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Registros recuperados: 6
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A New Mechanism for Mode Water Formation involving Cabbeling and Frontogenetic Strain at Thermohaline Fronts 5
Thomas, Leif N.; Shakespeare, Callum J..
A simple analytical model is used to elucidate a potential mechanism for steady-state mode water formation at a thermohaline front that involves frontogenesis, submesoscale lateral mixing, and cabbeling. This mechanism is motivated in part by recent observations of an extremely sharp, density-compensated front at the North Wall of the Gulf Stream. Here, the intergyre, along-isopycnal, salinity-temperature difference is compressed into a span of a few kilometers, making the flow susceptible to cabbeling. The sharpness of the front is caused by frontogenetic strain, which is presumably balanced by submesoscale lateral mixing processes. The balance is studied with the simple model, and a scaling is derived for the amount of water mass transformation resulting...
Tipo: Text Palavras-chave: Circulation/ Dynamics; Frontogenesis/frontolysis; Fronts; Ocean dynamics; Atm/Ocean Structure/ Phenomena; Water masses.
Ano: 2015 URL: https://archimer.ifremer.fr/doc/00351/46243/46107.pdf
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Cyclones and Anticyclones in Seismic Imaging 5
Barbosa Aguiar, A. C.; Menesguen, Claire; Le Gentil, Sylvie; Schopp, Richard; Carton, Xavier.
Nearly all the subsurface eddies detected in seismic imaging of sections in the northeast Atlantic have been assumed to be anticyclones containing Mediterranean Water (MW). Fewer MW cyclones have been observed and studied. In this study, the work of previous numerical studies is extended to investigate some characteristics of layering surrounding MW cyclones, using a primitive equation model with equal diffusivities for salinity and temperature to suppress the effects of double diffusion. It is shown that, after a stable state is reached, both anticyclones and cyclones display similar patterns of layering: stacked thin layers of high acoustic reflectivity located above and below the core of each vortex, which do not match isopycnals. The authors conclude...
Tipo: Text Palavras-chave: Geographic location/entity; North Atlantic Ocean; Circulation/ Dynamics; Small scale processes; Atm/Ocean Structure/ Phenomena; Eddies; Vortices; Observational techniques and algorithms; Acoustic measurements/effects; Models and modeling; Primitive equations model.
Ano: 2015 URL: http://archimer.ifremer.fr/doc/00281/39190/37746.pdf
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Geostrophic Closure of the Zonally Averaged Atlantic Meridional Overturning Circulation 5
Sevellec, Florian; Huck, Thierry.
It is typically assumed that the meridional density gradient in the North Atlantic is well and positively correlated with the Atlantic meridional overturning circulation (AMOC). In numerical "water-hosing" experiments, for example, imposing an anomalous freshwater flux in the Northern Hemisphere leads to a slowdown of the AMOC. However, on planetary scale, the first-order dynamics are linked to the geostrophic balance, relating the north-south pressure gradient to the zonal circulation. In this study, these two approaches are reconciled. At steady state and under geostrophic dynamics, an analytical expression is derived to relate the zonal and meridional pressure gradient. This solution is only valid where the meridional density gradient length scale is...
Tipo: Text Palavras-chave: Meridional overturning circulation; Thermohaline circulation; Atm/Ocean Structure/ Phenomena; Ocean circulation; Baroclinic flows; Geographic location/entity; Ekman pumping; Circulation/ Dynamics; Atlantic Ocean.
Ano: 2016 URL: http://archimer.ifremer.fr/doc/00323/43456/42843.pdf
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On the Mediterranean Water Composition 5
Carracedo, Lidia; Pardo, P. C.; Flecha, S.; Perez, Ff.
The Mediterranean Outflow Water (MOW) spills from the Mediterranean Sea (east North Atlantic basin) west off the Strait of Gibraltar. As MOW outflows, it entrains eastern North Atlantic Central Waters (ENACW) and Intermediate Waters to form the neutrally buoyant Mediterranean Water (MW) that can be traced over the entire North Atlantic basin. Its high salinity content influences the thermohaline properties of the intermediate-deep water column in the North Atlantic and its dynamics. Here, the composition of MW in its source region (the Gulf of Cadiz, west off Strait of Gibraltar) is investigated on the basis of an optimum multiparameter analysis. The results obtained indicate that mixing of MOW (34.1% +/- 0.3%) occurs mainly with overlying ENACW (57.1% +/-...
Tipo: Text Palavras-chave: Water masses; Geographic location/entity; Physical Meteorology and Climatology; North Atlantic Ocean; Entrainment; Circulation/ Dynamics; Mixing; Atm/Ocean Structure/ Phenomena; Climatology.
Ano: 2016 URL: https://archimer.ifremer.fr/doc/00629/74110/73547.pdf
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Surface Roughness Imaging of Currents Shows Divergence and Strain in the Wind Direction 5
Rascle, Nicolas; Chapron, Bertrand; Ponte, Aurelien; Ardhuin, Fabrice; Klein, Patrice.
Images of sea surface roughness-for example, obtained by synthetic aperture radars (SAR) or by radiometers viewing areas in and around the sun glitter-at times provide clear observations of meso- and sub-mesoscale oceanic features. Interacting with the surface wind waves, particular deformation properties of surface currents are responsible for those manifestations. Ignoring other sources of surface roughness variations, the authors limit their discussion to the mean square slope (mss) variability. This study confirms that vortical currents and currents with shear in the wind direction shall not be expressed in surface roughness images. Only divergent currents or currents with no divergence but strained in the wind direction can exhibit surface roughness...
Tipo: Text Palavras-chave: Circulation/ Dynamics; Ageostrophic circulations; Atmosphere-ocean interaction; Mesoscale processes; Wind waves; Atm/Ocean Structure/ Phenomena; Boundary layer; Sea state.
Ano: 2014 URL: https://archimer.ifremer.fr/doc/00210/32170/30619.pdf
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Tracer stirring around a meddy: The formation of layering 5
Meunier, Thomas; Menesguen, Claire; Schopp, Richard; Le Gentil, Sylvie.
The dynamics of the formation of layering surrounding meddy-like vortex lenses is investigated using primitive equation (PE), quasigeostrophic (QG), and tracer advection models. Recent in situ data inside a meddy confirmed the formation of highly density-compensated layers in temperature and salinity at the periphery of the vortex core. Very high-resolution PE modeling of an idealized meddy showed the formation of realistic layers even in the absence of double-diffusive processes. The strong density compensation observed in the PE model, in good agreement with in situ data, suggests that stirring might be a leading process in the generation of layering. Passive tracer experiments confirmed that the vertical variance cascade in the periphery of the vortex...
Tipo: Text Palavras-chave: Circulation/ Dynamics; Advection; Dynamics; Atm/Ocean Structure/ Phenomena; Vortices; Models and modeling; Primitive equations model; Quasigeostrophic models; Tracers.
Ano: 2015 URL: http://archimer.ifremer.fr/doc/00255/36599/35160.pdf
Registros recuperados: 6
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