–2997 | Cite as

The Equatorial Undercurrent in the central Atlantic and its relation to tropical Atlantic variability

  • Peter BrandtEmail author
  • Andreas Funk
  • Alexis Tantet
  • William E. Johns
  • Jürgen Fischer


Seasonal to interannual variations of the Equatorial Undercurrent (EUC) in the central Atlantic at 23°W are studied using shipboard observation taken during the period 1999–2011 as well as moored velocity time series covering the period May 2005–June 2011. The seasonal variations are dominated by an annual harmonic of the EUC transport and the EUC core depth (both at maximum during September), and a semiannual harmonic of the EUC core velocity (maximum during April and September). Substantial interannual variability during the period of moored observation included anomalous cold/warm equatorial Atlantic cold tongue events during 2005/2008. The easterly winds in the western equatorial Atlantic during boreal spring that represent the preconditioning of cold/warm events were strong/weak during 2005/2008 and associated with strong/weak boreal summer EUC transport. The anomalous year 2009 was instead associated with weak preconditioning and smallest EUC transport on record from January to July, but during August coldest SST anomalies in the eastern equatorial Atlantic were observed. The interannual variations of the EUC are discussed with respect to recently described variability of the tropical Atlantic Ocean.


Equatorial Atlantic circulation Moored and shipboard observations Cold tongue Seasonal cycle Interannual variability African monsoon 



This study was funded by the Deutsche Bundesministerium für Bildung und Forschung (BMBF) as part of the projects NORDATLANTIK (03F0443B), RACE (03F0651B), MIKLIP (01LP1114A) and by the Deutsche Forschungsgemeinschaft through several research cruises with RV Meteor and RV Maria S. Merian and as part of the Sonderforschungsbereich 754 “Climate–Biogeochemistry Interactions in the Tropical Ocean”. Moored velocity observations were acquired in cooperation with the PIRATA project. We would like to thank Verena Hormann and Ingo Richter for helpful discussion and two anonymous reviewers for their comments that lead to significant improvements in the manuscript.


