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| Gula, Jonathan; Molemaker, Maarten Jeroen; Mcwilliams, James C.. |
| Most of the ocean kinetic energy is contained in the large scale currents and the vigorous geostrophic eddy field, at horizontal scales of order 100 km. To achieve equilibrium the geostrophic currents must viscously dissipate their kinetic energy at much smaller scale. However, geostrophic turbulence is characterized by an inverse cascade of energy towards larger scale, and the pathways of energy toward dissipation are still in question. Here, we present a mechanism, in the context of the Gulf Stream, where energy is transferred from the geostrophic flow to submesoscale wakes through anticyclonic vertical vorticity generation in the bottom boundary layer. The submesoscale turbulence leads to elevated local dissipation and mixing outside the oceanic... |
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| Ano: 2016 |
URL: http://archimer.ifremer.fr/doc/00357/46814/46679.pdf |
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| Vic, C.; Roullet, Guillaume; Capet, Xavier; Carton, Xavier; Molemaker, Maarten Jeroen; Gula, J.. |
| The Persian Gulf feeds a warm and salty outflow in the Gulf of Oman (northern Arabian Sea). The salt climatological distribution is relatively smooth in the Gulf of Oman, and the signature of a slope current carrying salty waters is difficult to distinguish hundreds of kilometers past the Strait of Hormuz, in contrast to other outflows of the world ocean. This study focuses on the mechanisms involved in the spreading of Persian Gulf Water (PGW) in the Gulf of Oman, using a regional primitive equation numerical simulation. The authors show that the dispersion of PGW occurs through a regime that is distinct from, for example, the one responsible for the Mediterranean outflow dispersion. The background mesoscale eddy field is energetic and participates... |
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| Ano: 2015 |
URL: http://archimer.ifremer.fr/doc/00302/41332/40512.pdf |
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| Mcwilliams, James C.; Gula, Jonathan; Molemaker, Maarten Jeroen. |
| Eastward zonal jets are common in the ocean and atmosphere, for example, the Gulf Stream and jet stream. They are characterized by atypically strong horizontal velocity, baroclinic vertical structure with an upward flow intensification, large change in the density stratification meridionally across the jet, large-scale meanders around a central latitude, narrow troughs and broad crests, and a sharp and vertically sloping northern (poleward) "wall" defined by horizontal maxima in the lateral gradients of both velocity and density. Measurements and realistic oceanic simulations show these features in the Gulf Stream downstream from its western boundary separation point. A diagnostic theory based on the conservative balance equations is developed to calculate... |
| Tipo: Text |
Palavras-chave: Ageostrophic circulations; Frontogenesis/frontolysis; Ocean models. |
| Ano: 2019 |
URL: https://archimer.ifremer.fr/doc/00486/59786/62925.pdf |
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| Roullet, Guillaume; Molemaker, Maarten Jeroen; Ducousso, Nicolas; Dubos, Thomas. |
| In anticipation of relaxing the hydrostatic assumption in a sigma coordinates primitive equations ocean model, we show how a projection method can be designed with the use of a compact symmetric 15-point stencil for the Poisson equation. This is achieved by recognizing that, owing the non-orthogonality of the grid, the velocity has a contravariant and covariant set of components. The two sets play a different role in the primitive equations: the contravariant components enter the definition of the model fluxes, whereas the covariant components experience the forces and in particular the pressure gradient. By treating these two sets separately, the discretized gradient and divergence operators are simple finite differences. The two sets of components are... |
| Tipo: Text |
Palavras-chave: Non-hydrostatic; Sigma coordinates; Poisson equation. |
| Ano: 2017 |
URL: http://archimer.ifremer.fr/doc/00399/51045/51818.pdf |
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| Renault, Lionel; Molemaker, Maarten Jeroen; Gula, Jonathan; Masson, Sebastien; Mcwilliams, James C.. |
| The Gulf Stream (GS) is known to have a strong influence on climate, for example, by transporting heat from the tropics to higher latitudes. Although the GS transport intensity presents a clear interannual variability, satellite observations reveal its mean path is stable. Numerical models can simulate some characteristics of the mean GS path, but persistent biases keep the GS separation and postseparation unstable and therefore unrealistic. This study investigates how the integration of ocean surface currents into the ocean–atmosphere coupling interface of numerical models impacts the GS. The authors show for the first time that the current feedback, through its eddy killing effect, stabilizes the GS separation and postseparation, resolving long-lasting... |
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| Ano: 2016 |
URL: http://archimer.ifremer.fr/doc/00358/46879/46760.pdf |
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