The mid-depth circulation of the northwestern tropical Atlantic observed by floats

Type Article
Date 2009-10
Language English
Author(s) Lankhorst Matthias1, 2, Fratantoni David3, Ollitrault Michel4, Richardson Philip3, Send Uwe1, 2, Zenk Walter2
Affiliation(s) 1 : Scripps Inst Oceanog, La Jolla, CA 92093 USA.
2 : IFM GEOMAR, Leibniz Inst Meereswissensch, Kiel, Germany.
3 : Woods Hole Oceanog Inst, Woods Hole, MA 02543 USA.
4 : IFREMER, F-29280 Plouzane, France.
Source Deep Sea Research Part I: Oceanographic Research Papers (0967-0637) (Elsevier), 2009-10 , Vol. 56 , N. 10 , P. 1615-1632
DOI 10.1016/j.dsr.2009.06.002
WOS© Times Cited 7
Keyword(s) Equatorial currents, North Atlantic Deep Water, Antarctic Intermediate Water, Tropical Atlantic, Floats
Abstract A comprehensive analysis of velocity data from subsurface floats in the northwestern tropical Atlantic at two depth layers is presented: one representing the Antarctic Intermediate Water (AAIW, pressure range 600-1050dbar), the other the upper North Atlantic Deep Water (uNADW, pressure range 1200-2050dbar). New data from three independent research programs are combined with previously available data to achieve blanket coverage in space for the AAIW layer, while coverage in the uNADW remains more intermittent. Results from the AAIW` mainly confirm previous studies on the mean flow, namely the equatorial zonal and the boundary currents, but clarify details on pathways, mostly by virtue of the spatial data coverage that sets float observations apart from e.g. shipborne or mooring observations. Mean transports in each of five zonal equatorial current bands is found to be between 2.7 and 4.5 Sv. Pathways carrying AAIW northward beyond the North Brazil Undercurrent are clearly visible in the mean velocity field, in particular a northward transport of 3.7Sv across 16 degrees N between the Antilles islands and the Mid-Atlantic Ridge. New maps of Lagrangian eddy kinetic energy and integral time scales are presented to quantify mesoscale activity. For the uNADW, mean flow and mesoscale properties are discussed as data availability allows. Trajectories in the uNADW east of the Lesser Antilles reveal interactions between the Deep Western Boundary Current (DWBC) and the basin interior, which can explain recent hydrographic observations of changes in composition of DWBC water along its southward flow. (C) 2009 Elsevier Ltd. All rights reserved.
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Lankhorst Matthias, Fratantoni David, Ollitrault Michel, Richardson Philip, Send Uwe, Zenk Walter (2009). The mid-depth circulation of the northwestern tropical Atlantic observed by floats. Deep Sea Research Part I: Oceanographic Research Papers, 56(10), 1615-1632. Publisher's official version : , Open Access version :