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On the origins of water masses exported along both sides of Greenland: A Lagrangian model analysis ArchiMer
Lique, Camille; Treguier, Anne-marie; Blanke, Bruno; Grima, Nicolas.
The origin of the water masses exported from the Arctic to the North Atlantic along both sides of Greenland is investigated using an original numerical method. A quantitative Lagrangian analysis is applied to the monthly climatological 3-D output of a global ocean/sea ice high-resolution model. It allows quantification of the different branches of the export to the North Atlantic, as well as related timescales and water mass transformations. In the model, the outflow through Davis Strait consists in equal parts of Pacific and Atlantic water, whilst the export through Fram Strait consists almost fully of Atlantic water (contrary to observations). Pacific water is transferred quickly (O(10 years)) to the North Atlantic through the Beaufort Gyre, where...
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Ano: 2010 URL: http://archimer.ifremer.fr/doc/00005/11591/8232.pdf
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Lagrangian ocean analysis: fundamentals and practices ArchiMer
Van Sebille, Erik; Griffies, Stephen M.; Abernathey, Ryan; Adams, Thomas P.; Berloff, Pavel; Biastoch, Arne; Blanke, Bruno; Chassignet, Eric P.; Cheng, Yu; Cotter, Colin J.; Deleersnijder, Eric; Doos, Kristofer; Drake, Henri F.; Drijfhout, Sybren; Gary, Stefan F.; Heemink, Arnold W.; Kjellsson, Joakim; Koszalka, Inga Monika; Lange, Michael; Lique, Camille; Macgilchrist, Graeme A.; Marsh, Robert; Adame, C. Gabriela Mayorga; Mcadam, Ronan; Nencioli, Francesco; Paris, Claire B.; Piggott, Matthew D.; Polton, Jeff A.; Ruehs, Siren; Shah, Syed H. A. M.; Thomas, Matthew; Wang, Jinbo; Wolfram, Phillip J.; Zanna, Laure; Zika, Jan D..
Lagrangian analysis is a powerful way to analyse the output of ocean circulation models and other ocean velocity data such as from altimetry. In the Lagrangian approach, large sets of virtual particles are integrated within the three-dimensional, time-evolving velocity fields. Over several decades, a variety of tools and methods for this purpose have emerged. Here, we review the state of the art in the field of Lagrangian analysis of ocean velocity data, starting from a fundamental kinematic framework and with a focus on large-scale open ocean applications. Beyond the use of explicit velocity fields, we consider the influence of unresolved physics and dynamics on particle trajectories. We comprehensively list and discuss the tools currently available for...
Tipo: Text Palavras-chave: Ocean circulation; Lagrangian analysis; Connectivity; Particle tracking; Future modelling.
Ano: 2018 URL: http://archimer.ifremer.fr/doc/00412/52324/53099.pdf
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Ocean variability over the Agulhas Bank and its dynamical connection with the southern Benguela upwelling system ArchiMer
Blanke, Bruno; Penven, Pierrick; Roy, Claude; Chang, Nicolette; Kokoszka, Florian.
This study analyzes the oceanic pathway connecting the Agulhas Bank to the southern Benguela upwelling system by means of a quantitative Lagrangian interpretation of the velocity field calculated by a high-resolution numerical simulation of the ocean around the southwestern tip of Africa. The regional ocean model is forced with National Centers for Environmental Prediction surface winds over 1993-2006 and offers a relevant numerical platform for the investigation of the variability of the water transferred between both regions, both on seasonal and intraseasonal time scales. We show that the intensity of the connection fluctuates in response to seasonal wind variability in the west coast upwelling system, whereas intraseasonal anomalies are mostly related...
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Ano: 2009 URL: http://archimer.ifremer.fr/doc/2009/publication-7388.pdf
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A surface “super-convergence” pathway connecting the South Indian Ocean to the subtropical South Pacific gyre ArchiMer
Maes, C.; Grima, N.; Blanke, Bruno; Martinez, E.; Paviet-salomon, T.; Huck, Thierry.
We study the dispersion and convergence of marine floating material by surface currents from a model reanalysis that represents explicitly mesoscale eddy variability. Lagrangian experiments about the long-term evolution (29 years) of an initially homogeneous concentration of particles are performed at global scale with horizontal current at ¼° resolution and refreshed daily over the 1985-2013 period. Results confirm and document the five known sites of surface convergence at the scale of individual oceanic basins, but also reveal a convergent pathway connecting the South Indian subtropical region with the convergence zone of the South Pacific through the Great Australian Bight, the Tasman Sea and the southwest Pacific Ocean. This “super-convergent” pathway...
