Upper-layer circulation in the eastern Equatorial and South Atlantic Ocean in January-March 1995

Type Article
Date 2003-07
Language English
Author(s) Mercier HerleORCID3, Arhan Michel1, Lutjeharms Johann2
Affiliation(s) 1 : IFREMER, Ctr Brest, UBO, CNRS,Lab Phys Oceans, F-29280 Plouzane, France.
2 : Univ Cape Town, Dept Oceanog, ZA-7700 Rondebosch, South Africa.
Source Deep Sea Research Part I: Oceanographic Research Papers (0967-0637) (Elsevier), 2003-07 , Vol. 50 , N. 7 , P. 863-887
DOI 10.1016/S0967-0637(03)00071-2
WOS© Times Cited 37
Keyword(s) Hydrography, Current, Circulation, South Atlantic, Equatorial Atlantic
Abstract The upper-layer circulation in the eastern basin of the South Atlantic was studied from hydrographic and direct velocity measurements along WOCE lines A11, A13 and A14. A13 and A14 provide quasi-meridional samplings of the equatorial, subequatorial and subtropical circulation regimes. A13 was carried out along the African coast at about 600 km offshore from it, and A 14 along the nominal longitude 9degreesW. A11 intersects the Cape Basin between 46degreesS in the west and 30degreesS in the east. Transport estimates were derived from direct velocity measurements and a box inverse model. In the equatorial eastern Atlantic, the Equatorial Undercurrent (EUC) transport decreases from 25x10(6) m(3) s(-1) at 9degreesW to 13x10(6) m(3) s(-1) at 5degreesE. Re-circulations of the EUC into the northern and equatorial branches of the South Equatorial Current (SEC) are evidenced at 5degreesE and quantified. In the tropical Atlantic, we estimate 7.5x10(6) and 4.2x10(6) m(3) s(-1) for the transports at 9degreesW of the South Equatorial Undercurrent (SEUC) and South Equatorial Countercurrent (SECC), respectively. Both the SEUC and SECC extend vertically down to intermediate depths and contribute to the northern limb of the Angola Gyre. The Angola Current transport is estimated to be 16+/-5x10(6) m(3) s(-1) for sigma(1)<32.1 at 13&DEG;S. South of the Angola Gyre, the transports show an apparent cyclonic circulation, developed mostly at the intermediate level. The water mass properties suggest that it is, at least partially, a re-circulation of the Benguela Current. Further south and for the subtropical gyre, we estimate 10&PLUSMN;5x10(6) m(3) s(-1) for the transport of the South Atlantic Current across 9&DEG;W and 28&PLUSMN;4x10(6) m(3) s(-1) for the transport of the Benguela Current at 10&DEG;E for σ(1)<32.1.
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