Water masses and currents in the upper tropical Northeast Atlantic off Northwest Africa

Stramma, Lothar, Hüttl, Sabine and Schafstall, Jens (2005) Water masses and currents in the upper tropical Northeast Atlantic off Northwest Africa Journal of Geophysical Research - Oceans, 110 . C12006. DOI 10.1029/2005JC002939.

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Recent current measurements in the tropical eastern North Atlantic reproduce the components of the large scale flow field. However, the observations as well as the 1/12°-FLAME model computations indicate that a lot of eddy scale variability is superimposed on the mean flow field. Despite of the disturbance by variability the signature of the Guinea Dome is well present. In November 2002 the Guinea Dome transport from direct observations was about 2.8 Sv above σ θ = 25.8 kg/m3 and 4 Sv between σ θ = 25.8 and 27.1 kg/m3. The oxygen minimum in the shadow zone comprises the central water and the Antarctic Intermediate Water (AAIW) layers and is located between the equatorial current system and the North Equatorial Current. The North Equatorial Counter- and Undercurrents at 3° to 6°N are major oxygen sources for the central water layer of the low-oxygen regions in the northeastern tropical Atlantic. A second, northern North Equatorial Countercurrent (nNECC) band exists at 8° to 10°N. The nNECC carries oxygen rich water from the southern hemisphere eastward but with an admixture of water from the northern hemisphere. A float at 200 m depth was spreading eastward in the North Equatorial Undercurrent (NEUC), at 28°W it shifted northward into the nNECC, and then was trapped in the Guinea Dome region for more than 3 years. The model indicates the region 22° to 32°W as the area of exchange between the NECC/NEUC and the nNECC bands. In the AAIW layer the northern Intermediate Countercurrent acts as oxygen source for the oxygen minimum zone.

Document Type: Article
Keywords: ocean circulation, water mass spreading, numerical simulation, Guinea Dome; physical oceanography
Research affiliation: OceanRep > GEOMAR > FB1 Ocean Circulation and Climate Dynamics > FB1-TM Theory and Modeling
OceanRep > GEOMAR > FB1 Ocean Circulation and Climate Dynamics > FB1-PO Physical Oceanography
Refereed: Yes
DOI etc.: 10.1029/2005JC002939
ISSN: 0148-0227
Date Deposited: 03 Dec 2008 16:52
Last Modified: 06 Jul 2012 14:56
URI: http://eprints.uni-kiel.de/id/eprint/5767

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