  1. Arhan M, Treguier AM, Bourles B, Michel S (2006) Diagnosing the annual cycle of the equatorial undercurrent in the Atlantic Ocean from a general circulation model. J Phys Oceanogr 36(8):1502–1522. doi: 10.1175/Jpo2929.1 CrossRefGoogle Scholar
  2. Athie G, Marin F (2008) Cross-equatorial structure and temporal modulation of intraseasonal variability at the surface of the Tropical Atlantic Ocean. J Geophys Res Oceans 113(C8). doi: 10.1029/2007jc004332
  3. Barnett TP (1983) Interaction of the monsoon and Pacific trade-wind system at interannual time scales. Part I: the equatorial zone. Mon Weather Rev 111(4):756–773. doi: 10.1175/1520-0493(1983)111<0756:Iotmap>2.0.Co;2 CrossRefGoogle Scholar
  4. Brandt P, Schott FA, Provost C, Kartavtseff A, Hormann V, Bourles B, Fischer J (2006) Circulation in the central equatorial Atlantic: mean and intraseasonal to seasonal variability. Geophys Res Lett 33(7). doi: 10.1029/2005gl025498
  5. Brandt P, Hormann V, Bourles B, Fischer J, Schott FA, Stramma L, Dengler M (2008) Oxygen tongues and zonal currents in the equatorial Atlantic. J Geophys Res Oceans 113(C4). doi: 10.1029/2007jc004435
  6. Brandt P, Caniaux G, Bourles B, Lazar A, Dengler M, Funk A, Hormann V, Giordani H, Marin F (2011a) Equatorial upper-ocean dynamics and their interaction with the West African monsoon. Atmos Sci Lett 12(1):24–30CrossRefGoogle Scholar
  7. Brandt P, Funk A, Hormann V, Dengler M, Greatbatch RJ, Toole JM (2011b) Interannual atmospheric variability forced by the deep equatorial Atlantic Ocean. Nature 473(7348):497–500. doi: 10.1038/Nature10013 CrossRefGoogle Scholar
  8. Brandt P, Greatbatch RJ, Claus M, Didwischus SH, Hormann V, Funk A, Hahn J, Krahmann G, Fischer J, Kortzinger A (2012) Ventilation of the equatorial Atlantic by the equatorial deep jets. J Geophys Res Oceans 117. doi: 10.1029/2012jc008118
  9. Bunge L, Provost C, Kartavtseff A (2007) Variability in horizontal current velocities in the central and eastern equatorial Atlantic in 2002. J Geophys Res Oceans 112(C2). doi: 10.1029/2006jc003704
  10. Bunge L, Provost C, Hua BL, Kartavtseff A (2008) Variability at intermediate depths at the equator in the Atlantic ocean in 2000–06: annual cycle, equatorial deep jets, and intraseasonal meridional velocity fluctuations. J Phys Oceanogr 38(8):1794–1806. doi: 10.1175/2008jpo3781.1 CrossRefGoogle Scholar
  11. Caniaux G, Giordani H, Redelsperger JL, Guichard F, Key E, Wade M (2011) Coupling between the Atlantic cold tongue and the West African monsoon in boreal spring and summer. J Geophys Res Oceans 116. doi: 10.1029/2010jc006570
  12. Chang P, Yamagata T, Schopf P, Behera SK, Carton J, Kessler WS, Meyers G, Qu T, Schott F, Shetye S, Xie SP (2006) Climate fluctuations of tropical coupled systems—the role of ocean dynamics. J Clim 19(20):5122–5174. doi: 10.1175/Jcli3903.1 CrossRefGoogle Scholar
  13. Cromwell T, Montgomery RB, Stroup ED (1954) Equatorial undercurrent in Pacific Ocean revealed by new methods. Science 119(3097):648–649. doi: 10.1126/Science.119.3097.648 CrossRefGoogle Scholar
  14. Firing E, Lukas R, Sadler J, Wyrtki K (1983) Equatorial Undercurrent disappears during 1982–1983 El-Nino. Science 222(4628):1121–1123. doi: 10.1126/Science.222.4628.1121 CrossRefGoogle Scholar
  15. Foltz GR, McPhaden MJ (2010) Abrupt equatorial wave-induced cooling of the Atlantic cold tongue in 2009. Geophys Res Lett 37. doi: 10.1029/2010gl045522
  16. Foltz GR, McPhaden MJ, Lumpkin R (2012) A strong Atlantic Meridional Mode event in 2009: the role of mixed layer dynamics. J Clim 25(1):363–380. doi: 10.1175/Jcli-D-11-00150.1 CrossRefGoogle Scholar
