Circulation, variability and near equatorial meridional flow in the central tropical Atlantic.

Stramma, Lothar , Fischer, Jürgen , Brandt, Peter and Schott, Friedrich (2003) Circulation, variability and near equatorial meridional flow in the central tropical Atlantic. In: Interhemispheric Water Exchange in the Atlantic Ocean. , ed. by Goni, G. and Malanotte-Rizzoli, P.. Elsevier Oceanography Series, 68 . Elsevier, Amsterdam, Netherlands, pp. 1-22. DOI 10.1016/S0422-9894(03)80141-1.

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Observations in the central tropical Atlantic are used to investigate the circulation, the variability, and the near-equatorial meridional flow in this oceanic region. Meridional sections confirm that the southern band of the South Equatorial Current is a broad sluggish flow transporting subtropical water northwestward toward the western boundary. Variability in the South Equatorial Current is weak with an annual signal of about 2 cm/s. Recent equatorial flow observations agree with the previously proposed mean flow field, indicating that a permanent tropical circulation exists that is composed of several zonal current and countercurrent bands of small vertical and meridional extent compared to the subtropical gyres. However, wave phenomena superimpose on the mean flow field. On seasonal time scales the variability in the zonal flow field near the equator is dominated by the semiannual cycle in the central and eastern part while the annual cycle dominates in the western part. This seasonal variability is caused by the propagation of equatorial Rossby and Kelvin waves generated mainly by the zonal wind anomaly at the equator. Despite the observations of instantaneous cross-equatorial velocities and of floats crossing the equator it remains unclear whether there is a net cross-equatorial flow in the central tropical Atlantic in addition to cross-equatorial exchanges via thermocline convergence, upwelling and Ekman divergence. Three floats deployed at 200 m and 400 m depth either leave their deployment region at the equator to join the North Equatorial Undercurrent and progress further northward or in two cases have been deployed in the southern hemisphere and drift towards the equator.

Document Type: Book chapter
Research affiliation: OceanRep > GEOMAR > FB1 Ocean Circulation and Climate Dynamics > FB1-PO Physical Oceanography
Refereed: Yes
DOI etc.: 10.1016/S0422-9894(03)80141-1
ISSN: 0078-3226
Projects: WOCE, CLIVAR
Date Deposited: 18 Feb 2008 17:25
Last Modified: 16 Aug 2019 09:09

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