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Ano: 2018 URL: http://archimer.ifremer.fr/doc/00425/53631/54461.pdf
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Atlantic meridional overturning circulation and the Southern Hemisphere supergyre ArchiMer
Speich, Sabrina; Blanke, Bruno; Cai, Wenju.
The ocean's role in climate manifests itself through its high heat capacity, its own rich internal dynamics and its ability to transport vast quantities of heat and freshwater. Of particular interest is the global ocean circulation associated with the Atlantic meridional overturning (AMOC). Because observations are sparse, the detailed global structure of the AMOC remains poorly understood, particularly the pathways along which water returns to the Atlantic to compensate the export of North Atlantic Deep Water (NADW). Here we provide the first quantitative 3-dimensional global view of the AMOC using a Lagrangian reconstruction which integrates hundred of thousands water particle trajectories in an ocean model. The resulting pattern elucidates the role of...
Tipo: Text Palavras-chave: Antarctic circumpolar current; Indian ocean; Intermediate water; Thermohaline circulation; Pacific oceans; Conveyor belt; Model; Transport; Tracers.
Ano: 2007 URL: https://archimer.ifremer.fr/doc/00203/31420/29821.pdf
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Mesoscale and Submesoscale Processes in the Southeast Atlantic and Their Impact on the Regional Thermohaline Structure ArchiMer
Capuano, Tonia Astrid; Speich, Sabrina; Carton, Xavier; Blanke, Bruno.
The turbulent processes in the Cape Basin, the southeasternmost gate of the Atlantic Ocean, play a key role in the transport and mixing of upper to intermediate water masses entering the area from the Indian Ocean, making them especially relevant for the Indo-Atlantic transfer of heat and salt. In this paper, two numerical simulations at different horizontal resolutions are used to study mesoscale and submesoscale dynamics, their phenomenology, their evolution, and their impact on the local water masses. Submesoscale processes seasonally affect both, the upper and intermediate layers, but there are clear dynamical differences between the two layers. Several types of instabilities underline this spatial and temporal variability. Near the surface, mixed...
Tipo: Text Palavras-chave: Meso- and submesoscale dynamics; Cape Basin water masses; Indo-Atlantic exchange.
Ano: 2018 URL: https://archimer.ifremer.fr/doc/00600/71247/69618.pdf
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Lagrangian water mass tracing from pseudo-Argo, model-derived salinity, tracer and velocity data: An application to Antarctic Intermediate Water in the South Atlantic Ocean ArchiMer
Blanke, Bruno; Speich, Sabrina; Rusciano, Emanuela.
We use the tracer and velocity fields of a climatological ocean model to investigate the ability of Argo-like data to estimate accurately water mass movements and transformations, in the style of analyses commonly applied to the output of ocean general circulation model. To this end, we introduce an algorithm for the reconstruction of a fully non-divergent three-dimensional velocity field from the simple knowledge of the model vertical density profiles and 1000-m horizontal velocity components. The validation of the technique consists in comparing the resulting pathways for Antarctic Intermediate Water in the South Atlantic Ocean to equivalent reference results based on the full model information available for velocity and tracers. We show that the...
Tipo: Text Palavras-chave: Ocean circulation; Conservation equations; Mathematical models; Density field; Subsurface drifters; Intermediate water masses.
Ano: 2015 URL: https://archimer.ifremer.fr/doc/00238/34910/33597.pdf
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Linking wind and interannual upwelling variability in a regional model of the southern Benguela - art. no. 2188 ArchiMer
Blanke, Bruno; Roy, Claude; Penven, Pierrick; Speich, Sabrina; Mcwilliams, James; Nelson, Greville.
We quantify the wind contribution to the development of interannual sea surface temperature (SST) anomalies along the shelf of southern Africa. We compare numerical simulations that differ only in the amount of variability kept in the ERS1/2-derived surface wind forcing. Surprisingly, most of the cold and warm episodes over the Agulhas Bank are strictly related to local fluctuations of the forcing, whereas the shelf of the west coast extending 400 km north of Cape Columbine is equally sensitive to open-sea wind fluctuations. We diagnose the respective role of mesoscale eddy activity and of low frequency and intra-monthly wind fluctuations in generating interannual SST variability. The fair degree of correlation obtained at a few locations between the model...
