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Registros recuperados: 7
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Observations of the vertical and temporal evolution of a Natal Pulse along the Eastern Agulhas Bank ArchiMer
Pivan, Xavier; Krug, Marjolaine; Herbette, Steven.
This study re-investigates the work of Lutjeharms et al. [2001,2003] who documented the properties of a Natal Pulse using isopycnal Lagrangian floats. We combined Lagrangian analyses and Eulerian maps derived from objective analysis to better describe the evolution of a Natal Pulse along three density surfaces referred to as the surface (satellite-observed), shallow (isopycnal-1026.8 kg.m−3) and deep (isopycnal-1027.2 kg.m−3) layer. Our observations show that this Natal Pulse extended to a depth of 1000m and was associated with cyclonic relative vorticity values of about 6.5 to 8.5x10−5.s−1 in the surface and shallow layer and 4x10−5.s−1 in the deep layer. This Natal Pulse contributed to cross-shelf exchange through the offshore advection of Eastern...
Tipo: Text Palavras-chave: Agulhas Current; Natal Pulse; Lagrangian floats.
Ano: 2016 URL: http://archimer.ifremer.fr/doc/00350/46162/45860.pdf
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Seasonal phasing of Agulhas Current transport tied to a baroclinic adjustment of near-field winds ArchiMer
Hutchinson, Katherine; Beal, Lisa M.; Penven, Pierrick; Ansorge, Isabelle; Hermes, Juliet.
The Agulhas Current plays a significant role in both local and global ocean circulation and climate regulation, yet the mechanisms that determine the seasonal cycle of the current remain unclear, with discrepancies between ocean models and observations. Observations from moorings across the current and a 22 year proxy of Agulhas Current volume transport reveal that the current is over 25% stronger in austral summer than in winter. We hypothesize that winds over the Southern Indian Ocean play a critical role in determining this seasonal phasing through barotropic and first baroclinic mode adjustments and communication to the western boundary via Rossby waves. Our hypothesis is explored using single layer and one‐and‐a‐half layer models. We find that the...
Tipo: Text Palavras-chave: Agulhas Current; Seasonal cycle; Wind stress curl; Rossby waves; Indian Ocean; Reduced gravity model.
Ano: 2018 URL: https://archimer.ifremer.fr/doc/00454/56607/58300.pdf
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Submesoscale cyclones in the Agulhas current ArchiMer
Krug, M.; Swart, S.; Gula, J..
Gliders were deployed for the first time in the Agulhas Current region to investigate processes of interactions between western boundary currents and shelf waters. Continuous observations from the gliders in water depths of 100-1000m and over a period of 1month provide the first high-resolution observations of the Agulhas Current's inshore front. The observations collected in a nonmeandering Agulhas Current show the presence of submesoscale cyclonic eddies, generated at the inshore boundary of the Agulhas Current. The submesoscale cyclones are often associated with warm water plumes, which extend from their western edge and exhibit strong northeastward currents. These features are a result of shear instabilities and extract their energy from the mean...
Tipo: Text Palavras-chave: Western boundary current; Coastal and shelf; Sub-mesoscale; Agulhas Current; Ocean gliders; Instabilities.
Ano: 2017 URL: https://archimer.ifremer.fr/doc/00376/48687/69640.pdf
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Interactions between the Agulhas Current and the eastern margin of the Agulhas Bank ArchiMer
Krug, Marjolaine; Tournadre, Jean; Dufois, F..
Interactions between the Agulhas Current and the ecologically important region of the Agulhas Bank are studied through the analysis of high resolution along-track altimetry, merged mapped altimetry and in situ measurements of current speed and direction undertaken from a moored Accoustic Doppler Current Profiler (ADCP). Comparisons between current observations collected from the ADCP and the satellite altimeters are made to evaluate the validity of the analysis conducted on the altimetry. Both altimetry and in situ observations show that Natal Pulses are a major driver of variability along the eastern margin of the Agulhas Bank. On average, it is estimated that the circulation along the eastern margin of the Agulhas Bank is influenced by Natal Pulses for...
