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Registros recuperados: 11
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Arctic Ocean freshwater content and its decadal memory of sea-level pressure ArchiMer
Johnson, Helen L.; Cornish, Sam B.; Kostov, Yavor; Beer, Emma; Lique, Camille.
Arctic freshwater content (FWC) has increased significantly over the last two decades, with potential future implications for the Atlantic meridional overturning circulation downstream. We investigate the relationship between Arctic FWC and atmospheric circulation in the control run of a coupled climate model. Multiple linear lagged regression is used to extract the response of total Arctic FWC to a hypothetical step increase in the principal components of sea‐level pressure. The results demonstrate that the FWC adjusts on a decadal timescale, consistent with the idea that wind‐driven ocean dynamics and eddies determine the response of Arctic Ocean circulation and properties to a change in surface forcing, as suggested by idealized models and theory....
Tipo: Text Palavras-chave: Arctic Ocean; Climate change; Interannual variability; Freshwater; Adjustment timescales; Ocean dynamics.
Ano: 2018 URL: https://archimer.ifremer.fr/doc/00440/55117/56571.pdf
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Available Potential Energy in Density Coordinates ArchiMer
Colin De Verdiere, Alain; Huck, Thierry; Pogossian, Souren; Ollitrault, Michel.
The vertically integrated potential energy of an incompressible stratified fluid formulated in density coordinates can be simply written as a weighted vertical sum of the squares of the vertical displacements of density surfaces, a general expression valid for arbitrary displacements. The sum of this form of potential energy and kinetic energy is then a conserved quantity for the multilayer shallow water model. The formulation in density coordinates is a natural one to find the Lorenz reference state of available potential energy (APE).We describe the method to compute the APE of an ocean state and provide two applications. The first is the classical double-gyre, wind-driven circulation simulated by a shallow water model at high resolution.We show that the...
Tipo: Text Palavras-chave: Energy transport; Ocean circulation; Ocean dynamics; Isopycnal coordinates.
Ano: 2018 URL: https://archimer.ifremer.fr/doc/00464/57521/59707.pdf
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Diagnosing Surface Mixed Layer Dynamics from High-Resolution Satellite Observations: Numerical Insights ArchiMer
Ponte, Aurelien; Klein, Patrice; Capet, Xavier; Le Traon, Pierre-yves; Chapron, Bertrand; Lherminier, Pascale.
High-resolution numerical experiments of ocean mesoscale eddy turbulence show that the wind-driven mixed layer (ML) dynamics affects mesoscale motions in the surface layers at scales lower than O(60 km). At these scales, surface horizontal currents are still coherent to, but weaker than, those derived from sea surface height using geostrophy. Vertical motions, on the other hand, are stronger than those diagnosed using the adiabatic quasigeotrophic (QG) framework. An analytical model, based on a scaling analysis and on simple dynamical arguments, provides a physical understanding and leads to a parameterization of these features in terms of vertical mixing. These results are valid when the wind-driven velocity scale is much smaller than that associated with...
Tipo: Text Palavras-chave: Mesoscale processes; Ocean dynamics; Turbulence.
Ano: 2013 URL: http://archimer.ifremer.fr/doc/00170/28076/26291.pdf
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Effects of the submesoscale on the potential vorticity budget of ocean mode waters ArchiMer
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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Glacial Ocean Dynamics: Insight from Deep-Sea Coral Reconstructions and A Time-Dependent Dynamical Box Model ArchiMer
Hines, Sophia Katharine Vizza.
Glacial-interglacial cycles, occurring at a period of approximately 100,000 years, have dominated Earth's climate over the past 800,000 years. These cycles involve major changes in land ice, global sea level, ocean circulation, and the carbon cycle. While it is generally agreed that the ultimate driver of global climate is changes in insolation, glacial cycles do not look like insolation forcing. Notably, there is a highly non-linear warming response at 100,000 years to a relatively small forcing, implicating a more complicated system of biogeochemical and physical drivers. The ocean plays a pivotal role in glacial-interglacial climate through direct equator-to-pole transport of heat and its role in the carbon cycle. The deep ocean contains 60 times more...
Tipo: Text Palavras-chave: Paleoceanography; Oceanography; Climate change; Glacial cycles; Ocean circulation; Ocean dynamics.
Ano: 2018 URL: https://archimer.ifremer.fr/doc/00493/60447/63892.pdf
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Quantifying tracer dynamics in moving fluids: a combined Eulerian-Lagrangian approach ArchiMer
Chenillat, Fanny; Blanke, Bruno; Grima, Nicolas; Franks, Peter J. S.; Capet, Xavier; Rivière, Pascal.
Eulerian models coupling physics and biology provide a powerful tool for the study of marine systems, complementing and synthesizing in situ observations and in vitro experiments. With the monotonic improvements in computing resources, models can now resolve increasingly complex biophysical interactions. Quantifying complex mechanisms of interaction produces massive amounts of numerical data that often require specialized tools for analysis. Here we present an Eulerian-Lagrangian approach to analyzing tracer dynamics in moving fluids. As an example of its utility, we apply this tool to quantifying plankton dynamics in oceanic mesoscale coherent structures. In contrast to Eulerian frameworks, Lagrangian approaches are particularly useful for revealing...
Tipo: Text Palavras-chave: Biophysicalinteractions; Planktondynamics; Ecosystemfunctioning; Lagrangiantrajectories; Ocean dynamics; Mesoscaleprocesses; Eddytracking; Coherentstructures.
