An evaluation of the classical and extended Rossby wave theories in explaining spectral estimates of the first few baroclinic modes in the South Pacific Ocean |
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Authors: | Angela M Maharaj Paolo Cipollini Neil J Holbrook Peter D Killworth Jeffrey R Blundell |
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Institution: | (1) Department of Physical Geography, Macquarie University, Sydney, 2109, Australia;(2) National Oceanography Centre, Southampton, European Way, Southampton, SO14 3ZH, UK |
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Abstract: | Previous literature has suggested that multiple peaks in sea level anomalies (SLA) detected by two-dimensional Fourier Transform
(2D-FT) analysis are spectral components of multiple propagating signals, which may correspond to different baroclinic Rossby
wave modes. We test this hypothesis in the South Pacific Ocean by applying a 2D-FT analysis to the long Rossby wave signal
determined from filtered TOPEX/Poseidon and European Remote Sensing-1/2 satellite altimeter derived SLA. The first four baroclinic
mode dispersion curves for the classical linear wave theory and the Killworth and Blundell extended theory are used to determine the spectral signature and energy contributions of each mode. South of 17°S, the first two extended
theory modes explain up to 60% more of the variance in the observed power spectral energy than their classical linear theory
counterparts. We find that Rossby wave modes 2–3 contribute to the total Rossby wave energy in the SLA data. The second mode
contributes significantly over most of the basin. The third mode is also evident in some localized regions of the South Pacific
but may be ignored at the large scale. Examination of a selection of case study sites suggests that bathymetric effects may
dominate at longer wavelengths or permit higher order mode solutions, but mean flow tends to be the more influential factor
in the extended theory. We discuss the regional variations in frequency and wave number characteristics of the extended theory
modes across the South Pacific basin. |
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Keywords: | Extended theory Classical linear theory South Pacific Ocean Rossby waves Baroclinic modes Fourier transform |
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