Tipo: Text Palavras-chave: Numerical simulation; Wind fluctuation; Sea surface temperature; Upwelling.
Ano: 2002 URL: https://archimer.ifremer.fr/doc/2002/publication-770.pdf
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A Lagrangian numerical investigation of the origins and fates of the salinity maximum water in the Atlantic ArchiMer
Blanke, Bruno; Arhan, Michel; Lazar, A; Prevost, Gwenaelle.
The origins and fates of the Atlantic salinity maximum water (SMW), formed through excess evaporation in the tropics and subtropics of both hemispheres, are studied using monthly mean outputs of a numerical simulation of the world ocean climatological circulation. After defining formation domains from the surface salinity field and the vertical stratification, a Lagrangian technique is used to estimate the formation rates and main pathways in each hemisphere and the role of this water in the framework of the warm water return flow of the meridional overturning cell. Formation rates around 9 and 11 Sv are found in the Southern and Northern Hemispheres, respectively. While the export of the southern SMW from its formation area is realized by the western...
Tipo: Text Palavras-chave: Atlantic ocean; Lagrangian method; Numerical simulation; Salinity; Sea water.
Ano: 2002 URL: https://archimer.ifremer.fr/doc/2002/publication-769.pdf
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Large impact of Stokes drift on the fate of surface floating debris in the South Indian Basin ArchiMer
Dobler, Delphine; Huck, Thierry; Maes, Christophe; Grima, Nicolas; Blanke, Bruno; Martinez, Elodie; Ardhuin, Fabrice.
In the open ocean, floating surface debris such as plastics concentrate in five main accumulation zones centered around 30° latitude, far from highly turbulent areas. Using Lagrangian advection of numerical particles by surface currents from ocean model reanalysis, previous studies have shown long-distance connection from the accumulation zones of the South Indian to the South Pacific oceans. An important physical process affecting surface particles but missing in such analyses is wave-induced Stokes drift. Taking into account surface Stokes drift from a wave model reanalysis radically changes the fate of South Indian particles. The convergence region moves from the east to the west of the basin, so particles leak to the South Atlantic rather than the...
Tipo: Text Palavras-chave: Marine debris; Microplastics; Stokes drift; Indian Ocean; Lagrangian analysis; Ocean surface pathways.
Ano: 2019 URL: https://archimer.ifremer.fr/doc/00512/62320/69273.pdf
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Extratropical sources of equatorial Pacific upwelling in an OGCM ArchiMer
Rodgers, Kb; Blanke, Bruno; Madec, G; Aumont, O; Ciais, P; Dutay, Jc.
The extratropical sources of equatorial undercurrent (EUC) water have been identified for an ocean circulation model using Lagrangian trajectory analysis. It has been found that the EUC waters emenate from a wide range of latitudes in the Pacific basin, with its densest constituent watermass being Subantarctic Mode Water (SAMW) from 50degreesS. Further analysis of the basin-scale circulation fields has revealed significant advective diapycnal mass fluxes associated with intergyre exchange. As a result of these diapycnal mass fluxes, the EUC transport as a function of density at 151degreesW (an Eulerian diagnostic) looks quite different from the original subduction rate as a function of density for the same collection of water particles. This implicates...
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Ano: 2003 URL: http://archimer.ifremer.fr/doc/00000/10613/9403.pdf
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Role of fronts in the formation of Arabian Sea barrier layers during summer monsoon ArchiMer
De Boyer Montegut, Clement; Durand, Fabien; Bourdalle-badie, Romain; Blanke, Bruno.
The barrier layer (BL) - a salinity stratification embedded in the upper warm layer - is a common feature of the tropical oceans. In the northern Indian Ocean, it has the potential to significantly alter the air-sea interactions. In the present paper, we investigate the spatio-temporal structure of BL in the Arabian Sea during summer monsoon. This season is indeed a key component of the Asian climate. Based on a comprehensive dataset of Conductivity-Temperature-Depth (CTD) and Argo in situ hydrographic profiles, we find that a BL exists in the central Arabian Sea during summer. However, it is highly heterogeneous in space, and intermittent, with scales of about similar to 100 km or less and a couple of weeks. The BL patterns appear to be closely associated...
Tipo: Text Palavras-chave: Barrier layer; Arabian Sea; Summer monsoon; ARGO; ASHSW.