  17. Foltz GR, Schmid C, Lumpkin R (2013) Seasonal cycle of the mixed layer heat budget in the northeastern tropical Atlantic Ocean. J Clim 26(20):8169–8188. doi: 10.1175/JCLI-D-13-00037.1 CrossRefGoogle Scholar
  18. Ganachaud A, Wunsch C (2000) Improved estimates of global ocean circulation, heat transport and mixing from hydrographic data. Nature 408(6811):453–457. doi: 10.1038/35044048 CrossRefGoogle Scholar
  19. Giarolla E, Nobre P, Malagutti M, Pezzi LP (2005) The Atlantic equatorial undercurrent: PIRATA observations and simulations with GFDL Modular Ocean model at CPTEC. Geophys Res Lett 32(10). doi: 10.1029/2004gl022206
  20. Goes M, Wainer I (2003) Equatorial currents transport changes for extreme warm and cold events in the Atlantic Ocean. Geophys Res Lett 30(5). doi: 10.1029/2002gl015707
  21. Greatbatch RJ, Brandt P, Claus M, Didwischus SH, Fu Y (2012) On the width of the equatorial deep jets. J Phys Oceanogr 42(10):1729–1740. doi: 10.1175/Jpo-D-11-0238.1 CrossRefGoogle Scholar
  22. Han WQ, Webster PJ, Lin JL, Liu WT, Fu R, Yuan DL, Hu AX (2008) Dynamics of intraseasonal sea level and thermocline variability in the equatorial Atlantic during 2002–03. J Phys Oceanogr 38(5):945–967. doi: 10.1175/2008jpo3854.1 CrossRefGoogle Scholar
  23. Hormann V, Brandt P (2007) Atlantic Equatorial Undercurrent and associated cold tongue variability. J Geophys Res Oceans 112(C6). doi: 10.1029/2006jc003931
  24. Hormann V, Brandt P (2009) Upper equatorial Atlantic variability during 2002 and 2005 associated with equatorial Kelvin waves. J Geophys Res Oceans 114. doi: 10.1029/2008jc005101
  25. Hummels R, Dengler M, Bourlès B (2013) Seasonal and regional variability of upper ocean diapycnal heat flux in the Atlantic cold tongue. Prog Oceanogr 111:52–74. doi: 10.1016/j.pocean.2012.11.001 CrossRefGoogle Scholar
  26. Johnson GC, Zhang DX (2003) Structure of the Atlantic Ocean equatorial deep jets. J Phys Oceanogr 33(3):600–609. doi: 10.1175/1520-0485(2003)033<0600:Sotaoe>2.0.Co;2 CrossRefGoogle Scholar
  27. Johnson GC, Sloyan BM, Kessler WS, McTaggart KE (2002) Direct measurements of upper ocean currents and water properties across the tropical Pacific during the 1990s. Prog Oceanogr 52(1):31–61. doi: 10.1016/S0079-6611(02)00021-6 CrossRefGoogle Scholar
  28. Jouanno J, Marin F, du Penhoat Y, Molines JM, Sheinbaum J (2011a) Seasonal modes of surface cooling in the Gulf of Guinea. J Phys Oceanogr 41(7):1408–1416. doi: 10.1175/Jpo-D-11-031.1 CrossRefGoogle Scholar
  29. Jouanno J, Marin F, du Penhoat Y, Sheinbaum J, Molines JM (2011b) Seasonal heat balance in the upper 100 m of the equatorial Atlantic Ocean. J Geophys Res Oceans 116. doi: 10.1029/2010jc006912
  30. Kessler WS, Johnson GC, Moore DW (2003) Sverdrup and nonlinear dynamics of the Pacific equatorial currents. J Phys Oceanogr 33(5):994–1008. doi: 10.1175/1520-0485(2003)033<0994:Sandot>2.0.Co;2 CrossRefGoogle Scholar
  31. Kolodziejczyk N, Bourles B, Marin F, Grelet J, Chuchla R (2009) Seasonal variability of the equatorial undercurrent at 10 degrees W as inferred from recent in situ observations. J Geophys Res Oceans 114. doi: 10.1029/2008JC004976
  32. Lumpkin R, Speer K (2003) Large-scale vertical and horizontal circulation in the North Atlantic Ocean. J Phys Oceanogr 33(9):1902–1920CrossRefGoogle Scholar
  33. Marin F, Caniaux G, Bourles B, Giordani H, Gouriou Y, Key E (2009) Why were sea surface temperatures so different in the eastern equatorial Atlantic in June 2005 and 2006? J Phys Oceanogr 39(6):1416–1431. doi: 10.1175/2008jpo4030.1 CrossRefGoogle Scholar
