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A model perspective on the dynamics of the shadow zone of the eastern tropical North Atlantic - Part 1: the poleward slope currents along West Africa ArchiMer
Kounta, Lala; Capet, Xavier; Jouanno, Julien; Kolodziejczyk, Nicolas; Sow, Bamol; Gaye, Amadou Thierno.
The West African seaboard is one of the upwelling sectors that has received the least attention, and in situ observations relevant to its dynamics are particularly scarce. The current system in this sector is not well known and understood, e.g., in terms of seasonal variability, across-shore structure, and forcing processes. This knowledge gap is addressed in two studies that analyze the mean seasonal cycle of an eddy-permitting numerical simulation of the tropical Atlantic. Part 1 is concerned with the circulation over the West African continental slope at the southernmost reach of the Canary Current system, between similar to 8 and 20 degrees N. The focus is on the depth range most directly implicated in the wind-driven circulation (offshore and coastal...
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Ano: 2018 URL: https://archimer.ifremer.fr/doc/00458/56969/58862.pdf
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A numerical modeling study of the Southern Senegal upwelling shelf: Circulation and upwelling source waters ArchiMer
Ndoye, S; Capet, Xavier; Estrade, Philippe; Machu, Eric; Kounta, L; Sow, B; Diakhate, M; Gayet, At.
The regional ocean circulation along the Southern Senegal shelf is studied using a numerical model for varying forcing fields during the upwelling season (November-May). The main objective is to study the shelf circulation of the marine environment in the Southern Senegal Upwelling Shelf (SSUS), the Lagrangian pathways by which waters are transported to the surface in the upwelling tongue and the fate of these waters. Model results are compared with hydrographic measurements during UPSEN2-ECOAO survey and satellite images datasets. The upwelling source waters and also the warm nearshore waters are analyzed, from a Lagrangian point of view, by computing the paths of particles that are passively advected by the regional ocean model velocity field (ROMS). It...
Tipo: Text Palavras-chave: Upwelling; Ocean circulation; Modeling; Coastal dynamics; Shelf; ROMS..
Ano: 2018 URL: https://archimer.ifremer.fr/doc/00472/58346/60900.pdf
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California Coastal Upwelling Onset Variability: Cross-Shore and Bottom-Up Propagation in the Planktonic Ecosystem ArchiMer
Chenillat, Fanny; Riviere, Pascal; Capet, Xavier; Franks, Peter J. S.; Blanke, Bruno.
The variability of the California Current System (CCS) is primarily driven by variability in regional wind forcing. In particular, the timing of the spring transition, i.e., the onset of upwelling-favorable winds, varies considerably in the CCS with changes in the North Pacific Gyre Oscillation. Using a coupled physical-biogeochemical model, this study examines the sensitivity of the ecosystem functioning in the CCS to a lead or lag in the spring transition. An early spring transition results in an increased vertical nutrient flux at the coast, with the largest ecosystem consequences, both in relative amplitude and persistence, hundreds of kilometers offshore and at the highest trophic level of the modeled food web. A budget analysis reveals that the...
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Ano: 2013 URL: http://archimer.ifremer.fr/doc/00146/25706/24010.pdf
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Complex small pelagic fish population patterns arising from individual behavioral responses to their environment ArchiMer
Brochier, Timothee; Auger, Pierre-amael; Pecquerie, Laure; Machu, Eric; Capet, Xavier; Thiaw, Modou; Mbaye, Baye Cheikh; Braham, Cheikh-baye; Ettahiri, Omar; Charouki, Najib; Sene, Ousseynou Ndaw; Werner, Francisco; Brehmer, Patrice.
Small pelagic fish (SPF) species are heavily exploited in eastern boundary upwelling systems (EBUS) as their transformation products are increasingly used in the world food chain. Management relies on regular monitoring, but there is a lack of robust theories for the emergence of the populations’ traits and their evolution in highly variable environments. This work aims to address existing knowledge gaps by combining physical and biogeochemical modelling with an individual life-cycle based model applied to round sardinella (Sardinella aurita) off northwest Africa, a key species for regional food security. Our approach focused on the processes responsible for seasonal migrations, spatio-temporal size-structure, and interannual biomass fluctuations....
Tipo: Text Palavras-chave: Small pelagic fish; Sardinella aurita; Fish migration; Eastern boundary upwelling system; Individual based biophysical models; Dynamic energy budget.
Ano: 2018 URL: https://archimer.ifremer.fr/doc/00433/54433/56088.pdf
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Diagnosing Surface Mixed Layer Dynamics from High-Resolution Satellite Observations: Numerical Insights ArchiMer
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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Dissipation of the energy imparted by mid-latitude storms in the Southern Ocean ArchiMer
Jouanno, Julien; Capet, Xavier; Madec, Gurvan; Roullet, Guillaume; Klein, Patrice.