Ano: 2014 URL: http://archimer.ifremer.fr/doc/00198/30959/29358.pdf
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The exchange of Intermediate Water in the southeast Atlantic: Water mass transformations diagnosed from the Lagrangian analysis of a regional ocean model ArchiMer
Rimaud, Julie; Speich, Sabrina; Blanke, Bruno; Grima, Nicolas.
Results from a regional ocean model and numerical Lagrangian analyses are compared with in situ measurements to describe the properties and dynamics of Antarctic Intermediate Water (AAIW) in the region of the Cape Basin. The AAIW that originates in the South Atlantic (A-AAIW) at 8 degrees W follows two branches. A southern branch, flowing mostly south of 40 degrees S, is blocked by topography and is deflected westward without significant changes in its physical properties. A northern branch crosses the Cape Basin with strong modification of its physical properties. The AAIW that originates in the Indian Ocean (I-AAIW) flows into the Atlantic Ocean via the Agulhas Current and undergoes small physical changes in the Cape Basin. In the model, the salinity...
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Ano: 2012 URL: http://archimer.ifremer.fr/doc/00098/20921/18532.pdf
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Two Decades [1992-2012] of Surface Wind Analyses based on Satellite Scatterometer Observations ArchiMer
Desbiolles, Fabien; Bentamy, Abderrahim; Blanke, Bruno; Roy, Claude; Mestas-nunez, Alberto M.; Grodsky, Semyon A.; Herbette, Steven; Cambon, Gildas; Maes, Christophe.
Surface winds (equivalent neutral wind velocities at 10 m) from scatterometer missions since 1992 have been used to build up a 20-year climate series. Optimal interpolation and kriging methods have been applied to continuously provide surface wind speed and direction estimates over the global ocean on a regular grid in space and time. The use of other data sources such as radiometer data (SSM/I) and atmospheric wind reanalyses (ERA-Interim) has allowed building a blended product available at 1/4° spatial resolution and every 6 hours from 1992 to 2012. Sampling issues throughout the different missions (ERS-1, ERS-2, QuikSCAT, and ASCAT) and their possible impact on the homogeneity of the gridded product are discussed. In addition, we assess carefully the...
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Ano: 2017 URL: http://archimer.ifremer.fr/doc/00366/47686/47725.pdf
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Improvement in airsea flux estimates derived from satellite observations ArchiMer
Bentamy, Abderrahim; Grodsky, Semyon A.; Katsaros, Kristina; Mestas-nunez, Alberto M.; Blanke, Bruno; Desbiolles, Fabien.
A new method is developed to estimate daily turbulent airsea fluxes over the global ocean on a 0.25 degrees grid. The required surface wind speed (w(10)) and specific air humidity (q(10)) at 10m height are both estimated from remotely sensed measurements. w(10) is obtained from the SeaWinds scatterometer on board the QuikSCAT satellite. A new empirical model relating brightness temperatures (T-b) from the Special Sensor Microwave Imager (SSM/I) and q(10) is developed. It is an extension of the author's previous q(10) model. In addition to T-b, the empirical model includes sea surface temperature (SST) and airsea temperature difference data. The calibration of the new empirical q(10) model utilizes q(10) from the latest version of the National Oceanography...
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Ano: 2013 URL: http://archimer.ifremer.fr/doc/00137/24825/23575.pdf
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High-resolution atmospheric forcing for regional oceanic model: the Iroise Sea ArchiMer
Muller, Heloise; Dumas, Franck; Blanke, Bruno; Mariette, Vincent.
This study was aimed at modeling, as realistically as possible, the dynamics and thermodynamics of the Iroise Sea by using the Model for Applications at Regional Scale (MARS), a regional ocean 3D model. The horizontal resolution of the configuration in use is 2 km with 30 vertical levels. The 3D model of the Iroise Sea is embedded in a larger model providing open boundary conditions. As regards the atmospheric forcing, the originality of this study is to force the regional ocean model with the high-resolution (6 km) regional meteorological model, Weather Research and Forecasting (WRF). In addition, as the air surface temperature is highly sensitive to the sea surface temperature (SST), this regional meteorological model is improved by taking into account a...
Tipo: Text Palavras-chave: High frequency radar data; WRF; MARS; Iroise Sea.
