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Jeudi 14 mars - Warm-core rings in the Gulf of Mexico: from basin scale to fine scale

by SEMSOU last modified Feb 28, 2019 03:00 PM
When Mar 14, 2019
from 02:00 PM to 03:00 PM
Where salle Coriolis
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Thomas Meunier

Chercheur au CICESE, Ensenada (Mexique)

Title : Warm-core rings in the Gulf of Mexico: from basin scale to fine scale.


Abstract : Loop current eddies (LCE) are large warm-core rings sporadically detaching from the Loop current (LC), and drifting through the Gulf of Mexico (GoM). They largely dominate the GoM's circulation and control the redistribution of heat and salt towards the basin's interior, dramatically affecting hurricanes and storm cells formation. They also have a significant impact on the oil industry, eventually forcing deep water drilling operations to stop for weeks. For the past 2 decades, LCEs have mostly been studied through altimetry and regional numerical modelling, and little is known about their vertical thermohaline structure. In the frame of the CIGOM project, a series of glider missions repeatedly sampled a LCE, from its detachment until its agony along the GoM's western platform, revealing its thermohaline properties. Thanks to their fine spatial resolution, the glider surveys revealed an unsuspected richness of processes, from submesoscale to fine scale, occurring within the LCE. The presence of at least three intrathermocline eddies, embedded in the main thermocline of the LCE was obvious in the Brunt-Väisälä sections. They were associated with strong negative potential vorticity anomalies. They are believed to form through mixing and Rossby adjustment, possibly through internal wave breaking, or frictional processes in the Yucatan channel prior to LCE detachment. Evidences of layering below, and near the edges of the recently detached LCE, also brought a new candidate for the diffusion of thermohaline properties towards the surrounding GoM's water. High resolution QG modeling of an idealized warm-core ring showed that the vertical variance cascade leading to the observed layering was likely triggered by the stirring of tracer anomalies by the eddy's vertically sheared azimuthal flow, similar to layering around interior vortices. The LCE was also associated with unexpectedly large temperature and salinity anomalies, carrying integrated heat and salt excesses of nearly 1 billion TJ and 22 billion tons, respectively. Their impact on the basin scale seasonal and long term heat and salt budgets will also be discussed.

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Mardi 12 Mars - Reconstruction de l’histoire du niveau marin relatif et détermination des taux et moteurs de la subsidence : exemples du delta du Gange et de la mer de Marmara

by SEMSOU last modified Feb 27, 2019 10:00 AM
When Mar 12, 2019
from 02:00 PM to 03:00 PM
Where salle Pyrénées
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Céline Grall

Chercheur associé au Lamont-Doherty Earth Observatory de l’Université Columbia, NY, Etats-Unis


Titre: Reconstruction de l’histoire du niveau marin relatif et détermination des taux et moteurs de la subsidence : exemples du delta du Gange et de la mer de Marmara.

Résumé: La subsidence et l’histoire du niveau marin relatif (NMR) dans le delta du Gange et la mer de Marmara seront abordées dans cette présentation.  Ces deux régions se trouvent en contexte de tectonique active et présentent un contexte paléo-environnemental particulier. La mer de Marmara connait des phases de connexion et déconnexion avec l’Océan global, rythmées par les oscillations glacio-eustatiques. Le delta du Gange, quant à lui, forme la plus grande plaine deltaïque du monde, et est caractérisé par des apports sédimentaires extrêmement forts depuis plusieurs millions d’années.  Les résultats qui seront présentés incluront (i) des reconstructions stratigraphiques de l’histoire du NMR à partir des données de puits, carottes, et de sismique réflexion (ii) des modèles numériques reconstruisant le NMR prenant en compte l’histoire de chargements isostatiques et la compaction sédimentaire. Ces résultats, placés dans les contextes régionaux respectifs de ces sites d’étude, permettront de discuter des facteurs locaux qui contrôlent l’histoire du NMR depuis les derniers cycles glaciaires.

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Vendredi 15 Février - GEOVIDE: The French GEOTRACES North Atlantic Transect (GA01). Insights into the main results

by SEMSOU last modified Jan 30, 2019 12:28 PM
When Feb 15, 2019
from 10:00 AM to 11:00 AM
Where Salle Jules Verne
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Géraldine Sarthou

Directrice de Recherche CNRS au LEMAR, France


Title: GEOVIDE: The French GEOTRACES North Atlantic Transect (GA01). Insights into the main results.

Abstract: The GEOVIDE cruise, a collaborative project within the framework of the international GEOTRACES programme, was conducted along the French‐led section in the North Atlantic Ocean (Section GA01), between 15 May and 30 June 2014. In this talk, I will present an overview of the main results from GEOVIDE, including physical oceanography and trace element and isotope cyclings. The main GEOVIDE results have helped to improve our understanding of the TEI cycles in the North Atlantic. The strong physical oceanography background of the GEOVIDE project was a strength for interpreting our data. For many TEIs, a strong link was observed between their distributions and water masses. On the other hand, TEIs also helped to constrain oceanic circulation, notably in the subpolar gyre and Labrador Sea. Important sources (sediments, fluvial, and meteoric) and sinks (biological uptake and scavenging) of TEIs were highlighted. The biological carbon pump was studied and showed different efficiencies in the various studied regions.


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