Meunier Thomas

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Meunier
First Name
Thomas
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0000-0002-9465-0113

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A Deep Water Dispersion Experiment in the Gulf of Mexico

2021-09-18 , Meunier, Thomas , Pérez-Brunius, Paula , Rodríguez Outerelo, Javier , García-Carrillo, Paula , Ronquillo-Mendez, Argelia , Furey, Heather H. , Ramsey, Andree L. , Bower, Amy S.

The Deep Water Horizon oil spill dramatically impacted the Gulf of Mexico from the seafloor to the surface. While dispersion of contaminants at the surface has been extensively studied, little is known about deep water dispersion properties. This study describes the results of the Deep Water Dispersion Experiment (DWDE), which consisted of the release of surface drifters and acoustically tracked RAFOS floats drifting at 300 and 1,500 dbar in the Gulf of Mexico. We show that surface diffusivity is elevated and decreases with depth: on average, diffusivity at 1,500 dbar is 5 times smaller than at the surface, suggesting that the dispersion of contaminants at depth is a significantly slower process than at the surface. This study also examines the turbulent regimes driving the dispersion, although conflicting evidences and large uncertainties do not allow definitive conclusions. At all depths, while the growth of dispersion and kurtosis with time supports the possibility of an exponential regime at very short time scales, indicating that early dispersion is nonlocal, finite size Lyapunov exponents support the hypothesis of local dispersion, suggesting that eddies of size comparable to the initial separation (6 km), may dominate the early dispersion. At longer time scales, the quadratic growth of dispersion is indicative of a ballistic regime, where a mean shear flow would be the dominating process. Examination of the along- and across-bathymetry components of float velocities supports the idea that boundary currents could be the source for this shear dispersion.

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Reconstructing the three-dimensional structure of loop current rings from satellite altimetry and in situ data using the gravest empirical modes method

2022-08-25 , Meunier, Thomas , Pérez-Brunius, Paula , Bower, Amy S.

The three-dimensional structure of Gulf of Mexico’s warm-core rings, detaching from the Loop Current, is investigated using satellite altimetry and a large set of ARGO float profiles. Reconstruction of the Loop Current rings (LCRs) vertical structure from sea surface height observations is made possible by the use of the gravest empirical modes method (GEM). The GEMs are transfer functions that associate a value of temperature and salinity for each variable pair {dynamic height; pressure}, and are computed by estimating an empirical relationship between dynamic height and the vertical thermohaline structure of the ocean. Between 1993 and 2021, 40 LCRs were detected in the altimetry and their three-dimensional thermohaline structure was reconstructed, as well as a number of dynamically relevant variables (geostrophic and cyclogeostrophic velocity, relative vorticity, potential vorticity, available potential energy and kinetic energy density, etc.). The structure of a typical LCR was computed by fitting an analytical stream function to the LCRs dynamic height signature and reconstructing its vertical structure with the GEM. The total heat and salt contents and energy of each LCR were computed and their cumulative effect on the Gulf of Mexico’s heat, salt and energy balance is discussed. We show that LCRs have a dramatic impact on these balances and estimate that residual surface heat fluxes of −13 W m−2 are necessary to compensate their heat input, while the fresh water outflow of the Mississippi river approximately compensates for their salt excess input. An average energy dissipation of O [10−10–10−9] W kg−1 would be necessary to balance their energy input.

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The energy decay of warm‐core eddies in the Gulf of Mexico

2024-01-04 , Meunier, Thomas , Bower, Amy S. , Perez-Brunius, Paula , Graef, Federico , Mahadevan, Amala

The Gulf of Mexico (GoM) is home to some of the most energetic eddies in the ocean. Warm-core rings detach from the Loop-Current and drift through the basin, transporting large amounts of heat and salt. These eddies, known as Loop Current rings (LCRs) have a crucial role in the GoM's dynamics and in the weather of the eastern US, and this role is largely conditioned by their longevity and decay properties. Here, we use an empirical method to estimate the energy evolution of all LCRs detached since 1993. We found that, contrary to the commonly accepted idea that LCRs conserve their energy as they drift through the GoM and decay suddenly against the western platform, LCRs' energy decay is faster in the eastern basin, and they typically lose three-quarter of their energy before encountering the continental shelf. We also show that wind-current feedback contributes to the energy decay and conversion.