The aim of this study is to clarify the role of the Southern Ocean storms on interior mixing and meridional overturning circulation. A periodic and idealized numerical model has been designed to represent the key physical processes of a zonal portion of the Southern Ocean located between 70 and 40° S. It incorporates physical ingredients deemed essential for Southern Ocean functioning: rough topography, seasonally varying air–sea fluxes, and high-latitude storms with analytical form. The forcing strategy ensures that the time mean wind stress is the same between the different simulations, so the effect of the storms on the mean wind stress and resulting impacts on the Southern Ocean dynamics are not considered in this study. Level and distribution of...
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Ano: 2016 URL: http://archimer.ifremer.fr/doc/00343/45404/44919.pdf
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Eddy properties in the California Current System ArchiMer
Kurian, Jaison; Colas, Francois; Capet, Xavier; Mcwilliams, James C.; Chelton, Dudley B..
Eddy detection and tracking algorithms are applied to both satellite altimetry and a high-resolution (dx = 5 km) climatological model solution of the U.S. West Coast to study the properties of surface and undercurrent eddies in the California Current System. Eddy properties show remarkable similarity in space and time, and even somewhat in polarity. Summer and fall are the most active seasons for undercurrent eddy generation, while there is less seasonal variation at surface. Most of the eddies have radii in the range of 25-100 km, sea level anomaly amplitudes of 1-4 cm, and vorticity normalized by f amplitudes of 0.025-0.2. Many of the eddies formed near the coast travel considerable distance westward with speeds about 2 km/day, consistent with the beta...
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Ano: 2011 URL: http://archimer.ifremer.fr/doc/00044/15484/12873.pdf
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Eddy-topography interactions and the fate of the Persian Gulf Outflow ArchiMer
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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First Evidence of Anoxia and Nitrogen Loss in the Southern Canary Upwelling System ArchiMer
Machu, Eric; Capet, Xavier; Estrade, Philippe; Ndoye, S.; Brajard, J.; Baurand, Francois; Auger, P.-a.; Lazar, A.; Brehmer, Patrice.
The northeastern Atlantic hosts the most ventilated subsurface waters of any eastern boundary upwelling system, while coastal upwelling source waters are slightly above hypoxic levels. Anoxic conditions have previously been found offshore inside mesoscale eddies whose core waters undergo oxygen consumption for many months. Based on circumstantial in situ observations this study demonstrates that the Senegalese coastal ocean is subjected to episodic occurrence of zero dissolved oxygen concentration at depth along with elevated nitrite concentration (11 mmol/m3) and nitrate/nitrite deficit to phosphate, thereby indicating severe anoxia and intense nitrogen loss. The anoxic event was associated with a prolonged upwelling relaxation episode in March 2012 and a...
Tipo: Text Palavras-chave: Oxygen; Canary upwelling system; Anoxia; Denitrification; Shallow continental shelf.
Ano: 2019 URL: https://archimer.ifremer.fr/doc/00479/59020/61640.pdf
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Getting to the bottom of the ocean ArchiMer
De Lavergne, Casimir; Madec, Gurvan; Capet, Xavier; Maze, Guillaume; Roquet, Fabien.
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Ano: 2016 URL: http://archimer.ifremer.fr/doc/00359/46988/47129.pdf
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Global Interior Eddy Available Potential Energy Diagnosed from Argo Floats ArchiMer
Roullet, Guillaume; Capet, Xavier; Maze, Guillaume.
By combining all Argo profiles for the period 2002 to present, a cumulative density function is constructed on a 3D grid of the global ocean. This function quantifies the statistics of isopycnals: time-averaged density, root- mean square (rms) of isopycnal displacement, and Eddy Available Potential Energy (EAPE). EAPE is the analogue of the eddy kinetic energy, but for the potential energy reservoir. Because it is essentially tied to the spatial struc- ture and magnitude of mesoscale activity, EAPE is an important quantity that should be useful to evaluate eddy resolving/permitting model turbu- lence and circulation. Among other striking features are the turbulent be- havior of Pacific and southern Atlantic Tsuchiya jets and subsurface EAPE maxima in some...
Tipo: Text Palavras-chave: Argo floats; Eddy available potential energy; Interior turbulence.
Ano: 2014 URL: http://archimer.ifremer.fr/doc/00175/28579/26966.pdf
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Heat balance and eddies in the Peru-Chile current system ArchiMer
Colas, Francois; Mcwilliams, James C.; Capet, Xavier; Kurian, Jaison.
