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| Registros recuperados: 31 | |
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| Morel, Yves; Gula, Jonathan; Ponte, Aurelien. |
| Taking advantage of alternative expressions for potential vorticity (PV) in divergence forms, we derive balances between volume integral of PV and boundary conditions, that are then applied to practical computations of PV: • we propose a new method for diagnosing the Ertel potential vorticity from model output, that preserves the balances; • we show how the expression of PV can be derived in general coordinate systems. This is here emphasised with isopycnic coordinates by generalising the PV expression to the general Navier-Stokes equations; • we propose a generalised derivation for the Haynes-McIntyre impermeability theorem, which highlights the role of the bottom boundary condition choice (e.g. no-slip vs free-slip) and mixing near the bottom boundary... |
| Tipo: Text |
Palavras-chave: Potential vorticity; Boundary conditions; General circulation; Vortex; Fronts; Boundary layers. |
| Ano: 2019 |
URL: https://archimer.ifremer.fr/doc/00494/60525/63988.pdf |
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| Ayata, Sakina-dorothee; Stolba, Robin; Comtet, Thierry; Thiebaut, Eric. |
| The relationship between meroplankton distribution and spatio-temporal variability of coastal mesoscale hydrological structure was investigated in the northern Bay of Biscay, North-East Atlantic. For the three coastal polychaetes studied, i.e. Pectinaria koreni, Owenia fusiformis and Sabellaria alveolata, the highest larval abundances were sampled in low-salinity, low-density and high-temperature river plume waters. For two species (P. koreni and O. fusiformis), maximal abundances were observed in the surface and thermocline layers due to ontogenic migrations. Variance partitioning based on multiple regression and redundancy analyses was used to assess the relative roles played by the hydrological environment alone, the geographical space alone and their... |
| Tipo: Text |
Palavras-chave: Meroplankton; Larval transport; Mesoscale structures; River plume; Fronts; Owenia fusiformis; Pectinaria koreni; Sabellaria alveolata; Bay of Biscay. |
| Ano: 2011 |
URL: https://archimer.ifremer.fr/doc/00240/35131/33632.pdf |
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| 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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| Garreau, Pierre; Dumas, Franck; Louazel, Stephanie; Correard, Stephanie. |
| The Mediterranean Sea is often referred as a “pocket ocean” exhibiting many processes that are primary interest the global ocean circulation given the opportunity to investigate a large panel of oceanic features in a relatively restrained area. Recent field experiments based on the multi-plateform integrated monitoring MOOSE or on intensive targeted experiment HYMEX revisited the hydrology and the dynamics of the Western Basin. Such approaches emphasized the ubiquity of the fine scale dynamics in the Mediterranean dynamics. An overview of the observed processes during 5 recent fields experiments are presented and discussed regarding meso- and submeso-scale processes. |
| Tipo: Text |
Palavras-chave: Mesoscale phenomena; Western Mediterranean; Fronts. |
| Ano: 2019 |
URL: https://archimer.ifremer.fr/doc/00582/69398/67247.pdf |
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| Bauer, Robert Klaus; Fromentin, Jean-marc; Demarcq, Herve; Bonhommeau, Sylvain. |
| We investigated the habitat utilization, vertical and horizontal behaviour of Atlantic bluefin tuna Thunnus thynnus (ABFT) in relation to oceanographic conditions in the northwestern Mediterranean Sea, based on 36 pop-up archival tags and different environmental data sets. Tags were deployed on early mature ABFT (127–255 cm) between July and November in 2007-2014, on the shelf area off Marseille, France. The data obtained from these tags provided 1643 daily summaries of ABFT vertical behaviour over 8 years of tag deployment. Based on a hierarchical clustering of this data, we could identify four principle daily vertical behaviour types, representing surface (≦10m) and subsurface (10–100 m) orientation, moderate (50–200 m) and deep (≧200m) diving behaviour.... |
| Tipo: Text |
Palavras-chave: Thunnus thynnus; Habitat use; Spike dives; Fronts; Thermal stratification; Archival tags. |
| Ano: 2017 |
URL: http://archimer.ifremer.fr/doc/00382/49329/49709.pdf |
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| Marchal, Olivier; Waelbroeck, Claire; Colin De Verdiere, Alain. |
| Three sediment records of sea surface temperature (SST) are analyzed that originate from distant locations in the North Atlantic, have centennial-to-multicentennial resolution, are based on the same reconstruction method and chronological assumptions, and span the past 15 000 yr. Using recursive least squares techniques, an estimate of the time-dependent North Atlantic SST field over the last 15 kyr is sought that is consistent with both the SST records and a surface ocean circulation model, given estimates of their respective error (co)variances. Under the authors' assumptions about data and model errors, it is found that the 10 degrees C mixed layer isotherm, which approximately traces the modern Subpolar Front, would have moved by ~15 degrees of... |