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The dynamical structure of a warm core ring as I\inferred from glider observations and along-track altimetry

2021-06-23 , Meunier, Thomas , Pallás-Sanz, Enric , de Marez, Charly , Pérez, Juan , Tenreiro, Miguel , Ruiz-Angulo, Angel , Bower, Amy S.

This study investigates the vertical structure of the dynamical properties of a warm-core ring in the Gulf of Mexico (Loop Current ring) using glider observations. We introduce a new method to correct the glider’s along-track coordinate, which is, in general, biased by the unsteady relative movements of the glider and the eddy, yielding large errors on horizontal derivatives. Here, we take advantage of the synopticity of satellite along-track altimetry to apply corrections on the glider’s position by matching in situ steric height with satellite-measured sea surface height. This relocation method allows recovering the eddy’s azimuthal symmetry, precisely estimating the rotation axis position, and computing reliable horizontal derivatives. It is shown to be particularly appropriate to compute the eddy’s cyclo-geostrophic velocity, relative vorticity, and shear strain, which are otherwise out of reach when using the glider’s raw traveled distance as a horizontal coordinate. The Ertel potential vorticity (PV) structure of the warm core ring is studied in details, and we show that the PV anomaly is entirely controlled by vortex stretching. Sign reversal of the PV gradient across the water column suggests that the ring might be baroclinically unstable. The PV gradient is also largely controlled by gradients of the vortex stretching term. We also show that the ring’s total energy partition is strongly skewed, with available potential energy being 3 times larger than kinetic energy. The possible impact of this energy partition on the Loop Current rings longevity is also discussed.

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OceanGliders: A component of the integrated GOOS

2019-10-02 , Testor, Pierre , de Young, Brad , Rudnick, Daniel L. , Glenn, Scott , Hayes, Daniel J. , Lee, Craig M. , Pattiaratchi, Charitha , Hill, Katherine Louise , Heslop, Emma , Turpin, Victor , Alenius, Pekka , Barrera, Carlos , Barth, John A. , Beaird, Nicholas , Bécu, Guislain , Bosse, Anthony , Bourrin, François , Brearley, J. Alexander , Chao, Yi , Chen, Sue , Chiggiato, Jacopo , Coppola, Laurent , Crout, Richard , Cummings, James A. , Curry, Beth , Curry, Ruth G. , Davis, Richard F. , Desai, Kruti , DiMarco, Steven F. , Edwards, Catherine , Fielding, Sophie , Fer, Ilker , Frajka-Williams, Eleanor , Gildor, Hezi , Goni, Gustavo J. , Gutierrez, Dimitri , Haugan, Peter M. , Hebert, David , Heiderich, Joleen , Henson, Stephanie A. , Heywood, Karen J. , Hogan, Patrick , Houpert, Loïc , Huh, Sik , Inall, Mark E. , Ishii, Masao , Ito, Shin-ichi , Itoh, Sachihiko , Jan, Sen , Kaiser, Jan , Karstensen, Johannes , Kirkpatrick, Barbara , Klymak, Jody M. , Kohut, Josh , Krahmann, Gerd , Krug, Marjolaine , McClatchie, Sam , Marin, Frédéric , Mauri, Elena , Mehra, Avichal , Meredith, Michael P. , Meunier, Thomas , Miles, Travis , Morell, Julio M. , Mortier, Laurent , Nicholson, Sarah , O'Callaghan, Joanne , O'Conchubhair, Diarmuid , Oke, Peter , Pallás-Sanz, Enric , Palmer, Matthew D. , Park, Jong Jin , Perivoliotis, Leonidas , Poulain, Pierre Marie , Perry, Ruth , Queste, Bastien , Rainville, Luc , Rehm, Eric , Roughan, Moninya , Rome, Nicholas , Ross, Tetjana , Ruiz, Simon , Saba, Grace , Schaeffer, Amandine , Schönau, Martha , Schroeder, Katrin , Shimizu, Yugo , Sloyan, Bernadette M. , Smeed, David A. , Snowden, Derrick , Song, Yumi , Swart, Sebastiaan , Tenreiro, Miguel , Thompson, Andrew , Tintore, Joaquin , Todd, Robert E. , Toro, Cesar , Venables, Hugh J. , Wagawa, Taku , Waterman, Stephanie N. , Watlington, Roy A. , Wilson, Doug

