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To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.dsr.2009.06.002 Byline: Matthias Lankhorst (a)(d), David Fratantoni (b), Michel Ollitrault (c), Philip Richardson (b), Uwe Send (a)(d), Walter Zenk (a) 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 4.5Sv. 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. Author Affiliation: (a) Leibniz-Institut fur Meereswissenschaften (IFM-GEOMAR), Kiel, Germany (b) Woods Hole Oceanographic Institution (WHOI), Woods Hole, MA, USA (c) Institut francais de recherche pour l'exploitation de la mer (Ifremer), Plouzane, France (d) Scripps Institution of Oceanography (SIO), 9500 Gilman Drive, Mail code 0230, La Jolla, CA 92093-0230, USA Article History: Received 29 April 2008; Revised 29 May 2009; Accepted 2 June 2009

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.dsr.2005.12.007 Byline: Torsten Kanzow (a)(b), Uwe Send (a)(c), Walter Zenk (a), Alan D. Chave (d), Monika Rhein (e) Keywords: Geostrophic transport; Time series; Bottom pressure; Density; Meridional overturning circulation Abstract: As a component of the meridional overturning variability experiment in the tropical North Atlantic, a four-year-long time series of meridional transport of North Atlantic deep water has been obtained from moored end point measurements of density and bottom pressure. This study presents a quality assessment of the measurement elements. Rigorous pre- and post- deployment in situ calibration of the density sensors and subsequent data processing establish an accuracy of O(1.5Sv) in internal transport in the 1200-5000dbar range at subinertial time scales. A similar accuracy is reached in the bottom pressure-derived external transport fluctuations. However, for pressure, variability with periods longer than a deployment's duration (presently about one year) is not measurable. This effect is demonstrated using numerical simulations and a possible solution for detecting long-term external transport changes is presented. Author Affiliation: (a) Leibniz-Institut fur Meereswissenschaften, Dusternbrooker Weg 20, 24105 Kiel, Germany (b) National Oceanography Centre, Empress Dock, Southampton, SO14 3ZH, UK (c) Scripps Institution of Oceanography, University of California San Diego, La Jolla, CA 92093-0230, USA (d) Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA (e) Institut fur Umweltphysik, Otto Hahn Allee NW1, 28334 Bremen, Germany Article History: Received 7 September 2004; Revised 1 November 2005; Accepted 27 December 2005

Modelling alone cannot provide a comprehensive understanding of ocean circulation and its transport properties. High-quality acoustic-tomographic and altimetric data can be used to test the combined power of satellite altimetry and acoustic tomography for estimating oceanic flows. A detailed spatio-temporal record of flow over basin-scale volumes of fluid can be recovered from acoustic-tomographic and altimetric data using state-of-the-art numerical models.

Tests are conducted to determine the comparative performance and accuracy of Sippican Inc.'s eXpendable Conductivity Temperature Depth (XCTD) probes as opposed to CTD sondes. As previously seen in the THETIS-I experiment, errors that occurred due to experimental conditions are segregated from errors caused by the equipment. Results show the relative accuracy of XCTD sensors based on the manufacturer's specifications.

The meridional overturning variability experiment (MOVE) in the tropical Northwest Atlantic Ocean is an ongoing multi-year moored geostrophic experiment. A quality assessment of the first four years of the MOVE mass transport time series is presented with a focus on measurement accuracy and the long-term performance of the experiment.

The temperature (T) and salinity (S) of the deep ocean are established at mid- and high latitudes where intermediate and deep waters are formed through subduction and deep convection. These [...]