Characterization of westward propagating signals in the South Atlantic from altimeter and radiometer records

Oliveira, Fabricio Sanguinetti Cruz de; Polito, P. S.

doi:10.1016/j.rse.2013.03.019

Cited by 20 publications

(21 citation statements)

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“…Previous work at the western boundary at 34.5°S has shown that the dominant source of variability in those boundary currents is westward propagation of Rossby wave‐like features toward the boundary from the basin interior (e.g., Meinen et al, ). Westward propagating signals in the eastern South Atlantic have been observed from altimeter and radiometer records between 10.5°S and 24.5°S (Oliveira & Polito, ). According to that study, the dominant variability source switches south of 24.5°S from Rossby wave variability to variability associated with Agulhas Rings.…”

Section: Resultsmentioning

confidence: 99%

Shallow and Deep Eastern Boundary Currents in the South Atlantic at 34.5°S: Mean Structure and Variability

et al. 2019

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The first in situ continuous full‐water‐column observations of the eastern boundary currents (EBCs) at 34.5°S in the South Atlantic are obtained using 23 months of data from a line of Current and Pressure recording Inverted Echo Sounders (CPIES) spanning the Cape Basin. The CPIES are used to evaluate the mean structure of the EBC, the associated water masses, and the volume transport variability. The estimated northward time‐mean Benguela Current absolute geostrophic transport is 24 Sv, with a temporal standard deviation of 17 Sv. Beneath this current the time‐mean transport is southward, indicating the presence of a deep‐EBC (DEBC), with a time‐mean transport of 12 Sv, and a standard deviation of 17 Sv. Offshore of these currents, the shallow and deep flows are more variable with weak time means, likely influenced by Agulhas Rings transiting through the region. Hydrographic data collected along the CPIES line demonstrate that the DEBC is carrying recently ventilated North Atlantic Deep Water, as it flows along the continental slope. This is consistent with a previously hypothesized interior pathway bringing recently ventilated North Atlantic Deep Water from the Deep Western Boundary Current across the Atlantic to the Cape Basin. The observations further indicate that much of the DEBC must recirculate within the basin. Spectral analyses of the shallow and deep EBC transport time series demonstrate that the strongest variability occurs on timescales ranging from 30 to 90 days, associated with the propagation of Agulhas Rings.

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Section: Resultsmentioning

confidence: 99%

Shallow and Deep Eastern Boundary Currents in the South Atlantic at 34.5°S: Mean Structure and Variability

et al. 2019

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“…In the FC, while observational evidence suggests that first baroclinic Rossby waves are linked with changes in the FC transport at the 3–12 years frequency band [ DiNezio et al ., ], an analysis focused on the semi‐annual/annual band may provide additional insight on the seasonal variability induced by remotely forced signals. Because the signals of first baroclinic Rossby waves and of westward propagating mesoscale eddies are often superimposed in the sea surface height anomaly (SHA) data [ Oliveira and Polito , ; Polito and Sato , ], the generic term westward propagating signals is adopted here for convenience.…”

Section: Introductionmentioning

confidence: 99%

Remote sources for year‐to‐year changes in the seasonality of the Florida Current transport

2016

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The seasonal variability of the Florida Current (FC) transport is often characterized by the presence of an average annual cycle (8% of the variance) of ∼3 Sv range peaking in boreal summer. However, the seasonality displayed by the FC transport in any individual year may have very distinct characteristics. In this study, the analysis focuses on seasonal changes (73–525 day frequency band) in the FC transport that are associated with a variable annual phase, which is defined as the transient seasonal component (FCt, 27% of the variance). It is shown that the FCt is largely modulated by westward propagating sea height anomaly (SHA) signals that are formed in the eastern North Atlantic 4–7 years earlier than observed at 27°N in the Florida Straits. These westward propagating SHA signals behave approximately like first baroclinic Rossby waves that can modulate changes in the FC seasonal variability upon arrival at the western boundary. The main finding from this study is that changes in coastal sea‐level between 25°N and 42°N linked with westward propagating signals account for at least 50% of the FCt. The integrated changes in the coastal sea‐level between 25°N and 42°N, in turn, drive adjustments in the geostrophic transport of the FC at 27°N. Results reported here provide an explanation for previously reported year‐to‐year changes in the FC seasonality, and suggest that large sea‐level variations along the coast of Florida may be partially predictable, given that these Rossby‐wave‐like signals propagate approximately at fixed rates in the open ocean along 27°N.

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“…Por fim, em 40°S (Tabela 5) grande parte do sinal total é representado pelas componentes η r e η E , somando 65% da variância do sinal total do altímetro e 74% do modelo, resultado similar ao encontrado por (Oliveira and Polito, 2013). Em ambas as componentes o modelo reproduz a amplitude com um ∆ < 5%, ou seja, do ponto de vista estatístico o modelo reproduz com exatidão essas amplitudes.…”

Section: Resultsunclassified

“…Dessa forma, a área de estudo deste trabalho abrange o oceano Atlântico Sul Subtropical, entre 10°S e 40°S. O limite sul foi escolhido de forma a cobrir as regiões do oceano definidas por Oliveira and Polito (2013) como sendo dominadas por ondas de Rossby (entre 10°e 25,5°S), transição entre ondas de Rossby e vórtices de mesoescala (entre 25,5°e 34,5°S) e a região dominada por vórtices (ao sul de 34,5°S). Na figura 2 é apresentada a área de estudo sobre a batimetria ETOPO1 (Amante and Eakins, 2009), que ilustra o relevo da superfície da Terra, integrando a topografia do terreno com a batimetria oceânica.…”

Section: áRea De Estudounclassified

“…Além do campo de anomalia da altura da superfície do mar, é possível se observar ondas de Rossby em dados de temperatura da superfície do mar (SST) (Cipollini et al, 1997;Hill et al, 2000;Oliveira and Polito, 2013), em variações da profundidade da isoterma de 20°C (White, 1977), em perfis de temperatura subsuperficial (Chu et al, 2007) ou através da concentração de clorofila (Machu et al, 1999;Cipollini et al, 2001;Uz et al, 2001;Kawamiya and Oschlies, 2001;Ryan et al, 2002;Killworth et al, 2004) com resultados bastante convincentes e correlacionados (Quartly et al, 2003). Mais recentemente, Menezes et al (2014) observou a assinatura de ondas planetárias na salinidade de superfície do oceano Índico Sul, utilizando os dois primeiros anos de dados do satélite Aquarius/SAC-D. Apesar dos dados de satélite serem de grande utilidade, por estarem disponíveis apenas há pouco mais de duas décadas, afirmações sobre tendências decadais do nível do mar, bem como o papel das ondas de Rossby no ajuste dos giros se mostram complicados (Sasaki et al, 2008).…”

Section: Introductionunclassified

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Análise comparativa da dinâmica das ondas de Rossby a partir de anomalias da altura da superfície do mar obtidas por satélite e modelos numéricos

Baldasso¹

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Characterization of westward propagating signals in the South Atlantic from altimeter and radiometer records

Cited by 20 publications

References 34 publications

Shallow and Deep Eastern Boundary Currents in the South Atlantic at 34.5°S: Mean Structure and Variability

Shallow and Deep Eastern Boundary Currents in the South Atlantic at 34.5°S: Mean Structure and Variability

Remote sources for year‐to‐year changes in the seasonality of the Florida Current transport

Análise comparativa da dinâmica das ondas de Rossby a partir de anomalias da altura da superfície do mar obtidas por satélite e modelos numéricos

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