| Tipo: Text |
Palavras-chave: Inverse methods; Kalman filters; Climate variability; Circulation/ Dynamics; Geographic location/entity; Oceanic variability; Variability; Mathematical and statistical techniques; Fronts; North Atlantic Ocean. |
| Ano: 2016 |
URL: http://archimer.ifremer.fr/doc/00318/42922/42423.pdf |
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| De Boer, Agatha M.; Graham, Robert M.; Thomas, Matthew; Kohfeld, Karen E.. |
| In recent years the latitudinal position of the Subtropical Front (STF) has emerged as a key parameter in the global climate. A poleward positioned front is thought to allow a greater salt flux from the Indian to the Atlantic Ocean and so drive a stronger Atlantic Meridional Overturning Circulation. Here the common view that the STF aligns with the zero wind stress curl (WSC) is challenged. Based on the STF climatologies of Orsi et al. (1995), Belkin and Gordon (1996), Graham and De Boer (2013), and on satellite scatterometry winds, we find that the zero WSC contour lies on average approximate to 10 degrees, approximate to 8 degrees, and approximate to 5 degrees poleward of the front for the three climatologies, respectively. The circulation in the region... |
| Tipo: Text |
Palavras-chave: Subtropical Front; Wind stress curl; Southern Ocean; Satellite data; Fronts; Dynamical Subtropical Front. |
| Ano: 2013 |
URL: http://archimer.ifremer.fr/doc/00169/28046/26248.pdf |
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| Gladyshev, S; Arhan, Michel; Sokov, A; Speich, Sabrina. |
| The properties and circulation of water masses leaving and entering the Atlantic Ocean south of Africa are examined using data from a hydrographic and Lowered acoustic Doppler current profiler section from South Africa to the southern limit of the Antarctic Circumpolar Current (ACC). At the upper levels, the ACC fronts are well determined using either classical water mass definitions or gradient-based criteria. While the locations of the Subantarctic Front (SAF), Polar Front (PF), and Southern ACC Front (SACCF) seem controlled by the neighbouring ridges, that of the Subtropical Front (STF) is much influenced in this region (similar to 10 degrees E) by northwestward propagating Agulhas rings. No large amount of Subantarctic Mode Water (SAMW) is observed,... |
| Tipo: Text |
Palavras-chave: Water masses; Fronts; Bottom circulation; Transport; Agulhas eddies; Antarctic Circumpolar Current. |
| Ano: 2008 |
URL: http://archimer.ifremer.fr/doc/2008/publication-6097.pdf |
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| Floodgate, G.d.; Lochte, K.; Egan, B.. |
| The data obtained in surveys to investigate the bacteriological aspects of the biology of two contrasting frontal systems has shown that the Inherent homeostasis and the complexity of the environment, together with the Imprecision of the data, lead to biomass values that are difficult to interpret in terms of the physical factors governing the formation of fronts. Although biochemical measurements offer some promise of providing more reliable and less confusing information, the oeed to develop high precision methods that can be made very frequently is emphasised. |
| Tipo: Text |
Palavras-chave: Bacteria; Discontinuities; Fronts; Methodology. |
| Ano: 1982 |
URL: http://archimer.ifremer.fr/doc/00306/41742/40953.pdf |
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| Drushka, Kyla; Asher, William E.; Sprintall, Janet; Gille, Sarah T.; Hoang, Clifford. |
| Surface salinity variability on O(1-10) km lateral scales (the submesoscale) generates density variability and thus has implications for submesoscale dynamics. Satellite salinity measurements represent a spatial average over horizontal scales of approximately 40-100 km but are compared to point measurements for validation, so submesoscale salinity variability also complicates validation of satellite salinities. Here, we combine several databases of historical thermosalinograph (TSG) measurements made from ships to globally characterize surface submesoscale salinity, temperature, and density variability. In river plumes; regions affected by ice melt or upwelling; and the Gulf Stream, South Atlantic, and Agulhas Currents, submesoscale surface salinity... |
| Tipo: Text |
Palavras-chave: Small scale processes; Freshwater; Fronts; Sea surface temperature; Oceanic variability. |
| Ano: 2019 |
URL: https://archimer.ifremer.fr/doc/00676/78805/81042.pdf |
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| Barton, Benjamin I.; Lenn, Yueng-djern; Lique, Camille. |
