Water masses and zonal current in the Western Tropical Atlantic in October 2007 and January 2008 (AMANDES project) A. C. Silva1, M. Grenier2, R. Chuchla2, J. Grelet3, F. Roubaud3, B. Hamelin4, F. Lyard2, and C. Jeandel2 1Laboratório de Oceanografia Física, Departamento de Oceanografia da Universidade Federal de Pernambuco, Av. Arquitetura s/n, 50740-550, Campus Universitário, Recife, PE, Brazil 2Laboratoire d'Etudes en Géophysique et Océanographie Spatiale (LEGOS), UPS/CNES/CNRS/IRD, Observatoire Midi-Pyrénées, 14 av. E. Belin, 31400 Toulouse, France 3US IMAGO, IRD Brest, 29240 Plouzané, France 4CEREGE (CNRS/Univ Paul Cezane) Technopôle de l'Arbois, Aix en Provence, France
Received: 16 October 2010 – Accepted: 10 November 2010 – Published: 30 November 2010
Abstract. The properties and circulation of water masses are examined using data
collected from a hydrographic and Acoustic Doppler Current profiler in
the Western Tropical Atlantic during two cruises of the GEOTRACES
process study "AMANDES" (AMazon-ANDEans): AMANDES I (October–November 2007)
and AMANDES II (January 2008). In the upper layer (from the sea surface to
150 m) means of vertical sections of velocity are showing the structure of
the Current (NBC) and North Equatorial Countercurrent.
In the lower layer (below 150 m) the subsurface velocity core of the North
Brazil UnderCurrent, Western Boundary Undercurrent (WBUC) and
northern branch of the South Equatorial Current (nSEC) could be observed. In
October the WBUC flows southeastward with a velocity of about 0.3 m s−1. In the studied area during October 2007, the NBUC and nSEC are
transporting South Atlantic Central Water (SACW) from the Southern
Hemisphere whereas the WBUC transports North Atlantic Central Water (NACW)
southeastward. In the deep layers, the North Atlantic Deep Water (NADW) is
composed of three components: the Upper North Atlantic Deep Water – UNADW
(between 1310 and 1650 m), the Middle North Atlantic Deep Water (between
1930 and 2400 m), the Lower North Atlantic Deep Water (centered around 3430 m).
Off Guyana, the Antartic Intermediate Water (AAIW) changes of composition
between October 2007 (45.2% ACW, 32.2% AAIWsource and 22.6% UNADW)
and January 2008 (62.4% ACW, 23.5% AAIWsource and
These intermediate waters are significantly warmer, less oxygenated and
saltier than their southern source, reflecting both oxygen consumption and
mixing with the Atlantic Central Water (ACW) and the Upper North Atlantic
Deep Water during their northward transit.
Citation: Silva, A. C., Grenier, M., Chuchla, R., Grelet, J., Roubaud, F., Hamelin, B., Lyard, F., and Jeandel, C.: Water masses and zonal current in the Western Tropical Atlantic in October 2007 and January 2008 (AMANDES project), Ocean Sci. Discuss., 7, 1953-1976, doi:10.5194/osd-7-1953-2010, 2010.