|
|
|
|
|
| Lahaye, Noe; Gula, Jonathan; Thurnherr, Andreas M.; Reverdin, Gilles; Bouruet-aubertot, Pascale; Roullet, Guillaume. |
| Over mid-ocean ridges, the interaction between the currents and the topography gives rise to complex flows, which drive the transport properties of biogeochemical constituents, and especially those associated with hydrothermal vents, thus impacting associated ecosystems. This paper describes the circulation in the rift valley along the Azores sector of the North Mid-Atlantic Ridge, using a combination of in-situ data from several surveys and realistic high-resolution modeling. It confirms the presence of a mean deep current with an up-valley branch intensified along the right inner flank of the valley (looking downstream), and a weaker down-valley branch flowing at shallower depth along the opposite flank. The hydrographic properties of the rift-valley... |
| Tipo: Text |
Palavras-chave: Deep currents; Transport; Deep turbulence; Internal waves and tides; Realistic modeling; In situ observation. |
| Ano: 2019 |
URL: https://archimer.ifremer.fr/doc/00584/69630/67486.pdf |
| |
|
|
| Sarrazin, Jozee; Portail, Marie; Legrand, E.; Cathalot, Cecile; Laes, Agathe; Lahaye, Noe; Sarradin, Pierre-marie; Husson, Berengere. |
| The factors influencing the structure of hydrothermal communities are not necessarily similar across geographical regions and vent fields. In the present study, we explore the role of environmental conditions on vent community structure at local and regional spatial scales, focusing on the assemblages dominated by the engineer species Bathymodiolus azoricus. Their presence in several vent fields on the northern Mid-Atlantic Ridge (MAR) represents a unique opportunity to compare their associated fauna and to better understand large-scale biodiversity patterns. Two types of factors were considered: exogenous ones such as the presence of biogeographical barriers, depth, and distance between sites, and those linked to the intrinsic characteristics of each... |
| Tipo: Text |
Palavras-chave: Intra-field variability; Inter-field variability; Hydrothermal fauna; Abiotic factors; Diversity measures; Macrofauna; Meiofauna; Environmental drivers; Community structure; Habitats. |
| Ano: 2020 |
URL: https://archimer.ifremer.fr/doc/00615/72661/71671.pdf |
| |
|
|
| Yu, Xiaolong; Ponte, Aurelien; Lahaye, Noe; Caspar-cohen, Zoe; Menemenlis, Dimitris. |
| urrent satellite altimeters map sea surface height (SSH) with an effective spatial scale of O(100 km) and, as a result, surface ocean velocity can be appropriately estimated from merged SSH fields by assuming geostrophic equilibrium. The validity of the geostrophic assumption down to the spatial scale of O(10 km) that will be newly resolved by the next generation of satellite altimeters, such as the Surface Water Ocean Topography (SWOT) mission, remains unknown. In this study, the accuracy of geostrophy for the estimation of surface currents from a knowledge of instantaneous sea level is quantified using the hourly fields from a tide- and eddy-resolving global numerical simulation. Geostrophic balance is found to be the leading-order balance in frontal... |
| Tipo: Text |
|
| Ano: 2021 |
URL: https://archimer.ifremer.fr/doc/00688/79962/82890.pdf |
| |
|
|
| De Marez, Charly; Lahaye, Noe; Gula, Jonathan. |
| The generation of lee waves in the Gulf Stream along the U.S. seaboard is investigated using high resolution realistic simulations. The model reproduces the surface signature of the waves, which compares favourably with observations from satellite sun glitter images in the region. In particular, a large number of internal waves are observed above the Charleston Bump. These waves match well with the linear theory describing topographically-generated internal waves, which can be used to estimate the associated vertical transport of momentum and energy extracted from the mean flow. Finally, small scale topographic features are shown to have a significant impact on the mean flow in this region of the Gulf Stream, and the specific role of lee waves in this... |
| Tipo: Text |
|
| Ano: 2020 |
URL: https://archimer.ifremer.fr/doc/00609/72075/70786.pdf |
| |
|
|
| Lahaye, Noe; Gula, Jonathan; Roullet, Guillaume. |
| Internal tides are a predominant source of high‐frequency variability and diapycnal mixing in the ocean. Understanding their dynamics and lifecycle is necessary to better understand their role in the ocean circulation. In this paper, we describe and quantify internal tide generation, propagation and dissipation in a sector of the North Mid‐Atlantic Ridge, using high‐resolution numerical simulations with realistic bathymetry and stratification. We show that the generation and dissipation of internal tides, as well as the distribution of internal tides amongst vertical modes, exhibit high spatial variability. We find that topographic scattering leads to a significant transfer of energy towards high vertical modes and thereby enhances internal tide... |
| Tipo: Text |
Palavras-chave: Energy dissipation & Mixing; Internal tides; Internal waves; Topographic scattering. |
| Ano: 2020 |
URL: https://archimer.ifremer.fr/doc/00658/77003/78259.pdf |
| |
|
|
| Lahaye, Noe; Llewellyn Smith, Stefan G.. |
| Coupled-mode equations describing the propagation and scattering of internal waves over large amplitude arbitrary topography in a two-dimensional stratified fluid are derived. They consist of a simple set of ordinary differential equations describing the evolution of modal amplitudes, based on an orthogonality condition that allows one to distinguish leftward and rightward propagating modes. The coupling terms expressing exchange of energy between mode are given in a analytical form using perturbation theory. This allows the derivation of a weak-topography approximate solution, generalizing previous linear solutions for a barotropic forcing (Llewellyn Smith and Young 2002). In addition, the orthogonality condition derived is valid for a different set of... |
| Tipo: Text |
|
| Ano: 2020 |
URL: https://archimer.ifremer.fr/doc/00590/70186/68202.pdf |
| |
|
|
| Lahaye, Noe; Gula, Jonathan; Roullet, Guillaume. |
| The upper ocean is energetic at scales below the Rossby deformation radius owing to the existence of internal waves and submesoscale fronts and vortices. These contribute significantly to energy dissipation, tracer mixing and exchanges between the ocean surface layer, the ocean interior, and the atmospheric boundary layer. Internal waves and submesoscale motions both undergo strong spatial and seasonal variations, driven by different mechanisms. Here, we investigate the sea surface signature of internal waves and its seasonality using linear wave theory and a high‐resolution realistic simulation. In summer, internal waves are greatly amplified near the surface mostly due to a thin mixed layer bounded by a seasonal pycnocline. This surface amplification is... |
| Tipo: Text |
Palavras-chave: Internal tide; Submesosacle dynamics; Seasonality. |
| Ano: 2019 |
URL: https://archimer.ifremer.fr/doc/00486/59746/62847.pdf |
| |
|
|
| Gouzien, E.; Lahaye, Noe; Zeitlin, V.; Dubos, T.. |
| A specific instability of vortices is found in rotating shallow water equations with horizontal density/temperature gradients, which is used for modelling atmospheric and oceanic mixed layers. The model is re-interpreted as dynamics of rotating non-isentropic two-dimensional gas. The instability, which was not reported previously, develops in a way suggesting its convective character. It appears when anomaly of buoyancy at the center of the vortex and the vorticity have opposite signs (for positive Coriolis parameters), and coexists with the standard barotropic instability, having higher growth rates in a wide range of parameters and leading to efficient mixing at a nonlinear stage. Published by AIP Publishing. |
| Tipo: Text |
|
| Ano: 2017 |
URL: https://archimer.ifremer.fr/doc/00600/71251/69629.pdf |
| |
|
|
|