| Barents Sea Water (BSW) is formed from Atlantic Water that is cooled through atmospheric heat loss and freshened through seasonal sea ice melt. In the eastern Barents Sea, the BSW and fresher, colder Arctic Water meet at the surface along the Polar Front (PF). Despite its importance in setting the northern limit of BSW ventilation, the PF has been poorly-documented, mostly eluding detection by observational surveys that avoid seasonal sea ice. In this study, satellite sea surface temperature (SST) observations are used in addition to a temperature and salinity climatology to examine the location and structure of the PF, and characterise its variability over the period 1985 – 2016. It is shown that the PF is independent of the position of the sea ice edge... |
| Tipo: Text |
Palavras-chave: Arctic; Sea ice; Fronts; Sea surface temperature; Satellite observations. |
| Ano: 2018 |
URL: https://archimer.ifremer.fr/doc/00448/56003/57509.pdf |
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| Swart, Sebastiaan; Speich, Sabrina. |
| Swart et al. (2010) applied altimetry data to the gravest empirical mode south of Africa to yield a 16 year time series of temperature and salinity sections. In this study we use these thermohaline sections to derive weekly estimates of heat content (HC) and salt content (SC) at the GoodHope meridional transect of the Antarctic Circumpolar Current (ACC). These estimates compare favorably to observed data. The resulting 16 year time series of HC and SC estimates are used to explain the subsurface thermohaline variability at each ACC front and frontal zone. The variability at the Subantarctic Zone (SAZ) is principally driven by the presence of Agulhas Rings, which occur in this region approximately 2.7 times per annum and are responsible for the longest and... |
| Tipo: Text |
Palavras-chave: Altimetry; ACC; Fronts. |
| Ano: 2010 |
URL: http://archimer.ifremer.fr/doc/00002/11307/7892.pdf |
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| Wenegrat, Jacob O.; Thomas, Leif N.; Gula, Jonathan; Mcwilliams, James C.. |
| Non-conservative processes change the potential vorticity (PV) of the upper ocean, and later, through the subduction of surface waters into the interior, affect the general ocean circulation. Here we focus on how boundary layer turbulence, in the presence of submesoscale horizontal buoyancy gradients, generates a source of potential vorticity at the ocean surface through a balance known as the Turbulent ThermalWind. This source of PV injection at the submesoscale can be of similar magnitude to PV fluxes from the wind and surface buoyancy fluxes, and hence can lead to a net injection of PV onto outcropped isopycnals even during periods of surface buoyancy loss. The significance of these dynamics is illustrated using a high-resolution realistic model of the... |
| Tipo: Text |
Palavras-chave: Ageostrophic circulations; Atmosphere-ocean interaction; Fronts; Ocean dynamics; Potential vorticity; Boundary layer. |
| Ano: 2018 |
URL: http://archimer.ifremer.fr/doc/00452/56347/57937.pdf |
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| Buckingham, Christian; Gula, Jonathan; Carton, Xavier. |
| We continue our study of the role of curvature in modifying frontal stability. In Part I, we obtained an instability criterion valid for curved fronts and vortices in gradient wind balance (GWB): Φ′ = L′q′ < 0, where L′ and q′ are the nondimensional absolute angular momentum and Ertel potential vorticity (PV), respectively. In Part II, we investigate this criterion in a parameter space representative of low-Richardson-number fronts and vortices in GWB. An interesting outcome is that, for Richardson numbers near 1, anticyclonic flows increase in q′, while cyclonic flows decrease in q′, tending to stabilize anticyclonic and destabilize cyclonic flow. Although stability is marginal or weak for anticyclonic flow (owing to multiplication by L′), the... |
| Tipo: Text |
Palavras-chave: Eddies; Fronts; Instability; Ocean circulation; Potential vorticity; Frontogenesis/frontolysis; Vortices; Angular momentum. |
| Ano: 2021 |
URL: https://archimer.ifremer.fr/doc/00677/78919/81286.pdf |
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| Buckingham, Christian; Gula, Jonathan; Carton, Xavier. |
| In this study, we examine the role of curvature in modifying frontal stability. We first evaluate the classical criterion that the Coriolis parameter f multiplied by the Ertel potential vorticity (PV) q is positive for stable flow and that instability is possible when this quantity is negative. The first portion of this statement can be deduced from Ertel’s PV theorem, assuming an initially positive fq. Moreover, the full statement is implicit in the governing equation for the mean geostrophic flow, as the discriminant, fq, changes sign. However, for curved fronts in cyclogeostrophic or gradient wind balance (GWB), an additional term enters the discriminant owing to conservation of absolute angular momentum L. The resulting expression, (1 + Cu)fq < 0 or... |
| Tipo: Text |
Palavras-chave: Instability; Ocean dynamics; Potential vorticity; Turbulence; Frontogenesis/frontolysis; Fronts; Vortices; Angular momentum. |
| Ano: 2021 |
URL: https://archimer.ifremer.fr/doc/00677/78920/81288.pdf |
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| Registros recuperados: 31 | |
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