The OceanGliders program started in 2016 to support active coordination and enhancement of global glider activity. OceanGliders contributes to the international efforts of the Global Ocean Observation System (GOOS) for Climate, Ocean Health, and Operational Services. It brings together marine scientists and engineers operating gliders around the world: (1) to observe the long-term physical, biogeochemical, and biological ocean processes and phenomena that are relevant for societal applications; and, (2) to contribute to the GOOS through real-time and delayed mode data dissemination. The OceanGliders program is distributed across national and regional observing systems and significantly contributes to integrated, multi-scale and multi-platform sampling strategies. OceanGliders shares best practices, requirements, and scientific knowledge needed for glider operations, data collection and analysis. It also monitors global glider activity and supports the dissemination of glider data through regional and global databases, in real-time and delayed modes, facilitating data access to the wider community. OceanGliders currently supports national, regional and global initiatives to maintain and expand the capabilities and application of gliders to meet key global challenges such as improved measurement of ocean boundary currents, water transformation and storm forecast.

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Spreading and vertical structure of the Persian Gulf and Red Sea outflows in the Northwestern Indian Ocean

2021-03-29 , L'Hégaret, Pierre , de Marez, Charly , Morvan, Mathieu , Meunier, Thomas , Carton, Xavier

In the Indian Ocean, salty water masses from the Persian Gulf and Red Sea are important sources of salt, heat, and nutrients. Across the Arabian Sea, these outflows impact human and biological activities, their thermohaline characteristics and shapes exhibiting important spatial and seasonal variability. The knowledge of the water masses properties is important to validate realistic simulations of the Indian Ocean. A classical approach to study these water masses is to track them on specific isopycnal levels. Nevertheless, their peaking thermohaline characteristics are not always found at a specific density but rather spread over a range. Here, we develop a detection algorithm able to capture the full vertical structure of the outflows, that we applied to a data set of about 126,000 vertical profiles. We are thus able to quantify the changes in their thermohaline signatures and in their vertical structures, characterized here by the intensity of the salinity peaks of the water masses and lateral injection of fresh and salty waters, and describe their spatial variability. Across the northwestern Indian Ocean, the salty outflows undergo several changes, diminishing their thermohaline signatures and peaks and layering. In their early stages in the narrow Gulf of Oman and Aden, the outflows present configurations indicative of diapycnal mixing. In the same regions and along the western edge of the Arabian Sea, these water masses are subject to lateral mixing. All over the Arabian Sea, salt fingering conditions are met for lower layers of the outflows.

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Internal wave activity in the deep Gulf of Mexico

2023-11-15 , Meunier, Thomas , Le Boyer, Arnaud , Molodtsov, Sergey , Bower, Amy S. , Furey, Heather H. , Robbins, Pelle E.

Internal wave activity in the Gulf of Mexico (GoM) is investigated using a fleet of profiling floats. The floats continuously measured temperature and salinity as they drifted at a parking depth of 1500 dbar, allowing for the reconstruction of 2615 time series of isopycnal displacements. Thanks to the dense sampling of the eastern part of the GoM (east of 90°W), the geographical distribution of the internal waves displacement variance and available potential energy (APE) is revealed. The Loop Current (LC) influence region, between the Yucatan shelf to the west and the southern West Florida shelf to the east exhibits increased displacement variance and APE both in the continuum and near-inertial bands, while the north-eastern and central GoM show reduced internal wave activity. As the LC position fluctuates between a retracted and extended mode, we assessed the impact of the presence or absence of the LC in the increased internal wave activity region. It is shown that in the LC influence region, APE is increased (decreased) when the LC is present (absent), suggesting a strong control of the LC on deep internal waves activity. The 1500 dbar flow velocity, bottom roughness, and float altitude also seem to contribute to increased internal waves APE, but their influence is more subtle. Oppositely, no correlation with wind speed or wind intermittency is found.

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