Ano: 2015 URL: https://archimer.ifremer.fr/doc/00469/58028/60447.pdf
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QuasiGeostrophic Diagnosis of Mixed-Layer Dynamics Embedded in a Mesoscale Turbulent Field ArchiMer
Chavanne, Cedric P.; Klein, Patrice.
A quasigeostrophic model is developed to diagnose the three-dimensional circulation, including the vertical velocity, in the upper ocean from high-resolution observations of sea surface height and buoyancy. The formulation for the adiabatic component departs from the classical surface quasigeostrophic framework considered before since it takes into account the stratification within the surface mixed layer that is usually much weaker than that in the ocean interior. To achieve this, the model approximates the ocean with two constant stratification layers: a finite-thickness surface layer (or the mixed layer) and an infinitely deep interior layer. It is shown that the leading-order adiabatic circulation is entirely determined if both the surface...
Tipo: Text Palavras-chave: Circulation; Dynamics; Ageostrophic circulations; Mesoscale processes; Ocean dynamics; Vertical motion; Models and modeling; Diagnostics; Quasigeostrophic models.
Ano: 2016 URL: http://archimer.ifremer.fr/doc/00309/42031/41330.pdf
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Reconstructing Upper Ocean Vertical Velocity Field from Sea Surface Height in the Presence of Unbalanced Motion ArchiMer
Qiu, Bo; Chen, Shuiming; Klein, Patrice; Torres, Hector; Wang, Jinbo; Fu, Lee-lueng; Menemenlis, Dimitris.
Reconstructability of upper ocean vertical velocity (w) and vorticity (ζ) fields from high-resolution sea surface height (SSH) data is explored using the global 1/48° horizontal-resolution MITgcm output in the context of the forth-coming Surface Water and Ocean Topography (SWOT) mission. By decomposing w with an omega equation of the primitive-equation system and by taking into account the measurement design of the SWOT mission, this study seeks to reconstruct the subinertial, balanced w and ζ signals. By adopting the effective surface quasi-geostrophic (eSQG) framework and applying to the Kuroshio Extension region of the North Pacific, we find that the target and reconstructed fields have a spatial correlation of ~0.7 below the mixed layer for w and 0.7 ~...
Tipo: Text Palavras-chave: Eddies; Mesoscale processes; Ocean dynamics; Vertical motion; Altimetry.
Ano: 2020 URL: https://archimer.ifremer.fr/doc/00593/70561/68744.pdf
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Reconstruction of the 3-D Dynamics From Surface Variables in a High-Resolution Simulation of North Atlantic ArchiMer
Fresnay, S.; Ponte, Aurelien; Le Gentil, Sylvie; Le Sommer, J..
Several methods that reconstruct the three-dimensional ocean dynamics from sea level are presented and evaluated in the Gulf Stream region with a 1/60° realistic numerical simulation. The use of sea level is motivated by its better correlation with interior pressure or quasigeostrophic potential vorticity (PV) compared to sea surface temperature and sea surface salinity, and, by its observability via satellite altimetry. The simplest method of reconstruction relies on a linear estimation of pressure at depth from sea level. Another method consists in linearly estimating PV from sea level first and then performing a PV inversion. The last method considered, labeled SQG for surface quasigeostrophy, relies on a PV inversion but assumes no PV anomalies. The...
Tipo: Text Palavras-chave: Ocean dynamics; Quasi-geostrophy; Potential vorticity; Sea surface height; Correlation analysis; Spectral analysis.
Ano: 2018 URL: http://archimer.ifremer.fr/doc/00425/53632/54468.pdf
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Satellite altimetry and ocean dynamics ArchiMer
Fu, Lee Lueng; Le Traon, Pierre-yves.
This paper provides a summary of recent results derived from satellite altimetry. It is focused on altimetry and ocean dynamics with synergistic use of other remote sensing techniques, in-situ data and integration aspects through data assimilation. Topics include mean ocean circulation and geoid issues, tropical dynamics and large-scale sea level and ocean circulation variability, high-frequency and intraseasonal variability, Rossby waves and mesoscale variability.
Tipo: Text Palavras-chave: Rossby waves; Large scale; Mesoscale; Sea level; Ocean dynamics; Satellite altimetry; Ondes de Rossby; Grande échelle; Mésoéchelle; Niveau de la mer; Dynamique de l'océan; Altimétrie satellitaire.
Ano: 2006 URL: http://archimer.ifremer.fr/doc/2006/publication-2175.pdf
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The Vertical Structure of Large-Scale Unsteady Currents ArchiMer
Hochet, Antoine; Colin De Verdiere, Alain; Scott, Robert.
A linear model based on the quasigeostrophic equations is constructed in order to predict the vertical structure of Rossby waves and, more broadly, of anomalies resolved by altimeter data, roughly with periods longer than 20 days and with wavelengths larger than 100 km. The subsurface field is reconstructed from sea surface height and climatological stratification. The solution is calculated in periodic rectangular regions with a 3D discrete Fourier transform. The effect of the mean flow on Rossby waves is neglected, which the authors believe is a reasonable approximation for low latitudes. The method used has been tested with an idealized double- gyre simulation [performed with the Miami Isopycnal Coordinate Ocean Model (MICOM)]. The linear model is able...
Tipo: Text Palavras-chave: Circulation/ Dynamics; Ocean dynamics; Rossby waves; Waves; Oceanic; Mathematical and statistical techniques; Fourier analysis; Models and modeling; Quasigeostrophic models.
Ano: 2015 URL: http://archimer.ifremer.fr/doc/00260/37081/35586.pdf
Registros recuperados: 11
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