Tipo: Text Palavras-chave: Agulhas Current; Agulhas Bank; Natal pulse; Satellite oceanography; Altimetry.
Ano: 2014 URL: http://archimer.ifremer.fr/doc/00186/29676/28457.pdf
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Generation of submesoscale frontal eddies in the Agulhas Current ArchiMer
Tedesco, Pauline; Gula, Jonathan; Ménesguen, Claire; Penven, Pierrick; Krug, M..
This study addresses the dynamics of the Agulhas inshore front in the submesoscale range upstream of 26°E. Submesoscale frontal eddies are observed in the vicinity of Port Elizabeth (26°E) from satellite images and in observations collected from under‐water gliders. Using a submesoscale‐resolving numerical model (dx ~ 0.75 km) we are able to simulate similar submesoscale eddies. Barotropic instability is confirmed as the generation mechanism by a 1D linear stability analysis and an eddy kinetic energy budget. Kinetic energy is transferred from the mean flow to the eddies through the mean horizontal shear, which is a signature of barotropic instability. When the Agulhas Current is in a non‐meandering state, submesoscale eddy generation is a recurrent...
Tipo: Text Palavras-chave: Submesoscale; Numerical Modelling; Barotropic Instability; Agulhas Current; Frontal Eddies.
Ano: 2019 URL: https://archimer.ifremer.fr/doc/00514/62520/66827.pdf
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Echanges indo-atlantiques d'eau subtropicale en relation aux structures frontales et de méso-échelle: Utilisation de la série temporelle altimétrique de niveau de la mer ArchiMer
Dencausse, Guillaume.
Indo-Atlantic exchanges of subtropical water play a crucial role in controlling global climate. The intense mesoscale activity south of Africa contributes to these exchanges, yet remains poorly described. A commonly accepted circulation scheme of those waters assmues that the subtropical gyres of the neighbouring oceans are partially connected, forming a super-gyre. Using an altimeter-derived sea-level time series spanning over 12 years, we study the exchanges through the "northern branch" of the super-gyre (Indian to Atlantic ocean), and through the "southern branch" (opposite direction). Regarding the northern branch, an initial study of the Agulhas Current Retroflection yields a statistical description of its behaviour, and shows the disrupting role of...
Tipo: Text Palavras-chave: Courant des Aiguilles; Anneaux des Aiguilles; Front Subtropical; Retroflection; Altimétrie; Échanges indo-atlantiques; Mésoéchelle; Agulhas Current; Agulhas Rings; 3subtropical Front; Retroflection; Altimetry; Indo-atlantic exchanges; Mesoscale.
Ano: 2009 URL: http://archimer.ifremer.fr/doc/00030/14091/11310.pdf
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A late Quaternary record of seasonal sea surface temperatures off southern Africa ArchiMer
Loftus, E.; Sealy, J.; Leng, M. J.; Lee-thorp, J. A..
The southern Cape coastal region is important for understanding both the behavioural history of modern humans, and regional and global climate dynamics, because it boasts a long archaeological record and occupies a key geographical location near the intersection of two major oceans. The western boundary Agulhas Current, implicated in global heat exchange dynamics, is an important modulator of southern African climates and yet we understand its past behaviour only broadly as the Current itself scours the coastal shelf and marine sediment core records necessarily provide little detail. Numerous archaeological sites from both the late Pleistocene and Holocene provide the opportunity for reconstruction of near shore seasonal SST records, which respond both to...
Tipo: Text Palavras-chave: Late Pleistocene; Holocene; Palaeoclimatology; Southern Africa; Agulhas Current; Oxygen isotopes; Mollusc shells; Westerly winds.
Ano: 2017 URL: https://archimer.ifremer.fr/doc/00495/60711/83613.pdf
Registros recuperados: 7
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