Energy Transmission by Barotropic Rossby Waves Revisited

R. P. Matano College of Oceanic and Atmospheric Sciences, Oregon State University, Corvallis, Oregon

Search for other papers by R. P. Matano in
Current site
Google Scholar
PubMed
Close
and
E. D. Palma Departamento de Física, Universidad Nacional del Sur, Bahia Blanca, Argentina

Search for other papers by E. D. Palma in
Current site
Google Scholar
PubMed
Close
Restricted access

Abstract

This article presents a semianalytic method to investigate the properties of energy transmission across bottom topography by barotropic Rossby waves. The method is first used to revisit the analytical estimates derived from wave-matching techniques and Wentzel–Kramers–Brillouin (WKB) approximations. The comparison between the semianalytic method and WKB indicates that the results of the latter are valid for waves with periods longer than a month and ridges taller than ∼1000 m and wider than ∼500 km. For these parameter values both methods predict the passage of low-frequency waves and the reflection of high-frequency waves. The semianalytic method is then used to discuss the energy transmission properties of a cross section of the Mid-Atlantic Ridge. It is shown that the filtering characteristics of realistic bottom topographies depend not only on the spatial scale set by the cross-section envelope, but also on the scales of the individual peaks. This dependence is related to the fact that topographies narrower than ∼400 km (e.g., peaks) are high-pass filters of incoming waves, while topographies wider than that (e.g., cross-section envelopes) are low-pass filters. In the particular case of the Mid-Atlantic Ridge the neglect of the contribution of individual peaks leads to an erroneous estimate of the filtering properties of the massif.

Corresponding author address: Dr. Ricardo P. Matano, College of Oceanic and Atmospheric Sciences, Oregon State University, Corvallis, OR 97331-5503. Email: rmatano@coas.oregonstate.edu

Abstract

This article presents a semianalytic method to investigate the properties of energy transmission across bottom topography by barotropic Rossby waves. The method is first used to revisit the analytical estimates derived from wave-matching techniques and Wentzel–Kramers–Brillouin (WKB) approximations. The comparison between the semianalytic method and WKB indicates that the results of the latter are valid for waves with periods longer than a month and ridges taller than ∼1000 m and wider than ∼500 km. For these parameter values both methods predict the passage of low-frequency waves and the reflection of high-frequency waves. The semianalytic method is then used to discuss the energy transmission properties of a cross section of the Mid-Atlantic Ridge. It is shown that the filtering characteristics of realistic bottom topographies depend not only on the spatial scale set by the cross-section envelope, but also on the scales of the individual peaks. This dependence is related to the fact that topographies narrower than ∼400 km (e.g., peaks) are high-pass filters of incoming waves, while topographies wider than that (e.g., cross-section envelopes) are low-pass filters. In the particular case of the Mid-Atlantic Ridge the neglect of the contribution of individual peaks leads to an erroneous estimate of the filtering properties of the massif.

Corresponding author address: Dr. Ricardo P. Matano, College of Oceanic and Atmospheric Sciences, Oregon State University, Corvallis, OR 97331-5503. Email: rmatano@coas.oregonstate.edu

Save
  • Barnier, B., 1984: Energy transmission by barotropic Rossby waves across large-scale topography. J. Phys. Oceanogr., 14 , 438447.

  • LeBlond, P. H., and L. A. Mysak, 1978: Waves in the Ocean. Elsevier Oceanography Series, Vol. 20, Elsevier, 602 pp.

  • Matano, R. P., 1995: Numerical experiments on the effects of a meridional ridge on the transmission of energy by barotropic Rossby waves. J. Geophys. Res., 100 , 1827118280.

    • Search Google Scholar
    • Export Citation
  • Pedlosky, J., 2000: The transmission and transformation of baroclinic Rossby waves by topography. J. Phys. Oceanogr., 30 , 30773101.

  • Pedlosky, J., and M. A. Spall, 1999: Rossby normal modes in basins with barriers. J. Phys. Oceanogr., 29 , 23322349.

  • Pratt, L. J., and M. A. Spall, 2003: A porus-medium theory for barotropic flow through ridges and archipelagos. J. Phys. Oceanogr., 33 , 27022718.

    • Search Google Scholar
    • Export Citation
  • Press, W. H., B. P. Flannery, S. A. Teukolsky, and W. T. Vetterling, 1992: Numerical Recipes. Cambridge University Press, 818 pp.

  • Rhines, P. B., 1969: Slow oscillations in an ocean of varying depth, I. Abrupt topography. J. Fluid Mech., 37 , 161189.

All Time Past Year Past 30 Days
Abstract Views 0 0 0
Full Text Views 90 23 2
PDF Downloads 37 19 2