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| Registros recuperados: 17 | |
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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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| Siegelman, Lia; Klein, Patrice; Thompson, Andrew F.; Torres, Hector S.; Menemenlis, Dimitris. |
| Recent studies demonstrate that energetic sub-mesoscale fronts (10–50 km width) extend in the ocean interior, driving large vertical velocities and associated fluxes. However, diagnosing the dynamics of these deep-reaching fronts from in situ observations remains challenging because of the lack of information on the 3-D structure of the horizontal velocity. Here, a realistic numerical simulation in the Antarctic Circumpolar Current (ACC) is used to study the dynamics of submesocale fronts in relation to velocity gradients, responsible for the formation of these fronts. Results highlight that the stirring properties of the flow at depth, which are related to the velocity gradients, can be inferred from finite-size Lyapunov exponent (FSLE) at the surface.... |
| Tipo: Text |
Palavras-chave: Altimetry; Finite-size Lyapunov exponent; Ocean dynamics; Sub-mesoscale. |
| Ano: 2020 |
URL: https://archimer.ifremer.fr/doc/00645/75666/76532.pdf |
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| 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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| 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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| 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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| 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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| 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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| 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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| Regan, Heather; Lique, Camille; Talandier, Claude; Meneghello, Gianluca. |
| The Beaufort Gyre in the Arctic Ocean has spun up over the past two decades in response to changes of the wind forcing and sea ice conditions, accumulating a significant amount of freshwater. Here a simulation performed with a high-resolution, eddy resolving model is analyzed in order to provide a detailed description of the total and eddy kinetic energy, and their response to this spin up of the gyre. On average, and in contrast to the typical open ocean conditions, the levels of mean and eddy kinetic energy are of the same order of magnitude, and the eddy kinetic energy is only intensified along the boundary and in the subsurface. In response to the strong anomalous atmospheric conditions in 2007, the gyre spins up and the mean kinetic energy almost... |
| Tipo: Text |
Palavras-chave: Ocean; Arctic; Eddies; Ocean dynamics; Ocean models. |
| Ano: 2020 |
URL: https://archimer.ifremer.fr/doc/00598/71015/69288.pdf |
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| Saher, Margot H.; Gehrels, W. Roland; Barlow, Natasha L. M.; Long, Antony J.; Haigh, Ivan D.; Blaauw, Maarten. |
| We present a new, diatom-based sea-level reconstruction for Iceland spanning the last similar to 500 years, and investigate the possible mechanisms driving the sea-level changes. A sea-level reconstruction from near the Icelandic low pressure system is important as it can improve understanding of ocean atmosphere forcing on North Atlantic sea-level variability over multi-decadal to centennial timescales. Our reconstruction is from Vioarholmi salt marsh in Snafellsnes in western Iceland, a site from where we previously obtained a 2000-yr record based upon less precise sea-level indicators (salt-marsh foraminifera). The 20th century part of our record is corroborated by tide-gauge data from Reykjavik. Overall, the new reconstruction shows ca 0.6 m rise of... |
| Tipo: Text |
Palavras-chave: Diatoms; Ocean dynamics; Iceland; Little Ice Age; Sea-level rise; NAO. |
| Ano: 2015 |
URL: https://archimer.ifremer.fr/doc/00352/46283/45963.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: 17 | |
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