Observations of Extreme Upwelling Filaments in the Southeast Atlantic Ocean

Lütjeharms, J. R. E.; Shillington, F. A.; Rae, C. M. Duncombe

doi:10.1126/science.253.5021.774

Cited by 81 publications

(39 citation statements)

References 13 publications

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“…Bang and Andrews (1974) report a strongly baroclinic frontal zone near the shelfbreak that contain a strong equatorward jet with maximum velocity of 1.2 m/s and suggest an association with the local wind forcing. Lutjeharms et al (1991) observed a long 770 km filament that extended from the shelf in association with an Agulhas eddy near the Luderitz upwelling cell. Filaments are known to form in association with the elongation of an Agulhas ring and indicate tracer leakage (de Steur et al, 2004;Whittle et al, 2008).…”

Section: S Baker-yeboah Et Al: Transformation Of An Agulhas Eddy Nementioning

confidence: 99%

Transformation of an Agulhas eddy near the continental slope

et al. 2010

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Abstract. The transformation of Agulhas eddies near the continental slope of southern Africa and their subsequent self-propagation are analyzed in both observational data and numerical simulations. Self-propagation results from a net dipole moment of a generalized heton structure consisting of a surface-intensified anticyclonic eddy and deep cyclonic pattern. Such Agulhas vortical structures can form near the retroflection region and further north along the western coast of southern Africa. We analyze nonlinear topographic wave generation, vortex deformations, and filament production as an important part in water mass exchange. Self-propagating structures provide a conduit for exchange between the deep ocean and shelf regions in the Benguela upwelling system.

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Section: S Baker-yeboah Et Al: Transformation Of An Agulhas Eddy Nementioning

confidence: 99%

Transformation of an Agulhas eddy near the continental slope

et al. 2010

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“…They may then encircle rings. In extreme cases, especially when there is a strong berg wind -an offshore movement of air from the higher continental escarpment -such interaction may result in upwelling filaments being drawn up to 1000 km offshore (Lutjeharms et al, 1991).…”

Section: Agulhas Ringsmentioning

confidence: 99%

Three decades of research on the greater Agulhas Current

Lütjeharms

2007

Ocean Sci.

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Abstract. The greater Agulhas Current has been shown to be a key link in the global thermohaline circulation and an increased understanding of this current system is therefore of more than just local interest. Knowledge on the Agulhas Current system has in fact increased enormously over the past 30 years. This review covers some aspects of what has been learnt on the northern and the southern parts of the Agulhas Current proper and their influence on the waters and circulation of the adjoining continental shelf. It also discusses the Natal Pulse and new information that has been gained on how it is triggered and what influence it has. It deals with the Agulhas retroflection, the shedding of Agulhas rings and the movement and characteristics of these rings that contributes to the meridional overturning circulation of the global ocean. The Agulhas Return Current forms part of the final outflow of the system and current knowledge on that current is appraised. The sources of the Agulhas Current have been a controversial subject for many years and this dispute continues. This is described and discussed, based on what information has been gained from research over the past three decades. Building on what is currently known, some suggestions are given on the most important remaining knowledge gaps and how these could most efficaciously be filled.

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“…For example, warm Agulhas rings entrain cold water from the Benguela upwelling system on their flanks and advect upwelled water far offshore as long filaments (Lutjeharms et al 1991). Likewise, warm core rings shed from the Gulf Stream and advected into the northern recirculation gyre often entrain shelf water, slope water, and/or Gulf Stream water on their fringes, creating important onshore and offshore fluxes of very diverse water masses-and their associated heat, freshwater and biogeochemical contents (Nof 1988, Ryan et al 2001).…”

Section: Discussionmentioning

confidence: 99%

Interaction of Mediterranean Water lenses with Antarctic Intermediate Water off Northwest Africa

Machín¹,

Pelegrí²

2016

Sci. Mar.

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Summary:Mediterranean Water lenses (meddies) in the eastern North Atlantic, north of the Canary Islands, appear to often have their salty and nutrient-poor core accompanied by relatively fresh and nutrient-rich waters on top. We describe several occurrences of freshwater halos and berets for meddies sampled north of the Canary Islands-with instrumented moorings, Argo floats and oceanographic cruises-and identify the source of these fresh anomalies as diluted Antarctic Intermediate Water (AAIW). We propose that this capping takes place off Northwest Africa, as the southward-advected meddy interacts with the northward-advected AAIW. This interpretation is consistent with a simple analysis of the relevant advectivediffusive time scales associated with the passage of meddies under a layer of AAIW, and suggests that meddies may be a mechanism for AAIW export far into the North Atlantic Ocean.Keywords: meddies; Antarctic Intermediate Water; eastern North Atlantic. Interacción de remolinos de agua mediterránea con Agua Intermedia Antártica al noroeste de ÁfricaResumen: Los Meddies en el Atlántico Norte oriental, al norte de las Islas Canarias, a menudo parecen tener su núcleo salado y pobre en nutrientes acompañado de aguas relativamente frescas y ricas en nutrientes en la parte superior. Se describen varios casos de halos y boinas de agua dulce para meddies muestreados al norte de las Islas Canarias -con instrumentos anclados, perfiladores Argo y campañas oceanográficas-identificando así el origen de estas anomalías frescas como Agua Intermedia Antártica (AIAA) diluida. Proponemos que esta interacción se lleva a cabo en el noroeste de África, cuando el meddy advectado hacia el sur interactúa con el AIAA advectada hacia el norte. Esta interpretación es coherente con un simple análisis de las escalas de tiempo advectivo-difusivas asociadas con el paso de meddies bajo una capa de AIAA, y sugiere que los meddies pueden ser un mecanismo para exportar AIAA hacia el océano interior en el Atlántico Norte.Palabras clave: meddies; agua intermedia antártica; Atlántico Norte oriental.Citation/Como citar este artículo: Machín F

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Observations of Extreme Upwelling Filaments in the Southeast Atlantic Ocean

Cited by 81 publications

References 13 publications

Transformation of an Agulhas eddy near the continental slope

Transformation of an Agulhas eddy near the continental slope

Three decades of research on the greater Agulhas Current

Interaction of Mediterranean Water lenses with Antarctic Intermediate Water off Northwest Africa

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