Subtropical mode waters in the South Atlantic Ocean

Provost, Christine; Escoffier, Christelle; Maamaatuaiahutapu, Keitapu; Kartavtseff, Annie; Garçon, Véronique

doi:10.1029/1999jc900049

Cited by 75 publications

(145 citation statements)

References 36 publications

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“…However, the spatial pattern of subduction, with three cores of maximum subduction, was invariant to the vertical discretization in the simulations, suggesting this is a robust result, independent aspect of the model vertical resolution. These results also suggest that the division of the STMWs in the South Atlantic ocean in three distinct classes, as proposed by Provost et al (1999), may be arbitrary. To the contrary, the modal structure seems to be better represented by a continuum of colder and denser mode waters eastward along the Subtropical Front.…”

Section: Discussionsupporting

confidence: 51%

“…The regions of maximum thickness in the model simulation can be associated with the three STMWs described by Provost et al (1999) The model results show a warm bias in the mixed layer, produc-ing lighter mode waters than observations. This is reflected in the model as a small drift from the initial conditions, and results in a migration of the lower layers to the upper portions of the thermocline.…”

Section: Resultsmentioning

confidence: 94%

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Subduction of South Atlantic Subtropical Mode Waters

Mill¹,

Paiva²

2013

Rev. Bras. Geof.

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ABSTRACT. The formation of the Subtropical Mode Waters (STMW) in the South Atlantic, part of the South Atlantic Central Water (SACW), by the subduction process, transferring mixed layer fluid into the permanent thermocline, is investigated using results of numerical simulations with the HYbrid Coordinate Ocean Model (HYCOM). Subduction rates were estimated by the kinematic method, adding the lateral induction of fluid through the sloping base of winter mixed layer with the vertical velocities at the base of winter mixed layer. Subduction rates above 100 m/year were found over the South Atlantic Subtropical Front, with maximum rates larger than 200 m/year in three distinct regions. The subduction pattern is dominated by the contribution of lateral induction, specially over the Subtropical Front, with rates significantly larger than the maximum rate of Ekman pumping. Different STMW were identified, associated with maximum layers thickness in isopycnals representative of upper and middle portion of SACW. The regions of maximum subduction rates were associated with the formation of the STMW.Keywords: mixed layer, ventilation, SACW, permanent thermocline, lateral induction. RESUMO. A formação deÁguas Modais Subtropicais (AMS) no Atlântico Sul, que fazem parte daÁgua Central do Atlântico Sul (ACAS), transferindo fluido da camada de mistura para a termoclina permantente pelo processo de subducção, foi estudada a partir dos resultados de simulações numéricas com um modelo oceânico de coordenadas híbridas (HYCOM -Hybrid Coordinate Ocean Model). A subducção foi calculada pelo método cinemático, somando as contribuições da indução lateral de fluido através da base da camada de mistura e as velocidades verticais na base da camada de mistura de inverno. Foram encontradas taxas de subducção superiores a 100 m/ano ao longo da Frente Subtropical do Atlântico Sul, com três núcleos distintos de máxima subducção atingindo mais de 200 m/ano. A indução lateral mostrou-se o processo dominante na subducção, especialmente ao longo da frente, com taxas significativamente superiores ao bombeamento de Ekman.Foram identificadas diferentes AMS associadasàs máximas espessuras de camadas representativas das porções média e superior daÁgua Central do Atlântico Sul (ACAS). As regiões de máximas taxas de subducção estão associadasà formação das AMS.Palavras-chave: camada de mistura, ventilação, ACAS, termoclina permanente, indução lateral.

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Section: Discussionsupporting

confidence: 51%

Section: Resultsmentioning

confidence: 94%

Subduction of South Atlantic Subtropical Mode Waters

Mill¹,

Paiva²

2013

Rev. Bras. Geof.

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“…The South Atlantic subtropical gyre has several prominent fronts, each with its own Subtropical Mode Water (Tsuchiya et al 1994;Provost et al 1999; shown in Fig. 6), which can be classified as South Atlantic Subtropical Mode Water (Provost et al 1999), shown as a patch with mean density s u 5 26:4 kg m 23 , and the South Atlantic Eastern Subtropical Mode Water (Provost et al 1999), shown as a patch with mean density s u 5 25:9 kg m 23 .…”

Section: ) Subtropical South Atlantic Oceanmentioning

confidence: 99%

“…6), which can be classified as South Atlantic Subtropical Mode Water (Provost et al 1999), shown as a patch with mean density s u 5 26:4 kg m 23 , and the South Atlantic Eastern Subtropical Mode Water (Provost et al 1999), shown as a patch with mean density s u 5 25:9 kg m 23 . Moreover, there is another subtropical mode water (Tsuchiya et al 1994), formed mainly in the region between 158 and 208S (shown as a patch with mean density s u 5 25:4 kg m 23 in Fig.…”

Section: ) Subtropical South Atlantic Oceanmentioning

confidence: 99%

The Global Subduction/Obduction Rates: Their Interannual and Decadal Variability

Liu

Huang

2012

Journal of Climate

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Ventilation, including subduction and obduction, for the global oceans was examined using Simple Ocean Data Assimilation (SODA) outputs. The global subduction rate averaged over the period from 1959 to 2006 is estimated at 505.8 Sv (1 Sv [ 10 6 m 3 s 21 ), while the corresponding global obduction rate is estimated at 482.1 Sv. The annual subduction/obduction rates vary greatly on the interannual and decadal time scales. The global subduction rate is estimated to have increased 7.6% over the past 50 years, while the obduction rate is estimated to have increased 9.8%. Such trends may be insignificant because errors associated with the data generated by ocean data assimilation could be as large as 10%. However, a major physical mechanism that induced these trends is primarily linked to changes in the Southern Ocean. While the Southern Ocean plays a key role in global subduction and obduction rates and their variability, both the Southern Ocean and equatorial regions are critically important sites of water mass formation/erosion.

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“…The process of mode water formation can be related to the formation of a regular mixed layer. In both cases the loss of buoyancy during winter and early spring causes convective mixing processes (Provost et al 1999;Hanawa and Talley 2001). After that, the restratification of the upper layer creates a seasonal thermocline that isolates mode waters from surface and they are transported by local advection away from their formation site.…”

Section: List Of Abbreviationsmentioning

confidence: 99%

Observations of the South Atlantic Subtropical Mode Water using PIES data

Cortezi¹

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Subtropical mode waters in the South Atlantic Ocean

Cited by 75 publications

References 36 publications

Subduction of South Atlantic Subtropical Mode Waters

Subduction of South Atlantic Subtropical Mode Waters

The Global Subduction/Obduction Rates: Their Interannual and Decadal Variability

Observations of the South Atlantic Subtropical Mode Water using PIES data

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