Observed variability of the South Pacific westward sea level anomaly signal in the presence of bottom topography

Maharaj, Angela M.; Cipollini, Paolo; Holbrook, Neil J.

doi:10.1029/2004gl020966

Cited by 15 publications

(24 citation statements)

References 16 publications

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“…7c). In contrast, no real bathymetric influence is apparent at 13°S, 177°W across the Kermadec Ridge, where Maharaj et al (2005) found slow Rossby wave speeds. The extended theory curves are well represented by the mean flow configuration, which also best models the energy observed (Fig.…”

Section: Tropicsmentioning

confidence: 51%

“…This suggests that the energy accounted for by the extended theory contains a large contribution from its representation of the mean flow. We also note that the southwest Pacific basin contains very complicated bathymetry, which may lead to more localized or regional variability (Killworth and Blundell 1999;Maharaj et al 2005). The large improvement in energy explained by the extended theory in the Western Subtropics compared with Fig.…”

Section: Basin-wide Maps Of First To Fourth Baroclinic Mode Energy Ramentioning

confidence: 73%

“…The extended theory explains up to 90% of the total energy in the western and eastern Pacific regions where the extended theory first and second modes peak. Maharaj et al (2005) reported a significant band of high energy in the westward propagat- Fig. 2 Energy ratios quantifying the proportion of variance in the power spectrum of the SLA that can be explained by the classical theory modes 1-4.…”

Section: Basin-wide Maps Of First To Fourth Baroclinic Mode Energy Ramentioning

confidence: 99%

“…This is at the edge of the Kermadec Ridge (extends to < 2,000 m below sea level) and in a region of general westward flow in the South Equatorial Current (SEC). This section also corresponds to regions of very slow long Rossby wave speeds (Maharaj et al 2005). In the Central Tropics, a section centered at 16°S, 147°W is chosen.…”

Section: Case Study Regions With Dispersion Curves For Various Configmentioning

confidence: 99%

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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

et al. 2007

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Previous literature has suggested that multiple peaks in sea level anomalies (SLA) detected by twodimensional 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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Section: Tropicsmentioning

confidence: 51%

Section: Basin-wide Maps Of First To Fourth Baroclinic Mode Energy Ramentioning

confidence: 73%

Section: Basin-wide Maps Of First To Fourth Baroclinic Mode Energy Ramentioning

confidence: 99%

Section: Case Study Regions With Dispersion Curves For Various Configmentioning

confidence: 99%

See 2 more Smart Citations

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

et al. 2007

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“…Chelton and Schlax (1996) first used the RT to study the characteristics (especially the phase speed) of westward-propagating planetary waves in satellite altimeter data. Since then, several authors have applied the 2-D RT on SST or SLA datasets (Hill et al, 2000;Maharaj et al, 2004Maharaj et al, , 2005Cipollini et al, 2001Cipollini et al, , 2006. Superimposed propagating signals locally extracted by the 2-D RT are generally interpreted as various baroclinic modes of Rossby waves (Maharaj et al, 2004;Cipollini et al, 2006).…”

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confidence: 99%

Depth dependence of westward-propagating North Atlantic features diagnosed from altimetry and a numerical 1/6° model

et al. 2008

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Abstract. A 1/6• numerical simulation is used to investigate the vertical structure of westward propagation between 1993 and 2000 in the North Atlantic ocean. The realism of the simulated westward propagating signals, interpreted principally as the signature of first-mode baroclinic Rossby waves (RW), is first assessed by comparing the simulated amplitude and zonal phase speeds of Sea Level Anomalies (SLA) against TOPEX/Poseidon-ERS satellite altimeter data. Then, the (unobserved) subsurface signature of RW phase speeds is investigated from model outputs by means of the Radon Transform which was specifically adapted to focus on firstmode baroclinic RW. The analysis is performed on observed and simulated SLA and along 9 simulated isopycnal displacements spanning the 0-3250 m depth range. Simulated RW phase speeds agree well with their observed counterparts at the surface, although with a slight slow bias. Below the surface, the simulated phase speeds exhibit a systematic deceleration with increasing depth, by a factor that appears to vary geographically. Thus, while the reduction factor is about 15-18% on average at 3250 m over the region considered, it appears to be much weaker (about 5-8%) in the eddy-active Azores Current, where westward propagating structures might be more coherent in the vertical. In the context of linear theories, these results question the often-made normal mode assumption of many WKB-based theories that the phase speed is independent of depth. Alternatively, these results could also suggest that the vertical structure of westward propagating signals may significantly depend on their degree of nonlinearity, with the degree of vertical coherence possibly increasing with the degree of nonlinearity.

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Storm tracks in the Southern Hemisphere subtropical oceans

et al. 2014

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Ocean storm tracks have previously been associated with the midlatitude western boundary currents (WBCs) and the Antarctic Circumpolar Current (ACC). Here we identify and examine large-scale baroclinically unstable waves occurring within waveguides associated with potential density gradients in the subtropical regions of the Southern Hemisphere (SH) oceans where the trade winds and westerlies meet and at depths associated with mode water formation. In contrast to the Northern Hemisphere subtropics, the SH pathways are more extensive allowing large-scale coherent disturbances to communicate information westward from the midlatitudes to the subtropics (South Pacific Ocean) and from the subtropics to the tropics (Indian Ocean). Particular consideration is given to the subtropical South Pacific Ocean as this is a region where resonant interactions between large-scale Rossby waves and significant topographic features have been reported to occur. Using an ocean general circulation model and a simple potential energy transfer diagnostic, we identify the relevant nonlinearly modified structures comparing their propagation characteristics to planetary Rossby waves calculated using a shallow water model. Although at first appearance baroclinic disturbances resemble planetary Rossby waves, we show they are inherently nonlinear, multiscale and are amplified where topography occurs. The location of the disturbances coincides with regions of high variability in sea surface height observed in satellite altimetry and their speeds closely match the large-scale coherent westward propagating structures described in the observational literature. Our study provides evidence that, in addition to the midlatitude WBCs and the ACC, significant ocean storm tracks are also manifest in the SH subtropics.

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Observed variability of the South Pacific westward sea level anomaly signal in the presence of bottom topography

Cited by 15 publications

References 16 publications

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

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

Depth dependence of westward-propagating North Atlantic features diagnosed from altimetry and a numerical 1/6° model

Storm tracks in the Southern Hemisphere subtropical oceans

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