The Peru-Chile current System (PCS) is a region of persistent biases in global climate models. It has strong coastal upwelling, alongshore boundary currents, and mesoscale eddies. These oceanic phenomena provide essential heat transport to maintain a cool oceanic surface underneath the prevalent atmospheric stratus cloud deck, through a combination of mean circulation and eddy flux. We demonstrate these behaviors in a regional, quasi-equilibrium oceanic model that adequately resolves the mesoscale eddies with climatological forcing. The key result is that the atmospheric heating is large (> 50 W m(-2)) over a substantial strip > 500 km wide off the coast of Peru, and the balancing lateral oceanic flux is much larger than provided by the offshore...
Tipo: Text Palavras-chave: Regional modelling; South-East Pacific; Heat Balance; Oceanic eddies; Regional climate.
Ano: 2012 URL: http://archimer.ifremer.fr/doc/00088/19892/17756.pdf
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Improvements of simulated Western North Atlantic current system and impacts on the AMOC ArchiMer
Talandier, Claude; Deshayes, Julie; Treguier, Anne-marie; Capet, Xavier; Benshila, Rachid; Debreu, Laurent; Dussin, Raphael; Molines, J. -m.; Madec, Gerard.
Previous studies have shown that low horizontal resolution (of the order of 1°) ocean models, hence climate models, are not able to adequately represent boundary currents nor mesoscale processes which affect the dynamics and thermohaline circulation of the ocean. While the effect of mesoscale eddies can be parameterized in low resolution models, boundary currents require relatively high horizontal resolution. We clarify the impact of increasing the resolution on the North Atlantic circulation, with emphasis on the Atlantic Meridional Overturning Circulation (AMOC), by embedding a 1/8° nest covering the North Atlantic into a global 1/2° model. Increasing the resolution in the nest leads to regional improvements of the circulation and thermohaline...
Tipo: Text Palavras-chave: Deep Western Boundary Current; Atlantic Meridional Overturning Circulation; North Atlantic Current; Gulf Stream; Subpolar gyre.
Ano: 2014 URL: http://archimer.ifremer.fr/doc/00173/28472/26812.pdf
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Intensification of upper ocean submesoscale turbulence through Charney baroclinic instability ArchiMer
Capet, Xavier; Roullet, Guillaume; Klein, Patrice; Maze, Guillaume.
This study focuses on the description of an oceanic variant of the Charney baroclinic instability, arising from the joint presence of i) an equatorward buoyancy gradient that extends from the surface into the ocean interior and ii) reduced subsurface stratification, e.g., as produced by wintertime convection or subduction. We analyze forced-dissipative simulations with and without Charney baroclinic instability (C-BCI). In the former C-BCI strengthens near-surface frontal activity with important consequences in terms of turbulent statistics: increased variance of vertical vorticity and velocity, increased vertical turbulent fluxes. Energetic consequences are explored. Despite the atypical enhancement of submesoscale activity in the simulation subjected to...
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Ano: 2016 URL: http://archimer.ifremer.fr/doc/00347/45785/45429.pdf
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North Pacific Gyre Oscillation modulates seasonal timing and ecosystem functioning in the California Current upwelling system ArchiMer
Chenillat, Fanny; Riviere, Pascal; Capet, Xavier; Di Lorenzo, E.; Blanke, Bruno.
On interannual and longer time scales, dynamical and biogeochemical fluctuations in the North Pacific are dominated by two modes of variability, namely the Pacific Decadal Oscillation and the North Pacific Gyre Oscillation (NPGO). In this study the regional expression of the NPGO in the California Current System (CCS) is detailed. The statistical relationship between the NPGO index and nearshore wind variability (mostly upwelling favorable) along the U. S. West coast is strongest in the wintertime (December to March) off Central California. Most importantly, NPGO fluctuations are associated with a seasonal shift of 1-2 months in the onset of the upwelling season. Regional numerical simulations show that an early (late) onset of upwelling during the...
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Ano: 2012 URL: http://archimer.ifremer.fr/doc/00063/17396/15062.pdf
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Observing submesoscale activity in the Bay of Biscay with satellite-derived SST and Chlorophyll concentration ArchiMer
Yelekci, Ozge; Charria, Guillaume; Mawren, Daneeja; Capet, Xavier; Reverdin, Gilles; Gohin, Francis; Sudre, Joel; Yahia, Hussein.
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Ano: 2014 URL: http://archimer.ifremer.fr/doc/00197/30787/29145.pdf
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On the Dynamics of the Southern Senegal Upwelling Center: Observed Variability from Synoptic to Superinertial Scales ArchiMer
Capet, Xavier; Estrade, Philippe; Machu, Eric; Ndoye, Siny; Grelet, Jacques; Lazar, Alban; Marie, Louis; Dausse, Denis; Brehmer, Patrice.
