Open AccessWater masses and currents in the upper tropical northeast Atlantic off northwest Africa
Author(s) -
Stramma Lothar,
Hüttl Sabine,
Schafstall Jens
Publication year - 2005
Publication title -
journal of geophysical research: oceans
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2005jc002939
Subject(s) - geology , antarctic intermediate water , oceanography , north atlantic deep water , gulf stream , northern hemisphere , southern hemisphere , dome (geology) , current (fluid) , tropical atlantic , water mass , climatology , thermohaline circulation , sea surface temperature , geomorphology
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/m 3 and 4 Sv between σ θ = 25.8 and 27.1 kg/m 3 . 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.