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Trends in Atlantic equatorial current variability

Veränderlichkeiten im äquatorialen Stromsystem des Atlantiks

Variabilité du Courant a l'équateur dans Ocean Atlantique

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Summary

Approximately twice-monthly expendable bathythermograph (XBT) sections between Europe and Brazil, are used to characterize trends in the equatorial geostrophic surface currents orthogonal to the sections between September, 1980 and May, 1984. Using mean temperature-salinity relationships the upper layer temperature profiles are converted to density and used to compute 0/300 db dynamic height. Applying a second derivative method, at and near the equator, geostrophic surface currents are computed along each quasimeridional XBT section and time/space series of the equatorial currents are developed using spline interpolations in both time and space. Equatorial currents are mapped as time series of dynamic height and geostrophic current.

Zusammenfassung

Es werden zweimonatliche Bathythermographenschnitte zwischen Europa und Brasilien vom September 1980 bis Mai 1984 vorgestellt. Die Daten werden zur Darstellung eines mehrjährigen Trends im oberflächennahen äquatorialen Stromsystem verwandt, welches senkrecht zu den Schnitten liegt. Unter Ausnutzung einer mittleren Temperatur-Salzgehaltsbeziehung werden die Temperaturprofile in Dichteprofile überführt. Aus diesen wird die dynamische Tiefe (0/300 dbar) errechnet. In Äquatornähe wird eine rechnerische Näherung für die geostrophischen Ströme verwandt. Ferner wird ein Spline-Interpolationsverfahren für die raumzeitliche Herleitung der quasi-meridionalen Strömungsverteilung genutzt. Das äquatoriale Stromsystem wird als eine Zeitserie der dynamischen Tiefe und der geostrophischen Ströme dargestellt.

Résumé

Des coupes thermiques au moyen de Bathythermographes à tête perdue (XBT) entre l'Europe et le Brésil environ deux fois par mois de septembre 1980 à mai 1984 sont utilisées pour caracteriser des tendances dans les courants géostrophiques équatoriaux perpendiculaires à ces coupes. Les profils de température dans les couches superficielles sont convertis en profils de densité au moyen de relations temperature-salinité moyennes, et permettent de calculer la hauteur dynamique 0/300 db. Après interpolation (spline) dans le temps et l'espace, on obtient une série spatio-temporelle, présentée sous la forme de cartes trimestrielles de hauteurs dynamiques et de courants géostrophiques.

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Author notes

  1. William J. Emery

    Present address: CCAR, University of Colorado, Box 431, 80309, Boulder, CO, USA

  2. Walter Zenk

    Present address: Institut für Meereskunde der Universität Kiel, Düsternbrooker Weg 20, 2300, Kiel 1

  3. Klaus Huber

    Present address: Deutsches Hydrographisches Institut, Bernhard-Nocht-Straße 78, 2000, Hamburg 4

  4. Pierre Rual

    Present address: Centre O.R.S.T.O.M., BPA5, Noumea, New Caledonia, France

  5. Paul Nowlan

    Present address: Department of Oceanography, University of British Columbia, V6T 1W5, Vancouver, B.C., Canada

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    1. William J. Emery
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    2. Walter Zenk
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    3. Klaus Huber
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    4. Pierre Rual
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    5. Paul Nowlan
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    Emery, W.J., Zenk, W., Huber, K. et al. Trends in Atlantic equatorial current variability. Deutsche Hydrographische Zeitschrift 40, 261–276 (1987). https://doi.org/10.1007/BF02226280

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    • DOI: https://doi.org/10.1007/BF02226280

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