  34. McCreary JP, Lu P (1994) Interaction between the subtropical and equatorial ocean circulations—the subtropical cell. J Phys Oceanogr 24(2):466–497CrossRefGoogle Scholar
  35. Metcalf WG, Voorhis AD, Stalcup MC (1962) The Atlantic equatorial undercurrent. J Geophys Res 67(6):2156–2202. doi: 10.1029/JZ067i006p02499 Google Scholar
  36. Okumura Y, Xie SP (2006) Some overlooked features of tropical Atlantic climate leading to a new Nino-like phenomenon. J Clim 19(22):5859–5874. doi: 10.1175/Jcli3928.1 CrossRefGoogle Scholar
  37. Philander SGH, Pacanowski RC (1980) The generation of equatorial currents. J Geophys Res Oceans 85(Nc2):1123–1136. doi: 10.1029/Jc085ic02p01123 CrossRefGoogle Scholar
  38. Philander SGH, Pacanowski RC (1981) The oceanic response to cross-equatorial winds (with application to coastal upwelling in low latitudes). Tellus 33(2):201–210CrossRefGoogle Scholar
  39. Polo I, Lazar A, Rodriguez-Fonseca B, Arnault S (2008) Oceanic Kelvin waves and tropical Atlantic intraseasonal variability: 1. Kelvin wave characterization. J Geophys Res Oceans 113(C7). doi: 10.1029/2007jc004495
  40. Provost C, Arnault S, Chouaib N, Kartavtseff A, Bunge L, Sultan E (2004) TOPEX/Poseidon and Jason equatorial sea surface slope anomaly in the Atlantic in 2002: comparison with wind and current measurements at 23 W. Mar Geod 27(1–2):31–45. doi: 10.1080/01490410490465274 CrossRefGoogle Scholar
  41. Qiao L, Weisberg RH (1997) The zonal momentum balance of the equatorial undercurrent in the central Pacific. J Phys Oceanogr 27(6):1094–1119CrossRefGoogle Scholar
  42. Richter I, Behera SK, Masumoto Y, Taguchi B, Sasaki H, Yamagata T (2013) Multiple causes of interannual sea surface temperature variability in the equatorial Atlantic Ocean. Nat Geosci 6(1):43–47. doi: 10.1038/Ngeo1660 Google Scholar
  43. Schott FA, Fischer J, Stramma L (1998) Transports and pathways of the upper-layer circulation in the western tropical Atlantic. J Phys Oceanogr 28(10):1904–1928CrossRefGoogle Scholar
  44. Schott FA, Mccreary JP, Johnson GC (2004) Shallow overturning circulations of the tropical–subtropical oceans. In: Wang C, Xie S-P, Carton JA (eds) Earth climate: The ocean–atmosphere interaction. Geophys Monogr 147. American Geophysical Union, Washington, DC, pp 261–304Google Scholar
  45. Sutton RT, Jewson SP, Rowell DP (2000) The elements of climate variability in the tropical Atlantic region. J Clim 13(18):3261–3284. doi: 10.1175/1520-0442(2000)013<3261:Teocvi>2.0.Co;2 CrossRefGoogle Scholar
  46. von Schuckmann K, Brandt P, Eden C (2008) Generation of tropical instability waves in the Atlantic Ocean. J Geophys Res Oceans 113(C8). doi: 10.1029/2007jc004712
  47. Weisberg RH, Hickman JH, Tang TY, Weingartner TJ (1987) Velocity and temperature observations during the seasonal response of the Equatorial Atlantic Experiment at 0°, 28°W. J Geophys Res Oceans 92(C5):5061–5075. doi: 10.1029/Jc092ic05p05061 CrossRefGoogle Scholar

Copyright information

© Springer-Verlag Berlin Heidelberg 2014

Authors and Affiliations

  • Peter Brandt
    • 1
    Email author
  • Andreas Funk
    • 2
  • Alexis Tantet
    • 1
    • 3
  • William E. Johns
    • 4
  • Jürgen Fischer
    • 1
  1. 1.GEOMAR Helmholtz-Zentrum für Ozeanforschung KielKielGermany
  2. 2.WTD 71/FWGForschungsbereich für Wasserschall und GeophysikKielGermany
  3. 3.Institute for Marine and Atmospheric ResearchUtrecht UniversityUtrechtThe Netherlands
  4. 4.RSMAS/MPOUniversity of MiamiMiamiUSA

Personalised recommendations