Upwelling off southern Senegal and Gambia takes place over a wide shelf with a large area where depths are shallower than 20 m. This results in typical upwelling patterns that are distinct (e.g., more persistent in time and aligned alongshore) from those of other better known systems, including Oregon and Peru where inner shelves are comparatively narrow. Synoptic to superinertial variability of this upwelling center is captured through a 4-week intensive field campaign, representing the most comprehensive measurements of this region to date. The influence of mesoscale activity extends across the shelf break and far over the shelf where it impacts the midshelf upwelling (e.g., strength of the upwelling front and circulation), possibly in concert with wind...
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Ano: 2017 URL: http://archimer.ifremer.fr/doc/00374/48541/48842.pdf
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On the pathways of the equatorial subsurface currents in the eastern equatorial Pacific and their contributions to the Peru-Chile Undercurrent ArchiMer
Montes, Ivonne; Colas, Francois; Capet, Xavier; Schneider, Wolfgang.
The connections between the Equatorial Current System and the Peru Current System in the eastern tropical Pacific (ETP) are examined with a primitive equations eddy-resolving regional model. The quasi-equilibrium solutions reproduce three eastward equatorial subsurface currents of interest: the Equatorial Undercurrent (EUC, located between 1 degrees N and 1 degrees S), the primary Southern Subsurface Countercurrent (pSSCC, between 3 degrees and 4 degrees S) and, farther south the secondary Southern Subsurface Countercurrent (sSSCC, between 7 degrees and 8 degrees S). Using a Lagrangian tracking procedure, the fate of these currents in the ETP and their contribution to the Peru-Chile Undercurrent (PCUC) are studied. Lagrangian diagnostics show that for the...
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Ano: 2010 URL: http://archimer.ifremer.fr/doc/00013/12438/9249.pdf
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Quantifying tracer dynamics in moving fluids: a combined Eulerian-Lagrangian approach ArchiMer
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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SEASTAR: A Mission to Study Ocean Submesoscale Dynamics and Small-Scale Atmosphere-Ocean Processes in Coastal, Shelf and Polar Seas ArchiMer
Gommenginger, Christine; Chapron, Bertrand; Hogg, Andy; Buckingham, Christian; Fox-kemper, Baylor; Eriksson, Leif; Soulat, Francois; Ubelmann, Clément; Ocampo-torres, Francisco; Nardelli, Bruno Buongiorno; Griffin, David; Lopez-dekker, Paco; Knudsen, Per; Andersen, Ole; Stenseng, Lars; Stapleton, Neil; Perrie, William; Violante-carvalho, Nelson; Schulz-stellenfleth, Johannes; Woolf, David; Isern-fontanet, Jordi; Ardhuin, Fabrice; Klein, Patrice; Mouche, Alexis; Pascual, Ananda; Capet, Xavier; Hauser, Daniele; Stoffelen, Ad; Morrow, Rosemary; Aouf, Lotfi; Breivik, Øyvind; Fu, Lee-lueng; Johannessen, Johnny A.; Aksenov, Yevgeny; Bricheno, Lucy; Hirschi, Joel; Martin, Adrien Ch; Martin, Adiran P; Nurser, George; Polton, Jeff; Wolf, Judith; Johnsen, Harald; Soloviev, Alexander; Jacobs, Gregg A.; Collard, Fabrice; Groom, Steve; Kudryavtsev, Vladimir; Wilkin, John; Navarro, Victor; Babanin, Alex; Martin, Matthew; Siddorn, John; Saulter, Andrew; Rippeth, Tom; Emery, Bill; Maximenko, Nikolai; Romeiser, Roland; Graber, Hans; Azcarate, Aida Alvera; Hughes, Chris W.; Vandemark, Doug; Silva, Jose Da; Leeuwen, Peter Jan Van; Naveira-garabato, Alberto; Gemmrich, Johannes; Mahadevan, Amala; Marquez, Jose; Munro, Yvonne; Doody, Sam; Burbidge, Geoff.
High-resolution satellite images of ocean color and sea surface temperature reveal an abundance of ocean fronts, vortices and filaments at scales below 10 km but measurements of ocean surface dynamics at these scales are rare. There is increasing recognition of the role played by small scale ocean processes in ocean-atmosphere coupling, upper-ocean mixing and ocean vertical transports, with advanced numerical models and in situ observations highlighting fundamental changes in dynamics when scales reach 1 km. Numerous scientific publications highlight the global impact of small oceanic scales on marine ecosystems, operational forecasts and long-term climate projections through strong ageostrophic circulations, large vertical ocean velocities and mixed layer...
Tipo: Text Palavras-chave: Satellite; Air sea interactions; Upper ocean dynamics; Submesoscale; Coastal; Marginal ice zone; Radar; Along-track interferometry.
Ano: 2019 URL: https://archimer.ifremer.fr/doc/00510/62121/66325.pdf
Registros recuperados: 25
Primeira ... 12 ... Última
 

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