Ano: 2007 URL: http://archimer.ifremer.fr/doc/2007/publication-3518.pdf
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A Lagrangian analysis of the Indian-Atlantic interocean exchange in a regional model - art. no. L14611 ArchiMer
Doglioli, Andrea; Veneziani, M; Blanke, Bruno; Speich, Sabrina; Griffa, A.
We present a new numerical Lagrangian technique based on the coupling of transport computation with spin analysis of trajectories. This method was applied to results from a high-resolution numerical model of the oceanic region around South Africa. We estimated an Indian-Atlantic leakage of about 14 Sv. In the western Cape Basin, approximately 30% of this transport is due to trapping eddies with a ratio between cyclones and anticyclones transport of 1.3. These findings are briefly discussed with respect to recent observations of the highly nonlinear regime found in this area of the Cape Basin.
Tipo: Text Palavras-chave: Anticyclones transport; Cyclones transport; The Indian Atlantic interocean exchange; South Africa; Numerical model.
Ano: 2006 URL: http://archimer.ifremer.fr/doc/2006/publication-1847.pdf
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Ocean Acidification from Below in the Tropical Pacific ArchiMer
Ishii, Masao; Rodgers, Keith B.; Inoue, Hisayuki Y.; Toyama, Katsuya; Sasano, Daisuke; Kosugi, Naohiro; Ono, Hisashi; Enyo, Kazutaka; Nakano, Toshiya; Iudicone, Daniele; Blanke, Bruno; Aumont, Olivier; Feely, Richard A..
Identifying ocean acidification and its controlling mechanisms is an important priority within the broader question of understanding how sustained anthropogenic CO2 emissions are harming the health of the ocean. Through extensive analysis of observational data products for ocean inorganic carbon, here we quantify the rate at which acidification is proceeding in the western tropical Pacific Warm Pool, revealing ‐0.0013 ±0.0001 yr‐1 for pH and ‐0.0083±0.0007 yr‐1 for the saturation index of aragonite for the years 1985‐2016. However, the mean rate of total dissolved inorganic carbon increase (+0.81 ±0.06 μmol kg‐1 yr‐1) sustaining acidification was ~20% slower than what would be expected if it were simply controlled by the rate of atmospheric CO2 increase...
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Ano: 2020 URL: https://archimer.ifremer.fr/doc/00641/75337/76003.pdf
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Modulation of wave-current interactions by horizontal mixing and spatial resolution ArchiMer
Bennis, A. -c.; Dumas, Franck; Blanke, Bruno.
The mechanics of rip currents are complex, involving interactions between waves, currents, water levels and bathymetry that pose particular challenges for numerical modeling. Horizontal turbulent diffusion in a rip system is difficult to measure using dye dilution or surfzone drifters, as shown by the range of published values for the horizontal diffusion coefficient. Here, we studied the effects of horizontal mixing on wave–current interactions by testing several diffusivity estimates in a fully coupled 3D wave–current model run at two different spatial resolutions. Published results using very low diffusion have found that near the shore the wave rays converge towards the rip channel because of refraction by the currents. We showed that this process is...
Tipo: Text Palavras-chave: Coastal ocean modelling; Nearshore processes; Rip currents; Wave current interactions; Horizontal mixing.
Ano: 2016 URL: https://archimer.ifremer.fr/doc/00309/42060/41530.pdf
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Tracking coherent structures in a regional ocean model with wavelet analysis: Application to Cape Basin eddies - art. no. C05043 ArchiMer
Doglioli, Andrea; Blanke, Bruno; Speich, Sabrina; Lapeyre, Guillaume.
[1] This study is mainly aimed at proposing objective tools for the identification and tracking of three-dimensional eddy structures. It is conducted with a high-resolution numerical model of the ocean region around South Africa, and emphasis is put on Cape Basin anticyclones and cyclones thought to be actively implicated in the Indian-Atlantic interocean exchange. We settle on wavelet analysis for the decomposition and processing of successive maps of relative vorticity for a simulation run with 1/10 degrees resolution. The identification of three- dimensional coherent structures comes with the calculation of eddy trajectories and the time evolution of eddy properties. Instantaneous mass transport and momentum of eddies are calculated from the knowledge...
Tipo: Text Palavras-chave: Southeast Atlantic ocean; Agulhas current system; Wavelet analysis; Regional modeling; Oceanic eddies.
Ano: 2007 URL: http://archimer.ifremer.fr/doc/2007/publication-2684.pdf
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