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Soliton generation by internal tidal beams impinging on a pycnocline: laboratory experiments

Published online by Cambridge University Press:  29 June 2012

Matthieu J. Mercier ,
Manikandan Mathur ,
Louis Gostiaux ,
Theo Gerkema ,
Jorge M. Magalhães ,
José C. B. Da Silva  and
Thierry Dauxois
Matthieu J. Mercier*
Affiliation:
Department of Mechanical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA Laboratoire de Physique de l’École Normale Supérieure de Lyon, Université de Lyon, CNRS, 46 Allée d’Italie, F-69364 Lyon CEDEX 07, France
Manikandan Mathur
Affiliation:
Department of Mechanical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA Laboratoire des Ecoulements Geophysiques et Industriels (LEGI), UMR 5519 CNRS-UJF-INPG, 21 rue des Martyrs, 38000 Grenoble, France Laboratoire de Météorologie Dynamique, École Polytechnique, 91128 Palaiseau, France
Louis Gostiaux
Affiliation:
Laboratoire des Ecoulements Geophysiques et Industriels (LEGI), UMR 5519 CNRS-UJF-INPG, 21 rue des Martyrs, 38000 Grenoble, France
Theo Gerkema*
Affiliation:
Royal Netherlands Institute for Sea Research (NIOZ), PO Box 59, 1790 AB Den Burg, Texel, The Netherlands
Jorge M. Magalhães
Affiliation:
CIMAR/CIIMAR, Centro Interdisciplinar de Investigacão Marinha e Ambiental and Departamento de Geociências, Ambiente e Ordenamento do Território, Universidade do Porto, Rua do Campo Alegre, 687, 4169-007 Porto, Portugal
José C. B. Da Silva
Affiliation:
CIMAR/CIIMAR, Centro Interdisciplinar de Investigacão Marinha e Ambiental and Departamento de Geociências, Ambiente e Ordenamento do Território, Universidade do Porto, Rua do Campo Alegre, 687, 4169-007 Porto, Portugal
Thierry Dauxois
Affiliation:
Laboratoire de Physique de l’École Normale Supérieure de Lyon, Université de Lyon, CNRS, 46 Allée d’Italie, F-69364 Lyon CEDEX 07, France
*
†Email addresses for correspondence: mmercier@mit.edu, Theo.Gerkema@nioz.nl
†Email addresses for correspondence: mmercier@mit.edu, Theo.Gerkema@nioz.nl
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Abstract

In this paper, we present the first laboratory experiments that show the generation of internal solitary waves by the impingement of a quasi-two-dimensional internal wave beam on a pycnocline. These experiments were inspired by observations of internal solitary waves in the deep ocean from synthetic aperture radar (SAR) imagery, where this so-called mechanism of ‘local generation’ was argued to be at work, here in the form of internal tidal beams hitting the thermocline. Nonlinear processes involved here are found to be of two kinds. First, we observe the generation of a mean flow and higher harmonics at the location where the principal beam reflects from the surface and pycnocline; their characteristics are examined using particle image velocimetry (PIV) measurements. Second, we observe internal solitary waves that appear in the pycnocline, detected with ultrasonic probes; they are further characterized by a bulge in the frequency spectrum, distinct from the higher harmonics. Finally, the relevance of our results for understanding ocean observations is discussed.

JFM classification

Geophysical and Geological Flows: Internal waves Geophysical and Geological Flows: Ocean processes Waves/Free-surface Flows: Solitary waves
Type
Papers
Information
Journal of Fluid Mechanics , Volume 704 , 10 August 2012 , pp. 37 - 60
Copyright
Copyright © Cambridge University Press 2012

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